JP2018137206A - Electrochemical reaction unit and electrochemical reaction cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the performance of an electrochemical reaction unit. An electrochemical reaction unit (102) includes an electrolyte layer (112), a fuel electrode (116) arranged on one side in a first direction with respect to the electrolyte layer, and a fuel electrode (116) on the other side in the first direction with respect to the electrolyte layer. And a single cell having an air electrode 114 arranged. The air electrode includes a first air electrode layer 210 that constitutes the other surface of the air electrode in the first direction, and a second air electrode layer that is arranged between the first air electrode layer and the electrolyte layer. 220 and. The electrochemical reaction unit further includes a current collector 190 having a plurality of protrusions 192 in contact with the surface of the first air electrode layer on the other side in the first direction. The porosity of the first air electrode layer is 30% or more. Regarding the specific convex portion of the plurality of convex portions, the ratio (β/γ) of the thickness β of the air electrode to the width γ of the portion of the specific convex portion in contact with the first air electrode layer is 0.07 or more, The ratio (δ/γ) of the thickness δ of the first air electrode layer to the width γ is 0.06 or more. [Selection diagram] Fig. 14

Description

  The technology disclosed herein relates to electrochemical reaction units.

  A solid oxide fuel cell (hereinafter referred to as “SOFC”) is known as one type of fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen. A fuel cell power generation unit that is a constituent unit of SOFC includes a single fuel cell. The fuel cell unit cell includes an electrolyte layer, a fuel electrode disposed on one side of a predetermined direction (hereinafter referred to as “first direction”) with respect to the electrolyte layer, and a first direction with respect to the electrolyte layer. And an air electrode disposed on the other side.

  The fuel cell power generation unit includes a conductive current collector disposed at a position facing the air electrode constituting the fuel cell single cell. The current collector is a member for taking out the electric power generated by the power generation reaction in the single fuel cell. The current collector has a plurality of convex portions in contact with the surface on the other side in the first direction of the air electrode. During the power generation operation, electrons are exchanged between the air electrode and the current collector at a portion where the surface of the air electrode is in contact with each convex portion of the current collector. In addition, the oxidant gas supplied to the air chamber facing the air electrode from the portion of the surface of the air electrode that is not in contact with each convex portion of the current collector (not covered by each convex portion). Flows in.

  Conventionally, in order to improve the performance of the fuel cell power generation unit, a preferable range of the thickness of the air electrode (thickness in the first direction) has been proposed (see, for example, Patent Document 1).

JP 2013-229511 A

  However, simply considering the preferable range of the thickness of the air electrode as in the past, the performance of the fuel cell power generation unit cannot be sufficiently improved, and there is room for further performance improvement.

  In general, the fuel cell power generation unit configured as described above is an electrolytic cell that is a structural unit of a solid oxide electrolytic cell (hereinafter referred to as “SOEC”) that generates hydrogen using an electrolysis reaction of water. It can also be used as a unit. When a fuel cell power generation unit is used as an electrolysis cell unit, a voltage is applied between both electrodes so that the air electrode is positive (anode) and the fuel electrode is negative (cathode), and the fuel chamber faces the fuel electrode. To supply water vapor. Thereby, an electrolysis reaction of water occurs in the fuel cell single cell (in this case, functioning as an electrolytic single cell), and hydrogen is generated at the fuel electrode. Even when the fuel cell power generation unit is used as an electrolysis cell unit, the performance cannot be sufficiently improved only by considering the preferable range of the thickness of the air electrode as in the past, and there is room for further performance improvement. is there.

In this specification, the fuel cell unit cell and the electrolysis unit cell are collectively referred to as an electrochemical reaction unit cell, and the fuel cell power generation unit and the electrolysis cell unit are collectively referred to as an electrochemical reaction unit. A fuel cell stack including a single cell (fuel cell power generation unit) and an electrolytic cell stack including a plurality of electrolytic single cells (electrolytic cell unit) are collectively referred to as an electrochemical reaction cell stack.

  In this specification, the technique which can solve the subject mentioned above is disclosed.

  The technology disclosed in the present specification can be realized as, for example, the following forms.

(1) The electrochemical reaction unit disclosed in the present specification includes an electrolyte layer, a fuel electrode disposed on one side in a first direction with respect to the electrolyte layer, and the first with respect to the electrolyte layer. An air electrode disposed on the other side of the air electrode, the first air electrode layer constituting the surface of the other side of the air electrode in the first direction, the first air electrode layer, and the air electrode An electrochemical reaction unit cell comprising: a second air electrode layer disposed between the electrolyte layer; and the other side of the first air electrode layer in the first direction. And a conductive current collector having a plurality of convex portions in contact with the surface of the first electrode, the porosity of the first air electrode layer is 30% or more, and the plurality of convex portions A specific convex portion that is at least one of the two in a second direction orthogonal to the first direction. The first ratio (β / γ), which is the ratio of the thickness β of the air electrode in the first direction to the width γ of the portion of the specific convex portion in contact with the first air electrode layer, is 0. The second ratio (δ / γ), which is a ratio of the thickness δ of the first air electrode layer in the first direction to the width γ, is 0.06 or more. . In this electrochemical reaction unit, the porosity of the first air electrode layer constituting the other surface of the air electrode in the first direction is 30% or more, so the electrochemical reaction unit is used as a fuel cell power generation unit. When performing (hereinafter referred to as “FC mode”), the oxidant gas used for the electrochemical reaction in the second air electrode layer functioning as a reaction field in the air electrode is excellent in the first air electrode layer. In the case where the electrochemical reaction unit is used as an electrolysis cell unit (hereinafter referred to as “EC mode”), the second air electrode can be suppressed. Oxygen generated by the electrochemical reaction in the layer can be favorably passed through the first air electrode layer, and the separation of the air electrode due to the retention of oxygen and pressure on the air electrode is suppressed. be able to. Further, in the present electrochemical reaction unit, since the second ratio (δ / γ) is somewhat large, the thickness δ of the first air electrode layer is somewhat thick and / or the specific convex portion of the current collector Since the width γ of the portion in contact with the first air electrode layer is narrow to some extent, in the FC mode, the direction in which the oxidant gas flowing into the first air electrode layer has a certain degree of inclination with respect to the first direction. , The region where the oxidant gas is difficult to reach can be reduced throughout the thickness direction of the second air electrode layer, and an increase in gas diffusion polarization can be suppressed. In addition, since the first reaction ratio (β / γ) is large to some extent in the electrochemical reaction unit, the thickness β of the air electrode is somewhat thick and / or the first air of the specific convex portion of the current collector In the EC mode, oxygen generated in the second air electrode layer is directed toward the air chamber along a direction in which the inclination with respect to the first direction is within a certain range because the width γ of the portion in contact with the electrode layer is somewhat narrow. This is because the oxygen generated in the second air electrode layer is less likely to be discharged into the air chamber over the entire thickness direction of the second air electrode layer, and oxygen is retained and pressure is applied to the air electrode. Separation of the air electrode can be suppressed. Therefore, according to this electrochemical reaction unit, the performance of the electrochemical reaction unit can be improved.

(2) In the electrochemical reaction unit, with respect to the specific convex portion, the first relative to the shortest distance α between the specific convex portion and the convex portion located next to the specific convex portion in the second direction. The third ratio (β / α), which is the ratio of the thickness β of the air electrode in the direction 1, is 0.035 or more, and the first ratio in the first direction with respect to the shortest distance α. The fourth ratio (δ / α), which is the ratio of the thickness δ of the air electrode layer, may be 0.02 or more. In the present electrochemical reaction unit, the fourth ratio (δ / α) is large to some extent, so that the thickness δ of the first air electrode layer is thick to some extent, and / or the convex and convex portions of the current collector In the FC mode, when the electrons that have entered the first air electrode layer move along a direction in which the inclination with respect to the first direction is within a certain range, in the FC mode, The region where electrons are difficult to reach can be reduced over the entire thickness direction of the second air electrode layer, and an increase in activation polarization can be suppressed. In addition, since the third ratio (β / α) is large to some extent in the electrochemical reaction unit, the thickness β of the air electrode is somewhat thick and / or between the convex portion and convex portion of the current collector. In the EC mode, when electrons generated in the second air electrode layer flow toward the current collector along the direction of a certain range in the EC mode. In addition, it is possible to reduce the region in which the electrons generated there hardly reach the convex portions of the current collector throughout the thickness direction of the second air electrode layer, and suppress an increase in activation polarization. Therefore, according to this electrochemical reaction unit, the performance of the electrochemical reaction unit can be effectively improved.

(3) In the electrochemical reaction unit, for the specific convex portion, the first ratio (β / γ) is 0.16 or less, and the second ratio (δ / γ) is 0. .14 or less. According to this electrochemical reaction unit, since the upper limit of the second ratio (δ / γ) is set, the thickness δ of the first air electrode layer can be suppressed from becoming excessively thick, and / or Alternatively, since the width γ of the portion of the specific convex portion of the current collector that is in contact with the first air electrode layer can be suppressed from being excessively narrow, the gas due to the excessively long diffusion path of the oxidant gas in the FC mode. An increase in diffusion polarization can be suppressed, and breakage of the air electrode due to stress concentration can be suppressed. Further, according to the present electrochemical reaction unit, since the upper limit of the first ratio (β / γ) is set, it is possible to suppress the thickness β of the air electrode from becoming excessively thick, and / or Since it is possible to suppress the width γ of the portion of the specific convex portion of the current collector that is in contact with the first air electrode layer from being excessively narrow, the oxygen discharge path in the EC mode is excessively long and pressure is applied to the air electrode. As a result, it is possible to suppress separation of the air electrode and to prevent damage to the air electrode due to stress concentration. Therefore, according to this electrochemical reaction unit, the performance of the electrochemical reaction unit can be further effectively improved.

(4) In the electrochemical reaction unit, for the specific convex portion, the third ratio (β / α) is 0.05 or more, and the fourth ratio (δ / α) is 0. .04 or more. According to the present electrochemical reaction unit, since the fourth ratio (δ / α) is even larger, the thickness δ of the first air electrode layer is made thicker and / or the convex portion of the current collector and Since the shortest distance α between the convex portions can be further shortened, in the FC mode, the region in which electrons are difficult to reach can be more effectively reduced throughout the thickness direction of the second air electrode layer. And increase in activation polarization can be more effectively suppressed. Further, according to the present electrochemical reaction unit, since the third ratio (β / α) is further increased, the thickness β of the air electrode is increased, and / or the convex portion and the convex portion of the current collector In the EC mode, the generated electrons are unlikely to reach the convex portions of the current collector throughout the thickness direction of the second air electrode layer in the EC mode. Can be more effectively reduced, and an increase in activation polarization can be more effectively suppressed. Therefore, according to the present electrochemical reaction unit, the performance of the electrochemical reaction unit can be further effectively improved.

(5) In the electrochemical reaction unit, for the specific convex portion, the third ratio (β / α) is 0.13 or less, and the fourth ratio (δ / α) is 0. .12 or less may be adopted. According to this electrochemical reaction unit, since the upper limit of the fourth ratio (δ / α) is set, it is possible to suppress the thickness δ of the first air electrode layer from becoming excessively thick, and / or Or since it can suppress that the shortest distance (alpha) between the convex part of an electrical power collector becomes too short, in the FC mode, the diffusion path | route of oxidizing gas becomes too long, or the 1st air electrode layer It is possible to effectively suppress an increase in gas diffusion polarization due to an excessively small area of a portion not covered by the convex portion of the current collector. Further, according to the present electrochemical reaction unit, since the upper limit of the third ratio (β / α) is set, it is possible to suppress the thickness β of the air electrode from becoming excessively thick, and / or Since it can suppress that the shortest distance (alpha) between the convex part of an electrical power collector becomes short too much, in the EC mode, the discharge path | route of oxygen becomes long too much, or the electrical power collector in a 1st air electrode layer When the area of the portion that is not covered with the convex portion becomes excessively small, it is possible to effectively suppress the separation of the air electrode due to an increase in the pressure of the air electrode. Therefore, according to this electrochemical reaction unit, the performance of the electrochemical reaction unit can be improved extremely effectively.

(6) In the electrochemical reaction unit, the porosity of the other side portion of the air electrode in the first direction is higher than the porosity of the one side portion of the air electrode in the first direction. It is good also as a structure. According to this electrochemical reaction unit, an increase in gas diffusion polarization can be suppressed while ensuring a reaction field (three-phase interface length).

  The technology disclosed in the present specification can be realized in various forms. For example, an electrochemical reaction unit (a fuel cell power generation unit and / or an electrolytic cell unit), a plurality of electrochemical reaction units are included. It can be realized in the form of an electrochemical reaction cell stack (fuel cell stack and / or electrolysis cell stack), a manufacturing method thereof, and the like.

It is a perspective view which shows the external appearance structure of the electrochemical reaction cell stack 100 in embodiment. It is explanatory drawing which shows the XZ cross-section structure of the electrochemical reaction cell stack 100 in the position of II-II of FIG. It is explanatory drawing which shows the YZ cross-section structure of the electrochemical reaction cell stack 100 in the position of III-III of FIG. FIG. 3 is an explanatory diagram showing an XZ cross-sectional configuration of two reaction 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 structure of the two reaction units 102 adjacent to each other in the same position as the cross section shown in FIG. FIG. 5 is an explanatory diagram showing an XY cross-sectional configuration of a reaction unit 102 at a position VI-VI in FIG. 4. FIG. 5 is an explanatory diagram showing an XY cross-sectional configuration of a reaction unit 102 at a position VII-VII in FIG. 4. It is explanatory drawing which shows cross section SE1 used for specification of the convex part contact part width | variety (gamma) and the shortest distance between convex parts (alpha). It is explanatory drawing which shows cross section SE1 used for specification of the convex part contact part width | variety (gamma) and the shortest distance between convex parts (alpha). It is explanatory drawing which shows the measurement position of convex part contact part width | variety (gamma) and the shortest distance between convex parts (alpha). It is explanatory drawing which shows a performance evaluation result. It is explanatory drawing which shows notionally the relationship between 2nd ratio R2 (= delta / gamma) and the performance in FC mode. It is explanatory drawing which shows notionally the relationship between 2nd ratio R2 (= delta / gamma) and the performance in FC mode. It is explanatory drawing which shows notionally the relationship between 2nd ratio R2 (= delta / gamma) and the performance in FC mode. It is explanatory drawing which shows notionally the relationship between 1st ratio R1 (= (beta) / (gamma)) and the performance in EC mode. It is explanatory drawing which shows notionally the relationship between 1st ratio R1 (= (beta) / (gamma)) and the performance in EC mode. It is explanatory drawing which shows notionally the relationship between 1st ratio R1 (= (beta) / (gamma)) and the performance in EC mode. It is explanatory drawing which shows notionally the relationship between 4th ratio R4 (= (delta) / (alpha)) and the performance in FC mode. It is explanatory drawing which shows notionally the relationship between 4th ratio R4 (= (delta) / (alpha)) and the performance in FC mode. It is explanatory drawing which shows notionally the relationship between 4th ratio R4 (= (delta) / (alpha)) and the performance in FC mode. It is explanatory drawing which shows notionally the relationship between 3rd ratio R3 (= (beta) / (alpha)) and the performance in EC mode. It is explanatory drawing which shows notionally the relationship between 3rd ratio R3 (= (beta) / (alpha)) and the performance in EC mode. It is explanatory drawing which shows notionally the relationship between 3rd ratio R3 (= (beta) / (alpha)) and the performance in EC mode. It is explanatory drawing which shows the specific method of the porosity of each layer of the air electrode 114. FIG. It is explanatory drawing which shows the structure of the electrical power collector 190 vicinity in a modification.

A. Embodiment:
A-1. Constitution:
(Configuration of electrochemical reaction cell stack 100)
FIG. 1 is a perspective view showing an external configuration of an electrochemical reaction cell stack 100 in the embodiment, and FIG. 2 is an electrochemical reaction cell stack at a position II-II in FIG. 1 (and FIGS. 6 and 7 described later). FIG. 3 is an explanatory diagram showing an XZ sectional configuration of 100, and FIG. 3 is an explanatory diagram showing a YZ sectional configuration of the electrochemical reaction cell stack 100 at the position of III-III in FIG. 1 (and FIGS. 6 and 7 described later). . In each figure, XYZ axes orthogonal to each other for specifying the direction are shown. In this specification, for 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. However, the electrochemical reaction cell stack 100 is actually different from such an orientation. It may be installed in the direction. The same applies to FIG.

  The electrochemical reaction cell stack 100 is a device (so-called reversible electrochemical reaction cell stack) that can be used as a fuel cell stack or an electrolytic cell stack. That is, the electrochemical reaction cell stack 100 functions as a fuel cell stack that generates power using an electrochemical reaction between hydrogen and oxygen in the first mode (hereinafter referred to as “FC mode”). In this mode (hereinafter referred to as “EC mode”), it functions as an electrolytic cell stack that generates hydrogen by utilizing an electrolysis reaction of water.

  The electrochemical reaction cell stack 100 includes a plurality (seven in this embodiment) of electrochemical reaction units (hereinafter simply referred to as “reaction units”) 102 and a pair of end plates 104 and 106. The seven reaction 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 assembly composed of seven reaction units 102 from above and below. The arrangement direction (vertical direction) corresponds to the first direction in the claims.

  A plurality of (eight in the present embodiment) holes penetrating in the vertical direction are formed in the periphery of each layer (reaction unit 102, end plates 104, 106) constituting the electrochemical reaction cell stack 100 around the Z direction. The corresponding holes formed in each layer 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 electrochemical reaction cell stack 100 to form the communication holes 108 may also be referred to as the communication holes 108.

  Bolts 22 extending in the vertical direction are inserted into the communication holes 108, and the electrochemical reaction cell stack 100 is fastened by the bolts 22 and nuts 24 fitted on both sides of the bolts 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 electrochemical reaction cell stack 100, and The insulating sheet 26 is interposed between the nut 24 fitted on the other side (lower side) of the bolt 22 and the lower surface of the end plate 106 constituting the lower end of the electrochemical reaction cell stack 100. . However, in a place where a gas passage member 27 described later is provided, an insulating sheet disposed between the nut 24 and the surface of the end plate 106 on the upper and lower sides of the gas passage member 27 and the gas passage member 27, respectively. 26 is interposed. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder 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 vicinity of the midpoint of one side (the side on the X-axis positive direction of two sides parallel to the Y-axis) on the outer periphery around the Z-direction of the electrochemical reaction cell stack 100 The space formed by the bolt 22 (bolt 22A) located at the position and the communication hole 108 through which the bolt 22A is inserted is introduced with the oxidizing gas OG from the outside of the electrochemical reaction cell stack 100 in the FC mode. It functions as an oxidant gas introduction manifold 161 that is a gas flow path for supplying the oxidant gas OG to each reaction unit 102, and is on the opposite side of the side (the negative direction of the X axis of two sides parallel to the Y axis). The space formed by the bolt 22 (bolt 22B) located near the midpoint of the side edge and the communication hole 108 through which the bolt 22B is inserted is the air chamber 1 of each reaction unit 102 in the FC mode. To function as a gas discharged from 6 oxidant off-gas OOG as the oxidant gas discharge manifold 162 for discharging to the outside of the electrochemical reaction cell stack 100. In the present embodiment, for example, air is used as the oxidant gas OG.

  Further, as shown in FIGS. 1 and 3, in one side (a side on the Y axis positive direction side of two sides parallel to the X axis) on the outer periphery around the Z direction of the electrochemical reaction cell stack 100. In the space formed by the bolt 22 (bolt 22D) located near the point and the communication hole 108 through which the bolt 22D is inserted, the fuel gas FG is introduced from the outside of the electrochemical reaction cell stack 100 in the FC mode. It functions as a fuel gas introduction manifold 171 for supplying the fuel gas FG to each reaction unit 102, and is located in the opposite side of the side (the side on the Y axis negative direction side of the two sides parallel to the X axis). A space formed by the bolt 22 (bolt 22E) located near the point and the communication hole 108 through which the bolt 22E is inserted is discharged from the fuel chamber 176 of each reaction unit 102 in the FC mode. The fuel off-gas FOG is gas serving as a fuel gas exhaust manifold 172 for discharging to the outside of the electrochemical reaction cell stack 100. In the present embodiment, as the fuel gas FG, for example, hydrogen-rich gas obtained by reforming city gas is used.

  Note that, as described above, in this specification, each manifold is referred to by a name representing a function in the FC mode. Moreover, the gas flow direction shown in FIGS. 1 to 7 is the gas flow direction in the FC mode. In the EC mode, the oxidant gas discharge manifold 162 functions as a gas flow path for discharging oxygen generated in the air electrode 114 of each reaction unit 102 from the air chamber 166 to the outside of the electrochemical reaction cell stack 100, The agent gas introduction manifold 161 serves as a gas flow path for supplying a recovered gas (for example, air) for promoting the discharge of oxygen from the air chamber 166 from the outside of the electrochemical reaction cell stack 100 to the air chamber 166 of each reaction unit 102. Function. In the EC mode, the fuel gas introduction manifold 171 functions as a gas flow path for supplying water vapor to the fuel chamber 176 of each reaction unit 102 from the outside of the electrochemical reaction cell stack 100, and the fuel gas discharge manifold 172 It functions as a gas flow path for discharging hydrogen generated in the fuel electrode 116 of each reaction unit 102 from the fuel chamber 176 to the outside of the electrochemical reaction cell stack 100.

  The electrochemical reaction 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 part 29 communicates with the hole of the main body part 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 portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> A forming the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. The hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> B that forms 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 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 The hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> E forming the discharge manifold 172 communicates with the fuel gas discharge manifold 172.

