Barium titanate sub-nanosheet and polymer compounded dielectric energy storage film as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of dielectric energy storage films, and relates to a barium titanate sub-nanosheet and polymer compounded dielectric energy storage film as well as a preparation method and application thereof. The barium titanate sub-nanosheet is prepared by taking barium hydroxide, sodium hydroxide and a sub-nanosheet TiO2 as raw materials and adopting a hydrothermal method, and the barium titanate sub-nanosheet has a perovskite structure; and compounding the prepared barium titanate sub-nanosheets with a polymer to prepare the dielectric energy storage thin film material. Barium titanate of a perovskite structure not only has a very high dielectric constant, but also has an ultra-large specific surface area, a high atomic ratio and abundant active sites, forms charge traps on an interface while hindering breakdown path propagation, and meanwhile, is very good in dispersion uniformity; and the breakdown field strength and the energy density of the dielectric energy storage film can be greatly improved under the ultralow loading capacity, so that the purpose of improving the dielectric energy storage performance is achieved.

Description

Technical Field

[0001] This invention belongs to the field of energy storage thin film technology, and relates to a dielectric energy storage thin film composed of barium titanate subnanosheets and polymers, its preparation method and application. Background Technology

[0002] Dielectric capacitors play a vital role in modern electronic and electrical systems due to their fast charging and discharging speeds and high reliability. Higher energy density is required in their applications. U e), and the energy density is related to the energy density of dielectric materials. Energy density is generally related to the dielectric constant and electric field strength of the material. Therefore, the core technical approach to improving the energy density of dielectric materials is to increase the dielectric constant and breakdown field strength of the material.

[0003] Energy storage dielectric materials mainly include ceramic dielectrics and polymer dielectrics. Although traditional ceramic materials typically have high dielectric constants... But breaking through the field strength E b Limited; in contrast, polymer dielectrics have higher breakdown field strength. E b Good flexibility and mechanical properties, but low dielectric constant. The low (typically <10) value limits its application. To address these issues, a high-performance... The introduction of ceramics as fillers with high breakdown field strength E b High-performance composite materials that combine the advantages of both materials are prepared within a polymer matrix (such as polyvinylidene fluoride, abbreviated as PVDF). For example, patent document CN102558718B describes a barium titanate-polyvinylidene fluoride composite dielectric film and its preparation method. High-dielectric-constant ceramic particles of barium titanate are added to the polymer PVDF, thereby preparing a composite thin-film dielectric material that combines the high dielectric constant of barium titanate and the high breakdown field strength of PVDF. Patent document CN116355331B prepares a "core-shell" structured BaTiO3@Al2O3 nanofiber-doped PVDF-based composite film, achieving an effective improvement in breakdown strength and energy density. Furthermore, see patent document CN119639050A, which describes the composite of two-dimensional high-entropy ceramic nanosheets KNN@LNBCT with PVDF-PMMA, achieving relatively high... U e .

[0004] While the above studies can improve the breakdown strength and energy density of composite materials to some extent, the poor compatibility between fillers with high dielectric constants and polymers with high breakdown field strength, coupled with the high volume fraction of fillers, leads to the agglomeration of ceramic fillers, thereby reducing the breakdown field strength of the composite materials.E b , hindered U e Substantial improvements, etc. Referring to patent document CN115985687A, a sub-nanomaterial-polymer composite dielectric film for energy storage capacitors, its preparation method, and application, forms an interface with fewer voids and defects between the sub-nanomaterial and PEI, thereby hindering the propagation of the breakdown path and improving the breakdown field strength and energy density of PEI. Although the breakdown field strength and energy density of the polymer can be improved through sub-nanomaterials, the following problems exist: because the sub-nanosheets used are copper oxide... Phosphomolybdic acid sub-nanosheets, zinc oxide Polyacid subnanosheets and copper oxide Phosphomolybdic acid Silver subnanosheets require grafting with high amounts of surfactants to improve their dispersibility in PEI. However, both the subnanosheets and surfactants are low-dielectric-constant components. A high proportion of surfactants dilutes the inorganic phase contribution of the subnanosheets, limiting the improvement of the dielectric constant of the composite system and making it difficult to meet the requirements for high dielectric constant. At the same time, the dielectric constant mismatch between the subnanosheets and PEI leads to electric field distortion at the interface, which can easily cause local breakdown and limit further improvement of the breakdown field strength.

[0005] In summary, how to develop a new sub-nanosheet material and prepare inorganic fillers with both high dielectric constant and high surface activity, thereby simultaneously improving the dielectric energy storage performance of dielectric materials, is a research hotspot and core challenge that urgently needs to be addressed in the field of dielectric energy storage materials. Summary of the Invention

[0006] To address the technical bottlenecks in the field of existing dielectric energy storage composite films regarding the dielectric constant, surface activity, and energy storage performance of sub-nanosheet materials, this invention provides a dielectric energy storage film composed of barium titanate sub-nanosheets and polymers, along with its preparation method and applications.

