JP2017073246A - Electrochemical reaction single cell and electrochemical chemical reaction cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve: the increase in gas diffusibility in at least one electrode of an air electrode and a fuel electrode; the suppression of occurrence of electrode cracking; and the suppression of occurrence of delamination.SOLUTION: In an electrochemical reaction single cell, at least one of an air electrode and a fuel electrode includes: a first layer; and a second layer. Supposing that a side where an electrolyte layer is present with respect to the electrode is one side, and a side opposite thereto is the other side, the second layer is disposed on the other side of the first layer. In the second layer, a first region on the one side, and a second region on the other side satisfy the following relations V, W and X. Relation V: (First region porosity)<(Second region porosity). Relation W: (Second region particle diameter D)×0.5≤(First region particle diameter D)≤(Second region particle diameter D)×1.5. Relation X: (First region particle diameter D)-(First region particle diameter D)>(Second region particle diameter D)-(Second region particle diameter D).SELECTED DRAWING: Figure 9

Description

  The technology disclosed by the present specification relates to an electrochemical reaction unit cell.

  One type of fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen is a solid oxide fuel cell (hereinafter also referred to as “SOFC”) that includes an electrolyte layer containing a solid oxide. Are known. A fuel cell single cell (hereinafter also simply referred to as “single cell”), which is the smallest structural unit of the SOFC, is mutually connected in a predetermined direction (hereinafter also referred to as “first direction”) with the electrolyte layer interposed therebetween. The air electrode and the fuel electrode that face each other are included (see, for example, Patent Document 1). In the following, with the air electrode or fuel electrode as a reference, the electrolyte layer side is referred to as one side in the first direction, and the opposite side of one side is referred to as the other side.

  In general, the surface of a single cell, that is, the surface of an air electrode or a fuel electrode faces an air chamber or a fuel chamber through which an oxidant gas or a fuel gas flows. The oxidant gas or the fuel gas flowing through the air chamber or the fuel chamber is supplied to the air electrode or the fuel electrode, and is diffused in the air electrode or the fuel electrode and used for a power generation reaction. In general, a stress is generated in a single cell due to a pressing force from another member that contacts the surface of the single cell (for example, a current collecting member that collects electricity generated in the single cell).

International Publication No. 2013/11481

  In the single cell, at least one of the air electrode and the fuel electrode includes a first layer (also referred to as an active layer) and a second layer (also referred to as a current collecting layer) disposed on the other side of the first layer. May be configured to include. In the single cell having such a configuration, all of the improvement in gas diffusibility in the electrode, the suppression of the occurrence of electrode cracking due to the stress, and the suppression of the occurrence of peeling between the first layer and the second layer are all achieved. The technology to achieve is not known.

 Such a problem is common to an electrolytic cell that is a minimum constituent unit of a solid oxide electrolytic cell (hereinafter also referred to as “SOEC”) that generates hydrogen using an electrolysis reaction of water. It is a problem. In the present specification, the fuel cell unit cell and the electrolysis cell are collectively referred to as an electrochemical reaction unit cell. Such a problem is not limited to SOFC and SOEC, but is common to other types of electrochemical reaction single cells.

  In this specification, the technique which can solve the subject mentioned above is disclosed.

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

(1) An electrochemical reaction unit cell disclosed in the present specification is an electrochemical reaction unit cell including an electrolyte layer, and an air electrode and a fuel electrode facing each other in a first direction with the electrolyte layer interposed therebetween. And at least one of the air electrode and the fuel electrode has a first layer, the air electrode or the fuel electrode as a reference, the electrolyte layer side as one side in the first direction, and the one side A second layer disposed on the other side of the first layer when the opposite side is the other side, and in the second layer, the first region on the one side; and The second region on the other side satisfies the following relationships V, W, and X.
Relationship V: (Porosity of the first region) <(Porosity of the second region)
Relationship W :( the particle diameter _{D 10} of the second region) × 0.5 ≦ (particle diameter _{D 10} of the first particle diameter _{D 10} of the region) ≦ (the second region) × 1.5
Relationship X: (Particle size D _{90 in} the first region) − (Particle size D _{10 in} the first region)> (Particle size D _{90 in} the second region) − (Particles in the second region) diameter _{D 10)}

  According to the present electrochemical reaction single cell, the porosity of the second region disposed closer to the air chamber or the fuel chamber through which the gas flows in the second layer is higher than the porosity of the first region. (Relationship V) It is possible to improve gas diffusibility in the electrode while suppressing a decrease in the structural strength of the electrode. In addition, since the porosity of the second region arranged closer to the surface of the electrochemical reaction unit cell is relatively high (Relation V), the hardness of the second region is relatively low, and the electrochemical reaction unit cell When a stress is generated by contact of another member with the surface, the stress is dispersed by the second region, and generation of electrode cracks can be suppressed. In addition, since the first region and the second region contain substantially the same fine particles (Relationship W), and the second region has a smaller particle size variation (Relationship X) than the first region, the first region More pores (holes) are formed in the second region than in the first region, and the hardness of the second region is relatively low (that is, lower than that in the first region). Generation of cracks can be effectively suppressed. Furthermore, since the first region has a relatively large particle size variation and particles having a relatively large diameter and particles having a relatively small diameter are mixed, the first region has an interface at the interface between the first region and the first layer. As the number of contact points increases, the anchor effect increases, and the occurrence of peeling at this interface can be suppressed.

(2) The electrochemical reaction single cell may be configured to satisfy the relationship Y of (particle diameter D _{85 in} the first region)> (particle diameter D _{90 in} the second region). According to the present electrochemical reaction single cell, the first region contains more particles having a relatively large diameter compared to the second region (relationship Y), so the first region, the first layer, The anchor effect at the interface becomes larger, and the occurrence of peeling at this interface can be more effectively suppressed.

(3) In the electrochemical reaction single cell, the second layer includes a layer including the first region and a layer including the second region, and (the first layer in the first direction). The thickness of the layer including one region) <(the thickness of the layer including the second region in the first direction) may be satisfied. According to this electrochemical reaction single cell, the thickness of the layer including the second region having a higher porosity is increased while suppressing the occurrence of peeling at the interface between the first region and the first layer. As a result, the gas diffusibility in the electrode can be further improved, and the thickness of the layer including the second region having a lower hardness can be increased, and the generation of cracks in the electrode can be more effectively suppressed. it can.

(4) In the electrochemical reaction single cell, the electrochemical reaction single cell may be configured such that the electrolyte contained in the electrolyte layer is a solid oxide or carbonate electrochemical reaction single cell. According to the present electrochemical reaction single cell, it is possible to suppress the occurrence of electrode cracking and delamination in an electrochemical reaction single cell that is operated at a relatively high temperature and easily causes electrode cracking and delamination. .

