JPH0945356A - Stack structure of plate type solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a structure, and enhance reliability by mutually arranging plate-like unit cells where the same electrodes Are opposed and connected to each other at constant intervals inside a cell holder. SOLUTION: Plural unit cells 20 are held in a cell holder 24 by maintaining its peripheral part in an airtight condition while opposing mutual air electrodes 22 and mutual fuel electrodes 23 to each other. An (air) manifold 27 communicated with an air passage 29 between the air electrodes 22 and a fuel gas manifold communicated with a fuel gass passage 30 between the fuel electrodes 23 are isolatedly formed in an outer peripheral part of the cell holder 24 in a mutually airtight condition, and conductive members 31 and 33 to electrically continue these with each other are also arranged between the mutually opposing air electrodes 22 and between the fuel electrodes 23, and current collecting bodies 32 electrically continuing with the conductive members 31 and 33 are arranged inside the respective manifolds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolyte type fuel cell, and more particularly to a separatorless type fuel cell stack structure in which flat type single cells are stacked.

[0002]

2. Description of the Related Art A solid oxide fuel cell is a perovskite-type lanthanum-based fuel cell on both sides of which a thin-film solid electrolyte made of yttria-stabilized zirconia (YSZ) or calcia-stabilized zirconia (CSZ) having oxygen ion permeability is sandwiched. A porous air electrode made of a composite oxide (LaMnOx) or the like and a porous fuel electrode mainly made of nickel (Ni) or the like are formed. In this type of fuel cell, the solid electrolyte is heated to about 1000 ° C., which has excellent oxygen ion permeability, a fuel gas such as hydrogen (H ₂ ) gas is circulated to the fuel electrode side, and oxygen (O 2 Oxidizing gas containing O ₂ ) gas is circulated, and these gases react electrochemically through the solid electrolyte to extract electromotive force through each electrode. Since the electromotive force obtained by a single unit (single cell) of such a solid oxide fuel cell is small, it is common to use a plurality of single cells connected in series and parallel.

An example of a conventional stack structure is shown in FIG. 5. The single cell 1 used here is a YSZ or CS.
LaMnO is formed on both sides of the flat solid electrolyte 2 made of Z.
An air electrode 3 made of x or the like and a fuel electrode 4 mainly composed of Ni are formed, and each is formed in a rectangular or square flat plate shape as a whole. These unit cells 1 are stacked with a separator 5 sandwiched therebetween, and are housed inside a cell holder 6. This cell holder 6 is provided with holding portions 7 at regular intervals, and the unit cells 1 stacked as described above are
Each of the separator 5 and the separator 5 is held in a hermetically sealed state at the peripheral portion thereof by the holding member 7 with a sealing material 8 interposed therebetween.

The separator 5 is provided with a current collector 10 for air electrodes and a current collector 11 for fuel electrodes on both sides of a conductive plate 9, and the current collector 10 for air electrodes is adjacent to the unit cell 1. The air electrode 3 is electrically connected, and the fuel electrode current collector 11 is electrically connected to the fuel electrode 4 of the adjacent single cell 1. Since the current collectors 10 and 11 are for electrically connecting the air electrode 3 and the fuel electrode 4, they are made of a material having a high conductivity, and are stable in an oxidizing atmosphere or a reducing atmosphere. It is composed of high-quality materials. For example, the air electrode current collector 10 is formed of LaMnOx described above, and the fuel electrode side current collector 11 is formed of Ni or Ni / YSZ cermet. The conductive plate 9 is used as the collector 1
It is made of a material whose difference in thermal expansion coefficient between 0 and 11 is small.

Further, each of the current collectors 10 and 11 is formed in a thin plate shape, and is arranged in a state in which the electrodes 3 and 4 are spaced at a constant distance in the surface direction. Therefore, a space is formed on the surface side of each of the electrodes 3 and 4, the space on the surface side of the air electrode 3 serves as the air flow path 12, and the space on the surface side of the fuel electrode 4 is the fuel gas flow. It is designated as road 13. The cell holder 6 is formed with openings communicating with the flow paths 12 and 13.

