JPH0644954A - Battery and selective permeation film used therefor - Google Patents

Abstract

PURPOSE:To prevent the permeation of water vapor, and allow the efficient permeation of only oxygen by providing a selective permeation film having permeation holes. CONSTITUTION:Regarding a battery 1 where an air electrode 5 utilizing oxygen as an active material is laid inside a positive electrode vessel 2 having air holes 21, at least one layer of a selective permeation film 7 having a plurality of permeation holes is provided in a gap between the air electrode 5 and the positive electrode vessel 2. Also, an air diffusion porous body 8 may be laid in a gap between the film 7 and the electrode 5, or between the film 7 and the vessel 2, or between the film 7 and both of the electrode 5 and vessel 2, whenever necessary. Also, polytetra-fluoroethylene porous film may be laid so as to be adjacent to the air electrode 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery and a selective permeable membrane used in the battery, and its object is to change the weight of the battery and the operating voltage of the battery even when environmental conditions such as humidity change. A battery that has both a heavy load discharge characteristic that is not significantly affected by environmental changes and a long-term discharge characteristic in an atmosphere of high and low humidity, and that suppresses the permeation of water vapor and allows only oxygen to permeate appropriately, and a battery To provide an excellent selective permeable membrane that has an extremely small effect on the performance of. In addition, in this specification, the opening ratio refers to a ratio of the total area of the open hole portion, and refers to a numerical value represented by the following Expression 1 (Equation 1).

[Equation 1]

[0002]

BACKGROUND OF THE INVENTION At the present time, the use of "alkaline batteries" has become the mainstream as a powerful type battery replacing manganese dry batteries. This "alkaline battery" has an electrolyte of 30-40
% Of potassium hydroxide, it is a high-performance battery that can be continuously used as a power source for motors and lamps, and is also suitable for continuous discharge of large currents. Batteries "," alkaline manganese batteries ", or" mercury batteries ".

However, these alkaline batteries also have various problems. In other words, the "silver oxide battery" has a problem that the price of "silver", which is a raw material, fluctuates so much that a stable supply cannot be provided over a long period of time. However, there was a problem that the voltage gradually decreased. On the other hand, the "mercury battery" has a larger capacity than the "silver oxide battery" and the "alkaline manganese battery", and moreover, when discharged, mercury in the positive electrode is reduced and the internal resistance decreases, so the voltage is more constant than the "silver oxide battery". It has excellent performance such as easy to keep,
It is necessary to pay sufficient attention to the method of collecting used batteries and the incineration process, and the current situation is that their production has been refrained from the problems of environmental pollution. Therefore, in recent years, attention has been paid to "fuel cells" and "air cells" as batteries that hardly use heavy metals such as mercury and have no problem of environmental pollution.

[0004]

2. Description of the Related Art This "fuel cell" has a mechanism in which hydrogen sent to the negative electrode is used as fuel and oxygen sent to the positive electrode is reacted in an electrolytic solution as an oxidant, and is used in space development and undersea operations. It is a next-generation battery that has received a great deal of attention. Further, the "air battery" is a battery having a semi-fuel type button type or a cylindrical shape in which hydrogen in the negative electrode of the "fuel cell" is zinc. Taking a button type as an example of this, as shown in FIG. 8, a diffusion paper (k) for diffusing air inside, a water repellent film (c) for controlling the inflow and outflow of air, and preventing air leakage, The positive electrode container (p) in which the electrode (b) and the cellophane separator (s) are arranged, and the negative electrode container (m) in which the negative electrode zinc (z) made of a mixture of an electrolytic solution and zinc powder are provided, respectively. It is configured to be sealed via a gasket (g). In this air battery (E),
There is an air hole (a) at the bottom of (p).
Peel off the seal (t) on (a) and take in air naturally,
The oxygen was used as an active substance.

In the air battery (E) having such a structure, it is easily affected by the external environment, and in particular, water vapor enters and leaves the air electrode (b) due to a change in humidity.
As a result, the performance of the battery is affected. In other words, when the relative humidity of the outside is higher than the relative humidity of the electrolyte, the humidity of the outside air is taken into the battery, which reduces the concentration of the electrolyte and reduces the discharge performance and leakage of the electrolyte. When the relative humidity of the outside is less than the relative humidity of the electrolyte, the evaporation of the electrolyte occurs and the internal resistance in the battery increases and the battery life (the battery characteristics after being left for a long time) There were problems such as inferiority. Therefore, in order to reduce the influence of such relative humidity, the air electrode (b)
Research is progressing on the film provided between the air hole (a) and the air hole (a), and development of a silicon-based uniform thin film or a film in which a porous film and an organic compound are laminated is under development. .

