Patent Application
20230387422
The present disclosure relates to a cell, a cell stack device, a module, and a module housing device.
In recent years, various fuel cell stack devices each including a plurality of fuel cells have been proposed as next-generation energy sources. A fuel cell is a type of cell capable of obtaining electrical power by using a fuel gas such as a hydrogen-containing gas and an oxygen-containing gas such as air.
In an aspect of an embodiment, a cell includes an air electrode layer, a fuel electrode layer, and a solid electrolyte layer. The fuel electrode layer contains a first rare earth element and a second rare earth element different from the first rare earth element. The solid electrolyte layer is located between the air electrode layer and the fuel electrode layer, and contains the second rare earth element. The fuel electrode layer has a first site and a second site. The second site is located between the first site and the solid electrolyte layer and contains at least the second rare earth element.
A cell stack device of the present disclosure includes a cell stack including at least one of the cells mentioned above.
A module of the present disclosure includes the cell stack device mentioned above and a storage container that houses the cell stack device.
A module housing device of the present disclosure includes the module mentioned above, an auxiliary device for operating the module, and an external case that houses the module and the auxiliary device.
Hereinafter, embodiments of a cell, a cell stack device, a module, and a module housing device disclosed in the present application will be described in detail with reference to the accompanying drawings. The present invention is not limited by the following embodiments.
Note that the drawings are schematic and that the dimensional relationships between elements, the proportions thereof, and the like may differ from the actual ones. There may be differences between the drawings in the dimensional relationships, proportions, and the like.
First, with reference to
In the example illustrated in
As illustrated in
The element portion 3 is located on the flat surface n1 of the support substrate 2. The element portion 3 includes a fuel electrode layer 5, a solid electrolyte layer 6, and an air electrode layer 8. In the example illustrated in
As illustrated in
Hereinafter, each of constituent members constituting the cell 1 will be described.
The support substrate 2 includes gas-flow passages 2a, in which gas flows. The example of the support substrate 2 illustrated in
The material of the support substrate 2 includes, for example, an iron group metal component and an inorganic oxide. For example, the iron group metal component is, for example, Ni (nickel) and/or NiO. The inorganic oxide may be, for example, a specific rare earth element oxide. The rare earth element oxide may contain, for example, one or more rare earth elements selected from Sc, Y, La, Nd, Sm, Gd, Dy, and Yb.
As the material of the fuel electrode layer 5, a commonly known material may be used. The fuel electrode layer 5 may use a porous electrically conductive ceramic, for example, a ceramic containing an ion conductive material such as ZrO2 in which a rare earth element oxide is in solid solution, and also containing Ni and/or NiO. The above rare earth element oxide contains a plurality of rare earth elements selected from, for example, Sc, Y, La, Nd, Sm, Gd, Dy, and Yb. Hereinafter, ZrO2 in which a rare earth element oxide is in solid solution may be referred to as stabilized zirconia. Stabilized zirconia also includes partially stabilized zirconia. Details of the fuel electrode layer 5 will be described later.
The solid electrolyte layer 6 is an electrolyte and serves as a bridge for ions between the fuel electrode layer 5 and the air electrode layer 8. At the same time, the solid electrolyte layer 6 has gas blocking properties, and makes leakage of the fuel gas and the oxygen-containing gas less likely to occur.
The material of the solid electrolyte layer 6 may be, for example, an ion conductive material such as ZrO2 in which, for example, a 3-mol % to 15-mol % rare earth element oxide is in solid solution. The rare earth element oxide may contain, for example, one or more rare earth elements selected from Sc, La, Nd, Gd, and Yb. Hereinafter, a material in which a rare earth element oxide is in solid solution may be simply referred to as a material in which a rare earth element is in solid solution. The solid electrolyte layer 6 may contain, for example, ZrO2 in which Yb, Sc, or Gd is in solid solution, CeO2 in which La, Nd, or Yb is in solid solution, BaZrO3 in which Sc or Yb is in solid solution, or BaCeO3 in which Sc or Yb is in solid solution. The solid electrolyte layer 6 includes a material in which a second rare earth element is in solid solution. In other words, the rare earth element that is in solid solution in the ion conductive material contained in the solid electrolyte layer 6 is a second rare earth element.
