JP2018195414A - Electrochemical reaction single cell, electrochemical reaction cell stack, and method for producing electrochemical reaction single cell - Google Patents

Abstract

A solid oxide fuel cell (SOFC) suppresses an increase in IR resistance due to an excessively large thickness of an electrolyte layer, while suppressing gas leakage due to a decrease in the density of the electrolyte layer. Provided is an electrochemical reaction cell that suppresses the deterioration of the performance of the electrochemical reaction single cell. An electrochemical reaction single cell, an electrolyte layer containing a solid oxide, a porous fuel electrode arranged on one side of the electrolyte layer in a first direction, and a first electrode of the electrolyte layer 112. And a porous air electrode 114 disposed on the other side in the direction, and the surface roughness Rz of the surface of the specific electrode, which is one of the fuel electrode 116 and the air electrode 114, facing the electrolyte layer 112 is 30 μm or less. An electrochemical reaction cell. An electrochemical reaction cell in which the aperture ratio of a portion of the specific electrode on the electrolyte 112 side is less than 5 to 35%. The electrolyte layer 112 is an electrochemical cell including yttria-stabilized zirconia as a solid oxide and having a thickness of 20 μm or less. [Selection diagram] Fig. 6

Description

  The technology disclosed by the present specification relates to an electrochemical reaction unit cell.

  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 single cell (hereinafter referred to as “single cell”) which is a constituent unit of SOFC includes an electrolyte layer containing a solid oxide such as yttria-stabilized zirconia (hereinafter referred to as “YSZ”), and one side of the electrolyte layer. And a porous air electrode disposed on the other side of the electrolyte layer.

  The electrolyte layer is formed, for example, by firing a paste for the electrolyte layer. Alternatively, the electrolyte layer is formed by performing film formation by a vapor phase method such as a sputtering process using a fuel electrode or an air electrode as a base layer (see, for example, Non-Patent Document 1).

Tomoaki Miichi and two others, “Preparation of Solid Oxide Fuel Cell by High Frequency Magnetron Sputtering Method—Dependence on Annealing Temperature of Single Cell”, J. Vac. Soc. Jpn. (Vacuum), February 14, 2004, Vol. 47, no. 3, 2004, p. 128 (36) -131 (39)

  In a single cell, when the thickness of the electrolyte layer is increased, the IR resistance of the electrolyte layer is increased and the performance of the single cell is lowered. Therefore, it is not preferable that the thickness of the electrolyte layer is excessive. However, when the electrolyte layer is made thin, the density of the electrolyte layer is reduced due to the occurrence of a defective portion in the electrolyte layer, etc., and there is a possibility that gas leak occurs and the performance of the single cell is lowered. As described above, the conventional technique has room for improvement in terms of suppressing the deterioration of the performance of the single cell due to the increase in IR resistance and the occurrence of gas leak.

 Such a problem is also a problem common to electrolytic single cells, which are constituent units of solid oxide electrolytic cells (hereinafter referred to as “SOEC”) that generate hydrogen using an electrolysis reaction of water. It is. In the present specification, the fuel cell unit cell and the electrolysis unit cell are collectively referred to as an electrochemical reaction unit cell.

  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) An electrochemical reaction unit cell disclosed in this specification includes an electrolyte layer containing a solid oxide, a porous fuel electrode disposed on one side in a first direction of the electrolyte layer, and the electrolyte. An electrochemical reaction unit cell comprising a porous air electrode disposed on the other side of the first direction of the layer, facing the electrolyte layer in a specific electrode that is one of the fuel electrode and the air electrode The surface roughness Rz of the surface is 30 μm or less. According to the present electrochemical reaction single cell, since the surface roughness Rz of the surface of the specific electrode facing the electrolyte layer is relatively small, the surface of the specific electrode has a relatively low height of the convex portion, and The depth of the recess is a relatively shallow surface. Therefore, in this electrochemical reaction single cell, it is possible to suppress a decrease in denseness due to the occurrence of a defective portion in the electrolyte layer without excessively increasing the thickness of the electrolyte layer. Therefore, according to the present electrochemical reaction single cell, while suppressing an increase in IR resistance due to an excessive increase in the thickness of the electrolyte layer, it is possible to suppress the occurrence of gas leak due to a decrease in the density of the electrolyte layer. As a result, it can suppress that the performance of an electrochemical reaction single cell falls.

(2) The electrochemical reaction single cell may have a configuration in which the opening ratio of the portion on the electrolyte layer side of the specific electrode is higher than 5% and lower than 35%. If the aperture ratio of the portion on the electrolyte layer side of the specific electrode is excessively high, there is a possibility that a defect portion is formed in the electrolyte layer and the denseness is lowered and gas leakage occurs. On the other hand, if the aperture ratio of the portion on the electrolyte layer side of the specific electrode is excessively low, the gas diffusion resistance of the specific electrode may increase. According to the present electrochemical reaction single cell, it is possible to avoid that the opening ratio of the portion on the electrolyte layer side of the specific electrode becomes excessively high or excessively low, and as a result, the performance of the electrochemical reaction single cell. Can be suppressed.

(3) In the electrochemical reaction single cell, the electrolyte layer may include yttria-stabilized zirconia (YSZ) as the solid oxide. According to the present electrochemical reaction unit cell, the electrolyte layer containing YSZ can ensure the denseness of the electrolyte layer while suppressing the electrolyte layer from becoming excessively thick. It can suppress that the performance of this falls.

(4) In the electrochemical reaction single cell, the thickness of the electrolyte layer in the first direction may be 20 μm or less. According to this electrochemical reaction single cell, it is possible to suppress an increase in IR resistance due to an excessively thick electrolyte layer, and as a result, the performance of the single electrochemical reaction single cell is improved. It can suppress that it falls.

(5) In the electrochemical reaction single cell, the growth direction of the particles in the electrolyte layer is a direction having an inclination angle of 75 degrees or more and 90 degrees or less with respect to the surface of the specific electrode facing the electrolyte layer. It is good also as a certain structure. When the inclination angle of the particle growth direction in the electrolyte layer with respect to the surface of the specific electrode facing the electrolyte layer is excessively small, the movement of oxygen ions in the first direction in the electrolyte layer is inhibited by the grain boundaries in the electrolyte layer, There is a possibility that the oxygen ion transport efficiency is lowered and the performance of the electrochemical reaction single cell is lowered. According to the present electrochemical reaction single cell, it is possible to avoid an excessively small inclination angle of the growth direction of the particles in the electrolyte layer with respect to the surface of the specific electrode facing the electrolyte layer. It can suppress that the performance of a single cell falls.

(6) In the above electrochemical reaction single cell, the full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement using the CoKα ray for the electrolyte layer may be 0.2 deg or less. According to this electrochemical reaction unit cell, when this FWHM is excessively large, particles constituting the electrolyte layer are excessively small, the oxygen ion transport efficiency in the electrolyte layer is reduced, and the performance of the electrochemical reaction unit cell is reduced. May decrease. According to this electrochemical reaction single cell, it can avoid that this FWHM becomes large too much, As a result, it can suppress that the performance of an electrochemical reaction single cell falls.

(7) The electrochemical reaction unit cell may further include a porous metal support that is disposed on the side opposite to the electrolyte layer with respect to the specific electrode and supports the electrochemical reaction unit cell. Good. According to this electrochemical reaction single cell, it is possible to ensure the denseness of the electrolyte layer while suppressing an excessively thick electrolyte layer formed on the specific electrode supported by the metal support. It can suppress that the performance of an electrochemical reaction single cell falls.

(8) An electrochemical reaction cell stack disclosed in the present specification is an electrochemical reaction cell stack including a plurality of electrochemical reaction unit cells arranged side by side in the first direction. At least one of the cells is the above electrochemical reaction single cell. According to this electrochemical reaction cell stack, it is possible to suppress a decrease in the performance of at least one electrochemical reaction single cell included in the electrochemical reaction cell stack.

(9) A method for producing an electrochemical reaction unit cell disclosed in the present specification includes an electrolyte layer containing a solid oxide, and a porous fuel electrode disposed on one side in the first direction of the electrolyte layer. A specific electrode that is one of the fuel electrode and the air electrode in a method for producing an electrochemical reaction single cell comprising a porous air electrode disposed on the other side of the electrolyte layer in the first direction. A step of preparing the specific electrode having a surface roughness Rz of 30 μm or less, a step of forming the electrolyte layer on the surface of the specific electrode by a vapor phase method, Forming the other electrode of the fuel electrode and the air electrode on a side opposite to the side facing the specific electrode of the electrolyte layer. In this method for producing an electrochemical reaction single cell, when an electrolyte layer is formed on the one surface of a specific electrode by a vapor phase method, a defect portion is not formed in the electrolyte layer without excessively increasing the thickness of the electrolyte layer. It is possible to suppress the reduction of the denseness due to the occurrence of the above. Therefore, according to the manufacturing method of the electrochemical reaction single cell, the increase in the IR resistance due to the excessive increase in the thickness of the electrolyte layer is suppressed, and the occurrence of gas leak due to the decrease in the denseness of the electrolyte layer is prevented. As a result, it can suppress that the performance of an electrochemical reaction single cell falls.

(10) In the method for manufacturing an electrochemical reaction single cell, the gas phase method may be a sputtering process. In the sputtering process, the energy of the particles forming the film is larger than that in other vapor phase methods such as vapor deposition. Therefore, according to the method for manufacturing an electrochemical reaction single cell, an electrolyte layer having strong adhesion to the surface of a specific electrode can be formed, and as a result, the denseness of the electrolyte layer can be more reliably ensured. It can suppress more effectively that the performance of an electrochemical reaction single cell falls.