However, in general, a polymer film or membrane has a property of allowing water vapor to permeate better than oxygen, so that not only hydrophilic materials but also hydrophobic materials such as fluororesins selectively allow water vapor to pass therethrough. There is a tendency. Therefore, even if the film is thinned to improve the oxygen permeability or a film having a high oxygen permeability such as a silicon resin is used, the water vapor is still more permeable than oxygen. Therefore, when such a membrane is used in a battery, as described above, the permeation of water vapor inside and outside the battery is unavoidable. Therefore, even if a large amount of oxygen, which is an active substance, is taken in to obtain a high current value, There is a problem that properties such as storability, life, and discharge characteristics are deteriorated.

As described above, almost all polymer films have selective permeability to water vapor, and therefore, most of the air batteries currently in practical use use a polytetrafluoroethylene porous film. ing. Unlike other polymer films, polytetrafluoroethylene porous membrane has the property of permeating oxygen and water vapor at almost the same rate, and was an excellent material as a selective permeable membrane for use in batteries. .

[0008]

However, even in the above-mentioned porous membrane made of polytetrafluoroethylene,
After all, there was a problem that water vapor transmission was unavoidable. Therefore, a technique for minimizing the aperture ratio and the pore diameter of the polytetrafluoroethylene porous membrane has been attempted, but if the aperture ratio and the pore diameter are reduced in this way,
Although the permeation of water vapor is suppressed, at the same time, the permeation of oxygen, which is an active substance, is also hindered more than the permeation of water vapor, and when such a membrane is used in a battery, sufficient essential current can be obtained. There was a problem of disappearing. That is, as shown in FIG. 10, in the above-mentioned porous film made of polytetrafluoroethylene, when the aperture ratio is made small, the current obtained in this film is extremely lowered, and further, the value of the obtained current is increased. There was a problem that variation occurred in the. Moreover, in such a porous membrane made of polytetrafluoroethylene, it is difficult to control the opening ratio and the pore diameter, and variations easily occur, and the variations in the opening ratio and the pore diameter greatly affect the performance of the battery. There was a problem of being lost. Therefore, in the industry, a battery that suppresses the permeation of water vapor, selectively allows only oxygen to permeate, and exhibits excellent characteristics even when the environmental conditions of the outside air such as humidity change, and the battery used in this battery It has been desired to create an excellent selective permeable membrane.

[0009]

According to the present invention, there is provided a battery in which an air electrode having oxygen as an active substance is provided inside a positive electrode container having an air hole, the air electrode and the positive electrode container. At least one layer of permselective membrane is interposed in the gap of the cell, and the permselective membrane is provided with a plurality of permeation holes.
The selective permeation membrane is characterized in that a plurality of permeation holes having a diameter of μm or less are formed, the aperture ratio of the permeation holes is 10% or less, and the obtained current density is at least 10 mA / cm ² or more. By providing a selectively permeable membrane, the above-mentioned conventional problems are solved.

[0010]

The water vapor from the outside air is blocked by the permeation holes of the selectively permeable membrane disposed in the gap between the inside of the positive electrode container and the air electrode, and the permeation of the water vapor is blocked, and sufficient oxygen for batteries is used. A permeation rate is exhibited, and excellent practical performance and stable long-term storage stability are obtained even under heavy load. Also,
An air diffusion porous body is provided in the gap between the positive electrode container and the selective permeable membrane, the gap between the air electrode and the selective permeable membrane, the gap between the positive electrode container and the selective permeable membrane, and the gap between the air electrode and the selective permeable membrane. When the structure is provided, oxygen can be efficiently sent to the air electrode. Furthermore, when the structure is such that a polytetrafluoroethylene (PTFE) porous film is provided adjacent to the air electrode, high water repellency can be exhibited. Further, even if a plurality of permeation holes having a diameter of 300 μm or less are formed in a polymer film or a uniform film and the opening ratio of the permeation holes is reduced to 10% or less, the permeability to oxygen is not impaired and the permeation of water vapor It becomes an excellent selective permeable membrane that can selectively inhibit only the conductivity and obtain a current of a certain level or more.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A battery according to the present invention and a selective permeable membrane used in this battery will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional explanatory view showing an embodiment of a battery according to the present invention, in which a positive electrode container (2) provided with an air hole (21) and a negative electrode zinc (31) are filled. The negative electrode container (3) is sealed with a gasket (4). Positive electrode container
An air electrode (5) and a separator (6) are provided inside the (2), and oxygen in the air taken in through the air holes (21) is used as an active substance. (7) is a permselective membrane having a plurality of perforations. The selective permeable membrane (7) is not particularly limited, but polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, fluorinated ethylene propylene copolymer, perfluoroalkyl vinyl ether polymer, perylene Fluoroalkyl vinyl ester polymers, ethylene tetrafluoroethylene copolymers and other fluorine-based polymers or copolymers, as well as polyolefins such as polyethylene and polypropylene,
A versatile polymer film such as polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, polystyrene or the like, or a uniform film has a high water vapor transmission inhibiting ability even if it is a relatively thin film, and is therefore desirable.

In the present invention, a permeation hole is formed in the polymer film or the uniform film having a high water vapor transmission inhibiting ability to form a selective permeable membrane, so that the water vapor transmission inhibiting ability is not lowered so much and We have succeeded in dramatically improving oxygen permeability. The shape of the perforated hole to be perforated may be circular or elliptical, and various shapes may be appropriately determined by the perforating means, and are not particularly limited. Regarding the size of the perforated holes, the diameter at the longest part is 300 μm or less, preferably 100 μm or less. Further, it is desirable that the opening ratio is 10% or less, preferably 3% or less of the area where oxygen effectively permeates on the inner surface of the positive electrode container (2).

The reason for this is that if the diameter of the permeation holes exceeds 300 μm and the opening ratio exceeds 10% of the area through which oxygen effectively permeates, the water vapor permeation inhibiting ability is extremely reduced, which is not preferable. . On the other hand, in the present invention, there is no lower limit on the diameter of the permeation hole and the opening ratio,
If the aperture ratio is too small, not only steam,
It is not preferable because it does not permeate oxygen and cannot be practically used as a battery.

Further, the selective permeable membrane before forming the permeation holes
Water vapor transmission rate of (7) is 5 × 10 ^-5 cc (STP) / cm
² / sec / cmHg or less. The reason for this is that if the water vapor transmission rate exceeds 5 × 10 ⁻⁵ cc (STP) / cm ² / sec / cmHg, the water vapor permeation inhibiting ability, which is the object of the present invention, is not effectively exhibited, which is not preferable. . The thickness, shape, etc. of the selectively permeable membrane (7) are not particularly limited in the present invention. Further, the method of piercing the permeation hole may be appropriately selected depending on the physical properties of the selective permeable membrane (7) and is not particularly limited, but a method of piercing using a pointed object having a sharp tip, selection, Method of adding a soluble component such as salt at the time of forming the permeable membrane (7) and extracting the soluble component with a solvent after forming the film, or heat, electron beam, 400 n
A method of forming a film containing a component foamed by ultraviolet light of m or less, or a solvent, by heat, electron beam, or ultraviolet light of 400 nm or less to foam and perforate, a mask having various pore diameters and shapes. , Or by irradiating condensed laser light, electron beam, or energy such as gamma ray to form a hole, or adding a sensitizer using ultraviolet light of 400 nm or less to form a hole. A method of crushing a porous body having pores with a roll or the like to adjust the aperture ratio and the pore diameter is exemplified.

FIG. 9 shows a selectively permeable membrane (7) according to the present invention.
The relationship between the aperture ratio and the current density is shown in the figure. In the present invention, the aperture ratio is 10% or less, that is, 1
Even if it is set as small as 0 ^-1 , 10 ^-2 , the obtained current is 10
It is mA / cm or more, and suppressing the permeation of water vapor does not affect the obtained current. Furthermore, in this selective permeable membrane (7), a current that is approximately directly proportional to the size of the aperture ratio is obtained. Therefore, a battery using such a selectively permeable membrane (7) does not cause an extreme decrease in current and the like, and has a small variation in performance given to the battery. Further, in this invention,
The current density obtained with the selectively permeable membrane (7) should be at least 10
The current density obtained is 10 m or more because it is set to be mA / cm 2 or more.
This is because if it is less than A / cm, the performance as a battery is not sufficiently exhibited, which is not preferable.

2 to 7 are sectional views showing another embodiment of the battery according to the present invention. In the present invention, as shown in FIG. 2, the selectively permeable membrane (7) and the positive electrode container (2) are shown. The permeability of oxygen may be further improved by interposing an air diffusion porous body (8) for diffusing air into the inside of the battery in the gap with the inside. The air-diffusing porous body (8) is exemplified by nylon non-woven fabric, polypropylene non-woven fabric, etc. having a mesh-like porosity with a thickness of about 100 to 200 μm as a preferred example.
There is no particular limitation. Further, as shown in FIG. 3, the air diffusion porous body (8) may be interposed in the gap between the selective permeable membrane (7) and the air electrode (5), or as shown in FIG. A multi-layer structure may be provided by interposing them in the gap between the permeable membrane (7) and the positive electrode container (2) and in the gap between the selectively permeable membrane (7) and the air electrode (5). It may be set appropriately according to

Further, as shown in FIGS. 5 to 7, a polytetrafluoroethylene porous membrane (9) having high water repellency is used as an air electrode.
A structure may be provided adjacent to (5) to further improve water repellency and improve the sealing property of the battery so that the electrolyte solution in the battery does not leak.

[0018]

EXAMPLES The effects of the battery according to the present invention will be described more clearly below with reference to examples. Example 1 Using polytetrafluoroethylene film (thickness 50 μm), permeation holes having a pore diameter of 75 μm and an opening ratio of 3.20E-02% were perforated to prepare a selective permeable membrane. The perforation was performed using a needle having a sharp tip. The battery having the obtained selectively permeable membrane shown in FIG. 7 (diameter 35 mm, height 13 mm)
The battery of Example 1 was arranged in the above. As the air diffusion porous body disposed in this battery, a polypropylene non-woven fabric having a thickness of 150 μm was used, and as shown in the figure, the gap between the positive electrode container and the selective permeable membrane and the gap between the air electrode and the selective permeable membrane. Intervened in each. Further, a polytetrafluoroethylene (PTFE) porous film was provided adjacent to the air electrode.

Example 2 A selective permeable membrane similar to that of Example 1 was prepared except that the opening ratio was changed to 1.60E-01%.
A battery of Example 2 was obtained by disposing the same battery as described above.

Example 3 Polyethylene terephthalate (thickness 40 μm) was used to form permeation holes having a pore diameter of 25 μm and an opening ratio of 3.20E-02% to form a selective permeable membrane. The penetration hole was formed by applying a stainless steel mask having a pore size of 25 μm and using a KrF laser having an oscillation wavelength of 248 nm. The obtained selectively permeable membrane was placed in the same battery as in Example 1 to obtain the battery of Example 3.

Example 4 The same selective permeable membrane as in Example 1 was placed in the battery shown in FIG. 5 (diameter 35 mm, height 13 mm) to give a battery of Example 4. As the air diffusion porous body disposed in this battery, a polypropylene non-woven fabric having a thickness of 150 μm was used, and it was interposed only in the gap between the air electrode and the selectively permeable membrane as shown in the figure, and the A fluoroethylene (PTFE) porous membrane was provided next to it.

(Example 5) The same selectively permeable membrane as in Example 1 was arranged in the battery (diameter 35 mm, height 13 mm) shown in Fig. 6 to obtain a battery of Example 4. As the air-diffusing porous body disposed in this battery, a polypropylene non-woven fabric having a thickness of 150 μm was used, and it was interposed only in the gap between the positive electrode container and the selectively permeable membrane as shown in the figure, and the air electrode was made of poly A tetrafluoroethylene (PTFE) porous membrane was provided next to it.

(Comparative Example) Opening ratio 8% as a selectively permeable membrane
A battery was obtained in the same manner as in Example 1 except that the porous polytetrafluoroethylene membrane was used.

Test Example 1 The oxygen permeable rate (RO2) and water vapor permeable rate (RH2O) of the selective permeable membranes prepared in Examples 1 to 3 and Comparative Example were measured before and after perforation of permeation holes, respectively. did. The method for measuring the gas permeability of the film is ASTE-D-1434-63, JIS-
It was performed based on the method disclosed in Z0208. The results are shown in Table 1.