  The technology disclosed in the present specification can be realized in various forms, and includes, for example, an electrochemical reaction single cell (fuel cell single cell or electrolytic cell) and a plurality of electrochemical reaction single cells. It can be realized in the form of an electrochemical reaction cell stack (fuel cell stack or electrolytic cell stack), a manufacturing method thereof, and the like.

1 is a perspective view showing an external configuration of a fuel cell stack 100 in the present embodiment. It is explanatory drawing which shows the XZ cross-section structure of the fuel cell stack 100 in the position of II-II of FIG. FIG. 3 is an explanatory diagram showing a YZ cross-sectional configuration of a fuel cell stack 100 at a position of III-III in FIG. 1. It is explanatory drawing which shows XZ cross-section structure of the two electric power generation units 102 adjacent to each other in the same position as the cross section shown in FIG. It is explanatory drawing which shows the YZ cross-section structure of the two electric power generation units 102 adjacent to each other in the same position as the cross section shown in FIG. It is explanatory drawing which shows the detailed structure of the air electrode 114. FIG. It is explanatory drawing which shows an example of the frequency distribution of the particle size of the current collection layer. 6 is an explanatory diagram illustrating an example of a cumulative distribution of particle diameters of a current collecting layer. FIG. It is explanatory drawing which shows the characteristic of the electrolyte side current collection layer 421 and the collector side current collection layer 422 in the Example of the single cell 110. FIG. It is explanatory drawing which shows the measurement result of Vickers hardness. It is explanatory drawing which shows schematically the structure of the fuel cell stack of a modification. It is explanatory drawing which shows roughly the structure of the single cell 1 which comprises the fuel cell stack in a modification. FIG. 13 is an explanatory diagram showing a detailed configuration of a current collector 20 and an air electrode 4 in the fuel cell stack of the modification shown in FIGS. 11 and 12.

A. Embodiment:
A-1. Constitution:
(Configuration of fuel cell stack 100)
FIG. 1 is a perspective view showing an external configuration of a fuel cell stack 100 in the present embodiment, and FIG. 2 is an explanatory diagram showing an XZ cross-sectional configuration of the fuel cell stack 100 at a 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 of III-III in FIG. In each figure, XYZ axes orthogonal to each other for specifying the direction are shown. In this specification, for the sake of convenience, the positive direction of the Z axis is referred to as the upward direction, and the negative direction of the Z axis is referred to as the downward direction. It may be installed. The same applies to FIG.

  The fuel cell stack 100 includes a plurality of (seven in this embodiment) power generation units 102 and a pair of end plates 104 and 106. The seven power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in the present embodiment). The pair of end plates 104 and 106 are arranged so as to sandwich an assembly 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 the present embodiment) holes penetrating in the vertical direction are formed in the peripheral portion around the Z direction of each layer (power generation unit 102, end plates 104, 106) constituting the fuel cell stack 100. 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.

  Bolts 22 extending in the vertical direction are inserted into the communication holes 108, and the fuel cell stack 100 is fastened by the bolts 22 and nuts 24 fitted on both sides of the bolts 22. 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 22 and the lower surface of the end plate 106 constituting the lower end of the fuel cell stack 100. However, in a place where a gas passage member 27 described later is provided, an insulating sheet disposed between the nut 24 and the surface of the end plate 106 on the upper and lower sides of the gas passage member 27 and the gas passage member 27, respectively. 26 is interposed. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder 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 fuel cell stack 100 is located near the midpoint of one side (the X-axis positive direction side of two sides parallel to the Y-axis) on the outer periphery around the Z-direction. The space formed by the bolt 22 (bolt 22A) and the communication hole 108 through which the bolt 22A is inserted is introduced with the oxidant gas OG from the outside of the fuel cell stack 100, and the oxidant gas OG is generated by each power generation. It functions as an oxidant gas introduction manifold 161 that is a gas flow path to be supplied to the unit 102, and is the midpoint of the side opposite to the side (X-axis negative direction side of two sides parallel to the Y-axis) The space formed by the bolts 22 (bolts 22B) located in the vicinity and the communication holes 108 through which the bolts 22B are inserted contains the oxidant off-gas OOG that is the gas discharged from the air chamber 166 of each power generation unit 102. Burning Functions as the oxidizing gas discharging manifold 162 for discharging to the outside of the cell stack 100. In the present 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 Y axis positive direction side of two sides parallel to the X axis) on the outer periphery of the fuel cell stack 100 around the Z direction The space formed by the bolt 22 (bolt 22D) positioned at the position and the communication hole 108 through which the bolt 22D is inserted is introduced with the fuel gas FG from the outside of the fuel cell stack 100, and the fuel gas FG is generated by each power generation. Bolt 22 that functions as a fuel gas introduction manifold 171 to be supplied to the unit 102 and is located in the vicinity of the midpoint of the opposite side (the side on the Y axis negative direction side of the two sides parallel to the X axis). The space formed by the (bolt 22E) and the communication hole 108 through which the bolt 22E is inserted is a fuel cell stack 1 that uses the fuel off-gas FOG that is a gas discharged from the fuel chamber 176 of each power generation unit 102 as the fuel cell stack 1 Functions as a fuel gas exhaust manifold 172 for discharging to the outside of the 0. In the present embodiment, as the fuel gas FG, for example, 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 part 29 communicates with the hole of the main body part 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 portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> A forming the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. The hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> B that forms 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 portion 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 the fuel gas The hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> E forming the discharge manifold 172 communicates with the fuel gas discharge manifold 172.

(Configuration of end plates 104 and 106)
The pair of end plates 104 and 106 are substantially rectangular flat plate-shaped conductive members, and are formed of, for example, stainless steel. One end plate 104 is disposed on the upper side of the power generation unit 102 located on the uppermost side, and the other end plate 106 is disposed on the lower side of the power generation unit 102 located on the lowermost side. 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.

(Configuration of power generation unit 102)
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 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 structure of the two electric power generation units.

  As shown in FIGS. 4 and 5, the power generation unit 102 that is the minimum unit of power generation includes a single cell 110, a separator 120, an air electrode side frame 130, an air electrode side current collector 134, and a fuel electrode side frame. 140, a fuel electrode side current collector 144, and a pair of interconnectors 150 constituting the uppermost layer and the lowermost layer of the power generation unit 102. The separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the periphery of the interconnector 150 around the Z direction are formed with holes corresponding to the communication holes 108 through which the bolts 22 are inserted.

  The interconnector 150 is a substantially rectangular flat plate-shaped conductive member, and is formed of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generation units 102 and prevents reaction gas from being mixed 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 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 the pair of end plates 104 and 106, the power generation unit 102 located at the top in the fuel cell stack 100 does not include 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 unit cell 110 includes an electrolyte layer 112, and an air electrode (cathode) 114 and a fuel electrode (anode) 116 that face each other in the vertical direction (the arrangement direction in which the power generation units 102 are arranged) with the electrolyte layer 112 interposed therebetween. The single cell 110 of the present embodiment is a fuel electrode-supported single cell that supports the electrolyte layer 112 and the air electrode 114 with the fuel electrode 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 oxide It is formed with solid oxides such as. The air electrode 114 is a substantially rectangular flat plate-shaped member, and is formed of, for example, a perovskite oxide (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), LNF (lanthanum nickel iron)). Has been. The configuration of the air electrode 114 will be described in detail later. The fuel electrode 116 is a substantially rectangular flat plate-like member, and is formed of, for example, Ni (nickel), cermet made of Ni and ceramic particles, Ni-based alloy, or the like. Thus, the single cell 110 (power generation unit 102) of the present embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte.

  The separator 120 is a frame-like member in which a substantially rectangular hole 121 penetrating in the vertical direction is formed near the center, and is made of, for example, metal. The peripheral part of the hole 121 in the separator 120 is opposed to the peripheral part of the surface of the electrolyte layer 112 on the air electrode 114 side. 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 brazing) disposed in the facing portion. The separator 120 divides 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 in the peripheral portion of the single cell 110. It is suppressed. The single cell 110 to which the separator 120 is bonded is also referred to as a single cell with a separator.

 The air electrode side frame 130 is a frame-like member in which a substantially rectangular hole 131 penetrating in the vertical direction is formed near the center, and is formed of an insulator such as mica, for example. The hole 131 of the air electrode side frame 130 forms an air chamber 166 that faces the air electrode 114. The air electrode side frame 130 is in contact with the peripheral edge portion of the surface of the separator 120 opposite to the side facing the electrolyte layer 112 and the peripheral edge portion of the surface of the interconnector 150 facing the air electrode 114. . The pair of interconnectors 150 included in the power generation unit 102 is electrically insulated by the air electrode side frame 130. The air electrode side frame 130 has an oxidant gas supply communication hole 132 communicating the oxidant gas introduction manifold 161 and the air chamber 166, and an oxidant gas communicating 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-like member in which a substantially rectangular hole 141 penetrating in the vertical direction is formed near the center, and is made of, for example, metal. The hole 141 of the fuel electrode side frame 140 forms a fuel chamber 176 that faces the fuel electrode 116. The fuel electrode side frame 140 is in contact with the peripheral portion of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral portion of the surface of the interconnector 150 facing the fuel electrode 116. Further, the fuel electrode side frame 140 has a fuel gas supply communication hole 142 that connects the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that connects the fuel chamber 176 and the fuel gas discharge manifold 172. And are formed.

  The fuel electrode side current collector 144 is disposed 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 that connects the electrode facing portion 145 and the interconnector facing portion 146. For example, nickel or a nickel alloy It is made of stainless steel or the like. The electrode facing portion 145 is in contact with the surface of the fuel electrode 116 on the side 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 electrode 116. In contact. However, as described above, since the lowermost power generation unit 102 in the fuel cell stack 100 does not include the lower interconnector 150, the interconnector facing portion 146 in the power generation unit 102 has a lower end plate. 106 is in contact. Since the fuel electrode side current collector 144 has such a configuration, the fuel electrode 116 and the interconnector 150 (or the end plate 106) are electrically connected. Note that a spacer 149 made of, for example, mica is disposed 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. The electrical connection with is maintained well.

  The air electrode side current collector 134 is disposed in the air chamber 166. The air electrode side current collector 134 is composed of a plurality of current collector elements 135 having a substantially quadrangular prism shape, 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 facing the air electrode 114. However, as described above, since the power generation unit 102 located at the top in the fuel cell stack 100 does not include the upper interconnector 150, the air electrode side current collector 134 in the power generation unit 102 includes the upper end plate. 104 is in contact. Since the air electrode side current collector 134 has such a configuration, the air electrode 114 and the interconnector 150 (or the end plate 104) are electrically connected. In the present embodiment, the air electrode side current collector 134 and the interconnector 150 are formed as an integral member. That is, a flat plate portion perpendicular to the vertical direction (Z-axis direction) of the integrated member functions as the interconnector 150 and is formed so as to protrude from the flat plate portion toward the air electrode 114. The current collector element 135 that is a plurality of convex portions functions as the air electrode side current collector 134. Moreover, the integral member of the air electrode side current collector 134 and the interconnector 150 may be covered with a conductive coat, and between the air electrode 114 and the air electrode side current collector 134, A conductive bonding layer to be bonded may be interposed.

A-2. Operation of the fuel cell stack 100:
As shown in FIGS. 2 and 4, the oxidant gas OG is supplied through a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161. Then, the oxidant gas OG is supplied to the oxidant gas introduction manifold 161 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28, and the oxidant 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 through a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. Then, the fuel gas FG is supplied to the fuel gas introduction manifold 171 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28, and the fuel gas supply communication of each power generation unit 102 from the fuel gas introduction manifold 171. The fuel chamber 176 is supplied 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 an electrochemical reaction between the oxidant gas OG and the fuel gas FG in the single cell 110. Is called. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to one interconnector 150 via the air electrode side current collector 134, and the fuel electrode 116 is connected via the fuel electrode side current collector 144. The other interconnector 150 is electrically connected. The plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, electrical energy generated in each power generation unit 102 is taken out from the end plates 104 and 106 that function as output terminals of the fuel cell stack 100. Since SOFC generates power at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the fuel cell stack 100 is heated by a heater (after the start-up until the high temperature can be maintained by the heat generated by the power generation. (Not shown).

  The oxidant off-gas OOG discharged from the air chamber 166 of each power generation unit 102 is discharged to the oxidant gas discharge manifold 162 via the oxidant gas discharge communication hole 133 as shown in FIGS. The fuel cell stack 100 is connected to the branch portion 29 via a gas pipe (not shown) 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 agent gas discharge manifold 162. Is discharged outside. 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 via the fuel gas discharge communication hole 143, and further to the fuel gas. The gas passage member 27 provided at the position of the discharge manifold 172 passes through the body portion 28 and the branch portion 29 and passes through a gas pipe (not shown) connected to the branch portion 29 to the outside of the fuel cell stack 100. Discharged.

