JP2009260112A - Producing method of positive-electrode active material for electrochemical capacitor - Google Patents

Producing method of positive-electrode active material for electrochemical capacitor Download PDF

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JP2009260112A
JP2009260112A JP2008108700A JP2008108700A JP2009260112A JP 2009260112 A JP2009260112 A JP 2009260112A JP 2008108700 A JP2008108700 A JP 2008108700A JP 2008108700 A JP2008108700 A JP 2008108700A JP 2009260112 A JP2009260112 A JP 2009260112A
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active material
positive electrode
electrode active
electrochemical capacitor
pitch
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Yasushi Miki
泰 三樹
Takuro Oshida
卓朗 大信田
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Mitsubishi Gas Chemical Co Inc
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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 a producing method of a positive-electrode active material for an electrochemical capacitor substituting for activated charcoal by alkali activation. <P>SOLUTION: The producing method of a positive-electrode active material for an electrochemical capacitor using lithium salt in the electrolyte includes the steps of (a) heating the raw material pitch in the temperature range of 500°C or higher and 800°C or lower, (b) milling the material obtained by the heating step (a), (c) cleaning the milled material obtained by the milling step (b), and (d) separating and drying the material obtained by the cleaning step (c). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、電気化学キャパシタ用正極活物質の製造方法および該方法によって得られる電気化学キャパシタ用正極活物質に関する。   The present invention relates to a method for producing a positive electrode active material for an electrochemical capacitor and a positive electrode active material for an electrochemical capacitor obtained by the method.

電気二重層キャパシタ（以下、ＥＤＬＣと称する）は、大電流充放電が可能で、長寿命かつ高温安定性に優れるため、例えばハイブリッド自動車などの蓄電デバイスとして理想的な特性を有している。しかし、ＥＤＬＣは２次電池に比較してエネルギー密度が不充分であることが欠点となっていた。   An electric double layer capacitor (hereinafter referred to as EDLC) is capable of charging / discharging a large current, has a long life and is excellent in high-temperature stability, and therefore has ideal characteristics as a power storage device such as a hybrid vehicle. However, EDLC has a drawback in that the energy density is insufficient compared to the secondary battery.

この欠点を解消するために、負極材料にリチウムイオンを吸蔵、脱着することができる炭素材料をもちいた電気化学キャパシタ（以下、ＥＣＣと称する）が提案されている（例えば、特許文献１〜３参照）。このＥＣＣにおいてはリチウムイオンを吸蔵した炭素材料を用いることで負極電位を卑な電位とすることが可能となる。よって充電状態での正極活性炭との電位差を４Ｖ以上と大きくすることができ、従来のＥＤＬＣよりエネルギー密度を高くできる。このＥＣＣでは、正極の活性炭に貯蔵される電荷量よりも、負極炭素材料に貯蔵される電荷量が数十倍大きい。したがって、セルの静電容量は正極活性炭の静電容量で支配されることになり、静電容量の大きな活性炭を用いることでより大きな静電容量となる。   In order to eliminate this defect, an electrochemical capacitor (hereinafter referred to as ECC) using a carbon material capable of inserting and extracting lithium ions in a negative electrode material has been proposed (see, for example, Patent Documents 1 to 3). ). In this ECC, the negative electrode potential can be reduced to a base potential by using a carbon material that occludes lithium ions. Therefore, the potential difference with the positive electrode activated carbon in the charged state can be increased to 4 V or more, and the energy density can be made higher than that of the conventional EDLC. In this ECC, the amount of charge stored in the negative electrode carbon material is several tens of times larger than the amount of charge stored in the activated carbon of the positive electrode. Therefore, the electrostatic capacity of the cell is governed by the electrostatic capacity of the positive electrode activated carbon, and a larger electrostatic capacity is obtained by using activated carbon having a large electrostatic capacity.

活性炭を用いて高い静電容量を得るためには、単位重量あたりの静電容量が高く、かつ電極密度が高いことが必要である。単位重量あたりの静電容量を得るためには、高比表面積が必要とされ、電極密度を高くしようとすれば、比表面積としては小さくしなければならない（例えば、非特許文献１参照）。該文献で開示された正極には、易黒鉛化性炭素前駆体を熱処理し炭素化物とした後、ＫＯＨ賦活された活性炭が用いられている。しかしながらＫＯＨ賦活はアルカリ金属の生成と水素の副生を伴うため、製造時の安全性と反応器の腐食等、工業生産には大きな課題があった。
特開平８−１０７０４８号公報 特開平９−２７５０４１号公報 特開２００６−２８６９１９号公報 Journal of Power Sources 166 (2007) 462-470 In order to obtain a high capacitance using activated carbon, it is necessary that the capacitance per unit weight is high and the electrode density is high. In order to obtain the capacitance per unit weight, a high specific surface area is required, and if the electrode density is to be increased, the specific surface area must be reduced (for example, see Non-Patent Document 1). The positive electrode disclosed in this document uses activated carbon activated by KOH after heat treating a graphitizable carbon precursor to obtain a carbonized product. However, since KOH activation involves generation of alkali metal and hydrogen by-product, there are significant problems in industrial production such as safety during production and corrosion of the reactor.
Japanese Patent Laid-Open No. 8-1007048 Japanese Patent Laid-Open No. 9-275041 JP 2006-286919 A Journal of Power Sources 166 (2007) 462-470

本発明は、上記問題に鑑み、従来のＫＯＨ賦活による活性炭に代わるＥＣＣ用正極活物質の製造方法を提供する。   This invention provides the manufacturing method of the positive electrode active material for ECC instead of the activated carbon by the conventional KOH activation in view of the said problem.

