JP2007087747A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell capable of preventing the generation of a pin hole in an electrolyte layer. <P>SOLUTION: The solid oxide fuel cell (10) includes an electrolyte layer (11), a pair of porous electrode layers (12, 13) pinching the electrolyte layer (11), and an interlayer (14) arranged between one of the porous electrode layers (12) and the electrolyte layer (11). The interlayer (14) includes a component material of the one of the porous electrodes (12), and pores (14a) in the interlayer (14) have an average particle size of 1μm or less. With this, the electrolyte layer (11) of a uniform film thickness can be formed on the interlayer (14), so that the generation of pin holes in the electrolyte layer (11) can be prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell including an electrolyte layer and a pair of porous electrode layers sandwiching the electrolyte layer.

  Solid oxide fuel cells (SOFCs) are currently being developed as third-generation power generation fuel cells, and three types are proposed: cylindrical, monolith, and flat plate stack. Each of them has a laminate in which a solid electrolyte (electrolyte layer) made of an oxide ion conductor is sandwiched between an air electrode layer (cathode) and a fuel electrode layer (anode). Usually, the single cell which consists of this laminated body is laminated | stacked alternately with a separator, and the fuel cell stack is comprised (for example, refer patent document 1).

In the solid oxide fuel cell, oxygen (air) is supplied to the air electrode layer side, and fuel gas (H ₂ , CO, CH _4, etc.) is supplied to the fuel electrode layer side. The air electrode layer and the fuel electrode layer are both porous layers so that the gas can reach the interface with the electrolyte layer. Oxygen supplied to the air electrode layer passes through the pores in the air electrode layer and reaches the vicinity of the interface with the electrolyte layer, and receives electrons from the air electrode layer at this portion to form oxide ions (O ²⁻ ). Ionized. The oxide ions move (diffuse) in the electrolyte layer toward the fuel electrode layer. The oxide ions that reach the vicinity of the interface with the fuel electrode layer react with the fuel gas at this portion to become reaction products (H ₂ O, CO _2, etc.), and simultaneously release electrons. The electrons reach the air electrode layer after performing electrical work through an external electric circuit.

The electrode reaction that occurs on the air electrode layer side, that is, the ionization reaction from oxygen molecules to oxide ions (1 / 2O ₂ + 2e ⁻ → O ²⁻ ), involves the three components of oxygen molecules, electrons, and oxide ions. It occurs at a three-phase interface between an electrolyte layer that carries oxide ions, an air electrode layer that carries electrons, and a gas phase (air) that supplies oxygen molecules. Similarly, on the fuel electrode layer side, an electrode reaction occurs at the three-phase interface of the electrolyte layer, the fuel electrode layer, and the gas phase (fuel gas). Therefore, it is considered that increasing the three-phase interface is advantageous for smooth progress of the electrode reaction.

  The electrolyte layer is a moving medium for oxide ions and also functions as a partition wall for preventing the fuel gas and air from coming into direct contact with each other. Therefore, the electrolyte layer has a dense structure that is impermeable to gas. This electrolyte layer is composed of a material that has high oxide ion conductivity, is chemically stable under conditions from the oxidizing atmosphere on the air electrode layer side to the reducing atmosphere on the fuel electrode layer side, and is resistant to thermal shock. As materials satisfying these requirements, stabilized zirconia (hereinafter abbreviated as “YSZ”) added with yttria, scandia stabilized zirconia (hereinafter abbreviated as “ScSZ”), samaria doped ceria ( Hereinafter, a metal oxide film made of gadolinium-doped ceria (hereinafter abbreviated as “GDC”), lanthanum garade, or the like is generally used.

On the other hand, both the air electrode layer and the fuel electrode layer need to be made of a material having high electron conductivity. Since the material of the air electrode layer must be chemically stable in an oxidizing atmosphere at around 1000 ° C., metals are inappropriate. For example, perovskite type oxide materials having electron conductivity, specifically LaMnO ₃ or LaCoO ₃ or a solid solution in which a part of La in these materials is substituted with Sr, Ca or the like is generally used. Further, as a material for the fuel electrode layer, a metal such as Ni or a cermet such as Ni—YSZ is generally used. The metal such as Ni is usually in an oxide state such as nickel oxide when the fuel electrode layer is formed, but is reduced to metal (Ni or the like) during operation of the fuel cell (during power generation).

  As this type of solid oxide fuel cell, for example, on a porous support substrate that also serves as one electrode layer (fuel electrode layer or air electrode layer), a thin-film electrolyte layer and the other electrode layer (fuel electrode layer or And an air electrode layer) are formed sequentially (see, for example, Patent Document 2). In order for the electrolyte layer to function as a gas partition, it is desirable that the electrolyte layer be densely formed. In addition, in order for the electrolyte layer to function as an ion conductive film, it is desirable to make the film thickness thinner. .