Further, a terminal 16 is connected to the surface side of the uppermost air electrode 3 in the drawing via a current collector 14 and a current collector plate 15 having the same structure as the air electrode current collector 10 described above. A terminal 17 is connected to the lowermost fuel electrode via a collector and a collector plate (not shown) similar to the collector 11 for the fuel electrode described above.

Therefore, in the above conventional stack structure, the temperature of the unit cell 1 is raised to about 1000 ° C., which is excellent in the oxygen ion permeability of the solid electrolyte 2, and air is circulated in the air flow passage 12 in that state. When, for example, H ₂ gas is circulated in the fuel gas flow path 13, an electrochemical reaction between oxygen and hydrogen occurs through the solid electrolyte 2 of each unit cell 1, and the electromotive force at that time causes the electromotive force of each of the terminals 16 and 19. It is taken out via. In that case, in each unit cell 1, the air electrode 3 serves as an anode and the fuel electrode 4 serves as a cathode, so that the unit cells 1 are connected in series.

[0008]

As described above, in the conventional stack structure, each unit cell 1 is electrically connected through the separator 5, but the separator 5
The air electrode current collector 10 contains chromium (Cr) in order to ensure thermal compatibility. As a result, due to the diffusion of Cr in a high temperature state, the electrodes 3 and 4 and the solid state. The characteristics of the electrolyte 2 are gradually deteriorated, and the service life as a whole is shortened. Further, since it is necessary to sandwich the separator 5 between each unit cell 1, the structure as a whole becomes large and the cost becomes high.

Further, since the separator 5 also has a function of isolating the upper and lower air flow passages 12 and 13 in the figure, it is necessary to seal the peripheral portion in an airtight state.
Therefore, in addition to the sealing of the peripheral portion of each unit cell 1, there are many places to be sealed in an airtight state, which may cause an increase in cost and a decrease in reliability. Further, in the above-mentioned conventional structure, since the single cells 1 are connected in series, if any one of the single cells 1 becomes abnormal, conduction failure occurs at that portion, and as a result, the power generation capability of the entire stack is impaired. There was an inconvenience.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a stack structure of a flat plate type fixed electrolyte fuel cell having a simple structure and excellent reliability.

[0011]

In order to achieve the above-mentioned object, the present invention laminates a plurality of flat plate-shaped single cells in which an air electrode and a fuel electrode are formed with a flat plate-shaped solid electrolyte sandwiched therebetween, and each of them is laminated. In the stack structure of the flat plate solid oxide fuel cell in which the electrodes are electrically connected, the adjacent single cells are arranged so that the air electrodes or the fuel electrodes face each other with a predetermined gap. In addition, those single cells are held in the cell holder while maintaining an airtight state in the peripheral portion thereof, the outer periphery of the cell holder, an air manifold communicated with the space between the air electrodes, A fuel gas manifold that communicates with the space between the fuel electrodes is formed so as to be airtightly isolated from each other, and the air electrodes that face each other are provided between the air electrodes. A conductive member electrically connecting the air electrodes to each other is interposed, and a conductive member electrically connecting the fuel electrodes to each other is interposed between the fuel electrodes facing each other. A current collector, in which a conductive member between air electrodes is connected, is housed inside the manifold, and inside the fuel gas manifold,
It is characterized in that a current collector, to which a conductive member is connected between the fuel electrodes, is housed.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to FIGS.
This will be described more specifically with reference to FIG. The unit cell 20 used in the present invention has a flat plate-like solid electrolyte 2 as in the conventional case.
Air electrodes 22 made of LaMnOx, etc. on both sides of 1.
And a fuel electrode 23 formed mainly of Ni, and configured as a rectangular or square flat plate as a whole. These unit cells 20 are arranged inside the cell holder 24 with the air electrodes 22 and the fuel electrodes 23 facing each other.

