JP2006196751A - Electric double-layer capacitor with chemically modified carbon nano fiber as polarized electrode - Google Patents

Electric double-layer capacitor with chemically modified carbon nano fiber as polarized electrode Download PDF

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JP2006196751A
JP2006196751A JP2005007683A JP2005007683A JP2006196751A JP 2006196751 A JP2006196751 A JP 2006196751A JP 2005007683 A JP2005007683 A JP 2005007683A JP 2005007683 A JP2005007683 A JP 2005007683A JP 2006196751 A JP2006196751 A JP 2006196751A
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electric double
carbon
chemically modified
layer capacitor
double layer
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Hisahiro Ando
寿浩 安藤
Kiyoharu Nakagawa
清晴 中川
Hirokazu Oda
廣和 小田
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National Institute for Materials Science
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor whose power storage capacity density is larger than a conventional electric double-layer capacitor. <P>SOLUTION: A polarized electrode made of chemically modified carbon nano tube fiber is used. The electric double-layer capacitor using the chemically modified carbon nano tube fiber as the polarized electrode is approximately 1.3 times larger than that using carbon nano tube fiber as the polarized electrode, and is approximately 1.4 times larger than that using the activated carbon as the polarized electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、蓄電量の大きな電気二重層キャパシタに関する。   The present invention relates to an electric double layer capacitor having a large charged amount.

電気二重層キャパシタは、電極と電解液との界面に形成される電気二重層を利用して蓄電するため、化学反応を利用して蓄電する２次電池に較べて、急速な充放電に耐えることができる。このため電気二重層キャパシタは、例えば、燃料電池自動車やハイブリッド自動車の蓄電システム、特に自動車の減速時に散逸させる運動エネルギーを回収する回生エネルギー蓄電システムに必要不可欠となっている。
一方、電気二重層キャパシタの単位体積当たりの蓄電量、すなわち、蓄電容量密度は２次電池に較べて小さく、同等の蓄電量を得るためには容積がより大きくなってしまうことが難点であり、このため、電気二重層キャパシタの蓄電容量密度を向上することが重要課題となっている。 Electric double layer capacitors store electricity using the electric double layer formed at the interface between the electrode and the electrolyte, so they can withstand rapid charge and discharge compared to secondary batteries that store using chemical reactions. Can do. For this reason, the electric double layer capacitor is indispensable for, for example, a power storage system of a fuel cell vehicle or a hybrid vehicle, particularly a regenerative energy storage system that recovers kinetic energy dissipated when the vehicle is decelerated.
On the other hand, the amount of electricity stored per unit volume of the electric double layer capacitor, that is, the electricity storage capacity density is smaller than that of the secondary battery, and in order to obtain an equivalent amount of electricity storage, it is difficult to increase the volume. For this reason, it is an important issue to improve the storage capacity density of the electric double layer capacitor.

電気二重層キャパシタは、電気二重層を形成できる電極、すなわち分極性電極と、電解液と、電解液のイオンのみを通過させるセパレータと、分極性電極の電荷を集電して取り出す集電極とからなり、背面に集電極を有する一対の分極性電極をセパレータを挟んで対向させた構造体に電解液を封入した構造を有する。   An electric double layer capacitor includes an electrode capable of forming an electric double layer, that is, a polarizable electrode, an electrolytic solution, a separator that allows only ions of the electrolytic solution to pass through, and a collecting electrode that collects and extracts charges from the polarizable electrode. Thus, it has a structure in which an electrolytic solution is sealed in a structure in which a pair of polarizable electrodes having a collecting electrode on the back face each other with a separator interposed therebetween.

従来の分極性電極には活性炭がもっぱら用いられている。活性炭は、炭素を成分とする原料を炭化して整粒し、さらに賦活して製造される。活性炭は、極めて多くの細孔を有すし、これらの細孔の表面が電気二重層を形成するので、蓄電容量密度が現在知られている材料の中で最も大きい（非特許文献１参照）。
しかしながら、電気二重層キャパシタの蓄電容量密度は、２次電池と較べていまだ小さく、電気二重層キャパシタの蓄電容量密度のさらなる増大が求められている。 Activated carbon is exclusively used for conventional polarizable electrodes. Activated carbon is produced by carbonizing a raw material containing carbon as a component, sizing and further activating. Activated carbon has an extremely large number of pores, and since the surfaces of these pores form an electric double layer, the storage capacity density is the largest among currently known materials (see Non-Patent Document 1).
However, the storage capacity density of the electric double layer capacitor is still smaller than that of the secondary battery, and further increase in the storage capacity density of the electric double layer capacitor is required.

ところで、上述のように、従来は分極性電極として活性炭がもっぱら利用されているが、蓄電容量密度を増大するために活性炭の比表面積（単位重量当たりの表面積）を増やすと、かさ密度が極端に減少するという（非特許文献２参照）活性炭の性質のために、これ以上の比表面積の増大による蓄電容量密度の増大は困難な状況にある。このような状況の中で、本発明者らは既に、活性炭と同様に炭素を成分とする材料であるが、活性炭のように無定型炭素ではなく、ナノサイズの炭素構造体（以後、カーボンナノ構造体と呼ぶ）である、カーボンナノチューブ、及び／又は、コイン積層型カーボンナノグラファイトを分極性電極として使用すると、蓄電容量密度を、活性炭を分極性電極とした場合よりも大きくできることを見いだした（特許文献１参照）。
ところで、活性炭を分極性電極とした電気二重層キャパシタにおいて、炭素の表面に導入された官能基、特に含酸素官能基は電気二重層を形成する化学的、及び、電気化学的活性度が高く、キャパシタの蓄電能力に大きな役割を果たしていることが報告されている（非特許文献３，４参照）。
特願２００３−３６８３５６号 岡村廸夫著、“電気二重層キャパシタと蓄電システム”ｐ７７、図３−１２、日刊工業新聞社、２００１年２月第二版 田村英雄監修、“電子とイオンの機能化学シリーズ Ｖｏｌ．２ 大容量電気二重層キャパシタの最前線”ｐ４０、株式会社エヌ・ティー・エス ２００２年１月 初版第一刷 Ａ．Ｙｏｓｈｉｄａ，Ｉ．Ｔａｎａｈａｓｈｉ ａｎｄ Ａ．Ｎｉｓｈｉｎｏ：Ｃａｒｂｏｎ，２８，６１１（１９９０） 門間聰之，逢坂哲弥，Ｘｉｎｇｊｉａｎｇ Ｌｉｕ：電気化学及び工業物理化学，６４，１４３（１９８８） 菊池英一，瀬川幸一，多田旭男，射水雄三，服部英，共著“新しい触媒化学”第二版 ｐ１８６〜ｐ１９０ 三共出版 By the way, as described above, activated carbon is conventionally used exclusively as a polarizable electrode. However, if the specific surface area (surface area per unit weight) of activated carbon is increased in order to increase the storage capacity density, the bulk density becomes extremely large. Due to the property of activated carbon that decreases (see Non-Patent Document 2), it is difficult to increase the storage capacity density by increasing the specific surface area. In such a situation, the present inventors have already made a material containing carbon as in the case of activated carbon, but not amorphous carbon as in activated carbon, but a nano-sized carbon structure (hereinafter referred to as carbon nanostructure). It was found that when carbon nanotubes and / or coin-stacked carbon nanographite, which is a structure, is used as a polarizable electrode, the storage capacity density can be made larger than when activated carbon is used as a polarizable electrode ( Patent Document 1).
By the way, in an electric double layer capacitor using activated carbon as a polarizable electrode, the functional group introduced on the surface of carbon, particularly the oxygen-containing functional group, has a high chemical and electrochemical activity to form an electric double layer, It has been reported that it plays a major role in the storage capacity of capacitors (see Non-Patent Documents 3 and 4).
Japanese Patent Application No. 2003-368356 Okamura Ikuo, “Electric Double Layer Capacitor and Power Storage System” p77, Fig. 3-12, Nikkan Kogyo Shimbun, February 2001, 2nd edition Supervised by Hideo Tamura, “Functional Chemistry Series of Electrons and Ions Vol.2 The Forefront of High-Capacity Double-Layer Capacitors” p40, NTS Corporation January 2002 First Edition First Print A. Yoshida, I .; Tanahashi and A.M. Nishino: Carbon, 28, 611 (1990) Tomoyuki Kadama, Tetsuya Osaka, Xingjiang Liu: Electrochemistry and industrial physical chemistry, 64, 143 (1988) Eiichi Kikuchi, Koichi Segawa, Asao Tada, Yuzo Imizu, Ei Hattori, Co-authored “New Catalytic Chemistry” Second Edition p186-p190 Sankyo Publishing

本発明者らは、カーボンナノ構造体と、カーボンナノ構造体の表面に導入された含酸素官能基を有する、化学修飾カーボンナノ繊維（本発明者らによる本願と同日出願の”化学修飾カーボンナノ繊維及びその製造方法”を参照）を分極性電極とすることにより、従来にない高蓄電容量密度の電気二重層キャパシタが実現できることを見いだし、本発明に到った。   The present inventors have developed a chemically modified carbon nanofiber having a carbon nanostructure and an oxygen-containing functional group introduced on the surface of the carbon nanostructure (“chemically modified carbon nanofiber filed on the same day as the present application by the present inventors”). It has been found that an electric double layer capacitor having a high storage capacity density which has not been conventionally achieved can be realized by using a polarizable electrode as a fiber and a method for producing the same), and the present invention has been achieved.

上記目的を達成するために、本発明の化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタは、分極性電極と電解液を用いる電気二重層キャパシタにおいて、分極性電極が化学修飾カーボンナノ繊維から成ることを特徴とする。
化学修飾カーボンナノ繊維は、カーボンナノチューブと、カーボンナノチューブの表面に導入したカルボニル基及び／又はエーテル基からなることを特徴とする。また、化学修飾カーボンナノ繊維は、カップ積層型カーボンナノフィラメントと、カップ積層型カーボンナノフィラメントの表面に導入したカルボニル基及び／又はエーテル基からなることを特徴とする。
また、化学修飾カーボンナノ繊維は、コイン積層型カーボンナノフィラメントと、コイン積層型カーボンナノフィラメントの表面に導入したカルボニル基及び／又はエーテル基からなることを特徴とする。
この構成によれば、従来にない高蓄電容量密度の電気二重層キャパシタが得られる。 In order to achieve the above object, an electric double layer capacitor using a chemically modified carbon nanofiber of the present invention as a polarizable electrode is an electric double layer capacitor using a polarizable electrode and an electrolyte solution. It consists of fiber.
The chemically modified carbon nanofiber is characterized by comprising a carbon nanotube and a carbonyl group and / or an ether group introduced on the surface of the carbon nanotube. The chemically modified carbon nanofiber is characterized by comprising a cup-stacked carbon nanofilament and a carbonyl group and / or an ether group introduced on the surface of the cup-stacked carbon nanofilament.
Further, the chemically modified carbon nanofiber is characterized by comprising a coin laminated carbon nanofilament and a carbonyl group and / or an ether group introduced on the surface of the coin laminated carbon nanofilament.
According to this configuration, an electric double layer capacitor having an unprecedented high storage capacity density can be obtained.

この作用効果は以下のように推定される。
化学修飾カーボンナノ繊維は、カーボンナノチューブ等のカーボンナノ構造体をカルボニル基及び／又はエーテル基で化学修飾したものであり（本発明者らによる本願と同日出願の”化学修飾カーボンナノ繊維及びその製造方法”を参照）、カルボニル基は、炭素と酸素の２重結合による状態と、炭素原子の電子が酸素原子側に強く引きつけられたイオン性結合状態とが共存した共鳴状態を有するので、化学修飾カーボンナノ繊維は大きな電気分極を有している。この電気分極は、電気二重層の分極をより大きくするものと考えられ、また、カーボンナノ構造体はグラファイト端（ｅｄｇｅ）密度が活性炭に比べて大きい（特許文献１参照）ので、電気分極による効果とカーボンナノ構造体の構造的特徴による効果とが組み合わされて、従来にない高蓄電容量密度が実現できると推定される。 This effect is estimated as follows.
Chemically modified carbon nanofibers are carbon nanostructures such as carbon nanotubes that have been chemically modified with carbonyl groups and / or ether groups ("chemically modified carbon nanofibers filed on the same day as the present application by the present inventors and their production"). The carbonyl group has a resonance state in which the state due to the double bond between carbon and oxygen and the ionic bond state in which the electron of the carbon atom is strongly attracted to the oxygen atom side coexist. Carbon nanofibers have a large electrical polarization. This electrical polarization is considered to increase the polarization of the electric double layer, and the carbon nanostructure has a higher graphite edge (edge) density than activated carbon (see Patent Document 1). It is presumed that an unprecedented high storage capacity density can be realized by combining the effects of the structural characteristics of carbon nanostructures with carbon.

本発明の化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタによれば、電極の単位面積当たりの蓄電容量が従来の電気二重層キャパシタよりも大きい。   According to the electric double layer capacitor using the chemically modified carbon nanofiber of the present invention as a polarizable electrode, the storage capacity per unit area of the electrode is larger than that of the conventional electric double layer capacitor.

以下に、実施例に基づいて本発明の化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタの実施の形態を詳細に説明する。なお、電気二重層キャパシタは、分極性電極と、電解液と、電解液のイオンのみを通過させるセパレータと、分極性電極の電荷を集電して取り出す集電極とからなり、背面に集電極を有する一対の分極性電極をセパレータを挟んで対向させた構造体に電解液を封入した構造を有している。本発明の電気二重層キャパシタは上記の構成の電気二重層キャパシタであり、分極性電極が化学修飾カーボンナノ繊維から成ることが従来技術と異なる。上記の電気二重層キャパシタの構成は周知
であるので説明を省略する。 Below, based on an Example, Embodiment of the electric double layer capacitor which used the chemically modified carbon nanofiber of this invention as a polarizable electrode is described in detail. The electric double layer capacitor includes a polarizable electrode, an electrolytic solution, a separator that allows only ions of the electrolytic solution to pass through, and a collector electrode that collects and extracts charges from the polarizable electrode. It has a structure in which an electrolytic solution is sealed in a structure in which a pair of polarizable electrodes having the separator are opposed to each other with a separator interposed therebetween. The electric double layer capacitor of the present invention is an electric double layer capacitor having the above-described configuration, and differs from the prior art in that the polarizable electrode is made of chemically modified carbon nanofibers. Since the structure of the electric double layer capacitor is well known, the description thereof is omitted.

初めに、本発明の化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタの分極性電極に用いる化学修飾カーボンナノ繊維の製造方法について説明する。尚、本発明者らによる本願と同日出願の”化学修飾カーボンナノ繊維及びその製造方法”も参照されたい。
本実施例では、カーボンナノ繊維としてカーボンナノチューブを用いた。
カーボンナノチューブは、アーク放電法、レーザー蒸着法、ＣＶＤ法などで大量に合成でき、その方法は周知であるので説明を省略する。
カーボンナノチューブを酸化剤中で酸化することにより、カーボンナノチューブ表面にカルボニル基及び／又はエーテル基を導入した。酸化剤として気相Ｎ2 Ｏを用い、５００℃、３０分の酸化を行った。酸化条件は、５００℃、３０分が最適であり、これ以上の温度では、カーボンナノチューブがＣＯ2 ガス（炭酸ガス）となって消失してしまい、これ未満の温度では、カーボンナノチューブが酸素と反応しなかった。 First, a method for producing chemically modified carbon nanofibers used for a polarizable electrode of an electric double layer capacitor using the chemically modified carbon nanofiber of the present invention as a polarizable electrode will be described. Please also refer to “Chemically modified carbon nanofibers and production method thereof” filed on the same day as the present application by the present inventors.
In this example, carbon nanotubes were used as the carbon nanofibers.
Carbon nanotubes can be synthesized in large quantities by an arc discharge method, a laser vapor deposition method, a CVD method, or the like, and the method is well known, and thus the description thereof is omitted.
Carbon nanotubes and / or ether groups were introduced on the surface of carbon nanotubes by oxidizing the carbon nanotubes in an oxidizing agent. Gas phase N 2 O was used as an oxidizing agent, and oxidation was performed at 500 ° C. for 30 minutes. The oxidation conditions are optimal at 500 ° C. for 30 minutes. At temperatures higher than this, the carbon nanotubes disappear as CO 2 gas (carbon dioxide gas), and at temperatures below this, the carbon nanotubes react with oxygen. I did not.

次に、作製した化学修飾カーボンナノ繊維（以下の説明では、化学修飾カーボンナノチューブ繊維と呼ぶ）の走査電子顕微鏡像を示す。
図１は、作製した化学修飾カーボンナノチューブ繊維の走査電子顕微鏡像を示す図であり、（ａ）は酸化前のカーボンナノチューブの像、（ｂ）は酸化後のカーボンナノチューブ、すなわち、化学修飾カーボンナノチューブ繊維の像を示す。
図１（ｂ）のカーボンナノチューブは、図１（ａ）のカーボンナノチューブと比べて、著しくカーボンナノチューブの表面の像コントラストが一様でないことがわかる。これは、酸化によってカーボンナノチューブの表面に酸素が導入され、その表面の導電性が減少し、走査電子線の電子が帯電（ｃｈａｒｇｅ ｕｐ）したためである。すなわち、カーボンナノチューブの表面に酸素が導入されたことがわかる。 Next, a scanning electron microscope image of the produced chemically modified carbon nanofiber (referred to as a chemically modified carbon nanotube fiber in the following description) is shown.
FIG. 1 is a view showing a scanning electron microscope image of a chemically modified carbon nanotube fiber produced, (a) is an image of a carbon nanotube before oxidation, and (b) is a carbon nanotube after oxidation, that is, a chemically modified carbon nanotube. The image of a fiber is shown.
It can be seen that the carbon nanotubes of FIG. 1B have a remarkably non-uniform image contrast on the surface of the carbon nanotubes as compared to the carbon nanotubes of FIG. This is because oxygen is introduced into the surface of the carbon nanotube by oxidation, the conductivity of the surface is reduced, and the electrons of the scanning electron beam are charged up. That is, it can be seen that oxygen was introduced to the surface of the carbon nanotube.

図２は、作製した化学修飾カーボンナノ繊維のフーリエ変換赤外吸収測定結果を示す図であり、横軸は波数（ｃｍ-1）、縦軸は吸光度（任意メモリ）である。図から、１６５０−１８５０ｃｍ-1のカルボニル基の赤外吸収ピーク位置、及び１１５０−１２５０ｃｍ-1のエーテル基の赤外吸収ピーク位置に赤外吸収が見られることから、導入された酸素は、カルボニル基及びエーテル基を形成していることがわかる。 FIG. 2 is a diagram showing the results of Fourier transform infrared absorption measurement of the produced chemically modified carbon nanofibers, in which the horizontal axis represents wave number (cm −1 ) and the vertical axis represents absorbance (arbitrary memory). From the figure, infrared absorption is observed at the infrared absorption peak position of the carbonyl group of 1650-1850 cm −1 and the infrared absorption peak position of the ether group of 1150-1250 cm −1. It can be seen that a group and an ether group are formed.

図１、図２から、作製した化学修飾カーボンナノチューブ繊維は、カーボンナノチューブの表面にカルボニル基及び／又はエーテル基を有することがわかる。   1 and 2 that the chemically modified carbon nanotube fiber produced has a carbonyl group and / or an ether group on the surface of the carbon nanotube.

図３は、カーボンナノチューブの炭素が酸素と結合した状態を示す模式図である。図において、＝Ｏはカーボンナノチューブの炭素１個と二重結合した酸素とからなるカルボニル基を示しており、＞Ｏはカーボンナノチューブの炭素２個と結合した酸素とからなるエーテル基を示している。なお、図を見やすくするため、カーボンナノチューブの平面外形に沿った部分の官能基のみを図示しているが、もちろん側壁全面に亘って均一な密度で官能基が導入されている。   FIG. 3 is a schematic view showing a state in which carbon of the carbon nanotube is bonded to oxygen. In the figure, = O represents a carbonyl group composed of one carbon of the carbon nanotube and oxygen double bonded, and> O represents an ether group composed of oxygen bonded to two carbons of the carbon nanotube. . In order to make the drawing easier to see, only the functional groups in the portion along the planar outline of the carbon nanotube are shown, but of course, the functional groups are introduced at a uniform density over the entire side wall.

カーボンナノチューブは、規則正しい六員環配列構造を有するグラファイト層からなり、グラファイト層の最外殻電子状態はπ電子状態であり、導電性は有していても電気分極は小さい。酸化により、グラファイト層の炭素−炭素結合手の一部が切断され、切断された炭素の結合手と酸素とが化学結合し、及び／又は、グラファイト端のダングリングボンドと酸素とが化学結合する。化学結合の形態には、二通りがあり、１個の炭素と１個の酸素が結合した場合には、Ｃ＝Ｏであるカルボニル基、及び、２個の炭素と１個の酸素が結合した場合には、Ｃ−Ｏ−Ｃであるエーテル基が形成され、上記の作製条件ではカルボニル基とエーテル基とが混在して形成される。このうち、カルボニル基Ｃ＝Ｏは、炭素と酸
素の２重結合による状態と、炭素原子の電子が酸素原子側に強く引きつけられたイオン性結合状態とが共存した共鳴状態を有するので、カルボニル基を有するカーボンナノチューブは、その表面に大きな電気分極を有するようになる。カルボニル基を導入したカーボンナノチューブは次のような効果を生ずる。カルボニル基を導入したカーボンナノチューブを電気二重層キャパシタの分極性電極として用いた場合には、カーボンナノチューブのグラファイト端密度が高い（特許文献１参照）ことと、カルボニル基の電気分極が電気二重層の分極密度を大きくする効果とが組み合わされ、従来よりも蓄電容量が大きい電気二重層キャパシタを実現できる。 The carbon nanotube is composed of a graphite layer having a regular six-membered ring arrangement structure. The outermost electronic state of the graphite layer is a π-electron state, and the electric polarization is small even though it has conductivity. Oxidation cuts part of the carbon-carbon bond in the graphite layer, chemically bonds the broken carbon bond and oxygen, and / or chemically bonds the dangling bond and oxygen at the graphite end. . There are two types of chemical bonds. When one carbon and one oxygen are bonded, a carbonyl group in which C═O and two carbons and one oxygen are bonded. In this case, an ether group that is C—O—C is formed, and a carbonyl group and an ether group are formed together under the above-described manufacturing conditions. Among them, the carbonyl group C═O has a resonance state in which a state due to a double bond of carbon and oxygen and an ionic bond state in which electrons of the carbon atom are strongly attracted to the oxygen atom side coexist. Carbon nanotubes having a large electric polarization on the surface thereof. Carbon nanotubes introduced with carbonyl groups produce the following effects. When carbon nanotubes introduced with carbonyl groups are used as polarizable electrodes of electric double layer capacitors, the carbon nanotube has a high graphite edge density (see Patent Document 1), and the electric polarization of the carbonyl groups is that of the electric double layer. Combined with the effect of increasing the polarization density, it is possible to realize an electric double layer capacitor having a larger storage capacity than the conventional one.

次に、作製した化学修飾カーボンナノチューブ繊維を用いて、化学修飾カーボンナノチューブ繊維を分極性電極とした電気二重層キャパシタを作製した。
以下に作製方法を説明する。ポリテトラフルオロエチレン樹脂をバインダーとして、化学修飾カーボンナノチューブ繊維とエタノールとを所定の比率で混合し、乳鉢で良く混練してスラリーを作製し、このスラリーを鋳型に入れて１１０℃、２時間の真空乾燥によって板状に成型した。この板から１ｃｍ×１ｃｍの大きさで切り出したものを分極性電極とした。
ポリプロピレン不織布をセパレータとして、上記２枚の分極性電極を対向させ、電解液として１モル％濃度のＨ2 ＳＯ4 水溶液を用い、真空中で１時間放置して、分極性電極に電解液を含浸させた。なお、集電極と分極性電極は接着剤を用いずに、圧着によって接触させた。
なお、静電容量の比較のために、カーボンナノチューブ繊維を分極性電極とした電気二重層キャパシタ、及び、活性炭を分極性電極とした電気二重層キャパシタを、分極性電極の材料が異なる点を除いては、上記と同一の方法で作製した。 Next, an electric double layer capacitor using the chemically modified carbon nanotube fiber as a polarizable electrode was produced using the produced chemically modified carbon nanotube fiber.
A manufacturing method will be described below. Using polytetrafluoroethylene resin as a binder, chemically modified carbon nanotube fibers and ethanol are mixed at a predetermined ratio and kneaded well in a mortar to produce a slurry. The slurry is placed in a mold and vacuumed at 110 ° C. for 2 hours. Molded into a plate by drying. What was cut out from this plate with a size of 1 cm × 1 cm was used as a polarizable electrode.
Using a polypropylene nonwoven fabric as a separator, the above two polarizable electrodes face each other, and a 1 mol% concentration H 2 SO 4 aqueous solution is used as an electrolytic solution, which is left in a vacuum for 1 hour to impregnate the polarizable electrode with the electrolytic solution. I let you. The collector electrode and the polarizable electrode were brought into contact with each other without using an adhesive.
For comparison of capacitance, the electric double layer capacitor using carbon nanotube fiber as a polarizable electrode and the electric double layer capacitor using activated carbon as a polarizable electrode, except that the material of the polarizable electrode is different. The same method as described above was used.

次に、静電容量の測定方法を説明する。充電電流密度１．０ｍＡ／ｃｍ2 で１ｖｏｌｔまで充電し、その後、放電電流密度０．１〜１．０ｍＡ／ｃｍ2 の範囲の種々の一定電流密度で放電させ、放電電流を放電時間で積分して全放電電荷量を求め、全放電電荷量と充電電圧とから放電容量を求めた。 Next, a method for measuring capacitance will be described. Was charged at a charging current density of 1.0 mA / cm 2 to 1 Volt, then the discharge current density 0.1~1.0mA / cm was discharged at various constant current density of 2 range, it integrates the discharge current in the discharge time Thus, the total discharge charge amount was obtained, and the discharge capacity was obtained from the total discharge charge amount and the charge voltage.

図４は、作製した化学修飾カーボンナノチューブ繊維を分極性電極とした電気二重層キャパシタと、カーボンナノチューブ繊維を分極性電極とした電気二重層キャパシタと、活性炭を分極性電極材料とした電気二重層キャパシタとの、単位電極面積あたりの放電容量の比較を示す図である。図には測定した比表面積も示している。比表面積は、冷却した試料にＮ2 ガスを流して吸着させ、吸着平衡圧から表面積を求めるＢＥＴ法（非特許文献５参照）を用いた。
図から、各々の電気二重層キャパシタの単位面積あたりの放電容量を比較すると、本発明の化学修飾カーボンナノチューブ繊維を分極性電極とした電気二重層キャパシタは、カーボンナノチューブ繊維を分極性電極とした電気二重層キャパシタと比べて約１．３倍大きく、また、活性炭を分極性電極とした電気二重層キャパシタと較べ約１．４倍大きいことがわかる。
この結果は、化学修飾カーボンナノチューブ繊維の官能基が放電容量を増大させることを実証し、また、化学修飾カーボンナノチューブ繊維のカーボンナノチューブ構造体の構造的特徴による効果と官能基による効果とが組み合わされて、従来にない高蓄電容量密度が実現できることを実証したものである。 FIG. 4 shows an electric double layer capacitor using the produced chemically modified carbon nanotube fiber as a polarizable electrode, an electric double layer capacitor using carbon nanotube fiber as a polarizable electrode, and an electric double layer capacitor using activated carbon as a polarizable electrode material. It is a figure which shows the comparison of the discharge capacity per unit electrode area. The figure also shows the measured specific surface area. For the specific surface area, a BET method (see Non-Patent Document 5) was used in which N 2 gas was allowed to flow through a cooled sample and adsorbed, and the surface area was determined from the adsorption equilibrium pressure.
From the figure, when comparing the discharge capacity per unit area of each electric double layer capacitor, the electric double layer capacitor using the chemically modified carbon nanotube fiber of the present invention as a polarizable electrode has an electric capacity using the carbon nanotube fiber as a polarizable electrode. It is about 1.3 times larger than the double layer capacitor and about 1.4 times larger than the electric double layer capacitor using activated carbon as a polarizable electrode.
This result demonstrates that the functional group of the chemically modified carbon nanotube fiber increases the discharge capacity, and the effect of the structural feature of the carbon nanotube structure of the chemically modified carbon nanotube fiber is combined with the effect of the functional group. Thus, it has been demonstrated that an unprecedented high storage capacity density can be realized.

本発明の化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタによれば、従来の電気二重層キャパシタよりも蓄電容量密度が大きいので、電子機器のバックアップ電源、モバイル通信機の電源、あるいは、燃料電池自動車やハイブリッド自動車の蓄電システム、特に自動車の減速時に散逸させる運動エネルギーを回収する回生エネルギー蓄
電システムに使用すれば、有用である。 According to the electric double layer capacitor using the chemically modified carbon nanofiber of the present invention as a polarizable electrode, since the storage capacity density is higher than that of a conventional electric double layer capacitor, a backup power source for electronic devices, a power source for mobile communication devices, or It is useful when used in a power storage system of a fuel cell vehicle or a hybrid vehicle, particularly a regenerative energy storage system that recovers kinetic energy dissipated when the vehicle is decelerated.

化学修飾カーボンナノチューブ繊維の走査電子顕微鏡像を示す図であり、（ａ）は酸化前のカーボンナノチューブの像、（ｂ）は酸化後のカーボンナノチューブ、すなわち、化学修飾カーボンナノチューブ繊維の像を示す。It is a figure which shows the scanning electron microscope image of a chemically modified carbon nanotube fiber, (a) is the image of the carbon nanotube before oxidation, (b) shows the image of the carbon nanotube after oxidation, ie, a chemically modified carbon nanotube fiber. 化学修飾カーボンナノ繊維のフーリエ変換赤外吸収測定結果を示す図であり、横軸は波数（ｃｍ-1）、縦軸は吸光度（任意メモリ）である。It is a figure which shows the Fourier-transform infrared absorption measurement result of a chemically modified carbon nanofiber, A horizontal axis is a wave number (cm <-1> ) and a vertical axis | shaft is a light absorbency (arbitrary memory). カーボンナノチューブの炭素の酸素との結合状態を示す模式図である。It is a schematic diagram which shows the coupling | bonding state with the oxygen of carbon of a carbon nanotube. 本発明の化学修飾カーボンナノチューブ繊維を分極性電極とした電気二重層キャパシタと、カーボンナノチューブ繊維を分極性電極とした電気二重層キャパシタと、活性炭を分極性電極材料とした電気二重層キャパシタとの、単位電極面積あたりの放電容量の比較を示す図である。An electric double layer capacitor having a chemically modified carbon nanotube fiber of the present invention as a polarizable electrode, an electric double layer capacitor having a carbon nanotube fiber as a polarizable electrode, and an electric double layer capacitor having activated carbon as a polarizable electrode material, It is a figure which shows the comparison of the discharge capacity per unit electrode area.

Claims (4)

分極性電極と電解液を用いる電気二重層キャパシタにおいて、分極性電極が化学修飾カーボンナノ繊維から成ることを特徴とする、化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタ。   An electric double layer capacitor using a chemically modified carbon nanofiber as a polarizable electrode, wherein the polarizable electrode is composed of a chemically modified carbon nanofiber in an electric double layer capacitor using a polarizable electrode and an electrolyte. 前記化学修飾カーボンナノ繊維は、カーボンナノチューブと、カーボンナノチューブの表面に導入したカルボニル基及び／又はエーテル基からなることを特徴とする、請求項１に記載の化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタ。   The chemically modified carbon nanofiber according to claim 1, wherein the chemically modified carbon nanofiber comprises a carbon nanotube and a carbonyl group and / or an ether group introduced on the surface of the carbon nanotube. Electric double layer capacitor. 前記化学修飾カーボンナノ繊維は、カップ積層型カーボンナノフィラメントと、カップ積層型カーボンナノフィラメントの表面に導入したカルボニル基及び／又はエーテル基からなることを特徴とする、請求項１に記載の化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタ。   The chemically modified carbon nanofiber according to claim 1, wherein the chemically modified carbon nanofiber includes a cup-stacked carbon nanofilament and a carbonyl group and / or an ether group introduced on the surface of the cup-stacked carbon nanofilament. Electric double layer capacitor with carbon nanofibers as polarizable electrodes. 前記化学修飾カーボンナノ繊維は、コイン積層型カーボンナノフィラメントと、コイン積層型カーボンナノフィラメントの表面に導入したカルボニル基及び／又はエーテル基からなることを特徴とする、請求項１に記載の化学修飾カーボンナノ繊維を分極性電極とした電気二重層キャパシタ。   The chemically modified carbon nanofiber according to claim 1, wherein the chemically modified carbon nanofiber includes a coin laminated carbon nanofilament and a carbonyl group and / or an ether group introduced on the surface of the coin laminated carbon nanofilament. Electric double layer capacitor with carbon nanofibers as polarizable electrodes.
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WO2010059729A1 (en) * 2008-11-18 2010-05-27 Johnson Controls Technology Company Electrical power storage devices
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US11233293B2 (en) 2008-12-18 2022-01-25 Clarios Germany Gmbh & Co. Kg Laminar textile material for a battery electrode
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