JPH02220373A - Battery - Google Patents

Abstract

PURPOSE:To improve the capacity, energy density and durability by using a porous film consisting of specified conductive polyaniline for positive pole active material. CONSTITUTION:A porous film consisting of conductive polyaniline having the illustrated expression for a repetition unit, which is soluble in organic solvent in a dedoped condition having a limiting viscosity (eta) of more than 0.40dl/g as measured in N-methylpyrolidone at 30 deg.C, but which is doped by proton acid of a pKa value of less than 4.0 to be insoluble in organic solvent, is used for positive pole active material. In the expression, (m) and (n) refert to the molar fraction of quinoimidine structure unit and a phenylene diamine structure unit in the repetition unit respectively, where 0<=m<=1, 0<=n<=1, m+n=1. It is preferable to use solvent-soluble polyaniline of a limiting viscosity of more than 0.40 for obtaining a porous film having a high strength and flexibility.

Description

[Detailed Description of the Invention] The present invention relates to a battery with high capacity density and a positive electrode active material using a novel porous conductive organic polymer obtained by chemical oxidation of aniline. and energy density.

It was already discovered around 1980 that conductive organic polymers are useful as active materials for secondary batteries, and since then, much research has been conducted in this regard. In the early stages of research, for example, aniline oxidized polymers, so-called polyaniline (J,
Polymer Sci, + Part C, 22+1
187 (1969)), ^, G, McDiarm
polyacetylene (J, C, S, Chew,
Com+sun, 317 (1891)). In particular, batteries using polyaniline as a positive electrode active material have attracted attention in recent years because of their excellent environmental stability, large charge/discharge capacity, and excellent durability.

Generally, electrochemical oxidation methods and chemical oxidation methods are known as methods for producing polyaniline. When electrochemical oxidation is used, the polymer is obtained as a film on an electrode.
When using the chemical oxidation method, it is obtained as a powder. Therefore, conventionally, aqueous or non-aqueous batteries using such films or powder moldings have been produced using A, G,
McDiarmid et al. ACS (Polymer Pre
prints, 25. No, 2+ 248 (1
984)), Kika et al. (Electrochemistry and Industrial Physical Chemistry,
53(8).

592 (1985)), Koura et al. (Electrochemistry and Industrial Physical Chemistry, Competition (5), 386 (1987)), JP-A-61-200669, etc.

In batteries using such conventional polyaniline,
When polyaniline is obtained electrochemically, the polyaniline is deposited as a porous film on the electrode, so it can be used as it is as an electrode, and therefore, the assembly of the battery is relatively easy. However, producing polyaniline by electrochemical methods requires a large amount of electrical energy;
In addition to being industrially disadvantageous, the resulting porous membrane has low strength and easily falls off the electrode, making various post-processing difficult. Manufacturing large-area films is also not easy.

On the other hand, as mentioned above, when using the chemical oxidation method, polyaniline is usually obtained as a powder, so in order to use it as an electrode, the powder must be processed by means such as pressure molding. The resulting molded product is brittle and easily cracks.
Therefore, it is not easy to make the film thin.

For example, by chemically oxidizing and polymerizing aniline with a chemical oxidizing agent,
Contains electrolyte ions as dopants and has a conductivity of 10
-'S/am or higher is already known, and furthermore, in the production of conductive polyaniline by such chemical oxidative polymerization, in the reduction half-cell reaction based on a standard hydrogen electrode, It has already been reported in JP-A No. 61-258831 that an oxidizing agent having a standard electrode potential defined as an electromotive force of 0.6 V or more is particularly suitable for use.
As described in the above publication, the polyaniline obtained in this manner is insoluble and infusible.

Therefore, various methods have been proposed in the past in which an intermediate soluble in an organic solvent is produced, the solution is formed into a film by a casting method, and then the intermediate is converted into a conductive polymer by physical or chemical means. ing. However, when using this method, high temperature treatment is required, or the conversion of the intermediate to the conductive polymer does not necessarily proceed as theoretically. However, this method is not practical as a method for producing a conductive organic polymer film.

In the field of polypyrrole or polythiophene, polymers soluble in organic solvents are known. That is, thiophene having a long-chain alkyl group as a substituent and virol having an alkylsulfonic acid group as a substituent are subjected to electrolytic oxidation polymerization to obtain organic solvent-soluble poly3-alkylthiophene and polythiophenealkanesulfonic acid, respectively. .

A film can be obtained from a solution of any of these polymers by a casting method. However, since all of these methods use special monomers and undergo electrolytic oxidation polymerization, the manufacturing cost is extremely high.

On the other hand, in the field of chemical oxidative polymerization of aniline, it has recently been reported that aniline is chemically oxidatively polymerized by using about 1/4 molar amount of ammonium beroxonisulfate as an oxidizing agent to obtain organic solvent-soluble polyaniline. It has been reported that (A, G, Ma
cDiarmid et al., 5yn-thet
ic Metals+ 21+ 21 (1987);
A, G, MacDiar-mid at a
L, L, Alcacer (ed,)+
Conducting Polymers+ 105-
120 (D, Re1del Publishing
Co, +1987). However, since this polymer is soluble not only in N-methyl-2-pyrrolidone and dimethyl sulfoxide but also in 80% acetic acid and 60% formic acid aqueous solutions, its molecular weight is low. In addition, the polymer N-methyl-2
- It is also described that self-supporting films can be obtained from solutions of pyrrolidone or dimethyl sulfoxide. Furthermore, it is also described that a conductive polymer film doped with acetic acid can be obtained from an acetic acid solution, and that this is made into a film dedoped with ammonia. However, this dedoped film a has low strength due to the low molecular weight of polyaniline and easily cracks when bent, so it cannot be put to practical use.

It is also known that aniline can be oxidized with ammonium belloxonisulfate to obtain polyaniline, which is soluble in tetrahydrofuran (J, Tang, et al.
5ynthetic Metals+ 2C231(
1988).

However, this polymer also appears to have a low molecular weight considering its solubility in tetrahydrofuran.

Furthermore, the polyaniline film obtained as described above is dense and ions do not easily diffuse within the film, so it is not suitable for use as an electrode active material for batteries.

The present inventors have conducted intensive research to obtain organic solvent-soluble high-molecular organic polymers by chemical oxidative polymerization of aniline. Although it has a high molecular weight, it is soluble in various organic solvents in a dedoped state, and a self-supporting film can be easily obtained from the solution by a casting method.
Moreover, it has already been discovered that this film is strong, has excellent flexibility, and has high tensile strength. Furthermore, by doping this film with protonic acid, it is possible to create a strong, high molecular weight, highly conductive organic polymer. It has also already been found that films can be obtained.

Therefore, the present inventors conducted further intensive research into the use of such conductive organic polymers in batteries, and found that a so-called wet film forming method, in which the solvent is removed after casting a solution of the above-mentioned organic solvent-soluble high molecular weight polyaniline, was developed. By adopting a method called ``method,'' it is possible to obtain a flexible porous membrane, and by using this as a positive electrode active material in a battery, it is possible to obtain a membrane with high capacity, high energy density, and durability. The inventors have discovered that it is possible to obtain a battery with excellent properties, leading to the present invention.

The battery according to the present invention for ``°'' has the general formula (where m and n respectively represent the molar fraction of the quinonediimine structural unit and the phenylenediamine structural unit in the repeating unit, 0≦m≦1, O ≦n≦1, m+n=1) as the main repeating unit, is soluble in organic solvents in the dedoped state, and has an intrinsic viscosity [η ] is 0.40
dl/g or more, but a porous membrane made of conductive polyaniline doped with a protic acid having a pKa value of 4.0 or less and made insoluble in organic solvents as a positive electrode active material. .

First, the production of organic solvent-insoluble polyaniline doped with protonic acid and the production of organic solvent-soluble polyaniline by dedoping will be explained.

When oxidatively polymerizing aniline in the presence of a protonic acid to produce polyaniline doped with the protonic acid, the oxidizing agent may include manganese dioxide,
Ammonium peroxonisulfate, hydrogen peroxide, ferric salts, iodates, and the like are particularly preferably used. Among these, for example, ammonium beroxonisulfate and manganese dioxide both produce 2 per molecule in their oxidation reaction.
Since 2 electrons are involved, amounts ranging from 1 to 1.25 moles per mole of aniline are usually used.

The above protonic acid is not particularly limited as long as the acid dissociation constant pKa value is 3.0 or less, and examples include hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, hydrofluoroboric acid, hydrofluoric acid, Inorganic acids such as hydrofluoric acid and hydroiodic acid, aromatic sulfonic acids such as benzenesulfonic acid and p-toluenesulfonic acid, alkanesulfonic acids such as methanesulfonic acid and ethanesulfonic acid, and phenols such as picric acid. m
Examples include aromatic carboxylic acids such as -nitrobenzoic acid and aliphatic carboxylic acids such as dichloroacetic acid.

Polymeric acids can also be used. Examples of such polymer acids include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallylsulfonic acid, polyvinyl sulfuric acid, and the like.

The amount of protic acid used depends on the reaction mode of the oxidizing agent used. For example, in the case of manganese dioxide, the oxidation reaction is expressed as Mn0t+4H"+2e--Mn"+2H,0, so it is necessary to use a protonic acid capable of supplying at least four times the molar amount of protons as the manganese dioxide used. Also, in the case of hydrogen peroxide, the oxidation reaction is expressed as LOz+211"+2e--*2H!0, so it is necessary to use a protonic acid that can supply at least twice the molar amount of protons as the hydrogen peroxide used. .On the other hand,
In the case of ammonium belloxonisulfate, the oxidation reaction is represented by S,O,"-+2e--250,"-, so there is no particular need to use a protonic acid. However, in the present invention, even when ammonium beroxonisulfate is used as the oxidizing agent, it is preferable to use a protonic acid in an equimolar amount to the oxidizing agent.

As a solvent for oxidative polymerization of aniline, aniline,
A substance that dissolves the protonic acid and the oxidizing agent and is not oxidized by the oxidizing agent is used.

Water is most preferably used, but if necessary, alcohols such as methanol and ethanol, nitriles such as acetonitrile, N-methyl-2-pyrrolidone,
Polar solvents such as dimethyl sulfoxide, ethers such as tetrahydrofuran, and organic acids such as acetic acid can also be used. Moreover, a mixed solvent of these organic solvents and water can also be used.

In a method for obtaining a solvent-soluble aniline oxidized polymer,
It is important to maintain the temperature of the reaction mixture below 5°C at all times during the reaction, especially during the addition of the oxidizing agent solution to the aniline solution. Therefore, the oxidizing agent solution must be added gradually to the aniline so that the temperature of the reaction mixture does not exceed 5°C.

When adding an oxidizing agent rapidly, external cooling may raise the temperature of the reaction mixture and produce a low molecular weight polymer, or even after dedoping as described below, a solvent-insoluble oxidized polymer may be produced. do.

In particular, in the present invention, it is preferable to maintain the reaction temperature at 0°C or lower, so that after dedoping, N-
Measured in methyl-2-pyrrolidone at 30°C (hereinafter referred to as
same. ) A high molecular weight, solvent-soluble aniline oxidation polymer having an intrinsic viscosity [η] of 1.0 dl/g or more can be obtained.

In this way, an oxidized polymer of aniline doped with the protic acid used, ie polyaniline, can be obtained. In a doped state, this polyaniline forms a salt with a protonic acid, and therefore does not dissolve in an organic solvent as described below. It is well known that salts of high molecular weight amines are generally poorly soluble in organic solvents. However, according to the present invention, by dedoping this organic solvent-insoluble polyaniline, it is possible to make it into an organic solvent-soluble polyaniline.

Since dedoping of polyaniline doped with such protonic acid is a kind of neutralization reaction, it is not particularly limited as long as it is a basic substance that can neutralize the protonic acid as a dopant. ,Preferably,
Metal hydroxides such as aqueous ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, magnesium hydroxide, and calcium hydroxide are used. Dedoping may be carried out by adding a basic substance directly into the reaction mixture after the oxidative polymerization of aniline, or by once isolating the polymer,
A basic substance may also be applied.

Doped polyaniline obtained by oxidative polymerization of aniline usually has an electrical conductivity of 1 O-bS/cm or more and has a black edge color, but after dedoping, it has a purple or purplish copper color. . This discoloration is due to the conversion of the amine nitrogen in the salt structure into free amine in the polymer. The conductivity is usually on the order of 10-105/am.

The dedoped polyaniline thus obtained has a high molecular weight and is soluble in various organic solvents. Such organic solvents include aprotic polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, 1,3-dimethyl-2-imidazolidinone, and sulfolane. Organic solvents may be mentioned.

The solubility of dedoped polyaniline in such organic solvents depends on the average molecular weight of polyaniline and the solvent, but 1 to 100% of the polyaniline dissolves, and a solution of 1 to 30% by weight can be obtained. In particular, undoped polyaniline shows high solubility in N-methyl-2-pyrrolidone, usually 20-100% of it is dissolved, and 3-30% by weight of N-methyl-2-pyrrolidone.
A solution can be obtained. However, it does not dissolve in tetrahydrofuran, 80% aqueous acetic acid, 60% aqueous formic acid, acetonitrile, etc.

Next, the production of a conductive porous membrane using such solvent-soluble polyaniline will be explained.

According to the present invention, first, such a solvent-soluble polyaniline is dissolved in an aprotic polar organic solvent as described above or such an aprotic polar organic solvent containing an additive as described below to prepare a film forming solution. After coating the membrane solution on a suitable support substrate, it is miscible with the above organic solvent, but
Contact with a coagulating solvent that does not dissolve the polyaniline,
The solvent is removed to obtain a porous membrane. As the organic solvent for the film-forming solution, aprotic organic solvents such as those mentioned above are used in order to keep polyaniline in a dedoped state, but in particular, N-methyl-2-pyrrolidone has a negative effect on the solubility of polyaniline. Because of its excellent properties, it is preferably used in the present invention.

