JPH01246769A - Fuel cell of molten carbonate type - Google Patents

Abstract

PURPOSE:To enhance contacting perrormance of different metal members with one other and prevent deterioration of the performance due to increase in the electric resistance by interposing a metal film layer, which is welded fast in a specific range of operating temp., between metal members in their electrical contacting areas. CONSTITUTION:By sputtering, Ag film layers 3 of approx. 20mum thick are provided in the portions of a gas dispersion plate 1 and a partition plate 2 which are in contact with an undulated plate for passage of gas, and through this layer 3 undulated plate 4 for passage of gas is arranged between the dispersed plate 1 and partition plate 2. Unitary cells are assembled using a laminate of cathode and anode with electrolyte liquid interposed and the component members, and the temp. is raised to the range from 300 deg.C to the actuating temp. to bond the dispersion plate 1 of component members with undulated plate 4 and the partition plate 2 with the undulated plate 4 by the layer 3. Thereby good electrical bond is secured between the metal members, and the contacting portions are prevented from oxidation and corrosion.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a molten carbonate fuel cell, and particularly to a molten carbonate fuel cell with improved electrical contact between metal members. Involved.

(Prior Art) Molten carbonate fuel cells are considered as second generation fuel cells following phosphoric acid fuel cells because of their high power generation efficiency. In this molten carbonate fuel cell, an electrolyte plate mainly composed of alkali carbonate is sandwiched between the cathode and anode electrodes, which are arranged facing each other, and an oxidant gas and a fuel gas are uniformly distributed to the respective picture electrodes. It has a structure in which various metal members are provided to extract the obtained current efficiently.

By the way, the operating temperature of a molten carbonate fuel cell is 850~
As the temperature is as high as 700°C and alkali carbonate (electrolyte) oozes out from the electrolyte plate, various metal members are subject to significant oxidation and corrosion. Oxidation and corrosion are caused by gases, water vapor, and highly corrosive alkali carbonates flowing on the anode and cathode sides.

That is, on the cathode side, oxidation occurs with oxygen, which is an oxidant gas necessary for power generation, and on the anode side, oxidation occurs with water vapor generated as a result of the reaction between hydrogen, which is a fuel gas, and oxygen, and alkali carbonates in particular ooze out. Oxidation is significantly accelerated. In particular, alkali carbonates severely corrode the oxide film on the metal surface and the metal base material itself.

The various metal members constituting a molten carbonate fuel cell need to have conductivity in order to transmit the resulting current, and therefore, if the contact resistance between the metal members increases, the cell performance will deteriorate. Such contact resistance means not only that caused by mechanical contact between metal members, but also ohmic resistance that occurs as a result of oxidation or corrosion on the surface of metal members, and resistance caused by a Schottky barrier that occurs between oxide films. Among these, the ohmic resistance and the resistance due to the Schottky barrier are related to oxidation and corrosion of metal members, so they become more noticeable as the battery operates for a longer time, and the battery performance deteriorates over a longer time.

On the other hand, an increase in resistance due to poor mechanical contact between metal members mainly causes a decrease in the initial characteristics of the battery. The main causes of such poor mechanical contact between metal members are that the larger the area of the cell component, the more difficult it is to flatten it, resulting in waviness, and the generation of thermal stress due to temperature distribution in the plane and vertical directions. This is to deform a metal member. In this case, since the various metal members are not joined when assembling the battery, the waviness and deformation are directly involved in mechanical failure. Mechanically defective locations between metal members are more susceptible to oxidation than locations where they are in complete contact because gas flows freely. Particularly, in parts that are in slight contact to maintain electrical connection, oxidation progresses as the battery operates, increasing ohmic resistance and Schottky barrier resistance, and exhibiting insulating properties.

For this reason, the entire battery is held down with high stress,
It is possible to improve mechanical contact between metal members. However, in a fuel cell in which a breakable electrolyte plate is incorporated, it is difficult to significantly increase the stress because it causes deterioration of the cell performance.

(Problems to be Solved by the Invention) The present invention was made to solve the above-mentioned conventional problems, and it improves the contact between various metal members and prevents long-term deterioration of battery performance due to increased electrical resistance. It is an object of the present invention to provide a molten carbonate fuel cell in which

(Means for Solving the Problems) In a molten carbonate fuel cell constructed by assembling various metal members, the present invention provides bonding at an electrical contact portion between the metal members at an operating temperature range of 300°C. This is a molten carbonate fuel cell characterized by having a metal thin film layer interposed therebetween.

The metal thin film layer does not participate in bonding between the metal members during battery assembly, but softens during the temperature rising process of the battery, from 300° C. to the operating temperature, and serves to bond the metal members together. In particular, from the viewpoint of suppressing oxidation of the contact parts of metal parts and deformation of the metal parts themselves as much as possible, it is necessary to select a metal that softens below the temperature at which the alkali carbonate in the electrolyte plate melts and joins the metal parts. is desirable. Examples of such metals include Ag, Au, Cu, N1, and alloys thereof. Among these, C
Since u is easily oxidized by oxidizing gas and becomes brittle, it is desirable to use it for joining metal members on the fuel gas side. Said N1
Because it is severely corroded in the coexistence of oxidizing gas and alkali carbonate, it is desirable to use it for joining metal members on the fuel gas side.

For this reason, Ag is preferable because it is relatively inexpensive and resistant to oxidation and corrosion.

The metal thin film layer may be interposed between the metal members, but in order to improve workability during assembly, the contact areas of the metal members may be pre-plated, coated, coated, etc.
It is desirable that the coating be performed by a VD method, a sputtering method, a vapor deposition method, or the like. In particular, plating and sputtering methods are preferred in consideration of adhesion to metal members. Further, when coating the metal thin film layer, it is sufficient to coat one of the metal members, but depending on the case, the contact portion between both metal members may be coated with the same or different metal thin film layer.

Furthermore, the thickness of the metal thin film layer is set to 5 μm from the viewpoint of improving the contact between metal members by the thin film layer and the construction accuracy of the fuel cell.
It is desirable that the thickness be ˜0.2 rtus, and the more preferable thickness is in the range of 10 to 100 μm.

(Function) According to the present invention, the electrical contact area between metal members has a
By interposing a metal thin film layer that joins within the operating temperature range from ℃ to the operating temperature, the contact areas between each metal member can be firmly joined and integrated by the metal thin film layer during the temperature rise process during operation, so the metal parts can be bonded together. Good electrical continuity can be ensured, and the contact area can be prevented from being oxidized and corroded by surrounding gas. In particular, it is possible to avoid an increase in electrical resistance at contact points between metal members, which is a problem during long-term use, and to realize a fuel cell that has stable performance over a long period of time. Furthermore, it has the advantage of structurally suppressing thermal deformation due to temperature distribution, which cannot be avoided with fuel cells.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to FIG.

First, as shown in Fig. 1, the contact portion of the gas distribution plate (perforated plate) made of 5US310 with the corrugated plate for gas passage described below,
After providing an Ag thin film layer 3 with a thickness of about 20 μm by sputtering at the contact portion of the partition plate 2 made of 5US310 and the corrugated plate, a layer 3 of Ag thin film 3 with a thickness of about 20 μm is provided between the dispersion plate 1 and the partition plate 2 made of 5US310 for gas passage. The corrugated plate 4 was arranged with each of the Ag thin film layers 3 interposed therebetween to produce a battery component.

Subsequently, a mixed alkali carbonate (at a molar ratio of Li 2 CO3 / 2
A 4 cm square unit battery is assembled using a laminate sandwiching an electrolyte plate containing a mixture of CO3-62/38) and LIA and an eO2 powder holding material, and this unit battery is heated to 650℃, which is the power generation temperature.
When the temperature was raised to 300° C., the temperature was maintained at 300° C. for 1 hour to bond the components between the dispersion plate and the corrugated plate and between the partition plate and the corrugated plate with an Ag thin film layer.

Comparative Example Except for using a dispersion plate, a corrugated gas passage plate, and a partition plate stacked one on top of the other without bonding each other as battery components.
A unit battery having a configuration similar to that of the example was assembled.

Therefore, for the unit batteries of this example and comparative example, approximately 3
000 hours of power generation. As a result, in the battery of the example, the initial voltage of 0.85V at 150mA/m was 3000V.
Even after hours, the voltage remained at 0.83V, and the deterioration was slight at 0.02V. On the other hand, in the battery of the comparative example, the initial voltage was 0.
．． 80V decreased to 0.64V after 3000 hours.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to ensure good electrical conduction between metal members, prevent contact areas from being oxidized and corroded by surrounding gas, and further improve temperature distribution. Accordingly, it is possible to suppress the thermal deformation of the metal member caused by the thermal deformation of the metal member, and furthermore, it is possible to provide a high-performance molten carbonate fuel cell that can maintain a stable initial voltage for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing battery components used in an example of the present invention. ■... Gas distribution plate (perforated plate), 2... Partition plate,
3...Ag thin film layer, 4...Corrugated plate for gas passage. Applicant's agent Patent attorney Takehiko Suzue 111 Figure

Claims (1)

[Claims] In a molten carbonate fuel cell constructed by assembling various metal members, there is a
A molten carbonate fuel cell characterized by interposing a metal thin film layer that is bonded at an operating temperature ranging from 0°C.