Spherical cerium oxide-based electrolyte powder material and preparation method thereof

Abstract

The invention discloses a spherical cerium oxide-based electrolyte powder material and a preparation method thereof. The spherical cerium oxide-based electrolyte powder material is mainly prepared from soluble cerium salt, main doping salt, auxiliary doping salt, an organic additive and a precipitator, the powder material is micron-sized, and the specific surface area is 0.84-1.3 m < 2 > / g. The preparation method comprises the following steps: preparing a reaction precursor from the components, and carrying out hydrothermal treatment, washing, drying and annealing treatment on the reaction precursor to obtain the cerium oxide-based electrolyte powder material. The cerium oxide-based electrolyte powder disclosed by the invention is simple in preparation process, and has large granularity, low specific surface, high sintering activity and spherical morphology, so that the solid content of slurry can be remarkably increased, the sintering densification difficulty of an electrolyte layer is reduced, and the popularization and application of an SOFC (Solid Oxide Fuel Cell) are promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cells, and in particular to a spherical cerium oxide-based electrolyte powder material and a preparation method thereof. Background Art

[0002] A solid oxide fuel cell (SOFC) is a device that efficiently converts chemical energy directly into electrical energy. It is environmentally friendly, has high conversion efficiency, and has broad application prospects. The structure of a solid oxide fuel cell generally consists of three parts: an anode, an electrolyte, and a cathode. The cathode and anode are both porous materials, while the electrolyte is a dense solid ceramic. During operation, fuel gas (such as hydrogen or methane) enters the anode, and oxygen (usually air) enters the cathode, completing the redox reaction at the cathode and anode. The dense electrolyte layer not only isolates the cathode and anode, preventing contact between the gases, but also acts as an oxygen ion conductor to transport oxygen ions.

[0003] As a key component of the cell structure, the performance of the electrolyte layer plays a crucial role in the overall performance of the SOFC, directly affecting the performance of the entire cell. Currently, depending on the type of SOFC cell, the mainstream preparation process for the electrolyte layer is screen printing or tape casting. Electrolyte powder is typically used as the primary material, mixed with various organic solvents, dispersants, binders, and plasticizers to prepare the screen printing / tape casting slurry required for the screen printing or tape casting process. Therefore, the performance of the electrolyte powder will directly affect the performance of the entire electrolyte layer.

[0004] Because SOFC systems operate at high temperatures (600-1000°C) in a redox atmosphere, electrolyte materials must meet requirements such as high ionic conductivity, excellent high-temperature chemical stability, and good thermomechanical compatibility with electrode materials. Ceria-based electrolytes (10 mol% gadolinium oxide or samarium oxide-doped ceria) are common SOFC electrolytes. They offer excellent high-temperature stability and, under equivalent conditions, oxygen ion conductivity approximately three times that of the commonly used 8YSZ (typically 8 mol% yttria-stabilized zirconia) electrolyte, making them highly promising for widespread application.

[0005] Currently, in SOFC cells, the electrolyte layer must be absolutely dense to prevent contact between the air (oxygen) and fuel gas at the anode and cathode. Therefore, ceria-based electrolyte powders are typically prepared using liquid-phase methods (hydrothermal, co-precipitation, etc.) to obtain a small-particle, high-specific surface area powder material. This results in high sintering activity, enabling the electrolyte layer to be dense during the cell preparation (sintering) process.

[0006] However, the currently used small-particle, high-specific-surface-weight cerium oxide-based electrolyte powder is prone to agglomeration and difficult to disperse. On the other hand, it is difficult to prepare a screen printing / tape casting slurry with a high solid content, which increases the difficulty of densifying the electrolyte layer and ultimately increases the preparation cost of the entire SOFC cell.

[0007] Existing technologies primarily use solid-phase methods to prepare large-particle cerium oxide-based powder materials. However, due to the large primary particles, the cerium oxide-based powder materials prepared by this method have very low sintering activity, and impurities are easily introduced during the preparation process, affecting the conductivity of the electrolyte. Therefore, they are not feasible for use in SOFC cells. In addition to the solid-phase method, spray granulation is generally used to obtain large-particle, high-flowability spherical cerium oxide-based electrolyte powders. However, the electrolyte powders prepared by this method are extremely large (usually over 20 μm) and extremely fragile (generally easy to crush by hand). It is not feasible to maintain the particle size and morphology during the electrolyte slurry preparation process, and can only be used in processes such as dry pressing or plasma spraying.

[0008] Therefore, it is of great significance to develop a method for preparing cerium oxide-based electrolyte powder materials with large particle size and high sintering activity. Summary of the Invention

[0009] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a spherical cerium oxide-based electrolyte powder material and its preparation method. Based on the existing technology, a new powder preparation method is developed to prepare the cerium oxide-based electrolyte powder with large particle size (micron level), low specific surface area (0.84~1.3 m 2 / g), high sintering activity (can be sintered densely at 1200℃) and spherical morphology, which can significantly increase the solid content of the slurry, reduce the difficulty of sintering and densifying the electrolyte layer, and promote the promotion and application of SOFC batteries.

