JP2005347517A - Method of manufacturing activated charcoal for electric double layer capacitor electrode - Google Patents
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Abstract
Description
本発明は、電気二重層キャパシタ電極用活性炭の製造方法に関し、例えば、次世代の高性能電気二重層キャパシタ用電極に好適に使用し得る電極用活性炭の製造方法に関する。 The present invention relates to a method for producing an activated carbon for an electric double layer capacitor electrode, for example, a method for producing an activated carbon for an electrode that can be suitably used for an electrode for a next generation high performance electric double layer capacitor.
従来、電気二重層キャパシタの静電容量密度を高めるため、電極に用いる活性炭の比表面積を大きくする試みがなされてきたが、近年、活性炭の比表面積を高めることが、キャパシタの静電容量値（Ｆ／ｃｍ3）を向上させる必要条件とはなり得ないことがわかってきた。
すなわち、比表面積が大きくなるに従って、静電容量値（μＦ／ｃｍ2）が低下し、ある値に漸近することが報告されている（非特許文献１：電気二重層キャパシタと蓄電システム）。
また、難黒鉛化性炭素前駆体であるフェノール炭の賦活実験においては、ある比表面積値のところで静電容量値（Ｆ／ｃｍ3）が最大となり、さらに賦活条件を過酷にしても、比表面積の増大に反し、静電容量値は減少する傾向が認められている。
Conventionally, attempts have been made to increase the specific surface area of the activated carbon used for the electrode in order to increase the capacitance density of the electric double layer capacitor. However, in recent years, increasing the specific surface area of the activated carbon has increased the capacitance value of the capacitor ( It has been found that it cannot be a necessary condition for improving F / cm 3 ).
That is, it has been reported that as the specific surface area increases, the capacitance value (μF / cm 2 ) decreases and approaches a certain value (Non-patent Document 1: Electric double layer capacitor and power storage system).
Further, in the activation experiment of phenol charcoal, which is a non-graphitizable carbon precursor, the capacitance value (F / cm 3 ) becomes maximum at a certain specific surface area value, and even if the activation conditions are severe, the specific surface area Contrary to the increase in the capacitance, the capacitance value tends to decrease.
そこで、最近、キャパシタの静電容量値改善に寄与する因子として、使用する活性炭の結晶構造と細孔構造が注目され始めている。
この点に関して、活性炭を用いたキャパシタ電極では、電極と電解液との界面において、黒鉛結晶の基底面よりエッジ面が露出している場合に、発現する静電容量値が大きくなるという知見がある（非特許文献２：Ｊ．Ｅｌｅｃｔｒｏａｎａｌ．Ｃｈｅｍ．、１９７２年、非特許文献３：Ｊ．Ｅｌｅｃｔｒｏａｎａｌ．Ｃｈｅｍ．、１９７５年）。また、電解質イオンの出入りが円滑に行われるナノ細孔を選択的に炭素体内部に空けることが重要であることが指摘されるとともに、最適な細孔構造が報告されている（特許文献１：特開２００２−１２８５１４号公報）。
Thus, recently, attention has been focused on the crystal structure and pore structure of the activated carbon used as a factor contributing to the improvement of the capacitance value of the capacitor.
In this regard, in the capacitor electrode using activated carbon, there is a finding that when the edge surface is exposed from the basal plane of the graphite crystal at the interface between the electrode and the electrolytic solution, the expressed capacitance value increases. (Non-patent document 2: J. Electronal. Chem., 1972, Non-patent document 3: J. Electronal. Chem., 1975). In addition, it is pointed out that it is important to selectively open nanopores in which electrolyte ions smoothly enter and exit inside the carbon body, and an optimum pore structure has been reported (Patent Document 1 :). JP 2002-128514 A).
これらの点に鑑み、黒鉛類似微結晶体からなる易黒鉛化性炭素前駆体である針状生コークスを出発原料とし、これをアルカリ賦活化して得られた活性炭を電気二重層キャパシタの電極材に用いる研究が行われている（特許文献２：特開２００２−２５８６７号公報、特許文献３：特開２００３−５１４３０号公報等）。
しかしながら、これらの方法は、賦活薬品代が高いだけでなく、薬品の安全性を考慮した場合、設備投資費も高くなるため、安価な活性炭製造法とはなり得ない。しかも、アルカリ賦活活性炭特有のキャパシタ集電体の膨張現象や、ガス発生現象等に起因する容器材料の歪み等により、サイクル特性が低下し易いという問題もある。
In view of these points, acicular raw coke which is a graphitizable carbon precursor composed of graphite-like microcrystals is used as a starting material, and activated carbon obtained by alkali activation is used as an electrode material for an electric double layer capacitor. Research has been carried out (Patent Document 2: Japanese Patent Laid-Open No. 2002-25867, Patent Document 3: Japanese Patent Laid-Open No. 2003-51430, etc.).
However, these methods are not only expensive for the activation chemicals, but also take into account the equipment investment cost when considering the safety of the chemicals. In addition, there is also a problem that the cycle characteristics are liable to deteriorate due to the expansion phenomenon of the capacitor current collector unique to the alkali activated carbon, the distortion of the container material due to the gas generation phenomenon, and the like.
アルカリ賦活活性炭からなる電極の欠点である膨張を抑制するため、易黒鉛化性炭素用原料に酸素付加処理を施した後、アルカリ賦活を行う手法が報告されている（特許文献４：特開２００２−１３４３６９号公報）。しかし、この方法でも膨張を完全に抑制することは不可能であるのみならず、高価であるとともに危険性のある薬品を使用する方法であることには変わりがないため、上記問題点を根本的に解決する手法とはなり得ない。
一方、フェノール樹脂炭、フラン樹脂炭、ポリ塩化ビニリデン炭等の難黒鉛化性炭素前駆体を出発原料とした場合でも、上述した製造コストの高いアルカリ賦活法を除いては、賦活条件を工夫したところで静電容量や電極密度を高めることには限界があり、容積あたりの高い性能が要求される次世代キャパシタの電極材料を安価に得ることは困難である。
In order to suppress expansion, which is a defect of an electrode made of alkali-activated activated carbon, a method of performing alkali activation after subjecting a graphitizable carbon raw material to oxygen addition treatment has been reported (Patent Document 4: Japanese Patent Laid-Open No. 2002-2002). -134369). However, this method is not only impossible to completely suppress the expansion, but is still expensive and uses a dangerous chemical, so the above problem is fundamentally solved. It cannot be a method to solve this problem.
On the other hand, even when a non-graphitizable carbon precursor such as phenol resin charcoal, furan resin charcoal, or polyvinylidene chloride charcoal is used as a starting material, the activation conditions have been devised except for the alkali activation method with high production costs described above. However, there is a limit to increasing the capacitance and electrode density, and it is difficult to obtain an electrode material for a next-generation capacitor that requires high performance per volume at low cost.
さらに最近、石炭、ピッチ、コークス等の炭素前駆体を、酸素存在下で加熱処理した後、塩化亜鉛等による薬品賦活を行って得られた活性炭が、電気二重層キャパシタの電極材に好適であることが報告されている（特許文献５：特開２００３−２８２３６９号公報等）。
しかしながら、この方法を、易黒鉛化性炭素前駆体である針状生コークスやバルクメソフェーズ等に適用すると、細孔の発達が悪く、充分な静電容量および電極密度の向上効果を得ることができない。
More recently, activated carbon obtained by heat treatment of carbon precursors such as coal, pitch and coke in the presence of oxygen and then chemical activation with zinc chloride or the like is suitable as an electrode material for electric double layer capacitors. (Patent Document 5: JP 2003-282369 A).
