JP7324983B2 - INTERCONNECTOR MEMBER AND METHOD FOR MANUFACTURING INTERCONNECTOR MEMBER - Google Patents

Description

The technology disclosed by this specification relates to an interconnector member.

A solid oxide fuel cell (hereinafter referred to as "SOFC") is known as one of fuel cells that generate electricity using an electrochemical reaction between hydrogen and oxygen. A fuel cell power generation unit (hereinafter referred to as a "power generation unit"), which is a structural unit of an SOFC, includes a fuel cell single cell (hereinafter referred to as a "single cell") and an interconnector member. A single cell includes an electrolyte layer, and an air electrode and a fuel electrode facing each other in a predetermined direction (hereinafter referred to as "first direction") with the electrolyte layer interposed therebetween. The interconnector member is electrically connected to the air electrode or fuel electrode that constitutes the single cell.

The interconnector member includes a metal member made of a metal containing Fe and Cr (for example, ferritic stainless steel). When Cr contained in the metal member constituting the interconnect member reacts with oxygen in the air, an oxide film layer containing Cr oxide (for example, Cr ₂ O ₃ (chromia)) is formed on the surface of the metal member. be. Since the oxide film layer containing Cr oxide has low oxygen permeability, it suppresses the oxidation of Fe, which is more undesirable for metal members. On the other hand, since the oxide film layer containing Cr oxide has high electrical resistance, further growth of the oxide film layer may increase the electrical resistance of the interconnector member and degrade the performance of the power generation unit.

In addition, when the Cr contained in the metal member that constitutes the interconnect member evaporates and adheres to the electrode of the single cell, a phenomenon called "Cr poisoning" occurs, in which the reaction rate at the electrode decreases. ) performance may be degraded.

In order to suppress the performance degradation of power generation units such as these, on the surface of the metal member that constitutes the interconnector member (more specifically, on the oxide film layer disposed on the surface of the metal member, A structure in which a coating layer containing a spinel-type oxide containing Mn and Co (for example, MnCo ₂ O ₄ ) (hereinafter referred to as “Mn—Co coating layer”) is formed on the surface of the is known (see, for example, Patent Document 1). In the interconnect member having such a configuration, the Mn—Co coating layer suppresses permeation of oxygen, so further growth of the oxide coating layer is suppressed. performance deterioration) can be suppressed. In addition, in the interconnect member having such a configuration, the Mn—Co coating layer suppresses the transpiration of Cr from the metal member, thereby suppressing the occurrence of Cr poisoning of the single cell, and as a result, the performance of the power generation unit is lowered. can be suppressed.

JP 2011-99159 A

The present inventors have found that in the above-described conventional interconnector member, the electrical resistance particularly increases for a predetermined time (hereinafter referred to as "initial period") after the current is started to flow through the interconnector member (for example, for the first time after manufacturing), As a result, in this interconnector member, a new problem was discovered that the current could not flow efficiently.

In addition, such a problem constitutes an electrolytic cell unit which is a structural unit of a solid oxide type electrolytic cell (hereinafter also referred to as "SOEC") that generates hydrogen using the electrolysis reaction of water. This is also a common problem with interconnect members. In this specification, the fuel cell power generation unit and the electrolysis cell unit are collectively referred to as an electrochemical reaction unit. Moreover, such problems are not limited to SOFCs and SOECs, but are common to other types of electrochemical reaction units.

This specification discloses a technology capable of solving the above-described problems.

The technology disclosed in this specification can be implemented, for example, in the following forms.

(1) The interconnect member disclosed in the present specification includes a metal member containing Fe and Cr, a first coating layer containing Cr oxide disposed on the surface of the metal member, and the a second coating layer disposed on the surface of the first coating layer opposite to the metal member and containing a spinel-type oxide containing Mn and Co, wherein , the second coating layer contains a specific element that is at least one of Ni, Cu, Zn and Co, and the concentration (atm%) of the specific element contained in the second coating layer is The further away from the first coating layer, the lower. In the present interconnect member, due to the presence of the specific element contained in the second coating layer, the initial (for example, for the first time after manufacturing) electric resistance increases for a predetermined time after the start of current flow through the interconnect member. Suppressed. Therefore, according to this interconnector member, an electric current can flow efficiently. In addition, in the present interconnect member, the concentration (atm %) of the specific element contained in the second coating layer decreases as the distance from the first coating layer increases, so that the second coating layer contains It is possible to relatively reduce the amount of the specific element contained in the second coating layer, thereby suppressing deterioration of the oxygen permeation prevention performance originally possessed by the second coating layer. This suppresses an increase in electrical resistance due to progress of oxidation of the metal member. Therefore, according to this interconnector member, the current can flow more efficiently.

(2) In the above interconnect member, the concentration of the specific element in a region of the second coating layer up to 1 μm from the first coating layer may be 0.5 atm % or more. In this interconnect member, since the concentration of the specific element in the region of the second coating layer sufficiently close to the first coating layer is sufficiently high, the presence of the specific element can be more effectively detected. Thus, an increase in initial electrical resistance is suppressed. Therefore, according to this interconnector member, the current can flow more efficiently.

(3) In the above interconnect member, the metal member contains the same element as the specific element contained in the second coating layer, and the concentration of the specific element contained in the metal member (atm% ) may be configured to be lower the further away from the first coating layer. According to this interconnect member, the presence of the specific element contained in the metal member suppresses an increase in initial electrical resistance. Therefore, according to this interconnector member, the current can flow more efficiently. In addition, in the present interconnect member, the concentration (atm%) of the specific element contained in the metal member decreases as the distance from the first coating layer increases, so that the first coating layer and the metal member An increase in electrical resistance due to cracks occurring between them is suppressed. Therefore, according to this interconnector member, the current can flow more efficiently.

(4) In the method for manufacturing an interconnector member, a first step of preparing a metal member; a second step of forming a specific element plating layer containing the specific element on the metal member by plating; a third step of forming a Mn oxide layer on the specific element plating layer by migration electrodeposition; a fourth step of forming a Co plating layer containing Co on the Mn oxide layer by plating; By firing the metal member that has undergone the first step, the second step, the third step, and the fourth step, the first coating layer and the second coating layer are formed on the metal member. It is good also as a structure provided with the 5th process of forming. According to the present interconnect member manufacturing method, the second coating layer contains the specific element, and the concentration (atm%) of the specific element contained in the second coating layer is the same as the first It is possible to easily manufacture the above-mentioned interconnector member, which is configured so that the distance from the film layer is lower. Further, in the method for manufacturing an interconnector member, after the Mn oxide layer is formed by migration electrodeposition (the third step), a Co plating layer is formed in the gaps generated in the Mn oxide layer. (Fourth step), the adhesion between the second coating layer and the first coating layer becomes good, so that the second coating layer (from the first coating layer) Peeling is suppressed.

(5) In the method for manufacturing an interconnector member, in the third step, a ketone solvent may be used as the solvent for soaking the metal member. According to this method for manufacturing an interconnector member, the Mn oxide layer can be formed on the specific element plated layer more efficiently in the third step.

The technology disclosed in this specification can be realized in various forms. an electrochemical reaction unit (fuel cell power generation unit or electrolysis cell unit), an electrochemical reaction cell stack (fuel cell stack or electrolysis cell stack) comprising a plurality of electrochemical reaction units, a manufacturing method thereof, etc. Is possible.

