A method for producing a porous anode support

Abstract

The application discloses a preparation method of a porous anode support body, and has the characteristics that the method comprises the following steps: S1: ball milling nickel oxide, zirconium oxide, silicon dioxide, a solvent and a binder to obtain a ball milling slurry; drying the ball milling slurry to obtain a mixed powder; S2: tabletting the mixed powder prepared in the step S1, and then performing glue removal sintering to obtain an anode support intermediate; S3: soaking the anode support intermediate prepared in the step S2 in a hydrofluoric acid solution to dissolve silicon, and obtaining the anode support intermediate after silicon dissolution; and S4: performing secondary sintering on the anode support intermediate after silicon dissolution prepared in the step S3 to obtain the porous anode support body. In the application, the silicon dioxide is used as a pore-forming agent, and after the silicon dioxide is dissolved by the hydrofluoric acid, the prepared porous anode support body can increase a three-phase interface of an electrochemical reaction, reduce concentration polarization, and thus improve output power density of a battery and stability of operation.

Description

Technical Field

[0001] This invention belongs to the field of solid oxide fuel cells, and specifically relates to a method for preparing a porous anode support. Background Technology

[0002] Solid oxide fuel cells (SOFCs) are devices that directly convert the chemical energy of fuel gas into electrical energy through electrochemical reactions. Unlike other fuel cells, SOFCs use all-solid-state materials, mainly including a dense solid electrolyte layer, a porous anode layer, and a porous cathode layer. For a complete SOFC cell, in addition to the functional anode, cathode, and electrolyte components, a structural support component is also needed to ensure sufficient mechanical strength for stable long-term operation; this component is the support structure. Based on the support structure, SOFCs are classified into electrolyte-supported, metal-supported, and electrode-supported types. Electrolyte-supported SOFCs were the earliest developed, typically using an electrolyte layer 100-300 micrometers thick as the support. Due to their higher ohmic losses, they mostly operate at high temperatures. Metal-supported SOFCs have complex fabrication processes and are more difficult to manufacture, resulting in relatively less research. Electrode-supported SOFCs can be divided into cathode-supported and anode-supported types. By thinning the electrolyte, the ohmic resistance caused by the electrolyte can be effectively reduced, allowing the SOFC to operate in the intermediate temperature range. The thicker cathode support results in greater polarization resistance and ohmic resistance, making cathode-supported cells relatively uncommon. In contrast, the anode support typically employs a metal-ceramic structure, which has higher mechanical strength and electrical conductivity. Therefore, the anode support is currently the most widely used type of support.

[0003] Nickel-based anode supports are characterized by simple preparation processes, low cost, and high catalytic activity, making nickel oxide the most advantageous anode support material for SOFCs. Besides sufficient strength, anode supports also require high porosity to ensure rapid diffusion of fuel gas to the three-phase reaction interface for participation in the reaction. Simultaneously, they should ensure rapid gas escape after the reaction to reduce concentration polarization and achieve high output power density. To increase the porosity of the anode support, a certain amount of pore-forming agent is often added to the initial powder. This agent volatilizes during the high-temperature sintering process, leaving pores and improving the microstructure of the anode support. Traditional Ni-based composite ceramic anode supports use pore-forming agents such as flour, starch, graphite, carbon powder, lignocellulose, and paper fiber. However, the pyrolysis of these agents creates tortuous gas channels, increasing the gas transport path and length, which is detrimental to rapid gas migration and diffusion. Therefore, further improving the pore structure of nickel-based anode supports and accelerating gas migration and diffusion is of great significance for improving the output power and stability of SOFCs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a porous anode support with uniform pore distribution, high porosity, and the ability to form interconnected pores.

[0005] In a first aspect, the present invention provides a method for preparing a porous anode support, which adopts the following technical solution:

[0006] A method for preparing a porous anode support includes the following steps:

[0007] S1: Nickel oxide, zirconium oxide, silicon dioxide, solvent and binder are ball-milled to obtain a ball-milled slurry; the ball-milled slurry is dried to obtain a mixed powder;

[0008] S2: The mixed powder prepared in step S1 is compressed into tablets, and then debinding and sintering are performed to obtain an anode support intermediate.

