JP5444022B2 - Horizontally-striped solid oxide fuel cell stack and fuel cell - Google Patents

Description

  The present invention relates to a horizontal stripe type solid oxide fuel cell stack and a fuel cell using the same.

  In recent years, fuel cells have attracted attention as a power generation method having high power generation efficiency in which the number of energy conversion stages is reduced and chemical energy is directly converted into electric energy. In particular, a solid oxide fuel cell has a high power generation temperature of 600 ° C. to 1000 ° C. and a low internal resistance in the cell, and therefore has the highest power generation efficiency among fuel cells. It can be used as a heat source for further power generation or cogeneration, and has the property of converting chemical energy into electrical energy with high conversion efficiency. In particular, a horizontal stripe solid oxide fuel cell can obtain a high voltage with a small number of fuel cell stacks, but it needs to be a fuel cell stack resistant to thermal stress caused by a heat cycle between room temperature and a high operating temperature. There is.

  A conventional horizontally-striped solid oxide fuel cell stack includes a gas flow path for flowing a fuel gas along the longitudinal direction, and has a fuel gas inlet for the gas flow path at one end. A fuel cell having a multilayer structure in which a fuel electrode layer, a solid electrolyte layer, and an air electrode layer are sequentially laminated on an electrically insulating porous support having the fuel gas discharge port of the gas flow path on the end side Have a plurality.

  In such a horizontal stripe type solid oxide fuel cell stack, there is a problem that the other end side which is the fuel gas discharge port may be destroyed by the repetition of the above heat cycle. For example, in order to shorten the start-up time until power generation, an operation (heat cycle) in which the temperature is suddenly heated to around 900 ° C. and lowered to room temperature is repeated, or the fuel gas discharged from the fuel gas discharge port is burned Then, if the operation (heat cycle) for stopping the supply of the fuel gas and lowering the temperature to room temperature is repeated, the other end side that is the fuel gas discharge port may be destroyed at an early stage.

In order to solve such a problem, Patent Document 1 proposes chamfering the corner of the end surface of the porous support on the fuel gas discharge side.
Patent Document 2 proposes impregnating a porous support around a fuel gas discharge port with an inorganic component mainly composed of zirconia.

Further, in Patent Document 3, in order to prevent oxidative expansion due to an oxygen-containing gas, Y ₂ O _{3 is provided} on the end surface on the fuel gas discharge side and the inner surface of the fuel gas flow path in the porous support near the fuel gas discharge port. It has been proposed to form a dense inorganic coating film such as ZrO ₂ (hereinafter sometimes referred to as YSZ) in which is dissolved.

JP 2004-234969 A JP 2004-259604 A JP 2006-59789 A

  However, in the fuel cells described in Patent Documents 1 to 3, the end of the porous support on the fuel gas discharge side is broken (specifically, vertically cracked) by repeating the heat cycle as described above. There is a problem in that the end portion is not sufficient to suppress the erosion and the end portion is easily broken.

  Accordingly, an object of the present invention is to provide a horizontally-striped solid oxide fuel cell stack in which the end of the porous support on the fuel gas discharge side is not easily broken by repeated heat cycles and a fuel cell using the same. To do.

  As described above, the inventor of the present invention, in the process of earnestly researching to solve the above-mentioned problems, destroys the end of the porous support on the fuel gas discharge side by the heat cycle. It was speculated that a large temperature difference between the end portion side of the body and the other region caused thermal stress on the end portion side, and the porous support could not withstand the strength. Therefore, in order to suppress the end portion breakage of the porous support on the fuel gas discharge side, it was considered necessary to increase the strength and the low thermal expansion of the end portion of the porous support. As a result, an inorganic coating containing, as a main component, a silicate containing at least one of Group 2 elements of the periodic table is provided on at least a part of the end region on the gas discharge side of the porous support. As a result, the inventors have obtained the knowledge that a laterally striped solid oxide fuel cell stack in which end destruction on the fuel gas discharge side is suppressed can be provided, and the present invention has been completed.

That is, the present invention has the following configuration.
(1) A gas flow path for flowing fuel gas along the longitudinal direction is provided inside, the fuel gas introduction port of the gas flow path is provided on one end side, and the fuel gas discharge of the gas flow path is provided on the other end side. A fuel cell having a multilayer structure in which a fuel electrode layer, a solid electrolyte layer and an air electrode layer are sequentially laminated on an electrically insulating porous support having an outlet is provided in the longitudinal direction of the porous support. A plurality of horizontally-striped solid oxide fuel cell stacks arranged along the inner surface of the gas flow channel on the other end side of the porous support member, and an end surface on the other end side of the porous support member. An inorganic coating containing, as a main component, one type selected from forsterite (Mg ₂ SiO ₄ ), steatite (MgSiO ₃ ) and wollastonite (CaSiO ₃ ) is provided on the outer surface of the porous support. Horizontal stripes characterized by Oxide fuel cell stack.
(2) The laterally striped solid oxide fuel cell stack according to (1), wherein corners of the outer periphery at the other end of the porous support are chamfered.
(3) The inorganic coating contains 85 mol% or more of one type selected from the forsterite (Mg ₂ SiO ₄ ), steatite (MgSiO ₃ ), and wollastonite (CaSiO ₃ ) ( The horizontally-striped solid oxide fuel cell stack according to 1) or (2) .
( 4 ) The inorganic coating was formed by firing a slurry containing as a main component one selected from the forsterite (Mg ₂ SiO ₄ ), steatite (MgSiO ₃ ), and wollastonite (CaSiO ₃ ) . The horizontally-striped solid oxide fuel cell stack according to any one of (1) to ( 3 ), wherein
( 5 ) A fuel cell comprising a plurality of horizontally-striped solid oxide fuel cell stacks according to any one of (1) to ( 4 ) in a storage container.

