JP7715693B2 - Electrochemical reaction cell stack - Google Patents

Description

The technology disclosed in this specification relates to an electrochemical reaction cell stack.

Solid oxide fuel cells (SOFCs) are a type of fuel cell that generates electricity through an electrochemical reaction between hydrogen and oxygen. SOFCs are generally used in the form of a fuel cell stack, in which multiple structural units (power generation units) are arranged in a predetermined direction (the first direction). Each power generation unit includes a fuel cell unit (simply referred to as a "unit cell") and a unit cell separator. The unit cell includes an electrolyte layer containing solid oxide, and an air electrode and a fuel electrode that face each other in the predetermined direction across the electrolyte layer. The unit cell separator also has a through-hole formed in it, and the portion of the unit cell separator surrounding the through-hole is bonded to the periphery of the unit cell. A unit cell separator configured in this way separates the air chamber facing the air electrode of the unit cell from the fuel chamber facing the fuel electrode.

Some such fuel cell stacks are equipped with gas flow members to prevent gas flow obstruction and to prevent performance degradation of the fuel cell stack due to deformation of the unit cell separators. The unit cell separators have a curved shape that protrudes to one side in the first direction, and a gas flow member is disposed on the flat portion of the curved shape of the unit cell separator. The gas flow member has at least one of holes and grooves formed therein through which gas flows. (See, for example, Patent Document 1.)

Japanese Patent Application Laid-Open No. 2021-174593

In conventional fuel cell stack configurations, gas flow members are positioned on the flat portions of the curved shape of the single-cell separator. However, single-cell separators have portions that are more easily deformed than the flat portions, such as the bent portions located on both sides of the curved shape. Therefore, when stress is generated in the single-cell separator that separates the fuel chamber and the air chamber due to a gas pressure difference between the fuel chamber and the air chamber, the portions that are more easily deformed than the flat portions deform preferentially. As a result, gas flow between each manifold and the fuel chamber or air chamber may be obstructed, potentially reducing fuel cell stack performance. In other words, conventional fuel cell stack configurations leave room for further improvement in order to achieve the effect of preventing fuel cell stack performance degradation due to deformation of the single-cell separator while suppressing gas flow obstruction.

Note that this issue is not limited to unit cell separators, but is also common to fuel cell stacks equipped with gas flow path defining members that define gas flow paths composed of manifolds and communication paths that connect the manifolds to unit cells. This issue is also common to electrolysis cell stacks equipped with multiple electrolysis cell units, 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 and an electrolysis 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 and an electrolysis cell stack are collectively referred to as an electrochemical reaction cell stack. This issue is not limited to SOFCs and SOECs, but is also common to other types of electrochemical reaction cell stacks.

This specification discloses 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 cell stack disclosed in this specification is an electrochemical reaction cell stack having a plurality of electrochemical reaction units, each having an electrochemical reaction unit cell including an electrolyte layer and an air electrode and a fuel electrode facing each other across the electrolyte layer, wherein a manifold is formed to exchange gas between a specific electrode, which is at least one of the air electrode and the fuel electrode, in each of the electrochemical reaction units, and each of the electrochemical reaction units has a communication flow path that communicates the manifold with the specific electrode, and the manifold The flow path defining member, which defines the gas flow path composed of the hold and the communication flow path, has a plate-shaped first defining portion extending in the gas flow direction, and a plate-shaped second defining portion adjacent to the first defining portion in the gas flow direction and extending in the gas flow direction; the second defining portion is more easily deformed than the first defining portion; and a gas flow member having a space forming portion that forms a space through which gas flows is disposed in at least the second gas flow path defined by the second defining portion of the flow path defining member.

The second defining portion of the flow path defining member that defines the gas flow path is relatively susceptible to deformation. Therefore, if deformation occurs in a direction that reduces the flow path cross-section of the gas flow path, the gas flow in the gas flow path is likely to be obstructed, adversely affecting the performance of the electrochemical reaction cell stack. In this electrochemical reaction cell stack, a gas distribution member is disposed in at least the second gas flow path that defines the second defining portion of the gas flow path. Therefore, the presence of the gas distribution member can prevent the second defining portion of the flow path defining member, which is susceptible to deformation, from deforming in a direction that reduces the flow path cross-section, thereby preventing obstruction of gas flow in the gas flow path due to such deformation and ultimately preventing performance degradation of the electrochemical reaction cell stack. Furthermore, because the gas distribution member has a space-forming portion that defines a space through which gas flows, obstruction of gas flow in the gas flow path can be prevented even when the gas distribution member is disposed within the gas flow path. Based on the above, this electrochemical reaction cell stack can prevent performance degradation of the electrochemical reaction cell stack due to deformation of the flow path defining member while preventing obstruction of gas flow in the gas flow path.

(2) In the above electrochemical reaction cell stack, the gas flow member may be configured to include a gas flow portion disposed in the second gas flow path of the gas flow path and having the space-forming portion formed therein, and a support portion disposed in a first gas flow path of the gas flow path defined by the first defining portion of the flow path defining member and supporting the gas flow portion. In this electrochemical reaction cell stack, the gas flow portion disposed in the second gas flow path, which is relatively easy to deform, is supported by the support portion disposed in the first gas flow path, which is relatively difficult to deform. Therefore, compared to a configuration in which the gas flow portion is disposed in the second gas flow path alone, it is possible to prevent the gas flow portion from moving to a position outside the second gas flow path due to deformation of the second gas flow path, and it is possible to effectively prevent a decrease in performance of the electrochemical reaction cell stack due to deformation of the flow path defining member.

(3) In the above electrochemical reaction cell stack, the support portion may have a shape extending in a direction intersecting the gas flow direction, and the gas flow portion may have a plurality of legs extending from the support portion to the second gas flow path. In this electrochemical reaction cell stack, the support portion has a shape extending in a direction intersecting the gas flow direction, and is stably positioned in the first gas flow path, thereby more effectively suppressing misalignment of the gas flow portion with respect to the second gas flow path. Furthermore, because the gas flow portion is a plurality of legs extending from the support portion to the second gas flow path, obstruction of gas flow within the gas flow path can be suppressed compared to, for example, a configuration in which the gas flow portion is plate-shaped and extends along the support portion.

(4) In the above electrochemical reaction cell stack, at least a portion of the grooves between the multiple legs may be positioned away from the support portions when viewed in the gas flow direction. This electrochemical reaction cell stack can prevent the flow of gas in the gas flow path from being obstructed by the presence of the support portions.

(5) In the above electrochemical reaction cell stack, at least some of the multiple legs may have a portion that extends in the first gas flow path in a direction that intersects both the gas flow direction and the extension direction of the support portion. This electrochemical reaction cell stack can prevent the flow of gas in the first gas flow path from being obstructed.

(6) In the above-described electrochemical reaction cell stack, the width of the foot portion in the extension direction of the support portion may be configured to be narrower than the distance between adjacent foot portions. With this electrochemical reaction cell stack, it is possible to suppress obstruction of gas flow within the gas flow path, compared to, for example, a configuration in which the width of the foot portion is wider than the distance between the foot portions.

(7) In the above electrochemical reaction cell stack, the rigidity of the foot portion may be configured to be greater than the rigidity of the second defining portion of the flow path defining member. According to this electrochemical reaction cell stack, the presence of the foot portion can more reliably prevent the second defining portion from deforming in a direction that reduces the cross-sectional area of the gas flow path, thereby preventing the flow of gas in the gas flow path from being obstructed due to such deformation.

(8) In the above electrochemical reaction cell stack, the flow path defining member may have a pair of the second defining portions and a first defining portion located between the pair of second defining portions, and the first defining portion may be located on the opposite side of the flow path of the flow path defining member from the pair of second defining portions as viewed in the gas flow direction, and the gas distribution member may have a pair of the gas distribution portions located in each of the pair of second gas flow paths. According to this electrochemical reaction cell stack, the gas distribution member is arranged so that the pair of gas distribution portions straddles the first gas flow path, which makes it easier to ensure space in the first gas flow path, and therefore makes it possible to prevent obstruction of gas flow not only in the second gas flow path but also in the first gas flow path.

