JP7073441B2 - Electrochemical reaction Single cell manufacturing method - Google Patents

Description

The techniques disclosed herein relate to methods of making electrochemical reaction single cells.

A solid oxide fuel cell (hereinafter referred to as "SOFC") is known as one of the types of fuel cells that generate power by utilizing an electrochemical reaction between hydrogen and oxygen. The fuel cell single cell (hereinafter, simply referred to as “single cell”), which is a constituent unit of SOFC, has, for example, an electrolyte layer containing a solid oxide and a predetermined direction (hereinafter, “first direction”) with respect to the electrolyte layer. It is provided with an air electrode arranged on one side and a fuel electrode arranged on the other side in the first direction with respect to the electrolyte layer. The fuel electrode includes a substrate layer constituting the surface on the other side of the first direction in the fuel electrode, and a functional layer located between the substrate layer and the electrolyte layer and having a porosity smaller than that of the substrate layer. The substrate layer and the functional layer include, for example, Ni and an ion conductive oxide (for example, YSZ). The substrate layer mainly exerts a function of supporting the functional layer, the electrolyte layer, and the air electrode. The functional layer mainly exerts a function of reacting oxygen ions supplied from the electrolyte layer with hydrogen or the like to generate electrons and water vapor.

Conventionally, a single cell has a plurality of green sheets (green sheet for electrolyte layer, green for fuel electrode substrate layer) for forming each layer (electrolyte layer, substrate layer of fuel electrode, functional layer of fuel electrode) constituting the single cell. The first step of preparing a laminated body (hereinafter referred to as "green sheet laminated body") in which a sheet and a green sheet for a fuel electrode functional layer) are laminated, and the second step of firing the green sheet laminated body are performed. (See, for example, Patent Document 1).

In the conventional single cell manufacturing method, the shrinkage rate during firing of the green sheet for the fuel electrode functional layer is smaller than the shrinkage rate during firing of the green sheet for the electrolyte layer, and the shrinkage rate during firing of the green sheet for the fuel electrode substrate layer is smaller. The shrinkage rate is smaller than the shrinkage rate at the time of firing of the green sheet for the fuel electrode functional layer. Further, in the conventional single cell manufacturing method, the green sheet laminate is further formed on the opposite side of the green sheet for the fuel electrode substrate layer and the green sheet for the fuel electrode functional layer from the green sheet for the electrolyte layer. A green sheet for suppressing warpage (hereinafter referred to as "warp suppression green sheet") is provided. The warp suppressing green sheet is formed of, for example, YSZ. Further, the shrinkage rate of the green sheet for suppressing warpage during firing is larger than both the shrinkage rate of the green sheet for the fuel electrode substrate layer during firing and the shrinkage rate of the green sheet for the fuel electrode functional layer during firing.

In the conventional single cell manufacturing method described above, the relationship between the magnitude relationship of the shrinkage rate at the time of firing of the green sheet for the electrolyte layer as compared with the green sheet for the fuel electrode substrate layer and the green sheet for the fuel electrode functional layer and the fuel electrode substrate The magnitude relationship of the shrinkage rate at the time of firing of the warp suppressing green sheet as compared with the layer green sheet and the fuel electrode functional layer green sheet is the same. Therefore, when the laminate containing the warp suppressing green sheet is fired, the stress generated by the shrinkage of the electrolyte layer green sheet is offset by the stress generated by the shrinkage of the warp suppressing green sheet, which simply causes the stress. The warp of the cell is suppressed.

Japanese Unexamined Patent Publication No. 2014-7127

In the above-mentioned conventional manufacturing method, the warp of a single cell is suppressed by forming the above-mentioned green sheet for suppressing warpage, but there is room for improvement.

It should be noted that such a problem is also common to the electrolytic single cell, which is a constituent unit of a solid oxide type electrolytic cell (hereinafter referred to as “SOEC”) that generates hydrogen by utilizing the electrolysis reaction of water. It is an issue. In the present specification, the fuel cell single cell and the electrolytic single cell are collectively referred to as an electrochemical reaction single cell. Further, such a problem is not limited to SOFC and SOEC, but is a problem common to other types of electrochemical reaction single cells.

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

The techniques disclosed herein can be realized, for example, in the following forms.

(1) The method for producing an electrochemical reaction single cell disclosed in the present specification is for an electrolyte layer, an air electrode arranged on one side of the first direction with respect to the electrolyte layer, and the electrolyte layer. A fuel electrode arranged on the other side in the first direction, which is located between a substrate layer constituting the surface of the other side of the fuel electrode, the substrate layer, and the electrolyte layer. A method for manufacturing an electrochemical reaction single cell comprising a functional layer having a pore ratio smaller than that of a substrate layer and a fuel electrode including a green sheet for an electrolyte layer, a green sheet for a fuel electrode substrate layer, and the electrolyte layer. It is located between the green sheet for fuel electrode substrate layer and the green sheet for fuel electrode substrate layer. The first step of preparing a green sheet laminate comprising a green sheet for a fuel electrode functional layer having the same magnitude relationship with the shrinkage rate at the time of firing when compared with the above, and firing the green sheet laminate. Thereby, the electrolyte layer formed by the green sheet for the electrolyte layer, the substrate layer formed by the green sheet for the fuel electrode substrate layer, and the functional layer formed by the green sheet for the fuel electrode functional layer. And a second step of producing a sintered body containing the above. According to the method for producing an electrochemical reaction single cell, the warp of the electrochemical reaction single cell can be suppressed.

