JP2016051699A - Fuel battery unit cell with interconnector and method of manufacturing the same, fuel battery stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery unit cell with an interconnector excellent in reliability, and capable of suppressing reduction of weldability.SOLUTION: A fuel battery unit cell 2 with an interconnector is constituted by laminating a tabular unit cell 2, a fuel electrode frame 13, and a tabular interconnector 14. The fuel electrode frame 13 and interconnector 14 are joined via weld zones 70, 71. In a region R1 of the surface 41 of the interconnector 14 facing the fuel electrode frame 13, excepting at least the weld zones 70, 71, a first coating layer 42 is formed. A second coating layer 45 is formed entirely on the other surface 44, i.e., the back side of the surface 41 of the interconnector 14.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fuel cell single cell with an interconnector formed by stacking a fuel cell single cell, a frame and an interconnector, a fuel cell stack formed by stacking a plurality of fuel cell single cells with the interconnector, and a fuel with an interconnector The present invention relates to a method for manufacturing a battery single cell.

  Conventionally, as a fuel cell, for example, a solid oxide fuel cell (SOFC) including a solid electrolyte layer (solid oxide layer) is known. This fuel cell includes a fuel cell stack formed by stacking a plurality of single cells that are the minimum unit of power generation.

  Specifically, the single cell includes an air electrode, a fuel electrode, and a solid electrolyte layer, and generates electric power through a power generation reaction. In addition, in the fuel cell, a fuel cell stack is configured by stacking a plurality of frames, separators, and interconnectors in addition to a single cell. The frame, the separator, and the interconnector are made of metal members, and each member is joined by laser welding or the like to constitute a fuel cell single cell with an interconnector.

  More specifically, the frame is formed in a frame shape using stainless steel or the like so as to surround the side surface of the single cell. The separator is also formed of stainless steel or the like, and has a rectangular frame shape having an opening for placing a single cell in the center. And in the state which has arrange | positioned the single cell inside the opening part of a separator, a separator is joined to the peripheral part of a single cell, and a single cell with a separator is comprised. In a single cell with a separator, the separator functions as a partition plate for partitioning an air chamber or a fuel chamber to which a reaction gas (oxidant gas or fuel gas) is supplied. Further, the interconnector is also formed in a plate shape with stainless steel or the like, and the electrical connection of the single cell is secured by the interconnector.

  The separator, the frame, and the interconnector are formed with a plurality of holes for forming a gas flow path. When a single cell with a separator, a frame, and an interconnector are joined to form a fuel cell single cell with an interconnector, a gas flow path is formed by sealing the periphery and outer periphery of each hole by laser welding. The sealing performance is ensured.

  Stainless steel, which is a material for forming the interconnector, is a metal material containing chromium. For this reason, in the interconnector, a coating layer for preventing chromium poisoning is formed on the cathode side surface in contact with the air electrode (see Patent Document 1 and the like). The coating layer disclosed in Patent Document 1 is a conductive oxide film made of an M-based metal oxide (an oxide containing at least one kind of metal M selected from Mn, Fe, Co, and Ni). It is.

In the fuel cell stack disclosed in Patent Document 2, a bonding layer (coating layer) for fixing a current collector made of a porous metal body containing nickel is formed on the anode side surface of the interconnector. Yes. Further, in Patent Document 3, coating layers are formed on both surfaces (cathode side surface and anode side surface) of the interconnector. The coating layer formed on the anode side surface is made of a material containing nickel (for example, NiO). In this case, when the fuel gas (hydrogen H ₂ ) is supplied to the fuel electrode in a high temperature environment during power generation, the NiO of the coating layer becomes Ni and the bondability between the interconnector and the fuel electrode side current collector is improved. Is done.

Japanese Patent No. 3712733 Japanese Patent No. 5346402 Special table 2010-503157

  By the way, in the fuel cell single cell with an interconnector, a welded part is formed by laser welding around the hole part and the outer peripheral part constituting the gas flow path. It is necessary to obtain a stable welding quality free from (poor penetration, blowhole, insufficient joint length). Further, since the fuel cell is used for a long time at a high temperature (a temperature of about 700 ° C. to 1000 ° C.), the durability of the welded portion must be ensured. That is, heat resistance, wear resistance, and corrosion resistance at the welded portion are required.

  However, when the coating layer is provided on the surface of the interconnector made of stainless steel as described above, the weldability deteriorates. When a coating layer is present on the surface of stainless steel, the metal component of the coating layer has a low melting point, and therefore volatilizes preferentially during welding. As a result, spatter and blowholes are generated at the welded portion between the interconnector and the frame, resulting in poor weldability due to poor weldability and problems such as gas leak failure. In particular, when coating layers are formed on both sides of the interconnector, the weldability is extremely deteriorated, resulting in frequent welding defects. In addition, removing the coating layer on the surface of the interconnector improves weldability, but causes problems such as chromium poisoning and reduced reliability (wear resistance and corrosion resistance) at the weld. End up.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell unit cell with an interconnector and a fuel cell stack that can suppress a decrease in weldability and is excellent in reliability. is there. Another object is to provide a method of manufacturing a single fuel cell with an interconnector suitable for manufacturing the above single cell with an interconnector.

  As means for solving the above problems (means 1), a flat plate fuel cell unit cell having a fuel electrode, an air electrode and an electrolyte layer, an electrolyte layer in the frame, and a part of the fuel electrode or air electrode A fuel cell single cell with an interconnector, in which a frame-shaped frame on which a frame is disposed and a plate-shaped interconnector disposed on one surface of the frame are stacked, and the frame and the interconnector are welded A first coating layer is formed on the surface of the interconnector surface that is joined via a portion and faces the frame at least except for the welded portion, and is formed on the entire other surface that is the back side of the interconnector surface. There is a fuel cell single cell with an interconnector characterized in that a second coating layer is formed.

  According to the invention described in Means 1, since the first coating layer is not formed on the welded portion on the surface of the interconnector facing the frame, it is possible to suppress a decrease in weldability as in the prior art. Therefore, the interconnector and the frame can be reliably joined by welding, and leakage of fuel gas or oxidant gas at the welded portion can be suppressed. A current collector that is electrically connected to the electrodes is disposed on the surface of the interconnector. By forming the first coating layer on the interconnector surface in the region excluding at least the welded portion, the contact resistance between the interconnector and the current collector can be kept low by the first coating layer. Furthermore, the durability of the welded portion is increased by mixing a part of the second coating layer into the welded portion. Specifically, for example, when Mn is contained in the component of the second coating layer, it is present as an impurity in the steel and combined with S that causes a decrease in weldability, so that the weldability is improved. Moreover, it plays the role of a deoxidizer at the time of welding, and can prevent the oxidation at the time of welding. For this reason, the power generation performance of the single fuel cell can be maintained in a good state, and the product reliability can be improved.

  Here, the current collector is preferably made of a porous metal body, and the current collector and the first coating layer are preferably formed to contain the same metal. Further, the current collector and the first coating layer may be formed of the same metal material. When the current collector and the first coating layer are formed by including the same metal as described above, the current collector can be fixed to the interconnector via the first coating layer, and the interconnector and the current collector Connection resistance can be kept low.

  The interconnector is made of a material containing chromium, and the second coating layer may be formed of a metal oxide film for preventing the fuel electrode or the air electrode from being poisoned by chromium. By forming this second coating layer, chromium poisoning of the fuel electrode or air electrode can be reliably prevented.

  The thickness of the second coating layer is preferably thinner than the first coating layer. Specifically, the thickness of the second coating layer is preferably 5 μm or less, and more preferably 1 μm or less. Thus, since the weldability can be improved by thinning the second coating layer, the leakage of the fuel gas or the oxidant gas in the welded portion can be reliably suppressed. Furthermore, chromium poisoning of the fuel electrode or the air electrode can be reliably prevented by the second coating layer.

  The surface of the interconnector facing the frame is divided into a region where the frame contacts and a region which does not contact the frame located inside the region where the frame contacts. On the surface of the interconnector, a first coating layer may be formed in a region not in contact with the frame, and a film containing chromium oxide may be formed in a region in contact with the frame. Specifically, on the surface of the interconnector, a current collector that is electrically connected to the fuel electrode is disposed in a region that does not contact the frame, and the current collector has a metal part including nickel. The first coating layer may contain nickel. In this case, since the metal part of the current collector and the first coating layer contain the same metal component, the current collector and the interconnector can be reliably fixed by the first coating layer. Therefore, the contact resistance between the interconnector and the current collector can be kept low. In addition, since a film containing chromium oxide is formed in a region in contact with the frame on the surface of the interconnector, generation of an unstable film (abnormal film) during power generation can be prevented. In addition, by forming a chromium oxide film in a region in contact with the frame, it is possible to suppress the volatilization (movement) of chromium and to avoid a decrease in power generation performance.

  The weld may be a laser weld mark. Moreover, you may use a fiber laser as a laser when forming a welding part. In the welding by the fiber laser, since it is possible to focus on a small spot size, the line width of the linear welded portion can be 0.2 mm or less. Therefore, the interconnector can be reliably welded to the frame while suppressing thermal distortion. In addition to laser welding, welding may be performed by resistance welding or the like.

  The frame may be formed using an aluminum-containing metal material containing aluminum. Moreover, it is preferable that an aluminum containing metal material contains aluminum with the content rate of 1 mass% or more and 10 mass% or less. In this case, an oxide film made of alumina can be formed on the surface of the welded portion, and the corrosion resistance of the welded portion can be improved.

  The second coating layer is a conductive oxide film made of a metal oxide containing at least one transition metal selected from iron group elements, chromium group elements, and manganese group elements. Specifically, the second coating layer is a conductive material made of an M-based metal oxide containing at least one kind of metal M selected from manganese, iron, cobalt, nickel, and chromium, which are transition metals that are the fourth periodic elements. It is preferable that it is an oxide film. When the second coating layer is formed of such a metal oxide, it is possible to reliably prevent chromium poisoning of the fuel electrode or the air electrode.

The electrolyte layer is preferably a solid electrolyte layer made of a solid oxide. As a material for forming the solid electrolyte layer, for example, ZrO ₂ ceramic, LaGaO ₃ ceramic, or the like is used.

The air electrode is in contact with an oxidant gas serving as an oxidant, and functions as a positive electrode in a single fuel cell. Here, examples of the material for forming the air electrode include metal materials and metal composite oxides. Preferable examples of the metal material include Pt, Au, Ag, Pd, Ir, Ru, Rh, etc., and alloys thereof. Preferable examples of metal composite oxides include, for example, composite oxides containing La, Pr, Sm, Sr, Ba, Co, Fe, and Mn (La _1-x Sr _x CoO ₃ -based composite oxide, La _{1 -x} Sr _x FeO _3-based composite _{oxide, La 1-x Sr x Co} 1-y Fe y O 3 composite _{oxide, La 1-x Sr x MnO} 3 composite _oxide, Pr _1-x Ba _x CoO ₃ type composite oxide, Sm _1-x Sr _x CoO ₃ type composite oxide) and the like.

The fuel electrode is in contact with a fuel gas serving as a reducing agent and functions as a negative electrode in a single fuel cell. Here, as the material for forming the fuel electrode, for example, ZrO ₂ ceramics stabilized by rare earth elements (Sc, Y, etc.), CeO ₂ ceramics doped with rare earth elements (Sm, Gd, etc.), etc. Among them, a metal ceramic material in which at least one ceramic material is mixed with at least one of metal materials such as Pt, Au, Ag, Pd, Ir, Ru, Rh, Ni, Fe and alloys of these metal materials. Mixtures (cermets) can be used.

  As another means (means 2) for solving the above-mentioned problem, there is a fuel cell stack in which a plurality of the interconnector-attached fuel cell single cells described in means 1 are stacked.

  According to the invention described in the means 2, in the fuel cell stack, the weldability and durability at the joint portion of each fuel cell single cell are enhanced, so that the reaction gas does not leak and the favorable battery characteristics are maintained. be able to.

  Further, as another means (means 3) for solving the above-mentioned problem, there is provided a manufacturing method for manufacturing the interconnector-attached fuel cell unit cell described in means 1, wherein the holes constituting the gas flow path are respectively provided. A preparation step of preparing the formed frame and the interconnector, and the first coating layer avoiding a region around the hole and serving as the welded portion on the surface of the interconnector facing the frame; And a coating step for forming the second coating layer on the entire other surface which is the back side of the surface of the interconnector facing the frame, and an arrangement step of arranging the frame and the interconnector in an overlapping manner. And a welding step for irradiating a region around the hole and serving as the weld with a laser. There are provided methods for producing the interconnector with the fuel cell unit, characterized in Mukoto.

  Therefore, according to the invention described in the means 3, in the coating step, the first coating layer is formed on the surface of the interconnector facing the frame at least around the hole portion and avoiding the region to be a welded portion. Then, after arranging the frame and the interconnector so as to overlap each other, in the welding step, a laser is irradiated to the area around the hole portion to become the welded portion, thereby closing the periphery of the hole portion. The weld is formed. At this time, since the 1st coating layer is not formed in the welding part, the fall of weldability like a prior art can be suppressed. Therefore, the interconnector and the frame can be reliably joined by welding.