  The technology disclosed in this specification can be realized in various forms. For example, an electrochemical reaction single cell (fuel cell single cell or electrolytic single cell), a plurality of electrochemical reaction single cells It can be realized in the form of an electrochemical reaction cell stack (fuel cell stack or electrolytic cell stack), a manufacturing method thereof, and the like.

1 is a perspective view showing an external configuration of a fuel cell stack 100 in a first embodiment. It is explanatory drawing which shows the XZ cross-section structure of the fuel cell stack 100 in the position of II-II of FIG. FIG. 3 is an explanatory diagram showing a YZ cross-sectional configuration of a fuel cell stack 100 at a position of III-III in FIG. 1. It is explanatory drawing which shows XZ cross-section structure of the two electric power generation units 102 adjacent to each other in the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross-section structure of the two electric power generation units 102 adjacent to each other in the same position as the cross section shown in FIG. 2 is an explanatory diagram showing a detailed configuration of an interface of a fuel electrode 116, an electrolyte layer 112, and an air electrode 114 in a single cell 110. FIG. 3 is an explanatory diagram showing a configuration of an electrolyte layer 112 of a single cell 110. FIG. It is explanatory drawing which shows the result of the XRD measurement which made the electrolyte layer 112 of the single cell 110 object. It is explanatory drawing which shows an example of the manufacturing method of the single cell 110 in 1st Embodiment. It is a perspective view which shows the external appearance structure of the electrolytic cell stack 100a in 2nd Embodiment. It is explanatory drawing which shows the XZ cross-section structure of the electrolytic cell stack 100a in the position of XI-XI of FIG. It is explanatory drawing which shows the YZ cross-section structure of the electrolytic cell stack 100a in the position of XII-XII of FIG. It is explanatory drawing which shows the XZ cross-section structure of the two electrolysis units 102a adjacent to each other in the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross-section structure of the two electrolysis units 102a adjacent to each other in the same position as the cross section shown in FIG. It is explanatory drawing which shows an example of the manufacturing method of the single cell 110a in 2nd Embodiment. It is explanatory drawing which shows the result of gas leak characteristic evaluation. It is explanatory drawing which shows the result of electrical property evaluation.

A. First embodiment:
A-1. Device configuration:
(Configuration of fuel cell stack 100)
As a first embodiment of the present invention, the case where the present invention is applied to a single fuel cell 110 constituting a fuel cell stack 100 will be described. FIG. 1 is a perspective view showing an external configuration of the fuel cell stack 100 in the first embodiment, and FIG. 2 is an explanatory diagram showing an XZ cross-sectional configuration of the fuel cell stack 100 at a position II-II in FIG. FIG. 3 is an explanatory view showing a YZ cross-sectional configuration of the fuel cell stack 100 at the position of III-III in FIG. In each figure, XYZ axes orthogonal to each other for specifying the direction are shown. In this specification, for the sake of convenience, the positive direction of the Z axis is referred to as the upward direction, and the negative direction of the Z axis is referred to as the downward direction. However, the fuel cell stack 100 is actually different from such an orientation. It may be installed. The same applies to FIG. In this specification, a direction perpendicular to the Z-axis direction is referred to as a plane direction.

  The fuel cell stack 100 includes a plurality (seven in this embodiment) of fuel cell power generation units (hereinafter simply referred to as “power generation units”) 102 and a pair of end plates 104 and 106. The seven power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in the present embodiment). The pair of end plates 104 and 106 are arranged so as to sandwich an assembly composed of seven power generation units 102 from above and below. The arrangement direction (vertical direction) corresponds to the first direction in the claims.

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

  Bolts 22 extending in the vertical direction are inserted into the communication holes 108, and the fuel 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 fuel cell stack 100, and the bolt An insulating sheet 26 is interposed between the nut 24 fitted on the other side (lower side) of 22 and the lower surface of the end plate 106 constituting the lower end of the fuel 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 fuel cell stack 100 is located near the midpoint of one side (the X-axis positive direction side of two sides parallel to the Y-axis) on the outer periphery around the Z-direction. The space formed by the bolt 22 (bolt 22A) and the communication hole 108 through which the bolt 22A is inserted is introduced with the oxidant gas OG from the outside of the fuel cell stack 100, and the oxidant gas OG is generated by each power generation. It functions as an oxidant gas introduction manifold 161 that is a gas flow path to be supplied to the unit 102, and is the midpoint of the side opposite to the side (X-axis negative direction side of two sides parallel to the Y-axis) The space formed by the bolts 22 (bolts 22B) located in the vicinity and the communication holes 108 through which the bolts 22B are inserted contains the oxidant off-gas OOG that is the gas discharged from the air chamber 166 of each power generation unit 102. Burning Functions as the oxidizing gas discharging manifold 162 for discharging to the outside of the 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, the vicinity of the midpoint of one side (the side on the Y axis positive direction side of two sides parallel to the X axis) on the outer periphery of the fuel cell stack 100 around the Z direction The space formed by the bolt 22 (bolt 22D) positioned at the position and the communication hole 108 through which the bolt 22D is inserted is introduced with the fuel gas FG from the outside of the fuel cell stack 100, and the fuel gas FG is generated by each power generation. Bolt 22 that functions as a fuel gas introduction manifold 171 to be supplied to the unit 102 and is located in the vicinity of the midpoint of the opposite side (the side on the Y axis negative direction side of the two sides parallel to the X axis). The space formed by the (bolt 22E) and the communication hole 108 through which the bolt 22E is inserted is a fuel cell stack 1 that uses the fuel off-gas FOG that is a gas discharged from the fuel chamber 176 of each power generation unit 102 as the fuel cell stack 1 Functions as a fuel gas exhaust manifold 172 for discharging to the outside of the 0. In the present embodiment, as the fuel gas FG, for example, hydrogen-rich gas obtained by reforming city gas is used.

  The fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body portion 28 and a hollow cylindrical branch portion 29 branched from the side surface of the main body portion 28. The hole of the branch 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 on the upper side of the power generation unit 102 located on the uppermost side, and the other end plate 106 is disposed on the lower side of the power generation unit 102 located on the lowermost side. A plurality of power generation units 102 are held in a pressed state by a pair of end plates 104 and 106. The upper end plate 104 functions as a positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as a negative output terminal of the fuel cell stack 100.

(Configuration of power generation unit 102)
4 is an explanatory diagram showing an XZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 2, and FIG. 5 is 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 electric power generation units.

  As shown in FIGS. 4 and 5, the power generation unit 102 includes a fuel cell single cell (hereinafter referred to as “single cell”) 110, a separator 120, an air electrode side frame 130, and an air electrode side current collector 134. The fuel electrode side frame 140, the fuel electrode side current collector 144, and a pair of interconnectors 150 constituting the uppermost layer and the lowermost layer of the power generation unit 102 are provided. 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 that is substantially orthogonal to the Z-axis direction, and is formed of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generation units 102 and prevents reaction gas from being mixed between the power generation units 102. In the present embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. That is, the upper interconnector 150 in a power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102. Further, since the fuel cell stack 100 includes the pair of end plates 104 and 106, the power generation unit 102 located at the top in the fuel cell stack 100 does not include the upper interconnector 150 and is located at the bottom. The power generation unit 102 does not include the lower interconnector 150 (see FIGS. 2 and 3).

  The single cell 110 includes an electrolyte layer 112, a fuel electrode 116 disposed on one side (lower side) of the electrolyte layer 112 in the Z-axis direction, and an air electrode 114 disposed on the other side (upper side) of the electrolyte layer in the Z-axis direction. And a metal support 118 disposed on the opposite side (lower side) of the electrolyte layer 112 with respect to the fuel electrode 116.

  The metal support 118 is a substantially rectangular flat plate-like porous member as viewed in the Z-axis direction. The metal support 118 is made of metal (for example, ferritic stainless steel having a thermal expansion coefficient relatively close to that of YSZ). The porosity of the metal support 118 is, for example, 20 to 70%. The metal support 118 supports the single cell 110 while having gas permeability and conductivity (that is, ensuring the mechanical strength of the single cell 110). As described above, the single cell 110 according to this embodiment is a so-called metal support type (metal support type) single cell in which the mechanical strength of the single cell 110 is secured by the metal support 118. Compared with other types (for example, fuel electrode support type) single cells, metal-supported single cells are less prone to cracking due to thermal shock and have high startability. The thickness of the metal support 118 is preferably thicker than the thicknesses of the other layers constituting the single cell 110, and is preferably 200 μm to 1000 μm, for example.

  The fuel electrode 116 is a substantially rectangular flat plate-shaped porous member smaller than the metal support 118 as viewed in the Z-axis direction. In the present embodiment, the fuel electrode 116 functions as a base layer electrode that serves as a base layer when forming the electrolyte layer 112. The fuel electrode 116 is made of, for example, Ni (nickel), cermet made of Ni and ceramic particles (for example, YSZ particles), Ni-based alloy, or the like. The porosity of the fuel electrode 116 is, for example, 20 to 50%. The lower surface of the fuel electrode 116 is substantially flat, and substantially the entire surface is in contact with the upper surface of the metal support 118 that is also substantially flat.

  The electrolyte layer 112 is a film-like dense member. In the present embodiment, the electrolyte layer 112 is formed so as to continuously cover the upper surface of the fuel electrode 116 and the region of the upper surface of the metal support 118 that is not covered by the fuel electrode 116. Yes. The electrolyte layer 112 is made of, for example, YSZ (yttria stabilized zirconia) which is a solid oxide. Thus, the single cell 110 of this embodiment is a solid oxide fuel cell (SOFC) using a solid oxide as an electrolyte. Since the electrolyte layer 112 is a dense layer, it is preferable that no pores exist. Further, even when pores exist in the electrolyte layer 112, the gas does not pass through the electrolyte layer 112, so that the pores penetrating the electrolyte layer 112 do not have to exist.

  The air electrode 114 is a substantially rectangular flat plate-shaped porous member smaller than the metal support 118 as viewed in the Z-axis direction. In the present embodiment, the air electrode 114 functions as a counter electrode facing the electrolyte layer 112 formed on the base layer (fuel electrode 116). The air electrode 114 is made of, for example, a perovskite oxide (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), LNF (lanthanum nickel iron)). The porosity of the air electrode 114 is, for example, 20 to 50%.

  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 portion surrounding the hole 121 in the separator 120 faces the peripheral edge of the upper surface of the electrolyte layer 112. The separator 120 is bonded to the dense electrolyte layer 112 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.

 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. 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. . The pair of interconnectors 150 included in the power generation unit 102 is electrically insulated by the air electrode side frame 130. 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.

  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 made 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.

  The air electrode side current collector 134 is composed of a plurality of substantially square columnar current collector elements 135 disposed in the air chamber 166, and is made 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. Since the air electrode side current collector 134 has such a configuration, the air electrode 114 and the interconnector 150 are electrically connected.

  The fuel electrode side current collector 144 is composed of a plurality of substantially square columnar current collector elements 145 arranged in the fuel chamber 176, and is formed of, for example, ferritic stainless steel. The fuel electrode side current collector 144 is in contact with the surface of the metal support 118 opposite to the side facing the fuel electrode 116 and the surface of the interconnector 150 facing the metal support 118. Since the fuel electrode side current collector 144 has such a configuration, the metal support 118 and the interconnector 150 are electrically connected.

  In the present embodiment, the air electrode side current collector 134, the fuel electrode side current collector 144, and the interconnector 150 are formed as an integral member. That is, a flat plate portion perpendicular to the vertical direction (Z-axis direction) of the integrated member functions as the interconnector 150 and is formed so as to protrude from the flat plate portion toward the air electrode 114. The current collector element 135, which is a plurality of convex portions, functions as the air electrode side current collector 134, and is a plurality of convex portions formed so as to protrude from the flat plate portion toward the metal support 118. The current collector element 145 functions as the fuel electrode side current collector 144.

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

  The oxidant gas OG supplied to the air chamber 166 of each power generation unit 102 enters the porous air electrode 114, and the fuel gas FG supplied to the fuel chamber 176 passes through the inside of the porous metal support 118. When entering the porous fuel electrode 116, the single cell 110 generates power by an electrochemical reaction between oxygen contained in the oxidant gas OG and hydrogen contained in the fuel gas FG. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to one interconnector 150 via the air electrode side current collector 134, and the fuel electrode 116 is connected to the metal support 118 and the fuel electrode side. It is electrically connected to the other interconnector 150 via the current collector 144. The plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, electrical energy generated in each power generation unit 102 is taken out from the end plates 104 and 106 that function as output terminals of the fuel cell stack 100. Since SOFC generates power at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the fuel cell stack 100 is heated by a heater (after the start-up until the high temperature can be maintained by the heat generated by the power generation. (Not shown).

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

A-3. Detailed configuration of the single cell 110:
Next, a detailed configuration of the single cell 110 according to the present embodiment will be described. FIG. 6 is an explanatory diagram showing a detailed configuration of the interfaces of the fuel electrode 116, the electrolyte layer 112, and the air electrode 114 in the single cell 110. FIG. 6 is an enlarged view of the XZ cross-sectional configuration of the portion X1 in FIG. FIG. 7 is an explanatory diagram showing the configuration of the electrolyte layer 112 of the single cell 110. 7A is an SEM image of a cross section of the electrolyte layer 112 substantially parallel to the Z-axis direction, and FIG. 7B is obtained by adding a grain growth interface BL described later to the SEM image. is there. In addition, the area | region showing the fuel electrode 116 in (A) and (B) of FIG. 7 is a binarized SEM image in order to clarify the pore structure.

  In the single cell 110 of the present embodiment, the thickness T1 of the electrolyte layer 112 is 20 μm or less. That is, in the single cell 110 of this embodiment, the electrolyte layer 112 is relatively thin. The thickness T1 of the electrolyte layer 112 is specified as follows. As shown in FIG. 6, in the split section of the unit cell 110 substantially parallel to the Z-axis direction, the minimum two surfaces of the fuel electrode 116 on the side facing the electrolyte layer 112 (hereinafter referred to as “first surface SU1”). The average of the average line by multiplication (hereinafter referred to as “fuel electrode surface average line AL1”) and the surface of the electrolyte layer 112 facing the air electrode 114 (hereinafter referred to as “second surface SU2”) by the method of least squares. A line (hereinafter referred to as “electrolyte layer surface average line AL2”) is specified. The shortest distance between the fuel electrode surface average line AL1 and the electrolyte layer surface average line AL2 is defined as the thickness T1 of the electrolyte layer 112.

  In the single cell 110 of the present embodiment, the electrolyte layer 112 is composed of columnar crystal particles PA extending in the grain growth direction D1. In this specification, the particle PA is columnar when the ratio (L1 / L2) of the particle size L1 in the grain growth direction D1 to the particle size L2 in the direction orthogonal to the grain growth direction D1 is 1.3 or more. It means that there is.

  Here, the grain growth direction D1 of the particles PA constituting the electrolyte layer 112 is specified as follows. As shown in FIG. 7A, an SEM image of a split section of the single cell 110 that is substantially parallel to the Z-axis direction is observed, and as shown in FIG. 7B, each particle PA constituting the electrolyte layer 112 is formed. The grain growth interface BL is identified. In addition, as shown in FIG. 6, for each particle PA constituting the electrolyte layer 112, the intersections of one grain growth interface BL1, the fuel electrode surface average line AL1, and the electrolyte layer surface average line AL2 are respectively set to the first The intersection point P1 and the second intersection point P2, and the intersection point of the other grain growth interface BL2, the fuel electrode surface average line AL1, and the electrolyte layer surface average line AL2 are defined as a third intersection point P3 and a fourth intersection point P4, respectively. . The direction from the midpoint MP1 of the line connecting the first intersection P1 and the third intersection P3 toward the midpoint MP2 of the line connecting the second intersection P2 and the fourth intersection P4 is the grain growth direction. Let D1.

  Further, in the single cell 110 of the present embodiment, for each particle PA constituting the electrolyte layer 112, an inclination angle (hereinafter, referred to as a grain growth direction D1) with respect to the first surface SU1 (fuel electrode surface average line AL1) of the fuel electrode 116. “Inclination angle θ” (where 0 ° ≦ θ ≦ 90 °) is substantially the same value. That is, in the single cell 110 of this embodiment, the grain growth direction D1 of each particle PA constituting the electrolyte layer 112 is substantially the same direction. In the present specification, the inclination angle θ in the grain growth direction D1 of each particle PA being substantially the same value means that the difference in the inclination angle θ in the grain growth direction D1 between the particles PA is within ± 10 degrees. Means. In the single cell 110 of this embodiment, the inclination angle θ in the grain growth direction D1 of each particle PA constituting the electrolyte layer 112 is not less than 75 degrees and not more than 90 degrees.

  As described later, the electrolyte layer 112 having such a configuration is realized by forming the electrolyte layer 112 by a vapor phase method such as a sputtering process using the fuel electrode 116 (or the air electrode 114) as a base layer. When the electrolyte layer 112 is formed by a vapor phase method, the shape of the particle PA becomes columnar for most of the plurality of particles PA (for example, 80% or more) constituting the electrolyte layer 112, and the inclination of the particle growth direction D1 of each particle PA is increased. The angle θ is approximately the same value. That is, for most (for example, 80% or more) of the plurality of particles PA constituting the electrolyte layer 112, the shape of the particles PA is columnar and / or the inclination angle θ in the grain growth direction D1 of each particle PA is It can be said that technically synonymous with substantially the same value and that the electrolyte layer 112 is formed by the vapor phase method.

  In the unit cell 110 of the present embodiment, the surface roughness (maximum height roughness) Rz of the surface (first surface SU1) on the side facing the electrolyte layer 112 in the fuel electrode 116 is 30 μm or less. The surface roughness Rz of the first surface SU1 of the fuel electrode 116 can be specified as follows. In the field of view in which the width in the plane direction of the cross section parallel to the Z-axis direction of the fuel electrode 116 (for example, the XZ cross section shown in FIG. 6) is 20 μm, the average line of the first surface SU1 (fuel electrode surface average Line AL1), and the average value of the heights of the first to fifth highest peaks (the distance between the peak and the average line) relative to the average line, and 1 to 5 based on the average line The average value of the depth of the deepest valley bottom (the distance between the valley bottom and the average line) is obtained, and the sum of both average values is defined as the surface roughness Rz. In the unit cell 110 of the present embodiment, the surface roughness Rz of the first surface SU1 of the fuel electrode 116 is relatively small. Therefore, the height of the convex portion of the first surface SU1 of the fuel electrode 116 is relatively low. And it can be said that it is a surface where the depth of a recessed part is comparatively shallow.