However, when this method is applied to acicular graphitizable carbon precursors such as acicular raw coke and bulk mesophase, the development of pores is poor, and sufficient electrostatic capacity and electrode density improvement effects cannot be obtained. .
本発明は、このような事情に鑑みてなされたものであり、キャパシタ電極として用いた場合に、サイクル特性に優れるキャパシタが得られるとともに、単位体積あたりの静電容量を高めることのできる電気二重層キャパシタ電極用活性炭の製造方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and when used as a capacitor electrode, an electric double layer capable of obtaining a capacitor having excellent cycle characteristics and increasing the capacitance per unit volume. It aims at providing the manufacturing method of the activated carbon for capacitor electrodes.
本発明者らは、上記目的を達成するために鋭意検討を重ねた結果、黒鉛類似微結晶体を主成分とする易黒鉛化性炭素前駆体を酸化した後、脱水反応触媒下で加熱処理し、さらにガス賦活するという、複合賦活化処理を施すことで、比表面積や全細孔容積はさほど大きくないにもかかわらず、電気二重層キャパシタ電極に用いた場合に、単位体積あたりの静電容量を向上できるとともに、キャパシタのサイクル特性を向上し得る活性炭が得られることを見出し、本発明を完成した。 As a result of intensive studies to achieve the above object, the present inventors oxidized a graphitizable carbon precursor mainly composed of graphite-like microcrystals and then heat-treated them under a dehydration reaction catalyst. In addition, by applying a composite activation treatment, gas activation, the capacitance per unit volume when used for an electric double layer capacitor electrode even though the specific surface area and total pore volume are not so large. As a result, it was found that activated carbon capable of improving the cycle characteristics of the capacitor was obtained, and the present invention was completed.
すなわち、本発明は、
１．黒鉛類似微結晶体を主成分とする易黒鉛化性炭素前駆体を酸化する酸化処理工程と、この酸化処理工程により得られた酸化処理物を脱水反応触媒下で加熱処理する脱水処理工程と、この脱水処理工程により得られた脱水処理物をガス賦活して活性炭を得る賦活処理工程と、を含むことを特徴とする電気二重層キャパシタ電極用活性炭の製造方法、
２．前記酸化処理工程が、湿式酸化により行われることを特徴とする１の電気二重層キャパシタ電極用活性炭の製造方法、
３．前記湿式酸化が、５０〜１００℃で行われることを特徴とする２の電気二重層キャパシタ電極用活性炭の製造方法、
４．前記脱水処理工程が、不活性ガス雰囲気中、常温から６００〜９００℃まで昇温速度０．５〜５℃／分で加熱することにより行われることを特徴とする１〜３のいずれかの電気二重層キャパシタ電極用活性体の製造方法、
５．前記ガス賦活処理工程が、水蒸気賦活により行われることを特徴とする１〜４のいずれかの電気二重層キャパシタ電極用活性炭の製造方法、
６．前記易黒鉛化性炭素前駆体が、針状生コークス、バルクメソフェーズ、晶質ピッチ、メソカーボンマクロビーズおよびメソフェーズピッチ紡糸生繊維から選ばれる少なくとも１種であることを特徴とする１〜５のいずれかの電気二重層キャパシタ用活性炭の製造方法、
７．黒鉛類似微結晶体を主成分とする易黒鉛化性炭素前駆体から得られ、ＢＥＴ比表面積３５０〜１２００ｍ2／ｇ、ＭＰ法による全細孔容積０．２０〜１．００ｍＬ／ｇ、結晶格子面間隔（ｄ００２）０．３４〜０．３８ｎｍであり、ＢＪＨ法によるメソ孔容積とＭＰ法による全細孔容積との比（メソ孔／全細孔）が０．３５超０．７５以下であることを特徴とする電気二重層キャパシタ用活性炭、
８．７の活性炭を含んで構成されることを特徴とする電気二重層キャパシタ用電極、
９．８の電極を備えることを特徴とする電気二重層キャパシタ
を提供する。
That is, the present invention
1. An oxidation treatment step of oxidizing a graphitizable carbon precursor mainly composed of graphite-like microcrystals, a dehydration treatment step of heat-treating an oxidized product obtained by this oxidation treatment step under a dehydration reaction catalyst, An activation treatment step of activating the dehydrated product obtained by this dehydration step to obtain activated carbon by gas activation, and a method for producing an activated carbon for an electric double layer capacitor electrode,
2. The method for producing activated carbon for an electric double layer capacitor electrode according to 1, wherein the oxidation treatment step is performed by wet oxidation,
3. The method for producing activated carbon for an electric double layer capacitor electrode according to 2, wherein the wet oxidation is performed at 50 to 100 ° C,
4). The electricity according to any one of 1 to 3, wherein the dehydration step is performed by heating from normal temperature to 600 to 900 ° C. at a heating rate of 0.5 to 5 ° C./min in an inert gas atmosphere. Method for producing active body for double layer capacitor electrode,
5). The method for producing activated carbon for an electric double layer capacitor electrode according to any one of 1 to 4, wherein the gas activation treatment step is performed by steam activation,
6). Any of 1-5, wherein the graphitizable carbon precursor is at least one selected from acicular raw coke, bulk mesophase, crystalline pitch, mesocarbon macrobeads, and mesophase pitch spun raw fibers. Manufacturing method of activated carbon for the electric double layer capacitor,
7). Obtained from an easily graphitizable carbon precursor mainly composed of graphite-like microcrystals, BET specific surface area of 350 to 1200 m 2 / g, total pore volume by MP method of 0.20 to 1.00 mL / g, crystal lattice The surface spacing (d002) is 0.34 to 0.38 nm, and the ratio of the mesopore volume by the BJH method to the total pore volume by the MP method (mesopore / total pore) is more than 0.35 and 0.75 or less. Activated carbon for electric double layer capacitor,
An electrode for an electric double layer capacitor, characterized by comprising 8.7 activated carbon,
Provided is an electric double layer capacitor comprising 9.8 electrodes.
本発明の電気二重層キャパシタ電極用活性炭の製造方法によれば、従来、ガス賦活法等では炭化歩留まりが悪く、細孔が形成され難いとされ、アルカリ賦活法のみが採用されてきた易黒鉛化性炭素前駆体を原料として用い、これに酸化処理、脱水処理およびガス賦活処理を施すだけで（アルカリ賦活処理を施さずに）、キャパシタ電極材として良好な特性を有する活性炭を得ることができる。
しかも、アルカリ賦活処理ではなく、ガス賦活法等の安価な工業的賦活技術を採用しているため、製造コストを削減でき、経済的に有利な製法である。
さらに、得られる活性炭は、黒鉛類似微結晶構造をその骨格として有しているため、高密度で電気伝導性・イオン伝導性に優れており、電気二重層キャパシタの電極材として用いた場合、内部抵抗が低く、かつ、静電容量およびサイクル特性に優れたキャパシタを得ることができる。
According to the method for producing activated carbon for an electric double layer capacitor electrode of the present invention, graphitization in which the carbonization yield has been poor in the gas activation method or the like and pores are hardly formed, and only the alkali activation method has been employed. Activated carbon precursor can be used as a raw material, and activated carbon having good characteristics as a capacitor electrode material can be obtained only by subjecting it to oxidation treatment, dehydration treatment, and gas activation treatment (without performing alkali activation treatment).
