WO2016140111A1

WO2016140111A1 - Fuel cell unit

Info

Publication number: WO2016140111A1
Application number: PCT/JP2016/055319
Authority: WO
Inventors: 陽介朝重
Original assignee: 株式会社村田製作所
Priority date: 2015-03-02
Filing date: 2016-02-24
Publication date: 2016-09-09

Abstract

Each of fuel cells 20a, 20b has a via conductor which is exposed in the upper surface and the lower surface, and the fuel cells 20a, 20b are laminated in the Z axis direction. A collector layer 16a is arranged between a fixing plate 14a and the fuel cell 20a; a conductive layer 22 is arranged between the fuel cell 20a and the fuel cell 20b; and a collector layer 16b is arranged between the fuel cell 20b and a fixing plate 14b. The thermal stresses of the fuel cells 20a, 20b are relaxed by the thus-arranged collector layers 16a, 16b and conductive layer 22. In addition, the collector layers 16a, 16b, the fuel cells 20a, 20b and the conductive layer 22 are bonded together by means of conductive bonding materials.

Description

Fuel cell unit

The present invention relates to a fuel cell unit, and in particular, a solid oxide type (SOFC) comprising a plurality of fuel cell cells each having a surface electrode exposed on one main surface and the other main surface facing in the stacking direction. Type) fuel cell unit.

This type of fuel cell unit is disclosed in Patent Documents 1 to 4. According to Patent Literature 1, the fuel cell stack includes a plurality of fuel cells each formed in a cylindrical shape, and a current collecting member that electrically connects these fuel cells. A sheet layer made of conductive metal particles and a resin binder is sandwiched between the fuel cell and the current collecting member. Thereby, the fuel cell is connected to the current collecting member.

According to Patent Document 2, the fuel cell stack is configured by stacking a power generation cell, a fuel electrode current collector, an oxidant electrode current collector, and a separator in a predetermined order, and applying a tightening load between the separators at both ends in the stacking direction. Consists of. The oxidant electrode current collector is fixed to the power generation cell by applying a predetermined contact load to the contact surface of the power generation cell while the fuel cell stack is heated in the heating furnace.

According to Patent Document 3, the single cell has an interconnector plate, a gas seal layer, an air electrode frame, a separator, and a fuel electrode frame stacked in a predetermined order, and bolts are inserted into the mounting holes of the members to fix the members. It is composed by doing. By pressing the single cell in the stacking direction with a bolt, the gas seal layer functions as a compression seal material.

According to Patent Document 4, a current collector made of a metal connecting plate and a mesh structure is used as one unit module, and is configured so that series and parallel connections between fuel cells can be freely constructed.

JP 2008-71676 A JP 2009-245485 A JP 2011-210423 A JP 2013-134984 A

In Patent Document 1, Ni is used as the conductive metal particles. However, when oxygen is present at the operating temperature, Ni becomes NiO and loses conductivity. For this reason, Ni has a problem that it can be used only in a reducing atmosphere.

In Patent Document 2, the fuel cell or the cell stack is deformed by repeating the heat cycle of the fuel cell or the power generation cycle by load following, and the problem of electrical continuity failure with the current collector is likely to occur. There is. In order to prevent this, a mechanism capable of applying a tightening load to the entire cell stack is necessary, which leads to an increase in cost and size.

Even in Patent Document 3, a compression mechanism such as a bolt is necessary, which leads to an increase in cost and size as in Patent Document 2.

In Patent Document 4, there is no description regarding a conductive material for joining the current collector and the fuel battery cell, and it is considered that they are electrically connected by physical contact. However, this has a problem that the contact resistance is too high.

Therefore, a main object of the present invention is to provide a fuel cell unit that can suppress a decrease in reliability of electrical connection due to thermal stress without providing a compression mechanism.

A fuel cell unit of the present invention is a solid oxide fuel cell unit comprising a plurality of fuel cells having surface electrodes provided on one main surface facing the stacking direction and the other main surface, viewed from the stacking direction. A metal member that is provided between the fuel cells and that relieves thermal stress of the plurality of fuel cells, and a conductive bonding material that electrically connects the metal members to the surface electrode. Prepare.

By relaxing the thermal stress of the fuel battery cell with the metal member, the concern of the fuel battery cell peeling off is reduced. Moreover, the resistance between the surface electrode and the metal member is reduced by electrically connecting the metal member and the surface electrode by the conductive bonding material. In this way, it is possible to suppress a decrease in reliability of electrical connection due to thermal stress without providing a compression mechanism.

Preferably, the conductive bonding material is made of conductive ceramics, and the metal member is electrically connected to the surface electrode by sintering of the conductive ceramics. By employing conductive ceramics, stable and high conductivity is ensured under the operating environment of the fuel cell unit. Further, by sintering the conductive ceramic, it is possible to prevent an increase in resistance between the surface electrode and the metal member, and thus a decrease in power generation efficiency.

Preferably, the conductive bonding material is made of LaSrCoO3, LaSrCoFeO3, MnCoO3, SmSrCoO3, LaCaMnO3, LaCaCoO3, LaCaCoFeO3, LaNiFeO3, or (LaSr) 2NiO4. These materials exhibit stable and high conductivity in the operating environment of the fuel cell unit. For this reason, the electrical resistance of a junction part can be made small and by extension, the fall of power generation efficiency can be prevented.

Preferably, the conductive bonding material is composed of a plurality of types of powders having different particle sizes. By mixing a plurality of types of powders having different particle diameters, the neck formation during sintering is dominated by surface diffusion from powders having a small diameter, and powders having a large diameter do not move from the spot. That is, the shrinkage rate as the conductive bonding material can be suppressed, and the seizure property to the metal member and the fuel battery cell and the adhesion during the power generation operation are improved.

