JP7016334B2 - Electrochemical reaction single cell and electrochemical reaction cell stack - Google Patents

Description

The technique disclosed herein relates to an electrochemical reaction single cell.

A solid oxide fuel cell (hereinafter referred to as "SOFC") is known as one of the types of fuel cells that generate power by utilizing an electrochemical reaction between hydrogen and oxygen. A fuel cell single cell (hereinafter, simply referred to as “single cell”), which is a constituent unit of SOFC, has an electrolyte layer containing a solid oxide and a predetermined direction (hereinafter, referred to as “first direction”) with the electrolyte layer interposed therebetween. It is provided with an air electrode and a fuel electrode facing each other. The air electrode includes an active layer and a current collector layer arranged on the opposite side of the active layer from the electrolyte layer (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2018-26217

In the above-mentioned SOFC in which the air electrode includes the active layer and the current collector layer, there is a problem that the active layer and the current collector layer are likely to be separated from each other. It should be noted that such a problem is not limited to the active layer and the current collector layer, but is a problem common to SOFCs in which the air electrode includes the first layer and the second layer. Further, such a problem is common to the electrolytic single cell, which is a constituent unit of a solid oxide type electrolytic cell (hereinafter, also referred to as “SOEC”) that generates hydrogen by utilizing the electrolysis reaction of water. It is an issue. Further, in the present specification, the fuel cell single cell and the electrolytic single cell are collectively referred to as an electrochemical reaction single cell.

This specification discloses a technique capable of solving the above-mentioned problems.

The techniques disclosed herein can be realized, for example, in the following forms.

(1) The electrochemical reaction single cell disclosed in the present specification includes an electrolyte layer containing a solid oxide, and an air electrode and a fuel electrode that face each other in a first direction with the electrolyte layer interposed therebetween. In the chemical reaction single cell, the air electrode includes a first layer and a second layer arranged on the opposite side of the first layer from the electrolyte layer, and the air electrode is the same as the air electrode. Coarse particles having a maximum length larger than the average particle size of the first layer and larger than the average particle size of the second layer in at least one cross section substantially parallel to the first direction. There are coarse particles located so as to straddle the first layer and the second layer.

In this electrochemical reaction single cell, coarse particles are present in at least one cross section substantially parallel to the first direction of the air electrode. The maximum length of the coarse particles is larger than the average particle size of the first layer and larger than the average particle size of the second layer. Further, the coarse particles are located so as to straddle the first layer and the second layer. Therefore, the coarse particles are located in the vicinity of the boundary between the first layer and the second layer in comparison with the non-coarse particles whose maximum length is equal to or smaller than the average particle size of the first layer and the second layer. The contact length with the existing first layer and other particles forming the second layer is relatively long, and as a result, the coarse particles strengthen the bonding force between the first layer and the second layer. ing. Thereby, according to the present electrochemical reaction single cell, it is possible to suppress the separation between the first layer and the second layer of the air electrode.

(2) In the electrochemical reaction single cell, further, in the at least one cross section, at least one of the first layer and the second layer, one coarse particle is a plurality of other particles. It may be in contact with each other. According to the present electrochemical reaction single cell, in both the first layer and the second layer, the coarse particles are used as compared with the configuration in which one or less other particles are in contact with one coarse particle. Since the bonding force between the first layer and the second layer is strong, the separation of the first layer and the second layer of the air electrode can be suppressed more effectively.

(3) In the electrochemical reaction single cell, the maximum length of the coarse particles may be 2 μm or more in the at least one cross section. According to this electrochemical reaction single cell, the contact length with other particles existing in the vicinity is further longer than that of the configuration in which the maximum length of the coarse particles is less than 2 μm, so that the first air electrode is used. The peeling between the layer and the second layer can be suppressed more effectively.

(4) In the electrochemical reaction single cell, the maximum length of the coarse particles may be 4 μm or less in the at least one cross section. According to the present electrochemical reaction single cell, it is possible to suppress the generation of cracks in, for example, the first layer due to the presence of the coarse particles, as compared with the configuration in which the maximum length of the coarse particles is wider than 4 μm. ..

(5) In the electrochemical reaction single cell, the number of the coarse particles per 100 μm of the boundary line between the first layer and the second layer is one or more in the at least one cross section. It may be configured. According to the present electrochemical reaction single cell, the first layer and the second layer are compared with the configuration in which the number of coarse particles per 100 μm at the boundary line between the first layer and the second layer is less than one. Since many coarse particles are scattered near the boundary with the layer, the bonding force between the first layer and the second layer by the coarse particles is strong, so that the first layer and the second layer of the air electrode are formed. The peeling with and can be suppressed more effectively.

(6) In the electrochemical reaction cell stack, a plurality of electrochemical reaction single cells arranged side by side in the first direction are provided, and at least one of the plurality of electrochemical reaction single cells is the above-mentioned electrochemical reaction. It may be configured as a single cell.

The technique disclosed in the present specification can be realized in various forms, for example, an electrochemical reaction single cell (fuel cell single cell or electrolytic single cell), and a plurality of electrochemical reaction single cells. It can be realized in the form of an electrochemical reaction cell stack (fuel cell stack or electrolytic cell stack) provided, a method for manufacturing the same, and the like.

It is a perspective view which shows the appearance structure of the fuel cell stack 100 in embodiment. It is explanatory drawing which shows the XZ cross-sectional structure of the fuel cell stack 100 at the position of II-II of FIG. It is explanatory drawing which shows the YZ cross-sectional structure of the fuel cell stack 100 at the position of III-III of FIG. It is explanatory drawing which shows the XZ cross section composition of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross section configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which shows the detailed structure of a single cell 110. It is explanatory drawing which shows the detailed structure of the single cell 110 of this embodiment and the single cell 110A of a comparative example. It is a flowchart which shows an example of the manufacturing method of a fuel cell stack 100. It is explanatory drawing which shows the performance evaluation result.

A. Embodiment:
A-1. Constitution:
(Structure of fuel cell stack 100)
FIG. 1 is a perspective view showing an external configuration of the fuel cell stack 100 in the embodiment, and FIG. 2 is an explanatory view showing an XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II in FIG. 3 is an explanatory diagram showing a YZ cross-sectional structure of the fuel cell stack 100 at the position III-III in FIG. 1. Each figure shows XYZ axes that are orthogonal to each other to identify the direction. In the present specification, for convenience, the Z-axis positive direction is referred to as an upward direction, and the Z-axis negative direction is referred to as a downward direction, but the fuel cell stack 100 is actually in a direction different from such an orientation. It may be installed. The same applies to FIGS. 4 and later.

The fuel cell stack 100 includes a plurality of (seven in this embodiment) fuel cell power generation unit (hereinafter, simply referred to as “power generation unit”) 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). The 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. The arrangement direction (vertical direction) corresponds to the first direction in the claims.

A plurality of holes (eight in this embodiment) penetrating in the vertical direction are formed on the peripheral edge of each layer (power generation unit 102, end plates 104, 106) constituting the fuel cell stack 100 around the Z direction. , The holes formed in each layer and corresponding to each other communicate with each other in the vertical direction to form a communication hole 108 extending in the vertical direction 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 communication holes 108.

A bolt 22 extending in the vertical direction is inserted into each communication hole 108, and the fuel cell stack 100 is fastened by the bolt 22 and the nuts 24 fitted on both sides of the bolt 22. As shown in FIGS. 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 the bolt. An insulating sheet 26 is interposed between the nut 24 fitted on the other side (lower side) of the 22 and the lower surface of the end plate 106 constituting the lower end of the fuel cell stack 100. However, in the place where the gas passage member 27 described later is provided, the insulating sheets arranged on the upper side and the lower side of the gas passage member 27 and the gas passage member 27 between the nut 24 and the surface of the end plate 106, respectively. 26 is intervening. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic dust sheet, a glass sheet, a glass-ceramic composite agent, 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, the position is located near the midpoint of one side (the side on the positive side of the X axis among the two sides parallel to the Y axis) on the outer circumference of the fuel cell stack 100 around the Z direction. In the space formed by the bolt 22 (bolt 22A) and the communication hole 108 through which the bolt 22A is inserted, the oxidant gas OG is introduced from the outside of the fuel cell stack 100, and the oxidant gas OG is generated for each power generation. It functions as an oxidizer gas introduction manifold 161 that is a gas flow path supplied to the unit 102, and is the midpoint of the side opposite to the side (the side on the negative side of the X-axis of the two sides parallel to the Y-axis). The space formed by the bolt 22 (bolt 22B) located in the vicinity and the communication hole 108 through which the bolt 22B is inserted provides the oxidant off-gas OOG, which is the gas discharged from the air chamber 166 of each power generation unit 102. It functions as an oxidizer gas discharge manifold 162 that discharges to the outside of the fuel cell stack 100. In this embodiment, for example, air is used as the oxidant gas OG.

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

The fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body portion 28 and a hollow cylindrical branch portion 29 branched from the side surface of the main body portion 28. The hole of the branch portion 29 communicates with the hole of 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 main body 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. The hole of the main body 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 main body 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 fuel gas. The hole of the main body 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.

(Structure of end plates 104 and 106)
The pair of end plates 104 and 106 are substantially rectangular flat plate-shaped conductive members, and are made of, for example, stainless steel. One end plate 104 is located above the power generation unit 102 located at the top, and the other end plate 106 is located below the power generation unit 102 located at the bottom. A plurality of power generation units 102 are sandwiched by a pair of end plates 104 and 106 in a pressed state. The upper end plate 104 functions as a positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as a negative output terminal of the fuel cell stack 100.

(Structure of power generation unit 102)
FIG. 4 is an explanatory diagram showing an 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. 5 is an explanatory view showing the XZ cross-sectional configuration of the two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross-sectional structure 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 pole side frame 130, an air pole side current collector 134, a fuel pole side frame 140, and a fuel pole side. The current collector 144 and a pair of interconnectors 150 constituting the uppermost layer and the lowermost layer of the power generation unit 102 are provided. A hole corresponding to the communication hole 108 through which the bolt 22 described above is inserted is formed in the peripheral portion of the separator 120, the air pole side frame 130, the fuel pole side frame 140, and the interconnector 150 in the Z direction.

The interconnector 150 is a substantially rectangular flat plate-shaped conductive member, and is made of, for example, ferritic stainless steel. The interconnector 150 ensures electrical conduction between the power generation units 102 and prevents mixing of the reaction gas between the power generation units 102. In this embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. That is, the upper interconnector 150 in one 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. Further, since the fuel cell stack 100 includes a pair of end plates 104 and 106, the power generation unit 102 located at the top of the fuel cell stack 100 does not have the upper interconnector 150 and is located at the bottom. The power generation unit 102 does not include the lower interconnector 150 (see FIGS. 2 and 3).

The single cell 110 is arranged on the electrolyte layer 112, the fuel electrode (anode) 116 arranged on one side (lower side) in the vertical direction of the electrolyte layer 112, and the other side (upper side) in the vertical direction of the electrolyte layer 112. It is provided with an air electrode (cathode) 114 and an intermediate layer 180 arranged between the electrolyte layer 112 and the air electrode 114. The single cell 110 of the present embodiment is a fuel pole support type single cell that supports other layers (electrolyte layer 112, air pole 114, intermediate layer 180) constituting the single cell 110 with the fuel pole 116.

The electrolyte layer 112 is a substantially rectangular flat plate-shaped member, and is formed so as to contain YSZ (yttria-stabilized zirconia) which is a solid oxide. That is, the electrolyte layer 112 contains Zr (zirconium) and Y (yttrium). The air electrode 114 is a substantially rectangular flat plate-shaped member, and is formed of a composition containing Sr (strontium). The configuration of the air electrode 114 will be described in detail later. The fuel electrode 116 is a substantially rectangular flat plate-shaped member, and is formed of, for example, Ni (nickel), a cermet composed of Ni and ceramic particles, a Ni-based alloy, or the like. As described above, the single cell 110 of the present embodiment is a solid oxide fuel cell (SOFC) using a solid oxide as an electrolyte.

The intermediate layer 180 is a substantially rectangular flat plate-shaped member, and is formed so as to include GDC (gadolinium-doped ceria). The intermediate layer 180 suppresses the reaction of Sr diffused from the air electrode 114 with Zr contained in the electrolyte layer 112 to generate highly resistant SZO (SrZrO ₃ ).

The separator 120 is a frame-shaped member in which a substantially rectangular hole 121 penetrating in the vertical direction is formed near the center, and is formed of, for example, metal. The peripheral portion of the hole 121 in the separator 120 faces the peripheral edge of the surface of the electrolyte layer 112 on the side of the air electrode 114. The separator 120 is bonded to the electrolyte layer 112 (single cell 110) by a bonding portion 124 formed of a brazing material (for example, Ag wax) arranged at the facing portions thereof. The separator 120 partitions the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116, and a gas leak from one electrode side to the other electrode side at the peripheral edge of the single cell 110. It is suppressed.

The air pole side frame 130 is a frame-shaped member in which a substantially rectangular hole 131 penetrating in the vertical direction is formed near the center, and is formed of, for example, an insulator such as mica. The hole 131 of the air pole side frame 130 constitutes an air chamber 166 facing the air pole 114. The air electrode side frame 130 is in contact with the peripheral edge of the surface of the separator 120 opposite to the side facing the electrolyte layer 112 and the peripheral edge of the surface of the interconnector 150 facing the air electrode 114. .. Further, the air electrode side frame 130 electrically insulates between the pair of interconnectors 150 included in the power generation unit 102. Further, in the air electrode side frame 130, the oxidant gas supply communication hole 132 that communicates the oxidant gas introduction manifold 161 and the air chamber 166, and the oxidant gas that communicates the air chamber 166 and the oxidant gas discharge manifold 162. A discharge communication hole 133 is formed.

The fuel pole side frame 140 is a frame-shaped member in which a substantially rectangular hole 141 penetrating in the vertical direction is formed near the center, and is formed of, for example, metal. The hole 141 of the fuel electrode side frame 140 constitutes a fuel chamber 176 facing the fuel electrode 116. The fuel electrode side frame 140 is in contact with the peripheral edge of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral edge of the surface of the interconnector 150 facing the fuel electrode 116. Further, in the fuel electrode side frame 140, 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 connecting the electrode facing portion 145 and the interconnector facing portion 146, for example, nickel or nickel alloy. , Stainless steel, etc. 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 on the surface of the interconnector 150 on the side facing the fuel pole 116. Are in contact. However, as described above, since the power generation unit 102 located at the bottom of the fuel cell stack 100 does not have the lower interconnector 150, the interconnector facing portion 146 in the power generation unit 102 is the lower end plate. It is in contact with 106. Since the current collector 144 on the fuel electrode side has such a configuration, the fuel electrode 116 and the interconnector 150 (or the end plate 106) are electrically connected to each other. A spacer 149 formed of, for example, a mica 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 the temperature cycle and the reaction gas pressure fluctuation, and the fuel electrode 116 and the interconnector 150 (or the end plate 106) via the fuel electrode side current collector 144 follow. Good electrical connection with is maintained.

The air pole 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 square columnar current collector elements 135, and is formed of, for example, ferritic stainless steel. The air pole side current collector 134 is in contact with the surface of the air pole 114 on the side opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 on the side facing the air pole 114. However, as described above, since the power generation unit 102 located at the top of the fuel cell stack 100 does not have the upper interconnector 150, the air electrode side current collector 134 in the power generation unit 102 has an upper end plate. It is in contact with 104. Since the current collector 134 on the air electrode side has such a configuration, the air electrode 114 and the interconnector 150 (or the end plate 104) are electrically connected to each other. The air electrode side current collector 134 and the interconnector 150 may be formed as an integral member. Further, the air electrode side current collector 134 may be covered with a conductive coat, and a conductive bonding layer for bonding the air electrode 114 and the air electrode side current collector 134 may be provided between the air electrode 114 and the air electrode side current collector 134. It may be intervening.

A-2. Operation of fuel cell stack 100:
As shown in FIGS. 2 and 4, the oxidant gas OG is supplied via 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 oxidant gas OG is supplied to the oxidant gas introduction manifold 161 through the holes of the branch portion 29 and the main body portion 28 of the gas passage member 27, and the oxidant gas introduction manifold 161 oxidizes each power generation unit 102. It is supplied to the air chamber 166 via the agent gas supply communication hole 132. Further, as shown in FIGS. 3 and 5, the fuel gas FG is supplied via 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 through the holes of the branch portion 29 and the main body portion 28 of the gas passage member 27, and the fuel gas supply communication of each power generation unit 102 is performed from the fuel gas introduction manifold 171. It is supplied to the fuel chamber 176 through the 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, power is generated by the electrochemical reaction of the oxidant gas OG and the fuel gas FG in the single cell 110. Will be. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air pole 114 of the single cell 110 is electrically connected to one of the interconnectors 150 via the air pole side current collector 134, and the fuel pole 116 is via the fuel pole side current collector 144. It is electrically connected to the other interconnector 150. Further, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, the electric energy generated in each power generation unit 102 is taken out from the end plates 104 and 106 that function as the output terminals of the fuel cell stack 100. Since the SOFC generates electricity at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the fuel cell stack 100 is a heater (for example, until the high temperature can be maintained by the heat generated by the power generation after the start-up. It may be heated by (not shown).

As shown in FIGS. 2 and 4, the oxidant off-gas 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 passed through the holes of the main body 28 and the branch 29 of the gas passage member 27 provided at the position of the agent gas discharge manifold 162, and the gas pipe (not shown) connected to the branch 29. It is discharged to the outside of. Further, as shown in FIGS. 3 and 5, the fuel off-gas 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, and further, the fuel gas. To the outside of 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 discharge manifold 172. It is discharged.

A-3. Detailed configuration of air pole 114:
FIG. 6 is an explanatory diagram showing a detailed configuration of the single cell 110. FIG. 6 shows the XZ cross-sectional configuration of the single cell 110 in the region X1 of FIG.

