JP2006092837A - Current collecting member for fuel cell, its manufacturing method, fuel cell stack using it and the fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress diffusion of Cr, as much as possible, in a current collection member formed of metal having conductivity and heat resistance and containing Cr. <P>SOLUTION: This current collecting member 20 is characterized by that a Cr diffusion prevention layer 202, formed of a single element oxide of a fourth-period metal element in the periodic table except for a perovskite structure or a composite oxide of the fourth-period metal element in the periodic table, and Cr is formed on a surface of a current collection body 201 formed of alloy-containing Cr. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a current collecting member for a fuel cell for electrically connecting a plurality of fuel cells, a method for manufacturing the same, a fuel cell stack using the same, 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.

  FIG. 4 shows a cell of a conventional solid oxide fuel cell. The fuel cell 1 has a fuel electrode 2 on the outer peripheral surface of a flat conductive support substrate 10 (the inside is a fuel gas passage 16). The solid electrolyte 3 and the air electrode 4 are sequentially provided, and the interconnector 5 is provided on the surface of the conductive support substrate 10 that is not covered by the fuel electrode 2, the solid electrolyte 3, and the air electrode 4. Yes.

In the fuel cell 1 described above, the fuel electrode 2 is generally formed of Ni and ZrO ₂ (YSZ) containing Y ₂ O ₃ , and the solid electrolyte 3 is ZrO ₂ (YSZ) containing Y ₂ O _3. The air electrode 4 is made of a lanthanum manganate perovskite complex oxide. Further, the interconnector 5 is not easily altered by oxygen-containing gas such as fuel gas and air, so that the fuel gas flowing inside the conductive support substrate 10 and the oxygen-containing gas flowing outside the air electrode 4 are surely cut off. In addition, it is made of dense conductive ceramics. A P-type semiconductor 14 is provided outside the interconnector 5 for current collection.

The fuel cell is configured by accommodating a fuel cell stack in which a plurality of fuel cells having the above-described structure are collected in a storage container. A fuel gas (hydrogen) is caused to flow inside the fuel electrode 5 and is in contact with the air electrode 2. In this way, power is generated at 600 to 900 ° C. by flowing air (oxygen). At this time, in order to obtain a high voltage, the fuel cells 1 are arranged in series as shown in FIG. 5, and are collected between the air electrode 4 of the fuel cell 1 and the P-type semiconductor 14 of the fuel cell 1 adjacent to the air electrode 4. An electric member 20 is interposed. As shown in FIG. 1, the current collecting member 20 is formed into a shape such as a plate-like member processed into a comb blade shape, and the adjacent blades are alternately bent to the opposite side to give elasticity, or formed in a mesh shape. Or a spiral one is used. And as such a current collection member 20, since a metal with high electrical conductivity is employ | adopted and it is used under high temperature, a heat-resistant metal is desirably employ | adopted. Here, as the heat-resistant metal having high conductivity, a metal containing 10 to 30 wt% of Cr is generally used.
JP 2004-228050 A

 However, when the fuel cell using the current collecting member 20 made of a metal containing Cr is used for a long time, Cr in the current collecting member 20 diffuses outside the current collecting member 20, and the diffused Cr is air. It reaches the interface between the electrode 4 and the electrolyte 3 and degrades the activity. This phenomenon is referred to as so-called Cr poisoning, and leads to a result that lowers the power generation capacity of the fuel cell.

  In addition, in general, Ag, Pt, Pd, etc. are mainly used as the bonding material 17 in order to uniformly contact the current collecting member 20 and the air electrode 4 and between the current collecting member 20 and the P-type semiconductor 14 to increase the current collecting ability. A bonding material obtained by applying and curing a conductive metal paste or a conductive ceramic paste is used. However, for example, an Ag-containing bonding material has a problem of promoting the above-described Cr poisoning.

