JP5727428B2 - Fuel cell with separator and fuel cell - Google Patents

Description

  The present invention relates to a fuel cell with a separator and a fuel cell.

  A solid oxide fuel cell using a solid oxide as an electrolyte (hereinafter also referred to as “SOFC” or simply “fuel cell”) is known. The SOFC has, for example, a stack (fuel cell stack) in which a large number of fuel cells each having a fuel electrode and an air electrode are stacked on each surface of a plate-like solid electrolyte layer. Electric power is generated by supplying a fuel gas (for example, hydrogen) and an oxidant gas (for example, oxygen in the air) to the fuel electrode and the air electrode, respectively, and causing a chemical reaction through the solid electrolyte layer.

  The fuel cell is used by being joined to a separator that divides a section where fuel gas and oxidant gas are present. For this joining, usually, a joining portion made of a brazing material such as Ag brazing is used to isolate the fuel gas and the oxidant gas.

  Here, it is known that during operation of the SOFC, hydrogen on the fuel electrode side and oxygen on the air electrode side diffuse and react in the joint, and generate voids in the joint. In order to prevent the formation of voids at the joint, a technique using various Ag alloys having a slow gas diffusion rate as the joint is disclosed (see Patent Documents 1 and 2). By using a material with a slow gas diffusion rate, the life of the brazing material can be extended.

JP 2010-207863 A Special table 2011-522353 gazette

However, with the techniques of Patent Documents 1 and 2, although it is possible to extend the life of the joint (fuel cell), it is not easy to ensure a practically sufficient life of, for example, tens of thousands of hours.
It is an object of the present invention to provide a separator-equipped fuel cell and a fuel cell in which the life of the joint is extended.

  A separator-equipped fuel cell according to the present invention includes a fuel cell main body configured by sandwiching a solid electrolyte layer between an air electrode and a fuel electrode, and an opening containing openings on the front and back surfaces, and includes Ag. A separator-equipped fuel cell comprising a plate-like metal separator, the back surface of which is attached to the main body of the fuel cell through a joint constituted by: On the part side and between the back surface of the metal separator and the cell body, and is disposed over the entire circumference of the opening. And a restraining portion that is disposed on the surface of the metal separator at a position facing the sealing portion and is made of the same material as the sealing material.

  Since the metallic separator is sandwiched between the sealing portion and the restraining portion made of the same material (same thermal expansion coefficient), deformation of the metallic separator during operation of the fuel cell is suppressed. As a result, the sealing portion is prevented from being damaged by the deformation of the metallic separator, and the fuel gas or the oxidant gas is prevented from reaching the joint portion.

It is preferable that the constraining portion is disposed over the entire circumference of the opening.
The sealing part is arrange | positioned over the perimeter of an opening part. For this reason, a deformation | transformation of a metal separator can be suppressed over the perimeter of an opening part by arrange | positioning a restraint part over the perimeter of an opening part.

It is preferable that the sealing portion and the restraining portion are integrally formed by a connecting portion disposed on the side surface of the opening of the metal separator.
Since the sealing portion and the restraining portion are integrated, it is possible to further suppress deformation (deflection) of the metallic separator.
Further, the integration of the sealing portion and the restraining portion contributes to a substantial increase in the width of the sealing portion, and the sealing performance by the sealing portion is improved.

The thermal expansion coefficient of the material constituting the restraint portion may be smaller than the thermal expansion coefficient of the metallic separator.
The metallic separator and the restraining part are each made of metal and glass, and the thermal expansion coefficient of the restraining part is usually smaller than that of the metallic separator. Even under such conditions, it is possible to suppress the deformation (deflection) of the metal separator by the restraining portion.

A gap may be provided between the joint portion and the sealing portion.
Even if the joint portion and the sealing portion are not in contact with each other, it is possible to suppress deformation (deflection) of the metal separator. In addition, even if gas is contained in the gap, the amount is small, and the influence on the reliability of the joint is small.

It is preferable that the thermal expansion coefficient of the sealing material is 8 ppm / K or more and 12 ppm / K or less in a temperature range from room temperature to 300 ° C.
With a thermal expansion coefficient in this range, it is possible to suppress deformation of the metal separator during fuel cell operation.

A fuel cell stack according to the present invention includes the fuel cell with a separator described above.
By using the fuel cell with a separator described above, the reliability of the entire fuel cell stack is improved.

  According to the present invention, a fuel cell with a separator, and a fuel cell, in which the failure of the sealing portion due to deformation of the metal separator is suppressed and the generation of voids in the joint portion is suppressed, thereby extending the life. Can provide.

1 is a perspective view showing a solid oxide fuel cell 10. FIG. 1 is a schematic cross-sectional view of a solid oxide fuel cell 10. FIG. 3 is a cross-sectional view of a fuel cell 40. FIG. It is a disassembled perspective view showing the state which decomposed | disassembled the fuel cell main body 44 and the metal separator 53 (fuel cell 50 with a separator). It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing of the fuel cell 40a. It is a disassembled perspective view showing the state which decomposed | disassembled the fuel cell main body 44 and the metal separator 53 (fuel cell 50 with a separator). It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing showing the fuel cell 50 with a separator in manufacture. It is sectional drawing of the fuel battery cell 40b. It is a disassembled perspective view showing the state which decomposed | disassembled the fuel cell main body 44 and the metal separator 53 (fuel cell 50 with a separator). 4 is a graph showing the results of a durability test of the solid oxide fuel cell 10.

  Hereinafter, a solid oxide fuel cell according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing a solid oxide fuel cell (fuel cell stack) 10 according to a first embodiment of the present invention. The solid oxide fuel cell 10 generates power by receiving supply of a fuel gas (for example, hydrogen) and an oxidant gas (for example, air (specifically, oxygen in the air)).

  In the solid oxide fuel cell 10, end plates 11 and 12, fuel cells 40 (1) to 40 (4) are laminated, bolts 21, 22 (22a, 22b), 23 (23a, 23b) and nuts 35. It is fixed with.

FIG. 2 is a schematic cross-sectional view of the solid oxide fuel cell 10.
The solid oxide fuel cell 10 is a fuel cell stack configured by stacking fuel cells 40 (1) to 40 (4). Here, for the sake of clarity, four fuel cells 40 (1) to 40 (4) are stacked, but in general, about 20 to 60 fuel cells 40 are often stacked. .

The end plates 11 and 12 and the fuel cells 40 (1) to 40 (4) have through holes 31 and 32 (32a and 32b) corresponding to the bolts 21 and 22 (22a and 22b) and 23 (23a and 23b), 33 (33a, 33b).
The end plates 11 and 12 are holding plates that press and hold the stacked fuel battery cells 40 (1) to 40 (4), and output current from the fuel battery cells 40 (1) to 40 (4). It is also a terminal.

  FIG. 3 is a cross-sectional view of the fuel battery cell 40. FIG. 4 is an exploded perspective view showing a state in which the fuel cell main body 44 and the metal separator 53 (the separator-equipped fuel cell 50) are disassembled.

  As shown in FIG. 3, the fuel cell 40 is a so-called fuel electrode support membrane type fuel cell, and includes interconnectors 41 and 45, a current collector 42, and a frame part 43.

  The fuel cell main body 44 includes a solid electrolyte layer 56 sandwiched between an air electrode (also referred to as a cathode or an air electrode layer) 55 and a fuel electrode (also referred to as an anode or a fuel electrode layer) 57. An air electrode 55 and a fuel electrode 57 are arranged on the oxidant gas flow channel 47 side and the fuel gas flow channel 48 side of the solid electrolyte layer 56, respectively.

  As the air electrode 55, perovskite oxides (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), various noble metals, and cermets of noble metals and ceramics can be used.

  For the solid electrolyte layer 56, materials such as YSZ (yttria stabilized zirconia), ScSZ (scandia stabilized zirconia), SDC (samarium doped ceria), GDC (gadolinium doped ceria), and perovskite oxide can be used.

  The fuel electrode 57 is preferably a metal, and Ni, Ni-ceramic cermets or Ni-based alloys can be used.

  The interconnectors 41 and 45 are plates having conductivity (for example, a metal such as stainless steel) that can secure conduction between the fuel cell main bodies 44 and prevent gas mixing between the fuel cell main bodies 44. Shaped member.

  In addition, only one interconnector (41 or 45) is disposed between the fuel cell main bodies 44 (one interconnector is shared between two fuel cell main bodies 44 connected in series). Because). Further, in each of the uppermost and lowermost fuel cell main bodies 44, conductive end plates 11 and 12 are disposed in place of the interconnectors 41 and 45, respectively.

  The current collector 42 is for ensuring electrical continuity between the fuel cell main body 44 (air electrode 55) and the interconnector 41, and is made of, for example, a metal material such as a nickel alloy. Further, the current collector 42 may have elasticity.

  The frame portion 43 has an opening 46 through which an oxidant gas and a fuel gas flow. The opening 46 is kept airtight and is divided into an oxidant gas passage 47 through which an oxidant gas flows and a fuel gas passage 48 through which fuel gas flows. Further, the frame portion 43 of this embodiment includes an air electrode frame 51, an insulating frame 52, a metal separator 53, and a fuel electrode frame 54.

  The air electrode frame 51 is a metal frame disposed on the air electrode 55 side, and has an opening 46 at the center. An oxidant gas flow path 47 is defined by the opening 46.

The insulating frame 52 is a frame that electrically insulates between the interconnectors 41 and 45. For example, ceramics such as Al ₂ O ₃ , mica, vermiculite, and the like can be used, and an opening 46 is provided at the center. An oxidant gas flow path 47 is defined by the opening 46. Specifically, the insulating frame 52 is disposed between the interconnectors 41 and 45 such that one surface contacts the air electrode frame 51 and the other surface contacts the metal separator 53. As a result, the interconnectors 41 and 45 are electrically insulated by the insulating frame 52.

  The metal separator 53 is a frame-shaped metal thin plate (for example, thickness: 0.1 mm) having an opening 58, is attached to the solid electrolyte layer 56 of the fuel cell main body 44, and has an oxidant gas. It is a metal frame that prevents mixing with fuel gas. The metal separator 53 divides the gap in the opening 46 of the frame portion 43 into an oxidant gas flow path 47 and a fuel gas flow path 48, thereby preventing mixing of the oxidant gas and the fuel gas.

  An opening 58 is formed in the metal separator 53 by a through-hole penetrating between the upper surface and the lower surface of the metal separator 53, and the air electrode 55 of the fuel cell main body 44 is disposed in the opening 58. . Further, the fuel cell main body 44 is joined and sealed in the opening 58. The fuel cell main body 44 to which the metal separator 53 is joined is referred to as a “fuel cell 50 with a separator”. Details of this will be described later.

  Like the insulating frame 52, the fuel electrode frame 54 is an insulating frame disposed on the fuel electrode 57 side, and has an opening 46 in the center. A fuel gas flow path 48 is defined by the opening 46.

  Bolts 21, 22 (22a, 22b), 23 (23a, 23b) are inserted into the air electrode frame 51, the insulating frame 52, the metal separator 53, and the fuel electrode frame 54, or an oxidant gas or a fuel gas is inserted. The through holes 31, 32 (32a, 32b), 33 (33a, 33b) that circulate are provided in the respective peripheral portions.

(Details of fuel cell 50 with separator)
The separator-equipped fuel cell 50 according to the present embodiment includes a joining portion 61, a sealing portion 62, and a restraining portion 63. A joining portion 61 and a sealing portion 62 are disposed between the fuel cell main body 44 and the metal separator 53. Along the opening 58, the lower surface of the metallic separator 53 and the upper surface of the solid electrolyte layer 56 are joined by the joining portion 61 and sealed by the sealing portion 62. The restricting portion 63 is disposed on the upper surface of the metallic separator 53 corresponding to the sealing portion 62.

  The joining portion 61 is made of a brazing material containing Ag, and joins the fuel cell body 44 and the metal separator 53 along the opening 58 over the entire circumference. The joining portion 61 (Ag solder) has, for example, a width of 2 to 6 mm and a thickness of 10 to 80 μm.

As the material of the joining portion 61, various brazing materials mainly composed of Ag can be employed. For example, as a brazing material, a mixture of Ag and an oxide, for example, Ag-Al ₂ O ₃ (a mixture of Ag and Al ₂ O ₃ (alumina)) can be used. Examples of the mixture of Ag and oxide include Ag—CuO, Ag—TiO ₂ , Ag—Cr ₂ O ₃ , and Ag—SiO ₂ . Further, an alloy of Ag and another metal (for example, Ag—Ge—Cr, Ag—Ti, Ag—Al) can be used as the brazing material.

  The brazing material containing Ag (Ag brazing) is not easily oxidized at the brazing temperature even in an air atmosphere. For this reason, the fuel cell main body 44 and the metal separator 53 can be joined in an air atmosphere using Ag wax, which is preferable in terms of process efficiency.

  The sealing portion 62 is disposed on the opening 58 side (inner peripheral side) of the joining portion 61 along the opening 58 over the entire circumference, and the oxidant gas in the opening 58 of the metallic separator 53 In order to prevent mixing with the fuel gas outside the opening 58, the space between the fuel cell main body 44 and the metal separator 53 is sealed.

Since the sealing portion 62 is disposed on the opening 58 side (inner peripheral side) with respect to the joint portion 61, the joint portion 61 does not come into contact with the oxidant gas, and the joint portion is connected from the oxidant gas flow path 47 side. Oxygen transfer to 61 is blocked. As a result, it is possible to prevent a gas leak from occurring in the junction 61 due to the reaction between hydrogen and oxygen.
The sealing part 62 has a width of 0.2 to 4 mm and a thickness of 10 to 80 μm, for example.

The restraining portion 63 is disposed over the entire circumference of the opening 58 on the surface of the metallic separator 53 at a position facing the sealing portion 62 with the metallic separator 53 interposed therebetween.
The restraining part 63 is made of the same material as that of the sealing part 62 (the same thermal expansion coefficient), and sandwiches the metallic separator 53 together with the sealing part 62. As a result, deformation of the metallic separator 53 during operation of the solid oxide fuel cell 10 is suppressed.

  The “same material” includes not only completely the same material but also substantially the same material. If it contributes to preventing the above-described peeling (decrease in sealing performance), a slight difference in composition is allowed. For example, materials having different composition ratios by about 1% by weight may be substantially the same material.

  When the restraint portion 63 is not disposed, the metal separator 53 and the sealing portion 62 are both heated to about 700 ° C. and deformed (thermal expansion) during operation of the solid oxide fuel cell 10. Here, since the metal separator 53 and the sealing portion 62 have different coefficients of thermal expansion, a difference occurs in the amount of deformation between the two, and the thermal stress that causes deformation such that the metal separator 53 warps is caused by the metal separator. It occurs between 53 and the sealing part 62. As a result, the interface between the sealing portion 62 and the metal separator 53 may be peeled off, and the sealing performance by the sealing portion 62 may be reduced.

  When the restraining portion 63 made of the same material as the sealing material is disposed at a position facing the sealing portion 62, the metal separator 53 and the sealing portion 62 are operated during operation of the solid oxide fuel cell 10. The thermal stress generated between the metallic separator 53 and the thermal stress generated between the metallic separator 53 and the restraining portion 63 (front side of the metallic separator 53) is balanced. As a result, warping deformation of the metal separator 53 is suppressed, and peeling between the metal separator 53 and the sealing portion 62 (decrease in sealing performance by the sealing portion 62) is prevented.

  When the metal separator 53 is thick, the rigidity of the metal separator 53 is increased, and it is difficult to relieve stress caused by the difference in thermal expansion between the fuel cell body 44 and the metal separator 53. As a result, the fuel The battery cell main body 44 may break. On the other hand, if the metal separator 53 is thin, the rigidity is lowered, so that it is easy to relieve stress due to the difference in thermal expansion and the occurrence of cracking of the fuel cell main body 44 is suppressed. The metal separator 53 is likely to warp due to the difference in thermal expansion between the bonding material and the sealing material constituting the sealing portion 62 during cooling. Here, the metal separator 53 is thinned to easily relieve stress caused by the difference in thermal expansion between the bonding material and the sealing material, and warpage is prevented by the restraining portion 63.

  Here, the sealing portion 62 is disposed between the metallic separator 53 and the fuel cell main body 44 in the same manner as the joining portion 61 (the brazing material). For this reason, the stress applied to the sealing part 62 is a shear stress, and the sealing part 62 is difficult to break.

The thickness of the sealing portion 62 is equivalent to that of the joint portion 61 (the brazing material) from the arrangement location.
Since the restraining effect is small when the restraining part 63 is thin, it is preferable that the restraining part 63 has a thickness equal to or greater than that of the sealing part 62.

  For the sealing portion 62, a sealing material containing glass, specifically, glass, glass ceramics (crystallized glass), or a composite of glass and ceramics can be used. As an example, glass manufactured by SCHOTT: G018-311 can be used.

