JP2664808B2 - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To convert into an amorphous substance and lower the crystal temperature and to make the movement of ions easier and increase the ion conductivity, by making an organic polymer out of a monomer having specific structure. CONSTITUTION:An organic polymer has a structure shown by a formula I, and an organic compound having a skeleton shown by a formula II is reacted to form bridges. Here, Z is a residue of an active hydrogen compound, Y is an active hydrogen group or a reactive functional group, m is an integer of 1-250, k is an integer of 1-12, and A is a structure shown by the formula II. And, n is an integer of 0-25, R is an alkyl group, an alkenyl group, an aryl group, or an alkyl aryl group of 1-20C. The organic compound shown by the formula II is obtained by reacting singly a glycidyl ether to a compound containing active hydrogen independently, or by reacting a glycidyl ether with ethylene oxide, or by reacting a compound containing a reactive functional group to polyether obtained by reacting with the ethylene oxide.

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 using a solid electrolyte.

[0002]

2. Description of the Related Art As a conventional electrolyte for an electric double layer capacitor, a liquid electrolyte, particularly a combination of an organic electrolyte and a quaternary ammonium salt, has been used. However, such an electrolyte leaks to the outside and has a problem in long-term reliability and stability.

In consideration of this point, solid electrolytes have been studied. Examples of the solid electrolyte include an organic polymer electrolyte of polyethylene oxide (PEO), an organic polymer electrolyte in which a polyethylene oxide portion and a propylene oxide portion of a polyfunctional polyether molecular structure are randomly copolymerized (JP-A-62-249361), Solid polymer electrolyte comprising ethylene oxide copolymer containing ionic compound in dissolved state (JP-A-61-83249)
Etc. are known.

[0004]

However, in the above-mentioned linear PEO, crystallization of the PEO occurs at a temperature lower than the melting point (around 60 ° C.), and the ionic conductivity sharply decreases. In other polymer electrolytes, the crystallization is suppressed, so that the conductivity at room temperature around 25 ° C. is improved, but the conductivity at a temperature lower than that is not a practically usable value and is 5 ° C. Below, it will drop extremely.

An object of the present invention is to provide an electric double layer capacitor which has high reliability and safety for a long time and has improved low-temperature characteristics, that is, has high ionic conductivity even at low temperatures, without any fear of liquid leakage to the outside. With the goal.

[0006]

The electric double layer capacitor of the present invention is an electric double layer capacitor using a solid electrolyte obtained by doping an organic polymer with an ionic compound as a binder of an electrode material or an electrolyte. The organic polymer is represented by the general formula: Z-[-(A) _m -Y] _k (where Z is an active hydrogen-containing compound residue, Y is an active hydrogen group or a reactive functional group, and m is 1 to An integer of 250, k is 1 to 1
And A is an integer of 2

Embedded image Wherein n is an integer of 0 to 25, and R is an alkyl group, an alkenyl group, an aryl group or an alkylaryl group having 1 to 20 carbon atoms.) It is.

In another electric double layer capacitor according to the present invention, the organic polymer has a general formula: Z-[-EY] _k (where Z is an active hydrogen-containing compound residue, Y is an active hydrogen group or The reactive functional group, k is an integer of 1 to 12, E is a block structure composed of (A) _m and (CH ₂ CH ₂ O) _p , and A is

Embedded image Wherein n is an integer of 0 to 25, R is an alkyl group, alkenyl group, aryl group or alkylaryl group having 1 to 20 carbon atoms, m is an integer of 1 to 250, and p is 1 to 4
And an organic compound having a skeleton represented by the following formula:

The organic compound used as the material of the organic polymer of the solid electrolyte includes an active hydrogen-containing compound,
(a) reacting glycidyl ethers alone, or (b)
Glycidyl ethers are reacted with ethylene oxide, or (c) are obtained by reacting a reactive functional group-containing compound with a polyether obtained by reacting glycidyl ethers with ethylene oxide, usually having an average molecular weight of It is preferable that it is 20,000 or less. In the above (a) and (b), Y in the above general formula
Is a compound having an active hydrogen group, and in (c) above, a compound having Y in the above general formula is a reactive functional group.