On the other hand, when a current collecting member made of metal is used at 600 ° C. or higher, a surface oxide layer is formed, the contact resistance is remarkably increased, the resistance loss of power is increased, and the fuel cell characteristics are deteriorated. . In order to solve this problem, a metal composite oxide La _1-x M ¹ _x M ² O ₃ (wherein M ¹ is an alkaline earth metal, M ² is Co, Fe, Mn, A heat-resistant component (current collecting member) characterized by covering Ni or Cr, 0 ≦ x <1) is known.

  However, in this coating structure, since a non-dense perovskite structure is adopted as the coating layer of the current collecting member, it is not possible to prevent the diffusion of Cr gas, and since it contains an alkaline earth metal, There is a problem that the alkaline earth metal promotes the diffusion of Cr gas.

  The present invention has been made in view of the above circumstances, and a fuel cell current collecting member capable of suppressing Cr diffusion as much as possible in a fuel cell current collecting member made of a metal containing conductive and heat-resistant Cr, and An object of the present invention is to provide a manufacturing method thereof, a fuel cell stack using the same, and a fuel cell.

  As a result of diligent study, the present inventor has found that a single element oxide of a metal element for preventing diffusion of Cr or a Cr diffusion composed of a compound of this metal element and Cr on the surface of a current collecting body made of an alloy containing Cr. The inventors have found that the object can be achieved by providing the prevention layer, and have reached the present invention.

  That is, according to the present invention, a single element oxide of the fourth periodic metal element of the periodic table excluding the perovskite structure or the fourth periodic metal element of the periodic table and Cr is formed on the surface of the current collecting body made of an alloy containing Cr. A current collector for a fuel cell comprising a Cr diffusion preventing layer made of a composite oxide.

  In the present invention, a layer containing a fourth periodic metal element of the periodic table excluding the perovskite structure or a single element oxide thereof is formed and baked on the surface of a current collecting body made of an alloy containing Cr. This is a current collecting member for a fuel cell.

  Here, it is preferable that the fourth periodic metal element of the periodic table is any one selected from the group of Fe, Co, and Ni. This is because these single element oxides or composite oxides of these with Cr can provide a particularly excellent Cr diffusion preventing effect.

  The present invention also provides a current collecting member for a fuel cell, wherein a conductive ceramic layer is further provided outside the Cr diffusion preventing layer. In such a current collecting member for a fuel cell, the conductive ceramic layer has an anchor effect, so that separation of the current collecting member for the fuel cell and the fuel cell can be prevented and voltage drop can be further suppressed.

Further, the present invention interposes the fuel cell current collecting member between a plurality of fuel cells, and joins the plurality of fuel cells and the fuel cell current collecting member with a joining material containing Ag, It is a fuel cell stack formed by electrically connecting the plurality of fuel cells in series. Furthermore, the present invention is a fuel cell in which the fuel cell stack is accommodated in a storage container. By such a fuel cell stack and a fuel cell, a fuel cell excellent in long-term reliability with little voltage drop can be obtained.

  Furthermore, the present invention provides a single element oxide of a fourth periodic metal element in the periodic table excluding the perovskite structure on the surface of the current collector body after chamfering the edge portion of the current collector body made of an alloy containing Cr. A method for producing a current collecting member for a fuel cell, comprising providing a Cr diffusion preventing layer made of a complex oxide of a fourth periodic metal element and Cr in the periodic table. Thus, by chamfering the edge portion, the Cr diffusion preventing layer can be reliably formed over the entire surface.

  The single element oxide of the fourth periodic metal element in the periodic table excluding the perovskite structure means an oxide composed of the fourth periodic metal element in the periodic table. In addition, the single element oxide of the fourth periodic metal element in the periodic table excluding the perovskite structure or the complex oxide of the fourth periodic metal element and Cr in the periodic table contains Cr constituting the current collector body. It is different from the alloy used.

