JP2022112590A - Electrochemical reaction single cell and electrochemical reaction cell stack - Google Patents

Abstract

To suppress a damage to an electrolyte layer owing to a stress caused in the electrolyte layer by the difference in thermal expansion between a particular electrode and an electrolyte layer and the like.SOLUTION: An electrochemical reaction single cell comprises: a solid oxide-containing electrolyte layer; and an air electrode and a fuel electrode which are opposed to each other in a first direction over the electrolyte layer. In the electrochemical reaction single cell, a plurality of bottomed recessed portions are formed in a particular surface of the electrolyte layer on the side of a particular electrode which is at least one of the air and fuel electrodes. The inside of the recessed portion makes a cavity.SELECTED DRAWING: Figure 6

Description

The technology disclosed by this specification relates to an electrochemical reaction single cell.

A solid oxide fuel cell (hereinafter referred to as "SOFC") having an electrolyte layer containing a solid oxide is known as one type of fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen. It is A fuel cell single cell (hereinafter simply referred to as "single cell"), which is the minimum structural unit of an SOFC, faces an electrolyte layer in a predetermined direction (hereinafter referred to as "first direction") across the electrolyte layer. Includes cathode and anode.

In the conventional single cell, the specific surface of the electrolyte layer on the side of the specific electrode, which is at least one of the air electrode and the fuel electrode, is the specific electrode (or the intermediate layer arranged between the electrolyte layer and the specific electrode). It is configured to be in contact with the entire surface (see Patent Documents 1 to 3, for example).

JP 2010-277825 A JP-A-5-307968 JP 2005-158739 A

In a single cell, stress may occur in the electrolyte layer due to the difference in thermal expansion between the electrolyte layer and the fuel electrode. In the above-described conventional single cell in which the specific surface of the electrolyte layer is in contact with the facing portion (specific electrode or intermediate layer) facing the electrolyte layer over the entire surface, the stress generated in the electrolyte layer is applied to any specific location. There is a problem that it concentrates and the electrolyte layer is easily damaged. Since the electrolyte layer is dense and hard, it is easily damaged (for example, cracks are generated and propagated) due to the generation of stress. Moreover, since the electrolyte layer also functions to separate the air chamber facing the air electrode and the fuel chamber facing the fuel electrode, it is particularly necessary to suppress damage.

Such problems are also common to electrolytic single cells, which are structural units of solid oxide electrolytic cells (hereinafter referred to as "SOEC") that generate hydrogen using the electrolysis reaction of water. It is an issue. In this specification, the fuel cell single cell and the electrolysis single cell are collectively referred to as an electrochemical reaction single cell.

The technology disclosed in this specification can be implemented, for example, in the following forms.

(1) The electrochemical reaction single cell disclosed in the present specification is an electric cell comprising an electrolyte layer containing a solid oxide, and an air electrode and a fuel electrode facing each other in a first direction with the electrolyte layer interposed therebetween. In the chemical reaction single cell, a plurality of bottomed recesses having hollow interiors are formed on the specific surface of the electrolyte layer on the side of the specific electrode, which is at least one of the air electrode and the fuel electrode. there is In this electrochemical reaction single cell, a plurality of recesses are formed on the surface of the electrolyte layer on the side of the specific electrode, which is at least one of the air electrode and the fuel electrode. The recess is bottomed and hollow inside. Therefore, the stress generated in the electrolyte layer due to, for example, the difference in thermal expansion between the specific electrode and the electrolyte layer is dispersed in the plurality of recesses. In addition, since the interior of each recess is hollow, transmission of stress generated in the recess to the surroundings is suppressed compared to a configuration in which the interior of the recess is not hollow. Thereby, according to this electrochemical reaction single cell, damage to the electrolyte layer can be suppressed.

(2) In the above electrochemical reaction single cell, the plurality of recesses include first recesses formed in a covered region of the specific surface of the electrolyte layer that is covered with the specific electrode. and a cavity exists between the inner wall surface of the electrolyte layer defining the first recess and the specific electrode. If the material for forming the specific electrode is embedded in the first recess, for example, the embedded portion of the specific electrode will separate from the inner wall surface of the first recess as the stress of the electrochemical reaction unit cell changes. As a result, the performance of the electrochemical reaction single cell tends to deteriorate. Moreover, the stress generated in the first recess is likely to be transmitted to the specific electrode, and the stress generated in the embedded portion of the specific electrode is likely to be transmitted to the electrolyte layer via the first recess. On the other hand, in the present electrochemical reaction single cell, since there is a cavity between the inner wall surface of the electrolyte layer defining the first recess and the specific electrode, the performance of the electrochemical reaction single cell deteriorates over time. Therefore, it is possible to suppress the reduction in stress and suppress the transmission of stress. Furthermore, even if a crack develops in the specific electrode with the stress change in the electrochemical reaction unit cell and the crack develops in the specific electrode, the inner wall surface of the electrolyte layer that defines the first recess can be identified. Since the stress is released in the cavities existing between the electrodes, it is possible to suppress the progress of cracks in the specific electrodes.

(3) In the above electrochemical reaction single cell, the specific electrode has a thin portion that is partially thin in a region overlapping with the covered region when viewed in the first direction, and the thin portion is the first electrode. It is good also as a structure which has overlapped with the said 1st recessed part in 1 direction view. In the present electrochemical reaction single cell, since the specific electrode has the thin portion at the position overlapping the first recess, the stress generated in the specific electrode is reliably released at the thin portion. It is possible to more effectively suppress the growth of cracks in. As a result, damage to specific electrodes can be minimized.

(4) The electrochemical reaction single cell has an intermediate layer formed between the electrolyte layer and the specific electrode, and the plurality of recesses are located on the intermediate surface of the specific surface of the electrolyte layer. A configuration in which a first recess formed in a covering region covered with a layer is included, and a cavity exists between the inner wall surface of the first recess and the intermediate layer good. If the material for forming the intermediate layer is embedded in the first recess, for example, the embedded portion of the intermediate layer will separate from the inner wall surface of the first recess as the stress of the electrochemical reaction unit cell changes. As a result, the performance of the electrochemical reaction single cell tends to deteriorate. Moreover, the stress generated in the first recess is likely to be transmitted to the intermediate layer, and the stress generated in the buried portion of the intermediate layer is likely to be transmitted to the electrolyte layer via the first recess. On the other hand, in the present electrochemical reaction single cell, since a cavity exists between the inner wall surface of the electrolyte layer defining the first recess and the intermediate layer, the performance of the electrochemical reaction single cell changes over time. Therefore, it is possible to suppress the reduction in stress and suppress the transmission of stress.

