JPH01144564A - Polyaniline electrode - Google Patents

Abstract

PURPOSE:To improve the durability, mechanical strength and reliability by using high-polymerization degree polyaniline with the specific content or below of the constituent solved in dimethylformamide as an electrolytic active material. CONSTITUTION:Aniline and its derivative are electrolyzed and oxidized by the electrolytic polymerization method in an acidic aqueous solution to manufacture a polyaniline electrode. A high-polymerization degree polyaniline electrode with the content of the constituent solved in dimethylformamide at 15wt.% or below, preferably 10wt.%, is obtained by properly selecting the concentration of aniline and acid, type of acid and electrolyzing method. An electrode with high reliability and no performance reduction after the repeated charge and discharge is thereby obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a polyaniline electrode useful for electrochromic devices, sensors, batteries, etc.

[Prior art] Conductive polymer materials such as polyacetylene, polypyrrole, and polyaniline are lighter than metal materials, and
When doped with anions or cations, it exhibits high electrical conductivity and is electrochemically active, so its application to electrodes for electrochromic devices, various sensors, batteries, etc. is being considered. Among them, polyaniline is attracting attention because of its excellent potential and charge retention, as well as its excellent switching characteristics. However, electrodes using polyaniline have problems that must be resolved. That is, electrodes using polyaniline are generally used in aqueous or non-aqueous solvents, but as the polyaniline electrode is repeatedly used in these solvents, the active material polyaniline may be eluted into the solvent, especially an organic solvent. However, the reliability of the electrode was low due to deterioration of the electrode properties, mechanical deterioration of the polyaniline due to elution, and the accompanying detachment of the polyaniline from the electrode. As a means to solve this problem, for example, JP-A-62-[1281
In No. 7, there is an example in which polyaniline consisting of a portion insoluble in dimethylformamide is used in a secondary battery, but in this case, polyaniline is treated with dimethylformamide to remove the soluble polyaniline portion, and then in order to use the insoluble polyaniline,
After treatment, the mechanical strength of the polyaniline film decreases, making it impossible to use polyaniline as an electrode.
After treatment, the polyaniline must be collected and molded again to be applied to electrodes.

[Purpose] In view of these circumstances, the present invention has been developed to ensure that even after repeated charging and discharging,
The purpose of this invention is to provide a highly reliable polyaniline electrode that does not deteriorate in performance and has excellent mechanical strength.

[Structure] The present inventor has conducted extensive research in order to solve the above problems, and has found that it is effective to use highly polymerized polyaniline, whose solubility in dimethylformamide is below a certain value, as an active material. This discovery led to the present invention.

That is, the present invention is a polyaniline electrode characterized in that a highly polymerized polyaniline having a content of components soluble in dimethylformamide of 15% by weight or less is used as an electrode active material.

The polyaniline electrode used in the present invention is manufactured by an electrolytic polymerization method. Electrolytic polymerization methods are generally used, for example, J, EI
cctrochcm, Soc, , Vol. 130. N
o, 7°150 (i ~ 1509 (1983), E
Iectroehem, ACta,.

Vol, 27. No. 1.81-65 (1982),
J, CheIIl, Soc.

Chem, Commun, 1199-(1984)
In this method, a monomer and an electrolyte dissolved in a solvent are placed in a specified electrolytic bath, the electrodes are immersed, and an electrolytic polymerization reaction is caused by anodic oxidation or cathodic reduction to form a surface of the electrode. The polymer can be obtained in the form of a film.

Generally, polyaniline is produced by electrolytic polymerization by electrolytically oxidizing aniline in an acidic aqueous solution, but as a result of various studies, the present inventors found that polyaniline can be produced by the concentration of aniline and acid, the type of acid, and the electrolytic method. We found that the morphology of polyaniline, its solubility in organic solvents, and electrode properties are greatly influenced by the properties of polyaniline. They discovered that by producing polyaniline, which has a low solubility in organic solvents, especially dimethylformamide, and using this, it was possible to provide polyaniline electrodes with high reliability, durability, and excellent electrode properties. Ta. The reason why polyaniline that is insoluble in organic solvents has excellent performance is not only because polyaniline is well fixed as described above, but also because polyaniline that is insoluble in organic solvents is considered to be a high molecular weight polyaniline, so the electrons within the polyaniline molecule are It is thought that the performance is excellent because of the good migration of molecules and the improved stability of the molecules. As mentioned above, the dissolved component of the polyaniline of the present invention in dimethylformamide is 15% by weight, preferably 10% by weight or less.

If the dissolved component exceeds 15ff (m%), performance and reliability will deteriorate as shown in the prior art.

The solubility of polyaniline changes depending on the treatment method, such as increasing the solubility of polyaniline in organic solvents by treating it with an alkali such as aqueous ammonia after production.

In the present invention, the polyaniline dissolved component refers to the polyaniline produced after electrochemically dedoping it in an acidic aqueous solution.
After thorough water washing, the polyaniline loo+g is immersed in dimethylformamide at 25°C for 48 hours, the insoluble polyaniline is washed with acetonitrile, and the weight of the polyaniline is measured by vacuum drying.

Now, the electrolytic polymerization method of the present invention for obtaining a polyaniline electrode insoluble in organic solvents will be explained.

Aniline and its derivatives are used as the monomers used in the present invention. The amount used is 0.001~5
IIlol/51 is preferably 0.01 to 2 mol/cross.

An acid is essential to the production of the polyaniline electrode of the present invention. The acid used is HCl.

HClO4, HBF4, CF35O3H.

Examples include acids such as CF3COOH, H2SO4, H2SO4, para-toluenesulfonic acid, and HBF4, but especially HCl.

H2504 is preferred. The amount of acid used is 0.51 Qol/11 or more in terms of acid concentration, preferably 1 to 6 Illo.
l/Q, particularly preferably 2.5 mol/Q ~
When 5mo1151, the production rate of polyaniline is fast,
Moreover, the polyaniline electrode of the present invention can be produced which is uniform and has good adhesion to the electrode. Water is preferably used as the solvent.

As the electrolytic polymerization method, any of the following methods is possible: constant current electrolytic polymerization, constant potential electrolytic polymerization, constant voltage electrolytic polymerization, and potential sweep electrolytic polymerization, but from the standpoint of mass production, constant current electrolytic polymerization is preferred. It's advantageous.

In the case of constant current method, the electrolytic current density used is 0.1 mA/C
[lI2~1000 mA/cn+', preferably 0
．． 05mAlcII12-1010l1lAIC particularly preferably 0. lnA/cII12-5IIIAICI
02. In the case of potentiostatic method, the anode potential is set to 0.8 to 2.5 V against a saturated calomel reference electrode, preferably 0.7
~1.8V.

When polyaniline is produced by the electrolytic polymerization method, polyaniline is produced uniformly on the electrolytic electrode, so if an electrolytic electrode that has been processed into a predetermined shape is used,
This method is economically advantageous because polyaniline electrodes are manufactured together with polyaniline.

As electrodes for electrolysis, A us P t SN is stainless steel, metals and alloys such as A1, SnO2, In2O
Examples include metal oxides such as No. 3 metal oxides, carbon, conductive polymers such as polypyrrole, and composite electrodes of these materials, but considering the economical efficiency and light weight of the polyaniline electrode to be manufactured, Al or A1 alloys are preferable. is most preferably used.

In general, aluminum forms an electrically inert and stable oxide film on its surface, and it is unsuitable to use it as an electrode for electrolysis, but the oxide film layer can be removed or the oxide film can be reduced to less than a few tens of angstroms. By doing so, it can be suitably used as an electrode for electrolysis. Methods for removing the oxide film include mechanical etching, electrolytic etching, and acid treatment, but electrolytic etching in particular can remove the oxide film uniformly over the entire aluminum surface, and also removes microscopic irregularities on the aluminum surface. can be formed. When electrolytically etched aluminum is used as an electrode for electrolytic polymerization, the polymer is produced so as to cover the microscopic irregularities on the etched aluminum surface. Composites with high mechanical and electrical adhesion can be produced.

