JPH01267973A - Battery - Google Patents

Abstract

PURPOSE:To prevent the CO2 gas and water vapor in the atmosphere from intruding into a battery for a long period of time by interposing a complex film, which is formed from a film of bisu (3-isocyanopropyle) tetramethyldisiloxane-4,4-diaminofenylether copolymer and a fine porosity film, between the air intake side of a gas diffusion electrode and the inner surface of a battery jar. CONSTITUTION:A battery is equipped with a gas diffusion electrode 1 using oxygen as active substance and a battery jar having an air intake hole 3 leading to the outside air, and an oxygen selective permeative complex film 11 formed from a film 2 of bisu (3-isocyanopropyle) tetramethyldisiloxane-4,4- diaminofenylether copolymer and a fine porosity film 4 supporting it is interposed between the inner surface of the battery jar and the air intake side of the gas diffusion electrode 1 of this battery. This permits provision of excellent performance in practical application, fine anti-leak property, and a long-time storing characteristic.

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, and a metal such as zinc, magnesium, or aluminum, or alcohol, hydrazine, or hydrogen. The present invention relates to a battery equipped with a negative electrode active material such as.

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 enters and exits from the gas diffusion electrode (oxygen electrode) depending on the internal vapor pressure, causing a change in concentration and volume of the electrolyte in the battery, and this changes the battery life. affected the characteristics. 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; 5.
6 is a separator, and 7 is a negative electrode made of a mixture of potassium hydroxide aqueous solution and frozen zinc powder. Generally, an aqueous potassium hydroxide solution is used as an alkaline electrolyte, and its concentration is 3
It is 0-36%. For this reason, when the relative humidity is higher than 47% to 59%, external moisture is taken in, causing a decrease in the concentration of the electrolyte 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 the figure, 8 is a negative electrode container, 9 is an insulating gasket, and 10 is a positive impact container.

In order to improve 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 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 holes extremely small and limiting the amount of oxygen supplied, but neither method prevents leakage. However, there remained major issues regarding discharge performance, especially performance during long-term discharge. 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 to supply air to the oxygen electrode through a membrane that suppresses the permeation of water vapor and carbon dioxide gas and selectively allows oxygen to permeate, for example, using polysiloxane-based membranes. A method has been proposed that uses a film in which a uniformly porous thin film, a thin film of a metal oxide, or a thin film of an organic compound containing metal atoms is integrated with a suitable porous film.

Problems to be Solved by the Invention However, to date, it has not been possible to obtain sufficiently effective selective permeability for oxygen gas or water vapor.

It has not been put into practical use because it has had technical issues such as insufficient ability to block carbon dioxide gas permeation, and therefore cannot obtain satisfactory discharge performance and cannot withstand long-term use or storage.

Therefore, the present invention aims to improve the storability and long-term use performance of the above-mentioned battery, as well as 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 of a battery equipped with a gas diffusion agent using oxygen as an active material and a battery container having an air intake hole communicating with the outside air to the inner surface of the battery container. In between, an oxygen selectively permeable composite membrane formed from a thin film of bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer and a microporous membrane supporting this thin film is interposed. It is something that makes you

The thin film of the above-mentioned bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer is a non-porous, homogeneous thin film with selective oxygen permeability and a sufficient oxygen permeation rate. In order to obtain permeation blocking ability for water vapor and carbon dioxide gas, the thickness is usually 1.0 μm or less, preferably 0.0 μm or less.
A thickness of 2 to 0.6 μm is suitable. The microporous membrane supporting this thin film is preferably a microporous membrane through which gas can easily permeate, and whose surface has smoothness and pore size suitable for supporting the above-mentioned thin film in a uniform and non-porous state. It is preferable that the average pore diameter on the surface of the microporous membrane is 3 to 0.01 μm.

The present invention is a thin film with excellent selective oxygen permeability.
3-isocyanopropyl)tetramethyldisiloxane-
Focusing on the characteristics of a homogeneous thin film of 4,4'-diaminophenyl ether copolymer, we also added materials such as polypropylene, polyolefin such as polyethylene, which has excellent alkali resistance, fluororesin, polysulfone, etc. to the microporous membrane that supports this thin film. 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 bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer was supported by a microporous membrane was disclosed in Japanese Patent Application Laid-open No. 54
There are polydimethylsiloxane and polysiloxane derivatives as disclosed in No. 56985, etc., and they are used for blast furnace ventilation, combustion assistance, petroleum protein process, waste liquid treatment aeration.

