JP2000311834A - Electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an electric double layer capacitor in which deterioration of capacitance is suppressed by containing the compositional members of the capacitor and a current collector utilizing an electric double layer formed of the interface between a polarizing electrode and an electrolyte in a stainless steel container. SOLUTION: A polarized electrode 9 comprising positive and negative electrodes 1, 5 is bonded through a graphite based conductive adhesive 2 to a stainless steel container 10 comprising a case 3 and a cover 4. The metal container 10 contains a current collector and the compositional members of a capacitor. After the metal container 10 and the polarizing electrode 9 are dried for two hours at 300 deg.C under a reduced pressure, the polarized electrode 9 is impregnated with electrolyte 6 in a globe box of dry nitrogen atmosphere. The polarized electrodes 9 are faced each other through a separator 7 of nonwoven polypropylene fabric and caulked using a polypropylene gasket 8. According to the structure, deterioration of capacitance and increase of internal resistance can be suppressed.

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 in which characteristic deterioration hardly occurs and long-term reliability is improved.

[0002]

2. Description of the Related Art A small electric double layer capacitor is formed as an element by sandwiching a separator such as a polypropylene non-woven fabric between a pair of polarizable electrodes having a polarizable electrode layer mainly composed of activated carbon formed on a current collector. This element is impregnated with an electrolytic solution and accommodated in a metal container, and has a coin-type structure sealed in the metal container with a sealing plate and a gasket.

In addition, in the case of a device having a relatively large capacity, a laminated sheet in which a separator is sandwiched between a pair of sheet-shaped polarizable electrodes is wound into an element, and the element is impregnated with an electrolytic solution to form a metal. 2. Description of the Related Art A wound-type capacitor that is housed in a container and has a metal opening sealed with a sealing member has been manufactured. These electric double layer capacitors are mainly used for IC memory backup and actuators.

[0004] A multilayer electric double layer capacitor having an element in which a large number of sheet-like polarizable electrode layers are stacked with a separator interposed therebetween has also been proposed for large current and large capacity (Japanese Patent Laid-Open No. 4-154106). JP-A-4-2861
08). Various reports have been made on current collectors and case materials for extracting electricity from the polarizable electrodes in these electric double layer capacitors (Japanese Patent Application Laid-Open No. 58-1983).
-206116, JP-A-63-289920, etc.).

[0005]

However, even when these materials are used, corrosion is caused by dissolution of the anode when high-voltage charging and discharging are performed. for that reason,
Even if activated carbon having a high oxidation potential or an electrolytic solution having a high decomposition potential is used, the withstand voltage of the capacitor is necessarily limited by the dissolution potential of the current collector, so that the situation has to be set low.

Also, the metal container materials reported so far are relatively expensive, such as providing an aluminum layer on the inner surface of stainless steel (Japanese Patent Application Laid-Open No. 62-94908), and are used on the anode side during charging. Used only for metal cases. Further, as the material used for the cathode side, an inexpensive material having low corrosion resistance has been used. Therefore, the capacitor is inevitably polar, and when the capacitor is reversely mounted on a circuit board, corrosion of the metal container, decomposition of the electrolytic solution, and leakage of the electrolytic solution due to the corrosion have been problems.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an inexpensive electric double layer capacitor excellent in long-term reliability.

[0008]

SUMMARY OF THE INVENTION The present inventor has made intensive efforts to develop an electric double layer capacitor which is inexpensive and has excellent long-term reliability. It has been found that by using SUS316L or SUS310 for the container, an electric double layer capacitor with little deterioration can be manufactured.

According to the present invention, the metal container accommodating the constituent members of the current collector and / or the capacitor is SUS31.
An electric double layer capacitor comprising 6L or SUS310 is obtained.

According to the present invention, an inexpensive SUS316L or SUS31 having excellent corrosion resistance and workability in an electrolytic solution.
By using 0 for the current collector and the container metal, the withstand voltage of the capacitor can be improved, and a non-polar capacitor having excellent long-term reliability can be obtained.

That is, the present invention provides a current collector utilizing an electric double layer formed at an interface between a polarizable electrode and an electrolytic solution, and / or
Alternatively, in the electric double layer capacitor in which the components of the capacitor are housed in a metal container, the metal container is stainless steel.

[0012] The present invention also relates to the present invention, wherein the stainless steel is SU.
The electric double layer capacitor of S316L or SUS310.

Further, the present invention is the electric double layer capacitor, wherein the polarizable electrode is made of carbon powder or activated carbon fiber.

The polarizable electrode used in the electric double layer capacitor of the present invention is not particularly limited, and various types of well-known or well-known ones can be used. For example, activated carbon fiber cloth and activated carbon having a large specific surface area can be used. Powders and the like can be used. In particular, a polarizable electrode formed by adding an alcohol to a conductive material such as carbon black and a binder such as polytetrafluoroethylene to an activated carbon powder, kneading the mixture, and forming a roll into a sheet is excellent in capacity per unit volume and strength. It is preferred.

[0015]

Embodiments of the present invention will be described below.

Conventionally, activated carbon used for a polarizable electrode of an electric double layer capacitor includes phenolic resin-based activated carbon, coconut-based activated carbon, petroleum coke-based activated carbon, and the like. In particular, phenolic resin-based activated carbon can provide a large-capacity electric double layer capacitor and has high purity.
It is preferably used.

In order to obtain an electric double layer capacitor having a large capacity and a low internal resistance, the activated carbon has an average particle diameter of 20 μm or less in the case of powder, and a fibrous material of 10 to 10 in the case of fibrous.
20 μm, both having a specific surface area of 2000 to 3000 m ²
/ G of activated carbon is preferred.

The activated carbon activation method includes a steam activation method and a molten KOH activation method.
It is preferable to use activated carbon by a steam activation treatment method since an electric double layer capacitor with little deterioration in characteristics and high reliability can be obtained.

As a binder for the polarizable electrode, a polytetrafluoroethylene-based binder is preferable because of its high chemical resistance when an organic solvent-based electrolyte is used.

The electrolytic solution used in the present invention is not particularly limited, and one generally used for an electric double layer capacitor, that is, one obtained by dissolving an electrochemically stable electrolyte in a polar organic solvent can be used. Used as appropriate.

Further, as the above-mentioned electrolyte, (C₂H₅)
₄N⁺And (C₄H₉)₄N⁺, (C ₂H₅)₄P⁺Such
Quaternary onium cation and BF₄ ⁻And PF₆ ⁻, C
10 ₄ ⁻And the like.

As the organic solvent, carbonates such as propylene carbonate, butylene carbonate and diethyl carbonate, lactones such as γ-butyrolactone, and sulfolane are preferable. These may be used alone or in combination of two or more.

The separator used in the present invention is not particularly limited, and ordinary separators for electric double layer capacitors, for example, glass fiber mixed paper and polypropylene nonwoven fabric can be used.

[0024]

The present invention will be described below in detail with reference to examples.

Example 1 80% by weight of a phenol resin-based steam activated activated carbon powder (average particle size: 5 μm), 10% by weight of carbon black (manufactured by Nippon Graphite), and 10% by weight of a polytetrafluoroethylene binder. Ethanol was added to the mixture, kneaded, and roll-rolled to form a sheet having a width of 8 cm, a length of 10 cm and a thickness of 0.6 cm, which was dried at 250 ° C for 2 hours.

FIG. 1 is a longitudinal sectional view of the coin-type electric double layer capacitor used in the first embodiment. In FIG. 1, a polarizable electrode 9 composed of a positive electrode 1 and a negative electrode 5 obtained by punching the sheet to a diameter of 10 mm is provided with a SUS316L case 3 and a lid 4 with a graphite-based conductive adhesive 2.
Was adhered to a metal container 10 made of

The metal container 10 and the polarizable electrode 9 are
After drying at 00 ° C. under reduced pressure for 2 hours, the polarizable electrode 9 was impregnated with the electrolytic solution 6 in a glove box in a dry nitrogen atmosphere. The electrolyte 6 was prepared by dissolving tetraethylammonium tetrafluoroborate at a concentration of 0.7 mol / l in propylene carbonate.

Next, the polarizable electrodes 9 impregnated with the electrolytic solution 6 were opposed to each other with a polypropylene non-woven fabric separator 7 interposed therebetween, and sealed with a gasket 8 made of polypropylene.

(Example 2) A coin-type electric double layer capacitor was assembled in the same manner as in Example 1 except that a metal container made of SUS310 was used. Further, as a comparative example, a coin-type electric double layer capacitor was assembled in the same manner as in Example 1 except that a metal container made of SUS304 was used.

In the first embodiment manufactured as described above,
The electric double layer capacitors of Example 2 and Comparative Example 1 were charged at an applied voltage of 3.0 V, and the initial capacitance (F) and ESR (Ω) when discharged at about 0.5 mA were measured. The capacity and ES after storage in this cell for 1000 hours in a constant temperature bath at 70 ° C. while applying a voltage of 3.0 V.
R was measured. Table 1 shows the measurement results.

[0031]

[Table 1]

As is clear from Table 1, the electric double layer capacitor using the metal container made of SUS316L of the present invention of Example 1 or SUS310 of Example 2 is the same as that of Comparative Example 1
As compared with the electric double-layer capacitor using the SUS304 metal container, it is understood that the electric double-layer capacitor has less capacity deterioration and increase in internal resistance and has high long-term reliability.

[0033]

As described above, according to the electric double layer capacitor of the present invention, an electric double layer capacitor having high long-term reliability can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electric double layer capacitor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 (Graphite type) conductive adhesive 3 Case 4 Lid 5 Negative electrode 6 Electrolyte 7 Separator 8 Gasket 9 Minute polarity electrode 10 (Made of stainless steel) Metal container

Claims (3)

[Claims] 1. An electric double layer capacitor in which a current collector and / or a component of a capacitor using an electric double layer formed at an interface between a polarizable electrode and an electrolytic solution are housed in a metal container. An electric double layer capacitor characterized in that the container is made of stainless steel. 2. The electric double layer capacitor according to claim 1, wherein the stainless steel is SUS316L or SUS310. 3. The electric double layer capacitor according to claim 1, wherein the polarizable electrode is made of carbon powder or activated carbon fiber.