JP2020072000A - Cell stack device - Google Patents

Abstract

To provide a cell stack device which allows improvement in durability while preventing gas leakage.SOLUTION: A cell stack device 1 comprises a fuel battery cell 100, a manifold 200, and a bonding material. The fuel battery cell 100 extends vertically. The manifold 200 supports a lower end portion of the fuel battery cell 100. The bonding material bonds between the fuel battery cell 100 and the manifold 200. The bonding material comprises a first region 310 and a second region 320. The first region 310 has an exposed surface 301 which is exposed into an internal space of the manifold 200. The second region 320 is located further on the outer side than the first region 310. The ratio of the porosity of the first region 310 to that of the second region 320 ranges from 1.25 to 200.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a cell stack device.

  Conventionally, there is known a cell stack device including a plurality of fuel battery cells and a seal member that fixes a manifold to which one end of the fuel battery cells is fixed. As such a cell stack device, for example, 2016-225035 (Patent Document 1) can be cited.

  The sealing material as the bonding material in Patent Document 1 has an inner surface that is the inner space side of the manifold and an outer surface that is the other end side of the fuel cell, and the inner surface is a surface more than the outer surface. The roughness is large. Patent Document 1 discloses that cracks on the outer surface accompanied by gas leakage are prevented by preferentially generating cracks on the inner surface having a large surface roughness.

JP, 2016-225035, A

  However, in the sealing material of the above-mentioned Patent Document 1, it may not be possible to preferentially generate cracks on the inner surface. In this case, a crack that connects the internal space of the manifold and the external space of the manifold is generated, and the fuel gas introduced into the internal space leaks from the internal space to the external space. Therefore, the cell stack device of Patent Document 1 has a problem that gas leak cannot be sufficiently suppressed.

  An object of the present invention is to provide a cell stack device capable of suppressing cracks in the bonding material.

  The present inventor has found that the problem that cracks occur in the bonding material is that tensile stress is applied to the lower side of the bonding material due to deformation of the manifold during operation of the cell stack device. .. Therefore, the present inventor has earnestly studied means for relaxing the tensile stress applied to the bonding material, and completed the present invention.

  A cell stack device according to a first aspect of the present invention includes a fuel cell, a manifold, and a bonding material. The manifold supports the fuel cells. The joining material joins the fuel cell and the manifold. The bonding material includes a first area and a second area. The first region has an exposed surface exposed in the internal space of the manifold. The second region is located outside the first region. The porosity of the first region is larger than that of the second region. The ratio of the porosity of the first region to the porosity of the second region is 1.25 or more and 200 or less.

  A cell stack device according to a second aspect of the present invention includes a fuel cell, a manifold, and a joining material. The manifold supports the fuel cells. The joining material joins the fuel cell and the manifold. The joining material joins the fuel cell and the manifold. The bonding material includes a first area and a second area. The first region has an exposed surface exposed in the internal space of the manifold. The second region is located outside the first region. The porosity of the first region is larger than that of the second region. The ratio of the distance from the exposed surface in the first region to the distance from the exposed surface in the bonding material is 0.00050 or more and 0.10.

  A cell stack device according to a third aspect of the present invention includes a fuel cell, a manifold, and a joining material. The fuel cell unit extends in the vertical direction. The manifold supports the lower end of the fuel cell unit. The joining material joins the fuel cell and the manifold. The bonding material includes a first area and a second area. The first region has an exposed surface exposed in the internal space of the manifold. The second region is located outside the first region. The porosity of the first region is larger than that of the second region. The exposed surface of the bonding material extends in a direction intersecting the direction in which the upper surface of the manifold extends, and the boundary between the first region and the second region is a surface along the exposed surface.

  A cell stack device according to a fourth aspect of the present invention includes a fuel cell, a manifold, and a joining material. The fuel cell unit extends in the vertical direction. The manifold supports the lower end of the fuel cell unit. The joining material joins the fuel cell and the manifold. The bonding material includes a first area and a second area. The first region has an exposed surface exposed in the internal space of the manifold. The second region is located outside the first region. The porosity of the first region is larger than that of the second region. The boundary between the first region and the second region is located below the upper surface of the manifold.

  According to these configurations, the bonding material has the first region having a large porosity and the second region having a small porosity. This can improve the deformability of the first region near the exposed surface to which tensile stress is applied. In addition, the second region separated from the exposed surface to which the stress is applied can suppress the strength decrease of the bonding material.

  When the ratio of the porosity of the first region to the porosity of the second region (porosity of the first region / porosity of the second region) is 1.25 or more and 200 or less, stress relaxation of the first region and It is possible to effectively suppress the decrease in strength of the two regions.

  Further, when the ratio (L1 / L) of the distance L1 from the exposed surface in the first region 310 to the distance L from the exposed surface in the bonding material is 0.00050 or more and 0.10 or less, stress relaxation in the first region is achieved. And, it is possible to effectively exhibit the reduction in strength of the second region.

  If the boundary between the first region and the second region is a surface along the exposed surface, the first region is evenly located from the exposed surface to which tensile stress is applied. Therefore, it is possible to prevent local effects of the stress relaxation of the first region, the stress relaxation of the first region, and the suppression of the strength reduction of the second region.

  When the boundary between the first region and the second region is located below the upper surface of the manifold, the first and second regions are located inside the manifold. Therefore, it is possible to prevent local effects of the stress relaxation of the first region, the stress relaxation of the first region, and the suppression of the strength reduction of the second region.

  As described above, the cell stack device according to the first to fourth aspects of the present invention can suppress cracks in the bonding material by stress relaxation by the first region and suppression of strength reduction by the remaining second region.

  Preferably, the first region has a distance from the exposed surface of less than 50 μm.

  Preferably, the porosity of the first region is 5% or more and the porosity of the second region is 4% or less. Preferably, the porosity of the first region is 25% or less, and the porosity of the second region is 0.1% or more.

  Preferably, the pore diameter of the first region is 0.1 μm or more and 20 μm or less.

  As described above, the present invention can provide a cell stack device that can suppress cracks in the bonding material.

