JP4999305B2 - Fuel cell and fuel cell - Google Patents

Description

  The present invention relates to a fuel cell and a fuel cell, and in particular, on a porous support body through which gas flows, a power generation unit that sandwiches a solid electrolyte with an electrode is provided, and the porous member is positioned opposite to the power generation unit. The present invention relates to a fuel cell having an interconnector provided on a support and a fuel cell.

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

  A fuel cell used in a conventional fuel cell has a power generation unit by sequentially laminating a porous inner electrode, a dense solid electrolyte, and a porous outer electrode on one main surface of a porous conductive support substrate. The other main surface is provided with a dense interconnector. A plurality of gas passages are formed in the conductive support substrate.

  The electrical connection between one fuel cell and the other fuel cell is accomplished by connecting the inner electrode of one fuel cell to the other fuel cell via an interconnector and a current collecting member provided on a conductive support substrate. This is done by electrically connecting to the outer electrode of the cell (see, for example, Patent Document 1).

In such a fuel cell, the current generated by the power generation unit of one fuel cell is transmitted to the power generation unit of the other fuel cell via the interconnector of the other fuel cell and the porous conductive support substrate. Flowing into. As a material constituting such a porous conductive support substrate, Ni and / or NiO and a ceramic material as a thermal expansion coefficient adjusting material are used for the reason that internal modification can be performed. Yes.
Japanese Patent Laid-Open No. 2004-234969

  However, in the above conventional fuel cell, the current generated by the power generation unit of one fuel cell is transmitted to the other fuel cell via the interconnector of the other fuel cell and the porous conductive support substrate. Since the current flows through the power generation unit, the current passes through the conductive support substrate. However, the conductive support substrate is porous and contains a ceramic material, so that the conductivity is still low, and between the power generation unit and the interconnector. There was a problem that resistance increased and power generation performance was still low.

  An object of this invention is to provide the fuel cell and fuel cell which can make resistance between an electric power generation part and an interconnector small.

The fuel battery cell of the present invention is provided with a power generation unit in which a solid electrolyte is sandwiched between electrodes on a conductive porous support through which gas flows, and the porous support at a position facing the power generation unit A fuel battery cell having an interconnector provided on a body, wherein the porous support body penetrates from the power generation unit side to the interconnector side and has a higher conductivity than the conductive porous support body. It is characterized in that a through conductor having a property is provided.

  In such a fuel cell, a through conductor is provided between the power generation unit side and the interconnector side, and the through conductor forms an electrode of the power generation unit and an interconnect formed at a position facing the power generation unit via the support. The connector can be electrically connected by the through conductor, and the resistance between the power generation unit and the interconnector can be reduced by using the through conductor having better conductivity than the porous support.

  The fuel battery cell of the present invention is characterized in that a reforming catalyst material is dispersedly contained in the porous support. In such a fuel cell, for example, even when a fuel gas containing hydrocarbon gas (part of city gas) that cannot be completely reformed in the reformer passes through the porous support, The hydrocarbon gas can be internally reformed to hydrogen gas by the reforming catalyst material in the porous support.

  Furthermore, the fuel battery cell of the present invention is characterized in that the porous support has a gas passage therein.

  Further, in the fuel cell of the present invention, the porous support has a flat plate shape, the power generation unit is provided on one main surface of the porous support, and the interconnector is provided on the other main surface. It is characterized by. In such a fuel cell, the through conductor is provided in the thickness direction of the porous support, the current path is also the shortest distance, and the resistance of the fuel cell can be further reduced.

  The fuel cell according to the present invention is characterized in that a plurality of the above-described fuel cells are accommodated in a storage container. In such a fuel cell, as described above, the resistance in the fuel cell can be reduced. Therefore, even if a large number of fuel cells are connected in series, the resistance is small and the power generation efficiency as a fuel cell is improved. be able to. Moreover, since the raw material cost of the support body which occupies most of the fuel battery cells can be reduced, the fuel battery cost can be reduced.

The porous support of the present invention is conductive. When the porous support is conductive , a material having a higher conductivity (lower resistance) than the porous support can be used as the through conductor. Further, the through conductor may be made of the same material as that of the porous support, but in this case, the through conductor needs to be denser than the porous support.

  The porous support of the present invention desirably has a plurality of gas passage holes in the length direction, but may have a three-dimensional network structure (which is already on the market) or a honeycomb shape. Further, the porous support may be not only a substrate shape but also a columnar shape.

