JP2008243723A - Solid oxide fuel cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell, and its manufacturing method capable of forming precise electrolyte at a low temperature inexpensively. <P>SOLUTION: The manufacturing method of the solid oxide fuel cell includes steps: coating paste for electrolyte on a metal substrate 4; forming a plurality of through-holes 41 communicating with the paste for electrolyte on the metal substrate 4 after drying the coated paste for electrolyte; pressing a surface of the paste for electrolyte including parts exposed from the through-holes 41; forming an electrolyte 1 by burning the paste for electrolyte; forming a fuel electrode 3 on a lower surface of the electrolyte 1 exposed from the through-holes 41; and forming an air electrode 2 on an upper surface of the electrolyte 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell that operates with a fuel gas and an oxidant gas, and a method for manufacturing the same.

A fuel cell is a cell that can directly convert chemical energy generated when fuel is oxidized into electric energy while continuously supplying fuel from the outside and exhausting combustion products. The types of fuel cells are classified according to the electrolyte, and those using metal oxides having ion conductivity for the electrolyte are called solid oxide fuel cells. Various types of solid oxide fuel cells have been proposed. For example, in Patent Document 1, a fuel electrode (anode) is formed on a porous support substrate, and the fuel electrode is formed on the fuel electrode. A solid oxide fuel cell is disclosed in which an electrolyte is formed and an air electrode (cathode) is formed on the electrolyte.
Japanese Patent Laid-Open No. 11-11309

  By the way, the fuel cell is a battery that generates power by separately supplying gas to the fuel electrode and the air electrode. Therefore, it is necessary to form an electrolyte that is a boundary between both electrodes densely so that gas does not permeate. As a method for forming such a dense film, for example, there is a method in which an electrolyte material is applied by screen printing and then sintered at a high temperature of about 1400 ° C. However, when the electrolyte is formed at such a high temperature, there is a problem that a metal cannot be used as the support substrate. In order to solve this, a low-temperature film forming method such as CVD has been proposed, but there is a problem that the cost is increased because the yield is poor.

  Therefore, an object of the present invention is to provide a solid oxide fuel cell capable of forming a dense electrolyte at a low temperature and at a low cost, and a method for producing the same.

  A first method for producing a solid oxide fuel cell according to the present invention has been made to solve the above-described problem, and includes a step of applying a material for an electrolyte on a metal substrate; Forming a plurality of through-holes communicating with the electrolyte material; pressing a surface of the electrolyte material including a portion exposed from the through-hole; firing the electrolyte material; Forming, forming one electrode of the fuel electrode and the air electrode on one surface of the electrolyte exposed from the through hole, and forming the other electrode on the other surface of the electrolyte. ing.

  According to this configuration, the baked electrolyte can be densely formed even if the temperature during firing is low by pressing the electrolyte material before firing the electrolyte material. Therefore, since the firing temperature can be lowered, even when a metal substrate is used, the metal substrate is not deformed or damaged during firing. As a result, the electrolyte can be formed by a simple method such as screen printing without using a low temperature film formation method such as CVD, so that the yield can be improved and the manufacturing cost can be reduced.

  Further, in the present invention, a plurality of through holes are formed in the metal substrate, an electrode in contact with one surface of the electrolyte is formed in the through hole, and another electrode is formed on the other surface of the electrolyte. . Thus, in the present invention, since the through hole and the surface on the opposite side are exposed in the electrolyte before firing, at least the surface on which the electrode is formed can be pressed. As a result, the portion in contact with both electrodes in the electrolyte can be densely formed, and as a solid oxide fuel cell, mixing of gases supplied to both electrodes can be prevented.

  Here, as a method for applying the electrolyte material, for example, various methods such as a dip coating method and a spin coating method can be used in addition to the screen printing described above. In addition, the electrolyte material referred to in the present invention refers to a liquid or paste-like material for forming an electrolyte suitable for the various methods described above.

