JP2020177839A - Electrochemical reaction cell stack - Google Patents

Abstract

To suppress the deterioration of the performance of an electrochemical reaction cell stack due to the adhesion of P diffused from a separator.SOLUTION: An electrochemical reaction cell stack includes a plurality of electrochemical reaction single cell 110, a separator 120 that is formed with a through hole 121, and in which a through hole peripheral portion 122 surrounding the through hole is joined to the surface of the electrochemical reaction single cell to partition an air chamber 166 facing an air pole 114 and a fuel chamber 176 facing the fuel pole 116, and a junction 124 that joins the periphery of the through hole of the separator and the surface of the electrochemical reaction single cell. The separator includes P (phosphorus) and includes a first surface 119 facing the gas flow path of the gas supplied to the fuel pole. The junction includes a second surface 123 facing the gas flow path. The electrochemical reaction cell stack includes a P diffusion suppression unit 129 that further covers at least a part of the first surface of the separator and reaches at least a boundary between the first surface of the separator and the second surface of the junction.SELECTED DRAWING: Figure 6

Description

The techniques disclosed herein relate to electrochemical reaction cell stacks.

A solid oxide fuel cell (hereinafter referred to as "SOFC") is known as one of the fuel cells that generate electricity by utilizing an electrochemical reaction between hydrogen and oxygen. SOFCs are generally used in the form of a fuel cell stack comprising a plurality of fuel cell single cells (hereinafter, simply referred to as "single cells") arranged side by side in a predetermined direction. Each single cell includes an electrolyte layer containing a solid oxide and an air electrode and a fuel electrode that face each other in a predetermined direction with the electrolyte layer in between.

A through hole is formed in the fuel cell stack, and a portion surrounding the through hole is joined to a single cell to partition an air chamber facing the air electrode and a fuel chamber facing the fuel electrode, and P (phosphorus phosphorus). ), And a joint portion for joining a portion surrounding the through hole of the separator and a single cell (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-49321

In the above-mentioned fuel cell stack provided with the separator containing P, since the surface of the separator is exposed in the fuel chamber, P diffused from the separator may move to the vicinity of the fuel electrode together with the gas supplied to the fuel electrode. There is. However, conventionally, the influence of the movement of P diffused from the separator to the vicinity of the fuel electrode on the performance of the fuel cell stack has not been sufficiently studied, and there is room for improvement.

In addition, such a problem is electrolysis including a plurality of electrolytic single cells which are constituent units of a solid oxide type electrolytic cell (hereinafter referred to as “SOEC”) that generates hydrogen by utilizing an electrolysis reaction of water. This is a common issue for cell stacks. In the present specification, the fuel cell single cell and the electrolytic single cell are collectively referred to as an electrochemical reaction single cell, and the fuel cell stack and the electrolytic cell stack are collectively referred to as an electrochemical reaction cell stack.

This specification discloses a technique capable of solving the above-mentioned problems.

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

(1) The electrochemical reaction cell stack disclosed in the present specification includes a plurality of electrochemical including an air electrode, a fuel electrode, and an electrolyte layer arranged between the air electrode and the fuel electrode. The reaction single cell and the through hole are formed, and the peripheral portion of the through hole surrounding the through hole is joined to the surface of the electrochemical reaction single cell, and the air chamber facing the air electrode and the fuel chamber facing the fuel electrode In an electrochemical reaction cell stack comprising a separator for partitioning and a joint for joining the perimeter of the through-hole of the separator and the surface of the electrochemical reaction single cell, the separator contains P (phosphorus). The joint has a first surface that is contained and faces the gas flow path of the gas supplied to the fuel electrode, and the joint has a second surface that faces the gas flow path, and further, said. It covers at least a part of the first surface of the separator and includes a P diffusion suppressing portion that reaches at least a boundary between the first surface of the separator and the second surface of the joint.

In the present electrochemical reaction cell stack, the separator contains P and has a first surface facing the gas flow path of the gas supplied to the fuel electrode. Further, the joint portion for joining the separator and the electrochemical reaction single cell has a second surface facing the gas flow path. After the operation of the electrochemical reaction cell stack is started, P diffused from the first surface of the separator is carried to the gas supplied to the fuel electrode, moves to the vicinity of the fuel electrode, adheres to the reaction field at the fuel electrode, and is electrochemical. The performance of the reaction cell stack may deteriorate. On the other hand, the present electrochemical reaction cell stack is provided with a P diffusion suppressing section. The P diffusion inhibitor covers at least a part of the first surface of the separator and reaches at least the boundary between the first surface of the separator and the second surface of the joint. Therefore, it is suppressed that P diffused from the vicinity of the electrochemical reaction single cell in the first surface of the separator moves to the vicinity of the fuel electrode. As a result, according to the present electrochemical reaction cell stack, the electrochemical reaction cell stack due to the adhesion of P diffused from the separator is compared with the configuration in which the first surface of the separator is not covered with the P diffusion suppressing portion. Performance degradation can be suppressed.

(2) In the electrochemical reaction cell stack, the P diffusion inhibitor further covers at least a part of the second surface of the joint, and at least the second surface of the joint and the electrolyte. The structure may reach the boundary with the side surface of the layer. P diffused from the separator may pass through the joint and move to the vicinity of the fuel electrode. On the other hand, in the present electrochemical reaction cell stack, the P diffusion inhibitor further covers at least a part of the second surface of the junction, and at least the second surface of the junction and the side surface of the electrolyte layer. Has reached the boundary of. Therefore, not only P that diffuses from the first surface of the separator but also P that diffuses from the separator and passes through the joint portion is suppressed from moving to the vicinity of the fuel electrode. As a result, according to the present electrochemical reaction cell stack, the electrochemical reaction cell stack due to the adhesion of P diffused from the separator is compared with the configuration in which the second surface of the joint portion is not covered with the P diffusion suppressing portion. Performance degradation can be suppressed more effectively.

(3) In the electrochemical reaction cell stack, the P-diffusion suppressing portion may further cover at least a part of the side surface of the fuel electrode. In the present electrochemical reaction cell stack, the P diffusion inhibitor further covers at least a part of the side surface of the fuel electrode. Therefore, it is suppressed that P diffused from the separator flows into the reaction field of the fuel electrode through the side surface of the fuel electrode and adheres to the reaction field. As a result, according to the present electrochemical reaction cell stack, the performance of the electrochemical reaction cell stack deteriorates due to the adhesion of P diffused from the separator, as compared with the configuration in which the side surface of the fuel electrode is not covered with the P diffusion suppressing portion. Can be suppressed more effectively.

(4) In the electrochemical reaction cell stack, the separator includes a peripheral portion of the through hole, and is a first flat substantially parallel to a second direction orthogonal to the first direction which is the axial direction of the through hole. The first flat portion includes a portion, a second flat portion substantially parallel to the second direction, and a portion whose position in the first direction is different from that of the first flat portion and the second flat portion. A connecting portion for connecting the flat portion of the above and the second flat portion may be provided, and the P diffusion suppressing portion may be configured to be separated from the connecting portion. In the present electrochemical reaction cell stack, the P diffusion suppressing portion is separated from the connecting portion of the separator. Therefore, it is possible to prevent the stress relaxation function of the separator from being lowered due to the presence of the P diffusion suppressing portion, as compared with the configuration in which the P diffusion suppressing portion is in contact with the connecting portion of the separator.

The technique disclosed in the present specification can be realized in various forms, for example, an electrochemical reaction cell stack (fuel cell stack or electrolytic cell stack), an electrochemical reaction cell stack including an electrochemical reaction cell stack. It can be realized in the form of a reaction system (fuel cell system or electrolytic cell system), a method for producing them, and the like.

It is a perspective view which shows the appearance structure of the fuel cell stack 100 in this embodiment. It is explanatory drawing which shows the XZ cross-sectional structure of the fuel cell stack 100 at the position of II-II of FIG. It is explanatory drawing which shows the YZ cross-sectional structure of the fuel cell stack 100 at the position of III-III of FIG. It is explanatory drawing which shows the XZ cross section configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross section configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which enlarges and shows the XZ cross-sectional structure of a part (Px part of FIG. 4) of a separator 120. It is explanatory drawing which shows the XY cross-sectional structure of the power generation unit 102 at the position of VII-VII of FIG. It is explanatory drawing which shows the performance evaluation result.

A. Embodiment:
A-1. Device configuration:
(Structure of fuel cell stack 100)
FIG. 1 is a perspective view showing an external configuration of the fuel cell stack 100 according to the present embodiment, and FIG. 2 is an XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II of FIG. 1 (and FIG. 7 described later). 3 is an explanatory view showing a YZ cross-sectional configuration of the fuel cell stack 100 at the position III-III of FIG. 1 (and FIG. 7 described later). Each figure shows XYZ axes that are orthogonal to each other to identify the direction. In the present specification, for convenience, the Z-axis positive direction is referred to as an upward direction, and the Z-axis negative direction is referred to as a downward direction, but the fuel cell stack 100 is actually in a direction different from such an orientation. It may be installed. The same applies to FIGS. 4 and later. Further, in the present specification, the direction orthogonal to the Z axis is referred to as a plane direction.

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

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

A bolt 22 extending in the vertical direction is inserted into each communication hole 108, and the fuel cell stack 100 is fastened by the bolt 22 and the nuts 24 fitted on both sides of the bolt 22. As shown in FIGS. 2 and 3, between the nut 24 fitted on one side (upper side) of the bolt 22 and the upper surface of the end plate 104 forming the upper end of the fuel cell stack 100, and the bolt. An insulating sheet 26 is interposed between the nut 24 fitted on the other side (lower side) of the 22 and the lower surface of the end plate 106 forming the lower end of the fuel cell stack 100. However, in the place where the gas passage member 27 described later is provided, the insulating sheets arranged on the upper side and the lower side of the gas passage member 27 and the gas passage member 27 between the nut 24 and the surface of the end plate 106, respectively. 26 is intervening. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic dust sheet, a glass sheet, a glass-ceramic composite agent, or the like.

The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each communication hole 108. Therefore, a space is secured between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each communication hole 108. As shown in FIGS. 1 and 2, the position is near the midpoint of one side (the side on the positive side of the X axis among the two sides parallel to the Y axis) on the outer circumference of the fuel cell stack 100 around the Z axis. In the space formed by the bolt 22 (bolt 22A) and the communication hole 108 through which the bolt 22A is inserted, the oxidant gas OG is introduced from the outside of the fuel cell stack 100, and the oxidant gas OG is generated for each power generation. It functions as an oxidizer gas introduction manifold 161 that is a gas flow path supplied to the unit 102, and is the midpoint of the side opposite to the side (the side on the negative side of the X axis among the two sides parallel to the Y axis). The space formed by the bolt 22 (bolt 22B) located in the vicinity and the communication hole 108 through which the bolt 22B is inserted provides the oxidant off-gas OOG, which is the gas discharged from the air chamber 166 of each power generation unit 102. It functions as an oxidant gas discharge manifold 162 that discharges to the outside of the fuel cell stack 100. In this embodiment, air is used as the oxidant gas OG. Further, in the present embodiment, a blower (not shown) is used for introducing the oxidant gas OG into the oxidant gas introduction manifold 161. Further, it is generated when heat exchange (for example, the oxidant off gas OOG discharged from the fuel cell stack 100 and the fuel off gas FOG are burned) before the oxidant gas OG is introduced into the oxidant gas introduction manifold 161. Preheating of the oxidant gas OG may be performed by utilizing heat exchange with heat).

Further, as shown in FIGS. 1 and 3, the vicinity of the midpoint of one side (the side on the positive side of the Y axis among the two sides parallel to the X axis) on the outer circumference of the fuel cell stack 100 around the Z axis. In the space formed by the bolt 22 (bolt 22D) located in the above and the communication hole 108 through which the bolt 22D is inserted, the fuel gas FG is introduced from the outside of the fuel cell stack 100, and the fuel gas FG is generated by each power generation. A bolt 22 that functions as a fuel gas introduction manifold 171 to be supplied to the unit 102 and is located near the midpoint of the side opposite to the side (the side on the negative side of the Y axis of the two sides parallel to the X axis). The space formed by (bolt 22E) and the communication hole 108 through which the bolt 22E is inserted sends the 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. It functions as a fuel gas discharge manifold 172 to be discharged. In the present embodiment, for example, a hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG.

The fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow tubular main body 28 and a hollow tubular branch 29 branched from the side surface of the main body 28. The hole of the branch portion 29 communicates with the hole of the main body portion 28. A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27. Further, as shown in FIG. 2, the hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22A forming the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. The hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22B forming the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162. Further, as shown in FIG. 3, the hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22D forming the fuel gas introduction manifold 171 communicates with the fuel gas introduction manifold 171 and fuel gas. The hole of the main body 28 of the gas passage member 27 arranged at the position of the bolt 22E forming the discharge manifold 172 communicates with the fuel gas discharge manifold 172.

(Structure of end plates 104 and 106)
The pair of end plates 104 and 106 are substantially rectangular flat plate-shaped conductive members, and are made of, for example, stainless steel. One end plate 104 is arranged above the power generation unit 102 located at the top, and the other end plate 106 is arranged below the power generation unit 102 located at the bottom. A plurality of power generation units 102 are held in a pressed state by a pair of end plates 104 and 106. The upper end plate 104 functions as a positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as a negative output terminal of the fuel cell stack 100.

(Structure of power generation unit 102)
FIG. 4 is an explanatory view showing an XZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 2, and FIG. 5 is an explanatory view showing an XZ cross-sectional configuration at the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross-sectional structure of two power generation units 102. 6 is an explanatory view showing an enlarged XZ cross-sectional configuration of a part of the separator 120 (Px portion in FIG. 4), and FIG. 7 is an XY cross-section of the power generation unit 102 at the position of VII-VII in FIG. It is explanatory drawing which shows the structure.

As shown in FIGS. 4 and 5, the power generation unit 102 includes a single cell 110, a separator 120, an air pole side frame 130, an air pole side current collector 134, a fuel pole side frame 140, and a fuel pole side. It includes a current collector 144 and a pair of interconnectors 150 that form the uppermost layer and the lowermost layer of the power generation unit 102. Holes corresponding to the communication holes 108 through which the above-mentioned bolts 22 are inserted are formed on the peripheral edges of the separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the interconnector 150 around the Z axis. As described above, since the fuel cell stack 100 includes a plurality of (seven in the present embodiment) power generation units 102, the fuel cell stack 100 has a plurality of (seven in the present embodiment) single cells. It can be said that it has 110.

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

The single cell 110 includes an electrolyte layer 112, an air electrode (cathode) 114 and a fuel electrode (anode) 116 facing each other in the vertical direction (arrangement direction in which the power generation units 102 are arranged) with the electrolyte layer 112 in between. The single cell 110 of the present embodiment is a flat plate type single cell, and is a fuel pole support type single cell in which the electrolyte layer 112 and the air pole 114 are supported by the fuel pole 116.

The electrolyte layer 112 is a flat plate-shaped member that is substantially rectangular in the Z-axis direction, and is a dense layer. The electrolyte layer 112 is formed of, for example, a solid oxide such as YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), GDC (gadolinium-doped ceria), and perovskite-type oxide. There is. As described above, 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 substantially rectangular flat plate-shaped member smaller than the electrolyte layer 112 in the Z-axis direction, and is a porous layer. The air electrode 114 is formed of, for example, a perovskite-type oxide (for example, LSCF (lanternstrontium cobalt iron oxide), LSM (lanternstrontium manganese oxide), LNF (lantern nickel iron)). The fuel electrode 116 is a substantially rectangular flat plate-shaped member having substantially the same size as the electrolyte layer 112 in the Z-axis direction, and is a porous layer. The fuel electrode 116 is formed of, for example, a cermet composed of Ni and oxide ion conductive ceramic particles (for example, YSZ).

The separator 120 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 made of, for example, metal. As shown in FIG. 6, the portion of the separator 120 that surrounds the through hole 121 (hereinafter, referred to as “through hole peripheral portion 122”) is a peripheral portion of the surface of one side (upper side in the drawing) in the vertical direction of the single cell 110. Facing. In the present embodiment, since the size of the air electrode 114 in the Z-axis direction is smaller than that of the electrolyte layer 112, the peripheral portion 122 of the through hole in the separator 120 is formed by the electrolyte layer 112 in the upper surface of the single cell 110. Facing the constructed surface. The separator 120 is joined to the single cell 110 (electrolyte layer 112) by a joining portion 124 arranged at the opposite portion thereof. The separator 120 separates the air chamber 166 facing the air pole 114 and the fuel chamber 176 facing the fuel pole 116. The joint portion 124 is formed of, for example, an Ag (silver) brazing material.

An air chamber side glass seal portion 125 containing glass is arranged on the air chamber 166 side with respect to the joint portion 124. The air chamber side glass seal portion 125 is formed so as to be in contact with both the surface of the through-hole peripheral portion 122 of the separator 120 and the surface of the single cell 110 (in the present embodiment, the electrolyte layer 112 constituting the single cell 110). Has been done. The air chamber side glass seal portion 125 effectively suppresses a gas leak (cross leak) between the air chamber 166 and the fuel chamber 176.

In the present embodiment, the joint portion 124 is formed so as to protrude from the region where the separator 120 and the single cell 110 face each other toward the air chamber 166 side, and the air chamber side glass seal portion 125 is formed in the joint portion 124. It is formed so as to be in contact with the protruding portion. That is, a part of the joint portion 124 is covered with the air chamber side glass seal portion 125. Further, in the present embodiment, the air chamber side glass seal portion 125 covers the surface of the separator 120 on the side opposite to the side facing the single cell 110 (upper side), and is joined to the air chamber side glass seal portion 125. The 124 and the separator 120 face each other in the Z-axis direction with the separator 120 in between.

The separator 120 includes a first flat portion 126 that includes a through hole peripheral portion 122 and is substantially parallel to a direction (that is, a plane direction) orthogonal to the Z-axis direction (vertical direction), and an outer peripheral side of the first flat portion 126. It is provided with a second flat portion 127 which is located at and substantially parallel to the plane direction. The positions of the first flat portion 126 and the second flat portion 127 in the Z-axis direction are substantially the same as each other.

The separator 120 further includes a connecting portion 128 that connects the end of the first flat portion 126 and the end of the second flat portion 127. In the present embodiment, the connecting portion 128 has a curved shape so as to project from the positions of the first flat portion 126 and the second flat portion 127 toward the fuel chamber 176 side (lower side). That is, the fuel chamber 176 side (lower side) of the connecting portion 128 is a convex portion, and the air chamber 166 side (upper side) of the connecting portion 128 is a concave portion. As described above, the connecting portion 128 includes a portion whose position in the Z-axis direction is different from that of the first flat portion 126 and the second flat portion 127. The connecting portion 128 is formed so as to surround the through hole 121 in the Z-axis direction. Further, the connecting portion 128 in the separator 120 is formed by, for example, press working. Since the connecting portion 128 of the separator 120 has the above-described configuration, it functions like a spring that easily expands and contracts in the surface direction. Therefore, the separator 120 of the present embodiment is more likely to be deformed in the plane direction at the position of the connecting portion 128 as compared with the configuration not provided with the connecting portion 128.

The air electrode side frame 130 is a frame-shaped member in which a substantially rectangular hole 131 penetrating in the vertical direction is formed near the center, and is formed of, for example, an insulator such as mica. The hole 131 of the air electrode side frame 130 constitutes an air chamber 166 facing the air electrode 114. The air electrode side frame 130 is in contact with the peripheral edge of the surface of the separator 120 opposite to the side facing the electrolyte layer 112 and the peripheral edge of the surface of the interconnector 150 facing the air electrode 114. .. That is, the air electrode side frame 130 is sandwiched between the separator 120 and the interconnector 150. Therefore, the air electrode side frame 130 realizes a seal (compression seal) of the air chamber 166. Further, the air electrode side frame 130 electrically insulates between the pair of interconnectors 150 included in the power generation unit 102. Further, in the air electrode side frame 130, the oxidant gas supply communication flow path 132 that communicates the oxidant gas introduction manifold 161 and the air chamber 166, and the oxidant that communicates the air chamber 166 and the oxidant gas discharge manifold 162. A gas discharge communication flow path 133 is formed.

As shown in FIG. 7, the fuel electrode side frame 140 is a frame-shaped member in which a substantially rectangular gas chamber hole 141 penetrating in the vertical direction is formed near the center, and is formed of, for example, metal. The fuel electrode side frame 140 is in contact with the peripheral edge of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral edge of the surface of the interconnector 150 facing the fuel electrode 116 (FIG. 4 and FIG. (See FIG. 5).

As shown in FIG. 7, the gas chamber hole 141 of the fuel electrode side frame 140 is a hole constituting the fuel chamber 176 facing the fuel electrode 116. The gas chamber hole 141 has a first inner surface IP1 and a second inner surface IP2 facing each other in the supply direction (Y-axis direction) of the fuel gas FG. Further, the fuel electrode side frame 140 has a fuel gas supply communication flow path 142 that communicates with the communication hole 108 constituting the fuel gas introduction manifold 171 and opens to the first inner surface IP1 of the gas chamber hole 141, and the fuel gas. A fuel gas discharge communication flow path 143 that communicates with the communication hole 108 constituting the discharge manifold 172 and opens to the second inner surface IP2 of the gas chamber hole 141 is formed.

The air pole side current collector 134 is arranged in the air chamber 166. The air electrode side current collector 134 is composed of a plurality of substantially square columnar current collector elements 135, and is formed of, for example, ferritic stainless steel. The air electrode side current collector 134 is in contact with the surface of the air electrode 114 opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 on the side facing the air electrode 114. However, as described above, since the power generation unit 102 located at the top of the fuel cell stack 100 does not have the upper interconnector 150, the air electrode side current collector 134 in the power generation unit 102 has an upper end plate. It is in contact with 104. Since the air electrode side current collector 134 has such a configuration, the air electrode 114 and the interconnector 150 (or the end plate 104) are electrically connected. The air electrode side current collector 134 may be covered with a conductive coat, and a conductive bonding layer for bonding the air electrode 114 and the air electrode side current collector 134 may be provided. It may be intervening. Further, the air electrode side current collector 134 may be configured as a member integrated with the interconnector 150.

The fuel electrode side current collector 144 is arranged in the fuel chamber 176. The fuel electrode side current collector 144 includes an interconnector facing portion 146, an electrode facing portion 145, and a connecting portion 147 connecting the electrode facing portion 145 and the interconnector facing portion 146. For example, nickel or nickel alloy. , Stainless steel, etc. The electrode facing portion 145 is in contact with the surface of the fuel pole 116 opposite to the side facing the electrolyte layer 112, and the interconnector facing portion 146 is on the surface of the interconnector 150 facing the fuel pole 116. Are in contact. However, as described above, since the power generation unit 102 located at the bottom of the fuel cell stack 100 does not have the lower interconnector 150, the interconnector facing portion 146 in the power generation unit 102 is the lower end plate. It is in contact with 106. Since the fuel pole side current collector 144 has such a configuration, the fuel pole 116 and the interconnector 150 (or the end plate 106) are electrically connected to each other. A spacer 149 formed of, for example, mica is arranged between the electrode facing portion 145 and the interconnector facing portion 146. Therefore, the fuel electrode side current collector 144 follows the deformation of the power generation unit 102 due to the temperature cycle and the reaction gas pressure fluctuation, and the fuel electrode 116 and the interconnector 150 (or the end plate 106) via the fuel electrode side current collector 144 follow. Good electrical connection with is maintained.

A-2. Operation of fuel cell stack 100:
As shown in FIGS. 2 and 4, the oxidant gas OG is supplied via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161. Then, the oxidant gas OG is supplied to the oxidant gas introduction manifold 161 through the holes of the branch portion 29 and the main body portion 28 of the gas passage member 27, and the oxidizer gas introduction manifold 161 oxidizes each power generation unit 102. It is supplied to the air chamber 166 via the agent gas supply communication flow path 132. Further, as shown in FIGS. 3, 5 and 7, the fuel gas is passed through a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. When the FG is supplied, the fuel gas FG is supplied to the fuel gas introduction manifold 171 through the holes of the branch portion 29 and the main body portion 28 of the gas passage member 27, and the fuel of each power generation unit 102 is supplied from the fuel gas introduction manifold 171. It is supplied to the fuel chamber 176 via the gas supply communication flow path 142.

When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, oxygen contained in the oxidant gas OG and hydrogen contained in the fuel gas FG in the single cell 110 are supplied. Power is generated by an electrochemical reaction with. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air pole 114 of the single cell 110 is electrically connected to one of the interconnectors 150 via the air pole side current collector 134, and the fuel pole 116 is via the fuel pole side current collector 144. It is electrically connected to the other interconnector 150. Further, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, the electric 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 electricity at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the fuel cell stack 100 is a heater (for example, until the high temperature can be maintained by the heat generated by the power generation after the start-up. (Not shown) may be heated.

As shown in FIGS. 2 and 4, the oxidant off-gas OOG discharged from the air chamber 166 of each power generation unit 102 is discharged to the oxidant gas discharge manifold 162 via the oxidant gas discharge communication flow path 133, and further. The fuel cell stack passes through the holes of the main body 28 and the branch 29 of the gas passage member 27 provided at the position of the oxidant gas discharge manifold 162, and via the gas pipe (not shown) connected to the branch 29. It is discharged to the outside of 100. Further, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generation unit 102 is discharged to the fuel gas discharge manifold 172 via the fuel gas discharge communication flow path 143 as shown in FIGS. 3, 5, and 7. Further, the fuel cell stack is passed through the holes of the main body 28 and the branch 29 of the gas passage member 27 provided at the position of the fuel gas discharge manifold 172, and via a gas pipe (not shown) connected to the branch 29. It is discharged to the outside of 100.

A-3. About the glass seal part 129 on the fuel chamber side:
Specifically, as shown in FIGS. 6 and 7, in the present embodiment, the separator 120 is a gas flow path of the fuel gas FG supplied from the fuel gas supply communication flow path 142 to the fuel electrode 116 (from FIG. 5). It has a fuel chamber side lower surface 119 facing the fuel gas FG flow in FIG. 7) (fuel chamber 176). The lower surface 119 on the fuel chamber side is a surface portion of the lower surface of the separator 120 located between the single cell 110 and the fuel electrode side frame 140, and is viewed in the Z-axis direction (axial direction of the through hole 121 of the separator 120). , A surface portion of an annular (rectangular annular) surrounding the entire circumference of the single cell 110. The fuel chamber side lower surface 119 is composed of a first fuel chamber side lower surface 119A, a pair of second fuel chamber side lower surfaces 119B, and a third fuel chamber side lower surface 119C (see FIG. 7). The first fuel chamber side lower surface 119A is a surface portion of the fuel chamber side lower surface 119 located on the upstream side of the gas flow path of the fuel gas FG with respect to the single cell 110. The pair of second fuel chamber side lower surfaces 119B is a pair of surface portions of the fuel chamber side lower surface 119 located on the side of the gas flow path of the fuel gas FG with respect to the single cell 110 in the Z-axis direction. is there. The third fuel chamber side lower surface 119C is a surface portion of the fuel chamber side lower surface 119 located on the downstream side of the gas flow path of the fuel gas FG with respect to the single cell 110. Further, the joint portion 124 has a fuel chamber side surface 123. As shown in FIG. 7, the joint portion 124 is formed so as to surround the entire circumference of the single cell 110 (through hole 121 of the separator 120) in the Z-axis direction. Therefore, the joint portion 124 has a fuel chamber side surface 123 that does not come into contact with either the separator 120 or the single cell 110 and faces the gas flow path (fuel chamber 176) side of the fuel gas FG. There is. That is, the fuel chamber side surface 123 is an annular (rectangular annular) surface located so as to surround the entire circumference of the single cell 110 (through hole 121 of the separator 120) in the Z-axis direction. The lower surface 119 on the fuel chamber side corresponds to the first surface in the claims, and the surface 123 on the fuel chamber side corresponds to the second surface in the claims.

