WO2015045682A1

WO2015045682A1 - Fuel-cell anode and fuel cell

Info

Publication number: WO2015045682A1
Application number: PCT/JP2014/071733
Authority: WO
Inventors: 新田　高弘; 朗齋藤
Original assignee: 株式会社デンソー
Priority date: 2013-09-25
Filing date: 2014-08-20
Publication date: 2015-04-02
Also published as: JP2015065013A; JP6118694B2

Abstract

This fuel cell (5) has a fuel-cell anode (10), a solid electrolyte layer (2), and a cathode (3). A fuel gas is supplied in the direction (F) of the plane of the fuel-cell anode (10). The fuel-cell anode (10) comprises a plurality of layers, and the outermost layer (11) thereof, i.e. the layer that is the farthest from the solid electrolyte layer (2), has different thicknesses in different sections. The downstream side of said outermost layer (11), where said downstream side is considered to extend from the center of the outermost layer (11) in the flow direction (F) of the fuel gas to a fuel-gas outlet, has more thin sections (111) than the upstream side of the outermost layer (11), where said upstream side is considered to extend from the aforementioned center to a fuel-gas inlet.

Description

Anode for fuel cell and single cell for fuel cell

The present invention relates to a fuel cell anode and a fuel cell single cell, and more particularly to a fuel cell anode used in a fuel cell single cell using a solid electrolyte as an electrolyte, and a fuel cell single cell using the same.

Conventionally, a solid electrolyte type fuel cell unit cell having an anode, a solid electrolyte layer, and a cathode is known. In general, in the fuel cell unit cell, the fuel gas supplied from the fuel gas inlet often flows along the surface of the anode and is discharged from the fuel gas outlet.

Prior Patent Document 1 discloses a fuel cell single cell in which a support having a fuel gas passage for circulating fuel gas therein, an anode layer, a solid electrolyte layer, and a cathode layer are laminated in this order. Has been. In Patent Document 1, it is assumed that the porosity in the anode layer portion located on the downstream side in the fuel gas flow direction is larger than the porosity in the anode layer portion located on the upstream side in the fuel gas flow direction. The structure is described.

JP 2012-94427 A

However, the conventional technique has the following problems. That is, in the fuel cell single cell to which fuel gas is supplied along the surface direction of the anode, a large amount of fuel gas is consumed on the fuel gas inlet side, and the amount of fuel gas reaching the fuel gas outlet side tends to decrease. In some cases, the fuel gas may be exhausted on the fuel gas outlet side. Therefore, there is a problem that the power generation distribution in the cell plane becomes large, and as a result, the temperature distribution in the cell plane becomes large. When the temperature distribution in the surface of the unit cell becomes large, local stress is generated in the unit cell, which may lead to cracking of the unit cell during power generation.

The present invention has been made in view of the above-described background, and when used in a single fuel cell, a fuel capable of uniformizing the power generation distribution in the plane of the single fuel cell caused by the flow of fuel gas. The present invention has been obtained in an attempt to provide a battery anode and a fuel cell unit cell using the same.

A preferred embodiment of the present invention is an anode for a fuel cell that is used in a fuel cell single cell that has an anode, a solid electrolyte layer, and a cathode, and is supplied with fuel gas along the surface direction of the anode. The fuel cell anode is composed of a plurality of layers, and of the plurality of layers of the fuel cell anode, the outermost layer disposed farthest from the solid electrolyte layer is partially thick. The anode for a fuel cell is characterized by being different.

Another aspect of the present invention includes the anode for a fuel cell, a solid electrolyte layer, and a cathode, and fuel gas is supplied along a surface direction of the anode for the fuel cell. It is in a single fuel cell.

The fuel cell anode has the above-described configuration. In particular, among the plurality of layers constituting the anode for the fuel cell, the outermost layer arranged farthest from the solid electrolyte layer is partially different in thickness. Therefore, when the fuel cell anode having the above-described structure is used for a single fuel cell, the gas diffusion distance of the fuel gas is shortened and the gas diffusion is increased in the portion where the thickness of the outermost layer is thin. The power generation distribution in the cell plane due to the flow of the fuel gas can be made uniform. As a result, when the fuel cell anode is used in a fuel cell single cell, the temperature distribution in the cell surface is reduced, local stress is less likely to occur in the cell, and cell cracking during power generation is less likely to occur. . Therefore, the fuel cell anode is effective in improving the reliability of a single fuel cell.

In the fuel cell anode, the anode is multilayered, and the gas diffusivity is controlled by partially changing the thickness of the outermost layer. Therefore, when compared with other fuel cell anodes that control the gas diffusibility by changing the porosity of the anode in the flow direction of the fuel gas, the fuel cell anode according to the present invention is easy to manufacture and reliable. There are advantages such as high and good.

The fuel cell single cell according to the present invention has the fuel cell anode, a solid electrolyte layer, and a cathode. Therefore, in the fuel cell unit cell, the temperature distribution in the cell surface becomes small, local stress is hardly generated in the cell, and cell cracking during power generation is difficult to occur. Therefore, the fuel cell single cell can exhibit high reliability.

It is a typical external appearance perspective view of the anode for fuel cells of Example 1 which concerns on this invention, and a fuel cell single cell. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 2. It is sectional drawing which shows the structure of the outermost layer of the anode for fuel cells of Example 2 which concerns on this invention, and a fuel cell single cell, and shows the structure of the outermost layer in the anode for fuel cells which concerns on Example 1, and a fuel cell single cell This corresponds to FIG.

