JP3791149B2 - Electric double layer capacitor and manufacturing method thereof - Google Patents
Electric double layer capacitor and manufacturing method thereof Download PDFInfo
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- JP3791149B2 JP3791149B2 JP26425297A JP26425297A JP3791149B2 JP 3791149 B2 JP3791149 B2 JP 3791149B2 JP 26425297 A JP26425297 A JP 26425297A JP 26425297 A JP26425297 A JP 26425297A JP 3791149 B2 JP3791149 B2 JP 3791149B2
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- 239000003990 capacitor Substances 0.000 title claims description 22
- 238000004519 manufacturing process Methods 0.000 title claims description 5
- 229920005989 resin Polymers 0.000 claims description 32
- 239000011347 resin Substances 0.000 claims description 32
- 229920001721 polyimide Polymers 0.000 claims description 26
- 239000009719 polyimide resin Substances 0.000 claims description 26
- 239000004962 Polyamide-imide Substances 0.000 claims description 19
- 229920002312 polyamide-imide Polymers 0.000 claims description 19
- 239000011230 binding agent Substances 0.000 claims description 15
- 239000002002 slurry Substances 0.000 claims description 12
- 239000002966 varnish Substances 0.000 claims description 9
- 239000000843 powder Substances 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 7
- 239000003960 organic solvent Substances 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 6
- 239000002243 precursor Substances 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 3
- 239000011255 nonaqueous electrolyte Substances 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 claims 1
- 238000000576 coating method Methods 0.000 claims 1
- 238000004070 electrodeposition Methods 0.000 claims 1
- 239000010410 layer Substances 0.000 description 38
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 23
- 239000002904 solvent Substances 0.000 description 11
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 6
- 239000006229 carbon black Substances 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 229910002804 graphite Inorganic materials 0.000 description 5
- 239000010439 graphite Substances 0.000 description 5
- 239000005486 organic electrolyte Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 239000008151 electrolyte solution Substances 0.000 description 4