Further, as shown in FIGS. 6 and 7, the fuel cell stack 100 in the present embodiment includes a glass seal portion 129 on the fuel chamber side. The fuel chamber side glass seal portion 129 is a dense body containing glass (crystallized glass), and the porosity of the fuel chamber side glass seal portion 129 is preferably 30% or less, preferably 15% or less. More preferred. The fuel chamber side glass seal portion 129 covers the fuel chamber side lower surface 119 of the separator 120 and is the first boundary B1 (see FIG. 6) which is a boundary between the fuel chamber side lower surface 119 and the fuel chamber side surface 123 of the joint portion 124. ) Has been reached. In the present embodiment, the fuel chamber side glass seal portion 129 is formed in an annular shape (rectangular annular shape) so as to surround the entire circumference of the single cell 110 (through hole 121 of the separator 120) in the Z-axis direction. Therefore, the fuel chamber side glass seal portion 129 covers the fuel chamber side lower surface 119 of the separator 120 over the entire circumference of the fuel chamber side glass seal portion 129, and reaches the first boundary B1 (see FIG. 7). ). The glass seal portion 129 on the fuel chamber side corresponds to the P diffusion suppressing portion within the scope of claims.

Further, as shown in FIG. 6, the fuel chamber side glass seal portion 129 further covers the fuel chamber side surface 123 of the joint portion 124 over the entire circumference of the fuel chamber side glass seal portion 129, and also covers the joint portion 124. It reaches the second boundary B2, which is the boundary with the electrolyte layer 112. Further, in the present embodiment, the joint portion 124 is formed so as to protrude from the region where the separator 120 and the single cell 110 face each other in the Z-axis direction toward the fuel chamber 176 side, and the fuel chamber side glass seal portion 129 is formed. , The joint portion 124 is formed so as to cover the entire surface of the protruding portion 124A. The protruding portion 124A of the joint portion 124 is sandwiched between the fuel chamber side glass seal portion 129 and the separator 120 in the Z-axis direction. Since the joining portion 124 includes the protruding portion 124A, it is possible to suppress the occurrence of local wax accumulation, for example, when brazing and joining the single cell 110 and the separator 120. That is, at the time of brazing and joining, among the brazing materials melted by heating, the excess brazing material protruding from between the single cell 110 and the separator 120 is along the brazing material layer formed so as to protrude in advance. leak. Therefore, at the time of brazing and joining, the wax material that protrudes is locally accumulated and it is difficult to form a wax pool. As a result, it is possible to suppress the occurrence of cell cracking due to the occurrence of local wax accumulation (see, for example, Japanese Patent Application Laid-Open No. 2015-135807). In FIG. 6, the fuel chamber side glass seal portion 129 is in contact with the entire surface of the protruding portion 124A, but may be separated from at least a part of the surface of the protruding portion 124A.

Further, as shown in FIGS. 6 and 7, the fuel chamber side glass seal portion 129 further covers the side surface 116A of the fuel electrode 116 over the entire circumference of the fuel chamber side glass seal portion 129.

Further, as described above, the fuel chamber side glass seal portion 129 covers the fuel chamber side lower surface 119 of the separator 120, but is separated from the connecting portion 128 of the separator 120. That is, the fuel chamber side glass seal portion 129 covers only the lower surface portion corresponding to the first flat portion 126 of the fuel chamber side lower surface 119 of the separator 120, and the boundary between the first flat portion 126 and the connecting portion 128. It has not reached the third boundary B3. The fuel chamber side glass seal portion 129 and the connecting portion 128 (third boundary B3) are preferably separated by 0.1 mm or more.

A-4. Effect of this embodiment:
As described above, the fuel cell stack 100 of the present embodiment includes a plurality of air poles 114, fuel poles 116, and an electrolyte layer 112 arranged between the air poles 114 and the fuel poles 116, respectively. It includes a single cell 110. Further, the fuel cell stack 100 includes a separator 120. A through hole 121 is formed in the separator 120, and a through hole peripheral portion 122 of the separator 120 is joined to the surface of the single cell 110 to partition the air chamber 166 and the fuel chamber 176. Further, the fuel cell stack 100 includes 124. The joining portion 124 is arranged between the separator 120 and the single cell 110, and joins the separator 120 and the single cell 110. Here, the separator 120 is made of, for example, stainless steel. Stainless steel generally contains P (for example, about 0.02 w%) as an impurity. Therefore, after the operation of the fuel cell stack 100 is started, P diffused from the lower surface 119 on the fuel chamber side of the separator 120 is carried to the fuel gas FG supplied to the fuel pole 116 and moves to the vicinity of the fuel pole 116, and the fuel pole 116 There is a risk of adhering (poisoning) to the reaction field in the fuel cell stack 100 and degrading the performance of the fuel cell stack 100.

Conventionally, since the amount of P contained in the separator 120 is generally very small, it has been considered that the adhesion of P to the fuel electrode 116 has almost no effect on the performance of the fuel cell stack 100. Therefore, in the conventional fuel cell stack, the entire lower surface 119 on the fuel chamber side of the separator 120 is exposed to the fuel chamber 176. However, under circumstances such as the demand for even higher performance of the fuel cell stack 100, the inventor of the present application has conducted extensive research, and as a result, the adhesion of P to the fuel electrode 116 affects the performance of the fuel cell stack 100. In particular, it was newly found that when the operating time of the fuel cell stack 100 is prolonged (for example, 5000 hours or more), the effect becomes remarkable.

On the other hand, as described above, the fuel cell stack 100 in the present embodiment includes a glass seal portion 129 on the fuel chamber side in order to suppress the diffusion of P from the separator 120 to the fuel electrode 116 side. That is, the fuel chamber side glass seal portion 129 covers the fuel chamber side lower surface 119 of the separator 120 and is the first boundary B1 which is the boundary between the fuel chamber side lower surface 119 and the fuel chamber side surface 123 of the joint portion 124 (FIG. 6) has been reached. Therefore, it is suppressed that P diffused from the vicinity of the single cell 110 in the lower surface 119 on the fuel chamber side of the separator 120 moves to the vicinity of the fuel electrode 116. As a result, according to the present embodiment, the fuel cell stack 100 is caused by the adhesion of P diffused from the separator 120, as compared with the configuration in which the entire lower surface 119 on the fuel chamber side of the separator 120 is exposed to the fuel chamber 176. Performance degradation can be suppressed.

Further, after the operation of the fuel cell stack 100 is started, the lower surface 119A on the fuel chamber side of the separator 120 is located on the upstream side of the gas flow path of the fuel gas FG with respect to the single cell 110. A particularly large amount of diffused P is carried by the fuel gas FG supplied to the fuel electrode 116, moves to the vicinity of the fuel electrode 116, and easily adheres (poisons) to the reaction field at the fuel electrode 116. On the other hand, in the present embodiment, the fuel chamber side glass seal portion 129 covers the first fuel chamber side lower surface 119A and the first fuel chamber side lower surface 119A and the joint portion 124 on the first fuel chamber side. It reaches the boundary with the surface 123A (first boundary B1). Therefore, it is possible to effectively suppress the deterioration of the performance of the fuel cell stack 100 due to the adhesion of P to the fuel electrode 116.

Further, among the fuel chamber side lower surface 119 of the separator 120, not only the first fuel chamber side lower surface 119A, but also a pair of fuel gas FGs located on the side of the gas flow path of the fuel gas FG with respect to the single cell 110 in the Z-axis direction. P diffused from the lower surface 119B on the second fuel chamber side is also carried by the fuel gas FG supplied to the fuel electrode 116, moves to the vicinity of the downstream side of the fuel electrode 116, adheres to the reaction field at the fuel electrode 116, and fuels. The performance of the battery stack 100 may deteriorate. On the other hand, in the present embodiment, the fuel chamber side glass seal portion 129 covers the second fuel chamber side lower surface 119B and the second fuel chamber side lower surface 119B and the joint portion 124 on the second fuel chamber side. It reaches the boundary with the surface 123B (first boundary B1). Therefore, it is possible to effectively suppress the deterioration of the performance of the fuel cell stack 100 due to the adhesion of P to the fuel electrode 116.

Further, among the fuel chamber side lower surface 119 of the separator 120, P diffused from the third fuel chamber side lower surface 119C located on the downstream side of the gas flow path of the fuel gas FG with respect to the single cell 110 is, for example, the fuel chamber 176. There is a risk that the performance of the fuel cell stack 100 will deteriorate due to being carried to the fuel gas FG that stays near the periphery of the fuel gas discharge communication flow path 143 and adheres to the reaction field at the fuel electrode 116. On the other hand, in the present embodiment, the fuel chamber side glass seal portion 129 covers the third fuel chamber side lower surface 119C and the third fuel chamber side lower surface 119C and the joint portion 124 on the third fuel chamber side. It reaches the boundary with the surface 123C (first boundary B1). Therefore, the performance deterioration of the fuel cell stack 100 due to the adhesion of P to the fuel electrode 116 can be effectively suppressed.

Further, P contained in the separator 120 may pass through the joint portion 124 and move to the vicinity of the fuel electrode 116. On the other hand, in the present embodiment, the fuel chamber side glass seal portion 129 further covers the fuel chamber side surface 123 of the joint portion 124 and is a second boundary which is a boundary between the joint portion 124 and the electrolyte layer 112. It has reached B2. Therefore, not only the P diffused from the lower surface 119 on the fuel chamber side of the separator 120 to the fuel chamber 176 moves to the vicinity of the fuel electrode 116, but also the P passing through the joint portion 124 from the separator 120 moves to the vicinity of the fuel electrode 116. Is suppressed. As a result, according to the present embodiment, the fuel cell stack 100 is caused by the adhesion of P diffused from the separator 120, as compared with the configuration in which the fuel chamber side surface 123 of the joint portion 124 is not covered with the P diffusion suppressing portion. Performance degradation can be suppressed more effectively. The electrolyte layer 112 is denser than the joint portion 124, and P diffused from the separator 120 does not easily pass through the electrolyte layer 112. Therefore, P from the separator 120 especially passes through the protruding portion 124A at the joint portion 124, passes through the fuel chamber 176, and moves to the vicinity of the fuel pole 116. Therefore, if the fuel cell side glass seal portion 129 is formed so as to cover the entire protruding portion 124A as in the present embodiment, the performance of the fuel cell stack 100 due to the adhesion of P diffused from the separator 120 The decrease can be suppressed more effectively.

Further, in the present embodiment, the fuel chamber side glass seal portion 129 further covers the side surface 116A of the fuel electrode 116. Therefore, it is suppressed that P diffused from the separator 120 flows into the reaction field of the fuel electrode 116 through the side surface 116A of the fuel electrode 116 and adheres to the reaction field. As a result, according to the present embodiment, the performance deterioration of the fuel cell stack 100 due to the adhesion of P diffused from the separator 120 is more effective than the configuration in which the side surface 116A of the fuel electrode 116 is exposed to the fuel chamber 176. Can be suppressed.

Further, in the present embodiment, the fuel chamber side glass seal portion 129 covers the fuel chamber side lower surface 119 of the separator 120, but is separated from the connecting portion 128 of the separator 120. Compared with the configuration in which the fuel chamber side glass seal portion 129 is in contact with the connecting portion 128 of the separator 120, it is possible to suppress the deterioration of the stress relaxation function of the separator 120 due to the presence of the fuel chamber side glass seal portion 129. be able to.

A-5. Performance evaluation:
Samples of a plurality of fuel cell stacks 100 having different characteristics were prepared, and performance evaluation was performed using the samples. FIG. 8 is an explanatory diagram showing the performance evaluation result.

A-5-1. For each sample:
As shown in FIG. 8, six samples (samples 11 to 6) of the fuel cell stack were used for this performance evaluation. Each sample differs from each other in at least one of the presence / absence of a seal portion 129 (P diffusion suppressing portion) covering the fuel chamber side lower surface 119 of the separator 120, the range covered by the seal portion 129, and the porosity of the seal portion 129. Specifically, the sample 1 does not have a seal portion 129 with respect to the above-mentioned fuel cell stack 100, and the entire lower surface 119 on the fuel chamber side of the separator 120 is exposed to the fuel chamber 176. different. In sample 2, the boundary between the point where the material for forming the seal portion 129 is ceramic felt and the lower surface 119 on the fuel chamber side and the surface 123 on the fuel chamber side of the joint portion 124 with respect to the above-mentioned fuel cell stack 100. The difference is that the side surface 112A of the electrolyte layer 112 is not covered by either the seal portion 129 or the joint portion 124 and is exposed to the fuel chamber 176 while reaching the first boundary B1. .. Sample 3 is common to the fuel cell stack 100 described above in that the material for forming the seal portion 129 is crystallized glass. However, the seal portion 129 reaches the first boundary B1 and the electrolyte layer is formed. The difference is that the side surface 112A of the 112 is not covered by either the seal portion 129 or the joint portion 124 and is exposed to the fuel chamber 176. Sample 4 is common to the above-mentioned fuel cell stack 100 in that the material for forming the seal portion 129 is crystallized glass, but the seal portion 129 reaches the first boundary B1 and the electrolyte layer. The difference is that the side surface 112A of the 112 is covered by the seal portion 129 instead of the joint portion 124. Samples 5 and 6 have substantially the same configuration as the fuel cell stack 100 described above. However, the separation distance between the seal portion 129 (fuel chamber side glass seal portion 129) in sample 6 and the connection portion 128 in the separator 120 is shorter than the separation distance between the seal portion 129 in sample 5 and the connection portion 128 in the separator 120. The porosity of the seal portion 129 in sample 2 is 21%, and the porosity of the seal portion 129 in samples 2 to 6 is 5.4%.

The porosity of each sample in the seal portion 129 is specified by the following method. An SEM image (for example, 1000 times) by FIB-SEM is obtained for the cross section of the seal portion 129, and a plurality of parallel lines are drawn at predetermined intervals (for example, 1 μm to 5 μm intervals) for the obtained image. The length of the portion corresponding to the pore on each straight line is measured, and the ratio of the total length of the portion corresponding to the pore to the total length of the straight line is defined as the porosity on the line. By calculating the average value of the porosity in the plurality of straight lines drawn in the obtained image, the porosity in the seal portion 129 is specified. The porosity of the seal portion 129 formed of a material having a relatively high porosity (for example, ceramic felt or mica) is specified by the following method. For the cross section of the seal portion 129, an SEM image (for example, 1000 times) by FIB-SEM is obtained, the obtained image is binarized, and the seal is obtained from the area ratio of the black portion and the white portion in the binarized image. The porosity in part 129 is specified.

Further, for each sample, the thickness of the electrolyte layer 112 is 3 μm or more and 9 μm or less, the thickness of the fuel electrode 116 is 300 μm or more and 1000 μm or less, and the thickness of the separator 120 is 50 μm or more and 200 μm or less. Is. Further, the thickness of the protruding portion 124A of the joint portion 124 is 10 μm or more and 200 μm or less, the protruding length of the protruding portion 124A is 10 μm or more and 300 μm or less, and the thickness of the fuel chamber side glass seal portion 129 is , 200 μm or more.

A-5-2. Evaluation items and evaluation methods:
In this performance evaluation, two items, the amount of P adhered to the fuel electrode 116 (ppm) and the deterioration rate% of the fuel cell stack, were evaluated. Specifically, for each sample, the oxidant gas OG is supplied to the air electrode 114 and the fuel gas to the fuel electrode 116 under thermal acceleration conditions equivalent to 12 years at about 750 ° C. (for example, at 850 ° C. for 10,000 hours). Perform a test to supply FG. The amount of P adhering to the fuel electrode 116 was measured using D-SIMS analysis (Dynamic-Spechondary Ion Mass Spectrometry Analysis). At the start of the test, the output voltage of the fuel cell stack when the current density is 0.55 (A / cm ² ) is measured and used as the initial voltage, and at the end of the test, the density is 0.55 (A / cm ² ). The output voltage of the fuel cell stack at this time was measured and used as the end voltage, and the ratio of the difference between the initial voltage and the end voltage force to the initial voltage was taken as the deterioration rate (%) of the fuel cell stack.

If the deterioration rate of the fuel cell stack is 10% or more, it is judged as "defective (x)", and if the deterioration rate of the fuel cell stack is higher than 2% and less than 10%, it is "good (good)". When the deterioration rate of the fuel cell stack was 2% or less, it was judged as “excellent (⊚)”.

A-5-3. Evaluation results:
As shown in FIG. 8, in sample 1 in which the entire lower surface 119 on the fuel chamber side of the separator 120 is exposed in the fuel chamber 176, the deterioration rate of the fuel cell stack was 10%, so that it was described as “defective (x)”. It was judged. The amount of P adhered to the fuel electrode 116 was 900 ppm, which was relatively high. From these facts, when the lower surface 119 on the fuel chamber side of the separator 120 is exposed in the fuel chamber 176, P diffused from the separator 120 becomes the fuel gas FG supplied to the fuel electrode 116 after the operation of the fuel cell stack is started. It can be seen that the fuel cell stack is deteriorated by being carried and moving to the vicinity of the fuel electrode 116 and adhering to the reaction field at the fuel electrode 116.

In Sample 2, in which the lower surface 119 of the separator 120 on the fuel chamber side was covered with the seal portion made of ceramic felt, the deterioration rate of the fuel cell stack was 8%, so that the sample 2 was judged to be “good (◯)”. The amount of P adhered to the fuel electrode 116 was 700 ppm, which was lower than the amount of P adhered to the fuel electrode 116 of sample 1. From these facts, by covering the lower surface 119 of the separator 120 on the fuel chamber side with the seal portion, the amount of P that diffuses from the separator 120 and adheres to the fuel electrode 116 can be reduced, and the deterioration of the fuel cell stack progresses. It can be seen that can be suppressed.

Compared to sample 2, in sample 3 in which the lower surface 119 on the fuel chamber side of the separator 120 was covered with a seal made of crystallized glass having a lower porosity than ramic felt, the deterioration rate of the fuel cell stack was 4%. It was judged as "good (○)". The amount of P adhered to the fuel electrode 116 was 150 ppm, which was lower than the amount of P adhered to the fuel electrode 116 of sample 2. Further, also in sample 4, since the deterioration rate of the fuel cell stack was 5%, it was judged as “good (◯)”, the amount of P adhered to the fuel electrode 116 was 170 ppm, and the P in the fuel electrode 116 of sample 2 was P. It was low compared to the amount of adhesion. From these facts, the higher the porosity of the seal portion, the more the amount of P that diffuses from the separator 120 and adheres to the fuel electrode 116 can be reduced, and the progress of deterioration of the fuel cell stack can be suppressed more effectively. I know I can do it.

In Sample 5, in which the side surface 116A of the fuel electrode 116 was covered with the seal portion with respect to Samples 3 and 4, the deterioration rate of the fuel cell stack was 2%, so that it was judged to be “excellent (⊚)”. The amount of P adhered to the fuel pole 116 was 60 ppm, which was lower than the amount of P adhered to the fuel poles 116 of Samples 3 and 4. From these facts, by covering the side surface 116A of the fuel pole 116 with the seal portion, the amount of P that diffuses from the separator 120 and adheres to the fuel pole 116 can be reduced, and the deterioration of the fuel cell stack can be prevented. It can be seen that it can be suppressed more effectively.

In sample 6, which is shorter than the separation distance between the seal portion and the connecting portion 128 in the separator 120 with respect to sample 5, the deterioration rate of the fuel cell stack was 1%, so that the sample 6 was judged to be “excellent (⊚)”. The amount of P adhered to the fuel electrode 116 was 50 ppm, which was lower than the amount of P adhered to the fuel electrode 116 of sample 5. From these facts, the shorter the separation distance between the seal portion and the connecting portion 128 in the separator 120, the more the amount of P diffused from the separator 120 and adhered to the fuel electrode 116 can be reduced, and the fuel cell stack deteriorates. It can be seen that the progress of the fuel can be suppressed more effectively.

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

The configuration of the single cell 110, the power generation unit 102, or the fuel cell stack 100 in the above embodiment is merely an example and can be variously modified. For example, in the above embodiment, the fuel cell stack 100 includes the air chamber side glass seal portion 125, but the fuel cell stack 100 may not include the air chamber side glass seal portion 125. Further, in the above embodiment, the separator 120 includes a connecting portion 128 including a portion whose position in the Z-axis direction is different from that of the first flat portion 126 and the second flat portion 127, but the separator 120 is the connecting portion. 128 may not be provided. Further, the connecting portion 128 in the separator 120 may have a curved shape so as to project from the positions of the first flat portion 126 and the second flat portion 127 toward the air chamber 166 side (upper side).

Further, in the above embodiment, the number of single cells 110 included in the fuel cell stack 100 is only an example, and the number of single cells 110 is appropriately determined according to the output voltage and the like required for the fuel cell stack 100. Further, the material constituting each member in the above embodiment is merely an example, and each member may be composed of another material. For example, the joint portion 124 may be formed of a material that does not contain Ag.

Further, the fuel chamber side glass seal portion 129 in the above embodiment is merely an example and can be variously deformed. For example, in the above embodiment, the fuel chamber side glass seal portion 129 is formed of crystallized glass, but may be formed of, for example, YSZ, ceramic felt (for example, alumina felt) or mica. Further, in the above embodiment, the fuel chamber side glass seal portion 129 is exemplified as the P diffusion suppressing portion, but it may be formed of a material other than glass. In short, the P diffusion suppressing unit may have a structure having a density sufficient to suppress the diffusion of P contained in the separator 120 into the fuel chamber 176. Further, it is preferable that the P content (including 0%) is formed of a material having a P content lower than that of the separator 120. The porosity of the P diffusion suppressing portion is preferably 30% or less, and more preferably 15% or less.

