JP2653048B2 - Conductive polymer composite and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel conductive polymer composite which can be used for a conductive material, an electromagnetic shielding material, a battery, a capacitor, and the like, and a method for producing the same.

2. Description of the Related Art A polymer film obtained by electrochemically polymerizing a five-membered heterocyclic compound such as pyrrole or thiophene on an electrode has a high conductivity and a relatively high stability. Research is being conducted. In this electrolytic polymerization, generally, a monomer such as pyrrole and a supporting electrolyte (eg, tetraethylammonium perchlorate (Et ₄ N · CIO ₄ )) are dissolved in a solvent (organic solvent or water), an electrode is put in the solution, and a voltage is applied. In this case, a polymer film is formed on the anode by an oxidation reaction, in which case the ▲ CIO ^- ₄ ions of the supporting electrolyte are doped into the pyrrole film,
Shows high conductivity. As the monomer, besides pyrrole, bipyrrole, thiophene, and other similar compounds such as bithiophene, α-terthienyl, or a similar compound such as thienylpyrrole, which is a comonomer of pyrrole and thiophene, can be used. Other monomers include condensed (polycyclic) aromatic compounds such as benzene, naphthalene, anthracene, and pyrene; heterocyclic compounds such as furan, indole, carbazole, phenothiazine, and thienothiophene; and aniline, phenylenediamine, and aminopyrene. Numerous compounds such as those having an amino group have been studied.

The characteristic of such an electropolymerized film is that it exhibits high conductivity up to 1000 S / cm. This is because the polymer (polymer) is in an ionized (oxidized) state, and is converted into an insulator when ions doped therein are removed by any method. It is best to dope and de-dope the polymerized film electrochemically with ions, and the resulting color change of the film can be used as a display element, or the effect of accumulating the charge by this can be used as a secondary battery. Available.

However, recently, various composite techniques have been developed as a technique for imparting functions other than display and energy storage to the electropolymerized film.

For example, the dopant has a function, such as a pyrrole-sulfonated phthalocyanine, a surfactant, and a polymer electrolyte (sulfonated polystyrene). Powder such as RuO ₂ or iron oxide can be dispersed in the polypyrrole film simultaneously with polymerization (filler type). Furthermore, there is an advanced composite technology in which a polymer alloy of pyrrole and a general-purpose polymer is made by electrolytic polymerization of pyrrole or the like on an electrode coated with a general-purpose polymer (polyvinyl chloride, polyvinylidene fluoride, polyvinyl alcohol). . (These composite technologies are summarized in detail in Susumu Yoshimura, Proceedings of the Symposium on Polymer Science, September 1986.) Problems to be Solved by the Invention Electropolymerization typified by polypyrrole described above Polymers not only have high conductivity and high stability, but also can be variously complexed to exhibit new functions. However, in order to promote higher functionality, it is necessary to develop new methods and materials. An object of the present invention is to obtain a conductive polymer composite having high electrochemical activity and high conductivity.
None of the methods analogized by extensions of the prior art described above are satisfactory.

Also, the new material dealt with in this invention is a composite conductor of manganese dioxide and polypyrrole with very high electrochemical activity. In order to produce this by a conventional technique, a method in which a monomer such as pyrrole is electrolytically polymerized in an electrolyte in which fine powder of manganese dioxide is suspended may be considered. However, in the polymer film obtained by this method, manganese dioxide particles are unevenly dispersed, the conductivity is not sufficiently controlled, and the electrochemical activity is not sufficient. Dispersions of other electrochemically active materials, such as powders of lead dioxide, in the polymerized pyrrole film in this way likewise give poor results.

An object of the present invention is to solve the above problems and to obtain a conductive polymer composite having high chemical activity and high conductivity.

Another object of the present invention is to establish a novel method for producing the above conductive polymer composite.

Means for Solving the Problems The conductive polymer composite of the present invention has a configuration containing a polymer obtained by electrolysis using an electrolyte containing an electrolytic polymerizable monomer and a manganese salt, and manganese dioxide.

