KR101335063B1 - Method of large powewr solid oxide fuel cell - Google Patents

Abstract

The present invention provides a cathode support-type electrolyte by forming a film by a tape casting method on a cathode support, an anode reaction layer, and an electrolyte layer, and laminating and co-sintering to form an anode support-type electrolyte. Was prepared by the screen printing method to produce a unit cell. In order to efficiently control the microstructure of the anode reaction layer constituting the solid oxide fuel cell unit cell, instead of adding a pore of carbon to the composition of NiO / YSZ, carbon is omitted and the ratio of the mixture ratio of NiO and YSZ is reduced. The high output of the solid oxide fuel cell was attempted by controlling the fine structure of the reaction layer by composition control and particle size control of YSZ.

Description

High output solid oxide fuel cell unit cell manufacturing technology {METHOD OF LARGE POWEWR SOLID OXIDE FUEL CELL}

The present invention relates to a method for manufacturing a unit cell of a solid oxide fuel cell that can improve the output characteristics even when operating the solid oxide fuel cell at low to low temperatures.

In manufacturing a unit cell of a solid oxide fuel cell, a unit cell design is generally classified into a cathode support type, an electrolyte support type, an cathode support type, and the like. This is being applied a lot. In addition, according to the shape of the unit cell is classified into a flat plate and a cylindrical (or cylindrical). In any type of unit cell of the solid oxide fuel cell of the present technology, the anode reaction layer exists, and the anode reaction layer oxidizes fuel (hydrogen) to produce hydrogen ions and electrons, and combines with oxygen ions to generate electricity and water. As a practical electrochemical reaction field to produce, it is very important to determine the output characteristics of the unit cell.

In order to maximize the electrochemical reaction characteristics of the anode reaction layer of a solid oxide fuel cell, conventionally, a microstructure control method by improving the porosity of the anode is used to stabilize nickel oxide (NiO) and yttria constituting the anode. The zirconia (Yttria Stabilized Zirconia, YSZ) was applied by adding a pore of carbon. However, this method can exhibit high output without any big problem when operating at high temperature above 800 ℃, but when operating at low and low temperature below 800 ℃, especially when operating temperature is lowered to 700 ℃, the unit cell output characteristics are improved. It is rather bad.

Carbon, which is used in the anode reaction layer to maintain high output even at low and low temperatures, may not be sufficiently removed during the calcination process. Particularly, when the operating temperature is low to low temperature, the electrochemical active polarization is increased. It is estimated that the output characteristics of the cell are deteriorated. In other words, when the carbon pore agent used for the microstructure control of the conventional anode reaction layer is not used, the porosity of the reaction layer is insufficient, so that the electrochemical reaction field is not sufficiently secured. have.

According to embodiments of the present invention to solve the lack of electrochemical activity of the anode of the solid oxide fuel cell to provide a solid oxide fuel cell reaction layer manufacturing technology having a high output.

The present invention relates to a unit cell manufacturing method for improving the output performance of a solid oxide fuel cell, a method of manufacturing a unit cell of a solid oxide fuel cell formed of a cathode support layer, a cathode reaction layer, an electrolyte layer and a cathode layer. The reaction layer is prepared by mixing two kinds of YSZ powders having different sizes with NiO powder.

The NiO powder has a size of 2 ~ 3㎛, the YZS powder is used by mixing the first powder of 0.2 ~ 0.5㎛ size and the second powder of 2 ~ 5㎛ size. The YZS powder is mixed in a weight ratio of the first powder and the second powder in a 1: 1 ratio.

The anode reaction layer includes mixing the NiO powder and the YSZ powder to prepare a slurry, and when the slurry is prepared, the NiO powder and the YSZ powder are mixed in a weight ratio of 55:45. In addition, the anode reaction layer does not include a pore agent in the preparation of the slurry.

As described above, according to the embodiments of the present invention, the microstructure is properly maintained by the particle size control of the reaction layer of the conventional solid oxide fuel cell unit cell YSZ, the fuel (hydrogen ), The reaction of ions and electrons is optimized, so it can show high power even at low and low temperatures.

1 is a schematic diagram showing the structure of a unit cell and a fuel electrode reaction layer.
2 and 3 are photographs showing the structure of a unit cell according to an embodiment of the present invention.
4 and 5 are microstructure photographs of the anode reaction layer according to the comparative examples.
Figure 6 is a graph showing the output performance when operating at 750 ℃ in Examples and Comparative Examples.
7 is a graph showing the output performance when operating at 700 ℃ in Examples and Comparative Examples.

The following examples are provided to provide a thorough understanding of the present invention in the technical field, and may be changed in various forms, and the scope of the present invention is not limited to the other embodiments.

Hereinafter, a method of manufacturing a unit cell of a solid oxide fuel cell according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 1 to 7. For reference, FIG. 1 is a schematic diagram illustrating a unit cell structure of a solid oxide fuel cell according to an exemplary embodiment of the present invention.