The air electrode layer 8 has gas permeability. The open porosity (void ratio) of the air electrode layer 8 may be, for example, in a range from 20% to 50%, and particularly may be in a range from 30% to 50%.
The material of the air electrode layer 8 is not particularly limited as long as the material is commonly used for the air electrode. The material of the air electrode layer 8 may be, for example, an electrically conductive ceramic such as a so-called ABO3 type perovskite-type oxide.
The material of the air electrode layer 8 may be, for example, a composite oxide in which Sr (strontium) and La (lanthanum) coexist in the A-site. Examples of such a composite oxide include LaxSr1-xCoyFe1-yO3, LaxSr1-xMnO3, LaxSr1-xFeO3, and LaxSr1-xCoO3. Here, x is 0<x<1, and y is 0<y<1.
When the element portion 3 has the intermediate layer 7, the intermediate layer 7 functions as a diffusion prevention layer. The intermediate layer 7 makes Sr (strontium) contained in the air electrode layer 8 less likely to diffuse into the solid electrolyte layer 6 containing Zr, for example, thereby making a resistive layer of SrZrO3 less likely to be formed in the solid electrolyte layer 6.
The material of the intermediate layer 7 is not particularly limited as long as it is generally used for the diffusion prevention layer of Sr. The material of the intermediate layer 7 may contain, for example, CeO2 (cerium oxide) in which rare earth elements other than Ce (cerium) are in solid solution. As such rare earth elements, for example, Gd (gadolinium), Sm (samarium), or the like may be used.
The interconnector 4 is dense, and makes the leakage of the fuel gas flowing through the gas-flow passages 2a located inside the support substrate 2, and of the oxygen-containing gas flowing outside the support substrate 2 less likely to occur. The interconnector 4 may have a relative density of 93% or more; particularly 95% or more.
The material of the interconnector 4 may be a lanthanum chromite-based perovskite-type oxide (LaCrO3-based oxide) or a lanthanum strontium titanium-based perovskite-type oxide (LaSrTiO3-based oxide). These materials have electrical conductivity, and are unlikely to be reduced and also unlikely to be oxidized even when brought into contact with a fuel gas such as a hydrogen-containing gas and an oxygen-containing gas such as air.
Configuration of Cell Stack Device Next, a cell stack device 10 according to the present embodiment using the cell 1 described above will be described with reference to
As illustrated in
The fixing member 12 includes a fixing material 13 and a support member 14. The support member 14 supports the cells 1. The fixing material 13 fixes the cells 1 to the support member 14. Further, the support member 14 includes a support body 15 and a gas tank 16. The support body 15 and the gas tank 16, constituting the support member 14, are made of metal and electrically conductive.
As illustrated in
The gas tank 16 includes an opening portion through which a reactive gas is supplied to the plurality of cells 1 via the insertion hole 15a, and a recessed groove 16a located in the periphery of the opening portion. The outer peripheral end portion of the support body 15 is joined to the gas tank 16 by a bonding material 21, with which the recessed groove 16a of the gas tank 16 is filled.
In the example illustrated in
A hydrogen-rich fuel gas can be produced, for example, by steam-reforming a raw fuel. When the fuel gas is produced by the steam-reforming, the fuel gas contains steam. In the example illustrated in
The insertion hole 15a has, for example, an oval shape in a top surface view. The length of the insertion hole 15a, for example, in an array direction of the cells 1, that is, the thickness direction T thereof, is greater than the distance between two end current collectors 17 located at two ends of the cell stack 11. The width of the insertion hole 15a is, for example, greater than the length of the cell 1 in the width direction W (see
As illustrated in
The fixing material 13 and the bonding material 21 may be of low electrical conductivity, such as glass. As the specific materials of the fixing material 13 and the bonding material 21, amorphous glass or the like may be used, and especially, crystallized glass or the like may be used.
As the crystallized glass, for example, any one selected from the group consisting of SiO2—CaO-based, MgO—B2O3-based, La2O3—B2O3—MgO-based, La2O3—B2O3—ZnO-based, and SiO2—CaO—ZnO-based materials may be used, or particularly, a SiO2—MgO-based material may be used.
