JP3496934B2 - Fuel cell - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel cell, and more particularly to a fuel cell suitable for miniaturization.

[0002]

2. Description of the Related Art As a social trend, it is desired to use fuel cells for OA equipment, audio equipment, wireless equipment and the like. Fuel cells not only have the advantage that they can generate electricity simply by supplying fuel and oxidant, but they also have the advantage that they can generate electricity continuously by exchanging the fuel, so if miniaturization is possible. It can be said that this system is extremely advantageous for operating small equipment such as OA equipment that consumes little power.

A methanol fuel cell using a mixed solution of methanol and water as a liquid fuel will be described as an example. Methanol fuel cells are
A liquid supply type that directly supplies liquid fuel to the battery main body,
It is roughly divided into a vaporization supply type in which liquid fuel is vaporized and then supplied to the cell body. Then, using a liquid fuel as the fuel, the liquid fuel introduced into the cell is disposed between the fuel permeation layer for introducing the liquid fuel into the cell by capillary force and the fuel permeation layer and the fuel electrode. There is also a fuel cell including a fuel vaporization layer for vaporizing and supplying the fuel electrode in the form of a gaseous fuel.

However, even the fuel cell having such a structure has the following problems. In other words, in these fuel cells, carbon dioxide gas is generated due to the cell reaction, but the remaining carbon dioxide gas interferes with the fuel supply and reaction, resulting in a decrease in output level and stable output over a long period of time. There was a problem such as not being able to. In particular, as a result of intensive studies by the present inventors, current is easily concentrated in this terminal attachment portion and a reaction locally progresses, so that gas is locally generated in the vicinity of this terminal, which is caused by this phenomenon. Then, a new problem was found that the power generation efficiency was significantly reduced.

[0005]

In the conventional fuel cell, current tends to concentrate near the output terminal of the external power, and the reaction for generating the electromotive force locally progresses. There is a problem that gas is generated and this phenomenon reduces the power generation efficiency.

The present invention has been made in order to solve the above problems, and provides a fuel cell capable of solving the problem of power generation efficiency deterioration due to gas generation near the output terminal and obtaining a higher output. Is an issue.

[0007]

In order to solve the above-mentioned problems, a fuel cell according to a first aspect of the present invention comprises a fuel electrode, an oxidant electrode arranged facing the fuel electrode and having an oxidant gas intake port,
An electrolyte layer sandwiched between the fuel electrode and the oxidant electrode, an exterior material that exposes the oxidant gas intake port and covers the fuel electrode and the oxidant electrode, and the oxidant electrode exposed from the exterior material. A first external lead terminal electrically connected to the fuel cell, and a second external lead terminal exposed from the outer package and electrically connected to the fuel electrode and having a generated gas discharge hole formed therein. Characterize.

According to a second aspect of the present invention, there is provided the fuel cell according to the first aspect, wherein a liquid / gas separation membrane is formed in the generated gas discharge hole.

According to a third aspect of the present invention, in the fuel cell according to the first aspect, the exterior material is a laminated film containing a resin.

A fuel cell is provided which is provided with a liquid / gas separation membrane at the discharge port to prevent leakage of liquid.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a configuration diagram showing a configuration of a main part of an example of a fuel cell of the present invention. In the figure, 5 is a fuel tank, 11 is a fuel holding layer, 7 is an oxidant gas diffusion layer, 10 is a fuel electrode, 9 is a solid electrolyte membrane, 8 is an oxidant electrode, 6 is an oxidant gas intake port, and 4 is A generated gas discharge port, 1 is an exterior material for accommodating a fuel cell for the purpose of protecting an electromotive portion, 2 is a fuel electrode lead, 3 is a liquid / gas separation membrane, and 12 is an oxidant electrode lead.

The mechanism of power generation will be described using FIG. 1 as an example. First, liquid fuel flows from the fuel tank 5 to the fuel holding layer 1
1 is supplied. As a method of supplying the liquid fuel, as shown in FIG. 1, any of a method of drawing from the fuel tank 5 to the fuel holding layer 11 by using a capillary force and a method of directly supplying the fuel to the fuel electrode are possible. For the fuel retaining layer 11, any material such as a porous organic material such as polyester or polyolefin, a porous inorganic material such as carbon or alumina, or a mesh-like metal porous body is acceptable. The fuel supplied to the fuel holding layer 11 is diffused and supplied at the fuel electrode 10. The fuel can be diffused even if a certain kind of material is physically present (a porous material similar to the above-mentioned fuel permeation material), or even if the fuel permeation material is simply a perforated space. Is. The fuel supplied to the fuel electrode 10 is oxidized by a fuel cell catalyst represented by platinum or its alloy supported on carbon particles formed of carbon particles inside the fuel electrode, and protons are taken out. Electrons are extracted during this fuel oxidation. The extracted protons are transmitted to the oxidant electrode 8 side through the electrolyte 9 provided adjacently. On the other hand, on the oxidant electrode 8 side, the reaction of the protons carried through the electrolyte 9 with the electrons flowing through the external circuit and the oxidant gas (oxygen, air, etc.) to become water is the platinum inside the oxidant electrode. It progresses on a catalyst represented by. The electrons taken out in the course of the reaction as described above flow through the external circuit to generate power and drive the external load.

Next, specific examples of the fuel cell of the present invention will be described in more detail with reference to examples. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the spirit of the invention.

[0015]

EXAMPLES Example 1 A small fuel cell having the structure shown in FIG. 1 was produced in the following manner. First, carbon powder was loaded with a Pt-Ru-based catalyst by a liquid phase method. This Pt-
After recovering the carbon powder supporting the Ru-based catalyst, it was calcined in an argon-hydrogen stream to stabilize the catalyst. Next, a solvent and a solid polymer solution were added to this catalyst powder as a binder to form a paste, which was applied onto carbon paper and dried to form a catalyst layer on the fuel electrode 10 side. Separately, a carbon powder carrying a Pt-based catalyst was prepared by the same process as the fuel electrode 10 side, and a solvent and a solid polymer solution were also added as a binder to form a paste, which was applied to carbon paper and dried. . The fuel electrode 10 and the oxidant electrode 8 produced as described above were each cut into 30 mm × 75 mm, and an electrolyte membrane (perfluorosulfonic acid membrane) having a film thickness of 200 μm was sandwiched. These at 135 ° C for 15
It was integrated at a pressure of 100 kg / cm ^{2 for} a minute. Next, the fuel holding layer 11 (a polyolefin plate having a rate of 85% of your own, a thickness of 2 mm) in contact with the fuel electrode 10 side of this electromotive portion (the joined body of the fuel electrode 10, the electrolyte membrane 9, and the oxidizer electrode 8) is preliminarily filled with fuel. Pole terminal (second
External lead terminal) 2 shape (length 15 mm, width 20 m
A hole was formed in m). The shape of the oxidizer electrode terminal (first external lead terminal) 12 (15 m long) is also provided on the oxidizer electrode side in advance.
m, width 20 mm), and a porous Teflon (registered trademark) sheet, which is the oxidant gas diffusion layer 7 provided with a large number of holes having a diameter of 0.5 μm, is installed, and the unit battery thus obtained In order to prevent the holes provided in the fuel electrode terminal 2 and the oxidant electrode terminal 12 from being displaced by using a thin film exterior film in which the holes (15 mm in length and 20 mm in width) of the fuel electrode terminal 2 and the oxidant electrode terminal 12 are previously formed. After positioning, it was thermocompression-bonded and sealed at 200 ° C to obtain a sealed body.

Next, the liquid / gas separation membrane 3 used in this embodiment.
2 will be described with reference to FIG. 1 along with FIG.

The liquid / gas separation membrane 20 is formed on each terminal plate 2,
It is composed of a multi-layer structure of an adhesive layer 23 that serves to fix it to 12, a porous body layer 21 that separates liquid and gas, and a polyolefin net 22 that serves to protect them.

The specific specifications of the liquid / gas separation membrane 20 used in this embodiment are shown below.

The total thickness of the liquid / gas separation membrane is 170 μm.
The outer diameter is 10 mmφ, the liquid / gas separation membrane 20 located in the inner diameter portion is a PTFE porous body having a thickness of 90 μm, a pore diameter of about 0.6 μm, and a porosity of about 85%, and the outer diameter is 6 mmφ.
For the adhesive layer 23, a conductive epoxy adhesive containing silver as a filler having conductivity and excellent organic solvent resistance was used.

The polyolefin net 22 is a polyolefin-based nonwoven fabric having a thickness of 80 μm and a basis weight of 20 g / m 2.

Next, the liquid / gas separation membrane 20 and the fuel electrode lead terminal 2 will be described with reference to FIG. 1 along with FIG.

A hole (10 for attaching the fuel electrode lead terminal 2)
mm fuel electrode terminal plate 2 (15 mm in length, 20 mm in width), which is two terminal pieces constituting the fuel electrode terminal plate 2.
A liquid / gas separation membrane 20 set so as to be interposed between a and 2b and the fuel electrode terminal pieces 2a and 2b was prepared (FIG. 3 (a)). Then, this fuel electrode terminal piece (vertical 15
mm, width 20 mm) The liquid / gas separation membrane 20 was attached between 2a and 2b (Fig. 3 (b)). The material of each terminal piece 2a and 2b was oxygen-free copper plated with gold. . Next, an oxidizer electrode terminal plate (15 mm in length, 20 mm in width) 12 and a liquid / gas separation membrane 20 in which oxygen-free copper was gold-plated were formed on a unit battery encapsulation body prepared in advance with the configuration shown in FIG. The attached fuel electrode terminal plate 2 was attached.

