JPS5931566A - Battery - Google Patents

Abstract

PURPOSE:To increase environmental stability of a battery having an oxygen electrode by placing an oxygen selective permeable membrane in a part on an oxygen electrode side to transmit oxygen which is necessary to a battery reaction and to prevent transmission of water vapor as much as possible. CONSTITUTION:An oxygen selective permeable membrane 4a is bonded with a porous supporter 4 to increase mechaical strength. The permeable membrane is placed on the air entrance side. Polydimethylsiloxane-polyhydroxystyrene copolymer with crosslinking is used as a membrane having large oxygen permeability and small water vapor permeability. The structual formula of this copolymer is shown in the formula. Thereby, the effect of environmental conditions is prevented and durability of a battery is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a battery equipped with a gas diffusion electrode using oxygen as an active material.

BACKGROUND OF THE INVENTION Conventional Structures and Problems There are air cells, fuel cells, etc., which are equipped with gas diffusion electrodes and use oxygen as an active material. The electrolyte used may be an alkaline, neutral or acidic solution, or a sweet or solid electrolyte. In particular, in batteries that use a solution as an electrolyte,
Water vapor flows in and out from the gas diffusion electrode (oxygen electrode) depending on the vapor pressure of the internal electrolyte, causing changes in concentration and volume of the electrolyte in the battery, which had an impact on battery characteristics. Taking a button-type air battery as an example, its situation will be explained using FIG. In the figure, 1 is an oxygen electrode (air electrode), and 2 is a polytetrafluoroethylene (PTFE) porous membrane that allows gas to diffuse but blocks liquid. 3 is an air intake hole from the outside, 4 is a porous body that supports the oxygen electrode and diffuses air, 5.6 is a separator, and 7 is a negative electrode made of a mixture of potassium hydroxide aqueous solution and zinc hydrate powder. be.

Generally, in an alkaline electrolyte, the potassium hydroxide concentration is 30
~36chi are used. Therefore, the relative humidity is 47
When it is higher than ~59%, external moisture is taken in, resulting in a decrease in electrolyte concentration and volumetric expansion, resulting in a decrease in discharge performance and a hot electrolyte solution.

On the other hand, when the relative humidity is below the above range, evaporation of the electrolytic solution occurs, resulting in an increase in internal resistance and a decrease in discharge performance. Therefore, since they are easily affected by the environmental atmosphere, air cells and fuel cells are designed for use in a specific field, and there have been major problems in trying to make them more general-purpose. In addition,
In the figure, 8 is a negative electrode container, 9 is an insulating gasket, and 1o is a positive electrode container.

OBJECTS OF THE INVENTION The present invention solves the conventional problems as described above, and aims to improve the environmental stability of a battery equipped with an oxygen electrode.

Structure of the Invention Namely, the present invention is characterized in that by providing an oxygen selective permeable membrane in a part of the oxygen electrode side, oxygen necessary for battery reaction passes through this permeable membrane, while water vapor permeation is prevented as much as possible. It is something.

Among silicone resins and copolymers of silicone resins and polymer resins, the present inventors selected polydimethylsiloxane,
It was discovered that polydimethylsiloxane-polyhydroxystyrene cross-linked copolymers, polydimethylsiloxane-polyhydroxystyrene-polysulfone ternary cross-linked copolymers, butyl rubber, and nitrocellulose are superior. In order to improve the oxygen permeability of these permeable membranes, it is necessary to reduce the thickness of the permeable membrane to 171 m or less, but in order to compensate for the lack of mechanical strength, porous membranes that also serve as supports for the oxygen electrodes are used. A uniform film of the resin was provided on the body, and a practical battery was used.

Description of examples Hereinafter, the present invention will be explained in detail with reference to Examples.

(Example 1) As an oxygen selective permeable membrane, polydimethylsiloxane-
A polyhydroxystyrene crosslinked copolymer was used. The structural formula of this copolymer is as follows.
It is possible to create a film with a thickness of 0.3 μm or less.

