JP6774230B2 - Current collector-electrochemical reaction single cell complex and electrochemical reaction cell stack - Google Patents

Description

The techniques disclosed herein relate to current collector-electrochemical reaction single cell complexes.

A solid oxide fuel cell (hereinafter referred to as "SOFC") having an electrolyte layer containing a solid oxide is known as one of the types of fuel cells that generate electricity by utilizing an electrochemical reaction between hydrogen and oxygen. Has been done. A fuel cell single cell (hereinafter, simply referred to as “single cell”), which is a constituent unit of an SOFC, includes an electrolyte layer, and an air electrode and a fuel electrode that face each other in a predetermined direction with the electrolyte layer in between. The air electrode is formed of, for example, a perovskite-type oxide such as LSCF (lanternstrontium cobalt iron oxide). The fuel electrode is formed to contain a conductive metal such as Ni (nickel) or a Ni-based alloy.

The SOFC is provided with a current collecting member that collects electrical energy obtained by a power generation reaction in a single cell. For example, a fuel electrode side current collector is arranged on the fuel electrode side of the single cell. The fuel electrode side current collecting member is configured to have a plurality of protrusions in contact with the surface of the fuel electrode in order to exert a current collecting function without obstructing the supply of fuel gas to the inside of the fuel electrode (for example,. See Patent Document 1). In this specification, a structure composed of a single cell and a fuel electrode side current collecting member is referred to as a current collecting member-fuel cell single cell composite.

Japanese Unexamined Patent Publication No. 2014-216297

In the conventional current collector-fuel cell single cell composite, the convex portion of the fuel electrode side current collector member may be peeled off from the surface of the fuel electrode, and there is room for improvement in terms of reliability.

It should be noted that such a problem is caused by the electrolytic single cell and the fuel electrode side collection, which are the constituent units of a solid oxide fuel cell (hereinafter referred to as “SOEC”) that generates hydrogen by utilizing the electrolysis reaction of water. It is also a common problem in the current collecting member-electrolyzed single cell composite composed of the electric member. In this specification, the current collector-fuel cell single cell composite and the current collector-electrolytic single cell composite are collectively referred to as a current collector-electrochemical reaction single cell composite. Further, such a problem is common not only to SOFC and SOEC but also to a current collector-electrochemical reaction single cell composite composed of another type of electrochemical reaction single cell and a fuel electrode side current collector. It is a problem of.

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 current collector-electrochemical reaction single cell composite disclosed in the present specification includes an air electrode and a fuel electrode containing a conductive metal that face each other in the first direction with the electrolyte layer and the electrolyte layer sandwiched between them. A current collector-electricity comprising an electrochemical reaction single cell including the above, and a current collector member arranged on the fuel electrode side of the electrochemical reaction single cell and having a plurality of protrusions in contact with the surface of the fuel electrode. In the chemical reaction single cell composite, the fuel electrode is a first portion including the surface in the convex overlapping region overlapping the convex portion in the first direction, and is the first direction. The content of conductive metal (vol%) from the second portion, which is located next to the first portion in the second direction orthogonal to the first portion and does not overlap with the convex portion in the first direction view. The first is high, and the thickness in the first direction is 25% or less of the thickness from the surface of the fuel electrode to the position where the pore ratio is first below the pore ratio of the first portion. Has a part. According to this current collector-electrochemical reaction single cell composite, the contact area between the conductive metal contained in the fuel electrode and the convex portion of the current collector member near the interface between the fuel electrode and the convex portion of the current collector member. As a result, the fuel electrode and the convex portion of the current collector member are firmly joined, and the occurrence of peeling between the fuel electrode and the convex portion of the current collector member can be suppressed. Further, according to this current collector-electrochemical reaction single cell composite, most of the parts other than the first part in the fuel electrode have a high porosity, so that the gas diffusivity in the fuel electrode is lowered. It can be suppressed.

(2) In the current collector-electrochemical reaction single cell composite, the fuel electrode contains oxide ion conductive ceramic particles, and the first portion has a porosity of the conductive metal of 30 (vol). %) Or more, and the content of the oxide ion conductive ceramic particles is 30 (vol%) or more, and in the second portion, the content of the oxide ion conductive ceramic particles is 30 (%) or more. It may be configured such that the porosity is 30 (vol%) or more and the porosity is 30 (vol%) or more. According to this current collector-electrochemical reaction single cell composite, the strength of the fuel electrode is maintained by keeping the content of oxide ion conductive ceramic particles in the first portion and the second portion of the fuel electrode high to some extent. By keeping the content of the conductive metal in the first portion of the fuel electrode high to some extent, it is possible to suppress the occurrence of peeling between the fuel electrode and the convex portion of the current collecting member. By keeping the porosity of the second portion of the fuel electrode high to some extent, it is possible to suppress a decrease in gas diffusivity at the fuel electrode.

(3) In the current collector-electrochemical reaction single cell composite, the conductive metal and the current collector member in the first portion may be configured to contain the same metal element. According to this current collector-electrochemical reaction single cell composite, the bondability between the first portion of the fuel electrode and the current collector member can be improved, and the bond between the fuel electrode and the convex portion of the current collector member can be improved. The occurrence of peeling can be effectively suppressed.

(4) In the current collector-electrochemical reaction single cell composite, the current collector member includes a current collector main body that forms a part of each of the convex portions, and the surface of the current collector main body and the fuel electrode. The conductive metal and the bonding layer in the first portion are the same, including a bonding layer that is interposed between the two and constitutes a portion of each of the convex portions that is in contact with the surface of the fuel electrode. The configuration may include a metal element. According to this current collector-electrochemical reaction single cell composite, the bondability between the first portion of the fuel electrode and the junction layer can be improved, and the separation between the fuel electrode and the convex portion of the current collector member can be improved. Can be effectively suppressed.

The technique disclosed in the present specification can be realized in various forms, for example, a current collector-electrochemical reaction single cell complex (current collector-fuel cell single cell complex or collection). (Electrical member-electrolytic single cell complex), current collector-electrochemical reaction single cell complex, electrochemical reaction unit (fuel cell power generation unit or electrolytic cell unit), multiple current collector-electrochemical reaction single cell or It can be realized in the form of an electrochemical reaction cell stack (fuel cell stack or electrolytic cell stack) including an electrochemical reaction unit, 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 1st 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 shows the detailed structure of the fuel electrode 116. It is explanatory drawing which shows the 1st performance evaluation result. It is explanatory drawing which shows the 2nd performance evaluation result. It is explanatory drawing which shows the 3rd performance evaluation result. It is explanatory drawing which shows the 4th performance evaluation result. It is explanatory drawing which shows the method of specifying the thickness Tx of the 1st part PA1.

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 in the present embodiment, and FIG. 2 is an explanatory view showing an XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II of FIG. FIG. 3 is an explanatory view showing a YZ cross-sectional configuration of the fuel cell stack 100 at the position III-III of FIG. 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.

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, 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. The arrangement direction (vertical direction) corresponds to the first direction in the claims.

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 in the vertical direction. , 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 direction. 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, for example, air is used as the oxidant gas OG.

Further, as shown in FIGS. 1 and 3, the vicinity of the midpoint of one side (the side on the positive direction 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 direction. 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.

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 pole side frame 130, the fuel pole side frame 140, and the interconnector 150 in the Z direction.

The interconnector 150 is a substantially rectangular flat plate-shaped conductive member larger than the single cell 110 in the Z direction, and is formed 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 fuel pole support type single cell in which the fuel pole 116 supports the electrolyte layer 112 and the air pole 114.

The electrolyte layer 112 is a substantially rectangular flat plate-shaped member, for example, YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), GDC (gadolinium-doped ceria), perovskite-type oxide. It is formed of solid oxides such as. The air electrode 114 is a substantially rectangular flat plate-shaped member, and is formed of, for example, a perovskite-type oxide (for example, LSCF (lanternstrontium cobalt iron oxide), LSM (lanternstrontium manganese oxide), LNF (lantern nickel iron)). Has been done. The fuel electrode 116 is a substantially rectangular flat plate-shaped member, and is formed of, for example, Ni (nickel), a cermet composed of Ni and ceramic particles, a Ni-based alloy, or the like. The configuration of the fuel electrode 116 will be described in detail later. As described above, the single cell 110 (power generation unit 102) of the present embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte.

The separator 120 is a frame-shaped member in which a substantially rectangular hole 121 penetrating in the vertical direction is formed near the center, and is made of metal, for example. The peripheral portion of the hole 121 in the separator 120 faces the peripheral edge of the surface of the electrolyte layer 112 on the side of the air electrode 114. The separator 120 is bonded to the electrolyte layer 112 (single cell 110) by a bonding portion 124 formed of a brazing material (for example, Ag wax) arranged at the opposite portion thereof. The separator 120 partitions the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116, and a gas leak from one electrode side to the other electrode side at the peripheral edge of the single cell 110. It is suppressed.

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. .. 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 hole 132 that communicates the oxidant gas introduction manifold 161 and the air chamber 166, and the oxidant gas that communicates the air chamber 166 and the oxidant gas discharge manifold 162. A discharge communication hole 133 is formed.

The fuel electrode side frame 140 is a frame-shaped member in which a substantially rectangular hole 141 penetrating in the vertical direction is formed near the center, and is formed of, for example, metal. Hole 141 of the fuel electrode side frame 140 constitutes a fuel chamber 176 facing the fuel electrode 116. The fuel electrode side frame 140 is in contact with the peripheral 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. Further, in the fuel electrode side frame 140, a fuel gas supply communication hole 142 that communicates the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that communicates the fuel chamber 176 and the fuel gas discharge manifold 172. And are formed.

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. In the present embodiment, the fuel electrode side current collector 144 is formed of Ni foil. A conductive bonding layer 310 is arranged on substantially the entire surface of the electrode facing portion 145 on the side facing the fuel electrode 116. In this embodiment, the bonding layer 310 is formed of NiO (nickel oxide). The bonding layer 310 arranged on the surface of the electrode facing portion 145 is a surface of the fuel pole 116 opposite to the side facing the electrolyte layer 112 (that is, a side of the fuel pole 116 facing the fuel pole side current collector 144). It is the surface of the above, and is in contact with the "current collector facing surface S1"). Further, the interconnector facing portion 146 is in contact with the surface of the interconnector 150 on the side facing the fuel electrode 116. 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 electrode side current collector 144 and the junction layer 310 have such a configuration, the fuel electrode 116 and the interconnector 150 (or the end plate 106) are electrically connected. 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.

As shown in FIG. 4, in the present embodiment, the fuel electrode side current collector 144 is manufactured by making a notch in a rectangular flat plate-shaped member and processing the plurality of rectangular portions so as to bend them up. The bent rectangular portion becomes the electrode facing portion 145, the flat plate portion having a hole other than the bent portion becomes the interconnector facing portion 146, and the portion connecting the electrode facing portion 145 and the interconnector facing portion 146 is connected. It becomes part 147. In the partially enlarged view shown in FIG. 4, in order to show the manufacturing method of the fuel electrode side current collector 144, a state before the bending raising process of a part of a plurality of rectangular portions is completed is shown. Further, in the present embodiment, the electrode facing portions 145 and the bonding layer 310 are arranged in a substantially grid pattern (on each intersection of the grids) in the Z direction. In the Z direction, the area of each electrode facing portion 145 (that is, the area of the bonding layer 310) is, for example, 1 to 1000 (mm ² ).

In this specification, in each power generation unit 102, an aggregate of the junction layer 310 located on the fuel pole 116 side of the single cell 110, the fuel pole side current collector 144, and the interconnector 150 is collected on the fuel pole side. It is called a member 400. Since the fuel electrode side current collector 400 has the same configuration as described above, a plurality of flat plate-shaped members (interconnectors 150) larger than the single cell 110 in the Z direction and a plurality of members in contact with the current collector facing surface S1 of the fuel electrode 116. (Aggregation of the electrode facing portion 145 of the fuel electrode side current collector 144 and the bonding layer 310 provided on the surface of the electrode facing portion 145, hereinafter referred to as "current collector convex portion 410". ) And (see FIG. 6). The fuel electrode side current collecting member 400 corresponds to a current collecting member in the claims, and the plurality of current collecting member convex portions 410 correspond to a plurality of convex portions in the claims. Further, the electrode facing portion 145 forming a part of each current collector convex portion 410 corresponds to the current collector main body within the claims, and the current collector of the electrode facing portion 145 (current collector main body) and the fuel electrode 116. The joint layer 310 interposed between the member facing surface S1 and forming a portion of each current collecting member convex portion 410 in contact with the current collecting member facing surface S1 of the fuel electrode 116 corresponds to the bonding layer within the scope of the claims. .. Further, in the present specification, a structure composed of a single cell 110 and a fuel pole side current collector 400 (fuel pole side current collector 144, junction layer 310, interconnector 150) is referred to as a current collector-fuel cell. It is referred to as a single cell composite (hereinafter, simply referred to as "current collector-single cell composite") 107.

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. In the present embodiment, the air electrode side current collector 134 and the interconnector 150 are formed as an integral member. That is, the flat plate-shaped portion of the integral member that is orthogonal to the vertical direction (Z-axis direction) functions as the interconnector 150, and is formed so as to project from the flat plate-shaped portion toward the air electrode 114. The current collector element 135, which is a plurality of convex portions, functions as the air electrode side current collector 134. Further, the integral member of the air electrode side current collector 134 and the interconnector 150 may be covered with a conductive coat, and both are placed between the air electrode 114 and the air electrode side current collector 134. A conductive bonding layer to be bonded may be interposed.

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 through the agent gas supply communication hole 132. Further, as shown in FIGS. 3 and 5, the fuel gas FG 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 fuel gas introduction manifold 171. Then, 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 gas supply communication of each power generation unit 102 is performed from the fuel gas introduction manifold 171. It is supplied to the fuel chamber 176 through the hole 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 through the oxidant gas discharge communication hole 133, and further oxidized. The fuel cell stack 100 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 agent gas discharge manifold 162, and the gas pipe (not shown) connected to the branch 29. It is discharged to the outside of. Further, as shown in FIGS. 3 and 5, the fuel off-gas FOG discharged from the fuel chamber 176 of each power generation unit 102 is discharged to the fuel gas discharge manifold 172 through the fuel gas discharge communication hole 143, and further, the fuel gas. To the outside of the fuel cell stack 100 via the holes of the main body 28 and the branch 29 of the gas passage member 27 provided at the position of the discharge manifold 172, and via a gas pipe (not shown) connected to the branch 29. It is discharged.

A-3. Detailed configuration of fuel pole 116:
FIG. 6 is an explanatory diagram showing a detailed configuration of the fuel electrode 116. FIG. 6 shows an enlarged configuration of the X1 portion of FIG. As shown in FIG. 6, the fuel electrode 116 includes a substrate layer 220 and an active layer 210. The substrate layer 220 is a portion on the side (lower side) closer to the fuel electrode side current collector 144 in the Z direction, and is a portion including the current collector facing surface S1. Further, the active layer 210 is a portion located between the substrate layer 220 and the electrolyte layer 112 in the Z direction, and is a portion of the fuel electrode 116 including a surface facing the electrolyte layer 112.

The substrate layer 220 of the fuel electrode 116 mainly supports other layers (active layer 210, electrolyte layer 112, air electrode 114) constituting the single cell 110, and diffuses the fuel gas FG supplied from the fuel chamber 176. It is a layer that functions as a place to collect electricity obtained by the power generation reaction. Further, the active layer 210 is a layer that mainly functions as a reaction field between the oxide ions supplied from the electrolyte layer 112 and hydrogen contained in the fuel gas FG supplied from the fuel chamber 176 via the substrate layer 220. is there. In this embodiment, in order to increase the activity of the active layer 210, the Ni content (vol%) in the active layer 210 is higher than the Ni content in the substrate layer 220. Further, in order to increase the strength of the substrate layer 220, the thickness of the substrate layer 220 is thicker than that of the active layer 210 in the Z direction. Further, in order to increase the gas diffusivity of the substrate layer 220, the porosity of the substrate layer 220 is higher than the porosity of the active layer 210.

In the present embodiment, both the active layer 210 and the substrate layer 220 of the fuel electrode 116 are formed of cermet particles of Ni, which is a conductive metal, and YSZ, which is an oxide ion conductive ceramic. As described above, in the present embodiment, the electrode facing portion 145 and the bonding layer 310 of the fuel electrode side current collector 144 constituting the current collector convex portion 410 of the fuel electrode side current collector 400 are also made of conductive metal. Contains some Ni. Therefore, it can be said that the fuel electrode 116 and the convex portion 410 of the current collector member (the electrode facing portion 145 of the current collector 144 on the fuel electrode side and the junction layer 310) contain the same metal element (Ni).

In the present embodiment, a region having a thickness Tx (hereinafter referred to as “surface layer region SP”) from the current collecting member facing surface S1 in the substrate layer 220 is arranged in a direction orthogonal to the Z direction (hereinafter referred to as “plane direction”). When divided into the first portion PA1 and the second portion PA2, the content (vol%) of the conductive metal (Ni) in the first portion PA1 is higher than the content of the conductive metal in the second portion PA2. It's getting higher. Here, the first portion PA1 faces the tip surface (that is, the fuel electrode 116 of the junction layer 310) of the current collector convex portion 410 (the aggregate of the electrode facing portion 145 and the junction layer 310) in the Z direction. The portion included in the convex overlapping region AR1 that overlaps with the surface on the side of the current collector), and the second portion PA2 is formed in the convex non-overlapping region AR2 that does not overlap with the tip surface of the current collecting member convex portion 410 in the Z direction. This is the part that is included. That is, in the present embodiment, the second portion PA2 is located between the two first portions PA1 in the plane direction. As described above, in the present embodiment, the content of the conductive metal in the portion (first portion PA1) in contact with the convex portion 410 of the current collecting member in the surface layer region SP of the substrate layer 220 is the convex portion of the current collecting member. It can be said that it is higher than the portion that does not touch the 410 (second portion PA2).

If the content of the oxide ion conductive ceramics is lowered in order to increase the content of the conductive metal in the first portion PA1, the strength of the first portion PA1 is lowered, which is not preferable. Therefore, in the present embodiment, in order to increase the content of the conductive metal in the first portion PA1, the porosity in the first portion PA1 is lowered. In other words, it can be said that the porosity in the first portion PA1 is lower than the porosity in the second portion PA2.

Further, in the present embodiment, the thickness Tx of the surface layer region SP (that is, the thickness of the first portion PA1 and the second portion PA2) is 25% or less of the thickness Ta of the substrate layer 220. Therefore, the ratio of the first partial PA1 to the entire substrate layer 220 is relatively small. In the present embodiment, the configuration (conducting metal content and porosity) of the region other than the surface layer region SP in the substrate layer 220 is substantially the same as the configuration of the second partial PA2. Further, the porosity of the active layer 210 is lower than the porosity of any portion of the substrate layer 220. Therefore, in the present embodiment, the thickness Ta of the substrate layer 220 is the thickness from the current collector facing surface S1 at the fuel electrode 116 to the position where the porosity is lower than the porosity of the first portion PA1 for the first time. I can say.

Further, in the present embodiment, the content of the conductive metal in the first portion PA1 is 30 (vol%) or more, and the content of the oxide ion conductive ceramic particles in the first portion PA1 is 30 (vol%). vol%) or more. Further, the content of the oxide ion conductive ceramic particles in the second partial PA2 is 30 (vol%) or more, and the porosity in the second partial PA2 is 30 (vol%) or more.

A-4. Manufacturing method of fuel cell stack 100:
The method for manufacturing the fuel cell stack 100 having the above-described configuration is, for example, as follows. First, a single cell 110 is produced. The method for producing the single cell 110 is, for example, as follows.

(Preparation of green sheet for fuel electrode substrate layer)
With respect to the mixed powder (100 parts by weight) of NiO powder (50 parts by weight) and YSZ powder (50 parts by weight), organic beads (15% by weight with respect to the mixed powder) which are pore-forming materials, and butyral resin , DOP which is a plasticizer, a dispersant, and a mixed solvent of toluene + ethanol are added and mixed with a ball mill to prepare a slurry. Organic beads are, for example, spherical particles formed of a polymer such as polymethyl methacrylate or polystyrene. The obtained slurry is thinned by the doctor blade method to prepare a plurality of green sheets for a fuel electrode substrate layer having a predetermined thickness. The ratio of NiO powder and YSZ powder in the green sheet for the fuel electrode substrate layer can be appropriately changed as long as the performance is satisfied. For example, even if the NiO powder: YSZ powder is 60:40 or 40:60. I do not care. That is, the NiO powder can be appropriately changed between 40 and 60 parts by weight so that the mixed powder of the NiO powder and the YSZ powder is 100 parts by weight, and the rest can be the YSZ powder.

Among the plurality of produced green sheets for the fuel electrode substrate layer, a pattern corresponding to the arrangement of the convex portion 410 of the current collector member is formed on the surface of the green sheet for the fuel electrode substrate layer corresponding to the surface layer region SP in the substrate layer 220 described above. Using a mask (considering shrinkage due to firing), low-viscosity NiO is applied by spraying or printing to the region corresponding to the first portion PA1 described above. After applying the low-viscosity NiO, the inside of the target fuel electrode substrate layer green sheet is impregnated with NiO by leaving it for a predetermined time. As a result, the content of NiO in the region corresponding to the first portion PA1 in the fuel electrode substrate layer green sheet corresponding to the surface layer region SP can be increased. For example, when low-viscosity NiO is applied to one of the four green sheets for the fuel electrode substrate layer, then the green sheet for the fuel electrode substrate layer is used as described later. When the substrate layer 220 is produced, the first portion PA1 having a thickness Tx of 25% of the thickness Ta of the substrate layer 220 is formed on the substrate layer 220.

(Preparation of green sheet for fuel polar active layer)
A butyral resin, a plasticizer DOP, a dispersant, and a toluene + ethanol mixed solvent are added to a mixed powder (100 parts by weight) of NiO powder (60 parts by weight) and YSZ powder (40 parts by weight). In addition, mix with a ball mill to prepare the slurry. The obtained slurry is thinned by the doctor blade method to prepare a green sheet for a fuel polar active layer having a predetermined thickness (for example, 10 μm to 30 μm). The ratio of NiO powder and YSZ powder in the green sheet for the fuel polar active layer can be appropriately changed as long as the performance is satisfied. For example, even if the NiO powder: YSZ powder is 50:50 or 40:60. I do not care. That is, the NiO powder can be appropriately changed between 40 and 60 parts by weight so that the mixed powder of the NiO powder and the YSZ powder is 100 parts by weight, and the rest can be the YSZ powder.

(Preparation of green sheet for electrolyte layer)
Butyral resin, plasticizer DOP, dispersant, and toluene + ethanol mixed solvent are added to YSZ powder (100 parts by weight) and mixed with a ball mill to prepare a slurry. The obtained slurry is thinned by the doctor blade method to prepare a green sheet for an electrolyte layer having a predetermined thickness (for example, 10 μm).

(Preparation of a laminate of the electrolyte layer 112 and the fuel electrode 116)
The green sheet for the fuel electrode substrate layer, the green sheet for the fuel electrode active layer, and the green sheet for the electrolyte layer are attached and degreased at about 280 ° C. Further, by firing at about 1350 ° C., a laminate of the electrolyte layer 112 and the fuel electrode 116 (active layer 210 and substrate layer 220) is obtained. The substrate layer 220 of the fuel electrode 116 in the produced laminate is formed with the first portion PA1 and the second portion PA2 having the above-described configuration.

(Formation of air pole 114)
A mixed solution of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder and isopropyl alcohol is prepared. The prepared mixed solution is spray-coated on the surface of the electrolyte layer 112 in the laminate and fired at 1100 ° C. to form an air electrode 114. A single cell 110 is produced by the above steps.

After that, the remaining assembly steps (for example, joining the current collector 144 on the fuel electrode side and the single cell 110 (fuel electrode 116) and fastening with bolts 22) are performed. For example, when joining the fuel electrode side current collector 144 and the single cell 110 (fuel electrode 116), the inside of the surface (current collector facing surface S1) of the fuel electrode 116 on the substrate layer 220 side of the single cell 110. , The paste for the bonding layer is printed on the region of the fuel electrode side current collector 144 facing the electrode facing portion 145 (that is, the surface of the first portion PA1), and the electrode facing portion 145 is pressed against the paste. By firing under the conditions of (1), a bonding layer 310 for joining the electrode facing portion 145 of the fuel electrode side current collector 144 and the substrate layer 220 (first portion PA1) of the fuel electrode 116 is formed. In addition, by performing the remaining assembly steps, the production of the fuel cell stack 100 having the above-described configuration is completed.

A-5. Effect of this embodiment:
As described above, the current collector-single cell composite composed of the single cell 110 and the fuel pole side current collector 400 (fuel pole side current collector 144, junction layer 310, interconnector 150) in the present embodiment. In body 107, the fuel pole 116 (the substrate layer 220 of the substrate layer 220) has a first portion PA1 and a second portion PA2. The first portion PA1 is a current collector facing surface S1 (at the fuel electrode 116) in the convex overlapping region AR1 that overlaps the current collecting member convex portion 410 (aggregate of the electrode facing portion 145 and the bonding layer 310) in the Z direction. It is a portion including a surface on the side facing the current collector 144 on the fuel electrode side). The second portion PA2 is located next to the first portion PA1 in the direction orthogonal to the Z direction (plane direction), and is a portion that does not overlap the current collecting member convex portion 410 in the Z direction. The first portion PA1 has a higher content (vol%) of the conductive metal (Ni) than the second portion PA2. Further, the thickness Tx of the first portion PA1 in the Z direction is 25% or less of the thickness Ta of the substrate layer 220 of the fuel electrode 116. Therefore, in the current collector-single cell composite 107 of the present embodiment, the conductive metal contained in the fuel pole 116 and the current collector convex portion 410 are formed near the interface between the fuel pole 116 and the current collector convex portion 410. The contact area with the contained conductive metal can be increased, and as a result, the diffusion of the conductive metal between the fuel electrode 116 and the current collector convex portion 410 is promoted, and the fuel electrode 116 and the current collector convex portion 410 are promoted. It is firmly joined to 410. Therefore, according to the current collector-single cell composite 107 in the present embodiment, it is possible to suppress the occurrence of peeling between the fuel electrode 116 and the convex portion 410 of the current collector member.

In addition, for example, by increasing the content of the conductive metal in the entire surface layer region SP of the substrate layer 220 of the fuel pole 116, peeling between the fuel pole 116 and the convex portion 410 of the current collector member may occur. It can be suppressed. However, in such a configuration, since the porosity of the entire surface layer region SP of the substrate layer 220 is low, the diffusivity of the fuel gas FG at the fuel electrode 116 is lowered, and the power generation performance may be lowered. On the other hand, in the current collector-single cell composite 107 of the present embodiment, only the first portion PA1 of the surface layer region SP of the substrate layer 220 that overlaps the current collector convex portion 410 in the Z direction is conductive. Since the metal content is increased and the porosity of the second portion PA2 that does not overlap with the current collector convex portion 410 in the Z direction is maintained in a high state, the fuel gas FG at the fuel electrode 116 While suppressing the decrease in diffusivity, it is possible to suppress the occurrence of peeling between the fuel electrode 116 and the convex portion 410 of the current collector member.

Further, in the current collector-single cell composite 107 of the present embodiment, the thickness Tx of the first portion PA1 in the substrate layer 220 of the fuel electrode 116 is set to 25% or less of the thickness Ta of the substrate layer 220. There is. Therefore, even in the convex overlap region AR1 that overlaps the current collecting member convex 410 in the Z direction of the substrate layer 220, most of the portions except the first portion PA1 are maintained in a high porosity. Therefore, according to the current collector-single cell composite 107 of the present embodiment, the fuel pole 116 and the current collector convex portion 410 are combined with each other while effectively suppressing the decrease in diffusivity of the fuel gas FG at the fuel pole 116. The occurrence of peeling between the two can be effectively suppressed.

In addition, in order to effectively suppress the decrease in diffusivity of the fuel gas FG at the fuel electrode 116 and effectively suppress the occurrence of peeling between the fuel electrode 116 and the convex portion 410 of the current collecting member, the first method is used. The difference between the content of the conductive metal in the partial PA1 (vol%) and the content of the conductive metal in the second partial PA2 (vol%) is 5 (vol%) or more and 30 (vol%) or less. Is preferable.

Further, in the current collector-single cell composite 107 of the present embodiment, the fuel electrode 116 contains YSZ particles which are oxide ion conductive ceramics. Further, the first portion PA1 in the substrate layer 220 of the fuel electrode 116 has a conductive metal (Ni) content of 30 (vol%) or more and contains oxide ion conductive ceramics (YSZ) particles. The rate is 30 (vol%) or more. Further, the second portion PA2 in the substrate layer 220 of the fuel electrode 116 has a content of oxide ion conductive ceramic particles of 30 (vol%) or more and a porosity of 30 (vol%) or more. .. Therefore, in the current collector-single cell composite 107 of the present embodiment, the content of the oxide ion conductive ceramic particles in the first portion PA1 and the second portion PA2 in the substrate layer 220 of the fuel electrode 116 is increased to some extent. By keeping it, the strength of the fuel electrode 116 can be ensured. Further, by keeping the content of the conductive metal of the first portion PA1 in the substrate layer 220 of the fuel electrode 116 high to some extent, it is possible to suppress the occurrence of peeling between the fuel electrode 116 and the convex portion 410 of the current collecting member. At the same time, by keeping the porosity of the second portion PA2 in the substrate layer 220 of the fuel pole 116 high to some extent, it is possible to suppress a decrease in the diffusivity of the fuel gas FG in the fuel pole 116.

Further, in the current collector-single cell composite 107 of the present embodiment, the fuel electrode side current collector 400 has an electrode facing portion 145 (current collector main body) forming a part of the current collector convex portion 410 and an electrode. A joint layer 310 that is interposed between the facing portion 145 and the current collecting member facing surface S1 of the fuel pole 116 and constitutes a portion of each current collecting member convex portion 410 that is in contact with the current collecting member facing surface S1 of the fuel pole 116. Be prepared. Further, the conductive metal and the bonding layer 310 in the first portion PA1 of the substrate layer 220 of the fuel electrode 116 contain the same metal element (Ni). Therefore, according to the current collector-single cell composite 107 of the present embodiment, the bondability between the first portion PA1 and the bonding layer 310 in the substrate layer 220 of the fuel electrode 116 can be improved, and the fuel electrode 116 and the fuel electrode 116 The occurrence of peeling from the convex portion 410 of the current collecting member can be effectively suppressed.

A-6. Performance evaluation:
Samples of a plurality of current collector-single cell composites 107 having different configurations of the substrate layer 220 of the fuel pole 116 are prepared, and it is difficult for peeling to occur between the fuel pole 116 and the convex portion 410 of the current collector. Performance evaluation was performed on (peeling resistance) and the diffusibility (gas diffusivity) of the fuel gas FG at the fuel electrode 116. 7 to 10 are explanatory views showing the performance evaluation results.

In the performance evaluation, as an evaluation index of peeling resistance, the rate at which the bonding layer 310 is peeled off at the interface with the single cell 110 (fuel electrode 116) when the single cell 110 is peeled off from the current collector-single cell composite 107. (Per 10 samples) was examined. It can be said that the higher this ratio is, the higher the peel resistance is. In addition, as an evaluation index of gas diffusivity, the initial voltage of the button cell (temperature: 700 ° C., current density: 0.55 A / cm ² , oxidant gas OG to be supplied: oxygen 50 ml / min and nitrogen 200 ml / min, supplied. Fuel gas FG: hydrogen 320 ml / min, dew point temperature 30 ° C.) was examined. It can be said that the higher the initial voltage value, the higher the gas diffusibility.

(First performance evaluation)
Each sample (Comparative Examples 1 and 2 and Example 1) used for the first performance evaluation shown in FIG. 7 has the composition of the first portion PA1 and the second portion PA2 of the substrate layer 220 of the fuel electrode 116. Different from each other. Specifically, in Example 1, the content of the conductive metal (Ni), the content of the oxide ion conductive ceramics (YSZ) particles, and the porosity in the first portion PA1 are 50, 30, and 20, respectively. (Vol%), and similar contents in the second partial PA2 are 40, 30, 30 (vol%), respectively. As described above, in the first embodiment, the first portion PA1 has a higher content of the conductive metal than the second portion PA2, and the porosity is correspondingly lower. In Example 1, the thickness Tx of the first portion PA1 is 8 μm, which corresponds to 1% of the thickness Ta (= 800 μm) of the substrate layer 220.

On the other hand, in Comparative Examples 1 and 2, the composition of the substrate layer 220 of the fuel electrode 116 is uniform throughout the substrate layer 220. Specifically, in Comparative Example 1, the content of the conductive metal (Ni), the content of the oxide ion conductive ceramics (YSZ) particles, and the porosity were 40 and 30, respectively, over the entire substrate layer 220. It is 30 (vol%), and in Comparative Example 2, the contents are 50, 30, and 20 (vol%), respectively, over the entire substrate layer 220. In FIG. 7, for convenience, the composition of the substrate layer 220 is described separately for the first partial PA1 and the second partial PA2 in Comparative Examples 1 and 2, but in reality, as described above. , The composition of the substrate layer 220 is uniform throughout. The same applies to FIGS. 8 and later.

As shown in FIG. 7, when the peel resistance and gas diffusivity of Comparative Example 1 are used as the reference values, in Comparative Example 2, the peel resistance is improved by 25% from the reference value, but the gas diffusivity is higher than the reference value. It decreased by 5.5%. In Comparative Example 2, since the content of the conductive metal is high throughout the substrate layer 220 of the fuel electrode 116, the peeling resistance is improved, while the porosity is low throughout the substrate layer 220 of the fuel electrode 116, so that the gas. It is probable that the diffusivity was greatly reduced. In the performance evaluation, it was determined that the gas diffusivity was rejected when the rate of decrease from the reference value was 0.1% or more. Therefore, Comparative Example 2 was determined to be rejected.

On the other hand, in Example 1, the peeling resistance was improved by 25% from the standard value, and the rate of decrease from the standard value of gas diffusivity was as small as 0.01%. In the first embodiment, since the content of the conductive metal in the first portion PA1 of the substrate layer 220 of the fuel electrode 116 is high, the peeling resistance is improved and the first portion of the substrate layer 220 of the fuel electrode 116 is improved. Although the pore ratio in PA1 is low, the pore ratio of most of the substrate layer 220, that is, the second portion PA2 and other portions (parts other than the surface layer region SP in the substrate layer 220) is about the same as in Comparative Example 1. It is considered that this is because the decrease in the diffusibility of the fuel gas FG as the entire substrate layer 220 of the fuel electrode 116 could be suppressed. In Example 1, since the rate of decrease from the reference value of gas diffusivity was less than 0.1%, it was judged to be acceptable.

From the results of the first performance evaluation shown in FIG. 7, the first portion PA1 of the substrate layer 220 of the fuel electrode 116 has a higher content of conductive metal than the second portion PA2, and the thickness of the first portion PA1 is higher. When Tx is 25% or less of the thickness of the substrate layer 220, the fuel electrode 116 and the current collecting member convex portion 410 are suppressed while suppressing a decrease in the diffusibility of the fuel gas FG as the entire substrate layer 220 of the fuel electrode 116. It can be said that the occurrence of peeling between the two can be suppressed. Further, the first portion PA1 preferably has a conductive metal content of 30 (vol%) or more and an oxide ion conductive ceramic particles content of 30 (vol%) or more. It can be said that it is preferable that the content of the oxide ion conductive ceramic particles in the second portion PA2 is 30 (vol%) or more and the porosity is 30 (vol%) or more.

(Second performance evaluation)
Each sample (Comparative Examples 1 and 3 and Example 2) used for the second performance evaluation shown in FIG. 8 is the first of the substrate layer 220 of the fuel electrode 116, similarly to the first performance evaluation described above. The compositions of the partial PA1 and the second partial PA2 are different from each other. Specifically, in Example 2, the content of the conductive metal (Ni), the content of the oxide ion conductive ceramics (YSZ) particles, and the porosity in the first portion PA1 are 40, 30, and 30, respectively. (Vol%), and similar contents in the second partial PA2 are 30, 30, 40 (vol%), respectively. As described above, in the second embodiment, the first portion PA1 has a higher content of the conductive metal than the second portion PA2, and the porosity is correspondingly lower. In Example 2, the thickness Tx of the first portion PA1 is 8 μm, which corresponds to 1% of the thickness Ta (= 800 μm) of the substrate layer 220.

On the other hand, in Comparative Example 3, the composition of the substrate layer 220 of the fuel electrode 116 is uniform throughout the substrate layer 220. Specifically, in Comparative Example 3, the content of the conductive metal (Ni), the content of the oxide ion conductive ceramics (YSZ) particles, and the porosity were 30, 30, respectively, over the entire substrate layer 220. It is 40 (vol%). Comparative Example 1 is the same as Comparative Example 1 in the above-mentioned first performance evaluation.

As shown in FIG. 8, when the peel resistance and gas diffusivity of Comparative Example 3 are used as the reference values, in Comparative Example 1, the peel resistance is improved by 33% from the reference value, but the gas diffusivity is higher than the reference value. It decreased by 1.03%. In Comparative Example 1, since the content of the conductive metal is high throughout the substrate layer 220 of the fuel electrode 116, the peeling resistance is improved, while the porosity is low throughout the substrate layer 220 of the fuel electrode 116, so that the gas. It is probable that the diffusivity was greatly reduced. In Comparative Example 1, since the rate of decrease from the reference value of gas diffusivity was 0.1% or more, it was determined to be unacceptable.

On the other hand, in Example 2, the peeling resistance was improved by 33% from the standard value, and the rate of decrease from the standard value of gas diffusivity was as small as 0.01%. In the second embodiment, since the content of the conductive metal in the first portion PA1 of the substrate layer 220 of the fuel electrode 116 is high, the peeling resistance is improved and the first portion of the substrate layer 220 of the fuel electrode 116 is improved. Although the pore ratio in PA1 is low, the pore ratio of most of the substrate layer 220, that is, the second portion PA2 and other portions (parts other than the surface layer region SP in the substrate layer 220) is about the same as in Comparative Example 3. It is considered that this is because the decrease in the diffusibility of the fuel gas FG as the entire substrate layer 220 of the fuel electrode 116 could be suppressed. In Example 2, since the rate of decrease from the reference value of gas diffusivity was less than 0.1%, it was judged to be acceptable.

From the second performance evaluation result shown in FIG. 8, the first portion PA1 of the substrate layer 220 of the fuel electrode 116 has a higher content of conductive metal than the second portion PA2, and the thickness of the first portion PA1 is higher. When Tx is 25% or less of the thickness of the substrate layer 220, the fuel electrode 116 and the current collecting member convex portion 410 are suppressed while suppressing a decrease in the diffusibility of the fuel gas FG as the entire substrate layer 220 of the fuel electrode 116. It can be said that the occurrence of peeling between the two can be suppressed. Further, the first portion PA1 preferably has a conductive metal content of 30 (vol%) or more and an oxide ion conductive ceramic particles content of 30 (vol%) or more. It can be said that it is preferable that the content of the oxide ion conductive ceramic particles in the second portion PA2 is 30 (vol%) or more and the porosity is 30 (vol%) or more.

(Third performance evaluation)
Each sample (Comparative Examples 3 and 4 and Examples 3 and 4) used for the third performance evaluation shown in FIG. 9 is of the first partial PA1 and the second partial PA2 of the substrate layer 220 of the fuel electrode 116. The composition and the thickness Tx of the first portion PA1 are different from each other. Specifically, in Examples 3 and 4, the content of the conductive metal (Ni), the content of the oxide ion conductive ceramics (YSZ) particles, and the porosity in the first portion PA1 are 30, 30, respectively. , 40 (vol%), and similar contents in the second portion PA2 are 20, 30, 50 (vol%), respectively. As described above, in Examples 3 and 4, the first portion PA1 has a higher content of the conductive metal (Ni) than the second portion PA2, and the porosity is correspondingly lower.

Further, in Example 3, the thickness Tx of the first portion PA1 is 8 μm, which corresponds to 1% of the thickness Ta (= 800 μm) of the substrate layer 220. Further, in Example 4, the thickness Tx of the first portion PA1 is 200 μm, which corresponds to 25% of the thickness Ta (= 800 μm) of the substrate layer 220.

On the other hand, in Comparative Example 4, the composition of the substrate layer 220 of the fuel electrode 116 is uniform throughout the substrate layer 220. Specifically, in Comparative Example 4, the content of the conductive metal (Ni), the content of the oxide ion conductive ceramics (YSZ) particles, and the porosity were 20, 30, respectively, over the entire substrate layer 220. It is 50 (vol%). Comparative Example 3 is the same as Comparative Example 3 in the above-mentioned second performance evaluation.

As shown in FIG. 9, when the peel resistance and gas diffusivity of Comparative Example 4 are used as the reference values, in Comparative Example 3, the peel resistance is improved by 50% from the reference value, but the gas diffusivity is higher than the reference value. It decreased by 0.72%. In Comparative Example 3, since the content of the conductive metal is high throughout the substrate layer 220 of the fuel electrode 116, the peeling resistance is improved, while the porosity is low throughout the substrate layer 220 of the fuel electrode 116, so that the gas. It is probable that the diffusivity was greatly reduced. In Comparative Example 3, since the rate of decrease from the reference value of gas diffusivity was 0.1% or more, it was determined to be unacceptable.

On the other hand, in Example 3, the peel resistance was improved by 50% from the reference value, and the gas diffusibility was almost the same as the reference value. Further, in Example 4, the peel resistance was improved by 50% from the standard value, and the rate of decrease from the standard value of gas diffusivity was as small as 0.09%. In Examples 3 and 4, since the content of the conductive metal in the first portion PA1 of the substrate layer 220 of the fuel electrode 116 is high, the peeling resistance is improved and the first portion of the substrate layer 220 of the fuel electrode 116 is improved. Although the pore ratio in the partial PA1 is low, the pore ratio of most of the substrate layer 220, that is, the second portion PA2 and other portions (parts other than the surface layer region SP in the substrate layer 220) is the same as in Comparative Example 4. It is considered that this is because the decrease in diffusivity of the fuel gas FG as a whole of the substrate layer 220 of the fuel electrode 116 could be suppressed. In Examples 3 and 4, since the rate of decrease from the reference value of gas diffusivity was less than 0.1%, it was judged to be acceptable.

From the third performance evaluation result shown in FIG. 9, the first portion PA1 of the substrate layer 220 of the fuel electrode 116 has a higher content of conductive metal than the second portion PA2, and the thickness of the first portion PA1 is higher. When Tx is 25% or less of the thickness of the substrate layer 220, the fuel electrode 116 and the current collecting member convex portion 410 are suppressed while suppressing a decrease in the diffusibility of the fuel gas FG as the entire substrate layer 220 of the fuel electrode 116. It can be said that the occurrence of peeling between the two can be suppressed. Further, the first portion PA1 preferably has a conductive metal content of 30 (vol%) or more and an oxide ion conductive ceramic particles content of 30 (vol%) or more. It can be said that it is preferable that the content of the oxide ion conductive ceramic particles in the second portion PA2 is 30 (vol%) or more and the porosity is 30 (vol%) or more.