(5) In the above electrochemical reaction single cell, the specific electrode may have a protruding portion that protrudes into the first recess and is spaced from the inner wall surface. In this electrochemical reaction single cell, it is possible to suppress damage to the electrolyte layer while suppressing separation between the electrolyte layer and the specific electrode, compared to a configuration in which the specific electrode does not have a projecting portion.

(6) In the above electrochemical reaction single cell, the intermediate layer may have a protruding portion that protrudes into the first recess and is spaced apart from the inner wall surface. In the present electrochemical reaction single cell, it is possible to suppress damage to the electrolyte layer while suppressing separation between the electrolyte layer and the intermediate layer, compared to a structure in which the intermediate layer does not have a projecting portion.

(7) In the above electrochemical reaction single cell, the maximum length of the opening of the first recess may be 1000 μm or less. According to the present electrochemical reaction single cell, the performance of the electrochemical reaction single cell is reduced due to the first recess compared to the configuration in which the maximum length of the opening of the first recess is greater than 1000 μm. can be suppressed.

(8) In the above electrochemical reaction single cell, the maximum depth of the first recess may be two-thirds or less of the thickness of the electrolyte layer. According to the present electrochemical reaction single cell, the maximum depth of the first recess in the electrolyte layer is greater than two-thirds of the thickness of the electrolyte layer. It is possible to suppress the occurrence of local current concentration due to excessively small resistance.

(9) In the above electrochemical reaction single cell, the plurality of recesses are formed in a non-overlapping region of the specific surface of the electrolyte layer that does not overlap the specific electrode in the first direction. may be configured to include a second recess of . In the present electrochemical reaction single cell, the second recess is formed in the non-overlapping region on the particular surface of the electrolyte layer. Therefore, the stress generated in the electrolyte layer is distributed to non-overlapping regions that do not contribute to the electrochemical reaction. As a result, according to the present electrochemical reaction single cell, damage to the electrolyte layer can be more effectively suppressed.

(10) In the above electrochemical reaction single cell, the maximum length of the opening of the recess may be 10 μm or more. According to the present electrochemical reaction single cell, the stress is dispersed without being excessively concentrated in the recesses, so that the electrolyte layer is less damaged than when the maximum length of the opening of the recesses is less than 10 μm. effectively suppressed.

(11) In the electrochemical reaction cell stack comprising a plurality of electrochemical reaction single cells, at least one of the plurality of electrochemical reaction single cells includes the above (1) to (10). It is good also as a structure which is any one electrochemical reaction single cell. According to this electrochemical reaction cell stack, damage to the electrolyte layer can be suppressed.

The technology disclosed in this specification can be implemented in various forms. It can be realized in the form of an electrochemical reaction cell stack (a fuel cell stack or an electrolysis cell stack) having a plurality of chemical reaction units, a manufacturing method thereof, and the like.

1 is a perspective view showing the external configuration of a fuel cell stack 100 according to the first embodiment; FIG. Explanatory drawing showing the XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II in FIG. Explanatory drawing showing the YZ cross-sectional configuration of the fuel cell stack 100 at the position III-III in FIG. Explanatory diagram showing the XZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. Explanatory diagram showing the YZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. Explanatory drawing showing the cross-sectional structure of the X1 portion of the single cell 110 in FIG. Explanatory diagram showing the cross-sectional configuration of the X2 portion of the single cell 110 in FIG. Explanatory drawing showing the cross-sectional configuration of the X1a portion of the single cell 110a in the second embodiment.

A. First embodiment:
A-1. Constitution:
(Configuration of fuel cell stack 100)
FIG. 1 is a perspective view showing the external configuration of the fuel cell stack 100 in this embodiment, and FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II in FIG. FIG. 3 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 100 at the position III-III in FIG. Each figure shows mutually orthogonal XYZ axes for specifying directions. In this specification, for the sake of convenience, the positive Z-axis direction is referred to as the upward direction, and the negative Z-axis direction is referred to as the downward direction. may be installed. The same applies to FIG. 4 and subsequent figures. The vertical direction is an example of the first direction in the scope of claims.

The fuel cell stack 100 includes a plurality of (seven in this embodiment) power generation units 102 and a pair of end plates 104 and 106 . The seven power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in this embodiment). A pair of end plates 104 and 106 are arranged so as to sandwich an aggregate composed of seven power generation units 102 from above and below.

A plurality of holes (eight in the present embodiment) penetrating in the vertical direction are formed in the peripheral edge portion around the Z-axis direction of each layer (the power generation unit 102, the end plates 104 and 106) constituting the fuel cell stack 100. Corresponding holes formed in each layer vertically communicate with each other to form communicating holes 108 extending vertically from one end plate 104 to the other end plate 106 . In the following description, the holes formed in each layer of the fuel cell stack 100 to form the communication holes 108 may also be referred to as the communication holes 108 .

A bolt 22 extending in the vertical direction is inserted through each communication hole 108 , and the fuel cell stack 100 is fastened by the bolt 22 and nuts 24 fitted on both sides of the bolt 22 . 2 and 3, between the nut 24 fitted on one side (upper side) of the bolt 22 and the upper surface of the end plate 104 constituting the upper end of the fuel cell stack 100, and between the bolt An insulating sheet 26 is interposed between the nut 24 fitted to the other side (lower side) of the fuel cell stack 22 and the lower surface of the end plate 106 forming the lower end of the fuel cell stack 100 . However, at a location where a gas passage member 27, which will be described later, is provided, between the nut 24 and the surface of the end plate 106, the insulating sheets disposed above and below the gas passage member 27 and the gas passage member 27, respectively. 26 intervenes. The insulating sheet 26 is composed of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder sheet, a glass sheet, a glass-ceramic composite, or the like.

The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each communication hole 108 . Therefore, a space is secured between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each communication hole 108 . As shown in FIGS. 1 and 2, one side of the outer circumference of the fuel cell stack 100 around the Z-axis direction (the side on the positive side of the X-axis among the two sides parallel to the Y-axis) is near the midpoint. The space formed by the bolt 22 (bolt 22A) positioned thereon and the communication hole 108 through which the bolt 22A is inserted receives the oxidant gas OG from the outside of the fuel cell stack 100, and the oxidant gas OG is introduced into each space. Functioning as an oxidant gas introduction manifold 161 which is a gas flow path for supplying to the power generation unit 102, the side opposite to the side (the side on the negative side of the X axis among the two sides parallel to the Y axis) The space formed by the bolt 22 (bolt 22B) located near the point and the communication hole 108 through which the bolt 22B is inserted is the oxidant offgas OOG which is the gas discharged from the air chamber 166 of each power generation unit 102. to the outside of the fuel cell stack 100 as an oxidizing gas discharge manifold 162 . In this embodiment, for example, air is used as the oxidant gas OG.

