JPS6273572A - Fuel cell - Google Patents

Abstract

PURPOSE:To prevent heat generation and performance decrease caused by mixing of fuel gas and oxidizing agent gas by filling a sealant in which phosphoric acid is used as dispersion medium between the peripheral, parallel in a gas flow direction, of electrode and a separator. CONSTITUTION:A sealant 4 is filled on the stacked surface of the peripheral, parallel in a gas flow direction, of a ribbed electrode 2 and a separator 3. The sealant 4 can keep steady sealing ability for a long time by using phosphoric acid as dispersion medium. The sealant absorbs recessed and projecting parts on the surface of the periphery of the ribbed electrode 2 or the separator 3 and eliminates spaces between them to bring the periphery into close contact with the separator 3, and increases airtightness between them. Thereby, gas leakage is eliminated and mixing of fuel gas flow B and oxidizing agent gas flow C is prevented. Therefore, heat generation of cell stack and decrease in cell performance caused by these problems can be pervented.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a fuel cell (1), and features (1) improves gas sealing properties between the electrode end periphery and the separator joint surface (C); The present invention relates to a fuel cell C whose sealing property can be maintained.

[Technical background of the invention and its problems] Fuel cells have been known as devices that directly convert energy contained in fuel into one unit of electrical energy.

This fuel cell usually has a pair of porous electrodes sandwiching an electrolyte between them, and a fuel gas such as hydrogen is brought into contact with the back of one electrode, and an oxidant gas such as oxygen is brought into contact with the back of the other electrode. The electrochemical reaction that occurs at this time is used to extract electrical energy from between the electrodes.As long as the fuel gas and oxidant gas are supplied, electrical energy can be extracted with high conversion efficiency. It is something that can be taken out.

Figure 3 shows a diagram based on the above principle using phosphoric acid as an electrolyte.
1 is a vertical cross-sectional perspective view showing an example of the configuration of a ribbed electrode type fuel cell. In the figure, a unit cell is composed of a pair of ribbed electrodes made of a carbon material, in which a matrix 1 impregnated with phosphoric acid as an electrolyte is sandwiched, and a pair of ribbed electrodes, each made of a carbon material, are arranged in a direction perpendicular to each other. It consists of placing 2,
A fuel cell stack is constructed by stacking a plurality of these unit cells. Here, the grooves of the ribbed electrode form flow paths for fuel gas and oxidant gas, respectively. In the case of stacking the above unit cells, in C:, a separator 3 having electrical conductivity and having no gas permeability is sandwiched between each unit cell so that the fuel gas and the oxidant gas do not mix. When stacking, it is necessary to airtightly seal between the separator 3 and the edge portion of the ribbed electrode 2 parallel to the gas flow direction l to prevent gas leakage from the stacked surface. In addition, the same treatment as in 4 is required for cells using flat plate-shaped poles.

If a gas leak occurs at the laminated surface, mixture of fuel gas and oxidant gas occurs, causing heat generation and deterioration of battery characteristics. FIG. 4 shows a conceptual diagram of this situation. :) If a leaker of fuel gas stream B causes mixing of fuel gas stream B and oxidant gas stream C, these reactants will no longer participate in power generation C; not only will the power generation efficiency decrease, but also an exothermic reaction will occur. Wake up T. If this mixed state flows into the cell, it will combust within the cell and generate heat, and the current density will become non-uniform due to a local decrease in power generation efficiency. Furthermore, abnormally high temperatures (−
This will further accelerate the deterioration of the catalyst. Further, in the case of mixed combustion within the manifold, there is a risk that the signal line may be damaged, making it impossible to monitor the operating status of the fuel cell stack.

For this reason, in the past, a sealing material was used between the peripheral part of the end of the electrode 2 parallel to the direction in which the gas flows and the separator 3 (using a high-temperature-resistant and chemical-resistant dispersion medium such as eufluorinated oil). When applied, the laminated surface of the edge portion is sealed.

By using these sealing materials, the sealing performance at the initial stage of operation becomes good, but the sealing performance deteriorates as the operating time passes. This is thought to be because the dispersion medium of the sealing material evaporates during cell operation, causing cracks in the sealing material f2.

[Purpose of the Invention] The present invention was made to solve the above-mentioned problems, and its purpose is to improve the gas sealing property between the separator and the peripheral part of the end parallel to the direction in which the gas flows of the electrode. To provide a fuel cell which is highly safe and reliable by improving heat generation and characteristic deterioration due to the mixture of fuel gas and oxidant gas, and furthermore, by providing a fuel cell in which the sealing property does not deteriorate over a long period of time. It is in.

"Summary of the Invention" In order to achieve the above object, the present invention has a battery operating temperature (20
A sealing material made of an electrolyte-resistant fine powder using phosphoric acid as a dispersion medium, which is stable at about 0°C), is placed in the fuel cell stack L: the direction in which the electrode gas flows: C: the parallel ends. It is characterized by filling the space between the laminated surfaces of the peripheral part and the separator and removing the gap that occurs between the electrode edge part and the separator.

[Embodiment of the Invention] An embodiment of the present invention will be described with reference to the drawings. 1st
Components that are the same as those of the fuel cell according to the present invention shown in FIG. A sealing material 4 is filled between the periphery of the end parallel to the flow direction (Y) and the laminated surface of the separator 3.

An example of the method for producing a sealing material according to the present invention will be described below.
4-John (Mikata Fluorochemicals.

