JPH02160823A - Production of conductive polymeric complex - Google Patents

Abstract

PURPOSE:To obtain the title complex which is a polythiophene/electrolyte complex which is a conductive polymer of a fixed dopant type having a high doping ratio by polymerizing a thiophene monomer in a solution of a specified polyelectrolyte through electrolytic oxidation. CONSTITUTION:A thiophene monomer (e.g. thiophene) is polymerized through electrolytic polymerization in a solution (e.g. alcoholic solution) of a polyelectrolyte having an anionic group having an F substituent in at least the position alpha (e.g. an electrolyte containing a copolymer of tetrafluoro-ethylene with perfluoro-3,6-dioxamethyl-7-octenesulfamic acid).

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for producing a conductive polymer composite, and more specifically, a method for producing a composite of polythiophenes and an electrolyte in which an anion group of an electrolyte is a fixed dopant. It's about how to do it.

Conductive polymers are currently attracting attention as new functional materials for conductors, semiconductors, batteries, display elements, charge conversion elements, sensors, etc. due to their novel physical and electrochemical properties.

(Conventional technology) The conductivity of polyacetylene was increased to 8 by the ion doping method.
Since it was discovered that the ion-doping type conductive polymer can increase the temperature by 100%, various ion-doped conductive polymers have been proposed.

It is thought that dopants for P-type conductive polymers can range from small things such as halogen ions to macrocyclic molecules and even polymer electrolytes. The development of doping methods with various dopants and the properties and applications of the resulting conductive polymers are being considered as new technologies that are attracting attention.

An example of the dopant is an inorganic anion. However, although a large amount of the dopant can be doped into the conductive polymer, there is a problem that the dopant is not doped uniformly, and therefore the resulting polymer is not satisfactory in terms of conductivity. Furthermore, this polymer has the disadvantage of poor self-standing and brittleness.

For this reason, it has recently been proposed to use a polymer electrolyte having an anionic group as a dopant, and for example, JP-A-59-98165 proposes a conductive polymer composition using a polymer as a dopant. The composition contains sulfonated polyethylene as a polymer dopant;
Examples include sulfonated polystyrene, sulfonated poly(2,5-dimethylphenylene oxide), sulfonated polyvinyl alcohol, sulfonated styrene/(hydrogenated) butadiene copolymer, and the anionic group is formed from a sulfonic acid group. There is. This proposal is attracting attention because it shows that a conductive polymer composite is more stable and self-supporting than conventional conductive polymers doped with inorganic anions. However, as a conductive material, it is not necessarily sufficient in terms of chemical and physical stability, and the doping rate, which is an important element of ion-doped conductive polymers, is Since the concentration is high and the polymer electrolyte concentration is high on the other side, there is a problem that it is lower than when using a general inorganic anion dopant. Furthermore, according to the studies of the present inventors, the sulfonic acid group of this sulfonated polymer dopant dissociates in an aqueous solution, but it is often difficult to dissociate it in a non-aqueous solvent. It is difficult to make molecular complexes function sufficiently in non-aqueous solvents, which is one barrier to their practical application.

It has also been proposed to use a fluoropolymer electrolyte, which has superior chemical stability compared to the above-mentioned sulfonated polymers, as a polymer dopant. For example, using a cell in which a fluoropolymer electrolyte is used as a diaphragm and a monomer solution that forms an isoelectric polymer and an oxidizing agent solution are separated, a conductive polymer is chemically polymerized from the oxidizing agent side surface of the fluoropolymer electrolyte. death,
Methods for synthesizing composite membranes of conductive polymers and fluoropolymer electrolytes have been proposed. However, even with this method, the doping rate of the polymer electrolyte is not necessarily satisfactory, and there is a problem that the resulting film is doped with dopant non-uniformly. In addition, complexes of conductive polymers and polymer electrolytes synthesized using chemical polymerization methods are
A composite membrane of a conductive polymer and a polymer electrolyte, in which an anion group of the polymer electrolyte and an anion introduced from an oxidation species are introduced as dopants, and thus a composite dopant of a fixed dopant and a mobile dopant is formed. begins to form.

Furthermore, JP-A-63-98972 proposes the use of a composite of a conductive polymer and a fluoropolymer electrolyte as a positive electrode active material of a secondary battery. This proposal is
It has been stated that when the composite is used as a battery positive electrode, the self-discharge rate of the positive electrode is reduced and the battery durability is improved. A method of manufacturing a composite powder is described. However, the doping rate of the polymer electrolyte in the composite obtained by this method is extremely low. Even if all of the anion groups are doped, the doping rate is only about 3% per unit of polyaniline.

In addition, since the discharge capacity of the composite is quite high, this composite has Dovan I, whose main anion is oxidized by the oxidizing agent ammonium persulfate, rather than the fluoropolymer electrolyte anion group. it is conceivable that. Therefore, this composite is not satisfactory in terms of stability or self-supporting properties, and also has disadvantages in terms of conductivity because the dopant is also doped non-uniformly into the conductive polymer.

As mentioned above, in the conventionally proposed electrolytes with anionic groups, especially in complexes of polymer electrolytes and conductive F3 polymers, the dob rate of polymer electrolytes has been reported for ordinary inorganic anions. This value is lower than the Dovan I rate. Further, in many cases, both the anionic groups of the polymer electrolyte and other inorganic anions are doped, and therefore, in the case of a fixed dopant and a mobile dopant I, it is considered to be a dopant type. Furthermore, the resulting film does not necessarily have a uniform composition, may have insufficient physical or chemical stability, and may not function satisfactorily in various solvents.

(Problem to be Solved by the Invention 21fi) An object of the present invention is to provide a fixed dopant type conductive polymer exhibiting a high doping rate. More specifically, only the anionic group of the electrolyte is used as a dopant, and the anionic group of the electrolyte is doped at a doping rate as high as that of an inorganic halogen anion, and is further immobilized within a conductive polymer. A method for producing a composite of a conductive polymer and an electrolyte with anionic groups that functions as a dopant, exhibits a uniform composition with excellent physical and chemical stability, and can function in various solvents. This is a proposal.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have found that a fixed dopant type that exhibits a high doping rate can be obtained by producing a composite by an electrolytic oxidation combination method. The inventors discovered that a conductive polymer could be obtained and completed the present invention. That is, the present invention provides a method for producing a composite of a polythiophene and an electrolyte, which comprises performing electrolytic oxidative polymerization of a thiophene monomer in a solution containing a polymer electrolyte having an anion group substituted with fluorine at least at the α position. It is.

The present invention will be specifically explained below.

FIG. 1 shows a redox model of the fixed dopant type conductive polymer in the present invention. In a general mobile dopant type conductive polymer containing an inorganic anion as a dopant, as shown in FIG. 2, the anion as a dopant moves in and out of the conductive polymer as a result of redox. On the other hand, in a fixed dopant type conductive polymer, the dopant is fixed within the conductive polymer as shown in FIG. 1, and cannot move inside or outside the conductive polymer due to redox. Therefore, in such fixed dopant type conductive polymers, counter ions of the anions fixed within the -9 conductive polymer, that is, cations, move in and out of the conductive polymer as a result of redox. Become. In this way, the fixed dopant type conductive polymer exhibits a redox mechanism that is clearly different from that of the mobile dopant type conductive polymer.

H
The polymer electrolyte used for this purpose is preferably an electrolyte that ranges from oligomers to polymers in which the anionic groups are not liberated into the solvent and can be hydrogenated. When a complex is formed, the dopant anion (electrolyte having an anion group) becomes a fixed dopant that does not move in or out of the conductive polymer due to redox. Furthermore, since at least the α-position of the electrolyte is fluorine-substituted, the resulting conductive polymer composite can function not only in an aqueous solution of 1 J but also in various solvents such as non-aqueous solutions. Although the reason for this is not clear, it is thought that the electrolyte used in the present invention can dissociate anion groups even in non-aqueous solvents due to the electron-accepting property of fluorine.

Examples of the above-mentioned electrolyte include the following oligomers or polymers.

5o3x "coo -x"OO COO 00F20F2S03 More specifically, tetrafluoroethylene and perfluoro-3,6-thioxermethyl-7 having the following structure
-Polymer electrolytes containing copolymers with octensulfamic acid may be mentioned.

1-E-CI+ CF+ CI? CI', y-1-
7-2n (OCT' CP) 0CF2CP2So3Hn p3 The solution used for electrolytic oxidative polymerization is obtained by dissolving the electrolyte in a soluble solvent, and the soluble solvent includes:
Polar solvents such as alcohols, ketones, organic acids,
Examples include aldehydes and esters. The concentration of the solution is not particularly limited, but the electrolyte is 10 to 111
It is preferable that the solution has a concentration of ol/dad3 or more.

Further, the thiophenes used in the present invention are thiophene or thiophene derivatives, and in particular, the derivative is preferably a derivative having a substituent at the 3rd and/or 4th position due to the structure of the conductive polymer. Examples of derivatives include 3-methylthiophene and 3-methoxythiophene.

Electrolytic oxidative polymerization is carried out by an anodic reaction, and any conductive substrate such as a metal such as platinum, conductive glass whose surface is coated with a conductive substance such as ITO, or glassy carbon may be used as the anode. Can be done.

The conditions for electrolytic oxidation polymerization are constant current electrolysis.

A constant potential electrolysis method, a pulse electrolysis method, a potential scanning electrolysis method, etc. can be used. For example, when carrying out the flow electrolysis method at 10-2, using an electrolyte solution containing thiophenes,
A conductive polymer composite can be obtained by performing electrolytic oxidation polymerization at a constant current of m8 to C- to 10' mA/cJ. Further, when performing constant potential electrolysis, a solution of an electrolyte containing thiophenes is used at a potential higher than the oxidation potential of the thiophenes, for example, +1. 5~+2.
A conductive polymer composite can be obtained by applying a potential of 5 V vs. SCE to the anode and performing electrolytic oxidative polymerization.

The solution temperature during electrolytic oxidation polymerization is adjusted appropriately depending on the properties of the desired conductive polymer composite. In order to obtain a functional polymer complex, it is desirable to keep the solution temperature below room temperature.

The conductive polymer composite obtained as described above has a fixed dopant type in which only the anion group of the electrolyte is used as a dopant, and the doping rate of the dopant is 0.15 to 0.3 per polythiophene unit. . This is a doping rate of anionic groups as high as that of inorganic halogen anions. Furthermore, the resulting conductive polymer composite has a uniform composition with excellent physical and chemical stability, and can function in various solvents.

The fixed dopant type conductive polymer obtained by the production method of the present invention can be applied to electrochemical devices because the moving ions are cations that are counter ions to the fixed anions.
For example, it has properties suitable as a positive electrode of a secondary battery, and when used as a positive electrode of a lithium battery, for example, the mobile species are the same in the positive electrode and negative electrode, making it possible to form a battery in which the electrolyte concentration does not change.

(Example) Examples will be described below, but the present invention is not limited thereto.

Example 1. Comparative Example 1 A platinum plate (effective electrode area: 0.5 cm) was used as an anode, and tetrafluoroethylene containing 0,01 a+ol/dn3 of thiophene and perfluoro-3,6-thioxermethyl-7-octensulfamic acid were used as an anode. Using an alcohol solution (containing 511% of electrolyte and 10% of water by weight) of an electrolyte (Nafion, manufactured by DuPont) containing a copolymer of 0. 0.6C at constant current of 5n+A/cd
Anodic oxidation polymerization was performed to /c- to obtain a conductive polymer composite of polythiophene and electrolyte. The resulting conductive polymer composite was a self-supporting film that remained stable without crumbling during drying.

Elemental analysis of the obtained conductive polymer composite was performed, and the composition of the composite was calculated from the ratio of each constituent element to the width of the composite. It was found that 1 mol of polythiophene It was found that 0.25 mol of electrolyte was contained.

Further, when the distribution of sulfur atoms in the depth direction of the obtained conductive polymer composite was examined by EPMA analysis, the sulfur atoms were found to be uniformly dispersed.

Next, cyclic voltammetry was performed in an aqueous solution containing 1 mol/d of potassium chloride using the obtained conductive polymer composite as a test electrode, platinum as a counter electrode, and a saturated calomel electrode as a reference electrode. The results are shown by the solid line in FIG.

In addition, the same ll constant was determined using sodium polystyrene sulfonate (
The test was carried out in a 20 weight 96 aqueous solution of molecule Q: 10000). The results are shown by the solid line in FIG.

As Comparative Example 1, thiophene was used at 0 and 01 sol/d.
0.6 C/c at a constant current of 0.5 mA/c using an acetonitrile solution containing tetraethylammonium verchlorate at a concentration of 0, 1 mol/da.
Anodic oxidation polymerization was carried out until - to obtain a polythiophene alone containing CIO ions of tetraethylammonium verchlorate as a dopant. The obtained polythiophene alone was brittle and unstable. Using this polythiophene alone as a test electrode, cyclic voltammetry was performed under the same conditions as in Example 1. The results are shown by the dotted line in FIG. 3 and the dotted line in FIG. 4. When used alone, no redox was observed in an aqueous solution of sodium polystyrene sulfonate, as shown in FIG. This indicates redox movement of anions, in which anions move in and out as a result of oxidation-reduction when used alone, but when the giant polystyrene sulfonate anion becomes an anion, it shows that anion movement is not possible. On the other hand, as is clear from FIGS. 3 and 4, the conductive polymer composite shows almost the same reversible portamogram regardless of the size of the anion species, and the conductive The polymer complexes were found to exhibit redox cation transfer.

Furthermore, the ions that migrate due to redox of this conductive polymer composite were identified by EPMA analysis. The results are shown in Figure 5-a. Further, the analysis results of the single substance obtained in Comparative Example 1 are shown in FIG. From Figure 5, it can be seen that the CIO ions increase and decrease in the single substance due to redox, indicating that the single substance exhibits redox of anion movement. On the other hand, as shown in Figure 5-a, potassium ions increase and decrease in the conductive polymer composite due to redox, so it is confirmed that the obtained conductive polymer composite exhibits redox of cation transfer. Ta.

Furthermore, since the sulfur in polythiophene and the sulfur in the anionic group of the electrolyte that is the dopant are not changed by redox, the anionic group of the electrolyte that is the dopant is
It was found that it functions as a fixed dopant.

In addition, the conductive polymer composite obtained in Example 1 was used as a test electrode, and lithium perchlorate was added to the electrolyte.
When cyclic voltammetry was performed using propylene carbonate containing OI3 and the redox capacity was measured from the obtained cyclic voltammogram, the capacity was about 95% of the redox capacity estimated from the amount of polymerization electricity. Moreover, during the measurement, this conductive polymer composite did not break down, and no change was observed in its redox properties against electrochemical redox in the electrolyte, and the obtained conductive polymer composite showed no physical damage. , was chemically stable.

Example 2 A conductive polymer composite was produced and evaluated in the same manner as in Example 1, except that 3-methylthiophene was used as a substitute for thiophene. As a result, the obtained conductive polymer composite was a physically and chemically stable self-supporting film, uniformly composited at a doping rate of 0.2.5, and from electrochemical evaluation, It was confirmed that it exhibits cation transfer type redox. Furthermore, 1 m of lithium perchlorate
A redox capacity of 95% was obtained in propylene carbonate containing ol/dm3.

Comparative Example 2 A platinum plate (effective electrode area: 0.5 cd) was used as an anode, and 0.1 mol/dm of thiophene was used as the electrolyte.
0.6C at a constant current of 0.511IA/c- using an aqueous solution containing 20g of potassium polystyrene sulfonate and 20g of potassium polystyrene sulfonate.
Anodic oxidation polymerization was performed to /c- to obtain a conductive polymer; 1 combination of polythiophene and polystyrene sulfonic acid.

Cyclic voltammetry was performed in propylene carbonate containing 1 mol/11w3 of lithium perchlorate using this conductive polymer composite as a test electrode, a platinum plate as a counter electrode, and a saturated calomel electrode as a reference electrode. = was the redox capacity estimated from the amount of polymerization electricity, which was 506. This is because it is difficult to dissociate the dopant polystyrene sulfonate anion in a non-aqueous solution, so it is presumed that a sufficient capacity cannot be obtained. Ru.

Comparative Example 3 Using 18 g of thiophene and 7 g of an electrolyte (Nafion 177 manufactured by DuPont) containing a copolymer of tetrafluoroethylene and perfluoro-3,6-thioxermethyl-7-octensulfamic acid, A blend of polythiophene and electrolyte was synthesized by a chemical polymerization method by mixing 20 g of ammonium persulfate as a dopant and a polymerization catalyst. The resulting composite was not a self-supporting film but a powder, and elemental analysis of the preparation revealed that the polythiophene contained 20% electrolyte. From this result, it was found that the doping rate of the jlled composite was 0.02.

When the same evaluation as in the example was carried out using a pellet formed from the powder of the obtained composite under pressure as a test electrode, the ions transferred due to redox were both cations and anions. This is thought to be due to problems with the doping rate and uniformity of the compound obtained by chemical polymerization.

(Effects of the Invention) As described above, the present invention exhibits a doping rate of anion groups as high as that of inorganic halogen anions, and has a uniform composition with excellent physical and chemical stability. Complexes that can function in various solvents are obtained.

Furthermore, the composite obtained in i-) has a novel function of a fixed dopant type (cation transfer type), and is attracting attention in various fields of application of conductive polymers.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a redox model of a fixed dopant type polymer obtained by the present invention. FIG. 2 is a diagram showing a redox model of a mobile dopant type conductive polymer. FIG. 3 is a diagram showing cyclic portamograms of the conductive polymers obtained in Example 1 and Comparative Example 1; FIG. 4 is a diagram showing cyclic portamograms of the conductive polymer composites and conductive polymers obtained in Example 1 and Comparative Example 1 in an aqueous solution of sodium polystyrene sulfonate. FIG. 5 is a diagram showing the results of EPMA analysis of the conductive polymer film combination and conductive polymer obtained in Example 1 and Comparative Example 1. Polythiophene Figure 2 Polythiophene

Claims (1)

[Claims] (1) A method for producing a composite of polythiophenes and the electrolyte, which comprises carrying out electrolytic oxidation polymerization of a thiophene monomer in a solution containing a polymer electrolyte having an anion group substituted with fluorine at least at the α position.