JP2016039004A - Fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery which makes possible to increase a speed of gas diffusion when supplying gas to an interface part of an electrode which performs a catalyst reaction, thereby enhancing a power generation performance.SOLUTION: A fuel battery 1 comprises: a unit cell 33 having a porous air electrode 55, a fuel electrode 53, and a solid electrolytic layer 51 disposed between the air electrode 55 and the fuel electrode 53. At least one electrode 55 or 53 of the air electrode 55 and the fuel electrode 53 is joined to a collector 37, 41 through a porous junction layer 71, 81 having conductivity. In addition, each junction layer 71, 81 is larger, in open porosity, than the electrode 55, 53 to which the junction layer 71, 81 is joined.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a fuel cell such as a solid oxide fuel cell including a single cell 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 porous fuel electrode in contact with a fuel gas is provided on one side of a solid electrolyte layer, and a porous oxidant electrode (for example, air) in contact with an oxidant gas (for example, air) on the other side. A single cell provided with an air electrode) is used.

  Further, in order to obtain a desired voltage, a current collector is disposed between the interconnector and the electrode of the fuel electrode or the air electrode, and a fuel in which a plurality of single cells are stacked via the interconnector and the current collector. Battery stacks (cell stacks) have been developed.

  In recent years, in order to improve the electrical conductivity between the current collector and the fuel electrode, research has been conducted to join the current collector and the fuel electrode with a porous bonding layer made of a conductive bonding agent. (See Patent Document 1).

  In addition to this, a technique of using a porous material as a structure of a fuel cell stack is also disclosed (see Patent Document 2).

Japanese Patent No. 5346402 JP 2011-222191 A

However, as described above, the technique for bonding the current collector and the electrode by the porous bonding layer has the following problems, and further improvement has been demanded.
Specifically, as schematically shown in FIG. 13, when the open porosity of the bonding layer P1 is smaller than the open porosity of the electrode (for example, air electrode) P2, the flow path (air flow) on the air electrode P2 side is used. Path) Oxidant gas (for example, air: oxygen: O _{2 in} detail) supplied to P3 is more likely to flow in the air electrode P2 than in the bonding layer P1. As a result, the speed at which oxygen spreads mainly to the interface portion P4 between the bonding layer P1 and the air electrode P2 that mainly causes a catalytic reaction is reduced, and the voltage generated in the single cell (and hence the fuel cell stack) is reduced. It was.

  That is, the catalytic reaction that contributes to power generation is likely to occur at the interface portion P4 between the bonding layer P1 and the air electrode P2 on the side where electrons are supplied via the current collector P5, but the open porosity of the bonding layer P1 is high. If it is smaller than the open porosity of the air electrode P2, a large amount of oxygen reaches the interface portion P4 from the surface of the air electrode P2 away from the interface portion P4 through the inside of the air electrode P2. For this reason, the path through which oxygen is supplied to the interface portion P4 becomes longer, so that the gas diffusion resistance (and hence the so-called polarization resistance) of the air electrode P4 increases, and the voltage generated in the single cell decreases. there were.

  The present invention has been made in view of such problems, and can increase the gas diffusion rate when supplying gas to the interface portion of the electrode that mainly performs the catalytic reaction, thereby improving the power generation performance. An object of the present invention is to provide a fuel cell capable of performing

  (1) A fuel cell according to a first aspect of the present invention includes a single cell having a porous air electrode and a fuel electrode, and an electrolyte body disposed between the air electrode and the fuel electrode. In this case, at least one of the air electrode and the fuel electrode is bonded to a conductive member via a porous bonding layer having conductivity, and the open porosity of the bonding layer is determined by the bonding layer being bonded. The open porosity of the electrode is larger.

  In the first aspect, at least one of the air electrode and the fuel electrode is bonded to the conductive member via a porous bonding layer having conductivity, and the open porosity of the bonding layer is determined by bonding. It is greater than the open porosity of the electrode to which the layers are joined.

  Therefore, as schematically shown in FIG. 8, gas (fuel gas or oxidant gas) is supplied from the periphery of the electrode or the bonding layer to the interface portion between the electrode and the bonding layer (that is, the place where the catalytic reaction is most likely to occur). In this case, since the open porosity of the bonding layer is larger than the open porosity of the electrode to which the bonding layer is bonded, the gas reaches the interface portion from the inside of the bonding layer rather than the inside of the electrode. easy.

  In other words, the first aspect is characterized in that the path (path) through which the gas reaches the interface portion is shorter and the gas diffusion resistance is smaller than in the prior art. Therefore, since the polarization resistance at the electrode is reduced, there is an effect that the voltage generated in the single cell (and hence the fuel cell) is increased.

