JPH0439868A - Separator for molten carbonate fuel cells - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a separator used in a molten carbonate fuel cell among fuel cells used in the energy sector that directly converts the chemical energy of fuel into electrical energy. It is related to.

[Prior Art] A conventional molten carbonate fuel cell, as shown schematically in FIG. The cathode 2 is sandwiched between both electrodes (oxygen electrode) 2 and anode (fuel electrode) 3, and oxidizing gas OG is supplied to the cathode 2 side, and fuel gas FG is supplied to the anode 3 side.
One cell is a cell in which a reaction is caused between the cathode 2 and the anode 3 side, and electricity is generated by the potential difference generated between the cathode 2 and anode 3, and each cell is laminated in multiple layers with a separator 4 in between. It is set up as a stack.

The separator 4 used in such a molten carbonate fuel cell has a three-layer structure with corrugated plates arranged as channel forming portions on both sides of the center plate 5.
A corrugated plate is used as a current collector 6, and when stacking fuel cells, the cathode 2
and the anode 3 are connected to the electrolyte plate 1 by the current collector 6.
I try to press against it.

Electrolyte plate 1 constituting the cell of the molten carbonate fuel cell
plays the role of separating gases that react on the picture electrode side of the cathode 2 and anode 3, and also plays the role of allowing carbonate ions (Co, = ) generated on the cathode 2 side to pass to the anode 3 side and blocking electrons. When the oxidizing gas OG is supplied to the cathode 2 side, the oxidizing gas flows through the gas passage formed by the corrugated plate as the current collector 6, so that Co2+1/202+ is generated on the cathode 2 side.
The reaction 2e-->CO3- is performed to generate carbonate ions (Co3=), and this CO3- migrates through the electrolyte plate 1 and reaches the anode 3. On the other hand, when fuel gas FG is supplied to the 7 node 3 side, while the fuel gas flows through the gas passage formed by the corrugated plate as the current collector 6, on the anode 3 side, CO3-+)+2-)H20+CO2+2e-, A reaction takes place and hydrogen gas is primarily consumed.

Therefore, in order to achieve the best performance of the fuel cell, the cathode 2,
The contact between each electrode of the anode 3 and the electrolyte plate 1 must be good. The quality of the contact between the electrode and the electrolyte plate 1 is determined by the contact between the corrugated plate as the current collector 6, the cathode 2, and the anode 3 in the case of the configuration example shown in FIG. The full-gate board requires high accuracy with a target of ±25 degrees, but at present it has not reached that level. Therefore, as shown in FIG. 8, the corrugated plate serving as the current collector 6 does not uniformly contact the cathode 2 or the anode 3 partially, and there may be a portion A where the corrugated plate does not contact the cathode 2 or the anode 3 uniformly.

[Problems to be Solved by the Invention] However, as shown in FIG. 8 above, if the contact of the current collector 6 with the electrode is not uniform and there is a portion A where no contact occurs, the cathode 2 or The contact between the anode 3 and the electrolyte plate 1 becomes poor, and between the cathode 2 and the electrolyte plate 1, carbonate ions (Go
, =) becomes difficult to flow into the electrolyte plate 1. In other words, the flow of carbonate ions (C03=) is impeded where the cathode 2 and electrolyte plate 1 are far apart, which not only increases the internal resistance of the battery, but also causes the reaction to proceed vigorously at locations where carbonate ions easily flow. This causes excessive heat generation, leading to the loss of carbonate. Furthermore, if there is poor contact between the anode 3 and the electrolyte plate 1, it becomes difficult for carbonate ions (Co3=) migrating in the electrolyte plate 1 to flow to the anode 2.

In order to eliminate this problem, it is necessary to improve the manufacturing accuracy of the corrugated plate as the current collector 6, the electrodes, and the electrolyte plate, but increasing the accuracy requires difficult manufacturing and inevitably increases costs.

