JP2011044632A - Electrolyte for electric double layer capacitor and electric double layer capacitor - Google Patents

Electrolyte for electric double layer capacitor and electric double layer capacitor Download PDF

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JP2011044632A
JP2011044632A JP2009192855A JP2009192855A JP2011044632A JP 2011044632 A JP2011044632 A JP 2011044632A JP 2009192855 A JP2009192855 A JP 2009192855A JP 2009192855 A JP2009192855 A JP 2009192855A JP 2011044632 A JP2011044632 A JP 2011044632A
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double layer
electric double
layer capacitor
electrolytic solution
sulfone
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JP5296637B2 (en
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Tsukasa Ueda
司 上田
Kazumi Chiba
一美 千葉
Yasufumi Yamaguchi
容史 山口
Takehiro Hiyama
武寛 檜山
Ichiro Fushiya
一郎 伏屋
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Sumitomo Seika Chemicals Co Ltd
Japan Carlit Co Ltd
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Japan Carlit Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for an electric double layer capacitor, which has high electrical conductivity and breakdown voltage, shows stable liquid state over a wide temperature range, particularly at low temperatures without solidification and without deposition of salt, shows excellent electric characteristics, and also has superior long-period reliability. <P>SOLUTION: The electrolyte for electric double layer capacitor is the electrolyte having quaternary ammonium salt dissolved in an organic solvent, wherein the organic solvent contains chain sulfone expressed by general formula (1) (R1, R2 represent linear or branched 1C-5C alkyl groups which may be identical or different), and the quaternary ammonium salt is represented by general formula (2) (m and n are integers of 4 to 6, and X<SP>-</SP>represents an acid component). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、電気二重層キャパシタ用電解液に関し、更に詳細には、スピロ型第4級アンモニウム塩及び鎖状スルホンを使用した、耐電圧が高く、広範な温度で使用可能であり、特に低温で凝固することなく優れた電気的特性を示し、長期信頼性にも優れる電気二重層キャパシタ用電解液及び該電解液を利用した電気二重層キャパシタに関する。   The present invention relates to an electrolytic solution for an electric double layer capacitor. More specifically, the present invention uses a spiro-type quaternary ammonium salt and a chain sulfone, has a high withstand voltage, and can be used at a wide range of temperatures. The present invention relates to an electrolytic solution for an electric double layer capacitor that exhibits excellent electrical characteristics without being solidified and has excellent long-term reliability, and an electric double layer capacitor using the electrolytic solution.

電気二重層キャパシタは、重金属等の環境負荷物質を含まず安全であり、パワー密度が大きく、優れた充放電サイクル寿命を有しているという特徴を持つため、近年、瞬停補償装置や電気自動車等様々な分野への利用が進められている。   Electric double layer capacitors are safe because they do not contain environmentally hazardous substances such as heavy metals, have high power density, and have excellent charge / discharge cycle life. Etc. are being used in various fields.

しかしながら、この電気二重層キャパシタの問題点として、分極性電極に活性炭を使用するため、電解液の分解電圧を越えるような高い電圧で使用すると、電気二重層キャパシタの内部抵抗増大や容量減少を招いてしまうことが挙げられる。   However, as a problem of this electric double layer capacitor, since activated carbon is used for the polarizable electrode, if it is used at a high voltage exceeding the decomposition voltage of the electrolyte, the internal resistance of the electric double layer capacitor is increased and the capacity is reduced. It can be mentioned.

したがって、電気二重層キャパシタに用いられる電解液は、高い電気伝導性を有するとともに、電気化学的安定性に優れることが要求される。加えて、電気二重層キャパシタは過酷な条件下において使用されることが想定されるため、その電解液としては、低温から高温に至るまでの広い温度範囲において、電気二重層キャパシタを長期間安定に作動させることのできる特性も重要である。   Therefore, the electrolytic solution used for the electric double layer capacitor is required to have high electrical conductivity and excellent electrochemical stability. In addition, since electric double layer capacitors are assumed to be used under severe conditions, the electrolyte solution is stable for a long time in a wide temperature range from low temperature to high temperature. The characteristics that can be activated are also important.

特許文献1及び非特許文献1に記載されているように、従来の一般的な電気二重層キャパシタ用電解液としては、有機溶媒であるプロピレンカーボネートに、電解質として脂肪族第4級アンモニウム塩であるテトラフルオロホウ酸テトラエチルアンモニウムを溶解させたものが使用されている。   As described in Patent Document 1 and Non-Patent Document 1, the conventional electrolyte for a general electric double layer capacitor is propylene carbonate, which is an organic solvent, and an aliphatic quaternary ammonium salt, which is an electrolyte. A solution in which tetraethylammonium tetrafluoroborate is dissolved is used.

しかしながら、上記のプロピレンカーボネートを溶媒とした電解液では、印加電圧が2.6〜2.8Vに達すると溶媒が分解し始めることから、該電解液を用いた場合の電気二重層キャパシタの最大印加電圧は、2.5V前後となり、耐電圧としては不十分であるという問題点があった。   However, in the electrolytic solution using propylene carbonate as a solvent, when the applied voltage reaches 2.6 to 2.8 V, the solvent starts to decompose, so that the maximum application of the electric double layer capacitor when using the electrolytic solution is performed. The voltage was around 2.5 V, and there was a problem that the withstand voltage was insufficient.

また、特許文献2に、耐電圧の向上を目的として、有機溶媒にスルホランと3−メチルスルホランの混合液、スルホランと2,4−ジメチルスルホランの混合液などを用いた電解液が提案されている。   Patent Document 2 proposes an electrolytic solution using a mixed solution of sulfolane and 3-methylsulfolane, a mixed solution of sulfolane and 2,4-dimethylsulfolane as an organic solvent for the purpose of improving withstand voltage. .

しかし、スルホランの融点が+29℃、3−メチルスルホランの融点が+6℃、2,4−ジメチルスルホランの融点が−3℃と比較的高いため、低温では電解液が凝固し、電気二重層キャパシタの特性が著しく低下してしまうという問題点があった。   However, the melting point of sulfolane is + 29 ° C., the melting point of 3-methylsulfolane is + 6 ° C., and the melting point of 2,4-dimethylsulfolane is relatively high at −3 ° C. There is a problem that the characteristics are remarkably deteriorated.

さらに、特許文献3及び特許文献4に、電解質としてテトラフルオロホウ酸テトラエチルアンモニウムを使用し、鎖状スルホンを有機溶媒に用いた電気二重層キャパシタ用電解液が提案されている。   Further, Patent Document 3 and Patent Document 4 propose an electrolytic solution for an electric double layer capacitor using tetraethylammonium tetrafluoroborate as an electrolyte and using a chain sulfone as an organic solvent.

しかしながら、テトラフルオロホウ酸テトラエチルアンモニウムは、鎖状スルホンに対する溶解度が1.0mol/L以下と著しく低く、実用的ではない。加えて、一般的な電気二重層キャパシタ用電解液の電解質である、テトラフルオロホウ酸トリエチルメチルアンモニウムやテトラフルオロホウ酸テトラエチルアンモニウムは、高電圧印加時にホフマン分解を起こし、エチル基が離脱しやすいという問題点があった。   However, tetraethylammonium tetrafluoroborate has a remarkably low solubility with respect to chain sulfone of 1.0 mol / L or less, and is not practical. In addition, triethylmethylammonium tetrafluoroborate and tetraethylammonium tetrafluoroborate, which are electrolytes for electrolytes for general electric double layer capacitors, cause Hoffman decomposition when a high voltage is applied, and the ethyl group is easily released. There was a problem.

また特許文献5に、溶媒がスルホラン又はその誘導体15〜85体積%、鎖状炭酸エステルとしてエチルメチルカーボネートを85〜15体積%を含む溶媒に、第4級オニウム塩を溶解した電解液を、ポリアセン骨格を有する有機半導体材料を電極に用いた有機電解質電池に用いる事が提案されている。   Patent Document 5 discloses an electrolyte solution in which a quaternary onium salt is dissolved in a solvent containing 15 to 85% by volume of sulfolane or a derivative thereof and 85 to 15% by volume of ethyl methyl carbonate as a chain carbonate. The use of an organic semiconductor material having a skeleton for an organic electrolyte battery using an electrode has been proposed.

しかし、電解液の耐電圧は、スルホランよりも耐酸化性に劣るエチルメチルカーボネートが律してしまうため、耐電圧が著しく劣ってしまうという問題点があった。   However, the withstand voltage of the electrolytic solution has a problem that the withstand voltage is remarkably inferior because ethylmethyl carbonate, which is inferior in oxidation resistance to sulfolane, is limited.

さらに特許文献6では、スルホラン:鎖状スルホンを70〜90:30〜10で混合した有機溶媒に、第4級アンモニウム塩であるテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウム等を溶解させた電解液を、電気二重層キャパシタに用いることが提案されている。   Furthermore, in Patent Document 6, tetrafluoroborate spiro- (1,1 ′)-bipyrrolidinium, which is a quaternary ammonium salt, is dissolved in an organic solvent in which sulfolane: chain sulfone is mixed at 70 to 90:30 to 10. It has been proposed that the electrolyte solution thus used is used for an electric double layer capacitor.

しかし、この電解液は、極低温下では凝固が生じる場合があり、また長期信頼性の面においても十分なものとはいえなかった。   However, this electrolytic solution may solidify at extremely low temperatures, and it cannot be said that the long-term reliability is sufficient.

特開2000−114105号公報JP 2000-114105 A 特開平7−74061号公報JP-A-7-74061 特開平9−92579号公報JP 9-92579 A 特開平9−205041号公報Japanese Patent Laid-Open No. 9-205041 特開平10−27623号公報Japanese Patent Laid-Open No. 10-27623 特開2008−171902号公報JP 2008-171902 A

監修:西野 敦、直井勝彦、「大容量キャパシタ技術と材料II −電気二重層キャパシタとスーパーキャパシタの最新動向−」、p.80〜p.93Supervision: Atsushi Nishino, Katsuhiko Naoi, "High-capacity capacitor technology and materials II-Latest trends in electric double layer capacitors and supercapacitors-", p. 80-p. 93

したがって、電気伝導度および耐電圧が高く、かつ、広い温度範囲、特に低温において凝固や塩の析出がなく安定した液状を呈し、優れた電気的特性を発現することができ、さらに長期信頼性に優れる電気二重層キャパシタ用電解液が望まれており、本発明は、そのような電気二重層キャパシタ用電解液およびこれを利用した電気二重層キャパシタを提供することをその課題とする。   Therefore, it has a high electrical conductivity and withstand voltage, and exhibits a stable liquid state without solidification or salt precipitation in a wide temperature range, especially at low temperatures, and can exhibit excellent electrical characteristics, and also has long-term reliability. An excellent electrolytic solution for an electric double layer capacitor is desired, and an object of the present invention is to provide such an electrolytic solution for an electric double layer capacitor and an electric double layer capacitor using the same.

本発明者らは鋭意検討を行った結果、一般式(2)に示した第4級アンモニウム塩が、他の第4級アンモニウム塩と比べて、鎖状スルホンに特異的に溶解するため電気伝導度が高く、耐電圧にも優れ、これを用いた電気二重層キャパシタは、非常に広い温度範囲で使用可能であり、特に低温でも凝固することなく優れた電気的特性を示し、かつ長期信頼性にも優れることを見出した。さらに、アルキル基の合計の炭素数が異なる鎖状スルホンを組み合わせることにより、単独使用の場合と比較して、凝固点を低下させることができるため、より低温での使用が可能となるとともに、電気的特性がさらに向上することを見出し、本発明を完成するに至った。   As a result of intensive studies, the present inventors have found that the quaternary ammonium salt represented by the general formula (2) specifically dissolves in the chain sulfone as compared with other quaternary ammonium salts. Electric double layer capacitors that use this high temperature, excellent withstand voltage, can be used in a very wide temperature range, exhibit excellent electrical characteristics without solidifying even at low temperatures, and have long-term reliability I also found it excellent. Furthermore, by combining chain sulfones with different total carbon numbers of alkyl groups, the freezing point can be lowered compared to the case of single use, so that use at a lower temperature is possible and electrical The inventors have found that the characteristics are further improved and have completed the present invention.

すなわち、本発明は、有機溶媒中に第4級アンモニウム塩を溶解した電解液であって、
前記有機溶媒が下記一般式(1)

Figure 2011044632
(式(1)中、R、Rは同一でも異なっていても良い直鎖又は分岐の炭素数1〜5のアルキル基を示す。)
で表される鎖状スルホンを含有し、
前記第4級アンモニウム塩が下記一般式(2)
Figure 2011044632
(式(2)中、m及びnは4〜6の整数を示す。Xは酸成分を示す。)
で表される第4級アンモニウム塩であることを特徴とする電気二重層キャパシタ用電解液である。 That is, the present invention is an electrolytic solution in which a quaternary ammonium salt is dissolved in an organic solvent,
The organic solvent is represented by the following general formula (1)

Figure 2011044632
(In Formula (1), R < 1 >, R < 2 > shows the linear or branched C1-C5 alkyl group which may be same or different.)
Containing a chain sulfone represented by
The quaternary ammonium salt is represented by the following general formula (2)
Figure 2011044632
(In the formula (2), m and n are .X represents an integer of 4 to 6 - shows the acid component.)
An electrolytic solution for an electric double layer capacitor, characterized in that it is a quaternary ammonium salt represented by the formula:

また発明は、前記有機溶媒が、RとRの炭素数の合計が2〜3である一般式(1)で表される鎖状スルホンおよびRとRの炭素数の合計が4〜8である一般式(1)で表される鎖状スルホンを含有する電気二重層キャパシタ用電解液である。 In the invention, the organic solvent is a chain sulfone represented by the general formula (1) in which the total number of carbon atoms of R 1 and R 2 is 2 to 3, and the total number of carbon atoms of R 1 and R 2 is 4 It is the electrolyte solution for electric double layer capacitors containing the chain | strand-shaped sulfone represented by General formula (1) which is -8.

さらに本発明は、前記有機溶媒中、一般式(1)で表される鎖状スルホンを75%以上含有する電気二重層キャパシタ用電解液である。   Furthermore, the present invention is an electrolytic solution for an electric double layer capacitor containing 75% or more of the chain sulfone represented by the general formula (1) in the organic solvent.

さらにまた本発明は、セパレータを挟み込んだ分極性電極に、上記電気二重層キャパシタ用電解液を含浸させてなる電気二重層キャパシタである。   Furthermore, the present invention is an electric double layer capacitor obtained by impregnating a polarizable electrode sandwiching a separator with the electrolytic solution for an electric double layer capacitor.

本発明の電気二重層キャパシタ用電解液は、耐電圧および電気伝導度が高く、また低温でも凝固することなく優れた電気的特性を発現し得るものであり、この電解液を用いることにより、使用可能な温度領域が非常に広く、特に低温特性に優れ、かつ長期信頼性にも優れる電気二重層キャパシタを得ることが可能である。   The electrolytic solution for electric double layer capacitor of the present invention has a high withstand voltage and electrical conductivity, and can express excellent electrical characteristics without solidifying even at low temperatures, and can be used by using this electrolytic solution. It is possible to obtain an electric double layer capacitor having a very wide possible temperature range, particularly excellent in low temperature characteristics and excellent in long-term reliability.

本発明に係るコイン型電気二重層キャパシタの構成の一例を示す概略断面図である。It is a schematic sectional drawing which shows an example of a structure of the coin-type electric double layer capacitor which concerns on this invention.

以下に、本発明の電気二重層キャパシタ用電解液について詳細に説明する。   Below, the electrolyte solution for electric double layer capacitors of this invention is demonstrated in detail.

本発明の電気二重層キャパシタ用電解液は、非水系であり、溶媒として有機溶媒を使用する。本発明は、有機溶媒として下記一般式(1)に示される鎖状スルホンを使用するものである。   The electrolytic solution for an electric double layer capacitor of the present invention is non-aqueous and uses an organic solvent as a solvent. In the present invention, a chain sulfone represented by the following general formula (1) is used as an organic solvent.

Figure 2011044632
Figure 2011044632

式(1)中、R及びRはそれぞれ同一であっても異なっていてもよい炭素数1〜5の直鎖又は分岐のアルキル基を示す。炭素数が5を超える場合、常温で固体を呈し、仮に電解液にしたとしても、著しく粘度が高くなってしまうことから、キャパシタの特性が悪化してしまう欠点がある。具体的には、ジメチルスルホン、エチルメチルスルホン、ジエチルスルホン、プロピルメチルスルホン、イソプロピルメチルスルホン、プロピルエチルスルホン、イソプロピルエチルスルホン、ジプロピルスルホン、ジイソプロピルスルホン等が例示できる。 In formula (1), R 1 and R 2 each represent a linear or branched alkyl group having 1 to 5 carbon atoms which may be the same or different. When the number of carbons exceeds 5, even if it is solid at room temperature and it is used as an electrolytic solution, the viscosity becomes remarkably high, and there is a drawback that the characteristics of the capacitor are deteriorated. Specific examples include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, propyl methyl sulfone, isopropyl methyl sulfone, propyl ethyl sulfone, isopropyl ethyl sulfone, dipropyl sulfone, and diisopropyl sulfone.

上記鎖状スルホンは、単独で使用してもよく、また、2種以上の混合溶媒として使用してもよい。混合溶媒とする場合は、上記一般式(1)中、R及びRの炭素数の合計が2〜3の鎖状スルホンと、R及びRの炭素数の合計が4〜8、好ましくは、4〜6の鎖状スルホンとを併用することにより、それぞれの単独使用と比較して電解液の凝固点を著しく低下させることができ、低温においても凝固することなく、優れた電気的特性を発現できる。R及びRの炭素数の合計が2〜3の鎖状スルホンとしては、ジメチルスルホンおよびエチルメチルスルホンが挙げられ、R及びRの炭素数の合計が4〜8の鎖状スルホンとしては、メチルイソプロピルスルホン、エチルイソブチルスルホン、ブチルイソブチルスルホン、エチルイソプロピルスルホン、プロピルイソブチルスルホン、イソプルピル−S−ブチルスルホン等が挙げられる。これらの中でも、エチルメチルスルホンとエチルイソプルピルスルホンの組み合わせが、低粘性率で高電気伝導度であるとともに、低温下でも凝固することなく電気的特性に優れるために好ましい。 The said chain | strand sulfone may be used independently and may be used as 2 or more types of mixed solvents. When a mixed solvent is, in the general formula (1), a chain sulfone total number of carbon atoms of R 1 and R 2 are 2-3, the total number of carbon atoms of R 1 and R 2 are 4-8, Preferably, by using together with 4 to 6 chain sulfone, the freezing point of the electrolytic solution can be remarkably lowered as compared with each single use, and excellent electrical characteristics without solidification even at low temperatures. Can be expressed. Examples of the chain sulfone having 2 to 3 carbon atoms in R 1 and R 2 include dimethyl sulfone and ethyl methyl sulfone, and the chain sulfone having 4 to 8 carbon atoms in total in R 1 and R 2. Examples thereof include methyl isopropyl sulfone, ethyl isobutyl sulfone, butyl isobutyl sulfone, ethyl isopropyl sulfone, propyl isobutyl sulfone, and isopropyl-S-butyl sulfone. Among these, a combination of ethyl methyl sulfone and ethyl isopropyl sulfone is preferable because it has a low viscosity and high electrical conductivity and is excellent in electrical characteristics without being solidified even at low temperatures.

及びRの炭素数の合計が2〜3の鎖状スルホンと、R及びRの炭素数の合計が4〜8の鎖状スルホンの混合比は、低温下での凝固を抑制し、静電容量を高く、内部抵抗を低くすることができるため、質量比で10:90〜90:10であることが好ましく、10:90〜50:50であることがより好ましく、10:90〜30:70がさらに好ましく、10:90〜20:80が特に好ましい。質量比において、R及びRの炭素数の合計が2〜3の鎖状スルホンが10未満では、極低温下で凝固する場合がある。炭素数の合計が2〜3の鎖状スルホンが電気伝導度の向上に寄与し、炭素数の合計が4〜8の鎖状スルホンが低温特性の改善に寄与すると考えられる。 And total 2-3 chain sulfones of the carbon atoms of R 1 and R 2, mixing ratio of the chain sulfone total number of carbon atoms of R 1 and R 2 are 4-8, inhibit coagulation at low temperatures In addition, since the capacitance can be increased and the internal resistance can be decreased, the mass ratio is preferably 10:90 to 90:10, more preferably 10:90 to 50:50, and more preferably 10: 90-30: 70 is more preferable, and 10: 90-20: 80 is particularly preferable. If the chain sulfone having a total number of carbon atoms of R 1 and R 2 of less than 10 in terms of mass ratio is less than 10, solidification may occur at an extremely low temperature. It is considered that the chain sulfone having 2 to 3 carbon atoms contributes to the improvement of electric conductivity, and the chain sulfone having 4 to 8 carbon atoms contributes to the improvement of the low temperature characteristics.

一方、単独使用の場合は、低温下での凝固を抑制できることから、上記一般式(1)中、R及びRの炭素数の合計が4〜8、好ましくは4〜6の鎖状スルホンを用いることが好適であり、具体的には、イソプロピルメチルスルホン、メチルイソプロピルスルホン、エチルイソブチルスルホンが好ましく用いられる。 On the other hand, in the case of single use, since solidification at low temperature can be suppressed, in the general formula (1), the total number of carbon atoms of R 1 and R 2 is 4-8, preferably 4-6. Specifically, isopropyl methyl sulfone, methyl isopropyl sulfone, and ethyl isobutyl sulfone are preferably used.

本発明の電気二重層キャパシタ用電解液において、有機溶媒中の上記一般式(1)の鎖状スルホンの含有量は、好ましくは75%以上であり、より好ましくは80%以上であり、さらに好ましくは98%以上であり、100%であることが特に好ましい。このような範囲とすることによって、耐電圧を低下させること無く優れた低温特性を有する電解液を得ることができる。   In the electrolytic solution for electric double layer capacitor of the present invention, the content of the chain sulfone of the general formula (1) in the organic solvent is preferably 75% or more, more preferably 80% or more, and further preferably. Is 98% or more, particularly preferably 100%. By setting it as such a range, the electrolyte solution which has the outstanding low-temperature characteristic can be obtained, without reducing a withstand voltage.

本発明の電気二重層キャパシタ用電解液に用いる有機溶媒には、本発明の効果を損なわない範囲において、上記一般式(1)で表される鎖状スルホン以外の他の有機溶媒を使用することができる。このような有機溶媒として、例えば、スルホラン、3−メチルスルホラン、ガンマ‐ブチロラクトン、プロピレンカーボネート、エチレンカーボネート、ビニレンカーボネート、ブチレンカーボネート等が例示できる。   As the organic solvent used for the electrolytic solution for electric double layer capacitor of the present invention, an organic solvent other than the chain sulfone represented by the above general formula (1) should be used as long as the effects of the present invention are not impaired. Can do. Examples of such an organic solvent include sulfolane, 3-methylsulfolane, gamma-butyrolactone, propylene carbonate, ethylene carbonate, vinylene carbonate, butylene carbonate, and the like.

本発明の電気二重層キャパシタ用電解液には、電解質として下記一般式(2)に示される第4級アンモニウム塩を使用する。   In the electrolytic solution for an electric double layer capacitor of the present invention, a quaternary ammonium salt represented by the following general formula (2) is used as an electrolyte.

Figure 2011044632
Figure 2011044632

式(2)中、m及びnは4〜6の整数を示す。Xは酸成分を示す。 In Formula (2), m and n show the integer of 4-6. X represents an acid component.

上記一般式(2)中のカチオンとして、具体的には、スピロ−(1,1’)−ビピロリジニウムイオン、スピロ−(1,1’)−ビピペリジニウムイオン、ピペリジン−1−スピロ−1’−ピロリジニウムイオン等が例示できる。これらのうち、スルホン系溶媒へ溶解度が高く、電気化学的安定性に優れ、電解液としたときに高い電気伝導度が得られるため、スピロ−(1,1’)−ビピロリジニウムイオンが好ましい。なお、これらのカチオンは、2種以上が混合されていてもよい。   Specific examples of the cation in the general formula (2) include spiro- (1,1 ′)-bipyrrolidinium ion, spiro- (1,1 ′)-bipiperidinium ion, piperidine-1-spiro- Examples thereof include 1′-pyrrolidinium ion. Of these, spiro- (1,1 ′)-bipyrrolidinium ions are preferred because of their high solubility in sulfone solvents, excellent electrochemical stability, and high electrical conductivity when used as electrolytes. . In addition, 2 or more types of these cations may be mixed.

上記一般式(2)中のXは、特に限定されるものではないが、非金属元素のみからなるアニオンが好ましく、例えば、BF 、PF 、CFSO 、N(CFSO 、N(CSO 、N(CFSO)(CSO、C(CFSO 、C(CSO が好ましい。これらの中でも、BF 、PF 、N(CFSO がスルホン系溶媒へ溶解度が高く、電気化学的安定性に優れ、電解液としたときに高い電気伝導度が得られるため特に好ましい。なお、これらのアニオンは、2種以上が混合されていてもよい。 X in the general formula (2) is not particularly limited, but an anion composed only of a nonmetallic element is preferable. For example, BF 4 , PF 6 , CF 3 SO 3 , N (CF 3 SO 2) 2 -, N (C 2 F 5 SO 2) 2 -, N (CF 3 SO 2) (C 4 F 9 SO 2) -, C (CF 3 SO 2) 3 -, C (C 2 F 5 SO 2 ) 3 is preferred. Among these, BF 4 , PF 6 , and N (CF 3 SO 2 ) 2 have high solubility in sulfone solvents, excellent electrochemical stability, and high electrical conductivity when used as an electrolyte. This is particularly preferable. In addition, 2 or more types of these anions may be mixed.