- 239000010419 fine particle Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- 239000002033 PVDF binder Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 229910052731 fluorine Inorganic materials 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- -1 polytetrafluoroethylene Polymers 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 229920001187 thermosetting polymer Polymers 0.000 description 3
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229920005575 poly(amic acid) Polymers 0.000 description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229920005992 thermoplastic resin Polymers 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- ZZXUZKXVROWEIF-UHFFFAOYSA-N 1,2-butylene carbonate Chemical compound CCC1COC(=O)O1 ZZXUZKXVROWEIF-UHFFFAOYSA-N 0.000 description 1
- 229920003026 Acene Polymers 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 229910020366 ClO 4 Inorganic materials 0.000 description 1
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000012790 adhesive layer Substances 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000006056 electrooxidation reaction Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 229910021397 glassy carbon Inorganic materials 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 150000002596 lactones Chemical class 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000000016 photochemical curing Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- HXJUTPCZVOIRIF-UHFFFAOYSA-N sulfolane Chemical compound O=S1(=O)CCCC1 HXJUTPCZVOIRIF-UHFFFAOYSA-N 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Electric Double-Layer Capacitors Or The Like (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は電気二重層キャパシタ、特に作動信頼性に優れた電気二重層キャパシタ、の製造方法に関する。
【０００２】
【従来の技術】
電気二重層キャパシタは、分極性電極と電解液との界面に形成される電気二重層に電荷を蓄積することを原理としており、電気二重層キャパシタの容量密度を向上させるため、分極性電極には高比表面積の活性炭、カーボンブラック等の炭素材料、金属又は導電性金属酸化物の微粒子等が用いられている。これらの高比表面積の分極性電極は、効率よく充電及び放電するため、集電体と呼ばれる金属や黒鉛等の抵抗の小さい層又は箔と接合されている。集電体としては、通常電気化学的に耐食性の高いアルミウム等のバルブ金属、ＳＵＳ３０４、ＳＵＳ３１６Ｌ等のステンレス鋼等が使用される。
【０００３】
電気二重層キャパシタの電解液としては有機電解液と水電解液があるが、作動電圧が高く、充電状態のエネルギ密度を大きくできることから、有機電解液を用いた電気二重層キャパシタが注目されている。有機電解液を用いる場合、電気二重層キャパシタセルの内部に水分が存在すると、水分の電気分解により性能が劣化するため、分極性電極を充分に脱水する必要があり、通常、減圧下で加熱する乾燥処理が施される。
【０００４】
分極性電極としては、主に活性炭が主成分として使用されるが、活性炭は通常粉末状であり、例えばポリテトラフルオロエチレン等の含フッ素樹脂を含む結合材と混合してあらかじめシート状に成形し、これを集電体と電気的に接続させて電極体として用いる。この際、活性炭を含む電極シートと集電体との接合強度が強く、かつ電気的な接触抵抗が小さくなるように、例えば導電性接着層を電極シートと集電体の間に介在させる。しかし、電極自体の抵抗の低減には電極層の厚さを薄くすることが有効であるのに対し、上記の方法で連続的に工業的に例えば１００μｍ程度の電極シートに成形することは困難である。
【０００５】
また、例えばカルボキシメチルセルロース等の炭化水素系結合材を水に溶解し、これに活性炭を分散させてスラリとなし、このスラリを集電体に塗布し乾燥して電極体とする方法もある。しかし、こうして得た電極体は、電極と集電体との接合強度が弱く、またカルボキシセルロース等のセルロースは耐熱性が乏しく、高温加熱や真空加熱により電極内の水分等の不純物を充分に除去できない。
【０００６】
カルボキシセルロースのかわりにポリフッ化ビニリデン等の含フッ素樹脂を結合材とし、これを有機溶媒に溶解した溶液に活性炭を分散させてスラリとなし、このスラリを集電体に塗布し乾燥して電極体とする方法もある。しかし、特定の有機溶媒に可溶なポリフッ化ビニリデン等の含フッ素樹脂からなる結合材では電極と集電体との接合強度が弱く、大きな接合強度は得られない。さらに耐熱性も充分ではなく、高温加熱や真空加熱により電極内の水分等の不純物を充分に除去できないため充分な充放電サイクル特性が得られず、さらなる充放電サイクル信頼性を向上させる必要があった。
【０００７】
【発明が解決しようとする課題】
本発明は、集電体と分極性電極層との接合強度が強く、容量が大きく、充放電サイクル耐久性に優れる電気二重層キャパシタの製造方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明は、ポリイミド樹脂、ポリアミドイミド樹脂、ポリイミド樹脂前駆体及びポリアミドイミド樹脂前駆体からなる群から選ばれる１種以上を有機溶媒に溶解させたワニスに炭素質粉末を分散させてスラリとし、該スラリを集電体の表面に塗工し、２００℃以上にて減圧下で加熱乾燥させて、ポリイミド樹脂及び／又はポリアミドイミド樹脂である結合材と炭素質粉末とを含む電極層が集電体と一体化された電極を製造し、該電極を非水系電解液を有する電気二重層キャパシタの正極体及び負極体として使用することを特徴とする電気二重層キャパシタの製造方法を提供する。
【０００９】
本明細書において、炭素質粉末と結合材とを含む電極層（以下、分極性電極層という）を集電体と一体化させたものを電極体という。そして、この電極体を正極側に用いる場合は正極体、負極側に用いる場合は負極体という。
【００１０】
本発明の電気二重層キャパシタの製造方法において、分極性電極層に含まれる結合材は、ポリイミド樹脂又はポリアミドイミド樹脂であり、これら樹脂の耐熱温度は通常２００〜４００℃の範囲にあり耐熱性が高い。ポリイミド樹脂はその主鎖の繰り返し単位中にイミド結合を有する樹脂の総称であり、耐薬品性、機械的性質、寸法安定性、電気的特性において優れている。
【００１１】
ポリイミド樹脂は、線状ポリイミド樹脂と硬化型ポリイミド樹脂に大別できる。線状ポリイミド樹脂には熱可塑性樹脂と非熱可塑性樹脂があり、硬化型樹脂には熱硬化性樹脂と光硬化性樹脂が含まれるが、いずれのタイプのポリイミド樹脂も、樹脂を溶剤に溶かしたワニスを結合材として使用するのが好ましい。
【００１２】
ポリアミドイミド樹脂は、その主鎖の繰り返し単位中にイミド結合とアミド結合とを有する樹脂の総称であり、ポリイミド樹脂に比べ耐熱性は少し劣るが可撓性に富み耐磨耗性が優れる。ポリアミドイミド樹脂も、樹脂を溶剤に溶かしたワニスを結合材として使用するのが好ましい。
【００１３】
ポリイミド樹脂又はポリアミドイミド樹脂のワニスには、溶剤に可溶なポリイミド樹脂又はポリアミドイミド樹脂を溶剤に溶解したものと、ポリアミック酸等のポリイミド樹脂前駆体又はポリアミドイミド樹脂前駆体を溶剤に溶解したものであって、高温の熱処理によりポリイミド樹脂又はポリアミドイミド樹脂になるものとがあるが、いずれも同様に使用できる。
【００１４】
ポリイミド樹脂のワニスの商品を具体的に例示すると、宇部興産社の「Ｕ−ワニス」（ポリアミック酸を溶剤に溶解したもの）、新日本理化社の「リカコート」（溶剤に可溶なポリイミド樹脂を溶剤に溶解したもの）、デュポン社の「パイヤーＭＬ」、日立化成社の「ＰＩＱ」、東レ社の「トレニース」、旭化成工業社の「パイメル」がある。また、溶剤に可溶なポリアミドイミド樹脂を溶剤に溶解したワニスとしては、東洋紡社の「Ｎ７５２５」や「ＮＡ−１１」等がある。
【００１５】
本発明における分極性電極は、抵抗を低くするためにカーボンブラックや黒鉛等の導電材を含んでもよい。本発明における電極体は例えば以下のようにして作製できる。
【００１６】
結合材として使用する樹脂は、粉末又はワニスとして使用することが好ましく、これらの形態の樹脂をＮ−メチル−２−ピロリドン（以下、ＮＭＰという）等の溶剤に溶解し、この溶液に例えば活性炭粉末、導電材としてカーボンブラック粉末や黒鉛微粒子を分散させてスラリとする。このスラリを集電体の表面にダイコータ、ドクターブレード、アプリケータ等によって塗工し、予備乾燥後、２００℃以上、好ましくは２５０℃以上の高温中、さらに好ましくは減圧下で加熱乾燥し、集電体上に分極性電極層を形成する。このようにして得られた電極体は、集電体箔と電極層とが強固に接合されている。
【００１７】
本発明において、分極性電極層中に結合材は３〜３０重量％含まれることが好ましい。結合材は分極性電極層中に３重量％以上含まれることによって実用性のある接合強度が得られる。しかし、あまり多く含まれると分極性電極の電気抵抗が大きくなるので３０重量％以下とするのが好ましい。より好ましくは５〜１５重量％である。
【００１８】
本発明の電気二重層キャパシタに使用される有機電解液は特に限定されず、公知の有機溶媒にイオン解離性の塩類を含む有機電解液を使用できる。なかでもＲ1 Ｒ2 Ｒ3 Ｒ4 Ｎ+ 、Ｒ1 Ｒ2 Ｒ3 Ｒ4 Ｐ+ （ただし、Ｒ1 、Ｒ2 、Ｒ3 、Ｒ4 はアルキル基で、それぞれ同じでも異なっていてもよい）等で表される第４級オニウムカチオンと、ＢＦ4 -、ＰＦ6 -、ＣｌＯ4 -、ＣＦ3 ＳＯ3 -等のアニオンとからなる塩を有機溶媒に溶解させた有機電解液を使用するのが好ましい。
【００１９】
上記有機溶媒としては、プロピレンカーボネート、ブチレンカーボネート、ジエチルカーボネート等のカーボネート類、γ−ブチロラクトン等のラクトン類、スルホラン又はこれらの混合溶媒が好ましく使用できる。
【００２０】
本発明の電気二重層キャパシタの分極性電極層には、電気化学的に不活性な高比表面積の材料であれば使用できるが、比表面積が大きい活性炭粉末を主成分とするのが好ましい。また、活性炭粉末以外の、カーボンブラック、ポリアセン、金属微粒子、導電性金属酸化物微粒子等の大比表面積の材料も好ましく使用できる。
【００２１】
上記の分極性電極層を電気的に接続するための集電体は、導電性に優れ、かつ電気化学的に耐久性のある材料であればよく、アルミニウム、チタン、タンタル等のバルブ金属、ステンレス鋼、金、白金等の貴金属、黒鉛、グラッシーカーボン、カーボンブラックを含む導電性ゴム等の炭素系材料等、いずれも好ましく使用できる。
【００２２】
【実施例】
［例１］
活性炭粉末４５重量部、カーボンブラック５重量部、ポリイミド樹脂（新日本理化社製、商品名：リカコート）２０重量％を含有するＮＭＰ溶液５０重量部、及びＮＭＰ１００重量部をボールミルで湿式混合し、この混合物に、コロイド状黒鉛１４．４重量％と熱硬化性ポリアミドイミド樹脂３．６重量％とを含有するＮＭＰ溶液１００重量部を加えてさらにボールミルにて混合して、固形分濃度２６重量％のスラリを調製した。幅１０ｃｍ、厚さ３０μｍのアルミニウムエッチング箔の片面にこのスラリを塗布して電極層を形成し、１２０℃で３０分乾燥後プレス圧延し、さらに２７０℃で３０分熱硬化させ、プレス圧延して厚さ１００μｍの電極体を作製した。
【００２３】
上記の電極体から有効電極面積４ｃｍ×６ｃｍの２枚の電極体を得てこれを正極体及び負極体とし、厚さ１６０μｍのガラス繊維マットからなるセパレータを介して電極層が対面するように対向させた。その後、２３０℃で５時間真空乾燥して不純物を除去した。次いで、１．５ｍｏｌ／ｌの（Ｃ2 Ｈ5 ）3 （ＣＨ3 ）ＮＰＦ6 のプロピレンカーボネート溶液を電解液として真空含浸させて、電解液含浸素子を作製し電気二重層キャパシタとした。
【００２４】
得られた電気二重層キャパシタの初期の放電容量及び内部抵抗を測定した後、４０℃の恒温槽中で０〜２．８Ｖの間で１Ａの定電流による充放電を３０００サイクル繰り返し、３０００サイクル後の放電容量及び内部抵抗を測定し、前後の性能変化を観察することにより、電気二重層キャパシタの長期的な作動信頼性を加速的に評価した。初期容量は６．５Ｆ、初期内部抵抗は０．２５Ωであり、サイクル試験後の容量は６．２Ｆ、内部抵抗は０．３０Ωであった。
【００２５】
［例２］
ポリイミド樹脂を使用せず、ポリアミドイミド樹脂（東洋紡社製、商品名：Ｎ７５２５）が電極層中に８重量％含まれるように調製した以外は例１と同様にして電気二重層キャパシタ素子を作製し、例１と同様に性能を評価した。初期容量は６．１Ｆ、初期内部抵抗は０．２５Ωであり、サイクル試験後の容量は５．８Ｆ、内部抵抗は１．１０Ωであった。
【００２６】
［例３］
ポリイミド樹脂のかわりにポリフッ化ビニリデンを使用し、かつ熱硬化させる温度を１８０℃、真空乾燥する温度を１５０℃とした以外は例２と同様にして電気二重層キャパシタ素子を作製し、例１と同様に性能を評価した。初期容量は４．２Ｆ、初期内部抵抗は０．２５Ωであり、サイクル試験後の容量は２Ｆ、内部抵抗は４．１Ωであった。
【００２７】
【発明の効果】
本発明の電気二重層キャパシタの製造方法において、分極性電極層に含まれる結合材であるポリイミド樹脂又はポリアミドイミド樹脂は耐熱性が高いため、分極性電極を高温で加熱処理したり減圧下で加熱処理したりできる。そのため、活性炭中にある水分を高度に乾燥除去できる。
【００２８】
また、ポリイミド樹脂及びポリアミドイミド樹脂は有機電解液に対する耐性があり、金属等の集電体への接着強度もきわめて優れる。このため、ポリイミド樹脂及び／又はポリアミドイミド樹脂を結合材として有する分極性電極を正極及び負極とする電気二重層キャパシタは、大電流密度で充放電サイクルを繰り返しても、長期間にわたって電圧を印加しても、作動性能が安定しており、電極自体の内部抵抗の増加も少ない。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing an electric double layer capacitor, particularly an electric double layer capacitor excellent in operation reliability.
