KR101254968B1 - Fabricating method of anode for molten carbonate fuel cell - Google Patents

Abstract

The present invention relates to a method for manufacturing an electrode for a molten carbonate fuel cell, comprising mixing and grinding a dispersant, a binder, a plasticizer, an antifoaming agent and a solvent in a mixed metal powder in which a nickel powder and an aluminum powder are mixed in a weight ratio of 91-95: 5-9. Manufacturing a slip, forming the slip by a tape casting method, manufacturing an electrode molded body of a molten carbonate fuel cell, and sintering the molded body at a temperature of 1050 to 1100 ° C, wherein the Provided is a method for producing an electrode for molten carbonate fuel cell, characterized in that the solid content of the mixed metal powder is 61 to 63% by weight based on the sum of the weights of the mixed metal powder and the solvent.

Molten Carbonate Fuel Cell, Cathode, Aluminum, Sintered

Description

Anode manufacturing method for molten carbonate fuel cell {FABRICATING METHOD OF ANODE FOR MOLTEN CARBONATE FUEL CELL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an anode for a molten carbonate fuel cell, comprising a cathode, an anode, an electrolyte of carbonate, and a molten carbonate. In manufacturing a cathode, the present invention relates to a method of sintering a green sheet produced by tape casting by adding aluminum (Al) powder to nickel (Ni).

In general, a molten carbonate fuel cell is composed of a cathode, an anode, an electrolyte, a matrix and a separator plate (FIG. 1), and a liquid carbonate with a reducing cathode and an oxidizing anode atmosphere. (Li ₂ / K ₂ CO ₃ , Li ₂ / Na ₂ CO ₃ ) It is operated at high temperature of 550 ~ 700 ℃ in the presence of electrolyte.

In the 1970s, anodes for molten carbonate fuel cells were mainly manufactured using nickel, but the anodes were exposed to high surface pressure of 1.5-2 kg / cm 2, resulting in sintering and creep of nickel particles, which reduced the reaction area of the cathodes and matrix cracks. There was a problem that caused crossover due to (matrix crack).

In order to suppress the creep of the nickel electrode, by adding chromium (Cr) or aluminum (Al) to the nickel, it is dissolved-strengthening, precipitation-strengthening and oxide-dispersion-enhancing The characteristics were improved by dispersion-strengthening mechanism.

However, the Ni-Cr cathode not only has lower creep resistance than the Ni-Al cathode, but also forms chromium oxide (Cr ₂ O ₃ ) and reacts with the electrolyte, and then forms lithium chromate (LiCrO ₂ ) for electrode instability and long-term operation. Has the problem of causing electrolyte loss.

On the other hand, the Ni-Al cathode is usually not a pure aluminum powder added to nickel, but using a Ni-Al alloy such as NiAl, NiAl ₃ , Ni: Al (95: 5wt%), etc., to creep nickel and Ni-Cr cathode. Although there is no problem with the instability and electrolyte loss, it is necessary to strictly control the sintering atmosphere in order to express the strengthening mechanism (creep suppression) of the added aluminum, and there is a disadvantage that the Ni-Al alloy raw material is expensive.

In addition, the size of the electrode used is increasing from 2500 cm 2 to 7500 cm 2 and 10000 cm 2 according to the large capacity of the molten carbonate fuel cell. The furnace should be used. In order to maintain the atmosphere of the continuous sintering furnace, it is necessary to use a hydrogen curtain that maintains the atmosphere by burning the used hydrogen at the inlet and outlet of the furnace.

In this way, in order to prevent the creep of the cathode electrode and improve the performance by adding aluminum to the nickel as a Ni-Al alloy, the molded article was manufactured by adding aluminum powder to nickel and tape casting the cathode for a molten carbonate fuel cell. The method of sintering in bulk and continuously is not reported.

The present invention provides a method for sintering a molten carbonate fuel cell negative electrode molded body which not only can produce a molded product prepared by adding aluminum powder to nickel in bulk and continuously, but also satisfies porosity, pore size and creep after sintering.

