Cell, module, and module housing device

Abstract

To provide a highly durable cell, module, and module housing device. The cell (1) includes an element section (3) having an anode (5), a solid electrolyte layer (6), an air electrode (8), and an intermediate layer (7) located between the solid electrolyte layer (6) and the air electrode (8). The solid electrolyte layer (6) or the intermediate layer (7) has a first region and a second region that is located closer to the air electrode (8) or closer to a central portion (1b) of the element section (3) than the first region and has a smaller porosity or a lower density than the first region.

Description

Technical Field

[0001] The present disclosure relates to cells, modules, and module housing devices.

Background Art

[0002] In recent years, various fuel cell cells and cell stack devices having a plurality of fuel cell cells have been proposed as next-generation energy sources. A fuel cell cell is a type of cell that can obtain electric power using a fuel gas such as a hydrogen-containing gas and an oxygen-containing gas such as air.

[0003] In such a fuel cell cell, for example, an intermediate layer may be provided between a solid electrolyte layer and an air electrode in an element portion inside the fuel cell cell (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] A cell according to one aspect of the embodiment includes First electricity an electrode, a solid electrolyte layer, Second electricity an electrode, the solid electrolyte layer, and Second electricity an intermediate layer positioned between the electrodes, and includes an element portion having the same. And , front the intermediate layer is contains cerium oxide in which rare earth elements excluding Ce (cerium) are solid-solved, and contains at least one element among Fe, Si, Na, Cl, Cu, Ti, and Al as an impurity .

Brief Description of the Drawings

[0006]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0007] Hereinafter, embodiments of the cell, module, and module housing device disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

[0008] Also, note that the drawings are schematic, and it is necessary to be aware that the dimensional relationships between elements, the ratios of the elements, etc. may be different from reality. Furthermore, there may be portions where the dimensional relationships and ratios between the drawings are different from each other.

[0009] In recent years, various types of fuel cell cells and cell stack devices having a plurality of fuel cell cells have been proposed as next-generation energy sources. A fuel cell cell is a type of cell that can obtain electric power using a fuel gas such as a hydrogen-containing gas and an oxygen-containing gas such as air.

[0010] In such a fuel cell cell, for example, an intermediate layer may be provided between the solid electrolyte layer and the air electrode in the element portion within the fuel cell cell.

[0011] However, in the above-described fuel cell cell, there was room for improvement in the durability of the fuel cell cell.

[0012] Therefore, the realization of a technology that can enhance the durability of fuel cell cells has been expected.

[0013] <Configuration of the Cell> First, with reference to FIGS. 1A and 1B, an example of a solid oxide type fuel cell cell will be used to describe the cell according to the embodiment.

[0014] FIG. 1A is a cross-sectional view showing an example of the cell 1 according to the embodiment, and FIG. 1B is a side view of an example of the cell 1 according to the embodiment as viewed from the interconnector 4 side. Note that FIGS. 1A and 1B show a part of each configuration of the cell 1 in an enlarged manner. In addition, a side view of an example of the cell 1 as viewed from the air electrode 8 side will be described later.

[0015] In the examples shown in FIGS. 1A and 1B, the cell 1 is of a hollow flat plate type and is in the shape of an elongated plate. As shown in FIG. 1B, the shape of the entire cell 1 as viewed from the side is, for example, a rectangle with the length of the side in the length direction L being 5 cm to 50 cm and the length in the width direction W orthogonal to this length direction L being 1 cm to 10 cm. The thickness in the thickness direction T of the entire cell 1 is 1 mm to 5 mm.

[0016] As shown in FIG. 1A, the cell 1 includes a conductive support substrate 2, an element part 3, and an interconnector 4. The support substrate 2 is columnar and has a pair of opposing flat surfaces n1, n2, and a pair of arc-shaped side surfaces m connecting such flat surfaces n1, n2.

[0017] The element part 3 is provided on the flat surface n1 of the support substrate 2. Such an element part 3 has a fuel electrode 5, a solid electrolyte layer 6, an intermediate layer 7, and an air electrode 8. Also, in the example shown in FIG. 1A, an interconnector 4 is provided on the flat surface n2 of the cell 1.

[0018] Also, as shown in FIG. 1B, the interconnector 4 may extend to the upper and lower ends of the cell 1. At the lower end portion of the cell 1, the interconnector 4 and the solid electrolyte layer 6 are exposed on the surface. Note that, as shown in FIG. 1A, the solid electrolyte layer 6 is exposed on the surface of the pair of arc-shaped side surfaces m of the cell 1. The interconnector 4 does not necessarily have to extend to the lower end of the cell 1. The cell 1 may include a reinforcing layer 9, which will be described later, in the region between the lower end and the interconnector 4.

[0019] Hereinafter, each component constituting the cell 1 will be described.

[0020] The support substrate 2 has a gas flow path 2a inside through which gas flows. The example of the support substrate 2 shown in Fig. 1A has six gas flow paths 2a. The support substrate 2 has gas permeability and allows the fuel gas flowing through the gas flow path 2a to permeate to the fuel electrode 5. The support substrate 2 may have conductivity. The support substrate 2 having conductivity collects the electricity generated in the element portion 3 and conducts it to the interconnector 4.

[0021] 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 may be Ni (nickel) and / or NiO. The inorganic oxide may be a specific rare earth element oxide.

[0022] As the material of the fuel electrode 5, generally known materials can be used. The fuel electrode 5 may be made of a ceramic containing porous conductive ceramics, such as zirconia (ZrO2) in which calcium oxide, magnesium oxide, or a rare earth element oxide is dissolved, and Ni and / or NiO. As this rare earth element oxide, for example, Y2O3 etc. are used. Zirconia in which calcium oxide, magnesium oxide, or a rare earth element oxide is dissolved is sometimes referred to as stabilized zirconia. Stabilized zirconia includes partially stabilized zirconia.

