JP2001217162A - Electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor having a large electrostatic capacity. SOLUTION: This electric double-layer capacitor, which is connected with a collector is provided with a polarization electrode, formed of a mixture of at least porous particles, a conductive carbon particle, and a metal oxide particle selected from among zinc oxide, magnesium oxide, titanium oxide, aluminum oxide, and silicon oxide, and at least one kind of binder elected from among butyl rubber, ethylene-propylene-diene rubber, butadiene rubber, and nitrile rubber.

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 large capacitance.

[0002]

2. Description of the Related Art An electric double layer capacitor is provided with a pair of polarizable electrodes via a porous separator and utilizes the capacitance of an electric double layer formed on the surface of the polarizable electrode in an electrolyte solution. There is a feature that a capacitor having an extremely large capacitance as compared with a general capacitor is obtained, and wide use is expected from a backup use of an electronic device to a power storage use.

A polarizable electrode used for an electric double layer capacitor is stable in an electrolyte solution, has a large specific surface area,
Activated carbon, which is advantageous for forming an electric double layer having a large capacitance, is generally used. The polarizable electrode is one using a sintered body in the form of an electrode, granular or fibrous activated carbon, and a slurry formed by kneading a conductive material and a binder into a sheet-like electrode, and a current collector. An application type electrode in which a slurry is applied on a conductor such as an aluminum foil by various application methods is used. In particular, coated electrodes are
It has features that the thickness and size of the polarizing electrode can be easily adjusted according to the purpose of use and the like, and that the polarizing electrode can be manufactured relatively easily by a coating device.

[0004] As a binder used in a coating type electrode,
Synthetic resin such as thermoplastic resin such as acrylic polymer, vinyl polymer, acetal resin, polyamide resin and polyester resin, and thermosetting resin such as epoxy resin, phenol resin and amino resin. Are insoluble in the solvents used as In the coating type electrode, it is necessary that the binder binds the activated carbon particles to each other and also binds to the current collector, and the binding between the activated carbons or the binding to the current collector is insufficient. If there is, the contact resistance increases, and on the other hand, if the surface of the activated carbon particles is widely covered with the binder, there is a problem that the contact between the electrolytic solution and the activated carbon cannot be achieved and a sufficient capacitance cannot be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a polarizable electrode formed by applying a slurry comprising activated carbon particles, a conductive substance and a binder on a current collector. To provide an electric double layer capacitor having good electric characteristics by binding without binding the surface of the activated carbon particles and the pores of the activated carbon, having a large binding force of the particles on the current collector, and a method for producing the same. It is an issue.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric double layer capacitor having a polarizable electrode joined to a current collector, wherein the polarizable electrode comprises at least porous carbon particles, conductive carbon particles, and metal. The problem can be solved by an electric double-layer capacitor formed by kneading the oxide particles with a binder. Also, the binder is
The electric double layer capacitor is at least one selected from butyl rubber, ethylene propylene diene rubber, butadiene rubber, and nitrile rubber. The electric double layer capacitor as described above, wherein the metal oxide particles are at least one selected from zinc oxide, magnesium oxide, titanium oxide, aluminum oxide, and silicon oxide. The kneaded product is the above electric double layer capacitor containing a crosslinking agent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a polarizable electrode obtained by kneading porous carbon particles such as activated carbon particles together with a binder and the like, and collecting a kneaded product. By mixing, the surface and the inside of the pores of the porous carbon particles are entirely covered with the binder while maintaining the binding force between the porous carbon particles and the binding force between the porous carbon particles and the current collector. It has been found that an electric double layer capacitor which can be prevented from being covered, has a large capacitance and a small electric resistance can be obtained.

That is, in the electric double layer capacitor of the present invention, the activated carbon particles are kneaded together with a conductive substance such as carbon black, a binder and metal oxide particles, and then applied on a current collector. The adhesive covers the surface of the activated carbon particles in a net-like manner, and does not hinder the conductivity of the activated carbon particles and the flow of the electrolytic solution, and an electric double layer capacitor having excellent characteristics can be obtained. As activated carbon particles, activated carbon obtained by activating a coconut shell, phenol resin, or charcoal of petroleum pitch to increase the surface area with water vapor, hydroxide, or the like, has a particle diameter of 2 μm to 30 μm, preferably 1 μm.
It is preferable to use particles sized to around 0 μm.

