JPS6226772A - Power generation device including oxygen depolarization electrode - Google Patents

Abstract

PURPOSE:To prevent any increase in the electric resistance of an oxygen depolarization electrode or the internal resistance of a power generation device including said electrode by making a cation exchanger in contact with the electrolyte- side surface of the positive body. CONSTITUTION:A positive body 11 consists of active carbon carrying a manganese oxide and is packed in a nickel-plated stainless screen used as the current collector. A porous film 10 made of an ion exchanger is made in contact with the positive body 11. Due to the above structure, even when carbon dioxide dissolves in the liquid electrolyte and as the result carbonate ions are produced, the cation exchanger 10 which is in contact with the electrolyte-side surface of the positive body 11 adsorbs carbonate ions which results in minimal production of carbonates. Consequently, it is possible to prevent any increase in the electric resistance of the oxygen depolarization electrode or the internal resistance of the power generation device.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to improvements in oxygen depolarization electrodes used as positive electrodes in power generation devices such as fuel cells and air cells.

Conventional fuel cells are not limited by the Carnot cycle and have very high energy conversion efficiency, theoretically having a conversion efficiency of 100q6. In addition, air batteries have a higher energy density per unit volume than those using other alkaline electrolytes. For the above reasons, power generation devices using oxygen depolarization electrodes are being put into practical use or for civilian use in various fields.

In particular, button-type air batteries are attracting attention as an alternative to mercury batteries due to their high capacity and low pollution.

No. 62 gave an overview of oxygen depolarization electrodes used in fuel cells and air cells. In this figure, 1 is an electrolytic solution,
2 is a porous membrane, and generally a porous polyethylene membrane or a polypropylene membrane is used. 3 is a positive electrode body, in which a catalyst is supported on activated carbon. A wide variety of catalysts are used, ranging from noble metals, metal oxides, metal compounds, and organic substances. 4 is a current collector, 5
is a water-repellent film intended to prevent the electrolyte from dissipating outside the system and not to impede the diffusion of air or oxygen into the catalyst layer. A propylene membrane is used. 6 is air or oxygen.

In the oxygen depolarized electrode having the above configuration, a three-layer interface is formed in the catalyst layer by the electrolyte, air (oxygen), and activated carbon, and the reaction proceeds in the alkaline solution as expressed by the following reaction formula.

one! -0+HO+2e-20H- Problems to be Solved by the Invention In the electrode configuration shown in FIG. However, when carbon dioxide is dissolved in the electrolyte, the following reaction proceeds.

-2M+Co3-M2CQ3↓Cation in CM idt solution] (M2++Co2-→MCo3↓) The carbonate (M2CO3) produced by the above reaction is deposited in the electrolyte and around the porous membrane. With storage, the amount of carbonate precipitated increases, and since carbonate is a nonconductor, the electrical resistance of the electrode increases.

For this reason, the internal resistance of the power generation device itself using the oxygen depolarization electrode increases, and as a result, the performance of the power generation device decreases due to storage.

The present invention solves the above-mentioned conventional problems, and eliminates the increase in the electrical resistance of the acid-odor depolarization electrode due to carbonate precipitation or the increase in the internal resistance of the power generation device using the oxygen depolarization electrode. The purpose of the present invention is to provide a power generation device using polar electrodes.

Means for Solving the Problem In order to solve this problem, the present invention provides a positive electrode body in which a cation exchanger is brought into contact with the surface of the positive electrode body that comes into contact with the electrolyte.

Effect: According to this configuration, even if carbon dioxide is dissolved in the electrolyte and carbonate ions are generated, the cation exchanger that is in contact with the surface of the positive electrode that comes into contact with the electrolyte adsorbs the carbonate ions.
Carbonate generation is significantly reduced compared to conventional methods. As a result, there is no increase in the electrical resistance of the oxygen depolarizing electrode or increase in the internal resistance of the power generator using the oxygen depolarizing electrode.

Example Examples of the present invention will be described below.

In this embodiment, an air button battery will be explained as an example of a power generation device using an oxygen depolarized electrode. Note that the size of the air button battery used was IEC standard 44 type.

