A spherical cerium oxide-based electrolyte powder material and preparation method thereof

Abstract

This invention discloses a spherical cerium oxide-based electrolyte powder material and its preparation method. The spherical cerium oxide-based electrolyte powder material of this invention is mainly composed of soluble cerium salt, main dopant salt, auxiliary dopant salt, organic additives, and a precipitant; the powder material is micron-sized with a specific surface area of ​​0.84~1.3 m². 2 / g. This invention utilizes the above-mentioned components to prepare a reaction precursor, which is then subjected to hydrothermal treatment, washing, drying, and annealing to obtain cerium oxide-based electrolyte powder material. The cerium oxide-based electrolyte powder preparation process of this invention is simple, exhibiting large particle size, low specific surface area, high sintering activity, and spherical morphology. This significantly improves the solid content of the slurry, reduces the difficulty of sintering and densifying the electrolyte layer, and promotes the widespread application of SOFC batteries.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cell technology, specifically to a spherical cerium oxide-based electrolyte powder material and its preparation method. Background Technology

[0002] Solid oxide fuel cells (SOFCs) are devices that efficiently convert chemical energy directly into electrical energy. They are environmentally friendly, have high conversion efficiency, and possess broad application prospects. A typical SOFC structure consists of three parts: an anode, an electrolyte, and a cathode. Both the anode and cathode are made of 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, where redox reactions occur. The dense electrolyte layer serves two purposes: firstly, it isolates the anode and cathode, preventing contact between the gases; secondly, it acts as an oxygen ion conductor, transporting oxygen ions.

[0003] As a crucial component of the battery structure, the performance of the electrolyte layer plays a vital role in the overall performance of SOFCs, directly impacting the performance of the entire battery. Currently, depending on the type of SOFC battery, the mainstream preparation process for the electrolyte layer is screen printing or casting. This typically requires using electrolyte powder as the main material, mixed with various organic solvents, dispersants, binders, and plasticizers to prepare the screen printing / casting paste needed for the screen printing or casting process. Therefore, the performance of the electrolyte powder directly affects the performance of the entire electrolyte layer.

[0004] Since SOFC systems need to operate at high temperatures (600~1000℃) and in redox atmospheres, the electrolyte material must meet conditions such as high ionic conductivity, good high-temperature chemical stability, and good thermomechanical property matching and chemical compatibility with the electrode material. Cerium oxide-based electrolytes (10 mol% gadolinium oxide or samarium oxide-doped cerium oxide) are one of the common SOFC electrolytes. They have good high-temperature stability, and under the same conditions, their oxygen ion conductivity is about three times that of the commonly used 8YSZ (usually 8 mol% yttrium-stabilized zirconium oxide) electrolyte, making them extremely promising for application and promotion.

[0005] Currently, in SOFC batteries, the electrolyte layer needs to be absolutely dense to ensure that the air (oxygen) and fuel gas at the anode and cathode do not come into contact. Therefore, cerium oxide-based electrolyte powder is usually prepared using liquid-phase methods (hydrothermal method, co-precipitation method, etc.) to obtain a powder material with a small particle size and high specific surface area. This allows the powder material to have high sintering activity, enabling the electrolyte layer to be dense during battery fabrication (sintering).

[0006] However, the cerium oxide-based electrolyte powder with small particle size and high specific surface area currently in use is prone to agglomeration and difficult to disperse. On the other hand, it is difficult to formulate screen printing / casting paste with high solid content, which increases the difficulty of making the electrolyte layer dense and ultimately increases the overall manufacturing cost of SOFC battery.

[0007] Existing technologies primarily employ solid-state methods to prepare large-particle cerium oxide-based powder materials. However, due to the large primary particle size, 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 application in SOFC batteries. In addition to solid-state methods, spray granulation can also be used to obtain large-particle, highly fluid spherical cerium oxide-based electrolyte powders. However, the electrolyte powder particles prepared by this method are extremely large (usually above 20 μm) and extremely fragile (generally easily crushed by hand). It is not feasible to maintain the particle size and morphology during the preparation of electrolyte slurry, and can only be applied to processes such as dry pressing or plasma spraying.

