JPH01195678A - Cell - Google Patents

Abstract

PURPOSE:To make it possible to be used and stored for a long term by interposing a compound film formed of a thin film poly [1trimethylsilyl)-1-propyne] and a microporous film between the air intake side of a gas diffusion electrode and the inside of a cell container. CONSTITUTION:A thin film of [1-(trimethylsilyl)-1-propyne] and a compound film 11 having oxygen selective permeability formed of a microporous film supporting this thin film are interposed between the air intake side of a gas diffusion electrode of a cell provided with the gas diffusion electrode having oxygen as an active material and a cell container having the air intake hole 3 connecting to the atmosphere, and the inside of the cell container. Thereby, excellent practical performance ranging heavy load of the cell having a neutral or alkaline water solution as an electrolyte to light load, leakageresisting property and long storage time can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a gas diffusion electrode using oxygen as an active material, an electrolyte such as an alkaline aqueous solution, a metal such as zinc, magnesium, or aluminum, or an alcohol, hydrazine, hydrogen, etc. The present invention relates to a battery comprising a negative electrode active material.

BACKGROUND OF THE INVENTION BACKGROUND ART Batteries equipped with gas diffusion electrodes and using oxygen as an active material include air cells, fuel cells, and the like. Especially alkaline aqueous solution,
In a battery that uses a neutral aqueous solution as an electrolyte, water vapor flows in and out from the gas diffusion electrode (oxygen electrode) depending on the internal vapor pressure, causing changes in concentration and volume of the electrolyte in the battery, which affect the battery characteristics. was influencing. Taking a button-type air battery as an example, the situation will be explained using FIG. 3. 1 is an oxygen electrode (air electrode), 2 is polytetrafluoroethylene (PTFE) that has gas diffusion properties but blocks liquids.
) is a porous membrane that supports an oxygen electrode. 3 is an air intake hole from the outside, 4 is a porous body that diffuses air, 6
, 6 is a separator, and 6 is a negative electrode made of a mixture of potassium hydroxide aqueous solution and zinc chloride powder. Generally, an aqueous potassium hydroxide solution is used as an alkaline electrolyte, and its concentration is 3
o~35%. For this reason, when the relative humidity is higher than 47 to 69%, external moisture is taken in, resulting in a decrease in electrolyte concentration and volume expansion, resulting in a decrease in discharge performance and leakage of the electrolyte. 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, there are problems with their properties after long-term storage. Air cells and fuel cells are only designed for use in a specific field, and there are major challenges in making them more general-purpose. had.

In Figure 2, 8 is a negative electrode container, 9 is an insulating gasket, and 10 is a positive electrode container.

Problems to be Solved by the Invention In order to solve these problems, various countermeasures have been considered in the past. For example, a substance that reacts with the electrolyte is inserted into a portion around the air intake hole to prevent the electrolyte from leaking to the outside of the battery. Alternatively, an electrolyte absorbing material such as a nonwoven fabric made of paper or a polymeric material is provided to prevent leakage of the electrolyte to the outside of the battery. Furthermore, proposals have been made to prevent water vapor and carbon dioxide from entering the battery by making the air intake holes extremely small and limiting the amount of oxygen supplied, but none of these methods work. There remained major problems in prevention and discharge performance, especially in long-term discharge performance. The main causes of these are the dilution and volumetric expansion of the electrolytic solution due to the intrusion of water vapor from the air into the battery, and the inhibition of the discharge reaction due to the formation of carbonates due to the intrusion of carbon dioxide gas and the blockage of the air circulation path.
Conversely, when the outside air is low-humidity, the loss of moisture in the electrolyte causes a decline in performance. In order to eliminate this cause, in recent years, methods have been developed in which air is supplied to the oxygen electrode through a membrane that suppresses the permeation of water vapor and carbon dioxide gas and selectively allows oxygen to permeate. A method using a film that integrates a uniform thin film of , a thin film of a metal oxide, or a thin film of an organic compound containing metal atoms with a suitable porous film has been proposed.

However, to date, it has not been possible to obtain sufficiently effective selective permselectivity for oxygen gas and water vapor.

Due to insufficient carbon dioxide permeation blocking ability, satisfactory discharge performance cannot be obtained, and the device cannot withstand long-term use or storage, so it has not been put into practical use.

Therefore, the present invention aims to improve the storability and long-term use performance of the above-mentioned battery, and to obtain satisfactory discharge performance under discharge conditions ranging from light loads to heavy loads. The purpose of this invention is to provide an effective means for preventing atmospheric water vapor and carbon dioxide from entering the battery over a long period of time.

Means for Solving the Problems The present invention provides a method for connecting the air intake side of the gas diffusion electrode and the inner surface of the battery container of a battery comprising a gas diffusion electrode using oxygen as an active material and a battery container having an air intake hole communicating with the outside air. In between, C
An oxygen-selective permeability composite membrane formed from a thin film of 1-(1-limethylsilyl)-1-propyne] and a microporous membrane supporting this thin film is interposed.

The poly(1-()limethylsilyl)-1-propyne) thin film is a non-porous, homogeneous thin film that has selective oxygen permeability, and has a sufficient oxygen permeation rate and water vapor permeability.

In order to obtain carbon dioxide permeation blocking ability, a thickness of usually 1.0 μm or less, preferably 0.05 to 0.5 μm is suitable. The microporous membrane that supports this thin film allows gas to easily permeate through it.
Furthermore, it is preferable that the surface thereof is a microporous membrane with smoothness and pore size suitable for supporting the above-mentioned thin film in a uniform and non-porous state, and the average pore size of the microporous membrane surface is 3 to 0.01 μm. is preferred.

In addition, the present invention has been made with important consideration given to the fact that it can be applied to batteries that use an alkaline aqueous electrolyte.
We focused on the characteristics of a homogeneous thin film of [1-()limethylsilyl)-1-propyne], and furthermore, the microporous membrane that supports this thin film contains polyolefins such as polypropylene and polyethylene, which have excellent alkali resistance, fluororesin, polysulfone, etc. After careful consideration, the project was completed. The microporous membrane may be a single layer, but in order to ensure strength during handling, manufacturing, or use, it may have a two-layer or more structure with an alkali-resistant nonwoven fabric further integrated as necessary. Also good.

A composite membrane in which a thin film of the above-mentioned poly(rl-(trimethylsilyl)-1-propyne) was supported by a microporous membrane was disclosed in Japanese Unexamined Patent Publication No. 55
Along with polydimethylsiloxane, organopolysiloxane copolymers, polysiloxane derivatives such as polyvinyl/L/)liorganosilane, and α-olefin sulfur dioxide copolymers, etc., as disclosed in Publication No. 4-56985, blast furnace Practical applications are being considered for purposes such as ventilation, combustion assistance, petroleum protein processing, waste liquid treatment aeration, and exhalation in medical care. Only the permeation rate is evaluated. In order for these membranes to be applied to batteries that can obtain satisfactory discharge performance even under heavy load discharge conditions, they must have a sufficiently high oxygen permeation rate and excellent water vapor and carbon dioxide permeation blocking ability. Although these are important requirements, until now many aspects of these characteristics have been unknown, and there have been few cases where their application to batteries has been considered.
As disclosed in Japanese Patent No. 582, it has been proposed to use a polysiloxane membrane, but the oxygen permeation rate is insufficient and satisfactory performance cannot be obtained in discharge under heavy loads. As a result of extensive studies on various oxygen-permeable membranes for batteries, the present invention has found that a thin film of polyIJ(1-()limethylsilyl)-1-propyne comprehensively satisfies the above-mentioned characteristics for batteries. It was discovered and completed that the performance of the battery to which this was applied was extremely superior.

There are various methods for producing the composite membrane used in the present invention, but typically, as disclosed in JP-A-54-148277, poly [1-(1-limethylsilyl/L/)-1-
Propyne] dissolved in a highly soluble solvent such as cyclohexene, cyclohexane, toluene, etc. is widely spread on a flat surface such as a glass plate, dried, the thin film is peeled off from the glass surface, and the film is superimposed on a porous film. , an on-water spreading method in which the above solution is dropped onto the water surface and the thin film formed by spreading it on the water surface is placed on a microporous membrane as a support below the water surface and then dried; It is classified as a method in which the above solution is directly applied onto a certain microporous membrane and dried. Either method may be used, but a thin film without pinholes is formed and poly[1-( It is necessary that the pores are not blocked by penetrating the pores.

Function: With this configuration, the above-mentioned composite membrane satisfies both the oxygen permeation rate for batteries and the effect of blocking water vapor and carbon dioxide from the atmosphere, as is clear from the results of battery tests in Examples described later. Due to this condition, both the heavy load discharge performance required of a practical battery and the performance when discharged for a long time in a high humidity or low humidity atmosphere are satisfied.

Example The effect of the present invention was demonstrated by polyr1-()rimethylsilyl)-1-
Propyne] A battery using a composite membrane, a battery using a polydimethylsiloxane composite membrane, and a battery not using the above composite membrane were prototyped and evaluated. First, in the case of a comparative example in which the above-mentioned composite membrane was not used, the structure was exactly the same as that shown in FIG. 3. Examples and comparative examples using composite membranes are almost the same as those shown in FIG. 3, and as shown in FIG. 1, the composite membrane is interposed between the porous PTFE membrane 2 and the porous body 4 that diffuses oxygen. , is different from FIG. 3 in that the thin film side of poly[1-()limethylsilyl)-1-propyne] of the composite membrane is arranged so as to face the side of the air intake hole 3.

The poly[1-(trimethylsilyl)-1-propyne] composite membrane tested was poly[1-()limethylsilyl)-1-propyne)(1-()limethylsilyl)-1-
An extremely thin film obtained by dropping a polymer solution of propyne (propylene polymerized) dissolved in cyclohexene onto the water surface was placed on a porous support film in water, and then dried. The thickness of the thin film layer of poly(C1-()limethylsilyl)-1-propyne) was adjusted by changing the temperature of the polymer solution and the water to which it was added dropwise. Further, a composite membrane of a polydimethylsiloxane thin film and a porous support membrane, which was used as a comparative example, was also prepared by forming a thin film on the water surface and integrating it with the support. All support membranes are microporous membranes (pore diameter: approximately 0.
A thin film layer was formed on the microporous membrane side using a single layer of 1 to 05 μm, thickness: about 30 Jim, and a composite layer in which this and a nonwoven fabric (thickness: about 160 μm) were integrally bonded.

The prototype battery has a diameter of 11.6 mm and a total height of 6.4 mm, and is resistant to relatively heavy loads (75 Ω) at 20°C and normal humidity (6.
The sufficiency of the oxygen uptake rate from the air into the battery was evaluated by continuous discharging at a relatively light load (3K).
(1) at 20°C2 high humidity (90% RH).

Continuous discharge for a long period of time at low humidity (20% RH) reduces the effects on battery performance, such as the intake of water vapor in the atmosphere, the dissipation of moisture within the battery, and the intake of carbon dioxide gas during the long-term discharge period. evaluated.

The details of the prototype battery are shown in Table 1.

Table 2 also shows the performance test results of the prototype batteries.

In Table 2, the end-of-discharge voltage is 0.9 V in all cases, and the change in weight indicates the increase or decrease before and after the discharge test, and is a numerical value that mainly indicates the amount of moisture taken in or dissipated during discharge.

In Examples 1 to 6, relatively thin uniform thin films were formed within the range in which a uniform thin film without pinholes could be obtained, and in Examples 6 and 9, the uniform thin films were slightly thinner. The former is designed to increase the permeation rate of oxygen, while the latter is designed to prevent the permeation of water vapor and carbon dioxide. In these cases, the support of the composite membrane is composed of an alkali-resistant material. The present invention can be most clearly explained in detail by comparing the characteristics of these batteries with Comparative Example 3 in which no composite membrane was used. First, in a heavy load test at 20°C and normal humidity, the discharge period is short, and the effects of moisture uptake and dissipation, as well as the effects of carbon dioxide gas, are small. There is no need to give much consideration to gas permeation prevention. Therefore, under such conditions, excellent characteristics can also be obtained in Comparative Example 3. On the other hand, among the above-mentioned examples, 1 to 6
Discharge characteristics equivalent to those of Comparative Example 3 were obtained, indicating that the rate at which oxygen permeates through the composite membrane sufficiently follows the rate at which oxygen is consumed in the discharge reaction. In the case of Examples 6 and 9, although the discharge voltage and duration were slightly inferior, they showed comparable good characteristics, and the supply of oxygen was carried out in a satisfactory manner. On the other hand, in the case of light load discharge, the discharge period is long, and when the outside air is high or low humidity, preventing the permeation of moisture and carbon dioxide gas, especially moisture, becomes more important than the oxygen supply rate in order to obtain excellent performance. The battery of Comparative Example 3, which does not have a mechanism to prevent the permeation of moisture and carbon dioxide gas, has a voltage drop during discharge due to depletion of moisture or, conversely, blockage of air holes due to leakage due to excess moisture intake. However, the capacity obtained is only a portion of the discharge capacity obtained in the heavy load test. Furthermore, it goes without saying that liquid leakage during discharge is a fatal problem from a practical standpoint. On the other hand, the Examples showed extremely excellent performance, with a capacity almost equal to the discharge capacity in the heavy load test, and among them, Examples 6 and 9, which had a relatively thick uniform thin film layer, were better. These trends are the same whether the test atmosphere is high humidity or low humidity. This shows that, in the case of the example, the composite membrane sufficiently exhibits the permeation blocking effect of moisture and carbon dioxide gas. In addition, since Examples 7 and 8 use a material with weak alkali resistance for the microporous membrane, it is gradually corroded by the electrolyte during the discharge period and the oxygen permeability deteriorates.
The performance is slightly inferior to Examples 1 to 8.9 in both heavy load characteristics and light load characteristics, but when compared with Comparative Example 3, the light load characteristics are far superior. In addition, in Comparative Examples 1 and 2, the water vapor and carbon dioxide gas permeation blocking ability of the uniform thin film is sufficient, but the oxygen permeation rate is not sufficient, so the discharge characteristics under light load are not much inferior to those of the example. However, the heavy load characteristics are significantly inferior to those of the examples.

Taking all the above into consideration, poly(1-(+-limethylsilicon/l)
Prototype batteries using a composite film of a uniform thin film of (1-propyne) and a microporous film have excellent both heavy-load and light-load characteristics, and are also responsive to changes in the external atmosphere. Provides an excellent battery when the uniform thin film of ['1-()limethylsilyl)-1-propyne] has a thickness of 0.06 to 1°Q/1m and an alkali-resistant porous film is used as the support. We can conclude that it is possible.

In addition, in the above example, a composite film in which a thin film of Bo'J [1-(1-limethylsilyl)-1-propyne] is attached to one side of a microporous support film or a support film that integrates a microporous film and a nonwoven fabric is used. However, the present invention also applies to the case of a composite film in which thin films are formed on both sides of a support film.
If the total film thickness is 0.05 to 1.0 μm, excellent battery performance can be obtained as described above. Furthermore, poly(1-()IJmethylsilyl)-1-propyne] shown in Examples
Similar effects can be obtained by using other alkali-resistant microporous membranes (for example, nylon microporous membranes) as the supporting microporous membrane. In addition, in the examples, a case where the support is a composite layer in which a microporous membrane and a nonwoven fabric made of polypropylene are integrated is explained, but if the nonwoven fabric is made of other alkali-resistant material such as polyethylene or nylon, a similar method may be used. Effects can be obtained.

Note that in the above embodiments, the composite membrane of the present invention was installed between the battery container and the porous body for air diffusion, but the composite membrane of the present invention is a microporous membrane, and in some cases, a nonwoven fabric is further integrated into the composite membrane of the present invention. It is composed of a support.

Therefore, there is no difference in battery characteristics even if the porous body for air diffusion is removed. However, if the composite membrane does not have sufficient strength and deforms toward the air intake hole, the composite membrane can maintain a stable shape by installing a porous body. Furthermore, in the above example, the composite membrane of the present invention was installed between the oxygen electrode and the porous membrane that supported the oxygen electrode, but if the oxygen electrode had sufficient strength, the porous membrane was unnecessary and could be removed. However, the battery characteristics remain unchanged.

It was also confirmed that an air battery using an aqueous solution of a neutral salt such as ammonium chloride or zinc chloride as an electrolyte has the same effect as a battery using an alkaline electrolyte shown in the example. .

Effects of the Invention As is clear from the above explanation, the oxygen gas diffusion electrode according to the present invention has excellent practical performance across heavy to light loads for batteries using a neutral or alkaline aqueous solution as the electrolyte, and excellent performance. Leak resistant.

The effect is that it can be stored for a long time.

[Brief explanation of the drawing]

Figure 1 is a half-sectional view of a button-type zinc-air battery used to study examples and comparative examples of the present invention, Figure 2 is a partially enlarged view of the main parts of Figure 1, and Figure 3 is a composite membrane used. FIG. 2 is a cross-sectional structural diagram of a conventional button-type zinc-air battery. 1... Oxygen electrode (air electrode), 2... Water-repellent membrane, 3... Air intake hole, 4... Porous membrane, 6, 6. ... Separator, 7 ... Negative electrode zinc, 8 ... Negative electrode container, 9 ... Insulating gasket, 1o ... Positive electrode container, 11 ...・・・
...Composite membrane.

Claims (7)

[Claims] (1) A gas diffusion electrode having oxygen as an active material and a battery container having an air intake hole communicating with the outside air, between the air intake side of the gas diffusion electrode and the inner surface of the battery container,
A battery characterized by interposing a composite film formed from a thin film of poly[1-(trimethylsilyl)-1-propyne] and one or more microporous membranes supporting the thin film. (2) Composite membrane poly[1-(trimethylsilyl)-1-
Claim 1, characterized in that the thin film side of the composite membrane (propyne) is in contact with the inner surface of the battery container having an air intake hole, and the gas diffusion electrode is in contact with the microporous membrane side of the composite membrane. battery. (3) The battery according to claim 2, characterized in that an air diffusion porous body is interposed between the composite membrane and the battery container. (4) The battery according to claim 2, characterized in that a microporous membrane for supporting the gas diffusion electrode made of polytetrafluoroethylene or the like is interposed between the composite membrane and the gas diffusion electrode. (5) An air diffusion porous material such as a nonwoven fabric is interposed between the composite membrane and the battery container, and a gas diffusion electrode support made of polytetrafluoroethylene or the like is provided between the composite membrane and the gas diffusion electrode. The battery according to claim 2, characterized in that a microporous membrane is interposed. (6) Any one of claims 1 to 5, wherein the microporous membrane is an alkali-resistant membrane whose main component is polyolefin such as polypropylene or polyethylene, fluororesin, polysulfone, etc. Batteries listed. (7) The battery according to any one of claims 1 to 6, wherein the microporous membrane is a composite layer in which an alkali-resistant nonwoven fabric whose main component is polypropylene or the like is integrated.