Also, as shown in FIGS. 1 and 3, the midpoint of one side (the side on the Y-axis positive side of the two sides parallel to the X-axis) on the outer circumference of the fuel cell stack 100 around the Z-axis direction Fuel gas FG is introduced from the outside of the fuel cell stack 100 into the space formed by the bolt 22 (bolt 22D) located nearby and the communication hole 108 through which the bolt 22D is inserted. A bolt that functions as the fuel gas introduction manifold 171 that supplies the power generation unit 102 and is located near the midpoint of the side opposite to the side (the side on the Y-axis negative direction side of the two sides parallel to the X-axis) 22 (bolt 22E) and the communication hole 108 through which the bolt 22E is inserted allows the fuel offgas FOG, which is the gas discharged from the fuel chamber 176 of each power generation unit 102, to flow outside the fuel cell stack 100. It functions as a fuel gas discharge manifold 172 that discharges to the In this embodiment, hydrogen-rich gas obtained by reforming city gas, for example, is used as the fuel gas FG.

Four gas passage members 27 are provided in the fuel cell stack 100 . Each gas passage member 27 has a hollow tubular body portion 28 and a hollow tubular branch portion 29 branched from a side surface of the main body portion 28 . A hole in the branch portion 29 communicates with a hole in the main body portion 28 . A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27 . Further, as shown in FIG. 2, the hole of the body portion 28 of the gas passage member 27 arranged at the position of the bolt 22A forming the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. A hole in the body portion 28 of the gas passage member 27 arranged at the position of the bolt 22B forming the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162 . Further, as shown in FIG. 3, the hole of the body portion 28 of the gas passage member 27 arranged at the position of the bolt 22D forming the fuel gas introduction manifold 171 communicates with the fuel gas introduction manifold 171, and the fuel gas A hole in the body portion 28 of the gas passage member 27 arranged at the position of the bolt 22E forming the discharge manifold 172 communicates with the fuel gas discharge manifold 172 .

(Configuration of end plates 104, 106)
The pair of end plates 104 and 106 is a substantially rectangular plate-shaped conductive member as viewed in the Z-axis direction, and is made of, for example, stainless steel. One end plate 104 is arranged above the uppermost power generating unit 102 and the other end plate 106 is arranged below the lowermost power generating unit 102 . A pair of end plates 104 and 106 sandwich a plurality of power generation units 102 in a pressed state. The upper end plate 104 functions as the positive side output terminal of the fuel cell stack 100 , and the lower end plate 106 functions as the negative side output terminal of the fuel cell stack 100 .

(Configuration of power generation unit 102)
4 is an explanatory diagram showing the XZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 2, and FIG. FIG. 3 is an explanatory diagram showing a YZ cross-sectional configuration of two power generation units 102;

As shown in FIGS. 4 and 5, the power generation unit 102 includes a single cell 110, a separator 120, an air electrode side frame 130, an air electrode side current collector 134, an anode side frame 140, an anode side It has a current collector 144 and a pair of interconnectors 150 forming the top layer and the bottom layer of the power generation unit 102 . The separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the interconnector 150 are provided with holes corresponding to the communication holes 108 through which the bolts 22 are inserted.

The interconnector 150 is a substantially rectangular plate-shaped conductive member when viewed in the Z-axis direction, and is made of a material containing Cr, such as ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generating units 102 and prevents mixing of reaction gases between the power generating units 102 . In this embodiment, when two power generation units 102 are arranged adjacently, one interconnector 150 is shared by the two adjacent power generation units 102 . That is, the upper interconnector 150 in a certain power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102 . In addition, since the fuel cell stack 100 has a pair of end plates 104 and 106, the power generation unit 102 located at the top in the fuel cell stack 100 does not have the upper interconnector 150, and is located at the bottom. The generating unit 102 does not have a lower interconnector 150 (see Figures 2 and 3).

The single cell 110 includes an electrolyte layer 112, an air electrode (cathode) 114 arranged above the electrolyte layer 112, a fuel electrode (anode) 116 arranged below the electrolyte layer 112, and an electrolyte An intermediate layer 180 is disposed between layer 112 and cathode 114 . The single cell 110 of this embodiment is a fuel electrode supporting type single cell in which the fuel electrode 116 supports the other layers (the electrolyte layer 112, the air electrode 114, and the intermediate layer 180) constituting the single cell 110. FIG.

The electrolyte layer 112 is a substantially rectangular plate-shaped member when viewed in the Z-axis direction, and is a dense (low porosity) layer. The electrolyte layer 112 contains a solid oxide (eg, YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), CSZ (calcia-stabilized zirconia)). Thus, the single cell 110 of this embodiment is a solid oxide fuel cell (SOFC) using a solid oxide as an electrolyte.

The air electrode 114 is a substantially rectangular flat member smaller than the electrolyte layer 112 when viewed in the Z-axis direction, and is a porous layer having a porosity higher than that of the electrolyte layer 112 . The cathode 114 is made of a perovskite-type oxide represented by _ABO3 (e.g., lanthanum strontium cobalt iron oxide (LSCF), lanthanum strontium iron oxide (LSF), lanthanum strontium cobalt oxide (LSC), lanthanum strontium manganese oxide (LSM), lanthanum nickel iron oxide (LNF), etc.).

The fuel electrode 116 is a substantially rectangular flat member having substantially the same size as the electrolyte layer 112 when viewed in the Z-axis direction, and is a porous layer having a porosity higher than that of the electrolyte layer 112 . Although not shown, in this embodiment, the fuel electrode 116 includes a substrate layer forming the lower surface of the fuel electrode 116 and a functional layer positioned between the substrate layer and the electrolyte layer 112 . The functional layer of the fuel electrode 116 is a layer that mainly reacts oxygen ions supplied from the electrolyte layer 112 with hydrogen or the like contained in the fuel gas FG to produce electrons and water vapor. It contains Ni, which is a conductive material, and an oxygen ion ion conductive oxide (eg, YSZ). Further, the substrate layer of the fuel electrode 116 is a layer that mainly exhibits the function of supporting the functional layer, the electrolyte layer 112, and the air electrode 114, and includes Ni, which is an electronically conductive substance, and an oxygen ion conductive oxide ( For example, YSZ).

The intermediate layer (reaction prevention layer) 180 is a substantially rectangular plate-shaped member when viewed in the Z-axis direction. The intermediate layer 180 is formed of an ionically conductive solid oxide such as SDC (samarium-doped ceria), GDC (gadolinium-doped ceria), LDC (lanthanum-doped ceria), YDC (yttrium-doped ceria), or the like.