Further, in Comparative Example 4, since the content of the conductive metal in the substrate layer 220 of the fuel electrode 116 is as low as 20 (vol%), the peeling between the fuel electrode 116 and the convex portion 410 of the current collector member occurs considerably. It was easy. From this, it can be said that the content of the conductive metal in the substrate layer 220 (first portion PA1) of the fuel electrode 116 is preferably 30 (vol%) or more.

(Fourth performance evaluation)
Each sample (Comparative Examples 5 and 6) used for the fourth performance evaluation shown in FIG. 10 has different compositions of the first partial PA1 and the second partial PA2 of the substrate layer 220 of the fuel electrode 116. Specifically, in Comparative Example 5, the content of the conductive metal (Ni), the content of the oxide ion conductive ceramics (YSZ) particles, and the porosity in the first portion PA1 are 30, 20, and 50, respectively. (Vol%), and similar contents in the second partial PA2 are 20, 20, 60 (vol%), respectively. Further, in Comparative Example 6, the content of the conductive metal (Ni), the content of the oxide ion conductive ceramics (YSZ) particles, and the porosity in the first portion PA1 were 40, 20, and 40 (vol%, respectively). ), And similar contents in the second partial PA2 are 30, 20, 50 (vol%), respectively. As described above, in Comparative Examples 5 and 6, the first portion PA1 has a higher content of the conductive metal than the second portion PA2, and the porosity is correspondingly lower.

As shown in FIG. 10, in Comparative Examples 5 and 6, the single cell 110 was cracked, so that the peel resistance and the gas diffusibility could not be evaluated. In Comparative Examples 5 and 6, since the content of the oxide ion conductive ceramic particles in the substrate layer 220 of the fuel electrode 116 is as low as 20 (vol%), the strength of the fuel electrode 116 cannot be ensured, and simply. It is probable that the cell 110 was cracked.

From the fourth performance evaluation result shown in FIG. 10, it can be said that the content of the oxide ion conductive ceramic particles in the first portion PA1 and the second portion PA2 is preferably 30 (vol%) or more.

A-7. Analysis method of fuel pole 116:
The analysis method of the fuel electrode 116 is as follows, for example.

(Method of specifying the content of conductive metal and oxide ion conductive ceramic particles)
The content of the conductive metal and the oxide ion conductive ceramic particles at each position (each region) of the fuel electrode 116 is specified by the following method. A cross section of a single cell 110 orthogonal to the plane direction is set, and an element mapping image (for example, 5000 times) by FIB-SEM (acceleration voltage 1.5 kV) is displayed at a position (region) in the cross section where the content ratio should be specified. obtain. By calculating the area ratio of the corresponding element at the above position (region) in the obtained image, the content rate of the conductive metal or the oxide ion conductive ceramic particles is specified.

(Method of identifying porosity)
The porosity at each position (each region) of the fuel electrode 116 is specified by the following method. Similar to the above-mentioned method for specifying the content rate, an SEM image (for example, 5000 times) by FIB-SEM is obtained, and a plurality of lines parallel to the plane direction are arranged at predetermined intervals at the above position (region) in the obtained image. Draw at intervals (eg, 1 μm to 5 μm intervals). 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 straight line. The porosity at the position (region) is specified by calculating the average value of the porosity in a plurality of straight lines drawn at the position (region) where the porosity should be specified.

(Method of specifying the thickness Tx of the first portion PA1)
The thickness Tx of the first portion PA1 is specified by the following method. FIG. 11 is an explanatory diagram showing a method of specifying the thickness Tx of the first portion PA1. As shown in FIG. 6, in the cross section of the fuel electrode 116, the virtual line L1 that equally divides each convex overlapping region AR1 in the plane direction and the virtual line L2 that equally divides each convex non-overlapping region AR2 in the plane direction. Is set, and the content rate of the conductive metal (Ni) at each position on the virtual lines L1 and L2 is specified. FIG. 11 shows a curve N (L1) and a curve N (L2) showing the content of the conductive metal at each position on the virtual line L1 and the virtual line L2.

Since the content of the conductive metal is substantially constant in the convex non-overlapping region AR2 in the substrate layer 220, the curve N (L2) indicating the content of the conductive metal at each position on the virtual line L2 is the current collection. It becomes a substantially straight line from the intersection P2 with the member facing surface S1 toward the Z-axis positive direction. On the other hand, in the convex overlapping region AR1 in the substrate layer 220, the content of the conductive metal in the first portion PA1 is relatively high, so that the curve N showing the content of the conductive metal at each position on the virtual line L1 ( L1) becomes substantially a straight line from the intersection P1 with the current collecting member facing surface S1 toward the Z-axis positive direction, and the content of the conductive metal decreases near the boundary between the first portion PA1 and the other portion. It becomes a curve like. As described above, the configuration of the region other than the surface layer region SP in the substrate layer 220 is substantially the same as the configuration of the second partial PA2. Therefore, it can be said that the configuration of the portion other than the first portion PA1 in the convex overlap region AR1 is substantially the same as the configuration of the second portion PA2. Therefore, the virtual line Lm at equal distances from both the substantially linear portion of the curve N (L2) and the substantially linear portion of the curve N (L1) is specified, and the virtual line Lm and the curve N (L1) are identified. ), And the distance from the intersection P1 to the intersection P3 in the Z direction is specified as the thickness Tx of the first partial PA1.

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 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 pole 116 is composed of two layers of the active layer 210 and the substrate layer 220, but the fuel pole 116 may be composed of a single layer or three or more layers. It may be configured. For example, the fuel electrode 116 is arranged between the active layer 210, the substrate layer 220, and the active layer 210 and the substrate layer 220, and has a higher porosity than the active layer 210 and a lower porosity than the substrate layer 220. It may have a three-layer structure including a third layer.

Further, in the above embodiment, the bonding layer 310 is interposed between the electrode facing portion 145 of the fuel pole side current collector 144 and the current collecting member facing surface S1 of the fuel pole 116, but the bonding layer 310 is provided. Instead, the electrode facing portion 145 of the fuel pole side current collector 144 may be in direct contact with the current collecting member facing surface S1 of the fuel pole 116. That is, the convex portion 410 of the current collecting member may be composed of the electrode facing portion 145. Even in such a configuration, if the content of the conductive metal in the first portion PA1 of the fuel pole 116 is higher than the content of the conductive metal in the second portion PA2, the fuel pole 116 and the convex portion of the current collector member are formed. It is possible to suppress the occurrence of peeling between the 410 and the 410. In such a configuration, if the conductive metal in the first portion PA1 and the electrode facing portion 145 contain the same metal element, the bondability between the first portion PA1 and the electrode facing portion 145 is enhanced. This is preferable because the occurrence of peeling between the fuel electrode 116 and the convex portion 410 of the current collecting member can be effectively suppressed.

Further, the configuration of the fuel electrode side current collector 144 in the above embodiment is merely an example and can be changed in various ways. For example, the fuel pole side current collector 144 has the same configuration as the integrated member of the air pole side current collector 134 and the interconnector 150 in the above embodiment, that is, a flat plate-shaped portion (interconnector 150) orthogonal to the Z direction. A plurality of convex portions (current collectors 134 on the air electrode side) formed so as to project from the flat plate-shaped portion toward the fuel electrode 116 may be provided. Further, in such a configuration, the surface of the flat plate-shaped portion opposite to the side on which the plurality of convex portions are formed may not be a flat surface but a surface on which irregularities are formed.

Further, in the above embodiment, for all the first partial PA1s in the fuel electrode 116, the content of the conductive metal in the first partial PA1 is the conductivity in the second partial PA2 next to the first partial PA1. Although it is said that the content is higher than that of the sex metal, it does not necessarily have to be such a configuration. For at least one first portion PA1 in the fuel electrode 116, the conductivity of the conductive metal in the first portion PA1 is greater than the content of the conductive metal in the second portion PA2 next to the first portion PA1. It should be high. With such a configuration, it is possible to suppress the occurrence of peeling between the fuel electrode 116 and the current collecting member convex portion 410 at the position of the first portion PA1. In addition, in order to effectively suppress the occurrence of peeling between the fuel electrode 116 and the convex portion 410 of the current collector member, 50% or more of all the first partial PA1s in the fuel electrode 116 are the first. It is preferable that the content of the conductive metal in the partial PA1 is higher than the content of the conductive metal in the second partial PA2 adjacent to the first partial PA1. When the number of the first partial PA1 in the fuel electrode 116 is 20 or less, the content of the conductive metal or the like is specified for all the first partial PA1 by the above-mentioned specific method. When the number of the first partial PA1s in the fuel electrode 116 exceeds 20, the content of the conductive metal or the like is specified by the above-mentioned specific method for any 20 first partials PA1s. The composition of the other first partial PA1 shall be estimated based on the obtained content.

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 forming each member in the above embodiment is merely an example, and each member may be formed of another material. For example, in the above embodiment, the fuel electrode 116 is formed by a cermet of Ni which is a conductive metal and particles of YSZ which is an oxide ion conductive ceramic, but the conductive metal is a metal other than Ni. (For example, Cu or Mo) may be used, or ceramics other than YSZ (for example, CSZ or ScSZ) may be used as the oxide ion conductive ceramics.

In the present specification, the fact that the member B and the member C face each other with the member (or a portion having the member, the same applies hereinafter) A sandwiching the member A is not limited to the form in which the member A and the member B or the member C are adjacent to each other. It includes a form in which another component is interposed between the member A and the member B or the member C. For example, another layer may be provided between the electrolyte layer 112 and the air electrode 114. Even with such a configuration, it can be said that the air electrode 114 and the fuel electrode 116 face each other with the electrolyte layer 112 interposed therebetween.

Further, the method for manufacturing 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 application of low-viscosity NiO to the surface of the green sheet for a specific fuel electrode substrate layer is performed before the firing step for producing a laminate of the electrolyte layer 112 and the fuel electrode 116. However, the application of low viscosity NiO may be performed after the firing step. Further, in order to form the first portion PA1 having a high content of the conductive metal on the fuel electrode 116, it is not always necessary to apply the conductive metal or its oxide (for example, NiO) by another method. A single cell 110 having such a configuration may be manufactured.

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 as described in, for example, Japanese Patent Application Laid-Open No. 2014-207120, but is generally the same as the fuel cell stack 100 in the above-described embodiment. It is a configuration. 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.

Further, in the above embodiment, the solid oxide fuel cell (SOFC) has been described as an example, but the present invention also applies to other types of fuel cells (or electrolytic cells) such as the molten carbonate fuel cell (MCFC). Applicable.

22: Bolt 24: Nut 26: Insulation sheet 27: Gas passage member 28: Main body 29: Branch 100: Fuel cell stack 102: Fuel cell power generation unit 104: End plate 106: End plate 107: Current collector-fuel cell Single cell composite 108: Communication hole 110: Single cell 112: Electrolyte layer 114: Air pole 116: Fuel pole 120: Separator 121: Hole 124: Joint 130: Air pole side frame 131: Hole 132: Oxidating agent gas supply communication Hole 133: Oxidizing agent gas discharge communication hole 134: Air electrode side current collector 135: Current collector element 140: Fuel pole side frame 141: Hole 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144: Fuel electrode 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 discharge manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber 210: Active layer 220: Substrate layer 310: Joint layer 400: Fuel pole side current collector 410: Current collector convex AR1: Convex overlapping area AR2: Convex non-overlapping area PA1: First part PA2: Second part S1: Current collecting member facing surface SP: Surface area

Claims (6)

An electrochemical reaction single cell containing an electrolyte layer and an air electrode and a fuel electrode containing a conductive metal facing each other in a first direction across the electrolyte layer, and arranged on the fuel electrode side of the electrochemical reaction single cell. In a current collecting member-electrochemical reaction single cell composite comprising a current collecting member having a plurality of convex portions in contact with the surface of the fuel electrode.
The fuel electrode, the first in a second direction perpendicular to the first portion is a portion including the surface of the raised portion overlapping region overlapping the convex portion in the first direction when viewed in the first direction A surface side portion having a second portion located next to the first portion and a portion that does not overlap the convex portion in the first directional view, and next to the surface side portion in the first direction. It has a specific portion composed of a non-surface side portion located in, and having a higher porosity than the first portion.
The thickness of the first portion in the first direction is 25% or less of the thickness of the specific portion.
The content of the conductive metal in the first portion (vol%) is higher than the content of the conductive metal in the second portion (vol%). Cell complex. In the current collector-electrochemical reaction single cell composite according to claim 1.
The fuel electrode is a current collector-electrochemical reaction single cell composite characterized by having a portion having a porosity lower than the porosity of the first portion at a position away from the surface of the specific portion. body. In the current collector-electrochemical reaction single cell composite according to claim 1 or 2 .
The fuel electrode contains oxide ion conductive ceramic particles.
In the first portion, the content of the conductive metal is 30 (vol%) or more, and the content of the oxide ion conductive ceramic particles is 30 (vol%) or more.
The second portion is a current collecting member characterized in that the content of the oxide ion conductive ceramic particles is 30 (vol%) or more and the porosity is 30 (vol%) or more. -Electrochemical reaction single cell complex. In the current collector-electrochemical reaction single cell composite according to any one of claims 1 to 3 .
A current collector-electrochemical reaction single cell composite, characterized in that the conductive metal and the current collector in the first portion contain the same metal element. In the current collector-electrochemical reaction single cell composite according to any one of claims 1 to 4 .
The current collector member
A current collector main body that constitutes a part of each convex portion,
A bonding layer that is interposed between the current collector main body and the surface of the fuel electrode and constitutes a portion of each convex portion that is in contact with the surface of the fuel electrode.
Including
A current collector-electrochemical reaction single cell composite, characterized in that the conductive metal and the bonding layer in the first portion contain the same metal element. In an electrochemical reaction cell stack including a plurality of current collector-electrochemical reaction single cell composites arranged side by side in the first direction.
At least one of the plurality of current collector-electrochemical reaction single cell composites is the current collector-electrochemical reaction single cell composite according to any one of claims 1 to 5. An electrochemical reaction cell stack characterized by.

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