JP4931365B2 - Support substrate for fuel cell, fuel cell, and fuel cell - Google Patents

Description

The present invention, Co and Ni as an iron group metal, Co / (Co + Ni) with molar ratio is contained at 5-30%, supporting group for a fuel cell containing _Y 2 _{O 3} as a rare earth oxide
The present invention relates to a plate, a fuel cell using the fuel cell support substrate, and a fuel cell.

  When the fuel cell is repeatedly generated and stopped, the fuel cell is alternately exposed to a reducing atmosphere and an oxidizing atmosphere, and the electrode and the support are subjected to a reduction / oxidation cycle. Conventionally, porous materials have been used as these electrodes and support materials.

  FIG. 4 shows a cell stack of a conventional solid oxide fuel cell, in which a plurality of fuel cells 1 are aligned and arranged, and one adjacent fuel cell 1a and the other fuel cell 1b. A current collecting member 5 made of metal felt is interposed between the fuel electrode 7 of one fuel cell 1a and an oxygen electrode (air electrode) 11 of the other fuel cell 1b. It had been.

  In the fuel cell 1 (1a, 1b), a solid electrolyte 9 and an oxygen electrode 11 made of conductive ceramics are sequentially provided on the outer peripheral surface of a fuel electrode 7 made of a cylindrical cermet (the inside becomes a fuel gas passage). An interconnector 13 is provided on the surface of the fuel electrode 7 that is configured and is not covered with the solid electrolyte 9 or the oxygen electrode 11. As apparent from FIG. 4, the interconnector 13 is electrically connected to the fuel electrode 7 so as not to be connected to the oxygen electrode 11.

  The interconnector 13 is formed of a conductive ceramic that is not easily altered by an oxygen-containing gas such as fuel gas and air. The conductive ceramic is formed between the fuel gas flowing inside the fuel electrode 7 and the outside of the oxygen electrode 11. It must be dense to shut off the flowing oxygen-containing gas.

  The current collecting member 5 provided between the adjacent fuel cells 1a, 1b is electrically connected to the fuel electrode 7 of one fuel cell 1a via the interconnector 13, and the other fuel cell. It is connected to the oxygen electrode 11 of the cell 1b, so that adjacent fuel cells are connected in series.

  The fuel cell is configured by accommodating a cell stack having the above structure in a storage container, and flowing fuel gas (hydrogen) into the fuel electrode 7 and flowing air (oxygen) into the oxygen electrode 11 to generate power at a high temperature. Is done.

In the fuel cell constituting the fuel cell described above, generally, the fuel electrode 7 is formed of Ni and ZrO ₂ (YSZ) containing Y ₂ O ₃ , and the solid electrolyte 9 contains Y ₂ O ₃ . It is formed from ZrO 2 _(YSZ) for the oxygen electrode 11 is composed of a perovskite-type composite oxide of lanthanum manganate system. Conventionally, a fuel electrode material made of nickel oxide, scandia-stabilized zirconia (electrolyte), and iron oxide is known as a fuel electrode material (see Patent Document 1).

  As a method for manufacturing such a fuel battery cell, a so-called co-sintering method in which the fuel electrode 7 and the solid electrolyte 9 are formed by simultaneous firing is known. This co-sintering method is a very simple process and has a small number of manufacturing steps, and is advantageous in improving the yield during manufacturing of cells and reducing costs.

However, although the solid electrolyte 9 is formed of Y ₂ O ₃ containing ZrO ₂ having a thermal expansion coefficient of 10.8 × 10 ⁻⁶ / ° C., the fuel electrode 7 supporting the solid electrolyte 9 has a thermal expansion. Since Ni has a coefficient of 16.3 × 10 ⁻⁶ / ° C., which is significantly larger than YSZ, there is a difference in thermal expansion between the solid electrolyte 9 and the fuel electrode 7 supporting the same during simultaneous firing. Largely, there were problems such as generation of cracks in the fuel electrode 7 and peeling of the solid electrolyte 9.