  In the state after the electrolyte layer 112 is formed on the fuel electrode 116, the surface roughness Rz of the first surface SU1 of the fuel electrode 116 is a 3D image of the cross section of the single cell 110 using FIB-SEM. The cross section polisher processing (also called ion milling processing or ion polishing processing) can also be specified by observing a cross-sectional SEM image after analyzing the cross section. In addition, in the state before forming the electrolyte layer 112, the surface roughness Rz of the first surface SU1 of the fuel electrode 116 is specified using a normal contact-type surface roughness meter or a non-contact-type surface shape measuring device. can do.

  In the single cell 110 of the present embodiment, the opening ratio (porosity) of the portion on the electrolyte layer 112 side (hereinafter referred to as “electrolyte layer side portion R1”) of the fuel electrode 116 is higher than 5% and 35 %. The electrolyte layer side portion R1 in the fuel electrode 116 passes through the average position of the heights of the first to fifth highest peaks used for specifying the surface roughness Rz described above, and is orthogonal to the Z axis. Between the first imaginary line VL1 and the second imaginary line VL2 that is parallel to the first imaginary line VL1 and located on the side away from the electrolyte layer 112 by a distance of 2 μm from the first imaginary line VL1. It is the part sandwiched. The aperture ratio of the electrolyte layer side portion R1 in the fuel electrode 116 is binarized from the SEM image of the fracture surface of the fuel electrode 116 (viewing field width of 20 μm) (see FIG. 7), and the electrolyte layer side portion R1 of the fuel electrode 116 is obtained. It can be specified by measuring the ratio of the area of the opening VO (black area after binarization) occupying the area of. Note that the quality of the electrolyte layer 112 is affected by the aperture ratio of the first surface SU1 of the fuel electrode 116 as an underlayer, but in this embodiment, the aperture ratio of the first surface SU1 of the fuel electrode 116 is After confirming that the aperture ratio of the electrolyte layer side portion R1 in the fuel electrode 116 is substantially the same as that described above, the aperture ratio of the electrolyte layer side portion R1 in the fuel electrode 116 is used as an index value. Further, the maximum opening diameter (pore diameter) in the fuel electrode 116 is preferably 1 μm or less in terms of an equivalent circle diameter (diameter of a circle having the same area as the opening area).

  FIG. 8 is an explanatory diagram showing the results of XRD measurement for the electrolyte layer 112 of the single cell 110. FIG. 8 shows the result of XRD measurement using CoKα rays. In the single cell 110 of the present embodiment, the full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement of the electrolyte layer 112 using CoKα rays is 0.2 deg or less. That is, in the single cell 110 of the present embodiment, the size of each particle PA constituting the electrolyte layer 112 is relatively large. Since the (111) plane or (200) plane of the YSZ diffraction line has higher strength than other planes and is easy to identify and measure, it is preferable to target these planes. Further, the full width at half maximum of the crystal plane may be measured using a peak of a specific crystal plane, or may be analyzed using an X-ray crystal structure analysis or a Rietveld method.

A-4. Manufacturing method of the single cell 110:
The single cell 110 of 1st Embodiment can be manufactured with the following manufacturing methods, for example. FIG. 9 is an explanatory diagram illustrating an example of a method for manufacturing the single cell 110 according to the first embodiment.

  First, the metal support 118 is prepared, and the fuel electrode 116 is formed on the metal support 118 (S110). More specifically, for example, the fuel electrode 116 is formed by applying a fuel electrode paste containing NiO and YSZ on the metal support 118 and firing it under predetermined conditions.

  Here, as described above, in the single cell 110 of the present embodiment, the surface roughness Rz of the surface (first surface SU1) on the side facing the electrolyte layer 112 in the fuel electrode 116 is 30 μm or less. The surface roughness Rz of the first surface SU1 of the fuel electrode 116 can be adjusted, for example, by adjusting the particle size of the raw material powder, the firing conditions, the diameter of the pore former mixed with the raw material, and the like. Specifically, when the particle size of the raw material powder is made fine, the surface roughness Rz of the first surface SU1 of the fuel electrode 116 becomes small. Further, when the firing temperature is lowered and / or the firing time is shortened, the surface roughness Rz of the first surface SU1 of the fuel electrode 116 is reduced. Further, when the pore former diameter is reduced, the surface roughness Rz of the first surface SU1 of the fuel electrode 116 is reduced.

  Further, as described above, in the single cell 110 of the present embodiment, the aperture ratio (porosity) of the electrolyte layer side portion R1 in the fuel electrode 116 is higher than 5% and lower than 35%. The aperture ratio of the electrolyte layer side portion R1 in the fuel electrode 116 can be adjusted, for example, by adjusting the particle size of the raw material powder, firing conditions, the diameter of the pore former mixed with the raw material, and the like. Specifically, when the particle size of the raw material powder is made fine, the aperture ratio of the electrolyte layer side portion R1 in the fuel electrode 116 becomes low. Further, when the firing temperature is lowered and / or the firing time is shortened, the aperture ratio of the electrolyte layer side portion R1 in the fuel electrode 116 is lowered. Further, when the pore former diameter is reduced, the aperture ratio of the electrolyte layer side portion R1 in the fuel electrode 116 is lowered.

  Next, the electrolyte layer 112 is formed on the surface of the fuel electrode 116 formed on the metal support 118 (S120). More specifically, the electrolyte layer 112 is formed by a vapor phase method (for example, sputtering process) using the fuel electrode 116 as a base layer. When the electrolyte layer 112 is formed by the vapor phase method, each particle PA constituting the electrolyte layer 112 grows in substantially the same (direction difference is within ± 10 degrees) grain growth direction D1, and finally The columnar crystal particles PA extend in the grain growth direction D1. From the viewpoint of the heat resistance of the metal support 118 and from the viewpoint of suppressing adverse effects due to element diffusion between members, the temperature during the formation of the electrolyte layer 112 is preferably 800 ° C. or lower. Among the vapor phase methods, a sputtering process is preferable because film formation can be performed at 500 ° C. or lower. In the present embodiment, the electrolyte layer 112 is also formed in a region of the metal support 118 on the fuel electrode 116 side that is not covered with the fuel electrode 116.

  Here, in the single cell 110 of this embodiment, the inclination angle θ in the grain growth direction D1 of each particle PA constituting the electrolyte layer 112 is not less than 75 degrees and not more than 90 degrees. This inclination angle θ can be adjusted, for example, by adjusting the work angle when the electrolyte layer 112 is formed by the vapor phase method. Specifically, when the work angle at the time of forming the electrolyte layer 112 by the vapor phase method is increased, the inclination angle θ is decreased.

  In the single cell 110 of this embodiment, the thickness T1 of the electrolyte layer 112 is 20 μm or less. The thickness T1 of the electrolyte layer 112 can be adjusted, for example, by adjusting the film formation conditions (temperature and time) of the electrolyte layer 112 by a vapor phase method. Specifically, when the temperature at the time of forming the electrolyte layer 112 by the vapor phase method is lowered, the thickness T1 of the electrolyte layer 112 is reduced. Further, when the deposition time of the electrolyte layer 112 by the vapor phase method is shortened, the thickness T1 of the electrolyte layer 112 is reduced.

  Moreover, in the single cell 110 of this embodiment, the full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement of the electrolyte layer 112 using CoKα rays is 0.2 deg or less. This FWHM can be adjusted, for example, by adjusting the film formation conditions (temperature and time) of the electrolyte layer 112 by a vapor phase method. Specifically, when the temperature at the time of forming the electrolyte layer 112 by the vapor phase method is increased, the FWHM is decreased.

  Next, the air electrode 114 is formed on the surface of the electrolyte layer 112 opposite to the side facing the fuel electrode 116 (S130). More specifically, for example, an air electrode paste containing LSCF powder is applied to the surface of the electrolyte layer 112 opposite to the side facing the fuel electrode 116, and fired under predetermined conditions to form the air electrode 114. To do. Through the above steps, the unit cell 110 having the above-described configuration is manufactured.

B. Second embodiment:
B-1. Configuration of the electrolytic cell stack 100a:
Next, as a second embodiment of the present invention, a case where the present invention is applied to an electrolytic cell 110a constituting the electrolytic cell stack 100a will be described. Since the configuration of the electrolytic cell stack 100a has many points in common with the configuration of the fuel cell stack 100 described above, in the following description, the configuration of the electrolytic cell stack 100a is the same as the configuration of the fuel cell stack 100 described above. About the structure of this, the description is suitably abbreviate | omitted by attaching | subjecting the same code | symbol. FIG. 10 is a perspective view showing an external configuration of the electrolytic cell stack 100a according to the second embodiment, and FIG. 11 is an explanatory diagram showing an XZ cross-sectional configuration of the electrolytic cell stack 100a at the position XI-XI in FIG. FIG. 12 is an explanatory diagram showing a YZ cross-sectional configuration of the electrolytic cell stack 100a at the position XII-XII in FIG.

  The electrolytic cell stack 100a includes a plurality of (seven in this embodiment) electrolytic units 102a and a pair of end plates 104 and 106. The seven electrolysis units 102a are arranged side by side in a predetermined arrangement direction (vertical direction in the present embodiment). The pair of end plates 104 and 106 are arranged so as to sandwich an assembly composed of seven electrolysis units 102a from above and below. The upper end plate 104 functions as a positive terminal of the electrolytic cell stack 100a, and the lower end plate 106 functions as a negative terminal of the electrolytic cell stack 100a.