The perspective view of a cell stack device. Sectional drawing of a cell stack apparatus. Sectional drawing of a cell stack apparatus. FIG. 3 is a perspective view of a fuel battery cell. Sectional drawing of a fuel cell. The expanded sectional view of a cell stack device. Sectional drawing of the manufacturing method of a cell stack apparatus. Sectional drawing of the manufacturing method of a cell stack apparatus. The schematic diagram for demonstrating the subject of the conventional cell stack apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The x-axis direction, the y-axis direction, and the z-axis direction in each figure correspond to the height direction, the lateral direction (width direction), and the longitudinal direction of the manifold. In addition, the x-axis direction, the y-axis direction, and the z-axis direction in each figure correspond to the longitudinal direction, the lateral direction (width direction), and the thickness direction of each fuel cell and the supporting substrate. Further, "upper" and "lower" in this specification are based on the height direction (x-axis direction) of the manifold when the manifold and the cell stack device are placed on a horizontal plane.

  With reference to FIGS. 1 to 6, a cell stack device and a fuel cell according to an embodiment of the present invention will be described. A cell stack device and a fuel cell are used for a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell).

[Cell stack device]
As shown in FIGS. 1 to 3, the cell stack device 1 includes a plurality of fuel cells 100, a manifold 200, and a first bonding material 300. Each fuel cell 100 is supported by a manifold 200. The first joining material 300 joins each fuel cell 100 and the manifold 200.

[Fuel cell]
As shown in FIGS. 1 to 3, the fuel cell unit 100 extends upward from the manifold 200. Specifically, each fuel cell unit 100 extends upward from the upper wall 230 of the manifold 200. The lower end portion 101 of the fuel cell 100 is inserted into the insertion hole 231 of the manifold 200. When the lower end 101 of the fuel cell 100 is inserted into the insertion hole 231, a gap is formed between the outer peripheral surface of the lower end 101 of the fuel cell 100 and the inner wall surface of the insertion hole 231. There is. The first bonding material 300 is filled in this gap. Therefore, the lower end portion 101 of the fuel cell unit 100 is supported by the manifold 200. On the other hand, the upper end portion 102 of the fuel cell 100 is a free end. The fuel cell 100 is supported by the manifold 200 in a cantilevered state and is self-supporting.

  The fuel cells 100 are arranged at intervals along the longitudinal direction of the manifold 200. As shown in FIG. 2, the fuel cells 100 are electrically connected to each other via the first current collecting member 4. The first current collecting member 4 is arranged between the fuel cells 100 and connects the adjacent fuel cells 100. The first current collecting member 4 is bonded to each fuel cell 100 by the second bonding material 5. The first current collecting member 4 is made of a conductive material. For example, the first current collecting member 4 is formed of a fired body of oxide ceramics, a metal, or the like.

  As shown in FIGS. 2 to 6, the fuel cell unit 100 includes a support substrate 110 and a plurality of power generation element units 120. Each power generation element section 120 is supported on both sides of the support substrate 110. Note that each power generation element section 120 may be supported only on one surface of the support substrate 110. The power generating element units 120 are arranged at intervals in the longitudinal direction of the fuel cell unit 100. That is, the fuel cell 100 according to the present embodiment is a so-called horizontal stripe fuel cell.

  The power generation element units 120 are electrically connected to each other by the electrical connection unit 160 (see FIG. 5). Further, on the side of the upper end portion 102 of the fuel cell 100, the power generation element portion 120 formed on one surface of the support substrate 110 and the power generation element portion 120 formed on the other surface thereof are the second current collecting member 6 (see FIG. 2). ) Is electrically connected by. The power generating element units 120 are connected in series.

  The support substrate 110 has therein a plurality of gas flow paths 111 extending in the longitudinal direction of the fuel cell 100. The gas flow channel 111 communicates with the internal space of the manifold 200 via the insertion hole 231 of the manifold 200.

  The longitudinal direction of the support substrate 110 is the same as the longitudinal direction of the fuel cell 100. Each gas channel 111 extends substantially parallel to each other. Each gas flow path 111 is open at both ends in the longitudinal direction of the fuel cell 100.

The support substrate 110 is insulative and is made of, for example, ceramics. Specifically, the support substrate 110 may be made of CSZ (calcia-stabilized zirconia), or NiO (nickel oxide) and YSZ (8YSZ) (yttria-stabilized zirconia), It may be composed of NiO and Y ₂ O ₃ (yttrium oxide), or may be composed of MgO (magnesium oxide) and MgAl ₂ O ₄ (magnesia alumina spinel). The support substrate 110 is porous. The porosity of the support substrate 110 is, for example, 20 to 60%.

  As shown in FIG. 5, the support substrate 110 has a plurality of first recesses 112. Each first recess 112 is formed on both sides of the support substrate 110. The first recesses 112 are formed at intervals in the longitudinal direction of the support substrate 110.

  Each power generation element section 120 has a fuel electrode 130, an electrolyte 140, and an air electrode 150. In addition, each power generation element section 120 further includes a reaction prevention film 121.

  The fuel electrode 130 is a fired body made of a porous material having electronic conductivity. The fuel electrode 130 has a fuel electrode current collector 131 and a fuel electrode active portion 132. The fuel electrode current collector 131 is arranged in the first recess 112. Each fuel electrode current collector 131 has a second recess 131a and a third recess 131b. The fuel electrode active part 132 is arranged in the second recess 131a.

The fuel electrode current collector 131 may be made of, for example, NiO and YSZ, NiO and Y ₂ O ₃ , or NiO and CSZ. The thickness of the fuel electrode current collector 131, that is, the depth of the first recess 112 is, for example, 50 to 500 μm.

The anode active portion 132 may be made of, for example, NiO and YSZ, or NiO and GDC = (Ce, Gd) O ₂ (gadolinium-doped ceria). The thickness of the fuel electrode active part 132 is, for example, 5 to 30 μm.

  The electrolyte 140 is arranged so as to cover the fuel electrode 130. Specifically, the electrolyte 140 extends in the longitudinal direction of the fuel cell 100 from one interconnector 161 to another interconnector 161. That is, the electrolyte 140 and the interconnector 161 are alternately arranged in the longitudinal direction of the fuel cell 100.

  The electrolyte 140 is a fired body made of a dense material having ion conductivity and not electron conductivity. The electrolyte 140 may be made of, for example, YSZ or LSGM (lanthanum gallate). The thickness of the electrolyte 140 is, for example, 3 to 50 μm.

