Electrochemical reaction cell stack

Abstract

To suppress reduction in performance of an electrochemical reaction cell stack caused by deformation of a passage defining member while suppressing disturbance of flow of a gas in a gas passage.SOLUTION: An electrochemical reaction cell stack comprises a plurality of electrochemical reaction units each including an electrochemical reaction unit cell. A communication passage communicating a manifold with a specific electrode is formed in each electrochemical reaction unit. A passage defining member defining a gas passage consisting of the manifold and the communication passage includes a tabular first defining portion extending in a flow direction of a gas and a tabular second defining portion being adjacent to the first defining portion in the flow direction of the gas and extending in the flow direction of the gas. The second defining portion is easier to deform than the first defining portion. A gas circulation member including a space forming part forming a space in which the gas flows is disposed in at least a second gas passage defined by the second defining portion of the passage defining member in the gas passage.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The technology disclosed by this specification relates to an electrochemical reaction cell stack.

Background Art

[0002] As one type of fuel cell that generates electricity by utilizing the electrochemical reaction between hydrogen and oxygen, a solid oxide fuel cell (hereinafter referred to as "SOFC") is known. An SOFC is generally used in the form of a fuel cell stack in which a plurality of constituent units (hereinafter referred to as "power generation units") are arranged side by side in a predetermined direction (hereinafter referred to as "the first direction"). Each power generation unit includes a fuel cell single cell (hereinafter simply referred to as "single cell") and a separator for the single cell. The single cell includes an electrolyte layer containing a solid oxide, and an air electrode and a fuel electrode that face each other in the above-mentioned predetermined direction with the electrolyte layer interposed therebetween. Further, through holes are formed in the separator for the single cell, and a portion surrounding the through holes in the separator for the single cell is joined to the peripheral edge portion of the single cell. The separator for the single cell having such a configuration partitions an air chamber facing the air electrode of the single cell and a fuel chamber facing the fuel electrode.

[0003] Among such fuel cell stacks, in order to suppress a decrease in the performance of the fuel cell stack due to deformation of the separator for the single cell while suppressing an obstruction to the gas flow, there are those provided with a gas flow member. The separator for the single cell has a curved shape that protrudes to one side in the first direction, and the gas flow member is disposed on a flat portion of the curved shape of the separator for the single cell. At least one of a hole and a groove through which gas flows is formed in the gas flow member. (For example, refer to Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the configuration of a conventional fuel cell stack, the gas flow member is arranged on the flat portion of the curved shape in the separator for a single cell. However, the separator for a single cell has portions that are more likely to deform than the flat portion, such as bent portions located on both sides of the curved shape, for example. Therefore, when stress is generated in the separator for a single cell that partitions the fuel chamber and the air chamber due to the gas pressure difference between the fuel chamber and the air chamber, the portions that are more likely to deform than the flat portion are preferentially deformed. As a result, the gas flow between each manifold and the fuel chamber or the air chamber may be obstructed, and the performance of the fuel cell stack may deteriorate. That is, in the configuration of the conventional fuel cell stack, there is room for further improvement in order to obtain the effect that the performance of the fuel cell stack deteriorates due to the deformation of the separator for a single cell while suppressing the obstruction of the gas flow.

[0006] Note that such problems are not limited to the separator for a single cell, but are also common problems in a fuel cell stack including a gas flow path defining member that defines a gas flow path composed of a manifold and a communication path that communicates the manifold and the single cell. Further, such problems are also common problems in an electrolytic cell stack including a plurality of electrolytic cell units that are constituent units of a solid oxide type electrolytic cell (hereinafter referred to as "SOEC") that generates hydrogen using the electrolysis reaction of water. In this specification, a fuel cell single cell and an electrolytic single cell are collectively referred to as an electrochemical reaction single cell, a fuel cell power generation unit and an electrolytic cell unit are collectively referred to as an electrochemical reaction unit, and a fuel cell stack and an electrolytic cell stack are collectively referred to as an electrochemical reaction cell stack. Further, such problems are not limited to SOFC and SOEC, but are also common problems in other types of electrochemical reaction cell stacks.

[0007] This specification discloses a technology capable of solving the above-described problems.

Means for Solving the Problems

[0008] The technology disclosed in this specification can be realized, for example, in the following forms.

[0009] (1) In an electrochemical reaction cell stack disclosed in this specification, which includes a plurality of electrochemical reaction units each having an electrochemical reaction single cell including an electrolyte layer, and an air electrode and a fuel electrode facing each other with the electrolyte layer interposed therebetween, a manifold for gas exchange is formed between at least one specific electrode, which is either the air electrode or the fuel electrode, in each of the electrochemical reaction units. In each of the electrochemical reaction units, a communication flow path that communicates the manifold and the specific electrode is formed. A flow path defining member that defines a gas flow path composed of the manifold 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 deformable 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 a second gas flow path defined by the second defining portion of the flow path defining member in the gas flow path.

[0010] The second defining portion of the flow path defining member that defines the gas flow path is relatively easily deformable, and when deformation occurs in the direction in which the flow path cross-section of the gas flow path decreases, the gas flow in the gas flow path is inhibited, which is likely to have an adverse effect on the performance of the electrochemical reaction cell stack. In this electrochemical reaction cell stack, at least in the second gas flow path defined by the second defining portion of the gas flow path, a gas flow member is disposed. Therefore, due to the presence of the gas flow member, it is possible to suppress the second defining portion, which is easily deformable as described above, of the flow path defining member from deforming in the direction in which the flow path cross-section decreases. Thus, it is possible to suppress the inhibition of the gas flow in the gas flow path due to the deformation, and ultimately suppress the degradation of the performance of the electrochemical reaction cell stack. Further, since the gas flow member has a space forming portion that forms a space through which the gas flows, even if the gas flow member is disposed in the gas flow path, it is possible to suppress the inhibition of the gas flow in the gas flow path. From the above, according to this electrochemical reaction cell stack, it is possible to suppress the inhibition of the gas flow in the gas flow path and suppress the degradation of the performance of the electrochemical reaction cell stack due to the deformation of the flow path defining member.

[0011] (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, and a support portion disposed in the first gas flow path defined by the first defining portion of the flow path defining member in the gas flow path and supporting the gas flow portion. In this electrochemical reaction cell stack, the gas flow portion disposed in the second gas flow path that is relatively easily deformable is supported by the support portion disposed in the first gas flow path that is relatively difficult to deform. Therefore, compared with a configuration in which the gas flow portion is disposed in the second gas flow path alone, it is possible to suppress the gas flow portion from moving to a position outside the second gas flow path as the second gas flow path deforms, and effectively suppress the degradation of the performance of the electrochemical reaction cell stack due to the deformation of the flow path defining member.

[0012] (3) In the above-described electrochemical reaction cell stack, the support portion may be shaped to extend in a direction intersecting the gas flow direction, and the gas flow-through portion may have a configuration including a plurality of legs extending from the support portion to the second gas flow path. In this electrochemical reaction cell stack, since the support portion is shaped to extend in a direction intersecting the gas flow direction, it is stably arranged in the first gas flow path, so that the displacement of the gas flow-through portion with respect to the second gas flow path can be more effectively suppressed. Further, since the gas flow-through portion is a plurality of legs extending from the support portion to the second gas flow path, for example, compared with a configuration in which the gas flow-through portion extends along the support portion in a plate shape, it is possible to suppress the gas flow in the gas flow path from being obstructed.

[0013] (4) In the above-described electrochemical reaction cell stack, at least a part of the grooves between the plurality of legs may be arranged at positions deviated from the support portion when viewed in the gas flow direction. According to this electrochemical reaction cell stack, it is possible to suppress the gas flow in the gas flow path from being obstructed due to the presence of the support portion.

[0014] (5) In the above-described electrochemical reaction cell stack, at least a part of the plurality of legs may have a portion extending in a direction intersecting both the gas flow direction and the extending direction of the support portion in the first gas flow path. According to this electrochemical reaction cell stack, it is possible to suppress the gas flow in the first gas flow path from being obstructed.

[0015] (6) In the above-described electrochemical reaction cell stack, in the extending direction of the support portion, the width of the leg may be configured to be narrower than the interval between adjacent legs. According to this electrochemical reaction cell stack, for example, compared with a configuration in which the width of the leg is wider than the interval between the legs, it is possible to suppress the gas flow in the gas flow path from being obstructed.

[0016] (7) In the above-described electrochemical reaction cell stack, the rigidity of the foot portion may be configured to be higher than the rigidity of the second defining portion of the flow path defining member. According to this electrochemical reaction cell stack, due to the presence of the foot portion, it is possible to more reliably suppress the deformation of the second defining portion in the direction in which the cross-sectional area of the gas flow path decreases, and thus it is possible to suppress the inhibition of the gas flow in the gas flow path due to the deformation.

[0017] (8) In the above-described electrochemical reaction cell stack, the flow path defining member has a pair of the second defining portions and the first defining portion located between the pair of the second defining portions, and in the view of the gas flow direction, the first defining portion is located at a position deviated to the side opposite to the gas flow path of the flow path defining member with respect to the pair of the second defining portions, and the gas distribution member may have a pair of the gas distribution portions disposed in each of the pair of the second gas flow paths. According to this electrochemical reaction cell stack, since the gas distribution member is disposed so as to straddle the first gas flow path by the pair of the gas distribution portions, it becomes easy to secure a space in the first gas flow path, and thus it is possible to suppress the inhibition of the gas flow not only in the second gas flow path but also in the first gas flow path.

[0018] (9) In the above-described electrochemical reaction cell stack, the gas distribution member may have a restricting portion that contacts the flow path defining member and restricts the movement of the gas distribution member in the gas flow direction. According to this electrochemical reaction cell stack, it is possible to effectively suppress the movement of the gas distribution member in the gas flow direction.

[0019] Note that the technology disclosed in this specification can be implemented in various forms. For example, it can be implemented in the form of an electrochemical reaction single cell (fuel cell single cell or electrolysis single cell), a single cell-separator composite having an electrochemical reaction single cell, a separator in which through holes are formed and a portion surrounding the through holes is joined to the peripheral edge of the electrochemical reaction single cell to partition an air chamber facing the air electrode and a fuel chamber facing the fuel electrode, an electrochemical reaction unit having an electrochemical reaction single cell (fuel cell power generation unit or electrolysis cell unit), an electrochemical reaction cell stack having a plurality of electrochemical reaction units (fuel cell stack or electrolysis cell stack), and manufacturing methods thereof.

Brief Description of Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0021] A. Embodiment: A-1. Configuration: (Configuration of the fuel cell stack 100) FIG. 1 is a perspective view showing the external configuration of the fuel cell stack 100 in the present embodiment, FIG. 2 is an explanatory drawing showing the XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II of FIG. 1 (and FIGS. 8 and 9 described later), FIG. 3 is an explanatory drawing showing the XZ cross-sectional configuration of the fuel cell stack 100 at the position III-III of FIG. 1 (and FIGS. 8 and 9 described later), and FIG. 4 is an explanatory drawing showing the YZ cross-sectional configuration of the fuel cell stack 100 at the position IV-IV of FIG. 1 (and FIGS. 8 and 9 described later). In each figure, XYZ axes orthogonal to each other for specifying directions are shown. In this specification, for convenience, the positive direction of the Z axis is referred to as the upward direction, and the negative direction of the Z axis is referred to as the downward direction, but the fuel cell stack 100 may actually be installed in a direction different from such a direction. The same applies to FIGS. 5 and later.

[0022] The fuel cell stack 100 includes a plurality of (seven in this embodiment) 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 and 106. The seven power generation units 102 are arranged side by side in a predetermined arrangement direction (the vertical direction in this embodiment). One of the pair of end plates 104 and 106 (hereinafter referred to as the "upper end plate 104") is arranged above an assembly (hereinafter referred to as the "power generation block 103") composed of the seven power generation units 102 and the lower end separator 189, and the other of the pair of end plates 104 and 106 (hereinafter referred to as the "lower end plate 106") is arranged below the power generation block 103. The pair of end plates 104 and 106 are arranged so as to sandwich an assembly (hereinafter referred to as the "power generation block 103") composed of the seven power generation units 102 and the lower end separator 189 from above and below.

[0023] As shown in FIGS. 1 and 4, holes penetrating the respective layers in the vertical direction are formed near the four corners of the outer periphery of each layer (the upper end plate 104, each power generation unit 102, the lower end separator 189) of the fuel cell stack 100 around the Z-axis direction, and holes (bolt holes) are formed on the upper surface near the four corners of the outer periphery of the lower end plate 106 around the Z-axis direction. The holes formed in these respective layers and corresponding to each other communicate in the vertical direction to constitute bolt holes 109 extending in the vertical direction. In the following description, the holes formed in each layer of the fuel cell stack 100 to constitute the bolt holes 109 may also be referred to as the bolt holes 109.

[0024] Bolts 22 are inserted into respective bolt holes 109. The lower end portions of the respective bolts 22 are screwed into screw holes formed in the lower end plate 106, and nuts 24 are fitted onto the upper end portions of the respective bolts 22. The lower surface of the nut 24 abuts against the upper surface of the end plate 104 via an insulating sheet 26. The respective layers of the fuel cell stack 100 are integrally fastened by the bolts 22 and nuts 24 configured as described above. The insulating sheet 26 is composed of, for example, a mica sheet, a ceramic fiber sheet, a ceramic compacted powder sheet, a glass sheet, a glass-ceramic composite, or the like.

[0025] Also, as shown in FIGS. 1 to 3, four holes penetrating each layer in the Z-axis direction are formed at the peripheral edges of the respective layers (each power generation unit 102, the lower end separator 189, the lower end plate 106) constituting the fuel cell stack 100, and the holes formed in the respective layers and corresponding to each other communicate in the vertical direction to constitute a communication hole 108 extending in the vertical direction from the uppermost power generation unit 102 to the lower end plate 106. In the following description, the holes formed in the respective layers of the fuel cell stack 100 to constitute the communication hole 108 may also be referred to as the communication hole 108.

[0026] As shown in FIGS. 1 and 2, one communication hole 108 located near one side (the side on the positive X-axis side of the two sides parallel to the Y-axis) constituting the outer periphery of the fuel cell stack 100 in the Z-axis direction functions as an oxidant gas supply manifold 161, which is a gas flow path through which oxidant gas OG is introduced from the outside of the fuel cell stack 100 and supplied to an air chamber 166 (to be described later) of each power generation unit 102. One communication hole 108 located near the opposite side (the side on the negative X-axis side of the two sides parallel to the Y-axis) of the side functions as an oxidant gas discharge manifold 162, which is a gas flow path through which oxidant off-gas OOG, which is the 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, for example, air is used as the oxidant gas OG.

[0027] Also, as shown in FIGS. 1 and 3, among the sides constituting the outer periphery of the fuel cell stack 100 around the Z-axis direction, another communication hole 108 located near the side closest to the communication hole 108 functioning as the above-described oxidant gas discharge manifold 162 serves as a fuel gas supply manifold 171, which is a gas flow path through which fuel gas FG is introduced from outside the fuel cell stack 100 and supplied to a fuel chamber 176 (described later) of each power generation unit 102. Another communication hole 108 located near the side closest to the communication hole 108 functioning as the above-described oxidant gas supply manifold 161 serves as a fuel gas discharge manifold 172, which is a gas flow path for discharging fuel off-gas FOG, which is the gas discharged from the fuel chamber 176 of each power generation unit 102, to the outside of the fuel cell stack 100. Note that, for example, a hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG. The fuel gas supply manifold 171 and the fuel gas discharge manifold 172 are examples of the manifold in the claims.

[0028] As shown in FIGS. 2 and 3, four gas passage members 27 are provided in the fuel cell stack 100. Each gas passage member 27 has a hollow cylindrical main body portion 28 and a hollow cylindrical branch portion 29 branched from the side surface of the main body portion 28. The holes of the branch portion 29 communicate with the holes of the main body portion 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 portion 28 of the gas passage member 27 arranged at the position of the oxidant gas supply manifold 161 communicates with the oxidant gas supply manifold 161, and the hole of the main body portion 28 of the gas passage member 27 arranged at the position of the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162. Also, as shown in FIG. 3, the hole of the main body portion 28 of the gas passage member 27 arranged at the position of the fuel gas supply manifold 171 communicates with the fuel gas supply manifold 171, and the hole of the main body portion 28 of the gas passage member 27 arranged at the position of the fuel gas discharge manifold 172 communicates with the fuel gas discharge manifold 172. Note that an insulating sheet 26 is interposed between each gas passage member 27 and the surface of the lower end plate 106.