(9) In the above electrochemical reaction cell stack, the gas flow member may have a restricting portion that contacts the flow path defining member and restricts movement of the gas flow member in the gas flow direction. This electrochemical reaction cell stack can effectively restrict movement of the gas flow member in the gas flow direction.

The technology disclosed in this specification can be realized in various forms, such as an electrochemical reaction unit cell (a fuel cell unit cell or an electrolysis unit cell), a unit cell-separator composite having an electrochemical reaction unit cell and a separator with a through-hole formed therein, the portion surrounding the through-hole being joined to the periphery of the electrochemical reaction unit cell, and separating an air chamber facing the air electrode from a fuel chamber facing the fuel electrode, an electrochemical reaction unit (a fuel cell power generation unit or an electrolysis cell unit) having an electrochemical reaction unit cell, an electrochemical reaction cell stack (a fuel cell stack or an electrolysis cell stack) having multiple electrochemical reaction units, or a manufacturing method thereof.

FIG. 1 is a perspective view showing the 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. 1. FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along the line III-III in FIG. 1. FIG. 4 is an explanatory diagram showing the YZ cross-sectional structure of the fuel cell stack 100 taken along the line IV-IV in FIG. 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 XZ cross-sectional configuration of two adjacent power generating units 102 at the same position as the cross-section shown in FIG. 3 . FIG. 5 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. FIG. 8 is an explanatory diagram showing the XY cross-sectional structure of the power generating unit 102 at the position VIII-VIII in FIGS. 5 to 7. FIG. 8 is an explanatory diagram showing the XY cross-sectional configuration of the power generating unit 102 at the position IX-IX in FIGS. 5 to 7. FIG. 10 is an explanatory diagram showing the external configuration of a fuel cell stack 100a as a modified example;

A. Embodiments:
A-1. composition:
(Configuration of fuel cell stack 100)
FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 100 according to this embodiment. FIG. 2 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along line II-II in FIG. 1 (and FIGS. 8 and 9 , which will be described later). FIG. 3 is an explanatory diagram showing the XZ cross-sectional configuration of the fuel cell stack 100 taken along line III-III in FIG. 1 (and FIGS. 8 and 9 , which will be described later). FIG. 4 is an explanatory diagram showing the YZ cross-sectional configuration of the fuel cell stack 100 taken along line IV-IV in FIG. 1 (and FIGS. 8 and 9 , which will be described later). Each figure shows orthogonal X, Y, and Z axes for specifying directions. For convenience, the positive Z-axis direction will be referred to as the upward direction and the negative Z-axis direction will be referred to as the downward direction. However, the fuel cell stack 100 may actually be installed in an orientation different from these orientations. The same applies to FIG. 5 and subsequent figures.

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 lower-end separator 189, 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). One of the pair of end plates 104, 106 (hereinafter referred to as the "upper end plate 104") is located above an assembly (hereinafter referred to as the "power generation block 103") consisting of the seven power generation units 102 and the lower-end separator 189, and the other of the pair of end plates 104, 106 (hereinafter referred to as the "lower end plate 106") is located below the power generation block 103. The pair of end plates 104, 106 are arranged to sandwich the assembly (hereinafter referred to as the "power generation block 103") consisting of the seven power generation units 102 and the lower-end separator 189 from above and below.

As shown in Figures 1 and 4, holes that penetrate each layer in the vertical direction are formed near the four corners of the outer periphery around the Z-axis of each layer (upper end plate 104, each power generating unit 102, and lower end separator 189) that make up the fuel cell stack 100, and holes (screw holes) are formed in the upper surface of the lower end plate 106 near the four corners of its outer periphery around the Z-axis. Corresponding holes formed in these layers are vertically connected to form bolt holes 109 that extend in the vertical direction. In the following description, the holes formed in each layer of the fuel cell stack 100 to form bolt holes 109 may also be referred to as bolt holes 109.

A bolt 22 is inserted into each bolt hole 109. The lower end of each bolt 22 threads into a threaded hole formed in the lower end plate 106, and a nut 24 is fitted onto the upper end of each bolt 22. The lower surface of the nut 24 abuts against the upper surface of the end plate 104 via an insulating sheet 26. The bolts 22 and nuts 24 configured in this way fasten the layers of the fuel cell stack 100 together. The insulating sheet 26 is made of, for example, a mica sheet, ceramic fiber sheet, ceramic powder sheet, glass sheet, glass ceramic composite, etc.

As shown in Figures 1 to 3, four holes that penetrate each layer in the vertical direction are formed in the peripheral portion around the Z axis direction of each layer (each power generation unit 102, lower-end separator 189, lower end plate 106) that make up the fuel cell stack 100, and corresponding holes formed in each layer are vertically connected to each other to form communication holes 108 that extend vertically from the uppermost power generation unit 102 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.

1 and 2, one communication hole 108 located near one side (the side on the positive X-axis of the two sides parallel to the Y-axis) that constitutes the outer periphery of the fuel cell stack 100 around the Z-axis 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 supplied to the air chamber 166 (described later) of each power generation unit 102. Another communication hole 108 located near the opposite side (the side on the negative X-axis of the two sides parallel to the Y-axis) functions as an oxidant gas discharge manifold 162, which is a gas flow path through which oxidant off-gas OOG, which is gas discharged from the air chamber 166 of each power generation unit 102, is discharged to the outside of the fuel cell stack 100. Note that air, for example, is used as the oxidant gas OG.

1 and 3, among the sides constituting the outer periphery of the fuel cell stack 100 around the Z axis, another communication hole 108 located near the side closest to the communication hole 108 functioning as the oxidant gas exhaust manifold 162 described above functions as a fuel gas supply manifold 171, a gas flow path through which fuel gas FG is introduced from outside the fuel cell stack 100 and supplied to the fuel chamber 176 described below of each power generation unit 102. Another communication hole 108 located near the side closest to the communication hole 108 functioning as the oxidant gas supply manifold 161 described above functions as a fuel gas exhaust manifold 172, a gas flow path through which fuel off-gas FOG, a gas exhausted from the fuel chamber 176 of each power generation unit 102, is exhausted to the outside of the fuel cell stack 100. Note that the fuel gas FG may be, for example, a hydrogen-rich gas obtained by reforming city gas. The fuel gas supply manifold 171 and the fuel gas exhaust manifold 172 are examples of manifolds within the scope of the claims.

2 and 3, 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 branching off from the side of the main body 28. The holes in the branch portion 29 are connected to the holes in 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 in the main body 28 of the gas passage member 27 positioned at the position of the oxidant gas supply manifold 161 is connected to the oxidant gas supply manifold 161, and the hole in the main body 28 of the gas passage member 27 positioned at the position of the oxidant gas discharge manifold 162 is connected to the oxidant gas discharge manifold 162. As shown in FIG. 3 , the holes in the main body 28 of the gas passage member 27 positioned at the position of the fuel gas supply manifold 171 are connected to the fuel gas supply manifold 171, and the holes in the main body 28 of the gas passage member 27 positioned at the position of the fuel gas exhaust manifold 172 are connected to the fuel gas exhaust manifold 172. An insulating sheet 26 is interposed between each gas passage member 27 and the surface of the lower end plate 106.

(Configuration of end plates 104, 106)
The pair of end plates 104, 106 are flat, plate-shaped members with a substantially rectangular outer shape as viewed in the Z-axis direction, and are made of a conductive material such as stainless steel. Holes 32, 34 are formed near the centers of the pair of end plates 104, 106, respectively, penetrating in the Z-axis direction. 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 later). Therefore, the compressive force in the Z-axis direction generated by fastening the bolts 22 and nuts 24 acts primarily on the periphery of each power generating unit 102 (the portion outer than each of the unit cells 110 (described later)). In this embodiment, 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 the lower end separator 189)
The lower-end separator 189 is a flat member having a substantially rectangular outer shape when viewed in the Z-axis direction, and is made of, for example, metal. The peripheral edge of the lower-end separator 189 is sandwiched between the power generation block 103 and the lower end plate 106, and is joined to the lower end plate 106 by welding, for example, and is electrically connected to the lower end plate 106.

(Configuration of power generation unit 102)
Fig. 5 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. 6 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. 3, and Fig. 7 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. 4. Also, Fig. 8 is an explanatory diagram showing the XY cross-sectional configuration of the power generating unit 102 at the position VIII-VIII in Figs. 5 to 7, and Fig. 9 is an explanatory diagram showing the XY cross-sectional configuration of the power generating unit 102 at the position IX-IX in Figs. 5 to 7.

As shown in Figures 5 to 7, the power generation unit 102 includes a single fuel cell (hereinafter referred to as a "single cell") 110, a single cell separator 120, an air electrode side frame 130, an anode side frame 140, an anode side current collecting member 144, a pair of interconnectors 190 and a pair of IC separators 180 that form the top and bottom layers of the power generation unit 102. Holes that form the communication holes 108 that function as the manifolds 161, 162, 171, and 172, and holes that form the bolt holes 109, are formed in the peripheral portions around the Z-axis direction of the single cell separator 120, the air electrode side frame 130, the anode side frame 140, and the IC separator 180.

The unit cell 110 comprises an electrolyte layer 112, an air electrode 114 disposed on one side (upper side) of the electrolyte layer 112 in the Z-axis direction, an anode 116 disposed on the other side (lower side) of the electrolyte layer 112 in the Z-axis direction, and a reaction prevention layer 118 disposed between the electrolyte layer 112 and the air electrode 114. Note that the unit cell 110 of this embodiment is an anode-supported unit cell in which the anode 116 supports the other layers (electrolyte layer 112, air electrode 114, reaction prevention layer 118) that make up the unit cell 110.

The electrolyte layer 112 is a substantially rectangular, flat-plate member when viewed in the Z-axis direction and is configured to contain 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 that is smaller than the electrolyte layer 112 when viewed in the Z-axis direction and is configured to contain, for example, a perovskite-type oxide (e.g., LSCF (lanthanum strontium cobalt iron oxide)). The anode 116 is a substantially rectangular, flat-plate member that is substantially the same size as the electrolyte layer 112 when viewed in the Z-axis direction and is formed of, for example, Ni (nickel), a cermet made of Ni and ceramic particles, a Ni-based alloy, or the like. The reaction prevention layer 118 is a substantially rectangular, flat-plate member that is substantially 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). The reaction prevention layer 118 has the function of preventing elements (e.g., Sr) diffused from the cathode 114 from reacting with elements (e.g., Zr) contained in the electrolyte layer 112 to produce a highly resistive substance (e.g., SrZrO ₃ ).

The single cell separator 120 is a frame-shaped component with a substantially rectangular through-hole 121 formed vertically near the center, and is made of a metal such as ferritic stainless steel. The single cell separator 120 is relatively thin, for example, between 0.05 mm and 0.2 mm. The portion of the single cell separator 120 surrounding the through-hole 121 (hereinafter referred to as the "through-hole surrounding portion") faces the upper surface of the peripheral portion of the single cell 110 (electrolyte layer 112). The single cell separator 120 is joined to the single cell 110 (electrolyte layer 112) by a joint 124 formed of a brazing material (e.g., Ag brazing) placed 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, thereby preventing gas leakage (cross leakage) from one electrode side to the other around the periphery of the single cell 110.

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

A glass seal portion 125 containing glass is disposed near the through-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 formed so as to contact both the surface surrounding the through-hole in the single-cell separator 120 and the surface of the single cell 110 (electrolyte layer 112 in this embodiment). The glass seal portion 125 effectively prevents gas leakage (cross leakage) from one electrode side to the other electrode side at the periphery of the single cell 110.

The interconnector 190 is a conductive member having a flat plate portion 150 with a substantially rectangular plate shape and multiple substantially columnar air electrode-side current collecting portions 134 protruding from the flat plate portion 150 toward the air electrode 114, and is formed from 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 will be simply referred to as the interconnector 190. In each power generation unit 102, the upper interconnector 190 (the flat plate portion 150 thereof) is positioned above the single cell 110, with the air chamber 166 sandwiched between them. The upper interconnector 190 (each of its air electrode-side current collecting portions 134) is joined to the air electrode 114 of the unit cell 110 via a conductive bonding material 196 made of, for example, a spinel-type oxide, and is thereby electrically connected to the air electrode 114 of the unit cell 110. In each power generating unit 102, the lower interconnector 190 is disposed below the unit cell 110, with the fuel chamber 176 sandwiched between them, and is electrically connected to the anode 116 of the unit cell 110 via an anode-side current collecting member 144 (described later). The interconnector 190 ensures electrical conduction between the power generating units 102 and suppresses mixing of reactant gases between the power generating units 102. In this embodiment, when two power generating units 102 are disposed adjacent to each other, one interconnector 190 is shared by the two adjacent power generating units 102. That is, the upper interconnector 190 of one power generating unit 102 is the same material as the lower interconnector 190 of another power generating unit 102 adjacent to the upper side of that power generating unit 102. Also, because the fuel cell stack 100 is equipped with a lower-end separator 189, the power generating unit 102 located at the bottom of the fuel cell stack 100 does not have a lower interconnector 190 (see Figures 2 to 4).

The IC separator 180 is a frame-shaped member with a substantially rectangular through-hole 181 formed near the center in the vertical direction, and is made of a metal such as ferritic stainless steel. The plate thickness of the IC separator 180 is relatively thin, for example, between 0.05 mm and 0.2 mm. The portion of the IC separator 180 surrounding the through-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 flat portion 150 of the interconnector 190. Of a pair of IC separators 180 included in a certain power generating unit 102, the upper IC separator 180 separates the air chamber 166 of that power generating unit 102 from the fuel chamber 176 of the other power generating unit 102 adjacent to that power generating unit 102 on the upper side. Furthermore, of the pair of IC separators 180 included in a certain power generating unit 102, the lower IC separator 180 separates the fuel chamber 176 of that power generating unit 102 from the air chamber 166 of the other power generating unit 102 adjacent to that power generating unit 102 on the lower side. In this way, the IC separator 180 suppresses gas leakage between the power generating units 102 at the periphery of the power generating units 102. The IC separator 180 joined to 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 end plate 104.

The IC separator 180 includes an inner portion 186 that includes the through-hole periphery of the IC separator 180 (the portion surrounding the through-hole 181), an outer portion 187 that is located radially outward of the inner portion 186, and a connecting portion 188 that connects the inner portion 186 and the outer portion 187. In this embodiment, the inner portion 186 and the outer portion 187 are generally flat plates that extend in a direction generally perpendicular to the Z-axis direction. The connecting portion 188 is curved so as to protrude downward relative to both the inner portion 186 and the outer portion 187. The lower portion of the connecting portion 188 (toward the air chamber 166) is a convex portion, and the upper portion of the connecting portion 188 (toward the fuel chamber 176) is a concave portion. Therefore, the connecting portion 188 includes portions whose positions in the Z-axis direction differ from those of the inner portion 186 and the outer portion 187.

As shown in Figures 5 to 8, the air electrode side frame 130 is a frame-shaped member with a substantially rectangular hole 131 formed near the center that penetrates in the Z-axis direction, and is formed from an insulating material such as mica. The hole 131 in the air electrode side frame 130 forms an air chamber 166 facing the air electrode 114. The air electrode side frame 130 is in contact with the upper surface of the peripheral portion of the single cell separator 120 and the lower surface of the peripheral portion of the upper IC separator 180, and functions as a sealing member that ensures gas sealing between the two (i.e., gas sealing of the air chamber 166). The air electrode side frame 130 also provides electrical insulation between a pair of IC separators 180 (i.e., between a pair of interconnectors 190) included in the power generation unit 102. The air electrode side frame 130 is also formed with an oxidant gas supply communication channel 132 that connects the oxidant gas supply manifold 161 to the air chamber 166, and an oxidant gas discharge communication channel 133 that connects the air chamber 166 to the oxidant gas discharge manifold 162.