A-3. Detailed configuration of the air electrode 114:
FIG. 6 is an explanatory diagram showing a detailed configuration of the air electrode 114. FIG. 6 shows an enlarged configuration of the P1 portion in FIG. As shown in FIG. 6, the air electrode 114 includes an active layer 410 and a current collecting layer 420. When the side of the electrolyte layer 112 (the lower side in FIG. 6) is defined as “one side” in the arrangement direction and the other side (the upper side in FIG. 6) is defined as the “other side” with respect to the air electrode 114 as a reference. The electric layer 420 is disposed on the other side (upper side) of the active layer 410.

  The active layer 410 is a layer that mainly functions as an ionization reaction field for oxygen contained in the oxidant gas OG. In the present embodiment, the active layer 410 includes a perovskite oxide and GDC (gadolinium-doped ceria) as an activating substance. The current collecting layer 420 is a layer mainly functioning as a field for collecting electricity obtained by the power generation reaction while diffusing the oxidant gas OG supplied from the air chamber 166. The current collecting layer 420 includes a perovskite oxide but does not include GDC. Note that the active layer 410 has a smaller particle size as a whole and is dense (that is, has a lower porosity) than the current collecting layer 420. The active layer 410 corresponds to the first layer in the claims, and the current collecting layer 420 corresponds to the second layer in the claims.

  The current collecting layer 420 includes an electrolyte side current collecting layer 421 and a current collector side current collecting layer 422 disposed on the other side (upper side) of the electrolyte side current collecting layer 421. In the present embodiment, the electrolyte side current collecting layer 421 is adjacent to the active layer 410, and the current collector side current collecting layer 422 is adjacent to the air electrode side current collector 134. As described above, the air electrode side current collector 134 is a plurality of convex portions formed so as to protrude toward the air electrode 114 in an integral member of the current collector element 135 and the interconnector 150. . Therefore, a part of the region on the upper surface of the current collector side current collector layer 422 is in contact with the air electrode side current collector 134, and the remaining part of the region is in contact with the air electrode side current collector 134 without being in contact with the air chamber. It faces 166.

Here, in the present embodiment, the current collecting layer 420 (the electrolyte side current collecting layer 421 and the current collector side current collecting layer 422) is configured to satisfy the following relationship V1 regarding the porosity. That is, in the present embodiment, the porosity of the current collector side current collecting layer 422 is higher than the porosity of the electrolyte side current collecting layer 421.
・ Relationship V1:
(Porosity of electrolyte-side current collecting layer 421) <(porosity of current-collecting side current collecting layer 422)

Moreover, in this embodiment, the current collection layer 420 is comprised so that the relationship W1-Y1 regarding the following particle sizes may be satisfy | filled. That is, in the present embodiment, the electrolyte-side current collection layer 421 and the current-collector side current collection layer 422 contain substantially the same fine particles (relationship W1), and the electrolyte-side current collection layer 421 is more current collector-side current collection layer 422. The particle size variation is larger (Relationship X1), and the electrolyte-side current collection layer 421 contains more particles having a relatively larger diameter than the current-collector-side current collection layer 422 (Relationship Y1).
・ Relationship W1:
(Particle diameter _{D 10} of the current collector side current collecting layer 422) × 0.5 ≦ (particle diameter _{D 10} of the electrolyte-side current collecting layer 421) ≦ (particle diameter _{D 10} of the current collector side current collecting layer 422) × 1. 5
・ Relationship X1:
(Particle diameter D _{90 of} electrolyte side current collecting layer 421) − (Particle diameter D _{10 of} electrolyte side current collecting layer 421)> (Particle diameter D ₉₀ of current collector side current collecting layer 422) − (Current collector side current collecting layer) 422 particle size D ₁₀ )
・ Relationship Y1:
(Particle diameter D _{85 of} electrolyte-side current collecting layer 421)> (Particle diameter D ₉₀ of current-collecting side current collecting layer 422)

7 and 8 are explanatory diagrams showing the characteristics of the particle size of the current collecting layer 420. FIG. FIG. 7 shows an example of the frequency distribution of the particle diameters of the electrolyte side current collecting layer 421 and the current collector side current collecting layer 422. Further, FIG. 8 shows an example of the cumulative distribution of particle diameters of the electrolyte side current collecting layer 421 and the current collector side current collecting layer 422. Note that “(1)” attached to the particle diameter D _{10 and the} like shown in FIG. 8 corresponds to the electrolyte side current collecting layer 421, and “(2)” corresponds to the current collector side current collecting layer 422. doing. For example, the particle diameter _D 10 (1) is a particle diameter _{D 10} of the electrolyte-side current collecting layer 421.

  As shown in FIGS. 7 and 8, the electrolyte side current collecting layer 421 and the current collector side current collecting layer 422 have substantially similar distribution characteristics in a region having a relatively small particle diameter, but the electrolyte side current collecting layer In 421, the frequency is higher in a region having a relatively large particle diameter. That is, the electrolyte side current collection layer 421 and the current collector side current collection layer 422 contain substantially the same fine particles, but the electrolyte side current collection layer 421 has a larger particle size variation than the current collector side current collection layer 422. Thus, the electrolyte-side current collecting layer 421 contains a large number of particles having a relatively large diameter as compared with the current collector-side current collecting layer 422. The above relationships W1 to Y1 show such characteristics.

As shown in FIG. 6, the current collecting layer 420 is equally divided into 100 regions along the vertical direction (Z-axis direction), and the five regions closest to the electrolyte layer 112 are defined as “first regions R1”. The five regions farthest from the electrolyte layer 112 are referred to as “second regions R2”. At this time, the boundary between the electrolyte side current collection layer 421 and the current collector side current collection layer 422 is not located in the first region R1 or the second region R2 (the first region R1 and the first region R1). 2 is located within a region sandwiched between two regions R2. As in the example of FIG. 6, the boundary between the electrolyte-side current collecting layer 421 and the current collector-side current collecting layer 422 is not located in the first region R1 or the second region R2, so that the first The region R1 is configured by the electrolyte side current collecting layer 421, and the second region R2 is configured by the current collector side current collecting layer 422. Therefore, it can be said that the first region R1 and the second region R2 of the current collecting layer 420 satisfy the following relationships V to Y regarding the porosity and the particle size. Here, the first region R1 corresponds to the first region in the claims, and the second region R2 corresponds to the second region in the claims.
・ Relationship V:
(Porosity of the first region R1) <(Porosity of the second region R2)
・ Relationship W:
(Particle diameter _{D 10} of the second region R2) × 0.5 ≦ (particle diameter _{D 10} of the first region R1) ≦ (particle diameter _{D 10} of the second region R2) × 1.5
・ Relationship X:
(Particle size D ₉₀ of first region R1) − (Particle size D ₁₀ of first region R1)> (Particle size D _{90 of} second region R2) − (Particle size D ₁₀ of second region R2) )
・ Relationship Y:
(Particle size D ₈₅ of first region R1)> (Particle size D ₉₀ of second region R2)

  Thus, in the present embodiment, in the current collecting layer 420, the porosity of the second region R2 disposed closer to the air chamber 166 through which the oxidant gas OG flows is higher than the porosity of the first region R1. Since it is high (Relationship V), it is possible to improve gas diffusibility in the air electrode 114 while suppressing a decrease in the structural strength of the air electrode 114.

  Further, as described above, a part of the upper surface of the air electrode 114 is in contact with the air electrode side current collector 134, and the air electrode 114 is in contact with the air electrode side current collector through the contact region. Stress is generated by receiving a pressing force from 134. In the present embodiment, since the porosity of the second region R2 disposed at a position closer to the air electrode side current collector 134 is relatively high (Relationship V), the hardness of the second region R2 is relatively low. Therefore, it is possible to suppress the stress from being dispersed by the second region R2 having a relatively low hardness and causing the air electrode 114 to crack.

  In the present embodiment, the first region R1 and the second region R2 contain substantially the same fine particles (Relationship W), and the second region R2 has a particle size variation more than the first region R1. Is small (Relationship X). In general, when the sintered body contains the same fine particles, the larger the particle size variation, the smaller the pores (voids) and the higher the hardness. On the contrary, the smaller the particle size variation, the smaller the pores (holes). Tend to be formed and the hardness tends to be low. Therefore, also from this point, since the hardness of the second region R2 is relatively low, the occurrence of cracks in the air electrode 114 is effectively suppressed.

  In the present embodiment, since the first region R1 has a relatively large particle size variation and particles having a relatively large diameter and particles having a relatively small diameter are mixed, the first region R1 and the first region R1 are active. The number of contact points at the interface with the layer 410 (that is, the interface between the current collecting layer 420 and the active layer 410) increases, so that the anchor effect increases, and the occurrence of peeling at this interface can be suppressed. In particular, since the first region R1 contains more particles having a relatively large diameter compared to the second region R2 (relationship Y), the anchor effect at the interface between the first region R1 and the active layer 410 is included. Becomes larger, and the occurrence of peeling at the interface can be more effectively suppressed.

Moreover, in this embodiment, the current collection layer 420 is comprised so that the relationship Z regarding the following layer thickness may be satisfy | filled. That is, in this embodiment, the thickness of the current collector side current collection layer 422 is greater than the thickness of the electrolyte side current collection layer 421 in the vertical direction (Z-axis direction) (see FIG. 6).
・ Relationship Z:
(Thickness of electrolyte side current collecting layer 421) <(thickness of current collector side current collecting layer 422)

  In this embodiment, since the thickness of the current collector layer 422 is larger than the thickness of the electrolyte current collector layer 421 (Relationship Z), the occurrence of peeling at the interface between the current collector layer 420 and the active layer 410 is suppressed. On the other hand, the collector-side current collecting layer 422 having a higher porosity can be made thicker, so that the gas diffusibility in the air electrode 114 can be further improved and the current-collecting side current collecting layer 422 having a lower hardness. Therefore, the occurrence of cracks in the air electrode 114 can be further effectively suppressed.

A-4. Manufacturing method of the single cell 110:
An example of the manufacturing method of the single cell 110 in this embodiment is as follows.

(Formation of laminated body of electrolyte layer 112 and fuel electrode 116)
For example, a butyral resin, dioctyl phthalate (DOP) as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added to a YSZ powder having a specific surface area of 5 to 7 m ² / g by the BET method. Then, a slurry is prepared by mixing with a ball mill. The obtained slurry is thinned by a doctor blade method to obtain a green sheet for an electrolyte layer having a thickness of about 10 μm, for example. Also, the NiO powder is the specific surface area, for example, 3 to 4 m ² / g by BET method, in terms of Ni by weight were weighed so as to be 55 parts by weight, 5 to 7 m is a BET specific surface area of for example ² / The mixed powder is obtained by mixing with 45 parts by mass of YSZ powder as g. To this mixed powder, a butyral resin, DOP as a plasticizer, a dispersant, and a mixed solvent of toluene and ethanol are added and mixed in a ball mill to prepare a slurry. The obtained slurry is thinned by a doctor blade method to obtain a fuel electrode green sheet having a thickness of, for example, 270 μm. An electrolyte layer green sheet and a fuel electrode green sheet are attached and dried. Thereafter, firing is performed at 1400 ° C., for example, to obtain a laminate of the electrolyte layer 112 and the fuel electrode 116.

(Formation of air electrode 114)
Next, LSCF powder, GDC powder, alumina powder, polyvinyl alcohol as an organic binder, and butyl carbitol as an organic solvent are mixed as materials for the active layer 410 of the air electrode 114 to adjust the viscosity. To prepare an active layer paste. The prepared paste for active layer is applied to the surface on the electrolyte layer 112 side in the laminate of the electrolyte layer 112 and the fuel electrode 116 by screen printing and dried.

  Further, as a material for the electrolyte-side current collecting layer 421 of the air electrode 114, LSCF powder, alumina powder, polyvinyl alcohol as an organic binder, and butyl carbitol as an organic solvent are mixed, and the viscosity is adjusted. An electrolyte side current collecting layer paste is prepared. The prepared electrolyte-side current collecting layer paste is applied onto the above-mentioned active layer paste by screen printing and dried.

  Furthermore, as a material of the current collector layer 422 of the air electrode 114, LSCF powder, alumina powder, polyvinyl alcohol as an organic binder, and butyl carbitol as an organic solvent are mixed to adjust the viscosity. A paste for the current collector layer is prepared. The adjusted current collector-side current collecting layer paste is applied onto the above-described electrolyte side current collecting layer paste by screen printing and dried. In addition, as a method for applying the paste for each layer of the air electrode 114, other methods such as spray application can be employed.

  Thereafter, for example, by firing at 1100 ° C., the active layer 410 and the current collecting layer 420 (the electrolyte side current collecting layer 421 and the current collecting layer 421 are collected on the surface on the electrolyte layer 112 side in the laminate of the electrolyte layer 112 and the fuel electrode 116. An air electrode 114 composed of the current collector layer 422) is formed.

In order to make the current collecting layer 420 of the air electrode 114 satisfy the above-described relationship V1 regarding the porosity, for example, the raw material powder of the current collector side current collecting layer 422 is burned off during firing such as resin beads or carbon powder. What is necessary is just to add comparatively much pore material which forms a pore. Further, in order for the current collecting layer 420 of the air electrode 114 to satisfy the above-mentioned relationships W1 to Y1 regarding the particle size, as the LSCF powder for the electrolyte side current collecting layer 421, for example, LSCF powder with D ₅₀ = 1 to 5 μm. using a mixture of LSCF powder _D 50 = 5 to 15 [mu] m at a ratio of 10 to 30 wt% to as LSCF powder for the current collector side current collecting layer 422, for example, by using the _D 50 = 1 to 5 [mu] m of LSCF powder Good. Further, in order to satisfy the above relationship Z relating to the layer thickness of the current collecting layer 420 of the air electrode 114, for example, the coating thickness of the collector side current collecting layer paste is changed to the coating thickness of the electrolyte side current collecting layer paste. It should be thicker.

