JPH06310146A - Insulating coated electrode - Google Patents

Abstract

PURPOSE:To avoid a short circuit depending on a deposition by the charge and discharge, and to obtain an electrode having a high charge and discharge cycle, by providing an insulating coating membrane with good adhesion and durability, to the outer side of a collector. CONSTITUTION:In an electrode used for an alkaline battery, the outer surface of a metallic holder to cover the active material is covered by an organic material with the thickness more than 0.1mum and less than 2mum to form an electrode 3. The feature of the metallic holder is that it is formed of either one sort of copper, nickel, iron, and lead, or a complex of some of them. The feature of the organic material is to be a fluorine compound. And the feature of the coating method of the organic material is to be a plasma polymerization.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to electrodes for alkaline batteries. For details, nickel-cadmium battery, nickel-
The present invention relates to an insulating coated electrode used in iron batteries, nickel-zinc batteries, and the like.

[0002]

2. Description of the Related Art Generally, an electrode of an alkaline battery is used by filling a current collector for taking out an electric current with an active material. For example, an electrode called a pocket type is used by including an active material with a metal plate and a metal net. This electrode is in contact with the other electrode through the separator, but when the active material is dissolved in the electrolytic solution by discharge and deposited on the electrode by charging,
Often, it deposits on the outside of the current collector, destroys the separator, and causes a short circuit.

In order to avoid this precipitation, it is possible to electrically insulate the outside of the current collector with an organic material. Resins used for this treatment include epoxy resin, silicone resin, sealing wax, etc., but the insulation treatment by coating the resin requires a film thickness of 1 mm or more to eliminate pinholes. Voids may occur between the separators, and the active material may leak. At present, most of these resins do not exhibit stable adhesion for a long time in an electrolytic solution.

On the other hand, there is a plasma polymerization method as a known technique for modifying the surface, which has been applied to modification of surface wettability, improvement of surface adhesiveness, etc.
No. 229932, JP-A No. 62-240542). It is known that treatment with fluorine-containing plasma is effective for making the substrate surface hydrophobic (Japanese Patent Laid-Open No. 55-99932). However, most of these plasma-polymerized films were limited to modification of the polymer surface.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides an electrode having a high charge / discharge cycle by providing an insulating coating film having good adhesion and durability on the outside of a current collector to avoid a short circuit due to deposition due to charge / discharge. It is provided.

[0006]

The present invention relates to an electrode used in an alkaline battery, in which an outer surface of a metal support for enclosing an active material is coated with an organic material having a thickness of 0.1 μm or more and 2 μm or less. FIG. 1 shows a cross section of an example of the insulating coated electrode of the present invention. In the figure, 1 is an insulating film, 2 is a metal support,
3 is an active substance. The metal support used at this time is any of copper, nickel, iron, lead, or a composite material. Any organic material may be used as long as it is stable in an alkaline electrolyte, but a fluorine compound is preferable in consideration of the denseness and durability of the film. Further, this organic material has a thickness of 0.1 μm or more and 2 μm or less. Film thickness is 0.1
If it is less than μm, the electrical insulation is poor, and if it is more than 2 μm, it may peel due to the stress in the film.

As a method for producing the organic material-coated electrode, plasma polymerization can be mentioned.
It is a method of forming an organic film on a metal support using active species therein. In the method of converting the monomer into plasma,
There are a method of directly applying an electric field to the monomer and an indirect method of bringing a non-polymerized gas made into a plasma into contact with the monomer, and all hydrocarbon compounds can be used as the monomer. Further, as the non-polymerization gas used in the indirect method, an inert gas such as argon or helium is used. There are two methods of plasma conversion, an inductive coupling method in which a high frequency voltage is applied to the coil, and a capacitive coupling method in which a high frequency is applied between opposed parallel plates, and either method can be used. In the plasma polymerization method, the gas flow rate is 0.1 to 10.0 cc / min (argon conversion) for both the non-polymerized gas and the monomer, and the total pressure is 0.
In the range of 01 to 1.0 Torr, the power supply frequency is 10kHz or less,
And 13.56MHz, 27.12MHz, 2.48GHz,
It is carried out under the conditions of 5.8 GHz, 22.125 GHz and an output of 10 to 200 W, but since it changes depending on the shape of the plasma generator and the metal support, the size of the treated surface, etc., it is necessary to obtain the optimum value each time.

In the plasma polymerization method, an ionized or excited inert gas collides with the surface of the metal support to generate active points on the surface, which are bonded to the film atoms to improve the adhesion. The film obtained by the plasma polymerization method is a dense film having no pinhole because it has a three-dimensional crosslinked structure. Furthermore, since it is an organic film, it has a high insulating property, and when a fluorine compound is used as a monomer, the polymerized film produced becomes a hydrophobic film, making it difficult to contain an electrolytic solution in the film and improving the insulating property. Hexafluorobenzene, hexafluoro-n-hexane, and tetradecafluoro-2-methylpentane are examples of these fluorine-based monomers. However, fluorine-based monomers are similar in hydrophobicity except that the film-forming speed is different. The effect of is obtained. Further, a non-fluorine compound and a fluorine compound may be mixed and used, and as the non-fluorine compound, ethylene, acetylene, benzene or the like may be used. Examples will be shown below.

[0009]

【Example】

(Example) As a plasma polymerization, an inductively coupled afterglow method is used. First, a nickel support (30 mm x 30 mm) having small holes on the surface is used for several minutes to improve adhesion.
The surface of (× 0.1 mm) is exposed to argon plasma (argon flow rate 4.0 cc / min, pressure 0.2 Torr, output 30 W,
The surface was washed at a power supply frequency of 13.56 MHz), and then monomers were introduced into the reaction tube to generate plasma, and a polymerized film was formed on the outer surface of the support placed in the reaction tube for 30 minutes. The flow rate of gas during polymerization was 4.0 cc / min (argon conversion) for both argon and monomer, and total pressure was 0.2 Tor.
Also, the output was 30 W. Hexafluorobenzene, which forms a hydrophobic film, was used as the monomer.
Next, a mixture of 94 wt% zinc oxide, 4 wt% Teflon, and 2 wt% lead oxide was mixed with water, clathrated with this nickel support, and dried at 400 ° C. for 30 minutes to obtain a negative electrode. . Further, a nickel (II) hydroxide negative electrode having the same charge amount as this negative electrode was similarly prepared and used as a positive electrode. The positive and negative electrodes were placed in a 30% aqueous potassium hydroxide solution together with a separator containing cellulose as a main component, and 0.2 C
The charging / discharging for 5 hours was repeated 200 times. At this time, no deposition of the active material was observed on the outer surface of the electrode, and no short circuit occurred.

(Comparative Example 1) 94 wt% zinc oxide and 4 wt%
A mixture of Teflon and 2 wt% lead oxide was mixed with water, and a nickel support (30 mm x 30 mm) with small holes on the surface was mixed.
× 0.1 mm), and dried at 400 ° C. for 30 minutes to obtain a negative electrode. Further, a nickel (II) hydroxide negative electrode having the same charge amount as this negative electrode was similarly prepared and used as a positive electrode. The positive and negative electrodes were placed in a 30% aqueous potassium hydroxide solution together with a separator containing cellulose as a main component, and charging and discharging were repeated 200 times at 0.2 C for 5 hours.
At this time, zinc was deposited on the outer surface of the negative electrode, and a short circuit was generated from around the 50th time.

(Comparative Example 2) 94 wt% zinc oxide and 4 wt%
A mixture of Teflon and 2 wt% lead oxide was mixed with water, and a nickel support (30 mm x 30 mm) with small holes on the surface was mixed.
× 0.1 mm) and dried at 400 ° C. for 30 minutes, and the outer surface of the support was coated with an epoxy resin to obtain a negative electrode. Further, a nickel (II) hydroxide negative electrode having the same charge amount as this negative electrode was similarly prepared and used as a positive electrode. The positive and negative electrodes were placed in a 30% aqueous solution of potassium hydroxide together with a separator containing cellulosic as a main component, and the positive and negative electrodes were heated to 5 at 0.2
The time charge / discharge was repeated 200 times. At this time, zinc was locally deposited on the outer surface of the negative electrode, and the epoxy resin was peeled off. Furthermore, a short circuit occurred around the 100th charge / discharge cycle.

[0012]

According to the present invention, it is possible to provide an electrode having a high charge / discharge cycle by providing an insulating coating film having good adhesion and durability on the outside of a current collector, avoiding a short circuit due to deposition due to charge / discharge. .

[Brief description of drawings]

FIG. 1 is a sectional view of an insulating coated electrode of the present invention.

[Explanation of symbols]

 1 Insulation coated organic film 2 Metal support 3 Active material

Claims (4)

[Claims] 1. In an electrode used in an alkaline battery, the outer surface of a metal support for enclosing an active material has a thickness of 0.1 μm.
An insulating coated electrode, characterized by being coated with an organic material having a thickness of m or more and 2 μm or less. 2. The insulating coated electrode according to claim 1, wherein the metal support is any of copper, nickel, iron, lead, or a composite material. 3. The organic material is a fluorine compound.
The insulation-coated electrode described. 4. The insulating coated electrode according to claim 1, wherein the organic material is coated by plasma polymerization.