JPH0697617B2 - Molten carbonate fuel cell - Google Patents

Description

The present invention relates to the structure of a molten carbonate fuel cell.

[Conventional technology]

A conventional molten carbonate fuel cell is shown in FIG. In the figure, (1) and (2) are manifolds for supplying fuel gas and oxidant gas, respectively. FIG. 9 is a perspective view showing a state in which the manifolds (1) and (2) are removed. In the figure, (3) is a separator plate, which separates the fuel gas channel provided facing the fuel electrode (6) and the oxidant gas channel provided facing the oxidant electrode (7). Flow passage plates (4) and (5) are provided in the fuel gas passage and the oxidant gas passage, respectively.
Is provided. Fuel electrode (6) and oxidizer electrode (7)
Are opposed to each other with the electrolyte layer (8) interposed therebetween to form a unit cell. The fuel electrode (6) is formed of, for example, a nickel porous plate, and the oxidant electrode (7) is formed of, for example, a NiO porous body. (9) is a current collector plate that holds the oxidant electrode (7) and allows the generated current to pass therethrough, (10) is an upper end plate, (11) is a lower end plate, and (12) and (13) are separator plates ( The fuel side wet seal portion and the oxidant side wet seal portion, which are provided in 3) and separate and seal the inside and outside of the cell. The molten carbonate fuel cell is a laminate formed by alternately stacking unit cells and separator plates (3), and end plates (10) and (11) are provided at the upper and lower ends. FIG. 10 is a perspective view showing the separator plate (3). For example, the wet seal parts (12) and (13) formed of a metal flat plate are joined to the separator part (3a) of the separator plate (3). . The manifold facing portions (12a) and (13a) are in contact with the manifolds (1) and (2), respectively, and prevent the reaction gas from flowing out of the battery.

Next, the operation of this type of molten carbonate fuel cell will be described. The fuel cell uses the chemical energy of the fuel gas such as hydrogen supplied from the fuel gas supply manifold (1) and the chemical energy of the oxidant gas such as air supplied from the oxidant gas supply manifold (2) to be electrochemically converted. It is a device that obtains electric power by directly converting into electrical energy by a dynamic reaction. In order to efficiently carry out this electrochemical reaction, generally porous electrodes (6) and (7) are used.

The reactions at the fuel electrode (6) and the oxidant electrode (7) are as follows.

The fuel electrode ^{_{H 2 + ▲ CO 2- 3 ▼}} → H 2 O + CO 2 + 2a ... (1) oxidizer electrode _{CO 2 + 1 / 2O 2 +} 2e → ▲ CO 2- 3 ▼ ... (2) In the fuel electrode, equation (1) as in, H ₂ in the fuel gas flowing through the fuel gas passage is reacted with ▲ CO ^2- ₃ ▼ in the electrolyte, water and a C
Generates O ₂ and electrons. After being sent to the external load through the fuel electrode (6), the electrons flow into the oxidant electrode (7). In the oxidant electrode (7), that this generates electrons and CO ₂ and the oxidant gas flow path from O ₂ in the oxidizing gas flowing ▲ CO ^2- ₃ ▼, dissolved in the electrolyte layer (8) Therefore, the battery reaction proceeds.

Since the wet seal parts (12) and (13) of the molten carbonate fuel cell as described above are formed of a metal flat plate and have no flexibility, the thickness design of the electrodes (6) and (7) is unsatisfactory. If appropriate, the electrolyte layer (8), the electrodes (6), (7), etc. may cause poor contact or the reaction gas may leak. Further, even when the electrodes (6) and (7) become thin with the lapse of operating time of the battery, the wet seal parts (12) and (13) arranged at both ends of the electrodes (6) and (7) are Since it does not deform, there is a problem that the internal resistance of the battery increases due to poor contact.

As a molten carbonate fuel cell that solves such problems, a partial perspective view of the one disclosed in USP 4514475 is shown in FIG.
It is shown in FIG. 1 and a perspective view of the separator plate is shown in FIG. In the figure, (14) is a separator plate, and the four corners of the metal plate as shown in FIG. 13 are cut into quadrangles, and the two opposite sides (12b) parallel to the fuel gas flow path are shown on the fuel electrode side as shown by arrows. That is, it is folded back to the front side of the paper surface, and two opposite sides (13b) parallel to the oxidant gas flow path are folded back to the oxidant electrode side, that is, the back side of the paper surface to form the wet seal parts (12) and (13). This is a constitution of the separator plate (14) shown in FIG. Inside the folded sides (12b) and (13b),
A spacer (15) shown in FIG. 14 is arranged to hold the wet seal portion. The wet seal parts (12) and (13) of the molten carbonate fuel cell having such a structure are flexible and can keep good contact with the electrodes (6) and (7) and the electrolyte layer (8). Therefore, the internal resistance of the battery can be prevented from increasing. However, when the manifolds (1) and (2) are attached, the wet seal parts (12) and (13) face the manifolds (12a) and (13a).
It is difficult to cover the entire surface of the manifold with the manifolds (1) and (2). Therefore, the gas sealability is poor,
The gas leaks from the manifold facing portions (12a) and (13a), and the battery characteristics are deteriorated.