Preferably, the conductive bonding material includes a pore former that disappears by sintering. Thereby, the shrinkage of the conductive bonding material during sintering is suppressed, and the seizure property to the metal member and the fuel battery cell and the adhesion during the power generation operation are further improved.

Preferably, the metal member is a member produced by applying a meshing process, a punching process, an expanding process, or an embossing process to a metal plate material. As a result, stress due to the difference in thermal expansion coefficient existing between the material of the fuel cell, the conductive bonding material, and the metal member is relieved, and peeling that leads to deterioration can be prevented.

Preferably, the material of the metal member includes at least one of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, and Cr. These materials have excellent heat resistance and are stable under the operating environment of the fuel cell unit. At the same time, since the material has a high conductivity, the electric resistance between the fuel cells can be reduced, and the power generation characteristics can be improved.

Preferably, the metal member has an oxidation-resistant surface coated with a material containing an element constituting the conductive bonding material and an element that diffuses at the interface. This improves the bonding strength between the metal member and the conductive bonding material, and thus the reliability of the electrical connection between the fuel cells.

Preferably, the coating material includes an alloy made of NiCo or MnCo or an oxide thereof. This improves the bonding strength between the metal member and the conductive bonding material, and thus the reliability of the electrical connection between the fuel cells.

More preferably, the coating material matches the material of the conductive bonding material. This improves the bonding strength between the metal member and the conductive bonding material, and thus the reliability of the electrical connection between the fuel cells.

Preferably, there is further provided a soaking plate sandwiched between the fuel cells through the metal member so as to disperse the heat generated in the fuel cell. By interposing the metal member, the surface electrode is connected to the metal member via the conductive bonding material. Thereby, it is possible to prevent an increase in resistance between the surface electrode and the metal member and a decrease in power generation efficiency.

According to the present invention, the thermal stress of the fuel cell is relaxed by the metal member, and the metal member and the surface electrode are electrically connected by the conductive bonding material, so that the thermal stress can be reduced without providing a compression mechanism. It is possible to suppress a decrease in reliability of the electrical connection caused.

The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is a perspective view which shows the external appearance of the fuel cell unit of this Example. It is a perspective view which shows an example of the state which looked at some disassembled fuel cell units from diagonally upward. It is a perspective view which shows an example of the state which looked at another part of the decomposed | disassembled fuel cell unit from diagonally upward. It is a perspective view which shows an example of the state which looked at the decomposed | disassembled fuel battery cell from diagonally upward. It is a perspective view which shows an example of the state which looked at the fuel electrode side conductor layer which comprises a fuel battery cell from diagonally downward. It is a side view which expands and shows the side surface of the fuel cell unit shown in FIG. It is a perspective view which shows the state which looked at the soaking | uniform-heating conductive layer inserted every predetermined number of fuel battery cells from diagonally upward, when the number of stacks of a fuel battery cell increases. FIG. 8 is a cross-sectional view showing an AA cross section of the soaking conductive layer shown in FIG. 7. FIG. 8 is a cross-sectional view showing a BB cross section of the soaking conductive layer shown in FIG. 7. It is a side view which expands and shows a part of side surface of the fuel cell unit to which the heat equalization conductive layer was added. It is a graph which shows the result of a tension test.

[First embodiment]
1 to 5, the fuel cell unit 10 of the first embodiment is a solid oxide fuel cell unit, and includes two

fuel cells

20a and 20b and a single conductive layer 22. . The

fuel cells

20a and 20b and the conductive layer 22 are deposited so that the side surfaces thereof are flush with each other, thereby forming the flat plate type fuel cell stack 12. Note that the side surfaces of the fuel cell stack 12 are not necessarily flush with each other.

Via conductors (surface electrodes) VHf, VHf,... Electrically connected to the anodes AN1 to AN4 are exposed on the upper surface (one main surface) of each of the

fuel cells

20a and 20b (see FIG. 4). Via conductors (surface electrodes) VHa, VHa,... Electrically connected to the cathodes CT1 to CT4 are exposed on the lower surfaces (the other main surfaces) of the fuel cells 20a to 20d (see FIGS. 4 and 5). ). The current generated based on the fuel electrode gas and the air electrode gas is taken out by the via conductors VHf, VHf,... On the anodes AN1 to AN4 side and the via conductors VHa, VHa,.

In this embodiment, the X axis, the Y axis, and the Z axis are assigned to the width direction, the depth direction, and the height direction of the rectangular parallelepiped forming the fuel cell stack 12, respectively.

In each of the

fuel cells

20a and 20b, manifolds MFf1 and MFf2 for propagating the fuel electrode gas in the Z-axis direction are formed, and further, manifolds MFa1 and MFa2 for propagating the air electrode gas in the Z-axis direction are formed.

When viewed from the Z-axis direction, the manifolds MFf1 and MFf2 are formed on straight lines extending in the Y-axis direction from the center of the upper surface of each of the

fuel cells

20a and 20b, and the manifolds MFa1 and MFa2 are each of the

fuel cells

20a and 20b. Is formed on a straight line extending in the X-axis direction with the center of the upper surface of the substrate as the base point.

More specifically, the manifold MFf1 is arranged on the positive side in the Y-axis direction from the center of the upper surface, and the manifold MFf2 is arranged on the negative side in the Y-axis direction from the center of the upper surface. The manifold MFa1 is arranged on the positive side in the X-axis direction from the center of the upper surface, and the manifold MFa2 is arranged on the negative side in the X-axis direction from the center of the upper surface.

Therefore, the via conductors VHf, VHf,... On the anode AN1 to AN4 side are divided into four parts based on the manifolds MFf1, MFf2, MFa1 and MFa2. Similarly, via conductors VHa, VHa,... On the cathodes CT1 to CT4 side are also divided into four parts based on the manifolds MFf1, MFf2, MFa1, and MFa2.

As shown in FIG. 4, the fuel cell 20a includes an air electrode side conductor layer 121 having a separator SP1 as a base material, an air electrode layer 122 having a separator SP2 as a base material, an electrolyte layer 123 having an electrolyte EL as a base material, The fuel electrode layer 124 having the separator SP4 as a base material and the fuel electrode side conductor layer 125 having the separator SP5 as a base material are laminated in this order.

The separator SP2 is composed of partial separators SP21 to SP23, and the separator SP4 is composed of partial separators SP41 to SP43 (details will be described later). Moreover, since the

fuel cells

20a and 20b have the same structure, the description regarding the structure of the fuel cell 20b is abbreviate | omitted by attaching | subjecting a common referential mark to a common member.

In addition to the above-described via conductors VHa, VHa,..., The separator SP1 that forms the air electrode side conductor layer 121 includes two through-holes that form the manifolds MFf1, MFf2, MFa1, and MFa2, each in the Y-axis direction. Four air electrode gas flow paths GRa, GRa,... Extending and arranged in the X-axis direction are provided. The total number of through holes is eight, and all of the through holes form a perfect circle when viewed from the Z-axis direction.

Also, the four air electrode gas flow paths GRa, GRa,... Are all formed on the upper surface of the separator SP1. Of these, the two air electrode gas flow paths GRa and GRa respectively overlap with two through holes forming the manifold MFa1. The remaining two air electrode gas flow paths GRa and GRa overlap with the two through holes forming the manifold MFa2, respectively.

Via conductors VHa, VHa,... Are provided at positions that avoid these through holes and air electrode gas flow paths GRa, GRa,. Further, the via conductors VHa, VHa,... Extend in the Z-axis direction, and one end and the other end thereof are exposed on the upper surface and the lower surface of the separator SP1, respectively.

In addition to the above-described via conductors VHf, VHf,..., The separator SP5 that forms the fuel electrode side conductor layer 125 also has two through-holes that form the manifolds MFf1, MFf2, MFa1, and MFa2, each in the X-axis direction. Four fuel electrode gas passages GRf, GRf,... Extending and arranged in the Y-axis direction are provided. The total number of through holes is eight, and all the through holes form a perfect circle when viewed from the Z-axis direction.

Further, as shown in FIG. 5, all of the four fuel electrode gas flow paths GRf, GRf,... Are formed on the lower surface of the separator SP5. Of these, the two fuel electrode gas flow paths GRf and GRf respectively overlap the two through holes forming the manifold MFf1. The remaining two fuel electrode gas flow paths GRf and GRf overlap with the two through holes forming the manifold MFf2, respectively.

Via conductors VHf, VHf,... Are provided at positions that avoid these through holes and fuel electrode gas flow paths GRf, GRf,. Further, the via conductors VHf, VHf,... Extend in the Z-axis direction, and one end and the other end thereof are exposed on the upper surface and the lower surface of the separator SP5, respectively.

In the air electrode layer 122 shown in FIG. 4, the partial separators SP21 to SP23 are formed in a stick shape having a common thickness. The partial separator SP21 extends in the Y-axis direction at the position of the positive end in the X-axis direction, the partial separator SP22 extends in the Y-axis direction at the center in the X-axis direction, and the partial separator SP23 is the negative end in the X-axis direction. The position of the part extends in the Y-axis direction.

The width of the partial separator SP21 matches the width of the partial separator SP23, and the width of the partial separator SP22 is approximately twice the width of each of the partial separators SP21 and SP23. The partial separator SP22 is formed with two through holes that form the manifolds MFf1 and MFf2. Each through-hole is rectangular when viewed from the Z-axis direction, and its long side extends in the Y-axis direction.

In a region sandwiched between the partial separators SP21 and SP22, two plate-like cathodes CT1 and CT4 are provided side by side in the Y-axis direction. Further, two plate-like cathodes CT2 and CT3 are provided side by side in the Y-axis direction in a region sandwiched between the partial separators SP22 and SP23. At this time, the cathodes CT1 and CT2 are arranged on the positive side in the Y-axis direction, and the cathodes CT3 and CT4 are arranged on the negative side in the Y-axis direction.

All of the cathodes CT1 to CT4 have the same thickness as that of the partial separators SP21 to SP23 and are rectangular when viewed from the Z-axis direction. Each side of the rectangle extends in the X-axis direction or the Y-axis direction, and the length of the side extending in the Y-axis direction is less than ½ of the length of each of the partial separators SP21 to SP23. Further, the side surface facing the positive side in the Y-axis direction is flush with the cathodes CT1, CT2 and the partial separators SP21 to SP23. Similarly, the side surface facing the negative side in the Y-axis direction is flush with the cathodes CT3, CT4 and the partial separators SP21 to SP23.

Therefore, a rectangular through-hole is formed between the cathodes CT1 and CT4 as viewed from the Z-axis direction, and a rectangular through-hole is also formed between the cathodes CT2 and CT3 as viewed from the Z-axis direction. For any rectangle, the long side extends along the X axis and the short side extends along the Y axis. The two through holes formed in this way form manifolds MFa1 and MFa2.

In the fuel electrode layer 124, the partial separators SP41 to SP43 have a common thickness and are formed in a stick shape. The partial separator SP41 extends in the X-axis direction at the position of the positive end in the Y-axis direction, the partial separator SP42 extends in the X-axis direction at the center in the Y-axis direction, and the partial separator SP43 is the negative end in the Y-axis direction. The position of the part extends in the X-axis direction.

The width of the partial separator SP41 matches the width of the partial separator SP43, and the width of the partial separator SP42 is approximately twice the width of each of the partial separators SP41 and SP43. The partial separator SP42 is formed with two through holes that form the manifolds MFa1 and MFa2. Each through-hole is rectangular when viewed from the Z-axis direction, and its long side extends in the X-axis direction.

In a region sandwiched between the partial separators SP41 and SP42, two plate-like anodes AN1 and AN2 are provided side by side in the X-axis direction. Further, two plate-like anodes AN3 and AN4 are provided side by side in the X-axis direction in a region sandwiched between the partial separators SP42 and SP43. At this time, the anodes AN1 and AN4 are arranged on the positive side in the X-axis direction, and the anodes AN2 and AN3 are arranged on the negative side in the X-axis direction.

All of the anodes AN1 to AN4 have the same thickness as that of the partial separators SP41 to SP43 and are rectangular when viewed from the Z-axis direction. Each side of the rectangle extends in the X-axis direction or the Y-axis direction, and the length of the side extending in the X-axis direction is less than ½ of the length of each of the partial separators SP41 to SP43. Further, the side surface facing the positive side in the X-axis direction is flush with the anodes AN1, AN4 and the partial separators SP41 to SP43. Similarly, the side surface facing the negative side in the X-axis direction is flush with the anodes AN3 and AN4 and the partial separators SP41 to SP43.

Therefore, a rectangular through-hole is formed between the anodes AN1 and AN2 as viewed from the Z-axis direction, and a rectangular through-hole is also formed between the anodes AN3 and AN4 as viewed from the Z-axis direction. In any rectangle, the long side extends along the Y axis, and the short side extends along the X axis. The two through holes formed in this way form manifolds MFf1 and MFf2.

The electrolyte layer 123 is formed by forming, in the electrolyte EL, four through holes that respectively form manifolds MFf1, MFf2, MFa1, and MFa2. All the through holes are rectangular when viewed from the Z-axis direction. However, the long side of the rectangle forming each of the manifolds MFf1 and MFf2 extends along the Y axis, while the long side of the rectangle forming each of the manifolds MFa1 and MFa2 extends along the X axis. The upper surfaces of the cathodes CT1 to CT4 provided on the air electrode layer 122 are in contact with the lower surface of the electrolyte layer 123, and the lower surfaces of the anodes AN1 to AN4 provided on the fuel electrode layer 124 are in contact with the upper surface of the electrolyte layer 123.

Referring back to FIG. 2, the current collecting layer 16a is formed by four small current collecting plates 161a to 164a and a single spacer 18a. Each of the small current collectors 161a to 164a is made of a metal that relaxes the thermal stress of the

fuel cells

20a and 20b, and is formed by folding a strip-shaped metal member into a U shape. In the state of being folded in a U shape, the area of the upper surface or the lower surface of each of the small current collectors 161a to 164a is slightly less than ¼ of the area of the upper surface or the lower surface of the fuel cell 20a. Further, the thicknesses of the small current collectors 161a to 164a coincide with each other.

The small current collecting plate 161a is arranged at a position on the X axis direction positive side and the Y axis direction positive side of the upper surface of the fuel cell 20a so that the lower surface thereof faces a part of the via conductors VHf, VHf,. The The small current collecting plate 162a is positioned at the X axis direction negative side and the Y axis direction positive side of the upper surface of the fuel cell 20a so that the lower surface of the small current collecting plate 162a faces another part of the via conductors VHf, VHf,. Arranged.

The small current collecting plate 163a is positioned at the X axis direction negative side and the Y axis direction negative side of the upper surface of the fuel cell 20a so that the lower surface of the small current collecting plate 163a faces the other part of the via conductors VHf, VHf,. Arranged. The small current collector plate 164a is positioned on the X axis direction positive side and the Y axis direction negative side of the upper surface of the fuel cell 20a so that the lower surface of the small current collector plate 164a faces the other part of the via conductors VHf, VHf,. Arranged.

Thus, the small current collectors 161a to 164a are electrically connected to the via conductors VHf, VHf,.

The spacer 18a has the same thickness as the small current collecting plates 161a to 164a, and is disposed at a position where the small current collecting plates 161a to 164a are missing. Since the small current collectors 161a to 164a are arranged as described above, the upper surface or the lower surface of each spacer 18a forms a cross. Note that the thickness of the spacer 18a is not necessarily the same as the thickness of the small current collectors 161a to 164a. This is because the difference in thickness can be adjusted by a conductive material or a sealing material.

Further, the current collecting layer 16b shown in FIG. 3 is formed by four small current collecting plates 161b to 164b and a single spacer 18b. Each of the small current collecting plates 161b to 164b is made of a metal that relaxes the thermal stress of the

fuel cells

20a and 20b, and a strip-shaped metal member is folded in a U shape. In the state of being folded in a U shape, the area of the upper surface or the lower surface of each of the small current collectors 161b to 164b is slightly less than ¼ of the area of the upper surface or the lower surface of the fuel cell 20b. Further, the thicknesses of the small current collectors 161b to 164b coincide with each other.

The small current collecting plate 161b is arranged at a position on the X axis direction positive side and the Y axis direction positive side of the lower surface of the fuel cell 20b so that the upper surface thereof faces a part of the via conductors VHa, VHa,. The The small current collecting plate 162b is positioned at the X-axis direction negative side and the Y-axis direction positive side of the lower surface of the fuel cell 20b so that the upper surface of the small current collecting plate 162b faces the other part of the via conductors VHa, VHa,. Arranged.

The small current collecting plate 163b is positioned at the X axis direction negative side and the Y axis direction negative side of the lower surface of the fuel cell 20b so that the upper surface of the small current collecting plate 163b faces the other part of the via conductors VHa, VHa,. Arranged. The small current collector plate 164b is positioned on the X axis direction positive side and the Y axis direction negative side of the lower surface of the fuel cell 20b so that the upper surface of the small current collector plate 164b faces the other part of the via conductors VHa, VHa,. Arranged.

