JP2826850B2 - Method for producing polyaniline - Google Patents

Description

The present invention relates to a method for producing a polyaniline, and more particularly, to a method for producing a polyaniline by electrolytic polymerization.

<Conventional technology> Since conductive polymer materials such as polyaniline, polypyrrole, and polyacetylene become conductive by doping and change color, they are applied to various electrodes such as secondary batteries, sensors, electrochromic devices, and capacitors. I have. In particular, polyaniline has attracted attention because it has high stability against oxidation and reduction and has a large doping amount.

Polyaniline is generally obtained by electrolytically oxidizing aniline in an acidic aqueous solution. There are many proposals for a method for producing this polyaniline. For example, in JP-A-60-235831, 0.7 V
A method has been proposed for producing a polyaniline film having good electropolymerization efficiency and film quality by performing a constant potential electrolysis at or below SCE. The present inventors have also reported that polyaniline electrolytically polymerized at a low polymerization potential is excellent as an electrode for a battery (IEICE OME 87-39).

<Problems to be Solved by the Invention> However, when constant potential electrolytic polymerization is started at a low potential with polyaniline at a low potential, the polymerization reaction does not readily proceed until the polyaniline covers the electrode surface, which poses a problem in terms of productivity.
In the case of a high potential, the production rate of polyaniline is too fast, and the film quality of polyaniline obtained by increasing the temperature of the polymerization system due to Joule heat or the like becomes poor in mechanical strength and uniformity, and propylene carbonate, gamma-butyrolactone, It is easily dissolved in non-aqueous solvents for batteries such as dimethylformamide. On the other hand, in the case of constant-current electrolytic polymerization, a current is forced to flow to cause a polymerization reaction. Therefore, the production rate of polyaniline is constant, and the production amount can be easily controlled even in low-current electrolytic polymerization. Performing electrolytic polymerization at a low set current value tends to produce polyaniline that is good in mechanical strength and uniformity and is difficult to dissolve in non-aqueous solvents in terms of uniformity. The production speed will be slow.

Therefore, it has been an important issue to produce polyanilines having high productivity and good film quality.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing a polyaniline having high productivity, good mechanical strength, good film quality in terms of uniformity, and insoluble in a non-aqueous solvent. It is in.

<Means for Solving the Problems> The present invention provides a method for producing polyanilines by electrolytic polymerization, in which the initial stage of electrolytic polymerization is carried out by constant-current electrolytic polymerization,
Thereafter, the present invention provides a method for producing polyaniline, characterized in that a constant potential electrolytic polymerization is continued at a polymerization potential of 0.55 to 0.8 V vs SCE.

Next, the present invention will be described in detail. The method for electrolytic polymerization of polyanilines of the present invention is generally, for example, J. Electroche
m.Soc., Vol. 130, No. 7, 1506-1509 (1983), Electrochem. A
cta., Vol. 27, No. 1, 61-65 (1982), J. Chem. Soc., Chem. Co.
mmun., 1199- (1984), etc., it can be carried out by placing a solution obtained by dissolving a monomer and an electrolyte in a solvent in a predetermined electrolytic tank and performing electrolysis.

As the polymerization current of constant current electrolytic polymerization at the beginning of electrolytic polymerization,
0.5 to 50 mA / cm ² , preferably 1 to 20 mA / cm ²
Range. If it is less than 0.5 mA / cm ² , the production rate of the polyaniline is low, and it is difficult to reach the potential at which the polyaniline can be polymerized. If it exceeds 50 mA / cm ² , the film quality of polyaniline due to Joule heat or the like is poor in mechanical strength and uniformity, and it is easily dissolved in a non-aqueous solvent. Initially, the electrode potential is fairly high until the polyaniline coats the electrode, but once the polyaniline coating is complete, the electrode potential continues to decrease gradually. Since the film quality of polyaniline is related to the polymerization potential rather than the current value, it is more advantageous in terms of production speed to perform constant-current electrolytic polymerization, and then perform constant-potential electrolytic polymerization when the electrode potential rises once and then falls to the set potential. It is.