  The reaction prevention film 121 is a fired body made of a dense material, has substantially the same shape as the fuel electrode active portion 132 in a plan view, and is arranged at substantially the same position as the fuel electrode active portion 132. The reaction preventive film 121 prevents a phenomenon in which YSZ in the electrolyte 140 reacts with Sr (strontium) in the air electrode 150 to form a reaction layer having a large electric resistance at the interface between the electrolyte 140 and the air electrode 150. It is provided to suppress. The reaction prevention film 121 is composed of, for example, GDC. The thickness of the reaction prevention film 121 is, for example, 3 to 50 μm.

The air electrode 150 is arranged on the reaction prevention film 121. The air electrode 150 is a fired body made of a porous material having electronic conductivity. The air electrode 150 includes, for example, LSCF = (La, Sr) (Co, Fe) O ₃ (lanthanum strontium cobalt ferrite), LSF = (La, Sr) FeO ₃ (lanthanum strontium ferrite), LNF = La (Ni, Fe). ) O ₃ (lanthanum nickel ferrite), LSC = (La, Sr) CoO ₃ (lanthanum strontium cobaltite) and the like. The air electrode 150 may be composed of two layers, a first layer (inner layer) made of LSCF and a second layer (outer layer) made of LSC. The thickness of the air electrode 150 is, for example, 10 to 100 μm.

The electrical connection section 160 is configured to electrically connect the adjacent power generation element sections 120. The electrical connection section 160 has an interconnector 161 and an air electrode current collecting film 162. The interconnector 161 is arranged in the third recess 131b. The interconnector 161 is a fired body made of a dense material having electronic conductivity. The interconnector 161 may be made of, for example, LaCrO ₃ (lanthanum chromite) or (Sr, La) TiO ₃ (strontium titanate). The interconnector 161 has a thickness of, for example, 10 to 100 μm.

The air electrode current collecting film 162 is arranged so as to extend between the interconnector 161 and the air electrode 150 of the adjacent power generating element units 120. The air electrode current collector film 162 is a fired body made of a porous material having electronic conductivity. The air electrode current collecting film 162 may be composed of, for example, LSCF = (La, Sr) (Co, Fe) O ₃ , LSC = (La, Sr) CoO ₃ , or Ag. (Silver) and Ag-Pd (silver-palladium alloy) may be used. The thickness of the air electrode current collecting film 162 is, for example, 50 to 500 μm.

  As shown in FIG. 6, the lower end portion 101 of the fuel cell 100 is covered with a dense film 122. Specifically, the dense film 122 covers the support substrate 110. The dense film 122 is electrically connected to the power generation element part 120 formed on the lower end side. Specifically, the dense film 122 is electrically connected to the electrical connection portion 160. The dense film 122 extends from between the air electrode current collecting film 162 and the support substrate 110 toward the proximal side.

  The dense film 122 has a gas sealing function of preventing mixing of the fuel gas flowing in the space inside the dense film 122 and the air flowing in the space outside the dense film 122. In order to exert the gas sealing function, the dense film 122 has a porosity of, for example, 10% or less. Further, the dense film 122 is made of insulating ceramics.

  Specifically, the dense film 122 can be composed of the electrolyte 140 and the reaction preventing film 121 described above. The electrolyte 140 that constitutes the dense film 122 covers the support substrate 110 and extends from the interconnector 161 to the vicinity of the lower end of the support substrate 110. Further, the reaction prevention film 121 that constitutes the dense film 122 is disposed between the electrolyte 140 and the air electrode current collecting film 162. The dense film 122 may be composed only of the electrolyte 140, or may be composed of a material other than the electrolyte 140 and the reaction prevention film 121.

[Manifold]
As shown in FIGS. 1 to 3, the manifold 200 supplies the reaction gas to the fuel cell 100. The manifold 200 is hollow and has an internal space. As shown in FIG. 1, the fuel gas is supplied to the internal space of the manifold 200 through the introduction pipe P. As shown in FIG. 2, the manifold 200 has a plurality of insertion holes 231 that connect the internal space and the outside.

  The manifold 200 has a substantially rectangular parallelepiped shape. As shown in FIG. 3, the manifold 200 includes a box-shaped manifold main body having an opening at the upper side, and a plate-like member closing the opening. Specifically, the manifold body includes a bottom wall 210, a side wall 220, and a first flange portion 240. The plate-shaped member that closes the opening of the manifold body is the upper wall 230.

  The bottom wall 210, the side wall 220, and the first flange portion 240 are integrally formed. The integrally formed bottom wall 210, side wall 220, and first flange portion 240, and the upper wall 230 are separate members and are joined together. The bottom wall 210, the side wall 220, the upper wall 230, and the first flange portion 240 are made of, for example, a metal having heat resistance.

  The bottom wall 210 has a rectangular shape in a plan view (view in the x-axis direction). The bottom wall 210 has a longitudinal direction and a width direction in a plan view.

  The side wall 220 extends upward from the outer peripheral portion of the bottom wall 210. As shown in FIG. 1, the sidewall 220 has a pair of first sidewalls 221 and a pair of second sidewalls 222.

  The pair of first side walls 221 extends upward from each of a pair of opposing edge portions of the bottom wall 210. Specifically, each of the first side walls 221 extends upward from a pair of edges of the bottom wall 210 that extend in the longitudinal direction. The first side wall 221 extends in the longitudinal direction of the manifold 200. That is, it extends in the direction in which the plurality of fuel cells 100 are arranged. The pair of first side walls 221 face each other in the width direction of the manifold 200.

  The pair of second side walls 222 extend upward from the remaining opposite edges of the bottom wall 210. In detail, each second side wall 222 extends upward from a pair of edge portions extending in the width direction among the edge portions of the bottom wall 210. Further, each second side wall 222 extends in the width direction of the manifold 200. That is, each second side wall 222 extends in the width direction of the fuel cell unit 100. The second side walls 222 face each other in the longitudinal direction of the manifold 200. The introduction pipe P is connected to one of the second side walls 222 of the pair of second side walls 222. Therefore, one of the second side walls 222 has a through hole to which the introduction pipe P is connected.

  The first flange portion 240 extends outward from the upper end portion of the side wall 220. Specifically, the first flange portion 240 extends outward from the upper ends of the first side walls 221 and the second side walls 222. The first flange portion 240 has an annular shape.

  The first boundary portion 202 between the first side wall 221 and the second side wall 222 has an R shape. Specifically, the inner side surface and the outer side surface of the first boundary portion 202 between the first side wall 221 and the second side wall 222 are R-shaped. The radius of curvature of the inner side surface and the outer side surface of the first boundary portion 202 is, for example, 3 to 30 mm. The four first boundary portions 202 extend in the height direction of the manifold 200.

  As shown in FIG. 3, the second boundary portion 203 between the bottom wall 210 and the side wall 220 has an R shape. Specifically, the inner surface and the outer surface of the second boundary portion 203 between the bottom wall 210 and the first side wall 221 and the second side wall 222 are R-shaped. The radius of curvature of the inner side surface and the outer side surface of the second boundary portion 203 is, for example, 2 to 20 mm. The second boundary portion 203 has a ring shape.

  The third boundary portion 204 between the side wall 220 and the first flange portion 240 has an R shape. Specifically, the inner side surface and the outer side surface of the third boundary portion 204 between the first side wall 221 and the second side wall 222 and the first flange portion 240 have an R shape. The radius of curvature of the side surface and the outer surface of the third boundary portion 204 is, for example, 1 to 10 mm. The third boundary portion 204 has a ring shape.

  In addition, the "R shape" in this specification is a shape curved in an arc shape. The inner side surfaces of the first to third boundary portions 202 to 204 are surfaces that face the internal space of the manifold 200. The outer surfaces of the first to third boundary portions 202 to 204 are surfaces that face the outer side of the manifold 200.

  The upper wall 230 is configured to close the upper end of the side wall 220. Specifically, the outer peripheral portion of the upper wall 230 is arranged on the first flange portion 240. In order to seal the internal space of the manifold 200, the upper wall 230 is joined to the first flange portion 240 over the entire circumference. The upper wall 230 is joined to the first flange portion 240 by, for example, a joining material or welding.

  As shown in FIG. 2, the upper wall 230 has a plurality of insertion holes 231 into which the fuel cells 100 are inserted. Each insertion hole 231 extends in the width direction (y-axis direction) of the manifold 200. Further, the insertion holes 231 are arranged at intervals in the longitudinal direction of the manifold 200.

[First joining material]
The first bonding material 300 fixes the fuel cell 100 to the manifold 200. Specifically, the first joining material 300 joins the lower end portion 101 of the fuel cell 100 and the upper wall 230 of the manifold 200. Further, the first bonding material 300 is in contact with the dense film 122. It should be noted that the insertion hole 231 and the gas flow path 111 communicate with each other in a state where the fuel cell 100 is fixed to the manifold 200.

  The first bonding material 300 divides the internal space of the manifold 200 (the space exposed to the fuel gas) and the outside of the cell stack device 1 (the space exposed to the oxygen-containing gas) into the fuel gas. And has a function of preventing the mixture of oxygen-containing gas. Therefore, as shown in FIG. 6, the first bonding material 300 has an exposed surface 301 that is a surface exposed to the fuel gas and an outer surface 302 that is exposed to a gas containing oxygen. The exposed surface 301 is exposed in the internal space of the manifold 200. The exposed surface 301 may be exposed in a space continuous with the internal space of the manifold 200. The outer surface 302 is exposed to the outside of the cell stack device 1.

  As shown in FIG. 6, the exposed surface 301 extends in a direction intersecting with the extending direction of the upper surface 232 of the upper wall 230 of the manifold 200. In this embodiment, the exposed surface 301 extends from the outer peripheral portion of the insertion hole 231 of the manifold so as to incline upward toward the central portion. The exposed surface 301 and the outer surface 302 are substantially parallel to each other. Although the exposed surface 301 and the outer surface 302 are schematically shown as flat surfaces in FIG. 6, in reality, irregularities are formed.

  The first bonding material 300 includes a first region 310 and a second region 320. That is, the first bonding material 300 has a two-layer structure.

  The first region 310 is an inner region having the exposed surface 301. The second region 320 is located outside of the first region 310. The second area 320 is an outer area having an outer surface 302.

  The porosity of the first region 310 is larger than that of the second region 320. Therefore, the first region 310 has high deformability, and the second region 320 has high strength and sealability.

  The ratio of the porosity of the first region 310 to the porosity of the second region 320 (porosity of the first region 310 / porosity of the second region 320) is 1.25 or more and 200 or less, preferably 6.30. It is above 40.0. By setting the amount within the above range, it is possible to achieve both the effect of sealing property and stress relaxation.

  The porosity of the first region 310 is preferably 5% or more and 25% or less, and more preferably 5% or more and 20% or less. When it is 5% or more, the deformability is further improved and the effect of relieving stress is further obtained. When it is 25% or less, the effect of strength reduction is small.

  The porosity of the second region 320 is preferably 0.1% or more and 4% or less, more preferably 0.1% or more and 3% or less. If it is 4% or less, good sealability can be secured. The porosity of the second region 320 is preferably as small as possible from the viewpoint of sealing property, but is preferably 0.1% or more from the viewpoint of ease of production.

  The above "porosity" is a value measured by digitizing a pore portion by image analysis of a cross-sectional image of FE-SEM. Specifically, an image enlarged 1000 to 20000 times by FE-SEM is analyzed by image analysis software HALCON manufactured by MVTec. On the cross-sectional image after the analysis, the area occupancy rate of each of the material portion and the pore portion forming the bonding material is obtained, and the area occupancy rate of the pore portion is defined as the porosity. The cross-sectional image is photographed for each of 10 fields of view in both the first region 310 and the second region 320, and the porosity is converted into a numerical value, and the average value thereof is taken as the porosity of the first region 310 and the second region 320.

  The pore size of the first region 310 is, for example, 0.1 μm or more and 20 μm, preferably 0.1 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 8 μm or less. When it is 0.1 μm or more, the deformability is improved, and the effect of further relaxing the stress is obtained. When the thickness is 20 μm or less, the effect of strength reduction is small.

  The above-mentioned "pore diameter" is the value of the equivalent circle diameter of the pores obtained by image analysis of the FE-SEM cross-sectional image. Here, the equivalent circle diameter is a diameter of a circle having an area value of a measurement target (particles or pores) obtained by image analysis of a cross section. Similar to the calculation of the porosity, the cross-sectional image is photographed for 10 fields of view to quantify the pore diameter. The average pore diameter of each visual field is calculated, and the average of the average pore diameters of the 10 visual fields is further defined as the pore diameter.

  The porosity and the pore diameter of the first region 310 and the second region 320 are controlled by, for example, adjusting the size and amount (volume ratio) of the pore-forming material containing the organic component added before the heat treatment. it can.

  A boundary B between the first area 310 and the second area 320 is a surface along the exposed surface 301. That is, the direction along the exposed surface 301 is the boundary B. In the present embodiment, the boundary B is substantially parallel to the exposed surface 301 and the outer surface 302. Although the boundary B is schematically shown as a plane in FIG. 6, unevenness is actually formed.

  The boundary B is located below the upper surface 232 of the manifold 200. Specifically, the uppermost end of the boundary B is located below the upper surface 232. Therefore, the first region 310 and the second region 320 exist below the upper surface 232. In FIG. 6, the entire first region 310 and a part of the second region 320 exist below the upper surface 232.

  The ratio (L1 / L) of the distance L1 from the exposed surface 301 in the first region 310 to the distance L from the exposed surface 301 in the first bonding material 300 is 0.0005 or more and 0.10 or less, preferably 0. It is 0.0013 or more and 0.050 or less. Within the above range, the effects of the strength and stress relaxation of the first bonding material 300 can be made compatible.

  The “distance L from the exposed surface 301 in the first bonding material 300” is the maximum value of the distance connecting the exposed surface 301 and the outer surface 302. Specifically, for the distance L, the length from the exposed surface 301 to the outer surface 302 is obtained on a straight line perpendicular to the tangent line at each position of the exposed surface 301, and the maximum length is L. The “distance L1 from the exposed surface in the first region 310” is the maximum value of the distance connecting the exposed surface 301 and the boundary B. Specifically, for the distance L1, the length from the exposed surface 301 to the boundary B on a straight line perpendicular to the tangent line at each position of the exposed surface 301 is determined, and the maximum length is set to L1.

  Specifically, the boundary B is preferably a position where the distance L1 from the exposed surface 301 is less than 50 μm. That is, the first region 310 is preferably a region in which the distance L1 from the exposed surface 301 is more than 0 μm and less than 50 μm, and more preferably a region in which the distance L1 is 2 μm or more and 45 μm or less.

  Further, in a cross section (viewed in the z-axis direction) along the width direction of the fuel cell unit, the ratio of the area of the first region 310 to the area of the first bonding material 300 (the area of the first region 310 / the area of the first bonding material 300). The area) is, for example, 0.0005 or more and 0.10 or less, and preferably 0.0013 or more and 0.050 or less. Within the above range, the effects of glass strength and stress relaxation can be made compatible.

  The distance and area between the first region 310 and the second region 320 can be controlled by adjusting the amount and range of application of the material to be the first region 310 and the second region 320.

The materials forming the first region 310 and the second region 320 may be the same or different. The first bonding material 300 is, for example, crystallized glass. As the crystallized glass, for example, SiO ₂ —B ₂ O ₃ system, SiO ₂ —CaO system, or SiO ₂ —MgO system can be adopted. In the present specification, the crystallized glass has a ratio (crystallinity) of “volume occupied by crystalline phase” to the total volume of 60% or more, and “volume occupied by amorphous phase and impurities with respect to the total volume. Refers to glass having a ratio of less than 40%. Note that as the material of the first bonding material 300, amorphous glass, a brazing material, ceramics, or the like may be adopted. Specifically, the first bonding material 300 is at least one selected from the group consisting of SiO ₂ —MgO—B ₂ O ₃ —Al ₂ O ₃ system and SiO ₂ —MgO—Al ₂ O ₃ —ZnO system. ..

  Here, the first region 310 and the second region 320 may further include a plurality of portions having different porosities. In this case, it is preferable that the porosity of the first bonding material 300 decreases toward the upper side. That is, the porosity of the first bonding material 300 is always the same or decreases from the exposed surface 301 upward.

[Production method]
Subsequently, a method for manufacturing the cell stack device 1 according to the present embodiment will be described with reference to FIGS.

  First, a plurality of fuel cells 100 and a manifold 200 are prepared. Then, as shown in FIG. 7, the fuel cells 100 are connected to each other by using the materials to be the first current collecting member 4 and the second bonding material 5, and the cell assembly 103 is manufactured. In addition, at this stage, the material to be the second bonding material 5 has not been fired, and the fuel cell units 100 are temporarily fixed to each other.

  Next, as shown in FIG. 8, the lower end portion 101 of each fuel cell unit 100 of the cell assembly 103 is inserted into each insertion hole 231 of the manifold 200. A jig may be used to hold each fuel cell unit 100 at a predetermined interval along the thickness direction.

  Next, as shown in FIG. 2, a material that becomes the first bonding material 300 is applied so as to bond the fuel cell 100 inserted into the insertion hole 231 and the upper wall 230 of the manifold. The material to be the first bonding material 300 is applied along the base of the fuel cell 100. Further, the material that becomes the first bonding material 300 may be filled in the gap between the outer peripheral surface of the lower end portion 101 of the fuel cell 100 and the inner wall surface of the insertion hole 231.

  The step of applying the material to be the first bonding material is performed as follows, for example. First, the insertion hole 231 of the manifold 200 is filled with a material to be the first region 310. After that, the material to be the second region 320 is arranged on the material to be the first region 310. In this step, after the heat treatment, the materials for the first region 310 and the second region 320 are made so that the ratio of the porosity of the first region 310 to the porosity of the second region 320 is 1.25 or more and 200 or less. Add pore former. Further, after the heat treatment, a pore former is added to the material forming the first region 310 and the second region 320 so that L1 / L becomes 0.00050 or more and 0.10 or less. Further, after the heat treatment, the material to be the first region 310 and the second region 320 is arranged such that the boundary B is located along the exposed surface 301 and below the upper surface 232 of the manifold.

  Next, heat treatment is applied to the materials that will be the first bonding material 300 and the second bonding material 5. By this heat treatment, the first bonding material 300 and the second bonding material 5 are solidified, and the cell stack device 1 is completed. Specifically, the second bonding material 5 is baked by being subjected to heat treatment. As a result, each fuel cell 100 and the first current collecting member 4 are fixed. Further, the temperature of the amorphous material reaches the crystallization temperature of the first bonding material 300 by being heat-treated. Then, a crystal phase is generated inside the material at the crystallization temperature, and crystallization proceeds. As a result, the amorphous material is solidified and made into ceramics to become crystallized glass. As a result, the first bonding material 300 made of crystallized glass exerts its function, and the lower end portion 101 of each fuel cell 100 is fixed to the upper wall 230 of the manifold 200.

  By performing the above steps, the cell stack device shown in FIGS. 1 to 6 can be manufactured.

[motion]
The operation of the cell stack device 1 of the present embodiment will be described with reference to FIGS. The cell stack device 1 operates as follows, for example.

A fuel gas (hydrogen gas or the like) is caused to flow through the manifold 200 into the gas flow path 111 of each fuel cell 100, and both surfaces of the support substrate 110 are exposed to a gas containing oxygen (air or the like), whereby An electromotive force is generated due to the difference in oxygen partial pressure between the two side surfaces. When the cell stack device 1 is connected to an external load, an electrochemical reaction represented by the following formula 1 occurs at the air electrode 150, and an electrochemical reaction represented by the following formula 2 occurs at the fuel electrode 130.
(1/2) O ₂ + 2e ⁻ → O ² −... (Equation 1)
^{_{H 2 + O 2- → H 2}} O + 2e - ··· ( Formula 2)

  Further, of the fuel gas flowing through the gas flow passage 111 of the support substrate 110, the surplus fuel gas that has not been used for power generation is discharged to the outside from the discharge port located on the other end side of the gas flow passage 111. Then, the excess fuel gas discharged from the discharge port and the gas containing oxygen are mixed and burned.

[Action]
Next, the operation of the cell stack device 1 of this embodiment will be described.

  First, the problem of the conventional cell stack device such as the above Patent Document 1 will be described with reference to FIG. During operation of the conventional cell stack device, the manifold 200 bends. Therefore, as shown in FIG. 9, tensile stress is applied to the lower side of the bonding material 350. A crack may occur in the bonding material 350 due to this tensile stress. This crack may grow and connect the internal space of the manifold and the external space of the manifold. In this case, the fuel gas introduced into the internal space leaks from the internal space to the external space. Therefore, the conventional cell stack device has a problem that the gas leak cannot be sufficiently suppressed.

  Therefore, in order to relieve the tensile stress applied to the lower side of the first bonding material 300, the present inventor increased the porosity in the vicinity of the exposed surface 301 of the first bonding material 300 exposed to the manifold 200 to deform the first bonding material 300. I thought about securing sex. That is, the technical idea that the first bonding material 300 is easily bent according to the bending of the manifold 200 by the pores is conceived. On the other hand, when the porosity is too large, the strength of the first bonding material 300 as a whole is lowered, and it is considered to deal with the problem that cracks are generated. As described above, in order to realize the first bonding material 300 that suppresses cracks by making both the stress relaxation of the first region 310 and the strength of the second region 320 compatible, as a result of diligent study, as a result, It was found that the ratio of the distance L1 of the first region 310 to the distance L was controlled, and the findings in Table 1 below were obtained.

  Table 1 relates to the cell stack device in which the exposed surface 301 of the first bonding material 300 is formed to incline upward from the side surface of the insertion hole 231 toward the fuel cell 100, as shown in FIG. 6. Forty fuel cells are fixed to the manifold. The first bonding material is crystallized glass. In the cell stack device, the porosity of the first bonding material 300 is measured in the cross section along the width direction (z-axis direction) of the fuel cell 100. The distance L1 from the exposed surface 301 where the boundary B between the first region 310 having a large porosity and the second region 320 having a small porosity is located, and the distance L from the exposed surface 301 in the first bonding material 300 are as described above. It is as described in Table 1.

  In the first bonding material, the porosity of the first region is 41 to 42% and the porosity of the second region is 0.2 to 0.3%. The "porosity" was measured by digitizing the pore portion by image analysis of a cross-sectional image of FE-SEM. Specifically, an image enlarged 1000 to 20000 times by FE-SEM was analyzed by image analysis software HALCON manufactured by MVTec. The area occupancy of each of the glass material portion and the pore portion was obtained on the cross-sectional image after analysis, and the area occupancy of the pore portion was defined as the porosity. The cross-sectional image was photographed for each of 10 fields of view in both the first region 310 and the second region 320, and the porosity was converted into a numerical value, and the average value thereof was taken as the porosity of the first region 310 and the second region 320.

  The pore size of the first region 310 is 0.1 μm. The "pore diameter" is the value of the equivalent circle diameter of the pores obtained by image analysis of the FE-SEM cross-sectional image. The equivalent circle diameter is the diameter of a circle having an area value of a measurement target (particles and pores) obtained by image analysis of a cross section. Similar to the calculation of the porosity, the cross-sectional image was photographed in 10 fields of view to quantify the pore diameter. The average pore diameter of each visual field was calculated, and the average of the average pore diameters of the 10 visual fields was further defined as the pore diameter.

  Sample No. With respect to the cell stack devices 1 to 22, the amount of gas leak and the presence or absence of cracks were examined by a thermal cycle test. Specifically, each cell stack device was installed in an electric furnace, and the temperature was raised and lowered from room temperature to 850 ° C. at a temperature rising / falling rate of 400 ° C./hr 20 times, then taken out from the electric furnace and gas leak amount and crack generation occurred. The presence and absence of The results are shown in Table 1 above.

  In Table 1 above, regarding the gas leak amount, argon gas is supplied from the introduction pipe P of the manifold 200 after sealing the outlet end of the gas flow passage 111 of the fuel cell 100, and the inside of the manifold 200 is increased to an applied pressure of 20 kPa. Was held and the amount of gas leak at that time was measured. The presence or absence of cracks was confirmed by applying a penetrant flaw detection agent to the surface of the first bonding material and observing with a microscope.

  As shown in Table 1, sample No. 1 having no first region having a large porosity. 1, 6, 11 and 16 are hardly deformable. In addition, Sample No. 1 having a first region having a large porosity but a small proportion was used. No. 22 has a too small deformation amount. Therefore, when the manifold 200 is deformed during the heat cycle test (operation), a crack is generated from the exposed surface 301 exposed in the internal space of the manifold 200. As a result, a crack connecting the inside and outside of the manifold was generated, and the argon gas introduced into the internal space leaked to the external space.

