JP2011192483A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell capable of suppressing occurrence of cracks and breakages, or the like, due to thermal stress. <P>SOLUTION: The solid electrolyte fuel cell of a fuel electrode supporting type has a structure in which a power generation cell 1 is provided with an air electrode 4; a fuel electrode 2, and an electrolyte layer 3 interposed between them; and the electrolyte layer 3 and the air electrode 4 are supported by the fuel electrode 2. The electrolyte layer 3 is constituted of a first electrolyte layer 31; a second electrolyte layer 32 that is arranged between the fuel electrode 2 and the first electrolyte layer 31; and a third electrolyte layer 33 that is arranged between the air electrode 4 and the first electrolyte layer 31. The first electrolyte layer 31 is formed of an oxide ion conductor containing La and Ga as a main component, and its thickness of the layer is 50 μm or less, while the second electrolyte layer 32 and the third electrolyte layer 33 have bending strength which is larger than that of the first electrolyte layer 31, and the thickness of the electrolyte layer 3 is less than 1/10 the thickness of the fuel electrode layer 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell. In particular, the present invention relates to an improvement in electrolyte structure for enabling improvement in performance and reliability of a power generation cell.

  A fuel cell obtains an electromotive force by utilizing a reaction between a reducing gas fuel such as hydrogen and oxygen, and various types are known depending on the type of electrolyte. Specifically, solid polymer form (PEFC: Polymer Electrolyte Fuel Cell), phosphoric acid form (PAFC: Phosphoric Acid Fuel Cell), molten carbonate form (MCFC: Molten Carbonate Fuel Cell), solid oxide form (SOFC: Solid Oxide Fuel Cell).

  Among these, solid oxide fuel cells, for example, have higher power generation efficiency than solid polymer fuel cells, etc., and are capable of hybrid power generation and internal reforming of fuel using waste heat. Since it has advantages such as being there and is highly practical, improvements are being made in various directions. In particular, since the electrolyte structure has a great influence directly on the performance of the fuel cell, its improvement is the key to practical use.

  Under such circumstances, various proposals have been made regarding the electrolyte structure. For example, Patent Document 1 discloses that in a solid electrolyte fuel cell in which an anode and a cathode are disposed via a solid electrolyte, the solid electrolyte has a multilayer structure of oxygen ion conductive oxide solid solutions having different additive ratios. It is disclosed.

  In the invention described in Patent Document 1, in a solid electrolyte of a self-supporting membrane type, a solid solution having a slightly lower oxygen ion conductivity but a relatively high mechanical strength, and a solid solution having a relatively high mechanical strength but a relatively low mechanical strength. By adopting a multilayer structure (three-layer structure), the mechanical strength of the entire solid electrolyte is improved. When the solid electrolyte is formed with the same thickness, the three-layered solid electrolyte has higher mechanical strength than the single-layered solid electrolyte.

In Patent Document 2, in a solid oxide fuel cell in which mechanical strength is maintained by an air electrode, the solid electrolyte membrane is a first electrolyte made of a LaGaO ₃ -based oxide whose ion transport number is substantially equal to 1. It is disclosed to have a two-layer structure including a layer and a second electrolyte layer made of a LaGaO ₃ -based oxide having a lower ion transport number and higher oxygen ion conductivity than the first electrolyte layer. In the invention described in Patent Document 2, output performance is improved by making the solid electrolyte have the two-layer structure.

  In Patent Document 3, in a solid oxide fuel cell, an electrolyte membrane is formed of a first layer made of a material having oxygen ion conductivity S1 on the air electrode side and a material having oxygen ion conductivity S3 on the fuel electrode side. It is disclosed that it is constituted by a third layer and a second layer which is provided between the first layer and the third layer and has an oxygen ion conductivity S2 and which is made of a material containing at least zirconia. In the invention described in Patent Document 3, by forming the first layer and the third layer made of a material having a high oxygen ion conductivity, oxygen ions generated by a reaction occurring between the air electrode and the electrolyte membrane are efficiently converted into the electrolyte membrane. Because it can supply well, the reaction that takes place between the electrolyte membrane and the fuel electrode can proceed efficiently, and since it has a second layer made of a material containing zirconia, there is no gas permeability and oxygen ions are efficient It is said that a solid oxide fuel cell excellent in output performance can be provided by being able to supply well to the fuel electrode side.