This membrane was bonded to a conventionally used PTFE membrane having a porosity of 40%, a pore diameter of 0.271 m or less, and a thickness of 200 μm to increase its mechanical strength. As in the conventional example, the oxygen selective permeable membrane of the present invention was applied to a button-type air cell. The battery construction method is exactly the same as the conventional one, and the PT shown in Figure 1
Instead of the FE membrane 2, a PTFE membrane laminated with the aforementioned oxygen-selective permeable membrane was placed so that the permeable membrane side faced the outside air, and a R44 size (diameter 11.6 mm, height 5, 4 m)
m) battery was constructed. In order to evaluate the environmental stability, Figure 2A shows the results of continuous discharge with a load of 16Ω connected to the battery under conditions of a temperature of 20° C. and a relative humidity of 70%. For comparison with a conventional product, a conventional battery B using a PTFE membrane without an oxygen-selective permeable membrane was discharged under the same conditions. As a result, conventional product B became liquid after about 1500 hours.
The porous body 4 used as a support for the oxygen electrode was filled with liquid, causing a stinging sensation and leaking, and the discharge was stopped at the same time. On the other hand, product A of the present invention having an oxygen-selective permeable membrane has approximately 3
The battery was discharged for 4,630 hours. The discharge capacity of a button-type air battery of this size is about 400 mAh, and the product of the present invention discharged almost satisfactorily. As can be seen from the examples,
Button-type air batteries have an open oxygen (air) intake hole under discharge conditions, so they are easily affected by the environment, and their use is mainly limited to hearing aids that can be used for a short period of about two weeks. Ta. However, the product of the present invention can be used for applications such as electronic desktop calculators and game watches that are used for a relatively long period of time.

(Example 2) The present invention was applied to a material that replaced the porous body 4 of the conventional example. Conventionally, filter paper or a porous membrane of polyethylene or polypropylene has been used as a porous support. In the present invention, an oxygen selective permeable membrane 4a is used in combination with these materials, particularly polyethylene and polypropylene porous membranes. The oxygen selective permeable membrane 4a has a structure using a polydimethylsiloxane-polyhydroxystyrene-polysulfone ternary crosslinked copolymer. This material can also be made into a thin film, and in this example, the oxygen selective permeable membrane 4a with a thickness of 0.171 m was made into a thin film.
It was provided on both sides of a polypropylene porous membrane having a thickness of 0.00 μm. Using this, a battery was constructed in the same manner as in Example 1 and in the conventional manner. Its structure is shown in FIG.

In the figure, 4' is a porous support provided with the oxygen-selective permeable membrane of the present invention on both sides. As a result of testing this battery under exactly the same environment and discharge conditions as in Example 1, almost the same results as in Example 10 and the product of the present invention were obtained.

Effects of the Invention By providing an oxygen-selective permeable membrane in a part of the oxygen electrode side, the permeation of water vapor is significantly smaller than that of conventional porous bodies, making it less susceptible to changes in environmental conditions. 4 of batteries using gas-permeable electrodes, especially oxygen electrodes.
It has become possible to improve usability.

[Brief explanation of drawings]

Figure 1 is a cross-sectional structural diagram of a conventional button-type air battery, Figure 2 is a discharge characteristic diagram comparing the button-type air battery according to an embodiment of the present invention with a conventional product, and No. A cross-sectional structural diagram of a button-type air battery in an example is shown. 1... Gas diffusion electrode (oxygen electrode), 2...
Polytetrafluoroethylene porous membrane, 3... Air intake hole, 4.4'... Porous body that also serves as a support for the oxygen electrode, 4a... Oxygen selective permeation film,
5, 6...Separator, 7...Negative electrode,
8... Negative electrode container, 9... Insulating gasket, 1o... Positive electrode container. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4: Kenkeishi Prefecture)

Claims (2)

[Claims] (1) A battery equipped with a gas diffusion electrode using oxygen as an active material, and an oxygen selective permeable membrane provided on the air intake side of the gas diffusion electrode. (2) The oxygen selective permeable membrane is polydimethylsiloxane,
Patent made of any material from the group consisting of polydimethylsiloxane-polyhydroxystyrene cross-linked copolymer, polydimethylsiloxane-polyhydroxystyrene-polysulfone ternary cross-linked copolymer, butyl rubber, and nitrocellulose A battery according to claim 1.