JPH08255626A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE: To prevent the diffusion of chrome or the like to a cathode, and to prolong the lifetime of a cell by coating the surface of a heat exchanging material or the like, which is made of the heat resistant metal, with the ceramics protecting film. CONSTITUTION: This fuel cell 21 formed of a stack of unit cells, which are respectively formed by pinching the solid electrolyte with a fuel electrode and an oxidation electrode, is operated at, for example, 1,000 deg.C. Pipelines 23, 24, 25, 26 for supplying and discharging the reaction gas to the fuel electrode and the oxidation electrode are provided with a heat exchanging material, and the oxidant gas is heated by the heat of the reacted gas through the heat exchanging material. The pipelines and the heat exchanging material are made of the heat resistant alloy such as Ni-Cr group and Fe-Ni-Cr group, which includes Cr at 5% or more, or the cermet of this heat resistant alloy and ceramics such as alumina. Furthermore, the contact surface of the pipeline and the heat exchanging material with the oxidant gas is coated with the protecting film of ceramics such as alumina at 1-200μm so as to prevent the diffusion of the Cr component of the substance in the oxidation electrode through the oxidant gas.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a solid electrolyte having high density, high strength, excellent heat resistance and corrosion resistance, and which does not deteriorate battery performance, and optionally a heat exchange material. Type fuel cell.

[0002]

2. Description of the Related Art A fuel cell uses a combustible chemical substance such as hydrogen, carbon monoxide, or hydrocarbon or a fuel containing the same as an active material and causes an oxidation reaction of the chemical substance or the fuel to be performed electrochemically. A battery that directly converts energy changes in the oxidation process into electric energy, and is expected to have high energy conversion efficiency.

[0003] Among them, the third-generation solid oxide fuel cells, which follow the first-generation phosphoric acid type and the second-generation molten carbonate type, have been attracting attention in recent years as particularly high efficiency can be expected. Since this solid oxide fuel cell is operated at a high temperature of around 1000 ° C., it is usually used as a pipe material or a heat exchange material for a chromium-containing heat-resistant metal material that has high strength, heat resistance and corrosion resistance even under such a high temperature. Is used.

However, this chromium-containing heat-resistant metal material has a drawback that it deteriorates the battery performance under high temperature operation as described above.

[0005]

Under the circumstances, the present invention has a high density, a high strength, excellent heat resistance and corrosion resistance, and a piping material or heat which does not deteriorate the battery performance. The purpose of the present invention is to provide a solid oxide fuel cell provided with an exchange material.

[0006]

The inventors of the present invention have conducted various studies to develop a pipe / heat exchange material for a solid oxide fuel cell having the above-mentioned preferable properties, and as a result, a heat-resistant metal containing chromium. Or, if you use it and the cermet of ceramics as it is as a material for the above piping and heat exchange material,
Even if it shows good performance as a pipe / heat exchange material itself,
When contacting with a high temperature oxidant gas, chromium or chromium oxide diffuses into the oxidant gas, and when this chrome-containing oxidant gas contacts the cathode, chromium diffuses into the cathode, degrading the cathode performance, resulting in battery performance. Is reduced,
Therefore, it has been found that providing a ceramic protective film on the surface of such a pipe / heat exchange material that is in contact with the oxidant gas can prevent this, and has completed the present invention based on this finding.

That is, the present invention has (1) a stack structure composed of an assembly of unit cells in which a solid electrolyte material is sandwiched between a fuel electrode and an oxidant electrode, and the fuel electrode and the oxidant electrode are respectively formed. An oxidant that supplies fuel gas and oxidant gas as a reaction gas and that is connected to a supply / discharge pipe material that discharges a reacted gas or a pipe material and an oxidant gas supply pipe material of the pipe material. In a solid oxide fuel cell provided with a heat exchange material for raising the temperature of a gas, a pipe material for supplying an oxidant gas or a heat-resistant metal containing 5% or more of chromium as the pipe material and the heat exchange material, and the heat-resistant material. A coating material comprising a base material made of at least one selected from cermets of metal and ceramics and a ceramics protective film provided on a surface of the base material corresponding to an oxidant gas is used. There is provided a solid oxide fuel cell that.

