KR101222867B1 - Anode support using spherical pore former and solid oxide fuel cell and the fabrication method therefor - Google Patents

Abstract

The present invention relates to a fuel cell support for a solid oxide fuel cell, a solid oxide fuel cell including the same, and a method for manufacturing the same. The method for manufacturing a fuel cell support for a solid oxide fuel cell according to the present invention includes (a) a fuel cell support powder and a spherical pore precursor. (B) forming the anode support using the mixture or slurry; and (c) removing the spherical pore precursor by performing a high temperature heat treatment of the anode support to include spherical pores. Forming a porous anode support, step (b), (b ') using the mixture or slurry to form granules by spray drying, freeze drying or liquid condensation process, using the pressure molding method Forming the anode support, or (b '') mixing the mixture or slurry By using the tape casting process may be a step of forming the anode support.

Description

Anode support using spherical pore former and solid oxide fuel cell and the fabrication method therefor}

The present invention relates to an anode support for a solid oxide fuel cell, a solid oxide fuel cell including the same, and a manufacturing method thereof, and more particularly, to an anode support for a solid oxide fuel cell including spherical pores and a solid oxide fuel cell including the same. will be.

Solid Oxide Fuel Cell (SOFC) is a type of fuel cell that converts chemical energy of fuel directly into electrical energy by electrochemical reaction. It is used to use solid oxide which shows ion conductivity at high temperature as electrolyte. It features.

The solid oxide fuel cell has an electrolyte support type and an electrode support type according to the structural support, and the electrode support type is further divided into a cathode support and a cathode support. The anode supported solid oxide fuel cell has a structure in which a cathode functional layer, an electrolyte layer, and an cathode layer are sequentially formed on an anode substrate.

The anode support of the anode-supported solid oxide fuel cell must satisfy both the electrochemical and structural properties required as the main components of the fuel cell. That is, the support should have sufficient mechanical strength and high electrical conductivity, electrochemical activity, and excellent gas permeability. In addition, in recent years, since the thickness of the electrolyte is gradually decreased to improve the performance of the fuel cell, a mechanism for suppressing the occurrence of a defect in the electrolyte accordingly needs to be introduced to the anode support.

As the anode support of SOFC, a composite sintered by mixing NiO and YSZ (Yttria-Stabilized Zirconia) is mainly used. In the conventional technology, the volume fraction of NiO and YSZ powder is controlled to control the porosity of the anode support. A method of controlling the porosity by changing the composition of the fibrous / powder mixture or by adding a carbon-based pore precursor has been attempted. However, the above methods are complicated due to the change in powder composition, and the process conditions themselves may be adjusted, and the size of the pores may not be arbitrarily adjusted, and the shape of the pores may be uneven, thereby lowering the mechanical strength of the anode support.

The present invention is to provide an anode support that satisfies the various characteristics required as an anode support and a method for manufacturing the same, as described above, while significantly improving the stability of the upper electrolyte while satisfying the structural and electrochemical properties required for the anode support. It is an object of the present invention to provide an anode support for a solid oxide fuel cell and a method of manufacturing the same. In addition, by providing a method of applying the present invention to the anode support raw material composition and the molded article manufacturing process that can vary depending on the application field of the solid oxide fuel cell, it is intended to provide a method that can be applied to the improved raw materials and processes in the future.

Method for producing a cathode support for a solid oxide fuel cell of the present invention comprises the steps of (a) preparing a mixture or slurry containing the anode support constituent powder and the spherical pore precursor, (b) forming the anode support using the mixture or slurry And (c) hot-heating the anode support to remove the spherical pore precursors to form a porous anode support comprising spherical pores, wherein step (b) comprises: (b ') the admixture or slurry Forming granules by spray drying, freeze drying, or liquid condensation, and molding the anode support by pressure molding, or (b '') by tape casting using the mixture or slurry. It may be a step of forming the anode support.

In addition, the manufacturing method of the solid oxide fuel cell of the present invention is to sequentially form the anode functional layer, the electrolyte layer and the cathode layer on the anode support for a solid oxide fuel cell comprising a spherical pore inside prepared according to the above method. The solid oxide fuel cell of the present invention is prepared according to the above method, and includes spherical pores therein.

The method of manufacturing a cathode support for a solid oxide fuel cell according to the present invention has a spherical shape and forms pores using various pore precursors, and thus the pore size can be freely controlled, and the shape of the pores is spherical, thereby improving structural stability of the support. I can keep it. In addition, there is no complexity of changing the composition of the support raw material powder or the process conditions in order to form pores. In particular, by using this method, the porosity can be maintained while increasing the plastic shrinkage rate of the anode support, so that the degree of freedom in selecting the sintering temperature can be greatly improved. Furthermore, since the plastic shrinkage rate of the anode support can be increased, defects between the anode functional layer and the electrolyte formed on the anode support can be greatly reduced. This design principle and manufacturing method can be applied in the same way even if a new material or a new process is introduced, and it is possible to design and manufacture a high-performance anode support for each application and temperature, and a solid oxide fuel cell and a manufacturing method using the same By providing the, it can contribute to the improvement of the performance and stability of the solid oxide fuel cell.