As illustrated in
Further, as illustrated in
Further, as illustrated in
The positive electrode terminal 19A functions as a positive electrode when the electrical power generated by the cell stack 11 is output to the outside, and is electrically connected to the end current collector 17 on a positive electrode side in the cell stack 11A. The negative electrode terminal 19B functions as a negative electrode when the electrical power generated by the cell stack 11 is output to the outside, and is electrically connected to the end current collector 17 on a negative electrode side in the cell stack 11B.
The connection terminal 19C electrically connects the end current collector 17 on a negative electrode side in the cell stack 11A and the end current collector 17 on a positive electrode side in the cell stack 11B.
Details of Fuel Electrode Layer Details of the fuel electrode layer 5 according to the first embodiment will be described next with reference to
As illustrated in
The second particle body P2 is an oxide having ion conductivity and containing a rare earth element. The second particle body P2 has a particulate shape (first-order particle) with an equivalent circle diameter average in a range from about 0.1 μm to about 2 μm in a cross-sectional view, for example. The second particle body P2 includes a first particle 51 containing a first rare earth element and a second particle 52 containing a second rare earth element different from the first rare earth element.
The locations of the first particle body P1 and the second particle body P2 (the first particle 51 and second particle 52) may be confirmed by observing a cross section of the fuel electrode layer 5 using an electron probe micro analyzer (EPMA). The equivalent circle diameter of each of the first particle body P1 and the second particle body P2 (the first particle 51 and second particle 52) may be calculated based on a result obtained by observing the cross section of the fuel electrode layer 5 using a scanning electron microscope (SEM).
The first particle 51 contains a rare earth element selected from the group consisting of, for example, Sc, Y, La, Nd, Sm, Gd, Dy, and Yb as the first rare earth element. The first particle 51 may contain a plurality of the first rare earth elements.
The second particle 52 contains the second rare earth element contained in the solid electrolyte layer 6. The second particle may contain a rare earth element selected from the group consisting of, for example, Nd, Sc, La, Gd, and Yb as the second rare earth element. The first particle 53 may contain a rare earth element that is not contained in the second particle 52 among Nd, Sc, La, Gd, and Yb.
The second particle 52 has ion conductivity higher than that of the first particle 51. The ion conductivity of each of the first particle 51 and the second particle 52 may be evaluated by, for example, preparing a rectangular sintered body having the composition of the first particle 51 and a rectangular sintered body having the composition of the second particle 52, and measuring the ion conductivity of each sintered body at 600° C. to 900° C. by a four-terminal method.
The first particle body P1 is uniformly distributed over the entire fuel electrode layer 5. On the other hand, in the second particle body P2, the first particle 51 and the second particle 52 are unevenly distributed inside the fuel electrode layer 5. This point will be further described with reference to
The first site 5A is located to be in contact with the support substrate 2. The second site 5B is located between the first site 5A and the solid electrolyte layer 6 and contains at least the second rare earth element. In the second site 5B, the content of the second rare earth element may be larger than the content of the first rare earth element. The contents of the first rare earth element and the second rare earth element in the second site 5B may be confirmed by, for example, elemental analysis using EPMA. Specifically, for example, the cross section of the element portion 3 in a layering direction is mirror-polished to bisect the fuel electrode layer 5 in the thickness direction, and a portion on the support substrate 2 side is defined as the first site 5A and a portion on the solid electrolyte layer 6 side is defined as the second site 5B. The content of each of the first rare earth element and the second rare earth element may be calculated by performing semi-quantitative analysis on each of the first rare earth element and the second rare earth element in a predetermined area of the cross section defined as the second site 5B. The area subjected to the elemental analysis may be, for example, an area of a quadrilateral with one side having a length equal to or less than the thickness of the second site 5B. The content of each rare earth element in the first site 5A described below may also be calculated in the same and/or a similar manner. The content of the first rare earth element or the second rare earth element is a molar ratio (atomic ratio) calculated by taking the total of elements excluding O (oxygen) among the elements contained in the second particle body P2, that is, contained in the ion conductive material as a denominator and taking the first rare earth element or the second rare earth element as a numerator. In a case where the distribution state of the first particle body P1 and the second particle body P2 is substantially uniform in the fuel electrode layer 5, the molar ratio (atomic ratio) calculated by taking the total of elements excluding O (oxygen) among the elements contained in the fuel electrode layer 5 as a denominator and taking the first rare earth element or the second rare earth element as a numerator, may be regarded as the content of the first rare earth element or the second rare earth element.
As described above, by including the second site 5B, in which the content of the second rare earth element is higher than that of the first rare earth element, the ion conductivity of the second site 5B located closer to the solid electrolyte layer 6 than the first site 5A may be increased. Due to this, since the actual resistance in the second site 5B can be reduced, the polarization resistance in the fuel electrode layer 5 is reduced. This can improve the battery performance of the cell 1.
The first site 5A may contain the same rare earth element as the rare earth element contained in the support substrate 2. When the first site 5A and the support substrate 2 contain the same rare earth element, the fuel electrode layer 5 is less likely to peel off from the support substrate 2. This can enhance the durability of the cell 1. By positioning the first site between the support substrate 2 and the second site 5B, for example, element diffusion from the support substrate 2 into the second site 5B can be suppressed, which makes it possible to make the ion conductivity of the second site 5B less likely to decrease.
The second site 5B may contain the same rare earth element as the rare earth element contained in the solid electrolyte layer 6. When the second site 5B and the solid electrolyte layer 6 contain the same rare earth element, the fuel electrode layer 5 is less likely to peel off from the solid electrolyte layer 6. This can enhance the durability of the cell 1.
The first site 5A and the second site 5B of the fuel electrode layer 5 may be distinguished from each other, for example, by taking a portion where the content of the second rare earth element is judged to be larger than the content of the first rare earth element by elemental analysis using the EPMA as the second site 5B and taking the remaining portion as the first site 5A. Specifically, for example, a cross section of the element portion 3 in the layering direction is mirror-polished, and each element is subjected to surface analysis or line analysis in the layering direction by the EPMA to obtain a concentration mapping or concentration profile of each element. From the obtained concentration mapping result or concentration profile result of each element, a region in which the first rare earth element is less than the second rare earth element in the fuel electrode layer 5 is taken as the second site and the other region is taken as the first site 5A.
The fuel electrode layer 5 may be positioned such that the content of the first rare earth element is larger in the first site 5A than in the second site 5B, for example. This makes it possible to suppress the deformation of the fuel electrode layer 5 because the coefficient of thermal expansion of the first site 5A can be made smaller than that of the second site 5B in some cases. This can enhance the durability of the cell 1. For example, the ion conductivity of ZrO2 (8YbSZ) in which 8-mol % Yb2O3 is in solid solution is higher than the ion conductivity of ZrO2 (8YSZ) in which 8-mol % Y2O3 is in solid solution. The coefficient of linear thermal expansion of a porous sintered body containing 50-vol % 8YSZ and 50-vol % Ni is 13.2 ppm at 1000° C., and the coefficient of linear thermal expansion of a porous sintered body containing 50-vol % 8YbSZ and 50-vol % Ni is 13.4 ppm at 1000° C. That is, the coefficient of linear thermal expansion of the sintered body containing YSZ is smaller than that of the sintered body containing YbSZ. When the first particle 51 is YSZ containing Y as the first rare earth element and the second particle 52 is YbSZ containing Yb as the second rare earth element to constitute the first site 5A and the second site 5B, respectively, the fuel electrode layer 5 may be constituted in such a manner that the ion conductivity of the second site 5B is high and the coefficient of linear thermal expansion of the first site 5A is small, thereby making it possible to realize the cell 1 having high battery performance and high durability.
The fuel electrode layer 5 may be positioned such that the ratio of the content of the first rare earth element to the sum of the contents of the first rare earth element and the second rare earth element ((content of first rare earth element)/((content of first rare earth element)+(content of second rare earth element))) is greater in the first site 5A than in the second site 5B. This makes it possible to suppress the deformation of the fuel electrode layer 5 because the coefficient of thermal expansion of the first site 5A can be made smaller than that of the second site 5B in some cases. This can enhance the durability of the cell 1.