[0023] The solid electrolyte layer 6 is an electrolyte and serves as a bridge for ions between the fuel electrode 5 and the air electrode 8. At the same time, the solid electrolyte layer 6 has gas barrier properties and makes it difficult for fuel gas and oxygen-containing gas to leak.

[0024] The material of the solid electrolyte layer 6 may be, for example, ZrO2 in which 3 to 15 mol% of a rare earth element oxide is dissolved. As this rare earth element oxide, for example, Y2O3 etc. are used. As long as the above characteristics are satisfied, other materials etc. may be used as the material of the solid electrolyte layer 6.

[0025] The intermediate layer 7 has a function as a diffusion suppression layer. When Sr (strontium) contained in the air electrode 8 described later diffuses into the solid electrolyte layer 6, a resistance layer of SrZrO3 is formed in the solid electrolyte layer 6. The intermediate layer 7 suppresses the diffusion of Sr and makes it difficult for SrZrO3 to be formed.

[0026] The material of the intermediate layer 7 is not particularly limited as long as it is generally used for a Sr diffusion suppression layer. The material of the intermediate layer 7 includes, for example, cerium oxide (CeO2) in which rare earth elements excluding Ce (cerium) are solid-solved. As such rare earth elements, Gd (gadolinium), Sm (samarium), etc. are used.

[0027] The material of the air electrode 8 is not particularly limited as long as it is generally used for an air electrode. The material of the air electrode 8 may be, for example, a conductive ceramic such as a so-called ABO3-type perovskite oxide.

[0028] The material of the air electrode 8 may be, for example, a composite oxide in which Sr and La coexist at the A site. Examples of such composite oxides include La x Sr 1-x Co y Fe 1-y O3, La x Sr 1-x MnO3, La x Sr 1-x FeO3, La x Sr 1-x CoO3, etc. Here, x is 0 < x < 1 and y is 0 < y < 1.

[0029] Also, the air electrode 8 has gas permeability. The open porosity of the air electrode 8 may be, for example, 20% or more, particularly in the range of 30% to 50%.

[0030] As the material of the interconnector 4, a lanthanum chromite-based perovskite oxide (LaCrO3-based oxide) or a lanthanum strontium titanium-based perovskite oxide (LaSrTiO3-based oxide) may be used. These materials have conductivity and are not reduced or oxidized even when they come into contact with fuel gases such as hydrogen-containing gases and oxygen-containing gases such as air.

[0031] Further, the interconnector 4 is dense and hardly causes leakage of the fuel gas flowing through the gas flow path 2a inside the support substrate 2 and the oxygen-containing gas flowing outside the support substrate 2. The interconnector 4 may have a relative density of 93% or more, particularly 95% or more.

[0032] <Configuration of the cell stack device> Next, the cell stack device 10 according to the present embodiment using the cell 1 described above will be described with reference to FIGS. 2A to 2C. FIG. 2A is a perspective view showing an example of the cell stack device 10 according to the embodiment, FIG. 2B is a cross-sectional view taken along line A-A shown in FIG. 2A, and FIG. 2C is a top view showing an example of the cell stack device 10 according to the embodiment.

[0033] As shown in FIG. 2A, the cell stack device 10 includes a cell stack 11 having a plurality of cells 1 arranged (stacked) in the thickness direction T (see FIG. 1A) of the cell 1, and a fixing member 12.

[0034] The fixing member 12 has a fixing material 13 and a support member 14. The support member 14 supports the cell 1. The fixing material 13 fixes the cell 1 to the support member 14. Further, the support member 14 has a support body 15 and a gas tank 16. The support body 15 and the gas tank 16, which are the support members 14, are made of metal and have conductivity.

[0035] As shown in FIG. 2B, the support body 15 has insertion holes 15a into which the lower end portions of the plurality of cells 1 are inserted. The lower end portions of the plurality of cells 1 and the inner walls of the insertion holes 15a are joined by the fixing material 13.

[0036] The gas tank 16 has an opening for supplying a reaction gas to the plurality of cells 1 through the insertion hole 15a, and has a concave groove 16a provided around the opening. One end of the support 15 is joined to the gas tank 16 by a bonding material 21 filled in the concave groove 16a of the gas tank 16.

[0037] In the example shown in FIG. 2A, fuel gas is stored in the internal space 22 formed by the support 15, which is a support member 14, and the gas tank 16. A gas flow pipe 20 is connected to the gas tank 16. The fuel gas is supplied to the gas tank 16 through this gas flow pipe 20, and is supplied from the gas tank 16 to the gas flow path 2a (see FIG. 1A) inside the cell 1. The fuel gas supplied to the gas tank 16 is generated by a reformer 102 (see FIG. 10) described later.

[0038] A hydrogen-rich fuel gas can be generated by steam reforming or the like of a raw fuel. When generating a fuel gas by steam reforming, the fuel gas contains steam.

[0039] In the example shown in FIG. 2A, two rows of cell stacks 11 having a plurality of cells 1 are provided, and the two rows of cell stacks 11 are each fixed to the support 15. Two through holes are provided on the upper surface of the gas tank 16. Each support 15 is arranged in the two through holes so as to align with the insertion hole 15a. The internal space 22 is formed by one gas tank 16 and two supports 15.

[0040] The shape of the insertion hole 15a is, for example, oval in top view. The insertion hole 15a has, for example, a length in the arrangement direction of the cells 1, that is, the thickness direction T, which is larger than the distance between the two end current collecting members 17 located at both ends of the cell stack 11. The width of the insertion hole 15a is, for example, larger than the length in the width direction W (see FIG. 1A) of the cell 1.

[0041] As shown in FIG. 2B, at the joint between the inner wall of the insertion hole 15a and the lower end of the cell 1, the solidified fixing material 13 is filled. As a result, the inner wall of the insertion hole 15a and the lower ends of the plurality of cells 1 are joined and fixed respectively, and the lower ends of the cells 1 are joined and fixed to each other. The gas flow path 2a of each cell 1 communicates with the internal space 22 of the support member 14 at the lower end.

