JP2016152144A - Manufacturing method of membrane electrode assembly for solid oxide fuel cell having anode with pore arrangement structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for improving fuel gas diffusion effect of an anode support substrate of a membrane electrode assembly for a solid oxide fuel cell, and achieving a high conductivity and a low resistivity.SOLUTION: A manufacturing method of a membrane electrode assembly for a solid oxide fuel cell is for b) forming a structure so that a pore is arranged to a front surface of a green tape of an anode substrate to be a) formed by a tape casting method; d) forming an anode support substrate by laminating and sintering with the green tape to which the pore arrangement structure is not formed, and polish-processing and smoothing, laminating and forming an electrolyte layer to the substrate front surface by a spin coating method or the like, and sintering for obtaining a half battery; and e) obtaining a whole battery of a solid oxide fuel cell by further laminating and forming a cathode by a screen printing method, and sintering. By executing the polish-processing to the anode surface of the whole battery, a nickel deficient layer caused by a multistep sintering step is eliminated, and a single cell is obtained.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fuel cell membrane electrode assembly, and more particularly to a method for producing a solid oxide fuel cell membrane electrode assembly having an anode having a pore arrangement structure.

A solid oxide fuel cell (SOFC) is an energy conversion device that outputs fuel by converting it into electric power through an electrochemical reaction. The conventional solid oxide fuel cell uses YSZ as an electrolyte support substrate. Since the operating temperature of (ESC: Electrolyte Supported Cell) is 800 to 1000 ° C. and the thickness of the electrolyte supporting substrate is about 150 to 300 μm, it must operate at a high temperature because of the thickness of the electrolyte. Since the current mainstream is an anode (NiO + YSZ) supported cell (Anode Supported Cell, ASC), and its feature is that its electrolyte layer is 10 μm or less in thickness, the operating temperature is kept between 800-1000 ° C. be able to. Since the manufacturing process of a membrane electrode assembly (MEA) of a normal anode-supported cell generally includes a process of synthesizing an anode and sequentially sintering an electrolyte and a cathode, there are at least three high-temperature sintering processes. is necessary. This multi-stage sintering process causes densification of the ceramic electrode and increases the gas diffusion resistivity of the battery. Therefore, the present invention uses an anode having a pore arrangement structure in the conventional membrane electrode manufacturing process, effectively reducing the gas diffusion resistivity and increasing the power output density of the battery while maintaining a stable power output for a long time. Can be maintained. Thereby, the bad influence to the electrode by a sintering process is solved, and the power generation efficiency of a solid oxide fuel cell is improved.

  The conventional anode-supported solid oxide fuel cell manufacturing process involves forming a green tape using a tape casting method, adjusting the thickness and geometric structure of the green tape substrate through a laminating process, and calcining / sintering. To form an electrolyte layer and an anode-supported half-cell substrate, and finally a cathode is printed on the half-cell substrate by a silk screen printing method to complete the manufacture of the whole cell. The main drawback of batteries made by this manufacturing method is poor stability and durability (Redox Cycling) / Thermal cycling resistance. Considering the basic requirement that the cathode and anode must have porosity (due to the gas-solid reaction mechanism), the sacrifice of mechanical strength is unavoidable, but the subsequent cell stack assembly and packaging process It tends to break down and is easy to fail. Since this drawback hinders the completeness of the structure of the solid oxide fuel cell, a method for solving these disadvantages and effectively improving the performance of the solid oxide fuel cell single cell is desirable.

Japanese Patent No. 5166080

The present invention relates to a method for producing a solid oxide fuel cell membrane electrode assembly (SOFC-MEA), and uses a tape casting method to produce a green tape constituting an anode support substrate, and to form one or a plurality of green tapes. After applying the pore arrangement structure, the anode support substrate was formed by sintering, and the conductivity of the anode was improved with low gas diffusion resistivity through the manufacturing process of silk screen printing method and / or sputtering method and / or spray method. A solid oxide fuel cell is obtained. Further, a precise polishing step is performed on the anode to remove the nickel-deficient layer, thereby obtaining a solid oxide fuel cell single cell having excellent performance.