In general, the method of manufacturing porous membranes from membrane-forming solutions containing polymers is already well known as a wet method, and ultrafiltration membranes and reverse osmosis membranes are manufactured by such methods. . Such a membrane is a so-called anisotropic porous membrane in which a dense so-called skin layer on the surface is integrally supported by a porous layer. The porous layer may include a finger-like structure having cavities. The porous membrane obtained from the solvent-soluble polyaniline obtained as described above is also an anisotropic membrane having such a structure.

In the present invention, in order to obtain a porous membrane with excellent toughness and flexibility, it is desirable to use the above-mentioned solvent-soluble polyaniline having an intrinsic viscosity [η] of 0.40 or more. Also,
The concentration of polyaniline in the film forming solution is usually 0.5
-30% by weight, preferably 1-20% by weight.

In the present invention, various additives may be added to the membrane forming solution in order to adjust the porosity and surface area of the resulting porous membrane. Such additives need to be dissolved in the membrane forming solution, and for example, alkali metal salts and alkaline earth metal salts are preferably used. Specific examples include, but are not limited to, lithium nitrate, potassium nitrate, lithium bromide, and the like. Such inorganic additives are usually used in an amount of 100 parts by weight or less per 100 parts by weight of polyaniline.

When too much additive is used, it tends to impair the uniformity of the membrane forming solution, making it difficult to obtain a uniform selectively permeable membrane.

Moreover, organic compounds can also be used as additives. Examples of such organic additives include -hydric alcohols, polyhydric alcohols, ketones, nitriles, hydrocarbons, ethers, alkylene glycols, polyalkylene glycols, and esters. Specific examples include ethanol, propatool, butanol, glycerin, butanediol, acetone, methyl ethyl ketone,
Acetonitrile, propionitrile, butyronitrile,
Examples include, but are not limited to, hexane, heptane, benzene, toluene, diethyl ether, tetrahydrofuran, 1,4-dioxane, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and the like.

Although such additives are preferably dissolved in the membrane forming solution, it is also possible to use additives that are not dissolved.

These organic additives are usually used in an amount of 1000 parts by weight or less per 100 parts by weight of polyaniline.

If necessary, the above-mentioned inorganic additives and organic additives can be used together.

The supporting base material to which the film-forming solution is applied is not particularly limited.
By using a plate member with a smooth surface made of materials such as glass, stainless steel, aluminum, polyethylene, and polypropylene, polyaniline can be easily peeled off from these substrates after solidifying, so that sheet-like porous membranes can be used. can be obtained.

The coating thickness of the membrane-forming solution on the support substrate varies depending on the intended use of the selectively permeable membrane and the type of substrate, but usually,
The coating is applied so that the resulting porous membrane has a thickness of 10 to 700 um, preferably 50 to 200 um. If the film thickness is too thin, the resulting porous film will have poor mechanical strength, while if it is too thick, it will have poor ion diffusivity, both of which will be poor in practicality as a positive electrode material. becomes.

It is thus preferable to apply a thin layer of the film-forming solution onto the supporting substrate and then partially evaporate the organic solvent from this layer to promote the formation of the skin layer. The conditions for evaporating the solvent are appropriately selected depending on the component composition of the film-forming solution, etc., but if the temperature is below the boiling point of the solvent, for example, when the solvent is N-methyl-2-pyrrolidone, the temperature is 0 to 0. The temperature is within the range of 200°C, and the time for evaporation is not particularly limited.
May last from a few seconds to several hours.

Next, the base material coated with the membrane forming solution is immersed in a coagulating solvent to remove the solvent and coagulate the polyaniline to form a porous membrane. The coagulating solvent does not dissolve polyaniline, but has good compatibility with the solvent of the membrane-forming solution, preferably in an arbitrary proportion, and is further required to dissolve the aforementioned additives. , typically water is used. Other examples of coagulating solvents include mixed solvents of water and organic solvents that are compatible with water, and specific examples of such organic solvents include acetone, glycerin, methanol, etc. . If necessary, such an organic solvent can be used alone as a coagulation solvent.

The temperature at which polyaniline is brought into contact with a coagulating solvent to form a porous film is - for boat fishing, a temperature below the boiling point of the coagulating solvent used. When water is used as a coagulating solvent, the temperature is usually in the range of 0 to 80°C, preferably 0 to 50°C. The time required for coagulation is not particularly limited, but may range from 1 minute to 20 hours.

According to the present invention, the polyaniline porous membrane thus obtained is then doped with a protonic acid having a pKa value of 4.0 or less to impart electrical conductivity to the polyaniline, thus making the polyaniline conductive. A polyaniline porous membrane is obtained.

As such a doping agent, for example, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, hydrofluoroboric acid, and hydrofluoric phosphoric acid are preferably used.

However, if necessary, aromatic sulfonic acids such as benzenesulfonic acid and p-toluenesulfonic acid, aliphatic sulfonic acids such as methanesulfonic acid and ethanesulfonic acid, phenols such as picric acid, m-nitrobenzoic acid, etc. Organic acids such as aromatic carboxylic acids and aliphatic carboxylic acids such as dichloroacetic acid can also be used.

Doping of a polyaniline porous membrane can be carried out by immersing the membrane in a solution containing the above-mentioned doping agent for several hours to several days, followed by washing and drying.

According to the present invention, when the polyaniline porous membrane is completely reduced with a reducing agent such as hydrazine or phenylhydrazine, maximum capacity can be obtained as an electrode active material. Maximum capacity refers to the case where one unit of aniline can undergo redox of one electron, and when polyaniline is incorporated into a battery, in the formula, 0<m≦1 and m is All the nitrogen atoms in the repeating unit of the quinonediimine structure represented by the formula are protonated and are in the doped state represented by the formula, or m is 0 and the repeating unit of the phenylenediamine structure is completely reduced. This is the case when it consists only of units.

In these cases, the theoretical capacity obtained is 290 Ah/kg based on the weight of polyaniline alone, and based on the weight including (for example) lBF4 as a dopant.
It is 290Ah/kg.

Note that polyaniline that has been doped and given conductivity is doped with a protic acid, similar to polyaniline prepared in the presence of a protic acid.
For the reasons mentioned above, it does not dissolve in the organic solvents mentioned above.

The soluble aniline oxidation polymer according to the present invention can be determined from elemental analysis, infrared absorption spectrum, ESR spectrum, thermogravimetric analysis, solubility in solvents, and visible to near infrared absorption spectrum. The molar fraction of the quinonediimine structural unit and the phenylenediamine structural unit in the unit is 0≦n≦1.0≦n≦1, m+n=1) as the main repeating unit.

As described above, since the aniline oxidation polymer according to the present invention has a quinone diimine structural unit and a phenylene diamine structural unit as repeating units, in a state doped with a protonic acid, the oxidized polymer of aniline does not undergo a redox reaction. It is described as having electrical conductivity only through acid-base reactions. This conductivity/mechanism is 8, G, MacD
iarmid et al. (A, G, M
acDiarmid et al., J. Chew
.

Soc, Chell, Commun, 19B
? + 1784), by doping with a protic acid, the quinone diimine structure is protonated as shown below, and this forms a semiquinone cation radical structure, which has electrical conductivity. Such a state is called a polaron state.

IHX <protonic acid) ↓ Intramolecular redox reaction HH (semiquinone cation radical (polaron)) The electrical conductivity of a porous membrane made of polyaniline obtained by doping depends on the pKa value of the protonic acid used. A protonic acid with a pKa value of 4.0 or less is effective for doping polyaniline, and when using a protonic acid with a pKa value of 1 to 4, the smaller the pKa value, the more
The stronger the acidity, the higher the conductivity of the resulting film. but,
When the pKa value is less than 1, the conductivity of the resulting membrane no longer changes much and is almost constant.

The conductivity of polyaniline after doping with protic acid is usually greater than l(m's/am, often 10-
'S/as or more, and this conductivity is not affected by humidity at all. In particular, it has a characteristic that the conductivity does not change in a low humidity region.

Next, a battery according to the present invention will be explained.

The battery according to the present invention uses the above-mentioned conductive porous membrane made of polyaniline as a positive electrode active material.

On the other hand, examples of negative electrode active materials include lithium, potassium, sodium, magnesium, aluminum, zinc,
Cadmium, tin, lead, iron, alloys thereof, and the like are used, but are not limited to these.

In addition to water, when an alkali metal is used for the negative electrode, an aprotic organic solvent may also be used as the electrolyte solvent. Examples of such aprotic organic solvents include:
Ethylene carbonate, propylene carbonate, tetrahydrofuran, dioxane, dimethoxyethane, γ-
Butyrolactone, dimethylformamide, dimethylsulfoxide, acetonitrile, sulfolane, etc. are also used.

The electrolyte to be dissolved in such a solvent is preferably a salt of a negative electrode metal that is easily soluble in the above solvent, such as a chloride, a sulfate, a nitrate, a tetrafluoroborate, a perchlorate, a hexafluorophosphate, etc. used.

As described above, in the porous membrane made of conductive polyaniline used in the present invention, polyaniline, which is a conductive polymer, has an extremely high molecular weight compared to conventionally known conductive polyaniline. Therefore, according to the present invention, by using such a conductive polyaniline porous membrane as a positive electrode active material, it has excellent toughness, flexibility, and heat resistance, and high conductivity. A battery with high capacity and high energy density can be obtained.

Furthermore, the conductive polyaniline porous membrane used in the present invention can be easily obtained in any area by forming a film using a casting method from solvent-soluble polyaniline obtained by a chemical oxidation method and doping the film. This makes it possible to manufacture batteries at a low level.

Reference examples and examples according to the present invention relating to the production of polyaniline and porous membranes made of the same are listed below, but the present invention is not limited to these examples in any way.

Reference Example 1 (Production of doped conductive organic polymer by oxidative polymerization of aniline Part 1) In a 31-volume separable flask equipped with a stirrer, a thermometer, and a dropping funnel, 1500 g of distilled water and 90 g of 36% hydrochloric acid were added.
m1 and 100 g (1.07 mol) of aniline were charged in this order to dissolve the aniline. Separately, while cooling with ice water, 107 g (1.09 mol) of 97% concentrated sulfuric acid was added to 370 g of distilled water in a beaker and mixed to prepare an aqueous sulfuric acid solution. This aqueous sulfuric acid solution was added to the separable flask, and the entire flask was cooled with ice water to a temperature of -3°C or less.

Next, 245 g (1.07 mol) of ammonium beroxonisulfate was added and dissolved in 573 g of distilled water in a beaker to prepare an oxidizing agent aqueous solution.

The entire flask was cooled in a low-temperature constant temperature bath, and while the temperature of the reaction mixture was maintained at -3°C or below, the above aqueous solution of ammonium beroxonisulfate was gradually added dropwise to the aqueous solution of the aniline salt over a period of 200 minutes while stirring. Initially, the colorless and transparent solution turned from greenish-blue to a black-rimmed color as the polymerization progressed, and then a black-rimmed powder was precipitated. After the dropwise addition of the aqueous solution of ammonium belloxonisulfate was completed, stirring was continued for an additional 25 minutes at a temperature of -3°C.

A portion of the obtained polymer powder was collected, washed with water and acetone, and vacuum-dried at room temperature to obtain a black-rimmed polymer powder. This was pressure-molded into a disk with a diameter of 131 m and a thickness of 700 μm, and its electrical conductivity was measured by the van der Pauw method and found to be 3°708/country.

The obtained polymer slurry was diluted with distilled water 31 times twice, and
After filtering and washing three times with acetone 31, the polymer was dried under reduced pressure at room temperature.

(Dedoping of conductive organic polymer with ammonia) The doped conductive polymer powder was dispersed in 25% ammonia water 21, stirred for 2 hours under cooling, and then diluted with acetone once in distilled water 31. The stirring washing and filtration were repeated four times at 31°C. Voltage drying was performed at room temperature to obtain 79.5 g of dedoped polyaniline powder.

This polyaniline was soluble in N-methyl-2-pyrrolidone. Further, the intrinsic viscosity [η] measured at 30° C. after removing the solvent was 1.24.

This polymer had a solubility of less than 1% in dimethyl sulfoxide and dimethyl formamide.

Tetrahydrofuran, pyridine, 80% acetic acid aqueous solution, 6
It was not substantially dissolved in 0% formic acid aqueous solution and acetonitrile.

Reference Example 2 (Production of doped conductive organic polymer by oxidative polymerization of aniline, Part 2) In Reference Example 1, the reaction temperature was controlled somewhat loosely, and the average temperature during the reaction was set to about 1°C (however, Doped conductive polyaniline was obtained in the same manner as in Reference Example 1 except that the temperature did not exceed 5° C. during the reaction. The electrical conductivity of this polyaniline was 2°8S1011.

Further, the solvent-soluble polyaniline obtained by dedoping in the same manner as above had an intrinsic viscosity of 0.67.

Reference Example 3 (Preparation of self-supporting film using soluble aniline oxide polymer) 5 g of the dedoped aniline oxide polymer powder obtained in Reference Example 1 was added little by little to 95 g of N-methyl-2-pyrrolidone, and the mixture was heated to room temperature. A black-blue solution was obtained. When this solution was vacuum filtered using a 03 glass filter, extremely small amounts of insoluble matter remained on the filter. This filter was washed with acetone, and after drying the remaining insoluble matter, the weight was measured and found to be 75 cm. Therefore, 98.5% of the polymer is dissolved, and the insoluble matter is 1.5%.
%Met.

The polymer solution thus obtained was cast on a glass plate, squeezed with a glass rod, and then N-methyl-2-pyrrolidone was evaporated and evaporated in a hot air circulation drying ear.

After this, by immersing the glass plate in cold water, the polymer film will peel off naturally from the glass plate, thus
A polymer film with a thickness of 40 μm was obtained.

After washing this film with acetone, it was air-dried at room temperature to obtain a film with copper-colored metallic luster.

Films differ in strength and solubility depending on their drying temperature. When the drying temperature is 100° C. or less, the resulting film dissolves in N-methyl-2-pyrrolidone to a small extent and has relatively low strength. However, the film obtained by heating at a temperature of 130° C. or higher is very tough and does not dissolve in N-methyl-2-pyrrolidone or other organic solvents. It also does not dissolve in concentrated sulfuric acid. Thus, it appears that when heated at high temperatures, the polymer molecules crosslink with each other in the process and become insoluble.

The dedoped films obtained in this way all had electrical conductivities on the order of IO-''S/am.

Further, the film did not crack even after being bent 10,000 times, and its tensile strength was 840 kg/ci.

Example 4 (Dobin's force due to protonic acid on self-supporting film) In Reference Example 3, the self-supporting films obtained by heating and drying at 150°C for 30 minutes were placed in IN aqueous solutions of sulfuric acid, perchloric acid, and hydrochloric acid at room temperature. After soaking in water for 66 hours, they were washed with acetone and air-dried to obtain conductive films.

Both films exhibit a deep blue color and have electrical conductivities of 8.2 S/CSIS11 S/am and 5 S/am, respectively.
It was cm. Further, the tensile strength of the film doped with perchloric acid was 500 kg/-.

Reference Example 5 (Spectrum and structure of soluble polymer and insoluble film-formed polymer both in dedoped state) Spectrum and structure of soluble polymer powder obtained in Reference Example 1 and insoluble polymer film obtained in Reference Example 3. FT-IR spectra obtained by the KBrBr method are shown in FIGS. 1 and 2, respectively. Since the two spectra are almost the same, it can be seen that although the polymer becomes insolubilized by crosslinking by heating and drying the solvent after casting the solvent-soluble polymer, no major change has occurred in the chemical structure.

The results of thermogravimetric analysis of the above-mentioned soluble polymer powder and insoluble polymer film are shown in FIG. Both have high heat resistance. Considering that insoluble films are insoluble in concentrated sulfuric acid, they do not decompose up to higher temperatures, indicating that the polymer molecules are crosslinked in insoluble films.

Further, FIG. 4 shows the ESR spectrum. The spin concentration was 1.4X10'' spins/g for the soluble polymer and 2.7X10'' spins/g for the insoluble polymer.The decrease in spin concentration from the soluble to the insoluble polymer was
As mentioned above, this appears to be due to crosslinking of polymer molecules during the heating and drying process of the solvent during film preparation.

Next, the results of elemental analysis of the soluble polymer and insoluble polymer are shown below.

Soluble polymer C, 77,9'7; H, 5,05; N, 14.6
8 (Total 97.70) Insoluble polymer C,? 8.31. H, 5,38; N, 15.31
(Total 99.00) Based on this elemental analysis, C
I 2. The compositional formula of the soluble polymer standardized to OO is C
82,. . H9,zbN+, qa, and the compositional formula of the insoluble polymer is CI□. . H9,ll! Nz. It is 1. On the other hand, similarly, the quinonediimine structural unit and phenylenediamine structural unit standardized to C12,OO are:
Each is as follows.

Quinonediimine structural unit c+t)IsL Phenylenediamine structural unit C+tH+aNz Therefore, as described above, both the soluble polymer and the solvent-insoluble polymer are polymers having quinonediimine structural units and phenylenediamine structural units as main repeating units.

Next, FIG. 5 shows the reflection spectra in the visible to near-infrared region of the dedoped film obtained in Reference Example 3 and the perchloric acid-doped film obtained in Reference Example 4, respectively.

In the undoped state, most of the near-infrared light is reflected, but after doping, the near-infrared light is absorbed and almost no reflection is observed. This is based on absorption by polarons or bipolarons resulting in conductivity generated by protic acid doping.

Furthermore, by doping the undoped film with perchloric acid, the ESR absorption increases significantly, and the spin concentration reaches 3.8×10” spin/g. It originates from.

Reference Example 6 The polymer film obtained in Reference Example 3 was immersed in aqueous or alcoholic solutions of protonic acids having various pKa values, and the possibility of doping was examined. The results are shown in Figure 6.