[0042] For the fixing material 13 and the joining material 21, those with low conductivity such as glass can be used. As a specific material, amorphous glass or the like may be used, or crystallized glass may also be used.

[0043] As the crystallized glass, for example, SiO2-CaO system, MgO-B2O3 system, La2O3-B2O3-MgO system, La2O3-B2O3-ZnO system, SiO2-CaO-ZnO system can be adopted, or any material of the SiO2-MgO system may be used.

[0044] Also, as shown in FIG. 2B, between adjacent cells 1 among the plurality of cells 1, a conductive member 18 is interposed. The conductive member 18 electrically connects the fuel electrode 5 of one adjacent cell 1 and the air electrode 8 of the other cell 1 in series. Details of the conductive member 18 connected to the adjacent cells 1 will be described later.

[0045] Also, as shown in FIG. 2B, an end collecting member 17 is connected to the cell 1 located on the outermost side in the arrangement direction of the plurality of cells 1. The end collecting member 17 is connected to a conductive portion 19 protruding outside the cell stack 11. The conductive portion 19 collects the electricity generated by the power generation of the cell 1 and draws it out to the outside. In FIG. 2A, the illustration of the end collecting member 17 is omitted.

[0046] Also, as shown in FIG. 2C, the cell stack device 10 has two cell stacks 11A and 11B formed by arranging cells 1 in a row in series, and functions as one battery. Therefore, the conductive portion 19 of the cell stack device 10 is distinguished into a positive terminal 19A, a negative terminal 19B, and a connection terminal 19C.

[0047] The positive terminal 19A is the positive electrode when the cell stack 11 outputs the generated power to the outside, and is electrically connected to the end collector member 17 on the positive electrode side in the cell stack 11A. The negative terminal 19B is the negative electrode when the cell stack 11 outputs the generated power to the outside, and is electrically connected to the end collector member 17 on the negative electrode side in the cell stack 11B.

[0048] The connection terminal 19C electrically connects the end collector member 17 on the negative electrode side in the cell stack 11A and the end collector member 17 on the positive electrode side in the cell stack 11B.

[0049] <Details of the element part> Next, the details of the element part 3 according to the embodiment will be described with reference to FIGS. 3 to 9. FIG. 3 is a side view of an example of the cell 1 according to the embodiment as viewed from the air electrode 8 side.

[0050] As shown in FIG. 3, the intermediate layer 7 is formed over the entire surface of the solid electrolyte layer 6 as viewed from the air electrode 8 side, excluding the upper and lower end portions of the cell 1. In other words, at the upper and lower end portions of the cell 1 as viewed from the air electrode 8 side, a third portion 30 is provided where the intermediate layer 7 is not located on the surface of the solid electrolyte layer 6.

[0051] Such a third portion 30 is provided along at least two sides of the cell 1 and is formed to have a predetermined width, for example, about 5 mm, from each side. In the embodiment, the third portion 30 is formed along the upper side and the lower side, which are two sides of the cell 1, with a substantially uniform width.

[0052] Also, above the third portion 30 at the lower end portion of the cell 1, a reinforcing layer 9 is provided between the solid electrolyte layer 6 and the intermediate layer 7. When the lower end portion of the cell 1 is fixed by the fixing member 12 (see FIG. 2A), the cell 1 may be damaged by the stress from the fixing member 12. Such a reinforcing layer 9 makes it difficult for the cell 1 to be damaged when the cell 1 is fixed.

[0053] When the interconnector 4 does not extend to the lower end of the cell 1, a reinforcing layer 9 may be provided in the region between the lower end portion of the cell 1 and the interconnector 4 on the flat surface 2n of the support substrate 2.

[0054] The reinforcing layer 9 is formed, for example, from ZrO2 in which 3 to 15 mol% of rare earth element oxide is solid-solved. As this rare earth element oxide, for example, Y2O3 or the like is used. As long as the above characteristics are satisfied, the reinforcing layer 9 may be formed using other materials or the like.

[0055] Also, an air electrode 8 is provided on the surface of the intermediate layer 7 in the region between the third part 30 on the upper side of the cell 1 and the reinforcing layer 9.

[0056] Furthermore, the element part 3 of the cell 1 according to the embodiment has an outer peripheral part 1a and a central part 1b. The outer peripheral part 1a is a region located near each side when the cell 1 is viewed from the air electrode 8 side, and the central part 1b is a central region surrounded by the outer peripheral part 1a when the cell 1 is viewed from the air electrode 8 side.

[0057] The outer peripheral part 1a may be a region located near the contour of the element part 3 or near the contour of the air electrode 8 when the cell 1 is viewed from the air electrode 8 side. In that case, the outer peripheral part 1a includes the contour of the element part 3 or the air electrode 8. The outer peripheral part 1a may include the inside of the contour of the element part 3 in the cell 1 or may include the outside of the contour of the element part 3.

[0058] As shown in FIG. 4, the outer peripheral part 1a is a region in the element part 3 where the distance from the long side along the length direction L is equal to or less than a predetermined distance X1 and the distance from the short side along the width direction W is equal to or less than a predetermined distance X2. FIG. 4 is a diagram for explaining the outer peripheral part 1a and the central part 1b of the element part 3 according to the embodiment.

[0059] In the embodiment, the distance X1 is, for example, 25% of the length W1 of the short side of the element part 3. Also, the distance X2 is, for example, 15% of the length L1 of the long side of the element part 3.

[0060] FIG. 5 is an enlarged cross-sectional view showing an example of the element part 3 according to the embodiment, and is a cross-sectional view enlarging the intermediate layer 7 and its vicinity. As shown in FIG. 5, in the element part 3, a solid electrolyte layer 6 is laminated on the fuel electrode 5 (see FIG. 1A), the intermediate layer 7 is laminated on the solid electrolyte layer 6, and the air electrode 8 is laminated on the intermediate layer 7.