As shown in Figures 5 to 7 and 9, the fuel electrode side frame 140 is a frame-shaped member formed with a substantially rectangular hole 141 penetrating in the Z-axis direction near the center, and is made of, for example, metal. The hole 141 in the fuel electrode side frame 140 forms a fuel chamber 176 facing the fuel electrode 116. The fuel electrode side frame 140 is in contact with the lower surface of the peripheral portion of the single cell separator 120 and the upper surface of the peripheral portion of the lower IC separator 180. The fuel electrode side frame 140 also has a fuel gas supply communication channel 142 that connects the fuel gas supply manifold 171 and the fuel chamber 176, and a fuel gas discharge communication channel 143 that connects the fuel chamber 176 and the fuel gas discharge manifold 172. The configuration of the fuel chamber 176, including the portion defined by the single cell separator 120 and the IC separator 180, the fuel gas supply communication channel 142, and the fuel gas discharge communication channel 143, is an example of a communication channel within the scope of the claims.

As shown in Figures 5 to 7, the fuel electrode side current collecting member 144 is disposed within the fuel chamber 176. The fuel electrode side current collecting member 144 includes an interconnector facing portion 146, an electrode facing portion 145, and a connecting portion 147 connecting the electrode facing portion 145 and the interconnector facing portion 146, and is formed of, for example, nickel, a nickel alloy, stainless steel, or the like. The electrode facing portion 145 contacts the lower surface of the fuel electrode 116, and the interconnector facing portion 146 contacts the upper surface of the interconnector 190 (the flat portion 150 thereof). However, as described above, the power generating unit 102 located at the bottom of the fuel cell stack 100 does not include a lower interconnector 190, and therefore the interconnector facing portion 146 of the fuel electrode side current collecting member 144 of that power generating unit 102 contacts the lower end separator 189. Because of this configuration, the fuel electrode side current collecting member 144 electrically connects the fuel electrode 116 to the interconnector 190 (or the lower end separator 189). A spacer 149, made of, for example, mica, is disposed between the electrode-facing portion 145 and the interconnector-facing portion 146 of the fuel electrode side current collecting member 144. This allows the fuel electrode side current collecting member 144 to adapt to deformation of the power generating unit 102 due to temperature cycles and reactant gas pressure fluctuations, maintaining good electrical connection between the fuel electrode 116 and the interconnector 190 (or the lower end separator 189) via the fuel electrode side current collecting member 144.

A-2. Operation of the fuel cell stack 100:
2 and 5, when 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 then supplied from the oxidant gas supply manifold 161 to the air chamber 166 through the oxidant gas supply communicating passage 132 of each power generating unit 102. Also, as shown in FIGS. 3 and 6, when 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 then supplied from the fuel gas supply manifold 171 to the fuel chamber 176 through the fuel gas supply communicating passage 142 of each power generating unit 102.

When oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and fuel gas FG is supplied to the fuel chamber 176, power is generated in the single cell 110 through an electrochemical reaction between the oxidant gas OG and the fuel gas FG. This power generation reaction is exothermic. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to the upper interconnector 190, and the fuel electrode 116 is electrically connected to the lower interconnector 190 (or the lower-end separator 189) via the fuel electrode-side current collecting member 144. In other words, the multiple power generation units 102 included in the fuel cell stack 100 are electrically connected in series. The upper interconnector 190 and IC separator 180 of the uppermost power generating unit 102 are electrically connected to the upper end plate 104, and the lower end separator 189, which is electrically connected to the anode-side current collecting member 144 of the lowermost power generating unit 102, is electrically connected to the lower end plate 106. Therefore, electrical energy generated in each power generating unit 102 is extracted from the end plates 104, 106, which function as output terminals for the fuel cell stack 100. Because 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 heat generated by power generation can maintain the high temperature.

As shown in FIGS. 2 and 5, the oxidant off-gas OOG discharged from the air chamber 166 of each power generating unit 102 to the oxidant gas discharge manifold 162 via the oxidant gas discharge communicating channel 133 passes through holes in the main body 28 and branch portion 29 of the gas passage member 27 located at the position of the oxidant gas discharge manifold 162, and is then discharged to the outside of the fuel cell stack 100 via a gas pipe (not shown) connected to the branch portion 29. Also, as shown in FIGS. 3 and 6, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generating unit 102 to the fuel gas discharge manifold 172 via the fuel gas discharge communicating channel 143 passes through holes in the main body 28 and branch portion 29 of the gas passage member 27 located at the position of the fuel gas discharge manifold 172, and is then discharged to the outside of the fuel cell stack 100 via a gas pipe (not shown) connected to the branch portion 29.

In the fuel cell stack 100 of this embodiment, as shown in Figures 8 and 9, when viewed in the Z-axis direction, the oxidant gas supply communication passage 132 communicating with the oxidant gas supply manifold 161 and the fuel gas discharge communication passage 143 communicating with the fuel gas discharge manifold 172 are arranged to face (in the same direction) one side of the unit cell (the second side SI2 shown in Figures 8 and 9), and the oxidant gas discharge communication passage 133 communicating with the oxidant gas discharge manifold 162 and the fuel gas supply communication passage 142 communicating with the fuel gas supply manifold 171 are arranged to face (in the same direction) another side (the first side SI1 shown in Figures 8 and 9) opposite the second side SI2 of the unit cell across the center point of the unit cell 110. That is, the power generation unit 102 (fuel cell stack 100) of this embodiment is a counterflow type SOFC in which the main flow direction of oxidant gas OG in the air chamber 166 (direction from the positive X-axis to the negative X-axis) and the main flow direction of fuel gas FG in the fuel chamber 176 (direction from the negative X-axis to the positive X-axis) are substantially opposite (facing each other).

A-3. Configuration of flow path defining members (120, 180):
As shown in FIG. 6 , the single cell separator 120 (connecting portion 128) has a flat portion 122 and a pair of bent portions 123. The flat portion 122 is a flat portion extending in the flow direction of the fuel gas FG (X-axis direction). The pair of bent portions 123 are located on either side of the flat portion 122 in the flow direction of the fuel gas FG. Each bent portion 123 is adjacent to the flat portion 122 and has one or more bent portions. In FIG. 6 , the bent portion 123 has two bent portions: a first bent portion that bends from the end of the flat portion 122 toward the fuel chamber 176, and a second bent portion that bends from a portion extending from the first bent portion toward the opposite side of the flat portion 122. Because the bent portion 123 has bent portions, it is more easily deformed than the flat portion 122.

The connecting portion 188 of the IC separator 180 has a flat portion 182 and a pair of bent portions 183. The flat portion 182 is a flat portion extending in the flow direction of the fuel gas FG. The pair of bent portions 183 are located on either side of the flat portion 182 in the flow direction of the fuel gas FG. Each bent portion 183 is adjacent to the flat portion 182 and has one or more bent portions. In FIG. 6, the bent portion 183 has two bent portions: a first bent portion that bends from the end of the flat portion 182 toward the fuel chamber 176, and a second bent portion that bends from the portion extending from the first bent portion toward the opposite side of the flat portion 182. Because the bent portion 183 has bent portions, it is more easily deformed than the flat portion 182.

The single cell separator 120 and the IC separator 180 are examples of flow path defining members within the scope of the claims. The flat portions 122 and 182 are examples of first defining portions within the scope of the claims, and the space within the fuel chamber 176 defined by the flat portions 122 and 182 is an example of a first gas flow path within the scope of the claims. The curved portions 123 and 183 are examples of second defining portions within the scope of the claims, and the space within the fuel chamber 176 defined by the curved portions 123 and 183 is an example of a second gas flow path within the scope of the claims.

A-4. Configuration of gas flow member 50:
The fuel cell stack 100 of this embodiment further includes a gas distribution member 50. The configuration of the gas distribution member 50 will be described below. In this embodiment, the gas distribution member 50 includes a gas distribution member 50A arranged on the fuel gas supply communication channel 142 side of the unit cell 110, and a gas distribution member 50B arranged on the fuel gas discharge communication channel 143 side of the unit cell 110. The shapes of the gas distribution members 50A and 50B are symmetrical with respect to the unit cell 110. FIG. 5 schematically illustrates the gas distribution members 50 (50A, 50B). FIG. 6 schematically illustrates the gas distribution members 50 (50A, 50B) with an enlarged view of the detailed configuration of the X1 portion of the gas distribution member 50A. FIG. 9 schematically illustrates the gas distribution members 50 (50A, 50B) with an enlarged view of the detailed configuration of the X2 portion of the gas distribution member 50B.

As shown in FIG. 9 , the gas flow member 50 is an elongated member that extends overall in a predetermined direction (the Y-axis direction in this embodiment) and is formed from a metal such as ferritic stainless steel, the same as the single cell separator 120 and IC separators. The gas flow member 50 has a main body 60 and multiple foot portions 70.

The main body portion 60 has a shape that extends in a direction (Y-axis direction) that intersects with the flow direction (X-axis direction) of the fuel gas FG. The main body portion 60 is disposed in a space within the fuel chamber 176 that overlaps the flat portion 122 of the unit cell separator 120 and the flat portion 182 of the IC separator 180 when viewed from the top-bottom direction. That is, the main body portion 60 is disposed in the first gas flow path defined by the flat portion 122 and the flat portion 182 within the fuel chamber 176. When viewed in the flow direction of the fuel gas FG, both ends of the main body portion 60 are located outside the ends of the unit cell 110. The main body portion 60 is an example of a support portion within the scope of the claims.

Each foot portion 70 has a linear shape extending from the main body portion 60 in a direction intersecting the main body portion 60 (the X-axis direction, the flow direction of the fuel gas FG). When viewed in the flow direction of the fuel gas FG, the multiple foot portions 70 are arranged over the entire length of the unit cell 110. In this embodiment, the gas flow member 50 has multiple inner foot portions 70A and multiple outer foot portions 70B. The portion of the foot portion 70 that is arranged in the second gas flow path defined by the bent portion 123 and the bent portion 183 is an example of a gas flow portion within the scope of the claims.

The inner leg portion 70A extends from the main body portion 60 toward the single cell 110. The multiple inner leg portions 70A are aligned at intervals along a direction intersecting the flow direction of the fuel gas FG (the Y-axis direction, the extension direction of the main body portion 60). That is, the gas flow member 50 has a groove VA formed by two adjacent inner leg portions 70A. Note that in this embodiment, the multiple inner leg portions 70A are aligned at equal intervals (see FIG. 9). In the gas flow member 50, when viewed in the flow direction of the fuel gas FG, at least a portion of the groove VA between the multiple inner leg portions 70A is positioned away from the main body portion 60 in a direction intersecting the flow direction of the fuel gas FG (on the opposite side from the single cell separator 120).

Furthermore, each inner leg portion 70A has a portion extending in a direction (Z-axis direction) intersecting both the flow direction of fuel gas FG (X-axis direction) and the extension direction of the main body portion 60 (Y-axis direction) within the first gas flow path defined by the flat portion 122 and the flat portion 182. Specifically, each inner leg portion 70A has a first step portion 72A and a second step portion 74A (see FIG. 6). The first step portion 72A is a step portion located on the opposite side of the IC separator 180 (single cell separator 120 side) from the main body portion 60 in the vertical direction. The second step portion 74A is a step portion located on the opposite side of the IC separator 180 from the first step portion 72A in the vertical direction, and is located on the single cell 110 side from the first step portion 72A in the flow direction of fuel gas FG.

The outer legs 70B extend from the main body 60 toward the opposite side of the unit cell 110 (toward the fuel electrode-side frame 140). The multiple outer legs 70B are aligned at intervals along a direction (Y-axis direction) intersecting the flow direction of the fuel gas FG. That is, the gas flow member 50 has a groove VB formed by two adjacent outer legs 70B. Note that in this embodiment, the multiple outer legs 70B are aligned at equal intervals (see FIG. 9). In the gas flow member 50, when viewed in the flow direction of the fuel gas FG, at least a portion of the groove VB between the multiple outer legs 70B is positioned away from the main body 60 in a direction intersecting the flow direction of the fuel gas FG (away from the IC separator 180).

Furthermore, each outer leg portion 70B has a portion extending in a direction (Z-axis direction) intersecting both the flow direction of the fuel gas FG (X-axis direction) and the extension direction of the main body portion 60 (Y-axis direction) within the first gas flow path defined by the flat portion 122 and the flat portion 182. Specifically, each outer leg portion 70B has a first step portion 72B and a second step portion 74B (see FIG. 6). The first step portion 72B is a step portion located on the opposite side of the IC separator 180 (single cell separator 120 side) from the main body portion 60 in the vertical direction. The second step portion 74B is a step portion located on the opposite side of the IC separator 180 from the first step portion 72B in the vertical direction, and is located on the opposite side of the single cell 110 from the first step portion 72B in the flow direction of the fuel gas FG.

In this embodiment, the positions of the multiple inner legs 70A and the multiple outer legs 70B are aligned with one another in the extension direction of the main body 60. That is, the positions of each inner leg 70A and each outer leg 70B are aligned with one another in the extension direction of the main body 60. In other words, the positions of each inner leg 70A and each outer leg 70B are aligned with one another in the extension direction of the main body 60. In other words, when viewed in the flow direction of the fuel gas FG, the inner legs 70A and the outer legs 70B are arranged to overlap each other. Furthermore, in this embodiment, when viewed in the vertical direction, the length LB of the outer leg 70B is longer than the length LA of the inner leg 70A. In this embodiment, the space defined by the bent portion 123 and the bent portion 183 of the unit cell separator 120 and the IC separator 180, located on the opposite side from the unit cell 110 (the fuel electrode-side frame 140 side), is the maximum crushable space, which is the most easily crushed. Therefore, by arranging the relatively long outer legs 70B in this maximum crushable space, obstruction of gas flow in the maximum crushable space is suppressed.

In the extension direction (Y-axis direction) of the main body 60, the width D1 of the foot portions 70 (70A, 70B) is narrower than the distance D2 between adjacent foot portions 70 (see Figure 9). Furthermore, the rigidity of the foot portions 70 is greater than the rigidity of the single cell separator 120 and the IC separator 180. Specifically, the thickness of the foot portions 70 is greater than the thickness of the single cell separator 120 and the IC separator 180 (see Figure 6).

The gas flow member 50 has a pair of restricting portions 80 that contact the IC separator 180 and restrict movement of the gas flow member 50 in the flow direction of the fuel gas FG. Specifically, each of the pair of restricting portions 80 is an engaging claw that engages with an engaging hole 148 formed in the fuel electrode side frame 140 from the tip of each outer leg portion 70B located at the end of the main body portion 60 (see Figure 9). Note that, when viewed in the flow direction of the fuel gas FG, the restricting portions 80 are positioned outside the unit cells 110.

The thickness t1 of the foot portion 70 of the gas flow member 50 is approximately 0.05 mm or more and 0.2 mm or less, for example, 0.1 mm. The thickness t1 of the main body portion 70 of the gas flow member 50 is approximately 0.05 mm or more and 1 mm or less, for example, 0.1 mm. The height h1 (size in the Z-axis direction) of the gas flow member 50 is approximately 0.4 mm or more and 1.0 mm or less, for example, 0.7 mm. The width D1 of the foot portions 70 (70A, 70B) is approximately 1 mm or more and 7 mm or less, for example, 4 mm. The distance D2 between two adjacent foot portions 70 of the gas flow member 50 is approximately 5 mm or more and 15 mm or less, for example, 10 mm.

A-5. Effects of this embodiment:
As described above, the fuel cell stack 100 of this embodiment includes the gas flow member 50 (see FIGS. 5, 6, and 9). The gas flow member 50 has a main body 60 and a plurality of foot portions 70. The main body 60 is disposed in the first gas flow path defined by the flat portion 122 and the flat portion 182 of the fuel chamber 176, and supports the plurality of foot portions 70.

The multiple foot portions 70 (70A, 70B) are spaced apart from one another to form grooves VA and VB. Each foot portion 70 has a stepped portion (72A, 74A, 72B, 74B) located on the opposite side of the main body 60 from the IC separator 180 (the unit cell separator 120 side) within the second gas flow path defined by the bent portion 123 and the bent portion 183. This configuration allows fuel gas FG to pass through the second gas flow path via the grooves VA and VB in the gas flow member 50 (see the arrows in portion X1 of Figure 6). In other words, the multiple foot portions 70 in the gas flow member 50 form spaces (grooves VA and VB) through which fuel gas FG flows in the second gas flow path. The foot portion 70 is an example of a space-forming portion within the scope of the claims.