[Table 1]

Test Example 2 The batteries obtained in Examples 1 to 5 and Comparative Example were tested for the following items. Continuous discharge duration (hr) and average operating voltage (V) under conditions of humidity 60% / 25 ° C and load 130Ω. Long term under humidity of 35% / 25 ℃ and humidity of 80% / 25 ℃
(1,500 hours) Weight change (mg) and operating voltage (V) of the battery due to moisture in and out of the battery after storage. The results are shown in Table 2.

[Table 2]

[0026]

As described above in detail, the present invention is a battery in which an air electrode having oxygen as an active substance is disposed inside a positive electrode container having air holes, wherein the air electrode and the positive electrode are At least one layer of the selective permeable membrane is interposed in the gap with the container, and the selective permeable membrane is provided with a plurality of permeable holes.
As is clear from the above examples, it is clear that the permeation holes of the selectively permeable membrane disposed inside the positive electrode container prevent the permeation of water vapor and efficiently permeate only oxygen. It exhibits excellent practicability such as good discharge characteristics and long-term discharge characteristics in an atmosphere of high and low humidity, and has an excellent effect of becoming a battery capable of stable long-term storage. Further, according to the present invention, a plurality of permeation holes having a diameter of 300 μm or less are formed, the aperture ratio of the permeation holes is 10% or less, and the obtained current density is at least 10.
Since it is a selective permeable membrane composed of a polymer membrane or a uniform film characterized by having a mA / cm ² or more, while it suitably inhibits the permeation of water vapor, it has an excellent selective permeability with respect to oxygen. The effect is that the selective permeable membrane for an excellent battery has an extremely small effect on the battery performance.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional explanatory view showing an embodiment of a battery according to the present invention.

FIG. 2 is a schematic cross-sectional explanatory view showing a first modified example of the battery according to the present invention.

FIG. 3 is a schematic cross-sectional explanatory view showing a second modified example of the battery according to the present invention.

FIG. 4 is a schematic cross-sectional explanatory view showing a third modified example of the battery according to the present invention.

FIG. 5 is a schematic cross-sectional explanatory view showing a fourth modified example of the battery according to the present invention.

FIG. 6 is a schematic cross-sectional explanatory view showing a fifth modification of the battery according to the present invention.

FIG. 7 is a schematic cross-sectional explanatory view showing a sixth modification of the battery according to the present invention.

FIG. 8 is a schematic cross-sectional explanatory view showing a conventional battery.

FIG. 9 is a diagram showing the relationship between the aperture ratio and the current density in the selective transmission film according to the present invention.

FIG. 10 is a diagram showing a relationship between an opening ratio and a current density in a conventional polytetrafluoroethylene porous film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2 Positive electrode container 21 Air hole 5 Air electrode 7 Selective permeable membrane 8 Air diffusion porous body 9 Polytetrafluoroethylene porous membrane

Claims (9)

[Claims] 1. A battery in which an air electrode having oxygen as an active substance is disposed inside a positive electrode container having an air hole, and at least one layer is provided in a gap between the air electrode and the positive electrode container. A battery, wherein a selective permeable membrane is interposed and a plurality of permeation holes are formed in the selective permeable membrane. 2. The water vapor permeation rate of the selective permeable membrane is 5
The battery according to claim 1, wherein the battery has a density of x10 ^-5 cc (STP) / cm ² / sec / cmHg or less. 3. The battery according to claim 1, wherein the diameter of the through hole is 300 μm or less. 4. The total area of the permeation holes formed in the selectively permeable membrane is 10% or less of the area of the inner surface of the battery container in which oxygen is effectively permeated. The battery according to 1. 5. The battery according to claim 2, wherein an air diffusion porous body is interposed in a gap between the selectively permeable membrane and the positive electrode container. 6. The battery according to claim 2, wherein an air diffusion porous body is interposed in a gap between the selectively permeable membrane and the air electrode. 7. An air diffusion porous body is provided in a gap between the selective permeable membrane and the positive electrode container, and an air diffusion porous body is provided in a gap between the selective permeable membrane and an air electrode. The battery according to claim 2, wherein the battery is a battery. 8. The battery according to claim 1, wherein a polytetrafluoroethylene porous film is provided adjacent to the air electrode. 9. A plurality of permeation holes having a diameter of 300 μm or less are formed, the aperture ratio of the permeation holes is 10% or less, and the obtained current density is at least 10 mA / cm ² or more. Selective permeable membrane consisting of polymer membrane or uniform film.