JP6169429B2 - Fuel cell with separator and fuel cell stack - Google Patents

Description

  The present invention provides a fuel cell unit with a separator comprising a solid electrolyte layer, a fuel cell main body having an air electrode and a fuel electrode, and a separator attached to the fuel cell main body, and a plurality of fuel cell units with a separator are laminated. It is related with the fuel cell stack which becomes.

  Conventionally, as a fuel cell, for example, a solid oxide fuel cell (SOFC) including a solid electrolyte layer (solid oxide layer) is known. The SOFC includes a fuel cell main body in which a fuel electrode in contact with the fuel gas and an air electrode in contact with the oxidant gas are disposed on both sides of the solid electrolyte layer. Then, hydrogen in the fuel gas and oxygen in the oxidant gas react (power generation reaction) through the solid electrolyte layer, so that direct current power is generated with the air electrode as the positive electrode and the fuel electrode as the negative electrode. Become.

  By the way, the separator which divides the fuel gas chamber in which fuel gas exists, and the oxidant gas chamber in which oxidant gas exists is normally joined to the fuel cell main body. For this reason, in recent years, various techniques for joining the fuel cell body and the separator have been proposed. For example, a technique for maintaining airtightness between a fuel gas chamber and an oxidant gas chamber by joining components of a solid oxide fuel cell via a brazing material has been proposed (for example, Patent Documents). 1). Moreover, the technique which joins a separator and a fuel cell main body through sealing materials, such as glass, is also proposed (for example, refer patent document 2).

  However, the reliability at the time of joining the fuel cell body and the separator via the brazing material or the sealing material is not always sufficient. Specifically, in the technique described in Patent Document 1 in which bonding is performed via a brazing material, the brazing material is arranged at the boundary between the fuel gas chamber and the oxidant gas chamber due to the structure. Therefore, when the fuel cell is used for a long time, the constituent atoms (hydrogen) of the fuel gas enter the brazing material from the fuel gas chamber side and diffuse, and the constituent atoms (oxygen) of the oxidant gas from the oxidant gas chamber side. Gets into the brazing material and diffuses. As a result, hydrogen and oxygen react with each other in the brazing material and voids are generated in the brazing material, which may cause the fuel gas to leak into the oxidant gas chamber or the oxidant gas to leak into the fuel gas chamber. . Moreover, in the technique of patent document 2 joined through sealing materials, such as glass, the joining strength of a fuel cell main body and a separator is comparatively weak. Moreover, since the separator is a metal foil formed of ferritic stainless steel or the like, it is easily deformed. Therefore, when the separator is deformed during use of the fuel cell and a stress is generated at the joint portion, the sealing material may be peeled off or cracked even if it is slightly deformed.

  Therefore, it is conceivable to join the fuel cell body and the separator through both the brazing material and the sealing material (see FIGS. 8 and 9). FIG. 8 shows a specific example in which a brazing material 103 that joins the fuel cell main body 101 and the separator 102 is disposed in the vicinity of the opening 104 of the separator 102. FIG. 9 shows a specific example in which the brazing material 113 for joining the fuel cell main body 111 and the separator 112 is arranged at a position on the outer periphery side of the opening 114 in the separator 112.

JP 2010-207863 A (Fig. 3 etc.) Japanese Patent No. 0346960 (Fig. 1 etc.)

  However, in the specific example shown in FIG. 8, when the separator 102 and the fuel cell main body 101 are deformed, for example, along the surface direction (refer to the directions of arrows F <b> 1 and F <b> 2 in FIG. 8), Tensile stress acts on the portion in contact with the inner surface, and the crack 106 is likely to occur. As a result, gas sealing with the sealing material 105 may not be possible.

  Further, in the specific example shown in FIG. 9, even if sealing with the sealing material 115 is performed after joining with the brazing material 113, the gap 116 formed between the separator 102 and the fuel cell main body 111 is narrow, and thus heat treatment is performed. There is a problem that the previous sealing material 115 is difficult to flow into the gap 116. Also in this case, since a tensile stress acts on a portion of the sealing material 115 that is in contact with the inner surface of the opening 114, a crack (not shown) is likely to occur. Further, since the forming material of the sealing material 115 entraps a large amount of bubbles (air in the gap 116), the bubbles are repelled during the heat treatment, so that a defect portion is generated in the sealing material 115, and gas sealing by the sealing material 115 is performed. The problem of not being able to occur.

  The present invention has been made in view of the above problems, and the object thereof is to reliably form a sealing portion that is not easily damaged between the separator and the fuel cell body, thereby allowing the fuel cell body and the separator to It is an object of the present invention to provide a separator-equipped fuel cell and a fuel cell stack that can improve the reliability of the joint portion.

Means for solving the above problems (means 1) include a solid electrolyte layer, an air electrode arranged on the first main surface of the solid electrolyte layer, and a fuel electrode arranged on the second main surface of the solid electrolyte layer. And a separator attached to the fuel cell body through a joint portion made of a brazing material containing Ag and having a frame shape having an opening. The brazing material is bonded to a position on the outer periphery side of the opening in the separator, and a portion of the separator located on the opening side of the brazing material and the fuel cell body A sealing portion having a sealing material including glass is provided therebetween, and a gap generated between the separator and the fuel cell main body increases from the brazing material side to the opening side. It is set so that, the sealing material, it is a separator with a fuel cell, characterized in that is in close contact with the end face of the opening side of the brazing material.