The present invention relates to a solid oxide fuel cell membrane electrode assembly (SOFC-MEA) having an anode having a pore arrangement structure, and in a special anode pore forming process, a thin stainless steel tube is pressed against a green tape. By creating pores with an array structure, the formation of irregular or irregular pore perimeters can be prevented, and the reaction capacity of the three-phase interface can be increased by low gas diffusion resistivity during the battery operation process, improving the power density of the battery output While providing long-term stable power output, it improves the electrical performance of solid oxide fuel cell membrane electrode assemblies or single cells (SOFC-MEA or Unit Cell).

Another object of the present invention relates to a method of manufacturing a solid oxide fuel cell membrane electrode assembly (SOFC-MEA) having an anode having a pore arrangement structure, and the arrangement structure is arranged on one or more green tapes on the outside. In addition to improving the electrical performance of the completed single cell by more than 25%, the gas diffusion resistivity can also be reduced by more than 40%.

FIG. 1 shows a schematic diagram of an embodiment of a method for producing a membrane electrode assembly for a flat solid oxide fuel cell having high conductivity and low resistivity (8YSZ / SDC / LSGM). Process.

  First, a green tape forming an anode support substrate of a flat solid oxide fuel cell is formed using a tape casting method, and an array structure is formed on the surface side of the green tape with a thin stainless steel tube having a diameter of 0.1 to 0.5 cm. The anode support substrate having a total thickness of 300 to 800 μm is formed by laminating the green tape having the pore arrangement structure and the green tape that is not subjected to the pore forming process, and laminating the thermal tape and the wet laminate. Sintering is carried out at 1200-1500 ° C. for several hours, with 1250 ° C. being the optimum temperature, to obtain a pre-fired anode support substrate for the solid oxide fuel cell in the initial stage. As the substrate at this stage, one of NiO / YSZ, NiO / SDC, and NiO / LSGM can be used.

Next, the anode support substrate is washed with a vibration ultrasonic cleaner, dried, and then the electrolyte is thinned by sputtering, spin coating, and screen printing to form an electrolyte layer having a thickness of 10 μm or less. And calcining at 1200 to 1500 ° C. for several hours to complete the half-cell manufacturing process. Microstructure analysis of the half-cell is performed with a scanning electron microscope (abbreviated as SEM), and it is confirmed that the electrolyte layer reaches a completely dense state without open pores. If there are still open pores in the electrolyte layer, repair with thin film forming technology such as spin coating, readjust the sintering conditions, and repeat until the electrolyte layer is completely dense. Provide good bondability at the interface with the electrolyte layer.

Finally, a porous cathode (generally made of LSM or LSCF) is formed on the electrolyte layer of the half-cell by screen printing, and calcined again at 900 to 1200 ° C. for about 3 hours to complete the process. A solid oxide fuel cell is obtained. Polishing is performed to remove a thickness of about 10 to 20 μm from the anode side surface of all the batteries.

According to the method of the present invention, a green tape constituting an anode is manufactured using a tape casting method, and a pore array structure is formed on the green tape to form an initial fuel gas diffusion path, which is laminated and calcined, and / or An anode support substrate is completed by a sintering process. Furthermore, the electrolyte is laminated on the anode support substrate by sputtering, spin coating, or screen printing, and the anode layer and electrolyte layer are sintered to form a half-cell, and the cathode is formed on the half-cell by screen printing. Then, it is sintered again to obtain a whole solid oxide fuel cell. By polishing the anodes of all the batteries, the nickel-deficient layer caused by the multi-step sintering process is removed. All the cells with the pore arrangement structure and the polishing treatment show remarkable performance improvement because of the large electric resistance generated between the membrane electrode assembly and the current collecting layer and the gas diffusion resistance generated inside the anode. This is due to a significant decrease. Therefore, a solid oxide fuel cell with high conductivity and low resistivity is obtained.