  According to the present invention, it is possible to prevent Cr from diffusing from the current collector body made of an alloy containing Cr and reaching the interface between the air electrode and the electrolyte, and to suppress a decrease in power generation capacity of the fuel cell.

Hereinafter, an embodiment of a current collecting member of the present invention will be described based on the drawings.
FIG. 1 is a perspective view showing a current collecting member 20 of the present invention, and FIGS. 2 and 3 are explanatory views showing a covering state of a Cr diffusion preventing layer of the current collecting member 20 shown in FIG. 1 is a cross-sectional view taken along line AA shown in FIG. 1, and FIG. 3 is a partial cross-sectional view taken along line BB shown in FIG. In the present invention, a single element oxide of the fourth periodic metal element of the periodic table excluding the perovskite structure or the fourth periodic metal element of the periodic table excluding the perovskite structure is formed on the surface of the current collecting body 201 made of an alloy containing Cr. The current collecting member 20 is provided with a Cr diffusion preventing layer 202 made of a complex oxide with Cr.

  As the current collecting body 201 in the current collecting member 20 of the present invention, an alloy containing 10 to 30 wt% of Cr having high conductivity and heat resistance, for example, Fe—Cr based metal, Ni—Cr based metal or the like is employed. Here, as the shape of the current collecting member 20, for example, a heat-resistant alloy plate is processed into a comb blade shape, and adjacent blades are alternately bent to the opposite side to have a shape as shown in FIG. However, there is no particular limitation.

In order to prevent the diffusion of Cr contained in the current collector body 201, the surface of the current collector body 201 is a single element oxide of the fourth periodic metal element of the periodic table excluding the perovskite structure or the periodic rule. A Cr diffusion preventing layer 202 made of a complex oxide of Table 4 periodic metal element and Cr is provided. The Cr diffusion preventing layer made of the single element oxide or the complex oxide with Cr is densely formed and has an effect of capturing Cr as described later. Here, Fe, Ni, Co, etc. can be preferably employed as the metal element of the fourth period of the periodic table. At this time, examples of the single element oxide of this metal element include Fe ₂ O ₃ , NiO, and Co ₃ O ₄ , and examples of composite oxides of this metal element and Cr include FeCr ₂ O ₄ and CoCr ₂ O. ₄ , NiCr ₂ O ₄ , CoCrO ₄ , Co ₂ CrO _{4 and the} like.

  Here, Cr gasifies, and if there is any gap, it diffuses from the gap. Therefore, this Cr diffusion prevention layer 202 needs to be provided on the entire surface of the current collector body 201. At this time, the Cr diffusion prevention layer 202 is formed by dipping (a dip coating method in which the current collector main body 201 is immersed in the Cr diffusion prevention layer paste) or plating, or the fourth periodic metal element of the periodic table excluding the perovskite structure It is coated by forming and baking a layer of single element oxide.

This baking may be performed simultaneously with the formation of the conductive ceramic layer.

  In the case of dipping, the Cr diffusion preventing layer 202 is obtained by immersing the current collector body 201 in a paste composed of the fourth periodic metal element of the periodic table and an organic component such as a desired binder and solvent, and drying and baking it. However, the thickness of the Cr diffusion preventing layer 202 is preferably 5 to 50 μm, more preferably 10 to 30 μm. There may be a gap due to air entrainment at the time of dipping. However, if the thickness is less than 5 μm, the gap cannot be reliably closed, and there is a possibility that Cr may diffuse through this, 50 μm If it exceeds, cracks may occur due to the difference in thermal expansion with the current collector body 201, and the inside is difficult to dry, resulting in poor production efficiency, and may also reduce conductivity. Because.

  On the other hand, in the case of plating, the Cr diffusion prevention layer 202 is formed by forming a plating film on the surface of the current collector body 201 by a normal plating method, and after forming a conductive ceramic layer on the surface of the plating film, the plating film And a conductive ceramic film are simultaneously baked. The thickness of the Cr diffusion preventing layer 202 is preferably 3 to 30 μm, more preferably 5 to 20 μm. If the thickness is less than 3 μm, air will not be engulfed like dipping, but there is a possibility that a part that will not be plated due to slight dirt may occur. This is because there is a risk of occurrence. Here, in the case of plating, since it is formed denser than dipping, the upper limit of the thickness tends to be set lower.

  In forming the Cr diffusion preventing layer 202, dipping that is cheaper than plating is likely to be employed. Here, when the current collecting member 20 having a shape as shown in FIG. 1 is formed, the processing of the comb blade-shaped portion is usually performed by an etching process or a push-cut by a cutter, but depending on these methods, an edge portion is formed. Therefore, if an attempt is made to provide a Cr diffusion prevention layer by dipping, there is a possibility that the Cr diffusion prevention layer will not be formed well at this edge portion. Therefore, as a pretreatment for providing the Cr diffusion prevention layer, it is preferable that the edge portion is subjected to chamfering treatment such as C surface and R surface by sandblasting, ultrasonic processing machine or the like.

Furthermore, it is preferable that a conductive ceramic layer (not shown) is provided further outside the Cr diffusion preventing layer 202. The fuel cell and the current collecting member are joined mainly via a Ag-containing joining material. If a conductive ceramic layer is not provided outside the Cr diffusion preventing layer 202, the surface of the Cr diffusion preventing layer is Since it is smooth, the current collecting member 20 and the bonding material may be peeled off. On the other hand, by providing a conductive ceramic layer, the conductive ceramic layer has an anchor effect. This conductive ceramic layer is preferably formed by dipping on the entire surface of the Cr diffusion preventing layer 202 and preferably has a thickness of 10 to 50 μm. This is because if it is less than 10 μm, voids may be formed, and if it exceeds 50 μm, cracks may occur. The conductive ceramic is not particularly limited as long as it has conductivity, but a so-called ABO ₃ type perovskite oxide, such as La _0.6 Sr _0.4 Co _0.4 Fe _0.6 O ₃ , La _0.6 Sr _0.4 Co _1.0 O ₃ , La _0.6 Sr _0.4 Mn _1.0 O _{3 and the} like are preferably employed.

Next, prevention of Cr diffusion will be described in detail.
In order to generate electric power with the fuel cell, the current collecting member of the present invention is used at a high temperature of 600 to 1000 ° C. At this time, Cr diffuses from the current collecting body 201 as Cr gas.

Here, in the case where a Cr diffusion prevention layer made of a single element oxide of the fourth periodic metal element excluding the perovskite structure is provided on the surface of the current collector body 201, Cr diffused from the current collector body 201 gas, or forming a film of _Cr 2 _{O 3} in the vicinity of the interface between the collector body 201 and the Cr diffusion preventing layer 202, and a Cr metal element contained as _Cr 2 _{O 3} Cr diffusion preventing layer 202 on the outside of the membrane To produce the compound Thus, since Cr gas is trapped by the Cr diffusion prevention layer 202, it is possible to prevent the Cr gas from reaching the interface between the air electrode and the electrolyte.

Further, when the Cr diffusion prevention layer 202 made of a complex oxide of a periodic metal fourth periodic metal element excluding the perovskite structure and Cr is provided on the surface of the current collecting body 201, the Cr diffusion prevention layer 202 is The Cr diffusion prevention layer made of the single element oxide just captures Cr gas and produces a compound of metal element and Cr, and can produce a compound of metal and Cr any more. First, a Cr ₂ O ₃ film is only formed near the interface between the current collector body 201 and the Cr diffusion prevention layer 202.
Thereby, Cr gas can be prevented from reaching the interface between the air electrode and the electrolyte.

  The current collecting member 20 of the present invention is a fuel cell stack in which a fuel cell is joined with an Ag-containing joining material, and a plurality of fuel cell current collecting members and fuel cells are alternately arranged in series. It can be preferably used for (not shown). Furthermore, it can be preferably used for a fuel cell (not shown) in which the fuel cell stack is accommodated in a storage container.

Hereinafter, the fuel battery cell 1 will be described.
As shown in FIG. 4, the fuel battery cell 1 includes a flat support substrate 10 in which a plurality of fuel gas passages 10 a are formed at appropriate intervals, and various members are provided on the support substrate 10. Have a structure.

  The support substrate 10 is composed of a flat portion and arcuate portions at both ends of the flat portion. A fuel electrode layer 2 is provided so as to cover one of a pair of opposed surfaces of the flat portion and arc-shaped portions on both sides thereof, and a dense solid electrolyte layer 3 is formed so as to cover the fuel electrode layer 2. The air electrode 4 is laminated on the solid electrolyte layer 3 so as to correspond to the fuel electrode layer 2. An interconnector 5 is formed on the other surface of the flat portion where the fuel electrode layer 2 and the solid electrode layer 3 are not stacked. As is clear from FIG. 4, the fuel electrode layer 2 and the solid electrolyte layer 3 extend to both sides of the interconnector 5 and are configured so that the surface of the support substrate 10 is not exposed to the outside.

In the fuel cell 1 having such a structure, the portion of the fuel electrode layer 2 facing the air electrode 4 operates as a fuel electrode to generate electric power. That is, by flowing an oxygen-containing gas such as air outside the air electrode 4 and flowing a fuel gas (hydrogen) through a gas passage in the support substrate 10 and heating to a predetermined operating temperature, Electricity is generated by causing the electrode reaction of (1) and the electrode reaction of the following formula (2), for example, at the portion that becomes the fuel electrode of the fuel electrode layer 2.
Air electrode: 1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte) (1)
Fuel electrode: O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻ (2)
The current generated by the power generation is collected through the interconnector 5 attached to the support substrate 10.

  Here, the support substrate 10 is required to be gas permeable in order to allow the fuel gas to permeate to the fuel electrode, and to be conductive in order to collect current via the interconnector. In order to satisfy such requirements and to avoid inconveniences caused by simultaneous firing, the support substrate 10 is composed of an iron group metal component and a specific rare earth oxide.

  The iron group metal component is for imparting conductivity to the support substrate 10 and may be an iron group metal alone, 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 changed to iron group because it is inexpensive and stable in fuel gas. It is preferable to contain as a component.

The rare earth oxide component is used for approximating the thermal expansion coefficient of the support substrate 10 to the stabilized zirconia forming the solid electrolyte layer 3, maintains a high conductivity, and is a solid electrolyte layer. In order to prevent diffusion to 3 etc., oxides Y ₂ O ₃ and Yb ₂ O ₃ containing rare earth elements are used in combination with the iron group component.

  In particular, the iron group component described above is included in the support substrate 10 in an amount of 35 to 65% by volume in terms of approximating the thermal expansion coefficient of the support substrate 10 to stabilized zirconia, and the rare earth oxide is included in the support substrate 10. It is preferably contained in an amount of 35 to 65% by volume.

  Since the support substrate 10 composed of the iron group metal component and the rare earth oxide as described above needs to have fuel gas permeability, the open porosity is usually 30% or more, particularly 35. It is preferable to be in the range of up to 50%. The conductivity of the support substrate 10 is preferably 300 S / cm or more, particularly 440 S / cm or more.

  The length of the flat portion of the support substrate 10 is usually 15 to 35 mm, the length of the arc-shaped portion (arc length) is about 3 to 8 mm, and the thickness of the support substrate 10 is (both surfaces of the flat portion). Is preferably about 2.5 to 5 mm.

The fuel electrode layer 2 causes the electrode reaction of the above-described formula (2), and is formed from a known porous conductive ceramic. For example, it is formed from ZrO ₂ in which a rare earth element is dissolved, and Ni and / or NiO. As ZrO ₂ (stabilized zirconia) in which the rare earth element is dissolved, the same one used for forming the solid electrolyte layer 3 described below is preferably used.

  Further, in the example of FIG. 4, the fuel electrode layer 2 extends to both sides of the interconnector 5, but the fuel electrode only has to be formed at a position facing the air electrode 4, For example, the fuel electrode layer 2 may be formed only on the flat portion on the side where the air electrode 4 is provided.

The solid electrolyte layer 3 provided on the fuel electrode layer 2 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 air electrode 4 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.

The interconnector 5 provided on the support substrate 10 is generally made of a lanthanum chromite perovskite oxide (LaCrO ₃ oxide). Further, in order to prevent leakage of the fuel gas passing through the inside of the support substrate 10 and the oxygen-containing gas passing through the outside of the support substrate 10, such conductive ceramics must be dense, for example 93% or more, particularly 95%. It is preferable to have the above relative density.

  A P-type semiconductor layer 14 is preferably provided on the outer surface (upper surface) of the interconnector 5. A conductive current collecting member (not shown) is connected to the interconnector 5. However, if the current collecting member is directly connected to the interconnector 5, the potential drop increases due to non-ohmic contact, and the current collecting is performed. Performance will be degraded. As such a P-type semiconductor, a transition metal perovskite oxide can be exemplified.

Here, the manufacturing method of a fuel cell is demonstrated.
First, a slurry is prepared by mixing an iron group metal such as Ni or its oxide powder, a rare earth oxide powder such as Y ₂ O ₃ , an organic binder, and a solvent, and extrusion using this slurry. A support substrate molded body is produced by molding and dried.

  Next, a fuel electrode layer forming 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 electrode layer is prepared using this slurry. Further, instead of producing a sheet for the fuel electrode layer, a paste in which the fuel electrode forming material is dispersed in a solvent is applied to a predetermined position of the formed support substrate and dried, and then the fuel electrode layer is formed. A coating layer may be formed.

  Furthermore, a stabilized zirconia powder, an organic binder, and a solvent are mixed to prepare a slurry, and a solid electrolyte layer sheet is prepared using this slurry.

  The support substrate molded body, the fuel electrode sheet, and the solid electrolyte layer sheet formed as described above are laminated so as to have a layer structure as shown in FIG. 4, for example, and dried. In this case, when the coating layer for the fuel electrode layer is formed on the surface of the support substrate molded body, only the solid electrolyte layer sheet may be laminated on the support substrate molded body and dried.

Thereafter, the interconnector material (e.g., LaCrO ₃ based oxide powder), an organic binder and a solvent were mixed to prepare a slurry, to produce the interconnector sheet.

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

Next, the above-mentioned fired laminate is subjected to binder removal treatment, and co-fired at 1300 to 1600 ° C. in an oxygen-containing atmosphere, and an air electrode forming material (for example, LaFeO ₃₎ 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. Bake with.
A fuel cell is produced through the above processes.

  The fuel cell stack is formed by arranging a plurality of the above fuel cells together with the current collecting member in series on the manifold, and sealing the connection between the fuel cells and the manifold with glass or the like.

  The fuel cell is prepared by arranging the plurality of cell stacks in a storage container and piping a fuel gas introduction pipe and an air introduction pipe for sending the fuel cell to the fuel cell for use in power generation.

Hereinafter, the fuel cell and the current collecting member were actually produced, and the current collecting member of the present invention was evaluated.
First, in order to create a fuel cell, a volume ratio after firing NiO powder or Ni powder having an average particle size of 0.5 μm and Y ₂ O ₃ powder (average particle size is 0.8 to 1.0 μm). However, after firing, NiO was mixed at 65 volume% in terms of Ni, and Y ₂ O ₃ was mixed at 35 volume%.