The thickness of the polyaniline to be subjected to constant current electrolytic polymerization is as follows.
It is 0.1 to 50 μm, preferably 1 to 20 μm. If it is less than 0.1 μm, it is difficult to coat the electrode uniformly with polyaniline, and if it exceeds 50 μm, the effect of the present invention is thin and there is no great difference from the galvanostatic polymerization. After constant-current electropolymerization, switch to constant-potential electropolymerization, but the set potential is 0.55 to 0.80 V vs S
It is in the range of CE, preferably 0.55 to 0.70 V vs SCE. Below 0.55V vs SCE, polymerization reaction is slow, 0.8V vs SC
If it exceeds E, the mechanical strength and uniformity of the film are poor, and the film is easily dissolved in a non-aqueous solvent.

Examples of the polyaniline monomer include the following general formula (I)
Or (II) (Wherein, R _{1 to} R ₄ represent a hydrogen atom, an alkyl group, or an aryl group.) Specifically, aniline, 4-
Aminodiphenylamine, N-methylaniline, N-ethylaniline, 4- (N-methylamino) diphenylamine, diphenylamine, o-methylaniline, o-ethylaniline, m-methylaniline, m-ethylaniline, 4- (N- Ethylamino) diphenylamine, N,
N'-diphenyl-p-phenylenediamine and the like. These anilines and their derivatives can be used alone or as a mixture of two or more. Most preferred, however, is aniline.

The monomer concentration during the electrolytic polymerization is about 0.001 to 4 mol /, preferably 0.01 to 2 mol /. If it is less than 0.001 mol /, the reaction progresses slowly, and if it exceeds 4 mol /, it is difficult to dissolve.

In general, polyanilines are synthesized in a reaction medium containing a protonic acid. Examples of protonic acids that can be used in the polymerization of anilines include hydrochloric acid, sulfuric acid, perchloric acid,
Examples include borofluoric acid, methanesulfonic acid, trifluoroacetic acid, and paratoluenesulfonic acid. In particular, polyaniline synthesized in hydrochloric acid, sulfuric acid, and tetrafluoroboric acid has low solubility in a non-aqueous solvent, and thus is preferable.

It is desirable to add the protonic acid so that the pH of the electrolytic solution for polymerization is 3 or less, preferably 2 or less. If the pH value is more than 3, the growth rate of the polymer is slow,
In addition, since the produced polymer has many portions that are dissolved in a solvent such as dimethylformamide, the degree of polymerization is low,
The stability of the material against charge and discharge is also poor.

Also, LiBF ₄ , Li
An electrolyte salt such as ClO ₄ , (n-Bu) ₄ ClO ₄ , (n-Bu) ₄ BF ₄
You may add in the range of 0.01-2 mol /.

As the solvent, water, propylene carbonate, dimethoxyethane, tetrahydrofuran, or the like is used, and water is preferably used.

The reaction temperature is from -50 ° C to 100 ° C. Preferably it is -30 to 50 degreeC, More preferably, it is 0 to 25 degreeC. It is necessary to appropriately set the reaction time depending on the desired amount of the polymer, the reaction temperature, the reaction system, and the current density to be applied.

As the electrolytic electrode, a conductive material having an electrical conductivity of 10 ^-2 S / cm or more, a composite of a conductive material on a substrate,
Alternatively, a material in which a conductive polymer material is coated on a metal surface may be used. That is, as a conductive material itself,
Metals such as Ni, Pt, Au, Al, alloys such as stainless steel, or conductive polymers with high mechanical strength such as polypyrrole, or carbon fibers and carbon powders uniformly mixed and molded with resin Are used. As a composite of a conductive material on a base material, Au, P
Metal oxides such as t, Ni, Al, metal oxides such as SnO ₂ , In ₂ O ₃ , ITO, carbon bodies, etc. Those coated with polypyrrole or the like are used. Examples of a metal having a conductive polymer material coated on its surface include a metal such as aluminum coated with polypyrrole by oxidative polymerization.

The surface of the electrolytic electrode (current collector) is preferably roughened with an abrasive, a polishing machine, and an electrochemical method to improve the specific surface area of the current collector, and more preferably 0.5 to 1500 μm, preferably 1 to
It is preferable to have a through hole of up to 1000 μm. Since the current collector having a high surface area and a through-hole has a large area in contact with the polyaniline, the use efficiency of the active material is high, and when used in a battery, a battery having a large short-circuit current must be manufactured. Can be. In addition, due to the presence of the through-hole, the polyanilines on both surfaces of the current collector are integrated through the through-hole, so that the adhesion between the current collector and the active material is further improved.

Since the polyaniline obtained by electrolytic polymerization is produced with good adhesion on the electrolytic electrode, if this is used for the electrodes of various devices, the production of the polyaniline and the production of the electrode can be performed, which is economically advantageous.