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

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a spherical cerium oxide-based electrolyte powder material and its preparation method. Based on existing technologies, a new powder preparation method has been developed, resulting in cerium oxide-based electrolyte powder with large particle size (micrometer scale) and low specific surface area (0.84~1.3 μm). 2 The high sintering activity (can be sintered and densified at 1200℃) and spherical morphology of the slurry can significantly increase the solid content of the slurry, reduce the difficulty of sintering and densifying the electrolyte layer, and promote the application of SOFC batteries.

[0010] To achieve the above objectives, the technical solution designed by the present invention is as follows:

[0011] This invention provides a method for preparing spherical cerium oxide-based electrolyte powder materials, comprising the following steps:

[0012] (1) Preparation of reaction precursor solution: Using water as solvent, soluble cerium salt, main doped salt, auxiliary doped salt, organic additives and precipitant as raw materials, mix them evenly to obtain reaction precursor solution;

[0013] (2) Hydrothermal treatment: The precursor solution is placed in a reaction vessel and kept at a constant temperature to obtain an emulsion;

[0014] (3) Washing and drying: The emulsion is washed and dried to obtain a powder sample;

[0015] (4) Annealing treatment: The powder sample is annealed to obtain spherical cerium oxide-based electrolyte powder material.

[0016] Furthermore, in 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.

[0017] 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.

[0018] Furthermore, in step (1), the main doping salt is any one or a combination of two of gadolinium salt and samarium salt; wherein, in the reaction precursor solution, the molar ratio of cerium ions to the 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.

[0019] Furthermore, the main doping salt is a combination of gadolinium nitrate and samarium nitrate, wherein the molar ratio of cerium ions to the cations of the main doping salt is 1:0.11; and the molar ratio of gadolinium ions to samarium ions is 1:0.5.

[0020] 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 the cations of the auxiliary doping salt is 1:0.01~0.06.

[0021] Furthermore, 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.

[0022] Furthermore, in step (1), the organic additive is any one or more combinations of citric acid, polyethylene glycol-400, hexadecyltrimethylammonium 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.

[0023] Furthermore, when the concentration of the organic additive is 0.8 mol / L, and 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.

[0024] 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.

[0025] Furthermore, when urea is used as the precipitant, the molar concentration of urea is 0.4 mol / L;

[0026] Alternatively, when the precipitant is ammonia, the molar concentration of ammonia is 0.4 mol / L.

[0027] Furthermore, in step (2), the heat preservation temperature is 120~180℃ and the treatment time is 6~48 h.

[0028] Furthermore, the heat preservation treatment temperature is 140~160℃, and the treatment time is 12~24 h.

[0029] Furthermore, in step (3), the drying temperature is 60~80℃;

[0030] In step (4), the annealing temperature is 600~900℃.

[0031] Furthermore, in step (4), the annealing temperature is 900°C.

[0032] 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 m². 2 / g.

[0033] The present invention also provides an application of the spherical cerium oxide-based electrolyte powder material prepared by the above preparation method in the preparation of solid oxide fuel cells.

[0034] The principle of this invention:

[0035] 1. The method of this invention produces a spherical cerium oxide-based micron-sized (1~20 μm) electrolyte powder. The micron-sized morphology of this electrolyte powder is composed of nano-sized primary particles, thus reducing the specific surface area of ​​the powder (0.84~1.3 μm). 2 Even after ( / g), it still exhibits good sintering activity.

[0036] 2. This invention primarily controls the morphology and particle size of the cerium oxide-based micron-sized electrolyte powder by controlling the concentration and type of organic additives. In solution, part of the organic additives complexes with cations in the solution, while another part fills various parts of the solution, acting as a dispersant. This further hinders the random aggregation of small particles during the hydrothermal process, resulting in the described micron-sized spherical aggregates.

[0037] 3. This invention uses soluble cerium salts, dopant salts, precipitants, and organic additives as reactants. By controlling the concentrations of cerium salts and dopant salts, the concentration and type of precipitants, and the concentration and type of organic additives, cerium oxide-based electrolyte powders with large size, small specific surface area, good dispersibility, high purity, and good sintering activity can be obtained. Electrolyte sheets prepared from this electrolyte powder exhibit good ionic conductivity. Furthermore, the process of this invention is simple and low-cost, which is beneficial for large-scale production and for improving the electrical performance of SOFCs.

[0038] The beneficial effects of this invention are:

[0039] 1. The cerium oxide-based electrolyte powder prepared by this invention has a spherical morphology, which improves the powder's flowability and reduces its irregular agglomeration, thereby enabling a greater packing density to be obtained during the green body preparation process.

[0040] 2. The cerium oxide-based electrolyte powder prepared by this invention has a smaller specific surface area, which enables the preparation of slurries with higher solid content, and is more conducive to the preparation of denser electrolyte layers by thin film preparation processes such as screen printing.

[0041] 3. The cerium oxide-based electrolyte powder prepared by this invention can achieve higher density in the green stage, thus the sintering temperature required for battery preparation can be reduced to a lower level (1100℃), which is more conducive to the production and application of SOFC batteries. Attached Figure Description

[0042] Figure 1 A process flow diagram for the preparation of a cerium oxide-based electrolyte powder;

[0043] Figure 2 The XRD pattern of a cerium oxide-based electrolyte powder 1;

[0044] Figure 3 SEM image of a cerium oxide-based electrolyte powder 1;

[0045] Figure 4 SEM image of the internal morphology of a cerium oxide-based electrolyte powder 1 particle;

[0046] Figure 5 A cross-sectional SEM image of a cerium oxide-based powder electrolyte sheet;

[0047] Figure 6 Electrochemical impedance spectroscopy for cerium oxide-based powder electrolyte sheets;

[0048] Figure 7 SEM image of cerium oxide-based electrolyte powder 10;

[0049] Figure 8 SEM image of cerium oxide-based electrolyte powder 14;

[0050] Figure 9 SEM image of cerium oxide-based electrolyte powder 20;

[0051] Figure 10 SEM image of cerium oxide-based electrolyte powder 21;

[0052] Figure 11 SEM image of cerium oxide-based electrolyte powder 22;

[0053] Figure 12 SEM image of cerium oxide-based electrolyte powder 23;

[0054] Figure 13 This is a SEM image of cerium oxide-based electrolyte powder 24. Detailed Implementation

[0055] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can understand it.

[0056] This invention provides a method for preparing spherical cerium oxide-based electrolyte powder materials (process flow diagram shown below). Figure 1 (As shown), including the following steps:

[0057] (1) Preparation of reaction precursor solution: Using water as solvent, soluble cerium salt, main doped salt, auxiliary doped salt, organic additives and precipitant as raw materials, mix them evenly to obtain reaction precursor solution;

[0058] 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 dopant 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.

[0059] In the reaction precursor solution, the molar ratio of cerium ions to the 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 the cations of the main doping salt is 1:0.11; and the molar ratio of gadolinium ions to samarium ions is 1:0.5.

[0060] 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 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.

[0061] The organic additive is any one or more combinations of citric acid, polyethylene glycol-400, hexadecyltrimethylammonium 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.

[0062] The precipitant is any one of urea, sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, and ammonia water. In the reaction precursor solution, the molar concentration of the precipitant 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.

[0063] (2) Hydrothermal treatment: The precursor solution is placed in a reaction vessel and kept at a constant temperature to obtain an emulsion;

[0064] The heat preservation treatment temperature is 120~180℃, and the treatment time is 6~48 h.

[0065] (3) Washing and drying: The emulsion is washed and dried to obtain powder samples; the drying temperature is 60~80℃.

[0066] (4) Annealing treatment: The powder sample is annealed to obtain spherical cerium oxide-based electrolyte powder material; the annealing temperature is 600~900℃.

[0067] The spherical cerium oxide-based electrolyte powder material has a particle size of 1 μm to 20 μm; and its specific surface area is 0.84 to 1.3 m².2 / g.

[0068] Example 1

[0069] A method for preparing a spherical cerium oxide-based electrolyte powder 1 includes the following steps:

[0070] 1. Preparation of the reaction precursor solution: Using water as the solvent, cerium nitrate, gadolinium nitrate, ferric nitrate, organic additives, and urea are mixed and stirred at 60°C until homogeneous. The molar concentrations of cerium nitrate, gadolinium nitrate, ferric nitrate, organic additives (citric acid: polyethylene glycol-400: ethylenediaminetetraacetic acid molar ratio = 0.5:0.2:0.3) are 0.2 mol / L, and urea is 0.4 mol / L.

[0071] 2. Hydrothermal treatment: The prepared precursor solution is placed in a hydrothermal reactor (the relevant equipment and operating methods should be familiar to those skilled in the art), and then kept at 140°C for 24 h to obtain an emulsion;

[0072] 3. Washing and drying: The emulsion obtained after hydrothermal treatment is washed three times with deionized water and anhydrous ethanol. The washing method can be vacuum filtration or centrifugation (the relevant equipment and operation methods should be well known to those skilled in the art). Then, it is kept at 80°C in an oven until the powder is completely dry to obtain a powder sample.

[0073] 4. Annealing treatment: The dried powder sample is placed in a corundum crucible and then annealed in a muffle furnace at a temperature of 900℃ for 2 hours (the relevant equipment and operating methods should be well known to those skilled in the art). After annealing, spherical cerium oxide-based electrolyte powder 1 is obtained.

[0074] Performance testing of the spherical cerium oxide-based electrolyte powder 1 prepared in Example 1 above:

[0075] 1. XRD analysis was performed on spherical cerium oxide-based electrolyte powder 1. Figure 2 As can be seen, the diffraction peaks of the powder are completely consistent with the standard PDF of 10GDC (10mol% gadolinium-doped cerium oxide) powder, and there are no impurity phases.

[0076] 2. SEM analysis was performed on spherical cerium oxide-based electrolyte powder 1, from... Figure 3 It can be seen that the cerium oxide-based electrolyte powder 1 is spherical in shape, with a particle size greater than 1 μm and a particle size of 1~10 μm. Furthermore, the specific surface area of ​​the powder, as measured by a BET surface area analyzer, is 0.97 m². 2 / g, consistent with SEM image observations, a smaller specific surface area is beneficial for reducing the content of organic solvents, thereby increasing the solid content of powder in casting / screen printing paste.

[0077] 3. The internal morphology of spherical cerium oxide-based electrolyte powder 1 was analyzed by SEM. Figure 4 As can be seen, the interior of the large powder particles is entirely 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.

[0078] 4. Preparation of cerium oxide-based powder electrolyte tablets: 25 wt% PVA aqueous solution (concentration: 3 wt%) was 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 was placed in a steel mold and dry-pressed under a pressure of 300 MPa. After demolding, it was placed in a box furnace and calcined at 1200℃ for 4 h to obtain cerium oxide-based powder electrolyte tablets.

[0079] SEM analysis was performed on the cross-section of the cerium oxide-based powder electrolyte sheet. Figure 5 As can be seen, after sintering at 1200℃, the grain size is around 300 nm, and the cross-sectional fracture mode of the electrolyte sheet is a mixture of dilatational and transgranular fracture, with no pores observed.

[0080] 5. The true density of the cerium oxide-based powder electrolyte tablets was obtained by Archimedes' water displacement method, and was 7.15 g / cm³. 3 The theoretical density of cerium oxide-based materials is 7.2 g / cm3, and the calculated relative density (actual density / theoretical density) of the sintered body is 99.3%, indicating that the ceramic body has been almost completely sintered and dense.

[0081] 7. Ionic conductivity test of cerium oxide-based powder electrolyte sheet: A cerium oxide-based powder electrolyte sheet was used, with silver paste uniformly coated on both sides as electrodes. Two silver wires were fixed on the silver electrodes on each side as conductors. The prepared sample was placed in a tube furnace and heated to 800°C in an air atmosphere. The temperature was then maintained for 30 min 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. The ionic conductivity of the cerium oxide-based powder prepared in this invention can then be obtained.

[0082] EIS analysis was performed on cerium oxide-based powder electrolyte tablets, from Figure 6As can be seen, the resistivity of the cerium oxide-based electrolyte powder at 800℃ is 10.2 Ω·cm, and the converted conductivity is 0.098 S / cm, which is about three times that of the common YSZ electrolyte (0.03 S / cm). This indicates that the spherical cerium oxide-based electrolyte powder 1 has good ionic conductivity and can meet the requirements of SOFC.

[0083] In summary, the spherical cerium oxide-based electrolyte powder 1 can be sintered to a dense state at 1200℃, while under normal circumstances, the sintering temperature of cerium oxide-based electrolyte powder is usually greater than 1400℃. This indicates that the spherical cerium oxide-based electrolyte powder 1 of this embodiment, with its larger particle size, has sintering activity far exceeding that of general cerium oxide-based electrolyte powder, and is more likely to obtain a dense electrolyte layer in the preparation process of SOFC single cells.

[0084] Examples 2-7

[0085] The preparation methods of spherical cerium oxide-based electrolyte powders in Examples 2-7 are the same as those in Example 1, except that the concentration of the metal salt solution is different, as detailed below:

[0086] Example 2: The concentration of metal salt ions 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;

[0087] Example 3: The concentration of metal salt ions was increased by 2 times, with a molar concentration of cerium nitrate of 0.2 mol / L, a molar concentration of gadolinium nitrate of 0.022 mol / L, and a molar concentration of ferric nitrate of 0.003 mol / L;

[0088] Example 4: The concentration of metal salt ions was increased by 4 times, with a molar concentration of cerium nitrate of 0.4 mol / L, a molar concentration of gadolinium nitrate of 0.044 mol / L, and a molar concentration of ferric nitrate of 0.006 mol / L;

[0089] Example 5: The concentration of metal salt ions was increased by 6 times, with a molar concentration of cerium nitrate of 0.6 mol / L, a molar concentration of gadolinium nitrate of 0.066 mol / L, and a molar concentration of ferric nitrate of 0.009 mol / L;

[0090] Example 6: The concentration of metal salt ions was increased by 8 times, with a molar concentration of cerium nitrate of 0.8 mol / L, a molar concentration of gadolinium nitrate of 0.088 mol / L, and a molar concentration of ferric nitrate of 0.012 mol / L;

[0091] 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.

[0092] Table 1 shows the test results of cerium oxide-based electrolyte powders 2-7 prepared in Examples 2-7. As can be seen from Table 1, when all 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 2-7 prepared in Examples 2-7 is all between 1 and 10 μm, and the specific surface area is between 0.96 and 1.3 m². 2 The sintered bodies all exhibited high sintering density, indicating that changing the concentration of the metal salt solution did not affect the particle size and specific surface area of ​​the powder. However, electrical performance tests showed that the ionic conductivity of the prepared cerium oxide-based electrolyte powder continuously decreased with increasing metal salt solution concentration. This is because simply changing the concentration of the metal salt solution, while keeping the molar amount of precipitant constant, resulted in two issues: firstly, the metal ions in the solution were limited by Ksp and could not co-precipitate; secondly, a large number of metal ions in the solution could not precipitate due to insufficient precipitant, thus leading to a continuous decrease in the ionic conductivity of the cerium oxide-based electrolyte powder.

[0093] Therefore, in the preparation method of the 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 doped salt is 0.0055~0.11 mol / L, and the optimal molar concentration of the auxiliary doped salt is 0.00075~0.015 mol / L.

[0094] Table 1. Test results of cerium oxide-based electrolyte powders 2-7

[0095]

[0096] Examples 8-13

[0097] The preparation methods of cerium oxide-based electrolyte powders 8-13 in Examples 8-13 are the same as those in Example 1, except that the concentration of the metal salt ion is increased while the concentration of the precipitant is increased proportionally, as shown in Table 2.

[0098] Table 2. Concentrations of metal salt ions and precipitants in Examples 8-13

[0099]

[0100] Table 3 shows the test results of cerium oxide-based electrolyte powders 8-13 prepared in Examples 8-13. As can be seen from the table, in Examples 8 and 9, the primary particle size range of cerium oxide-based electrolyte powders 8 and 9 remains 1-10 μm, and the specific surface area is 0.95-0.98 m². 2 / g, after sintering at 1200℃, the sintered body has high density and a relatively high ionic conductivity. However, with further increases in 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, the SEM image reveals the coexistence of large particles (around 10 μm) and small particles (around 0.5 μm). Therefore, the specific surface area of ​​the powder continuously increases starting from Example 10, leading to a decrease in sintering density and ionic conductivity. This may be because as the concentration of metal ions and precipitant increases, the number of small particles precipitating in the solution also increases, making it more difficult for small particles to regularly aggregate into large spherical particles. In this case, some small particles can no longer regularly aggregate into a large spherical particle.

[0101] Therefore, in the preparation method of the 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.

[0102] Table 3 Test results of cerium oxide-based electrolyte powders 8-13

[0103]

[0104] Examples 14-19

[0105] The preparation methods of spherical cerium oxide-based electrolyte powders in Examples 14-19 are the same as those in Example 9, except that the concentration of organic additives is different, as shown in Table 4.

[0106] Table 4 Citric acid concentrations in Examples 14-19

[0107]

[0108] Table 5 shows the test results of cerium oxide-based electrolyte powders prepared in Examples 14-19. The table shows that when 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 sintering density all initially increase and then remain constant, while the ionic conductivity of the sintered body initially increases and then decreases sharply. This may be because when the concentration of the organic additive is low, the small particles cannot agglomerate into larger particles as regularly as designed in this invention.

[0109] like Figure 8 As shown in the figure, the cerium oxide-based electrolyte powder 14 prepared in Example 14 exhibits a particle morphology of coexisting large particles of approximately 2 μm and small particles of approximately 0.2 μm. This particle size distribution leads to a decrease in the sintering density of the powder, thereby further affecting the ionic conductivity. Furthermore, when the concentration of organic additives is high, citric acid, being an acidic substance, reacts with the alkaline precipitant. This results in insufficient concentration of the precipitant for metal ions in the solution to co-precipitate, ultimately causing a sharp decrease in the ionic conductivity of the sintered body.

[0110] Therefore, in the preparation method of the 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.

[0111] Table 5 Test results of cerium oxide-based electrolyte powders 14-19

[0112]

[0113] Examples 20-24

[0114] The preparation method of the spherical cerium oxide-based electrolyte powders in Examples 20-24 is the same as that in Example 9, except that the type of cerium ion salt provided is different (the total calculated cerium ion concentration is 0.2 mol / L, which remains unchanged), as follows:

[0115] Example 20: Cerium nitrate was replaced with cerium sulfate, and the concentration of cerium sulfate was 0.2 mol / L;

[0116] Example 21: Cerium nitrate was replaced with cerium chloride, and the concentration of cerium chloride was 0.2 mol / L;

[0117] Example 22: Cerium nitrate was replaced with cerium nitrate and cerium sulfate, with the concentration of cerium sulfate being 0.1 mol / L and the concentration of cerium nitrate being 0.1 mol / L;

[0118] Example 23: Cerium nitrate was replaced with cerium sulfate and cerium chloride, with the concentration of cerium sulfate being 0.1 mol / L and the concentration of cerium chloride being 0.1 mol / L;

[0119] Example 24: Cerium nitrate was replaced with cerium nitrate and cerium chloride, with the concentration of cerium nitrate being 0.1 mol / L and the concentration of cerium chloride being 0.1 mol / L.

[0120] Table 6 shows the test results of cerium oxide-based electrolyte powders 20-24 prepared in Examples 20-24. SEM analysis was performed on the cerium oxide-based electrolyte powders 20-24. The results are shown in Table 6 and... Figures 9-13It can be seen that using cerium sulfate alone as the cerium source (Example 20) can yield similar results to using cerium nitrate alone as the cerium source (Example 9): the primary particle size of the powder ranges from 1 to 10 μm, and the specific surface area is 0.99 m². 2 / g, exhibiting high sintering density and good ionic conductivity. However, when cerium nitrate and cerium sulfate are used simultaneously as a mixed cerium source (Example 22), such as Figure 11 As shown, this method can effectively reduce the particle size range of powder to 4~8 μm. Powder in this state also has a small specific surface area, high density of sintered body, and higher ionic conductivity.

[0121] For powder materials, particle size distribution is an important indicator. Generally speaking, the narrower the particle size distribution range, the better the flowability of the powder, which is more conducive to the smooth operation of feeding and other actions in the production process.

[0122] Therefore, in the preparation method of the 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.

[0123] Table 6 Test results of cerium oxide-based electrolyte powder 20-24

[0124]

[0125] Examples 25-30

[0126] The preparation method of the spherical cerium oxide-based electrolyte powders 25-30 in Examples 25-30 is the same as that in Example 9, except that the type of precipitant is different (the molar concentration of the precipitant remains unchanged), as detailed below:

[0127] Example 25: The precipitant is ammonia water;

[0128] Example 26: The precipitant is ammonium carbonate;

[0129] Example 27: The precipitant is ammonium bicarbonate;

[0130] Example 28: The precipitant is sodium hydroxide;

[0131] Example 29: The precipitant is sodium carbonate;

[0132] Example 30: The precipitant is sodium bicarbonate.

[0133] Table 7 shows the test results of cerium oxide-based electrolyte powders prepared in Examples 25-30. As can be seen from the table, the test results show that all the indicators of the powder 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.

[0134] 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, ammonium carbonate, ammonium bicarbonate, sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0135] Table 7 Test results of cerium oxide-based electrolyte powder 25-30

[0136]

[0137] Examples 31-34

[0138] The preparation methods of spherical cerium oxide-based electrolyte powders 31-34 in Examples 31-34 are the same as those in Example 1, except that the main doping salts used are different in type and content. The total concentration of metal salt ions of the main doping salts is 0.011 mol / L, which remains unchanged, as shown in Table 8.

[0139] Table 8. Types and contents of main doped salts in Examples 31-34

[0140]

[0141] Table 9 shows the test results of cerium oxide-based electrolyte powders 31-34 prepared in Examples 31-34. After changing the type and content of the main dopant salt, the performance results were obtained. As can be seen from the table, all performance parameters are at the same level, indicating that changing the type and amount of the main dopant salt has no effect on the performance of the cerium oxide-based electrolyte powder prepared in this invention.

[0142] 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.

[0143] Table 9 Test results of cerium oxide-based electrolyte powders 31-34

[0144]

[0145] Examples 35-38

[0146] The preparation methods of cerium oxide-based electrolyte powders in Examples 35-38 are the same as those in Example 1, except that the types of auxiliary doping salts used are different, as detailed below:

[0147] Example 35: The auxiliary doping salt was bismuth nitrate;

[0148] Example 36: The auxiliary doping salt was copper nitrate;

[0149] Example 37: The auxiliary doping salt was lithium nitrate;

[0150] Example 38: The auxiliary doping salt is cobalt nitrate.

[0151] Table 10 shows the test results of cerium oxide-based electrolyte powders prepared in Examples 35-38. As can be seen from the table, although changing the type of auxiliary dopant salt has no effect on the primary particle size range and specific surface area of ​​the powder, it significantly affects the sintering density of the sintered body, thereby further influencing the ionic conductivity. In this invention, the addition of auxiliary dopant salt can effectively reduce the sintering temperature of the powder, and selecting a suitable auxiliary dopant salt can effectively improve the density of the sintered body, which is more conducive to the performance expression of SOFC batteries.

[0152] 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.

[0153] Table 10 Test results of cerium oxide-based electrolyte powder 35-38

[0154]

[0155] All other parts not described in detail are existing technologies. Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing spherical cerium oxide-based electrolyte powder material, characterized in that: Includes the following steps: (1) Preparation of reaction precursor solution: Using water as solvent, soluble cerium salt, main doped salt, auxiliary doped salt, organic additives and precipitant as raw materials, mix them evenly to obtain reaction precursor solution; (2) Hydrothermal treatment: The precursor solution is placed in a reaction vessel and kept at a constant temperature 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 spherical cerium oxide-based electrolyte powder material; The soluble cerium salt is any one or a combination of two of cerium nitrate and cerium sulfate; and the molar concentration of cerium ions in the reaction precursor solution is 0.05~1 mol / L. The main doping salts are any one or a combination of two of gadolinium and samarium salts; In the reaction precursor solution, the molar ratio of cerium ions to the 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. 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. The organic additive is a combination of citric acid, polyethylene glycol-400 and ethylenediaminetetraacetic acid, with a molar ratio of 0.5:0.2:0.3; and the molar concentration of the organic additive in the reaction precursor solution is 0.2~1 mol / L. The precipitant is any one of urea, sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, and ammonia water. The molar concentration of the precipitant in the reaction precursor solution is 0.2~0.8 mol / L.

2. The preparation method according to claim 1, 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 the 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 ions to the cations of the auxiliary doping salt is 1:0.

015.

3. The preparation method according to claim 1, characterized in that: The concentration of the organic additive is 0.8 mol / L.

4. The preparation method according to claim 1, characterized in that: When urea is used as the precipitant, the molar concentration of urea is 0.4 mol / L; Alternatively, when the precipitant is ammonia, the molar concentration of ammonia is 0.4 mol / L.

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

6. A spherical cerium oxide-based electrolyte powder material prepared by the method of claim 1, characterized in that: The spherical cerium oxide-based electrolyte powder material has a particle size of 1 μm to 20 μm; and its specific surface area is 0.84 to 1.3 m². 2 / g.

7. The application of spherical cerium oxide-based electrolyte powder material prepared by the method described in claim 1 in the preparation of solid oxide fuel cells.

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