  A support substrate slurry formed by mixing the above-mentioned mixed powder with a pore-forming agent, an organic binder (polyvinyl alcohol) and water (solvent) is extruded into a rectangular parallelepiped shape, and a flat support substrate molded body is obtained. Prepared and dried. The obtained molded body was debindered and calcined at 1000 ° C. in the air.

Next, for forming a fuel electrode layer using a slurry obtained by mixing ZrO ₂ (YSZ) powder containing 8 mol% Y ₂ O ₃ , NiO powder, organic binder (acrylic resin), and solvent (toluene). A sheet was prepared, and a sheet for a solid electrolyte layer was prepared using a slurry in which the YSZ powder, an organic binder (acrylic resin), and a solvent made of toluene were mixed, and these sheets were laminated. The laminated sheet was wound around the support substrate molded body so that both ends thereof were separated from each other with a predetermined interval, and dried.

On the other hand, an interconnector sheet was prepared using a slurry in which an LaCrO ₃ oxide powder having an average particle diameter of 2 μm, an organic binder (acrylic resin), and a solvent (toluene) was mixed. A laminated sheet for sintering was prepared by laminating on the exposed portion of the support substrate molded body in the sheet, and comprising a support substrate molded body, a fuel electrode layer sheet, and a solid electrolyte layer sheet. Next, the laminated sheet for sintering was subjected to binder removal treatment and co-fired at 1500 ° C. in the atmosphere.

The obtained sintered body was immersed in a paste made of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ (LSCF) powder having an average particle diameter of 2 μm and a solvent (normal paraffin). The air electrode coating layer is provided on the surface of the solid electrolyte layer formed on the sintered body, and at the same time, the paste is applied to the outer surface of the interconnector formed on the sintered body, and the P-type semiconductor coating layer is formed. Was further baked at 1150 ° C. to produce a fuel cell as shown in FIG.

Further, the current collecting member is formed by first processing a 0.4 mm-thick Fe—Cr heat-resistant alloy plate into a comb blade shape, and alternately bending adjacent blades to the opposite side, thereby collecting the current as shown in FIG. The main body was made and the corners of the current collector main body were chamfered with a sandblast machine. Thereafter, Fe ₂ O ₃ , Co ₃ O ₄ or Ni powder, an acrylic binder, and toluene as a diluent are mixed at a weight ratio of 3: 2: 1.5, and the raw material for the Cr diffusion prevention layer is prepared. (Raw material 1) was produced. Similarly, a powder of La _0.6 Sr _0.4 Co _0.4 Fe _0.6 O ₃ (LSCF) was prepared in a weight ratio of 3: 2: 1 to toluene as an acrylic binder and diluent. A raw material (raw material 2) for the conductive ceramic layer was prepared. And the raw material 1 was dipped in the current collection main body of the said shape. Thereafter, the binder was removed at 130 ° C. for 1 hour and at 500 ° C. for 2 hours, and then baked in a furnace at 1050 ° C. for 2 hours. Then, the raw material 2 was apply | coated and the baking was performed by the same temperature specification. When the raw material 1 is Fe ₂ O ₃ , the Cr diffusion prevention layer formed by the raw material 1 is Fe ₂ O ₃ or a composite oxide of Fe and Cr. When the raw material 1 is NiO, the raw material 1 The Cr diffusion prevention layer formed by NiO or a composite oxide of Ni and Cr. When the raw material 1 is Co ₃ O ₄ , the Cr diffusion prevention layer formed by the raw material 1 is Co ₃ O ₄ or Co And a complex oxide of Cr. At this time, the thickness of the Cr diffusion preventing layer was 20 μm, and the thickness of the conductive ceramic layer was 20 μm.

