JP6780920B2 - Fuel cell single cell and fuel cell stack - Google Patents

Description

The techniques disclosed herein relate to fuel cell single cells.

A solid oxide fuel cell (hereinafter, also referred to as "SOFC") using a solid oxide as an electrolyte is known. The fuel cell single cell provided in this SOFC includes an electrolyte layer and an air electrode and a fuel electrode facing each other with the electrolyte layer in a predetermined direction (hereinafter, also referred to as "opposing direction"), and oxidizes to the air electrode. Agent gas is supplied, and fuel gas is supplied to the fuel electrode to generate power. In such a fuel cell single cell (hereinafter, also referred to as “single cell”), for example, a substance contained in the air electrode is contained in the electrolyte layer near the interface between the electrolyte layer and the air electrode. It is known that an intermediate layer containing an ionic conductive material is arranged between an air electrode and an electrolyte layer in order to suppress the formation of a high resistance layer by reaction (for example, Patent Document 1). ..

Japanese Unexamined Patent Publication No. 2010-3478

In the fuel cell single cell including the above-mentioned intermediate layer, the material constituting the air electrode and having electron conductivity and the material constituting the intermediate layer and having ionic conductivity are used. An ionization reaction of oxygen molecules contained in the oxidant gas occurs at the connection point where the two are connected. Therefore, if the surface area of the connecting portion is small, the amount of oxide ions generated by the ionization reaction is small, which causes a problem that the power generation efficiency of the fuel cell single cell is low.

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

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

(1) The fuel cell single cell disclosed in the present specification includes an electrolyte layer containing a solid oxide, an air electrode and a fuel electrode facing each other across the electrolyte layer, and the electrolyte layer and the air electrode. In a fuel cell single cell provided with an intermediate layer arranged between them, the average particle size of the air electrode material contained in the air electrode and having electron conductivity is 0.2 μm or more and 0.7 μm. The average particle size of the material contained in the intermediate layer and having ionic conductivity is 0.4 μm or more and 1 μm or less, and is intermediate between the average particle size of the air electrode material and the intermediate layer material. The difference from the average particle size of the layer material is 0.1 μm or more and 0.3 μm or less. The smaller the difference between the average particle size of the air electrode material and the average particle size of the intermediate layer material, the larger the area of the connecting portion where the air electrode material and the intermediate layer material are connected. On the other hand, even if the above difference is made small, if the average particle size of the air electrode material and the intermediate layer material is too large, the area of the connecting portion cannot be increased. According to this fuel cell single cell, the average particle size of the air electrode material is 0.2 μm or more and 0.7 μm or less, the average particle size of the intermediate layer material is 0.4 μm or more and 1 μm or less, and air. The difference between the average particle size of the polar material and the average particle size of the intermediate layer material is 0.1 μm or more and 0.3 μm or less. As a result, for example, the average particle size of the air electrode material is larger than 0.7 μm, the average particle size of the intermediate layer material is larger than 1 μm, and the difference between the average particle size of the air electrode material and the average particle size of the intermediate layer material is large. Since the area of the connecting portion where the air electrode material and the intermediate layer material are connected can be increased as compared with the case where the size is larger than 0.3 μm, the power generation efficiency of the fuel cell single cell can be improved.

(2) In the fuel cell single cell, the air electrode material has ionic conductivity in addition to electron conductivity, and the average particle size of the air electrode material is smaller than the average particle size of the intermediate layer material. May be. When the air electrode material has electron conductivity and ionic conductivity, not only the oxide ions generated on the surface of the air electrode material in which the intermediate layer material is present in the vicinity but also the air electrode in which the intermediate layer material is not present in the vicinity. The oxide ions generated on the surface of the material are transferred to the intermediate layer side by the air electrode material. Therefore, when the air electrode material has electron conductivity and ionic conductivity as described above, the power generation efficiency of the fuel cell single cell is higher than that when the air electrode material does not have ionic conductivity. The larger the area of the exposed portion exposed in the space through which the oxidant gas passes on the surface of the air electrode material, the more oxide ions are generated and transmitted to the intermediate layer side, so that this intermediate layer material is used. The amount of power generated based on the oxide ions generated on the surface of the air electrode material that does not exist in the vicinity increases. Therefore, according to this fuel cell single cell, the average particle size of the air electrode material is smaller than the average particle size of the intermediate layer material. As a result, the area of the exposed portion of the air electrode material is larger than that when the average particle size of the air electrode material is larger than the average particle size of the intermediate layer material, so that the power generation efficiency of the fuel cell single cell can be improved. it can.

The techniques disclosed in the present specification can be realized in various forms, for example, in the form of a fuel cell stack, a power generation module including a fuel cell stack, a fuel cell system including a power generation module, and the like. It is possible to do.

It is a perspective view which shows the appearance structure of the fuel cell stack 100 in this embodiment. It is explanatory drawing which shows the XZ cross-sectional structure of the fuel cell stack 100 at the position of II-II of FIG. It is explanatory drawing which shows the YZ cross-sectional structure of the fuel cell stack 100 at the position of III-III of FIG. It is explanatory drawing which shows the XZ cross section configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross section configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. It is explanatory drawing which shows the XZ cross-sectional structure of a part (air electrode 114, intermediate layer 300) of a single cell 110. It is explanatory drawing which shows the analysis image M of the XZ cross-sectional structure of a part (air electrode 114, intermediate layer 300) of a single cell 110. It is a graph which shows the relationship between the degree of connection and the IR resistance value. It is a graph which shows the relationship between the 5 patterns of the combination of the average particle diameter of the air electrode material 310 and the average particle diameter of the intermediate layer material 330, and the degree of connectivity. 6 is a graph showing the relationship between the particle size difference and the degree of connectivity for the five patterns shown in FIG. It is a schematic diagram which showed the state that the average particle diameter of the air electrode material 310 is extremely small with respect to the average particle diameter of the intermediate layer material 330. It is a schematic diagram which showed the state which the average particle diameter of the air electrode material 310 is extremely large with respect to the average particle diameter of the intermediate layer material 330.

A. First 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 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 power generation units 102 (seven in this embodiment) and a pair of end plates 104 and 106. The seven power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in the present embodiment). The pair of end plates 104 and 106 are arranged so as to sandwich an aggregate composed of seven power generation units 102 from above and below.

A plurality of holes (eight in this embodiment) penetrating in the vertical direction are formed on the peripheral edge of each layer (power generation unit 102, end plates 104, 106) constituting the fuel cell stack 100 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 into 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 into which the bolt 22B is inserted provides the oxidizer off-gas OOG, which is the gas discharged from the air chamber 166 of each power generation unit 102. It functions as an oxidizer 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 into 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 into 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, which is the minimum unit of power generation, includes a single cell 110, a separator 120, an air pole side frame 130, an air pole side current collector 134, and a fuel pole side frame. It includes 140, a fuel electrode side 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 into which the bolts 22 described above are inserted are formed in 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, and is made of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generation units 102 and prevents mixing of reaction gases between the power generation units 102. In the present embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. That is, the upper interconnector 150 in a certain power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102. Further, since the fuel cell stack 100 includes a pair of end plates 104 and 106, the power generation unit 102 located at the top of the fuel cell stack 100 does not have the upper interconnector 150 and is located at the bottom. The power generation unit 102 does not include the lower interconnector 150 (see FIGS. 2 and 3).

The single cell 110 includes an electrolyte layer 112, an air electrode (cathode) 114 and a fuel electrode (anode) 116 facing each other in the vertical direction (arrangement direction in which the power generation units 102 are arranged) with the electrolyte layer 112 interposed therebetween, and the electrolyte layer 112. It includes an intermediate layer 300 arranged between the air electrode 114 and the air electrode 114. The single cell 110 of the present embodiment is a fuel pole support type single cell in which the electrolyte layer 112, the intermediate layer 300, and the air pole 114 are supported by the fuel pole 116.

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 has electrons such as perovskite-type oxides (for example, LSCF (lanternstrontium cobalt iron oxide), LSM (lanternstrontium manganese oxide), and LNF (lantern nickel iron)). It is made of a conductive material. The LSCF is an example of an oxide ion-electron mixed conductive air electrode material having ionic conductivity in addition to electron conductivity. The fuel electrode 116 is a 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. 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.

As shown in FIGS. 4 and 5, the intermediate layer 300 is arranged between the electrolyte layer 112 and the air electrode 114. The intermediate layer 300 is a square flat plate-shaped member having substantially the same size as the air electrode 114, and is formed of, for example, a solid oxide having ionic conductivity such as SDC, GDC, and perovskite type oxide. If there is no intermediate layer 300 between the electrolyte layer 112 and the air electrode 114, metal elements (for example, Sr and La) contained in the air electrode 114 under high temperature conditions such as during the operation of the fuel cell stack 100. (Hereinafter, also referred to as “diffusing element”)) reacts with a transition element (for example, Zr) contained in the electrolyte layer 112 to form a high resistance layer (for example, SrZrO ₃ ) near the boundary between the air electrode 114 and the electrolyte layer 112. The formation of the single cell 110 may reduce the power generation efficiency of the single cell 110.

On the other hand, in the single cell 110 of the present embodiment, the intermediate layer 300 is arranged between the electrolyte layer 112 and the air electrode 114. Therefore, the intermediate layer 300 functions as a reaction prevention layer that prevents the metal element contained in the air electrode 114 and the transition element contained in the electrolyte layer 112 from reacting to form a high resistance layer. Have. Further, the intermediate layer 300 is formed of a solid oxide having ionic conductivity. Therefore, the intermediate layer 300 has a function of apparently moving the oxide ions generated at the air electrode 114 by the ionization reaction of the oxygen molecules contained in the oxidant gas OG to the electrolyte layer 112.

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 single cell 110 to which the separator 120 is joined is also referred to as a single cell with a separator.

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

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

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, 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. (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 composition of the middle layer:
FIG. 6 shows a cross-sectional configuration (cross-sectional configuration parallel to the XZ plane) parallel to the vertical direction (Z direction) of a part of the single cell 110 (air pole 114, intermediate layer 300). As shown in FIG. 6, the air electrode 114 contains an ion conductive material 320 having ionic conductivity in addition to the air electrode material 310, and the intermediate layer 300 includes the intermediate layer material 330. ing. The air electrode material 310 is, for example, LSCF, and the ionic conductive material 320 and the intermediate layer material 330 may be the same material, for example, GDC. In this way, by including the same material as the intermediate layer 300 in the air electrode 114, the difference in the coefficient of thermal expansion between the air electrode 114 and the intermediate layer 300 becomes small, so that the air electrode is caused by the difference in the coefficient of thermal expansion. It is possible to prevent the 114 and the intermediate layer 300 from peeling off. Further, the concentration of the ionic conductive material 320 (GDC) at the air electrode 114 is preferably less than 90 mol%, more preferably less than 50 mol%. Further, the concentration of the intermediate layer material 330 (GDC) in the intermediate layer 300 is preferably 90 mol% or more.

Further, the air electrode 114 and the intermediate layer 300 satisfy all of the following three conditions 1 to 3.
Condition 1: The average particle size of the air electrode material 310 is 0.2 μm or more and 0.7 μm or less.
Condition 2: The average particle size of the intermediate layer material 330 is 0.4 μm or more and 1 μm or less.
Condition 3: The difference between the average particle size of the air electrode material 310 and the average particle size of the intermediate layer material 330 is 0.1 μm or more and 0.3 μm or less.
Further, the average particle size of the air electrode material 310 is smaller than the average particle size of the intermediate layer material 330.

The average particle size of the air electrode material 310 referred to here is the average particle size of the air electrode material 310 that can form a functional layer (a portion that substantially functions as an air electrode) or a three-phase interface in the air electrode 114. Refers to the diameter. More specifically, the average particle size of the air electrode material 310 is, for example, the direction in which the air electrode 114 and the fuel electrode 116 face each other from the boundary B between the air electrode 114 and the intermediate layer 300 in the air electrode 114. Air existing in a region up to the central position of the air electrode 114 in the Z direction) or a position 0.5 μm away from the boundary B in the opposite direction (Z direction) between the air electrode 114 and the fuel electrode 116. The average particle size of the polar material 310. The average particle size of the intermediate layer material 330 means the average particle size of the intermediate layer material 330 that can form a three-phase interface among the intermediate layers 300. More specifically, the average particle size of the intermediate layer material 330 is, for example, the average particle size of the intermediate layer 300 in the fuel electrode 116 in the opposite direction (Z direction) between the air electrode 114 and the fuel electrode 116 from the boundary B. It refers to the average particle size of the intermediate layer material 330 existing in the region up to the central position or the region up to a position 0.5 μm away from the boundary B in the direction opposite to the air pole 114 and the fuel pole 116.

A-4. Manufacturing method of single cell 110:
An example of the manufacturing method of the single cell 110 is as follows.
(Preparation of green sheet for solid electrolyte layer)
Butyral resin, dioctylphthalate (DOP) as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added to YSZ powder having a specific surface area of 5 to 7 m ² / g by the BET method. , Mix in a ball mill to prepare a slurry. By using the doctor blade method on the obtained slurry, a green sheet for a solid electrolyte layer having a thickness of 10 μm is obtained.