Examples of the active hydrogen-containing compound include monohydric alcohols such as methanol and ethanol, polyhydric alcohols such as ethylene glycol, propylene glycol, 1,4-butanediol, glycerin, trimethylolpropane and polyglycerin, butylamine, and the like. Amine compounds such as 2-ethylhexylamine, ethylenediamine, hexamethylenediamine, and triethylenetetramine;
Examples thereof include phenolic active hydrogen compounds such as bisphenol A and hydroquinone, and compounds having different types of active hydrogen-containing groups in one molecule such as monoethanolamine and diethanolamine. Among them, polyhydric alcohols are preferable.

The above-mentioned glycidyl ethers include the following chemical formula 5:

Embedded image (Where n is an integer of 0 to 25, and R is an alkyl group, alkenyl group, aryl group or alkylaryl group having 1 to 20 carbon atoms). As a typical example, R is, for example, a linear alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group; a branched alkyl group such as an isopropyl group, a sec-butyl group or a tert-butyl group; Alkenyl groups such as allyl group, 1-propenyl group and 1,3-butadienyl group; aryl groups such as phenyl group and benzyl group; and alkylaryl groups. Is more preferably 1 to 12.

As described above, the organic compound may be a compound in which a glycidyl ether is singly bonded to an active hydrogen-containing compound or a compound in which glycidyl ether is bonded by block copolymerization with ethylene oxide. In any case, the number of moles of the glycidyl ether added is 1 to 250 per active hydrogen of the active hydrogen-containing compound.
It is preferable that the number of moles of ethylene oxide to be block-copolymerized with the glycidyl ether is 1 to 450 mole per one active hydrogen. In the case of block copolymerizing glycidyl ethers and ethylene oxide, there is no particular limitation on the positional relationship and the number of blocks, but it is appropriate to appropriately select the number of moles added so that the average molecular weight of the organic compound does not become larger than 20,000. preferable.

When the main chain terminal group Y is a reactive functional group, a glycidyl ether or a glycidyl ether and ethylene oxide are reacted with an active hydrogen-containing compound to obtain a polyether, and the end of the main chain is reacted. The reactive functional group is an alkenyl group such as a vinyl group, a group having an unsaturated bond such as an acryloyl group or a methacryloyl group, or a group having a linear or cyclic portion containing Si. Can be mentioned. These groups are introduced into the molecule by reacting the polyether with a reactive functional group-containing compound.

The reactive functional group-containing compound includes, for example, an unsaturated bond with a carboxyl group in one molecule such as acrylic acid, methacrylic acid, cinnamic acid, maleic acid, fumaric acid and p-vinylbenzoic acid. Having, or maleic anhydride, acid anhydrides of the above compounds such as itaconic anhydride, or acid chlorides of the above compounds, allyl glycidyl ether, glycidyls such as glycidyl methacrylate, isocyanates such as methacryloyl isocyanate, dichlorosilane, Examples include compounds containing Si, such as dimethylvinylchlorosilane.

As the catalyst used for the reaction for producing the organic compound, a basic catalyst such as sodium methylate, caustic soda, caustic potash, lithium carbonate and the like is generally used, but an acidic catalyst such as boron trifluoride, a trimethylamine Also, amine catalysts such as triethylamine are useful. The amount of the catalyst used is arbitrary.

The reaction of crosslinking the organic compound into an organic polymer is performed using a crosslinking agent when Y in the above general formula is an active hydrogen group. Useful crosslinking agents include organic compounds having an isocyanate group, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, triphenylmethane diisocyanate, tris (isocyanatophenyl) thiophosphate. To
Examples include aromatic compounds such as trimethylolpropane TDI 3-mol adduct, aliphatic compounds such as hexamethylene diisocyanate, and mixtures thereof. When an isocyanate is used, the quantitative ratio of such a crosslinking agent is preferably such that the number of isocyanate groups is 1 to 1.5 times the number of active hydrogen groups at the main chain terminal of the organic compound. At this time, as a catalyst for completing the crosslinking reaction at an early stage, for example, an organic metal catalyst such as dibutyltin dilaurate, dibutyltin diacetate, lead octenoate, triethylenediamine, N, N'-dimethylpiperazine, N-methylmorpholine, triethylamine And the like may be used.

The reaction of crosslinking an organic compound in which the main chain terminal group Y is a reactive functional group into an organic polymer is carried out by polymerization or condensation. This reaction is carried out by light, heat, ionizing radiation or the like using a polymerization initiator or a sensitizer as necessary.

As the ionic compound to be doped into the organic polymer, for example, LiClO ₄ , LiSCN, LiCl
BF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ C
L of O ₂ , NaI, NaSCN, NaBr, KSCN, etc.
i. an inorganic ionic salt containing one of Na, K, (C
H ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NCl
_{O 4, (C 2 H 5} ) 4 NI, (C 3 H 7) 4 NBr, (n-C 4
_{H 9) 4 NClO 4, (} n-C 4 H 9) 4 NI, (C 2 H 5) 4
_{N-maleate, (C 2 H} 5) 4 -benzoat
_{e, (C 2 H 5)} 4 quaternary ammonium salts such as N-phtalate, lithium stearyl sulfonate, sodium octyl sulfonate, and organic ion salts of lithium dodecylbenzenesulfonate. These ionic compounds may be used in combination of two or more.

The compounding ratio of the ionic compound is 0.0001 to 5.0 mol, preferably 0.005 to 2.0 mol, based on the number of ether-bonded oxygen in the organic polymer. Preferably it is. If the amount of the ionic compound used is too large, an excessive amount of the ionic compound, for example, an inorganic ionic salt is not dissociated, but merely mixed, resulting in a decrease in ionic conductivity.

The method of doping the ionic compound into the organic polymer is not particularly limited. For example, methyl ethyl ketone (MEK) or tetrahydrofuran (T
After dissolving in an organic solvent such as HF) and uniformly mixing with the organic compound, the organic solvent is removed by vacuum reduction.

In the present invention, the solid electrolyte may contain a substance capable of dissolving the ionic compound contained in the organic polymer. By including such a substance, the conductivity can be significantly improved without changing the basic skeleton of the organic polymer. Examples of the substance capable of dissolving the ionic compound include cyclic carbonates such as propylene carbonate and ethylene carbonate, cyclic esters such as γ-butyrolactone, tetrahydrofuran or a derivative thereof, dioxolane or a derivative thereof, and sulfolane or a derivative thereof. These may be used alone or in combination of two or more. However, the present invention is not limited to these, and the mixing ratio and the mixing method are arbitrary.

Examples of the electrode material include electrode materials which do not involve the capacitance of the oxide film derivative in the electrolytic capacitor, such as activated carbon or carbon fiber having a large specific surface area and being electrochemically inert. It is preferable to use the above-described solid electrolyte as a binder for the carbon material. Of course, a substance other than the solid electrolyte, for example, polytetrafluoroethylene or the like may be used, and in that case, the solid electrolyte may be used in combination.

[0022]

Since the organic polymer is composed of a monomer having a specific structure, the organic polymer structure becomes amorphous, and has a side chain similar to the main chain, so that the crystallization temperature of the organic polymer is lowered. For this reason, the movement of ions is facilitated, the ion conductivity in a temperature range equal to or lower than room temperature is improved, and the quality is stable. Furthermore, because it is thermosetting, it can take various shapes,
A film having excellent adhesion to the electrode surface can be produced. Further, since the solid electrolyte is used, there is no danger of liquid leakage to the outside, and the long-term reliability and safety are extremely high. Therefore, it is possible to provide a very excellent and practical electric double-layer capacitor with improved low-temperature characteristics and reliability and safety.