As a fuel cell for solving this problem, a support substrate in which a rare earth oxide (Y ₂ O ₃ , Yb ₂ O _3, etc.) having a lower thermal expansion coefficient than ZrO ₂ and Ni is combined, a fuel electrode, a solid electrolyte, A fuel battery cell in which an oxygen electrode is formed is known (see Patent Document 2).

According to the fuel cell described above, the thermal expansion coefficient of the support substrate can be brought close to the thermal expansion coefficient of the solid electrolyte, thereby suppressing cracking at the fuel electrode and simultaneous separation of the solid electrolyte from the fuel electrode. it can.
JP 2003-327411 A JP 2004-146334 A

  However, after co-firing, when performing reduction treatment to activate the catalytic metal or actually generating power, fuel gas (hydrogen etc.) is supplied into the fuel gas passage formed in the support substrate. Therefore, when the inside of the support substrate is exposed to a reducing atmosphere and power generation is stopped, the inside of the support substrate is exposed to an oxidizing atmosphere, so that the support substrate repeatedly receives a reduction / oxidation cycle, and the support substrate expands. There was a risk of cracks occurring in the solid electrolyte.

An object of the present invention is to provide a support substrate for a fuel cell, a fuel cell, and a fuel cell that can effectively suppress shrinkage / expansion due to a reduction / oxidation cycle.

The present inventors consider that the expansion due to the reduction / oxidation cycle of the support substrate of the fuel cell is only due to the oxidation expansion and reduction contraction of Ni in the support substrate, and the expansion of the support substrate is offset by the reduction / oxidation cycle. It was supposed to return to the original, but experimentally found that it does not actually return. The cause seems to be due to a change in the skeleton structure inside the support substrate. As one of the driving forces for this skeletal structure change, although not clear, it was considered that Ni temporarily expands during reduction and Ni or NiO changes during reduction / oxidation. The driving force for changing the shape of Ni or NiO was the surface tension, which was considered to be affected by the wettability of Y ₂ O ₃ . As a result of studying an additive element that improves the wettability of Ni (or NiO) and Y ₂ O ₃ and suppresses expansion due to the reduction / oxidation cycle, it was found that Co is effective, and the present invention has been achieved.

That is, the support substrate for a fuel cell of the present invention, Co and Ni as an iron group metal, with Co / (Co + Ni) molar ratio is contained at 5~30%, _Y 2 _{O 3} as a rare earth oxide It contains .

The support substrate for a fuel cell of the present invention can be suitably used when it has conductivity. Co,及Beauty N i is less insulating in each case a support substrate for a fuel cell, it can be used the present invention, Co,及Beauty N i is the supporting substrate for a fuel cell having more conductive In such a case, the contraction / expansion due to the reduction / oxidation cycle becomes large, so that the present invention can be preferably used.

Furthermore, the supporting substrate for a fuel cell of the present invention, the absolute value of the linear expansion coefficient between repeated 3 times the original-oxidation cycle instead is equal to or less than 0.2%.

Such a support substrate for fuel cells can suppress expansion of the support substrate due to the reduction / oxidation cycle. Although the cause of the volume expansion in the reduction / oxidation cycle is not clear, such a phenomenon does not occur unless Ni is added, so it is considered that the influence of Ni on the volume expansion is great. Co is effective as an additive element for suppressing volume expansion due to the shape change of Ni or NiO during such reduction / oxidation. The reason for this is that, when Co is dissolved in Ni and NiO, the wettability of (Ni, Co), (Ni, Co) O and Y ₂ O ₃ is improved, and the shape of Ni and NiO particles changes. It seems that rearrangement at the time becomes easier and volume expansion is suppressed.

Fuel cell of the present invention comprises a support substrate for a fuel cell provided a fuel gas passage therein, the fuel electrode layer provided on the fuel cell supporting substrate, so as to cover the fuel electrode layer And a solid electrolyte layer provided on the fuel cell support substrate and an oxygen electrode provided on the solid electrolyte layer so as to face the fuel electrode layer. In such a fuel cell, since the expansion due to the reduction / oxidation cycle of the support substrate can be suppressed, for example, even if the support substrate of the fuel cell is alternately exposed to an oxidizing atmosphere and a reducing atmosphere, the surface of the supporting substrate It is possible to effectively suppress cracks and peeling in the fuel electrode and solid electrolyte formed on the substrate.