The cell holder 24 has therein rectangular or rectangular frame-shaped holding portions 25 arranged at regular intervals, in which the single cells 20 are arranged and the outer peripheral portion thereof is arranged. By filling the sealant 26 with the sealing material 26, the airtightness between the upper and lower spaces of each unit cell 20 in FIGS. 1 and 2 is maintained. Also, as shown in FIG.
On the outer peripheral side of the holding portion 25 of the cell holder 24,
The manifold 27 in the vertical direction of FIGS. 1 and 2,
28 are formed. That is, the air manifolds 27 are formed vertically on the left and right sides in FIG. 1, and the fuel gas manifolds 28 are formed vertically on the right and left sides at positions orthogonal to the air manifolds 27. . The air manifold 27 and the fuel gas manifold 28 are airtightly isolated from each other.

As described above, among the space portions between the unit cells 20 held at regular intervals, the space portions where the air electrodes 22 face each other are the air passages 29. The holding portion 2 defining the air flow path 29
5 is open on the side of the air manifold 27, and therefore each of the air flow paths 29 is formed in the air manifold 27.
Is in communication with. Further, a space portion where the fuel electrodes 22 face each other is a fuel gas flow passage 30, and a portion of the holding portion 25 that defines the fuel gas flow passage 30 on the fuel gas manifold 28 side is a portion. It is open and therefore each fuel gas channel 30 communicates with the fuel gas manifold 28.

Further, inside the air flow path 29, a plurality of conductive members 31 are arranged along the direction in which the air manifolds 27 on both sides thereof are connected. These conductive members 31
Is for electrically connecting the air electrodes 22 that are opposed to each other with the air electrode 22 sandwiched therebetween, and is sandwiched in close contact with the air electrodes 22.
They are arranged at intervals so as to secure a flow path for allowing air to flow between them. An anode current collector 32 electrically connecting these air electrode conductive members 31 is arranged inside the air manifold 27. Since the air electrode conductive member 31 and the anode current collector 32 are placed in a high temperature oxidizing atmosphere, for example, the air electrode 22 is used.
It is made of the same material as (MnOx, etc.).

Similarly, a plurality of conductive members 33 are arranged inside the fuel gas passage 30 along the direction in which the fuel gas manifolds 28 on both sides thereof are connected. This fuel electrode conductive member 33 has, for example, a structure in which a Ni felt 35 is wound around the outer periphery of a Ni rod 34 in order to ensure stability in a high-temperature reducing atmosphere, and is sandwiched in close contact with the fuel electrode 23. This electrically connects the fuel electrode 23. A cathode current collector 36 electrically connecting the Ni rod 34 is arranged inside the fuel gas manifold 28. Since the cathode current collector 36 is also placed in a high-temperature reducing atmosphere, it is made of the same material as the fuel electrode 23, that is, Ni or a cermet of Ni and YSZ.

Therefore, the unit cells 20 in the above fuel cell stack are connected in parallel with each other, and the state thereof is schematically shown in FIG.

Next, the operation of the above fuel cell stack will be described. Single cell 20 in the stack described above
Has a solid electrolyte 21 made of YSZ or CSZ, and therefore has a high oxygen ion permeability of about 100.
Heat to 0 ° C. and heat up. In this state, air is supplied from one air manifold 27 and exhausted from the other air manifold 27, so that air is circulated in each air flow path 29. Further, by supplying H ₂ gas from one fuel gas manifold 28 and exhausting it from the other fuel gas manifold 28, each fuel gas passage 30
H ₂ gas is passed through.

Air electrode 2 facing each air flow path 29
Since 2 has a porous structure, the air flowing in the air flow path 29 permeates the inside of the air electrode 22 and diffuses to the surface of the solid electrolyte 21. In addition, H flowing in the fuel gas passage 30
_{The 2} gas permeates the fuel electrode 23 having a porous structure and diffuses on the surface of the solid electrolyte 21. As a result, oxygen is ionized on the air electrode 22 side due to the difference in oxygen concentration on both sides of the solid electrolyte 21, and the oxygen ions are
Permeate to the fuel electrode 23 side, and H ₂ on the fuel electrode 23 side.
Reacts with and emits an electron.

The electromotive force generated by the electrochemical reaction between oxygen and hydrogen generated in this way is
It is taken out to the outside through 32 and the current collectors 32 and 36. In that case, since the single cells 20 are connected in parallel, the voltage is low and the current is high. Moreover, each single cell 20
Since the electric power is individually taken out of the stack, even if an abnormality such as a breakage occurs in any of the unit cells 20, the power generation capacity of the entire stack is not significantly affected.

Further, the above-mentioned conductive members 31 and 33 and current collectors 32 and 36 are placed in a single environment such as an oxidizing atmosphere or a reducing atmosphere, and only contact members of the same material type. , While there is almost no change in characteristics over time,
There is no risk of damage due to thermal stress. Since the sealing for ensuring the airtight state only needs to be performed on the single cell 20, the sealing portion is reduced, and therefore the fuel cell stack can be made inexpensive and highly reliable.

[0022]

As described above, according to the stack structure of the present invention, only flat plate-shaped single cells are placed inside the cell holder.
Since the structure is such that the same electrodes are arranged facing each other and connected at regular intervals, the conventional separator and similar members are unnecessary, and as a result, the number of components is reduced and the size is reduced. The weight can be reduced and the cost can be reduced. Further, since there is no member exposed to both the oxidizing atmosphere and the reducing atmosphere, it is possible to prevent the life from being shortened due to the change in characteristics, and further it is possible to improve reliability by reducing the sealing portion. Further, in the stack structure of the present invention, since the single cells are connected in parallel, it is possible to prevent power generation failure due to an abnormality such as breakage of any one single cell.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an example embodying the present invention.

FIG. 2 is a vertical sectional view cut at a position rotated by 90 degrees.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a diagram showing an electrical connection state of each unit cell.

FIG. 5 is a sectional view showing an outline of a stack structure of a conventional flat plate solid oxide fuel cell.

[Explanation of symbols]

20 ... Single cell, 21 ... Solid electrolyte, 22 ... Air electrode, 23 ... Fuel electrode, 24 ... Cell holder, 25 ...
Holding part, 27, 28 ... Manifold, 29 ... Air flow path, 30 ... Fuel gas flow path, 31, 33 ... Conductive member,
32, 36 ... Current collector.

Front page continued (72) Inventor Riki Iwasawa 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Satoru Yamaoka 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Ltd.

Claims (1)

[Claims] 1. A stack of a flat-plate solid electrolyte fuel cell in which a plurality of flat-plate single cells each having an air electrode and a fuel electrode formed by sandwiching a flat-plate solid electrolyte are stacked and each electrode is electrically connected. In the structure, the unit cells that are stacked adjacent to each other are arranged so that the air electrodes or the fuel electrodes face each other with a predetermined gap, and the unit cells maintain an airtight state in the peripheral portion. Then, an air manifold connected to the space between the air electrodes and a fuel gas manifold connected to the space between the fuel electrodes are provided on the outer periphery of the cell holder. , Electrically conductive members that are formed to be airtightly isolated from each other and that electrically connect the air electrodes to each other between the air electrodes facing each other. A conductive member for electrically connecting the fuel electrodes to each other is interposed between the fuel electrodes facing each other, and a current collector in which a conductive member between the air electrodes is connected inside the air manifold. And a current collector in which a conductive member between the fuel electrodes is connected is housed inside the fuel gas manifold, and a stack structure of a flat plate solid oxide fuel cell.