stack

Abstract

The present invention provides a stack that can reduce the occurrence of narrowing or short circuits between the first separator and the second separator. [Solution] The stack comprises a cell containing an electrolyte that separates a fuel electrode and an air electrode in the thickness direction; a first separator fixed to the cell and extending outwards from the outer circumference of the cell; an interconnector in contact with the air electrode; a second separator fixed to the interconnector and extending outwards from the outer circumference of the interconnector; an electrically insulating frame disposed between the first separator and the second separator in the thickness direction; and an insulator disposed in the space between the first separator and the second separator, wherein the insulator is fixed to at least one of the first separator and the second separator.

Description

[Technical Field]

[0001] The present invention relates to a stack in which cells comprising, in order, a fuel electrode, an electrolyte, and an air electrode are stacked. [Background technology]

[0002] Patent Document 1 discloses a stack comprising a cell containing an electrolyte that separates a fuel electrode and an air electrode in the thickness direction, a first separator fixed to the cell, an interconnect in contact with the air electrode, a second separator fixed to the interconnect, and an electrically insulating frame disposed between the first separator and the second separator. In the prior art disclosed in Patent Document 1, an insulator is placed in the portion where the cell and the interconnect face each other in order to prevent a short circuit between the first separator and the interconnect due to thermal expansion and contraction of the cell and the interconnect. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-49810 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the prior art, if the first or second separator deforms due to creep or other factors, there is a risk of narrowing or short-circuiting between the first and second separators.

[0005] This invention was made to solve this problem and aims to provide a stack that can reduce the occurrence of narrowing or short circuits between the first separator and the second separator. [Means for solving the problem]

[0006] A first embodiment for achieving this objective includes a cell containing an electrolyte that separates a fuel electrode and an air electrode in the thickness direction, a first separator fixed to the cell and extending outwards from the outer circumference of the cell, an interconnector in contact with the air electrode, a second separator fixed to the interconnector and extending outwards from the outer circumference of the interconnector, an electrically insulating frame disposed between the first separator and the second separator in the thickness direction, and an insulator disposed in the space between the first separator and the second separator, wherein the insulator is fixed to at least one of the first separator and the second separator.

[0007] In a second embodiment, the first separator and the second separator include stress buffers that are curved in the same direction in the thickness direction, and the insulator is positioned on the side with the longer distance between the frame and the stress buffer and the distance between the cell or interconnect and the stress buffer.

[0008] A third embodiment is the first or second embodiment, wherein the first separator and the second separator include stress buffers that are curved in the same direction in the thickness direction, and the insulator is disposed in the stress buffers.

[0009] A fourth aspect is that, in any of the first to third aspects, the frame includes gas inlets and gas outlets connected to space, the cell is a quadrilateral with four sides including a first side facing the gas inlets and a second side facing the gas outlets, and the insulator is disposed between the first side and the frame and between the second side and the frame.

[0010] A fifth aspect is that, in any of the first to fourth aspects, the insulator includes an end fixed to one of the first separator and the second separator, with a gap between the other end of the insulator in the thickness direction and the other of the first separator and the second separator. [Effects of the Invention]

[0011] According to the present invention, even if the first separator or the second separator deforms and the distance between the first separator and the second separator shortens, the distance between the first separator and the second separator is maintained by the insulator fixed to at least one of the first separator and the second separator, thereby reducing the occurrence of narrowing or short circuits between the first separator and the second separator. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view of the stack in the first embodiment. [Figure 2] This is a cross-sectional view of the stack at line II-II. [Figure 3] This is a cross-sectional view of the stack at line III-III. [Figure 4] This is a cross-sectional view of the stack in the second embodiment. [Modes for carrying out the invention]

[0013] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1 is a perspective view of the stack 10 in the first embodiment. The stack 10 includes reaction units 11, a laminate 12 formed by stacking a plurality of reaction units 11 in the thickness direction, conductive plates 13 and 15 electrically connected to the laminate 12, and end plates 17 and 18 that sandwich the laminate 12 and the conductive plates 13 and 15 in the thickness direction. The laminate 12 is made up of, for example, 10 to 30 reaction units 11 stacked on top of each other.

[0014] Conductive plate 13 is positioned between the laminate 12 and the end plate 17, and conductive plate 15 is positioned between the laminate 12 and the end plate 18. Terminals 14 and 16 are connected to conductive plates 13 and 15, respectively. Stainless steel is an example of the material used for conductive plates 13 and 15 and terminals 14 and 16.

[0015] The insulating plate 19 is disposed between the conductive plate 13 and the end plate 17, and electrically insulates between the conductive plate 13 and the end plate 17. The insulating plate 20 is disposed between the conductive plate 15 and the end plate 18, and electrically insulates between the conductive plate 15 and the end plate 18. Bolts 21 that penetrate through the end plates 17, 18, the insulating plates 19, 20, the conductive plates 13, 15, and the laminated body 12 in the thickness direction are disposed on the peripheral edge of the stack 10. The stack 10 is fastened by the bolts 21.

[0016] The four spaces penetrating the peripheral edge of the stack 10 in the thickness direction are respectively: a passage 22 that supplies fuel gas from the outside of the stack 10 to the fuel chamber 36 (described later) of the reaction unit 11, a passage 23 that discharges gas from the fuel chamber 36 to the outside of the stack 10, a passage 24 that supplies oxidant gas from the outside of the stack 10 to the air chamber 37 (described later) of the reaction unit 11, and a passage 25 that discharges gas from the air chamber 37 to the outside of the stack 10, and they function as these passages respectively.

[0017] Figure 2 is a cross-sectional view of the stack 10 cut along line II-II in Figure 1, which passes through the passages 24 and 25, and a part of the laminated body 12 is illustrated. In Figure 2, the thickness of each part is illustrated in an exaggerated manner.

[0018] As shown in Figure 2, the reaction unit 11 includes, in order in the thickness direction, a fuel electrode frame 26, a first separator 27, an air electrode frame 28, and a second separator 29. Holes (the passages 22 to 25) penetrate through the fuel electrode frame 26, the first separator 27, the air electrode frame 28, and the second separator 29. Inside the fuel electrode frame 26, the first separator 27, the air electrode frame 28, and the second separator 29, a cell 30, an interconnector 34, and a current collector 35 are disposed.

[0019] The cell 30 includes an electrolyte 31, a fuel electrode 32 and an air electrode 33 that are separated from each other in the thickness direction by the electrolyte 31. Although a flat-plate-shaped cell 30 is described in the present embodiment, the cell 30 is not limited thereto. The cell 30 may be a metal-supported type (metal-supported flat-plate type) that supports an electrode and an electrolyte with a porous metal body such as an Fe-Cr-based one. The cell 30 may be an electrode-supported type or an electrolyte-supported type.

[0020] The material of the electrolyte 31 is a solid oxide, and examples thereof include stabilized zirconia, ceria-based solid solutions, and solid solutions of alumina with one or more selected from stabilized zirconia and ceria-based solid solutions. Examples of the stabilizer for stabilized zirconia include CaO, MgO, Y₂O₃, Sc₂O₃, and Yb₂O₃. Examples of the element that forms a solid solution with ceria in the ceria-based solid solution include Gd, Sm, and Y.

[0021] Examples of the material of the fuel electrode 32 include materials containing a catalyst containing Ni and zirconia in which Y is solid-solved, and materials containing a catalyst containing Ni and ceria in which Gd is solid-solved. Examples of the catalyst include cermets which are composites (sintered bodies) of Ni, Ni-based alloys, NiO and an oxide (solid electrolyte).

[0022] The material of the air electrode 33 is perovskite-type oxide La 1-X Sr X MnO 3-δ , La 1-X Sr X CoO 3-δ , La 1-X Sr X Co 1-Y Fe Y O 3-δ , Pr 1-X Sr X MnO 3-δ are exemplified.

[0023] The fuel electrode frame 26 is a frame-shaped member disposed between the conductive plate 15 or the second separator 29 and the first separator 27, and surrounding the cell 30 and the current collector 35. Stainless steel is exemplified as the material of the fuel electrode frame 26.

[0024] The first separator 27 is a frame-shaped member that is airtightly joined to the electrolyte 31 by brazing material or the like, avoiding the air electrode 33. Stainless steel is an example of a material for the first separator 27.