  For example, when the air electrode is joined to a conductive member (eg, air electrode conductor) by a joining layer (eg, air electrode joining layer), the open porosity of the air electrode joining layer is the open pore of the air electrode. Greater than rate. Similarly, when the fuel electrode is bonded to a conductive member (for example, a fuel electrode current collector) by a bonding layer (for example, a fuel electrode bonding layer), the open porosity of the fuel electrode bonding layer is determined by the opening of the fuel electrode. Greater than porosity.

(2) In the fuel cell according to the second aspect of the present invention, the single cell has a plate shape, and the fuel cell is a fuel cell stack in which a plurality of the single cells are stacked in the thickness direction.
The second aspect exemplifies a fuel cell stack in which plate-shaped single cells are stacked as a fuel cell to which the present invention can be suitably applied.

  (3) In the fuel cell according to the third aspect of the present invention, the conductive member joined by the air electrode and the joining layer separates a gas flow path between the single cells and conducts between the single cells. The interconnector is a separate member or part of the interconnector.

  The third aspect illustrates the configuration of the conductive member on the air electrode side. As the conductive member on the air electrode side, an interconnector and a separate member or a structure integrated with the interconnector can be adopted.

  As a member separate from the interconnector, for example, an air electrode current collector can be adopted. Moreover, as a structure integrated with the interconnector, a convex portion that protrudes from the surface of the interconnector to the air electrode side facing the interconnector can be employed. With this integrated configuration, the number of members used can be reduced, and the configuration can be simplified. In this case, a bonding layer can be provided between the tip end surface of the convex portion and the air electrode.

  (4) In the fuel cell according to the fourth aspect of the present invention, the conductive member joined to the fuel electrode by the joining layer separates a gas flow path between the single cells and conducts between the single cells. The interconnector is a separate member or part of the interconnector.

  The fourth aspect illustrates the configuration of the conductive member on the fuel electrode side. As the conductive member on the fuel electrode side, a structure separate from the interconnector or a member integrated with the interconnector can be adopted.

  As a member separate from the interconnector, for example, a fuel electrode current collector can be adopted. Moreover, as a structure integrated with the interconnector, a convex portion that protrudes from the surface of the interconnector to the opposite fuel electrode side can be employed. With this integrated configuration, the number of members used can be reduced, and the configuration can be simplified. In this case, a bonding layer can be provided between the tip surface of the convex portion and the fuel electrode.

(5) In the fuel cell according to the fifth aspect of the present invention, the bonding layer bonded to the air electrode and the conductive member on the air electrode side is made of a spinel oxide.
The fifth aspect exemplifies the material constituting the bonding layer on the air electrode side. Since this spinel type oxide is excellent in heat resistance and conductivity, it is suitable as a material for the bonding layer.

In addition, since spinel type oxide is hard to be decomposed in an oxidizing atmosphere, it is preferable to use it as a material for the bonding layer on the air electrode side.
Below, each structure of this invention is further demonstrated.

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).
When power generation is performed using a single cell (and hence a fuel cell), fuel gas is introduced to the fuel electrode side and oxidant gas is introduced to the air electrode side.

  The open porosity indicates the ratio of open pores in each porous configuration (fuel electrode, air electrode, bonding layer). In addition, the open pores indicate pores in which gas paths communicate with each other so that the gas reaches the surface directly from inside or through other pores in each configuration. In the configuration of the fuel cell, the pores can be regarded as substantially open pores.

As the fuel cell, for example, a solid oxide fuel cell (SOFC) using a ZrO ₂ ceramic as an electrolyte, a solid polymer fuel cell (PEFC) using 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.

1 is a perspective view of a fuel cell stack of Example 1. FIG. It is a perspective view of the fuel cell cassette which comprises a fuel cell stack. It is a perspective view which decomposes | disassembles and shows a fuel cell cassette. It is a perspective view which shows a part of air electrode electrical power collector. It is a perspective view which shows the single cell joined to the separator. It is a perspective view which expands and shows an anode current collector and its principal part. It is sectional drawing which expands and shows the principal part while showing a fuel cell cassette fractured | ruptured in the lamination direction (AA cross section of FIG. 2). It is explanatory drawing which fractures | ruptures the joining part of an air electrode joining layer and an air electrode, etc. in the lamination direction, expands, and is shown typically. It is the electron micrograph (SEM photograph) which fractures | ruptures the junction part of an air electrode joining layer and an air electrode, etc. in the lamination direction, and shows the cross section. It is sectional drawing which expands and shows the principal part while cut | disconnecting and showing the fuel cell cassette of the fuel cell stack of Example 2 in the lamination direction (cross section similar to the AA cross section of FIG. 2). It is sectional drawing which expands the principal part while showing the fuel cell cassette of the fuel cell stack of Example 3 fractured | ruptured in the lamination direction (cross section similar to the AA cross section of FIG. 2). It is sectional drawing which expands the principal part while showing the fuel cell cassette of the fuel cell stack of Example 4 fractured | ruptured in the lamination direction (cross section similar to the AA cross section of FIG. 2). It is explanatory drawing of a prior art.

  Hereinafter, a solid oxide fuel cell will be described as an example of a fuel cell to which the present invention is applied.

a) First, the schematic configuration of the fuel cell of Example 1 will be described.
As shown in FIG. 1, a solid oxide fuel cell 1 (hereinafter abbreviated as a solid oxide type) 1 of Example 1 includes a fuel gas (for example, hydrogen) and an oxidant gas (for example, air, more specifically, in the air). This is a device that generates power by being supplied with oxygen. 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).

  This 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, 25 stages) fuel cell cells 7 (hereinafter referred to as fuel cells) disposed between the end plates 3 and 5. This is a fuel cell stack in which a cassette is referred to (see FIG. 2).

  Each of the end plates 3 and 5 and each fuel cell cassette 7 is provided with a plurality of (for example, eight) through holes 9 penetrating them in the stacking direction (vertical direction in FIG. 1). The end plates 3, 5 and the fuel cell cassettes 7 are integrated by bolts 11 a, 11 b, 11 c, 11 d, 11 e, 11 f, 11 g, 11 h (collectively referred to as 11) and nuts 13 screwed into the bolts 11. It is fixed to.

  In addition, the specific (four) bolts 11b, 11d, 11f, and 11h among the bolts 11 have an internal flow path 15 through which the oxidant gas or the fuel gas flows along the axial direction (vertical direction in FIG. 1). Is formed. The bolt 11b is used for discharging fuel gas, the bolt 11d is used for discharging oxidant gas, the bolt 11f is used for introducing fuel gas, and the bolt 11h is used for introducing oxidant gas.

b) Next, the configuration of the fuel cell cassette 7 will be described in detail.
As shown in FIG. 3, 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 insulating frame 29. The metal interconnector 31 and the like are laminated. Each of the stacked members 21 to 31 is formed with each through hole 9 through which each bolt 11 is inserted.

  In addition, a single cell 33 (to be described later) is joined to the separator 25, and an air electrode current collector that is a conductive member is provided in a flow path (air flow path in which the oxidant gas flows) 35 in the frame of the air electrode insulating frame 23. 37 is disposed, and a fuel electrode current collector 41, which is a conductive member, is disposed in a flow path (fuel flow path through which fuel gas flows) 39 in the frame of the fuel electrode frame 27 (or the fuel electrode insulating frame 29). Yes.

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). In addition, the interconnectors 21 and 31 should just be arrange | positioned when arrange | positioning between the adjacent single cells 33. FIG.

  The air electrode insulating frame 23 is a square frame-like plate material having electrical insulation, and is a mica frame made of soft mica. The air electrode insulating frame 23 is formed with a rectangular opening 23a constituting the air flow path 35 at the center (in plan view).

  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.

  The air electrode current collector 37 is a long conductive member (for example, a stainless steel column such as SUS430: see FIG. 4). A plurality of the air electrode current collectors 37 are arranged along the arrangement direction of the pair of through holes 9 (9d, 9h) in the opening 23a of the air electrode insulating frame 23, that is, along the air flow path. Is arranged.

  The separator 25 is a rectangular frame-like conductive plate material (for example, a metal plate such as stainless steel such as SUS430). As shown in FIG. 5, the outer peripheral edge (upper surface side) of the single cell 33 is brazed and joined to the separator 25 at the inner peripheral edge (lower surface side) along the rectangular opening 25 a at the center. ing. That is, the single cell 33 is joined so as to close the opening 25 a of the separator 25.

  As will be described later, the single cell 33 has a solid electrolyte body (solid electrolyte layer) 51, a fuel electrode 53, and an air electrode 55 (whose outer shape is smaller than that of the solid electrolyte layer 51 and the fuel electrode 53 in plan view). The separators 25 are laminated, and the separator 25 is bonded to the upper surface of the outer peripheral edge of the solid electrolyte layer 51.

  Therefore, the air flow path 35 and the fuel flow path 39 are separated by the separator 25 to which the single cells 33 are joined so that the oxidant gas and the fuel gas are not mixed in the fuel cell cassette 7. Yes.

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.

  As shown in FIG. 6, the anode current collector 41 is a combination of a spacer 61, which is a core material made of mica, and a metal conductive plate (for example, a flat plate-like net or foil made of nickel) 63. It is a well-known lattice-like member (for example, refer to the current collecting member 19 described in JP2013-55042A).