  The second method for producing a solid oxide fuel cell according to the present invention has been made to solve the above-described problem, and includes a step of forming a plurality of through holes in a metal substrate, and the through holes. A step of disposing an electrolyte material on the metal substrate so as to cover the surface, a step of pressing the surface of the electrolyte material including a portion exposed from the through hole, and firing the electrolyte material A step of forming an electrolyte; a step of forming one of a fuel electrode and an air electrode on one surface of the electrolyte exposed from the through hole; and a step of forming the other electrode on the other surface of the electrolyte; It is equipped with.

  This method is different from the first invention in that an electrolyte material is disposed on a metal substrate in which a through hole is formed. As such an electrolyte material, for example, a so-called green body can be used. Thereby, even if the through-hole is formed, the electrolyte material can be disposed on the metal substrate. And even if it is such a structure, the effect similar to the said 1st invention can be acquired.

  The press in the present invention can be, for example, an isostatic press. In this case, either a cold isostatic press or a hot isostatic press can be used. For example, when a hot isostatic press is used, it is preferable to apply heat of 80 to 200 ° C. By applying a temperature of 80 ° C. or higher, the synergistic effect of temperature and pressure can be used to remove vacancies rather than cold and increase the density. On the other hand, when the temperature is 200 ° C. or higher, melting or volatilization of the binder in the material occurs, resulting in poor moldability. In addition, a known uniaxial press or the like can be applied to the exposed surface of the electrolyte material.

The pressure of the press is preferably 1 to 4 × 10 ³ kg / cm ² , for example. By setting the pressing pressure to 1 × 10 ³ kg / cm ² or more, the electrolyte becomes dense and gas leakage can be prevented. Moreover, since there exists a possibility that an electrolyte and an electrode may be damaged when press pressure is raised too much, it is preferable to set it as 4 x10 < ³ > kg / cm < ² > or less.

  The solid oxide fuel cell according to the present invention includes a metal substrate having at least one through-hole formed therein, an electrolyte formed on one surface of the metal substrate so as to close the through-hole, and the through-hole. A fuel electrode or an air electrode formed on one surface of the electrolyte exposed from the hole, and the other electrode formed on the other surface of the electrolyte, the electrolyte comprising the one surface and It has a dense layer on the other side.

  According to the method for producing a solid oxide fuel cell according to the present invention, a dense electrolyte can be formed at a low temperature and at a low cost.

  Hereinafter, an embodiment of a solid oxide fuel cell according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a solid oxide fuel cell according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

  As shown in FIG. 1, the solid oxide fuel cell according to the present embodiment is a thin film-like fuel disposed on the upper surface of a metal substrate 4 on which a plurality of through holes 41 are formed so as to close the through holes 41. An electrolyte 1 and a thin film-like air electrode 2 disposed on the upper surface thereof are provided. A thin-film fuel electrode 3 that contacts the lower surface of the electrolyte 1 is formed in the through hole 41 of the metal substrate 4. As shown in FIG. 2, the metal substrate 4 is formed in a mesh shape in plan view by forming a plurality of through holes 41.

  Subsequently, materials constituting the fuel cell will be described. As a material constituting the metal substrate 4, in consideration of heat resistance and strength conductivity, conductive metals such as Fe, Ti, Cr, Cu, Ni, Ag, Au, and Pt can be used. May be used alone, or two or more may be mixed. For example, stainless steel heat-resistant materials can be used. Specifically, austenitic stainless steel, ferritic stainless steel, Inconel, Hastelloy, etc. A nickel-based heat-resistant alloy or the like can be used.

  As the material of the electrolyte 1, those known as electrolytes for solid oxide fuel cells can be used. For example, ceria oxide (GDC) doped with samarium or gadolinium, lanthanum doped with strontium or magnesium An oxygen ion conductive ceramic material such as a galide oxide, zirconia oxide (YSZ) containing scandium or yttrium can be used.

  The fuel electrode 3 and the air electrode 2 can be formed of a ceramic powder material. The average particle size of the powder used at this time is preferably 10 nm to 100 μm, more preferably 50 nm to 50 μm, and particularly preferably 100 nm to 10 μm. In addition, an average particle diameter can be measured according to JISZ8901, for example.

