JPS58112269A - Fuel cell - Google Patents

Abstract

PURPOSE:To make no changes in the characteristic to be caused even when a fuel cell is used under an operational condition, in which electrolyte has a high temperature and a high concentration, for a long time by sealing the peripheries and the corners of a stacked body by means of a three-layered adhesive consisting of the first and the third fluorine-rubber-system adhesive layers and the second silicone-rubber-system adhesive layer. CONSTITUTION:After a fluorine-rubber-system adhesive usually diluted in a solvent is applied to joined parts such as the corners and the peripheries of the stacked body, the adhesive coats are changed into rubber-like form by vaporizing the solvent at room temperature or under a heated condition. On the other hand, silicone rubber can be easily formed in a thick layer since it is not an adhesive dissolved into a solvent and it causes almost no voluminal shrinkage during the time when it is changed into rubber-like form. The thickness of the first and the third fluorine-rubber-system adhesive layers should be around 0.2- 0.3mm., and the thickness of the second silicone-rubber-system adhesive layer should be around 1.5-2.0mm.. The desired thickness of each of these layers can be easily achieved by applying the adhesive about two or three times.

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 whose corners and periphery are well sealed with hermetic sealing material.

[Technical background of the invention]

As is well known, a fuel cell consists of a fuel electrode, which is a negative electrode, which uses a fuel such as hydrogen, carbon oxide, or hydrogen sulfide as an active material, an oxidizer electrode, which is a positive electrode, which uses oxygen or air as an active material, and a caustic potash, phosphoric acid, etc. Depending on the type, these fuel cells operate at room temperature or at elevated temperatures.

For example, a fuel cell that uses phosphoric acid as an electrolyte and operates at a high temperature of 190 to 100 DEG C. is normally constructed as shown in FIG. In this figure, a normally square plate-shaped unit cell consisting of an electrolyte and an oxidizer electrode is shown in the fuel 141 (as in the dFi notation). This interconnector 2 has grooves on both sides to facilitate the supply of reaction gas, but one JFi interconnector has a pipe Jt-embedded through which the cooling medium circulates. Many have been replaced with interconnectors with cooling pipes.

A manifold 6 is attached around the stacked body 5 thus formed as shown in FIG.
．． This makes it possible to supply and discharge gas, as well as to separate fuel gas and oxidant gas.

And the above-mentioned cell battery! It is unavoidable that errors occur in the dimensions of elements such as interfunctors and FIers, and it is unavoidable that errors occur when stacking these elements, and as a result, as shown in Fig. 3, This results in the formation of steps at the corners and around the edges.

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. An adhesive was applied to make it even more airtight.

[Problems with background technology]

In fuel cells using phosphoric acid as the electrolyte, De! ~100
% phosphoric acid and operate at high temperatures ranging from 200°C to 200°C, the sealing rubber adhesive must withstand high temperatures with the electrolyte, i.e., phosphoric acid, and must have such electrolyte resistance, heat resistance and and 4. Airtightness: 1: Flexibility and adhesiveness are required.

Conventionally, silicone rubber-based adhesives have been mainly used as this type of adhesive, but fuel cells using such adhesives as sealing materials have been used for long periods of time (more than iooo hours).
As a result of conducting an electromotive reaction at high temperatures (over 110°C), the following problems were discovered: When using a silicone rubber adhesive, the ash of the adhesive is generated at the part that comes into contact with the unit cell. There were some cracks and cracks, and the sealing performance had deteriorated. That is, it has been found that silicone rubber adhesives have excellent heat resistance and rubber elasticity, but do not have excellent phosphoric acid resistance, that is, electrolyte resistance. As described above, conventionally used silicone rubber adhesives have insufficient phosphoric acid resistance and heat resistance69, and therefore cannot be used well as sealing materials for fuel cells that use phosphoric acid as an electrolyte and operate at high temperatures. could not.

[Purpose of the invention]

Thus, the present invention solves the above-mentioned problems and improves electrolyte resistance, -,! The object of the present invention is to provide a fuel cell in which the corners and periphery of the stack are sealed using a rail material with excellent airtightness, flexibility, and adhesiveness.

[Summary of the invention]

According to the research and experiments of the present inventor, the periphery and corners of the laminate are formed by a composite adhesive layer in which the first and third layers are a fluororubber adhesive and the second layer is a silicone rubber adhesive. It has been found that by sealing K, the above object is achieved.

Thus, the present invention provides a fuel cell in which unit cells having a fuel electrode, an electrolyte, and an oxidizer electrode are stacked via interconnectors to form a laminate, and a manifold is attached around the laminate. The fuel cell is characterized in that the corners and periphery of the fuel cell are sealed with a composite adhesive layer in which the first and third layers are a fluororubber adhesive and the second layer is a silicone rubber adhesive. be.

To further explain the present invention, fluororesins such as polyfluoroethylene, polyfluoroethylene propylene, and polychlorofluoroethylene 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 for the corners and surroundings of the stack of cell and interconnector as explained earlier, and when using this, any electrolyte,
Fuel cells that operate at any operating temperature, especially fuel cells that use phosphoric acid as an electrolyte and operate at high temperatures of 1 to 2□θ°C, may experience deterioration in performance such as ashing and embrittlement of sealing materials even after long-term use. Therefore, it was found that the material has excellent heat resistance, electrolytic resistance, airtightness, flexibility, and adhesiveness.

In use, a fluororubber adhesive, which is usually diluted with a solvent, is applied to the adhesive areas such as the corners and periphery of the laminate, and the solvent is evaporated at room temperature or under heating to form a rubber. However, the thickness of the coating film seen after - times of coating is at most Q, / , Q, , lII+, so if you want to coat it thickly, you can coat it many times and evaporate the varying solvent each time. It is necessary to repeat.

On the other hand, as mentioned above, silicone rubber is attacked by phosphoric acid at a high concentration of high-1 and has poor electrolyte resistance, but it has excellent heat resistance and rubber elasticity KFi. Furthermore, since this rubber is not a solvent-soluble type adhesive, there is almost no volumetric shrinkage during rubberization, making it easy to form a thick layer.

Thus, in the present invention, taking advantage of the advantages of both fluororubber adhesives and silicone rubber adhesives, a fluororubber adhesive with high heat resistance and electrolyte resistance is used on the outer surface that contacts the electrolyte, and the central part Although it has poor electrolyte resistance, silicone rubber adhesive is used because it has high heat resistance and rubber elasticity and can easily form a thick layer. When sealed with a three-layer composite adhesive layer that uses a silicone rubber adhesive for the second layer and a fluoro rubber adhesive for the third layer, it maintains heat resistance and electrolyte resistance, and has excellent rubber elasticity. Therefore, performance deterioration such as ashing and embrittlement occurs even when used for long periods of time under harsh operating conditions such as operating at high temperatures and using highly concentrated electrolytes. Therefore, it can be used successfully without any problems.

The thickness of each of the first to third layers is approximately 0.1 to 0.3 mm for the fluorinated rubber adhesive in the first and third layers, and the silicone rubber adhesive in the second layer covered by them. The thickness of the adhesive varies by about /j to 0, and the desired thickness can be easily obtained by coating each layer about 1 to J times. If there is a step difference, it is necessary to cover at least the edges of the unit cell with a fluororubber adhesive.

The following are the results of a comparative test in which the composite adhesive of the present invention and a silicone rubber adhesive were maintained for a long time under the same operating conditions as the fuel cell as described above.

(Test example) An interconnector whose main component is graphite and has four sides and a thickness of J■, has a convex width of Jllll, a concave width of 3wm, and has a deep grooved T- groove, and then a fluororubber based as the first layer. Apply adhesive (room-temperature-curing fluororubber manufactured by Nissan Riko Co., Ltd.) twice to form a coating film with a thickness of θ, 311I+. As a second layer, apply silicone rubber adhesive (fluoro rubber that cures at room temperature) until the hollows in the grooves are completely invisible. Toshiba Silicone Corporation Seal-f
h Adhesive material: ``IA J?ORTV'' was applied, and then a fluororubber adhesive was applied on top of it twice in the same manner as before to obtain a coating film of the same thickness.