  In the coating step, the first coating layer forming material is applied to the surface of the interconnector facing the frame, and the second coating layer forming material is applied to the other surface on the back side of the interconnector surface facing the frame. Then, a heat treatment is performed to bake the first coating layer and the second coating layer, and a film containing chromium oxide is formed in the non-formation region of the first coating layer on the interconnector surface facing the frame. Also good.

  If it does in this way, compared with the case where a 1st coating layer and a 2nd coating layer are baked separately, manufacturing cost can be held down. In addition, since a chromium oxide film is formed in a region where the first coating layer is not formed on the surface of the interconnector, it is possible to prevent the generation of an unstable film (abnormal film) during power generation. Furthermore, by forming a chromium oxide film on the surface of the interconnector, it is possible to suppress the volatilization (migration) of chromium, and to avoid a decrease in power generation performance due to chromium poisoning.

  In the coating step, the first coating layer and the second coating layer may be formed on each surface of the interconnector by spraying a sol-form forming material by a spray process. In this way, the first coating layer and the second coating layer can be efficiently and reliably formed on each surface of the interconnector.

  In the coating step, heat treatment in a reducing atmosphere (reduction treatment) and heat treatment in an oxidizing atmosphere (oxidation treatment) are performed as the heat treatment. In addition, the heating temperature in heat processing is 500 degreeC or more and 1150 degrees C or less, for example. By performing this heat treatment, the first coating layer and the second coating layer can be reliably formed on each surface of the interconnector.

The perspective view which shows schematic structure of the fuel cell stack in one embodiment. AA sectional view taken on the line AA of FIG. Sectional drawing which shows schematic structure of the fuel cell single cell with an interconnector. The top view of the interconnector which shows the formation area of a 1st coating layer. The top view of the fuel cell single cell with an interconnector which shows the welding part in an interconnector. Sectional drawing which shows schematic structure of the fuel cell single cell with an interconnector. Sectional drawing which shows a welding jig apparatus. No. The principal part sectional drawing which shows the formation state of each coating layer in 1 sample. No. The principal part sectional drawing which shows the formation state of each coating layer in the sample of 2. FIG. The top view of the interconnector which shows the formation area of the 1st coating layer in another embodiment.

  Hereinafter, an embodiment in which the present invention is embodied in a fuel cell stack will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, the fuel cell stack 3 of the present embodiment is a stack of a solid oxide fuel cell (SOFC). The fuel cell stack 3 is formed by stacking a plurality of (for example, 20) fuel cell single cells 2 with an interconnector. In the fuel cell stack 3, end plates 8 and 9 are disposed at both end portions (upper end portion and lower end portion in FIG. 1) in the stacking direction of the single fuel cell unit 2 with interconnector. Furthermore, a plurality of through holes 4 are formed in the peripheral portion of the fuel cell stack 3 so as to penetrate the stack 3 in the thickness direction (vertical direction in FIGS. 1 and 2). The fastening bolts 5 are inserted into the four through holes 4 at the four corners of the fuel cell stack 3, and a nut (not shown) is screwed to the lower end portion of the fastening bolt 5 protruding from the lower surface of the fuel cell stack 3. Further, the gas circulation fastening bolts 6 are inserted into the remaining four through holes 4, and nuts 7 are screwed onto both ends of the gas circulation fastening bolts 6 protruding from the upper surface and the lower surface of the fuel cell stack 3. As a result, a plurality of interconnector-attached fuel cell single cells 2 are fixed in the fuel cell stack 3. Further, the end plates 8 and 9 arranged at both ends of the fuel cell stack 3 serve as output terminals for current output from the fuel cell stack 3.

  As shown in FIGS. 2 and 3, each interconnector-equipped fuel cell single cell 2 includes a flat fuel cell single cell 11 (hereinafter also simply referred to as “single cell”), which is a minimum unit of power generation, and a separator. 12, a fuel electrode frame 13, and an interconnector 14 are laminated and each member is joined by welding. Further, in the adjacent fuel cell single cell 2 with an interconnector, the separator 12 of the fuel cell single cell 2 with one interconnector (lower in FIGS. 2 and 3) and the fuel with the other (upward in FIGS. 2 and 3). An air electrode insulating frame 15 is interposed between the interconnector 14 of the single battery cell 2.

  The single cell 11 includes an air electrode 21, a fuel electrode 22, and a solid electrolyte layer 23, and generates power by a power generation reaction. The separator 12 is formed with a thickness of 0.1 mm, and has a substantially rectangular frame shape having a rectangular opening 30 at the center. In the present embodiment, separator 12 is formed using ferritic stainless steel containing aluminum (for example, an aluminum-containing metal material such as NCA-1: “NCA-1” is a product name of Nisshin Steel Co., Ltd.). ing. The separator 12 is joined to the peripheral portion of the single cell 11 (solid electrolyte layer 23) by brazing using a brazing material containing silver, and is disposed on one surface 34 (upper surface in FIG. 2) of the fuel electrode frame 13. Is done. The separator 12 functions as a partition plate between the cells 11 and separates the oxidant gas (air) in contact with the air electrode 21 and the fuel gas in contact with the fuel electrode 22.

  The fuel electrode frame 13 is a substantially rectangular frame-shaped member made of a conductive material having a thickness of about 2 mm, and is disposed so as to surround the side surface of the unit cell 11. In other words, a rectangular opening 31 that penetrates the fuel electrode frame 13 in the thickness direction is provided at the center of the fuel electrode frame 13, and is disposed on the inner side (inside the frame) of the opening 31. A part of the air electrode 21, the fuel electrode 22, and the solid electrolyte layer 23 constituting the cell 11 is disposed. In the present embodiment, the fuel electrode frame 13 is formed using the same material (for example, NCA-1) as the separator 12.

  The interconnector 14 is formed in a substantially rectangular plate shape with a conductive material having a thickness of about 0.8 mm. The interconnector 14 of this embodiment is a ferritic alloy that is made of chromium-containing stainless steel and hardly contains aluminum (for example, a metal material that does not contain aluminum such as Crofer 22H: “Crofer” is a registered trademark of ThyssenKrupp VDM GmbH) It is formed using. The interconnector 14 is disposed on one surface 35 (lower surface in FIG. 2) which is the back side of the surface 34 (upper surface in FIG. 2) on which the separator 12 is disposed in the fuel electrode frame 13. In a state where a plurality of interconnected fuel cell unit cells 2 are stacked in the fuel cell stack 3, a pair of interconnectors 14 are arranged on both sides of the unit cell 11 in the thickness direction. And each interconnector 14 ensures conduction between the single cells 11 in the thickness direction.

  The air electrode insulating frame 15 is formed in a substantially rectangular frame shape by a mica sheet which is an insulating material having a thickness of about 1.0 mm. A rectangular opening 37 that penetrates the insulating frame 15 in the thickness direction is provided at the center of the air electrode insulating frame 15.

  The solid electrolyte layer 23 is formed in a rectangular plate shape by a ceramic material (oxide) such as yttria stabilized zirconia (YSZ). The solid electrolyte layer 23 is fixed to the lower surface of the separator 12 and is disposed so as to close the opening 30 of the separator 12. The solid electrolyte layer 23 functions as an oxygen ion conductive solid electrolyte body. The thickness of the solid electrolyte layer 23 is about 10 μm.

  An air electrode 21 that contacts the oxidant gas supplied to the fuel cell stack 3 is formed on the upper surface of the solid electrolyte layer 23, and the fuel supplied to the fuel cell stack 3 is also formed on the lower surface of the solid electrolyte layer 23. A fuel electrode 22 in contact with the gas is formed. That is, the air electrode 21 and the fuel electrode 22 are disposed on both sides with the solid electrolyte layer 23 interposed therebetween. The air electrode 21 is disposed in the opening 30 of the separator 12 so as not to contact the separator 12. In the present embodiment, the fuel chamber 17 is formed below the separator 12 by the opening 31 of the fuel electrode frame 13 and the interconnector 14, and the opening 37 of the air electrode insulating frame 15, the interconnector 14 and the like. Thus, an air chamber 18 is formed above the separator 12.

In the single cell 11 of the present embodiment, the air electrode 21 is formed in a rectangular plate shape by LSCF (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ ) which is a metal complex oxide. ing. The fuel electrode 22 is formed in a rectangular plate shape by a mixture of nickel and yttria-stabilized zirconia (Ni-YSZ). The air electrode 21 is electrically connected to the interconnector 14 by an air electrode side current collector 38, and the fuel electrode 22 is electrically connected to the interconnector 14 by a fuel electrode side current collector 39. In the present embodiment, the air electrode side current collector 38 is formed integrally with the interconnector 14. The air electrode side current collector 38 may be formed of a member different from the interconnector 14. Further, the fuel electrode side current collector 39 is made of, for example, a nickel metal body so that the fuel gas can pass therethrough. In the present embodiment, the fuel electrode side current collector 39 is electrically connected between the interconnector 14 and the fuel electrode 22 in such a manner that the spacer 40 is sandwiched between the metal body portions and bent into a substantially U shape. Are arranged to connect to each other.

As shown in FIGS. 3 and 4, the fuel electrode side current collector 39 is connected to the interconnector 14 in the region R <b> 1 that does not contact the fuel electrode frame 13 on the surface 41 of the interconnector 14 facing the fuel electrode frame 13. A first coating layer 42 for fixing is formed. The first coating layer 42 is made of an oxide (NiO) containing the same metal (specifically, nickel) as the metal constituting the fuel electrode side current collector 39. The thickness of the first coating layer 42 is about 10 μm. Further, an oxide film 43 (chromia coating) made of chromium oxide (Cr ₂ O ₃ ) is formed in a region R2 in contact with the fuel electrode frame 13 on the surface 41 of the interconnector 14. The thickness of the oxide film 43 is about 1 μm. Further, a second coating layer 45 for preventing the air electrode 21 from being poisoned by chromium is formed on the entire other surface 44 which is the back side of the surface 41 of the interconnector 14 facing the fuel electrode frame 13. Is formed. The second coating layer 45 is made of, for example, a spinel type metal oxide film containing manganese and cobalt. The thickness of the second coating layer 45 is thinner than the first coating layer 42 and is 5 μm or less.

  The fuel cell stack 3 is formed with a gas flow path for flowing an oxidant gas and a fuel gas. Specifically, as shown in FIG. 2, as a gas flow path of the fuel cell stack 3, a fuel supply path 50 for supplying the fuel gas to the fuel chamber 17 of each single cell 11, and the fuel gas from the fuel chamber 17. A fuel discharge path 51 for discharging is formed. The fuel supply path 50 includes a fuel supply hole 52 that extends in the axial direction at the center of the gas circulation fastening bolt 6, and a fuel supply lateral hole 53 that allows the fuel supply hole 52 and the fuel chamber 17 to communicate with each other. . The fuel discharge path 51 includes a fuel discharge hole 54 that extends along the axial direction at the center of the gas circulation fastening bolt 6, and a fuel discharge lateral hole 55 that allows the fuel discharge hole 54 and the fuel chamber 17 to communicate with each other. ing. Therefore, the fuel gas is supplied to the fuel chamber 17 through the fuel supply hole 52 and the fuel supply lateral hole 53 in order, and is discharged from the fuel chamber 17 through the fuel discharge lateral hole 55 and the fuel discharge hole 54 in order. Is done.

  Further, as a gas flow path of the fuel cell stack 3, an air supply path (not shown) for supplying air to the air chamber 18 of each single cell 11 and an air discharge path (not shown) for discharging air from the air chamber 18 are provided. I have. The air supply path has substantially the same structure as the fuel supply path 50, and includes an air supply hole (not shown) extending along the axial direction at the center of the gas distribution fastening bolt 6, an air supply hole, and air An air supply lateral hole (not shown) for communicating the chamber 18 is formed. The air discharge path has substantially the same structure as the fuel discharge path 51, and includes an air discharge hole (not shown) extending in the axial direction at the center of the gas circulation fastening bolt 6, and an air discharge hole. And an air discharge lateral hole (not shown) for communicating the air chamber 18. Therefore, air passes through the air supply hole and the air supply lateral hole in order and is supplied to the air chamber 18, and passes through the air discharge lateral hole and the air discharge hole in order and is discharged from the air chamber 18.

  In the present embodiment, flat metal members such as the separator 12, the fuel electrode frame 13, and the interconnector 14 constituting the interconnector-equipped fuel cell single cell 2 are joined by laser welding. FIG. 5 shows welds 70 and 71 with the fuel electrode frame 13 as viewed from the interconnector 14 side in the fuel cell single cell 2 with an interconnector.

  As shown in FIG. 5, the interconnector 14 has a plurality of holes 60 formed through the outer edge. The separator 12, the fuel electrode frame 13, and the air electrode insulating frame 15 are also formed with a plurality of holes 60 at the same position (see FIG. 3). Each hole 60 constitutes a part of the through hole 4 (see FIG. 2) through which the fastening bolt 5 and the gas circulation fastening bolt 6 are inserted, and includes a circular hole 60a and an elliptical hole 60b. Including.

  Here, the elliptical hole 60b formed in the interconnector 14, the fuel electrode frame 13, or the like is a hole for forming the gas flow path described above. More specifically, in the elliptical hole 60b formed above and below the interconnector 14 in FIG. 5 (pointing up and down in FIG. 5), the upper side is a gas flow path for fuel gas supply (fuel supply path 50). The lower side is a hole for forming a gas flow path for fuel gas discharge (fuel discharge path 51). Further, in the elliptical hole 60b formed on the left and right sides of the interconnector 14 (pointing to the left and right directions in FIG. 5), the left side is for forming a gas flow path (air supply path) for supplying an oxidant gas. The right side is a hole for forming a gas flow path (air discharge path) for discharging the oxidant gas.

  As shown in FIGS. 5 and 6, the outer peripheral portion 65 of the interconnector 14 has a closed circuit-shaped welded portion 70 (linear laser welding trace) formed by laser welding in order to join the fuel electrode frame 13. Is formed. Further, a welded portion 71 having a closed circuit shape by laser welding is also formed around each hole 60b in the interconnector 14. Further, in order to join the separator 12 to the fuel electrode frame 13, closed circuit-shaped welds 72 and 73 formed by laser welding are similarly formed. The line widths of the welds 70 to 73 on the surface 44 of the interconnector 14 and the surface of the separator 12 are about 0.1 mm, and the welds 70 to 73 from the surfaces 34 and 35 of the fuel electrode frame 13 to a depth of about 70 μm. Is formed.

  On the surface 41 of the interconnector 14 facing the fuel electrode frame 13, the welded portions 70, 71 are not provided with the first coating layer 42, and the welded portions 70, 71 do not include the components of the first coating layer 42. 71 is formed. In addition, since the second coating layer 45 is provided on the surface 44 of the interconnector 14, the components of the second coating layer 45 are melted and stirred during welding, so that the components of the second coating layer 45 are included. The welds 70 and 71 are formed in the state.

  Next, a method for manufacturing the fuel cell stack 3 will be described.

  First, the interconnector 14 having the holes 60 (60a, 60b) is formed by punching out a metal plate made of a predetermined conductive material (Crofer 22H). Further, the air electrode side current collector 38 is formed on the surface 44 of the interconnector 14 by performing press working or cutting work. Similarly, the fuel electrode frame 13 and the separator 12 having the holes 60 (60a, 60b) are formed by punching a metal plate made of a predetermined material (NCA-1). Further, the air electrode insulating frame 15 having the hole portions 60 (60a, 60b) is formed by forming the mica sheet in a predetermined shape. Thus, the separator 12, the fuel electrode frame 13, the interconnector 14, and the air electrode insulating frame 15 in which the respective hole portions 60 constituting the gas flow path are formed are prepared (preparation step).

  Next, the single cell 11 with the separator 12 is formed according to a conventionally known technique. Specifically, a green sheet to be the solid electrolyte layer 23 is laminated on the green sheet to be the fuel electrode 22 and fired. Then, a material for forming the air electrode 21 is printed on the solid electrolyte layer 23. Further, after applying a brazing material to the outer periphery of the solid electrolyte layer 23, the brazing material is melted by heating at 850 to 1100 ° C. in an air atmosphere, and the separator 12 is brazed to the solid electrolyte layer 23. . Further, the air electrode 21 is baked by the heat treatment at the time of brazing and baked on the surface of the solid electrolyte layer 23. As a result, the single cell 11 to which the separator 12 is bonded is produced.

Further, the first coating layer 42 and the second coating layer 45 are formed on the respective surfaces 41 and 44 of the interconnector 14 (coating step). Here, first, on the surface 41 of the interconnector 14 facing the fuel electrode frame 13, a mask material is disposed in an outer region R <b> 2 where the fuel electrode frame 13 contacts. In this state, a sol-form forming material (NiO) for forming the first coating layer 45 is sprayed on the inner region R1 not in contact with the fuel electrode frame 13 by spraying. Further, in the interconnector 14, a sol-like forming material (MnCo ₂ O ₄ ) for forming the second coating layer 45 on the other surface 44 on the other side of the surface 41 of the interconnector 14 facing the fuel electrode frame 13. Spray by spraying.

Thereafter, as heat treatment, heat treatment (reduction treatment) in a reducing atmosphere and heat treatment (oxidation treatment) in an oxidizing atmosphere are sequentially performed. Note that as the reduction treatment, heat treatment is performed at 1000 ° C. for 4 hours in nitrogen containing 3% of water vapor and 5% of hydrogen. Further, as the oxidation treatment, heat treatment is performed under conditions of 1000 ° C. for 2 hours in an air atmosphere. By performing these heat treatments, the first coating layer 42 made of a nickel oxide film (NiO) is baked in the inner region R1 that does not contact the fuel electrode frame 13 on the surface 41 of the interconnector 14 facing the fuel electrode frame 13. (See FIG. 4). In the interconnector 14, the other surface 44, which is the back side of the surface 41 facing the fuel electrode frame 13, is formed of a (Mn, Co) O ₄ metal oxide film having a spinel crystal structure. Two coating layers 45 are baked. Further, on the surface 41 of the interconnector 14 facing the fuel electrode frame 13, chromium oxide (Cr ₂ O ₃ ) is not formed in the region where the first coating layer 42 is not formed, which is the outer region R 2 in contact with the fuel electrode frame 13. An oxide film 43 is formed (see FIG. 4).

  Next, the separator 12 and the fuel electrode frame 13 are joined by laser welding. Specifically, each hole 60 in the separator 12 and the fuel electrode frame 13 joined to the single cell 11 is aligned. Then, as shown in FIG. 7, the separator 12 and the fuel electrode frame 13 are placed on the welding jig device 100 (between the upper jig 101 and the lower jig 102) in an overlapping state (placement step). Further, the separator 12 and the fuel electrode frame 13 are fixed by tightening the upper jig 101 and the lower jig 102 with fixing members (not shown) such as bolts, nuts, and clamp members.

  In the upper jig 101 of the welding jig apparatus 100, an opening 103 that exposes the welds 72 and 73 is formed. Then, the laser irradiation apparatus 105 is used to irradiate the laser L1 along the opening 103 of the upper jig 101 under predetermined irradiation conditions (for example, the output is about 150 W and the beam diameter is about 0.1 mm) (welding step). . Here, the laser L <b> 1 is irradiated from the separator 12 side around the hole 60 and along the outer peripheral portion 65. The separator 12 is laser welded to the fuel electrode frame 13 by melting the material (NCA-1) of the separator 12 and the material (NCA-1) of the fuel electrode frame 13 by the irradiation heat of the laser L1. As a result, closed circuit-shaped welds 72 and 73 that seal the periphery of the hole 60 and the outer peripheral part 65 are formed.

  As the laser irradiation device 105, for example, an irradiation device such as a fiber laser is used. The fiber laser is a solid-state laser that irradiates a laser L1 having a wavelength of 1080 nm. Further, the welding jig apparatus 100 is moved in the horizontal direction using an XY table (not shown) so that the laser L 1 is irradiated along the opening 103 of the upper jig 101.

  Thereafter, the interconnector 14 is joined to the fuel electrode frame 13 by laser welding using the same welding jig apparatus as described above. Specifically, the fuel electrode frame 13 and the interconnector 14 are placed in an overlapped state while aligning the holes 60 in the fuel electrode frame 13 and the interconnector 14 (placement step). Then, the interconnector 14 is laser welded to the front surface 35 side (back surface side) of the fuel electrode frame 13 (welding step). Here, the laser irradiation device 105 irradiates the laser L1 from the interconnector 14 side along the periphery of the hole 60 and along the outer peripheral portion 65. Since the interconnector 14 is thicker than the separator 12, the laser L1 is irradiated with the laser output at 300W. The material of the interconnector 14 (Crofer 22H, which is an aluminum-free metal material) and the material of the fuel electrode frame 13 (NCA-1, which is an aluminum-containing metal material) are melted by the irradiation heat of the laser L1, so that the fuel The interconnector 14 is laser welded to the pole frame 13. As a result, the closed circuit-shaped welded portions 70 and 71 that seal the periphery of the hole 60 and the outer peripheral portion 65 are formed. By performing the welding step in this way, the interconnector-attached fuel cell single cell 2 that is a joined body of the members 11 to 14 is manufactured.

  Then, the fuel cell stack 3 is formed by alternately stacking and integrating a plurality of the single unit fuel cell with interconnector 2 and the air electrode insulating frame 15. Further, the fastening bolts 5 are inserted into the four through holes 4 at the four corners of the fuel cell stack 3, and a nut (not shown) is screwed to the lower end portion of the fastening bolt 5 protruding from the lower surface of the fuel cell stack 3. Further, the gas circulation fastening bolts 6 are inserted into the remaining four through holes 4, and nuts 7 are screwed onto both ends of the gas circulation fastening bolts 6 protruding from the upper surface and the lower surface of the fuel cell stack 3. As a result, each fuel cell unit cell 2 with an interconnector is fixed, and the fuel cell stack 3 is completed.

  In the fuel cell stack 3 manufactured as described above, for example, the fuel gas is introduced into the fuel chamber 17 from the fuel supply path 50 while being heated to the operating temperature (about 700 ° C.), and the air chamber 18 is connected from the air supply path. To supply air. As a result, hydrogen in the fuel gas and oxygen in the air react through the solid electrolyte layer 23 (power generation reaction), and DC power is generated with the air electrode 21 as the positive electrode and the fuel electrode 22 as the negative electrode. In the fuel cell stack 3 of the present embodiment, a plurality of interconnector-attached fuel cell single cells 2 are stacked and connected in series, so that the upper end plate 8 electrically connected to the air electrode 21 is positive. Thus, the lower end plate 9 electrically connected to the fuel electrode 22 becomes a negative electrode.

Further, in the above manufacturing method, a plurality of samples (No. of the fuel cell unit cell 2 with interconnector are changed by changing the formation conditions of the first coating layer 42 and the second coating layer 45 on the respective surfaces 41 and 44 of the interconnector 14. .1 to No. 7) and their weldability and durability reliability were confirmed. The results are shown in Table 1. In addition, as weldability, the presence or absence (leakability) of the gas leak in each welding part 70 and 71 was confirmed. In addition, a durability test in which high-temperature heat of about 700 ° C. that is the operating temperature of the fuel cell stack 3 is repeatedly applied was performed, and the durability reliability of the welds 70 and 71 was confirmed.

  As shown in Table 1, no. In the sample 1, laser welding is performed without providing the first coating layer 42 and the second coating layer 45 on the welded portions 70 and 71 of the respective surfaces 41 and 44 of the interconnector 14, and the fuel cell single cell 2 with the interconnector is obtained. It produced (refer FIG. 8). No. In the sample 2, the first coating layer 42 having a thickness of 10 μm is provided in the region R2 of one surface 41 to be the welded portions 70 and 71 in the interconnector 14, and the second coating layer having a thickness of 5 μm is provided on the other surface 44. 45 was provided for laser welding to produce a single fuel cell 2 with an interconnector (see FIG. 9). No. In the sample No. 3, laser welding is performed by providing the second coating layer 45 having a thickness of 5 μm on the other surface 44 without providing the first coating layer 42 in the region R2 of the one surface 41 of the interconnector 14. A fuel cell single cell 2 with a connector was produced (see FIG. 6). No. In the sample No. 4, laser welding is performed without providing the second coating layer 45 on the other surface 44 by providing the first coating layer 42 having a thickness of 10 μm on the region R2 of the one surface 41 of the interconnector 14, A fuel cell unit cell 2 was prepared. No. In the sample No. 5, the first coating layer 42 having a thickness of 10 μm is provided in the region R2 of one surface 41 of the interconnector 14, and the second coating layer 45 having a thickness of 3 μm is provided on the other surface 44, and laser welding is performed. The fuel cell single cell 2 with an interconnector was manufactured. No. In the sample No. 6, laser welding is performed by providing a second coating layer 45 having a thickness of 3 μm on the other surface 44 without providing the first coating layer 42 in the region R2 of the one surface 41 of the interconnector 14, A fuel cell single cell 2 with a connector was produced. No. In the sample No. 7, the first coating layer 42 is not provided in the region R2 of the one surface 41 of the interconnector 14, but the second coating layer 45 having a thickness of 1 μm is provided on the other surface 44, and laser welding is performed. A fuel cell single cell 2 with a connector was produced.

  As shown in Table 1, No. 1 in which the first coating layer 42 is provided on one surface 41 of the welded portions 70 and 71. 2, no. 4, no. In each sample of No. 5, weldability deteriorated and gas leakage occurred in the welds 70 and 71. Further, No. 2 in which the second coating layer 45 is not provided on the other surface 44 of the welds 70 and 71. 1, no. In the sample No. 4, durability reliability (chromium volatility, wear resistance, and corrosivity) in the welds 70 and 71 could not be ensured.

  In contrast, no. 3, no. 6, no. As in sample 7 (fuel cell unit cell 2 with an interconnector of the present embodiment), the first coating layer 42 is not provided in the region R2 of the one surface 41, and the thickness is 5 μm or less on the other surface 44. In the case where the second coating layer 45 was provided, it was confirmed that the leakage property and the durability reliability were good. No. It was confirmed that when the second coating layer 45 is made thin like the sample 7, the weldability is further improved.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the present embodiment, the first coating layer 42 is not formed on the welded portions 70 and 71 by laser welding on the surface 41 of the interconnector 14 facing the fuel electrode frame 13. Here, when the 1st coating layer 42 is formed in the welding parts 70 and 71, since the metal component of the 1st coating layer 42 has low melting | fusing point, it volatilizes preferentially at the time of welding. In this case, spatter and blowholes are generated in the welded portions 70 and 71 between the interconnector 14 and the fuel electrode frame 13, and weldability is deteriorated. On the other hand, in this Embodiment, since the 1st coating layer 42 is not formed in the welding parts 70 and 71, the fall of weldability like a prior art can be suppressed. Therefore, the interconnector 14 and the fuel electrode frame 13 can be reliably joined by laser welding. In addition, the first coating layer 42 is formed in the region R1 that does not contact the fuel electrode frame 13 on the surface 41 of the interconnector 14, so that the interconnector 14 and the fuel electrode side current collector 39 are separated by the first coating layer 42. It becomes possible to keep contact resistance low. In particular, the fuel electrode side current collector 39 of the present embodiment is made of a nickel metal body, and the first coating layer 41 is made of a nickel oxide film (NiO). For this reason, when the fuel gas (hydrogen H2) is supplied to the fuel electrode 22 in a high temperature environment during power generation, NiO of the first coating layer 42 becomes Ni, and the Ni and the interconnector 14 and the fuel electrode side current collection are caused by the Ni. The body 39 can be fixed to improve the bondability.

  (2) In the present embodiment, the interconnector 14 is made of a stainless steel material containing chromium, and a spinel-type second coating layer 45 containing manganese and cobalt is formed on the entire other surface 44 of the interconnector 14. ing. In this way, by forming the second coating layer 45 on the surface 44 of the interconnector 14, it is possible to reliably prevent chromium poisoning of the air electrode 21. In this case, the durability (abrasion resistance and corrosion resistance) of the welded portions 70 and 71 is increased by mixing a part of the second coating layer 45 into the welded portions 70 and 71. For this reason, the power generation performance of the fuel cell stack 3 can be maintained in a good state, and the product reliability can be improved.

  (3) In the present embodiment, in the interconnector 14, the thickness of the second coating layer 45 formed on the surface 44 is smaller than the thickness of the first coating layer 41 formed on the surface 41 and is 5 μm or less. ing. Here, when the second coating layer 45 is formed thick, the metal component of the second coating layer 45 has a low melting point, so that it preferentially volatilizes during welding, resulting in spatter and blow holes in the welds 70 and 71. It becomes easy to do and weldability falls. On the other hand, since the weldability can be improved by reducing the thickness of the second coating layer 45 as in the present embodiment, the leakage of the fuel gas or the oxidant gas in the welds 70 and 71 is ensured. It can be avoided. Further, by reducing the thickness of the second coating layer 45 to 5 μm or less, it is possible to avoid a decrease in the corrosion resistance of the welded portions 70 and 71.

  (4) In the present embodiment, an oxide film 43 made of chromium oxide is formed on the surface 41 of the interconnector 14 facing the fuel electrode frame 13 in a region R2 where the fuel electrode frame 13 contacts. In this case, the surface 41 of the interconnector 14 can be prevented from generating an unstable film (abnormal film) during power generation. Further, by forming the oxide film 43 in the region R2 in contact with the fuel electrode frame 13 on the surface 41 of the interconnector 14, it is possible to suppress the volatilization (movement) of chromium and to avoid the deterioration of the power generation performance. .

  (5) In the present embodiment, the separator 12, the fuel electrode frame 13, and the interconnector 14 are joined by laser welding using a fiber laser. In the welding by the fiber laser, since it is possible to focus on a small spot size, the line width of the linear welded portions 70 to 73 can be set to about 0.1 mm. Therefore, the interconnector 14 and the separator 12 can be reliably welded to the fuel electrode frame 13 while suppressing thermal distortion.

  (6) In the present embodiment, the fuel electrode frame 13 is formed using an aluminum-containing metal material (NCA-1) containing aluminum. In this case, when the fuel electrode frame 13 and the interconnector 14 are joined, the welded portions 70 and 71 cause the aluminum-containing metal material of the fuel electrode frame 13 and the non-aluminum-containing metal material of the interconnector 14 to melt. As a result of stirring, it is formed in a state containing aluminum. If it does in this way, since the oxide film which consists of alumina is formed in the surface of the welding parts 70 and 71, the corrosion resistance can be improved.

  (7) In the present embodiment, in the coating step, the first coating layer 42 and the second coating layer 45 are simultaneously baked on the surfaces 41 and 44 of the interconnector 14 facing the fuel electrode frame 13. If it does in this way, compared with the case where the 1st coating layer 42 and the 2nd coating layer 45 are baked separately, manufacturing cost can be held down.

  In addition, you may change embodiment of this invention as follows.

  In the above embodiment, the first coating layer 42 is not provided in the region R2 in contact with the fuel electrode frame 13 on the surface 41 of the interconnector 14 facing the fuel electrode frame 13, but the present invention is not limited to this. It is not something. As shown in FIG. 10, the first coating layer 42 may be provided in a region R <b> 2 where the fuel electrode frame 13 contacts to avoid the welds 70 and 71. Moreover, in the said embodiment, although the 1st coating layer 42 was provided in the whole area | region R1 which does not contact the fuel electrode flame | frame 13 in the surface 41 of the interconnector 14, it is not limited to this. In the region R1 of the surface 41 of the interconnector 14, the first coating layer 42 may be provided at least at the contact portion of the fuel electrode side current collector 39. For example, the island-shaped first coating layer 42 is provided at the contact portion. Also good.

  In the above embodiment, the mask material is disposed on the surface 41 of the interconnector 14 in the region R2 that contacts the fuel electrode frame 13, and the first coating layer 42 is formed in the region R1 that does not contact the fuel electrode frame 13. However, the present invention is not limited to this. Specifically, after the first coating layer 42 is formed on the entire surface 41 of the interconnector 14, the first coating layer 42 on the surface of the welded portions 70 and 71 is removed by sandblasting. Good. Moreover, you may make it remove the 1st coating layer 42 in the surface of the location used as the welding parts 70 and 71 by irradiating a laser with the output lower than the time of welding.

  In the above embodiment, the coating layers 42 and 45 are formed by spraying a sol-form forming material on the surface of the interconnector 14 by spraying. However, other than this, plating, spin coating, thermal spraying, etc. The coating layers 42 and 45 may be formed by the above method.

  In the above embodiment, the fuel electrode frame 13 and the interconnector 14 are joined by laser welding using a fiber laser, but they are joined by laser welding using a carbon dioxide laser or YAG laser in addition to the fiber laser. May be. Further, in addition to laser welding, the fuel electrode frame 13 and the interconnector 14 may be joined by other methods such as seamless welding (resistance welding).

  In the above embodiment, the solid oxide fuel cell is embodied. However, other fuel cells such as a molten carbonate fuel cell (MCFC) may be embodied.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiments described above are listed below.

  (1) In the means 1, the metal for preventing the fuel electrode or the air electrode from being poisoned by the chromium on the entire other surface on the back side of the surface of the interconnector facing the frame A second coating layer made of an oxide film is formed. The second coating layer is made of an M-based metal oxide containing at least one metal M selected from manganese, iron, cobalt, nickel, and chromium. A fuel cell unit cell with an interconnector, characterized in that it is a conductive oxide film.

  (2) In the means 1, the metal for preventing the fuel electrode or the air electrode from being poisoned by the chromium on the entire other surface which is the back side of the surface of the interconnector facing the frame A second coating layer made of an oxide film is formed, and the second coating layer is made of a metal oxide containing at least one transition metal selected from an iron group element, a chromium group element, and a manganese group element. A fuel cell unit cell with an interconnector, characterized in that it is a conductive oxide film.

  (3) In the means 1, the metal for preventing the fuel electrode or the air electrode from being poisoned by the chromium on the entire other surface on the back side of the surface of the interconnector facing the frame A second coating layer made of an oxide film is formed, and the second coating layer is a conductive oxide film made of a metal oxide containing a transition metal that is a fourth periodic element. Single fuel cell with interconnector.

  (4) In the means 1, the metal for preventing the fuel electrode or the air electrode from being poisoned by the chromium on the entire other surface which is the back side of the surface of the interconnector facing the frame A fuel cell unit cell with an interconnector, wherein a second coating layer made of an oxide film is formed, and the second coating layer contains manganese and cobalt.

  (5) In any of the technical ideas (1) to (4), the thickness of the second coating layer is 1 μm or less.

  (6) The fuel cell unit cell with an interconnector according to means 1, wherein the frame is formed using an aluminum-containing metal material containing aluminum.

  (7) In the technical idea (6), the aluminum-containing metal material contains aluminum at a content of 1% by mass or more and 10% by mass or less.

  (8) The interconnector-attached fuel cell single cell according to means 1, wherein the welded portion is a linear laser welding mark, and the line width is 0.2 mm or less.

  (9) The fuel cell single cell with an interconnector according to means 1, wherein the electrolyte layer is a solid electrolyte layer made of a solid oxide.

  (10) In the means 4, in the coating step, the first coating layer and the second coating layer are formed on each surface of the interconnector by spraying the forming material in a sol form by a spray process. The manufacturing method of the fuel cell single cell with an interconnector.

  (11) The method of manufacturing a fuel cell unit cell with an interconnector, wherein, in the means 4, in the coating step, a heat treatment in a reducing atmosphere and a heat treatment in an oxidizing atmosphere are performed as the heat treatment.

  (12) In the method 4, the heating temperature in the heat treatment is 500 ° C. or higher and 1150 ° C. or lower.

2 ... Fuel cell single cell with interconnector 3 ... Fuel cell stack 11 ... Single cell as fuel cell single cell 13 ... Fuel electrode frame as frame 14 ... Interconnector 21 ... Air electrode 22 ... Fuel electrode 23 ... Solid electrolyte layer 35 ... One side of frame 39 ... Current collector on fuel electrode side as current collector 41 ... Surface of interconnector 42 ... First coating layer 43 ... Oxide film as a film containing chromium oxide 44 ... The other side of interconnector Surface 45 ... Second coating layer 60, 60a, 60b ... Hole 70, 71 ... Welded part as joining part L1 ... Laser R1 ... Area not in contact with frame R2 ... Area in contact with frame

Claims (10)

A planar fuel cell single cell having a fuel electrode, an air electrode and an electrolyte layer;
A frame-like frame in which a part of the electrolyte layer and the fuel electrode or the air electrode is disposed in the frame;
A fuel cell single cell with an interconnector formed by laminating a plate-like interconnector disposed on one surface of the frame,
The frame and the interconnector are joined via a weld,
A first coating layer is formed in a region excluding at least the weld on the surface of the interconnector facing the frame,
A fuel cell single cell with an interconnector, wherein a second coating layer is formed on the entire other surface which is the back side of the interconnector surface The interconnector is made of a material containing chromium,
2. The fuel cell with interconnector according to claim 1, wherein the second coating layer is made of a metal oxide film for preventing the fuel electrode or the air electrode from being poisoned by the chromium. cell.   The single-cell fuel cell with interconnector according to claim 2, wherein the thickness of the second coating layer is thinner than that of the first coating layer. The surface of the interconnector facing the frame is divided into a region where the frame contacts and a region which does not contact a frame located inside the region where the frame contacts,
The first coating layer is formed in a region not in contact with the frame,
The fuel cell single cell with an interconnector according to any one of claims 1 to 3, wherein a film containing chromium oxide is formed in a region in contact with the frame.   In the interconnector, a current collector that is electrically connected to the fuel electrode is disposed in a region that does not contact the frame, and the current collector has a metal body portion containing nickel, The fuel cell single cell with an interconnector according to any one of claims 1 to 4, wherein the coating layer contains nickel.   4. The single-cell fuel cell with an interconnector according to claim 2, wherein the second coating layer has a thickness of 5 μm or less.   The interconnector-attached fuel cell unit cell according to any one of claims 1 to 6, wherein the weld is a laser welding mark.   8. A fuel cell stack, wherein a plurality of the interconnector-attached fuel cell single cells according to claim 1 are stacked. A manufacturing method for manufacturing the interconnector-equipped fuel cell unit cell according to any one of claims 1 to 7,
A preparation step of preparing the frame and the interconnector each having a hole portion constituting a gas flow path;
Forming the first coating layer on the surface of the interconnector facing the frame at least around the hole and avoiding the region to be the welded portion, and the back side of the interconnector surface facing the frame A coating step for forming the second coating layer on the entire other surface,
An arrangement step of superposing the frame and the interconnector;
And a welding step of irradiating a region around the hole and serving as the welded portion with a laser. In the coating step,
The material for forming the first coating layer is applied to the surface of the interconnector facing the frame, and the material for forming the second coating layer is applied to the other surface on the back side of the surface of the interconnector facing the frame. After
The first coating layer and the second coating layer are baked by performing a heat treatment, and a film containing chromium oxide is formed in a region where the first coating layer is not formed on the surface of the interconnector facing the frame. The manufacturing method of the fuel cell single cell with an interconnector of Claim 9 characterized by the above-mentioned.

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