[0007] This invention first uses a hydrothermal method to prepare barium titanate subnanosheets with a perovskite phase structure. Then, these barium titanate subnanosheets are composited with a polymer (PVDF-PMMA) to prepare a dielectric energy storage film. The perovskite-structured barium titanate of this invention not only has a high dielectric constant but also possesses an ultra-large specific surface area, high atomic ratio, and abundant active sites. It hinders breakdown path propagation while forming charge traps at the interface, exhibiting excellent dispersion uniformity. Under ultra-low loading, it can significantly improve the breakdown field strength and energy density of the dielectric energy storage film, thereby achieving the goal of improving dielectric energy storage performance.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing barium titanate subnanosheets involves using barium hydroxide, sodium hydroxide, and subnanosheet TiO2 as raw materials and employing a hydrothermal method. The barium titanate subnanosheets exhibit a perovskite structure. The average thickness of the barium titanate subnanosheets is 1.2 nm, and the highest specific surface area is 154.81 m². 2 / g.

[0009] Further specifying, the preparation method of the barium titanate subnanosheets is as follows: Barium hydroxide and sodium hydroxide were dissolved in water sequentially, and then sub-nanosheets of TiO2 were added and ultrasonically dispersed to prepare barium titanate sub-nanosheets by hydrothermal method.

[0010] Further specifying, the barium hydroxide (Ba(OH)2) The mass ratio of 8H2O, sodium hydroxide, sub-nanosheet TiO2 and water is (0.35~0.85):(2.0~6.0):(0.05~0.2):100.

[0011] Further specifying the conditions for preparing barium titanate sub-nanosheets by hydrothermal method, the conditions are: temperature of 170 ℃~210 ℃ and time of 10 min~1 h.

[0012] Barium titanate sub-nanosheets prepared using the aforementioned method.

[0013] Applications of barium titanate subnanosheets in improving polymer dielectric constant, breakdown field strength, and energy density.

[0014] A dielectric energy storage film composed of barium titanate subnanosheets and a polymer is made of barium titanate subnanosheets and a polymer formed from polyvinylidene fluoride and polymethyl methacrylate.

[0015] Further specified, in the dielectric energy storage film composed of barium titanate subnanosheets and polymer, the mass ratio of barium titanate subnanosheets to polymer is (0.1%~5.0%):1; the mass ratio of polyvinylidene fluoride to polymethyl methacrylate is 0.2:0.05.

[0016] The method for preparing the dielectric energy storage thin film composed of barium titanate subnanosheets and polymer includes the following steps: S1. Polyvinylidene fluoride and polymethyl methacrylate are uniformly dispersed in N,N-dimethylformamide and stirred evenly to obtain solution A; S2. Disperse barium titanate subnanosheets in solution A by ultrasonication and stir to obtain suspension B; S3. The suspension B is uniformly coated onto the glass using the casting method. The glass is first dried at 50 ℃~80 ℃ for 10~14 h to remove the solvent. Then it is heated at 180 ℃~220 ℃ for 5 min~20 min and quenched to obtain the final product.

[0017] Application of barium titanate subnanosheets and polymer composite dielectric energy storage films in high dielectric energy storage capacitors.

[0018] Compared with the prior art, the beneficial effects of the technical solution of the present invention are: 1. This invention uses barium hydroxide, sodium hydroxide, and sub-nanosheet TiO2 as raw materials and employs a hydrothermal method to prepare barium titanate sub-nanosheets with a perovskite structure. These barium titanate sub-nanosheets are then combined with a polymer (PVDF-PMMA) to prepare a composite dielectric energy storage film. The perovskite-structured barium titanate sub-nanosheets possess a large dielectric constant, an ultra-large specific surface area, a high atomic ratio, and abundant active sites. They hinder breakdown path propagation while forming charge traps at the interface. Furthermore, they exhibit excellent flexibility, significantly improving the breakdown field strength and energy density of the dielectric energy storage film under ultra-low loading conditions, thereby enhancing the dielectric energy storage performance of the dielectric material.

[0019] 2. Through testing, the barium titanate subnanosheets prepared in this invention have an average thickness of 1.2 nm and a maximum specific surface area of ​​154.81 m². 2 g -1 Because barium titanate subnanosheets are very thin, most atoms are exposed on the sample surface, meaning they have a large specific surface area. This results in good compatibility between barium titanate subnanosheets and the polymer (PVDF-PMMA) matrix, eliminating the need for additional surfactants. Furthermore, barium titanate possesses a perovskite structure, thus exhibiting high dielectric constant, breakdown field strength, and energy density even with relatively low amounts of barium titanate subnanosheets. This makes them suitable for use in capacitors and high-power electrostatic energy storage materials, improving the performance of dielectric energy storage capacitors. 3. In the preparation of this invention, the ultra-low loading and high dispersibility of barium titanate sub-nanosheets are achieved by optimizing the raw material ratio. The resulting composite dielectric film can maintain good flexibility and bendability, which solves the problems of filler agglomeration, polymer matrix embrittlement and loss of flexibility caused by high loading of traditional high dielectric fillers, and meets the application scenarios of flexible high dielectric energy storage capacitors.

[0020] 4. This invention prepares barium titanate sub-nanosheets via a hydrothermal method and obtains composite dielectric energy storage films via a casting method. The preparation methods are simple and easy to industrialize. Attached Figure Description

[0021] Figure 1The XRD pattern of sample #3 BaTiO3SNSs in Example 3; Figure 2 The XRD pattern of the #2 thin film sample in Example 9; Figure 3 The XRD pattern of the PVDF-PMMA sample in the comparative example; Figure 4 The images shown are TEM images, HAADF images, and energy dispersive spectroscopy of sample #3 BaTiO3SNSs in Example 3. Figure 5 The image shows the AFM image of sample #3 BaTiO3SNSs in Example 3; Figure 6 The BET plot of sample #3 BaTiO3SNSs in Example 3; Figure 7 This is a cross-sectional SEM image of the #2 thin film sample in Example 9; Figure 8 Here is a cross-sectional SEM image of the PVDF-PMMA sample in the comparative example; Figure 9 The dielectric properties of the #2 thin film sample in Example 9 are shown in the diagram. Figure 10 The dielectric properties of the PVDF-PMMA sample in the comparative example are shown in the figure. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0023] This invention discloses a method for preparing barium titanate subnanosheets, which uses barium hydroxide, sodium hydroxide, and subnanosheet TiO2 as raw materials and is prepared by a hydrothermal method. The barium titanate subnanosheets have a perovskite structure, an average thickness of 1.2 nm, and a maximum specific surface area of ​​154.81 m². 2 / g.

[0024] In this invention, the preparation method of barium titanate subnanosheets is as follows: Barium hydroxide (Ba(OH)2) Barium titanate sub-nanosheets with a perovskite structure were prepared by hydrothermal method after dissolving 8H2O and sodium hydroxide (NaOH) sequentially in water, adding sub-nanosheet TiO2 and ultrasonically dispersing it evenly.

[0025] Preferably, barium hydroxide (Ba(OH)2) The mass ratio of 8H2O, sodium hydroxide, sub-nanosheet TiO2 and water is (0.35~0.85):(2.0~6.0):(0.05~0.2):100.

[0026] Preferably, the conditions for the hydrothermal method are: temperature of 170 ℃ to 210 ℃ and time of 10 min to 1 h.

[0027] Preferably, the sub-nanosheet TiO2 is prepared by a hydrothermal method using titanium trichloride, water, and ethylene glycol as raw materials.

[0028] The present invention also provides an application of barium titanate subnanosheets with a perovskite structure in improving polymer breakdown field strength and energy density.

[0029] The present invention also provides a dielectric energy storage film composed of barium titanate subnanosheets and a polymer, which is made of barium titanate subnanosheets with a perovskite structure and a polymer formed of polyvinylidene fluoride and polymethyl methacrylate.

[0030] Preferably, in the dielectric energy storage film composed of barium titanate subnanosheets and polymer, the mass ratio of barium titanate subnanosheets to polymer is (0.1%~5.0%):1; and the mass ratio of polyvinylidene fluoride to polymethyl methacrylate is 0.2:0.05.

[0031] This invention also provides a method for preparing a dielectric energy storage thin film composed of barium titanate subnanosheets and polymers, comprising the following steps: S1. Polyvinylidene fluoride and polymethyl methacrylate are uniformly dispersed in N,N-dimethylformamide and stirred evenly to obtain solution A; S2. Disperse barium titanate subnanosheets in solution A by ultrasonication and stir to obtain suspension B; S3. The suspension B is uniformly coated onto the glass using the casting method. The glass is first dried at 50 ℃~80 ℃ for 10~14 h to remove the solvent. Then it is heated at 180 ℃~220 ℃ for 5 min~20 min and quenched to obtain the final product.

[0032] The dielectric energy storage film composed of barium titanate subnanosheets and polymers of the present invention has good breakdown strength and energy density, and can be used in high dielectric energy storage capacitors.

[0033] The technical solution of the present invention and the performance of the composite thin film material are described below with several examples.

[0034] It should be noted that, unless otherwise specified, the chemicals, reagents, or solvents used in the following examples are all commercially available products commonly used in the field.

[0035] It should be noted that, unless otherwise specified, the operating methods and conditions used in the following embodiments are all conventional operating methods or conditions. For example, unless otherwise specified, the temperature is room temperature and the pressure is atmospheric pressure. The testing methods used are all conventional testing methods in this field or industry. Example 1 This embodiment uses a hydrothermal method to prepare barium titanate subnanosheets, and the specific steps are as follows: S1, 0.1577 g Ba(OH)2 8 H₂O and 1.2 g NaOH were dissolved sequentially in 30 mL of H₂O and stirred to disperse and dissolve them. 0.04 g of sub-nanosheet TiO₂ was weighed and added to the mixed solution, and stirred for 10 min to disperse it evenly, resulting in a suspension. In this embodiment, the sub-nanosheet TiO2 is prepared by a hydrothermal method using titanium trichloride, water, and ethylene glycol as raw materials. The specific preparation process is as follows: S1.1 Mix 1.0 mL TiCl3 solution, 1.0 mL deionized water and 30.0 mL ethylene glycol evenly and transfer the mixture to a 50 mL hydrothermal reactor. Place the reactor in an oven and react at 160 °C for 6 hours.

[0036] S1.2 After completion, the product was separated by centrifugation and washed three times with water and alcohol respectively. Finally, it was vacuum dried in an oven at 60 °C to obtain sub-nanosheet TiO2, denoted as TiO2SNSs.

[0037] S2. Transfer the suspension to a 50 mL reaction vessel and place it in an oven at 180 °C for 10 min. After the reaction, separate the product using a centrifuge and wash it three times each with acetic acid, water, and alcohol. Finally, vacuum dry it in an oven at 60 °C to obtain the product, barium titanate subnanosheets, denoted as #1 BaTiO3SNSs.

[0038] Example 2 This embodiment uses a hydrothermal method to prepare barium titanate subnanosheets, and the specific steps are as follows: S1, 0.1577 g Ba(OH)2 8 H₂O and 1.2 g NaOH were dissolved sequentially in 30 mL H₂O and stirred to disperse and dissolve them. 0.04 g of TiO₂SNSs from Example 1 was weighed and added to the mixed solution, and stirred for 10 min to disperse it evenly, resulting in a suspension. S2. Transfer the suspension to a 50 mL reaction vessel and place it in an oven at 180 °C for 20 min. After the reaction, separate the product using a centrifuge and wash it three times each with acetic acid, water, and alcohol. Finally, vacuum dry it in an oven at 60 °C to obtain the product, barium titanate subnanosheets, denoted as #2 BaTiO3SNSs.

[0039] Example 3 This embodiment uses a hydrothermal method to prepare barium titanate subnanosheets, and the specific steps are as follows: S1, 0.1577 g Ba(OH)2 8 H₂O and 1.2 g NaOH were dissolved sequentially in 30 mL H₂O and stirred to disperse and dissolve them. 0.04 g of TiO₂SNSs from Example 1 was weighed and added to the mixed solution, and stirred for 10 min to disperse it evenly, resulting in a suspension. S2. Transfer the suspension to a 50 mL reaction vessel and place it in an oven at 180 °C for 30 min. After the reaction, separate the product using a centrifuge and wash it three times each with acetic acid, water, and alcohol. Finally, vacuum dry it in an oven at 60 °C to obtain the product, barium titanate subnanosheets, denoted as #3 BaTiO3SNSs.

[0040] In this embodiment, the microstructure of sample #3 BaTiO3SNSs is studied. The XRD pattern of sample #3 BaTiO3SNSs is shown below. Figure 1 As shown; TEM image and energy spectrum are as follows. Figure 4 As shown; AFM diagram as follows Figure 5 As shown; nitrogen adsorption-desorption curve is shown in the figure. Figure 6 As shown.

[0041] Example 4 This embodiment uses a hydrothermal method to prepare barium titanate subnanosheets, and the specific steps are as follows: S1, 0.1577 g Ba(OH)2 8 H₂O and 1.2 g NaOH were dissolved sequentially in 30 mL H₂O and stirred to disperse and dissolve them. 0.04 g of TiO₂SNSs from Example 1 was weighed and added to the mixed solution, and stirred for 10 min to disperse it evenly, resulting in a suspension. S2. Transfer the suspension to a 50 mL reaction vessel and place it in an oven at 180 °C for 1 h. After the reaction, separate the product using a centrifuge and wash it three times each with acetic acid, water, and alcohol. Finally, vacuum dry it in an oven at 60 °C to obtain the product, barium titanate subnanosheets, denoted as #4 BaTiO3SNSs.

[0042] Example 5 This embodiment uses a hydrothermal method to prepare barium titanate subnanosheets, and the specific steps are as follows: S1, 0.1262 g Ba(OH)2 8 H₂O and 1.2 g NaOH were dissolved sequentially in 30 mL H₂O and stirred to disperse and dissolve them. 0.04 g of TiO₂SNSs from Example 1 was weighed and added to the mixed solution, and stirred for 10 min to disperse it evenly, resulting in a suspension. S2. Transfer the suspension to a 50 mL reaction vessel and place it in an oven at 180 °C for 1 h. After the reaction, separate the product using a centrifuge and wash it three times each with acetic acid, water, and alcohol. Finally, vacuum dry it in an oven at 60 °C to obtain the product, barium titanate subnanosheets, denoted as #5 BaTiO3SNSs.

[0043] Example 6 This embodiment uses a hydrothermal method to prepare barium titanate subnanosheets, and the specific steps are as follows: S1, 0.1893 g Ba(OH)2 8 H₂O and 1.2 g NaOH were dissolved sequentially in 30 mL H₂O and stirred to disperse and dissolve them. 0.04 g of TiO₂SNSs from Example 1 was weighed and added to the mixed solution, and stirred for 10 min to disperse it evenly, resulting in a suspension. S4. Transfer the suspension to a 50 mL reaction vessel and place it in an oven at 180 °C for 1 h. After the reaction, separate the product using a centrifuge and wash it three times each with acetic acid, water, and alcohol. Finally, vacuum dry it in an oven at 60 °C to obtain the product, barium titanate subnanosheets, denoted as #6 BaTiO3SNSs.

[0044] Example 7 This embodiment uses a hydrothermal method to prepare barium titanate subnanosheets, and the specific steps are as follows: S1, 0.2208 g Ba(OH)2 8 H₂O and 1.2 g NaOH were dissolved sequentially in 30 mL H₂O and stirred to disperse and dissolve them. 0.04 g of TiO₂SNSs from Example 1 was weighed and added to the mixed solution, and stirred for 10 min to disperse it evenly, resulting in a suspension. S2. Transfer the suspension to a 50 mL reaction vessel and place it in an oven at 180 °C for 1 h. After the reaction, separate the product using a centrifuge and wash it three times each with acetic acid, water, and alcohol. Finally, vacuum dry it in an oven at 60 °C to obtain the product, barium titanate subnanosheets, denoted as #7 BaTiO3SNSs.

[0045] Example 8 This embodiment uses a casting method to prepare a dielectric energy storage film composed of barium titanate subnanosheets and polymers, including the following steps: S1. Disperse 0.2 g of polyvinylidene fluoride (PVDF) and 0.05 g of polymethyl methacrylate (PMMA) in 2.5 mL of N,N-dimethylformamide (DMF) and stir for 12 h to obtain solution A.

[0046] S2. 0.00125 g of barium titanate sub-nanosheets were ultrasonically dispersed in solution A and stirred for 12 h to obtain suspension B; the barium titanate sub-nanosheets were #3 BaTiO3SNSs prepared in Example 3.

[0047] S3. First, 70 μL of suspension B is uniformly coated onto a clean glass using a casting machine. Then, it is dried at 60 °C for 12 h to remove the solvent. Finally, the obtained film is heated at 200 °C for 10 min and then immediately placed in ice water for quenching to obtain a dielectric energy storage film composed of barium titanate subnanosheets and polymer (abbreviated as BaTiO3 / PVDF-PMMA), which is designated as film sample #1.

[0048] Example 9 This embodiment uses a casting method to prepare a dielectric energy storage film composed of barium titanate subnanosheets and polymers, including the following steps: S1. Disperse 0.2 g PVDF and 0.05 g PMMA in 2.5 mL DMF and stir for 12 h to obtain solution A.

[0049] S2. 0.0025 g of barium titanate subnanosheets were ultrasonically dispersed in solution A and stirred for 12 h to obtain suspension B.

[0050] S3. First, 70 μL of suspension B is uniformly coated onto a clean glass substrate using a casting machine, and then dried at 60 ℃ for 12 h to remove the solvent. Finally, the obtained film is heated at 200 ℃ for 10 min and then immediately quenched in ice water to obtain a dielectric energy storage film composed of sub-nanosheets and polymer (abbreviated as BaTiO3 / PVDF-PMMA), denoted as film sample #2.

[0051] In this embodiment, the microstructure and dielectric energy storage performance of the #2 thin film sample are studied.

[0052] The XRD pattern of the #2 thin film sample is shown below. Figure 2 As shown; cross-sectional SEM images are as follows Figure 7 As shown; dielectric properties are as follows Figure 9 As shown.

[0053] Example 10 This embodiment uses a casting method to prepare a dielectric energy storage film composed of barium titanate subnanosheets and polymers, including the following steps: S1. Disperse 0.2 g PVDF and 0.05 g PMMA in 2.5 mL DMF and stir for 12 h to obtain solution A.

[0054] S2. 0.00375 g of barium titanate subnanosheets were ultrasonically dispersed in solution A and stirred for 12 h to obtain suspension B.

[0055] S3. First, 70 μL of suspension B is uniformly coated onto a clean glass using a casting machine, and then dried at 60 ℃ for 12 h to remove the solvent. Finally, the obtained film is heated at 200 ℃ for 10 min and then immediately quenched in ice water to obtain a dielectric energy storage film composed of sub-nanosheets and polymer (abbreviated as BaTiO3 / PVDF-PMMA), denoted as film sample #3.

[0056] Example 11 This embodiment uses a casting method to prepare a dielectric energy storage film composed of barium titanate subnanosheets and polymers, including the following steps: S1. Disperse 0.2 g PVDF and 0.05 g PMMA in 2.5 mL DMF and stir for 12 h to obtain solution A.

[0057] S2. 0.0050 g of barium titanate subnanosheets were ultrasonically dispersed in solution A and stirred for 12 h to obtain suspension B.

[0058] S3. First, 70 μL of suspension B is uniformly coated onto a clean glass substrate using a casting machine, and then dried at 60 ℃ for 12 h to remove the solvent. Finally, the obtained film is heated at 200 ℃ for 10 min and then immediately quenched in ice water to obtain a dielectric energy storage film composed of sub-nanosheets and polymer (abbreviated as BaTiO3 / PVDF-PMMA), denoted as film sample #4.

[0059] In the above embodiments 1 to 7 of the present invention, the parameters for preparing barium titanate sub-nanosheets by hydrothermal method can be arbitrarily selected within the following ranges: the mass of Ba(OH)2·8H2O is 0.1262 g to 0.2208 g; the stirring time is 5 min to 30 min; the temperature of hydrothermal method is 170 ℃ to 200 ℃, and the time is 10 min to 1 h; drying is carried out at 50 ℃ to 80 ℃ for 4 h to 24 h.

[0060] In Examples 8-11 of the present invention, the preparation parameters in step S1 can be arbitrarily selected within the following ranges: stirring time is 10 h to 24 h; the mass ratio of barium titanate subnanosheets to polymer (PVDF-PMMA) is (0.1% to 5.0%): 1. The preparation parameters in step S2 can also be arbitrarily selected within the following ranges: the volume of suspension B is 50 μL to 100 μL; and the barium titanate subnanosheets are prepared in Examples 1, 2, or 4-7.

[0061] To demonstrate the technical advantages of the present invention, a dielectric energy storage film composed of barium titanate subnanosheets and polymers (hereinafter referred to as dielectric energy storage film, denoted as BaTiO3 / PVDF-PMMA), its physicochemical properties were experimentally verified, and the specific experiments are as follows.

[0062] In the experimental verification, in order to highlight the performance advantages of the sub-nanosheet and polymer composite dielectric energy storage film of the present invention, the following comparative examples were designed for comparison.

[0063] Comparative Example In this comparative example, PVDF-PMMA dielectric energy storage thin film material was prepared by casting using PVDF and PMMA as raw materials. Specifically, the preparation steps of the PVDF-PMMA dielectric energy storage thin film material are as follows: First, mix 0.2 g PVDF and 0.05 g PVDF. g PMMA was dispersed in 2.5 mL of DMF and stirred until homogeneous to obtain suspension A; Then, 70 μL of suspension A was uniformly coated onto a clean glass and dried at 60 °C for 12 h to remove the solvent; the film was then heated at 200 °C for 10 min and immediately placed in ice water for quenching to obtain the PVDF-PMMA dielectric energy storage film material, denoted as PVDF-PMMA sample.

[0064] In this comparative example, the microstructure and dielectric energy storage performance of the PVDF-PMMA sample were studied.

[0065] The XRD pattern of the PVDF-PMMA sample is shown below. Figure 3 As shown; cross-sectional SEM images are as follows Figure 8 As shown; dielectric properties are as follows Figure 10 As shown.

[0066] The performance results of the samples in the above embodiments and comparative examples are as follows.

[0067] Experiment 1 The #3 BaTiO3SNSs sample prepared in Example 3, the #2 thin film sample prepared in Example 9, and the PVDF-PMMA sample prepared in the comparative example were characterized by XRD analysis.

[0068] The experimental procedure was as follows: the phase composition of the powder was directly detected by powder X-ray diffraction (XRD), and the test conditions were: Cu-K α The target was used as the radiation source. The test tube voltage was 40 kV, the test tube current was 40 mA, the scan step size was 0.02°, and the scan rate was 0.05° / s. Analysis was performed using Jade software, and the results are as follows: Figures 1-3 As shown.

[0069] pass Figure 1 It can be seen that the XRD pattern shows that all diffraction peaks correspond one-to-one with the standard card BaTiO3 (PDF#75-0212), and the (200) diffraction peak does not show any splitting phenomenon, thus it can be determined that the obtained sample is cubic phase BaTiO3. The diffraction peaks at 22.1°, 31.5°, 38.8°, 45.1°, 56.0°, 65.7° and 74.7° correspond to the (100), (110), (111), (200), (211), (220) and (310) crystal planes of cubic perovskite phase BaTiO3, respectively. No other impurity peaks appear in the figure, which indicates that the prepared #3 BaTiO3SNSs is perovskite phase. The peak height of the diffraction peaks indicates that the crystallinity of the product is relatively low, which is consistent with the crystallization characteristics of sub-nanomaterials, indicating that the barium titanate sub-nanosheets with perovskite structure were successfully prepared.

[0070] pass Figure 2 It can be seen that in the dielectric energy storage film composed of barium titanate sub-nanosheets with perovskite structure and polymer prepared in Example 9, the PVDF... α、β and γ The phases coexist; PMMA is amorphous, therefore there are no obvious diffraction peaks. In The diffraction peaks at 22.1°, 31.5°, 38.8°, 45.1°, 56.0°, and 65.7° are attributed to the (100), (110), (111), (200), (211), and (220) crystal planes of the cubic perovskite phase BaTiO3, respectively. All diffraction peaks can be attributed to the filler and matrix, respectively, with no other impurity peaks. Furthermore, the positions of the characteristic peaks of PVDF did not change significantly before and after the addition of BaTiO3SNSs, indicating that the addition of BaTiO3SNSs did not alter the phase structure of PVDF.

[0071] pass Figure 3 It can be seen that: the PVDF-PMMA sample prepared in the comparative example has PVDF in the thin film material. α、β and γ Since they coexist, PMMA is almost amorphous, so its diffraction peaks are very weak.

[0072] Experiment 2 The #3 BaTiO3SNSs sample prepared in Example 3 was dispersed in ethanol, diluted, and then a small amount of liquid was added dropwise onto a copper mesh microgrid. After drying for approximately 1 hour, the sample was analyzed using a combination of transmission electron microscopy (TEM, Tecnai G2 F20S-TWIN) and energy-dispersive spectroscopy (EDS) elemental analysis. The results are as follows: Figure 2 As shown.

[0073] from Figure 4 It can be seen that the barium titanate subnanosheets (BaTiO3SNSs) have a sheet-like structure and are as soft as silk, proving that the sheet-like structure is very thin and has good flexibility. Elemental analysis shows that Ba, Ti, and O elements are present in the elemental distribution diagram of BaTiO3SNSs, and these elements are uniformly dispersed. The lattice fringes of HR-TEM show that some regions are latticeally ordered, which also confirms the conclusion of weak crystallinity drawn from the XRD pattern in Experiment 1. The interplanar spacing shown in the figure is about 2.30 Å, which can be attributed to the (111) crystal plane of BaTiO3 (PDF#75-0212). This further verifies the successful preparation of the barium titanate subnanosheet sample with a perovskite structure.

[0074] Experiment 3 The #3 BaTiO3SNSs sample prepared in Example 3 was dispersed in ethanol, diluted, and then a small amount of liquid was added dropwise onto a mica sheet. The thickness of the sample was studied using atomic force microscopy (AFM, Bruker Dimension Icon). The results are as follows: Figure 5 As shown.

[0075] from Figure 5 It can be seen that the average height of the barium titanate subnanosheet's transverse cross-section determines its average thickness to be 1.2 nm. This further verifies the successful preparation of barium titanate subnanosheets with a perovskite structure.

[0076] Experiment 4 The #3 BaTiO3SNSs sample prepared in Example 3 was measured using a Brunauer-Emmett-Teller (BET, micro TriStar-3020) to determine the specific surface area of ​​the powder sample. The results are as follows: Figure 6 As shown.

[0077] from Figure 6 It can be seen that the sample adsorption curve conforms to the Type II isotherm among the five BDDT adsorption types, indicating adsorption by non-porous or macroporous materials, and the BET specific surface area of ​​the barium titanate subnanosheets is 154.81 m². 2 g -1Because barium titanate subnanosheets are very thin and have excellent flexibility, with most atoms exposed on the sample surface and abundant active sites, they also have a large specific surface area. This allows them to be well-matched and integrated with polymers, thereby improving the dielectric constant and breakdown field strength of dielectric energy storage films.

[0078] Experiment 5 SEM observations were performed on the cross-sections of the #2 thin film sample prepared in Example 9 and the PVDF-PMMA sample prepared in the comparative example. The results are as follows: Figure 7 and Figure 8 As shown.

[0079] See Figure 8 The PVDF-PMMA sample was approximately 10 μm thick, dense, and smooth, with no obvious defects. (See also...) Figure 7 The dielectric energy storage film has a thickness of 9.8 μm, is dense and flat with no obvious defects, and the barium titanate subnanosheets are well dispersed as fillers with indistinguishable interfaces. This indicates that the barium titanate subnanosheets have good compatibility with the polymer (PVDF-PMMA) matrix.

[0080] Experiment 6 The #2 thin film samples prepared in Examples 8-11 and the PVDF-PMMA samples prepared in the comparative examples were used to fabricate gold electrodes with a diameter of 2 mm on both sides using an ion sputtering instrument. Their dielectric properties were tested using conventional testing methods, and the specific results are shown in Table 1 below. The test results for Example 9 and the comparative examples are shown below. Figure 9 and Figure 10 As shown.

[0081] From Table 1, Figure 9 and Figure 10 It can be seen that the dielectric constant of the dielectric energy storage films prepared in Examples 8 to 11 is improved compared with the PVDF-PMMA samples; indicating that the composite of barium titanate subnanosheets with perovskite structure and polymer can improve the dielectric properties of dielectric energy storage films; at the same time, the dielectric energy storage film of barium titanate subnanosheets and polymer prepared in Example 9 has the highest dielectric properties.

[0082] Table 1. Dielectric properties of Examples 8-11 and Comparative Samples Experiment 7 The thin film samples prepared in Examples 8-11 and the PVDF-PMMA samples prepared in the comparative examples were used to prepare gold electrodes with a diameter of 2.0 mm on both sides using an ion sputtering instrument. Their energy storage performance was tested according to conventional detection methods, and the results are shown in Table 2 below.

[0083] Table 2 Energy storage performance of Examples 8-11 and comparative sample Compared with PVDF-PMMA dielectric energy storage film materials, the dielectric energy storage films prepared in Examples 8-11 all showed improved breakdown field strength and energy density, indicating that barium titanate subnanosheets with perovskite structure can significantly improve the breakdown field strength and energy density of polymer PVDF-PMMA films as fillers. Meanwhile, the dielectric energy storage film composed of barium titanate subnanosheets and polymer prepared in Example 9 exhibited high breakdown field strength and energy density.

[0084] The above tests were conducted using the barium titanate subnanosheets with a perovskite structure prepared in Example 3 and the dielectric energy storage film prepared from the barium titanate subnanosheets as examples to verify performance. When the target products prepared in Examples 1, 2, 4-7 were used for experimental testing and composite dielectric energy storage films were prepared, they exhibited the same or similar performance as the barium titanate subnanosheets in Example 3, and all of them could improve the breakdown field strength and energy density of the polymer.

[0085] In summary, the dielectric energy storage film formed by combining barium titanate subnanosheets with a perovskite structure and a polymer at a relatively low content, as described in this invention, exhibits improved breakdown field strength and energy density, meeting the dielectric energy storage performance requirements of high-dielectric-capacitors. Furthermore, this invention employs a hydrothermal method to prepare the perovskite-structured barium titanate subnanosheets and the dielectric energy storage film, which is simple in process, allows for easy control of material composition and ratio, and results in a dielectric energy storage film with good reliability and toughness, enabling industrial-scale production.

[0086] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for preparing barium titanate subnanosheets, characterized in that, It is prepared by hydrothermal method using barium hydroxide, sodium hydroxide, and sub-nanosheet TiO2 as raw materials; the barium titanate sub-nanosheets have a perovskite structure; the average thickness of the barium titanate sub-nanosheets is 1.2 nm, and the highest specific surface area is 154.81 m². 2 / g.

2. The method for preparing barium titanate subnanosheets according to claim 1, characterized in that, The specific method for preparing the barium titanate subnanosheets is as follows: Barium hydroxide and sodium hydroxide were dissolved in water sequentially, and then sub-nanosheets of TiO2 were added and ultrasonically dispersed to prepare barium titanate sub-nanosheets by hydrothermal method.

3. The method for preparing barium titanate subnanosheets according to claim 2, characterized in that, The barium hydroxide (Ba(OH)2) The mass ratio of 8H2O, sodium hydroxide, sub-nanosheet TiO2 and water is (0.35~0.85):(2.0~6.0):(0.05~0.2):

100.

4. The method for preparing barium titanate subnanosheets according to claim 2, characterized in that, The conditions for preparing barium titanate sub-nanosheets by hydrothermal method are: temperature of 170 ℃ to 210 ℃ and time of 10 min to 1 h.

5. Barium titanate subnanosheets prepared using the preparation method described in claim 1.

6. The application of the barium titanate subnanosheets according to claim 5 in improving polymer breakdown field strength and energy density.

7. A dielectric energy storage thin film composed of barium titanate subnanosheets and a polymer, characterized in that, It is made of a polymer and the barium titanate sub-nanosheets as described in claim 5, wherein the polymer is formed from polyvinylidene fluoride and polymethyl methacrylate.

8. The dielectric energy storage thin film composed of barium titanate subnanosheets and polymer according to claim 7, characterized in that, In the barium titanate subnanosheet and polymer composite dielectric energy storage film, the mass ratio of barium titanate subnanosheet to polymer is (0.1%~5.0%):1; the mass ratio of polyvinylidene fluoride to polymethyl methacrylate is 0.2:0.

05.

9. The method for preparing the dielectric energy storage thin film composed of barium titanate subnanosheets and polymer as described in claim 7, characterized in that, Includes the following steps: S1. Polyvinylidene fluoride and polymethyl methacrylate are uniformly dispersed in N,N-dimethylformamide and stirred evenly to obtain solution A; S2. Disperse barium titanate subnanosheets in solution A by ultrasonication and stir to obtain suspension B; S3. The suspension B is uniformly coated onto the glass using the casting method. The glass is first dried at 60 °C for 10 h to remove the solvent, and then heated at 200 °C for 10 min and quenched to obtain the final product.

10. The application of the dielectric energy storage film composed of barium titanate subnanosheets and polymers as described in claim 7 in high dielectric energy storage capacitors.

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