Examples of the binder that can be used in the present invention include at least one elastomer selected from butyl rubber, ethylene propylene diene rubber, butadiene rubber, and nitrile rubber. Of these, butyl rubber is preferred. The binder is preferably used in an amount of 3 to 20 parts by weight based on 100 parts by weight of the activated carbon particles. If the amount is less than 3 parts by weight, it is difficult to achieve sufficient binding, and if the amount is more than 20 parts by weight, adverse effects are exerted on resistance and capacity.

As the metal oxide particles, zinc oxide, magnesium oxide, aluminum oxide, silicon oxide, vanadium oxide and the like which are stable in the electric potential range of the electric double layer capacitor are preferable. The metal oxide particles are preferably used in an amount of 1 to 8 parts by weight, more preferably 1 to 5 parts by weight, and still more preferably 1 to 3 parts by weight, based on 100 parts by weight of the binder. . Further, the metal oxide particles have an average particle size of 0.1 as measured by a light scattering method.
1 μm to 5 μm, preferably 0.5 μm
More preferably, it is 1 μm.

The conductive particles include carbon black, acetylene black and graphite.
The average particle size is preferably from 0.05 μm to 1.0 μm, more preferably from 0.1 μm to 0.5 μm. Further, a crosslinking agent for crosslinking the elastomer may be added to the binder. By adding a cross-linking agent, an electric double layer capacitor having a small change with time can be obtained. Examples of the crosslinking agent include sulfur, peroxides such as dicumyl peroxide, tetraalkylthiuram disulfide, rubber crosslinking agents such as carbamine zinc derivatives,
A crosslinking aid may be added to these. The crosslinking agent is a binder 1
Preferably 0.5 to 8 parts by weight, more preferably 1 to 5 parts by weight, and even more preferably 1 to 3 parts by weight, per 100 parts by weight.

The kneaded product of the present invention is produced by kneading a binder together with activated carbon particles, a conductive substance, metal oxide particles and the like, and an organic solvent. As the organic solvent, many substances can be used as long as they are substances that dissolve the elastomer and do not adversely affect the materials used, but toluene, xylene, tetrahydrofuran, cyclohexane, normal hexane and the like are preferable. The kneading can be performed by a kneader, a mixer or the like.

[0013] The polarizable electrode of the electric double layer capacitor is formed by applying a kneaded material onto a current collector by various coating means such as a doctor blade, a coater, a spray or the like to form a coating film, followed by drying, followed by calender roll or the like. To a predetermined thickness. As the current collector, a thin or net-like base made of aluminum, stainless steel, nickel, titanium, a conductive elastomer, or the like can be used. In addition, fine irregularities may be formed on the surface of these substrates by etching or the like to enhance the adhesion to the coating layer, or a substrate coated with colloidal carbon or the like may be used. Further, in the electric double layer capacitor of the present invention, a propylene carbonate solution of tetraethylammonium tetrafluoroborate, trimethylammonium tetrafluoroborate or the like can be used as the electrolyte.

[0014]

The present invention will be described below with reference to examples. Example 1 A butyl rubber (Nihon Butyl II
R065) and 100 parts by weight of toluene were added and heated to 80 ° C. to dissolve the butyl rubber. Next, 2.5 parts by weight of zinc oxide was added and stirred for 2 hours. Then, activated carbon (M25 manufactured by Osaka Gas Chemicals, particle size: 10 μm) 80
0 parts by weight, 5 parts by weight of carbon black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size: 0.53 μm), and 5 parts by weight of colloidal carbon (Bunny Height manufactured by Nippon Graphite Industry Co., Ltd., average particle size: 0.3 μm) are added and stirred for 24 hours. And completely dispersed. The obtained kneaded material was applied on an aluminum foil having a thickness of 30 μm with a width of 100 mm, dried, and then calendered to prepare a polarizable electrode having a thickness of 150 μm.

Next, a polarizable electrode having a width of 100 mm and a length of 100 mm of an effective portion is interposed on both sides of a cellulose separator (MR5D50 manufactured by Nippon Kodoshi) to form a 200
Dried in a vacuum oven at 25 ° C. for 25 hours. Scan the surface of the polarizing electrode with a scanning electron microscope (JSM-JSM-
6340F) at an accelerating voltage of 5 kV, and the photograph is shown in FIG. The activated carbon particles were not completely covered with the binder, and the electrolyte sufficiently reached the activated carbon particles. Next, a laminate of a pair of polarizable electrodes via a separator is impregnated with a propylene carbonate solution of tetraethylammonium tetrafluoroborate having a concentration of 1 M, and then a polyethylene film is laminated on the inside of aluminum and polypropylene is laminated on the outside. The resultant was covered with a film and sealed to produce an electric double layer capacitor.