本発明者らは、ＥＣＣの正極に用いる電極材料の出発原料、処理方法、条件等を詳細に検討した結果、アルカリ賦活によらずに比較的高い静電容量を示す正極活物質が製造できることを見いだし本発明に到達した。即ち、本発明は以下のとおりである。
１． 電解液にリチウム塩を用いる電気化学キャパシタにおいて、つぎの工程（ａ）〜（ｄ）を含む電気化学キャパシタ用正極活物質の製造方法。
（ａ）原料ピッチを５００℃以上８００℃以下の温度範囲で熱処理する、
（ｂ）工程（ａ）で得られる熱処理物を粉砕処理する、
（ｃ）工程（ｂ）で得られる粉砕処理物を溶剤で洗浄処理する、
（ｄ）工程（ｃ）で得られる洗浄処理物を分離・乾燥処理する。
２． 前記工程（ａ）において、原料ピッチにカーボンブラックを添加したのち、熱処理する第１項記載の電気化学キャパシタ用正極活物質の製造方法。
３． 前記カーボンブラックの添加量が原料ピッチ１００重量部に対して２〜３０重量部である第２項記載の電気化学キャパシタ用正極活物質の製造方法。
４． 前記カーボンブラックのジブチルフタレート（ＤＢＰ）吸油量が１００〜５００ｍｌ／１００ｇである第２項記載の電気化学キャパシタ用正極活物質の製造方法。
５． 前記ピッチが光学的異方性ピッチである第１項記載の電気化学キャパシタ用正極活物質の製造方法。
６． 前記光学的異方性ピッチが縮合多環炭化水素をフッ化水素・三フッ化ホウ素の共存下で重合させて得られるものである第５項記載の電気化学キャパシタ用正極活物質の製造方法。
７． 第１項〜第６項のいずれかに記載の方法によって得られる電気化学キャパシタ用正極活物質。
８． 前記正極活物質のＢＥＴ比表面積が５００ｍ２／ｇ以下である第７項記載の電気化学キャパシタ用正極活物質。
９． 第７項記載の正極活物質を用いる電気化学キャパシタ。 As a result of examining the starting materials, processing methods, conditions, etc. of the electrode material used for the positive electrode of the ECC in detail, the present inventors have found that a positive electrode active material exhibiting a relatively high capacitance can be produced regardless of alkali activation. We found out and reached the present invention. That is, the present invention is as follows.
1. In the electrochemical capacitor which uses lithium salt for electrolyte solution, the manufacturing method of the positive electrode active material for electrochemical capacitors including the following process (a)-(d).
(A) heat-treating the raw material pitch in a temperature range of 500 ° C. or higher and 800 ° C. or lower;
(B) The heat-treated product obtained in step (a) is pulverized.
(C) The pulverized product obtained in step (b) is washed with a solvent.
(D) The washed product obtained in step (c) is separated and dried.
2. The method for producing a positive electrode active material for an electrochemical capacitor according to claim 1, wherein in the step (a), carbon black is added to the raw material pitch, followed by heat treatment.
3. The method for producing a positive electrode active material for an electrochemical capacitor according to claim 2, wherein the addition amount of the carbon black is 2 to 30 parts by weight with respect to 100 parts by weight of the raw material pitch.
4). The manufacturing method of the positive electrode active material for electrochemical capacitors of Claim 2 whose dibutyl phthalate (DBP) oil absorption amount of the said carbon black is 100-500 ml / 100g.
5. The method for producing a positive electrode active material for an electrochemical capacitor according to claim 1, wherein the pitch is an optically anisotropic pitch.
6). 6. The method for producing a positive electrode active material for an electrochemical capacitor according to claim 5, wherein the optically anisotropic pitch is obtained by polymerizing a condensed polycyclic hydrocarbon in the presence of hydrogen fluoride / boron trifluoride.
7). A positive electrode active material for an electrochemical capacitor obtained by the method according to any one of Items 1 to 6.
8). The positive electrode active material for electrochemical capacitors according to claim 7, wherein the positive electrode active material has a BET specific surface area of 500 m 2 / g or less.
9. An electrochemical capacitor using the positive electrode active material according to item 7.

