JP2011035122A - Electric double-layer capacitor, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor superior in reliability. <P>SOLUTION: The electric double-layer capacitor includes: a pair of laminates comprising an electrolyte gel or electrolyte solution, a polarizing electrode, a collecting electrode, and an external electrode; and a separator. The electric double-layer capacitor is configured by connecting an electrode terminal with the external electrode and sealing a part other than the electrode terminal with a molding comprising an expansive resin composition. The external electrode for carrying out electrical conduction to the outside of the compact body is made to adhere to the polarizing electrode. Moreover, the electric double-layer capacitor device configured by alternately laminating the electrolyte gel or the electrolyte solution is sealed and molded by an expansive resin composition, the expansive resin composition being prepared by mixing a thermosetting resin (a) with an additive (b) exhibiting an expansion behavior under a mold-process temperature. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an electric double layer capacitor and a method for producing the same, and more specifically, a capacitor element is completely sealed by integrally molding a resin composition comprising a curable resin and an additive having an expanding action, The present invention relates to an electric double layer capacitor with little change in electrical characteristics during storage and operation, and a method for easily molding and manufacturing the electric double layer capacitor cell.

The electric double layer capacitor can be rapidly charged / discharged, is strong against overcharge / discharge, has no chemical reaction, has a long life, and can be used in a wide temperature range. In addition, since it does not contain heavy metals, it has characteristics not found in batteries, such as being environmentally friendly, and has been used for memory backup power supplies and the like. Furthermore, in recent years, the development of large capacity has progressed rapidly, the development of applications for high-performance energy devices has been promoted, and the use of solar cells and fuel cells in combination with power storage systems, hybrid car engine assist, etc. has been considered. ing.
An electric double layer capacitor usually has a structure in which a pair of positive and negative polarizable electrodes made of activated carbon or the like are opposed to each other via a separator in a solution or electrolyte gel containing electrolyte ions.
And, to maintain the connection stability between the capacitor element and the external electrode, to reduce the fluctuation of the electrical characteristics due to the deformation due to temperature change and the deformation of the capacitor element due to energization (body expansion in the electric field direction in the polarizable electrode when voltage is applied) In order to stabilize the shape of the element, an electric double layer capacitor made of a resin that does not corrode by an electrolyte and has a highly rigid spring-like pressing plate or wedge-shaped member installed therein has been proposed (Patent Literature) 1 and 2).
In addition, an electric double layer capacitor has been proposed in which a carbon fiber having a hollow structure inside is used as an electrode material imparted with a function as a cushioning material during expansion, and the deformation of the capacitor element is mitigated (see Patent Document 3).
In addition, the capacitor element and the electrode terminal are fixed with a conductive material, and then temporarily fixed inside the box-shaped case material, and the inside of the case is sealed with glass, ceramic, or insulating resin. A double layer capacitor has been proposed (see Patent Document 4).
Furthermore, instead of mechanically suppressing the expansion of the electrode, the activated carbon of the petroleum raw coke is used as an electrode material by using activated carbon having a small electrode expansion coefficient during charging, thereby reducing the deformation of the capacitor element. A capacitor has been proposed (see Patent Document 5).

JP 2002-25867 A JP 2002-110480 A Japanese Patent Laid-Open No. 2005-136397 JP 2005-276885 A JP 2008-66528 A

However, in these conventional electric double layer capacitors, the propagation of the pressing force by the pressing plate or the wedge-shaped member is not uniform, and it is not sufficient in terms of uniform shape stabilization in the capacitor element, and the creep does not occur over time. As a result, the pressing force decreases, and as a result, there is a problem in that fluctuations in electrical characteristics cannot be sufficiently reduced. From the viewpoint of reducing fluctuations in electrical characteristics, carbon fiber with a hollow structure, glass, ceramic or insulating resin sealed, and special activated carbon with a small expansion coefficient are used as electrode materials. Not.
The present invention has been made in view of the circumstances as described above, and it is an object of the present invention to provide an electric double layer capacitor in which conduction between a capacitor element and an electrode terminal is ensured and connection stability is excellent.

As a result of intensive studies, the present inventors have found that the above problem can be solved by using a specific resin composition, and have completed the present invention.
That is, the present invention is (1) an electric double layer comprising a pair of a laminate in which an electrolyte gel or electrolyte, a polarizable electrode, a collecting electrode, and an external electrode are laminated and a separator, and an electrode terminal is connected to the external electrode. In the capacitor element, an electric double layer capacitor formed by sealing other than the electrode terminal with a molded body of an expandable resin composition,
(2) The electric double layer capacitor according to the above (1), wherein the expandable resin composition is obtained by blending the thermosetting resin (a) with an additive (b) having an expansion action at the molding processing temperature,
(3) The electric double layer capacitor according to the above (1) or (2), wherein the additive (b) is a core-shell polymer,
(4) The electric double layer capacitor according to (2), wherein the thermosetting resin (a) is an epoxy resin,
(5) The electric double layer capacitor according to any one of (1) to (3) above, wherein the polarizable electrode is an activated carbon fiber cloth, and (6) an external electrode for conducting electricity to the outside of the molded body is attached to the polarizable electrode. And an electric double layer capacitor element obtained by alternately laminating an electrolyte gel or an electrolytic solution with an thermosetting resin (a) and an additive (b) having an expansion action at the molding processing temperature. Provided is a method for producing an electric double layer capacitor, wherein the composition is encapsulated with a composition.

According to the present invention, the expandable resin composition expands during charging and is in close contact with the current collecting electrode. As a result, the contact resistance between the polarizable electrode and the current collecting electrode is more effectively reduced, suppressing the deterioration of the function, and having excellent connection stability in a completely sealed state. A double layer capacitor can be provided.

It is a schematic diagram which shows the condition at the time of shape | molding the electric double layer capacitor of this invention. It is a schematic diagram which shows an example of the structure of a capacitor element (an external electrode and an electrode terminal are not shown). It is sectional drawing which shows the structure of what laminated | stacked the several capacitor element produced in Example 1 (an external electrode and an electrode terminal are not shown).

Hereinafter, preferred embodiments (structures) and manufacturing methods of the electric double layer capacitor of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a schematic view showing a situation when the electric double layer capacitor of the present invention is molded. 1 and 2 are molding dies, 3 is a capacitor element, 4 is an electrode terminal, 5 is an electrode terminal, and 6 is an expandable resin. A molded body 7 of the composition is an external electrode. FIG. 2 is a schematic diagram showing an example of the structure of the capacitor element, where 8 is a polarizable electrode, 9 is an electrolyte gel or electrolyte, 10 is a current collecting electrode, 11 is a separator, and 12 is a gasket.
As the molds 1 and 2 in FIG. 1, it is usually preferable to use those processed from a metal such as stainless steel having heat resistance and corrosion resistance or polyimide which is a heat resistance and corrosion resistance resin.
The capacitor element 3 in FIG. 1 is basically composed of components as shown in FIG. 2, and the electrolyte gel or electrolyte solution 9, the polarizable electrode 8, and the collecting electrode 10 are laminated in this order on both sides of the separator 11. Alternatively, the separator 11 may have a structure in which the polarizable electrode 8, the collector electrode 10, the electrolyte gel, or the electrolytic solution 9 are laminated in this order on both sides of the separator 11.
Further, the polarizable electrode 8 and the electrolyte gel or the electrolytic solution 9 may be one in which 9 is impregnated in the inside of 8 and integrated.

An electrode terminal 4 or 5 is attached to the external electrode 7, and an aluminum or copper foil or lead wire having excellent conductivity is used. The electrode terminal 4 or 5 is exposed to the outside when the entire capacitor element is sealed with an expandable resin composition described later. The external electrode 7 and the electrode terminal 4 or 5 may be integrated.
The polarizable electrode 8 is usually a porous or non-porous carbon material, more specifically a graphitic carbon material obtained by heat treatment of mesophase pitch, petroleum or coal distillation pitch, coke, chemical synthesis pitch, etc. An activated carbon fiber cloth or the like obtained by carbonization activation of phenol resin fibers (novoloid fibers) is preferably used.
The thickness obtained by laminating the polarizable electrode 8 on the current collecting electrode 10 is preferably 30 μm to 0.5 mm. The thicker the thickness, the smaller the amount of separator 11 or current collecting electrode 10 used per capacitance. As a result, the cost of the capacitor can be reduced, but the internal resistance increases. The water content of the polarizable electrode is preferably less than 0.01% by mass, more preferably less than 0.003% by mass.

Examples of the electrolyte gel or the electrolytic solution 9 include tetraethylammonium tetrafluoroborate (Et ₄ NBF) in addition to inorganic salt water-based electrolytic solutions such as sulfuric acid, potassium hydroxide solution, lithium hexafluorophosphate (LiPF ₆ ) and the like. ₄ ), quaternary ammonium salts such as tetramethylammonium tetrafluoroborate, tetrapropylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, trimethylethylammonium tetrafluoroborate (Et ₃ MeNBF ₄ ), triethylmethylammonium tetrafluoroborate , Diethyldimethylammonium tetrafluoroborate, N-ethyl-N-methylpyrrolidinium tetrafluoroborate, N, N-tetramethylenepyrrolidinium tetrafluoroborate, 1-ethyl-3 -Ammonium tetrafluoroborates such as methylimidazolium tetrafluoroborate, tetraethylammonium perchlorate, tetramethylammonium perchlorate, tetrapropylammonium perchlorate, tetrabutylammonium perchlorate, trimethylethyl perchlorate, triethylmethylammonium perchlorate, Ammonium perchlorates such as diethyldimethylammonium perchlorate, N-ethyl-N-methylpyrrolidinium perchlorate, N, N-tetramethylenepyrrolidinium perchlorate, 1-ethyl-3-methylimidazolium perchlorate Phosphonium salts such as tetraethylammonium hexafluorophosphate, tetramethylammonium hexafluoro Ammonium hexafluorophosphates such as sulfate, tetrapropylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, trimethylethylhexafluorophosphate, triethylmethylammonium hexafluorophosphate, diethyldimethylammonium hexafluorophosphate, lithium hexafluorophosphate, lithium Organic electrolytes such as tetrafluoroborate are listed.

Examples of the organic electrolyte solvent include aprotic organic solvents such as chain carbonates such as dimethyl carbonate and diethyl carbonate, cyclic carbonates such as ethylene carbonate and propylene carbonate, and nitriles such as acetonitrile and propionitrile. , Lactones such as γ-butyrolactone, α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, 3-methyl-γ-valerolactone, dimethyl sulfoxide, diethyl sulfoxide, etc. Sulfoxides, amides such as dimethylformamide and diethylformamide, cyclic ethers such as tetrahydrofuran, dimethoxyethane and dioxolane, dimethylsulfolane and sulfolane. These organic solvents can also be used as one or a mixture of two or more.
The concentration of the electrolyte is preferably 0.5 mol / liter (M / L) to 5 M / L. Particularly preferred is 1 M / L to 2.5 M / L. By setting the electrolyte concentration to 0.5 M / L or more, the capacitance is prevented from decreasing. The stability is prevented from being lowered by setting the electrolyte concentration to 5 M / L or less.

As the current collecting electrode 10, a known material and shape can be used. For example, a metal such as aluminum, titanium, tantalum, or nickel, or an alloy such as stainless steel can be used. The thickness of the current collecting electrode 10 is 5 to 100 μm, preferably 10 to 50 μm. The thinner the capacitor, the higher the volume density of the capacitor. However, if it is too thin, it is easy to cut during manufacturing, and continuous production becomes difficult.
As the separator 11, a polymer microporous material having chemical resistance and heat resistance, such as polyethylene, polypropylene, sulfonated polypropylene, polyphenylene, polyphenylene sulfide, polyethylene terephthalate, polyamide, polytetrafluoroethylene (PTFE), polyacetal, and the like. Known insulating materials such as quality films and glass fiber nonwoven fabrics are used.
The thickness of the separator 11 is about 10 to 200 μm, preferably about 15 to 25 μm. By setting the thickness to 10 μm or more, the strength required for processing can be secured, and by setting the thickness to 200 μm or less, the volume density of the capacitor can be increased.
The gasket 12 in FIG. 2 is a packing material for preventing the electrolyte gel or the electrolyte from leaking to the outside.
In any structure, the external electrode 7 must be attached in direct contact with the collecting electrode 10. The external electrode 7 must be provided with an electrode terminal 5 for conducting to the outside.

Next, the molded article of the expandable resin composition will be described in detail.
The subject of the present invention is not limited to the combination of components constituting the electric double layer capacitor, etc., and the whole is sealed with an expansive resin composition to make the contact of each component close and conduct electricity reliably. An object of the present invention is to provide an electric double layer capacitor having excellent connection stability.
The molded body of the expandable resin composition is molded from an expandable resin composition containing a thermosetting resin (a) used as an insulating material as a basic composition and an additive (b) having an expansion action at the molding processing temperature. It is a thing.
The thermosetting resin (a) is not particularly limited as long as it is an insulating material used as a thermosetting material used as a molding material such as an epoxy resin, a phenol resin, an unsaturated polyester resin, or a melamine resin.
Among the above materials, an epoxy resin is preferably used, and any curable epoxy resin having two or more epoxy groups in one molecule may be used. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin Bisphenol AD type epoxy resin, novolak type epoxy resin, glycidyl ester type epoxy resin, or alicyclic epoxy resin. These epoxy resins are preferably those having little chloride ion or sodium ion, and can be used alone or in combination of two or more.
In addition to the above epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, heterocyclic epoxy resins, hydrogenated bisphenol A type epoxy resins, aliphatic epoxy resins, aromatic, aliphatic or alicyclic carboxylic acids An epoxy resin obtained by the reaction of chloroquine with epichlorohydrin, a spiro ring-containing epoxy resin, or the like can be used in combination as appropriate.

Any epoxy resin curing agent can be used as long as it can react with the epoxy resin to cure the epoxy resin.
Specific examples of the curing agent include tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, novolac phenol resin, cresol novolac phenol resin, dicyandiamide, imidazole, aluminum chelate, and BF ₃ . Examples include Lewis acid amine complexes. These curing agents can be used singly or in combination of two or more as long as the curing is not inhibited. A curing accelerator can be used together with the curing agent.

A filler can be added to the thermosetting resin (a).
As the filler, spherical silica powder or fused silica is generally used. Alumina, silicon nitride, boron nitride, calcium carbonate, aluminum hydroxide, talc, and the like can be used. These can be used alone or in combination of two or more.
Of these, those having a low impurity concentration are preferred.
In the thermosetting resin (a), an inorganic filler other than the above, a coupling agent, a fungicidal agent, a pigment, a dye, a shape maintaining agent, and the like can be appropriately blended as long as the present invention is not inhibited. .

Next, the additive (b) having an expansion action at the molding processing temperature of the thermosetting resin (a) will be described.
A typical example of the additive (b) having an expanding action is a core-shell polymer, more specifically, a thermally expandable microcapsule having a double structure, and a low-boiling hydrocarbon or fluorine-based core as an inner layer core. The compound is encapsulated, and the shell of the outer layer is made of a thermoplastic resin such as a polymer selected from styrene, acrylonitrile, methyl methacrylate, methacrylonitrile and vinylidene chloride or a copolymer thereof.
The microcapsules usually have a diameter of about 5 to 50 μm, and the thickness of the outer shell is about 2 to 15 μm. The outer shell is softened by heating, and encapsulated hydrocarbons such as low-boiling isopentane or isobutane, fluorine compounds such as perfluorobutane, perfluoropentane, perfluorohexyne, or water is a gas. Therefore, it has the characteristic of expanding 50 to 100 times.
Examples of commercially available products, Matsumoto Microsphere ^R F Series [for example, "Matsumoto Microsphere F-20", Matsumoto Yushi-Seiyaku Co., Ltd.], EXPANCEL ^R series [for example, "Expancel DU", Expancel Manufactured by Co., Ltd.].
The addition amount of the additive (b) is 5 to 20 parts by mass (solid content conversion), preferably about 10 parts by mass with respect to 100 parts by mass of the thermosetting resin (a). By setting it to 5 parts by mass or more, an appropriate expansion effect can be exhibited, and by setting it to 20 parts by mass or less, excessive expansion is prevented from occurring and an increase in cost is suppressed.
A thermally expandable microcapsule having a double structure in which a low-boiling point hydrocarbon or fluorine-based compound is encapsulated as the core of the inner layer and the shell of the outer layer is made of a thermoplastic resin is disclosed in, for example, JP-T-2002-511900. And WO 2004/074396.