The separator 120 is a frame-like member in which a substantially rectangular hole 121 penetrating in the vertical direction is formed near the center, and is made of metal, for example. The peripheral portion of the separator 120 around the hole 121 faces the peripheral portion of the surface of the electrolyte layer 112 on the air electrode 114 side. The separator 120 is joined to the electrolyte layer 112 (single cell 110) by a joining portion 124 formed of brazing material (for example, Ag brazing) arranged at the opposing portion. The air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116 are separated by the separator 120 to prevent gas leakage from one electrode side to the other electrode side in the peripheral portion of the unit cell 110 . Suppressed.

The air electrode side frame 130 is a frame-shaped member having a substantially rectangular hole 131 penetrating vertically in the vicinity of the center thereof, and is made of an insulator such as mica, for example. A hole 131 in the cathode-side frame 130 constitutes an air chamber 166 facing the cathode 114 . The air electrode-side frame 130 is in contact with the peripheral edge portion of the surface of the separator 120 opposite to the side facing the electrolyte layer 112 and the peripheral edge portion of the surface of the interconnector 150 facing the air electrode 114 . . Also, the pair of interconnectors 150 included in the power generation unit 102 are electrically insulated by the air electrode side frame 130 . Further, the air electrode side frame 130 has an oxidizing gas supply communication hole 132 that communicates the oxidizing gas introduction manifold 161 and the air chamber 166, and an oxidizing gas supply communication hole 132 that communicates the air chamber 166 and the oxidizing gas discharge manifold 162. A discharge communication hole 133 is formed.

The fuel electrode-side frame 140 is a frame-shaped member having a substantially rectangular hole 141 vertically penetrating near the center thereof, and is made of metal, for example. A hole 141 in the anode-side frame 140 constitutes a fuel chamber 176 facing the anode 116 . The fuel electrode-side frame 140 is in contact with the periphery of the surface of the separator 120 facing the electrolyte layer 112 and the periphery of the surface of the interconnector 150 facing the fuel electrode 116 . The fuel electrode side frame 140 also has a fuel gas supply communication hole 142 that communicates the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that communicates the fuel chamber 176 and the fuel gas discharge manifold 172. and are formed.

The fuel electrode side current collector 144 is arranged in the fuel chamber 176 . The fuel electrode-side current collector 144 includes an interconnector-facing portion 146, an electrode-facing portion 145, and a connecting portion 147 that connects the electrode-facing portion 145 and the interconnector-facing portion 146. For example, nickel or a nickel alloy is used. , stainless steel or the like. The electrode facing portion 145 is in contact with the surface of the fuel electrode 116 opposite to the side facing the electrolyte layer 112 , and the interconnector facing portion 146 is in contact with the surface of the interconnector 150 facing the fuel electrode 116 . in contact. However, as described above, since the lowest power generation unit 102 in the fuel cell stack 100 does not have the lower interconnector 150, the interconnector facing portion 146 of the power generation unit 102 is the lower end plate. 106 is in contact. Fuel electrode-side current collector 144 having such a configuration electrically connects fuel electrode 116 and interconnector 150 (or end plate 106). A spacer 149 made of mica, for example, is arranged between the electrode facing portion 145 and the interconnector facing portion 146 . Therefore, the fuel electrode side current collector 144 follows the deformation of the power generation unit 102 due to temperature cycles and reaction gas pressure fluctuations, and the fuel electrode 116 and the interconnector 150 (or the end plate 106) through the fuel electrode side current collector 144. good electrical connection with

The air electrode side current collector 134 is arranged in the air chamber 166 . The air electrode side current collector 134 is composed of a plurality of substantially quadrangular prism-shaped current collector elements 135, and is made of a material containing Cr, such as ferritic stainless steel. The air electrode-side current collector 134 is in contact with the surface of the air electrode 114 opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 facing the air electrode 114 . However, as described above, the uppermost power generation unit 102 in the fuel cell stack 100 does not have the upper interconnector 150, so the air electrode side current collector 134 in the power generation unit 102 is the upper end plate 104 is in contact. Since the air electrode side current collector 134 has such a configuration, it electrically connects the air electrode 114 and the interconnector 150 (or the end plate 104). A conductive bonding layer may be interposed between the air electrode 114 and the air electrode side current collector 134 to bond the two. The cathode-side current collector 134 and the interconnector 150 may be configured as an integral member.

A-2. Operation of fuel cell stack 100:
As shown in FIGS. 2 and 4, the oxidant gas OG is supplied through a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161. Then, the oxidizing gas OG is supplied to the oxidizing gas introduction manifold 161 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28 , and the oxidizing gas OG is supplied from the oxidizing gas introduction manifold 161 to each power generation unit 102 . The agent gas is supplied to the air chamber 166 through the agent gas supply communication hole 132 . 3 and 5, the fuel gas FG is supplied through a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. Then, the fuel gas FG is supplied to the fuel gas introduction manifold 171 via the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28, and the fuel gas supply communication of each power generation unit 102 from the fuel gas introduction manifold 171. It is supplied to fuel chamber 176 through hole 142 .

When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, electric power is generated in the single cell 110 by the electrochemical reaction of the oxidant gas OG and the fuel gas FG. will be This power generation reaction is an exothermic reaction. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to one interconnector 150 through the air electrode side current collector 134, and the fuel electrode 116 is electrically connected through the fuel electrode side current collector 144. It is electrically connected to the other interconnector 150 . Also, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, the electrical energy generated in each power generation unit 102 is taken out from the end plates 104 and 106 that function as output terminals of the fuel cell stack 100 . Since the SOFC generates power at a relatively high temperature (for example, 700° C. to 1000° C.), the fuel cell stack 100 is heated by the heater ( (not shown).

As shown in FIGS. 2 and 4, the oxidant offgas OOG discharged from the air chamber 166 of each power generation unit 102 is discharged to the oxidant gas discharge manifold 162 through the oxidant gas discharge communication hole 133 and further oxidized. The fuel cell stack 100 is supplied to the fuel cell stack 100 via a gas pipe (not shown) connected to the branch portion 29 through the holes of the main body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the agent gas discharge manifold 162 . is discharged to the outside of the Further, as shown in FIGS. 3 and 5, the fuel offgas FOG discharged from the fuel chamber 176 of each power generation unit 102 is discharged to the fuel gas discharge manifold 172 through the fuel gas discharge communication hole 143. Through the holes in the body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the exhaust manifold 172, the gas is supplied to the outside of the fuel cell stack 100 via a gas pipe (not shown) connected to the branch portion 29. Ejected.

