JPH03110761A - High temperature type fuel battery - Google Patents

Abstract

PURPOSE:To make it possible to stabilize battery voltage for a long time by letting welding or soldering be done at both positions where each current collecting plate comes in contact with each separator and each reinforcing plate and positions where each rib plate comes in contact with reinforcing plate at a number of spots. CONSTITUTION:Welding or soldering shall be done at both positions where each current collecting plate 8 in a wave shape interposed between each separator 4 and each reinforcing plate 6, comes in contact with the separator 4 and the reinforcing plate 6 and positions where each rib plate projected out of the separator 4 comes in contact with the reinforcing plate 6, at a number of spot so as to be joined. Electrical connection between respective members is positively made in the inside of joined sections even when the outsides of the joined sections are covered by an insulating oxide film formed by oxidizing gas. By this constitution, no contact resistance among the respective members is increased even if operating time is lengthened, battery voltage is thereby stabilized for a long time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the structure of a single cell of a molten carbonate fuel cell and a solid oxide fuel cell, which are high-temperature fuel cells, and particularly to the structure of a reactant gas passage in a single cell. Regarding the structure of the department.

[Conventional technology]

As high-temperature fuel cells operated at high temperatures, molten carbonate fuel cells having an electrolyte plate containing and retaining carbonate and solid electrolyte fuel cells having an electrolyte plate made of metal oxide such as zirconia are known. . A single cell in such a high-temperature fuel cell consists of the electrolyte plate described above, an anode and a cathode electrode arranged on both sides of the electrolyte plate, and an anode and a cathode electrode arranged on both sides of the electrolyte plate, which cover each electrode and serve as a reaction gas passage for a reaction gas supplied from the outside. It is composed of a metal separator that forms a gas chamber and that contacts the electrolyte plate at its periphery to sandwich the electrolyte plate. In addition, in order to collect current while forming a reaction gas passage in the gas chamber, there is generally a ribbed or corrugated metal current collector plate and a metal reinforcing plate with many holes to supplement the strength of the electrode. is set up.

With such a structure, in a high-temperature fuel cell, a reactive gas is passed from the outside through a reactive gas passage and supplied to each electrode of an anode and a cathode to cause a cell reaction and generate electricity.

By the way, since the voltage generated per fuel cell is low, a large number of fuel cells are stacked to form a stack, and power at a required voltage is extracted from this stack. In this case, it is necessary that not only the electrical connection between the electrode and the electrolyte plate but also the electrical connection between these members and the separator be sufficient and reliable.

That is, if the electrical connections between each part are insufficient, internal resistance increases, and the voltage decreases accordingly. Therefore,
During operation of a fuel cell stack, it is necessary to maintain good electrical connections between cell components such as electrodes, electrolyte plates, current collector plates, reinforcing plates, and separators at all times from the beginning of operation to the end of operation. For this reason, the current collector plate is a corrugated plate with spring properties (see Japanese Patent Laid-Open No. 61-279068), a corrugated plate with a cantilever structure with spring properties (see Japanese Patent Application No. 160942/1983),
A means for maintaining good contact between each member during operation has been proposed.

Note that conventionally, each component such as a separator, a current collector plate, and a reinforcing plate has been fixed as a component by adhesive, brazing, single-point welding, etc. to the extent that they do not move relative to each other in consideration of workability during assembly.

[Problem to be solved by the invention] Conventionally, separators, current collector plates, reinforcing plates, and electrolyte plates.

Contact resistance between battery components such as electrodes can be reduced by increasing the clamping force in the stacking direction of the battery or by making the current collector plate stretchable. We were able to maintain good contact. In this case, in the contact between the electrode and the electrolyte plate, or the electrode and the reinforcing plate, it was possible to absorb the unevenness of the contact surface because the electrode, electrolyte plate, and electrolyte plate have a tendency to creep slightly.

On the other hand, when contacting the separator, current collector plate, and reinforcing plate,
Regardless of the shape of the current collector plate or reinforcing plate, with conventional surface accuracy and processing accuracy, gaps will occur due to unevenness and undulations.However, since such gaps are small, It does not obstruct contact between the entire battery.

However, during battery operation, oxygen in the reaction gas on the cathode side, water vapor in the reaction gas on the anode side, or cathode gas crossover occurs on the surfaces of each component such as the separator, current collector plate, and reinforcing plate. In the presence of oxidizing gases such as oxygen, an oxide film, which is an electrical insulator, is formed. And as the driving time becomes longer,
Oxidizing gas enters the small gaps between the separator, current collector plate, and reinforcing plate, gradually forming an oxide film and reducing the area of the parts with good conductivity, so contact between each member is good. However, there is a problem in that the electrical connection between each member deteriorates, that is, the internal resistance increases and the battery voltage decreases.

An object of the present invention is to provide a high-temperature fuel cell that can reduce the increase in contact resistance between a separator, a current collector plate, and a reinforcing plate from the beginning of operation to the end of operation of the fuel cell.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, each electrode of an anode and a cathode arranged on both sides of an electrolyte plate containing and retaining carbonate or an electrolyte plate made of metal oxide, and a separator covering each of these electrodes are provided. A wavy current collector plate is placed between the separator and a reinforcing plate having a large number of holes arranged in contact with each electrode in the gas chamber, which serves as a passage for the reaction gas supplied from the outside. Alternatively, in a high-temperature fuel cell having a rib plate protruding from a separator, the parts where the current collecting plate contacts the separator and the reinforcing plate, and the parts where the rib plate contacts the reinforcing plate are welded or brazed at multiple points. It shall be.

