High-entropy super-paramagnetic bnt-knn-sst ceramic material and preparation method thereof

Abstract

The application provides a high-entropy super-conductive BNT-KNN-SST ceramic material and a preparation method thereof. The chemical composition of the ceramic material is (1-x-y)Bi 0.5 Na 0.5 TiO3-xK 0.5 Na 0.5 NbO3-ySr(Sc 0.5 Ta 0.5 )O3, wherein x and y are molar percentages, 0.2<=x<=0.3 and 0<=y<=0.25. The technical scheme provided by the application improves the comprehensive performance index of the ceramic material through multiple strategies such as multiphase coexistence synergistic regulation, high-entropy engineering design, super-conductive state regulation and defect compensation. The prepared BNT-KNN-SST-based lead-free energy storage ceramic has a storage energy density of 8.0 J / cm 3 Above, the storage energy efficiency is more than 91%, and the highest can reach 95.5%. In addition, the material also has excellent high-temperature stability (20-240 DEG C) and fatigue performance (>10 6 ). Through the BNT-KNN-SST-based lead-free energy storage ceramic provided by the application, high storage energy density, high efficiency and excellent high-temperature and fatigue stability are simultaneously realized under a medium electric field for the first time, and the application has important commercial application prospects in the fields of energy storage equipment and power electronics.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy storage, and particularly relates to a high-entropy super-conductive BNT-KNN-SST ceramic material and a preparation method thereof. BACKGROUND

[0002] In the fields of renewable energy, smart grid and high-performance energy storage devices, ceramic capacitors are attracting much attention due to their fast charge-discharge capability and high power density. However, the existing energy storage ceramic materials generally have the technical problems of insufficient energy storage density, low energy efficiency and poor high-temperature and fatigue resistance.

[0003] So far, the relatively high energy storage density of dielectric ceramics is almost obtained at a high breakdown strength (BDS) (> 500 kV / cm). However, operating a capacitor at a high electric field (more than ~ 500 kV / cm) not only requires an additional voltage conversion system compatible with the dielectric ceramic, but also increases the additional risk to the insulation performance of the system, thereby increasing the cost and reducing the safety of the system. Therefore, it is of great practical significance to explore dielectric ceramics with high energy storage density and high energy storage efficiency under moderate electric field conditions (lower than ~ 500 kV / cm).

[0004] Energy storage efficiency refers to the ratio of recoverable energy in the discharge process to the total energy stored in the charging process, which directly reflects the efficiency of the conversion process between electrical energy and mechanical energy of piezoelectric materials. High energy storage efficiency means less energy loss in the conversion process, which is crucial for energy storage and conversion applications. However, there are few effective solutions in the prior art that can further improve the energy storage efficiency while considering the comprehensive performance under moderate electric field strength. For example, Realization of superior thermal stability and high-power density in BNT-based ceramics with excellent energy storage performance discloses a scheme of introducing NaTaO3 (NT) into 0.7Bi0.5Na 0.5 TiO3-0.3Sr 0.7 La0.2TiO3 (BNSLT) ceramics to increase the content of highly stable P4bm phase, thereby improving the energy storage density and energy storage efficiency. However, the energy storage efficiency of the ceramic material in the article is still less than 90%. Moreover, the energy storage density decreases from 89% to 78% during the cyclic charge-discharge test, and the fatigue stability is insufficient. The inability to further improve the energy storage efficiency and fatigue stability seriously limits the widespread application of energy storage ceramics in practical industrial fields.

[0005] Furthermore, in some special application scenarios, capacitors need to operate in high-temperature environments close to 200°C. To date, the operating temperature of most reported energy storage ceramics is below 100-150°C. Therefore, further improving the high-temperature operating stability of dielectric energy storage ceramics is an urgent task.

[0006] In summary, the research aims to explore the advantages of high comprehensive energy storage performance, high temperature stability (200℃) and fatigue stability (charge and discharge cycle times exceeding 10 6 , the efficiency is always not less than 90% of the energy storage ceramic material is not only a challenge, but also a technical problem that needs to be solved urgently by those skilled in the art. In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a high entropy superparaelectric BNT-KNN-SST ceramic material. In view of the problems in the prior art, the present invention innovatively introduces Sr (Sc) into BNT-KNN based ceramics. 0.5 Ta 0.5 )O3(SST), through high entropy engineering and superparaelectric state regulation, significantly improves the comprehensive energy storage performance of the material, especially achieving high energy storage density, high efficiency and excellent high temperature and fatigue stability under medium electric fields, breaking through the technical bottleneck of existing energy storage ceramic systems and providing a new material solution for the commercial application of advanced energy storage devices.

[0008] To achieve the above objectives, the present invention provides a high-entropy superparaelectric BNT-KNN-SST ceramic material, the specific chemical composition formula of which is:

[0009] (1-xy)Bi 0.5 Na 0.5 TiO3-xK 0.5 Na 0.5 NbO3-ySr(Sc 0.5 Ta 0.5 )O3; wherein, x and y are molar percentages, 0.2≤x≤0.3, 0≤y≤0.25.

[0010] In a preferred embodiment,

[0011] 0.6Bi 0.5 Na 0.5 TiO3-0.2K 0.5 Na 0.5 NbO3-0.2Sr(Sc 0.5 Ta 0.5 )O3 energy storage density under a medium electric field of 420kV / cm>7J / cm 3, the energy storage efficiency is greater than 95%, the temperature stability range is 20-240 DEG C, the fatigue resistance is greater than 10 6 .

[0012] In a preferred embodiment,

[0013] The 0.55Bi 0.5 Na 0.5 TiO3-0.3K 0.5 Na 0.5 NbO3-0.15Sr(Sc 0.5 Ta 0.5 )O3 has an energy storage density greater than 8J / cm 3 under a medium electric field of 500kV / cm, the energy storage efficiency is greater than 91%, the temperature stability range is 20-240 DEG C, and the fatigue resistance is greater than 10 6 .

[0014] Another purpose of the present application is to provide a preparation method of high-entropy super-conductive BNT-KNN-SST ceramic material, comprising the following steps:

[0015] S1, Bi2O3, Na2CO3, TiO2, K2CO3, Nb2O5 and Sr2CO3, Sc2O3 and Ta2O5 are weighed according to the stoichiometric ratio;

[0016] S2, the weighed raw materials, ethanol and zirconium oxide balls are loaded into a ball mill tank, and mixed ball milling is carried out;

[0017] S3, the slurry after ball milling is separated, dried to constant weight, and dry powder is obtained;

[0018] S4, the dry powder is heated to 750-850 DEG C, and kept for 1-3 hours, and then cooled to room temperature, crushed and sieved to obtain a pre-sintered powder;

[0019] S5, 0.1-0.2wt% manganese dioxide, ethanol and zirconium oxide balls are added to the pre-sintered powder, mixed ball milling is carried out, the slurry after ball milling is separated, dried to constant weight, and then granulated with a polyvinyl alcohol solution with a mass concentration of 4-6wt%, and the obtained powder is filtered;

[0020] S6, the filtered powder is pressed into a ceramic green body, degassing is carried out at 550-650 DEG C, and then cold isostatic pressing is carried out, and then the temperature is raised to 1130-1180 DEG C at a rate of 3-7 DEG C / min, kept for 1-3 hours, and then cooled in the furnace;

[0021] S7, the sample is polished, double-sided coated with high-temperature silver paste, and then heat treated, and the high-entropy super-conductive BNT-KNN-SST ceramic material is obtained.

[0022] In a preferred embodiment, in order to remove the moisture in the raw materials and avoid cracking in the sintering process, after the raw materials are weighed in step S1, the raw materials are dried in an environment of 110-130 DEG C for 2-4 hours.

[0023] In a preferred embodiment, in step S2, the mass ratio of the raw materials, ethanol and zirconia balls is 1:1:2.

[0024] In a preferred embodiment, in step S2, the rotation speed of the ball mill is 200-600 r / min, and the ball milling time is 6-18 hours.

[0025] In a preferred embodiment, in step S4, the heating rate is 3-7 DEG C / min; preferably, the heating rate is 5 DEG C / min, and the temperature is raised to 800 DEG C and maintained for 2 hours.

[0026] In a preferred embodiment, in step S5, the mass ratio of the pre-sintered powder, ethanol and zirconia balls is 1:1:2.

[0027] In a preferred embodiment, in step S5, the rotation speed of the ball mill is 200-600 r / min, and the ball milling time is 6-18 hours.

[0028] In a preferred embodiment, in step S5, the granulation using a polyvinyl alcohol solution with a mass concentration of 4-6 wt% is a conventional method known to those skilled in the art, and will not be described here; the mesh size of the filter screen is 100 mesh.

[0029] In a preferred embodiment, in step S6, the diameter of the ceramic green body is 8-12 mm, and the thickness is 0.5-1.5 mm, and the pressing pressure is 150-250 MPa.

[0030] In a preferred embodiment, in step S6, the heating rate during the degassing treatment is 0.5-1.5 DEG C / min.

[0031] In a preferred embodiment, in step S7, the holding condition includes holding at 500-700 DEG C for 5-15 minutes.

[0032] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0033] The present application innovatively designs and modifies the BNT-KNN-based energy storage ceramic material by combining high-entropy ion doping with super-conductive engineering. Specifically, the present application includes the following steps:

[0034] A-site and B-site high-entropy strategy is adopted, Sr 2+ is introduced at the A-site, 3+ and Ta is introduced at the B-site.5+ , significantly improving the local chemical disorder and lattice distortion of the system, further inducing local polarization distortion, and optimizing the superparaelectric structure of multiphase coexistence. At the same time, the introduction of KNN realizes The three-phase coexistence state of the material can be realized, the maximum dielectric constant temperature (Tm) is reduced, and the room temperature superparaelectric state is constructed, which significantly improves the energy storage performance and stability. This high entropy structure significantly reduces the dielectric loss of the material while enhancing the energy storage performance. The multi-phase coexistence significantly improves the reversibility of polarization-depolarization and reduces the polarization hysteresis loss, thereby significantly improving the energy storage efficiency. In addition, the use of heterovalent ions (Sr 2 +、Sc 3 + and Ta 5 +) Effectively compensate for the inherent defects and vacancies in the material, thereby significantly improving fatigue resistance and long-term stability.

[0035] The BNT-KNN-SST-based lead-free energy storage ceramics prepared according to the above formula and preparation method can achieve an energy storage density of 8.0 J / cm under a medium electric field. 3 The energy storage efficiency is over 91%, and can reach up to 95.5%. Moreover, the material not only has excellent energy storage performance, but also exhibits excellent high temperature stability (20-240℃) and fatigue performance (>10 6 ), far exceeding the comprehensive performance of existing energy storage ceramic materials under medium electric fields (300-500kV / cm).

[0036] Therefore, the technical solution provided by the present invention has important commercial application prospects in the fields of energy storage equipment, power electronics, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] These and / or other aspects and advantages of the present invention will become more apparent and more readily understood from the following detailed description of embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0038] Figure 1 The (0.8-x)BNT-0.2KNN-xSST ceramics prepared in Example 1 of the present invention are b The unipolarized PE hysteresis loop and the corresponding energy storage performance under φ;

[0039] Figure 2 The fatigue resistance of the 0.6BNT-0.2KNN-0.2SST ceramic material prepared in Example 1 of the present invention;

[0040] Figure 3 The (0.7-x)BNT-0.3KNN-xSST ceramics prepared in Example 2 of the present invention are b The unipolarized PE hysteresis loop and the corresponding energy storage performance under φ;

[0041] Figure 4 Fatigue resistance of 0.55BNT-0.3KNN-0.15SST ceramic material prepared for the embodiment 2 of the present application;

[0042] Figure 5 High-temperature stability of 0.55BNT-0.3KNN-0.15SST ceramic material prepared for the embodiment 2 of the present application;

[0043] Figure 6 Comparison chart of dielectric temperature spectrum of (0.7-x)BNT-0.3KNN-xSST ceramic material prepared for the embodiment 2 of the present application at 10 kHz. DETAILED DESCRIPTION

[0044] In order for those skilled in the art to better understand the present application, the present application will be further described in detail below in combination with the drawings and specific embodiments, but it should be understood that the protection scope of the present application is not limited by the specific embodiments.

[0045] The embodiment of the present application provides a high-entropy super-ferroelectric BNT-KNN-SST ceramic material and a preparation method thereof, and solves the technical problem that the existing ceramic capacitor is difficult to simultaneously consider high energy storage density, high energy efficiency and high temperature and fatigue stability under moderate electric field intensity.

[0046] The technical solution in the present application realizes the optimization of material performance through the following strategies, thereby solving the above problems.

[0047] 1. Synergistic regulation of multiphase coexistence: realized by combining BNT and KNN to realize the three-phase coexistence state, optimize the polarization response and thermal stability of the material.

[0048] 2. High-entropy engineering design: by introducing Sr(Sc 0.5 Ta 0.5 )O3(SST), construct high-entropy components at A and B sites of perovskite structure, significantly enhance the local polarization diversity and the distribution of polar nanoregions (PNRs).

[0049] 3. Super-ferroelectric state regulation: by inducing a room-temperature super-ferroelectric state, reducing the polarization hysteresis loss of the material, and improving the energy storage efficiency.

[0050] 4. Defect compensation and enhancement of fatigue resistance: using heterovalent ions (Sr 2 +, Sc 3 + and Ta 5 +) to effectively compensate for the inherent defect vacancies of the material, thereby significantly improving the fatigue resistance and long-term stability.

[0051] By successful application of the above strategy, the BNT-KNN-SST ceramic material prepared by the present application can simultaneously consider excellent comprehensive performance under a medium electric field, excellent high-temperature stability and excellent fatigue resistance.0.6Bi 0.5 Na 0.5 TiO3-0.2K 0.5 Na 0.5 NbO3-0.2Sr(Sc 0.5 Ta 0.5 )O3 ceramic realizes high energy storage density (Wrec>7J / cm 3 ) and super-high energy efficiency (η>95%) under a medium electric field of 420kV / cm;0.55Bi 0.5 Na 0.5 TiO3-0.3K 0.5 Na 0.5 NbO3-0.15Sr(Sc 0.5 Ta 0.5 )O3 ceramic realizes Wrec>8J / cm 3 and η>91% under a medium electric field of 500kV / cm. Moreover, the energy storage performance of the above two ceramic materials remains stable within the range of 20–240℃. After being subjected to more than 10 6 times of electric field cycles, the energy storage density and efficiency of the material do not significantly decay, showing extremely strong fatigue resistance.

[0052] The technical solutions of the present application are described in detail below through specific embodiments:

[0053] If not specifically indicated, the technical means used in the present application are conventional means familiar to those skilled in the art, and various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods. The reagents used in the present application are analytical pure unless otherwise specified.

[0054] Example 1

[0055] A high-entropy super-conductive BNT-KNN-SST ceramic material, a preparation method thereof comprises the following steps:

[0056] 1. Raw material weighing: according to the stoichiometric ratio design, 6.051g Bi2O 3、 1.835g Na2CO3, 4.149g TiO2, 0.598g K2CO3, 2.301g Nb2O5 and 2.556g, Sr2CO3, 0.597g Sc2O3, 1.913g Ta2O5 are weighed. All raw materials are pre-dried at 120℃ for 3 hours.

[0057] 2. Mixing and ball milling: Put all the raw materials, ethanol and zirconia balls into the ball mill tank with the mass ratio of 1:1:2, and use the planetary ball mill to mill for 12 hours at 400 r / min.

[0058] 3. Powder drying: Separate the ball mill slurry and dry to constant weight.

[0059] 4. Pre-sintering: Put the dried powder into an alumina crucible, heat to 800°C at a heating rate of 5°C / min in a muffle furnace, and keep for 2 hours, then cool to room temperature.

[0060] 5. Secondary ball milling and granulation: Add 0.15wt% manganese dioxide to the pre-sintered powder, repeat the ball milling process of step 2, dry, and then granulate with 5wt% polyvinyl alcohol solution, and filter through a 100 mesh screen.

[0061] 6. Tabletting and forming: Press the granulated powder into a ceramic green body with a diameter of 10mm and a thickness of 1mm at 200MPa.

[0062] 7. Sintering: Heat the green body to 600°C at a rate of 1°C / min to remove the binder, then embed it in the same composition of ceramic powder, heat to 1160°C at a rate of 5°C / min, keep for 2 hours, and cool in the furnace.

[0063] 8. Polishing and electrode coating: Polish the sample, use screen printing to coat both sides with high-temperature silver paste, and heat at 600°C for 10 minutes. A BNT-KNN-SST-based lead-free energy storage ceramic with the general formula 0.6Bi 0.5 Na 0.5 TiO3-0.2K 0.5 Na 0.5 NbO3-0.2Sr(Sc 0.5 Ta 0.5 )O3 is obtained.

[0064] The prepared ceramic material is tested for performance, and the results are as follows: 0.6Bi 0.5 Na 0.5 TiO3-0.2K 0.5 Na 0.5 NbO3-0.2Sr(Sc 0.5 Ta 0.5 )O3 has a stored energy density of 7.02 J / cm 3 under an electric field of 420 kV / cm, a stored energy efficiency of 95.5% (see Figure 1 ), and a temperature stability range of 20-240°C. In the fatigue stability test, the test results are shown in Figure 2 , and from the figure it can be seen that the prepared 0.6BNT-0.2KNN-0.2SST ceramic material has a fatigue stability of up to 106 The energy storage efficiency after cycling is always more than 90%.

[0065] Example 2

[0066] A high-entropy super-paraelectric BNT-KNN-SST ceramic material, which differs from Example 1 only in the composition of the material:

[0067] 0.55Bi 0.5 Na 0.5 TiO3-0.3K 0.5 Na 0.5 NbO3-0.15Sr(Sc 0.5 Ta 0.5 )O3, and the sintering temperature was increased to 1150°C at a rate of 5°C / min. The rest of the preparation method was exactly the same as Example 1.

[0068] The prepared ceramic material was tested for performance, and the results were as follows: 0.55Bi 0.5 Na 0.5 TiO3-0.3K 0.5 Na 0.5 NbO3-0.15Sr(Sc 0.5 Ta 0.5 )O3 had an energy storage density of 8.15 J / cm 3 under an electric field of 500 kV / cm, and an energy storage efficiency of 91.3% (see Figure 3 ). In the fatigue stability test, the test results were as shown in Figure 4 From the graph, it can be seen that the prepared 0.55BNT-0.3KNN-0.15SST ceramic material had an energy storage efficiency of more than 93% after as many as 10 6 cycles, and there was still no downward trend. In the temperature stability test, the test results were as shown in Figure 5 The temperature stability range was 20-240°C. As Figure 6 can be seen, the Tm of the 0.55BNT-0.3KNN-0.15SST ceramic material dropped to room temperature (<25°C), i.e., the super-paraelectric state at room temperature was achieved, and the successful construction of the super-paraelectric state at room temperature was the main reason for significantly improving the energy storage performance and stability.

[0069] The foregoing description of specific exemplary embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. A high-entropy superparaelectric BNT-KNN-SST ceramic material, characterized in that: The general chemical formula of the ceramic material is: (1-xy)Bi 0.5 Na 0.5 TiO3−xK 0.5 Na 0.5 NbO3−ySr(Sc 0.5 Ta 0.5 )O3; wherein, x and y are molar percentages, 0.2≤x≤0.3, 0<y≤0.

25.

2. The high-entropy superparaelectric BNT-KNN-SST ceramic material according to claim 1, characterized in that: The 0.6Bi 0.5 Na 0.5 TiO3−0.2K 0.5 Na 0.5 NbO3−0.2Sr(Sc 0.5 Ta 0.5 )O3 has an energy storage density of >7 J / cm³ at a medium electric field of 420 kV / cm, an energy storage efficiency η >95%, a temperature stability range of 20–240°C, and a fatigue resistance of >10 6 .

3. The high-entropy superparaelectric BNT-KNN-SST ceramic material according to claim 1, characterized in that: 0.55Bi 0.5 Na 0.5 TiO3−0.3K 0.5 Na 0.5 NbO3−0.15Sr(Sc 0.5 Ta 0.5 )O3 has an energy storage density of >8 J / cm³ at a medium electric field of 500 kV / cm, an energy storage efficiency η >91%, a temperature stability range of 20–240°C, and a fatigue resistance of >10 6 .

4. The method for preparing the high-entropy superparaelectric BNT-KNN-SST ceramic material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1 weigh Bi2O3, Na2CO3, TiO2, K2CO3, Nb2O5 and Sr2CO3, Sc2O3, Ta2O5 according to the stoichiometric ratio; S2: weighing raw materials, ethanol and zirconium oxide balls into a ball mill, mixing and ball milling; S3 separates the ball-milled slurry and dries it to constant weight to obtain dry powder; S4: heating the dried powder to 750-850°C, keeping the temperature for 1-3 hours, cooling it to room temperature, and then crushing and sieving it to obtain a pre-calcined powder; S5: adding 0.1-0.2 wt% manganese dioxide, ethanol, and zirconium oxide balls to the calcined powder, ball-milling the mixture, separating the milled slurry, drying it to a constant weight, granulating it with a polyvinyl alcohol solution having a mass concentration of 4-6 wt%, and filtering the resulting powder; S6: Press the filtered powder into a ceramic green body, heat it to 550-650℃ for debinding, and after cold isostatic pressing, heat it to 1130-1180℃ at a rate of 3-7℃ / min, keep it at this temperature for 1-3 hours, and cool it with the furnace; S7 polishes the sample, coats high-temperature silver paste on both sides, and keeps it warm.

5. The method for preparing the high-entropy superparaelectric BNT-KNN-SST ceramic material according to claim 4, characterized in that: In step S2, the mass ratio of the raw material, ethanol and zirconia balls is 1:1:

2.

6. The method for preparing the high-entropy superparaelectric BNT-KNN-SST ceramic material according to claim 4, characterized in that: In step S4, the heating rate is 3-7°C / min.

7. The method for preparing the high-entropy superparaelectric BNT-KNN-SST ceramic material according to claim 4, characterized in that: In step S6, the ceramic green body has a diameter of 8-12 mm and a thickness of 0.5-1.5 mm, and the pressing pressure is 150-250 MPa.

8. The method for preparing the high-entropy superparaelectric BNT-KNN-SST ceramic material according to claim 4, characterized in that: In step S6, the heating rate during the debinding treatment is 0.5-1.5°C / min.

9. The method for preparing the high-entropy superparaelectric BNT-KNN-SST ceramic material according to claim 4, characterized in that: In step S7, the heat preservation condition includes: heat preservation at 500-700° C. for 5-15 minutes.

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