A-3. Detailed configuration of specific surface 113 of electrolyte layer 112:
Next, the detailed configuration of the specific surface 113 of the electrolyte layer 112 in the single cell 110 that constitutes the fuel cell stack 100 of this embodiment will be described. In this embodiment, the specific surface 113 of the electrolyte layer 112 is the surface (upper surface) of the electrolyte layer 112 on the air electrode 114 side and adjacent to the intermediate layer 180 in the vertical direction.

FIG. 6 is an explanatory diagram showing the cross-sectional structure of the X1 portion of the single cell 110 in FIG. FIG. 6 shows a cross-sectional structure parallel to the up-down direction of the vicinity of the power generation region 113A of the specific surface 113 of the electrolyte layer 112. As shown in FIG. The power generation region 113A is a region of the specific surface 113 of the electrolyte layer 112 that is covered with the intermediate layer 180 when viewed from above. FIG. 7 is an explanatory diagram showing the cross-sectional structure of the X2 portion of the single cell 110 in FIG. FIG. 7 shows a cross-sectional configuration parallel to the up-down direction of the non-power generation region 113B vicinity of the specific surface 113 of the electrolyte layer 112 . The non-power generating region 113B is a non-overlapping region of the specific surface 113 of the electrolyte layer 112 that does not overlap the air electrode 114 in the vertical direction. FIGS. 6 and 7 schematically show SEM images (for example, 90 times magnification) taken by SEM (accelerating voltage of 15 kV) showing vertical cross sections of X1 and X2 portions. The air electrode 114 is an example of a specific electrode in the claims. The power generation area 113A is an example of a covered area in the scope of claims, and the non-power generation area 113B is an example of a non-overlapping area in the scope of claims.

A plurality of recesses 200 are formed in the specific surface 113 of the electrolyte layer 112 . The recess 200 is bottomed and hollow inside. Specifically, the recess 200 is open on the intermediate layer 180 (air electrode 114) side and closed on the fuel electrode 116 side. That is, the material of the intermediate layer 180 does not enter the interior of the recess 200, and the bottom of the recess 200 and the lower surface of the intermediate layer 180 are spaced apart to secure a cavity. The opening shape of the recess 200 in the vertical direction is substantially circular (including an ellipse). Moreover, the opening shape of the recess 200 in the vertical direction may be a groove shape extending in a predetermined direction.

The plurality of recesses 200 formed in the specific surface 113 of the electrolyte layer 112 includes power generation side recesses 210 and non-power generation side recesses 220 . The power generation side recess 210 is an example of a first recess in the claims, and the non-power generation side recess 220 is an example of a second recess in the claims.

As shown in FIG. 6 , the power generation side recess 210 is a recess 200 formed in the power generation region 113A of the electrolyte layer 112 . A plurality of power generation side recesses 210 are formed in the power generation region 113A. Specifically, power generation side recesses 210 are scattered throughout the power generation region 113A. A cavity exists between the inner wall surface 212 of the electrolyte layer 112 defining the power generation side recess 210 and the intermediate layer 180 . Intermediate layer 180 has protruding portions 182 . The protruding portion 182 protrudes into the power generation side recess 210 and is separated from the inner wall surface 212 (bottom surface) of the electrolyte layer 112 . The protruding portion 182 protrudes so as to continuously approach the bottom surface of the inner wall surface 212 from the open end of the recess 200 toward the center of the opening.

In addition, as shown in FIGS. 6 and 7, the inner wall surface 212 of the recess 200 is preferably curved. This suppresses concentration of stress at a specific location. Moreover, it is preferable that the opening area of the recess 200 becomes smaller as it approaches the specific surface 113 of the electrolyte layer 112 . As a result, it is possible to ensure a large intermediate layer contact area between the electrolyte layer 112 and the intermediate layer 180 and secure a cavity of a size sufficient for stress relaxation.

The maximum length L1 of the opening of the power generation side recess 210 is, for example, 1000 μm or less. The maximum length L1 of the opening of the power generation side recess 210 is, for example, 10 μm or more. Further, the maximum depth D1 of the power generation side recess 210 (the distance from the opening of the power generation side recess 210 to the bottom surface of the power generation side recess 210) is 2/3 or less of the thickness D2 of the electrolyte layer 112.

As shown in FIG. 7 , the non-power generation side recess 220 is a recess 200 formed in the non-power generation region 113B of the electrolyte layer 112 . A plurality of non-power generation side recesses 220 are formed in the non-power generation region 113B. Specifically, non-power generation side recesses 220 are scattered throughout the non-power generation region 113B. The non-power generation side recess 220 is hollow and communicates with the outside through the opening of the non-power generation side recess 220 . That is, the inner wall surface 222 of the non-power generation side recess 220 faces the air chamber 166 .

The maximum length L2 of the opening of the non-power generation side recess 220 is, for example, 1000 μm or less. The maximum length L2 of the opening of the non-power generation side recess 220 is, for example, 10 μm or more. Also, the maximum depth D3 of the non-power generation side recess 220 is two thirds or less of the thickness D2 of the electrolyte layer 112 . In this embodiment, the thickness D2 of the electrolyte layer 112 in the vertical direction is 10 μm or less, the thickness of the functional layer of the fuel electrode 116 in the vertical direction is 20 μm or less, and the substrate layer of the fuel electrode 116 has a vertical thickness of 20 μm or less. The thickness in the direction is 1000 μm or less.

A-4. Manufacturing method of fuel cell stack 100:
A method for manufacturing the fuel cell stack 100 of the present embodiment is, for example, as follows.

(Formation of laminate of electrolyte layer 112 and fuel electrode 116)
A butyral resin, a plasticizer dioctyl phthalate (DOP), a dispersant, and a mixed solvent of toluene and ethanol are added to the YSZ powder and mixed in a ball mill to prepare a slurry. The obtained slurry is thinned by a doctor blade method to obtain a green sheet for electrolyte layer having a predetermined thickness (for example, about 6 μm). Further, organic beads as a pore-forming material, butyral resin, DOP as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added to a mixed powder of NiO powder and YSZ powder, A slurry is prepared by mixing in a ball mill. The obtained slurry is thinned by a doctor blade method to obtain a green sheet for a fuel electrode substrate layer having a predetermined thickness (for example, about 400 μm). Further, a butyral resin, a plasticizer DOP, a dispersant, and a mixed solvent of toluene and ethanol are added to a mixed powder of NiO powder and YSZ powder, and mixed in a ball mill to form a slurry. Prepare. The obtained slurry is thinned by a doctor blade method to obtain a green sheet for fuel electrode functional layer having a predetermined thickness (for example, about 11 μm). By adhering and press-bonding the respective green sheets, a compact in which the fuel electrode substrate layer green sheet, the fuel electrode functional layer green sheet, and the electrolyte layer green sheet are laminated in this order is obtained.