Here, during power generation operation of the fuel cell stack 100, a difference occurs between the gas pressure in the fuel chamber 176 and the gas pressure in the air chamber 166 in each power generation unit 102. Specifically, the gas pressure in the air chamber 166 becomes higher than the gas pressure in the fuel chamber 176. Therefore, due to the gas pressure difference between the fuel chamber 176 and the air chamber 166, stress is generated in the single cell separator 120 and the IC separator 180 that separate the fuel chamber 176 from the air chamber 166. In particular, the bent portion 123 of the single cell separator 120 and the bent portion 183 of the IC separator 180 are likely to deform preferentially, resulting in deformation that reduces the height of the fuel chamber 176. This narrows the second gas flow path defined by bent portion 123 and bent portion 183, which may impede the flow of gas between the fuel gas supply manifold 171 and the fuel gas discharge manifold 172 and the fuel chamber 176, potentially adversely affecting the performance of the fuel cell stack 100.

However, as described above, in the fuel cell stack 100 of this embodiment, the gas flow member 50 is disposed in the second gas flow path within the fuel chamber 176. Therefore, the presence of the gas flow member 50 can prevent the above-mentioned deformation of the unit cell separator 120 and the IC separator 180 from occurring at positions between the fuel gas supply communicating channel 142 and the fuel gas discharge communicating channel 143 and the unit cell 110, as viewed in the Z-axis direction, compared to a configuration in which the gas flow member 50 is not disposed. This can prevent the flow of gas between the fuel gas supply manifold 171 and the fuel gas discharge manifold 172 and the fuel chamber 176 from being obstructed due to deformation of the unit cell separator 120 and the IC separator 180, and ultimately prevent a decrease in performance of the fuel cell stack 100.

The gas flow member 50 also has grooves VA and VB formed therein through which the fuel gas FG flows. Therefore, even if the gas flow member 50 is positioned within the fuel chamber 176, as viewed in the Z-axis direction, between the fuel gas supply communication channel 142 and the fuel gas discharge communication channel 143 and the unit cell 110, the presence of the gas flow member 50 can be prevented from obstructing the flow of gas within the fuel chamber 176.

As a result of the above, the fuel cell stack 100 of this embodiment can prevent the flow of fuel gas FG within the fuel chamber 176 from being obstructed, while also preventing the performance of the fuel cell stack 100 from deteriorating due to deformation of the single cell separator 120 or the IC separator 180.

In this embodiment, all of the power generating units 102 included in the fuel cell stack 100 are equipped with a gas distribution member 50. This prevents differences in pressure loss in the fuel gas FG flow path between power generating units 102 due to deformation of the single cell separator 120 or IC separator 180 of a certain power generating unit 102, and prevents differences in the supply amount of fuel gas FG between power generating units 102 due to these pressure loss differences. As a result, a decrease in the performance of the entire fuel cell stack 100 can be prevented.

In this embodiment, the foot portion 70, which is arranged in the second gas flow path, which is relatively easy to deform, is supported by the main body portion 60, which is arranged in the first gas flow path, which is relatively difficult to deform (see Figures 6 and 9). Therefore, compared to a configuration in which the foot portion 70 is arranged alone in the second gas flow path, it is possible to prevent the foot portion 70 from moving to a position outside the second gas flow path as the second gas flow path deforms, and it is possible to effectively prevent a decrease in performance of the fuel cell stack 100 due to deformation of the single cell separator 120 or the IC separator 180.

In this embodiment, the main body 60 has a shape that extends in a direction intersecting the flow direction of the fuel gas FG (see Figure 9). Therefore, by being stably positioned in the first gas flow path, it is possible to more effectively prevent the foot 70 from shifting position relative to the second gas flow path. Furthermore, a gas flow portion is formed by multiple foot portions 70. Therefore, compared to a configuration in which the gas flow portion is formed by, for example, plate-shaped portions that extend continuously along the main body 60, it is possible to prevent the flow of fuel gas FG in the gas flow path (particularly the second gas flow path) from being obstructed.

In this embodiment, when viewed in the flow direction of the fuel gas FG, at least a portion of the groove VA between the multiple inner legs 70A is positioned away from the main body 60 (see Figure 6). This prevents the flow of fuel gas FG in the gas flow path (particularly the first gas flow path) from being obstructed due to the presence of the main body 60.

In this embodiment, each foot portion 70 (70A, 70B) has a portion (the inclined portion of the first step portion 72A, 72B) that extends in a direction (Z-axis direction) that intersects both the flow direction of the fuel gas FG (X-axis direction) and the extension direction of the main body portion 60 (Y-axis direction) within the first gas flow path (see Figure 6). This makes it possible to prevent the flow of fuel gas FG within the first gas flow path from being obstructed.

In this embodiment, in the extension direction (Y-axis direction) of the main body 60, the width D1 of the foot portions 70 (70A, 70B) is narrower than the distance D2 between adjacent foot portions 70 (see Figure 9). This makes it possible to prevent the flow of fuel gas FG in the gas flow path from being obstructed, compared to, for example, a configuration in which the width D1 of the foot portions 70 is wider than the distance D2 between the foot portions 70.

In this embodiment, the rigidity of the foot portion 70 is higher than the rigidity of the single cell separator 120 and the IC separator 180. As a result, compared to a configuration in which the rigidity of the foot portion 70 is equal to or less than the rigidity of the single cell separator 120 or the IC separator 180, the presence of the foot portion 70 more reliably ensures that the single cell separator 120 or the IC separator 180 does not deform in a direction that reduces the cross-sectional area of the gas flow path, thereby preventing the flow of fuel gas FG in the gas flow path from being obstructed due to such deformation.

In this embodiment, the gas flow member 50 has a pair of legs 70 (70A, 70B) arranged in each of the pair of second gas flow paths (see Figures 6 and 9). This allows the gas flow member 50 to be positioned so that it straddles the first gas flow path via the pair of legs 70, making it easier to ensure space in the first gas flow path. As a result, it is possible to prevent obstruction of the flow of fuel gas FG not only in the second gas flow path but also in the first gas flow path.

The gas flow member 50 has a pair of restriction portions 80 that contact the single cell separator 120 and restrict movement of the gas flow member 50 in the flow direction of the fuel gas FG (see Figure 9). This effectively restricts movement of the gas flow member 50 in the flow direction of the fuel gas FG. In addition, in this embodiment, movement of the gas flow member 50 in a direction intersecting the flow direction of the fuel gas FG can also be restricted.

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

The configuration of the fuel cell stack 100 and the configuration of each component of the fuel cell stack 100 in the above embodiment are merely examples and are subject to various modifications. For example, in the above embodiment, the gas flow member 50 was positioned so as to overlap the connecting portions 128, 188 (flat portions 122, 182 and bent portions 123, 183) of the unit cell separator 120 and the IC separator 180 when viewed in the Z-axis direction. However, the gas flow member 50 may be positioned so as to overlap the bent portions 123, 183 of the connecting portions 128, 188 but not the flat portions 122, 182 when viewed in the Z-axis direction. Furthermore, the gas flow member 50 may be positioned so as to overlap portions of the unit cell separator 120 and the IC separator 180 other than the connecting portions 128, 188 (for example, portions of the unit cell separator 120 that are relatively thin and easily deformed). Furthermore, in the above embodiment, the unit cell separator 120 and the IC separator 180 have connecting portions 128, 188, but the unit cell separator 120 and the IC separator 180 do not necessarily have to have connecting portions 128, 188.

In the above embodiment, one gas flow member 50 (50A) is disposed between the fuel gas supply communication channel 142 and the unit cell 110 in the fuel chamber 176 as viewed in the Z-axis direction, but multiple gas flow members 50 may be disposed at this position. Similarly, in the above embodiment, one gas flow member 50 (50B) is disposed between the fuel gas discharge communication channel 143 and the unit cell 110 in the fuel chamber 176 as viewed in the Z-axis direction, but multiple gas flow members 50 may be disposed at this position. Furthermore, in the above embodiment, a gas flow member may be disposed, for example, between the oxidant gas supply communication channel 132 (or the oxidant gas discharge communication channel 133) and the unit cell 110 in the air chamber 166 as viewed in the Z-axis direction.