As a method for forming the electrolyte layer, for example, there is a method in which a slurry containing electrolyte material powder is applied on a porous electrode layer by a screen printing method or the like, and these are sintered to form an electrolyte layer. In this method, a dense electrolyte layer is generally formed by sintering at 1200 to 1700 ° C. At this time, in consideration of the difference in thermal shrinkage between the porous electrode layer and the electrolyte layer, it is important to prevent the porous electrode layer from being damaged and to form the electrolyte layer densely. For example, Patent Document 3 proposes a method of forming an electrolyte layer by applying a slurry containing a plurality of types of powders having different specific surface areas (average particle diameters). According to this method, economic efficiency and mass productivity are improved, and it is easy to increase the area of the electrolyte layer. Patent Document 4 proposes a slurry capable of forming a homogeneous and dense electrolyte layer.
JP 2004-79332 A JP 2004-158313 A JP 2001-23653 A JP 2002-15757 A

  However, when forming the electrolyte layer on the porous electrode layer, if the thickness of the electrolyte layer is reduced for the purpose of improving the ionic conductivity of the electrolyte layer, depending on the pore size of the porous electrode layer, May cause pinholes in the resulting electrolyte layer. If pinholes are generated in the electrolyte layer, the electrolyte layer may not function as a gas partition.

  The present invention has been made in view of such circumstances, and provides a solid oxide fuel cell capable of preventing the occurrence of pinholes in an electrolyte layer.

The solid oxide fuel cell of the present invention is a solid oxide fuel cell comprising an electrolyte layer and a pair of porous electrode layers sandwiching the electrolyte layer,
Including an intermediate layer disposed between the one porous electrode layer and the electrolyte layer;
The intermediate layer includes a constituent material of the one porous electrode layer,
The pores in the intermediate layer have an average diameter of 1 μm or less.

  The solid oxide fuel cell of the present invention includes an intermediate layer disposed between one porous electrode layer and the electrolyte layer, and the average diameter of pores in the intermediate layer is 1 μm or less. An electrolyte layer having a uniform film thickness can be formed on the layer. Thereby, generation | occurrence | production of the pinhole in an electrolyte layer can be prevented.

  The solid oxide fuel cell of the present invention includes an electrolyte layer, a pair of porous electrode layers sandwiching the electrolyte layer, and an intermediate layer disposed between the one porous electrode layer and the electrolyte layer. The intermediate layer contains a constituent material of the one porous electrode layer. The pores in the intermediate layer have an average diameter of 1 μm or less (preferably 0.5 μm or less). By having the said structure, the said electrolyte layer of a uniform film thickness can be formed on the said intermediate | middle layer. Thereby, when forming an electrolyte layer, for example, generation of pinholes in the electrolyte layer can be prevented. Therefore, for example, even when the electrolyte layer is formed thin, the gas impermeability of the electrolyte layer can be maintained. The average diameter can be measured by, for example, cross-sectional observation with a scanning electron microscope (SEM), gas adsorption measurement, mercury intrusion, small-angle X-ray scattering, and the like. When the intermediate layer includes an oxide ion conductor, the intermediate layer may be a dense film. This is because the intermediate layer can play the same role as the electrolyte layer. Of course, when the intermediate layer is a porous layer, the intermediate layer can play the same role as the porous electrode layer.

  As the material constituting the electrolyte layer, for example, a composite metal oxide containing at least one selected from zirconium oxide, cerium oxide and lanthanum oxide, which is widely known as an electrolyte material for a solid oxide fuel cell, is used. it can. Specific examples of such composite metal oxides include YSZ, ScSZ, SDC, GDC, lanthanum garade, and the like. The composite metal oxide preferably has a fluorite-type or perovskite-type crystal structure from the viewpoint of oxide ion conductivity.

  The thickness of the electrolyte layer is usually 10 nm to 50 μm, preferably 10 nm to 10 μm, more preferably 100 nm to 5 μm, and most preferably 100 nm to 1 μm. When the thickness is less than 10 nm, the pair of porous electrode layers may come into contact with each other. On the other hand, if the thickness exceeds 50 μm, the oxide ion conductivity of the electrolyte layer may be reduced.

  As the pair of porous electrode layers, a fuel electrode layer and an air electrode layer can be used. In this case, the intermediate layer may be disposed between at least one of the fuel electrode layer and the electrolyte layer and between the air electrode layer and the electrolyte layer.