Practical use is only being considered for use in exhalation in medicine, and the main purpose is oxygen enrichment, with only the oxygen and nitrogen separation coefficient and oxygen permeation rate being evaluated. In order to apply these membranes to batteries that can obtain satisfactory discharge performance even under heavy load discharge conditions, it is important that the oxygen permeation rate be sufficiently high and that the permeation blocking ability of water vapor and carbon dioxide gas be excellent. However, until now, many of these characteristics have been unknown, and there have been few cases where application to batteries has been considered. For example, as disclosed in JP-A-59-75582, polydimethylsiloxane.

The use of membranes such as polydimethylsiloxane-polyhydroxystyrene crosslinked copolymers has been proposed, but the oxygen permeation rate is insufficient and satisfactory performance cannot be obtained in discharge under heavy loads. As a result of extensive research into various types of oxygen permeable membranes for batteries, the present invention has developed bis(3-isocyanopropyl)
A composite membrane in which a thin film of tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer is integrated with a microporous membrane comprehensively satisfies the above-mentioned characteristics for batteries, and the performance of batteries using this membrane is improved. It was completed after discovering that it was extremely superior.

There are various methods for manufacturing the composite membrane used in the present invention, but typically, as disclosed in JP-A-54-146277,
A solution of bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer dissolved in a highly soluble solvent such as toluene is applied thinly to a flat surface such as a glass plate and dried. A method of peeling a thin film from a glass surface and superimposing it on a porous membrane, or a method of dropping the above solution onto the water surface and spreading it on the water surface to form a thin film and placing it under the water surface as a microporous membrane as a support. There are two types of methods: the water spreading method, in which the solution is applied directly onto the microporous membrane that is the support, and then dried. A thin film is formed, and bis(3-isocyanopropyl)tetramethyldisiloxane-4,4' is formed in the microporous film.
- It is necessary that the diaminophenyl ether copolymer penetrates and the pores are not blocked.

Effect: With this configuration, the above-mentioned composite membrane should satisfy 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 the battery tests in the examples described later. This condition satisfies both the heavy load discharge performance required of a practical battery and the performance when discharged for a long time in a high temperature and low humidity atmosphere.

EXAMPLE The effects of the present invention were demonstrated in a battery using a bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer composite membrane.

A battery using a single polydimethylsiloxane membrane and a battery not using the above-mentioned 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 the composite membrane 11 are almost the same as those shown in FIG. 3, and as shown in FIG. The membrane 11 (see Figure 2) or a single membrane of a comparative example is interposed, and the composite membrane 11 has a thin film side of bis(3-isocyanopropyl)tetramethyldisiloxane-4°4'-diaminophenyl ether copolymer. The only difference from FIG. 3 is that it is arranged so as to face the air intake hole 3 side.

The tested bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer composite film was bis(3-isocyanopropyl)tetramethyldisiloxane-4°4'-diaminophenyl. An ultrathin film obtained by dropping a polymer solution of an ether copolymer dissolved in toluene onto the water surface was placed on a porous support film in water, and then dried. The thickness of the thin film layer of bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer was adjusted by changing the temperature of the polymer solution and the water into which it was dropped. . The polydimethylsiloxane thin film used as a comparative example was prepared by applying a thin layer of a solution dissolved in toluene onto a glass plate and drying it. All of the support membranes in Examples were microporous membranes (pore diameter: approximately 0.1 to 0.05 μm,
A thin film layer was formed on the microporous membrane side using a single layer (thickness: approximately 30 μm) or a composite layer in which this was integrated with a nonwoven fabric (thickness: approximately 150 μm).

The prototype battery has a diameter of 11.5ff and a total height of 6.4n.
20'C under relatively heavy load (75Ω), normal humidity (6
The sufficiency of the oxygen uptake rate from the air into the battery was evaluated by continuous discharging at 0% RH) at 20°C9 high humidity (90% RH) at a relatively light load (3Ω), and low humidity (20
%RH), and evaluate the influence 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 during the long-term discharge period. did.

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

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

(Hereinafter referred to as Gold and White) In Table 2, the discharge end voltages are both O and SV, and the weight change shows the increase and decrease before and after the discharge test, mainly due to the amount of moisture taken in or dissipated during discharge. This is a suggestive number.

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 to 9, uniform thin films were formed with a slightly higher uniformity. 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 the heavy load test at 20'C1 normal humidity, the discharge period is short and there is little effect of moisture uptake and dissipation, as well as the influence of carbon dioxide gas, so if the oxygen supply rate is sufficient, the battery performance There is no need to consider blocking the permeation of carbon dioxide or carbon dioxide gas. Therefore, under such conditions, excellent characteristics can be obtained even in Comparative Example 3. On the other hand, among the above-mentioned embodiments, 1 to 1
In Example 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. Examples 6-9
In the case of , the discharge voltage and duration are slightly inferior, but the characteristics are comparable and good, and the supply of oxygen is being carried out satisfactorily. 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 excessive intake of moisture. death,
A capacity equivalent to only a portion of the discharge capacity obtained in the heavy load test is obtained. 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 being obtained, and among them, Examples 6 to 9, in which the uniform thin film layer was relatively thick, were more excellent.

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, in Comparative Example 1.2, the film thickness is thick, so the water vapor and carbon dioxide 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 as good as the examples. Although it is comparable in comparison, the heavy load characteristics are significantly inferior to the examples.

Taking all the above into account, the prototype battery using a composite film of a homogeneous thin film of bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer and a microporous film can be used under heavy loads. Characteristic.

It has excellent light load characteristics and good response to changes in the external atmosphere, especially the uniformity and thin film thickness of bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer. Sao 0.2~1.0
It can be concluded that an excellent battery can be provided when an alkali-resistant porous membrane with a micrometer diameter is used as a support.

In addition, in the above example, a thin film of bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer is integrated with a microporous support film or a microporous film and a nonwoven fabric. Although the case in which a composite membrane is used in which a thin film is formed on one side of a supporting membrane has been described, the present invention also applies to a composite membrane in which a thin film is formed on both sides of a supporting membrane.
3-isocyanopropyl)tetramethyldisiloxane-
If the total film thickness of the 4,4'-diaminophenyl ether copolymer is 0.2 to 1.0 μm, excellent battery performance can be obtained as described above. Furthermore, the screws (3-
isocyanopropyl)tetramethyldisiloxane-4,
Similar effects can be obtained by using other alkali-resistant microporous membranes (for example, nylon microporous membranes) as the microporous membrane supporting the 4'-diaminophenyl ether copolymer. Also,
In the example, 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 the same effect can be obtained if the nonwoven fabric is made of other alkali-resistant material such as polyethylene or nylon. can get.

In addition, although the example shows the case where the thin film side of the composite membrane is brought into contact with the air intake hole side, it has been confirmed that almost the same result will be obtained even if the thin film side of the composite membrane is brought into contact with the gas diffusion electrode side. .

In addition, in the above examples, the composite membrane of the present invention was installed between the battery container and the porous material for air diffusion, but the composite membrane of the present invention is a microporous membrane, and in some cases, a nonwoven fabric integrated into the composite membrane. The battery is composed of a support body, and 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. We also confirmed that an air battery using an aqueous solution of neutral salts such as ammonium chloride or zinc chloride as an electrolyte has the same effect as the battery using an alkaline electrolyte shown in the example. The present invention can be explained in detail for the same reason as the examples.

Effects of the Invention As is clear from the above explanation, the acid according to the present invention
The elemental gas diffusion electrode has excellent practical performance under heavy to light loads for batteries that use a neutral or alkaline aqueous solution as the electrolyte, and excellent leakage resistance.

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 Figure 1, and Figure 3 shows no composite membrane used. FIG. 1 is a half-sectional view 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, 10... Positive electrode container, 11...・
...Composite membrane.

Claims (8)

[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 composite membrane formed from a thin film of bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer and one or more microporous membranes supporting the thin film is interposed. A battery characterized by: (2) the thin film side of the bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer of the composite membrane is brought into contact with the inner surface of the battery container having an air intake hole; 2. The battery according to claim 1, wherein a gas diffusion electrode is in direct contact with the microporous membrane side of the composite membrane. (3) The microporous membrane side of the bis(3-isocyanopropyl)tetramethyldisiloxane-4,4'-diaminophenyl ether copolymer of the composite membrane contacts the inner surface of the battery container having air intake holes. 2. The battery according to claim 1, wherein a gas diffusion electrode is in direct contact with the thin film side of the composite membrane. (4) The battery according to claim 2 or 3, characterized in that an air diffusion porous material such as a nonwoven fabric is interposed between the composite membrane and the battery container. (5) A microporous membrane that supports an oxygen electrode made of a porous film such as polytetrafluoroethylene (PTFE) is interposed between the composite membrane and the gas diffusion electrode. A battery according to scope 2 or 3. (6) A porous air diffusion material such as a nonwoven fabric is interposed between the composite membrane and the battery container, and a porous film such as polytetrafluoroethylene is interposed between the composite membrane and the gas diffusion electrode. The battery according to claim 2 or 3, characterized in that a microporous membrane supporting the oxygen electrode is interposed. (7) The microporous membrane forming the composite membrane is an alkali-resistant microporous membrane containing polyolefin such as polypropylene, polyethylene, fluororesin, polysulfone, etc. as a main component. The battery according to any of paragraph 6. (8) Claims 1 to 6 are characterized in that the microporous membrane forming the composite membrane is a composite layer integrated with an alkali-resistant nonwoven fabric mainly composed of polypropylene or the like. A battery described in any of the above.