Thus, the small current collectors 161b to 164b are electrically connected to the via conductors VHa, VHa,.

The spacer 18b has the same thickness as the small current collecting plates 161b to 164b, and is disposed at a position where the small current collecting plates 161b to 164b are missing. Since the small current collectors 161b to 164b are arranged as described above, the upper surface or the lower surface of each spacer 18b forms a cross.

Further, with respect to the spacer 18b, four through holes that form the manifolds MFf1, MFf2, MFa1, and MFa2 are formed. Each through hole is rectangular when viewed from the Z-axis direction. However, the long side of the rectangle forming each of the manifolds MFf1 and MFf2 extends along the Y axis, while the long side of the rectangle forming each of the manifolds MFa1 and MFa2 extends along the X axis.

2 has an area that substantially matches the area of the upper surface of the fuel cell stack 12, and the upper surface or lower surface of the fixing plate 14b shown in FIG. 3 has an area of the lower surface of the fuel cell stack 12. It has almost the same area.

The fixing plate 14a is disposed on the upper surface of the current collecting layer 16a so that a part of the lower surface thereof faces the upper surface of the current collecting layer 16a. The fixing plate 14b is disposed on the lower surface of the current collecting layer 16b so that a part of the upper surface thereof faces the lower surface of the current collecting layer 16b. Here, the side surfaces of the fixing

plates

14a and 14b are flush with the side surface of the fuel cell stack 12 (however, it is not essential that they be flush).

Further, two through holes forming each of the manifolds MFf1, MFf2, MFa1 and MFa2 are provided for the fixing plate 14b. The total number of through holes is eight, and all of the through holes form a perfect circle when viewed from the Z-axis direction.

The conductive layer 22 provided between the

fuel cells

20a and 20b transmits the current extracted from the

fuel cells

20a and 20b to the current collecting layers 16a and 16b.

The conductive layer 22 is also formed by four small conductive plates 221 to 224 and a single spacer 24. Each of the small conductive plates 221 to 224 is made of a metal that relaxes the thermal stress of the

fuel cells

20a and 20b, and a strip-shaped metal member is folded in a U shape. In the state of being folded in a U shape, the area of the upper surface or the lower surface of each of the small conductive plates 221 to 224 is slightly less than 1/4 of the area of the upper surface or the lower surface of the

fuel cells

20a, 20b. Further, the thicknesses of the small conductive plates 221 to 224 coincide with each other.

The small conductive plate 221 has a top surface facing a part of the via conductors VHa, VHa,... And a bottom surface facing a part of the via conductors VHf, VHf,. Are arranged on the X axis direction positive side and the Y axis direction positive side. The small conductive plate 222 has an upper surface facing another part of the via conductors VHa, VHa,... And a lower surface facing the other part of the via conductors VHf, VHf,. And 20b between the X axis direction negative side and the Y axis direction positive side.

The small conductive plate 223 has an upper surface facing the other part of the via conductors VHa, VHa,... And a lower surface facing the other part of the via conductors VHf, VHf,. And 20b between the X axis direction negative side and the Y axis direction negative side. The small conductive plate 224 has a top surface facing another part of the via conductors VHa, VHa,... And a bottom surface facing another part of the via conductors VHf, VHf,. It is arranged at a position between the

cells

20a and 20b on the X axis direction positive side and the Y axis direction negative side.

Via conductors VHa, VHa,... Provided in the fuel cell 20a are electrically connected to via conductors VHf, VHf,... Provided in the fuel cell 20b via the small conductive plates 221 to 224 thus arranged. Connected.

The spacer 24 has the same thickness as the small conductive plates 221 to 224, and is disposed at a position where the small conductive plates 221 to 224 are missing. Since the small conductive plates 221 to 224 are arranged as described above, the upper surface or the lower surface of each spacer 24 forms a cross.

The spacer 24 is also formed with four through holes that form the manifolds MFf1, MFf2, MFa1, and MFa2. Each through hole is rectangular when viewed from the Z-axis direction. However, the long side of the rectangle forming each of the manifolds MFf1 and MFf2 extends along the Y axis, while the long side of the rectangle forming each of the manifolds MFa1 and MFa2 extends along the X axis.

Referring to FIG. 6, a paste-like conductive bonding material 26 is disposed between the upper surface of the fuel cell 20a and the lower surfaces of the small current collectors 161a to 164a. A paste-like conductive bonding material 26 is also disposed between the lower surface of the fuel cell 20b and the upper surfaces of the small current collectors 161b to 164b. When the conductive bonding material 26 is sintered, the via conductors VHa, VHa,... Are joined to the small current collectors 161a to 164a, and the via conductors VHf, VHf,... Are joined to the small current collectors 161b to 164b.

The minute gap generated between the fuel battery cell 20a and the small current collector plates 161a to 164a or the minute gap generated between the fuel battery cell 20b and the small current collector plates 161b to 164b is a conductive bonding material. 26.

Also, a sealing material 28 made of crystallized glass is disposed between the upper surface of the fuel cell 20a and the lower surface of the spacer 18a, and between the upper surface of the spacer 18a and the lower surface of the fixing plate 14a. The sealing material 28 is also disposed between the lower surface of the fuel battery cell 20b and the upper surface of the spacer 18b, and between the lower surface of the spacer 18b and the upper surface of the fixing plate 14b. As a result, the fixing plate 14a is fixed to the fuel cell 20a via the spacer 18a, and the fixing plate 14b is fixed to the fuel cell 20b via the spacer 18b.

Further, a paste-like conductive bonding material 26 is disposed between the lower surface of the fuel cell 20a and the upper surfaces of the small conductive plates 221 to 224. A conductive bonding material 26 is also disposed between the upper surface of the fuel cell 20b and the lower surfaces of the small conductive plates 221 to 224. When the conductive bonding material 26 is sintered, the via conductors VHf, VHf, ..., VHa, VHa, ... are bonded to the small conductive plates 221 to 224. Small gaps generated between the small conductive plates 221 to 224 and each of the

fuel cells

20a and 20b are filled with the conductive bonding material 26.

Also, a sealing material 28 is disposed between the lower surface of the fuel cell 20a and the upper surface of the spacer 24, and the sealing material 28 is also disposed between the upper surface of the fuel cell 20b and the lower surface of the spacer 24. As a result, the

fuel cells

20 a and 20 b are fixed to each other via the spacer 24.

The air electrode gas flowing through the manifolds MFa1 and MFa2 is discharged to the outside of the fuel cell stack 12 through the air electrode gas flow paths GRa, GRa,. Further, the fuel electrode gas flowing through the manifolds MFf1 and MFf2 is discharged to the outside of the fuel cell stack 12 via the fuel electrode gas flow paths GRf, GRf,.

When the air electrode gas flows through the manifolds MFa12, MFa22 and the air electrode gas flow paths GRa, GRa,..., The air electrode gas contacts the cathodes CT1 to CT4. Further, the fuel electrode gas contacts the anodes AN1 to AN4 when flowing through the manifolds MFf14, MFf24 and the fuel electrode gas flow paths GRf, GRf,. The air electrode gas and the fuel electrode gas undergo a chemical reaction according to the chemical formulas 1 and 2, and as a result, a positive voltage and a negative voltage appear on both surfaces of the electrolyte EL.
[Chemical 1]
1 / 2O ₂ + 2e ⁻ → O ²⁻
[Chemical 2]
H ₂ + O ²⁻ → H ₂ O + 2e ⁻

A part of the air electrode gas and the fuel electrode gas is discharged outside the

fuel cells

20a and 20b without causing a chemical reaction. The air electrode gas is discharged through the air electrode gas flow paths GRa, GRa,..., And the fuel electrode gas is discharged through the fuel electrode gas flow paths GRf, GRf,. The discharged air electrode gas and fuel electrode gas react with each other to generate heat, thereby achieving heat independence.

As the conductive bonding material 26, conductive ceramic (La0.8Sr0.2) 0.95MnO3 (hereinafter referred to as "LSM") is employed. The reason for the adoption is that the material of the conductive pad (not shown) provided on the outermost surface of the cell is LSM, that the LSM is stable in high-temperature air to which the fuel cell unit 10 is exposed, and past adoption results. There are many cases.

Also, the conductive bonding material 26 is a mixture of two types of powders having a large and small particle size distribution. In this way, in the neck formation during sintering, surface diffusion from the powder having a small diameter becomes dominant, and the powder having a large diameter does not move from the spot. That is, the shrinkage rate can be suppressed, and the seizure property to the small current collecting plates 161a to 164a, 161b to 164b, the small conductive plates 221 to 224 and the

fuel cells

20a and 20b, and the adhesion during power generation operation are improved. .

The conductive bonding material 26 was further mixed with carbon as a pore former. By adding carbon, shrinkage of the LSM during sintering is suppressed, and the small current collectors 161a to 164a, 161b to 164b, the small conductive plates 221 to 224, the seizure to the

fuel cells

20a and 20b, and the power generation operation The adhesion at the time is further improved.

Each of the small current collectors 161a to 164a, 161b to 164b, and the small conductive plates 221 to 224 is made of Crofer22APU (trade name) manufactured by VDM. This material has a composition based on ferritic stainless steel having a thermal expansion coefficient close to that of the

fuel cells

20a and 20b, and exhibits high oxidation resistance by adding a trace element.

A metal plate made of such a material is meshed to produce a mesh-like metal member, which is cut into a strip shape and folded into a U-shape, whereby the small current collector plates 161a to 164a, 161b to 164b, Each of the conductive plates 221 to 224 is obtained. The size of the mesh is adjusted to a wire diameter of φ0.2 mm and 50 mesh. By adopting a structure that can be easily deformed like a mesh, the

fuel cells

20a, 20b and the fixing

plates

14a, 14b can be electrically connected without a compression mechanism. Furthermore, it is possible to follow the deformation of the

fuel cells

20a and 20b due to a heat cycle or a power generation cycle.

Further, the surfaces of the small current collecting plates 161a to 164a, 161b to 164b, and the small conductive plates 221 to 224 are coated with NiCo plating and heat-treated in advance. NiCo plating becomes NiCo spinel by oxidation.

The paste-like conductive bonding material 26 is impregnated in the mesh by applying to such a surface. When dried and fired in this state, interdiffusion of elements occurs between LSM and NiCo during sintering. As a result, the bonding strength with the

fuel cells

20a and 20b and thus the connection reliability is improved.

In addition, at least one of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, and Cr having excellent heat resistance is contained in the materials of the small current collectors 161a to 164a, 161b to 164b, and the small conductive plates 221 to 224 By doing so, the small current collecting plates 161a to 164a, 161b to 164b and the small conductive plates 221 to 224 are stabilized under the operating environment of the fuel cell unit 10. At the same time, since these materials exhibit high electrical conductivity, the electrical resistance between the

fuel cells

20a and 20b can be reduced, and the characteristics of the fuel cell stack 12 can be enhanced.

When the number of fuel cell stacks is increased, it is necessary to insert the soaking conductive layer 30 shown in FIGS. 7 to 9 instead of the conductive layer 22. The reason is that cracks may occur in the fuel cell due to heat generation during power generation. However, it is not necessary to replace all the

conductive layers

22, 22,... With the soaking conductive layer 30. For example, the soaking conductive layer 30 may be replaced with one of the five

conductive layers

22, 22,.

7 to 9, the soaking conductive layer 30 is formed by four small conductive plates 301 to 304, four small soaking plates 321 to 324, and two spacers 34a to 34b.

Each of the small conductive plates 301 to 304 is made of a metal that relaxes the thermal stress of the two fuel cells sandwiching the soaking conductive layer 30, and a strip-shaped metal member is folded in a U shape. When folded in a U shape, the area of the upper surface or lower surface of each of the small conductive plates 301 to 304 is slightly less than ¼ of the area of the upper surface or lower surface of each fuel cell. Further, the thicknesses of the small conductive plates 301 to 304 coincide with each other. However, this thickness exceeds the thickness of the small conductive plates 221 to 224.

The small conductive plate 301 is disposed at a position on the positive side in the X-axis direction and on the positive side in the Y-axis direction between the two fuel cells. The small conductive plate 302 is disposed between the two fuel cells in the position on the X axis direction negative side and the Y axis direction positive side. The small conductive plate 303 is disposed at a position on the negative side in the X-axis direction and on the negative side in the Y-axis direction between the two fuel cells. The small conductive plate 304 is disposed between the two fuel cells in a position on the positive side in the X-axis direction and on the negative side in the Y-axis direction.

The upper surfaces of the small conductive plates 301 to 304 face the via conductors VHa, VHa,... Of the upper fuel cell, and the lower surfaces of the small conductive plates 301 to 304 have via conductors VHf, VHf,. Opposite…. Via conductors VHa, VHa,... Provided in the upper fuel cell are connected to via conductors VHf, VHf,... Provided in the lower fuel cell via the small conductive plates 301 to 304 thus arranged. Electrically connected.

Each of the small soaking plates 321 to 324 has a common area in a range slightly below the area of the upper surface or the lower surface of the small conductive plates 301 to 304. The small heat soaking plate 321 is inserted into the space inside the small conductive plate 301 with the fold of the small conductive plate 301 as a valley. The small uniform heat plate 322 is inserted into a space inside the small conductive plate 302 where the fold of the small conductive plate 302 is a valley. The small uniform heat plate 323 is inserted into the space inside the small conductive plate 303 with the fold of the small conductive plate 303 as a valley. The small soaking plate 324 is inserted into the space inside the small conductive plate 304 with the fold of the small conductive plate 304 as a valley.

Each of the

spacers

34a and 34b has a thickness approximately half of the thickness of the small conductive plates 301 to 304, and is disposed at a position where the small conductive plates 301 to 304 are missing. The spacer 34a is disposed at a positive position in the Z-axis direction, and the spacer 34b is disposed at a negative position in the Z-axis direction. Since the small conductive plates 301 to 304 are arranged as described above, the upper surface or the lower surface of each of the

spacers

34a and 34b forms a cross. The thickness of each of the

spacers

34a and 34b does not necessarily have to be approximately ½ of the thickness of the small conductive plates 301 to 304.

Each of the

spacers

34a and 34b is also formed with four through holes that form manifolds MFf1, MFf2, MFa1 and MFa2, respectively. Each through hole is rectangular when viewed from the Z-axis direction. However, the long side of the rectangle forming each of the manifolds MFf1 and MFf2 extends along the Y axis, while the long side of the rectangle forming each of the manifolds MFa1 and MFa2 extends along the X axis.

Referring to FIG. 10, paste-like conductive bonding material 26 is disposed between the lower surface of air electrode side conductor layer 121 forming the upper fuel battery cell and the upper surfaces of small conductive plates 301-304. The conductive bonding material 26 is also disposed between the upper surface of the fuel electrode side conductor layer 125 forming the lower fuel cell and the lower surfaces of the small conductive plates 301 to 304. When the conductive bonding material 26 is sintered, the via conductors VHf, VHf, ..., VHa, VHa, ... are bonded to the small conductive plates 301-304. A minute gap generated between the small conductive plates 301 to 304 and each of the air electrode side conductor layer 121 and the fuel electrode side conductor layer 125 is filled with the conductive bonding material 26.

Further, between the lower surface of the air electrode side conductor layer 121 and the upper surface of the spacer 34a, between the lower surface of the spacer 34a and the upper surface of the spacer 34b, and between the lower surface of the spacer 34b and the upper surface of the air electrode side conductor layer 121. Is provided with a sealing material 28. As a result, the two fuel cells sandwiching the soaking conductive layer 30 are fixed to each other via the

spacers

34a and 34b.

ZMG232G10 manufactured by Hitachi Metals, Ltd. is used as the material for the small heat plates 321 to 324. This has almost the same composition and properties as the above-mentioned Crofer22APU.
[Second Embodiment]

The fuel cell unit of the second embodiment is the same as the fuel cell unit 10 of the first embodiment except that the coating on each of the small current collector plate and the small conductive plate is omitted. A duplicate description of the configuration other than the small conductive plate is omitted.

Each of the small current collector plate and the small conductive plate is also made by mesh processing using Crofer22APU made by VDM, Germany. By adopting a structure that can be easily deformed, such as a mesh, the fuel cell and the fixing plate can be electrically connected without a compression mechanism. Furthermore, it is possible to follow the deformation of the fuel cell due to the heat cycle or the power generation cycle.
[Third embodiment]

In the fuel cell unit of the third embodiment, each of the small current collector plate and the small conductive plate is produced by subjecting ZMG232G10 manufactured by Hitachi Metals to expansion processing (network processing), and the small current collector plate and small conductive plate. Except for the point that coating of each of the plates is omitted, the fuel cell unit 10 is the same as the fuel cell unit 10 of the first embodiment.

