JPH0745299A - Air fuel cell - Google Patents

Abstract

PURPOSE:To solve the point in which a button type air-zinc primary cell, though excellent in principle, is difficult to provide a large capacity by a structural cause. CONSTITUTION:In an air fuel cell formed by setting up an oxidant electrode 10 opened to the atmosphere and a fuel electrode 12 through an electrolyte 11, this fuel electrode 12 is connected to a fuel accumulating part 15. The electrode is formed in an electrode of arranging a metal catalyst in a porous substrate applying a water repellent process, and the electrolyte 11 is constituted of ion hydroxide or hydrogen ion conductive substance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air fuel cell, and more particularly to an air fuel cell which employs a fuel cell power generation system and is capable of discharging for a long time using hydrogen as a negative electrode active material.

[0002]

2. Description of the Related Art An air battery is a generic term for a battery constructed by using oxygen in the atmosphere as an oxidant as shown in FIG. 3 and containing only a reducing agent in a battery body. Causes the transfer of electrons due to the oxidation of the reducing agent itself and the reduction of oxygen, and a current flows through the load. In the figure, 30 is a seal paper, 31 is a negative electrode, 32 is zinc (reducing agent), 33 is a gasket, 34 is a separator, 35 is an air electrode, 36
A water-repellent film, 37 is a diffusion paper, 38 is an air hole, and 39 is a positive electrode case.

[0003]

As described above, since oxygen in the atmosphere is used as the oxidant, it is not necessary to keep it in the battery, and it is possible to improve the energy density of the battery as a whole. There are features. However, the reducing agent 32
Must be kept in the battery. For example, in the case of the button type air-zinc primary battery currently used as shown in FIG. 3, Zn is used as a reducing agent to enhance the reactivity. Therefore, it is used in the form of gel or in combination with Teflon to make it porous. By taking such measures, it is possible to maintain the reactivity of the Zn electrode. However, in order to configure an air battery having a large capacity with this configuration, it is difficult to secure highly reactive gel Zn located in the vicinity of the electrolyte simply by increasing the amount of gel Zn. During this period, the resistance increased and the discharge characteristics deteriorated, and a large capacity could not always be obtained.

On the other hand, a method of enlarging the electrode area as a thin film is also conceivable, but in this case, there are problems in practical use such as an unnecessarily large battery area and a complicated battery structure. Therefore, it was basically impossible to obtain an air battery having a large capacity with such a conventional structure.

The present invention has been made to solve the above-mentioned problems, and provides a button-type air-zinc primary battery which is excellent in principle but has a large capacity due to its structural cause. The purpose is to solve the difficulty.

[0006]

In order to solve the above problems, an air fuel cell according to the present invention is an air fuel cell in which an oxidant electrode open to the atmosphere through an electrolyte and a fuel electrode are installed. In the fuel cell, the fuel electrode is connected to the fuel storage part, the electrode is an electrode in which a metal catalyst is arranged on a porous substrate subjected to water repellent treatment, and the electrolyte is hydroxide ion or hydrogen ion. It is characterized in that it is made of a conductive material.

The most significant feature of the present invention is that an oxidant electrode and a fuel electrode are arranged via an electrolyte to form a power generation section similar to a fuel cell. Oxygen in the inside is used, hydrogen gas is used as a reducing agent, and a container storing a hydrogen storage alloy is used as a method for storing hydrogen gas. Conventionally,
As an air battery using oxygen in the atmosphere as an active material and a battery using a hydrogen storage alloy, there is a nickel hydrogen battery. However, no air fuel cell based on the principle as shown in the present invention has been proposed so far.

[0008]

EXAMPLE FIG. 1 shows the structure of the air fuel cell of the present invention. In FIG. 1, 10 is an oxidizer electrode, 11 is an electrolyte,
12 is a fuel electrode, 13 is a container, 14 is a pressure regulator, 15
Is a hydrogen storage part, 16 is an exhaust part, 17 is a reaction chamber, 18
Is an exhaust pressure regulator, and 19 is a load.

As is apparent from FIG. 1, the oxidizer electrode 10
And the fuel electrode 12 are provided via the electrolyte 11,
The fuel electrode 12 is connected to a hydrogen storage unit 17 via a reaction chamber 17 and a pressure regulator 17. The reaction chamber 17 has an exhaust part 16, and the exhaust part 16 is connected to an exhaust part pressure regulator 18. Further load 19
Is connected between the fuel electrode 12 and the oxidizer electrode 10.

The two electrodes 10, 12 need only be active in oxidizing hydrogen and reducing oxygen, and here, a porous carbon plate,
A sintered porous nickel plate or a nickel net was used as a support for the electrode, and platinum, palladium, rhodium, Raney nickel, Raney silver, etc. were held as a catalyst on the support. A KOH solution was used as an electrolyte, and this was impregnated into a porous body such as silicon carbide. The concentration of KOH was 40 to 60%.

The hydrogen storage unit 15 is a container containing a hydrogen storage alloy. The hydrogen storage alloy used here basically has no problem as long as it has a hydrogen storage capacity, but a lower hydrogen dissociation pressure can simplify the structures of the hydrogen storage part 15 and the pressure adjusting part 14, and as a result, The configuration can be facilitated. For example, MmNi ₅ (M
m: misch metal), and part of Ni is Mn, C
When the alloy is replaced with o, Al, Cr or the like, the dissociation pressure of 1 to several atmospheres can be obtained, and the configuration of the hydrogen storage part can be facilitated. The absorption / desorption of hydrogen in the hydrogen storage alloy is as follows. First, when the pressure P ₁ is applied at the temperature T ₁ , a corresponding amount of hydrogen is stored. When releasing, the temperature is set to T ₂ (T ₂ >
By setting T ₁ ), hydrogen having a pressure of P ₂ (> P ₁ ) is released. Therefore, after the hydrogen is stored in the hydrogen storage unit 15, the storage unit is heated to release the hydrogen, the pressure of the hydrogen is adjusted by the pressure adjuster 14, and then the hydrogen reaches the reaction chamber 17 to carry out the reaction. can do.

In the reaction, since the air fuel cell of the present invention corresponds to a kind of low temperature fuel cell, it is necessary to raise the temperature of the power generation section, but the temperature is 40 to 8
It can be operated sufficiently at about 0 ° C. By doing so, the hydrogen gas accumulated in the hydrogen storage alloy is released, and the gas pressure is controlled by the pressure adjusting unit 14 so that the reaction chamber 17 can be controlled.
Reach An exhaust part pressure regulator 18 is provided at the outlet of the discharge part 16 of the reaction chamber 17 so that the hydrogen pressure in the reaction chamber 17 is adjusted to be constant. As a result, the electrons released from hydrogen reach the oxygen electrode 10 side through the external circuit, and the hydroxide ions generated at the oxygen electrode 10 reach the fuel electrode 12 side through the inside of the electrolyte 11 to generate water. The discharge reaction proceeds.

Next, as shown in FIG. 2, another embodiment using a polymer ion exchange membrane as an electrolyte material will be described. In FIG. 2, reference numerals 11 to 19 indicate the same as those in FIG.
Reference numeral 20 represents a current collector. The structure of FIG. 2 is almost the same as the structure of FIG. 1, but the load 19 is connected to the current collector 20 provided on the oxidant electrode 10.

Here, a polymer material having proton conductivity is used as the electrolyte 11, and specifically, a fluororesin ion exchange membrane (Nafion 117) manufactured by DuPont (USA) is used. Then, for the electrodes 10 and 12, an electrode plate was used in which polytetrafluoroethylene having water repellency and binding property and platinum or platinum-supporting carbon were kneaded and molded as catalyst particles. The electrodes 10 and 12 are bonded to the electrolyte 11 by thermocompression bonding to form a reaction part of the battery. By pressing the current collector 20 on the surface of the electrodes, the current generated by the reaction on the electrodes is transferred. Can be taken out.

An air fuel cell formed by using such a polymer exchange membrane as an electrolyte also uses a container having a hydrogen storage alloy housed therein as the hydrogen storage unit 15 as in the previous example. It is configured to generate 70 to 10 power during power generation.
It only needs to be heated to about 0 ° C. When this proton conductive material is used for the electrolyte 11, in the battery power generation section, the protons generated by releasing electrons pass through the electrolyte 11 to reach the oxygen electrode 10 side, and receive the electrons emitted earlier. It reacts with the generated hydroxide ion to produce water.
As described above, when the material of the electrolyte is different, the kinds of ions moving in the electrolyte are different, but the direction of the current flowing through the external circuit is not different.