[0002]
[Prior art]
The electric double layer capacitor is based on the principle that electric charges are accumulated in the electric double layer formed at the interface between the polarizable electrode and the electrolyte. In order to improve the capacity density of the electric double layer capacitor, Carbon materials such as activated carbon and carbon black having a high specific surface area, fine particles of metal or conductive metal oxide, and the like are used. These polarizable electrodes having a high specific surface area are joined to a low-resistance layer or foil, such as a metal or graphite, called a current collector, in order to charge and discharge efficiently. As the current collector, valve metals such as aluminum having high electrochemical corrosion resistance, stainless steel such as SUS304 and SUS316L, and the like are usually used.
[0003]
There are two types of electrolytes for electric double layer capacitors: organic electrolytes and water electrolytes. However, since the operating voltage is high and the energy density of the charged state can be increased, electric double layer capacitors using organic electrolytes are attracting attention. . When using an organic electrolyte, if water is present inside the electric double layer capacitor cell, the performance deteriorates due to the electrolysis of the water. Therefore, the polarizable electrode needs to be sufficiently dehydrated and is usually heated under reduced pressure. A drying process is performed.
[0004]
As a polarizable electrode, activated carbon is mainly used as a main component. However, activated carbon is usually in the form of a powder, for example, mixed with a binder containing a fluorine-containing resin such as polytetrafluoroethylene and formed into a sheet in advance. This is electrically connected to a current collector and used as an electrode body. At this time, for example, a conductive adhesive layer is interposed between the electrode sheet and the current collector so that the bonding strength between the electrode sheet containing activated carbon and the current collector is high and the electrical contact resistance is reduced. However, while it is effective to reduce the thickness of the electrode layer to reduce the resistance of the electrode itself, it is difficult to industrially form an electrode sheet of, for example, about 100 μm continuously by the above method. is there.
[0005]
There is also a method in which a hydrocarbon-based binder such as carboxymethyl cellulose is dissolved in water, activated carbon is dispersed therein to form a slurry, and this slurry is applied to a current collector and dried to form an electrode body. However, the electrode body obtained in this way has a weak bonding strength between the electrode and the current collector, and cellulose such as carboxycellulose has poor heat resistance, and sufficiently removes impurities such as moisture in the electrode by high-temperature heating or vacuum heating. Can not.
[0006]
Instead of carboxycellulose, a fluorine-containing resin such as polyvinylidene fluoride is used as a binder, and activated carbon is dispersed in a solution in which this is dissolved in an organic solvent to form a slurry. This slurry is applied to a current collector and dried to form an electrode body. There is also a method. However, a bonding material made of a fluorine-containing resin such as polyvinylidene fluoride that is soluble in a specific organic solvent has a low bonding strength between the electrode and the current collector, and a large bonding strength cannot be obtained. Furthermore, the heat resistance is not sufficient, and impurities such as moisture in the electrode cannot be sufficiently removed by high temperature heating or vacuum heating, so that sufficient charge / discharge cycle characteristics cannot be obtained, and further charge / discharge cycle reliability needs to be improved. It was.
[0007]
[Problems to be solved by the invention]
The present invention, bonding strength between the collector and the polarizable electrode layer is strong, has large capacity, and an object thereof is to provide an electric double layer Capacity data producing method which is excellent in charge-discharge cycle durability.
[0008]
[Means for Solving the Problems]
The present invention provides a slurry by dispersing carbonaceous powder in a varnish obtained by dissolving one or more selected from the group consisting of polyimide resin, polyamideimide resin, polyimide resin precursor and polyamideimide resin precursor in an organic solvent, The slurry is applied to the surface of the current collector, heated and dried at 200 ° C. or higher under reduced pressure, and an electrode layer containing a binder that is a polyimide resin and / or a polyamide-imide resin and a carbonaceous powder is obtained. to produce an integrated electrode and provides an electrical double layer Capacity data producing method characterized that you use as positive electrode and negative electrode element of the electric double layer capacitor having a non-aqueous electrolyte said electrode.
[0009]
In this specification, a binder and carbonaceous powder including conductive electrode layer (hereinafter, polarizable referred electrode layer) is called a current collector that is integrated with the electrode body. When this electrode body is used on the positive electrode side, it is called a positive electrode body, and when it is used on the negative electrode side, it is called a negative electrode body.
[0010]
In the method for producing an electric double layer capacitor of the present invention, the binder contained in the polarizable electrode layer is a polyimide resin or a polyamideimide resin, and the heat resistance temperature of these resins is usually in the range of 200 to 400 ° C. and has heat resistance. high. Polyimide resin is a general term for resins having an imide bond in the repeating unit of the main chain, and is excellent in chemical resistance, mechanical properties, dimensional stability, and electrical characteristics.
[0011]
Polyimide resins can be broadly classified into linear polyimide resins and curable polyimide resins. Linear polyimide resins include thermoplastic resins and non-thermoplastic resins, and curable resins include thermosetting resins and photo-curing resins. Both types of polyimide resins dissolve the resin in a solvent. It is preferred to use varnish as a binder.
[0012]
Polyamideimide resin is a general term for resins having an imide bond and an amide bond in the repeating unit of the main chain, and is slightly inferior in heat resistance to polyimide resin but rich in flexibility and excellent in wear resistance. As for the polyamide-imide resin, a varnish obtained by dissolving the resin in a solvent is preferably used as the binder.
[0013]
In the varnish of polyimide resin or polyamideimide resin, a polyimide resin or polyamideimide resin soluble in a solvent is dissolved in a solvent, and a polyimide resin precursor such as polyamic acid or a polyamideimide resin precursor is dissolved in a solvent. However, there are some which become a polyimide resin or a polyamide-imide resin by high-temperature heat treatment, and any of them can be used similarly.
[0014]
Specific examples of polyimide resin varnish products include Ube Industries' “U-Varnish” (polyamic acid dissolved in a solvent), Shin Nippon Rika Co., Ltd.'s “Rika Coat” (a solvent-soluble polyimide resin. Solvent dissolved in a solvent), Du Pont's "Pier ML", Hitachi Chemical's "PIQ", Toray's "Trenice", and Asahi Kasei's "Paimel". Examples of varnishes obtained by dissolving a polyamideimide resin soluble in a solvent in a solvent include “N7525” and “NA-11” manufactured by Toyobo.
[0015]
The polarizable electrode in the present invention may contain a conductive material such as carbon black or graphite in order to reduce the resistance. The electrode body in the present invention can be produced, for example, as follows.
[0016]
The resin used as the binder is preferably used as a powder or varnish, and these forms of resin are dissolved in a solvent such as N-methyl-2-pyrrolidone (hereinafter referred to as NMP), and activated carbon powder is added to this solution. Then, carbon black powder or graphite fine particles are dispersed as a conductive material to form a slurry. This slurry is applied to the surface of the current collector by a die coater, doctor blade, applicator, etc., and after preliminary drying, it is dried by heating at a high temperature of 200 ° C. or higher, preferably 250 ° C. or higher, more preferably under reduced pressure. A polarizable electrode layer is formed on the electric body. In the electrode body thus obtained, the current collector foil and the electrode layer are firmly bonded.