[0025] The air electrode frame 28 is positioned between the first separator 27 and the second separator 29 and is a frame-shaped member that surrounds the interconnector 34. An example of the material for the air electrode frame 28 is an insulator such as mica.

[0026] The second separator 29 is a frame-shaped member and is airtightly joined to the interconnector 34 by brazing material or the like. Stainless steel is an example of a material for the second separator 29.

[0027] The current collector 35 electrically connects adjacent interconnectors 34 and fuel electrodes 32 in the thickness direction. An example of a current collector 35 is one that includes a bent conductor and a spacer such as mica placed within the conductor. Examples of conductive materials include nickel, nickel-based alloys, and stainless steel. The interconnectors 34 electrically connect adjacent current collectors 35 and air electrodes 33 in the thickness direction. An example of interconnectors 34 is stainless steel.

[0028] A fuel chamber 36 is provided inside the fuel electrode frame 26, and an air chamber 37 (space) is provided inside the air electrode frame 28. A gas supply port 38 and a gas outlet 39 are provided in the air electrode frame 28. The air chamber 37 is connected to passage 24 through the gas supply port 38 and to passage 25 through the gas outlet 39. The fuel chamber 36 is connected to passage 22 (see Figure 1) through a gas supply port (not shown) and to passage 23 (see Figure 1) through a gas outlet (not shown). The first separator 27 and the second separator 29 separate the fuel chamber 36 and the air chamber 37, preventing the fuel gas in the fuel chamber 36 from mixing with the oxidizer gas in the air chamber 37.

[0029] The first separator 27 has a curved portion 41 that curves in an arc shape toward the fuel chamber 36, extending around its entire circumference. The second separator 29 has a curved portion 42 that curves in an arc shape toward the air chamber 37, located at a position corresponding to the curved portion 41, extending around its entire circumference. The stress buffer portion 40, which includes the curved portions 41 and 42 that curve in the same direction (downward in this embodiment) in the thickness direction of the cell 30, is more easily deformed than the parts of the first separator 27 and the second separator 29 other than the stress buffer portion 40. As a result, when the stack 10 is fastened with bolts 21 (see Figure 1), the stress buffer portion 40 deforms, reducing the force applied to the cell 30 and reducing damage to the cell 30.

[0030] If stack 10 is a fuel cell, examples of fuel gases include hydrogen, carbon monoxide, and hydrocarbons, and examples of oxidizer gases include oxygen and air. If stack 10 is an electrolytic device (cell 30 is an electrolytic cell that has the function of electrolyzing the fuel gas), examples of fuel gases include water vapor, carbon dioxide, and mixtures thereof, and examples of oxidizer gases include oxygen and air. Stack 10 also includes configurations that allow for reversible operation as both a fuel cell and an electrolytic device.

[0031] Multiple cells 30 are electrically connected in series between terminals 14 and 16 via an interconnector 34 and a current collector 35. When the stack 10 is an electrolytic device, electrons flow out toward the fuel electrode 32 of the cell 30 when the positive electrode of a power supply (not shown) is connected to terminal 14 and the negative electrode of the power supply is connected to terminal 16. The fuel gas that enters the fuel chamber 36 is reduced by the fuel electrode 32. Since electrons are removed at the air electrode 33, oxide ions that have moved to the air electrode 33 via the electrolyte 31 are oxidized at the air electrode 33. This generates energy carriers such as hydrogen and hydrocarbons in the fuel chamber 36. The energy carriers generated in the fuel chamber 36 exit the stack 10 through the passage 23.

[0032] When the pressure in the fuel chamber 36, where energy carriers are generated, becomes higher than the pressure in the air chamber 37, the first separator 27 and the second separator 29, being less rigid than the cell 30 and the interconnector 34, may creep deform and bend toward the air chamber 37. As the distance between the first separator 27 and the second separator 29 in the air chamber 37 shortens, making it difficult for gas to flow through the air chamber 37, the performance of the stack 10 deteriorates. Furthermore, if the bending of the first separator 27 and the second separator 29 increases and they come into contact within the air chamber 37, a short circuit will occur.