In the above embodiment, the gas flow member 50 is arranged within the fuel chamber 176, as viewed in the Z-axis direction, between the fuel gas supply communication channel 142 and the fuel gas discharge communication channel 143 and the unit cell 110. However, the gas flow member 50 may also be arranged within the fuel chamber 176, as viewed in the Z-axis direction, between one of the fuel gas supply communication channel 142 and the fuel gas discharge communication channel 143 and the unit cell 110.

In the above embodiment, all of the power generation units 102 included in the fuel cell stack 100 are equipped with a gas distribution member 50, but it is not necessary for all of the power generation units 102 included in the fuel cell stack 100 to be equipped with a gas distribution member 50; it is sufficient for at least one power generation unit 102 to be equipped with a gas distribution member 50.

In the above embodiment, the gas flow member 50 is arranged within the fuel chamber 176, as viewed in the Z-axis direction, between the fuel gas supply communication channel 142 and the fuel gas discharge communication channel 143 and the interconnector 190, and is arranged overlapping the IC separator 180, but this configuration is not necessarily required. Furthermore, the fuel cell stack 100 does not need to include the IC separator 180, and the interconnector 190 may extend to the peripheral portion of the fuel cell stack 100 (the portion overlapping the air electrode side frame 130 and the fuel electrode side frame 140 as viewed in the Z-axis direction).

The configuration of the gas flow member 50 can be varied in various ways. For example, the gas flow member 50 may be configured without either the inner foot portion 70A or the outer foot portion 70B, or may be configured with only one inner foot portion 70A or one outer foot portion 70B. The extension direction of the gas flow member 50 (main body portion 60) may be any direction intersecting the flow direction of the fuel gas FG. The gas flow member 50 may be, for example, a member fabricated by bending a plate material so that its cross section has a corrugated shape. The gas flow member 50 may be configured such that multiple flat first portions extending in a direction (XZ plane direction) perpendicular to the extension direction (Y-axis direction) of the entire gas flow member 50 and multiple flat second portions connecting the ends of two adjacent first portions are alternately arranged in the extension direction (Y-axis direction) of the entire gas flow member 50. Furthermore, the gas flow member 50 is not limited to grooves VA and VB, and may instead be configured with spaces formed by through-holes or the like through which gas flows (for example, a mesh-like member with many holes through which gas flows).

In the above embodiment, the foot portion 70 of the gas flow member 50 may be configured to lack at least one of the first step portions 72A, 72B and the second step portions 74A, 74B, or may be configured to have three or more step portions. Furthermore, the inner foot portion 70A and the outer foot portion 70B may be positioned at different positions in the extension direction of the main body portion 60. While the length LA of each of the inner foot portions 70A is the same, the lengths LA of at least some of the inner foot portions 70A may be different from each other. The same applies to the outer foot portion 70B. Furthermore, the length LA of the inner foot portion 70A and the length LB of the outer foot portion 70B may be the same. The width D1 of the foot portion 70 (70A, 70B) may be the same as the distance D2 between adjacent foot portions 70, or may be wider than the distance D2. The rigidity of the foot portion 70 may be equal to or less than the rigidity of the unit cell separator 120 or the IC separator 180. The gas flow member 50 may not be configured to include the restriction portion 80.

The flow path defining member is not limited to the single cell separator 120 or the IC separator 180. The flow path defining member may be any member that defines the gas flow path and has the first and second defining portions described above, such as a manifold or gas pipe that forms the gas flow path. The second defining portion is not limited to the bent portion 123, 183 having a bent section, but may also be a portion that is thinner than the other portions, a portion made of a softer material than the other portions, or a portion closer to the free end than the other portions. Factors that cause deformation of the second defining portion are not limited to the pressure difference between the fuel chamber and the air chamber, but include, for example, the difference in thermal expansion between the flow path defining member and an adjacent member.

Figure 10 is an explanatory diagram showing the external configuration of a modified fuel cell stack 100a. The modified fuel cell stack 100a shown in Figure 10 includes multiple unit cells 110a. Each unit cell 110a has a columnar support extending in the vertical direction. The support has a flat cross section and a pair of opposing flat surfaces. A gas flow path extending in the vertical direction is formed inside the support. A fuel electrode, a solid electrolyte layer, and an air electrode are sequentially stacked on one flat surface of the support, and an interconnector is stacked on the portion of the other flat surface where the air electrode is not formed. By disposing a conductive member 150a between adjacent unit cells 110a, the unit cells 110a are electrically connected in series. The unit cells 110a are an example of an electrochemical reaction unit cell or electrochemical reaction unit as defined in the claims.

The lower end of each unit cell 110a is fixed to a manifold 171a by a sealing material 124a such as glass. Gas flow paths formed in the support of each unit cell 110a are connected to the internal space of the manifold 171a. A fuel gas supply pipe 27a is connected to the side of the manifold 171a to supply fuel gas into the manifold 171a. The fuel gas supplied to the manifold 171a via the fuel gas supply pipe 27a is then supplied from the manifold 171a to the fuel electrode via the gas flow paths formed in the support of each unit cell 110a.

In the modified fuel cell stack 100a shown in FIG. 11, gas flow paths such as the manifold 171a and fuel gas supply pipe 27a function as manifolds for gas exchange between the fuel electrode of each unit cell 110a, and the portion of the gas flow path formed in the support of each unit cell 110a, from the end of the support on the manifold 171a side to the fuel electrode, serves as a communication flow path connecting the manifold and the fuel electrode. The manifold 171a has a flat portion 122a and a curved portion 123a. The curved portion 123a is more easily deformed than the flat portion 122a. A gas flow member 50a is disposed within this manifold 171a. Specifically, the gas flow member 50a has a gas flow portion 70a and a support portion 60a. The gas flow portion 70a is disposed within the space defined by the curved portion 123a (directly below the curved portion 123a). The gas flow portion 70a has a through-hole 72a formed therein, through which fuel gas flows from the fuel gas supply pipe 27a. The support portion 60a is positioned on the opposite side of the gas flow portion 70a from the fuel gas supply pipe 27a, and supports the gas flow portion 70a. This configuration prevents the flow of fuel gas within the manifold 171a from being obstructed, while also preventing performance degradation of the fuel cell stack 100a due to deformation of the manifold 171a. The manifold 171a is an example of a gas dividing member.

In the above embodiment, the fuel cell stack 100 may be configured, for example, without including manifolds 161, 162 for the air electrodes, with the oxidant gas supply communication channel 132 and oxidant gas discharge communication channel 133 of the air chamber 166 opening directly to the outside of the fuel cell stack 100.

In addition, in the above embodiment, holes 32, 34 are formed in the pair of end plates 104, 106, but the holes 32, 34 do not have to be formed in at least one of the pair of end plates 104, 106. In addition, in the above embodiment, the pair of end plates 104, 106 function as terminal plates, but a terminal plate may be provided separately from the pair of end plates 104, 106.

Furthermore, in the above embodiment, the interconnector 190 includes a conductive coating layer 194, but the interconnector 190 may not include the coating layer 194. Further, in the above embodiment, the unit cell 110 includes a reaction prevention layer 118, but the unit cell 110 may not include the reaction prevention layer 118. Further, 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, etc. Further, the materials constituting each component in the above embodiment are merely examples, and each component may be made of other materials.

In addition, while the fuel cell stack 100 in the above embodiment is a counterflow type SOFC, the technology disclosed in this specification is similarly applicable to coflow type SOFCs. In a coflow type SOFC, when viewed in the Z-axis direction, the fuel gas supply communication channel 142 and the oxidant gas supply communication channel 132 are arranged to face one side of the unit cell 110, and the fuel gas discharge communication channel 143 and the oxidant gas discharge communication channel 133 are arranged to face the other side of the unit cell 110 that faces the one side across the center point of the unit cell 110. The technology disclosed in this specification is similarly applicable to crossflow type SOFCs.