(Configuration of end plates 104 and 106)
The pair of end plates 104 and 106 are substantially rectangular flat plate-shaped conductive members, and are formed of, for example, stainless steel. One end plate 104 is disposed above the uppermost reaction unit 102, and the other end plate 106 is disposed below the lowermost reaction unit 102. A plurality of reaction units 102 are held in a pressed state by a pair of end plates 104 and 106. In the FC mode, the upper end plate 104 functions as a positive output terminal of the electrochemical reaction cell stack 100, and the lower end plate 106 functions as a negative output terminal of the electrochemical reaction cell stack 100. To do. In the EC mode, the upper end plate 104 functions as a positive input terminal of the electrochemical reaction cell stack 100, and the lower end plate 106 serves as a negative input terminal of the electrochemical reaction cell stack 100. Function as.

(Configuration of reaction unit 102)
4 is an explanatory diagram showing an XZ cross-sectional configuration of two reaction units 102 adjacent to each other at the same position as the cross section shown in FIG. 2, and FIG. 5 is adjacent to each other at the same position as the cross section shown in FIG. FIG. 4 is an explanatory diagram showing a YZ cross-sectional configuration of two reaction units 102. In the upper part of FIG. 5, an enlarged YZ cross-sectional configuration of a part of the reaction unit 102 is shown. 6 is an explanatory diagram showing an XY cross-sectional configuration of the reaction unit 102 at the position VI-VI in FIG. 4, and FIG. 7 shows an XY cross-sectional configuration of the reaction unit 102 at the position VII-VII in FIG. It is explanatory drawing shown.

  The reaction unit 102 functions as a fuel cell power generation unit in the FC mode, and functions as an electrolysis cell unit in the EC mode. As shown in FIGS. 4 and 5, the reaction unit 102 includes a single cell 110, a separator 120, an air electrode side frame 130, an air electrode side current collector 134, a fuel electrode side frame 140, and a fuel electrode side. A current collector 144 and a pair of interconnectors 150 constituting the uppermost layer and the lowermost layer of the reaction unit 102 are provided. The separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the periphery of the interconnector 150 around the Z direction are formed with holes corresponding to the communication holes 108 through which the bolts 22 are inserted.

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

  The single cell 110 functions as a fuel cell single cell in the FC mode, and functions as an electrolytic single cell in the EC mode. The unit cell 110 includes an electrolyte layer 112, a fuel electrode 116 disposed on one side (lower side) of the electrolyte layer 112 in the vertical direction (first direction), and the other side (upper side) of the electrolyte layer 112 in the vertical direction. And an intermediate layer 180 disposed between the electrolyte layer 112 and the air electrode 114. The single cell 110 of this embodiment is a fuel electrode-supported single cell that supports the other layers (the electrolyte layer 112, the air electrode 114, and the intermediate layer 180) constituting the single cell 110 with the fuel electrode 116.

  The electrolyte layer 112 is a substantially rectangular flat plate member as viewed in the Z direction, and is a dense layer. The electrolyte layer 112 is formed of a solid oxide such as YSZ (yttria stabilized zirconia), ScSZ (scandia stabilized zirconia), SDC (samarium doped ceria), GDC (gadolinium doped ceria), perovskite oxide, and the like. Yes. That is, the single cell 110 (reaction unit 102) of the present embodiment is a solid oxide fuel cell (SOFC) or electrolytic cell (SOEC) using a solid oxide as an electrolyte.

  The air electrode 114 is a substantially rectangular flat plate-shaped member smaller than the electrolyte layer 112 when viewed in the Z direction, and is a porous layer. As shown in FIG. 5, in the present embodiment, the air electrode 114 includes a current collecting layer 210 that constitutes an upper surface of the air electrode 114 (a surface facing a current collector 190 described later), and a current collecting layer. 210 and an active layer 220 disposed between the electrolyte layer 112 (and the intermediate layer 180). The active layer 220 is a layer that mainly functions as a field for the reaction at the air electrode 114 (reaction in which oxide ions are generated from oxygen in the FC mode, and reaction in which oxygen ions are generated from the oxide ions in the EC mode). is there. The current collecting layer 210 mainly functions as a field for collecting (or transmitting) electricity while diffusing the oxidant gas OG supplied from the air chamber 166 or the oxygen gas generated in the active layer 220. Is a layer. The active layer 220 is formed to include, for example, a perovskite oxide such as LSCF (lanthanum strontium cobalt iron oxide) and GDC (gadolinium doped ceria). The current collecting layer 210 is formed so as to include a perovskite oxide such as LSCF, for example. The current collecting layer 210 corresponds to the first air electrode layer in the claims, and the active layer 220 corresponds to the second air electrode layer in the claims.

  In the present embodiment, the porosity RO1 of the current collecting layer 210 is higher than the porosity RO2 of the active layer 220. That is, the porosity of the upper part of the air electrode 114 is higher than the porosity of the lower part of the air electrode 114. Note that the porosity of the current collecting layer 210 and the active layer 220 is substantially uniform in a direction parallel to the Z-axis direction. According to such a configuration, an increase in gas diffusion polarization can be suppressed while ensuring a reaction field (three-phase interface length). The porosity RO1 of the current collecting layer 210 is preferably high to some extent in order to ensure gas diffusibility. Specifically, the porosity RO1 of the current collecting layer 210 is preferably 30% or more, and preferably 45% or less. The porosity RO2 of the active layer 220 is preferably 15% or more, and preferably 40% or less.

  The fuel electrode 116 is a substantially rectangular flat plate member having substantially the same size as the electrolyte layer 112 when viewed in the Z direction, and is a porous layer. The fuel electrode 116 is formed of, for example, a cermet made of Ni and oxide ion conductive ceramic particles (for example, YSZ).

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 indicates that an element (for example, Sr) diffused from the air electrode 114 reacts with an element (for example, Zr) contained in the electrolyte layer 112 to generate a high-resistance material (for example, SrZrO ₃ ). Suppress.

  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, for example, metal. The peripheral part of the hole 121 in the separator 120 is opposed to the peripheral part of the surface of the electrolyte layer 112 on the air electrode 114 side. 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 brazing) disposed in the facing portion. The separator 120 divides the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116, and gas leaks from one electrode side to the other electrode side in the peripheral portion of the single cell 110. It is suppressed.

As shown in FIGS. 4 to 6, the air electrode side frame 130 is a frame-like member in which a substantially rectangular hole 131 penetrating in the vertical direction is formed near the center, and is formed of an insulator such as mica, for example. ing. The hole 131 of the air electrode side frame 130 forms an air chamber 166 that faces the air electrode 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. . Further, the air electrode side frame 130 electrically insulates the pair of interconnectors 150 included in the reaction unit 102. The air electrode side frame 130 has an oxidant gas supply communication hole 132 communicating the oxidant gas introduction manifold 161 and the air chamber 166, and an oxidant gas communicating the air chamber 166 and the oxidant gas discharge manifold 162. A discharge communication hole 133 is formed.

  As shown in FIGS. 4, 5, and 7, the fuel electrode side frame 140 is a frame-like 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 forms a fuel chamber 176 that faces the fuel electrode 116. The fuel electrode side frame 140 is in contact with the peripheral portion of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral portion of the surface of the interconnector 150 facing the fuel electrode 116. Further, the fuel electrode side frame 140 has a fuel gas supply communication hole 142 that connects the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that connects the fuel chamber 176 and the fuel gas discharge manifold 172. And are formed.

  As shown in FIGS. 4, 5 and 7, the fuel electrode side current collector 144 is disposed 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 It is made of stainless steel or the like. The electrode facing portion 145 is in contact with the surface of the fuel electrode 116 on the side 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 electrode 116. In contact. However, as described above, the lowermost reaction unit 102 in the electrochemical reaction cell stack 100 does not include the lower interconnector 150, and thus the interconnector facing portion 146 in the reaction unit 102 has a lower side. It is in contact with the end plate 106. Since the fuel electrode side current collector 144 has such a configuration, the fuel electrode 116 and the interconnector 150 (or the end plate 106) are electrically connected. Note that a spacer 149 made of, for example, mica is disposed 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 reaction 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. The electrical connection with is maintained well.

  As shown in FIGS. 4 to 6, the air electrode side current collector 134 is disposed in the air chamber 166. The air electrode side current collector 134 is composed of a plurality of current collector elements 135 having a substantially quadrangular prism shape, and is formed of, for example, 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, since the uppermost reaction unit 102 in the electrochemical reaction cell stack 100 does not include the upper interconnector 150, the air electrode side current collector 134 in the reaction unit 102 is It is in contact with the end plate 104. Since the air electrode side current collector 134 has such a configuration, the air electrode 114 and the interconnector 150 (or the end plate 104) are electrically connected.

  The space between two adjacent current collector elements 135 constituting the air electrode side current collector 134 functions as a gas flow path. As shown in FIG. 6, in the present embodiment, each current collector element 135 is arranged so that the axial direction (longitudinal direction) substantially coincides with the X-axis direction and is aligned in the X-axis direction and the Y-axis direction. ing. Therefore, the gas flow path has a shape extending in a lattice shape in the X-axis direction and the Y-axis direction when viewed in the Z-axis direction.

  In the present embodiment, the air electrode side current collector 134 (current collector element 135) and the interconnector 150 are formed as an integral member. That is, a flat plate-shaped portion perpendicular to the vertical direction (Z-axis direction) of the integral member functions as the interconnector 150 and is formed so as to protrude toward the air electrode 114 from the flat plate-shaped portion. The plurality of current collector elements 135 function as the air electrode side current collector 134.

As shown in FIGS. 4 and 5, the surface of the air electrode side current collector 134 (current collector element 135) is covered with a conductive coat 136. The coat 136 is formed of, for example, a spinel oxide (for example, Mn _1.5 Co _1.5 O ₄ , MnCo ₂ O ₄ , ZnCo ₂ O ₄ , ZnMn ₂ O ₄ , ZnMnCoO ₄ , CuMn ₂ O ₄ ). ing. The coating 136 is formed on the surface of the air electrode side current collector 134 by a known method such as spray coating, ink jet printing, spin coating, dip coating, plating, sputtering, or thermal spraying. As described above, in the present embodiment, the air electrode side current collector 134 (current collector element 135) and the interconnector 150 are formed as an integral member. The boundary surface with the interconnector 150 is not covered with the coat 136 among the surfaces of the electric body 134 (the current collector element 135), while at least the surface facing the gas flow path among the surfaces of the interconnector 150 (for example, The surface of the interconnector 150 on the air electrode 114 side) is covered with a coat 136. Further, a chromium oxide film may be formed by heat treatment on the air electrode side current collector 134 or the like. In that case, the coat 136 is not the film but the air electrode side current collector 134 on which the film is formed. It is the layer formed so that it might cover. In the following description, unless otherwise specified, the air electrode side current collector 134 (current collector element 135) means “the air electrode side current collector 134 (current collector element 135) covered with the coat 136”. In FIG. 6, the illustration of the coat 136 is omitted.

As shown in FIGS. 4 and 5, the air electrode 114 and the air electrode side current collector 134 (current collector element 135) are bonded together by a conductive bonding layer 138. The bonding layer 138 is formed of, for example, a spinel oxide (for example, Mn _1.5 Co _1.5 O ₄ , MnCo ₂ O ₄ , ZnCo ₂ O ₄ , ZnMn ₂ O ₄ , ZnMnCoO ₄ , CuMn ₂ O ₄ ). Has been. In the present embodiment, the bonding layer 138 that bonds one current collector element 135 and the air electrode 114 and the bonding layer 138 that bonds the other current collector element 135 and the air electrode 114 are independent of each other. Yes. Further, the bonding layer 138 covers a corner portion of the tip portion (portion close to the air electrode 114) of the current collector element 135. In the bonding layer 138 having such a configuration, for example, the paste for the bonding layer is printed on the tip portion of each current collector element 135 constituting the air electrode side current collector 134 and pressed against the surface of the air electrode 114. It can be formed by firing under predetermined conditions. The air electrode 114 and the air electrode side current collector 134 are electrically connected by the bonding layer 138. Although it has been described above that the air electrode side current collector 134 is in contact with the surface of the air electrode 114, the bonding layer 138 is precisely between the air electrode side current collector 134 and the air electrode 114. Intervene.

  As shown in FIG. 5, in the above-described configuration, an integrated member of the interconnector 150 and the air electrode side current collector 134 (current collector element 135), a coat 136, and a bonding layer 138 are combined into one member (hereinafter referred to as “a member”). , Referred to as “current collector 190”), a plurality of portions (hereinafter referred to as “current collector 190”) including a combination of the current collector element 135 covered with the coat 136 and the bonding layer 138. The projecting portion 192 ”is projected from the portion constituted by the interconnector 150 to the air electrode 114 side. Further, each of the plurality of convex portions 192 is in contact with the upper surface of the current collecting layer 210 constituting the air electrode 114. That is, the current collector 190 has a plurality of convex portions 192 that are in contact with the upper surface of the current collecting layer 210 constituting the air electrode 114. The current collector 190 in the present embodiment corresponds to the current collector in the claims, and the convex portion 192 in the present embodiment corresponds to the convex portion in the claims.

A-2. Operation of the electrochemical reaction cell stack 100:
(Operation in FC mode)
In the FC mode, as shown in FIGS. 2 and 4, the oxidizer is connected 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. When the gas OG is supplied, the oxidant gas OG is supplied to the oxidant gas introduction manifold 161 through the branch part 29 of the gas passage member 27 and the hole of the main body part 28, and each reaction is performed from the oxidant gas introduction manifold 161. The air is supplied to the air chamber 166 through the oxidant gas supply communication hole 132 of the unit 102. Further, as shown in FIGS. 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 through 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 reaction unit 102 from the fuel gas introduction manifold 171. The fuel chamber 176 is supplied through the hole 142.

  When the oxidant gas OG is supplied to the air chamber 166 of each reaction unit 102 and the fuel gas FG is supplied to the fuel chamber 176, power generation is performed in the single cell 110 by the electrochemical reaction of the oxidant gas OG and the fuel gas FG. Is called. This power generation reaction is an exothermic reaction. In each reaction unit 102, the air electrode 114 of the single cell 110 is electrically connected to a current collector 190 (an assembly of an interconnector 150, an air electrode side current collector 134, a coat 136, and a bonding layer 138). 116 is electrically connected to the interconnector 150 via the fuel electrode side current collector 144. The plurality of reaction units 102 included in the electrochemical reaction cell stack 100 are electrically connected in series. Therefore, electrical energy generated in each reaction unit 102 is taken out from the end plates 104 and 106 that function as output terminals of the electrochemical reaction cell stack 100. Since SOFC generates power at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the electrochemical reaction cell stack 100 is heated until the high temperature can be maintained by heat generated by power generation after startup. It may be heated by a vessel (not shown).

  The oxidant off-gas OOG discharged from the air chamber 166 of each reaction unit 102 is discharged to the oxidant gas discharge manifold 162 via the oxidant gas discharge communication hole 133 as shown in FIGS. Electrochemical reaction cell through 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 It is discharged outside the stack 100. Further, as shown in FIGS. 3 and 5, the fuel off-gas FOG discharged from the fuel chamber 176 of each reaction unit 102 is discharged to the fuel gas discharge manifold 172 via the fuel gas discharge communication hole 143, and further, the fuel gas The electrochemical reaction cell stack 100 of the electrochemical reaction cell stack 100 is passed through 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 outside.

(Operation in EC mode)
In the EC mode, when water vapor 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, the water vapor is 27 is supplied to the fuel gas introduction manifold 171 via the holes 29 and the holes of the main body 28, and is supplied from the fuel gas introduction manifold 171 to the fuel chamber 176 via the fuel gas supply communication holes 142 of each reaction unit 102. The Further, when the recovered gas (for example, air) 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, the recovered gas. Is supplied to the oxidant gas introduction manifold 161 through the holes 29 of the gas passage member 27 and the main body 28, and from the oxidant gas introduction manifold 161 through the oxidant gas supply communication holes 132 of each reaction unit 102. And supplied to the air chamber 166.

  When a voltage is applied to the end plates 104 and 106 functioning as input terminals of the electrochemical reaction cell stack 100 in a state where the water vapor and the recovered gas are supplied in this way, the interconnector 150 constituting each reaction unit 102 or A voltage is applied to each single cell 110 through the air electrode side current collector 134, the fuel electrode side current collector 144, and the like, and an electrolysis reaction of water occurs in each single cell 110. By this electrolysis reaction of water, hydrogen is generated at the fuel electrode 116 and oxygen is generated at the air electrode 114.

  Hydrogen generated in the fuel electrode 116 of each unit cell 110 is discharged from the fuel chamber 176 to the fuel gas discharge manifold 172 via the fuel gas discharge communication hole 143, and further, a gas passage provided at the position of the fuel gas discharge manifold 172. The material 27 is taken out of the electrochemical reaction cell stack 100 through a gas pipe (not shown) connected to the branch portion 29 through the body portion 28 and the branch portion 29 of the member 27. Further, oxygen generated in the air electrode 114 of each single cell 110 is discharged from the air chamber 166 to the oxidant gas discharge manifold 162 through the oxidant gas discharge communication hole 133 and further to the position of the oxidant gas discharge manifold 162. It is discharged to the outside of the electrochemical reaction 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 provided gas passage member 27. .

A-3. Performance evaluation:
Each reaction unit 102 constituting the electrochemical reaction cell stack 100 of this embodiment is characterized by the relationship between the air electrode 114 and the current collector 190. Hereinafter, performance evaluation performed on the relationship between the air electrode 114 and the current collector 190 will be described.

(About each parameter)
As shown in FIG. 5, in this performance evaluation, the thickness of the air electrode 114 in the Z-axis direction is called “air electrode thickness β”, and the thickness of the current collecting layer 210 of the air electrode 114 in the Z-axis direction is , Referred to as “air electrode current collecting layer thickness δ”. When the thickness of the air electrode 114 is not uniform, the air electrode thickness β is the thickness of the thinnest part in the air electrode 114 (however, the portion in contact with the convex portion 192 of the current collector 190). . Similarly, when the thickness of the current collecting layer 210 of the air electrode 114 is not uniform, the current collecting layer thickness δ of the air electrode 114 is equal to the current collecting layer 210 of the air electrode 114 (however, the convexity of the current collector 190). The thickness of the thinnest part in the part in contact with the part 192).

  Further, the width (Z) of the air electrode 114 in contact with the current collecting layer 210 in each convex portion 192 of the current collector 190 (combination of the air electrode side current collector 134 (current collector element 135) and the bonding layer 138). The size in the direction perpendicular to the axial direction) is referred to as “convex portion contact width γ”.

  In addition, as shown in FIG. 8 and FIG. 9, the convex contact portion width γ is specified at four points (P1 to P4) or more on the outer circumferential line of the current collector element 135 in the XY cross section of the current collector element 135. When the inscribed virtual ellipse VE is set, the cross section SE1 includes the minor axis Am of the virtual ellipse VE and is parallel to the Z-axis direction (YZ cross section in the examples of FIGS. 8 and 9).

  Further, the measurement position of the convex portion contact portion width γ in the cross section SE1 is from the upper end position of the thinnest portion in the current collecting layer 210 of the air electrode 114 (however, the portion in contact with the convex portion 192 of the current collector 190) upward. And a position separated by a distance Lx (= 10 μm). For example, as shown in FIG. 5, in the configuration in which the thickness of the current collecting layer 210 of the air electrode 114 is substantially uniform, the convex contact portion width γ is in the cross section SE1 (YZ cross section in the example of FIG. 5). The position is specified on a virtual straight line VL1 that is located above the upper surface of the current collecting layer 210 of the air electrode 114 by a distance Lx (= 10 μm) and orthogonal to the Z-axis direction. Similarly, for example, as shown in FIG. 10, the thickness of the current collecting layer 210 of the air electrode 114 is substantially uniform, and the bonding layer 138 does not cover the corner of the front end portion of the current collector element 135. Also in the configuration, the convex contact portion width γ is located above the upper surface of the current collecting layer 210 of the air electrode 114 by a distance Lx (= 10 μm) in the cross section SE1 (YZ cross section in the example of FIG. 10), and , Specified on a virtual straight line VL1 orthogonal to the Z-axis direction.

  In addition, the shortest distance between one convex portion 192 and another convex portion 192 located adjacent thereto (shortest distance in a direction orthogonal to the Z-axis direction) is referred to as “shortest distance between convex portions α”. The shortest distance α between the convex portions is specified on the virtual straight line VL1 in the cross section SE1 similarly to the convex portion contact portion width γ (see FIGS. 5 and 10).

  Further, the ratio (β / γ) of the air electrode thickness β to the convex portion contact width γ is referred to as “first ratio R1”. A high value of the first ratio R1 means that the value of the convex portion contact portion width γ is small (that is, the width of the convex portion 192 is narrow) and / or the value of the air electrode thickness β is large. Means. Further, the ratio (δ / γ) of the air electrode current collecting layer thickness δ to the convex portion contact width γ is referred to as “second ratio R2”. A high value of the second ratio R2 means that the value of the convex portion contact portion width γ is small (that is, the width of the convex portion 192 is narrow) and / or the value of the air electrode current collector layer thickness δ. Means big. Further, the ratio (β / α) of the air electrode thickness β to the shortest distance α between the protrusions is referred to as “third ratio R3”. The high value of the third ratio R3 means that the value of the shortest distance α between the protrusions is small (that is, the distance between the two protrusions 192 is narrow) and / or the value of the air electrode thickness β. Means big. Further, the ratio (δ / α) of the air electrode current collecting layer thickness δ to the shortest distance α between the protrusions is referred to as a “fourth ratio R4”. A high value of the fourth ratio R4 means that the value of the shortest distance α between the protrusions is small (that is, the distance between the two protrusions 192 is narrow) and / or the thickness of the air electrode current collector layer. It means that the value of δ is large.