  On the other hand, Sample No. 1 having the first region 310 having a large porosity. L1 / L of Nos. 2 to 4, 7 to 10, 12 to 15, and 17 to 20 were 0.00050 or more, and thus were sufficiently deformable. Therefore, even if the manifold 200 is deformed by the stress during the heat cycle test, the tensile stress generated in the first bonding material 300 can be relaxed. That is, the sample No. In 2 to 4, 7 to 10, 12 to 15, and 17 to 20, the stress relaxation due to the deformation of the first region 310 effectively functions, so that the crack in the first bonding material 300 can be suppressed. As a result, the sample No. It was confirmed that no gas leak occurred in 2 to 4, 7 to 10, 12 to 15, and 17 to 20.

  Further, in the sample No. 1 having a large first region. Sample Nos. 5 and 21 having L1 / L of 0.10. Compared with No. 4, the deformability is comparable. From this, it is understood that the deformability cannot be significantly improved even if L1 / L exceeds 0.10. Therefore, even if L1 / L is 0.10 or less, high deformability of the first bonding material 300 can be exhibited, which is effective for bending the manifold during operation.

  Further, the sample No. In Nos. 5 and 21, although the deformability was high, the second region 320 was small, so that the strength of the entire glass constituting the first bonding material 300 was lowered and many cracks were generated. As a result, a crack connecting the inside and outside of the manifold was generated, and the argon gas introduced into the internal space leaked to the external space.

  Sample No. In 2 to 4, 7 to 10, 12 to 15, and 17 to 20, the boundary between the first region 310 and the second region 320 is a surface along the exposed surface. In addition, sample No. In 2 to 4, 7 to 10, 12 to 15, and 17 to 20, the boundary B between the first region 310 and the second region 320 is located below the upper surface 232 of the manifold 200.

  From the above, in the first bonding material 300 of the present embodiment, the ratio (L1 / L) of the distance L from the exposed surface 301 in the first region 310 to the distance L from the exposed surface 301 in the first bonding material 300 is It is 0.00050 or more and 0.10 or less. Therefore, since the cell stack device 1 of the present embodiment including the first bonding material 300 can achieve both high deformability and high strength, cracks can be suppressed. Therefore, the cell stack device of the present invention can suppress gas leakage caused by cracks.

  In addition, sample No. In 2 to 4, 7 to 9, 12 to 14, and 17 to 19, since the distance from the exposed surface 301 to the first region 310 was controlled to less than 50 μm, cracks in the first bonding material 300 could be further suppressed.

  In addition, as a result of earnest studies, the present inventor has made earnest studies in order to realize the first bonding material 300 that suppresses cracks by making the stress relaxation of the first region 310 compatible with the strength of the second region 320. It was found that the ratio of the porosity of the first region 310 to the porosity of 320 (ratio of porosity of the first region 310 / porosity of the second region 320) was controlled, and the findings in Table 2 below were obtained.

  Table 2 relates to the cell stack device in which the exposed surface 301 of the first bonding material 300 is formed to incline upward from the side surface of the insertion hole 231 toward the fuel cell 100, as shown in FIG. 6. Forty fuel cells are fixed to the manifold. The first bonding material is crystallized glass. Sample No. L1 / L of 23-41 was 0.0048-0.00052. In the cell stack device, the porosity of the first bonding material 300 is measured in the cross section along the width direction (z-axis direction) of the fuel cell 100. The porosities of the first region 310 and the second region 320 are as described in Table 2 above. Sample No. Regarding the gas leak amount and the presence / absence of cracks in the cell stack devices of Nos. 23 to 41, Sample No. It evaluated by the same heat cycle test as 1-22.

  As shown in Table 2, the sample No. having the ratio of the porosity of the first region 310 to the porosity of the second region 320 of 1.25 or more and 200 or less. No gas leak occurred in the cell stack devices of 23 to 26 and 28 to 40.

  Sample No. 1 in which the ratio of the porosity of the first region 310 to the porosity of the second region 320 is less than 1.25. Since No. 41 had a small deformability, many cracks were generated, and the argon gas introduced into the internal space leaked to the external space. Moreover, in the sample No. 2 in which the ratio of the porosity of the first region 310 to the porosity of the second region 320 exceeds 200. In No. 27, many cracks were generated due to the decrease in strength, and the argon gas introduced into the internal space leaked to the external space.

  In addition, as shown in Table 2, sample No. 1 having a porosity of 5% or more in the first region and a porosity of 4% or less in the second region 320. Sample Nos. 24 to 26 and 28 to 39 outside this range are sample Nos. As compared with Nos. 23 and 40, cracking can be suppressed. Therefore, the effect of increasing the deformability of the first region and increasing the strength of the second region can be further exhibited.

  Sample No. In 23 to 26 and 28 to 40, the boundary between the first region 310 and the second region 320 is a surface along the exposed surface 301. In addition, sample No. In 23 to 26 and 28 to 40, the boundary B between the first region 310 and the second region 320 is located below the upper surface 232 of the manifold 200.

  As described above, in the first bonding material 300 of the present embodiment, the ratio of the porosity of the first region 310 to the porosity of the second region 320 is 1.25 or more and 200 or less. Therefore, since the cell stack device 1 of the present embodiment including the first bonding material 300 can achieve both high deformability and high strength, cracks can be suppressed. Therefore, the cell stack device of the present invention can suppress gas leakage caused by cracks.

  Further, the inventor of the present invention has made the above sample No. In the cell stack device of No. 4, the knowledge of Table 3 below was obtained regarding the effect of the pore size of the first region 310. Sample No. Regarding the gas leak amount and the presence / absence of cracks in the cell stack devices of Nos. The same heat cycle test as in 4 was performed.

  As shown in Table 3, sample No. 1 having a pore size of the first region 310 of 0.1 μm or more and 20 μm or less. Nos. 4, 43 to 46 are sample Nos. Crack generation can be suppressed as compared with 42 and 47. Therefore, the effect of improving the deformability of the first region 310 can be further exhibited.

  Sample No. In the cell stack devices of Nos. 42 and 47, since L1 / L was 0.00050 or more and 0.10 or less, although small cracks occurred, gas leak did not occur.

  In addition, the present inventor has conducted extensive studies to realize a first bonding material that suppresses cracks by making the stress relaxation of the first region 310 compatible with the strength of the second region 320. It was found that the exposed surface 301 of 300 and the boundary B were controlled, and the following findings were obtained.

  The exposed surface 301 of the first bonding material 300 extends in a direction intersecting with the extending direction of the upper surface 232 of the manifold, and the boundary B is parallel to the upper surface 232. 48 was prepared. Sample No. L1 / L of 48 was 0.00049, and the ratio of the porosity of the first region to the porosity of the second region was 1.24.

  This sample No. Regarding the gas leak amount and the presence / absence of cracks of the cell stack device of No. 48, sample No. It evaluated by the same heat cycle test as 1-22. As a result, the sample No. In the case of 48, a crack is generated from the exposed surface 301 exposed in the internal space of the manifold 200. As a result, a crack connecting the inside and outside of the manifold was generated, and the argon gas introduced into the internal space leaked to the external space.

  As shown in FIG. 6, the exposed surface 301 of the first bonding material 300 extends in a direction intersecting with the extending direction of the upper surface 232 of the manifold, and the boundary B is a surface along the exposed surface 301. 2 to 4, 7 to 10, 12 to 15, 17 to 20, 23 to 26, 28 to 40 can balance the high deformability of the first region 310 and the high strength of the second region 320 in a well-balanced manner, Cracks can be suppressed. Therefore, the cell stack device of the present invention can suppress gas leakage caused by cracks.

  In addition, as a result of earnest studies, the inventor of the present invention has made a diligent study in order to realize a first bonding material that suppresses cracks by making the stress relaxation of the first region 310 compatible with the strength of the second region 320. It was found that the position of the boundary B with respect to is controlled, and the following findings have been obtained.

  Sample No. 1 in which the boundary B between the first region 310 and the second region 320 is located above the upper surface 232 of the manifold. Prepared 49. Sample No. L1 / L of 49 was 0.00049, and the ratio of the porosity of the first region to the porosity of the second region was 1.24.

  This sample No. Regarding the gas leak amount and the presence / absence of cracks in the cell stack device of No. 49, sample No. It evaluated by the same heat cycle test as 1-22. As a result, the sample No. 49, a crack is generated from the exposed surface 301 exposed in the internal space of the manifold 200. As a result, a crack connecting the inside and outside of the manifold was generated, and the argon gas introduced into the internal space leaked to the external space.

  As shown in FIG. 6, sample No. 3 in which the boundary B between the first region 310 and the second region 320 is located below the upper surface 232 of the manifold 200. 2 to 4, 7 to 10, 12 to 15, 17 to 20, 23 to 26, 28 to 40 can balance the high deformability of the first region 310 and the high strength of the second region 320 in a well-balanced manner, Cracks can be suppressed. Therefore, the cell stack device of the present invention can suppress gas leakage caused by cracks.

Modification 1
The cell stack device of the above-described embodiment has been described by taking the lateral stripe type in which the plurality of power generation element portions 120 are arranged on one main surface of the support substrate 110 as an example. The vertical stripe type in which one power generating element is arranged on one main surface of Further, although the cell stack device 1 of the present embodiment includes the cylindrical flat plate type support substrate 110, the cell stack device of the present invention may include a cylindrical support substrate.

Modification 2
In the above embodiment, the lower end of one fuel cell is inserted into one insertion hole 231 formed in the manifold 200, but in the present invention, a plurality of fuel cells are inserted into one insertion hole. May be.

Modification 3
The manifold 200 of the above-described embodiment has a structure in which the upper surface of the side wall 220 is open and the upper surface 230 is closed, but the manifold of the present invention is not limited to this. For example, the side wall and the upper wall may be integrated, and the lower surface of the side wall may be opened, and the lower surface may be closed by the bottom wall.

Modification 4
In the manifold 200 of the above embodiment, the side wall 220 extends upward from the bottom wall 210 substantially vertically, but the manifold of the present invention is not limited to this. For example, the side wall 220 may be inclined so as to expand outwardly toward the upper side, or may be inclined so as to expand outwardly toward the lower side.

1 Cell Stack Device 100 Fuel Cell 200 Manifold 300 First Bonding Material 301 Exposed Surface 302 Outer Surface 310 First Area 320 Second Area B Boundary L, L1 Distance

Claims (8)

A fuel cell,
A manifold supporting the fuel cells,
A joining material that joins the fuel cell and the manifold,
Equipped with
The bonding material is
A first region having an exposed surface exposed to the internal space of the manifold;
A second region located outside the first region,
Consists of
The porosity of the first region is larger than the porosity of the second region,
The ratio of the porosity of the first region to the porosity of the second region is 1.25 or more and 200 or less,
Cell stack device.
A fuel cell,
A manifold supporting the fuel cells,
A joining material that joins the fuel cell and the manifold,
Equipped with
The bonding material is
A first region having an exposed surface exposed to the internal space of the manifold;
A second region located outside the first region,
Consists of
The porosity of the first region is larger than the porosity of the second region,
The ratio of the distance from the exposed surface in the first region to the distance from the exposed surface in the bonding material is 0.00050 or more and 0.10 or less.
Cell stack device.
Fuel cells extending in the vertical direction,
A manifold supporting the lower end of the fuel cell,
A joining material that joins the fuel cell and the manifold,
Equipped with
The bonding material is
A first region having an exposed surface exposed to the internal space of the manifold;
A second region located outside the first region,
Consists of
The porosity of the first region is larger than the porosity of the second region,
The exposed surface extends in a direction intersecting a direction in which an upper surface of the manifold extends, and a boundary between the first region and the second region is a surface along the exposed surface.
Cell stack device.
Fuel cells extending in the vertical direction,
A manifold supporting the lower end of the fuel cell,
A joining material that joins the fuel cell and the manifold,
Equipped with
The bonding material is
A first region having an exposed surface exposed to the internal space of the manifold;
A second region located outside the first region,
Consists of
The porosity of the first region is larger than the porosity of the second region,
The boundary between the first region and the second region is located below the upper surface of the manifold,
Cell stack device.
The first region has a distance from the exposed surface of less than 50 μm,
The cell stack device according to claim 1.
The porosity of the first region is 5% or more,
The porosity of the second region is 4% or less,
The cell stack device according to claim 1.
The porosity of the first region is 25% or less,
The porosity of the second region is 0.1% or more,
The cell stack device according to claim 6.
The pore diameter of the first region is 0.1 μm or more and 20 μm or less,
The cell stack device according to any one of claims 1 to 7.

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