The present invention

As a first aspect, a step of preparing a slip by mixing and grinding a dispersant, a binder, a plasticizer, an antifoaming agent, and a solvent to a mixed metal powder in which a nickel powder and an aluminum powder are mixed in a weight ratio of 91-95: 5-9; Forming an electrode molded body of a molten carbonate fuel cell by molding the slip by a tape casting method; And a step of sintering the molded body at a temperature of 1050 ~ 1100 ℃,

Wherein the solids content of the mixed metal powder is 61 to 63% by weight based on the sum of the weights of the mixed metal powder and the solvent;

As a second aspect, the pulverization is molten carbonate fuel cell electrode manufacturing method, which is to grind the slip to an average particle diameter of 10 to 15㎛,

As a third aspect, the aluminum powder is a method of manufacturing an electrode for molten carbonate fuel cell having an average particle diameter of 8 to 20㎛,

As a fourth aspect, a method of manufacturing an electrode for molten carbonate fuel cell, the viscosity of the slip is 7000 to 20,000 cP,

As a fifth aspect, the dispersant is a method of manufacturing an electrode for molten carbonate fuel cell is added in an amount of 0.5 to 1.5 parts by weight based on 100 parts by weight of mixed metal powder,

As a sixth aspect, the binder is a manufacturing method of an electrode for molten carbonate fuel cell is added in an amount of 4.5 to 8.0 parts by weight based on 100 parts by weight of mixed metal powder,

As a seventh aspect, the plasticizer is a method of manufacturing an electrode for molten carbonate fuel cell is added in an amount of 3.6 to 5.6 parts by weight based on 100 parts by weight of mixed metal powder,

As an eighth aspect, the antifoaming agent provides a method for producing an electrode for molten carbonate fuel cell is added in an amount of 0.5 to 1.5 parts by weight based on 100 parts by weight of the mixed metal powder.

According to the sintering method of the negative electrode specimen for molten carbonate fuel cell of the present invention, not only the negative electrode can be prepared by sintering a molded body prepared by adding aluminum powder to nickel in a large amount and continuously, but also the porosity, pore size and creep after sintering. Provided is a cathode that satisfies.

The present invention manufactures a slip by mixing a dispersant, a binder, a plasticizer, an antifoaming agent, and a solvent with a mixed metal powder composed of nickel and aluminum powder, crushing the slip, and molding the slip by tape casting. By providing a method for producing an electrode for a molten carbonate fuel cell for producing an electrode molded body of a molten carbonate fuel cell, the present invention will be described in more detail with reference to the accompanying drawings.

The cathode electrode of the molten carbonate fuel cell of the present invention uses a mixed metal powder of nickel and aluminum powder, and further includes a dispersant, a binder, a plasticizer, an antifoaming agent, and a solvent.

The nickel powder is preferably 91 to 95% by weight. If the nickel content is less than 91% by weight, the sintering does not proceed, and if it is 95% by weight or more, the excessive porosity and porosity suitable for the negative electrode cannot be obtained.

The aluminum powder is preferably 5 to 9% by weight of the aluminum powder. If aluminum powder is added at less than 5% by weight, sintering of nickel may be promoted and sufficient pores may not be obtained. In addition, aluminum oxide formed by oxidizing aluminum suppresses creep of the nickel electrode, but when the amount of aluminum powder added is less than 5%, it is difficult to distribute such aluminum oxide sufficiently and uniformly. On the other hand, when the aluminum powder is more than 9% by weight, too much aluminum oxide is produced to reduce the performance of the electrode, and it is difficult to control the pore size and porosity of the electrode.

On the other hand, the average particle size of the aluminum powder is preferably 8 to 20㎛, which is difficult to manufacture if the average particle size of aluminum is less than 8㎛, not only expensive, but also difficult to be uniformly mixed with nickel, the average particle diameter If it is larger than 20 mu m, the aluminum is too heavy when sinking the nickel-aluminum slip, and it is difficult to produce a uniform slip.

