JPS6059704B2 - Separator for silver batteries - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in separators for silver batteries.

As is well known, cellophane thin films have traditionally been used as separators in silver batteries.

This cellophane thin film is effective in blocking the migration of silver ions and preventing internal discharge of the battery, but it is degraded by the strong oxidizing power of the silver battery, which is the anode, and the anode itself is also susceptible to this oxidation reaction. Therefore, it is partially consumed. In order to improve this drawback, composite separators have been proposed in which an ion-permeable synthetic resin thin film is laminated on a cellophane thin film, or a composite separator in which an ion-permeable synthetic resin thin film is laminated on a cellophane thin film using an adhesive.

In such a composite separator, the permeation of silver ions is blocked by the cellophane thin film, and deterioration of the cellophane thin film itself due to the anode can be avoided by placing the ion-permeable synthetic resin thin film between the cellophane thin film and the anode. This can be prevented by loading, so the function can be effectively demonstrated.

However, conventional silver batteries use silver oxide as an anode, but recently high-capacity silver batteries that use silver peroxide as an anode have appeared. Since silver peroxide has a stronger oxidizing power than silver oxide, conventional laminate products of an ion-permeable synthetic resin thin film and a cellophane thin film cannot prevent cellophane from being oxidized by the anode. The present invention aims to overcome these drawbacks and provide a yaparator particularly suitable for silver peroxide.

In the present invention, instead of directly laminating a cellophane thin film and an ion-permeable synthetic resin thin film as in the past, we use a film-forming material that is soluble in an organic solvent and insoluble in an aqueous alkali solution on one or both sides of the ion-permeable synthetic resin thin film. Silver peroxide can be removed by applying and drying a solvent solution containing a surfactant, forming a film, and then laminating a cellophane thin film on top of it to form a three- or four-layer structure. Even when used as a separator for a silver battery with an anode, a cellophane thin film that does not deteriorate can be obtained, and the electrical resistance value is equivalent to that of conventional products.

Therefore, the product of the present invention has an extremely long life as a separator for high capacity silver peroxide batteries. Of course, the product of the present invention can also be used as a separator for silver oxide. The ion-permeable synthetic resin thin film used in the present invention is a microporous polyolefin film such as polypropylene or polyethylene.
A microporous polypropylene film commercially available from Co., Ltd. under the trade name 1 Jyuragardo is suitable.

Film-forming materials that are soluble in organic solvents and insoluble in alkaline aqueous solutions used in the present invention include cellulose esters such as cellulose acetate, celluloses such as notyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Cellulosic polymers such as ethers are suitable. As the surfactant, a nonionic surfactant such as polyoxyethylene alkyl ether is used.

The organic solvent may be used alone or in combination. Further, the presence of water in the solution to an extent that does not dissolve the film-forming material may be sufficient. According to the present invention, a solution of a cellulose polymer such as cellulose acetate and a nonionic surfactant in an organic solvent is applied to one or both sides of a microporous polypropylene film such as Jyuraguard to form a cellulose polymer film. Then, on top of this, use adhesive such as CMC or PVA to a thickness of 25 mm.
A separator for a silver battery is provided, which is formed by laminating one or more layers of cellophane thin films of about -40 μm.

At this time, in order to improve the adhesion of the film before coating, it is preferable to perform an appropriate pretreatment on the surface of JURAGARD. The separator of the present invention is simple and easy to manufacture, and the electrical resistance increases significantly when no surfactant is added. It can be used as a separator without any problem.

In the present invention, the appropriate thickness of the film is about 1 to 40 microns, and the amount of surfactant is about 5 to 1.
Approximately 00% is appropriate.

Examples of the present invention will be shown below.

Example: A mixed solvent of methylene chloride 220y1 ethanol 22f, cellulose acetate (oxidation degree 55%) 12y, nonionic surfactant (polyoxyethylene alkyl ether) 4'
The dope dissolved in Jyuragard 2400 is
(Microporous polypropylene film manufactured by Polyplastics Co., Ltd.) was coated on one side.

Claims (1)

[Claims] 1. Apply an organic solvent solution of a mixture of a cellulose polymer and a nonionic surfactant to one or both sides of a microporous polypropylene film and dry it to form a cellulose polymer film, and then layer a cellophane thin film on the coated surface. A separator for silver batteries.