Composite doped bismuth oxide-based sofc electrolyte material with core-shell structure and preparation method and application thereof

Abstract

This invention discloses a core-shell structured composite doped bismuth oxide-based SOFC electrolyte material, its preparation method, and its applications. The preparation method includes the following steps: mixing the doped bismuth oxide-based electrolyte material with a nanoscale highly conductive ionic conductor, adding a binder and a dispersant, and mixing thoroughly to obtain a stable slurry; spray granulating the slurry using a dual-fluid nozzle structure to obtain core-shell structured particles; and hot-air drying the core-shell structured particles followed by sintering to obtain the core-shell structured composite doped bismuth oxide-based SOFC electrolyte material. The core-shell structured composite doped bismuth oxide-based SOFC electrolyte material provided by this invention has advantages such as uniform particle size, good density, high conductivity, and good stability.

Description

Technical Field

[0001] This invention relates to the field of fuel cell and materials processing technology, specifically to a core-shell structured composite doped bismuth oxide-based SOFC electrolyte material, its preparation method, and its application. Background Technology

[0002] Bismuth oxide-based electrolyte materials have been widely used in solid oxide fuel cells (SOFCs) due to their high oxygen ion conductivity at medium and low temperatures. However, pure bismuth oxide and its single dopants suffer from problems such as insufficient phase stability at high temperatures, easy reduction under low oxygen partial pressures, significant volatilization losses, and conductivity decay. Rare earth element doping and bilayer electrolyte structures are currently the mainstream methods to solve the problems of easy reduction and conductivity decay in bismuth oxide-based electrolytes. Some researchers have achieved good electrochemical performance and reduction resistance by preparing YSB and ESB electrolyte thin films through plasma spraying, but these are limited by factors such as the flowability of the raw material powder and the uneven particle size. Existing spray granulation methods can usually only obtain simple doped mixed particles with insufficient particle structure uniformity, making it difficult to achieve ideal electrochemical performance. In addition, existing spray granulation technology has failed to effectively control the internal structure of the particles, resulting in undesirable particle morphology, uneven particle size distribution, low particle density, and a high proportion of hollow particles, which seriously restricts the practical application performance of bismuth-based SOFC electrolyte materials. Summary of the Invention

[0003] In view of the above-mentioned shortcomings, the present invention provides a core-shell structured composite doped bismuth oxide-based SOFC electrolyte material, its preparation method and application. The core-shell structured composite doped bismuth oxide-based SOFC electrolyte material of the present invention has the advantages of uniform particle size, good density, high conductivity and good stability.

[0004] To achieve the above objectives, the present invention provides a method for preparing a core-shell structured composite doped bismuth oxide-based SOFC electrolyte material, comprising the following steps:

[0005] S1. Mix the bismuth oxide-based electrolyte material with a nanoscale highly conductive ionic conductor, add a binder and a dispersant, and mix thoroughly to obtain a stable slurry;

[0006] S2. The slurry is spray-granulated using a spray granulation device with a dual-fluid nozzle structure to obtain core-shell structured particles.

[0007] S3. After the core-shell structured particles are dried by hot air, they are then sintered to obtain a composite doped bismuth oxide-based SOFC electrolyte material with a core-shell structure.

[0008] According to one aspect of the present invention, in step S1, the binder is polyvinyl alcohol (PVA) and its addition amount is 2-5 wt%; the dispersant is polyvinylpyrrolidone (PVP) and its addition amount is 0.5-2 wt%.

[0009] According to one aspect of the present invention, in step S1, the mass ratio of the doped bismuth oxide-based electrolyte material to the nanoscale highly conductive ionic conductor is 70-90:10-30; the doped bismuth oxide-based electrolyte material is Bi2O3-Y2O3 (abbreviated as YSB) or Bi2O3-Er2O3 (abbreviated as ESB); the nanoscale highly conductive ionic conductor is Gd-doped CeO2 (abbreviated as GDC) or Y-doped ZrO2 (abbreviated as YSZ).

[0010] It should be noted that the GDC powder and YSZ powder in this application are both commercially available powders. The CeO2 doping content in GDC is 20 wt% and the ZrO2 doping content in YSZ is 8 wt%.

[0011] It should be noted that the Bi2O3-Y2O3 (YSB) or Bi2O3-Er2O3 (ESB) in this application are all self-made; the doping amount of Y2O3 in Bi2O3-Y2O3 (YSB) is 20-25 wt%; the doping amount of Er2O3 in Bi2O3-Er2O3 (ESB) is 20-25 wt%.

[0012] According to one aspect of the present invention, in step S1, the adhesive is polyvinyl alcohol, and the amount of the adhesive added is 2-5 wt%; the dispersant is polyvinylpyrrolidone, and the amount of the dispersant added is 0.5-2 wt%.

[0013] According to one aspect of the present invention, the doped bismuth oxide-based electrolyte material is prepared by a microemulsion method.

[0014] According to one aspect of the present invention, the preparation process of the Bi2O3-Y2O3 is as follows:

[0015] Bi(NO3)3·5H2O and Y(NO3)3·6H2O were dissolved in deionized water, and surfactants and co-emulsifiers were added to form an aqueous phase. The aqueous phase was slowly added dropwise to an oil phase (n-hexane) containing surfactants and co-emulsifiers, and stirred to form a homogeneous microemulsion system. The microemulsion system was reacted at 60℃ for 4 h to obtain Bi2O3-Y2O3 nanoparticles.

[0016] The preparation process of Bi2O3-Er2O3 is as follows:

[0017] Bi(NO3)3·5H2O and Er(NO3)3·5H2O were dissolved in dilute nitric acid at a molar ratio of 3:1 to form a transparent solution. The transparent solution was added to an oil phase composed of cyclohexane, Triton X-100 and 1-hexanol to form a microemulsion. Ammonia was added to adjust the pH to 8.8-9 to form a precipitate. After centrifugation, washing and drying, the precipitate was calcined at 800℃ for 2 hours to obtain Bi2O3-Er2O3 nanoparticles.

[0018] According to one aspect of the invention, the slurry has a solid content of 30-50 wt%.

[0019] According to one aspect of the present invention, in step S3, the inlet air temperature of the spray granulation molding is 220-280°C, the spray pressure is 1.0-2.5 bar, and the feed rate is 100-130 ml / min.

[0020] According to one aspect of the present invention, in step S3, the temperature of the hot air drying is 50-80°C; the temperature of the sintering treatment is 700-850°C, and the time is 1-3 hours.

[0021] Based on the same inventive concept, the present invention also provides a composite doped bismuth oxide-based SOFC electrolyte material with a core-shell structure prepared by the above preparation method.

[0022] Based on the same inventive concept, the present invention also provides the application of the above-mentioned core-shell structured composite doped bismuth oxide-based SOFC electrolyte material in solid oxide fuel cells.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) Significantly improves the oxygen ion conductivity of the material:

[0025] This invention marks the first time that composite-doped bismuth oxide-based SOFC electrolyte particles with a clearly defined core-shell structure have been directly prepared via spray granulation. The core-shell structure design features a core of highly oxygen-ion-conductive doped bismuth oxide material (such as Bi₂O₃-Y₂O₃ or Bi₂O₃-Er₂O₃) and a shell of nanoscale highly conductive ionic conductors (such as GDC or YSZ). After hot-pressing sintering or plasma spraying to form the electrolyte layer, the nanoscale highly conductive ionic conductor core tightly encapsulates the highly conductive core, effectively forming a continuous and abundant coating layer at the microscale. This protects the bismuth-based electrolyte core from reduction, ensuring a high oxygen ion migration rate. Simultaneously, the nanoscale shell material possesses a higher specific surface area and more active sites, significantly improving the density and activity of the three-phase interface. This allows the oxygen ion conductivity of the electrolyte particles to stably reach above 0.1 S / cm at 600℃.

[0026] (2) Effectively improves the high-temperature phase stability of materials and reduces volatility:

[0027] In existing technologies, pure bismuth oxide electrolytes exhibit poor phase stability at medium and high temperatures, are easily reduced and volatilized under low oxygen partial pressures, and experience rapid performance degradation. The core-shell structured electrolyte particles proposed in this invention introduce Y₂O₃ or Er₂O₃ dopants into the core material, effectively stabilizing the high-temperature δ-phase structure of Bi₂O₃. The shell material, which is not easily reduced, forms a physical barrier on the particle surface, effectively suppressing the volatilization and structural changes of bismuth at high temperatures. This significantly improves the long-term stability and durability of the electrolyte material, extending the actual working life of SOFC batteries.

[0028] (3) Significantly reduces the proportion of hollow particles and improves particle uniformity and density:

[0029] By finely optimizing the slurry composition, viscosity, surface tension, and spray drying parameters in the spray granulation process, nanoscale shell materials are preferentially deposited and form a dense coating layer on the particle surface. This effectively reduces the probability of hollow particle formation during the drying process, lowering the hollow particle ratio to below 5%. Furthermore, the uniform coating structure of the shell effectively ensures high particle size uniformity (D50 = 15-30 μm, D90 ≤ 45 μm), significantly improving the efficiency of subsequent processing steps and the stability of product quality.

[0030] (4) Significantly improves spray granulation yield, reduces production costs, and enhances the economic benefits of industrialization:

[0031] Traditional spray granulation processes suffer from low particle recovery rates due to poor particle morphology and a high proportion of hollow particles. This invention, through core-shell structure design and optimized spray parameters, results in more stable and denser particle structures during spray granulation, significantly improving the effective particle recovery rate to over 85%. Simultaneously, the increased density and uniformity of the particles reduce material loss and costs in subsequent processing and sintering, significantly improving production efficiency and lowering overall production costs, demonstrating clear industrialization advantages. Attached Figure Description

[0032] Figure 1 The images show the microscopic images of the YSB-GDC core-shell composite electrolyte particles prepared in Example 1 of this invention: (a) a partial TEM image of the particles; (b) a partial HRTEM image of the particles; (c) a SAED diffraction pattern of the YSB particles; (d) a SAED diffraction pattern of the GDC particles; (e) a SEM image of the particles; and (f) a particle size distribution diagram.

[0033] Figure 2The images show microscopic images of the ESB-YSZ core-shell composite electrolyte particles prepared in Example 2 of this invention: (a) a partial TEM image of the particles; (b) a partial HRTEM image of the particles; (c) a SAED diffraction pattern of ESB; and (d) a SAED diffraction pattern of YSZ.

[0034] Figure 3 The images show SEM images of the YSB electrolyte particles without GDC coating in Comparative Example 1 of this invention; (a) is a SEM image magnified 1000 times; (b) is a SEM image magnified 100 times.

[0035] Figure 4 The images show the detection results of the undoped Bi2O3 electrolyte particles in Comparative Example 2 of this invention; (a) is a SEM image; (b) is the electrolyte sheet after the test was completed.

[0036] Figure 5 This is a particle size distribution diagram of the electrolyte particles prepared in Comparative Example 4 of the present invention.

[0037] Figure 6 The following are the ionic conductivity curves of the electrolytes in Examples 1-2 and Comparative Examples 1-4 of the present invention: (a) Arrhenius conductivity curve; (b) conductivity at 600°C for different operating times. Detailed Implementation

[0038] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved herein can be purchased commercially or obtained by known methods.

[0039] Example 1

[0040] A method for preparing YSB-GDC core-shell structured composite electrolyte particles. The method includes the following steps:

[0041] S1. A bismuth oxide-based electrolyte material YSB (Bi₂O₃-Y₂O₃) (80 wt%) (particle size 50 nm) is mixed with a nanoscale high-conductivity ion conductor GDC (Gd-doped CeO₂) (20 wt%) (particle size 10 nm). A binder and dispersant are added, and the mixture is thoroughly mixed to obtain a stable slurry. The slurry has a solid content of 40 wt%, a binder of polyvinyl alcohol (PVA) added at 3 wt%, and a dispersant of polyvinylpyrrolidone (PVP) added at 1 wt%. The preparation steps of YSB are as follows: Bi(NO₃)₃· 5H2O and Y(NO3)3·6H2O were dissolved in deionized water at a molar ratio of 3:1. A surfactant (CTAB) and a co-emulsifier (octylphenol polyoxyethylene ether) were added to form an aqueous phase. The aqueous phase was slowly added dropwise to an oil phase (n-hexane) containing surfactant (CTAB) (0.05 mol / L) and co-emulsifier (octylphenol polyoxyethylene ether), and stirred to form a uniform and transparent water-in-oil (W / O) microemulsion system (water-to-oil ratio of 0.3, pH 6.5). The microemulsion system was reacted at 60℃ for 4 h to obtain Bi2O3-Y2O3 nanoparticles (YSB).

[0042] S2. The slurry is sprayed and granulated using a spray granulation device with a dual-fluid nozzle structure to obtain core-shell structured particles; wherein, the parameters for spray granulation are: air inlet temperature 260℃, slurry feed rate 120ml / min, and spray pressure 1.8bar.

[0043] S3. The core-shell structured particles are dried with hot air and then sintered to obtain a composite doped bismuth oxide-based SOFC electrolyte material with a core-shell structure. The hot air drying temperature is 50-80℃; the sintering temperature is 800℃ and the time is 2 hours.

[0044] The electrolyte material prepared above was subjected to microscopic analysis, and the results are as follows: Figure 1 As shown. By Figure 1 As can be seen, the electrolyte particles prepared in Example 1 exhibit a significant core-shell structure with excellent sphericity and particle size distribution of D10 = 12 μm, D50 = 20 μm, and D90 = 35 μm. The particles are dense, with hollow particles accounting for only 4.6%, and the yield reaches 85.7%.

[0045] Example 2

[0046] A method for preparing ESB-YSZ core-shell structured composite electrolyte particles. The method includes the following steps:

[0047] S1. A bismuth oxide-based electrolyte material ESB (Bi₂O₃-Er₂O₃, particle size approximately 200 nm) (80 wt%) was mixed with a nanoscale highly conductive ionic conductor YSZ (Y-doped ZrO₂) (20 wt%) (particle size 10 nm). A binder and dispersant were added, and the mixture was thoroughly mixed to obtain a stable slurry. The slurry had a solid content of 40 wt%, polyvinyl alcohol (PVA) as the binder (3 wt%), and polyvinylpyrrolidone (PVP) as the dispersant (1 wt%). The preparation steps of ESB were as follows: Bi(NO₃)₃·5H₂O and Er(NO₃)₃·5H₂O were dissolved in dilute nitric acid at a molar ratio of 3:1 to form a transparent solution. The transparent solution was added to an oil phase composed of cyclohexane, Triton X-100, and 1-hexanol to form a microemulsion with a water-to-oil ratio of 0.3. Ammonia was added to adjust the pH to approximately 9, resulting in a precipitate. After centrifugation, washing, and drying, ESB powder with a particle size of approximately 200 nm was obtained by calcination at 800°C for 2 hours.

[0048] S2. The slurry is sprayed and granulated using a spray granulation device with a dual-fluid nozzle structure to obtain core-shell structured particles; wherein, the parameters for spray granulation are: air inlet temperature 260℃, slurry feed rate 120ml / min, and spray pressure 1.8bar.

[0049] S3. The core-shell structured particles are dried with hot air and then sintered to obtain a composite doped bismuth oxide-based SOFC electrolyte material with a core-shell structure. The hot air drying temperature is 50-80℃; the sintering temperature is 800℃ and the time is 2 hours.

[0050] The electrolyte material prepared above was subjected to microscopic analysis, and the results are as follows: Figure 2 As shown. By Figure 2 As can be seen, the electrolyte particles prepared in Example 2 exhibit a distinct core-shell structure, excellent sphericity, and a particle size distribution of D10 = 13 μm, D50 = 21 μm, and D90 = 36 μm. The particles are dense, with a hollow particle ratio of 4.8%, and a yield of 84.9%.

[0051] Comparative Example 1

[0052] The difference between this comparative example and Example 1 is that the nanoscale highly conductive ionic conductor GDC is not added. Other steps and parameters are the same as in Example 1.

[0053] The electrolyte particles prepared above were analyzed by scanning electron microscopy (SEM), and the results are as follows: Figure 3 As shown. By Figure 3 It can be seen that the electrolyte particles prepared in Comparative Example 1 have poor sphericity, wide particle size distribution, hollow particle ratio of 12.3%, and yield of 72.1%.

[0054] Comparative Example 2

[0055] The difference between this comparative example and Example 1 is that the bismuth oxide base is not doped; that is, YSB(Bi2O3-Y2O3) is replaced with Bi2O3. Other steps and parameters are the same as in Example 1.

[0056] The electrolyte particles prepared above were analyzed, and the results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the electrolyte particles prepared in Comparative Example 2 have poor sphericity, wide particle size distribution, hollow particle ratio of 15.7%, and yield of 68.9%.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 is that the sintering temperature is 600℃. Other steps and parameters are the same as in Example 1.

[0059] The electrolyte particles prepared above were not sufficiently densified. The prepared electrolyte particles had poor density, a wide particle size distribution, a hollow particle ratio of 20.4%, and a yield of 50.2%.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that the sintering temperature is 800℃. Other steps and parameters are the same as in Example 1.

[0062] Although the electrolyte particles prepared above have a relatively dense morphology, the excessively high sintering temperature led to partial reduction of the bismuth oxide-based material, resulting in significant grain coarsening and a particle size distribution as shown in the figure. Figure 5 As shown, the particle size distribution is D10 = 13 μm, D50 = 35 μm, and D90 = 56 μm. The proportion of hollow particles is 5.8%, and the particle yield is 83.0%.

[0063] Performance testing and results analysis:

[0064] The electrolyte thin films obtained by hot-pressing and sintering the electrolyte particles of Examples 1-2 and Comparative Examples 1-4 were subjected to conductivity tests, and the results are as follows: Figure 6 As shown. By Figure 6It can be seen that the electrolyte of Example 1 exhibits an oxygen ion conductivity of over 0.25 S / cm at 600°C, with a conductivity decrease of less than 20% after 400 hours of continuous testing. This indicates that the introduction of the core-shell structure can effectively improve conductivity. The electrolyte of Example 2 exhibits an oxygen ion conductivity of 0.22 S / cm at 600°C, with a conductivity decrease of less than 22% after 400 hours of continuous testing, demonstrating that the electrolyte of Example 2 of this invention has good electrochemical performance and long-term stability. In contrast, the electrolyte of Comparative Example 1 exhibits an oxygen ion conductivity of only 0.18 S / cm at 600°C, with a conductivity decrease of over 25% after 400 hours of continuous testing, indicating that materials lacking nano-GDC doping have significant disadvantages in terms of electrochemical performance and stability. In Comparative Example 2, the electrolyte exhibited an oxygen ion conductivity of 0.28 S / cm at 600°C. However, at 550°C, the structure became unstable, and the conductivity decreased to only 0.001 S / cm, making further testing impossible. This indicates that the undoped bismuth oxide-based material has significant disadvantages in terms of electrochemical performance and stability. In Comparative Example 3, the electrolyte showed an oxygen ion conductivity of only 0.05 S / cm at 600°C. After 400 hours of continuous testing, the conductivity decreased by more than 80%, indicating that the low sintering temperature resulted in poor material density and a significant decrease in electrochemical performance and stability. In Comparative Example 4, the electrolyte showed an oxygen ion conductivity of 0.20 S / cm at 600°C, 20% lower than that of Example 1. This demonstrates that sintering temperature has a significant impact on the stability and conductivity of the material. This is because higher sintering temperatures lead to grain coarsening, reducing the density of the electrolyte layer and thus decreasing ion conductivity and mechanical strength. Compared to the material prepared without a core-shell structure in Comparative Example 1, the reducing power under low oxygen partial pressure is increased by 4 times and the conductivity is increased by more than 30%, demonstrating the significant superiority and effectiveness of the electrolyte particles in Example 1 of this invention.

[0065] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a composite doped bismuth oxide-based SOFC electrolyte material having a core-shell structure, characterized in that, Includes the following steps: S1. A bismuth oxide-based electrolyte material is mixed with a nanoscale highly conductive ionic conductor, and a binder and dispersant are added. After mixing, a stable slurry is obtained. The mass ratio of the bismuth oxide-based electrolyte material to the nanoscale highly conductive ionic conductor is 70-90:10-30. The bismuth oxide-based electrolyte material is Bi₂O₃-Y₂O₃ or Bi₂O₃-Er₂O₃. The nanoscale highly conductive ionic conductor is Gd-doped CeO₂ or Y-doped ZrO₂. S2. The slurry is spray-granulated using a spray granulation device with a dual-fluid nozzle structure to obtain core-shell structured particles. S3. The core-shell structured particles are dried by hot air and then sintered to obtain a composite doped bismuth oxide-based SOFC electrolyte material with a core-shell structure; wherein the hot air drying temperature is 50-80℃; the sintering temperature is 700-850℃ and the time is 1-3h.

2. The method of producing a composite doped bismuth oxide-based SOFC electrolyte material with a core-shell structure according to claim 1, characterized in that, In step S1, the adhesive is polyvinyl alcohol, and the amount of adhesive added is 2-5 wt%; the dispersant is polyvinylpyrrolidone, and the amount of dispersant added is 0.5-2 wt%.

3. The method for preparing a core-shell structured composite doped bismuth oxide-based SOFC electrolyte material according to claim 1, characterized in that, The doped bismuth oxide-based electrolyte material was prepared using a microemulsion method.

4. The method for preparing the core-shell structured composite doped bismuth oxide-based SOFC electrolyte material according to claim 3, characterized in that, The preparation process of Bi2O3-Y2O3 is as follows: Bi(NO3)3·5H2O and Y(NO3)3·6H2O were dissolved in deionized water, and surfactants and co-emulsifiers were added to form an aqueous phase. The aqueous phase was slowly added dropwise to n-hexane containing surfactants and co-emulsifiers, and stirred to form a homogeneous microemulsion system. The microemulsion system was reacted at 60℃ for 4 h to obtain Bi2O3-Y2O3 nanoparticles. The preparation process of Bi2O3-Er2O3 is as follows: Bi(NO3)3·5H2O and Er(NO3)3·5H2O are dissolved in dilute nitric acid at a molar ratio of 3:1 to form a transparent solution; A clear solution was added to an oil phase consisting of cyclohexane, Triton X-100, and 1-hexanol to form a microemulsion; ammonia was added to adjust the pH to 8.8-9, resulting in a precipitate. After centrifugation, washing, and drying, Bi2O3-Er2O3 nanoparticles were obtained by calcination at 800℃ for 2 hours.

5. The method for preparing a core-shell structured composite doped bismuth oxide-based SOFC electrolyte material according to claim 1, characterized in that, The solid content of the slurry is 30-50 wt%.

6. The method for preparing a core-shell structured composite doped bismuth oxide-based SOFC electrolyte material according to claim 1, characterized in that, In step S3, the inlet air temperature of the spray granulation molding is 220-280 ℃, the spray pressure is 1.0-2.5 bar, and the feed rate is 100-130 ml / min.

7. A composite doped bismuth oxide-based SOFC electrolyte material with a core-shell structure prepared by any one of the preparation methods described in claims 1-6.

8. The application of the core-shell structured composite doped bismuth oxide-based SOFC electrolyte material according to claim 7 in solid oxide fuel cells.

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