[0033] If the stack 10 is a fuel cell, when fuel gas flows into the fuel chamber 36 and oxidant gas flows into the air chamber 37, gaseous oxygen reacts with electrons at the air electrode 33 of the cell 30 to generate oxide ions. These oxide ions move through the electrolyte 31 and react with the fuel gas at the fuel electrode 32 to generate electrons. This causes current to flow to the load (not shown) connected to terminals 14 and 16 (see Figure 1). In this case as well, the first separator 27 and the second separator 29 creep and deform, bending toward the air chamber 37. As the distance between the first separator 27 and the second separator 29 in the air chamber 37 shortens, gas flow through the air chamber 37 becomes difficult, or a short circuit occurs between the first separator 27 and the second separator 29.

[0034] In the stack 10, an insulator 43 fixed to at least one of the first separator 27 and the second separator 29 is placed in the air chamber 37. In this embodiment, the insulator 43 is point-shaped and fixed to the stress buffer portion 40 (curved portion 41) of the first separator 27 at intervals from each other in the circumferential direction of the cell 30. The height of the insulator 43 is greater than the depth of the curved portion 41.

[0035] Examples of materials for the insulator 43 include glass and ceramics. Examples of means for fixing the insulator 43 to at least one of the first separator 27 and the second separator 29 include applying an inorganic adhesive in dots, bonding ceramics using an inorganic adhesive, and firing glass. When the inorganic adhesive is applied in dots, the hardened inorganic adhesive itself is the insulator 43; when ceramics are bonded using an inorganic adhesive, the ceramics and the hardened inorganic adhesive together are the insulator 43; and in the case of firing glass, the hardened glass itself is the insulator 43.

[0036] Since the insulator 43 fixed to at least one of the first separator 27 and the second separator 29 is placed in the air chamber 37, even if the first separator 27 or the second separator 29 deforms and the distance between the first separator 27 and the second separator 29 shortens, the distance between the first separator 27 and the second separator 29 can be maintained by the height of the insulator 43. Since the insulators 43 are spaced apart from each other, gas flow between the insulators 43 is ensured, and the occurrence of narrowing or short circuits between the first separator 27 and the second separator 29 can be reduced.

[0037] Since the stress buffer section 40 is the most flexible of the first separator 27 and the second separator 29, when creep deformation occurs, constriction and short circuits are likely to occur near the stress buffer section 40. Because the point-shaped insulators 43 are fixed to the stress buffer section 40 at intervals from each other, the insulators 43 can be prevented from hindering the deformation of the stress buffer section 40, and furthermore, gas can pass through the gaps between the insulators 43, thus reducing the occurrence of constriction and short circuits near the stress buffer section 40.

[0038] The insulator 43 includes an end 44 fixed to the first separator 27 and the other end 45 in the thickness direction of the insulator 43. There is a gap 46 between the end 45 of the insulator 43 and the second separator 29. Because the first separator 27 and the second separator 29 can deform by the amount of the gap 46, when the stack 10 is fastened with bolts 21 (see Figure 1), the first separator 27 and the second separator 29 deform, reducing the force applied to the cell 30 and thus reducing damage to the cell 30.

[0039] Figure 3 is a cross-sectional view of stack 10 along line III-III in Figure 2. Cell 30 is a quadrilateral in plan view from the thickness direction of cell 30, including a first side 47 facing the gas supply port 38, a second side 48 facing the gas outlet 39, a third side 49 connecting the first side 47 and the second side 48, and a fourth side 50 facing the third side 49. The angles where the first side 47 and the third side 49 intersect, the angles where the third side 49 and the second side 48 intersect, the angles where the second side 48 and the fourth side 50 intersect, and the angles where the fourth side 50 and the first side 47 intersect may be pointed or rounded. The corners may also be chamfered. The size of the rounding or chamfering can be set as appropriate.

[0040] The insulator 43 is positioned between the first side 47 of the cell 30 and the air electrode frame 28, and between the second side 48 of the cell 30 and the air electrode frame 28. Even when the first separator 27 or the second separator 29 is deformed, the insulator 43 positioned between the first side 47 of the cell 30 and the air electrode frame 28 ensures that the gas flow between the gas supply port 38 and the cell 30. The insulator 43 positioned between the second side 48 of the cell 30 and the air electrode frame 28 ensures that the gas flow between the cell 30 and the gas outlet 39 is ensured even when the first separator 27 or the second separator 29 is deformed.

