JP2004362913A - Electrolyte for solid oxide fuel cell and method for producing the same - Google Patents

Abstract

An electrolyte for a solid oxide fuel cell capable of improving a mechanical strength without deteriorating ionic conductivity, obtaining a high-performance and highly reliable fuel cell, and such an electrolyte And a cell plate for a solid oxide fuel cell using such an electrolyte.
A modified region (8YSZ) 2a having a high yttria concentration is provided by further impregnating yttria at a desired portion in a planar direction of a plate-like electrolyte (3YSZ) 2 composed of zirconia and yttria, and a peripheral portion and a central lattice are provided. The ionic conductivity in the region 2a is improved while securing the mechanical strength of the shape portion.
[Selection diagram] Fig. 4

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid oxide fuel cell, and more particularly, to a structure of an electrolyte for a solid oxide fuel cell having excellent mechanical strength, a method for producing the same, and a solid oxide using such an electrolyte. The present invention relates to a cell plate for a physical fuel cell.
[0002]
[Prior art]
Depending on the type of electrolyte used, the fuel cell is a phosphoric acid type (hereinafter abbreviated as “PAFC”), a molten carbonate type (hereinafter abbreviated as “MCFC”), a solid polymer type (hereinafter “PEFC”). ) And solid oxide type (hereinafter abbreviated as “SOFC”).
Among them, the SOFC fuel cell uses a solid oxide electrolyte material having ionic conductivity instead of a liquid material such as a phosphoric acid aqueous solution or a molten carbonate as an electrolyte material, and uses a PAFC type or an MCFC type. It is expected to be applied to an on-site cogeneration system because of its higher power generation efficiency and higher-temperature exhaust heat than that of the conventional fuel cell.
[0003]
As a typical and specific fuel cell structure of an SOFC fuel cell, for example, a parallel plate fuel cell can be mentioned.
The structure of this parallel plate fuel cell is basically the same as that of the PAFC type or MCFC type, and is a flat cell in which a fuel electrode layer and an air electrode layer are laminated on both sides of a substrate constituting an electrolyte layer. It has a structure in which plates and separators / interconnectors having a fuel gas flow path on one side and an air flow path on the other side are alternately bonded. In addition, in order to reduce the internal resistance of the electrolyte layer and improve the power generation efficiency with respect to such an electrolyte support type structure, in order to reduce the thickness of the electrolyte layer, one of a porous fuel electrode and an air electrode is used. An electrode supporting type structure in which an electrolyte membrane and the other electrode layer are formed using a layer as a support has been proposed.
[0004]
In such a solid oxide fuel cell, it is conceivable to increase the power generation capacity by increasing the plate area of the electrolyte layer. However, in order to increase the plate area of the electrolyte layer, the material of the electrolyte substrate must be increased. It is necessary to increase strength. However, when the electrolyte substrate is simply made thicker (0.2 to 0.3 mm) to improve the strength, the internal resistance is increased as compared with the case where the electrolyte substrate is thinner, and the electric power is reduced due to a decrease in conductivity. There is a problem that characteristics are impaired. Therefore, an electrolyte layer having low internal resistance and high mechanical strength is desired.
[0005]
In general, in a solid oxide electrolyte material, oxygen ion conductivity and mechanical strength have an opposite relationship. This is because the conduction of oxygen ions is caused by the occurrence of crystal defects caused by doping the substrate oxide and the distortion of the crystal lattice, and improving the ion conductivity means that Increasing such defects and strains naturally leads to a decrease in the strength of the base material.
As one of the solutions to such a problem, it is known to increase the strength of the electrolyte layer by providing a support member for supporting the electrolyte layer on one or both of the upper surface and the lower surface of the electrolyte layer ( Patent Document 1).
[0006]
[Patent Document 1]
JP 2000-133284 A
[0007]
[Problems to be solved by the invention]
However, in the method described in Patent Document 1, since a support member is additionally provided on the surface of the electrolyte layer, it is necessary to separately manufacture the support member and further integrate the support member with the electrolyte layer. . Therefore, there is a problem that a material and a manufacturing process of the support member, a bonding process of the electrolyte layer and the support member, and the like are newly generated, and the manufacturing process is complicated and long, and the cost is high.
In the above-described fuel cell having the electrode support type structure, the electrode substrate requires a considerably porous structure for gas supply, but also requires a mechanical strength as a support substrate. In addition to forming a thin electrolyte on such a porous electrode substrate, extremely high technology is required.
