JPS58112268A - Fuel cell - Google Patents

Abstract

PURPOSE:To obtain a fuel cell which contains electrolyte having a high temperature and a high concentration, and which has a long life by using as a sealing agent either a fluorine-rubber-system adhesive or a mixture consisting of said adhesive and a specific extending agent. CONSTITUTION:A fluorine-system rubber adhesive is used as a sealing agent applied to the corners and the peripheries of a stacked body consisting of unit cells and interconnectors. In using such an adhesive, a solution usually containing 30- 60wt% of a fluorine-rubber-system adhesive is applied to joined parts such as the corners and the peripheries of the stacked body, and the adhesive coats are changed into rubber-like form by vaporizing the solvent at room temperature or under a heated condition. When it is desired that the adhesive is applied in a thick layer, the adhesive is applied several times, the solvent is evaporated every time of the application of the adhesive, and such a process is carried out repeatedly. As a fluorine resin, polyfluoroethylene, polyfluoroethylene propylene, polyphlorofluoroethylene or the like is employed. As an extending electrolyte resistance and, especially, a high phosphoric-acid resistance is desired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a novel fuel cell, and more particularly to a fuel cell in which the inner and surrounding areas are well sealed with an airtight sealing material.

[Technical background of the invention]

As is well known, fuel cells use hydrogen, carbon oxide.

A fuel electrode, which is a negative electrode that uses fuel such as hydrocarbon as an active material,
These fuel cells are composed of an oxidizer electrode, which is a positive electrode, using oxygen or air as an active material, and an electrolyte, such as caustic potash or phosphoric acid. Depending on the type, these fuel cells operate at room temperature or high temperature.

For example, a fuel cell that uses phosphoric acid as an electrolyte and operates at a high temperature of 0.degree. C. to 00.degree. C. is normally constructed as shown in FIG. In this figure, (1) shows a unit cell consisting of a fuel electrode, an electrolyte, and an oxidizer electrode as described above, and this unit cell 1 is stacked alternately with interconnectors mainly composed of graphite etc. . This interconnector has # processing on both sides to facilitate the supply of reaction gas, and this interconnector has cooling pipes embedded in seven out of every several pipes, through which the cooling medium circulates. It has been replaced by Connectada.

As shown in Fig. 2, a manifold base is installed around the laminate j formed in this manner to enable supply and discharge of the reaction gas and to separate the fuel gas and oxidant gas. It makes it possible.

And the above-mentioned cell battery! It is unavoidable that errors occur in the dimensions of elements such as interconnectors and dams, and it is also unavoidable that errors occur when stacking these elements. As a result, as shown in FIG. This results in a step being created around the area.

A gasket is attached to the manifold, but with only this gasket, the airtightness between the laminate and the manifold is insufficient due to the above-mentioned level difference.Therefore, conventionally, an airtight and elastic sealing rubber is used between the gasket and the laminate. Further airtightness was achieved by applying adhesive 7.

[Problems with background technology]

In a fuel cell using phosphoric acid as an electrolyte, it is 95 to 100.
Since the sealing rubber adhesive is operated at a high temperature of 0 to 200'C using E4 phosphoric acid, the sealing rubber adhesive must withstand high temperatures with the electrolyte, i.e., phosphoric acid, and has such electrolyte resistance and heat resistance. In addition, airtightness, flexibility, and adhesiveness are required.

Conventionally, silicone rubber and nitrile rubber-based adhesives have been mainly used as adhesives of this type.
As a result of carrying out the electromotive reaction at a high temperature (110° C. or more) (longer than 00 hours), the following problems were found.

l] When a silicone rubber adhesive was used, ashing and chipping of the adhesive was observed at the portions that came into contact with the unit cell, and the sealing performance was reduced. In other words, silicone rubber adhesive is heat resistant,
It was found that although it has excellent rubber elasticity, it does not have excellent phosphoric acid resistance, that is, electrolyte resistance.

J) When using a nitrile rubber adhesive, the manifold was loosened and a decrease in sealing performance was observed. This is thought to be due to the loss of rubber elasticity and plastic deformation due to exposure to a high temperature atmosphere, which caused the manifold to tighten due to a decrease in surface pressure.

However, the silicone rubber adhesives and nitrile rubber adhesives that have been used in the past have insufficient phosphoric acid resistance and heat resistance, and are therefore not suitable as sealing materials for fuel cells that use phosphoric acid as an electrolyte and operate at high temperatures. could not be used properly.

[Purpose of the invention]

Thus, the present invention solves the above-mentioned problems and provides a fuel in which the corners and surroundings of the laminate are sealed with a sealing material that has excellent electrolyte resistance, heat resistance, airtightness, flexibility, and adhesiveness. The purpose is to provide batteries.

[Summary of the invention]

According to the research and experiments of the present inventor, it was found that a fluororubber adhesive or a mixture of a fluororubber adhesive and a phosphoric acid-resistant and heat-resistant filler is suitable as the sealing material. .

Therefore, the present invention provides a fuel cell in which a unit cell having a fuel electrode, an electrolyte, and an oxidizer electrode, and an interconnector are alternately stacked to form a laminate, and a manifold is attached around the laminate. The present invention provides a fuel cell characterized in that the corners and periphery of the fuel cell are sealed with a fluorine-based rubber adhesive or a mixture of the adhesive and an electrolyte-resistant and heat-resistant filler.

To further explain the present invention, fluororesins such as polyfluorinated ethylene, polyfluoroethylene propylene, and polyfluorofluoroethylene have been well known as materials with excellent thermal and chemical properties such as heat resistance and chemical resistance. However, in recent years, this type of rubber adhesive has been developed and is used as a thin coating material for areas that require heat resistance and chemical resistance. It is used as a sealing material around the corners and surroundings of the stack of unit cells and interconnectors.When using this, any electrolyte can be used for fuel cells that operate at any operating temperature, especially when phosphoric acid is used as the electrolyte and the temperature between 110 and 100℃ is used. Even after long-term use in fuel cells that operate at high temperatures, the sealing material does not show any deterioration in performance such as ashing or embrittlement, and therefore has excellent heat resistance, electrolysis resistance, airtightness, flexibility, and adhesive properties. It turned out to be excellent.

In use, a fluororubber adhesive diluted with X) to 60% by weight of a solvent is usually applied to the adhesive area of the concave corner circumference of the laminate, and the solvent is removed at room temperature or in a heated state. Evaporate and turn into rubber.

- The thickness of the coating film obtained by one application is at most a, / - 0, con, so if you want to apply a thick coating, you can apply it many times, evaporate the solvent each time, and repeat this process. is necessary.

When such a thick coating film is used as a jacket, a mixture of a fluororubber adhesive and an extender as described above is used in the present invention. This extender has excellent heat resistance, electrolyte resistance, and especially phosphoric acid resistance, such as silicon carbide (8
Powders of various inorganic or organic substances such as 1C), zirconium oxide, tantalum oxide, and polytetrafluoroethylene are used. This filler can be used within a range that does not cause loss of the rubber elasticity of the fluororubber, such as fluororubber solid content/'! It is used by adding 1 part by weight of l-da to 1 part of m and kneading it. With such a mixture of fluororubber and extender, a thick coating film can be obtained by applying it two or three times. The coating film of this mixture also has heat resistance, electrolysis resistance, and airtightness without ashing, embrittlement, etc. even when used for a long time in the operating environment as a sealing material for fuel cell stacks. It has excellent flexibility and adhesive properties.

Thus, the present invention includes not only cases in which sealing is performed using only fluororubber adhesive-j, but also cases in which sealing is performed using a mixture of a fluororubber adhesive and a heat-resistant and electrolyte-resistant extender.

The results of a comparative test on the sealing material used in the present invention and conventionally used sealing materials are shown below.

(Sample 1) Three countries and four sides with graphite as the main component, thickness! Convex width for intestinal interconnector! A groove with a concave width of 1 cm and a depth of 1 cm was made, and a fluororubber adhesive (room-temperature curing fluororubber manufactured by Nissan Riko Co., Ltd.) was applied and dried many times until the groove became completely invisible.

(Sample J) (Sample/) Silicon carbide 1 was applied to the same fluororubber adhesive and weight part to the same groove-shaped interconnect as in the fabrication.
The mixture obtained by adding 0 parts by weight and kneading (Sample 1)
It was applied in the same way. In this sample, a coating film of the desired thickness was obtained with one application.

(Sample J) For comparison, the same amount of silicone rubber adhesive (manufactured by Toshiba Silicone Corporation) was applied to the same interconnector as the sample /.
Adhesive sealing material: (T!ilc, 77t7R?v) was applied to prepare sample 3.

The above samples 7 to J were immersed in a S tyric acid solution at ivo°C, and the temperature was 100, -〇〇, ! ? After 00 hours, each sample was observed for swelling, peeling, and dissolution. The results are shown in the table below.

1: Almost no change +: Slightly observed 10: Clearly observed +++: Very clearly observed As is clear from this table, in the sample of the present invention, high temperature (7
ioo to phosphoric acid at high concentration (95 s).

No change in properties was observed even after exposure for 200 and 100 hours. On the other hand, in the case of the silicone adhesive used for comparison, no change was observed after 100 hours, but aO
A change was observed at O hours, and a clear change was observed at 300 hours. Although not shown in this table, almost no change was observed in the rubber elasticity of the samples of the present invention.

Thus, in accordance with the fifth aspect of the present invention, a fluororubber adhesive is applied to the corners and surroundings of the laminate formed by stacking unit cells and interconnectors alternately, or a heat-resistant and electrolyte-resistant adhesive is applied to this adhesive. When a mixture with an extender is used as a sealing material, a long-life fuel cell can be obtained with high temperature and high concentration electrolyte, and the present invention provides a truly effective fuel cell of this type. It is.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the stacked body of the fuel cell according to the present invention disassembled and towed, Fig. 2 is an explanatory diagram showing the structure of the same type unit and a manifold, and Fig. 3 is an enlarged view of the stacked state of the same stacked body. FIG. l...Battery, Ko, 4! ...interconnector, J
-・Pipe! ...Laminated body, 6... Manifold, 7
···glue. Applicant's agent Kiyoshi Inomata Figure 1

Claims (1)

[Claims] In a fuel cell in which a unit cell having a fuel electrode, an electrolyte, an oxidizer electrode, and an interconnector are alternately stacked to form a laminate, and a manifold is attached around the laminate, the corners and surroundings of the laminate are covered with fluororubber. 1. A fuel cell, characterized in that the fuel cell is sealed with an adhesive, or a mixture of the adhesive and an electrolyte-resistant and heat-resistant filler.