  Through the above steps, the unit cell 110 having the above-described configuration is manufactured. In addition, after the single cell 110 is manufactured, for example, an assembly process such as joining of the air electrode 114 and the air electrode side current collector 134 and fastening of the fuel cell stack 100 by the bolt 22 is performed. The fuel cell stack 100 is manufactured.

A-5. Example:
According to the manufacturing method described above, an example of the single cell 110 was manufactured. FIG. 9 is an explanatory diagram showing characteristics of the electrolyte-side current collecting layer 421 and the current-collecting side current collecting layer 422 in the embodiment of the single cell 110. As shown in FIG. 9, in this embodiment, all of the above relationships V1 to Y1 are satisfied.

  Using the example of the single cell 110 shown in FIG. 9, the Vickers hardness (HV) of the electrolyte side current collecting layer 421 and the current collector side current collecting layer 422 was measured. FIG. 10 is an explanatory diagram showing measurement results of Vickers hardness. In the graph shown in FIG. 10, the measured values of Vickers hardness at a plurality of positions and the average value (AV) are plotted for each of the electrolyte-side current collecting layer 421 and the current-collecting side current collecting layer 422. . The average value of the Vickers hardness was 14 for the current collector layer 422 and 27 for the electrolyte current collector layer 421. As described above, if the electrolyte side current collector layer 421 and the current collector side current collector layer 422 are manufactured so as to satisfy the above-described relationships V1 to Y1, the hardness of the current collector side current collector layer 422 is the same as that of the electrolyte side current collector layer 421. Compared to hardness.

A-6. Analysis method of the air electrode 114:
(Acquisition method of analysis image M1)
A method for analyzing the air electrode 114 with respect to porosity, particle size, and the like will be described. First, the analysis image M1 used for the analysis of the air electrode 114 is acquired by the following method. In the single cell 110, one cross section (however, the cross section including the air electrode 114) parallel to the vertical direction (Z-axis direction) is arbitrarily set, and an image in which the entire vertical direction of the air electrode 114 can be confirmed in the cross section, Obtained as an analysis image M1. More specifically, the upper surface of the air electrode 114 (the surface in contact with the air electrode side current collector 134) is the uppermost of the ten divided regions obtained by dividing the image vertically into 10 equal parts. An image in which the boundary between the air electrode 114 and the electrolyte layer 112 is located in the lowest divided region is taken by, for example, a scanning electron microscope (SEM), and the analysis image M1 is located in the divided region. Get as. The analysis image M1 may be a binarized image obtained by binarizing an image photographed by the SEM. However, when the pores in the binarized image are significantly different from the actual form, the contrast of the image before binarization processing photographed by the SEM is adjusted, and the image after the binarization processing is adjusted. Good. In addition, the analysis image M1 may be an image before binarization processing that is taken by an SEM. The magnification of the SEM image is set to such a value that the whole of the air electrode 114 in the vertical direction fits in the analysis image M1 as described above, and can be set to 200 to 20,000 times, for example, but is not limited thereto. However, it can be changed as appropriate.

(Determination method of boundary between active layer 410 and current collecting layer 420)
The boundary between the active layer 410 and the current collecting layer 420 constituting the air electrode 114 is specified by the following method using the feature that the porosity of the active layer 410 is lower than the porosity of the current collecting layer 420. First, a plurality of virtual lines K perpendicular to the vertical direction (Z-axis direction) are drawn in order from the upper surface of the air electrode 114 at intervals of 0.3 μm with respect to the analysis image M1, and virtual lines K1, K2, K3,..., Km,..., K (m + 9), K (m + 10),. And the length of the part which overlaps with a pore in each virtual line K is measured, the sum total of the length of the part which overlaps with a pore is calculated, and the total length of the part which overlaps with the pore with respect to the full length of each virtual line K Is the ratio of the pores existing on the virtual line K (porosity Ks). Next, among the porosity Ks1, Ks2, Ks3,..., Ksm,..., Ks (m + 9), Ks (m + 10),. Each data group having the porosity Ks of each virtual line K is set, and the average value (Ave) of the 10 porosity Ks of each data group and the standard deviation (σ) of the porosity Ks of each data group are calculated. To do.

In order from the top, the data group G1 is composed of Ks1, Ks2,..., Ks10, the data group G2 is composed of Ks2, Ks3,..., Ks11, and the data group Gm is composed of Ksm, Ks (m + 1). ), Ks (m + 2),..., Ks (m + 9), and the data group G (m + 1) includes Ks (m + 1), Ks (m + 2),. That is, the data group G (m + 1) means nine porosity (Ks (m + 1),..., Ks) obtained by removing the porosity Ksm of the first virtual line Km of the data group Gm from the data group Gm. (M + 9)) is added to the porosity Ks (m + 10) of the virtual line K (m + 10) next to the last virtual line K (m + 9) of the data group, which means one group consisting of 10 porosity Ks. . The “average value of the porosity Ks of G (m + 1)” is a value obtained by adding a value twice the standard deviation (σ) of 10 porosity Ks of Gm to the average value of the porosity Ks of Gm. Or the average value of the porosity Ks of G (m + 1) is 2 of the standard deviation (σ) of 10 porosity Ks of Gm from the average value of the porosity Ks of Gm. The virtual line K (m + 10) corresponding to the tenth porosity Ks (m + 10) of the data group G (m + 1) when the value is lower than the “value obtained by subtracting the double value” for the first time is represented by the active layer 410 and the current collecting layer. It is set as a boundary with 420. That is, when the average value of the porosity Ks of the data group Gm is Gmave, the average value of the porosity Ks of the data group G (m + 1) is G (m + 1) Ave, and the standard deviation of the porosity Ks of the data group Gm is σm. The virtual line K (m + 10) corresponding to the tenth porosity Ks (m + 10) of the first data group G (m + 1) satisfying the following formula (1) is defined as the boundary between the active layer 410 and the current collecting layer 420. To do. If this boundary is determined, the active layer 410 and the current collecting layer 420 can be distinguished on the analysis image M1.
| (G (m + 1) Ave) − (GmAve) |> 2σm (1)

(Measuring method of particle size)
The frequency distribution and cumulative distribution of the particle size in the current collecting layer 420 of the air electrode 114 are as follows: "Mizutani Satoshi, Ozaki Yoshiharu, Kimura Toshio, Yamaguchi Satoshi," Ceramic Processing ", Gihodo Publishing Co., Ltd. , Pages 192 to 195 ”(intercept method). Specifically, in the analysis image M1, the current collecting layer 420 is orthogonal to the vertical direction (Z-axis direction). A plurality of straight lines to be drawn are drawn at predetermined intervals (for example, 4 μm intervals), and the length of the portion corresponding to each particle on each straight line is measured as the particle size. The particle size of each particle is measured, and the frequency distribution and cumulative distribution of the particle size shown in FIGS. 7 and 8 are created using the measured values.

(Measurement method of porosity)
The porosity of each member or region is specified by the following method. In the analysis image M1, a plurality of straight lines perpendicular to the vertical direction (Z-axis direction) are drawn at a predetermined interval (for example, 4 μm intervals), the length of the portion corresponding to the pores on each straight line is measured, and the porosity in the straight line is measured. The ratio of the total length of the portion corresponding to the pores to the length of the portion overlapping the target (for example, the electrolyte-side current collecting layer 421) is defined as the porosity on the straight line. Let the average value of the porosity in the 1 or several straight line drawn by the measuring object of porosity be the porosity of the said measuring object.

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

  In the above embodiment, the unit cell 110 has a substantially flat plate shape, but the present invention is a unit cell having another configuration, for example, a unit cell having a substantially elliptical column shape as described in JP-A-2008-59797, and The present invention can be similarly applied to a fuel cell stack including a plurality of such single cells. FIG. 11 is an explanatory diagram schematically showing a configuration of a fuel cell stack according to a modification. FIG. 11 shows a cross-sectional configuration of a part of the fuel cell stack (two single cells 1 and one current collector 20). However, the fuel cell stack includes more single cells 1 and current collectors 20. You may have. Moreover, FIG. 12 is explanatory drawing which shows roughly the structure of the single cell 1 which comprises the fuel cell stack in a modification. The fuel cell stack of the modification shown in FIGS. 11 and 12 has a configuration in which a plurality of single cells 1 are connected in series as in the above embodiment, but the configuration of each single cell 1 is different from that in the above embodiment. . In the description of the fuel cell stack of the modification shown in FIGS. 11 and 12, configurations, materials, and the like that are not particularly described are the same as those in the fuel cell stack 100 of the above-described embodiment.

  The fuel cell stack of the modification shown in FIGS. 11 and 12 includes a plurality of single cells 1 and a plurality of current collectors 20 arranged between the single cells 1. Each single cell 1 includes a support 10, a fuel electrode 2, an electrolyte layer 3, an air electrode 4, an interconnector 5, and an air electrode material layer 14. The support 10 is a columnar body having a substantially elliptical cross section, and is formed of a porous material. A plurality of fuel gas passages (fuel chambers) 16 extending in the extending direction of the columnar body are formed inside the support body 10. The fuel electrode 2 is provided so as to cover one of a pair of flat surfaces that are substantially parallel to each other and two curved surfaces that connect the ends of the flat surfaces among the side surfaces of the support 10. The electrolyte layer 3 is provided so as to cover the side surface of the fuel electrode 2 opposite to the support 10 side. The air electrode 4 is provided so as to cover a portion of the electrolyte layer 3 located on the flat surface of the support 10 out of the side surface opposite to the fuel electrode 2 side. The interconnector 5 is provided so as to contact a flat surface of the support 10 that is not covered with the fuel electrode 2. The air electrode material layer 14 is disposed on the surface of the interconnector 5 opposite to the support 10 side. The current collector 20 is bonded to the air electrode 4 of the single cell 1 by the bonding layer 25 and is bonded to the air electrode material layer 14 of another single cell 1 adjacent to the single cell 1 by the bonding layer 25. Yes. When the oxidizing gas is supplied to the outside of the air electrode 4 and the fuel gas is supplied to the fuel gas passage 16 of the support 10 and heated to a predetermined operating temperature, power generation is performed in the fuel cell stack.

  FIG. 13 is an explanatory diagram showing a detailed configuration of the current collector 20 and the air electrode 4 in the fuel cell stack of the modification shown in FIGS. 11 and 12. As shown in FIG. 11 and FIG. 13, in this modification, a protruding portion that protrudes toward the air electrode 4 in the current collector 20 is in contact with the surface of the air electrode 4 via a bonding layer 25. Therefore, stress is generated in the air electrode 4 by receiving a pressing force from the current collector 20 through the contact portion.

  As shown in FIG. 13, in this modification, the air electrode 4 includes an active layer 41 and a current collecting layer 42 as in the above embodiment. The current collecting layer 42 includes an electrolyte side current collecting layer 45 and a current collector side current collecting layer 46. Further, the electrolyte side current collecting layer 45 and the current collector side current collecting layer 46 are the above relations V1 to W1 and Z that are satisfied by the electrolyte side current collecting layer 421 and the current collector side current collecting layer 422 in the above embodiment. Satisfy similar relationships. Therefore, also in this modification, the current collecting layer 42 is arranged in 10 regions along the arrangement direction of the unit cells 1 (the vertical direction in FIG. 13 and corresponds to the first direction in the claims). When the three regions closest to the electrolyte layer 3 are defined as “first regions” and the three regions farthest from the electrolyte layer 3 are defined as “second regions”, the first region and the second region This region satisfies the same relationship as the above relationships V to W. Therefore, also in this modified example, the gas diffusibility in the air electrode 4 can be improved while suppressing the decrease in the structural strength of the air electrode 4, and the occurrence of cracks in the air electrode 4 can be suppressed. Furthermore, the occurrence of peeling at the interface between the current collecting layer 42 and the active layer 41 can be suppressed.

  In the above embodiment (or a modified example, the same applies hereinafter), the current collection layer 420 of the air electrode 114 is configured to satisfy the above relationships V to Z. However, the current collection layer 420 is at least the above relationship. If it is configured so as to satisfy V to X, it is possible to improve gas diffusibility in the air electrode 114, suppress the occurrence of cracks in the air electrode 114, and further, an active layer of the air electrode 114. Occurrence of peeling at the interface between 410 and current collecting layer 420 can be suppressed.

  Further, in the above embodiment, the current collecting layer 420 of the air electrode 114 has a two-layer configuration of the electrolyte side current collecting layer 421 and the current collector side current collecting layer 422, but the current collecting layer 420 is the electrolyte side current collecting layer. A layer other than the current layer 421 and the current collector layer 422 may be included. In the above embodiment, the active layer 410 of the air electrode 114 has a single-layer structure, but the active layer 410 may be composed of a plurality of layers.

  In the above embodiment, the number of unit cells 110 included in the fuel cell stack 100 is merely an example, and the number of unit cells 110 is appropriately determined according to the output voltage required for the fuel cell stack 100 or the like. Moreover, the material which forms each member in the said embodiment is an illustration to the last, and each member may be formed with another material.

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

  In the above-described embodiment, all the single cells 110 included in the fuel cell stack 100 are configured to satisfy the relationships V to Z. However, at least one single cell 110 included in the fuel cell stack 100 is used. As for the single cell 110, the gas diffusibility in the air electrode 114 can be improved and the occurrence of cracks in the air electrode 114 can be suppressed. Generation of peeling at the interface between the layer 420 and the active layer 410 can be suppressed.

  In the above embodiment, the SOFC that generates electricity using the electrochemical reaction between hydrogen contained in the fuel gas and oxygen contained in the oxidant gas is targeted. The present invention can be similarly applied to an electrolytic cell which is a minimum unit of a solid oxide electrolytic cell (SOEC) that generates hydrogen by using hydrogen, and an electrolytic cell stack including a plurality of electrolytic cells. The configuration of the electrolytic cell stack is well known as described in, for example, Japanese Patent Application Laid-Open No. 2014-207120, and thus will not be described in detail here. It is a configuration. That is, the fuel cell stack 100 in the above-described embodiment may be read as an electrolytic cell stack, the power generation unit 102 may be read as an electrolytic cell unit, and the single cell 110 may be read as an electrolytic cell. However, when the electrolysis cell stack is operated, a voltage is applied between the two electrodes so that the air electrode 114 is positive (anode) and the fuel electrode 116 is negative (cathode). Water vapor as a source gas is supplied. As a result, an electrolysis reaction of water occurs in each electrolysis cell unit, hydrogen gas is generated in the fuel chamber 176, and hydrogen is taken out of the electrolysis cell stack through the communication hole. Also in the electrolytic cell and the electrolytic cell stack having such a configuration, the gas diffusibility in the air electrode 114 can be improved if the above relationships V to Z are satisfied, as in the above embodiment. At the same time, the occurrence of cracks in the air electrode 114 can be suppressed, and further, the occurrence of peeling at the interface between the current collecting layer 420 and the active layer 410 can be suppressed.

  In the above embodiment, the air electrode 114 is configured to include the active layer 410 and the current collecting layer 420 including the electrolyte side current collecting layer 421 and the current collector side current collecting layer 422. In place of the electrode 114 or together with the air electrode 114, the fuel electrode 116 includes an active layer, an electrolyte-side current collecting layer, and a current collector-side current collecting layer, similarly to the structure of the air electrode 114 described above. It is good also as a structure containing a layer. At this time, the current collecting layer of the fuel electrode 116 may be configured to satisfy the above relations V to Z in the same manner as the current collecting layer 420 of the air electrode 114 described above. In this way, gas diffusibility in the fuel electrode 116 can be improved, cracking of the fuel electrode 116 can be suppressed, and the interface between the active layer and the current collecting layer of the fuel electrode 116 can be suppressed. Generation | occurrence | production of peeling in can be suppressed.

 In the above embodiment, the solid oxide fuel cell (SOFC) has been described as an example. However, the present invention is applicable to other types of fuel cells (or electrolytic cells) such as a molten carbonate fuel cell (MCFC). Applicable. The present invention is more suitable for a fuel cell of a type in which gas temperature such as SOFC or MCFC becomes relatively high and cell cracking or delamination tends to be a problem.

1: single cell 2: fuel electrode 3: electrolyte layer 4: air electrode 5: interconnector 10: support 14: air electrode material layer 16: fuel gas passage 20: current collector 22: bolt 24: nut 25: bonding layer 26: Insulating sheet 27: Gas passage member 28: Body portion 29: Branching portion 41: Active layer 42: Current collecting layer 45: Electrolyte side current collecting layer 46: Current collector side current collecting layer 100: Fuel cell stack 102: Power generation unit 104: End plate 106: End plate 108: Communication hole 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 121: Hole 124: Joint part 130: Air electrode side frame 131: Hole 132: Oxidation Agent gas supply communication hole 133: Oxidant gas discharge communication hole 134: Air electrode side current collector 135: Current collector element 140: Fuel electrode side frame 141: Hole 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144: Fuel electrode side current collector 145: Electrode facing portion 146: Interconnector facing portion 147: Connecting portion 149: Spacer 150: Inter Connector 161: Oxidant gas introduction manifold 162: Oxidant gas discharge manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber 410: Active layer 420: Current collection layer 421: Electrolyte side current collection Layer 422: current collector side current collector layer

Claims (6)

An electrolyte layer;
In an electrochemical reaction single cell comprising an air electrode and a fuel electrode facing each other in a first direction across the electrolyte layer,
At least one of the air electrode and the fuel electrode is
A first layer;
With respect to the air electrode or the fuel electrode, when the electrolyte layer side is one side of the first direction and the opposite side of the one side is the other side, the other side of the first layer is A second layer disposed;
Including
In the second layer, the first region on one side and the second region on the other side satisfy the following relations V, W, and X.
Relationship V: (Porosity of the first region) <(Porosity of the second region)
Relationship W :( the particle diameter _{D 10} of the second region) × 0.5 ≦ (particle diameter _{D 10} of the first particle diameter _{D 10} of the region) ≦ (the second region) × 1.5
Relationship X: (Particle size D _{90 in} the first region) − (Particle size D _{10 in} the first region)> (Particle size D _{90 in} the second region) − (Particles in the second region) diameter _{D 10)} The electrochemical reaction single cell according to claim 1,
An electrochemical reaction single cell satisfying the relationship Y: (particle diameter D _{85 in} the first region)> (particle diameter D _{90 in} the second region). The electrochemical reaction single cell according to claim 1 or 2,
The second layer is
A layer comprising the first region;
A layer comprising the second region;
Including
Satisfying the relationship Z: (thickness of the layer including the first region in the first direction) <(thickness of the layer including the second region in the first direction) Electrochemical reaction single cell. In the electrochemical reaction single cell as described in any one of Claim 1- Claim 3,
The electrochemical reaction single cell is an electrochemical reaction single cell in which the electrolyte contained in the electrolyte layer is a solid oxide or carbonate electrochemical reaction single cell. In an electrochemical reaction cell stack comprising a plurality of electrochemical reaction single cells,
5. The electrochemical reaction cell stack according to claim 1, wherein at least one of the plurality of electrochemical reaction single cells is the electrochemical reaction single cell according to claim 1. The electrochemical reaction cell stack according to claim 5,
Each of the plurality of electrochemical reaction single cells is a fuel cell single cell that generates electric power.

Images