[0041] Partitions 51 are placed between the third side 49 of cell 30 and the air electrode frame 28, and between the fourth side 50 of cell 30 and the air electrode frame 28. Because of the placement of partitions 51, the amount of oxidizing gas that bypasses cell 30 and passes through the air chamber 37 can be reduced so that more oxidizing gas flows from the first side 47 to the second side 48 of cell 30. This ensures that a sufficient amount of oxidizing gas reacts at the air electrode 33.

[0042] The material of the partition 51 is not particularly limited as long as it is a material that prevents gas from easily flowing through it and has electrical insulating properties. Examples of materials for the partition 51 include minerals such as mica, glass, ceramics, and ceramic felt made by intertwining inorganic fibers into a sheet.

[0043] The stack 60 in the second embodiment will be described with reference to Figure 4. In the first embodiment, the case in which an insulator 43 is placed in the stress buffer portion 40 was described. In the second embodiment, the case in which an insulator 43 is placed in places other than the stress buffer portion 40 will be described. In the second embodiment, the same numbers are used for the same parts as in the first embodiment, and some of the following descriptions will be omitted.

[0044] Figure 4 is a cross-sectional view of the stack 60 in the second embodiment. Similar to Figure 2, Figure 4 is a cross-sectional view of the stack 60 cut along the line II-II passing through passages 24, 25 (see Figure 1), and mainly shows the first separator 27 and the second separator 29 near the gas outlet 39.

[0045] The first separator 27 and the second separator 29 include a stress buffer portion 40. In this embodiment, an insulator 43 is fixed to the second separator 29. There is a gap between the insulator 43 and the first separator 27.

[0046] The insulator 43 is positioned at the longer of the two distances: the distance L1 between the air electrode frame 28 and the stress buffer section 40, and the distance L2 between the stress buffer section 40 and the interconnector 34. In this embodiment, since distance L1 is longer than distance L2, the space between the air electrode frame 28 and the stress buffer section 40 is more prone to bending than the space between the stress buffer section 40 and the interconnector 34. Therefore, to reduce blockage or short circuits between the air electrode frame 28 and the stress buffer section 40, the insulator 43 is positioned between the air electrode frame 28 and the stress buffer section 40.

[0047] Furthermore, the insulator 43 is positioned at the longer of the two distances: the distance L1 between the air electrode frame 28 and the stress buffer portion 40, and the distance L3 between the stress buffer portion 40 and the cell 30. In this embodiment, distance L3 is shorter than distance L2. The end of the stress buffer portion 40 necessary for determining distances L1, L2, and L3 is the part where the curvature of the stress buffer portion 40 begins.

[0048] In this embodiment, since the distance L1 is longer than the distance L3, the space between the air electrode frame 28 and the stress buffer section 40 is more prone to bending than the space between the stress buffer section 40 and the cell 30. Therefore, to reduce blockage and short circuits between the air electrode frame 28 and the stress buffer section 40, the insulator 43 is placed between the air electrode frame 28 and the stress buffer section 40. Furthermore, since the insulator 43 is also placed in the stress buffer section 40, the occurrence of narrowing and short circuits near the stress buffer section 40 can be reduced.

[0049] Although the present invention has been described above based on embodiments, it can be easily inferred that the present invention is not limited in any way to the above embodiments, and that various improvements and modifications are possible without departing from the spirit of the present invention.

[0050] In the first embodiment, a case was described in which the insulator 43 is fixed to the first separator 27 and not to the second separator 29, and in the second embodiment, a case was described in which the insulator 43 is fixed to the second separator 29 and not to the first separator 27, but the invention is not necessarily limited to these cases. It is certainly possible to fix the insulator 43 to both the first separator 27 and the second separator 29 and arrange multiple insulators 43 in the air chamber 37 so that the insulators 43 do not come into contact with each other. In this case as well, the occurrence of narrowing or short circuits between the first separator 27 and the second separator 29 can be reduced.

[0051] In the second embodiment, the case where distance L3 is shorter than distance L2 was described, but it is not necessarily limited to this. It is certainly possible to make distance L3 equal to distance L2 or to make distance L3 longer than distance L2.

[0052] In the second embodiment, the case in which the insulator 43 is placed between the air electrode frame 28 and the stress buffer section 40 because the distance L1 is longer than the distance L2 and the distance L3 is longer than the distance L3 was described, but it is not necessarily limited to this. If the distance L2 is longer than the distance L1, it is of course possible to place the insulator 43 between the interconnector 34 and the stress buffer section 40, or if the distance L3 is longer than the distance L1, it is possible to place the insulator 43 between the stress buffer section 40 and the cell 30. If the distances L2 and L1 are equal, or if the distances L3 and L1 are equal, it is of course possible to place the insulator 43 between the air electrode frame 28 and the stress buffer section 40, or between the stress buffer section 40 and the cell 30.

[0053] In the second embodiment, a case in which an insulator 43 is also placed in the stress buffer portion 40 was described, but this is not necessarily the only case. It is certainly possible to omit the insulator 43 in the stress buffer portion 40.

[0054] In the embodiment, the case in which the curved portions 41 and 42 of the stress buffer portion 40 are curved downward (see Figure 2) was described, but it is not necessarily limited to this. The direction in which the curved portions 41 and 42 curve may be upward, opposite to that in the embodiment.

[0055] In the embodiment, a case in which the first separator 27 and the second separator 29 include a stress buffer portion 40 has been described, but the embodiment is not necessarily limited to this. It is of course possible to omit the stress buffer portion 40 of the first separator 27 and the second separator 29. If the stress buffer portion 40 is omitted, the insulator 43 is placed between the air electrode frame 28 and the interconnector 34, or between the air electrode frame 28 and the cell 30.

[0056] In the embodiment, the case where the shape of cell 30 is a rectangle was described, but it is not necessarily limited to this. The shape of cell 30 may be a circle or an ellipse, or it may be a polygon other than a rectangle, such as a triangle or a pentagon.

[0057] In the embodiment, the case in which gas passages 22, 23, 24, and 25 are built into the stacks 10 and 60 has been described, but it is not necessarily limited to this. It is of course possible to connect the manifolds serving as passages 22, 23, 24, and 25 to the cells and provide them outside the cells. Examples of manifold materials include ceramics with high high-temperature strength.

[0058] In the embodiments, stacks 10 and 60 including solid oxide type cells 30 have been described, but the invention is not necessarily limited to these. It is certainly possible to apply the techniques of the embodiments to stacks including other types of cells, such as molten carbonate type cells. [Explanation of Symbols]

[0059] 10,60 stacks 27 First separator 28. Air pole frame (frame) 29 Second separator 30 cells 31 Electrolytes 32 Fuel electrode 33 Air pole 34 Interconnectors 37. Air chamber (space) 38 Gas supply port 39 Gas outlet 40 Stress buffer section 43 Insulator 44,45 End 46 gaps 47 First side 48. Second side L1,L2,L3 distance

Claims

1. A cell containing an electrolyte that separates the fuel electrode and the air electrode in the thickness direction, A first separator fixed to the cell and extending outwards from the outer circumference of the cell, The interconnector in contact with the aforementioned air electrode, A second separator is fixed to the interconnect and extends outwards from the outer circumference of the interconnect, A stack comprising an electrically insulating frame disposed between the first separator and the second separator in the thickness direction, The device comprises an insulator disposed in the space between the first separator and the second separator, The insulator is a stack fixed to at least one of the first separator and the second separator.

2. The first separator and the second separator include stress buffer portions that are curved in the same direction in the thickness direction, The stack according to claim 1, wherein the insulator is arranged on the side with the longer distance when comparing the distance between the frame and the stress buffer and the distance between the cell or the interconnect and the stress buffer.

3. The first separator and the second separator include stress buffer portions that are curved in the same direction in the thickness direction, The stack according to claim 1, wherein the insulator is disposed in the stress buffer portion.

4. The frame includes a gas supply port and a gas discharge port connected to the space, The cell is a quadrilateral having four sides, including a first side facing the gas supply port and a second side facing the gas outlet. The stack according to any one of claims 1 to 3, wherein the insulator is disposed between the first side and the frame, and between the second side and the frame.

5. The insulator includes an end portion fixed to one of the first separator and the second separator. The stack according to any one of claims 1 to 3, wherein there is a gap between the other end of the insulator in the thickness direction and the other of the first separator and the second separator.

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