In addition, when a fuel cell is operated at high temperatures for a long period of time, the cathode 2 is damaged due to creep of parts, as shown schematically in FIG.
When the electrode surface of the anode 3 is deformed, areas 8 where the current collector 6, cathode 2, and anode 3 do not touch are generated, and the cathode 2, anode 3, and electrolyte plate 1
However, the conventional current collector 6 is made of a corrugated board, and if you look at the curved part of one peak, as shown in Fig. 10, it has a rigid structure with support at both ends and is not flexible, so it has low elasticity. Even if the contact between the electrode and the electrolyte plate 1 becomes poor due to the deformation caused by the above-mentioned creep, the current collector 6 cannot follow the deformation, and it is difficult to produce a flat product with large distortions, which may occur during manufacturing. Not only can it absorb uneven hits due to dimensional errors, but it also cannot absorb the amount of creep.

Furthermore, since the corrugated plate used as the conventional current collector 6 has a large surface area, the wetted area is large and the loss of carbonate is large.

Therefore, the present invention makes it possible to obtain uniform contact at each part even if the current collector, electrode, and electrolyte plate are not made with high precision, and also easily follows deformation due to creep, thereby making it possible to always obtain good contact. The present invention aims to provide a separator for a molten carbonate fuel cell that can be manufactured more easily.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an electrolyte plate that is sandwiched between both electrodes, a cathode and an anode, to supply oxidizing gas to the cathode side and supply fuel gas to the anode side. In a separator for a molten carbonate fuel cell, which is used as a partition when stacking cells in a multi-layered manner, for forming gas passages between the center plate and the cathode and between the center plate and the anode. The current collectors disposed on both sides of the center plate have a structure in which a large number of rectangular openings are formed in the plate and one pressed piece is bent in each opening with a cantilever support structure, and The aperture ratio is 30% to 6.
0% and the narrower width of the opening is 2Nn~6
The configuration is set to m. Moreover, it is preferable that the tip of the press-cut piece is curved so that the curved part contacts the center plate.

[Function] The aperture ratio of the plate constituting the current collector is 30.
% to 60%, gas is well diffused into the electrode and the electrode is sufficiently supported. In addition, if the narrower dimension of each opening is set to 2#1 to 6M, it is possible to reduce the wear of the press die that forms the opening and bends the pressed piece, and also prevents the support of the electrode from becoming a problem. Not at all. The pressed piece bent toward the center plate is cantilevered and flexible, so even if there are manufacturing errors in the current collector itself, electrodes, or electrolyte plate,
Furthermore, even if creep occurs, the elasticity of the current collector makes it possible for the current collector to uniformly contact the electrode and bring the electrode and electrolyte plate into uniform contact over the entire surface. In addition, the current collector is easy to manufacture because it can be molded in one step using a press. Further, if the tip of the pressed piece serving as the current collector is press-cut so as to be curved, the height of the tip becomes uniform, and the height accuracy can be improved.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of the present invention, in which an electrolyte plate 1 is sandwiched between both electrodes, a cathode 2 and an anode 3, and oxidizing gas OG is supplied to the cathode 2 side, while the anode 3 In a separator for a molten carbonate fuel cell, which is used as a partition plate when stacking cells in multiple layers to supply fuel gas FG to the side thereof, the separator 7 of the present invention includes a center plate 8 and a center plate 8. gas passages are formed between the center plate 8 and the cathode 2 and between the center plate 8 and the anode 3, and between the cathode 2 and the anode 3.
The current collector 9 has a function of supporting the current collector 9, and the oxidizing gas OG on the cathode 2 side and the fuel gas FG on the anode 3 side are separated as a whole.

When the current collector 9 is pressed to form a large number of openings 9b in the plate 9a using a press die 10 having an inclined working surface as shown in FIG. The cut piece 9C is bent to protrude from one side of the plate 9a, and the aperture ratio when forming each of the openings 9b is 30% to 6.
0%, and the narrower width e of the opening is 2 mm to 6 m.

The above-mentioned aperture ratio is set to 30% to 60% because if it is less than 30%, there will be fewer holes and gas distribution and diffusion to the electrode will be poor, and if it is more than 60%, there will be too many holes and the electrode will not be connected to the electrolyte plate. This is because the electrodes may sag if they are not pressed firmly against the electrodes, making it impossible to function as an electrode support plate. Also, the width of the narrower side of the opening 9b is 2#! ! ! The reason why it is set at 1 to 61 Mt is because if it is less than 2 m, the press mold will be severely worn during press forming, and when the mold wears, there will be a problem that burrs will appear on the cut end. This is because if the electrode is more than I11, the electrode will not be supported sufficiently and there will be a problem that the electrode will sag.

When molding the current collector 9 using the press mold 10 as shown in FIG. 4, the plate 9 as shown in FIG.
When the opening 9b of a is pressed with the press die 10, the cut end is torn and a burr 11 is generated. The burr 11 at the tip will be formed on the inside.

In this case, if the burr 11 is formed on the outside of the tip of the pressed piece 9C, the burr 11 comes into contact with the center plate 8, making it impossible to adjust the height of the current collector 9 itself, and the burr 11 deforms. Therefore, height accuracy cannot be achieved, but in the present invention, the burr 11 is formed inside the tip of the press-off piece 9C, so the above problem does not occur.

In the present invention, a large number of press molds 10 as shown in FIG. 4 are set for one plate 9a, and each press mold 10 is
Since the extrusion molding is performed by operating the 0, the formation of a large number of openings 9b and the bending of the extrusion pieces 9C can be performed in the - step, making it possible to easily manufacture the current collector 9.

In the separator 7 of the present invention manufactured as described above, the current collector 9 is cantilevered at each opening 9b and has 7 flexibilities. 9C is set so as to be in contact with the center plate 8, and when it is used as a cell partition plate and a tightening force is applied in the stacking direction, the tip of the press-cut piece 9C of the current collector 9 aligns with the center plate 8. While sliding, it can escape in the direction of the arrow due to its elasticity and can be easily deformed. In addition, when a change occurs in which the gap between the electrode and the center plate 8 widens due to creep of the electrode while the predetermined tightening force is being applied, the center plate 8 at the corresponding location is While sliding along the center plate 8, the tip of the pressing piece 9C that is in contact with it can be elastically deformed so as to move in the direction of arrow C and rise up. Therefore, when there is an error in the dimensional accuracy of the current collector 6, as in the conventional method shown in FIG. Even if the current collector 6 was applied with the clamping force as described above, the bent portion of the current collector 6 had a structure with both sides supported and had high rigidity and low elasticity, so the portion that did not contact the electrode remained as it was. When this is applied, the contact part of the push-cut piece 9C with the center plate 8 can be elastically deformed, so that the contact part with the center plate of the part that is already in contact with the electrode becomes the current collector of the part that is not in contact with the electrode yet. Since the deformation continues until the current collector 9 hits the electrode, even if there is a dimensional error in manufacturing the current collector 9, that error can be absorbed. Even if the manufacturing precision of the electrodes and electrolyte plate 1 is poor, resulting in poor contact between the electrode and electrolyte plate 1, uniform contact can be achieved by elastic deformation of the press-cut pieces 9C of the current collector 9. . In addition, when a fuel cell is operated at high temperatures for a long period of time, for example, the amount of creep in the cathode 2 and anode 3 electrodes increases, and the contact of the current collector 9 with these parts becomes weaker, causing contact between the electrodes and the electrolyte plate. Even if a situation that worsens over time occurs, in the present invention, the push piece 9c of the current collector 9 has a cantilever support structure and has elasticity, so it absorbs the amount of creep and remains connected to the electrode. Uniform contact with the electrolyte plate 1 can be obtained over the entire surface.

Next, FIG. 6 shows another example of the present invention, in which the tip of the press-cut piece 9C is bent so as to be curved, and the curved tip of the press-cut piece 9C is brought into contact with the center plate 8. It was designed so that they were in contact with each other.

According to this example, regardless of the length of the press-cut piece 9C, the curved surface of the tip of the press-cut piece 9C is
Since the cut surface at the tip of the pressed cut piece 9C does not come into contact with the center plate 8, the height accuracy of the current collector 9 can be made good.

In addition, in the above embodiment, the case where the opening 9b is rectangular and the push-cut piece 9c is extended to a part of the wide width is shown.
The molding may be performed using a press mold in which the pressed piece 9C extends to a part of the narrow side, and the extending direction of the pressed piece 9C of each opening 9b is the same direction. Although the case is shown, the extension directions of the push-cut pieces 9C may be arranged to face each other between the adjacent openings 9b.

[Effects of the Invention] As described above, according to the molten carbonate fuel cell separator of the present invention, a large number of openings are formed in the plate using a press die, and one piece is formed for each opening. A current collector having a structure in which a pressed piece is bent to one side to protrude, the aperture ratio of the opening is in the range of 30% to 60%, and the width of the narrower side of each opening is 2IMt to 6Al11, Since it is arranged on both sides of the center plate, the following excellent effects can be achieved.

(1) Increase the aperture ratio of the current collector from 30% to 60
%, the gas can diffuse well into the electrode, and the electrode can be supported sufficiently. Also, since the narrower dimension of the opening is 2#1 to 6#EI11, it can be easily used in press molds. It is possible to reduce wear on the press die when forming the opening, and at the same time prevent the electrode from sagging when supporting the electrode.

(IT) Since one pressed piece is bent into one opening to form a cantilever support structure, the current collector has elasticity, and the manufacturing accuracy of the current collector, electrode, and electrolyte plate is poor. Even if there is an error in dimensional accuracy,
When assembled as a fuel cell and applying a predetermined tightening force, it is possible to absorb the above error and obtain a similar hit, and there is no need to improve the manufacturing precision of the current collector, electrode, and electrolyte plate, making the manufacturing process easier. It is easy and can be manufactured at low cost.

(lli) Even if parts are deformed due to creep during operation, the elasticity of the current collector can follow the deformation and absorb the amount of creep, and the contact between the electrode and the electrolyte plate becomes worse due to creep. The situation can be avoided.

(Translation) A conventional current collector has a rigid structure in which a single curved part of a corrugated board is supported at both ends, but the central part of the single curved part is cut to provide elasticity, resulting in a cantilever support structure. It can also be formed into However, this type of product requires two steps, a pressing process and a cutting process, and when cutting the center part and making it cantilever supported, when the cutter blade becomes hard to cut, the edge of the cut part will move outward. The precision of the current collector deteriorates when the current collector is moved out, but in the present invention, one pressed piece is molded in one opening with cantilever support, so the pressing process using a press mold is sufficient. , it can be manufactured more easily, and even if there is a burr at the cut end, the burr will come out on the inside, so the height accuracy will not be degraded.

(V) Curving the tip of the pressed piece of each opening,
By bringing the outside of the curved portion into contact with the center plate or electrode, the height of the current collector can be made uniform even if the tips of the pressed pieces are uneven, and the height accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a part of a molten carbonate fuel cell using the separator of the present invention, FIG. 2 is a perspective view showing an example of a current collector in the separator of the present invention, and FIG. 3 is the same as that of FIG. Fig. 4 is a schematic diagram of the press mold used for forming the current collector in the separator of the present invention, Fig. 5 is an enlarged view of part ①, and Fig. 5 is a schematic diagram of the press mold used to form the current collector in the separator of the present invention. 6 is a sectional view of a current collector showing an example of the separator of the present invention, FIG. 7 is a partial sectional view showing an example of a conventional molten carbonate fuel cell, and FIG. 8 9 is a cross-sectional view showing a state where the current collector and electrode do not touch each other, FIG. 9 is a schematic diagram showing a state where the electrode is deformed due to creep and there are places where the current collector does not touch, and FIG. 10 is a conventional FIG. 3 is a diagram showing the structure of a current collector. DESCRIPTION OF SYMBOLS 1... Electrolyte plate, 2... Cathode, 3... Anode, 4.7... Separator, 8... Center plate, 9... Current collector, 9a... Plate, 9b...・Opening part, 9C... Press cut piece, 10...
Press mold.・Figure 2

Claims (2)

[Claims] (1) An electrolyte plate is sandwiched between the cathode and anode electrodes to supply oxidizing gas to the cathode side and fuel gas to the anode side. Used as a partition plate when stacking cells in multiple layers. In a separator for a molten carbonate fuel cell, a plate is provided with a large number of rectangular openings, each opening is formed by bending one pressed piece in a cantilevered manner, and the aperture ratio of the openings is 30%~6
0% and the narrower width of the opening is 2mm to 6mm.
1. A separator for a molten carbonate fuel cell, characterized in that current collectors having a diameter of 1 mm are arranged in contact with both sides of a center plate. (2) The separator for a molten carbonate fuel cell according to claim (1), wherein the tip of the press-cut piece of the current collector is curved inward so that the outside of the curved portion is in contact with the center plate.