[0029] (Configuration of End Plates 104 and 106) The pair of end plates 104 and 106 are flat plate members with a substantially rectangular outer shape when viewed in the Z-axis direction, and are formed of a conductive material such as stainless steel. Near the center of the pair of end plates 104 and 106, holes 32 and 34 penetrating in the Z-axis direction are respectively formed. When viewed in the Z-axis direction, the inner circumferences of the holes 32 and 34 formed in each of the pair of end plates 104 and 106 enclose each single cell 110 described later. Therefore, the compressive force in the Z-axis direction generated by the fastening of each bolt 22 and nut 24 acts mainly on the peripheral portions of each power generation unit 102 (the portions on the outer peripheral side of each single cell 110 described later). Also, in the present embodiment, the upper end plate 104 functions as the positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as the negative output terminal of the fuel cell stack 100.

[0030] (Configuration of the Lower Separator 189) The lower separator 189 is a flat plate member with a substantially rectangular outer shape when viewed in the Z-axis direction, and is formed of, for example, metal. The peripheral portion of the lower 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, for example, welding, and is electrically connected to the lower end plate 106.

[0031] (Configuration of the Power Generation Unit 102) FIG. 5 is an explanatory view showing the XZ cross-sectional configuration of two adjacent power generation units 102 at the same position as the cross-section shown in FIG. 2, FIG. 6 is an explanatory view showing the XZ cross-sectional configuration of two adjacent power generation units 102 at the same position as the cross-section shown in FIG. 3, and FIG. 7 is an explanatory view showing the YZ cross-sectional configuration of two adjacent power generation units 102 at the same position as the cross-section shown in FIG. 4. Also, FIG. 8 is an explanatory view showing the XY cross-sectional configuration of the power generation unit 102 at the VIII-VIII position in FIGS. 5 to 7, and FIG. 9 is an explanatory view showing the XY cross-sectional configuration of the power generation unit 102 at the IX-IX position in FIGS. 5 to 7.

[0032] As shown in FIGS. 5 to 7, the power generation unit 102 includes a fuel cell single cell (hereinafter referred to as "single cell") 110, a separator 120 for the single cell, an air electrode side frame 130, a fuel electrode side frame 140, a fuel electrode side current collecting member 144, and a pair of interconnects 190 and a pair of separator 180 for IC that constitute the uppermost and lowermost layers of the power generation unit 102. At the peripheral portions in the Z-axis direction of the separator 120 for the single cell, the air electrode side frame 130, the fuel electrode side frame 140, and the separator 180 for IC, holes forming each communication hole 108 functioning as each manifold 161, 162, 171, 172 and holes forming each bolt hole 109 are formed.

[0033] The single cell 110 includes an electrolyte layer 112, an air electrode 114 disposed on one side (upper side) in the Z-axis direction of the electrolyte layer 112, a fuel electrode 116 disposed on the other side (lower side) in the Z-axis direction of the electrolyte layer 112, and a reaction prevention layer 118 disposed between the electrolyte layer 112 and the air electrode 114. Note that the single cell 110 of the present embodiment is a fuel electrode support type single cell in which the fuel electrode 116 supports other layers (electrolyte layer 112, air electrode 114, reaction prevention layer 118) constituting the single cell 110.

[0034] The electrolyte layer 112 is a flat plate-shaped member that is substantially rectangular when viewed in the Z-axis direction, and is configured to contain a solid oxide (e.g., YSZ (yttria-stabilized zirconia)). That is, the single cell 110 of the present embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte. The air electrode 114 is a flat plate-shaped member that is substantially rectangular and 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 ferrite)). The fuel electrode 116 is a flat plate-shaped member that is substantially rectangular and has 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 composed of Ni and ceramic particles, a Ni-based alloy, or the like. The reaction prevention layer 118 is a flat plate-shaped member that is substantially rectangular and has 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 a function of suppressing the reaction between an element (e.g., Sr) diffused from the air electrode 114 and an element (e.g., Zr) contained in the electrolyte layer 112 to generate a high-resistance substance (e.g., SrZrO3).

[0035] The separator 120 for a single cell is a frame-shaped member in which a substantially rectangular through-hole 121 penetrating in the vertical direction is formed near the center, and is formed of a metal such as ferritic stainless steel, for example. The plate thickness of the separator 120 for a single cell is relatively thin, for example, about 0.05 mm or more and 0.2 mm or less. The portion surrounding the through-hole 121 in the separator 120 for a single cell (hereinafter referred to as the "portion around the through-hole") faces the upper surface at the peripheral edge of the single cell 110 (electrolyte layer 112). The separator 120 for a single cell is joined to the single cell 110 (electrolyte layer 112) by a joint portion 124 formed by a brazing material (e.g., Ag brazing material) disposed at the facing portion. The separator 120 for a single cell partitions the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116, and suppresses gas leakage (cross leakage) from one electrode side to the other electrode side at the peripheral edge of the single cell 110.

[0036] The separator 120 for single cells includes an inner portion 126 including a portion around the through-hole of the separator 120 for single cells (a portion surrounding the through-hole 121), an outer portion 127 located on the outer peripheral side of the inner portion 126, and a connecting portion 128 connecting the inner portion 126 and the outer portion 127. In the present embodiment, the inner portion 126 and the outer portion 127 are substantially flat plate-shaped and extend in a direction substantially orthogonal to the Z-axis direction. Further, the connecting portion 128 has a curved shape so as to protrude downward with respect to 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 where the position in the Z-axis direction is different from that of the inner portion 126 and the outer portion 127.

[0037] A glass seal portion 125 containing glass is disposed near the through-hole 121 in the separator 120 for single cells. The glass seal portion 125 is located on the air chamber 166 side with respect to the joint portion 124 and is formed so as to be in contact with both the surface of the portion around the through-hole of the separator 120 for single cells and the surface of the single cell 110 (the electrolyte layer 112 in the present embodiment). The glass seal portion 125 effectively suppresses gas leakage (cross leakage) from one electrode side to the other electrode side at the peripheral edge of the single cell 110.

[0038] The interconnector 190 is a conductive member having a flat plate portion 150 in 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 (for example, ferritic stainless steel). In the present embodiment, a conductive coating layer 194 made 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. In each power generation unit 102, the upper interconnector 190 (the flat plate portion 150 thereof) is disposed above the single cell 110 with the air chamber 166 interposed therebetween. The upper interconnector 190 (each air electrode side current collecting portion 134 thereof) is joined to the air electrode 114 of the single cell 110 via a conductive joining material 196 made of, for example, a spinel-type oxide, and is thereby electrically connected to the air electrode 114 of the single cell 110. Further, in each power generation unit 102, the lower interconnector 190 is disposed below the single cell 110 with the fuel chamber 176 interposed therebetween, and is electrically connected to the fuel electrode 116 of the single cell 110 via a fuel electrode side current collecting member 144 described later. The interconnector 190 ensures electrical conduction between the power generation units 102 and suppresses mixing of the reaction gases between the power generation units 102. In the present embodiment, when two power generation units 102 are disposed adjacent to each other, one interconnector 190 is shared by the two adjacent power generation units 102. That is, the upper interconnector 190 in a certain power generation unit 102 is the same member as the lower interconnector 190 in another power generation unit 102 adjacent to the upper side of that power generation unit 102. Further, since the fuel cell stack 100 includes a lower end separator 189, the lowermost power generation unit 102 in the fuel cell stack 100 does not include the lower interconnector 190 (see FIGS. 2 to 4).

[0039] The separator 180 for IC is a frame-shaped member with a substantially rectangular through-hole 181 penetrating vertically near the center, and is formed of a metal such as ferritic stainless steel, for example. The plate thickness of the separator 180 for IC is relatively thin, for example, about 0.05 mm or more and 0.2 mm or less. The portion surrounding the through-hole 181 in the separator 180 for IC (hereinafter referred to as the "portion around the through-hole") is joined to the upper surface of the peripheral edge of the flat plate portion 150 of the interconnector 190 by welding, for example. Among the pair of separators 180 for IC included in a certain power generation unit 102, the upper separator 180 for IC partitions the air chamber 166 of the power generation unit 102 and the fuel chamber 176 of another power generation unit 102 adjacent to the upper side of the power generation unit 102. Also, among the pair of separators 180 for IC included in a certain power generation unit 102, the lower separator 180 for IC partitions the fuel chamber 176 of the power generation unit 102 and the air chamber 166 of another power generation unit 102 adjacent to the lower side of the power generation unit 102. Thus, the separator 180 for IC suppresses the leakage of gas between the power generation units 102 at the peripheral edge of the power generation unit 102. Note that the separator 180 for IC joined to the upper interconnector 190 of the power generation unit 102 located at the uppermost position in the fuel cell stack 100 is electrically connected to the upper end plate 104.

[0040] The separator 180 for IC includes an inner portion 186 including the portion around the through-hole of the separator 180 for IC (the portion surrounding the through-hole 181), an outer portion 187 located on the outer peripheral side of the inner portion 186, and a connecting portion 188 connecting the inner portion 186 and the outer portion 187. In the present embodiment, the inner portion 186 and the outer portion 187 are substantially flat plate-shaped and extend in a direction substantially orthogonal to the Z-axis direction. Also, the connecting portion 188 has a shape curved so as to protrude downward with respect to both the inner portion 186 and the outer portion 187. The lower portion (on the air chamber 166 side) of the connecting portion 188 is a convex portion, and the upper portion (on the fuel chamber 176 side) of the connecting portion 188 is a concave portion. For this reason, the connecting portion 188 includes a portion where the position in the Z-axis direction is different from that of the inner portion 186 and the outer portion 187.

[0041] As shown in FIGS. 5 to 8, the air electrode side frame 130 is a frame-shaped member having a substantially rectangular hole 131 penetrating in the Z-axis direction near the center, and is formed of an insulator such as mica, for example. 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 upper surface at the peripheral portion of the single cell separator 120 and the lower surface at the peripheral portion of the upper IC separator 180, and functions as a seal member for ensuring the gas sealability between the two (that is, the gas sealability of the air chamber 166). Further, the air electrode side frame 130 electrically insulates the space between the pair of IC separators 180 included in the power generation unit 102 (that is, between the pair of interconnects 190). Further, the air electrode side frame 130 is formed with an oxidant gas supply communication passage 132 that communicates the oxidant gas supply manifold 161 and the air chamber 166, and an oxidant gas discharge communication passage 133 that communicates the air chamber 166 and the oxidant gas discharge manifold 162.

[0042] As shown in FIGS. 5 to 7 and 9, the fuel electrode side frame 140 is a frame-shaped member having a substantially rectangular hole 141 penetrating in the Z-axis direction near the center, and is formed of metal, for example. 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 lower surface at the peripheral portion of the single cell separator 120 and the upper surface at the peripheral portion of the lower IC separator 180. Further, the fuel electrode side frame 140 is formed with a fuel gas supply communication passage 142 that communicates the fuel gas supply manifold 171 and the fuel chamber 176, and a fuel gas discharge communication passage 143 that communicates the fuel chamber 176 and the fuel gas discharge manifold 172. The configuration including the fuel chamber 176 including the portion defined by the single cell separator 120 and the IC separator 180, the fuel gas supply communication passage 142, and the fuel gas discharge communication passage 143 is an example of the communication passage in the claims.

[0043] As shown in FIGS. 5 to 7, the fuel electrode side current collecting member 144 is disposed in 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 that connects 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 is in contact with the lower surface of the fuel electrode 116, and the interconnector facing portion 146 is in contact with the upper surface of the interconnector 190 (flat plate portion 150 thereof). However, as described above, since the power generation unit 102 located at the lowermost side in the fuel cell stack 100 does not include the lower interconnector 190, the interconnector facing portion 146 of the fuel electrode side current collecting member 144 in the power generation unit 102 is in contact with the lower end separator 189. Since the fuel electrode side current collecting member 144 has such a configuration, the fuel electrode 116 and the interconnector 190 (or the lower end separator 189) are electrically connected. A spacer 149 formed 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. Therefore, the fuel electrode side current collecting member 144 follows the deformation of the power generation unit 102 due to temperature cycles and reaction gas pressure fluctuations, and the electrical connection between the fuel electrode 116 and the interconnector 190 (or the lower end separator 189) through the fuel electrode side current collecting member 144 is maintained well.

[0044] A-2. Operation of the fuel cell stack 100: As shown in FIGS. 2 and 5, 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 the holes of the main body portion 28, and is supplied from the oxidant gas supply manifold 161 to the air chamber 166 through the oxidant gas supply communication flow path 132 of each power generation unit 102. Further, as shown in FIGS. 3 and 6, 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 the holes of the main body portion 28, and is supplied from the fuel gas supply manifold 171 to the fuel chamber 176 through the fuel gas supply communication flow path 142 of each power generation unit 102.

[0045] When an oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and a fuel gas FG is supplied to the fuel chamber 176, power generation by the electrochemical reaction of the oxidant gas OG and the fuel gas FG is performed in the single cell 110. 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 upper interconnector 190, and the fuel electrode 116 is electrically connected to the lower interconnector 190 (or the separator 189 for the lower end) via the fuel electrode side current collecting member 144. That is, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Further, the upper interconnector 190 and the separator 180 for IC of the power generation unit 102 located at the uppermost side are electrically connected to the upper end plate 104, and the separator 189 for the lower end electrically connected to the fuel electrode side current collecting member 144 of the power generation unit 102 located at the lowermost side is electrically connected to the lower end plate 106. Therefore, the electrical energy generated in each power generation unit 102 is taken out from the end plates 104 and 106 that function as the output terminals of the fuel cell stack 100. Since the SOFC generates power at a relatively high temperature (for example, from 700°C to 1000°C), after startup, the fuel cell stack 100 may be heated by a heater (not shown) until the high temperature can be maintained by the heat generated by power generation.

[0046] As shown in FIGS. 2 and 5, the oxidant off-gas OOG discharged from the air chamber 166 of each power generation unit 102 to the oxidant gas discharge manifold 162 through the oxidant gas discharge communication flow path 133 passes through the holes in the main body portion 28 and the branch portion 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 a gas pipe (not shown) connected to the branch portion 29. Further, as shown in FIGS. 3 and 6, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generation unit 102 to the fuel gas discharge manifold 172 through the fuel gas discharge communication flow path 143 passes through the holes in the main body portion 28 and the branch portion 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 a gas pipe (not shown) connected to the branch portion 29.

[0047] In the fuel cell stack 100 of the present embodiment, as shown in FIGS. 8 and 9, in a view in the Z-axis direction, the oxidant gas supply communication flow path 132 communicating with the oxidant gas supply manifold 161 and the fuel gas discharge communication flow path 143 communicating with the fuel gas discharge manifold 172 are arranged to face one side of the single cell (the second side SI2 shown in FIGS. 8 and 9) in the same direction, and the oxidant gas discharge communication flow path 133 communicating with the oxidant gas discharge manifold 162 and the fuel gas supply communication flow path 142 communicating with the fuel gas supply manifold 171 are arranged to face the other side (the first side SI1 shown in FIGS. 8 and 9) that sandwiches the center point of the single cell 110 with respect to the second side SI2 of the single cell in the same direction. That is, the power generation unit 102 (fuel cell stack 100) of the present embodiment is a counter-flow type SOFC in which the main flow direction of the oxidant gas OG in the air chamber 166 (the direction from the positive X-axis direction to the negative X-axis direction) and the main flow direction of the fuel gas FG in the fuel chamber 176 (the direction from the negative X-axis direction to the positive X-axis direction) are substantially opposite directions (opposite to each other).

[0048] A-3. Configuration of the flow path defining members (120, 180): As shown in FIG. 6, the separator 120 (connection portion 128) for a single cell 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 (X-axis direction) of the fuel gas FG. The pair of bent portions 123 are respectively located on both sides of the flat portion 122 in the flow direction of the fuel gas FG. Each bent portion 123 is a portion adjacent to the flat portion 122 and having one or more bent sites. In FIG. 6, the bent portion 123 has two bent sites, a first bent site that bends from the end of the flat portion 122 toward the fuel chamber 176 side, and a second bent site that bends from the portion extending from the first bent site to the side opposite to the flat portion 122. Since the bent portion 123 has bent sites, it is more likely to deform than the flat portion 122.