The fuel cell anode according to the present invention is applied as an anode in a solid electrolyte fuel cell single cell using a solid electrolyte as an electrolyte. As the solid electrolyte constituting the solid electrolyte layer, a solid oxide ceramic exhibiting oxygen ion conductivity can be used.

A fuel cell using solid oxide ceramics as a solid electrolyte is called a solid oxide fuel cell (SOFC). The battery structure of the single fuel cell can be a flat plate having a layered anode as a support from the viewpoint of excellent manufacturability and high power generation efficiency.

Specifically, the fuel cell single cell includes a solid electrolyte layer, a fuel cell anode laminated on one surface (first surface) of the solid electrolyte layer, and the other surface (second surface) of the solid electrolyte layer. And a cathode laminated with or without an intermediate layer, and a fuel cell anode as a support. The intermediate layer is a layer mainly for preventing a reaction that occurs between the material constituting the cathode and the material constituting the solid electrolyte layer. The cathode and the intermediate layer can be composed of one layer or two or more layers. The fuel gas and oxidant gas supply method is such that the fuel gas supplied to the fuel cell anode along the surface direction of the fuel cell anode and the oxidant gas supplied to the cathode along the surface direction of the cathode. A so-called cross flow method in which the fuel cells are supplied to the fuel cell so as to be orthogonal to each other can be employed.

In the structure of the fuel cell anode, the outermost layer of the fuel cell anode is a layer disposed farthest from the solid electrolyte layer. Fuel gas flows from the outermost layer surface. The outermost layer is partially different in thickness. Therefore, the outermost layer includes a relatively thin portion and a relatively thick portion. The outermost layer can include a portion where the thickness is partially zero. The outermost layer can have a plurality of thin portions. In this case, the thin portions may have the same thickness or different thicknesses. Further, the thin portions may have the same form or different forms. Specifically, the thin portion can be in the form of a hole, a groove or the like. The hole or groove may or may not penetrate from the outermost layer surface to the outermost solid electrolyte layer side surface.

In the fuel cell anode, when the fuel gas inlet side is the upstream side of the gas flow with respect to the intermediate point in the gas flow direction of the fuel gas and the fuel gas outlet side is the downstream side of the gas flow with respect to the intermediate point. The outer layer may have a structure in which many portions having a smaller thickness are formed on the gas flow downstream side than on the gas flow upstream side.

In this case, the consumption of the fuel gas on the upstream side of the gas flow is suppressed, and the depletion of the fuel gas on the downstream side of the gas flow is easily suppressed. In addition, in a relatively low concentration fuel gas atmosphere downstream of the gas flow, gas diffusion increases, so the amount of power generation increases and it is easier to make the power generation distribution in the cell plane uniform due to the flow of fuel gas. There are advantages.

In the fuel cell anode, the layer configuration of the fuel cell anode is, for example, an active layer disposed on the solid electrolyte layer side, and an active layer surface of the active layer on the solid electrolyte layer side (second surface). ) And the outermost layer laminated on the surface (first surface) of the diffusion layer opposite to the solid electrolyte layer side in the diffusion layer. It can be set as the structure provided. The active layer is a layer that mainly serves as a reaction field for electrochemical reaction on the anode side for the fuel cell. The diffusion layer is a layer that can mainly diffuse the supplied fuel gas.

In this case, the fuel gas inflow amount can be controlled in the gas flow direction by the outermost layer. Further, the fuel gas that has flowed in can be appropriately diffused by the diffusion layer. Also, the active layer can cause an electrochemical reaction uniformly in the gas flow direction as compared with the case where the outermost layer is not provided. Therefore, in this case, there is an advantage that the distribution of power generation in the cell plane due to the flow of the fuel gas can be easily uniformed by sufficiently exerting each function by each layer to which the functions are shared.

The outer dimensions of the outermost layer, the diffusion layer, and the active layer are not particularly limited. The outer dimensions of the outermost layer, the diffusion layer, and the active layer can all be the same. In addition, the diffusion layer may be configured to cover the remaining surface of the active layer other than the surface in contact with the solid electrolyte layer. In this case, the fuel gas can be diffused from the side surface of the active layer, which is advantageous in improving gas diffusibility.

The fuel cell anode can be configured such that the pore diameter of the diffusion layer is larger than the pore diameter of the outermost layer, that is, the relationship of the outermost layer pore diameter <the diffusion layer pore diameter.

In this case, although the gas diffusibility of the fuel gas is suppressed by the outermost layer, excessive consumption of the fuel gas on the upstream side of the gas flow is eliminated, and the fuel gas is easily sent to the downstream side of the gas flow. And gas diffusion increases in the thin part in the outermost layer. Therefore, in this case, there is an advantage that the power generation distribution in the cell plane due to the flow of the fuel gas can be made more uniform. In particular, when the outermost layer has a configuration in which the portion on the downstream side of the gas flow has a smaller thickness than the upstream side of the gas flow, the effect is increased.

The fuel cell anode is preferably configured to satisfy the relationship of the pore size of the active layer <the pore size of the outermost layer <the pore size of the diffusion layer. In this case, in addition to the above effects, the diffusion layer is unlikely to be a gas diffusion rate-determining field for the fuel gas supplied to the active layer, and the diffusion of the fuel gas to the active layer is difficult to be inhibited. In addition, an increase in reaction points (high surface area) in the active layer is advantageous for improving the power generation characteristics of the single fuel cell.