  The fuel cell according to the present invention is characterized in that the fuel cell is housed in a plurality of housings. In such a fuel cell, since damage to the fuel cell can be prevented, long-term reliability can be improved.

In the fuel cell supporting substrate of the present invention, Co and Ni as an iron group metal, with Co / (Co + Ni) molar ratio is contained at 5-30%, containing _Y 2 _{O 3} as the rare earth element oxides such a Rukoto, since it is possible to suppress the expansion due to reduction-oxidation cycle, for example, be a supporting substrate for a fuel cell that is exposed alternately to a reducing atmosphere and an oxidizing atmosphere, the fuel electrode formed on the surface of the support substrate And cracks and separation in the solid electrolyte can be effectively suppressed.

FIG. 1 shows a cross section of a fuel cell using a support substrate for a fuel cell (hereinafter sometimes abbreviated as a support substrate) of the present invention . It has a flat cross section and is provided with a support substrate (support) 31 that is an elongated substrate as a whole. Inside the support substrate 31, a plurality of fuel gas passages 31 a are formed penetrating in the length direction at appropriate intervals in the width direction. The fuel cell 30 has various members on the support substrate 31. It has a provided structure. A plurality of such fuel cells 30 are connected to each other in series by a current collecting member 40 as shown in FIG. 2, thereby forming a cell stack constituting the fuel cell.

  As understood from the shape shown in FIG. 1, the support substrate 31 includes a flat portion A and arc-shaped portions B at both ends of the flat portion A. Both surfaces of the flat portion A are formed substantially parallel to each other, and a fuel electrode layer 32 is provided so as to cover one surface of the flat portion A and the arc-shaped portions B on both sides. A dense solid electrolyte layer 33 is laminated so as to cover, and an oxygen electrode 34 is laminated on one surface of the flat portion A so as to face the fuel electrode layer 32 on the solid electrolyte layer 33. Has been. 1 and 2, the fuel electrode layer 32 is indicated by a bold line.

  An interconnector 35 is formed on the other surface of the flat portion A where the fuel electrode layer 32 and the solid electrode layer 33 are not stacked. As is clear from FIG. 1, the fuel electrode layer 32 and the solid electrolyte layer 33 extend to both sides of the interconnector 35 and are configured so that the surface of the support substrate 31 is not exposed to the outside.

  In the fuel cell having the above structure, the portion of the fuel electrode layer 32 facing the oxygen electrode 34 operates as a fuel electrode to generate electric power. That is, an oxygen-containing gas such as air is allowed to flow outside the oxygen electrode 34, and a fuel gas (hydrogen) is allowed to flow through the gas passage 31a in the support substrate 31 and heated to a predetermined operating temperature. Electricity is generated by generating an electrode reaction of the formula (1) and generating an electrode reaction of the following formula (2), for example, in the portion of the fuel electrode layer 32 that becomes the fuel electrode.

Oxygen electrode: 1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte) (1)
Fuel electrode: O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻ (2)
The current generated by the power generation is collected through the interconnector 35 attached to the support substrate 31.

(Support substrate 31)
In the fuel cell 30 having the above-described structure, the support substrate 31 is gas permeable so as to allow the fuel gas to permeate to the fuel electrode 32, and to collect current through the interconnector 35. It is required to be conductive and to be free from cracks and peeling of the solid electrolyte 35 due to the difference in thermal expansion during simultaneous firing. At the same time, the volume of the support substrate 31 in the reduction / oxidation cycle is satisfied. For the purpose of suppressing cracks in the solid electrolyte 35 and the like due to expansion, it contains Co and Ni as an iron group metal at a Co / (Co + Ni) molar ratio of 5 to 30%, and an oxide of a rare earth element as Y It is constituted by containing ₂ O ₃ .

Ni is for imparting conductivity to the support substrate 31, and may be a single metal, or an oxide, an alloy, or an alloy oxide. In the present invention, any of them can be used, but Ni and / or NiO are preferable because they are inexpensive and stable in fuel gas.