本発明によれば、アルカリ賦活によらないで安全かつ安価にＥＣＣ用電極材料を製造できる。また、本発明の方法で得られる電極材料をＥＣＣの正極として用いることにより、高い静電容量が発現する。さらに、エネルギー密度はＥＤＬＣより高く長寿命となるため、ハイブリッド自動車、ＵＰＳ等の電源として非常に有用である。   According to the present invention, an electrode material for ECC can be manufactured safely and inexpensively without using alkali activation. Further, by using the electrode material obtained by the method of the present invention as the positive electrode of ECC, a high capacitance is developed. Furthermore, since the energy density is higher than that of EDLC and has a long life, it is very useful as a power source for hybrid vehicles, UPS, and the like.

本発明は単位体積当りで比較的高い静電容量が得られるＥＣＣ用正極活物質を提供するものである。ＥＣＣの静電容量（Ｃ）は正極の静電容量（Ｃ＋）と負極の静電容量（Ｃ−）とから式（１）によって求められる。ここで、正極に活性炭、負極にリチウムイオンを吸蔵、脱着することができる炭素材料を用いたＥＣＣにおいてはＣ＋≪Ｃ−となることから、式（１）における１／Ｃ−はほぼ無視することが出来、正負両極からなるセルの静電容量は式（２）のようになる。すなわち、セルの静電容量は正極活性炭の静電容量で支配される。
（数１）
１／Ｃ＝１／Ｃ＋ ＋ １／Ｃ− ・・・式（１）
１／Ｃ≒１／Ｃ＋ （１／Ｃ＋≪１／Ｃ−の場合） ・・・式（２）
したがって、高い静電容量を有するＥＣＣを得るためには、高い静電容量を有する活物質を正極として用いることが好ましい。 The present invention provides a positive electrode active material for ECC that can obtain a relatively high capacitance per unit volume. The capacitance (C) of the ECC is obtained by the equation (1) from the capacitance (C +) of the positive electrode and the capacitance (C−) of the negative electrode. Here, in ECC using a carbon material that can store and desorb lithium ions in the positive electrode and activated carbon in the positive electrode, C + << C-, so 1 / C- in the equation (1) should be almost ignored. The capacitance of a cell composed of both positive and negative electrodes can be expressed by equation (2). That is, the capacitance of the cell is governed by the capacitance of the positive active carbon.
(Equation 1)
1 / C = 1 / C + + 1 / C− Expression (1)
1 / C≈1 / C + (in the case of 1 / C + << 1 / C−) (2)
Therefore, in order to obtain an ECC having a high capacitance, it is preferable to use an active material having a high capacitance as the positive electrode.

高い静電容量を得るためには、単位重量あたりの静電容量と電極密度のいずれもが高いことが必要である。一般に比表面積の大きな活性炭は単位重量あたりの静電容量は高いが、細孔が多く電極密度は低くなってしまう。本発明に用いる活物質は５００ｍ２／ｇ以下であり、好ましくは３００ｍ２／ｇ以下である。 In order to obtain a high capacitance, both the capacitance per unit weight and the electrode density must be high. In general, activated carbon having a large specific surface area has a high capacitance per unit weight, but has many pores and a low electrode density. The active material used for this invention is 500 m < 2 > / g or less, Preferably it is 300 m < 2 > / g or less.

本発明において用いられる活物質の原料としては、石油系ピッチ、石炭系ピッチ又は合成系ピッチが挙げられる。また、本発明に用いられるピッチとしては、光学的異方性ピッチ（以下、メソフェーズピッチということがある）が好ましい。   Examples of the active material used in the present invention include petroleum pitch, coal pitch, and synthetic pitch. The pitch used in the present invention is preferably an optical anisotropic pitch (hereinafter sometimes referred to as mesophase pitch).

さらに、光学的異方性ピッチの中でも特に好ましいものとしては、特許第２９３１５９３号公報、特許第２６２１２５３号公報、特許第２５２６５８５号公報又は特開２０００−３１９６６４号公報に示されるように、ナフタレン、メチルナフタレン、アントラセン、フェナントレン、アセナフテン、アセナフチレン、ピレン等の縮合多環炭化水素を超強酸触媒のフッ化水素・三フッ化ホウ素の共存下で重合させて得られる合成系メソフェーズピッチが挙げられる。これらは他のピッチ類と異なり、化学純度が高く、性状を自由に制御可能であることから特に好適に用いられる。   Further, among optically anisotropic pitches, particularly preferable examples include naphthalene, methyl as shown in Japanese Patent No. 2931593, Japanese Patent No. 2612253, Japanese Patent No. 2526585, or Japanese Patent Application Laid-Open No. 2000-319664. Examples thereof include synthetic mesophase pitches obtained by polymerizing condensed polycyclic hydrocarbons such as naphthalene, anthracene, phenanthrene, acenaphthene, acenaphthylene, and pyrene in the presence of hydrogen fluoride and boron trifluoride as super strong acid catalysts. Unlike other pitches, these are particularly preferably used because they have high chemical purity and the properties can be freely controlled.

本発明において得られる活物質が正極として用いられる場合、充電時に正極が膨張することがある。この膨張を抑制するには原料ピッチにあらかじめカーボンブラックを添加するのが効果的である。   When the active material obtained in the present invention is used as a positive electrode, the positive electrode may expand during charging. In order to suppress this expansion, it is effective to add carbon black to the raw material pitch in advance.

ピッチへカーボンブラックを添加する場合は、通常原料ピッチ１００重量部対して、カーボンブラック２〜３０重量部の範囲が好ましい。さらに好ましくは２〜１５重量部の範囲、特に好ましくは２〜５重量部の範囲である。カーボンブラックの添加量が少なすぎると、光学モザイク組織の発達が不十分になる。また、添加量が多すぎるとＥＣＣ用活物質としての静電容量の低下が著しくなる。   When carbon black is added to the pitch, the range of 2 to 30 parts by weight of carbon black is usually preferable with respect to 100 parts by weight of the raw material pitch. More preferably, it is the range of 2-15 weight part, Most preferably, it is the range of 2-5 weight part. If the amount of carbon black added is too small, the development of the optical mosaic structure becomes insufficient. Moreover, when there is too much addition amount, the fall of the electrostatic capacitance as an active material for ECC will become remarkably.

本発明において上記ピッチに添加するカーボンブラックは特に限定されないが、ジブチルフタレート（ＤＢＰ）吸油量が１００〜５００ｍｌ／１００ｇのものが好ましい。さらに好ましくは１００〜３６０ｍｌ／１００ｇの範囲、特に好ましくは１５０〜２００ｍｌ／１００ｇの範囲である。   In the present invention, the carbon black added to the pitch is not particularly limited, but preferably has a dibutyl phthalate (DBP) oil absorption of 100 to 500 ml / 100 g. More preferably, it is the range of 100-360 ml / 100g, Most preferably, it is the range of 150-200 ml / 100g.

ピッチへのカーボンブラックの添加には公知の方法が用いられ、両成分をブレンダーで混合する方法や、押出機を用いて溶融混合する方法がある。   A known method is used to add carbon black to the pitch, and there are a method of mixing both components with a blender and a method of melt-mixing using an extruder.

ピッチまたはピッチにカーボンブラックを添加したもの（以下、ピッチ等ということがある）の熱処理は、５００℃以上８００℃以下の温度で行なう。さらに好ましくは５００℃以上６５０℃以下、特に好ましくは５００℃以上５５０℃以下の範囲である。５００℃未満の熱処理で得られたものをＥＣＣ用電極活物質に用いると、２Ｖ以上の電圧領域において有機系電解液の分解反応が激しくＥＣＣの長期的な性能を劣化させる。一方、熱処理温度が８００℃を超えると、炭素網面からなるクラスターの発達が進むため、クラスター間の空隙量が減少する。そのため、電解賦活によるクラスター空隙への電解液イオンの侵入が妨げをうけるため、静電容量が低下する。   The heat treatment of pitch or pitch-added carbon black (hereinafter sometimes referred to as pitch) is performed at a temperature of 500 ° C. or higher and 800 ° C. or lower. More preferably, it is 500 degreeC or more and 650 degrees C or less, Most preferably, it is the range of 500 degreeC or more and 550 degrees C or less. When a material obtained by heat treatment at less than 500 ° C. is used as an electrode active material for ECC, the decomposition reaction of the organic electrolyte solution is severe in a voltage region of 2 V or more, and the long-term performance of ECC is deteriorated. On the other hand, when the heat treatment temperature exceeds 800 ° C., the development of clusters composed of the carbon network surface advances, and the amount of voids between the clusters decreases. For this reason, the electrolyte ions are prevented from entering the cluster voids due to electrolytic activation, so that the capacitance decreases.

本発明におけるピッチ等の熱処理時間は、０．５Ｈｒ〜４Ｈｒであることが好ましい。さらに好ましくは０．５Ｈｒ〜２Ｈｒ、特に好ましくは１Ｈｒ〜２Ｈｒの範囲である。   In the present invention, the heat treatment time such as pitch is preferably 0.5Hr to 4Hr. More preferably, it is 0.5Hr-2Hr, Most preferably, it is the range of 1Hr-2Hr.

本発明におけるピッチ等の熱処理は、窒素、アンモニア等の非酸化性ガス雰囲気下で行われることが好ましい。     The heat treatment such as pitch in the present invention is preferably performed in an atmosphere of a non-oxidizing gas such as nitrogen or ammonia.

得られた熱処理物は粉砕処理される。粉砕方法として衝撃式粉砕機、ボールミル、ローラーミル、ジェットミル等から適宜、最適機種が選択される。所望の粒度を得るために分級機を組み合わせて用いてもよい。   The obtained heat-treated product is pulverized. As the pulverization method, an optimum model is appropriately selected from an impact pulverizer, a ball mill, a roller mill, a jet mill and the like. In order to obtain a desired particle size, a classifier may be used in combination.

粉砕処理の際には、平均粒子径で通常１〜５０μｍになるよう粒度調整することが好ましい。より好ましくは、５〜３０μｍの範囲、特に好ましくは、１０〜２５μｍの範囲である。   In the pulverization treatment, it is preferable to adjust the particle size so that the average particle size is usually 1 to 50 μm. More preferably, it is the range of 5-30 micrometers, Most preferably, it is the range of 10-25 micrometers.

粉砕処理後の熱処理物（粉砕処理物）は、溶剤を用いて洗浄処理する。溶剤は特に種類を限定するものではないが、例えば アセトン、メタノール、エータノール、プロパノール、イソプロピルアルコール、ブタノール、ヘキサン、ヘプタン、ベンゼン、トルエン、キシレン、キノリン、ピリジン、テトラハイドロフランを挙げることができる。好ましくは沸点が５０℃以上の有機溶剤である。特にキノリン、ピリジンが好ましい。   The heat-treated product (pulverized product) after the pulverization treatment is washed with a solvent. The type of solvent is not particularly limited, and examples include acetone, methanol, ethanol, propanol, isopropyl alcohol, butanol, hexane, heptane, benzene, toluene, xylene, quinoline, pyridine, and tetrahydrofuran. Preferably, the organic solvent has a boiling point of 50 ° C. or higher. Particularly preferred are quinoline and pyridine.

上記溶剤は、粉砕処理物１重量部に対して１０〜５０重量部用いることが好ましい。洗浄処理の温度は、１０〜２５０℃、好ましくは６０〜２５０℃、より好ましくは１２０〜２３０℃である。洗浄処理の時間は、１〜２４０時間、好ましくは７２〜１２０時間、より好ましくは４８〜７２時間である。   The solvent is preferably used in an amount of 10 to 50 parts by weight with respect to 1 part by weight of the pulverized product. The temperature of the washing treatment is 10 to 250 ° C, preferably 60 to 250 ° C, more preferably 120 to 230 ° C. The cleaning treatment time is 1 to 240 hours, preferably 72 to 120 hours, and more preferably 48 to 72 hours.

洗浄処理後の粉砕処理物（洗浄処理物）を回収するには、公知の分離方法を用いることができる、例えば、ろ過、遠心分離法が使用できる。溶剤が残存した回収物をＥＣＣ用正極活物質に用いると、ＥＣＣの長期的な性能を劣化させるため、分離回収後に乾燥処理（脱溶剤処理）を行う。例えば、洗浄処理に用いた溶媒よりも、低沸点の溶媒を用いて洗浄処理後の回収粉砕処理物を再度洗浄し、不活性雰囲気下で真空乾燥等を行う。 In order to collect the pulverized processed product (cleaned processed product) after the cleaning treatment, a known separation method can be used, for example, filtration or centrifugation can be used. If the recovered material in which the solvent remains is used as the positive electrode active material for ECC, the long-term performance of the ECC is deteriorated. For example, the recovered pulverized product after the washing treatment is washed again using a solvent having a lower boiling point than the solvent used in the washing treatment, and vacuum drying or the like is performed in an inert atmosphere.

こうして得られた乾燥処理物をＥＣＣの正極活物質として用いることで、エネルギー密度の高いＥＣＣが得られる。   By using the dried product thus obtained as a positive electrode active material for ECC, ECC with high energy density can be obtained.

ピッチ等を熱処理すると熱重合により炭素網面が成長する。本発明のようにピッチ等を５００℃以上８００℃以下で熱処理して得られる熱処理物を溶剤で洗浄処理した後の比表面積は９０ｍ２／ｇ以下であるが、高静電容量を発現する。これは、溶剤洗浄により、炭素網面エッジの低分子物質が除去され、炭素網面エッジが露出され、電解賦活によるイオンの炭素クラスター空隙への侵入と、さらには炭素網面の層間へのイオンの挿入が容易になることによって容量が発現すると考えられる。 When the pitch or the like is heat-treated, the carbon network surface grows by thermal polymerization. The specific surface area of the heat-treated product obtained by heat-treating the pitch or the like at 500 ° C. or more and 800 ° C. or less as in the present invention with a solvent is 90 m 2 / g or less, but exhibits a high capacitance. This is because solvent cleaning removes low-molecular substances at the carbon network edge, exposes the carbon network edge, penetrates ions into the carbon cluster voids by electrolytic activation, and further ions between the layers of the carbon network surface. It is considered that the capacity is developed by facilitating the insertion of.

本発明においては、電解液としてリチウム塩が用いられる。また負極に用いる炭素材料にリチウムイオンが吸蔵できるものを用いる。負極にはリチウムをあらかじめ吸蔵させてもよく、例えば、化学的にリチウム金属を直接接触させた負極炭素材料を電解液に浸漬し、リチウムをイオン化させて吸蔵したり、セパレーターをはさんで対向させたリチウム金属と負極炭素材料を電解液中で定電流または定電圧で充電し、それぞれを短絡させて充電する方法がある。   In the present invention, a lithium salt is used as the electrolytic solution. Moreover, what can occlude lithium ion is used for the carbon material used for a negative electrode. Lithium may be preliminarily occluded in the negative electrode. For example, a negative electrode carbon material that is in direct contact with lithium metal is immersed in an electrolytic solution, and lithium is ionized and occluded, or sandwiched between separators. There is a method in which the lithium metal and the negative electrode carbon material are charged in an electrolytic solution at a constant current or a constant voltage, and each is short-circuited and charged.

負極に用いる炭素材料は特に限定されないが、光学的異方性ピッチ等の易黒鉛化性炭素前駆体を２５００℃以上で黒鉛化した黒鉛材料や天然黒鉛、また易黒鉛化性炭素前駆体を２０００℃以下で焼成した炭素材料や、難黒鉛化性炭素前駆体を２０００℃以下で焼成した炭素などを用いることが出来る。   The carbon material used for the negative electrode is not particularly limited, but a graphite material or natural graphite obtained by graphitizing an easily graphitizable carbon precursor such as an optically anisotropic pitch at 2500 ° C. or more, or an easily graphitizable carbon precursor is 2000 A carbon material fired at a temperature of ℃ or lower, carbon obtained by firing a non-graphitizable carbon precursor at a temperature of 2000 ℃ or lower, or the like can be used.

本発明における有機電解液の溶質であるリチウム塩としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣＦ３ＳＯ３、ＬｉＣ（ＳＯ２ＣＦ３）３、ＬｉＡｓＦ６およびＬｉＳｂＦ６等が挙げられる。溶媒としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート、スルホラン等が挙げられ、これらの１種または２種以上の混合溶媒を用いることが出来る。 Examples of the lithium salt that is the solute of the organic electrolyte in the present invention include LiPF 6 , LiBF 4 , LiClO 4 , LiN (CF 3 SO 2 ) 2 , LiCF 3 SO 3 , LiC (SO 2 CF 3 ) 3 , LiAsF 6 and LiSbF 6, and the like. Examples of the solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, and the like, and one or more mixed solvents thereof can be used.

（分極性電極の膨張率測定法）
厚み約１５０μｍシート状分極性電極を２ｃｍ２の有効電極面積に打ち抜いた後、ＴＥＣＬＯＣＫ製厚みゲージ（ＳＭ−１１２）を用いて、正極、負極の電極厚みを計測した。さらに、充放電試験後、評価用セルから正極、負極を回収し電極厚みを計測した。 (Measurement method of expansion coefficient of polarizable electrode)
After punching the sheet-like polarizable electrode having a thickness of about 150 μm to an effective electrode area of 2 cm 2 , the electrode thicknesses of the positive electrode and the negative electrode were measured using a TECLOCK thickness gauge (SM-112). Furthermore, after the charge / discharge test, the positive electrode and the negative electrode were collected from the evaluation cell, and the electrode thickness was measured.

電極膨張比は、充放電後回収した正極、負極厚みの合計厚みを充放電前の正極、負極厚みの合計厚みで除する事により算出し、下式に従って算出した。
電極膨張比＝（充放電後回収 正極厚み＋負極厚み）／（充放電前 正極厚み＋負極厚み） The electrode expansion ratio was calculated by dividing the total thickness of the positive electrode and negative electrode collected after charging / discharging by the total thickness of the positive electrode and negative electrode before charging / discharging, and was calculated according to the following formula.
Electrode expansion ratio = (recovered positive electrode thickness + negative electrode thickness after charge / discharge) / (positive electrode thickness + negative electrode thickness before charge / discharge)

次に、実施例及び比較例を挙げて本発明を具体的に説明するが、本発明はこれら実施例によって何ら限定されるものではない。   EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited at all by these Examples.

実施例１
フッ化水素・三フッ化ホウ素の共存下、ナフタレンを重合させてメソフェーズピッチ（メトラー法による軟化点：２８３℃、光学異方性：１００％）を合成した。該ピッチ１００重量部に対して、カーボンブラック（デンカブラック、ＤＢＰ吸油量１７５ｍｌ／１００ｇ）を５重量部添加し、両成分をブレンダーで１分間混合した後、該ピッチとカーボンブラックの混合粉末を、窒素流通下、アルミナボールを３０ｋｇ入れたロータリーキルン（内容積０．１５ｍ３）に連続的に供給し、５５０℃で１時間保持して熱処理した。室温まで冷却したのち、該熱処理物を３２μｍ以下に粉砕し、２０ｇを３００ｇのキノリン中、１２０℃で攪拌しながら７２時間加熱した。その後、吸引ろ過してキノリンを除き、ケーキを３００ｇのメタノールに加え、３０分間超音波洗浄し、２５℃で７２時間攪拌した。その後、吸引ろ過してメタノールを除き、回収したケーキを、２００℃で１４時間真空乾燥し、ＥＣＣ用正極活物質を得た。該正極活物質の比表面積は７３．５ｍ２／ｇであった。該活性炭と導電性カーボンブラック、バインダーとしてのＰＴＦＥとを重量比で８：１：１となるように混合、混錬、圧延してシート状とし、２ｃｍ２の有効電極面積に打ち抜き、厚さ１５０μｍ、電極密度０．８０ｇ／ｃｃの正極電極を得た。
負極活物質としては、石炭系コールタールに酸性の硫酸アンモニウム溶液を３ｗｔ％混合し、攪拌しながら５００℃まで熱処理し固化した。該固化物を不活性雰囲気下１１００℃で熱処理を行い、炭素化物を得た。
該炭素化物を３２μｍ以下に粉砕した後に、１重量部の該炭素化物の粉末とＮ−メチルピロリドン１重量部を十分に混合することでスラリーを得た。該スラリーを厚さ３０μｍの銅箔に塗工し、乾燥、プレスを行い、２ｃｍ２の有効電極面積に打ち抜き、厚さ１２０μｍの負極電極を得た。
負極電極とリチウム金属を、セルロース系セパレーターを介して対向させ１ｍｏｌ／ＬのＬｉＰＦ６／ＰＣ電解液に浸漬した。それぞれの電極を短絡させ、室温で２４ｈ静置した。２４ｈ後にリチウムイオンが吸蔵した負極電極を取り出し、セパレーターを介して正極活性炭電極と対向させた。同電解液を用いて、４．５Ｖから２．２Ｖ間での充放電を行ったところ、静電容量は７３Ｆ／ｃｃを得た。電極膨張比は１．４７であった。 Example 1
Naphthalene was polymerized in the presence of hydrogen fluoride and boron trifluoride to synthesize mesophase pitch (softening point by Mettler method: 283 ° C., optical anisotropy: 100%). 5 parts by weight of carbon black (Denka black, DBP oil absorption 175 ml / 100 g) is added to 100 parts by weight of the pitch, and both components are mixed with a blender for 1 minute, and then the mixed powder of the pitch and carbon black is Under a nitrogen flow, a rotary kiln (with an internal volume of 0.15 m 3 ) containing 30 kg of alumina balls was continuously supplied and heat treated by holding at 550 ° C. for 1 hour. After cooling to room temperature, the heat-treated product was pulverized to 32 μm or less, and 20 g was heated in 120 g of quinoline at 120 ° C. for 72 hours. Thereafter, the quinoline was removed by suction filtration, the cake was added to 300 g of methanol, ultrasonically washed for 30 minutes, and stirred at 25 ° C. for 72 hours. Thereafter, suction filtration was performed to remove methanol, and the recovered cake was vacuum dried at 200 ° C. for 14 hours to obtain a positive electrode active material for ECC. The specific surface area of the positive electrode active material was 73.5 m 2 / g. The activated carbon, conductive carbon black, and PTFE as a binder are mixed, kneaded and rolled to a weight ratio of 8: 1: 1 to form a sheet, punched into an effective electrode area of 2 cm 2, 150 μm in thickness, A positive electrode having an electrode density of 0.80 g / cc was obtained.
As a negative electrode active material, 3 wt% of an acidic ammonium sulfate solution was mixed with coal-based coal tar, and the mixture was heat-treated to 500 ° C. with solidification and solidified. The solidified product was heat-treated at 1100 ° C. in an inert atmosphere to obtain a carbonized product.
After the carbonized product was pulverized to 32 μm or less, a slurry was obtained by thoroughly mixing 1 part by weight of the carbonized product powder and 1 part by weight of N-methylpyrrolidone. The slurry was applied to a copper foil having a thickness of 30 μm, dried and pressed, and punched into an effective electrode area of 2 cm 2 to obtain a negative electrode having a thickness of 120 μm.
The negative electrode and the lithium metal were opposed to each other through a cellulose-based separator and immersed in 1 mol / L LiPF 6 / PC electrolyte. Each electrode was short-circuited and allowed to stand for 24 hours at room temperature. After 24 hours, the negative electrode in which lithium ions were occluded was taken out and opposed to the positive electrode activated carbon electrode through a separator. When charging / discharging between 4.5V and 2.2V was performed using the electrolytic solution, the capacitance was 73 F / cc. The electrode expansion ratio was 1.47.

実施例２
実施例１において合成したピッチにカーボンブラックを添加せず、該ピッチを直接連続的に投入し、実施例１と同一操作を行った。静電容量は７０Ｆ／ｃｃ、電極膨張比は１．７８であった。 Example 2
The same operation as in Example 1 was performed without adding carbon black to the pitch synthesized in Example 1, but continuously adding the pitch directly. The capacitance was 70 F / cc, and the electrode expansion ratio was 1.78.

実施例３
実施例１で合成したピッチｇとカーボンブラック（デンカブラック、ＤＢＰ吸油量１７５ｍｌ／１００ｇ）の混合粉末２０ｇを、アルミナ容器に入れ、管状炉中、窒素雰囲気下９．５℃／分で５５０℃まで昇温して、５５０℃で１時間保持して熱処理物を得た以外は、実施例１と同様にした。充放電を行ったところ体積当たり静電容量６０Ｆ／ｃｃであった。電極膨張比は１．５０であった。 Example 3
20 g of the mixed powder of pitch g and carbon black (Denka black, DBP oil absorption 175 ml / 100 g) synthesized in Example 1 was put in an alumina container, and in a tubular furnace up to 550 ° C. in a nitrogen atmosphere at 9.5 ° C./min. The temperature was raised and held at 550 ° C. for 1 hour to obtain a heat-treated product. When charging / discharging was performed, the capacitance per volume was 60 F / cc. The electrode expansion ratio was 1.50.

比較例１
正極活物質として、等方性ピッチをガス賦活することによって得た比表面積１３５０ｍ２／ｇの活性炭を用いた。電極密度は０．７０ｇ／ｃｃであった。そのほかは実施例１と同様にして充放電を行ったところ、静電容量は３７Ｆ／ｃｃであった。電極膨張比は１．４２であった。 Comparative Example 1
As the positive electrode active material, activated carbon having a specific surface area of 1350 m 2 / g obtained by gas activation of isotropic pitch was used. The electrode density was 0.70 g / cc. Otherwise, charging / discharging was performed in the same manner as in Example 1, and the capacitance was 37 F / cc. The electrode expansion ratio was 1.42.

Claims (9)

電解液にリチウム塩を用いる電気化学キャパシタにおいて、つぎの工程（ａ）〜（ｄ）を含む電気化学キャパシタ用正極活物質の製造方法。
（ａ）原料ピッチを５００℃以上８００℃以下の温度範囲で熱処理する、
（ｂ）工程（ａ）で得られる熱処理物を粉砕処理する、
（ｃ）工程（ｂ）で得られる粉砕処理物を溶剤で洗浄処理する、
（ｄ）工程（ｃ）で得られる洗浄処理物を分離・乾燥処理する。 In the electrochemical capacitor which uses lithium salt for electrolyte solution, the manufacturing method of the positive electrode active material for electrochemical capacitors including the following process (a)-(d).
(A) heat-treating the raw material pitch in a temperature range of 500 ° C. or higher and 800 ° C. or lower;
(B) The heat-treated product obtained in step (a) is pulverized.
(C) The pulverized product obtained in step (b) is washed with a solvent.
(D) The washed product obtained in step (c) is separated and dried. 前記工程（ａ）において、原料ピッチにカーボンブラックを添加したのち、熱処理する請求項１記載の電気化学キャパシタ用正極活物質の製造方法。   The method for producing a positive electrode active material for an electrochemical capacitor according to claim 1, wherein in the step (a), carbon black is added to the raw material pitch, followed by heat treatment. 前記カーボンブラックの添加量が原料ピッチ１００重量部に対して２〜３０重量部である請求項２記載の電気化学キャパシタ用正極活物質の製造方法。   The method for producing a positive electrode active material for an electrochemical capacitor according to claim 2, wherein the amount of carbon black added is 2 to 30 parts by weight with respect to 100 parts by weight of the raw material pitch. 前記カーボンブラックのジブチルフタレート（ＤＢＰ）吸油量が１００〜５００ｍｌ／１００ｇである請求項２記載の電気化学キャパシタ用正極活物質の製造方法。   The method for producing a positive electrode active material for an electrochemical capacitor according to claim 2, wherein the carbon black has a dibutyl phthalate (DBP) oil absorption of 100 to 500 ml / 100 g. 前記ピッチが光学的異方性ピッチである請求項１記載の電気化学キャパシタ用正極活物質の製造方法。   The method for producing a positive electrode active material for an electrochemical capacitor according to claim 1, wherein the pitch is an optically anisotropic pitch. 前記光学的異方性ピッチが縮合多環炭化水素をフッ化水素・三フッ化ホウ素の共存下で重合させて得られるものである請求項５記載の電気化学キャパシタ用正極活物質の製造方法。   6. The method for producing a positive electrode active material for an electrochemical capacitor according to claim 5, wherein the optically anisotropic pitch is obtained by polymerizing a condensed polycyclic hydrocarbon in the presence of hydrogen fluoride / boron trifluoride. 請求項１〜６のいずれかに記載の方法によって得られる電気化学キャパシタ用正極活物質。   A positive electrode active material for an electrochemical capacitor obtained by the method according to claim 1. 前記正極活物質のＢＥＴ比表面積が５００ｍ２／ｇ以下である請求項７記載の電気化学キャパシタ用正極活物質。 The positive electrode active material for an electrochemical capacitor according to claim 7, wherein the positive electrode active material has a BET specific surface area of 500 m 2 / g or less. 請求項７記載の正極活物質を用いる電気化学キャパシタ。   An electrochemical capacitor using the positive electrode active material according to claim 7.
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