JP5171159B2 - Fuel cell and fuel cell stack, and fuel cell - Google Patents

Description

  The present invention provides a fuel cell and a fuel comprising an oxygen-side electrode on one surface of a solid electrolyte and a fuel-side electrode on the other surface, and having an intermediate layer between the solid electrolyte and the oxygen-side electrode. The present invention relates to a battery cell stack and a fuel cell.

  In recent years, various fuel cells have been proposed as next-generation energy, in which a fuel cell stack in which a plurality of fuel cells are electrically connected in series is accommodated in a storage container.

  FIG. 3 shows a conventional solid oxide fuel cell stack, in which a plurality of fuel cells 21 (21a, 21b) are aligned and assembled, and one fuel cell 21a and the other A current collecting member 25 made of metal felt is interposed between the fuel cell 21b and the fuel side electrode 27 of one fuel cell 21a and the oxygen side electrode 23 of the other fuel cell 21b are electrically connected. Configured.

  The fuel cell 21 (21a, 21b) is configured by sequentially providing a solid electrolyte 29 and an oxygen-side electrode 23 made of conductive ceramics on the outer peripheral surface of a fuel-side electrode 27 made of a cylindrical metal, The interconnector 22 is provided on the fuel side electrode 27 exposed from the solid electrolyte 29 and the oxygen side electrode 23 so as not to be connected to the oxygen side electrode 23, and is electrically connected to the fuel side electrode 27.

  Since the interconnector 22 reliably shuts off the fuel gas flowing inside the fuel side electrode 27 and the oxygen-containing gas flowing outside the oxygen-side electrode 23, the interconnector 22 is dense and hardly deteriorates by the fuel gas and the oxygen-containing gas. It is made of conductive ceramics.

  The electrical connection between one fuel cell 21a and the other fuel cell 21b is made by connecting the fuel side electrode 27 of one fuel cell 21a to the interconnector 22 and the current collecting member 25 provided on the fuel side electrode 27. And is connected to the oxygen side electrode 23 of the other fuel battery cell 21b.

  In addition, the fuel cell is configured by housing the fuel cell stack in a storage container, flowing fuel (hydrogen gas) into the fuel side electrode 27 and flowing air (oxygen-containing gas) into the oxygen side electrode 23. Power is generated at about 1000 ° C.

In such a fuel cell 21, in general, the fuel side electrode 27 is made of ZrO ₂ (YSZ) containing Ni and Y ₂ O ₃ , and the solid electrolyte 29 is ZrO ₂ (YSZ containing Y ₂ O _3). The oxygen side electrode 23 is made of a LaMnO ₃ composite oxide.

  Recently, a production method in which a solid electrolyte and an oxygen-side electrode are simultaneously sintered (fired) has also been proposed. However, in the case where the solid electrolyte and the oxygen side electrode are simultaneously sintered, the components in the solid electrolyte and the oxygen side electrode react to form a reaction layer having a high electrical resistance, thereby reducing the performance of the fuel cell. There was a problem of causing.

  Therefore, in order to prevent the deterioration of the performance of the fuel cell in simultaneous sintering of the solid electrolyte and the oxygen side electrode, a fuel cell having an intermediate layer formed between the solid electrolyte and the oxygen side electrode and its Manufacturing methods have been proposed (see, for example, Patent Document 1 and Patent Document 2).

  In addition, in order to provide a solid electrolyte fuel cell with excellent heat cycle durability and sufficient power generation performance, a solid electrolyte layer, a reaction preventing layer, a mixed layer, and an air electrode layer are sequentially laminated on the surface of the fuel electrode substrate. In addition, a solid electrolyte fuel cell has been proposed in which the mixed layer contains materials for a reaction preventing layer and an air electrode layer (see, for example, Patent Document 3).

Furthermore, in order to provide a fuel cell with excellent durability and power generation performance, a solid electrolyte, a reaction preventing layer, and an air electrode layer are sequentially laminated on the upper surface of the fuel electrode substrate, and the reaction preventing layer is the first reaction preventing layer. There has been proposed a solid electrolyte fuel cell comprising a layer and a second reaction prevention layer having voids, and produced by simultaneously sintering the solid electrolyte layer, the first reaction prevention layer, and the second reaction prevention layer (for example, , See Patent Document 4).
JP 2003-288914 A JP 2004-63226 A JP 2005-327637 A JP-A-2005-327507

  However, even when a single-layer intermediate layer is formed between the solid electrolyte and the oxygen-side electrode, Zr contained in the solid electrolyte diffuses into the intermediate layer and power is generated over a long period of time. In addition, Zr in the diffused solid electrolyte reacts with the oxygen-side electrode component to form a reaction layer having a high electric resistance, thereby deteriorating the power generation performance of the fuel cell.

  Also, in the fuel cell in which the solid electrolyte is first fired and then the intermediate layer is baked, when the solid electrolyte and the intermediate layer have insufficient adhesion, and the power generation of the fuel cell is performed for a long time, the solid electrolyte and There was also a problem that peeling occurred between the intermediate layer and the power generation performance of the fuel cell deteriorated.

  Furthermore, as in Patent Document 3, in order to prevent the separation between the solid electrolyte layer and the oxygen electrode side electrode, a reaction preventing layer is provided on the surface of the solid electrolyte layer, and an oxygen electrode material is contained on the surface of the reaction preventing layer. When the mixed layer is provided, when power generation of the fuel cell is performed for a long period of time, the oxygen electrode material contained in the mixed layer reacts with the solid electrolyte component diffused in the reaction preventing layer. There is a problem that a reaction layer having a high resistance is formed and the power generation performance of the fuel cell is deteriorated.

  Further, as in Patent Document 4, even when the reaction preventing layer is composed of two layers, when the solid electrolyte, the first reaction preventing layer and the second reaction preventing layer are simultaneously sintered, the solid electrolyte component is not sintered. In the sintering process, it may diffuse into the reaction prevention layer (up to the second reaction prevention layer). When power generation is performed for a long time, the components of the solid electrolyte diffused into the reaction prevention layer (up to the second reaction prevention layer) The reaction with the component of the oxygen side electrode forms a reaction layer having a high electric resistance, and there is a problem that the power generation performance of the fuel cell deteriorates.

  Therefore, the present invention suppresses the diffusion of Zr contained in the solid electrolyte to the oxygen side electrode, suppresses the formation of a reaction layer having a high electrical resistance, and suppresses the deterioration of power generation performance. An object of the present invention is to provide a fuel cell stack and a fuel cell in which a plurality of them are connected.

The fuel battery cell of the present invention comprises an intermediate layer and an oxygen side electrode in this order on the surface on one side of the solid electrolyte containing Zr, and the fuel side on the surface on the other side opposite to the surface on the one side. A fuel cell including an electrode, wherein the intermediate layer contains Zr in a first layer forming a surface layer region on the solid electrolyte side, and forms a second region other than the surface layer region . The layer does not contain Zr , the first layer and the solid electrolyte are simultaneously sintered, and the second layer has a temperature higher than the simultaneous sintering temperature of the solid electrolyte and the first layer. Sintered at low temperature
Characterized in that that.

In such a fuel cell, an intermediate layer is provided between the solid electrolyte containing Zr (zirconium) and the oxygen side electrode, and the intermediate layer has a surface layer region on the solid electrolyte side containing Zr, and Zr. Since the solid electrolyte and the intermediate layer (surface layer region) contain the same element (Zr) and the thermal expansion coefficient can be made closer because it is composed of other regions not containing the solid electrolyte and the intermediate layer, It is possible to effectively suppress the separation of the intermediate layer (surface layer region) from the solid electrolyte.
Further, by simultaneously sintering (co-firing) the solid electrolyte and the first layer forming the surface layer region of the intermediate layer, Zr in the solid electrolyte diffuses into the first layer, so that the solid electrolyte and the first layer It is possible to increase the adhesion with the layer and to prevent the first layer from peeling from the solid electrolyte. Thereby, deterioration of the power generation performance of the fuel cell in long-time power generation can be suppressed.

  In addition, since the other region of the intermediate layer does not contain Zr, a reaction layer having a high electric resistance is formed in the intermediate layer (other region) and the oxygen side electrode due to the reaction between Zr and the oxygen side electrode. Can be suppressed.

  Accordingly, it is possible to suppress the separation of the intermediate layer (surface layer region) from the solid electrolyte, and it is possible to suppress the formation of a reaction layer having a high electrical resistance due to the reaction between Zr and the oxygen side electrode. It is possible to suppress the deterioration of the power generation performance of the cell, and it is possible to suppress the deterioration of the power generation performance of the fuel cell during long-time power generation.

  In the fuel cell of the present invention, it is preferable that the first layer and the second layer contain the same rare earth element (excluding elements contained in the oxygen side electrode).

  In such a fuel cell, the first layer and the second layer of the intermediate layer contain the same rare earth element (except for the element contained in the oxygen-side electrode), whereby the first layer And the second layer can be made closer to each other, and the bonding strength between the first layer and the second layer can be improved. Therefore, the second layer can be prevented from peeling from the first layer, the deterioration of the power generation performance of the fuel cell in long-time power generation can be suppressed, and the fuel cell excellent in long-term reliability can do.

  In the fuel battery cell of the present invention, it is preferable that the first layer has a thickness of 1 to 10 μm and the second layer has a thickness of 5 to 20 μm.

  In such a fuel cell, by setting the thickness of the first layer to 1 to 10 μm, Zr in the solid electrolyte can be sufficiently diffused into the first layer, and the solid electrolyte and the first layer can be diffused. Can be firmly joined. Moreover, it can suppress that a 2nd layer peels from a 1st layer by the thickness of a 2nd layer being 5-20 micrometers.

  Therefore, deterioration of the power generation performance of the fuel cell in long-time power generation can be suppressed, and a fuel cell excellent in long-term reliability can be obtained.

  The fuel cell stack of the present invention is characterized in that a plurality of the fuel cells described above are electrically connected in series.

  Such a fuel cell stack is configured by electrically connecting a plurality of fuel cells that are capable of suppressing deterioration in power generation performance during long-time power generation and that have excellent long-term reliability. It is possible to provide a fuel cell stack that can supply sufficient electric power to the load to be applied and has excellent long-term reliability.

  The fuel cell of the present invention is characterized in that the fuel cell stack is stored in a storage container.

  In such a fuel cell, since the fuel cell stack having excellent long-term reliability is stored in the storage container, a fuel cell having excellent long-term reliability can be obtained.

The fuel battery cell of the present invention includes an intermediate layer and an oxygen side electrode in this order on the surface of one side of the solid electrolyte containing Zr, and the intermediate layer forms a surface layer region on the side of the solid electrolyte containing Zr. A first layer and a second layer forming another region not containing Zr , wherein the first layer and the solid electrolyte are simultaneously sintered; Since it is sintered at a temperature lower than the co-sintering temperature with the first layer, it is possible to provide a fuel cell with excellent long-term reliability that suppresses deterioration in power generation performance during long-time power generation. . Furthermore, it is possible to provide a fuel cell stack having excellent long-term reliability and a fuel cell having excellent long-term reliability, which are configured using the fuel cell of the present invention.

  FIG. 1A shows a cross section of a hollow flat plate fuel cell 10, and FIG. 1B is a perspective view of the fuel cell 10. In both drawings, each configuration of the fuel cell 10 is partially enlarged. FIG. 2 is an enlarged cross-sectional view of a part of the fuel battery cell 10 according to the present invention that is involved in power generation.

  The fuel battery cell 10 includes a conductive support substrate 3 having a flat cross section and an elliptical column shape as a whole. Inside the conductive support substrate 3, a plurality of fuel gas flow paths 5 are formed in the longitudinal direction at appropriate intervals, and the fuel cell 10 is provided with various members on the conductive support substrate 3. Have a structure.