Further, in the above embodiment, the side surface of the electrolyte layer 112 is covered with the protruding portion 124A of the joint portion 124, but the side surface of the electrolyte layer 112 may not be covered with the joint portion 124. (See Samples 2-4 in FIG. 8). Further, in the above embodiment, the joint portion 124 may have a configuration that does not have the protruding portion 124A. Further, in the above embodiment, the fuel chamber side glass seal portion 129 does not cover the fuel chamber side surface 123 of the joint portion 124 (see samples 2 and 3 in FIG. 8), and the fuel chamber side glass seal portion 129 is the joint portion. The configuration may be such that only a part of the fuel chamber side surface 123 of 124 is covered, or the fuel chamber side glass seal portion 129 does not cover the side surface 116A of the fuel electrode 116 (Samples 2 to 4 in FIG. 8). reference). Further, in the above embodiment, the fuel chamber side glass seal portion 129 may have a configuration that reaches the third boundary B3, which is the boundary between the first flat portion 126 and the connecting portion 128.

Further, in the above embodiment, the fuel chamber side glass seal portion 129 is configured to cover only a part of the fuel chamber side lower surface 119 of the separator 120 in the circumferential direction of the axis (Z axis) of the through hole 121. May be good. For example, the fuel chamber side glass seal portion 129 is any one of the first fuel chamber side lower surface 119A, the second fuel chamber side lower surface 119B, and the third fuel chamber side lower surface 119C among the fuel chamber side lower surfaces 119. It may be configured to cover only one or only two. Further, at least two of a seal portion covering the first fuel chamber side lower surface 119A, a seal portion covering the second fuel chamber side lower surface 119B, and a seal portion covering the third fuel chamber side lower surface 119C are formed. At least one of the materials and porosity may be different.

In the above embodiment, for all the separators 120 joined to each of the plurality of single cells 110 provided with the fuel cell stack 100, the fuel chamber side lower surface 119 of the separator 120 is covered with the fuel chamber side glass seal portion 129. However, with respect to only a part of the separator 120 joined to each of the plurality of single cells 110, the fuel chamber side lower surface 119 of the separator 120 is covered with the fuel chamber side glass seal portion 129. You may.

Further, in the above embodiment, the fuel cell stack 100 is configured to include a plurality of flat plate type single cells 110, but the present invention also includes a fuel cell stack including a plurality of other types (for example, cylindrical) single cells. It is applicable as well.

Further, in the above embodiment, the SOFC that generates power by utilizing the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidizing agent gas is targeted, but the present invention comprises an electrolysis reaction of water. It is also applicable to an electrolytic single cell, which is a constituent unit of a solid oxide fuel cell (SOEC) that uses it to generate hydrogen, and an electrolytic cell stack including a plurality of electrolytic single cells. The configuration of the electrolytic cell stack is not described in detail here because it is known, for example, as described in Japanese Patent Application Laid-Open No. 2016-81813, but is generally the same as the fuel cell stack 100 in the above-described embodiment. It is the composition of. That is, the fuel cell stack 100 in the above-described embodiment may be read as an electrolytic cell stack, the power generation unit 102 may be read as an electrolytic cell unit, and the single cell 110 may be read as an electrolytic single cell. However, during the operation of the electrolytic cell stack, a voltage is applied between both electrodes so that the air electrode 114 is positive (anode) and the fuel electrode 116 is negative (cathode), and the voltage is applied through the communication hole 108. Water vapor as a raw material gas is supplied. As a result, an electrolysis reaction of water occurs in each electrolytic cell unit, hydrogen gas is generated in the fuel chamber 176, and hydrogen is taken out to the outside of the electrolytic cell stack through the communication hole 108. By applying the present invention to the electrolytic cell unit and the electrolytic cell stack having such a configuration, it is possible to suppress the deterioration of the performance of the electrochemical reaction cell stack due to the adhesion of P diffused from the separator.

22: Bolt 24: Nut 26: Insulation sheet 27: Gas passage member 28: Main body 29: Branch 100: Fuel cell stack 102: Power generation unit 104, 106: End plate 108: Communication hole 110: Single cell 112: Electrolyte layer 112A: Side surface 114: Air pole 116: Fuel pole 116A: Side surface 119: Fuel chamber side lower surface 119A: First fuel chamber side lower surface 119B: Second fuel chamber side lower surface 119C: Third fuel chamber side lower surface 120: Separator 121: Through hole 122: Through hole peripheral part 123: Fuel chamber side surface 123A: First fuel chamber side surface 123B: Second fuel chamber side surface 123C: Third fuel chamber side surface 124: Joint portion 124A: Overhang Part 125: Air chamber side glass seal part 126: First flat part 127: Second flat part 128: Connecting part 129: Fuel chamber side glass seal part 130: Air electrode side frame 131: Hole 132: Oxidating agent gas supply Communication flow path 133: Oxidizing agent gas discharge communication flow path 134: Air pole side current collector 135: Current collector element 140: Fuel pole side frame 141: Gas chamber hole 142: Fuel gas supply communication flow path 143: Fuel gas Discharge communication flow path 144: Fuel pole side current collector 145: Electrode facing part 146: Interconnector facing part 147: Connecting part 149: Spacer 150: Interconnector 161: Oxidizing agent gas introduction manifold 162: Oxidizing agent gas discharging manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber B1: First boundary B2: Second boundary B3: Third boundary FG: Fuel gas FOG: Fuel off gas IP1: First inner surface IP2: Second inner surface OG: Oxidizing agent gas OOG: Oxidizing agent off gas

Claims (4)

A plurality of electrochemical reaction single cells including an air electrode, a fuel electrode, and an electrolyte layer arranged between the air electrode and the fuel electrode, respectively.
A separator is formed, and the peripheral portion of the through hole surrounding the through hole is joined to the surface of the electrochemical reaction single cell to separate the air chamber facing the air electrode and the fuel chamber facing the fuel electrode. When,
In an electrochemical reaction cell stack including a joint portion for joining the peripheral portion of the through hole of the separator and the surface of the electrochemical reaction single cell.
The separator contains P (phosphorus) and has a first surface facing the gas flow path of the gas supplied to the fuel electrode.
The joint has a second surface facing the gas flow path.
Further, the P diffusion suppressing portion covers at least a part of the first surface of the separator and at least reaches the boundary between the first surface of the separator and the second surface of the joint. ,
It is characterized by an electrochemical reaction cell stack. In the electrochemical reaction cell stack according to claim 1,
The P-diffusion inhibitor further covers at least a part of the second surface of the joint and reaches at least the boundary between the second surface of the joint and the side surface of the electrolyte layer.
It is characterized by an electrochemical reaction cell stack. In the electrochemical reaction cell stack according to claim 2.
The P diffusion suppressing portion further covers at least a part of the side surface of the fuel electrode.
It is characterized by an electrochemical reaction cell stack. In the electrochemical reaction cell stack according to any one of claims 1 to 3.
The separator is
A first flat portion including a peripheral portion of the through hole and substantially parallel to a second direction orthogonal to the first direction which is the axial direction of the through hole.
A second flat portion substantially parallel to the second direction,
A connecting portion that includes a portion whose position in the first direction is different from the first flat portion and the second flat portion, and connects the first flat portion and the second flat portion.
With
The P diffusion suppressing portion is separated from the connecting portion.
It is characterized by an electrochemical reaction cell stack.

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