JP2019139894A - Conductive member, electrochemical reaction unit and electrochemical reaction cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve oxidation resistance of a conductive member as a whole. A conductive member includes a base having a first surface, and a conductive base including a protrusion protruding from the first surface of the base, and at least the base. And a conductive coat that covers the first surface of the section and the protrusion. The coat contains oxygen, manganese, and cobalt, and the manganese concentration (atm %) in the component elements other than oxygen among the component elements of the coat and the cobalt concentration in the component element other than oxygen among the component elements of the coat. The total of (atm%) is 90 atm% or more. In addition, the cobalt concentration in the first coat portion that covers the first surface of the base portion of the coat is higher than the cobalt concentration in the second coat portion that covers the tip of the protrusion in the protruding direction of the coat. [Selection diagram] Figure 2

Description

  The technology disclosed in this specification relates to a conductive member.

  A solid oxide fuel cell (hereinafter referred to as “SOFC”) is known as one type of fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen. A fuel cell power generation unit (hereinafter referred to as “power generation unit”), which is a constituent unit of SOFC, includes a fuel cell single cell (hereinafter referred to as “single cell”) and a conductive current collecting member. The single cell includes an electrolyte layer, and an air electrode and a fuel electrode facing each other in a predetermined direction with the electrolyte layer interposed therebetween. The current collecting member is electrically connected to an air electrode or a fuel electrode constituting the single cell.

  Generally, a current collecting member disposed on the air electrode side of a single cell includes a conductive base material and a conductive coat. The base material includes a base portion and a protruding portion that protrudes from the surface of the base portion toward the air electrode. The conductive coat covers the surface of the base portion and the protruding portion. The leading end portion of the protruding portion of the base material in the protruding direction is bonded to the air electrode of the single cell through the coat and, for example, the bonding portion. Moreover, the surface of the base part of a base material is arrange | positioned so that it may space apart from an air electrode, and is exposed to the air chamber which faces an air electrode. As a material for forming a coat, an oxide composed of manganese (Mn) and cobalt (Co), which are materials having high conductivity at high temperatures (for example, manganese concentration (atm%) in component elements excluding oxygen among coat component elements) And a coat having a total of 90 atm% or more of the cobalt concentration (atm%) in the component elements excluding oxygen among the coat component elements.

International Publication No. 2016/152924

  However, a coating composed of manganese and cobalt (for example, manganese concentration (atm%) in a component element excluding oxygen among the coat component elements) and cobalt concentration (atm%) in a component element excluding oxygen among the coat component elements, In the case of a coat having a total of 90 atm% or more, the higher the manganese concentration (atm%) in the coat, the lower the oxygen permeability of the coat. As a result, the surface of the base portion exposed to the air chamber is more prone to permeate the coat on the surface of the base portion exposed to the air chamber than the protruding portion that is not exposed to the air chamber by being in contact with the joint portion. There arises a problem that it becomes impossible to suppress the oxidation of.

  Such a problem is that an electrolytic cell unit which is a constituent unit of a solid oxide electrolytic cell (hereinafter also referred to as “SOEC”) in which hydrogen and oxygen are generated using an electrolysis reaction of water. This is a problem common to the current collecting members. In the present specification, the fuel cell power generation unit and the electrolysis cell unit are collectively referred to as an electrochemical reaction unit. Such a problem is not limited to SOFC and SOEC, but is common to other types of electrochemical reaction units. In addition, such a problem is not limited to the current collecting member constituting the electrochemical reaction unit, but includes a base portion having a first surface and a protruding portion protruding from the first surface of the base portion. It is a common problem in general for conductive members including a conductive base material and a conductive coat covering at least the first surface of the base portion and the protruding portion of the base material.

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

  The technology disclosed in this specification can be implemented as the following forms.

(1) The conductive member disclosed in the present specification includes a base portion having a first surface, and a conductive base material including a protruding portion protruding from the first surface of the base portion, Among the base materials, in a conductive member comprising at least a conductive coat that covers the first surface of the base portion and the protruding portion, the coat includes oxygen, manganese, and cobalt. The total of the manganese concentration (atm%) in the component elements excluding oxygen in the component elements of the coat and the cobalt concentration (atm%) in the component elements excluding oxygen in the component elements of the coat is 90 atm. And the cobalt concentration in the first coat portion that covers the first surface of the base portion of the coat is the second that covers the tip portion of the protrusion in the protruding direction of the coat. of Higher than the concentration of cobalt in the over preparative portion. In this conductive member, the cobalt concentration in the first coat portion that covers the first surface of the base portion of the base material in the coat is the second coat portion that covers the tip portion in the protruding direction of the protruding portion of the base material. Higher than the cobalt concentration. That is, the oxygen permeability of the first coat, which is relatively easily exposed to air, is higher than the oxygen permeability of the second coat, which is relatively difficult to be exposed to air. Thereby, the oxidation resistance as the whole electroconductive member can be improved.

(2) In the conductive member, the cobalt concentration in a third coat portion that covers a side surface portion of the coat that is located between the tip portion and the base portion of the protrusion portion may be It is good also as a structure which is lower than the said cobalt concentration in 1 coat part, and higher than the said cobalt concentration in a said 2nd coat part. According to this conductive member, the cobalt concentration in the third coat portion covering the side surface portion of the protruding portion is the same as the cobalt concentration in either the first coat portion or the second coat portion. It is possible to suppress the occurrence of cracks due to the difference in thermal expansion coefficient in the coat.