The rare earth element oxide is used to approximate the thermal expansion coefficient of the support substrate 31 to the stabilized zirconia or lanthanum gallate perovskite composition forming the solid electrolyte layer 33, and the like. In order to maintain high conductivity and prevent diffusion to the solid electrolyte layer 33 and the like, an oxide containing Y in particular is used in combination with the iron group component. As a specific example of such a rare earth element oxide, Y ₂ O ₃ is preferable. In particular, in terms of approximating the thermal expansion coefficient of the support substrate 31 to that of a solid electrolyte material such as stabilized zirconia, when the total of the iron group component (metal equivalent amount) and the rare earth element oxide is 100% by volume, the iron group described above is used. The metal conversion amount of the component is preferably included in the support substrate 31 in an amount of 35 to 65% by volume, and the rare earth element oxide is preferably included in the support substrate 31 in an amount of 35 to 65% by volume. is there.

Incidentally, the Y raw material powder if example embodiment, other if it contains other rare earth elements traces and to the Y as a main, it is also possible to use a raw material powder, for example Y and Yb.

In the present invention, in particular, for the purpose of suppressing expansion due to reduction / oxidation cycle, Co metal (including a solid solution) such as Co metal or its oxide is contained in the support substrate 31 in a Co / (Co + Ni) molar ratio of 5 to 30%. that it has been included in the amount of. In particular, 10 to 20% is desirable. Co is considered to exist in a solid solution with NiO in the support substrate and constitute a skeleton of the support substrate together with Y ₂ O ₃ as the main phase to form a porous structure. Co compounds include CoO and Co ₃ O ₄ .

  The support substrate 31 may contain other metal components and oxide components as long as required characteristics are not impaired.

  Since the support substrate 31 as described above needs to have fuel gas permeability, it is usually preferable that the open porosity is 30% or more, particularly 35 to 50%. Further, the conductivity of the support substrate 31 is preferably 300 S / cm or more, and particularly preferably 440 S / cm or more.

  Further, the length of the flat portion A of the support substrate 31 is normally 15 to 35 mm, the length of the arc-shaped portion B (the length of the arc) is about 3 to 8 mm, and the thickness of the support substrate 31 is (flat portion). The distance between both surfaces of A) is preferably about 2.5 to 5 mm.

(Fuel electrode layer 32)
In the present invention, the fuel electrode layer 32 causes the electrode reaction of the above-described formula (2), and is formed of a known porous conductive ceramic. For example, it is formed from ZrO ₂ in which a rare earth element is dissolved, and Ni and / or NiO. As ZrO ₂ (stabilized zirconia) in which the rare earth element is dissolved, the same one used for forming the solid electrolyte layer 33 described below is preferably used.

  The stabilized zirconia content in the fuel electrode layer 32 is preferably in the range of 35 to 65% by volume, and the Ni or NiO content is preferably 65 to 35% by volume. Further, the open porosity of the fuel electrode layer 32 is preferably 15% or more, particularly preferably in the range of 20 to 40%, and the thickness is preferably 1 to 30 μm. For example, if the thickness of the fuel electrode layer 32 is too thin, the performance may be deteriorated, and if it is too thick, there is a risk of peeling due to a difference in thermal expansion between the solid electrolyte layer 33 and the fuel electrode layer 32. .

  Further, in the example of FIG. 1, the fuel electrode layer 32 extends to both sides of the interconnector 35, but it is sufficient that the fuel electrode layer 32 is formed at a position facing the oxygen electrode 34. Therefore, for example, the fuel electrode layer 32 may be formed only in the flat portion A on the side where the oxygen electrode 34 is provided. Furthermore, the fuel electrode layer 32 can be formed over the entire circumference of the support substrate 31. In order to increase the bonding strength between the solid electrolyte layer 33 and the support substrate 31, the entire solid electrolyte layer 33 is preferably formed on the fuel electrode layer 32.

(Solid electrolyte layer 33)
The solid electrolyte layer 33 provided on the fuel electrode layer 32 is generally formed of a dense ceramic called ZrO ₂ (usually stabilized zirconia) in which 3 to 15 mol% of a rare earth element is dissolved. . Examples of rare earth elements include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, but they are inexpensive. From the point, Y and Yb are desirable.

  The stabilized zirconia ceramics forming the solid electrolyte layer 33 is desirably a dense material having a relative density (according to Archimedes method) of 93% or more, particularly 95% or more from the viewpoint of preventing gas permeation. It is desirable that the thickness is 10 to 100 μm.

(Oxygen electrode 34)
The oxygen electrode 34 is formed of a conductive ceramic made of a so-called ABO ₃ type perovskite oxide. As such a perovskite oxide, at least one of transition metal perovskite oxides, particularly LaMnO ₃ oxides, LaFeO ₃ oxides, and LaCoO ₃ oxides having La at the A site is preferable. LaFeO ₃ -based oxides are particularly suitable because they have high electrical conductivity at an operating temperature of about 1000 ° C. In the perovskite oxide, Sr and the like may exist together with La at the A site, and Co and Mn may exist together with Fe at the B site.

  The oxygen electrode 34 must have gas permeability. Therefore, the conductive ceramic (perovskite oxide) forming the oxygen electrode 34 has an open porosity of 20% or more, particularly 30 to 50. It is desirable to be in the range of%.

  The thickness of the oxygen electrode 34 is preferably 30 to 100 μm from the viewpoint of current collection.

(Interconnector 35)
The interconnector 35 provided on the support substrate 31 at the position facing the oxygen electrode 34 is made of conductive ceramics, but is in contact with the fuel gas (hydrogen) and the oxygen-containing gas. It is necessary to have oxidation resistance. For this reason, lanthanum chromite perovskite oxides (LaCrO ₃ oxides) are generally used as the conductive ceramics. Further, in order to prevent leakage of the fuel gas passing through the inside of the support substrate 31 and the oxygen-containing gas passing through the outside of the support substrate 31, such conductive ceramics must be dense, for example, 93% or more, particularly 95%. It is preferable to have the above relative density.

  The interconnector 35 is desirably 10 to 200 μm from the viewpoint of preventing gas leakage and electrical resistance. That is, if the thickness is smaller than this range, gas leakage is likely to occur, and if the thickness is larger than this range, the electric resistance is large, and the current collecting function may be reduced due to a potential drop. .

Further, as is clear from FIG. 1, in order to prevent gas leakage, a dense solid electrolyte layer 33 is in close contact with both sides of the interconnector 35. _A bonding layer (not shown) made of ₂ O ₃ or the like can be provided between both side surfaces of the interconnector 35 and the solid electrolyte layer 33.

  A P-type semiconductor layer 39 is preferably provided on the outer surface (upper surface) of the interconnector 35. That is, in the cell stack assembled from the fuel battery cells (see FIG. 2), a conductive current collecting member 40 is connected to the interconnector 35, and the current collecting member 40 is connected via the P-type semiconductor layer 39. By connecting to the interconnector 35, the contact between the two becomes an ohmic contact, the potential drop is reduced, and it is possible to effectively avoid a decrease in the current collection performance. For example, the oxygen electrode of one fuel cell 30 The current from 34 can be efficiently transmitted to the support substrate 31 of the other fuel cell 30. As such a P-type semiconductor, a transition metal perovskite oxide can be exemplified.

Specifically, those having higher electronic conductivity than LaCrO ₃ oxides constituting the interconnector 35, for example, LaMnO ₃ oxides and LaFeO ₃ oxides in which Mn, Fe, Co, etc. exist at the B site P-type semiconductor ceramics made of at least one of LaCoO ₃ -based oxides can be used. In general, the thickness of the P-type semiconductor layer 39 is preferably in the range of 30 to 100 μm.

  The interconnector 35 can also be provided directly on the flat portion A of the support substrate 31 on the side where the solid electrolyte layer 33 is not provided. The fuel electrode layer 32 is also provided in this portion, and this fuel electrode layer 32 is provided. An interconnector 35 can also be provided on the top. That is, the fuel electrode layer 32 can be provided over the entire circumference of the support substrate 31, and the interconnector 35 can be provided on the fuel electrode layer 32. That is, when the interconnector 35 is provided on the support substrate 31 via the fuel electrode layer 32, it is advantageous in that the potential drop at the interface between the support substrate 31 and the interconnector 35 can be suppressed. is there.

(Manufacture of fuel cells)
The fuel battery cell having the above structure is manufactured as follows. First, for example, Ni or its oxide powder, Y ₂ O ₃ powder, Co oxide powder such as Co ₃ O ₄ , an organic binder, and a solvent are mixed to prepare a slurry. A support substrate molded body is prepared by extrusion molding, and is dried.

  Next, a fuel electrode layer forming material (Ni or NiO powder and stabilized zirconia powder), an organic binder, and a solvent are mixed to prepare a slurry, and a sheet for the fuel electrode layer is prepared using this slurry. Further, instead of producing a sheet for the fuel electrode layer, a paste in which the fuel electrode forming material is dispersed in a solvent is applied to a predetermined position of the formed support substrate and dried, and then the fuel electrode layer is formed. A coating layer may be formed.

  Furthermore, a stabilized zirconia powder, an organic binder, and a solvent are mixed to prepare a slurry, and a solid electrolyte layer sheet is prepared using this slurry.

  The support substrate molded body, the fuel electrode sheet, and the solid electrolyte layer sheet formed as described above are laminated so as to have a layer structure as shown in FIG. 1, for example, and dried. In this case, when the coating layer for the fuel electrode layer is formed on the surface of the support substrate molded body, only the solid electrolyte layer sheet may be laminated on the support substrate molded body and dried.

Thereafter, the interconnector material (e.g., LaCrO ₃ based oxide powder), an organic binder and a solvent were mixed to prepare a slurry, to produce the interconnector sheet.

  This interconnector sheet is further laminated at a predetermined position of the laminate obtained above to produce a firing laminate.

Next, the above-mentioned fired laminate is subjected to binder removal treatment, and co-fired at 1300 to 1600 ° C. in an oxygen-containing atmosphere, and an oxygen electrode forming material (for example, LaFeO ₃₎ is placed at a predetermined position of the obtained sintered body. And paste containing a P-type semiconductor layer forming material (for example, LaFeO ₃ -based oxide powder) and a solvent by dipping or the like, if necessary. The fuel cell 30 of the present invention having the structure shown in FIG. 1 can be manufactured by baking.

  In the case where Ni alone is used to form the support substrate 31 and the fuel electrode layer 32, Ni is oxidized to NiO by firing in an oxygen-containing atmosphere. , Ni can be returned.

In the fuel cell of the present invention, a fuel electrode layer, a solid electrolyte layer, and an oxygen electrode are formed on a support substrate formed using NiCo alloys (including solid solutions) or their oxides and Y ₂ O _3. This effectively avoids inconveniences such as peeling of the solid electrolyte layer and generation of cracks during simultaneous firing due to thermal expansion differences, and at the same time, the volume of the support substrate due to the reduction / oxidation cycle (for example, starting and stopping of the fuel cell) Expansion can also be suppressed.

  In addition, even if the Co element present in the support substrate diffuses into the solid electrolyte layer at the time of co-firing, it does not adversely affect the ionic conductivity of the solid electrolyte, the conductivity of the oxygen side electrode, etc.

(Cell stack)
As shown in FIG. 2, the cell stack includes a plurality of the fuel cells 30 described above, and a metal felt and / or between one fuel cell 30 and the other fuel cell 30 adjacent in the vertical direction. A current collecting member 40 made of a metal plate is interposed, and both are connected in series with each other. That is, the support substrate 31 of one fuel battery cell 30 is electrically connected to the oxygen electrode 34 of the other fuel battery cell 30 via the interconnector 35, the P-type semiconductor layer 39, and the current collecting member 40. . Such cell stacks are arranged side by side as shown in FIG. 2, and adjacent cell stacks are connected in series by a conductive member 42.

  The fuel cell of the present invention is configured by accommodating the cell stack of FIG. 2 in a storage container. The storage container is provided with an introduction pipe for introducing a fuel gas such as hydrogen into the fuel battery cell 30 from the outside, and an introduction pipe for introducing an oxygen-containing gas such as air into the external space of the fuel battery cell 30. The fuel cell is heated to a predetermined temperature (for example, 600 to 900 ° C.) to generate electric power, and the used fuel gas and oxygen-containing gas are discharged out of the storage container.

  In addition, this invention is not limited to the said form, A various change is possible in the range which does not change the summary of invention. For example, the shape of the support substrate 31 can be a cylindrical shape, and an intermediate layer having appropriate conductivity can be formed between the oxygen electrode 34 and the solid electrolyte layer 33. Furthermore, in the above embodiment, the case where the fuel electrode layer 32 is formed on the support substrate 31 has been described. However, the support substrate itself is provided with a function as a fuel electrode, and a solid electrolyte and an oxygen electrode layer are formed on the support substrate. Also good.

NiO powder having an average particle size of 0.5 μm and Y ₂ O ₃ powder (average particle size is 0.6 to 0.9 μm), after firing, NiO is 48 vol% in terms of Ni, and Y ₂ O ₃ is 52 vol. % Were mixed (Sample No. 1).

Next, NiO powder having an average particle diameter of 0.5 μm, Co ₃ O ₄ powder (average particle diameter of 0.7 μm), and Y ₂ O ₃ powder (average particle diameter of 0.6 to 0.9 μm) are fired. _48% by volume NiCo alloy in terms _after, were mixed so Y 2 _{O 3} is 52% by volume (sample No.2~5).

  A slurry for a supporting substrate formed by mixing a pore agent, an organic binder (polyvinyl alcohol), and water (solvent) into the above mixed powder is extruded into a rectangular parallelepiped shape, dried, debindered, Firing was performed at 1500 ° C. in the air.

The obtained sintered body was processed to a height of 3 mm, a width of 4 mm, and a length of 40 mm, and subjected to a reduction treatment at 850 ° C. for 16 hours in a reducing atmosphere at an oxygen partial pressure of about 10 ⁻¹⁹ Pa. Cooling naturally, measuring the length in the longitudinal direction before and after reduction, and taking the length obtained by subtracting the length before reduction from the length after reduction as the elongation in the longitudinal direction ((extension in the longitudinal direction) / (The length in the longitudinal direction immediately after sintering (before reduction))). Further, after oxidation treatment at 850 ° C. for 16 hours in the air (oxidizing atmosphere), it was naturally cooled in the air, and the linear expansion coefficient was determined in the same manner as described above. Further, these cycles were repeated three times, and the results are shown in FIG.

Furthermore, the electrical conductivity of the sintered body immediately after production was measured by a four-terminal method at 850 ° C. in a reducing atmosphere at an oxygen partial pressure of about 10 ⁻¹⁹ Pa. The results are shown in Table 1.

  As understood from the results of Table 1, it can be seen that the expansion due to the reduction / oxidation cycle can be suppressed by adding Co oxide.

  Further, each sample powder used in Example 1 was extruded in the same manner as in Example 1 to produce a flat support substrate molded body, which was dried.

Next, for forming a fuel electrode layer using a slurry obtained by mixing ZrO ₂ (YSZ) powder containing 8 mol% Y ₂ O ₃ , NiO powder, organic binder (acrylic resin), and solvent (toluene). A sheet was prepared, and a sheet for a solid electrolyte layer was prepared using a slurry in which the YSZ powder, an organic binder (acrylic resin), and a solvent made of toluene were mixed, and these sheets were laminated.

  The laminated sheet was wound around the support substrate molded body so that both ends thereof were separated from each other with a predetermined interval (see FIG. 1), and dried.

On the other hand, an interconnector sheet was prepared using a slurry in which an LaCrO ₃ oxide powder having an average particle diameter of 2 μm, an organic binder (acrylic resin), and a solvent (toluene) was mixed. A laminated sheet for sintering was prepared by laminating on the exposed portion of the support substrate molded body in the sheet, and comprising a support substrate molded body, a fuel electrode layer sheet, and a solid electrolyte layer sheet.