  According to the invention described in Means 1, since the gap generated between the separator and the fuel cell body is set to increase from the brazing material side to the opening side, the sealing material is spread. It can be easily poured into the gap from the opening side. In this case, in the portion between the separator and the fuel cell main body in the sealing portion, a shear stress acts on the boundary portion between the sealing material and the separator instead of a tensile stress, so that cracking hardly occurs. Moreover, it becomes difficult for the sealing material to entrap bubbles (air in the gap), and damage to the sealing material due to the bubbles blowing during the heat treatment can be prevented. Therefore, gas sealing with a sealing material can be performed more reliably. From the above, the reliability of the joint portion between the fuel cell body and the separator can be improved.

  In addition, since a sealing portion having a sealing material is provided between a portion of the separator that is located on the opening side of the brazing material and the fuel cell body, the separator is disposed between the separator and the fuel cell body. The brazing material is not in direct contact with the oxidant gas in contact with the air electrode or the fuel gas in contact with the fuel electrode. As a result, movement of the oxidant gas or fuel gas to the brazing material is prevented, so that diffusion of the oxidant gas or fuel gas in the brazing material is suppressed, and voids caused by the reaction between hydrogen and oxygen are suppressed. Occurrence can be prevented.

  The solid electrolyte layer constituting the fuel cell body has a property (ion conductivity) in which a part of the fuel gas in contact with the fuel electrode and the oxidant gas in contact with the air electrode move as ions. Examples of ions that move in the solid electrolyte layer include oxygen ions and hydrogen ions.

As a material for forming the solid electrolyte layer (solid oxide layer), for example, ZrO ₂ ceramic, CeO ₂ ceramic, LaGaO ₃ ceramic, BaCeO ₃ ceramic, SrCeO ₃ ceramic, SrZrO ₃ ceramic, CaZrO ₃ ceramic and so on.

The air electrode constituting the fuel cell main body is in contact with an oxidant gas serving as an oxidant and functions as a positive electrode in the fuel cell with a separator. Here, examples of the material for forming the air electrode include a metal material, a metal oxide, and a metal composite oxide. Preferable examples of the metal material include Pt, Au, Ag, Pd, Ir, Ru, Rh, etc., and alloys thereof. Preferable examples of the metal oxide include La, Sr, Ce, Co, Mn, Fe oxide (La ₂ O ₃ , SrO, Ce ₂ O ₃ , Co ₂ O ₃ , MnO ₂ , FeO), etc. There is. 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.

  Examples of the oxidant gas include a mixed gas of oxygen and another gas. This mixed gas may contain an inert gas such as nitrogen or argon. The mixed gas is preferably safe and inexpensive air.

The fuel electrode constituting the fuel cell body is in contact with a fuel gas serving as a reducing agent and functions as a negative electrode in the fuel cell with a separator. Here, examples of the material for forming the fuel electrode include ZrO ₂ ceramics stabilized by rare earth elements (Sc, Y, etc.), and CeO ₂ ceramics doped with rare earth elements (Sm, Gd, 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.

  Moreover, as fuel gas, hydrogen gas, hydrocarbon gas, the mixed gas of hydrogen gas and hydrocarbon gas, etc. are mentioned, for example. When the hydrocarbon gas is selected as the fuel gas, the type of the hydrocarbon gas is not particularly limited, but is preferably natural gas, naphtha, coal gasification gas, or the like. It is obtained by mixing water vapor with fuel gas obtained by passing gas (hydrogen gas, hydrocarbon gas, mixed gas) in water and humidifying it, or gas (hydrogen gas, hydrocarbon gas, mixed gas). The fuel gas to be used may be selected. Further, only one type of fuel gas may be used, or a plurality of types of fuel gas may be used in combination. Further, the fuel gas may contain an inert gas such as nitrogen or argon. Moreover, what vaporized the liquid raw material can be used as fuel gas, or hydrogen gas produced by reforming a gas other than hydrogen gas can be used as fuel gas.

  The separator attached to the solid electrolyte layer of the fuel cell body is preferably a metal separator in consideration of heat resistance, chemical stability, strength, thermal expansion difference from the fuel cell body, and the like. Suitable examples of the metal separator forming material include ferritic stainless steels such as SUS430, SUS444, and SUH21.

In addition, since the glass contained in a sealing material may react with a chromia when using the material (for example, said stainless steel) which forms a chromia (chromium oxide) film as a metal separator, a sealing material The reliability will be reduced. Therefore, the separator contains, for example, 2% by mass or more and 10% by mass or less of aluminum (Al), and the joining material (brazing material) constituting the joint is, for example, 2% by volume or more and 15% by volume or less of aluminum oxide. or comprises a complex oxide, sealant, for example, in terms of Al ₂ O _3, it is to contain 20 mass% of aluminum 2 mass% or more. In this case, since all of the separator, the joining portion, and the sealing portion contain aluminum, the affinity between the separator, the joining portion, and the sealing portion is improved, so that the reliability of joining and sealing is improved. Sex is further improved. More specifically, when the separator contains 2% by mass or more of aluminum, the oxidation resistance of the separator is improved by forming an alumina coating on the surface. In addition, when the brazing material contains 2% by volume or more of an aluminum oxide or a composite oxide, the brazing material functions as an anchor material in affinity with the alumina coating of the separator, so that the bonding strength with the separator is improved. At the same time, since the wettability with the alumina coating is also improved, the problem that the brazing material is repelled from the separator during brazing can be solved. Further, when the sealing material contains aluminum in an amount of 2% by mass or more in terms of Al ₂ O ₃ , the sealing material has an affinity with the alumina coating of the separator and the aluminum of the joint, and therefore the interface with the separator and the interface with the joint. It is possible to solve the problem that a gap is generated in the substrate. From the above, the reliability of the sealing material is improved. If the separator contains more than 10% by mass of aluminum, the material for forming the separator becomes hard and difficult to process. Further, if the brazing material contains more than 15% by volume of aluminum oxide or composite oxide, necking between Ag in the joint becomes weak and the strength of the brazing material is lowered. Furthermore, if the sealing material contains more than 20% by mass of aluminum in terms of Al ₂ O ₃ , the sealing material may be cracked due to a difference in thermal expansion from the separator because the thermal expansion coefficient of the sealing material is reduced. There is.

  Moreover, it is preferable that the thickness of a metal separator is 0.5 mm or less (for example, 0.1 mm). If the thickness of the metal separator is greater than 0.5 mm, mechanical stresses and thermal stresses acting on the metal separators may occur when a fuel cell stack is formed by stacking a plurality of separator-attached fuel cells. Since it becomes difficult to relieve, there is a possibility that the fuel cell body may be damaged. Specifically, for example, when forming a solid oxide fuel cell (fuel cell stack), mechanical stress or thermal stress applied to a joint or sealing portion that connects the fuel cell body and the separator. Is not relaxed, and the fuel cell body may be damaged (cracked).

  In addition, when the burr | flash produced at the time of the punching process of a metal plate remains in an opening part, the separator is a fuel battery cell in the state which faced the side where the burr | flash does not protrude in the separator toward the fuel cell body side. It is preferable to attach to the main body. In this case, the separator is arranged such that the gap increases as it goes from the base end side of the burr to the front end side. As a result, the gap generated between the separator and the fuel cell body can be set to increase from the brazing material side to the opening side without bending the separator. Therefore, the manufacturing cost of the fuel cell with separator can be reduced.

The separator is attached to the fuel cell main body through a joint portion made of a brazing material containing Ag. Examples of the brazing material include a mixture of Ag and oxide, specifically, Ag—Al ₂ O ₃ , Ag—CuO, Ag—TiO ₂ , Ag—Cr ₂ O ₃ , Ag—SiO _{2 and the} like. . Furthermore, an alloy of Ag and another metal, specifically, Ag—Ge—Cr, Ag—Ti, Ag—Al, Ag—Pd, or the like can be used as the brazing material. The brazing material is preferably brazed in an air atmosphere. This is because, if brazing is performed in a vacuum or a reducing atmosphere, the characteristics of the forming material such as the air electrode may change.

  The separator is attached to the fuel cell body. Here, the following is mentioned as an aspect with which a separator is attached. For example, the air electrode provided in the fuel cell main body is arranged at the center of the first main surface of the solid electrolyte layer, while the fuel electrode provided in the fuel cell main body is arranged on the entire second main surface of the solid electrolyte layer. In some cases, the separator is preferably attached to the outer peripheral portion of the first main surface via a brazing material. In this case, even if the separator is attached to the first main surface of the solid electrolyte layer, the air electrode does not get in the way. When the air electrode is disposed on the entire first main surface while the fuel electrode is disposed on the central portion of the second main surface, the separator is disposed on the outer peripheral portion of the second main surface via the brazing material. Preferably it is attached. Further, when the air electrode is arranged at the center of the first main surface and the fuel electrode is arranged at the center of the second main surface, the separator is arranged on the outer periphery of the first main surface via the brazing material. It is preferable to attach to at least one of the outer peripheral part of a part and a 2nd main surface.

  Further, a sealing portion having a sealing material containing glass is provided between a portion of the separator that is positioned closer to the opening than the brazing material and the fuel cell body. The sealing portion covers a facing surface facing the fuel cell body in the separator and a surface located on the opposite side of the facing surface in the separator, and the separator may be sandwiched between sealing materials. preferable. In this case, in addition to the separator facing surface, the sealing portion also contacts a surface of the separator that is located on the opposite side of the facing surface. Therefore, the deformation of the separator due to the difference in thermal expansion between the sealing material and the separator ( (Deformation in which the separator tends to warp on the opposite side of the opposing surface) can be suppressed. As a result, the portion of the sealing portion that is in contact with the opposing surface is unlikely to crack, so that gas sealing with the sealing material can be performed more reliably. Moreover, since a separator is inserted | pinched with a sealing material, a deformation | transformation of a separator is suppressed. As a result, it is possible to prevent the sealing portion from being damaged due to the deformation of the separator, and thus it is possible to suppress the arrival of the fuel gas or the oxidant gas to the joint portion.

  Here, as the sealing material containing glass, specifically, glass, glass ceramic (crystallized glass), a composite material of glass and ceramic, or the like can be used. As an example, G018-811 manufactured by SCHOTT can be used.

In addition, the sealing material containing glass has the problem that reliable gas sealing cannot be performed if the wettability with the alumina coating of the separator is poor. For this reason, it is preferable that Mg and Zn are contained in the sealing material. Since Mg and Zn react with the alumina coating to form chemically stable reactants such as MgAl ₂ O ₄ and ZnAl ₂ O ₄ , wettability is improved and durability is also improved.

  Moreover, it is preferable that the sealing part has a plurality of bubbles having a diameter of 0.1 μm to 50 μm inside. This is because crack propagation can be prevented by bubbles. If the bubble diameter is less than 0.1 μm, the effect of preventing the propagation of cracks cannot be obtained. On the other hand, when the diameter of the bubble exceeds 50 μm, the sealing material is easily broken.

  As another means (means 2) for solving the above-mentioned problem, there is a fuel cell stack characterized by stacking a plurality of separator-attached fuel cells as described in the means 1.

  According to the invention described in the means 2, the sealing portion having the sealing material is provided between the separator and the fuel cell body, and the gap generated between the separator and the fuel cell body is on the brazing material side. It is set so that it becomes large as it goes to the opening side from. For this reason, the sealing material can be easily poured into the gap from the widened opening side. In this case, in the portion between the separator and the fuel cell main body in the sealing portion, a shear stress acts on the boundary portion between the sealing material and the separator instead of a tensile stress, so that cracking hardly occurs. In addition, since the sealing material is less likely to entrap bubbles (air in the gap) and damage to the sealing material due to the blowing of bubbles during heat treatment can be suppressed, gas sealing with the sealing material is performed more reliably. be able to. From the above, it is possible to improve the reliability of the joint portion between the fuel cell body and the separator, and hence the reliability of the fuel cell stack.

  In addition, since a sealing portion having a sealing material is provided between a portion of the separator that is located on the opening side of the brazing material and the fuel cell body, the separator is disposed between the separator and the fuel cell body. The brazing material is not in direct contact with the oxidant gas in contact with the air electrode or the fuel gas in contact with the fuel electrode. As a result, movement of the oxidant gas or fuel gas to the brazing material is prevented, so that diffusion of the oxidant gas or fuel gas in the brazing material is suppressed, and voids caused by the reaction between hydrogen and oxygen are suppressed. Occurrence can be prevented.

The schematic perspective view which shows the fuel cell in this embodiment. AA sectional view taken on the line AA of FIG. The schematic sectional drawing which shows the fuel cell with a separator. The principal part sectional drawing which shows the fuel cell with a separator. The principal part sectional drawing which shows the fuel cell with a separator in other embodiment. The principal part sectional drawing which shows the fuel cell with a separator in other embodiment. The principal part sectional drawing which shows the fuel cell with a separator in other embodiment. Sectional drawing which shows the principal part which shows the problem of a prior art. Sectional drawing which shows the principal part which shows the problem of a prior art.

  Hereinafter, an embodiment in which the present invention is embodied in a fuel cell 1 will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, the fuel cell 1 of the present embodiment is a solid oxide fuel cell (SOFC). The fuel cell 1 includes a fuel cell stack 10 formed by stacking a plurality of separator-attached fuel cells 11 that are the minimum unit of power generation. The fuel cell stack 10 has a substantially rectangular parallelepiped shape with a length of 180 mm × width of 180 mm × height of 80 mm. The fuel cell stack 10 has eight through holes 40 that penetrate the fuel cell stack 10 in the thickness direction. The fastening bolts 41 are inserted into the four through holes 40 at the four corners of the fuel cell stack 10, and a nut (not shown) is screwed to the lower end portion of the fastening bolt 41 protruding from the lower surface of the fuel cell stack 10. Further, gas circulation fastening bolts 42 are inserted into the remaining four through holes 40, and nuts 43 are screwed onto both end portions of the gas circulation fastening bolts 42 protruding from the upper and lower surfaces of the fuel cell stack 10. As a result, a plurality of separator-equipped fuel cells 11 are fixed.

  As shown in FIGS. 2 and 3, the fuel cell 1 is configured by stacking and arranging fuel cells 11 with separators, current collectors 66, and connector plates 51 and 60. The separator-equipped fuel cell 11 is configured by stacking an air electrode frame 52, an insulating frame 53, a separator 54, a fuel cell body 55, and a fuel electrode frame 56 in order.

  The connector plates 51 and 60 are formed in a substantially rectangular plate shape by a metal material such as stainless steel having excellent heat resistance and conductivity, and are disposed at the upper end and the lower end of the separator-equipped fuel cell 11. The connector plates 51 and 60 form a gas flow path in the fuel cell 11 with a separator and make the adjacent fuel cells 11 with a separator conductive. More specifically, the connector plates 51 and 60 located between the adjacent separator-equipped fuel cells 11 become so-called interconnectors, and partition the adjacent separator-attached fuel cells 11. The connector plate 60 of this embodiment also serves as the connector plate 51 of the separator-equipped fuel cell 11 adjacent to the lower side. The connector plate 51 disposed at the upper end of the fuel cell stack 10 serves as the upper end plate 12, and the connector plate 60 disposed at the lower end of the fuel cell stack 10 serves as the lower end plate 13. Both end plates 12 and 13 sandwich the fuel cell stack 10 and serve as output terminals for current output from the fuel cell stack 10. In addition, the connector plates 51 and 60 used as the end plates 12 and 13 are thicker than the connector plates 51 and 60 used as the interconnector.

  The air electrode frame 52 shown in FIGS. 2 and 3 is formed in a substantially rectangular frame shape by a conductive material such as stainless steel. Therefore, a rectangular opening 61 that penetrates the air electrode frame 52 in the thickness direction is provided at the center of the air electrode frame 52. The insulating frame 53 is formed in a substantially rectangular frame shape by a mica sheet having a thickness of 0.5 mm. Therefore, a rectangular opening 63 that penetrates the insulating frame 53 in the thickness direction is provided at the center of the insulating frame 53. Further, the fuel electrode frame 56 is formed in a substantially rectangular frame shape by a mica sheet. Therefore, a rectangular opening 62 that penetrates the fuel electrode frame 56 in the thickness direction is provided at the center of the fuel electrode frame 56.

  As shown in FIGS. 2 to 4, the separator 54 of the present embodiment is a metal separator formed by bending a metal foil (metal plate). The metallic separator is made of a metal material mainly composed of iron (Fe), and contains 2% by mass or more and 10% by mass or less (3% by mass in this embodiment) of aluminum (Al). An alumina film is formed on the surface of the separator 54. The thermal expansion coefficient of the separator 54 is specified in JIS Z 2285; 2003, and specifically, is about 10 to 12 ppm / ° C. The thermal expansion coefficient of the separator 54 is an average value of measured values between room temperature and 300 ° C. The thickness of the separator 54 is preferably set to 0.5 mm or less, and particularly preferably set to 0.05 mm or more and 0.1 mm or less (0.1 mm in this embodiment). Further, the separator 54 has a facing surface 93 that faces the solid electrolyte layer 81 in the separator 54, and a surface 94 that is located on the opposite side of the facing surface 93 in the separator 54. The separator 54 has a substantially rectangular frame shape with a rectangular separator opening 64 penetrating the separator 54 in the thickness direction at the center. And the end part 65 by the side of the separator opening part 64 of the separator 54 has comprised the cross-sectional circular arc shape curved so that it might protrude upwards. Therefore, the gap S1 generated between the separator 54 and the solid electrolyte layer 81 is set so as to increase from the brazing material 91 side toward the separator opening 64 side.

  As shown in FIGS. 2 and 3, the fuel cell main body 55 of this embodiment includes a solid electrolyte layer 81, an air electrode 82, and a fuel electrode 83, and generates electric power through a power generation reaction. The solid electrolyte layer 81 is formed of a ceramic material such as yttria stabilized zirconia (YSZ) and has a rectangular plate shape with a thickness of 0.01 mm. The thermal expansion coefficient of the solid electrolyte layer 81 is specified in JIS Z 2285; 2003, and specifically, is about 8 to 10 ppm / ° C. The thermal expansion coefficient of the solid electrolyte layer 81 is an average value of measured values between room temperature and 300 ° C. The solid electrolyte layer 81 is fixed to the lower surface of the separator 54. The solid electrolyte layer 81 functions as an oxygen ion conductive solid electrolyte body. The air electrode 82 is affixed to the central portion of the first main surface 84 (the upper surface in FIGS. 2 and 3) of the solid electrolyte layer 81 and comes into contact with the air (oxidant gas) supplied to the fuel cell stack 10. It has become. On the other hand, the fuel electrode 83 is affixed to the entire second main surface 85 (the lower surface in FIGS. 2 and 3) of the solid electrolyte layer 81 and is in contact with the fuel gas supplied to the fuel cell stack 10. That is, the air electrode 82 and the fuel electrode 83 are arranged on both sides of the solid electrolyte layer 81. The air electrode 82 is disposed in the separator opening 64 of the separator 54 so as not to contact the separator 54. The fuel electrode 83 is formed of a mixture of nickel and yttria-stabilized zirconia (Ni-YSZ) and has a rectangular shape in a plan view with a thickness of 0.8 mm.

  As shown in FIG. 4, the separator 54 is attached to the fuel cell body 55, specifically, the outer peripheral portion of the first main surface 84 of the solid electrolyte layer 81 via the joint portion 90. Further, the joining portion 90 is constituted by a brazing material 91 containing silver (Ag), and is an oxide or composite oxide of aluminum (Al) that is 2% by volume or more and 15% by volume or less (8% by volume in this embodiment). Is included. The brazing material 91 is joined to a position on the outer peripheral side of the separator opening 64 in the separator 54, and is disposed over the entire circumference of the opening end of the separator opening 64. Note that the width L1 of the brazing material 91 indicates the distance from the inner end to the outer end of the cut surface in the cross-sectional view (see FIG. 4) cut in the thickness direction, specifically 2 mm or more and 6 mm or less. (4 mm in this embodiment) is set. The thickness of the brazing material 91 is preferably set to 10 μm or more and 80 μm or less, and particularly preferably set to 20 μm or more and 50 μm or less (30 μm in the present embodiment).

A sealing portion 95 is provided between the solid electrolyte layer 81 and a portion of the separator 54 that is located closer to the separator opening 64 than the brazing material 91. The sealing part 95 has a sealing material 92 including glass (G018-811 manufactured by SCHOTT), and is 2% by mass or more and 20% by mass or less (10% by mass in this embodiment) in terms of Al ₂ O _3. ) Aluminum (Al). The thermal expansion coefficient of the sealing material 92 is specified in JIS R 3102; 1995, and specifically, is about 8 to 12 ppm / ° C. In addition, the thermal expansion coefficient of the sealing material 92 means the average value of the measured value between normal temperature and 300 degreeC. Further, the sealing material 92 is disposed at a position on the outer peripheral side of the separator opening 64 in the separator 54. The sealing material 92 is disposed over the entire circumference of the opening end of the separator opening 64. Further, the sealing material 92 (sealing portion 95) includes an opposing surface 93 of the separator 54, a surface 94 positioned on the opposite side of the opposing surface 93 in the separator 54, and an end surface (separator of the separator 54 on the separator opening 64 side). The inner surface of the opening 64 is covered. For this reason, the separator 54 is sandwiched between the sealing materials 92. In addition to being in close contact with the surface of the separator 54, the sealing material 92 is in close contact with the end surface of the brazing material 91 on the separator opening 64 side and the first main surface 84 of the solid electrolyte layer 81. The width L2 of the sealing material 92 indicates the distance from the inner end of the cut surface to the outer end (contact portion with the brazing material 91) in the cross-sectional view (see FIG. 4) cut in the thickness direction. Specifically, it is set to 1 mm or more and 4 mm or less (2 mm in this embodiment). The thickness of the sealing material 92 is set to 80 μm or more and 500 μm or less (300 μm in this embodiment).

  As shown in FIGS. 2 and 3, in the fuel cell with separator 11 of this embodiment, the fuel chamber 15 is provided below the separator 54 by the opening 62 of the fuel electrode frame 56, the connector plate 60, and the like. It is supposed to be formed. A solid electrolyte layer 81 and a fuel electrode 83 are accommodated in the fuel chamber 15.

  In the separator-equipped fuel cell 11 of the present embodiment, the air chamber 16 is formed above the separator 54 by the connector plate 51, the opening 61 of the air electrode frame 52, the opening 63 of the insulating frame 53, and the like. It has become so. A current collector 66 made of a metal material such as a nickel alloy is installed on the surface side of the air electrode 82. As a result, the air electrode 82 and the connector plate 51 are electrically connected via the current collector 66.

  Further, as shown in FIG. 2, the fuel cell stack 10 includes a fuel supply path 70 that supplies fuel gas to the fuel chamber 15 of each separator-equipped fuel cell 11, and a fuel discharge that discharges fuel gas from the fuel chamber 15. And a path 71. The fuel supply path 70 includes a fuel supply hole 72 that extends along the axial direction at the center of the gas circulation fastening bolt 42, and a fuel supply lateral hole 73 that allows the fuel supply hole 72 and the fuel chamber 15 to communicate with each other. . The fuel discharge path 71 includes a fuel discharge hole 74 that extends in the axial direction at the center of the gas circulation fastening bolt 42, and a fuel discharge horizontal hole 75 that allows the fuel discharge hole 74 and the fuel chamber 15 to communicate with each other. ing. Accordingly, the fuel gas is supplied to the fuel chamber 15 through the fuel supply hole 72 and the fuel supply lateral hole 73 in order, and is discharged from the fuel chamber 15 through the fuel discharge lateral hole 75 and the fuel discharge hole 74 in order. Is done.

  As shown in FIG. 2, the fuel cell stack 10 includes an air supply path (not shown) that supplies air to the air chamber 16 of each separator-equipped fuel cell 11, and air that discharges air from the air chamber 16. And a discharge path (not shown). The air supply path has substantially the same structure as the fuel supply path 70, and includes an air supply hole (not shown) extending in the axial direction at the center of the gas circulation fastening bolt 42, an air supply hole, and air An air supply lateral hole (not shown) for communicating the chamber 16 is formed. The air discharge path has substantially the same structure as the fuel discharge path 71, and includes an air discharge hole (not shown) extending in the axial direction at the center of the gas circulation fastening bolt 42, and an air discharge hole. And an air discharge lateral hole (not shown) for communicating the air chamber 16. Therefore, the air passes through the air supply hole and the air supply lateral hole in order and is supplied to the air chamber 16, and passes through the air discharge lateral hole and the air discharge hole in order and is discharged from the air chamber 16.

  For example, while the fuel cell 1 is heated to the operating temperature, fuel gas is introduced from the fuel supply path 70 to the fuel chamber 15 and air is supplied from the air supply path to the air chamber 16. As a result, hydrogen in the fuel gas and oxygen in the air react through the solid electrolyte layer 81 (power generation reaction), and DC power is generated with the air electrode 82 as the positive electrode and the fuel electrode 83 as the negative electrode. In the fuel cell stack 10 of the present embodiment, since a plurality of separator-attached fuel cells 11 are stacked and connected in series, the upper end plate 12 that is electrically connected to the air electrode 82 serves as a positive electrode. The lower end plate 13 electrically connected to the pole 83 is a negative electrode.

  Next, a method for manufacturing the fuel cell 1 will be described.

  First, the connector plates 51 and 60, the air electrode frame 52 and the separator 54 are formed by punching a stainless steel plate. In the formation of the separator 54, the separator opening 64 is formed, and at the same time, the end portion 65 of the separator 54 on the separator opening 64 side is formed so as to form a curved cross-sectional arc shape so as to protrude upward. Is done. Further, the insulating frame 53 and the fuel electrode frame 56 are formed by forming the mica sheet in a predetermined shape. Specifically, a commercially available mica sheet (a sheet made of a composite of mica and molding resin) is formed in substantially the same shape as other members (connector plates 51, 60, air electrode frame 52, separator 54, etc.). . In addition, the resin component contained in the mica sheet is evaporated by a heat treatment performed after being laminated together with other members. Furthermore, the mica sheet seals each member by being sandwiched between other members when the separator-equipped fuel cells 11 are bolted in the stacking direction.

  Next, the fuel cell 11 with a separator is formed according to a conventionally known technique. Specifically, a green sheet to be the solid electrolyte layer 81 is laminated on the green sheet to be the fuel electrode 83 and fired. Further, the material for forming the air electrode 82 is printed on the solid electrolyte layer 81 and then baked. At this point, the fuel cell body 55 is formed.

  Thereafter, the separator 54 is fixed to the solid electrolyte layer 81 by brazing. Specifically, the brazing material 91 is disposed on each of the solid electrolyte layer 81 and the separator 54. For example, the paste-like brazing material 91 is printed on the first main surface 84 of the solid electrolyte layer 81 and the opposing surface 93 of the separator 54. Instead of arranging the brazing material 91 by printing, the brazing material 91 may be arranged using a dispenser.

  Next, the brazing material 91 is melted, and the solid electrolyte layer 81 and the separator 54 are joined. Specifically, the solid electrolyte layer 81 on which the brazing material 91 is disposed and the separator 54 on which the brazing material 91 is disposed are in contact with each other, and heating is performed at, for example, 800 to 1200 ° C. in an air atmosphere. As a result, the brazing material 91 on the solid electrolyte layer 81 side and the brazing material 91 on the separator 54 side melt, and the solid electrolyte layer 81 and the separator 54 are joined to each other.

  Next, the gap S <b> 1 between the separator 54 and the solid electrolyte layer 81 is sealed with a sealing material 92. Specifically, the sealing material 92 is disposed in the gap S1 by printing a paste containing the sealing material 92. Furthermore, the paste containing the sealing material 92 is heated at a lower temperature (700 to 1000 ° C. in the present embodiment) than when the brazing material 91 is melted in an air atmosphere. As a result, the paste melts and the sealing material 92 is formed. Instead of disposing the sealing material 92 by paste printing, the sealing material 92 may be disposed by pouring the paste into the gap S1 using a dispenser or the like. Alternatively, the sealing material 92 may be formed by disposing a plate material having a cross-sectional wedge shape including glass in the gap S1 and then melting the material.

  Thereafter, the air electrode frame 52, the insulating frame 53, the separator 54 (with the solid electrolyte layer 81 fixed by brazing), the fuel electrode frame 56, and the like are laminated and integrated. At this point, the separator-equipped fuel cell 11 is formed.

  Next, the fuel cell stack 10 is formed by stacking and integrating a plurality of separator-equipped fuel cells 11, connector plates 51, 60, and the like. Then, the fastening bolts 41 are inserted into the four through holes 40 at the four corners of the fuel cell stack 10, and a nut (not shown) is screwed to the lower end portion of the fastening bolt 41 protruding from the lower surface of the fuel cell stack 10. Further, gas circulation fastening bolts 42 are inserted into the remaining four through holes 40, and nuts 43 are screwed onto both end portions of the gas circulation fastening bolts 42 protruding from the upper and lower surfaces of the fuel cell stack 10. As a result, each separator-equipped fuel cell 11 is fixed, and the fuel cell 1 is completed.

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

  (1) In the present embodiment, a sealing portion 95 having a sealing material 92 is provided between the separator 54 and the solid electrolyte layer 81, and a gap S1 generated between the separator 54 and the solid electrolyte layer 81 is provided. The size is set so as to increase from the brazing material 91 side toward the separator opening 64 side. For this reason, the sealing material 92 can be easily poured into the gap S1 from the widened separator opening 64 side. In this case, in the sealing material 92 that flows into the gap S1 (the portion of the sealing portion 95 between the facing surface 93 of the separator 54 and the first main surface 84 of the solid electrolyte layer 81), the sealing material 92 and Since shear stress acts on the boundary portion with the separator 54 instead of tensile stress, cracks are less likely to occur. In addition, since the sealing material 92 is less likely to entrain bubbles (air in the gap S1), and damage to the sealing material 92 due to bubbles blowing during heat treatment can be suppressed, gas sealing with the sealing material 92 is performed. This can be done more reliably. From the above, the reliability of the joint portion between the fuel cell main body 55 and the separator 54 can be improved.

  (2) In the present embodiment, since the sealing portion 95 having the sealing material 92 is provided between the portion of the separator 54 that is located closer to the separator opening 64 than the brazing material 91 and the solid electrolyte layer 81, The brazing material 91 disposed between the separator 54 and the solid electrolyte layer 81 is not in direct contact with the air in contact with the air electrode 82. As a result, since the movement of air to the brazing material 91 is blocked, the diffusion of air in the brazing material 91 is suppressed, and the generation of voids due to the reaction between hydrogen and oxygen can be prevented.

(3) Since the brazing material 91 used in the present embodiment contains Ag and hardly oxidizes even when reaching the brazing temperature in the air atmosphere, the brazing material can be brazed in the air atmosphere. Therefore, it is possible to prevent the performance deterioration of the fuel cell body 55 (particularly the air electrode 82) during brazing. Specifically, when the air electrode 82 is composed of, for example, LSCF (La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ ), this is caused by the change in the crystal structure of the LSCF. Performance degradation can be prevented. Furthermore, since it is not necessary to use an inert gas such as argon (Ar) as the brazing atmosphere in order to prevent performance degradation of the fuel cell main body 55, it is possible to prevent complication of the apparatus and process. .

  In addition, you may change this embodiment as follows.

  In the above embodiment, the separator opening 64 of the separator 54 is formed, and at the same time, the end 65 on the separator opening 64 side of the separator 54 is formed so as to have a circular arc shape that is curved so as to protrude upward. It was. However, the end portion 65 may be processed in the step after the separator opening 64 is formed.

  As shown in the separator-equipped fuel cell 21 in FIG. 5, the burr 22 generated during the punching process of the metal foil is left in the separator opening 24 of the separator 23, and the separator 23 is connected to the base end of the burr 22. You may arrange | position so that the clearance gap S2 may become large as it goes to the front end side from the side. The height of the burr 22 is set to 20 μm or more and 300 μm or less (here, 100 μm). In this way, the gap S2 can be set so as to increase from the brazing material 25 side to the separator opening 24 side without bending the separator 23. Therefore, the manufacturing cost of the fuel cell 21 with a separator can be reduced. The separator 23 may be bent while leaving the burr 22.

  In the above embodiment, the end portion 65 on the separator opening portion 64 side of the separator 54 is formed so as to have a circular arc shape that is curved so as to protrude upward, so that the separator 54 and the solid electrolyte layer 81 are spaced from each other. The gap S <b> 1 generated in step S <b> 1 is set so as to increase from the brazing material 91 side toward the separator opening 64 side. However, by providing the solid electrolyte layer 81 with a recess that becomes deeper as it goes from the brazing material 91 side to the separator opening 64 side, the gap S1 becomes larger as it goes from the brazing material 91 side to the separator opening 64 side. It may be set. Alternatively, the separator 54 may be formed in an arc shape in cross section and the solid electrolyte layer 81 may be provided with a recess so that the gap S1 increases from the brazing material 91 side toward the separator opening 64 side.

  The separator-equipped fuel cell 11 of the above embodiment is a so-called fuel electrode-supported fuel cell, in which the air electrode 82 is disposed at the center of the first main surface 84 of the solid electrolyte layer 81, while the fuel electrode 83 is arranged on the entire second main surface 85 of the solid electrolyte layer 81, and the separator 54 is attached to the outer peripheral portion of the first main surface 84.

  However, as shown in FIG. 6, the air electrode 33 is disposed on the entire first main surface 35, while the fuel electrode 34 is disposed on the center portion of the second main surface 36, and the outer peripheral portion of the second main surface 36. The separator 32 may be attached to the so-called air electrode support type fuel cell 31 with a separator. In addition, as shown in FIG. 7, the air electrode 123 is disposed at the center portion of the first main surface 125, and the fuel electrode 124 is disposed at the center portion of the second main surface 126. A so-called electrolyte-supported fuel cell 121 with a separator in which a separator 122 is attached to the outer periphery may be used. The separator 122 may be attached to the outer peripheral portion of the second main surface 126, or may be attached to both the outer peripheral portion of the first main surface 125 and the outer peripheral portion of the second main surface 126.

  Next, the technical ideas grasped by the embodiment described above are listed below.

  (1) In the above means 1, the sealing material is a facing surface facing the solid electrolyte layer in the separator, a surface located on the opposite side of the facing surface in the separator, an end surface on the opening side of the separator, A separator-equipped fuel cell, wherein the brazing material is in close contact with an end face on the opening side and the first main surface.

  (2) A fuel cell with a separator according to the above means 1, wherein the sealing material has a melting point lower than the melting point of the brazing material.

  (3) The separator-equipped fuel cell according to the above means 1, wherein the separator has a plate shape, and a bent portion or a burr is formed in the opening. In this case, since the separator has a plate shape, the rigidity becomes low. For this reason, it becomes easy to relieve the stress resulting from a thermal expansion difference, and generation | occurrence | production of the crack of a fuel cell main body can be suppressed.

  (4) In the above means 1, burrs generated at the time of punching a metal plate are left in the opening, and the gap of the separator increases from the base end side to the tip end side of the burrs. The separator-equipped fuel cell, which is arranged as described above.

  (5) In the above means 1, the air electrode is disposed at the center of the first main surface, while the fuel electrode is disposed on the entire second main surface, and the separator is interposed via the brazing material. A separator-equipped fuel cell, wherein the fuel cell is attached to an outer peripheral portion of the first main surface.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack 11, 21, 31, 121 ... Fuel cell 23, 32, 54, 122 with a separator ... Separator 55 ... Fuel cell main body 24, 64 ... Separator opening 81 as an opening part ... Solid electrolyte layer 33 , 82, 123 ... air electrodes 34, 83, 124 ... fuel electrodes 35, 84, 125 ... first main surfaces 36, 85, 126 ... second main surfaces 90 ... joints 25, 91 ... brazing material 92 ... sealing material 93 ... Opposing surface 94 ... Surface 95 located on the opposite side of the opposing surface ... Sealing portions S1, S2 ... Clearance generated between the separator and the fuel cell body

Claims (5)

A fuel cell body having a solid electrolyte layer, an air electrode disposed on a first main surface of the solid electrolyte layer, and a fuel electrode disposed on a second main surface of the solid electrolyte layer;
A separator-equipped fuel battery cell comprising a separator attached to the fuel battery cell main body through a joint portion formed of a brazing material containing Ag, having a frame shape having an opening,
The brazing material is bonded to a position on the outer peripheral side of the opening in the separator,
In the separator, a sealing portion having a sealing material containing glass is provided between the portion located on the opening side of the brazing material and the fuel cell body,
The gap generated between the separator and the fuel cell body is set so as to increase from the brazing material side to the opening side ,
The fuel cell with a separator, wherein the sealing material is in close contact with an end face of the brazing material on the opening side .   The fuel cell with a separator according to claim 1, wherein the separator is a metal separator formed by bending a metal plate. The sealing portion covers a facing surface facing the fuel cell body in the separator and a surface located on the opposite side of the facing surface in the separator,
The separator-equipped fuel cell according to claim 1, wherein the separator is sandwiched between the sealing materials. The separator contains 2% by mass or more and 10% by mass or less of aluminum;
The brazing material contains 2% by volume or more and 15% by volume or less of aluminum oxide or composite oxide,
The sealing material is, in terms of Al ₂ O _3, a separator with a fuel cell according to any one of claims 1 to 3, characterized in that it comprises 2 to 20 mass% of aluminum.   5. A fuel cell stack comprising a plurality of separator-attached fuel cells according to claim 1.

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