Further, the fuel electrode layer 5 may be positioned such that the coefficient of linear thermal expansion of the first site 5A is smaller than that of the second site 5B. With this, the deformation of the fuel electrode layer 5 may be suppressed, and thus the durability of the cell 1 may be enhanced. The contents of the first rare earth element and the second rare earth element in the second site 5B may be confirmed by, for example, elemental analysis using the EPMA. Specifically, the contents of the first rare earth element and the second rare earth element may be measured by mirror-polishing a cross section of the element portion 3 in the layering direction and performing semi-quantitative analysis on each of the first rare earth element and the second rare earth element in a predetermined area of the cross section of the first site 5A. The area subjected to the elemental analysis may be, for example, an area of a quadrilateral with one side having a length equal to or less than the thickness of the first site 5A.
The fuel electrode layer 5 does not necessarily need to have the first site 5A and the second site 5B. For example, the content of the second rare earth element may change stepwise inside the fuel electrode layer 5. For example, when a surface of the fuel electrode layer 5 in contact with the solid electrolyte layer 6 is referred to as a first surface and a surface thereof located on the opposite side to the solid electrolyte layer 6 is referred to as a second surface, the content of the second rare earth element in the fuel electrode layer 5 may gradually decrease from the first surface toward the second surface. As described above, when the content of the second rare earth element gradually decreases from the first surface toward the second surface, the ion conductivity of the fuel electrode layer 5 at a position closer to the solid electrolyte layer 6 may be made higher than that of the fuel electrode layer 5 at a position farther from the solid electrolyte layer 6. Due to this, since the actual resistance in the fuel electrode layer 5 at a position closer to the solid electrolyte layer 6 can be reduced, the polarization resistance in the fuel electrode layer 5 is reduced. This can improve the battery performance of the cell 1.
Module A module 100 according to an embodiment of the present disclosure using the cell stack device 10 described above will be described next with reference to
As illustrated in
The reformer 102 generates a fuel gas by reforming a raw fuel such as natural gas and kerosene, and supplies the fuel gas to the cell 1. The raw fuel is supplied to the reformer 102 through a raw fuel supply pipe 103. The reformer 102 may include a vaporizing unit 102a for vaporizing water and a reforming unit 102b. The reforming unit 102b includes a reforming catalyst (not illustrated) for reforming the raw fuel into a fuel gas. Such a reformer 102 can perform steam reforming, which is a highly efficient reforming reaction.
Then, the fuel gas generated by the reformer 102 is supplied to the gas-flow passage 2a (see
In the module 100 having the configuration mentioned above, the temperature in the module 100 during normal power generation is about from 500° C. to 1000° C. due to combustion of gas and power generation by the cell 1.
The above-discussed module 100 is configured such that the cell stack device 10 with improved battery performance is housed therein as described above, whereby the module 100 with the improved battery performance may be realized.
Module Housing Device
The external case 111 of the module housing device 110 illustrated in
The dividing plate 114 includes an air circulation hole 117 for causing air in the auxiliary device housing room 116 to flow into the module housing room 115 side. The external plate 113 constituting the module housing room 115 includes an exhaust hole 118 for discharging air inside the module housing room 115.
In the module housing device 110 discussed above, the module 100 with improved battery performance is provided in the module housing room 115 as described above, whereby the module housing device 110 with the improved battery performance may be realized.
In the embodiment mentioned above, the case where the support substrate having the hollow flat plate shape is used has been exemplified; however, the embodiment can also be applied to a cell stack device using a cylindrical support substrate.
Next, a cell and a cell stack device according to a second embodiment will be described with reference to
In the embodiment described above, a so-called “vertically striped” cell stack device, in which only one element portion including a fuel electrode layer, a solid electrolyte layer, and an air electrode layer is provided on the surface of a support substrate, is exemplified. However, the present disclosure may be applied to a horizontally striped cell stack device with an array of so-called “horizontally striped” cells, in which element portions are provided on the surface of a support substrate at mutually separated locations, and adjacent element portions are electrically connected to each other.
The cell 1A has a shape that is vertically symmetric with respect to a plane that passes through a center in the thickness direction (Z axis direction) and is parallel to a main surface of the support substrate 2.