  As the material for the fuel electrode layer, for example, a mixture of an oxide ion conductor such as a ceramic powder material and a metal catalyst can be used. As the oxide ion conductor, one having a fluorite-type or perovskite-type crystal structure can be preferably used. Examples of those having a fluorite-type crystal structure include SDC, GDC, ScSZ, and YSZ. Examples of those having a perovskite type crystal structure include lanthanum galide oxides doped with strontium and magnesium. As a metal constituting the metal catalyst, a material that is stable in a reducing atmosphere and has a hydrogen oxidation activity can be used. For example, nickel, iron, cobalt, or the like, or a noble metal (platinum, ruthenium, palladium, or the like) ) Etc. can be used. Among the above metals, nickel having high hydrogen oxidation activity is preferable. Nickel has higher reforming performance of fuel gas such as methane than other metals, and has a lower overvoltage (resistance) than other metals. Therefore, it is preferable to form the fuel electrode layer with a mixture of an oxide ion conductor and nickel oxide. Note that the mixture of the oxide ion conductor and nickel oxide may be a mixture of both, or a modification of the oxide ion conductor to nickel oxide. Moreover, the oxide ion conductor mentioned above may be used individually by 1 type, and may mix and use 2 or more types. The porosity of the fuel electrode layer is usually about 20 to 50%, and the average diameter of the pores in the fuel electrode layer is usually about 3 to 100 μm. The thickness of the fuel electrode layer is usually about 5 to 50 μm.

As the material of the air electrode layer, for example, a metal oxide having a perovskite crystal structure can be used. Specifically, (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Sr) (Fe, Co , Ni) O _{3 and the} like, and (La, Sr) MnO ₃ is preferably used from the viewpoint of stability in an oxidizing atmosphere. One kind of the metal oxides described above may be used alone, or two or more kinds may be mixed and used. Moreover, noble metals, such as platinum, ruthenium, and palladium, can also be used as a material for forming the air electrode layer. The porosity of the air electrode layer is usually about 20 to 50%, and the average diameter of the pores in the air electrode layer is usually about 3 to 100 μm. The thickness of the air electrode layer is usually about 5 to 50 μm.

  In this invention, it is preferable that the thickness of the said intermediate | middle layer is 0.05-10 micrometers, and it is more preferable that it is 0.1-5 micrometers. If it is in the said range, generation | occurrence | production of the pinhole in the said electrolyte layer can be prevented, without reducing the diffusibility of the gas or oxide ion in the said intermediate | middle layer.

  In the present invention, when the one porous electrode layer in contact with the intermediate layer is a fuel electrode layer containing nickel oxide, the intermediate layer comprises nickel oxide and a metal oxide constituting the electrolyte layer. It is preferable to contain. This is because adhesion between the fuel electrode layer and the intermediate layer and between the intermediate layer and the electrolyte layer is enhanced. In this case, the intermediate layer includes a first intermediate layer in contact with the fuel electrode layer and a second intermediate layer in contact with the electrolyte layer, and the mass content of nickel oxide in the first intermediate layer. Is an intermediate layer in which the mass content of nickel oxide in the fuel electrode layer is less than or equal to the mass content of nickel oxide in the second intermediate layer is less than the mass content of nickel oxide in the first intermediate layer. There may be. The intermediate layer serves as a buffer layer that eliminates thermal distortion caused by the difference in thermal expansion coefficient between the one porous electrode layer and the electrolyte layer, and can prevent deformation of the solid oxide fuel cell, for example. Because. In order to ensure the above effects, the first and second intermediate layers preferably have a thickness in the range of 0.025 to 9.975 μm.

  Next, an example of a preferred method for producing the above-described solid oxide fuel cell of the present invention will be described.

  In this method, the intermediate layer is formed by bringing the intermediate layer forming solution containing the metal source or the intermediate layer forming sol into contact with the heated porous electrode layer substrate (hereinafter, this forming method is referred to as “contact method”). Sometimes). The porous electrode layer substrate may be a fuel electrode layer substrate or an air electrode layer substrate. According to this method, the intermediate layer having an average pore diameter of 1 μm or less can be formed. In addition, it does not specifically limit about the manufacturing method of the said porous electrode layer board | substrate, For example, the method etc. which were disclosed by the said patent document 2 can be used. In addition, before forming the intermediate layer by a contact method, the main surface of the porous electrode layer substrate that contacts the intermediate layer may be polished by mechanical polishing or the like. In this case, for example, when the arithmetic average roughness Ra (based on JIS B0601) of the main surface is polished to 10 μm or less, the formation of the electrolyte layer described later more reliably prevents the occurrence of pinholes in the electrolyte layer. it can.

  The metal source only needs to include a metal constituting the porous electrode layer substrate. For example, a metal salt, a metal complex in which an inorganic substance or an organic substance is coordinated with a metal ion, an organometallic compound having a metal-carbon bond in the molecule, or the like can be used. The said metal source may be used individually by 1 type, and may mix and use 2 or more types.