The present invention also provides (2) 5% chromium used in the solid oxide fuel cell according to the above item (1).
A piping material for a solid oxide fuel cell, comprising a base material made of the above-mentioned heat-resistant metal and a ceramics protective film provided on a surface of the base material corresponding to an oxidant gas, (3) The solid electrolyte according to the item (1). For a solid oxide fuel cell, comprising a base material made of a refractory metal containing 5% or more of chromium, and a ceramic protective film provided on a surface of the base material corresponding to an oxidant gas, which is used in a fuel cell for a fuel cell. (4) A base material, which is used in the solid oxide fuel cell according to the item (1) and is made of a cermet of refractory metal containing 5% or more of chromium and ceramics, and an oxidant gas-corresponding surface of the base material. A pipe material for a solid oxide fuel cell, which comprises a ceramic protective film,
(5) The solid electrolyte fuel cell according to the above (1) is provided with a base material made of a refractory metal containing 5% or more of chromium and cermet of ceramics, and a surface of the base material corresponding to an oxidant gas. A heat exchange material for a solid oxide fuel cell, which comprises a ceramics protective film.

In a preferred embodiment of the present invention,
(6) The solid electrolyte fuel cell according to (1) above, wherein the refractory metal is at least one selected from nickel-based alloys and iron-based alloys, and (7) the ceramic is alumina or a rare earth-based composite oxide. The solid oxide fuel cell according to (1) above, (8) The refractory metal is at least one selected from a nickel-based alloy and an iron-based alloy, and (2) or (4) above. Solid electrolyte fuel cell piping material, (9) The solid electrolyte fuel cell piping material according to the above (2) or (4), wherein the ceramic is alumina or a rare earth compound oxide, (10) The heat-resistant metal is The heat exchange material for a solid oxide fuel cell according to the above (3) or (5), which is at least one selected from nickel-based alloys and iron-based alloys, (11) the ceramic is alumina or a rare earth-based composite. Is an oxide The heat exchange material for a solid oxide fuel cell according to item (3) or (5), (12) the volume ratio of the refractory metal in the cermet is 20 to 60%, (1), (6) or (7) The solid oxide fuel cell, (13) The solid electrolyte fuel cell piping material according to (4) or (9), wherein the volume ratio of the refractory metal in the cermet is 20 to 60%. (14) The heat exchange material for a solid oxide fuel cell according to the item (5) or (10), wherein the volume ratio of the refractory metal in the cermet is 20 to 60%, (15) the thickness of the ceramic protective film is 0. 1 to 200 μm, the above item (1), item (6),
(7) The solid oxide fuel cell according to any one of (7) and (12), (16) The ceramic protective film has a thickness of 0.
1 to 200 μm, (2), (4) and (8)
Item, the pipe material for a solid oxide fuel cell according to any one of Items (9) and (13), (17) The thickness of the ceramic protective film is 0.1 to 200 μm, and the above (3) Item,
The heat exchange material for a solid oxide fuel cell according to any one of (5), (10), (11) and (14).

The solid oxide fuel cell of the present invention has a stack structure composed of an assembly of unit cells in which a solid electrolyte material is sandwiched between a fuel electrode and an oxidant electrode, and the fuel electrode and the oxidant electrode are provided with the stack structure. The fuel gas and the oxidant gas as reaction gases are respectively supplied, and the supply / discharge pipe material for discharging the reacted gas or the pipe material and the oxidant gas supply pipe material of the pipe material are connected to each other, and the oxidation is performed. It is provided with a heat exchange material for raising the temperature of the agent gas, and may be a known type such as a vertical striped cylinder type or a horizontal striped cylindrical type or a flat plate type. Among them, as the flat plate type, a unit cell in which a solid electrolyte plate is sandwiched between a fuel electrode and an oxidant electrode is integrated through a separator provided with a flow path in which each reaction gas can contact each electrode, A solid oxide fuel cell is preferred in which an external terminal plate provided with a flow path that can contact the reaction gas corresponding to the electrodes of the solid electrolyte plates at both ends is provided.

Further, the solid oxide fuel cell of the present invention comprises a heat-resistant metal containing 5% or more of chromium and a cermet of the heat-resistant metal and ceramics as a pipe material for supplying an oxidant gas or the pipe material and the heat exchange material. It is important to use a coating material composed of a base material made of at least one selected from the above and a ceramic protective film provided on the surface of the base material corresponding to the oxidant gas. In the solid oxide fuel cell of the present invention, preferably, a supply / discharge pipe material, that is, an oxidant gas supply pipe material, a reacted oxidant gas discharge pipe material, a fuel gas supply pipe material, a reacted fuel gas discharge The piping material and the stack type solid oxide fuel cell are connected to each other via a manifold.

In the oxidant gas supply piping material used in the present invention and the heat exchange material optionally used (hereinafter referred to as piping / heat exchange material), the base material is chromium.
% Or more of a refractory metal (hereinafter referred to as Cr-containing refractory metal) or a cermet of Cr-containing refractory metal and ceramics. 5 as a Cr-containing heat-resistant metal
% Or more, preferably 8 to 30% of a heat-resistant alloy containing chromium, or an alloy containing chromium, preferably a mixture of a heat-resistant alloy and a heat-resistant metal element such as nickel, cobalt or iron. However, 5% or more of chromium may be contained in the total amount. The heat-resistant alloy is
Those containing at least one metal selected from nickel, cobalt and iron in addition to chromium are preferable, and as such, nickel-based alloys and iron-based alloys containing chromium are particularly preferable, and Inconel is particularly preferable. 600,
Ni-Cr alloys such as Hastelloy 800 and SUS
Fe-N like 410, SUS430, SUS630
An i-Cr type alloy is mentioned. Each of these heat-resistant alloys and heat-resistant metal elements may be used alone, or two or more kinds may be used in combination.

The ceramic of one component of the cermet is not particularly limited as long as it is heat resistant, and for example, oxide ceramics such as alumina, silica, zirconia, stabilized zirconia, titania, mullite, spinel, and cordierite. Composite ceramics such as lights, carbide ceramics such as silicon carbide, nitride ceramics,
Rare earth complex oxides such as lanthanum chromite complex oxides and yttrium chromite complex oxides, stannic oxide, indium oxide, zinc oxide and the like, among others, alumina, silica such as cristobalite, among others,
Spinel, lanthanum chromite complex oxide, and yttrium chromite complex oxide are preferable. These ceramics may be used alone or in combination of two or more.

In the cermet, the ratio of the Cr-containing heat-resistant metal to the ceramics can be adjusted appropriately, but the volume ratio of the Cr-containing heat-resistant metal is preferably 20 to 60%, more preferably 30 to 50%. . Further, it is preferable that the Cr-containing refractory metal is present as a matrix and the ceramic is present as a dispersoid. Further, those having a relative density of 90% or more are preferable.

Further, as the cermet, the volume ratio of the Cr-containing refractory metal is 20 to 60%, preferably 30 to 5.
0%, Cr-containing refractory metal as a matrix, ceramics as a dispersoid, and a relative density of 90.
% Or more, especially a cermet of a chromium-containing nickel-based alloy and alumina, and the volume ratio of the alloy is 35-35.
45%, when the alloy is used as a matrix, alumina is present as a dispersoid, and the relative density is 90% or more, it is possible to have a high bending strength of 25 kgf / mm ² or more. Increasing the bending strength is also important for improving the sealing property and making the plate thinner.

In the pipe / heat exchange material of the present invention, a protective film is provided on the surface of the pipe / heat exchange material corresponding to the oxidant gas so that the base does not come into direct contact with the oxidant gas.
This protective film is made of ceramics, is stable in an oxidizing atmosphere at a high temperature near the operating temperature of the solid oxide fuel cell, and serves to prevent vapor phase or solid phase diffusion of chromium or its compounds.

Examples of such ceramics include oxide-based ceramics such as alumina, silica, zirconia, doped stabilized zirconia such as yttria-stabilized zirconia, titania, mullite, spinel, and the like.
Examples include composite ceramics such as cordierite, carbide-based ceramics such as silicon carbide, nitride-based ceramics, and various glass materials. Among them, alumina, silica,
Zirconia, stabilized zirconia and silicon nitride are preferred.

The above-mentioned protective film is required to have required characteristics such as excellent gas tightness, particularly excellent shielding from an oxidizing atmosphere, and no cracking or peeling. Further, in the protective film, the film quality such as the density and the film thickness have a relationship that the film thickness can be made thinner as the film quality becomes more dense, in order to obtain the same effect. The film thickness depends on the chromium content and the form of existence in the piping / heat exchange material substrate, but is usually 0.
Considering the relative density, it is 0.1 to 10 μm when the density is 90% or more, and 10 to 200 μm when the density is less than 90%. If the film thickness is too thick, the difference in thermal expansion characteristics between the substrate and the ceramics tends to cause cracking or peeling, resulting in poor adhesion.If it is too thin, gas tightness will be a problem, and the substrate surface will be completely shielded from the oxidizing atmosphere. However, the effect of the present invention is not sufficiently achieved.

The piping / heat exchange material of the present invention is manufactured as follows. That is, (13) after the substrate of the pipe / heat exchange material is prepared, the protective film is provided by depositing ceramics on the surface of the substrate facing the oxidant gas.

When the substrate is made of the cermet, the substrate is manufactured as follows. Cr-containing
After mixing the refractory metal or Cr-containing refractory metal source with ceramics or ceramics source in powder form, the mixture is pressure-molded, and the mixture is pressure-molded in a non-oxidizing atmosphere such as a reducing atmosphere or an inert atmosphere or in a vacuum. Obtained by firing in.

Above all, the volume ratio of the Cr-containing refractory metal is 20.
-60%, a Cr-containing refractory metal as a matrix, ceramics as a dispersoid, and a relative density of 90% or more, and a base made of cermet is preferably (14) (a) non-granulated The average particle size of the ceramic granules prepared by granulating the heat-resistant alloy powder of (b) and the ceramic powder of (b) is as follows: Particle size of ceramic powder <particle size of heat-resistant alloy powder (a) <
The ceramic granules (b) are selected so as to satisfy the particle size thereof, and these are mixed, and then the mixture is pressure-molded, and the mixture is subjected to a non-oxidizing atmosphere, for example, a reducing atmosphere or an inert atmosphere, or Obtained by firing in vacuum.

To further explain this preferred method, first, the powder particles selected as described above are thoroughly mixed. At this time, be careful not to break the granulated product of (b). Then, the obtained mixture is subjected to pressure molding, for example, cold isostatic pressing or hot isostatic pressing, and then the protective film ceramics is sintered, and in the temperature range in which the substrate does not melt. Firing is performed in a non-oxidizing atmosphere, such as a reducing atmosphere or an inert gas atmosphere, or in vacuum. When firing in a reducing atmosphere, the hydrogen concentration in the atmosphere is not particularly limited, but is preferably 0.1.
It is good to be about 5%. The firing temperature is 1100.
It is preferably in the range of -1500 ° C. Since the sinterability of ceramics also depends on the particle size of the powder, the sinterability can be improved by using a relatively fine primary particle size of 0.05 to 5 μm.

When the substrate of the pipe / heat exchange material is formed of cermet, the cermet is manufactured by firing without press-molding into a predetermined shape as described above, and then formed into a predetermined shape. Good.

Then, a ceramic film is formed on the surface of the substrate of the pipe / heat exchange material corresponding to the oxidizing gas so that it does not come into direct contact with the oxidizing gas. As the film forming method, a sputtering method, a vapor deposition method such as a CVD method, a thermal spraying method such as a plasma spraying method, a solution coating method such as an alkoxide method or an organometallic compound method, and the like are used. Among them, the solution coating method is used. It is preferable because it can be applied to complicated places such as inside the pipe.