The element portion 3 includes a fuel electrode layer 5, a solid electrolyte layer 6, an intermediate layer 7, and an air electrode layer 8 layered in that order. The connection layer 8A for electrically connecting the element portions 3 adjacent to each other in the X axis direction is located on the surface of the air electrode layer 8. A fuel electrode current collector 5a having electron conductivity is located on the surface of the fuel electrode layer 5.
The solid electrolyte layer 6 contains a second rare earth element. In the second site the content of the second rare earth element may be larger than the content of a first rare earth element. With this, the ion conductivity of the second site 5B located closer to the solid electrolyte layer 6 than the first site 5A may be increased. Due to this, since the actual resistance in the second site 5B can be reduced, the polarization resistance in the fuel electrode layer 5 is reduced. This can improve the battery performance of the cell 1A.
As illustrated in
As illustrated in
The support member 94 may be a so-called separator that separates the flow passage 98 of the fuel gas and the flow passage 97 of the oxygen-containing gas. The material of the support members 94 and 95 may be, for example, an electrically conductive metal, or may be an insulating ceramic. When the bonding material 93 is, for example, insulating glass, both the support members 94 and 95 may be metal, or one of the support members 94 and 95 may be an insulating material. When the bonding material 93 is an electrically conductive metal, both or one of the support members 94 and 95 may be an insulating material. When the support members 94 and 95 are metal, the support members 94 and 95 may be formed integrally with the electrically conductive member 92.
One of the bonding material 93 and the support members 94 and 95 has insulating properties, and causes the two electrically conductive members 91 and 92 sandwiching the flat plate cell to be electrically insulated from each other.
The solid electrolyte layer 6 contains a second rare earth element. In the second site the content of the second rare earth element may be larger than the content of a first rare earth element. With this, the ion conductivity of the second site 5B located closer to the solid electrolyte layer 6 than the first site 5A may be increased. Due to this, since the actual resistance in the second site 5B can be reduced, the polarization resistance in the fuel electrode layer 5 is reduced. This can improve the battery performance of the cell 1B.
Other Variations Subsequently, a cell stack device according to other variations of the embodiments will be described.
In the above embodiments, a fuel cell, a fuel cell stack device, a fuel cell module, and a fuel cell device are illustrated as examples of the “cell”, the “cell stack device”, the “module”, and the “module housing device”; they may also be an electrolytic cell, an electrolytic cell stack device, an electrolytic module, and an electrolytic device, respectively, as other examples.
While the present disclosure has been described in detail, the present disclosure is not limited to the aforementioned embodiment, and various changes, improvements, and the like can be made without departing from the gist of the present disclosure.
As described above, the cell 1 according to the embodiment includes the air electrode layer 8, the fuel electrode layer 5, and the solid electrolyte layer 6. The fuel electrode layer 5 contains a first rare earth element and a second rare earth element different from the first rare earth element. The solid electrolyte layer 6 is located between the air electrode layer 8 and the fuel electrode layer 5, and contains the second rare earth element. The fuel electrode layer 5 has the first site 5A and the second site 5B. The second site 5B is located between the first site 5A and the solid electrolyte layer 6, and contains at least the second rare earth element. This can improve the battery performance of the cell 1.
The cell stack device 10 according to the embodiment includes the cell stack 11 provided with at least one of the cells 1 described above. As a result, the cell stack device 10 with improved battery performance may be realized.
Further, the module 100 according to the embodiment includes the cell stack device described above, and the storage container 101 configured to house the cell stack device 10. As a result, the module 100 with improved battery performance may be realized.
Further, the module housing device 110 according to the embodiment includes the module 100 described above, the auxiliary device for operating the module 100, and the external case that houses the module 100 and the auxiliary device. Thus, the module housing device 110 with improved battery performance may be realized.
Note that the embodiments disclosed herein are exemplary in all respects and not restrictive. The aforementioned embodiments can be embodied in a variety of forms. The aforementioned embodiments may be omitted, replaced, or changed in various forms without departing from the scope of the appended claims and the purpose thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-183197 | Oct 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/039906 | 10/28/2021 | WO |