1 is a perspective view showing an external configuration of a fuel cell stack 100 according to this embodiment; FIG. FIG. 2 is an explanatory view showing the XZ cross-sectional configuration of the fuel cell stack 100 at the position II-II in FIG. 1; FIG. 2 is an explanatory view showing the YZ cross-sectional configuration of the fuel cell stack 100 at the position III-III in FIG. 1; FIG. 3 is an explanatory diagram showing the 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 ; FIG. 4 is an explanatory diagram showing the YZ cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 3 ; FIG. 5 is an explanatory view showing the XY cross-sectional configuration of the power generation unit 102 at the position VI-VI in FIG. 4; FIG. 5 is an explanatory view showing the XY cross-sectional configuration of the power generation unit 102 at the position of VII-VII in FIG. 4; FIG. 2 is an explanatory diagram showing the detailed configuration of an interconnector composite 200 in this embodiment; 4 is a flow chart showing an example of a method for manufacturing an interconnector composite 200 according to this embodiment. It is an explanatory view showing roughly a part of an example of a manufacturing method of interconnector complex 200 in this embodiment. It is an explanatory view showing roughly a part of an example of a manufacturing method of interconnector complex 200 in this embodiment. FIG. 5 is an explanatory diagram showing performance evaluation results in this embodiment; FIG. 4 is an explanatory diagram showing measurement results of electrical resistance (only samples S1 and S3) in performance evaluation in the present embodiment; It is explanatory drawing which shows the performance evaluation result in the modification using Cu as a specific element.

A. Embodiment:
A-1. Configuration of fuel cell stack 100:
(Configuration of fuel cell stack 100)
FIG. 1 is a perspective view showing the external configuration of a fuel cell stack 100 in this embodiment, and FIG. 2 is an XZ view of the fuel cell stack 100 at the position II-II in FIG. 1 (and FIGS. 6 and 7 to be described later). FIG. 3 is an explanatory view showing the cross-sectional structure, and FIG. 3 is an explanatory view showing the YZ cross-sectional structure of the fuel cell stack 100 at the position III-III in FIG. 1 (and FIGS. 6 and 7 described later). Each figure shows mutually orthogonal XYZ axes for specifying directions. In this specification, for the sake of convenience, the positive Z-axis direction is referred to as the upward direction, and the negative Z-axis direction is referred to as the downward direction. may be installed. The same applies to FIG. 4 and subsequent figures.

The fuel cell stack 100 includes a plurality of (seven in this embodiment) fuel cell power generation units (hereinafter simply referred to as “power generation units”) 102 and a pair of end plates 104 and 106 . The seven power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in this embodiment). A pair of end plates 104 and 106 are arranged so as to sandwich an aggregate composed of seven power generation units 102 from above and below.

A plurality of holes (eight in the present embodiment) penetrating in the vertical direction are formed in the peripheral edge portion around the Z-axis direction of each layer (the power generation unit 102, the end plates 104 and 106) constituting the fuel cell stack 100. Corresponding holes formed in each layer vertically communicate with each other to form communicating holes 108 extending vertically 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 the communication holes 108 .

A bolt 22 extending in the vertical direction is inserted through each communication hole 108 , and the fuel cell stack 100 is fastened by the bolt 22 and nuts 24 fitted on both sides of the bolt 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 between the bolt An insulating sheet 26 is interposed between the nut 24 fitted to the other side (lower side) of the fuel cell stack 22 and the lower surface of the end plate 106 forming the lower end of the fuel cell stack 100 . However, at a location where a gas passage member 27, which will be described later, is provided, between the nut 24 and the surface of the end plate 106, the insulating sheets disposed above and below the gas passage member 27 and the gas passage member 27, respectively. 26 intervenes. The insulating sheet 26 is composed of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder sheet, a glass sheet, a glass-ceramic composite, 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, one side of the outer circumference of the fuel cell stack 100 around the Z-axis direction (the side on the positive side of the X-axis among the two sides parallel to the Y-axis) is near the midpoint. The space formed by the bolt 22 (bolt 22A) positioned thereon and the communication hole 108 through which the bolt 22A is inserted receives the oxidant gas OG from the outside of the fuel cell stack 100, and the oxidant gas OG is introduced into each space. Functioning as an oxidant gas introduction manifold 161 which is a gas flow path for supplying to the power generation unit 102, the side opposite to the side (the side on the negative side of the X axis among the two sides parallel to the Y axis) The space formed by the bolt 22 (bolt 22B) located near the point and the communication hole 108 through which the bolt 22B is inserted is the oxidant offgas OOG which is the gas discharged from the air chamber 166 of each power generation unit 102. to the outside of the fuel cell stack 100 as an oxidizing gas discharge manifold 162 . In this embodiment, for example, air is used as the oxidant gas OG.

In addition, as shown in FIGS. 1 and 3, the midpoint of one side (the side on the Y-axis positive side of the two sides parallel to the X-axis) on the outer circumference of the fuel cell stack 100 around the Z-axis direction Fuel gas FG is introduced from the outside of the fuel cell stack 100 into the space formed by the bolt 22 (bolt 22D) located nearby and the communication hole 108 through which the bolt 22D is inserted. A bolt that functions as the fuel gas introduction manifold 171 that supplies the power generation unit 102 and is located near the midpoint of the side opposite to the side (the side on the Y-axis negative direction side of the two sides parallel to the X-axis) 22 (bolt 22E) and the communication hole 108 through which the bolt 22E is inserted allows the fuel offgas FOG, which is the gas discharged from the fuel chamber 176 of each power generation unit 102, to flow outside the fuel cell stack 100. It functions as a fuel gas discharge manifold 172 that discharges to the In this embodiment, hydrogen-rich gas obtained by reforming city gas, for example, is used as the fuel gas FG.

Four gas passage members 27 are provided in the fuel cell stack 100 . Each gas passage member 27 has a hollow tubular body portion 28 and a hollow tubular branch portion 29 branched from a side surface of the main body portion 28 . A hole in the branch portion 29 communicates with a hole in the main body portion 28 . A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27 . Further, as shown in FIG. 2, the hole of the body portion 28 of the gas passage member 27 arranged at the position of the bolt 22A forming the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. A hole in the body portion 28 of the gas passage member 27 arranged at the position of the bolt 22B forming the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162 . Further, as shown in FIG. 3, the hole of the 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 A hole in the body portion 28 of the gas passage member 27 arranged at the position of the bolt 22E forming the discharge manifold 172 communicates with the fuel gas discharge manifold 172 .

(Configuration of end plates 104, 106)
The pair of end plates 104 and 106 are substantially rectangular plate-shaped conductive members, and are made of, for example, stainless steel. One end plate 104 is arranged above the uppermost power generating unit 102 and the other end plate 106 is arranged below the lowermost power generating unit 102 . A pair of end plates 104 and 106 hold a plurality of power generation units 102 in a pressed state. The upper end plate 104 functions as the positive side output terminal of the fuel cell stack 100 , and the lower end plate 106 functions as the negative side output terminal of the fuel cell stack 100 .

(Configuration of power generation unit 102)
4 is an explanatory diagram showing the 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. FIG. 3 is an explanatory diagram showing a YZ cross-sectional configuration of two power generation units 102; In the upper portion of FIG. 5, the YZ cross-sectional configuration of a portion of the power generation unit 102 is shown enlarged. 6 is an explanatory diagram showing the XY cross-sectional configuration of the power generation unit 102 at the position VI-VI in FIG. 4, and FIG. 7 is the XY cross-sectional configuration of the power generation unit 102 at the position VII-VII in FIG. It is an explanatory diagram showing.

As shown in FIGS. 4 and 5, the power generation unit 102 includes a single cell 110, a separator 120, an air electrode side frame 130, an air electrode side current collector 134, an anode side frame 140, an anode side It has a current collector 144 and a pair of interconnectors 150 forming the top layer and the bottom 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 provided with holes corresponding to the communication holes 108 through which the bolts 22 are inserted.

