JP2006278364A - Polarizable electrode for electric double layer capacitor and electric double layer capacitor - Google Patents
Polarizable electrode for electric double layer capacitor and electric double layer capacitor Download PDFInfo
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Abstract
Description
本発明は、活性炭を分極性電極の材料に用いた電気二重層キャパシタに関する。 The present invention relates to an electric double layer capacitor using activated carbon as a material for a polarizable electrode.
電気二重層キャパシタは、蓄電デバイスの一種であり、多孔質導電材料からなる電極の界面にイオンを吸脱着させることで電気を充放電する。イオンは電極界面に吸着することから、多孔質導電材料として高比表面積の活性炭等の多孔質炭素材料が主に使用されている。
電気二重層キャパシタは、これまで、小型電子部品用永久電源として商品化されてきたが、近年、ハイブリッド自動車（ＨＥＶ）用電源、無停電電源（ＵＰＳ）等の大容量用途での使用が検討されており、この用途では、高性能化、特に高速充放電特性の向上が望まれている
An electric double layer capacitor is a kind of electricity storage device, and charges and discharges electricity by adsorbing and desorbing ions at the interface of an electrode made of a porous conductive material. Since ions are adsorbed on the electrode interface, porous carbon materials such as activated carbon having a high specific surface area are mainly used as the porous conductive material.
The electric double layer capacitor has been commercialized as a permanent power source for small electronic components so far. However, in recent years, the use for a large capacity application such as a power source for a hybrid vehicle (HEV) and an uninterruptible power source (UPS) has been studied. In this application, high performance, especially high-speed charge / discharge characteristics, is desired.
かかる高性能化要求に対し、電極に使用される多孔質炭素材料に関してさまざまな提案がなされており、そのなかで上記の高速充放電特性の改善要求に対しては、活性炭粒子間の抵抗を減らす手法が多く提案されている。 Various proposals have been made regarding porous carbon materials used for electrodes in response to such demands for high performance, and among them, the resistance between activated carbon particles is reduced in response to the above-mentioned demands for improving the high-speed charge / discharge characteristics. Many methods have been proposed.
例えば、内蔵される分極性電極が活性炭とカーボンウイスカーを含有するものであり、活性炭の粒子とカーボンウイスカーが電気的に接続された電気二重層キャパシタが開示されている。分極性電極は、活性炭原料樹脂とカーボンウイスカーを焼成、賦活することにより製造される（特許文献１参照。）。
しかし、この場合、物理的な混合では、繰り返し充放電時の活性炭粒子の膨張等により、活性炭の粒子とカーボンウイスカーの接触状態が変動し、電気的接続が不良となる可能性がある。
For example, an electric double layer capacitor in which a built-in polarizable electrode contains activated carbon and carbon whiskers, and particles of activated carbon and carbon whiskers are electrically connected is disclosed. A polarizable electrode is manufactured by baking and activating activated carbon raw material resin and a carbon whisker (refer patent document 1).
However, in this case, in the physical mixing, the contact state between the activated carbon particles and the carbon whiskers may fluctuate due to the expansion of the activated carbon particles during repeated charging / discharging, resulting in poor electrical connection.
また、活性炭粉末に直径数μｍのメソカーボン微粒子を混合し、焼結した電極体を用いる電気二重層キャパシタが開示されている（特許文献２参照。）。
しかし、この場合、焼結によりメソカーボンは強固に活性炭粉末に結着しうるが、メソカーボンの焼結体の炭化度が高くないため、焼結による導電性の向上は不十分と考えられる。
In addition, an electric double layer capacitor using an electrode body obtained by mixing activated carbon powder with mesocarbon fine particles having a diameter of several μm and sintering it is disclosed (see Patent Document 2).
However, in this case, the mesocarbon can be firmly bound to the activated carbon powder by sintering, but since the carbonization degree of the mesocarbon sintered body is not high, the improvement in conductivity by the sintering is considered insufficient.
また、活性炭粒子外に一部が突出するようにして、金属、導電性セラミックス、カーボンウイスカー等の繊維状導電化材が埋め込まれた電極を用いる電気二重層キャパシタが開示されている方法が開示されている。電極は、予め繊維状導電化材を内蔵させた炭素複合体を作り、その炭素部分を賦活し、粉砕することにより製造される（特許文献３参照。）。
しかし、この場合、繊維状導電化材は材質によっては賦活反応の際に劣化するおそれがある。また、賦活後、粉砕して所定の粒子径にする際、異種材料間での剥離が予想され、活性炭表面から繊維状導電化材の一部が突出した電極を得ることは困難が予想される。
Also disclosed is a method in which an electric double layer capacitor is disclosed that uses an electrode in which a fibrous conductive material such as metal, conductive ceramics, carbon whisker or the like is embedded so that a part protrudes from the activated carbon particles. ing. An electrode is manufactured by making a carbon composite in which a fibrous conductive material is previously incorporated, activating and pulverizing the carbon portion (see Patent Document 3).
In this case, however, the fibrous conductive material may be deteriorated during the activation reaction depending on the material. In addition, after activation, when pulverized to a predetermined particle size, separation between different materials is expected, and it is expected that it is difficult to obtain an electrode in which a part of the fibrous conductive material protrudes from the activated carbon surface. .