  As the fuel electrode 3, for example, a mixture of a metal catalyst and a ceramic powder material made of an oxide ion conductor can be used. As the metal catalyst used at this time, a material that is stable in a reducing atmosphere, such as nickel, iron, cobalt, or a noble metal (platinum, ruthenium, palladium, etc.) and has hydrogen oxidation activity can be used. In addition, as the oxide ion conductor, one having a fluorite structure or a perovskite structure can be preferably used. Examples of those having a fluorite structure include ceria-based oxides doped with samarium, gadolinium, and the like, and zirconia-based oxides containing scandium and yttrium. In addition, examples of those having a perovskite structure include lanthanum galide oxides doped with strontium and magnesium. Among the above materials, it is preferable to form the fuel electrode 2 with a mixture of an oxide ion conductor and nickel. The mixed form of the ceramic material made of the oxide ion conductor and nickel may be a physical mixed form, or may be a powder modification to nickel or a nickel modification to ceramic material. Good. Moreover, the ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types. Moreover, the fuel electrode 3 can also be comprised using a metal catalyst alone.

As the ceramic powder material forming the air electrode 2, for example, a metal oxide made of Co, Fe, Ni, Cr, Mn or the like having a perovskite structure or the like 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) (Fe, Co) O ₃ is preferable. The ceramic material mentioned above can be used individually by 1 type or in mixture of 2 or more types.

  The fuel electrode 3 and the air electrode 2 are formed by adding appropriate amounts of a binder resin, an organic solvent, and the like with the above-described material as a main component. More specifically, it is preferable to add a binder resin or the like so that the main component is 50 to 95% by weight in the mixing of the main component and the binder resin. Similarly to the fuel electrode 3 and the air electrode 2, the electrolyte 1 is molded by adding an appropriate amount of a binder resin, an organic solvent, or the like with the above-described material as a main component. In the mixing, it is preferable to mix so that the ratio of the main component is 80% by weight or more. And the film thickness of the fuel electrode 3 and the air electrode 2 is formed so that it may become 5-100 micrometers, but it is preferable to set it as 20-50 micrometers. The thickness of the electrolyte 1 is preferably 1 to 100 μm, and more preferably 5 to 50 μm.

Next, a method for manufacturing the fuel cell will be described with reference to FIGS. FIG. 3 is an explanatory view of a method for producing a fuel cell according to this embodiment, and FIG. 4 is a schematic view showing an enlarged cross section of the electrolyte. First, the metal substrate 4 described above is prepared. Subsequently, the above-described powder materials for the electrolyte 1, the fuel electrode 3, and the air electrode 2 are used as main components, and an appropriate amount of a binder resin, an organic solvent, and the like are added and kneaded to each of them, and an electrolyte paste (electrolyte material), A fuel electrode paste (fuel electrode material) and an air electrode paste (air electrode material) are prepared. The viscosity of each paste is preferably about 10 ³ to 10 ⁶ mPa · s.

And after apply | coating the paste for electrolyte to the upper surface of the metal substrate 4 in the shape of a thin film, it dries at predetermined temperature for predetermined time (FIG. 3 (a)). Next, a plurality of through holes 41 are formed in the metal substrate 4 by etching or the like (FIG. 3B). That is, after appropriately masking the lower surface of the metal substrate 4, a through hole 41 is formed by etching, and the electrolyte paste 1 is exposed from the through hole 41. The through hole 41 is formed only in a range where the electrolyte 1 paste is disposed. Subsequently, the dried electrolyte paste is pressed (FIG. 3C). That is, cold isostatic pressing (CIP) is performed on the surface of the electrolyte paste exposed to the outside, that is, the upper surface of the electrolyte paste and the lower surface exposed from the through hole 41 by a known hydrostatic press. The pressure here can be set to, for example, 1 to 4 × 10 ³ kg / cm ² .

  After pressing, the electrolyte 1 is formed by sintering at 900 to 1100 ° C. By this step, as shown in FIG. 4, the vicinity of the pressed surface of the electrolyte 1 becomes dense, and the other portions become porous. Subsequently, a fuel electrode paste is applied by screen printing so as to be in contact with the lower surface of the electrolyte 1 in the through hole 41 of the metal substrate 4, and is dried and sintered at a predetermined time and at a predetermined temperature. 3 is obtained (FIG. 3 (d)). The temperature at the time of sintering can be 900-1100 degreeC, for example. Finally, an air electrode paste made of the above-described material is applied to the upper surface of the electrolyte 1 by screen printing, and dried and sintered for a predetermined time to obtain a porous air electrode 2. The temperature at the time of sintering can be 900-1100 degreeC, for example. Thus, the fuel cell shown in FIG. 1 is completed. The electrolyte paste, fuel electrode paste, and air electrode paste can be applied by various methods, for example, screen printing method, transfer method, electrophoresis method, doctor blade method, dispenser coating method, spray coating method, dip coating. It can be formed by a coating method or the like.

  Thereafter, if necessary, a current collecting layer, a conductive wire, a seal member for partitioning the fuel electrode 2 and the air electrode 4 and the like are provided, thereby completing the solid oxide fuel cell.

  In the above method, the through hole 41 is formed after applying the electrolyte material to the metal substrate 4, but the metal substrate 4 in which the through hole 41 is formed in advance can also be used. In this case, the electrolyte material is preferably manufactured as a so-called green body. Hereinafter, a manufacturing method in the case of using a green body will be described. First, a binder, a solvent, a plasticizer, and a dispersant are mixed with the above-described material for preparing an electrolyte, and dispersed by a ball mill, and then subjected to vacuum degassing to prepare an electrolyte paste. This paste is printed on a film of polyethylene terephthalate (PET) or the like coated with a release layer with a doctor blade or the like so as to have a predetermined film thickness. Then, by drying at about 120 ° C., an electrolyte green body is formed on the film.

Subsequently, the electrolyte green body is bonded to the upper surface of the metal substrate 4 in which the through holes 41 are formed. Then, the film is pressed by applying heat from the film, the green body is fused on the metal substrate 4, and then the film is peeled off. Next, the green body for electrolyte on the metal substrate 4 is pressed by a known hydrostatic press. That is, cold isostatic pressing (CIP) is performed on the surface of the electrolyte paste exposed to the outside, that is, the upper surface of the electrolyte paste and the lower surface exposed from the through hole 41. The pressure here can be set to, for example, 1 to 4 × 10 ³ kg / cm ² . The subsequent steps are the same as those described above, and thus are omitted.

  The fuel cell configured as described above generates power as follows. First, a fuel gas composed of hydrogen or a hydrocarbon such as methane or ethane is supplied to the fuel electrode 3 through the through hole 41 of the metal substrate 4. On the other hand, an oxidant gas such as air is supplied to the air electrode 2. The fuel gas and the oxidant gas such as air supplied at this time are supplied at a high temperature of 400 to 1000 ° C., for example. Thus, since the fuel electrode 3 and the air electrode 2 are in contact with the fuel gas and the oxidant gas, respectively, oxygen ion conduction through the electrolyte 1 occurs between the fuel electrode 3 and the air electrode 2, and power generation is performed. At this time, since the electrolyte 1 contains a dense layer, the fuel gas and the oxidant gas are blocked by the electrolyte 1 and supplied to the electrodes 2 and 4 without being mixed in each fuel cell. .

  As described above, according to the present embodiment, before the electrolyte paste is fired, the electrolyte paste is subjected to an isostatic press so that the fired electrolyte can be made dense even at a low firing temperature. Can be formed. Therefore, since the firing temperature can be lowered, even when the metal substrate 1 is used, the metal substrate is not deformed or damaged during firing. As a result, the electrolyte can be formed by a simple method such as screen printing without using a low temperature film formation method such as CVD, so that the yield can be improved and the manufacturing cost can be reduced. Further, in the fuel cell, since the metal substrate 4 enters the fuel electrode 3, the metal substrate 4 becomes a conductive path. As a result, the current collecting effect can be greatly increased, and high output can be achieved. You can expect.