[0010] To achieve the above purpose, the technical solution designed by the present invention is as follows: The present invention provides a method for preparing a spherical cerium oxide-based electrolyte powder material, comprising the following steps: (1) Preparing a reaction precursor solution: using water as a solvent, a soluble cerium salt, a main doping salt, an auxiliary doping salt, an organic additive and a precipitant as raw materials, mixing them uniformly to obtain a reaction precursor solution; (2) Hydrothermal treatment: placing the reaction precursor solution in a reactor for heat preservation treatment to obtain an emulsion; (3) Washing and drying: The emulsion is washed and dried to obtain a powder sample; (4) Annealing treatment: The powder sample is annealed to obtain a spherical cerium oxide-based electrolyte powder material.

[0011] Furthermore, in the step (1), the soluble cerium salt is any one or a combination of two of cerium nitrate, cerium sulfate and cerium chloride; and the molar concentration of cerium ions in the reaction precursor solution is 0.05-1 mol / L.

[0012] Furthermore, the soluble cerium salt is a combination of cerium nitrate and cerium sulfate, and the molar ratio of cerium nitrate to cerium sulfate is 1:1.

[0013] Furthermore, in step (1), the main doping salt is any one or a combination of gadolinium salt and samarium salt; wherein, in the reaction precursor solution, the molar ratio of cerium ion to cation of the main doping salt is 1:0.1-0.3; when the main doping salt is a combination of gadolinium salt and samarium salt, the molar ratio of gadolinium ion to samarium ion is 1:0.1-4.

[0014] Furthermore, the main doping salt is a combination of gadolinium nitrate and samarium nitrate, wherein the molar ratio of cerium ions to cations of the main doping salt is 1:0.11; and the molar ratio of gadolinium ions to samarium ions is 1:0.5.

[0015] Furthermore, in step (1), the auxiliary doping salt is any one of iron salt, copper salt, cobalt salt, lithium salt and bismuth salt; wherein, in the reaction precursor solution, the molar ratio of cerium ions to cations of the auxiliary doping salt is 1:0.01-0.06.

[0016] Furthermore, the auxiliary doping salt is ferric nitrate or cobalt nitrate, and the molar ratio of cerium ions to cations of the auxiliary doping salt is 1:0.015.

[0017] Furthermore, in step (1), the organic additive is any one or more combinations of citric acid, polyethylene glycol-400, cetyltrimethylammonium bromide, polyvinylpyrrolidone, sodium citrate and ethylenediaminetetraacetic acid; and the molar concentration of the organic additive in the reaction precursor solution is 0.2~1 mol / L.

[0018] Furthermore, the concentration of the organic additive is 0.8 mol / L, and when the organic additive is a combination of citric acid, polyethylene glycol-400 and ethylenediaminetetraacetic acid, the molar ratio of citric acid, polyethylene glycol-400 and ethylenediaminetetraacetic acid is 0.5:0.2:0.3.

[0019] Furthermore, in step (1), the precipitant is any one of urea, sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate and ammonia water, and the molar concentration of the precipitant in the reaction precursor solution is 0.2-0.8 mol / L.

[0020] Furthermore, when the precipitant is urea, the molar concentration of urea is 0.4 mol / L; Alternatively, when the precipitant is aqueous ammonia, the molar concentration of the aqueous ammonia is 0.4 mol / L.

[0021] Furthermore, in step (2), the heat preservation treatment temperature is 120-180° C., and the treatment time is 6-48 h.

[0022] Furthermore, the heat preservation treatment temperature is 140-160° C., and the treatment time is 12-24 h.

[0023] Furthermore, in step (3), the drying temperature is 60-80°C; In the step (4), the annealing temperature is 600-900°C.

[0024] Furthermore, in the step (4), the annealing temperature is 900°C.

[0025] Furthermore, the particle size of the spherical cerium oxide-based electrolyte powder material is 1 μm to 20 μm; and the specific surface area of the spherical cerium oxide-based electrolyte powder material is 0.84 to 1.3 m 2 / g.

[0026] The present invention also provides an application of the spherical cerium oxide-based electrolyte powder material prepared by the preparation method in the preparation of a solid oxide fuel cell.

[0027] Principle of the present invention: 1. The method of the present invention prepares a spherical cerium oxide-based micron-sized (1-20 μm) electrolyte powder. The micron-sized morphology of the electrolyte powder is composed of nano-sized primary particles, thereby reducing the specific surface area of the powder (0.84-1.3 m 2 / g), it still has good sintering activity.

