JPS61126771A - Fuel cell - Google Patents

Abstract

PURPOSE:To prevent electrode damage, through making the thickness of an electrolyte layer uniform so as to give uniform stress to an electrode surface, by laying such fiber as asbestos fiber, etc., with specified thickness having excellent anti-electrolytic properties in the electrolyte layer as its supporting material. CONSTITUTION:The rod shaped asbestos fiber 30 with specified thickness, impregnated with phosphoric acid, is arranged on the cathode catalyst 13a, making it so as to have some angles at an angle of 0-90 deg. corresponding to grooves 15a of a cathode electrode 12a, and placing it in parallel to each other with some spacing. And then, matrix is applied to the surface uniformly so as to have the same thickness as the fiber 30 has, and the other anode electrode, which has the same structure as the cath ode electrode has, is set on the cathode electrode as its flat surface is in contact with the matrix, and that is attached by pressure. Thereby, when they are attached by pressure, the thickness of matrix may be able to hole uniformly by thickness equiva lent to the fiber 30 has, and the surface pressure is held regularly, and further, since the fiber 30 is arranged so as to have some angles corresponding to grooves of the electrode, the concentrated stress to thin shaped portion, where the grooves are carved, becomes smaller.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a fuel cell with an improved electrolyte layer structure.

[Technical background of the invention and its problems]

A fuel cell (hereinafter abbreviated as battery) is a device that directly converts chemical energy contained in fuel into electrical energy. Batteries usually have a pair of porous electrodes with an electrolyte layer in between, 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. let The structure is such that electrical energy is extracted from between the two electrodes by utilizing the electrochemical reaction that occurs between the two electrodes at this time.

Although there are molten salts, alkaline solutions, acid solutions, etc. as electrolytes, the principle of a typical battery using phosphoric acid as an electrolyte will be explained. In the second stage, the electrolyte layer 1 is a fibrous sheet or mineral powder impregnated with phosphoric acid. An anode electrode 2 and a cathode electrode 2& are provided on both sides of this electrolyte layer 1. Both electrodes 2 and 2a are formed from porous members made of carbonaceous material. Further, a platinum catalyst is usually coated on the electrolyte layer 1 side of each of these electrodes 2.21. The anode electrode 2 and the cathode electrode 2a are provided with a fuel gas chamber 3 through which the fuel gas flows and an oxidant gas chamber 3a through which the oxidant gas flows, respectively, on the side opposite to the electrolyte layer 1 side. Generally, in a phosphoric acid fuel cell, the fuel gas is hydrogen gas, and the oxidant gas is air.

The operation of such a phosphoric acid battery will be explained. Hydrogen gas in the gas that has flowed into the fuel gas chamber 3 diffuses into the cavity of the porous anode electrode 2 and reaches the catalyst. Then, the hydrogen gas is dissociated into hydrogen ions and electrons by the action of the catalyst.

That is, the reaction formula is H2→2H''+2e.

Next, this hydrogen ion needle enters the electrolyte layer 1 and migrates toward the cathode electrode 2a due to concentration diffusion. On the other hand, electrons flow into the anode electrode 2, and this anode electrode 2
is negatively charged.

In the cathode electrode 21, hydrogen ions H+ migrating from the anode electrode 2 and oxygen 0□ in the air that has flowed into the oxidant gas chamber 3a diffuse into the void space of the porous cathode electrode 2&. The following reaction occurs on the catalyst surface between the diffused oxygen 02, the electrons and hydrogen ions H+ that have returned to the battery from the anode electrode 2 through the external electrical load.

That is, 4 H" + 4 e + 02 → 2 H
2O thus completing the loop as an electrical circuit, the hydrogen and oxygen provide electrical energy to the external electrical load and become water on the cathode electrode 2&. In other words, the energy used when hydrogen and oxygen react to create water is given to the electrical load. And a part of this electrical energy is transferred to the electrolyte layer 1.
A voltage drop occurs inside the battery as internal resistance and near the catalyst due to concentration polarization, and is consumed internally as battery loss. Many improvements have been made to reduce the voltage drop inside the battery, that is, to increase efficiency and to increase the output per unit area of the electrode.

Since the '-voltage of one battery is 0.6 V to O.SV, which is too small to be used as a power supply device, a large number of unit batteries 10 are stacked. Layering in this way has two functions: a groove for supplying fuel or oxidant gas to the entire surface of the electrode, and conductivity with low resistance so as to serve as a connection body to create an electrical series circuit. Intermediate connecting members, so-called interconnectors, made of, for example, grooved graphite plates are alternately stacked with the unit batteries 10.

FIG. 3 shows the structure of a battery in which unit batteries 10 are stacked. Electrodes 12 and 12a corresponding to an anode electrode and a cathode electrode are provided on both sides of an electrolyte layer impregnated with an electrolyte, that is, a matrix 11, respectively. Catalyst layers 13 and 13a made of platinum catalyst are formed on the sides of these electrodes 12 and 12m in contact with the matrix 11, respectively.

Then, grooves 15, 15* and lips 16, 16h are formed on the opposite side of the catalyst layers 13 and 13a of the electrodes 12 and 12h.
At the same time, the groove 15 and lip 16 of the electrode 12
The groove 151 and the lip 16& are formed so as to be perpendicular to each other. By stacking a selected plurality of unit batteries 10 formed in this way with a separator 17 in between, abutting a current collector plate 18 at the end, and tightening and fixing the whole unit through a tightening member (not shown). A battery stack 19 is configured. Note that the separator 17 is formed of a sheet made of carbon or graphite material, and is provided to prevent the respective gas flows between the two adjacent electrodes 12.12a from mixing.

As shown in FIG. 4, this battery stack 19 includes a manifold 21 that supplies fuel gas, a manifold 21E that collects fuel exhaust gas, a manifold 23 that supplies oxidizing gas, and a manifold 23 that collects and discharges oxidizing gas. Manifold 2
3E are attached via gaskets (not shown). This socket plays the dual role of electrical insulation and airtightness. Further, the manifold 2 is provided with a pipe 22 for supplying fuel gas, and the manifold 21E is provided with a pipe 22E for discharging fuel exhaust gas. Similarly, the manifolds 23 and 23E are provided with pipes 24 and 24E for supplying and discharging the oxidant gas, respectively.

In the battery 25 formed in this way, fuel gas flows into the manifold 21 from the vias '' and ?2.

Next, the fuel gas divided into a large number of grooves 17 flows into each unit cell 1.
0 electrode 12. Components other than fuel flowing in with the fuel gas and unreacted fuel, i.e., surplus fuel, become fuel exhaust gas and are transferred to the manifold 21'B and the exhaust gas 22.
It is discharged via Y.

The same applies to the oxidizing gas. The fuel gas and oxidant gas thus supplied are fed to the porous electrode 12.12.
* Diffuses inside and reaches matrix 11. It is then converted into electrical energy using the principles described above.

The voltage of this battery 25 is the sum of the voltages of the unit batteries 10.

Further, the current flows through each unit battery 10 in series and is taken out to the outside through the current collector plate.

By the way, the matrix 11 is generally made by impregnating an electrolyte holding agent with phosphoric acid, which is an electrolyte. The electrolyte retaining agent here is a fine powder that has excellent phosphoric acid resistance and retains phosphoric acid, and is currently made of silicon carbide (Si).
C) is often used. Further, the matrix 11 is generally in the form of a paste, and is applied onto one of the electrodes 121. In this case, it is applied over the entire surface of the electrode while maintaining a uniform thickness, and then combined with the other electrode 12. Furthermore, in order to improve the contact state, crimping is performed using a press, but in this case, if the crimping force is too weak, it will result in poor contact, and if the crimping force is too strong, it will cause uneven stress on the electrode surface, resulting in electrode 12.12. There are problems such as damage to *.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned problems, and its purpose is to make the electrolyte layer uniform in thickness, uniformize the stress on the electrode surface, and eliminate damage to the electrode. Our goal is to provide long-life fuel cells.

[Summary of the invention]

In order to achieve the above object, in the present invention, a pair of porous electrodes are arranged with an electrolyte layer in between, and a fuel gas is brought into contact with the back surface of one electrode, and an oxidizing gas is brought into contact with the back surface of the other electrode. In a fuel cell that extracts electrical energy from between the pair of electrodes using the electrochemical reaction that occurs, asbestos fibers of a predetermined thickness with excellent electrolyte resistance are used as a support for the electrolyte layer. It is characterized by having fibers such as these buried therein.

[Embodiments of the invention]

An embodiment of the present invention shown in the drawings will be described below.

In other words, in this embodiment, rod-shaped asbestos fibers having a predetermined thickness and having excellent phosphoric acid resistance are buried in parallel at certain intervals as supports in the electrolyte layer matrix in the fuel cell described above. It is something to do. Then, such a cell battery formed by sandwiching the IJ Fuchs between a pair of porous electrodes is obtained as follows.

That is, in FIG. 1, the cathode electrode 12 & has a flat surface formed on one side, and a surface formed with grooves 151 for reactant gas circulation on the opposite surface. Furthermore, a cathode catalyst 13& for promoting electrochemical reactions is applied on the flat surface. Next, on the cathode catalyst 13a, a rod-shaped asbestos fiber 30 of a predetermined thickness, which has excellent phosphoric acid resistance and has been impregnated with phosphoric acid as an electrolyte, is placed on the cathode catalyst 13a. θ~90° (preferably 45°) with respect to the direction of flow
They are arranged parallel to each other at a certain angle, each at a certain interval. Thereafter, a matrix is uniformly applied onto the asbestos fibers 30 placed on the cathode catalyst 13a so as to have the same thickness as the fibers 30. Thereafter, another anode electrode having the same structure as the cathode electrode 12a is placed on top of the cathode electrode 12a so that its flat surface is in contact with the matrix, and the anode electrode is pressed to obtain a P unit cell. Note that the asbestos fibers 30 used above have a certain thickness, that is, a thickness ranging from several tens of micrometers to several nanometers.

In the unit battery thus obtained, the thickness of the matrix is ensured to be uniform by the thickness of the asbestos fibers 30 during compression bonding.

Therefore, a unit battery can be obtained without causing poor contact between the electrode and the matrix as described above, and while minimizing the protrusion of the matrix. In addition, the thickness of the matrix becomes uniform and the surface pressure is kept constant.
In addition, since the asbestos fibers 30 are arranged at a certain angle with respect to the grooves of the electrode, concentrated stress on the thin part of the electrode groove, which is the groove, is reduced, and damage to the electrode due to crimping is reduced. It is possible to reliably prevent this and extend the lifespan.

In addition, in the above example, asbestos fiber was used as the fiber,
Furthermore, although phosphoric acid was used as the solute, other materials such as molten carbonate may be used as the electrolyte, and fibers with excellent electrolyte resistance may be used.

〔Effect of the invention〕

As explained above, according to the present invention, fibers having a predetermined thickness and excellent electrolyte resistance are embedded in the electrolyte layer as its support, thereby making the thickness of the electrolyte layer uniform and reducing stress on the electrode surface. It is possible to provide an extremely reliable and long-life fuel cell in which damage to the electrodes can be eliminated with uniformity.

[Brief Description of the Drawings] Figure 1 is a perspective view showing an embodiment of the present invention, Figure 2 is an explanatory diagram showing the operating principle of a cynic acid fuel cell, and Figure 3 is a conventional fuel cell unit. Perspective view showing a state in which batteries are stacked, No. 4
This figure is a perspective view showing a state in which a manifold is attached to the battery stack of FIG. 3. 1... Electrolyte layer, 2.12... Anode electrode, 2a
. 12h...Cathode gutter, 3...Fuel gas pump, 3&
...oxidant gas chamber, 10... unit battery, 1 no..
Matrix, 13... Anode catalyst, 13 &...
Cathode side groove, J5... Anode side groove, 15a...
Cathode gutter, 16.161L... lip, 17...
Catalyst, 18... Separator, 19... Battery laminate,
21.21E, 23... Manifold, 22, 22E
, 24.24E...Nonoib, 25...Battery, 30
···fiber. Applicant's agent Patent attorney Takehiko Suzue ￥711

Claims (4)

[Claims] (1) Electrochemical reactions occur by arranging a pair of porous electrodes with an electrolyte layer in between, and bringing fuel gas into contact with the back surface of one electrode and contacting oxidant gas with the back surface of the other electrode. The fuel cell is characterized in that a fiber of a predetermined thickness with excellent electrolyte resistance is embedded in the electrolyte layer as a support for the electrolyte layer. Fuel cell. (2) The fuel cell according to claim (1), characterized in that asbestos fibers are used as the fibers. (3) The fuel cell according to claim (1), wherein the fibers are arranged in parallel at certain intervals. (4) The fiber is 45 mm in direction of gas flow in the electrode.
The fuel cell according to claim 3, wherein the fuel cell is arranged at an angle of .degree.