30J) Add 1 part by weight of 105 tyric acid to 2 parts by weight and stir. At this time, the container needs to be cooled because it generates heat. After that, silicon carbide (S), which is a fine powder with electrolyte resistance, is
Add IM part of iC) and stir. In addition to the above-mentioned SIC, as the electrolyte-resistant fine powder, tungsten carbide, silicon nitride, zirconium oxide, tantalum pentoxide, zirconium phosphate, silicon phosphate, etc., or mixtures thereof are preferable. After that, put it in a drying oven at 150℃2.
Concentrate phosphoric acid by holding at 200°C for 3 hours. Through the above-described operation C, it is possible to obtain a sealing material having an appropriate hardness as a sealing material.

Fuel cell stack 1 constructed by stacking a plurality of unit cells according to the present invention thus constructed: In this case, electrode with lip 2
It is possible to absorb the irregularities existing around the edges of the separator 3 or on the surface of the separator 3, to bring the edges and the separator 3 into close contact with each other, and to remove the gap that occurs between them, thereby increasing the airtightness therebetween.

Therefore, it is possible to eliminate the above-mentioned gas leak and prevent mixing of the fuel gas flow B and the oxidant gas flow C, and solve the problems of heat generation and deterioration of cell characteristics in the fuel cell stack based on this. Therefore, a fuel cell with high safety and reliability can be obtained.

especially. A feature of the sealing material of the present invention is that phosphoric acid is used as a dispersion medium. By using phosphoric acid, stable sealing performance can be maintained for a long time.

The following (-1) shows the results of a leak test of the conventional fuel cell stack and the fuel cell stack of this example. One end (gas outlet) on one side of the ribbed electrode in one unit cell is sealed, and the other end is sealed. (Gas population) The results of comparing the gas sealing properties evaluated by pressurizing with helium gas are shown below.
Figure 42 is shown. In FIG.

A is a battery that is directly laminated without filling a sealant between the electrode end periphery and the separator, B is a battery that is filled with a sealant that uses fluorine oil as a dispersion medium, and C is a battery that is filled with a sealant of the present invention. These are test results from the initial stage of battery operation. What? A,
Both B are conventional examples. D.

E has 5 batteries of B and C, respectively. These are the test results after driving for ooo hours.

As is clear from FIG. 2, batteries that do not use a sealant have large leaks from the beginning of operation. In addition, even with a battery using a sealing material, the sealing performance of battery B using a conventional sealing material deteriorated significantly as shown in battery D after approximately 100 hours of operation.
After 00 hours of operation, the dispersion medium in the sealing material of the cell had evaporated and turned into powder. On the other hand, battery C using the sealing material of the present invention had good sealing performance and was operated at 5,000 hours 1) 41 or more t.
As in case E, almost no deterioration in sealing performance was observed after the test.

There was no deterioration in the sealing material of the cell after 5,000 hours of operation.

In the above example, the case of a ribbed electrode type fuel cell was described, but it can also be applied to prevent leakage between the cell and the separator in a bipolar type fuel cell C- using a grooved separator. .

"Effects of the Invention" As explained above, according to the present invention (-) the direction in which the gas of the electrode flows;
''-, the structure is filled with a sealing material containing phosphoric acid as a dispersion medium.From the above, the gas sealing property between the electrode edge part and the separator is improved, and the mixture of fuel gas and oxidizing gas is improved. By using a sealing material that uses phosphoric acid as a dispersion medium, there is no deterioration of the sealing material due to evaporation of the dispersion medium. , it is possible to obtain a fuel cell with good sealing properties of the laminated surfaces for a long time.

[Brief explanation of drawings]

Fig. 1 is a side view showing one embodiment of the present invention, Fig. 2m2 is a characteristic diagram for understanding and clarifying the effects of the same embodiment, and Fig. 3 is a side view showing an embodiment of the present invention.
The figure is a vertical cross-sectional perspective view showing an example of the configuration of a fuel cell, and FIG. 4 is a side view showing a conventional unit cell. 1... Matrix layer 2... Ribbed electrode 3...
Separator 4... Sealing material according to the present invention (Fig. 1 △PCatrn) Fig. 2 Fig. 3

Claims (4)

[Claims] (1) A unit cell consisting of a pair of electrodes sandwiching a matrix impregnated with an electrolyte, which outputs electrical energy under conditions in which fuel gas flows through one electrode and oxidant gas flows through the other electrode. In a fuel cell configured by laminating a plurality of the above with a separator in between, a sealing material containing phosphoric acid as a dispersion medium is filled between the separator and the peripheral part of the end parallel to the direction in which the gas flows of the electrode. A fuel cell characterized by: (2) The fuel cell according to claim 1, wherein the sealing material is a mixture of fluoropolymer fine particles and electrolyte-resistant fine powder dispersed in phosphoric acid. (3) The fine particles of the fluoropolymer are polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE), etc.
), fluorinated alkoxyethylene (PFA), fluorinated ethylene propylene ether (EPE), and tetrafluorinated ethylene hexafluorinated propylene copolymer resin (FEP), or a mixed resin thereof. A fuel cell according to claim 2. (4) The electrolyte-resistant fine powder is composed of one type of powder of silicon carbide, tungsten carbide, silicon nitride, zirconium oxide, tantalum pentoxide, zirconium phosphate, silicon phosphate, or a mixed fine powder of these. A fuel cell according to claim 2, characterized in that: