JP2005216643A - Solid electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolyte fuel cell having a module structure excellent in durability against thermal cycles. <P>SOLUTION: The fitting 11 having a flat plate portion 13 is bent in a thermal resistant substrate 10b and takes out electric current in horizontal direction. The surroundings of the fitting are not fitted closely to the thermal resistant substrate 10b and a gap 20 is formed. A fuel gas 60 circulated so as to be turned back in the module 30 is filled in this gap 20 and constructed so as to become a reducing atmosphere, and works to prevent oxidation and corrosion of the fitting 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a solid oxide fuel cell, and more particularly to a flat plate type solid oxide fuel cell having a laminated structure excellent in durability against thermal cycling.

Solid Oxide Fuel Cell [Solid Oxide Fuel Cell
Also known as “Cell”], a flat-plate-type solid oxide fuel cell is known (for example, Patent Document 1). In this case, a single cell, which is the minimum unit of a battery, is unitized by a current collector and a gas separator, and a plurality of units are stacked in a state where they can be electrically connected to form a module.

  The fuel gas and the oxidant gas are supplied to the module at one introduction part, and the gas flow of each single cell is sequentially returned to each unit by turning back the gas flow at the end of each single cell. Gas is circulated through the road, and the fuel gas and the oxidant gas are each discharged from one discharge portion. As a mechanism for taking out the current generated in the module, for example, a metal plate is joined up and down so as to sandwich the module, and connected to an external circuit via the metal plate.

JP-A-9-129251

  As described above, in the conventional flat solid electrolyte fuel cell, the current is taken out by joining the metal plates. However, the solid oxide fuel cell is operated at a high temperature of about 1000 ° C. Therefore, the use of a metal material in an oxygen atmosphere should be avoided as much as possible.

  Moreover, in the solid oxide fuel cell module, the single cell (solid electrolyte membrane, fuel side electrode and oxygen side electrode), current collector, gas separator, etc., which are the main constituent members, are all made of a ceramic material. Yes. Since these ceramic materials and the metal plate for taking out current have different physical properties, the battery performance deteriorates when a large change in the thermal state is repeated (thermal cycle) such as when the fuel cell is started or stopped. May cause problems. Specifically, since the thermal expansion coefficient is different between the ceramic and the metal plate, when the temperature is changed, the amount of thermal elongation is different, and a stress is generated between the two. When this stress changes the joining state of the module constituent members, there is a problem in that the electrical conductivity between the conductive materials and the gas sealing property are affected, causing deterioration due to thermal cycling.

  In order to avoid the above problems, it is necessary to use a metal member for the solid oxide fuel cell module. However, since current extraction from the module is indispensable, a choice that no metal material is used is used. Is not realistic.

  Accordingly, an object of the present invention is to provide a solid oxide fuel cell having a module structure that prevents thermal cycle deterioration and has excellent durability.

  In the first aspect of the present invention, the unit unit is configured to include a single cell in which a fuel-side electrode and an oxygen-side electrode are arranged via a solid electrolyte membrane, a current collector, and a gas separator. A solid oxide fuel cell in which a plurality of unit units are stacked so as to be electrically connectable to form a module, wherein a pair of heat-resistant substrates incorporating a conduction portion are stacked from the outside of the module. It is a solid oxide fuel cell.

  According to the solid oxide fuel cell of the first aspect, by adopting a heat-resistant substrate incorporating a conducting portion, the difference in coefficient of thermal expansion from the component members of the module is reduced or eliminated, and the heat cycle is reduced. Durability can be greatly improved. The function of taking out current from the module is ensured by the conduction part.

  According to a second aspect of the present invention, in the first aspect, the conductive portion has a contact surface that is exposed from the heat-resistant substrate in a small area as compared with the area of the unit cell of the module and contacts the module. It is a solid oxide fuel cell characterized by having.

  According to this second aspect, by making the contact surface of the conducting portion that becomes the contact surface with the module or the like smaller than the area of the unit cell, for example, during the thermal cycle of metal and ceramics The stress due to the difference in thermal expansion coefficient can be kept small, and the durability against thermal cycling can be enhanced.

  According to a third aspect of the present invention, there is provided the solid oxide fuel cell according to the first or second aspect, wherein the conducting part is provided with a gap between the conductive part and the heat resistant substrate. .