The present inventors have also applied for P82-092791.
By providing perforations in the electrode, the adhesion of polyaniline is further improved. The thickness of the electrode for electrolysis used in the present invention is 0.01 mm to 5 mm, preferably 0.0
15 m+ to 0.2), a thin and lightweight polyaniline electrode can be manufactured.

Hereinafter, the present invention will be further explained with reference to Examples, taking as an example a polyaniline battery, which is most effective when the electrode of the present invention is applied.

Example 1 200 400 μm perforations were made in etched aluminum foil for a capacitor with a thickness of 30 μm and an area of 4C112.
0.3M aniline is used as the working electrode.
0.8vvsSCE of 3M H2SO4171 aqueous solution
After electrolytic polymerization at a constant potential, the working electrode was washed with water and dried in vacuum, followed by dedoping treatment at -0.4 V vs S CE in a 0.1 M H2SO4 aqueous solution using this electrode as a working electrode. Two polyaniline electrodes having an active material amount of 40 ag were manufactured by washing with water and vacuum drying. One polyaniline electrode was immersed in dimethylformamide 601 at 25° C. for 48 hours. After drying this polyaniline electrode under vacuum, the amount of polyaniline reduced was 0.4 n+g, and the amount of dissolved components in dimethylformamide was 1.0%. Next, use the other polyaniline electrode as the positive electrode, Li as the negative electrode, and 3M LiBF+ dissolved in a solvent with a ratio of 7 parts propylene carbonate to 3 parts dimethoxyethane as an electrolyte at 1 ilA/cm.
'The battery performance was tested by repeating charging and discharging.

Example 2 A polyaniline electrode was manufactured in the same manner as in Example 1 except that electrolytic polymerization was carried out at a constant current of 3IIIAlcII12, and the amount of components dissolved in dimethylformamide was measured in the same manner as in Example 1. It was found to be 3.9%. there were.

Next, battery performance was tested in the same manner as in Example 1.

Example 3 A nickel foil with a thickness of 30 μm and an area of 4 cm 2 was treated by electrolytic etching to roughen the surface.
A polyaniline electrode was prepared in the same manner as in Example 1, except that a working electrode with 0.00 μm perforations at a rate of 200 holes/cm2 was used as the polymerization solution, and a solution containing 0.3M aniline and 3M HCl dissolved in water was used as the polymerization solution. Manufactured. The amount of components dissolved in dimethylformamide was measured in the same manner as in Example 1 and found to be 5.1%. Next, battery performance was tested in the same manner as in Example 1.

Example 4 1.2V vs S CE using 0.3M aniline and 1.5M H2SO4 dissolved in water as polymerization liquid
A polyaniline electrode was manufactured in the same manner as in Example 3, except that electrolytic polymerization was performed at a constant potential.

The total amount of components dissolved in dimethylformamide was determined in the same manner as in Example 1, and was found to be 39.8%.

Next, battery performance was tested in the same manner as in Example 1.

Comparative Example 1 A polyaniline electrode was manufactured in the same manner as in Example 3 except that 3M HClO4 was used instead of 5M HCl. The amount of components dissolved in dimethylformamide was measured in the same manner as in Example 1 and found to be 17.3%. Next, battery performance was tested in the same manner as in Example 1.

[Effects] As explained above, the polyaniline electrode of the present invention is highly reliable as an electrode, with no deterioration in performance even after repeated charging and discharging.

Claims (1)

[Claims] The content of components soluble in dimethylformamide is 15
A polyaniline electrode characterized in that a polyaniline with a high polymerization degree of less than % by weight is used as an electrode active material.