In addition, while the above embodiment focuses on a fuel cell stack 100 that generates electricity using an electrochemical reaction between hydrogen contained in fuel gas and oxygen contained in oxidant gas, the technology disclosed in this specification can also be applied to an electrolysis cell stack that includes multiple electrolysis unit cells, which are constituent units of a solid oxide electrolysis cell (SOEC) that generates hydrogen using the electrolysis reaction of water. The basic configuration of an electrolysis cell stack is publicly known, as described in, for example, JP 2016-81813 A, and is roughly as follows: That is, the configuration of the electrolysis cell stack is the same as the configuration of the fuel cell stack 100 of the above-described embodiment, except that "power generation unit" is replaced with "electrolysis cell unit", "single cell" is replaced with "electrolysis single cell", "oxidant gas supply manifold" is replaced with "air discharge manifold", "oxidant gas discharge manifold" is replaced with "air supply manifold", "fuel gas supply manifold" is replaced with "hydrogen discharge manifold", "fuel gas discharge manifold" is replaced with "water vapor supply manifold", "oxidant gas supply communicating channel" is replaced with "air discharge communicating channel", "oxidant gas discharge communicating channel" is replaced with "air supply communicating channel", "fuel gas supply communicating channel" is replaced with "hydrogen discharge communicating channel", and "fuel gas discharge communicating channel" is replaced with "water vapor supply communicating channel".

During operation of the electrolysis cell stack, a voltage is applied to the electrolysis cell stack so that the air electrode 114 is positive (anode) and the fuel electrode (hydrogen electrode) 116 is negative (cathode). Steam is supplied as a raw material gas to the steam supply manifold via the gas passage member 27. The supplied steam may also contain hydrogen gas. The steam supplied to the steam supply manifold is then supplied to the fuel chamber 176 from the steam supply manifold via the steam supply communication channel of each electrolysis cell unit, and is used for the water electrolysis reaction in each electrolysis unit cell. The hydrogen gas generated in the fuel chamber 176 by the water electrolysis reaction in each electrolysis unit cell is discharged, along with any excess steam, via the hydrogen discharge communication channel to the hydrogen discharge manifold, and is then removed from the hydrogen discharge manifold via the gas passage member 27 to the outside of the electrolysis cell stack.

In addition, during operation of the electrolytic cell stack, air is supplied to the interior of the electrolytic cell stack as needed to control the temperature of the electrolytic cell stack, etc. In this case, air is supplied to the air supply manifold via the gas passage member 27, and then from the air supply manifold to the air chamber 166 via the air supply communication flow path of each electrolytic cell unit. The air supplied to the air chamber 166 is discharged to the air discharge manifold via the air discharge communication flow path together with oxygen generated at the air electrode 114, and then from the air discharge manifold to the outside of the electrolytic cell stack via the gas passage member 27.

By adopting a configuration similar to that of the fuel cell stack 100 in the above embodiment, an electrolysis cell stack with this configuration also achieves the same effects as those of the fuel cell stack 100 in the above embodiment.

Furthermore, while the above embodiment has been described using a solid oxide fuel cell (SOFC) as an example, the technology disclosed in this specification can also be applied to other types of fuel cells (or electrolytic cells), such as a molten carbonate fuel cell (MCFC).

22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 27a: Fuel gas supply pipe 28, 60: Main body 29: Branch portion 32, 34: Hole 50, 50A, 50B, 50a: Gas flow member 60a: Support portion 70: Foot portion 70A: Inner foot portion 70B: Outer foot portion 70a: Gas flow portion 72A, 72B: First step portion 72a, 121, 181: Through hole 74A, 74B: Second step portion 80: Restriction portion 100, 100a: Fuel cell stack 102: Power generation unit 103: Power generation block 104, 106: End plate 108: Communication hole 109: Bolt hole 110, 110a: Single cell 112: Electrolyte layer 114: Air electrode 116: Anode 118: Reaction prevention layer 120: Single cell separator 122, 182, 122a: Flat portion 123, 183, 123a: Bent portion 124: Joint portion 124a: Sealing material 125: Glass seal portion 126, 186: Inner portion 127, 187: Outer portion 128, 188: Connecting portion 130: Air electrode side frame 131, 141: Hole 132: Oxidant gas supply communicating channel 133: Oxidant gas discharge communicating channel 134: Air electrode side current collecting portion 140: Anode side frame 142: Fuel gas supply communicating channel 143: Fuel gas discharge communicating channel 144: Anode side current collecting member 145: Electrode opposing portion 146: Interconnector opposing portion 147: Connecting portion 148: Locking hole 149: Spacer 150: Flat plate portion 150a: Conductive member 161, 162, 171, 172, 171a: Manifold 166: Air chamber 176: Fuel chamber 180: IC separator 189: Lower end separator 190: Interconnector 194: Coating layer 196: Conductive adhesive material

Claims (9)

An electrochemical reaction cell stack including a plurality of electrochemical reaction units, each having an electrochemical reaction unit cell including an electrolyte layer and an air electrode and a fuel electrode facing each other with the electrolyte layer interposed therebetween,
a manifold is formed to exchange gas between a specific electrode, which is at least one of the air electrode and the fuel electrode, in each of the electrochemical reaction units;
Each of the electrochemical reaction units is disposed at a position different from the specific electrode when viewed in a first direction in which the air electrode and the fuel electrode face each other, and a communication flow path is formed that communicates the manifold with the specific electrode;
a flow path defining member defining a gas flow path formed from the communicating flow paths includes a plate-shaped first defining portion extending in the gas flow direction, and a pair of plate-shaped second defining portions located at both ends of the first defining portion in the gas flow direction and extending in the gas flow direction, the pair of second defining portions having bent portions adjacent to the first defining portions;
a gas flow member having a space forming portion that forms a space for the gas flowing through the second gas flow path is disposed in at least a second gas flow path defined by the second defining portion of the flow path defining member among the gas flow paths;
1. An electrochemical reaction cell stack comprising: The electrochemical reaction cell stack according to claim 1,
the gas flow member has a gas flow portion that is disposed in the second gas flow path of the gas flow path and in which the space forming portion is formed, and a support portion that is disposed in a first gas flow path of the gas flow path that is defined by the first defining portion of the flow path defining member and that supports the gas flow portion.
1. An electrochemical reaction cell stack comprising: The electrochemical reaction cell stack according to claim 2,
the support portion has a shape extending in a direction intersecting the gas flow direction,
the gas flow portion has a plurality of legs extending from the support portion to the second gas flow path.
1. An electrochemical reaction cell stack comprising: The electrochemical reaction cell stack according to claim 3,
When viewed in the gas flow direction, at least a part of the grooves between the plurality of legs is disposed at a position away from the support portion.
1. An electrochemical reaction cell stack comprising: The electrochemical reaction cell stack according to claim 4,
At least some of the plurality of foot portions have a portion that extends in the first gas flow path in a direction that intersects both the gas flow direction and the extension direction of the support portion.
1. An electrochemical reaction cell stack comprising: The electrochemical reaction cell stack according to any one of claims 3 to 5,
In the extension direction of the support portion, the width of the foot portion is narrower than the interval between the adjacent foot portions.
1. An electrochemical reaction cell stack comprising: The electrochemical reaction cell stack according to claim 3,
the foot portion has a stiffness greater than the stiffness of the second defining portion of the flow path defining member;
1. An electrochemical reaction cell stack comprising: The electrochemical reaction cell stack according to claim 2,
the flow path defining member has a pair of the second defining portions and the first defining portion located between the pair of second defining portions, and the first defining portion is located at a position away from the pair of second defining portions on an opposite side of the gas flow path of the flow path defining member as viewed in a gas flow direction,
the gas flow member has a pair of the gas flow portions disposed in the pair of second gas flow paths, respectively;
1. An electrochemical reaction cell stack comprising: The electrochemical reaction cell stack according to claim 1,
the gas flow member has a restricting portion that contacts the flow path defining member and restricts movement of the gas flow member in the gas flow direction;
1. An electrochemical reaction cell stack comprising: