JP2024108239A - Electrochemical reaction unit and method for manufacturing electrochemical reaction device - Google Patents

Abstract

[Problem] To improve the performance (particularly durability characteristics) of an electrochemical reaction unit. [Solution] An electrochemical reaction unit includes an electrochemical reaction unit cell including an electrolyte layer, and an air electrode and an anode facing each other in a first direction with the electrolyte layer sandwiched therebetween, and having a reaction section in which the electrolyte layer, the air electrode, and the anode overlap when viewed in the first direction. The anode reaction section, which is a portion of the anode included in the reaction section and which defines a reaction gas flow path, contains P. When the anode reaction section is divided into a first portion located upstream of the gas flow in a second direction intersecting the first direction, and a second portion located downstream of the gas flow in the second direction, the P content in the first portion is greater than the P content in the second portion. [Selected Figure] Figure 8

Description

The technology disclosed in this specification relates to an electrochemical reaction unit and a method for manufacturing an electrochemical reaction device.

Solid oxide fuel cells (hereinafter referred to as "SOFCs") are known as one type of fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen (see, for example, Patent Document 1). A fuel cell power generation unit (hereinafter referred to as "power generation unit"), which is a constituent unit of an SOFC, has a single fuel cell cell (hereinafter referred to as "single cell"). The single cell includes an electrolyte layer, and an air electrode and a fuel electrode that face each other in a specific direction (hereinafter referred to as "first direction") with the electrolyte layer in between. The single cell has a reaction section where the electrolyte layer, air electrode, and fuel electrode overlap when viewed in the first direction.

In addition, the power generation unit of the fuel cell is formed with a fuel chamber facing the fuel electrode, and a reactant gas flow path is formed as part of the fuel chamber. A part of the reactant gas flow path is defined by a part of the fuel electrode that is included in the reaction section (hereinafter referred to as the "fuel electrode reaction section"). In the reactant gas flow path, the reactant gas flows in a second direction that intersects with the first direction.

JP 2015-32489 A

The reaction gas that flows through the reaction gas flow path defined by the fuel electrode reaction section and is then supplied to the fuel electrode may contain Cl (chlorine) due to the water used to generate the reaction gas containing Cl. If this Cl adheres to the fuel electrode, it may cause "poisoning of the fuel electrode," which reduces the performance (especially the durability characteristics) of the single cell.

Note that these issues are also common to electrolysis cell units, including electrolysis unit cells, which are constituent units of solid oxide electrolysis cells (hereinafter referred to as "SOECs") that generate hydrogen using the electrolysis reaction of water. Note that in this specification, a fuel cell unit cell and an electrolysis unit cell are collectively referred to as an electrochemical reaction unit, a fuel cell power generation unit and an electrolysis cell unit are collectively referred to as an electrochemical reaction unit, and a fuel cell stack having multiple fuel cell power generation units and an electrolysis cell stack having multiple electrolysis cell units are collectively referred to as an electrochemical reaction cell stack. Furthermore, these issues are not limited to SOFCs and SOECs, but are common to electrochemical reaction devices in general, including other types of electrochemical reaction cell stacks, etc.

This specification discloses a technology that can solve the above-mentioned problems.

The technology disclosed in this specification can be realized, for example, in the following forms:

(1) The electrochemical reaction unit disclosed in this specification includes an electrolyte layer, an air electrode and an anode facing each other in a first direction with the electrolyte layer therebetween, and includes an electrochemical reaction unit having a reaction section in which the electrolyte layer, the air electrode, and the anode overlap when viewed in the first direction, and a reaction gas flow path that is at least a part of a fuel chamber facing the anode is defined by an anode reaction section that is a part of the anode that is included in the reaction section, and a reaction gas flow path in which a reaction gas flows in a second direction intersecting the first direction is formed, and the anode reaction section contains P, and when the anode reaction section is divided into a first section located upstream of the gas flow in the second direction and a second section located downstream of the gas flow in the second direction, the P content in the first section is greater than the P content in the second section. Therefore, in this electrochemical reaction unit, the performance of the electrochemical reaction unit can be efficiently improved.

(2) In the electrochemical reaction unit, when the fuel electrode reaction portion is divided into a third portion located on the electrolyte layer side in the first direction and a fourth portion located on the opposite side of the electrolyte layer in the first direction from the third portion, the P content in the third portion may be greater than the P content in the fourth portion. In this electrochemical reaction unit, the P content in the third portion is greater than the P content in the fourth portion, thereby efficiently improving the performance of the electrochemical reaction unit.

(3) In the electrochemical reaction unit, the electrochemical reaction single cell may be configured to include a fuel electrode non-reactive portion of the fuel electrode that is not included in the reaction portion and is located upstream of the gas flow in the second direction relative to the fuel electrode reaction portion and contains P. In this electrochemical reaction unit, Cl contained in the reaction gas flowing near the boundary reacts with P contained in the non-reactive portion to form a compound. Therefore, according to this electrochemical reaction unit, the performance of the electrochemical reaction single cell can be more effectively improved.

(4) In the electrochemical reaction unit, the P content in the non-reaction specific portion may be less than the P content in the fuel electrode reaction portion. According to this electrochemical reaction unit, even if another member such as a separator is joined to the non-reaction portion of the electrochemical reaction unit that is not included in the reaction portion via a solder material such as Ag solder or a joining material made of glass, adverse effects caused by P scattering in the joining material located near the non-reaction specific portion can be suppressed.

(5) In the manufacturing method of the electrochemical reaction device having the electrochemical reaction unit, the method may include a preparation step of preparing a pre-finished electrochemical reaction device having a pre-finished electrochemical reaction unit cell including an electrolyte layer member that is a member that becomes the electrolyte layer, an air electrode member that is a member that becomes the air electrode, and an anode member that is anode and contains P, and a specification step of operating the pre-finished electrochemical reaction device in a reaction operation, in which a reaction gas is caused to flow in the second direction in the reaction gas flow path, thereby moving P in the anode member in the second direction, so that the P content in the first part is greater than the P content in the second part. According to this manufacturing method, a configuration that satisfies the condition that "the P content in the first part is greater than the P content in the second part" can be easily realized (manufactured).

The technology disclosed in this specification can be realized in various forms, such as an electrochemical reaction unit, an electrochemical reaction device equipped with an electrochemical reaction unit (fuel cell stack, electrolysis cell stack, etc.), and a manufacturing method thereof.

FIG. 1 is a perspective view showing an external configuration of a fuel cell stack 100 according to an embodiment of the present invention; FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along the line II-II in FIG. FIG. 2 is an explanatory diagram showing a YZ cross-sectional configuration of the fuel cell stack 100 taken along the line III-III in FIG. 1. FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in FIG. 2 . FIG. 4 is an explanatory diagram showing the YZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in FIG. 3 . FIG. 6 is an explanatory diagram showing an enlarged view of the fuel electrode 116 and its periphery (part of FIG. 5) of the power generating unit 102. Flowchart showing a method for manufacturing a fuel cell stack 100 Diagram showing the performance evaluation results

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

The fuel cell stack 100 comprises a plurality (seven in this embodiment) of fuel cell power generation units (hereinafter simply referred to as "power generation units") 102, a pair of terminal plates 70, 80, and a pair of end plates 104, 106. The seven power generation units 102 are arranged in a predetermined arrangement direction (vertical direction in this embodiment). The arrangement direction (Z-axis direction) is an example of the first direction in the claims.

One of the pair of terminal plates 70, 80 (hereinafter referred to as the "upper terminal plate 70") is disposed on the upper side of an assembly (hereinafter referred to as the "power generation block 103") consisting of seven power generation units 102, and one of the pair of end plates 104, 106 (hereinafter referred to as the "upper end plate 104") is disposed on the upper side of the upper terminal plate 70. The other of the pair of terminal plates 70, 80 (hereinafter referred to as the "lower terminal plate 80") is disposed on the lower side of the power generation block 103, and the other of the pair of end plates 104, 106 (hereinafter referred to as the "lower end plate 106") is disposed on the lower side of the lower terminal plate 80. An insulating sheet 92 is interposed between the upper terminal plate 70 and the upper end plate 104, and between the lower terminal plate 80 and the lower end plate 106. The insulating sheet 92 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder sheet, a glass sheet, a glass ceramic composite, etc. More specifically, a cover separator 60 (described later) is interposed between the upper terminal plate 70 and the insulating sheet 92.