Next, an example of the manufacturing method (molding procedure) of the electric double layer capacitor of the present invention will be described in detail with reference to FIGS.
First, the electrolyte gel or electrolyte solution 9, the polarizable electrode 8, and the collector electrode 10 are laminated in this order. Two laminates are prepared, and then two laminates are arranged on both sides of the separator 11 so that the electrolyte gel or the electrolyte solution 9 is in contact with each other, and gaskets 12 are attached to the four end faces, as shown in FIG. The double layer capacitor element shown is produced. The external electrode 7 and the electrode terminal 5 are attached to the current collecting electrode 10 in advance.
Next, the produced double layer capacitor element is placed in molding dies 1 and 2 as shown in FIG. 1, and an expandable resin composition is injected from the injection hole, and then heated and cured under pressure.
Heat curing is preferably performed at 70 to 100 ° C. for about 10 minutes. Further, it is preferable to take out from the mold and post-cure as necessary.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.
[Example 1]
Two laminates were prepared in which an electrolyte gel layer was attached to one surface of the polarizable electrode layer, and a collector electrode, an external electrode and an electrode terminal were attached to the other surface. Next, the electrolyte gel layer side of the two laminates was attached to both sides of a separator (a porous polypropylene film having a thickness of 25 μm), and the periphery was fixed with a gasket to produce a capacitor element.
Next, 13 capacitor elements stacked and integrated (thickness: about 1.3 mm) (shown in FIG. 3) are placed in two molds as shown in FIG. The expandable resin composition was injected into the space between the molds and cured by heating at 90 ° C. for 10 minutes. Next, the molded body obtained by removing the two molds was further heated at 90 ° C. for 60 minutes to be post-cured, whereby parts other than the electrode terminals were sealed with an expandable resin composition. A multilayer capacitor was fabricated.
The expandable resin composition was separately prepared as follows.
Epicoat 828 as a thermosetting resin (Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent 190) 100 parts by mass, aliphatic polyamine as a curing agent [Jeffamine D230, manufactured by Mitsui Chemicals Fine Co., Ltd.] 30 150 parts by mass of fused silica [RD-8, manufactured by Tatsumori Co., Ltd.] as a filler, Matsumoto Microsphere F-20 [core-shell type polymer manufactured by Matsumoto Yushi Seiyaku Co., Ltd.] 5 parts by mass of the above microcapsules were mixed using a Henschel mixer to prepare an expandable resin composition.

[Example 2]
Sealed with an expandable resin composition in the same manner as in Example 1 except that EXPANSEL DU [Expandel Co., Ltd. core-shell type polymer, sold by Nippon Philite Co., Ltd.] was used as an additive having an expansion action. A stationary electric double layer capacitor was produced.

[Comparative Example 1]
A comparative electric double layer capacitor sealed with a curable resin was produced in the same manner as in the example except that Matsumoto Microsphere F-20 was not used.

〔Evaluation methods〕
Using the electric double layer capacitors obtained in Examples 1 and 2 and Comparative Example, an equivalent series using an LCR meter (Agilent Technology HP4284A) at 1 kHz and 1.0 V at the initial stage and after 1000 hours at 70 ° C. Resistance (ESR) was measured and the results are shown in Table 1.

As shown in Table 1 above, according to the present invention, it is possible to stably manufacture an electric double layer capacitor in which ESR is low and an increase in ESR over time is suppressed (change in electrical characteristics is small). This can contribute to miniaturization and high performance of portable devices. Furthermore, the reliability of the device is improved.

1: Mold 2: Mold 3: Capacitor element 4: Electrode terminal 5: Electrode terminal 6: Molding of expandable resin composition 7: External electrode 8: Polarizable electrode 9: Electrolyte gel or electrolyte 10: Current collection Electrode 11: Separator 12: Gasket

Claims (6)

  In an electric double layer capacitor element comprising a separator and a laminate of an electrolyte gel or electrolyte solution, a polarizable electrode, a collecting electrode, and an external electrode and an electrode terminal connected to the external electrode. An electric double layer capacitor formed by sealing with a molded body of an expandable resin composition.   The electric double layer capacitor according to claim 1, wherein the expandable resin composition is obtained by blending the thermosetting resin (a) with an additive (b) having an expansion action at the molding processing temperature. The electric double layer capacitor according to claim 1 or 2, wherein the additive (b) is a core-shell polymer. The electric double layer capacitor according to claim 2, wherein the thermosetting resin (a) is an epoxy resin. The electric double layer capacitor according to any one of claims 1 to 3, wherein the polarizable electrode is an activated carbon fiber cloth. An electric double layer capacitor element in which an external electrode for conducting electricity to the outside of a molded body is attached to a polarizable electrode and an electrolyte gel or an electrolytic solution is alternately laminated is formed on a thermosetting resin (a), and its molding processing temperature. A method for producing an electric double layer capacitor, comprising: sealing molding with an expandable resin composition containing an additive (b) having an expansion action in 1.

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