[0061] Further, the intermediate layer 7 has a first region 7a in the vicinity of the interface with the solid electrolyte layer 6 and a second region 7b in the vicinity of the interface with the air electrode 8 in a cross-sectional view. Such a first region 7a is a region where the distance from the interface between the solid electrolyte layer 6 and the intermediate layer 7 is a predetermined distance X3 or less.

[0062] Also, the second region 7b is a region where the distance from the interface between the intermediate layer 7 and the air electrode 8 is a predetermined distance X4 or less. In the embodiment, such distances X3 and X4 may be, for example, 1 / 3 of the thickness T1 of the intermediate layer 7.

[0063] Further, the solid electrolyte layer 6 has a third region 6a in the vicinity of the interface with the intermediate layer 7 in a cross-sectional view. Such a third region 6a is a region where the distance from the interface between the solid electrolyte layer 6 and the intermediate layer 7 is a predetermined distance X5 or less. In the embodiment, such a distance X5 may be, for example, 1 / 3 of the thickness T1 of the intermediate layer 7.

[0064] Here, in the embodiment, in order to improve the durability of the cell 1, the porosity of the above-described first region 7a, second region 7b, and third region 6a is controlled. FIG. 6 is a diagram showing the porosity of each region in the outer peripheral portion 1a and the central portion 1b of the element part 3.

[0065] As shown in FIG. 6, in the embodiment, the porosity of the intermediate layer 7 in the first region 7a, which is in the vicinity of the interface with the solid electrolyte layer 6, is larger than the porosity of the intermediate layer 7 in the second region 7b, which is in the vicinity of the interface with the air electrode 8.

[0066] The intermediate layer 7 in the first region 7a, which is in the vicinity of the interface with the solid electrolyte layer 6, is an example of the first part, and the intermediate layer 7 in the second region 7b, which is in the vicinity of the interface with the air electrode 8, is an example of the second part.

[0067] In the embodiment, in both the outer peripheral portion 1a and the central portion 1b of the element portion 3, the porosity of the first region 7a is larger than the porosity of the second region 7b.

[0068] In this way, by increasing the porosity of the first region 7a in the intermediate layer 7, the first region 7a of the intermediate layer 7 can function as a stress relaxation layer, so that it is possible to make it difficult for the intermediate layer 7 to peel off from the solid electrolyte layer 6.

[0069] Also, by reducing the porosity of the second region 7b in the intermediate layer 7, the function as a Sr diffusion suppression layer can be maintained.

[0070] That is, in the embodiment, the intermediate layer 7 can maintain the function as a Sr diffusion suppression layer, and the intermediate layer 7 can be made difficult to peel off from the solid electrolyte layer 6. Therefore, according to the embodiment, the durability of the cell 1 can be enhanced.

[0071] Also, in the embodiment, the porosity of the intermediate layer 7 in the outer peripheral portion 1a of the element portion 3 is larger than the porosity of the intermediate layer 7 in the central portion 1b of the element portion 3. The intermediate layer 7 in the outer peripheral portion 1a of the element portion 3 is another example of the first site, and the intermediate layer 7 in the central portion 1b of the element portion 3 is another example of the second site.

[0072] In the embodiment, in both the first region 7a and the second region 7b of the intermediate layer 7, the porosity of the outer peripheral portion 1a is larger than the porosity of the central portion 1b.

[0073] In this way, by increasing the porosity of the intermediate layer 7 in the outer peripheral portion 1a of the element portion 3, the intermediate layer 7 in the outer peripheral portion 1a, which makes a smaller contribution to power generation compared to the central portion 1b, can be made to function with an emphasis on the stress relaxation effect rather than the diffusion suppression effect.

[0074] That is, in the embodiment, by increasing the porosity of the outer peripheral portion 1a, it is possible to make it difficult for the intermediate layer 7 to peel off starting from the outer peripheral portion 1a of the element portion 3. Therefore, according to the embodiment, the durability of the cell 1 can be enhanced.

[0075] Also, in the embodiment, the porosity of the intermediate layer 7 may be in the range of 5 (%) to 30 (%). By setting the porosity of the intermediate layer 7 to 5 (%) or more, a sufficient stress relaxation effect due to the voids can be obtained, and even when a temperature cycle is applied to the cell 1 and thermal stress is applied to the intermediate layer 7, it becomes difficult for the intermediate layer 7 to peel off.

[0076] On the other hand, by setting the porosity of the intermediate layer 7 to 30 (%) or less, the intermediate layer 7 can have a strength such that the intermediate layer 7 does not peel off.

[0077] Thus, in the embodiment, since the porosity of the intermediate layer 7 is in the range of 5 (%) to 30 (%), it is possible to make it difficult for the intermediate layer 7 to peel off. Therefore, according to the embodiment, the durability of the cell 1 can be enhanced.

[0078] The porosity of the intermediate layer 7 may particularly be in the range of 10 (%) to 30 (%), and may further be in the range of 13 (%) to 25 (%). The porosity of the first region 7a may be in the range of 15 (%) to 30 (%), and particularly may be in the range of 16 (%) to 27 (%). The porosity of the second region 7b may be in the range of 10 (%) to 25 (%), and particularly may be in the range of 12 (%) to 22 (%).

[0079] Also, in the embodiment, the average diameter of the voids formed in the intermediate layer 7 may be in the range of 0.1 μm to 1.0 μm, particularly 0.2 μm to 0.8 μm. Thereby, it is possible to make it difficult for the intermediate layer 7 to peel off from the solid electrolyte layer 6 and to suppress the diffusion of Sr.

[0080] Further, in the embodiment, the porosity of the third region 6a of the solid electrolyte layer 6 in the outer peripheral portion 1a of the element portion 3 is larger than the porosity of the third region 6a of the solid electrolyte layer 6 in the central portion 1b of the element portion 3. That is, in the embodiment, the third region 6a of the solid electrolyte layer 6 in the outer peripheral portion 1a of the element portion 3 is denser than the third region 6a of the solid electrolyte layer 6 in the central portion 1b of the element portion 3.

[0081] Thereby, in the outer peripheral portion 1a of the element portion 3 where the peeling of the solid electrolyte layer 6 is likely to occur, by making the third region 6a dense, the strength of the solid electrolyte layer 6 can be increased. That is, in the embodiment, by making the solid electrolyte layer 6 in the outer peripheral portion 1a dense, it is possible to make it difficult for the solid electrolyte layer 6 to peel off starting from the outer peripheral portion 1a of the element portion 3.

[0082] Therefore, according to the embodiment, the durability of the cell 1 can be enhanced.

[0083] Note that in the embodiment, the case where the third region 6a of the solid electrolyte layer 6 in the outer peripheral portion 1a of the element portion 3 is denser than the third region 6a of the solid electrolyte layer 6 in the central portion 1b of the element portion 3 has been shown. However, the entire thickness direction of the solid electrolyte layer 6 in the outer peripheral portion 1a of the element portion 3 may be denser than the entire thickness direction of the solid electrolyte layer 6 in the central portion 1b of the element portion 3. The solid electrolyte layer 6 in the outer peripheral portion 1a of the element portion 3 is another example of the first site, and the solid electrolyte layer 6 in the central portion 1b of the element portion 3 is another example of the second site.

[0084] Thereby, since the strength of the entire solid electrolyte layer 6 in the outer peripheral portion 1a of the element portion 3 can be increased, it is possible to make it difficult for the solid electrolyte layer 6 to peel off starting from the outer peripheral portion 1a of the element portion 3.

[0085] Further, the location where the dense, that is, the solid electrolyte layer 6 with a small porosity, is disposed in the cell 1 according to the embodiment is not limited to the outer peripheral portion 1a. FIG. 7 is an enlarged cross-sectional view showing an example of the cell 1 according to the embodiment.

[0086] As shown in FIG. 7, the cell 1 has a curved portion 1c adjacent to the outer peripheral portion 1a. This curved portion 1c is a portion of the arc-shaped side surface m that is located near the air electrode 8. In other words, the curved portion 1c is a portion of the side surface m where the distance from the air electrode 8 is smaller than the distance from the interconnector 4. And in the embodiment, a solid electrolyte layer 6 that is denser than the central portion 1b (see FIG. 4) may also be disposed in such a curved portion 1c.

[0087] Thereby, since the strength of the solid electrolyte layer 6 in the curved portion 1c of the cell 1 can be increased, it is possible to make it difficult for the solid electrolyte layer 6 to peel off starting from the curved portion 1c of the cell 1.

[0088] Note that the porosity and the average diameter of the voids of the first region 7a, the second region 7b, and the third region 6a can be obtained, for example, by the following method. First, the cell 1 is cut so as to obtain cross-sections of the first region 7a, the second region 7b, and the third region 6a.

[0089] Next, the cross-sections of the first region 7a, the second region 7b, and the third region 6a are observed with an SEM (scanning electron microscope), and for example, a photograph at 3000 times magnification is taken. By performing image processing on this photograph and calculating the total area of the void portions with respect to the area of the entire image, the porosity can be obtained.

[0090] Also, by performing image processing on this photograph, the average diameter of the voids can be obtained. The average diameter of the voids obtained by image processing is the average value of the diameters obtained by converting the areas of the voids in the cross-sectional photograph into circles. For the image processing, for example, analysis by binarization using analysis software (software name: ImageJ, developer: Wayne Rasband) can be used.

[0091] Also, in the embodiment, as shown in FIG. 3, the cell 1 may have at least in the vicinity of two sides a third site 30 where the intermediate layer 7 is not located on the surface of the solid electrolyte layer 6 when viewed from the air electrode 8 side.

[0092] The intermediate layer 7 may have a dense film with a thickness smaller than that of the first region 7a at the interface with the solid electrolyte layer 6. At this time, if, hypothetically, the third part 30 is not formed in the cell 1 and the dense film of the intermediate layer 7 is formed so as to reach each side of the cell 1, when an external impact is applied to the cell 1, the impact is directly applied to the dense film of the intermediate layer 7 that has reached the side where the impact is applied. As a result, cracks may occur in the dense film of the intermediate layer 7, which is thin and dense and thus prone to cracking, and there is a risk that the cracks will spread to the element part 3.

[0093] On the other hand, in the embodiment, since the cell 1 has the third part 30, even if an external impact is applied to the side where the third part 30 is formed, it is possible to make it difficult for cracks to occur in the dense film of the intermediate layer 7.

[0094] That is, in the embodiment, it is possible to make it difficult for cracks to occur in the intermediate layer 7. Therefore, according to the embodiment, the durability of the cell 1 can be enhanced.

[0095] Note that the arrangement of the third part 30 in the cell 1 according to the embodiment is not limited to the example in FIG. 3. FIGS. 8 and 9 are side views showing another example of the element part 3 according to the embodiment. Note that in FIGS. 8 and 9, for ease of understanding, the illustration of the air electrode 8 and the reinforcing layer 9 is omitted.

[0096] As shown in FIG. 8, the third part 30 may be provided such that four corners of the cell 1 as viewed from the air electrode 8 side are cut out. Further, as shown in FIG. 9, the third part 30 may be provided in a rectangular shape at a part of the upper end portion and a part of the lower end portion of the cell 1 as viewed from the air electrode 8 side.

[0097] Further, in the embodiment, as shown in FIG. 3, the intermediate layer 7 may also be formed on the surface of the reinforcing layer 9 that does not require a diffusion suppression layer because the air electrode 8 is not formed.

[0098] Further, the intermediate layer 7 according to the embodiment may contain at least one of Fe (iron), Si (silicon), Na (sodium), Cl (chlorine), Cu (copper), Ti (titanium), and Al (aluminum) as an impurity.

[0099] Thereby, when forming the intermediate layer 7, since the growth of crystal grains in the intermediate layer 7 can be suppressed, it is possible to make it difficult for cracks to occur in the intermediate layer 7. Therefore, according to the embodiment, the durability of the cell 1 can be enhanced.

[0100] The intermediate layer 7 according to the embodiment may contain, for example, a total of 1000 ppm (0.1 mass%) or less of the elements serving as the above-described impurities. For example, the contents of Fe, Si, Na, and Cl may each be 200 ppm (0.02 mass%) or less. For example, the contents of Cu, Ti, and Al may each be 50 ppm (0.005 mass%) or less.

[0101] The intermediate layer 7 may contain rare earth elements other than Gd and Sm described above, for example, La (lanthanum), Pr (praseodymium), Nd (neodymium), Y (yttrium), etc. For example, when the material of the intermediate layer 7 is cerium oxide (CeO2) in which Gd is dissolved, the intermediate layer 7 may contain at least one of La, Pr, Nd, Sm, and Y in a total amount of about 20 ppm (0.002 mass%).

[0102] The intermediate layer 7 may contain Zr (zirconium), Ca (calcium), Sr (strontium), Mg (magnesium), Co (cobalt), Mn (manganese), Ni (nickel), etc. These elements may diffuse from the members disposed around the intermediate layer 7 into the intermediate layer 7.

[0103] Further, in the embodiment, the first region 7a of the intermediate layer 7 may contain flat crystal grains. Further, in the first region 7a of the intermediate layer 7, the major axis of the flat crystal grains may be in the range of 10 nm to 100 μm, and the average value of the major axis may be in the range of 100 nm to 10 μm. Such flat crystal grains may form the dense film of the intermediate layer 7 described above.

[0104] Also, at the boundary between the first region 7a of the intermediate layer 7 and the solid electrolyte layer 6, the contact length per unit length of the boundary between the crystal grains of the intermediate layer 7 and the crystal grains of the solid electrolyte layer 6 may be greater than the contact length per unit length of the boundary between the crystal grains of the intermediate layer 7 and the crystal grains of the air electrode 8 at the boundary between the second region 7b of the intermediate layer 7 and the air electrode 8.

[0105] <Module> Next, the module 100 according to the embodiment of the present disclosure using the cell stack device 10 described above will be described with reference to FIG. 10. FIG. 10 is an external perspective view showing the module 100 according to the embodiment. FIG. 10 shows a state in which a part of the front and rear surfaces of the storage container 101 is removed and the cell stack device 10 of the fuel cell stored inside is taken out backward.

[0106] As shown in FIG. 10, the module 100 includes a storage container 101 and a cell stack device 10 stored in the storage container 101. A reformer 102 is disposed above the cell stack device 10.

[0107] Such a reformer 102 reforms a raw fuel such as natural gas or kerosene to generate a fuel gas and supplies it to the cell 1. The raw fuel is supplied to the reformer 102 through the raw fuel supply pipe 103. The reformer 102 may include a vaporization unit 102a that vaporizes water and a reforming unit 102b. The reforming unit 102b includes a reforming catalyst (not shown) and reforms the raw fuel into a fuel gas. Such a reformer 102 can perform steam reforming, which is an efficient reforming reaction.

[0108] Then, the fuel gas generated in the reformer 102 is supplied to the gas flow path 2a (see FIG. 1A) of the cell 1 through the gas flow pipe 20, the gas tank 16, and the support member 14.

[0109] Further, in the module 100 having the above-described configuration, the temperature inside the module 100 during normal power generation becomes about 500 to 1000°C due to the combustion of the gas and the power generation of the cell 1.

[0110] In such a module 100, as described above, by housing the highly durable cell stack device 10, a highly durable module 100 can be obtained.

[0111] <Module housing device> FIG. 11 is an exploded perspective view showing an example of a module housing device 110 according to an embodiment. The module housing device 110 according to the embodiment includes an exterior case 111, the module 100 shown in FIG. 10, and auxiliary equipment (not shown). The auxiliary equipment operates the module 100. The module 100 and the auxiliary equipment are housed inside the exterior case 111. Note that a part of the configuration is omitted in FIG. 11.

[0112] The exterior case 111 of the module housing device 110 shown in FIG. 11 has a support column 112 and an exterior plate 113. A partition plate 114 vertically divides the inside of the exterior case 111. The space above the partition plate 114 inside the exterior case 111 is a module housing chamber 115 for housing the module 100, and the space below the partition plate 114 inside the exterior case 111 is an auxiliary equipment housing chamber 116 for housing the auxiliary equipment that operates the module 100. Note that in FIG. 11, the auxiliary equipment housed in the auxiliary equipment housing chamber 116 is omitted.

[0113] Further, the partition plate 114 has an air flow port 117 for flowing the air in the auxiliary equipment housing chamber 116 to the module housing chamber 115 side. The exterior plate 113 constituting the module housing chamber 115 has an exhaust port 118 for exhausting the air inside the module housing chamber 115.

[0114] In such a module housing device 110, as described above, by providing the highly durable module 100 in the module housing chamber 115, a highly durable module housing device 110 can be obtained.

[0115] <Various Modifications> Next, the element parts according to various modifications of the embodiment will be described with reference to FIGS. 12 to 18.

[0116] In the above-described embodiment, the so-called "vertical stripe type" in which only one element part including a fuel electrode, a solid electrolyte layer, and an air electrode is provided on the surface of the support substrate is exemplified. However, the element parts are provided at a plurality of locations on the surface of the support substrate that are separated from each other, and the so-called "horizontal stripe type" cells in which adjacent element parts are electrically connected are arranged. It can be applied to a horizontal stripe type cell stack device.