A plurality of holes (eight in this embodiment) that penetrate in the vertical direction are formed in the peripheral portion around the Z axis direction of each layer (power generation unit 102, terminal plates 70, 80, end plates 104, 106) that constitutes the fuel cell stack 100, and corresponding holes formed in each layer communicate with each other in the vertical direction to form communication holes 108 that extend in the vertical direction from the upper end plate 104 to the lower end plate 106. In the following description, the holes formed in each layer of the fuel cell stack 100 to form the communication holes 108 may also be referred to as communication holes 108.

A bolt 22 extending in the vertical direction is inserted into each communication hole 108, and the fuel cell stack 100 is fastened by the vertical compressive force of the bolt 22 and the nuts 24 fitted on both sides of the bolt 22. As shown in Figs. 2 and 3, an insulating sheet 26 is interposed between the nut 24 fitted on one side (upper side) of the bolt 22 and the upper surface of the upper end plate 104, and between the nut 24 fitted on the other side (lower side) of the bolt 22 and the lower surface of the lower end plate 106. However, at the location where the gas passage member 27 described later is provided, the gas passage member 27 and the insulating sheets 26 arranged on the upper and lower sides of the gas passage member 27 are interposed between the nut 24 and the surface of the lower end plate 106. 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, etc.

The outer diameter of the shaft of each bolt 22 is smaller than the inner diameter of each communication hole 108. Therefore, a space is provided between the outer peripheral surface of the shaft of each bolt 22 and the inner peripheral surface of each communication hole 108. As shown in Figures 1 and 2, a space formed by a bolt 22 (bolt 22A) located near the midpoint of one side (the side on the positive X-axis side of two sides parallel to the Y-axis) on the outer periphery of the fuel cell stack 100 around the Z-axis direction and the communication hole 108 through which the bolt 22A is inserted functions as an oxidant gas supply manifold 161, which is a gas flow path through which oxidant gas OG is introduced from outside the fuel cell stack 100 and the oxidant gas OG is supplied to each power generating unit 102, and a space formed by a bolt 22 (bolt 22B) located near the midpoint of the side opposite to the side (the side on the negative X-axis side of two sides parallel to the Y-axis) and the communication hole 108 through which the bolt 22B is inserted functions as an oxidant gas discharge manifold 162 that discharges oxidant off-gas OOG, which is gas discharged from an air chamber 166 of each power generating unit 102, to the outside of the fuel cell stack 100. In this embodiment, air, for example, is used as the oxidant gas OG.

As shown in Figures 1 and 3, the space formed by the bolt 22 (bolt 22D) located near the midpoint of one side (the side on the positive Y-axis side of the two sides parallel to the X-axis) on the outer periphery of the fuel cell stack 100 around the Z-axis direction and the communication hole 108 through which the bolt 22D is inserted functions as a fuel gas supply manifold 171 through which fuel gas FG is introduced from outside the fuel cell stack 100 and the fuel gas FG is supplied to each power generation unit 102, and the space formed by the bolt 22 (bolt 22E) located near the midpoint of the opposite side (the side on the negative Y-axis side of the two sides parallel to the X-axis) and the communication hole 108 through which the bolt 22E is inserted functions as a fuel gas exhaust manifold 172 that exhausts fuel off-gas FOG, which is gas exhausted from the fuel chamber 176 of each power generation unit 102, to the outside of the fuel cell stack 100. In this embodiment, the fuel gas FG is, for example, hydrogen-rich gas obtained by reforming city gas.

The fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body 28 and a hollow cylindrical branch portion 29 branched from the side of the main body 28. The hole of the branch portion 29 is connected to the hole of the main body 28. A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27. As shown in FIG. 2, the hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22A forming the oxidizing gas supply manifold 161 is connected to the oxidizing gas supply manifold 161, and the hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22B forming the oxidizing gas exhaust manifold 162 is connected to the oxidizing gas exhaust manifold 162. Also, as shown in FIG. 3, the hole in the body 28 of the gas passage member 27 located at the position of the bolt 22D that forms the fuel gas supply manifold 171 is connected to the fuel gas supply manifold 171, and the hole in the body 28 of the gas passage member 27 located at the position of the bolt 22E that forms the fuel gas exhaust manifold 172 is connected to the fuel gas exhaust manifold 172.

(Configuration of end plates 104, 106)
The pair of end plates 104, 106 are flat members having an approximately rectangular outer shape as viewed in the Z-axis direction, and are made of, for example, stainless steel. Holes 32, 34 penetrating in the Z-axis direction are formed near the centers of the pair of end plates 104, 106, respectively. As viewed in the Z-axis direction, the inner circumferential lines of the holes 32, 34 formed in each of the pair of end plates 104, 106 encompass each of the unit cells 110 described below. Therefore, the compressive force in the Z-axis direction by each bolt 22 and nut 24 acts mainly on the peripheral portion of each power generating unit 102 (the portion on the outer periphery of each of the unit cells 110 described below).

(Configuration of Terminal Plates 70, 80)
The pair of terminal plates 70, 80 are flat members having an approximately rectangular outer shape as viewed in the Z-axis direction, and are made of, for example, stainless steel. A hole 71 is formed near the center of the upper terminal plate 70, penetrating in the Z-axis direction. As viewed in the Z-axis direction, the inner circumferential line of the hole 71 formed in the upper terminal plate 70 includes each of the unit cells 110 described later. In this embodiment, as viewed in the Z-axis direction, the inner circumferential line of the hole 71 formed in the upper terminal plate 70 approximately coincides with the inner circumferential line of the hole 32 formed in the upper end plate 104. As viewed in the Z-axis direction, the upper terminal plate 70 has a protruding portion 78 that protrudes outward from the outer circumferential line of the upper end plate 104, and the protruding portion 78 functions as a positive output terminal of the fuel cell stack 100. In addition, the lower terminal plate 80 has a protrusion 88 that protrudes outward from the outer periphery of the lower end plate 106 when viewed in the Z-axis direction, and the protrusion 88 functions as the negative output terminal of the fuel cell stack 100.

(Configuration of power generation unit 102)
FIG. 4 is an explanatory diagram showing the XZ cross-sectional configuration of two adjacent power generation units 102 (the two power generation units 102 located at the top) at the same position as the cross-section shown in FIG. 2, and FIG. 5 is an explanatory diagram showing the YZ cross-sectional configuration of two adjacent power generation units 102 (the two power generation units 102 located at the top) at the same position as the cross-section shown in FIG. 3.

As shown in Figures 4 and 5, the power generation unit 102 includes a fuel cell unit (hereinafter referred to as a "unit cell") 110, a unit cell separator 120, an air electrode side frame 130, a fuel electrode side frame 140, a fuel electrode side current collecting member 148, and a pair of interconnectors 190 and a pair of interconnector separators (hereinafter referred to as "IC separators") 180 that constitute the uppermost and lowermost layers of the power generation unit 102. Holes corresponding to the communication holes 108 through which the bolts 22 described above are inserted are formed in the peripheral portions around the Z-axis direction of the unit cell separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the IC separator 180.

The single cell 110 includes an electrolyte layer 112, an air electrode 114 arranged on one side (upper side) of the electrolyte layer 112 in the Z-axis direction, a fuel electrode 116 arranged on the other side (lower side) of the electrolyte layer 112 in the Z-axis direction, and an intermediate layer 118 arranged between the electrolyte layer 112 and the air electrode 114. The single cell 110 of this embodiment is an anode-supported single cell in which the fuel electrode 116 supports the other layers (electrolyte layer 112, air electrode 114, intermediate layer 118) that constitute the single cell 110. The single cell 110 has a power generation section PG in which the electrolyte layer 112, the air electrode 114, and the fuel electrode 116 overlap when viewed in the Z-axis direction. The power generation section PG is an example of a reaction section in the claims.

The electrolyte layer 112 is a substantially rectangular flat-plate member as viewed in the Z-axis direction, and is configured to include a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). That is, the unit cell 110 of this embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte. The air electrode 114 is a substantially rectangular flat-plate member smaller than the electrolyte layer 112 as viewed in the Z-axis direction, and is configured to include, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The fuel electrode 116 is a substantially rectangular flat-plate member having substantially the same size as the electrolyte layer 112 as viewed in the Z-axis direction, and is formed porously from, for example, Ni (nickel), a cermet made of Ni and ceramic particles (e.g., YSZ), a Ni-based alloy, or the like. The thickness of the fuel electrode 116 in the Z-axis direction is, for example, 5 μm or more and 1200 μm or less. The intermediate layer 118 is a generally rectangular flat-plate member having approximately the same size as the air electrode 114 when viewed in the Z-axis direction, and is configured to contain, for example, GDC (gadolinium-doped ceria) and YSZ. The intermediate layer 118 has the function of suppressing the reaction of an element (e.g., Sr) diffused from the air electrode 114 with an element (e.g., Zr) contained in the electrolyte layer 112 to generate a highly resistive substance (e.g., _SrZrO3 ).

The single cell separator 120 is a frame-shaped conductive member having a substantially rectangular hole 121 penetrating in the Z-axis direction near the center, and is formed of, for example, metal. The single cell separator 120 is joined to the single cell 110 in a state where it overlaps with at least a part of the single cell 110 in the Z-axis direction. More specifically, the portion surrounding the hole 121 in the single cell separator 120 (hereinafter referred to as the "through hole surrounding portion") faces the peripheral portion of the surface of the electrolyte layer 112 on the side (upper side) of the air electrode 114. The single cell separator 120 is joined to the electrolyte layer 112 (single cell 110) by a joint 124 formed of a brazing material (e.g., Ag brazing) arranged in the facing portion. The single cell separator 120 separates the air chamber 166 facing the air electrode 114 from the fuel chamber 176 facing the fuel electrode 116, suppressing gas leakage (cross leakage) from one electrode side to the other electrode side at the periphery of the single cell 110.

The single cell separator 120 includes an inner portion 126 including the through-hole periphery (the portion surrounding the hole 121) of the single cell separator 120, an outer portion 127 located on the outer periphery side of the inner portion 126, and a connecting portion 128 connecting the inner portion 126 and the outer portion 127. In this embodiment, the inner portion 126 and the outer portion 127 are substantially flat plates extending in a direction substantially perpendicular to the Z-axis direction. The connecting portion 128 is curved so as to protrude downward from both the inner portion 126 and the outer portion 127. The lower portion (fuel chamber 176 side) of the connecting portion 128 is a convex portion, and the upper portion (air chamber 166 side) of the connecting portion 128 is a concave portion. Therefore, the connecting portion 128 includes a portion whose position in the Z-axis direction is different from that of the inner portion 126 and the outer portion 127.

An insulating glass seal portion 125 containing glass is disposed near the hole 121 in the single cell separator 120. The glass seal portion 125 is located on the air chamber 166 side of the joint portion 124, and is disposed across the surface of the area surrounding the through-hole of the single cell separator 120 and the surface of the single cell 110 (electrolyte layer 112 in this embodiment). The glass seal portion 125 seals between the single cell 110 and the single cell separator 120, effectively suppressing gas leakage (cross leakage) from one electrode side to the other electrode side at the periphery of the single cell 110.

4 and 5, the interconnector 190 is a conductive member having a flat plate portion 150 having a substantially rectangular flat plate shape and a plurality of substantially columnar air electrode side current collecting portions 134 protruding from the flat plate portion 150 toward the air electrode 114 side, and is formed of a metal (e.g., ferritic stainless steel). In this embodiment, a conductive coating layer 194 composed of, for example, a spinel-type oxide is formed on the surface of the interconnector 190 (the surface facing the air chamber 166). Hereinafter, the interconnector 190 covered with the coating layer 194 is simply referred to as the interconnector 190. The interconnector 190 (more specifically, each air electrode side current collecting portion 134 of the interconnector 190) is electrically connected to the air electrode 114 of the single cell 110 by being joined to the air electrode 114 via a conductive bonding material 196 composed of, for example, a spinel-type oxide. The interconnector 190 ensures electrical conduction between the power generating units 102 and prevents the reaction gases from mixing between the power generating units 102. In this embodiment, when two power generating units 102 are arranged adjacent to each other, one interconnector 190 is shared by the two adjacent power generating units 102. That is, the upper interconnector 190 of a certain power generating unit 102 is the same material as the lower interconnector 190 of the other power generating unit 102 adjacent to the upper side of the power generating unit 102. In addition, the lower interconnector 190 of the power generating unit 102 located at the bottom of the fuel cell stack 100 is electrically connected to the lower terminal plate 80 via a conductive bonding material 196. In addition, the upper interconnector 190 of the power generating unit 102 located at the top of the fuel cell stack 100 is electrically connected to the upper terminal plate 70 via an IC separator 180 and/or other members (connecting member 48, cover member 50, cover separator 60) described later.

The IC separator 180 is a frame-shaped conductive member with a substantially rectangular hole 181 formed near the center that penetrates in the Z-axis direction, and is made of, for example, metal. The portion of the IC separator 180 that surrounds the hole 181 (hereinafter referred to as the "through hole surrounding portion") is joined, for example by welding, to the upper surface of the peripheral portion of the interconnector 190 (the flat portion 150 thereof). Of a pair of IC separators 180 included in a certain generating unit 102, the upper IC separator 180 partitions the air chamber 166 of the generating unit 102 and the fuel chamber 176 of the other generating unit 102 adjacent to the generating unit 102 on the upper side. In addition, of the pair of IC separators 180 included in a certain generating unit 102, the lower IC separator 180 separates the fuel chamber 176 of the generating unit 102 from the air chamber 166 of the other generating unit 102 adjacent to the generating unit 102 on the lower side. In this way, the IC separator 180 suppresses gas leakage between the generating units 102 at the periphery of the generating units 102.

The IC separator 180 includes an inner portion 186 including the through-hole periphery (the portion surrounding the hole 181) of the IC separator 180, an outer portion 187 located on the outer periphery side of the inner portion 186, and a connecting portion 188 connecting the inner portion 186 and the outer portion 187. In this embodiment, the inner portion 186 and the outer portion 187 are substantially flat plates extending in a direction substantially perpendicular to the Z-axis direction. The connecting portion 188 is curved so as to protrude downward from both the inner portion 186 and the outer portion 187. The lower portion (air chamber 166 side) of the connecting portion 188 is a convex portion, and the upper portion (fuel chamber 176 side) of the connecting portion 188 is a concave portion. Therefore, the connecting portion 188 includes a portion whose position in the Z-axis direction is different from that of the inner portion 186 and the outer portion 187.

4 and 5, the air electrode side frame 130 is a frame-shaped member with a substantially rectangular hole 131 formed near the center penetrating in the Z-axis direction, and is formed of an insulator such as mica. The hole 131 of the air electrode side frame 130 constitutes an air chamber 166 facing the air electrode 114. The air electrode side frame 130 is in contact with the peripheral portion of the surface of the single cell separator 120 opposite the side facing the electrolyte layer 112 (upper side) and the peripheral portion of the surface of the upper IC separator 180 facing the air chamber 166 (lower side), and functions as a sealing member that ensures gas sealing between the two (i.e., gas sealing of the air chamber 166). In addition, the air electrode side frame 130 electrically insulates a pair of IC separators 180 included in the power generation unit 102 (i.e., a pair of interconnectors 190). In addition, the air electrode side frame 130 is formed with an oxidant gas supply communication hole 132 that connects the oxidant gas supply manifold 161 to the air chamber 166, and an oxidant gas discharge communication hole 133 that connects the air chamber 166 to the oxidant gas discharge manifold 162.

4 and 5, the fuel electrode side frame 140 is a frame-shaped conductive member with a substantially rectangular hole 141 formed near the center that penetrates in the Z-axis direction, and is made of, for example, metal. The hole 141 of the fuel electrode side frame 140 constitutes a fuel chamber 176 facing the fuel electrode 116. The fuel electrode side frame 140 is in contact with the peripheral portion of the surface of the side (lower side) of the single cell separator 120 that faces the electrolyte layer 112, and the peripheral portion of the surface of the side (upper side) of the lower IC separator 180 that faces the fuel chamber 176. In addition, the fuel electrode side frame 140 is formed with a fuel gas supply communication hole 142 that communicates the fuel gas supply manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that communicates the fuel chamber 176 and the fuel gas discharge manifold 172.

The fuel electrode side current collecting member 148 is disposed in the fuel chamber 176. The fuel electrode side current collecting member 148 has a conductive portion 144 and an elastic portion 149. The conductive portion 144 is a portion that electrically connects the fuel electrode 116 and the interconnector 190, and is formed of, for example, nickel, a nickel alloy, stainless steel, or the like. The conductive portion 144 has an electrode facing portion 145 that contacts the lower surface of the fuel electrode 116, an interconnector facing portion 146 that contacts the upper surface of the interconnector 190, and a connecting portion 147 that connects the electrode facing portion 145 and the interconnector facing portion 146. The elastic portion 149 is a portion for ensuring the elasticity of the fuel electrode side current collecting member 148, and is formed of, for example, mica, or the like. The interconnector facing portion 146 of the conductive portion 144 is disposed between the interconnector 190 and the elastic portion 149 in the Z-axis direction, and the electrode facing portion 145 of the conductive portion 144 is disposed between the fuel electrode 116 and the elastic portion 149 in the Z-axis direction. This allows the fuel electrode side current collecting member 148 to follow the deformation of the power generating unit 102 due to temperature cycles and reactant gas pressure fluctuations, and the electrical connection between the fuel electrode 116 and the interconnector 190 via the fuel electrode side current collecting member 148 is well maintained. The fuel electrode side current collecting member 148 is produced, for example, by making cuts in a flat plate-shaped material (for example, nickel foil having a thickness of 10 to 200 μm), disposing a sheet-shaped elastic portion 149 having a plurality of holes formed therein on the material, and bending and raising the plurality of rectangular portions to sandwich the elastic portion 149. Each bent rectangular portion becomes the electrode facing portion 145, the flat portion with holes other than the bent portions becomes the interconnector facing portion 146, and the portion connecting the electrode facing portion 145 and the interconnector facing portion 146 becomes the connection portion 147.

As shown in Figures 4 and 5, each generating unit 102 of this embodiment further includes a felt member 41 arranged in the air chamber 166 and the fuel chamber 176. The felt member 41 is an insulating member made of an alumina-silica (silicon dioxide) based felt material. In other words, the felt member 41 contains alumina, which is a ceramic, and a silica component. The inclusion of alumina in the felt member 41 can improve the heat resistance and flexibility of the felt member 41.

4 and 5, in the air chamber 166, the felt members 41 are filled at both ends in the direction (Y-axis direction) perpendicular to the main flow direction (X-axis direction) of the oxidizer gas OG (positions that do not overlap with the air electrode 114 of the single cell 110 in the Z-axis direction). In the air chamber 166, a part of the felt member 41 (a part closer to the center of the single cell 110) is arranged to face the outer periphery of the interconnector 190 in the Z-axis direction. Also, as shown in FIGS. 4 and 5, in the fuel chamber 176, the felt members 41 are filled at both ends in the direction (X-axis direction) perpendicular to the main flow direction (Y-axis direction) of the fuel gas FG (positions that do not overlap with the air electrode 114 of the single cell 110 in the Z-axis direction). The presence of the felt member 41 can prevent the oxidant gas OG supplied to the air chamber 166 or the fuel gas FG supplied to the fuel chamber 176 from passing through areas that do not contribute much to power generation and being discharged from the air chamber 166 or the fuel chamber 176, improving power generation efficiency.

As shown in FIG. 4 and FIG. 5, the fuel cell stack 100 of this embodiment includes a cover member 50 and a cover separator 60 arranged above the uppermost generating unit 102 (hereinafter also referred to as the "specific generating unit 102X"). The cover member 50 is a flat plate-shaped member that is approximately rectangular when viewed in the Z-axis direction, and is made of a conductive material (e.g., metal). The cover member 50 is arranged in a hole 71 formed in the upper terminal plate 70, and is adjacent to the upper interconnector 190 included in the specific generating unit 102X while being spaced apart in the Z-axis direction. That is, a space (a space formed by the hole 71 of the upper terminal plate 70, hereinafter referred to as the "specific space 58") is formed between the cover member 50 and the upper interconnector 190 included in the specific generating unit 102X. The specific space 58 is located above the multiple single cells 110 (all the single cells 110) included in the fuel cell stack 100.

The cover separator 60 is a frame-like member with a substantially rectangular hole 61 formed near the center that penetrates in the Z-axis direction, and is made of, for example, metal. The portion of the cover separator 60 that surrounds the hole 61 (hereinafter referred to as the "through hole surrounding portion") is joined to the upper surface of the peripheral portion of the cover member 50, for example, by welding. The peripheral portion of the cover separator 60 is joined to the upper surface of the terminal plate 70, for example, by brazing. The specific space 58 is defined by the cover separator 60 (and the IC separator 180 joined to the upper interconnector 190 included in the specific power generation unit 102X).

The cover separator 60 includes an inner portion 66 including the through-hole periphery (the portion surrounding the hole 61) of the cover separator 60, an outer portion 67 located on the outer periphery side of the inner portion 66, and a connecting portion 68 connecting the inner portion 66 and the outer portion 67. In this embodiment, the inner portion 66 and the outer portion 67 are substantially flat plates extending in a direction substantially perpendicular to the Z-axis direction. The connecting portion 68 is curved so as to protrude downward from both the inner portion 66 and the outer portion 67. The lower portion (the specific space 58 side) of the connecting portion 68 is a convex portion, and the upper portion (the external space side) of the connecting portion 68 is a concave portion. Therefore, the connecting portion 68 includes a portion whose position in the Z-axis direction is different from that of the inner portion 66 and the outer portion 67.

The fuel cell stack 100 of this embodiment further includes a connection member 48 disposed in the specific space 58. In this embodiment, the connection member 48 has the same configuration as the fuel electrode side current collecting member 148. That is, the connection member 48 has a conductive portion 44 and an elastic portion 49. The conductive portion 44 is a portion that electrically connects the cover member 50 and the upper interconnector 190 included in the specific power generating unit 102X, and is formed of, for example, nickel, a nickel alloy, stainless steel, or the like. The conductive portion 44 has a cover member facing portion 45 that contacts the lower surface of the cover member 50, an interconnector facing portion 46 that contacts the upper surface of the interconnector 190, and a connecting portion 47 that connects the cover member facing portion 45 and the interconnector facing portion 46. The elastic portion 49 is a portion for ensuring the elasticity of the connection member 48, and is formed of, for example, mica, or the like. The interconnector facing portion 46 of the conductive portion 44 is disposed between the interconnector 190 and the elastic portion 49 in the Z-axis direction, and the cover member facing portion 45 of the conductive portion 44 is disposed between the cover member 50 and the elastic portion 49 in the Z-axis direction. The connection member 48 can be manufactured, for example, by a method similar to the manufacturing method of the fuel electrode side current collecting member 148 described above.