(Function) The part where the wavy current collector plate placed between the separator and the reinforcing plate contacts the separator and the reinforcing plate, and the part where the rib plate protruding from the separator contacts the reinforcing plate are welded at multiple points, or By joining by brazing, even if the outside of the joint is covered with an insulating oxide film formed by oxidizing gas, the electrical connection between the parts is ensured inside the joint. Even if the operating time becomes longer, the contact resistance between each member does not increase, and the battery voltage remains stable over a long period of time.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of a molten carbonate fuel cell, which is a high temperature fuel cell according to an embodiment of the present invention, and FIG. 2 is a fragmented perspective view of FIG. Figure 1.

In FIG. 2, reference numeral 1 denotes an electrolyte plate that impregnates and retains carbonate, and an anode electrode 2 and a cathode electrode 3 are arranged on both sides of the electrolyte plate 1, sandwiching the electrolyte plate 1 therebetween.

Reference numeral 4 designates a metal separator, which covers the anode electrode 2 and the cathode electrode 3, respectively, forms a gas chamber 5 serving as a passage for the reaction gas, and its peripheral portion is in contact with the electrolyte plate 1. In the gas chamber 5, a reinforcing plate 6 having a large number of holes 6a for reinforcing the anode electrode 2 and the cathode electrode 3, respectively, is arranged in contact with each electrode. A corrugated metal current collector plate 8 is installed between the reinforcing plate 6 and the separator 4 to form a reactive gas passageway for supplying fuel gas to the anode electrode 2 and oxidant gas to the cathode electrode 3. ing.

The regions where the wavy current collector plate 8 contacts the separator 4 and the reinforcing plate 6 at their peaks and valleys are the subject of the present invention, and are spot welded or doweled at a large number of junction points IO.

By joining at such a joining point 10, the separator 4
．． Current collector plate 8. The reinforcing plate 6 is reliably electrically connected. The number of junctions depends on the area of the junction, but normally up to about 3 amperes per junction is permissible, and in fuel cells a current of 0.15 to 0.5 amperes per electrode area is acceptable. flows, so it is sufficient to provide joint portions at a rate of 1 or more points, preferably 1 to 4 points per 20 mm.

With this configuration, the stack of unit cells is tightened and operated. At this time, separator 4. Current collector plate 8. The reinforcing plates 6 are joined by the above-mentioned spot welding or spot brazing to ensure electrical connection without being affected by the above-mentioned oxidizing gas. On the other hand, the reinforcing plate 6 and the anode,
The cathode electrodes 2.3 each maintain electrical connection by creeping slightly due to the tightening force in the battery stacking direction and the expansion/contraction force of the current collector plate 8, and absorbing the unevenness on the surface of the reinforcing plate 6. There is. In addition, the anode, cathode electrode 2.3, and electrolyte plate 1 may creep slightly due to the tightening force in the battery stacking direction and the expansion/contraction force of the current collector plate 8, causing unevenness of each other. maintains electrical connection by absorbing

The contact resistance between the members during operation is reduced by the electrical connection between each member as described above, especially the reliable electrical connection between the separator, the current collector plate, and the reinforcing plate.

Fig. 3 is a graph showing the electrode effective area of 200 - molten carbonate type twisting. It is understood that the increase in contact resistance is much smaller in the case of the contact resistance even during long operating periods.

FIG. 4 is a cross-sectional view of a molten carbonate fuel cell according to a different embodiment of the present invention. In FIG. The structure is the same as that shown in FIG. 1, except that a plurality of joint points 13 are spot welded or brazed in the same manner as described above.

The same effects as described above can be obtained with the fuel cell having the above structure.

In this embodiment, a molten carbonate fuel cell was explained, but a separator and a current collector plate are used in a single cell in a solid oxide fuel cell as well.

The same effect can be achieved by joining the reinforcing plates by spot welding or brazing.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the wavy current collector plate provided in the gas chamber of the reaction gas passage of a unit cell contacts the separator and the reinforcing plate of the electrode, or the rib plate protrudes from the separator. By welding or brazing the parts that contact the reinforcing plates of the electrodes at multiple points, even if the fuel cell is tightened in the cell stacking direction and operated for a long time, the joints made by spot welding or brazing will not be formed by oxidizing gas. Since it is not affected by the oxide film, it has the effect of maintaining good electrical connection over a long period of time and stabilizing the battery voltage over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a molten carbonate fuel cell according to an embodiment of the present invention, FIG. 2 is a fragmented perspective view of FIG. 1, and FIG. 3 is a separator and electrode of an embodiment of the present invention and a conventional one. FIG. 4 is a cross-sectional view of a molten carbonate fuel cell according to a different embodiment of the present invention. 1: Electrolyte plate, 2 near-node electrode, 3: cathode bridge,
4: Separator, 4a: Rib plate, 5: Gas chamber, 6: Reinforcement plate, 8: Current collector plate. Figure 1 Figure 2

Claims (1)

[Claims] 1) Reactant gas supplied from the outside between the anode and cathode electrodes arranged on both sides of an electrolyte plate containing and retaining carbonate or an electrolyte plate made of metal oxide and a separator covering each electrode. A gas chamber serving as a passage is formed, and a corrugated current collector plate or a rib plate protruding from the separator is arranged between the separator and a reinforcing plate having a large number of holes arranged in contact with each electrode in the gas chamber. A high-temperature fuel cell characterized in that the portions where the current collector plate contacts the separator and the reinforcing plate, and the portions where the rib plate contacts the reinforcing plate are welded or brazed at multiple points.