  Specifically, the fuel electrode current collector 41 includes a spacer (ladder mica) 61 in which a number of long holes 61a are opened in parallel, and a conductive plate 63 in which each piece 63a of the conductive plate 63 is bent and attached to the spacer 61. And is composed of.

Next, the single cell 33 will be described.
As shown in FIG. 7, the single cell 33 has a so-called fuel electrode support membrane type structure, and is a thin solid electrolyte layer 51 and a fuel formed on one side thereof (downward in FIG. 7). An electrode (anode) 53 and a thin film air electrode (cathode) 55 formed on the other side (upper side in FIG. 7) are integrally laminated.

  Further, an air flow path 35 is provided on the air electrode 55 side of the single cell 33, and a fuel flow path 39 is provided on the fuel electrode 53 side. The air flow direction in the air flow path 35 is perpendicular to the paper surface, and the fuel gas flow direction in the fuel flow path 39 is the left-right direction (left to right) in FIG.

Among these, the air electrode 55 is a porous layer through which the oxidant gas can pass, and the open porosity thereof is, for example, 30% in the range of 20 to 50%.
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 dense layer made of a solid oxide, and can move oxidant gas (oxygen) introduced into the air electrode 55 as ions during operation (power generation) of the fuel cell 1. Conductive.

  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 through which fuel gas can pass, and the open porosity thereof is, for example, 35% in the range of 20 to 60%. Although not shown, the fuel electrode 53 is composed of an active layer that causes a catalytic reaction by exchange of electrons and a support layer that supports the active 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 a mixture of these with ceramics. Further, a metal such as Ni, or a cermet or Ni-based alloy of Ni and the ceramic can be used.

  In the first embodiment, a porous material that has conductivity and allows oxidant gas to pass between the front end surface (bottom surface) of the plurality of air electrode current collectors 37 on the air electrode 55 side and the surface of the air electrode 55. A bonding layer (air electrode bonding layer) 71 is provided, and the air electrode current collector 37 and the air electrode 55 are bonded by the air electrode bonding layer 71.

  As a result, the plurality of air electrode bonding layers 71 are in contact with the surface of the air electrode 55, and the air electrode current collector 37 is in contact with each air electrode bonding layer 71. That is, each air electrode bonding layer 71 is in contact with a part of the surface of the air electrode 55, and the surface of the air electrode 55 is partially exposed to the air flow path 35.

Since the air electrode current collector 37 is a long member, the air electrode bonding layer 71 formed along the bottom surface of the air electrode current collector 37 also has a strip shape in plan view long in a predetermined direction (see FIG. 4).
The open porosity of the air electrode bonding layer 71 is, for example, 40% in the range of 30 to 60%, and has an open porosity larger than the open porosity of the air electrode 55 as schematically shown in FIG. ing. The thickness of the air electrode bonding layer 71 is, for example, 5 to 50 μm.

Therefore, the oxidant gas (and hence oxygen: O ₂ ) in the air flow path 35 around the air electrode 55 and the air electrode bonding layer 71 has a larger open porosity in the air electrode bonding layer 71 than in the air electrode 55. Thus, the air electrode bonding layer 71 can be more easily distributed than the air electrode 55. That is, the gas diffusion resistance in the air electrode bonding layer 71 is smaller than the gas diffusion resistance in the air electrode 55.

  Examples of the material constituting the air electrode bonding layer 71 include a conductive spinel oxide. This conductive spinel oxide is a metal oxide having a spinel crystal structure, and is not particularly limited as long as it has conductivity and forms a porous structure.

The conductive spinel oxide is an oxide represented by a composition formula of AB ₂ O ₄ and has two sites where cations called A site and B site are arranged in the crystal. Examples of the metal element indicating the A site and the B site include Cu, Mn, Co, Fe, Cr, Ni, and Zn. As the conductive spinel oxide, CuMn ₂ O ₄ , MnCo ₂ O ₄ , CoMn ₂ O ₄ , MnFe ₂ O ₄ , ZnMn ₂ O ₄ , CuFe ₂ O ₄ , CuFe ₂ O ₄ , NiMn ₂ O ₄ , CoCr ₂ O ₄ etc. are mentioned. Among these, it is preferable that CuMn ₂ O ₄ having high conductivity is included in the air electrode bonding layer. A part of the A site and the B site may be substituted with a metal element other than the metal element.

As for the fuel electrode current collector 41, as shown in FIG. 7, the piece 63 a of the conductive plate 63 arranged so as to sandwich the spacer 61 is in contact with the fuel electrode 53 as it is.
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.

  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.

[Manufacturing Process of Single Cell 33]
A single cell 33 was manufactured according to a conventional method.
Specifically, first, in order to make the fuel electrode 53 a porous layer having the above-described open porosity, for example, 40 to 70 mass of yttria-stabilized zirconia (YSZ) powder having an average particle size of 0.5 to 5 μm is used. A fuel electrode paste was prepared using a material composed of 40 parts by weight of nickel oxide powder having an average particle size of 0.5 to 5 μm and a binder solution. In addition, in order to raise an open porosity, you may use 5-30 mass parts of resin beads of 1-5 micrometers for a fuel electrode paste, for example. Then, using this fuel electrode paste, a fuel electrode green sheet was produced by a known doctor blade method.

  Moreover, in order to produce the solid electrolyte layer 51, for example, a solid electrolyte paste was produced using a material composed of a YSZ powder having an average particle size of 0.5 to 3 μm and a binder solution. And using this solid electrolyte paste, the solid electrolyte green sheet was produced by the doctor blade method.

  Next, a solid electrolyte green sheet was laminated on the fuel electrode green sheet. And the laminated body was sintered by heating at 1200-1500 degreeC for 1 to 10 hours, and the sintered laminated body was formed.

Further, in order to make the air electrode 55 a porous layer having the above-described open porosity, it is composed of La _1-x Sr _x Co _1-y Fe _y O ₃ powder having an average particle diameter of _{1 to 4} μm and a binder solution. Using the material, an air electrode paste was prepared.

  Next, an air electrode paste was printed on the surface of the solid electrolyte layer 51 in the sintered laminate. Then, the printed air electrode paste was baked at 900 to 1200 ° C. for 1 to 5 hours so as not to become dense by baking, and the air electrode 55 was formed.

Thereby, the single cell 33 was completed. The single cell 33 was fixed to the separator 25 by brazing.
[Manufacturing Process of Air Electrode Bonding Layer 71]
30 to 70 parts by mass of metal powder or oxide powder having an average particle size of 5 μm or more (for example, 5 to 30 μm), and 30 to 70 mass of metal powder or metal oxide powder having an average particle size of 5 μm or less (for example, 0.1 to 5 μm). An air electrode bonding layer paste was prepared by mixing and mixing a metal mixed powder containing a part, a solvent, a binder, a dispersant, a plasticizer, and the like.

As the metal powder, for example, any one of Cu, Mn, Co, Fe, Cr, Ni, and Zn was used, and as the metal oxide powder, for example, the above metal oxide was used.
The air electrode bonding layer paste was applied to the surface (bottom surface) of the air electrode current collector 37 on the air electrode 55 side and the surface of the air electrode 55 facing the air electrode current collector 37 by screen printing or the like. Then, it dried at the temperature (80-120 degreeC) by which the adhesiveness of an air electrode joining layer paste is not lost.

[Manufacturing process of fuel cell stack 7]
Next, the single cell 33 (with the air electrode bonding layer paste applied to the surface of the air electrode 55) and the air electrode current collector 37 (with the air electrode bonding layer paste applied to the bottom surface) are opposed to each other. They were superposed so as to be in contact with the air electrode bonding layer paste.

  At the same time, the interconnectors 21 and 31, the air electrode insulating frame 23, the fuel electrode frame 27, the fuel electrode current collector 41, the fuel electrode insulating frame 29 and the like described above are arranged and stacked as shown in FIG. Each fuel cell cassette 7 was assembled.

And each such fuel cell cassette 7 was laminated | stacked, and the end plates 3 and 5 were laminated | stacked on the both ends of the lamination direction, and the laminated body was comprised.
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.

Next, this laminate was heated in an oxidizing atmosphere, and the air electrode current collector 37 and the air electrode 55 were bonded together by the air electrode bonding layer 71.
As the conditions for the oxidation treatment, the laminate is put in an electric furnace, the fuel gas is supplied to the fuel flow path 39 in the range of 300 to 900 ° C., and the oxidant having an oxygen concentration of 15 to 100% is supplied to the air flow path 35. The method of hold | maintaining for 2 to 10 hours, flowing gas is mentioned.

  As a result, the metal powder and the metal oxide powder contained in the air electrode bonding layer paste are oxidized to change into a conductive spinel oxide. Further, by performing heat treatment under these conditions, sintering can be performed while maintaining a predetermined open porosity.

Thereby, the fuel cell 1 of Example 1 was completed.
d) Next, a method for measuring the open porosity of the air electrode 55 and the air electrode bonding layer 71 formed in the manufacturing direction described above will be described.

  For the air electrode 55 and the air electrode bonding layer 71 formed by the manufacturing method described above, a cross section is taken out along the stacking direction, and the cross section is imaged to obtain, for example, an SEM image as shown in FIG.

The magnification of this SEM image is 500 times.
Next, a plurality of straight lines parallel to the direction perpendicular to the stacking direction are drawn at a constant interval (for example, at an interval of 1 to 5 μm) from the SEM image.

Next, the length of the portion corresponding to the pores on the drawn straight line is measured.
Here, a value obtained by dividing the sum of the lengths of a plurality of pore portions on one straight line by the total straight line length corresponds to the porosity.

And the average value of the porosity of a plurality of (for example, 3 to 30) straight lines is obtained, and the average value is set as the porosity (of the air electrode 55 and the air electrode bonding layer 71).
In the fuel cell configured as in the present invention, normally, most of the pores communicate with other pores, and this porosity corresponds to the open porosity. That is, in the present invention, the porosity obtained by the measurement method described above can be adopted as the open porosity of the present invention.

In this measurement, the open porosity was measured using a 500-fold SEM image. However, the open-pore ratio can be measured by the above measurement method using a 500-2000-fold SEM image. .
e) The effect of the first embodiment will be described.

  In the first embodiment, the air electrode 55 is bonded to the air electrode current collector 37 via a porous air electrode bonding layer 71 having conductivity, and the open porosity of the air electrode bonding layer 71 is also determined. Is larger than the open porosity of the air electrode 55.

  Therefore, as shown in FIG. 8, when the oxidant gas is supplied from the air flow path 35 to the interface portion 73 between the air electrode 5 and the air electrode bonding layer 71 (that is, the place where the catalytic reaction mainly occurs) or the like. Since the open porosity of the air electrode bonding layer 71 is larger than the open porosity of the air electrode 55 to which the air electrode bonding layer 71 is bonded, the oxidant gas is more in the air electrode bonding layer 71 than inside the air electrode 55. It is easy to reach the interface portion 73 from inside.

  That is, the first embodiment is characterized in that the path (path) through which the oxidant gas reaches the interface portion 73 is shorter and the gas diffusion resistance is smaller than in the prior art. Therefore, there is an effect that the polarization resistance in the air electrode 55 is small and the voltage generated in the single cell 33 (and hence the fuel cell 1) is large.

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 fuel cell of Example 2, a porous bonding layer is provided not only on the air electrode side but also on the fuel electrode side. Details will be described below.

a) First, the configuration of the fuel cell of the second embodiment will be described.
In addition, since it is the same as that of the said Example 1 except the structure inside a fuel cell cassette, below, the structure of a fuel cell cassette is demonstrated.

  As shown in FIG. 10, in the fuel cell cassette 7 in the fuel cell 1 of the second embodiment, the air electrode insulating frame 23, the separator 25, the fuel electrode are interposed between the interconnectors 21 and 31, as in the first embodiment. A frame 27, a fuel electrode insulating frame 29, and the like are laminated.

  The separator 25 is joined with a single cell 33 (in which the air electrode 55, the solid electrolyte layer 51, and the fuel electrode 53 are integrated), and an air electrode assembly 37 is disposed in the air flow path 35. A fuel electrode assembly 41 is disposed in the fuel flow path 39.

Further, the air electrode current collector 37 and the air electrode 55 are joined by a porous joining layer (air electrode joining layer) 71.
In particular, in the second embodiment, the fuel electrode current collector 41 and the fuel electrode 53 are joined by a porous joining layer (fuel electrode joining layer) 81 through which the fuel gas can pass. The fuel electrode bonding layer 81 is made of any one of metals that are not oxidized in the atmosphere of the fuel electrode 53 during power generation, such as Ni, Fe, Co, and noble metals.

Specifically, a fuel electrode bonding layer 81 is formed between the surface of the piece 63a (surface on the fuel electrode 53 side) of the conductive plate 63 of the fuel electrode current collector 41 and the fuel electrode 53 facing the piece 63a. Yes.
That is, the fuel electrode bonding layer 81 is arranged on a part of the surface of the fuel electrode 53 so that the fuel electrode 53 is partially exposed on the surface. Specifically, the fuel electrode bonding layers 81 are formed in a plurality of rows vertically and horizontally so as to be disposed within the lattice frame (the surface of the piece 63a in FIG. 6) in plan view.

  In the second embodiment, the open porosity of the air electrode bonding layer 71 is larger than the open porosity of the air electrode 55, and the open porosity of the fuel electrode bonding layer 81 is larger than the open porosity of the fuel electrode 53. Is set. Note that the open porosity of the air electrode 55 is smaller than the open porosity of the fuel electrode 53.

  For example, the air electrode bonding layer 71 has an open porosity of 30 to 60%, the air electrode 55 has an open porosity of 20 to 50%, the fuel electrode bonding layer 81 has an open porosity of 30 to 60%, and the fuel electrode 53 is open. The porosity is 20-50%.

b) Next, a method for manufacturing the fuel cell cassette 7 will be described.
In addition, since it is the same as that of the said Example 1 except the formation method of the fuel electrode joining layer 81, here, the formation method of the fuel cell joining layer 81 is demonstrated.

  Mixing / mixing metal powder consisting of any one of Ni, Fe, Co and precious metals with an average particle size of 1-10 μm or oxide powder of the above metal, solvent, binder, dispersant, plasticizer, etc. To produce a fuel electrode bonding layer paste.

  The fuel electrode bonding layer paste is applied to the surface of the conductive plate 63 of the fuel electrode current collector 41 (the surface on the fuel electrode 53 side) and the surface facing the piece 63a of the fuel electrode 53 by screen printing or the like. did. Then, it dried at the temperature (80-120 degreeC) which does not lose the adhesiveness of a fuel electrode joining layer paste.

  Next, the air electrode is applied to the single cell 33 in which the air electrode bonding layer paste is applied to the surface of the air electrode 55 and the fuel electrode bonding layer paste is applied to the surface of the fuel electrode 53 (as in the first embodiment). The air electrode current collector 37 coated with the bonding layer paste was superposed so as to be in contact with each facing air electrode bonding layer paste. At the same time, the fuel electrode current collector 41 coated with the fuel electrode bonding layer paste was superposed so as to be in contact with each facing fuel electrode bonding layer paste.

  Then, the interconnectors 21 and 31, the air electrode insulating frame 23, the fuel electrode frame 27, the fuel electrode current collector 41, the fuel electrode insulating frame 29 and the like described above are arranged and stacked as shown in FIG. The fuel cell cassette 7 was assembled.

Thereafter, the fuel cell 1 was produced in the same manner as in Example 1.
c) Also in the second embodiment, the same effect as in the first embodiment is obtained, and the open porosity of the fuel electrode bonding layer 81 is set larger than the open porosity of the fuel electrode 53, so that the fuel gas is reduced. It is easy to reach the interface portion between the fuel electrode bonding layer 81 and the fuel electrode 53, and therefore there is an advantage that the voltage drop in the fuel cell cassette 7 and the like can be more suitably suppressed.

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 the fuel cell of Example 3, the air electrode current collector and the fuel electrode current collector are formed integrally with the interconnector. That is, an interconnector having a convex portion is used as a conductive member.

  Hereinafter, the configuration of the fuel cell according to the third embodiment will be described. Since the configuration other than the internal configuration of the fuel cell cassette is the same as that of the first embodiment, the configuration of the fuel cell cassette will be described below.

  As shown in FIG. 11, in the fuel cell cassette 101 in the fuel cell 1 of the third embodiment, the air electrode insulating frame 23, the separator 25, the fuel electrode are interposed between the interconnectors 103 and 105, as in the first embodiment. A frame 27 and a fuel electrode insulating frame 29 are stacked.

In addition, a single cell 33 (in which the air electrode 55, the solid electrolyte layer 51, and the fuel electrode 53 are integrated) is joined to the separator 25.
Particularly in the third embodiment, the air electrode current collectors 107 and 109 and the fuel electrode current collectors 111 and 113 of the interconnectors 103 and 105 are integrally formed with the interconnectors 103 and 105.

  Specifically, the interconnectors 103 and 105 project from the interconnector bodies 115 and 117 to the air electrode 55 side (downward in the figure) from the interconnector bodies 115 and 117 (for example, arranged in a plurality of rows vertically and horizontally in plan view). The cathode current collectors 107 and 109 which are projections and the projections protruding from the interconnector bodies 115 and 117 toward the fuel electrode 53 (upward in the figure) (for example, arranged in a plurality of rows vertically and horizontally in plan view) It is comprised from the fuel electrode current collectors 111 and 113 which are parts.

  An air electrode bonding layer 121 similar to that of the first embodiment is formed between the air electrode current collector 107 and the air electrode 55. On the other hand, the fuel electrode current collector 113 and the fuel electrode 53 are in direct contact.

The air electrode 55, the air electrode bonding layer 121, and the fuel electrode 53 are porous layers having the same open porosity as in the first embodiment.
Also in the third embodiment, the same effects as in the first embodiment can be obtained, and since a separate current collector is not used, the number of parts can be reduced and the configuration can be simplified.

Next, the fourth embodiment will be described, but the description of the same contents as the third embodiment will be omitted.
In addition, the same number is attached | subjected and demonstrated to the structure similar to Example 3. FIG.
In the fuel cell of Example 4, as in Example 3, the air electrode current collector and the fuel electrode current collector are formed integrally with the interconnector (that is, the interconnector provided with a convex portion). In particular, the fuel electrode current collector is also joined by the fuel electrode joining layer.

  As shown in FIG. 12, in the fuel cell cassette 101 in the fuel cell 1 of the fourth embodiment, the air electrode insulating frame 23, the separator 25, the fuel electrode are interposed between the interconnectors 103 and 105, as in the third embodiment. A frame 27 and a fuel electrode insulating frame 29 are stacked.

In addition, a single cell 33 (in which the air electrode 55, the solid electrolyte layer 51, and the fuel electrode 53 are integrated) is joined to the separator 25.
Further, the air electrode current collectors 107 and 109 and the fuel electrode current collectors 111 and 113 of the interconnectors 103 and 105 are integrally formed.

  Specifically, the interconnectors 103 and 105 include plate-like interconnector bodies 115 and 117 and an air electrode current collector 107 that is a convex portion protruding from the interconnector bodies 115 and 117 toward the air electrode 55 (downward in the figure). , 109, and fuel electrode current collectors 111, 113 which are convex portions protruding from the interconnector bodies 115, 117 to the fuel electrode 53 side (upward in the figure).

  Then, an air electrode bonding layer 121 similar to those in the first and third embodiments is formed between the air electrode current collector 107 and the air electrode 55, and the fuel electrode current collector 113 and the fuel electrode 55 are interposed between them. In addition, a fuel electrode joining layer 123 similar to that of the second embodiment is formed.

The air electrode 55, the air electrode bonding layer 121, the fuel electrode 53, and the fuel electrode bonding layer 123 are porous layers having the same open porosity as in the second embodiment.
Also in the fourth embodiment, the same effects as in the second embodiment can be obtained, and since a separate current collector is not used, the number of parts can be reduced and the configuration can be simplified.

As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, A various aspect can be taken.
(1) For example, the present invention provides, for example, a solid oxide fuel cell (SOFC) using a ZrO ₂ ceramic as an electrolyte, a solid polymer fuel cell (PEFC) using a polymer electrolyte membrane as an electrolyte, Li- The present invention can be applied to fuel cells such as a molten carbonate fuel cell (MCFC) using Na / K carbonate as an electrolyte, and a phosphoric acid fuel cell (PAFC) using phosphoric acid as an electrolyte.

(2) In the first and second embodiments, only one of the air electrode current collector and the fuel electrode current collector may be a convex portion integrated with the interconnector as in the third and fourth embodiments.
(3) Further, in the present invention, in addition to the fuel cell stack in which the plate-shaped single cells as in each of Examples 1 to 4 are stacked, the conductive member and the porous electrode are bonded by the porous bonding layer. It can be applied to various types of fuel cells.

1. Fuel cell (fuel cell stack)
3, 5 ... End plate 7, 101 ... Fuel cell (fuel cell cassette)
DESCRIPTION OF SYMBOLS 21, 31, 103, 105 ... Interconnector 33 ... Single cell 35 ... Air flow path 37, 107 ... Cathode current collector 39 ... Fuel flow path 41, 113 ... Fuel electrode current collector 51 ... Solid electrolyte layer 53 ... Fuel Electrode 55 ... Air electrode 71, 121 ... Air electrode bonding layer 81,123 ... Fuel electrode bonding layer

Claims (5)

In a fuel cell comprising a single cell having a porous air electrode and a fuel electrode, and an electrolyte body disposed between the air electrode and the fuel electrode,
At least one of the air electrode and the fuel electrode is bonded to a conductive member via a porous bonding layer having conductivity,
The fuel cell according to claim 1, wherein an open porosity of the bonding layer is larger than an open porosity of the electrode to which the bonding layer is bonded.   2. The fuel cell according to claim 1, wherein the single cell has a plate shape, and the fuel cell is a fuel cell stack in which a plurality of the single cells are stacked in a plate thickness direction.   The conductive member bonded to the air electrode by the bonding layer separates the gas flow path between the single cells and separates the interconnector that conducts between the single cells or one of the interconnectors. The fuel cell according to claim 2, wherein the fuel cell is a part.   The conductive member bonded to the fuel electrode by the bonding layer separates the gas flow path between the single cells and separates the interconnector that conducts between the single cells or one of the interconnectors. The fuel cell according to claim 1, wherein the fuel cell is a part.   The fuel cell according to any one of claims 1 to 4, wherein the bonding layer bonded to the air electrode and the conductive member on the air electrode side is made of a spinel oxide.