A-2. Operation of the fuel cell stack 100:
2 and 4, when 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 supply manifold 161, the oxidant gas OG is supplied to the oxidant gas supply manifold 161 through the branch portion 29 of the gas passage member 27 and a hole in the main body 28, and is supplied from the oxidant gas supply manifold 161 to the air chamber 166 through the oxidant gas supply passage hole 132 of each power generating unit 102. Also, as shown in Figs. 3 and 5, when 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 supply manifold 171, the fuel gas FG is supplied to the fuel gas supply manifold 171 through the branch portion 29 of the gas passage member 27 and a hole in the main body 28, and is supplied to the fuel chamber 176 from the fuel gas supply manifold 171 through the fuel gas supply passage hole 142 of each power generating unit 102.

When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, power is generated in the single cell 110 by an electrochemical reaction of the oxidant gas OG and 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 the interconnector 190 via a conductive bonding material 196, and the fuel electrode 116 is electrically connected to the interconnector 190 via the fuel electrode side current collecting member 148. That is, the multiple power generation units 102 included in the fuel cell stack 100 are electrically connected in series. In addition, in the fuel cell stack 100, the upper interconnector 190 of the power generation unit 102 located at the top is electrically connected to the upper terminal plate 70, and the lower interconnector 190 of the power generation unit 102 located at the bottom is electrically connected to the lower terminal plate 80. Therefore, the electrical energy generated in each power generating unit 102 is extracted from a pair of terminal plates 70, 80 that function as output terminals of the fuel cell stack 100. Since SOFCs generate electricity at relatively high temperatures (e.g., 700°C to 1000°C), the fuel cell stack 100 may be heated by a heater (not shown) after startup until the high temperature can be maintained by the heat generated by power generation.

As shown in Figs. 2 and 4, the oxidant off-gas OOG discharged from the air chamber 166 of each power generation unit 102 is discharged to the oxidant gas discharge manifold 162 through the oxidant gas discharge communication hole 133, and then through the holes in the main body 28 and the branching part 29 of the gas passage member 27 provided at the position of the oxidant gas discharge manifold 162, and is discharged to the outside of the fuel cell stack 100 through the gas pipe (not shown) connected to the branching part 29. Also, as shown in Figs. 3 and 5, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generation unit 102 is discharged to the fuel gas discharge manifold 172 through the fuel gas discharge communication hole 143, and then through the holes in the main body 28 and the branching part 29 of the gas passage member 27 provided at the position of the fuel gas discharge manifold 172, and is discharged to the outside of the fuel cell stack 100 through the gas pipe (not shown) connected to the branching part 29.

A-3. Detailed configuration of the fuel electrode 116 and its surroundings of the power generating unit 102:
FIG. 6 is an explanatory diagram showing an enlarged view of the periphery of the fuel electrode 116 of the power generating unit 102 (part of FIG. 5).

As described above, the single cell 110 of the power generation unit 102 has a power generation section PG in which the electrolyte layer 112, the air electrode 114, and the fuel electrode 116 overlap when viewed in the Z-axis direction.

The fuel electrode 116 has a portion FPG (hereinafter referred to as the "fuel electrode power generation portion") that is included in the power generation portion PG. The fuel electrode power generation portion FPG is part of the fuel chamber 176, and defines a part of the fuel gas flow path FP, which is a space through which the fuel gas FG flows in the Y-axis direction that intersects the Z-axis direction. The fuel electrode power generation portion FPG is an example of a fuel electrode reaction portion in the claims. The Y-axis direction is an example of a second direction in the claims. The fuel gas FG is an example of a reaction gas in the claims. The fuel gas flow path FP is an example of a reaction gas flow path in the claims.

The fuel electrode 116 contains P (phosphorus). The fuel electrode power generation part FPG also contains P.

When the fuel electrode power generation part FPG is divided into a first part FPG1 located on the upstream side of the gas flow in the Y-axis direction (positive side of the Y-axis) and a second part FPG2 located on the downstream side of the gas flow in the Y-axis direction (negative side of the Y-axis), the P content in the first part FPG1 is greater than the P content in the second part FPG2. The first part FPG1 is the upstream side of the gas flow (positive side of the Y-axis) when the fuel electrode power generation part FPG is divided into two parts (FPG1, FPG2) with a virtual plane B1 perpendicular to the gas flow direction (Y-axis direction) and passing through the center of the fuel electrode power generation part FPG as a boundary. The second part FPG2 is the downstream side of the gas flow (negative side of the Y-axis) of the two parts (FPG1, FPG2). Hereinafter, the above condition that "the P content in the first portion FPG1 is greater than the P content in the second portion FPG2" will be referred to as the first specific condition.

The method for identifying the P content of each portion (first portion FPG1, second portion FPG2) is as follows. First, the evaluation points (five points included in the first portion FPG1, five points included in the second portion FPG2) in the cross section along the Z-axis direction of the fuel electrode 116 were analyzed using secondary ion mass spectrometry (hereinafter referred to as "SIMS") to identify the P content (unit: ppm). As described above, the average value of the P content of the five points of each portion (first portion FPG1, second portion FPG2) to be compared is calculated, and if the average value of the first portion FPG1 is larger when the average values of the respective portions are compared, it can be said that the first specific condition (the P content of the first portion FPG1 is greater than the P content of the second portion FPG2) is satisfied. In addition, in this definition, the number of measurement points when determining the above-mentioned P content may be one of the parts to be compared (the first part FPG1, the second part FPG2). In addition, in these definitions, the first specific condition may be satisfied if the difference between the values to be compared (P content) is 10 ppm or more.

When the fuel electrode power generation part FPG is divided into a third part FPG3 located on the electrolyte layer 112 side in the Z-axis direction (positive side of the Z-axis) and a fourth part FPG4 located on the opposite side of the electrolyte layer 112 in the Z-axis direction (negative side of the Z-axis) from the third part FPG3, the P content in the third part FPG3 is greater than the P content in the fourth part FPG4. The third part FPG3 is the part on the electrolyte layer 112 side (positive side of the Z-axis) when the fuel electrode power generation part FPG is divided into two parts (FPG3, FPG4) with a virtual plane B2 perpendicular to the Z-axis direction and passing through the center of the fuel electrode power generation part FPG as a boundary. The second part FPG2 is the part of the two parts (FPG3, FPG4) on the opposite side of the electrolyte layer 112 (negative side of the Z-axis). Hereinafter, the above condition that "the P content in the third portion FPG3 is greater than the P content in the fourth portion FPG4" will be referred to as the second specific condition.

The method for identifying the P content of each portion (third portion FPG3, fourth portion FPG4) is the same as the method described above (method for first portion FPG1, second portion FPG2). The definition of whether the second specific condition is satisfied (number of measurement points, difference in values to be compared) is also the same as the definition described above (definition for first portion FPG1, second portion FPG2).

The P content in the first portion FPG1 and the third portion FPG3 is, for example, 50 ppm or more and 500 ppm or less. The P content in the second portion FPG2 and the fourth portion FPG4 is, for example, 1 ppm or more and 50 ppm or less.

The single cell 110 has a fuel electrode non-power generation portion FN of the fuel electrode 116 that is not included in the power generation portion PG.

The fuel electrode non-power generation portion FN has a portion FNS (hereinafter referred to as the "non-power generation specific portion") located upstream of the gas flow in the Y-axis direction (positive Y-axis direction) relative to the fuel electrode power generation portion FPG. As described above, the fuel electrode 116 contains P, and the non-power generation specific portion FNS also contains P. The non-power generation specific portion is an example of a non-reaction specific portion in the claims.

The P content in the non-power generation specific portion FNS is less than the P content in the fuel electrode power generation portion FPG. Hereinafter, this "P content in the non-power generation specific portion FNS is less than the P content in the fuel electrode power generation portion FPG" is referred to as the third specific condition.

The method for determining the P content of each portion (fuel electrode power generation portion FPG, non-power generation specific portion FNS) is the same as the method described above (method for the first portion FPG1 and the second portion FPG2). The definition of whether or not the third specific condition is satisfied (the number of measurement points, the difference in the values to be compared) is also the same as the definition described above (definition for the first portion FPG1 and the second portion FPG2).

The P content in the fuel electrode non-power generation portion FN (including the non-power generation specific portion FNS) is, for example, 0.1 ppm or more and 50 ppm or less, which is less than the P content in the fuel electrode power generation portion FPG.

A-4. Manufacturing method of the fuel cell stack 100:
7 is a flowchart showing a method for manufacturing the fuel cell stack 100. The fuel cell stack 100 of this embodiment can be manufactured, for example, as follows.

A-4-1. Preparation of the uncompleted fuel cell stack 200 (preparation process)
First, a pre-completed fuel cell stack 200 is prepared, which includes a pre-completed unit cell 210 including an electrolyte layer member 212 that is to become the electrolyte layer 112, an air electrode member 214 that is to become the air electrode 114, and an anode member 216 that is to become the anode 116 and contains P (ST1 in FIG. 7). Hereinafter, this step will be referred to as a "preparation step ST1." The pre-completed fuel cell stack 200 is an example of a pre-completed electrochemical reaction device in the claims.

A-4-1-1. Preparation of unfinished single cell 210 (forming a laminate of electrolyte layer member 212 and anode member 216)
Butyral resin, dioctyl phthalate (DOP) as a plasticizer, dispersant, and a mixed solvent of toluene and ethanol are added to the YSZ powder, and mixed in a ball mill to prepare a slurry. The obtained slurry is thinned by a doctor blade method to obtain a green sheet for an electrolyte layer. In addition, NiO powder is weighed out so that it is 55 parts by mass in terms of Ni weight, and mixed with 45 parts by mass of YSZ powder to obtain a mixed powder. Butyral resin, DOP as a plasticizer, dispersant, and a mixed solvent of toluene and ethanol are added to this mixed powder, and mixed in a ball mill to prepare a slurry. At this time, P is contained in the slurry by using a dispersant containing P. The obtained slurry is thinned by a doctor blade method to obtain a green sheet for an anode containing P. Next, the green sheet for an electrolyte layer and the green sheet for an anode are attached and dried. Then, for example, sintering is performed at 1400° C. for 1 to 5 hours. This results in a laminate of the electrolyte layer member 212 and the anode member 216. The distribution of the P content in the anode member 216 of the laminate thus obtained is basically uniform, and does not satisfy the first specific condition (the P content in the first portion FPG1 is greater than the P content in the second portion FPG2) or the third specific condition (the P content in the first portion FPG1 is greater than the P content in the second portion FPG2).

(Formation of Air Electrode Member 214)
The LSCF powder, polyvinyl alcohol as an organic binder, and butyl carbitol as an organic solvent are mixed, and the viscosity is adjusted to prepare a paste for the air electrode. The adjusted paste for the air electrode is applied to the surface of the electrolyte layer member 212 in the laminate of the electrolyte layer member 212 and the anode member 216 described above, for example, by screen printing, and dried, and the laminate on which the paste for the air electrode is applied is fired under predetermined firing conditions (for example, 1000 to 1200 ° C., 1 to 20 hours). This forms the air electrode member 214, and the unfinished unit cell 210 including the electrolyte layer member 212, the air electrode member 214, and the anode member 216 is produced. Note that various conventional methods (for example, the method described in JP 2020-113504 A) can be used as a method for producing the unfinished unit cell 210.

A plurality of unfinished single cells 210 are produced by the above-mentioned method, and a composite is prepared by combining these with a plurality of separators 120 and an air electrode side frame 130, etc., and this composite is fastened with bolts 22 and nuts 24. Furthermore, the composite is pressurized in the Z-axis direction while hardening the joints 124, and the remaining assembly and other processes are performed to prepare the unfinished fuel cell stack 200. After that, in order to make the unfinished fuel cell stack 200 ready for power generation, a reduction process is performed to reduce the fuel electrode member 216 (i.e., to reduce NiO contained in the fuel electrode member 216 to Ni). The reduction process is performed, for example, by exposing the fuel electrode member 216 to a hydrogen atmosphere at a predetermined temperature for a predetermined time. Note that the reduction gas used in the reduction process is not limited to hydrogen, and may be other gases such as methane gas. With the above, the preparation of the unfinished fuel cell stack 200 ready for power generation is completed.

A-4-1-2. Identification step Next, the unfinished fuel cell stack 200 is subjected to power generation (reaction) (for example, under conditions of 700°C and 15 hours). As a result, the fuel gas FG is caused to flow in the Y-axis direction in the fuel gas flow path FP, and the flow of the fuel gas FG causes the P in the fuel electrode member 216 to move in the Y-axis direction. As a result, the fuel electrode 116 is formed that satisfies the first specified condition (the P content in the first portion FPG1 is greater than the P content in the second portion FPG2) (ST2 in FIG. 7). In this embodiment, as described above, the second specified condition (the P content in the third portion FPG3 is greater than the P content in the fourth portion FPG4) and the second specified condition (the P content in the non-power generation specified portion FNS is less than the P content in the fuel electrode power generation portion FPG) are also satisfied. Hereinafter, this step will be referred to as the "identification step ST2".

The range and degree of movement of P in the fuel electrode member 216 can be adjusted by appropriately changing the temperature at which the uncompleted fuel cell stack 200 is operated to generate electricity, and the flow rate and flow speed of the fuel gas FG flowing through the fuel gas flow path FP.

This completes the manufacture of a fuel cell stack 100 that satisfies the first specific condition (the second specific condition, and the third specific condition).

A-5. Advantages of this embodiment:
As described above, the power generation unit 102 included in the fuel cell stack 100 of this embodiment includes a single cell 110. The single cell 110 includes an electrolyte layer 112, and an air electrode 114 and an anode 116 that face each other in the Z-axis direction with the electrolyte layer 112 sandwiched therebetween. The single cell 110 has a power generation section PG in which the electrolyte layer 112, the air electrode 114, and the anode 116 overlap when viewed in the Z-axis direction. The fuel cell stack 100 is formed with a fuel gas flow path FP that is a part of the fuel chamber 176 that faces the anode 116. The fuel gas flow path FP is defined by an anode power generation section FPG that is a part of the anode 116 that is included in the power generation section PG. In the fuel gas flow path FP, a fuel gas FG flows in the Y-axis direction that intersects the Z-axis direction. The anode power generation section FPG contains P. When the fuel electrode power generation portion FPG is divided into a first portion FPG1 located upstream of the gas flow in the Y-axis direction (positive Y-axis side) and a second portion FPG2 located downstream of the gas flow in the Y-axis direction (negative Y-axis side), the P content in the first portion FPG1 is greater than the P content in the second portion FPG2.

The fuel gas FG that flows through the fuel gas flow path FP and is then supplied to the fuel electrode 116 may contain Cl due to the fact that the water used to generate the fuel gas FG contains Cl (chlorine). If this Cl adheres to the fuel electrode 116, there is a risk of "poisoning of the fuel electrode 116," which reduces the performance (power generation performance, particularly durability) of the unit cell 110. This is presumably because Cl adheres to Ni in the fuel electrode 116, reducing the area of the Ni exposed to the fuel gas FG, thereby inhibiting the reaction (H ₂ ⇒ 2H++ ^2e- ) at the interface between the Ni and the fuel gas FG.

In the power generating unit 102 of this embodiment, Cl contained in the fuel gas FG reacts with P contained in the anode power generating portion FPG to form a compound (e.g., POCl ₃ ). This prevents Cl contained in the fuel gas FG from adhering to the anode 116. Therefore, according to the power generating unit 102 of this embodiment, it is possible to prevent the anode 116 from being poisoned, and thus improve the performance (power generating performance, particularly durability characteristics) of the single cell 110. However, as will be described later, a condition for obtaining this effect is that the P content in the anode power generating portion FPG must be appropriately distributed.