Such a sample (sample 1) was immersed in a phosphoric acid aqueous solution of f:ldeo"c, 9317 and 100, 200, !t00
The presence or absence of swelling, peeling, and dissolution of the ridge sample was observed over time. For comparison, a similar test was also conducted on Sample 2, which was coated with a silicone rubber adhesive to the same thickness.

The results of the test are shown in Table 1 below.

Table I -: Almost no change+: Only K111 observed ++: Clearly observed +10+: Extremely Kf-j, 1m clearly observed! /
As is clear, the samples of the present invention were exposed to high temperatures of 161) lF.
No swelling, peeling, or dissolution was observed, and no change in properties was observed even after exposure to electrolyte D & cioo, wo, zoo for hours. On the other hand, in the case of the comparative sample, there was no change at 100 hours, but a slight change was observed at 200 hours, and a clear change was observed at the SOO time. Although not shown in the table, almost no change was observed in the rubber elasticity of the samples of the present invention. As described above, the composite adhesive according to the present invention can provide good sealing even under such harsh operating environments, but with silicone rubber adhesives, significant changes over time are observed and it is clear that good sealing cannot be achieved. [Example of the Invention] Next, an example will be given in which an actual fuel cell was implemented and tested.

(Example) A 1,051-square-foot structure with a fuel electrode using hydrogen as fuel, an electrolyte using 93% phosphoric acid aqueous solution, and an oxidizer electrode using air as an oxidant.
Thickness 1. The plate-shaped unit cells (1) are stacked together via interconnectors as shown in Figure 1 of the drawing. This interconnector had grooves formed on both sides as in the test example, and a three-layer adhesive was applied in the same manner. One in three interconnectors is equipped with a cooling pipe. In this way, a 10 cm high stack was formed, and around it a 10 erllK height for supplying and discharging fuel and oxidizer.
A manifold with a width of 10 CWIX and a depth of 5 cIn was installed.

The fuel cell formed in this way has a main body temperature of 0 to 0.
The electromotive reaction was carried out at /90°C and 00 mA/cryT per unit area. Fuel, oxidizer: unit time, hydrogen 10j
/mMs, supplied with air xt 7 mm and for 100 hours,
! After the waiting time of 1ooo hours has elapsed, use a hydrogen gas detector to measure the leakage of hydrogen gas from the manifold.

After too much time had elapsed, the manifold was removed and the deterioration of the seal rubber was observed.

Furthermore, as a comparative example, the same silicone rubber adhesive as used in the test example was used as the adhesive, and a fuel cell manufactured in the same manner with the exception of 9 was tested in the same manner. The results of these tests are shown in Table 1 below. Table 1 -: No hydrogen gas detected +: Slight amount of hydrogen gas detected ++: Large amount of hydrogen gas detected As is clear from Table 1, In a fuel cell sealed with a three-layer adhesive as in the invention, no reaction gas leakage was detected even after 100θ hours, and a disassembly investigation showed no ashing or embrittlement in the rubber seal, indicating no deterioration. Not observed.

On the other hand, in a comparative fuel cell sealed with only silicone rubber adhesive, reactive gas leakage was detected over time, and a disassembly investigation revealed that the seal surface had turned to ash and become brittle, making it difficult to use as a sealing material. It was found that the characteristics deteriorated significantly.

As described above, according to the present invention, the periphery and corners of a laminate formed by alternately stacking unit cells and interconnectors are coated with a fluororubber adhesive for the first and third layers, and a silicone rubber adhesive for the second layer. By sealing with a three-layer adhesive layer, there is no change in characteristics even after long-term use under high temperature and high concentration electrolyte operating environment conditions.
It can be used successfully.

Therefore, the present invention can provide four truly effective fuel cells of this type.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an exploded view of a laminate of a phosphorescent battery according to the present invention, FIG. 1 is an explanatory diagram showing the structure of the laminate and a manifold, and FIG. It is an explanatory view enlarged and shown. l...Battery, K, D...Interconnector, J.
・-Vibe! ...Laminated body, 6...w=Holt, 7
...Adhesive・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 A fuel cell characterized in that the first and third layers are sealed with a composite adhesive layer in which a fluororubber adhesive is used and the second layer is a silicone rubber adhesive.