In addition, since an inexpensive industrial activation technique such as a gas activation method is employed instead of the alkali activation treatment, the production cost can be reduced and the production method is economically advantageous.
Furthermore, since the obtained activated carbon has a graphite-like microcrystalline structure as its skeleton, it has high density and excellent electrical conductivity and ion conductivity. When used as an electrode material for an electric double layer capacitor, A capacitor having low resistance and excellent capacitance and cycle characteristics can be obtained.
以下、本発明についてさらに詳しく説明する。
本発明に係る電気二重層キャパシタ電極用活性炭の製造方法は、黒鉛類似微結晶体を主成分とする易黒鉛化性炭素前駆体を酸化する酸化処理工程と、この酸化処理工程により得られた酸化処理物を脱水反応触媒下で加熱処理する脱水処理工程と、この脱水処理工程により得られた脱水処理物をガス賦活して活性炭を得る賦活処理工程と、を含むことを特徴とする。
Hereinafter, the present invention will be described in more detail.
The method for producing activated carbon for an electric double layer capacitor electrode according to the present invention includes an oxidation treatment step for oxidizing a graphitizable carbon precursor mainly composed of graphite-like microcrystals, and an oxidation process obtained by the oxidation treatment step. It is characterized by including a dehydration process step of heat-treating the treated product under a dehydration reaction catalyst, and an activation treatment step of obtaining activated carbon by gas activation of the dehydrated product obtained by this dehydration process step.
本発明において、黒鉛類似微結晶体を主成分とする易黒鉛化性炭素前駆体としては、特に限定されるものではなく、例えば、クリーンな石油系重質油（流動接触分解残渣油、熱分解タール、ナフサ分解タール、低硫黄直留残渣油など）、不純物が除去されたコールタール、またはポリ塩化ビニル（ＰＶＣ）を熱処理して得られる炭素前駆体等の黒鉛類似微結晶体等を主成分とするものを用いることができる。具体的には、例えば、針状生コークス、バルクメソフェーズ、晶質ピッチ、メソカーボンマイクロビーズ、メソフェーズピッチ紡糸生繊維等が挙げられる。これらは１種単独で、または２種以上組み合わせて用いることができる。中でも、黒鉛類似微結晶体のエッジ面が多く露出していることから、針状生コークス、バルクメソフェーズ、メソカーボンマイクロビーズを用いることが好適である。 In the present invention, the graphitizable carbon precursor mainly composed of graphite-like microcrystals is not particularly limited. For example, clean petroleum heavy oil (fluid catalytic cracking residue oil, pyrolysis Tar, naphtha cracked tar, low-sulfur straight-run residue oil, coal tar from which impurities are removed, or graphite-like microcrystals such as carbon precursors obtained by heat treatment of polyvinyl chloride (PVC) Can be used. Specifically, for example, acicular raw coke, bulk mesophase, crystalline pitch, mesocarbon microbeads, mesophase pitch-spun raw fibers and the like can be mentioned. These can be used alone or in combination of two or more. Among them, it is preferable to use acicular raw coke, bulk mesophase, and mesocarbon microbeads because many edge surfaces of the graphite-like microcrystal are exposed.
上記易黒鉛化性炭素前駆体の粒子径としては、使用する炭素前駆体の種類によって好適な範囲が異なるため、一概には規定できないが、一般的には、７４μｍ以下、好ましくは、１０μｍ以下である。特に、針状生コークスの場合は、４５μｍ以下が好ましく、１０μｍ以下がより好ましい。また、バルクメソフェーズの場合は、１０μｍ以下が好ましく、５μｍ以下がより好ましい。
なお、粒子径は、レーザー回折式粒度分布測定装置マイクロトラックＨＲＡ（日機装（株）製）による測定値である。
As the particle diameter of the graphitizable carbon precursor, the preferred range varies depending on the type of carbon precursor used, and thus cannot be defined unconditionally. However, in general, it is 74 μm or less, preferably 10 μm or less. is there. In particular, in the case of acicular raw coke, it is preferably 45 μm or less, and more preferably 10 μm or less. In the case of bulk mesophase, it is preferably 10 μm or less, and more preferably 5 μm or less.
The particle diameter is a value measured by a laser diffraction particle size distribution measuring device Microtrac HRA (manufactured by Nikkiso Co., Ltd.).
酸化処理工程は、上述の易黒鉛化性炭素前駆体を酸化して、炭素前駆体に酸素官能基を付与したり、炭素前駆体中に酸素架橋を形成させたりする工程である。
この場合、酸化方法としては、空気，酸素，オゾン等を用いた乾式酸化を用いてもよく、硝酸，硫酸等の無機酸などを用いた湿式酸化を用いてもよいが、最終生成物である活性炭をキャパシタ電極材として用いた場合におけるキャパシタ静電容量をより一層向上させるためには、湿式酸化を用いることが好ましい。
The oxidation treatment step is a step of oxidizing the graphitizable carbon precursor described above to impart an oxygen functional group to the carbon precursor or to form an oxygen bridge in the carbon precursor.
In this case, as the oxidation method, dry oxidation using air, oxygen, ozone or the like may be used, or wet oxidation using an inorganic acid such as nitric acid or sulfuric acid may be used, but this is the final product. In order to further improve the capacitor capacitance when activated carbon is used as the capacitor electrode material, it is preferable to use wet oxidation.
乾式酸化処理の条件としては、特に限定されるものではなく、公知の乾式酸化処理条件から適宜選択して用いることができる。空気酸化をする場合の一例を挙げると、炭素前駆体４０ｇに対して、１〜４Ｌ／分の流量で空気を流通させた状態で、１〜１０℃／分で常温から１５０〜３００℃まで加熱した後、５〜１０時間保持して酸化する方法がある。酸化処理後の冷却は、自然冷却でもよく、急冷してもよい。 The conditions for the dry oxidation treatment are not particularly limited, and can be appropriately selected from known dry oxidation treatment conditions. An example of air oxidation is as follows. Heating from room temperature to 150 to 300 ° C. at 1 to 10 ° C./min with air flowing at a flow rate of 1 to 4 L / min for 40 g of the carbon precursor. Then, there is a method of oxidizing by holding for 5 to 10 hours. Cooling after the oxidation treatment may be natural cooling or rapid cooling.
一方、湿式酸化処理の条件としても、特に限定されるものではなく、公知の湿式酸化処理条件から適宜選択して用いることができるが、酸化剤の分解や沸点を考慮すると、処理温度を１００℃以下とすることが好ましく、５０〜１００℃がより好ましく、７０〜９０℃がより一層好ましい。また、処理時間は、通常、５〜１０時間、好ましくは６〜８時間である。
酸化処理に用いられる酸としては、硝酸、硫酸およびこれらの混酸等が挙げられるが、これらに限定されるものではない。
On the other hand, the conditions for the wet oxidation treatment are not particularly limited and can be appropriately selected from known wet oxidation treatment conditions. However, in consideration of decomposition and boiling point of the oxidizing agent, the treatment temperature is set to 100 ° C. The following is preferable, 50 to 100 ° C is more preferable, and 70 to 90 ° C is even more preferable. Moreover, processing time is 5 to 10 hours normally, Preferably it is 6 to 8 hours.
Examples of the acid used for the oxidation treatment include nitric acid, sulfuric acid, and mixed acids thereof, but are not limited thereto.