Then, in order to perform an evaluation test described later, as shown in FIG. 6, an Ag-Pd-based paste (becomes a bonding material 17 by a heat treatment described later) on the surface of the current collecting member 20 on which the Cr diffusion preventing layer is formed. The same Ag—Pd paste was applied to the air electrode of the fuel cell and the surface of the P-type semiconductor, and the current collecting member 20 was disposed on the surface of the air electrode 4. In addition, the mesh 30 made of Pt to which the current application lead wire 301 and the measurement lead wire 302 are connected is disposed so as to sandwich the fuel cell and the current collecting member 20, and an insulating tube is provided so that the mesh 30 does not fall. These were bound with a Pt wire 31 coated with 32, placed in a test furnace in this state, heated to 850 ° C. and held for 2 hours. During the holding, first, 200 cc / min of nitrogen and 100 cc / min of hydrogen were flown into the fuel cell. Thereafter, the amount was gradually changed, and after 2 hours, nitrogen was shut off and hydrogen was controlled to flow at 200 cc / min. This state was maintained for another 6 hours. Thereafter, the furnace temperature was lowered to 250 ° C., and a current of 8.98 A was passed between the electrodes of the fuel battery cell to generate power. And the voltage after 1000 hours was compared with the sample (No. 1 and No. 2) in which the Cr diffusion prevention layer is not formed, and deterioration was confirmed. The results are shown in Table 1.

  As can be seen from Table 1, the sample No. in which the Cr diffusion preventing layer and the conductive ceramic layer were not provided. No. 1 has a voltage drop rate of 41.2% after 1000 hours, and sample No. 1 in which only the conductive ceramic layer was provided without providing the Cr diffusion prevention layer. 2 had a bad voltage drop rate of 10.2% after 1000 hours. 3 to 8 were good results with a voltage drop rate of 10% or less after 1000 hours. Thus, by providing the Cr diffusion preventing layer on the surface of the current collecting member, Cr poisoning can be eliminated and the voltage drop rate can be set to a good value. Sample No. Samples Nos. 3 to 5 have sample nos. The voltage drop rate which may be compared with 6-8 is obtained.

It is a perspective view which shows an example of the current collection member by which Cr diffusion prevention layer of this invention was coat | covered. It is the sectional view on the AA line shown in FIG. It is a BB line partial sectional view shown in FIG. It is explanatory drawing of the fuel cell used together with the current collection member of this invention. It is explanatory drawing of the fuel cell stack of this invention. It is explanatory drawing of the evaluation test of the current collection member of this invention.

Explanation of symbols

20 ... Current collecting member 201 ... Current collecting body 202 ... Cr diffusion preventing layer

Claims (7)

A single element oxide of the fourth periodic metal element of the periodic table excluding the perovskite structure or a complex oxide of the fourth periodic metal element and Cr of the periodic table on the surface of the current collector body made of an alloy containing Cr A current collecting member for a fuel cell, comprising a Cr diffusion preventing layer comprising: A layer containing a fourth periodic metal element or a single element oxide excluding the perovskite structure is formed and baked on the surface of a current collecting body made of an alloy containing Cr. The current collector for a fuel cell according to claim 1. The current collecting member for a fuel cell according to claim 1 or 2, wherein the fourth periodic metal element of the periodic table is composed of any one selected from the group consisting of Fe, Co, and Ni. The current collecting member for a fuel cell according to any one of claims 1 to 3, wherein a conductive ceramic layer is further provided outside the Cr diffusion preventing layer. The fuel cell current collecting member according to any one of claims 1 to 4 is interposed between the plurality of fuel cells, and the plurality of fuel cells and the fuel cell current collecting member are joined together with Ag. A fuel cell stack formed by joining materials together and electrically connecting the plurality of fuel cells in series. A fuel cell comprising the fuel cell stack according to claim 5 housed in a housing container. After chamfering the edge portion of the current collector body made of an alloy containing Cr, a single element oxide of the fourth periodic metal element in the periodic table excluding the perovskite structure on the surface of the current collector body or the periodic table A method for producing a current collecting member for a fuel cell, comprising providing a Cr diffusion preventing layer comprising a complex oxide of a four-period metal element and Cr.

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