Finally, the end portion of the thin film exterior film 1 and each of the terminal plates 2 and 12 were sealed with an epoxy resin having excellent airtightness. Similarly, an oxidizer electrode lead 12 having a thickness of 3 mm is attached to the encapsulant, and a conductive epoxy using silver as a filler having excellent airtightness and excellent organic solvent resistance is provided between the end portion of the thin film exterior film 1 and the terminal plates 2 and 12. Sealed with adhesive.

Fuel tank 5 provided outside the small fuel cell
From the above, a 1: 1 (molar ratio) mixture of methanol and water was supplied by utilizing the capillary force of the fuel retaining layer 11. The oxidant gas was supplied by natural diffusion from a plurality of oxidant gas intake ports 6 provided on the oxidant gas side. The assembled battery shown in FIG. 6 in which four unit cells thus formed were connected in series with the connection terminal 60 was completed and the output characteristics thereof were examined. The solid line in FIG. 4 shows the relationship between the current density and the output density of this fuel cell. As shown in FIG. 4, a load can be applied up to a current density of about 95 mA / cm 2, and the maximum output was 51 mw / cm 2. Further, although not shown, it was confirmed that a stable voltage was maintained even after a lapse of about 12 hours, and a highly reliable small fuel cell could be manufactured. (Comparative Example 1) In Comparative Example 1, a part manufactured by the same method as in Example 1 was used except that the generated gas discharge port 4 described in Example 1 was not formed. The output change when the output was taken out was measured by the same method as in Example 1. The results are shown by the dashed line in FIG. As compared with Example 1, the load could not be taken on the high current side. Also, although not shown, fuel oozing and voltage drop were observed after about 2 hours,
It was found that the stability was inferior to that of Example 1.

As is clear from the results of the above-mentioned Examples and Comparative Examples, according to the present invention, the problem of fuel leakage and the problem of carbon dioxide emission can be effectively solved, and the battery output can be maintained for a long time. Thus, it is possible to provide a fuel cell which is stably and efficiently taken out and whose reliability is improved. (Embodiment 2) FIG. 5 is the same as Embodiment 1 except that the formation position of the generated gas discharge port of Embodiment 1 is modified. The generated gas discharge port 54 is formed at a position overlapping with one side of the end of the fuel electrode lead terminal 52.

By forming the generated gas discharge port 54 at such a position, the gas which is likely to be locally generated at the end portion which is the terminal mounting portion of the fuel electrode lead terminal 52 is discharged to the outside of the fuel cell in a short time. In addition to improving power generation efficiency as in the first embodiment, it is possible to provide a fuel cell having stable transient characteristics even at the initial stage of start-up during fuel cell operation or a large load change.

[0027]

With the above structure, it is possible to provide a fuel cell having a higher output by solving the problem of power generation efficiency deterioration due to gas generation near the output terminal.

[Brief description of drawings]

FIG. 1 is a plan view of a fuel cell according to a first embodiment of the present invention.

FIG. 2 is a plan view and a sectional view of an important part according to the first embodiment of the present invention.

FIG. 3 is an assembly diagram of important parts according to the first embodiment of the present invention.

FIG. 4 is a power generation characteristic diagram according to Example 1 of the present invention and Comparative Example 1.

FIG. 5 is a plan view of an important part related to Example 2 of the invention.

FIG. 6 is an overall view of a fuel cell according to Embodiment 1 of the present invention.

[Explanation of symbols]

1 Exterior material 2 Fuel electrode lead (second lead terminal) 3 Liquid / gas separation membrane 4 Generated gas outlet 5 fuel tank 6 Oxidant gas intake 7 Oxidant gas diffusion layer 8 oxidizer poles 9 Solid electrolyte membrane 10 fuel pole 11 Fuel retaining layer 12 Oxidizer electrode lead (first lead terminal)

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Claims (3)

(57) [Claims] 1. A fuel electrode, an oxidant electrode arranged facing the fuel electrode and having an oxidant gas intake port, an electrolyte layer sandwiched between the fuel electrode and the oxidant electrode, and the oxidant gas. An exterior material that exposes the intake port and covers the fuel electrode and the oxidant electrode, and a first external lead terminal exposed from the exterior material and electrically connected to the oxidant electrode,
A fuel cell, comprising: a second external lead terminal exposed from the exterior material, electrically connected to the pole fuel electrode, and having a generated gas discharge hole formed therein. 2. The fuel cell according to claim 1, wherein a liquid / gas separation membrane is formed in the generated gas discharge hole. 3. The fuel cell according to claim 1, wherein the exterior material is a laminated film containing a resin.