The interconnector 150 is a substantially rectangular plate-shaped conductive member, and is made of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generating units 102 and prevents mixing of reaction gases between the power generating units 102 . In this embodiment, when two power generation units 102 are arranged adjacently, one interconnector 150 is shared by the two adjacent power generation units 102 . That is, the upper interconnector 150 in a certain power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102 . In addition, since the fuel cell stack 100 has a pair of end plates 104 and 106, the power generation unit 102 located at the top in the fuel cell stack 100 does not have the upper interconnector 150, and is located at the bottom. The generating unit 102 does not have a lower interconnector 150 (see Figures 2 and 3).

The single cell 110 includes an electrolyte layer 112, a fuel electrode (anode) 116 disposed on one side (lower side) of the electrolyte layer 112 in the vertical direction (first direction), and a fuel electrode (anode) 116 disposed on the other side of the electrolyte layer 112 in the vertical direction. It comprises an air electrode (cathode) 114 located on the (upper side) and an intermediate layer 180 located between the electrolyte layer 112 and the air electrode 114 . The single cell 110 of this embodiment is a fuel electrode supporting type single cell in which the fuel electrode 116 supports the other layers (the electrolyte layer 112, the air electrode 114, and the intermediate layer 180) constituting the single cell 110. FIG.

The electrolyte layer 112 is a substantially rectangular plate-shaped member when viewed in the Z-axis direction, and is a dense layer. The electrolyte layer 112 is formed of a solid oxide such as YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), GDC (gadolinium-doped ceria), perovskite-type oxide, or the like. there is That is, the single cell 110 (power generation unit 102) of this embodiment is a solid oxide fuel cell (SOFC) using a solid oxide as an electrolyte.

The air electrode 114 is a substantially rectangular plate-shaped member smaller than the electrolyte layer 112 when viewed in the Z-axis direction, and is a porous layer. The air electrode 114 is made of, for example, a perovskite oxide (eg, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), LNF (lanthanum nickel iron)).

The fuel electrode 116 is a substantially rectangular plate-shaped member having substantially the same size as the electrolyte layer 112 when viewed in the Z-axis direction, and is a porous layer. The fuel electrode 116 is made of, for example, a cermet made of Ni and oxide ion conductive ceramic particles (eg, YSZ).

The intermediate layer 180 is a substantially rectangular plate-shaped member, and is formed so as to contain GDC (gadolinium-doped ceria). The intermediate layer 180 is formed so that an element (eg, Sr) diffused from the air electrode 114 reacts with an element (eg, Zr) contained in the electrolyte layer 112 to generate a high resistance substance (eg, SrZrO ₃ ). Suppress.

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 metal, for example. The peripheral portion of the separator 120 around the hole 121 faces the peripheral portion of the surface of the electrolyte layer 112 on the air electrode 114 side. The separator 120 is joined to the electrolyte layer 112 (single cell 110) by a joining portion 124 formed of brazing material (for example, Ag brazing) arranged at the opposing portion. The air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116 are separated by the separator 120 to prevent gas leakage from one electrode side to the other electrode side in the peripheral portion of the unit cell 110 . Suppressed.

As shown in FIGS. 4 to 6, the cathode-side frame 130 is a frame-shaped member having a substantially rectangular hole 131 extending vertically through the vicinity of the center thereof, and is made of an insulator such as mica. ing. A hole 131 in the cathode-side frame 130 constitutes an air chamber 166 facing the cathode 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 . . Also, the pair of interconnectors 150 included in the power generation unit 102 are electrically insulated by the air electrode side frame 130 . The air electrode side frame 130 also has an oxidizing gas supply communication hole 132 that communicates between the oxidizing gas introduction manifold 161 and the air chamber 166, and an oxidizing gas supply communication hole that communicates between the air chamber 166 and the oxidizing gas discharge manifold 162. A discharge communication hole 133 is formed.

As shown in FIGS. 4, 5, and 7, the fuel electrode side frame 140 is a frame-shaped member having a substantially rectangular hole 141 extending vertically through the vicinity of the center thereof, and is made of metal, for example. . A hole 141 in the anode-side frame 140 constitutes a fuel chamber 176 facing the anode 116 . The fuel electrode-side frame 140 is in contact with the periphery of the surface of the separator 120 facing the electrolyte layer 112 and the periphery of the surface of the interconnector 150 facing the fuel electrode 116 . The fuel electrode side frame 140 also has a fuel gas supply communication hole 142 that communicates the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that communicates the fuel chamber 176 and the fuel gas discharge manifold 172. and are formed.

As shown in FIGS. 4, 5 and 7, the fuel electrode side current collector 144 is arranged within 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 is used. , stainless steel or the like. The electrode facing portion 145 is in contact with the surface of the fuel electrode 116 opposite to the side facing the electrolyte layer 112 , and the interconnector facing portion 146 is in contact with the surface of the interconnector 150 facing the fuel electrode 116 . in contact. However, as described above, since the lowest power generation unit 102 in the fuel cell stack 100 does not have the lower interconnector 150, the interconnector facing portion 146 of the power generation unit 102 is the lower end plate. 106 is in contact. Fuel electrode-side current collector 144 having such a configuration electrically connects fuel electrode 116 and interconnector 150 (or end plate 106). A spacer 149 made of mica, for example, is arranged between the electrode facing portion 145 and the interconnector facing portion 146 . Therefore, the fuel electrode side current collector 144 follows the deformation of the power generation unit 102 due to temperature cycles and reaction gas pressure fluctuations, and the fuel electrode 116 and the interconnector 150 (or the end plate 106) through the fuel electrode side current collector 144. good electrical connection with

As shown in FIGS. 4 to 6, the cathode-side current collector 134 is arranged within the air chamber 166 . The air electrode-side current collector 134 is composed of a plurality of substantially quadrangular prism-shaped current collector elements, and is made of, for example, ferritic stainless steel. The air electrode-side current collector 134 is formed in a convex shape protruding from the interconnector 150 toward the air electrode 114 (in the negative direction of the Z-axis in this embodiment). 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, the uppermost power generation unit 102 in the fuel cell stack 100 does not have the upper interconnector 150, so the air electrode side current collector 134 in the power generation unit 102 is the upper end plate 104 is in contact. Since the air electrode side current collector 134 has such a configuration, it electrically connects the air electrode 114 and the interconnector 150 (or the end plate 104).

As shown in FIGS. 4 and 5, in this embodiment, the air electrode side current collector 134 and the interconnector 150 are formed as an integral member. That is, of the integral member (hereinafter referred to as "metal member 190"), a flat plate-shaped portion perpendicular to the vertical direction (Z-axis direction) functions as an interconnector 150, and air is discharged from the flat plate-shaped portion. A plurality of current collector elements formed to protrude toward the pole 114 function as the air electrode side current collector 134 .

As shown in FIG. 5, an oxide film layer 194 containing Cr oxide (for example, Cr ₂ O ₃ (chromia)) is formed on the surface of the metal member 190 . Further, as shown in FIGS. 4 and 5, the surface of the metal member 190 (more specifically, the surface of the oxide film layer 194 disposed on the surface of the metal member 190 opposite to the metal member 190) is It is covered by a conductive Mn—Co coating layer 196 . The oxide film layer 194 corresponds to the first film layer in the claims, and the Mn--Co film layer 196 corresponds to the second film layer in the claims.

As shown in FIGS. 4 and 5 , the air electrode 114 and the air electrode side current collector 134 are joined by a conductive joint 138 . The junction ₁₃₈ is made of, for example, an oxide _{having a} spinel crystal structure ₍ eg, _Mn1.5Co1.5O4 , _MnCo2O4 , _{ZnCo2O4 , ZnMn2O4} , _ZnMnCoO4 , _{CuMn2O 4} ). The air electrode 114 and the air electrode side current collector 134 are electrically connected to each other by the joint portion 138 . Although the cathode-side current collector 134 was previously described as being in contact with the surface of the air electrode 114 , more precisely, a joint 138 is interposed between the cathode-side current collector 134 and the air electrode 114 . are doing.

