JP2010021038A - Solid oxide fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell stack provided with sealing structure capable of preventing gas from being leaked between a cell and a separator, even under an electric power generating environment operated at 600°C-800°C. <P>SOLUTION: Bent structure 30a along an outer circumference of each plane-shaped solid oxide fuel cell 10 (cell 10 hereinafter) is extended in an outer circumferential part abutting on an outer circumferential part of an electrolyte 12 of the cell 10 in a metal cell frame 30 provided to connect the cell 10 to the separator, or separator itself, when constituting the solid oxide fuel cell stack each cell having the electrolyte 12 sandwiched with an air electrode 11 and a fuel electrode 13, by connecting the plurality of cells 10 through the metal separators. Further, a brazing material containing Ag as a main component and containing at least one kind of a metal becoming an oxide after joined and a metal oxide, is used when brazing-joining the cell frame 30 or the separator to the outer circumferential part of the electrolyte 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell stack, and more particularly to a seal structure for a solid oxide fuel cell, and more specifically, a configuration of a solid oxide fuel cell operating at 600 ° C. to 800 ° C. The present invention relates to a structure for maintaining a gas seal between a fuel gas and an oxidant gas between materials and an operating environment atmosphere.

  A fuel electrode and an oxidant electrode are arranged via a ceramic electrolyte, and finally hydrogen is supplied as a fuel and oxygen or air is supplied as an oxidant to utilize the reverse reaction of water electrolysis. In a solid oxide fuel cell (SOFC) that generates electricity, in order to obtain a practically sufficient power generation amount of the fuel cell, the unit component of the solid oxide fuel cell described above (single component) A plurality of cells) are electrically connected in series and / or in parallel (that is, stacked) to form a solid oxide fuel cell stack.

For example, oxides such as yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) are used as the electrolyte material of the cell (unit cell) of the solid oxide fuel cell. A porous body made of a mixture of the electrolyte material and nickel is used for the fuel electrode, and strontium doped plantan manganite (Sr-doped LaMnO ₃ ) or lanthanum nickel ferrite (La (NiFe) O ₃ ) is used for the oxidizer electrode. A porous body of a metal oxide conductor is used.

  When actually operating such a single cell (cell) as a fuel cell, a plurality of single cells (cells) are stacked, the negative electrode side (fuel electrode side) of the battery is placed in a reducing atmosphere, and the positive electrode side (oxidant) The electrode side must be kept in an oxidizing atmosphere.

  Furthermore, in order to obtain sufficient power generation efficiency, it is necessary to ensure the ionic conductivity of the electrolyte and easily maintain the fuel cell main body at a high temperature of 600 ° C. or higher at which oxidation and reduction occur.

  In order to achieve this, the positive electrode and the negative electrode exposed to different atmospheres are electrically connected using gas-impermeable and electrically conductive parts, and each electrode is connected to a fuel. In order to properly distribute and supply the gas and the oxidant gas, a part (separator) made of a metal such as heat-resistant stainless steel is disposed between the cells.

  However, in the SOFC stack configured as described above, the fuel and oxidant gas used are all gases, and the operating temperature is as high as 600 ° C to 800 ° C. Meanwhile, when the seal where the gas seal is necessary due to other structures is in an insufficient state, the gas leaks and the performance of the battery is deteriorated or damaged, which is fatal for the establishment of the fuel cell. On the other hand, since a good gas seal brings about higher efficiency and longer life of the fuel cell, the development of a good gas seal has become an important technical issue. Among these, the seal between the cell and the separator is particularly important because it greatly affects the power generation performance and durability.

  In the case of a flat plate type cell, a seal is used to separate the fuel gas and oxidant gas between the front and back of the electrolyte surface of the cell, so that it contacts the electrolyte surface of the cell. In many cases, a separator, a metal plate, a metal foil or the like is disposed on the surface of the substrate and sealed.

  At this time, the problem is how to maintain the airtightness by bringing the electrolyte surface and the separator into close contact with each other.

  For example, in order to eliminate as much as possible the gap between the cell and the separator that causes the sealing failure, sealing is performed using a sealing material in which ceramic powder or ceramic fiber and glass are mixed, or the sealing portion is pressed to reduce gas as much as possible. In order to increase the resistance of the flow path, the sealing performance is ensured.

  However, methods such as stuffing or pressing these gaps do not provide sufficient sealing performance, and there are various factors such as variations caused by individual differences between cells and separators. The problem was left.

  Under such circumstances, a glass material that melts at a temperature higher than the operating temperature of the fuel cell is placed between the cell and the separator, and sealing is performed using glass fusion sealing, or a brazing material of metal other than glass A method using bonding by means of is also considered.

  When glass sealing or brazing is used as such a gas seal for a fuel cell, the sealing structure must be formed by joining ceramics as the cell electrolyte material and metal as the separator material.

  In this case, generally, the ceramic material that is the electrolyte material of the cell to be joined and the metal material that constitutes the separator are not completely the same in thermal properties, so warping and distortion may occur after joining, or in extreme cases Causes problems such as destroying cells. In addition, a destructive force is often applied to the joint due to the thermal cycle of the fuel cell itself, which may cause the seal to fail.

  In order to avoid such problems, sealing is also performed using a thin metal foil that applies as little force as possible to the joint, but this is not sufficient when considering the long-term use of fuel cells. .

  On the other hand, sufficient consideration is required for the properties of the bonding material used to form the seal structure.

  Constructing a sealing structure using glass that melts shows good sealing performance as long as the bonding state is maintained, but the mechanical strength of the bonding itself is weak, so a force that breaks the bonding is It is necessary to give sufficient consideration so as not to join.

  On the other hand, a molybdenum-manganese method or an active metal brazing method in which a metallization process is performed on the ceramic surface is employed as a joining method using a brazing material and, moreover, as a method for joining metal-ceramics as described above. Many things have been done.

  The molybdenum-manganese method, the active metal brazing method, and the like require heat treatment in a non-oxidizing atmosphere such as a vacuum or a nitrogen atmosphere in order to realize a brazed bonding state.

  However, it is difficult to apply the heat treatment to the cell in such a non-oxidizing atmosphere because it changes the characteristics of the metal oxide ceramics that is the cathode material of the cell.

Based on the current situation such as this, K. K. et al. In “Reactive Air Brazing: A Novel Method of Sealing SOFCs and Other Solid-State Electrochemical Devices” by Scott Weil et al., CuO (copper oxide) is used as a brazing material as a method that enables ceramic-metal bonding in the atmosphere. Including methods have been developed and reported.
K. Scott Weil et al. "Reactive Air Brazing: A Novel Method of Sealing SOFCs and Other Solid-State Electrochemical Devices", Electrochem. Sol. Stat. Lett. 8 2005

  However, in the solid oxide fuel cell stack as reported in Non-Patent Document 1, CuO is contained in the brazing material for ceramic-metal bonding as described above. This CuO is a material that plays an important role in strengthening the bonding. However, under the power generation conditions of a solid oxide fuel cell operated at 600 ° C. to 800 ° C., a part of this CuO is present. Therefore, there is a problem that the bonding strength is lost and the sealing performance is impaired.

  Furthermore, the ceramic material, which is the electrolyte material of the solid oxide fuel cell, and the metal material constituting the separator are not completely the same in thermal properties, so warping and distortion may occur after joining, In the thermal cycle of the oxide fuel cell itself, there is a problem that a destructive force is applied to the joint portion and the seal is broken.

  The present invention has been made to solve such a problem, and gas leakage between a separator (interconnector) and a solid oxide fuel cell also in a power generation environment operated at 600 ° C. to 800 ° C. An object of the present invention is to provide a solid oxide fuel cell stack having a seal structure capable of preventing the above.

  The present invention has been made to solve the above-described problems. First, an electrolyte surface (ceramics) of a solid oxide fuel cell and a metal separator are joined to seal between the cell and the separator. As a structure, on the outer peripheral portion of the portion that contacts the cell of the separator joined to the solid oxide fuel cell or the metal cell frame joined to the solid oxide fuel cell and connected to the separator, A bent structure is provided extending along the outer periphery of the solid oxide fuel cell. When the bent structure is joined to the solid oxide fuel cell, the bent structure falls from the electrolyte to the side of the fuel electrode along the outer periphery of the solid oxide fuel cell, and then the position of the side of the fuel electrode. A fold structure of a crank shape (also referred to as a bead or a corrugated shape) that bends outward in an L shape.

  Furthermore, as a brazing material when performing ceramic-metal bonding between the cell (ceramics) and the separator (metal) or between the cell (ceramics) and the cell frame (metal), the ceramic-metal bonding can be performed in the atmosphere. Use possible brazing material.

  As such a brazing material, for example, a brazing material containing silver as a main component and further containing at least one metal or metal oxide that becomes an oxide after bonding is used. In addition, these metals or metal oxides contained in the brazing material are selected from materials that are not easily reduced again under the oxygen partial pressure, temperature, and atmosphere of the operating conditions of the fuel cell.

  That is, specifically, the present invention includes the following technical means.

  A first technical means is a solid oxide in which a plurality of flat solid oxide fuel cells each having an oxide electrolyte sandwiched between an air electrode and a fuel electrode are connected via a metal separator. The fuel cell stack further comprises a metal cell frame for connecting the solid oxide fuel cell and the separator, and when the cell frame and the solid oxide fuel cell are joined, A bending structure extending along the outer periphery of the solid oxide fuel cell is provided on the outer periphery of the cell frame in contact with the outer periphery of the electrolyte.

  According to a second technical means, in the solid oxide fuel cell stack according to the first technical means, the cell frame is made of either ferritic stainless steel or a nickel-based heat-resistant alloy. To do.

  According to a third technical means, a solid oxide in which a plurality of flat solid oxide fuel cells each having an oxide electrolyte sandwiched between an air electrode and a fuel electrode are connected via a metal separator. In the fuel cell stack, when the separator and the solid oxide fuel cell are joined, the outer periphery of the separator is in contact with the outer periphery of the electrolyte, along the outer periphery of the solid oxide fuel cell. The bent structure is extended and provided.

  A fourth technical means is the solid oxide fuel cell stack according to any one of the first to third technical means, wherein the bent structure is provided to extend to an outer peripheral portion of the cell frame or the separator. However, when joined to the solid oxide fuel cell, after falling from the electrolyte to the side of the fuel electrode along the outer periphery of the solid oxide fuel cell, the side of the fuel electrode It is characterized by comprising a crank shape that bends in an L shape outward from the position.

  A fifth technical means is the solid oxide fuel cell stack according to any one of the first to fourth technical means, wherein the separator is made of either ferritic stainless steel or a nickel-based heat resistant alloy. It is characterized by being.

  Sixth technical means is the solid oxide fuel cell stack according to any one of the first to fifth technical means, wherein the solid oxide fuel cell and the cell frame are joined, or The joining between the solid oxide fuel cell and the separator is performed by brazing between a ceramic and a metal.

  According to a seventh technical means, in the solid oxide fuel cell stack according to the sixth technical means, the brazing material used for the brazing is a metal that contains Ag as a main component and is not reduced again after joining. Alternatively, it contains at least one metal oxide.

  The eighth technical means is the solid oxide fuel cell stack according to the seventh technical means, wherein the metal contained in the brazing material and becomes an oxide after bonding is Ti, Al, Cr, Mg. , TiAl alloy, TiNi alloy, TiCr alloy, and NiCr alloy.

According to a ninth technical means, in the solid oxide fuel cell stack according to the seventh technical means, the metal oxide that is contained in the brazing material and becomes an oxide after bonding is SiO ₂ , Ti oxide, It is characterized by being made of a material containing at least one of V ₂ O ₅ , MgO, Al ₂ O ₃ , Cr ₂ O ₃ , Mn oxide, CaO, ZnO, Y ₂ O ₃ , and BaO.

  A tenth technical means is the solid oxide fuel cell stack according to any one of the first to fifth technical means, wherein the solid oxide fuel cell and the cell frame are joined, or The joining between the solid oxide fuel cell and the separator is performed by sealing glass.

  According to the solid oxide fuel cell stack of the present invention, the following effects can be obtained.

  First, a cell frame or separator after joining is formed because a bent structure (crank-shaped crease structure) extending along the outer periphery of the cell is provided on the outer peripheral portion of the cell frame in contact with the cell. It is possible to suppress the distortion due to the thermal stress and to reduce the force applied to the joint portion. By providing a bending structure such as this, it is possible to make the joint seal structure robust and to improve the reliability of the seal by glass fusion bonding, which was difficult with the prior art, and by using a metal brazing material Also in brazing joining, it is possible to prevent cell damage and deterioration of sealing performance due to distortion after joining.

  Furthermore, it is possible to perform metal-ceramic bonding in the atmosphere, and the cell-cell frame or cell-separator is bonded using a predetermined brazing material in which oxide is not easily reduced again after bonding. Since it has a seal structure, the joint itself that has a bending structure and minimizes the application of extra stress also forms a strong bond by the precipitation of the oxide after the brazing filler metal melts, which is good Sealing performance can be obtained.

  In addition, since the metal or metal oxide that plays an important role in bonding formation is made of a material that does not reduce again after bonding, good sealing characteristics can be obtained even after long-time fuel cell power generation. Can be maintained.

  Hereinafter, an example of the best embodiment of the solid oxide fuel cell stack according to the present invention will be described in detail with reference to the drawings.

(Features of the present invention)
Prior to the description of the embodiments of the present invention, an outline of the features of the present invention will be described first. The solid oxide fuel cell stack according to the present invention is a solid oxide fuel cell (unit cell: hereinafter abbreviated as “cell”), and fuel gas leaks between a cell (ceramics) and a separator (metal). When forming a seal structure that prevents the cell, the outer periphery of the separator or cell frame joined to the cell (single cell) has a bent structure (a fold structure with a crank shape (also called a bead shape or a corrugated shape)) It is characterized by having a structure provided with.

  By realizing a solid oxide fuel cell stack like this, it is possible to suppress deformation of the joint due to stress imbalance or thermal deformation of the joint between the cell and separator, thus improving the fuel gas sealing performance The effect that it can be done can be obtained.

(Embodiment)
Hereinafter, an example of an embodiment of a solid oxide fuel cell stack according to the present invention will be described in detail. Note that the present invention is not limited to the present embodiment.

  FIG. 1 is an exploded view showing an example of a stack structure of a solid oxide fuel cell stack according to the present invention, and a plurality of solid oxide fuel cell cells (unit cell) of a flat plate type (FIG. 1: disc type). ) Shows an example of a structure that is stacked so as to be connected in series and / or in parallel via a metallic separator. In the structure of FIG. 1, the solid oxide fuel is produced by sealing the cell and the separator to a circular fuel electrode supported solid oxide fuel cell via a cell frame that mediates the separator. An example of forming a battery stack is shown.

  In other words, as shown in FIG. 1, the solid oxide fuel cell stack 100 includes a metal cell frame 30 for connecting the cells 10 and the separators 20 between the electrolyte surfaces of the cells 10 and the separators 20. It consists of an intervening structure. The cell frame 30 is made of the same metal material as the separator 20 (for example, a heat-resistant metal material such as stainless steel or Ni-based heat-resistant alloy), and is used as a thin metal plate or metal foil as an electrolyte of the disk-shaped cell 10. At the same time, a bending structure 30a is extended and provided on the outer peripheral side.

  As will be described later with reference to FIG. 3, the bending structure 30 a falls from the electrolyte to the side of the fuel electrode along the outer periphery of the cell 10 and then moves outward from the position of the side of the fuel electrode. It is formed into a fold structure having a crank shape (also called a bead shape or a corrugated shape) that is bent in an L shape. The cell frame 30 in FIG. 1 is planarly bonded to the outer peripheral portion of the electrolyte surface of the cell 10, but by providing a bending structure 30 a like this, distortion due to the thermal stress of the cell frame 30 after bonding is suppressed. In addition, it is possible to reduce the extra stress applied to the joint portion.

  FIG. 2 is an explanatory diagram for explaining a joint portion between the cell 10 and the cell frame 30 constituting the solid oxide fuel cell stack 100 shown in FIG. 1, and FIG. FIG. 2 is a perspective view seen from the front surface of the fuel cell stack 100, and FIG. 2B is a perspective view seen from the back surface of the solid oxide fuel cell stack 100. As shown in FIG. 2, the cell 10 includes an air electrode 11, an electrolyte 12, and a fuel electrode 13, and an outer peripheral portion of a ring-shaped cell frame 30 that is planarly joined to the outer peripheral portion of the electrolyte 12 of the cell 10. Is formed by extending a bending structure 30 a along the outer periphery of the cell 10. When the cell 10 and the cell frame 30 are joined, the outer periphery of the cell 10 is fitted along the bending structure 30a so that the joint between the cell 10 and the cell frame 30 is covered, and a seal structure is formed. Is done.

  FIG. 3 is a cross-sectional view showing a structure of the cell 10 constituting the solid oxide fuel cell stack 100 shown in FIG. 1, and shows a joined state with the cell 10-cell frame 30 of FIG. As shown in FIG. 3, the cell 10 includes an air electrode 11, an electrolyte 12, and a fuel electrode 13, and has a flat plate structure in which an oxide 12 made of an oxide is sandwiched between the air electrode 11 and the fuel electrode 13. The cell frame 30 is planarly bonded to the outer peripheral portion 12a of the electrolyte 12, and the sealed portion is covered with a bending structure 30a provided to extend to the outer peripheral portion of the cell frame 30. It is structured.

  Here, as shown in FIG. 3, the bending structure 30 a falls to the side of the fuel electrode 13 after falling from the electrolyte 12 to the side of the fuel electrode 13 along the outer periphery of the cell 10 when joined to the cell 10. It is formed into a fold structure having a crank shape (also referred to as a bead shape or a corrugated shape) that is bent in an L shape outward from the position of the portion. In addition, after joining the cell 10 and the cell frame 30, by combining with the separator 20, the oxidant gas flow path is formed on the air electrode 11 side, and the fuel gas flow path is formed on the fuel electrode 13 side as a groove of the separator 20. It will be in the state where it is arranged.

  That is, the seal structure of the present embodiment shown in FIGS. 1 to 3 has a structure in which the outer peripheral portion 12a of the surface of the electrolyte 12 constituting the solid oxide fuel cell 10 having a flat plate shape is in flat contact. The cell frame 30 is disposed, and the electrolyte 12 and the portion of the cell frame 30 that is in contact with the surface of the electrolyte 12 are joined to ensure gas sealing properties, and the electrolyte 12 surface of the cell 10 of the metal cell frame 30 The bending structure 30a provided to extend along the outer periphery of the cell 10 at the outer peripheral portion of the abutting portion has a structure that suppresses an extra stress applied to the joint portion.

  In the present embodiment, in order to connect the cell 10 and the separator 20, a cell frame 30 made of a thin metal plate or metal foil is interposed, and after the cell frame 30 and the cell 10 are joined, A structure for joining the separator 20 will be described. In some cases, a bending structure 30 a as shown in FIG. 3 is provided to extend to the outer peripheral portion of the separator 20, and the separator 20 itself is attached to the electrolyte 12 of the cell 10. It is also possible to adopt a structure in which the outer peripheral portion 12a is directly joined.

  However, the bent structure 30a is provided so as to extend on the outer peripheral portion that contacts the electrolyte 12 surface of the cell 10 of the separator 20 itself, and the outer peripheral portion of the separator 20 provided with the bent structure 30a is provided on the electrolyte 12 surface of the cell 10. It is complicated in manufacturing to align and join with the outer peripheral portion of the.

  Therefore, a thin metal part that mediates between the cell 10 and the separator 20, that is, a cell frame 30, a bending structure 30 a is formed on the outer periphery of the cell frame 30, and the cell frame 30 and the cell 10 are joined to each other. After the integration, combining the integrated cell 10-cell frame 30 assembly with the separator 20 is desirable in that the manufacturing can be facilitated. In this case, since the joining (seal) between the cell 10-cell frame 30 assembly and the separator 20 is joining (seal) between the metal parts between the cell frame 30 and the separator 20, this is a relatively easy technique. is there. When the cell frame 30 is provided, as described above, the bending structure 30a extending along the outer periphery of the cell 10 is provided on the outer peripheral portion of the cell frame 30 in contact with the electrolyte 12 surface on the cell 10 side. Structure.

  Further, in the present embodiment, when the cell 10-cell frame 30 junction structure or the cell 10-separator 20 junction structure is constructed, the electrolyte 12 surface of the cell 10 is made of yttria stabilized zirconia (YSZ) or scandia stabilized zirconia. Since the cell frame 30 is made of a heat-resistant metal such as ferritic stainless steel or Ni-type heat-resistant alloy similar to the material constituting the separator 20, the cell 10 is made of (ScSZ). The junction between the electrolyte 12 surface and the cell frame 30 or the junction between the cell 10 and the cell frame 30 is a ceramic-metal junction.

Usually, on the surface of the electrolyte 12 of the cell 10, as the air electrode 11, lanthanum strontium manganite (LSM: (Ln, Sr) MnO ₃ ), lanthanum strontium ferrite cobaltite (LSCF: (Ln, Sr, Fe) CoO ₃ ) Metal oxide conductors such as lanthanum nickel ferrite (LNF: La (Ni, Fe) O ₃ ) are fired and provided, but these metal oxide conductors are subjected to high temperature and low oxygen partial pressure. Since the performance of the fuel cell as the air electrode 11 is impaired, the temperature between the cell 10 and the cell frame 30 or between the cell 10 and the separator 20 is increased in the atmosphere when the brazing material is used for joining. Need to be done only by

  In the present embodiment, as a brazing material for joining the outer peripheral portion 12a of the electrolyte 12 to the cell frame 30 or the separator 20, Ag is a main component, and further becomes an oxide after joining and may be reduced again. A material containing at least one kind of non-metal or metal oxide is deposited on the outer peripheral portion 12a of the electrolyte 12, or on the outer peripheral portion of the cell frame 30 or the separator 20, and the outer peripheral portion 12a of the electrolyte 12 and the cell frame 30 or the separator 20 is joined in the atmosphere.

  In other words, by raising the temperature in the atmosphere to a temperature equal to or higher than the melting point of silver, which is the main component of the brazing material, the silver dissolves without being oxidized and becomes a metal that becomes an oxide after joining contained in the brazing material. Alternatively, the metal oxide is deposited as an oxide on the surface of the electrolyte 12 and the surface oxide of the cell frame 30 or the separator 20 on the metal side. Using the oxide as an anchor, the main component silver is solidified to form a good metal-ceramic bond, and in turn, a seal structure showing good sealing performance is formed.

  In the case of a seal structure formed by joining the cell 10 and the cell frame 30, it is further combined with a separator 20 having a function of supplying and discharging fuel gas and oxidant gas at a portion of the metal cell frame 30. Thus, a single cell structure is produced. The single cell structure in which the cells 10 and the separators 20 are joined and combined is combined with other single cell structures as necessary, and a solid oxide in which a plurality of cells 10 are electrically connected. The fuel cell stack 100 is formed. At this time, once a seal structure is formed by joining the outer peripheral portion 12a of the electrolyte 12 and the cell frame 30, the remaining seal required portions in the solid oxide fuel cell stack 100 (for example, integral with the cell 10). Since the cell frame 30 and the separator 20 that have been converted into a seal (such as a seal portion) serve as a joint (seal) between metal parts, it is technically easy.

  Each cell 10 constituting the seal structure, that is, the solid oxide fuel cell stack 100 formed here, is exposed to a high temperature oxidizing atmosphere on one side and a high temperature reducing atmosphere on the other side in a power generation state. Therefore, the metal or metal oxide that is contained in the brazing material and becomes an oxide after bonding is an element that is not reduced by the fuel for power generation, that is, in the oxygen partial pressure, temperature, or atmosphere that is the operating condition of the fuel cell. Must be selected from elements that are not easily re-reduced. Therefore, Cu and Ni are not suitable as metals to be included in the brazing material.

  Examples of the metal that is contained in such a brazing material and becomes an oxide after bonding include metal materials such as Ti, Al, Cr, Mg, TiAl alloy, TiNi alloy, TiCr alloy, and NiCr alloy.

The metal oxide comprising an oxide after _{bonding, SiO} 2, Ti _{oxide, V 2 O 5, MgO,} Al 2 O 3, Cr 2 O 3, Mn _{oxide, CaO, ZnO, Y 2 O} 3 , BaO and the like.

  In the above description, the cell frame 30 and the outer peripheral portion 12a surface of the electrolyte 12 of the cell 10 have been discussed. However, the cell frame 30 is originally formed of the same metal material as the separator 20. Therefore, the cell frame 30 and the separator 20 can be formed integrally.

  Further, in constructing the cell 10-cell frame 30 junction structure or the cell 10-separator 20 junction structure described above, in this embodiment, a bending structure 30a that can prevent an excessive stress from being applied to the junction. Therefore, instead of the brazing material, it is also possible to constitute by sealing with glass that softens and melts at a temperature higher than the operating temperature of the fuel cell.

  Below, the specific example of the seal structure at the time of using the cell frame 30 of embodiment mentioned above is demonstrated. However, the present invention is not particularly limited to the present embodiment, and the same effect can be obtained if formed using the materials described above.

  The cell frame 30 uses the same ferritic stainless steel as the separator 20, such as ZMG232 (manufactured by Hitachi Metals, Ltd.). Use of alumina former stainless steel containing Al in the material of the cell frame 30 is preferable because it is excellent in oxidation resistance, and alumina forms a stronger bond when bonded by brazing. is there.

  The thickness of the plate material forming the cell frame 30 is superior in terms of reducing thermal stress, but if it is too thin, problems such as tearing or tearing or being easily brittle due to corrosion occur. . On the other hand, if it is too thick, thermal stress cannot be relaxed even if the bending structure 30a is formed on the outer periphery. Eventually, the thickness is selected from a thickness of about 10 microns (μm) to about 500 microns, but in reality, it is preferable to use a material having a thickness of about 100 to 200 microns.

  As for specific bonding, for example, when the cell 10-cell frame 30 structure as shown in FIGS. 2 and 3 is formed, Ag is the main component, and TiAl alloy and Cr are each 1 wt%. Using a brazing material added to the extent, the cell frame 30 and the outer peripheral portion 12a of the electrolyte 12 of the cell 10 may be heated to 970 ° C. in the atmosphere and joined to produce a seal structure. .

  Bonds made using brazing materials such as these are strong against thermal stresses caused by thermal cycling, etc., and have good sealing performance even when exposed to both redox atmospheres, such as power generation conditions. Can be maintained.

  Once a sealing structure such as the cell 10-cell frame 30 structure is manufactured, the solid oxide fuel cell stack 100 as shown in FIG. 1 is combined with the separator 20 and other stack components. It is not difficult to build.

Also, good sealing characteristics can be realized by using sealing with a glass material instead of brazing. For example, by performing glass sealing in the atmosphere at 970 ° C. using glass powder in which BaO, CaO, and SrO are contained in SiO ₂ having a softening point near 890 ° C., about 10 Wt% each, The 10-cell frame 30 structure was fabricated, and then the solid oxide fuel cell stack 100 was fabricated in combination with the separator 20 and other stack components, and the characteristics were evaluated. At an operating temperature of 800 ° C. As a result, a sealing structure showing good sealing properties was obtained.

  In addition, although this embodiment demonstrated the application to a circular fuel electrode support type solid oxide fuel cell, not only the form shown here but the solid oxide fuel cell of various shapes and configurations, The same applies to a solid oxide fuel cell stack.

It is an exploded view showing an example of a stack structure of a solid oxide fuel cell stack according to the present invention. It is explanatory drawing for demonstrating the junction part of the cell and cell frame which comprise the solid oxide fuel cell stack shown in FIG. It is sectional drawing which shows the structure of the cell which comprises the solid oxide fuel cell stack shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Cell, 11 ... Air electrode, 12 ... Electrolyte, 12a ... Outer peripheral part, 13 ... Fuel electrode, 20 ... Separator, 30 ... Cell frame, 30a ... Bending structure, 100 ... Solid oxide fuel cell stack.

Claims (10)

  In the solid oxide fuel cell stack in which a plurality of flat plate solid oxide fuel cells each having an oxide electrolyte sandwiched between an air electrode and a fuel electrode are connected via a metal separator, A metal cell frame for connecting the solid oxide fuel cell and the separator is further provided, and contacts the outer periphery of the electrolyte when the cell frame and the solid oxide fuel cell are joined. A solid oxide fuel cell stack, wherein a bent structure extending along the outer periphery of the solid oxide fuel cell is provided on the outer periphery of the cell frame.   2. The solid oxide fuel cell stack according to claim 1, wherein the cell frame is made of either ferritic stainless steel or a nickel-based heat-resistant alloy.   In the solid oxide fuel cell stack in which a plurality of flat plate solid oxide fuel cells each having an oxide electrolyte sandwiched between an air electrode and a fuel electrode are connected via a metal separator, A bending structure along the outer periphery of the solid oxide fuel cell extends to the outer peripheral portion of the separator that contacts the outer peripheral portion of the electrolyte when the separator and the solid oxide fuel cell are joined. A solid oxide fuel cell stack characterized by being provided.   4. The solid oxide fuel cell stack according to claim 1, wherein the bent structure provided to extend on an outer peripheral portion of the cell frame or the separator includes the solid oxide fuel cell. A crank that, when joined, falls from the electrolyte to the side of the fuel electrode along the outer periphery of the solid oxide fuel cell, and then bends in an L shape outward from the position of the side of the fuel electrode. A solid oxide fuel cell stack characterized by having a shape.   5. The solid oxide fuel cell stack according to claim 1, wherein the separator is made of either ferritic stainless steel or a nickel-based heat-resistant alloy. Battery stack.   The solid oxide fuel cell stack according to any one of claims 1 to 5, wherein the solid oxide fuel cell and the cell frame are joined together, or the solid oxide fuel cell and the cell frame. A solid oxide fuel cell stack, characterized in that joining between the separators is performed by brazing between ceramics and metal.   7. The solid oxide fuel cell stack according to claim 6, wherein the brazing material used for brazing contains at least one metal or metal oxide that is mainly composed of Ag and becomes an oxide that is not re-reduced after joining. A solid oxide fuel cell stack.   The solid oxide fuel cell stack according to claim 7, wherein the metal contained in the brazing material and becomes an oxide after bonding is Ti, Al, Cr, Mg, TiAl alloy, TiNi alloy, TiCr alloy, A solid oxide fuel cell stack comprising a material containing at least one of NiCr alloys. In the solid oxide fuel cell stack according to claim 7, is contained in the brazing material, a metal oxide comprising an oxide after bonding, _SiO 2, Ti _{oxide, V 2 O 5, MgO,} Al 2 O _3. A solid oxide fuel cell stack comprising a material containing at least one of ₃ , Cr ₂ O ₃ , Mn oxide, CaO, ZnO, Y ₂ O ₃ , and BaO.   The solid oxide fuel cell stack according to any one of claims 1 to 5, wherein the solid oxide fuel cell and the cell frame are joined together, or the solid oxide fuel cell and the cell frame. A solid oxide fuel cell stack, wherein bonding between the separator and the separator is performed by sealing glass.

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