A rare earth doped layered perovskite flexible dielectric energy storage film and a preparation method thereof

Abstract

The application belongs to the technical field of flexible electronic dielectric materials, and particularly relates to a rare earth doped layered perovskite flexible dielectric energy storage film and a preparation method thereof. 2+ The insulating layer and the (A n‑1 B n O 3n+1 ) 2‑ The perovskite layers are alternately stacked along the c-axis direction, and the doping ion Pr 3+ exists in the (Bi2O2) 2+ The insulating layer and the (A n‑1 B n O 3n+1 ) 2‑ The perovskite layers, the film is deposited on a flexible fluorophlogopite substrate, is prepared by using a chemical solution deposition method, and is obtained by sequentially performing precursor preparation, spin coating, segmented heat treatment, cycle film preparation and high-temperature crystallization. Relying on the double-dipole synergistic effect, the film synchronously improves the polarization intensity and the breakdown field strength, and the energy density and the charge and discharge efficiency are far superior to those of existing materials. The film has excellent bending cycle and charge and discharge cycle stability, can stably work in a wide frequency and wide temperature range, and is suitable for use in dielectric capacitors in flexible intelligent systems such as wearable electronics and flexible robots.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronic dielectric materials technology, and particularly relates to a rare earth-doped layered perovskite flexible dielectric energy storage film and its preparation method. Background Technology

[0002] Flexible dielectric capacitors are core energy storage components for next-generation flexible intelligent systems such as wearable electronic devices, flexible displays, and flexible robots. Currently, the core problem restricting the application of flexible dielectric capacitors is that their energy density is much lower than that of traditional rigid capacitors. The root causes are twofold: first, it is difficult to achieve high-quality thin film crystallization on the surface of flexible substrates; second, existing material systems cannot simultaneously obtain high polarization intensity and high breakdown field strength on flexible substrates.

[0003] Currently, the mainstream flexible dielectric films on the market are mainly divided into two categories: the first category is organic polymer films, such as polyvinylidene fluoride composite materials. These materials have excellent flexibility and breakdown strength, but their inherent dielectric constant is low, which directly leads to a significant bottleneck in energy density. If high dielectric ceramic fillers are filled into the polymer matrix to improve performance, problems such as poor compatibility between the filler and the matrix interface and an increase in internal defects of the film will occur.

[0004] The second category is inorganic perovskite thin films, such as lead zirconate titanate and bismuth ferrite-based thin films. These materials have high polarization intensity, but high-performance thin films must be prepared by epitaxial growth on a rigid single crystal substrate. If they are prepared on a flexible mica substrate, the lattice mismatch between the thin film and the substrate and the large difference in thermal expansion coefficient will result in an increase in thin film defects and a significant decrease in breakdown strength.

[0005] In summary, existing technologies have two major drawbacks:

[0006] Currently, there is no dielectric material system that is compatible with flexible substrates, can be crystallized with high quality, and simultaneously possesses high polarization strength and high breakdown field strength.

[0007] Inorganic dielectric films prepared on flexible substrates have performance far lower than those of rigid systems, and cannot meet the high energy density requirements of flexible electronic devices. Summary of the Invention

[0008] To address the technical problems of existing flexible dielectric films, such as the inability to simultaneously achieve high polarization strength and high breakdown field strength, poor film crystal quality on flexible substrates, and low overall energy density, this invention proposes a rare earth-doped layered perovskite flexible dielectric energy storage film and its preparation method. By relying on the synergistic effect of double dipoles, the overall performance of the film is improved, making it suitable for flexible application scenarios.

[0009] To achieve the above objectives, the present invention provides a rare-earth-doped layered perovskite flexible dielectric energy storage film, wherein the film has an Aurivillius phase layered perovskite structure and is composed of (Bi2O2). 2+ Insulating layer and (A) n-1 B n O 3n+1 ) 2- The perovskite layers are alternately stacked along the c-axis, and doped with Pr ions. 3+ Simultaneously present in the (Bi2O2) 2+ Insulating layer and the (A) n-1 B n O 3n+1 ) 2- In the perovskite layer;

[0010] Pr 3+ Doping in the insulating layer causes a shift in the charge center between the insulating layer and the perovskite layer, forming an interlayer dipole along the c-axis; this interlayer dipole interacts with the AO-type charge center within the perovskite layer. 12 The intrinsic dipoles generated by the offset of the polyhedral and BO6 octahedral cation centers form a bi-dipole synergistic coupling effect, which simultaneously enhances the maximum polarization intensity and breakdown field strength of the thin film.

[0011] The chemical formula of the thin film is SrBi. 5-x Pr x Ti4AlO 18 , where x represents the doping coefficient, and its value range is: 0.4≤x≤1.2.

[0012] Preferably, the doping coefficient x = 0.8, and the thin film chemical formula is SrBi. 4.2 Pr 0.8 Ti4AlO 18 .

[0013] Preferably, the thin film is deposited on the surface of a flexible fluorophlogopite substrate.

[0014] Preferably, a method for preparing a rare-earth-doped layered perovskite flexible dielectric energy storage film is also provided, comprising the following steps:

[0015] (1) Preparation of precursor solution: Strontium nitrate, bismuth nitrate pentahydrate, praseodymium nitrate hexahydrate, aluminum nitrate nonahydrate and tetrabutyl titanate were dissolved in ethylene glycol solvent according to stoichiometric ratio, and acetylacetone was added as a chelating agent to prepare a precursor solution with a concentration of 0.1 mol / L and aged for 48 h;

[0016] (2) Spin coating deposition: The precursor solution is spin coated onto a flexible mica substrate. The spin coating is divided into two stages: the first stage is 700 rpm for 10 s; the second stage is 6500 rpm for 50 s.

[0017] (3) Heat treatment: Place the spin-coated film in an oxygen atmosphere, heat-treat at 300℃ for 5 min, and then heat-treat at 700℃ for 5 min;

[0018] (4) Repeat steps (2) and (3) until the film reaches the preset thickness;

[0019] (5) Final crystallization: The multilayer film is placed in an oxygen atmosphere and annealed at 750°C for 20 min to complete the crystallization, and finally a well-crystallized rare earth doped layered perovskite flexible dielectric energy storage film is obtained.

[0020] Compared with existing technologies, the advantages and positive effects of the rare-earth-doped layered perovskite flexible dielectric energy storage film and its preparation method provided by the present invention are as follows:

[0021] 1. Significantly improved electrical energy storage performance: This invention utilizes Pr 3+ Co-doping creates a synergistic effect of double dipoles. Under an electric field of 4000 kV / cm, the optimally doped film can achieve a maximum polarization intensity of 67 μC / cm², an energy density of 131.1 J / cm³, and a charge-discharge efficiency of 70.5%. Compared with the undoped film of the same system, the energy density is increased by 179% and the charge-discharge efficiency is increased by 20%, solving the problem that the polarization intensity and breakdown field strength of traditional flexible dielectric films cannot be balanced.

[0022] 2. Excellent mechanical cycling stability: The film exhibits good crystallinity on a flexible fluorophlogopite substrate, maintaining stable performance under 2000 kV / cm electric field and bending curvature of 0.15. -1 Under these conditions, after 10 6 After several consecutive bending cycles, the energy density and charge / discharge efficiency remained basically stable; after 10 7 After one charge-discharge cycle, the energy storage performance shows no significant degradation, making it suitable for use scenarios involving repeated bending and long-term operation of flexible equipment.

[0023] 3. Strong wide frequency and wide temperature range operation capability: The thin film of this invention can work stably in a wide frequency and wide temperature range: the energy density can reach 41.1J / cm³ at a working frequency of 25kHz; the energy density can reach 42J / cm³ at a high temperature of 160℃, showing strong environmental adaptability.

[0024] 4. Strongly defined doping range and controllable process: The doping coefficient x is limited to the range of 0.4~1.2 to form the double dipole synergistic effect: when x < 0.4, Pr 3+ If the rare earth doping only enters the perovskite layer, it cannot generate interlayer dipoles, resulting in low performance. When x>1.2, excessive rare earth doping will cause the intralayer dipoles to collapse, and the performance will drop sharply. The present invention preferably uses x=0.8 as the optimal ratio, and the material composition and performance can be precisely controlled.

[0025] 5. Simple preparation process and good compatibility: The mature chemical solution deposition method is adopted, the process parameters are clear, the operation is simple, it can be prepared on a large scale, and the process is highly compatible with flexible mica substrates, resulting in high-quality thin film crystallization. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1(a) is a schematic diagram of the XRD patterns of the thin films prepared in this invention under different doping conditions;

[0028] Figure 1(b) shows the Raman spectra of the thin films prepared in this invention under different doping conditions;

[0029] Figure 1(c) is a schematic diagram of the crystal structure of the thin film prepared in this invention under different doping samples;

[0030] Figure 2 (a, d, g, j) are schematic diagrams of the crystal structure of the thin films prepared in this invention under different doping conditions;

[0031] Figure 2 (b, e, h, k) shows the electron density distribution of the thin films prepared in this invention under different doping conditions;

[0032] Figure 2 (c, f, i, l) shows the electron density difference distribution and the electron density difference (Δρ) curve along the z-axis for different doped samples of the thin film prepared in this invention.

[0033] Figure 3 (a, b, c, d) shows the PE curves of the thin films prepared in this invention under different doping conditions;

[0034] Figure 3(e) Comparison of energy density and efficiency between the thin film prepared by the present invention and existing dielectric materials;

[0035] Figure 3(f) shows the magnetoresistive-magnetic field curves of the thin film prepared in this invention under different doping conditions;

[0036] Figure 3(g) shows the reflectance-wavelength curves of the thin film prepared in this invention under different doping conditions;

[0037] Figure 3(h) shows the Tauc diagrams of the thin films prepared in this invention under different doping conditions;

[0038] Figures 3(i), (k), (m), and (o) are schematic diagrams of the band structure of the thin films prepared in this invention under different doping conditions;

[0039] Figures 3(j), (l), (n), and (p) show the total density of states (DOS) of the thin films prepared in this invention under different doping conditions;

[0040] Figures 4(a) and (b) show the PE curves and corresponding energy density and efficiency curves of the thin film prepared by the present invention at different temperatures;

[0041] Figures 4(c) and (d) show the PE curves and corresponding energy density and efficiency curves of the thin film prepared in this invention at different frequencies;

[0042] Figures 4(e) and (f) show the PE curves and corresponding performance curves of the thin film prepared in this invention under different charge-discharge cycles;

[0043] Figures 4(g) and h) show the PE curves and corresponding performance curves of the film prepared by the present invention under different bending cycles;

[0044] Figures 4(i) and (k) show the pulse curves of current, energy density, and power density of the thin film prepared in this invention under different electric field intensities;

[0045] Figure 4(j) shows the pulse energy density-time curves of the thin film prepared in this invention under different electric field intensities;

[0046] Figure 4(l) is a photograph of the actual flexible film prepared by the present invention under bending conditions. Detailed Implementation

[0047] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0048] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0049] As shown in Figures 1-4, Figure 1 shows the XRD pattern, Raman spectrum, and crystal structure diagram of the rare-earth-doped layered perovskite flexible dielectric energy storage film of the present invention. Figure 2 shows the density functional theory (DFT) calculation spectrum of the film prepared in this invention, including the calculation results of four doped samples: P0, P4, P8, and P12. P0, P4, P8, and P12 represent the sample numbers for doping coefficients x=0, 0.4, 0.8, and 1.2, respectively, facilitating intuitive differentiation of the doping gradient and characterizing Pr. 3+The doping effect on the internal electron distribution of the crystal is verified to confirm the generation mechanism of interlayer dipoles and the electronic origin of the synergistic effect of double dipoles. Figure 3 shows the electrical performance test spectrum of the thin film prepared in this invention, which is used to characterize the changes of polarization intensity, energy density, and charge-discharge efficiency of the thin film with temperature, frequency and electric field intensity, and to verify its energy storage performance in a wide temperature range, wide frequency range and high field. Figure 4 shows the cycle stability test spectrum and flexible physical image of the thin film prepared in this invention, which is used to characterize the performance stability of the thin film under repeated charge-discharge and bending cycles, and to verify its long-term reliability in flexible electronic devices.

[0050] Example 1: A method for preparing a rare-earth-doped layered perovskite flexible dielectric energy storage film with the chemical formula SrBi was used. 4.2 Pr 0.8 Ti4AlO 18 The specific fabrication process of the rare-earth-doped layered perovskite flexible dielectric energy storage film is as follows:

[0051] (1) Weigh the raw materials according to the stoichiometric ratio, use ethylene glycol as solvent and acetylacetone as chelating agent to prepare a 0.1 mol / L precursor solution, and age it at room temperature for 48 h;

[0052] (2) Spin coating parameter settings: 700rpm spin coating for 10s, 6500rpm spin coating for 50s;

[0053] (3) Segmented heat treatment: hold at 300℃ for 5 min in oxygen atmosphere, and hold at 700℃ for 5 min;

[0054] (4) Repeat the spin coating and segmented heat treatment processes until the film reaches the target thickness;

[0055] (5) Final crystallization treatment: Anneal at 750°C for 20 min in an oxygen atmosphere to obtain the finished film.

[0056] The specific test results are described as follows:

[0057] Phase structure verification: As shown in the XDR spectrum of Figure 1(a), the thin film prepared in this embodiment has a pure phase Aurivillius phase layered perovskite structure with no impurity phase generated.

[0058] Doping site verification: The Raman spectrum and peak fractionation results in Figure 1(b) confirm that the dopant ion Pr 3+ Simultaneously distributed in (Bi2O2) 2+ The insulating layer and the interior of the perovskite layer;

[0059] Dipole mechanism verification: The Pr mechanism can be visually demonstrated through the DFT calculation spectrum shown in Figure 2. 3+Successful doping induces the shift of the interlayer charge center, forming an interlayer dipole along the c-axis, which generates a synergistic coupling effect with the intrinsic dipole within the layer.

[0060] Energy storage performance testing: Based on the electrical performance test spectrum in Figure 3(c), under an electric field of 4000 kV / cm, the maximum polarization intensity of the thin film in this embodiment is 67 μC / cm², the energy density reaches 131.1 J / cm³, and the charge / discharge efficiency is 70.5%. As a control, undoped Pr... 3+ SrBi5Ti4AlO 18 Under the same testing conditions, the thin film has an energy density of only 47.0 J / cm². 3 The charge-discharge efficiency is 58.8%. In comparison, the energy density of the thin film of the present invention is increased by 179% and the charge-discharge efficiency is increased by 20%.

[0061] Example 2, Stability Test

[0062] SrBi prepared using Example 1 4.2 Pr 0.8 Ti4AlO 18 The flexible thin film underwent mechanical cycling, charge-discharge cycling, wide frequency, and wide temperature adaptability tests. All test data are taken from the corresponding attached figures.

[0063] Bending stability test: under an electric field of 2000 kV / cm and a bending curvature of 0.15 mm -1 Under the given conditions, complete 10 6 After several consecutive bending cycles, as shown in Figures 4(g) and 4(h), the energy density of the thin film remains at 36.8 J / cm³, and the charge-discharge efficiency remains at 70.6%, indicating that mechanical bending has minimal impact on energy storage performance.

[0064] Charge-discharge cycle stability test: Completed 10 7 After several consecutive charge-discharge cycles, as shown in Figures 4(e) and 4(f), the energy density of the thin film stabilizes at 37.2 J / cm³, demonstrating excellent long-term cycling capability.

[0065] Frequency adaptability test: Tests were conducted at an operating frequency of 25 kHz. According to the frequency-dependent electrical curves in Figures 3(c) and 3(d), the thin film energy density can reach 41.1 J / cm² under this condition. 3 ;

[0066] Temperature adaptability test: The test was carried out at a high temperature of 160℃. According to the temperature-related performance curves in Figure 3(a) and Figure 3(b), the energy density of the thin film can reach 42J / cm³ at this temperature.

[0067] In summary, this embodiment demonstrates that the thin film possesses excellent mechanical stability and electrochemical cycling stability, and can operate stably over a wide frequency and temperature range.

[0068] Example 3 is a comparative example. Comparative samples were prepared with doping coefficients of x=0.4 and x=1.2 respectively. The preparation process was completely consistent with that of Example 1. The influence of doping amount on crystal structure, ion distribution, dipole effect and energy storage performance was analyzed with reference to the attached figures.

[0069] Comparative Example 1: x = 0.4, chemical formula SrBi 4.6 Pr 0.4 Ti4AlO 18

[0070] Combining the Raman spectrum in Figure 1(b) and the calculated electron density spectrum in Figure 2, it can be seen that when x=0.4, Pr 3+ It only penetrates the perovskite layer and cannot penetrate (Bi2O2). 2+ The energy density of this sample is significantly lower than that of the optimal sample in Example 1, as it is distributed within the insulating layer and therefore cannot form interlayer dipoles. The synergistic effect of the two dipoles is missing. Combined with the electrical performance spectrum in Figure 3, it can be seen that the energy storage density of this sample is significantly lower than that of the optimal sample in Example 1.

[0071] Comparative Example 2: x = 1.2, chemical formula SrBi 3.8 Pr 1.2 Ti4AlO 18

[0072] As can be seen from the crystal structure diagram in Figure 1 and the electronic distribution diagram in Figure 2, Pr 3+ Excessive doping can damage the original crystal structure and cause the intralayer dipoles to collapse; combined with the electrical test results in Figure 3, the energy storage performance of the sample decreased sharply.

[0073] The combined test results of the two sets of comparative examples, along with Figures 1, 2, and 3, fully demonstrate that the effective range for achieving the synergistic effect of the double dipoles is the doping coefficient range of 0.4 ≤ x ≤ 1.2, where x = 0.8 is the optimal doping ratio.

[0074] In the above process, the flexible dielectric energy storage film prepared by a rare earth-doped layered perovskite flexible dielectric energy storage film exhibits significantly improved electrical energy storage performance, solving the problem of the inability to simultaneously achieve polarization strength and breakdown field strength in traditional flexible dielectric films. It also demonstrates excellent mechanical cycling stability with no significant attenuation of energy storage performance, making it suitable for applications involving repeated bending and long-term operation of flexible devices. Furthermore, it boasts strong wide-frequency and wide-temperature operating capabilities and strong environmental adaptability. The doping range is highly defined, and the process is controllable. The preparation process is simple and compatible: employing a mature chemical solution deposition method, the process parameters are clear, the operation is simple, and it can be mass-produced. Moreover, the process is highly compatible with flexible mica substrates, resulting in high-quality film crystallization.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A rare-earth-doped layered perovskite flexible dielectric energy storage film, characterized in that, The thin film has an Aurivillius phase layered perovskite structure, composed of (Bi2O2). 2+ Insulating layer and (A) n-1 B n O 3n+1 ) 2- The perovskite layers are alternately stacked along the c-axis, and doped with Pr ions. 3+ Simultaneously present in the (Bi2O2) 2+ Insulating layer and the (A) n-1 B n O 3n+1 ) 2- In the perovskite layer; The Pr 3+ In the insulating layer, the interlayer charge center is shifted to form an interlayer dipole, and the interlayer dipole forms a double dipole synergistic coupling effect with the intrinsic dipole in the perovskite layer. The chemical formula of the thin film is SrBi. 5-x Pr x Ti4AlO 18 , where x represents the doping coefficient, and its value ranges from 0.4 to 1.

2.

2. The rare-earth-doped layered perovskite flexible dielectric energy storage film according to claim 1, characterized in that, The doping coefficient x = 0.8, and the thin film chemical formula is SrBi. 4.2 Pr 0.8 Ti4AlO 18 .

3. The rare-earth-doped layered perovskite flexible dielectric energy storage film according to claim 1, characterized in that, The thin film is deposited on a flexible fluorophlogopite substrate.

4. A method for preparing a rare-earth-doped layered perovskite flexible dielectric energy storage thin film as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Preparation of precursor solution: Strontium nitrate, bismuth nitrate pentahydrate, praseodymium nitrate hexahydrate, aluminum nitrate nonahydrate and tetrabutyl titanate were dissolved in an alcohol solvent in stoichiometric ratio, an organic chelating agent was added, and a precursor solution with a concentration of 0.1 mol / L was prepared and aged for 48 h; (2) Spin-coating deposition: The precursor solution is spin-coated onto a flexible mica substrate; (3) Heat treatment: The spin-coated film is placed in an oxygen atmosphere and heat-treated at 300℃ for 5 min, and then heat-treated at 700℃ for 5 min. (4) Repeat steps (2) and (3) until the film reaches the preset thickness; (5) Final crystallization: The multilayer film is placed in an oxygen atmosphere and annealed at 750°C for 20 min to obtain the finished flexible dielectric energy storage film.

5. The method for preparing a rare-earth-doped layered perovskite flexible dielectric energy storage film according to claim 4, characterized in that, In step (2), spin coating is divided into two stages: the first stage is 700 rpm for 10 seconds, and the second stage is 6500 rpm for 50 seconds.

6. The method for preparing a rare-earth-doped layered perovskite flexible dielectric energy storage film according to claim 4, characterized in that, In steps (3) and (5), an oxygen atmosphere is maintained throughout the heat treatment and annealing process.

7. The method for preparing a rare-earth-doped layered perovskite flexible dielectric energy storage film according to claim 4, characterized in that, The alcohol solvent is ethylene glycol, and the organic chelating agent is acetylacetone.

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