  The horizontally-striped solid oxide fuel cell stack of the present invention has an effect that durability and reliability are improved because the end portion on the fuel gas discharge side of the porous support is not easily broken even if the heat cycle is repeated. .

It is a perspective view which fractures | ruptures and shows a part of horizontal stripe type solid oxide fuel cell stack concerning one Embodiment of this invention. It is a longitudinal cross-sectional view which expands and shows the one end part by the side of the fuel gas discharge | emission of the horizontal stripe type solid oxide fuel cell stack concerning one Embodiment of this invention. It is a longitudinal cross-sectional view which expands and shows the one end part by the side of the fuel gas discharge | emission of the horizontal stripe type solid oxide fuel cell stack concerning other one Embodiment of this invention. It is a longitudinal cross-sectional view which expands and shows the one end part by the side of the fuel gas discharge | emission of the horizontal stripe type solid oxide fuel cell stack concerning other one Embodiment of this invention. It is a longitudinal cross-sectional view which shows the porous support body molded object concerning one Embodiment of this invention. (A)-(i) is process drawing which shows the manufacturing method of the horizontal stripe type solid oxide fuel cell stack concerning one Embodiment of this invention.

  Hereinafter, an embodiment of a horizontal stripe solid oxide fuel cell stack of the present invention and a fuel cell using the same will be described in detail with reference to the drawings.

<Horizontal stripe type solid oxide fuel cell stack>
FIG. 1 is a perspective view showing a part of a horizontally-striped solid oxide fuel cell stack (hereinafter sometimes simply referred to as a fuel cell stack) according to the present embodiment. FIG. 2 is an enlarged vertical cross-sectional view showing a part of the end portion on the fuel gas discharge side of the horizontally striped solid oxide fuel cell stack according to the present embodiment.

  As shown in FIG. 1, the fuel cell stack 1 a has a plurality of fuel cells 13 along the longitudinal direction of the porous support 11 on the front and back surfaces of a hollow flat plate-like electrically insulating porous support 11. And a plurality of them are connected in series via the inter-cell connecting member 17 and are called “horizontal stripe type”.

  As shown in FIG. 1, the plurality of fuel cells 13 are arranged on the front and back surfaces of the porous support 11 at predetermined intervals in the longitudinal direction. Each fuel cell 13 has a layered structure in which a current collecting fuel electrode layer 13d, an active fuel electrode layer 13a, a solid electrolyte layer 13b, and an air electrode layer 13c are sequentially stacked, and an interconnector is formed on the active fuel electrode layer 13a. 17a is arranged.

  Adjacent fuel cells 13 on the front and back surfaces of the porous support 11 are connected in series by an inter-cell connecting member 17 (see FIG. 2). That is, an interconnector 17a is formed on the active fuel electrode layer 13a of one fuel battery cell 13, and the interconnector 17a is covered with the solid electrolyte layer 13b in a gas-sealed state, including both ends in the longitudinal direction. The strip is exposed from the solid electrolyte layer 13b. The exposed portion of the interconnector 17a is covered with a cell connecting material 17b, and this cell connecting material 17b is formed on the air electrode layer 13c of the other fuel cell 13 so that the fuel cells 13 are connected in series. It is the structure electrically connected to.

  The porous support 11 is porous, and a plurality of gas flow passages 12 having a small inner diameter are provided through the porous support 11 so as to extend in the longitudinal direction separated by the partition walls 51. The number of the gas flow paths 12 is preferably 3 to 20, for example, and more preferably 6 to 17, in terms of power generation performance and structural strength. In this way, by forming a plurality of gas flow paths 12 inside the porous support 11, the porous support 11 is compared with the case where one large gas flow path is formed inside the porous support 11. Can be made into a flat plate shape, and the area of the fuel cell 13 per volume of the fuel cell 1 can be increased to increase the amount of power generation. Therefore, the number of fuel cells for obtaining the required power generation amount can be reduced.

  By flowing fuel gas (hydrogen gas) through the gas flow path 12 and exposing the air electrode layer 13c to an oxygen-containing gas such as air, the following formula (i) is established between the active fuel electrode layer 13a and the air electrode layer 13c. And the electrode reaction shown to (ii) arises, a potential difference generate | occur | produces between both poles, and it generates electric power.

In addition, at least a part of the group 2 elements of the periodic table are formed on at least a part of the end region including the inside of the gas flow path 12 of the porous support 11 on the fuel gas discharge side of the fuel cell stack 1a. An inorganic coating 25 containing a silicate containing as a main component is provided.
Here, the end region refers to a region including the outer surface from the inner surface of the gas flow path 12 at the end of the porous support 11 on the fuel gas discharge side, as shown in FIG. In the present invention, the inorganic coating 25 may be provided on the entire surface of these regions. However, at least a part of the regions may be provided as long as the destruction of the end portion on the fuel gas discharge side of the porous support can be suppressed in the heat cycle. For example, only the end surface of the end portion or the inner surface of the gas flow channel 12, or both the end surface and the inner surface of the gas flow channel 12, or both the end surface and the outer surface may be used.

Furthermore, as shown in FIGS. 3 and 4, the fuel cell stack 1 a preferably has a shape in which the corner of the outer edge of the end surface on the fuel gas discharge side of the porous support 11 is chamfered.
The fuel cell stack 1b shown in FIG. 3 has a chamfered chamfered corner at the outer edge of the end surface of the porous support 11 on the fuel gas discharge side, and an inorganic coating 25 is provided on the surface. It has been.
The fuel cell stack 1c shown in FIG. 4 is chamfered so as to have an R-surface shape at the outer edge corner of the end surface of the porous support 11 on the fuel gas discharge side, and an inorganic coating 25 is provided on the surface. It has been.
Specifically, the inorganic coating film 25 is provided as described above.

  By chamfering the corner of the outer edge of the end surface on the fuel gas discharge side of the porous support 11, it is possible to reduce the concentration of thermal stress on the end portion on the fuel gas discharge side, and at the time of manufacturing the fuel cell stack, The occurrence of cracks in the inorganic coating 25 can be suppressed. Furthermore, it is possible to prevent the fuel cell stack from being damaged during the production of the fuel cell stack or during the operation of the fuel cell device that houses the fuel cell stack.

  In the fuel cell stack 1b or 1c, the size of chamfering applied to the corner of the outer edge of the end surface of the porous support 11 on the fuel gas discharge side can be appropriately set. For example, the porous support 11 In the case of the thickness of 2 to 5 mm, considering the strength of the end of the porous support 11 on the fuel gas discharge side, the end of the gas flow path 12 of the porous support 11 on the fuel gas discharge side It is preferable that the length from the end of the gas channel 12 to the corner after chamfering is at least 350 μm.

  3 and 4, the chamfering of the C-surface shape and the R-surface shape of the outer peripheral corner of the end surface on the fuel gas discharge side of the porous support 11 has been described. In addition to the surface shape and the R surface shape, generally known chamfering shapes such as a combination of the C surface shape and the R surface shape can be appropriately set.

Hereinafter, the material of each member constituting the fuel cell stack 1a will be described in detail.
(Porous support 11)
The porous support 11 according to the present invention is made of Mg oxide (MgO), Ni or Ni oxide (NiO), and a rare earth element oxide. Examples of rare earth elements constituting rare earth element oxides include Y, La, Yb, Tm, Er, Ho, Dy, Gd, Sm, and Pr. Examples of rare earth element oxides include Y Examples thereof include ₂ O ₃ and Yb ₂ O ₃ , and Y ₂ O ₃ is particularly preferable.

MgO is 70 to 80% by volume, rare earth element oxide is 10 to 20% by volume, Ni or NiO (NiO is usually reduced by hydrogen gas and present as Ni during power generation) is 10 to 25 in terms of NiO. It is good to contain in the porous support body 11 in the range of volume%, especially 15-20 volume%.
The thermal expansion coefficient of the porous support 11 is usually about 10.5 to 12.5 × 10 ⁻⁶ (1 / K).

The porous support 11 needs to be electrically insulating in order to prevent an electrical short circuit between the fuel cells 13, and normally has a resistivity of 10 Ω · cm or more. When the content of Ni or the like exceeds the above range, the electric resistance value tends to decrease. Further, when the content of Ni or the like is less than the above range, it is not different from the case where a rare earth element oxide (for example, Y ₂ O ₃ ) is used alone, and it is difficult to adjust the thermal expansion coefficient with the fuel cell 13. Tend to be.

  The porous support 11 must be able to introduce the fuel gas in the gas flow path 12 up to the surface of the active fuel electrode layer 13a, and therefore needs to be porous. In general, the open porosity should be 25% or more, especially in the range of 30-40%.

(Fuel electrode layer)
The fuel electrode layer causes the electrode reaction of the formula (ii). In this embodiment, the active fuel electrode layer 13a on the solid electrolyte layer 13b side and the current collecting fuel electrode on the porous support 11 side are used. It is formed in a two-layer structure with the layer 13d.

<Active fuel electrode layer 13a>
The active fuel electrode layer 13a on the solid electrolyte layer 13b side is formed of a known porous conductive ceramic. For example, it is composed of ZrO ₂ (stabilized zirconia) in which a rare earth element is dissolved, and Ni and / or NiO (hereinafter referred to as Ni or the like). As the stabilized zirconia in which the rare earth element is dissolved, the same one used for the solid electrolyte layer 13b described later is preferably used.

The stabilized zirconia content in the active fuel electrode layer 13a is preferably in the range of 35 to 65% by volume, and the content of Ni or the like is 65 to 35% in terms of NiO in order to exhibit good current collecting performance. % Should be in the range.
Further, the open porosity of the active fuel electrode layer 13a is preferably 15% or more, particularly preferably in the range of 20 to 40%.

The thermal expansion coefficient of the active fuel electrode layer 13a is usually about 12.3 × 10 ⁻⁶ (1 / K).
In addition, the thickness of the active fuel electrode layer 13a is 5 in that it absorbs thermal stress generated due to the difference in thermal expansion from the solid electrolyte layer 13b and prevents cracking or peeling of the active fuel electrode layer 13a. It is desirable to be in the range of ˜15 μm.

<Current collecting fuel electrode layer 13d>
In the fuel electrode layer, the current collecting fuel electrode layer 13 d on the porous support 11 side is formed of Ni or a mixture of Ni oxide and rare earth element oxide, as with the porous support 11.

The Ni or Ni oxide (NiO is usually reduced by hydrogen gas and present as Ni during power generation) is contained in the rare earth element oxide in a range of 30 to 60% by volume in terms of NiO. Is good. By adjusting within this range, the difference in thermal expansion between the porous support 11 and the current collecting fuel electrode layer 13d can be made 2 × 10 ⁻⁶ (1 / K) or less. The current collecting fuel electrode layer 13d needs to be conductive so as not to impair the flow of current, and it is generally desirable that the current collecting fuel electrode layer 13d have a conductivity of 400 S / cm or more. From the viewpoint of having good electrical conductivity, the content of Ni or the like is desirably 30% by volume or more.

The thermal expansion coefficient of the current collecting fuel electrode layer 13d is usually about 11.5 × 10 ⁻⁶ (1 / K). Further, the thickness of the current collecting fuel electrode layer 13d is preferably 80 to 200 μm from the viewpoint of improving electric conductivity.

As described above, if the fuel electrode layer is formed in two layers, the active fuel electrode layer 13a on the solid electrolyte layer 13b side and the current collecting fuel electrode layer 13d on the porous support member 11 side, the porous support body The thermal expansion coefficient is adjusted to the thermal expansion coefficient of the solid electrolyte layer 13b described later by adjusting the Ni amount or NiO amount in terms of NiO of the current collecting fuel electrode layer 13d on the 11th side within the range of 30 to 60% by volume. For example, the difference in thermal expansion between the two can be made less than 2 × 10 ⁻⁶ / (1 / K). Therefore, since the thermal stress generated due to the difference in thermal expansion between the fuel cell stack 1a, the heating, and the cooling can be reduced, the fuel electrode layer can be prevented from cracking or peeling. Can do. For this reason, even when fuel gas (hydrogen gas) is supplied to generate power, the consistency of the thermal expansion coefficient with the porous support 11 is maintained stably, and cracks due to thermal expansion differences can be effectively avoided. it can.

(Solid electrolyte layer 13b)
The solid electrolyte layer 13b is composed of a dense ceramic made of stabilized ZrO ₂ composed of ZrO ₂ which was a solid solution of rare earth or an oxide thereof.
Here, as rare earth elements to be dissolved or oxides thereof, for example, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. Or oxides thereof, and the like, preferably Y, Yb, or oxides thereof. The solid electrolyte layer 13b is made of lanthanum gallate (LaGaO) having a thermal expansion coefficient substantially equal to that of stabilized ZrO ₂ (8 mol% Yttoria Stabilized Zirconia, hereinafter referred to as “8YSZ”) in which 8 mol% of Y is dissolved. ₃ ) solid electrolyte layer can also be mentioned. The solid electrolyte layer 13b has a thickness of 10 to 100 μm, for example, and has a relative density (according to Archimedes method) of 93% or 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.

(Air electrode layer 13c)
The air electrode layer 13c is made of conductive ceramics. Examples of conductive ceramics include ABO ₃ type perovskite oxides. Examples of such perovskite oxides include transition metal type perovskite oxides, preferably LaMnO ₃ oxides, LaFeO ₃ oxides. Examples thereof include transition metal type perovskite oxides having La at the A site, such as oxides based on oxides and LaCoO ₃ oxides. More preferably, from the viewpoint of high electrical conductivity at a relatively low temperature of about 600 to 1000 ° C., a LaCoO-based oxide is used.
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 (i).
The open porosity of the air electrode layer 13c is set to, for example, 20% or more, preferably 30 to 50%. If the open porosity is within the above-described range, the air electrode layer 13c can have good gas permeability.
The thickness of the air electrode layer 13c is set in the range of 30 to 100 μm, for example. If it exists in an above-described range, the air electrode layer 13c can have favorable current collection property.

(Cell connecting member 17)
The inter-cell connection member 17 used for connecting adjacent fuel cell units 13 in series is an active electrode layer 13a of one fuel cell 13 and an air electrode layer of the other fuel cell 13 adjacent. 13c is electrically connected to each other, and includes an interconnector 17a and a cell connecting member 17b, which are electrically connected.

<Interconnector 17a>
The interconnector 17a is made of conductive ceramics, but needs to have reduction resistance and oxidation resistance in order to come into contact with an oxygen-containing gas such as fuel gas (hydrogen gas) and air. For this reason, lanthanum chromite perovskite oxides (LaCrO ₃ oxides) are generally used as the conductive ceramics. Further, in order to prevent leakage of fuel gas passing through the gas flow path 12 in the porous support 11 and oxygen-containing gas such as air passing outside the air electrode layer 13c, the conductive ceramics must be dense. For example, it is preferable to have a relative density (Archimedes method) of 93% or more, particularly 95% or more. In addition, a sealing property can also be improved by interposing an appropriate bonding layer (for example, Y ₂ O ₃ ) between the end face of the interconnector 17a and the end face of the solid electrolyte layer 13b.
Further, the interconnector 17a may have a two-layer structure of a metal layer and a metal glass layer containing glass. The metal layer is made of, for example, an alloy of Ag and Ni, and the metal glass layer is made of Ag and glass. The metallic glass layer effectively prevents leakage of fuel gas through the gas flow path 12 in the porous support 11 to the cell connecting material and leakage of oxygen-containing gas through the outside of the air electrode layer 13c to the metallic layer. Can be prevented.

<Cell connecting material 17b>
On the other hand, the cell connecting material 17b is porous. The cell connecting material 17b can be made of a porous material composed of a conductive ceramic (eg, air electrode material) such as LaCoO ₃ or the like, or a noble metal such as Ag—Pd. When the amount of the cell connection material 17b applied to the air electrode layer 13c is small, the material of the cell connection material 17b penetrates into the pores of the air electrode layer 13c and is not formed as a layer. In particular, since noble metals such as Ag-Pd have a small coating amount for cost reduction, the air electrode layer 13c is configured by mixing an air electrode layer material and a current collecting material such as Ag-Pd, and the cell connecting material 17b is Not formed. On the other hand, a conductive ceramic such as LaCoO ₃ is applied in a large amount. In this case, the cell connecting material 17b is formed on the air electrode layer 13c. The air electrode layer 13c may also serve as the cell connection material 17b. In this case, the adjacent fuel cell 13 is connected by connecting the air electrode layer 13c of the other fuel cell 13 adjacent to the interconnector 17a provided on the active fuel electrode layer 13a of the one fuel cell 13. Can be electrically connected in series.
Furthermore, even when the air electrode layer 13c and the interconnector 17a are electrically connected, the cell connecting material 17b can be provided on the air electrode layer 13c. In this case, the current flowing in one fuel cell 13 can be efficiently supplied to the other fuel cell 13.

(Inorganic coating 25)
The inorganic coating 25 contains, as a main component, a silicate containing at least one of Group 2 elements of the Periodic Table.
As the silicate containing at least one of the elements in Group 2 of the periodic table (hereinafter sometimes simply referred to as silicate), for example, Mg is included as the element in Group 2 of the periodic table. Forsterite (Mg ₂ SiO ₄ ), steatite (MgSiO ₃ ), akermanite (Ca ₂ MgSiO ₇ ), diopsite (Ca ₂ MgSiO ₆ ), and wollastonite containing Ca as a group 2 element in the periodic table (CaSiO ₃ ), anorsite (CaAl ₂ Si ₂ O ₈ ), gehlenite (Ca ₂ Al ₂ SiO ₇ ), celsian (BaAl ₂ Si ₂ O ₈ ) containing Ba as a group 2 element in the periodic table, and the like. It is preferable that the fuel cell stack 1a is appropriately selected and used in consideration of the thermal expansion coefficient with each component constituting the fuel cell stack 1a. In particular, any one of forsterite (Mg ₂ SiO ₄ ), steatite (MgSiO ₃ ), and wollastonite (CaSiO ₃ ) is considered in consideration of the thermal expansion coefficient of the active fuel electrode layer 13a and the solid electrolyte layer 13b. One type is preferably used, and in particular, forsterite (Mg ₂ SiO ₄ ) is preferably used.

  The inorganic coating 25 is preferably dense so as to suppress oxidation of the porous support 11. Therefore, the inorganic coating 25 is preferably a dense material having a relative density (according to Archimedes method) of 85% or more, particularly 90% or more. Thereby, it can suppress that the fuel cell stack 1a (porous support body 11) oxidizes, and can suppress that the fuel cell stack 1a is damaged.

  Specifically, the inorganic coating 25 preferably contains 85 mol% or more of silicate. Thereby, the above-mentioned relative density (according to Archimedes method) can be 85% or more, particularly 90% or more, and the fuel cell stack 1a can be prevented from being damaged.

  In addition, the thickness of the inorganic coating film 25 can be set as appropriate. For example, the inorganic coating film 25 on the end surface on the fuel gas discharge side can have a thickness of 20 to 30 μm, and the one end on the fuel gas discharge side. The thickness of the inorganic coating 25 on the porous support 11 in the gas flow path 12 in the part can be 10 to 15 μm. Thereby, the oxidation of the porous support 11 on the fuel gas discharge side can be suppressed, the strength of one end on the fuel gas discharge side can be improved, and the damage of the fuel cell can be suppressed. it can.

(Fuel cell stack manufacturing method)
Next, a manufacturing method of the above-described horizontal stripe solid oxide fuel cell stack 1a will be described with reference to FIGS.
First, the porous support body molded body 41 is produced. As the material of the porous support molded body 41, MgO powder having an average particle diameter (D ₅₀ ) (hereinafter simply referred to as “average particle diameter”) on a volume basis is 0.1 to 10.0 μm, and if necessary, heat Ni powder, NiO powder, Y ₂ O ₃ powder, rare earth element stabilized zirconia powder (YSZ), etc. are mixed and mixed at a predetermined ratio for adjusting the expansion coefficient or improving the bonding strength, and heat after mixing Adjustment is made so that the expansion coefficient substantially matches that of the solid electrolyte layer 13b. This mixed powder is mixed with a solvent composed of a pore agent, a cellulosic organic binder, and water, extruded, and formed into a hollow plate shape having a gas flow path 42 therein as shown in FIG. Then, a flat porous support body molded body 41 is prepared, dried, and calcined at 900 ° C. to 1100 ° C. for 2 to 4 hours. The diameter of the gas channel is adjusted during extrusion.

  When chamfering (for example, C chamfering, R chamfering, etc.) is performed on the corner of the outer edge of the porous support body molded body 41 on the fuel gas discharge side of the fuel cell stack 1a, It can be processed using paper, a jig, a surface grinder, or the like.

Next, a fuel electrode layer and a solid electrolyte layer are produced. First, for example, NiO powder, Ni powder, and YSZ powder are mixed, a pore agent is added thereto, an acrylic binder and toluene are mixed to form a slurry, and the slurry is applied by a doctor blade method and dried. Then, the active fuel electrode layer tape 43a having a thickness of 5 to 20 μm is produced (FIG. 6A).
Next, in the same manner as the active fuel electrode layer tape 43a, for example, NiO powder, Ni powder, and rare earth element oxide such as Y ₂ O ₃ are mixed, a pore agent is added thereto, an acrylic binder, Toluene is mixed to form a slurry, and the slurry is applied by a doctor blade method and dried to prepare a current collecting fuel electrode layer tape 43 having a thickness of 80 to 200 μm. The active fuel electrode layer tape 43a is attached to the current collecting fuel electrode layer tape 43 (FIG. 6B). The bonded tape is cut in accordance with the shape of the fuel battery cell 13, and a portion for forming an insulating portion is punched (FIG. 6C).

Thereafter, as shown in FIG. 6 (d), the current collecting fuel electrode layer tape 43 with the active fuel electrode layer tape 43a attached thereto is attached to the calcined porous support molded body 41 in the form of horizontal stripes. . This is repeated, and a plurality of current collecting fuel electrode layer tapes 43 are affixed to the surface of the porous support molded body 41. At this time, one current collecting fuel electrode layer tape 43 and the other current collecting fuel electrode layer tape 43 are arranged with an interval of 3 to 20 mm in width.
Next, it dries in the state which affixed this current collection fuel electrode layer tape 43, and is calcined for 2 to 4 hours after that in the temperature range of 900-1300 degreeC (FIG.6 (d)). Then, a masking tape 48 is affixed to the portion of the active fuel electrode layer 43a where the interconnector 47a is to be formed (FIG. 6 (e)).

Next, this laminate is immersed in a solid electrolyte layer molded body solution obtained by adding an acrylic binder and toluene to 8YSZ to form a slurry, and then taken out from the solid electrolyte layer molded body solution. As a result, the solid electrolyte layer molded body 43b is applied to the entire surface, and the space punched out in FIG. 6C is filled with the solid electrolyte layer molded body 43b as an insulator.
In order to provide an inorganic coating on one end of the porous support molded body on the fuel gas discharge side (one end of the non-power generation section), the end of the porous support molded body on the fuel gas discharge side is 20 A solid electrolyte layer molded body is provided with a gap of ˜25 μm.
In this state, calcining is performed at 900 to 1200 ° C. for 2 to 4 hours. During the calcination, the masking tape 48 and the layer of the solid electrolyte layer molded body 43b applied thereon can be removed. (FIG. 6 (f)).

Next, a material for an interconnector formed by mixing a lanthanum chromite-based perovskite oxide (LaCrO ₃ oxide) powder and an organic binder is applied to a portion where the interconnector 47a is to be formed (FIG. 6G). ). This is followed by firing at 1450-1550 ° C. for 2-8 hours.

  Subsequently, in a solution (slurry) containing 95 wt% or more of a silicate (for example, forsterite) containing at least one of the Group 2 elements of the periodic table, a glass component, a solvent, and the like, At least a part of the end region on the fuel gas discharge side of the porous support molded body 41 where the solid electrolyte layer molded body 43b is not formed is dipped to produce an inorganic film molded body. In addition, immersion time can be suitably set so that an inorganic film molded object may become the target thickness.

  Next, the inorganic film molded body is fired to produce the inorganic film 25. In firing the inorganic film molded body, it is preferably 200 ° C. or lower than the firing temperature of the solid electrolyte layer molded body 43b, for example, preferably 1200 to 1400 ° C., and the firing time is 2 to 6 It can be time.

Next, a slurry obtained by mixing lanthanum cobaltite (LaCoO ₃ ) and an organic binder is printed on the solid electrolyte layer molded body 43b to form an air electrode layer molded body 43c having a thickness of 10 to 100 μm. Then, baking is performed at 950 to 1150 ° C. for 2 to 5 hours (FIG. 6 (h)).

Finally, a slurry in which lanthanum cobaltite (LaCoO ₃ ) and an organic binder are mixed is printed on a portion where the cell connecting material 47b is to be formed, and baked at 900 to 1150 ° C. for 2 to 5 hours, whereby the fuel cell stack 1a Can be obtained (FIG. 6 (i)).

  In addition, about the lamination | stacking method of each above-mentioned layer, you may use any lamination method of tape lamination | stacking, paste printing, dip coating, and spray spraying. Preferably, the drying process at the time of lamination is short, and each layer is laminated by dip coating from the viewpoint of shortening the process.