[0049] The connection portion 188 of the separator 180 for an IC 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 respectively located on both sides of the flat portion 182 in the flow direction of the fuel gas FG. Each bent portion 183 is a portion adjacent to the flat portion 182 and having one or more bent sites. In FIG. 6, the bent portion 183 has two bent sites, a first bent site that bends from the end of the flat portion 182 toward the fuel chamber 176 side, and a second bent site that bends from the portion extending from the first bent site to the side opposite to the flat portion 182. Since the bent portion 183 has bent sites, it is more likely to deform than the flat portion 182.

[0050] The separator 120 for a single cell and the separator 180 for an IC are examples of the flow path defining members in the claims. The flat portion 122 and the flat portion 182 are examples of the first defining portion in the claims, and the space defined by the flat portion 122 and the flat portion 182 in the fuel chamber 176 is an example of the first gas flow path in the claims. The bent portion 123 and the bent portion 183 are examples of the second defining portion in the claims, and the space defined by the bent portion 123 and the bent portion 183 in the fuel chamber 176 is an example of the second gas flow path in the claims.

[0051] A-4. Configuration of Gas Flow Member 50: The fuel cell stack 100 of the present embodiment further includes a gas flow member 50. Hereinafter, the configuration of the gas flow member 50 will be described. In the present embodiment, the gas flow member 50 includes a gas flow member 50A disposed on the fuel gas supply communication flow path 142 side with respect to the single cell 110 and a gas flow member 50B disposed on the fuel gas discharge communication flow path 143 side with respect to the single cell 110. The shape of the gas flow member 50A and the shape of the gas flow member 50B are symmetric with respect to the single cell 110. In FIG. 5, the gas flow member 50 (50A, 50B) is schematically shown. In FIG. 6, the gas flow member 50 (50A, 50B) is schematically shown, and the detailed configuration of the X1 portion in the gas flow member 50A is shown enlarged. In FIG. 9, the gas flow member 50 (50A, 50B) is schematically shown, and the detailed configuration of the X2 portion in the gas flow member 50B is shown enlarged.

[0052] As shown in FIG. 9, the gas flow member 50 is a long member extending in a predetermined direction (Y-axis direction in the present embodiment) as a whole, and is formed of a metal such as ferrite-based stainless steel similar to the single cell separator 120 and the IC separator, for example. The gas flow member 50 has a main body portion 60 and a plurality of leg portions 70.

[0053] The main body portion 60 has a shape extending in a direction (Y-axis direction) intersecting the flow direction (X-axis direction) of the fuel gas FG. The main body portion 60 is disposed in a space in the fuel chamber 176 that overlaps the flat portion 122 of the single cell separator 120 and the flat portion 182 of the IC separator when viewed in the vertical 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 in the fuel chamber 176. Note that, when viewed in the flow direction of the fuel gas FG, both ends of the main body portion 60 are located outside both ends of the single cell 110. The main body portion 60 is an example of a support portion in the claims.

[0054] Each foot portion 70 has a linear shape extending from the main body portion 60 in a direction (X-axis direction, the flow direction of the fuel gas FG) intersecting the main body portion 60. When viewed in the flow direction of the fuel gas FG, the plurality of foot portions 70 are arranged over the entire length of the single cell 110. In the present embodiment, the gas flow member 50 has a plurality of inner foot portions 70A and a plurality of outer foot portions 70B. Among the foot portions 70, the portion disposed in the second gas flow path defined by the bent portion 123 and the bent portion 183 is an example of the gas flow portion in the claims.

[0055] The inner foot portion 70A extends from the main body portion 60 toward the single cell 110 side. The plurality of inner foot portions 70A are arranged at intervals along a direction (Y-axis direction, the extending direction of the main body portion 60) intersecting the flow direction of the fuel gas FG. That is, the gas flow member 50 has a groove VA formed by two adjacent inner foot portions 70A. In the present embodiment, the plurality of inner foot portions 70A are arranged 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 part of the groove VA between the plurality of inner foot portions 70A is disposed at a position deviated from the main body portion 60 in a direction (opposite to the single cell separator 120) intersecting the flow direction of the fuel gas FG.

[0056] Further, each inner foot portion 70A has a portion extending in a direction (Z-axis direction) intersecting both the flow direction (X-axis direction) of the fuel gas FG and the extending direction (Y-axis direction) of the main body portion 60 within the first gas flow path defined by the flat portion 122 and the flat portion 182. Specifically, each inner foot portion 70A has a first stepped portion 72A and a second stepped portion 74A (see FIG. 6). The first stepped portion 72A is a stepped portion located on the side opposite to the IC separator 180 (single cell separator 120 side) with respect to the main body portion 60 in the vertical direction. The second stepped portion 74A is located on the side opposite to the IC separator 180 with respect to the first stepped portion 72A in the vertical direction, and is located on the single cell 110 side with respect to the first stepped portion 72A in the flow direction of the fuel gas FG.

[0057] The outer foot portion 70B extends from the main body portion 60 to the side opposite to the single cell 110 (the fuel electrode side frame 140 side). The plurality of outer foot portions 70B are arranged at intervals along the 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 foot portions 70B. In the present embodiment, the plurality of outer foot portions 70B are arranged at equal intervals (see FIG. 9). In the gas flow member 50, at least a part of the groove VB between the plurality of outer foot portions 70B is arranged at a position deviated from the main body portion 60 in the direction intersecting the flow direction of the fuel gas FG (the side opposite to the IC separator 180).

[0058] Further, each outer foot 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 extending direction of the main body portion 60 (Y-axis direction) in the first gas flow path defined by the flat portion 122 and the flat portion 182. Specifically, each outer foot 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 side opposite to the IC separator 180 (the single cell separator 120 side) with respect to the main body portion 60 in the vertical direction. The second step portion 74B is located on the side opposite to the IC separator 180 with respect to the first step portion 72B in the vertical direction, and is located on the side opposite to the single cell 110 with respect to the first step portion 72B in the flow direction of the fuel gas FG.

[0059] In this embodiment, each of the plurality of inner legs 70A and each of the plurality of outer legs 70B are aligned with each other one by one in the extending direction of the main body 60. That is, in the extending direction of the main body 60, the positions of the inner legs 70A and the positions of the outer legs 70B coincide with each other. 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 so as to overlap each other. Further, 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, among the single-cell separator 120 and the IC separator 180, the space defined by the bent portion 123 and the bent portion 183 located on the side opposite to the single cell 110 (the fuel electrode side frame 140 side) is the maximum collapsible space that is most likely to be collapsed. Therefore, by arranging the relatively long outer legs 70B in this maximum collapsible space, it is suppressed that the gas flow in the maximum collapsible space is inhibited.

[0060] In the extending direction (Y-axis direction) of the main body 60, the width D1 of the legs 70 (70A, 70B) is narrower than the interval D2 between adjacent legs 70 (see Fig. 9). Further, the rigidity of the legs 70 is higher than the rigidity of the single-cell separator 120 and the IC separator 180. Specifically, the thickness of the legs 70 is thicker than the thicknesses of the single-cell separator 120 and the IC separator 180 (see Fig. 6).

[0061] The gas flow member 50 contacts the IC separator 180 and has a pair of restricting portions 80 that restrict the 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 a locking hole 148 formed in the fuel electrode side frame 140 from the tip of each outer leg 70B located at the end of the main body 60 (see Fig. 9). Note that, when viewed in the flow direction of the fuel gas FG, the restricting portion 80 is arranged outside the single cell 110.

[0062] The plate thickness t1 of the leg portion 70 of the gas flow member 50 is about 0.05 mm or more and 0.2 mm or less, for example, 0.1 mm. The plate thickness t1 of the main body portion 70 of the gas flow member 50 is about 0.05 mm or more and 1 mm or less, for example, 0.1 mm. Further, the height h1 (size in the Z-axis direction) of the gas flow member 50 is about 0.4 mm or more and 1.0 mm or less, for example, 0.7 mm. Further, the width D1 of the leg portions 70 (70A, 70B) is about 1 mm or more and 7 mm or less, for example, 4 mm. Further, the interval D2 between two adjacent leg portions 70 in the gas flow member 50 is, for example, about 5 mm or more and 15 mm or less, for example, 10 mm.

[0063] A-5. Effects of this embodiment: As described above, the fuel cell stack 100 of this embodiment includes a gas flow member 50 (see FIGS. 5, 6, and 9). The gas flow member 50 has a main body portion 60 and a plurality of leg portions 70. The main body portion 60 is disposed in the first gas flow path defined by the flat portion 122 and the flat portion 182 in the fuel chamber 176 and supports the plurality of leg portions 70.

[0064] The plurality of leg portions 70 (70A, 70B) are arranged at intervals from each other to form grooves VA and VB. Further, each leg portion 70 has stepped portions (72A, 74A, 72B, 74B) located on the side opposite to the IC separator 180 (the single cell separator 120 side) than the main body portion 60 in the second gas flow path defined by the bent portion 123 and the bent portion 183. With such a configuration, the fuel gas FG can pass through the second gas flow path through the grooves VA and VB in the gas flow member 50 (see the arrow at the X1 portion in FIG. 6). That is, in the gas flow member 50, a space (grooves VA, VB) through which the fuel gas FG flows is formed by the plurality of leg portions 70. The leg portion 70 is an example of a space forming portion in the claims.

[0065] <( Here, during the power generation operation of the fuel cell stack 100, a difference occurs between the pressure of the gas in the fuel chamber 176 and the pressure of the gas in the air chamber 166 in each power generation unit 102. Specifically, the pressure of the gas in the air chamber 166 becomes higher than the pressure of the gas 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 separator 120 for a single cell and the separator 180 for IC that partition the fuel chamber 176 and the air chamber 166. In particular, the bent portion 123 of the separator 120 for a single cell and the bent portion 183 of the separator 180 for IC are preferentially deformed, and there is a risk of deformation such that the height of the fuel chamber 176 becomes lower. Then, the second gas flow path defined by the bent portion 123 and the bent portion 183 becomes narrower, and as a result, the gas flow between the fuel gas supply manifold 171 and the fuel gas discharge manifold 172 and the fuel chamber 176 may be obstructed, which may adversely affect the performance of the fuel cell stack 100.

[0066] However, as described above, in the fuel cell stack 100 of the present embodiment, the gas flow member 50 is disposed in the second gas flow path in the fuel chamber 176. Therefore, due to the presence of the gas flow member 50, compared with the form in which the gas flow member 50 is not disposed, in the view in the Z-axis direction, at the position between the fuel gas supply communication flow path 142 and the fuel gas discharge communication flow path 143 and the single cell 110, the above-described deformation of the separator 120 for a single cell and the separator 180 for IC can be suppressed. Therefore, it is possible to suppress the gas flow between the fuel gas supply manifold 171 and the fuel gas discharge manifold 172 and the fuel chamber 176 from being obstructed due to the deformation of the separator 120 for a single cell and the separator 180 for IC, and thus it is possible to suppress a decrease in the performance of the fuel cell stack 100.

[0067] In addition, grooves VA and VB through which the fuel gas FG flows are formed in the gas flow member 50. Therefore, even if the gas flow member 50 is disposed between the fuel gas supply communication flow path 142 and the fuel gas discharge communication flow path 143 and the single cell 110 in the fuel chamber 176 in the Z-axis direction view, it is possible to suppress the gas flow in the fuel chamber 176 from being obstructed by the presence of the gas flow member 50.

[0068] From the above, according to the fuel cell stack 100 of the present embodiment, it is possible to suppress the flow of the fuel gas FG in the fuel chamber 176 from being obstructed and to suppress a decrease in the performance of the fuel cell stack 100 due to deformation of the separator 120 for single cells and the separator 180 for ICs.

[0069] In the present embodiment, all the power generation units 102 included in the fuel cell stack 100 are provided with the gas flow member 50. Therefore, it is possible to suppress a difference in pressure loss of the flow path of the fuel gas FG for each power generation unit 102 due to deformation of the separator 120 for single cells and the separator 180 for ICs in a certain power generation unit 102, and it is possible to prevent a difference in the supply amount of the fuel gas FG for each power generation unit 102 due to the difference in the pressure loss. As a result, it is possible to suppress a decrease in the performance of the entire fuel cell stack 100.

[0070] In the present embodiment, the leg portion 70 disposed in the second gas flow path that is relatively easy to deform is supported by the main body portion 60 disposed in the first gas flow path that is relatively difficult to deform (see FIGS. 6 and 9). Therefore, compared with a configuration in which the leg portion 70 is disposed in the second gas flow path alone, it is possible to suppress the leg 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 suppress a decrease in the performance of the fuel cell stack 100 due to deformation of the separator 120 for single cells and the separator 180 for ICs.

[0071] In this embodiment, the main body 60 is shaped to extend in a direction intersecting the flow direction of the fuel gas FG (see FIG. 9). Therefore, by being stably arranged in the first gas flow path, the displacement of the leg portion 70 with respect to the second gas flow path can be more effectively suppressed. Further, a gas flow portion is formed by a plurality of leg portions 70. Therefore, for example, compared with a configuration in which the gas flow portion is formed by a plate-like portion extending continuously along the main body 60, it is possible to suppress the flow of the fuel gas FG in the gas flow path (particularly the second gas flow path) from being obstructed.

[0072] In this embodiment, at least a part of the groove VA between the plurality of inner leg portions 70A is arranged at a position deviated from the main body 60 when viewed in the flow direction of the fuel gas FG (see FIG. 6). Thereby, it is possible to suppress the flow of the 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.

[0073] In this embodiment, each leg portion 70 (70A, 70B) has a portion (the inclined portions of the first step portions 72A, 72B) extending in a direction (Z-axis direction) intersecting both the flow direction (X-axis direction) of the fuel gas FG and the extending direction (Y-axis direction) of the main body 60 in the first gas flow path (see FIG. 6). Thereby, it is possible to suppress the flow of the fuel gas FG in the first gas flow path from being obstructed.

[0074] In this embodiment, in the extending direction (Y-axis direction) of the main body 60, the width D1 of the leg portion 70 (70A, 70B) is narrower than the interval D2 between adjacent leg portions 70 (see FIG. 9). Thereby, for example, compared with a configuration in which the width D1 of the leg portion 70 is wider than the interval D2 between the leg portions 70, it is possible to suppress the flow of the fuel gas FG in the gas flow path from being obstructed.

[0075] In this embodiment, the rigidity of the leg portion 70 is higher than that of the separator 120 for single cells and the separator 180 for ICs. Thereby, for example, compared with a configuration in which the rigidity of the leg portion 70 is equal to or lower than that of the separator 120 for single cells and the separator 180 for ICs, due to the presence of the leg portion 70, it is possible to more reliably ensure that the separator 120 for single cells and the separator 180 for ICs are deformed in a direction in which the cross-sectional area of the gas flow path decreases. Therefore, it is possible to suppress the flow of the fuel gas FG in the gas flow path from being inhibited due to the deformation.

[0076] In this embodiment, the gas flow member 50 has a pair of leg portions 70 (70A, 70B) disposed in each of the pair of second gas flow paths (see FIGS. 6 and 9). Thereby, when the gas flow member 50 is disposed so as to straddle the first gas flow path by the pair of leg portions 70, a space is easily secured in the first gas flow path. As a result, it is possible to suppress the flow of the fuel gas FG not only in the second gas flow path but also in the first gas flow path from being inhibited.

[0077] The gas flow member 50 is in contact with the separator 120 for single cells and has a pair of restricting portions 80 that restrict the movement of the gas flow member 50 in the flow direction of the fuel gas FG (see FIG. 9). Thereby, it is possible to effectively suppress the gas flow member 50 from moving in the flow direction of the fuel gas FG. Further, in this embodiment, it is also possible to suppress the gas flow member 50 from moving in a direction intersecting the flow direction of the fuel gas FG.

[0078] B. Modification example: The technology disclosed in this specification is not limited to the above-described embodiment, and can be deformed into various forms without departing from the gist thereof. For example, the following modifications are also possible.

[0079] The configuration of the fuel cell stack 100 and the configurations of the respective components constituting the fuel cell stack 100 in the above-described embodiment are merely examples and can be variously modified. For example, in the above-described embodiment, the gas flow member 50 is arranged at a position overlapping the respective connecting portions 128 and 188 (flat portions 122 and 182 and bent portions 123 and 183) of the single-cell separator 120 and the IC separator 180 when viewed in the Z-axis direction. However, the gas flow member 50 may be arranged at a position overlapping the bent portions 123 and 183 among the respective connecting portions 128 and 188 and not overlapping the flat portions 122 and 182 when viewed in the Z-axis direction. Further, the gas flow member 50 may be arranged at a position overlapping a portion other than the respective connecting portions 128 and 188 in the single-cell separator 120 and the IC separator 180 (for example, a portion that is relatively thin and easily deformable in the single-cell separator 120 or the like). Also, in the above-described embodiment, the single-cell separator 120 and the IC separator 180 have the connecting portions 128 and 188, but the single-cell separator 120 and the IC separator 180 may not have the connecting portions 128 and 188.

[0080] In the above-described embodiment, one gas flow member 50 (50A) is arranged between the fuel gas supply communication flow path 142 and the single cell 110 when viewed in the Z-axis direction within the fuel chamber 176, but a plurality of gas flow members 50 may be arranged at this position. Similarly, in the above-described embodiment, one gas flow member 50 (50B) is arranged between the fuel gas discharge communication flow path 143 and the single cell 110 when viewed in the Z-axis direction within the fuel chamber 176, but a plurality of gas flow members 50 may be arranged at this position. Further, in the above-described embodiment, the gas flow member may be arranged, for example, between the oxidant gas supply communication flow path 132 (or the oxidant gas discharge communication flow path 133) and the single cell 110 when viewed in the Z-axis direction within the air chamber 166.

[0081] In the above-described embodiment, the gas flow member 50 is disposed between the fuel gas supply communication passage 142 and the fuel gas discharge communication passage 143 and the single cell 110 in the fuel chamber 176 as viewed in the Z-axis direction. However, the gas flow member 50 may be disposed between one of the fuel gas supply communication passage 142 and the fuel gas discharge communication passage 143 and the single cell 110 in the fuel chamber 176 as viewed in the Z-axis direction.

[0082] In the above-described embodiment, all the power generation units 102 included in the fuel cell stack 100 are provided with the gas flow member 50. However, it is not necessarily required that all the power generation units 102 included in the fuel cell stack 100 be provided with the gas flow member 50, and at least one power generation unit 102 may be provided with the gas flow member 50.

[0083] In the above-described embodiment, the gas flow member 50 is disposed between the fuel gas supply communication passage 142 and the fuel gas discharge communication passage 143 and the interconnector 190 in the fuel chamber 176 as viewed in the Z-axis direction, and is disposed overlapping the separator 180 for IC. However, it is not necessarily required to have such a configuration. Further, the fuel cell stack 100 does not necessarily need to include the separator 180 for IC, 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).

[0084] The configuration of the gas flow member 50 can be variously deformed. For example, in the gas flow member 50, it may have a configuration in which either the inner foot portion 70A or the outer foot portion 70B is not provided, or a configuration in which only one inner foot portion 70A is provided, or a configuration in which only one outer foot portion 70B is provided. Further, the extending direction of the gas flow member 50 (main body portion 60) may be in another direction as long as it intersects the flowing direction of the fuel gas FG. Further, the gas flow member 50 is, for example, a member produced by bending a plate material so that its cross section becomes corrugated, and a plurality of flat first portions extending in a direction (in the XZ plane direction) orthogonal to the extending direction (Y-axis direction) of the entire gas flow member 50, and a plurality of flat second portions each connecting between the ends of two adjacent first portions may be alternately arranged in the extending direction (Y-axis direction) of the entire gas flow member 50. Further, the gas flow member 50 may have a configuration in which a space is formed not only by the grooves VA and VB but also by through-holes through which gas flows (for example, a mesh-like member in which a large number of holes through which gas flows are formed).

[0085] In the above embodiment, the foot portion 70 of the gas flow member 50 may have a configuration in which it does not have at least one of the first step portions 72A and 72B and the second step portions 74A and 74B, or a configuration in which it has three or more step portions. Further, the inner foot portion 70A and the outer foot portion 70B may be arranged at different positions in the extending direction of the main body portion 60. Further, although the lengths LA of the plurality of inner foot portions 70A were all 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. Further, the length LA of the inner foot portion 70A and the length LB of the outer foot portion 70B may be the same as each other. The width D1 of the foot portion 70 (70A, 70B) may be the same as the interval D2 between adjacent foot portions 70, or may be wider than the interval D2. The rigidity of the foot portion 70 may be equal to or lower than the rigidity of the separator 120 for a single cell or the separator 180 for an IC. The gas flow member 50 may have a configuration in which it does not include the restricting portion 80.

[0086] The flow path defining member is not limited to the separator 120 for a single cell or the separator 180 for an IC. The flow path defining member may be any member that defines a gas flow path and has the above-described first defining portion and second defining portion. For example, it may be a manifold or a gas pipe that constitutes a gas flow path. The second defining portion is not limited to the bent portions 123 and 183 having a bent site, and may be a portion having a thinner wall thickness than other portions, a portion formed of a softer material than other portions, or a portion closer to the free end than other portions. Note that the factor causing the second defining portion to deform is not limited to the pressure difference between the fuel chamber and the air chamber, and examples include the difference in thermal expansion between the flow path defining member and the member adjacent thereto.

[0087] FIG. 10 is an explanatory view showing the external configuration of a fuel cell stack 100a as a modified example. The fuel cell stack 100a of the modified example shown in FIG. 10 includes a plurality of single cells 110a. The single cell 110a has a columnar support body extending in the vertical direction. The support body has a flat cross section and has a pair of opposing flat surfaces. A gas flow path extending in the vertical direction is formed inside the support body. On one flat surface of the support body, a fuel electrode, a solid electrolyte layer, and an air electrode are sequentially laminated. An interconnector is laminated at a site where the air electrode is not formed on the other flat surface. By disposing a conductive member 150a between adjacent single cells 110a, the single cells 110a are electrically connected in series. The single cell 110a is an example of an electrochemical reaction single cell or an electrochemical reaction unit in the claims.

[0088] The lower end of each single cell 110a is fixed to the manifold 171a by a sealing material 124a such as glass. The gas flow path formed in the support body of each single cell 110a communicates with the internal space of the manifold 171a. A fuel gas supply pipe 27a for supplying fuel gas into the manifold 171a is connected to the side surface of the manifold 171a. The fuel gas supplied to the manifold 171a via the fuel gas supply pipe 27a is supplied to the fuel electrode through the gas flow path formed in the support body of each single cell 110a from the manifold 171a.

[0089] In the fuel cell stack 100a of the modified example shown in FIG. 11, gas flow paths such as the manifold 171a and the fuel gas supply pipe 27a communicate gas with the fuel electrodes of the respective single cells 110a through the manifold. Among the gas flow paths formed in the support of each single cell 110a, the portion from the end on the manifold 171a side of the support to the fuel electrode is a communication flow path that communicates the manifold with the fuel electrode. The manifold 171a has a flat portion 122a and a bent portion 123a. The bent portion 123a is more deformable than the flat portion 122a. A gas flow member 50a is disposed in the 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 in the space defined by the bent portion 123a (directly below the bent portion 123a). A through hole 72a through which fuel gas from the fuel gas supply pipe 27a flows is formed in the gas flow portion 70a. The support portion 60a is disposed on the side opposite to the fuel gas supply pipe 27a with respect to the gas flow portion 70a and supports the gas flow portion 70a. With such a configuration, it is possible to suppress the performance of the fuel cell stack 100a from deteriorating due to deformation of the manifold 171a while suppressing the flow of fuel gas in the manifold 171a from being inhibited. The manifold 171a is an example of a gas defining member.

[0090] In the above embodiment, the fuel cell stack 100 may be configured such that, for example, the oxidant gas supply communication flow path 132 and the oxidant gas discharge communication flow path 133 of the air chamber 166 directly open to the outside of the fuel cell stack 100 without including the manifolds 161 and 162 for the air electrodes.

[0091] Further, in the above embodiment, the holes 32 and 34 are formed in the pair of end plates 104 and 106, but the holes 32 and 34 may not be formed in at least one of the pair of end plates 104 and 106. Further, in the above embodiment, the pair of end plates 104 and 106 function as terminal plates, but a terminal plate may be provided separately from the pair of end plates 104 and 106.

[0092] Also, in the above embodiment, the interconnector 190 includes the conductive coating layer 194, but the interconnector 190 may not include the coating layer 194. Further, in the above embodiment, the single cell 110 has the reaction prevention layer 118, but the single cell 110 may not have the reaction prevention layer 118. Also, in the above embodiment, the number of single cells 110 included in the fuel cell stack 100 (the number of power generation units 102) is merely an example, and the number of single cells 110 is appropriately determined according to the output voltage required for the fuel cell stack 100 and the like. Also, the materials constituting each member in the above embodiment are merely examples, and each member may be constituted by other materials.

[0093] Also, the fuel cell stack 100 of the above embodiment is a counterflow type SOFC, but the technology disclosed in this specification is similarly applicable to a coflow type SOFC. Note that, in a coflow type SOFC, in a view in the Z-axis direction, the fuel gas supply communication flow path 142 and the oxidant gas supply communication flow path 132 are arranged so as to face one side of the single cell 110, and the fuel gas discharge communication flow path 143 and the oxidant gas discharge communication flow path 133 are arranged so as to face the other side that faces the one side of the single cell 110 with the center point of the single cell 110 interposed therebetween. Also, the technology disclosed in this specification is similarly applicable to a crossflow type SOFC.

[0094] In addition, in the above-described embodiment, the fuel cell stack 100 that generates power by utilizing the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidant gas is targeted. However, the technology disclosed in this specification is similarly applicable to an electrolytic cell stack including a plurality of electrolytic single cells that are constituent units of a solid oxide electrolysis cell (SOEC) that generates hydrogen by utilizing the electrolysis reaction of water.\n\nThe basic configuration of the electrolytic cell stack is known, for example, as described in Japanese Patent Application Laid-Open No. 2016-8-1813, and is generally as follows. That is, in the configuration of the fuel cell stack 100 of the above-described embodiment, the electrolytic cell stack has a configuration in which the \"power generation unit\" is read as the \"electrolytic cell unit\", the \"single cell\" is read as the \"electrolytic single cell\", the \"oxidant gas supply manifold\" is read as the \"air discharge manifold\", the \"oxidant gas discharge manifold\" is read as the \"air supply manifold\", the \"fuel gas supply manifold\" is read as the \"hydrogen discharge manifold\", the \"fuel gas discharge manifold\" is read as the \"steam supply manifold\", the \"oxidant gas supply communication flow path\" is read as the \"air discharge communication flow path\", the \"oxidant gas discharge communication flow path\" is read as the \"air supply communication flow path\", the \"fuel gas supply communication flow path\" is read as the \"hydrogen discharge communication flow path\", and the \"fuel gas discharge communication flow path\" is read as the \"steam supply communication flow path\".

[0095] During the operation of the electrolytic cell stack, a voltage is applied to the electrolytic cell stack so that the air electrode 114 becomes positive (anode) and the fuel electrode (hydrogen electrode) 116 becomes negative (cathode). Further, steam as a raw material gas is supplied to the steam supply manifold through the gas passage member 27. Note that the supplied steam may contain hydrogen gas. The steam supplied to the steam supply manifold is supplied from the steam supply manifold to the fuel chamber 176 through the steam supply communication flow path of each electrolytic cell unit and is used for the electrolysis reaction of water in each electrolytic single cell. The hydrogen gas generated in the fuel chamber 176 by the electrolysis reaction of water in each electrolytic single cell is discharged to the hydrogen discharge manifold through the hydrogen discharge communication flow path together with the remaining steam, and is taken out of the electrolytic cell stack from the hydrogen discharge manifold through the gas passage member 27.

[0096] Also, during the operation of the electrolytic cell stack, air is supplied into the electrolytic cell stack as necessary for controlling the temperature of the electrolytic cell stack and the like. In this case, the air supplied to the air supply manifold through the gas passage member 27 is supplied to the air chamber 166 from the air supply manifold through the air supply communication flow path for each electrolytic cell unit. The air supplied to the air chamber 166 is discharged to the air discharge manifold through the air discharge communication flow path together with the oxygen generated at the air electrode 114, and is discharged to the outside of the electrolytic cell stack from the air discharge manifold through the gas passage member 27.

[0097] Even in the electrolytic cell stack having such a configuration, by adopting the same configuration as the fuel cell stack 100 in the above embodiment, the same operational effects as those of the fuel cell stack 100 in the above embodiment can be achieved.

[0098] In the above embodiment, a solid oxide fuel cell (SOFC) has been described as an example. However, the technology disclosed in this specification is also applicable to other types of fuel cells (or electrolytic cells) such as molten carbonate fuel cells (MCFC).

Description of Reference Numerals

[0099] 22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 27a: Fuel gas supply pipe 28, 60: Main body part 29: Branch part 32, 34: Hole 50, 50A, 50B, 50a: Gas flow member 60a: Support part 70: Foot part 70A: Inner foot part 70B: Outer foot part 70a: Gas flow part 72A, 72B: First step part 72a, 121, 181: Through hole 74A, 74B: Second step part 80: Regulation part 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: Fuel electrode 118: Reaction prevention layer 120: Separator for single cell 122, 182, 122a: Flat part 123, 183, 123a: Bent part 124: Joint part 124a: Sealing material 125: Glass seal part 126, 186: Inner part 127, 187: Outer part 128, 188: Connection part 130: Air electrode side frame 131, 141: Hole 132: Oxidant gas supply communication flow path 133: Oxidant gas discharge communication flow path 134: Air electrode side current collecting part 140: Fuel electrode side frame 142: Fuel gas supply communication flow path 143: Fuel gas discharge communication flow path 144: Fuel electrode side current collecting member 145: Electrode facing part 146: Interconnector facing part 147: Connection part 148: Locking hole 149: Spacer 150: Flat plate part 150a: Conductive member 161, 162, 171, 172, 171a: Manifold 166: Air chamber 176: Fuel chamber 180: Separator for IC 189: Separator for lower end 190: Interconnector 194: Coating layer 196: Conductive bonding material

Claims

1. In an electrochemical reaction cell stack including a plurality of electrochemical reaction units each having an electrochemical reaction single cell including an electrolyte layer, an air electrode, and a fuel electrode that face each other with the electrolyte layer therebetween, a manifold for gas exchange is formed between at least one specific electrode of the air electrode and the fuel electrode in each of the electrochemical reaction units, in each of the electrochemical reaction units, the air electrode and the fuel electrode are arranged at positions different from the specific electrode in a view in a first direction in which the air electrode and the fuel electrode face each other, and a communication flow path that communicates the manifold and the specific electrode is formed, a flow path defining member that defines a gas flow path composed of the communication flow path 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, and having a bent portion adjacent to the first defining portion, 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, An electrochemical reaction cell stack characterized by the above.

2. In the electrochemical reaction cell stack according to Claim 1, the gas flow member includes a gas flow portion disposed in the second gas flow path of the gas flow path and having the space forming portion, and a support portion disposed in a first gas flow path defined by the first defining portion of the flow path defining member among the gas flow paths and supporting the gas flow portion, An electrochemical reaction cell stack characterized by the above.

3. In 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, An electrochemical reaction cell stack characterized by the above.

4. In the electrochemical reaction cell stack according to Claim 3, at least a part of the groove between the plurality of legs is disposed at a position deviated from the support portion in a view in the gas flow direction, An electrochemical reaction cell stack characterized by the above.

5. In the electrochemical reaction cell stack according to Claim 4, At least a part of the plurality of legs has a portion extending in a direction intersecting both the gas flow direction and the extending direction of the support portion in the first gas flow path. An electrochemical reaction cell stack characterized by this.

6. In the electrochemical reaction cell stack according to any one of Claims 3 to 5, In the extending direction of the support portion, the width of the leg is narrower than the interval between the adjacent legs. An electrochemical reaction cell stack characterized by this.

7. In the electrochemical reaction cell stack according to Claim 3, The rigidity of the leg is higher than the rigidity of the second defining portion of the flow path defining member. An electrochemical reaction cell stack characterized by this.

8. In 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 the second defining portions, and, when viewed in the gas flow direction, the first defining portion is located at a position offset to the opposite side of the gas flow path of the flow path defining member with respect to the pair of the second defining portions. The gas flow member has a pair of the gas flow portions disposed in each of the pair of the second gas flow paths. An electrochemical reaction cell stack characterized by this.

9. In the electrochemical reaction cell stack according to Claim 1, The gas flow member is in contact with the flow path defining member and has a restricting portion for restricting the movement of the gas flow member in the gas flow direction. An electrochemical reaction cell stack characterized by this.

Images