(2) In the method for producing an electrochemical reaction single cell, the porosity of the functional layer is 4% or less, and in the first step, the green sheet for the electrolyte layer and the green sheet for the fuel electrode substrate layer. The green sheet laminate provided with the green sheet for the fuel electrode functional layer, which has a smaller shrinkage rate at the time of firing than any of the above, may be prepared. According to the method for producing an electrochemical reaction single cell, the functional layer can be made into a denser layer as compared with the production method described in Patent Document 1, and the strength of the functional layer can be improved. As a result, the strength of the electrochemical reaction single cell can be improved more effectively.

(3) In the method for producing an electrochemical reaction single cell, the thickness of the substrate layer in the first direction is thicker than the thickness of either the electrolyte layer or the functional layer in the first direction. In the first step, the green sheet for the electrolyte layer having a shrinkage rate during firing smaller than that for the green sheet for the fuel electrode substrate layer, and the fuel electrode having a shrinkage rate during firing smaller than that for the green sheet for the electrolyte layer. The green sheet laminate comprising the functional layer green sheet may be prepared. According to the method for producing the present electrochemical reaction single cell, the shrinkage rate at the time of firing of the green sheet for the fuel electrode substrate layer is smaller than the shrinkage rate at the time of firing of the green sheet for the electrolyte layer. The strength of the substrate layer can be improved, and thus the strength of the electrochemical reaction single cell can be more effectively improved.

The technique disclosed in the present specification can be realized in various forms, for example, an electrochemical reaction cell (fuel cell single cell or electrolytic single cell), and electricity including a plurality of electrochemical reaction cells. It can be realized in the form of a chemical reaction cell stack (fuel cell stack or electrolytic cell stack), a method for manufacturing 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 composition 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 YZ cross-sectional structure of the X1 part (a part of a single cell 110) of FIG. It is explanatory drawing which shows the YZ cross-sectional structure of the green sheet laminated body GL. It is a flowchart which shows the manufacturing method of the fuel cell stack 100. It is explanatory drawing which shows the performance evaluation result.

A. Embodiment:
A-1. Constitution:
(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 in FIG. FIG. 3 is an explanatory diagram 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 power generation units 102 (seven in this embodiment) and a pair of end plates 104, 106. The seven power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in this 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 (eight in this embodiment) holes 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 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 constituting 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 constituting 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, 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 direction. In the space formed by the positioned 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 introduced into each of the spaces. It functions as an oxidant gas introduction manifold 161 which is a gas flow path supplied to the power generation unit 102, and is inside the side opposite to the side (the side on the negative side of the X-axis of the two sides parallel to the Y-axis). The space formed by the bolt 22 (bolt 22B) located near the point and the communication hole 108 through which the bolt 22B is inserted is an oxidant off-gas OOG which is a gas discharged from the air chamber 166 of each power generation unit 102. Functions as an oxidant gas discharge manifold 162 that discharges the gas 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 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 direction. In the space formed by the bolt 22 (bolt 22D) located in the vicinity 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 introduced into each of the spaces. A bolt that functions as a fuel gas introduction manifold 171 to be supplied to the power generation unit 102 and is located near the midpoint of the opposite side (the side on the negative side of the Y axis of the two sides parallel to the X axis). The space formed by the 22 (bolt 22E) and the communication hole 108 through which the bolt 22E is inserted is a fuel off-gas FOG, which is a gas discharged from the fuel chamber 176 of each power generation unit 102, outside the fuel cell stack 100. It functions as a fuel gas discharge manifold 172 that discharges to. In this embodiment, as the fuel gas FG, for example, a hydrogen-rich gas obtained by reforming city gas is used.

The fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body portion 28 and a hollow cylindrical branch portion 29 branched from the side surface of the main body portion 28. The 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 located above the power generation unit 102 located at the top, and the other end plate 106 is located below the power generation unit 102 located at the bottom. A plurality of power generation units 102 are sandwiched by a pair of end plates 104 and 106 in a pressed state. 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 diagram 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 the XZ cross-sectional configuration of the 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-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 constituting the uppermost layer and the lowermost layer of the power generation unit 102. A hole corresponding to the communication hole 108 into which the bolt 22 described above is inserted is formed in the peripheral portion of the separator 120, the air pole side frame 130, the fuel pole side frame 140, and the interconnector 150 around the Z-axis direction.

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 conduction between the power generation units 102 and prevents mixing of the reaction gas between the power generation units 102. In this 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 one 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 arranged above the electrolyte layer 112, and a fuel electrode (anode) 116 arranged below the electrolyte layer 112. An intermediate layer 180 arranged between the electrolyte layer 112 and the air electrode 114 is provided. The upper part corresponds to one of the first directions in the claims, and the lower part corresponds to the other in the first direction in the claims. In the present embodiment, the thickness of the fuel pole 116 (thickness in the vertical direction, the same applies hereinafter) is thicker than the thickness of the electrolyte layer 112, and the fuel pole 116 supports other layers constituting the single cell 110. That is, the single cell 110 of the present embodiment is a fuel electrode support type single cell.

The electrolyte layer 112 is a flat plate-shaped member having a substantially rectangular shape in the vertical direction, and is a dense layer (with a low porosity). The electrolyte layer 112 contains a solid oxide such as YSZ (yttria-stabilized zirconia). As described above, the single cell 110 of the present embodiment is a solid oxide fuel cell (SOFC) using 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 vertical direction, and is a porous layer having a porosity higher than that of the electrolyte layer 112. The air electrode 114 is formed of, for example, a perovskite-type oxide (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), LNF (lanthanum nickel iron oxide)).

The fuel electrode 116 is a substantially rectangular flat plate-shaped member having substantially the same size as the electrolyte layer 112 in the vertical direction, and is a porous layer having a porosity higher than that of the electrolyte layer 112.

