KR102544924B1 - Method for manufacturing solid oxide fuel cell and solid oxide fuel cell manufactured thereby - Google Patents

Abstract

The present application relates to forming an electrolyte layer by coating a composition for forming an electrolyte layer containing an oxygen ion conductive inorganic material on a substrate; forming an intermediate layer by coating a composition for forming an intermediate layer containing doped ceria on the electrolyte layer; forming a cathode by coating a composition for forming a cathode including at least one of strontium-based ferrite and platinum and bismuth oxide (Bi ₂ O ₃ ) on the intermediate layer; and simultaneously heat-treating the intermediate layer and the cathode, and a solid oxide fuel cell manufactured thereby.

Description

Manufacturing method of solid oxide fuel cell and solid oxide fuel cell manufactured thereby

This application relates to a method for manufacturing a solid oxide fuel cell and a solid oxide fuel cell manufactured thereby.

Recently, as depletion of existing energy resources such as oil and coal is predicted, interest in energy that can replace them is increasing. As one of these alternative energies, a fuel cell has attracted particular attention due to its advantages such as high efficiency, no emission of pollutants such as NOx and SOx, and abundant fuel.

A fuel cell is a power generation system that converts chemical reaction energy between a fuel and an oxidizing agent into electrical energy, and hydrocarbons such as hydrogen, methanol, and butane are typically used as fuel and oxygen as an oxidizing agent.

Fuel cells include polymer electrolyte fuel cells (PEMFC), direct methanol fuel cells (DMFC), phosphoric acid fuel cells (PAFC), alkali fuel cells (AFC), molten carbonate fuel cells (MCFC), and solid oxide fuel cells. There is a battery (SOFC) and the like.

In general, SOFC has a structure in which a plurality of electricity generation units composed of unit cells and separators are stacked. The unit cell includes an electrolyte layer, an anode (air electrode) positioned on one side of the electrolyte layer, and a cathode (fuel electrode) positioned on the other side of the electrolyte layer.

In SOFC, when oxygen is supplied to the anode and hydrogen is supplied to the cathode, oxygen ions generated by the reduction reaction of oxygen at the anode pass through the electrolyte membrane to the cathode, and then react with the hydrogen supplied to the cathode to produce water. At this time, electrons generated at the cathode are transferred to the anode and in the process of being consumed, the electrons flow to the external circuit, and the unit cell produces electrical energy using this flow of electrons.

Since the electrode reaction of SOFC occurs at the interface between the electrolyte layer and the electrode, it is important to prepare a dense electrolyte layer in order to manufacture a high-performance SOFC.

Korean Patent Publication No. 10-2005-0016431

The present application is intended to provide a method for manufacturing a solid oxide fuel cell and a solid oxide fuel cell manufactured thereby.

In one embodiment of the present specification,

Forming an electrolyte layer by coating a composition for forming an electrolyte layer containing an oxygen ion conductive inorganic material on a substrate;

forming an intermediate layer by coating a composition for forming an intermediate layer including doped ceria on the electrolyte layer;

forming a cathode by coating a composition for forming a cathode including at least one of strontium-based ferrite and platinum (Pt), and bismuth oxide (Bi ₂ O ₃ ) on the intermediate layer; and

Simultaneous heat treatment of the intermediate layer and the cathode

It provides a method for manufacturing a solid oxide fuel cell comprising a.

In addition, one embodiment of the present specification provides a solid oxide fuel cell manufactured according to the above manufacturing method.

A method for manufacturing a solid oxide fuel cell according to an exemplary embodiment of the present specification includes bismuth oxide in a composition for forming a cathode and allows the bismuth oxide to flow into the intermediate layer during sintering, thereby forming a dense structure in the intermediate layer even at a relatively low sintering temperature. make it possible Accordingly, since sintering can be performed simultaneously with the electrode, there is an advantage in that the sintering process is reduced by one step in the manufacturing process of the solid oxide fuel cell.