  In the fuel cell of the present invention, a through conductor is provided between the power generation unit side of the porous support and the interconnector side, and the electrode of the power generation unit is formed at the position facing the power generation unit via the support. The connector can be electrically connected by the through conductor, and the resistance between the power generation unit and the interconnector can be reduced by using the through conductor having better conductivity than the porous support.

  As shown in FIG. 1, the fuel cell of the present invention includes, for example, a fuel side electrode 33b, a solid electrolyte 33c, an oxygen side electrode 33d, and an interconnector layer 33e on a porous support substrate (porous support) 33a. It is configured by laminating and has a hollow flat plate shape.

  That is, the support substrate 33a is a plate-like and rod-like porous body, and six gas passages 34 having a circular cross section in the length direction are provided in the support substrate 33a. 34) is configured to circulate gas.

  A porous fuel side electrode 33b, a dense solid electrolyte 33c, and a porous oxygen side electrode 33d are sequentially stacked on the lower surface of the support substrate 33a to form a power generation unit 36, and the upper surface is dense. An interconnector layer 33e is laminated. In other words, a power generation unit 36 is provided on the lower surface (one main surface) of the support substrate 33a so that the solid electrolyte 33c is sandwiched between the fuel side electrode 33b and the oxygen side electrode 33d, and the position facing the power generation unit 36 is provided. An interconnector layer 33e is provided on the upper surface (the other main surface) of the support substrate 33a.

  The fuel side electrode 33b and the solid electrolyte 33c laminated on the fuel side electrode 33b are extended from the lower surface of the support substrate 33a to the upper surface via both sides thereof, and both ends thereof are interconnector layers. The outer peripheral surface of the support substrate 33a is covered with a dense solid electrolyte 33c or an interconnector layer 33e, which is an insulating material, except for both end surfaces in the length direction.

  As will be described later, the support substrate 33a is configured by joining and firing a pair of divided molded bodies produced by press molding that divides the passage area of the gas passage 34 into two. In FIG. 1, the joint portion is indicated by a broken line. By confirming the joint surface on the side surface forming the gas passage 34, it can be confirmed whether or not the support substrate 33a is produced by press molding.

  In the fuel cell of the present invention, the porous support substrate 33a is formed with a plurality of through holes penetrating from the power generation unit 36 to the interconnector 33e side, in other words, in the thickness direction of the support substrate 33a. The through hole is filled with a conductive material, and a through conductor 37 is formed. The through conductors 37 have a circular cross section, and as shown in FIG. 2, the through conductors 37 are not exposed between the gas passages 34 of the porous support substrate 33a and in the gas passages 34, and It is formed along the gas passage 34 at a predetermined interval in the cell length direction.

(Penetration conductor 37)
Tungsten, molybdenum, platinum, Ni, Fe, Co, or the like can be used for the through conductor 37. In particular, it is desirable to use Ni. Furthermore, Ni is a fuel-side electrode material from the viewpoint of the thermal expansion coefficient. And YSZ cermet material can be preferably used.

  In addition, when the porous support substrate 33a has conductivity, the through conductor 37 is made of a material having a higher conductivity than the support substrate 33a. In order to have a conductivity higher than that of the support substrate 33a, when the same material as the fuel side electrode 33b is used for the through conductor 37, the density is higher than that of the fuel side electrode 33b, or higher than that of the fuel side electrode 33b. Increase the amount of Ni.

(Support substrate 33a)
The support substrate 33a has a substantially rectangular cross section and is plate-like and rod-like as a whole, and both end surfaces in the width direction have curved surfaces protruding outward. The support substrate 33a is gas permeable to allow the fuel gas to permeate to the fuel side electrode 33b.

In addition , the conductive porous support substrate 33a is composed of an iron group metal component and a specific rare earth oxide, for example, in order to avoid inconvenience caused by simultaneous firing.

  The iron group metal component is for imparting conductivity to the support substrate 33a, and may be a single iron group metal, or an iron group metal oxide, an iron group metal alloy or an alloy oxide. May be. The iron group metals include iron, nickel, and cobalt. In the present invention, any of them can be used, but Ni and / or NiO is contained as an iron group component because it is stable in fuel gas. Preferably it is.