  Next, the laminated sheet for sintering was subjected to binder removal treatment and co-fired at 1500 ° C. in the atmosphere.

The obtained sintered body was immersed in a paste made of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder having an average particle diameter of 2 μm and a solvent (normal paraffin), and sintered. A coating layer for oxygen electrode is provided on the surface of the solid electrolyte layer formed on the body, and at the same time, the paste is applied to the outer surface of the interconnector formed on the sintered body, and a coating layer for P-type semiconductor is provided, Furthermore, it baked at 1150 degreeC and produced the fuel battery cell as shown in FIG. 1 (sample No. 6-10).

  In the fabricated fuel cell, the length of the flat portion A of the support substrate is 26 mm, the length of the arc-shaped portion B is 3.5 mm, the thickness is 2.8 mm, the thickness of the fuel electrode layer is 10 μm, and the thickness of the solid electrolyte layer is 40 μm, the thickness of the oxygen electrode was 50 μm, the thickness of the interconnector was 50 μm, and the thickness of the P-type semiconductor layer was 50 μm.

  The cross section of the solid electrolyte layer of the obtained fuel cell is analyzed by EPMA to confirm the diffusing element from the support substrate, and hydrogen gas is allowed to flow in the gas passage of the support substrate, and the outside of the fuel cell (oxygen electrode) Air is allowed to flow at 850 ° C. for 100 hours, after which hydrogen gas is stopped and naturally cooled (the support substrate is oxidized), so that water does not enter the fuel cell. Pressurized and immersed in water, the presence or absence of gas leakage was observed, and cracks in the support substrate and the solid electrolyte layer, and peeling of the solid electrolyte layer and the fuel electrode layer from the support substrate were observed with a stereomicroscope. This cycle was repeated three times and the results are listed in Table 2.

The power generation performance per fuel cell after 100 hours at 850 ° C. (first power generation) was measured and listed in Table 2.

As understood from the results in Table 2, the sample No. In 8-10, the crack of a fuel electrode layer and a solid electrolyte layer, and peeling of the solid electrolyte layer and a fuel electrode layer from a support substrate were not seen. Further, there was no significant diffusion of Co from the support substrate to the solid electrolyte, and the power generation performance was as good as 0.40 W / cm ² or more.

  On the other hand, sample No. In No. 6, since the expansion of the support substrate was as large as 0.4% or more in the first oxidation, cracks occurred in the fuel electrode layer and the solid electrolyte layer.

It is a cross-sectional view showing a hollow flat fuel cell. It is a cross-sectional view which shows the cell stack formed with the fuel cell of FIG. It is a graph which shows the linear expansion coefficient of the support substrate after a reduction | restoration and an oxidation cycle test. It is a cross-sectional view showing a cell stack composed of cylindrical fuel cells.

Explanation of symbols

31 ... support substrate 31a ... fuel gas passage 32 ... fuel electrode 33 ... solid electrolyte 34 ... oxygen electrode 35 ... interconnector 40 ... current collecting member

Claims (5)

Co and Ni as an iron group metal, Co / (Co + Ni) with molar ratio is contained at 5-30%, fuel cell, characterized by containing a _Y 2 _{O 3} as a rare earth oxide Support substrate . 2. The fuel cell support substrate according to claim 1, wherein an absolute value of a linear expansion coefficient during the reduction / oxidation cycle is repeated three times is 0.2% or less. Fuel cell supporting substrate according to claim 1 or 2, characterized in that electrically conductive. A supporting substrate for a fuel cell according to any one of claims 1 to 3 fuel gas passage is provided inside the fuel electrode layer provided on the fuel cell supporting substrate, fuel electrode layer A solid electrolyte layer provided on the fuel cell support substrate and an oxygen electrode provided on the solid electrolyte layer so as to face the fuel electrode layer. Fuel cell. A fuel cell comprising the fuel cell according to claim 4 housed in a plurality of housing containers.

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