[Problems to be solved by the invention]

Since the conventional molten carbonate fuel cell is configured as described above, the wet seal portion is not flexible, and if the thickness design of the electrode is improper, the electrolyte layer, the electrode, or the like may cause poor contact, Reaction gas leaks. Further, when the electrode becomes thin with the lapse of operating time of the battery, the wet seal portion does not follow this deformation, so that there is a problem that the internal resistance of the battery increases due to poor contact.

In addition, in the molten carbonate fuel cell having a structure in which the wet seal portion has flexibility, there is a problem that the gas seal is not perfect and gas leaks from the portion of the wet seal portion facing the manifold, resulting in deterioration of cell characteristics. Atsuta

The present invention has been made to solve the problems of the conventional ones described above, reduces the contact failure of the electrode and the electrolyte, does not increase the internal resistance even when the electrode is thin, and gas sealability It is an object of the present invention to provide a molten carbonate fuel cell having good cell characteristics and high cell characteristics.

[Means for Solving the Problems] In a molten carbonate fuel cell according to the present invention, two opposing sides of a metal plate forming a separator plate, which are parallel to a fuel gas flow path, are on the fuel electrode side, and an oxidizer gas is provided. Two opposite sides parallel to the flow path are folded back to the oxidizer electrode side, and a thin metal plate is bonded to the corner portion side except the folded piece tip end side of the manifold facing portion at both ends of the folded portion formed by this folding, The corner portion side of the manifold facing portion is hermetically sealed and flattened to form a wet seal portion, and the separator plate is formed by laminating separator plates so that the folded pieces of the wet seal portion are in contact with the electrolyte layer.

[Action]

Since the wet seal portion in the present invention is formed by folding back the metal plate, it has flexibility and absorbs the variation in the thickness of the electrode to prevent the contact failure of the electrode or the electrolyte layer. Furthermore, since the cap is joined to the corner side except the tip of the folded piece of the manifold facing portion at both ends of the folded portion to seal the corner side of the manifold facing portion and to make it flat, the folded piece of the manifold facing portion is It can move up and down with the tip of the cap as a fulcrum, absorbs fluctuations in the electrode thickness even in the manifold facing part to prevent contact failure of electrodes and electrolytes, etc. from the manifold facing part of the wet seal part and between the manifold and the wet seal part. Prevent gas from leaking.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, (14) is a separator plate, and (16) is a cap joined to the manifold facing portions (12a) and (13a) of the wet seal portions (12) and (13), respectively. The separator plate (14) is, for example, a nickel-nickel plate having a thickness of 0.1 to 1.0 mm and a stainless steel plate (for example, SUS 316L or SUS 310s), and the nickel plate has a thickness ratio of 1/1/1 in consideration of corrosion resistance.
It is formed of 9 to 1/6. As shown in FIG. 13, the clad plate is folded back to the fuel electrode side, that is, the front side of the paper, with the two opposite sides (12b) parallel to the fuel gas passage, and the oxidizer provided orthogonally to the fuel gas passage. The two sides (13b) parallel to the gas flow path are folded back to the oxidizer electrode side, that is, the back side of the paper, and the folding pieces (12b) and (13b) face the separator plate (14) as shown in FIG. And are formed in parallel. The folded pieces (12b) and (13b) form the wet seal portions (12) and (13), respectively, and the nickel surface faces the fuel gas passage due to corrosion resistance, and
A separator plate (14) is laminated so that the folded back pieces (12b) and (13b) contact the electrolyte layer (8). further,
Flatten the arc-shaped end side, that is, the corner side, except for the tip side of the folded-back pieces (12b) and (13b), on the manifold facing portions (12a) and (13a) of the folded-back section, which are flat and sealed. The cap (16) for joining is joined. The cap (16) has, for example, a shape as shown in FIG. 3, and is formed of a nickel plate having a thickness of about 0.05 to 1 mm and a stainless steel (for example, SUSU 316L or SUS 310s) cladding plate, and as shown in FIG. Manifold facing part (12a),
It is fitted in (13a) and the periphery is welded by plasma arc welding or the like. The cap (16) is configured to seal, for example, the center of the manifold facing portions (12a) and (13a) to the corner portion side, holds the wet seal portions (12) and (13) to some extent, and also the cap (16). Manifold facing part (12)
a), (13a) and the central portions of the wet seal parts (12), (13) have flexibility, and the electrodes (6), (7) can be formed even when the thickness of the electrodes (6), (7) is inappropriate. 7) and electrolyte layer (8)
Prevents poor contact such as. Further, as the operating time of the battery elapses, the thickness of the electrodes (6) and (7) becomes 50 μm to 100 μm.
Even if it is reduced by about μm, the folded pieces (12a) and (13a) are lowered in the central portion to some extent, and the folded pieces (12a) and (13a) from the middle to the free end are halfway at the corners. The point serves as a fulcrum to lower to some extent to prevent contact failure of the electrodes (6) and (7) and the electrolyte layer (8) and leakage of reaction gas. Therefore, increase in internal resistance is prevented. Also, manifold facing parts (12a), (13a)
In the state where the manifolds (1) and (2) are attached, since the corner portions of the wet seal portions (12) and (13) are hermetically sealed, the gas flow passage can be hermetically sealed and the gas sealability is improved. . Manifold facing part (12
Since a) and (13a) are configured flat and have close contact with the mounting surfaces of the manifolds (1) and (2) and no space is created between them, high battery characteristics that prevent gas leakage from this part Can be obtained.

Fig. 4 shows the wet seal part (13) on the top plate (10).
In this case, the cap (16) having the shape shown in FIG. 5 is turned upside down and joined to the manifold facing portion (13a), and the lower end plate (11) is also the same. In the above embodiment, the lower end plate (11) is opposed to the fuel gas flow passage, and the surface of the cap (16) facing the fuel gas flow passage is configured to be a nickel surface due to corrosion resistance. Since the plate (10) faces the oxidant gas flow path, SUS
It may be composed of a thin plate of 316L or SUS 310S. FIG. 6 shows the fuel electrode (6) used in the above-mentioned embodiment, in which the thickness of both end portions (6a) inserted between the folded piece (12b) and the separator plate (14) is changed to the folded piece ( The thickness of 12b) is reduced. In this embodiment, the fuel electrode (6) having such a structure and the flow channel plate (4) forming the fuel gas flow channel are inserted between the folded piece (12b) and the separator plate (14). The fuel electrode (6) and the flow path plate (4)
Acts as a spacer for holding the wet seal part (12) and the surface facing the electrolyte layer (8) becomes flat.
Further, with time, the electrode inserted between the folded piece (12b) on which the cap (16) is not formed and the separator plate (14) and the electrode at the center of the battery deform at the same rate, The portion of the folded piece (12b) that comes into contact with the electrode (6) is not separated from the electrode (6), and the heights of the wet seal portion (12) and the surface of the electrode (6) are always the same. Further, the electrode (6) is held by the folded piece (12b), and it is possible to prevent misalignment. The above is
The same applies to the oxidant side.

The metal plate constituting the separator plate (14) is about 0.1 to 1 mm, and if it is 0.1 mm or less, there is a problem in corrosion resistance, and if it is 1 mm or more, there is a problem in flexibility. Particularly preferably, it is about 0.1 to 0.5 mm. Similarly, the cap (1
The metal plate that constitutes 6) is also 0.05 in terms of corrosion resistance and flexibility.
Approximately 1 mm is used, and in particular approximately 0.1 mm to 0.5 mm is preferable. The material of the separator plate (14) and the cap (16) is either SUS 316L or SUS 310S alone, or nickel and stainless steel (eg SUS 316L or SUS 310S).
Clad boards can be used. However, it is desirable that the one used on the fuel side has a nickel surface because of its corrosion resistance.

FIG. 7 is a perspective view showing a cap (16) according to another embodiment of the present invention, the side surface (16a) of which is formed in a wavy shape. If this cap (16) is used, in addition to the above effects, the flexibility of the corner portions of the wet seal portions (12) and (13) is improved. When the paste is put in the corrugated concave portion to make the manifold facing portion flat, a cap (16) having flexibility and having a flat manifold facing portion can be realized. Further, the method of joining the cap (16) to the manifold facing portion of the folded portion that can be folded back can be realized by electric resistance welding, laser welding, electron beam welding, plasma arc welding, brazing, or the like.

〔The invention's effect〕

As described above, according to the present invention, a single cell having a fuel electrode and an oxidant electrode that face each other with an electrolyte layer interposed therebetween, and a fuel gas flow path that is provided to face the fuel electrode and a fuel that faces the oxidant electrode are provided. A laminated body in which a separator plate having a wet seal portion that separates and seals the inside and outside of the battery is separated from the oxidant gas flow path provided orthogonal to the gas flow path, and a fuel gas flow path and an oxidant gas flow path. In a molten carbonate fuel cell equipped with a manifold for supplying fuel gas and oxidant gas respectively, the wet seal part has two opposite sides parallel to the fuel gas flow path of the metal plate forming the separator plate on the fuel electrode side. , The two opposite sides parallel to the oxidant gas flow path are folded back toward the oxidant electrode side, except for the tip of the folded piece at the opposite end of the manifold formed by this fold. Joining thin metal plate Na side,
It is configured to seal and flatten the corner side of the manifold facing part, and the separator plate is laminated so that the folded piece of the wet seal part is in contact with the electrolyte layer, so when the electrode design is inappropriate or the electrode is Even if it is made thin, it is possible to prevent an increase in internal resistance, improve the gas sealability of the wet seal portion, and provide a molten carbonate fuel cell having high cell characteristics.

[Brief description of drawings]

1 is a perspective view showing a molten carbonate fuel cell according to an embodiment of the present invention, FIG. 2 is a perspective view showing a separator plate according to an embodiment of the present invention, and FIG. 3 is used for FIG. 4 is a perspective view showing an end plate according to an embodiment of the present invention, FIG. 5 is a perspective view showing the cap used in FIG. 4, and FIG. 6 is a perspective view showing the cap used in FIG. FIG. 7 is a perspective view showing an electrode according to an embodiment of the present invention, FIG. 7 is a perspective view showing a cap according to another embodiment of the present invention, and FIG. 8 is a perspective view showing a manifold attached to a general molten carbonate fuel cell. Figure, No. 9
FIG. 10 is a perspective view showing a conventional molten carbonate fuel cell, FIG. 10 is a perspective view showing the separator plate used in FIG. 9, and FIG.
FIG. 12 is a partial perspective view showing a part of another conventional molten carbonate fuel cell, FIG. 12 is a perspective view showing a separator plate used in FIG. 11, and FIG. 13 is used in FIG. FIG. 14 is a plan view showing a metal plate forming a separator plate, and FIG. 14 is a perspective view showing a spacer used in FIG. (1) ... Manifold for supplying fuel gas, (2) ... Manifold for supplying oxidant gas, (4) ... Fuel gas flow path plate,
(5) ... Oxidant gas flow channel plate, (6) ... Fuel electrode, (7)
... oxidant electrode, (8) ... electrolyte layer, (12), (13) ... wet seal part, (12a), (13a) ... manifold facing part, (12b), (13b) ... folded piece, (14) ... Separator plate. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A unit cell having a fuel electrode and an oxidant electrode which face each other with an electrolyte layer interposed therebetween, and a fuel gas channel provided to face the fuel electrode and a fuel gas channel which faces the oxidant electrode and is orthogonal to the fuel gas channel. A laminate for alternately separating separator plates having a wet seal portion for separating and sealing the inside and outside of the battery, and a fuel gas in the fuel gas passage and the oxidizing gas passage, respectively. In a molten carbonate fuel cell equipped with a manifold supplying oxidant gas,
The wet seal portion is formed by folding back two opposite sides of the metal plate constituting the separator plate, which are parallel to the fuel gas flow path, to the fuel electrode side and two opposite sides parallel to the oxidant gas flow path to the oxidant electrode side. , A thin metal plate is joined to the corner portion side except the tip end side of the folded piece of the manifold facing portion at both ends of the folded portion formed by this folding, and the corner portion side of the manifold facing portion is hermetically sealed and flattened. The molten carbonate fuel cell is characterized in that the separator plate is laminated so that the folded piece of the wet seal portion is in contact with the electrolyte layer. 2. The molten carbonate fuel according to claim 1, wherein an electrode and a flow path plate are inserted between the folded piece of the wet seal portion formed by folding back and the separator plate. battery. 3. The molten carbonate fuel cell according to claim 2, wherein the electrode in the portion inserted between the folded piece and the separator plate is thinned by the thickness of the folded piece.