JPH01267971A - 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 polyvinyltriorganosilane and a fine porosity film supporting it, 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 polyvinyltriorganosilane 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. This film of polyvinyltriorganosilane is non-porous, homogeneous, and having oxygen selective permeability, and is suitably of 1.0mum thick or less in order to provide sufficient oxygen permeating speed and the permeation hindering ability for water vapor and CO2 gas. 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 flows in and out from the gas diffusion electrode (oxygen electrode) depending on the internal vapor pressure, causing changes in the concentration and volume of the electrolyte in the battery, and this changes the battery characteristics. was influencing. Taking a button-type air battery as an example, the situation will be explained using FIG. 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, and 5 is a porous body that diffuses air.
, 6 is a separator, and 7 is a negative electrode made of a mixture of an aqueous potassium hydroxide solution and frozen zinc powder. Generally, potassium hydroxide solution is used as alkaline electrolyte, and its concentration is 3
It is 0 to 36chi. For this reason, when the relative humidity is higher than 47 to 69 degrees, 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 addition,
In the figure, 8 is a negative electrode container, 9 is an insulating gasket, and 1o is a positive electrode 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. 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.

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 prevent 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 and the inner surface of the battery container of a battery having a gas diffusion electrode using oxygen as an active material and a battery capacity having an air intake hole communicating with the outside air. In between, an oxygen selectively permeable composite membrane formed from a thin film of polyvinyl 1) organosilane and a microporous membrane supporting this thin film is interposed.

The above-mentioned polyvinyltriorganosilane is a polymer represented by the structural formula, and its thin film is a non-porous, homogeneous thin film that has selective permeability for oxygen, and has sufficient oxygen permeation rate and ability to block the permeation of water vapor and carbon dioxide gas. To obtain this, a thickness of usually 1.0 μm or less, preferably 0.2 to 0.571 m 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 focuses on the characteristics of a homogeneous thin film of polyvinyltriorganosilane as a thin film with excellent selective oxygen permeability, and furthermore, the microporous membrane supporting this thin film is made of polyolefin such as polypropylene, polyethylene, etc. with excellent alkali resistance. , fluorinated ST fat, polysulfone, etc., were selected and completed after careful consideration. Note that the microporous membrane may be a single layer, but
In order to ensure strength during handling, manufacturing, or use, a two-layer or more structure may be provided in which an alkali-resistant nonwoven fabric is further integrated, if necessary.

Composite membranes in which a thin film of abolyvinyltriorganosilane is supported by a porous membrane include polydimethylsiloxane and polysiloxane transparent conductors as disclosed in JP-A No. 54-56985, etc.; Combustion aid 9
Practical use is only being considered for applications such as petroleum protein processing, waste liquid treatment aeration, and exhalation in medical care. It is targeted. 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 their application to batteries has been considered.For example, as disclosed in JP-A-69-76582, polydimethylsiloxane, Application 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 intensive studies on various oxygen permeable membranes for use in batteries, the present invention has developed a composite membrane in which a polyvinyltriorganosilane thin film is integrated with a microporous membrane, which comprehensively satisfies the above-mentioned characteristics for use in 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 manufacturing the composite membrane used in the present invention, but typically, as disclosed in JP-A-54-146277,
A method in which a solution of polyvinyltriorganosilane dissolved in a solvent such as toluene with high solubility is applied thinly to a flat surface such as a glass plate, dried, the thin film is peeled off from the glass surface, and superimposed on a porous film, or the method described above The above-mentioned solution is dropped onto the water surface, and the formed thin film is placed on a microporous membrane as a support below the water surface and then dried. It is classified into methods such as applying the above solution directly onto the microporous membrane and drying it. Either method can be used, but a thin film without pinholes is formed and the polyvinyltriorganosilane penetrates into the microporous membrane. It is necessary that the pores are not occluded.

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 for a practical battery and the performance when discharged for a long time in a high temperature and low humidity atmosphere are satisfied.

Examples The effects of the present invention were demonstrated in a battery using a composite membrane using polyvinyltriorganosilane with R1=R2=R3=CH3, a battery using a polydimethylsiloxane single membrane, and a battery not using the above composite membrane. The battery was prototyped and evaluated. First 1. In the case of a comparative example in which the above 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. 11 (see FIG. 2) or a single membrane of the comparative example, and the only difference from FIG. 3 is that the composite membrane 11 is arranged so that the polyvinyltriorganosilane thin film side faces the air intake hole 3 side It is.

The polyvinyltriorganosilane composite membrane tested was prepared by dropping a polymer solution of polyvinyltriorganosilane in toluene onto the water surface, placing the obtained ultrathin membrane on a porous support membrane in water, and then drying it. did. The thickness of the polyvinyltriorganosilane thin film layer was adjusted by varying the temperature of the polymer solution and the water into which it was added. 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: about 30 μm) or a composite layer made by integrating this with a nonwoven fabric (thickness: about 150 μm).

The prototype battery has a diameter of 11.6 m and a total height of 5.4 m, and is rated at 20°C and room temperature (60%) under a relatively heavy load (76Ω).
The sufficiency of the rate of oxygen uptake from the air into the battery was evaluated by continuous discharge at a relatively light load (3Ω).
at 20°C and high humidity (90% RH).

Continuous discharge for a long period of time at low humidity (20% RH) will affect 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. The degree was 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 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 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 be obtained even in the comparative example. On the other hand, among the aforementioned Examples 1 to 6, discharge characteristics equivalent to those of Comparative Example 3 were obtained, and the rate at which oxygen permeates through the composite membrane sufficiently follows the rate at which oxygen is consumed in the discharge reaction. It shows that you are doing it. In Examples 6 to 9, although the discharge voltage and duration were slightly inferior, they exhibited 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, the oxygen supply rate may be lower than the oxygen supply rate, and moisture and carbon dioxide gas, especially moisture permeation prevention, is required to obtain excellent performance. The battery of Comparative Example 3, which does not have a mechanism to prevent water and carbon dioxide permeation, has a voltage drop during discharge due to depletion of water or, conversely, blockage of air holes due to leakage due to excessive water intake. However, the capacity obtained is only a portion of the discharge capacity obtained in the heavy load test. Needless to say, liquid leakage during discharge is a fatal problem in practical terms. 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 occur when the test atmosphere is highly humid.

The same applies to both cases of 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 Examples 1 and 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 uniform thin film of polyvinyltriorganosilane and a microporous film has excellent both heavy-load and light-load characteristics, and has good responsiveness to changes in the external atmosphere. In particular, it can be concluded that an excellent battery can be provided when the uniform thin film of polyvinyltriorganosilane has a thickness of 0.2 to 1.0 μm and an alkali-resistant porous film is used as the support.

In the above example, a composite film using polyvinyltriorganosilane with R1=R2=R3=CH3 was explained, but some of R1, R2, and R3 were all H, C2S5. It has been confirmed that almost the same effect can be obtained with a composite film using C3H7 polyvinyltriorganosilane.

However, in the above embodiments, a composite film in which a thin film of polyvinyltriorganosilane is attached to one side of a microporous support film or a support film in which a microporous film and a nonwoven fabric are integrated is used. Even in the case of a composite membrane in which thin films are formed on both sides of a support membrane, if the total film thickness of polyvinyltriorganosilane is 0.2 to 1.0 μm, excellent battery performance can be obtained in the same way as described above. Furthermore, the microporous membrane supporting polyvinyltriorganosilane shown in the examples can also be used with other microporous membranes having alkali resistance (for example, microporous nylon membranes) to obtain the same effect. 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.

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 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. The battery is composed of a support, 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 embodiments, 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 could be unnecessary. Even if it is removed, the battery characteristics will not change.

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. Now, the present invention can be explained in detail for the same reasons as the examples.

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 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 Wi (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,
1. A battery comprising a composite membrane formed from a polyvinyltriorganosilane thin film and one or more microporous membranes supporting the thin film. (2) The polyvinyltriorganosilane thin film side of the composite membrane is in contact with the inner surface of the battery container having air intake holes, and the gas diffusion electrode is in direct contact with the microporous membrane side of the composite membrane. A battery according to claim 1, characterized in that: (3) The polyvinyltriorganosilane microporous film side of the composite membrane is in contact with the inner surface of the battery container having air intake holes, and the gas diffusion electrode is in direct contact with the thin film side of the composite membrane. A battery according to claim 1, characterized in that: (4) The battery according to claim 2 or 3, characterized in that air diffusion porosity 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. The battery according to item 2 or 3. (6) An air-diffusion porous material such as a non-woven fabric is interposed between the composite membrane and the battery container, and a porous film such as polytetrafluoroethylene is provided 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 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.