(Making a green sheet for the fuel electrode layer)
NiO powder having a specific surface area of 3 to 4 m ² / g by the BET method is weighed so as to be 55 parts by mass in terms of Ni weight, and the specific surface area by the BET method is 5 to 7 m ² / g. Mix with 45 parts by mass of YSZ powder to obtain a mixed powder. To this mixed powder, a butyral resin, a plasticizer DOP, a dispersant, and a mixed solvent of toluene and ethanol are added and mixed with a ball mill to prepare a slurry. By using the doctor blade method on the obtained slurry, a green sheet for a fuel polar active layer having a thickness of 10 μm is obtained.

(Lamination of solid electrolyte layer and fuel electrode layer)
The green sheet for the solid electrolyte layer and the green sheet for the fuel electrode layer are attached and dried. Further, firing is performed at 1400 ° C. to obtain a laminate of the electrolyte layer 112 and the fuel electrode (fuel electrode layer) 116.

(Preparation, printing, and firing of slurry for intermediate layer formation)
A solvent composed of an acrylic binder and isopropyl alcohol is added to the GDC powder and mixed to prepare a slurry for forming an intermediate layer. The prepared slurry is applied to the surface of the laminate of the electrolyte layer 112 and the fuel electrode 116 on the solid electrolyte molded body side by a screen printing method, and the laminated body after coating is fired. At this time, the initial raw material particle size of the intermediate layer material 330 and the firing temperature of the laminate are adjusted so that the average particle size of the intermediate layer material 330 satisfies the above condition 2. For example, the smaller the particle size of the GDC powder, the smaller the average particle size of the intermediate layer material 330 in the laminated body after firing. Further, the higher the firing temperature, the larger the average particle size of the intermediate layer material 330 in the laminated body after firing.

(Formation of air pole 114)
A mixed solution consisting of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder and isopropyl alcohol was prepared. The prepared mixed liquid is spray-coated on the surface of the intermediate layer 300 in the above-mentioned laminate in which the intermediate layer 300 is formed, and fired at 1100 ° C. to form the air electrode 114. At this time, the initial raw material particle size of the air electrode material 310 and the firing temperature of the laminate are adjusted so that the average particle size of the air electrode material 310 satisfies the above condition 1. For example, the higher the particle size of the La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder, the smaller the average particle size of the air electrode material 310 in the laminated body after firing. Further, the higher the firing temperature, the larger the average particle size of the air electrode material 310 in the laminated body after firing. In this way, the single cell 110 that satisfies all of the above conditions 1 to 3 can be manufactured.

A-5. Analysis method of intermediate layer 300:
(Acquisition method of analytical image M)
FIG. 7 shows an analytical image M having a cross-sectional structure (cross-sectional structure parallel to the XZ plane) parallel to the vertical direction (Z direction) of a part of the single cell 110 (air pole 114, intermediate layer 300). First, with respect to the intermediate layer 300, an analysis image M for analyzing the average particle size and the like of the air electrode material 310 and the intermediate layer material 330 is acquired as follows.

First, in the image observed by the scanning electron microscope (SEM), the air electrode 114 and the intermediate layer 300 can be distinguished from each other by the difference in the diameter of each particle, the presence or absence of the air electrode material 310, and the like. It can be inferred that the boundary between the two regions is the boundary B between the air electrode 114 and the intermediate layer 300. For example, since the region in which the air electrode material 310 exists (air electrode 114) and the region in which the air electrode material 310 does not exist (intermediate layer 300) can be distinguished, the boundary between these two regions is defined as the air electrode 114. It can be inferred that it is the boundary B with the intermediate layer 300. Then, as shown in FIG. 7, the portion presumed to be the boundary B between the air electrode 114 and the intermediate layer 300 is an image arranged at a substantially central position in the vertical direction (Z direction), and the intermediate layer. An image including a region of the 300 and the air electrode 114 from a portion presumed to be the boundary B to a position approximately 0.5 μm away in the vertical direction (Z direction) can be observed by, for example, SEM. Then, the analysis image M is acquired by taking the image observed by the SEM.

The analysis image M may be a binarized image after binarizing the image observed by the SEM. However, if the morphology of the air electrode material 310 or the like in the binarized image is significantly different from the actual one, the contrast of the image before the binarization process observed by SEM is adjusted, and the adjusted image is set to 2. The image may be binarized. Further, the image itself before the binarization process observed by SEM may be used. The magnification of the SEM image can be 5,000 to 20,000 times. The method of acquiring the analysis image M is not limited to this, and can be appropriately changed in order to obtain an image suitable for this analysis. The analysis image M may be acquired not only by SEM but also by taking an image obtained by FIB-SIM (focused ion beam scanning ion microscope) or EBSD (electron backscatter diffraction method).

(Measuring method of average particle size)
For the measurement of the average particle size of the air electrode material 310 and the intermediate layer material 330, see "Yasuyasu Mizutani, Yoshiharu Ozaki, Toshio Kimura, Takashi Yamaguchi," Ceramic Processing ", Gihodo Publishing Co., Ltd., March 25, 1985, No. It can be carried out according to the method (intercept method) described on pages 192 to 195. Specifically, in the analysis image M, the air electrode 114 is substantially parallel to the portion presumed to be the boundary B. Draw a plurality of straight lines (L (1) to L (5) in FIG. 7), measure the particle length of the air electrode material 310 located on this straight line for each particle, and measure the average value of these lengths. Is the average particle size of the air electrode material 310. Further, a plurality of straight lines substantially parallel to the portion presumed to be the boundary B are formed in the intermediate layer 300 (L (-1) to L (-) in FIG. 7). 5)) The length of the particles of the intermediate layer material 330 located on this straight line is measured for each particle, and the average value of these lengths is taken as the average particle size of the intermediate layer material 330.

(Measurement method of connectivity)
In the present embodiment, the degree of connection between the air electrode 114 and the intermediate layer 300 is used as a parameter for evaluating the power generation efficiency of the single cell 110 (fuel cell stack 100). The degree of connection indicates the degree of connection between the air electrode material 310 and the intermediate layer material 330 at the boundary B. Note that the connection means that the air electrode material 310 and the intermediate layer material 330 face each other without a gap or through a slight gap. This high degree of connectivity means that the length of the three-phase interface formed by the air electrode material 310, the intermediate layer material 330, and the oxidant gas OG is long, and the length of the three-phase interface is long. This means that the amount of oxide ions produced by the ionization reaction is large, and the power generation efficiency of the fuel cell single cell is high. Therefore, the degree of connection between the air electrode 114 and the intermediate layer 300 can be used as one of the parameters for evaluating the power generation efficiency of the single cell 110. The degree of connectivity is preferably 50% or more for the following reasons. FIG. 8 shows a graph showing the relationship between the degree of connectivity and the IR resistance value. According to this graph, when the degree of connection is less than 50%, the IR resistance value between the air electrode 114 and the intermediate layer 300 becomes extremely large, and the power generation efficiency of the single cell 110 decreases.

Further, the long length of the three-phase interface means that the total length of the first connecting portion R1 between the air electrode material 310 and the intermediate layer material 330 in the analysis image M is long. Therefore, the degree of connection between the air electrode 114 and the intermediate layer 300 can be expressed by, for example, the following equation (1).
Degree of connectivity (%) = ((total length of first connection point R1 between air electrode material 310 and intermediate layer material 330) / (length of boundary B-ion conductive material 320 and intermediate layer material 330 Total length of the second connected points R2 that are connected)) × 100 ・ ・ ・ (1)
The first connection portion R1 is the air electrode material 310 and the intermediate layer material in at least one cross section (analytical image M) parallel to the vertical direction (Z direction) of a part of the single cell 110 (air electrode 114, intermediate layer 300). The connection point is connected to the 330, and the length of the connection point is the length of the first connection point R1. The second connecting portion R2 is formed by the ion conductive material 320 and the intermediate layer in at least one cross section (analytical image M) parallel to the vertical direction (Z direction) of a part of the single cell 110 (air electrode 114, intermediate layer 300). It is a connecting portion where the material 330 is connected, and the length of the connecting portion is the length of the second connecting portion R2. The length of the boundary B is the length of the portion estimated to be the boundary B in the analysis image M.

(Relationship between the average particle size of the air electrode material 310 and the intermediate layer material 330 and the degree of connectivity)
FIG. 9 shows a graph showing the relationship between the five patterns of the combination of the average particle size (P1 to P5) of the air electrode material 310 and the average particle size (Q1 to Q5) of the intermediate layer material 330 and the degree of connectivity. It is shown. In FIG. 10, the difference between the average particle size of the air electrode material 310 and the average particle size of the intermediate layer material 330 for the five patterns shown in FIG. 9 (S1 to S5 (hereinafter, also simply referred to as “particle size difference”)). ) And the graph showing the relationship with the degree of connection are shown.

Comparing the first pattern (P1, Q1) with other patterns, the average particle size P1, Q1 and the particle size difference S1 of the first pattern are the smallest. As a result, the degree of connection of the first pattern is the highest. Next, when the second pattern (P2, Q2) and the third pattern (P3, Q3) are compared, the average particle size of the intermediate layer material 330 is substantially the same, but the average particle size of the air electrode material 310 is the second. Since the two patterns are larger, the particle size difference S2 of the second pattern is smaller than the particle size difference S3 of the third pattern. As a result, the degree of connection of the second pattern is higher than the degree of connection of the third pattern. Further, when the second pattern (P2, Q2) and the fifth pattern (P5, Q5) are compared, the average particle size of the air electrode material 310 is substantially the same, but the average particle size of the intermediate layer material 330 is the second. Since the pattern is smaller, the particle size difference S2 of the second pattern is smaller than the particle size difference S5 of the fifth pattern. As a result, the degree of connection of the second pattern is higher than the degree of connection of the fifth pattern. According to these results, the smaller the particle size difference, the higher the degree of connectivity.

On the other hand, when the third pattern (P3, Q3) and the fourth pattern (P4, Q4) are compared, the difference in particle size between the two is substantially the same, but the average particle size of the air electrode material 310 and the intermediate layer material 330 is In both cases, the third pattern is smaller. As a result, the degree of connection of the third pattern is higher than the degree of connection of the fourth pattern. Based on both this result and the above-mentioned results, it is necessary to comprehensively consider the particle size difference and the average particle size of each of the air electrode material 310 and the intermediate layer material 330 in order to increase the degree of connectivity. It turns out that. That is, the degree of connection varies depending on the degree of unevenness between the air electrode material 310 and the intermediate layer material 330 at the boundary B and whether the air electrode material 310 and the intermediate layer material 330 mesh well. Then, it can be seen that the degree of unevenness and the degree of meshing can be controlled by the difference in particle size and the average particle size of the air electrode material 310 and the intermediate layer material 330.

On the other hand, the air electrode 114 and the intermediate layer 300 of the single cell 110 of the present embodiment satisfy the above-mentioned conditions 1 to 3, and according to the results of FIGS. 9 and 10, the degree of connection is 50%. It can be more than that. Conditions 4 to 6 (conditions including the first pattern and the second pattern) for increasing the degree of connection to 55% or more are as follows.
Condition 4: The average particle size of the air electrode material 310 is 0.2 μm or more and 0.4 μm or less.
Condition 5: The average particle size of the intermediate layer material 330 is 0.4 μm or more and 0.6 μm or less.
Condition 6: The difference between the average particle size of the air electrode material 310 and the average particle size of the intermediate layer material 330 is 0.1 μm or more and 0.25 μm or less.

(Degree of average particle size of air electrode material 310 and intermediate layer material 330)
Next, the degree of the average particle size of the air electrode material 310 and the intermediate layer material 330 will be described. FIG. 11 is a schematic view showing a state in which the average particle size of the air electrode material 310 is extremely smaller than the average particle size of the intermediate layer material 330, and FIG. 12 is a schematic view showing a state in which the average particle size of the air electrode material 310 is intermediate. It is a schematic diagram which showed the state which was extremely large with respect to the average particle diameter of a layer material 330. In addition, in FIG. 11 and FIG. 12, the ionic conductive material 320 is omitted.

As shown in FIG. 11, as the average particle size of the air electrode material 310 is extremely smaller than the average particle size of the intermediate layer material 330, the area of the first connecting portion R1 becomes smaller, so that the degree of connection becomes lower. Moreover, if the average particle size of the air electrode material 310 is extremely small, it becomes difficult for the oxidant gas OG to pass through the air electrode 114, so that the amount of oxide ions generated by the ionization reaction decreases, and the single cell 110 generates power. Efficiency may decrease.

