JPH06310173A - Electrochemical device and secondary battery - Google Patents

Abstract

PURPOSE:To charge and discharge reversible electrodes containing polyaniline at heavy-current by employing specified organic solvent as electrolyte. CONSTITUTION:In the electrochemical device equipped with reversible electrodes containing polyaniline, and a secondary battery employing a positive electrode containing polyaniline, electrolyte is equipped therewith, which is in contact with the reversible electrodes containing polyaniline, or in contact with a positive and a negative electrode containing polyaniline. When peroxide lithium and organic solvent containing 25-dimercapto-1,3,4-thiadiazole, is used as electrolyte, the charge/discharge of the reversible electrodes containing polyaniline can thereby be carried out at heavy-current.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrochemical device provided with a reversible electrode containing polyaniline, and a secondary battery using a positive electrode containing polyaniline.

[0002]

2. Description of the Related Art When conductive polymers are used as electrode materials, it can be expected to realize lightweight and high energy density batteries, large-area electrochromic devices, and electrochemical devices such as biochemical sensors using microelectrodes. Therefore, the practical use of the conductive polymer electrode has been actively studied. Beginning with polyacetylene discovered by Shirakawa et al. In 1971, π-electron conjugated conductive polymers such as polyaniline, polypyrrole, polyacene and polythiophene were found, and secondary batteries using these as electrodes were developed. . The energy density of the electrode using these conductive polymers is 250 to 400 Wh / kg per conductive polymer.
Then, the effective energy density at the stage of forming an actual battery is about 10 to 30%, that is, 20 to 120 W.
It becomes h / kg. Among these conductive polymers, when polyaniline is used as the positive electrode and metallic lithium, a lithium aluminum alloy, or a carbon material capable of reversibly taking lithium ions in and out is used for the negative electrode, the theoretical energy density is about polyaniline. About 400 Wh / k
Since it is g, it can be expected as a high capacity secondary battery.

[0003]

However, the secondary battery using a conductive polymer as an electrode has a drawback that the redox current per area is small and it is difficult to charge and discharge a large current. . An object of the present invention is to enable charging / discharging of a reversible electrode containing polyaniline with a large current.

[0004]

According to the present invention, at least lithium perchlorate and 2,5-dimercapto-1,3,4 represented by Chemical Formula 1 are used as electrolytes for electrolytic redox of electrodes containing polyaniline. -Characterized by using an organic solvent containing thiadiazole.

[0005]

[Chemical 1]

Here, 2,5-dimercapto-1,3
The amount of 4-thiadiazole added is from 1 mmol / l to 1
It is preferably between 00 mmol / l.

[0007]

By allowing 2,5-dimercapto-1,3,4-thiadiazole to exist in the electrolyte, the dope dedoping reaction (oxidation-reduction reaction) of the electrolyte anion to polyaniline is activated, and charging with a large current is performed. Discharge becomes possible. In particular, it is effective when the lithium metal salt contained in the organic electrolyte is lithium perchlorate and the electrolyte anion to be doped and dedoped is the perchlorate anion. In the present invention, as the organic solvent containing at least lithium perchlorate and 2,5-dimercapto-1,3,4-thiadiazole, propylene carbonate, ethylene carbonate, dimethoxyethane, tetrahydrofuran, sulfolane, and a single solvent of dimethyl sulfoxide. Alternatively, two or more kinds of mixed solvents selected from these may be used, but are not limited thereto.

Further, a terminal cross-linked polymer of polyethylene oxide or polypropylene oxide, a terminal cross-linked polymer such as a copolymer of ethylene oxide and propylene oxide, a polyacrylonitrile or a copolymer of acrylonitrile and methacrylic acid, and at least lithium perchlorate, 2, In addition to an organic solvent containing 5-dimercapto-1,3,4-thiadiazole, a gelled product can also be used as the electrolyte of the present invention. A solid polymer electrolyte can also be used as a medium for dissolving lithium perchlorate and 2,5-dimercapto-1,3,4-thiadiazole. Such polymers include, but are not limited to, end-crosslinked polymers of polyethylene oxide and polypropylene oxide and end-linked polymers of copolymers of ethylene oxide and propylene oxide.