In the following description, the metal member 190 (integrated member of the interconnector 150 and the air electrode side current collector 134), the oxide film layer 194 formed on the surface of the metal member 190, and the metal member in the oxide film layer 194 The Mn—Co coating layer 196 formed on the surface opposite to the surface facing 190 is collectively referred to as interconnector composite 200 . The interconnector complex 200 is electrically connected to the air electrode 114 via the junction 138 and electrically connected to the anode 116 via the anode-side current collector 144 . The configuration of the interconnector complex 200 will be detailed later. The interconnector composite 200 corresponds to an interconnector member in the claims.

A-2. Operation of 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 oxidizing gas OG is supplied to the oxidizing 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 oxidizing gas OG is supplied from the oxidizing gas introduction manifold 161 to each power generation unit 102 . The agent gas is supplied to the air chamber 166 through the agent gas supply communication hole 132 . 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 via 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. It is supplied to fuel chamber 176 through 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, electric power is generated in the single cell 110 by the electrochemical reaction of the oxidant gas OG and the fuel gas FG. will be 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 the interconnector composite 200 (the assembly of the metal member 190, the oxide layer 194, and the Mn--Co layer 196) through the junction 138. , and the fuel electrode 116 is electrically connected to the interconnector composite 200 via the fuel electrode side current collector 144 . That is, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series. Therefore, the 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 the SOFC generates power at a relatively high temperature (for example, 700° C. to 1000° C.), the fuel cell stack 100 is heated by the heater ( (not shown).

As shown in FIGS. 2 and 4, the oxidant offgas OOG discharged from the air chamber 166 of each power generation unit 102 is discharged to the oxidant gas discharge manifold 162 through the oxidant gas discharge communication hole 133 and further oxidized. The fuel cell stack 100 is supplied to the fuel cell stack 100 via a gas pipe (not shown) connected to the branch portion 29 through the holes of the main body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the agent gas discharge manifold 162 . discharged to the outside of the Further, as shown in FIGS. 3 and 5, the fuel offgas FOG discharged from the fuel chamber 176 of each power generation unit 102 is discharged to the fuel gas discharge manifold 172 through the fuel gas discharge communication hole 143. Through the holes in the body portion 28 and the branch portion 29 of the gas passage member 27 provided at the position of the exhaust manifold 172, the gas is supplied to the outside of the fuel cell stack 100 via a gas pipe (not shown) connected to the branch portion 29. Ejected.

A-3. Detailed configuration of interconnector complex 200:
FIG. 8 is an explanatory diagram showing the detailed configuration of the interconnector composite 200 in this embodiment. FIG. 8 shows an enlarged cross-sectional configuration of the X1 portion (peripheral portion of the cathode-side current collector 134) in FIG. The upper right side of FIG. 8 shows a graph showing the relationship between the distance (μm) from the oxide film layer 194 (in the Z-axis direction) in the metal member 190 and the Ni concentration (atm %). The lower right side of FIG. 8 shows a graph showing the relationship between the distance (μm) from the oxide film layer 194 (in the Z-axis direction) in the Mn—Co film layer 196 and the Ni concentration (atm %). It is Although the slopes of the respective graphs shown in FIG. 8 are similar to each other, they may actually differ slightly from each other. As described above, the interconnector composite 200 includes the metal member 190 (an integral member of the air electrode side current collector 134 and the interconnector 150), the oxide layer 194 disposed on the surface of the metal member 190, and a Mn—Co coating layer 196 disposed on the surface of the oxide coating layer 194 opposite the metal member 190 .

As shown in FIG. 8, the metal member 190 contains Fe as a main component and also contains Cr. In addition, in this specification, the main component means the component with the highest concentration. Metal member 190 further contains Ni. As shown in the graph on the upper right side of FIG. 8, the concentration of Ni in the region up to 2 μm from the oxide film layer 194 in the metal member 190 is 0.5 atm % or more. Therefore, the concentration of Ni in the region of the metal member 190 up to 1 μm from the oxide film layer 194 is 0.5 atm % or more. Note that the concentration of Ni in a region of the metal member 190 up to 2 μm from the oxide film layer 194 may be less than 0.5 atm %. The concentration of Ni contained in the metal member 190 decreases with increasing distance from the oxide film layer 194 . This “the concentration of Ni is low” means that the oxide film When the regions (hereinafter referred to as “unit specific regions”) are divided in order every 2 μm from the side close to the layer 194, the Ni concentration (atm%) in each unit specific region is higher than that of the oxide film in the unit specific region. that the concentration of Ni in the unit specific region adjacent to the layer 194 is 0.1 atm% or more (more preferably 0.2 atm% or more, more preferably 0.3 atm% or more) lower means. Therefore, in the metal member 190, in a region outside the specific region (for example, a region separated from the oxide film layer 194 by a distance longer than 10 μm), for example, a portion where the Ni concentration (decrease) converges Sometimes there is

The oxide layer 194 contains Cr oxide (for example, Cr ₂ O ₃ (chromia)). The Cr concentration of the oxide film layer 194 is higher than the Cr concentration of the metal member 190 . The thickness of the oxide layer 194 is preferably 0.5 μm or more, for example. Since the oxide film layer 194 has low oxygen permeability, it suppresses oxidation of Fe, which is undesirable for the metal member 190 . That is, the oxide film layer 194 functions as an oxidation-resistant film. On the other hand, since the oxide layer 194 has a relatively high electrical resistance, it is undesirable for the oxide layer 194 to grow further as the fuel cell stack 100 is used, for example.

The Mn—Co coating layer 196 is a conductive layer that has a spinel crystal structure and contains a spinel-type oxide containing Mn and Co (eg, MnCo ₂ O ₄ ). The Mn--Co coating layer 196 also contains Ni. The thickness of the Mn--Co coating layer 196 is preferably, for example, 6 μm or more (more preferably 8 to 20 μm). Since the Mn—Co coating layer 196 suppresses permeation of oxygen, it can suppress the growth of the oxide coating layer 194 with high electrical resistance, and as a result, the electrical resistance of the interconnector composite 200 increases (and thus the power generation performance degradation of the unit 102) can be suppressed. In addition, since the Mn—Co coating layer 196 suppresses evaporation of Cr from the metal member 190, it is possible to suppress the occurrence of Cr poisoning of the electrode (for example, the air electrode 114) of the single cell 110. As a result, Performance degradation of the power generation unit 102 can be suppressed.

As shown in the lower right graph of FIG. 8, the concentration of Ni in the region of the Mn—Co coating layer 196 up to 2 μm from the oxide coating layer 194 is 0.5 atm % or more. Therefore, the concentration of Ni in the region of the Mn—Co coating layer 196 up to 1 μm from the oxide coating layer 194 is 0.5 atm % or more. The concentration of Ni contained in the Mn—Co coating layer 196 decreases as the distance from the oxide coating layer 194 increases. The meaning of "the concentration of Ni is low" is the same as the meaning of "the concentration of Ni is low" in the case of the metal member 190 described above.

The ratio of the Mn concentration (atm %) to the Co concentration (atm %) in the Mn—Co coating layer 196 is 1:1-2. The reason why the ratio of the concentration of Mn to the concentration of Co in the Mn—Co coating layer 196 is set to such a value is that in a configuration in which the ratio deviates from such a value, the metal member 190 and oxidation This is because the difference in coefficient of thermal expansion with the coating layer 194 is increased, and the Mn--Co coating layer 196 is easily peeled off (from the oxide coating layer 194).

Note that the upper right graph and the lower right graph of FIG. 8 show that the concentration of Ni in a region up to 2 μm from the oxide film layer 194 is greater than 0.5 atm %, but this region The Ni concentration in (a region of at least one of the Mn—Co coating layer 196 and the metal member 190 up to 2 μm from the oxide coating layer 194) may be 0.5 atm %.

In the present embodiment, not only the portion of the interconnector composite 200 (the surface 201 facing the air electrode 114) where the air electrode side current collector 134 is formed, but also the air electrode side current collector 134 is The concentration (distribution) of Ni in the metal member 190 and the Mn—Co coating layer 196 is the concentration (distribution) described above throughout the entirety including the portions where it is not formed.

A-4. Method for manufacturing interconnector composite 200:
Next, a method for manufacturing the interconnector composite 200 will be described. FIG. 9 is a flow chart showing an example of a method for manufacturing the interconnector composite 200 according to this embodiment. 10 and 11 are explanatory diagrams schematically showing an example of a method for manufacturing the interconnector composite 200 according to this embodiment.

First, the metal member 190 is prepared (S110). In order to clean the surface of the metal member 190, a degreasing treatment using acetone may be performed. The step of S110 corresponds to the first step in the claims.

Next, a Ni plating layer 151 containing Ni is formed on the metal member 190 by plating (S120, A in FIG. 10). The step of S120 corresponds to the second step in the scope of claims.

Next, a Mn oxide layer 152 is formed on the Ni plated layer 151 by migration electrodeposition (S130, B in FIG. 10). More specifically, first, the electrolytic cell Ec1 is prepared. A solution Es1 containing a ketone solvent (eg, acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone) is placed in the electrolytic cell Ec1. Next, powder of Mn oxide (for example, MnO) is added to the solution Es1 in the electrolytic cell Ec1. Also, I ₂ (iodine) is added to the solution Es1 in the electrolytic cell Ec1 (for example, I ₂ is dispersed at a concentration of 0.6 g/L). As a result, keto-enol tautomerism occurs, protons (hydrogen ions) are generated, and the generated protons are adsorbed to the Mn oxide and become charged. A metal member 190 and an electrode E1 made of, for example, C (carbon) are placed in a solution Es1, and a voltage is applied between the metal member 190 and the electrode E1 using a power source P1 (in this embodiment, , the metal member 190 becomes the negative electrode, and the electrode E1 becomes the positive electrode). As a result, an electric field is generated in the solution Es1, and the proton-attached Mn oxide is attracted to the Ni plating layer 151 side and adheres to the Ni plating layer 151. FIG. Protons adhering _to the Ni plating layer 151 receive electrons and become H ₂ (hydrogen). Thereby, a porous Mn oxide layer 152 is formed. The step of S130 corresponds to the third step in the claims.

Next, a Co plating layer 153 containing Co is formed on the Mn oxide layer 152 by plating (plating treatment) (S140, C and D in FIG. 11). More specifically, first, as shown in FIG. 11C, a solution Es2 containing Co ions is prepared in an electrolytic cell Ec2. Next, the metal member 190 and the electrode E2 made of Co, for example, are placed in the solution Es2, and a voltage is applied between the metal member 190 and the electrode E2 using the power supply P2 (in this embodiment, , the metal member 190 becomes a negative electrode, and the electrode E2 becomes a positive electrode). This creates an electric field in the solution Es2. As a result, the Co ions are attracted to the side of the Mn oxide layer 152 and adhere to the Mn oxide layer 152 (so as to fill the pores formed in the Mn oxide layer 152). As a result, a Co plated layer 153 is formed (D in FIG. 11). The step of S140 corresponds to the fourth step in the scope of claims. In FIG. 11D, of the parts indicated by reference numerals "152, 153", the parts hatched with dots are the Co plating layer 153 filling the pores formed in the Mn oxide layer 152 for comparison. This is a portion with a relatively low porosity (therefore, the porosity is relatively high). It is a relatively large portion (and thus relatively low porosity).

Next, the metal member 190 (more strictly, the Ni plated layer 151, the Mn oxide layer 152, and the Co plated layer 153 are formed on the surface) through the steps of S110, S120, S130, and S140. By firing the formed metal member 190), an oxide film layer 194 and a Mn—Co film layer 196 are formed on the metal member 190 (S150). More specifically, heat treatment is performed at a predetermined temperature of, for example, 1000° C. or less for a predetermined time. By performing the heat treatment, Cr contained in the metal member 190 diffuses to the surface of the metal member 190 and reacts with oxygen in the atmosphere. As a result, an oxide film layer 194 containing Cr oxide (for example, Cr ₂ O ₃ (chromia)) is formed on the surface of the metal member 190 . Further, by performing the heat treatment, Co and other elements (Mn) contained in the Co plating layer 153 interdiffuse and react with oxygen in the atmosphere. As a result, a Mn—Co coating layer 196 containing Co oxide (eg, MnCo ₂ O ₄ ) is formed on the surface of the oxide coating layer 194 . At this time, the concentration of Ni contained in the Mn--Co coating layer 196 decreases with increasing distance from the oxide coating layer 194 as described above. The interconnector composite 200 having the configuration described above is manufactured by the manufacturing method described above. The step of S150 corresponds to the fifth step in the claims.

A-5. Effect of this embodiment:
As described above, the interconnector composite 200 in the present embodiment includes the metal member 190 containing Fe and Cr, and the oxide film layer 194 containing Cr oxide disposed on the surface of the metal member 190. , and a Mn--Co coating layer 196 disposed on the surface of the oxide coating layer 194 opposite to the metal member 190 and containing a spinel-type oxide containing Mn and Co. The Mn--Co coating layer 196 contains Ni. The concentration (atm %) of Ni contained in the Mn—Co coating layer 196 decreases with increasing distance from the oxide coating layer 194 .

In the configuration in which the Mn—Co coating layer 196 does not contain Ni, the electrical resistance is reduced for a predetermined time (hereinafter referred to as “initial stage”) after the current is started to flow through the interconnector composite 200 (for example, for the first time after manufacturing). In particular, it increases, and as a result, the current cannot flow efficiently. The reason why such a problem arises is not necessarily clear, but is presumed as follows. In the structure in which the Mn—Co coating layer 196 does not contain Ni, when a current is passed through the interconnector member, a layer ( hereinafter referred to as "Cr--Mn reaction layer") is formed. In this interconnect member, the presence of the Cr--Mn reaction layer particularly increases the electrical resistance in the initial stage.

In response to such a problem, the inventors of the present application have found that in the configuration in which the Mn—Co coating layer 196 contains Ni as in the present embodiment, the increase in electrical resistance in the initial stage of the interconnector composite 200 can be suppressed. I discovered something new. Although the reason why the effect is obtained by the above configuration is not necessarily clear, it is presumed as follows.

In the interconnector composite 200 of this embodiment, as described above, the Mn—Co coating layer 196 contains Ni. The electric resistance of Ni contained in the Mn--Co coating layer 196 is lower than that of Cr and Mn contained in the Mn--Co coating layer 196. FIG. In addition, Ni contained in the Mn--Co coating layer 196 reacts with Cr contained in the metal member 190, so that the amount of the Cr--Mn reaction layer formed is smaller than in the case where Ni does not exist. Become. Therefore, the presence of Ni contained in the Mn--Co coating layer 196 suppresses the initial increase in electrical resistance due to the presence of the Cr--Mn reaction layer. Therefore, according to the interconnector composite 200 of the present embodiment, current can flow more efficiently than in a configuration in which the Mn—Co coating layer 196 does not contain Ni.

Here, as the amount of Ni contained in the Mn--Co coating layer 196 increases, the electrical resistance increases due to the decrease in the oxygen permeation prevention performance that the Mn--Co coating layer 196 originally has. For example, in a configuration in which the concentration (atm %) of Ni contained in the Mn—Co coating layer 196 is uniform, the amount of Ni contained in the Mn—Co coating layer 196 is large, so that the metal member 190 The electrical resistance tends to increase due to the fact that the oxidation of the metal tends to progress relatively easily.

In contrast, in the interconnector composite 200 of the present embodiment, as described above, the Ni concentration (atm %) contained in the Mn—Co coating layer 196 decreases with distance from the oxide coating layer 194 . Therefore, in the interconnector composite 200 of the present embodiment, Ni is relatively low, so the concentration of Ni in the entire Mn—Co coating layer 196 is relatively low. Therefore, in the interconnector composite 200 of the present embodiment, the amount of Ni contained in the Mn--Co coating layer 196 can be relatively small, thereby reducing the amount of oxygen originally contained in the Mn--Co coating layer 196. A decrease in permeation prevention performance is suppressed. This suppresses an increase in electrical resistance that accompanies the progress of oxidation of the metal member 190 . Therefore, according to the interconnector composite 200 of the present embodiment, current can flow more efficiently.

Further, in the interconnector composite 200 of the present embodiment, the concentration of Ni in the region of the Mn—Co coating layer 196 up to 1 μm from the oxide coating layer 194 is 0.5 atm % or more. In the interconnector composite 200 of the present embodiment, since the concentration of Ni in the region sufficiently close to the oxide film layer 194 is sufficiently high, the presence of Ni effectively suppresses the existence of the Cr—Mn reaction layer. The increase in the initial electrical resistance caused by this is suppressed. Therefore, according to the interconnector composite 200 of the present embodiment, the current can flow more efficiently.

In the interconnector composite 200 of this embodiment, the metal member 190 contains Ni, which is the same element as Ni contained in the Mn—Co coating layer 196 . The Ni concentration (atm %) contained in the metal member 190 decreases as the distance from the oxide film layer 194 increases.

In the interconnector composite 200 of this embodiment, the metal member 190 contains Ni, which is the same element as Ni contained in the Mn—Co coating layer 196, as described above. The electrical resistance of Ni contained in the metal member 190 is lower than the electrical resistance of Cr and Mn contained in the Mn—Co coating layer 196 . In addition, since the Ni contained in the metal member 190 reacts with Cr, the amount of the Cr--Mn reaction layer formed is reduced as compared with the structure in which Ni does not exist. Therefore, the presence of Ni contained in the metal member 190 suppresses an increase in initial electrical resistance. Therefore, according to the interconnector composite 200 of the present embodiment, the current can flow more efficiently.

In addition, in the interconnector composite 200 of the present embodiment, as described above, the concentration (atm %) of Ni contained in the metal member 190 decreases with increasing distance from the oxide film layer 194 . In the configuration in which the concentration distribution is uniform, the presence of Ni contained in the metal member 190 produces the above effect (suppressing an increase in initial electrical resistance) for the reasons described above. However, on the other hand, as the amount of Ni contained in the metal member 190 increases, the coefficient of thermal expansion of the metal member 190 increases, and cracks caused by the difference in thermal expansion between the oxide film layer 194 and the metal member 190 occur. There is also an aspect that the electrical resistance increases due to the occurrence of In contrast, in the interconnector composite 200 of the present embodiment, the concentration (atm %) of Ni contained in the metal member 190 decreases as the distance from the oxide film layer 194 increases. Therefore, in the interconnector composite 200 of the present embodiment, Ni is relatively low, so the concentration of Ni in the entire metal member 190 is relatively low. Therefore, in the interconnector composite 200 of the present embodiment, the amount of Ni contained in the metal member 190 can be relatively reduced, thereby suppressing the coefficient of thermal expansion of the metal member 190 to a low value. can. Therefore, deterioration of the original oxygen permeation prevention performance of the Mn—Co coating layer 196 is suppressed. This suppresses an increase in electrical resistance due to cracks occurring between the oxide film layer 194 and the metal member 190 . Therefore, according to the interconnector composite 200 of the present embodiment, current can flow more efficiently.

Further, the method for manufacturing the interconnector composite 200 of the present embodiment includes a step of preparing the metal member 190 (S110) and a step of forming the Ni plating layer 151 containing Ni on the metal member 190 by plating (S120). a step of forming a Mn oxide layer 152 on the Ni plating layer 151 by migration electrodeposition (S130); and a step of forming a Co plating layer 153 containing Co on the Mn oxide layer 152 by plating (S140). and a step of forming oxide film layer 194 and Mn—Co film layer 196 on metal member 190 by firing metal member 190 that has undergone steps S110, S120, S130, and S140 (S150 ). According to the method for manufacturing the interconnector composite 200 of the present embodiment, the Mn—Co coating layer 196 contains Ni, and the concentration (atm%) of Ni contained in the Mn—Co coating layer 196 is the oxide film Interconnector composites 200 can be readily manufactured that are configured lower away from layer 194 . Further, in the method for manufacturing the interconnector composite 200 of the present embodiment, after the Mn oxide layer 152 is formed by migration electrodeposition (S130), the Co plating layer 153 is formed in the gaps generated in the Mn oxide layer 152. Therefore, (S140), the adhesion between the Mn—Co coating layer 196 and the Mn oxide layer 152 is improved, thereby suppressing the peeling of the Mn—Co coating layer 196 (from the oxide coating layer 194). .

Further, in the method for manufacturing the interconnector composite 200 of the present embodiment, a ketone solvent is used as the solvent for soaking the metal member 190 in the step of S130. Therefore, according to the method for manufacturing the interconnector composite 200 of the present embodiment, the Mn oxide layer 152 can be formed on the Ni plating layer 151 more efficiently in the step of S130.

The presence of Ni contained in the Mn--Co coating layer 196 and the metal member 190 suppresses an increase in initial electrical resistance, and Ni contained in the Mn--Co coating layer 196 and the metal member 190 is oxidized. From the viewpoint of both suppressing an increase in electrical resistance caused by , it is preferable that there are a particularly large number of them arranged, and it is preferable that a particularly small number of them are arranged at some distant position. Specifically, the concentration of Ni in a region within 2.0 μm from the oxide film layer 194 is 0.5 atm % or more (more preferably 0.8 atm % or more), and the distance from the oxide film layer 194 is It is more preferable that the concentration of Ni in the region of 6.0 μm or more is 90% or less (more preferably 80% or less) of the concentration in the region of 2.0 μm or less. Also, if the concentration (atm%) of Ni contained in the Mn—Co coating layer 196 and the metal member 190 is too high, the presence of the Ni causes the Mn—Co coating layer 196 to peel off (from the oxide coating layer 194). becomes more likely to occur. From this point of view, the concentration (atm %) of Ni contained in the Mn—Co coating layer 196 and the metal member 190 is preferably 5 atm % or less, for example.

A-6. Performance evaluation:
A sample of the interconnector composite 200 was produced, and the performance was evaluated using the sample. FIG. 12 is an explanatory diagram showing performance evaluation results in this embodiment. The "Ni concentration gradient" in FIG. 12 means that the Ni concentration (atm %) in the Mn--Co coating layer 196 decreases as the distance from the oxide coating layer 194 increases. ” means the concentration of Ni in the region of the Mn—Co coating layer 196 up to 2.0 μm from the oxide coating layer 194 .

A-6-1. For each sample:
As shown in FIG. 12, four samples (samples S1, S2, S3, and S4) were used for this performance evaluation.

Sample S1 and sample S2 are samples of the interconnector complex 200 of the present embodiment described above. In sample S1, the concentration of Ni in the region of the Mn—Co coating layer 196 up to 2 μm from the oxide coating layer 194 is 0.5 atm% or more (more specifically, 0.8 atm%). On the other hand, sample S2 differs from sample S1 only in that the concentration of Ni in the region is less than 0.5 atm % (more specifically, 0.4 atm %). In samples S1 and S2, the concentration (atm%) of Ni contained in the Mn—Co film layer 196 and the concentration (atm%) of Ni contained in the metal member 190 decreased with increasing distance from the oxide film layer 194. ing. More specifically, in this performance evaluation, the unit specific regions were sequentially divided by 2 μm from the side closer to the oxide film layer 194 in the specific regions whose distance from the oxide film layer 194 was within 6 μm for the samples S1 and S2. When divided, the Ni concentration (atm%) of each unit specific region is lower than the Ni concentration of the unit specific region adjacent to the unit specific region on the side closer to the oxide film layer 194 by 0.1 atm% or more. I used what I had.

Sample S3 and sample S4 are samples of interconnector composites of comparative examples. The interconnector composite of sample S3 differs from the interconnector composites 200 of samples S1 and S2 (this embodiment) in that the Mn—Co coating layer 196 does not contain Ni. In the interconnector composite of sample S4, the Mn—Co coating layer 196 and the metal member 190 contain Ni, but the Ni concentration (atm%) contained in the Mn—Co coating layer 196 and the metal member 190 The Ni concentration (atm %) contained therein is uniform (that is, it does not decrease with increasing distance from the oxide film layer 194), which is different from the interconnector composites 200 of samples S1 and S2 (this embodiment). . Note that the concentration of Ni in the region of the Mn—Co coating layer 196 up to 2 μm away from the oxide coating layer 194 and the concentration of Ni in the region up to 2 μm away from the oxide coating layer 194 of the metal member 190 are Both are 0.5 atm % or more (more specifically, 0.8 atm %).

A-6-2. Evaluation method and evaluation results:
Under the conditions of 900° C. and 2000 hours in an air atmosphere, a constant current (for example, 0.5 A/cm ² ) is passed through each of the above samples (samples S1, S2, S3, and S4), and the electrical resistance (contact resistance) (Ωcm ² ) was measured. Electric resistance (hereinafter also referred to as “initial resistance”) during 90 hours (in this evaluation, the time set as the time corresponding to the above “initial”) from the start of current flow (for the first time after manufacturing), and the current Electrical resistance (hereinafter also referred to as “long-term resistance”) for 1500 hours after the start of flowing (in this evaluation, the time set as the time when the increase in electrical resistance due to oxidation of Ni reaches a certain level). was evaluated based on Regarding the initial resistance, the smaller the increase in electrical resistance (the difference between the electrical resistance when the current started to flow and the electrical resistance after 90 hours) during 90 hours after the start of current flow, the higher the evaluation. Similarly, for the long-term resistance, the increase in electrical resistance during 1500 hours after the start of current flow (the difference between the electrical resistance when the current started to flow and the electrical resistance after 1500 hours) was It was determined that the smaller the value, the higher the evaluation. Specifically, if the initial resistance is 1.0 Ωcm ² or less, "⊚", if the increase in initial resistance is greater than 1.0 Ωcm ² and 2.0 Ωcm ² or less, "○" If the increase value of was larger than 2.0 Ωcm ² and 3.0 Ωcm ² or less, it was judged as "Δ", and if it was larger than 3.0 Ωcm ² , it was judged as "X". Regarding the long-term resistance, if it was 4.0 Ωcm ² or less, it was judged as “◯”, and if it was greater than 4.0 Ωcm ² , it was judged as “X”. Then, if both the evaluation of the initial resistance and the evaluation of the long-term resistance are not "x", it is determined to be "passed", and at least one of the evaluation of the initial resistance and the evaluation of the long-term resistance is "x". was judged to be “failed”. In this performance evaluation, the measurement time for the initial resistance is set to "90 hours" and the measurement time for the long-term resistance is set to "1500 hours", which is just an example, and an appropriate measurement time for the initial resistance, Appropriate measurement time for long-term resistance varies depending on environmental temperature, etc. in which interconnector composite 200 is used.

FIG. 13 is an explanatory diagram showing measurement results of electrical resistance (only samples S1 and S3) in performance evaluation in this embodiment.

As shown in FIG. 13, in the interconnector complex of sample S3, the electrical resistance increased for about 90 hours (corresponding to the above-mentioned "initial stage") after the current started to flow through the interconnector complex, and then After gradually decreasing with the passage of time, it increased again. The increase in electrical resistance was greater than 3.0 Ωcm ² 90 hours after the start of current flow through the interconnector composite. Therefore, the evaluation of the initial resistance in the interconnector complex of sample S3 was "x". The increase in electrical resistance was 4.0 Ωcm ² or less after 1500 hours from when the current started to flow through the interconnector composite. Therefore, the long-term resistance of the interconnector composite of sample S3 was evaluated as "good". Based on these results, the evaluation result of the interconnector composite of sample S3 was set as "failed".

The reason why the electrical resistance increased particularly for about 90 hours is, as described above, the Cr—Mn reaction layer formed in the oxide film layer 194 containing Cr oxide (Cr and Mn react with each other). It is presumed that this is due to the existence of the layer). Further, the reason why the electric resistance once gradually decreased is not necessarily clear, but it is presumed that the amount of the Cr--Mn reaction layer decreased due to the decomposition of the Cr--Mn reaction layer. In addition, the reason why the electrical resistance increased again is presumed to be that the excessive amount of Ni contained in the Mn—Co coating layer 196 and the metal member 190 accelerated the oxidation of the metal member 190. .

In the interconnector composite of sample S4, the increase in initial resistance was 1.0 Ωcm ² or less. Therefore, the evaluation of the initial resistance of the interconnector composite of sample S4 was "⊚". The increase in electrical resistance at 1500 hours after the start of current flow through the interconnector complex was greater than 4.0 Ωcm ² . Therefore, the evaluation for long-term resistance in the interconnector composite of sample S4 was "x". Based on these results, the evaluation result of the interconnector composite of sample S4 was "failed".

On the other hand, as shown in FIG. 13 , in the interconnector composite 200 of sample S1, the current increased for about 90 hours (corresponding to the above “initial stage”) after the current started to flow through the interconnector composite 200 . 90 hours after the start of current flow, the increase in electrical resistance was 1.0 Ωcm ² or less. Therefore, the evaluation of the initial resistance in the interconnector composite 200 of sample S1 was "⊚". The increase in electrical resistance was 4.0 Ωcm ² or less after 1500 hours from the start of current flow through the interconnector composite 200 . Therefore, the evaluation of the initial resistance of the interconnector composite 200 of sample S1 was "good". Based on these results, the evaluation result of the interconnector composite 200 of sample S1 was "passed".

In addition, the interconnector composite 200 of the sample S2 had roughly the same evaluation results as the interconnector composite 200 of the sample S1, but the electrical resistance increased by 1.0 Ωcm ² after 90 hours from the start of the current flow. larger and less than or equal to 2.0 Ωcm ² . Therefore, the evaluation of the initial resistance of the interconnector composite 200 of sample S1 was "good". The increase in electrical resistance was 4.0 Ωcm ² or less after 1500 hours from the start of current flow through the interconnector composite 200 . Therefore, the evaluation of the initial resistance of the interconnector composite 200 of sample S1 was "good". Based on these results, the evaluation result of the interconnector composite 200 of sample S2 was "passed".

B. Variant:
The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the scope of the invention. For example, the following modifications are possible.

The configurations of the single cell 110, the power generating unit 102, or the fuel cell stack 100 in the above embodiment are merely examples, and can be modified in various ways.

