JP4518223B2 - Polarizable electrode for electric double layer capacitor and manufacturing method thereof - Google Patents
Polarizable electrode for electric double layer capacitor and manufacturing method thereof Download PDFInfo
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Abstract
Description
【０００１】
【発明が属する技術分野】
この発明は、電気二重層コンデンサ用分極性電極とその製造方法に関し、特に所定投影面積あたりの内部抵抗値が低く、かつ所定体積あたりの容量が大きく、破壊強度に優れた分極性電極に関するものである。
【０００２】
【従来の技術】
大電力電源のロードレベリング用として、あるいはハイブリッドカーなどの高出力密度の蓄電源として、大容量でかつ内部抵抗の低い電気二重層コンデンサを用いることが期待されている。
【０００３】
しかし従来の電気二重層コンデンサでは内部抵抗が高く、大きな電流を取り出せないため、直列接続によって高電圧の電気二重層コンデンサバンクを構成し、コンバータ等を利用した周辺の回路技術によって高出力を得ているが、コスト高を招いている。
【０００４】
従来の有機系電解液を用いた電気二重層コンデンサでは分極性電極の投影単位面積あたりの抵抗が高く、電流密度は１〜２０ｍＡ／ｃｍ2で用いられており、それ以上の電流密度では電圧降下が大きくなり、出力が著しく低下する。ゆえに、電極面積を広くする目的で分極性電極の塗布厚を薄くして抵抗を下げる試みがなされているが、この場合、電気二重層コンデンサのパッケージあたりの分極性電極の充填量が減少し、電気二重層コンデンサのパッケージあたりの容量が低下して十分なエネルギー密度が得られなくなる。
【０００５】
このような従来の有機系の電解液と分極性電極では分極性電極の投影単位面積あたりの抵抗の限界により、必要なエネルギー密度を保持した状態で高出力密度を得るのは困難であった。
【０００６】
電気二重層コンデンサの分極性電極の製造方法には、活性炭粉末状と導電性助剤とバインダー樹脂を含むスラリーを集電板上に塗布、乾燥したものと活性炭粉末、導電性助剤および含フッ素高分子樹脂の混和物を成型した後延伸処理してシート状に成形したものがある。
【０００７】
塗布法による分極性電極は、活性炭粉末の結着性が弱く脱離しやすく、また活性炭粒子間に結着材として入り込んでいるため、粒子間の接触抵抗が大きく、結果として電気二重層コンデンサの内部抵抗を増大させている。
さらに塗布のみでは活性炭の密度が上がらず単位体積あたりの容量が小さい傾向にある。
【０００８】
そこで、延伸処理によってシート状に成形する方法で機械的強度を増すことで粒子の脱離を抑制し、密度を高くすることが行われている。たとえば、特公平７−１０５３１６号公報には、炭素微粉、含フッ素重合体樹脂および液状潤滑剤からなる混和物をシート成形し、さらに延伸処理する方法が示されている。
【０００９】
【発明が解決しようとする課題】
この特公平７−１０５３１６号公報に記載された従来の延伸処理によってシート状に成形した分極性電極では、液状潤滑剤があるため、混和物に十分な圧力がかからず、シート成形時に含フッ素重合体樹脂が十分な結着性を発揮するには前記樹脂を多量に添加しなければならない。
【００１０】
さらに炭素微粉は含フッ素重合体樹脂に含まれてしまうため炭素微粉間の接触抵抗の増大および炭素微粉の充填量が制限されることによる容量不足になり、大容量でかつ内部抵抗が低い電気二重層コンデンサの用途には適用が困難である。そのために、シート状に成型した後に、さらにこのシートを延伸処理し、炭素微粉を含フッ素重合体樹脂の微小結節に含ませる２次工程が不可欠となっていた。
【００１１】
この発明は、電気二重層コンデンサの分極性電極の所定投影面積あたりの内部抵抗値が低く、かつ所定体積あたりの容量が大きく、破壊強度も強い分極性電極およびその製造方法を提供することを目的とする。特に、分極性電極の投影面積あたりの放電電流密度が２０ｍＡ／ｃｍ2を超える大電流密度での出力の低下を低減した高出力密度の電気二重層コンデンサ用分極性電極およびその製造方法の提供を目的とする。
【００１２】
【課題を解決するための手段】
この発明は、電気二重層コンデンサ用分極性電極の製造方法において、粒子径が０．５〜２００μｍの活性炭粉末に対し、粒子径が０．１μｍ以下の導電性助剤粉末を１〜２０重量％、およびラメラ構造をとる含フッ素高分子樹脂粉末０．１〜３０重量％添加し、さらに、水または液状炭化水素のうち少なくともひとつを含む分散溶媒を添加して湿式混合した後、分散溶媒を除去するとともに粉砕して混合粉末を形成し、この混合粉末を０．１から２．０ｍｍの粒子径のものに分級して２次粒子とし、この混合２次粒子粉末を圧縮してシート状に成型することを特徴としている。
【００１３】
また、ラメラ構造をとる含フッ素高分子樹脂が、ポリテトラフルオロエチレンであってもよい。
【００１５】
さらに、前記混合粉末を、室温〜２００℃で圧縮し、好ましくは５０℃〜１００℃で加熱圧縮することを特徴としている。
【００１６】
また、この発明は、電気二重層コンデンサ用分極性電極において、粒子径が０．５〜２００μｍの活性炭粉末に対し、粒子径が０．１μｍ以下の導電性助剤粉末を１〜２０重量％、およびラメラ構造をとる含フッ素高分子樹脂粉末０．１〜３０重量％添加し、さらに、水または液状炭化水素のうち少なくともひとつを含む分散溶媒を添加して湿式混合した後、分散溶媒を除去するとともに粉砕して混合粉末を形成し、この混合粉末を０．１から２．０ｍｍの粒子径のものに分級して２次粒子とし、この混合２次粒子粉末を圧縮してシート状に成型することで、活性炭が、ラメラ構造の破壊で形成される含フッ素高分子樹脂の微細繊維からなる三次元網目構造体によって保持されるように結合したことを特徴としている。
【００１７】
この電気二重層コンデンサ用分極性電極においては、活性炭、導電性助剤およびラメラ構造をとる含フッ素高分子樹脂を含む分極性電極であって、３６Å以上の気孔の占める容積が水銀圧入法による測定で０．３〜０．６ｃｃ／ｃｃ、密度が０．５〜０．８ｇ／ｃｃであることを特徴としている。
【００１８】
また、活性炭の粒子径が０．５〜２００μｍであり、あるいは導電性助剤の粒子径が０．１μｍ以下、またラメラ構造の破壊で形成される含フッ素高分子樹脂の微細繊維の径が０．３μｍ以下であることを特徴としている。
【００１９】
さらに、この発明の電気二重層コンデンサ用分極性電極では、含フッ素高分子樹脂が、ポリテトラフルオロエチレンであることを特徴とし、厚み１０〜２０００μｍのシート状成形物であることを特徴としている。
【００２０】
【発明の実施の形態】
この発明の分極性電極は、活性炭粉末、導電性助剤、およびラメラ構造をとる含フッ素高分子樹脂からなる粉末状の乾式混合物を圧縮し、必要に応じて加熱することでシート状に成形しており、さらに具体的には次のように製造される。
【００２１】
１）粉末状混合物の調整
活性炭粉末に対して導電性助剤を１〜２０重量％、好ましくは５〜１５％、ラメラ構造をとる含フッ素高分子樹脂粉末を０．１〜３０重量％、好ましくは１〜１０重量％を混合し、回転混合機で均一に乾式混合して混合粉末の調整を行う。
また混合時に活性炭粉末に対して、水または液状炭化水素のうち少なくともひとつを含む分散溶媒を５０〜２００重量％添加して湿式混合してもよく、この場合は、均一混合した後に分散溶媒を乾燥させて取り除き、再び粉末状に粉砕して混合粉末を得る。
【００２２】
２）混合粉末の分級
混合粉末は、分級し、必要に応じては粉砕し、凝集した２次粒子の径を、０．１〜２ｍｍの範囲とする。
【００２３】
３）シート成形
分級した混合粉末を圧縮し、必要に応じて加熱してシート状成形物にする。加熱は、室温〜２００℃、好ましくは５０℃〜１００℃で圧縮してシート状に成形する。少なくとも室温を下回る温度ではシート状に成形することが困難になり、またこれを上回る温度で加熱しても、フッ素樹脂が約２６０℃で熱分解してしまうため、やはりシートが脆弱になってしまう。
【００２４】
なお、混合粉末の圧縮と必要に応じて施す加熱工程では、プレス機を用いることができるほか、加熱したロールを用いて行うこともできる。この場合、ロールの隙間に混合粉末を連続的に供給することで連続的にシート成形ができるようになる。また、シート状の分極性電極の厚みは、ロールを用いる場合、直径および間隔を調節することで、１０μｍ〜２０００μｍまでの間の任意の厚みをえることができる。さらにその後にカレンダーロールなどに通すことで薄くすることもでき、任意の厚みを得ることができるようになる。
【００２５】
以上のような製造方法で製造される分極性電極では、図１の電子顕微鏡写真で示すように、ラメラ構造の含フッ素高分子樹脂が、前記製造方法における圧縮や必要に応じて施される加熱処理によって破壊されて繊維化し、この繊維よりも粒径の小さい導電性助剤粒子が、微細繊維状の含フッ素高分子樹脂に付着、凝集、接触または連続化する。さらに、微細繊維状の含フッ素高分子樹脂が、この繊維よりも粒子径の大きい活性炭に接触するように相互に結合し、その結果、活性炭は、微細繊維状の含フッ素高分子樹脂、ならびにこの微細繊維状の含フッ素高分子樹脂に付着、凝集した導電性助剤粒子によって接触または連続化するように相互に結合されるため、活性炭が、ラメラ構造の破壊で形成される含フッ素高分子樹脂の微細繊維からなる三次元網目構造体によって保持されるように結合することになる。
【００２６】
この分極性電極の構造を図２に示した模式図で説明する。この図２は、先に示した電子顕微鏡写真の図１を基にこれを模式化したもので、繊維化したラメラ構造の含フッ素高分子樹脂は破線３で、導電性助剤粒子の凝集体は楕円２で、活性炭は網掛けの多角形１でそれぞれ表している。
【００２７】
すなわち、この発明による分極性電極は、含フッ素高分子樹脂の繊維３に、この繊維３よりも粒径の小さい導電性助剤粒子２が付着、凝集、接触または連続化し、さらに繊維３が、この繊維３よりも粒子径の大きい活性炭１に接触するように相互に結合し、その結果、活性炭１が繊維３の三次元網目構造体によって保持されるように結合している。
【００２８】
以上の構造的な特徴を持つシート状の分極性電極は、３６Å以上の気孔の占める容積が水銀圧入法による測定で０．３〜０．６ｃｃ／ｃｃ、密度が０．５〜０．８ｇ／ｃｃであり、引張強度が０．１ＭＰａ以上である。
【００２９】
活性炭粒径は、０．５〜２００μｍ、好ましくは１〜１００μｍであり、導電性助剤粉末は粒子径が０．１μｍ以下のものが好適である。
【００３０】
このように、活性炭および導電性助剤を、最小限の含フッ素高分子樹脂の量で結着し、かつ前記樹脂の繊維による捕捉効果によってシート状の連続構造体とすることで活性炭の充填密度密度が高くなるため、シート状の分極性電極の体積あたりの容量が増加するとともに破壊強度が増し、さらには、最小限の含フッ素高分子樹脂の量により粒子間空隙量が保たれるため、イオンの移動抵抗が減少して、分極性電極の所定投影面積あたりの内部抵抗値が低減するようになる。
【００３１】
【実施例】
ついで、この発明の実施例について説明する。
（実施例１）
平均粒子径が２７μｍで比表面積１３００ｍ2／ｇの活性炭に対して、１次粒子径が０．１μｍ以下のカーボンブラックを１０重量％、添加した粉末混合物に対して水とイソプロピルアルコール（ＩＰＡ）９：１の混合分散溶媒を１７０重量％添加し、回転混合機に投入し混合した後、平均直径が０．１５〜０．３μｍのラメラ構造を有するポリテトラフルオロエチレン（ＰＴＦＥ）を水に対して６０重量％分散したディスパージョンを１３重量％（ＰＴＦＥ固形分換算で７．８重量％）添加し、さらに回転混合機で混合した。
【００３２】
つぎに、混合物を取り出し減圧乾燥機で８５℃に加熱して分散溶媒を取り除いた後、カッティングミキサーにより粉砕し、０．１〜２ｍｍの粒径に分級した粉体を、あらかじめ６０℃に加熱した直径１２０ｍｍの２本のロールの０．１８ｍｍに設定した隙間に連続的に投入し加熱圧縮して連続的に厚さ０．２ｍｍのシート状の分極性電極を得た。
【００３３】
このシート状の分極性電極を直径２０ｍｍの円板状に打ち抜き、厚さ５０μｍのセルロース繊維不織布セパレータを挟んで対向させ素子としさらにその外側に白金板を配置し集電板とし、さらにその外側からテフロン板で挟み込んで固定して、電気二重層コンデンサセルとした。このセルを１モルになるように、テトラエチルアンモニウム、テトラフルオロボレートをプロピレンカーボネートに溶解した電解液に浸漬して減圧含浸した。
【００３４】
次に、このセル２．５Ｖで３０分間定電圧充電後、電極投影面積に対する放電電流密度２０ｍＡ／ｃｍ2、５０ｍＡ／ｃｍ2で定電流放電して容量を測定した。また放電電流密度５０ｍＡ／ｃｍ2の時の放電初期の電圧降下から内部抵抗を算出した。
【００３５】
（実施例２）
２−１）実施例１においてロール加熱温度を８０℃としたこと以外はすべて実施例１と同様に行った。
【００３６】
２−２）実施例１においてロール直径を１６０ｍｍとしロールの隙間を０．１ｍｍにしたほかはすべて実施例１と同様に行った。
【００３７】
２−３）実施例１においてＰＴＦＥの添加量を固形分換算で５重量％にしたほかはすべて実施例１と同様に行った。
【００３８】
（実施例３）
実施例１において平均粒子径が８μｍで比表面積２４００ｍ2／ｇの活性炭を用いたほかはすべて実施例１と同様に行った。
【００３９】
（比較例１）
実施例１において回転混合機から取り出した混合物を乾燥せずにロール成形機により圧延し厚さ１ｍｍのシートとした後、カレンダーロールで加熱延伸処理して連続的に厚さ０．２ｍｍのシート状の分極性電極を得たほかはすべて実施例１と同様に行った。
【００４０】
（比較例２）
実施例１においてカッティングミキサーにより粉砕した粉体の分級を行わなかったほかはすべて実施例１と同様に行った。
【００４１】
（比較例３）
実施例１においてＰＴＦＥの添加量を固形分換算で４０重量％にしたほかはすべて実施例１と同様に行った。
【００４２】
（比較例４）
実施例１において導電性助剤に平均粒子径３μｍで炭化温度１２００℃以上のフェノール炭化物を用いたことのほかはすべて実施例１と同様に行った。
以上の実施例および比較例のシート状分極性電極の特性値を（表１）に示す。
【００４３】
【表１】
表１から明らかなように、本発明によれば、最小限の含フッ素高分子樹脂の量によりシート状の連続構造体を作成できるため、活性炭の充填量多く、前記シート状の分極性電極の体積あたりの容量が増加するとともに、破壊強度が増し、さらに粒子間空隙量（気孔容積）が保たれるため、イオンの移動抵抗が減少して、分極性電極の所定投影面積あたりの内部抵抗値が低減したことがわかる。
【００４５】
なお、比較例２では粉体の分級を行わなかったためロールに巻きこまれない大きさの物も含まれてしまいシート状成形物に穴が多数あいて連続構造体としての試料を取得できなかった。
【００４６】
【発明の効果】
以上のように、この発明は、従来のように液状の潤滑剤などを用いることなく、混合粉末をそのまま圧縮し、必要に応じて加熱処理してシート状に成型するため、混和物に十分な圧力をかけることができるようになり、シート状に成形する際に、含フッ素重合体樹脂が十分な結着性を発揮でき、破壊強度に優れた分極性電極を得ることができる。
【００４７】
また、活性炭粉末間の接触抵抗が減少するため、大容量でかつ内部抵抗が低い電気二重層コンデンサを実現できる。
【００４８】
さらに、シート状に成型した後に、さらにこのシートを延伸処理するなどの２次工程が必要なくなり、２０ｍＡ／ｃｍ2を超える大電流密度での出力の低下を低減した高出力密度の電気二重層コンデンサを作成することができる。
【図面の簡単な説明】
【図１】 この発明による分極性電極の構造を示す電子顕微鏡写真
【図２】 この発明による分極性電極の構造を示す模式図
【符号の説明】
１ 活性炭
２ 導電性助剤
３ 繊維[0001]
[Technical field to which the invention belongs]
The present invention relates to a polarizable electrode for an electric double layer capacitor and a method for manufacturing the same, and more particularly to a polarizable electrode having a low internal resistance per predetermined projected area, a large capacity per predetermined volume, and an excellent breaking strength. is there.
[0002]
[Prior art]
An electric double layer capacitor having a large capacity and a low internal resistance is expected to be used for load leveling of a large power source or as a high power density storage power source such as a hybrid car.
[0003]
However, conventional electric double layer capacitors have high internal resistance and cannot extract a large current. Therefore, a high voltage electric double layer capacitor bank is configured by series connection, and high output is obtained by peripheral circuit technology using a converter or the like. However, the cost is high.
[0004]
A conventional electric double layer capacitor using an organic electrolyte has a high resistance per unit area of the polarizable electrode, and a current density of 1 to 20 mA / cm 2 is used. Becomes larger and the output is significantly reduced. Therefore, an attempt has been made to reduce the resistance by reducing the coating thickness of the polarizable electrode for the purpose of increasing the electrode area, but in this case, the filling amount of the polarizable electrode per package of the electric double layer capacitor is reduced, The capacity per package of the electric double layer capacitor is lowered, and a sufficient energy density cannot be obtained.
[0005]
With such conventional organic electrolytes and polarizable electrodes, it has been difficult to obtain a high output density while maintaining the necessary energy density due to the limit of resistance per projected unit area of the polarizable electrode.
[0006]
In the method for producing a polarizable electrode of an electric double layer capacitor, activated carbon powder, a slurry containing a conductive auxiliary agent and a binder resin are applied on a current collector plate, dried, activated carbon powder, conductive auxiliary agent and fluorine-containing electrode There is one in which a polymer resin mixture is molded and then stretched to form a sheet.
[0007]
The polarizable electrode by the coating method has a weak binding property of the activated carbon powder and is easily detached, and the activated carbon particles enter as a binder between the activated carbon particles, resulting in a large contact resistance between the particles, resulting in the inside of the electric double layer capacitor. The resistance is increased.
Furthermore, the density of activated carbon does not increase only by application, and the capacity per unit volume tends to be small.
[0008]
Therefore, by increasing the mechanical strength by a method of forming into a sheet by stretching treatment, particle detachment is suppressed and the density is increased. For example, Japanese Examined Patent Publication No. 7-105316 discloses a method in which an admixture composed of fine carbon powder, a fluoropolymer resin and a liquid lubricant is formed into a sheet and further subjected to a stretching treatment.
[0009]
[Problems to be solved by the invention]
In the polarizable electrode formed into a sheet shape by the conventional stretching process described in Japanese Patent Publication No. 7-105316, since there is a liquid lubricant, sufficient pressure is not applied to the mixture, and the fluorine-containing electrode is formed at the time of forming the sheet. In order for the polymer resin to exhibit sufficient binding properties, a large amount of the resin must be added.
[0010]
Furthermore, since carbon fine powder is contained in the fluoropolymer resin, capacity increases due to an increase in contact resistance between the carbon fine powder and the amount of carbon fine powder is limited, resulting in a large capacity and low internal resistance. It is difficult to apply to the use of multilayer capacitors. For this reason, after forming into a sheet, a secondary process in which the sheet is further stretched and carbon fine powder is included in the fine nodules of the fluoropolymer resin has become indispensable.
[0011]
An object of the present invention is to provide a polarizable electrode having a low internal resistance per predetermined projected area of a polarizable electrode of an electric double layer capacitor, a large capacity per predetermined volume, and a high breaking strength, and a method for manufacturing the same. And In particular, the provision of a polarizable electrode for an electric double layer capacitor having a high output density in which a decrease in output at a large current density with a discharge current density per projected area of the polarizable electrode exceeding 20 mA / cm 2 is reduced, and a method for producing the same. Objective.
[0012]
[Means for Solving the Problems]
In the method for producing a polarizable electrode for an electric double layer capacitor, the present invention provides 1 to 20% by weight of conductive auxiliary powder having a particle size of 0.1 μm or less with respect to activated carbon powder having a particle size of 0.5 to 200 μm. In addition, 0.1 to 30% by weight of a fluorine-containing polymer resin powder having a lamellar structure is added, and further, a dispersion solvent containing at least one of water and liquid hydrocarbon is added and wet mixed, and then the dispersion solvent is removed. And then pulverized to form a mixed powder. The mixed powder is classified into particles having a particle size of 0.1 to 2.0 mm to form secondary particles, and the mixed secondary particle powder is compressed into a sheet shape. It is characterized by doing.
[0013]
The fluorine-containing polymer resin having a lamellar structure may be polytetrafluoroethylene.
[0015]
Further, the mixed powder is compressed at room temperature to 200 ° C, and preferably heated and compressed at 50 ° C to 100 ° C.
[0016]
Further, in the polarizable electrode for an electric double layer capacitor according to the present invention, 1 to 20% by weight of a conductive auxiliary powder having a particle size of 0.1 μm or less with respect to the activated carbon powder having a particle size of 0.5 to 200 μm, And 0.1 to 30% by weight of a fluorine-containing polymer resin powder having a lamellar structure, and further, a dispersion solvent containing at least one of water and liquid hydrocarbon is added and wet-mixed, and then the dispersion solvent is removed. Then, the mixed powder is pulverized to form a mixed powder, and the mixed powder is classified into particles having a particle size of 0.1 to 2.0 mm to form secondary particles. The mixed secondary particle powder is compressed and molded into a sheet shape. Thus, the activated carbon is characterized in that it is bonded so as to be held by a three-dimensional network structure composed of fine fibers of a fluorine-containing polymer resin formed by destruction of a lamellar structure.
[0017]
This polarizable electrode for an electric double layer capacitor is a polarizable electrode containing activated carbon, a conductive auxiliary, and a fluorine-containing polymer resin having a lamellar structure, and the volume occupied by pores of 36 mm or more is measured by a mercury intrusion method. 0.3 to 0.6 cc / cc and the density is 0.5 to 0.8 g / cc.
[0018]
Moreover, the particle diameter of the activated carbon is 0.5 to 200 μm, or the particle diameter of the conductive auxiliary agent is 0.1 μm or less, and the diameter of the fine fiber of the fluoropolymer resin formed by destruction of the lamellar structure is 0. .3 μm or less.
[0019]
Furthermore, the polarizable electrode for an electric double layer capacitor according to the present invention is characterized in that the fluorine-containing polymer resin is polytetrafluoroethylene, and is a sheet-like molded product having a thickness of 10 to 2000 μm.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The polarizable electrode of the present invention is formed into a sheet by compressing a powdery dry mixture composed of activated carbon powder, a conductive auxiliary, and a fluorine-containing polymer resin having a lamellar structure, and heating it as necessary. More specifically, it is manufactured as follows.
[0021]
1) Adjustment of powdery mixture 1 to 20% by weight, preferably 5 to 15% of conductive auxiliary agent for activated carbon powder, 0.1 to 30% by weight of fluorine-containing polymer resin powder having a lamellar structure, preferably 1 to 10% by weight is mixed and uniformly mixed by dry mixing with a rotary mixer to adjust the mixed powder.
In addition, 50 to 200% by weight of a dispersion solvent containing at least one of water or liquid hydrocarbon may be added to the activated carbon powder at the time of mixing, and wet mixing may be performed. In this case, the dispersion solvent is dried after uniform mixing. And then pulverized again to obtain a mixed powder.
[0022]
2) Classification of mixed powder The mixed powder is classified and, if necessary, pulverized, and the aggregated secondary particles have a diameter of 0.1 to 2 mm.
[0023]
3) The mixed powder obtained by the sheet molding classification is compressed and heated as necessary to form a sheet-like molded product. The heating is performed at room temperature to 200 ° C., preferably 50 ° C. to 100 ° C., and formed into a sheet shape. At least at a temperature below room temperature, it becomes difficult to form into a sheet, and even if heated at a temperature above this, the fluororesin is thermally decomposed at about 260 ° C., so that the sheet becomes fragile as well. .
[0024]
In addition, in the compression process of the mixed powder and the heating process performed as necessary, a press machine can be used, or a heated roll can be used. In this case, the sheet can be continuously formed by continuously supplying the mixed powder to the gap between the rolls. Moreover, the thickness of a sheet-like polarizable electrode can obtain arbitrary thickness between 10 micrometers-2000 micrometers by adjusting a diameter and a space | interval, when using a roll. Furthermore, it can also be made thin by passing through a calendar roll or the like thereafter, and an arbitrary thickness can be obtained.
[0025]
In the polarizable electrode manufactured by the above manufacturing method, as shown in the electron micrograph of FIG. 1, the lamellar structure fluorine-containing polymer resin is compressed or heated as necessary in the manufacturing method. The conductive auxiliary agent particles having a particle diameter smaller than that of the fibers adhere to, agglomerate, contact, or become continuous with the fine fibrous fluorine-containing polymer resin. Further, the fine fibrous fluorine-containing polymer resin is bonded to the activated carbon having a particle diameter larger than that of the fiber, and as a result, the activated carbon is divided into the fine fibrous fluorine-containing polymer resin and the Fluorine-containing polymer resin formed by destruction of the lamellar structure because activated carbon is bonded to each other so as to be contacted or continuous by the conductive auxiliary agent particles adhered and aggregated to the fine-fiber-like fluorine-containing polymer resin They are bonded so as to be held by a three-dimensional network structure made of fine fibers.
[0026]
The structure of this polarizable electrode will be described with reference to the schematic diagram shown in FIG. FIG. 2 is a schematic diagram based on FIG. 1 of the electron micrograph shown above. The fiber-containing lamellar fluorine-containing polymer resin is indicated by a broken line 3, and an aggregate of conductive auxiliary particles. Is an ellipse 2 and activated carbon is represented by a shaded polygon 1.
[0027]
That is, in the polarizable electrode according to the present invention, the conductive auxiliary agent particles 2 having a particle diameter smaller than that of the fibers 3 are adhered, aggregated, contacted or continuous to the fibers 3 of the fluorine-containing polymer resin, and the fibers 3 The activated carbon 1 having a particle diameter larger than that of the fibers 3 is bonded to each other so that the activated carbon 1 is held by the three-dimensional network structure of the fibers 3.
[0028]
In the sheet-like polarizable electrode having the above structural features, the volume occupied by pores of 36 mm or more is 0.3 to 0.6 cc / cc as measured by the mercury intrusion method, and the density is 0.5 to 0.8 g / cc and the tensile strength is 0.1 MPa or more.
[0029]
The activated carbon particle size is 0.5 to 200 μm, preferably 1 to 100 μm, and the conductive auxiliary powder having a particle size of 0.1 μm or less is suitable.
[0030]
In this way, the packing density of the activated carbon is obtained by binding the activated carbon and the conductive auxiliary agent in a minimum amount of the fluorine-containing polymer resin and forming a sheet-like continuous structure by the trapping effect of the resin fibers. Since the density increases, the capacity per volume of the sheet-like polarizable electrode increases and the breaking strength increases, and furthermore, the amount of voids between particles is maintained by the minimum amount of fluorine-containing polymer resin. The ion transfer resistance is reduced, and the internal resistance value per predetermined projected area of the polarizable electrode is reduced.
[0031]
【Example】
Next, examples of the present invention will be described.
Example 1
10% by weight of carbon black having an average particle size of 27 μm and a specific surface area of 1300 m 2 / g and a primary particle size of 0.1 μm or less, and water and isopropyl alcohol (IPA) 9 are added to the powder mixture. 170% by weight of the mixed dispersion solvent of 1 was added, and the mixture was put into a rotary mixer and mixed, and then polytetrafluoroethylene (PTFE) having a lamellar structure with an average diameter of 0.15 to 0.3 μm was added to water. The dispersion in which 60% by weight was dispersed was added by 13% by weight (7.8% by weight in terms of PTFE solid content), and further mixed by a rotary mixer.
[0032]
Next, the mixture was taken out and heated to 85 ° C. with a vacuum drier to remove the dispersion solvent, then pulverized with a cutting mixer, and the powder classified to a particle size of 0.1 to 2 mm was heated to 60 ° C. in advance. A sheet-shaped polarizable electrode having a thickness of 0.2 mm was obtained by continuously putting it into a gap set to 0.18 mm between two rolls having a diameter of 120 mm and heating and compressing it.
[0033]
This sheet-like polarizable electrode is punched into a disk shape having a diameter of 20 mm, and is made to face with a cellulose fiber nonwoven fabric separator having a thickness of 50 μm interposed therebetween, and a platinum plate is arranged on the outside thereof to form a current collector plate, and further from the outside. An electric double layer capacitor cell was obtained by sandwiching and fixing with a Teflon plate. This cell was immersed in an electrolytic solution in which tetraethylammonium and tetrafluoroborate were dissolved in propylene carbonate so as to be 1 mol, and impregnated under reduced pressure.
[0034]
Next, the cell was charged at a constant voltage of 2.5 V for 30 minutes and then discharged at a constant current density of 20 mA / cm 2 and 50 mA / cm 2 with respect to the electrode projection area, and the capacity was measured. The internal resistance was calculated from the voltage drop at the initial stage of discharge when the discharge current density was 50 mA / cm 2 .
[0035]
(Example 2)
2-1) The same procedure as in Example 1 was performed except that the roll heating temperature was set to 80 ° C. in Example 1.
[0036]
2-2) The same operation as in Example 1 was performed except that the roll diameter was 160 mm and the gap between the rolls was 0.1 mm.
[0037]
2-3) The same procedure as in Example 1 was conducted except that the amount of PTFE added in Example 1 was 5% by weight in terms of solid content.
[0038]
(Example 3)
The same procedure as in Example 1 was conducted except that activated carbon having an average particle diameter of 8 μm and a specific surface area of 2400 m 2 / g was used in Example 1.
[0039]
(Comparative Example 1)
The mixture taken out from the rotary mixer in Example 1 was rolled by a roll molding machine without drying to a sheet having a thickness of 1 mm, and then heated and stretched by a calendar roll to continuously form a sheet having a thickness of 0.2 mm. The same procedure as in Example 1 was performed except that the polarizable electrode was obtained.
[0040]
(Comparative Example 2)
The same procedure as in Example 1 was performed except that classification of the powder pulverized by the cutting mixer in Example 1 was not performed.
[0041]
(Comparative Example 3)
The same procedure as in Example 1 was conducted except that the amount of PTFE added in Example 1 was 40% by weight in terms of solid content.
[0042]
(Comparative Example 4)
The same procedure as in Example 1 was performed except that phenol carbide having an average particle diameter of 3 μm and a carbonization temperature of 1200 ° C. or higher was used as the conductive auxiliary agent in Example 1.
The characteristic values of the sheet-like polarizable electrodes of the above examples and comparative examples are shown in (Table 1).
[0043]
[Table 1]
As is apparent from Table 1, according to the present invention, since a sheet-like continuous structure can be prepared with a minimum amount of the fluorine-containing polymer resin, a large amount of activated carbon is charged. As the capacity per volume increases, the fracture strength increases, and the interparticle void volume (pore volume) is maintained, so that the ion migration resistance decreases and the internal resistance value per predetermined projected area of the polarizable electrode It can be seen that is reduced.
[0045]
In Comparative Example 2, since the powder was not classified, a product having a size that could not be wound on a roll was included, and a sample as a continuous structure could not be obtained due to many holes in the sheet-like molded product.
[0046]
【The invention's effect】
As described above, the present invention compresses the mixed powder as it is without using a liquid lubricant as in the prior art, and heat-treats it as necessary to form a sheet. It becomes possible to apply pressure, and when forming into a sheet shape, the fluoropolymer resin can exhibit sufficient binding properties, and a polarizable electrode excellent in breaking strength can be obtained.
[0047]
In addition, since the contact resistance between the activated carbon powders is reduced, an electric double layer capacitor having a large capacity and low internal resistance can be realized.
[0048]
Further, after forming into a sheet shape, a secondary process such as drawing the sheet is not necessary, and an electric double layer capacitor having a high output density in which a decrease in output at a large current density exceeding 20 mA / cm 2 is reduced. Can be created.
[Brief description of the drawings]
FIG. 1 is an electron micrograph showing the structure of a polarizable electrode according to the present invention. FIG. 2 is a schematic diagram showing the structure of a polarizable electrode according to the present invention.
1 Activated carbon 2 Conductive auxiliary agent 3 Fiber
Claims (8)
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| JP5136188B2 (en) * | 2008-04-28 | 2013-02-06 | Ｔｄｋ株式会社 | Electrode for electric double layer capacitor and electric double layer capacitor |
| WO2021039979A1 (en) * | 2019-08-30 | 2021-03-04 | 株式会社ダイセル | Method for producing fiber articles |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6216506A (en) * | 1985-03-06 | 1987-01-24 | 株式会社村田製作所 | Electric double layer capacitor |
| JPS62196028A (en) * | 1986-02-20 | 1987-08-29 | トヨタ自動車株式会社 | Wireless power transmission apparatus |
| JPH1027733A (en) * | 1996-07-12 | 1998-01-27 | Matsushita Electric Ind Co Ltd | Electric double-layer capacitor and manufacture thereof |
| JPH11102844A (en) * | 1997-07-28 | 1999-04-13 | Matsushita Electric Ind Co Ltd | Electrical double layer capacitor and manufacture thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6239223B1 (en) * | 1997-09-05 | 2001-05-29 | Chemfab Corporation | Fluoropolymeric composition |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6216506A (en) * | 1985-03-06 | 1987-01-24 | 株式会社村田製作所 | Electric double layer capacitor |
| JPS62196028A (en) * | 1986-02-20 | 1987-08-29 | トヨタ自動車株式会社 | Wireless power transmission apparatus |
| JPH1027733A (en) * | 1996-07-12 | 1998-01-27 | Matsushita Electric Ind Co Ltd | Electric double-layer capacitor and manufacture thereof |
| JPH11102844A (en) * | 1997-07-28 | 1999-04-13 | Matsushita Electric Ind Co Ltd | Electrical double layer capacitor and manufacture thereof |
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