[0017]
In the present invention, the polarizable electrode layer preferably contains 3 to 30% by weight of the binder. When the binder is contained in the polarizable electrode layer by 3% by weight or more, practical bonding strength can be obtained. However, if too much is included, the electric resistance of the polarizable electrode increases, so it is preferable to make it 30% by weight or less. More preferably, it is 5 to 15% by weight.
[0018]
The organic electrolyte used for the electric double layer capacitor of the present invention is not particularly limited, and an organic electrolyte containing ion-dissociable salts in a known organic solvent can be used. Among them, R 1 R 2 R 3 R 4 N + , R 1 R 2 R 3 R 4 P + (where R 1 , R 2 , R 3 and R 4 are alkyl groups, which may be the same or different. ) And the like, and an organic electrolytic solution in which a salt made of an anion such as BF 4 − , PF 6 − , ClO 4 − , CF 3 SO 3 − is dissolved in an organic solvent. Is preferred.
[0019]
As the organic solvent, carbonates such as propylene carbonate, butylene carbonate, and diethyl carbonate, lactones such as γ-butyrolactone, sulfolane, or a mixed solvent thereof can be preferably used.
[0020]
For the polarizable electrode layer of the electric double layer capacitor of the present invention, any material that is electrochemically inert and has a high specific surface area can be used, but it is preferable that the activated carbon powder having a large specific surface area be the main component. Further, materials having a large specific surface area such as carbon black, polyacene, metal fine particles, and conductive metal oxide fine particles other than the activated carbon powder can be preferably used.
[0021]
The current collector for electrically connecting the polarizable electrode layers may be any material that has excellent conductivity and is electrochemically durable, such as valve metals such as aluminum, titanium, and tantalum, and stainless steel. Any precious metal such as steel, gold or platinum, carbon-based material such as graphite, glassy carbon, or conductive rubber containing carbon black can be preferably used.
[0022]
【Example】
[Example 1]
45 parts by weight of activated carbon powder, 5 parts by weight of carbon black, 50 parts by weight of NMP solution containing 20% by weight of polyimide resin (manufactured by Shin Nippon Chemical Co., Ltd., trade name: Rika Coat), and 100 parts by weight of NMP are wet-mixed with a ball mill. To the mixture, 100 parts by weight of an NMP solution containing 14.4% by weight of colloidal graphite and 3.6% by weight of thermosetting polyamide-imide resin was added and further mixed by a ball mill to obtain a solid content of 26% by weight. A slurry was prepared. This slurry is applied to one side of an aluminum etching foil having a width of 10 cm and a thickness of 30 μm to form an electrode layer, dried at 120 ° C. for 30 minutes, press-rolled, further thermally cured at 270 ° C. for 30 minutes, and press-rolled. An electrode body with a thickness of 100 μm was produced.
[0023]
Two electrode bodies having an effective electrode area of 4 cm × 6 cm are obtained from the above electrode bodies, which are used as a positive electrode body and a negative electrode body, and are opposed so that the electrode layers face each other through a separator made of a glass fiber mat having a thickness of 160 μm. I let you. Thereafter, impurities were removed by vacuum drying at 230 ° C. for 5 hours. Next, 1.5 mol / l of a propylene carbonate solution of (C 2 H 5 ) 3 (CH 3 ) NPF 6 was vacuum impregnated as an electrolytic solution to produce an electrolytic solution impregnated element to obtain an electric double layer capacitor.
[0024]
After measuring the initial discharge capacity and internal resistance of the obtained electric double layer capacitor, it was charged and discharged with a constant current of 1 A between 0 and 2.8 V in a constant temperature bath at 40 ° C. for 3000 cycles, and after 3000 cycles The long-term operation reliability of the electric double layer capacitor was acceleratedly evaluated by measuring the discharge capacity and the internal resistance of the capacitor and observing the change in performance before and after. The initial capacity was 6.5F, the initial internal resistance was 0.25Ω, the capacity after the cycle test was 6.2F, and the internal resistance was 0.30Ω.
[0025]
[Example 2]
An electric double layer capacitor element was produced in the same manner as in Example 1 except that the polyimide resin was not used and the polyamide imide resin (trade name: N7525, manufactured by Toyobo Co., Ltd.) was prepared so as to be contained by 8 wt% in the electrode layer. The performance was evaluated in the same manner as in Example 1. The initial capacity was 6.1F, the initial internal resistance was 0.25Ω, the capacity after the cycle test was 5.8F, and the internal resistance was 1.10Ω.
[0026]
[Example 3]
An electric double layer capacitor element was prepared in the same manner as in Example 2 except that polyvinylidene fluoride was used instead of polyimide resin, the temperature for thermosetting was 180 ° C., and the temperature for vacuum drying was 150 ° C. Similarly, the performance was evaluated. The initial capacity was 4.2F, the initial internal resistance was 0.25Ω, the capacity after the cycle test was 2F, and the internal resistance was 4.1Ω.
[0027]
【The invention's effect】
In the manufacturing method of the electric double layer capacitor of the present invention, since the polyimide resin or the polyamideimide resin, which is a binder contained in the polarizable electrode layer, has high heat resistance, the polarizable electrode is heat-treated at high temperature or heated under reduced pressure. Can be processed. Therefore, the water in the activated carbon can be highly dried and removed.
[0028]
Further, the polyimide resin and the polyamideimide resin are resistant to an organic electrolytic solution, and have extremely excellent adhesion strength to a current collector such as a metal. For this reason, an electric double layer capacitor having a polarizable electrode having a polyimide resin and / or a polyamideimide resin as a binder as a positive electrode and a negative electrode applies a voltage over a long period of time even when charge / discharge cycles are repeated at a large current density. However, the operation performance is stable, and the increase in the internal resistance of the electrode itself is small.
Claims (2)
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26425297A JP3791149B2 (en) | 1997-09-29 | 1997-09-29 | Electric double layer capacitor and manufacturing method thereof |
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|---|---|---|---|
| JP26425297A JP3791149B2 (en) | 1997-09-29 | 1997-09-29 | Electric double layer capacitor and manufacturing method thereof |
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| JP3791149B2 true JP3791149B2 (en) | 2006-06-28 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6709560B2 (en) | 2001-04-18 | 2004-03-23 | Biosource, Inc. | Charge barrier flow-through capacitor |
| WO2003009920A1 (en) | 2001-07-25 | 2003-02-06 | Biosource, Inc. | Electrode array for use in electrochemical cells |
| JP2006100163A (en) * | 2004-09-30 | 2006-04-13 | Kri Inc | Electrode material and secondary power supply using it |
| JP2006253450A (en) * | 2005-03-11 | 2006-09-21 | Nisshinbo Ind Inc | Composition for electrode, accumulation device and electrode therefor |
| US7554792B2 (en) * | 2007-03-20 | 2009-06-30 | Avx Corporation | Cathode coating for a wet electrolytic capacitor |
| CN103597649B (en) * | 2011-03-09 | 2016-05-25 | 亚奎尼能源公司 | Metal-free aqueous electrolyte energy storing device |
| US8298701B2 (en) | 2011-03-09 | 2012-10-30 | Aquion Energy Inc. | Aqueous electrolyte energy storage device |
| KR101166701B1 (en) | 2011-03-21 | 2012-07-19 | 비나텍주식회사 | Composite for electrode of supercapacitor, method for manufacturing supercapacitor electrode using the composite, and supercapacitor using the method |
| KR20150115751A (en) * | 2013-02-04 | 2015-10-14 | 스미토모덴키고교가부시키가이샤 | Electrode for sodium molten-salt battery and sodium molten-salt battery |
| US9293268B2 (en) | 2013-11-22 | 2016-03-22 | Corning Incorporated | Ultracapacitor vacuum assembly |
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