JP2002033243A - Electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor, with which electrical contact of a polarizable electrode and a current collector is satisfactory, current collection efficiency is improved, contact resistance between the both is a small, and internal resistance is lowered. SOLUTION: For the electric double-layer capacitor, utilizing an electric- double layer formed from a polarizable electrode 4, with which an electrode member 3 mainly composed of carbon is applied or carried on a current collector 2 in a honeycomb structure and an electrolyte interface, the current collector in the honeycomb structure is a conductive body structure, on which plural through-holes exist, and the through hole parts of the current collector 2 are filled with the electrode members 3 composed mainly of activated charcoal.

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, and more particularly to an electric double layer capacitor having a low internal resistance.

[0002]

2. Description of the Related Art Conventionally, an electric double layer capacitor is a capacitor using activated carbon as a polarizable electrode and utilizing electric double layer capacitance accumulated in an electric double layer formed at an interface between activated carbon and an electrolyte. There are two types of such electric double layer capacitors, one using an organic solution based on an electrolyte dissolved in an organic solvent such as propylene carbonate, and the other using an aqueous solution based on an aqueous solution of sulfuric acid. FIG. 4 and FIG. 5 show configurations of typical examples of both.

As shown in FIG. 4, an organic electrolyte-based electric double layer capacitor is formed by kneading activated carbon powder with an appropriate binder to form a sheet or a woven fabric of activated carbon fibers as a polarizable electrode 22. The polarizable electrodes are respectively housed in a metal lid 23 and a metal case 24 made of stainless steel or aluminum via a conductive adhesive, and are opposed to each other via a separator 25 containing an organic electrolyte between the two polarizable electrodes. Then, the peripheral edges of the metal case and the metal lid are closed with a gasket 26 therebetween.

On the other hand, an aqueous solution type electric double layer capacitor has a structure shown in FIG. Polarizing electrodes 32 are arranged facing each other with a separator 34 interposed therebetween, and current collectors 31 made of conductive rubber are arranged outside the polarizable electrodes. The current collector is insulated by the gasket ring 33. Here, the polarizable electrode is formed by adding a sulfuric acid aqueous solution to activated carbon to form a slurry.

[0005]

However, in the electric double layer capacitor manufactured by the above-described method, the current collector layer is formed only on the surface of the polarizable electrode, and the current from the inside of the polarizable electrode is not enough. However, there is a problem that the contact resistance increases, that is, an electric double layer capacitor having a large internal resistance value is obtained.

Accordingly, an object of the present invention is to improve the electrical contact between the polarizable electrode and the current collector and improve the current collection efficiency.
Another object of the present invention is to provide an electric double layer capacitor in which the contact resistance between the two is small and the internal resistance is reduced.

[0007]

The electric double layer capacitor of the present invention has been made in order to solve the above-mentioned problems, and uses a conductive structure having a through-hole as a current collector. An electric double layer capacitor comprising a polarizable electrode in which an electrode material mainly composed of activated carbon is supported in a gap portion of a conductor, a separator interposed between a pair of polarizable electrodes, and an electrolytic solution.

Here, the material of the current collector is a simple metal such as aluminum, copper, and stainless steel or an alloy of these metals, or a conductive ceramic,
The conductive rubber and the conductive resin are used.

Here, a through hole exists in the current collector,
Since the voids are filled with the polarizable electrode mainly composed of carbon, the electrical contact between the polarizable electrode and the current collector is improved, and the current collection efficiency is improved. Also, the contact resistance between the two becomes small, and the internal resistance of the electric double layer capacitor decreases.

That is, the present invention relates to an electric double layer capacitor using an electric double layer formed at the interface between a polarizable electrode having a current collector coated or supported with an electrode material mainly composed of carbon and an electrolyte solution. The current collector is a conductive structure having a plurality of through-holes, and is an electric double layer capacitor in which the through-hole portion of the current collector is filled with an electrode material mainly composed of activated carbon.

[0011] In the present invention, the material of the current collector may be:
An electric double layer capacitor made of a single metal or an alloy of these metals, wherein the metal is any of aluminum, copper, and stainless steel.