The obtained electric double layer capacitor was charged to 2.5 V with a constant current of 1 A, held at 2.5 V for 1 hour, and then subjected to a charge / discharge test of discharging at a constant current of 1 A. The charge / discharge energy was calculated, and the capacitance C was obtained from the following equation. The results are shown in Table 1. E = 0.5 CV ² At the same time, the internal resistance of the electric double layer capacitor was measured from the voltage drop during discharging, and the results are shown in Table 1.

Comparative Example 1 An electric double layer capacitor was manufactured in the same manner as in Example 1 except that zinc oxide particles were not added, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 The particle size of the activated carbon was changed to 30 μm in order to make it easy to confirm the surface condition while replacing the binder with polyvinylidene fluoride.
An electric double layer capacitor was fabricated in the same manner as in Example 1 except that the value was changed to m, and the evaluation was performed in the same manner as in Example 1. As a result, the capacitance was 136 F and the internal resistance was 0.055 Ω. FIG. 2 shows the result of photographing the electrode surface with a scanning electron microscope in the same manner as in Example 1. The activated carbon particle surface was widely covered with the binder.

Example 2 An electric double layer capacitor was manufactured in the same manner as in Example 1 except that the amount of zinc oxide particles was changed to manufacture electric double layer capacitors having different blending amounts. Evaluation was performed in the same manner, and the results are shown in Table 1.

Example 3 Except that magnesium oxide particles were used instead of zinc oxide particles, and the amount of magnesium oxide was varied to produce electric double layer capacitors having different amounts of magnesium oxide particles. An electric double layer capacitor was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 Except that, instead of using zinc oxide particles, silicon oxide particles were used and the amount of silicon oxide particles was varied to produce electric double layer capacitors having different amounts of silicon oxide particles, An electric double layer capacitor was produced in the same manner as in Example 1, evaluated in the same manner as in Example 1, and the results were shown in Table 1.
Shown in

Example 5 Except that, instead of using zinc oxide particles, titanium oxide particles were used and the amount of titanium oxide particles was varied to produce electric double layer capacitors having different amounts of titanium oxide particles. An electric double layer capacitor was produced in the same manner as in Example 1, evaluated in the same manner as in Example 1, and the results were shown in Table 1.
Shown in

Example 6 Except that aluminum oxide particles were used instead of zinc oxide particles, and the amount of aluminum oxide particles was varied to produce electric double layer capacitors having different amounts of aluminum oxide particles. An electric double layer capacitor was produced in the same manner as in Example 1, evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0024]

Table 1 Metal oxide particles Capacitance Internal resistance type Mixing ratio (F) (Ω) Zinc oxide 0 153 0.051 1.0 221 0.036 2.5 356 0.024 5.0 361 0.023 7.5 305 0.026 10 283 0.036 Magnesium oxide 1.0 203 0.043 2.5 351 0.028 5.0 348 0.031 7.5 320 0.038 10 301 0.041 Silicon oxide 1 0.0 251 0.029 2.5 368 0.021 5.0 372 0.025 7.5 351 0.032 10 325 0.039 Titanium oxide 1.0 243 0.047 2.5 336 0.033 0 321 0.034 7.5 301 0.038 10 258 0.043 aluminum oxide 1.0 281 0.028 2.5 304 0.02 5.0 258 0.038 7.5 233 0.041 10 187 0.045

Example 7 The mixing amount of zinc oxide particles was changed to 5 parts by weight, and the compounding amount of a phenolic resin-based cross-linking agent (Takkiroll 201, manufactured by Taoka Chemical Industry Co., Ltd.) was changed from 0 parts by weight to 10 parts by weight. Then, electric double layer capacitors having different mixing ratios of the cross-linking agent were produced, and immediately after the production, the capacitance and the internal resistance were measured in the same manner as in Example 1.
After storage for 000 hours, the capacitance and the internal resistance were measured in the same manner, and the rate of change with respect to the value immediately after production is shown in Table 2.

Example 8 Except that 2.5 parts by weight of magnesium oxide particles were used instead of zinc oxide particles, electric double layer capacitors having different mixing ratios of the crosslinking agent were prepared in the same manner as in Example 6. 6
The capacitance and the internal resistance were measured immediately after production and after storage in the same manner as described above, and the rate of change with respect to the value immediately after production was shown in Table 2.