Note that the size relationship between the pore sizes can be determined by cross-sectional observation with a scanning electron microscope (SEM). In addition, if the cross-sectional observation alone cannot clearly determine the size relationship between the pore sizes, the average pore size of the outermost layer, the average pore size of the diffusion layer, and the average pore size of the active layer are measured. Can be compared. In addition, the said average pore diameter is an average value of the pore diameter computed from the pore distribution measured with the palm porometer.

The average pore size of the active layer is preferably within the range of 0.1 to 5 μm, more preferably within the range of 0.2 to 3 μm, even more preferably within the range of 0.3 to 2 μm, and even more preferably 0.4. It can be in the range of ˜1.5 μm. In this case, since the water generated by the electrode reaction is smoothly discharged, it is easy to suppress a momentary drop in the power generation output due to the water remaining without being discharged. In addition, it is easy to secure the number of reaction points, and it is easy to suppress a decrease in output density. The average pore size of the diffusion layer is preferably within the range of 0.3 to 20 μm, more preferably within the range of 0.4 to 17 μm, even more preferably within the range of 0.5 to 15 μm, and even more preferably 1 to 10 μm. Can be within the range. In this case, it is easy to quickly diffuse the fuel gas into the active layer by the diffusion layer, which is advantageous for suppressing a decrease in output density.

The fuel cell anode can be configured such that the porosity of the diffusion layer is larger than the porosity of the outermost layer, that is, the relationship of the porosity of the outermost layer <the porosity of the diffusion layer is satisfied. Also in this case, as described above, the same effect as in the case of satisfying the relationship of the pore diameter of the outermost layer <the pore diameter of the diffusion layer can be obtained. In the fuel cell anode, preferably, the porosity of the outermost layer is larger than the porosity of the active layer, and the porosity of the diffusion layer is larger than the porosity of the outermost layer, that is, the porosity of the active layer. <The porosity of the outermost layer <the porosity of the diffusion layer can be satisfied. In this case, the same effect as that in the case of satisfying the relationship of the pore size of the active layer <the pore size of the outermost layer <the pore size of the diffusion layer can be obtained. The porosity is a numerical value calculated by {1− (bulk density / apparent density)} × 100 by calculating the apparent density and the bulk density by the Archimedes method.

The porosity of the active layer is preferably within the range of 30-50%, more preferably within the range of 33-48%, even more preferably within the range of 36-46%, and even more preferably within the range of 39-44%. It can be. In this case, since the water generated by the electrode reaction is smoothly discharged, it is easy to suppress a momentary drop in the power generation output due to the water remaining without being discharged. In addition, it is easy to secure the number of reaction points, and it is easy to suppress a decrease in output density. The porosity of the diffusion layer is preferably within the range of 30-60%, more preferably within the range of 36-57%, even more preferably within the range of 42-54%, and even more preferably within the range of 45-51%. It can be. In this case, it is easy to quickly diffuse the fuel gas into the active layer by the diffusion layer, which is advantageous for suppressing a decrease in output density. Further, when the anode is used as a support, it is easy to ensure the strength as the support, and it is advantageous because it is difficult to break when stacking the fuel cell single cells.

In the fuel cell anode, each layer constituting the fuel cell anode can be composed of, for example, a mixture containing a catalyst and a solid electrolyte. Specific examples of the material of the catalyst include nickel (Ni), nickel oxide (NiO, etc.), cobalt (Co), noble metals (Au, Ag, platinum group elements Ru, Rh, Pd, Os, Ir. , Pt, preferably Pt, Pd, Ru) and the like. These can be used alone or in combination of two or more. The catalyst in each layer may be in the form of particles, and all may be the same material or different materials. As the material of the catalyst, nickel and / or nickel oxide can be suitably used. Nickel (nickel oxide becomes nickel in the reducing atmosphere of the anode) has a sufficiently large affinity with hydrogen, which is suitably used for fuel gas, and is less expensive than other metals. Is appropriate.

As the material of the solid electrolyte, specifically, for example, one or more oxides selected from Y ₂ O ₃ , Sc ₂ O ₃ , Yb ₂ O ₃ , and CaO are solid. ZrO ₂ dissolved oxide such as ZrO ₂ ; lanthanum gallate oxide; CeO ₂ , CeO ₂ and Gd, Sm, Y, La, Nd, Yb, Ca, Dr, and Ho Alternatively, a cerium oxide-based oxide such as a ceria-based solid solution doped with two or more elements can be exemplified. These can be used alone or in combination of two or more. The solid electrolyte in each layer constituting the anode for a fuel cell can be in the form of particles, and may be the same material or different materials. As the material of the solid electrolyte, a zirconia solid electrolyte can be preferably used from the viewpoints of oxygen ion conductivity, mechanical strength, and the like.

In addition, the mixture that can constitute the outermost layer of the anode for a fuel cell contains, for example, a mass ratio of the catalyst and the solid electrolyte of 30/70 to 70/30, preferably 40/60 to 60/40. Can be contained within. In addition, the mixture that can constitute the diffusion layer contains the catalyst and the solid electrolyte in a mass ratio of, for example, 30/70 to 70/30, preferably 40/60 to 60/40. it can. The above-mentioned mixture that can constitute the active layer contains the catalyst and the solid electrolyte, for example, in a mass ratio of 30/70 to 70/30, preferably in the range of 40/60 to 60/40. it can.