[0028] 2. This invention primarily controls the concentration and type of organic additives to further manipulate the morphology and particle size of the ceria-based micron-sized electrolyte powder. In solution, the organic additive partially complexes with cations in the solution, while another portion fills the solution, acting as a dispersant. This further inhibits the random aggregation of small particles during the hydrothermal process, resulting in the described micron-sized spherical aggregates.

[0029] 3. The present invention utilizes a soluble cerium salt, a doping salt, a precipitant, and an organic additive as reaction raw materials. By controlling the concentrations of the cerium salt and doping salt, the concentration and type of the precipitant, and the concentration and type of the organic additive, a cerium oxide-based electrolyte powder with large size, small specific surface area, good dispersibility, high purity, and excellent sintering activity can be obtained. The electrolyte sheet prepared from this electrolyte powder exhibits excellent ionic conductivity. Furthermore, the present invention features a simple process and low cost, facilitating large-scale production and improving the electrical performance of SOFCs.

[0030] Beneficial effects of the present invention: 1. The morphology of the cerium oxide-based electrolyte powder prepared by the present invention is spherical, which improves the fluidity of the powder and improves the irregular agglomeration of the powder, thereby achieving a higher packing density during the green body preparation process.

[0031] 2. The cerium oxide-based electrolyte powder prepared by the present invention has a smaller specific surface area, thereby being able to prepare a slurry with a higher solid content, which is more conducive to preparing a denser electrolyte layer by thin film preparation processes such as screen printing.

[0032] 3. Since the cerium oxide-based electrolyte powder prepared by the present invention can achieve a higher density in the green stage, the sintering temperature required for battery preparation can be reduced to a lower temperature (1100°C), which is more conducive to the production and application promotion of SOFC batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The following is a process flow chart for preparing a cerium oxide-based electrolyte powder; Figure 2 is an XRD pattern of a cerium oxide-based electrolyte powder 1; Figure 3 is a SEM image of a cerium oxide-based electrolyte powder 1; Figure 4 This is a SEM image of the internal morphology of a cerium oxide-based electrolyte powder 1 particle; Figure 5 This is a cross-sectional SEM image of a cerium oxide-based powder electrolyte sheet; Figure 6 This is the electrochemical impedance spectroscopy of the cerium oxide-based powder electrolyte sheet; Figure 7 is a SEM image of the cerium oxide-based electrolyte powder 10; Figure 8 is a SEM image of the cerium oxide-based electrolyte powder 14; Figure 9 is a SEM image of the cerium oxide-based electrolyte powder 20; Figure 10 is a SEM image of the cerium oxide-based electrolyte powder 21; Figure 11 is a SEM image of the cerium oxide-based electrolyte powder 22; Figure 12 is a SEM image of the cerium oxide-based electrolyte powder 23; Figure 13 2 is a SEM image of the cerium oxide-based electrolyte powder 24. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below with reference to specific embodiments so that those skilled in the art can understand.

[0035] The present invention provides a method for preparing a spherical cerium oxide-based electrolyte powder material (the preparation process flow chart is as follows Figure 1 ), including the following steps: (1) Preparing a reaction precursor solution: using water as a solvent, a soluble cerium salt, a main doping salt, an auxiliary doping salt, an organic additive and a precipitant as raw materials, mixing them uniformly to obtain a reaction precursor solution; The soluble cerium salt is any one or a combination of two of cerium nitrate, cerium sulfate and cerium chloride; and the molar concentration of cerium ions in the reaction precursor solution is 0.05~1 mol / L; the main doping salt is any one or a combination of two of gadolinium salt and samarium salt; preferably, the soluble cerium salt is a combination of cerium nitrate and cerium sulfate, and the molar ratio of cerium nitrate to cerium sulfate is 1:1.

[0036] In the reaction precursor solution, the molar ratio of cerium ions to cations of the main doping salt is 1:0.1~0.3; when the main doping salt is a combination of gadolinium salt and samarium salt, the molar ratio of gadolinium ions to samarium ions is 1:0.1~4; preferably, the main doping salt is a combination of gadolinium nitrate and samarium nitrate, wherein the molar ratio of cerium ions to cations of the main doping salt is 1:0.11; and the molar ratio of gadolinium ions to samarium ions is 1:0.5.

[0037] The auxiliary doping salt is any one of an iron salt, a copper salt, a cobalt salt, a lithium salt and a bismuth salt; wherein, in the reaction precursor solution, the molar ratio of cerium ions to the cations of the auxiliary doping salt is 1:0.01~0.06; preferably, the auxiliary doping salt is ferric nitrate or cobalt nitrate, and the molar ratio of cerium ions to the cations of the auxiliary doping salt is 1:0.015.

[0038] The organic additive is any one or more combinations of citric acid, polyethylene glycol-400, cetyltrimethylammonium bromide, polyvinylpyrrolidone, sodium citrate and ethylenediaminetetraacetic acid; and the molar concentration of the organic additive in the reaction precursor solution is 0.2~1 mol / L; preferably, the concentration of the organic additive is 0.8 mol / L, and when the organic additive is a combination of citric acid, polyethylene glycol-400 and ethylenediaminetetraacetic acid, the molar ratio of citric acid, polyethylene glycol-400 and ethylenediaminetetraacetic acid is 0.5:0.2:0.3.

[0039] The precipitant is urea, any one of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate and ammonia water, and the molar concentration of the precipitant in the reaction precursor solution is 0.2~0.8 mol / L; preferably, when the precipitant is urea, the molar concentration of urea is 0.4 mol / L; or, when the precipitant is ammonia water, the molar concentration of ammonia water is 0.4 mol / L.

[0040] (2) Hydrothermal treatment: placing the reaction precursor solution in a reactor for heat preservation treatment to obtain an emulsion; The insulation treatment temperature is 120~180℃, and the treatment time is 6~48 hours.

[0041] (3) Washing and drying: The emulsion is washed and dried to obtain a powder sample; the drying temperature is 60~80℃.

[0042] (4) Annealing treatment: The powder sample is annealed to obtain a spherical cerium oxide-based electrolyte powder material; the annealing temperature is 600~900℃.

[0043] The particle size of the spherical cerium oxide-based electrolyte powder material is 1 μm to 20 μm; and the specific surface area of the spherical cerium oxide-based electrolyte powder material is 0.84 to 1.3 m 2 / g.

[0044] Example 1 A method for preparing spherical cerium oxide-based electrolyte powder 1 comprises the following steps: 1. Prepare the reaction precursor solution: Use water as the solvent and cerium nitrate, gadolinium nitrate, ferric nitrate, an organic additive, and urea as the raw materials. Mix and stir at 60°C until uniformly mixed. The molar concentration of cerium nitrate is 0.1 mol / L, the molar concentration of gadolinium nitrate is 0.011 mol / L, the molar concentration of ferric nitrate is 0.0015 mol / L, the molar concentration of the organic additive (molar ratio of citric acid: polyethylene glycol-400: ethylenediaminetetraacetic acid = 0.5:0.2:0.3) is 0.2 mol / L, and the concentration of urea is 0.4 mol / L. 2. Hydrothermal Treatment: Place the prepared reaction precursor solution into a hydrothermal reactor (the relevant apparatus and operation method should be familiar to those skilled in the art), and then maintain the temperature at 140°C for 24 hours to obtain an emulsion; 3. Washing and Drying: The emulsion obtained after the hydrothermal treatment is washed three times with deionized water and anhydrous ethanol, respectively. The washing method can be filtration or centrifugation (the relevant equipment and operation methods should be familiar to those skilled in the art). Then, it is kept in an oven at 80°C until the powder is completely dry to obtain a powder sample. 4. Annealing: The dried powder sample is placed in a corundum crucible and then annealed in a muffle furnace at 900°C for 2 hours (the relevant equipment and operation methods should be well known to those skilled in the art). After annealing, spherical ceria-based electrolyte powder 1 is obtained.

[0045] Performance test of the spherical cerium oxide-based electrolyte powder 1 prepared in Example 1 above: 1. XRD analysis was performed on the spherical cerium oxide-based electrolyte powder 1. Figure 2 It can be seen that the diffraction peaks of the powder are completely consistent with the standard PDF of 10GDC (10 mol% gadolinium-doped cerium oxide) powder, without any impurity phase.

[0046] 2. SEM analysis of spherical cerium oxide-based electrolyte powder 1 was performed. Figure 3 It can be seen that the shape of the cerium oxide-based electrolyte powder 1 is spherical, the particle size is greater than 1 μm, and the particle size is 1~10 μm. At the same time, the specific surface area of the powder obtained by the BET specific surface area meter test is 0.97 m 2 / g, which is consistent with the results of SEM observations. A smaller specific surface area is beneficial to reducing the content of organic solvents, thereby increasing the solid content of the powder in the casting / screen printing slurry.

[0047] 3. SEM analysis was performed on the internal morphology of the spherical cerium oxide-based electrolyte powder 1. Figure 4 It can be seen that the interior of the large powder particles is completely composed of smaller nanoparticles. This special structure can reduce the specific surface area of the powder while ensuring that the cerium oxide-based electrolyte powder 1 still has good sintering activity.

[0048] 4. Preparation of cerium oxide-based powder electrolyte sheets: 25 wt% PVA aqueous solution (concentration: 3 wt%) is added to the prepared cerium oxide-based electrolyte powder for granulation (the relevant steps should be well known to those skilled in the art). After granulation, the powder is placed in a steel mold and dry-pressed at a pressure of 300 MPa. After demolding, it is placed in a box-type electric furnace and calcined at 1200°C for 4 h to obtain a cerium oxide-based powder electrolyte sheet.