また、粉末活性炭が熱処理され、その粒子表面にカーボンウイスカーを成長させたカーボンペースト電極を用いる電気二重層キャパシタが開示されている。熱処理は、２８００℃以上の超高温で行われる（特許文献４参照。）。
しかし、この場合、通常の活性炭は、このような超高温での熱処理を受けると、細孔構造自体が変化し、活性炭が有していた充放電特性自体が変化すると考えられる。
However, in this case, when the activated carbon is subjected to heat treatment at such an ultra-high temperature, the pore structure itself is changed, and the charge / discharge characteristics of the activated carbon itself are considered to be changed.
上記のように、従来の電気二重キャパシタは、いずれも、低速度の充放電では十分な静電容量を発現するが、高速充放電を行わせるときに高性能を得ることは難しいものと考えられる。 As described above, all of the conventional electric double capacitors exhibit sufficient capacitance at low speed charging / discharging, but it is difficult to obtain high performance when performing high speed charging / discharging. It is done.
本発明は、上記の課題に鑑みてなされたものであり、高速充放電での静電容量が高い電気二重層キャパシタを提供することを目的とする。 The present invention has been made in view of the above problems, and an object thereof is to provide an electric double layer capacitor having a high electrostatic capacity during high-speed charge / discharge.
本発明者らは、電気二重層キャパシタの分極性電極として、活性炭表面に繊維状炭素質を気相成長させた炭素複合材を用いることで、高速充放電特性を顕著に改善できることを見出し本発明に想達した。 The present inventors have found that high-speed charge / discharge characteristics can be remarkably improved by using a carbon composite material in which a fibrous carbonaceous material is vapor-grown on an activated carbon surface as a polarizable electrode of an electric double layer capacitor. I thought.
上記目的を達成するために、本発明に係る電気二重層キャパシタ用分極性電極は、活性炭の表面に繊維状炭素質を気相成長させてなる炭素複合材を主成分とすることを特徴とする。 In order to achieve the above object, a polarizable electrode for an electric double layer capacitor according to the present invention is characterized by comprising as a main component a carbon composite material obtained by vapor-phase growth of fibrous carbonaceous material on the surface of activated carbon. .
また、本発明に係る電気二重層キャパシタ用分極性電極は、前記炭素複合材中における前記繊維状炭素質の質量分率が０．１〜５０質量％であることを特徴とする。 The polarizable electrode for an electric double layer capacitor according to the present invention is characterized in that a mass fraction of the fibrous carbonaceous material in the carbon composite material is 0.1 to 50% by mass.
また、本発明に係る電気二重層キャパシタ用分極性電極は、前記繊維状炭素質がカーボンナノファイバーであることを特徴とする。 The polarizable electrode for an electric double layer capacitor according to the present invention is characterized in that the fibrous carbonaceous material is carbon nanofiber.
また、本発明に係る電気二重層キャパシタ用分極性電極は、炭素複合材の質量分率が１０〜９５質量％であることを特徴とする。 The polarizable electrode for an electric double layer capacitor according to the present invention is characterized in that the mass fraction of the carbon composite material is 10 to 95% by mass.
また、本発明に係る電気二重層キャパシタ用分極性電極は、前記繊維状炭素質が、繊維径（直径）５〜２００ｎｍ、繊維長５〜１０００ｎｍであることを特徴とする。 The polarizable electrode for an electric double layer capacitor according to the present invention is characterized in that the fibrous carbonaceous material has a fiber diameter (diameter) of 5 to 200 nm and a fiber length of 5 to 1000 nm.
また、本発明に係る電気二重層キャパシタ用分極性電極は、前記活性炭が、ディレードコーカー法で製造したピッチコークスの生コークスを賦活したものであり、かつ、その平均径が５〜５００μｍであることを特徴とする。 In the polarizable electrode for an electric double layer capacitor according to the present invention, the activated carbon is obtained by activating raw coke of pitch coke produced by the delayed coker method, and the average diameter thereof is 5 to 500 μm. It is characterized by.
また、本発明に係る電気二重層キャパシタ用分極性電極は、前記活性炭が、ピッチ系炭素繊維を水蒸気賦活した活性炭素繊維であり、かつ、その繊維径が５〜５０μｍであることを特徴とする。 Moreover, the polarizable electrode for an electric double layer capacitor according to the present invention is characterized in that the activated carbon is activated carbon fiber obtained by steam-activating pitch-based carbon fibers, and the fiber diameter is 5 to 50 μm. .
また、本発明に係る電気二重層キャパシタは、上記の電気二重層キャパシタ用分極性電極を有することを特徴とする。 In addition, an electric double layer capacitor according to the present invention is characterized by having the above polarizable electrode for an electric double layer capacitor.
本発明に係る電気二重層キャパシタは、分極性電極が、活性炭表面に繊維状炭素質を気相成長させた炭素複合材であるため、充放電速度を速くしても静電容量の低下が小さく、特に高速充放電性が要求されるＨＥＶやＵＰＳ電源として好適である。 In the electric double layer capacitor according to the present invention, since the polarizable electrode is a carbon composite material in which fibrous carbonaceous material is vapor-grown on the activated carbon surface, the decrease in capacitance is small even if the charge / discharge rate is increased. In particular, it is suitable as a HEV or UPS power supply that requires high-speed charge / discharge characteristics.
本発明に係る電気二重層キャパシタ用分極性電極および電気二重層キャパシタの好適な実施の形態について、以下に説明する。 Preferred embodiments of the polarizable electrode for an electric double layer capacitor and the electric double layer capacitor according to the present invention will be described below.
電気二重層キャパシタは、例えば、正負一対の分極性電極（電極）の間にセパレータを挟んだ素子を電解質液（電解質を含む電解液）とともにケースに収容するとともに、電極に集電体を設けた構造とすることができる。
本発明に係る電気二重層キャパシタは、分極性電極が、活性炭表面に繊維状炭素質を気相成長させた炭素複合材を主成分とするものである。
An electric double layer capacitor includes, for example, an element in which a separator is sandwiched between a pair of positive and negative polarizable electrodes (electrodes) together with an electrolyte solution (electrolyte solution including an electrolyte) and a current collector provided on the electrode. It can be a structure.
In the electric double layer capacitor according to the present invention, the polarizable electrode is mainly composed of a carbon composite material obtained by vapor-phase growth of fibrous carbonaceous material on the surface of activated carbon.
すなわち、本発明に係る分極性電極は、粉砕した活性炭原料を賦活し、必要に応じて粒径を調製したものを、炭化触媒の存在下で炭化水素を流通させて、活性炭表面に繊維状炭素質を気相成長させることにより得られる。繊維状炭素質は、好ましくは、繊維径５〜２００ｎｍ、繊維長５〜１０００ｎｍとする。 That is, the polarizable electrode according to the present invention is obtained by activating the pulverized activated carbon raw material and adjusting the particle size as necessary, by circulating hydrocarbons in the presence of a carbonization catalyst, so that the fibrous carbon is formed on the activated carbon surface. It can be obtained by vapor phase growth. The fibrous carbonaceous material preferably has a fiber diameter of 5 to 200 nm and a fiber length of 5 to 1000 nm.
活性炭は、公知の方法で製造したものが使用でき、特に限定されない。
活性炭原料としては、例えばフェノール樹脂等の熱硬化性樹脂を炭化して得た粒状炭や炭素繊維、ピッチ系炭素繊維、椰子殻炭、石炭、ピッチ、タール等を熱重合して得られる炭素質等が使用できる。また、ディレードコーカー法で製造したピッチコークスの生コークスを使用してもよい。
The activated carbon can be produced by a known method and is not particularly limited.
As the activated carbon raw material, for example, carbonaceous material obtained by thermal polymerization of granular charcoal and carbon fiber obtained by carbonizing a thermosetting resin such as phenol resin, pitch-based carbon fiber, coconut shell charcoal, coal, pitch, tar, etc. Etc. can be used. Moreover, you may use the raw coke of the pitch coke manufactured by the delayed coker method.
活性炭は、電気二重層キャパシタの設計用途に応じて、必要な粒子径に粉砕する。通常、粒子径として、電極厚み以下、数〜数百μｍの平均径になるように粉砕する。活性炭として、ディレードコーカー法で製造したピッチコークスの生コークスを賦活したものを使用するときは、平均径（直径）を５〜５００μｍとする。
粉砕方法は公知の方法を採用でき、粉砕は、活性炭原料の段階であるいは活性炭を生成した段階であるいはまたその両者の段階で行う。
炭素繊維を原料に用いる場合は、繊維径５〜５０μｍのものを、賦活前あるいは後に、公知の粉砕機を用いて例えば数μｍ〜１００μｍ程度の長さに切断したものを用いる。
The activated carbon is pulverized to a required particle size according to the design application of the electric double layer capacitor. Usually, it grind | pulverizes so that it may become below an electrode thickness and an average diameter of several to several hundred micrometers as a particle diameter. When using activated carbon coke of pitch coke produced by the delayed coker method as the activated carbon, the average diameter (diameter) is set to 5 to 500 μm.
As the pulverization method, a known method can be adopted, and the pulverization is performed at the stage of the activated carbon raw material, at the stage of generating the activated carbon, or at both stages.
When carbon fiber is used as a raw material, a fiber having a fiber diameter of 5 to 50 μm is cut into a length of, for example, about several μm to 100 μm using a known pulverizer before or after activation.
活性炭原料の賦活については、公知の賦活手段が使用でき、特に限定されない。例えば、水蒸気・二酸化炭素を用いるガス賦活、塩化亜鉛を用いる薬品賦活、アルカリ金属を用いるアルカリ賦活、電界賦活等が適用でき、これらを組み合わせてもよい。 About activation of activated carbon raw material, a well-known activation means can be used and it does not specifically limit. For example, gas activation using water vapor / carbon dioxide, chemical activation using zinc chloride, alkali activation using an alkali metal, electric field activation, and the like can be applied, and these may be combined.
賦活した活性炭の表面上に、繊維状炭素（繊維状炭素質）より好ましくはカーボンナノファイバー（以下、ＣＮＦという。）を形成するには、公知の方法が使用できる。以下、気相法炭素繊維の形成法によりＣＮＦを製造する例を示すがこれに限定されない。
まず、炭化触媒となる鉄、ニッケル、コバルト等の金属塩の水溶液を活性炭に含浸させる。次いで、活性炭から溶媒（水）を除去して後、金属塩が担持した活性炭を水素雰囲気下で加熱・還元し、金属の微粒子を活性炭表面に形成する。この活性炭を、不活性ガス雰囲気下で加熱し、炭化水素ガスを接触させると、金属の微粒子を核としてＣＮＦが成長する。成長するＣＮＦの長さ（繊維長）・太さ（繊維径）・活性炭の見かけ表面積当たりの数密度は、製造条件の制御で調整することができる。
A known method can be used to form carbon nanofibers (hereinafter referred to as CNF), more preferably fibrous carbon (fibrous carbonaceous), on the surface of activated activated carbon. Hereinafter, an example of producing CNF by a method of forming a vapor grown carbon fiber is shown, but the present invention is not limited to this.
First, activated carbon is impregnated with an aqueous solution of a metal salt such as iron, nickel, cobalt, or the like, which serves as a carbonization catalyst. Next, after removing the solvent (water) from the activated carbon, the activated carbon supported by the metal salt is heated and reduced in a hydrogen atmosphere to form metal fine particles on the activated carbon surface. When this activated carbon is heated in an inert gas atmosphere and brought into contact with a hydrocarbon gas, CNF grows with metal fine particles as nuclei. The length (fiber length), thickness (fiber diameter), and the number density per apparent surface area of activated carbon can be adjusted by controlling the production conditions.
得られるＣＮＦが活性炭粒子表面に成長した炭素複合材は、必要に応じて、酸洗浄等を行い、炭素複合体中に残存する金属触媒等の不純物を除去してもよい。 The carbon composite obtained by growing the obtained CNF on the surface of the activated carbon particles may be subjected to acid washing or the like, if necessary, to remove impurities such as a metal catalyst remaining in the carbon composite.
炭素複合材中のＣＮＦの含有率（質量分率）は、０．１〜５０質量％とする。０．１質量％未満では、高速充放電時の静電容量保持効果が少なく、５０質量％を超えると、高速充放電性はよいが、電気二重層キャパシタの体積あたりの静電容量が低下する。 The content (mass fraction) of CNF in the carbon composite material is 0.1 to 50% by mass. If it is less than 0.1% by mass, the effect of maintaining the electrostatic capacity at the time of high-speed charge / discharge is small, and if it exceeds 50% by mass, the high-speed charge / discharge property is good, but the capacitance per volume of the electric double layer capacitor decreases. .
得られた炭素複合材を用いて、シート電極、スラリー電極等の公知の製造法を用いて分極性電極を製造する。 Using the obtained carbon composite material, a polarizable electrode is produced using a known production method such as a sheet electrode or a slurry electrode.
分極性電極の電極構成としては、結合材を含むことが好ましい。
結合材としては、特に制限がないが、シート電極法では例えばポリテトラフルオロエチレン（ＰＴＦＥ）等、スラリー電極法では例えばポリビニリデンフルオライド（ＰＶＤＦ）、ＰＶＡ等が使用できる。
スラリー電極法における溶媒としては、例えばＮ−メチル−2−ピロリドン（ＮＭＰ）、ジメチルフォルムアミド（ＤＭＦ）、トルエン等又はその混合溶媒を使用することができる。
The electrode configuration of the polarizable electrode preferably includes a binder.
The binder is not particularly limited, and for example, polytetrafluoroethylene (PTFE) can be used in the sheet electrode method, and polyvinylidene fluoride (PVDF), PVA, or the like can be used in the slurry electrode method.
As a solvent in the slurry electrode method, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), toluene, or a mixed solvent thereof can be used.
また、分極性電極の電極構成として、さらに導電性助剤を加えてもよい。
導電性助剤としては、ケッチェンブラック、アセチレンブラック、天然／人造黒鉛等を用いることができる。
Moreover, you may add a conductive support agent as an electrode structure of a polarizable electrode.
As the conductive auxiliary agent, ketjen black, acetylene black, natural / artificial graphite or the like can be used.
また、分極性電極の電極構成として、本発明の性能を満たす範囲で、ＣＮＦを含まない従来の活性炭を加えてもよい。 Moreover, you may add the conventional activated carbon which does not contain CNF in the range with which the performance of this invention is satisfy | filled as an electrode structure of a polarizable electrode.
分極性電極中の上記各成分の構成比は、特に制限はないが、炭素複合材として５０〜９５質量％、結合材として１〜２５質量％、導電性助剤として０〜２５質量％の範囲で選択するのがよい。 The composition ratio of each component in the polarizable electrode is not particularly limited, but ranges from 50 to 95% by mass as a carbon composite material, from 1 to 25% by mass as a binder, and from 0 to 25% by mass as a conductive auxiliary. It is good to select with.
集電体は、特に制限はなく、公知の例えば、表面エッチングしたアルミ箔、ステンレス箔等が適用できる。 There is no restriction | limiting in particular in a collector, For example, well-known surface-etched aluminum foil, stainless steel foil, etc. can be applied.
電解液は、水系、有機溶剤系の制限はなく、いずれの系であってもよい。また、電解液にイオン性液体を適用しても良い。キャパシタ内に貯蔵できるエネルギーは充電電圧の２乗と静電容量の１乗に比例することから、電解液は、分解電圧の高いものを用いることが好ましい。有機溶媒を用いる場合、例えばプロピレンカーボネート（ＰＣ）は適当なもののひとつである。 The electrolytic solution is not limited to an aqueous system or an organic solvent system, and may be any system. Moreover, you may apply an ionic liquid to electrolyte solution. Since the energy that can be stored in the capacitor is proportional to the square of the charging voltage and the first power of the capacitance, it is preferable to use an electrolyte having a high decomposition voltage. When using an organic solvent, for example, propylene carbonate (PC) is one suitable one.
電解質は、特に制限されない。例えば、有機溶媒系に適する電解質としては、公知の（Ｃ２Ｈ５）４ＮＢＦ４、ＣＨ３（Ｃ２Ｈ５）３ＮＢＦ４等が使用できる。水系では,硫酸、塩酸などが使用できる。 The electrolyte is not particularly limited. For example, as the electrolyte suitable for the organic solvent system, known (C 2 H 5 ) 4 NBF 4 , CH 3 (C 2 H 5 ) 3 NBF 4 and the like can be used. In aqueous systems, sulfuric acid, hydrochloric acid, etc. can be used.
電気二重層キャパシタのセパレータは、製造プロセス、用途から求められる、耐薬品性、耐熱性等の要件を満たせば特に限定されない。例えば、ポリエチレン多孔膜、ポリプロピレン製不織布、ガラス繊維性不織布、セルロース性特殊紙等の公知の材料が使用可能である。 The separator of the electric double layer capacitor is not particularly limited as long as it satisfies requirements such as chemical resistance and heat resistance required from the manufacturing process and application. For example, known materials such as polyethylene porous film, polypropylene nonwoven fabric, glass fiber nonwoven fabric, and cellulosic special paper can be used.
必要に応じて、電気二重層キャパシタのセル内に、脱水剤、副反応で生成すると考えられるガスの捕集剤を加えてもよい。
セルの形状は、特に制限はなく、コイン型、角型、円筒型等のいずれの方式も採用できる。
If necessary, a dehydrating agent and a gas scavenger considered to be generated by a side reaction may be added to the cell of the electric double layer capacitor.
The shape of the cell is not particularly limited, and any system such as a coin type, a square type, or a cylindrical type can be adopted.
以下、本発明の電気二重層キャパシタ用分極性電極の実施例及び比較例を説明する。なお、本発明は、以下に説明する実施例に限定されるものではない。 Hereinafter, examples and comparative examples of the polarizable electrode for an electric double layer capacitor of the present invention will be described. In addition, this invention is not limited to the Example demonstrated below.
実施例１
（活性炭の調製）
活性炭原料として、新日鐵化学株式会社製の石炭系ピッチコークス（ＬＰＣ−Ｕ）の生コークスを用い、これをアトマイザーを用いて平均径３０μｍに粒度調製し、水蒸気賦活した。
このとき、（１時間あたりの導入水蒸気量：２００ｇ／時間）／（仕込み生コークス量：２００ｇ）比とし、温度８５０℃で８時間反応させた。反応後、５％塩酸で洗浄後、純水で洗浄し、活性炭を得た。得られた活性炭のＢＥＴ比表面積は６００ｍ２／ｇであった。賦活後、ジェットミルで、平均径２０μｍに粉砕した。活性炭の歩留は２０％であった。
Example 1
(Preparation of activated carbon)
As the activated carbon raw material, raw pitch coke of coal-based pitch coke (LPC-U) manufactured by Nippon Steel Chemical Co., Ltd. was used, and the particle size was adjusted to an average diameter of 30 μm using an atomizer, and steam activated.
At this time, the reaction was carried out at a temperature of 850 ° C. for 8 hours at a ratio of (introduced water vapor amount per hour: 200 g / hour) / (prepared raw coke amount: 200 g). After the reaction, it was washed with 5% hydrochloric acid and then with pure water to obtain activated carbon. The obtained activated carbon had a BET specific surface area of 600 m 2 / g. After activation, it was pulverized to an average diameter of 20 μm by a jet mill. The yield of activated carbon was 20%.
（炭素複合材の調製）
鉄／ニッケルのモル比が１:４になるよう調製した硝酸鉄と硝酸ニッケルのエタノール混合液を調製した。次いで、この混合液を活性炭質量の５質量％に相当する量、活性炭に混合し、減圧乾燥させ、溶剤を除去して金属塩混合物を活性炭に担持させた。次いでこの活性炭をアルミナポートに乗せ、石英製管状炭化炉に挿入した。
石英製管状炭化炉では、まず、ヘリウム／水素の流量比９：１の混合気流下、温度６００℃で２時間処理し、金属塩を還元させた。次いで温度６００℃で、エチレン／水素の流量比１：１の混合ガスを石英製管状炭化炉に導入し、接触時間２０分で活性炭表面にＣＮＦを成長させ、炭素複合材を得た。
ＣＮＦの平均径（繊維径）は２０ｎｍ、平均長さ（繊維長）は１００ｎｍであった。
得られた炭素複合材のＢＥＴ比表面積および炭素複合材中におけるＣＮＦの含有率（質量分率）を表１に示す。以下の他の実施例および比較例についても同様である。
(Preparation of carbon composite)
An ethanol mixture of iron nitrate and nickel nitrate was prepared so that the molar ratio of iron / nickel was 1: 4. Next, this mixed solution was mixed with activated carbon in an amount corresponding to 5% by mass of the activated carbon, dried under reduced pressure, the solvent was removed, and the metal salt mixture was supported on activated carbon. The activated carbon was then placed on an alumina port and inserted into a quartz tubular carbonization furnace.
In the quartz tubular carbonization furnace, first, the metal salt was reduced by treatment at a temperature of 600 ° C. for 2 hours under a mixed air flow of 9: 1 helium / hydrogen flow ratio. Next, a mixed gas having an ethylene / hydrogen flow rate ratio of 1: 1 at a temperature of 600 ° C. was introduced into a quartz tubular carbonization furnace, and CNF was grown on the activated carbon surface in a contact time of 20 minutes to obtain a carbon composite material.
The average diameter (fiber diameter) of CNF was 20 nm, and the average length (fiber length) was 100 nm.
Table 1 shows the BET specific surface area of the obtained carbon composite and the content (mass fraction) of CNF in the carbon composite. The same applies to other examples and comparative examples described below.
（シート電極の調製）
得られた炭素複合材をバインダーと９：１の質量比（炭素複合材／バインダー）で混合、分散し、シート化して、厚み1００μｍ、直径１６ｍｍのシート電極を得た。
このとき、バインダーは、三井デュポンフルオロケミカル株式会社のテフロン(登録商標)樹脂ＰＴＦＥ ６−Ｊを用いた。
(Preparation of sheet electrode)
The obtained carbon composite material was mixed with a binder at a mass ratio of 9: 1 (carbon composite material / binder) and dispersed into a sheet to obtain a sheet electrode having a thickness of 100 μm and a diameter of 16 mm.
At this time, Teflon (registered trademark) resin PTFE 6-J manufactured by Mitsui Dupont Fluorochemical Co., Ltd. was used as the binder.
得られたシート電極を用いて２極式テストセルを組んだ。
電解質として１モル／ｋｇの濃度のテトラエチルアンモニウムテトラフルオロブロマイド（Ｅｔ４ＮＢＦ４）を含有するプロピレンカーボネート電解液を用いた。
上記のセルで所定の電流密度で充放電を行い、それぞれの条件での電気二重層容量を求めた。
充放電装置は、ＴＯＹＯ ＳＹＳＴＥＭ製ＴＯＳＣＡＴ−３０００Ｋ装置を用いた。
（静電容量の測定）
テストセルを２．７Ｖまで充電した後、０Ｖまで放電した。この操作を繰り返し、５回目の放電挙動から、次式で静電容量Ｃ（単位：Ｆ）を求めた。電流値は、シート電極重量あたりの電流密度が１００mA/gとなるよう、設定した。
Ｃ＝Ｉ(Ｔ２−Ｔ１)／（Ｖ１−Ｖ２）
Ｖ１：充電電圧の８０％となる値（単位：Ｖ）
Ｖ２：充電電圧の４０％となる値 （単位：Ｖ）
Ｔ１：Ｖ１における時間 （単位：ｓｅｃ）
Ｔ２：Ｖ２における時間 （単位：ｓｅｃ）
Ｉ：放電電流（単位：Ａ）
体積毎静電容量（単位体積当たり静電容量）は、得られた静電容量Ｃを、シート電極体積で割って算出した。
（サイクリックボルタンメトリー（CV）の測定）
得られた炭素複合材をバインダーと９：１の質量比（炭素複合材／バインダー）で混合、分散し、シート化して、厚み1００μｍ、直径１６ｍｍのシート電極を得た。 このとき、バインダーは、三井デュポンフルオロケミカル株式会社のテフロン(登録商標)樹脂ＰＴＦＥ ６−Ｊを用いた。測定装置は、北斗電工製 ＨＺ-３０００を用いた。
上記シート電極を用い、3極セルを組み、CVを測定した。電解質液は2極テストセル同様で、参照極はAg/Ag+電極とし、対極は実施例３で用いた市販の活性炭素繊維を用い、作用極に取り付けた試料の表面積に対し、2倍になるよう取り付けた。
電圧掃引速度は、１０ｍV/秒と、１００ｍV/秒とした。高速充放電特性は、10ｍV/秒での静電容量と、１００ｍV/秒での静電容量の比として求めた。
A bipolar test cell was assembled using the obtained sheet electrode.
A propylene carbonate electrolyte containing tetraethylammonium tetrafluorobromide (Et 4 NBF 4 ) at a concentration of 1 mol / kg was used as the electrolyte.
The cell was charged and discharged at a predetermined current density, and the electric double layer capacity under each condition was determined.
As the charge / discharge device, a TOSCAT-3000K device manufactured by TOYO SYSTEM was used.
(Measurement of capacitance)
The test cell was charged to 2.7V and then discharged to 0V. This operation was repeated, and the capacitance C (unit: F) was determined from the fifth discharge behavior according to the following equation. The current value was set so that the current density per sheet electrode weight was 100 mA / g.
C = I (T2-T1) / (V1-V2)
V1: A value that is 80% of the charging voltage (unit: V)
V2: Value that is 40% of the charging voltage (unit: V)
T1: Time at V1 (unit: sec)
T2: Time in V2 (unit: sec)
I: Discharge current (unit: A)
The capacitance per volume (capacitance per unit volume) was calculated by dividing the obtained capacitance C by the sheet electrode volume.
(Measurement of cyclic voltammetry (CV))
The obtained carbon composite material was mixed with a binder at a mass ratio of 9: 1 (carbon composite material / binder) and dispersed into a sheet to obtain a sheet electrode having a thickness of 100 μm and a diameter of 16 mm. At this time, Teflon (registered trademark) resin PTFE 6-J manufactured by Mitsui Dupont Fluorochemical Co., Ltd. was used as the binder. As a measuring device, HZ-3000 manufactured by Hokuto Denko was used.
Using the sheet electrode, a triode cell was assembled and CV was measured. The electrolyte solution is the same as the two-electrode test cell, the reference electrode is an Ag / Ag + electrode, the counter electrode is the commercially available activated carbon fiber used in Example 3, and doubles the surface area of the sample attached to the working electrode. It was attached.
The voltage sweep rate was 10 mV / second and 100 mV / second. The fast charge / discharge characteristics were determined as the ratio of the capacitance at 10 mV / sec and the capacitance at 100 mV / sec.
（比表面積測定）
以上説明した各材料の比表面積は、ユアサアイオニクス社製ＡＵＴＯＳＯＲＢ Ｉ型装置によりＢＥＴ比表面積を求めた。
(Specific surface area measurement)
As for the specific surface area of each material described above, the BET specific surface area was obtained with an AUTOSORB I type apparatus manufactured by Yuasa Ionics.
静電容量の測定結果を表１に示す。以下の他の実施例および比較例についても同様である。 The capacitance measurement results are shown in Table 1. The same applies to other examples and comparative examples described below.
実施例２
エチレン／水素と活性炭の接触時間を１０分にしたほかは、実施例１と同等の条件で炭素複合材およびシート電極を調製した。
Example 2
A carbon composite material and a sheet electrode were prepared under the same conditions as in Example 1 except that the contact time of ethylene / hydrogen and activated carbon was 10 minutes.
実施例３
ピッチ系炭素繊維を水蒸気賦活した、市販の活性炭素繊維を短繊維化したもの（直径１０μｍ、繊維長２ｍｍ、ＢＥＴ比表面積1５３０ｍ２／ｇ）を用いた以外は、実施例１と同等の条件で炭素複合材およびシート電極を調製した。
得られた炭素複合材は、ＣＮＦの平均直径が２０ｎｍであった。
Example 3
Under the same conditions as in Example 1 except that a commercial activated carbon fiber obtained by steam activation of pitch-based carbon fiber (diameter 10 μm, fiber length 2 mm, BET specific surface area 1530 m 2 / g) was used. Carbon composites and sheet electrodes were prepared.
The obtained carbon composite material had an average diameter of CNF of 20 nm.
実施例４
エチレン／水素との接触時間を４０分とした以外は、実施例３と同等の条件で炭素複合材およびシート電極を調製した。
得られた炭素複合材は、ＣＮＦの直径が２０ｎｍであった。
Example 4
A carbon composite material and a sheet electrode were prepared under the same conditions as in Example 3 except that the contact time with ethylene / hydrogen was 40 minutes.
The obtained carbon composite material had a CNF diameter of 20 nm.
実施例５
実施例１で用いた活性炭の代りに、新日鐵化学株式会社製の石炭系ピッチコークス（ＬＰＣ−Ｕ）の生コークスを、平均径１５０μｍに粒度を調製し、ＮａＯＨアルカリ賦活した。
ＮａＯＨと生コークスは、ＮａＯＨ／生コークス質量比４：１で、温度６５０℃で、１時間反応させた。反応後は、５％塩酸で洗浄後、純水で洗浄し、活性炭を得た。活性炭の表面積は１２００ｍ２／ｇであった。賦活後、ジェットミルで、平均径２０μｍに粉砕した。
賦活した活性炭とエチレン／水素との接触時間を６分とした以外は、実施例１と同等の条件で炭素複合材およびシート電極を調製した。
得られた炭素複合材は、ＣＮＦの直径が２０ｎｍであった。
Example 5
In place of the activated carbon used in Example 1, a raw coke of coal-based pitch coke (LPC-U) manufactured by Nippon Steel Chemical Co., Ltd. was prepared to have an average particle size of 150 μm and activated with NaOH alkali.
NaOH and raw coke were reacted at a temperature of 650 ° C. for 1 hour at a NaOH / raw coke mass ratio of 4: 1. After the reaction, it was washed with 5% hydrochloric acid and then with pure water to obtain activated carbon. The surface area of the activated carbon was 1200 m 2 / g. After activation, it was pulverized to an average diameter of 20 μm by a jet mill.
A carbon composite material and a sheet electrode were prepared under the same conditions as in Example 1 except that the contact time between activated carbon and ethylene / hydrogen was 6 minutes.
The obtained carbon composite material had a CNF diameter of 20 nm.
比較例１
炭素複合体の代りに、炭素繊維を成長させる前の活性炭そのものを用いたほかは、実施例１と同等の条件でシート電極を調製した。
Comparative Example 1
A sheet electrode was prepared under the same conditions as in Example 1 except that the activated carbon itself before growing the carbon fiber was used instead of the carbon composite.
比較例２
市販のＶＧＣＦ（登録商標）気相法炭素繊維と、実施例１で用いた、炭素繊維を成長させる前の活性炭を、実施例１と同じ配合比で混合し、炭素複合材およびシート電極を調製した。ＶＧＣＦの物性は、ＢＥＴ比表面積が１３ｍ２／ｇ、炭素繊維の直径が１５０ｎｍ、繊維長が約１５μｍであった。
Comparative Example 2
Commercially available VGCF (registered trademark) vapor grown carbon fiber and activated carbon used in Example 1 before growing the carbon fiber were mixed at the same blending ratio as in Example 1 to prepare a carbon composite material and a sheet electrode. did. The physical properties of VGCF were a BET specific surface area of 13 m 2 / g, a carbon fiber diameter of 150 nm, and a fiber length of about 15 μm.
比較例３
実施例３のピッチ系活性炭素繊維を、表面にＣＮＦを生成させることなく、そのまま用いた以外は、実施例３と同一条件でシート電極を調製した。
Comparative Example 3
A sheet electrode was prepared under the same conditions as in Example 3 except that the pitch-based activated carbon fiber of Example 3 was used as it was without generating CNF on the surface.
比較例４
ＶＧＣＦと、実施例１で用いた、炭素繊維を成長させる前の活性炭を、実施例３と同じ配合比で混合し、炭素複合材およびシート電極を調製した。
Comparative Example 4
VGCF and activated carbon used in Example 1 before carbon fiber growth were mixed at the same blending ratio as in Example 3 to prepare a carbon composite material and a sheet electrode.
上記の実施例、比較例および参考例によれば、所定含有率のＣＮＦを活性炭表面に生成させた炭素複合材を用いた実施例のシート電極（分極性電極）と比べ、活性炭単独、繊維状炭素単独、単に活性炭とＶＧＣＦを機械的に混合したもの、過度にＣＮＦを生成させた炭素複合材を用いた比較例のシート電極（分極性電極）では、何れも良好な高速充放電性又は静電容量が得られないことがわかり、本発明の効果は明らかである。
上記本発明のシート電極（分極性電極）を用いた電気二重層キャパシタは、特に高速充放電性が要求されるＨＥＶやＵＰＳ電源として好適である。
According to the above-mentioned Examples, Comparative Examples, and Reference Examples, compared with the sheet electrode (polarizable electrode) of the example using the carbon composite material in which CNF having a predetermined content is generated on the activated carbon surface, the activated carbon alone, the fibrous form The sheet electrode (polarizable electrode) of the comparative example using carbon alone, simply a mixture of activated carbon and VGCF mechanically, or a carbon composite material that excessively generated CNF produced good high-speed charge / discharge characteristics or static electricity. It turns out that electric capacity cannot be obtained, and the effect of this invention is clear.
The electric double layer capacitor using the sheet electrode (polarizable electrode) of the present invention is particularly suitable as a HEV or UPS power supply that requires high-speed charge / discharge characteristics.
Claims (8)
An electric double layer capacitor comprising the polarizable electrode for an electric double layer capacitor according to any one of claims 1 to 7.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009152446A (en) * | 2007-12-21 | 2009-07-09 | Ube Ind Ltd | Electrode evaluation method and evaluation device |
| JP2010034300A (en) * | 2008-07-29 | 2010-02-12 | Jfe Chemical Corp | Carbon material for use of polarizable electrode of electric double-layer capacitor, its manufacturing method, and the electric double-layer capacitor |
| WO2010074281A1 (en) * | 2008-12-22 | 2010-07-01 | アイシン精機株式会社 | Composite carbon and manufacturing method therefor |
-
2005
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009152446A (en) * | 2007-12-21 | 2009-07-09 | Ube Ind Ltd | Electrode evaluation method and evaluation device |
| JP2010034300A (en) * | 2008-07-29 | 2010-02-12 | Jfe Chemical Corp | Carbon material for use of polarizable electrode of electric double-layer capacitor, its manufacturing method, and the electric double-layer capacitor |
| WO2010074281A1 (en) * | 2008-12-22 | 2010-07-01 | アイシン精機株式会社 | Composite carbon and manufacturing method therefor |
| JP5318120B2 (en) * | 2008-12-22 | 2013-10-16 | アイシン精機株式会社 | Hybrid carbon and method for producing the same |
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