(3) In the conductive member, the cobalt concentration of the second coat portion may be 45 atm% or more and 70 atm% or less. According to this conductive member, the oxidation resistance is improved as compared with the configuration in which the cobalt concentration in the second coat portion is less than 45 atm% and the configuration in which the cobalt concentration in the second coat portion is higher than 70 atm%. High electrical conductivity can be maintained.

(4) In the conductive member, a difference between the cobalt concentration in the first coat portion and the cobalt concentration in the second coat portion may be 2 atm% or more. According to this conductive member, compared with the configuration in which the difference between the cobalt concentration in the first coat portion and the cobalt concentration in the second coat portion is less than 2 atm%, the oxidation resistance is improved more reliably and the conductivity is improved. Compatibility with the maintenance of sex.

  The technology disclosed in the present specification can be realized in various forms, and includes, for example, a current collecting member-fuel cell single cell complex, a fuel cell power generation unit, and a plurality of fuel cell power generation units. FUEL CELL STACK, POWER GENERATION MODULE WITH FUEL CELL STACK, FUEL CELL SYSTEM WITH POWER GENERATION MODULE, COLLECTING MEMBER-ELECTROLYTIC CELL COMPOSITE, ELECTROLYTIC CELL UNIT, ELECTROLYTIC CELL STACK WITH A plurality of electrolytic cell units It can be realized in the form of a generation module, a hydrogen generation system including a hydrogen generation module, or the like.

1 is a perspective view showing an external configuration of a fuel cell stack 100 in an embodiment. It is explanatory drawing (XZ sectional drawing) which shows the structure of the electric power generation unit 102 roughly. It is explanatory drawing (YZ sectional drawing) which shows the structure of the electric power generation unit 102 roughly. It is explanatory drawing (XY sectional drawing) which shows the structure of the electric power generation unit 102 roughly. It is explanatory drawing (XY sectional drawing) which shows the structure of the electric power generation unit 102 roughly. It is explanatory drawing which shows a performance evaluation result. It is explanatory drawing which expands and shows the oxidation state of a part in current collection member.

A. Embodiment:
A-1. Constitution:
(Configuration of fuel cell stack 100)
FIG. 1 is an external perspective view schematically showing a configuration of a fuel cell stack 100 in the present embodiment. FIG. 1 shows XYZ axes orthogonal to each other for specifying the direction. In this specification, for 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. However, the fuel cell stack 100 is installed in a direction different from such a direction. Also good. The same applies to FIG.

  The fuel cell stack 100 is arranged such that a plurality (seven in this embodiment) of power generation units 102 arranged in a predetermined arrangement direction (vertical direction in the present embodiment) and the seven power generation units 102 are sandwiched from above and below. And a pair of end plates 104 and 106. The number of power generation units 102 included in the fuel cell stack 100 shown in FIG. 1 is merely an example, and the number of power generation units 102 is appropriately determined according to the output voltage required for the fuel cell stack 100 or the like. The arrangement direction (vertical direction) corresponds to the first direction in the claims.

  A plurality of (eight in this embodiment) through-holes 108 extending in the vertical direction from the upper end plate 104 to the lower end plate 106 are formed in the peripheral portion around the Z direction of the fuel cell stack 100. The layers constituting the fuel cell stack 100 are fastened and fixed by bolts 22 inserted into the through holes 108 and nuts 24 fitted to the bolts 22.

  The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each through 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 through hole 108. Bolt 22 (bolt 22A) and through-hole located near the midpoint of one side (the two sides parallel to the Y-axis on the X-axis positive direction side) on the outer periphery around the Z-direction of the fuel cell stack 100 108, the oxidant gas OG is introduced from the outside of the fuel cell stack 100, and functions as an oxidant gas introduction manifold 161 that is a gas flow path for supplying the oxidant gas OG to each power generation unit 102. And a bolt 22 (bolt 22B) located near the midpoint of the opposite side (the side on the negative X-axis side of the two sides parallel to the Y-axis) and the through hole 108. The space functions as an oxidant gas discharge manifold 162 that discharges the oxidant off-gas OOG, which is a gas discharged from the air chamber 166 of each power generation unit 102, to the outside of the fuel cell stack 100 (FIG. Reference). Also, a bolt 22 (bolt 22D) located near the midpoint of the other side (the side on the Y-axis positive direction side of the two sides parallel to the X-axis) on the outer periphery around the Z-direction of the fuel cell stack 100; The space formed by the through hole 108 functions as a fuel gas introduction manifold 171 to which the fuel gas FG is introduced from the outside of the fuel cell stack 100 and supplies the fuel gas FG to each power generation unit 102, opposite to the side. The space formed by the bolt 22 (bolt 22E) and the through hole 108 located near the midpoint of the side edge (the Y-axis negative direction side of the two sides parallel to the X-axis) It functions as a fuel gas discharge manifold 172 that discharges the fuel off-gas FOG that is the gas discharged from the fuel chamber 176 of the unit 102 to the outside of the fuel cell stack 100 (see FIG. 3). In the present embodiment, for example, air is used as the oxidant gas OG, and hydrogen-rich gas obtained by reforming, for example, city gas is used as the fuel gas FG.

(Configuration of end plates 104 and 106)
The pair of end plates 104 and 106 are conductive, are substantially rectangular flat plate-like members, and are made 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)
2 to 5 are explanatory diagrams schematically showing the configuration of the power generation unit 102. FIG. 2 shows a cross-sectional configuration of the power generation unit 102 at the position II-II in FIGS. 1, 4 and 5, and FIG. 3 shows the position at III-III in FIGS. 1, 4 and 5. 4 shows a cross-sectional configuration of the power generation unit 102, FIG. 4 shows a cross-sectional configuration of the power generation unit 102 at the position IV-IV in FIG. 2, and FIG. 5 shows a position at VV in FIG. The cross-sectional structure of the power generation unit 102 in FIG.

  As shown in FIGS. 2 and 3, 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 interconnector 150 are formed with holes corresponding to the above-described through holes 108 into which the bolts 22 are inserted.

  The interconnector 150 is a substantially rectangular flat plate member having conductivity, 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.

  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 and contains at least Zr. For example, solid oxide such as YSZ (yttria stabilized zirconia), ScSZ (scandia stabilized zirconia), CaSZ (calcia stabilized zirconia), and the like. It is formed by things. 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 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.

  As shown in FIGS. 2 to 4, 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. For example, the air electrode side frame 130 is formed of an insulator such as mica. Has been. 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.

  As shown in FIGS. 2, 3 and 5, 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 formed of, for example, metal. ing. 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.

  As shown in FIGS. 2, 3, and 5, 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, a plurality of electrode facing portions 145, and a connecting portion 147 that connects each electrode facing portion 145 and the interconnector facing portion 146. Or nickel alloy, stainless steel or the like. Specifically, the fuel electrode side current collector 144 is manufactured by cutting a square flat plate member and bending a plurality of square portions. The bent rectangular portion becomes the electrode facing portion 145, the perforated flat plate portion other than the bent raised portion becomes the interconnector facing portion 146, and the portion connecting the electrode facing portion 145 and the interconnector facing portion 146 is connected. Part 147. In addition, in the partial enlarged view in FIG. 5, in order to show the manufacturing method of the fuel electrode side collector 144, the state before the bending raising process of a part of several square part is shown. 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.

  As shown in FIGS. 2 to 4, 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 substantially square columnar current collector elements 135, and is formed of a metal containing Cr (chromium) such as ferritic stainless steel, for example. Here, the surface of the interconnector 150 on the side facing the air electrode 114 is referred to as an air chamber-side surface 152 of the interconnector 150. The plurality of current collector elements 135 are formed to protrude from the air chamber side surface 152 while being spaced apart from each other in a plane direction (X direction, Y direction) perpendicular to the vertical direction (Z direction). Hereinafter, the tip of the air electrode side current collector 134 in the protruding direction toward the air electrode 114 will be referred to as the front end portion 135B of the air electrode side current collector 134. Further, among the air electrode side current collector 134, a side surface portion connecting the tip end portion 135 </ b> B and the air chamber side surface 152 of the interconnector 150 is referred to as a side surface portion 135 </ b> C of the air electrode side current collector 134. The tip portion 135B of the air electrode side current collector 134 is in contact with the surface of the air electrode 114 on the side opposite to the side facing the electrolyte layer 112. In the present embodiment, the interconnector 150 corresponds to the base portion in the claims, and the air chamber side surface 152 corresponds to the first surface in the claims. The air electrode side current collector 134 corresponds to a protruding portion in the claims, and the interconnector 150 and the air electrode side current collector 134 correspond to a base material in the claims. 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 this case, the upper end plate 104 corresponds to the base portion in the claims, and the surface of the upper end plate 104 facing the air electrode 114 corresponds to the first surface in the claims. . The upper end plate 104 and the air electrode side current collector 134 correspond to the base material in the claims. The air electrode side current collector 134 and the interconnector 150 may be formed as an integral member.

As shown in FIGS. 2 and 3, the surface of the air electrode side current collector 134 (the surface of the tip portion 135B and the side surface portion 135C) and the air chamber side surface 152 of the interconnector 150 (the air electrode in the upper end plate 104). 114 is covered with a conductive coat 136. The coat 136 contains oxygen (O), manganese (Mn), and cobalt (Co). More specifically, the coat 136 is made of a spinel oxide (eg, Mn _1.5 Co _1.5 O ₄ , MnCo ₂ O ₄ ) containing manganese and cobalt. The coating 136 is formed on the surface of the air electrode side current collector 134 by a known method such as spray coating, ink jet printing, spin coating, dip coating, plating, sputtering, or thermal spraying. Note that a chromium oxide film may be formed by heat treatment on the air electrode side current collector 134. In this case, the coat 136 is not the film but the air electrode side current collector 134 on which the film is formed. It is the layer formed so that it might cover. In the following description, unless otherwise specified, the air electrode side current collector 134 (or current collector element 135) means “the air electrode side current collector 134 (or current collector element 135) covered with the coat 136”. To do. The air electrode side current collector 134 and the interconnector 150 (upper end plate 104) covered with the coat 136 correspond to conductive members in the claims, and are hereinafter referred to as “current collector member 200”. The detailed configuration of the coat 136 will be described later.

The air electrode 114 and the air electrode side current collector 134 are joined by a conductive joining layer 138. The bonding layer 138 includes a spinel oxide containing at least one of Zn (zinc), Mn, Co, and Cu (copper) (for example, Mn _1.5 Co _1.5 O ₄ , MnCo ₂ O ₄ , ZnCo _2). O ₄ , ZnMnCoO ₄ , CuMn ₂ O ₄ ). In the bonding layer (bonding portion) 138, for example, the bonding layer paste is printed on a portion of the surface of the air electrode 114 facing the tip of each current collector element 135 constituting the air electrode side current collector 134. Then, the current collector element 135 is formed by firing under a predetermined condition in a state where the tip portion of the current collector element 135 is pressed against the paste. The air electrode 114 and the air electrode side current collector 134 are electrically connected by the bonding layer 138. As described above, it is described that the air electrode side current collector 134 is in contact with the surface of the air electrode 114. To be precise, the air electrode side current collector 134 (covered by the coat 136), the air electrode 114, A bonding layer 138 is interposed therebetween.

A-2. Power generation operation in the fuel cell stack 100:
As shown in FIG. 2, when the oxidant gas OG is supplied to the oxidant gas introduction manifold 161, the oxidant gas OG passes through the oxidant gas supply communication holes 132 of the power generation units 102 from the oxidant gas introduction manifold 161. Then, the air is supplied to the air chamber 166. As shown in FIG. 3, when the fuel gas FG is supplied to the fuel gas introduction manifold 171, the fuel gas FG passes through the fuel gas supply communication hole 142 of each power generation unit 102 from the fuel gas introduction manifold 171 to the fuel gas FG. Supplied to chamber 176.

  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. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to one interconnector 150 through the air electrode side current collector 134 (and the coat 136, the bonding layer 138), and the fuel electrode 116 is a fuel. It is electrically connected to the other interconnector 150 via the pole side current collector 144. A plurality of power generation units 102 included in the fuel cell stack 100 are 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 to 1000 degrees Celsius), the fuel cell stack 100 is a heater until the high temperature can be maintained by the heat generated by power generation after startup. May be heated.

  The oxidant off-gas OOG (oxidant gas not used for the power generation reaction in each power generation unit 102) passes through the oxidant gas discharge communication hole 133 and the oxidant gas discharge manifold 162 from the air chamber 166 as shown in FIG. The fuel cell stack 100 is discharged outside. Further, as shown in FIG. 3, the fuel off-gas FOG (fuel gas not used for the power generation reaction in each power generation unit 102) passes through the fuel gas discharge communication hole 143 and the fuel gas discharge manifold 172 from the fuel chamber 176. It is discharged outside the battery stack 100.

A-3. Detailed configuration of the coat 136:
As described above, the coat 136 of the current collecting member 200 is formed of a spinel oxide containing manganese and cobalt. Further, the sum of the manganese concentration and the cobalt concentration in the coat 136 is 90 atm% or more. The manganese concentration means the atomic ratio (atm%) of manganese in the component elements excluding oxygen among the component elements of the coat 136. The cobalt concentration means the atomic ratio (atm%) of cobalt in the component elements excluding oxygen among the component elements of the coat 136. For example, when the coat 136 is formed of Mn _1.5 Co _1.5 O ₄ , the component elements excluding oxygen among the component elements of the coat 136 are manganese and cobalt.

  Further, as shown in FIGS. 2 and 3, the coat 136 includes a base coat portion 136A, a tip coat portion 136B, and a side surface coat portion 136C. The base coat portion 136A covers the entire surface of the air chamber-side surface 152 of the interconnector 150 (the surface on the side facing the air electrode 114 in the upper end plate 104). The tip coating portion 136B covers the entire surface of the tip portion 135B of the current collector element 135. The side coat part 136C covers the entire side part 135C of the current collector element 135. The base coat portion 136 </ b> A and the side surface coat portion 136 </ b> C are exposed to the air chamber 166, while the tip coat portion 136 </ b> B is not exposed to the air chamber 166. For this reason, the base coat portion 136A and the side surface coat portion 136C are required to have higher oxygen permeation resistance than the tip coat portion 136B. On the other hand, the tip coat portion 136B is joined to the air electrode 114 via the joining layer 138, whereas the base coat portion 136A and the side coat portion 136C are not joined to the air electrode 114 and are separated from each other. Yes. For this reason, the tip coat portion 136B is required to have higher conductivity than the base coat portion 136A and the side coat portion 136C. The base coat portion 136A corresponds to the first coat portion in the claims, the tip coat portion 136B corresponds to the second coat portion in the claims, and the side coat portion 136C in the claims. This corresponds to the third coat portion.

