JP2010087315A - Electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric double layer capacitor that is usable at 85°C. <P>SOLUTION: The electric double layer capacitor uses an electrolyte containing γ-butyrolactone as a main solvent, and includes a sealing member for sealing an opening. Since a safety valve made of ethylene propylene terpolymer is fitted to a transparent hole bored in the sealing member, there is no deterioration in characteristics due to resolution of the solvent even in its use at 85°C and deterioration due to moisture is suppressed possibly because of suppression of immersion of moisture from the safety valve, thereby providing the electric double layer capacitor having excellent characteristics in its use at 85°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric double layer capacitor using a non-aqueous electrolyte.

  An electric double layer capacitor is wound with a separator interposed between polarizable electrodes in which a polarizable electrode layer is provided on the surface of a metal foil made of aluminum, for example, or a laminated capacitor element is impregnated with an electrolytic solution. The capacitor element is housed in a metal case and the opening end is sealed.

  The electric double layer capacitor described above is required to have a high capacity and excellent long-term reliability, and a carbonate-based solvent such as propylene carbonate is used as an electrolytic solution of a conventional electric double layer capacitor. According to this, an electric double layer capacitor having a high capacity and excellent in high temperature load can be obtained.

However, in an electrolytic solution using a carbonate-based solvent, carbon monoxide (CO) gas is generated due to decomposition of the solvent at a high temperature, so that the internal pressure of the container containing the polarizable electrode, the electrolytic solution, etc. increases. Problems arise. For this reason, 60 degreeC is a limit and there existed a problem that it cannot respond to the further high temperature use of 70-85 degreeC. On the other hand, there is an attempt to enable use at 70 ° C. using γ-butyrolactone. (Patent Document 1).
JP 2001-217150 A

However, if it is further possible to use at 85 ° C., deterioration of characteristics cannot be suppressed. Therefore, an object of the present invention is to solve this problem and provide an electric double layer capacitor that can be used at 85 ° C.

  The electric double layer capacitor of the present invention comprises a capacitor element constituted by a pair of polarizable electrode bodies and a separator interposed between the pair of polarizable electrode bodies, and γ-butyrolactone impregnated in the capacitor element. A safety valve comprising an electrolytic solution as a main solvent, a case for housing the capacitor element, and a sealing member for sealing an opening of the case, and an ethylene propylene terpolymer formed in a through hole formed in the sealing member It is characterized by being fitted.

  The electric double layer capacitor of the present invention comprises an electrolytic solution containing γ-butyrolactone as a main solvent, and a sealing member that seals the opening. From the ethylene propylene terpolymer to the through-hole formed in the sealing member. It seems that there is no deterioration of the characteristics due to the decomposition of the solvent even when used at 85 ° C., and further the infiltration of moisture from the safety valve is suppressed, but the deterioration due to moisture is suppressed, An electric double layer capacitor having good characteristics when used at 85 ° C. can be provided.

In the electric double layer capacitor of the present invention, a capacitor element is manufactured by facing a metal current collector foil made of aluminum with a polarizable electrode layer facing through a separator, and the capacitor element is impregnated with an electrolytic solution. An electric double layer capacitor is obtained.

  An aluminum etching foil is used as the metal current collector foil used for the electrode. As the aluminum foil, high-purity aluminum having a purity of 99.9% or more is used. As the thickness, an aluminum foil having a thickness of about 10 to 50 μm is usually used.

  For example, a paste obtained by mixing activated carbon powder, a conductive additive, a binder, and a solvent such as an organic solvent or water is applied to the metal current collector foil. Alternatively, the paste is formed into a sheet shape, and this sheet is pressed against a current collector to form a polarizable electrode.

  The raw material of the activated carbon is plant-based wood, sawdust, coconut husk, pulp waste liquid, fossil fuel-based coal, heavy petroleum oil, or coal and petroleum-based pitch, petroleum coke obtained by pyrolyzing them. Activated carbon is obtained by carbonizing these raw materials and then activating them.

As the conductive assistant, carbon black and graphite, which are carbon materials having conductivity, can be used. Examples of the carbon black include acetylene black, ketjen black, channel black, furnace black, and thermal black. Among these, ketjen black is preferable. Examples of graphite include natural graphite and artificial graphite.
Any binder may be used as long as it is usually used, for example, rubbers such as fluorine rubber, diene rubber and styrene rubber, fluorine-containing polymers such as polytetrafluoroethylene and polyvinylidene fluoride, and the like. , Polyolefin resin, acrylic resin, nitrile resin, polyester resin, phenol resin, polyvinyl acetate resin, polyvinyl alcohol resin, epoxy resin and the like.
A capacitor element is produced by making the electrodes face each other via a separator, and the capacitor element is impregnated with an electrolytic solution to obtain an electric double layer capacitor.

      The water content contained in this polarizable electrode is 70 to 150 ppm, preferably 80 to 120 ppm.

  In the present invention, γ-butyrolactone is used as the main solvent as the electrolytic solution. In addition, as a co-solvent, carbonates such as ethylene carbonate, butylene carbonate, dimethyl carbonate and diethyl carbonate; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran Sulfoxides such as dimethyl sulfoxide; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; nitrogen-containing compounds such as acetonitrile and nitromethane; methyl formate, methyl acetate, ethyl acetate, butyl acetate, Organic acid esters such as methyl propionate and ethyl propionate; inorganic acid esters such as phosphoric acid triester and diester carbonate such as dimethyl carbonate, diethyl carbonate and dipropyl carbonate; diglyme ; Triglyme like; sulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; 1,3-propane sultone, 1,4-butane sultone can be used sultone like such Nafutasuruton.

Examples of the electrolyte dissolved in the organic solvent include metal cations, quaternary ammonium cations, carbonium cations, and the like, BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , and AlCl _4. ^-, or ^{_{RfSO 3 -, (RfSO 2)}} 2 N -, RfCO 2 - (Rf is a fluoroalkyl group having 1 to 8 carbon atoms) can be exemplified salts of anions selected from.

    The water content contained in the electrolytic solution mainly composed of γ-butyrolactone is 10 to 40 ppm, preferably 20 to 30 ppm.

  The electric double layer capacitor of the present invention may have any shape such as a wound type and a laminated type. Such an electric double layer capacitor is obtained by, for example, cutting an electrode sheet into a desired size and shape, stacking or winding the separator sheet between both electrodes, inserting the electrolyte into the container, It can be manufactured by caulking the seal using a sealing member, that is, a sealing plate, a gasket or the like.

  Here, in the present invention, a safety valve made of ethylene propylene terpolymer is fitted into a through hole formed in the sealing member.

The present invention will be described more specifically with reference to the following examples.

Example 1
Activated carbon (AC) 52 g, Ketjen black (KB) 5.6 g, isopropyl alcohol (IPA) 110 g are stirred, and 60% polytetrafluoroethylene (PTFE) aqueous solution 5.2 g is mixed with this AC-KB-IPA mixture. Thus, a kneaded product was prepared. The kneaded product was rolled with a rolling roller to produce a 150 μm sheet.

    This sheet was bonded to an aluminum etching foil provided with external terminals using a carbon-based adhesive, and this was used as an electrode.

    An electric double layer capacitor element was produced by disposing the positive electrode and the negative electrode thus produced via a cellulose-based separator. This element was impregnated with 1.8M boron tetrafluoride triethylmethylammonium / gamma-butyrolactone solution (1.8MTEMABF4 / GBL) as an electrolyte, sealed in an aluminum case with a sealing plate, and applied with voltage to form a wound electric double layer. A capacitor cell was produced.

    Here, a safety valve made of ethylene propylene terpolymer was fitted into a through-hole formed in the sealing plate.

(Comparative example)
An electric double layer capacitor was produced in the same manner as in the example except that silicon was used as a safety valve.

  The electric double layer capacitors of Examples and Conventional Examples obtained by the above methods were subjected to a 2.3V, 85 ° C. load standing test, and the rate of decrease in capacitance and the rate of increase in internal resistance were measured. The results are shown in (Table 1).

  As can be seen from (Table 1), the change rate of DCIR is reduced in the example as compared with the comparative example, and the effect of the present invention is understood.

Claims (1)

A capacitor element composed of a pair of polarizable electrode bodies and a separator interposed between the pair of polarizable electrode bodies, an electrolyte containing γ-butyrolactone impregnated in the capacitor element as a main solvent, An electric double layer comprising a case for storing a capacitor element and a sealing member for sealing the opening of the case, and a safety valve made of ethylene propylene terpolymer being fitted into a through hole formed in the sealing member Capacitor.