JPH06140018A - Separator for alkali battery and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an alkali battery having improved utilization rate of active material and good life time characteristic by using porous body made of polyolefine to whose boundary surface active agent is applied after fuming sulfuric acid or strong sulfuric acid is brought in contact with the porous body for sulfonation process. CONSTITUTION:A polyopropylene non-woven cloth having thickness of 0.15mm and porosity degree of 60% is dipped in strong sulfuric acid including fuming sulfuric acid of 5% for 7 minutes at a room temperature. Then, sulfuric acid is removed by using a centrifugal separator and the non-woven cloth is washed by water and dried. The non-woven cloth turns to brown from white through this process. Water solution containing neutral boundary surface active agent (alkyl ether sulfuric acid ester sodium) sold in markets by 1% is applied to the non-woven cloth and the non-woven cloth is heated and dried at 100 degree centigrade to obtain a separator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separator used in alkaline batteries such as nickel-cadmium batteries and nickel-hydrogen batteries, and a method for producing the same.

[0002]

2. Description of the Related Art There are lead batteries and alkaline batteries as storage batteries used as various power sources. Of these, alkaline batteries have been widely used for various portable devices, and large ones have been widely used as an industry for the reason that they can be expected to have high reliability and can be made compact and lightweight.

In this alkaline storage battery, zinc, iron, hydrogen and the like of cadmium are targeted as the active material of the negative electrode. As the positive electrode, an air electrode, a silver oxide electrode, and the like are partially taken up, but in most cases, the nickel electrode is used.
The characteristics have been improved from the pocket type to the sintered type, and it has become possible to further seal and expand the applications. In addition to the sintering type, high-capacity foaming type and felt type have been taken up and put into practical use.

As a separator, a polyamide fiber cloth or a non-woven cloth, and a combination thereof with cellophane, a polyvinyl alcohol film or the like have been adopted. Recently, fiber cloths and non-woven fabrics made of polyolefin have been partially used especially in view of alkali resistance and oxidation resistance. In the closed type, gas permeation is required, so that a film separator is not preferable, and a nonwoven fabric that is preferable in terms of impregnation with an electrolytic solution is generally used.

[0005]

DISCLOSURE OF THE INVENTION As the separator,
There is a demand for low electric resistance, excellent alkali resistance and oxidation resistance, and good impregnation with the electrolyte solution. In addition, gas permeation is required for the sealed type.

To meet these requirements, polyamide fiber cloths, non-woven cloths, and combinations of these with cellophane, polyvinyl alcohol film and the like have been adopted. However, since there are problems in terms of alkali resistance and oxidation resistance, polyolefin fiber cloth and non-woven cloth have been partially used. However, polyolefin fiber cloths and non-woven fabrics are insufficient in terms of impregnation with the electrolyte solution, and the surfactants included in the manufacturing method are inferior in electrolyte solution resistance and oxidation resistance, so they are lyophilic over a long period of time. Can't keep up. Therefore, we have improved the electrophilicity by treating the polyolefin porous material with fuming sulfuric acid and concentrated sulfuric acid.

However, if extreme treatment with fuming sulfuric acid or concentrated sulfuric acid is performed to improve the electrophilicity, the fabrics made of polyolefin fibers are deteriorated and the strength is lowered. In addition, there is a problem that the process is particularly complicated and the cost is increased.

In order to solve the above conventional problems, it is an object of the present invention to provide a low cost alkaline battery separator and a method for manufacturing the same, which prevents the strength from being lowered and simplifies the process.

[0009]

In order to achieve the above-mentioned object, the alkaline battery separator of the present invention is an alkaline battery separator using a sulfonated polyolefin porous body. Characterized by the presence of a surfactant.

Next, the method for producing a separator for alkaline batteries of the present invention is a method for producing a separator for alkaline batteries in which fluorinated sulfuric acid or concentrated sulfuric acid is brought into contact with a porous body made of polyolefin to carry out a sulfonation treatment. It is characterized in that a surfactant is added later.

In the above structure, it is preferable that the polyolefin porous body is a polypropylene nonwoven fabric.

[0012]

According to the constitution of the present invention, since the surfactant is present in the porous body of the separator, the polyolefin porous body can be formed to the extent that the fuming sulfuric acid and / or the concentrated sulfuric acid does not drastically reduce the strength. Can be processed. The wettability (impregnating property) of the electrolytic solution can be improved by the synergistic effect of the sulfonation treatment and the presence of the surfactant. Further, in the case of a sealed battery, the electrolytic solution does not move or is extremely small once the electrolytic solution is impregnated in the battery separator, so that the surfactant does not move much from the separator. As the polyolefin porous body, polyethylene or polypropylene is generally used, and polypropylene nonwoven fabric is preferable in consideration of heat resistance and price.

Next, according to the structure of the manufacturing method of the present invention, first, the polyolefin porous body is treated with fuming sulfuric acid and / or concentrated sulfuric acid to the extent that the strength is not extremely reduced, thereby improving the lyophilic property. This is probably due to the formation of sulfone groups in the polyolefin. Thereafter, a surfactant is added to this. Non-woven fabrics made of polyethylene or polypropylene are included in these commercially available non-woven fabrics because a surfactant is used in the manufacturing process thereof as described above. However, since the polyolefin is destroyed in the process of fuming sulfuric acid or concentrated sulfuric acid treatment, or it is washed with water, the surfactant is removed. In the treatment with fuming sulfuric acid or concentrated sulfuric acid to the extent that the strength does not extremely decrease, it is not possible to provide a sufficient amount of the electrolyte solution, which requires a balance of the amount of the electrolyte solution, but this can be achieved by using both treatments together.

That is, if the electrolyte is less lyophilic when it is injected, it has a good gas permeability and is suitable for gas absorption during charging. However, since the electrolyte is scarce in the separator, the essential discharge characteristics and life are shortened. It doesn't matter. By additionally improving the lyophilicity with a surfactant, the separator becomes easier to wet with the electrolytic solution than in the case of extreme sulfuric acid treatment, uniform penetration into the electrode does not cause any problems, performance improves, and gas absorption No deterioration in characteristics.

[0015]

EXAMPLES The present invention will be described in more detail with reference to the following examples. First, in the sulfonation treatment, the polyolefin porous body is treated with fuming sulfuric acid and / or concentrated sulfuric acid to the extent that the strength is not extremely lowered.

The surfactant that can be used in the present invention may be any of anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants. . The amount of surfactant added is
There is no particular limitation, but it is several ppm to several wt% with respect to the nonwoven fabric.
It is a degree.

Example 1 A commercially available polypropylene nonwoven fabric having a thickness of 0.15 mm and a porosity of about 60% was immersed in concentrated sulfuric acid containing 5% fuming sulfuric acid at room temperature for 7 minutes. After that, the sulfuric acid was removed by a centrifuge, followed by washing with water and drying. This treatment changed the non-woven fabric from white to light brown.
To this was added a 0.1% aqueous solution of a commercially available neutral surfactant (sodium alkyl ether sulfate). Next, it was heated and dried at 100 ° C. to obtain a separator.

Next, a sealed nickel-hydrogen storage battery was constructed by using a known foamed nickel electrode filled with nickel hydroxide powder, cobalt powder and nickel powder as a positive electrode and a paste type MmNi type hydrogen storage alloy electrode as a negative electrode. . 30 g / l as an electrolyte in a caustic potash solution with a specific gravity of 1.30
Lithium hydroxide of was used by dissolving. The battery is a SubC type. This battery is designated as A.

Next, for comparison, a battery obtained by the same production method as in A except that the addition of the surfactant was omitted was added as B, by immersing it in fuming sulfuric acid. First, the initial discharge voltage and capacity were compared. The battery is 10 cells each, and the capacity is 130 at 0.2C.
% Constant current charge, and then constant current discharge at 0.5 C to 0.9 V, the average voltage was 1.22 to 1.
There was no difference at 23V. The discharge capacity A is 2.75 to 2.
80 Ah and B was 2.69-2.77 Ah.

Next, 10 cells were used for each battery, and the life characteristics were compared. Capacity of 12 at 0.5C at 20 ℃
After 5% constant current charging, charging / discharging was repeated under the condition of discharging at 0.5C to 0.9V. When the capacity at 10 cycles is 100, A averages 98 after 300 cycles.
%, Whereas B averaged 95%. While A was 94% in 600 cycles,
In B, it was 87%. Thus, A was excellent in terms of life.

Example 2 A commercially available polypropylene nonwoven fabric having a thickness of 0.15 mm and a porosity of about 60% is immersed in a commercially available 95% sulfuric acid at 105 ° C. for 1 hour. Sulfuric acid was removed by a centrifuge, washed with water and dried. This treatment changed the non-woven fabric from white to black. A 1% aqueous solution of a commercially available neutral surfactant (sodium alkyl ether sulfate) was added to this, and dried by heating at 100 ° C. to obtain a separator.

A sealed nickel-cadmium storage battery was constructed by using a known foamed nickel electrode as a positive electrode and a pasted cadmium electrode as a negative electrode, as in Example 1. As an electrolytic solution, 25 g / l of lithium hydroxide was dissolved in a caustic potash aqueous solution having a specific gravity of 1.30 and used. The battery is a SubC type.
This battery is designated as C. Next, for comparison, a battery obtained by dipping in fuming sulfuric acid, omitting the addition of the activator, and using the same production method as C was added as D.

First, the initial discharge voltage and capacity were compared. When 10 cells were used, a constant current charge of 130% of capacity was performed at a rate of 5 hours, and then constant current discharge of 1.0 A to 0.9 V was performed. There wasn't. The discharge capacity of C is 2.73 to 2.78 Ah, and the discharge capacity of D is 2.69. Was about 2.76 Ah.

Next, 10 cells were used for each of the batteries, and the life characteristics were compared. Capacity of 12 at 0.5C at 20 ℃
After 5% constant current charging, charging / discharging was repeated under the condition of discharging up to 0.5C0.9V. When the capacity at 10 cycles is 100, C averages 96% at 300 cycles.
On the other hand, in D, the average was 92%. After 600 cycles, C was 91%, while D was 82%. Thus, C was excellent in terms of life.

In any of the examples, the treatment with fuming sulfuric acid or concentrated sulfuric acid was performed more complicatedly than in the examples, and the process became complicated and the strength of the nonwoven fabric decreased.

[0026]

As described above, according to the present invention, since the surfactant is present in the porous body of the separator,
The polyolefin porous body can be treated with fuming sulfuric acid and / or concentrated sulfuric acid to the extent that there is no extreme decrease in strength. The wettability (impregnating property) of the electrolytic solution can be improved by the synergistic effect of the sulfonation treatment and the presence of the surfactant.

Further, according to the production method of the present invention, by using a separator obtained by treating a polyolefin porous body with fuming sulfuric acid and / or concentrated sulfuric acid, and then impregnating this with a surfactant solution, a gas is obtained. There is no deterioration in absorption characteristics, the utilization factor of the active material is improved, and a long-life alkaline battery can be obtained.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoichiro Tsuji 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A separator for an alkaline battery using a sulfonated polyolefin porous body, wherein a surfactant is present in the porous body. 2. A method for manufacturing a separator for an alkaline battery, which comprises subjecting a polyolefin porous body to contact with fuming sulfuric acid or concentrated sulfuric acid to perform a sulfonation treatment, wherein a surfactant is added after the sulfonation treatment. A method for manufacturing an alkaline battery separator. 3. The method for producing the alkaline battery separator according to claim 1 or the alkaline battery separator according to claim 2, wherein the polyolefin porous body is a polypropylene nonwoven fabric.