JP-A-5-62700 JP 2004-296204 A JP 2004-303712 A

  In order to improve the performance of a solid oxide fuel cell, it is advantageous to form a thin material having high oxide ion conductivity to form an electrolyte membrane. By reducing the thickness of the electrolyte membrane, the electric resistance is reduced and the power generation performance is improved.

  As a form of the solid oxide fuel cell, there are an electrolyte support cell in which an electrolyte is thickened to form a self-supporting membrane, and an electrode support cell in which a fuel electrode or an air electrode of the electrode is thickened to form an electrolyte membrane thereon. However, from the viewpoint of power generation performance, it can be said that the electrode support cell that can make the electrolyte thinner is more advantageous. In general, since the electrode overvoltage that causes a decrease in power generation performance is higher in the air electrode, the fuel electrode side having a small overvoltage is thickened to form the fuel electrode support cell.

As a material having high oxide ion conductivity, LaGaO ₃ -based materials are known. For example, when a fuel electrode support cell structure is adopted and the thickness is reduced to a certain thickness or less, the influence of electron conductivity is caused. There is a problem that a short circuit is formed inside the cell, and the power generation performance may be reduced.

  In addition, the electrolyte must be dense, but when the thickness of the electrolyte is reduced, there is a problem in that the electrolyte is liable to crack, resulting in a decrease in performance. In consideration of these problems, the techniques described in the above-mentioned patent documents are not necessarily sufficient.

  For example, the invention described in Patent Document 1 employs an electrolyte support cell structure in which the electrolyte is a self-supporting membrane, so there is a limit to reducing the thickness of the electrolyte membrane, and it is difficult to improve power generation performance. Moreover, since the material which comprises electrolyte is expensive, there exists a possibility of causing the increase in the manufacturing cost of the whole power generation cell.

  Since the invention described in Patent Document 2 has a structure in which two dense electrolyte layers are laminated, the stress tends to be biased to one side, and problems such as cell cracking and electrolyte / electrode interface breakdown due to long-time operation, etc. May occur. In addition, since the same material system is used for the first electrolyte layer and the second electrolyte layer, there is a problem that the diffusion of elements proceeds during firing and power generation, and the reliability is significantly reduced.

  In the invention described in Patent Document 3, the first layer and the third layer do not expect performance as an electrolyte, but prioritize the function as a layer that promotes the reaction between the fuel electrode and the electrolyte membrane. For this reason, there is a concern that the performance improvement may be insufficient.

  An object of the present invention is to provide a solid oxide fuel cell that can operate at a low temperature by taking advantage of the fuel electrode support cell.

  In order to solve the above-described problems and achieve the object, the solid oxide fuel cell of the present invention has the following configuration.

  The solid oxide fuel cell of the present invention is a solid oxide fuel cell including an air electrode, a fuel electrode, and an electrolyte layer interposed therebetween, wherein the fuel electrode includes the electrolyte layer and the air. The electrolyte layer is supported between the first electrolyte layer, the second electrolyte layer disposed between the fuel electrode and the first electrolyte layer, and between the air electrode and the first electrolyte layer. And a thickness of the electrolyte layer is less than 1/10 of a thickness of the fuel electrode layer, and the first electrolyte layer is mainly composed of La and Ga. The first electrolyte layer has a thickness of 50 μm or less, and the second electrolyte layer and the third electrolyte layer have a bending strength greater than that of the first electrolyte layer. To do.

  The second electrolyte layer and the third electrolyte layer are preferably formed of zirconium oxide (YSZ) in which yttrium is dissolved.

  The ratio of the thickness of the second electrolyte layer to the thickness of the third electrolyte layer is preferably 1 <thickness of the second electrolyte layer / thickness of the third electrolyte layer <5.

  The solid oxide fuel cell of the present invention employs a fuel electrode support structure and can reduce the thickness of the electrolyte, so that power generation performance is ensured and low temperature operation is possible. The thinner the electrolyte, the better the power generation performance, and it can operate at lower temperatures. This is because if the electrolyte is thin, the resistance is lowered and the power generation efficiency is improved, so that the temperature rise is suppressed.

  In addition, since the second electrolyte layer and the third electrolyte layer having high strength are provided between the first electrolyte layer, which is the main electrolyte, and the electrodes (fuel electrode and air electrode), the electrode containing metal as a main component and the oxidation are provided. The difference in thermal expansion between the electrolytes made of the material is alleviated, and cracks and cracks due to thermal stress are suppressed.

  In addition, since the second electrolyte layer and the third electrolyte layer having high strength are provided on both sides of the first electrolyte layer, which is the main electrolyte, cracks due to stress bias, interface breakage, and the like are also suppressed.

  According to the solid oxide fuel cell of the present invention, since the fuel electrode support cell structure is adopted, it is possible to provide a fuel cell that has excellent power generation performance and can be operated at a low temperature.

FIG. 1 is a schematic cross-sectional view showing a configuration example of a solid oxide fuel cell (power generation cell) according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the form (embodiment) for implementing the following invention. In addition, constituent elements in the following include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. The configurations disclosed below can be combined as appropriate.

  FIG. 1 is a schematic cross-sectional view showing a configuration example of a solid oxide fuel cell (power generation cell) according to an embodiment of the present invention. A solid oxide fuel cell (power generation cell) 1 includes a fuel electrode 2, an electrolyte layer 3, and an air electrode 4. The electrolyte layer 3 is interposed between the fuel electrode 2 and the air electrode 4. In the power generation cell 1, the fuel electrode 2 has a structure that supports the electrolyte layer 3 and the air electrode 4. That is, the power generation cell 1 has a fuel electrode support cell structure. Therefore, the thickness of the fuel electrode 2 is set to be thicker than other elements (the electrolyte layer 3 and the air electrode 4) of the power generation cell 1. In the present embodiment, the relationship is the total thickness of the electrolyte layer 3 × 10 <the thickness of the fuel electrode 2. By increasing the thickness of the fuel electrode 2, the mechanical strength of the power generation cell 1 can be ensured, and the electrolyte layer 3 can be made thinner.

Thereby, the usage-amount of expensive electrolyte material can be reduced. If the power generation cell has an electrolyte supporting cell structure and the electrolyte is a self-supporting membrane, it is necessary to increase the thickness of the electrolyte in order to maintain mechanical strength. Since the LaGaO ₃ -based material that is an electrolyte material is expensive, using such a material as the electrolyte may cause a significant increase in the manufacturing cost of the power generation cell.

  If the power generation cell 1 has a fuel electrode support cell structure as in the present embodiment, the amount of electrolyte material used can be suppressed as much as possible, so that the manufacturing cost of the power generation cell 1 can be minimized. Moreover, since the electric resistance is reduced and the power generation loss can be reduced by thinning the electrolyte, the power generation performance of the power generation cell 1 can be improved.

  By making the fuel electrode 2 thick, the reactivity becomes good. Since the operating temperature of a solid oxide fuel cell is as high as 500 ° C. or higher, it is possible to generate electricity by reforming a hydrocarbon gas such as city gas or propane gas inside. However, the gas that has passed through the former reformer is not necessarily 100% reformed gas, and residual hydrocarbon gas may be mixed. Residual hydrocarbon gas not only deteriorates the power generation performance but also may cause carbon deposition. By increasing the thickness of the fuel electrode and increasing the Ni catalyst, it is possible to reform this residual hydrocarbon gas and improve the power generation performance.

In the present embodiment, a LaGaO ₃ oxide is used as the electrolyte material. Since LaGaO ₃ -based oxides have a slight electronic conductivity, when a LaGaO ₃ -based oxide is used as the electrolyte material, a short circuit is generated inside when the film is thinned, which may cause a reduction in efficiency. Further, when the electrolyte layer 3 is thinned, there is a risk that cracks or cracks may occur due to thermal stress.

  Therefore, in the present embodiment, the electrolyte 3 has a three-layer structure including a first electrolyte layer 31, a second electrolyte layer 32, and a third electrolyte layer 33. In the three-layer structure, the second electrolyte layer 32 and the third electrolyte layer 33 are formed on both sides of the first electrolyte layer 31, respectively. A second electrolyte layer 32 is disposed between the first electrolyte layer 31 and the fuel electrode 2, and a third electrolyte layer 33 is disposed between the first electrolyte layer 31 and the air electrode 4.

The first electrolyte layer 31 is for forming a main body of the electrolyte layer 3, in this embodiment, LaGaO ₃ based material excellent in oxide ion conductivity is used. The LaGaO ₃ -based material is an oxide ion conductor containing La and Ga as main components, and a LaGaO ₃ -based material represented by the following formula (1) is preferable.
La _1-X M ^I _X Ga _1-YZ M ^II _Y M ^III _Z O ₃ (1)
In formula (1), M ^I represents one or two selected from Sr and Ca, M ^II represents one or two selected from Mg, Al, and In, and M ^III represents Co, Each represents one or two selected from Fe, Ni, and Mn. Further, 0.1 ≦ X ≦ 0.4, 0.1 ≦ Y ≦ 0.4, 0 ≦ Z ≦ 0.15, and 0.1 ≦ Y + Z ≦ 0.4.

  The first electrolyte layer 31 should be as thin as possible. Specifically, the thickness of the first electrolyte layer 31 is preferably 50 μm or less. When the thickness of the first electrolyte layer 31 exceeds 50 μm, the electric resistance increases, and the power generation performance of the power generation cell 1 may be reduced. Since the increase in electrical resistance can be suppressed by setting the thickness of the first electrolyte layer 31 to 50 μm or less, a decrease in power generation performance of the power generation cell 1 can be suppressed.

When the thickness of the first electrolyte layer 31 is reduced, there is a possibility that a crack (crack) or a crack due to thermal stress occurs. In addition, since the LaGaO ₃ -based material has a slight electron conductivity, this effect is increased when the thickness of the first electrolyte layer 31 is reduced. In order to eliminate these disadvantages, the second electrolyte layer 32 and the third electrolyte layer 33 are formed on both sides of the first electrolyte layer 31.

  In order to suppress electron conduction, it is not necessary to form sub-electrolyte layers such as the second electrolyte layer 32 and the third electrolyte layer 33 on both surfaces of the first electrolyte layer 31, and either the second electrolyte layer or the third electrolyte layer is used. Either one is enough. However, the second electrolyte layer 32 and the third electrolyte layer 33 are formed on both sides of the first electrolyte layer 31 in order to prevent stress bias, relieve the stress of the entire electrolyte layer 3, and suppress cracks and the like. It is preferable to do.

  In the present embodiment, the second electrolyte layer 32 and the third electrolyte layer 33 have higher mechanical strength (here, bending strength) than the first electrolyte layer 31. Here, the bending strength is a value measured according to Japanese Industrial Standard JIS R1601 (bending strength test method). By disposing the second electrolyte layer 32 and the third electrolyte layer 33 having higher bending strength than the first electrolyte layer 31 on both sides of the first electrolyte layer 31, the strength of the entire electrolyte layer 3 is ensured. Further, the balance of strength is maintained, and the stress bias is sufficiently reduced. As a result, since the stress of the electrolyte layer 3 as a whole can be relieved, the occurrence of cracks and cracks can be effectively suppressed.

  The second electrolyte layer 32 and the third electrolyte layer 33 have an oxide ion transport number of 1. The second electrolyte layer 32 and the third electrolyte layer 33 also need to function as an electrolyte. At the same time, it is necessary to have a function of blocking the electronic conductivity of the first electrolyte layer 31.

Examples of the electrolyte material that satisfies these requirements include YSZ-based materials such as zirconium oxide (zirconia) in which yttrium is dissolved. The composition of the YSZ-based material is Amol% R ₂ O ₃ —ZrO ₂ (wherein R is one or two selected from Y, Sc and La, and A is 3 to 15). ) Is preferable. By using the YSZ-based material for the second electrolyte layer 32 and the third electrolyte layer 33, it becomes possible to effectively prevent the passage of electrons. And the operating temperature can be set low, and since the temperature difference by ON / OFF of the electric power generation cell 1 decreases, the effect that the influence of thermal expansion can be relieved is acquired. As a result, the power generation cell 1 can withstand repeated temperature changes from normal temperature to several hundred degrees due to on / off of operation.

  The thicknesses of the second electrolyte layer 32 and the third electrolyte layer 33 are arbitrary. However, when these layers are thickened, the thickness of the electrolyte layer 3 as a whole becomes thick, and the advantages of the fuel electrode support cell structure may not be utilized. . Considering this, the total thickness of the electrolyte layer 3 (the thickness of the first electrolyte layer 31 + the thickness of the second electrolyte layer 32 + the thickness of the third electrolyte layer 33) × 10 <the thickness of the fuel electrode 2. It is preferable.

  The second electrolyte layer 32 and the third electrolyte layer 33 may be formed with the same thickness, but may have different thicknesses. As will be described later, the main component of the fuel electrode 2 is metallic nickel, which is larger in expansion and contraction due to heat than the ceramic material of the electrolyte layer 3 and the air electrode 4, and gives stress to the electrolyte layer 3. In consideration of this, the thickness of the second electrolyte layer 32 formed on the fuel electrode 2 side can be formed thicker than the thickness of the third electrolyte layer 33 formed on the air electrode 4 side. . In this case (when the thickness of the second electrolyte layer 32 is formed thicker than the thickness of the third electrolyte layer 33), the thickness is set as follows: 1 <thickness of the second electrolyte layer 32 / third electrolyte layer 33 A thickness of <5 is preferred.

  The film form of the second electrolyte layer 32 and the third electrolyte layer 33 is usually a dense film. However, after the transport density is secured by forming the third electrolyte layer 33 on the air electrode 4 side densely, the fuel It is also possible to form the second electrolyte layer 32 on the pole 2 side porous.

The fuel electrode 2 is preferably a composite electrode having a composite material (cermet) of Ni and a ceramic material. To specifically illustrate the composite electrode, Ni / Ce _1-B M ^IV _B O ₂ (wherein M ^IV represents one or two selected from Sm, Gd, La, 0.1 ≦ B ≦ 0.4.) And the like. Alternatively, a composite electrode including a composite material of Ni / first electrolyte layer forming material, a composite material of Ni / second electrolyte layer forming material, and the like can also be used.

The air electrode 4 is preferably formed of a ceramic material represented by the following formula (2).
La _1-C Sr _C Co _1-D M ^V _D O ₃ (2)
However, where, ^{M V} represents one or two elements selected Fe, Ni, from Mn, is 0 ≦ C ≦ 0.5,0 ≦ D ≦ 0.8.

  Table 1 shows the material, representative composition, characteristics, shape, bending strength, and thickness range of each component.

  In order to produce the solid oxide fuel cell (power generation cell 1) having the above-described configuration, for example, a laminated sintered body having a structure in which the fuel electrode 2 and the electrolyte layer 3 are laminated after firing is formed. What is necessary is just to form the air electrode 4 on top.

(Formation of laminated sintered body)
In order to form a laminated sintered body having a structure in which the fuel electrode 2 and the electrolyte layer 3 are laminated after firing, first, a green sheet for forming a fuel electrode including the constituent material of the fuel electrode 2 is formed from a polyethylene terephthalate (PET) film. It is formed on the top by a doctor blade method.

  Next, an electrolyte forming paste is printed on the formed fuel electrode forming green sheet by screen printing to form an electrolyte forming sheet. The electrolyte forming sheet has a three-layer structure by sequentially printing the second electrolyte forming paste, the first electrolyte layer forming paste, and the third electrolyte layer forming paste.

  After the electrolyte forming paste is printed on the fuel electrode forming green sheet, firing is performed. The firing may be performed at a firing temperature of 1400 ° C., for example.

(Formation of air electrode)
An air electrode forming paste containing the constituent material of the air electrode 4 is screen-printed on the obtained laminated sintered body to form an air electrode forming sheet. This is fired again and baked to obtain a power generation cell 1. The firing temperature at this time is, for example, 1100 ° C.

The produced solid oxide fuel cell (power generation cell 1) has an electrolyte structure in which the first electrolyte layer 31 is sandwiched between the second electrolyte layer 32 and the third electrolyte layer 33 having high mechanical strength. . For this reason, the solid oxide fuel cell (power generation cell 1) is relieved of thermal stress, can respond to temperature changes, and is prevented from being destroyed by the overall structure of the battery. In addition, the first electrolyte layer 31 is made of LaGaO ₃ -based material, and the second electrolyte layer 32 and the third electrolyte layer 33 are made of YSZ-based material, thereby preventing electron transmission even when the electrolyte layer 3 is made thin. The operating temperature can be lowered (for example, set to about 500 ° C.). Further, the influence of thermal expansion can be reduced by reducing the temperature difference caused by turning on / off the operation of the fuel cell. Furthermore, by setting the thicknesses of the second electrolyte layer 32 and the third electrolyte layer 33 appropriately, it is also possible to realize good temperature rising / falling characteristics without reducing the output.

The materials used for the main electrolyte (first electrolyte layer), sub-electrolyte layer (second electrolyte layer and third electrolyte layer), air electrode, and fuel electrode in the experiment are as follows.
Main electrolyte: La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _3-δ (bending strength 200 MPa)
Subelectrolyte: 3 mol% Y ₂ O ₃ —ZrO ₂ (bending strength 800 MPa)
Air electrode: La _0.6 Sr _0.4 Fe _0.8 Co _0.2 O _3-α
Fuel electrode: Ni-Ce _0.8 Sm _0.2 O _2-β composite material

  Using these materials, a power generation cell having a fuel electrode support cell structure with strength at the fuel electrode was produced. In the produced power generation cell, the thickness of the fuel electrode is 500 μm, and the thickness of the air electrode is 20 μm. The thicknesses of the first electrolyte layer, the second electrolyte layer, and the third electrolyte layer in each example are as shown in Table 2. Comparative Examples 1 and 2 are examples of power generation cells having an electrolyte support cell structure. The electrolyte layer is only the main electrolyte layer.

  The power generation performance evaluation test was performed by producing a small cell having a diameter of 20 mm, supplying air to the air electrode side at 200 ml / min, and supplying hydrogen to the fuel electrode side at 200 ml / min. The measurement items are output density at 500 ° C. and 600 ° C., durability at 500 ° C. and 600 ° C., and temperature rise / fall test at 600 ° C. In addition, durability measured the time until a voltage fell 0.5V, and the temperature increase / decrease test repeated 10 times temperature increase / decrease, and measured the difference of the initial performance and the performance after 10 times temperature increase / decrease. The results are shown in Table 2.

  In Comparative Example 1 having an electrolyte supporting cell structure and a thick main electrolyte, the output density is low due to the large electrolyte resistance. In Comparative Example 2 having an electrolyte supporting cell structure and a thin main electrolyte, the output density is slightly reduced due to the influence of electronic conductivity. Furthermore, by repeatedly raising and lowering the temperature, a stress was applied to the cell and cell cracking occurred.

  In each embodiment, the power density is ensured and no cell cracking occurs. Looking at Examples 9-13, the ratio of the thickness of the second electrolyte layer to the thickness of the third electrolyte layer is 1 <thickness of second electrolyte layer / thickness of third electrolyte layer <5. The density is large and the results of the temperature increase / decrease test are also good.

  As described above, the solid oxide fuel cell according to the present invention is useful for enabling low-temperature operation.

1 Solid oxide fuel cell (power generation cell)
2 Fuel electrode 3 Electrolyte layer 31 1st electrolyte layer 32 2nd electrolyte layer 33 3rd electrolyte layer 4 Air electrode

Claims (3)

A solid oxide fuel cell comprising an air electrode, a fuel electrode, and an electrolyte layer interposed therebetween,
The fuel electrode supports the electrolyte layer and the air electrode,
The electrolyte layer includes a first electrolyte layer, a second electrolyte layer disposed between the fuel electrode and the first electrolyte layer, and a first electrolyte layer disposed between the air electrode and the first electrolyte layer. 3 electrolyte layers, and the thickness of the electrolyte layer is less than 1/10 of the thickness of the fuel electrode layer,
The first electrolyte layer is formed of an oxide ion conductor containing La and Ga as main components, and the thickness of the first electrolyte layer is 50 μm or less,
The second electrolyte layer and the third electrolyte layer have higher bending strength than the first electrolyte layer,
A solid oxide fuel cell.   2. The solid oxide fuel cell according to claim 1, wherein the second electrolyte layer and the third electrolyte layer are formed of zirconium oxide (YSZ) in which yttrium is dissolved. The ratio of the thickness of the second electrolyte layer to the thickness of the third electrolyte layer is:
1 <thickness of second electrolyte layer / thickness of third electrolyte layer <5,
The solid oxide fuel cell according to claim 1 or 2, wherein the fuel cell is a solid oxide fuel cell.

Images