  Further, in the present embodiment, a plurality of through holes 41 are formed in the metal substrate 4, the fuel electrode 3 that contacts the lower surface of the electrolyte 1 is formed in the through hole 41, and the air electrode 2 is formed on the upper surface of the electrolyte 1. Is forming. Thus, since the lower surface and the upper surface exposed from the through hole 41 are exposed in the electrolyte 1 before firing, the surface on which the electrodes 2 and 3 are formed can be pressed. As a result, the portion in contact with both electrodes 2 and 3 in electrolyte 1 can be densely formed, and as a two-chamber solid oxide fuel cell, mixing of gases supplied to both electrodes can be prevented.

  The embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the fuel electrode 3 is formed in the through hole 41 of the metal substrate 4, but the air electrode 2 may be formed here and the fuel electrode 3 may be formed on the upper surface of the electrolyte 1.

  In the above method, a cold isostatic press is used to press the electrolyte 1, but a hot isostatic press or the like can also be used. In this way, there is an advantage that pores can be removed and further densification can be achieved compared to a normal cold isostatic press by utilizing the synergistic effect of temperature and pressure. It is preferable to apply heat of ˜200 ° C. Moreover, it can also press by a well-known uniaxial press.

Examples according to the present invention will be described below. However, the present invention is not limited to the following examples. Below, the some battery shown in FIG. 1 is created. At that time, in manufacturing each battery, different pressures are applied to the dried electrolyte paste. First, the following materials are prepared.
Example 1
Metal substrate
SUS material ZMG232 (manufactured by Hitachi Metals) was prepared.
Electrolyte paste
Add GDC (Ce: Gd: O = 0.9: 0.1: 1.9) powder (particle size range 0.1--3μm, average particle size: 1μm) and ethyl cellulose to ethyl carbitol so that mass ratio is 90:10 The paste was adjusted.
NiO powder (average particle size: 1 μm) and SDC (Ce: Sm: O = 0.8: 0.2: 1.9) were added to the paste for fuel electrode ethyl carpitol, and ethyl cellulose was used as a binder in a mass ratio of 80:20. Then, the fuel electrode paste (viscosity: 5 × 10 ⁵ mPa · s) for forming the fuel electrode layer was adjusted by mixing them with a ball mill.
After adding Sm0.5Sr0.5CoO3 powder (average particle size: 3 μm) to the ethyl carpitol paste for air electrode, and adding ethyl cellulose as a binder so that the mass ratio becomes 80:20, An air electrode paste (viscosity: 5 × 10 ⁵ mPa · s) for forming an air electrode layer by mixing with a ball mill was adjusted.

Next, an electrolyte paste having a film thickness of about 20 μm is applied on the metal substrate by screen printing and dried at 130 ° C. for 15 minutes. Then, after appropriately masking the lower surface of the metal substrate, a through hole is formed by etching so that the dried electrolyte paste is exposed from the through hole. Thereafter, cold isostatic pressing (CIP) is applied to the electrolyte paste from above and below by a cold hot water combined isotropic pressure press (Nikkiso Co., Ltd., model number CWL4-14-60). The applied pressure is about 2 t / cm ² . After pressing, the electrolyte paste is sintered at 1100 ° C. for 5 hours. More specifically, the temperature was raised to 1100 ° C. at 220 ° C./hour, held for 1 hour, and then naturally cooled. Subsequently, a fuel electrode paste was applied by screen printing to the lower surface of the electrolyte through the through hole of the metal substrate to a film thickness of about 30 μm, dried at 130 ° C. for 15 minutes, and then 5 at 1100 ° C. Sintering for a time to form a fuel electrode. Subsequently, an air electrode paste having a film thickness of about 30 μm is applied to the upper surface of the electrolyte by screen printing, dried at 130 ° C. for 15 minutes, and then sintered at 1000 ° C. for 5 hours to form an air electrode.