[0117] In addition, in the present embodiment, the case where a hollow flat plate type support substrate is used is exemplified, but it can also be applied to a cell stack device using a cylindrical support substrate. Further, as will be described later, it can also be applied to a flat plate type cell stack device in which so-called "flat plate type" cells are stacked in the thickness direction.

[0118] In the above embodiment, an example in which a fuel electrode is provided on the support substrate and the air electrode is disposed on the surface of the cell is shown. However, it can also be applied to a cell stack device in which the air electrode is provided on the support substrate and the fuel electrode is disposed on the surface of the cell, which is the reverse arrangement.

[0119] In the above embodiment, a fuel cell, a fuel cell stack device, a fuel cell module, and a fuel cell device are shown as examples of the "cell", "cell stack device", "module", and "module housing device". However, as other examples, an electrolytic cell, an electrolytic cell stack device, an electrolytic module, and an electrolytic device may be used, respectively.

[0120] FIG. 12 is a cross-sectional view showing a cell according to Modification 1 of the embodiment. As shown in FIG. 12, in the cell stack device 10A, a plurality of cells 1A extend in the length direction L from a pipe 73 through which fuel gas flows. The cell 1A has a plurality of element portions 3A on a support substrate 71. Inside the support substrate 71, a gas flow path 74 through which gas from the pipe 73 flows is provided. Each element portion 3A on the support substrate 71 is electrically connected by a connection portion (not shown). The plurality of cells 1A are electrically connected to each other via a conductive member 78. The conductive member 78 is located between the element portions 3A each cell 1A has, and connects adjacent cells 1A.

[0121] And also in Modification 1, the porosity of the intermediate layer in the first region near the interface with the solid electrolyte layer is larger than the porosity of the intermediate layer in the second region near the interface with the air electrode. Thereby, the durability of the cell 1A can be enhanced.

[0122] Also in Modification 1, the porosity of the intermediate layer at the outer peripheral portion of the element portion 3A is larger than the porosity of the intermediate layer at the central portion of the element portion 3A. Thereby, the durability of the cell 1A can be enhanced.

[0123] Also in Modification 1, the third region of the solid electrolyte layer at the outer peripheral portion of the element portion 3A is denser than the third region of the solid electrolyte layer at the central portion of the element portion 3A. Thereby, the durability of the cell 1A can be enhanced.

[0124] FIG. 13 is a perspective view showing a flat cell according to Modification 2 of the embodiment, and FIG. 14 is a view for explaining the outer peripheral portion 1Ba and the central portion 1Bb in the element portion 90 according to Modification 2 of the embodiment.

[0125] As shown in FIG. 13, the cell 1B has an element part 90 in which a fuel electrode 5, a solid electrolyte layer 6, an intermediate layer 7, and an air electrode 8 are laminated. In a cell stack device in which a plurality of flat plate type cells are laminated, for example, a plurality of cells 1B are electrically connected by conductive members 91 and 92 which are metal layers adjacent to each other. The conductive members 91 and 92 electrically connect adjacent cells 1B to each other and have gas flow paths for supplying gas to the fuel electrode 5 or the air electrode 8.

[0126] Further, as shown in FIG. 14, the element part 90 of the cell 1B has an outer peripheral part 1Ba and a central part 1Bb. The outer peripheral part 1Ba is a region located in the vicinity of each side of the element part 90 when the cell 1B is viewed in plan, and the central part 1Bb is a central region surrounded by the outer peripheral part 1Ba when the cell 1B is viewed in plan. When the cell is viewed in plan in FIGS. 13 and 14, the outer shape of the cell 1B coincides with the outer shape of the element part 90. The outer shape of the cell 1B may be larger than the outer shape of the element part 90, or the contour of the cell 1B may be arranged so as to surround the contour of the element part 90.

[0127] As shown in FIG. 14, such an outer peripheral part 1Ba is a region in the element part 90 where the distance from one side S1 is equal to or less than a predetermined distance X6 and the distance from the other side S2 is equal to or less than a predetermined distance X7.

[0128] In Modification 2, the distance X6 is, for example, 25% of the length L3 of the other side S2 of the element part 90. Further, the distance X7 is, for example, 25% of the length L4 of one side S1 of the element part 90.

[0129] And also in Modification 2, the porosity of the intermediate layer 7 in the first region (that is, in the vicinity of the interface with the solid electrolyte layer 6) is larger than the porosity of the intermediate layer 7 in the second region (that is, in the vicinity of the interface with the air electrode 8). Thereby, the durability of the cell 1B can be enhanced.

[0130] Also, in Modification 2 as well, the porosity of the intermediate layer 7 in the outer peripheral portion 1Ba of the element portion 90 is larger than the porosity of the intermediate layer 7 in the central portion 1Bb of the element portion 90. Thereby, the durability of the cell 1B can be enhanced.

[0131] Also, in Modification 2 as well, the third region of the solid electrolyte layer 6 in the outer peripheral portion 1Ba of the element portion 90 is denser than the third region of the solid electrolyte layer 6 in the central portion 1Bb of the element portion 90. Thereby, the durability of the cell 1B can be enhanced.

[0132] FIG. 15 is a bottom view showing an example of the element portion 90 according to Modification 2 of the embodiment, and is a diagram for explaining the arrangement of the intermediate layer 7 and the third portion 30 in the cell 1B. As shown in FIG. 15, in Modification 2, the third portion 30 may be provided along each of two opposing sides in the cell 1B.

[0133] Thereby, even if an external impact is applied to the two sides where such a third portion 30 is formed, it is possible to make it difficult for cracks to occur in the intermediate layer 7. Therefore, according to Modification 2, the durability of the cell 1B can be enhanced.

[0134] Note that the arrangement of the third portion 30 in the cell 1B according to Modification 2 is not limited to the example of FIG. 15. FIGS. 16 to 18 are bottom views showing another example of the element portion 90 according to Modification 2 of the embodiment.