[0009] S3: The anode support intermediate prepared in step S2 is immersed in hydrofluoric acid solution to dissolve silicon, and the dissolved silicon anode support intermediate is obtained.

[0010] S4: The silicon-solidified anode support intermediate prepared in step S3 is subjected to secondary sintering to obtain a porous anode support.

[0011] Preferably, in step S1, the mass ratio of silicon dioxide to the total mass of nickel oxide and zirconium oxide is (2~8):(16~20).

[0012] Preferably, in step S1, the particle size of silicon dioxide is 200~400nm.

[0013] Preferably, in step S1, the mass ratio of nickel oxide to zirconium oxide is (8~10):(8~10);

[0014] The solvent is one or more of ethanol and butanone, and the ratio of the mass of the solvent to the total mass of nickel oxide and zirconium oxide is (15~30):(16~20);

[0015] The adhesive is one or more of polyvinyl butyral and polymethyl methacrylate, and the ratio of the adhesive to the total mass of nickel oxide and zirconium oxide is (1~3):(16~20).

[0016] Preferably, in step S1, the ball milling is divided into two ball milling processes. The first ball milling involves mixing nickel oxide, zirconium oxide powder, silicon dioxide, and solvent and then ball milling them. After the first ball milling is completed, a binder is added to the slurry after the first ball milling and ball milling is performed. After the ball milling is completed, a ball milled slurry is obtained.

[0017] More preferably, the first ball milling time is 2-10 hours and the ball milling speed is 50-100 rpm; the second ball milling time is 5-10 hours and the ball milling speed is 50-100 rpm.

[0018] Preferably, in step S1, the drying temperature is 90~150℃ and the drying time is 5~15h.

[0019] Preferably, in step S2, the glue removal temperature is 300~600℃, the glue removal time is 2~6h, the sintering temperature is 900~1300℃, the sintering holding time is 1~5h, and the sintering heating rate is 2~8℃ / min.

[0020] Preferably, in step S3, the concentration of hydrofluoric acid is 30-50 wt%, and the soaking time is 1-4 h.

[0021] Preferably, in step S4, the sintering temperature of the secondary sintering is 900~1300℃, the holding time of the secondary sintering is 1~5h, and the heating rate is 2~8℃ / min.

[0022] Secondly, the present invention provides a porous anode support, which is prepared by the aforementioned preparation method.

[0023] The beneficial effects of this invention are:

[0024] (1) In this invention, silicon dioxide is used as a pore-forming agent. After being dissolved by hydrofluoric acid, the porous anode support prepared has a uniform pore distribution, high porosity, and can form interconnected pores, which is beneficial to gas transport and diffusion. It can increase the three-phase interface of electrochemical reaction, reduce concentration polarization, and thus improve the output power density and operating stability of the battery.

[0025] (2) In this invention, hydrofluoric acid also has a slight etching effect on nickel oxide and zirconium oxide. Therefore, there will be pores formed by etching on the support skeleton of the porous anode support. Thus, while ensuring the strength of the substrate, the porosity can be further improved, thereby further improving the performance of the solid oxide fuel cell. Attached Figure Description

[0026] Figure 1 The process flow diagram of this invention.

[0027] Figure 2 The images show the surface (a) and cross-section (b) of the nickel-based porous anode support in Example 1. Detailed Implementation

[0028] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0029] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0031] The process flow diagram of this invention is as follows: Figure 1 As shown, the specific preparation method can be found in the examples.

[0032] Example 1

[0033] The method for preparing the nickel-based porous anode support in this embodiment includes the following steps:

[0034] S1 Ball Milling: Add 9g of nickel oxide, 9g of zirconium oxide, 2g of silicon dioxide (average particle size of 250nm), and 20g of ethanol to a 1L ball milling jar. Perform the first ball milling for 2 hours at 100rpm. After the first ball milling, a primary slurry is obtained. Add 2g of PVB to the primary slurry and perform a second ball milling for 5 hours at 100rpm. After the ball milling, a slurry is obtained. Place the slurry in an oven and dry it at 100℃ for 5 hours to obtain a mixed powder.