[0008]
The present invention has been made in view of the above-described problems in the conventional solid oxide fuel cell, without impairing the ionic conductivity of the electrolyte as a substrate or an electrolyte layer formed on another substrate. An electrolyte for a solid oxide fuel cell capable of improving a mechanical strength and obtaining a high-performance and highly reliable fuel cell, a method for producing such an electrolyte, and further such an electrolyte An object of the present invention is to provide a cell plate for a solid oxide fuel cell using the same.
[0009]
[Means for Solving the Problems]
The solid oxide fuel cell electrolyte of the present invention is a plate-like or membrane-like electrolyte composed of zirconia and a first additive, in which a modified region having a different concentration or composition of the additive is provided at a desired position in a planar direction. It is characterized in that such a configuration in the solid oxide fuel cell electrolyte is a means for solving the above-mentioned conventional problems.
[0010]
The method for producing an electrolyte for a solid oxide fuel cell of the present invention is suitable for producing the above-mentioned electrolyte for a fuel cell, and comprises zirconia and a first additive such as Y. ₂ O ₃ , Sc ₂ O ₃ , CaO, MgO, etc., are molded into a desired shape and calcined to form a calcined body having a low sintering density, and then a second additive such as Y, Sc, Ca, Mg, Ti, It is characterized in that a solution containing Nb, Ta, Mn, Al, or the like is applied to a desired region of the calcined body and is impregnated, and the sintering is performed to increase the sintering density.
[0011]
Furthermore, the cell plate for a solid oxide fuel cell of the present invention is characterized in that the solid oxide fuel cell electrolyte is sandwiched between an upper electrode layer and a lower electrode layer.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the electrolyte for a solid oxide fuel cell of the present invention will be described in more detail.
[0013]
As described above, the solid oxide fuel cell electrolyte of the present invention is in the form of a plate or a film made of zirconia and the first additive, and has a modified region at a desired portion in the planar direction, that is, another region. Since there is a region where the concentration of the additive is higher than the portion and a region containing another additive in addition to the additive, the additive can reduce the physical properties such as the mechanical strength and ionic conductivity of the denatured region. The electrolyte can be adjusted according to the site, and the electrolyte has both mechanical strength and ionic conductivity.
[0014]
In the electrolyte for a solid oxide fuel cell of the present invention, zirconia is used as a main component as an electrolyte base material, and a first additive which is a component contributing to stabilization of zirconia, for example, Y ₂ O ₃ , Sc ₂ O ₃ , CaO, MgO and the like are used alone or in any combination.
[0015]
Since these first additives have a function of improving the ionic conductivity of the electrolyte, they can be used by increasing the concentration of desired portions or as the first additives from the above group. By adding an oxide other than the above as the second additive, the ionic conductivity of the region is improved, and the power generation performance when a cell is formed is improved.
In addition to the above additives, oxides of 4A group, 5A group, 7A group, and 4B group, for example, TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , MnO ₂ And the like also have a function of improving ion conductivity, so that the same effect can be obtained by adding them to desired portions as second additives. In addition, about these additives, not only a single addition but a composite addition may be sufficient.
[0016]
On the other hand, for example, Al ₂ O ₃ And MgAl ₂ O ₄ Has a function of increasing the mechanical strength of the electrolyte base material, and thus can be strengthened by adding these as a third additive to a desired region, for example, the outer peripheral portion.
[0017]
That is, the conventional electrolyte for a solid oxide fuel cell is a uniform material in the in-plane direction, so that even if the functions required in the plane are different, it is necessary for the single material to fulfill all functions. In other words, the cell portion where high ion conductivity is required, the outer peripheral portion where the ion conductivity is not required, and the manifold portion where the strength is required have to be formed of the same material.
[0018]
On the other hand, according to the electrolyte of the present invention, using an electrolyte base material having excellent mechanical strength, a portion requiring strength, that is, a reason for securing gas sealing properties and reducing contact resistance at the time of stacking, etc. Thereby, the first additive concentration in other portions is increased while leaving the outer peripheral portion where strong stress is applied, the periphery of the gas manifold, or a beam-like portion for strengthening the cell forming portion in the central portion, or the like. By adding the second additive, or by increasing the concentration of the first additive and then further adding the second additive, the ion conductivity of the cell equivalent part can be increased. Thus, an electrolyte having excellent power generation characteristics and excellent strength can be obtained.
In addition, by using an electrolyte base material having excellent ion conductivity and adding a third additive only to a portion where the above strength is required, the ion conductivity of a cell equivalent portion is secured. Meanwhile, the mechanical strength of the region can be increased, and an electrolyte having both power generation characteristics and strength can be obtained. Needless to say, it is of course possible to increase the ion conductivity of the cell-equivalent portion by the first or second additive, and further increase the strength of the outer peripheral portion or the like by the third additive.
[0019]
As described above, the solid oxide fuel cell electrolytes having different ionic conductivities and mechanical strengths depending on parts can be manufactured by, for example, separately forming regions having different components and concentrations and then laminating them. Is zirconia and a first additive, namely Y ₂ O ₃ , Sc ₂ O ₃ , CaO, MgO, etc., are molded into a desired shape, and then calcined to form a calcined body having a low sintering density, and a second additive such as Y, Sc is added to a desired region of the calcined body. , Ca, Mg, Ti, Nb, Ta, Mn, Al, etc., can be easily manufactured by applying and impregnating the solution and then performing main firing.
[0020]
Here, press molding, extrusion molding, a doctor blade method, or the like can be employed for molding the electrolyte material. Alternatively, it can be formed on a substrate made of silicon or an electrode material. In this case, a slurry or paste-like material is applied to the substrate by a coating method or a printing method, molded, dried, and then dried. Together with the calcination.
When applying the solution containing the second additive to the calcined body that has been calcined, it is desirable to apply masking to a portion that is not to be impregnated with, for example, a commercially available masking tape. If a fine pattern is required, a film resist or the like can be used.By performing masking using a photolithography technique using a film resist or the like, a high-strength portion such as a lattice or honeycomb is formed in a cell equivalent region. Since it can be left or formed and functions as a beam supporting the cell part, the area of the power generation unit (cell) can be increased without impairing the mechanical strength, and the power generation efficiency can be further improved. Can be expected.
[0021]
Furthermore, in order to reduce the contact resistance of the electrical connection at the time of current collection, a pressing force is required. However, current collection can be performed intensively in a region where the strength is improved. It is also possible to improve the performance and reliability by reducing the amount of light.
[0022]
The cell plate for a solid oxide fuel cell of the present invention has the above-mentioned electrolyte for a solid oxide fuel cell sandwiched between an upper electrode layer and a lower electrode layer, and therefore has excellent power generation efficiency per unit volume and gas Thus, a high-performance fuel cell having excellent sealing properties and little current collection loss can be obtained.
[0023]
In the cell plate for a solid oxide fuel cell, the air electrode material is La. _1-X Sr _X MnO ₃ (LSM), La _1-X Ca _X MnO ₃ (LCM), La _1-X Sr _X CoO ₃ (LSC), Pt, and the like can be used. On the other hand, as an anode material, NiO-YSZ cermet, Ni-SDC (samarium-doped ceria) cermet, Pt, and the like can be used. However, the present invention is not limited to this.
To form the electrode layer, for example, a slurry coating method, a printing method, a sputtering method, an electron beam evaporation method, a plasma spray method, an ion plating method, a frame spray method, a plasma jet torch method, an EVD method, and a CVD method The law can be adopted.
[0024]
【Example】
Hereinafter, the present invention will be specifically described based on examples. In the present specification, the portion composed of the three layers of the electrolyte layer, the fuel electrode layer, and the air electrode layer includes a battery cell, or simply a cell, a battery cell and a gas supply / exhaust manifold portion on the outer periphery thereof. A cell plate, a single cell unit as a repeating unit composed of the cell plate and the separator, a cell stack of stacked single cell units, and a cell stack having a function of supplying and discharging gas to and from each single cell unit constituting the cell stack The internal flow paths are referred to as a supply manifold and an exhaust manifold, respectively. In addition, oxidizing gas and air are synonymous.
[0025]
(Example 1)
FIGS. 1 to 4 show, as a first embodiment of the present invention, an example in which the present invention is applied to an electrolyte-supported parallel plate solid oxide fuel cell. FIG. FIG. 1B is a top view of the cell plate in the example, FIG. 1B is a cross-sectional view thereof, and FIG. 3C is an enlarged view of a cell periphery.
[0026]
As will be described later, the electrolyte layer 2 in the cell plate 1 shown in FIGS. 1A to 1C has a 3 mol% yttria (Y ₂ O ₃ ) Containing yttria-stabilized zirconia (hereinafter referred to as “3YSZ”), and 8 mol% of yttria (Y ₂ O ₃ ), A region (modified region) 2 a made of yttria-stabilized zirconia (hereinafter referred to as “8YSZ”) is formed. An air electrode layer 3 is formed on the upper surface of the electrolyte layer 2 and a fuel electrode layer 4 is formed on the lower surface thereof so as to sandwich the region 2a made of 8YSZ from above and below.
In the 3YSZ region on the outer peripheral portion of the electrolyte layer 2, a manifold for supplying air and fuel gas to each cell in a stacked state, that is, an air supply manifold 2c, an air exhaust manifold 2d, a fuel A supply manifold 2e and a fuel exhaust manifold 2f are formed.