[0023]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to these.

Example 1 An activated carbon electrode was used as an electrode. The activated carbon electrode used was a mixture of activated carbon (having a specific surface area of about 2000 m ² / g) and a solid electrolyte. As the organic polymer of the solid electrolyte, a compound represented by the following general formula:

Embedded image n: 2, m: 9, R: —CH ₃ , Y: OCCH =
CH ₂ , an organic compound having an average molecular weight of k: 3 and having an average molecular weight of 5,000 (calculated from a hydroxyl value) was used.

The electrodes were manufactured as follows. That is, 1 part by weight of lithium perchlorate and 0.05 part by weight of azobisisobutyronitrile were dissolved in 10 parts by weight of the above organic compound, and this was dissolved in a dry inert gas atmosphere with activated carbon at a ratio of 1: 1. The mixture was mixed, cast on a stainless steel substrate, and cured by leaving it at 100 ° C. for 1 hour in an inert gas atmosphere to obtain an electrode sheet. The sheet thickness is 0.60m
m. The sheet was punched to a diameter of 13 mm to obtain an activated carbon electrode.

Next, an electrolyte layer was formed on the activated carbon electrode as follows. That is, 1 part by weight of lithium perchlorate and 0.05 part by weight of azobisisobutyronitrile were dissolved in 10 parts by weight of the organic compound, and the resultant was cast on the activated carbon electrode. ° C, 1
It was cured by leaving it to stand for a time.

The above-described activated carbon electrode was brought into contact with the electrolyte of the composite sheet of the activated carbon electrode and the electrolyte formed in this manner to produce an electric double layer capacitor. FIG. 1 is a sectional view of the electric double layer capacitor.
1 is an electrolyte layer, 2 is an activated carbon electrode, and 3 is a gasket for insulating the case and the sealing plate. The gasket 3 is made of a material such as modified polypropylene and modified polyethylene. The size of the electric double layer capacitor is 18.4 m in outer diameter.
m, and the total height was 2.0 mm.

Comparative Example In place of the organic compound of the solid electrolyte of Example 1, an organic compound having a main chain linear type ethylene oxide (molecular weight 2
500) was used. Others are the same as the first embodiment.

With respect to the electric double layer capacitors of Example 1 and Comparative Example, the following constant current continuous tests (I) and (II) were performed to check the capacitance. (I) 1 hour at a constant current of 1.0 mA at 25 ° C. or a maximum of 1.
After charging to 5 V, discharging was performed at a constant current of 100 μA until the voltage reached 0 V. (II) 1 hour at 25 ° C. and a constant current of 1.0 mA or up to 2.
After charging to 5 V, discharging was performed at a constant current of 500 μA until the voltage reached 0 V.

FIG. 2 and FIG. 3 show discharge curves obtained in the above constant current continuous test. In the above (I), the capacitance of the capacitor of Example 1 was 1.20 F, while the capacitance of the comparative example was 0.20 F.
It was 1F. In the above (II), the capacitance of the capacitor of Example 1 was 0.32F, whereas that of the comparative example was 0.05F.

Example 2 Instead of 1 part by weight of the ionic compound of Example 1, ie, lithium perchlorate, 1.2 parts by weight of tetrabutylammonium perchlorate was used. Others are the same as the first embodiment.

The tests of the above (I) and (II) were also performed on the capacitor of Example 2. 2 and 3 show discharge curves. The capacitance of the capacitor of Example 2 was 0.91 F in (I) and 0.24 F in (II).

EXAMPLE 3 0.05 parts by weight of azobisisobutyronitrile was dissolved in 10 parts by weight of the same organic compound as in Example 1, and 1 part by weight of lithium perchlorate and 20 parts by weight of propylene carbonate were mixed. This was mixed with activated carbon at a ratio of 1: 1 under a dry inert gas atmosphere, cast on a stainless steel substrate, and allowed to stand at 100 ° C. for 1 hour under an inert gas atmosphere to be cured to obtain an electrode sheet. This sheet was punched out to a diameter of 13 mm to produce an activated carbon electrode. The thickness of the sheet was 0.60 mm. Next, an electrolyte layer was formed on the activated carbon electrode. That is, 10 parts by weight of the same organic compound as in Example 1 was added to azobisisobutyronitrile 0.1 part by weight.
05 parts by weight, 1 part by weight of lithium perchlorate and 20 parts by weight of propylene carbonate are mixed, cast on the activated carbon electrode, and left at 100 ° C. for 1 hour in an inert gas atmosphere. To form an electrolyte layer. The same activated carbon electrode as described above was brought into contact with the electrolyte of the composite sheet composed of the activated carbon electrode and the electrolyte thus formed to produce an electric double layer capacitor. The size of the capacitor is the same as that of the first embodiment.

The tests of the above (I) and (II) were also performed on the capacitor of Example 3. 2 and 3 show discharge curves. The capacitance of the capacitor of Example 3 was 1.70 F in the above (I) and 1.58 F in the above (II). In this embodiment, propylene carbonate, which is a substance capable of dissolving the ionic compound, is added.
The conductivity of the electrolyte is increased, and energy loss for ion transfer to the electrolyte-side interface can be reduced.

Example 4 1.2 parts by weight of tetrabutylammonium perchlorate was used in place of 1 part by weight of the ionic compound of Example 3, ie, lithium perchlorate. Others are the same as the third embodiment.

The tests of the above (I) and (II) were also performed on the capacitor of Example 4. 2 and 3 show discharge curves. The capacitance of the capacitor of Example 4 was 1.72F in the above (I) and 1.58F in the above (II).

Example 5 As an organic compound to be an organic polymer, a compound represented by the following general formula:
In the formula, Z:

Embedded image n: 2, m: 9, R: -CH 3, Y: H, k:
3 was used. To 10 parts by weight of this organic compound, 20 parts by weight of propylene carbonate, 0.5 part by weight of a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate at 80:20, and a trace amount of dibutyltin diacetate were added. In addition, the mixture was sufficiently mixed, and an activated carbon electrode and a solid electrolyte were prepared in the same manner as in Example 1 using the mixture.

The test of the above (I) and (II) was also performed on the capacitor of Example 5. 2 and 3 show discharge curves. The capacitance of the capacitor of Example 5 was 1.69 F in the above (I) and 1.57 F in the above (II).

Examples 6 to 12 Capacitors were prepared in the same manner as in Example 3 by using the compounds shown in Table 1 in the general formulas (3), (3) and (4) as the organic compound to be the organic polymer. And the above-mentioned tests (I) and (II). Table 1 also shows the results.

[0040]

[Table 1]

[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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[0046]

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[0047]

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[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

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[0055]

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[0056]

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[0057]

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[0058]

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As is apparent from the above embodiments, the electric double layer capacitor of the present invention has a good electric capacity even at a low temperature.

[0060]

As described above, according to the present invention, it is possible to provide an electric double layer capacitor having improved low-temperature characteristics, that is, having high ionic conductivity even at low temperatures. Moreover, since a solid electrolyte is used, an electric double-layer capacitor with high reliability and safety for a long time can be provided without any fear of leakage to the outside.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a discharge curve obtained by a constant current continuous test under one condition for the electric double layer capacitors of the respective examples and comparative examples.

FIG. 3 is a diagram showing a discharge curve obtained in a constant current continuous test under different conditions for the electric double layer capacitors of the respective examples and comparative examples.