[0035] S2. Pressing and Debinding Sintering: The mixed powder obtained in step S1 is placed in a mold and pressed into a disc with a diameter of 15 mm and a thickness of 0.5 mm. The disc is then placed in a muffle furnace for debinding sintering at a debinding temperature of 400℃ for 2 hours; the sintering temperature is 1200℃ for 2 hours, and the sintering holding time is 5℃ / min. After sintering, an anode support intermediate is obtained.

[0036] S3 Dissolution: The anode support intermediate from step S3 is immersed in 40wt% hydrofluoric acid for 2 hours to dissolve silicon, thus obtaining the dissolved anode support intermediate.

[0037] S4 Sintering: The anode support intermediate after silicon melting in step S3 is placed in a muffle furnace, heated to 1200℃ at 5℃ / min, and sintered at this temperature for 2h to obtain a nickel-based porous anode support.

[0038] SEM image of the nickel-based porous anode support prepared in this embodiment, as shown below. Figure 2 As shown, the surface and cross-section of the anode support exhibit a loose and porous characteristic, with a relatively uniform pore distribution. Figure 2 (b) It can be seen that a small number of holes penetrate the entire support, forming through holes.

[0039] Example 2

[0040] Example 2 is basically the same as Example 1, except that the amount of silicon dioxide added in step S1 of Example 2 is 4.5g.

[0041] Example 3

[0042] Example 3 is basically the same as Example 1, except that the amount of silicon dioxide added in step S1 of Example 3 is 7.7g.

[0043] Comparative Example 1

[0044] The preparation method of the nickel-based porous anode support in this comparative example includes the following steps:

[0045] S1 Ball Milling: Add 9g of nickel oxide, 9g of zirconium oxide, 4.5g of graphite (average particle size of 250nm), and 20g of ethanol to a 1L ball milling jar. Perform the first ball milling for 2 hours at 100rpm. After the first ball milling, a primary slurry is obtained. Add 2g of PVB to the primary slurry and perform the second ball milling for 5 hours at 100rpm. After the ball milling, a slurry is obtained. Place the slurry in an oven and dry it at 100℃ for 5 hours to obtain a mixed powder.

[0046] S2. Pressing and sintering with binder removal: The mixed powder obtained in step S1 is placed in a mold and pressed into a disc to obtain a disc with a diameter of 15 mm and a thickness of 0.5 mm. The disc is then placed in a muffle furnace for binder removal and sintering at a binder removal temperature of 400℃ for 2 hours; the sintering temperature is 1200℃ for 2 hours, and the sintering holding time is 5℃ / min. After sintering, an anode support is obtained.

[0047] Example 4

[0048] The process is basically the same as in Example 1, except that a ball milling process is performed in step S1, as detailed below:

[0049] S1 Ball milling: Add 9g nickel oxide, 9g zirconium oxide, 2g silicon dioxide, 20g ethanol and 2g PVB to a 1L ball milling jar. Ball mill at 100rpm for 7 hours. After ball milling, place the slurry in an oven and dry at 100℃ for 5 hours to obtain a mixed powder.

[0050] Example 5

[0051] It is basically the same as Example 2, except that the soaking time for silicon dissolution is 1 hour.

[0052] Example 6

[0053] It is basically the same as Example 2, except that the soaking time for silicon dissolution is 4 hours.

[0054] Example 7

[0055] The method for preparing the nickel-based porous anode support in this embodiment includes the following steps:

[0056] S1 Ball Milling: Add 8g of nickel oxide, 8g of zirconium oxide, 6g of silicon dioxide (average particle size of 220nm), and 25g of ethanol to a 1L ball milling jar. Perform the first ball milling for 4 hours at a speed of 80rpm. After the first ball milling, a primary slurry is obtained. Add 1g of PVB to the primary slurry and perform a second ball milling for 7 hours at a speed of 80rpm. After the ball milling, a slurry is obtained. Place the slurry in an oven and dry it at 90℃ for 10 hours to obtain a mixed powder.