In the fuel cell anode, the thickness of the outermost layer constituting the fuel cell anode in which the thickness is not reduced is preferably 5 μm or more, more preferably 7 μm or more, and still more preferably from the viewpoint of manufacturing. It can be 10 μm or more. The thickness of the outermost layer where the thickness is not reduced is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less, from the viewpoint of relaxation of power generation distribution and the like. The thickness of the diffusion layer is preferably 300 μm or more, more preferably 400 μm or more, and further preferably 500 μm or more, from the viewpoint of strength and the like when used as a support. From the viewpoint of gas diffusion and the like, the thickness of the diffusion layer is preferably 1500 μm or less, more preferably 1000 μm or less, and even more preferably 800 μm or less. The thickness of the active layer is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more, from the viewpoint of securing a reaction field for gas, electrons, and ions. The thickness of the active layer is preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 60 μm or less from the viewpoint of oxygen ion conductivity and the like.

In the fuel cell unit cell, examples of the material constituting each layer of the fuel cell unit cell include the following, but are not particularly limited.

Examples of the solid electrolyte constituting the solid electrolyte layer include zirconium oxide-based oxides such as yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ); lanthanum gallate-based oxides; CeO ₂ , CeO ₂ with Gd, Examples include cerium oxide-based oxides such as ceria-based solid solutions doped with one or more elements selected from Sm, Y, La, Nd, Yb, Ca, Dr, and Ho. it can. The solid electrolyte layer has an advantage that the ohmic resistance is reduced by reducing its thickness and the output density is improved, but if the thickness is excessively thin, the probability of occurrence of holes penetrating the solid electrolyte layer increases. The fuel gas or oxidant gas may cross leak through the solid electrolyte layer, resulting in a decrease in power density. From the above viewpoint, the thickness of the solid electrolyte layer is preferably 1 to 20 μm, more preferably 3 to 10 μm.

Examples of the cathode material include conductive perovskite oxides such as lanthanum-manganese oxides, lanthanum-cobalt oxides, lanthanum-iron oxides, the perovskite oxides, and the solid electrolytes. The mixture of these can be illustrated. The thickness of the cathode is preferably 10 to 100 μm, more preferably 30 from the viewpoint of increasing the number of reaction active fields in which oxygen contained in an oxidant gas such as air receives and ionizes electrons on the surface of the cathode forming material. It can be ˜50 μm.

Examples of the material for the intermediate layer include the cerium oxide-based oxides. The thickness of the intermediate layer is preferably 1 to 10 μm, more preferably 3 to 7 μm from the viewpoint of preventing diffusion of the cathode constituent element into the solid electrolyte.

The fuel cell anode and the fuel cell single cell having the fuel cell anode can be suitably manufactured through the following first to third steps, but this is not particularly limited.

The first step includes an unfired outermost layer forming material that becomes an outermost layer by firing, and an unfired other layer forming material that becomes another layer excluding the outermost layer of the plurality of layers by firing. The unfired solid electrolyte layer forming material that becomes a solid electrolyte layer by firing, and the unfired intermediate layer forming material that becomes an intermediate layer by firing, if necessary, are layered in this order and pressed. This is a step of obtaining a laminate. The laminated body can be degreased as necessary.

The other layer forming material can be, for example, an unfired diffusion layer forming material that becomes a diffusion layer by firing and an unfired active layer formation material that becomes an active layer by firing. Further, the outermost layer forming materials partially differ in thickness so that a predetermined outermost layer is obtained. The outermost layer forming material, the diffusion layer forming material, and the active layer forming material can be configured to include catalyst particles, solid electrolyte particles, a pore-forming agent, a binder, a plasticizer, and the like. The outermost layer forming material, the diffusion layer forming material, and the active layer forming material have a pore-forming agent content and its content so that the pore diameter is different when the outermost layer, the diffusion layer, and the active layer are formed by firing, respectively. The size, the catalyst particles, the particle diameter of the solid electrolyte particles, and the like can be appropriately adjusted. A sheet-like material can be used for each forming material. The diffusion layer forming material can be formed by laminating a plurality of sheets. In the above, it is also possible to form a paste-like outermost layer forming material in a layer shape partially different in thickness by a printing method or the like on one surface of the sheet-like diffusion layer forming material.

The second step is a step of co-firing the laminate at, for example, 1300 to 1500 ° C. As a result, a fired body in which an anode composed of a plurality of layers including the outermost layer (in the above example, outermost layer, diffusion layer, active layer), solid electrolyte layer, and if necessary, an intermediate layer is laminated in this order is obtained. It is done.

The third step is a step of laminating a cathode forming material that becomes a cathode by firing on the surface of the intermediate layer or the surface of the solid electrolyte layer in the fired body, and firing at 900 to 1200 ° C., for example. is there.

A paste-like material can be used as the cathode forming material. The cathode forming material can be applied in a layer form on the surface of the intermediate layer or the surface of the solid electrolyte layer by a printing method or the like.

Thereby, a fuel cell single cell having the fuel cell anode and the fuel cell anode can be obtained.

In addition, each structure mentioned above can be arbitrarily combined as needed, in order to obtain each effect mentioned above.

Hereinafter, the anode for a fuel cell and the single cell of the fuel cell of the example will be described with reference to the drawings. In addition, about the same member, it demonstrates using the same code | symbol.

Example 1
A fuel cell anode and a single fuel cell according to Example 1 will be described with reference to FIGS. As shown in FIG. 1 to FIG. 3, the fuel cell single cell 5 has the anode 10 for the fuel cell of the first embodiment, the solid electrolyte layer 2, and the cathode 3. Fuel gas is supplied along the surface direction F. As described above, the fuel cell anode 10 according to the first embodiment is used for the single fuel cell 5.

The fuel cell anode 10 is composed of a plurality of layers, and among these layers, the outermost layer 11 disposed farthest from the solid electrolyte layer 2 is partially different in thickness.

Further, as shown in FIG. 1, the fuel cell single cell 5 of the first embodiment includes the fuel cell anode 10 of the first embodiment, the solid electrolyte layer 2, and the cathode 3, and the fuel cell. Fuel gas is supplied along the surface direction of the anode 10 for use. Specifically, the fuel cell single cell 5 includes a solid electrolyte layer 2, a fuel cell anode 10 laminated on one surface (first surface) of the solid electrolyte layer 2, and the other surface of the solid electrolyte layer 2 ( The cathode 2 is laminated on the second surface) with the intermediate layer 4 interposed therebetween, and is a flat single cell having the fuel cell anode 10 as a support. Further, the fuel gas and oxidant gas supply method is specifically, along the surface direction of the fuel gas anode 10 and the cathode 3 along the surface direction F of the fuel cell anode 10. A so-called cross flow system is used in which the oxidant gas supplied to the cathode 3 is supplied to the single fuel cell 5 so as to be orthogonal to each other. These are described in detail below.

In the fuel cell anode 10 of the first embodiment, the outermost layer 11 includes a relatively thin portion 111 and a relatively thick portion 112 (portion where the thickness is not reduced). The outermost layer 11 has a plurality of thin portions 111. Specifically, the thin portions 111 are perpendicular to the gas flow direction F of the fuel gas, as shown in FIGS. A plurality of rows of holes 111a arranged in the direction are arranged in the gas flow direction F of the fuel gas. The hole 111a is a non-through hole that does not penetrate from the surface (first surface) of the outermost layer 11 to the surface (second surface) of the outermost layer 11 on the solid electrolyte layer 2 side.

In the first embodiment, the fuel gas inlet side (left side in FIG. 2) from the intermediate point in the gas flow direction F of the fuel gas is the gas flow upstream side, and the fuel gas outlet side (right side in FIG. 2) from the intermediate point. ) On the downstream side of the gas flow. In the fuel cell anode 10 of the first embodiment, specifically, the outermost layer 11 is formed with more thin portions 111 on the gas flow downstream side than on the gas flow upstream side.

Specifically, the fuel cell anode 10 of the first embodiment includes an active layer 13 disposed on the solid electrolyte layer 2 side (that is, the first surface side of the solid electrolyte layer 2), and a solid in the active layer 13. The diffusion layer 12 laminated on the surface opposite to the electrolyte layer 2 side (namely, the first surface side of the active layer 13), and the surface opposite to the solid electrolyte layer 2 side in the diffusion layer 12 (namely, the diffusion layer) 12 and the outermost layer 11 stacked on the first surface side. The anode 10 for the fuel cell of Example 1 has a configuration in which the pore diameter of the diffusion layer 12 is larger than the pore diameter of the outermost layer 11, that is, the relationship of the pore diameter of the outermost layer 11 <the pore diameter of the diffusion layer 12. It is configured. In Example 1, the average pore diameter of the outermost layer 11 is 0.3 to 10 μm, the average pore diameter of the diffusion layer 12 is 0.3 to 20 μm, and the average pore diameter of the active layer 13 is 0.1 to 5 μm. Selected. Further, the porosity of the outermost layer 11 is selected from 80 to 95%, the porosity of the diffusion layer 12 is selected from 30 to 60%, and the porosity of the active layer 13 is selected from 30 to 50%.

In the fuel cell anode 10 of the first embodiment, each of the

layers

11, 12, and 13 is composed of a mixture containing a catalyst and a solid electrolyte. The catalyst is specifically NiO, and the solid electrolyte is specifically yttria-stabilized zirconia (hereinafter, 8YSZ) containing 8 mol% Y ₂ O ₃ as a zirconia-based solid electrolyte. .

Each

layer

11, 12, 13 is configured to satisfy the above pore diameter relationship by adjusting the particle diameter of the catalyst, the solid electrolyte, the amount of pore-forming agent added during production, the size thereof, and the like. ing. Further, the thickness of the portion 112 where the thickness is not reduced in the outermost layer 11 is 50 μm, and the thickness of the thin portion 111 in the outermost layer 11 is 5 μm. The diffusion layer 12 has a thickness of 400 μm, and the active layer 13 has a thickness of 20 μm.

In Example 1, the solid electrolyte layer 2 is specifically formed of a zirconia solid electrolyte. More specifically, the zirconia-based solid electrolyte is 8YSZ, which is a zirconium oxide-based oxide, and the thickness thereof is 10 μm.

In the first embodiment, the intermediate layer 4 is specifically formed of ceria (hereinafter, 10GDC) doped with 10 mol% of Gd, which is a cerium oxide-based oxide, and has a thickness of 10 μm. .

In the first embodiment, the cathode 3 is specifically formed in a layer form from a mixture containing a perovskite oxide and a solid electrolyte. More specifically, the perovskite oxide is La _1-x Sr _x Co _1-y F _y O ₃ (x = 0.4, y = 0.8, hereinafter, LSCF), and the solid electrolyte is 10GDC, which is a cerium oxide-based oxide. The thickness of the cathode is 20 μm.

In Example 1, the fuel cell anode 10 (outermost layer 11, diffusion layer 12, active layer 13), solid electrolyte layer 2, intermediate layer 4, and cathode 3 are all rectangular in plan view. It has a shape. Further, the outer shapes of the fuel cell anode 10 (outermost layer 11, diffusion layer 12, active layer 13), solid electrolyte layer 2, and intermediate layer 4 are equal in size. On the other hand, the outer shape of the cathode 3 is formed smaller than the outer shape of the solid electrolyte layer 2. That is, in Example 1, the fuel cell single cell 5 is configured such that the outer dimensions of the cathode 3 and the solid electrolyte layer 2 satisfy the relationship of the outer shape of the cathode 3 <the outer shape of the solid electrolyte layer 2. .

The function and effect of the fuel cell anode of the first embodiment will be described.

The fuel cell anode 10 has the above-described configuration. In particular, the outermost layer is composed of a plurality of layers (in the first embodiment, the outermost layer 11, the diffusion layer 12, and the active layer 13). 11 is partially different in thickness. Therefore, when the fuel cell anode 10 is used in the fuel cell single cell 5, in the thin portion 111 of the outermost layer 11, the gas diffusion distance of the fuel gas is shortened and the gas diffusion is increased. Power generation is promoted, and the power generation distribution in the cell plane due to the flow of fuel gas can be made uniform. As a result, when the fuel cell anode 10 is used for the single fuel cell 5, the temperature distribution in the cell surface becomes small, local stress is hardly generated in the cell, and cell cracking during power generation is difficult to occur. Become. Therefore, the fuel cell anode 10 is effective in improving the reliability of the single fuel cell 5.

Further, in the fuel cell anode 10 of the first embodiment, the fuel gas inlet side of the fuel gas in the gas flow direction F (see FIGS. 1 and 2) is located on the upstream side of the gas flow and the intermediate point. In the case where the outlet side of the fuel gas is the downstream side of the gas flow, the outermost layer 11 is configured such that the portion 111 having a smaller thickness is formed on the downstream side of the gas flow than on the upstream side of the gas flow. ing. Therefore, in the fuel cell anode 10 of the first embodiment, the consumption of the fuel gas on the upstream side of the gas flow is suppressed, and the depletion of the fuel gas on the downstream side of the gas flow is easily suppressed. Also, in a relatively low concentration fuel gas atmosphere downstream of the gas flow, gas diffusion increases, so the amount of power generation increases, and it is even easier to make the power generation distribution in the cell plane uniform due to the fuel gas flow. There are advantages.

Also, the anode 10 for the fuel cell of Example 1 is configured by laminating the outermost layer 11, the diffusion layer 12, and the active layer 13 in this order. Therefore, in the fuel cell anode 10 of the first embodiment, the fuel gas inflow amount can be controlled in the gas flow direction by the outermost layer 11. Further, the fuel layer that has flowed in can be appropriately diffused by the diffusion layer 12. In addition, the active layer 13 can cause an electrochemical reaction uniformly in the gas flow direction as compared with the case where the outermost layer 11 is not provided. Therefore, the anode 10 for the fuel cell according to the first embodiment is caused by the flow of the fuel gas because the outermost layer 11, the diffusion layer 12, and the active layer 13 to which the functions are shared sufficiently perform their respective functions. There is an advantage that it is easy to make the power generation distribution in the cell plane uniform.

The anode 10 for the fuel cell of Example 1 is configured to satisfy the relationship of the pore diameter of the outermost layer 11 <the pore diameter of the diffusion layer 12. Therefore, in the fuel cell anode 10 of the first embodiment, although the gas diffusibility of the fuel gas is suppressed by the outermost layer 11, the excessive consumption of the fuel gas on the upstream side of the gas flow is eliminated, and the downstream side of the gas flow. Fuel gas can be sent easily. And in the thin part 111 in the outermost layer 11, gas diffusion increases. Therefore, the fuel cell anode 10 of the first embodiment has an advantage that it is easier to make the power generation distribution in the cell plane uniform due to the flow of the fuel gas. In particular, the configuration of the outermost layer 11 is more effective because there are more thin portions 111 on the downstream side of the gas flow than on the upstream side of the gas flow.

Further, in the fuel cell anode 10 of Example 1, the thin portion 111 in the outermost layer 11 is composed of a plurality of holes 111a. Therefore, the anode 10 for the fuel cell according to the first embodiment is made to correspond to the fuel gas flow path according to the shape of the fuel gas flow path included in the separator when the fuel cell single cells 5 are stacked via the separator. By arranging the holes 111a, there is an advantage that the gas diffusibility can be easily improved.

The function and effect of the single fuel cell of Example 1 will be described.

The fuel cell single cell 5 has a fuel cell anode 10, a solid electrolyte layer 2, and a cathode 3. Therefore, in the fuel cell single cell 5, the temperature distribution in the cell surface becomes small, local stress is hardly generated in the cell, and cell cracking during power generation is difficult to occur. Therefore, the fuel cell single cell 5 can exhibit high reliability.

(Example 2)
A fuel cell anode and a single fuel cell of Example 2 will be described with reference to FIG. As shown in FIG. 4, the anode 10 for the fuel cell of the second embodiment is most suitable by arranging a plurality of grooves 111b extending in the direction perpendicular to the gas flow direction F of the fuel gas in the gas flow direction F of the fuel gas. It differs from the anode 10 for fuel cells of Example 1 by the point in which the thin part 111 in the outer layer 11 is comprised. Further, the single fuel cell 5 of the second embodiment is different from the single fuel cell 5 of the first embodiment in that the anode 10 for the fuel cell of the second embodiment is used. Other configurations are the same as those of the first embodiment.