The polyaniline or polyaniline electrode produced by the production method of the present invention is a secondary battery, a sensor,
It shows excellent properties as electrodes or electrode active materials of devices such as electrochromic devices and capacitors.

Next, the most effective secondary battery using the polyaniline electrode manufactured by the manufacturing method of the present invention will be described. A secondary battery using a polyaniline produced by the production method of the present invention as an electrode is basically composed of a positive electrode, a negative electrode and an electrolytic solution, and a separator can be provided between the electrodes. The electrolyte is composed of a solvent and an electrolyte. Polyanilines produced by the production method of the present invention are used for the positive electrode.

As the negative electrode active material, conductive polymers such as polyacetylene, polythiophene, polyparaphenylene, and polypyridine, and alloys of Li with Al, Mg, Pb, Si, Ga, and In can be used. For the negative electrode, the sheet-shaped negative electrode active material can be used alone.However, in order to improve the handleability of the sheet-shaped negative electrode and the current collection efficiency, the composite of the negative electrode active material and the current collector is required. Can be used.

As a material of the negative electrode current collector, Ni, Al, Cu, Pt, Au, stainless steel and the like are preferable, but Al is more preferable from the viewpoint of weight reduction. Conventionally, Al-Li is used as a negative electrode to prevent dendrite, but Al and Li may not be alloyed.

Examples of the method of laminating the negative electrode active material on the negative electrode current collector include a method of forming the negative electrode active material by vapor deposition or an electrochemical method, and a mechanical method such as bonding of the current collector to an active material such as Li. Can be

In the electrochemical method, Li or the like may be deposited using the negative electrode current collector itself as an electrode. However, if the negative electrode current collector is coated with an ionic conductive polymer and then electrolytically deposited, the current collector may be deposited. -An active material such as Li can be uniformly deposited on a polymer interface.

Examples of the electrolyte (dopant) of the battery electrolyte include the following anions or cations. The cation-doped polymer complex is an n-type conductive polymer, and the anion is doped with an anion. The polymer complex gives a p-type conductive polymer. The polymer complex doped with an anion can be used for the positive electrode, and the polymer complex doped with the cation can be used for the negative electrode. The _{^{anion, PF 6 -, SbF 6 -}} , As
_{^{F 6 -, SbCl 6 - V}} a group of earth halide anions such _{^{as; BF 4 -, BR 4 -}} (R: phenyl group, an alkyl group) II such as
Halide anion of I a group of elements; ClO ₄ ^- perchlorate anions such ^{as; Cl -, Br -, I} - halogen anion can be exemplified such as.

Examples of the cation include alkali metal ions such as Li ⁺ , Na ⁺ , and K ⁺ , (R ₄ N) ⁺ [R: a hydrocarbon group having 1 to 20 carbon atoms], and the like.

Specific examples of the compound that gives the above dopant,
LiPF ₆ , LiSbF ₆ , LiA _s F ₆ , LiClO ₄ , NaClO ₄ , KI, KPF ₆ , KSbF ₆ , KA
_{sF 6, KClO 4 [(n} -Bu) 4 N] + · AsF 6 -, [(n-Bu)
^{_{4 N] + · ClO 4 -}} , [(n-Bu) 4 N] + · BF 4 -, LiAlCl 4, LiB
F ₄ , LiCF ₃ SO _{3 and the} like can be mentioned. Note that polyanilines are p-type conductive polymers.

The solvent constituting the electrolyte solution is not particularly limited, but a solvent having a relatively large polarity is preferably used.
Specifically, propylene carbonate, ethylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolan, triethyl phosphate,
Examples thereof include one or a mixture of two or more of organic solvents such as triethyl phosphite, dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, dimethoxyethane, polyethylene glycol, sulfolane, dichloroethane, chlorobenzene, and nitrobenzene.

As the separator, a separator having low resistance to ion movement of the electrolyte solution and excellent in solution retention is used. For example, glass fiber filters; polyester,
Polymer pore filters such as Teflon, polyflon, and polypropylene, and nonwoven fabrics; and nonwoven fabrics composed of glass fibers and these polymers can be used.