酸の使用量は、使用する酸の種類によっても異なるため一概には規定できないが、通常、炭素前駆体１００ｇに対して、５０〜１５０ｇ程度の量で使用する。
上記各酸化処理後における表面への酸素付与量は、特に限定されるものではないが、Ｃ／Ｏ原子比で示した場合に２〜９であることが好ましく、３〜７であることがより好ましい。なお、Ｃ／Ｏ原子比は、Ｘ線光電子分析装置（ＥＳＣＡ）による測定値である。
The amount of acid used varies depending on the type of acid used and cannot be defined unconditionally, but is usually used in an amount of about 50 to 150 g with respect to 100 g of the carbon precursor.
The amount of oxygen applied to the surface after each of the oxidation treatments is not particularly limited, but is preferably 2 to 9 and more preferably 3 to 7 in terms of C / O atomic ratio. preferable. The C / O atomic ratio is a value measured by an X-ray photoelectron analyzer (ESCA).
脱水処理工程は、脱水反応触媒の存在下で酸化処理物を加熱することで、酸化処理物中の揮発成分を揮散させ、細孔を発現させて収縮を起こさせる工程である。
脱水反応触媒としては、例えば、リン酸ナトリウム、リン酸カリウム、リン酸水素ナトリウム等のリン酸類、塩化亜鉛等の亜鉛、ニッケル、チタン、その他の無機金属塩などが挙げられる。中でも、安価でかつ回収作業が容易であるという点から、塩化亜鉛を用いることが好ましい。
脱水反応触媒の使用量は、酸化処理物１００ｇに対して、通常、１００〜１５０ｇ程度であるが、これに限定されるものではない。
The dehydration process is a process in which the oxidized product is heated in the presence of a dehydration reaction catalyst, thereby volatilizing the volatile components in the oxidized product and causing the pores to shrink.
Examples of the dehydration reaction catalyst include phosphoric acids such as sodium phosphate, potassium phosphate and sodium hydrogen phosphate, zinc such as zinc chloride, nickel, titanium, and other inorganic metal salts. Among these, zinc chloride is preferably used because it is inexpensive and easy to collect.
The amount of the dehydration catalyst used is usually about 100 to 150 g with respect to 100 g of the oxidized product, but is not limited thereto.
脱水処理方法としては、特に限定されるものではないが、窒素ガス，アルゴンガス等の不活性ガス雰囲気下、常温（１５〜３０℃程度）から、炭素前駆体中の揮発成分が急速に揮散して収縮現象が起こる温度領域である６００〜９００℃程度、好ましくは７５０〜８５０℃まで、昇温速度０．５〜５℃／分、好ましくは０．５〜３℃／分程度の比較的穏やかな条件で加熱する手法が好適である。なお、この場合、脱水処理を完結させるという点から、最終到達温度において１〜２時間保持することが好ましい。
また、脱水処理後は、脱水処理物を冷却し、減圧乾燥等により乾燥させて次のガス賦活工程に用いることになるが、乾燥前に、希塩酸等の酸で洗浄し、さらに水洗してもよい。
Although it does not specifically limit as a dehydration processing method, Volatile components in a carbon precursor volatilize rapidly from normal temperature (about 15-30 degreeC) by inert gas atmosphere, such as nitrogen gas and argon gas. The temperature range is about 600 to 900 ° C., preferably 750 to 850 ° C., and the rate of temperature increase is 0.5 to 5 ° C./min, preferably about 0.5 to 3 ° C./min. A method of heating under various conditions is suitable. In this case, it is preferable to hold at the final temperature for 1 to 2 hours from the viewpoint of completing the dehydration process.
In addition, after the dehydration treatment, the dehydrated product is cooled and dried by drying under reduced pressure or the like and used in the next gas activation step. Before drying, it may be washed with an acid such as dilute hydrochloric acid and further washed with water. Good.
この脱水処理工程により得られた脱水処理物は、その中に脱水反応により微細な気孔が形成されるとともに、収縮によって細かい亀裂が発生しているが、この段階では、通常、ＢＥＴ比表面積が３００ｍ2／ｇ以下程度と小さく、ＭＰ法による全細孔容積０．２ｍＬ／ｇ以下程度、およびＢＪＨ法によるメソ孔容積０．０２ｍＬ／ｇ程度であり、キャパシタ電極用活性炭として充分に満足できる特性を有しているとは言い難い。 In the dehydrated product obtained by this dehydration process, fine pores are formed in the dehydration reaction and fine cracks are generated due to shrinkage. At this stage, the BET specific surface area is usually 300 m. 2 / g or less, the total pore volume by MP method is about 0.2mL / g or less, and the mesopore volume by BJH method is about 0.02mL / g. It is hard to say that it has.
そこで、脱水処理物を、さらにガス賦活処理することで、キャパシタにおける電解質イオンの出入りが円滑に行われるような特異な細孔を有し、かつ、黒鉛類似微結晶構造を持つ活性炭へと変化させる。
すなわち、ガス賦活処理工程は、脱水処理物内に形成された微細かつ微小な空隙をきっかけとし、さらにこの空隙をガス賦活により上述の特異な細孔へと導くものである。
この場合、ガス賦活処理に用いられるガスとしては、例えば、水蒸気、炭酸ガス等が挙げられるが、取扱い性、反応速度および安全性などを考慮すると、水蒸気を用いることが好ましい。
Therefore, by subjecting the dehydrated product to further gas activation treatment, it is changed to activated carbon having unique pores that allow electrolyte ions to enter and exit smoothly in the capacitor and has a graphite-like microcrystalline structure. .
That is, in the gas activation treatment step, fine and minute voids formed in the dehydrated product are used as a trigger, and the voids are further led to the above-described unique pores by gas activation.
In this case, examples of the gas used for the gas activation treatment include water vapor, carbon dioxide gas, and the like, but it is preferable to use water vapor in consideration of handling properties, reaction speed, safety, and the like.
ガス賦活処理方法としては、特に限定されるものではなく、使用するガスに応じた公知の手法を適宜採用することができる。水蒸気賦活処理方法の一例を挙げると、例えば、２〜３Ｌ／分の窒素ガス流通下、７００〜９００℃、好ましくは８００〜９００℃まで、１．５〜５時間、好ましくは２〜４時間で昇温した後、最終到達温度で１〜４時間、好ましくは２〜３時間保持し、窒素ガス共存下で水蒸気処理をする方法がある。 The gas activation treatment method is not particularly limited, and a known method according to the gas to be used can be appropriately employed. As an example of the steam activation treatment method, for example, under a nitrogen gas flow of 2 to 3 L / min, 700 to 900 ° C., preferably up to 800 to 900 ° C., 1.5 to 5 hours, preferably 2 to 4 hours. After raising the temperature, there is a method in which the final temperature is held for 1 to 4 hours, preferably 2 to 3 hours, and steam treatment is performed in the presence of nitrogen gas.
上述した本発明の電気二重層キャパシタ電極用活性炭の製造方法では、結晶構造の発達した易黒鉛化性炭素性前駆体の有する「生まれ」の特徴と、脱水処理とガス賦活の複合賦活法で処理することによる「育ち」の特徴とを組み合わせることにより、キャパシタ電極として用いた場合に、電気伝導性に優れ、静電容量が大きく、電極密度の高い活性炭を得ることができる。 In the method for producing activated carbon for an electric double layer capacitor electrode of the present invention described above, the characteristics of “born” possessed by the graphitizable carbonaceous precursor having a developed crystal structure and the combined activation method of dehydration and gas activation are used. When combined with the characteristics of “bringing”, activated carbon having excellent electrical conductivity, large capacitance, and high electrode density can be obtained when used as a capacitor electrode.
本発明に係る電気二重層キャパシタ電極用活性炭は、黒鉛類似微結晶体を主成分とする易黒鉛化性炭素前駆体から得られ、ＢＥＴ比表面積３５０〜１２００ｍ2／ｇ、ＭＰ法による全細孔容積０．２０〜１．００ｍＬ／ｇ、結晶格子面間隔（ｄ００２）０．３４〜０．３８ｎｍであり、ＢＪＨ法によるメソ孔容積とＭＰ法による全細孔容積との比（メソ孔／全細孔）が０．３５超０．７５以下であることを特徴とするものである。 The activated carbon for an electric double layer capacitor electrode according to the present invention is obtained from an easily graphitizable carbon precursor mainly composed of graphite-like microcrystals, has a BET specific surface area of 350 to 1200 m 2 / g, and all pores by the MP method. The volume is 0.20 to 1.00 mL / g, the crystal lattice spacing (d002) is 0.34 to 0.38 nm, and the ratio of the mesopore volume by the BJH method to the total pore volume by the MP method (mesopore / total Pore) is more than 0.35 and 0.75 or less.
ここで、ＢＥＴ比表面積が３５０ｍ2／ｇ未満であると、キャパシタ電極材として用いた場合に充分な静電容量が得られない虞があり、１２００ｍ2／ｇを超えると、得られるキャパシタの電極密度が低下する虞がある。これらのことを考慮すると、より好ましいＢＥＴ比表面積の範囲は、３７０〜１２００ｍ2／ｇ、特に、５００〜１２００ｍ2／ｇである。 Here, if the BET specific surface area is less than 350 m 2 / g, there is a possibility that sufficient capacitance may not be obtained when used as a capacitor electrode material. If the BET specific surface area exceeds 1200 m 2 / g, the obtained capacitor electrode There is a possibility that the density is lowered. Considering these, a more preferable range of the BET specific surface area is 370 to 1200 m 2 / g, and particularly 500 to 1200 m 2 / g.
ＭＰ法による全細孔容積が０．２０ｍＬ／ｇ未満であると、充分な静電容量を得ることができない虞があり、一方、１．００ｍＬ／ｇを超えると、メソ孔やマクロ孔が増大して得られたキャパシタの電極密度が低下する結果、容積あたりの静電容量が低減する虞がある。
結晶格子面間隔（ｄ００２）が０．３４ｎｍ未満であると、脱水反応触媒との反応性の低下や、ガス賦活時の反応性の低下を招く虞があり、一方、０．３８ｎｍを超えると、黒鉛化の程度が低すぎるため、充放電効率が低下する虞がある。
If the total pore volume by the MP method is less than 0.20 mL / g, sufficient electrostatic capacity may not be obtained, while if it exceeds 1.00 mL / g, mesopores and macropores increase. As a result of the decrease in the electrode density of the capacitor obtained in this manner, the capacitance per volume may be reduced.
If the crystal lattice spacing (d002) is less than 0.34 nm, there may be a decrease in reactivity with the dehydration reaction catalyst and a decrease in reactivity at the time of gas activation. Since the degree of graphitization is too low, the charge / discharge efficiency may be reduced.
ＢＪＨ法によるメソ孔容積とＭＰ法による全細孔容積との比（メソ孔／全細孔）が０．３５以下であると、電解液と電極界面が形成するヘルムホルツ層が生成困難になる可能性が高い。より好ましくは、メソ孔／全細孔が０．４０以上、さらに好ましくは０．４５以上である。また、その上限値は特に限定されるものではないが、通常０．７５程度である。
さらに、本発明の活性炭のＭＰ法によるミクロ孔容積は、特に限定されるものではないが、電解質イオンの挿入、吸着のされ易さを考慮すると、０．１５ｍＬ／ｇ以上であることが好ましく、より好ましくは、０．３０ｍＬ／ｇ以上、さらに好ましくは０．５０ｍＬ／ｇ以上である。
なお、本発明において、メソ孔とは、直径２〜５０ｎｍの細孔を、ミクロ孔とは、直径０．８〜２ｎｍの細孔を意味する。
If the ratio of the mesopore volume by the BJH method to the total pore volume by the MP method (mesopore / total pore) is 0.35 or less, it may be difficult to form a Helmholtz layer formed by the electrolyte and electrode interface High nature. More preferably, the mesopores / total pores are 0.40 or more, and further preferably 0.45 or more. The upper limit is not particularly limited, but is usually about 0.75.
Furthermore, the micropore volume by the MP method of the activated carbon of the present invention is not particularly limited, but it is preferably 0.15 mL / g or more in consideration of the ease of insertion and adsorption of electrolyte ions, More preferably, it is 0.30 mL / g or more, More preferably, it is 0.50 mL / g or more.
In the present invention, the mesopore means a pore having a diameter of 2 to 50 nm, and the micropore means a pore having a diameter of 0.8 to 2 nm.
本発明の活性炭の製造法としては、黒鉛類似微結晶体を主成分とする易黒鉛化性炭素前駆体を原料とし、上記の特性を満たす活性炭が得られる方法であれば特に限定されるものではないが、先に説明した複合賦活化を行う本発明の活性炭製造法によれば、上記特性を有する活性炭を容易に得ることができる。 The method for producing the activated carbon of the present invention is not particularly limited as long as it is a method capable of obtaining an activated carbon satisfying the above characteristics using a graphitizable carbon precursor mainly composed of a graphite-like microcrystal as a raw material. However, according to the activated carbon production method of the present invention in which the composite activation described above is performed, activated carbon having the above characteristics can be easily obtained.
以上のような特性を有する本発明の活性炭は、黒鉛類似微結晶構造を有するとともに、キャパシタにおける電解質イオンの出入りが円滑に行われるような特異な細孔を有しているものである。このため、電気二重層キャパシタ電極材として用いた場合に、静電容量および電極密度の高いキャパシタを得ることができる。
電気二重層キャパシタ電極材とする場合、上述した本発明の活性炭を主成分とし、さらにこの活性炭にバインダーポリマー（結着剤）および必要に応じて導電材を配合してなる電極組成物を集電体上に塗布してなるものを用いることができる。
この場合、バインダーポリマー、導電材、集電体としては、特に限定されるものではなく、公知のものから適宜選択して用いればよい。
The activated carbon of the present invention having the above characteristics has a graphite-like microcrystalline structure and unique pores that allow electrolyte ions to smoothly enter and exit the capacitor. For this reason, when used as an electric double layer capacitor electrode material, a capacitor having a high capacitance and high electrode density can be obtained.
In the case of an electric double layer capacitor electrode material, an electrode composition comprising the above-described activated carbon of the present invention as a main component and further containing a binder polymer (binder) and, if necessary, a conductive material in the activated carbon is collected. What was apply | coated on the body can be used.
In this case, the binder polymer, the conductive material, and the current collector are not particularly limited, and may be appropriately selected from known ones.
バインダーポリマーとしては、例えば、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、カルボキシメチルセルロース、フルオロオレフィン共重合体架橋ポリマー、ポリビニルアルコール、ポリアクリル酸、ポリイミド、石油ピッチ、石炭ピッチ、フェノール樹脂等を用いることができる。
バインダーポリマーの添加量は、例えば、活性炭１００質量部に対して０．５〜２０質量部とすることができ、好ましくは１〜１０質量部である。
As the binder polymer, for example, polytetrafluoroethylene, polyvinylidene fluoride, carboxymethyl cellulose, fluoroolefin copolymer crosslinked polymer, polyvinyl alcohol, polyacrylic acid, polyimide, petroleum pitch, coal pitch, phenol resin, and the like can be used. .