(Example 2)
In this embodiment, the electrolyte is produced using a green body. Other materials are the same as those in the first embodiment.
Green body for electrolyte
GDC (Ce: Gd: O = 0.9: 0.1: 1.9) powder (particle size range 0.1--3 μm, average particle size: 1 μm) and ethyl cellulose as binder, ammonium polyacrylate as dispersant, dibutyl phthalate as plasticizer -The paste was prepared by adding to the mass ratio of 100: 13: 2.5: 10 and adding to ethyl carbitol. Thereafter, the mixture was stirred for 24 hours with a ball mill, vacuum degassed, applied onto a PET film coated with a silicone resin peelability-imparting agent with a doctor blade, dried at 100 ° C., and molded.

After preparing the above-described materials, first, a mask is appropriately provided on the lower surface of the metal substrate, and then a through hole is formed by blasting. Then, a green body is pasted on the metal substrate so as to cover the through hole, and an electrolyte green body having a film thickness of about 50 μm is fused by a hot press at 130 ° C. and 50 kg / cm ² , and then the film is formed. Remove. Thus, the electrolyte green body attached from the through hole is exposed. Thereafter, cold isostatic pressing (CIP) is applied to the electrolyte green body from above and below by a cold hot water combined isotropic pressure press (Nikkiso Co., Ltd., model number CWL4-14-60). The applied pressure is about 2 t / cm ² . After pressing, the electrolyte paste is sintered at 1100 ° C. for 5 hours. Specific temperature adjustment is the same as that in the first embodiment. And a fuel electrode and an air electrode are formed like Example 1, and a fuel cell is completed.

Thus, the completed Examples 1 and 2 are examined. FIG. 5 is an electron micrograph showing the upper surface of the electrolyte before the air electrode is formed and its vicinity in the manufacture of the fuel cell of Example 1, and the case where the press is not performed and the press at about 2 t / cm ^2. The case where it gave is shown. According to this, it can be seen that a dense layer is formed in the vicinity of the surface of the electrolyte even when the sintering temperature is about 1100 ° C. when pressed. Although not shown, a similar dense layer was also observed in Example 2.

1 is a cross-sectional view showing an embodiment of a solid oxide fuel cell according to the present invention. It is the sectional view on the AA line of FIG. It is sectional drawing which shows the manufacturing method of the fuel cell of FIG. In electrolyte, it is a schematic diagram which shows the front and back at the time of giving CIP. In manufacture of the fuel cell of Example 1, it is an electron micrograph which shows the electrolyte upper surface before forming an air electrode, and its vicinity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte 2 Air electrode 3 Fuel electrode 4 Metal body 41 Through-hole

Claims (6)

Applying an electrolyte material on a metal substrate;
Forming a plurality of through holes communicating with the electrolyte material in the metal substrate;
Pressing the surface of the electrolyte material including a portion exposed from the through hole; and
Firing the electrolyte material to form an electrolyte; and
Forming one electrode of the fuel electrode and the air electrode on one surface of the electrolyte exposed from the through hole;
Forming the other electrode on the other surface of the electrolyte;
A method for producing a solid oxide fuel cell. Forming a plurality of through holes in a metal substrate;
Disposing an electrolyte material on the metal substrate so as to cover the through hole;
Pressing the surface of the electrolyte material including a portion exposed from the through hole; and
Firing the electrolyte material to form an electrolyte; and
Forming one electrode of the fuel electrode and the air electrode on one surface of the electrolyte exposed from the through hole;
Forming the other electrode on the other surface of the electrolyte;
A method for producing a solid oxide fuel cell.   The method for producing a solid oxide fuel cell according to claim 1, wherein the press is an isostatic press.   The said press is a hot isostatic press, The manufacturing method of the solid oxide fuel cell of Claim 3 to which the heat | fever of 80-200 degreeC is provided. 5. The method for producing a solid oxide fuel cell according to claim 1, wherein the pressure of the press is 1 to 4 × 10 ³ kg / cm ² . A metal substrate on which at least one through hole is formed;
An electrolyte formed on one surface of the metal substrate so as to close the through hole;
Either the fuel electrode or the air electrode formed on one surface of the electrolyte exposed from the through hole;
The other electrode formed on the other surface of the electrolyte, and
The electrolyte is a solid oxide fuel cell having a dense layer on the one side and the other side.