In addition, since bismuth oxide flows into the intermediate layer after the intermediate layer has already been formed, a problem of lowering the ionic conductivity of the intermediate layer due to bismuth oxide can be prevented.

1 is a diagram schematically illustrating a principle of generating electricity in a solid oxide fuel cell.
2 is a schematic diagram showing a method of manufacturing a solid oxide fuel cell according to an exemplary embodiment of the present specification.
3 and 4 are views showing scanning electron microscope (SEM) photographs of cells prepared in Example 1 and Comparative Example 1, respectively.

Hereinafter, this specification will be described in more detail.

In this specification, when a member is said to be located “on” another member, this includes not only the case where a member is in contact with another member, but also the case where another member exists between the two members.

In this specification, when a part is said to "include" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

Strontium-based ferrite, which is a cathode material, reacts with a zirconia-based electrolyte at an interface to generate SrZrO ₃ having low ionic conductivity. The generation of these compounds reduces the rate at which oxygen ions formed at the cathode diffuse through the electrolyte layer and react with hydrogen at the anode, thereby deteriorating overall performance of the fuel cell.

As a method of suppressing the generation of SrZrO ₃ , an intermediate layer containing doped ceria may be inserted between the cathode and the electrolyte layer, but since the doped ceria forms a dense structure at a high temperature of 1,400 ° C or higher, the porosity is reduced at a temperature below that. Since it has a high structure, there is a problem in that it is impossible to prevent the diffusion of Sr from the cathode and the generation of SrZrO ₃ .

Accordingly, the inventors of the present invention introduced bismuth oxide as a sintering aid of the intermediate layer. However, when bismuth oxide is directly introduced during the formation of the intermediate layer, there is a problem in that the bismuth oxide reacts with the intermediate layer material to lower the ion conductivity of the intermediate layer. did

As shown in FIG. 2, when bismuth oxide is included in the cathode and subjected to heat treatment, the bismuth oxide does not remain in the cathode but moves to the intermediate layer, which has the effect of making only the doped ceria denser. It was found to have no adverse effects.

In one embodiment of the present specification, a method of manufacturing a solid oxide fuel cell includes forming an electrolyte layer by coating a composition for forming an electrolyte layer including an oxygen ion conductive inorganic material on a substrate; forming an intermediate layer by coating a composition for forming an intermediate layer including doped ceria on the electrolyte layer; forming a cathode by coating a composition for forming a cathode including at least one of strontium-based ferrite and platinum (Pt), and bismuth oxide (Bi ₂ O ₃ ) on the intermediate layer; and simultaneously heat-treating the intermediate layer and the cathode.

In one embodiment of the present specification, the heat treatment is 800 ° C to 1,200 ° C, preferably 900 ° C to 1,100 ° C, more preferably 900 ° C to 1,000 ° C.

As described above, since the sintering temperature of the intermediate layer can be lowered due to the addition of bismuth oxide, a high temperature sintering condition exceeding 1,200° C. is not required. However, when the heat treatment temperature is less than 800° C., a problem may occur in that bismuth oxide present in the cathode does not flow into the intermediate layer including doped ceria.

In one embodiment of the present specification, after the heat treatment, the bismuth oxide (Bi ₂ O ₃ ) is present in the intermediate layer.

In one embodiment of the present specification, since the bismuth oxide flows into the intermediate layer and serves as a sintering aid, the dope ceria of the intermediate layer can have a dense structure even through heat treatment at 1,200° C. or less. Therefore, since the intermediate layer can be sintered even at the cathode sintering temperature, simultaneous sintering of the two layers is possible through the step of simultaneously heat-treating the intermediate layer and the cathode.

In one embodiment of the present specification, the bismuth oxide may be in a powder form.

In one embodiment of the present specification, the oxygen ion conductive inorganic material is at least one selected from yttria stabilized zirconia (YSZ) and scandia stabilized zirconium oxide (ScSZ), preferably yttria stabilized zirconia. Yttria-stabilized zirconia has the advantage of having high stability even in a reducing atmosphere.

In one embodiment of the present specification, the composition for forming the electrolyte layer may further include toluene as a solvent, but is not limited thereto.

In one embodiment of the present specification, the content of the oxygen ion conductive inorganic material is 40 wt% to 60 wt%, preferably 45 wt% to 55 wt%, based on 100 wt% of the composition for forming an electrolyte layer.

In one embodiment of the present specification, the composition for forming the electrolyte layer may further include 0.01 wt% to 20 wt% of additives such as a binder resin, a plasticizer, and a dispersant, and the types of the binder resin, plasticizer, and dispersant are specifically limited Instead, conventional materials known in the art may be used.

In one embodiment of the present specification, all of the balance other than the oxygen ion conductive inorganic material and the additive in the composition for forming an electrolyte layer is a solvent.

In one embodiment of the present specification, the substrate may be an anode.

In one embodiment of the present specification, the dope ceria is at least one selected from gadolinium dope ceria (GDC), samarium dope ceria (SDC), and yttria dope ceria (YDC).

In one embodiment of the present specification, the composition for forming the intermediate layer further includes an alcohol such as ethanol as a solvent, but is not limited thereto.

In one embodiment of the present specification, the content of the dope ceria is 50 wt% to 80 wt%, preferably 60 wt% to 70 wt%, based on 100 wt% of the composition for forming an intermediate layer. When the content of dope ceria is within the above range, there is an advantage to the screen printing process in terms of viscosity.

In one embodiment of the present specification, the composition for forming the intermediate layer may further include 0.01 wt% to 20 wt% of additives such as a binder resin, a plasticizer, and a dispersant, and the types of the binder resin, plasticizer, and dispersant are not particularly limited. Ordinary materials known in the art may be used.

In one embodiment of the present specification, all of the remainder except for the dope ceria and the additives in the composition for forming the intermediate layer is a solvent.

In one embodiment of the present specification, the manufacturing method of the solid oxide fuel cell further comprises a process of drying the intermediate layer using an oven at 80 ° C. to 100 ° C. for 10 minutes to 30 minutes after coating the composition for forming the intermediate layer. can include

In one embodiment of the present specification, the strontium ferrite is strontium ferrite (SF), lanthanum strontium ferrite (LSF), lanthanum strontium cobalt ferrite (LSCF), lanthanum strontium nickel ferrite (LSNF) and barium strontium cobalt ferrite (BSCF) At least one selected from among.

In one embodiment of the present specification, the bismuth oxide can be represented by Bi ₂ O ₃ . The reason why bismuth oxide is generally used in fuel cells is to compensate for the ionic conductivity that drops when the temperature rises, and for this purpose, doped bismuth oxide is used. On the other hand, since the bismuth oxide used in the present invention serves as a sintering aid, separate doping is not required.

In one embodiment of the present specification, the composition for forming a cathode further includes an alcohol such as ethanol as a solvent, but is not limited thereto.

In one embodiment of the present specification, the composition for forming an air electrode may further include 0.01 wt% to 20 wt% of additives such as a binder resin, a plasticizer, and a dispersant, and the types of the binder resin, plasticizer, and dispersant are not particularly limited. Ordinary materials known in the art may be used.

In one embodiment of the present specification, the content of the strontium-based ferrite is 50 wt% to 80 wt%, preferably 60 wt% to 70 wt%, based on 100 wt% of the cathode-forming composition. When the content of strontium-based ferrite is included in the above range, there is an advantage to the screen printing process in terms of viscosity.

In one embodiment of the present specification, the content of the bismuth oxide (Bi ₂ O ₃ ) is 0.1 wt% to 5 wt%, preferably 1 wt% to 3 wt%, based on 100 wt% of the composition for forming a cathode. When the content of bismuth oxide (Bi ₂ O ₃ ) exceeds 5wt%, all of the bismuth oxide may not be transferred to the intermediate layer later and some bismuth oxide may remain in the cathode.