The unit cell 10 of the solid oxide fuel cell is formed by sequentially stacking the anode support layer 11, the anode reaction layer 12, the electrolyte layer 13, and the cathode layer 14. Has a structure. For example, the anode support layer 11 and the anode reaction layer 12 are nickel oxide (hereinafter referred to as 'NiO') and yttria stabilized zirconia (hereinafter referred to as 'YSZ'). Complex is used. The electrolyte layer 13 is formed of YSZ material, and the cathode layer 14 is composed of a strontium-doped lanthanum manganite (hereinafter, referred to as 'LSM') and YSZ.

The unit cell 10 of the solid oxide fuel cell is formed by laminating and sintering an electrolyte layer 13 on a fuel electrode composed of the anode support layer 11 and the anode reaction layer 12 using a tape casting method. 14 to form.

Here, if the carbon used in the slurry production in the conventional tape casting method is not sufficiently removed during the calcination process, the polarization reaction may increase during operation of the unit cell may reduce the output characteristics. In order to prevent this, embodiments of the present invention is characterized in that the carbon is not used in the manufacture of the anode reaction layer 12 in order to maintain a high output even at mid-low temperature below 800 ℃, the two to each other for microstructure control Powders with different particle sizes are mixed and used.

In detail, the anode reaction layer 12 is prepared by mixing NiO powder having a level of 2 to 3 µm and two kinds of YSZ powder. For example, YSZ powder is prepared by mixing the fine first powder of 0.2 ~ 0.5㎛ level and the coarse second powder of 2 ~ 5㎛ level in an appropriate ratio. As such, by mixing powders having different sizes, the pore size, porosity, and pore structure of the anode reaction layer 12 can be effectively controlled. Further, when the high temperature type materials YSZ and LSM are used as the electrolyte and the cathode layer 14, a unit cell exhibiting excellent output characteristics at medium temperature (750 ° C.) can be manufactured.

The specific manufacturing process of the solid oxide fuel cell is as follows.

First, a fuel electrode reaction layer slurry is prepared.

The slurry of the anode reaction layer is prepared by mixing NiO powder, two coarse YSZ powders and nano YSZ powders having different particle sizes. Here, the mixing ratio of NiO and YSZ powder is 55:45 by weight so that Ni and YSZ ratio may be 4: 6 after reduction. After mixing nano YSZ powder (first powder) and coarse YSZ powder (second powder) with NiO in a weight ratio of 1: 1, toluene and ethanol weight ratio 4: 1 as a solvent for uniform dispersion of the powder, and a dispersant ( The first ball mill is performed at a speed of 200 rpm for 24 hours by adding fish oil. After 24 hours, a second ball mill is performed for another 24 hours by adding an amount of binder corresponding to the viscosity of 200. And a reaction layer film having a thickness of 22㎛ is prepared by a tape casting process.

Next, the anode reaction layer (Ni / YSZ) is laminated on the anode diffusion layer (Ni / YSZ / CB) support having a thickness of 1 to 1.5 mm to form a fuel electrode, and the YSZ of the thin film is placed on the anode to support the anode support type electrolyte ( Prepare an anode-supported electrolyte assembly. In addition, an air electrode (LSM / YSZ) is coated on the anode support electrolyte to prepare a unit cell. Here, the anode and the electrolyte are manufactured using a tape casting method, and the cathode is manufactured using a screen printing method.

Here, in the anode support layer, a 40 μm-thick sheet was manufactured by tape casting using a slurry formed by mixing a ratio of NiO and YSZ in a ratio of 60:40. A cathode support having a thickness of ˜1.6 mm is formed. In the case of the electrolyte, after laminating about 10 μm YSZ thin film sheet formed by the same method as the anode support on the anode support, lamination was carried out at a temperature of 70 ° C. for about 20 minutes at 400 kgf / cm 2 and then calcined. And co-firing to form the anode support electrolyte.

Here, the conditions for calcining the anode support-type electrolyte are raised to 1000 ° C. in order to remove the solvent and binder of the slurry, and maintained at room temperature after maintaining for about 3 hours. This is because there is no bending at 1000 ° C. or lower but sintering is not easy and breakage is very severe at 1000 ° C. or higher, so that calcination is performed at around 1000 ° C.

As such, the calcination-completed green type anode support-type electrolyte was mounted on a plate-shaped zirconia ceramic support having a constant size and weight, and pressed simultaneously with a force of about 38 g / cm 2 to perform co-firing at about 1350 ° C.

In the cathode, a mixed powder powder of LSM anode powder and YSZ and a solvent are mixed at a ratio of 60:40 (wt%) to prepare a cathode paste using a 3-rollmil group. Since the paste prepared in the above composition has good wettability, it is excellent in leveling effect without depending on the surface defect of the anode support type electrolyte. Next, the paste is formed by a screen printing method to form a multilayer structure having a thickness of 30 to 50 μm, and then a cathode is manufactured through a sintering process at 1150 ° C.

≪ Comparative Example 1 &

In order to determine the effect of the porosity, pore structure, and size of the anode reaction layer on the performance, a unit cell was prepared in the same manner as described above. After the unit cell was prepared. However, when carbon black is added, the amount of NiO and YSZ added is slightly reduced by the amount of carbon black added.

≪ Comparative Example 2 &

A unit cell was prepared for the same purpose as in <Comparative Example 1>, but a slurry was prepared using only one type of YSZ particles when preparing a reaction layer slurry, and then a unit cell was manufactured to evaluate performance.

2 and 3 are SEM cross-sectional image of the unit cell after evaluating the output characteristics of the unit cell according to an embodiment of the present invention, FIG. It shows the level of porosity due to pore formation. 4 and 5 are photographs showing microstructures in which portions of a cathode reaction layer of a unit cell are enlarged in Comparative Examples 1 and 2, respectively.

Referring to the drawings, it can be seen that the microstructures of the Examples and Comparative Examples 1 and 2 are similar. However, referring to FIG. 4, it can be confirmed that Comparative Example 1 has a larger porosity than that of Example. This can be seen that the pores were generated by adding carbon black as a pore agent in the composition of the embodiment. Comparative Example 2 is a cathode reaction layer manufactured using only NiO and dense YSZ. As shown in FIG. 5, the microstructure has a very dense structure and has a particle size with a constant size and shape. It can be estimated that the pore layer was not sufficiently secured.

Next, with reference to FIG. 6 and FIG. 7, the output characteristic of the Example at the time of operation at medium temperature, and Comparative Examples 1 and 2 is demonstrated.

Referring to Figure 6, when operating at 750 ℃, it can be seen that the embodiment shows a very good output characteristics of about 0.9W / ㎠ at a current density of 1.7A / ㎠, which is about 30- It can be seen that it has a 50% improved effect.

Referring to FIG. 7, as a result of operating at a low temperature of 700 ° C. for a unit cell under the same condition as in FIG. 5, the embodiment shows a very good output characteristic of about 0.6 W / cm 2 at a current density of 1.7 A / cm 2. It can be seen that this has about 20-50% improvement compared to the conventional research results.

In particular, when carbon black is added (Comparative Example 1), a phenomenon in which the output characteristics are significantly reduced can be confirmed, which indicates that the carbon black remaining in the anode reaction layer inhibits the electrochemical reaction rather than concentration polarization due to the diffusion of the fuel. It is estimated that the reaction polarization acts more largely, which causes a decrease in the output performance of the unit cell.

As can be seen from the above results, in the production of a unit cell of a solid oxide fuel cell using an YSZ electrolyte material, a unit cell is manufactured by a cathode support type electrolyte and a screen printing method by a tape casting and co-sintering method, and a fuel electrode. In manufacturing the reaction layer, it is possible to manufacture a unit cell that realizes high output performance by controlling the microstructure only by controlling the particle size of the YSZ ion conductor without using a pore agent.

According to the exemplary embodiments of the present invention, the unit cell of the solid oxide fuel cell exhibits excellent characteristics at medium and low temperatures of 800 ° C. or lower, and shows a lower output temperature than the conventional unit cell. That is, since the unit cell manufactured by the present invention does not use a carbon-based pore-forming agent, the electrochemical reaction polarization characteristic of the residual carbon is controlled at low and low temperatures, and pores are naturally formed by particle size control of YSZ instead of the pore-forming agent. It can be seen that the reaction characteristics are greatly improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The present invention is not limited to the above-described embodiments, and various modifications and changes may be made thereto by those skilled in the art to which the present invention belongs. Therefore, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, are included in the scope of the present invention.

10: unit cell of a solid oxide fuel cell
11: anode support layer
12: anode reaction layer
13: electrolyte layer
14: cathode layer

Claims (5)

In the method of manufacturing a unit cell of a solid oxide fuel cell formed of an anode support layer, an anode reaction layer, an electrolyte layer and an anode layer,
A cathode support layer was prepared using a slurry prepared by adding a solvent and a dispersant to a powder obtained by mixing a NiO powder and an YSZ powder having a particle size in a weight ratio of 60:40,
The NiO powder is prepared by mixing YSZ powder formed by mixing two kinds of first powder and second powder having different particle sizes in a weight ratio of 1: 1, and mixing the NiO powder and the YSZ powder with a weight ratio of 55:45. A fuel electrode reaction layer was prepared by using a slurry prepared by adding a solvent and a binder to the mixed powder mixed with a pore and omitting a pore agent.
Particles of NiO powder of the anode reaction layer has a size of 2 ~ 3㎛
The YZS powder of the anode reaction layer is a unit cell manufacturing method of a solid oxide fuel cell, characterized in that the particles of the first powder has a size of 0.2 ~ 0.5㎛, the particles of the second powder has a size of 2 ~ 5㎛. .
delete delete The method of claim 1,
The anode reaction layer is a unit cell manufacturing method of a solid oxide fuel cell comprising the step of mixing the NiO powder and the YSZ powder to produce a slurry.
5. The method of claim 4,
The anode reaction layer is a unit cell manufacturing method of a solid oxide fuel cell, characterized in that it does not contain a pore agent in the production of the slurry.

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