JPH07123046B2 - Molten carbonate fuel cell - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a molten carbonate fuel cell, and more particularly to the structure of a gas supply path to a porous electrode plate.

[Technical background of the invention and its problems]

In recent years, a molten carbonate fuel cell has been developed as a highly efficient energy conversion device. A molten carbonate fuel cell is a unit cell composed of a pair of gas diffusion electrode plates arranged opposite to each other, that is, an oxidizer electrode and a fuel electrode, and an electrolyte layer having an alkali carbonate as an electrolyte interposed between these electrodes. , For example, a plurality of layers are stacked via an interconnector. Then, during operation, the alkali carbonate is brought into a molten state at a high temperature of 600 to 700 ° C., and the carbonate is reacted with the oxidant gas and the fuel gas diffused in each electrode plate to perform an electrochemical process. To obtain a DC output.

By the way, the above-mentioned electromotive reaction occurs at the reaction site (three-phase interface) of the electrode, the carbonate and the reaction gas in the porous electrode. In order to allow this electromotive reaction to proceed efficiently, it is necessary to form a gas supply path for uniformly distributing and supplying the reaction gas to the reaction site.

FIG. 8 shows the structure of a conventional gas supply passage. The structure shown in FIG. 8 (a) has a corrugated plate 2 having a gas supply passage and a current collecting function installed on a separator 1. The structure shown in FIG. 2B in which the current collector plate 3, the electrode 4, the electrolyte layer 5 and the like are arranged on top of this has a groove 7 formed in an electrode 6 made of a thick porous body, and this groove is formed. 7 is a gas passage (rib electrode type).

However, the conventional molten carbonate fuel cell thus configured has the following problems.

That is, in this type of battery, a wet seal is usually formed at the end of the unit battery to prevent the reaction gas from leaking to the unintended side. This wet seal is formed by forming a bank portion 8 at the end of the separator 1 and using molten carbonate that is a stain between the bank portion 8 and the electrolyte layer 5. However, normally, the thickness t1 of this bank portion 8 and the thickness t2 of the corrugated plate 2 + current collector plate 3 + electrode 4 (or the thickness t of the electrode 6)
2) means that even if the batteries have almost the same dimensions when assembled, they change due to thermal expansion during operation, and because the materials that make up each differ, they do not show exactly the same change. Cause a dimensional difference.
When such a dimensional difference occurs, excessive stress acts on the electrolyte layer 5 to cause cracks, and a gap is generated between the bank portion 8 and the electrolyte layer 5 to cause gas leakage. There was a problem.

[Object of the Invention]

The present invention has been made in consideration of such problems,
The purpose is to provide a molten carbonate fuel cell that prevents local dimensional changes in the electrode support structure and does not cause problems such as cracks in the electrolyte layer or gas leakage at the cell edges. To do.

[Outline of Invention]

The present invention, on both sides of the unit battery formed by arranging a pair of porous electrodes on both sides of the molten carbonate electrolyte layer, while arranging an electrode support plate made of a porous body for guiding a reaction gas to the porous electrode, It is characterized in that a gas seal portion is integrally formed at a peripheral portion of the electrode support plate which is not used for introducing and discharging the reaction gas.

〔The invention's effect〕

According to the present invention, since the gas seal portion is integrally formed at the peripheral portion of the electrode supporting plate that is not used for introducing and discharging the reaction gas, a local dimensional change may occur in the electrode supporting plate. Absent. Since the electrode and the electrolyte layer are supported by this electrode support plate, a problem that excessive stress acts on a part of the electrolyte layer to cause cracks, or gas is generated at the end of the unit battery. The problem of leakage can be solved.

Therefore, according to the present invention, the heat cycle performance and the gas utilization rate can be improved.

Example of Invention

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

<Example 1> As shown in FIG. 1, a pair of opposite ends of an electrode supporting plate 11 made of a Ni porous body (foamed metal) having a porosity of 90% and a thickness of 1.2 mm, that is, the electrode supporting plate 11 A portion of the peripheral portion of the above which is not used for introduction and discharge of fuel gas P described later is impregnated with a slurry of alumina fine powder and deposited on a portion 5 mm from the end portion, and then that portion is sufficiently impregnated with molten salt. Dense structure part
12 was formed and this was made into the gas seal part. An electrode (anode) 13, an electrolyte layer 14, and an electrode (cathode) 15 are laminated on this electrode supporting plate 11, and another electrode supporting plate 16 formed by the same method as described above is further laminated thereon. did. Note that the electrode support plate 11 and the electrode support plate 16 were arranged with the dense structure portions 12 being different by 90 °. A 100 mm square unit battery 18 was constructed by disposing conductive separator plates 17 on both surfaces of such a laminate.

The unit battery 18 is heated to 650 ° C., the fuel gas P is supplied to the electrode support plate 11 and the oxidant gas Q is supplied to the electrode support plate 16 so as to be orthogonal to each other as shown in the figure, and the electromotive reaction is performed. Caused. Then, when repeatedly operating at a temperature cycle of 200 to 650 ° C. and measuring the voltage at 650 ° C. and 150 mA / cm ² ,
The value of ± 5% of the initial value was maintained even after 30 cycles.