  Examples of the metal salt include chlorides, nitrates, sulfates, perchlorates, acetates, phosphates, bromates and the like containing the above metal elements. Among these, in this method, it is preferable to use chloride, nitrate, and acetate. This is because these compounds are easily available as general-purpose products.

  Examples of the metal complex and the organometallic compound include a metal acetylacetonate compound, a metal chelate compound, and a metal alkoxide.

  The solvent used for the intermediate layer forming solution is not particularly limited as long as it can dissolve the metal source described above. For example, lower alcohols having a total carbon number of 5 or less, such as methanol, ethanol, 1-propanol, 2-propanol, and butanol, water, toluene, a mixed solvent thereof and the like can be used.

  The concentration of the metal source in the intermediate layer forming solution is usually 0.001 to 10 mol / liter, and preferably 0.01 to 1 mol / liter. When the concentration is less than 0.001 mol / liter, the formation reaction of the intermediate layer is difficult to occur and the desired intermediate layer may not be obtained. When the concentration exceeds 10 mol / liter, a precipitate is formed. Because there is a possibility of doing.

  As the solvent for the intermediate layer forming sol, a solvent capable of hydrolyzing a metal source is preferable. For example, a solvent containing an alcohol such as ethanol is preferable. The other conditions (for example, the concentration of the metal source) of the intermediate layer forming sol are the same as those of the intermediate layer forming solution. In addition, as a metal source hydrolyzed, the metal alkoxide containing the metal which comprises the said porous electrode layer board | substrate is preferable.

  When the porous electrode layer substrate is a fuel electrode layer substrate, for example, a metal source including a metal constituting an oxide ion conductor such as a ceramic powder material and a metal constituting a metal catalyst is used. be able to.

  Examples of the metal source containing the metal constituting the oxide ion conductor include cerium (III) acetylacetonate, cerium chloride, cerium acetate, cerium ammonium nitrate (III), cerium nitrate (III), and diammonium cerium nitrate (IV). , Cerium (III) sulfate, cerium (IV) sulfate, samarium (III) chloride, samarium (III) acetylacetonate, samarium (III) nitrate, gadolinium nitrate, zirconium (IV) chloride, zirconium chloride, zirconium oxide, Zirconium (IV) ethoxide, zirconium sulfate, zirconium normal propyrate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium acetylcetonate bisethylacetoacetate, di Konium acetate, zirconium monostearate, scandium acetate, yttrium chloride, yttrium acetate, yttrium nitrate, yttrium fluoride, lanthanum chloride, lanthanum acetate, lanthanum nitrate, lanthanum acetylacetonate, gallium (III) trifluoromethanesulfonate, strontium chloride Strontium acetate, strontium bromide, strontium nitrate, strontium sulfate, magnesium chloride, magnesium perchlorate, magnesium acetate, magnesium nitrate, magnesium lactate, magnesium sulfate, magnesium phosphate and the like.

  As the metal source containing the metal constituting the metal catalyst, nickel chloride, nickel nitrate, nickel (II) acetylacetonate dihydrate, nickel acetate (II), nickel sulfide (II), iron (II) chloride, Iron (III) chloride, iron (III) perchlorate, iron (III) citrate, iron (II) acetate, iron (III) nitrate, iron (II) acetylacetonate, iron (III) acetylacetonate, iron (III) benzoylacetonate, iron (II) lactate, iron (II) fluoride, iron (II) sulfide, iron (II) sulfate, iron (II) sulfate, iron (III) sulfate, iron (II) phosphate , Cobalt chloride (II), cobalt (II) acetylacetonate, cobalt (III) acetylacetonate, cobalt acetate (II), cobalt nitrate (II), cobalt stearate, cobalt chloride (II) ammonium, cobalt nitrite ( III) Sodium, sulfur Cobalt (II), chloroplatinic acid, platinum (IV) chloride, ruthenium trichloride, ammonium hexachlororuthenate (IV), palladium (II) chloride, palladium (II) acetate, palladium (II) nitrate, palladium chloride (II) ) Sodium and the like.

  When the porous electrode layer substrate is an air electrode layer substrate, examples of the metal source include iron (II) chloride, iron (III) chloride, iron (III) perchlorate, and iron (III) citrate. , Iron (II) acetate, iron (III) nitrate, iron (II) acetylacetonate, iron (III) acetylacetonate, iron (III) benzoylacetonate, iron (II) lactate, iron (II) fluoride, Iron sulfide (II), ammonium iron sulfate (II), iron sulfate (II), iron sulfate (III), iron phosphate (II), cobalt chloride (II), cobalt (II) acetylacetonate, cobalt (III) acetyl Acetonate, cobalt (II) acetate, cobalt (II) nitrate, cobalt stearate, cobalt (II) ammonium chloride, cobalt (III) sodium nitrite, cobalt (II) sulfate, manganese (III) acetylacetonate, permanganese Potassium acid, acetic acid Ngan (III), manganese acetate (II), manganese nitrate (II), manganese sulfate (II), lanthanum chloride, lanthanum acetate, lanthanum nitrate, lanthanum acetylacetonate, strontium chloride, strontium acetate, strontium bromide, strontium nitrate, Strontium sulfate or the like can be used.

  Next, the contact method of the intermediate layer forming solution or the intermediate layer forming sol (hereinafter referred to as “intermediate layer forming solution”) on the porous electrode layer substrate in this method will be described. The contact method in the present method is not particularly limited, but may be a method that does not lower the temperature of the porous electrode layer substrate when the intermediate layer forming liquid and the porous electrode layer substrate are in contact with each other. preferable. This is because when the temperature of the porous electrode layer substrate is lowered, the formation reaction of the intermediate layer is difficult to occur, and a desired intermediate layer may not be obtained. Examples of the method of not lowering the temperature of the porous electrode layer substrate include a method of bringing the intermediate layer forming liquid into contact with the porous electrode layer substrate as droplets. At this time, the droplet preferably has a small diameter of, for example, about 0.1 to 1000 μm. If the diameter of the droplet is within the above range, the solvent of the intermediate layer forming liquid can be instantly evaporated, and the temperature drop of the porous electrode layer substrate can be suppressed, and the droplet diameter is small. This is because a homogeneous intermediate layer can be obtained.

  The method of bringing the droplet of the intermediate layer forming liquid into contact with the porous electrode layer substrate is not particularly limited. For example, the method described above is performed on the porous electrode layer substrate by spraying the intermediate layer forming liquid. The method for contacting the intermediate layer forming liquid or the method for contacting the intermediate layer forming liquid on the porous electrode layer substrate by passing the porous electrode layer substrate through a space in which the liquid for forming the intermediate layer is mist-shaped. And the like. The method of contacting the intermediate layer forming liquid onto the porous electrode layer substrate in this method may be a method other than the method of bringing the intermediate layer forming liquid into contact with the porous electrode layer substrate as droplets. . For example, the surface of the porous electrode layer substrate may be brought into direct contact with the liquid surface of the intermediate layer forming liquid.

  Examples of the method of spraying the intermediate layer forming liquid onto the porous electrode layer substrate include a method of spraying using a spray device or the like. When spraying using the said spray apparatus etc., the diameter of a droplet is 0.1-1000 micrometers normally, and it is preferable that it is 0.5-300 micrometers especially. This is because if the diameter of the droplet is within the above range, a decrease in the temperature of the porous electrode layer substrate can be suppressed, and a homogeneous intermediate layer can be obtained.

  Further, the spray gas of the spray device is not particularly limited as long as it does not inhibit the formation of the intermediate layer, and examples thereof include air, nitrogen, argon, helium, oxygen, etc. Gases such as nitrogen, argon, and helium are preferable. Further, the spray amount of the intermediate layer forming liquid is usually 0.001 to 1 liter / minute, and in order to obtain a more uniform intermediate layer, it is 0.001 to 0.05 liter / minute. preferable. Under the present circumstances, the thickness of the intermediate | middle layer formed can be arbitrarily adjusted by spraying repeatedly. The spray device may be a fixed device, a movable device, a device that sprays the liquid by rotation, a device that sprays the liquid by pressure, and the like. As such a spray device, a commonly used spray device can be used, and for example, hand spray (manufactured by ASONE) or the like can be used. Moreover, you may spray using a spray gun, an air spray, an airless spray, an ultrasonic spray apparatus, an electrostatic spray, a rotary atomization spray, a spray vial, a nebulizer, etc.

  When using a method in which the porous electrode layer substrate is passed through a space in which the liquid for forming the intermediate layer is made into a mist, the diameter of the droplet is usually 0.01 to 300 μm, and in particular, 1 to 100 μm. preferable. This is because if the diameter of the droplet is within the above range, a decrease in the temperature of the porous electrode layer substrate can be suppressed, and a homogeneous intermediate layer can be obtained. At this time, the thickness of the intermediate layer to be formed can be arbitrarily adjusted by allowing the porous electrode layer substrate to pass through or repeatedly passing it.

  In this method, in order to promote the formation reaction of the intermediate layer, the porous electrode layer substrate is heated when the intermediate layer forming liquid is brought into contact with the porous electrode layer substrate. For example, the porous electrode layer substrate may be heated to an intermediate layer formation temperature or higher. Here, the “intermediate layer forming temperature” is the lowest temperature at which the metal element constituting the metal source is combined with oxygen to form an intermediate layer on the porous electrode layer substrate. The intermediate layer forming temperature varies greatly depending on the type of the metal source and the composition of the intermediate layer forming liquid such as a solvent, and is usually in the range of 150 to 800 ° C. In particular, from the viewpoint of productivity, it is preferable to select the type of metal source, the solvent, and the like so that the temperature is within a range of 400 to 550 ° C.

  The intermediate layer forming temperature can be measured by the following method. First, an intermediate layer forming liquid containing a desired metal source is prepared. Next, an intermediate layer is formed by bringing the intermediate layer forming liquid into contact with the porous electrode layer substrate while changing the surface temperature of the porous electrode layer substrate by heating the porous electrode layer substrate. Among the surface temperatures of the porous electrode layer substrate that can be measured, the lowest surface temperature is measured. This minimum surface temperature can be used as the “intermediate layer forming temperature” in the present specification. At this time, whether or not the intermediate layer has been formed is determined from the result obtained by, for example, an X-ray diffraction apparatus (RINT-1500, manufactured by Rigaku) when the obtained intermediate layer has crystallinity. Is an amorphous film, for example, it can be determined from a result obtained by a photoelectron spectroscopic analyzer (manufactured by VG Scientific, ESCALAB 200i-XL).

  Further, the heating method of the porous electrode layer substrate is not particularly limited, and examples thereof include a heating method using a hot plate, oven, firing furnace, infrared lamp, hot air blower, etc. Use of a plate is preferable because the temperature of the porous electrode layer substrate can be reliably maintained at a desired temperature.

  In this method, the intermediate layer forming liquid may be brought into contact with the porous electrode layer substrate in an oxidizing gas atmosphere. This is because the formation reaction of the intermediate layer is promoted because oxidation of the metal ion or the like formed by dissolving the metal source is rapidly performed. Such an oxidizing gas is not particularly limited as long as it can oxidize metal ions and the like obtained by dissolving the metal source. For example, oxygen, ozone, nitrous acid gas, nitrogen dioxide, chlorine dioxide In particular, oxygen and ozone are preferably used, and ozone is particularly preferably used. This is because it is easy to obtain industrially and can realize cost reduction.

  Further, in the present method, the obtained intermediate layer may be washed and dried. The cleaning of the intermediate layer is performed to remove impurities existing on the surface of the intermediate layer. As a washing | cleaning method, the method etc. which wash | clean using the solvent used for the liquid for intermediate | middle layer formation can be mentioned, for example. Moreover, when drying the said intermediate | middle layer, you may dry by leaving at normal temperature, but you may dry in heating apparatuses, such as oven.

  Next, a method for forming an electrolyte layer on the intermediate layer obtained by the above-described method will be described. The method for forming the electrolyte layer is not particularly limited. For example, a paste containing the material for the electrolyte layer is applied on the intermediate layer by a coating method such as a screen printing method or a doctor blade method, and these are baked. The electrolyte layer may be formed by bonding. Further, the electrolyte layer may be formed by the same contact method as described above. When the electrolyte layer is formed by a contact method, the electrolyte layer can be formed under the same conditions as those described above, except that a metal source containing a metal constituting the electrolyte layer is used. According to the contact method, for example, a heat treatment step at a high temperature of 1000 ° C. or higher is not required, so that the electrolyte layer can be easily densified. Further, when the electrolyte layer is formed directly on the porous electrode layer substrate by the contact method, the above-described pinhole is relatively easily generated. However, by providing the intermediate layer by the above-described method, the pin in the electrolyte layer is surely formed. The generation of holes can be prevented.

  Next, a method for forming the other porous electrode layer (fuel electrode layer or air electrode layer) on the electrolyte layer obtained by the above-described method will be described. The method for forming the other porous electrode layer is not particularly limited, and it may be formed by the contact method described above or by a conventional method. In the case of forming by a conventional method, for example, a paste is prepared by adding the material of the electrode layer and a binder to a solvent, and this paste is applied onto the electrolyte layer by a coating method such as a screen printing method or a doctor blade method. The fuel electrode layer or the air electrode layer may be formed on the electrolyte layer by, for example, sintering these at a temperature of 1000 ° C. or higher for several hours. With the above method, the solid oxide fuel cell of the present invention is obtained.

  The manufacturing method of the solid oxide fuel cell of the present invention has been described above, but the above manufacturing method is an example of a preferable manufacturing method of the solid oxide fuel cell of the present invention, and the solid oxide fuel cell of the present invention. You may manufacture a fuel cell by methods other than the said manufacturing method.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings as appropriate.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 to be referred to is a schematic cross-sectional view showing a solid oxide fuel cell according to a first embodiment of the present invention.

  As shown in FIG. 1, the solid oxide fuel cell 10 according to the first embodiment includes an electrolyte layer 11, a fuel electrode layer 12 and an air electrode layer 13 that sandwich the electrolyte layer 11, a fuel electrode layer 12, and an electrolyte. And an intermediate layer 14 disposed between the layers 11. The intermediate layer 14 includes a constituent material of the fuel electrode layer 12. And the pore 14a in the intermediate | middle layer 14 has an average diameter of 1 micrometer or less. According to the solid oxide fuel cell 10 having the above-described configuration, the electrolyte layer 11 having a uniform film thickness can be formed on the intermediate layer 14, so that pinholes can be prevented from being generated in the electrolyte layer 11.

  Next, an example of a method for manufacturing the solid oxide fuel cell 10 according to the first embodiment will be described with reference to the drawings. FIGS. 2A and 2B and FIGS. 3A and 3B to be referred to are schematic process diagrams showing an example of a manufacturing method of the solid oxide fuel cell 10. 2A and 2B and FIGS. 3A and 3B, the same components as those in FIG.

  First, a metal source containing a constituent metal of the fuel electrode layer 12 is dissolved in a solvent to prepare a fuel electrode layer forming solution 1 (see FIG. 2A). Next, as shown in FIG. 2A, the fuel electrode layer 12 (fuel electrode layer substrate) is heated to a temperature higher than the fuel electrode layer formation temperature by, for example, a hot plate (not shown), and the fuel electrode layer 12 is sprayed by the spray device 2. The layer forming solution 1 is sprayed on the fuel electrode layer 12. Thereby, as shown in FIG. 2B, the intermediate layer 14 is formed on the fuel electrode layer 12. According to this method, the average diameter of the pores 14a in the intermediate layer 14 is 1 μm or less.

  Next, as shown in FIG. 3A, the electrolyte layer 11 is formed on the intermediate layer 14 by, for example, the contact method described above. At this time, since the average diameter of the pores 14 a in the intermediate layer 14 is 1 μm or less, the electrolyte layer 11 having a uniform film thickness can be formed on the intermediate layer 14. Thereby, generation | occurrence | production of the pinhole in the electrolyte layer 11 can be prevented. Subsequently, as shown in FIG. 3B, an air electrode layer 13 is formed on the electrolyte layer 11 by means of a screen printing method or the like to obtain a solid oxide fuel cell 10.

  The solid oxide fuel cell 10 and the manufacturing method thereof according to the first embodiment of the present invention have been described above, but the present invention is not limited to the above embodiment. For example, a solid oxide fuel cell in which an intermediate layer, an electrolyte layer, and a fuel electrode layer are sequentially formed on the air electrode layer may be used.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 to be referred to is a schematic cross-sectional view showing a solid oxide fuel cell according to a second embodiment of the present invention. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the solid oxide fuel cell 20 according to the second embodiment, the fuel electrode layer 12 includes nickel oxide, and the intermediate layer 14 includes nickel oxide and a metal oxide constituting the electrolyte layer 11. As shown in FIG. 4, the intermediate layer 14 includes a first intermediate layer 21 that contacts the fuel electrode layer 12 and a second intermediate layer 22 that contacts the electrolyte layer 11. The mass content of nickel oxide in the first intermediate layer 21 is equal to or less than the mass content of nickel oxide in the fuel electrode layer 12, and the mass content of nickel oxide in the second intermediate layer 22 is the first content. It is less than the mass content of nickel oxide in the intermediate layer 21. As a result, the intermediate layer 14 becomes a buffer layer that eliminates thermal strain caused by the difference in thermal expansion coefficient between the fuel electrode layer 12 and the electrolyte layer 11. In the present embodiment, one (or more) intermediate layers may be interposed between the first intermediate layer 21 and the second intermediate layer 22. In this case, the mass content of nickel oxide in the intermediate layer interposed is preferably smaller than the mass content of nickel oxide in the first intermediate layer 21 and larger than the mass content of nickel oxide in the second intermediate layer 22. . This is because the thermal strain can be more effectively eliminated.

  The pores 21a in the first intermediate layer 21 and the pores 22a in the second intermediate layer 22 both have an average diameter of 1 μm or less. Thereby, since the electrolyte layer 11 with a uniform film thickness can be formed on the intermediate layer 14, the occurrence of pinholes in the electrolyte layer 11 can be prevented. Note that the manufacturing method of the solid oxide fuel cell 20 is the same as that described above except that in the step of forming the intermediate layer 14, the first intermediate layer 21 and the second intermediate layer 22 are formed in two steps. Since it is the same as that of the solid oxide fuel cell 10 according to the embodiment, the description thereof is omitted.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

In this example, a solid oxide fuel cell having a structure as shown in FIG. 1 was produced. First, nickel oxide powder (average particle size: 1 μm), Ce _0.8 Sm _0.2 O _1.9 powder (average particle size: 0.1 μm) and acetylene black are mixed in a mass ratio (nickel oxide: Ce _0.8 Sm _0.2 O _1.9 : acetylene black). Was added to ethanol so as to be 45: 50: 5, and these were mixed while being pulverized in ethanol. Next, these were dried and the ethanol was sufficiently volatilized, then formed with a uniaxial press and cut (trimmed) to a predetermined size with a ceramic cutter. And this was sintered at 1400 degreeC for 5 hours, and the fuel electrode layer board | substrate (thickness: 0.5 mm) was produced.