The solution coating method is preferably a method in which a predetermined substrate is coated with at least one solution selected from polysiloxane, polysilazane and polyzirconoxane, and then baked.

Examples of the polysiloxane include, for example, the general formula — (SiR ¹ R ² —O) — (wherein R ¹ and R ² are hydrogen atoms or hydrocarbon groups).
Those having a repeating unit represented by Examples of the polysilazane include, for example, the general formula — (SiR ³ R ⁴ —NR ⁵ ) — (wherein R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, An aryl group, an aralkyl group, an alkylsilyl group, an alkylamino group or an alkoxy group, provided that at least one of R ³ , R ⁴ and R ⁵ is a hydrogen atom) and the like. To be A methyl group is preferred as the hydrocarbon group in these formulas.

The polyzirconoxane is represented by the general formula (I)-(ZrMM'-O) _n- (I) [wherein M and M'independently represent a hydroxyl group, R or OR (wherein R is a hydrocarbon group) or a ligand, and n is 2 to 5], and a compound mainly having a chain structure represented by the formula (II) R ⁶ — ^{_{(ZrMM'-O) n -R 7}} (II) (M in the formula, M 'and n are as defined above, R ⁶
And R ⁷ is a hydrocarbon group, an acyloxyl group or a hydrocarbyloxy group), and particularly, for the groups represented by M and M ′ in the general formula (I) or the general formula (II), One of which is a hydroxyl group and the other is an OR or R group, especially OR or R
The group represented by is one having 3 or more carbon atoms, particularly one that causes steric hindrance, such as a cyclopentadienyl group, a phenyl group, a dihydroquinoid group, or a ligand, particularly one that causes steric hindrance, especially a polydentate group. Examples include ligands, particularly acetoacetic acid esters such as ethyl acetoacetate, diols such as ethylene glycol, and β-diketones such as acetylacetone. Further, regarding the groups represented by R ⁶ and R ⁷ in the general formula (II), the hydrocarbon group is an alkyl group, especially an isopropyl group, a propyl group and a methylpentyl group, and the acyloxyl group is an acetoxyl group or benzoyloxyl group. As the group, and as the hydrocarbyloxyl group, a methoxyl group, an isopropoxyl group, a phenoxy group and a benzyloxy group are preferable. Further, the polyzirconoxane may have a structure in which a part of the above-mentioned chain-like structure is three-dimensionally polymerized by cross-linking the M-group and M'group in the structure are eliminated.

The polyzirconoxane has a subscript n of 2 to 5 in the general formula (I) or the general formula (II).
If this n is too large, cracks during film formation increase,
Further, when n is 1, it exhibits almost the same properties as alkoxide and becomes unstable.

The polyzirconoxane is preferably used in combination with a metal-containing organic compound containing yttrium, gadolinium or ytterbium. Examples of the metal-containing organic compound include tri- (π-cyclopentadienyl) yttrium, triphenyl yttrium, tri-
(Π-Cyclopentadienyl) ytterbium, bis (2,4-cyclopentadien-1-yl) phenyl ytterbium, tri- (π-cyclopentadienyl) gadolinium, bis (2,4-cyclopentadiene-1-
Yl) phenylgadolinium, yttrium acetate, yttrium alkoxide and other organometallic compounds,
Examples thereof include complexes such as tris (acetylacetonato) yttrium. Among them, those containing yttrium are preferable, and tris (acetylacetonato) yttrium is particularly preferable.

In the case of this combined use, the ratio of the polyzirconoxane and the metal-containing organic compound used is preferably L ₂ O ₃ / ZrO ₂ (where L
Is Y, Gd or Yb) in a molar ratio of 0.03 to 0.
15, preferably 0.05 to 0.1, especially 0.07 to
It is chosen to be 0.09.

