Fluorite structure Bi12TiO20 electrolyte and preparation method thereof

Abstract

The invention discloses a fluorite structure Bi12TiO20 electrolyte and a preparation method thereof, and belongs to the technical field of solid oxide fuel cell electrolyte materials. The preparation method comprises the following steps: (1) mixing Bi < 2 > O < 3 > and TiO < 2 >, and sequentially performing wet grinding, drying and sieving to obtain oxide mixed powder; (2) pressing the oxide mixed powder to obtain a ceramic green body; (3) sintering the ceramic green body to obtain a ceramic preform; and (4) crushing the ceramic preform into small blocks, placing the small blocks in a suspension container, continuously introducing gas into small holes in the bottom of the suspension container, heating, stopping heating after the melt sample is stably suspended in the gas flow, and cooling to room temperature to obtain a finished product. The shape of the finished product prepared by the method is an irregular polyhedron shape; the block is high in compactness and free of two phases, so that the continuity of an ion transmission path can be ensured.

Description

Technical Field

[0001] This invention belongs to the field of solid oxide fuel cell electrolyte materials technology, specifically involving fluorite-structured Bi12TiO20 electrolyte and its preparation method. Background Technology

[0002] Solid oxide fuel cells (SOFCs), as a continuous energy supply system, have become one of the most promising new energy technology fields in the 21st century. Their unique advantages, such as high oxygen ion conductivity, high-temperature stability, all-solid-state operation, and high energy conversion efficiency, make them highly advantageous in distributed power generation, stationary power plants, and marine propulsion. Currently, systems such as yttrium-doped zirconium oxide, scandium-stabilized zirconium oxide, and gadolinium-doped cerium oxide all exhibit a strong dependence on rare earth elements, which significantly increases their practical application costs. Furthermore, the high energy consumption caused by high-temperature, long-duration sintering contradicts the vision of energy conservation and emission reduction. Therefore, there is an urgent need to develop a new generation of medium- and low-temperature electrolyte materials to expand the application scenarios of solid oxide fuel cells.

[0003] The industrial application of solid-state fuel cells is largely influenced by solid-state electrolytes, and crystal structure is the main factor determining the performance of solid-state electrolytes. Obtaining materials with specific crystal structures and improving their conductivity is the most critical aspect of solving solid-state electrolyte problems. Bismuth oxide-based materials, as characteristic materials for oxygen ion conductivity, are among the most promising materials for breakthroughs in current fuel cell applications. In the bismuth oxide-based system, Bi... 12 TiO 20 It has a similar crystal structure to Bi2O3, but Bi 12 TiO 20 Materials research has primarily focused on the crystal structure of bismuthite, lacking exploration of the characteristics of cubic fluorite structures with high ionic conductivity. Bismuthite structures typically exhibit low oxygen ion conductivity, failing to meet the practical application requirements of solid oxide fuel cell electrolytes. In contrast, fluorite structures with high oxygen ion conductivity can well meet the industrial application standards for novel solid oxide fuel cell electrolytes.

[0004] In summary, fluorite crystal structure materials are of significant research importance for developing high oxygen ion conductivity. However, while existing technologies are highly feasible for obtaining bismuth sublimite crystal structure materials, problems such as two-phase precipitation and abnormal grain growth remain. Furthermore, existing technical solutions cannot solve the challenge of synthesizing cubic fluorite-structured solid oxide electrolyte materials. Therefore, a fluorite-structured Bi... 12 TiO 20 Electrolyte preparation technology scheme. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a fluorite-structured Bi12TiO20 electrolyte and its preparation method, thereby solving problems such as the easy occurrence of two-phase precipitation and abnormal grain growth in existing preparation methods.

[0006] To achieve the above objectives, the present invention discloses the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a fluorite-structured Bi12TiO20 electrolyte, comprising the following steps:

[0008] (1) Mix Bi2O3 with a purity of 99.99% with TiO2 with a purity of 99.99%, and then perform wet milling, drying and sieving in sequence to obtain oxide mixed powder;

[0009] (2) Press the oxide mixture powder obtained in step (1) to obtain a ceramic green body;

[0010] (3) Sinter the ceramic green body obtained in step (2) to obtain a ceramic preform;

[0011] (4) The ceramic preform obtained in step (3) is broken into small pieces, placed in a suspension container, and gas is continuously introduced into the small hole at the bottom of the suspension container so that the sample preform is placed in a gas flow with a stable flow rate.

[0012] (5) The small pieces of the ceramic preform broken in step (4) are heated and melted to achieve a stable suspension state. After the molten sample is suspended and stabilized in the gas flow, the heating is stopped and cooled to room temperature to obtain the cubic fluorite structure ceramic block.

[0013] Further, in step (1), the molar ratio of Bi2O3 and TiO2 is x:y, where x is 5.5-6.5 and y is 1.

[0014] In this invention, by limiting the molar ratio of Bi₂O₃ to TiO₂, the phase change law under different Bi / Ti ratios can be obtained, and the single-phase Bi can be determined. 12 TiO 20 Forming an interval.

[0015] Further, in step (1), the wet grinding is carried out by a drum ball mill with a drum speed of 100-500 r / min and a grinding time of 24-96 hours.

[0016] Furthermore, the ball milling involves adding YSZ grinding balls and isopropanol with a purity of 99.99% (by mass). The amount of isopropanol used is related to the volume of the Bi₂O₃, TiO₂ powder, and the YSZ grinding balls, requiring the volume of isopropanol to be 50-80 mL greater than the combined volume of the Bi₂O₃, TiO₂ powder, and YSZ grinding balls.

[0017] Further, the drying in step (1) is to dry in a blower drying oven at 70-100℃ for 24-48 hours.

[0018] Further, in step (2), the pressing process involves loading the oxide mixed powder into a stainless steel mold, applying pressure to the sample to stabilize it at 5-10 MPa, and then maintaining it for 10-30 minutes.

[0019] Further, in step (3), the ceramic green body sintering process is to heat to 800-1000℃ at a heating rate of 1-20℃ / min, hold for 120-210min, and then cool in the furnace to room temperature.

[0020] Furthermore, in step (4), the gas is one of argon, air, or oxygen.

[0021] Furthermore, in this invention, the gas flow rate is calculated using the following formula:

[0022]

[0023] Where R is the radius of the suspended sphere. The drag coefficient of the airflow. The velocity of the airflow as it bypasses the object. It is the acceleration due to gravity. , These represent the densities of suspended objects and airflow, respectively.

[0024] Further, in step (5), the heating and melting is carried out by heating with a CO2 laser at a laser heating rate of 4-6 W / s, and the temperature is raised to 100-200°C above the melting point of the ceramic preform.

[0025] In this invention, gas is continuously introduced into the bottom of the suspension container, so that the sample is suspended in the gas flow. Since the melt is in a suspended state, the heat dissipation of the melt is determined by the thermal conductivity of the gas. Such a device provides different heat dissipation environments for the melt during rapid cooling, and the high thermal conductivity gas provides a more extreme cooling environment for the melt to achieve rapid cooling.

[0026] In a second aspect, the present invention provides a fluorite-structured Bi12TiO20 electrolyte prepared by the preparation method of the fluorite-structured Bi12TiO20 electrolyte described in the first aspect.

[0027] The product obtained by this invention is an excellent ionic conductor. Through deep supercooling and rapid solidification, the sample can reach a deep supercooled state and achieve rapid solidification under extreme conditions. This invention obtains samples with different compositional ratios by grinding, pressing, and heat-treating Bi₂O₃ and TiO₂. The samples are then melted and suspended in a gas. Because the samples are suspended in the gas flow, an environment without container contact is provided, which provides a very high cooling rate to the melt, thus preserving the metastable phase at high temperatures. The non-equilibrium solidification process differs from the cooling process of the equilibrium phase diagram. The non-equilibrium solidification process alters the equilibrium solidification phase region of the sample, optimizing the phase formation path and the types of phases precipitated. It also helps to expand the single-phase formation region, enabling the preparation of single-phase, homogeneous cubic fluorite-structured bismuth titanate ceramic blocks within a wider compositional range and synthesis atmosphere.

[0028] The beneficial effects of this invention are:

[0029] 1. A one-step synthesis of fluorite-structured Bi12TiO20 electrolyte was achieved using deep supercooling rapid solidification technology. This method has advantages such as short synthesis cycle, wide range of process parameters, and high operational tolerance, and has reference value for actual industrial production.

[0030] 2. The fluorite-structured Bi12TiO20 electrolyte obtained by this invention has strong tolerance to electrolyte composition, and the Bi / Ti ratio can be adjusted without affecting the formation of a single phase; it has wide compatibility with synthesis atmospheres and can obtain single-phase products under conditions such as argon, air and oxygen, with an irregular polyhedral shape; the bulk is highly dense and has no two phases, which can ensure the continuity of ion transport paths.

[0031] 3. The fluorite-structured Bi12TiO20 electrolyte prepared by this invention exhibits high oxygen ion conductivity at high temperatures, which fully meets the standards for industrial application in medium- and low-temperature solid oxide fuel cells. Attached Figure Description

[0032] Figure 1 SEM images of the finished products prepared in Examples 1, 2, and 3.

[0033] Figure 2 SEM images of the finished products prepared in Examples 2, 4, and 5.

[0034] Figure 3 XRD patterns of the finished products prepared in Examples 1-5

[0035] Figure 4 XPS full spectrum of the finished products prepared in Examples 2, 4, and 5

[0036] Figure 5 XPS fine spectra of the finished products prepared in Examples 2, 4, and 5

[0037] Figure 6AC impedance spectra of the finished products prepared in Examples 1-3

[0038] Figure 7 AC impedance spectra of the finished products prepared in Examples 2, 4, and 5

[0039] Figure 8 EIS spectra of the finished product prepared in Example 4 within the temperature range of 150-400 °C.

[0040] Figure 9 The conductivity of the finished product prepared in Example 4 within the temperature range of 150-400 °C Detailed Implementation

[0041] Those skilled in the art can refer to the content of this document to appropriately improve the process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention.

[0042] The products and methods of the present invention have been described through preferred embodiments. Those skilled in the art will be able to make modifications or appropriate alterations and combinations to the products and methods described herein without departing from the content, spirit and scope of the present invention, so as to realize and apply the technology of the present invention.

[0043] Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. Materials, reagents, etc., used are commercially available unless otherwise specified. Unless otherwise stated, substances described in this invention are calculated as percentages and parts by mass.

[0044] Example 1

[0045] (1) Place Bi2O3 with a purity of 99.9%, TiO2 with a purity of 99.99%, YSZ grinding balls, and isopropanol in a ball mill jar and grind them on a drum ball mill at a speed of 300 r / min for 48 h until the slurry is fine and free of particles. Place the mixture after ball milling in a forced-air drying oven and dry it at 90 °C for 36 h. Pass the dried powder sample through a 400-mesh sieve. Grind the unsieved part with an agate mortar until all of it passes through a 400-mesh sieve to obtain powdered ingredients. The molar ratio of Bi2O3 to TiO2 is 5.5:1. The amount of isopropanol used is related to the volume of Bi2O3, TiO2 powder, and YSZ grinding balls. The volume of isopropanol is required to be greater than 50 mL of the total volume of Bi2O3, TiO2 powder, and YSZ grinding balls.

[0046] (2) Place the powdered ingredients obtained in step (1) into a stainless steel cylindrical mold with a diameter of 20 mm, then apply a pressure of 8 MPa and hold for 20 minutes to obtain the pressed green body.

[0047] (3) The green blank obtained in step (2) is heat-treated in a muffle furnace to obtain a sintered preform; wherein the heat treatment procedure is as follows: starting from room temperature, the temperature is heated to 1000 °C at a heating rate of 8 °C / min and held for 200 minutes, and then the furnace is cooled to room temperature;

[0048] (4) Break the sample obtained in step (3) into small pieces and place them in a metal nozzle. Connect a water-cooling device to the bottom of the metal nozzle and continuously introduce argon gas into the bottom of the metal nozzle. The argon gas flow rate is Q = 437ccm / min. At the same time, heat the sample with the laser spot of the CO2 laser. The laser heating rate is 5 W / s. Heat the sample to 100°C above the melting point to melt it. After the molten sample is suspended and stable in the gas, stop heating and then cool it to room temperature to obtain the finished product.

[0049] Example 2

[0050] (1) Place Bi2O3 with a purity of 99.9%, TiO2 with a purity of 99.99%, YSZ grinding balls, and isopropanol in a ball mill jar and grind them on a drum ball mill at a speed of 300 r / min for 48 h until the slurry is fine and free of particles. Place the mixture after ball milling in a forced-air drying oven and dry it at 90 °C for 36 h. Pass the dried powder sample through a 400-mesh sieve. Grind the unsieved part with an agate mortar until all of it passes through a 400-mesh sieve to obtain powdered ingredients. Among them, the molar ratio of Bi2O3 to TiO2 is 6:1. The amount of isopropanol is related to the volume of Bi2O3, TiO2 powder, and YSZ grinding balls. It is required that the volume of isopropanol is greater than 50 mL of the total volume of Bi2O3, TiO2 powder, and YSZ grinding balls.

[0051] (2) Place the powdered ingredients obtained in step (1) into a stainless steel cylindrical mold with a diameter of 20 mm, then apply a pressure of 8 MPa and hold for 20 minutes to obtain the pressed green body.

[0052] (3) The green blank obtained in step (2) is heat-treated in a muffle furnace to obtain a sintered preform; wherein the heat treatment procedure is as follows: starting from room temperature, the temperature is heated to 1000 °C at a heating rate of 8 °C / min and held for 200 minutes, and then the furnace is cooled to room temperature;

[0053] (4) Break the sample obtained in step (3) into small pieces and place them in a metal nozzle. Connect a water-cooling device to the bottom of the metal nozzle and continuously introduce argon gas into the bottom of the metal nozzle. The argon gas flow rate is Q = 437ccm / min. At the same time, heat the sample with the laser spot of the CO2 laser. The laser heating rate is 5 W / s. Heat the sample to 100°C above the melting point to melt it. After the molten sample is suspended and stable in the gas, stop heating and then cool it to room temperature to obtain the finished product.

[0054] Example 3

[0055] (1) Place Bi2O3 with a purity of 99.9%, TiO2 with a purity of 99.99%, YSZ grinding balls, and isopropanol in a ball mill jar and grind them on a drum ball mill at a speed of 300 r / min for 48 h until the slurry is fine and free of particles. Place the mixture after ball milling in a forced-air drying oven and dry it at 90 °C for 36 h. Pass the dried powder sample through a 400-mesh sieve. Grind the unsieved part with an agate mortar until all of it passes through a 400-mesh sieve to obtain powdered ingredients. The molar ratio of Bi2O3 to TiO2 is 6.5:1. The amount of isopropanol used is related to the volume of Bi2O3, TiO2 powder, and YSZ grinding balls. The volume of isopropanol is required to be greater than 50 mL of the total volume of Bi2O3, TiO2 powder, and YSZ grinding balls.

[0056] (2) Place the powdered ingredients obtained in step (1) into a stainless steel cylindrical mold with a diameter of 20 mm, then apply a pressure of 8 MPa and hold for 20 minutes to obtain the pressed green body.

[0057] (3) The green blank obtained in step (2) is heat-treated in a muffle furnace to obtain a sintered preform; wherein the heat treatment procedure is as follows: starting from room temperature, the temperature is heated to 1000 °C at a heating rate of 8 °C / min and held for 200 minutes, and then the furnace is cooled to room temperature;

[0058] (4) Break the sample obtained in step (3) into small pieces and place them in a metal nozzle. Connect a water-cooling device to the bottom of the metal nozzle and continuously introduce argon gas into the bottom of the metal nozzle. The argon gas flow rate is Q = 437ccm / min. At the same time, heat the sample with the laser spot of the CO2 laser. The laser heating rate is 5 W / s. Heat the sample to 100°C above the melting point to melt it. After the molten sample is suspended and stable in the gas, stop heating and then cool it to room temperature to obtain the finished product.

[0059] Example 4

[0060] (1) Place Bi2O3 with a purity of 99.9%, TiO2 with a purity of 99.99%, YSZ grinding balls, and isopropanol in a ball mill jar and grind them on a drum ball mill at a speed of 300 r / min for 48 h until the slurry is fine and free of particles. Place the mixture after ball milling in a forced-air drying oven and dry it at 90 °C for 36 h. Pass the dried powder sample through a 400-mesh sieve. Grind the unsieved part with an agate mortar until all of it passes through a 400-mesh sieve to obtain powdered ingredients. Among them, the molar ratio of Bi2O3 to TiO2 is 6:1. The amount of isopropanol is related to the volume of Bi2O3, TiO2 powder, and YSZ grinding balls. It is required that the volume of isopropanol is greater than 50 mL of the total volume of Bi2O3, TiO2 powder, and YSZ grinding balls.

[0061] (2) Place the powdered ingredients obtained in step (1) into a stainless steel cylindrical mold with a diameter of 20 mm, then apply a pressure of 8 MPa and hold for 20 minutes to obtain the pressed green body.

[0062] (3) The green blank obtained in step (2) is heat-treated in a muffle furnace to obtain a sintered preform; wherein the heat treatment procedure is as follows: starting from room temperature, the temperature is heated to 1000 °C at a heating rate of 8 °C / min and held for 200 minutes, and then the furnace is cooled to room temperature;

[0063] (4) Break the sample obtained in step (3) into small pieces and place them in a metal nozzle. Connect a water-cooling device to the bottom of the metal nozzle and continuously introduce air into the bottom of the metal nozzle at a flow rate of Q = 522 cm / min. At the same time, heat the sample with the laser spot of the CO2 laser at a rate of 5 W / s until the sample melts at 100°C above its melting point. After the molten sample is suspended and stabilized in the gas, stop heating and then cool it to room temperature to obtain the finished product.

[0064] Example 5

[0065] (1) Place Bi2O3 with a purity of 99.9%, TiO2 with a purity of 99.99%, YSZ grinding balls, and isopropanol in a ball mill jar and grind them on a drum ball mill at a speed of 300 r / min for 48 h until the slurry is fine and free of particles. Place the mixture after ball milling in a forced-air drying oven and dry it at 90 °C for 36 h. Pass the dried powder sample through a 400-mesh sieve. Grind the unsieved part with an agate mortar until all of it passes through a 400-mesh sieve to obtain powdered ingredients. Among them, the molar ratio of Bi2O3 to TiO2 is 6:1. The amount of isopropanol is related to the volume of Bi2O3, TiO2 powder, and YSZ grinding balls. It is required that the volume of isopropanol is greater than 50 mL of the total volume of Bi2O3, TiO2 powder, and YSZ grinding balls.

[0066] (2) Place the powdered ingredients obtained in step (1) into a stainless steel cylindrical mold with a diameter of 20 mm, then apply a pressure of 8 MPa and hold for 20 minutes to obtain the pressed green body.

[0067] (3) The green blank obtained in step (2) is heat-treated in a muffle furnace to obtain a sintered preform; wherein the heat treatment procedure is as follows: starting from room temperature, the temperature is heated to 1000 °C at a heating rate of 8 °C / min and held for 200 minutes, and then the furnace is cooled to room temperature;

[0068] (4) Break the sample obtained in step (3) into small pieces and place them in a metal nozzle. Connect a water-cooling device to the bottom of the metal nozzle and continuously introduce oxygen into the bottom of the metal nozzle at a rate of Q = 516 cm / min. Simultaneously, heat the sample with the laser spot of the CO2 laser at a rate of 5 W / s until the sample melts at 100°C above its melting point. After the molten sample is suspended and stabilized in the gas, stop heating and then cool it to room temperature to obtain the finished product.

[0069] The gas flow rates in Examples 1-5 were calculated using the following formula:

[0070]

[0071] Where R is the radius of the suspended sphere. The drag coefficient of the airflow. The velocity of the airflow as it bypasses the object. It is the acceleration due to gravity. , These represent the densities of suspended objects and airflow, respectively.

[0072] Result detection:

[0073] 1. The finished products obtained in Examples 1-5 were analyzed by scanning electron microscopy, and the results are as follows: Figure 1-2 As shown, the obtained ceramic bulk sample is a single phase, therefore there is no phase contrast difference in the backscattered mode of SEM. The fluorite-structured Bi prepared by the method of this invention... 12 TiO 20 The electrolyte has a high density, and its basic unit is an irregular polyhedral grain structure, which ensures the continuity of ion transport paths.

[0074] 2. The ceramic blocks obtained in Examples 1-5 were ground into powder and then subjected to X-ray diffraction analysis. The results are shown in the figure. Figure 3 As shown in the figure, the phase is Bi with a cubic fluorite structure. 12 TiO 20 Mutually.

[0075] 3. Combining Figure 6-7 Analysis shows that when Bi / Ti = 13, the conductivity is extremely low and the impedance is very high. The impedance spectrum of Bi / Ti = 11 exhibits similar characteristics to that of Bi / Ti = 12; when Bi / Ti = 11, the impedance is minimum and the conductivity is maximum. The impedance of the ceramic bulk varies under different atmospheres. The impedance is minimum in air atmosphere and maximum in argon atmosphere, with both the impedance and conductivity being minimum.

[0076] 4. Combination Figure 8-9Analysis shows that the finished product obtained in Example 4 of this invention exhibits high oxygen ion conductivity at high temperatures, which fully meets the standards for industrial application in medium and low temperature solid oxide fuel cells.

[0077] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention 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 can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a fluorite-structured Bi12TiO20 electrolyte, characterized in that, Includes the following steps: (1) Mix Bi2O3 with a purity of 99.99% with TiO2 with a purity of 99.99%, and then perform wet milling, drying and sieving in sequence to obtain oxide mixed powder; (2) Press the oxide mixture powder obtained in step (1) to obtain a ceramic green body; (3) Sinter the ceramic green body obtained in step (2) to obtain a ceramic preform; (4) The ceramic preform obtained in step (3) is broken into small pieces, placed in a suspension container, and gas is continuously introduced into the small hole at the bottom of the suspension container so that the sample preform is placed in a gas flow with a stable flow rate. (5) The small pieces of the ceramic preform broken in step (4) are heated and melted to achieve a stable suspension state. After the molten sample is suspended and stabilized in the gas flow, the heating is stopped and cooled to room temperature to obtain the cubic fluorite structure ceramic block.

2. The method for preparing the fluorite-structured Bi12TiO20 electrolyte according to claim 1, characterized in that, In step (1), the molar ratio of Bi2O3 to TiO2 is x:y, where x is 5.5-6.5 and y is 1.

3. The method for preparing the fluorite-structured Bi12TiO20 electrolyte according to claim 1, characterized in that, In step (1), the wet grinding is carried out by a drum ball mill with a drum speed of 100-500 r / min and a grinding time of 24-96 hours.

4. The method for preparing the fluorite-structured Bi12TiO20 electrolyte according to claim 1, characterized in that, In step (2), the pressing process involves loading the oxide mixed powder into a stainless steel mold, applying pressure to the sample to stabilize it at 5-10 MPa, and then maintaining it for 10-30 minutes.

5. The method for preparing the fluorite-structured Bi12TiO20 electrolyte according to claim 1, characterized in that, In step (3), the ceramic green body sintering process is to heat to 800-1000℃ at a heating rate of 1-20℃ / min, hold for 120-210min, and then cool in the furnace to room temperature.

6. The method for preparing the fluorite-structured Bi12TiO20 electrolyte according to claim 1, characterized in that, In step (4), the gas is one of argon, air, or oxygen.

7. The method for preparing the fluorite-structured Bi12TiO20 electrolyte according to claim 1, characterized in that, In step (5), the heating and melting is carried out by heating with a CO2 laser at a laser heating rate of 4-6 W / s, and heating to 100-200°C above the melting point of the ceramic preform.

8. The fluorite-structured Bi12TiO20 electrolyte prepared by the method according to any one of claims 1-7. 12 TiO 20 Electrolytes.

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