  By the manufacturing method as described above, it is possible to easily produce the fuel cell stacks 1a to 1c in which the inorganic coating 25 is formed on at least a part of the one end region on the fuel gas discharge side of the porous support 11. it can.

(Fuel cell)
By combining a plurality of the fuel cell stacks as described above, a horizontally-striped solid oxide fuel cell stack bundle is formed, and the bundle and an auxiliary device for operating the fuel cell stack are stored in a storage container. Thus, the fuel cell of the present invention can be obtained. Thereby, a fuel cell with improved long-term reliability can be obtained.

  In addition, this invention is not limited to the above embodiment, A various improvement and change are possible within the range as described in a claim. For example, the formation order of the inorganic coating 25 is not particularly limited, and the inorganic coating 25 may be formed after the air electrode layer is formed.

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

<Fabrication of horizontal stripe type solid oxide fuel cell stack>
First, a porous support molded body was produced. As the material of the porous support molded body, NiO and Y ₂ O ₃ powder are blended and mixed with MgO powder having an average particle diameter (D ₅₀ ) of 2.8 μm, and the thermal expansion coefficient thereof is that of the solid electrolyte layer. Adjustment was made so that they were almost the same (that is, 11.0 × 10 ⁻⁶ (1 / K)). This mixed powder is mixed with a solvent composed of a pore agent, a cellulose organic binder, and water, extruded, and formed into a hollow plate-like shape having a gas channel inside, and a flat porous support. A molded body was prepared (see FIG. 5), and after drying, it was calcined at 1100 ° C. for 4 hours.

  Next, C-face machining was performed at the corners on the outer periphery of the end face on the fuel gas discharge side so that the shape after chamfering became a C-face shape. The C surface was processed so that the length from the end of the gas flow path to the corner after C surface processing was 500 μm.

  Next, NiO powder and YSZ powder are mixed, a pore agent is added thereto, acrylic binder and toluene are mixed to form a slurry, the slurry is applied by the doctor blade method and dried, and the thickness is 20 μm. An active fuel electrode layer tape was prepared (see FIG. 6A).

Next, NiO powder and Y ₂ O ₃ rare earth element oxide are mixed, a pore agent is added thereto, acrylic binder and toluene are mixed to form a slurry, and the slurry is applied by a doctor blade method. Then, it was dried to produce a current collecting fuel electrode layer tape having a thickness of 130 μm. The active fuel electrode layer tape is affixed on the current collecting fuel electrode layer tape (see FIG. 6B), and the bonded tape is cut in accordance with the shape of the fuel cell to form an insulating portion. (See FIG. 6C).

  Thereafter, a plurality of current collecting fuel electrode layer tapes to which the active fuel electrode layer tape is attached are attached to the calcined porous support body molded body in the form of horizontal stripes at intervals of 5 mm in width along the longitudinal direction. It was.

  Next, it is dried with the current collecting fuel electrode layer tape attached, and then calcined at 1200 ° C. for 2 hours (see FIG. 6 (d)), where the interconnector on the active fuel electrode layer is to be formed. A masking tape was affixed to the substrate (see FIG. 6E).

  Next, this laminate was immersed in a solution for a solid electrolyte layer molded body that was made into a slurry by adding an acrylic binder and toluene to 8YSZ, and then taken out from the solution for a solid electrolyte layer molded body. In order to provide an inorganic coating on one end of the porous support molded body on the fuel gas discharge side (one end of the non-power generation section), the porous support molded body was spaced 20 μm from the end on the fuel gas discharge side of the porous support molded body As a result of this immersion, a solid electrolyte layer molded body was formed on the entire surface, and a solid electrolyte layer molded body was also provided on the insulating portion between adjacent cells.

  In this state, calcination was performed at 900 ° C. for 2 hours. When the calcination was finished, the masking tape and the unnecessary solid electrolyte layer formed body on the masking tape were removed (see FIG. 6F).

Next, a material for an interconnector formed by mixing a lanthanum chromite-based perovskite oxide (LaCrO ₃ oxide) powder and an organic binder is applied to a portion where the interconnector is to be formed (see FIG. 6G). ), And fired at 1480 ° C. for 2 hours in a state where the collector fuel electrode layer molded body, the active fuel electrode layer molded body, the solid electrolyte layer molded body and the interconnector raw material are laminated on the porous support molded body It was.

Subsequently, forsterite (Mg ₂ ) is formed from one end portion (one end portion of the non-power generation portion) on the fuel gas discharge side of the fuel cell molded body to the porous support body molded body on which the solid electrolyte layer molded body is not formed. It is immersed in a solution containing 95 mol% of forsterite (Mg ₂ SiO ₄ ) containing SiO ₄ ) as a main component and containing a glass component and a solvent. An inorganic film formed body was formed on the substrate, and calcination was performed at 1300 ° C. for 3 hours to form an inorganic film.

Next, a slurry obtained by mixing lanthanum cobaltite LaCoO ₃ and isopropyl alcohol is printed on a solid electrolyte layer molded body to form an air electrode layer molded body. This air electrode layer molded body is heated at 1100 ° C. for 2 hours. Baking was performed under the conditions to form an air electrode layer having a thickness of 50 μm (see FIG. 6H).

Finally, a slurry obtained by mixing lanthanum cobaltite (LaCoO ₃ ) and isopropyl alcohol is printed on the solid electrolyte layer of the adjacent fuel cell from the air electrode layer, and baked at 1000 ° C. for 4 hours. A cell connecting material was formed to obtain the fuel cell stack of the example (see FIG. 6 (i)).

(Comparative Example 1)
A fuel cell stack was obtained in the same manner as in the example except that an inorganic film of 8YSZ was formed instead of the inorganic film in the example.

(Comparative Example 2)
A fuel cell stack was obtained in the same manner as in the example except that the inorganic coating film of the example was not formed.

<Evaluation test>
(1) 900 ° C. temperature increase / decrease cycle test A fuel cell stack is stored in a storage container, N ₂ and H ₂ are stored as fuel gases, and N _{2 is} 1.67 L / in each gas path in the fuel cell stack. H ₂ : Flowed at a flow rate of 0.42 L / min, and further heated from the outside of the storage container while flowing air to the outer surface of the fuel cell stack at a flow rate of 48 L / min. The temperature was raised to 900 ° C. at the rate of temperature rise. After reaching 900 ° C., the air flow rate was kept as it was, the N ₂ jet was stopped, and the H ₂ flow rate was increased to 0.644 L / min and held for 30 minutes. Thereafter, the temperature was lowered at a rate of temperature reduction of 500 ° C./hour under the same gas ejection as that at the time of temperature increase, and the time when the temperature dropped to room temperature (about 50 ° C.) was defined as one cycle. Then, the number of cycles at which the tip of the fuel cell stack on the fuel gas discharge side breaks was examined.

(2) Room temperature cycle test City gas is used as fuel gas at room temperature, flowed at a flow rate of 0.4 L / min into the gas flow path in the fuel cell stack, and the fuel gas discharged from the tip is ignited by a burner did. The combustion state was maintained for 10 minutes, and then the ejection of fuel gas was stopped. One cycle was defined as the time when the temperature in the storage container decreased to room temperature (about 50 ° C.). Then, the number of cycles at which the end of the fuel cell stack on the fuel gas discharge side breaks was examined.

The results of the above test are shown in Table 1.

  As shown in Table 1, it is a silicate containing at least one of Group 2 elements in the periodic table at one end of the porous support on the fuel gas discharge side (one end of the non-power generation unit). In the fuel cell stack of the example provided with the inorganic coating mainly composed of forsterite, compared to the fuel cell stack of Comparative Example 1 in which the inorganic coating was 8YSZ and Comparative Example 2 without the inorganic coating, The number of times until the tip breaks can be improved in both the 900 ° C. temperature increase / decrease cycle and the room temperature cycle. Therefore, forsterite, which is a silicate containing at least one of Group 2 elements of the periodic table, is mainly formed at one end of the porous support on the fuel gas discharge side (one end of the non-power generation unit). It was confirmed that the edge destruction can be suppressed by providing an inorganic coating as a component.

1a, 1b, 1c Horizontally striped solid oxide fuel cell stack 11 Porous support 12 Gas flow path 13 Fuel cell 13a Active fuel electrode layer 13b Solid electrolyte layer 13c Air electrode layer 13d Current collecting fuel electrode layer 17a Interconnector 17b Cell connecting material 25 Inorganic coating 41 Porous support molded body 43 Current collecting fuel electrode layer tape 43a Active fuel electrode layer formed body 43b Solid electrolyte layer formed body 43c Air electrode layer formed body 47a Interconnector 47b Cell connecting material 48 Masking Tape 51 Bulkhead

Claims (5)

A gas flow path for flowing fuel gas along the longitudinal direction is provided inside, and has a fuel gas introduction port for the gas flow path on one end side and a fuel gas discharge port for the gas flow path on the other end side. A fuel cell having a multilayer structure in which a fuel electrode layer, a solid electrolyte layer, and an air electrode layer are sequentially laminated on an electrically insulating porous support is formed along the longitudinal direction of the porous support. A horizontally-striped solid oxide fuel cell stack that is arranged in a plurality,
Forsterite (Mg ₂ SiO ₄ ), steatite from the inner surface of the gas flow path on the other end side of the porous support to the outer surface of the porous support via the end surface on the other end side of the porous support A horizontal-striped solid oxide fuel cell stack comprising an inorganic coating containing as a main component one selected from (MgSiO ₃ ) and wollastonite (CaSiO ₃ ) .   The laterally striped solid oxide fuel cell stack according to claim 1, wherein corners of the outer periphery at the other end of the porous support are chamfered. The inorganic coating contains 85 mol% or more of one kind selected from the forsterite (Mg ₂ SiO ₄ ), steatite (MgSiO ₃ ), and wollastonite (CaSiO ₃ ). 2. A horizontally-striped solid oxide fuel cell stack according to 1. The inorganic coating is formed by firing a slurry containing as a main component one selected from the forsterite (Mg ₂ SiO ₄ ), steatite (MgSiO ₃ ), and wollastonite (CaSiO ₃ ). The horizontal-striped solid oxide fuel cell stack according to any one of claims 1 to 3 . Fuel cell characterized by comprising a plurality accommodated in the storage container a segmented-in-series solid oxide fuel cell stack according to any one of claims 1-4.

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