The organic solvent used for preparing the solution of the above-mentioned polymer is not particularly limited, but alcohols such as methanol, ethanol, isopropyl alcohol and butanol, esters such as ethyl acetate, ethers such as tetrahydrofuran, xylene, toluene and benzene. Hydrocarbons such as

Among the above polymer solutions, polyzirconoxane alcohol solutions, especially methanol solutions, are yellow, transparent and viscous liquids having spinnability, and the viscosity can be greatly changed by adding a solvent. It is advantageous in that the viscosity suitable for coating can be adjusted. Moreover, this polyzirconoxane has a usable atmosphere in a film-forming technique using a conventional alkoxide such as zirconium isopropoxide because it is hydrolyzed and gelated due to the humidity in the air during application. In addition to the limitation, it has a drawback that the yield is low. On the other hand, even in the air, at room temperature, the gelation rate is slow, gelation does not occur at the time of application, and white turbidity does not occur. Does not gel in about 2 hours,
Since it can maintain a nearly transparent state, it is an excellent film forming material.

As the method for applying the solution of the above-mentioned polymer, brush coating method, screen printing method, spin coating method, dipping method, doctor blade method, migration method,
A conventional method such as a spray method is used.

The coating amount of the above polymer solution is influenced by the polymer concentration of the solution, the coating area of the above substrate, the surface roughness, etc., but the thickness of the coating film formed by the subsequent baking step is 0.1 to 200 μm. Is adjusted to be a thin film.

In the method of the present invention, after the application of the polymer solution and before firing, if necessary, drying may be carried out and, if necessary, further moistening treatment with water or thermal decomposition treatment, or It is preferable to form a solidified film by repeating the operation. Particularly, the formation of such a solidified film is advantageous when polyzirconoxane is used as the polymer.

The drying treatment is usually carried out at 0 to 200 ° C. for 5 minutes to 2 hours, although it depends on the kind and molecular weight of the above-mentioned polymer, the concentration of the solution of the polymer, the kind of solvent, the coating amount and the like. When polyzirconoxane is used as the polymer, it is preferably carried out at 10 to 40 ° C. for 10 to 60 minutes.

The humidification treatment with water is preferably 50 to 8
It is carried out in a saturated steam atmosphere at 0 ° C. Among them, when polyzirconoxane is used as the polymer, the groups M and M ′ in the general formula (I) or the general formula (II) are eliminated by hydrolysis by this humidification treatment, and the white turbidity and gelation occur. A zirconium oxide precursor forms and solidifies. Polyzirconoxane is a viscous liquid at room temperature, and its viscosity decreases with increasing temperature, but the zirconium oxide film precursor does not have such characteristics. If the film thickness does not reach the desired thickness by performing this process only once, the same coating and humidifying processes as described above are repeated to obtain the desired thickness.

The thermal decomposition treatment used as another method for forming the solidified film is preferably carried out by heating in an air atmosphere. The heating temperature varies depending on the type of the above-mentioned polymer, and is, for example, 200 to 500 ° C, preferably 300 to 400 ° C in the case of polyzirconoxane. If the film thickness does not reach the desired thickness by performing this treatment only once, the same coating and thermal decomposition treatments as described above are repeated to obtain the desired thickness.

The solidified film thus obtained is a precursor of a desired film, and it is presumed that crosslinking and three-dimensional polymerization proceeded. The thickness of this coating film is 0.05 to 100 μm.
m, preferably 0.05 to 5 μm, more preferably 0.
It is 05-2 micrometers.

Next, it is necessary to bake after coating the solution of the above-mentioned polymer or further forming a solidified film. In the firing treatment, the polymer is silicon oxide,
The calcination temperature and calcination time are controlled so that the calcination temperature and calcination time are decomposed into at least one selected from silicon nitride and zirconium oxide, and the predetermined thin film is formed as a coating. Normally, the calcination temperature is the operating temperature of a high temperature fuel cell. As described above, preferably at least one selected from silicon oxide, silicon nitride and zirconium oxide is at a temperature at which it is sufficiently crystallized, particularly in the range of 1000 to 1300 ° C., and the firing time is 1 to 1
It is in the range of 0 hours, preferably 1 to 4 hours.

As described above, it is possible to form at least one kind of coating film selected from crack-free silicon oxide, silicon nitride or zirconium oxide by one pass or by repeating steps less than the conventional one.

The formed coating film is flat and extremely dense, and firmly adheres to the surface of a predetermined base material. Therefore, the surface of the base material is covered and protected with a dense film and has high strength. Further, the formed coating film may be subjected to a firing treatment, if necessary, in order to improve the adhesiveness and the denseness of the film. In this way, the pipe / heat exchange material provided with the predetermined protective film can be manufactured.

[0043]

INDUSTRIAL APPLICABILITY The present invention has excellent heat resistance and corrosion resistance in pipes and heat exchange materials, which have excellent properties due to the chromium-containing heat-resistant metal and the cermet material containing the same, that is, high density and high strength. In particular, when a cermet material is used, it is possible to adjust the thermal expansion characteristics such as the coefficient of thermal expansion by appropriately changing the composition ratio of the metal and the ceramic, while maintaining good physical properties of the piping and heat exchange material, while further protecting the ceramic. Since the membrane can prevent the diffusion of compounds such as chromium and its oxides which are the constituents of the piping and heat exchange material, it is possible to prevent the adverse effect of the diffusion of chromium to the cathode due to the chromium-containing oxidant gas. The remarkable effect is that good battery performance can be maintained for a long time. In particular, it is preferable to form the protective film by a solution coating method, because the coating can spread even to complicated places such as the inside of the pipe. Further, if a solution of polysiloxane, polysilazane or polyzirconoxane is used as the coating solution, it is protected. It is advantageous because it is excellent in covering property such as adhesion and smoothness of the film and denseness.

Further, according to the present invention, by using an appropriate material for the pipe and the heat exchange material, it is possible to match the thermal expansion characteristics such as the coefficient of thermal expansion with the battery material almost equally. For example, when the material of the battery body is mainly zirconia-based material, the heat resistance of the pipe and heat exchange material is higher than that of zirconia-based material, such as Cr-containing refractory metal, and lower than that of zirconia-based material, lanthanum chromite composite. Ceramics cermets such as oxides and yttrium chromite composite oxides may be used. By matching the thermal expansion characteristics in this way, it becomes possible to firmly join the respective members in the fuel cell, the stability of gas sealing is improved, and the cell characteristics are improved. In particular, in the piping / heat exchange material, the volume ratio of the Cr-containing heat-resistant metal is 20 to 60% as the cermet material, the Cr-containing heat-resistant metal is the matrix, the ceramics are present as the dispersoid, and the relative density is 90%. When the above-mentioned composite having a content of 10% or more is used, the strength of the pipe / heat exchange material itself can be further improved, and further excellent performance can be exhibited, which is advantageous.

[0045]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Example A solid oxide fuel cell of a three-stage series cell was produced according to the assembly mode of FIG. As the solid electrolyte plate 11, a 50 × 50 × 0.2 mm plate made of stabilized zirconia, which is zirconia to which 8 mol% of yttria was added, was used. La _0.8 Sr _0.2 MnO ₃ powder (average particle size about 5 μm) on the air passage side
To a thickness of 0.1 mm by a slurry coating method to form a cathode 12, and a cermet mixed powder having a weight ratio of Ni to zirconia of 1: 1 is applied to the hydrogen passage side to a thickness of 0.1 mm by a slurry coating method.
Then, the anode 13 was formed by applying the coating solution to the thickness of mm. The separator 14 and the external terminals 15 and 16 were made of lanthanum chromite. The solid electrolyte plate 11, the separator 14 and the external terminals 15 and 16 are laminated as shown in FIG. 1, and the operating temperature of the battery is between the solid electrolyte plate 11 and the separator 14 and between the solid electrolyte plate 11 and the external terminals 15 and 16. Glass for softening in the vicinity was sandwiched for gas sealing. As this glass, a glass that is resistant to hydrogen reduction at high temperatures up to the operating temperature of the battery, resistant to oxidation to air, and resistant to water vapor is selected. Next, as shown in FIG. 2, a cylindrical alumina-made manifold 22 was attached to the battery 21 thus integrated, and glass was sandwiched between the manifold and the battery for gas sealing. A platinum lead wire was welded and electrically connected to the electrical outlet.