Further, according to the present invention, the current collector may be made of a single non-metallic material, wherein the non-metal is made of conductive ceramics,
An electric double layer capacitor made of either conductive rubber or conductive resin.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric double layer capacitor according to an embodiment of the present invention will be described below.

FIG. 1 shows an example of a current collector used in the electric double layer capacitor of the present invention. The current collector 1 has a shape of a honeycomb-shaped structure having a through hole 100.

The shape of the through hole is not limited.
Other examples include a lattice shape, a circle shape, and a wavy shape, and a honeycomb-shaped through hole is preferable from the viewpoint of mechanical strength and porosity.
A polarizable electrode is formed by coating or carrying an electrode material mainly composed of activated carbon in the voids of the current collector.

Examples of the material for the current collector include simple metals or alloys such as aluminum and stainless steel, conductive ceramics, and conductive rubber. Here, from the viewpoint of corrosion resistance and conductivity, the current collector of the organic solution-based electric double layer capacitor is preferably a simple metal such as aluminum or stainless steel or an alloy thereof, while the current collector of the aqueous solution-based electric double layer capacitor is preferable. It is preferable to use conductive ceramics, conductive rubber and conductive resin.

[0017]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. The materials and the structure of the current collector, and the types, forms, compositions, and mixing ratios of the electrode materials are as follows. It is not limited to examples only.

(Embodiment 1) FIG. 2 is a sectional view of an organic electrolytic solution type electric double layer capacitor according to Embodiment 1 of the present invention. As a current collector, the surface area of the void is 5000 m ² / m ³
Was used. As the electrode material, phenol-based activated carbon having a specific surface area of 1500 m ² / g and acetylene black were mixed at a ratio of 8: 1. Polyvinylidene fluoride dissolved in N-methylpyrrolidone as a binder was added to the mixed powder and kneaded to form a slurry.

Next, the electrode material 3 was uniformly applied to the current collector 2 and dried at 150 ° C. for 3 hours. Next, rolling was performed to such an extent that the current collector 2 was not deformed, and a polarizable electrode 4 was obtained. The polarizable electrode is impregnated with a 0.6 mmol / m ³ tetraethylammonium tetrafluoroborate-propylene carbonate solution as an electrolytic solution, and is overlapped between the polarizable electrodes with a separator 7 interposed therebetween. By closing the peripheral portion of the metal case 6 via the gasket 8, an electric double layer capacitor was formed.

Example 2 An electric double layer capacitor was manufactured using the same material and the same manufacturing method as in Example 1 below, using a stainless honeycomb structure having a void surface area of 5000 m ² / m ³ as a current collector.

(Example 3) A copper honeycomb structure having a void surface area of 5000 m ² / m ³ was used as a current collector, and an electric double layer capacitor was manufactured using the same materials and manufacturing method as in Example 1 below.

(Embodiment 4) FIG. 3 is a cross-sectional view of an aqueous electric double layer capacitor manufactured in Embodiment 4 of the present invention. Here, as the current collector, a sheet-shaped current collector 11 made of unvulcanized butyl rubber obtained by mixing carbon black powder and butyl rubber, and a current collector 12 having a honeycomb structure were used as the current collector. A cylindrical gasket ring 15 made of butyl rubber was arranged in the form of a sheet-like current collector, and a current collector having a honeycomb structure was arranged inside the gasket ring. An electrode material 13 containing 30% sulfuric acid electrolyte, phenol-based activated carbon and carbon black was injected into the voids of the current collector of the honeycomb-shaped structure to produce a polarizable electrode 14. A basic cell in which a pair of polarizable electrodes were opposed to each other via a porous separator 16 and sealed by vulcanization was produced.

Example 5 Here, a conductive ceramic sheet having a honeycomb structure was used as a current collector. Hereinafter, an electric double layer capacitor was manufactured using the same materials and the same manufacturing method as in Example 4.

(Example 6) Here, a conductive resin having a honeycomb structure was used as a current collector. Hereinafter, an electric double layer capacitor was manufactured using the same materials and manufacturing method as in the example.

Comparative Example 1 As Comparative Example 1, as shown in FIG. 4, a specific surface area of the polarizable electrode 22 was 1500 m.
² / g phenolic activated carbon and acetylene black were mixed at a ratio of 8: 1. Polyvinylidene fluoride dissolved in N-methylpyrrolidone was added as a binder to the mixed powder, and the mixture was kneaded to form a slurry. Next, the polarizable electrode 22 was uniformly applied to the aluminum foil of the current collector 21 and dried at 150 ° C. for 3 hours. Next, the current collector 2
Rolling was performed so that No. 1 was not deformed, and a polarizable electrode 22 was obtained. Hereinafter, an electric double layer capacitor was manufactured by the same manufacturing method as in Example 1.

Comparative Example 2 As Comparative Example 2, an unvulcanized butyl rubber sheet made of carbon black powder and butyl rubber was used as the current collector 21 as shown in FIG. A cylindrical gasket ring 33 made of butyl rubber is arranged in the form of a sheet-like current collector, and an electrode material 32 containing 30% sulfuric acid electrolyte, phenol-based activated carbon (specific surface area 1500 m ² / g) and carbon black is placed in this gap. Injected. Hereinafter, Example 2
A basic cell was manufactured by the same manufacturing method as that described above.

(Evaluation) The results of the capacitance and the equivalent series resistance (ESR) at 1 kHz of the electric double layer capacitors obtained in the above Examples and Comparative Examples will be described. The capacitance of the electric double layer capacitor was measured at the time of discharging with a discharging current of 1 mA. The ESR was measured by measuring the impedance at a test signal frequency of 1 kHz by an AC four-terminal method and calculating the real part thereof.

Table 1 shows the characteristics of the organic electrolytic solution type electric double layer capacitors obtained in Examples 1 to 3 and Comparative Example 1.
Shown in Table 2 shows the characteristics of the aqueous double-layer capacitors obtained in Examples 4 to 6 and Comparative Example 2.

[0029]

[Table 1]

[0030]

[Table 2]

As can be seen from Tables 1 and 2, as a result of comparing the characteristics of each embodiment and the comparative example, the capacitance of the electric double layer capacitor is slightly reduced, but the value of the equivalent series resistance is greatly reduced. It has been demonstrated to decrease.

As another example of the effect of decreasing the value of the equivalent series resistance, the same effect as described above can be obtained even when a conductive material such as acetylene black is used or without a binder. Presumed.

[0033]

As described above, according to the electric double layer capacitor of the present invention, by using a conductive structure having a through hole as a current collector, carbon is used as a main material in the void. Since the polarizable electrode is supported, the electrical contact between the polarizable electrode and the current collector is improved, the current collection efficiency is improved, the contact resistance between the two is reduced, and the internal resistance of the electric double layer capacitor is reduced. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a honeycomb structure in an electric double layer capacitor according to an embodiment of the present invention.

FIG. 2 is a sectional view of an organic electrolyte-based electric double layer capacitor according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of an aqueous double-layer capacitor according to an embodiment of the present invention.

FIG. 4 is a sectional view of an organic electrolyte-based electric double layer capacitor according to a conventional method.

FIG. 5 is a cross-sectional view of a conventional aqueous double-layer capacitor of an aqueous solution type.

[Explanation of symbols]

 1, 2 Current collector of honeycomb structure 3, 13 Electrode material 4, 14-polarity electrode 5, 23 Metal cover 6, 24 Metal case 7, 25, 34 Separator 8, 26 Gasket 11 Sheet current collector 12 Honeycomb structure Current collector 15,23 Gasket ring 16 Porous separator 21,31 Current collector 22,32 Polarized electrode 100 Through hole

Claims (3)

[Claims] An electric double layer capacitor using an electric double layer formed at an interface between a polarizable electrode having an electrode material mainly composed of carbon coated or carried on a current collector and an electrolyte solution, wherein the current collector is An electric double layer capacitor comprising a conductive structure having a plurality of through-holes, wherein a through-hole portion of the current collector is filled with an electrode material mainly composed of activated carbon. 2. The electric collector according to claim 1, wherein the current collector is made of a single metal or an alloy of these metals, and the metal is any of aluminum, copper, and stainless steel. Multilayer capacitor. 3. The material of the current collector is a non-metal simple substance, and the non-metal is any one of conductive ceramics, conductive rubber, and conductive resin. Electric double layer capacitor.