In an exemplary embodiment of the present specification, all of the remainder except for strontium-based ferrite, bismuth oxide (Bi ₂ O ₃ ), and the additives in the composition for forming a cathode are solvents.

In one embodiment of the present specification, the manufacturing method of the solid oxide fuel cell further comprises a process of drying the cathode using an oven at 80° C. to 100° C. for 10 minutes to 30 minutes after coating the composition for forming the cathode. can include

In one embodiment of the present specification, the method for manufacturing a solid oxide fuel cell uses a composition for forming an anode including at least one selected from yttria-stabilized oxidized zirconia, scandia-stabilized oxidized zirconia, samarium-doped ceria, and gadolinium-doped ceria. The method may further include manufacturing an anode by doing so.

Specifically, the fuel electrode-forming composition is coated on the electrolyte layer, dried and fired, or the fuel-electrode-forming composition is coated on a separate release paper and dried to prepare a green sheet for an anode, and one or more anode green sheets are prepared. An anode may be manufactured by firing alone or together with a green sheet of an adjacent layer.

In one embodiment of the present specification, the solid oxide fuel cell is manufactured according to the above-described manufacturing method.

In one embodiment of the present specification, each component of the solid oxide fuel cell may refer to the description of the method of manufacturing the solid oxide fuel cell described above.

In one embodiment of the present specification, the solid oxide fuel cell further includes a fuel electrode, and the fuel electrode may be formed on a surface opposite to a surface of the electrolyte layer on which the air electrode is provided. That is, the electrolyte layer may be provided on the fuel electrode.

In one embodiment of the present specification, the thickness of the electrolyte layer may be 10 μm to 100 μm, preferably 20 μm to 50 μm.

In one embodiment of the present specification, the thickness of the intermediate layer may be 1 μm to 10 μm, preferably 2 μm to 5 μm.

In one embodiment of the present specification, the thickness of the air electrode may be 10 μm to 100 μm, preferably 20 μm to 50 μm.

In one embodiment of the present specification, the thickness of the fuel electrode may be 10 μm to 1,000 μm, preferably 100 μm to 800 μm.

In one embodiment of the present specification, the porosity of the intermediate layer may be 90% or less, preferably 80% to 90%. The fact that the porosity of the intermediate layer is 90% or less means that the intermediate layer is densely sintered even at a temperature of 1,200 ° C or less.

In one embodiment of the present specification, the content of the bismuth oxide (Bi ₂ O ₃ ) is 1wt% to 10wt%, preferably 2wt% to 5wt% based on 100wt% of the intermediate layer.

1 schematically illustrates the principle of generating electricity in a solid oxide fuel cell. The solid oxide fuel cell includes an electrolyte layer, an air electrode formed on both sides of the electrolyte layer, and a fuel electrode. It consists of As air is electrochemically reduced at the air electrode (anode), oxygen ions are generated, and the generated oxygen ions are transferred to the fuel electrode (cathode) through the electrolyte layer. In the fuel electrode (cathode), fuel such as hydrogen, methanol, or butane is injected, and the fuel is electrochemically oxidized by combining with oxygen ions to release electrons and generate water. This reaction causes the movement of electrons in the external circuit.

Hereinafter, the present specification will be described in more detail through examples. However, the following examples are only for exemplifying the present specification, and are not intended to limit the present specification.

<Experimental Example: Manufacturing and Performance Evaluation of SOFC>

Example 1.

A slurry for an electrolyte layer was prepared by mixing and mixing 8 mol% Y ₂ O ₃ stabilized zirconia (8YSZ) with toluene, a dispersant, and a binder, and then tape-casting the slurry to prepare a green sheet. After laminating them, pre-sintering was performed at 1,100° C. for 3 hours and then sintered at 1,400° C. for 2 hours to prepare an electrolyte substrate. After screen printing the interlayer paste containing GDC on the sintered 8YSZ substrate, it was dried at 80° C. for 30 minutes. Thereafter, a Pt paste (Tanaka Kikinzoku Co., Ltd., TR-7905) containing 2 wt% of commercially available bismuth oxide (Bi ₂ O ₃ ) was screen-printed on the middle layer as a composition for forming a cathode, and then dried at 80° C. for 30 minutes. . A cathode was prepared by sintering the dried half cell at a temperature of 950° C. for 1 hour. A SEM picture of the prepared half cell is shown in FIG. 3 .