FIG. 6 is an explanatory view showing an enlarged YZ cross-sectional configuration of the X1 portion (a part of the single cell 110) of FIG. In FIG. 6, a part of the electrolyte layer 112, a part of the substrate layer 310 of the fuel electrode 116, and a part of the functional layer 320 are shown. As shown in FIG. 6, the fuel electrode 116 includes a substrate layer 310 constituting a lower surface of the fuel electrode 116, and a functional layer 320 located between the substrate layer 310 and the electrolyte layer 112.

The porosity of the functional layer 320 is smaller than the porosity of the substrate layer 310. The porosity of the functional layer 320 is, for example, 5% or less. The porosity of the functional layer 320 is preferably smaller in order to secure the strength of the functional layer 320 (and thus the strength of the single cell 110). Therefore, the porosity of the functional layer 320 is more preferably set to, for example, 4% or less.

In this embodiment, the functional layer 320 is adjacent to the electrolyte layer 112, and the substrate layer 310 is adjacent to the functional layer 320.

The functional layer 320 mainly exerts a function of reacting oxygen ions supplied from the electrolyte layer 112 with hydrogen or the like contained in the fuel gas FG to generate electrons and water vapor. The functional layer 320 contains Ni, which is an electron conductive substance, and an ion conductive oxide (for example, YSZ), which is a substance having oxygen ion conductivity. The thickness of the functional layer 320 is, for example, 10 μm to 40 μm. The substrate layer 310 mainly exerts a function of supporting the functional layer 320, the electrolyte layer 112, and the air electrode 114. The thickness of the substrate layer 310 is, for example, 200 μm to 1000 μm. The thickness of the substrate layer 310 is thicker than that of either the electrolyte layer 112 or the functional layer 320. In this embodiment, the substrate layer 310 also contains Ni, which is an electron conductive substance, and an ion conductive oxide having oxygen ion conductivity (for example, YSZ).

The intermediate layer 180 is a substantially rectangular flat plate-shaped member, and has ionic conductivity such as SDC (samarium-doped ceria), GDC (gadolinium-doped ceria), LDC (lanthanum-doped ceria), and YDC (yttrium-doped ceria). It is formed of solid oxide. In the intermediate layer 180, the metal (for example, Sr) contained in the air electrode 114 and the transition element (for example, Zr) contained in the electrolyte layer 112 react with each other under high temperature conditions such as during the operation of the fuel cell stack 100. As a result, it functions as a reaction prevention layer that suppresses the formation of a high resistance layer (for example, SrZrO ₃ ). Since the intermediate layer 180 has ionic conductivity, it also has a function of moving oxide ions generated by the ionization reaction of oxygen molecules contained in the oxidant gas OG to the electrolyte layer 112 at the air electrode 114.

As shown in FIGS. 4 and 5, the separator 120 is a frame-shaped member having a substantially rectangular hole 121 penetrating in the vertical direction near the center, and is formed of, for example, metal. 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 facing portions 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 gas leaks from one electrode side to the other electrode side at the peripheral edge of the single cell 110. It is suppressed.

The air pole 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 pole side frame 130 constitutes an air chamber 166 facing the air pole 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 pole 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. The hole 141 of the fuel electrode side frame 140 constitutes a fuel chamber 176 facing the fuel electrode 116. The fuel electrode side frame 140 is in contact with the peripheral 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. The electrode facing portion 145 is in contact with the surface of the fuel electrode 116 opposite to the side facing the electrolyte layer 112, and the interconnector facing portion 146 is on the surface of the interconnector 150 on the side 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 current collector 144 on the fuel electrode side has such a configuration, the fuel electrode 116 and the interconnector 150 (or the end plate 106) are electrically connected to each other. A spacer 149 formed of, for example, a 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.

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, and is formed of, for example, ferritic stainless steel. The air pole side current collector 134 is in contact with the surface of the air pole 114 on the side opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 on the side facing the air pole 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 is the upper end plate. It is in contact with 104. Since the current collector 134 on the air electrode side has such a configuration, the air electrode 114 and the interconnector 150 (or the end plate 104) are electrically connected to each other. The air electrode side current collector 134 and the interconnector 150 may be configured as an integral member. Further, the air electrode side current collector 134 may be covered with a conductive coat, and a conductive bonding layer for bonding the two is interposed between the air electrode 114 and the air electrode side current collector 134. You may be doing it.

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 oxidant gas introduction manifold 161 oxidizes each power generation unit 102. It is supplied to the air chamber 166 via 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, power is generated by the electrochemical reaction of the oxidant gas OG and the fuel gas FG in the single cell 110. Will be. 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. It may be heated by (not shown).

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 a gas pipe (not shown) connected to the branch portion 29 through the holes of the main body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the discharge manifold 172. It is discharged.

A-3. Manufacturing method of fuel cell stack 100:
An example of the method for manufacturing the fuel cell stack 100 in the present embodiment is as follows. FIG. 7 is an explanatory view showing a YZ cross-sectional structure of the green sheet laminated body GL. The green sheet laminate GL is a laminate including a green sheet 112G for an electrolyte layer, a green sheet 310G for a fuel electrode substrate layer, and a green sheet 320G for a fuel electrode functional layer. FIG. 8 is a flowchart showing a method of manufacturing the fuel cell stack 100. The "predetermined condition" shown in FIG. 8 means that the "green sheet 320G for the functional layer is located between the green sheet 112G for the electrolyte layer and the green sheet 310G for the substrate layer, and is used for the electrolyte layer." The magnitude relationship of the shrinkage rate at the time of firing when compared with the green sheet 112G is the same as the magnitude relationship of the shrinkage rate at the time of firing when compared with the green sheet 310G for the substrate layer. "

(Preparation of green sheet 112G for electrolyte layer)
To the YSZ powder, a butyral resin, a plasticizer DOP (dioctyl phthalate), a dispersant, and a mixed solvent of toluene and ethanol are added and mixed with a ball mill to prepare a slurry. The obtained slurry is thinned by a doctor blade method to prepare a green sheet 112G for an electrolyte layer having a predetermined thickness (for example, about 10 μm).