On the other hand, as shown in FIG. 12, as the average particle size of the air electrode material 310 is extremely larger than the average particle size of the intermediate layer material 330, the area of the first connecting portion R1 becomes smaller, so that the degree of connection is lower. Become. Here, when the air electrode material 310 has electron conductivity and ionic conductivity as in LSCF, the oxide produced on the surface of the air electrode material 310 near the boundary B where the intermediate layer material 330 exists in the vicinity. Not only the ions but also the oxide ions generated on the surface of the air electrode material 310 separated from the boundary B where the intermediate layer material 330 does not exist in the vicinity are transmitted to the intermediate layer 300 side by the air electrode material 310. Therefore, when the air electrode material 310 has electron conductivity and ionic conductivity in this way, the power generation efficiency of the single cell 110 is higher than when the air electrode material 310 does not have ionic conductivity. Then, as the area of the exposed portion H (the portion not in contact with other particles) exposed in the space through which the oxidant gas OG passes on the surface of the air electrode material 310 is larger, more oxide ions are generated. Since the intermediate layer material 330 is transmitted to the intermediate layer 300 side, the amount of power generated based on the oxide ions generated on the surface of the air electrode material 310 in which the intermediate layer material 330 does not exist in the vicinity increases.

However, if the average particle size of the air electrode material 310 is extremely large, the area of the exposed portion H becomes small, so that the intermediate layer material 330 becomes an oxide ion generated on the surface of the air electrode material 310 that does not exist in the vicinity. Based on this, the amount of power generation may decrease, and the power generation efficiency of the single cell 110 may decrease. From the above, it is not preferable that the average particle size of the air electrode material 310 is extremely large or small, and it is preferable that the average particle size of the air electrode material 310 satisfies the above condition 1. Further, it is preferable that the average particle size of the intermediate layer material 330 satisfies the condition 2 while satisfying the above-mentioned condition 3 with the average particle size of the air electrode material 310.

A-6. Effect of this embodiment:
The smaller the difference between the average particle size of the air electrode material 310 and the average particle size of the intermediate layer material 330, the larger the area of the first connecting portion R1 in which the air electrode material 310 and the intermediate layer material 330 are connected. .. On the other hand, even if the particle size difference is reduced, if the average particle size of the air electrode material 310 and the intermediate layer material 330 is too large, the area of the first connecting portion R1 cannot be increased. On the other hand, according to the present embodiment, the average particle size of the air electrode material 310 is 0.2 μm or more and 0.7 μm or less, and the average particle size of the intermediate layer material 330 is 0.4 μm or more and 1 μm. The particle size difference is 0.1 μm or more and 0.3 μm or less. As a result, for example, the average particle size of the air electrode material 310 is larger than 0.7 μm, the average particle size of the intermediate layer material 330 is larger than the condition 1 μm, and the particle size difference is larger than 0.3 μm. Since the area of the connecting portion R1 can be increased, the power generation efficiency of the single cell 110 can be improved.

Further, the average particle size of the air electrode material 310 is smaller than the average particle size of the intermediate layer material 330. As a result, the area of the exposed portion H of the air electrode material 310 is larger than that when the average particle size of the air electrode material 310 is larger than the average particle size of the intermediate layer material 330, so that the power generation efficiency of the single cell 110 is improved. Can be made to.

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.

In the above embodiment, as the air electrode, the air electrode 114 including the ionic conductive material 320 in addition to the air electrode material 310 has been exemplified, but the air electrode is not limited to this, and the air electrode may include only the air electrode material 310. , In addition to the air electrode material 310 and the ionic conductive material 320, further materials may be included. Further, as the air electrode material, the air electrode material 310 having electron conductivity and ionic conductivity has been exemplified, but the air electrode material is not limited to this, and may not have ionic conductivity.

In the above embodiment, the intermediate layer 300 composed of one layer is illustrated as the intermediate layer, but the intermediate layer is not limited to this, and the intermediate layer is an intermediate composed of a plurality of layers arranged in the vertical direction (Z direction). The layer is also good. In this case, the above conditions 1 to 3 may be satisfied for the layer adjacent to the air electrode and the air electrode among the plurality of layers. Further, the intermediate layer is not limited to one that functions as a reaction prevention layer, and may not function as a reaction prevention layer. Further, the intermediate layer may include another material in addition to the intermediate layer material having ionic conductivity.

Further, in the above embodiment, the number of power generation units 102 included in the fuel cell stack 100 is only an example, and the number of power generation units 102 is appropriately determined according to the output voltage and the like required for the fuel cell stack 100.

In addition, in this specification, parallel means that the angle formed by each other is -1 degree or more and 1 degree or less.

Further, in the above embodiment, it is assumed that the nuts 24 are fitted on both sides of the bolt 22, but it is assumed that the bolt 22 has a head and the nut 24 is fitted only on the opposite side of the head of the bolt 22. May be good. Further, in the above embodiment, the bolt 22 is used as the fastening member, but the fuel cell stack 100 may be fastened by a fastening member other than the bolt 22.