<Example 2> As shown in FIG. 2, the same method as in Example 1 was applied to a pair of opposing ends of an electrode supporting plate 21 made of a Ni porous body having a porosity of 90% and a thickness of 1.2 mm. The dense structure portion 22 was formed and used as a gas seal portion. Furthermore, on the upper surface of this electrode support plate 21,
Ni fine powder having an average pore diameter of 3 μm was applied in a slurry form to form a dense layer 23. Then, the dense layer 23 was used as an electrode.

<Embodiment 3> The dense portion 12 of the electrode support plate 11 of the first embodiment is thickened by the thickness of the electrode 13 to form an electrode support plate 31 as shown in FIG. The dense structure portion 32 was used as the gas seal portion. Then, the electrode 33 was fitted in the groove formed by the thick portion to form a combined body of the electrode and the electrode support plate.

By the way, in Examples 1 and 2 described above, the vertical and horizontal dimensions of the electrode and the electrode support plate are the same. This is because it is considered that the electrode is extremely thin, so that it is sufficiently impregnated with the molten carbonate and there is almost no leakage of the reaction gas at the end of the electrode. However, with the structure of the third embodiment, the sealing performance of the electrode end portion can be further improved.

<Example 4> Both ends of an electrode support plate 41 made of a Ni porous body having a porosity of 90% and a thickness of 1.2 mm were compressed and crushed as shown in FIG. Formed in the dense structure portion 42 by the method,
A gas seal was formed. At the end of the separator 43, a bank portion 44 that fits with both ends of the electrode support plate 41 was formed.

<Embodiment 5> As shown in FIG. 5, both ends of an electrode support plate 51 made of a Ni porous body having a porosity of 94% and a thickness of 1.2 mm were attached to a Fe-layer having a thickness of 0.2 mm.
A thin plate 52 of Cr-Al alloy was covered in a U-shape and integrally bonded to form a gas seal portion.

<Example 6> As shown in FIG. 6, the integrated electrode support plate of Example 2 was prepared.
A plurality of grooves 61 for gas flow were formed by electric discharge machining, and an electrode support plate 62 was formed.

<Embodiment 7> As shown in FIG. 7, a plurality of ridges formed by the grooves 61 of the electrode support plate 62 of Embodiment 6 are connected by ribs 71 to form an electrode support plate 72 having increased strength. did.

The same tests as in Example 1 were performed on the unit batteries using the electrode support plates of Examples 2 to 7 above, and as a result, good aging characteristics could be obtained as in Example 1.

On the other hand, when the conventional unit battery shown in FIG. 8 was tested in the same manner as described above for comparison, a significant performance deterioration occurred after 10 cycles.

The present invention is not limited to the above embodiment.

Although the foam metal of Ni is used as the electrode support plate in the above embodiment, other foam metal such as Ni-based alloy or stainless steel-based metal may be used. Further, a porous body made of an ordinary powder sintered body or a metal fiber sintered body may be used.

Further, in the present invention, the one in which the reaction gas is supplied from the external manifold and the inside of the electrode supporting plate is made to flow in the orthogonal direction is used, but it is also applicable to other manifold type fuel cells such as the internal manifold. is there. In this case, it is necessary to form a gas-sealed portion having a dense structure all around the periphery of the electrode support plate.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of a unit cell of a molten carbonate fuel cell according to an embodiment of the present invention, and FIGS. 2 to 7 show electrode supports according to other embodiments of the present invention. Showing the figure,
FIG. 8 is a sectional view showing a partial configuration of a conventional unit battery. 1,17 ... Separator, 2 ... Corrugated plate, 3 ... Current collector plate, 4,6,
13,15,33 …… Electrode, 5,14 …… Electrolyte layer, 8,44 …… Bank portion, 11,16,21,31,41,51,62,72 …… Electrode support plate, 12,22, 3
2,42 ... Dense structure part, 23 ... Dense layer, 52 ... Thin plate, P
…… Fuel gas, Q …… Oxidizer gas.

Claims (3)

[Claims] 1. A unit cell comprising a pair of porous electrodes on both sides of a molten carbonate electrolyte layer, and a porous body disposed on both sides of the unit cell to guide a reaction gas to the porous electrode. A molten carbonate fuel cell, comprising: an electrode supporting plate, wherein a gas seal part is integrally formed at a peripheral portion of the electrode supporting plate that is not used for introducing and discharging the reaction gas. 2. The gas seal portion is characterized in that the portion of the electrode support plate is formed more densely than other portions, and this portion is impregnated with molten carbonate. 2. A molten carbonate fuel cell according to claim 1. 3. The molten carbonate fuel cell according to claim 1, wherein the gas seal portion is formed by covering the portion of the electrode support plate with a thin metal plate.