  As understood from the shape shown in FIG. 1, the conductive support substrate 3 includes a flat portion n and arc-shaped portions m at both ends of the flat portion n. Both surfaces of the flat portion n are formed substantially parallel to each other, and a fuel side electrode 7 is provided so as to cover one surface (lower surface) of the flat portion n and the arc-shaped portions m on both sides. A dense solid electrolyte 9 is laminated so as to cover the electrode 7. On the solid electrolyte 9, the oxygen side electrode 1 is laminated so as to face the fuel side electrode 7 through the intermediate layer 4. An interconnector 2 is formed on the other surface of the flat portion n where the fuel side electrode 7 and the solid electrolyte 9 are not laminated. As is clear from FIG. 1, the fuel-side electrode 7 and the solid electrolyte 9 extend to both sides of the interconnector 2 via the arc-shaped portions m at both ends, and the surface of the conductive support substrate 3 is not exposed to the outside. It is configured as follows.

  Here, in the fuel cell 10, the portion of the fuel side electrode 7 facing (opposed) to the oxygen side electrode 1 functions as a fuel side electrode to generate electric power. That is, by flowing an oxygen-containing gas such as air outside the oxygen-side electrode 1 and flowing a fuel gas (hydrogen gas) through the fuel gas channel 5 in the conductive support substrate 3 and heating it to a predetermined operating temperature. Generate electricity. The current generated by the power generation is collected via the interconnector 2 attached to the conductive support substrate 3.

In the present invention, the solid electrolyte 9 provided on the outer surface of the conductive support substrate 3 contains 3 to 15 mol% of a rare earth element such as Y (yttrium), Sc (scandium), or Yb (ytterbium). It is preferable to use dense ceramics made of stabilized or stabilized ZrO ₂ . As the rare earth element, Y is preferable because it is inexpensive. Further, the solid electrolyte 9 is desirably a dense material having a relative density (according to Archimedes method) of 93% or more, particularly 95% or more in terms of preventing gas permeation, and a thickness of 5 to 50 μm. It is preferable.

  In the present invention, the intermediate layer 4 is provided on the surface of the solid electrolyte 9. Here, the intermediate layer 4 is constituted by a surface layer region (indicated by 4a in the figure) on the side of the solid electrolyte 9 containing Zr and another region (indicated by 4b in the drawing) not containing Zr. ing.

  As a result, the solid electrolyte 9 and the intermediate layer 4 (surface layer region 4a) contain the same element (Zr) and can have a close thermal expansion coefficient, thereby improving the bonding strength between the solid electrolyte and the intermediate layer. 9 can suppress separation of intermediate layer 4 (surface layer region 4a) from 9, and can further suppress formation of a reaction layer having high electrical resistance between intermediate layer 4 (other region 4b) and oxygen-side electrode 1. Therefore, it is possible to suppress deterioration of the power generation performance of the fuel battery cell 10 during long-time power generation.

  In addition, since the other region 4b does not contain Zr, a reaction layer having high electrical resistance due to the reaction between Zr and the oxygen side electrode 1 in the oxygen side electrode 1 and the intermediate layer (other region 4b). Can be prevented from being formed.

  The intermediate layer 4 (surface layer region 4a) only needs to contain Zr when the fuel cell 10 of the present invention is manufactured, and may not contain Zr as a raw material of the surface layer region 4a. Therefore, for example, when the fuel cell 10 is manufactured, Zr in the solid electrolyte 9 may diffuse into the surface layer region 4a, and as a result, the surface layer region 4a may contain Zr.

  Here, the surface layer region 4a of the intermediate layer 4 and the other region 4b of the intermediate layer 4 may be formed such that the surface layer region 4a is the first layer 4a and the other region 4b is the second layer 4b. it can. In this case, the second layer 4b may be formed of a plurality of layers. Therefore, for example, the second layer 4b can be formed of two layers, and the intermediate layer 4 can be formed of three layers as a whole, or can be formed with a larger number of layers.

  In the case where the intermediate layer 4 is formed of the first layer 4a and the second layer 4b, the first layer 4a and the second layer 4b are contained in the same rare earth element (contained in the oxygen-side electrode 1). It is preferable that the element is formed so as to contain the above-mentioned elements. Thereby, the thermal expansion coefficients of the first layer 4a and the second layer 4b can be brought close to each other, and the bonding strength between the first layer 4a and the second layer 4b can be improved. Here, what is included in the oxygen-side electrode 1 is excluded because the Zr contained in the intermediate layer 4 reacts with the components of the oxygen-side electrode 1 due to long-term power generation, resulting in a reaction with high electrical resistance. This is for effectively suppressing the formation of the layer.

Such an identical rare earth element includes, for example, Ce (cerium). In particular, when the first layer 4a and the second layer 4b are produced, the raw material powder is, for example, the following formula (1): : (CeO ₂ ) _1-x (REO _1.5 ) _x
In the formula (1), RE is preferably at least one of Sm, Y, Yb, and Gd, and x preferably has a composition represented by a number satisfying 0 <x ≦ 0.3. .

  Here, examples of the rare earth element RE other than Ce include Sm (samarium), Y, Yb, and Gd (gadolinium), and these rare earth elements can be appropriately selected and used.

  As a result, when the first layer 4a and the second layer 4b are formed of the raw material powder containing at least one kind of the same rare earth element, the thermal expansion coefficients of the first layer 4a and the second layer 4b are reduced. can do. Thereby, since the thermal expansion coefficient of the intermediate layer 4 can be brought close to the thermal expansion coefficient of the solid electrolyte 9 containing Zr, it is possible to suppress the occurrence of cracks and peeling due to the difference in thermal expansion. Note that the first layer 4a and the second layer 4b can be formed with the same composition.