[0135] As shown in FIG. 16, the third portion 30 may be provided so that four corner portions in the cell 1B as viewed from the air electrode 8 (see FIG. 13) side are cut out. Also, as shown in FIG. 17, the third portion 30 may be provided in a rectangular shape on a part of two opposing sides in the cell 1B as viewed from the air electrode 8 side. Also, as shown in FIG. 18, the third portion 30 may be provided along all four sides of the cell 1B as viewed from the air electrode 8 side.

[0136] As described above, the cell 1 (1A, 1B) according to the embodiment includes an element portion 3 (3A, 90) having a fuel electrode 5, a solid electrolyte layer 6, an air electrode 8, and an intermediate layer 7 positioned between the solid electrolyte layer 6 and the air electrode 8. And, the solid electrolyte layer 6 or the intermediate layer 7 has a first portion and a second portion that is located closer to the air electrode 8 than the first portion or closer to the central portion 1b of the element portion 3 (3A, 90) and has a porosity smaller than that of the first portion or a density lower than that of the first portion. Thereby, the durability of the cell 1 (1A, 1B) can be enhanced.

[0137] Further, in the cell 1 (1A, 1B) according to the embodiment, the porosity of the intermediate layer 7 in the vicinity of the interface with the solid electrolyte layer 6 is larger than the porosity of the intermediate layer 7 in the vicinity of the interface with the air electrode 8. Thereby, the durability of the cell 1 (1A, 1B) can be enhanced.

[0138] Further, in the cell 1 (1A, 1B) according to the embodiment, the porosity of the intermediate layer 7 in the outer peripheral portion 1a of the element portion 3 (3A, 90) is larger than the porosity of the intermediate layer 7 in the central portion 1b. Thereby, the durability of the cell 1 (1A, 1B) can be enhanced.

[0139] Further, in the cell 1 (1A, 1B) according to the embodiment, the porosity of the intermediate layer 7 is in the range of 5 (%) to 30 (%). Thereby, peeling of the intermediate layer 7 can be suppressed.

[0140] Further, in the cell 1 (1A, 1B) according to the embodiment, the intermediate layer 7 contains cerium oxide in which rare earth elements excluding Ce are solid-solved. Thereby, a function as a diffusion suppression layer for suppressing the formation of a resistance layer of SrZrO3 in the solid electrolyte layer 6 can be imparted to the intermediate layer 7.

[0141] Further, in the cell 1 (1A, 1B) according to the embodiment, the intermediate layer 7 contains at least one element among Fe, Si, Na, Cl, Cu, Ti, and Al as an impurity. Thereby, the durability of the cell 1 (1A, 1B) can be enhanced.

[0142] Further, in the cell 1 (1A, 1B) according to the embodiment, when viewed from the air electrode 8 side, the solid electrolyte layer 6 has a third portion 30 where the intermediate layer 7 is not located on the surface, in the vicinity of at least two sides. Thereby, it is possible to suppress the occurrence of cracks in the intermediate layer 7.

[0143] Further, in the cell 1 (1A, 1B) according to the embodiment, the solid electrolyte layer 6 located at the outer peripheral portion 1a of the element portion 3 (3A, 90) is denser than the solid electrolyte layer 6 located at the central portion 1b. Thereby, it is possible to make it difficult for the solid electrolyte layer 6 to peel off starting from the outer peripheral portion 1a of the element portion 3 (3A, 90).

[0144] Further, in the cell 1 (1A, 1B) according to the embodiment, the solid electrolyte layer 6 is denser in the vicinity of the interface with the intermediate layer 7 at the outer peripheral portion 1a of the element portion 3 (3A, 90) than at the central portion 1b. Thereby, it is possible to make it difficult for the solid electrolyte layer 6 to peel off starting from the outer peripheral portion 1a of the element portion 3 (3A, 90).

[0145] Further, the module 100 according to the embodiment includes a cell stack device 10 including a plurality of the cells 1 (1A, 1B) described above, and a storage container 101 that stores the cell stack device 10. Thereby, it is possible to obtain a highly durable module 100.

[0146] Further, the module housing device 110 according to the embodiment includes the module 100 described above, auxiliary equipment for operating the module 100, and an exterior case 111 that houses the module 100 and the auxiliary equipment. Thereby, it is possible to obtain a highly durable module housing device 110.

[0147] It should be considered that all the embodiments disclosed this time are illustrative in all respects and not restrictive. Indeed, the above-described embodiments can be embodied in various forms. Further, the above embodiments may be omitted, substituted, or changed in various forms without departing from the scope and spirit of the appended claims.

Explanation of Reference Numerals

[0148] 1, 1A, and 1B cells 1a and 1Ba outer peripheral parts 1b and 1Bb central parts 3, 3A, and 90 element parts 5 fuel electrode 6 solid electrolyte layer 6a third region 7 intermediate layer 7a first region 7b second region 8 air electrode 10 cell stack device 30 third site 100 module 101 storage container 110 module housing device 111 exterior case

Claims

1. An element unit having a first electrode, a solid electrolyte layer, a second electrode, and an intermediate layer located between the solid electrolyte layer and the second electrode, wherein the intermediate layer contains cerium oxide in which rare earth elements excluding Ce (cerium) are dissolved, and contains at least one of Fe, Si, Na, Cl, Cu, Ti, and Al as impurities in a total amount more than an inevitable amount and 0.1% by mass or less. Cell.

2. When viewed from the second electrode side, the element unit has four sides, and the solid electrolyte layer has, in the vicinity of at least two opposing sides of the four sides, a portion where the intermediate layer is not located on the surface. The cell according to claim 1.

3. A cell stack device including a plurality of cells including the cell according to claim 1 or 2, and a storage container for storing the cell stack device Module provided with.

4. The module according to claim 3, auxiliary equipment for operating the module, and an exterior case for housing the module and the auxiliary equipment Module housing device provided with.

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