The addition amount of a binder polymer can be 0.5-20 mass parts with respect to 100 mass parts of activated carbon, for example, Preferably it is 1-10 mass parts.
必要に応じて添加される導電材としては、例えば、カーボンブラック、ケッチェンブラック、アセチレンブラック、カーボンウイスカー、炭素繊維、天然黒鉛、人造黒鉛、酸化チタン、酸化ルテニウム、アルミニウム，ニッケル等の金属ファイバなどが挙げられ、これらの１種を単独でまたは２種以上を組み合わせて用いることができる。
導電材の添加量は、例えば、活性炭１００質量部に対して０．１〜２０質量部とすることができ、好ましくは０．５〜１０質量部である。
Examples of conductive materials added as necessary include carbon fibers such as carbon black, ketjen black, acetylene black, carbon whiskers, carbon fibers, natural graphite, artificial graphite, titanium oxide, ruthenium oxide, aluminum, and nickel. These can be used alone or in combination of two or more.
The amount of the conductive material added can be, for example, 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the activated carbon.
なお、電極組成物の調製法には、特に限定はなく、例えば、活性炭、バインダーポリマーおよび必要に応じて添加される導電材を溶液状に調製することもでき、またこの溶液に必要に応じて溶媒を添加して調製することもできる。
このようにして得られた電極組成物を集電体上に塗布することにより、電極を得ることができる。塗布の方法は、特に限定されず、ドクターブレード、エアナイフ等の公知の塗布法を適宜採用すればよい。
正極集電体としては、アルミニウム箔または酸化アルミニウム箔を用いることが好ましく、一方、負極集電体としては、銅箔、ニッケル箔または表面が銅めっき膜もしくはニッケルめっき膜にて形成された金属箔を用いることが好ましい。
In addition, there is no limitation in particular in the preparation method of an electrode composition, For example, activated carbon, a binder polymer, and the electrically conductive material added as needed can also be prepared in a solution form, Moreover, as needed to this solution It can also be prepared by adding a solvent.
An electrode can be obtained by applying the electrode composition thus obtained onto a current collector. The application method is not particularly limited, and a known application method such as a doctor blade or an air knife may be appropriately employed.
As the positive electrode current collector, an aluminum foil or an aluminum oxide foil is preferably used. On the other hand, as the negative electrode current collector, a copper foil, a nickel foil or a metal foil whose surface is formed of a copper plating film or a nickel plating film is used. Is preferably used.
上記各集電体を構成する箔の形状としては、薄い箔状、平面に広がったシート状、孔が形成されたスタンパブルシート状等を採用できる。また、箔の厚さとしては、通常、１〜２００μｍ程度であるが、電極全体に占める活性炭の密度および電極の強度等を考慮すると、８〜１００μｍが好ましく、特に８〜３０μｍがより好ましい。
なお、電極は、電極組成物を溶融混練した後、押出し、フィルム成形することにより形成することもできる。
As the shape of the foil constituting each of the current collectors, a thin foil shape, a sheet shape spread on a plane, a stampable sheet shape with holes formed, or the like can be adopted. The thickness of the foil is usually about 1 to 200 μm, but considering the density of the activated carbon in the entire electrode, the strength of the electrode, etc., 8 to 100 μm is preferable, and 8 to 30 μm is particularly preferable.
The electrode can also be formed by melt-kneading the electrode composition and then extruding and film-forming.
本発明に係る電気二重層キャパシタは、上記のようにして得られる一対の電極を用いてなるものであればよく、電極以外のその他のキャパシタ構成部材としては、公知の部材から適宜選択して採用すればよい。
その製造方法の一例を挙げると、上記のようにして得られる一対の電極間に、必要に応じてセパレータを介在させてなる電気二重層キャパシタ構造体を積層、折畳、または捲回し、これを電池缶またはラミネートパック等の電池容器に収容した後、電解液を充填し、電池缶であれば封缶することにより、一方、ラミネートパックであればヒートシールすること等により、組み立てる方法があるが、これに限定されるものではなく、キャパシタ構成部材の種類により適宜な手法を用いればよい。
The electric double layer capacitor according to the present invention is only required to use the pair of electrodes obtained as described above, and other capacitor components other than the electrodes are appropriately selected from known members and employed. do it.
As an example of the manufacturing method, an electric double layer capacitor structure having a separator interposed between the pair of electrodes obtained as described above is laminated, folded, or wound as necessary. After being housed in a battery container such as a battery can or a laminate pack, there is a method of assembling by filling the electrolyte, sealing the battery can, and heat sealing the laminate pack. However, the present invention is not limited to this, and an appropriate method may be used depending on the type of capacitor constituent member.
本発明の電気二重層キャパシタは、携帯電話、ノート型パソコンや携帯用端末等のメモリーバックアップ電源用途、携帯電話、携帯用音響機器等の電源、パソコン等の瞬時停電対策用電源、太陽光発電、風力発電等と組み合わせることによるロードレベリング電源等の種々の小電流用蓄電デバイスに好適に使用することができる。また、大電流で充放電可能な電気二重層キャパシタは、電気自動車、電動工具等の大電流を必要とする大電流蓄電デバイスとして好適に使用することができる。 The electric double layer capacitor of the present invention is a memory backup power source for mobile phones, notebook computers and portable terminals, power sources for mobile phones and portable audio equipment, power supplies for instantaneous power failures such as personal computers, solar power generation, It can be suitably used for various low current power storage devices such as a load leveling power source by combining with wind power generation. An electric double layer capacitor that can be charged and discharged with a large current can be suitably used as a large current storage device that requires a large current, such as an electric vehicle or a power tool.
以下、実施例および比較例を挙げて、本発明をより具体的に説明するが、本発明は、下記の実施例に限定されるものではない。
なお、以下において、粒子径は、レーザー回折式粒度分布測定装置マイクロトラックＨＲＡ（日機装（株）製）による測定値である。
EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example.
In the following, the particle diameter is a value measured by a laser diffraction particle size distribution measuring device Microtrac HRA (manufactured by Nikkiso Co., Ltd.).
〈電気二重層キャパシタ電極用活性炭の製造〉
［実施例１］
［１］酸化処理工程
石炭系バルクメソフェーズ（固定炭素分８３質量％、トルエン不溶分９７質量％、キノリン不溶分９３質量％、酸素含有量４質量％）の粉末（粒子径２〜５μｍ、ＪＦＥケミカル社製）４０ｇと、２０質量％硝酸水溶液２００ｍＬとを、５００ｍＬのガラス容器に投入し、攪拌しながらオイルバス中９５℃で６時間加熱し、湿式酸化処理を行った。
得られた酸化処理物を水洗・乾燥し、収率を求めたところ、酸化収率１１９質量％であり、ＥＳＣＡ（ＪＰＳ−９０ＭＸ、日本電子（株）製）で測定した試料表面への酸素付与量（Ｃ／Ｏ原子比）は３．７であった。
<Manufacture of activated carbon for electric double layer capacitor electrode>
[Example 1]
[1] Oxidation treatment step Coal bulk mesophase (fixed carbon content 83% by mass, toluene insoluble content 97% by mass, quinoline insoluble content 93% by mass, oxygen content 4% by mass) (particle size 2-5 μm, JFE Chemical) 40 g) and 20 mL of 20% by mass nitric acid aqueous solution were put into a 500 mL glass container and heated in an oil bath at 95 ° C. for 6 hours with stirring to perform wet oxidation treatment.