Table 1 shows the electrical conductivity of polymer films doped with protic acids having various pKa values.

The results in Table 1 and above show that protonic acids having a pKa value of 4.0 or less are effective for doping polymers.

Reference Example 7 (Production of conductive polyaniline porous membrane as positive electrode active material) The solvent-soluble polyaniline obtained in Reference Example 1 was dissolved in N-methyl-2-pyrrolidone at a concentration of 5% by weight to prepare a membrane forming solution. was prepared. Similarly, 8% by weight of the solvent-soluble polyaniline obtained in Reference Example 2 was added to N-methyl-2-pyrrolidone.
A film-forming solution was prepared by dissolving at a certain concentration.

These film-forming solutions were each cast at room temperature onto a glass plate on which a 590 μm thick spacer was placed, and then treated at the temperature and time shown in Table 2 to evaporate the solvent. The casting layer was then immersed in water together with the glass plate for 1 minute to solidify the polyaniline and peel it off from the glass plate. The obtained porous membrane was sufficiently washed with acetone until the washing solution was no longer colored, and then dried under reduced pressure at room temperature to obtain a flexible polyaniline porous membrane in an undoped state.

Next, in order to impart electrical conductivity to this porous membrane, the porous membrane was immersed in a 42% aqueous borofluoric acid solution for about 12 hours, and then dried under reduced pressure at 80°C for 3 hours. Used as a substance.

Reference Example 8 A film-forming solution was prepared by dissolving the solvent-soluble polyaniline obtained in Reference Example 1 in N-methyl-2-pyrrolidone to a predetermined concentration together with the additives shown in Table 2.

These film-forming solutions were each cast at room temperature on a glass plate with a 590 μm thick spacer placed thereon.
After heating at a temperature of 0°C for 15 minutes to evaporate and remove a portion of the solvent, the casting layer and the glass plate were immersed in distilled water at 25°C to remove the remaining solvent, solidify the polyaniline, and remove the glass plate. It was peeled off from. A porous membrane was obtained.

The obtained porous membrane was sufficiently washed with acetone until the washing solution was no longer colored, and then dried under reduced pressure at room temperature to obtain a flexible polyaniline porous membrane in an undoped state.

Next, in order to impart electrical conductivity to this porous membrane, the porous membrane was immersed in a 42% aqueous borofluoric acid solution for about 12 hours, and then dried under reduced pressure at 80°C for 3 hours. Used as a substance.

(Battery Performance Test) The above polyaniline porous membrane was cut into a sample in an approximately 1-mm length in argon gas, and after measuring its thickness and weight, it was wrapped in a platinum mesh with a lead wire to form a positive electrode.

As a battery separator, polypropylene nonwoven fabric is used.
In addition, for the negative electrode, a piece of 200 μm thick lithium foil cut into 2 cm square pieces and integrated with a stainless steel mesh as a current collector was used. Further, a purified propylene carbonate solution in which 1 mole of lithium fluoroborate was dissolved was used as the electrolyte.

Charging and discharging are performed at a constant current with a discharge end voltage of 2■1. The charging was carried out at a charging end voltage of 4V. The results are shown in Table 3.

[Brief explanation of the drawing]

Figure 1 shows the KB of soluble polyaniline in the dedoped state.
FT-IR spectrum obtained by the r-tablet method; FIG. 2 is an FT-IR spectrum obtained by the KBr tablet method of a solvent-insoluble film obtained by casting the above solvent-soluble polyaniline; FIG. 3 is an FT-IR spectrum obtained by the KBr tablet method. Thermogravimetric analysis of the film. Figure 4 shows the ESR spectra of the above-mentioned soluble polyaniline and insoluble polyaniline. Figure 5 shows the visible to near-infrared region of the undoped polyaniline film and the film doped with perchloric acid. Figure 6 is a graph showing the relationship between the pKa value of the protonic acid and the conductivity of the resulting film when a dedoped polyaniline film is doped with protonic acids having various pKa values. be.

Claims (1)

[Claims] (1) General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, m and n respectively indicate the molar fraction of the quinonediimine structural unit and phenylenediamine structural unit in the repeating unit, 0≦m≦1, 0≦n≦1, m+n=1) as the main repeating unit, is soluble in organic solvents in the dedoped state, and has an intrinsic viscosity measured at 30°C in N-methylpyrrolidone [ η] is 0.40d
l/g or more, but has a pKa value of 4.0 or less, and is characterized by having a porous membrane made of conductive polyaniline doped with a protic acid to make it insoluble in organic solvents as a positive electrode active material. battery.