[Explanation of symbols]

 1 electrolyte layer 2 activated carbon electrode 3 gasket

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomohiko Noda 6-6 Josaicho, Takatsuki-shi, Osaka Yuasa Battery Co., Ltd. (72) Inventor Kenji Hongami No.2 A-25-106, Nobomachi, Takatsuki-shi, Osaka (72) Inventor Shigeo Mori 35-1 Katsura-Chiyoharacho, Nishikyo-ku, Kyoto-shi, Kyoto (56) Reference JP-A-62-249361 (JP, A) JP-A-61-83249 (JP, A)

Claims (10)

(57) [Claims] An electric double layer capacitor using a solid electrolyte obtained by doping an organic polymer with an ionic compound as an electrolyte, wherein the organic polymer has a general formula: Z-[-(A) _m -Y] _k (where Z is an active hydrogen-containing compound residue, Y is an active hydrogen group or a reactive functional group, m is an integer of 1 to 250, and k is 1 to 1
A is an integer of 2, and A is Wherein n is an integer of 0 to 25, and R is an alkyl group, an alkenyl group, an aryl group or an alkylaryl group having 1 to 20 carbon atoms.) An electric double layer capacitor characterized by the following. 2. An electric double layer capacitor using a solid electrolyte obtained by doping an ionic compound into an organic polymer as a binder of an electrode material, wherein the organic polymer is
General formula: Z-[-(A) _m -Y] _k (where Z is an active hydrogen-containing compound residue, Y is an active hydrogen group or a reactive functional group, m is an integer of 1 to 250, and k is 1 ~ 1
And A is an integer of 2 Wherein n is an integer of 0 to 25, and R is an alkyl group, an alkenyl group, an aryl group or an alkylaryl group having 1 to 20 carbon atoms.) An electric double layer capacitor characterized by the following. 3. An electric double-layer capacitor using a solid electrolyte obtained by doping an organic polymer with an ionic compound as an electrolyte, wherein the organic polymer has a general formula: Z-[-EY] _k . Here, Z is an active hydrogen-containing compound residue, Y is an active hydrogen group or a reactive functional group, k is an integer of 1 to 12, and E is a block consisting of (A) _m and (CH ₂ CH ₂ O) _p A structure, wherein A is: Wherein n is an integer of 0 to 25, R is an alkyl group, alkenyl group, aryl group or alkylaryl group having 1 to 20 carbon atoms, m is an integer of 1 to 250, and p is 1 to 4
An electric double layer capacitor characterized by being cross-linked by reacting an organic compound having a skeleton represented by the following formula: 4. An electric double layer capacitor using a solid electrolyte obtained by doping an ionic compound into an organic polymer as a binder for an electrode material, wherein the organic polymer is
General formula: Z-[-EY] _k (where Z is an active hydrogen-containing compound residue, Y is an active hydrogen group or a reactive functional group, k is an integer of 1 to 12, and E is (A A) a block structure consisting of _m and (CH ₂ CH ₂ O) _p , wherein A is Wherein n is an integer of 0 to 25, R is an alkyl group, alkenyl group, aryl group or alkylaryl group having 1 to 20 carbon atoms, m is an integer of 1 to 250, and p is 1 to 4
An electric double layer capacitor characterized by being cross-linked by reacting an organic compound having a skeleton represented by the following formula: 5. The electric double layer capacitor according to claim 1, wherein the solid electrolyte contains a substance capable of dissolving the ionic compound. 6. The organic compound having an average molecular weight of 2,000
The electric double layer capacitor according to any one of claims 1 to 4, wherein the value is 0 or less. 7. The electric double layer capacitor according to claim 1, wherein the organic polymer is obtained by crosslinking the organic compound in which Y is an active hydrogen group using a crosslinking agent. . 8. The electric double layer capacitor according to claim 7, wherein the crosslinking agent is an organic compound having an isocyanate group. 9. The electric double layer capacitor according to claim 8, wherein the organic compound having an isocyanate group is an aromatic compound. 10. The electric double layer capacitor according to claim 1, wherein the organic polymer is obtained by crosslinking the organic compound in which Y is a reactive functional group by polymerization or condensation. .