  A communication hole 108 is formed in a peripheral portion around the Z direction of each layer (electrolysis unit 102a, end plates 104, 106) constituting the electrolytic cell stack 100a, and a bolt 22 is inserted into the communication hole 108. Since the outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each communication hole 108, 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. 10 and 11, the electrolytic cell stack 100 a is located near the midpoint of one side (the side on the X axis positive direction side of the two sides parallel to the Y axis) on the outer periphery around the Z direction. The space formed by the bolts 22 (bolts 22A) and the communication holes 108 through which the bolts 22A are inserted is supplied to the fuel chambers 176 of the respective electrolysis units 102a from the outside of the electrolysis cell stack 100a as the fuel electrode side supply gas G2. It functions as a fuel electrode side gas introduction manifold 171a for supplying water vapor and is located near the midpoint of the opposite side (side of the two sides parallel to the Y axis on the X axis negative direction side). The space formed by the bolt 22 (bolt 22B) and the communication hole 108 through which the bolt 22B is inserted allows hydrogen generated in the fuel electrode 116 of each electrolysis unit 102a to flow into the fuel electrode side exhaust gas G. Functions as a fuel electrode side gas exhaust manifold 172a for discharging from the fuel chamber 176 to the outside of the electrolytic cell stack 100a as one.

  Further, as shown in FIGS. 10 and 12, the vicinity of the midpoint of one side (the Y-axis positive direction side of two sides parallel to the X-axis) on the outer periphery around the Z-direction of the electrolysis cell stack 100a. The space formed by the bolt 22 (bolt 22D) located at the position and the communication hole 108 through which the bolt 22D is inserted is an air electrode side supply gas G1 (for example, for promoting the discharge of oxygen from the air chamber 166) Air) from the outside of the electrolysis cell stack 100a to the air chamber 166 of each electrolysis unit 102a, functioning as an air electrode side gas introduction manifold 161a, and opposite sides (of the two sides parallel to the X axis) The space formed by the bolt 22 (bolt 22E) located near the midpoint of the Y-axis negative direction side and the communication hole 108 through which the bolt 22E is inserted is the air electrode of each electrolysis unit 102a. The oxygen generated at 14, which functions as an air electrode side gas exhaust manifold 162a for discharging the air electrode side exhaust gas G11 from the air chamber 166 to the outside of the electrolytic cell stack 100a.

(Configuration of electrolysis unit 102a)
13 is an explanatory diagram showing an XZ cross-sectional configuration of two electrolysis units 102a adjacent to each other at the same position as the cross section shown in FIG. 11, and FIG. 14 is adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross-sectional structure of two electrolysis units 102a. As shown in FIGS. 13 and 14, the electrolysis unit 102a includes an electrolysis unit cell 110a, a separator 120, an air electrode side frame 130, an air electrode side current collector 134, a fuel electrode side frame 140, a fuel electrode. A side current collector 144 and a pair of interconnectors 150 constituting the uppermost layer and the lowermost layer of the electrolysis unit 102a are provided. Hereinafter, the electrolytic single cell 110a is referred to as a single cell 110a. In order to distinguish from the (fuel cell) unit cell 110 in the first embodiment, “a” is added to the end of the symbol of the (electrolysis) unit cell.

  The single cell 110a includes an electrolyte layer 112, an air electrode 114 disposed on one side (lower side) of the electrolyte layer 112 in the Z-axis direction, and a fuel electrode 116 disposed on the other side (upper side) of the electrolyte layer in the Z-axis direction. And a metal support 118 disposed on the opposite side (lower side) of the electrolyte layer 112 with respect to the air electrode 114.

  The air electrode 114 is a substantially rectangular flat plate-shaped porous member smaller than the metal support 118 as viewed in the Z-axis direction. The lower surface of the air electrode 114 is substantially flat, and substantially the entire surface is in contact with the upper surface of the metal support 118 that is also substantially flat. In the present embodiment, the air electrode 114 functions as a base layer electrode that serves as a base layer when the electrolyte layer 112 is formed.

  The electrolyte layer 112 is formed so as to continuously cover the upper surface of the air electrode 114 and the region of the upper surface of the metal support 118 that is not covered by the air electrode 114. The electrolyte layer 112 is made of, for example, YSZ (yttria stabilized zirconia) which is a solid oxide. Thus, the single cell 110a of this embodiment is a solid oxide electrolytic cell (SOEC) using a solid oxide as an electrolyte.

  The fuel electrode 116 is a substantially rectangular flat plate-shaped porous member smaller than the metal support 118 as viewed in the Z-axis direction. In the present embodiment, the fuel electrode 116 functions as a counter electrode facing the electrolyte layer 112 formed on the base layer (air electrode 114).

 The air electrode side frame 130 has an air electrode side gas supply manifold 132a that communicates the air electrode side gas introduction manifold 161a and the air chamber 166, and an air electrode that communicates the air chamber 166 and the air electrode side gas discharge manifold 162a. A side gas discharge communication hole 133a is formed. Further, the fuel electrode side frame 140 communicates the fuel electrode side gas supply manifold 142a that communicates the fuel electrode side gas introduction manifold 171a and the fuel chamber 176, and the fuel chamber 176 and the fuel electrode side gas discharge manifold 172a. A fuel electrode side gas discharge communication hole 143a is formed.

  The detailed configuration of the electrolyte layer 112 in the second embodiment is the same as the detailed configuration of the electrolyte layer 112 shown in FIG. 6 in the first embodiment (however, the base layer electrode is not the fuel electrode 116 but the air electrode 116). Pole 114). That is, the thickness T1 of the electrolyte layer 112 is 20 μm or less. The electrolyte layer 112 is composed of columnar crystal particles PA extending in the grain growth direction D1. Further, the grain growth direction D1 of each particle PA constituting the electrolyte layer 112 is substantially the same direction. Further, the inclination angle θ in the grain growth direction D1 of each particle PA constituting the electrolyte layer 112 is not less than 75 degrees and not more than 90 degrees. The full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement of the electrolyte layer 112 using CoKα rays is 0.2 deg or less.

  In the second embodiment, the surface roughness and aperture ratio of the air electrode 114 functioning as the base layer electrode are the same as the surface roughness and aperture ratio of the fuel electrode 116 functioning as the base layer electrode in the first embodiment. . That is, the surface roughness (maximum height roughness) Rz of the air electrode 114 on the side facing the electrolyte layer 112 is 30 μm or less. Further, the aperture ratio (porosity) of the portion of the air electrode 114 on the electrolyte layer 112 side is higher than 5% and lower than 35%. The maximum opening diameter (pore diameter) in the air electrode 114 is preferably 1 μm or less in terms of a circle-equivalent diameter (diameter of a circle having the same area as the opening area).

B-2. Operation of the electrolytic cell stack 100a:
As shown in FIGS. 11 and 13, the fuel electrode side supply gas 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 fuel electrode side gas introduction manifold 171 a. When the water vapor as G2 is supplied, the water vapor is supplied to the fuel electrode side gas introduction manifold 171a through the branching portion 29 of the gas passage member 27 and the hole of the main body portion 28, and is supplied from the fuel electrode side gas introduction manifold 171a. The fuel is supplied to the fuel chamber 176 through the fuel electrode side gas supply communication hole 142a of the electrolysis unit 102a. Further, as shown in FIGS. 12 and 14, the air electrode side 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 air electrode side gas introduction manifold 161a. When the supply gas G1 (for example, air) is supplied, the air electrode side supply gas G1 is supplied to the air electrode side gas introduction manifold 161a through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28, and the air The air is supplied from the electrode side gas introduction manifold 161a to the air chamber 166 through the air electrode side gas supply communication hole 132a of each electrolysis unit 102a.

  In this state, with the fuel electrode side supply gas G2 (water vapor) and the air electrode side supply gas G1 (air) supplied, a voltage is applied to the end plates 104 and 106 that function as electrical terminals of the electrolysis cell stack 100a. In addition, a voltage is applied to each single cell 110a via the interconnector 150, the air electrode side current collector 134, the fuel electrode side current collector 144, and the like constituting each electrolysis unit 102a, and the electric power of the water in each single cell 110a. Decomposition occurs. 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 110a is discharged as fuel electrode side exhaust gas G21 from the fuel chamber 176 to the fuel electrode side gas discharge manifold 172a through the fuel electrode side gas discharge communication hole 143a. The electrolytic cell stack 100a is connected to 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 pole side gas discharge manifold 172a. It is taken out outside. Further, oxygen generated in the air electrode 114 of each single cell 110a is discharged from the air chamber 166 to the air electrode side gas discharge manifold 162a through the air electrode side gas discharge communication hole 133a as the air electrode side exhaust gas G11. Further, 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 air electrode side gas discharge manifold 162a, electrolysis is performed via a gas pipe (not shown) connected to the branch portion 29. It is discharged outside the cell stack 100a.

B-3. Manufacturing method of the single cell 110a:
The single cell 110a of 2nd Embodiment can be manufactured with the following manufacturing methods, for example. FIG. 15 is an explanatory diagram illustrating an example of a method for manufacturing the single cell 110a according to the second embodiment. In the following description, the description of the same method as the manufacturing method of the single cell 110 of the first embodiment described above in the manufacturing method of the single cell 110a of the second embodiment will be omitted as appropriate.

  First, the metal support 118 is prepared, and the air electrode 114 is formed on the metal support 118 (S110a). More specifically, for example, the air electrode 114 including the LSCF powder is applied on the metal support 118 and baked under predetermined conditions to form the air electrode 114.

  Here, as described above, in the single cell 110a of the present embodiment, the surface roughness Rz of the air electrode 114 on the side facing the electrolyte layer 112 is 30 μm or less. The surface roughness Rz of the surface of the air electrode 114 can be adjusted, for example, by adjusting the particle size of the raw material powder, the firing conditions, the diameter of the pore former mixed with the raw material, and the like. Further, as described above, in the single cell 110a of the present embodiment, the aperture ratio (porosity) of the portion of the air electrode 114 on the electrolyte layer 112 side is higher than 5% and lower than 35%. The opening ratio of the portion of the air electrode 114 can be adjusted by adjusting the particle size of the raw material powder, the firing conditions, the diameter of the pore former mixed with the raw material, and the like.

  Next, the electrolyte layer 112 is formed on the surface of the air electrode 114 formed on the metal support 118 (S120a). More specifically, the electrolyte layer 112 is formed by a vapor phase method (for example, sputtering process) using the air electrode 114 as a base layer. In the present embodiment, the electrolyte layer 112 is also formed in the region of the metal support 118 on the air electrode 114 side that is not covered with the air electrode 114.

  Next, the fuel electrode 116 is formed on the surface of the electrolyte layer 112 opposite to the side facing the air electrode 114 (S130a). More specifically, for example, a fuel electrode paste containing NiO and YSZ is applied to the surface of the electrolyte layer 112 opposite to the side facing the air electrode 114, and fired under predetermined conditions to form the fuel electrode 116. Form. Through the above steps, the single cell 110a having the above-described configuration is manufactured.

C. Performance evaluation:
Next, performance evaluation performed on the gas leak characteristics and electrical characteristics of the single cell will be described. For the performance evaluation, a sample corresponding to the single cell 110a of the second embodiment, that is, the single cell 110a using the air electrode 114 as a base layer electrode was used. FIG. 16 is an explanatory diagram showing the results of gas leak characteristic evaluation. FIG. 17 is an explanatory diagram showing the results of electrical characteristic evaluation.

(Gas leak characteristic evaluation)
As shown in FIG. 16, the gas leak characteristic evaluation was performed using six samples (samples S1 to S6). Samples S1 to S6 are obtained by forming a YSZ layer (corresponding to the electrolyte layer 112) on a base layer (corresponding to the air electrode 114). In this performance evaluation, a La—Sr—Mn-based perovskite material (hereinafter referred to as “LSM”) is pressed by a uniaxial press method to form a 25 mmφ disk, and this is any temperature in the range of 1000 to 1300 ° C. A porous sintered body produced by firing for 3 hours was used as an underlayer. A YSZ layer was formed by a magnetron sputtering process using the porous sintered body as an underlayer. Samples S1 to S6 are different from each other in the film formation conditions (more specifically, the film formation time) of the YSZ layer, the surface roughness Rz of the surface of the base layer, and the aperture ratio (porosity) of the base layer. Yes. Note that the difference in the surface roughness Rz and the aperture ratio of the underlayer of each sample was realized by varying the temperature during the firing described above. In addition, samples S1 to S6 have different YSZ layer thicknesses due to these differences.

  In the gas leak characteristic evaluation, a tubular jig was attached to the YSZ layer side of each sample via an O-ring, and the inside of the jig was depressurized, and then the presence or absence of pressure fluctuation was confirmed. If there is no pressure fluctuation after 3 hours after depressurization, it is judged as good (◯), and if there is no differential pressure before 3 hours, it is judged as bad (x), and there is a differential pressure after 3 hours However, when there was a pressure fluctuation from the beginning, it was judged as acceptable (Δ).

  As shown in FIG. 16, the sample S3 was determined to be defective (x). In sample S3, the surface roughness Rz of the underlayer is 45 μm, and the surface roughness of the underlayer is higher than those of other samples S1, S2, S4 to S6 (all of which the surface roughness Rz of the underlayer is 31 μm or less). Rz is large. In light of the definition of the surface roughness Rz described above, the surface roughness Rz of the underlayer is relatively large, which means that the surface of the underlayer has a relatively high height of the convex portion and a depth of the concave portion. Means relatively deep. Therefore, in sample S3, since the height of the convex portion on the surface of the underlayer is relatively high and the depth of the concave portion is relatively deep, a defect portion is not formed in the YSZ layer when the YSZ layer is formed on the underlayer. It is considered that gas leak occurred from the missing part.

  Sample S2 was determined to be acceptable (Δ). In sample S2, although the surface roughness Rz of the underlayer is 30 μm or less, the opening ratio of the underlayer is 35%, and other samples S1, S4 to S6 (all of which the underlayer opening ratio is less than 35%) The aperture ratio of the underlayer is higher than Therefore, in sample S2, since there are a relatively large number of openings in the underlayer, it is considered that there were some defects in the YSZ layer when the YSZ layer was formed on the underlayer, and gas leaks occurred from the defects. It is done.

  On the other hand, samples S1, S4 to S6 were determined to be good (◯). In these samples, the surface roughness Rz of the underlayer is 31 μm or less, and the aperture ratio of the underlayer is less than 35%. From the above results, in order to suppress the gas leakage of the YSZ layer formed on the underlayer by the vapor phase method, the surface roughness Rz of the underlayer is preferably 31 μm or less (more preferably 30 μm or less). It can be said that the aperture ratio of the underlayer is preferably less than 35%.

(Electrical characteristics evaluation)
As shown in FIG. 17, the electrical property evaluation was performed using six samples (samples S11 to S17). Samples S11 to S17 are the same as the samples used for the gas leak characteristic evaluation described above, that is, a YSZ layer formed on an LSM underlayer by a magnetron sputtering process, and platinum on the YSZ layer. (Pt) is applied by screen printing. Samples S11 to S17 are different from each other in the film formation conditions (specifically, the film formation temperature, the film formation time, the work angle during film formation) of the YSZ layer (electrolyte layer 112) and the aperture ratio of the underlayer. Yes. In addition, the difference in the aperture ratio of the underlayer of each sample was realized by changing the temperature at the time of firing described above. In addition, the samples S11 to S17 are caused by these differences, and the YSZ layer using the thickness of the YSZ layer, the inclination angle θ (see FIG. 6) of the grain growth direction D1 of the particles PA in the YSZ layer, and the CoKα line. The full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement is different from each other.

  In the electrical characteristic evaluation, the LSM side that functions as the air electrode 114 in each sample is an air atmosphere, the platinum side that functions as the fuel electrode 116 is a hydrogen and water vapor atmosphere, and the power generation operation is performed at 700 to 800 ° C. The voltage drop amount is specified from the -V characteristic, and when the voltage drop amount is relatively small, it is judged as good (◎ or ○), and the one with the lowest performance among the relatively good ( ○). Further, when the voltage drop amount was relatively large, it was determined to be defective (×), and when the voltage drop amount was about the middle between good (◯) and defective (×), it was determined to be acceptable (Δ).

  As shown in FIG. 17, the sample S12 was determined to be defective (x). In sample S12, the YSZ layer has a thickness of 25 μm, and the YSZ layer is thicker than the other samples S11, S13 to S15 (all of which have a thickness of 21 μm or less). Therefore, in sample S12, it is considered that the IR resistance of the YSZ layer is increased and the amount of voltage drop is increased.

  Sample S16 was determined to be defective (x). In sample S16, the aperture ratio of the base layer is 5%, and the aperture ratio of the base layer is lower than those of other samples S11 and S13 to S15 (all of which have an aperture ratio of the base layer higher than 5%). Therefore, in sample S16, it is considered that the gas diffusion resistance of the underlayer is increased and the amount of voltage drop is increased.

  Sample S15 was determined to be acceptable (Δ). In sample S15, although the thickness of the YSZ layer is 20 μm or less and the aperture ratio of the underlayer is higher than 5%, the inclination angle θ in the grain growth direction D1 in the YSZ layer is 70 degrees, and other samples S11 , S13 (both have an inclination angle θ of 75 degrees or more), the inclination angle θ is small. In the sample S15, the inclination angle θ is decreased because the work angle during the formation of the YSZ layer is set to a relatively large angle (15 degrees). In sample S15, since the inclination angle θ in the grain growth direction D1 in the YSZ layer is relatively small, the movement of oxygen ions in the stacking direction in the YSZ layer is hindered by the grain boundaries in the YSZ layer, and the oxygen ion transport efficiency decreases. It is thought that the amount of voltage drop has increased.

  Sample S14 was determined to be good (◯). In sample S14, although the thickness of the YSZ layer is 20 μm or less and the aperture ratio of the underlayer is higher than 5%, the full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement of the YSZ layer is 0.4 deg. The FWHM is larger than the other samples S11 and S13 (both FWHM is 0.2 deg or less) (that is, the particles constituting the YSZ layer are relatively small). In Sample S14, the FWHM increased because the temperature at the time of forming the YSZ layer was set to a relatively low temperature (room temperature). In sample S14, FWHM is relatively large (that is, particles constituting the YSZ layer are relatively small), and thus it is considered that the oxygen ion transport efficiency in the YSZ layer is reduced and the voltage drop amount is increased.

  On the other hand, samples S11, S13, and S17 were determined to be good (◎). In these samples, the thickness of the YSZ layer is 20 μm or less, the aperture ratio of the underlayer is higher than 5%, and the inclination angle θ in the grain growth direction D1 in the YSZ layer is 75 degrees or more (and 90 degrees or less). And the full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement of the YSZ layer is 0.2 deg or less. From the above results, in order to suppress a decrease in the electrical characteristics of the YSZ layer formed on the underlayer by the vapor phase method, it is preferable that the aperture ratio of the underlayer is higher than 5%. The inclination angle θ in the growth direction D1 is preferably 75 ° or more and 90 ° or less, and the full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement of the YSZ layer is preferably 0.2 deg or less. It can be said that the thickness of the layer is preferably 20 μm or less.

  In the performance evaluation, a sample corresponding to a single cell having the air electrode 114 as a base layer electrode was used. However, the configuration (performance) of the electrolyte layer 112 formed on the base layer electrode is the base layer electrode. Therefore, it is considered that the same result is obtained even in a single cell in which the fuel electrode 116 is used instead of the air electrode 114 instead of the air electrode 114 (the surface roughness Rz and the aperture ratio).

  In light of the above performance evaluation results, the surface roughness Rz of the surface of the base layer electrode (fuel electrode 116 or air electrode 114) facing the electrolyte layer 112 in the unit cell 110 (or 100a) of each of the above embodiments. Is preferably 30 μm or less, and the opening ratio (porosity) of the base layer electrode (fuel electrode 116 or air electrode 114) on the side of the electrolyte layer 112 is higher than 5% and lower than 35%. It is preferable that the grain growth direction D1 in the electrolyte layer 112 has an inclination angle of 75 degrees or more and 90 degrees or less with respect to the surface of the base layer electrode (the fuel electrode 116 or the air electrode 114) facing the electrolyte layer 112. The direction having θ is preferable, and the full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement of the electrolyte layer 112 using CoKα rays is 0.2. Preferably eg at most, the thickness of the electrolyte layer 112 in the Z axis direction, it can be said that it is preferable that 20μm or less.

D. Effect of each embodiment:
As described above, the single cell 110 (or 110a) of each of the above embodiments includes the electrolyte layer 112 containing a solid oxide and the porous fuel electrode 116 disposed on one side of the electrolyte layer 112 in the Z-axis direction. And a porous air electrode 114 disposed on the other side of the electrolyte layer 112 in the Z-axis direction, and one of the fuel electrode 116 and the air electrode 114 (an electrode functioning as a base layer electrode, hereinafter referred to as “specific”). The surface roughness Rz of the surface facing the electrolyte layer 112 in the “electrode” is 30 μm or less. In the unit cell 110 (or 110a) of each of the above embodiments, the surface roughness Rz of the surface of the specific electrode (fuel electrode 116 or air electrode 114) facing the electrolyte layer 112 is relatively small. The surface is a surface in which the height of the convex portion is relatively low and the depth of the concave portion is relatively shallow. Therefore, in the single cell 110 (or 110a) of each of the above embodiments, even if the thickness of the electrolyte layer 112 is not excessively increased, it is possible to suppress a decrease in denseness due to a defective portion occurring in the electrolyte layer 112. can do. Therefore, according to the single cell 110 (or 110a) of each of the above embodiments, the denseness of the electrolyte layer 112 is reduced while suppressing an increase in IR resistance due to an excessively thick electrolyte layer 112. As a result, it is possible to suppress the performance of the single cell 110 (or 110a) from being deteriorated.

  In the case where the electrolyte layer 112 is formed by a vapor phase method, the quality of the electrolyte layer 112 is particularly susceptible to the surface state of the underlayer. In the single cell 110 (or 110a) including the electrolyte layer 112 formed by the vapor phase method as in the above embodiments, the surface of the specific electrode (fuel electrode 116 or air electrode 114) on the side facing the electrolyte layer 112 When the surface roughness Rz is 30 μm or less, it is possible to suppress a decrease in the density due to the occurrence of a defective portion in the electrolyte layer 112 and the performance of the single cell 110 (or 110a) is deteriorated. Can be suppressed.

  In addition, when the electrolyte layer 112 is formed by a vapor phase method, the electrolyte layer 112 can be formed at a lower temperature than other methods (for example, a firing method). Can be suppressed. From the viewpoint of heat resistance of the metal support 118, the method for forming the electrolyte layer 112 by the vapor phase method is suitable for a metal support type single cell.

  In the single cell 110 (or 110a) of each of the above embodiments, the opening ratio of the specific electrode (fuel electrode 116 or air electrode 114) on the electrolyte layer 112 side is higher than 5% and lower than 35%. is there. If the aperture ratio of the specific electrode (the fuel electrode 116 or the air electrode 114) on the electrolyte layer 112 side is excessively high, the electrolyte layer 112 may have a defective portion, which may reduce the density and cause gas leakage. is there. On the other hand, if the aperture ratio of the specific electrode (fuel electrode 116 or air electrode 114) on the electrolyte layer 112 side is excessively low, the gas diffusion resistance of the specific electrode (fuel electrode 116 or air electrode 114) may increase. is there. According to the single cell 110 (or 110a) of each of the above embodiments, the aperture ratio of the specific electrode (fuel electrode 116 or air electrode 114) on the electrolyte layer 112 side may be excessively high or excessively low. As a result, it is possible to suppress the performance of the single cell 110 (or 110a) from being deteriorated.

  In the unit cell 110 (or 110a) of each of the above embodiments, the grain growth direction D1 of the particles PA in the electrolyte layer 112 is relative to the surface of the specific electrode (fuel electrode 116 or air electrode 114) facing the electrolyte layer 112. And a direction having an inclination angle θ of 75 degrees or more and 90 degrees or less. When the inclination angle θ is excessively small, the movement of oxygen ions in the stacking direction in the electrolyte layer 112 is hindered by the grain boundary in the electrolyte layer 112, the oxygen ion transport efficiency is lowered, and the performance of the single cell 110 (or 110a) is reduced. May decrease. According to the single cell 110 (or 110a) of each of the above embodiments, it is possible to avoid the inclination angle θ of the particle growth direction D1 of the particle PA in the electrolyte layer 112 from becoming excessively small. As a result, the single cell 110 It can suppress that the performance of (or 110a) falls.

  In the unit cell 110 (or 110a) of each of the above embodiments, the electrolyte layer 112 includes yttria-stabilized zirconia (YSZ) as a solid oxide. According to the single cell 110 (or 110a) of each of the embodiments described above, the electrolyte layer 112 containing YSZ is ensured to be dense while suppressing the electrolyte layer 112 from becoming excessively thick. It can suppress that the performance of the single cell 110 (or 110a) falls.

  In the single cell 110 (or 110a) of each of the above embodiments, the full width at half maximum (FWHM) of the YSZ diffraction line obtained by XRD measurement using the CoKα ray for the electrolyte layer 112 is 0.2 deg or less. . If the FWHM is excessively large, the particles constituting the electrolyte layer 112 are excessively small, the oxygen ion transport efficiency in the electrolyte layer 112 is decreased, and the performance of the single cell 110 (or 110a) may be decreased. According to the single cell 110 (or 110a) of each of the above embodiments, the FWHM can be prevented from becoming excessively large, and as a result, the performance of the single cell 110 (or 110a) can be prevented from being deteriorated. Can do.

  In the single cell 110 (or 110a) of each of the above embodiments, the thickness of the electrolyte layer 112 in the Z-axis direction is 20 μm or less. Therefore, according to the single cell 110 (or 110a) of each of the above embodiments, it is possible to suppress an increase in IR resistance due to an excessively thick electrolyte layer 112, and as a result, It can suppress that the performance of the single cell 110 (or 110a) falls. In addition, the thickness of the electrolyte layer 112 in the Z-axis direction is more preferably 10 μm or less, and further preferably 5 μm or less. Further, from the viewpoint of ensuring the denseness of the electrolyte layer 112, the thickness of the electrolyte layer 112 in the Z-axis direction is preferably 1 μm or more, more preferably 2 μm or more, and further preferably 3 μm or more.

  The single cell 110 (or 110a) of each of the above embodiments is further disposed on the opposite side of the electrolyte layer 112 with respect to the specific electrode (fuel electrode 116 or air electrode 114), and the single cell 110 (or 110a). A porous metal support 118 is provided. Therefore, according to the single cell 110 (or 110a) of each of the above embodiments, the thickness of the electrolyte layer 112 formed on the specific electrode (the fuel electrode 116 or the air electrode 114) supported by the metal support 118 is excessive. Therefore, it is possible to ensure the denseness of the electrolyte layer 112 while suppressing the thickness of the single cell 110 (or 110a) from being deteriorated.

  In addition, the manufacturing method of the unit cell 110 (or 110a) of each of the above embodiments includes a step of preparing a specific electrode (the fuel electrode 116 or the air electrode 114) having a surface roughness Rz of 30 μm or less, and a specific surface. The step of forming the electrolyte layer 112 on the one surface of the electrode (fuel electrode 116 or air electrode 114) by the vapor phase method and the side of the electrolyte layer 112 facing the specific electrode (fuel electrode 116 or air electrode 114) Forming the other electrode (the air electrode 114 or the fuel electrode 116) on the opposite side. The manufacturing method of the unit cell 110 (or 110a) of each of the above embodiments includes a step of preparing a specific electrode (the fuel electrode 116 or the air electrode 114) having a surface roughness Rz of one surface of 30 μm or less. One surface of the electrode (the fuel electrode 116 or the air electrode 114) is a surface in which the height of the convex portion is relatively low and the depth of the concave portion is relatively shallow. Therefore, in the method of manufacturing the single cell 110 (or 110a) of each of the embodiments described above, when the electrolyte layer 112 is formed on the one surface of the specific electrode (the fuel electrode 116 or the air electrode 114) by the vapor phase method, the electrolyte Even if the thickness of the layer 112 is not excessively increased, it is possible to prevent the denseness from being lowered due to the occurrence of a defective portion in the electrolyte layer 112 or the like. Therefore, according to the method of manufacturing the single cell 110 (or 110a) of each of the embodiments described above, the denseness of the electrolyte layer 112 is suppressed while suppressing an increase in IR resistance due to an excessively thick electrolyte layer 112. Generation | occurrence | production of the gas leak by falling can be suppressed, As a result, it can suppress that the performance of the single cell 110 (or 110a) falls.