[0057] S2. Pressing and sintering with binder removal: The mixed powder obtained in step S1 is placed in a mold and pressed into a disc to obtain a disc with a diameter of 15 mm and a thickness of 0.5 mm. The disc is then placed in a muffle furnace for binder removal and sintering at a binder removal temperature of 300℃ for 4 hours; the sintering temperature is 900℃ for 5 hours, and the sintering holding time is 3℃ / min. After sintering, an anode support intermediate is obtained.

[0058] S3 Dissolution: The anode support intermediate from step S3 is immersed in 30wt% hydrofluoric acid for 3 hours to dissolve silicon, thus obtaining the dissolved anode support intermediate.

[0059] S4 Sintering: The anode support intermediate after silicon melting in step S3 is placed in a muffle furnace, heated to 900°C at 5°C / min, and sintered at this temperature for 5 hours to obtain a nickel-based porous anode support.

[0060] Example 8

[0061] The method for preparing the nickel-based porous anode support in this embodiment includes the following steps:

[0062] S1 Ball Milling: Add 10g nickel oxide, 10g zirconium oxide, 5g silica (average particle size 300nm), and 30g ethanol to a 1L ball milling jar. Perform the first ball milling for 8 hours at 50rpm. After the first ball milling, a primary slurry is obtained. Add 3g PVB to the primary slurry and perform a second ball milling for 8 hours at 50rpm. After the ball milling, a slurry is obtained. Place the slurry in an oven and dry it at 120℃ for 5 hours to obtain a mixed powder.

[0063] S2. Pressing and Debinding Sintering: The mixed powder obtained in step S1 is placed in a mold and pressed into a disc with a diameter of 15 mm and a thickness of 0.5 mm. The disc is then placed in a muffle furnace for debinding sintering at a debinding temperature of 500℃ for 2 hours; the sintering temperature is 1300℃ for 1 hour, and the sintering holding time is 7℃ / min. After sintering, an anode support intermediate is obtained.

[0064] S3 Dissolution: The anode support intermediate from step S3 is immersed in 50wt% hydrofluoric acid for 1 hour to dissolve silicon, thus obtaining the dissolved anode support intermediate.

[0065] S4 Sintering: The anode support intermediate after silicon melting in step S3 is placed in a muffle furnace, heated to 1300℃ at 7℃ / min, and sintered at this temperature for 1h to obtain a nickel-based porous anode support.

[0066] The porosity, flexural strength, and electrochemical performance of Examples 1-8 and Comparative Example 1 of this invention were tested. The specific test methods are as follows:

[0067] Porosity was measured using the Archimedes method. The specific test steps were as follows: First, the mass m1 of the sample when dry was measured. Then, the sample was placed in a beaker containing deionized water and heated to boiling on an electric stove for 3 hours. After the temperature cooled to room temperature, the water on the sample surface was wiped off with weighing paper, and the mass m2 of the saturated sample in air was measured. Next, the saturated sample was placed in a tray, and the tray was suspended from the bottom of the balance using a homemade wire. Simultaneously, the tray was immersed in a beaker containing water, and the mass m3 of the saturated sample in water was measured. Finally, the porosity q of the sample was calculated using the formula:

[0068]

[0069] 2. The method for testing flexural strength is as follows:

[0070] During testing, the sample is fixed on a sample stage, and an external load is applied by a universal testing machine. The flexural strength of the sample is calculated using the following formula: σ = (FL) / (wd) 2)

[0071] Where: σ represents the material strength in MPa; F represents the maximum applied force; L represents the length of the sample; w represents the width of the sample; and d represents the thickness of the sample.

[0072] 3. Electrochemical performance testing includes the following steps:

[0073] Preparation of YSZ electrolyte:

[0074] Preparation of YSZ electrolyte slurry: Weigh 0.75 g PVB and 10 g anhydrous ethanol into a beaker, seal it and place it in a 60°C oven. Wait until the PVB in the solution is completely dissolved and the solution becomes viscous to obtain a PVB-ethanol solution.

[0075] Weigh 15 g YSZ, 45 g anhydrous ethanol, 0.75 g DOP (dioctyl phthalate), 0.75 g TEA (triethanolamine) and 0.75 g PEG into a ball mill jar, ball mill for 3 h, then add PVB-ethanol solution and continue ball milling for 2 h to obtain a uniform YSZ electrolyte slurry.

[0076] A YSZ electrolyte membrane was prepared on the surface of a NiO-YSZ anode support using an impregnation method. The specific steps were as follows: one side of the nickel-based porous anode support was adhered with double-sided tape and then placed on the top of a corundum tube; YSZ electrolyte slurry was added to a beaker (the depth of the slurry needed to be greater than the thickness of the anode support), and then the other side of the nickel-based porous anode support (the side without double-sided tape) was completely immersed in the slurry. After 10 seconds, the nickel-based porous anode support was removed from the YSZ slurry, and the nickel-based porous anode support was rotated at a uniform speed to ensure that the electrolyte slurry was evenly distributed on its surface. Then, excess slurry was absorbed with a cotton swab, and the support was allowed to stand for 15 minutes. The above steps were repeated twice to obtain the electrolyte layer; finally, the nickel-based porous anode support with the electrolyte layer was placed in a high-temperature muffle furnace and sintered at 1500℃ for 4 hours. After cooling to room temperature, the nickel-based porous anode support material with the electrolyte layer was obtained.

[0077] Preparation of LSM-YSZ and LSM cathode pastes

[0078] Preparation of LSM cathode paste: 15 g of terpineol and 1.5 g of PVB were placed in a clean beaker, sealed, and placed in a 60°C oven. The PVB in the solution was completely dissolved and the solution became viscous, thus obtaining the PVB-terpineol solution.

[0079] 7.5 g of LSM powder and 15 g of anhydrous ethanol were placed in a ball mill jar and ball-milled for 2 hours to form a uniform slurry. The slurry was then heated and evaporated to dryness to obtain the ball-milled LSM powder. 3 g of PVB-terpineol solution and 2 g of LSM powder were placed in a mortar and ground thoroughly for 2 hours to obtain the LSM cathode slurry.

[0080] Preparation of LSM-YSZ composite cathode paste: Weigh 2g of YSZ powder and 2.5g of LSM powder into a ball mill jar, add 15g of anhydrous ethanol, and ball mill for 2 hours to obtain a paste. Heat the paste to dryness to obtain LSM-YSZ composite powder. Place 2.5g of PVB-terpineol solution and 2g of LSM-YSZ composite powder in a mortar and grind thoroughly for 2 hours to obtain LSM-YSZ composite cathode paste.

[0081] Preparation of SOFC cathode: LSM-YSZ composite cathode paste was coated onto the electrolyte layer of nickel-based porous anode support material with a composite electrolyte layer, and the coating thickness was 20 μm; then dried in an oven at 120 °C for 15 min; the coating was repeated once more according to the same process; thus, composite LSM-YSZ cathode-electrolyte layer-anode support material was obtained.

[0082] Following the preparation method of LSM-YSZ composite cathode, an LSM cathode layer was prepared on an LSM-YSZ composite cathode-electrolyte layer-anode support material, and then SOFC single cell was obtained after sintering at 1100℃ for 3 h.

[0083] Battery performance test

[0084] The assembled SOFC single cells were heated in a tubular furnace using hydrogen as fuel at 750–850 °C. The performance of all cells was tested using an IM6ex electrochemical workstation, with a test voltage range of 0–1.2 V and a voltage scan rate of 5 mV s. -1 The test frequency range is 0.1 to 106 Hz, and the disturbance voltage is 10 mV; the IV cycle curve is measured, and the maximum voltage and maximum current are read from the IV cycle curve; the maximum power density of the battery is calculated according to the following formula.

[0085]

[0086] The test results of porosity and flexural strength of the anode supports prepared in Examples 1-8 and Comparative Example 1 are shown in Table 1; the test results of the maximum power density of the SOFC battery assembled from the anode supports are also shown in Table 1.

[0087] Table 1

[0088]

[0089] The main difference in the preparation methods of Examples 1-3 lies in the amount of silicon dioxide added. Test results show that the higher the amount of silicon dioxide added, the higher the porosity of the nickel-based porous anode support and the lower the bending strength; the maximum power density of the assembled SOFC battery initially increases and then decreases. Examples 1-3 all exhibit good performance, but overall, Example 2 shows the best results.