The obtained oxidized product was washed with water and dried, and the yield was determined. The oxidation yield was 119% by mass, and oxygen was applied to the sample surface measured by ESCA (JPS-90MX, manufactured by JEOL Ltd.). The amount (C / O atomic ratio) was 3.7.
［２］脱水処理工程
次いで酸化処理したバルクメソフェーズ（２０ｇ）１００質量部と、脱水触媒である塩化亜鉛（和光純薬工業（株）製）１５０質量部とを混合した後、この混合物に１０ｍＬの水を加えて混合攪拌してなる泥状物を、一般的な黒鉛ボートに入れ、小型ガラス管式管状炉（ＴＫ−３０Ｎ、星和理工（株）製）内で熱処理を行った。この際、熱処理は、窒素ガス流通下、昇温速度２℃／分で８５０℃まで昇温し、同温度で１時間保持することで行った。
反応終了後、得られた脱水処理物を室温まで冷却した。冷却後、希塩酸で洗浄し、さらに水洗・減圧乾燥を施した（収率８６％）。
[2] Dehydration treatment step Next, 100 parts by mass of oxidized bulk mesophase (20 g) and 150 parts by mass of zinc chloride (manufactured by Wako Pure Chemical Industries, Ltd.) as a dehydration catalyst were mixed, and 10 mL of this mixture was added to this mixture. Mud obtained by adding water and mixing and stirring was put in a general graphite boat and heat-treated in a small glass tube tubular furnace (TK-30N, manufactured by Seiwa Riko Co., Ltd.). Under the present circumstances, heat processing was performed by heating up to 850 degreeC with the temperature increase rate of 2 degree-C / min under nitrogen gas circulation, and hold | maintaining at the same temperature for 1 hour.
After completion of the reaction, the obtained dehydrated product was cooled to room temperature. After cooling, it was washed with dilute hydrochloric acid, further washed with water and dried under reduced pressure (yield 86%).
［３］ガス賦活処理工程
得られた脱水処理物１４ｇを、ガラス管式小型賦活炉（ＴＫ−３０Ｎ、星和理工（株）製）に投入し、窒素ガス流通下（２Ｌ／分）、９００℃まで２時間で昇温した後、窒素導入管を、水蒸気発生装置に繋ぎ代え、窒素共存下、上記温度で２時間水蒸気処理を行った。得られた水蒸気処理物を、室温まで冷却後、乾燥して活性炭を得た（収率８．６％）。
得られた活性炭について、窒素吸着によるＢＥＴ法で比表面積を、ＭＰ法により全細孔容積を、ＢＪＨ法によりメソ孔容積を、ＭＰ法によりミクロ孔容積を、Ｘ線回折法（ＲＩＮＰ−１５００、理学電機（株）製）により結晶格子面間隔（ｄ００２）を、それぞれ求めた。結果を表１に示す。
[3] Gas activation treatment step 14 g of the obtained dehydrated product was put into a glass tube small activation furnace (TK-30N, manufactured by Hoshiwa Riko Co., Ltd.), under nitrogen gas flow (2 L / min), 900 After raising the temperature to 2 ° C. in 2 hours, the nitrogen inlet tube was connected to a steam generator, and steam treatment was performed at the above temperature for 2 hours in the presence of nitrogen. The obtained steam-treated product was cooled to room temperature and dried to obtain activated carbon (yield 8.6%).
About the obtained activated carbon, specific surface area by BET method by nitrogen adsorption, total pore volume by MP method, mesopore volume by BJH method, micropore volume by MP method, X-ray diffraction method (RINP-1500, The crystal lattice spacing (d002) was determined by Rigaku Denki Co., Ltd.). The results are shown in Table 1.
［実施例２］
塩化亜鉛の使用量を１００質量部として酸化処理工程を行った以外は、実施例１と同様にして活性炭を得た。酸化処理物、水蒸気処理物および活性炭について、実施例１と同様の物性を測定した。結果を表１に示す。
[Example 2]
Activated carbon was obtained in the same manner as in Example 1 except that the oxidation treatment step was performed with the amount of zinc chloride used being 100 parts by mass. The same physical properties as in Example 1 were measured for the oxidized product, the steam-treated product and the activated carbon. The results are shown in Table 1.
［実施例３］
酸化処理工程を以下の手法により行い、ガス賦活化処理時間を３時間とした以外は、実施例１と同様にして活性炭を得た。酸化処理物、水蒸気処理物および活性炭について、実施例１と同様の物性を測定した。結果を表１に示す。
［１］酸化処理工程
石油系針状生コークス粒（揮発分６質量％、炭素分９５質量％、水素分３．４質量％、平均粒子径１〜５ｍｍ）を、ボールミルにて粒子径５．８５〜４５μｍに粉砕してなる粉末４０ｇを、小型ガラス管式管状炉に投入し、空気流通下（２Ｌ／分）、２５０℃まで昇温し、同温度で７時間保持することにより乾式酸化処理を行った。処理後、急冷して酸化処理物を回収した（酸化収率８１質量％）。
[Example 3]
Activated carbon was obtained in the same manner as in Example 1 except that the oxidation treatment step was performed by the following method and the gas activation treatment time was 3 hours. The same physical properties as in Example 1 were measured for the oxidized product, the steam-treated product and the activated carbon. The results are shown in Table 1.
[1] Oxidation treatment process Petroleum needle-shaped raw coke grains (volatile content 6 mass%, carbon content 95 mass%, hydrogen content 3.4 mass%, average particle diameter 1 to 5 mm) were measured with a ball mill. 40g of powder pulverized to 85-45μm is put into a small glass tube tube furnace, heated to 250 ° C under air flow (2L / min), and kept at the same temperature for 7 hours to dry oxidation treatment Went. After the treatment, the product was rapidly cooled to collect the oxidized product (oxidation yield 81% by mass).
［比較例１］
実施例１と同様にして得られた脱水処理物を、そのまま比較例の活性炭とした（ガス賦活処理工程を施していない）。
脱水処理物について、実施例１と同様にして、比表面積、全細孔容積、メソ孔容積、ミクロ孔容積をそれぞれ求めた。結果を表１に示す。
[Comparative Example 1]
The dehydrated product obtained in the same manner as in Example 1 was directly used as a comparative activated carbon (no gas activation treatment step was performed).
For the dehydrated product, the specific surface area, total pore volume, mesopore volume, and micropore volume were determined in the same manner as in Example 1. The results are shown in Table 1.
〈電気二重層キャパシタの作製〉
［実施例４〜６、比較例２］
上記各活性炭、導電材（デンカブラック ＨＳ１００、電気化学工業（株）製）、および結着剤（ｐｏｌｙ（ｖｉｎｙｌｉｄｅｎｅ ｆｌｕｏｒｉｄｅ）、アルドリッチ社製）を、活性炭：導電材：結着剤＝９０：５：５の配合比（質量比）で混合して得られた充填物質と、Ｎ−メチル−２−ピロリドン（以下ＮＭＰという、ゴードー溶剤工業（株）製）を、充填物質：ＮＭＰ＝１００：２１２．５（質量比）の割合で混合した電極スラリーを調製した。
この電極スラリーを、Ａｌ／ＡｌＯXシート（３０ＣＢ、日本蓄電器工業（株）製）の片面上に、乾燥後の塗布厚が０．０７０ｍｍになるように塗布後、乾燥（８０℃）、圧延（充填密度、約０．６ｇ／ｃｍ3）して電極シートを得た。その後、電極シートを打ち抜き機でφ１２ｍｍに打ち抜き、１２０℃で２時間減圧乾燥し、試験電極とした。
続いて、二極式コインセル（北斗電工（株）製）を用い、上記試験電極２枚をセルロース系セパレータ（ＴＦ４０−３５、日本高度紙工業（株）製）を介してコインセルに組み立て、電解質として、Ｎ，Ｎ−ジエチル−Ｎ−メチル−Ｎ−（２−メトキシエチル）アンモニウムテトラフルオロボレート（関東化学（株）製）の１ｍｏｌ／Ｌプロピレンカーボネート（関東化学（株）製）溶液を用いて各実施例および比較例キャパシタセルを作製した。
<Production of electric double layer capacitor>
[Examples 4 to 6, Comparative Example 2]
Each activated carbon, conductive material (Denka Black HS100, manufactured by Denki Kagaku Kogyo Co., Ltd.), and binder (poly (vinylidene fluoride), manufactured by Aldrich) were used as activated carbon: conductive material: binder = 90: 5: 5 and a N-methyl-2-pyrrolidone (hereinafter referred to as NMP, manufactured by Gordo Solvent Industry Co., Ltd.), and the packing material: NMP = 100: 212. An electrode slurry mixed at a ratio of 5 (mass ratio) was prepared.
This electrode slurry was applied on one side of an Al / AlO X sheet (30CB, manufactured by Nippon Electric Power Industry Co., Ltd.) so that the coating thickness after drying was 0.070 mm, then dried (80 ° C.), rolled ( An electrode sheet was obtained with a packing density of about 0.6 g / cm 3 . Thereafter, the electrode sheet was punched to φ12 mm with a punching machine and dried under reduced pressure at 120 ° C. for 2 hours to obtain a test electrode.
Subsequently, using a bipolar coin cell (made by Hokuto Denko Co., Ltd.), the above two test electrodes were assembled into a coin cell via a cellulose separator (TF40-35, made by Nippon Kogyo Paper Industries Co., Ltd.) as an electrolyte. , N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate (manufactured by Kanto Chemical Co., Ltd.) 1 mol / L propylene carbonate (manufactured by Kanto Chemical Co., Ltd.) Example and Comparative Example Capacitor cells were prepared.
上記実施例４〜６および比較例２で得られたキャパシタセルについて、下記手法により、静電容量および電極密度を測定した。結果を表２に示す。
［１］静電容量
上記各キャパシタセルについて、充放電システム（１００５ＳＭ８、北斗電工（株）製）で充放電することにより、評価した。
評価方法は、初期容量確認試験として、室温環境において電流密度０．８８ｍＡ／ｃｍ2、設定電圧２．５０Ｖ、定電圧時間１５分（終止条件）で充電し、電流密度０．８８ｍＡ／ｃｍ2、終止電圧０．０Ｖで放電した。
［２］電極密度
上記各キャパシタセルについて、質量、厚みを測定し、得られた値から電極密度を算出した。算出は、両極の総質量（Ａｌ／ＡｌＯxシートの質量は含まない）を、φ１２ｍｍに打ち抜いた電極の体積（Ａｌ／ＡｌＯxシートの厚みは含まない）で除すことにより、行った。
For the capacitor cells obtained in Examples 4 to 6 and Comparative Example 2, the capacitance and electrode density were measured by the following method. The results are shown in Table 2.
[1] Capacitance Each capacitor cell was evaluated by charging / discharging with a charge / discharge system (1005SM8, manufactured by Hokuto Denko Co., Ltd.).
As an initial capacity confirmation test, a current density of 0.88 mA / cm 2 in a room temperature environment, a setting voltage of 2.50 V, a constant voltage time of 15 minutes (end condition), and a current density of 0.88 mA / cm 2 The battery was discharged at a final voltage of 0.0V.
[2] Electrode density About each said capacitor cell, mass and thickness were measured and the electrode density was computed from the obtained value. The calculation was performed by dividing the total mass of both electrodes (not including the mass of the Al / AlO x sheet) by the volume of the electrode punched to φ12 mm (not including the thickness of the Al / AlO x sheet).
表２に示されるように、実施例１〜３の複合賦活化処理により得られた活性炭を用いた実施例４〜６のキャパシタセルでは、静電容量および電極密度の双方とも、水蒸気処理をしていない比較例１の活性炭を用いたキャパシタよりも優れていることがわかる。特に、湿式酸化処理を施した実施例１，２の活性炭を用いた場合、静電容量の著しい増加が見られていることがわかる。 As shown in Table 2, in the capacitor cells of Examples 4 to 6 using activated carbon obtained by the composite activation treatment of Examples 1 to 3, both the capacitance and the electrode density were subjected to steam treatment. It turns out that it is superior to the capacitor using the activated carbon of the comparative example 1 which is not. In particular, it can be seen that when the activated carbons of Examples 1 and 2 subjected to the wet oxidation treatment are used, the electrostatic capacity is remarkably increased.
さらに、実施例４，５で得られたキャパシタセルについて、上記と同様の充放電サイクルを繰り返し、２０回までのサイクル毎に静電容量を求めた。結果を表３に示す。 Further, for the capacitor cells obtained in Examples 4 and 5, the same charge / discharge cycle as described above was repeated, and the capacitance was determined for each cycle up to 20 times. The results are shown in Table 3.
表３に示されるように、複合賦活化処理により得られた活性炭を用いたキャパシタセルでは、サイクルを重ねても静電容量は維持されており、サイクル特性に優れていることがわかる。
As shown in Table 3, in the capacitor cell using activated carbon obtained by the composite activation treatment, it can be seen that the capacitance is maintained even after repeated cycles, and the cycle characteristics are excellent.
Claims (9)
この酸化処理工程により得られた酸化処理物を脱水反応触媒下で加熱処理する脱水処理工程と、
この脱水処理工程により得られた脱水処理物をガス賦活して活性炭を得る賦活処理工程と、を含むことを特徴とする電気二重層キャパシタ電極用活性炭の製造方法。 An oxidation treatment step of oxidizing a graphitizable carbon precursor mainly composed of graphite-like microcrystals;
A dehydration treatment step of heat-treating the oxidation-treated product obtained by this oxidation treatment step under a dehydration reaction catalyst;
And an activation treatment step of activating the dehydrated product obtained by this dehydration step to obtain activated carbon, thereby producing an activated carbon for an electric double layer capacitor electrode.
ＢＥＴ比表面積３５０〜１２００ｍ2／ｇ、ＭＰ法による全細孔容積０．２０〜１．００ｍＬ／ｇ、結晶格子面間隔（ｄ００２）０．３４〜０．３８ｎｍであり、ＢＪＨ法によるメソ孔容積とＭＰ法による全細孔容積との比（メソ孔／全細孔）が０．３５超０．７５以下であることを特徴とする電気二重層キャパシタ用活性炭。 Obtained from an easily graphitizable carbon precursor mainly composed of graphite-like microcrystals,
BET specific surface area 350-1200 m 2 / g, total pore volume 0.20-1.00 mL / g by MP method, crystal lattice spacing (d002) 0.34-0.38 nm, mesopore volume by BJH method The ratio of the total pore volume by the MP method and the total pore volume (mesopores / total pores) is more than 0.35 and not more than 0.75, and the activated carbon for electric double layer capacitors.
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