KR101185010B1 - Method for manufacturing cathode of cathode supported solid oxide fuel cell - Google Patents

Abstract

An object of the present invention is to provide a manufacturing method that facilitates a manufacturing process, improves product quality, and enables production of a negative electrode plate having a larger area by manufacturing a negative electrode plate of a solid oxide fuel cell manufactured by a press method by a bulk slicing method. It is done.

In the negative electrode plate manufacturing method of the negative electrode support solid oxide fuel cell according to the present invention for achieving the above object, stabilized zirconia (YSZ) powder, nickel oxide (NiO) powder and various additives mixed by wet mixing for 1 to 24 hours. Making a powder; Putting the mixed powder into a mold and pressing the powder at a pressure of 500 to 5000 kg / cm 2 to form a bulk shaped body; Sintering the molded body for 3 to 24 hours at a temperature of 1300 to 1500 ° C; Processing the sintered molded body in the form of a negative electrode plate.

Solid Oxide Fuel Cell, Bulk Slicing Method, Negative Plate, Stabilized Zirconia

Description

Method for manufacturing cathode of cathode supported solid oxide fuel cell

1 is a flow chart of a manufacturing method according to the present invention.

2 is a flow chart of another manufacturing method according to the present invention.

Figure 3 is a flow chart of another manufacturing method according to the present invention.

4 is a flow chart of another manufacturing method according to the present invention.

The present invention relates to a method of manufacturing a cathode plate of a cathode support solid oxide fuel cell (SOFC), and more particularly, by manufacturing a cathode plate using a bulk slicing method, unlike the conventional press method. The present invention relates to a manufacturing method capable of mass production and to improve product quality.

A fuel cell is a power generation device designed to convert chemical energy generated during combustion of a fuel directly into electrical energy by chemically reacting hydrogen and a flammable gas in a battery. Fuel cell is not only high power generation efficiency, but also cogeneration power generation using waste heat of chemical reaction, excellent partial load characteristics, no pollution problems such as pollution of the air environment, noise, etc. It is attracting attention as a new energy field. In addition, since power generation capacity can be arbitrarily adjusted by stacking unit cells, a power generation device having an appropriate capacity can be installed near a real power source and in a building.

The solid oxide fuel cell, which is attracting attention for the next generation's high-capacity power generation, has higher efficiency than the currently known phosphate type, polymer type, and molten carbonate type, and there is no pollution problem, and it can generate a large amount of thermal energy during power generation. A small power generation system such as a power supply unit or the like or a combined power generation system with a gas turbine is possible. Solid oxide fuel cells can be operated at temperatures of 600 ~ 1000 ℃ depending on the type of electrolyte.

Among the fuel cells currently known, the highest total generation efficiency (including waste heat) is a solid oxide fuel cell, which operates at a high temperature of 600 to 1000 ° C., thereby accelerating the electrochemical reaction without using an expensive catalyst and generating high temperature waste heat. It is available. In addition, since carbon monoxide, methane, and the like can be used as the fuel, the fuel pretreatment process is simpler, and the unit cell has a high voltage, which is excellent in terms of power generation efficiency.

A simple structure of a solid oxide fuel cell is described by repeatedly stacking a separator, an anode, an electrolyte, an air cathode, and a separator. Electrolytes are generally stabilized zirconia (Yttria-Stabilized-ZrO ₂ , YSZ), Sc-YSZ, anodes are Ni-ZrO2, and cathodes are Sr-LaMnO ₃ . It exists in the solid state. Electricity is generated by the following electrochemical reaction.

A fuel electrode ^{_{(anode): H 2 + O 2- →}} H 2 O + 2e - (1)

An air electrode ^{_{(cathode): O 2 + 4e - →}} 2O 2 2- (2)

Total reaction: H2 + 1 / 2O ₂ → H ₂ O (3)

The separator of the fuel cell is also called an interconnector as a component that connects the cell, and Sr-doped LaCrO ₃ is most widely used, and as a metal material, CrFe alloy (Cr ₅ FeY ₂ O ₃ ), ferritic stainless steel Ferritic steel is used. The negative electrode plate basically has about 35% by volume of pores through which fuel gas can pass. In the case of the negative electrode support type, a unit cell is formed by electrolytic and positive electrode coating using a negative electrode plate as a substrate.

Currently, negative electrode plates in negative electrode supported solid oxide fuel cells are generally manufactured by using a press method. However, the negative electrode plate manufacturing process by the press method is press molding a single sheet of negative electrode plate, and the manufacturing speed is also slow, and due to the low thickness of the negative electrode plate is less than 2mm, it is difficult to handle the molded body, and even after sintering, it causes various defects. In addition, the press method has a limitation in producing a thin plate-shaped with a considerable size. In addition, in the manufacturing process, each plate is pressed and sintered one by one, so the manufacturing cost is high and product quality does not maintain flatness of the product during sintering, and the plate may be bent, resulting in product defects.

The present invention has been proposed to solve the above problems, by manufacturing the negative electrode plate of the solid oxide fuel cell, which has been conventionally manufactured by the press method by the bulk slicing method, to facilitate the manufacturing process, improve product quality and An object of the present invention is to provide a manufacturing method capable of manufacturing a negative electrode plate.

In the negative electrode plate manufacturing method of the negative electrode support solid oxide fuel cell according to the present invention for achieving the above object, stabilized zirconia (YSZ) powder, nickel oxide (NiO) powder and various additives mixed by wet mixing for 1 to 24 hours. Making a powder; Putting the mixed powder into a mold and pressing the powder at a pressure of 500 to 5000 kg / cm 2 to form a bulk shaped body; Sintering the molded body for 3 to 24 hours at a temperature of 1300 to 1500 ° C; Processing the sintered molded body in the form of a negative electrode plate.

In addition, the forming step and the sintering step may be performed at the same time.

In addition, the step of pre-sintering the stabilized zirconia powder for 30 seconds to 2 hours at 950 ~ 1350 ℃ before the step of making the mixed powder.

In addition, the step of making the mixed powder further comprises the step of drying the mixed powder at 95 ~ 150 ℃, this drying step is to put the mixed powder in a spray dryer (spray dryer) to rotate at 7000 ~ 9000rpm of the mixed powder It is drying while increasing the size.

In addition, the step of processing further includes the step of heat-treating the processed negative plate at 1300 ~ 1500 ℃.

Hereinafter, a method of manufacturing a negative electrode plate of a solid oxide fuel cell for supporting a negative electrode according to the present invention will be described in detail with reference to the accompanying drawings. Figure 1 shows the simplest step constituting the manufacturing method of the present invention, largely composed of powder mixing step, molding step, sintering step, processing step.

The powder mixing step (S10) is a step of wet-mixing various additives such as starch powder to stabilized zirconia (YSZ) powder and nickel oxide (NiO) powder used as raw materials of the negative electrode plate for 1 to 24 hours using a ball mill. Stabilized zirconia reduced the volume change by incorporating oxides such as calcium and yttrium (Y) in zirconia (ZrO ₂ ), whose crystal structure changes from monoclinic to tetragonal at 1150 ° C and changes by 9% in volume. It becomes the main raw material of the negative electrode plate. In wet mixing using a ball mill, the above-mentioned raw powder is agglomerated to form a mixed powder by using the mechanical shearing force of a corner of the ball mill by rotating the ball mill. The raw powder is safely dispersed in a dispersion solvent (water) to uniformly disperse. It is mainly used for the mixing of fine ceramics because one powder can be obtained.

The mixing time depends on the mixing ratio of the raw material powders and the final mixing ratio of the required mixing powder, etc., usually 1 to 24 hours. If the mixing time is less than 1 hour, the mixing ratio above the reference value cannot be obtained, and even if mixing for 24 hours or more, the mixing ratio no longer increases. On the other hand, the various additives include a dispersant, a pore-forming agent (starch powder) and the like.

Forming step (S20) is a step of preparing a bulk-shaped molded product by putting the mixed powder obtained in the powder mixing step into a mold prepared according to the shape of the negative electrode plate, such as a square or a circle, and pressing at a pressure of 500 ~ 5000kg / ㎠. Since the negative electrode plate serves as a substrate in the negative electrode supported fuel cell, its shape varies depending on the shape of the case. Therefore, the molded powder in bulk form, for example, cube or cylinder form, is prepared by putting the mixed powder into a rectangular or circular mold according to the shape of the negative electrode plate and pressing. According to the size of the mold can be produced a very large bulk shaped body, by cutting this can produce a large area negative electrode plate that was impossible by the conventional press method.

The pressure applied during molding depends on the size of the bulk or the porosity of the negative electrode plate, which is usually used in the range of 500 to 5000 kg / ㎠. If the pressure is less than 500kg / ㎠ the strength of the molded body is too weak to be processed in the post-process, while if it exceeds 5000kg / ㎠ the internal porosity of the molded body is too small to be used as a negative electrode plate.

Sintering step (S30) is a step of sintering the molded product obtained in the forming step for 3 to 24 hours at 1300 ~ 1500 ℃. Sintering is a process in which a powder or powdered compact is heated to near the melting point of the constituent particles so as to be bonded or deposited to form a lump, thereby having a certain strength. In the present invention, the sintered compact is heated to a high temperature of 1300 to 1500 ° C in consideration of the fact that stabilized zirconia, nickel oxide and the like, which are constituent particles of the mixed powder, are high melting point materials. If the sintering temperature is less than 1300 ℃ the surface of the mixed powder does not dissolve and do not bond with each other, if the temperature exceeds 1500 ℃ because many parts are dissolved and solidified, the porosity is lowered.

On the other hand, since the sintering process is also performed under a constant pressure, the molding step and the sintering step may be performed simultaneously if the required pressure and temperature range are correct.

The machining step (S40) is a step of cutting the sintered bulk shaped body into a required thickness and shape by using a diamond wheel cutter so that it can be used as a substrate of a fuel cell. As described above, the present invention is called a bulk slicing method because the first production of the molded body in the bulk form and then cutting it to the required specifications to produce a negative electrode plate. As described above, it is possible to produce a large-area negative electrode plate by cutting it according to the size of the bulk.

The manufacturing method of the present invention basically manufactures the negative electrode plate by the four steps described above, but some steps may be added to produce a more precise and excellent quality negative plate.

First, as shown in FIG. 2, the step of pre-sintering the stabilized zirconia powder for 30 seconds to 2 hours at 950 to 1350 ° C. before the mixing powder is made. This pre-sintering step (S5) is to control the porosity by pretreating the stabilizing zirconia powder that is the main raw material of the negative electrode plate before the powder mixing step (S10). As described above, the negative electrode plate should have a high porosity of 35% by volume. When the powders of stabilized zirconia are bonded to each other by plastic sintering to have internal pores, the porosity of the negative electrode plate, which is the final product, is greater than that of the non-plasticized product.

Since stabilized zirconia is a high melting point material, when the sintering temperature is lower than 950 ° C., it is not bonded to each other. If the sintering temperature is higher than 1350 ° C., the powder is bonded too much, making powder mixing difficult in subsequent processes. The sintering time is set between 30 seconds and 2 hours depending on the porosity required by the final product. If it is shorter than 30 seconds, the sintering effect does not appear, and if it is longer than 2 hours, powder mixing becomes difficult due to oversintering.

On the other hand, as shown in Figure 3, after the powder mixing step (S10) may be carried out a step of drying the mixed powder at 95 ~ 150 ℃. This drying step (S15) is for removing moisture contained in the mixed powder. Since the powder mixing step is performed in a wet manner, the mixed powder has a high water content. Therefore, it is preferable to dry the mixed powder first in order to increase energy efficiency in the molding or sintering step which is a post process. If the drying temperature is less than 95 ℃, even after drying, there is still moisture in the mixed powder to increase the energy consumption in the post-process, and if it exceeds 150 ℃ to affect the physical properties of the mixed powder itself.

In the drying step S15, the mixed powder may be placed in a spray dryer and rotated at 7000 to 9000 rpm to increase the size of the mixed powder and to dry it. Increasing the mixed powder is advantageous not only in the later forming and sintering processes but also in increasing the porosity of the negative electrode plate, which is the final product. The rotation rate of the spray dryer is set in a range capable of optimizing the size of the mixed powder in consideration of the porosity of the negative electrode plate.

Finally, as shown in FIG. 4, after the processing step S40, the processed negative electrode plate may be heat treated at 1300 to 1500 ° C. FIG. This heat treatment step (S50) is carried out to improve the properties of the negative electrode plate, which is the final product, for example, by bonding more of the mixed powder can adjust the porosity of the negative electrode plate. The critical significance of the heat treatment temperature is the same as the sintering temperature described above.

(Example)

In order to confirm the effect of the present invention three examples and two comparative examples according to the present invention were made to investigate the physical properties of each.

In Example 1, stabilized zirconia was sintered at 1350 ° C. for 30 seconds, and nickel oxide and starch powder were mixed for 1 hour. This mixed powder was spray dried to rotate at 8000 rpm at 95 ° C. , charged into a square mold, and molded at a pressure of 500 kg / cm 2. The molded body was sintered at 1500 ° C. and then cut into 2 mm thick with a diamond blade cutter to prepare a negative electrode plate.

In Example 2, the stabilized zirconia was sintered at 950 ° C. for 2 hours, and nickel oxide and starch powder were mixed for 24 hours. The mixed powder was spray dried to rotate at 8000 rpm at 150 ° C. , charged into a square mold, and molded at a pressure of 5000 kg / cm 2. The molded body was sintered at 1300 ° C. and cut to 2 mm in thickness with a diamond blade cutter to prepare a negative electrode plate.

In Example 3, the stabilized zirconia was sintered at 1100 ° C. for 1 hour, and nickel oxide and starch powder were mixed for 12 hours. This mixed powder was spray dried to rotate at 8000 rpm at 120 ° C. , charged into a square mold, and molded at a pressure of 2000 kg / cm 2. The molded body was sintered at 1400 ° C. and then cut into 2 mm thick with a diamond blade cutter to prepare a negative electrode plate.

In Comparative Example 1, the stabilized zirconia was sintered at 900 ° C. for 3 hours, and nickel oxide and starch powder were mixed for 1 hour. This mixed powder was spray dried to rotate at 8000 rpm at 160 ° C. , charged in a square mold, and molded at a pressure of 6000 kg / cm 2. The molded body was sintered at 1550 ° C. and then cut into 2 mm thick with a diamond blade cutter to prepare a negative electrode plate.

In Comparative Example 2, the stabilized zirconia was sintered at 1400 ° C. for 25 hours, and nickel oxide and starch powder were mixed for 1 hour. The mixed powder was spray dried to rotate at 8000 rpm at 90 ° C. , charged into a square mold, and molded at a pressure of 450 kg / cm 2. The molded body was sintered at 1250 ° C. and then cut into 2 mm thick with a diamond blade cutter to prepare a negative electrode plate.

The physical properties of the examples and comparative examples described above were measured based on moldability (with or without cracks in the production of a bulk molded body), workability (with or without defects when cutting a bulk molded body), and durability (strength of the cut negative electrode plate). Same as the table.

Properties of Negative Plate Formability Processability durability Example 1 ◎ ◎ ◎ Example 2 ◎ ◎ ◎ Example 3 ◎ ◎ ◎ Comparative Example 1 △ △ × Comparative Example 2 △ △ ×

◎: Excellent △: Normal ×: Poor

As described above, according to the negative electrode plate manufacturing method of the negative electrode-supported solid oxide fuel cell according to the present invention, since the negative electrode plate is manufactured by the bulk slicing method, a large area negative electrode plate can be produced, and the conventional press in the flatness of the product Better than the law In addition, mass production is possible, thereby reducing manufacturing costs.

Claims (6)

A negative electrode plate manufacturing method of a solid oxide fuel cell for supporting a negative electrode having a large area, Pre-sintering the stabilized zirconia powder at more than 1200 ° C. for less than 1350 ° C. for 30 seconds to 2 hours; Making a mixed powder by wet mixing the stabilized zirconia (YSZ) powder, nickel oxide (NiO) powder, a dispersant and a pore former for 1 to 24 hours; Putting the mixed powder into a mold and pressurizing at a pressure of more than 1000 kg / cm 2 to 5000 kg / cm 2 or less to form a bulk shaped molded product as an intermediate product; Sintering the molded body for 3 to 24 hours at a temperature of 1300 to 1500 ° C; A method for manufacturing a negative electrode plate of a solid oxide fuel cell for supporting a negative electrode, characterized in that the step of cutting the molded product in the form of a sintered bulk form as an intermediate product in the form of a negative electrode plate as a final product. The method of claim 1, wherein the forming step and the sintering step are performed at the same time. delete The negative electrode plate manufacturing method of claim 1 or 2, wherein the preparing of the mixed powder further comprises drying the mixed powder at 95 to 150 ° C. The negative electrode plate manufacturing method of claim 4, wherein the mixed powder is placed in a spray dryer and rotated at 7000 to 9000 rpm to increase the size of the mixed powder and to dry it. The negative electrode plate manufacturing method of claim 1 or 2, wherein the processing further comprises heat treating the processed negative electrode plate at 1300 to 1500 ° C.

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