  Moreover, in the manufacturing method of the single cell 110 (or 110a) of each said embodiment, it is preferable that a sputtering process is employ | adopted as a gaseous-phase method. In the sputtering process, the energy of the particles forming the film is larger than in other vapor phase methods such as vapor deposition, so that the electrolyte layer 112 having strong adhesion to the surface of the specific electrode (the fuel electrode 116 or the air electrode 114). As a result, the denseness of the electrolyte layer 112 can be more reliably ensured, and the deterioration of the performance of the single cell 110 (or 110a) can be more effectively suppressed.

E. Variation:
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 (or 110a) and the fuel cell stack 100 (or electrolysis cell stack 100a) in each of the above embodiments is merely an example, and various modifications can be made. For example, in the first embodiment, the metal support 118 is disposed on the side opposite to the electrolyte layer 112 with respect to the fuel electrode 116, but the metal support 118 is disposed on the electrolyte layer 112 with respect to the air electrode 114. It may be arranged on the opposite side. In this case, the electrolyte layer 112 is formed on the surface of the air electrode 114 on the side facing the electrolyte layer 112 using the air electrode 114 formed on the metal support 118 as a base layer. Therefore, the surface roughness Rz of the surface of the air electrode 114 facing the electrolyte layer 112 is set to 30 μm or less, and the aperture ratio of the portion of the air electrode 114 on the electrolyte layer 112 side is higher than 5% and less than 35%. It is said that. In this case, the air electrode 114 corresponds to the specific electrode in the claims.

  Similarly, in the second embodiment, the metal support 118 is disposed on the side opposite to the electrolyte layer 112 with respect to the air electrode 114, but the metal support 118 is disposed on the electrolyte layer with respect to the fuel electrode 116. It may be arranged on the side opposite to 112. In this case, the electrolyte layer 112 is formed on the surface of the fuel electrode 116 on the side facing the electrolyte layer 112 using the fuel electrode 116 formed on the metal support 118 as a base layer. Therefore, the surface roughness Rz of the surface facing the electrolyte layer 112 in the fuel electrode 116 is set to 30 μm or less, and the opening ratio of the portion on the electrolyte layer 112 side in the fuel electrode 116 is higher than 5% and less than 35%. It is said that. In this case, the fuel electrode 116 corresponds to the specific electrode in the claims.

  Further, the single cell 110 (or 110a) is not necessarily provided with the metal support 118. When the single cell 110 (or 110a) does not include the metal support 118, the single cell 110 (or 110a) is formed by any layer (for example, the fuel electrode 116 or the air electrode 114) constituting the single cell 110 (or 110a). ) Is ensured. That is, the present invention is not limited to the metal-supported single cell 110 (or 110a) but can be similarly applied to other types (for example, a fuel electrode support type or an air electrode support type) single cell 110 (or 110a). It is.

  Further, in each of the above embodiments, the electrolyte layer 112 includes the specific electrode (fuel electrode 116 or the electrode among the upper surfaces of the metal support 118 in addition to the upper surface of the specific electrode (fuel electrode 116 or air electrode 114). The region not covered with the air electrode 114 is also formed so as to cover, but other means (for example, the peripheral portion of the metal support 118 is made dense, the dense peripheral portion of the metal support 118 and the separator 120 are formed. If the gas leakage suppression between the fuel chamber 176 and the air chamber 166 can be realized by means of joining the two, the electrolyte layer 112 does not necessarily have to cover the surface of the metal support 118.

  Further, a diffusion suppression layer that suppresses element diffusion between the metal support 118 and the electrode may be disposed between the metal support 118 and the electrode (the fuel electrode 116 or the air electrode 114). The diffusion suppression layer is formed of, for example, a spinel or perovskite electron conductor material. When the diffusion suppression layer is used in the fuel electrode atmosphere, the diffusion suppression layer may be formed of a ceria-based electron conductor material.

In addition, an element (for example, Sr) diffused from the air electrode 114 reacts with an element (for example, Zr) contained in the electrolyte layer 112 between the air electrode 114 and the electrolyte layer 112, and a high resistance substance (for example, A reaction preventing layer that suppresses generation of SrZrO ₃ ) may be disposed. The reaction preventing layer is formed of, for example, a ceria-based ion conductor material.

  Further, in each of the above-described embodiments, the requirements regarding the surface roughness Rz and the like described above need not be satisfied for all the single cells 110 (or 110a) included in the fuel cell stack 100 (or the electrolysis cell stack 100a). Instead, it is only necessary that at least one single cell 110 (or 110a) included in the fuel cell stack 100 (or electrolysis cell stack 100a) satisfies the above-described requirements.

  In each of the above embodiments, the number of power generation units 102 (or electrolysis units 102a) included in the fuel cell stack 100 (or electrolysis cell stack 100a) (that is, the number of single cells 110 (or 110a)) is merely an example. The number of power generation units 102 (or electrolysis units 102a) is appropriately determined according to the performance required for the fuel cell stack 100 (or electrolysis cell stack 100a). Moreover, the material which comprises each member in each said embodiment is an illustration to the last, and each member may be comprised with the other material. For example, in each of the above embodiments, the electrolyte layer 112 is formed of YSZ, but the electrolyte layer 112 may be formed of other solid oxides such as ceria-based and LSGM-based.

  Moreover, the manufacturing method of the single cell 110 (or 110a) in the said embodiment is an example to the last, and can be variously modified. For example, the electrolyte layer 112 may be formed by a method other than the vapor phase method (for example, a firing method).

22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 28: Body portion 29: Branch portion 100: Fuel cell stack 100a: Electrolytic cell stack 102: Fuel cell power generation unit 102a: Electrolysis unit 104: End plate 106: End Plate 108: Communication hole 110: Fuel cell single cell 110a: Electrolytic single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 118: Metal support 120: Separator 121: Hole 124: Junction 130: Air electrode side frame 131 : Hole 132: Oxidant gas supply communication hole 132a: Air electrode side gas supply communication hole 133: Oxidant gas discharge communication hole 133a: Air electrode side gas discharge communication hole 134: Air electrode side current collector 135: Current collector element 140: Fuel electrode side frame 141: Hole 142: Fuel gas supply Supply communication hole 142a: Fuel electrode side gas supply communication hole 143: Fuel gas discharge communication hole 143a: Fuel electrode side gas discharge communication hole 144: Fuel electrode side current collector 145: Current collector element 150: Interconnector 161: Oxidant Gas introduction manifold 161a: Air electrode side gas introduction manifold 162: Oxidant gas discharge manifold 162a: Air electrode side gas discharge manifold 166: Air chamber 171: Fuel gas introduction manifold 171a: Fuel electrode side gas introduction manifold 172: Fuel gas discharge manifold 172a: Fuel electrode side gas discharge manifold 176: Fuel chamber

Claims (10)

An electrolyte layer containing a solid oxide; a porous fuel electrode disposed on one side of the electrolyte layer in a first direction; and a porous electrode disposed on the other side of the electrolyte layer in the first direction. In an electrochemical reaction single cell comprising an air electrode,
The electrochemical reaction unit cell characterized in that the surface roughness Rz of the surface facing the electrolyte layer in the specific electrode which is one of the fuel electrode and the air electrode is 30 μm or less. The electrochemical reaction single cell according to claim 1,
The electrochemical reaction unit cell, wherein an opening ratio of a portion on the electrolyte layer side of the specific electrode is higher than 5% and lower than 35%. The electrochemical reaction single cell according to claim 1 or 2,
The electrochemical reaction unit cell, wherein the electrolyte layer includes yttria stabilized zirconia (YSZ) as the solid oxide. In the electrochemical reaction single cell as described in any one of Claim 1- Claim 3,
The electrochemical reaction unit cell, wherein a thickness of the electrolyte layer in the first direction is 20 μm or less. In the electrochemical reaction single cell according to any one of claims 1 to 4,
The growth direction of the particles in the electrolyte layer is a direction having an inclination angle of 75 degrees or more and 90 degrees or less with respect to the surface of the specific electrode facing the electrolyte layer. cell. The electrochemical reaction single cell according to claim 3,
A single cell for electrochemical reaction, wherein the full width at half maximum (FWHM) of a YSZ diffraction line obtained by XRD measurement using CoKα rays is 0.2 deg or less for the electrolyte layer. The electrochemical reaction single cell according to any one of claims 1 to 6, further comprising:
An electrochemical reaction single cell comprising a porous metal support disposed on the opposite side of the electrolyte layer with respect to the specific electrode and supporting the electrochemical reaction single cell. In an electrochemical reaction cell stack comprising a plurality of electrochemical reaction single cells arranged side by side in the first direction,
The electrochemical reaction cell stack according to claim 1, wherein at least one of the plurality of electrochemical reaction single cells is the electrochemical reaction single cell according to claim 1. An electrolyte layer containing a solid oxide; a porous fuel electrode disposed on one side of the electrolyte layer in a first direction; and a porous electrode disposed on the other side of the electrolyte layer in the first direction. In a method for producing an electrochemical reaction single cell comprising an air electrode,
Preparing the specific electrode which is one of the fuel electrode and the air electrode, the surface roughness Rz of one surface being 30 μm or less;
Forming the electrolyte layer on the one surface of the specific electrode by a vapor phase method;
Forming the other electrode of the fuel electrode and the air electrode on the opposite side of the electrolyte layer from the side facing the specific electrode;
A method for producing an electrochemical reaction single cell, comprising: In the manufacturing method of the electrochemical reaction single cell according to claim 9,
The method for producing an electrochemical reaction single cell, wherein the vapor phase method is a sputtering process.