As described above, when oxygen in the atmosphere is used as the active material on the side of the oxidant electrode as in the conventional air battery, it is not necessary to store this active material in the battery, and the battery is used as a fuel gas. It only needs to store the hydrogen inside.

As a method for storing this hydrogen, it is possible to use a high-pressure compressed gas such as a hydrogen cylinder, but in the present invention, a method using a hydrogen storage alloy that has a larger storage amount than such a method is used. In the case of a high-pressure compressed gas, the pressure is on the order of several tens to hundreds of tens of atmospheres, which complicates the mechanism of the present air fuel cell. On the other hand, when a hydrogen storage alloy is used, the operating pressure can be lowered to 10 atm or less by selecting the alloy, and the entire system configuration can be simplified. Further, in a conventional air battery, Zn, which is the negative electrode active material, is in a sol state, and even if a large amount of sol-state zinc is stored, the reactivity decreases as it moves away from the electrolyte, so it is effectively used for the reaction. There is a limit to the amount of storage that occurs, and it is not possible to obtain a large capacity with such a structure. On the other hand, when hydrogen gas is directly used as the active material of the negative electrode, the hydrogen gas can reach the active portion of the surface of the electrode very easily, and the stored hydrogen can be effectively reacted. Therefore, it is possible to provide a practical air battery having a large capacity, although a mechanical mechanism is partially required such as the pressure adjusting unit.

[0018]

As described above, the air fuel cell of the present invention is provided on both sides of an electrolyte formed of a material having hydroxide ion or hydrogen ion conductivity to reduce oxygen and oxidize hydrogen. A gas electrode formed by containing an active metal, and oxygen in the atmosphere is used as oxygen,
Only hydrogen is stored in the battery. The method for storing hydrogen depends not on the conventional high-pressure compressed gas, but on the method in which the hydrogen-absorbing alloy absorbs it. Therefore, the storage amount of hydrogen is smaller than that of high-pressure gas, and the pressure of hydrogen gas at the time of power generation is low, so that the entire system of the fuel cell can be configured with a simple structure. By using such a gas as the active material for the battery reaction, the active material is effectively supplied to the interface between the electrode and the electrolyte, and the hydrogen gas stored inside can be effectively consumed, and the battery with a large capacity can be obtained. Can be configured.

In the air fuel cell of the present invention, the reactivity of the supplied hydrogen is high, so there is no limitation on the cell or shape derived from the reactivity between the electrode / electrolyte part and the negative electrode side active material. In this way, it is possible to provide an air fuel cell that can be used in various forms, and it has a great effect in practical use.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of an air fuel cell of the present invention.

FIG. 2 is a sectional view showing the structure of a conventional zinc-air battery.

FIG. 3 is a sectional view showing the structure of another embodiment of the air fuel cell of the present invention.

[Explanation of symbols]

 10 Oxidizer Electrode 11 Electrolyte 12 Fuel Electrode 13 Container 14 Pressure Regulator 15 Hydrogen Storage Section 16 Exhaust Section 17 Reaction Chamber 18 Exhaust Section Pressure Regulator 19 Load 20 Current Collector 30 Seal Paper 31 Negative Electrode 32 Zinc 33 Gasket 34 Separator 35 Air Electrode 36 Water repellent film 37 Diffusion paper 38 Air holes 39 Positive electrode case

Claims (2)

[Claims] 1. An air fuel cell in which an oxidant electrode open to the atmosphere via an electrolyte and a fuel electrode are installed, the fuel electrode being connected to a fuel storage section, and the electrode being
An air fuel cell, characterized in that it is an electrode in which a metal catalyst is arranged on a porous substrate that has been subjected to a water-repellent treatment, and the electrolyte is composed of a hydroxide ion or hydrogen ion conductive material. 2. The air fuel cell according to claim 1, wherein the fuel storage unit is a container having a hydrogen storage alloy housed therein.