In addition, this conductive polymer composite includes a step of preparing a pair of electrodes, a manganese salt that is any of manganese sulfate, manganese chloride, manganese nitrate and manganese perchlorate, and pyrrole, thiophene, thienylpyrrole, aniline,
A step of preparing an electrolyte containing an indole or furan electropolymerizable monomer, and from the electropolymerizable monomer by electrolytic polymerization on the anode of the pair of electrodes by electrolysis using the electrolyte. Forming a polymer and also forming manganese dioxide on the anode by electrolytic synthesis to form a conductive polymer composite.

Action The composite of the above constitution obtained by the above production method has high electrical activity because almost completely amorphous manganese dioxide is uniformly dispersed in the electropolymerized film, and has a continuous conductivity in a wide range. Can be controlled.

Examples Hereinafter, the present invention will be described in detail based on examples.

The basic process of the method of synthesizing the composite material of the present invention is to simultaneously perform the electrolytic polymerization of manganese dioxide and the electrolytic polymerization of the electrolytically polymerizable monomer. Manganese dioxide is classified in various ways depending on how it is made. Among them, electrolytic manganese dioxide (ECM) is made by keeping an aqueous solution of manganese sulfate at 80-90 ° C and precipitating on the anode at a voltage of about 3V. In the present invention, this electrolytic oxidation reaction
We started by examining whether it could proceed simultaneously with the oxidative polymerization reaction of pyrrole and the like, and for the first time confirmed that it was possible.

FIG. 1 is a conceptual diagram of an electrolytic polymerization apparatus used for producing a conductive polymer composite according to the present invention. In the figure, reference numeral 1 denotes a glass container in which an electrolyte solution 2 is stored. An anode 3 and a cathode 4 are provided in the electrolyte solution 2, and given a predetermined current value and voltage value by a constant current / constant voltage power supply 5. 6 and 7 are an ammeter and a voltmeter for monitoring these.

Electropolymerization can be performed in principle by a constant current method or a constant voltage method. However, depending on the material, polymerization may occur only at a specific potential, and the potential for forming MnO ₂ may also depend on the electrolyte composition. In specific electrolytic polymerization, platinum, a transparent electrode (indium-tin oxide), stainless steel having a high chromium content, or the like was used as an anode, and a large-area noble metal such as platinum black or a platinum mesh was used as a cathode.

As the monomer, pyrrole, thiophene, thienylpyrrole, aniline, indole, furan and the like can be used. Among them, pyrrole, thiophene, aniline, and furan could be used in an aqueous solution. A manganese salt such as manganese sulfate, manganese nitrate, manganese chloride or the like was used as a supporting electrolyte. Depending on the purpose, it is also possible to add a conventionally used salt at the same time to carry out the polymerization. As the supporting salt, (abbreviated as Tos) tosylate, sulfate (▲ SO ^2- ₄ ▼), perchlorate ion _{^{(▲ ClO - 4 ▼),}} 4 boron fluoride ions (▲ BF ^- ₄ ▼) , nitrate ion (▲ NO ^- ₃ ▼), oxalate (COO ^-) ₂ salt, such as selected and used high solubility in organic solvents or water.

First, free of pyrrole, in a system of an aqueous solution containing MnSO ₄ only 0.2 mol / l and the electrolyte, by applying a voltage greater than 2.5~3.0V at a constant temperature, blackish brown uniform film can be obtained on the anode Was. This film had poor adhesion to the substrate and was very brittle, but the X-ray diffraction spectrum showed that it was γ-type MnO ₂ . Next, when 0.1 mol / l of pyrrole was added to this electrolyte and a voltage was applied, a black uniform film was deposited on the anode. When the film was observed with an electron microscope at a magnification of 100,000, no particles that seemed to be MnO ₂ were present at all. Also, the presence of γ-MnO ₂ was not recognized by X-ray diffraction. However, the fluorescent X-ray spectrum showed that Mn atoms were present in an amount of 10 to 20%, indicating that a uniform composite (molecular composite) of polypyrrole and MnO ₂ was realized.

The present invention is based on such a finding, and proposes a novel method for producing a composite in which MnO ₂ is uniformly dispersed in an electropolymerized film.

In general, MnO ₂ is thermally decomposed (γ-MnO ₂
(Type 1) It is said that it has higher electrochemical activity than MnO ₂ . It corresponds to the ease of movement of ions such as protons and hydroxyl groups in MnO ₂ . As shown above, the polypyrrole / MnO ₂ composite electropolymerized film obtained in the present invention is a film containing almost completely amorphous MnO ₂ uniformly, and therefore high electrical activity is expected. Also, since the conductivity of polypyrrole is 500 S / cm and that of γ-MnO ₂ is about 0.1 S / cm, in such a uniform composite film, 500 to 0.1 S / cm
It is expected that the conductivity during can be controlled continuously.

In addition, since MnO ₂ alone does not form a film and has very low adhesiveness, it is impossible to form a film on a substrate to form a thin-film device. Will be possible.

Example 1 Pyrrole was dropped at 0.2 mol / l into purified water 1 and NaTos
Is dissolved in 0.8 mol / l, and ultrasonic waves are applied thereto and left for about 30 minutes. Then, the oily pyrrole is completely dissolved in water, and a homogeneous solution is obtained. There, 0.4 mol / l of MnSO ₄ is added and dissolved. Using high chromium stainless steel as the anode in this solution,
It was immersed while keeping the distance from the platinum cathode at 2 cm, and a constant voltage was applied to cause polymerization. When the voltage was changed to 2.0, 2.5, 3.0, 3.5, 4.0, and 5.0 V and electrolysis was performed for 10 minutes each, a black film grew at 2.5 V or more. At 4.0 V or more, the growth of the film was not uniform, and there were some areas separated from the substrate. The thicknesses of the films obtained at 2.5, 3.0 and 3.5 V were 5, 16, and 14 μm, respectively, and their electrical conductivities were 25, 40, and 16 S / cm. Since the conductivity without adding MnSO ₄ was _{400 S} / cm, it is clear that the combination of MnO ₂ lowered the conductivity. X-ray fluorescence and X-ray photoemission spectra (XPS) determined the Mn content to be 26% by weight. MnO _{2 in} X-ray diffraction
No crystal system was found.

Example 2 Thiophene or thienylpyrrole was added to a mixed solvent of acetonitrile and water at 0.1 mol%, and tetraethylammonium tosylate (TEA · Tos) 0.1 m was used as an electrolyte.
ol% and 0.05 mol% of MnSO ₄ were dissolved, and a polymerization reaction was carried out in the same manner as in Example 1. Thiophene is most efficiently polymerized at 4.5 V and thienylpyrrole at 2.5 V, and is about 20 μm in 10 minutes
Was obtained. The conductivity was 2.1 and 0.4 S / cm, respectively. In this case, the content of Mn was about 5%.

In addition, aniline and furan use MnSO ₄ and tetraethylammonium / perchloric acid (TEA / CIO ₄ ) as supporting electrolytes,
Polymerization was possible at a potential of 3 to 4 V using a mixed solvent of water and acetonitrile or isopropyl alcohol. In particular, in the case of aniline, a high-quality film could be obtained by adding hydrochloric acid, sulfuric acid, etc. to a low pH state.

Example 3 An aqueous solution containing 0.2 mol / l of pyrrole and 0.5 mol / l of NaTos and an aqueous solution containing 0.2 mol / l of pyrrole and 0.5 mol / l of MnSO ₄ were prepared.
Prepare the different solutions and mix them 10: 0, 8: 2,…, 2: 8, 0:
A polymerization reaction was carried out using the electrolyte mixed in Step No. 10. The electrolytic conductivity was fixed at 3.5 V, and the electric conductivity of each film polymerized for 20 minutes is shown in FIG. It can be seen that the conductivity varies logarithmically between about 100 S / m and 1 S / cm. This is also an effect of dispersing polypyrrole uniformly in MnO ₂ .

When the ratio of pyrrole 0.2 mol / l, NaTos 0.5 mol / l and MnSO ₄ was changed, the conductivity could be changed between 100 S / cm and 0.1 S / cm. However, in this case, when the content of MnSO ₄ is 75% or more, the amount of MnO ₂ increases, so that the film becomes very brittle, which is a practical problem.

Example 4 A second MnO 2 solution was added to an aqueous solution of pyrrole 0.25 mol / l and sodium salt of sulfonated polystyrene (NaSPS) 0.1 mol / l.
Electrolytic polymerization at 3.0 V on a transparent electrode in which 0.5 mol / l of manganese nitrate (Mn (NO ₃ ) ₂ ) was dissolved as a _second source gave a black uniform film similar to that of Example 1. Compared to MnSO ₄ , this film was characterized by high strength and high conductivity of 250 S / cm.

According to the X-ray diffraction spectrum, in the polypyrrole composite film made of Mn (NO ₃ ) ₂ , MnO ₂ was basically amorphous, but a small amount of ε-type MnO ₂ was observed. Was done.

A similar experiment was performed using a mixed electrolyte of manganese chloride, manganese perchlorate and NaTos, and a composite electropolymerized membrane having essentially the same properties was obtained.

Example 5 A polypyrrole-MnO ₂ composite film was formed on a platinum plate using an electrolyte composed of pyrrole 0.5 mol / l, NaTos 0.4 mol / l, and MnSO ₄ 0.4 mol / l. Next, this electrode was transferred into an electrolyte containing 0.1 mol / l of NaTos, and a current of 1 mA / cm ² was passed (charging) using the apparatus shown in FIG. Since the voltage reached 1.9 V in about 10 minutes, the load was left to pass through a load resistance of 100 KΩ, and the voltage was changed with a voltmeter.
According to this, the voltage stability was very good, indicating that a secondary battery can store an energy density of about 60 Ah / kg. This battery has a composite conductive film having an electric conductivity of 50.
Since the S / cm is very high, the internal impedance is low, and the device has a possibility of a large current device.

Effect of the Invention As described above, the present invention realizes a conductive polymer composite in which manganese dioxide is molecularly dispersed in a conventionally well-known electrolytically polymerized film.
It is based on a completely new electrochemical reaction in which the manganese salt is oxidized simultaneously with the electropolymerization of monomers such as pyrrole.

By using the conductive polymer composite of the present invention, a conductive film whose conductivity is controlled in a wide range can be produced, and can be used as a resistor for an electronic component, an electromagnetic shielding material, and the like.
Further, since this composite has higher electrochemical activity than MnO _2, it can be used as an active material for a battery or a solid electrolyte for a solid electrolytic capacitor.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an electropolymerization apparatus used in the present invention, and FIG. 2 is a diagram showing an electrolyte composition-dependent characteristic of the electric conductivity of a polymer film when pyrrole is polymerized using sodium tosylate and manganese sulfate as a supporting electrolyte. is there. 2 ... Electrolyte solution, 3 ... Anode, 4 ... Cathode, 5 ... Constant current and constant voltage power supply.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01M 4/04 H01M 4/04 A

Claims (3)

(57) [Claims] 1. A conductive polymer composite containing manganese dioxide and a polymer obtained by electrolysis using an electrolyte containing an electrolytic polymerizable monomer and a manganese salt. 2. The conductive polymer composite according to claim 1, wherein the polymer is any one of polypyrrole, polythiophene, polythienylpyrrole, polyaniline, polyindole and polyfuran. 3. A process for preparing a pair of electrodes, comprising: a manganese salt which is any of manganese sulfate, manganese chloride, manganese nitrate and manganese perchlorate, pyrrole, thiophene,
Thienyl pyrrole, aniline, a step of preparing an electrolyte containing an electropolymerizable monomer of any of indole and furan, and electrolytically using the electrolyte to electrolytically polymerize on the anode of the pair of electrodes on the anode. Forming a polymer from the electrolytic polymerizable monomer and also forming manganese dioxide on the anode by electrolytic synthesis to form a conductive polymer composite.