In the present embodiment, the air electrode 114 is composed of a current collector layer 210 and an active layer 220 arranged between the current collector layer 210 and the electrolyte layer 112 (and the intermediate layer 180). The active layer 220 of the air electrode 114 is a layer that mainly functions as a field for the ionization reaction of oxygen contained in the oxidant gas OG, and mainly conducts electrons LSCF (lanternstrontium cobalt iron oxide) and mainly oxygen. It is formed to contain GDC (gadrinium-doped ceria) that conducts ions. When the active layer 220 contains GDC, the bondability between the active layer 220 and the intermediate layer 180 containing the GDC can be enhanced, and the reactivity in the active layer 220 can be improved. Further, the current collector layer 210 of the air electrode 114 is a layer that mainly diffuses the oxidant gas OG supplied from the air chamber 166 and functions as a place for collecting electricity obtained by the power generation reaction, and is LSCF. Is formed to include.

In the present embodiment, the average particle size of the material (LSCF) constituting the current collector layer 210 and the average particle size of the material (LSCF, GDC) constituting the active layer 220 are different. Specifically, the average particle size of the material constituting the current collector layer 210 is larger than the average particle size of the material constituting the active layer 220. Further, in order to enhance the diffusivity of the oxidant gas OG in the current collector layer 210, the porosity in the current collector layer 210 is higher than the porosity in the active layer 220. As described above, the larger the difference in average particle size and porosity between the current collector layer 210 and the active layer 220, the larger the difference in thermal expansion between the two layers, and the smaller the contact area between the two, so that the current collector layer 210 and the active layer 220 are active. Peeling from the layer 220 is particularly likely to occur. The current collector layer 210 has, for example, a thickness of 30 μm or more and 200 μm or less in the vertical direction, a porosity of 20% or more and 35% or less, and an average particle size of less than 1 μm. The active layer 220 has, for example, a vertical thickness of 5 μm or more and 30 μm or less, a porosity of 5% or more and 25% or less, and an average particle size of less than 0.6 μm. Further, the active layer 220 corresponds to the first layer in the claims, and the current collector layer 210 corresponds to the second layer in the claims.

FIG. 7 is an explanatory diagram showing a detailed configuration of the single cell 110 of the present embodiment and the single cell 110A of the comparative example. FIG. 7A shows an XZ cross-sectional configuration near the boundary between the current collector layer 210 and the active layer 220 in the single cell 110 of the present embodiment, and FIG. 7B shows a simple comparative example. The XZ cross-sectional structure near the boundary between the current collector layer 210 and the active layer 220 in the cell 110A is shown. In FIG. 7, the particles of reference numeral 212 mean the particles of LSCF constituting the current collecting layer 210, the particles of reference numeral 222 mean the particles of LSCF constituting the active layer 220, and the particles of reference numeral 224 are active. It means the particles of GDC constituting the layer 220, and the particles of reference numeral 214 mean the coarse particles described below. In the present embodiment, the average particle size of the LSCF particles constituting the current collector layer 210 is larger than the average particle size of the LSCF particles constituting the active layer 220.

In this embodiment, the air electrode 114 satisfies the following first requirement.
First requirement: At least one coarse particle 214 is present in at least one cross section (eg, the XZ cross section of FIG. 6) substantially parallel to the direction (vertical direction) in which the air pole 114 and the fuel pole 116 face each other across the electrolyte layer 112. There is one. As shown in FIG. 7A, the maximum length of the coarse particles 214 (the maximum length in the direction perpendicular to the vertical direction (X-axis direction) of the coarse particles 214 in the above cross section) is the average particle size of the active layer 220. It is larger and larger than the average particle size of the current collector layer 210. Further, the coarse particles 214 are located so as to straddle the current collecting layer 210 and the active layer 220 constituting the air electrode 114. Here, the coarse particles 214 are located so as to straddle the current collector layer 210 and the active layer 220, as shown in FIG. 7A, at least one cross section substantially parallel to the vertical direction. In, a part of one coarse particle 214 is located on the current collector layer 210 side with respect to the boundary line C between the current collector layer 210 and the active layer 220, and the other part of the one coarse particle 214 is the boundary line. It means that it is located on the active layer 220 side with respect to C.

The maximum length of the coarse particles 214 is 1.5 times or more the average particle size of the active layer 220, and may be 2 times or more, or 4 times or more. However, the maximum thickness of the coarse particles 214 is preferably shorter than the vertical thickness of the current collector layer 210 and shorter than the vertical thickness of the active layer 220. Further, in one coarse particle 214, a portion having an area of 10% or more (more preferably 20% or more) of the total area of the coarse particle 214 is located in each region of the current collector layer 210 and the active layer 220. It is located (see FIG. 7 (A)). Further, the coarse particles 214 are in contact with at least one other particle (LSCF particle) constituting the current collector layer 210, and the coarse particle 214 is in contact with at least one other particle (LSCF particle, GDC particle) constituting the active layer 220. Particles) are in contact.

Further, the air electrode 114 satisfies the following second requirement.
Second requirement: In at least one cross section of the current collector layer 210 and the active layer 220, at least one coarse particle 214 is in contact with a plurality of other particles. For example, in FIG. 6, one coarse particle 214 located on the right side is in contact with the particles 212 of the three LSCFs constituting the current collector layer 210 on the current collector layer 210 side, and is on the active layer 220 side. , Two LSCF particles 222 and one GDC particle 224 constituting the active layer 220 are in contact with each other. In this embodiment, as shown in FIG. 7A, the current collector layer 210 is parallel to the vertical direction (Z-axis direction) and substantially orthogonal to the vertical direction (along the boundary line C). At least one other particle is in contact with each of one side and the other side of one coarse particle 214 with respect to the virtual straight line LC passing through the center of the coarse particle 214 in the direction). Similarly, on the active layer 220 side, at least one other particle is in contact with each of one side and the other side of one coarse particle 214.

Further, the air electrode 114 satisfies the following third requirement.
Third requirement: In at least one cross section, the maximum length of the coarse particles 214 is 2 μm or more.

Further, the air electrode 114 satisfies the following fourth requirement.
Fourth requirement: In at least one cross section, the maximum length of the coarse particles 214 is 4 μm or less.

Further, the air electrode 114 satisfies the following fifth requirement.
Fifth requirement: In at least one cross section, the number of coarse particles 214 per 100 μm of the boundary line C between the current collector layer 210 and the active layer 220 (hereinafter, “214 per unit length on the boundary line C”). The frequency of appearance of 214 is one or more. The frequency of appearance of 214 per unit length on one boundary line C is preferably two or more, more preferably three or more, and more preferably three or more. The frequency of appearance of the coarse particles 214 around the unit length is such that a plurality of images (analyzed images below) at different positions in the vertical direction are obtained in the cross section of the air electrode 114, and the plurality of images are used. The number of coarse particles 214 per 100 μm is determined.

A-4. Analytical method of air electrode 114:
(Acquisition method of analytical image)
A method of analyzing the air electrode 114 with respect to the particle size and the like will be described. First, an analytical image used for the analysis of the air electrode 114 is acquired by the following method. In the single cell 110, one cross section parallel to the vertical direction (Z-axis direction) (however, a cross section including the air pole 114) is arbitrarily set, and an image in which the entire vertical direction of the air pole 114 can be confirmed in the cross section is displayed. Acquire as an analysis image. More specifically, the upper surface of the air electrode 114 (the surface in contact with the air electrode side current collector 134) is the top of the 10 divided regions obtained by dividing the image into 10 equal parts in the vertical direction. An image located in the divided region and where the boundary between the air electrode 114 and the electrolyte layer 112 is located in the lowest divided region is taken by, for example, a scanning electron microscope (SEM) and used as an analytical image. get. The analyzed image may be a binarized image after the binarized image taken by the SEM. However, if the particles in the binarized image are significantly different from the actual form, the contrast of the image before the binarization process taken by SEM is adjusted, and the image after the adjustment is binarized. It may be. Further, the analysis image may be the image itself before the binarization process taken by SEM. The magnification of the SEM image is set to a value such that the entire vertical direction of the air electrode 114 fits in the analysis image as described above, for example, 200 to 30,000 times (more specifically, 5,000 times). However, the present invention is not limited to this, and can be changed as appropriate.

(Method of determining the boundary line C between the current collector layer 210 and the active layer 220)
The boundary line C between the active layer 220 and the current collector layer 210 is specified by the following method by utilizing the feature that the porosity of the current collector layer 210 is higher than the porosity of the active layer 220. First, a plurality of virtual lines K orthogonal to the vertical direction (Z-axis direction) are drawn in order from the upper surface of the air electrode 114 at intervals of 0.3 μm with respect to the analysis image, and the virtual lines K1, K2, and K3 are drawn in order. , ..., Km, ..., K (m + 9), K (m + 10), ..., Kn are obtained. Then, the length of the portion overlapping the pores in each virtual line K is measured, the total length of the portion overlapping the pores is calculated, and the total length of the portion overlapping the pores with respect to the total length of each virtual line K is calculated. The ratio of is taken as the ratio of pores existing on the virtual line K (porosity Ks). Next, among the porosities Ks1, Ks2, Ks3, ..., Ksm, ..., Ks (m + 9), Ks (m + 10), ..., Ksn of each virtual line K, 10 in order from the upper side. Each data group having the porosity Ks of the virtual lines K is set, and the mean value (Ave) of the 10 porosities Ks of each data group and the standard deviation (σ) of the porosity Ks of each data group are calculated. do.

In order from the upper side, the data group G1 is composed of Ks1, Ks2, ..., Ks10, the data group G2 is composed of Ks2, Ks3, ..., Ks11, and the data group Gm is Ksm, Ks (m + 1). ), Ks (m + 2), ..., Ks (m + 9), and the data group G (m + 1) is composed of Ks (m + 1), Ks (m + 2), ..., Ks (m + 10). That is, the data group G (m + 1) means nine porosities (Ks (m + 1), ..., Ks) obtained by excluding the porosity Ksm of the first virtual line Km of the data group Gm from the data group Gm. (M + 9)) plus the porosity Ks (m + 10) of the virtual line K (m + 10) next to the last virtual line K (m + 9) of the data group means one group consisting of 10 porosities Ks. .. Then, "the average value of the pore ratio Ks of G (m + 1)" is "the average value of the pore ratio Ks of Gm plus the value twice the standard deviation (σ) of the ten pore ratio Ks of Gm". , Or the "mean value of the pore ratio Ks of G (m + 1)" is 2 of the standard deviation (σ) of 10 pore ratios Ks of Gm from the average value of the pore ratio Ks of Gm. The virtual line K (m + 10) corresponding to the tenth pore ratio Ks (m + 10) of the data group G (m + 1) when it falls below the "value obtained by subtracting the double value" for the first time is the active layer 220 and the current collector layer. The boundary with 210 (boundary line C). That is, when the average value of the porosity Ks of the data group Gm is GmAve, the average value of the porosity Ks of the data group G (m + 1) is G (m + 1) Ave, and the standard deviation of the porosity Ks of the data group Gm is σm. , The virtual line K (m + 10) corresponding to the tenth porosity Ks (m + 10) of the first data group G (m + 1) satisfying the following equation (1) is provided at the boundary between the active layer 220 and the current collector layer 210. do. Once this boundary is determined, the active layer 220 and the current collector layer 210 can be distinguished on the analytical image.
| (G (m + 1) Ave)-(GmAve) |> 2σm ... (1)

(Measurement method of particle size and pore size)
The particle size (average particle size) of the active layer 220 and current collector layer 210 of the air electrode 114 is "Ceramic Processing" by Satoshi Mizutani, Yoshiharu Ozaki, Toshio Kimura, Takashi Yamaguchi, Gihodo Publishing Co., Ltd., March 1985. It is specified according to the method (intercept method) described in "Issued on 25th, pp. 192 to 195". Specifically, as shown in FIG. 6, in the above-mentioned analytical image, the current collector layer 210 is moved up and down. Three straight lines M1 in the direction orthogonal to the vertical direction are drawn on the current collector layer 210 so as to be divided into four equal parts in the direction (Z-axis direction), and particles on each straight line M1 (however, present near the boundary line C). The length of the portion corresponding to the coarse particles 214) is measured as the particle size. Further, the active layer 220 is orthogonal to the active layer 220 in the vertical direction so as to divide the active layer 220 into four equal parts in the vertical direction (Z-axis direction). Three straight lines M2 in the direction to be drawn are drawn, and the length of the portion corresponding to the particles on each straight line M2 (excluding the coarse particles 214 existing near the boundary line C) is measured as the particle size. , All particles on one or more straight lines (M1, M2) located in the active layer 220) (excluding coarse particles 214 existing near the boundary line C) are measured and measured values. The average value of the particle size (average particle size) shall be calculated using.

A-5. Manufacturing method of fuel cell stack 100:
The method for manufacturing the fuel cell stack 100 having the above-described configuration is, for example, as follows. FIG. 9 is a flowchart showing an example of a method for manufacturing the fuel cell stack 100.

(Formation of a laminate of the electrolyte layer 112 and the fuel electrode 116)
First, a laminate of the electrolyte layer 112 and the fuel electrode 116 is formed (S110). Specifically, to YSZ powder, butyral resin, dioctyl phthalate (DOP) which is a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added and mixed by a ball mill to prepare a slurry. Prepare. The obtained slurry is thinned by the doctor blade method to obtain a green sheet for an electrolyte layer. Further, with respect to the mixed powder of NiO powder and YSZ powder, organic beads which are pore-forming materials, butyral resin, DOP which is a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are used. In addition, mix in a ball mill to prepare a slurry. The obtained slurry is thinned by the doctor blade method to obtain a green sheet for a fuel electrode. The green sheet for the electrolyte layer and the green sheet for the fuel electrode are attached and dried, and fired at, for example, 1400 ° C. to obtain a laminate of the electrolyte layer 112 and the fuel electrode 116.

(Formation of intermediate layer 180)
Next, the intermediate layer 180 is formed (S120). Specifically, polyvinyl alcohol as an organic binder and butyl carbitol as an organic solvent are added to GDC powder and mixed to adjust the viscosity to prepare a paste for an intermediate layer. The obtained paste for an intermediate layer is applied to the surface of the above-mentioned laminate of the electrolyte layer 112 and the fuel electrode 116 on the side of the electrolyte layer 112 by, for example, screen printing, and fired at, for example, 1180 ° C. As a result, the intermediate layer 180 is formed, and a laminate of the fuel electrode 116, the electrolyte layer 112, and the intermediate layer 180 (hereinafter referred to as “intermediate laminate L”) is produced (see FIG. 6).

(Formation of air electrode 114)
Next, the air pole 114 is formed. First, for an active layer, which is a material for forming an active layer 220 by mixing LSCF powder, GDC powder, polyvinyl alcohol as an organic binder, and butyl carbitol as an organic solvent to adjust the viscosity. Prepare the paste (S130).

Next, the prepared paste for the active layer is applied to, for example, a screen on the surface of the intermediate laminate L on the intermediate layer 180 side (that is, the surface of the intermediate laminate L on the electrolyte layer 112 side with respect to the fuel electrode 116). It is applied by printing and dried (S140).

Next, LSCF powder, polyvinyl alcohol as an organic binder, and butyl carbitol as an organic solvent are mixed to adjust the viscosity to form a collection of coarse particles 214 and a current collector layer 210. A paste for an electric layer is prepared (S150). The coarse particles 214 are, for example, LSCF particles.

Next, the paste for the current collector layer containing the prepared coarse particles 214 is applied to the surface of the intermediate laminate L on the active layer 220 side by, for example, screen printing. At this time, since the paste for the current collector layer contains an organic component and has flexibility, the coarse particles 214 contained in the paste for the current collector layer are the paste for the current collector layer and the paste for the active layer due to their own weight. It is easy to move to the boundary side with. Next, the intermediate laminate L coated with the current collector paste is dried, and the intermediate laminate L is fired at a predetermined firing temperature (for example, 1100 ° C.) (S160). Hereinafter, by this firing step, a current collector layer 210 is formed, and a laminate of a fuel electrode 116, an electrolyte layer 112, an intermediate layer 180, an active layer 220, and a current collector layer 210, that is, a single cell 110 is manufactured.

A plurality of single cells 110 are manufactured by the above-mentioned method, and the plurality of single cells 110 are connected to each other via a current collector member such as an air pole side current collector 134, a fuel pole side current collector 144, and an interconnector 150. The fuel cell stack 100 described above is manufactured by arranging them side by side in the axial direction and fastening them with bolts 22 (S170).

A-6. Effect of this embodiment:
In the single cell 110A of the comparative example shown in FIG. 7B, the coarse particles 214 do not exist near the boundary between the current collector layer 210 and the active layer 220. Therefore, the contact area between the particles constituting the current collector layer 210 and the particles constituting the active layer 220 is small and the bondability is low, and as a result, the current collector layer 210 and the active layer 220 are likely to be separated from each other. On the other hand, as described above, in the fuel cell stack 100 in the present embodiment, the coarse particles 214 are present in at least one cross section substantially parallel to the vertical direction (Z-axis direction) of the air electrode 114. (See FIG. 7 (A) of the first requirement above). The maximum length of the coarse particles 214 is larger than the average particle size of the active layer 220 and larger than the average particle size of the current collector layer 210. Further, the coarse particles 214 are located so as to straddle the current collector layer 210 and the active layer 220. Therefore, the coarse particles 214 are present in the vicinity of the boundary between the current collector layer 210 and the active layer 220, as compared with the non-coarse particles whose maximum length is equal to or smaller than the average particle size of the current collector layer 210 and the active layer 220. The contact length with the current collector layer 210 and other particles forming the active layer 220 is relatively long, and as a result, the binding force between the current collector layer 210 and the active layer 220 is strengthened by the coarse particles 214. .. Thereby, according to the present embodiment, it is possible to suppress the separation of the current collector layer 210 and the active layer 220 at the air electrode 114.

Further, in the present embodiment, in at least one cross section of the current collector layer 210 and the active layer 220 constituting the air electrode 114, at least one coarse particle 214 is in contact with a plurality of other particles. (The second requirement above). Therefore, according to the present embodiment, in both the current collector layer 210 and the active layer 220, the coarse particles 214 are compared with the configuration in which one or less other particles are in contact with one coarse particle 214. Since the binding force between the current collector layer 210 and the active layer 220 is strong, the separation of the current collector layer 210 and the active layer 220 at the air electrode 114 can be more effectively suppressed.

Further, in the present embodiment, the maximum length of the coarse particles 214 is 2 μm or more in at least one cross section (the third requirement). Therefore, according to the present embodiment, the contact length with other particles existing in the vicinity is further longer than that of the configuration in which the maximum length of the coarse particles 214 is less than 2 μm, so that the collection at the air electrode 114 is performed. The peeling between the electric layer 210 and the active layer 220 can be suppressed more effectively.

Further, in the present embodiment, in the at least one cross section, the maximum length of the coarse particles 214 is 4 μm or less (the fourth requirement above). Therefore, according to the present embodiment, cracks occur in, for example, the current collector layer 210 and the active layer 220 due to the presence of the coarse particles 214, as compared with the configuration in which the maximum length of the coarse particles 214 is wider than 4 μm. Can be suppressed.

Further, in the present embodiment, in at least one cross section, the number of coarse particles 214 per 100 μm of the boundary line C between the current collector layer 210 and the active layer 220 is one or more (the fifth requirement above). ). Therefore, according to the present embodiment, the number of coarse particles 214 per 100 μm of the fuel cell stack at the boundary line C between the current collector layer 210 and the active layer 220 is less than one, as compared with the current collector layer. Since many coarse particles 214 are scattered near the boundary between the 210 and the active layer 220, the binding force between the current collector layer 210 and the active layer 220 by the coarse particles 214 is strong, so that the current collector layer 210 at the air electrode Separation from the active layer 220 can be suppressed more effectively.

A-7. Performance evaluation:
Samples of a plurality of single cells 110 were prepared, and various performance evaluations were performed using the prepared samples of the plurality of single cells 110. FIG. 9 is an explanatory diagram showing the performance evaluation result. Hereinafter, this performance evaluation will be described.

A-7-1. For each sample:
As shown in FIG. 9, the evaluation of the presence or absence of separation between the active layer 220 and the current collector layer 210 at the air electrode 114 was performed for samples 1 to 10. In each sample, in a cross section substantially parallel to the vertical direction of the single cell 110, the average particle size (μm) of the active layer 220, the average particle size (μm) of the current collector layer 210, and the coarse particles 214 located on the boundary line C. The magnitude relationship with the maximum length (μm) of is different from each other. In this evaluation, the maximum length of the coarse particles 214 is the maximum length in the direction perpendicular to the direction (vertical direction) in which the active layer 220 and the current collecting layer 210 face each other in the above cross section.

Specifically, in each of the samples 1 to 10, coarse particles 214 are present. However, in sample 1, the maximum length of the coarse particles 214 is less than 2.0 μm, and in sample 2, the maximum length of the coarse particles 214 is longer than 4.0 μm. Further, in the samples 3 and 4, the maximum length of the coarse particles 214 is 2.0 μm or more and 4.0 μm or less, and the average particle size of the current collector layer 210 is 2.0 μm or more. In the samples 5 to 10, the maximum length of the coarse particles 214 is 2.0 μm or more and 4.0 μm or less, and the average particle size of the current collector layer 210 is less than 1.0 μm. Further, in the samples 5 to 10, the appearance frequencies of the coarse particles 214 around the unit length on the boundary line C are different from each other.

A-7-2. Evaluation items and evaluation methods:
As described above, in this performance evaluation, the presence or absence of separation between the active layer 220 and the current collector layer 210 at the air electrode 114 was evaluated.

(Evaluation method for the presence or absence of peeling)
A commercially available cellophane adhesive tape is attached to the surface of the current collector layer 210 of the air electrode 114 in the single cell 110 of each prepared sample, and the presence or absence of peeling between the current collector layer 210 and the active layer 220 when the cellophane adhesive tape is peeled off is confirmed. did. If some peeling occurs to the extent that it does not affect the quality of the single cell 110, it is judged as acceptable (Δ), and if the current collecting layer 210 and the active layer 220 do not peel off, it is judged as good (◯). Further, it was judged to be the best (⊚) when the peeling in the current collector layer 210 did not occur.

A-7-3. Evaluation results:
As shown in FIG. 9, in sample 1, it was determined to pass (Δ). In sample 1, the maximum length of the coarse particles 214 is less than 2.0 μm, which does not satisfy the above-mentioned third requirement, and therefore the number of other particles in contact with one coarse particle 214 is small, so that current collection is possible. It is considered that the separation between the layer 210 and the active layer 220 is relatively easy to occur.

In sample 2, it was determined to pass (Δ). In sample 2, the maximum length of the coarse particles 214 is longer than 4.0 μm and does not satisfy the above-mentioned fourth requirement, so that the maximum length of the coarse particles 214 is relative to the vertical thickness of the active layer 220. It is considered that cracks are likely to occur in the active layer 220 due to the increase in size, and as a result, peeling between the current collector layer 210 and the active layer 220 is relatively likely to occur.

In Samples 3 and 4, it was judged to be acceptable (Δ). In Samples 3 and 4, since the maximum length of the coarse particles 214 is 2.0 μm or more and 4.0 μm or less, the bondability between the coarse particles 214 and the particles constituting the active layer 220 is ensured. Since the average particle size of the current collector layer 210 is 2.0 μm or more, there are few contact points between the coarse particles 214 and other particles constituting the current collector layer 210, so that peeling is likely to occur in the current collector layer 210. Conceivable.

Samples 5 to 10 were judged to be the best (⊚). In the samples 5 to 10, the maximum length of the coarse particles 214 is 2.0 μm or more and 4.0 μm or less, and the average particle size of the current collector layer 210 is less than 1.0 μm. Therefore, it is considered that not only the peeling between the current collector layer 210 and the active layer 220 but also the peeling in the current collector layer 210 did not occur. Further, in Samples 5 to 10, it was found that the higher the frequency of appearance of the coarse particles 214 around the unit length on the boundary line C, the higher the bond between the current collector layer 210 and the active layer 220, and the more difficult it is to peel off. rice field.

B. Modification example:
The technique disclosed in the present specification is not limited to the above-described embodiment, and can be transformed into various forms without departing from the gist thereof, and for example, the following modifications are also possible.

The configuration of the single cell 110 or the fuel cell stack 100 in the above embodiment is merely an example and can be variously modified. For example, in the above embodiment, the air electrode 114 has a two-layer structure consisting of an active layer 220 and a current collector layer 210, but the air electrode 114 includes a layer other than the active layer 220 and the current collector layer 210. May be. Further, the first layer and the second layer may be layers other than the current collector layer 210 and the active layer 220, and in short, they may be two layers adjacent to each other in the vertical direction at the air electrode 114. Further, in the above embodiment, the single cell 110 includes the intermediate layer 180, but the single cell 110 does not necessarily have to include the intermediate layer 180.

Further, in the above embodiment, the number of single cells 110 included in the fuel cell stack 100 is only an example, and the number of single cells 110 is appropriately determined according to the output voltage and the like required for the fuel cell stack 100.

Further, in the above embodiment, the air electrode 114 may have a configuration that does not satisfy at least one of the above-mentioned second to fifth requirements. Further, in the above embodiment, at least one coarse particle 214 is present in at least one cross section of the air electrode 114 (first requirement). However, it is preferable that a plurality of coarse particles 214 are present in one cross section of the air electrode 114, and it is preferable that each of the plurality of cross sections of the air electrode 114 satisfies the first requirement.

Further, the material constituting each member in the above embodiment is merely an example, and each member may be composed of another material. For example, in the above embodiment, the air electrode 114 (active layer 220 and current collector layer 210) contains LSCF, but instead of LSCF or in addition to LSCF, for example, LSM (lantern strontium manganese oxide) or LSC. Other materials such as (lanternstrontium cobalt oxide) may be included. Further, in the above embodiment, the active layer 220 and the intermediate layer 180 include the GDC, but the active layer 220 and the intermediate layer 180 may be replaced with the GDC or in addition to the GDC, for example, SDC (samarium-doped ceria) or the like. Other materials may be included.

Further, in the above embodiment, the fuel cell stack 100 has a configuration in which a plurality of flat plate-shaped single cells 110 are laminated, but the present invention is described in another configuration, for example, International Publication No. 2012/1655409. As described above, it is similarly applicable to a configuration in which a plurality of substantially cylindrical fuel cell single cells are connected in series.

Further, in the above embodiment, the SOFC that generates power by utilizing the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidizing agent gas is targeted, but the present invention relates to an electrolysis reaction of water. It is also applicable to an electrolytic single cell, which is a constituent unit of a solid oxide type electrolytic cell (SOEC) that uses it to generate hydrogen, and an electrolytic cell stack including a plurality of electrolytic single cells. The configuration of the electrolytic cell stack is not described in detail here because it is known, for example, as described in Japanese Patent Application Laid-Open No. 2016-81813, but is schematically the same as the fuel cell stack 100 in the above-described embodiment. It is the composition of. That is, the fuel cell stack 100 in the above-described embodiment may be read as an electrolytic cell stack, the power generation unit 102 may be read as an electrolytic cell unit, and the single cell 110 may be read as an electrolytic cell. However, during the operation of the electrolytic cell stack, a voltage is applied between both electrodes so that the air electrode 114 is positive (anode) and the fuel electrode 116 is negative (cathode), and the voltage is applied through the communication hole 108. Steam as a raw material gas is supplied. As a result, an electrolysis reaction of water occurs in each electrolytic cell unit, hydrogen gas is generated in the fuel chamber 176, and hydrogen is taken out to the outside of the electrolytic cell stack through the communication hole 108. By applying the present invention to an electrolytic single cell having such a configuration, it is possible to suppress the separation of the current collector layer 210 and the active layer 220 at the air electrode 114.

22: Bolt 24: Nut 26: Insulation sheet 27: Gas passage member 28: Main body 29: Branch 100: Fuel cell stack 102: Power generation unit 104, 106: End plate 108: Communication hole 110: Single cell 110A: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 121: Hole 124: Joint 130: Air electrode side frame 131: Hole 132: Oxidating agent gas supply communication hole 133: Oxidating agent gas discharge communication hole 134: Air Polar side current collector 135: Current collector element 140: Fuel pole side frame 141: Hole 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144: Fuel pole side current collector 145: Electrode facing part 146: Inter Connector facing part 147: Connecting part 149: Spacer 150: Interconnector 161: Oxidizing agent gas introduction manifold 162: Oxidizing agent gas discharge manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber 180: Intermediate layer 210: Collector layer 214: Coarse particles 220: Active layer C: Boundary line FG: Fuel gas FOG: Fuel off gas L: Intermediate laminate LC: Virtual straight line M1: Straight line M2: Straight line OG: Oxidating agent gas OOG: Oxidation Agent off gas X1: region

Claims (6)

In 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 across the electrolyte layer.
The air electrode includes a first layer and a second layer arranged on the opposite side of the first layer from the electrolyte layer.
In at least one cross section of the air electrode substantially parallel to the first direction.
Coarse particles having a maximum length larger than the average particle size of the first layer and larger than the average particle size of the second layer, straddling the first layer and the second layer. There are coarse particles that are located so that they are
It is characterized by an electrochemical reaction single cell. In the electrochemical reaction single cell according to claim 1, further
In the at least one cross section
At least one of the first layer and the second layer, one of the coarse particles is in contact with a plurality of other particles.
It is characterized by an electrochemical reaction single cell. In the electrochemical reaction single cell according to claim 1 or 2.
In the at least one cross section
The maximum length of the coarse particles is 2 μm or more.
It is characterized by an electrochemical reaction single cell. In the electrochemical reaction single cell according to any one of claims 1 to 3.
In the at least one cross section
The maximum length of the coarse particles is 4 μm or less.
It is characterized by an electrochemical reaction single cell. In the electrochemical reaction single cell according to any one of claims 1 to 4.
In the at least one cross section
The number of the coarse particles present per 100 μm of the boundary line between the first layer and the second layer is one or more.
It is characterized by an electrochemical reaction single cell. In an electrochemical reaction cell stack comprising a plurality of electrochemical reaction single cells arranged side by side in the first direction.
The electrochemical reaction cell stack according to any one of claims 1 to 5, wherein at least one of the plurality of electrochemical reaction single cells is the electrochemical reaction single cell.

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