Next, the surface side of the electrolyte layer green sheet of the compact is subjected to laser processing (laser spot irradiation) to form recesses that will become the recesses 200 after firing. Well-known lasers such as CO ₂ laser, YAG laser, and fiber laser can be used for laser processing. After that, the compact having the recesses is degreased at a predetermined temperature (eg, about 280° C.), and then fired at a predetermined temperature (eg, about 1350° C.) for a predetermined time (eg, about 1 hour). Thereby, a laminate of the electrolyte layer 112 and the fuel electrode 116 is obtained. A recess 200 is formed in the specific surface 113 of the electrolyte layer 112 in this laminate.

(Formation of intermediate layer 180)
Polyvinyl alcohol as an organic binder and butyl carbitol as an organic solvent are added to the GDC powder and mixed to adjust the viscosity to prepare an intermediate layer paste. The obtained intermediate layer paste is applied, for example, by screen printing, to the surface of the electrolyte layer 112 in the laminate in which the recesses 200 are formed, and is fired at a predetermined temperature (eg, 1200° C.). Thereby, the intermediate layer 180 is formed, and a laminate of the intermediate layer 180, the electrolyte layer 112, and the fuel electrode 116 is obtained. Since the intermediate layer paste is viscous, when it is applied to the surface of the electrolyte layer 112 , it does not completely fill the recesses 200 , and cavities are ensured within the recesses 200 . By firing in that state, the cavity of the recess 200 is maintained, and the intermediate layer 180 is formed with the projecting portion 182 described above.

In this way, by providing a bottomed recess on the surface of the electrolyte layer precursor before firing, the degreasing gas generated when simultaneously firing the molded body can be discharged from the specific surface 113 of the electrolyte layer precursor (electrolyte layer 112). By rapidly releasing the degreasing gas and suppressing retention of the degreasing gas at the interface between the electrolyte layer 112 and the intermediate layer 180, peeling occurring at the interface between the electrolyte layer 112 and the intermediate layer 180 can be suppressed.

(Formation of air electrode 114)
A mixed powder of a perovskite-type oxide (for example, LSCF) powder and a sulfate (for example, SrSO ₄ ) powder is prepared, and polyvinyl alcohol as an organic binder and butyl carbitol as an organic solvent are added to the mixed powder. are added and mixed to adjust the viscosity to prepare an air electrode paste. The obtained air electrode paste is applied, for example, by screen printing to the surface of the intermediate layer 180 in the laminate of the intermediate layer 180, the electrolyte layer 112, and the fuel electrode 116, and dried, and the air electrode paste is applied. The stacked body is fired at a predetermined temperature (for example, about 1100° C.). Thereby, the air electrode 114 is formed, and the unit cell 110 including the fuel electrode 116, the electrolyte layer 112, the intermediate layer 180, and the air electrode 114 is produced.

After manufacturing a plurality of single cells 110 according to the above-described method, an assembly process (for example, a process of attaching other members such as separators 120 to each single cell 110, a process of stacking a plurality of single cells 110, and fastening with bolts 22) is performed. process, etc.). The manufacturing of the fuel cell stack 100 is thus completed.

A-5. Effect of this embodiment:
As described above, the single cell 110 that constitutes the fuel cell stack 100 of this embodiment includes the electrolyte layer 112, and the air electrode 114 and the fuel electrode 116 facing each other with the electrolyte layer 112 interposed therebetween. Further, an intermediate layer 180 is formed between the cathode 114 and the anode 116 . Here, as described above, since the electrolyte layer 112 is dense and hard, it is easily damaged (for example, cracks are generated and propagated) due to the generation of stress. Moreover, since the electrolyte layer 112 also functions to separate the air chamber 166 and the fuel chamber 176, it is particularly necessary to prevent damage.

In contrast, in this embodiment, a plurality of recesses 200 are formed in the specific surface 113 of the electrolyte layer 112 . The recess 200 is bottomed and hollow inside. Therefore, the stress generated in the electrolyte layer 112 due to, for example, the difference in thermal expansion between the air electrode 114 and the electrolyte layer 112 is dispersed in the plurality of recesses 200, and as a result, the occurrence of cracks, for example, can be suppressed. . Moreover, delamination between the electrolyte layer 112 and the intermediate layer 180 can be suppressed. Certainly, in this embodiment, compared to the configuration in which the electrolyte layer 112 and the intermediate layer 180 are in full contact with no gap, the power generation performance may be slightly lower. It is possible to effectively suppress deterioration in power generation performance over time due to delamination or the like between the layer 112 and the intermediate layer 180 . Also, because the interior of each recess 200 is hollow, stresses are distributed without being overly concentrated in the recesses 200, as compared to configurations in which the interior of the recesses 200 is not hollow, resulting in, for example, cracks and delamination. progress can be restrained. As described above, according to the present embodiment, damage to the electrolyte layer 112 can be suppressed.

If the material for forming the intermediate layer 180 is embedded in the power generation side recess 210, for example, the embedded portion of the intermediate layer 180 will peel off from the inner wall surface of the power generation side recess 210 as the stress of the single cell 110 changes. As a result, the performance of the single cell 110 tends to deteriorate. In addition, stress generated in the power generation side recess 210 is likely to be transmitted to the intermediate layer 180 and stress generated in the embedded portion of the intermediate layer 180 is likely to be transmitted to the electrolyte layer 112 via the power generation side recess 210 . In contrast, in the present embodiment, since a cavity exists between the inner wall surface 212 of the electrolyte layer 112 that defines the power generation side recess 210 and the intermediate layer 180, the performance of the single cell 110 changes over time. It is possible to suppress the decrease and suppress the transmission of stress.

In this embodiment, intermediate layer 180 has protruding portions 182 . The protruding portion 182 protrudes into the power generation side recess 210 and is separated from the inner wall surface 212 (bottom surface) of the electrolyte layer 112 . Therefore, the separation between the electrolyte layer 112 and the intermediate layer 180 is suppressed by the engagement between the projecting portion 182 and the power generation side recess 210 . As a result, according to the present embodiment, the separation between the electrolyte layer 112 and the intermediate layer 180 is suppressed, and damage to the electrolyte layer 112 is prevented, as compared with the configuration in which the intermediate layer 180 does not have the projecting portion 182 . can be suppressed.

In this embodiment, the maximum length L1 of the opening of the power generation side recess 210 is, for example, 1000 μm or less. Therefore, according to the present embodiment, the contact area between the electrolyte layer 112 and the intermediate layer 180 due to the presence of the power generation side recesses 210 is larger than that of the configuration in which the maximum length L1 of the opening of the power generation side recesses 210 is greater than 1000 μm. It is possible to suppress the deterioration of the performance of the single cell 110 due to the deterioration of the .

In this embodiment, the maximum depth D1 of the power generation side recess 210 is two thirds or less of the thickness D2 of the electrolyte layer 112 . Therefore, according to the present embodiment, the power generation side recesses 210 are formed in the electrolyte layer 112 compared to the configuration in which the maximum depth D1 of the power generation side recesses 210 is longer than 2/3 of the thickness D2 of the electrolyte layer. It is possible to suppress the occurrence of local current concentration due to the excessively small resistance of the portion where the insulating film is formed.

In this embodiment, the non-power generation side recess 220 is a recess 200 formed in the non-power generation region 113B of the electrolyte layer 112 . Therefore, the stress generated in the electrolyte layer 112 is dispersed in the non-power generation region 113B that does not contribute to the power generation reaction. Thus, according to the present embodiment, damage to the electrolyte layer 112 can be more effectively suppressed.

In this embodiment, the maximum length L1 of the opening of the recess 200 (the power generation side recess 210 and the non-power generation side recess 220) is, for example, 10 μm or more. Therefore, according to the present embodiment, the stress generated in the recess 200 is more effectively suppressed from being transmitted to the surroundings, compared to the configuration in which the maximum lengths L1 and L2 of the opening of the recess 200 are smaller than 10 μm. be.

B. Second embodiment:
FIG. 8 is an explanatory diagram showing the cross-sectional configuration of the X1a portion of the single cell 110a in the fuel cell stack 100 of the second embodiment. The X1a portion is the same position as the above-mentioned X1 portion in FIG. In the following, among the configurations of the unit cell 110a of the second embodiment, the same configurations as those of the above-described first embodiment 110 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

The plurality of recesses 200a formed in the specific surface 113a of the electrolyte layer 112a includes power generation side recesses 210a and non-power generation side recesses (not shown). As shown in FIG. 8, the power generation side recess 210a is a recess 200a formed in the power generation region 113Aa of the electrolyte layer 112a. A plurality of power generation side recesses 210a are formed in the power generation region 113Aa. Specifically, power generation side recesses 210a are scattered throughout the power generation region 113Aa. A cavity exists between the inner wall surface 212a of the electrolyte layer 112a defining the power generation side recess 210a and the air electrode 114a.

The air electrode 114a has a plurality of thin portions 182a. The thin portion 182a is formed in a region of the air electrode 114a that overlaps with the power generation side recess 210a in the power generation region 113Aa when viewed from above. The thin portion 182a is a partially thinned portion of the air electrode 114a, in other words, a portion thinner in the vertical direction than the surrounding portion of the thin portion 182a. Specifically, each thin portion 182a is formed by an upper recess 184a and a lower recess 186a. The upper recess 184a is a recess formed on the surface of the air electrode 114a opposite to the electrolyte layer 112a (upper surface in FIG. 8). The lower recess 186a is a recess formed in the surface of the air electrode 114a on the side of the electrolyte layer 112a (lower surface in FIG. 8). The upper recess 184a and the lower recess 186a are formed at positions overlapping each other when viewed in the vertical direction. The lower recess 186a forms an integral space together with the vertically opposed power generation side recess 210a.

Intermediate layer 180a is disposed between cathode 114a and electrolyte layer 112a. However, for example, as shown in the power generation side recess 210a on the left side of FIG. good. Further, as shown in the power generation side recess 210a on the right side of FIG. 8, the intermediate layer 180a may be arranged along and covering the inner wall surface 212a of the electrolyte layer 112a that defines the power generation side recess 210a. The configuration shown in FIG. 8 can be obtained by adjusting the printing pressure and the viscosity of the paste when printing the intermediate layer paste and the air electrode paste, for example, in the method of manufacturing the fuel cell stack 100 of the first embodiment. can be formed.

According to the above description, in the present embodiment, in the unit cell 110a, the air electrode 114a has the thin portion 182a. The thin portion 182a overlaps the power generation side recess 210a when viewed in the vertical direction. As a result, the stress generated in the air electrode 114a is reliably released at the thin portion 182a, so that the propagation of cracks in the air electrode 114a can be more effectively suppressed. As a result, damage to the cathode 114a can be minimized. Further, even when the intermediate layer 180a covers the wall surface of the power generation side recess 210a and the cavity is defined by the intermediate layer 180a, it is possible to suppress deterioration in the performance of the single cell 110a over time and to suppress transmission of stress. can be achieved.

C. Variant:
The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the scope of the invention. For example, the following modifications are possible.

The configuration of the single cells 110, 110a or the fuel cell stack 100 in the above embodiments is merely an example, and various modifications are possible. For example, although the single cells 110 and 110a include the intermediate layer 180 in the above embodiments, the single cells 110 and 110a may not include the intermediate layers 180 and 180a. In such a configuration without intermediate layers 180, 180a, air electrodes 114, 114a directly cover and contact specific surfaces 113, 113a of electrolyte layers 112, 112a. Even with such a configuration, the power generation side recesses 210, 210a are formed in the specific surfaces 113, 113a, and the inner wall surfaces 212, 212a of the electrolyte layers 112, 112a that define the power generation side recesses 210, 210a. If there is a cavity between the air electrodes 114 and 114a, it is possible to suppress deterioration in the performance of the single cells 110 and 110a over time and to suppress transmission of stress.

In the above embodiment, the fuel electrode 116 has a two-layer structure of the substrate layer and the functional layer, but the fuel electrode 116 may have a single-layer structure, or may have a structure of three or more layers. Further, in the above embodiment, the number of the single cells 110, 110a included in the fuel cell stack 100 is merely an example, and the number of the single cells 110, 110a depends on the output voltage required for the fuel cell stack 100, etc. can be determined as appropriate.

In the above embodiment, the space between the outer peripheral surface of the shaft of each bolt 22 and the inner peripheral surface of each communicating hole 108 is used as each manifold. An axial hole may be formed in the portion and the hole may be used as each manifold. Also, each manifold may be provided separately from each communication hole 108 into which each bolt 22 is inserted.

In the above embodiments, the air electrodes 114 and 114a are illustrated as specific electrodes, but the fuel electrode 116 may be used. In such a configuration, damage to the electrolyte layers can be suppressed if a plurality of recesses are formed in the surfaces of the electrolyte layers 112 and 112a on the fuel electrode 116 side (lower surfaces in FIG. 1 and the like). In short, if the recess is formed in at least one specific surface of the electrolyte layer in the first direction, damage to the electrolyte layer can be suppressed. In addition, if there is a cavity between the inner wall surface of the electrolyte layer that defines the recess and the portion (layer, electrode) adjacent to the surface, deterioration of the performance of the electrochemical reaction unit cell over time can be suppressed. and suppression of stress transmission. Further, if the fuel electrode 116 has a protruding portion that protrudes into the first recess and is spaced apart from the inner wall surface (bottom surface) that defines the first recess, the electrolyte layer and the specific electrode Damage to the electrolyte layer can be suppressed while suppressing detachment between the electrodes.