上記一般式(2)で表される第4級アンモニウム塩としては、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジウム、テトラフルオロホウ酸ピペリジン−1−スピロ−1’−ピロリジニウム、テトラフルオロホウ酸スピロ−(1,1’)−ビピペリジニウム、トリフルオロメタンスルホン酸スピロ−(1,1’)−ビピロリジウム、トリフルオロメタンスルホン酸ピペリジン−1−スピロ−1’−ピロリジニウム、トリフルオロメタンスルホン酸スピロ−(1,1’)−ビピペリジニウム、ヘキサフルオロリン酸スピロ−(1,1’)−ビピロリジウム、ヘキサフルオロリン酸ピペリジン−1−スピロ−1’−ピロリジニウム、ヘキサフルオロリン酸スピロ−(1,1’)−ビピペリジニウム、スピロ−1,1’−ビピロリニウムビス(トリフルオロメチルスルホニル)イミド、ピペリジン−1−スピロ−1’−ピロリジニウムビス(トリフルオロメチルスルホニル)イミド、スピロ−(1,1’)−ビピペリジニウムビス(トリフルオロメチルスルホニル)イミド等が挙げられる。   Examples of the quaternary ammonium salt represented by the general formula (2) include spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate, piperidine-1-spiro-1′-pyrrolidinium tetrafluoroborate, tetrafluoroborate. Spiro- (1,1 ′)-bipiperidinium borate, spiro- (1,1 ′)-bipyrrolidinium trifluoromethanesulfonate, piperidine-1-spiro-1′-pyrrolidinium trifluoromethanesulfonate, spiro-trifluoromethanesulfonate ( 1,1 ′)-bipiperidinium, hexafluorophosphate spiro- (1,1 ′)-bipyrrolidinium, hexafluorophosphate piperidine-1-spiro-1′-pyrrolidinium, hexafluorophosphate spiro- (1,1 ′) -Bipiperidinium, spiro-1,1'-bipyrrolinium bi (Trifluoromethylsulfonyl) imide, piperidine-1-spiro-1′-pyrrolidinium bis (trifluoromethylsulfonyl) imide, spiro- (1,1 ′)-bipiperidinium bis (trifluoromethylsulfonyl) imide Etc.

上記一般式(2)で表される第4級アンモニウム塩は公知の方法に従って製造することができる。例えば、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジウムは、まず、ピロリジンにハロゲン化剤としてジハロゲン化ブタンを反応させて、ハロゲン化スピロ−(1,1’)−ビピロリジニウムを合成した後、イオン交換膜を用いた電気透析法により、水酸化スピロ−(1,1’)−ビピロリジニウム水溶液を得て、これにテトラフルオロホウ峻(HBF)を当量添加して中和反応させた後、減圧下で脱水させることによって得られる。 The quaternary ammonium salt represented by the general formula (2) can be produced according to a known method. For example, after spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is synthesized by first reacting pyrrolidine with dihalogenated butane as a halogenating agent to synthesize halogenated spiro- (1,1 ′)-bipyrrolidinium. Then, an aqueous solution of spiro- (1,1 ′)-bipyrrolidinium hydroxide was obtained by electrodialysis using an ion exchange membrane, and an equivalent amount of tetrafluoroborin (HBF 4 ) was added thereto for neutralization reaction. Obtained by dehydration under reduced pressure.

また、テトラフルオロホウ酸ピペリジン−1−スピロ−1’−ピロリジニウムは、まず、ピペリジンにハロゲン化剤としてジハロゲン化ブタンを反応させて、ハロゲン化ピペリジン−1−スピロ−1’−ピロリジニウムを合成した後、イオン交換膜を用いた電気透析法により、水酸化ピペリジン−1−スピロ−1’−ピロリジニウム水溶液を得て、これにテトラフルオロホウ酸(HBF)を当量添加して中和反応させた後、減圧下で脱水させることによって得ることができる。またHBFをKCFSO、HPF、又はLiN(CFSO等に代えて同様に合成することによって、対応するアニオンを有する第4級アンモニウム塩を得ることができる。 Piperidine-1-spiro-1′-pyrrolidinium tetrafluoroborate is synthesized by first reacting piperidine with a dihalogenated butane as a halogenating agent to synthesize halogenated piperidine-1-spiro-1′-pyrrolidinium. Then, an aqueous solution of piperidine-1-spiro-1′-pyrrolidinium hydroxide is obtained by electrodialysis using an ion exchange membrane, and an equivalent amount of tetrafluoroboric acid (HBF 4 ) is added thereto for neutralization reaction. Can be obtained by dehydration under reduced pressure. Further, by synthesizing HBF 4 in the same manner in place of KCF 3 SO 3 , HPF 6 , LiN (CF 3 SO 2 ) 2 or the like, a quaternary ammonium salt having a corresponding anion can be obtained.

上記第4級アンモニウム塩の濃度は、電解液全体に対して、0.1〜3.0mol/Lが好ましく、0.5〜2.0mol/Lがより好ましく、1.3〜1.7mol/Lが特に好ましい。第4級アンモニウム塩の濃度が0.1mol/L未満では、電気伝導度が不足する場合があり、また3.0mol/Lより多いと、電解液の粘度が増大するため含浸性が低下し、電気二重層キャパシタにした場合に、電気特性が劣る場合がある。   The concentration of the quaternary ammonium salt is preferably 0.1 to 3.0 mol / L, more preferably 0.5 to 2.0 mol / L, and 1.3 to 1.7 mol / L with respect to the entire electrolyte solution. L is particularly preferred. When the concentration of the quaternary ammonium salt is less than 0.1 mol / L, the electrical conductivity may be insufficient. When the concentration is more than 3.0 mol / L, the viscosity of the electrolytic solution increases, so that the impregnation property decreases. When an electric double layer capacitor is used, the electrical characteristics may be inferior.

本発明の電気二重層キャパシタ用電解液は、含浸性向上や難燃性を付与するような添加剤を加えてもよい。このような添加剤として、具体的には、ヘキサメチルジシロキサン、ヘキサメチルシクロトリシロキサン等のシロキサン化合物が例示できる。   The electrolytic solution for an electric double layer capacitor of the present invention may contain an additive that imparts improved impregnation and flame retardancy. Specific examples of such additives include siloxane compounds such as hexamethyldisiloxane and hexamethylcyclotrisiloxane.

本発明の電気二重層キャパシタ用電解液は、以下の製造方法により調製することができる。   The electrolytic solution for electric double layer capacitors of the present invention can be prepared by the following production method.

すなわち、上記溶媒に、上記一般式(2)に示す第4級アンモニウム塩からなる電解質塩を加え、攪拌して塩が完全に溶解したことを確認する。得られた電解液を脱水し、電解液中の水分を100ppm以下、好ましくは20ppm以下にまで減少させることで、目的とする電気二重層キャパシタ用電解液が得られる。   That is, an electrolyte salt composed of a quaternary ammonium salt represented by the general formula (2) is added to the solvent and stirred to confirm that the salt is completely dissolved. The obtained electrolytic solution is dehydrated, and the water content in the electrolytic solution is reduced to 100 ppm or less, preferably 20 ppm or less, whereby the intended electrolytic solution for electric double layer capacitors is obtained.

このようにして調製された電解液を使用して電気二重層キャパシタを作製することができる。本発明のキャパシタの作製は、一般的なキャパシタの製造方法によることができ、すなわち、セパレータを挟み込んだ分極性電極に、駆動用電解液となる本発明の電気二重層キャパシタ用電解液を含浸させ、これを容器に密封することにより行われる。   An electric double layer capacitor can be produced using the electrolytic solution thus prepared. The production of the capacitor of the present invention can be performed by a general method for producing a capacitor. That is, a polarizable electrode sandwiching a separator is impregnated with an electrolytic solution for an electric double layer capacitor of the present invention that serves as a driving electrolytic solution. This is done by sealing it in a container.

キャパシタ電極に用いられる分極性電極としては、活性炭粉末、活性炭繊維などの多孔性炭素材料や、金属酸化物材料、あるいは導電性高分子材料などが用いられるが、多孔性炭素材料が安価で好ましい。また、セパレータとしては、セルロース、ポリエチレン、ポリプロピレン系不織布などの素材からなるセパレータを用いることができる。   As the polarizable electrode used for the capacitor electrode, porous carbon materials such as activated carbon powder and activated carbon fibers, metal oxide materials, conductive polymer materials, and the like are used, but porous carbon materials are preferable because they are inexpensive. Moreover, as a separator, the separator which consists of raw materials, such as a cellulose, polyethylene, a polypropylene-type nonwoven fabric, can be used.