Further, the first layer 4a and the second layer 4b are preferably, for example, CeO ₂ in which Sm or Gd is dissolved, and the raw material powder is represented by the following formula (2) :( CeO ₂ ) _1-x (SmO _1.5 ) _x
(3): (CeO ₂ ) _1-x (GdO _1.5 ) _x
In the formulas (2) and (3), x preferably has a composition represented by a number satisfying 0 <x ≦ 0.3. Furthermore, from the viewpoint of reducing electrical resistance, it is preferable that 10 to 20 mol% of _{SmO 1.5} or _{GdO 1.5} consists of CeO ₂ was dissolved. In addition, in order to increase the effect of blocking or suppressing the diffusion of Zr in the solid electrolyte 9, the raw material powder contains oxides of other rare earth elements (for example, Y ₂ O ₃ , Yb ₂ O _3, etc.). May be.

  Then, between the solid electrolyte 9 and the oxygen-side electrode 1, an intermediate layer 4 including a first layer 4 a containing Zr and a second layer 4 b that is formed on the surface and does not contain Zr. Formation of the intermediate layer 4 from the solid electrolyte 9 can be prevented from peeling, and the reaction between the component (Zr) contained in the intermediate layer 4 and the oxygen-side electrode 1 can be effectively suppressed. It is possible to provide a fuel cell that has excellent long-term reliability and suppresses deterioration in power generation performance during power generation.

  In addition, since the first layer 4a and the second layer 4b contain the same rare earth element (Ce or the like), the bonding strength between the first layer 4a and the second layers 4b can be improved.

Here, the solid electrolyte 9 and the first layer 4a are co-sintered (co-fired), the second layer 4b and the oxygen-side electrode 1 that is formed in this order on the first layer 4a. That is, the second layer 4b, after the solid electrolyte 9 and the first layer 4a is co-sintered, and is formed in a separate step.

  Although such a manufacturing method will be described later, since the solid electrolyte 9 and the first layer 4a are simultaneously sintered at a high temperature, Zr of the solid electrolyte 9 diffuses into the first layer 4a, and the solid electrolyte 9 Can be firmly bonded to the first layer 4a, and the first layer 4a can be made dense.

  Further, the second layer 4b can be formed on the surface of the first layer 4a in a step different from the simultaneous sintering, thereby reducing the density. Therefore, for example, when the oxygen side electrode 1 is formed after the second layer 4b is formed, the second layer 4b and the oxygen side electrode 1 can improve the bonding strength by the anchor effect. it can. Thereby, it can suppress that the oxygen side electrode 1 peels from the 2nd layer 4b, and can suppress degradation of the electric power generation performance of the fuel cell 10 in long-time electric power generation.

  The second layer 4b only needs to have a lower density than the first layer 4a, and does not limit the densification of the second layer 4b. However, it is preferable that the second layer 4b is appropriately adjusted to be the second layer 4b so that the second layer 4b and the oxygen-side electrode 1 can be firmly bonded by the anchor effect. In addition, in densifying the second layer 4b, the second layer 4b is subjected to a heat treatment temperature and a heat treatment time by appropriately changing the second layer 4b according to the particle size of the raw material to be the second layer 4b. The layer 4b can be densified.

  Here, in the case where the second layer 4b is composed of a plurality of layers, it is preferable that the layer bonded to the oxygen side electrode 1 is bonded by the anchor effect. Therefore, the layers constituting the second layer 4b are sequentially arranged. After the formation, the second layer 4b can be appropriately adjusted by, for example, separately forming a layer bonded to the oxygen side electrode 1.

  By the way, the presence or absence of Zr in the intermediate layer 4 means whether or not Zr can be confirmed in the intermediate layer 4 when surface analysis is performed using, for example, EPMA (X-ray microanalyzer). It can also be determined by a method capable of confirming the presence or absence of Zr.

  Here, the second layer 4b is preferably sintered at a temperature lower than the simultaneous sintering temperature of the solid electrolyte 9 and the first layer 4a.

  After the solid electrolyte 9 and the first layer 4a are simultaneously sintered, the second layer 4b is sintered on the surface of the first layer 4a at a temperature lower than that of the simultaneous sintering. It is possible to suppress the contained Zr from diffusing into the second layer 4b. Thereby, the second layer 4b does not contain Zr, and it is possible to suppress the formation of a reaction layer having a high electrical resistance in the oxygen-side electrode 1 provided on the second layer 4b.

  Furthermore, the density of the second layer 4b can be lowered by sintering the second layer 4b at a temperature lower than the simultaneous sintering temperature of the solid electrolyte 9 and the first layer 4a. Thereby, the 2nd layer 4b and the oxygen side electrode 1 can be firmly joined by the anchor effect.

  The sintering of the second layer 4b at a temperature lower than the simultaneous sintering temperature of the solid electrolyte 9 and the first layer 4a is specifically, for example, 200 higher than the firing temperature at the time of simultaneous sintering. It is preferable to sinter at a temperature lower by at least ° C. As such a specific temperature, for example, the second layer 4b is preferably sintered at 1100 to 1300 ° C.

  In the fuel cell of the present invention, the thickness of the first layer 4a is preferably 1 to 10 μm, and the thickness of the second layer 4b is preferably 5 to 20 μm.

  By setting the thickness of the first layer 4a to 1 to 10 μm, Zr contained in the solid electrolyte 9 can be sufficiently diffused into the first layer 4a, and the solid electrolyte 9 and the first layer 4a are It can join firmly and can suppress that the 1st layer 4a peels from the solid electrolyte 9. FIG.

  Furthermore, by setting the thickness of the second layer 4b to 5 to 20 μm, the bonding strength between the first layer 4a and the second layer 4b can be improved, and the second layer 4a from the first layer 4a can be improved. The peeling of the layer 4b can be suppressed. When the thickness of the second layer 4b is 20 μm or more, the second layer 4b may be peeled off from the first layer 4a due to a difference in thermal expansion from the first layer 4a. Attention is required.

In the present invention, the oxygen-side electrode 1 is preferably formed of a conductive ceramic made of a so-called ABO ₃ type perovskite oxide. Such perovskite oxides include transition metal perovskite oxides, particularly LaMnO ₃ oxides, LaFeO ₃ oxides, and LaCoO ₃ oxides in which Sr (strontium) and La (lanthanum) coexist at the A site. One type is preferable, and LaCoO ₃ oxide is particularly preferable from the viewpoint of high electrical conductivity at an operating temperature of about 600 to 1000 ° C. In the perovskite oxide, Fe (iron) or Mn (manganese) may exist at the B site together with Co (cobalt).

  Further, the oxygen side electrode 1 needs to have gas permeability. Therefore, the conductive ceramic (perovskite oxide) forming the oxygen side electrode 1 has an open porosity of 20% or more, particularly 30 to 50%. It is preferable that it exists in the range. Furthermore, it is preferable that the thickness of the oxygen side electrode 1 is 30-100 micrometers from the point of current collection.

  Below, the other member which comprises the fuel cell 10 of this invention is demonstrated.

  Since the conductive support substrate 3 is required to be gas permeable to allow the fuel gas to permeate to the fuel side electrode 7 and to be conductive to collect current via the interconnector 2, For example, it is preferably formed of an iron group metal component and a specific rare earth oxide.

  Examples of the iron group metal component include an iron group metal element, an iron group metal oxide, an iron group metal alloy or an alloy oxide, and the like. More specifically, for example, iron group metals include Fe, Ni (nickel), and Co. In the present invention, any of them can be used, but it is preferable that Ni and / or NiO is contained as an iron group component because it is inexpensive and stable in fuel gas.

The specific rare earth oxide is used to make the thermal expansion coefficient of the conductive support substrate 3 close to the thermal expansion coefficient of the solid electrolyte 9, and is Y, Lu (lutetium), Yb, Tm (thulium). ), Er (erbium), Ho (holmium), Dy (dysprosium), Gd, Sm, Pr (praseodymium), a rare earth oxide containing at least one element selected from the group consisting of the iron group component and Used in combination. Specific examples of such rare earth oxides include Y ₂ O ₃ , Lu ₂ O ₃ , Yb ₂ O ₃ , Tm ₂ O ₃ , Er ₂ O ₃ , Ho ₂ O ₃ , Dy ₂ O ₃ , Gd ₂ O. ₃ , Sm ₂ O ₃ , Pr ₂ O ₃ can be exemplified, there is almost no solid solution and reaction with the iron group metal oxide, and the thermal expansion coefficient is almost the same as that of the solid electrolyte 9. and from the point that it is _{inexpensive, Y 2 O 3, Yb 2} O 3 it is preferred.

  In the present invention, the iron group metal component: rare earth oxide component = 35: 65 in that the good conductivity of the conductive support substrate 3 is maintained and the thermal expansion coefficient is approximated to that of the solid electrolyte 9. It is preferably present in a volume ratio of 65:35. The conductive support substrate 3 may contain other metal components and oxide components as long as required characteristics are not impaired.

  Moreover, since the electroconductive support substrate 3 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 conductive support substrate 3 is preferably 300 S / cm or more, and particularly preferably 440 S / cm or more.

  The length of the flat portion n of the conductive support substrate 3 (length in the width direction of the conductive support substrate 3) is normally 15 to 35 mm, and the length of the arc-shaped portion m (arc length) is 2 It is preferable that the thickness of the conductive support substrate 3 (thickness between both surfaces of the flat portion n) is 1.5 to 5 mm.

In the present invention, the fuel side electrode 7 causes an electrode reaction, and is preferably formed of a known porous conductive ceramic. For example, it is formed from ZrO _{2 in which a} rare earth element is dissolved or CeO ₂ in which a rare earth element is dissolved, and Ni and / or NiO.

The content of ZrO ₂ in which the rare earth element is dissolved in the fuel-side electrode 7 or CeO ₂ in which the rare earth element is dissolved is preferably in the range of 35 to 65% by volume, and the Ni or NiO content is 65%. It is preferably ~ 35% by volume. Further, the open porosity of the fuel side electrode 7 is preferably 15% or more, particularly preferably in the range of 20 to 40%, and the thickness thereof is preferably 1 to 30 μm. For example, if the thickness of the fuel side electrode 7 is too thin, the performance may be deteriorated. If the thickness is too thick, there is a possibility that separation due to a difference in thermal expansion occurs between the solid electrolyte 9 and the fuel side electrode 7.

  1A and 1B, the fuel side electrode 7 extends to both sides of the interconnector 2, but exists at a position facing the oxygen side electrode 1 so that the fuel side electrode 7 Therefore, for example, the fuel side electrode 7 may be formed only in the flat portion n on the side where the oxygen side electrode 1 is provided. In addition, the interconnector 2 can be provided directly on the flat portion n of the conductive support substrate 3 on the side where the solid electrolyte 9 is not provided. In this case, the interconnector 2 is provided between the interconnector 2 and the conductive support substrate 3. Can be suppressed.

  Further, a layer having a composition similar to that of the fuel-side electrode 7 is provided between the interconnector 2 and the conductive support substrate 3 in order to reduce a difference in thermal expansion coefficient between the interconnector 2 and the conductive support substrate 3. 8 may be formed. FIG. 1 shows a state in which a layer 8 having a composition similar to that of the fuel-side electrode 7 is formed between the interconnector 2 and the conductive support substrate 3.

The interconnector 2 provided on the conductive support substrate 3 through the layer 8 having a composition similar to that of the fuel side electrode 7 at a position facing the oxygen side electrode 1 is formed of conductive ceramics. Although it is preferable to have contact with the fuel gas (hydrogen gas) and the oxygen-containing gas, it is necessary to have reduction resistance and oxidation resistance. For this reason, lanthanum chromite-based perovskite oxides (LaCrO ₃ -based oxides) are generally used as conductive ceramics having reduction resistance and oxidation resistance. Further, in order to prevent leakage of the fuel gas passing through the inside of the conductive support substrate 3 and the oxygen-containing gas passing through the outside of the conductive support substrate 3, such conductive ceramics must be dense, for example 93% or more In particular, it is preferable to have a relative density of 95% or more.

  The thickness of the interconnector 2 is preferably 10 to 200 μm from the viewpoint of preventing gas leakage and electrical resistance. If the thickness is smaller than this range, gas leakage is liable to occur. If the thickness is larger than this range, the electric resistance is large, and the current collecting function may be lowered due to a potential drop.

  Moreover, it is preferable to provide the P-type semiconductor layer 6 on the outer surface (upper surface) of the interconnector 2. By connecting the current collecting member to the interconnector 2 via the P-type semiconductor layer 6, the contact between the two becomes an ohmic contact, the potential drop can be reduced, and the deterioration of the current collecting performance can be effectively avoided. Become.

Examples of such a P-type semiconductor layer 6 include a layer made of a transition metal perovskite oxide. Specifically, those having higher electron conductivity than LaCrO ₃ oxides constituting the interconnector 2, 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 6 is preferably in the range of 30 to 100 μm.

  The manufacturing method of the fuel cell 10 of the present invention described above will be described. In the description, the case where the second layer 4b is formed as one layer is shown.

First, a clay is prepared by mixing an iron group metal such as Ni or its oxide powder, a rare earth oxide powder such as Y ₂ O ₃ , an organic binder, and a solvent, and using this clay A conductive support substrate 3 molded body is prepared by extrusion molding and dried. As the conductive support substrate 3 molded body, a calcined body obtained by calcining the conductive support substrate 3 molded body at 900 to 1000 ° C. for 2 to 6 hours may be used.

Next, the raw material of ZrO ₂ (YSZ) in which NiO and Y ₂ O ₃ are dissolved, for example, is weighed and mixed according to a predetermined composition. Thereafter, an organic binder and a solvent are mixed with the mixed powder to prepare a slurry for the fuel side electrode 7.

Further, a slurry obtained by adding toluene, a binder, a commercially available dispersant, etc. to a ZrO ₂ powder in which a rare earth element is solid-solubilized is molded to a thickness of 7 to 75 μm by a method such as a doctor blade. A solid electrolyte 9 compact is produced. The fuel-side electrode 7 slurry is applied on the obtained sheet-like solid electrolyte 9 molded body to form a fuel-side electrode 7 molded body, and the surface on the fuel-side electrode 7 molded body side is formed on the conductive support substrate 3 molded body. Laminate to. The slurry for the fuel side electrode 7 is applied to a predetermined position of the conductive support substrate 3 molded body and dried, and the solid electrolyte 9 molded body coated with the slurry for the fuel side electrode 7 is laminated on the conductive support substrate 3 molded body. You may do it.

Subsequently, for example, CeO ₂ powder in which SmO _1.5 is dissolved is heat-treated at 800 to 900 ° C. for 2 to 6 hours, and then wet crushed to adjust the aggregation degree to 5 to 35, The raw material powder for layer 4 compact is prepared. The wet crushing is desirably ball milled for 10 to 20 hours using a solvent. The same applies to the case where the intermediate layer 4 is formed of CeO ₂ powder in which GdO _1.5 is dissolved.

  In the present invention, toluene as a solvent is added to the raw material powder of the intermediate layer 4 molded body whose coagulation degree is adjusted to produce a slurry for the intermediate layer 4, and this slurry is applied onto the solid electrolyte 9 molded body. The coating film of the 1st layer 4a is formed, and the 1st layer 4a molded object is produced. Alternatively, a sheet-like first layer 4a molded body may be produced and laminated on the solid electrolyte 9 molded body.

Subsequently, a material for the interconnector 2 (for example, LaCrO ₃ -based oxide powder), an organic binder and a solvent are mixed to prepare a slurry, a sheet for the interconnector 2 is produced, and a solid electrolyte 9 molded body is formed. No conductive support substrate 3 is laminated on the exposed surface of the molded body.

  Next, the above-mentioned laminated molded body is subjected to binder removal treatment and simultaneously sintered (simultaneously fired) in an oxygen-containing atmosphere at 1400 to 1600 ° C. for 2 to 6 hours.

  Thereafter, the slurry for the intermediate layer 4 is applied to the surface of the formed first layer 4a sintered body to produce a second layer 4b molded body and sintered. In the present invention, in sintering the molded body of the second layer 4b, it is preferably 200 ° C. or more lower than the simultaneous sintering temperature of the solid electrolyte 9 and the first layer 4a, for example, 1100 ° C. to 1300 ° C. It is preferable to carry out with.

  In addition, when forming the 2nd layer 4b from a some layer, it can produce by adjusting suitably the production methods, such as sintering each layer which comprises the 2nd layer 4b in order.

  Here, in densifying the second layer 4b, the sintering time can be appropriately adjusted depending on the particle size, sintering temperature, and the like of the intermediate layer 4 raw material. It is also possible to densify the second layer 4b by sintering the second layer 4b and the first layer 4a and fixing them, followed by further baking. In this case, it is preferable to appropriately adjust the baking temperature and baking time so that the second layer 4b and the oxygen-side electrode 1 can be firmly bonded. The sintering time for fixing the second layer 4b and the first layer 4a can be 2 to 6 hours.

  Moreover, the solid electrolyte 9 molded body of the present invention is a concept including the solid electrolyte 9 calcined body, and the intermediate layer 4 molded body may be laminated on the solid electrolyte 9 calcined body.

Further, a slurry containing a material for the oxygen side electrode 1 (for example, LaCoO ₃ oxide powder), a solvent, and a pore increasing agent is applied on the intermediate layer 4 by dipping or the like. Further, a slurry containing a material for the P-type semiconductor layer 6 (for example, LaCoO ₃ oxide powder) and a solvent, if necessary, is applied to a predetermined position of the interconnector 2 by dipping or the like. By baking for 6 hours, the fuel cell 10 of the present invention having the structure shown in FIG. 1 can be produced. In addition, it is preferable that the fuel cell 10 thereafter causes hydrogen gas to flow therein to reduce the conductive support substrate 3 and the fuel-side electrode 7. In that case, it is preferable to perform a reduction process at 750-1000 degreeC for 5 to 20 hours, for example.

  As described above, when the fuel cell 10 of the present invention is manufactured, the first layer 4a and the second layer 4b are manufactured by separate processes, and after the second layer 4b is baked, the oxygen side Since the electrode 1 is baked (sintered), the second layer 4 b does not contain the component of the oxygen-side electrode 1. Thereby, it can suppress that the component contained in the oxygen side electrode 1 diffuses to the solid electrolyte 9 side immediately after producing the fuel cell 10.

  In addition, the fuel cell stack of the present invention is fixed to the manifold in a state where a plurality of the fuel cells 10 produced as described above are arranged upright and arranged between the fuel cells 10 and a current collecting member. Is bonded to the oxygen-side electrode 1 of one fuel cell 10 by a conductive adhesive such as conductive ceramics, and is bonded to the P-type semiconductor layer 6 of the other adjacent fuel cell 10 by a conductive adhesive, Thereby, the some fuel cell 10 is electrically connected in series, and a fuel cell stack is comprised.

  The fuel cell stack of the present invention can supply sufficient power to the required load by electrically connecting a plurality of fuel cells 10 manufactured as described above in series. In addition, a fuel cell stack having excellent long-term reliability can be obtained.

  Furthermore, the fuel cell according to the present invention is configured to store the fuel cell stack in a storage container, supply a fuel gas introduction pipe for supplying a fuel gas such as city gas, and air as an oxygen-containing gas to the storage container. It is comprised by arrange | positioning an air introduction pipe | tube.

  Since the fuel cell of the present invention is formed by storing the fuel cell stack in a storage container, it can be a fuel cell excellent in long-term reliability in which deterioration of power generation performance during long-time power generation is prevented. At that time, a plurality of fuel cell stacks can be connected and stored in the storage container.

First, NiO powder having an average particle diameter of 0.5 μm and Y ₂ O ₃ powder having an average particle diameter of 0.9 μm are calcined and reduced to a volume ratio of 48% by volume of NiO and 52% by volume of Y ₂ O _3. Then, the kneaded material prepared with an organic binder and a solvent was molded by an extrusion molding method, dried and degreased to prepare a conductive support substrate 3 molded body. Sample No. In No. 1, the volume ratio of the Y ₂ O ₃ powder after calcination and reduction was such that NiO was 45% by volume and Y ₂ O ₃ was 55% by volume.

Next, a slurry for the fuel-side electrode 7 is prepared by mixing a NiO powder having an average particle size of 0.5 μm, a ZrO ₂ powder in which Y ₂ O ₃ is solid-solved, an organic binder, and a solvent. The coating layer for the fuel side electrode 7 was formed on the top by applying and drying by screen printing. Next, using a slurry obtained by mixing a ZrO ₂ powder (solid electrolyte 9 raw material powder) having a particle size of 0.8 μm by solid-solution method in which 8 mol% of Y is dissolved, an organic binder, and a solvent, A sheet for solid electrolyte 9 having a thickness of 30 μm was prepared by a doctor blade method. This sheet for the solid electrolyte 9 was attached on the coating layer for the fuel side electrode 7 and dried. Sample No. In No. 3, the particle size of the ZrO ₂ powder was 1.0 μm. In No. 4, the thickness of the solid electrolyte 9 sheet was 40 μm.

  Subsequently, the laminated molded body in which the molded bodies were laminated as described above was calcined at 1000 ° C. for 3 hours.

Next, a composite oxide containing 85 mol% of CeO ₂ and 15 mol% of any other rare earth element oxide (SmO _1.5 , YO _1.5 , YbO _1.5 , GdO _1.5 ) is prepared. , Using isopropyl alcohol (IPA) as a solvent, pulverized in a vibration mill or ball mill, calcined at 900 ° C. for 4 hours, pulverized again in a ball mill to adjust the degree of aggregation of ceramic particles, Intermediate layer 4 raw material powder was obtained. The slurry for the intermediate layer 4 prepared by adding and mixing an acrylic binder and toluene to the powder is applied on the solid electrolyte 9 calcined body of the obtained laminated calcined body by a screen printing method. And the 1st layer 4a molded object was produced. Sample No. In No. 5, the oxide of another rare earth element was 10 mol%, and sample No. In No. 6, the oxide of another rare earth element was set to 20 mol%. In No. 7, the calcining temperature was 850 ° C.

Subsequently, the LaCrO ₃ type oxide, to produce an organic binder and a slurry for the interconnector 2 and a mixture of solvents, which, exposed conductive support substrate 3 calcined solid electrolyte 9 calcined body is not formed It was laminated on the body and co-fired at 1510 ° C. in the atmosphere for 3 hours.

  Next, the slurry for the intermediate layer 4 is applied to the surface of the formed first layer 4a sintered body by a screen printing method to form a second layer 4b film. Time sintering was performed.

  Sample No. 22-No. In 33, the other rare earth elements contained in the first layer 4a and the second layer 4b were different rare earth elements.

  Sample No. 12-No. In No. 15, the first layer 4a was not formed simultaneously and sintered, and only the second layer 4b was sintered in a separate process.

  Thereafter, the fracture surface was observed with a scanning electron microscope, and the presence or absence of peeling between the intermediate layer 4 and the solid electrolyte 9 was observed. Further, the thicknesses of the first layer 4a and the second layer 4b were obtained and listed in Table 1.

  Further, the adhesion force between the second layer 4b and the solid electrolyte 9 or the first layer 4a is determined to be no adhesion force when it is peeled off when rubbed with a finger or applied to an ultrasonic cleaner. When it did not peel off, it was judged that there was an adhesive force.

Next, a mixed liquid composed 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 isopropyl alcohol was prepared, and the surface of the intermediate layer 4 of the laminated sintered body 1 to form an oxygen-side electrode 1 molded body, which was baked at 1100 ° C. for 4 hours to form the oxygen-side electrode 1 to produce the fuel battery cell 10 shown in FIG.