Here, the coat 136 satisfies at least the following first requirement with respect to the cobalt concentration.
<First requirement>
“Cobalt concentration in base coat portion 136A”> “Cobalt concentration in tip coat portion 136B”
The coat 136 further preferably satisfies the following first requirement A with respect to the manganese concentration.
<First requirement A>
“Manganese concentration in base coat portion 136A” <“Manganese concentration in tip coat portion 136B”

Furthermore, the coat 136 preferably satisfies the following second requirement regarding the cobalt concentration.
<Second requirement>
“Cobalt concentration in base coat portion 136A”> “Cobalt concentration in side coat portion 136C”> “Cobalt concentration in tip coat portion 136B”
The coat 136 preferably further satisfies the following second requirement A with respect to the manganese concentration.
<Second requirement A>
“Manganese concentration in base coat portion 136A” <“Manganese concentration in side coat portion 136C” <“Manganese concentration in tip coat portion 136B”

Furthermore, the coat 136 preferably satisfies the following third requirement with respect to the cobalt concentration in the tip coat portion 136B.
<Third requirement>
45 atm% ≦ “Cobalt concentration in tip coating portion 136B” ≦ 70 atm%
It is more preferable that 50 atm% ≦ “cobalt concentration in the tip coat portion 136B” ≦ 67 atm%.

Furthermore, the coat 136 preferably satisfies the following fourth requirement regarding the cobalt concentration in the base coat portion 136A and the tip coat portion 136B.
<Fourth requirement>
“Cobalt concentration in base coat portion 136A” − “Cobalt concentration in tip coat portion 136B” ≧ 2 atm%
It is more preferable that “cobalt concentration in base coat portion 136A” − “cobalt concentration in tip coat portion 136B” ≧ 5 atm%.

  In addition, as an example of the manufacturing method of the current collection member 200 including the coat 136 that satisfies the first to fourth requirements, there is the following method. That is, for example, the surface (the air chamber side surface 152 of the interconnector 150, the tip of the air electrode side current collector 134) disposed on the air chamber 166 side of the base material composed of the interconnector 150 and the air electrode side current collector 134, for example. An alloy layer of manganese and cobalt is formed on the part 135B and the side part 135C) by plating. Next, manganese is apply | coated only to the alloy layer part formed in the front-end | tip part 135B of the air electrode side collector 134 among the base materials after plating. Next, heat treatment at about 950 ° C. is performed on the base material after plating and manganese application in an air atmosphere. Thereby, the current collection member 200 including the coat 136 satisfying at least the first requirement can be manufactured. In addition, when applying manganese, the coat 136 that satisfies the second requirement is further applied to the side surface portion 135C of the air electrode side current collector 134 by applying an amount of manganese smaller than the amount applied to the tip portion 135B. The current collecting member 200 including this can be manufactured. Moreover, the current collection member 200 including the coat 136 that satisfies the third requirement and the fourth requirement can be produced by appropriately changing the manganese application amount.

A-4. Effects of this embodiment:
As described above, the coat 136 of the current collecting member 200 of the present embodiment contains oxygen, manganese, and cobalt. Since the coat 136 contains manganese, it has high conductivity. However, the higher the manganese concentration (atm%) in the coat 136, the lower the oxygen permeation resistance of the coat 136, making it impossible to suppress oxidation of the substrate. Here, as shown in FIGS. 2 and 3, the base coat portion 136 </ b> A of the coat 136 is exposed to the air chamber 166. For this reason, when the oxygen permeability of the base coat portion 136A is low, the air in the air chamber 166 is likely to permeate from the base coat portion 136A, thereby suppressing the oxidation of the base material (side surface portion 135C of the current collector element 135). become unable. On the other hand, the tip coat portion 136 </ b> B of the coat 136 is not exposed to the air chamber 166. For this reason, even if the oxygen permeability of the tip coat portion 136B is low, the influence on the oxidation of the base material is small.

  Therefore, in the current collecting member 200 of the present embodiment, the coat 136 satisfies the first requirement A (“cobalt concentration in the base coat portion 136A”> “cobalt concentration in the tip coat portion 136B”). Here, from the evaluation results described later, it is presumed that the higher the cobalt concentration in the coat 136, the better the oxygen permeability of the coat 136. For this reason, in the current collecting member 200 of the present embodiment, the oxygen permeability of the base coat portion 136A that is relatively easily exposed to air is higher than the oxygen resistance permeability of the base coat portion 136A that is relatively difficult to be exposed to air. As a result, the oxidation resistance of the current collecting member 200 as a whole can be improved.

  Further, when the coat 136 satisfies the above first requirement A (“manganese concentration in the base coat portion 136A” <“manganese concentration in the tip coat portion 136B”), both improvement in oxidation resistance and maintenance of conductivity are achieved. Can be achieved. That is, that the coat 136 satisfies the first requirement A means that the conductivity of the base coat portion 136A is lower than the conductivity of the tip coat portion 136B. Here, the tip coat portion 136 </ b> B is bonded to the air electrode 114 via the bonding layer 138 and functions as a conductive portion between the base material and the air electrode 114. For this reason, if the conductivity of the tip coat portion 136B is low, the conductivity of the entire current collecting member 200 is low. On the other hand, the base coat portion 136A is separated from the air electrode 114 via the air chamber 166, and does not function as a conduction portion between the base material and the air electrode 114. For this reason, even if the conductivity of the base coat portion 136A is low, the influence on the conductivity between the base material and the air electrode 114 is small. Therefore, the coating 136 satisfies the first requirement A in addition to the first requirement, so that both the improvement of the oxidation resistance and the maintenance of the conductivity can be achieved as the entire current collecting member 200.

  Further, for example, in the configuration X in which the cobalt concentration in the side surface coating portion 136C is the same as the cobalt concentration in either the first coating portion or the second coating portion, the coating 136 is heated due to the difference in cobalt concentration. There is a part where the difference in expansion coefficient is extremely large. A portion where the difference in coefficient of thermal expansion is extremely large is likely to crack due to thermal stress. On the other hand, when the coat 136 satisfies the second requirement (“cobalt concentration in the base coat portion 136A”> “cobalt concentration in the side surface coat portion 136C >>“ cobalt concentration in the tip coat portion 136B ”), Compared to the configuration X, the coat 136 does not have a portion where the difference in coefficient of thermal expansion is extremely large, so that the occurrence of cracks due to the cobalt concentration in the coat 136 can be suppressed. If the coat 136 satisfies the above-mentioned second requirement A (“manganese concentration in the base coat portion 136A” <“manganese concentration in the side coat portion 136C” <“manganese concentration in the tip coat portion 136B”), It can suppress that a crack generate | occur | produces due to the manganese density | concentration in.

  Further, when the coat 136 satisfies the above-described third requirement (45 atm% ≦ “cobalt concentration in the tip coat portion 136B” ≦ 70 atm%), the cobalt concentration in the tip coat portion 136B is less than 45 atm%, Compared with a configuration in which the cobalt concentration of the coat portion 136B is higher than 70 atm%, it is possible to maintain high conductivity while improving oxidation resistance.

  Further, when the coat 136 satisfies the above-described fourth requirement (“cobalt concentration in the base coat portion 136A” − “cobalt concentration in the tip coat portion 136B” ≧ 2 atm%), the cobalt concentration in the base coat portion 136A and the tip coat portion 136B. Compared to the configuration in which the difference from the cobalt concentration in the sample is less than 2 atm%, it is possible to achieve both improvement in oxidation resistance and maintenance of conductivity more reliably.

A-5. Performance evaluation:
A plurality of current collecting member samples were produced, and performance evaluation was performed using the produced plurality of current collecting member samples. FIG. 6 is an explanatory diagram showing the performance evaluation results.

A-5-1. For each sample:
As shown in FIG. 6, the performance evaluation was performed on samples A to L of the current collecting member. Each of the samples A to L includes the above-described base material and the coat 136, and at least one of the manganese concentration and the cobalt concentration in the coat 136 is different from each other. In all of the coats 136 of the samples A to L, the total of the manganese concentration and the cobalt concentration in the coat 136 is approximately 100 atm%. For this reason, for example, when the cobalt concentration in the coat 136 is W (atm%), the manganese concentration in the coat 136 is 100-W (atm%).

  Samples A, C, F, I, and K all have the same cobalt concentration in the tip coat portion 136B and the cobalt concentration in the base coat portion 136A, and do not satisfy the first requirement (first requirement A). . Samples A, C, F, I, and K have different cobalt concentration values in the tip coat portion 136B and the base coat portion 136A.

  On the other hand, the samples B, D, E, G, H, J, and L all have a cobalt concentration in the base coat portion 136A higher than the cobalt concentration in the tip coat portion 136B, and satisfy the first requirement (first requirement A). Fulfill. Samples B, D, E, G, H, J, and L are different from each other in at least one of the cobalt concentration in the tip coat portion 136B and the cobalt concentration in the base coat portion 136A. Samples D, E, G, H, and J have a cobalt concentration of 45 atm% or more and 70 atm% or less in the tip coat portion 136B, satisfy the third requirement, and samples B and L Does not meet requirements.

A-5-2. About evaluation method:
The manganese concentration and cobalt concentration in the coat of each sample A to L of the current collecting member are specified by elemental analysis using an energy dispersive X-ray spectrometer (EDS) attached to a scanning electron microscope (SEM). can do.

  “Electric conductivity (S / cm)” in FIG. 6 means the electric conductivity at 800 ° C. of the base coat portion 136A of the coat 136 in each sample. The electric conductivity of the base coat portion 136A was calculated from the cobalt concentration and the manganese concentration in the base coat portion 136A, and the electric conductivity of each element of cobalt and manganese.

  The thickness of the oxide film in FIG. 6 is the thickness of the oxide film formed on the air chamber side surface 152 of the interconnector 150 covered with the base coat part 136A. For example, in a state where each sample is incorporated in the fuel cell stack 100, an oxidant gas OG is supplied to the air chamber 166, and after lapse of 800 hours at 800 ° C., an oxide film is formed on the air chamber side surface 152 of the interconnector 150. Is done. It means that the thinner the oxide film is, the higher the oxygen permeability resistance in the base coat portion 136A. A specific method for measuring the thickness of the oxide film is as follows.

FIG. 7 is an explanatory diagram showing, in an enlarged manner, a partial oxidation state in the current collecting member. FIG. 7 shows a cross section parallel to the vertical direction in the vicinity of the air chamber side surface 152 of the interconnector 150 covered with the base coat portion 136A. An oxide film S is formed on the air chamber side surface 152 of the interconnector 150. R in FIG. 7 is an EDS analysis region R (rectangular region having an area of 300 μm ² ) for specifying the manganese concentration and the cobalt concentration in the base coat portion 136A. In this evaluation, the thickness of the film portion located in the region P surrounded by the extension lines on both sides in the left and right direction (X direction) of the EDS analysis region R is measured. For the film portion located in the region P, the thickness in the vertical direction (Z direction) at 15 points arranged at equal intervals in the direction along the oxide film S (X direction) is measured, and the average of the thicknesses of the 15 points The value was the thickness of the oxide film S.

A-5-3. About evaluation results:
As shown in FIG. 6, in sample A, the thickness of oxide film S was 3.8 μm, whereas in sample B, the thickness of oxide film S was 3.5 μm. From this evaluation result, satisfying the first requirement A (“manganese concentration in the base coat portion 136A” <“manganese concentration in the tip coat portion 136B”) may improve the oxidation resistance of the current collecting member 200 as a whole. I understand. In Sample A and Sample B, since the cobalt concentration (manganese concentration) in the tip coat portion 136B is the same value, the electrical conductivity of the tip coat portion 136B was the same value (27 S / cm).

  In Sample C, the thickness of the oxide film S was 3.5 μm, whereas in Sample D, the thickness of the oxide film S was 3.3 μm. In Sample E, the thickness of the oxide film S was The thickness was 3.0 μm. Also from this evaluation result, it can be seen that satisfying the first requirement A improves the oxidation resistance of the current collecting member 200 as a whole. Moreover, it turns out that the oxidation resistance as the current collection member 200 whole improves, so that the cobalt concentration in 136 A of basecoat parts is high. In Sample C and Samples D and E, since the cobalt concentration (manganese concentration) in the tip coat portion 136B is the same value, the electrical conductivity of the tip coat portion 136B was the same value (60 S / cm).

  In Sample F, the thickness of the oxide film S was 3.3 μm, whereas in Sample G, the thickness of the oxide film S was 3.0 μm. In Sample H, the thickness of the oxide film S was The thickness was 2.8 μm. Also from this evaluation result, it can be seen that satisfying the first requirement A improves the oxidation resistance of the current collecting member 200 as a whole. Moreover, it turns out that the oxidation resistance as the current collection member 200 whole improves, so that the cobalt concentration in 136 A of basecoat parts is high. In Sample F and Samples G and H, since the cobalt concentration (manganese concentration) in the tip coat portion 136B is the same value, the electrical conductivity of the tip coat portion 136B was the same value (45 S / cm).

  In Sample I, the thickness of the oxide film S was 3.0 μm, whereas in Sample J, the thickness of the oxide film S was 2.8 μm. Also from this evaluation result, it can be seen that satisfying the first requirement A improves the oxidation resistance of the current collecting member 200 as a whole. In Sample I and Sample J, since the cobalt concentration (manganese concentration) in the tip coat portion 136B is the same value, the electrical conductivity of the tip coat portion 136B was the same value (67 S / cm).

  In sample K, the thickness of oxide film S was 2.8 μm, whereas in sample L, the thickness of oxide film S was 2.6 μm. Also from this evaluation result, it can be seen that satisfying the first requirement A improves the oxidation resistance of the current collecting member 200 as a whole. In Sample K and Sample L, since the cobalt concentration (manganese concentration) in the tip coat portion 136B is the same value, the electrical conductivity of the tip coat portion 136B was the same value (75 S / cm).

  Further, in Samples D, E, G, H, and J, the electrical conductivity of the tip coat portion 136B is higher than that in Sample B. From this evaluation result, it can be seen that satisfying the third requirement (45 atm% ≦ “cobalt concentration in the tip coat portion 136B” ≦ 70 atm%) can maintain high conductivity while improving oxidation resistance.

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

  In the above embodiment, the coat 136 of the current collecting member 200 is formed of a spinel oxide containing manganese and cobalt, but the coat 136 only needs to contain oxygen, manganese, and cobalt. For example, oxides other than spinel oxide may be included. The coat 136 may further contain component elements (for example, zinc (Zn), copper (Cu)) other than oxygen, manganese, and cobalt.

  In the above embodiment, the side coat portion 136C is configured such that the cobalt concentration decreases stepwise (two or more steps) or continuously as it goes from the base coat portion 136A side to the tip coat portion 136B side. It is good.

  Moreover, in the said embodiment, it is good also as a structure where the cobalt concentration in 136 C of side surface coating parts is the same as the cobalt concentration in any one of a 1st coating part and a 2nd coating part. Moreover, in the said embodiment, it is good also as a structure where the cobalt concentration of the tip coat part 136B is less than 45 atm%, or a structure where the cobalt concentration of the tip coat part 136B is higher than 70 atm%. In the above embodiment, the difference between the cobalt concentration in the base coat portion 136A and the cobalt concentration in the tip coat portion 136B may be less than 2 atm%.

  Moreover, in the said embodiment, although the width | variety of the horizontal direction (Y-axis direction) of the collector element 135 is substantially the same over the full length of the collector element 135 in the up-down direction, for example, the collector element 135 The width may be narrower as it approaches the air electrode 114.

  In each of the above embodiments, the electrolyte layer 112 is formed of a solid oxide. However, the electrolyte layer 112 may include other substances in addition to the solid oxide. Moreover, the material which forms each member in each said embodiment is an illustration to the last, and each member may be formed with another material. For example, in each of the embodiments described above, the air electrode side current collector 134 is formed of a metal containing Cr, but the air electrode side current collector 134 is formed of another material as long as it is covered with the coat 136. May be. In addition, the shape of each current collector element 135 constituting the air electrode side current collector 134 is not limited to a rectangular column shape, but may be any other shape as long as it projects from the interconnector 150 side to the air electrode 114 side. There may be.

  In each of the above embodiments, a reaction prevention layer containing, for example, ceria is provided between the electrolyte layer 112 and the air electrode 114, and zirconium or the like in the electrolyte layer 112 reacts with strontium or the like in the air electrode 114. It is possible to suppress an increase in electrical resistance between the electrolyte layer 112 and the air electrode 114. In each of the above embodiments, the air electrode side current collector 134 and the adjacent interconnector 150 may be separate members. Further, the fuel electrode side current collector 144 may have the same configuration as the air electrode side current collector 134, or the fuel electrode side current collector 144 and the adjacent interconnector 150 may be an integral member. Good. Further, the fuel electrode side frame 140 instead of the air electrode side frame 130 may be an insulator. The air electrode side frame 130 and the fuel electrode side frame 140 may have a multilayer structure.

  In the above embodiment, the coat 136 satisfies the first requirement for all the power generation units 102 included in the fuel cell stack 100. However, for at least one power generation unit 102 included in the fuel cell stack 100, the coat 136 If it is such a structure, there exists an effect that the oxidation resistance as the whole current collection member 200 can be improved.

  Moreover, in the said embodiment, although the fuel cell stack 100 is the structure by which the several flat single cell 110 was laminated | stacked, this invention is described in other structures, for example, international publication 2012/165409. Thus, the present invention can be similarly applied to a configuration in which a plurality of substantially cylindrical fuel cell single cells are connected in series.

  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 unit that 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 cell units. The configuration of the electrolysis cell stack is well known as described in, for example, Japanese Patent Application Laid-Open No. 2006-81813, and therefore will not be described in detail here, but is roughly the same as the fuel cell stack 100 in the above-described embodiment. It is the composition. That is, the fuel cell stack 100 in the above-described embodiment may be read as an electrolytic cell stack, and the power generation unit 102 may be read as an electrolytic cell unit. 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), and through the through hole 108. 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 through hole 108. Also in the electrolytic cell unit and the electrolytic cell stack having such a configuration, as in the above embodiment, if the configuration in which the coat 136 satisfies at least the first requirement is adopted, the oxidation resistance of the current collecting member 200 as a whole is improved. There is an effect that it can be improved.

22: Bolt 24: Nut 100: Fuel cell stack 102: Power generation unit 104, 106: End plate 108: Through hole 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 121: Hole 124: Joining Part 130: Air electrode side frame 131: Hole 132: Oxidant gas supply communication hole 133: Oxidant gas discharge communication hole 134: Air electrode side current collector 135: Current collector element 135B: Tip part 135C: Side surface part 136: Coat 136A: Base coat part 136B: Tip coat part 136C: Side coat part 138: Bonding layer 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 47: Connecting portion 149: Spacer 150: Interconnector 152: Air chamber side surface 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 200: Current collecting member 700: Celsius FG: Fuel gas FOG: Fuel off gas P: Area OG: Oxidant gas OOG: Oxidant off gas S: Oxide coating

Claims (6)

A conductive base material including a base portion having a first surface and a protruding portion protruding from the first surface of the base portion;
Among the base materials, in a conductive member comprising at least a conductive coat covering the first surface of the base portion and the protruding portion,
The coat contains oxygen, manganese, and cobalt,
The sum of the manganese concentration (atm%) in the component elements excluding oxygen in the component elements of the coat and the cobalt concentration (atm%) in the component elements excluding oxygen in the component elements of the coat is 90 atm% or more. And
The cobalt concentration in the first coat portion covering the first surface of the base portion of the coat is the cobalt concentration in the second coat portion covering the tip portion of the protrusion portion in the protruding direction. Higher than cobalt concentration,
A conductive member characterized by that. The conductive member according to claim 1, further comprising:
Among the coats, the cobalt concentration in the third coat part that covers the side part located between the tip part and the base part in the protruding part is lower than the cobalt concentration in the first coat part, And higher than the cobalt concentration in the second coat part,
A conductive member characterized by that. In the conductive member according to claim 1 or 2,
The cobalt concentration of the second coat part is 45 atm% or more and 70 atm% or less.
A conductive member characterized by that. In the electroconductive member as described in any one of Claim 1- Claim 3,
The difference between the cobalt concentration in the first coat portion and the cobalt concentration in the second coat portion is 2 atm% or more.
A conductive member characterized by that. An electrochemical reaction unit cell including an electrolyte layer containing a solid oxide and an air electrode and a fuel electrode facing each other in a first direction across the electrolyte layer;
An electrochemical reaction unit comprising a current collecting member disposed on the air electrode side of the electrochemical reaction unit cell and electrically connected to the air electrode,
The current collecting member is a conductive member according to any one of claims 1 to 4.
An electrochemical reaction unit characterized by that. An electrochemical reaction unit cell including an electrolyte layer containing a solid oxide and an air electrode and a fuel electrode facing each other in a first direction across the electrolyte layer, and disposed on the air electrode side of the electrochemical reaction unit cell An electrochemical reaction cell stack comprising a plurality of electrochemical reaction units comprising: a current collecting member electrically connected to the air electrode;
At least one of the plurality of electrochemical reaction units is the electrochemical reaction unit according to claim 5.
An electrochemical reaction cell stack characterized by that.

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