  Since the sealing portion 62 is disposed over the entire circumference of the opening 58, the metal separator 53 can be deformed over the entire circumference of the opening 58 by arranging the restraining portion 63 over the entire circumference of the opening 58. Can be suppressed.

The thermal expansion coefficient of the material constituting the restraining portion 63 may be smaller than the thermal expansion coefficient of the metallic separator 53.
Each of the metallic separator 53 and the restraining portion 63 is made of metal and glass, and the thermal expansion coefficient of the restraining portion 63 is usually smaller than that of the metallic separator 53. Even under such conditions, the deformation of the metal separator 53 by the restraining portion 63 can be suppressed.

  As will be described later, the thermal expansion coefficient of the sealing material is preferably 8 ppm / K or more and 12 ppm / K or less in a temperature range from room temperature to 300 ° C.

  Hereinafter, a manufacturing method of the above-described separator-attached fuel cell 50 (the fuel cell main body 44 to which the metal separator 53 is joined) will be described. 5A to 5E are cross-sectional views showing the separator-equipped fuel cell 50 being manufactured.

  First, for example, a plate material made of SUH21 (18Cr-3Al (a kind of Al-containing ferritic stainless steel)) was punched to manufacture a metal separator 53 having an opening 58.

  In addition, a sheet of the solid electrolyte layer 56 was attached to one surface of the green sheet of the fuel electrode 57 to form a laminate, and the laminate was fired once. Thereafter, the material of the air electrode 55 was printed and fired to prepare the fuel cell main body 44.

The brazing materials 611 and 612 are disposed on the fuel cell main body 44 and the metal separator 53, respectively (see FIG. 5A). For example, a brazing material containing paste-like Ag is printed in a predetermined shape on the upper surface of the solid electrolyte layer 56 of the fuel cell body 44 and the lower surface of the metal separator 53, so that the fuel cell body 44 and the metal separator 53 respectively. The brazing materials 611 and 612 are disposed on the surface.
In addition, as a method of arranging the brazing materials 611 and 612, a dispenser or the like may be used in addition to the above.
For example, the brazing materials 611 and 612 have a width of 2 to 6 mm and a thickness of 10 to 80 μm.

Next, the sealing material 621 is disposed on the upper surface of the solid electrolyte layer 56 of the fuel cell main body 44 (see FIG. 5B). For example, the sealing material 621 can be disposed on the upper surface of the solid electrolyte layer 56 of the fuel cell main body 44 by printing a paste containing glass as the sealing material.
The sealing material 621 has, for example, a width of 0.2 to 4 mm and a thickness of 10 to 80 μm.

In addition, as a method of arranging the sealing material 621, a dispenser may be used in addition to the above.
The sealing material 621 may be printed not on the upper surface of the solid electrolyte layer 56 but on the lower surface of the metallic separator 53. Further, the sealing material 621 may be disposed on both the upper surface of the solid electrolyte layer 56 and the lower surface of the metallic separator 53.

  The brazing materials 611 and 612 and the sealing material 621 are melted, and the fuel cell body 44 and the metal separator 53 are joined (formation of the joining portion 61), and at the same time, the sealing portion 62 is formed (see FIG. 5C). . The fuel cell body 44 on which the brazing materials 611 and 612 are disposed and the metal separator 53 are brought into contact with each other and heated at, for example, 850 to 1100 ° C., so that the brazing materials 611 and 612 are melted and the fuel cell body 44 And the metal separator 53 are joined. At this time, the sealing material 621 is also melted at the same time, and the fuel cell main body 44 and the metal separator 53 are sealed.

A constraining material 631 having the same composition as that of the sealing material 621 is disposed on the metal separator 53 (see FIG. 5D). For example, the restraint material 631 can be arranged at a predetermined position by printing a paste containing glass as a sealing material on the upper surface of the metal separator 53. As a method of arranging the restraining material 631, other than the above, a dispenser may be used.
The restraining material 631 has, for example, a width of 0.2 to 4 mm, a thickness of 10 to 200 μm, and is thicker than the sealing material 621.

  The sealing material 621 and the restraining material 631 are melted to form the restraining portion 63 (see FIG. 5E). The fuel cell body 44 and the metal separator 53, which are joined by the joining portion 61 and sealed by the sealing portion 62 and further provided with the restraining material 631, are restrained by heating at 850 to 1100 ° C., for example. The material 631 is melted, and the restraining portion 63 is formed.

  Through the above steps, the separator-equipped fuel cell 50 (the fuel cell main body 44 to which the metal separator 53 was joined) of this example was produced.

(Method for producing solid oxide fuel cell (fuel cell stack) 10)
For example, the air electrode frame 51 and the fuel electrode frame 54 are manufactured by punching a plate material made of SUH 21 into a predetermined shape. On the other hand, the end plates 11 and 12 and the interconnectors 41 and 45 can be manufactured, for example, by punching a plate made of ZMG232 made of Hitachi Metals into a predetermined shape. The insulating frame 52 can be manufactured by processing a plate material made of mica, for example.

  On the air electrode 55 side of the fuel cell main body 44 of the fuel cell 50 with a separator produced by the manufacturing method described above, the insulating frame 52, the air electrode frame 51, and the interconnector 41 are arranged on the metal separator 53 in this order. The fuel cell 40 can be manufactured by arranging the fuel electrode frame 54 and the interconnector 45 in this order on the fuel electrode 57 side.

  A plurality of fuel cells 40 are stacked, end plates 11 and 12 are arranged on the uppermost layer and the lowermost layer, and the plurality of fuel cells 40 are sandwiched between the end plates 11 and 12 by bolts 21 to 23 and nuts 35. The fuel cell stack 10 was prepared by fixing.

(Second Embodiment)
A second embodiment will be described. FIG. 5 is a cross-sectional view of the fuel battery cell 40a according to the second embodiment. FIG. 6 is an exploded perspective view showing a state in which the fuel cell main body 44 and the metal separator 53 (the separator-equipped fuel cell 50a) according to the second embodiment are disassembled.

  The fuel cell 40a includes a connecting portion 64 that is disposed on the side surface of the opening 58 and is made of the same material as the constituent material (sealing material) of the sealing portion 62a. That is, the sealing portion 62a and the restraining portion 63a are connected by the connecting portion 64 and are integrally formed.

  Since the sealing portion 62a and the restraining portion 63a are integrated, it is possible to further suppress deformation (deflection) of the metallic separator 53. As described above, the restraining portion 63a is made of the same material (same thermal expansion coefficient) as the sealing portion 62a, and sandwiches the metal separator 53 together with the sealing portion 62a, so that the solid oxide fuel cell is interposed. The deformation of the metallic separator 53 during the operation of 10 is suppressed. In addition to the upper and lower sides of the metal separator 53 along the opening 58, the side material of the opening 58 is also made of the same material (thermal expansion coefficient is substantially the same) as the constituent material (sealing material) of the sealing portion 62a. By being arranged, deformation of the metal separator 53 is more effectively prevented.

  Further, the integration of the sealing portion 62a and the restraining portion 63a contributes to a substantial increase in the width of the sealing portion 62a, so-called seal path, and the sealing performance by the sealing portion 62a is improved. As described above, the sealing portion 62a prevents the oxidant gas from moving from the oxidant gas flow path 47 to the joint portion 61. Therefore, the sealing portion 62a and the restraining portion 63a are integrated to oxidize the sealing portion 62a. The length (seal path) of the sealing portion 62a on the path from the agent gas flow path 47 to the joint portion 61 becomes longer. As a result, the sealing performance by the sealing portion 62a is further improved.

  The fuel cell 50a with a separator (the fuel cell main body 44 to which the metal separator 53 is bonded) was prepared in the present example by the following manufacturing method. 8A to 8E are cross-sectional views showing the separator-equipped fuel cell 50a during manufacture.

  Since the steps other than the step of forming the bonding portion 61, the sealing portion 62, and the restraining portion 63 were performed in the same step, the description is omitted. Here, the bonding portion 61, the sealing portion 62, and the restraining portion 63 are formed. The process will be described.

The brazing materials 611 and 612 are disposed on the fuel cell main body 44 and the metal separator 53, respectively (see FIG. 8A). For example, a brazing material containing paste-like Ag is printed in a predetermined shape on the upper surface of the solid electrolyte layer 56 of the fuel cell body 44 and the lower surface of the metal separator 53, so that the fuel cell body 44 and the metal separator 53 respectively. The brazing materials 611 and 612 are disposed on the surface.
In addition, as a method of arranging the brazing materials 611 and 612, a dispenser or the like may be used in addition to the above.
For example, the brazing materials 611 and 612 have a width of 2 to 6 mm and a thickness of 10 to 80 μm.

  The brazing materials 611 and 612 are melted, and the fuel cell main body 44 and the metal separator 53 are joined (formation of the joining portion 61, see FIG. 8B). The fuel cell body 44 on which the brazing materials 611 and 612 are disposed and the metal separator 53 are brought into contact with each other and heated at, for example, 850 to 1100 ° C., so that the brazing materials 611 and 612 are melted and the fuel cell body 44 And the metal separator 53 are joined.

A restraint material 631 having the same composition as that of the sealing material 621 is disposed on the metal separator 53 from the fuel cell main body 44 (see FIG. 8C). For example, the constraining material 631 can be disposed from the fuel cell body 44 to the metal separator 53 by applying a paste containing glass as a sealing material. In addition to the above, the arrangement of the restraining material 631 may be performed by printing.
The restraining material 631 has, for example, a width of 0.2 to 4 mm and a thickness of 10 to 200 μm.

  A sealing material 621 is disposed in the gap between the fuel cell main body 44 and the metal separator 53 (see FIG. 8D). For example, the sealing material 621 can be disposed by removing bubbles between the fuel cell main body 44 and the metal separator 53 by vacuum defoaming.

For vacuum defoaming, for example, the fuel battery cell main body 44 and the metal separator 53 are accommodated in a container, air is evacuated by a vacuum pump or the like, and the container is evacuated. In this way, bubbles (air) in the gap between the fuel cell main body 44 and the metal separator 53 pass through the sealing material 621 and are discharged into the container (vacuum defoaming). As a result, the gap between the fuel cell main body 44 and the metal separator 53 is filled with the sealing material 621 (arrangement of the sealing material 621).
Note that the viscosity of the sealing material 621 is preferably low to some extent for discharging bubbles at this time. For example, it is conceivable that the temperature of the sealing material 621 is raised from room temperature to lower the viscosity.

  The sealing material 621 and the restraining material 631 are melted to form the sealing portion 62 and the restraining portion 63 (see FIG. 8E). The fuel cell main body 44 and the metal separator 53 that are joined at the joint 61 and on which the sealing material 621 and the restraining material 631 are arranged are heated at, for example, 850 to 1100 ° C. The material 631 is melted to form the sealing portion 62 and the restraining portion 63.

  Through the above steps, the separator-equipped fuel cell 50a (the fuel cell main body 44 to which the metal separator 53 was joined) of this example was produced.

(Modification of the second embodiment)
A modification of the second embodiment will be described. FIG. 9 is a cross-sectional view of a fuel cell 40b according to a modification of the second embodiment. FIG. 10 is an exploded perspective view showing a state in which the fuel cell main body 44 and the metal separator 53 (separator-equipped fuel cell 50b) according to a modification of the second embodiment are disassembled.

  In the fuel battery cell 40b, a gap (space) is provided between the joint portion 61 and the sealing portion 62b. Thus, even if the joining part 61 and the sealing part 62b are not in contact, the deformation of the metallic separator 53 can be suppressed.

In the fuel cells 40a and 40b, the joint portion 61 and the sealing portions 62a and 62b are in contact with each other over the entire circumference of the opening 58 or have a gap. As an intermediate aspect thereof, the joining portion 61 and the sealing portions 62a and 62b are in contact with each other at a part of the circumference of the opening 58, and the joining portion 61 and the sealing portion 62b are in contact with each other at a part of the circumference of the opening 58 It is also possible not to.
Further, a gap (space) may be provided between the joining portion 61 and the sealing portion 62 in a state where the connecting portion 64 is not provided as in the fuel battery cell 40.

(Durability test of solid oxide fuel cell 10)
Hereinafter, the durability test of the solid oxide fuel cell 10 will be described. Here, a solid oxide fuel cell 10 having a shape corresponding to the second embodiment was created and tested.

<sample>
The prepared sample (solid oxide fuel cell 10) will be described. The following sample was prepared by changing the boundary length L. The boundary length L is a linear distance between the oxidant gas atmosphere interface and the fuel gas atmosphere interface of the sealing material 621.

・ Metal separator 53
Component material of metal separator 53: Ferritic SUS (SUH21)
・ Junction 61
Constituent material of the joint portion 61 (brazing material): Ag braze Thickness of the joint portion 61: 10 to 80 μm
The width of the junction 61: 4 mm
Forming method of the joining part 61: The paste containing the brazing material is printed, and the melting / sealing part 62, the restraining part 63, the connecting part 64 in the atmosphere.
Constituent material of the sealing portion 62, the restraining portion 63, and the connecting portion 64: Glass having a thermal expansion coefficient of 10 ppm / K

<Test method>
The solid oxide fuel cell 10 was operated for 500 hours with hydrogen as the fuel gas and air as the oxidant gas and the metal separator 53 at 750 ° C.

  The porosity of the joint 61 in the sample after the test was measured. The porosity was measured by disassembling the sample and observing the cross section of the joint 61. Specifically, a cross-sectional photograph was taken with an optical microscope, and the area ratio between the hole portion (black) and the healthy portion (white portion) was calculated to obtain the porosity. Those having no holes have a porosity of 0%.

  FIG. 11 shows the relationship between the boundary length L and the porosity R. It can be seen that the porosity R can be significantly reduced by setting the boundary length L to 100 μm or more. This is because the connection between the sealing portion 62 and the restraining portion 63 (the connecting portion 64) improves the reliability of sealing by the sealing portion 62 and is effective in preventing the generation of holes in the joint portion 61. Indicates that there is.

  Here, some differences in the coefficient of thermal expansion are allowed. A sealing material of about 8 ppm / K or more and 12 ppm / K or less can be used in a temperature range from room temperature to 300 ° C.

(Other embodiments)
Embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.
In the above embodiment, the metal separator 53 is joined to the upper surface (the air electrode 55 side) of the solid electrolyte layer 56 in order to be applied to an anode-supported fuel cell. On the other hand, for example, in the solid electrolyte support type and the cathode support type, the metal separator 53 may be bonded to the lower surface (the fuel electrode 57 side) of the solid electrolyte layer 56. In this case, the fuel electrode 57 is formed smaller than the solid electrolyte layer 56 and is disposed in the opening 58 so as not to be exposed to the oxidizing gas.

DESCRIPTION OF SYMBOLS 10 Solid oxide fuel cell 10 Fuel cell stack 11, 12 End plate 21-23 Bolt 31, 32 Through hole 35 Nut 40 Fuel cell 41, 45 Interconnector 42 Current collector 43 Frame part 44 Fuel cell main body 45 Inter Connector 46 Opening 47 Oxidant gas flow path 48 Fuel gas flow path 50 Fuel cell with separator 51 Air electrode frame 52 Insulating frame 53 Metal separator 54 Fuel electrode frame 55 Air electrode 56 Solid electrolyte layer 57 Fuel electrode 58 Opening 61 Joining Portions 611 and 612 Brazing material 62 Sealing portion 621 Sealing material 63 Restraining portion 631 Restraining material 64 Connecting portion

Claims (7)

A fuel cell body configured by sandwiching a solid electrolyte layer between an air electrode and a fuel electrode;
A plate-shaped metal separator having openings on the front surface and the back surface, the back surface side being attached to the fuel cell body through a joint portion made of a joining material containing Ag;
A fuel cell with a separator, comprising:
A sealing part that is disposed over the entire periphery of the opening part on the opening part side of the joining part and between the back surface of the metallic separator and the cell body, and includes a sealing material including glass;
A constraining portion that is disposed on the surface of the metallic separator at a position facing the sealing portion across the metallic separator, and is made of the same material as the sealing material;
A fuel cell with a separator, comprising: The restraining portion is disposed over the entire circumference of the opening;
The separator-equipped fuel cell according to claim 1. The sealing portion and the restraining portion are integrally formed by a connecting portion disposed on the side surface of the opening of the metal separator.
The separator-equipped fuel cell according to claim 1 or 2. The thermal expansion coefficient of the material constituting the restraint is smaller than the thermal expansion coefficient of the metal separator.
The separator-equipped fuel cell according to any one of claims 1 to 3. Having a gap between the sealing portion and the joint portion;
The fuel cell body with a separator according to any one of claims 1 to 4, wherein the fuel cell body with a separator is provided. The thermal expansion coefficient of the sealing material is 8 ppm / K or more and 12 ppm / K or less in a temperature range from room temperature to 300 ° C.,
The fuel cell body with a separator according to any one of claims 1 to 5, wherein A fuel cell body with a separator according to any one of claims 1 to 6,
A fuel cell comprising:

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