JPS62139271A - Fuel cell - Google Patents

Abstract

PURPOSE:To surely prevent leakage of electrolyte and reaction gas by joining one separator in a unit cell to the other separator faced each other to independently form a unit cell, and stacking a plurality of these unit cells. CONSTITUTION:A unit cell is stacked on an outer wall plate 13 so as to come in contact with plate 13 to constitute a fuel cell stack. The circumference of the unit cell is covered with a sealing member 12 to shut out an oxidizing agent gas passage 4 from the outside. The sealing member 12 having internal manifold is in contact with a square frame 5 and the oxidizing agent side outer wall plate 13. In the unit, cell, the sealing member 12, a square frame 5, and the outer wall plate 3 are united. When an electrolyte plate is baked, a gap exists between an oxidizing agent side sealing member 12A and a fuel gasside sealing member 12B, and these members are strongly bonded except for a region 10. Unit cells are stacked and compressed in a stacked direction to reduce contact resistance between unit cells and increase gas sealing ability.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel cell using molten salt as an electrolyte, and in particular, to a fuel cell in which unit cells are individually and independently constructed, and a plurality of unit cells are stacked to form a battery. The present invention relates to a fuel cell constituted by a stack.

[Conventional technology]

A conventional molten carbonate fuel cell is shown in the second figure, which shows an overall perspective view.
As shown in FIG. 3, which shows a plan view, and FIG. 4, which shows a cross-sectional view, it is composed of individual battery elements such as an anode electrode 6, a cathode electrode 2, an electrolyte plate 1, and a separator 34 (for example, Hitachi Hyoron No. 66 Volume 2, No. 59). The electrolyte plate 1 is impregnated with molten carbonate, and is sandwiched between an anode electrode 6 and a cathode electrode 2. The anode electrode 6 and the cathode electrode 2, which sandwich the electrolyte plate 1, are each closely attached to a separator 34 via a current collector plate (not shown). That is, the separator 34 is configured to sandwich the anode electrode 6 and the cathode electrode 2. A gas flow groove 33 is formed between the separator and each electrode to allow a reactive gas (oxidant gas 4 or anode gas 8) to flow therethrough. A unit battery is constituted by the electrolyte plate 1 held between the separators 34, each electrode, and a current collector plate. The unit cell is provided with a gas supply hole 9 for guiding a reactive gas to each gas flow groove.

When configuring a battery stack, multiple unit batteries are stacked,
Fix the battery stack with end plates from above and below.

A wet seal is provided at the contact point between the electrolyte plate and the separator. Therefore, the required area of the electrolyte plate is approximately the same as that of the separator. Wet sealing is performed at the manifold hole 9.

Wet sealing is performed by heating the battery stack when all unit batteries are stacked to melt the electrolyte, which is molten carbonate. This wet seal can prevent leakage of reaction gas.

To improve wet sealing performance and eliminate electrolyte leakage during heating during wet sealing.

In addition, in order to improve the contact resistance between the electrodes, current collector plates, and separators, a vertical load is applied to the battery stack over time. This loading is carried out in a controlled manner under certain conditions. For example, this is to prevent cracking of the electrode plate or electrolyte plate.

[Problem that the invention seeks to solve]

In the current wet seal technology, unless a sufficient area of the wet seal portion 50 is secured, the sealing performance will not be satisfied. Therefore, in an internal manifold type fuel cell, the electrolyte plate area is approximately 1 of the effective power generation area 109.
．． It has increased five times. Therefore, in order to increase the output of the fuel cell, the area of the electrolyte plate must be increased. This may cause warping or cracking in the large electrolyte plate during drying and sintering during manufacture of the electrolyte plate.

If an electrolyte plate cracks, it cannot be used as a battery element. On the other hand, warping of the electrolyte plate becomes a big problem when battery elements are stacked. FIG. 5 shows a cross section taken along the line AA' in FIG. 3, and the problem will be explained in detail. An anode electrode 6 and a cathode electrode 2 are installed on both sides of the electrolyte plate 4), and separators 34 press them from both sides. This basic structure is repeated in sequence to form a stacked battery. However, as you can see from this structure,
If warpage occurs in the electrolyte plate 1 and the thickness of the electrodes is not uniform, a situation as described below will occur in the battery structure, which is a problem.