(About each sample)
FIG. 11 is an explanatory diagram showing the performance evaluation results. As shown in FIG. 11, each sample (S1 to S16) of the reaction unit 102 used for the performance evaluation has the above-described shortest distance α between the protrusions, the air electrode thickness β, the air electrode current collecting layer thickness δ, Further, the values of the protrusion contact portion width γ are different from each other, and as a result, the values of the first ratio R1 to the fourth ratio R4 are different from each other. Further, each sample has different values of the porosity RO1 of the current collecting layer 210 of the air electrode 114 and the porosity RO2 of the active layer 220 of the air electrode 114. As shown in FIG. 11, in all the samples used for performance evaluation, the porosity RO1 of the current collecting layer 210 of the air electrode 114 is higher than the porosity RO2 of the active layer 220 of the air electrode 114. A method for specifying the porosity RO1 and the porosity RO2 will be described later.

  In producing each sample, the air electrode 114 (the current collecting layer 210 and the active layer 220) was configured to include a perovskite oxide. Further, the porosity RO1 of the current collecting layer 210 of the air electrode 114 and the porosity RO2 of the active layer 220 were adjusted by adjusting the particle size of the raw material or adjusting the firing temperature. Further, the interconnector 150 and the air electrode side current collector 134 (current collector element 135) constituting the current collector 190 are made of metal (ferritic stainless steel), and the coat 136 and the bonding layer 138 are made of spinel oxide. Configured. For each sample, the values of the shortest distance between convex portions α and the convex portion contact portion width γ were made different from each other by making the shape and arrangement of the current collector elements 135 and the like different from each other. In all the samples, the bonding layer 138 was formed so as to cover the corner portion of the tip portion of the current collector element 135 covered with the coat 136 (see FIG. 5).

(About the evaluation method)
In this performance evaluation, the initial energization characteristics were evaluated. Specifically, for each sample of the produced reaction unit 102, the first mixed gas (a mixed gas of 20 vol% oxygen and 80 vol% nitrogen) is supplied to the air electrode 114 side, and the first mixed gas is supplied to the fuel electrode 116 side. 2 gas mixture (mixed gas of 95 vol% hydrogen and 5 vol% water vapor) is supplied, and at a temperature of 700 ° C., the current density is in the range of −0.1 A / cm ^{2 to} 0.55 A / cm ^2. Was energized and the voltage was measured. When the current density is a positive value, the reaction unit 102 is operating in the FC mode, and when the current density is a negative value, the reaction unit 102 is operating in the EC mode.

As the evaluation in the FC mode, the evaluation was made in six stages from “A” to “F” according to the voltage value when the current density was 0.55 A / cm ² (“A” was the best) And “F” is the worst evaluation).
-Evaluation: "A" ... Voltage: 0.920V or more -Evaluation: "B" ... Voltage: 0.915V or more, less than 0.920V -Evaluation: "C" ... Voltage: 0.910V or more Evaluation: “D”: Voltage: 0.900 V or more and less than 0.910 V • Evaluation: “E”: Voltage: 0.800 V or more, less than 0.900 V • Evaluation: “F "... Voltage: Less than 0.800V

Further, as an evaluation in the EC mode, evaluation was performed in six stages from “A” to “F” as follows according to the voltage value when the current density was −0.1 A / cm ² (“A”). Is the best rating, and “F” is the worst rating). In general, the operation in the EC mode is performed at a constant voltage, and it is evaluated that the performance is inferior as the current required for maintaining the voltage is lower. In this performance evaluation, operation was performed at a constant current, and it was evaluated that the higher the voltage, the worse the performance. Both evaluations have the same meaning.
-Evaluation: "A" ... Voltage: less than 1.125V -Evaluation: "B" ... Voltage: 1.125V or more, less than 1.130V -Evaluation: "C" ... Voltage: 1.130V or more Evaluation: “D”: Voltage: 1.140 V or more, less than 1.150 V • Evaluation: “E”: Voltage: 1.150 V or more, less than 1.160 V • Evaluation: “F "... Voltage: 1.160V or more

(About evaluation results)
(About sample S1)
As shown in FIG. 11, the evaluation result of the sample S1 was the lowest “F” evaluation in both the evaluation in the FC mode and the evaluation in the EC mode. In the sample S1, the porosity RO1 of the current collecting layer 210 of the air electrode 114 is 20%, which is a lower value than the other samples (both of which the porosity RO1 of the current collecting layer 210 is 30% or more). ing. Therefore, in the sample S1, in the FC mode, the oxidant gas OG supplied to the air chamber 166 does not enter the current collecting layer 210 of the air electrode 114 well and functions as a reaction field in the air electrode 114. It is considered that the gas diffusion polarization becomes extremely large due to the shortage of the oxidant gas OG at 220, resulting in extremely low performance. Further, in the sample S1, in the EC mode, oxygen generated in the active layer 220 functioning as a reaction field in the air electrode 114 does not pass through the current collecting layer 210 well, so that oxygen discharge is delayed, and the air electrode 114 It is considered that the air electrode 114 is peeled off due to the increase in gas pressure inside, and as a result, the performance is extremely lowered. From this result, it can be said that the porosity RO1 of the current collecting layer 210 of the air electrode 114 is preferably 30% or more in order to improve the performance of the reaction unit 102 (suppression of performance degradation).

(About samples S2 to S4)
The evaluation results of samples S2 to S4 were the second lowest “E” evaluation in both the FC mode evaluation and the EC mode evaluation. In samples S2 to S4, although the porosity RO1 of the current collecting layer 210 of the air electrode 114 is 30% or more, the first ratio R1 (= β / γ) is less than 0.07, and the samples S5 to S16 ( In any case, the first ratio R1 is 0.07 or more), the second ratio R2 (= δ / γ) is less than 0.06, and the samples S5 to S16 Both are lower values than the second ratio R2 is 0.06 or more. Therefore, in the samples S2 to S4, it is considered that the performance in the FC mode and the EC mode is lower than those of the samples S5 to S16 as described below.

  FIGS. 12 to 14 conceptually show the relationship between the second ratio R2 (= δ / γ) and the performance in the FC mode (denoted as “FCmode” in the figure (the same applies to other figures)). It is explanatory drawing. 12 to 14 show a YZ cross-sectional configuration of a part of the reaction unit 102 (X1 portion in FIG. 5). In the structure of the reaction unit 102 shown in FIG. 12, the value of the convex part contact part width γ is larger than that of the structure of the reaction unit 102 shown in FIG. Therefore, in the configuration of the reaction unit 102 shown in FIG. 12, the value of the second ratio R2 (= δ / γ) is smaller than that in the configuration of the reaction unit 102 shown in FIG. Further, in the configuration of the reaction unit 102 shown in FIG. 13, the value of the air electrode current collecting layer thickness δ is smaller than that of the configuration of the reaction unit 102 shown in FIG. Therefore, in the configuration of the reaction unit 102 shown in FIG. 13, the value of the second ratio R2 (= δ / γ) is smaller than that in the configuration of the reaction unit 102 shown in FIG.

  Here, in the FC mode, the oxidant gas OG supplied to the air chamber 166 is a portion of the surface of the current collecting layer 210 of the air electrode 114 that is in contact with the convex portion 192 of the current collector 190 (that is, convex portion contact). From the portion not corresponding to the convex portion 192 of the current collector 190 (that is, the portion corresponding to the shortest distance α between the convex portions) in the current collecting layer 210 of the air electrode 114. Flow into. The oxidant gas OG flowing into the current collecting layer 210 of the air electrode 114 is an active layer that functions as a reaction field in the air electrode 114 along a direction in which the inclination with respect to the Z-axis direction is approximately within a predetermined value θ1. It flows toward 220. Therefore, a configuration in which the value of the convex portion contact width γ is relatively large as shown in FIG. 12 or a configuration in which the value of the air current collector layer thickness δ is relatively small as shown in FIG. 13 (that is, the second ratio) In the configuration in which the value of R2 is relatively small), the oxidant gas OG hardly reaches the partial region Ax1 in the active layer 220 of the air electrode 114, thereby increasing the gas diffusion polarization. As a result, the reaction unit The performance of 102 is lowered.

  On the other hand, in the configuration of the reaction unit 102 shown in FIG. 14, the value of the convex contact portion width γ is smaller than that of the configuration of the reaction unit 102 shown in FIG. Compared with the configuration, the value of the air current collecting layer thickness δ is large. That is, in the configuration of the reaction unit 102 shown in FIG. 14, the value of the second ratio R2 (= δ / γ) is larger than that of the configuration of the reaction unit 102 shown in FIGS. In the configuration of the reaction unit 102 shown in FIG. 14, the value of the protrusion contact portion width γ is relatively small, so that the area of the active layer 220 of the air electrode 114 where the oxidant gas OG is difficult to reach can be reduced. it can. Further, in the configuration of the reaction unit 102 shown in FIG. 14, since the value of the air current collector layer thickness δ is relatively large, the oxidant gas OG that has entered the current collector layer 210 of the air electrode 114 has the Z-axis direction. The moving distance (diffusion distance) in the direction orthogonal to the direction can be made relatively long. In order to supply the oxidant gas OG satisfactorily over the entire thickness direction of the active layer 220 (including the vicinity of the interface between the active layer 220 and the current collecting layer 210), not the air electrode thickness β but the air electrode. It is preferable that the relationship between the current collecting layer thickness δ and the convex portion contact portion width γ (that is, the second ratio R2 (= δ / γ)) satisfies the above requirement. Therefore, as shown in FIG. 14, in the configuration in which the value of the second ratio R2 is relatively large, the region where the oxidant gas OG is difficult to reach is reduced over the entire thickness direction of the active layer 220 of the air electrode 114. It is possible to suppress the decrease in performance by suppressing an increase in gas diffusion polarization.

  FIGS. 15 to 17 conceptually show the relationship between the first ratio R1 (= β / γ) and the performance in the EC mode (labeled “ECmode” in the figure (the same applies to other figures)). It is explanatory drawing shown in. 15 to 17 show a YZ cross-sectional configuration of a part of the reaction unit 102 (X1 portion in FIG. 5). In the configuration of the reaction unit 102 shown in FIG. 15, the value of the convex portion contact portion width γ is larger than the configuration of the reaction unit 102 shown in FIG. 17. Therefore, in the configuration of the reaction unit 102 shown in FIG. 15, the value of the first ratio R1 (= β / γ) is smaller than that in the configuration of the reaction unit 102 shown in FIG. In addition, in the configuration of the reaction unit 102 shown in FIG. 16, the value of the air electrode thickness β is smaller than that in the configuration of the reaction unit 102 shown in FIG. Therefore, in the configuration of the reaction unit 102 shown in FIG. 16, the value of the first ratio R1 (= β / γ) is smaller than that in the configuration of the reaction unit 102 shown in FIG.