In the above embodiment, either one of the power generation side recesses 210, 210a and the non-power generation side recesses 220 may not be formed on the specific surfaces 113, 113a of the electrolyte layers 112, 112a. Further, in the first embodiment, the intermediate layer 180 may be configured without the projecting portion 182 . The maximum length L1 of the opening of the recess 200 (the power generation side recess 210, the non-power generation side recess 220) may be longer than 1000 μm, for example. The maximum depth D1 of the power generation side recess 210 may be longer than 2/3 of the thickness D2 of the electrolyte layer 112 .

In addition, the materials forming each member in the above-described embodiment are merely examples, and each member may be formed of another material.

Further, in the above-described embodiment, all the unit cells 110 included in the fuel cell stack 100 need to have a configuration in which the recesses 200, 200a are formed in the specific surfaces 113, 113a of the electrolyte layers 112, 112a. However, if at least one unit cell 110, 110a included in the fuel cell stack 100 has a configuration in which the recesses 200, 200a are formed in the specific surfaces 113, 113a of the electrolyte layers 112, 112a, the electrolyte Damage to the layers 112 and 112a can be suppressed.

Further, although the above-described embodiments deal with the flat-plate type single cells 110 and 110a, the technology disclosed in this specification can be similarly applied to other single cells than the flat-plate type.

Further, in the above embodiments, SOFCs that generate electricity by utilizing the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidant gas are targeted, but the technology disclosed in the present specification includes: It can also be applied to an electrolytic single cell, which is a structural unit of a solid oxide electrolysis cell (SOEC) that generates hydrogen using the electrolysis reaction of water, and an electrolytic cell stack comprising a plurality of electrolytic single cells. be. The configuration of the electrolysis cell stack is known, for example, as described in Japanese Patent Application Laid-Open No. 2016-81813, so it will not be described in detail here. Configuration. That is, the fuel cell stack 100 in the above-described embodiment can be read as an electrolytic cell stack, the power generation unit 102 can be read as an electrolytic cell unit, and the single cell 110 can be read as an electrolytic single cell. However, during the operation of the electrolysis cell stack, a voltage is applied between the two electrodes so that the air electrode 114 is positive (anode) and the fuel electrode 116 is negative (cathode). Water vapor is supplied as a source gas. As a result, an electrolysis reaction of water occurs in each electrolysis cell unit, hydrogen gas is generated in the fuel chamber 176 , and the hydrogen is taken out of the electrolysis cell stack through the communication hole 108 . Even in the electrolytic single cell and electrolytic cell stack having such a configuration, if a configuration in which the recess 200 similar to that of the above embodiment is formed is adopted, the same effect can be obtained.

The manufacturing method of the fuel cell stack 100 in the above embodiment is merely an example, and various modifications are possible. For example, in the above embodiment, laser processing is used to form the recesses 200, but the present invention is not limited to this, and other forming methods (for example, drilling) may be used.

22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 28: Body portion 29: Branch portion 100: Fuel cell stack 102: Power generation unit 104, 106: End plate 108: Communication hole 110, 110a: Single cell 112, 112a: electrolyte layer 113a, 113: specific surface 113A, 113Aa: power generation region 113B: non-power generation region 114, 114a: air electrode 116: fuel electrode 120: separator 121, 131, 141: hole 124: junction 130: air electrode side Frame 132: Oxidant gas supply passage 133: Oxidant gas discharge passage 134: Air electrode side current collector 135: Current collector element 140: Fuel electrode side frame 142: Fuel gas supply passage 143: Fuel gas discharge passage Hole 144: fuel electrode side current collector 145: electrode facing portion 146: interconnector facing portion 147: connecting portion 149: spacer 150: interconnector 161: oxidant gas introduction manifold 162: oxidant gas discharge manifold 166: air chamber 171 : fuel gas introduction manifold 172: fuel gas discharge manifold 176: fuel chamber 180: intermediate layer 182: projecting portion 200, 200a: recess 210, 210a: power generation side recess 212, 212a, 222: inner wall surface 220: non-power generation side Recess FG: Fuel gas FOG: Fuel off-gas OG: Oxidant gas OOG: Oxidant off-gas

Claims (11)

An electrochemical reaction single cell comprising an electrolyte layer containing a solid oxide, and an air electrode and a fuel electrode facing each other in a first direction with the electrolyte layer interposed therebetween,
In the electrolyte layer, a plurality of bottomed recesses whose interiors are hollow are formed on a specific surface on the side of a specific electrode, which is at least one of the air electrode and the fuel electrode,
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to claim 1,
the plurality of recesses include a first recess formed in a covered region of the specific surface of the electrolyte layer that is covered with the specific electrode;
a cavity exists between the inner wall surface of the electrolyte layer defining the first recess and the specific electrode;
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to claim 2,
The specific electrode has a thin portion that is partially thin in a region overlapping with the covered region when viewed in the first direction, and the thin portion overlaps with the first recess in the first direction. overlapping,
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to claim 1,
having an intermediate layer formed between the electrolyte layer and the specific electrode;
the plurality of recesses include a first recess formed in a covered region of the specific surface of the electrolyte layer that is covered with the intermediate layer;
a cavity exists between the inner wall surface of the first recess and the intermediate layer;
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to claim 2,
The specific electrode has a protruding portion that protrudes into the first recess and is spaced from the inner wall surface,
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to claim 4,
the intermediate layer has a protruding portion that protrudes into the first recess and is spaced from the inner wall surface;
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to any one of claims 2 to 6,
The maximum length of the opening of the first recess is 1000 μm or less.
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to any one of claims 2 to 7,
the maximum depth of the first recess is 2/3 or less of the thickness of the electrolyte layer;
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to any one of claims 1 to 8,
The plurality of recesses includes a plurality of second recesses formed in non-overlapping regions of the specific surface of the electrolyte layer that do not overlap the specific electrode in the first direction. ,
An electrochemical reaction single cell characterized by: In the electrochemical reaction single cell according to any one of claims 1 to 9,
The maximum length of the opening of the recess is 10 μm or more,
An electrochemical reaction single cell characterized by: In an electrochemical reaction cell stack comprising a plurality of electrochemical reaction single cells,
At least one of the plurality of electrochemical reaction single cells is the electrochemical reaction single cell according to any one of claims 1 to 10,
An electrochemical reaction cell stack characterized by:

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