By adopting an easily deformable structure such as expanded metal, the fuel cell and the fixing plate can be electrically connected without a compression mechanism. Furthermore, it is possible to follow the deformation of the fuel cell due to the heat cycle or the power generation cycle.
[Fourth embodiment]

In the fuel cell unit of the fourth embodiment, each of the small current collector plate and the small conductive plate is produced by subjecting Crofer22APU (plate thickness: 0.2 mm) manufactured by VDM to expand processing (network processing). The surface of each of the small current collector plate and the small conductive plate is the same as that of the fuel cell unit 10 of the first embodiment except that the surface of each of the small current collector plate and the small conductive plate is coated with NiCo plating or MnCo spraying and is preheated. A duplicate description of the configuration other than the current collector plate and the small conductive plate is omitted.

NiCo spinel or MnCo spinel is produced by performing coating and heat treatment by NiCo plating or MnCo spraying. The paste-like conductive bonding material 26 is impregnated in the expanded metal by being applied to such a surface. When dried and fired in this state, interdiffusion of elements occurs between LSM and MnCo or between LSM and NiCo during sintering. As a result, the bonding strength with respect to the fuel cell and thus the connection reliability is improved.
[Fifth embodiment]

In the fuel cell unit of the fifth embodiment, each of the small current collector plate and the small conductive plate is produced by subjecting ZMG232G10 manufactured by Hitachi Metals to expansion processing (network processing). Since each surface of the conductive plate is the same as the fuel cell unit 10 of the first embodiment except that the surface of each of the conductive plates is coated with LSM spraying and heat-treated in advance, the configuration other than the small current collector plate and the small conductive plate The duplicate description about is omitted.

By matching the material of the coating with the material of the conductive bonding material, an improvement in the bonding strength between each of the small current collector plate and the small conductive plate and the conductive bonding material can be expected.
[Tensile test results of first to fifth embodiments]

For reference, FIG. 11 shows the results of the tensile tests of the first to fifth examples. According to FIG. 11, the adhesion strength of the NiCo plated member in the fourth example was the highest, and the average was 40 N or more. Also, in the first example, an adhesion strength of 25 N or more was shown on average.

The adhesion strength of MnCo sprayed in the fourth example was weaker than the adhesion strength of NiCo plated in the fourth example, but an average adhesion strength of 20 N or more was confirmed. However, it is presumed that the adhesion strength required for the joint to withstand deformation caused by stress due to the difference in thermal expansion coefficient with the fuel cell / stack is 1 N or less. For this reason, it is considered that all of the first to fifth examples have sufficiently strong adhesion strength.

Needless to say, the configurations of the above-described embodiments can be appropriately combined within a consistent range.

In the above-described embodiment, LSM is adopted as a material for the conductive bonding material. However, the conductive bonding material may include LaSrCoO 3, LaSrCoFeO 3, MnCoO 3, SmSrCoO 3, LaCaMnO 3, LaCaCoO 3, LaCaCoFeO 3, LaNiFeO 3, or (LaSr) 2 NiO 4.

Furthermore, in the above-described embodiment, the metal member forming the small current collector plate and the small conductive plate is produced by applying mesh processing or expanding processing to a metal plate material. However, punching or embossing may be employed instead of meshing or expanding, and the metal member may be foamed or porous.

In the above-described embodiments, it is assumed that the coating material includes an alloy made of NiCo or MnCo or an oxide thereof, but a trace additive such as Fe may be added to NiCo or MnCo. Good.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell unit 12 ...

Fuel cell stack

16a, 16b ...

Current collection layer

20a, 20b ... Fuel cell 22 ... Conductive layer 26 ... Conductive joining material 122 ... Air electrode layer 123 ... Solid electrolyte layer 124 ... Fuel electrode layer VHf , VHa ... Via conductor (surface electrode)
MFf1, MFf2, MFa1, MFa2 ... manifold

Claims

A solid oxide fuel cell unit comprising a plurality of fuel cells having surface electrodes provided on one main surface and the other main surface facing the stacking direction,
A metal member that is positioned between the fuel cells as viewed from the stacking direction and that is provided between the fuel cells and that relieves thermal stress of the plurality of fuel cells, and the metal member as the surface electrode A fuel cell unit comprising a conductive bonding material for electrical connection.
2. The fuel cell unit according to claim 1, wherein the conductive bonding material is made of conductive ceramics, and the metal member is electrically connected to the surface electrode by sintering the conductive ceramics.
3. The fuel cell unit according to claim 1, wherein the conductive bonding material is made of LaSrCoO3, LaSrCoFeO3, MnCoO3, SmSrCoO3, LaCaMnO3, LaCaCoO3, LaCaCoFeO3, LaNiFeO3, or (LaSr) 2NiO4.
The fuel cell unit according to any one of claims 1 to 3, wherein the conductive bonding material is composed of a plurality of types of powders having different particle sizes.
The fuel cell unit according to any one of claims 1 to 4, wherein the conductive bonding material includes a pore former that disappears by sintering.
The fuel cell unit according to any one of claims 1 to 5, wherein the metal member is a member made by performing mesh processing, punching processing, expanding processing, or embossing processing on a metal plate material.
The fuel cell unit according to any one of claims 1 to 6, wherein a material of the metal member includes at least one of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, and Cr.
The fuel according to any one of claims 1 to 7, wherein the metal member has an oxidation-resistant surface coated with a material containing an element constituting the conductive bonding material and an element that interdiffuses at an interface. Battery unit.
The fuel cell unit according to claim 8, wherein the coating material includes an alloy made of NiCo or MnCo or an oxide thereof.
The fuel cell unit according to claim 8, wherein a material of the coating matches a material of the conductive bonding material.
The fuel cell unit according to any one of claims 1 to 10, further comprising a soaking plate sandwiched between the fuel cells through the metal member so as to disperse heat generated in the fuel cell.