FIG. 5(A) shows a case where an irises are generated in the gear between the electrolyte plate 1 and the electrodes 2 and 6 due to the warpage of the electrolyte plate 1 and the thickness of the electrode 2.6. In this state, the separator 34 is
and the electrolyte plate 1 come into contact with each other, resulting in good sealing performance. However, the effective contact area for power generation between the electrode and the electrolyte plate is reduced, and the leakage characteristics of the electrolyte are reduced, resulting in a decrease in output. On the other hand, FIG. 4(B) shows a case where 2 occurs in the gear between the separator 34 and the electrolyte plate 1 in the wet seal portion 50. In this case, electrodes 2, 6
There is no problem in the contact between the battery and the electrolyte plate 1, and the battery performance is good. However, the sealing performance deteriorates and the fuel leaks into the seal part 5.
0 leaks out of the battery, making it impossible for battery operation to continue.

As described above, in fuel cells that use the conventional wet seal method, gaps occur between the electrolyte plate and the electrode or between the electrolyte plate and the separator, which is a sealing member, due to poor dimensional accuracy such as warping of the electrolyte plate or uneven electrode thickness. However, in the event of an occurrence, it was not possible to take effective countermeasures, resulting in a very unreliable system.

There are other problems as well: In other words, when a battery stack is constructed by stacking multiple unit batteries,
It is technically quite difficult to apply heat and pressure to form a wet seal. This is due to the fact that the gas sealing properties, wetting properties, and contact resistance of many unit cells must be improved all at once under severe conditions such as high temperatures. Therefore, the reliability of the battery stack is not sufficient, and if a defective state occurs in a small number of unit cells in the battery stack, the entire stacked battery must be replaced. As a result, when considering the use of fuel cells in high-output industrial power plants, this naturally leads to significant maintenance difficulties. Also, from a practical point of view,
Furthermore, from the perspective of power generation costs, ease of maintenance is an issue that must be resolved.

In order to solve the above-mentioned problems, an object of the present invention is to provide a fuel cell that prevents leakage of electrolyte solution and reaction gas, is easy to maintain, and is highly reliable when stacked to a high degree.

[Substantive Means for Solving the Problems] In order to achieve the above object, the present invention provides electrolytic plates that are arranged opposite to each other with an electrolyte plate sandwiched between them, and electrolytic plates that are arranged opposite to each other by sandwiching an electrolyte plate, and In a fuel cell formed by stacking a plurality of unit cells, each of which includes a separator arranged facing each other and forming a reaction gas flow path between each of the electrode plates, one of the separators constituting the unit cell is arranged facing each other. The fuel cell is characterized in that the unit cells are independently configured by being insulatively joined to the other separator, and a plurality of the independently configured unit cells are stacked.

[Effect]

In the above structure of the present invention, when the electrolyte plate is fired, the electrolyte plate, electrode plate, and separator can be combined to form a unit battery individually, and the conventional wet seal part of the electrolyte plate is formed by insulating bonding, for example, ceramic bonding. The separators are dry sealed. Therefore, individual differences in the shapes of the electrodes and electrolyte plates can be absorbed by the dry seal portion, so that unit cells with good sealing properties for reactant gas and electrolyte can be independently obtained.

Since a fuel cell stack is constructed by stacking such unit cells, if a defect occurs in one of the unit cells, maintenance of the entire fuel cell can be performed by replacing only this unit cell. It becomes possible.

Furthermore, since a dry seal is used instead of a wet seal to prevent reaction gas leaks,
It is possible to avoid heavy loads during wet sealing of fuel cells. Therefore, cracking of the electrolytic soundboard and electrode plates can be prevented.

〔Example〕

Next, various preferred embodiments of the fuel cell according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows its cross-sectional configuration.

In FIG. 1, a cathode electrode 2 on the oxidizer side and an anode electrode 6 on the fuel side are in close contact with each other with an electrolyte plate 1 in between. Furthermore, current collector plates 3 and 7 are in close contact with the electrodes on the outside of the electrodes. On the outside of this current collector plate 3.7, an oxidizing agent,
Rectangular thin plates (rectangular frames) 5.degree. 15 for forming flow paths through which fuel gas flows are orthogonal to each other and in contact with the current collector plates 3 and 7, respectively. The rectangular frames 5 and 15 have a function as a separator.

The oxidant gas and the fuel gas are arranged to flow orthogonally to each other through the spaces 4 and 8 formed by the current collector plate 3.7 and the rectangular frames 5 and 15, respectively. Focusing on the oxidizing agent side in the upper part of the figure with the electrolyte plate 1 as the center, the rectangular frame 5 that forms the flow path for the oxidizing gas is located at the point where the rectangular frame 5 contacts the outer wall plate 13 that forms the outer shape of the battery body. It has a close-fitting structure. The outer wall flat plate 1 is in contact with this outer wall flat plate 13.
The next similar unit cell is stacked on top of No. 3 to form a fuel cell stack.

In order to isolate the oxidizing gas flow path 4 from the outside, a sealing member 12 is provided to cover the entire circumference of the unit cell. This sealing member 12 is provided with a flow path 9A for an internal manifold connected to the inlet and outlet portions of the reaction gas. Fuel gas flows through this flow path 9A, and the fuel gas flow path 8
An electrochemical reaction is caused within the electrode 6, and the generated gas passes through the flow path 11, flows through the outlet manifold 9B provided on the opposite side of the inlet, and is discharged to the outside. Although the manifold on the oxidizing gas side is not shown, the manifold is provided in a direction perpendicular to the fuel gas. The sealing member 12 having this internal manifold is in contact with the rectangular frame 5 and the oxidizing agent side outer wall flat plate 13 shown above, and a unit battery in which these sealing members 12, the rectangular frame 5, and the outer wall flat plate 3 are integrated is formed. is formed. Similarly, on the fuel gas side, the structure is such that the rectangular frame 15, the outer wall flat plate 14, and the seal member 12 on the fuel gas side are integrated.

When the electrolyte plate is fired, a gap is created between the oxidizer-side seal member 12A and the fuel gas-side seal member 12B, and they are firmly in contact with each other except for the region 10 where they face each other. Become. In fuel cells, gas seal electrical insulation is required in areas where seal members face each other.

This region 10 corresponds to a wet seal surface in a conventional fuel cell, and has the same function as a wet seal. In this embodiment, a ceramic coating is applied in advance to the region 10, which is the sealing surface of the sealing member 12, by plasma welding, and the previously applied ceramic coating surface is newly applied to the gap between the sealing members. Metalized to 75% metal surface
They are joined by brazing or diffusion at a temperature of 0 to 850°C, and gas-sealed during firing of the electrolyte plate.

Regarding the voltage insulation between the cathode 2 and the anode 6, sufficient insulation is obtained by the ceramic coating described above. The reason why the ceramic surface is metallized and the bonding surface is fixed in this way is to eliminate contact resistance at the bonding surface between the sealing members. Note that it is also possible to metallize the central portion and apply ceramic coating to the periphery so that the sealing member is in close contact with the central portion.

The independent unit batteries (hereinafter sometimes referred to as "packaged batteries") shown in this example are stacked and a load is applied in the stacking direction to reduce contact resistance between each unit battery or improve gas sealing performance. As a result, compared to conventional wet-sealed fuel cells, it is easier to assemble a highly laminated battery, and even if a defective battery occurs, it is possible to provide a fuel cell that can be replaced for each unit cell. In addition, in order to make the electrical resistance of the stacked battery extremely small and to ensure a perfect gas seal between the stacked batteries, the stacked battery surface 13.
It is also possible to eliminate contact resistance by bonding 14 at a predetermined temperature, for example at a temperature slightly lower than the bonding temperature.

Next, the sixth embodiment describes another embodiment according to the present invention.
7 and 7 are partial cross-sectional configuration diagrams of an embodiment in which the gas sealing performance from the stacked surface of a packaged unit cell with an internal manifold type structure is improved.

In FIG. 6, oxidant gas and fuel gas side electrodes 2 and 6 are in close contact with both sides of an electrolyte plate 1, and current collector plates 3 and 7 are in close contact with the outside thereof. There are gas channels 4 on both sides of this current collector plate 3゜7.
, 8 are formed. These points are similar to the embodiment shown in FIG.

On the other hand, a convex portion 22 and a concave portion 21 are provided at both ends of the unit cell of the internal manifold 9. Convex part 2 of one battery
2 is fitted into the recess 21 of the other unit battery, thereby forming a stacked battery in which the unit batteries are stacked.

By providing the concave and convex portions and inserting the unit batteries into each other in this manner, positioning during stacking becomes easy and lateral displacement after stacking can be prevented. As a result of preventing lateral slippage, the earthquake resistance of the fuel cell stack is improved. It should be noted that both seal members are joined at the joining surface 10 by the same method as in the embodiment shown in FIG. 1, and a packaged vehicle positioning battery is formed.

When stacking a plurality of packaged unit batteries having the above-mentioned concave portions and convex portions, as shown in FIG. Unit batteries can be stacked with the sealing material 22 interposed therebetween. As a result, the electrical conductivity of the laminated surfaces 13, 14 becomes good, making it possible to further improve gas sealing.

FIG. 8 shows a cross-sectional configuration diagram of a fuel cell in which a cooling cell 30 and a packaged unit cell are combined, as another embodiment of the fuel cell according to the present invention.

The structure of the battery is the same as that of the embodiment shown in FIG.
The difference is that 0 is incorporated between the outer flat plates 13, 14 of the unit cell. In this case, the refrigerant 32 is ejected from the cooling hole 31 provided in the separator outer flat plate 13 on the oxidizing gas side into the groove 33 of the rectangular separator 5, and the electrolyte plate 1
is being cooled.

The ejected refrigerant 32 is returned from one end of the groove 33 to an exhaust line (not shown). Further, the contact surface between the cooling cell 30 and the battery can be structured with unevenness and a packing as shown in FIGS. 6 and 7 to improve sealing performance and reduce electrical resistance.

According to this embodiment, it is possible to construct a stacked battery that has good cooling performance and good gas sealing performance, and further allows easy replacement of defective batteries. In addition, by changing the number of cooling holes 31 according to the temperature distribution of the battery, a battery with a uniform temperature distribution can be obtained, improving reliability.

A laminated battery with excellent battery life can be obtained.

FIG. 9 shows a cross-sectional configuration diagram of an embodiment of an external manifold type molten salt fuel cell. The structure of the cell is basically the same as the internal manifold type embodiment shown in FIG.
The surface 34 serves as a sealing surface between the external manifold and the stacked battery.

〔effect〕

As explained above, according to the fuel cell according to the present invention, since the opposing separators of the unit cells are insulated and bonded to each other, it is possible to reliably prevent leakage of the electrolyte and reaction gas, and also to improve power generation. The required effective area of the electrode becomes large. As a result, the power generation efficiency of the battery improves,
Furthermore, battery reliability is also improved.

Further, since each unit battery is sealed and these are stacked to form a battery stack, only the defective unit battery can be replaced. Therefore, it has excellent maintainability.

Furthermore, since a dry seal is used instead of a wet seal to prevent reaction gas leakage, the load during wet sealing can be avoided. Therefore, cracking of the electrolyte plate and the electrode plate can be prevented.

[Brief explanation of drawings]

FIG. 1 is a unit cell cross-sectional configuration diagram of an embodiment of the fuel cell according to the present invention, FIG. 2 is an overall perspective view showing a conventional fuel cell configuration, FIG. 3 is a plan view of FIG. 2, and FIG. 4 is a sectional view of FIG. 2, FIG. 5 is a sectional view taken along line A-A' of FIG. 3, and FIGS.
FIG. 8 is a cross-sectional configuration diagram showing the laminated state of the internal manifold part of another embodiment of the present invention, FIG. 8 is a cross-sectional configuration diagram showing a structure in which cooling cells are incorporated,
FIG. 9 is another embodiment of the present invention, which is a cross-sectional configuration diagram of an external manifold type fuel cell. DESCRIPTION OF SYMBOLS 1... Electrolyte plate, 3, 7... Current collector plate, 2... Cathode electrode, 4, 8... Reaction gas flow path, 6... Anode electrode, 10... Joint surface, 20 ... recess, 22...
・Protrusion.

Claims (1)

[Scope of Claims] 1. Electrode plates arranged opposite to each other while holding an electrolyte plate between them, and electrode plates arranged opposite to each other while holding the electrode plate and the electrolyte plate between each other, and a reaction gas flow path is formed between the electrodes and the respective electrodes. In a fuel cell formed by stacking a plurality of unit cells each comprising a separator, the separator forming the unit cell is insulatively joined to one of the separators disposed opposite to each other, so that the unit cell is independently configured, A fuel cell characterized in that a plurality of the independently configured unit cells are stacked. 2. The fuel cell according to claim 1, wherein the insulating joint portion has a convex portion fitted into a concave portion.