[0009]

EXAMPLES Examples of the present invention will be described below. [Example 1] 25 mg of reductive dedoped polyaniline powder (manufactured by Nitto Denko) and 10 g of N-methyl-2-pyrrolidinone
To prepare a casting solution. This solution 5
mg was cast on a glassy carbon electrode surface of 0.28 cm ² and vacuum dried at 60 ° C. for 2 hours to prepare a polyaniline-modified electrode. On the other hand, 2,5-dimercapto-1,3,4-thiadiazole was added at a concentration of 1 mmol / l to a propylene carbonate solution of lithium perchlorate prepared at a concentration of 1 mol / l to prepare an electrolytic solution.

A polyaniline-modified electrode was added to the Ag solution in this solution.
/ Ag ⁺ reference electrode, the potential was linearly increased and decreased at a rate of 100 mV / sec between −0.75 and +0.5 V, and electrolysis was performed. As a result, the current-potential characteristics shown by the curve A in FIG. 1 were obtained. It was Further, a model battery constituted by using a positive electrode obtained by applying the N-methyl-2-pyrrolidinone solution of polyaniline on a current collector and vacuum drying at 60 ° C. for 2 hours, a lithium metal foil and a separator. Then, in a propylene carbonate solution of lithium perchlorate prepared at a concentration of 1 mol / l in the electrolytic solution, 2,5-dimercapto-1,3,4-
A charge / discharge test was carried out using a thiadiazole-containing 1 mmol / l addition, and it was possible to perform stable charge / discharge at an operating voltage of 3.5 V or more and a current density of ² mA / cm ² .

Comparative Example 1 25 mg of reductive dedoped polyaniline powder (manufactured by Nitto Denko) was dissolved in 10 g of N-methyl-2-pyrrolidinone to prepare a casting solution. 5 mg of this solution was cast on a 0.28 cm ² glassy carbon electrode surface and vacuum dried at 60 ° C. for 2 hours to prepare a polyaniline-modified electrode. On the other hand, a propylene carbonate solution of lithium perchlorate prepared at a concentration of 1 mol / l was used as an electrolytic solution. A polyaniline-modified electrode was added in this solution to an Ag / Ag ⁺ reference electrode at −0.
When electrolysis was performed by linearly increasing and decreasing the potential between 75 and +0.5 V at a rate of 100 mV / sec, the current-potential characteristics shown by the curve B in FIG. 1 were obtained.

As in Example 1, the N of the polyaniline was
-Methyl-2-pyrrolidinone solution was applied onto a current collector, and a model battery constituted by using a positive electrode obtained by vacuum drying at 60 ° C for 2 hours, a lithium metal foil and a separator. A charge / discharge test was carried out using a propylene carbonate solution of lithium perchlorate prepared at a concentration of mol / l. At a working voltage of 3.5 V or higher, a current density of 0.
It was possible to charge and discharge at 05 mA / cm ² .

Example 2 25 mg of reductive dedoped polyaniline powder (manufactured by Nitto Denko) was dissolved in 10 g of N-methyl-2-pyrrolidinone to prepare a casting solution. 5 mg of this solution was cast on a 0.28 cm ² glassy carbon electrode surface and vacuum dried at 60 ° C. for 2 hours to prepare a polyaniline-modified electrode. On the other hand, 2,5-dimercapto-1,3,4-thiadiazole of 10 mmol / l was added to a mixed solution of lithium propylene carbonate and ethylene carbonate having a volume ratio of 1: 1 prepared at a concentration of 1 mol / l. It was dissolved at a concentration to prepare an electrolytic solution. A polyaniline-modified electrode was added in this solution to Ag /
The potential was linearly increased / decreased at a rate of 100 mV / sec between −0.75 and +0.5 V with respect to the Ag ⁺ reference electrode, and electrolysis was performed. As a result, the current-potential characteristics shown by the curve C in FIG. .

Further, N-methyl-of the above polyaniline
A model battery composed of a positive electrode obtained by applying a 2-pyrrolidinone solution on a current collector and vacuum drying at 60 ° C. for 2 hours, a lithium metal foil and a separator, and 1 mol / l of an electrolyte solution. Volume ratio of propylene carbonate and ethylene carbonate of lithium perchlorate prepared at the concentration of 1:
A charge-discharge test was conducted using a mixed solution of 1,2,5-dimercapto-1,3,4-thiadiazole added at a concentration of 10 mmol / l, and an operating voltage of 3.5 V or more and a current density of 2 mA. Stable charge / discharge was possible at / cm ² .

Comparative Example 2 25 mg of reductive dedoped polyaniline powder (manufactured by Nitto Denko) was dissolved in 10 g of N-methyl-2-pyrrolidinone to prepare a casting solution. 5 mg of this solution was cast on a 0.28 cm ² glassy carbon electrode surface and vacuum dried at 60 ° C. for 2 hours to prepare a polyaniline-modified electrode. On the other hand, a mixed solution of lithium perchlorate prepared at a concentration of 1 mol / l and having a volume ratio of 1: 1 of propylene carbonate and ethylene carbonate was used as an electrolytic solution. In this solution, the polyaniline-modified electrode was -0.75- + with respect to the Ag / Ag ⁺ reference electrode.
When electrolysis was performed by linearly increasing / decreasing the potential at a rate of 100 mV / sec between 0.5 V, the current-potential characteristics shown by the curve D in FIG. 2 were obtained.

Further, N-methyl-of the above polyaniline
A model battery composed of a positive electrode obtained by applying a 2-pyrrolidinone solution on a current collector and vacuum drying at 60 ° C. for 2 hours, a lithium metal foil and a separator, and 1 mol / l of an electrolyte solution. Volume ratio of propylene carbonate and ethylene carbonate of lithium perchlorate prepared at the concentration of 1:
When a charge / discharge test was performed using the mixed solution of No. 1, it was possible to perform charge / discharge at an operating voltage of 3.5 V or more and a current density of 0.05 mA / cm ² .

In the above embodiment, the amount of the electrolyte contained in the electrolyte solution is 2,
The thiol group of 5-dimercapto-1,3,4-thiadiazole is used in the -SH form as it is, but the lithium metal salt of 2,5-dimercapto-1,3,4-thiadiazole (-S.Li) is used. , Sodium metal salt (-S ・ N
It is also possible to use a) and a potassium metal salt (-S.K). In addition, although lithium metal is used as the negative electrode when constructing the model battery, a lithium aluminum alloy or
An electrode using lithium as an active material such as a carbon material capable of reversibly taking in and out lithium ions can be used.

[0018]

As described above, according to the present invention,
It becomes possible to charge and discharge a large current at room temperature of an electrode containing polyaniline.

[Brief description of drawings]

FIG. 1 is a graph showing the current of the electrodes of Example 1 and Comparative Example of the present invention.
It is a potential characteristic diagram.

FIG. 2 shows the currents of the electrodes of Example 2 and Comparative Example of the present invention.
It is a potential characteristic diagram.

Claims (2)

[Claims] 1. A reversible electrode containing polyaniline and an electrolyte in contact with the electrode, wherein the electrolyte is at least lithium perchlorate and 2,5-dimercapto-1,
An electrochemical device comprising an organic solvent containing 3,4-thiadiazole. 2. A positive electrode containing polyaniline, a negative electrode, and an electrolyte in contact with both electrodes, wherein the electrolyte is at least lithium perchlorate and 2,5-dimercapto-1,
A secondary battery, which is an organic solvent containing 3,4-thiadiazole.