JP2009238431A - Horizontal stripe type solid oxide fuel cell stack, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a horizontal stripe type solid oxide fuel cell stack in which variations of firing shrinkage and open-porosity of a support body are reduced and reliability is improved, and a fuel cell using it. <P>SOLUTION: The solid oxide fuel cell stack of lateral stripe type is composed of a plurality of fuel cells 13, in which a fuel electrode layer 13a, a solid electrolyte 13b, and an air electrode layer 13c are laminated in this order, are arranged side by side in the surface of a support body 11 equipped with a gas passage 12 inside, and the neighboring fuel cells 13 are connected electrically in series. The support body 11 is composed containing Ni and/or NiO and MgO, and since contents of SiO<SB>2</SB>and B<SB>2</SB>O<SB>3</SB>are respectively 200 ppm or less, the variations of the firing shrinkage and the open-porosity can be suppressed, and the variations in the power generation amount can be suppressed. This is the fuel cell composed by a plurality of these fuel cell stacks housed in a housing container. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a horizontally-striped solid oxide fuel cell stack and a fuel cell in which a plurality of them are accommodated in a storage container.

  In recent years, as next-generation energy, various fuel cells have been proposed in which a horizontal stripe type fuel cell stack in which a plurality of fuel cells are electrically connected to the surface of an electrically insulating support is accommodated in a storage container. . As such fuel cells, various types such as solid polymer fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells are known. In particular, solid oxide fuel cells have high power generation efficiency and high operating temperatures of 700 ° C. to 1000 ° C., so that the power generation efficiency can be increased by effectively using the exhaust heat. Have research and development.

  FIG. 14 is an enlarged longitudinal sectional view showing a part of a solid oxide fuel cell stack including a plurality of conventionally known solid oxide fuel cells. This solid oxide fuel cell stack has a fuel electrode layer 23a as an inner electrode layer, a solid electrolyte layer 23b, and an air electrode layer 23c as an outer electrode layer on the surface of a cylindrical support 21 that is an electrical insulator. Are stacked in this order with a predetermined interval in the longitudinal direction G (up and down direction on the paper surface) of the support 21 of the solid oxide fuel cell 23 having a multilayer structure (hereinafter sometimes abbreviated as fuel cell). A plurality are formed and electrically connected (for example, see Patent Document 1). The fuel cell stack having such a shape is called a so-called “horizontal stripe type”.

  Adjacent fuel cells 23 are electrically connected in series by interconnectors 24 as inter-cell connecting members. That is, the fuel electrode layer 23 a of one fuel battery cell 23 and the air electrode layer 23 c of the other fuel battery cell 23 are electrically connected by the interconnector 24. Further, one or more gas flow paths 27 are formed along the longitudinal direction G of the support 21 inside the support 21.

  In the solid oxide fuel cell stack in which the fuel electrode layer 23a, the solid electrolyte layer 23b, and the air electrode layer 23c are laminated in this order on the support 21, the oxygen ion conductivity of the solid electrolyte layer 23b is 600 ° C. or higher. Therefore, at such a temperature, a gas (air) containing oxygen is caused to flow around the fuel battery cell 23, and a gas (fuel gas) containing hydrogen is caused to flow through the gas flow path 27. The difference in oxygen concentration between the fuel electrode layer 23a and the fuel electrode layer 23a increases, and a potential difference is generated between the air electrode layer 23c and the fuel electrode layer 23a.

  Due to this potential difference, oxygen ions move from the air electrode layer 23c to the fuel electrode layer 23a through the solid electrolyte layer 23b. The moved oxygen ions combine with hydrogen in the fuel electrode layer 23a to become water, and at the same time, electrons are generated in the fuel electrode layer 23a. That is, the electrode reaction of the following formula (1) occurs in the air electrode layer 23c, and the electrode reaction of the following formula (2) occurs in the fuel electrode layer 23a.

  Then, by electrically connecting the fuel electrode layer 23a and the air electrode layer 23c, electrons move from the fuel electrode layer 23a to the air electrode layer 23c, and an electromotive force is generated between the electrode layers. As described above, in the fuel battery cell 23, by supplying oxygen (air) and hydrogen (fuel gas), the above reaction is continuously caused to generate an electromotive force to generate electric power.

In such a horizontal stripe type solid oxide fuel cell stack, the support 21 is produced using an electrically insulating material to prevent an electrical short circuit between the fuel cells 23. As the support 21, for example, a solid solution of Ni and MgAl ₂ O ₄ (spinel) or a solid solution of Ni and MgO is used (for example, see Patent Documents 2 to 6).

  However, when the support 21 is configured to contain Ni and / or NiO and MgO, impurities contained in these compositions may cause variations in the shrinkage rate of each support during firing. there were. Further, when a power generation test is performed using a bundle in which a plurality of horizontally-striped solid oxide fuel cell stacks are connected or a fuel cell in which a plurality of bundles are arranged, the open porosity of each support 21 is determined. In some cases, the power generation performance of the horizontally-striped solid oxide fuel cell stack varies. In a fuel cell using such a horizontally-striped solid oxide fuel cell stack, it may be difficult to stably obtain a certain amount of power generation.

JP-A-10-3932 JP-A-5-82146 JP-A-6-203855 JP-A-8-222246 JP-A-9-73906 JP-A-9-139220

  An object of the present invention is to provide a horizontal-striped solid oxide fuel cell stack and a fuel cell that can suppress variations in shrinkage of the support and variations in open porosity and suppress variations in power generation performance. It is.

As a result of intensive studies to solve the above problems, the present inventors have found the following findings. That is, among impurities contained in a support including Ni and / or NiO and MgO, SiO ₂ and B ₂ O ₃ affect variations in shrinkage of the support and variations in open porosity. Then, the content of these SiO ₂ and B ₂ O _3, when control each within a specific numerical range, it is possible to suppress variations in dispersion and open porosity of the shrinkage of the support, as a result, segmented-in-series It has become possible to suppress variations in the power generation performance of the solid oxide fuel cell stack.

That is, the horizontally-striped solid oxide fuel cell stack of the present invention has a fuel cell formed by laminating an inner electrode layer, a solid electrolyte layer, and an outer electrode layer in this order. The inner electrode layer of one of the fuel battery cells is electrically connected to the outer electrode layer of the other fuel battery cell adjacent to the one fuel battery cell. The plurality of fuel cells are connected in series, and the support includes Ni and / or NiO and MgO, and is composed of SiO ₂ and B ₂ O ₃ . Content is 200 ppm or less, respectively.

In such a horizontal stripe type solid oxide fuel cell stack, the content of SiO ₂ and B ₂ O ₃ which are trace components contained in the electrically insulating support is set to 200 ppm or less, respectively. Variation in shrinkage rate and variation in open porosity during firing can be suppressed. Thereby, the variation in the electric power generation amount of a horizontal stripe type solid oxide fuel cell stack can be controlled.

Moreover, in the horizontally-striped solid oxide fuel cell stack according to the present invention, the content of Al ₂ O ₃ in the support is preferably 200 ppm or less.

In such a horizontal stripe type solid oxide fuel cell stack, the content of Al ₂ O ₃ in the support is 200 ppm or less, so that the shrinkage varies during firing of the support and the open porosity varies. Can be further suppressed, and variation in the amount of power generation can be further suppressed.

  Moreover, it is preferable that the horizontal-striped solid oxide fuel cell stack of the present invention has an open porosity of 30 to 45% of the support.

  In such a horizontal stripe type solid oxide fuel cell stack, by setting the porosity of the support to 30 to 45%, the reaction gas (fuel gas) flowing through the gas flow path of the support is sufficiently fuel cell. While being able to introduce into a cell (fuel electrode layer), it can suppress that the intensity | strength of a support body falls.

  In the horizontal stripe solid oxide fuel cell stack of the present invention, the support preferably has a three-point bending strength of 70 to 120 MPa.

  In such a horizontal stripe type solid oxide fuel cell stack, by setting the three-point bending strength of the support to 70 to 120 MPa, the support can be prevented from being damaged and the strength of the support varies. Can be suppressed, and variations in the amount of power generation can be further suppressed.

  The fuel cell according to the present invention is characterized in that a plurality of the above-described horizontal-striped solid oxide fuel cell stacks are stored in a storage container.

  In such a fuel cell, a plurality of horizontally-striped solid oxide fuel cell stacks capable of suppressing the above-described variation in the amount of power generation are stored in a storage container. It can be.

In the horizontally-striped solid oxide fuel cell stack of the present invention, the electrically insulating support includes Ni and / or NiO and MgO, and the content of SiO ₂ and B ₂ O ₃ Since each of these is 200 ppm or less, it is possible to suppress variation in shrinkage rate and variation in open porosity during firing of the support. As a result, variations in the amount of power generation can be suppressed, a horizontal stripe solid oxide fuel cell stack with improved reliability, and a fuel cell with improved reliability can be obtained.

  Hereinafter, an embodiment of a horizontally-striped solid oxide fuel cell stack according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an enlarged vertical sectional view showing a part of a horizontally-striped solid oxide fuel cell stack according to the present embodiment, and FIG. 2 is a horizontal sectional view thereof.

  As shown in FIG. 1 and FIG. 2, a horizontally-striped solid oxide fuel cell stack (hereinafter sometimes abbreviated as “cell stack”) according to the present embodiment has a gas flow path 12 therein and an electric circuit. A plurality of fuel cells 13 are arranged in parallel at a predetermined interval on the surface of the insulating support 11.

  The fuel battery cell 13 is configured by sequentially laminating a fuel electrode layer 13a as an inner electrode layer, a solid electrolyte layer 13b, and an air electrode layer 13c as an outer electrode layer on the surface of the support 11 in this order. Adjacent fuel cells 13 are electrically connected by an interconnector 14 as an inter-cell connecting member. That is, the fuel electrode layer 13 a of one fuel cell 13 and the air electrode layer 13 c of the other fuel cell 13 are connected in series in the longitudinal direction of the support 11 by the interconnector 14. .

  In such a cell stack, a fuel gas containing hydrogen is caused to flow into the gas flow path 12 to expose the support 11 to a reducing atmosphere, and an oxygen-containing gas such as air is caused to flow on the surface of the air electrode layer 13c. By exposing the layer 13c to an oxidizing atmosphere, the electrode reaction represented by the above-described formulas (1) and (2) occurs in the fuel electrode layer 13a and the air electrode layer 13c, and a potential difference is generated between the two electrodes to generate power. Can do.

  The support 11 is formed in a hollow flat plate shape, and a plurality (six in FIG. 2) of gas flow paths 12 separated by a partition wall 11a are provided therein. By making the support 11 have a hollow plate shape, the area of the fuel cell 13 per volume of the support 11 can be increased, and the amount of power generation per volume of the cell stack can be increased. Therefore, the number and volume of cell stacks for obtaining the required power generation amount can be reduced, and the number of connection points between the cell stacks can also be reduced. As a result, the structure is simplified, the assembly is simplified, and the reliability of the fuel cell (horizontal stripe solid oxide fuel cell stack) can be improved. Further, since the plurality of gas flow paths 12 are provided inside the support 11, the structural strength of the support 11 can be improved, and the mechanical strength of the cell stack can be increased.

  From the viewpoint of preventing an electrical short circuit with the fuel cell 13, the support 11 is usually preferably set in a range of an electric resistance value of 10 Ω · cm or more. The electric resistance value can be measured by a four-terminal method in which both terminals of voltage and current are connected to both ends of a prismatic sample piece.

  The support 11 has a pair of flat portions n and arc-shaped portions m connecting both ends thereof, and the major axis dimension in the cross section (corresponding to the distance between the arc-shaped portions m at both ends) is, for example, 15 mm to 50 mm, The dimension of the minor axis (corresponding to the distance between the pair of flat portions n) can be set in the range of 2 mm to 4 mm, for example. Further, the support 11 can have an open porosity of, for example, 25% or more, preferably 30% to 45%. Thereby, the fuel gas flowing through the gas flow path 12 can flow to the surface of the fuel electrode layer 13a.

Here, the support 11 in this embodiment is configured to include Ni and / or NiO (NiO is usually reduced by hydrogen gas and present as Ni during power generation) and MgO, and SiO. The content of ₂ and B ₂ O ₃ is 200 ppm or less, preferably 100 ppm or less. That is, in producing the support 11 including the above-described components, a trace amount of impurities may be contained in the raw material of Ni or NiO or MgO. Depending on the composition and amount of the impurities, there may be variations in the shrinkage rate for each support 11 during firing or variations in the open porosity, which may cause variations in the amount of power generation.

The composition of the impurities affecting the variation of the shrinkage rate and the variation of the open porosity of the support 11 is SiO ₂ and B ₂ O ₃ , and the amounts thereof are each greater than 200 ppm. Therefore, in the present embodiment, when the support 11 is manufactured, the contents of SiO ₂ and B ₂ O ₃ that are one type of trace impurities contained in the raw materials NiO and MgO are set to 200 ppm or less, respectively. As a result, the contents of SiO ₂ and B ₂ O _{3 in} the support 11 become 200 ppm or less, respectively, and the variation in shrinkage rate and the variation in open porosity of the support 11 are achieved, and the power generation performance of the cell stack is reduced. Variations can be suppressed.

  On the other hand, when each of these trace components is more than 200 ppm, a region having high strength and low open porosity or a region having low strength and high open porosity is locally generated inside the support 11, and the cell stack Leading to power generation performance degradation and damage.

The contents of SiO ₂ and B ₂ O ₃ can be set to 200 ppm or less, respectively, by preventing contamination from being mixed during firing during raw material purification or mechanical pulverization during particle size adjustment. Further, as will be described later, commercially available raw materials with high purity can be used so that the contents of SiO ₂ and B ₂ O ₃ at the time of producing the support 11 are each 200 ppm or less. The content of SiO ₂ and B ₂ O ₃ can be measured by an ICP (Inductively Coupled Plasma) emission spectroscopic analysis method for an aqueous sample.

Further, in the support 11, it is preferable to control the content of Al ₂ O ₃ which is one of the impurities described above. Thereby, the dispersion | variation at the time of baking of the support body 11 and the dispersion | variation in open porosity can be suppressed more, and the dispersion | variation in electric power generation amount can further be suppressed. More specifically, the content of Al ₂ O ₃ is preferably 200 ppm or less, more preferably 100 ppm or less. Incidentally, the content of _Al 2 _{O 3} when shall be 200ppm or less, it is possible to employ the same method as the content of SiO ₂ and _B 2 _{O 3} as described above.

  By the way, although the support body 11 of this embodiment is comprised including Ni and / or NiO, and MgO, MgO which comprises the support body 11 in order to suppress destruction of the front-end | tip part of the support body 11, etc. The molar ratio of Ni and / or NiO to ([Ni and / or NiO) / MgO] is preferably in the range of 0.15 to 0.25. Thereby, the breakage at the tip of the support 11 can be suppressed.

Further, the ratio of Ni and / or NiO constituting the support 11 is preferably 10 to 20 mol% with respect to the total amount of the support 11. The support 11 preferably further contains Y ₂ O ₃ for the purpose of matching the thermal expansion coefficient with members such as a fuel electrode layer 13a and a solid electrolyte layer 13b described later.

  As described above, the open porosity of the support 11 is preferably 30 to 45%. That is, by setting the open porosity of the support 11 to 30% or more, the fuel gas flowing through the gas flow path 12 of the support 11 can be sufficiently introduced into the fuel electrode layer, and the fuel utilization rate is improved. Can do. Thereby, the power generation amount in the cell stack can be improved, and the number of cell stacks can be reduced in obtaining a predetermined power generation amount. In order to further improve the fuel utilization rate, the open porosity of the support 11 is more preferably 32% or more. In addition, when the porosity of the support 11 is greater than 45%, the strength of the support 11 may decrease, and further, a cell stack formed by disposing the fuel cells 13 on the surface of the support 11 is gasified. When it fixes to the manifold for supplying fuel gas etc. to the flow path 12, a crack may arise in the lower end side (manifold side) of a cell stack (support body 11). The open porosity can be calculated according to the Archimedes method. The open porosity can be arbitrarily set, for example, by adjusting the amount of burnt material added when producing the support molded body 51 described later.

The three-point bending strength of the support 11 is preferably 70 to 120 MPa. Thereby, while being able to suppress that the support body 11 breaks etc., the variation in the intensity | strength of the support body 11 can be suppressed, and the variation in the electric power generation amount can further be suppressed. The three-point bending strength is a value measured by a three-point bending strength based on the JIS standard (JIS R1601). For the purpose of improving the strength of the support 11, Fe ₂ O ₃ can be contained in an amount of 0.2 mol% or less with respect to the total amount of the support 11.

Next, the fuel electrode layer 13a can be formed of, for example, a porous conductive cermet made of ZrO ₂ (stabilized zirconia) in which a rare earth element is dissolved and Ni and / or NiO. Moreover, the material of the solid electrolyte layer 13b described later can also be used. In the fuel electrode layer 13a, the blending ratio of the stabilized zirconia is preferably in the range of 35% by volume to 65% by volume with respect to the total amount of the fuel electrode layer 13a, and the blending ratio of Ni is calculated in terms of NiO in the fuel electrode layer 13a. The range of 35 volume%-65 volume% is preferable with respect to the total amount. In addition, the fuel electrode layer 13a preferably has an open porosity of, for example, 15% or more, more preferably in the range of 20% to 40%. It is preferable to be in a range of ˜100 μm.

The solid electrolyte layer 13b may be composed of a dense ceramic made of stabilized ZrO ₂ composed of ZrO ₂ which was a solid solution of a rare earth element or its oxide. Here, examples of the rare earth element to be dissolved include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. From the viewpoint of being inexpensive, it is preferable to use Y, Yb, or Y ₂ O ₃ or Yb ₂ O ₃ which is an oxide thereof. More specifically, the solid electrolyte layer 13b includes stabilized ZrO ₂ (8 mol% Yttria Stabilized Zirconia, hereinafter referred to as “8YSZ”) in which 8 mol% Y is dissolved. Alternatively, a lanthanum gallate system (LaGaO ₃ system) having a shrinkage rate substantially equal to 8YSZ can be used.

  The thickness of the solid electrolyte layer 13b is preferably 10 μm to 100 μm, and the relative density (according to Archimedes method) is preferably set to 93% or more, more preferably 95% or more. Such a solid electrolyte layer 13b has a function as an electrolyte for bridging electrons between electrodes, and at the same time has a gas barrier property to prevent leakage of fuel gas or oxygen-containing gas (gas permeation). Yes.

The air electrode layer 13c is formed from conductive ceramics. Examples of the conductive ceramic include ABO ₃ type perovskite oxide. Examples of such perovskite oxides include transition metal perovskite oxides, preferably LaMnO ₃ -based oxides, LaFeO ₃ -based oxides, LaCoO ₃ -based oxides, etc., particularly transition metals having La at the A site. A type perovskite oxide can be used. From the viewpoint of high electrical conductivity at a relatively low temperature of about 600 ° C. to 1000 ° C., it is preferable to use a LaCoO ₃ -based oxide. In the perovskite oxide described above, La and Sr may coexist at the A site, and Fe, Co, and Mn may coexist at the B site.

  Such an air electrode layer 13c can cause the electrode reaction of the above-described formula (1). Moreover, it is preferable that the open porosity of the air electrode layer 13c is set in a range of, for example, 20% or more, and further 30% to 50%. By setting the open porosity of the air electrode layer 13c within this range, the air electrode layer 13c can have good gas permeability. Furthermore, by setting the thickness of the air electrode layer 13c to, for example, a range of 30 μm to 100 μm, the air electrode layer 13c can have good current collecting properties.

The interconnector 14 electrically connects the fuel electrode layer 13a of one fuel battery cell 13 and the air electrode layer 13c of the other fuel battery cell 13, and can be formed from conductive ceramics. Examples of such conductive ceramics include lanthanum chromite-based perovskite oxides (LaCrO ₃ -based oxides). Since the LaCrO ₃ oxide has good reduction resistance and oxidation resistance, corrosion and deterioration of the interconnector 14 can be effectively suppressed.

Further, the conductive ceramic forming the interconnector 14 is preferably set to have a relative density (Archimedes method) in a range of, for example, 93% or more, and more preferably 95% or more. By setting the relative density within this range, the conductive ceramic can be made dense, and the leakage of the fuel gas passing through the gas flow path 12 in the support 11 and the oxygen-containing gas passing through the outside of the air electrode layer 13c. Can be effectively suppressed. Further, by appropriately interposing a bonding layer such as Y ₂ O _{3 in} the connecting portion between the interconnector 14 and the solid electrolyte layer 13b, the sealing performance can be improved.

  In the embodiment described above, the fuel cell 13 formed on the surface of the support 11 has an example of a multilayer structure in which the inner electrode layer is the fuel electrode layer 13a and the outer electrode layer is the air electrode layer 13c. Although shown, the positional relationship between both electrode layers may be reversed. That is, the fuel cell 13 in which the air electrode layer 13c, the solid electrolyte layer 13b, and the fuel electrode layer 13a are sequentially laminated in this order can be disposed on the surface of the support 11. In this case, an oxygen-containing gas such as air is circulated in the gas flow path 12 of the support 11, and a fuel gas such as a hydrogen-containing gas is circulated on the surface of the fuel electrode layer 13a as the outer electrode layer.

  Next, a structure in which a plurality of horizontal stripe solid oxide fuel cell stacks described above are connected (hereinafter referred to as a bundle in the present specification) will be described with reference to FIG.

  FIG. 3 is an enlarged longitudinal sectional view showing an end portion (end portion of the cell stack) in a bundle in which a plurality (two) of the cell stacks described above are combined. As shown in FIG. 3, the cell stacks are electrically connected to each other via a current collecting member 19.

  At the end of the cell stack, the inter-cell stack connecting member 15 is provided at the end of one cell stack and is electrically connected to the fuel electrode layer 13a of the fuel cell 13 constituting one cell stack. In addition, the inter-cell stack connecting member 15 is electrically connected to the air electrode layer 13 c of the other fuel cell 13 through the current collecting member 19 at the end of the other cell stack.

  As described above, since the cell stacks can be arranged densely by electrically connecting the plurality of cell stacks via the current collecting member 19, the volume of the cell stack per power generation amount can be reduced. Can do. Therefore, a small and highly heat efficient cell stack can be provided.

  The inter-cell stack connecting member 15 is not particularly limited as long as it electrically connects the fuel electrode layer 13a of one cell stack and the air electrode layer 13c of the other cell stack. For example, the interconnector 14 It can be formed from the same material.

  The current collecting member 19 is not particularly limited as long as it is electrically connected to the air electrode layer 13c of the fuel battery cell 13 constituting the other cell stack and electrically connects the interconnector 14 and the air electrode layer 13c. For example, it can be formed from a heat-resistant metal, conductive ceramics, or the like. Specifically, for example, a metal felt and / or a heat-resistant metal plate, an inorganic material, and the like are mentioned. From the viewpoint of heat resistance, oxidation resistance, and electrical conductivity, Pt, Ag, Ni alloy, and Fe—Cr steel alloy are used. It is preferable to use at least one kind.

  Further, by applying a conductive adhesive such as a paste containing a noble metal such as Ag or Pt to the connecting portion between the current collecting member 19, the inter-cell stack connecting member 15 and the air electrode layer 13c, the current collecting member The connection reliability of 19 can also be improved. When the fuel electrode layer 13a is formed as an external electrode layer, the current collecting member 19 can be formed from, for example, Ni felt. Moreover, as a conductive adhesive, the paste containing Ni metal can be illustrated.

  FIG. 4 is a longitudinal sectional view showing a bundle in which a plurality (three) of the cell stacks described above are combined. In FIG. 4, the fuel cell 13, the interconnector 14, and the inter-cell stack connecting member 15 are shown in a simplified manner.

  A current collecting member 19 is interposed between the inter-cell stack connecting member 15 at the end of one cell stack and the air electrode layer 13c at the end of the other cell stack, thereby supporting the support 11 of one cell stack. The fuel electrode layer 13a formed on the surface is electrically connected to the air electrode layer 13c of the other fuel battery cell via the inter-cell stack connecting member 15 and the current collecting member 19. In FIG. 4, the conductive member 20 is a member for taking out the electric power generated in the cell stack, whereby the electric power generated in the plurality of cell stacks can be easily drawn out.

  The fuel cell of the present invention is configured by storing a plurality of the above-described cell stacks in a storage container. Accordingly, since the cell stack can be densely arranged in the storage container, the volume of the fuel cell per power generation amount can be reduced, and a small and highly efficient fuel cell can be provided.

  The storage container is provided with an introduction pipe for introducing a fuel gas such as a hydrogen-containing gas and an oxygen-containing gas such as air from the outside into the storage container, and the fuel after being used by the power generation of the cell stack. It is preferable to have an exhaust part for exhausting gas or oxygen-containing gas (excess gas).

Next, a method of manufacturing the cell stack according to the above-described embodiment will be described with reference to FIGS.
First, a support molded body 51 as shown in FIG. 5 is produced. Examples of the material of the support molded body 51 include 10 to 20 mol% of NiO powder having an average particle diameter (D50) (hereinafter simply referred to as “average particle diameter”) of 0.1 to 10.0 μm, and an average particle diameter. 0.2 to 0.1 mol% Fe ₂ O ₃ having a diameter of 0.1 to 5 μm, 10 to 15 mol% of Y ₂ O ₃ powder having an average particle diameter of 0.5 to 5 μm, and MgO having an average particle diameter of 0.5 to 5 μm The powder is blended at a ratio of 65 to 80 mol% and mixed. The said ratio is a ratio with respect to the total amount of the support body molded body 51 (namely, the support body 11). The average particle diameter is a value obtained by particle size distribution measurement using a laser diffraction scattering method.

  The mixed powder is mixed with a burned material, a cellulose organic binder, and a solvent composed of water and extruded to form a hollow flat plate having a gas flow passage 52 therein, as shown in FIG. The support body molded body 51 was prepared, and this was dried and calcined at 900 ° C. to 1200 ° C.

  In order to set the open porosity of the support 11 to 30 to 45%, the burnout material is added at a ratio of 10 to 20% by weight with respect to the total amount of the support molded body 51 (that is, the support 11). Is preferred. The average particle size of the burned material is preferably 5 to 30 μm. An organic resin (for example, an acrylic resin, a polyethylene resin, or the like) can be used as the burnout material.

Here, these impurity species are each 200 ppm or less so that the content of SiO ₂ and B ₂ O ₃ which are trace components contained in the NiO powder and MgO powder described above, and further Al ₂ O ₃ is 200 ppm or less. Select raw material species with high purity.

Next, a fuel electrode layer material and a solid electrolyte layer material are produced. For example, a NiO powder and a ZrO ₂ powder in which a rare earth element oxide such as Y ₂ O ₃ is dissolved are mixed, a burned-out material is added thereto, and an acrylic binder and toluene are mixed to form a slurry. The slurry is applied by a blade method and dried to produce a fuel electrode layer tape 53a having a thickness of 80 μm to 120 μm, as shown in FIG.

  Separately, 8YSZ is mixed with an acrylic binder and toluene to form a slurry, and the slurry is applied by a doctor blade method and dried. As shown in FIG. 6A, a solid electrolyte layer tape having a thickness of 10 μm to 50 μm. 53b is produced.

  Next, as shown in FIG. 6 (b), the fuel electrode layer tape 53a and the solid electrolyte layer tape 53b are overlapped so that the portions where they do not overlap each other have a width of 1 mm to 5 mm. And bonding as shown in FIG.

  Thereafter, as shown in FIG. 7A, the fuel electrode layer tape 53a and the solid electrolyte layer tape 53b bonded in FIG. 6C are calcined with the fuel electrode layer tape 53a side down. Affixed to the calcined body 51 in a horizontal stripe pattern. This is repeated, and a laminate of a plurality of fuel electrode layer tapes 53a and solid electrolyte layer tape 53b is attached to the surface of the support calcined body 51. At this time, the laminate of one fuel electrode layer tape 53a and the solid electrolyte layer tape 53b and the laminate of the other fuel electrode layer tape 53a and the solid electrolyte layer tape 53b are spaced from each other by a width of 3 mm to 20 mm. Deploy. Next, the support body molded body 51 is dried in a state where these laminates are adhered, and then calcined in a temperature range of 900 ° C. to 1300 ° C.

  Next, the interconnector molded body 54 and the inter-cell stack connecting member molded body 59 are formed. In addition, since the same material can be used for the interconnector 14 and the connection member 15 between cell stacks, both are formed in the same process here.

First, a dip slurry is prepared with lanthanum chromite (LaCrO ₃ ) and a polyvinyl alcohol (PVA) binder. Next, as shown in FIG. 7A, the portion (width 2 mm to 5 mm) excluding both ends of the solid electrolyte layer tape 53b is masked with a masking tape 61, and then as shown in FIG. 7B. Then, dip in the slurry for dip to form the interconnector molded body 54 and the inter-cell stack connecting member molded body 59. Thereafter, drying is performed, and then the masking tape 61 is removed as shown in FIG. Thereafter, firing is performed at 1450 ° C. to 1550 ° C. so that the interconnector 14 and the inter-cell stack connection member 15 cover the fuel electrode layer 13a and overlap the end portion of the solid electrolyte layer 13b with a width of about 2 mm to 5 mm. To do.

  Next, as shown in FIG. 8A, the entire surface of the inter-cell stack connecting member 15 and the substantially entire surface of the interconnector 14 (however, on the side opposite to the side where the interconnector 14 is connected to the fuel electrode layer 13a). Are masked with a masking tape 63.

Next, as shown in FIG. 8B, a slurry obtained by mixing lanthanum cobaltite (LaCoO ₃ ) and isopropyl alcohol is sprayed onto the masked laminate to form an air electrode layer molded body 53c having a thickness of 10 μm to 100 μm. . Thereafter, as shown in FIG. 8C, the masking tape 63 is removed, and heat treatment is performed at 1000 ° C. to 1200 ° C., whereby a horizontal stripe solid oxide fuel cell stack can be obtained.

  In the above description, each layer is laminated using tape lamination, dip and spray spraying, but the present invention may use only any lamination method. In particular, the drying process at the time of lamination is short, and it is preferable to laminate each layer by dipping from the viewpoint of shortening the process.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to a following example.

(Preparation of support molded body)
NiO powder having an average particle size of 0.5 to 1.0 μm, MgO powder having an average particle size of 0.8 to 3.0 μm, and Y ₂ O ₃ powder having an average particle size of 0.8 to 1.5 μm No. 1 (Sample No. 1 to Sample No. 7) were mixed and mixed. _{Incidentally, SiO} 2, B 2 _{O 3} is a minor component, and _Al 2 _{O 3,} the sample No. 4 based on the content of each sample No. 1 to 3 and 5 to 7 so that the sample No. 4 was prepared by adding trace components to the mixture.

Sample No. The contents of SiO ₂ , B ₂ O ₃ , and Al ₂ O ₃ in the mixture of No. 4 were measured by ICP emission spectroscopic analysis of an aqueous solution sample. More specifically, the mixture is mixed with boric acid and sodium carbonate, and the melted solution is dissolved in hydrochloric acid to form an aqueous solution. Then, first, qualitative analysis of elements contained in the sample is performed by atomic absorption analysis, and then Each of the specified elements was quantified by ICP emission spectroscopic analysis using a diluted standard solution as a standard sample.

  Subsequently, a burnt material (acrylic resin) having an average particle diameter of 20 μm, a cellulose organic binder, and a solvent made of water were mixed and mixed in each mixture to obtain a support material. . The burned-out material was added at a ratio of 15% by weight with respect to the total amount of the support material.

  The obtained support material is extruded and, as shown in FIG. 5, a support molded body 51 having a major axis dimension of 35 mm, a minor axis dimension of 4.2 mm, and a transverse cross section having a gas channel 52 inside. After drying this, this was degreased and calcined at 1200 ° C. Then, it baked on 1485 degreeC conditions.

(Measurement of firing shrinkage)
Sample No. Fifteen sintered bodies (i.e., supports) of 1 to 7 were produced (N = 15), and the width (major axis) dimension of each sintered body before and after firing was measured with a caliper. And the difference of the width dimension before baking and the width dimension after baking was remove | divided by the width dimension before baking, and baking shrinkage rate (%) was computed. Between 15 samples of each composition, the variation in the value of the firing shrinkage rate, that is, the value calculated from the formula: (maximum value of firing shrinkage rate) − (minimum value of firing shrinkage rate) is controlled within 5%. Was accepted. The results are shown in Table 2.

  As apparent from Table 2, the sample No. which is a comparative sample. Only in 5-7, the variation of the firing shrinkage rate exceeds 5%, and it can be seen that the variation among the samples is large. On the other hand, sample no. As for 1-4, the variation of the baking shrinkage rate was 5% or less, and the variation was small.

In particular, Sample No. ₂ has a content of SiO ₂ , B ₂ O ₃ , and Al ₂ O ₃ of 200 ppm or less and the smallest content of each trace component. No. 4 had the smallest variation in the firing shrinkage rate and was 2.2%. On the other hand, sample No. _{2 in which} only a trace amount component of Al ₂ O ₃ is larger than the predetermined content. No. 1 passed the determination of the firing shrinkage rate, but the variation was 3.9%.

(Measurement of open porosity and 3-point bending strength)
Sample No. of the present invention. 4 and comparative sample No. Using 12 each of the sintered bodies of No. 7, the open porosity and the firing strength were measured. The open porosity was measured by the Archimedes method, and the three-point bending strength was measured by the three-point bending strength based on JIS standards. The results are shown in FIG. 9 and FIG.

  From the relationship between the firing shrinkage rate and the open porosity shown in FIG. 9, it was confirmed that both samples were relatively correlated. However, sample no. There was a variation of about 8% in the firing shrinkage ratio of No. 7, and the variation of the open porosity increased accordingly, and there was a sintered body having an open porosity of less than 30%. On the other hand, sample No. The variation in the firing shrinkage ratio of No. 4 was within about 3%, and the open porosity was also in the range of 30 to 45%. Next, the relationship between the open porosity and the three-point bending strength was measured and evaluated using both samples. As a result, as shown in FIG. 10, the three-point bending strength tended to depend substantially on the open porosity. And sample no. In the sintered body of No. 7, since the open porosity varies greatly, the three-point bending strength also varies greatly. As a result, sample no. In the sintered body of No. 7, the low strength was about 50 MPa.

  Next, in order to confirm the variation in the three-point bending strength of both samples, evaluation was made by Weibull plot. The result is shown in FIG. As is clear from FIG. No. 4 was found to have little variation. From the above, it was confirmed that the variation in the firing shrinkage rate increased the variation in the open porosity and the three-point bending strength.

(Observation of support structure)
Sample No. obtained above. Among these, a sample having a firing shrinkage of about 25% was used, and the structure inside the support was observed. The result is shown in FIG. FIG. 7 is an enlarged image by a scanning electron microscope (SEM) showing a cross section of 7 (firing shrinkage rate of about 25%).

As is apparent from FIG. 12, in addition to the respective particles of MgO and Y ₂ O ₃ in which NiO is a solid material, which is a constituent material of the support, gray particles A are locally scattered. . As a result of performing composition analysis by energy dispersive spectroscopy (EDS), it was confirmed that this particle A is a reaction product of Si (considered as Si contained in the raw material of the constituent material) and Y. From the above, the factor that induces the variation in shrinkage rate during firing is very high due to the reaction of Si, which is one kind of impurities (trace component), with Y contained in the raw material constituting the support. it is conceivable that. Further, B, which is another impurity (a trace component), is considered to be a factor inducing variation in the firing shrinkage rate from the above evaluation results. In FIG. 12, particles that appear white are Y ₂ O ₃ and particles that appear black are particles in which NiO is dissolved in MgO.

(Production of fuel electrode layer tape and solid electrolyte layer tape)
As shown in FIG. 6 (a), a slurry obtained by mixing an acrylic binder and toluene with 8YSZ powder having an average particle size of 0.5 μm is applied by a doctor blade method and dried to obtain a solid electrolyte having a thickness of 40 μm. A layer tape 53b was produced.

  Next, Ni powder having an average particle size of 0.5 μm and 8YSZ powder having an average particle size of 0.5 μm were blended and mixed so that the volume ratio of Ni powder to 8YSZ powder was 48:52. A slurry obtained by mixing a burned material, an acrylic binder, and toluene into this mixture was applied by a doctor blade method and dried to prepare a fuel electrode layer tape 53a having a thickness of about 80 μm.

Next, as shown in FIG. 6B, the fuel electrode layer tape 53a and the solid electrolyte layer tape 53b are such that the portions where they do not overlap each other have a width of 3 mm. As shown in FIG. 6 (c), the layers were bonded together at a pressure of 2000 kg / cm ² . A laminated tape obtained by laminating these fuel electrode layer tape 53a and solid electrolyte layer tape 53b was used as a sample No. 1 shown in Table 1 in Example 1. It stuck on each support body molded object 51 comprised by the composition of 4 and 7 in the shape of a horizontal stripe. Further, one laminated tape and another laminated tape adjacent thereto were arranged with an interval of 10 mm. Then, this support body molded body 51 was dried and calcined at 1250 ° C.

(Production of interconnector molded body and cell stack connecting material molded body)
Next, a slurry for dip is prepared with lanthanum chromite (LaCrO ₃ ) and a PVA-based binder, and then, as shown in FIG. 7 (a), the portions excluding both ends of the previously prepared laminated tape are masked tape. Covered with 61. Thereafter, it was dipped with a slurry for dipping, then dried, the masking tape was removed to form the interconnector 14 and the inter-cell stack connection member 15, and then baked at 1485 ° C. for 2 hours.

(Preparation of air electrode layer compact)
Next, as shown in FIG. 8A, one of the entire surface of the inter-cell stack connecting member 15 and the surface of the interconnector 14 on the side opposite to the side where the interconnector 14 is connected to the fuel electrode layer tape 13a. The surface excluding the portion was masked with a masking tape 63. Next, as shown in FIG. 8B, a slurry obtained by mixing lanthanum cobaltite (LaCoO ₃ ) having an average particle diameter of 0.7 μm and isopropyl alcohol was sprayed on the masked laminate, and an air electrode layer having a thickness of 20 μm. A molded body 53c was formed.

(Production of horizontal stripe type solid oxide fuel cell stack)
Next, the masking tape 63 of the laminated body on which the air electrode layer molded body 53c was formed was removed, and thereafter, the treatment was performed at 1100 ° C. to produce the horizontal stripe solid oxide fuel cell stack shown in FIG.

(Performance evaluation of cell stack)
Using each of the prepared cell stacks, reducing gas (N ₂ / H ₂ ) was introduced into the gas flow path of the support, and oxidizing gas (air) was introduced into the outer periphery. The center of the cell stack was 750 ° C. (near the tip) The temperature was raised to 800 to 850 ° C. and held for 200 hours. Thereafter, the fuel utilization was changed by adjusting the flow rate of the reducing gas (N ₂ / H ₂ ), and at the same time, the cell voltage of the cell stack was measured and evaluated. The result is shown in FIG.

  As is clear from FIG. 13, sample No. The cell stack produced using the support No. 7 had a result that the voltage drop was remarkable when the open porosity of the support was about 22% and the fuel utilization rate (Uf) was about 62%. On the other hand, sample no. The cell stack produced using the support No. 4 had an open porosity of about 35%, and the same limit Uf as above was about 74%. From the above results, it was confirmed that when the open porosity of the support was small, the diffusion of the reducing gas was insufficient, and as a result, the voltage generated from the fuel cell decreased.

It is a longitudinal cross-sectional view which expands and shows a part of horizontal stripe type solid oxide fuel cell stack concerning one Embodiment of this invention. It is a cross-sectional view which expands and shows a part of horizontal stripe type solid oxide fuel cell stack concerning one embodiment of the present invention. It is a longitudinal cross-sectional view which expands and shows the edge part connection structure of the horizontal stripe type solid oxide fuel cell stack concerning one Embodiment of this invention. It is a longitudinal cross-sectional view which shows the bundle comprised by arranging three horizontally striped solid oxide fuel cell stacks concerning one Embodiment of this invention. It is a longitudinal cross-sectional view which shows the support body of the horizontal stripe type solid oxide fuel cell stack concerning one Embodiment of this invention. (A)-(c) is a longitudinal cross-sectional view which shows the manufacturing process of the fuel cell of the horizontal stripe type solid oxide fuel cell stack concerning one Embodiment of this invention. (A)-(c) is a longitudinal cross-sectional view which shows the formation process of the interconnector which electrically connects between the fuel cells of the horizontal stripe type solid oxide fuel cell stack concerning one embodiment of the present invention. . (A)-(c) is a longitudinal cross-sectional view which shows the preparation process of the air electrode layer of the horizontal stripe type solid oxide fuel cell stack concerning one Embodiment of this invention. It is a graph which shows the relationship between the baking shrinkage rate and the open porosity of the support body in an Example. It is a graph which shows the relationship between the open porosity of the support body in an Example, and baking strength. It is a graph which shows the Weibull plot of the support body in an Example. Sample No. in the examples. 7 is an enlarged image by a scanning electron microscope (SEM) showing a cross section of 7 (firing shrinkage rate of about 25%). It is a graph which shows the relationship between the fuel utilization factor and cell voltage of a horizontal stripe type solid oxide fuel cell stack in an example. It is a longitudinal cross-sectional view which expands and shows a part of conventional horizontal stripe type solid oxide fuel cell stack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Support body 12 Gas flow path 13 Fuel cell 13a Fuel electrode layer 13b Solid electrolyte layer 13c Air electrode layer 14 Interconnector 15 Inter-cell stack connection member 20 Conductive member

Claims (5)

A plurality of fuel cells, each of which is formed by laminating an inner electrode layer, a solid electrolyte layer, and an outer electrode layer in this order, are arranged side by side on the surface of an electrically insulating support provided with a gas flow path. A horizontal stripe type in which an inner electrode layer of a cell and an outer electrode layer of the other fuel cell adjacent to the one fuel cell are electrically connected, and the plurality of fuel cells are connected in series A solid oxide fuel cell stack,
The support is a Ni and / or NiO, while being configured to include a MgO, segmented-in-series solid oxide fuel, wherein the content of SiO ₂ and _B 2 _{O 3} is 200ppm or less, respectively Battery cell stack. The horizontal stripe-type solid oxide fuel cell stack according to claim 1, wherein the support has an Al ₂ O ₃ content of 200 ppm or less.   The horizontal stripe-type solid oxide fuel cell stack according to claim 1 or 2, wherein the support has an open porosity of 30 to 45%.   The horizontal stripe type solid oxide fuel cell stack according to any one of claims 1 to 3, wherein the support has a three-point bending strength of 70 to 120 MPa.   5. A fuel cell comprising a plurality of horizontally-striped solid oxide fuel cell stacks according to claim 1 in a storage container.