  Next, zirconium tetraacetylacetonate (manufactured by Matsumoto Pharmaceutical Co., Ltd., ORGATIZ ZC-150), yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.) and nickel chloride (manufactured by Kanto Chemical Co., Ltd.) each having a concentration of 0.05 mol The solution for forming an intermediate layer was prepared by dissolving in a mixed solvent having a volume ratio of toluene: ethanol = 70: 30 so as to be / mol, 0.004 mol / liter, and 0.05 mol / liter. Then, the intermediate layer forming solution (2 liters) is sprayed on the fuel electrode layer substrate heated to 400 ° C. with a nebulizer (NE-U17 manufactured by OMRON Corporation), and the intermediate layer ( (Thickness: 7 μm) was formed. The spray amount per unit time at this time was 0.003 liter / min. Moreover, it was confirmed by SEM cross-sectional observation that the average diameter of the pores in the intermediate layer was 1 μm or less.

  Next, zirconium tetraacetylacetonate (manufactured by Matsumoto Pharmaceutical Co., Ltd., Orgatics ZC-150) and yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.) were added at concentrations of 0.1 mol / liter and 0.08 mol / liter, respectively. Thus, an electrolyte layer forming solution was prepared by dissolving in a mixed solvent having a volume ratio of toluene: ethanol = 70: 30. Then, the electrolyte layer forming solution (2 liters) is sprayed on the intermediate layer heated to 500 ° C. with a nebulizer (NE-U17 manufactured by OMRON Corporation) to form an electrolyte layer (thickness: 7 μm) on the intermediate layer. did. The spray amount per unit time at this time was 0.003 liter / min.

Subsequently, Sm _0.5 Sr _0.5 CoO ₃ powder (average particle diameter: 3 μm) and cellulose binder resin were mixed with diethylene glycol monobutyl ether acetate so that the mass ratio (Sm _0.5 Sr _0.5 CoO ₃ : binder resin) was 80:20. In addition, a paste was prepared. Then, this paste is applied on the electrolyte layer by screen printing, and sintered at 1200 ° C. for 1 hour to form an air electrode layer (thickness: 30 μm) on the electrolyte layer. A fuel cell was obtained.

1 is a schematic cross-sectional view showing a solid oxide fuel cell according to a first embodiment of the present invention. A and B are schematic process diagrams showing an example of a method for producing a solid oxide fuel cell according to the first embodiment of the present invention. A and B are schematic process diagrams showing an example of a method for producing a solid oxide fuel cell according to the first embodiment of the present invention. It is a schematic cross section which shows the solid oxide fuel cell which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel electrode layer forming solution 2 Spray apparatus 10,20 Solid oxide fuel cell 11 Electrolyte layer 12 Fuel electrode layer 13 Air electrode layer 14 Intermediate layers 14a, 21a, 22a Pore 21 First intermediate layer 22 Second intermediate layer

Claims (6)

A solid oxide fuel cell comprising an electrolyte layer and a pair of porous electrode layers sandwiching the electrolyte layer,
Including an intermediate layer disposed between the one porous electrode layer and the electrolyte layer;
The intermediate layer includes a constituent material of the one porous electrode layer,
The solid oxide fuel cell according to claim 1, wherein the pores in the intermediate layer have an average diameter of 1 μm or less.   The solid oxide fuel cell according to claim 1, wherein the intermediate layer has a thickness of 0.05 to 10 μm. The one porous electrode layer is a fuel electrode layer containing nickel oxide,
The solid oxide fuel cell according to claim 1, wherein the intermediate layer includes nickel oxide and a metal oxide constituting the electrolyte layer.   The solid oxide fuel cell according to claim 3, wherein the metal oxide is a composite metal oxide containing at least one selected from zirconium oxide, cerium oxide, and lanthanum oxide. The intermediate layer includes a first intermediate layer in contact with the fuel electrode layer, and a second intermediate layer in contact with the electrolyte layer,
The mass content of nickel oxide in the first intermediate layer is less than or equal to the mass content of nickel oxide in the fuel electrode layer;
4. The solid oxide fuel cell according to claim 3, wherein a mass content of nickel oxide in the second intermediate layer is less than a mass content of nickel oxide in the first intermediate layer. 5. The first intermediate layer has a thickness of 0.025 to 9.975 μm,
The solid oxide fuel cell according to claim 5, wherein the second intermediate layer has a thickness of 0.025 to 9.975 μm.

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