JP2008146905A - Solid oxide fuel cell, its manufacturing method, and stack structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell capable of increasing limiting current density, and to provide its manufacturing method and a stack structure. <P>SOLUTION: The solid oxide fuel cell is equipped with an airtight member 10, a solid electrolyte 20, and a porous electrode 30, the airtight member 10 and the solid electrolyte 20 form a gas main passage A, the porous electrode 30 comes in contact with at least the solid electrolyte 20 and the airtight member 10 and is arranged in the gas main passage A and equipped with either one or both of a gas inflow side gas sub-passage and a gas exhaust side gas sub-passage. The manufacturing method of the solid oxide fuel cell uses a method such as pressing, pattern printing, mechanical grinding, etching, or ultrasonic machining, when the porous electrode 30 equipped with either one or both of the gas inflow side gas sub-passage and the gas exhaust side gas sub-passage is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell, a manufacturing method thereof, and a stack structure, and more particularly to a solid oxide fuel cell capable of improving a limit current density, a manufacturing method thereof, and a stack structure.

Conventionally, as a fuel cell capable of improving power generation efficiency, a power generation cell comprising a solid electrolyte layer formed of an oxide ion conductor and a fuel electrode layer and an oxidant electrode layer disposed on both sides of the solid electrolyte layer has been proposed. (N + 1) (n is a positive integer) stacked fuel cells, and the fuel electrode layer of the i-th (i = 1, 2,..., N) power generation cell and the fuel electrode layer A total of n separators each formed in a plate shape with a conductive material are interposed between the oxidant electrode layers of the (i + 1) th power generation cell adjacent to each other, and the fuel electrode of the i th power generation cell. A porous anode current collector having conductivity between the layer and the j-th (j = 1, 2,..., N) separator, and the oxidant of the (i + 1) -th power generation cell Porous oxidant electrode current collector having conductivity between an electrode layer and the j-th separator And a single first end plate formed in a plate shape with a conductive material via an oxidant electrode current collector is stacked on the oxidant electrode layer of the first power generation cell, and the (n + 1) ) A single second end plate made of a conductive material is laminated on the fuel electrode layer of the second power generation cell via a fuel electrode current collector, and the n separators separate the fuel gas from the outer periphery of the separator. A fuel supply passage that is introduced from the surface and is discharged from a substantially center of the separator toward the fuel electrode current collector, and an oxidant gas is introduced from the outer peripheral surface of the separator to face the oxidant electrode current collector of the separator Each of the first end plate introduces the oxidant gas from the outer peripheral surface of the first end plate and collects the oxidant electrode in the first end plate. An oxidant supply passage for discharging from a surface facing the electric body; There has been proposed a fuel cell in which two end plates have a fuel supply passage that introduces the fuel gas from the outer peripheral surface of the second end plate and discharges the fuel gas from a substantially center of the second end plate toward the anode current collector. (See Patent Document 1).
JP 2002-203579 A

  However, the fuel cell described in Patent Document 1 has a problem that, when generating electricity with a large current, the diffusion rate of gas in the electrode is rate limiting, and the current density cannot be improved.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a solid oxide fuel cell capable of improving the limit current density, a manufacturing method thereof, and a stack structure. There is to do.

  The present inventor has made extensive studies to achieve the above object, and as a result, the gas main passage is formed by the airtight member and the solid electrolyte, and the gas inflow side gas sub-passage having an opening on the gas inflow side and / or Alternatively, the above object can be achieved by arranging a porous electrode having a gas discharge side gas sub-passage having an opening on the gas discharge side in the gas main passage so as to be in contact with at least the solid electrolyte and the airtight member. As a result, the present invention has been completed.

  That is, the solid electrolyte fuel cell of the present invention is a solid electrolyte fuel cell comprising an airtight member, a solid electrolyte, and a porous electrode, wherein the airtight member and the solid electrolyte are gas main components. A gas inflow side gas sub-passage that forms a passage, the porous electrode is disposed in the gas main passage at least in contact with the solid electrolyte and the airtight member, and has an opening on the gas inflow side; A gas discharge side gas sub-passage having an opening on the gas discharge side is provided.

  The method for producing a solid oxide fuel cell according to the present invention is a method for producing a solid oxide fuel cell according to the present invention, wherein the gas inflow side gas sub-passage and / or the gas discharge having an opening on the gas inflow side. In forming a porous electrode having a gas discharge side gas sub-passage having an opening on the side, at least one kind selected from the group consisting of pressing, pattern printing, mechanical grinding, etching and ultrasonic processing The method is used.

  Furthermore, the solid oxide fuel cell stack structure of the present invention uses the solid oxide fuel cell of the present invention.

  According to the present invention, a gas main passage is formed by an airtight member and a solid electrolyte, and a gas inflow side gas sub-passage having an opening on the gas inflow side and / or a gas discharge side having an opening on the gas discharge side. A solid electrode fuel cell capable of improving the limit current density, and the like, because a porous electrode having a gas sub-passage is disposed in the gas main passage so as to be in contact with at least the solid electrolyte and the airtight member. And a stack structure can be provided.

Hereinafter, the solid oxide fuel cell of the present invention will be described.
As described above, the solid electrolyte fuel cell of the present invention includes an airtight member, a solid electrolyte, and a porous electrode, and the airtight member and the solid electrolyte form a gas main passage, and the porous electrode Is disposed in the gas main passage at least in contact with the solid electrolyte and the airtight member, and has a gas inflow side gas sub-passage having an opening on the gas inflow side and a gas discharge side gas having an opening on the gas discharge side One or both of the auxiliary passages are provided.
With such a configuration, it is possible to introduce a gas flow into the porous electrode, increase the flow rate of the gas flowing into the porous electrode, and improve the limit current density. .
Here, the “limit current density” indicates a phenomenon in which the fuel cell suddenly and drastically decreases when the supply of the reaction gas by diffusion reaches the limit and tries to extract a certain load current value. The current density.
The “individual gas sub-passage” refers to a groove provided in the surface of the porous electrode or a hole provided in the porous electrode that is smaller in width and diameter than the gas main passage.

The airtight member is not particularly limited as long as the supplied gas can flow into the porous electrode without being dissipated, and for example, an airtight current collector or an airtight separator is preferably applied. However, it is not limited to these. That is, a so-called gas seal member that does not have other functions such as current collection capability can be applied.
Examples of the airtight current collector include a nickel-based superalloy such as Inconel, a metal material such as stainless steel, and a ceramic material, and the airtight separator also includes, for example, Examples include nickel-base superalloys such as Inconel, metal materials such as stainless steel, and ceramic materials, and examples of gas seal members include glass materials and ceramic materials. Needless to say, it is not limited to these as long as it has the above-mentioned airtightness.
In particular, as the airtight member, an airtight current collector or an airtight separator can be suitably used from the viewpoint of reducing the number of parts and improving the power generation amount per volume in the stack structure described later.
Further, from the viewpoint that it is difficult to give a mechanical impact to the gas sub-passage provided in the porous electrode, it is easy to maintain a fine gas sub-passage, and durability is improved, the airtight member has elasticity, specifically A material composed of a nickel base superalloy such as Inconel or a metal plate material such as stainless steel can be suitably used.

In addition, as the solid electrolyte, for example, one having oxide ion conductivity or one having proton conductivity can be used. Specifically, as the solid electrolyte having oxide ion conductivity, 8 mol% yttrium is used. Examples of the solid electrolyte having proton conductivity include solid acid such as cesium hydrogen phosphate and cesium hydrogen sulfate. In addition, a material such as a ceramic such as a BaCeO ₃ oxide may be used, but the material is not limited thereto.
In addition, the said solid electrolyte is also airtight like the airtight member mentioned above.

Further, the porous electrode is not particularly limited as long as it has open pores through which gas flowing in the gas main passage and gas sub-passage passes. A porous electrode for a fuel electrode or a porous electrode for an air electrode applied to a solid electrolyte having a porous electrode for a fuel electrode or a porous electrode for an air electrode applied to a solid electrolyte having proton conductivity described above And so on.
As a porous electrode for a fuel electrode to be applied to the above solid electrolyte having oxide ion conductivity, since such a battery is used in a high temperature range of about 600 to 1000 ° C., specifically, A nickel (Ni) -yttrium-added stabilized zirconia (YSZ) cermet, a nickel (Ni) -lanthanum gallate cermet, a nickel (Ni) -samarium-added ceria (SDC) cermet, or the like is preferably used. The porous electrode for the air electrode applied to the solid electrolyte having oxide ion conductivity is specifically composed of LaSrMnO-based material, LaSrCoO-based material, SrSmCoO-based material, etc. However, it is needless to say that the present invention is not limited to these.
On the other hand, as a porous electrode for a fuel electrode applied to the above solid electrolyte having proton conductivity, since such a battery is used in a medium temperature range of about 150 to 400 ° C., specifically, What is comprised from the electrode which uses platinum (Pt) -carbon (C) as a main material can be used suitably, and as a porous electrode for air electrodes applied with respect to the solid electrolyte which has proton conductivity However, specifically, an electrode composed of an electrode whose main material is platinum (Pt) -carbon (C) can be suitably used, but it goes without saying that the present invention is not limited to this.

Furthermore, when the solid electrolyte has oxide ion conductivity, water vapor (H ₂ O) is generated on the fuel electrode side. Therefore, the porous electrode described above is a porous electrode for a fuel electrode. Is desirable. That is, water vapor (H ₂ O) generated by the battery reaction can be efficiently removed from the porous electrode by the introduced gas flow, and the limit current density can be further improved.
On the other hand, when the solid electrolyte has proton conductivity, water vapor (H ₂ O) is generated on the air electrode side, so that the above-mentioned porous electrode is a porous electrode for an air electrode. It is desirable for the same reason.

In the solid oxide fuel cell of the present invention, it is desirable that the porous electrode has one or both of a gas inflow side gas sub-passage and a gas discharge side gas sub-passage therein.
By adopting such a configuration, a gas flow can be further introduced into the porous electrode, a gas flow rate flowing into the porous electrode can be further increased, and a limit current density can be further improved. It becomes possible.

Furthermore, in the solid oxide fuel cell according to the present invention, the porous electrode includes a gas inflow side gas sub-passage and a gas exhaust side gas sub-passage, and the gas inflow side gas sub-passage and the gas discharge side gas sub-passage are substantially omitted. It is desirable to be parallel.
By adopting such a configuration, it is difficult for the gas flowing into the porous electrode and the gas discharged from the porous electrode to be mixed, and the gas after the cell reaction is caused by the inflow pressure of the gas before the cell reaction, Easily discharged. Therefore, the flow rate of the gas flowing into the porous electrode can be further increased, and the limit current density can be further improved.

Furthermore, in the solid oxide fuel cell of the present invention, it is desirable that the porous electrode defines a gas inflow side and a gas outflow side of the gas main passage.
By adopting such a configuration, not only can the gas flow be introduced into the porous electrode, but the supplied gas can surely flow into the porous electrode without being dissipated, and flow into the porous electrode. The gas flow rate can be further increased, and the limit current density can be further improved.
In addition, the amount of power generation per volume can be improved as compared with a case where a porous current collector or a separator having a flow path formed therein is used.

Next, the manufacturing method of the solid oxide fuel cell of this invention is demonstrated.
As described above, the method for manufacturing a solid oxide fuel cell according to the present invention is an example of the method for manufacturing the solid oxide fuel cell according to the present invention, and includes any one of a gas inflow side gas sub-passage and a gas exhaust side gas subpassage. In forming a porous electrode having one or both of them, a desired solid electrolyte is obtained by using a processing method according to press processing, pattern printing processing, mechanical grinding processing, etching processing, ultrasonic processing, and any combination thereof. Type fuel cell.
By such a processing method, a porous electrode having the gas inflow side gas sub-passage and the gas discharge side gas sub-passage described above can be formed with high productivity.

Next, the solid oxide fuel cell stack structure of the present invention will be described.
As described above, the solid oxide fuel cell stack structure of the present invention uses the solid oxide fuel cell of the present invention.
By assembling the above-described solid oxide fuel cell to form a stack structure, a gas flow can be introduced into the porous electrode, the gas flow rate flowing into the porous electrode can be increased, The voltage drop of the fuel cell due to the concentration overvoltage can be prevented, and the limit current density can be improved.
Moreover, it becomes a solid oxide fuel cell stack structure capable of improving the power generation amount per volume.

  Hereinafter, the present invention will be described in more detail with reference to some examples, but the present invention is not limited to these examples.

(Example 1)
FIG. 1 is an explanatory diagram showing the configuration of the solid oxide fuel cell of Example 1, and FIG. 2 is a cross-sectional view taken along the line II-II of the solid oxide fuel cell shown in FIG. 3 is a cross-sectional view taken along line III-III of the solid oxide fuel cell shown in FIG.
As shown in FIGS. 1 to 3, the solid oxide fuel cell of this example includes a gas seal member 14, which is an example of an airtight member 10, and an airtight current collector 12 (shown by broken lines in FIGS. 2 and 3). ), An oxide ion conductive solid electrolyte 22 (see FIGS. 2 and 3), which is an example of the solid electrolyte 20, a porous electrode 32 for a fuel electrode, which is an example of the porous electrode 30, and an air electrode 40. With.
Further, the gas seal member 14, the airtight current collector 12, and the oxide ion conductive solid electrolyte 22 form the gas main passage A.
Further, the fuel electrode porous electrode 32 is disposed in the gas main passage A in contact with the oxide ion conductive solid electrolyte 22 and the airtight current collector 12, and has an opening on the gas inflow side. A gas inflow side gas sub-passage a and a gas discharge side gas sub-passage b having an opening on the gas discharge side are provided, and the gas inflow side gas sub-passage a and the gas discharge side gas sub-passage b are substantially parallel.
1 to 3, the hydrogen gas (H ₂ ) flowing from the gas inflow side passes through the gas main passage A and the gas inflow side gas sub-passage a and is porous for the fuel electrode. The gas flows into the electrode 32, passes through the gas discharge side gas sub-passage b and the gas main passage A, and flows to the gas discharge side.
Here, in the solid oxide fuel cell of this example, an airtight current collector made of Inconel was used, and a gas seal member made of a glass material was used. The solid electrolyte is composed of 8YSZ, the fuel electrode is composed of Ni-8YSZ cermet, and the porous electrode has a diameter of 30 mm and a thickness of 1 mm. The width of the groove was 0.1 mm.

(Example 2)
FIG. 4 is an explanatory diagram showing the configuration of the solid oxide fuel cell of Example 2, and FIG. 5 is a cross-sectional view taken along line VV of the solid oxide fuel cell shown in FIG.
As shown in FIGS. 4 and 5, the solid oxide fuel cell of this example includes a gas seal member 14 that is an example of the airtight member 10, and an airtight current collector 12 (indicated by a broken line in FIG. 5). The oxide ion conductive solid electrolyte 22 (see FIG. 5), which is an example of the solid electrolyte 20, the fuel electrode porous electrode 32, which is an example of the porous electrode 30, and the air electrode 40.
Further, the gas seal member 14, the airtight current collector 12, and the oxide ion conductive solid electrolyte 22 form the gas main passage A.
Further, the fuel electrode porous electrode 32 is disposed in the gas main passage A in contact with the oxide ion conductive solid electrolyte 22 and the airtight current collector 12, and has an opening on the gas inflow side. A gas inflow side gas sub-passage a is provided. Furthermore, the fuel electrode porous electrode 32 defines a gas inflow side and a gas outflow side of the gas main passage A.
4 and 5, the hydrogen gas (H ₂ ) flowing from the gas inflow side passes through the gas main passage A and the gas inflow side gas sub-passage a and is porous for the fuel electrode. The gas flows into the electrode 32, passes through the gas discharge side gas sub-passage b and the gas main passage A, and flows to the gas discharge side.
Here, in the solid oxide fuel cell of this example, an airtight current collector made of Inconel is used, and a gas seal member made of a ceramic material is used, and oxide ion conductivity is used. The solid electrolyte is composed of SDC, the fuel electrode is composed of Ni-SDC cermet, and the porous electrode is 30 mm in diameter and 1 mm in thickness. The width of the groove was 0.2 mm.

(Example 3)
FIG. 6 is an explanatory diagram showing the configuration of the solid oxide fuel cell of Example 3, and FIG. 7 is a cross-sectional view taken along the line VII-VII of the solid oxide fuel cell shown in FIG.
As shown in FIGS. 6 and 7, the solid oxide fuel cell of this example includes a gas inflow side gas sub-passage a having an opening on the gas inflow side and an opening on the gas discharge side in the fuel electrode porous electrode 32. The configuration is the same as that of the second embodiment except that the gas discharge side gas sub-passage b having the above is provided. In addition, the cross-sectional view along the VV line of the solid oxide fuel cell in FIG. 6 is the same as FIG.
6 and 7, the hydrogen gas (H ₂ ) flowing from the gas inflow side passes through the gas main passage A and the gas inflow side gas sub-passage a and is porous for the fuel electrode. The gas flows into the electrode 32, passes through the gas discharge side gas sub-passage b and the gas main passage A, and flows to the gas discharge side.

Example 4
FIG. 8 is a cross-sectional view showing the configuration of the solid oxide fuel cell of Example 4.
As shown in the figure, the solid oxide fuel cell of this example includes a gas seal member 14, which is an example of an airtight member 10, an airtight current collector 12, and an oxide ion conduction which is an example of a solid electrolyte 20. The conductive solid electrolyte 22 and a fuel electrode porous electrode 32 which is an example of the porous electrode 30 are provided.
Further, the gas seal member 14, the airtight current collector 12, and the oxide ion conductive solid electrolyte 22 form the gas main passage A.
Further, the fuel electrode porous electrode 32 is disposed in the gas main passage A in contact with the oxide ion conductive solid electrolyte 22 and the airtight current collector 14 and has an opening on the gas inflow side. A gas inflow side gas sub-passage a and a gas discharge side gas sub-passage b having an opening on the gas discharge side are provided, and the gas inflow side gas sub-passage a and the gas discharge side gas sub-passage b are substantially parallel.
Further, the gas inflow side gas sub-passage a having an opening on the gas inflow side and the gas discharge side gas sub-passage b having an opening on the gas discharge side exist on the same plane, in other words, in the electrode thickness direction. In the same thickness position.
In FIG. 8, as indicated by the arrows, the hydrogen gas (H ₂ ) flowing from the gas inflow side passes through the gas main passage A and the gas inflow side gas sub-passage a, and the fuel electrode porous electrode 32. And flows to the gas discharge side through the gas discharge side gas sub-passage b and the gas main passage A.
Here, in the solid oxide fuel cell of this example, an airtight current collector made of Inconel was used, and a gas seal member made of a glass material was used. The solid electrolyte is made of lanthanum gallate, the fuel electrode is made of Ni-lanthanum gallate cermet, and the porous electrode has a diameter of 30 mm and a thickness of 1 mm. And the width of the groove was 0.15 mm.

(Example 5)
FIG. 9 is a cross-sectional view showing the configuration of the solid oxide fuel cell of Example 5.
As shown in the figure, the solid oxide fuel cell of this example has a gas inflow side gas sub-passage a having an opening on the gas inflow side and an opening on the gas discharge side in the porous electrode 32 for the fuel electrode. The gas discharge side gas sub-passage b has the same configuration as that of the fourth embodiment except that the gas discharge side gas sub-passage b exists on a different plane, in other words, at a different thickness position in the electrode thickness direction.
In FIG. 9, as indicated by arrows, the hydrogen gas (H ₂ ) flowing from the gas inflow side passes through the gas main passage A and the gas inflow side gas sub-passage a, and the fuel electrode porous electrode 32. And flows to the gas discharge side through the gas discharge side gas sub-passage b and the gas main passage A.

  Here, the relational expression (1) between the gas pressure and flow rate of the orifice pipe shown below

[In the formula (1), V is the gas flow rate, C is the outflow coefficient, A ₀ is the cross-sectional area, P ₁ and P ₂ are the gas pressure at the inlet / outlet of the orifice tube, and ρ is the gas density of the orifice tube, respectively. Show. ], It can be seen that the solid oxide fuel cell of the present invention in which the gas sub-passage is provided in the electrode has a limit current density of about 10 times that of the conventional solid oxide fuel cell. .

As mentioned above, although this invention was demonstrated by some suitable embodiment and an Example, this invention is not limited to this embodiment or an Example, A various deformation | transformation is possible within the range which does not deviate from the summary of this invention. It is.
For example, in the embodiment, the case where an airtight current collector and a gas seal member are used as the airtight member has been described. However, an airtight separator can also be used as the airtight member.
In the embodiments, the case where a circular thin film is used as the porous electrode has been described. However, the present invention is not limited to this, and a rectangular thin film such as a triangle or a quadrangle can also be used.
Further, in the examples, the case where the porous electrode for the fuel electrode is used as the porous electrode has been described. However, the porous electrode for the air electrode can also be used as the porous electrode.

1 is an explanatory diagram showing a configuration of a solid oxide fuel cell of Example 1. FIG. It is sectional drawing along the II-II line of the solid oxide fuel cell shown in FIG. It is sectional drawing along the III-III line of the solid oxide fuel cell shown in FIG. FIG. 3 is an explanatory diagram showing a configuration of a solid oxide fuel cell of Example 2. It is sectional drawing along the VV line of the solid oxide fuel cell shown in FIG. 6 is an explanatory view showing a configuration of a solid oxide fuel cell of Example 3. FIG. It is sectional drawing along the VII-VII line of the solid oxide fuel cell shown in FIG. 6 is a cross-sectional view showing a configuration of a solid oxide fuel cell of Example 4. FIG. 6 is a cross-sectional view showing a configuration of a solid oxide fuel cell of Example 5. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Airtight member 12 Airtight current collector 14 Gas seal member 20 Solid electrolyte 22 Oxide ion conductive solid electrolyte 30 Porous electrode 32 Porous electrode for fuel electrode 40 Air electrode A Gas main passage a Gas inflow side gas sub passage b Gas exhaust side gas sub-passage

Claims (9)

A solid oxide fuel cell comprising an airtight member, a solid electrolyte, and a porous electrode,
The airtight member and the solid electrolyte form a gas main passage,
The gas inflow side gas sub-passage and / or the gas discharge side, wherein the porous electrode is disposed in the gas main passage at least in contact with the solid electrolyte and the airtight member, and has an opening on the gas inflow side. A solid oxide fuel cell, comprising a gas discharge side gas sub-passage having an opening in a gas outlet side.   2. The solid oxide fuel cell according to claim 1, wherein the porous electrode includes the gas inflow side gas sub-passage and / or the gas discharge side gas sub-passage inside the porous electrode. . The porous electrode comprises the gas inflow side gas sub-passage and the gas discharge side gas sub-passage;
2. The solid oxide fuel cell according to claim 1, wherein the gas inflow side gas sub-passage and the gas discharge side gas sub-passage are substantially parallel. 3.   2. The solid oxide fuel cell according to claim 1, wherein the porous electrode defines a gas inflow side and a gas outflow side of the gas main passage. The solid electrolyte is a solid electrolyte having oxide ion conductivity,
2. The solid oxide fuel cell according to claim 1, wherein the porous electrode is a porous electrode for a fuel electrode. The solid electrolyte is a solid electrolyte having proton conductivity,
The solid oxide fuel cell according to claim 1, wherein the porous electrode is a porous electrode for an air electrode.   2. The solid oxide fuel cell according to claim 1, wherein the airtight member has an airtight current collector and / or an airtight separator. A method for producing a solid oxide fuel cell according to any one of claims 1 to 7,
In forming a porous electrode having a gas inflow side gas sub-passage having an opening on the gas inflow side and / or a gas discharge side gas sub-passage having an opening on the gas discharge side, press working, pattern printing, mechanical grinding A method for producing a solid oxide fuel cell, comprising using at least one method selected from the group consisting of processing, etching processing and ultrasonic processing.   A solid oxide fuel cell stack structure using the solid oxide fuel cell according to any one of claims 1 to 7.

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