The rare earth oxide component is used to approximate the thermal expansion coefficient of the support substrate 33a to ZrO ₂ containing the rare earth element forming the solid electrolyte 33c, and maintains high conductivity and An oxide containing at least one rare earth element selected from the group consisting of Y, Lu, Yb, Tm, Er, Ho, Dy, Gd, Sm, and Pr is used to prevent diffusion into the solid electrolyte 33c and the like. Used in combination with the above iron group components. Specific examples of such rare earth oxides include Y ₂ O ₃ , Lu ₂ O ₃ , Yb ₂ O ₃ , Tm ₂ O ₃ , Er ₂ O ₃ , Ho ₂ O ₃ , Dy ₂ O ₃ , Gd ₂ O. ₃ , Sm ₂ O ₃ , Pr ₂ O ₃ can be exemplified, and Y ₂ O ₃ and Yb ₂ O ₃ are preferable in that they are particularly inexpensive.

  An intermediate layer may be provided between the support substrate 33a and the interconnector layer 33e in order to increase the bonding strength. Further, a P-type semiconductor or the like may be provided outside the interconnector layer 33e in order to extract output.

(Interconnector layer 33e)
The interconnector layer 33e is made of conductive ceramics, but needs to have reduction resistance and oxidation resistance because it comes into contact with the fuel gas (hydrogen) and the oxygen-containing gas. For this reason, lanthanum chromite perovskite oxides (LaCrO ₃ oxides) are generally used as the conductive ceramics. Further, in order to prevent leakage of the fuel gas passing through the inside of the support substrate 33a and the oxygen-containing gas passing through the outside of the support substrate 33a, the conductive ceramics must be dense, for example, 93% or more, particularly 95%. It is preferable to have the above relative density.

  The interconnector layer 33e is preferably 10 to 200 μm from the viewpoint of preventing gas leakage and electrical resistance. That is, if the thickness is smaller than this range, gas leakage is likely to occur, and if the thickness is larger than this range, the electric resistance is large, and the current collecting function may be reduced due to a potential drop. .

(Fuel side electrode 33b)
The fuel side electrode 33b causes an electrode reaction, and is formed of a known porous conductive cermet. For example, it is formed from ZrO ₂ in which a rare earth element is dissolved, and Ni and / or NiO. As the ZrO ₂ (stabilized zirconia) in which the rare earth element is dissolved, the same one used for forming the solid electrolyte 33c described below is preferably used.

  The stabilized zirconia content in the fuel side electrode 33b is preferably in the range of 35 to 65% by volume, and the Ni or NiO content is preferably 65 to 35% by volume. Further, the open porosity of the fuel side electrode 33b is preferably 15% or more, particularly in the range of 20 to 40%, and the thickness is preferably 1 to 30 μm. For example, if the thickness of the fuel side electrode 33b is too thin, the performance may be lowered, and if it is too thick, there is a possibility that separation due to a difference in thermal expansion occurs between the solid electrolyte 33c and the fuel side electrode 33b.

(Solid electrolyte 33c)
The solid electrolyte 33c provided on the fuel side electrode 33b is generally formed of a dense ceramic called ZrO ₂ (usually stabilized zirconia) in which 3 to 15 mol% of a rare earth element is dissolved. Examples of rare earth elements include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, but they are inexpensive. From the point, Y and Yb are desirable.

  The stabilized zirconia ceramic forming the solid electrolyte 33c is desirably a dense material having a relative density (according to Archimedes method) of 93% or more, particularly 95% or more from the viewpoint of preventing gas permeation. Is desirably 10 to 100 μm. The solid electrolyte 33c may be composed of a lanthanum gallate perovskite type composition in addition to the stabilized zirconia.

(Oxygen side electrode 33d)
The oxygen side electrode 33d is formed of a conductive ceramic made of a so-called ABO ₃ type perovskite oxide. As such a perovskite oxide, at least one of transition metal perovskite oxides, particularly LaMnO ₃ oxides, LaFeO ₃ oxides, and LaCoO ₃ oxides having La at the A site is preferable. LaFeO ₃ -based oxides are particularly suitable because they have high electrical conductivity at an operating temperature of about 1000 ° C. In the perovskite oxide, Sr and the like may exist together with La at the A site, and Co and Mn may exist together with Fe at the B site.

  Further, the oxygen side electrode 33d must have gas permeability. Therefore, the conductive ceramic (perovskite oxide) forming the oxygen side electrode 33d has an open porosity of 20% or more, particularly 30. It is desirable to be in the range of ˜50%. The thickness of the oxygen side electrode 33d is preferably 30 to 100 μm from the viewpoint of current collection. Oxygen gas, air containing oxygen, or the like is supplied to the oxygen side electrode 33d.

(Manufacture of fuel cells)
The fuel battery cell having the above structure is manufactured, for example, as follows. First, a support substrate molded body is produced.

Supporting substrate molded body, for example, the raw material powder 100 parts by mass for forming the supporting lifting the substrate, the organic binder 2 to 7 parts by weight, the solvent of 100-200 parts by weight, an acrylic resin pore former 10-18 A mass part is added and mixed, dried and granulated, and a press molding machine 41 shown in FIG. 3A is used to produce a pair of divided molded bodies 33a1 and 33a2 as shown in FIG. Specifically, using FIG. 3, the press molding machine 41 includes a lower mold 41a, an upper mold 41b, and a press jig 41c for pressing the upper mold 41b. As shown in FIG. 3B, a plurality of protrusions 41a1 are formed on the lower mold 41a at predetermined intervals.

  Then, the raw powder (granulated powder) of the support substrate is accommodated on the lower mold 41a, the upper mold 41b is disposed on the mixed powder, and the upper mold 41b is pressed at a predetermined pressure by the press jig 41c. By applying pressure, the divided molded bodies 33a1 and 33a2 as shown in FIG. 4 are produced.

  Thereafter, 2-7 parts by mass of an organic binder is added to 100 parts by mass of the raw material powder for forming the support substrate between the bonding surfaces of the pair of divided molded bodies 33a1, 33a2 so as to form the gas passages 34. The side surfaces of the recesses are bonded together through a slurry obtained by adding and mixing 100 to 200 parts by mass of a solvent, heated to a predetermined temperature, debindered, and calcined. Thereby, a pair of division molded object 33a1, 33a2 is joined, and a support substrate molded object is produced.

  Next, as shown in FIG. 2, a through-hole penetrating from one main surface of the support substrate molded body to the other main surface is drilled between the gas passages 34 so as not to be exposed in the gas passages 34. Form. Further, a fuel electrode material (Ni or NiO powder and stabilized zirconia powder), an organic binder and a solvent were mixed to prepare a slurry, and the slurry was filled in the through hole and dried to form a through conductor. .

  Next, a fuel-side electrode material (Ni or NiO powder and stabilized zirconia powder), an organic binder and a solvent are mixed to prepare a slurry, and a sheet for the fuel-side electrode is prepared using this slurry. Further, instead of preparing a sheet for the fuel side electrode, a paste in which the fuel electrode side electrode forming material is dispersed in a solvent is applied to a predetermined position of the support substrate molded body formed above, and dried to obtain a fuel. A coating layer for the side electrode may be formed.

  Further, a stabilized zirconia (YSZ) powder, an organic binder, and a solvent are mixed to prepare a slurry, and a solid electrolyte sheet is prepared using the slurry.

  The support substrate molded body, the fuel electrode sheet, and the solid electrolyte sheet formed as described above are laminated so as to have a layer structure as shown in FIG. 1 and dried. In this case, when the coating layer for the fuel side electrode is formed on the surface of the support substrate molded body, only the solid electrolyte sheet may be laminated on the support substrate molded body and dried.

Thereafter, a material for an interconnector layer (for example, LaCrO ₃ oxide powder), an organic binder and a solvent are mixed to prepare a slurry, and an interconnector layer sheet is prepared.

  This interconnector layer sheet is further laminated at a predetermined position of the laminate obtained above to produce a fired laminate.

Next, the above laminate for firing is subjected to binder removal treatment, and co-fired at 1300 to 1600 ° C. in an oxygen-containing atmosphere, and an oxygen-side electrode material (for example, LaFeO ₃₎ is placed at a predetermined position of the obtained sintered body. And paste containing a P-type semiconductor layer forming material (for example, LaFeO ₃ -based oxide powder) and a solvent by dipping or the like, if necessary. The fuel battery cell 33 of the present invention shown in FIG. 1 can be manufactured by baking. The cross-sectional dimensions of the fuel cell are, for example, a thickness of 2.5 to 10 mm, a width of 15 to 40 mm, and a length of the fuel cell (length in the gas passage forming direction) of 100 to 200 mm.

  Note that when Ni alone is used to form the support substrate 33a, the fuel-side electrode 33b, and the through conductor 37, Ni is oxidized to NiO by firing in an oxygen-containing atmosphere. It can return to Ni by processing.

(Cell stack)
In the cell stack, a plurality of the fuel cells 33 described above are assembled, and a current collecting member made of a metal felt and / or a metal plate is interposed between one adjacent fuel cell 33 and the other fuel cell 33. The two are connected in series with each other. That is, the fuel side electrode 33b of one fuel battery cell 33 is electrically connected to the oxygen side electrode 33d of the other fuel battery cell 33 via the interconnector 33e, the through conductor 37, and the current collecting member. Such cell stacks are arranged side by side, and adjacent cell stacks are connected in series by a conductive member.

  The fuel cell is configured by accommodating the cell stack as described above in a storage container. The storage container is provided with an introduction pipe for introducing a fuel gas such as hydrogen into the fuel battery cell 33 from the outside, and an introduction pipe for introducing an oxygen-containing gas such as air into the external space of the fuel battery cell 33. The fuel cell is heated to a predetermined temperature (for example, 600 to 900 ° C.) to generate electric power, and the used fuel gas and oxygen-containing gas are discharged out of the storage container.

  In addition, this invention is not limited to the said form, A various change is possible in the range which does not change the summary of invention. For example, in the above embodiment, the case where the fuel side electrode 33b, the solid electrolyte 33c, and the oxygen side electrode 33d are formed on the support substrate 33a has been described. However, the oxygen side electrode, the solid electrolyte, and the fuel side electrode are sequentially formed on the support substrate. Even in this case, the present invention can be applied. In this case, since the oxygen-containing gas passes through the gas passage, the through conductor needs to be formed of a material that does not oxidize at a high temperature.

  In the above embodiment, the laminated molded body composed of the support substrate molded body, the fuel side electrode sheet, the solid electrolyte sheet, and the interconnector layer sheet is fired at the same time, and then the oxygen side electrode is formed. May be simultaneously fired, or may be immersed in a dipping solution containing a fuel-side electrode, a solid electrolyte, and an interconnector material in a support substrate molded body, and the respective layers may be sequentially formed.

  Furthermore, in the present invention, by changing the shape of the protrusion 41a1 of the mold, the sectional shape, sectional area, and overall shape of the gas passage can be easily changed.

  Moreover, although the example which formed the cylindrical penetration conductor 37 was described in the said form, as shown in FIG. 5, for example, you may form a penetration conductor with a rectangular cross section.

  Furthermore, in the said form, although the support substrate molded object was produced with the press molding machine 41, in this invention, a through-hole can also be formed in a support substrate molded object produced by extrusion molding with a drill.

The fuel cell of this invention is shown, (a) is a cross-sectional view, (b) is a cross-sectional perspective view. It is a top view of a support substrate. The press molding machine used for the manufacturing method of a support substrate is shown, (a) is explanatory drawing of a press molding machine, (b) is a perspective view of a lower metal mold | die. It is a perspective view which shows the state which bonds a division molded object. It is a top view which shows the support substrate in which the penetration conductor of rectangular cross section was formed.

Explanation of symbols

33a ... support substrate (support)
33b ... fuel side electrode 33c ... solid electrolyte 33d ... oxygen side electrode 33e ... interconnector 34 ... gas passage 36 ... power generation part 37 ... through conductor

Claims (5)

A power generation part is formed by sandwiching a solid electrolyte with an electrode on a conductive porous support through which gas flows, and an interconnector is provided on the porous support at a position facing the power generation part. The porous battery is provided with a penetrating conductor penetrating from the power generation unit side to the interconnector side and having a conductivity higher than that of the conductive porous support. A fuel battery cell characterized by comprising: The fuel cell according to claim 1 , wherein the porous support contains a reforming catalyst material in a dispersed manner. The porous support fuel cell according to claim 1 or 2 characterized by having a gas passage therein. The said porous support body is flat form, The said electric power generation part is provided in the one side main surface of this porous support body, The said interconnector is provided in the other side main surface. The fuel battery cell according to any one of 1 to 3 . A fuel cell comprising a plurality of fuel cells according to any one of claims 1 to 4 in a storage container.

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