JPS63148559A - Manufacture of bromine absorbing electrode - Google Patents

Abstract

PURPOSE:To increase the absorbing capacity of bromine which is active material by adding ion exchange resin having a cation exchange group, carbon black, extractable material, hydrophilic property forming agent to a polymer, and kneading them to form a porous electrode. CONSTITUTION:An ion exchange resin used for giving ion exchange property is polyvinyl alcohol cation exchanger having a sulfonic group. This ion exchange resin powder is mixed with carbon black powder for giving conductivity and the mixture is kneaded with polyethylene powder serving as the base material of an electrode, and a sheet is formed. Dioctyl phthalate is used as extractable material and extracted after forming the sheet to make the electrode porous. Silica or alumina powder gives hydrophlic property to the polymer and ion exchanger so as to uniformly wet in the extractable material. By forming the porous electrode having ion exchange property, an electrode having high bromine-absorbing capacity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application This invention relates to an electrode for a metal-halogen battery, and more particularly to an electrode capable of absorbing and retaining a bromine active material in a zinc-bromine battery.

B9 Summary of the Invention This invention provides an electrode having a polymer compound (thermoplastic resin) as a matrix, in which the above-mentioned polymer compound is combined with an ion exchanger having a cation exchange group, carbon black, an oil exudate, and a hydrophilic, aqueous polymer. The present invention provides a method for manufacturing a bromine-absorbing electrode in which a porous electrode is formed by adding and kneading an imparting agent, and the electrode has enhanced absorption capacity for retaining bromine as an active material.

C9 Prior Art In recent years, various applications using new types of batteries have been studied. For example, it is actively being applied to power storage and electric vehicle batteries.

Among new types of batteries, metal-halogen batteries are attracting attention, and among them, zinc-bromine batteries are being developed because they are inexpensive, have a simple structure, and are compact. Zinc-bromine batteries have been proposed since the 1800s, but since the positive electrode active material bromine is a liquid, after it precipitates, it partially dissolves in the electrolyte, causing self-discharge, and has strong oxidizing power. There were some problems, such as limitations on the materials used to construct it. However, recently, a complexing agent that combines with bromine to form an oil has been developed, greatly increasing the practicality of this battery. An oil-like bromine complex produced by the combination of this complexing agent and bromine molecules is generated on the electrode surface or in the electrolyte during charging, and is separated from the electrolyte. Therefore, the basic structure of this battery is to circulate the electrolyte using a pump as shown in Figure 1, store the generated bromine complex at the bottom of the tank, and circulate it together with the electrolyte during discharge. Seed ring zinc-bromine batteries are the current method.

Note that FIG. 1 is an explanatory diagram of the structure of a ring-type zinc-bromine battery using an electrolytic solution. In the figure, 1 is a battery reaction tank showing a single cell of the battery, 2 is a positive electrode chamber, 3 is a negative electrode chamber, 4 is a membrane as a separator, 5 is a positive electrode, 6 is a negative electrode, 7 is a positive electrode electrolyte, and 8 is a negative electrode electrolyte. 9 is a tank for positive electrode electrolyte, 10 is a tank for negative electrode electrolyte, 11 and 12 are pumps for electrolyte circulation, 1
3 and 13a are piping systems for electrolyte circulation, and 14 is the above-mentioned bromine complex. In addition, piping system 13
The arrows shown beside 13a and 13a indicate the flow direction of the electrolytic solution.

Since the zinc-bromine battery described above is well known and has already been put into practical use, a detailed explanation of its operating principle will be omitted.

D5 Problems to be Solved by the Invention Many positive electrodes for zinc and bromine batteries as described above have been studied in the past, and carbon plastic electrodes are currently the mainstream. This is a product made by adding carbon powder to polyolefin resin to give it electrical conductivity, kneading and molding it. This electrode surface is subjected to activation treatment to facilitate bromine generation (oxidation reaction) during charging, and to increase the reaction area with the bromine active material and facilitate reduction reaction during discharging. Bromine generated during charging during such activation treatment immediately migrates into the electrolyte and circulates together with the electrolyte. This means that the electrode and the active treatment surface on the electrode surface do not have the function of retaining the generated bromine. However, this retention function exists only slightly on conventional activated surfaces. This is because the carbon black powder or activated carbon powder has a slight adsorption function due to the normal activation treatment, so that a small amount of the bromine molecules generated thereby are retained on the electrode surface. For example, in the case of activated carbon fiber (CF-303 manufactured by Toyobo Co., Ltd.) bonded by thermocompression to the surface of a carbon plastic electrode, the current density is 20 mA/cm.
When charging with a 3 mol/Il zinc bromide solution at 2, the electrolyte is colorless and transparent for about 1 hour, that is, up to 20 mAh/cm2, and bromine is retained without being precipitated into the electrolyte. , indicating that the electrolyte becomes reddish-brown and bromine retention becomes impossible. With this level of holding power, the battery capacity is also small, making it insufficient as an electrode for electric vehicles or power storage batteries. Therefore, even in batteries that are required to be compact and have high performance, such as those used in electric vehicles, pumps, piping, tanks, etc. must be used, which is a major problem.

Means for Solving the E0 Problem This invention was made to solve the above problems, and includes an ion exchanger having cation exchange properties and carbon black etc. in the polymer compound that is the base material of the electrode. Electrodes are formed by adding and kneading extracts and hydrophilic agents in addition to conductive materials.The bromine active material generated on the surface of the special charging electrode is retained in the electrode, and is used as an active material during discharge. This is a method for producing a bromine-absorbing electrode that has dramatically increased bromine retention, and can be fully used in the above-mentioned application fields.

F0 effect In this invention, the ion exchange resin used to impart ion exchange properties has a sulfonic acid group (-SO3-H")
It is a cation exchanger of polyvinyl alcohol with
Experiments have shown that this plastic electrode is made by mixing this polyvinyl alcohol powder with carbon black powder, which provides conductivity, and kneading it with a thermoplastic resin (polyethylene powder), which is a polymeric compound that forms the electrode base, to form a sheet that absorbs bromine well. It has been found that it has the following properties.

In particular, it has been confirmed that the cation exchange resin fine powder present in the electrode immediately traps bromine molecules (s rz) generated on the positive electrode surface of the battery during charging, and does not dissolve them into the electrolyte.

However, although the detailed chemical basis is unknown, it was observed that this cation exchange fine powder turned red when absorbing bromine. In addition, by impregnating the above-mentioned electrode containing this fine powder with bromine, or during the charging and discharging process of the battery described below,
After charging, the electrode is taken out and heated to about 60 to 80°C, and the release of bromine from the electrode surface is observed under a microscope.

In addition to the above, among the additives used in the present invention, dioctyl phthalate is used as an extract, which is extracted and removed with a solvent after sheet forming to make the electrode porous. Furthermore, the silica or alumina powder imparts hydrophilicity so that the parent polymer compound and the ion exchange powder are uniformly wetted by the extract.

G0 Example of the Invention First, the conditions obtained in preliminary experiments, such as the manufacturing method and materials of the carbon plastic electrode, which is the electrode sheet according to the present invention, will be explained.

This sheet contains a polymer compound, carbon black to impart conductivity, ion exchange resin powder to impart ion exchange properties, a forming substance or extract to impart porosity, and an inorganic salt to increase wood affinity. After kneading and molding, the porous forming substance was removed from the sheet to produce a porous conductive sheet having ion exchange properties.

As the molding method, a general calender roll method, compression method, injection method, or molding method using an extruder is used. Examples of polymer compounds include polyolefins,
There are polyamide and polyimide types. Polyolefins are good because they are common and inexpensive. Especially when used in batteries for this purpose, chemical resistance is also required.
Polyethylene is best. Lipophilic extracts that give porosity to the sheet include petroleum oil and dioctyl phthalate, hydrophilic extracts such as polyvinyl alcohol, and inorganic salts such as potassium chloride, sodium chloride, silica, and alumina powder. is common.

Further, as an ion exchange powder, a copolymer of styrene and divinylbenzene is generally used as a polymer base. Recently, there are also ion exchange resins that use polyvinyl alcohol as a polymer matrix.

Therefore, from the viewpoint of the strength of the sheet, it is preferable that the ion exchanger powder be used in an amount of 10 to 90 parts by weight based on 100 parts by weight of the polymer compound that is the base sheet of the present electrode.

However, if it is desired to further increase the ion exchange ability of the electrode, the amount may be 90 parts by weight or more, and if the ability is acceptable to be low, the amount may be 10 parts by weight or less.

Generally, "ion exchange capacity" is used to judge the ion exchange ability of an ion exchange resin. In order to increase the ion exchange capacity of this electrode and the bromine absorption capacity of this sheet, it is sufficient to increase the amount of ion exchange resin powder added.

Moreover, it is preferable that the amount of extract is 20 to 50 parts by weight. It is preferable that the amount of the extract is such that the polymer substance and the ion exchange powder are uniformly wetted with the extract. Further, the amount of porous portion can be adjusted by this addition. If you want to increase the porous area, you can increase the amount of extract added, but if it is more than 150 parts by weight, the mechanical strength of the sheet will decrease, and if it is less than 20 parts by weight, the above structure It was found that it was insufficient to wet the raw materials uniformly.

In addition, regarding carbon brazing for imparting conductivity, the amount added may be increased to increase conductivity, but it is usually added in a range of 30 to 90 parts by weight. In addition, although the above ion exchange resin powder has some hydrophilicity, in order to further increase the hydrophilicity, 30 to 50 parts by weight of inorganic silica (SiO2) or alumina (Aj220.) powder may be added. It turned out to be a good thing.

Example: Based on the results of the preliminary experiments as described above, a porous bromine absorption electrode with ion exchange properties was produced. That is,
Polyethylene 10 with density 0.96g/c+n3, MFR (flow index) 0.80g/l 0mln
0 parts by weight, ion exchange resin powder manufactured by Chibi KK, ion exchange capacity 3.6 meq/g) and carbon black (manufactured by Lion Akzo KK, trademark: Ketjen EC)
50 parts by weight of each were added, and further 50 parts by weight of silica powder were added and uniformly mixed by drying. This mixture was kneaded with a Banbury mixer, a kneader, etc. at a mixing ratio of 100 parts by weight of dioctyl phthalate as an extract to 100 parts by weight of polyethylene. This kneaded material was formed into a sheet with a thickness of 1 mm by calendering. The above-mentioned extract dioctyl phthalate was extracted from this molded sheet using an organic solvent trichlorethylene to form a porous electrode sheet.

The specific surface area of the ion-exchangeable porous sheet obtained as described above is 600II12/g, the ion-exchange capacity is 1, O
meq/g. Further, the electrical resistance value of this electrode sheet was 0.370Ω for a 1 mm thick sheet. Also,
When I investigated the bromine absorption capacity of this sheet, it was found that 1 cmx
It was confirmed that about 0.5 g of bromine was absorbed by a 1 cm x 1 mm thick piece.

H1 Effects of the invention As explained above, this invention can be used as a carbon plastic electrode for positive electrodes used in zinc-bromine batteries, etc.
A porous electrode with ion-exchange properties was constructed by kneading ion-exchange resin, extracts, and carbon black into a matrix of polymeric compounds, and then treating this to remove the extracts. I was able to obtain the electrode.

For this reason, the bromine active material generated on the surface of the positive electrode during charging during battery operation can be absorbed and retained within the electrode and used as an active material during discharge, allowing the battery to be used separately from the electrolyte tank and piping system. Therefore, the mounting volume on an electric vehicle can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operating principle of an annular zinc-bromine battery using an electrolytic solution.

Claims (4)

[Claims] (1) In an electrode for a metal-halogen battery using a polymer compound as a matrix, 10 to 90 parts of ion exchanger powder having a cation exchange group is added to 100 parts by weight of the polymer compound.
parts by weight, 20 to 150 parts by weight of extract, 30 to 90 parts by weight of carbon black, and 30 to 5 parts by weight of hydrophilicity imparting agent powder.
1. A method for producing a bromine-absorbing electrode, which comprises adding 0 parts by weight of the bromine-absorbing electrode, kneading and forming the bromine-absorbing electrode, and then subjecting the porous electrode to a porous treatment so that the porous electrode has the ability to absorb a bromine active material. (2) The method for manufacturing an electrode according to claim 1, wherein the polymer compound is polyethylene, which is a thermoplastic resin. (3) The method for producing an electrode according to claim 1, wherein the cation exchange group is a sulfonic acid group. (4) The method for manufacturing an electrode according to claim 1, wherein the hydrophilicity imparting agent powder is either silica or alumina powder.