Comparative Example 1.

Half of Example 1 was prepared in the same manner as in Example 1, except that Pt paste (Tanaka Kikinzoku, TR-7070) not containing bismuth oxide (Bi ₂ O ₃ ) was used instead of TR-7905 as the cathode forming composition. Cell was prepared.

A SEM picture of the fabricated cell is shown in FIG. 4 .

Comparative Example 2.

A half cell was manufactured in the same manner as in Comparative Example 1, except that 2 wt% of bismuth oxide (Bi ₂ O ₃ ) was included in the intermediate layer paste in Comparative Example 1.

A SEM picture of the fabricated cell is shown in FIG. 5 .

Looking at FIGS. 3 and 4, it can be confirmed that in the case of FIG. 3, bismuth oxide acts as a sintering aid for the intermediate layer, and the dope ceria intermediate layer grows grains to form a dense structure. In the case of FIG. 4, the dope ceria intermediate layer It can be confirmed that the porous structure is formed without grain growth.

In addition, in the case of FIG. 5 in which bismuth oxide is directly added to the composition for forming the intermediate layer, it can be confirmed that the intermediate layer has a porous structure because the bismuth oxide does not serve as a sintering aid to help grain growth of the intermediate layer. In addition, when bismuth oxide flows into the grain boundary of the electrolyte and the sample is broken to observe the cross-sectional structure, it can be confirmed that grain boundary destruction has occurred. Considering that grain boundary destruction has occurred, it can be inferred that the mechanical strength of the electrolyte layer is weakened.

Claims (10)

Forming an electrolyte layer by coating a composition for forming an electrolyte layer containing an oxygen ion conductive inorganic material on a substrate;
forming an intermediate layer by coating a composition for forming an intermediate layer including doped ceria on the electrolyte layer;
forming a cathode by coating a composition for forming a cathode including at least one of strontium-based ferrite and platinum (Pt), and bismuth oxide (Bi ₂ O ₃ ) on the intermediate layer; and
Simultaneously heat-treating the intermediate layer and the cathode,
After the heat treatment, the bismuth oxide (Bi ₂ O ₃ ) exists in the intermediate layer, and the content of the bismuth oxide (Bi ₂ O ₃ ) included in the cathode-forming composition based on 100 wt% of the cathode-forming composition A method for producing a solid oxide fuel cell of 0.1wt% to 5wt%. The method of claim 1,
The heat treatment is a method of manufacturing a solid oxide fuel cell performed at 800 ° C to 1,200 ° C. delete The method of claim 1,
A method of manufacturing a solid oxide fuel cell, wherein the oxygen ion conductive inorganic material is at least one selected from yttria stabilized zirconia (YSZ) and scandia stabilized zirconium oxide (ScSZ); The method of claim 1,
The strontium-based ferrite is at least one selected from strontium ferrite (SF), lanthanum strontium ferrite (LSF), lanthanum strontium cobalt ferrite (LSCF), lanthanum strontium nickel ferrite (LSNF) and barium strontium cobalt ferrite (BSCF) Solid oxide Manufacturing method of fuel cell. The method of claim 1,
The method of manufacturing a solid oxide fuel cell, wherein the dope ceria is at least one selected from gadolinium dope ceria (GDC) and samarium dope ceria (SDC). delete A solid oxide fuel cell manufactured according to the manufacturing method of any one of claims 1, 2, and 4 to 6. The method of claim 8,
The solid oxide fuel cell of which the porosity of the intermediate layer is 90% or less. The method of claim 9,
The content of the bismuth oxide (Bi ₂ O ₃ ) present in the intermediate layer is 1wt% to 10wt% based on 100wt% of the intermediate layer.

Images