1 is a process flowchart of a method for manufacturing a cathode support by the liquid phase condensation step and the pressure molding method of Example 1;
2 is a flowchart of a method of manufacturing an anode support by the tape casting method of Example 2. FIG.
3 is a cross-sectional microstructure photograph of the anode support manufactured by the liquid phase condensation process and the press molding method of Example 1. FIG.
4 is a cross-sectional microstructure photograph of an anode support manufactured by the tape casting method of Example 2. FIG.
5 is a graph showing changes in fuel cell performance at 600 ° C. with or without PMMA polymer pore precursor.
6A is a microstructure photograph of an electrolyte membrane formed on a cathode support using spherical pore precursors according to an embodiment of the present invention.
6B is a microstructure photograph of an electrolyte membrane formed on an anode support without using a pore precursor according to a comparative example.

Method for producing a cathode support for a solid oxide fuel cell of the present invention comprises the steps of (a) preparing a mixture or slurry containing the anode support constituent powder and the spherical pore precursor, (b) forming the anode support using the mixture or slurry And (c) forming the porous anode support including the spherical pores by removing the spherical pore precursor by performing a high temperature heat treatment on the anode support.

The mixture or slurry of step (a) further comprises at least one additive selected from the group consisting of a dispersant, a plasticizer and a binder, and may be to remove the additive through the heat treatment of step (c).

Prior to step (c), (b '' ') further comprises forming an anode functional layer and an electrolyte layer on the anode support formed in step (b), wherein step (c) is performed by the spherical pore precursor. It may be a simultaneous sintering process of sintering the anode functional layer and the electrolyte layer simultaneously with removal.

The anode support constituent powder may be at least one selected from the group consisting of an ion conductive oxide such as yttria stabilized zirconia (YSZ) or Gd doped ceria (GZ), a metal having catalytic properties such as Ni or Cu, and a mixed conductor. The spherical pore precursor is at least one polymer selected from the group consisting of polymethyl methacrylate (PMMA), polycarbonate (PC) and polystyrene (PS). It may be

Step (b) is (b ') forming the granules by spray drying, freeze drying or liquid condensation using the mixture or slurry, and molding the anode support by pressure molding using the mixture or slurry (b'). '') May be the step of forming the anode support by a tape casting method using the mixture or slurry.

The spherical pore precursor may be 50 vol% or less in the blend or slurry, the blend includes NiO, YSZ and PMMA, the NiO in the blend or slurry 40 to 50 mass%, the YSZ is 30 to 40 % By mass, and the PMMA may be 5 to 15% by mass.

The diameter of the spherical pore precursor particles may be greater than or equal to the diameter of the anode support constituent powder, less than 10 times the diameter of the anode support constituent powder, and may be 1 μm to 50 μm.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example

1 and 2 are process flowcharts of a method of manufacturing a cathode support for a solid oxide fuel cell according to the present invention. As the anode support constituent powder, a composite of Ni and YSZ was used. The initial raw material of the anode support is NiO and YSZ, which is an oxide of Ni, to form a mixture, and becomes a Ni-YSZ composite, which is an actual anode, under a reducing atmosphere during fuel cell operation. As a spherical pore precursor, a fine spherical polymer PMMA powder (PMMA beads) having an average particle diameter of 5 μm was used.

Example 1 Preparation by Liquid Condensation Process and Pressure Molding Method

1 is a process flowchart of a method of manufacturing a cathode support by a liquid phase condensation step and a pressure molding method. This is explained step by step as follows.

First, a slurry is formed by mixing NiO powder, an YSZ powder, a spherical polymer pore precursor, PMMA beads, a binder, and a solvent, which are anode support constituent powders, and removing aggregates to prepare a slurry in which components are uniformly mixed (Step 1 -One).

Subsequently, the slurry is added to a nonsolvent having little or no solubility in the binder to form granules in which the anode support constituent powder, the spherical polymer pore precursor, and the binder are uniformly distributed (step 1-2).

The granules are dried and filled into molds of desired shape for hot press molding (steps 1-3).

The molded body is sintered and removed the binder and the spherical polymer pore precursor present therein at a high temperature (steps 1-4).

Example 2 Preparation by Tape Casting

2 is a flowchart of a method of manufacturing an anode support by a tape casting method. This is explained step by step as follows.

First, a slurry is formed by mixing NiO powder, an YSZ powder, a spherical polymer pore precursor, PMMA beads, a dispersant, a plasticizer, a binder, and a solvent, forming a slurry, and removing aggregates to prepare a slurry in which the constituent materials are uniformly mixed. (Step 2-1).

Subsequently, the slurry is loaded onto a moving conveying film and then formed into a plate by passing a blade of constant height (step 2-2).

The shaped body is sintered at high temperatures to remove the binder and spherical polymeric pore precursors present therein (step 2-3).

In particular, when the ratio of the constituent powder, NiO powder, YSZ powder, and the dispersant, plasticizer, and binder according to the pore precursor PMMA beads are optimally controlled, the molding process is easy and defects may be reduced in the sintering process. .

The ratios of the constituent powders and the additives used in Examples 1 and 2 are shown in Tables 1 and 2 below.

Raw Material Composition of the Slurry of Example 1 Composition of raw material Volume ratio (%) Mass ratio (%) NiO powder 42.54 46.25 YSZ powder 37.46 36.34 Spherical PMMA Powder 20.00 12.39 phenol Don't consider 3.78 EC Don't consider 1.24 Sum 100 100

Raw Material Composition of the Slurry of Example 2 Composition of raw material Volume ratio (%) Mass ratio (%) NiO powder 34.56 45.12 YSZ powder 30.44 35.45 Spherical PMMA Powder 35.00 8.15 KD-1 Don't consider 1.21 DBP Don't consider 6.04 PVB-79 Don't consider 4.03 Sum 100 100

As shown in Table 1 above, phenol was added as a binder for the production of a molded body by pressure molding, and ethyl cellulose (EC) was added to the PMMA mass to increase the adhesion between PMMA and the raw material powder and to facilitate the formation of granules. Contrast 1/10 was added. Increasing the content of PMMA can reduce the adhesiveness between PMMA or PMMA and other raw material powders, reducing the size of granules or making granules difficult, so that the content of ethyl cellulose or a polymer having a similar function can be proportionally increased.

In addition, as shown in Table 2, as a dispersant for the production of molded articles through a tape casting process KD-1, dibutylphthalate (DBP) as a plasticizer and polyvinyl butyral (PVB) as a binder were used. When the plasticizer is lacking in the slurry for tape casting, dry defects occur in the molded body, and when the excess is inferior to the uniformity of the slurry.

In this case, since the spherical polymer pore precursor in the slurry is replaced with pores as it is after the final process, it is preferable to introduce an amount not exceeding 50% of the total volume of the raw material powder of the negative electrode and the spherical polymer pore precursor. If too large pore formation can not guarantee the mechanical strength of the negative electrode. In addition, even if the particle size of the spherical polymer pore precursor is similar to or larger than the particle size distribution of other raw materials, the particle size does not exceed 10 times, and thus there is no problem in the formation of the molded body and the thermomechanical properties of the anode support. As compared to the particle size, the particle size of the spherical polymer pore precursor may be used between 1 μm and 50 μm. In addition, the process temperature until sintering during the manufacturing step should be made below the glass transition temperature of each polymer to prevent the deformation of the spherical polymer pore precursor, the pressure is also within the range that the shape of the spherical polymer pore precursor is not deformed. Should be done in In consideration of this, in the present embodiment, the process was performed at a temperature of up to 130 ° C. and a pressure of up to 30 MPa during hot press molding.

3 and 4 show cross-sectional microstructure photographs of the anode support prepared through the illustrated process. 3 is a cross-sectional microstructure photograph of the anode support manufactured by the liquid phase condensation process and the press molding method of Example 1, and FIG. 4 is a cross-sectional microstructure photograph of the anode support manufactured by the tape casting method of Example 2. FIG.

 As shown in FIGS. 3 and 4, the spherical pores may be secured in the anode support through the introduction of the spherical polymer pore precursor, thereby improving the porosity while maintaining the mechanical strength required by the support and greatly increasing the stability of the electrolyte. Can be.

In the method of manufacturing a cathode support for a solid oxide fuel cell according to the present invention, the introduction of a spherical polymer pore precursor induces the following effects for improving physical properties of the anode support.

First, it is possible to optimize the performance of the fuel cell without considering the porosity in the raw material powder particle size and sintering temperature selection. In particular, in order to increase the sintering degree of the upper layer and to reduce defects in the simultaneous firing process of the anode support, the functional layer and the electrolyte layer, it is necessary to use the fine powder in the anode support to increase the sinter shrinkage rate or to increase the temperature during sintering. Porosity will decrease. Therefore, it is possible to secure the porosity required for the anode support through artificial pore composition through the spherical polymer pore precursor.

Second, by maintaining the shape of the pores in the artificial pore composition in the spherical shape to prevent the concentration of fracture stress or micro-cracks can have a relatively high porosity while securing the mechanical strength required for the support. More specifically, the gas permeability of the anode support may be primarily improved by securing the porosity through the above effects, and thus, the movement of reactants and products may be freely performed when the fuel cell is operated. The plastic shrinkage of the anode support can be increased by controlling the firing temperature together with the presence of the spherical polymer pore precursor, thereby facilitating densification of the anode functional layer and the electrolyte layer formed on the anode support. In addition, it is possible to improve the stability of the electrolyte by reducing the thermal stress acting on the electrolyte formed on the support in accordance with the decrease in the elastic modulus of the anode support due to the high porosity. In particular, such an effect may be large as the thickness of the electrolyte becomes thinner.

5 shows the results of the experiment. The current-voltage curve and the current-power curve when the fuel cell is manufactured and operated with the anode support having a spherical pore formed therein by introducing PMMA beads as a spherical pore precursor and the anode support not having the same. Is a graph comparing at 600 ℃. In case of fuel cell with PMMA beads, the electrolyte membrane is stable and the open-circuit voltage appears close to the theoretical value when the ultra thin electrolyte thin film formed by pulsed laser deposition is applied. It can be seen that the electrolyte membrane is damaged during reduction, so that the open circuit voltage is only about 80% of the theoretical value. This is because as the plastic shrinkage of the anode support increases, densification of the anode functional layer proceeds better during the firing process, and the defects on the upper portion of the anode functional layer are greatly reduced, and the thin film electrolyte deposited thereon is formed without defects.

When the pore precursor is not used, a large number of defects exist on the surface of the anode functional layer. As a result, the electrolyte membrane is not continuously formed and thus the open circuit voltage is not properly expressed. 6A shows the microstructure of the electrolyte membrane on the substrate using the pore precursor, and FIG. 6B shows the microstructure of the electrolyte membrane on the substrate without the pore precursor. The part indicated by the arrow of FIG. 6B is the part which a defect generate | occur | produced.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and the present invention is not limited thereto.

Claims (12)

(a) preparing a mixture or slurry comprising a cathode support constituent powder and a spherical pore precursor;
(b) shaping the anode support using the mixture or slurry; And
(c) forming a porous anode support including spherical pores by removing the spherical pore precursor by performing a high temperature heat treatment on the anode support;
Step (b) is
(b ') forming granules by spray drying, freeze drying, or liquid condensation using the mixture or slurry, and molding the anode support by pressure molding using the same;
(b '') a method of manufacturing a cathode support for a solid oxide fuel cell, wherein the anode support is formed by a tape casting method using the mixture or slurry. The method of claim 1,
The mixture or slurry of step (a) further comprises at least one additive selected from the group consisting of dispersants, plasticizers and binders,
The method of manufacturing a cathode support for a solid oxide fuel cell to remove the additive through the heat treatment of step (c). The process of claim 1, wherein, prior to step (c),
(b ''') further comprising forming a cathode functional layer and an electrolyte layer on the anode support molded in step (b);
Step (c) is a simultaneous sintering process of sintering the anode functional layer and the electrolyte layer simultaneously with the removal of the spherical pore precursor. The method of claim 1, wherein the anode support constituent powder is at least one selected from the group consisting of an ion conductive oxide, a metal having a catalytic property, and a mixed conductor. The method of claim 1, wherein the spherical pore precursor is at least one polymer selected from the group consisting of PMMA, PC, and PS. delete The method of claim 1,
The spherical pore precursor is 50% by volume or less in the mixture or slurry of the anode support for a solid oxide fuel cell. The method of claim 1,
The admixture comprises NiO, YSZ and PMMA,
The NiO is 40 to 50% by mass, the YSZ is 30 to 40% by mass, and the PMMA is 5 to 15% by mass in the mixture or slurry of the method for producing a fuel cell support for a solid oxide fuel cell. The method of claim 1,
And a diameter of the spherical pore precursor particles is equal to or larger than the diameter of the anode support component powder and 10 times or less of the diameter of the anode support component powder. The method of claim 1,
The diameter of the spherical pore precursor particles is a method of producing a fuel cell support for a solid oxide fuel cell that is 1 ㎛ ~ 50 ㎛. The anode functional layer, the electrolyte layer, and the cathode layer are formed on a cathode support for a solid oxide fuel cell including spherical pores therein prepared according to any one of claims 1 to 5 and 7 to 10. Method of manufacturing a solid oxide fuel cell that is formed sequentially. A fuel cell support for a solid oxide fuel cell prepared according to any one of claims 1 to 5 and 7 to 10, and comprising spherical pores therein.

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