JP6460261B2 - Solid oxide fuel cell stack - Google Patents

Description

  The present invention relates to a solid oxide fuel cell stack in which a plurality of solid oxide fuel cells are stacked.

A solid oxide fuel cell (also referred to as SOFC: Solid Oxide Fuel Cell) is a fuel electrode (anode): H ₂ + O ²⁻ → H ₂ O + 2e ⁻ , an air electrode (cathode): (1 / 2) A device for extracting electric energy by a reaction of O ₂ + 2e ⁻ → O ²⁻ . In order to continuously extract electric energy, it is necessary to perform the reaction continuously. Therefore, oxidation of fuel gas (for example, H ₂ ) as an anode gas and air (O ₂ ) as a cathode gas supplied to the cathode is performed. The agent gas is continuously supplied. In a solid oxide fuel cell, a plurality of fuel cells are stacked in order to obtain a sufficient voltage. Thereby, a fuel cell (fuel cell stack) is configured. The fuel cell stack electrically connects a plurality of fuel cells. In order to increase the reliability of the connection, a metal layer is disposed between one fuel cell and the other fuel cell, and the metal layer and the fuel cell 2 are electrically connected to each other. It has been proposed to provide a conductive material layer between the fuel cell and the fuel cell (see, for example, Patent Document 1).

International Publication No. 2015/045926

  However, in the above case, the fuel cell made of ceramic and the metal layer made of metal have different coefficients of thermal expansion, and there is room for improvement in connectivity when a thermal cycle is applied. On the other hand, when a layer made of a conductive ceramic is used instead of the metal layer, there is a problem that heat tends to be trapped.

  The present invention solves the above-mentioned problems, and in the stacking (stacking) of solid oxide fuel cells, the reliability of electrical connection between the cells is improved and the heat generated with power generation is reduced. An object of the present invention is to provide a solid oxide fuel cell stack in which the cell in-plane temperature distribution is flattened and cracks are suppressed.

In order to achieve the above object, the solid oxide fuel cell stack of the present invention has a structure in which a plurality of fuel cells are stacked. The fuel cell includes a solid oxide electrolyte layer, a fuel electrode layer and an air electrode layer stacked via the solid oxide electrolyte layer, and a stack of layers stacked outside the fuel electrode layer and the air electrode layer. A plurality of connecting portions that electrically connect one fuel battery cell and the other fuel battery cell in a portion where the fuel battery cells are stacked, and the fuel electrode layer or A conductive via that electrically connects the air electrode layer and the connecting portion and penetrates the separator in the stacking direction, and the plurality of connecting portions are mutually positioned at positions corresponding to the conductive via. A heat conduction part made of a material having a higher thermal conductivity than the connection part is provided in the distance of the plurality of connection parts .

  In the solid oxide fuel cell stack according to the present invention, it is preferable that the heat conducting portion is substantially the same height as the connecting portion in a direction in which the fuel cells are stacked.

  In the solid oxide fuel cell stack of the present invention, it is preferable that the heat conducting portion has a comb shape.

  In the solid oxide fuel cell stack of the present invention, the heat conducting part is selected from the group consisting of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, Cr, Cu, Ti, Co, and Si. It is preferably made of a material mainly composed of at least one kind.

In the solid oxide fuel cell stack of the present invention, the connecting _{portion, LaSrMnO 3, LaSrCoO 3, LaSrCoFeO} 3, MnCoO 3, SmSrCoO 3, LaCaMnO 3, LaCaCoO 3, LaCaCoFeO 3, LaNiFeO 3, (LaSr) 2 NiO 4 Preferably, the conductive ceramic is mainly composed of at least one material selected from the group consisting of:

  According to the solid oxide fuel cell stack of the present invention, in the stacking (stacking) of solid oxide fuel cell, heat generated by power generation is improved while improving the reliability of electrical connection between cells. Therefore, it is possible to provide a solid oxide fuel cell stack in which the in-plane temperature distribution resulting from the above is flattened and cracks are suppressed.

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

FIG. 1 is a schematic front sectional view showing a main part of a fuel cell stack according to a first embodiment of the present invention. It is a disassembled perspective view of one fuel battery cell used for the fuel cell stack of the 1st Embodiment of this invention. It is a top view of one fuel cell used for the fuel cell stack concerning a 1st embodiment. 1 is a perspective view schematically showing a fuel cell stack according to a first embodiment. FIG. 5 is a schematic front sectional view showing the main part of the fuel cell stack according to the second embodiment. FIG. 6A is a plan view of a connecting portion of an example of the fuel cell stack according to the second embodiment as viewed from above. FIG. 6B is a plan view of the heat conducting portion of an example of the fuel cell stack according to the second embodiment as viewed from above.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited or limited to the following examples. The drawings referred to below are schematically described, and the ratio of the dimensions of objects drawn in the drawings may be different from the ratio of dimensions of actual objects. The dimensional ratio of the object may be different between the drawings. Each embodiment is an exemplification, and needless to say, partial replacement or combination of configurations shown in different embodiments is possible. In the second and subsequent embodiments, description of matters common to the first embodiment will be omitted, and only different points will be described. In particular, the same operation effect by the same configuration will not be sequentially described for each embodiment.

(First embodiment)
FIG. 1 is a schematic front sectional view of a fuel cell stack according to a first embodiment of the present invention. In the fuel cell stack 1, the upper fuel cell 2 and the middle fuel cell 2 are joined via a joint 4, and the middle fuel cell 2 and the lower fuel cell 2 are joined. 4 is joined. In FIG. 1, three fuel cells 2, 2, and 2 are shown. However, in the present embodiment, a structure in which the fuel cells 2 and 2 on both sides are stacked via another joint 4. Furthermore, it is lined up.

  Moreover, in FIG. 1, only the position in which the fuel battery cells 2, 2, and 2 are provided is schematically shown. Details of one fuel cell 2 will be described with reference to FIGS. 2 and 3.

  As shown in FIG. 2, the fuel battery cell 2 has a solid oxide electrolyte layer 7. The solid oxide electrolyte layer 7 is made of a ceramic having high ionic conductivity. Examples of such materials include stabilized zirconia and partially stabilized zirconia. More specifically, zirconia stabilized by Y or Sc is mentioned. Examples of the stabilized zirconia include 10 mol% yttria stabilized zirconia (10YSZ) and 11 mol% scandia stabilized zirconia (11ScSZ). Examples of the partially stabilized zirconia include 3 mol% yttria partially stabilized zirconia (3YSZ).

Incidentally, the material constituting the solid oxide electrolyte layer 7 is not limited to the above, Sm and Gd-doped ceria-based oxide _{and, La 0.8 Sr 0.2 Ga 0.8 Me} 0.2 O You may form by perovskite type oxides, such as _(3-delta) . Δ represents a positive number less than 3.

  The solid oxide electrolyte layer 7 is provided with a through hole 7a and a through hole 7b. The through hole 7a constitutes a fuel gas flow path. The through hole 7b constitutes an air flow path through which air as an oxidant gas passes.

  A fuel electrode layer 6 is laminated above the solid oxide electrolyte layer 7. The fuel electrode layer 6 can be composed of yttria-stabilized zirconia containing Ni, scandia-stabilized zirconia containing Ni, or the like. The fuel electrode layer 6 is provided with a slit 6a constituting a fuel gas flow path and a slit 6b constituting an air flow path.

  A separator 5 is laminated on the fuel electrode layer 6. The separator 5 can be formed of stabilized zirconia, partially stabilized zirconia, or the like. Through holes 5 a and 5 b are formed in the separator 5. The through hole 5a constitutes a fuel gas flow path. The through hole 5b constitutes an air flow path.

  On the other hand, the separator 5 is provided with a plurality of interconnectors 5 c for taking out electricity so as to penetrate the lower surface from the upper surface of the separator 5. That is, each interconnector 5c is formed by a via-hole conductor. The plurality of interconnectors 5 c are electrically connected to the fuel electrode layer 6.

The material of the interconnector 5c is not particularly limited. The interconnector 5c includes, for example, an Ag—Pd alloy, an Ag—Pt alloy, a lanthanum chromite (LaCrO ₃ ) added with an alkaline earth metal, a lanthanum ferrate (LaFeO ₃ ), a lanthanum strontium manganite (LSM). ) Or the like.

On the other hand, an air electrode layer 8 and a separator 9 are laminated below the solid oxide electrolyte layer 7. The air electrode layer 8 is provided with a slit 8a that constitutes a fuel gas passage and a slit 8b that constitutes an air passage. The air electrode layer 8 is preferably made of a porous material having high electron conductivity. Such an air electrode layer 8 includes, for example, scandia-stabilized zirconia (ScSZ), ceria doped with Gd, indium oxide doped with Sn, PrCoO ₃ oxide, LaCoO oxide, or LaMoO ₃ oxide. It can be formed by things. Examples of the LaMoO ₃ oxide include La _0.8 Sr _0.2 MnO ₃ (hereinafter abbreviated as LSM) and La _0.6 Ca _0.4 MnO ₃ .

  The separator 9 is configured similarly to the separator 5. Therefore, it has the through-hole 9a which comprises a fuel gas flow path, the through-hole 9b which comprises an air flow path, and the several interconnector 9c.

  The fuel battery cell 2 is prepared by mixing and molding the materials shown above with a binder and a solvent for each component, preparing a green sheet having a predetermined shape, and laminating and crimping these green sheets, It can obtain through the baking process integrated by co-sintering the obtained laminated body.

  FIG. 3 shows a plan view of the single fuel cell 2. As shown in FIG. 3, the fuel battery cell 2 has a cross-shaped flow path component 2a and four power generation units 2b, 2c, 2d, and 2e partitioned by the flow path component 2a when viewed in plan. . And the said interconnector 5c is exposed to the upper surface of the electric power generation parts 2b-2e.

  In the fuel cell stack 1 of the present embodiment, a plurality of such fuel cells 2 are stacked. FIG. 4 is a perspective view showing the fuel cell stack 1. As shown in FIG. 4, in the fuel cell stack 1, the fuel cells 2, 2, 2 are stacked via joints 4, 4.

  As shown in FIG. 1, the fuel cell stack 1 according to the present embodiment is characterized by the configuration of a joint 4 that joins the fuel cell 2 and the fuel cell 2.

  The joint 4 physically joins and integrates the upper fuel cell 2 and the lower fuel cell 2, and electrically connects the upper fuel cell 2 and the lower fuel cell 2 in series. Connected. The joint portion 4 is provided with a connection portion 10 in order to electrically connect the upper fuel cell 2 and the lower fuel cell 2. The connecting portion 10 is disposed at a position corresponding to the conductive via 11 provided in the fuel cell 2 with a space therebetween. The conductive via 11 is provided penetrating through the separator 5 or the separator 9 in the stacking direction, and electrically connects the fuel electrode layer 6 or the air electrode layer 8 and the connection portion 10. In this way, the connection portions 10 are arranged with a space therebetween, that is, by providing the connection portion 10 non-formation region in the joint portion 4, it is possible to suppress heat from being trapped inside the fuel cell stack 1. be able to. Furthermore, since the connection part 10 is arrange | positioned with the space | interval, the surface area per unit volume becomes large. Therefore, there is also an advantage that the degreasing property is improved when the connection part or the like is formed.

  The conductive via 11 is, for example, a surface electrode formed of a conductive oxide, and takes out the electricity generated by the fuel cell to the outside. The fuel cell stack 1 can be stacked by electrically connecting the surface electrodes of the opposing fuel cells 2 via a conductive material, and the output can be increased. However, when the output increases (when the amount of power generation increases), the heat generated by the power generation is trapped inside the fuel cell stack 1 and the temperature distribution is generated in the plane of the fuel cell 2, which may cause cracks. Get higher. The conventional joining between the fuel cells 2 and 2 has been performed by a method such as disposing a sheet-like conductive material over the entire joint. Alternatively, a method of alternately stacking (stacking) fuel cells and metal separators using a metal separator is also employed. Since the metal separator itself has a relatively high thermal conductivity, it is possible to flatten the temperature distribution in the fuel cell. However, since the fuel cell and the metal separator are electrically connected between different materials, the reliability is not sufficient. Moreover, Cr vapor | steam may generate | occur | produce from a metal separator. When Cr vapor poisons the electrode of the fuel cell, there is a possibility that a problem occurs in the durability of the fuel cell.

  Therefore, the reliability of the electrical connection was improved, and the poisoning of Cr was not a problem, and a fuel cell stack that could suppress the occurrence of cracks by suppressing the temperature distribution in the fuel cell was realized. Is the present invention.

In the present embodiment, the material constituting the connection portion 10 is made of LaSrMnO ₃ (LSM: Lanthanum Strontium Manganite) which is a conductive ceramic material. But the material which comprises the said connection part 10 is not specifically limited, What is necessary is just to have favorable electroconductivity. For example, in the case of a conductive ceramic material, a material having a crystal structure of ABO ₃ or A ₂ BO ₄ (A: one kind of rare earth, B: one kind of transition element) can be mentioned. Specifically, the above-mentioned LSM, LaSrCoO ₃ , LaSrCoFeO ₃ , MnCoO ₃ , SmSrCoO ₃ , LaCaMnO ₃ , LaCaCoO ₃ , LaCaCoFeO ₃ , LaNiFeO ₃ , (LaSr) ₂ NiO _4, etc. can be used. Since these materials have electrical conductivity, the electrical resistance between the fuel cells can be reduced by using the connection portion 10 and the stack characteristics can be improved. A noble metal such as Au or Pt can be used as the material constituting the connecting portion 10, but it is preferable to use a material such as LSM because the noble metal is expensive.

  Since electricity is taken out from the fuel cell 2 by the conductive via 11, the connecting portion 10 disposed between the fuel cells 2 only needs to exist at least on the surface electrode (conductive via 11). Therefore, the connection part 10 is preferably provided in a dot shape on the conductive via 11. When the area of the connection part 10 in plan view is larger than the area of the conductive via 11 in plan view, the resistance value of the connection part can be lowered, which is preferable. Alternatively, the material of the connection part 10 can be made into a paste and applied in a meandering manner so as to trace the adjacent conductive vias 11. As described above, the connection portion 10 is continuously provided at positions corresponding to the plurality of conductive vias 11, thereby facilitating manufacturing.

(Second Embodiment)
FIG. 5 is a schematic front sectional view of a fuel cell stack according to the second embodiment of the present invention. In the present embodiment, the heat conduction part 12 made of a material having a higher thermal conductivity than the connection part 10 is provided in the interval of the plurality of connection parts 10.

  In FIG. 6, an example of the shape of the connection part 10 and the heat conduction part 12 is shown. FIG. 6A is a plan view of a connecting portion of an example of the fuel cell stack according to the second embodiment as viewed from above. FIG. 6B is a plan view of the heat conducting portion of an example of the fuel cell stack according to the second embodiment as viewed from above. The connection part 10 in FIG. 6A is provided in a meandering manner so as to cover the conductive via 11. In addition, when the connection part 10 is formed in a meandering shape, the connection part 10 is connected to one line. In the present invention, “a plurality of connection parts are arranged with a space between each other” means, for example, FIG. 6 (a), when the cross section of the vicinity of the center is viewed with a vertical line, it is sufficient that there is a portion where a plurality of connecting portions are arranged with intervals, and the connecting portions may be connected at the end portions. Absent.

  In the present embodiment, a metal foil processed into a comb-teeth shape as shown in FIG. 6B is opposed to the heat conducting portion 12 between the meandering connection portions 10 shown in FIG. Two pieces are inserted. By providing a metal foil having a higher thermal conductivity than that of the connecting portion 10 as the heat conducting portion 12, the in-plane temperature distribution of the fuel cell 2 can be relaxed and the occurrence of cracks can be suppressed. Here, it is preferable that the heat conduction part 12 is substantially the same height as the connection part 10 in the direction in which the fuel cells (2, 2, 2) are stacked. Here, “substantially the same height” means that the height can include an error as long as the connection between the fuel cells of the connection portion 10 is not hindered. By making the height of the heat conduction part 12 substantially the same as the height of the connection part 10, it is possible to achieve both suppression of heat trapping inside the fuel cell stack 1 and suppression of thickening of the fuel cell stack. Therefore, it is preferable. Further, in the structure of the present embodiment in which the heat conducting portion 12 is provided in the space between the connecting portions 10, it is not necessary to add a new layer, so that the in-plane temperature distribution can be reduced in a small space. Therefore, it is useful for reducing the size of the fuel cell stack.

The heat conduction part 12 is made of a material mainly composed of at least one selected from the group consisting of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, Cr, Cu, Ti, Co, and Si. It is preferable to become. In this specification, “mainly” means to occupy 1/2 or more. The metal material is more preferably a low-cost material that has high thermal conductivity and can withstand the operating temperature environment of the solid oxide fuel cell. For example, NCA-1 (manufactured by Nisshin Steel) having a composition based on ferritic stainless steel can be preferably used. In the ferritic stainless steel, it is preferable that Al is added as a trace element. This is because the Al element forms an Al ₂ O ₃ layer on the metal surface at a high temperature, and the oxidation resistance becomes very high.

  In the present embodiment, the connection portion 10 is provided in a meandering manner so as to cover the conductive via 11, but the present invention is not limited to this. It is also preferable to provide the connection part 10 on the conductive via 11 in a dot shape. When the connection part 10 is provided in a dot shape, the metal foil used as the heat conduction part 12 may be a mesh in which the position of the conductive via 11 is a through hole, for example.

  As described above, according to the present invention, in the stacking of the solid oxide fuel cells, the in-plane temperature distribution caused by the heat generated by the power generation while improving the reliability of the electrical connection between the cells. It is possible to provide a solid oxide fuel cell stack in which the cracks are flattened and cracks are suppressed.

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Fuel cell 2a Flow path structure part 2b, 2c, 2d, 2e Power generation part 4 Joint part 5 Separator 5a, 5b Through-hole 5c Interconnector 6 Fuel electrode layer 6a, 6b Slit 7 Solid oxide electrolyte layer 7a , 7b Through-hole 8 Air electrode layer 8a, 8b Slit 9 Separator 9a, 9b Through-hole 9c Interconnector 10 Connection part 11 Conductive via 12 Thermal conduction part

Claims (5)

A solid oxide fuel cell stack having a structure in which a plurality of fuel cells are stacked,
The fuel cell includes a solid oxide electrolyte layer, a fuel electrode layer and an air electrode layer stacked via the solid oxide electrolyte layer, and a stack of layers stacked outside the fuel electrode layer and the air electrode layer. A set of separators,
In the portion where the fuel cells are stacked, a plurality of connection portions that electrically connect one fuel cell and the other fuel cell, and
Electrically connecting the fuel electrode layer or the air electrode layer and the connecting portion, and having a conductive via penetrating the separator in the stacking direction;
The plurality of connecting portions are arranged at intervals corresponding to the conductive vias, and a material having a higher thermal conductivity than the connecting portions within the intervals of the plurality of connecting portions. A solid oxide fuel cell stack provided with a heat conducting part . The heat-conducting portion, in a direction in which the fuel cells to each other are stacked, the height and approximately the same height of the connecting portion, according to claim 1 solid oxide fuel cell stack according. The heat-conducting portion is a comb-tooth shape, according to claim 1 or 2 solid oxide fuel cell stack according. The heat conducting portion is made of a material mainly composed of at least one selected from the group consisting of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, Cr, Cu, Ti, Co, and Si. Item 4. The solid oxide fuel cell stack according to any one of Items 1 to 3 . Said connection _{unit, LaSrMnO 3, LaSrCoO 3, LaSrCoFeO} 3, MnCoO 3, SmSrCoO 3, LaCaMnO 3, LaCaCoO 3, LaCaCoFeO 3, LaNiFeO 3, at least one material selected from the group consisting of _(LaSr) 2 NiO ₄ The solid oxide fuel cell stack according to any one of claims 1 to 4 , wherein the solid oxide fuel cell stack is a conductive ceramic mainly comprising:

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