  The size of the produced fuel cell 10 is 25 mm × 200 mm, the thickness of the conductive support substrate 3 (thickness between both surfaces of the flat portion n) is 2 mm, the open porosity is 35%, and the thickness of the fuel side electrode 7 is The thickness of the oxygen side electrode 1 was 50 μm, the open porosity was 40%, and the relative density was 97%.

  Next, hydrogen gas was allowed to flow inside the fuel cell 10 and the conductive support substrate 3 and the fuel side electrode 7 were subjected to reduction treatment at 850 ° C. for 10 hours.

  About the obtained fuel cell 10, the diffusion of Zr contained in the solid electrolyte 9 into the intermediate layer 4 (the first layer 4a and the second layer 4b) is surface analyzed by EPMA (X-ray microanalyzer). And the presence or absence of Zr is shown in Table 1.

  Here, the presence or absence of Zr was determined to be absent when Zr was not seen in the first layer 4a and the second layer 4b, and conversely, Zr was found as likely to be seen.

Subsequently, the fuel gas is circulated through the fuel gas passage 5 of the obtained fuel battery cell 10, the oxygen-containing gas is circulated outside the fuel battery cell 10, and the fuel battery cell 10 is 750 ° C. using an electric furnace. The power generation performance of the fuel cell 10 was confirmed by performing a power generation test for 3 hours. Thereafter, power generation was performed for 1000 hours under conditions of a fuel utilization rate of 75% and a current density of 0.6 A / cm ² . At that time, the value at 0 hours of power generation was set as the initial voltage, the voltage after 1000 hours was measured, the change from the initial voltage was determined as the deterioration rate, and the deterioration rate of the power generation performance was determined.

Regarding evaluation of power generation performance deterioration, the deterioration rate is less than 0.5%, the deterioration rate is 0.5-1%, the deterioration rate is 1-3%, and the deterioration rate is 1-3%. Table 1 shows the results of the evaluation, assuming that the deterioration rate is 3 to 5% in many cases and the deterioration rate is 5% or more.

  From the results in Table 1, the first layer 4a and the second layer 4b have the same composition, the first layer 4a and the solid electrolyte 9 are simultaneously sintered, and the second layer 4b is simultaneously sintered. When sintered at a temperature lower than 200 ° C. (samples No. 1 to No. 3, No. 17, No. 20, No. 21), there is no diffusion of Zr in the second layer 4b, and the second The result showed that the adhesion strength of the layer 4b was excellent and the power generation performance was very little deteriorated. Similarly, in the first layer 4a and the second layer 4b, Ce is used as a common rare earth element and other rare earth elements have different compositions (sample No. 22, No. 23, No. 28). No. 29), there was no diffusion of Zr in the second layer 4b, the adhesive strength of the second layer 4b was excellent, and the power generation performance was very little deteriorated.

  Moreover, when the thickness of the 2nd layer 4b is 5-20 micrometers (sample No. 4-No. 6, No. 18, No. 19, No. 24-No. 26, No. 30-No. 32). The results show that there is no Zr diffusion in the second layer 4b, the adhesion of the second layer 4b is excellent, and the power generation performance is very little deteriorated.

  When the first layer 4a and the second layer 4b are thickened or thinned (Sample Nos. 7 to 9), there is no Zr diffusion in the second layer 4b, and the second layer 4b. Although the adhesion strength was excellent, the power generation performance was hardly deteriorated due to the thickness of the first layer 4a and the second layer 4b.

  On the other hand, even when the first layer 4a is simultaneously sintered, when the second layer 4b is sintered at 1400 ° C. or higher, that is, although the temperature is lower than the simultaneous sintering temperature, the temperature difference is 200. In the case where the temperature is within (° C.) (Sample No. 10, No. 11, No. 27, No. 33), the second layer 4b showed excellent results in the adhesion strength of the second layer 4b. The result showed that Zr diffusion was observed and the power generation performance was greatly deteriorated (small in No. 27).

  Furthermore, when there is no first layer 4a and the second layer 4b is retrofitted to the sintered body (sample Nos. 12 to 15), or when the second layer 4b is not formed (sample No. 16). Showed that the power generation performance was severely degraded. Here, sample No. 14 and no. 15 shows the result that there is an adhesive force, which is considered to be because the adhesive force is improved by Zr in the solid electrolyte 9 and Zr diffused in the second layer 4b.

The example of the fuel cell of this invention is shown, (a) is a cross-sectional view, (b) is a perspective view of (a). FIG. 2 is an enlarged cross-sectional view showing a part of a part engaged in power generation in an example of a fuel cell of the present invention. It is a cross-sectional view which shows the cell stack which consists of the conventional fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Oxygen side electrode 2 ... Interconnector 3 ... Conductive support substrate 4a ... 1st layer (surface layer area | region)
4b .. 2nd layer (area other than surface area)
5 ... Fuel gas passage 7 ... Fuel side electrode 9 ... Solid electrolyte 10 ... Fuel cell

Claims (5)

In this fuel cell, an intermediate layer and an oxygen side electrode are provided in this order on the surface on one side of a solid electrolyte containing Zr, and a fuel side electrode is provided on the surface on the other side opposite to the surface on the one side. Te, the intermediate layer is configured to contain Zr in the first layer to form a surface layer region of the solid electrolyte side, he contains Zr in the second layer forming the other area other than the surface layer region First, the first layer and the solid electrolyte are simultaneously sintered, and the second layer is sintered at a temperature lower than the simultaneous sintering temperature of the solid electrolyte and the first layer. The fuel cell characterized by the above-mentioned. 2. The fuel cell according to claim 1 , wherein the first layer and the second layer contain the same rare earth element (excluding an element contained in the oxygen-side electrode). When the thickness of the first layer is 1 to 10 [mu] m, the fuel cell according to claim 1 or claim 2 the thickness of the second layer is characterized by a 5 to 20 [mu] m. A fuel cell stack comprising a plurality of the fuel cells according to any one of claims 1 to 3 electrically connected in series. 5. A fuel cell comprising the fuel cell stack according to claim 4 housed in a housing container.

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