本発明の電気二重層キャパシタの形状としては、特に限定されず、フィルム型、コイン型、円筒型、箱型などの形状に作製することができる。   The shape of the electric double layer capacitor of the present invention is not particularly limited, and can be produced in a film shape, a coin shape, a cylindrical shape, a box shape or the like.

図1は上記形状のうち、コイン型電気二重層キャパシタの例であり、本発明の電気二重層キャパシタの構成の一例を示す概略断面図である。   FIG. 1 is a schematic cross-sectional view showing an example of a coin-type electric double layer capacitor of the above shapes, and showing an example of the configuration of the electric double layer capacitor of the present invention.

図1中、負極キャップ1、負極電極2、集電体3からなる負極部と、集電体3、正極電極6、正極ケース7からなる正極部とを有し、正負両電極はセパレータ5を介し対向するよう配置される。電解液4は電極、セパレータ、及び容器中に含浸、充填される。負極キャップ1と正極ケース7とはガスケット8によって絶縁され、嵌合される。   In FIG. 1, a negative electrode portion including a negative electrode cap 1, a negative electrode electrode 2, and a current collector 3, and a positive electrode portion including a current collector 3, a positive electrode 6, and a positive electrode case 7. It arrange | positions so that it may oppose. The electrolytic solution 4 is impregnated and filled in electrodes, separators, and containers. The negative electrode cap 1 and the positive electrode case 7 are insulated and fitted by a gasket 8.

以下、実施例を挙げ、本発明を更に詳しく説明する。なお、本発明は実施例によりなんら限定されない。   Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited at all by the Example.

溶媒として使用した鎖状スルホン「ジメチルスルホン(東京化成工業株式会社製試薬)」「エチルメチルスルホン(東京化成工業株式会社製試薬)」「メチルイソプロピルスルホン(東京化成工業株式会社製試薬)」「エチルイソプロピルスルホン(住友精化株式会社製)」「エチルイソブチルスルホン(住友精化株式会社製)」と、比較として使用した環状スルホン「スルホラン(住友精化株式会社製)」について、それぞれの構造式とアルキル基の炭素数の合計を表1に示す。   Chain sulfone used as a solvent “dimethylsulfone (reagent made by Tokyo Chemical Industry Co., Ltd.)” “ethyl methyl sulfone (reagent made by Tokyo Chemical Industry Co., Ltd.)” “methylisopropylsulfone (reagent made by Tokyo Chemical Industry Co., Ltd.)” “ethyl” The structural formulas of isopropyl sulfone (manufactured by Sumitomo Seika Co., Ltd.), ethyl isobutyl sulfone (manufactured by Sumitomo Seika Co., Ltd.), and cyclic sulfone used as a comparison, sulfolane (manufactured by Sumitomo Seika Co., Ltd.), Table 1 shows the total number of carbon atoms of the alkyl group.

Figure 2011044632
Figure 2011044632

実 施 例 1
各鎖状スルホンに対する第4級アンモニウム塩の溶解度:
本発明に用いるテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムと、一般的な第4級アンモニウム塩であるテトラフルオロホウ酸トリエチルメチルアンモニウム及びテトラフルオロホウ酸テトラエチルアンモニウムについて、表1に示す各鎖状スルホンへの、25℃での溶解度を調査した。結果を表2に示す。
Example 1
Solubility of quaternary ammonium salts for each chain sulfone:
Table 1 shows spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate used in the present invention and triethylmethylammonium tetrafluoroborate and tetraethylammonium tetrafluoroborate which are general quaternary ammonium salts. The solubility at 25 ° C. in each chain sulfone was investigated. The results are shown in Table 2.

Figure 2011044632
Figure 2011044632

表2に示すように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムは、他の第4級アンモニウム塩に比べ、鎖状スルホンに対して特異的に溶解することが分かった。   As shown in Table 2, it was found that spiro- (1,1 ')-bipyrrolidinium tetrafluoroborate specifically dissolves in chain sulfone as compared with other quaternary ammonium salts.

実 施 例 2
電気二重層キャパシタ用電解液の調製及び物性測定:
[電気二重層キャパシタ用電解液の調製]
(1種の鎖状スルホン単独溶媒)
Example 2
Preparation and physical property measurement of electrolyte for electric double layer capacitor:
[Preparation of electrolyte for electric double layer capacitor]
(Single chain sulfone single solvent)

エチルメチルスルホンに濃度1.0mol/Lとなるようにテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品1」とする)。   An electrolytic solution for an electric double layer capacitor in which spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is added to ethylmethylsulfone to a concentration of 1.0 mol / L and dehydrated to a moisture value of 20 ppm or less is obtained. (This electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “Invention 1”).

メチルイソプロピルスルホンに濃度1.0mol/Lとなるようにテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品2」とする)。   An electrolytic solution for an electric double layer capacitor in which spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is added to methyl isopropyl sulfone to a concentration of 1.0 mol / L and dehydrated to a moisture value of 20 ppm or less is obtained. (This electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “Invention 2”).

エチルイソプロピルスルホンに濃度1.0mol/Lとなるようにテトラフルオロホウ酸スピロ−(11,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品3」とする)。   An electrolytic solution for an electric double layer capacitor in which spiro- (11,1 ′)-bipyrrolidinium tetrafluoroborate is added to ethyl isopropyl sulfone to a concentration of 1.0 mol / L and dehydrated to a moisture value of 20 ppm or less is obtained. (This electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “invention product 3”).

エチルイソブチルスルホンに濃度1.0mol/Lとなるようにテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品4」とする)。   An electrolytic solution for an electric double layer capacitor in which spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is added to ethyl isobutyl sulfone to a concentration of 1.0 mol / L and dehydrated to a moisture value of 20 ppm or less is obtained. (This electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “invention product 4”).

エチルメチルカーボネートに濃度1.0mol/Lとなるようにテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「比較品1」とする)。   An electrolytic solution for an electric double layer capacitor in which spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is added to ethyl methyl carbonate to a concentration of 1.0 mol / L and dehydrated to a moisture value of 20 ppm or less is obtained. (This electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “Comparative product 1”).

スルホランに濃度1.0mol/Lとなるようにテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「比較品2」とする)。   Spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate was added to sulfolane at a concentration of 1.0 mol / L and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less ( This electrolytic solution and the electric double layer capacitor using the electrolytic solution are referred to as “Comparative product 2”).

エチルメチルスルホンに濃度1.0mol/Lとなるようにテトラフルオロホウ酸トリエチルメチルアンモニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「比較品3」とする)。   Triethylmethylammonium tetrafluoroborate was added to ethylmethylsulfone to a concentration of 1.0 mol / L and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and electrolytic solution). The electric double layer capacitor using the liquid is referred to as “Comparative product 3”).

エチルイソプロピルスルホンに濃度1.0mol/Lとなるようにテトラフルオロホウ酸トリエチルメチルアンモニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「比較品4」とする)。   Triethylmethylammonium tetrafluoroborate was added to ethyl isopropyl sulfone to a concentration of 1.0 mol / L and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and electrolytic solution). The electric double layer capacitor using the liquid is referred to as “Comparative product 4”).

(2種の鎖状スルホンの混合溶媒) (Mixed solvent of two chain sulfones)

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=10:90で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品5」とする)。   In a mass ratio of ethyl methyl sulfone: ethyl isopropyl sulfone = 10: 90, superheated, dissolved, and returned to room temperature, a tetrafluoroboric acid spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “invention product 5”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=20:80で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品6」とする)。   In a mass ratio of ethyl methyl sulfone: ethyl isopropyl sulfone = 20: 80, superheated, dissolved and returned to room temperature, a tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a water content of 20 ppm or less (this electrolytic solution and an electric double layer capacitor using the electrolytic solution were referred to as “Invention 6”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=30:70で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品7」とする)。   In a mass ratio of ethyl methyl sulfone: ethyl isopropyl sulfone = 30: 70, the mixture was superheated, dissolved, and returned to room temperature, so that tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a water content of 20 ppm or less (this electrolytic solution and an electric double layer capacitor using the electrolytic solution were referred to as “Invention Product 7”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=40:60で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品8」とする)。   The mixture was heated at a mass ratio of ethyl methyl sulfone: ethyl isopropyl sulfone = 40: 60, heated, dissolved, and returned to room temperature, so that tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a water content of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “Invention 8”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=50:50で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品9」とする)。   The mixture was heated at a mass ratio of ethyl methyl sulfone: ethyl isopropyl sulfone = 50: 50, dissolved, and returned to room temperature to a concentration of 1.0 mol / L. Tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “Invention 9”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=60:40で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品10」とする)。   A mixture of ethylmethylsulfone: ethylisopropylsulfone = 60: 40 in a mass ratio, heated to a solvent, dissolved, and returned to room temperature so as to have a concentration of 1.0 mol / L, tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “invention product 10”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=70:30で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品11」とする)。   In a mass ratio of ethyl methyl sulfone: ethyl isopropyl sulfone = 70: 30, superheated, dissolved, and returned to room temperature, a tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “Invention Product 11”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=80:20で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品12」とする)。   A mixture of ethylmethylsulfone: ethylisopropylsulfone = 80: 20 by mass ratio, superheated, dissolved in a solvent returned to room temperature, and tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a water content of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “Invention 12”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=90:10で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品13」とする)。   A mixture of ethylmethylsulfone: ethylisopropylsulfone at a mass ratio of 90:10, superheated, dissolved in a solvent returned to room temperature so as to have a concentration of 1.0 mol / L, tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “invention product 13”. To do).

質量比でエチルメチルスルホン:メチルイソプロピルスルホン=10:90で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品14」とする)。   In a mass ratio of ethyl methyl sulfone: methyl isopropyl sulfone = 10: 90, the mixture was superheated, dissolved, and returned to room temperature, so that tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and an electric double layer capacitor using the electrolytic solution were referred to as “invention product 14”. To do).

質量比でエチルメチルスルホン:エチルイソブチルスルホン=10:90で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品15」とする)。   In a mass ratio of ethyl methyl sulfone: ethyl isobutyl sulfone = 10: 90, the mixture was heated, dissolved, and returned to room temperature, so that tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a water content of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “Invention 15”. To do).

質量比でジメチルスルホン:エチルイソプロピルスルホン=10:90で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.0mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品16」とする)。   The mixture was heated to dimethylsulfone: ethylisopropylsulfone = 10: 90 in a mass ratio, dissolved, and returned to room temperature to a concentration of 1.0 mol / L. Tetrafluoroborate spiro- (1, 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution are referred to as “invention product 16”). ).

質量比でエチルメチルスルホン:メチルイソプロピルスルホン=10:90で混合して過熱し、溶解させて室温に戻した溶媒に、濃度1.5mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品17」とする)。   In a mass ratio of ethyl methyl sulfone: methyl isopropyl sulfone = 10: 90, the mixture was superheated, dissolved, and returned to room temperature, so that tetrafluoroborate spiro- (1 , 1 ′)-bipyrrolidinium was added and dehydrated to obtain an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less (this electrolytic solution and the electric double layer capacitor using the electrolytic solution were referred to as “Invention 17”. To do).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=10:90で混合した溶媒に、濃度1.5mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品18」とする)。   Spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is added to a solvent mixed at a mass ratio of ethyl methyl sulfone: ethyl isopropyl sulfone = 10: 90 so that the concentration is 1.5 mol / L, followed by dehydration. Thus, an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less was obtained (this electrolytic solution and the electric double layer capacitor using the electrolytic solution are referred to as “invention product 18”).

質量比でエチルメチルスルホン:エチルイソブチルスルホン=10:90で混合した溶媒に、濃度1.5mol/Lとなるように、テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「発明品19」とする)。   Spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is added to a solvent mixed at a mass ratio of ethyl methyl sulfone: ethyl isobutyl sulfone = 10: 90 so that the concentration is 1.5 mol / L, and dehydrated. Thus, an electrolytic solution for an electric double layer capacitor having a moisture value of 20 ppm or less was obtained (this electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “Invention 19”).

質量比でスルホラン:エチルメチルカーボネート=75:25で混合した溶媒に濃度1.0mol/Lとなるようにテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「比較品5」とする)。   Spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is added to a solvent mixed at a mass ratio of sulfolane: ethyl methyl carbonate = 75: 25 to a concentration of 1.0 mol / L, and dehydrated to obtain a moisture value. An electrolytic solution for an electric double layer capacitor having a concentration of 20 ppm or less was obtained (this electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “Comparative Product 5”).

質量比でスルホラン:エチルメチルスルホン=80:20で混合した溶媒に濃度1.0mol/Lとなるようにテトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「比較品6」とする)。   Spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate is added to a solvent mixed at a mass ratio of sulfolane: ethyl methyl sulfone = 80: 20 so that the concentration is 1.0 mol / L, and dehydrated to obtain a moisture value. An electrolytic solution for an electric double layer capacitor having a concentration of 20 ppm or less was obtained (this electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “Comparative product 6”).

質量比でエチルメチルスルホン:エチルイソプロピルスルホン=10:90で混合した溶媒に濃度1.0mol/Lとなるようにテトラフルオロホウ酸トリエチルメチルアンモニウムを加え、脱水して水分値を20ppm以下にした電気二重層キャパシタ用電解液を得た(この電解液及び電解液を用いた電気二重層キャパシタを「比較品7」とする)。   Electricity in which triethylmethylammonium tetrafluoroborate was added to a solvent mixed at a mass ratio of ethylmethylsulfone: ethylisopropylsulfone = 10: 90 to a concentration of 1.0 mol / L and dehydrated to a moisture value of 20 ppm or less. An electrolytic solution for a double layer capacitor was obtained (this electrolytic solution and an electric double layer capacitor using the electrolytic solution are referred to as “Comparative Product 7”).

[電解液の物性測定]
得られた電解液(発明品1〜19及び比較品1〜7)について、25℃における粘性率(cp)と電気伝導度(mS/cm)及び電位窓(V)を測定した。なお、粘性率はサン科学製のCR−500DX、電気伝導度は、横河電機製の導電率計SC72を用いて測定した。また、電位窓は北斗電工製の電気化学システムHZ5000を用いてサイクリックボルタモグラムを測定することで得られた酸化分解電圧、還元分解電圧の値から求めた。すなわち、作用極に白金線(直径3mm)、対極に白金板、参照電極にAg/Ag、掃引速度10mV/sで0.1mA/cmの電流が流れるまでの電圧を測定し、還元分解及び酸化分解電圧値から電位窓を決定した。結果を表3および4に示す。
[Measurement of physical properties of electrolyte]
About the obtained electrolyte solution (Invention products 1-19 and Comparative products 1-7), the viscosity (cp), electrical conductivity (mS / cm), and electric potential window (V) in 25 degreeC were measured. The viscosity was measured using a CR-500DX manufactured by Sun Kagaku, and the electrical conductivity was measured using a conductivity meter SC72 manufactured by Yokogawa Electric. The potential window was determined from the values of the oxidation decomposition voltage and the reduction decomposition voltage obtained by measuring a cyclic voltammogram using an electrochemical system HZ5000 manufactured by Hokuto Denko. That is, a platinum wire (diameter 3 mm) as a working electrode, a platinum plate as a counter electrode, Ag / Ag + as a reference electrode, a voltage until a current of 0.1 mA / cm 2 flows at a sweep rate of 10 mV / s, and reductive decomposition is measured. The potential window was determined from the oxidative decomposition voltage value. The results are shown in Tables 3 and 4.

Figure 2011044632
Figure 2011044632

Figure 2011044632
Figure 2011044632

表中の略号は下記のとおりである。
SBP-BF4:テトラフルオロホウ酸スピロ−(1,1’)−ビピロリジニウム
TEMA-BF4:テトラフルオロホウ酸トリエチルメチルアンモニウム
DMS:ジメチルスルホン
EMS:エチルメチルスルホン
MIPS:メチルイソプロピルスルホン
EIPS:エチルイソプロピルスルホン
EIBS:エチルイソブチルスルホン
EMC:エチルメチルカーボネート
SL:スルホラン
Abbreviations in the table are as follows.
SBP-BF4: Spiro- (1,1 ')-bipyrrolidinium tetrafluoroborate
TEMA-BF4: Triethylmethylammonium tetrafluoroborate
DMS: Dimethylsulfone
EMS: Ethyl methyl sulfone
MIPS: Methyl isopropyl sulfone
EIPS: Ethyl isopropyl sulfone
EIBS: ethyl isobutyl sulfone
EMC: Ethyl methyl carbonate
SL: sulfolane

表3より、鎖状カーボネートを用いた比較品1は、鎖状スルホンを用いた発明品1〜4に対し低粘性率且つ高電気伝導度であるものの、電位窓は還元側で約0.3V、酸化側でも0.3V狭くなっており、耐電圧が大幅に劣ることは明らかである。また、発明品1〜4では、環状スルホンであるスルホランを用いた比較品2に対して、粘性率を約38〜12%低減することができ、また電気伝導度を約14〜43%向上することができた。さらに、電解質塩としてTEMA−BF4を用いた比較品3,4に対し、同一溶媒でSBP−BF4を用いた発明品1,3の方が、粘性率は19〜29%低減し、電気伝導度も5〜12%向上しており、SBP−BF4を用いることで更なる高性能化が可能となることがわかる。   From Table 3, Comparative Product 1 using chain carbonate has a low viscosity and high electrical conductivity compared to Inventions 1 to 4 using chain sulfone, but the potential window is about 0.3 V on the reduction side. On the oxidation side, the voltage is narrowed by 0.3 V, so that the withstand voltage is clearly inferior. In addition, the inventive products 1 to 4 can reduce the viscosity by about 38 to 12% and improve the electric conductivity by about 14 to 43% compared to the comparative product 2 using sulfolane, which is a cyclic sulfone. I was able to. Furthermore, compared with the comparative products 3 and 4 using TEMA-BF4 as the electrolyte salt, the inventive products 1 and 3 using SBP-BF4 in the same solvent have a viscosity reduced by 19 to 29% and the electric conductivity. 5-12%, and it can be seen that further performance can be improved by using SBP-BF4.

表4より、カーボネート系溶媒であるEMCと環状スルホンであるSLを用いた比較品5に対して、アルキル基の炭素数が異なる鎖状スルホンの混合溶媒を用いた発明品5〜19の方が、還元側で0.25〜0.3V、酸化側で0.1〜0.15V程度広くなっており、耐電圧が大幅に向上していることが分かる。また、発明品5〜20は、スルホン系溶媒のみで構成される比較品6と比較すると、電位窓はほぼ同等であるものの、粘性率および伝導度が著しく向上することが示された。さらに、比較品7と発明品5との比較では、電解質塩にSBP−BF4を用いることで、粘性率で約27%、電気伝導度で約9.5%それぞれ向上していることがわかる。塩濃度を1.0mol/Lから1.5mol/Lに増加させた発明品17〜19では、電気伝導度は約15〜20%向上し、最も高い電気伝導度を得られることが示された。   From Table 4, the inventive products 5 to 19 using a mixed solvent of a chain sulfone having a different number of carbon atoms in the alkyl group are compared to the comparative product 5 using the carbonate solvent EMC and the cyclic sulfone SL. It can be seen that the withstand voltage is greatly improved by 0.25 to 0.3 V on the reduction side and about 0.1 to 0.15 V on the oxidation side. In addition, the inventive products 5 to 20 showed that the viscosity and the conductivity were remarkably improved, although the potential windows were almost the same as the comparative product 6 composed only of the sulfone solvent. Further, in the comparison between the comparative product 7 and the inventive product 5, it is found that the use of SBP-BF4 as the electrolyte salt improves the viscosity by about 27% and the electrical conductivity by about 9.5%. In invention products 17 to 19 in which the salt concentration was increased from 1.0 mol / L to 1.5 mol / L, it was shown that the electric conductivity was improved by about 15 to 20%, and the highest electric conductivity was obtained. .

実 施 例 3
電気二重層キャパシタの作製及び評価:
[電気二重層キャパシタの作製]
実施例2で得られた電解液(発明品1〜19及び比較品1〜7)を用いて、図1に示すような電気二重層キャパシタを作製した。
Example 3
Fabrication and evaluation of electric double layer capacitors:
[Production of electric double layer capacitor]
An electric double layer capacitor as shown in FIG. 1 was produced using the electrolytic solutions obtained in Example 2 (Invention products 1 to 19 and Comparative products 1 to 7).

正極及び負極電極は活物質(活性炭:日本エンバイロケミカルズ株式会社、白鷺KA)、導電材(ケッチェンブラック:ライオン株式会社、ECP−600JD)、バインダー(PTFE:三井・デュポンフロロケミカル株式会社、30−J)を混合し作製した。その質量組成比は活物質:導電材:バインダー=80:10:10とした。これらの混合物にエタノールを加えながら十分に混錬し、圧延することで平均して厚み0.85mmの活性炭シート電極を得た。この活性炭シート電極をφ15のポンチで打ち抜いたものを、集電体(φ17のSUS316製プレート)が溶接されたケース、キャップ(何れもSUS316製)に導電性接着剤にて接着し、それぞれ正極部、負極部を得た。それらの電極に実施例1の電解液をそれぞれ注液し、0.060MPaで10分減圧含浸した後、ポリプロピレン製不織布をセパレータとして介し、ポリプロピレン製ガスケットをキャップに装着して組み立て、カシメ機にて嵌合して2032サイズのコイン型電気二重層キャパシタを完成した。   The positive electrode and the negative electrode are active materials (activated carbon: Nippon Envirochemicals Corporation, Shirasagi KA), conductive material (Ketjen Black: Lion Corporation, ECP-600JD), binder (PTFE: Mitsui / DuPont Fluorochemical Corporation, 30- J) was prepared by mixing. The mass composition ratio was active material: conductive material: binder = 80: 10: 10. These mixtures were sufficiently kneaded while adding ethanol, and rolled to obtain an activated carbon sheet electrode having an average thickness of 0.85 mm. This activated carbon sheet electrode punched out with a φ15 punch is adhered to a case and cap (both made of SUS316) welded with a current collector (φ17 made of SUS316) with a conductive adhesive, respectively. A negative electrode part was obtained. Each of these electrodes was injected with the electrolyte solution of Example 1 and impregnated under reduced pressure at 0.060 MPa for 10 minutes, and then assembled by attaching a polypropylene gasket to the cap with a polypropylene non-woven fabric as a separator. The 2032 size coin type electric double layer capacitor was completed by fitting.

[電気二重層キャパシタの評価]
(初期特性)
作製した電気二重層キャパシタの初期の特性を、それぞれの電気二重層キャパシタについて、20℃、0℃、−20℃、−25℃、−30℃、−35℃において充放電試験を行うことで求めた。具体的には、各キャパシタを所定の測定温度下に30分以上放置し、キャパシタが所定温度に達した後、定格電圧として2.5Vを30分印加後、放電電流2mAにて定電流放電し、キャパシタ端子間電圧が2Vから1Vになるまでの時間より静電容量を算出した。また、放電の下限値を0.0Vとした。内部抵抗は静電容量測定時と同様に定格電圧として2.5Vを30分印加後、放電電流100mAにて定電流放電したときのIRドロップより算出した。結果を表5,6,8,9に示す。
(長期信頼性試験)
初期特性と同様にして、電気二重層キャパシタに3.5Vを1000時間連続印加した後の静電容量と内部抵抗を測定し、初期に対するそれぞれの変化率を求めた。雰囲気温度は60℃とした。結果を表7および10に示す。
[Evaluation of electric double layer capacitor]
(Initial characteristics)
The initial characteristics of the produced electric double layer capacitor are obtained by performing a charge / discharge test at 20 ° C., 0 ° C., −20 ° C., −25 ° C., −30 ° C., and −35 ° C. for each electric double layer capacitor. It was. Specifically, each capacitor is left at a predetermined measurement temperature for 30 minutes or more, and after the capacitor reaches a predetermined temperature, 2.5 V is applied as a rated voltage for 30 minutes, and then a constant current discharge is performed at a discharge current of 2 mA. The capacitance was calculated from the time until the voltage between the capacitor terminals changed from 2V to 1V. Further, the lower limit value of discharge was set to 0.0V. The internal resistance was calculated from the IR drop when a constant current was discharged at a discharge current of 100 mA after applying 2.5 V as a rated voltage for 30 minutes as in the capacitance measurement. The results are shown in Tables 5, 6, 8, and 9.
(Long-term reliability test)
In the same manner as the initial characteristics, the electrostatic capacity and the internal resistance after continuously applying 3.5 V to the electric double layer capacitor for 1000 hours were measured, and the respective rates of change relative to the initial value were obtained. The ambient temperature was 60 ° C. The results are shown in Tables 7 and 10.

Figure 2011044632
Figure 2011044632

Figure 2011044632
Figure 2011044632

Figure 2011044632
Figure 2011044632

表5および6から、溶媒にカーボネート系であるEMCを用いた比較品1は、静電容量および内部抵抗共に最も優れた特性を示したが、表7に示すように長期信頼性が著しく劣るものであった。これは、上記したようにEMCが他のスルホン系溶媒を用いた場合に比べ電位窓が狭く、耐電圧として著しく劣ることから、印加により分解しているものと考えられる。また、純SL溶媒使用の比較品2やTEMA−BF4を使用した比較品3,4では、最も低温でも−20℃までしか特性が発現しないのに対し、発明品2〜4では、−30℃まで特性が発現していることがわかる。特に発明品3が優れた特性を示した。さらに、表7に示すように、発明品1〜4は、3.5Vという高電圧を1000hにわたり印加しても、静電容量の変化率は3.1%以下、内部抵抗の上昇率は約30%以下と特性の劣化はほとんど無く、比較品1〜4に対して優れた長期信頼性を示した。TEMA−BF4を用いた比較品3,4では、アルキルアンモニウム特有のホフマン分解によるエチル基の離脱などにより、内部抵抗の増大等が生じているものと考えられる。   From Tables 5 and 6, Comparative Product 1 using carbonate-based EMC as the solvent showed the most excellent characteristics in both capacitance and internal resistance, but as shown in Table 7, the long-term reliability was remarkably inferior. Met. As described above, this is considered to be decomposed by application because the potential window is narrower and the withstand voltage is remarkably inferior as compared with the case where EMC uses other sulfone solvents as described above. In comparison products 2 and 4 using pure SL solvent and comparison products 3 and 4 using TEMA-BF4, the characteristics are exhibited only up to −20 ° C. even at the lowest temperature, while in products 2 to 4 of the invention, −30 ° C. It can be seen that the characteristics are exhibited. In particular, Invention 3 exhibited excellent characteristics. Further, as shown in Table 7, the inventive products 1 to 4 have a capacitance change rate of 3.1% or less and an internal resistance increase rate of about 3.5% even when a high voltage of 3.5 V is applied for 1000 hours. There was almost no deterioration of the characteristics at 30% or less, and excellent long-term reliability was shown for the comparative products 1 to 4. In the comparative products 3 and 4 using TEMA-BF4, it is considered that an increase in internal resistance or the like occurs due to elimination of the ethyl group due to Hoffman decomposition peculiar to alkylammonium.

Figure 2011044632
Figure 2011044632

Figure 2011044632
Figure 2011044632

Figure 2011044632
Figure 2011044632

表8および9から、鎖状スルホンの混合溶媒を用いた発明品5〜19では、低温特性が−35℃まで測定可能となり、比較品5〜7よりも5〜10℃程度低温でも使用できることが分かった。またEMS:EIPS=10:90の組成で1.5mol/LのSBP−BF4を溶解した発明品18が最も優れた特性を示したが、これはSBP−BF4が鎖状スルホンに特異的に溶解することから、塩濃度を高めることで、モル凝固点降下の低下効果を向上することができ、その結果、より低温でも優れた特性が発現できるようになったものと考えられる。   From Tables 8 and 9, invention products 5 to 19 using a mixed solvent of chain sulfone have low temperature characteristics that can be measured up to −35 ° C., and can be used even at a temperature as low as about 5 to 10 ° C. than comparative products 5 to 7. I understood. Inventive product 18 in which 1.5 mol / L of SBP-BF4 was dissolved with a composition of EMS: EIPS = 10: 90 showed the most excellent characteristics. This was because SBP-BF4 was dissolved specifically in chain sulfone. Therefore, it is considered that by increasing the salt concentration, the effect of lowering the freezing point of the molar freezing point can be improved, and as a result, excellent characteristics can be expressed even at lower temperatures.

また表10から、発明品5〜19は3.5Vという高電圧を1000hにわたり印加しても、静電容量の変化率は3.8%以下、内部抵抗の上昇率は約30%以下と特性の劣化はほとんど無く、優れた長期信頼性を示した。それに比べて、カーボネート系溶媒を用いた比較品5は著しく特性の劣る結果となったが、これは溶媒そのものの分解が原因と考えられる。比較品6,7も発明品と比較して静電容量の減少や内部抵抗の増大が大きいものであった。比較品7では、電解質にTEMA−BF4を用いおり、アルキルアンモニウム特有のホフマン分解によるエチル基の離脱などが主原因であると考えられる。   Also, from Table 10, the inventive products 5 to 19 have characteristics that the rate of change in capacitance is 3.8% or less and the rate of increase in internal resistance is about 30% or less even when a high voltage of 3.5V is applied for 1000 hours. There was almost no deterioration, and excellent long-term reliability was exhibited. In comparison, Comparative Product 5 using a carbonate-based solvent resulted in significantly inferior properties, which is considered to be caused by decomposition of the solvent itself. The comparison products 6 and 7 also had a large decrease in capacitance and increase in internal resistance compared to the invention products. In Comparative Product 7, TEMA-BF4 is used as the electrolyte, and it is thought that the main cause is the elimination of the ethyl group due to Hoffman decomposition peculiar to alkylammonium.

本発明の電解液は、耐電圧が高く耐久性に優れ、また広範な温度範囲で使用可能であり、特に低温でも凝固することなく優れた電気的特性を有するため、小型電子機器から大型自動車用途まで種々の産業分野において使用される電気二重層キャパシタ用の電解液として極めて有用なものである。   The electrolytic solution of the present invention has a high withstand voltage, excellent durability, can be used in a wide temperature range, and has excellent electrical characteristics without solidifying even at low temperatures. It is extremely useful as an electrolytic solution for electric double layer capacitors used in various industrial fields.

1 負極キャップ
2 負極電極
3 集電体
4 電解液
5 セパレータ
6 正極電極
7 正極ケース
8 ガスケット
DESCRIPTION OF SYMBOLS 1 Negative electrode cap 2 Negative electrode 3 Current collector 4 Electrolytic solution 5 Separator 6 Positive electrode 7 Positive electrode case 8 Gasket

Claims (5)

有機溶媒中に第4級アンモニウム塩を溶解した電解液であって、
前記有機溶媒が下記一般式(1)
Figure 2011044632
(式(1)中、R、Rは同一でも異なっていても良い炭素数1〜5の直鎖又は分岐のアルキル基を示す。)
で表される鎖状スルホンを含有し、
前記第4級アンモニウム塩が下記一般式(2)
Figure 2011044632
(式(2)中、m及びnは4〜6の整数を示す。Xは酸成分を示す。)
で表される第4級アンモニウム塩であることを特徴とする電気二重層キャパシタ用電解液。
An electrolytic solution in which a quaternary ammonium salt is dissolved in an organic solvent,
The organic solvent is represented by the following general formula (1)
Figure 2011044632
(In Formula (1), R < 1 >, R < 2 > shows the C1-C5 linear or branched alkyl group which may be same or different.)
Containing a chain sulfone represented by
The quaternary ammonium salt is represented by the following general formula (2)
Figure 2011044632
(In the formula (2), m and n are .X represents an integer of 4 to 6 - shows the acid component.)
An electrolytic solution for an electric double layer capacitor, which is a quaternary ammonium salt represented by the formula:
前記有機溶媒が、RとRの炭素数の合計が2〜3である一般式(1)で表される鎖状スルホンおよびRとRの炭素数の合計が4〜8である一般式(1)で表される鎖状スルホンを含有するものである請求項1記載の電気二重層キャパシタ用電解液。 The organic solvent is a chain sulfone represented by the general formula (1) in which the total carbon number of R 1 and R 2 is 2 to 3, and the total carbon number of R 1 and R 2 is 4 to 8. The electrolytic solution for an electric double layer capacitor according to claim 1, which contains a chain sulfone represented by the general formula (1). とRの炭素数の合計が2〜3である一般式(1)で表される鎖状スルホンと、RとRの炭素数の合計が4〜8である一般式(1)で表される鎖状スルホンとの質量比が、10:90〜90:10である請求項2記載の電気二重層キャパシタ用電解液。 The chain sulfone represented by the general formula (1) in which the total carbon number of R 1 and R 2 is 2 to 3, and the general formula (1 in which the total carbon number of R 1 and R 2 is 4 to 8) The electrolytic solution for an electric double layer capacitor according to claim 2, wherein the mass ratio to the chain sulfone represented by the formula: 前記有機溶媒中、一般式(1)で表される鎖状スルホンを75%以上含有するものである請求項1ないし3のいずれかの項記載の電気二重層キャパシタ用電解液。   The electrolytic solution for an electric double layer capacitor according to any one of claims 1 to 3, wherein the organic solvent contains 75% or more of the chain sulfone represented by the general formula (1). セパレータを挟み込んだ分極性電極に、請求項1ないし4のいずれかの項に記載の電気二重層キャパシタ用電解液を含浸させてなる電気二重層キャパシタ。   An electric double layer capacitor obtained by impregnating a polarizable electrode sandwiching a separator with the electrolytic solution for an electric double layer capacitor according to any one of claims 1 to 4.
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