[0049] The cross section of the cerium oxide based powder electrolyte sheet was analyzed by SEM. Figure 5 It can be seen from the figure that after sintering at 1200℃, the grain size is about 300 nm, the cross-sectional fracture mode of the electrolyte sheet is a mixed fracture of extrinsic and transgranular fracture, and no pores are observed.

[0050] 5. The true density of the cerium oxide-based powder electrolyte sheet was measured by the Archimedes drainage method and was 7.15 g / cm 3 The theoretical density of the cerium oxide-based material is 7.2 g / cm3, and the calculated relative density (true density / theoretical density) of the sintered body is 99.3%, indicating that the ceramic body has been almost completely sintered and dense.

[0051] 7. Ionic conductivity test of cerium oxide-based powder electrolyte sheet: A cerium oxide-based powder electrolyte sheet was used, and silver paste was evenly coated on both sides as electrodes. Two silver wires were fixed on the silver electrodes on each side as conductors. The prepared sample to be tested was placed in a tube furnace, heated to 800°C in an air atmosphere, and then kept warm for 30 minutes to ensure thermal stability of the sample. Finally, the silver wires were connected using an electrochemical workstation, and the electrochemical impedance spectroscopy (EIS) spectrum of the electrolyte sheet was tested using the four-probe method to obtain the ionic conductivity of the cerium oxide-based powder prepared by the present invention.

[0052] EIS analysis of cerium oxide based powder electrolyte sheet was performed. Figure 6 It can be seen that the resistivity of the cerium oxide-based electrolyte powder at 800°C is 10.2 Ω·cm, which is converted to a conductivity of 0.098 S / cm, which is about three times that of the common YSZ electrolyte (0.03 S / cm). This shows that the spherical cerium oxide-based electrolyte powder 1 has good ionic conductivity and can meet the use requirements of SOFC.

[0053] In summary, the spherical cerium oxide-based electrolyte powder 1 can be sintered to a dense state at 1200°C. Under normal circumstances, the sintering temperature of cerium oxide-based electrolyte powder is usually greater than 1400°C. This shows that the spherical cerium oxide-based electrolyte powder 1 of this embodiment has a sintering activity far exceeding that of general cerium oxide-based electrolyte powders while having a larger particle size, and it is easier to obtain a dense electrolyte layer during the preparation process of SOFC single cells.

[0054] Examples 2 to 7 The preparation methods of the spherical cerium oxide-based electrolyte powders 2 to 7 of Examples 2 to 7 are the same as those of Example 1, except that the concentration of the metal salt solution is different, as follows: Example 2: The metal salt ion concentration was reduced to 0.5 times, the molar concentration of cerium nitrate was 0.05 mol / L, the molar concentration of gadolinium nitrate was 0.0055 mol / L, and the molar concentration of ferric nitrate was 0.00075 mol / L; Example 3: The metal salt ion concentration was doubled, the molar concentration of cerium nitrate was 0.2 mol / L, the molar concentration of gadolinium nitrate was 0.022 mol / L, and the molar concentration of ferric nitrate was 0.003 mol / L; Example 4: The metal salt ion concentration was increased by 4 times, the molar concentration of cerium nitrate was 0.4 mol / L, the molar concentration of gadolinium nitrate was 0.044 mol / L, and the molar concentration of ferric nitrate was 0.006 mol / L; Example 5: The metal salt ion concentration was increased by 6 times, the molar concentration of cerium nitrate was 0.6 mol / L, the molar concentration of gadolinium nitrate was 0.066 mol / L, and the molar concentration of ferric nitrate was 0.009 mol / L; Example 6: The metal salt ion concentration was increased 8 times, the molar concentration of cerium nitrate was 0.8 mol / L, the molar concentration of gadolinium nitrate was 0.088 mol / L, and the molar concentration of ferric nitrate was 0.012 mol / L; Example 7: The concentration of metal salt ions was increased 10 times, the molar concentration of cerium nitrate was 1 mol / L, the molar concentration of gadolinium nitrate was 0.11 mol / L, and the molar concentration of ferric nitrate was 0.015 mol / L.

[0055] Table 1 shows the test results of the cerium oxide-based electrolyte powders 2 to 7 prepared in Examples 2 to 7. It can be seen from Table 1 that when other conditions remain unchanged and only the concentration of the metal salt solution is changed, the primary particle size of the cerium oxide-based electrolyte powders 2 to 7 prepared in Examples 2 to 7 is all in the range of 1 to 10 μm, and the specific surface area is 0.96 to 1.3 m 2 / g, and the sintered bodies all have a high sintering density, which shows that changing the concentration of the metal salt solution does not affect the particle size and specific surface area of the powder. However, the electrical performance test results show that as the concentration of the metal salt solution increases, the ionic conductivity of the prepared cerium oxide-based electrolyte powder continues to decrease. This is because after simply changing the concentration of the metal salt solution, the molar amount of the precipitant remains unchanged. On the one hand, the metal ions in the solution are restricted by Ksp and cannot be co-precipitated. On the other hand, a large number of metal ions in the solution cannot be precipitated due to insufficient precipitant, resulting in a continuous decrease in the ionic conductivity of the cerium oxide-based electrolyte powder.

[0056] Therefore, in the preparation method of a spherical cerium oxide-based electrolyte powder material of the present invention, the optimal molar concentration of the soluble cerium salt is 0.05~1 mol / L, the optimal molar concentration of the main doping salt is 0.0055~0.11 mol / L, and the optimal molar concentration of the auxiliary doping salt is 0.00075~0.015 mol / L.

[0057] Table 1 Test results of cerium oxide-based electrolyte powders 2 to 7

[0058] Examples 8 to 13 The preparation method of the cerium oxide-based electrolyte powder 8-13 of Examples 8-13 is the same as that of Example 1, except that the concentration of the precipitant is increased proportionally while the concentration of the metal salt ion is increased, as shown in Table 2.

[0059] Table 2 Metal salt ion and precipitant concentrations of Examples 8 to 13

[0060] Table 3 shows the test results of the cerium oxide-based electrolyte powders 8 to 13 prepared in Examples 8 to 13. It can be seen from the table that in Examples 8 and 9, the primary particle size range of the prepared cerium oxide-based electrolyte powders 8 and 9 is still 1 to 10 μm, and the specific surface area is 0.95 to 0.98 m 2 / g, after sintering at 1200℃, the density of the sintered body is high and its ionic conductivity is also at a high level. However, with the further increase of the concentration of metal ions and precipitant, the primary particle size range of the prepared cerium oxide-based electrolyte powder begins to increase, such as Figure 7 As shown in the SEM image, it can be observed that large particles of 10 μm and small particles of about 0.5 μm coexist. Therefore, the specific surface area of the powder continues to increase from Example 10, which leads to a decrease in sintering density and ionic conductivity. The reason for this may be that as the concentration of metal ions and precipitants increases, the number of small particles precipitated in the solution also increases, and the difficulty of small particles regularly agglomerating into large spherical particles increases. In this case, some small particles can no longer regularly agglomerate into a large spherical particle.

[0061] Therefore, in the method for preparing a spherical cerium oxide-based electrolyte powder material of the present invention, the optimal molar concentration of the precipitant is 0.2-0.8 mol / L.

[0062] Table 3 Test results of cerium oxide-based electrolyte powders 8 to 13

[0063] Examples 14 to 19 The preparation methods of the spherical cerium oxide-based electrolyte powders 14-19 of Examples 14-19 are the same as those of Example 9, with the only difference being the concentration of the organic additive, as shown in Table 4.

[0064] Table 4 Citric acid concentrations of Examples 14 to 19

[0065] Table 5 shows the test results for ceria-based electrolyte powders 14-19 prepared in Examples 14-19. As can be seen from the table, as the concentration of the organic additive gradually increases from 0.05 mol / L to 1 mol / L, the primary particle size, specific surface area, and sintered density initially increase and then remain constant, while the ionic conductivity of the sintered body initially increases and then sharply decreases. This may be because, at low concentrations of the organic additive, small particles cannot aggregate into larger particles in the same regular manner as designed in the present invention.

[0066] like Figure 8 As shown in the figure, it can be seen that the particle morphology of the cerium oxide-based electrolyte powder 14 prepared in Example 14 is a coexistence of large particles of approximately 2 μm and small particles of approximately 0.2 μm. This particle size distribution leads to a decrease in the sintered density of the powder, which further affects the ionic conductivity. When the concentration of the organic additive is high, since the citric acid in the organic additive is an acidic substance, it will react with the alkaline precipitant, resulting in the inability of the metal ions in the solution to co-precipitate due to the insufficient precipitant concentration. The ultimate result is a sharp decrease in the ionic conductivity of the sintered body.

[0067] Therefore, in the method for preparing a spherical cerium oxide-based electrolyte powder material of the present invention, the optimal molar concentration of the organic additive is 0.2-1 mol / L.

[0068] Table 5 Test results of cerium oxide-based electrolyte powders 14 to 19

[0069] Examples 20-24 The preparation method of the spherical cerium oxide-based electrolyte powder 20-24 of Examples 20-24 is the same as that of Example 9, except that the type of cerium ion salt provided is different (the total calculated cerium ion concentration is 0.2 mol / L and remains unchanged), specifically as follows: Example 20: Cerium nitrate is replaced by cerium sulfate, and the concentration of cerium sulfate is 0.2 mol / L; Example 21: Cerium nitrate is replaced by cerium chloride, and the concentration of cerium chloride is 0.2 mol / L; Example 22: Cerium nitrate is replaced by cerium nitrate and cerium sulfate, the concentration of cerium sulfate is 0.1 mol / L, and the concentration of cerium nitrate is 0.1 mol / L; Example 23: Cerium nitrate was replaced by cerium sulfate and cerium chloride, the concentration of cerium sulfate was 0.1 mol / L, and the concentration of cerium chloride was 0.1 mol / L; Example 24: Cerium nitrate was replaced by cerium nitrate and cerium chloride, the concentration of cerium nitrate was 0.1 mol / L, and the concentration of cerium chloride was 0.1 mol / L.

[0070] Table 6 shows the test results of a cerium oxide-based electrolyte powder 20-24 prepared in Examples 20-24. The cerium oxide-based electrolyte powder 20-24 was subjected to SEM analysis. From Table 6 and Figures 9 to 13 It can be seen that using cerium sulfate alone as the cerium source (Example 20) can obtain similar results to using cerium nitrate alone as the cerium source (Example 9): the primary particle size of the powder is in the range of 1-10 μm, and the specific surface area is in the range of 0.99 m 2 / g, has a high sintering density and good ionic conductivity. When cerium nitrate and cerium sulfate are used as mixed cerium sources (Example 22), as shown in Figure 11 As shown, the particle size range of the powder can be effectively reduced to 4~8 μm. In this state, the powder also has a smaller specific surface area, a high density of the sintered body, and higher ionic conductivity.

[0071] For powder materials, particle size distribution is an important indicator. Generally speaking, the narrower the particle size distribution range, the better the fluidity of the powder, which is more conducive to the smooth progress of actions such as feeding in the production process.

[0072] Therefore, in the method for preparing a spherical cerium oxide-based electrolyte powder material of the present invention, the soluble cerium salt is any one or two of cerium nitrate, cerium chloride and cerium sulfate.

[0073] Table 6 Test results of cerium oxide-based electrolyte powders 20-24

[0074] Examples 25-30 The preparation method of the spherical cerium oxide-based electrolyte powder 25-30 of Examples 25-30 is the same as that of Example 9, except that the type of precipitant is different (the molar concentration of the precipitant remains unchanged), and is specifically as follows: Example 25: The precipitant is ammonia water; Example 26: The precipitant is ammonium carbonate; Example 27: The precipitant is ammonium bicarbonate; Example 28: The precipitant is sodium hydroxide; Example 29: The precipitant is sodium carbonate; Example 30: The precipitant is sodium bicarbonate.

[0075] Table 7 shows the test results of cerium oxide-based electrolyte powders 25 to 30 prepared in Examples 25 to 30. As can be seen from the table, the test results show that all indicators of the powders are at the same level, which indicates that changing the type of precipitant has no effect on the performance of the cerium oxide-based electrolyte prepared by the present invention.

[0076] Therefore, in the preparation method of the spherical cerium oxide-based electrolyte powder material of the present invention, the precipitant is any one of ammonia water, ammonium carbonate, ammonium bicarbonate, sodium hydroxide, sodium carbonate and sodium bicarbonate.

[0077] Table 7 Test results of cerium oxide-based electrolyte powder 25~30

[0078] Examples 31-34 The preparation method of spherical cerium oxide-based electrolyte powder 31-34 of Examples 31-34 is the same as that of Example 1, except that the type and content of the main doping salt used are different. The total metal salt ion concentration of the main doping salt is 0.011 mol / L and remains unchanged, as shown in Table 8.

[0079] Table 8 Types and contents of main doping salts in Examples 31 to 34

[0080] Table 9 shows the test results for ceria-based electrolyte powders 31-34 prepared in Examples 31-34. Performance results were obtained after varying the type and content of the primary doping salt. As can be seen from the table, all performance parameters remained at the same level, indicating that varying the type and amount of the primary doping salt had no effect on the performance of the ceria-based electrolyte powders prepared according to the present invention.

[0081] Therefore, in the preparation method of the spherical cerium oxide-based electrolyte powder material of the present invention, the main doping salt is any one or two of samarium nitrate and gadolinium nitrate.

[0082] Table 9 Test results of cerium oxide-based electrolyte powders 31 to 34

[0083] Examples 35-38 The preparation method of the cerium oxide-based electrolyte powder 35-38 of Examples 35-38 is the same as that of Example 1, except that the type of auxiliary doping salt used is different, as follows: Example 35: The auxiliary doping salt is bismuth nitrate; Example 36: The auxiliary doping salt is copper nitrate; Example 37: The auxiliary doping salt is lithium nitrate; Example 38: The auxiliary doping salt is cobalt nitrate.

[0084] Table 10 shows the test results for ceria-based electrolyte powders 35-38 prepared in Examples 35-38. As can be seen from the table, while varying the auxiliary doping salt type has no effect on the primary particle size range and specific surface area of the powders, it significantly impacts the sintered density, which in turn affects the ionic conductivity. In the present invention, the addition of auxiliary doping salts can effectively reduce the sintering temperature of the powders. Selecting the appropriate auxiliary doping salt can effectively improve the density of the sintered body, further enhancing SOFC cell performance.

[0085] Therefore, in the preparation method of the spherical cerium oxide-based electrolyte powder material of the present invention, the auxiliary doping salt is any one of bismuth nitrate, copper nitrate, lithium nitrate and cobalt nitrate.

[0086] Table 10 Test results of cerium oxide-based electrolyte powders 35-38

[0087] Although the above embodiments have been described in detail, they are only a part of the embodiments of the present invention, not all of them. People can also obtain other embodiments based on this embodiment without inventiveness, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a spherical cerium oxide-based electrolyte powder material, characterized in that: The following steps are involved: (1) Preparing a reaction precursor solution: using water as a solvent, a soluble cerium salt, a main doping salt, an auxiliary doping salt, an organic additive and a precipitant as raw materials, mixing them uniformly to obtain a reaction precursor solution; (2) Hydrothermal treatment: placing the reaction precursor solution in a reactor for heat preservation treatment to obtain an emulsion; (3) Washing and drying: The emulsion is washed and dried to obtain a powder sample; (4) Annealing treatment: The powder sample is annealed to obtain a spherical cerium oxide-based electrolyte powder material.

2. The preparation method according to claim 1, wherein: In the step (1), the soluble cerium salt is any one or a combination of two of cerium nitrate, cerium sulfate and cerium chloride; and the molar concentration of cerium ions in the reaction precursor solution is 0.05-1 mol / L; The main doping salt is any one of gadolinium salt and samarium salt or a combination of the two; The molar ratio of cerium ions to cations of the main doping salt in the reaction precursor solution is 1:0.1-0.3; when the main doping salt is a combination of gadolinium salt and samarium salt, the molar ratio of gadolinium ions to samarium ions is 1:0.1-4; The auxiliary doping salt is any one of iron salt, copper salt, cobalt salt, lithium salt and bismuth salt; wherein, in the reaction precursor solution, the molar ratio of cerium ion to cation of the auxiliary doping salt is 1:0.01-0.

06.

3. The preparation method according to claim 2, characterized in that: The soluble cerium salt is a combination of cerium nitrate and cerium sulfate, and the molar ratio of cerium nitrate to cerium sulfate is 1:1; The main doping salt is a combination of gadolinium nitrate and samarium nitrate, wherein the molar ratio of cerium ions to cations of the main doping salt is 1:0.11; and the molar ratio of gadolinium ions to samarium ions is 1:0.5; The auxiliary doping salt is ferric nitrate or cobalt nitrate, and the molar ratio of cerium ion to cation of the auxiliary doping salt is 1:0.

015.

4. The preparation method according to claim 1, wherein: In the step (1), the organic additive is any one or more combinations of citric acid, polyethylene glycol-400, cetyltrimethylammonium bromide, polyvinylpyrrolidone, sodium citrate and ethylenediaminetetraacetic acid; and the molar concentration of the organic additive in the reaction precursor solution is 0.2-1 mol / L.

5. The preparation method according to claim 4, characterized in that: The concentration of the organic additive is 0.8 mol / L. When the organic additive is a combination of citric acid, polyethylene glycol-400 and ethylenediaminetetraacetic acid, the molar ratio of citric acid, polyethylene glycol-400 and ethylenediaminetetraacetic acid is 0.5:0.2:0.

3.

6. The preparation method according to claim 1, characterized in that: In the step (1), the precipitant is any one of urea, sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate and ammonia water, and the molar concentration of the precipitant in the reaction precursor solution is 0.2-0.8 mol / L.

7. The preparation method according to claim 6, characterized in that: When the precipitant is urea, the molar concentration of urea is 0.4 mol / L; Alternatively, when the precipitant is aqueous ammonia, the molar concentration of the aqueous ammonia is 0.4 mol / L.

8. The preparation method according to claim 1, characterized in that: In the step (2), the heat preservation treatment temperature is 120-180°C and the treatment time is 6-48 hours; In the step (3), the drying temperature is 60-80°C; In the step (4), the annealing temperature is 600-900°C.

9. A spherical cerium oxide-based electrolyte powder material prepared by the preparation method of claim 1, characterized in that: The particle size of the spherical cerium oxide-based electrolyte powder material is 1 μm to 20 μm; and the specific surface area of the spherical cerium oxide-based electrolyte powder material is 0.84 to 1.3 m 2 / g.

10. Use of the spherical cerium oxide-based electrolyte powder material prepared by the method of claim 1 in preparing a solid oxide fuel cell.

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