Further, in the above embodiment, the end plates 104 and 106 function as output terminals, but instead of the end plates 104 and 106, another member connected to each of the end plates 104 and 106 (for example, the end plate 104). , 106, and a conductive plate arranged between each of the power generation units 102) may function as an output terminal.

Further, in the above embodiment, the space between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each communication hole 108 is used as each manifold, but instead of this, the shaft of each bolt 22 is used. Axial holes may be formed in the portion, and the holes may be used as each manifold. Further, each manifold may be provided separately from the communication hole 108 into which each bolt 22 is inserted.

Further, in the above 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, but even in such a case. The two power generation units 102 may include their respective interconnectors 150. Further, in the above embodiment, the upper interconnector 150 of the power generation unit 102 located at the top of the fuel cell stack 100 and the lower interconnector 150 of the power generation unit 102 located at the bottom are omitted. These interconnectors 150 may be provided without omission.

Further, in the above embodiment, the fuel pole side current collector 144 may have the same configuration as the air pole side current collector 134, and the fuel pole side current collector 144 and the adjacent interconnector 150 are integrated members. It may be. Further, the fuel pole side frame 140 may be an insulator instead of the air pole side frame 130. Further, the air pole side frame 130 and the fuel pole side frame 140 may have a multi-layer structure.

Further, the material forming each member in the above embodiment is merely an example, and each member may be formed of another material.

Further, in the above embodiment, the city gas is reformed to obtain a hydrogen-rich fuel gas FG, but the fuel gas FG may be obtained from other raw materials such as LP gas, kerosene, methanol, and gasoline. Pure hydrogen may be used as the fuel gas FG.

In the above embodiment, an example in which the present invention is applied to the fuel cell stack 100 has been described, but the present invention is not limited to this, and by applying the present invention to the power generation unit 102 alone or the single cell 110 alone, pores in the intermediate layer are formed. It is possible to suppress a decrease in the power generation efficiency of the fuel cell due to the above.

22: Bolt 24: Nut 26: Insulation sheet 27: Gas passage member 28: Main body 29: Branch 45: Powder 100: Fuel cell stack 102: Power generation unit 104, 106: End plate 108: Communication hole 110: Single cell 112 : Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 121: Hole 124: Joint 130: Air electrode side frame 131: Hole 132: Oxidizing agent gas supply communication hole 133: Oxidizing agent gas discharge communication hole 134: Air electrode Side current collector 140: Fuel pole side frame 141: Hole 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144: Fuel pole side current collector 145: Electrode facing part 146: Interconnector facing part 147: Connecting part 149: Spacer 150: Interconnector 161: Oxidizing agent gas introduction manifold 162: Oxidizing agent gas discharge manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber 300: Intermediate layer 310: Air electrode material 320: Ion conductive material 330: Intermediate layer material B: Boundary FG: Fuel gas FOG: Fuel off gas H: Exposed part M: Analytical image OG: Oxidizing agent gas OOG: Oxidizing agent off gas P1 to P5, Q1 to Q5: Average grains Diameter R1: First connection point R2: Second connection point S1 to S5: Particle size difference

Claims (4)

An electrolyte layer containing solid oxides and
With the air electrode and fuel electrode facing each other across the electrolyte layer,
In a fuel cell single cell including an intermediate layer arranged between the electrolyte layer and the air electrode.
The average particle size of the air electrode material contained in the air electrode and having electron conductivity is 0.2 μm or more and 0.7 μm or less.
The average particle size of the material contained in the intermediate layer and having ionic conductivity is 0.4 μm or more and 1 μm or less.
A fuel cell single cell, wherein the difference between the average particle size of the air electrode material and the average particle size of the intermediate layer material is 0.1 μm or more and 0.3 μm or less. In the fuel cell single cell according to claim 1,
The fuel cell single cell, characterized in that the intermediate layer material is at least one of SDC and GDC. In the fuel cell single cell according to claim 1 or 2 .
The air electrode material has ionic conductivity in addition to electron conductivity.
A fuel cell single cell, characterized in that the average particle size of the air electrode material is smaller than the average particle size of the intermediate layer material. In a fuel cell stack with multiple fuel cell single cells
The fuel cell stack according to any one of claims 1 to 3 , wherein at least one of the plurality of fuel cell single cells is the fuel cell single cell according to any one of claims 1 to 3 .

Images