Ethyl alcohol, toluene, xylene, or the like may be used as the solvent. The solvent is preferably added so that the sum of the solids content of the mixed metal powder is about 61 to 63 wt% based on the sum of the weights of the mixed metal powder and the solvent. If the sum of the solids content of the mixed metal powder is less than 61% by weight, the viscosity of the produced slip becomes too low, making it difficult to produce a uniform molded body with a tape casting device, and if the amount of solvent is too large, uneven drying of the molded body during drying This is because the defective molded body may occur. On the other hand, if the sum of the solids content exceeds 63% by weight, the viscosity of the slip is too high to produce a uniform molded body.

Meanwhile, as the dispersant, a copolymer of an acidic group, for example, a product name BYK110 (BYK Chemie) may be used, and the content thereof is 0.5 to 1.5 parts by weight based on 100 parts by weight of the mixed metal powder. It is preferable that it is about degree. This is because when the dispersant is added in less than 0.5 parts by weight, it is difficult to disperse the powder, and when it is added in excess of 1.5 parts by weight, the slip aggregates.

As the binder, polyvinyl butyral may be used, and the content thereof is preferably about 4.5 to 8.0 parts by weight based on 100 parts by weight of the mixed metal powder. If the binder is added in less than 4.5 parts by weight, the slip can not be molded to produce a sheet, and if it is added in excess of 8.0 parts by weight, the viscosity of the slip increases, making it difficult to manufacture a plate having a suitable thickness.

In addition, dibutyl phthalate may be used as the plasticizer, and the content thereof is preferably about 3.6 to 5.6 parts by weight based on 100 parts by weight of the mixed metal powder. If the plasticizer is added to less than 3.6 parts by weight, the non-plastic slip can not be molded to produce a sheet, and if it is added in excess of 5.6 parts by weight, slip viscosity control becomes difficult.

As the antifoaming agent, an acrylic polymer, for example, the trade name SN-D348 (Sannopco Co.) may be used, and the content thereof is preferably about 0.5 to 1.5 parts by weight based on 100 parts by weight of the mixed metal powder. If the antifoaming agent is added in less than 0.5 parts by weight, it is impossible to remove the bubbles generated during the manufacturing of the slip, if it is added in excess of 1.5 parts by weight it is difficult to produce a plate of a suitable thickness by increasing the viscosity of the slip.

The slip of the present invention may be prepared by adding a solvent, a dispersant, a binder, a plasticizer, and an antifoam simultaneously or separately to the mixed metal powder as described above, and then mixing them.

On the other hand, the slip of the present invention preferably has a viscosity of 7000 to 20,000 cP. This is because if the viscosity of the slip is less than 7000 cP, defects and defects are likely to occur during the process of drying the molded body after tape casting, and if the viscosity is greater than 20,000 cP, a molded product having a uniform thickness cannot be produced. The viscosity of the slip can be adjusted by removing solvent or bubbles by using an evaporator or a deaerator.

In addition, the slip is preferably pulverized through a ball mill or the like so that the particle diameter is about 10 to 15㎛. If the average particle diameter of the slip is smaller than 10 μm or larger than 15 μm, not only the viscosity of the slip in the above range suitable for tape casting can be adjusted, but also the pore size and porosity, which are the basic requirements of the electrode after sintering the electrode, can be adjusted. Because there is no.

The method of the present invention comprises the step of forming the electrode formed by molding the slip formed as described above by a tape casting method. In general, a doctor blade is used for the tape casting method, and the thickness of the manufactured molded product is affected by the height of the doctor blade, the moving speed, the viscosity of the slip, and the shrinkage rate during drying. Therefore, in consideration of these points, the moving speed of the doctor blade is set.

Further, the electrode molded body obtained includes the step of sintering at a temperature of 1050 to 1100 ℃ or less. Sintering the electrode molded body below 1050 ° C. causes the cathode to not be sufficiently sintered to increase porosity, not to be suitable for pore distribution, and to be difficult to apply to a stack because it does not have sufficient strength. When the sintering temperature is higher than 1100 ° C., the sintering of the electrode is promoted and the electrode for molten carbonate fuel cell does not have sufficient porosity and pore distribution. Therefore, it is preferable to sinter the electrode molded body within the above temperature range.

When the negative electrode molded body of the molten carbonate fuel cell is manufactured by the method of the present invention as described above, the negative electrode may be manufactured by sintering the molded body prepared by adding aluminum powder to nickel in a large quantity and continuously, and the electrode obtained thereby is melted. It satisfies the porosity (55 to 65%), the pore size (1.5 to 3.5 mu m) and the creep (10% or less), which are suitable as the cathode of the carbonate fuel cell.

Hereinafter, the present invention will be described in more detail with reference to the following examples.

[Examples 1 to 4 and Comparative Examples 1 to 3]

100 parts by weight of mixed powder obtained by mixing a chain type nickel powder (average particle size 16 µm, INCO) with an aluminum powder having an average particle diameter of 8 µm and 20 µm at a weight ratio shown in Table 1, and 63 parts by weight of ethyl alcohol as a dispersion medium. And 7.04 parts by weight of polyvinyl butyral as a binder and 1 part by weight of BYK110 manufactured by BYK Chemie as a dispersant. The resultant mixture was ball milled at 80 rpm for 3 hours and pulverized first, followed by the addition of a plasticizer and a dispersant, followed by ball milling for 2 hours to prepare a slip.

After removing the air contained in the slip with a vacuum degassing machine for about 10 minutes in the slip produced, the viscosity and particle size analysis was performed, the results are shown in Table 1.

And the molded object was manufactured using the tape casting apparatus on the conditions of the blade gap of 0.8 mm, the speed of 10 cm / min, and the temperature of 50 degreeC. The cathode molded body was sintered in a continuous sintering furnace at a temperature of 1100 ° C. while flowing nitrogen and hydrogen gas, and the results are shown in Table 1.

[Table 1]

nickel aluminum Viscosity (cP)
1.5 rpm Particle size analysis
(Μm) Sintered State 8㎛ 20 탆 Comparative Example 1 85 15 - 11260 10.82 Poor (Crack, Warp) Comparative Example 2 90 10 - 11400 11.24 Poor (break, crack) Comparative Example 3 88 - 12 13600 13.51 Poor (Bending) Example 1 95 5 - 12520 11.99 Good Example 2 95 - 5 10480 12.80 Good Example 3 93 7 - 9440 11.41 Good Example 4 92 - 8 8750 12.34 Good

As can be seen in Table 1, the negative electrode to which aluminum in the mixed powder is added in an amount of 10% by weight or more, the specimen breaks in half or in pieces or cracks when the specimen is sintered regardless of the particle size of the added aluminum. ) And the bending of the specimen. If such a phenomenon exists, it is not suitable for use as an electrode for an actual molten carbonate fuel cell. However, according to the present invention, the electrode added with 5 to 8% by weight of aluminum not only has excellent shape after sintering, but also has sufficient strength to be used as an electrode.

[Examples 5 to 6 and Comparative Examples 4 to 5]

Nickel powder (average particle diameter 16㎛, INCO) and aluminum powder having an average particle diameter of 8㎛ and 20㎛ in the same manner as in Example 1 except that 100 parts by weight of a mixed powder mixed with the weight ratio as shown in Table 2 was added The slip was made.

The slip was manufactured by removing the air contained in the slip with a vacuum deaerator for about 10 minutes, and then a molded article was formed using a tape casting apparatus under conditions of a blade gap of 0.8 mm, a speed of 10 cm / min, and a temperature of 50 ° C. Was prepared. The formed article was sintered in a continuous sintering furnace at a sintering temperature as shown in Table 2 while flowing nitrogen and hydrogen gas.

The porosity and pore distribution of each specimen were measured with a porosimeter using mercury by cutting the sintered specimens 10 mm long, 10 mm long and 0.7-0.8 mm thick. In order to confirm the deformation of the sintered specimens, the specimens were continuously measured at 650 ° C. in a hydrogen atmosphere at a width of 10 mm, a length of 10 mm, and a thickness of 0.7 to 0.8 mm. Creep was calculated as the ratio of deformation thickness to original thickness. The porosity, average pore size and creep results for these specimens are shown in Table 2.

[Table 2]

nickel aluminum Sintering temperature
(℃) Porosity
(%) Pore size
(Μm) Creep
(%) Microstructure 8㎛ 20 탆 Comparative Example 4 97 3 - 1100 44.5 2.1 8.4 5 Comparative Example 5 90 10 - 1100 71.0 6.3 1.9 6 Example 5 95 5 - 1100 60.5 1.7 7.6 7 Example 6 95 - 5 1050 55.5 1.6 4.2 8

As can be seen from Table 2, when the aluminum content of the mixed powder is very small, 3% by weight, the sintering of nickel is promoted, and the porosity is very low, so that the electrode does not have a porosity (55-65%) suitable for the anode for molten carbonate fuel cells. It was not suitable (Comparative Example 4). On the other hand, the creep of the specimen sintered by adding 10% by weight of aluminum to nickel was very good at 1.9%. However, due to the excessive production of aluminum oxide, the conductivity of the cathode was reduced, which was unsuitable, and the porosity was very high. The pore size (1.5-3.5 μm) suitable for the negative electrode for the molten carbonate fuel cell was too large and unsuitable for the negative electrode (Comparative Example 5).

The porosity and pore size of specimens sintered at 1100 ℃ and 1050 ℃ by adding 5wt% of aluminum and 5㎛ aluminum, respectively, are 60.5% and 1.7㎛ and 55.5% and 1.6㎛, respectively. Had

5 to 8 show cross-sectional microstructures of the specimens of Comparative Examples 4 and 5 and Examples 5 and 6, respectively. As can be seen from these microstructures, the specimen of Comparative Example 4 was densely sintered, but the pore size was large, and the Comparative Example 5 specimen had a high porosity and a large pore size, which showed an unsuitable microstructure. The specimens of Examples 5 and 6 exhibited uniform pore size and porosity compared to the comparative examples, and were suitable as the negative electrode. In addition, the creep of these specimens was 7.6% and 4.2%, respectively, and showed similar values to the creep of the specimen in which aluminum alloy was added to nickel, so that there was no problem even after long operation.

1 is a schematic cross-sectional view of a molten carbonate fuel cell.

2 is a photograph showing a broken shape of the electrode manufactured by Comparative Example 2. FIG.

3 is a photograph showing the shape of an electrode of the electrode prepared in Comparative Example 3. FIG.

Figure 4 is a photograph showing the shape of the electrode produced in Example 1.

5 is an electron micrograph showing the microstructure of the electrode prepared in Comparative Example 4.

6 is an electron micrograph showing the microstructure of the electrode prepared in Comparative Example 5.

7 is an electron micrograph showing the microstructure of the electrode prepared in Example 5.

8 is an electron micrograph showing the microstructure of the electrode prepared in Example 6.

Claims (8)

Preparing a slip by mixing and pulverizing a dispersant, a binder, a plasticizer, an antifoaming agent, and a solvent with a mixed metal powder in which a nickel powder and an aluminum powder are mixed in a weight ratio of 91-95: 5-9; Forming an electrode molded body of a molten carbonate fuel cell by molding the slip by a tape casting method; And Sintering the molded body at a temperature of 1050 ~ 1100 ℃, Wherein the solids content of the mixed metal powder is 61 to 63% by weight based on the sum of the weights of the mixed metal powder and the solvent. The method of claim 1, wherein the crushed slip has a mean particle size of 10 to 15㎛, molten carbonate fuel cell electrode manufacturing method, The method of claim 1, wherein the aluminum powder has an average particle diameter of 8 to 20㎛. 2. The method of claim 1, wherein the slip has a viscosity of 7000 to 20,000 cP. The method of claim 1, wherein the dispersing agent is added in an amount of 0.5 to 1.5 parts by weight based on 100 parts by weight of the mixed metal powder. The method of claim 1, wherein the binder is added in an amount of 4.5 to 8.0 parts by weight based on 100 parts by weight of the mixed metal powder. The method of claim 1, wherein the plasticizer is added in an amount of 3.6 to 5.6 parts by weight based on 100 parts by weight of the mixed metal powder. The method of claim 1, wherein the antifoaming agent is added in an amount of 0.5 to 1.5 parts by weight based on 100 parts by weight of the mixed metal powder.

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