(Manufacturing of green sheet 310G for fuel electrode substrate layer)
To the mixed powder of NiO powder and YSZ powder, add organic beads as a pore-forming material, butyral resin, DOP as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol to a ball mill. And mix to prepare a slurry. The organic beads are spherical particles formed of a polymer such as polymethyl methacrylate or polystyrene. The obtained slurry is thinned by a doctor blade method to prepare a green sheet 310G for a fuel electrode substrate layer having a predetermined thickness (for example, about 200 μm). In the present embodiment, as shown in FIG. 7, four green sheets 310G for the fuel electrode substrate layer are produced. The mixing ratio of the NiO powder and the YSZ powder when producing the green sheet 310G for the fuel electrode substrate layer may be appropriately set as long as the performance is satisfied. The mixed powder for preparing the slurry contains, for example, 50 parts by weight of NiO powder and 50 parts by weight of YSZ powder with respect to 100 parts by weight of the mixed powder. The amount of organic beads added to the mixed powder is, for example, 15 parts by weight with respect to 100 parts by weight of the mixed powder.

(Manufacturing of green sheet 320G for fuel electrode functional layer)
A butyral resin, a plasticizer DOP, a dispersant, and a mixed solvent of toluene and ethanol are added to a mixed powder of NiO powder and YSZ powder, and mixed with a ball mill to prepare a slurry. Similar to the method for producing the green sheet 310G for the fuel electrode substrate layer described above, organic beads as a pore-forming material may be added when preparing the slurry. The obtained slurry is thinned by the doctor blade method to prepare a green sheet 320G for a fuel electrode functional layer having a predetermined thickness (for example, about 20 μm). The mixing ratio of the NiO powder and the YSZ powder when producing the green sheet 320G for the fuel electrode functional layer may be appropriately set as long as the performance is satisfied. The mixed powder for preparing the slurry contains, for example, 50 parts by weight of NiO powder and 50 parts by weight of YSZ powder with respect to 100 parts by weight of the mixed powder. Further, in the present embodiment, no organic beads are added to the mixed powder.

When manufacturing each green sheet (green sheet 112G for the electrolyte layer, green sheet 310G for the fuel electrode substrate layer, green sheet 320G for the fuel electrode functional layer), "the green sheet 320G for the fuel electrode functional layer is for the electrolyte layer. The relationship between the magnitude of the shrinkage rate at the time of firing when compared with the green sheet 112G and the magnitude relationship of the shrinkage rate at the time of firing when compared with the green sheet 310G for the fuel electrode substrate layer are the same. " The shrinkage rate of each green sheet during firing is adjusted so as to be used. Here, "the relationship between the magnitude of the shrinkage rate of a certain substance A when compared with the substance B and the magnitude relationship of the shrinkage rate at the time of firing when compared with the substance C is the same". There is a shrinkage rate at the time of firing of a certain product A. There is a shrinkage rate at the time of firing of a product B, which is larger than both a shrinkage rate at the time of firing of a product C, or a shrinkage rate at the time of firing of a product A. It means that it is smaller than both the shrinkage rate of the product B at the time of firing and the shrinkage rate of the product C at the time of firing (the same applies hereinafter).

Therefore, for example, a green sheet laminate GL having a green sheet 320G for a fuel electrode functional layer having a smaller shrinkage rate at the time of firing than any of the green sheet 112G for the electrolyte layer and the green sheet 310G for the fuel electrode substrate layer is produced. Alternatively, a green sheet laminate GL having a green sheet 320G for a fuel electrode functional layer having a larger shrinkage rate at the time of firing than any of the green sheet 112G for the electrolyte layer and the green sheet 310G for the fuel electrode substrate layer may be produced. .. The method for adjusting the shrinkage rate during firing of each green sheet (green sheet 112G for electrolyte layer, green sheet 310G for fuel electrode substrate layer, green sheet 320G for fuel electrode functional layer) is described in the following "A-5. A method for adjusting each characteristic of the single cell 110 ”will be described.

(Preparation of a laminate of the electrolyte layer 112 and the fuel electrode 116)
A green sheet laminate GL is produced by pasting the four fuel electrode substrate layer green sheets 310G, the fuel electrode functional layer green sheet 320G, and the electrolyte layer green sheet 112G. At this time, the green sheet 320G for the fuel electrode functional layer is located between the green sheet 112G for the electrolyte layer and the green sheet 310G for the fuel electrode substrate layer (in this embodiment, the green sheet 310G for the four fuel electrode substrate layers). ing. By producing the green sheet laminated body GL as described above, the green sheet laminated body GL is prepared (S110 in FIG. 8). The step of S110 corresponds to the first step in the claims.

Next, the green sheet laminate GL is degreased at a predetermined temperature (for example, about 280 ° C.). Further, the degreased laminated body of the green sheet is fired at a predetermined temperature (for example, about 1350 ° C.) for a predetermined time (for example, about 1 hour) (S111 in FIG. 8). As a result, the electrolyte layer 112 formed by the green sheet 112G for the electrolyte layer, the substrate layer 310 formed by the green sheet 310G for the fuel electrode substrate layer, and the functional layer 320 formed by the green sheet 320G for the fuel electrode functional layer. And, a sintered body containing is produced. That is, a laminate of the electrolyte layer 112 and the fuel electrode 116 is produced. The step of S111 corresponds to the second step in the claims.

(Formation of intermediate layer 180)
Polyvinyl alcohol as an organic binder and butyl carbitol as an organic solvent are added to GDC powder and mixed to adjust the viscosity to prepare a paste for an intermediate layer. The prepared paste for the intermediate layer is applied to the surface of the above-mentioned laminate of the electrolyte layer 112 and the fuel electrode 116 on the side of the electrolyte layer 112 by, for example, screen printing, and is fired at, for example, 1200 ° C. As a result, the intermediate layer 180 is formed (S112 in FIG. 8).

(Formation of air electrode 114)
The LSCF powder, polyvinyl alcohol as an organic binder, and butyl carbitol as an organic solvent are mixed to adjust the viscosity to prepare a paste for an air electrode. The prepared air electrode paste is applied to the surface of the intermediate layer 180 in the above-mentioned laminate of the intermediate layer 180, the electrolyte layer 112, and the fuel electrode 116 by, for example, screen printing and dried, and the air electrode paste is applied. The laminated body is fired at a predetermined firing temperature (for example, about 1100 ° C.). As a result, the air electrode 114 is formed (S112 in FIG. 8), and a single cell 110 including the fuel electrode 116, the electrolyte layer 112, and the air electrode 114 is produced.

After producing a plurality of single cells 110 according to the method described above, an assembly step (for example, a step of attaching another member such as a separator 120 to each single cell 110, a step of laminating a plurality of single cells 110, and fastening with bolts 22). Steps and the like (S113 in FIG. 8)) are performed. As described above, the production of the fuel cell stack 100 is completed.

A-4. Effect of this embodiment:
As described above, the single cell 110 of the present embodiment has the electrolyte layer 112, the air electrode 114 arranged above (one of the vertical directions) with respect to the electrolyte layer 112, and the lower side with respect to the electrolyte layer 112. It is provided with a fuel electrode 116 arranged on the (the other side in the vertical direction) side. The fuel electrode 116 includes a substrate layer 310 constituting the lower surface of the fuel electrode 116, and a functional layer 320 located between the substrate layer 310 and the electrolyte layer 112 and having a porosity smaller than that of the substrate layer 310. I'm out.

Further, the method for manufacturing a single cell 110 of the present embodiment includes the above-mentioned steps of S110 and S111. In the process of S110, the fuel electrode functional layer located between the green sheet 112G for the electrolyte layer, the green sheet 310G for the fuel electrode substrate layer, the green sheet 112G for the electrolyte layer, and the green sheet 310G for the fuel electrode substrate layer. A green sheet laminated body GL comprising the green sheet 320G for use is prepared. At this time, the green sheet 320G for the fuel electrode functional layer has a magnitude relationship with the shrinkage rate at the time of firing when compared with the green sheet 112G for the electrolyte layer, and the green sheet 310G for the fuel electrode substrate layer at the time of firing. The magnitude relationship of the shrinkage rate is the same. In the step of S111, the electrolyte layer 112 formed by the green sheet 112G for the electrolyte layer by firing the green sheet laminate GL, the substrate layer 310 formed by the green sheet 310G for the fuel electrode substrate layer, and the fuel electrode A sintered body containing the functional layer 320 formed by the green sheet 320G for the functional layer is produced.

In the method for manufacturing the single cell 110 of the present embodiment, as described above, in the step of S110, the green sheet 320G for the fuel electrode functional layer has a large or small shrinkage rate at the time of firing as compared with the green sheet 112G for the electrolyte layer. The relationship and the magnitude relationship of the shrinkage rate at the time of firing when compared with the green sheet 310G for the fuel electrode substrate layer are the same. In other words, in the process of S110, the magnitude relationship of the shrinkage rate at the time of firing of the green sheet 310G for the fuel electrode substrate layer when compared with the green sheet 320G for the fuel electrode functional layer is compared with the green sheet 320G for the fuel electrode functional layer. The relationship between the magnitude and the shrinkage of the green sheet 112G for the electrolyte layer at the time of firing is the same. Therefore, according to the method for manufacturing the single cell 110 of the present embodiment, when the green sheet laminate GL is fired in the step of S111, the stress generated by the shrinkage of the green sheet 112G for the electrolyte layer is generated by the fuel electrode substrate layer. The stress generated by the contraction of the green sheet 310G cancels out the warpage of the single cell 110.

The direction of "shrinkage" of the "shrinkage rate" of the green sheet in the present specification is not particularly limited, and includes, for example, one or both of the shrinkage in the surface direction and the shrinkage in the thickness direction of the green sheet. However, in consideration of the warp of the single cell 110 described above, it may be interpreted as mainly shrinkage in the plane direction of the green sheet.

In the method for manufacturing the single cell 110 of the present embodiment, in the step of S110, the green for the fuel electrode functional layer has a smaller shrinkage rate during firing than any of the green sheet 112G for the electrolyte layer and the green sheet 310G for the fuel electrode substrate layer. A green sheet laminated body GL including the sheet 320G is prepared. In other words, both the shrinkage rate of the green sheet 112G for the electrolyte layer during firing and the shrinkage rate of the green sheet 310G for the fuel electrode substrate layer during firing are both the shrinkage of the green sheet 320G for the fuel electrode functional layer during firing. Greater than the rate. The porosity of the functional layer 320 manufactured by this manufacturing method is, for example, 4% or less.

Therefore, in the method for manufacturing the single cell 110 of the present embodiment, both the shrinkage rate of the green sheet 112G for the electrolyte layer during firing and the shrinkage rate of the green sheet 310G for the fuel electrode substrate layer during firing are both the fuel electrode. Compared with the configuration in which the shrinkage rate of the green sheet 320G for the functional layer is smaller than that of the green sheet 320G for the electrolyte layer, the shrinkage rate of the green sheet 112G for the electrolyte layer and the shrinkage rate of the green sheet 310G for the fuel electrode substrate layer during firing are higher. big. Therefore, the compressive stress applied to the fuel electrode functional layer green sheet 320G during firing in the step of S111 becomes relatively large. Therefore, according to the method for manufacturing the single cell 110 of the present embodiment, the functional layer 320 can be made into a dense layer, whereby the strength of the functional layer 320 can be improved, and the strength of the single cell 110 can be increased. Can be improved.

Further, in the single cell 110 of the present embodiment, the vertical thickness of the substrate layer 310 is larger than the vertical thickness of either the electrolyte layer 112 or the functional layer 320. Therefore, the shrinkage rate of the green sheet 310G for the fuel electrode substrate layer during firing has an effect on the strength of the single cell 110 as compared with the shrinkage rate of the green sheet 112G for the electrolyte layer and the green sheet 320G for the fuel electrode functional layer during firing. Is big. Further, in the method for manufacturing the single cell 110 of the present embodiment, in the step of S110, the shrinkage rate at the time of firing is smaller than that of the green sheet 310G for the fuel electrode substrate layer, and the shrinkage rate at the time of firing is the same as that of the green sheet 112G for the electrolyte layer. A green sheet laminate GL comprising a green sheet 320G for a fuel electrode functional layer smaller than the green sheet 112G for an electrolyte layer is prepared. Therefore, according to the method for manufacturing the single cell 110 of the present embodiment, the shrinkage rate of the green sheet 310G for the fuel electrode substrate layer at the time of firing is larger than the shrinkage rate of the green sheet 112G for the electrolyte layer at the time of firing. The electrolyte layer 112 can be made into a denser layer as compared with the structure in which the shrinkage rate of the green sheet 310G for the electrode substrate layer at the time of firing is smaller than the shrinkage rate of the green sheet 112G for the electrolyte layer at the time of firing. The strength of the electrolyte layer 112 can be improved, and thus the strength of the single cell 110 can be improved more effectively.

A-5. How to adjust each characteristic of single cell 110:
When manufacturing the fuel cell stack 100 according to the manufacturing method described above, each characteristic of the single cell 110 constituting the fuel cell stack 100 can be adjusted as follows, for example.

(Porosity of fuel electrode 116)
The porosity of each layer (functional layer 320, substrate layer 310) constituting the fuel electrode 116 can be adjusted, for example, by green sheet forming each layer (green sheet 320G for fuel electrode functional layer or green sheet 310G for fuel electrode substrate layer). This can be achieved by adjusting the amount of the pore-forming material added when preparing the slurry for producing the above. Specifically, when preparing the slurry, the larger the amount of the pore-forming material added, the higher the porosity. The porosity can be specified, for example, by measuring the porosity by the Archimedes method.

(Shrinkage rate during firing of each green sheet)
The shrinkage ratio of each green sheet during firing can be adjusted as follows, for example. When preparing a slurry for a green sheet, the smaller the particle size of each powder (for example, NiO powder or YSZ powder), the smaller the shrinkage rate of the green sheet during firing can be reduced. Further, when preparing a slurry for a green sheet, the smaller the amount of organic beads added as a pore-forming material, the smaller the shrinkage rate of the green sheet during firing can be reduced. To specify the shrinkage rate of each green sheet during firing, for example, the dimensions of the green sheet before and after firing when fired at 1350 ° C. for 1 hour are measured, and ((dimensions before firing)-(dimensions after firing). ) / (Dimensions before firing) × 100 (%) can be realized. This "dimension" may be interpreted as, for example, one or both of the dimension in the surface direction and the dimension in the thickness direction of the green sheet, but in consideration of the warp of the single cell 110 described above, the dimension in the surface direction of the green sheet is mainly used. It may be interpreted as the dimension of.

A-6. Performance evaluation:
Next, the performance evaluation of this embodiment will be described. Samples of a plurality of single cells 110 having different characteristics from each other were prepared, and performance evaluation was performed using the samples. FIG. 9 is an explanatory diagram showing the performance evaluation result.

A-6-1. For each sample:
As shown in FIG. 9, four samples (samples S1 to S4) of the single cell 110 were used for this performance evaluation. For each sample, each green sheet (green sheet 112G for electrolyte layer, green sheet 310G for four fuel electrode substrate layers, green sheet 320G for fuel electrode functional layer) produced according to the above-mentioned manufacturing method has a predetermined size (in detail). Is cut to a size of 200 mm × 200 mm), pasted and fired. The thickness of the green sheet 112G for the electrolyte layer is about 10 μm, the thickness of the green sheet 310G for the fuel electrode substrate layer is about 200 μm, and the thickness of the green sheet 320G for the fuel electrode functional layer is about 20 μm.

FIG. 9 shows the "shrinkage rate" and "porosity" of each sample. "Shrinkage rate" means the shrinkage rate at the time of firing of each green sheet (green sheet 112G for electrolyte layer, green sheet 310G for fuel electrode substrate layer, green sheet 320G for fuel electrode functional layer), and "porosity" is It means the porosity of each layer (electrolyte layer 112, substrate layer 310, functional layer 320) formed by firing. For the value of the shrinkage rate of the green sheet during firing, the green sheet was fired at 1350 ° C. for 1 hour, the dimensions of the green sheet before and after firing were measured, and ((dimensions before firing)-(dimensions after firing). ) / (Dimensions before firing) × 100 (%). When measuring the "shrinkage rate" and "porosity" of each sample, the same characteristics as those of the above-mentioned samples are used for convenience in consideration of handleability and ease of maintaining the shape of the sample before and after firing. Each sample having a thickness different from that of the above-mentioned sample was used. Specifically, the thickness of the green sheet 112G for the electrolyte layer used for measuring the "shrinkage rate" and the "porosity" is about 100 to about 200 μm (measured value is about 100 μm), and the fuel electrode substrate layer. The thickness of the green sheet 310G for fuel was about 100 to about 200 μm (measured value was about 200 μm), and the thickness of the green sheet 320G for fuel electrode functional layer was about 100 to about 200 μm (measured value was about 100 μm). ..

As shown in FIG. 9, in each sample, the shrinkage ratio of the green sheet 112G for the electrolyte layer at the time of firing is the same (specifically, “19.1%”), and the porosity of the electrolyte layer 112 is the same (specifically, “19.1%”). In detail, it is "0%").

In each sample, the shrinkage ratio of the green sheet 310G for the fuel electrode substrate layer at the time of firing is the same (specifically, "19.9%"), and the porosity of the substrate layer 310 is the same (specifically, "30"). % ").

The shrinkage rate of the green sheet 320G for the fuel electrode functional layer at the time of firing and the porosity of the functional layer 320 are different from each other in each sample. Specifically, the shrinkage rate of the green sheet 320G for the fuel electrode functional layer during firing is "19.5%" in sample S1, "17.8%" in sample S2, and "18" in sample S3. It is "0.5%", and in sample S4, it is "21.0%". The porosity of the functional layer 320 is 5% or less in all the samples, more specifically, it is "3%" in the sample S1, "0%" in the sample S2, and "2" in the sample S3. % ”, And in sample S4, it is“ 5% ”.

A-6-2. Evaluation items and evaluation methods:
FIG. 9 shows the “warp amount” and “strength” of each sample. The "warp amount" means the warp amount of the sample (single cell 110), and the "strength" means the strength of the sample (single cell 110). In this performance evaluation, the amount of warpage of the sample (hereinafter, simply referred to as "warp amount") and the strength of the sample (hereinafter, simply referred to as "strength") are evaluated, and the evaluation result based on these evaluations is ". Comprehensive evaluation ".

The amount of warpage was evaluated based on the value calculated by placing the manufactured sample on a horizontal plane, measuring the positions of the highest point and the lowest point with a laser displacement meter, and calculating the difference between them as the amount of warpage. Specifically, the amount of warpage was evaluated as "◯" if it was 1 mm or less, and as "x" if it was larger than 1 mm.

The strength was evaluated based on the value calculated by the three-point bending test. Specifically, regarding the strength, a bending load is applied until the sample cracks in the three-point bending test, and if the magnitude of the bending load when the sample cracks is 150 MPa or more, it is evaluated as "○" and the sample cracks. If the magnitude of the bending load at the time was smaller than 150 MPa, it was evaluated as "x".

As a comprehensive evaluation, if the evaluation result for the amount of warpage was "○" and the evaluation result for the strength was "○", it was passed and evaluated as "◎", which is the highest evaluation. Further, if the evaluation result for the amount of warpage was "○" and the evaluation result for the strength was "×", it was evaluated as "○", which was inferior to "◎" but passed. If the evaluation result for the amount of warpage was "x", it was evaluated as "x", which was a failure.

A-6-3. Evaluation results:
As shown in FIG. 9, in sample S1, the evaluation of the amount of warpage was “x”. Therefore, the overall evaluation of sample S1 was "x". The evaluation of strength was "○".

The reason why the evaluation of the amount of warpage of the sample S1 was "x" is presumed as follows. In sample S1, the shrinkage rate of the green sheet 320G for the fuel electrode functional layer at the time of firing is "19.5%", whereas the shrinkage rate of the green sheet 112G for the electrolyte layer at the time of firing is "19.1%". The shrinkage rate of the green sheet 310G for the fuel electrode substrate layer at the time of firing is "19.9%". Therefore, "the green sheet 320G for the fuel electrode functional layer has a magnitude relationship with the shrinkage rate at the time of firing when compared with the green sheet 112G for the electrolyte layer, and the green sheet 310G for the fuel electrode substrate layer at the time of firing. The condition of "the relationship between the magnitude of the shrinkage rate is the same" is not satisfied. Therefore, it is presumed that the stress caused by the shrinkage of each green sheet could not be sufficiently suppressed.

In sample S2, the evaluation of the amount of warpage was "○", and the evaluation of the strength was also "○". Therefore, the overall evaluation of sample S2 was "◎".

The reason why the evaluation of the amount of warpage in sample S2 was "○" is presumed as follows. In sample S2, the shrinkage rate of the green sheet 320G for the fuel electrode functional layer at the time of firing is "17.8%", whereas the shrinkage rate of the green sheet 112G for the electrolyte layer at the time of firing is "19.1%". The shrinkage rate of the green sheet 310G for the fuel electrode substrate layer at the time of firing is "19.9%". Therefore, "the green sheet 320G for the fuel electrode functional layer has a magnitude relationship with the shrinkage rate at the time of firing when compared with the green sheet 112G for the electrolyte layer, and the green sheet 310G for the fuel electrode substrate layer at the time of firing. The relationship between the magnitude of the shrinkage rate is the same. " Therefore, it is presumed that the stress generated by the contraction of the green sheet 112G for the electrolyte layer during firing is offset by the stress generated by the contraction of the green sheet 310G for the fuel electrode substrate layer.

In sample S3, the evaluation of the amount of warpage was "○", and the evaluation of the strength was also "○". Therefore, the overall evaluation of sample S3 was "◎".

In sample S4, the evaluation of the amount of warpage was "◯", and the evaluation of the strength was also "x". Therefore, the overall evaluation of sample S4 was "◯".

It is considered that the reason why the evaluation of the amount of warpage is “◯” in the sample S3 and the sample S4 is the same as the reason in the above-mentioned sample S2.

From the above-mentioned evaluation results, "when the green sheet 320G for the fuel electrode functional layer is compared with the green sheet 310G for the fuel electrode substrate layer, the relationship between the magnitude of the shrinkage rate at the time of firing when compared with the green sheet 112G for the electrolyte layer and when compared with the green sheet 310G for the fuel electrode substrate layer. It was confirmed that the warp of the sample (single cell 110) can be suppressed by satisfying the condition that "the relationship between the magnitude of the shrinkage rate at the time of firing is the same".

Further, as described above, the evaluation of the strength of the samples S2 and S3 was "◯", while the evaluation of the strength of the sample S4 was "x". Here, in the samples S2 and S3, both the shrinkage rate of the green sheet 112G for the electrolyte layer during firing and the shrinkage rate of the green sheet 310G for the fuel electrode substrate layer during firing are both green for the fuel electrode functional layer. It is larger than the shrinkage rate of the sheet 320G at the time of firing. Further, in the sample S4, both the shrinkage rate of the green sheet 112G for the electrolyte layer during firing and the shrinkage rate of the green sheet 310G for the fuel electrode substrate layer during firing are both of the green sheet 320G for the fuel electrode functional layer. It is smaller than the shrinkage rate during firing.

Therefore, from the above-mentioned evaluation results, "both the shrinkage rate of the green sheet 112G for the electrolyte layer at the time of firing and the shrinkage rate of the green sheet 310G for the fuel electrode substrate layer at the time of firing are both the green sheet for the fuel electrode functional layer. In the configuration of "greater than the shrinkage rate at the time of firing of 320G", both the shrinkage rate at the time of firing of the green sheet 112G for the electrolyte layer and the shrinkage rate at the time of firing of the green sheet 310G for the fuel electrode substrate layer are fuels. It was confirmed that the strength of the sample (single cell 110) can be improved as compared with the configuration of "smaller shrinkage rate at the time of firing of the green sheet 320G for the polar functional layer".

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, and for example, the following modifications are also possible.

The configuration of the single cell 110 or the fuel cell stack 100 in the above embodiment is merely an example and can be variously modified.

In the above embodiment, the intermediate layer 180 may not be arranged between the electrolyte layer 112 and the air electrode 114, and the electrolyte layer 112 and the air electrode 114 may be directly connected to each other.

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, 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 relates to an electrolysis reaction of water. It is also applicable to an electrolytic cell unit, which is a constituent unit of a solid oxide type electrolytic cell (SOEC) that uses it to generate hydrogen, and an electrolytic cell stack having a plurality of electrolytic cell units. 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 schematically 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 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. Steam 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. Also in the method for manufacturing the electrolytic cell unit and the electrolytic cell stack having such a configuration, as in the above embodiment, “the green sheet 320G for the fuel electrode functional layer shrinks during firing as compared with the green sheet 112G for the electrolyte layer”. Suppressing the warpage of the electrolytic cell by satisfying the condition that "the relationship between the magnitude of the rate and the magnitude relationship of the shrinkage rate at the time of firing when compared with the green sheet 310G for the fuel electrode substrate layer is the same". Can be done.

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

22: Bolt 22A: Bolt 22B: Bolt 22D: Bolt 22E: 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 112G: Green sheet for electrolyte layer 114: Air pole 116: Fuel pole 120: Separator 124: Joint 130: Air pole side frame 132: Oxidating agent gas supply communication hole 133: Oxidizing agent gas discharge communication hole 134: Air pole side current collector 140: Fuel pole side frame 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144: Fuel pole side current collector 145: Electrode facing part 146: Inter Connector 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 180: Intermediate layer 310: Substrate layer 310G: Fuel electrode Substrate layer green sheet 320: Functional layer 320G: Fuel electrode functional layer green sheet FG: Fuel gas FOG: Fuel off gas GL: Green sheet laminate OG: Oxidating agent gas OOG: Oxidation Agent off gas

Claims (3)

With the electrolyte layer,
An air electrode arranged on one side in the first direction with respect to the electrolyte layer,
A fuel electrode arranged on the other side of the first direction with respect to the electrolyte layer, and between the substrate layer constituting the surface of the other side of the fuel electrode, and between the substrate layer and the electrolyte layer. A fuel electrode including a functional layer having a porosity smaller than that of the substrate layer, which is located in
It is a manufacturing method of an electrochemical reaction single cell comprising.
Green sheet for electrolyte layer and
Green sheet for fuel electrode substrate layer and
It is located between the green sheet for the electrolyte layer and the green sheet for the fuel electrode substrate layer, and the magnitude relationship of the shrinkage rate at the time of firing when compared with the green sheet for the electrolyte layer and the fuel electrode substrate layer. The green sheet for the fuel electrode functional layer, which has the same magnitude relationship with the shrinkage rate during firing when compared to the green sheet for fuel,
The first step of preparing a green sheet laminate comprising
By firing the green sheet laminate, the electrolyte layer formed by the green sheet for the electrolyte layer, the substrate layer formed by the green sheet for the fuel electrode substrate layer, and the green for the fuel electrode functional layer. A second step of producing a sintered body containing the functional layer formed of a sheet.
A method for producing an electrochemical reaction single cell. In the method for producing an electrochemical reaction single cell according to claim 1,
The porosity of the functional layer is 4% or less, and the porosity is 4% or less.
In the first step, the green sheet laminate provided with the green sheet for the fuel electrode functional layer having a smaller shrinkage rate at the time of firing than any of the green sheet for the electrolyte layer and the green sheet for the fuel electrode substrate layer. prepare,
A method for producing an electrochemical reaction single cell. In the method for producing an electrochemical reaction single cell according to claim 2.
The thickness of the substrate layer in the first direction is thicker than the thickness of either the electrolyte layer or the functional layer in the first direction.
In the first step, the green sheet for the electrolyte layer having a shrinkage rate during firing smaller than that for the green sheet for the fuel electrode substrate layer, and the fuel electrode having a shrinkage rate during firing smaller than that for the green sheet for the electrolyte layer. The green sheet laminate comprising the green sheet for the functional layer is prepared.
A method for producing an electrochemical reaction single cell.

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