In addition, a solid electrolyte can be used as a component replacing the electrolytic solution and the separator. For example, in inorganic systems, metal halides such as AgCl, AgBr, AgI, LiI, RbA
g ₄ I ₅ , RbAg ₄ I ₄ CN and the like. In the organic system, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylamide, etc., as a polymer matrix, a complex obtained by dissolving the above-mentioned electrolyte salt in the polymer matrix, or a crosslinked product thereof, a low molecular weight polyethylene oxide And a polymer electrolyte in which an ion dissociating group such as a crown ether is grafted to a polymer main chain.

Although the form of the battery is not particularly limited,
It can be mounted on various batteries such as coin type, sheet type, cylindrical type, gum type and the like.

<Examples> Next, the present invention will be described with reference to examples and comparative examples.

Example 1 70 holes / cm of 50 μm diameter in SUS 304 foil of 10 μm thickness
^It was opened at a rate of ² . Then 1kg with # 200 emery particles
Blasting was performed with a pressing force of. 1M aniline, 3M HBF
_The above SUS 304 is used as an electrolytic electrode at 20 ° C in an aqueous solution containing ₄ .
Constant current electrolytic polymerization of 0 mA / cm ² was performed. Once the polymerization potential is 1.1
After the maximum value of V vs SCE was reached, when 0.70 V vs SCE was reached (at this time, the thickness of the polyaniline film was 20 μm), electrolytic polymerization was performed at a set potential to form a polyaniline electrode having a total thickness of 600 μm. Manufactured. The time required for polymerization was 1.
3 hours. After washing the polyaniline electrode with water, it was dedoped and vacuum dried. At this time, the tensile strength of the polyaniline film was 2.3 kg / cm ² .

Example 2 In Example 1, a constant current electrolytic polymerization was carried out at an initial polymerization current of 0.8 mA / cm ² , and when the polymerization potential reached 0.65 V vs. SCE (the polyaniline film thickness at this time was 50 μm). The potential was set at 0.65 V vs. SCE to perform the constant potential electrolytic polymerization. The time required for the polymerization was 2.1 hours. Next, polyaniline was obtained in the same manner as in Example 1. At this time, the tensile strength of the polyaniline was 2.7 kg / cm ² .

Comparative Example 1 Polyaniline was produced in the same manner as in Example 1 except that polyaniline was electrolytically polymerized at a constant current of 1.0 mA / cm ² . The time required for the polymerization was 5.5 hours. At this time, the tensile strength of the polyaniline was 2.8 kg / cm ² .

Comparative Example 2 A polyaniline was produced in the same manner as in Example 1 except that polyaniline was electrolytically polymerized at a constant potential of 0.65 V vs SCE.
The time required for the polymerization was 4.5 hours. At this time, the tensile strength of the polyaniline was 2.7 kg / cm ² .

Comparative Example 3 A polyaniline was produced in the same manner as in Example 1, except that polyaniline was electrolytically polymerized at a constant current of 10 mA / cm ² . The time required for the polymerization was 0.5 hour. At this time, the tensile strength of the polyaniline was 1.8 kg / cm ² .

<Battery performance test> The electrodes manufactured in Examples 1 and 2 and Comparative Example 3 were used as positive electrodes,
5 m in a test cell as shown in FIG. 1 using Li for the negative electrode, 3.5 M LiBF ₄ / propylene carbonate + dimethoxyethane (7: 3) for the electrolyte and polypropylene non-woven fabric for the separator.
The battery was charged and discharged at a constant current of A / cm ² and the battery characteristics were measured. Table 1 shows the results.

<Effects of the Invention> According to the manufacturing method of the present invention, high-performance polyaniline having good film quality can be manufactured in a short time, and a device using the polyaniline for an electrode or the like, particularly a secondary battery, is excellent. Has performance.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a secondary battery using the polyaniline produced in each of Examples and Comparative Examples as a positive electrode. 1 ... Positive electrode, 2 ... Negative electrode, 3 ... Positive electrode terminal, 4 ... Negative electrode terminal, 5 ... Separator, 6,7 ... Fluorine resin.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) C25B 1/00-9/04 C25B 13/00-15/08 C25D 9/02 C08F 2/58 C08G 73 / 00

Claims (1)

(57) [Claims] 1. A method for producing a polyaniline by electrolytic polymerization, wherein a constant current electrolytic polymerization is carried out at the start of the polymerization, and then the constant potential electrolytic polymerization is continued at a polymerization potential of 0.55 to 0.8 V vs. a set potential of SCE. A method for producing a polyaniline, comprising: