High-energy-storage sodium bismuth titanate-based ceramic material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of energy storage ceramic materials, and particularly discloses a high-energy storage sodium bismuth titanate-based ceramic material as well as a preparation method and application thereof, the chemical composition formula of the high-energy storage sodium bismuth titanate-based ceramic material is (1-x) (Na < 0.5 > Bi < 0.5 >) < 0.935 > Sr < 0.065 > TiO < 3-x > Na < 0.7 > Sm < 0.1 > NbO < 3 >, and x is more than 0 and less than or equal to 0.25. According to the invention, the Na element in the A site of NN is partially replaced by the rare earth element Sm, a local electric field is effectively constructed, a long-range ordered structure is broken through the random occupation of cations with different radiuses and electricity prices, high-activity polar nano micro-area PNRs is formed, and the dielectric property and frequency dispersivity of the ceramic are improved at the same time. Wherein the performance is optimal when x is equal to 0.22, the energy storage density (gt, 6.59 J / cm < 3 >) and the energy storage efficiency (gt, 88%) are remarkably improved under the field intensity of 300 kV / cm, and the working temperature range of the dielectric temperature stability (delta epsilon / epsilon 150 DEG C lt, 15%) can be expanded to 60-395 DEG C (broadened by 79-186 DEG C compared with a single doped system). Through the rare earth element doping modification mode, the performance of the energy storage ceramic is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of perovskite structure energy storage ceramics, in particular to a high energy storage sodium bismuth titanate-based ceramic material and a preparation method thereof, and application in a dielectric energy storage device. BACKGROUND

[0002] With the development of electronic devices towards miniaturization, integration and high performance, the demand for high-efficiency energy storage materials is increasingly urgent. Lead-free dielectric ceramics have become a research hotspot in the field of energy storage capacitors due to their environmental friendliness and excellent electrical properties. Among them, Bi 0.5 Na 0.5 TiO3 (BNT) based ceramics have attracted much attention due to their high polarization strength (P P max ≥ 35 μC / cm 2 ) and moderate Curie temperature (about 320 ℃), and have shown important application potential in lead-free energy storage materials.

[0003] However, BNT-based ceramics still face many technical challenges in practical applications. First, the material's remanent polarization (Pr P r = 10-15 μC / cm 2 ) and coercive field strength (Hc E c = 50-70 kV / cm) are still high, resulting in a generally lower energy storage efficiency (η η ) of less than 85%. Second, the low breakdown field strength (Eb E b = 120-180 kV / cm) severely restricts the improvement of energy storage density. More critically, existing modification methods have obvious limitations: ion substitution (such as La 3+ , Sr 2+ doping) can further reduce P P r to 5-10 μC / cm 2 , but will simultaneously reduce P P max to 20-30 μC / cm 2 ; second phase composite (such as forming a solid solution with SrTiO3) can improve Eb E b to about 200-250 kV / cm, but significantly weakens the polarization response capability (P P max < 15 μC / cm 2 ). In addition, these modification methods often result in a performance fluctuation of more than 20% in the temperature range of -50-150 ℃, and some high-performance components require special sintering processes (such as hot-press sintering), greatly increasing production costs.

[0004] By substituting Na with Sm, lattice distortion is introduced due to the difference in ionic radius, Curie temperature is adjusted to approach room temperature, and the morphotropic phase boundary is stabilized to optimize the structure and phase transition; the generation of impurities is inhibited, oxygen vacancies are reduced, the dielectric constant is enhanced, the loss is reduced, the grain size is refined to improve the breakdown field strength, and the polarization loop is improved, thereby improving the energy storage density and efficiency; it can also reduce the leakage current, enhance the fatigue resistance, and induce nano domains and polar nano regions. This makes the doped BNT-based ceramics exhibit unique advantages in achieving high breakdown field strength and excellent energy storage properties compared to traditional rare earth doped materials.

[0005] Therefore, it is necessary to develop a new type of BNT-based energy storage ceramic that can simultaneously achieve high breakdown field strength (E E b ≥ 300 kV / cm), low remanent polarization (P P r ≤5 μC / cm 2 ), excellent temperature stability (-50~200℃ performance fluctuation≤15%), and ensure that it can be prepared by conventional process, which has become a key technical requirement for promoting the practical application of lead-free energy storage materials. SUMMARY

[0006] The purpose of the present application is to solve the key technical problems of high remanent polarization, high dielectric loss and low breakdown field strength of sodium bismuth titanate-based ceramics, and to propose a new type of ceramic material and its preparation method, which significantly improves the comprehensive energy storage performance.

[0007] To achieve the above purpose, a high energy storage sodium bismuth titanate-based ceramic material is disclosed, the chemical composition of the ceramic is (1- x )(Na 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3- x Na 0.7 Sm 0.1 NbO3, wherein 0< x ≤0.25. The Sm element in the chemical composition can significantly improve the polarity response, breakdown strength and temperature stability of the ceramic material, forming a composite ceramic material with optimized performance.

[0008] Preferably, x =0.22, the chemical composition of the ceramic material is 0.78(Na 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3-0.22Na 0.7 Sm 0.1 NbO3.

[0009] Preferably, the ceramic material has an electric field strength of 150-300 kV / cm and a recoverable energy storage density of 1.6-6.59 J / cm 3 The performance fluctuation is less than 15% in the dielectric temperature range of 60-395 ℃.

[0010] It is another object of the present application to provide a preparation method of the high energy storage bismuth sodium titanate ceramic material. (1) Raw material pretreatment: Bi2O3, Na2CO3, Nb2O5, TiO2, SrCO3, and Sm2O3 are dried at 120 ℃ for 24 h, and then weighed according to the stoichiometric ratio; 0.5-1 wt% of each component is taken for pre-sintering as a seed crystal, and then put into the raw materials of the remaining components for pre-sintering; and the pre-sintered raw materials are mixed in proportion; (2) Ball milling: the mixture is put into a two-way ball mill for two-way alternating ball milling; (3) Drying: the mixed solution after ball milling is heated to 80-150 ℃ for drying, and the water content of the powder after drying is ≤0.3 wt%; (4) Pre-sintering: the powder prepared in step (3) is layered and loaded in an alumina crucible, heated to 850±10 ℃ for pre-sintering and heat preservation; (5) Particle size control: the pre-sintered material of step (4) is put into a ball mill for secondary ball milling, 0.1-0.3 wt% of oleic acid is added as a dispersant, and the powder with a particle size of 1.0±0.2 μm is obtained by passing through a 120 mesh sieve; (6) Forming: polyvinyl alcohol solution is added to the powder prepared in step (5), stirred uniformly, and then formed by stepwise pressing; (7) Sintering control: the material obtained in step (6) is put into a crucible and placed in a calcining furnace, first heated to 600 ℃ for sintering and heat preservation, then put into a sealed crucible and added with a Bi2O3 compensation block, heated to 1150 ℃ for sintering and heat preservation, and cooled to room temperature to obtain the ceramic material.

[0011] Preferably, in step (1), the purity of Bi2O3, TiO2, Sm2O3, and Nb2O5 is not less than 99.99%, the purity of Na2CO3 is not less than 99.8%, and the purity of SrCO3 is not less than 99%.

[0012] Preferably, in step (1), the pre-sintering temperature is 800 ℃, and the particle size is 0.5-1 μm.

[0013] Preferably, in step (2), the ball milling process adopts a three-stage ball milling process of coarse grinding, fine grinding, and fine grinding, and the ball milling medium is a mixture of deionized water and anhydrous ethanol, with a volume ratio of deionized water to anhydrous ethanol of 2:1, i.e. Coarse grinding stage: ball milling with zirconia balls (diameter 5mm), ball-to-material ratio 6:1, rotation speed 300r / min, forward ball milling for 4h, then standing for 0.5h; Fine grinding stage: ball milling with zirconia balls (diameter 2mm), ball-to-material ratio 4:1, rotation speed 250r / min, reverse ball milling for 6h, then standing for 0.5h; Fine grinding stage: ball milling with zirconia balls (diameter 2mm), ball-to-material ratio 4:1, rotation speed 250r / min, reverse ball milling for 6h, then standing for 0.5h;

[0014] Preferably, in step (3), the mixed solution is first dried at 80℃ for 6h to reduce the moisture content to less than 5%, and then heated to 150℃ for 6h; the water content of the powder after drying is less than or equal to 0.3wt%.

[0015] Preferably, in step (4), a φ2mm air hole is reserved on the crucible cover, and the crucible cover is pre-fired at a temperature of 850±10℃ with a temperature increasing rate of 5℃ / min for 1.5h.

[0016] Preferably, in step (6), the mass of the polyvinyl alcohol solution is 7% of the mass of the powder, and the mass concentration of the polyvinyl alcohol solution is 5%; the stepwise pressure forming is first pre-pressing at 100MPa for 30s, and then main pressing at 200MPa for 1min.

[0017] Preferably, the sintering control in step (7) is divided into three stages, which are as follows: First-stage degassing sintering: the green body is placed in the crucible, heated to 600℃ in air atmosphere at a temperature increasing rate of 2℃ / min, and kept for 2h to completely remove the binder and residual organic matter, so as to avoid the generation of bubbles due to high-temperature decomposition; Second-stage densification sintering: the degassed green body is placed in the crucible, Bi2O3 compensation blocks are added, the atmosphere is switched to inert atmosphere (Ar purity≥99.99%), the temperature is increased to 1150℃ (temperature increasing rate 5℃ / min), and kept for 3h; the Bi vapor concentration is monitored in real time by a furnace gas sensor, and the gap of the crucible cover is dynamically adjusted (Bi vapor pressure is controlled) to ensure that the ceramic composition is accurately matched with the stoichiometric ratio; Third-stage annealing modification: after sintering, the temperature is decreased from 1150℃ to 900℃ at a temperature decreasing rate of 5℃ / min, and then decreased from 900℃ to room temperature at a temperature decreasing rate of 2℃ / min; the green body is then placed in an Ar atmosphere at 600℃ for 2h, and then annealed and cooled to room temperature to eliminate internal residual stress and promote uniform grain growth.

[0018] Another object of the present application is to provide the application of the above-mentioned high-energy-storage sodium bismuth titanate-based ceramic material in a dielectric energy storage device.

[0019] Compared with the prior art, the application has the beneficial effects that: 1、The energy storage ceramic material of the application is prepared by a traditional high-temperature solid-phase method, the solid-phase reaction kinetics is optimized in the preparation process, the process is simple and has strong repeatability, and the breakdown strength and energy storage performance of the ceramic can be significantly improved.

[0020] 2、The ceramic material of the application, by partially replacing Na elements in the A position of NN with rare earth elements Sm, utilizing random occupation of different radius and electrically charged ions, effectively constructing a local electric field, breaking long-range ordered structure, forming high-activity polar nanoregions PNRs, and at the same time improving the dielectric performance and frequency dispersion of the ceramic.

[0021] 3、The breakdown field strength of the ceramic material of the application can reach 300 kV / cm, and the recoverable energy storage density can reach 6.59 J / cm 3 (remarkably improved compared with a pure NBST ceramic system), the energy storage efficiency is between 88% and 94%, and the working temperature range of the dielectric temperature stability (Δε / ε 150℃<15%) can be extended to 60℃ to 395℃ (257℃ wider than the range of 139℃~209℃ of the pure NBST ceramic). BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 XRD spectra of the ceramic materials prepared in Examples 1-6.

[0023] Figure 2 D-E loops of the ceramic materials prepared in Examples 1-6. P - E circuit.

[0024] Figure 3 NBST-E of the ceramic materials prepared in Examples 1-6 at 15 kV / mm under 10 Hz. x D-E loops of the NSN ceramic. W rec and η values.

[0025] Figure 4 D-E of the ceramic material prepared in Example 5 under different electric field strengths. W rec and η values.

[0026] Figure 5 D-E of the ceramic material prepared in Example 5 under different electric field strengths. ε / ε 150℃ variation with temperature and (b) temperature range Δ ε / ε 150℃ ≤ ±15%.

[0027] Figure 6 are the piezoelectric constants of the ceramic materials prepared in Comparative Examples 1-3 under different electric field intensities W rec and η values (a) of the material without Sr, (b) of the material without Sr and Sm elements, and (c) of the material without Sm elements. DETAILED DESCRIPTION

[0028] The present application is further illustrated by the following examples, which should not be construed as limiting the present application.

[0029] In the present disclosure, the chemical composition of the sodium bismuth titanate-based lead-free energy storage ceramic material is (1- x )(Na 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3- x Na 0.7 Sm 0.1 NbO3 (NBST-xNSN), x = 0.00-0.25. The doping components of the present application are designed independently. Sm³⁺ replaces Na at the A site of the antiferroelectric NaNbO3 (NN) by partial substitution + , and the ion radius (Sm 3+ about 0.096 nm, Na + about 0.102 nm) and electric charge difference of Sm³⁺ and Na⁺ are utilized to form random occupation in the crystal, construct local electric field and break long-range ordered structure, and then induce the generation of high-activity polar nanoregions (PNRs); at the same time, the introduction of Nb 5+ at the B site further increases the lattice disorder degree, and the relaxation characteristics and energy storage performance of the material are double-regulated, and finally a single-phase perovskite structure complete solid solution is formed without the generation of second phase impurities.

[0030] In the present application, the sodium bismuth titanate-based lead-free energy storage ceramic material is prepared by traditional solid-phase sintering process, and does not require special atmosphere throughout the process (conventional air atmosphere can inhibit the volatilization of Bi and Na). The process includes: after the ingredients are prepared according to the stoichiometric ratio, the main crystal phase powder is synthesized by one-time ball milling mixing and pre-sintering, and then the powder is refined by two-time ball milling, granulated by adding a binder, molded, debindered and sintered, and finally polished and plated with electrodes to obtain the finished ceramic sample. The process is stable and controllable, green and environmentally friendly, and the raw materials used are Bi2O3, Na2CO3, Nb2O5, TiO2, SrCO3 and Sm2O3 powders with a purity of ≥99%, which are easy to obtain and have controllable cost, suitable for large-scale production, and are the preferred material for multilayer dielectric energy storage capacitors.

[0031] In the present application, the ferroelectric analyzer (model Trek 609B, USA Radiant Technologies) is used to test the key performance of the sodium bismuth titanate-based lead-free energy storage ceramic: the breakdown field strength is 150-300kV / cm, the recoverable energy storage density is 1.6-6.59J / cm³, and the energy storage efficiency is 88%-94%; at the same time, the dielectric temperature spectrometer (model Agilent4294A, USA Agilent Corporation) is used to test the dielectric performance, and the change rate of the relative dielectric constant of the ceramic relative to 150℃ is ≤±15% in the temperature range of 60℃-395℃, meeting the wide temperature stability requirement.

[0032] The following further illustrates the embodiments to further illustrate the present application. It should also be understood that the following embodiments are only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application all belong to the protection scope of the present application. The specific process parameters in the following examples are only one example in the appropriate range, i.e. those skilled in the art can select within the appropriate range according to the description herein, and are not limited to the specific values in the following examples. In the following examples and comparative examples, if not otherwise specified, the Bi2O3, Na2CO3, Nb2O5, TiO2, SrCO3 and Sm2O3 powders with a purity of ≥99% are used as raw materials.

[0033] Example 2: (1-x)(Na 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3-xNa 0.7 Sm 0.1 NbO3, x=0.06 In this embodiment 2, except that x is 0.06, the other steps are exactly the same as those in embodiment 1.

[0034] Example 3: (1-x)(Na 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3-xNa 0.7 Sm 0.1 NbO3, x=0.12 In this embodiment 3, except that x is 0.12, the other steps are exactly the same as those in embodiment 1.

[0035] Example 4: (1-x)(Na 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3-xNa 0.7Sm 0.1 NbO3, x = 0.18 In this embodiment 4, except that x is 0.18, the other steps are exactly the same as in embodiment 1.

[0036] Example 5: (1-x)(Na) 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3-xNa 0.7 Sm 0.1 NbO3, x = 0.22 In this embodiment 5, except that x is 0.22, the other steps are exactly the same as in embodiment 1.

[0037] Example 6: (1-x)(Na) 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3-xNa 0.7 Sm 0.1 NbO3, x = 0.25 Comparative Example 1: (1-x)(Na) 0.5 Bi 0.5 TiO3-xNa 0.7 Sm 0.1 NbO3, x = 0.22 In Comparative Example 1, the material does not contain Sr, meaning that SrCO3 is not added to the raw material.

[0038] Comparative Example 2: (1-x)(Na) 0.5 Bi 0.5 TiO3-xNaNbO3, x=0.22 In Comparative Example 2, the material does not contain Sr or Sm elements, that is, SrCO3 and Sm2O3 are not added to the raw materials.

[0039] Comparative Example 3: (1-x)(Na) 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3-xNaNbO3, x=0.22 In Comparative Example 3, the material does not contain Sm element, that is, Sm2O3 is not added to the raw material.

[0040] Figure 1 is an XRD curve of sodium bismuth titanate-based lead-free energy storage ceramics prepared in Examples 1-6. The ceramic material sample of Example 1 was subjected to electrical performance testing. The ceramic materials prepared in Examples 2-6 were tested for electrical performance after being ground and polished on both sides and plated with electrodes. As can be seen from the curve, the NBST-xNSN ceramics with different x values all exhibit a single perovskite structure without the generation of impurity peaks, indicating that Na 0.7 Sm 0.1 NbO3(NSN) is completely solid-solved into the NBST matrix, and the (200) diffraction peak in the range of 46.4°-47.2° is split, and the existence of coexistence of the rhombohedral phase (R3c) and the tetragonal phase (P4bm) is confirmed by Gaussian peak fitting, which is a key characteristic of the phase structure of the material with excellent relaxor properties and temperature stability.

[0041] Figure 2 is a P-E (polarization-electric field) curve of sodium bismuth titanate-based lead-free energy storage ceramics prepared in Examples 1-6. As the amount of NSN doping (x) increases, the P-E loop of the ceramic gradually becomes slender, and at x=0.18, the loop still has slight widening; at x=0.22, the degree of slenderization of the loop is optimal, which is due to the increase in PNRs induced by Sm 3+ and effective inhibition of polarization hysteresis, which enhances the relaxor properties.

[0042] Figure 3 is a curve of the energy storage properties of sodium bismuth titanate-based lead-free energy storage ceramics prepared in Examples 1-6 as a function of x value. As can be seen from the figure, the recoverable energy storage density (W rec ) and energy storage efficiency (η) first increase and then decrease with increasing x value, and reach optimal values at x=0.22 (Example 5), where Wrec=6.59 J / cm 3 and η=88% at a field strength of 30 kV / mm.

[0043] Figure 4 is the energy storage density and energy storage efficiency of the ceramic material prepared in Example 5 under different electric field strengths. W rec and η As can be seen from the figure, as the electric field increases and at 30 kV / mm, a recoverable energy storage density of 6.59 J / cm 3 and a high energy storage efficiency of 88% are obtained.

[0044] Figure 5 is the dielectric constant deviation Δ ε / ε 150℃ of the ceramic materials prepared in Examples 1-6 as a function of temperature and temperature range Δ ε / ε 150℃≤ ±15%, the calculation formula is as follows ,in, ε 150℃ The dashed line represents the relative permittivity at 150℃. TCC With the introduction of NSN, a wider operating temperature range (139℃-209℃ to 60℃-395℃) is achieved compared to pure NBST, with a ≤ 15% operating temperature range. This can be seen while maintaining 6.59 J / cm². 3 While achieving high energy storage density, excellent temperature stability was also achieved. This demonstrates the temperature performance of the NBST-xNSN system ceramics over a wide temperature range, showcasing its potential in capacitor applications.

[0045] In addition to testing the above Examples 1-6, this invention also tested the key energy storage parameters of the ceramic materials prepared in Examples 1-6, specifically the recoverable energy storage density (W / mm) at 15 kV / mm and 10 Hz. rec The energy storage efficiency (η) was tested, and the test results are shown in Table 1.

[0046] Table 1. Energy storage characteristics of sodium bismuth titanate-based lead-free energy storage ceramics

[0047] As can be seen from Table 1, under a field strength of 15 kV / mm, the recoverable energy storage density (W) rec The values ​​of energy storage efficiency (η) and the field strength (x) both increase first and then decrease with increasing x value, reaching their optimal values ​​at x=0.22. Simultaneously, when the field strength is 15kV / mm, the energy storage efficiency η=90%. This indicates that as the field strength decreases, the energy storage efficiency η of the ceramic material increases, but the increase is not significant. Therefore, the influence of the field strength on the energy storage efficiency η can be ignored. For recyclable energy storage density (W... rec The impact is significant.

[0048] Figure 6 Ceramic materials prepared in Comparative Examples 1, 2, and 3 under different electric field intensities W rec and η The values ​​are shown in Table 2, which contains the specific test data. Figure 6 As can be seen, with the increase of the electric field and at 30 kV / mm, the energy storage efficiency of the recoverable energy storage density obtained is significantly lower than that of Example 5.

[0049] Table 2. Energy storage characteristics of ceramic materials in Comparative Examples 1-3 and Example 5

[0050] As can be seen from Table 2, compared with the ceramic material of Example 5 of the present application, the materials prepared in Comparative Examples 1-3 have a significantly decreased energy storage efficiency η and recoverable energy storage density W rec It can be seen that, by introducing Sr and Sm elements, the energy storage properties of the material are significantly improved, and the energy storage properties are better when the two elements synergize with each other. If one of the elements is missing, the energy storage performance of the material is significantly decreased.

Claims

1. A high energy storage sodium bismuth titanate-based ceramic material, characterized in that, The chemical composition of this ceramic material is (1- x (Na) 0.5 Bi 0.5 ) 0.935 Sr 0.065 TiO3- x Na 0.7 Sm 0.1 NbO3, where 0 < x ≤0.

25.

2. The high energy storage bismuth sodium titanate-based ceramic material of claim 1, wherein, The ceramic material has electric field intensity of 150-300 kV / cm, recoverable energy storage density of 1.60-6.59 J / cm 3 , and energy storage efficiency of 88%-94%, and the performance fluctuation is less than 15% in the dielectric temperature range of 60-395 ℃.

3. The method of producing a high energy storage bismuth sodium titanate-based ceramic material according to any one of claims 1 to 2, characterized by, The specific preparation steps are as follows: (1) raw material pretreatment: Bi2O3, Na2CO3, Nb2O5, TiO2, SrCO3, Sm2O3 are dried at 120°C for 24h respectively, then weighed according to the stoichiometric ratio; take 0.5-1wt% of each component of the above powder raw materials for pre-sintering as seed crystal, then put into the remaining component raw materials for pre-sintering, and then mix the pre-sintered raw materials according to the proportion; (2) ball milling: put the above mixture into a two-way ball mill for two-way alternating ball milling; (3) drying: heat the mixed solution after ball milling to 80-150℃ for drying, and the water content of the powder after drying is ≤0.3wt%; (4) pre-sintering: the powder prepared in step (3) is layered in an alumina crucible, heated to 850±10℃ for pre-sintering and heat preservation; (5) particle size control: put the pre-sintered material of step (4) into a ball mill for secondary ball milling, add 0.1-0.3wt% oleic acid as dispersant, and pass through a 120 mesh sieve to obtain a powder with a particle size of 1.0±0.2μm; (6) forming: add polyvinyl alcohol solution to the powder prepared in step (5), stir uniformly, and then perform stepwise pressure forming; (7) sintering control: put the material obtained in step (6) into a crucible and place it in a calcining furnace, first heat to 600℃ for sintering and heat preservation, then put into a sealed crucible and add Bi2O3 compensation block, then heat to 1150℃ for sintering and heat preservation, and cool to room temperature to obtain a ceramic material.

4. The method of claim 3, wherein the high energy storage BNT-based ceramic material is prepared by the steps of: preparing a BNT-based ceramic material; and coating the BNT-based ceramic material with a coating layer. The pre-sintering temperature in step (1) is 800℃, and the particle size is 0.5-1μm.

5. The method of claim 3, wherein the high energy storage BNT-based ceramic material is prepared by the steps of: preparing a BNT-based ceramic material; and coating the BNT-based ceramic material with a coating layer. In step (2), the ball milling process adopts a three-stage ball milling process of coarse grinding, fine grinding and fine grinding, and the ball milling medium is a mixture of deionized water and anhydrous ethanol, with a volume ratio of deionized water to anhydrous ethanol of 2:

1.

6. The method of producing a high energy storage bismuth sodium titanate-based ceramic material according to claim 3, characterized by, In step (3), the mixed solution is first dried at 80℃ for 6h to reduce the moisture content to below 5%, and then heated to 150℃ for 6h, and the water content of the powder after drying is ≤0.3wt%.

7. The method of claim 3, wherein the high energy storage BNT-based ceramic material is prepared by the steps of: preparing a BNT-based ceramic material; and coating the BNT-based ceramic material with a coating layer. In step (4), the crucible cover is reserved with a φ2mm air hole, and the temperature is raised to 850±10℃ at a rate of 5℃ / min for pre-sintering and heat preservation for 1.5h.

8. The method of claim 3, wherein the high energy storage BNT-based ceramic material is prepared by the steps of: preparing a BNT-based ceramic material; and coating the BNT-based ceramic material with a coating layer. In step (6), the mass of polyvinyl alcohol solution is 7% of the mass of powder, and the mass concentration of polyvinyl alcohol solution is 5%; the stepwise pressure forming is first pre-pressed at 100MPa for 30s, and then main-pressed at 200MPa for 1min.

9. The method of claim 3, wherein the high energy storage BNT-based ceramic material is prepared by the steps of: preparing a BNT-based ceramic material; and coating the BNT-based ceramic material with a coating layer. The sintering control in step (7) is divided into three stages, which are: First stage: put the green body into an alumina crucible, heat to 600℃ in air atmosphere at a rate of 2℃ / min, and heat for 2h; Second stage: put the degassed green body into a sealed graphite crucible, add a dynamic Bi2O3 compensation block, switch to pure argon gas with a purity of ≥99.99%, heat to 1150℃ at a rate of 5℃ / min, heat for 3h, and monitor the Bi vapor concentration in real time through the furnace gas sensor, dynamically adjust the gap of the crucible cover, and control the Bi vapor pressure; Third segment annealing modification: after sintering, gradient cooling is adopted, from 1150℃ to 900℃, the cooling rate is 5℃ / min; from 900℃ to room temperature, the cooling rate is 2℃ / min, then put into argon atmosphere at 600℃ for 2h, annealing, natural cooling to room temperature.

10. Use of the high energy storage bismuth sodium titanate-based ceramic material according to any one of claims 1-2 in a dielectric energy storage device.

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