For example, in the above embodiment, the Mn—Co coating layer 196 contains Ni, and the concentration (atm%) of Ni contained in the Mn—Co coating layer 196 is assumed to decrease as the distance from the oxide coating layer 194 increases. However, the Mn—Co coating layer 196 contains at least one type of element selected from Ni, Cu, Zn, and Co (hereinafter referred to as “specific element”). The concentration (atm %) of the specific element in the oxide film layer 194 may decrease as the distance from the oxide film layer 194 increases. In order to realize this configuration, basically, "Ni" in the above-described embodiment should be read as "specific element". Also in this configuration, for the same reason as in the above embodiment, the presence of the specific element contained in the Mn—Co coating layer 196 suppresses the initial increase in electrical resistance. Therefore, according to the interconnector composite 200 of the present embodiment, current can flow more efficiently than in a configuration in which the Mn—Co coating layer 196 does not contain the specific element. In addition, in the configuration of the modification, the metal member 190 contains the same element as the specific element contained in the Mn—Co coating layer 196, and the concentration of the specific element contained in the metal member 190 (atm% ) may be lower away from the oxide layer 194 . Also in this configuration, for the same reason as in the above embodiment, the presence of the specific element contained in the metal member 190 suppresses the initial increase in electrical resistance. Therefore, according to this interconnector complex 200, current can flow more efficiently. 14A and 14B are explanatory diagrams showing performance evaluation results in a modification using Cu as the specific element. As shown in FIG. 14, also in this modified example, evaluation results similar to those in the above-described embodiment using Ni as the specific element were obtained. From the evaluation results in the above embodiment using Ni or Cu as the specific element, even in the configuration using Zn or Co as the specific element, for the same reason as described above, the presence of the specific element increases the initial electrical resistance. is presumed to be suppressed. The content of the specific element (excluding Co) in the Mn—Co coating layer 196 and the content of the specific element in the metal member 190 are preferably 5 atm % or less, more preferably 2 atm % or less. . The content of the specific element in the Mn--Co coating layer 196 can be specified as follows, for example. First, powder of the Mn—Co coating layer 196 is obtained by scraping the Mn—Co coating layer 196 . By analyzing this powder with an ICP-AES device, the content of the specific element in the Mn--Co coating layer 196 can be specified. The content of the specific element in metal member 190 can also be specified by a similar method.

Further, in the above embodiment, in the entire interconnector composite 200 (the surface facing the air electrode 114), the concentration of the specific element in the region up to 2 μm from the oxide film layer 194 in the Mn—Co film layer 196 is configured to be 0.5 atm % or more, but only a portion (for example, the peripheral portion of the air electrode side current collector 134) of the interconnector composite 200 (the surface facing the air electrode 114) ), the concentration of the specific element in the region up to 2 μm from the oxide film layer 194 in the Mn—Co film layer 196 may be 0.5 atm % or more. Further, in the above embodiment, the concentration of the specific element contained in the Mn—Co coating layer 196 in the entire interconnector composite 200 (the surface facing the air electrode 114 in) decreases as the distance from the oxide coating layer 194 increases. However, only a portion of (the surface facing the air electrode 114 in) the interconnector composite 200 (for example, only a portion including the peripheral portion of the air electrode side current collector 134) , the concentration of the specific element contained in the Mn—Co coating layer 196 may be configured to decrease with increasing distance from the oxide coating layer 194 .

In the above embodiment, the Mn oxide layer 152 is formed by migration electrodeposition in the step of S130. A material layer 152 may be formed.

In the above embodiment, a ketone solvent is used as the solvent for immersing the metal member 190 in the step of S130, but other solvents (for example, a solvent in which hydrochloric acid is added to ethanol) may be used.

Further, in the above embodiment, the interconnector 150 and the air electrode side current collector 134 are integral members (metal member 190), but the interconnector 150 and the air electrode side current collector 134 are separate members. may In that case, the present invention can also be applied to an interconnector member composed of the interconnector 150 or the cathode-side current collector 134 , the oxide film layer 194 and the Mn—Co film layer 196 .

Further, in the above embodiment, the air electrode-side current collector 134 is in contact with the air electrode 114 through the joint 138 , but the air electrode-side current collector 134 is in contact with the air electrode 114 without the joint 138 . It may be

Further, in the above embodiments, SOFCs that generate electricity by utilizing the electrochemical reaction between the hydrogen contained in the fuel gas and the oxygen contained in the oxidant gas are used. It is also applicable to an electrolytic cell unit, which is a constituent unit of a solid oxide electrolysis cell (SOEC) that utilizes hydrogen to generate hydrogen, and an electrolytic cell stack comprising a plurality of electrolytic cell units. The configuration of the electrolysis cell stack is known, for example, as described in Japanese Patent Application Laid-Open No. 2016-81813, so it will not be described in detail here, but it is roughly the same as the fuel cell stack 100 in the above-described embodiment. is the configuration. That is, the fuel cell stack 100 in the above-described embodiment can be read as an electrolytic cell stack, the power generation unit 102 can be read as an electrolytic cell unit, and the single cell 110 can be read as an electrolytic single cell. However, during the operation of the electrolysis cell stack, 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 is supplied as a source gas. As a result, an electrolysis reaction of water occurs in each electrolysis cell unit, hydrogen gas is generated in the fuel chamber 176 , and the hydrogen is taken out of the electrolysis cell stack through the communication hole 108 . Even in the electrolytic cell unit and the electrolytic cell stack having such a configuration, an increase in initial electrical resistance is suppressed by adopting the interconnector composite 200 having the configuration described above. Therefore, according to the interconnector composite 200 of the present embodiment, the current can flow more efficiently.

Also, in the above embodiments, a solid oxide fuel cell (SOFC) was described as an example, but the present invention is also applicable to other types of fuel cells (or electrolysis cells) such as a molten carbonate fuel cell (MCFC). Applicable.

22: Bolt 24: Nut 26: Insulating sheet 27: Gas passage member 100: Fuel cell stack 102: Power generation unit 104: End plate 106: End plate 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 124: Joint 130: Air electrode side frame 132: Oxidant gas supply passage 133: Oxidant gas discharge passage 134: Air electrode side current collector 138: Joint 140: Fuel electrode side frame 142: Fuel gas supply Communication hole 143: Fuel gas discharge communication hole 144: Fuel electrode side current collector 149: Spacer 150: Interconnector 151: Ni plating layer 152: Mn oxide layer 153: Co plating layer 161: Oxidant gas introduction manifold 162: Oxidation Agent gas discharge manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas discharge manifold 176: Fuel chamber 180: Intermediate layer 190: Metal member 194: Oxide layer 196: Mn-Co layer 200: Interconnector composite E1: Electrode E2: Electrode Ec1: Electrolyzer Ec2: Electrolyzer FG: Fuel gas FOG: Fuel off-gas OG: Oxidant gas OOG: Oxidant off-gas P1: Power source P2: Power source Es1: Solution Es2: Solution

Claims (5)

a metal member containing Fe and Cr;
a first coating layer disposed on the surface of the metal member and containing Cr oxide;
a second coating layer disposed on the surface of the first coating layer opposite to the metal member and containing a spinel-type oxide containing Mn and Co. hand,
The second coating layer contains at least one specific element selected from Ni, Cu, Zn and Co,
The concentration (atm%) of the specific element contained in the second coating layer is lower as the distance from the first coating layer increases,
An interconnector member characterized by: The interconnect member according to claim 1,
The concentration of the specific element in a region of the second coating layer up to 1 μm away from the first coating layer is 0.5 atm% or more.
An interconnector member characterized by: The interconnect member according to claim 1 or claim 2,
The metal member contains the same element as the specific element contained in the second coating layer,
The concentration (atm%) of the specific element contained in the metal member decreases as the distance from the first coating layer increases.
An interconnector member characterized by: A method for manufacturing an interconnector member according to any one of claims 1 to 3,
A first step of preparing a metal member;
a second step of forming a specific element plating layer containing the specific element on the metal member by plating;
a third step of forming a Mn oxide layer on the specific element plating layer by migration electrodeposition;
a fourth step of forming a Co plating layer containing Co on the Mn oxide layer by plating;
By firing the metal member that has undergone the first step, the second step, the third step, and the fourth step, the first coating layer and the second coating layer are formed on the metal member. a fifth step of forming a coating layer;
A method of manufacturing an interconnector member characterized by: A method for manufacturing an interconnector member according to claim 4,
In the third step, a ketone solvent is used as a solvent for soaking the metal member,
A method of manufacturing an interconnector member characterized by:

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