FIG. 6 shows the results of a long-term performance evaluation test of a solid oxide fuel cell having an anode having a pore arrangement structure. When operated under the condition of a constant current of 400 mA / cm ² , a single cell lamp voltage (voltage As the ramp rate increases continuously, the pore structure provides an effective diffusion path for the fuel gas and increases the gas concentration at the three-phase point at the interface between the anode and the electrolyte layer to increase the efficiency of the electrochemical reaction. Improve.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a method for producing a membrane electrode assembly for a solid oxide fuel cell having an anode having a pore arrangement structure according to the present invention, and (a) producing an anode green tape, and (b) one or more The anode support substrate is formed by applying a pore arrangement structure to the green tape, and (c) the anode support substrate is formed by laminating the green tape and the non-hole-treated, and (d) the electrolyte layer is formed on the surface of the polished anode support substrate. And (e) the cathode layer is laminated to complete the entire battery. It is a figure which shows the basic type of the membrane electrode assembly for solid oxide fuel cells which has an anode with a pore arrangement | sequence structure of this invention. It is a figure which shows the pore size of the membrane electrode assembly for solid oxide fuel cells which has an anode with a pore arrangement | sequence structure of this invention. 1 is an embodiment of a pore arrangement of a membrane electrode assembly for a solid oxide fuel cell having an anode having a pore arrangement structure of the present invention. 1 is an embodiment of a pore arrangement of a membrane electrode assembly for a solid oxide fuel cell having an anode having a pore arrangement structure of the present invention. It is an external view of an anode supported solid oxide fuel cell. It is a microanalysis figure of a solid oxide fuel cell structure. It is a result figure of the performance evaluation test of the solid oxide fuel cell which is not subjected to pore forming treatment. It is a result figure of the performance evaluation test of the solid oxide fuel cell which has an anode with a pore arrangement structure. It is an impedance analysis result figure of a solid oxide fuel cell which is not subjected to pore forming treatment. It is an impedance analysis result figure of a solid oxide fuel cell which has an anode with a pore arrangement structure. It is a result figure of the long-term performance evaluation test of the solid oxide fuel cell which has an anode with a pore arrangement structure of the present invention.

2A to 2D show various embodiments related to the pore arrangement structure, and an embodiment of the present invention will be described in the following steps.

Step 1: Using a tape casting method, a green tape constituting an anode support substrate of a membrane electrode assembly is made with a basic material composed of 50 wt% NiO + 50 wt% 8YSZ and a specific amount of pore former (a in FIG. 1). .

Step 2: Apply a pore arrangement structure to the surface of one or more green tapes obtained in Step 1 above, and use a thin stainless steel tube with a diameter of about 0.3 cm to prevent deformation or irregular peripheral edges of the pores. On the surface side of the green tape, a pore arrangement structure with an adjacent interval distance of 1.4 cm is applied (b in FIG. 2), and the green tape having the pore arrangement structure and a green tape not subjected to the hole forming treatment are laminated, An anode supporting substrate having a thickness of 300 to 800 μm as a whole is formed through laminating and wet laminating. Since the size of the finished product of all the batteries is in the range of 5 × 5 cm ² to 10 × 10 cm ² , if the shrinkage due to sintering also takes into account the influence on the size of the anode support substrate, the size of the anode support substrate is 7 it is appropriate to the ^{× 7cm 2 ~12 × 12 cm 2} (c in FIG. 2).

Step 3: The anode support substrate obtained in Step 2 above is sintered at about 1250 ° C. for about 4 hours at a temperature increase / decrease rate of about 3 ° C./min. It becomes a pre-fired anode support substrate for the battery, and is polished in order from coarse to fine with a coarse sandpaper to ensure smoothness of the surface of the anode support base substrate for laminating the electrolyte layer.

Step 4: An electrolyte layer having a thickness of 10 μm or less is laminated on the surface of the anode support substrate obtained in the above step 3 by a spin coating method, about 1400 ° C. is optimum, and the temperature raising / lowering speed is about 3 ° C./min. In the following, sintering is performed at 1200 to 1600 ° C. for about 6 hours to obtain a half-cell of the solid oxide fuel cell in the initial stage. Microstructure analysis of the half-cell with an electron microscope confirmed that the interface between the anode and the electrolyte layer and that the electrolyte layer reached a completely dense state without open pores, and there were still open pores in the electrolyte layer In this case, the film is repaired by a thin film forming technique such as a spin coating method, or re-sintered at a temperature of 1200 to 1400 ° C. for about 6 hours to confirm a good interface bond between the anode and the electrolyte layer. The repairing and sintering processes are repeated until an appropriate electrolyte layer is obtained (d in FIG. 2).

Step 5: A porous cathode layer made of LSM is made by screen printing on the half-cell electrolyte layer obtained in Step 4 above, and the temperature rise / fall rate is about 3 ° C./min or less at about 1200 ° C. A 3 hour calcination step is performed to obtain all the batteries (e in FIG. 2). The electric performance test was performed on this single cell, and the results compared with the single cell that was not subjected to the hole forming process are shown in FIGS. 4 to 5. The circuit voltage (open circuit voltage) is close to the logical standard value (> 1.1V). Efficiency can be improved to 25% or more, and gas diffusion resistivity can be reduced by 40% or more.

