JP2016038984A - Solid oxide electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide electrochemical device, the power performance degradation of which can be suppressed by reducing toxification of an air electrode.SOLUTION: An air electrode insulation frame 23 for use in the fuel cell cassette 7 of a fuel cell 1 contains pollutants such as Si, and a pollution control layer 46 composed of GDC, for example, is formed on the surface (e.g., both principal surfaces) of the air electrode insulation frame 23. Consequently, even if the fuel gas passes around the air electrode insulation frame 23 and leaks to an air passage 35, outflow of the pollutants contained in the air electrode insulation frame 23 into the fuel gas can be suppressed. Since toxification of the air electrode 55 due to the pollutants contained in the fuel gas can be reduced, power performance degradation of the air electrode 55 can be suppressed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a solid oxide electrochemical device such as a solid oxide fuel cell or a solid oxide electrolytic device having an electrolyte body, an air electrode, and a fuel electrode.

Conventionally, as a fuel cell, for example, a solid oxide fuel cell (hereinafter also referred to as SOFC) using a solid electrolyte (solid oxide) is known.
In this SOFC, as a power generation unit, for example, a plate-shaped single cell in which a fuel electrode is provided on one side of a solid electrolyte layer and an oxidant electrode (air electrode) is provided on the other side is known.

  In addition, in this type of SOFC, a fuel cell (fuel cell cassette) in which a single cell is accommodated is used, and in order to obtain a desired voltage, a fuel cell stack in which a plurality of fuel cell cassettes are stacked. (Cell stack) has been developed (see Patent Document 1).

  As the above-described fuel cell cassette, for example, as shown in FIG. 9, there is one in which a single cell P3 is disposed between a pair of upper and lower interconnectors P1, P2, and an oxidant gas (for example, air) is disposed on the air electrode P4 side. Specifically, an air flow path P5 to which oxygen gas is supplied is provided, and a fuel flow path P7 to which fuel gas (for example, hydrogen gas) is supplied is provided on the fuel electrode P6 side.

  Further, for example, a square frame-shaped frame portion (partition wall portion) P8 is provided around the single cell P3 (in the plane direction) in a plan view, and the frame portion P8 has a stacking direction (vertical direction in the figure). ), An oxidant gas flow path P9 and a fuel gas flow path P10 are provided.

  The frame portion P8 includes, for example, an air electrode insulating frame P11 made of mica, a metal separator P12 (to which the single cell P3 is joined), a metal fuel electrode frame P13, and a fuel electrode insulating frame made of mica. P14 is laminated.

  Therefore, in the above-described fuel cell cassette, the oxidant gas passes through the oxidant gas flow path (introduction-side flow path) P9 and through the communication path (not shown) provided in the air electrode insulating frame P11. , Introduced into the air flow path P5. Although not shown, the oxidant gas after power generation is discharged from the air flow path P5 to another oxidant gas flow path via another communication path.

  On the other hand, the fuel gas passes through the fuel gas flow path (introduction-side flow path) P10 and is introduced into the fuel flow path P7 via the communication path P15 provided in the fuel electrode insulation frame P14. Although not shown, the fuel gas after power generation is discharged from the fuel flow path P7 to another fuel gas flow path via another communication path.

  As the fuel gas, for example, a reformed gas obtained by reforming a raw material gas such as natural gas with water vapor is usually used, and the reformed gas contains water vapor.

JP2013-51128A

  However, in the above-described prior art, although the air flow path P5 and the fuel gas flow path P10 are separated by the frame portion P8, some fuel gas passes through the frame P8 from the fuel gas flow path P10. Leakage (leakage) may occur in the air flow path P5 through the surroundings of the air electrode insulating frame P11 constituting the structure. This leaking gas is referred to as cross leak gas.

  In addition, this cross leak gas is an oxidant that is in contact with the air passage and the communication path connected to the flow path for supplying the fuel gas to the fuel electrode, even in the case of a solid oxide fuel cell having a flat or cylindrical single cell. This may occur when a seal (for example, a glass seal or a compression seal) is provided at a portion separating the gas flow path.

  Further, the air electrode insulating frame P11 made of, for example, mica usually contains a substance that pollutes the air electrode P4 (for example, a pollutant such as Si), and when the fuel gas contains water vapor. Since Si and the like are easily evaporated in the water vapor, the pollutant leaks to the air flow path P5 along with the leak of the fuel gas, and the air electrode P4 may be poisoned.

The same applies to the glass seal, and there is a possibility that the air electrode P4 is poisoned by contaminants such as Si contained in the glass.
When the air electrode P4 is poisoned, there is a problem that electrode performance (particularly, output voltage) is lowered. And when this electrode performance falls, the lifetime (hence the lifetime of a fuel cell) of the single cell P8 will become short.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a solid oxide electrochemical device that can reduce poisoning of the air electrode and suppress a reduction in power performance. To do.

  (1) The solid oxide electrochemical device according to the first aspect of the present invention includes a single cell having an air electrode and a fuel electrode, and an electrolyte body disposed between the air electrode and the fuel electrode. An air electrode channel that is a gas channel in contact with the air electrode, and a fuel electrode channel that is a gas channel in contact with the fuel electrode, and the air electrode channel and the fuel electrode channel. In a solid oxide electrochemical device having a structure in which the gas flow paths are separated, a communication gas flow path communicating with the fuel electrode flow path, and a partition wall separating the communication gas flow path and the air electrode flow path And the partition includes a seal member containing a substance that contaminates the air electrode, and at least part of a surface of the seal member that faces another member adjacent to the seal member, A contamination prevention layer is formed to prevent the air electrode from being poisoned by substances. And said that you are.

  In the first aspect, a communication gas flow path that communicates with a fuel electrode flow path that is a flow path of a gas that contacts the fuel electrode (hereinafter also referred to as fuel electrode side gas), and the communication gas flow path and the air electrode And a partition wall that separates an air electrode flow path that is a flow path of a gas in contact (hereinafter also referred to as an air electrode side gas). Further, the partition wall portion includes a seal member containing a substance that pollutes the air electrode (hereinafter also referred to as a pollutant), and the surface of the seal member that faces another member adjacent to the seal member. At least a part of the film is formed with a pollution prevention layer for preventing the poisoning of the air electrode by the pollutant.

  Therefore, even when the fuel electrode side gas leaks (leaks) into the air electrode flow path through the periphery of the seal member constituting the partition wall portion, the seal member is formed by the contamination prevention layer formed on the surface of the seal member. Can be prevented from flowing out into the leaked fuel electrode side gas due to transpiration or scattering. Thereby, since the poisoning of the air electrode due to the pollutant contained in the leaked fuel electrode side gas can be reduced, it is possible to suppress a decrease in the power performance (particularly the output voltage) of the air electrode. As a result, there is a remarkable effect that the life of the single cell, and thus the solid oxide electrochemical device is extended (that is, the durability is improved).

  In addition, since the pollution prevention layer has a function which suppresses "a pollutant flows out from the inside of a sealing member by fuel electrode side gas (especially fuel electrode side gas containing water vapor | steam)", a sealing member The area of the contamination prevention layer formed on the surface is preferably wider. For example, it is desirable to form so as to cover the entire surface facing the other member.

  Examples of the pollutants include Si, alkali elements (eg, K, Na), S, Cr, B, Cl, substances containing them (eg, those compounds), and carbon-based compounds such as carbide alcohols. Is mentioned.

Specifically, SO-based compounds include SOx, Si-based compounds include siloxane, and carbide-based compounds include CH ₃ H ₆ , CH ₄ O, and CH ₁₆ H ₃₄ O ₃ (diethylene glycol monododecyl ether). It is done.

  (2) In the solid oxide electrochemical device according to the second aspect of the present invention, the contamination prevention layer is formed on at least one of the surface on the communication gas flow path side and the surface on the air electrode flow path side of the seal member. ing.

  In the second aspect, in the seal member, a contamination prevention layer is formed not only on the surface facing the other member but also on at least one of the surface on the communication gas flow path side and the surface on the air electrode flow path side of the seal member. Therefore, the outflow of the contaminant contained in the seal member to the outside (specifically, the air electrode channel side) can be more effectively suppressed.

(3) In the solid oxide electrochemical device according to the third aspect of the present invention, the contamination prevention layer is formed so as to cover the entire surface of the seal member.
In the third aspect, since the contamination prevention layer is formed so as to cover the entire surface of the seal member, the outflow of the contaminant contained in the seal member to the outside (specifically, the air flow path side) is more effective. Can be suppressed.

  (4) The solid oxide electrochemical device according to the fourth aspect of the present invention has a stack structure in which the plate-like single cells are stacked, and the communication gas flow path is arranged to extend in the stacked direction. And is adjacent to the air electrode channel through the partition wall, the seal member is plate-shaped, and the contamination prevention layer is formed on at least one of both main surfaces of the seal member. Yes.

In the fourth aspect, the configuration of the solid oxide electrochemical device is illustrated, and the present invention can be suitably applied to the device having such a configuration.
(5) In the solid oxide electrochemical device according to the fifth aspect of the present invention, the contamination prevention layer is made of a material containing at least one of alumina, GDC, SDC, zirconia, ZnO, and CuO.

  In the fifth aspect, the contamination prevention layer is preferably made of a material that hardly contaminates the air electrode and includes at least one of alumina, GDC (gadolinium doped ceria), SDC (samarium doped ceria), zirconia, ZnO, and CuO. In addition, contamination of the air electrode can be prevented.

Among these, GDC is excellent in the function of collecting contaminants such as Si, and can effectively suppress the outflow of Si and the like.
In addition, it is preferable that a contamination prevention layer has the above-mentioned material as a main component, and it is still more suitable when comprised from the material mentioned above.

  Further, if the sealing member contains contaminants such as Si, the air electrode is easily poisoned by the contaminants. Therefore, the contamination prevention layer preferably has a lower content of contaminants than the sealing member. Most preferably it does not contain.

(6) In the solid oxide electrochemical device according to the sixth aspect of the present invention, the seal member is an elastic body.
In the sixth aspect, since the sealing member is an elastic body, gas leakage can be suitably suppressed (gas sealing can be performed) by pressing the sealing member with the other member or the like.

That is, the seal member can be used as a compression seal material.
As the elasticity of the seal member, one having a higher degree of elasticity than the other members (for example, one having a large Young's modulus) can be employed.

(7) In the solid oxide electrochemical device according to the seventh aspect of the present invention, the seal member is made of mica or vermiculite.
The seventh aspect exemplifies a material (for example, a ceramic gasket) used as a seal member. Mica or vermiculite is rich in elasticity, has high heat resistance, and can be suitably gas-sealed even at high temperatures (for example, in the range of 500 ° C. to 900 ° C.).

Here, mica (mica) is a kind of layered silicate mineral, and the main components are SiO ₂ · Al ₂ O ₃ · K ₂ O and crystal water.
In addition, the chemical composition of general mica is represented by IM _2-3 □ _1-0 T ₄ O ₁₀ A. Here, I is mainly K, Na, Ca, M is mainly Al, Mg, Fe, Li, Ti, □ is a void, T is mainly Si, Al, Fe, A is mainly. , OH. Note that mica usually contains a small amount of an adhesive component made of, for example, an epoxy compound or a silicon compound in addition to the component of the chemical formula.

In addition, as elastic mica, muscovite [KAl ₂ (Si ₃ Al) O ₁₀ (OH) ₂ ] mainly composed of hard mica K and phlogopite mainly composed of soft mica Mg [ KMg ₃ (Si ₃ Al) O ₁₀ (OH) ₂ ], among which soft mica is excellent in heat resistance (heat decomposability), and is therefore used in fuel cells operated at high temperatures. .

As is well known, vermiculite is obtained by heating and sintering a raw material meteorite.
(8) The solid oxide electrochemical device according to the eighth aspect of the present invention is a fuel cell that generates power using an oxidant gas and a fuel gas, and supplies the oxidant gas to the air electrode channel. The fuel electrode channel is configured to supply fuel gas via the communication gas channel.

The eighth aspect exemplifies a fuel cell (solid oxide fuel cell: SOFC) that generates power using an oxidant gas and a fuel gas as a solid oxide electrochemical device.
By applying the present invention to the fuel cell, poisoning of the air electrode can be suppressed even when fuel gas leaks from the partition wall and reaches the air electrode. Thereby, it is possible to suppress a decrease in the electrode performance of the air electrode, and thus it is possible to improve the durability of the fuel cell.

The fuel gas indicates a gas containing a reducing agent (for example, hydrogen) serving as a fuel, and the oxidant gas indicates a gas (for example, air) containing an oxidant (for example, oxygen).
Examples of the fuel gas include hydrogen gas or a reformed gas obtained by reforming various raw material gases (for example, hydrogen-rich with steam). In addition, as source gas, natural gas (for example, LNG), city gas, LPG, kerosene, methanol, biomethanol, etc. are employable, for example.

Examples of the fuel cell include a solid oxide fuel cell (SOFC) having a ZrO ₂ ceramic as an electrolyte, a solid polymer fuel cell (PEFC) having a polymer electrolyte membrane as an electrolyte, Li-Na / Examples of the fuel cell include a molten carbonate fuel cell (MCFC) using K-based carbonate as an electrolyte and a phosphoric acid fuel cell (PAFC) using phosphoric acid as an electrolyte.

  (9) The solid oxide electrochemical device according to the ninth aspect of the present invention is an electrolytic device that electrolyzes a raw material gas to generate an electrolytic gas, and the raw material is provided in the fuel electrode passage through the communication gas passage. By supplying a gas and applying a voltage between the air electrode and the fuel electrode, a first electrolytic gas is generated on the air electrode side and a second electrolytic gas is generated on the fuel electrode side. It has a configuration.

The ninth aspect exemplifies an electrolytic device (solid oxide electrolytic device: SOEC) that electrolyzes a raw material gas to generate an electrolytic gas as a solid oxide electrochemical device.
By applying the present invention to the electrolyzer, poisoning of the air electrode can be suppressed even when the source gas leaks from the partition wall and reaches the air electrode. Thereby, durability of an electrolyzer can be improved.

  In addition, as said raw material gas, water vapor | steam and hydrocarbon gas are mentioned. For example, examples of the hydrocarbon gas include the same gases as the source gas, such as natural gas (for example, LNG), city gas, LPG, kerosene, methanol, biomethanol, and the like. Moreover, oxygen gas is mentioned as 1st electrolysis gas, Hydrogen gas is mentioned as 2nd electrolysis gas.

1 is a perspective view of a fuel cell (fuel cell stack) of Example 1. FIG. FIG. 2 is a cross-sectional view showing a fuel cell stack cut away in the stacking direction (that is, showing the AA cross section of FIG. 1). It is a perspective view which decomposes | disassembles and shows a fuel cell cassette. FIG. 2 is a cross-sectional view of a fuel cell cassette broken in the stacking direction and enlarged to show a part thereof (that is, a part of the AA cross section of FIG. 1). 1 shows an air electrode insulating frame provided with a contamination prevention layer, wherein (a) is a plan view thereof, (b) is a sectional view showing a BB section of (a), and (c) is a CC section of (a). FIG. It is a perspective view which shows the single cell joined to the separator. It is sectional drawing which fractures | ruptures the air electrode insulation frame provided with the pollution prevention layer used for the fuel cell of Example 2 along the lamination direction (thickness direction), and expands one part. It is sectional drawing which fractures | ruptures the electrolysis cassette in the electrolysis apparatus of Example 3 in the lamination direction, expands, and shows a part (namely, showing a part corresponding to the AA cross section of FIG. 1). It is explanatory drawing of a prior art.

  Hereinafter, a fuel cell and an electrolysis device will be described as examples of a solid oxide electrochemical device to which the present invention is applied.

In the first embodiment, a solid oxide fuel cell will be described as an example of the fuel cell. In the following, the solid oxide form is omitted.
a) First, the schematic configuration of the fuel cell of Example 1 will be described.

  As shown in FIG. 1, the fuel cell 1 according to the first embodiment is a device that generates power by receiving supply of a fuel gas (for example, hydrogen) and an oxidant gas (for example, air, specifically oxygen in the air). . In the drawings, the oxidant gas is indicated by “O”, and the fuel gas is indicated by “F”. “IN” indicates that gas is introduced, and “OUT” indicates that gas is discharged (the same applies hereinafter).

  The fuel cell 1 includes end plates 3 and 5 disposed at both ends in the vertical direction of FIG. 1 and a plurality of (for example, 20 stages) fuel cell cells 7 (hereinafter referred to as fuel cells) disposed between the end plates 3 and 5. (Referred to as cassette).

  The end plates 3 and 5 and each fuel cell cassette 7 include a plurality of (for example, eight) through holes 9a, 9b, 9c, 9d, 9e, 9f, 9g that penetrate them in the stacking direction (vertical direction in FIG. 1), 9h (collectively referred to as 9) is provided.

  The end plate 3 is constituted by the bolts 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h (collectively referred to as 11) arranged in the through holes 9 and the nuts 13 screwed into the bolts 11. 5 and each fuel cell cassette 7 are fixed integrally.

  Further, specific (four) bolts 11b, 11d, 11f, and 11h among the bolts 11 have internal flow passages 15b through which an oxidant gas or a fuel gas flows along the axial direction (vertical direction in FIG. 1), 15d, 15f, and 15h (collectively referred to as 15) are formed.

  Further, the through holes 9b, 9d, 9f, 9h through which the bolts 11b, 11d, 11f, 11h are inserted and the internal flow paths 15 communicate with the bolts 11b, 11d, 11f, 11h, respectively. In addition, a communication hole (not shown) through which each gas can pass is provided.

  The internal flow path 15b and the through hole 9b of the bolt 11b are used for discharging the fuel gas, the internal flow path 15d and the through hole 9d of the bolt 11d are used for discharging the oxidant gas, and the internal flow path 15f of the bolt 11f. The through hole 9f is used for introducing fuel gas, and the internal flow path 15h of the bolt 11h and the through hole 9h are used for introducing oxidant gas.

  Here, as shown in FIG. 2, the flow path of the fuel gas that penetrates the fuel cell 1 in the stacking direction, that is, the flow path including the internal flow path 15b and the through hole 9b of the bolt 11b, and the internal flow path 15f of the bolt 11f. And the flow path consisting of the through holes 9f corresponds to the communication gas flow path of the present invention.

b) Next, the configuration of the fuel cell cassette 7 will be described in detail.
As shown in FIGS. 3 and 4, the fuel cell cassette 7 includes a metal interconnector 21, an air electrode insulating frame 23, a metal separator 25, a metal fuel electrode frame 27, and a fuel electrode insulation. A frame 29, a metal interconnector 31 and the like are laminated.

Among these, a single cell 33 (see FIG. 4) in which a solid electrolyte layer 51, a fuel electrode 53, and an air electrode 55 are laminated is joined to the separator 25, as will be described later.
Each of the stacked members 21 to 31 is formed with each through hole 9 through which each bolt 11 is inserted.

Hereinafter, each configuration will be described in more detail.
The interconnectors 21 and 31 are made of a conductive plate material (for example, a metal plate such as stainless steel such as SUS430). The interconnectors 21 and 31 ensure conduction between the single cells 33 and prevent gas mixing between the single cells 33 (and thus between the fuel cell cassettes 7).

  As shown in FIG. 4, the surface of the interconnectors 21, 31 on the air electrode 55 side (lower side in FIG. 4) has a number of convex portions protruding toward the air electrode 55 side so as to contact the air electrode 55. An air electrode current collector 37 is configured. The air electrode current collectors 37 are arranged in a plurality of rows (in a lattice pattern) vertically and horizontally in a plan view.

  That is, between the interconnectors 21, 31 and the air electrode 55, an air flow path 35 through which an oxidant gas flows is provided in the frame of the air electrode insulating frame 23. Air electrode current collectors 37 are arranged at intervals. Accordingly, the oxidant gas can pass around each air electrode current collector 37 in a plan view.

  Similarly, on the surface of the interconnectors 21, 31 on the fuel electrode 53 side (the upper side in FIG. 4), a number of fuel electrode current collectors that are convex portions protruding toward the fuel electrode 53 side so as to contact the fuel electrode 53. 41 is configured. The fuel electrode current collectors 41 are arranged in a plurality of rows (in a lattice pattern) vertically and horizontally in a plan view (see FIG. 3).

  That is, between the interconnectors 21, 31 and the fuel electrode 53, a fuel flow path 39 through which fuel gas flows is provided in the frame of the fuel electrode insulating frame 29, and a number of fuel electrodes are provided in the fuel flow path 39. Current collectors 41 are arranged at intervals. Thereby, fuel gas can pass the circumference | surroundings of each anode current collector 41 by planar view.

The air flow direction in the air flow path 35 is perpendicular to the paper surface of FIG. 4, and the fuel gas flow direction in the fuel flow path 39 is the left-right direction (left to right) in FIG.
Further, although not shown, the air electrode current collector 37 or the fuel electrode is also projected on the inner surface (on the unit cell 33 side) of the end plates 3 and 5 so as to protrude inward, like the interconnectors 21 and 31. A current collector 41 is provided.

  In the first embodiment, the air electrode current collector 37 or the fuel electrode current collector 41 is provided integrally with the interconnectors 21 and 31 and the end plates 3 and 5, but the interconnectors 21 and 31 and the end plate 3 are provided. Various known air electrode current collectors and fuel electrode current collectors separate from 5 may be used.

  Returning to FIG. 3, the air electrode insulating frame 23 is a mica frame made of soft mica, which is a plate material having a square frame thickness of 1 mm, for example, having electrical insulation properties. Since the air electrode insulating frame 23 is an elastic body made of soft mica, it is pressed by the bolt 11 and the nut 13 and functions as a compression seal.

  The air electrode insulating frame 23 is formed with a square opening 23a constituting an air flow path 35 at the center thereof (in plan view). The air electrode insulating frame 23 contains contaminants such as Si.

  Further, in the air electrode insulating frame 23, the long side communication holes 43 d and 43 h are respectively connected to the frame portions on each side where the pair of through holes 9 (9 d and 9 h) are provided so as to communicate with the respective through holes 9. Is provided. Further, the air electrode insulating frame 23 is provided with a plurality of grooves 45d and 45h as portions (communication portions) through which air passes so that the communication holes 43d and 43h communicate with the opening 23a.

  In particular, in the first embodiment, as shown in FIGS. 4 and 5, on both main surfaces of the air electrode insulating frame 23, specifically on both sides in the thickness direction (vertical direction in FIG. 4) of the air electrode insulating frame 23, Contamination prevention layers 46a and 46b (collectively referred to as 46) for preventing contaminants such as Si in the air electrode insulating frame 23 from flowing out are formed.

The contamination prevention layer 46 has a thickness in the range of 5 μm to 100 μm (for example, 20 μm), and is formed so as to cover the entire surface of both main surfaces (specifically, the surface in close contact with the opposing member).
As a material of the contamination prevention layer 46, for example, a material that does not contain a contaminant such as Si is used. As a material for the contamination prevention layer 46, a material having a contaminant content smaller than that of a contaminant such as Si in the air electrode insulating frame 23 may be used.

  Specifically, for example, GDC is used here, but a material partially including GDC (for example, a material having a main component) may be used. Alternatively, at least one of alumina, SDC, zirconia, ZnO, and CuO, or a material containing the one may be used.

  Returning to FIG. 3, the separator 25 is a plate material having a rectangular frame shape (for example, a metal plate such as stainless steel such as SUS430). As shown in FIG. 6, the outer peripheral edge portion (upper surface side) of the single cell 33 is brazed and joined to the separator 25 at the inner peripheral edge portion (lower surface side) along the square opening 25a at the center. ing. That is, the single cell 33 is joined so as to close the opening 25 a of the separator 25.

Here, the single cell 33 will be described.
The unit cell 33 has a so-called fuel electrode support membrane type structure, a thin-film solid electrolyte layer 51, and a fuel electrode (anode) 53 formed on one side thereof (downward in FIG. 6), A thin film air electrode (cathode) 55 formed on the other side (upper side in FIG. 5) is laminated integrally.

Since the air electrode 55 is smaller than (inside of) the solid electrolyte layer 51 in plan view, the separator 25 is bonded to the upper surface of the outer peripheral edge of the solid electrolyte layer 51.
The air electrode 55 is a porous layer, and examples of the material constituting the air electrode 55 include metals, metal oxides, and metal composite oxides. Examples of the metal include metals such as Pt, Au, Ag, Pd, Ir, Ru, and alloys thereof. Examples of the metal oxide include oxides such as La, Sr, Ce, Co, Mn, and Fe, such as La ₂ O ₃ , SrO, Ce ₂ O ₃ , Co ₂ O ₃ , MnO ₂ , and FeO. As the composite oxide, composite oxides containing La, Pr, Sm, Sr, Ba, Co, Fe, Mn, etc. (La _1-x Sr _x CoO ₃ -based composite oxide, La _1-x Sr _x FeO ₃₎ system composite _{oxide, La 1-x Sr x Co} 1-y Fe y O 3 composite _{oxide, La 1-x Sr x MnO} 3 composite _{oxide, Pr 1-x Ba x CoO} 3 composite oxide, Sm _1-x Sr _x CoO ₃ composite oxide) or the like can be used.

  The solid electrolyte layer 51 is a layer made of a solid oxide, and is capable of moving oxidant gas (oxygen) introduced into the air electrode 55 as ions during operation of the fuel cell 1 (power generation). Have

  Examples of the material constituting the solid electrolyte layer 51 include zirconia-based, ceria-based, and perovskite-based electrolyte materials. Examples of the zirconia-based material include yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (ScSZ), and calcia-stabilized zirconia (CaSZ). In general, yttria-stabilized zirconia (YSZ) is used. There are many examples. For ceria-based materials, so-called rare earth element-added ceria is used, and for perovskite-based materials, perovskite-type double oxides containing lanthanum elements are used.

The fuel electrode 53 is a porous layer. Examples of the material constituting the fuel electrode 53 include ZrO ₂ ceramics such as zirconia and CeO ceramics stabilized by at least one of metals such as Ni and Fe and rare earth elements such as Sc and Y. And mixtures with ceramics. Further, a metal such as Ni, or a cermet or Ni-based alloy of Ni and the ceramic can be used.

Although not shown, the fuel electrode 53 may be composed of a functional layer that causes a catalytic reaction by exchange of electrons and a support layer that supports the functional layer.
Returning to FIG. 3, the fuel electrode frame 27 is a rectangular frame-shaped plate material made of stainless steel such as SUS430 having conductivity.

Like the air electrode insulating frame 23, the fuel electrode insulating frame 29 is a square frame-like plate material having electrical insulation, and is a mica frame made of soft mica.
Similar to the air electrode insulation frame 23, the fuel electrode insulation frame 29 has a long opening communicating with a rectangular opening 29 a constituting the fuel passage 39 in the center and the pair of through holes 9 (9 b, 9 f). The communication holes 57b and 57f, and the grooves 59b and 59f that connect the communication holes 57b and 57f and the opening 29a are provided.

  In addition, members constituting the periphery of the through hole 9, for example, a part of the end plates 3 and 5 (part around the through hole 9), a part of the interconnectors 21 and 31 (part around the through hole 9), The air electrode insulating frame 23, the separator 25, the fuel electrode frame 27, the fuel electrode insulating frame 29, and the like constitute a partition wall 60 (see FIG. 4) in the present invention.

c) Next, a method for manufacturing the fuel cell 1 will be described.
[Manufacturing process of each member]
First, for example, a plate material made of SUS430 was punched out to produce interconnectors 21 and 31, a fuel electrode frame 27, a separator 25, and end plates 3 and 5.

Also, both the main surfaces of the interconnectors 21 and 31 and the inner side (single cell 33 side) surfaces of the end plates 3 and 5 are ground to form the air electrode current collector 37 and the fuel electrode current collector 41 in a convex shape. Produced.
Further, the frame-shaped air electrode insulating frame 23 and the fuel electrode insulating frame 29 shown in FIG. 3 were manufactured by punching or grooving a mica sheet made of known soft mica.

[Process for Producing Contamination Prevention Layer 46]
A GDC paste was prepared by mixing 50 g of GDC powder having an average particle size of 0.5 μm and 50 g of vehicle with three rolls. The vehicle was prepared by mixing 10 g of etosel and 100 g of α-terpineol as a solvent.

A screen mask having the same mask shape as that of the main surface of the air electrode insulating frame 23 was produced.
And using this screen mask, GDC paste was printed by screen printing with respect to one main surface of the air electrode insulation frame 23, and it dried at 100 degreeC after that for 30 minutes.

  Similarly, a GDC paste was printed by screen printing on the other main surface of the air electrode insulating frame 23 using a screen mask, and then dried at 100 ° C. for 30 minutes.

The printing thickness (on one side) after drying (the thickness of the coating layer) was 30 μm to 50 μm.
[Production Process of Single Cell 33]
A single cell 33 was produced according to a conventional method.

  Specifically, a fuel electrode slurry was prepared using the material of the fuel electrode 53. Then, using this fuel electrode slurry, a fuel electrode green sheet was prepared by a known doctor blade method.

  A solid electrolyte slurry was prepared using the material of the solid electrolyte layer 51. Then, using this solid electrolyte slurry, a solid electrolyte green sheet was produced by a doctor blade method.

Next, a solid electrolyte green sheet was laminated on the fuel electrode green sheet. The laminate was fired and sintered to form a sintered laminate.
In addition, an air electrode paste was produced using the material of the air electrode 55.

Next, an air electrode paste was printed on the surface of the solid electrolyte layer 51 in the sintered laminate. The printed air electrode paste was fired to form the air electrode 55.
Thereby, the single cell 33 was completed. The single cell 33 was fixed to the separator 25 by brazing.

[Assembly process of fuel cell 1]
Next, the above-described interconnectors 21 and 31, the air electrode insulating frame 23 (provided with a coating layer that becomes the contamination prevention layer 46), the fuel electrode frame 27, the fuel electrode current collector 41, the fuel electrode insulating frame 29, etc. As shown in FIG. 3, the fuel cell cassettes 7 were assembled by arranging and stacking them.

Each fuel cell cassette 7 was stacked, and end plates 3 and 5 were stacked at both ends in the stacking direction to form a stack.
And while inserting the bolt 11 in the through-hole 9 of this laminated body, the nut 13 was screwed and tightened to each bolt 11, and the laminated body was pressed and integrated and fixed. Thereby, the assembly of the fuel cell 1 was produced.

  Then, with respect to the assembly of the fuel cell 1 assembled as described above, in the electric furnace, while flowing air 2 L / min through the air flow path 35 and nitrogen 2 L / min through the fuel flow path 39, the furnace temperature The temperature was raised to 800 ° C. over 2 hours, and then maintained at 800 ° C. for 2 hours with 2 L / min of air flowing through the air channel 35 and 2 L / min of hydrogen flowing through the fuel channel 39. Thereby, the contamination prevention layer 46 is baked and formed.

Thereafter, the fuel cell 1 was completed by natural cooling.
d) Next, the effect of the first embodiment will be described.
In the first embodiment, a mica frame containing a contaminant such as Si is used as the air electrode insulating frame 23. On both main surfaces of the air electrode insulating frame 23, a pollution preventing layer 46 made of, for example, GDC is formed. ing.

  Accordingly, even when the fuel gas passes through the periphery of the air electrode insulating frame 23 (for example, the surface on the main surface side) and leaks (leaks) into the air flow path 35, the contamination formed on the surface of the air electrode insulating frame 23 The prevention layer 46 can prevent the contaminant contained in the air electrode insulating frame 23 from flowing out of the air electrode insulating frame 23 into the fuel gas due to transpiration or scattering. Thereby, since the poisoning of the air electrode 55 due to the leaked fuel gas can be reduced, a decrease in power performance (particularly, output voltage) of the air electrode 55 can be suppressed. As a result, there is a remarkable effect that the life of the single cell 33 and therefore the fuel cell 1 is extended (that is, the durability is improved).

(Modification)
As a modification of the first embodiment, the contamination prevention layer 61 may be provided only on one of the two main surfaces of the air electrode insulating frame 23.

Further, the contamination prevention layer 46 may be provided not on the entire main surface of the air electrode insulating frame 23 but on a part thereof.
The contamination prevention layer 46 is preferably provided so as to surround the entire circumference of the through holes 9f and 9b through which the fuel gas passes in a plan view.

Next, the second embodiment will be described, but the description of the same contents as the first embodiment will be omitted.
In addition, the same number is attached | subjected and demonstrated to the structure similar to Example 1. FIG.
In the second embodiment, as shown in FIG. 7, the contamination prevention layer 61 is formed on the entire circumference (the entire surface) of the air electrode insulating frame 23.

  That is, not only on both main surfaces of the air electrode insulating frame 23 but also on the surface on the through-hole 9 side, the surface on the air flow path 35 side, and the surfaces of the grooves 45d and 45h that are flow paths for the oxidant gas (air). Also, a contamination prevention layer 61 is formed.

The second embodiment has the same effects as the first embodiment and has the advantage that the effect of preventing contamination is greater than that of the first embodiment.
As another example, the contamination prevention layer 61 may be formed only on either the surface on the through hole 9 side or the surface on the air flow path 35 side. Further, the contamination prevention layer 61 may be formed not on the entire surface on the through hole 9 side or on the air flow path 35 side but on a part thereof.

Next, the third embodiment will be described, but the description of the same contents as the first embodiment will be omitted.
In addition, the same number is attached | subjected and demonstrated to the structure similar to Example 1. FIG.
In Example 3, a solid oxide electrolytic device (SOEC) will be described as an example of a solid oxide electrochemical device. (Hereafter, solid oxide form is omitted)
As shown in FIG. 8, the electrolyzer 71 of the third embodiment is made up of the metal interconnectors 21 and 31 and the air electrode insulating frame as the electrolyzer cassette 73 which is a unit of electrolysis, as in the first embodiment. 23, a metal separator 25, a metal fuel electrode frame 27, a fuel electrode insulating frame 29, a metal interconnector 31, and the like are laminated.

Among these, the single cell 33 in which the solid electrolyte layer 51, the fuel electrode 53, and the air electrode 55 are laminated is joined to the separator 25.
Also in the third embodiment, as in the first embodiment, the contamination prevention layers 46 are formed on both main surfaces of the air electrode insulating frame 23. In addition, the contamination prevention layer 46 may be provided all around like Example 2, and may be provided like the modification of Example 1,2.

  In this electrolyzer 71, a voltage is applied between the air electrode 55 and the fuel electrode 53 so that the air electrode side is + (anode) and the fuel electrode 51 is-(cathode). When, for example, water vapor is provided as a source gas from 9f, oxygen gas is generated on the air electrode 55 side, and hydrogen gas is generated on the fuel electrode 53 side.

Also in the third embodiment, the same effects as those of the first and second embodiments (that is, the effect of suppressing the poisoning of the air electrode 55) are obtained.
[Experimental example]
Next, experimental examples in which the effect of the present invention has been confirmed will be described.

<Experimental example 1>
In Experimental Example 1, the sample of the present invention (Sample Nos. 1 and 2) was prepared as described below, and a sample outside of the scope of the present invention (Sample No. 3) was prepared to improve the durability of the fuel cell. The property (deterioration rate) was examined.

  Specifically, as an example of the present invention, an air electrode insulating frame (GDC printing gasket of sample No. 1) provided with a contamination prevention layer (coating layer) made of GDC was produced in the same manner as in Example 1.

  As another example of the present invention, an alumina paste was prepared using 50 g of an alumina powder having an average particle diameter of 1.0 μm, 50 g of a vehicle (similar to Example 1) and 100 g of a solvent. Using this alumina paste, an air electrode insulating frame (alumina printing gasket of sample No. 2) provided with a contamination prevention layer (coating layer) made of alumina was produced in the same manner as in Example 1.

Furthermore, as a comparative example, an air electrode insulating frame (sample No. 3 non-printing gasket) without a contamination prevention layer was produced.
Then, a six-stage fuel cell incorporating two GDC printing gaskets, two alumina printing gaskets, and two non-printing gaskets, that is, two single cells each corresponding to sample Nos. 1, 2, and 3. A fuel cell stack in which three sets of were stacked was manufactured.

  Next, the fuel cell stack is placed in the electric furnace, and the temperature is raised to the furnace temperature of 800 ° C. over 2 hours in the electric furnace while flowing 2 L / min of air in the air channel and 2 L / min of nitrogen in the fuel channel. Thereafter, the temperature was maintained at 800 ° C. for 2 hours in a state where 2 L / min of air was supplied to the air flow path and 2 L / min of hydrogen was supplied to the fuel flow path.

Thereafter, the furnace temperature was lowered to 700 ° C., and a current-carrying durability experiment for 500 hours was performed at a generated current of 30 A with a constant load.
In this experiment, as described later, the transition of the voltage (cell voltage) in each single cell was recorded, and the deterioration rate was calculated from the difference between the initial voltage of each single cell and the voltage after 500 hours. . The results are shown in Table 1 below.

  The deterioration rate is defined by “[{(initial voltage−post-endurance voltage) ÷ initial voltage} ÷ endurance time] × 1000 hours”, and deterioration per hour using actual endurance time. By calculating the rate and multiplying by 1000 hours, the deterioration rate after 1000 hours is obtained by calculation.

  In Table 1, in a fuel cell stack including two (n = 2) single cells, the voltage before durability (initial voltage) is measured for each single cell, and the voltage after durability for 500 hours (voltage after durability) is measured. The measurement is performed for each single cell, and the average value of the voltage change of two single cells is used, and the deterioration rate is calculated using the above formula.

As is apparent from Table 1, in the case of the example of the present invention (Sample Nos. 1 and 2), the deterioration rate was as small as 0.94 or less, and the degree of deterioration was less than that of the comparative example.

In particular, a sample using GDC as a contamination prevention layer (Sample No. 1) has a very low deterioration rate of 0.78 and is more preferable.
<Experimental example 2>
In Experimental Example 2, the state of poisoning at the air electrode of the fuel cell was examined as follows.

  Specifically, in Experimental Example 2, the six-stage fuel cell stack after power generation in Experimental Example 1 was disassembled, and a single cell for the position where the gaskets of Sample Nos. 1 to 3 were disposed. A square sample piece having a side of 1 cm in a plan view was cut out from the same position of each unit cell with respect to the end portion of the air electrode on the inflow side of the oxidant gas.

  And the mass% (mass%) of the impurity of the air electrode was calculated | required with the fluorescent X ray analysis with respect to the surface by the side of the air electrode of the sample piece. The results are shown in Table 2 below.

As is apparent from Table 2, in the case of the present invention example (Sample Nos. 1 and 2), the content (mass) of impurities (Si, Al, Mg, Ca, Cl, S) in the air electrode %) Was less suitable than the comparative example. That is, the content of pollutants (Si, Cl, S) that pollute the air electrode is less than that of the comparative example, which is preferable.

In particular, a sample using GDC as a contamination prevention layer (Sample No. 1) has a very low content of contaminants and is more preferable.
[Correspondence between the present invention and the embodiment]
The electrolyte body of the present invention is a solid electrolyte layer, a seal member is an air electrode insulating frame, other members are separators, interconnectors, end plates, fuel electrode side gas is fuel gas or raw material gas, and air electrode side gas is The oxidant gas, the fuel electrode channel corresponds to the fuel channel, and the air electrode channel corresponds to the air channel.

As mentioned above, although the Example etc. of this invention were demonstrated, this invention is not limited to the said Example etc., A various aspect can be taken.
(1) For example, in the said Example 1, 2, although the groove | channel used as the flow path of oxidant gas was provided in the air electrode insulation frame, you may use the flat air electrode insulation frame without a groove | channel. In this case, an oxidizing gas channel having a groove function may be provided separately. For example, a metal air electrode plate (having the same shape as the air electrode insulating frame) may be disposed so as to be laminated on the air electrode insulating frame, and an oxidant gas flow path may be provided on the air electrode plate.

  (2) In addition, the electricity generated in the single cell can be taken out through, for example, a current collector, an interconnector, and an end plate. In this case, the interconnector, the end plate, and the current collector are It may be configured as a separate member or as an integral member.

(3) In addition to mica, vermiculite can be used as the air electrode insulating frame.
(4) The present invention provides, for example, a solid oxide fuel cell (SOFC) having a ZrO ₂ ceramic as an electrolyte, a solid polymer fuel cell (PEFC) having a polymer electrolyte membrane as an electrolyte, Li-Na / The present invention can be applied to fuel cell stacks of fuel cells such as a molten carbonate fuel cell (MCFC) using K-based carbonate as an electrolyte and a phosphoric acid fuel cell (PAFC) using phosphoric acid as an electrolyte.

1, 71 ... Fuel cell (fuel cell stack)
3, 5 ... End plate 7, 73 ... Fuel cell cassette 9, 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h ... Through-hole 21, 31 ... Interconnector 23 ... Air electrode insulation frame 33 ... Single cell 35 ... Air electrode channel (air channel)
39 ... Fuel electrode channel (fuel channel)
46, 61 ... Pollution prevention layer 51 ... Solid electrolyte layer 53 ... Fuel electrode 55 ... Air electrode 60 ... Partition wall

Claims (9)

A single cell having an air electrode and a fuel electrode, and an electrolyte body disposed between the air electrode and the fuel electrode;
An air electrode channel that is a gas channel that is in contact with the air electrode, and a fuel electrode channel that is a gas channel that is in contact with the fuel electrode, and the air electrode channel and the fuel electrode channel In a solid oxide electrochemical device having a structure in which gas flow paths are separated,
A communication gas flow channel communicating with the fuel electrode flow channel, and a partition wall that separates the communication gas flow channel and the air electrode flow channel,
The partition includes a seal member containing a substance that contaminates the air electrode,
A solid layer characterized in that a contamination prevention layer for preventing poisoning of the air electrode by the substance is formed on at least a part of a surface of the seal member facing another member adjacent to the seal member. Oxide-type electrochemical device.   2. The solid oxide electrochemical according to claim 1, wherein the anti-contamination layer is formed on at least one of the surface on the communication gas flow path side and the surface on the air electrode flow path side of the seal member. apparatus.   The solid oxide electrochemical device according to claim 2, wherein the contamination prevention layer is formed so as to cover the entire surface of the seal member. The solid oxide electrochemical device has a stack structure in which the plate-like single cells are stacked,
The communication gas channel is disposed so as to extend in the stacked direction and is adjacent to the air electrode channel via the partition wall,
The said sealing member is plate shape, Comprising: The said pollution prevention layer is formed in at least one of the both main surfaces of the said sealing member, The Claim 1 characterized by the above-mentioned. Solid oxide electrochemical device.   5. The solid oxide electricity according to claim 1, wherein the contamination prevention layer is made of a material containing at least one of alumina, GDC, SDC, zirconia, ZnO, and CuO. Chemical equipment.   The solid oxide electrochemical device according to claim 1, wherein the seal member is an elastic body.   The solid oxide electrochemical device according to claim 1, wherein the seal member is made of mica or vermiculite. The solid oxide electrochemical device is a fuel cell that generates power using an oxidant gas and a fuel gas,
The oxidant gas is supplied to the air electrode channel, and the fuel gas is supplied to the fuel electrode channel via the communication gas channel. The solid oxide electrochemical device according to Item. The solid oxide electrochemical device is an electrolytic device that electrolyzes a raw material gas to generate an electrolytic gas,
A source gas is supplied to the fuel electrode channel through the communication gas channel, and a voltage is applied between the air electrode and the fuel electrode to generate a first electrolytic gas on the air electrode side. The solid oxide electrochemical device according to claim 1, wherein the second electrolytic gas is generated on the fuel electrode side.