Example 9 An electric double layer capacitor having a different mixing ratio of a crosslinking agent was prepared in the same manner as in Example 6, except that 2.5 parts by weight of silicon oxide particles were used instead of zinc oxide particles. The capacitance and the internal resistance immediately after production and after storage were measured in the same manner as in Example 6, and the rate of change with respect to the value immediately after production is shown in Table 2.

Example 10 An electric double layer capacitor having a different blending ratio of a crosslinking agent was prepared in the same manner as in Example 6 except that 2.5 parts by weight of titanium oxide particles were blended in place of the zinc oxide particles. The capacitance and the internal resistance immediately after production and after storage were measured in the same manner as in Example 6, and the rate of change with respect to the value immediately after production is shown in Table 2.

Example 11 An electric double layer capacitor having a different blending ratio of a crosslinking agent was prepared in the same manner as in Example 6, except that 2.5 parts by weight of aluminum oxide particles were used instead of zinc oxide particles. 6
The capacitance and the internal resistance were measured immediately after production and after storage in the same manner as described above, and the rate of change with respect to the value immediately after production was shown in Table 2.

[0030]

Table 2 Metal oxide particles Crosslinking agent Capacitance change rate Resistance change rate Mixing ratio Mixing ratio (%) (%) Zinc oxide 5.00-16.1 111.3 5.0 0.5-12 6.6 109.5 5.0 1.0 -10.6 108.3 5.0 2.5 -5.3 104.6 5.0 5.0 -7.2 107.4 5.0 7.5 -11.1 113.9 5.0 10 -19.6 126.8 Magnesium oxide 2.50 -17.2 112.8 2.5 0.5 -13.8 110.1 2.5 1.0 -8.3 107.9 2.5 2.5 -8.5 108.1 2.5 5.0 -6.8 111.9 2.5 7.5 -7.9 115.3 2.5 10 -17.3 121.6 silicon oxide 2.5 0 -18.6 118.2 2.5 0.5 -15.3 114.9 2.5 1.0 9.8 106.3 2.5 2.5 -6.1 105.6 2.5 5.0 -8.9 108.1 2.5 7.5 -10.3 109.7 2.5 10 - 12.6 112.3 Titanium oxide 2.50-17.2 118.2 2.5 0.5-13.9 110.6 2.5 1.0-10.1 106.3 2.5 5-7.3 105.6 2.5 5.0-8.7 108.1 2.5 7.5 -10.9 109.7 2.5 10 -14.6 112.3 Aluminum oxide 2.5 0-19.1 118.1 2.5 0.5 -10.6 109.9 2.5 1.0 -6.1 106.2 2.5 2.5 -0.3 110.3 2.5 5.0-15.6 115.6 2.5 7.5-21.3 125.3 2.5 10-25.6 131.6

[0031]

As described above, in an electric double layer capacitor having a polarizable electrode formed by kneading porous carbon particles with a binder, by mixing metal oxide particles in the binder, the capacitance, An electric double layer capacitor with small internal resistance was obtained. Furthermore, in the case where the crosslinking agent is contained in the binder, it is possible to manufacture an electric double layer capacitor having a small change with time.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph of an electrode surface of an electric double layer capacitor according to an example of the present invention.

FIG. 2 is a scanning electron micrograph of an electrode surface of an electric double layer capacitor of a comparative example.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jin Nakamura 1-1, Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture 1 Inside the Power System Co., Ltd. (72) Dio Okamura 2-19 Minamiota, Minami-ku, Yokohama-shi, Kanagawa No. 6

Claims (4)

[Claims] 1. An electric double-layer capacitor having a polarizable electrode joined to a current collector, wherein the polarizable electrode is a kneaded product in which at least porous carbon particles, a conductive substance, and metal oxide particles are kneaded with a binder. An electric double-layer capacitor formed by: 2. The electric double layer capacitor according to claim 1, wherein the binder is at least one selected from butyl rubber, ethylene propylene diene rubber, butadiene rubber, and nitrile rubber. 3. The electric double layer capacitor according to claim 1, wherein the metal oxide particles are at least one selected from zinc oxide, magnesium oxide, titanium oxide, aluminum oxide, and silicon oxide. 4. The electric double layer capacitor according to claim 1, wherein the kneaded material contains a crosslinking agent.