FIG. 1 shows the configuration of the air button battery in this example. In this figure, 7 is a sealing plate using a three-layer clad plate of nickel/stainless steel/copper, 8 is a frozen zinc negative electrode, and 9
10 is a positive electrode case made of iron plated with nickel, and 10 is a porous membrane made of a cation exchanger, which is in contact with the positive electrode body. In this example, graft polymerized polyethylene substituted with sodium methacrylate was used. Reference numeral 11 denotes a positive electrode body in which manganese oxide is supported on activated carbon and filled in a nickel-plated stainless steel screen serving as a current collector, and 12 is a water-repellent film made of polytetrafluoroethylene.

13 is an air hole. As a conventional example for comparison with this example, a porous polypropylene membrane was used as the 1o porous membrane, and an air button battery having the same configuration as that shown in FIG. 1 was used except for the porous membrane.

Next, the air button batteries of the above embodiment and the conventional example were placed at 20'0
The battery was stored under conditions of 45%, and changes in internal resistance and discharge performance after storage were examined. FIG. 2 shows the change in internal resistance under the above storage conditions.

In the conventional example, the internal resistance increases with storage and increases to about 100 after 4 weeks, whereas in the present example, no increase in internal resistance is observed at all. Note that the internal resistance is 20
Individual measurements were taken and the average value is shown.

The discharge conditions shown in Figures 3 and 4 are 250Ω continuous discharge, 20'
050% R, H. At the initial stage, no difference is observed between the example and the conventional example, but after storage for 4 weeks, a difference in discharge voltage is observed, which is thought to be due to a difference in internal resistance.

However, the example also showed good results regarding the discharge time.

In addition, various cation exchangers other than the examples were investigated, and almost the same tendency was observed. However, graft polymerized polyethylene substituted with sodium methacrylate or sodium acrylate showed particularly good properties.

1 is a positive electrode body, and 16 is a porous membrane. No. 16 porous membranes were investigated in the same manner as the above-mentioned air button battery.

As a result, the same effects as those of the above-mentioned air button battery were obtained with such a box-shaped air battery as well as with a cylindrical air battery (not shown).

Effects of the Invention As is clear from the above, according to the configuration of the present invention, there is no increase in the electrical resistance of the oxygen depolarization electrode or the internal resistance of the power generation device using the oxygen depolarization electrode, and the oxygen depolarization has excellent storage stability. A power generation device using electrodes can be provided.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the air button battery in the embodiment of the present invention, Fig. 2 is a diagram of internal resistance change during storage of the battery of the embodiment and the conventional example, and Figs. 3 and 4 are the diagrams of the embodiment and conventional example. FIG. 5 is a schematic cross-sectional view showing a single cell for a box-type air battery, and FIG. 6 is a schematic view of an oxygen depolarization electrode. 1... Electrolyte, 2... Porous membrane, 3-...
- Positive electrode body, 4... Current collector, 5... Water repellent film,
6... Air or oxygen, 7-... Sealing plate, 8...
...-Zinc chloride, 9... Positive electrode case, 10.
- Porous membrane, 11... Positive electrode body, 12-... Water repellent membrane, 13... Air holes, 14... Zinc electrode, 15...
... Positive electrode body, 16-... Porous membrane. Name of agent: Patent attorney Toshio Nakao and 1 other person7-
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4 (week) 3 Figure 4 & V face r1 ()lr) Figure 5/4--Issei Button Goku/--Ichimo Kaito 4-, lt# 5--Ichifusui'' (6-- −!Kinu is #he

Claims (5)

[Claims] (1) Oxygen depolarization characterized by a cation exchanger being brought into contact with the entire surface in contact with the electrolyte of a film-like, plate-like, or lump-like positive electrode body that uses oxygen or air as a depolarizing material. A power generation device that uses electrodes. (2) A power generation device using an oxygen depolarization electrode according to claim 1, wherein the cation exchanger is a graft polymerized polyethylene membrane substituted with sodium acrylate or sodium methacrylate. (3) The oxygen depolarization electrode according to claim 1, wherein the positive electrode body is in the form of a film or a plate, and a water-repellent synthetic resin film is in contact with the surface in contact with air or oxygen. A power generation device using (4) A power generating device using the oxygen depolarizing electrode according to claim 1, wherein the power generating device is button-shaped. (5) A power generation device using the oxygen depolarization electrode according to claim 1, wherein the power generation device is cylindrical or box-shaped.