Here, in the EC mode, oxygen (O ₂ ) generated in the active layer 220 of the air electrode 114 passes through the current collection layer 210 from the active layer 220 and is exhausted to the air chamber 166, but the current collection layer 210. Of the surface of the current collector 190 is not discharged from the portion in contact with the convex portion 192 of the current collector 190 (that is, the portion corresponding to the convex portion contact portion width γ), and the portion not in contact with the convex portion 192 of the current collector 190 (that is, , The portion corresponding to the shortest distance α between the convex portions). Further, oxygen generated in the active layer 220 flows toward the air chamber 166 along a direction in which the inclination with respect to the Z-axis direction is approximately within a predetermined value θ2. Therefore, a configuration in which the value of the convex contact width γ is relatively large as shown in FIG. 15 or a configuration in which the value of the air electrode thickness β is relatively small as shown in FIG. 16 (that is, the value of the first ratio R1). Is relatively small), the oxygen generated in a part of the region Ax2 in the active layer 220 is less likely to be discharged into the air chamber 166, and the gas pressure is increased inside the air electrode 114, thereby increasing the air electrode 114. As a result, the performance of the reaction unit 102 is lowered.

  On the other hand, in the configuration of the reaction unit 102 shown in FIG. 17, the value of the convex contact portion width γ is smaller than that of the reaction unit 102 shown in FIG. Compared with the configuration, the value of the air electrode thickness β is large. That is, in the configuration of the reaction unit 102 shown in FIG. 17, the value of the first ratio R1 (= β / γ) is larger than that of the configuration of the reaction unit 102 shown in FIGS. In the configuration of the reaction unit 102 shown in FIG. 17, since the value of the convex contact portion width γ is relatively small, the area of the active layer 220 of the air electrode 114 where the generated oxygen is difficult to be discharged into the air chamber 166. Can be reduced. In the configuration of the reaction unit 102 shown in FIG. 17, since the value of the air electrode thickness β is relatively large, the movement distance of oxygen generated in the active layer 220 of the air electrode 114 in the direction orthogonal to the Z-axis direction. (Diffusion distance) can be made relatively long. In order to discharge oxygen generated in the entire thickness direction of the active layer 220 (including the vicinity of the interface between the active layer 220 and the intermediate layer 180), the air current collecting layer thickness δ is It is preferable that the relationship between the air electrode thickness β and the protrusion contact portion width γ (that is, the first ratio R1 (= β / γ)) satisfies the above requirement. Therefore, as shown in FIG. 17, in the configuration in which the value of the first ratio R <b> 1 is relatively large, oxygen generated there is difficult to be discharged into the air chamber 166 over the entire thickness of the active layer 220 of the air electrode 114. The area can be reduced, and the deterioration of the performance can be suppressed by suppressing the separation of the air electrode 114 due to the increase in gas pressure inside the air electrode 114.

  As described above, the evaluation of the samples S2 to S4 in which the first ratio R1 (= β / γ) is less than 0.07 and the second ratio R2 (= δ / γ) is less than 0.06. Considering that the results are inferior to the evaluation results of the samples S5 to S16 in which the first ratio R1 is 0.07 or more and the second ratio R2 is 0.06 or more, the performance improvement of the reaction unit 102 In order to (suppress performance degradation), it can be said that the first ratio R1 is preferably 0.07 or more and the second ratio R2 is preferably 0.06 or more.

(About sample S5)
The evaluation result of sample S5 was the third lowest “D” evaluation in both the FC mode evaluation and the EC mode evaluation. In the sample S5, the porosity RO1 of the current collecting layer 210 of the air electrode 114 is 30% or more, the first ratio R1 (= β / γ) is 0.07 or more, and the second ratio R2 ( = Δ / γ) is 0.06 or more, but the third ratio R3 (= β / α) is less than 0.035, and the samples S6 to S16 (all the third ratio R3 is 0.035 or more). And the fourth ratio R4 (= δ / α) is less than 0.02, and the samples S6 to S16 (all have a fourth ratio R4 of 0.02). It is a lower value than the above. For this reason, it is considered that the performance in the FC mode and the EC mode is lower in the sample S5 than in the samples S6 to S16, as described below.

  18 to 20 are explanatory views conceptually showing the relationship between the fourth ratio R4 (= δ / α) and the performance in the FC mode. 18 to 20 show a YZ cross-sectional configuration of a part of the reaction unit 102 (X1 portion in FIG. 5). In the configuration of the reaction unit 102 shown in FIG. 18, the value of the shortest distance α between the protrusions is larger than that of the reaction unit 102 shown in FIG. Therefore, in the configuration of the reaction unit 102 shown in FIG. 18, the value of the fourth ratio R4 (= δ / α) is smaller than that in the configuration of the reaction unit 102 shown in FIG. Further, in the configuration of the reaction unit 102 shown in FIG. 19, the value of the air electrode current collecting layer thickness δ is smaller than that in the configuration of the reaction unit 102 shown in FIG. Therefore, in the configuration of the reaction unit 102 shown in FIG. 19, the value of the fourth ratio R4 (= δ / α) is smaller than that in the configuration of the reaction unit 102 shown in FIG.

Here, in the FC mode, electrons (e ⁻ ) are exchanged between the current collector layer 210 of the air electrode 114 and the current collector 190. The portion of the current collector 190 that does not contact the convex portion 192 (that is, the portion corresponding to the convex portion contact portion width γ) is not performed in the portion that does not contact the convex portion 192 (that is, the portion corresponding to the shortest distance α between the convex portions). ). Further, the electrons that have entered the current collecting layer 210 of the air electrode 114 are directed toward the active layer 220 that functions as a reaction field in the air electrode 114 along a direction in which the inclination with respect to the Z-axis direction is approximately within a predetermined value θ3. Move. Therefore, a configuration in which the value of the shortest distance α between the protrusions is relatively large as shown in FIG. 18 or a configuration in which the value of the air current collector layer thickness δ is relatively small as shown in FIG. In the configuration in which the value of R4 is relatively small), the activation polarization becomes large because electrons do not easily reach a part of the region Ax3 in the active layer 220 of the air electrode 114. As a result, the performance of the reaction unit 102 is increased. Becomes lower.

  On the other hand, in the configuration of the reaction unit 102 shown in FIG. 20, the value of the shortest distance α between the protrusions is smaller than that of the reaction unit 102 shown in FIG. 18, and the reaction unit 102 shown in FIG. Compared with the configuration, the value of the air current collecting layer thickness δ is large. That is, in the configuration of the reaction unit 102 shown in FIG. 20, the value of the fourth ratio R4 is larger than the configuration of the reaction unit 102 shown in FIGS. In the structure of the reaction unit 102 shown in FIG. 20, since the value of the shortest distance α between the protrusions is relatively small, the area of the active layer 220 of the air electrode 114 that is difficult for electrons to reach can be reduced. In the configuration of the reaction unit 102 shown in FIG. 20, since the value of the air current collector layer thickness δ is relatively large, the electrons that have entered the current collector layer 210 of the air electrode 114 are orthogonal to the Z-axis direction. The moving distance in the direction can be made relatively long. In order to allow electrons to reach the entire active layer 220 in the thickness direction (including the vicinity of the interface between the active layer 220 and the current collecting layer 210), not the air electrode thickness β but the air electrode current collecting layer. It is preferable that the relationship between the thickness δ and the shortest distance α between the protrusions (that is, the fourth ratio R4 (= δ / α)) satisfies the above requirement. Therefore, as shown in FIG. 20, in the configuration in which the value of the fourth ratio R4 is relatively large, it is possible to reduce the region where electrons are difficult to reach over the entire thickness direction of the active layer 220 of the air electrode 114, By suppressing the increase in activation polarization, it is possible to suppress a decrease in performance.

  FIGS. 21 to 23 are explanatory diagrams conceptually showing the relationship between the third ratio R3 (= β / α) and the performance in the EC mode. 21 to 23 show the YZ cross-sectional configuration of a part of the reaction unit 102 (X1 portion in FIG. 5). In the configuration of the reaction unit 102 shown in FIG. 21, the value of the shortest distance α between the protrusions is larger than that of the reaction unit 102 shown in FIG. Therefore, in the configuration of the reaction unit 102 shown in FIG. 21, the value of the third ratio R3 (= β / α) is smaller than that of the configuration of the reaction unit 102 shown in FIG. Further, in the configuration of the reaction unit 102 shown in FIG. 22, the value of the air electrode thickness β is smaller than that of the configuration of the reaction unit 102 shown in FIG. Therefore, in the configuration of the reaction unit 102 shown in FIG. 22, the value of the third ratio R3 (= β / α) is smaller than that in the configuration of the reaction unit 102 shown in FIG.

  Here, in the EC mode, electrons generated in the active layer 220 of the air electrode 114 pass through the current collection layer 210 from the active layer 220 and enter the current collector 190. The exchange of electrons with the body 190 is not performed in the portion of the surface of the current collecting layer 210 that does not contact the convex portion 192 of the current collector 190 (that is, the portion corresponding to the shortest distance α between the convex portions). This is performed at a portion in contact with the convex portion 192 of the current collector 190 (ie, a portion corresponding to the convex portion contact portion width γ). Electrons generated in the active layer 220 flow toward the current collector 190 along a direction in which the inclination with respect to the Z-axis direction is approximately within a predetermined value θ4. Therefore, a configuration in which the value of the shortest distance between projections α is relatively large as shown in FIG. 21 or a configuration in which the value of the air electrode thickness β is relatively small as shown in FIG. 22 (that is, the value of the third ratio R3). Is relatively small), the electrons generated in a part of the region Ax4 in the active layer 220 are less likely to reach the convex portion 192 of the current collector 190, thereby increasing the activation polarization. The performance of the unit 102 is lowered.

  On the other hand, in the configuration of the reaction unit 102 shown in FIG. 23, the value of the shortest distance between convex portions α is smaller than that of the configuration of the reaction unit 102 shown in FIG. 21, and the reaction unit 102 shown in FIG. Compared with the configuration, the value of the air electrode thickness β is large. That is, in the configuration of the reaction unit 102 shown in FIG. 23, the value of the third ratio R3 (= β / α) is larger than that in the configuration of the reaction unit 102 shown in FIGS. In the structure of the reaction unit 102 shown in FIG. 23, the value of the shortest distance α between the convex portions is relatively small, so that the electrons generated in the active layer 220 of the air electrode 114 reach the convex portion 192 of the current collector 190. It is possible to reduce the area of the region that is difficult to perform. In the configuration of the reaction unit 102 shown in FIG. 23, since the value of the air electrode thickness β is relatively large, the movement distance of electrons generated in the active layer 220 of the air electrode 114 in the direction orthogonal to the Z-axis direction. Can be made relatively long. In order to satisfactorily reach the generated electrons 192 of the current collector 190 over the entire thickness of the active layer 220 (including the vicinity of the interface between the active layer 220 and the intermediate layer 180), It is preferable that the relationship between the air electrode thickness β, not the air electrode current collecting layer thickness δ, and the shortest distance α between the protrusions (that is, the third ratio R3 (= β / α)) satisfies the above requirement. Therefore, as shown in FIG. 23, in the configuration in which the value of the third ratio R3 is relatively large, the electrons generated there over the entire thickness direction of the active layer 220 of the air electrode 114 are the convex portions of the current collector 190. The region where it is difficult to reach 192 can be reduced, and a decrease in performance can be suppressed by suppressing an increase in activation polarization.

  As described above, the evaluation result of the sample S5 in which the third ratio R3 (= β / α) is less than 0.035 and the fourth ratio R4 (= δ / α) is less than 0.02. In consideration of being inferior to the evaluation results of the samples S6 to S16 in which the third ratio R3 is 0.035 or more and the fourth ratio R4 is 0.02 or more, further improvement in the performance of the reaction unit 102 ( In order to suppress performance degradation, it can be said that the third ratio R3 is preferably 0.035 or more and the fourth ratio R4 is preferably 0.02 or more.

(About samples S6 to S8)
The evaluation results of samples S6 to S8 were the fourth lowest (ie, third highest) “C” evaluation in both the FC mode evaluation and the EC mode evaluation (however, in the sample S6 EC mode evaluation) Is rated “D”). In samples S6 to S8, the porosity RO1 of the current collecting layer 210 of the air electrode 114 is 30% or more, the first ratio R1 (= β / γ) is 0.07 or more, and the second ratio R2 ( = Δ / γ) is 0.06 or more, the third ratio R3 (= β / α) is 0.035 or more, and the fourth ratio R4 (= δ / α) is 0.02 or more. It is. However, in the samples S6 and S8, the first ratio R1 exceeds 0.16, which is an excessively high value compared to the samples S9 to S16 (both of which the first ratio R1 is 0.16 or less). It has become. Further, in samples S6 and S7, the second ratio R2 exceeds 0.14, which is an excessively high value compared to samples S9 to S16 (both of which the second ratio R2 is 0.14 or less). It has become.

  That the first ratio R1 (= β / γ) is excessively high means that the value of the air electrode thickness β is excessively large and / or that the value of the convex portion contact width γ is excessively small. means. If the value of the air electrode thickness β is excessively large, the oxygen discharge path from each position (including the vicinity of the interface with the intermediate layer 180) of the active layer 220 in the EC mode to the air chamber 166 becomes excessively long. As a result of the pressure applied to the electrode 114, the air electrode 114 is peeled off. As a result, the performance is lowered, and the amount of material used to form the air electrode 114 is increased, and the electrochemical reaction cell stack 100 is driven. Even in a state where the air electrode 114 is not, the possibility of the interface peeling between the air electrode 114 and other layers is increased. In addition, if the value of the protrusion contact portion width γ is excessively small, the contact area between the air electrode 114 and the current collector 190 is excessively small, and stress is concentrated to cause the air electrode 114 to be damaged. , Performance decreases.

  Further, the second ratio R2 (= δ / γ) being excessively high means that the value of the air electrode current collecting layer thickness δ is excessively large and / or the value of the convex portion contact portion width γ is large. Means it is too small. When the value of the air electrode current collecting layer thickness δ is excessively large, the diffusion path of the oxidant gas OG from the air chamber 166 to each position of the active layer 220 (including the vicinity of the interface with the current collecting layer 210) in the FC mode. Is excessively long, resulting in an increase in gas diffusion polarization. As a result, the performance is lowered, and the amount of material used to form the current collecting layer 210 is increased, and the interface between the current collecting layer 210 and other layers is increased. Causes increased possibility of delamination. Further, as described above, if the value of the convex contact portion width γ is excessively small, the contact area between the air electrode 114 and the current collector 190 becomes excessively small, so stress concentrates and the air electrode 114 is damaged. Resulting in poor performance.

  For at least one of the reasons described above, it is considered that the performance of the samples S6 to S8 is low in at least one of the FC mode and the EC mode. The evaluation results of the samples S6 to S8 that do not satisfy the requirement that the first ratio R1 is 0.16 or less and the second ratio R2 is 0.14 or less indicate that the first ratio R1 is 0.16. In consideration of being inferior to the evaluation results of the samples S9 to S16 that satisfy the requirement that the second ratio R2 is equal to or less than 0.14, the performance of the reaction unit 102 is further improved (suppression of performance degradation). It can be said that the first ratio R1 is preferably 0.16 or less and the second ratio R2 is preferably 0.14 or less.

(About samples S9 to S11)
The evaluation results of samples S9 to S11 were the fifth lowest (ie second highest) “B” evaluation in both FC mode evaluation and EC mode evaluation (however, in sample S9 EC mode) (C rating). In samples S9 to S11, the porosity RO1 of the current collecting layer 210 of the air electrode 114 is 30% or more, the first ratio R1 (= β / γ) is 0.07 or more and 0.16 or less, 2 ratio R2 (= δ / γ) is 0.06 or more and 0.14 or less, the third ratio R3 (= β / α) is 0.035 or more, and the fourth ratio R4 ( = Δ / α) is 0.02 or more. However, in the sample S9, the third ratio R3 is less than 0.05, which is a lower value than the samples S12 to S16 (all the third ratio R3 is 0.05 or more). Further, in the samples S10 and S11, the fourth ratio R4 is less than 0.04, which is a lower value than the samples S12 to S16 (both the fourth ratio R4 is 0.04 or more). .

  As described above, the larger the value of the third ratio R3, the smaller the region of the active layer 220 of the air electrode 114 in which electrons generated there are less likely to reach the convex portion 192 of the current collector 190 in the EC mode. It is possible to suppress the decrease in performance by suppressing the increase in activation polarization. Further, as described above, as the value of the fourth ratio R4 is larger, in the FC mode, it is possible to reduce the region where the electrons are less likely to reach in the active layer 220 of the air electrode 114, and increase the activation polarization. By suppressing it, the performance degradation can be suppressed. Evaluation results of samples S9 to S11 that do not satisfy the requirement that the third ratio R3 is 0.05 or more and the fourth ratio R4 is 0.04 or more show that the third ratio R3 is 0.05. Considering that the evaluation results of the samples S12 to S16 that satisfy the above requirement and the fourth ratio R4 is 0.04 or more are considered, the performance of the reaction unit 102 is further improved (suppression of performance degradation). Therefore, it can be said that the third ratio R3 is preferably 0.05 or more and the fourth ratio R4 is preferably 0.04 or more.

(About sample S12)
The evaluation result of the sample S12 was the “B” evaluation that is the fifth lowest (that is, the second highest) in the EC mode (however, the evaluation in the FC mode is “A” evaluation). In the sample S12, the porosity RO1 of the current collecting layer 210 of the air electrode 114 is 30% or more, the first ratio R1 (= β / γ) is 0.07 or more and 0.16 or less, and the second The ratio R2 (= δ / γ) is 0.06 or more and 0.14 or less, the third ratio R3 (= β / α) is 0.05 or more, and the fourth ratio R4 (= δ / Α) is 0.04 or more. However, in the sample S12, the third ratio R3 exceeds 0.13, which is an excessively high value compared to the samples S13 to S16 (all the third ratio R3 is 0.13 or less). Yes. Further, in the sample S12, the fourth ratio R4 exceeds 0.12, which is an excessively high value compared with the samples S13 to S16 (all of which the fourth ratio R4 is 0.12 or less). Yes.

  If the third ratio R3 (= β / α) is excessively high, it means that the value of the air electrode thickness β is excessively large and / or the value of the shortest distance α between the convex portions is excessively small. means. If the value of the air electrode thickness β is excessively large, the oxygen discharge path from each position (including the vicinity of the interface with the intermediate layer 180) of the active layer 220 in the EC mode to the air chamber 166 becomes excessively long. As a result of the pressure applied to the electrode 114, the air electrode 114 is peeled off. As a result, the performance is lowered, and the amount of material used to form the air electrode 114 is increased, and the electrochemical reaction cell stack 100 is driven. Even in a state where the air electrode 114 is not, the possibility of the interface peeling between the air electrode 114 and other layers is increased. In addition, if the value of the shortest distance α between the protrusions is excessively small, the area of the current collector layer 210 of the air electrode 114 that is not covered with the protrusions 192 of the current collector 190 is excessively small. Sometimes oxygen generated in the active layer 220 is not well discharged into the air chamber 166, and pressure is applied to the air electrode 114 to cause separation of the air electrode 114, resulting in poor performance.

  Further, the fourth ratio R4 (= δ / α) being excessively high means that the value of the air electrode current collecting layer thickness δ is excessively large and / or the value of the shortest distance α between the convex portions is large. Means it is too small. As described above, if the value of the shortest distance α between the protrusions is excessively small, oxygen generated in the active layer 220 during the EC mode is not discharged well into the air chamber 166, and the air electrode 114 is pressurized and pressure is applied. The pole 114 peels off, resulting in poor performance.

  For at least one of the reasons described above, it is considered that the performance in the EC mode is low in the sample S12. The evaluation result of the sample S12 that does not satisfy the requirement that the third ratio R3 is 0.13 or less and the fourth ratio R4 is 0.12 or less is that the third ratio R3 is 0.13 or less. In view of being inferior to the evaluation results of the samples S13 to S16 that satisfy the requirement that the fourth ratio R4 is 0.12 or less, for further performance improvement of the reaction unit 102 (suppression of performance degradation) It can be said that the third ratio R3 is preferably 0.13 or less and the fourth ratio R4 is preferably 0.12 or less.

(Summary of performance evaluation results)
Referring to the performance evaluation results described above, the porosity RO1 of the current collecting layer 210 of the air electrode 114 is 30% or more to improve the performance of the reaction unit 102 (suppression of performance degradation), and the first ratio R1 (ratio of air electrode thickness β to convex contact width γ (β / γ)) is 0.07 or more, and second ratio R2 (air electrode current collecting layer to convex contact width γ) The ratio of thickness δ (δ / γ)) is preferably 0.06 or more, and the third ratio R3 (ratio of air electrode thickness β to shortest distance α between projections (β / α)) is 0. It is more preferable that the fourth ratio R4 (ratio of the air electrode current collecting layer thickness δ to the shortest distance α between the protrusions (δ / α)) is 0.02 or more. More preferably, the ratio R1 of 1 is 0.16 or less, and the second ratio R2 is 0.14 or less, and the third ratio 3 is 0.05 or more, and the fourth ratio R4 is more preferably 0.04 or more, the third ratio R3 is 0.13 or less, and the fourth ratio R4 is 0. It can be said that it is most preferable that it is 12 or less.

A-4. Method for specifying the porosity of each layer of the air electrode 114:
The porosity RO1 of the current collecting layer 210 of the air electrode 114 described above is specified by “Mitani Kaoru” “Ceramic Processing” (Gihodo Publishing) p. Referring to the description of 193-195, the following method was used (see FIG. 24). First, in the reaction unit 102 (single cell 110), they are arranged along the flow direction of the gas (oxidant gas OG or oxygen) in the air chamber 166 (X-axis direction in this embodiment as shown in FIGS. 4 and 6). Cross sections (YZ cross section in the present embodiment) that are substantially orthogonal to the flow direction are set at any three positions, and the current collector 190 side of the current collector layer 210 of the air electrode 114 is at any three positions in each cross section. The SEM image (5000 times) in FIB-SEM (acceleration voltage 1.5 kV) where the part containing the surface of this was reflected is obtained. That is, nine SEM images are obtained. In each SEM image, five virtual straight lines VL (VL11 to VL15) orthogonal to the Z-axis direction are set at intervals of 1 μm near the surface of the current collecting layer 210 of the air electrode 114 on the current collector 190 side. In each of the five virtual straight lines VL, the length of each portion corresponding to the pore is measured, and the ratio of the total length of each portion corresponding to the pore to the entire length of the virtual straight line VL is the porosity on the virtual straight line VL. . The average value of the porosity on all the virtual straight lines VL set in all the SEM images is defined as the porosity RO1 of the current collecting layer 210 of the air electrode 114.

  Similarly, the porosity RO2 of the active layer 220 of the air electrode 114 was specified according to the following method (see FIG. 24). First, in the reaction unit 102 (single cell 110), the flow at any three positions aligned along the flow direction (X-axis direction in the present embodiment) of the gas (oxidant gas OG or oxygen) in the air chamber 166. A cross section (YZ cross section in the present embodiment) that is substantially orthogonal to the direction is set, and a portion including the surface of the active layer 220 of the air electrode 114 on the electrolyte layer 112 side (intermediate layer 180 side) at any three positions in each cross section SEM image (5000 times) in FIB-SEM (acceleration voltage 1.5 kV) in which is shown. That is, nine SEM images are obtained. In each of the SEM images, five virtual straight lines VL (VL21 to VL25) orthogonal to the Z-axis direction are arranged at 1 μm intervals near the surface of the active layer 220 of the air electrode 114 on the electrolyte layer 112 side (intermediate layer 180 side). Set. The surface of the active layer 220 of the air electrode 114 on the electrolyte layer 112 side (intermediate layer 180 side) is a component of the constituent material of the active layer 220 of the air electrode 114 and the electrolyte layer 112 or the intermediate layer 180 in each SEM image. It can be specified based on differences. In each of the five virtual straight lines VL, the length of each portion corresponding to the pore is measured, and the ratio of the total length of each portion corresponding to the pore to the entire length of the virtual straight line VL is the porosity on the virtual straight line VL. . Let the average value of the porosity on all the virtual straight lines VL set in all the SEM images be the porosity RO2 of the active layer 220 of the air electrode 114.

B. Variations:
The technology disclosed in the present specification is not limited to the above-described embodiment, and can be modified into various forms without departing from the gist thereof. For example, the following modifications are possible.

  The configuration of the single cell 110, the reaction unit 102, or the electrochemical reaction cell stack 100 in the above embodiment is merely an example, and various modifications can be made. For example, in the above-described embodiment, the air electrode 114 has a two-layer structure, but the air electrode 114 may be formed of three or more layers of different constituent materials.

  In the above embodiment, the single cell 110 includes the intermediate layer 180, but the single cell 110 does not necessarily include the intermediate layer 180. In the above embodiment, the interconnector 150 and the air electrode side current collector 134 (current collector element 135) are integrated members, but the interconnector 150 and the air electrode side current collector 134 are separate members. May be.

  In the above embodiment, the air electrode side current collector 134 (current collector element 135) is covered with the coat 136, but the air electrode side current collector 134 may not be covered with the coat 136. In such a configuration, the current collector 190 does not include the coat 136. In the above embodiment, the air electrode side current collector 134 (covered by the coat 136) (the current collector element 135) is in contact with the air electrode 114 via the bonding layer 138. The body 134 may be in contact with the air electrode 114 without using the bonding layer 138. In such a configuration, the current collector 190 does not include the bonding layer 138.

  FIG. 25 is an explanatory diagram schematically showing a configuration in the vicinity of the current collector 190 in a modified example. In the modification shown in FIG. 25, the porosity of the bonding layer 138 is relatively high, for example, 30% to 45%, and the bonding layer 138 continuously covers the surface of the air electrode 114. In the modification shown in FIG. 25, the bonding layer 138 plays a role of current collection and gas diffusion, and thus is functionally part of the “air electrode (first air electrode layer)”. Therefore, in the modification shown in FIG. 25, the integrated member of the interconnector 150 and the air electrode side current collector 134 (current collector element 135) and the coat 136 function as the current collector 190, and the current collector Among the body 190, a plurality of portions composed of the current collector elements 135 covered with the coat 136 are convex portions 192 that are in contact with the upper surface of the first air electrode layer (current collection layer 210 + bonding layer 138). Function. In the modification shown in FIG. 25, the air electrode thickness β is the thickness of the thinnest part of the air electrode (air electrode 114 + bonding layer 138) that is in contact with the convex portion 192 of the current collector 190. The thickness δ of the air electrode current collecting layer is the thickness of the thinnest portion of the first air electrode layer (current collecting layer 210 + joining layer 138) in the portion in contact with the convex portion 192 of the current collector 190. In the modification shown in FIG. 25, the convex contact portion width γ and the shortest inter-convex distance α are the convex portions of the current collector 190 in the first air electrode layer (current collection layer 210 + joining layer 138). It is specified on an imaginary straight line VL1 that is located at a distance Lx (= 10 μm) from the upper end of the thinnest portion in the portion that contacts 192 and is orthogonal to the Z-axis direction.

In addition, it is preferable that the shortest distance α between the convex portions, the air electrode thickness β, the convex portion contact portion width γ, and the air electrode current collecting layer thickness δ described above are in the following ranges, respectively.
・ 1000μm ≦ shortest distance between protrusions α ≦ 2000μm
・ 30μm ≦ Air electrode thickness β ≦ 200μm
・ 300 μm ≤ convex contact part width γ ≤ 2000 μm
・ 20μm ≦ Cathode current collecting layer thickness δ ≦ 190μm

  Moreover, in the said embodiment, the number of the single cells 110 (reaction unit 102) contained in the electrochemical reaction cell stack 100 is an example to the last, and the number of the single cells 110 (reaction unit 102) is the electrochemical reaction cell stack 100. It is determined as appropriate according to the output voltage and the amount of hydrogen generation required. Moreover, the material which comprises each member in the said embodiment is an illustration to the last, and each member may be comprised with the other material.

  Further, the structural requirements for improving the performance of the reaction unit 102 described in the above embodiment (suppressing the performance degradation) (for example, the porosity RO1 of the current collecting layer 210 of the air electrode 114 is 30% or more, and the first The ratio R1 (= β / γ) is 0.07 or more and the second ratio R2 (δ / γ) is 0.06 or more) does not necessarily constitute the electrochemical reaction cell stack 100. It does not have to be filled in all of the plurality of reaction units 102, but may be filled in at least one of the plurality of reaction units 102 constituting the electrochemical reaction cell stack 100. Further, when focusing on one reaction unit 102, the constituent requirement does not necessarily have to be satisfied in all of the plurality of protrusions 192 included in the current collector 190, and the plurality of protrusions included in the current collector 190. It is sufficient that at least one of the portions 192 is satisfied. In addition, in order to effectively improve the performance of the reaction unit 102 (suppression of performance degradation), the above-described structural requirements are satisfied in 30% or more of the convex portions 192 among all the convex portions 192 included in the current collector 190. It is more preferable that 50% or more of the projections 192 satisfy the above-described configuration requirements, 70% or more of the projections 192 preferably satisfy the above-described configuration requirements, and 90% or more. It is more preferable that the above-mentioned constituent requirements are satisfied in the convex portion 192, and it is most preferable that the above-described constituent requirements are satisfied in 100% of the convex portions 192. The convex portion 192 that satisfies the constituent elements corresponds to the specific convex portion in the claims.

  In the above embodiment, a so-called reversible electrochemical reaction cell stack has been described as an example. Generally, a fuel cell stack can also be used as an electrolysis cell stack because of its configuration. Since it can be used as a fuel cell stack in terms of configuration, the present invention is not limited to the “reversible type”, and a general fuel cell stack (fuel cell power generation unit) and an electrolysis cell stack (electrolysis cell) (Unit).

In the above embodiment, the solid oxide fuel cell (SOFC) has been described as an example. However, the present invention is applicable to other types of fuel cells (or electrolytic cells) such as a molten carbonate fuel cell (MCFC). Applicable.

22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 28: Body portion 29: Branch portion 100: Electrochemical reaction cell stack 102: Electrochemical reaction unit 104: End plate 106: End plate 108: Communication hole 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 121: Hole 124: Joint part 130: Air electrode side frame 131: Hole 132: Oxidant gas supply communication hole 133: Oxidant gas discharge communication hole 134 : Air electrode side current collector 135: Current collector element 136: Coat 138: Bonding layer 140: Fuel electrode side frame 141: Hole 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144: Fuel electrode side current collection Body 145: Electrode facing portion 146: Interconnector facing portion 147: Connection 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 190: Current collector 192: Convex part 210: Current collecting layer 220: Active layer

Claims (7)

An electrolyte layer, a fuel electrode disposed on one side in a first direction with respect to the electrolyte layer, and an air electrode disposed on the other side in the first direction with respect to the electrolyte layer, A first air electrode layer constituting the surface of the other side of the air electrode in the first direction; a second air electrode layer disposed between the first air electrode layer and the electrolyte layer; An electrochemical reaction unit cell comprising: the air electrode comprising:
A conductive current collector having a plurality of convex portions in contact with the surface on the other side in the first direction in the first air electrode layer;
In an electrochemical reaction unit comprising:
The porosity of the first air electrode layer is 30% or more,
For the specific convex portion that is at least one of the plurality of convex portions, the width γ of the portion of the specific convex portion that is in contact with the first air electrode layer in the second direction orthogonal to the first direction The first ratio (β / γ), which is the ratio of the thickness β of the air electrode in the first direction, is 0.07 or more and the width γ with respect to the first direction. The electrochemical reaction unit, wherein the second ratio (δ / γ), which is the ratio of the thickness δ of the first air electrode layer, is 0.06 or more. The electrochemical reaction unit according to claim 1,
For the specific convex portion, the thickness of the air electrode in the first direction with respect to the shortest distance α between the specific convex portion in the second direction and the convex portion located next to the specific convex portion. The third ratio (β / α) which is the ratio of β is 0.035 or more, and the ratio of the thickness δ of the first air electrode layer in the first direction to the shortest distance α. The electrochemical reaction unit, wherein the fourth ratio (δ / α) is 0.02 or more. The electrochemical reaction unit according to claim 2,
Regarding the specific convex portion, the first ratio (β / γ) is 0.16 or less, and the second ratio (δ / γ) is 0.14 or less. , Electrochemical reaction unit. The electrochemical reaction unit according to claim 3,
For the specific convex portion, the third ratio (β / α) is 0.05 or more, and the fourth ratio (δ / α) is 0.04 or more. , Electrochemical reaction unit. The electrochemical reaction unit according to claim 4,
For the specific convex portion, the third ratio (β / α) is 0.13 or less, and the fourth ratio (δ / α) is 0.12 or less. , Electrochemical reaction unit. In the electrochemical reaction unit according to any one of claims 1 to 5,
The porosity of the other side portion in the first direction of the air electrode is higher than the porosity of the one side portion in the first direction of the air electrode. . In an electrochemical reaction cell stack comprising a plurality of electrochemical reaction units arranged side by side in the first direction,
The electrochemical reaction cell stack according to claim 1, wherein at least one of the plurality of electrochemical reaction units is the electrochemical reaction unit according to claim 1.

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