Bismuth oxide-based fuel cell electrolyte material and preparation method thereof

Abstract

The invention discloses a bismuth oxide-based fuel cell electrolyte material and a preparation method thereof, and relates to the technical field of cell electrolyte materials. The material is composed of a trication-doped delta-Bi2O3 core and a zirconium oxide coating layer, the trication-doped delta-Bi2O3 core is co-doped with erbium, tungsten and aluminum ions, and the material comprises the following components in parts by mass: 75-80 parts of bismuth oxide (Bi2O3); 14 to 19 parts of erbium oxide (Er2O3); 1 to 3 parts of tungsten oxide (WO3); 1 to 3 parts of aluminum oxide (Al2O3); the zirconium oxide coating layer is formed by a coprecipitation method, and the thickness of the zirconium oxide coating layer is 5-20nm, so that the technical problems that the working temperature range of delta-Bi2O3 is difficult to broaden, and the low-temperature phase change and reduction under low oxygen partial pressure are difficult to inhibit are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery electrolyte materials, and in particular relates to a bismuth oxide-based fuel cell electrolyte material and a preparation method thereof. Background Art

[0002] Solid oxide fuel cells (SOFCs) have become a key development direction in the fuel cell field due to their wide fuel application range, high energy density, low-cost materials, and green, low-carbon nature. They are used in distributed energy supply, coal gasification combined cycle power generation, and auxiliary power supplies for vehicles and ships. SOFCs primarily consist of an anode, electrolyte, and cathode. Developing electrolyte materials with high oxygen ion conductivity is essential for achieving large-scale commercialization of SOFCs.

[0003] Among the SOFC electrolyte materials currently under research, the one with the highest oxygen ion conductivity is fluorite-type bismuth oxide (δ-Bi2O3), which is 1-2 orders of magnitude higher than the existing yttrium-stabilized zirconia (YSZ) electrolyte material. However, δ-Bi2O3 only exists in a narrow temperature range of 729-824°C. Below 650°C, body-centered cubic β-Bi2O3 and tetragonal γ-Bi2O3 will also appear. At room temperature, it is monoclinic α-Bi2O3. The phase transition process is accompanied by a huge volume change, which seriously damages the mechanical properties of the material. In addition, Bi2O3 is easily reduced to produce electronic conductivity under low oxygen partial pressure.

[0004] The existing technology (JP2018125064A) uses ZrO2 mixed with Bi2O3, but it is a physical mixture rather than a core-shell structure.

[0005] Therefore, broadening the operating temperature range of δ-Bi2O3 and inhibiting its low-temperature phase transition and reduction under low oxygen partial pressure will be beneficial to the large-scale commercialization of bismuth oxide-based electrolyte SOFC. Summary of the Invention

[0006] In order to solve the above technical problems, a bismuth oxide-based fuel cell electrolyte material and a preparation method are proposed. The inventors have obtained the technical solution of the present invention through practice and summary. The present invention discloses a bismuth oxide-based fuel cell electrolyte material, which is composed of a tri-cation-doped δ-Bi2O3 core and a zirconium oxide coating layer. The tri-cation doping is co-doped with erbium, tungsten, and aluminum ions, and its mass composition is:

[0007]

[0008]

[0009] The zirconium oxide coating layer is formed by a co-precipitation method and has a thickness of 5-20 nm.

[0010] In a further technical solution, the aluminum oxide is α-Al2O3, and its particle size is 0.1-1 μm.

[0011] In a further technical solution, the coating layer has a gradient structure, and the Zr content increases gradually from 50 at % to 100 at % from the inside to the outside.

[0012] A method for preparing a bismuth oxide-based fuel cell electrolyte material comprises the following steps:

[0013] (1) Wet ball milling of bismuth oxide, erbium oxide, tungsten oxide, and aluminum oxide powders with anhydrous ethanol for 3-10 hours and spray drying to obtain a mixed powder; the present invention preferably uses anhydrous ethanol as a solvent to improve the dispersibility between the powders during the ball milling process, reduce the viscosity of the slurry, and make the dispersion between different components of the powder more uniform.

[0014] The added erbium oxide is used to broaden the operating temperature range of δ-Bi2O3 and inhibit its phase transition at low temperatures.

[0015] The added tungsten oxide is used to suppress the phase transition of δ-Bi2O3 at low temperature and its phase stability during long-term operation.

[0016] The added aluminum oxide is α-Al2O3, which is used to stabilize the phase structure of bismuth oxide, improve the density of bismuth oxide electrolyte, and increase thermal conductivity to improve the thermal shock resistance of the electrolyte material.

[0017] (2) calcining the powder from step (1) at 700-900°C for 2-5h, and sand-milling to obtain doped δ-Bi2O3 powder;

[0018] (3) The doped powder is dispersed in a 0.1-0.3 mol / L zirconium nitrate solution, urea and CTAB are added, and hydrothermal precipitation is carried out at 70-100°C for 2-4 hours to form a Zr(OH)4 coating layer; urea is hydrothermally precipitated uniformly with zirconium nitrate in the solution, so that the zirconium hydroxide precipitate is slowly and uniformly coated.

[0019] (4) calcining the coated powder at 600-800°C for 2-4h, dry pressing and sintering at 700-900°C.

[0020] In a further technical solution, the mass ratio of the powder to anhydrous ethanol in step (1) is (70-80):(20-30), and the ball milling speed is 200-300 rpm.

[0021] In a further technical solution, the amount of CTAB added in step (3) is 0.5-2 parts per 100 parts of the doped powder. Cetyltrimethylammonium bromide acts as a template, causing the zirconium hydroxide precipitate to coat the surface of the doped powder.

[0022] In a further technical solution, the zirconium oxide is coated on the surface of the doped powder to inhibit the reduction of Bi2O3 under low oxygen partial pressure.

[0023] In a further technical solution, in step (3), microwave-assisted hydrothermal precipitation is adopted, the microwave power is 300-500W, and the precipitation time is shortened to 0.5-1h.

[0024] In a further technical solution, the calcination in step (4) is carried out in a flowing nitrogen-oxygen mixed gas, wherein the volume fraction of O2 is 5-10%.

[0025] Compared with the prior art, the present invention can achieve the following technical effects:

[0026] The powder obtained through wet ball milling in this invention is uniformly distributed, has a small particle size, is free of impurities, and features a simple process, making it suitable for industrial production. Furthermore, the addition of erbium oxide, tungsten oxide, and aluminum oxide broadens the operating temperature range of δ-Bi2O3 and inhibits its phase transition at low temperatures. The zirconium oxide coating prevents the reduction of bismuth oxide at low oxygen partial pressures. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 This is a diagram of the preparation process of the bismuth oxide-based fuel cell electrolyte material of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] The application principle of the present invention is further described below with reference to the accompanying drawings and specific embodiments. A bismuth oxide-based fuel cell electrolyte material is composed of a δ-Bi2O3 core doped with three cations and a zirconium oxide coating layer. The three cations are co-doped with erbium, tungsten, and aluminum ions, and its mass composition is:

[0031]

[0032] The zirconium oxide coating layer is formed by a co-precipitation method and has a thickness of 5-20 nm.

[0033] In a further technical solution, the aluminum oxide is α-Al2O3, and its particle size is 0.1-1 μm.

[0034] In a further technical solution, the coating layer has a gradient structure, and the Zr content increases gradually from 50 at % to 100 at % from the inside to the outside.

[0035] A method for preparing a bismuth oxide-based fuel cell electrolyte material comprises the following steps:

[0036] (1) Wet-milling bismuth oxide, erbium oxide, tungsten oxide, and aluminum oxide powders with anhydrous ethanol for 3-10 hours, and spray drying to obtain a mixed powder;

[0037] (2) calcining the powder from step (1) at 700-900°C for 2-5h, and sand-milling to obtain doped δ-Bi2O3 powder;

[0038] (3) dispersing the doped powder in a 0.1-0.3 mol / L zirconium nitrate solution, adding urea and CTAB, and hydrothermally precipitating at 70-100 °C for 2-4 h to form a Zr(OH)4 coating layer;

[0039] (4) calcining the coated powder at 600-800°C for 2-4h, dry pressing and sintering at 700-900°C.

[0040] In a further technical solution, the mass ratio of the powder to anhydrous ethanol in step (1) is (70-80):(20-30), and the ball milling speed is 200-300 rpm.

[0041] In a further technical solution, the amount of CTAB added in step (3) is 0.5-2 parts per 100 parts of doped powder.

[0042] In a further technical solution, the zirconium oxide is coated on the surface of the doped powder to inhibit the reduction of Bi2O3 under low oxygen partial pressure.

[0043] In a further technical solution, in step (3), microwave-assisted hydrothermal precipitation is adopted, the microwave power is 300-500W, and the precipitation time is shortened to 0.5-1h.

[0044] In a further technical solution, the calcination in step (4) is carried out in a flowing nitrogen-oxygen mixed gas, wherein the volume fraction of O2 is 5-10%.

[0045] Example 1

[0046] A method for preparing a bismuth oxide-based fuel cell electrolyte material comprises using bismuth oxide, erbium oxide, tungsten oxide, and aluminum oxide powders as raw materials, preparing a bismuth oxide-based mixed powder by wet ball milling, calcining the mixed powder, sand milling, and spray drying to obtain a doped powder, coating the doped powder with zirconium hydroxide by hydrothermal homogenous precipitation, calcining the zirconium hydroxide-coated powder to obtain a zirconium oxide-coated doped powder, and finally dry-pressing and sintering the powder to produce the bismuth oxide-based electrolyte material. The specific steps are as follows:

[0047] (1) 468 g of bismuth oxide powder, 108 g of erbium oxide powder, 12 g of tungsten oxide powder, 12 g of aluminum oxide powder, and 200 mL of anhydrous ethanol were added to a ball mill and blended. The mixture was ball milled for 6 h to obtain a uniformly dispersed slurry. The slurry was then added to 2000 mL of deionized water and stirred for 1 h to obtain a uniformly dispersed suspension. Finally, the suspension was spray-dried to obtain a uniformly dispersed mixed powder.

[0048] (2) calcining the powder prepared in step (1) for 3 h at a calcination temperature of 800° C., and further sand-milling and spray-drying the powder obtained after calcination to obtain a micron-sized doped powder;

[0049] (3) The doped powder in step (2) was dispersed in 2000 mL of zirconium nitrate solution (0.1 mol / L), and then 12.5 g of urea and 2 g of hexadecyltrimethylammonium bromide were added and stirred and heated for precipitation for 3 h at a hydrothermal temperature of 90° C. Finally, the suspension was filtered, washed, and spray-dried to obtain a doped powder coated with zirconium hydroxide precipitate;

[0050] (4) calcining the powder prepared in step (3) for 3 h at a calcination temperature of 750° C., then sand-milling and filtering the powder obtained after calcination, and finally spray-drying the powder to obtain a micron-sized doped electrolyte powder;

[0051] (5) The zirconium oxide-coated doped powder obtained in step (4) is used as a raw material, dry-pressed into a shape, and then placed in a calcining furnace for sintering at a sintering temperature of 850° C. and a sintering time of 10 h to obtain a bismuth-based electrolyte material.

[0052] Example 2

[0053] (1) 468 g of bismuth oxide powder, 108 g of erbium oxide powder, 12 g of tungsten oxide powder, 12 g of aluminum oxide powder, and 300 mL of anhydrous ethanol were added to a ball mill and blended. The mixture was ball milled for 10 h to obtain a uniformly dispersed slurry. The slurry was then added to 2000 mL of deionized water and stirred for 1 h to obtain a uniformly dispersed suspension. Finally, the suspension was spray-dried to obtain a uniformly dispersed mixed powder. A grinding medium of 0.3 mm diameter zirconium oxide microspheres was used.

[0054] (2) calcining the powder prepared in step (1) for 3 h at a calcination temperature of 850° C. for 2 h; further sand-milling and spray-drying the powder obtained after calcination to obtain a micron-sized doped powder;

[0055] (3) The doped powder in step (2) was dispersed in 2000 mL of zirconium nitrate solution (0.1 mol / L), and then 12.5 g of urea and 2 g of hexadecyltrimethylammonium bromide were added and stirred and heated for precipitation for 5 h at a hydrothermal temperature of 90° C. Finally, the suspension was filtered, washed, and spray-dried to obtain a doped powder coated with zirconium hydroxide precipitate;

[0056] (4) calcining the powder prepared in step (3) for 3 h at a calcination temperature of 800° C. and sintering for 15 h, then sand-milling and filtering the powder obtained after calcination, and finally spray-drying it to obtain a micron-sized doped electrolyte powder;

[0057] (5) The zirconium oxide-coated doped powder obtained in step (4) is used as a raw material, dry-pressed into a shape, and then placed in a calcining furnace for sintering at a sintering temperature of 850° C. and a sintering time of 10 h to obtain a bismuth-based electrolyte material.

[0058] Ball milling optimization in this embodiment: extend the ball milling time, combine with small-particle grinding media, use high-energy mechanical force to reduce the powder to 0.5μm, and the ethanol volatilization rate is slower than water, reducing hard agglomeration, and SEM shows a 12% reduction in porosity. Calcination adjustment: the calcination temperature is increased to 850℃ but the time is shortened. Through the Ostwald ripening mechanism, the atoms on the grain surface are rearranged to form a more complete δ-Bi2O3 phase, and the phase purity is increased to 98%. Precipitation strengthening: extend the precipitation time to 5h, the urea decomposition rate is better matched with the zirconium ion hydrolysis, the coating thickness is increased from 5nm to 8nm, and the coverage is increased from 90% to 97%. Low-temperature long-time sintering: sintering at 800℃ for 15h controls grain boundary migration through diffusion, and the grain size distribution is narrowed.

[0059] Example 3

[0060] (1) 468 g of bismuth oxide powder, 108 g of erbium oxide powder, 12 g of tungsten oxide powder, 12 g of aluminum oxide powder, and 200 mL of anhydrous ethanol were added to a ball mill and blended. The ball milling was divided into two stages: coarse grinding at a speed of 200 rpm for 4 h, and then fine grinding at a speed of 400 rpm for 6 h to obtain a uniformly dispersed slurry; the slurry was then added to 2000 mL of deionized water and stirred for 1 h to obtain a uniformly dispersed suspension; finally, the suspension was spray-dried to obtain a uniformly dispersed mixed powder;

[0061] (2) calcining the powder prepared in step (1) for 3 h at a calcination temperature of 800° C., and further sand-milling and spray-drying the powder obtained after calcination. The sand-milling process uses three-level particle size grinding beads (1 mm → 0.5 mm → 0.1 mm) to crush the powder step by step to obtain micron-sized doped powder;

[0062] (3) The doped powder in step (2) was dispersed in 2000 mL of zirconium nitrate solution (0.1 mol / L), and then 12.5 g of urea and 2 g of hexadecyltrimethylammonium bromide were added for stirring and heating precipitation for 3 h. The hydrothermal temperature was 90 ° C. The hydrothermal precipitation was carried out twice: the first precipitation was carried out in 0.05 mol / L zirconium nitrate solution for 2 h, and the second precipitation was carried out in 0.15 mol / L solution for 3 h.

[0063] Finally, the suspension is filtered, washed and spray-dried to obtain doped powder coated with zirconium hydroxide precipitate;

[0064] (4) calcining the powder prepared in step (3) for 3 hours, with the calcination temperature increasing gradually from 500°C for 1 hour to 750°C for 2 hours to 850°C for 5 hours, and then sand-milling, filtering, washing, and finally spray-drying the powder obtained after calcination to obtain a micron-sized doped electrolyte powder;

[0065] (5) The zirconium oxide-coated doped powder obtained in step (4) is used as a raw material, dry-pressed into a shape, and then placed in a calcining furnace for sintering at a sintering temperature of 850° C. and a sintering time of 10 h to obtain a bismuth-based electrolyte material.

[0066] This embodiment uses segmented ball milling: the coarse grinding stage breaks up large particles, and the fine grinding stage optimizes dispersibility, thereby increasing the specific surface area of the powder and improving the density of active sites for subsequent coating reactions. The gradient precipitation method can ensure continuity in the first layer of coating with low-concentration zirconium liquid, while filling defects in the secondary coating at high concentrations, thereby optimizing the oxygen ion migration path. Graded sintering: the low-temperature stage (500°C) removes residual organic matter, the medium-temperature stage (750°C) promotes initial grain growth, and the high-temperature stage (850°C) achieves densification and suppresses Bi volatilization.

[0067] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0068] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A bismuth oxide-based fuel cell electrolyte material, characterized in that: It is composed of a δ-Bi2O3 core doped with three cations and a zirconium oxide coating layer. The three cations are co-doped with erbium, tungsten and aluminum ions, and the mass composition is: The zirconium oxide coating layer is formed by a co-precipitation method and has a thickness of 5-20 nm.

2. The bismuth oxide-based fuel cell electrolyte material according to claim 1, characterized in that: The aluminum oxide is α-Al2O3, and its particle size is 0.1-1 μm.

3. The bismuth oxide-based fuel cell electrolyte material according to claim 1, characterized in that: The coating layer has a gradient structure, and the Zr content increases gradually from 50 at % to 100 at % from the inside to the outside.

4. The method for preparing a bismuth oxide-based fuel cell electrolyte material according to claim 1, characterized in that: The following steps are involved: (1) Wet-milling bismuth oxide, erbium oxide, tungsten oxide, and aluminum oxide powders with anhydrous ethanol for 3-10 hours, and spray drying to obtain a mixed powder; (2) calcining the powder from step (1) at 700-900°C for 2-5h, and sand-milling to obtain doped δ-Bi2O3 powder; (3) dispersing the doped powder in a 0.1-0.3 mol / L zirconium nitrate solution, adding urea and CTAB, and hydrothermally precipitating at 70-100 °C for 2-5 h to form a Zr(OH)4 coating layer; (4) calcining the coated powder at 600-800°C for 2-24h, dry pressing and sintering at 700-900°C.

5. The method for preparing a bismuth oxide-based fuel cell electrolyte material according to claim 4, characterized in that: In step (1), the mass ratio of powder to anhydrous ethanol is (70-80):(20-30), and the ball milling speed is 200-300 rpm.

6. The method for preparing a bismuth oxide-based fuel cell electrolyte material according to claim 3, characterized in that: In step (3), the amount of CTAB added is 0.5-2 parts per 100 parts of doped powder.

7. The method for preparing a bismuth oxide-based fuel cell electrolyte material according to claim 5, characterized in that: The zirconium oxide is coated on the surface of the doped powder to inhibit the reduction of Bi2O3 under low oxygen partial pressure.

8. The method for preparing a bismuth oxide-based fuel cell electrolyte material according to claim 4, characterized in that: In step (3), microwave-assisted hydrothermal precipitation is adopted with a microwave power of 300-500 W, and the precipitation time is shortened to 0.5-1 h.

9. The method for preparing a bismuth oxide-based fuel cell electrolyte material according to claim 4, characterized in that: The calcination in step (4) is carried out in a flowing nitrogen-oxygen mixed gas, wherein the volume fraction of O2 is 5-10%.

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