[0027]
FIG. 2 shows an example of a separator for separating cells from each other while establishing electrical continuity between cells when a stack is formed using the cell plate 1. FIG. 3 shows the structure of a stack laminated using the separator 6.
The separator 6 has an air supply manifold 6c, an air exhaust manifold 6d, a fuel supply manifold 6e, and a fuel exhaust manifold 6f at positions corresponding to the respective manifolds formed on the electrolyte layer 2.
[0028]
Next, a method for manufacturing the electrolyte layer 2 and the cell plate 1 will be described with reference to FIG.
First, a slurry composed of 3YSZ raw material powder, a suitable binder and a dispersion medium is prepared, spread on a carrier film by a doctor blade method, and formed into a sheet. The sheet is dried and the dispersion medium is volatilized to produce a green sheet. The green sheet is cut, punched, or the like to have an appropriate size, and the air and fuel supply / exhaust manifolds 2c to 2f are opened. By performing a heat treatment at about 1000 ° C., a calcined body 2o of an electrolyte having a side of 10 cm and a thickness of about 100 μm is formed as shown in FIG. The calcined body 2o has a low sintering density due to a low sintering temperature, and includes voids of about 30 to 60% depending on the sintering temperature.
[0029]
Next, as shown in FIG. 4 (b), a masking 7 is applied to the obtained calcined body 2o, and a desired region 2a is formed by leaving the outer peripheral portion of the calcined body 2o and the lattice beam portion at the center. A solution containing yttrium and yttrium nitrate are applied and impregnated with the opening at the location. The amount of impregnation at this time is adjusted to 8 mol% with respect to zirconia in consideration of the thickness of the calcined body 2o and the amount of yttrium in the solution.
The masking 7 may be a commercially available masking tape or the like if a solution to be impregnated does not pass therethrough, or a film resist or the like if a fine pattern is required. The solution to be applied and impregnated on the calcined body 2o is preferably a solution containing yttrium, and other than the yttria component is volatilized by the calcination treatment. Organic metal salts represented by yttrium carbonate or alkoxides can be used.
[0030]
Then, after removing the mask 7, main firing is performed at about 1400 ° C. to obtain a dense electrolyte 2 as shown in FIG. At this time, the masked outer peripheral portion and the lattice portion become 3YSZ containing 3 mol% of yttria, which is almost the same as that of the raw material powder. As a result, 8YSZ is formed by being taken into zirconia as yttria.
[0031]
Finally, as shown in FIG. 4 (d), a Ni-cermet material made of NiO and zirconia is coated on the side of the electrolyte 2 to be the fuel electrode so as to cover the region 2a where the 8YSZ is formed and the lattice-like portion. And fired at a temperature of about 1000 to 1200 ° C. _X Sr _1-X CoO ₃ (Hereinafter referred to as “LSC”) is applied to a thickness of about 50 μm and then fired at about 800 to 900 ° C. to form a fuel electrode layer 4 and an air electrode layer 3 on both surfaces of the electrolyte layer 2, respectively. It is referred to as plate 1.
[0032]
In this example, 3YSZ having excellent mechanical strength was used as a base material, and 8YSZ having excellent ionic conductivity was formed in a region contributing to power generation while a portion functioning as a beam for maintaining strength was left in a lattice shape. ing. Therefore, when stacking is performed, the strength of the outer peripheral portion of the cell plate 1 and the periphery of the gas manifold where strong stress is applied in order to secure the gas sealing property, and the strength of the cell portion contributing to power generation by the grid-like beam are also reduced. While securing, the ionic conductivity of the cell portion can be increased, and the diameter of the cell can be increased, so that the cell plate 1 having excellent power generation characteristics and excellent strength can be obtained.
Further, by simply adding a simple process of selectively applying a solution containing yttria at the stage of calcining, the modified region 2a made of 8YSZ having high ionic conductivity can be formed in a portion corresponding to the cell. Thus, the electrolyte layer 2 having both mechanical strength and ionic conductivity can be realized at low cost.
[0033]
In the above embodiment, the doctor blade method was used for forming the electrolyte material. However, the present invention is not limited to this. For example, press molding or extrusion molding may be applied.
Further, the 8YSZ region 2a was formed by applying a solution containing yttria to the calcined body of 3YSZ and impregnating it, but the 3YSZ and 8YSZ regions may be separately formed and bonded. It is possible.
[0034]
Furthermore, in the above embodiment, zirconia was used as a main component as a base material and yttria was used as an additive (first additive). However, the present invention is not limited to this, and is not limited thereto. For example, Sc, Mg, Ca, or the like can be used. Although the same yttria as the additive of the base material was used as the additive for improving the ion conductivity, the same effect can be obtained with Sc, Mg, and Ca described above. Further, the additive for improving the ionic conductivity does not need to be the same as the additive of the base material, and may be an oxide of Group 4A, 5A, 7A, or 4B such as TiO. ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , MnO ₂ Etc. can be used as the second additive. In addition, these additives can be added alone or in combination.
[0035]
(Example 2)
Next, as a second embodiment of the present invention, an example in which the electrolyte of the present invention is similarly applied to an electrolyte-supported parallel plate solid oxide fuel cell will be described. In this embodiment, alumina (Al) was added to the calcined body of 8YSZ having excellent ion conductivity. ₂ O ₃ ) Is different from that of the first embodiment in that the strength of the desired portion, that is, the outer peripheral portion and the central lattice-shaped beam portion is improved by introducing (2).
[0036]
A method for manufacturing the electrolyte layer 2 and the cell plate 1 in the present embodiment will be described with reference to FIG.
First, an 8YSZ calcined body 2o is manufactured using the 8YSZ raw material powder in the same manner as in Example 1 as shown in FIG. 5A.
[0037]
Next, as shown in FIG. 5B, a masking 7 is applied to the calcined body 2o, and it is desired to improve the strength of a desired region 2a, in this case, the outer peripheral portion, the manifold portion, the central portion of the lattice, and the like. A region is opened, and an aqueous solution of aluminum oxalate is applied to the opening and impregnated. At this time, the impregnation amount is adjusted to, for example, 1 mol% with respect to zirconia in consideration of the thickness of the calcined body 2o and the amount of aluminum in the solution.
At the time of masking, a commercially available masking tape, a film resist, or the like can be used as in the first embodiment. Further, as the impregnating solution, it is preferable that the impregnating solution contains aluminum, and that the components other than the aluminum component volatilize by the baking treatment. In addition to the above-mentioned water-soluble aluminum oxalate, an organic metal salt represented by an alkoxide, etc. Can be used.
[0038]
Next, after removing the mask 7, main firing is performed at about 1400 ° C. to obtain a dense electrolyte 2 as shown in FIG. At this time, the masked area becomes 8YSZ containing 8 mol% of yttria, which is almost the same as the raw material powder. However, in the area 2a coated with aluminum oxalate, the oxalic acid component volatilizes, and the aluminum is oxidized to become alumina. It is dispersed in zirconia to form alumina-reinforced 8YSZ.
[0039]
Finally, as shown in FIG. 5 (d), a Ni-cermet material made of NiO and zirconia is applied to a thickness of about 50 μm on the fuel electrode side of the electrolyte 2 so as to cover a region made of 8YSZ. The fuel electrode layer 4 and the air electrode are formed on both surfaces of the electrolyte layer 2 by firing at a temperature of about 1000 to 1200 ° C., further applying LSC to the air electrode side to about 50 μm, and firing at about 800 to 900 ° C. Each of the layers 3 is formed to be a fuel cell plate 1.
[0040]
In this embodiment, 8YSZ having excellent ion conductivity is used as a base material, and the outer peripheral portion, the periphery of the gas manifold, and the lattice beam portion at the center portion are selectively made of alumina reinforced 8YSZ having excellent strength. As in the case of 1, the electrolyte layer 2 having excellent power generation characteristics and excellent strength is obtained.
[0041]
As a variation of these embodiments, the second embodiment and the first embodiment can be combined.
For example, the base material is 3YSZ, 8YSZ is formed in the cell portion where the ion conductivity is to be improved by using the first embodiment, and the alumina-reinforced YSZ is formed by applying the second embodiment to the outer peripheral portion where the strength is to be improved. , 8YSZ as a base material, the embodiment 1 can be applied to the cell portion to further improve the ionic conductivity, and the embodiment 2 can be applied to the portion where the strength is to be improved to form the alumina-reinforced 8YSZ. is there.
[0042]
(Example 3)
6 to 8 show a third embodiment of the present invention, in which the present invention is applied to an electrode-supporting type, specifically, an anode supporting type parallel plate solid oxide fuel cell using an anode as a supporting substrate. 6 (a) is a top view of a cell plate in the embodiment, FIG. 6 (b) is a cross-sectional view thereof, and FIG. 6 (c) is an enlarged view of a cell peripheral portion.
[0043]
In this cell plate 1, a porous fuel electrode substrate 4 is used as a supporting material, and an electrolyte layer 2 and an air electrode layer 3 are formed thereon. In the electrolyte layer 2, the outer and central beam portions are made of 3YSZ having excellent mechanical strength, and 8YSZ having excellent ion conductivity is formed in the 3YSZ region. The air electrode layer 3 is formed so as to cover the 8YSZ region, and the cell holder 8 made of a heat-resistant metal is joined to the outer 3YSZ region.
[0044]
The cell holder 8 has manifolds for supplying air and fuel gas to the stacked and stacked cells, that is, an air supply manifold 8c, an air exhaust manifold 8d, a fuel supply manifold 8e, and a fuel exhaust manifold 8f. ing.
FIG. 7 shows a structural example of a stack in which the above-mentioned cell plate 1 and the separator 6 similar to the first embodiment are stacked.
[0045]
Hereinafter, a method for manufacturing the electrolyte layer 2 and the cell plate 1 will be described with reference to FIG.
First, a slurry consisting of a binder and a dispersion medium is prepared using Ni-YSZ cermet as a raw material powder, spread over a carrier film by a doctor blade method, and formed into a sheet. Then, the sheet is dried to evaporate the dispersion medium to produce a green sheet. The green sheet is cut, punched, or the like, and is then adjusted to an appropriate size. A square fuel electrode substrate 4 of about 1 mm is formed.
[0046]
Next, a paste is made from the 3YSZ raw material powder, a suitable binder and a dispersion medium, a 3YSZ printed film is formed by a screen printing method, and a preliminary firing is performed at a temperature of several hundreds to 1200 ° C. lower than the firing temperature of the fuel electrode substrate 2. Then, a calcined body 2o made of 3YSZ is formed on the substrate 2 as shown in FIG.
[0047]
Next, as shown in FIG. 8 (b), a masking 7 is applied to the calcined body 2o on the fuel electrode substrate 2 to leave a desired region 2a by leaving the outer peripheral portion and the central lattice beam portion. Yttrium nitrate is applied and impregnated with four openings. The amount of impregnation at this time is adjusted to 8 mol% with respect to zirconia in consideration of the thickness of the calcined body 2o and the amount of yttrium in the solution.
[0048]
Then, after the mask 7 is removed, the main baking is performed at about 1400 ° C. to obtain a dense electrolyte layer 2 as shown in FIG. At this time, the masked outer peripheral portion and the grid-like portion become 3YSZ containing 3 mol% of yttria, which is almost the same as the raw material powder. However, in the region 2a coated with yttrium nitrate, the nitric acid component volatilizes and yttrium is oxidized. As a result, 8YSZ is formed by being taken into zirconia as yttria.
[0049]
Next, as shown in FIG. 8D, an LSC is applied to the electrolyte layer 2 to a thickness of about 50 μm, and then baked at about 800 to 900 ° C. to form an air electrode layer 3. A cell holder 8 having a frame shape made of a heat-resistant metal is joined to the outer periphery of the cell using a glass material 9 to obtain a cell plate 1 having manifolds 8c to 8f (see FIG. 6).
[0050]
In such an electrode-supporting cell, the supporting substrate is an electrode layer and has gas permeability. Therefore, it is necessary to prevent the fuel electrode substrate surface from being exposed to the air electrode so that the fuel gas does not leak to the air electrode. For this reason, a metal frame (cell holder) is bonded to a dense and gas leak-free electrolyte layer, or a dense sealing region made of a ceramic material having high mechanical strength and no gas leak, such as alumina, is formed in a region where the metal frame is bonded. It is necessary to form.
However, when importance is placed on the ionic conductivity of the electrolyte layer, the mechanical strength is insufficient and cracks occur at the joint. In addition, when a high-strength seal region is formed, an additional step is required, and in some cases, stress is generated due to a difference in thermal expansion coefficient due to a difference in material between the electrolyte layer and the seal region, resulting in cracks and other costs. There is also a problem in terms of reliability and reliability.
[0051]
According to this embodiment, the power generation region can be made 8YSZ excellent in ionic conductivity, and since the portion where the cell holder 8 is joined remains 3YSZ, it is excellent in mechanical strength. This solves the above problem.
[0052]
Further, when the current collector is pressed with a large force in order to reduce the contact resistance in the current collection, cracking and peeling of the electrolyte occur, which similarly causes a decrease in reliability. According to this, it is also possible to concentrate current in a region while improving the strength, which requires a pressing force. Further, it is possible to leave a 3YSZ region as a lattice-like or honeycomb-like beam in the 8YSZ region by masking using a photolithography technique using a film resist or the like, and the central portion of the electrolyte layer 2 contributing to power generation can be obtained. In addition, since the mechanical strength can be partially improved, performance improvement and reliability improvement can be expected by reducing the current collecting resistance.
[0053]
In the above embodiment, an example in which the 8YSZ region is formed by applying a solution containing yttria to the 3YSZ calcined body 2o is shown, but the fuel electrode substrate 4 made of Ni-YSZ cermet is used. It is also possible to form the 3YSZ area and the 8YSZ area by screen printing separately.
In addition, yttria used as an additive in the present embodiment can be replaced with another additive as in the first embodiment. Further, in such an electrode-supporting cell, as in the second embodiment, by introducing alumina or the like into the electrolyte layer having excellent ionic conductivity, the strength of a desired portion can be improved.
[0054]
(Example 4)
FIGS. 9 and 10 show, as a fourth embodiment of the present invention, an example in which the present invention is applied to a porous metal supported parallel plate solid oxide fuel cell having cells formed on a porous metal substrate. 9A is a top view of the cell plate in the embodiment, FIG. 9B is a cross-sectional view thereof, and FIG. 9C is an enlarged view of a cell peripheral portion.
[0055]
In the cell plate 1 according to this embodiment, a porous metal substrate 0 made of a heat-resistant metal having a manifold for supplying air and a fuel gas is used as a support material, and a fuel electrode layer 4 and an electrolyte layer 2 are formed thereon. , An air electrode layer 3 is formed. In the electrolyte layer 2, the outer and central beam portions are made of 3YSZ, and 8YSZ is formed in the 3YSZ region. The air electrode layer 3 is formed so as to cover the 8YSZ region, and a cell is formed.
FIG. 10 shows a structural example of a stack in which the cell plate 1 and the separator 6 similar to those in the first embodiment are stacked.
[0056]
In order to manufacture the cell plate 1, first, an air supply manifold 10c, an air exhaust manifold 10d, a fuel supply manifold 10e, and a fuel exhaust manifold 10f are formed on the outer peripheral side, and a porous portion 10b is further formed at a central portion by a porous treatment. The fuel electrode layer 4 is formed by screen-printing and firing a Ni-cermet material made of NiO and zirconia on the metal substrate 10 on which is formed.
Thereafter, the electrolyte layer 2 and the air electrode layer 3 are formed on the support substrate 10 by the same process as that of the third embodiment, and the cell plate 1 according to the third embodiment is obtained.
[0057]
In a cell plate using a porous metal substrate, there are usually problems around the boundary between the porous portion and the non-porous portion of the substrate due to differences in strength at the boundary portion and cracking of the electrolyte layer due to pressing of the current collector. However, according to the present embodiment, similarly to the above-described third embodiment, a portion requiring strength is made to have high strength, and a portion of the cell is made to have high ionic conductivity. can do.
[0058]
【The invention's effect】
As described above, in the solid oxide fuel cell electrolyte of the present invention, the concentration of the additive is higher than that of the other portion at a desired position in the planar direction in the electrolyte composed of zirconia and the specific additive, and Or the like, containing a denaturing region containing these additives, it is possible to adjust the physical properties such as the mechanical strength and ionic conductivity of the denaturing region with these additives, and to apply a high pressure to the outer peripheral machine. It has an extremely excellent effect that it is possible to increase the mechanical strength, improve the ionic conductivity of the central part where battery performance is required, and obtain an electrolyte having both strength and ionic conductivity.
[0059]
Further, the method for producing an electrolyte for a solid oxide fuel cell of the present invention can be suitably used for producing the above-mentioned electrolyte for a fuel cell, and the electrolyte material containing zirconia and the first additive is formed into a desired shape. Then, after calcining to temporarily form a low-sintering-density calcined body, a desired region of the calcined body is coated with a solution containing the second additive to be impregnated, and the main calcining is performed. The electrolyte for a solid oxide fuel cell according to the present invention can be easily manufactured at low cost.
[0060]
Further, the cell plate for a solid oxide fuel cell of the present invention has the above-described electrolyte for a solid oxide fuel cell of the present invention sandwiched between an upper electrode layer and a lower electrode layer. It is possible to obtain a high-performance fuel cell which is excellent in gas sealing property, has excellent gas sealing properties, and has little current collection loss.
[Brief description of the drawings]
FIG. 1 (a) is a plan view showing a structure of a cell plate using an electrolyte for a solid oxide fuel cell according to a first embodiment of the present invention.
(B) FIG. 2 is a cross-sectional view of the cell plate shown in FIG.
FIG. 2C is an enlarged sectional view of a main part of FIG.
2A and 2B are a plan view and a cross-sectional view illustrating a shape of a separator used in the fuel cell stack including the cell plates shown in FIG.
FIG. 3A is a cross-sectional view illustrating an air flow path of a fuel cell stack using the cell plates illustrated in FIG. 1;
FIG. 2B is a cross-sectional view illustrating a fuel gas flow path of the fuel cell stack using the cell plates illustrated in FIG. 1.
4 (a) to 4 (d) are process charts showing a manufacturing procedure of the cell plate shown in FIG.
FIGS. 5 (a) to 5 (d) are process diagrams showing a procedure for manufacturing a cell plate using an electrolyte for a solid oxide fuel cell according to a second embodiment of the present invention.
FIG. 6 (a) is a plan view showing a structure of a cell plate using an electrolyte for a solid oxide fuel cell according to a third embodiment of the present invention.
(B) It is sectional drawing of the cell board shown in FIG. 6 (a).
(C) It is a principal part expanded sectional view of FIG.6 (b).
7A is a cross-sectional view showing an air flow path of a fuel cell stack using the cell plates shown in FIG. 6;
FIG. 7B is a cross-sectional view illustrating a fuel gas flow path of the fuel cell stack using the cell plates illustrated in FIG. 6.
8 (a) to 8 (d) are process diagrams showing a procedure for manufacturing the cell plate shown in FIG.
FIG. 9 (a) is a plan view showing a structure of a cell plate using an electrolyte for a solid oxide fuel cell according to a fourth embodiment of the present invention.
(B) It is sectional drawing of the cell plate shown to Fig.9 (a).
(C) It is a principal part expanded sectional view of FIG.9 (b).
10A is a sectional view showing an air flow path of a fuel cell stack using the cell plates shown in FIG. 9;
FIG. 10B is a cross-sectional view illustrating a fuel gas flow path of the fuel cell stack using the cell plates illustrated in FIG. 9.
[Explanation of symbols]
1 Cell plate for solid oxide fuel cell
2 electrolyte (layer)
2a Denatured region
3 air electrode (layer)
4 Fuel electrode (layer)

Claims (15)

It has a plate-like or film-like shape made of zirconia and a first additive, has a denatured region at a desired portion in the plane direction, and has a higher concentration of the first additive in the denatured region than other portions. For solid oxide fuel cells. The first additive is _{Y 2 O 3, Sc 2 O} 3, CaO and solid oxide fuel cell according to claim 1, characterized in that at least one oxide selected from the group consisting of MgO For electrolyte. It has a plate-like or film-like shape composed of zirconia and a first additive, and has a denatured region at a desired portion in the plane direction, and the denatured region contains a second additive in addition to the first additive. An electrolyte for a solid oxide fuel cell. 4. The solid oxide fuel cell electrolyte according to claim 3, wherein the concentration of the first additive in the denatured region is higher than that of the other portion. The solid oxide type according to claim ₃ , wherein the first additive is at least one oxide selected from the group consisting of Y ₂ O ₃ , Sc ₂ O ₃ , CaO, and MgO. Electrolyte for fuel cells. The second additive is at least one oxide selected from the group consisting of Y ₂ O ₃ , Sc ₂ O ₃ , CaO and MgO other than the oxide used as the first additive. An electrolyte for a solid oxide fuel cell according to any one of claims 3 to 5. Second additive _{TiO 2, Nb 2 O 3,} Ta 2 O 3 and any one of claims 3-5, characterized in that at least one oxide selected from the group consisting of MnO ₂ Item 10. The electrolyte for a solid oxide fuel cell according to item 8. An electrolyte for a solid oxide fuel cell, which has a plate shape or a film shape made of zirconia and a first additive, and has a third additive in an outer peripheral portion thereof. The electrolyte for a solid oxide fuel cell according to any one of claims 1 to 7, wherein the outer peripheral portion contains a third additive. The third additive is _Al 2 _{O 3} and / or solid oxide fuel cell electrolyte according to claim 8 or 9, characterized in that a MgAl ₂ O _4. After the electrolyte material containing zirconia and the first additive is molded into a desired shape and calcined to temporarily form a calcined body having a low sintering density,
In a desired region of the calcined body, the second additive is applied in a solution state and impregnated,
Subsequently, a method for producing an electrolyte for a solid oxide fuel cell, comprising performing a main firing. The first additive is _{Y 2 O 3, Sc 2 O} 3, CaO and solid oxide fuel cell according to claim 11, characterized in that at least one oxide selected from the group consisting of MgO Manufacturing method of electrolyte for use. 13. The solid oxide type according to claim 11, wherein the second additive is at least one element selected from the group consisting of Y, Sc, Ca, Mg, Ti, Nb and Ta. A method for producing an electrolyte for a fuel cell. 13. The method for producing an electrolyte for a solid oxide fuel cell according to claim 11, wherein the second additive is Mn and / or Al. A cell plate for a solid oxide fuel cell, comprising the solid oxide fuel cell electrolyte according to any one of claims 1 to 10 sandwiched between an upper electrode layer and a lower electrode layer.

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