The manifold 22 is for supplying an oxidant gas.
Piping material 23, piping material 24 for discharging reacted oxidant gas, combustion
Material gas supply pipe material 25, pipe for discharging reacted fuel gas
The material 26 was arranged. As the oxidant gas supply pipe material,
Oxidizer gas in piping material substrate made of Inconel 600
Soluble in xylene on all surfaces that will be exposed to
Polysilazane [weight average molecular weight 700, repeated
Unit:-[Si (CH ₃)₂-NH]-] 10% solution?
Apply a polysilazane solution consisting of
A silica film with a relative density of 95% and a thickness of 1 μm is provided as a protective film.
I used a digit. Solid electrolyte prepared in this way
Type fuel cell is heated and kept at 1000 ℃, and the anode side
Hydrogen as the oxidant gas on the cathode side and 5
Power was generated for 1000 hours in A steady operation. By this driving
For the final battery output, measure the deterioration rate from the beginning of operation.
The Cr content in the cathode immediately after this operation was measured.
Was. The results are shown in Table 1.

COMPARATIVE EXAMPLE A battery was produced in the same manner as in the example except that the oxidant gas supply piping was replaced with Inconel 600 itself, and the power was generated, the deterioration rate of the battery output and the Cr content in the cathode.
The content was measured. Table 1 shows the results.

[0049]

[Table 1]

From the above, when the pipe material without the protective film of the comparative example is used, the battery performance is remarkably deteriorated and the Cr content in the cathode is large, whereas the pipe material with the protective film of the embodiment is provided. It was found that the battery performance was hardly deteriorated when Cr was used, and the Cr content in the cathode was suppressed to a low level. From this, it is possible to prevent the diffusion of Cr into the cathode by the ceramic protective film, and to improve the battery performance. It can be seen that can be maintained for a long time.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an example of a flat plate solid oxide fuel cell.

FIG. 2 is a perspective explanatory view of a fuel cell in which a manifold is arranged in the cell of FIG.

[Explanation of symbols]

 11 Solid Electrolyte Plate 12 Cathode 13 Anode 14 Separator 15, 16 External Terminal 21 Battery 22 Manifold 23 Oxidant Gas Supply Piping Material 24 Reacted Oxidant Gas Discharge Piping Material 25 Fuel Gas Supply Piping Material 26 Reacted Fuel Gas Discharge Piping material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Yoshida 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Research Institute

Claims (3)

[Claims] 1. A stack structure comprising an assembly of unit cells in which a solid electrolyte material is sandwiched between a fuel electrode and an oxidant electrode, and the fuel electrode and the oxidant electrode each have a fuel gas as a reaction gas and Supplying and discharging oxidant gas, and connecting / disconnecting piping material for discharging the reacted gas or piping material and piping material for oxidizing gas supply of the piping material, for heating the oxidizing gas to high temperature In a solid oxide fuel cell equipped with a heat exchange material, 5% of chromium is used as a pipe material for supplying an oxidant gas or the pipe material and the heat exchange material.
A covering material comprising a base material made of at least one selected from the above heat-resistant metals and cermets of the heat-resistant metals and ceramics, and a ceramic protective film provided on the surface of the base material corresponding to the oxidant gas. A solid oxide fuel cell characterized by the following. 2. A base material for use in the solid oxide fuel cell according to claim 1, comprising a heat-resistant metal containing 5% or more of chromium and at least one selected from cermets of the heat-resistant metal and ceramics. A pipe material for a solid oxide fuel cell, comprising a ceramic protective film provided on the surface of the base material corresponding to the oxidant gas. 3. A base material for use in the solid oxide fuel cell according to claim 1, comprising at least one selected from a heat-resistant metal containing 5% or more of chromium and a cermet of the heat-resistant metal and ceramics. A heat exchange material for a solid oxide fuel cell, comprising a ceramic protective film provided on the surface of the base material corresponding to the oxidant gas.