JP2000124077A - Electric double layer capacitor - Google Patents

Abstract

(57) [Problem] To provide an electric double layer capacitor and a lithium secondary battery with low resistance and high capacity. [MEANS FOR SOLVING PROBLEMS] In an electric double layer capacitor, an electrolytic solution containing a nitrile compound is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor using an electric double layer generated at an interface between a polarizable electrode and an electrolyte.

[0002]

2. Description of the Related Art At present, electric double layer capacitors are used as backup power supplies for microcomputers, memories, timers and the like. Further, applications to systems combined with EVs and solar cells are increasing. In addition, lithium batteries have been attempted to be applied as a high-capacity battery as a power source for small devices such as portable tape recorders and a power source for EVs. Propylene carbonate and the like are mainly used as electrolytes for these electric double layer capacitors and lithium secondary batteries.

[0003]

However, in recent years, high output characteristics and high capacity characteristics have been required for electric double layer capacitors and lithium secondary batteries.

[0004]

In order to solve the above problems, an electric double layer capacitor according to the present invention comprises a polarizable electrode and at least one of a nitrile compound represented by the general formula (Formula 2).
And an electrolytic solution containing the kind.

[0005]

Embedded image

At this time, the nitrile compound is desirably acetonitrile. Further, it is desirable that the electrolytic solution has a mixed solvent of a nitrile compound and one or more compounds selected from cyclic carbonates, cyclic carboxylate cyclic ethers, sulfolane and sulfolane derivatives.

It is desirable that the above-mentioned electrolyte has a quaternary onium salt as a solute. Further, it is desirable that the electrolyte salt constituting the electrolytic solution has BF ₄ ⁻ , PF ₆ ⁻ or ClO ₄ ⁻ as an anion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In a capacitor using an electric double layer formed at the interface between a polarizable electrode and an electrolytic solution, a solvent for the electrolytic solution contains at least one kind of a nitrile compound. It is a multilayer capacitor.

Since a nitrile compound having a low viscosity and a high dielectric constant is used as a solvent for the electrolytic solution for an electric double layer capacitor, the electric conductivity of the electrolytic solution is increased and the electric double layer capacitor or lithium battery having a low resistance and a high capacity is used. Can be realized.

Hereinafter, preferred embodiments of the present invention will be specifically described.

[0011]

EXAMPLES (Example 1) Acetonitrile (AN) 500
76 g (0.7 mol / L) of tetraethylammonium tetrafluoroborate (TEABF4) as a solute
An electrolyte for an electric double layer capacitor was used. Next, activated carbon,
Acetylene black, ammonium salt of carboxymethyl cellulose, water and methanol were weighed and mixed in a weight ratio of 10: 2: 1: 100: 40 to prepare a slurry. This slurry was dip-coated on one side of a 20 μm-thick aluminum foil, and was pre-dried at room temperature for 30 minutes. Then 120 ° C
For 30 minutes, and the steps of dipping, preliminary drying, and drying were again performed on the surface dipped previously. The thickness of the dip surface was 80 μm. This was cut into a diameter of 20 mm to form an electrode. The separator was cut to a diameter of 25 mm. One pair of two electrodes and a separator,
After vacuum drying, the electrolyte was impregnated overnight. The impregnation of the electrolyte was performed in an argon atmosphere. The impregnated electrodes are opposed via a separator so that the dip surface is on the inside,
A lead wire was taken out from the exposed surface of the outer aluminum and used as a test capacitor. After the test capacitor was charged at a constant voltage of 2.5 V for 10 minutes, a constant current discharge was performed at a discharge current of 1 mA. The DC resistance was calculated from the voltage drop immediately after the discharge, and the discharge capacity C (F) was calculated from the time when the discharge potential reached 0.5 V from 1 V by the following equation. C =
I × Δt × F / ΔV (where I: discharge current (A), Δ
t: time (second) required for the potential to change by ΔV, F: Faraday constant, ΔV: potential difference (V). ).

The results are shown in Table 1.

[0013]

[Table 1]

Embodiment 2 In this embodiment, the solvent and solute constituting the electrolytic solution were studied. Table 1 shows the composition of the electrolytic solution. As shown in Table 1, acetonitrile (A
N), ethylene carbonate (EC), γ-butyrolactone (GVL), tetrahydrofuran (THF), sulfolane (SL), or a mixture of 3-methylsulfolane (MSL) alone or as a solvent, and mixed with 4 ethyl tetrafluoroborate Ammonium (TEABF4), hexafluorophosphoric acid 4
An electrolyte was prepared using ethylammonium (TEAPF6) and 4-ethylammonium perchlorate (TEACLO4) as a solute. In Table 1, the numerical values in the columns indicating the solvents represent the mixing ratios of the respective solvents by volume ratio.

In addition, as a comparative example, a solvent prepared by using propylene carbonate (PC) as a solvent was prepared. All other configuration requirements were the same as in Example 1, test capacitors were fabricated, and their discharge capacities and DC resistances were measured in the same manner as in Example 1.

As is evident from Table 1, the electric double layer capacitor prepared in this embodiment is different from that of the comparative example.
A DC resistance having a small value and a high discharge capacity could be obtained.

Further, in this embodiment, an example is shown in which acetonitrile in which R is a methyl group is used as the nitrile compound represented by the general formula (Chemical Formula 1), but a nitrile compound in which R is an ethyl group or a propyl group is used. The same effect could be obtained by using.

[0018]

As described above, according to the present invention, an electric double layer capacitor having a low resistance and a high capacity can be obtained.

Continuation of the front page (72) Inventor Akihiko Yoshida 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5H029 AJ03 AK06 AL06 AM01 AM02 AM03 AM04 AM05 AM06 AM07 HJ02

Claims (5)

[Claims] 1. An electric double layer capacitor comprising a polarizing electrode and an electrolytic solution containing at least one kind of a nitrile compound represented by the general formula (1). Embedded image 2. The electric double layer capacitor according to claim 1, wherein the nitrile compound is acetonitrile. 3. An electrolytic solution comprising a mixed solvent of a nitrile compound and one or more compounds selected from cyclic carbonates, cyclic carboxylate cyclic ethers, sulfolane and sulfolane derivatives. The electric double layer capacitor according to claim 1 or 2, wherein 4. The electric double layer capacitor according to claim 1, wherein the electrolytic solution has a quaternary onium salt as a solute. 5. The electrolyte salt constituting the electrolytic solution is BF ₄ ⁻ ,
_4. The electric double layer capacitor according to claim 1, wherein PF ₆ ^- or ClO ₄ ^- is an anion.