[0090] In the preparation method of Example 4, only one ball milling was performed. Overall, the nickel-based porous anode support prepared by one ball milling in Example 4 has a lower overall performance compared to the nickel-based porous anode support prepared by two ball milling in Example 2.

[0091] The main difference in the preparation methods of Examples 2, 5, and 6 lies in the silicon immersion time. Data shows that a longer immersion time results in higher porosity and lower bending strength of the nickel-based porous anode support. The maximum power density of the assembled SOFC cells initially increases and then decreases with immersion time. Examples 2 and 5 exhibit better performance, while Example 6 may show a significant performance degradation due to excessive damage to the nickel-based porous anode support matrix during the immersion process.

[0092] Compared with Comparative Example 1, the porosity of the nickel-based porous anode support prepared in Example 2 and the maximum power density of the battery are significantly better than those of the nickel-based porous anode support prepared in Comparative Example 1.

[0093] Examples 7 and 8 mainly involve adjustments to the process parameters in the preparation method, and the performance of the prepared nickel-based porous anode supports will also fluctuate to some extent; however, overall, the nickel-based porous anode supports prepared in Examples 7 and 8 still have good comprehensive performance.

[0094] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a porous anode support, characterized in that, Includes the following steps: S1: Nickel oxide, zirconium oxide, silicon dioxide, solvent and binder are ball-milled to obtain a ball-milled slurry; the ball-milled slurry is dried to obtain a mixed powder; S2: The mixed powder prepared in step S1 is compressed into tablets, and then debinding and sintering are performed to obtain an anode support intermediate. S3: The anode support intermediate prepared in step S2 is immersed in hydrofluoric acid solution to dissolve silicon, and the dissolved silicon anode support intermediate is obtained. S4: The silicon-solidified anode support intermediate prepared in step S3 is subjected to secondary sintering to obtain a porous anode support; In step S3, the concentration of hydrofluoric acid is 30-50 wt%, and the soaking time is 1-3 hours. In step S1, the ratio of the mass of silicon dioxide to the total mass of nickel oxide and zirconium oxide is (2~8):(16~20).

2. The method for preparing the porous anode support according to claim 1, characterized in that, In step S1, the particle size of silicon dioxide is 200~400nm.

3. The method for preparing the porous anode support according to claim 1, characterized in that, In step S1, the mass ratio of nickel oxide to zirconium oxide is (8~10):(8~10); The solvent is one or more of ethanol and butanone, and the ratio of the mass of the solvent to the total mass of nickel oxide and zirconium oxide is (15~30):(16~20); The adhesive is one or more of polyvinyl butyral and polymethyl methacrylate, and the ratio of the adhesive to the total mass of nickel oxide and zirconium oxide is (1~3):(16~20).

4. The method for preparing the porous anode support according to claim 1, characterized in that, In step S1, the ball milling is divided into two ball milling processes. The first ball milling involves mixing nickel oxide, zirconium oxide, silicon dioxide, and a solvent and then ball milling them. After the first ball milling is completed, a binder is added to the slurry after the first ball milling and a second ball milling is performed. After the ball milling is completed, a ball milled slurry is obtained.

5. The method for preparing a porous anode support according to claim 4, characterized in that, The first ball milling time is 2-10 hours, and the ball milling speed is 50-100 rpm; the second ball milling time is 5-10 hours, and the ball milling speed is 50-100 rpm.

6. The method for preparing a porous anode support according to claim 1, characterized in that, In step S2, the adhesive removal temperature is 300~600℃, the adhesive removal time is 2~6h; the sintering temperature is 900~1300℃, the sintering holding time is 1~5h, and the sintering heating rate is 2~8℃ / min.

7. The method for preparing a porous anode support according to claim 1, characterized in that, In step S4, the sintering temperature of the secondary sintering is 900~1300℃, the holding time of the secondary sintering is 1~5h, and the heating rate is 2~8℃ / min.

8. A porous anode support, characterized in that, The porous anode support is prepared using any of the preparation methods described in claims 1 to 7.

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