In another embodiment of the present invention, the anode green tape having the pore arrangement structure shown in FIG. 2A may be arranged in a cross configuration as shown in FIG. 2C or 2D. Through the multi-layer laminating process, the pores are arranged in three dimensions to increase the flow rate of the fuel gas, while the pore arrangement distributed in different green tapes reduces the stress and enhances the supporting strength of each layer of the green tape.

2. The method for producing a membrane electrode assembly for a solid oxide fuel cell according to claim 1, wherein the number of laminates of the green tape of the present invention is 2 to 6 layers.

The above description is only an example of the present invention, and does not limit the scope of the present invention. Any equivalent changes and modifications that can be made based on the scope of the claims of the present invention are all described in the present invention. Shall belong to the scope covered by the rights.

Claims (6)

A method for producing a membrane electrode assembly for a solid oxide fuel cell having an anode having a pore arrangement structure,
Step a: Using a tape casting method, make a green tape constituting the anode support substrate,
Step b: Applying a pore arrangement structure having a specific hole diameter to the surface side of one or a plurality of the green tapes obtained in the step a, and the green tape having the pore arrangement structure and the green tape not subjected to the hole forming treatment. The anode support substrate having a total thickness of 300 to 800 μm is formed by laminating and thermal laminating and wet laminating processes, and the rate of temperature increase / decrease is about 3 ° C./min or less. Pre-sintering at 1250 ° C. for about 4 hours to form an anode support substrate for the solid oxide fuel cell in the initial stage,
Step c: An anode layer / electrolyte layer composite obtained by laminating an electrolyte layer on the surface of the anode support substrate prepared by polishing the anode support substrate obtained in step b with sandpaper from coarse to thin in order. As a base material,
Step d: The anode layer / electrolyte layer composite base material obtained in Step c is sintered at about 1400 ° C. at a temperature raising / lowering speed of about 3 ° C./min or less for about 6 hours to form a half-cell. If there are open pores, repair with thin film formation technology, or re-sinter for about 6 hours at a temperature of 1200-1400 ° C., repeat the repair and sintering process until a complete dense electrolyte layer,
Step e: A porous cathode layer is formed on the electrolyte layer of the half-cell obtained in Step d by screen printing, and at about 1200 ° C., the temperature rise / fall rate is about 3 ° C./min or less for about 3 hours. A firing process is performed to obtain a membrane electrode assembly for a solid oxide fuel cell,
Step f: Polishing the anode surface of the membrane electrode assembly for the solid oxide fuel cell obtained in Step e in order with sandpaper from coarse to narrow to complete a single cell.
The manufacturing method of the membrane electrode assembly for solid oxide fuel cells which has an anode with a pore arrangement | sequence structure characterized by including the above step. As the pore arrangement structure described in step b, the green tape is provided with a pore arrangement structure having an adjacent interval distance of 1 to 3 cm on the surface side of the green tape with a thin stainless steel tube having a diameter of about 0.1 to 0.5 cm. 2. The method for producing a membrane electrode assembly for a solid oxide fuel cell having an anode having a pore arrangement structure according to claim 1. 2. The solid having an anode having a pore arrangement structure according to claim 1, wherein the pores applied to the green tape according to the step b are crossed and have a diameter of 0.1 to 0.5 cm. Manufacturing method of membrane electrode assembly for oxide fuel cell. ^{2. The} membrane for a solid oxide fuel cell having an anode having a pore arrangement structure according to claim 1, wherein the substrate size of the single cell described in step f is 5 × 5 cm ² to 10 × 10 cm ^2. Manufacturing method of electrode assembly. 2. The method of manufacturing a membrane electrode assembly for a solid oxide fuel cell having an anode having a pore arrangement structure according to claim 1, wherein the number of laminates of the green tape in step b is 2 to 6 layers. . 2. The solid oxide type having an anode with a pore arrangement structure according to claim 1, wherein the depth of the polishing treatment applied to the anode surface of the membrane electrode assembly according to step f is 10 to 20 μm. Manufacturing method of fuel cell membrane electrode assembly.

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