Also with the configuration of the second embodiment, the same operational effects as the first embodiment can be obtained.

Further, in the fuel cell anode 10 of Example 2, the thin portion 111 in the outermost layer 11 is composed of a plurality of grooves 111b. Therefore, the anode 10 for the fuel cell according to the second embodiment is configured such that the fuel gas flow path provided in the separator when stacking the fuel cell single cells 5 through the separator is arranged so as to be orthogonal to the groove 111b. In the rib of the fuel gas flow path in contact with the fuel cell anode 10, there is an advantage that gas diffusion under the rib is facilitated.

Hereinafter, it demonstrates more concretely using an experiment example.
<Experimental example>
(Material preparation)

NiO powder (average particle size: 1 μm), 8YSZ powder (average particle size: 0.3 μm), spherical resin particles (average particle size: 1.5 μm), polyvinyl butyral (organic material), isoamyl acetate, 2 A slurry was prepared by mixing butanol and ethanol (mixed solvent) in a ball mill. The mass ratio of NiO powder and 8YSZ powder is 60:40. The above slurry is applied in layers on a plastic substrate having surface protrusions for forming holes in the outermost layer using a doctor blade method, and dried, so that the surface shown in FIGS. A sheet-shaped outermost layer forming material having a plurality of holes shown and having the other surface formed flat was prepared. That is, the outermost layer forming material is partially different in thickness so as to obtain an outermost layer having a partially different thickness. The average particle diameter is the particle diameter (diameter) d50 when the volume-based cumulative frequency distribution measured by the laser diffraction / scattering method shows 50% (hereinafter the same).

NiO powder (average particle size: 1 μm), 8YSZ powder (average particle size: 0.3 μm), spherical resin particles (average particle size: 1.5 μm), polyvinyl butyral (organic material), isoamyl acetate, 2 A slurry was prepared by mixing butanol and ethanol (mixed solvent) in a ball mill. The mass ratio of NiO powder and 8YSZ powder is 60:40. The slurry was applied in a layer form on a flat plastic substrate using a doctor blade method and dried to prepare a sheet-shaped diffusion layer forming material.

NiO powder (average particle size: 1 μm), 8YSZ powder (average particle size: 0.3 μm), spherical resin particles (average particle size: 0.8 μm), polyvinyl butyral (organic material), isoamyl acetate, 2 A slurry was prepared by mixing butanol and ethanol (mixed solvent) in a ball mill. The mass ratio of NiO powder and 8YSZ powder is 60:40. The slurry was applied in a layer form on a flat plastic substrate using a doctor blade method and dried to prepare a sheet-form active layer forming material. The addition amount of each resin particle in the outermost layer forming material, the diffusion layer forming material, and the active layer forming material is as follows. The added amount of the resin particles in the active layer forming material <the addition of the resin particles in the outermost layer forming material. The relationship of the amount <the amount of resin particles added to the diffusion layer forming material is satisfied.

A slurry was prepared by mixing 8YSZ powder (average particle diameter: 0.3 μm), polyvinyl butyral (organic material), isoamyl acetate, 2-butanol and ethanol (mixed solvent) with a ball mill. The slurry was applied in a layer form on a plastic substrate using a doctor blade method and dried to prepare a sheet-shaped solid electrolyte layer forming material.

A slurry was prepared by mixing 10 GDC powder (average particle size: 0.2 μm), polyvinyl butyral (organic material), isoamyl acetate, 2-butanol and ethanol (mixed solvent) with a ball mill. The slurry was applied in a layer form on a plastic substrate using a doctor blade method and dried to prepare a sheet-shaped intermediate layer forming material.

LSCF (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ ) powder (average particle size: 0.45 μm), 10 GDC powder (average particle size: 0.2 μm), ethyl cellulose (organic material) ) And terpineol (solvent) were mixed in a ball mill to prepare a paste-like cathode forming material. The mass ratio of the LSCF powder to the 10GDC powder is 90:10.

(First step)
The sheet-shaped outermost layer forming material, the sheet-shaped diffusion layer forming material, the sheet-shaped active layer forming material, the sheet-shaped solid electrolyte layer forming material, and the sheet-shaped intermediate layer forming material in this order. It laminated | stacked and crimped | bonded and the laminated body was obtained. At this time, the hole forming surface in the outermost layer forming material was disposed on the surface opposite to the layer on the diffusion layer forming material. Note that the CIP molding method was used for pressure bonding. The CIP molding conditions were a temperature of 80 ° C., a pressing force of 50 MPa, and a pressing time of 10 minutes. Moreover, the laminated body was degreased after the pressure bonding.

(Second step)
Next, the laminate was fired at 1350 ° C. for 2 hours. Thereby, an outermost layer, a diffusion layer, an active layer, a solid electrolyte layer, and an intermediate layer having partially different thicknesses were obtained in this order.

(Third step)
Next, a cathode forming material was applied to the surface of the intermediate layer in the sintered body by a screen printing method, and baked (baked) at 900 ° C. for 2 hours to form a layered cathode. The cathode forming material is not printed up to the outer edge of the intermediate layer, and the outer shape of the cathode layer is smaller than the outer shape of the solid electrolyte layer. As a result, as shown in FIGS. 1 to 3, the fuel cell anode (the outermost layer 11, the diffusion layer 12, and the active layer 13 having partially different thicknesses), the solid electrolyte layer 2, the intermediate layer 4, and the cathode 3 were laminated in this order, and a fuel cell single cell having a fuel cell anode as a support was obtained. In addition, an anode for a fuel cell was obtained in which three layers of an outermost layer, a diffusion layer and an active layer having partially different thicknesses were laminated. The obtained fuel cell anode and fuel cell single cell are referred to as Sample 1 fuel cell anode and fuel cell single cell. The outermost layer has a thickness of 50 μm at a portion where the thickness is not reduced and a thickness of 5 μm at a portion where the thickness is thin. The diffusion layer has a thickness of 400 μm, the active layer has a thickness of 20 μm, the solid electrolyte layer has a thickness of 10 μm, the intermediate layer has a thickness of 10 μm, and the cathode has a thickness of 40 μm. In addition, the anode for a fuel cell and the single fuel cell of Sample 1 satisfy the relationship of the pore size of the active layer <the pore size of the outermost layer <the pore size of the diffusion layer.

In the preparation of the fuel cell anode and fuel cell single cell of Sample 1, the same procedure was used except that the outermost layer forming material was prepared using a plastic substrate having a surface protrusion for forming a groove in the outermost layer. As shown in FIG. 4, a fuel cell anode and a fuel cell single cell of Sample 2 having an outermost layer partially different in thickness were obtained.

As mentioned above, although the Example of this invention was described in detail, this invention is not limited to the said Example, A various change is possible within the range which does not impair the meaning of this invention.

DESCRIPTION OF SYMBOLS 1 Anode 2 Solid electrolyte layer 3 Cathode 4 Intermediate | middle layer 5 Fuel cell single cell 10 Fuel cell anode 11 Outermost layer 12 Diffusion layer 13 Active layer 111 Thin part F The direction of gas flow of fuel gas

Claims

Used in a fuel cell single cell (5) having an anode (1), a solid electrolyte layer (2), and a cathode (3), and fuel gas is supplied along the surface direction of the anode (1). A fuel cell anode (10) comprising:
The fuel cell anode (10) is composed of a plurality of layers,
Of the plurality of layers, the outermost layer (11) disposed farthest from the solid electrolyte layer (2) has a partially different thickness, and the anode (10) for fuel cells.
When the fuel gas inlet side is a gas flow upstream side from the intermediate point in the gas flow direction (F) of the fuel gas and the fuel gas outlet side is a gas flow downstream side from the intermediate point, the above-mentioned maximum point is obtained. 2. The fuel cell according to claim 1, wherein the outer layer (11) is formed with a thinner portion (111) on the downstream side of the gas flow than on the upstream side of the gas flow. Anode (10).
The active layer (13) disposed on the first surface side of the solid electrolyte layer (2), and the active layer which is the surface of the active layer (13) opposite to the solid electrolyte layer (2) side The diffusion layer (12) laminated on the first surface side of (13), and the diffusion layer (12), which is the surface of the diffusion layer (12) opposite to the solid electrolyte layer (2) side. The anode (10) for a fuel cell according to claim 1 or 2, further comprising the outermost layer (11) laminated on the first surface side.
The pore diameter of the outermost layer (11) is smaller than the pore diameter of the diffusion layer (12), that is, the pore diameter of the outermost layer (11) <the pore diameter of the diffusion layer (12) is satisfied. A fuel cell anode (10) according to claim 3, characterized in that
A fuel cell anode according to any one of claims 1 to 4, a solid electrolyte layer (2), and a cathode (3), wherein the fuel cell anode (10) A fuel cell unit cell (5), wherein fuel gas is supplied along the surface direction.
In the fuel cell anode (10), the pore diameter of the outermost layer (11) is larger than the pore diameter of the active layer (13), and the diffusion layer (12) is larger than the pore diameter of the outermost layer (11). The pore diameter of the active layer (13) <the pore diameter of the outermost layer (11) <the pore diameter of the diffusion layer (12) is satisfied. Anode (10) for a fuel cell as described in 1. above.
The average pore diameter of the active layer (13) is in the range of 0.1 to 5 μm, and the average pore diameter of the diffusion layer (12) is in the range of 0.3 to 20 μm. The anode (10) for fuel cells according to claim 3 or 4.
The porosity of the diffusion layer (12) is larger than the porosity of the outermost layer (11), that is, the relationship of the porosity of the outermost layer (11) <the porosity of the diffusion layer (12) is satisfied. The anode (10) for fuel cells according to claim 3 or 4.
The porosity of the active layer (13) is in the range of 30 to 50%, and the porosity of the diffusion layer (12) is in the range of 30 to 60%. The anode (10) for fuel cells as described.
4. The thickness of the outermost layer (11) where the thickness is not thinned is 5 μm or more, and the thickness of the outermost layer (11) where the thickness is not thinned is 300 μm or less. Or the anode (10) for fuel cells of 4.
The fuel cell anode (10) according to claim 3 or 4, wherein the solid electrolyte layer (2) has a thickness of 1 to 20 µm.
The cathode (3) has a thickness of 10 to 100 μm, and the intermediate layer (4) formed between the cathode (3) and the solid electrolyte layer (2) has a thickness of 1 to 10 μm. The anode (10) for fuel cells according to claim 11.