The first part FPG1 located on the upstream side of the gas flow in the Y-axis direction (positive side of the Y-axis) contributes more to the power generation reaction than the second part FPG2 located on the downstream side of the gas flow in the Y-axis direction (negative side of the Y-axis), and is therefore relatively susceptible to the poisoning of the fuel electrode 116 described above. Therefore, it is preferable that the first part FPG1 has a higher P content than the second part FPG2, thereby particularly achieving the above effect (the effect of suppressing the poisoning of the fuel electrode 116 by the reaction of P with Cl). On the other hand, in the second part FPG2, which is relatively less susceptible to the poisoning of the fuel electrode 116, this effect is relatively unnecessary, and P, which does not react with Cl in the fuel electrode power generation part FPG, may deteriorate the fuel electrode 116 and thereby degrade the performance of the single cell 110, so it is preferable that the P content is relatively low. In the power generating unit 102 of this embodiment, which takes these points into consideration, the P content in the first portion FPG1 is greater than the P content in the second portion FPG2, which can efficiently improve the performance of the unit cell 110. From the viewpoint of this effect, the higher the ratio of the P content in the first portion FPG1 to the P content in the second portion FPG2, the better, and it is particularly preferable that the ratio is 101% or more, further 110% or more, further 150% or more, and further 200% or more.

In addition, in the fuel cell stack 100 of this embodiment, when the fuel electrode power generation portion FPG is divided into a third portion FPG3 located on the electrolyte layer 112 side (positive side of the Z axis) and a fourth portion FPG4 located on the opposite side of the electrolyte layer 112 in the Z axis direction from the third portion FPG3 (negative side of the Z axis), the P content in the third portion FPG3 is greater than the P content in the fourth portion FPG4.

The third part FPG3 located on the electrolyte layer 112 side (Z-axis positive side) contributes more to the power generation reaction than the fourth part FPG4 located on the opposite side of the electrolyte layer 112 in the Z-axis direction (Z-axis negative side) relative to the third part FPG3, and is therefore relatively susceptible to the poisoning of the fuel electrode 116 described above. Therefore, it is preferable that the third part FPG3 has a higher P content than the fourth part FPG4, thereby particularly achieving the above effect (the effect of suppressing the poisoning of the fuel electrode 116 by the reaction of P with Cl). On the other hand, in the fourth part FPG4, which is relatively less susceptible to the poisoning of the fuel electrode 116, this effect is relatively unnecessary, and P, which does not react with Cl in the fuel electrode power generation part FPG, may deteriorate the fuel electrode 116 and thereby degrade the performance of the single cell 110, so it is preferable that the P content is relatively low. In the power generation unit 102 of this embodiment, which takes these points into consideration, the P content in the third portion FPG3 is greater than the P content in the fourth portion FPG4, so that the performance of the unit cell 110 can be efficiently improved. From the viewpoint of this effect, the ratio of the P content in the third portion FPG3 to the P content in the fourth portion FPG4 is basically preferably as high as possible, and is particularly preferably 101% or more, further 110% or more, further 150% or more, and further 200% or more. In addition, the P content in the overlapping portion between the first portion FPG1 and the third portion FPG3 (the portion located upstream of the gas flow in the Y-axis direction (positive Y-axis side) and on the electrolyte layer 112 side (positive Z-axis side)) may be greater than the P content in the remaining portion of the anode power generation portion FPG.

In the fuel cell stack 100 of this embodiment, the single cell 110 includes an anode non-power generation portion FN of the anode 116 that is not included in the power generation portion PG. Among the anode non-power generation portions FN, the non-power generation portion FNS located upstream of the gas flow in the Y-axis direction (positive Y-axis direction) relative to the anode power generation portion FPG contains P.

If the non-power generation specific portion FNS of the fuel electrode non-power generation portion FN, located upstream of the gas flow in the Y-axis direction (positive Y-axis direction) relative to the fuel electrode power generation portion FPG, does not contain P, the fuel electrode 116 may become poisoned near the boundary BD between the non-power generation specific portion FNS and the fuel electrode power generation portion FPG due to Cl contained in the fuel gas FG that passes through the non-power generation specific portion FNS and flows up to the boundary BD between the non-power generation specific portion FNS and the fuel electrode power generation portion FPG.

In contrast, in the power generation unit 102 of this embodiment, Cl contained in the fuel gas FG flowing near the boundary BD reacts with P contained in the non-power generation specific portion FNS to form a compound. Therefore, according to the power generation unit 102 of this embodiment, poisoning of the fuel electrode 116 near the boundary BD can be suppressed.

In addition, in the fuel cell stack 100 of this embodiment, the P content in the non-power generation specific portion FNS is less than the P content in the fuel electrode power generation portion FPG. Therefore, according to the fuel cell stack 100 of this embodiment, even if the single cell separator 120 is joined via the joint 124 to a non-power generation portion of the single cell 110 that is not included in the power generation portion PG, the adverse effects caused by P scattering at the joint 124 located near the non-power generation specific portion FNS can be suppressed.

The manufacturing method of the fuel cell stack 100 of this embodiment includes the above-mentioned preparation step ST1 and specification step ST2. The preparation step ST1 is a step of preparing a pre-completed fuel cell stack 200 including a pre-completed single cell 210 including an electrolyte layer member 212 that is a member that becomes the electrolyte layer 112, an air electrode member 214 that is a member that becomes the air electrode 114, and an anode member 216 that is a anode member 216 that becomes the anode 116 and contains P. The specification step ST2 is a step of causing the pre-completed fuel cell stack 200 to undergo a reaction operation (power generation operation), in which fuel gas FG is caused to flow in the Y-axis direction in the fuel gas flow path FP, thereby moving P in the anode member 216 in the Y-axis direction, so that the P content in the first portion FPG1 is greater than the P content in the second portion FPG2. This manufacturing method makes it easy to realize (manufacture) a configuration that satisfies the condition (first specific condition) that "the P content in the first portion FPG1 is greater than the P content in the second portion FPG2."

A-6. Performance evaluation:
The performance evaluation of this embodiment will now be described with reference to FIG 8, which is an explanatory diagram showing the performance evaluation results.

Performance evaluation was performed on the power generation deterioration rate (% durability performance) using multiple single cell 110 samples with different P contents. Specifically, for each sample, a fuel cell stack 100 with the above-mentioned configuration was assembled, and the voltage after 1000 hours of rated power generation operation (post-test voltage) was measured, and the ratio of the difference between the initial voltage and the post-test voltage to the initial voltage was calculated as the power generation deterioration rate.

For each sample, if the power generation degradation rate was less than 1%, it was rated as "particularly good (A)", if the power generation degradation rate was 1% or more and less than 5%, it was rated as "good (B)", and if the power generation degradation rate was 5% or more, it was rated as "fail (C)".

As a result, as shown in FIG. 8, samples SA1 and SA2, which satisfy the condition (first specific condition) that "the fuel electrode power generation portion FPG contains P, and the P content in the first portion FPG1 is greater than the P content in the second portion FPG2," were evaluated as "good (B)" or better, while samples SA3 and SA4, which do not satisfy this condition, were evaluated as "fail (C)." From these results, it was confirmed that in a configuration that satisfies the first specific condition, the performance (power generation performance, particularly durability characteristics) of the single cell 110 can be improved. This is presumably due to the suppression of poisoning of the fuel electrode 116.

Furthermore, sample SA1, which satisfies the condition (second specific condition) that "the P content in the third portion FPG3 is greater than the P content in the fourth portion FPG4," was evaluated as "particularly good (A)," whereas sample SA2, which does not satisfy this condition, was evaluated as "good (B)." From these results, it was confirmed that in a configuration that satisfies the second specific condition, the performance (power generation performance, especially durability characteristics) of the single cell 110 can be particularly improved.

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

In the above embodiment, the configuration satisfies the first specific condition, the second specific condition, and the third specific condition described above, but the configuration may also satisfy the first specific condition described above and not satisfy one or both of the second specific condition and the third specific condition.

The configuration of the fuel cell stack 100 and the power generation unit 102 in the above embodiment is merely an example and can be modified in various ways.

In the above embodiment, a configuration that satisfies the first specific condition described above is adopted for all the power generating units 102 included in the fuel cell stack 100, but it is sufficient that the configuration is adopted for at least one of the power generating units 102 included in the fuel cell stack 100. The same applies to the second and third specific conditions.

In the above embodiment, the unit cell 110 is an anode-supported unit cell, but it may be another type of unit cell, such as an electrolyte-supported or metal-supported type.

In the above embodiment, the number of unit cells 110 (the number of power generation units 102) included in the fuel cell stack 100 is merely an example, and the number of unit cells 110 is determined appropriately depending on the output voltage required for the fuel cell stack 100. In addition, the materials constituting each member in the above embodiment are merely examples, and each member may be composed of other materials.

In the above embodiment, the SOFC generates electricity by utilizing an electrochemical reaction between hydrogen contained in a fuel gas and oxygen contained in an oxidant gas. However, the technology disclosed in this specification can be applied to an electrolysis cell unit, which is a constituent unit of a solid oxide electrolysis cell (SOEC) that generates hydrogen by utilizing an electrolysis reaction of water, and an electrolysis cell stack having a plurality of electrolysis cell units. The configurations of the electrolysis cell unit and the electrolysis cell stack are publicly known, for example, as described in JP 2016-81813 A, and will not be described in detail here, but are generally similar to the configurations of the power generation unit 102 and the fuel cell stack 100 in the above embodiment. That is, the fuel cell stack 100 in the above embodiment may be read as an electrolysis cell stack, the power generation unit 102 as an electrolysis cell unit, and the single cell 110 as an electrolysis single cell. However, when the electrolysis cell stack is operated, a voltage is applied between the electrodes so that the air electrode 114 is positive (anode) and the fuel electrode 116 is negative (cathode), and water vapor is supplied as a raw material gas through a manifold. As a result, a water electrolysis reaction occurs in each electrolysis cell unit, hydrogen gas is generated in the fuel chamber 176, and hydrogen is extracted to the outside of the electrolysis cell stack via the manifold. If a configuration similar to that of the above embodiment is adopted in an electrolysis cell stack with such a configuration, the same effect as that of the above embodiment can be achieved.

In the above embodiment, a so-called flat plate type fuel cell stack and power generation unit are used as an example, but the technology disclosed in this specification is not limited to the flat plate type and can be similarly applied to other types of fuel cell stacks and power generation units (so-called cylindrical flat plate type and cylindrical type).

In the above embodiment, a solid oxide fuel cell (SOFC) has been described as an example, but the technology disclosed in this specification can also be applied to other types of fuel cells (or electrolytic cells), such as a polymer electrolyte fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), and a molten carbonate fuel cell (MCFC).

22 (22A, ..., 22E): Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 28: Main body (of gas passage member) 29: Branching portion (of gas passage member) 32, 34: Hole 41: Felt member 44: Conductive portion 45: Cover member facing portion (of conductive portion) 46: Interconnector facing portion (of conductive portion) 47: Connection portion (of conductive portion) 48: Connection member (of conductive portion) 49: Elastic portion (of conductive portion) 50: Cover member 58: Specific space 60: Cover separator 61: Hole 66: Inner portion (of cover separator) 67: Outer portion (of cover separator) 68: Connection portion (of cover separator) 70: Upper terminal plate 71: Hole 78: Protrusion (of upper terminal plate) 80: Lower terminal plate 88: Protrusion (of lower terminal plate) 92: Insulating sheet 100: Fuel cell stack 102: Power generation unit 102X: Specific power generation unit 103: Power generation block 104: Upper end plate 106: Lower end plate 108: Communication hole 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 118: Intermediate layer 120: Single cell separator 121: Hole 124: Joint 125: Glass seal 126: Inner part (of single cell separator) 127: Outer part (of single cell separator) 128: Connection part (of single cell separator) 130: Air electrode side frame 131: Hole 132: Oxidant gas supply communication hole 133: Oxidant gas discharge communication hole 134: Air electrode side current collecting part 140: Fuel electrode side frame 141: Hole 142: Fuel gas supply passage 143: Fuel gas exhaust passage 144: Conductive part 145: Electrode facing part (of conductive part) 146: Interconnector facing part (of conductive part) 147: Connection part (of conductive part) 148: Fuel electrode side current collecting member 149: Elastic part (of fuel electrode side current collecting member) 150: Flat part (of fuel electrode side current collecting member) 161: Oxidant gas supply manifold 162: Oxidant gas exhaust manifold 166: Air chamber 171: Fuel gas supply manifold 172: Fuel gas exhaust manifold 176: Fuel chamber 180: IC separator 181: Hole 186: Inner part (of IC separator) 187: Outer part (of IC separator) 188: Connection part (of IC separator) 190: Interconnector 194: Coating layer 196: Conductive bonding material 200: Fuel cell stack before completion 210: Single cell before completion 212: Electrolyte layer member 214: Air electrode member 216: Fuel electrode member B1: Virtual plane B2: Virtual plane BD: Boundary FG: Fuel gas FN: Fuel electrode non-power generation part FNS: Non-power generation specific part FOG: Fuel off-gas FP: Fuel gas flow path FPG: Fuel electrode power generation part FPG1: First part (of fuel electrode power generation part) FPG2: Second part (of fuel electrode power generation part) FPG3: Third part (of fuel electrode power generation part) FPG4: Fourth part (of fuel electrode power generation part) OG: Oxidant gas OOG: Oxidant off-gas PG: Power generation part ST1: Preparation process ST2: Specification process

Claims (5)

The present invention provides an electrochemical reaction unit cell including an electrolyte layer, and an air electrode and an anode facing each other in a first direction with the electrolyte layer therebetween, and having a reaction section in which the electrolyte layer, the air electrode, and the anode overlap each other when viewed in the first direction;
a reactant gas flow path that is at least a part of a fuel chamber facing the anode, the reactant gas flow path being defined by an anode reaction portion that is a portion of the anode that is included in the reaction portion, and a reactant gas flow path is formed in which a reactant gas flows in a second direction that intersects with the first direction,
The anode reaction portion contains P,
When the anode reaction portion is divided into a first portion located on the upstream side of the gas flow in the second direction and a second portion located on the downstream side of the gas flow in the second direction,
The P content in the first portion is greater than the P content in the second portion.
Electrochemical reaction units. 2. The electrochemical reaction unit according to claim 1 ,
When the anode reaction portion is divided into a third portion located on the electrolyte layer side in the first direction and a fourth portion located on the opposite side of the electrolyte layer in the first direction with respect to the third portion,
The P content in the third portion is greater than the P content in the fourth portion.
Electrochemical reaction units. The electrochemical reaction unit according to claim 1 or 2,
The electrochemical reaction unit cell includes an anode non-reaction portion of the anode that is not included in the reaction portion,
the anode non-reaction portion includes a non-reaction specific portion located upstream of the anode reaction portion in the gas flow in the second direction, the non-reaction specific portion containing P;
Electrochemical reaction units. The electrochemical reaction unit according to claim 3,
The P content in the non-reaction specific portion is less than the P content in the anode reaction portion.
Electrochemical reaction units. A method for producing an electrochemical reaction device comprising the electrochemical reaction unit according to claim 1, comprising the steps of:
a preparation step of preparing a pre-completed electrochemical reaction device including a pre-completed electrochemical reaction unit cell including an electrolyte layer member which is a member that will become the electrolyte layer, an air electrode member which is a member that will become the air electrode, and an anode member which will become the anode and contains P;
a specifying step of subjecting the pre-completion electrochemical reaction device to a reaction operation, in which a reactant gas is caused to flow in the second direction in the reactant gas flow passage, thereby moving P in the anode member in the second direction, so that the P content in the first portion is greater than the P content in the second portion.
A method for manufacturing an electrochemical reactor.

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