  In the third aspect, since the gap is provided between the conductive portion and the heat resistant substrate, even if the thermal expansion coefficients of the two members are different, the gap becomes play and the generation of local stress can be avoided. .

  According to a fourth aspect of the present invention, there is provided the solid oxide fuel cell according to the third aspect, wherein the gap is maintained in a fuel gas atmosphere.

  In the fourth aspect, a fuel gas such as hydrogen is present between the conducting portion and the heat resistant substrate (gap). As a result, it becomes possible to place the periphery of the conducting part in a reducing atmosphere, and even when the operation is performed at a high temperature, it is possible to avoid oxidation, corrosion, or the like of the metal constituting the conducting part.

  According to a fifth aspect of the present invention, in the fourth aspect, the conducting portion is disposed in a state where the fuel gas in the gap is sealed by a gas seal portion disposed outside the heat resistant substrate. This is a solid oxide fuel cell.

  In the fifth aspect, by providing the gas seal portion, the fuel gas atmosphere in the gap can be maintained, and the effect of the fourth aspect can be ensured. Further, by arranging the gas seal portion outside the apparatus (outside the heat-resistant substrate), the heat change in this portion can be reduced, so that the durability of the gas seal can be sufficiently ensured.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, a current-carrying promoting member is disposed between the heat resistant substrate and the module. It is.

  According to the sixth aspect, by providing the energization promoting member, it is possible to promptly take out current from the module to the conducting portion, and sufficiently draw out the high-power battery performance by the module structure.

  A seventh aspect of the present invention is the solid oxide fuel cell according to the sixth aspect, wherein the energization promoting member is made of a conductive ceramic plate and a conductive buffer material.

  In the seventh aspect, the conductive ceramic and the conductive cushioning material can ensure the energization between the module and the conductive portion, and can provide adhesion and cushioning properties.

  According to an eighth aspect of the present invention, in any one of the first to seventh aspects, a gas supply part or a gas discharge part for supplying or discharging a gas is formed on the heat resistant substrate. It is a solid oxide fuel cell.

  In the eighth aspect, it is possible to provide a function as a gas communication path by providing the heat-resistant substrate with the gas supply unit or the gas discharge unit.

  According to the present invention, in a solid oxide fuel cell having a module structure, it is possible to prevent thermal cycle deterioration and improve durability.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an outline of a solid oxide fuel cell 100 according to a first embodiment of the present invention. In this solid oxide fuel cell 100, a unit 31 composed of a fuel-side current collector 301, a cell 305, an oxygen-side current collector 306, and a gas separator 307 is laminated in five stages, and one module 30. By adopting the module structure in this way, a large electrical output can be generated. In FIG. 1, for convenience of explanation, a space is provided between the stacked members.

  The module 30 is sandwiched from above and below by a pair of heat-resistant substrates 10a and 10b to constitute a solid oxide fuel cell 100. The extraction of the current from the module 30 is performed by the metal fittings 11 and 11 as “conduction portions” incorporated in the heat resistant substrates 10a and 10b, respectively. The metal fittings 11 and 11 project outside through the heat-resistant substrates 10a and 10b, and are connected to an external circuit (not shown).

The heat-resistant substrates 10a and 10b are solid, and preferably have a laminated structure in which a plurality of plates are bonded together. The material of the heat resistant substrates 10a and 10b may be any material that has heat resistance and a thermal expansion coefficient that is similar to each member (mainly ceramics) constituting the module 30. Preferably, an insulating ceramic material is used. Used. As insulating ceramics having such properties, for example, those having magnesia (MgO) and spinel (MgAl ₂ O ₄ ) as main components can be cited. Here, the mixing ratio of magnesia and spinel is 30:70 to 70:30 (preferably 40:60 to 50:50) in weight ratio, so that the cell 305 and the fuel-side current collector 301 constituting the module are used. In addition, consistency with the coefficient of thermal expansion of a member such as the oxygen-side current collector 306 can be obtained.

  The metal fittings 11, 11 incorporated in the heat-resistant substrates 10 a, 10 b are formed of a metal such as SUS, for example, and include flat plate portions 13, 13. The surfaces of the flat plate portions 13, 13 are “contact surfaces”. As exposed from the heat resistant substrates 10a and 10b. The surfaces of the flat plate portions 13 and 13 are pressed against the module 30 to enable electrical connection. The area of the flat plate portion 13 (the area of the exposed contact surface) is preferably about 10 to 30%, more preferably about 15 to 25% with respect to the area of one side of the flat cell 305. If the area of the flat plate portion 13 is too large, stress at the time of thermal cycling occurs at the contact portion with the module 30 and the problem of deterioration may not be solved. On the contrary, if the area of the flat plate portion 13 is too small, the conductivity is lowered, current extraction becomes insufficient, and the battery performance may be lowered.

  In addition, it is preferable to provide a gap for “play” between the metal fitting 11 and the heat-resistant substrate 10 in consideration of expansion and contraction during a thermal cycle, as will be described later.

  The unit 31a includes a fuel side current collector 301, a cell 305, an oxygen side current collector 306, and a gas separator 307.

  The fuel-side current collector 301 is made of conductive ceramics having a comb-like groove formed on one side (the surface facing the cell 305), and has a structure in which a fuel gas such as hydrogen can flow through the groove. It has become. As the material of the fuel-side current collector 301, for example, porous ceramics made of nickel, yttria-stabilized zirconia (YSZ), nickel, alumina, YSZ, or the like is preferably used.

  Similarly, the oxygen-side current collector 306 is made of conductive ceramics having a comb-like groove formed on one side (the surface facing the cell 305), and an oxidizing gas such as air can be circulated through the groove. It has a structure. As a material of the oxygen-side current collector 306, for example, porous ceramics such as lanthanum-strontium-manganite are preferably used.

The cell 305 is the minimum structural unit of the battery and has a structure in which a flat solid electrolyte membrane 303 is sandwiched between a fuel side electrode 302 and an oxygen side electrode 304. The fuel side electrode 302 is joined to the fuel side current collector 301, and the oxygen side electrode 304 is joined to the oxygen side current collector 306. As a material of the solid electrolyte membrane 303, for example, a material mainly containing YSZ is used. The material of the fuel side electrode 302 can be, for example, nickel-zirconia cermet porous ceramics, and the material of the oxygen side electrode 304 is, for example, lanthanum manganite (LaMnO ₃ ) based porous ceramics. be able to.

The gas separator 307 has a structure in which insulating ceramic plates are stacked (here, three ceramic plates are stacked), and an electron flow path material 308 and a connection portion 309 made of conductive ceramics are partially provided. Has been deployed. As the insulating ceramics constituting the gas separator 307, for example, those containing magnesia (MgO) and spinel (MgAl ₂ O ₄ ) as main components can be cited. Here, the mixing ratio of magnesia and spinel is set to 30:70 to 70:30 (preferably 40:60 to 50:50) by weight, so that the cell 305, the fuel-side current collector 301, the oxygen side Consistency with the coefficient of thermal expansion of a member such as the current collector 306 can be obtained.

As the material of the electron channel material 308, it is preferable to use lanthanum chromite (LaCrO ₃ ) -based conductive ceramics. Further, as the connection portion 309, conductive ceramics of the same material as described above can be used.

  By interposing the gas separator 307, the electronic flow path material 308 and the connection portion 309 enable electrical connection between the units while blocking the redox property between the units 31.

  Similarly to the unit 31a, the units 31b to 31e also have a structure in which a fuel-side current collector 301, a cell 305, an oxygen-side current collector 306, and a gas separator 307 are stacked. Here, five modules 31 a to 31 e are stacked to form one module 30.

  A mass flow controller (not shown) as a flow rate control means is disposed in the flow path upstream of the gas inlet of the module 30 in the gas flow direction. A gas controlled to a predetermined flow rate by the mass flow controller is supplied to the module 30.

  The flow of the fuel gas 60 in the module 30 having the above configuration is, for example, a path indicated by a broken line in FIG. 1, and the flow of the oxidant gas 70 is a path indicated by a solid line in FIG. The gas flow between the units 31 can be carried out, for example, by forming a through hole or the like in a frame portion of a member constituting the unit 31. Since the fuel gas 60 passes through the groove formed in the fuel-side current collector 301, it flows in a direction perpendicular to the paper surface of FIG. Similarly, the oxidant gas 70 passes through the groove formed in the oxygen-side current collector 306, and therefore flows in a direction perpendicular to the paper surface of FIG.

In the solid oxide fuel cell 100 of the present embodiment, a current collector 300 made of conductive ceramics is disposed between the unit 31e and the lower heat resistant substrate 10b. The current collector 300 can be made of the same material as the fuel-side current collector 301. The significance of arranging the current collector 300 is as follows.
In the present embodiment, the upper heat-resistant substrate 10a is in the state where the fuel-side current collector 301 is interposed, but is close to the flow path (broken line) of the fuel gas 60. Since the fuel gas 60 is a reducing gas such as hydrogen, even if the fuel gas 60 leaks beyond the fuel-side current collector 301 to the heat-resistant substrate 10a side, the periphery of the metal fitting 11 becomes a reducing atmosphere and is oxidized. There is little worry about corrosion. On the other hand, the lower heat-resistant substrate 10b is close to the flow path of the oxidant gas 70 although it is blocked by the oxygen-side current collector 306 and the separator 307 of the unit 31e in the case of a normal folded gas flow. It is in a state. For this reason, if the oxidant gas 70 leaks beyond the oxygen-side current collector 306 and the separator 307, the metal fitting 11 incorporated in the lower heat-resistant substrate 10b is oxidized or corroded, and the battery There is a risk of impairing performance. For this reason, in the present embodiment, a current collector 300 is provided separately from the units 31a to 31e, and a return flow path of the fuel gas 60 is added here, so that the periphery of the metal fitting 11 of the lower heat resistant substrate 10b is fueled. A gas atmosphere (reducing atmosphere) is set.

  FIG. 2 is a schematic view showing a main part of a solid oxide fuel cell 200 according to another embodiment (second embodiment) of the present invention. The basic configuration of the cell 305, the unit 31 including the cell 305, and the module 30 including the cell 305 in the solid oxide fuel cell 200 is the same as that of the first embodiment (FIG. 1). The explanation will be focused on 10b. The upper ceramic substrate 10a has a substantially similar configuration.

  The heat resistant substrate 10b is solidly configured and is formed by bonding a plurality of insulating ceramic plates. As the insulating ceramic material, the same material as in the first embodiment (FIG. 1) can be used. The metal fitting 11 incorporated in the heat resistant substrate 10b is formed of a conductive metal such as SUS, and includes a flat plate portion 13. The flat plate portion 13 is exposed from the heat resistant substrate 10 and is pressed against the module 30. And allows electrical connection. In the present embodiment, the metal fitting 11 having the flat plate portion 13 is bent in the heat-resistant substrate 10b, is extended in the lateral direction, and is connected to an external circuit (not shown), and takes out current. It has become. The periphery of the metal fitting 11 is not in close contact with the heat-resistant substrate 10b, and a gap 20 is formed. The air gap 20 is filled with the fuel gas 60 that has circulated in the module 30 so as to form a reducing atmosphere, and acts to prevent oxidation and corrosion of the metal fitting 11 as described above.

  In addition, the gap 20 functions as “play”, and the gap 20 can absorb the expansion / contraction difference between the metal fitting 11 and the heat-resistant substrate 10b during the thermal cycle.

  A seal member 15 is provided and sealed at a portion where the metal fitting 11 protrudes from the heat resistant substrate 10b, and the fuel gas 60 in the gap 20 is prevented from leaking out of the apparatus. Thus, by providing the sealing portion by the seal member 15 outside the apparatus, it is possible to avoid the influence of the thermal change accompanying the thermal cycle and to improve the durability. In addition, the other structure of the metal fitting 11 is the same as that of 1st Embodiment (FIG. 1).

  In FIG. 2, reference numeral 311 denotes nickel felt as a conductive buffer material, and reference numeral 313 denotes a conductive ceramic plate made of the same material as described above. Similarly to the first embodiment (FIG. 1), the area of the flat plate portion 13 of the metal fitting 11 is compared with the area of the member (for example, the cell 305) constituting the module 30 from the viewpoint of suppressing the stress during the thermal cycle. Is set to be small. For this reason, the contact area (area of the current-carrying portion) between the flat plate portion 13 of the metal fitting 11 and the current collector 300 is also reduced. Therefore, if a contact failure occurs in this portion, the energization becomes insufficient, which causes a decrease in battery performance. In the present embodiment, by providing a current-carrying promotion member 315 in which nickel felts 311 and 311 as conductive buffer materials are laminated on both surfaces of the conductive ceramic plate 313, current is received from the entire surface of the module 30 and transmitted to the metal fitting 11. Thus, sufficient current extraction efficiency is secured. In addition, between the current collector 300 and the module 30 (the lowermost separator 307), a nickel felt 311 as a conductive buffer material is provided to further enhance the conductivity.

  The heat-resistant substrate 10b (the same applies to the unillustrated 10a) is formed with flow paths 81 and 83 for gas supply (or discharge). These flow paths 81, 83 communicate with flow paths (not shown here) formed in the frame portions of the members constituting the module 30 to supply the fuel gas 60 or the oxidant gas 70. Discharge. The flow paths 81 and 83 can be produced, for example, by partially cutting out an insulating ceramic plate (part of the laminated structure) constituting the heat resistant substrate 10b, forming a groove, and then performing gas sealing.

  The present invention has been described above with reference to various embodiments. However, the present invention is not limited to the above embodiments, and can be applied to other embodiments within the scope of the invention described in the claims. It is.

  For example, in both the first embodiment (FIG. 1) and the second embodiment (FIG. 2), the current is taken out by one metal fitting 11 on each of the upper and lower sides, but a plurality of metal fittings 11 are provided on one side. It is also possible to deploy. Further, a plurality of contact surfaces (exposed surfaces of the flat plate portion 13) can be formed on one metal fitting 11.

  The present invention can be used as a solid oxide fuel cell in various applications such as industrial generators and cogeneration systems.

It is a schematic diagram which shows the outline | summary of the solid oxide fuel cell 100 of this invention. It is a schematic diagram which shows the principal part of the solid oxide fuel cell 200 of another embodiment of this invention.

Explanation of symbols

10a, 10b Heat-resistant substrate 11 Metal fitting 13 Flat plate portion 15 Seal member 20 Air gap 30 Module 31a, 31b, 31c, 31d, 31e Unit 60 Fuel gas 70 Oxidant gas 100 Solid electrolyte fuel cell 200 Solid electrolyte fuel cell 300 Current collector Body 301 Fuel-side current collector 302 Fuel-side electrode 303 Solid electrolyte membrane 304 Oxygen-side electrode 305 Cell 306 Oxygen-side current collector 307 Separator 308 Electron flow channel material 309 Connection portion 311 Nickel felt 313 Conductive ceramic plate 315 Conduction promoting member

Claims (8)

A unit unit is configured to include a single cell in which a fuel side electrode and an oxygen side electrode are disposed via a solid electrolyte membrane, a current collector, and a gas separator.
A solid oxide fuel cell in which a plurality of unit units are stacked so as to be electrically connected to form a module,
A solid oxide fuel cell characterized in that a pair of heat-resistant substrates incorporating conductive portions are stacked from the outside of the module.   2. The solid electrolyte fuel according to claim 1, wherein the conducting portion has a contact surface that is exposed from the heat-resistant substrate and abuts against the module with an area smaller than an area of a unit cell of the module. battery.   3. The solid oxide fuel cell according to claim 1, wherein the conducting portion is provided with a gap between the conductive portion and the heat resistant substrate.   4. The solid oxide fuel cell according to claim 3, wherein the gap is maintained in a fuel gas atmosphere.   5. The solid electrolyte fuel according to claim 4, wherein the conducting portion is provided in a state where the fuel gas in the gap is sealed by a gas seal portion provided outside the heat resistant substrate. battery.   6. The solid oxide fuel cell according to claim 1, wherein an energization promoting member is disposed between the heat resistant substrate and the module.   7. The solid oxide fuel cell according to claim 6, wherein the energization promoting member is made of a conductive ceramic plate and a conductive buffer material.   8. The solid oxide fuel cell according to claim 1, wherein a gas supply part or a gas discharge part for supplying or discharging a gas is formed on the heat resistant substrate.

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