JP3680883B2 - Electric double layer capacitor and manufacturing method thereof - Google Patents
Electric double layer capacitor and manufacturing method thereof Download PDFInfo
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- 239000003990 capacitor Substances 0.000 title claims description 38
- 238000004519 manufacturing process Methods 0.000 title claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 27
- 229910052782 aluminium Inorganic materials 0.000 claims description 27
- 239000011888 foil Substances 0.000 claims description 24
- 239000011230 binding agent Substances 0.000 claims description 14
- 239000011255 nonaqueous electrolyte Substances 0.000 claims description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical class [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 11
- 239000002033 PVDF binder Substances 0.000 claims description 11
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 9
- 239000006258 conductive agent Substances 0.000 claims description 8
- 239000007772 electrode material Substances 0.000 claims description 8
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 7
- 239000000843 powder Substances 0.000 claims description 7
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 6
- -1 tetraethylammonium tetrafluoroborate Chemical compound 0.000 claims description 6
- 239000006229 carbon black Substances 0.000 claims description 5
- 238000004804 winding Methods 0.000 claims description 5
- 238000005530 etching Methods 0.000 claims description 4
- 239000000243 solution Substances 0.000 claims description 2
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 8
- 239000008151 electrolyte solution Substances 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000002006 petroleum coke Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
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- 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
-
- 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
- H01G11/54—Electrolytes
- H01G11/58—Liquid electrolytes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Electric Double-Layer Capacitors Or The Like (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は生産性に優れ、内部抵抗が小さく、急速に充放電できる電気二重層コンデンサとその製造方法に関する。
【０００２】
【従来の技術】
電気二重層コンデンサは、集電体に比表面積が大きい活性炭粉末を主体とする分極性電極層を担持するとともに、リード線をそれぞれ集電体に固着した一対又は複数対のシート状分極性電極の間にセパレータを配置して重ね合せた素子を電解液中に浸し、活性炭粉末の大きい表面と接する電解液中に形成される電気二重層を利用して電荷を蓄めるコンデンサであり、他の形式のコンデンサと比べて静電容量が格段に大きいのが特徴である。又、充放電するときに化学反応を伴う二次電池と比較すると、原理的に化学反応を伴わない電気二重層コンデンサは繰り返し充放電しても静電容量の劣化が非常に少ないという特徴がある。
【０００３】
しかし、活性炭粉末を主体とする分極性電極層中の電気抵抗がかなり大きいため活性炭粉末より細かいカーボンブラックなどを導電剤として混入して電気抵抗を下げているが、導電剤を添加しても電気抵抗を充分に小さくできず、集電体と分極性電極層との間にも電気抵抗があり、要求されているような大電流による充放電ができないという問題があった。この問題をクリヤーするため、集電体のアルミニウム箔にエッチング処理を施して表面に凹凸のあるアルミニウム箔としたり、分極性電極シートを圧延したり、集電体と分極性電極のシートの間を黒鉛などを主成分とする導電性接着剤で接着したり、電気抵抗が小さい電解液を組み合せるなどの方法が検討されている。
【０００４】
さらに、特開平８−５５７６１号公報には、Ｎメチルピロリドン等の有機溶剤に可溶のポリビニリデンフルオライド等の含フッ素ポリマーを分極性電極のバインダーに使用し、Ｎメチルピロリドンを加えて混合、混練した分極性電極材料のペーストを集電体のアルミニウムエッチング箔の両面に塗工し、乾燥後ロール圧延してシート状とした一対の分極性電極の間にセパレータを挟んで捲回して素子とし、この素子をプロピレンカーボネイトにテトラエチルホスホニウムテトラフルオロボレイトを溶解した非水系電解液とともに容器中に封入して内部抵抗の小さい電気二重層コンデンサを得ている。
【０００５】
しかし、この電気二重層コンデンサの分極性電極は、アルミニウムエッチング箔の表面に分極性電極層を形成した後でロール圧延するので、分極性電極層と集電体との境界部に剪断応力が発生する。このため、この電気二重層コンデンサでは工程の設定条件がふれると分極性電極層が集電体から剥離しやすいという問題がある。また、分極性電極層をアルミニウムエッチング箔の両面に形成した一対のシート状分極性電極の間にセパレータを挟んで捲回して素子としているため、シート状分極性電極が少し厚く、厚い分だけ分極性電極層に大きい圧縮又は引っ張りの歪みが加わって分極性電極の内部抵抗が増加したり、分極性電極層が集電体から剥離したりして歩留が小さくなるなどの問題がある。さらに、分極性電極をリード線に接続するために分極性電極層の一部をはがしたり、分極性電極層の塗工による形成前に集電体にマスキングテープを貼っておいてこの部分にリード線を取り付けるなどの手間のかかる工程が必要という問題がある。
【０００６】
【発明が解決しようとする課題】
本発明の目的は、前述の問題点を解消して生産性と歩留に優れ、かつ内部抵抗が小さくて急速充放電が可能な電気二重層コンデンサとその製造方法を提供することにある。
【０００７】
【課題を解決するための手段】
本発明の電気二重層コンデンサは、活性炭粉末、導電剤粉末及びポリビニリデンフルオライドのバインダーを含む分極性電極層が集電体上に担持されたシート状分極性電極が、集電体をエッチング処理されたアルミニウム箔とし、分極性電極層が分極性電極材料のペーストを集電体の片面にのみ塗工されてなり、乾燥状態の分極性電極層の集電体上への担持量が１０〜５０ｇ／ｍ２となるように形成されており、一対のシート状分極性電極の間にセパレータを挟んだ状態で捲回して作られた素子が、非水系電解液とともに円筒状の容器中に封入されてなることを特徴とする。
【０００８】
本発明の電気二重層コンデンサでは、バインダーとして、溶媒に溶かすことができ、使用量を少量にしても結合強度が大きく、弾力性もあるポリビニリデンフルオライド（以下、ＰＶＤＦと略す）を使用しているので、バインダーの使用による分極性電極層の内部抵抗の増大を少なくできる。また、エッチング処理された表面に凹凸のあるアルミニウム箔の片面にのみ分極性電極材料のペーストを塗工して分極性電極層を形成してあるので、集電体と分極性電極層の間の密着強度が大きく、シート状分極性電極にセパレータを挟んで捲回しても分極性電極層に加わる歪みが小さく、分極性電極層の剥離や損傷も殆ど起きない。また、集電体としての使用条件下で安定で、電気伝導性に優れ屈曲が容易なアルミニウム箔を使用しているので、長期間使用しても安定した性能を示す。分極性電極材料のペーストを塗工して分極性電極層を形成する方法によれば、薄い分極性電極層の形成が容易で、分極性電極層と集電体の接合部における電気抵抗が安定して小さい。
【０００９】
分極性電極層を集電体の片側にのみ形成しておくのは、分極性電極を捲回する際に分極性電極層に大きい歪みが導入されるのを避け、歪みによって電気二重層コンデンサの内部抵抗が大きくなったり、あるいは部分的に内部抵抗が不均一になるのを避けるために有効である。この場合、分極性電極の片面にアルミニウム箔の集電体が露出しているので、分極性電極にリード線を取り付けるときには分極性電極層の一部を剥離した後にその部分にリード線の取り付けを行なう必要がなく、タブ付きのリード線をかしめ、超音波溶接又は冷間圧接などで直接簡単に取り付けられるという利点がある。
【００１０】
さらに、分極性電極層のアルミニウム箔上への担持量を１０〜５０ｇ／ｍ２としたのは、担持量が１０ｇ／ｍ２より少ないと単位体積の電気二重層コンデンサ当たりの静電容量が小さくなるからであり、５０ｇ／ｍ２より多いと集電体のアルミニウム箔と分極性電極との間の平均距離が大きくなり、その結果電気二重層コンデンサの内部抵抗が大きくなるからである。分極性電極層が薄いと静電容量が減ることになるので、分極性電極層のアルミニウム箔上への好ましい担持量は１０〜５０ｇ／ｍ２である。
【００１１】
アルミニウム箔上に担持される分極性電極層の厚さは、分極性電極材料の構成によって若干変わるが、１０〜５０ｇ／ｍ２の担持量は分極性電極層の厚さで表すと２０〜１００μｍに相当する。分極性電極層を塗工によって形成する方法によれば、集電体上に１０〜５０ｇ／ｍ２という比較的薄い分極性電極層を密着性よく形成することが容易であり、集電体の表面と分極性電極層との間の電気抵抗が小さい分極性電極層を形成でき、その結果、内部抵抗の小さい電気二重層コンデンサが得られる。使用する活性炭粉末の粒径は塗工表面に凹凸ができないよう１０μｍ以下とするのが好ましい。
【００１２】
アルミニウム箔の厚さは集電体を流れる電流に対する抵抗の影響が殆どないように、かつアルミニウム箔のエッチング処理を行ないやすくし、分極性電極を捲回する時等にアルミニウム箔が損傷するのを防ぐため、好ましくは５μｍ以上とする。他方、アルミニウム箔の厚さを１５０μｍを超えて厚くしても内部抵抗の低減効果がなく、素子の単位体積に占めるアルミニウム箔の体積が増えて、結果的に電気二重層コンデンサの単位体積当たりの静電容量が小さくなるので、好ましくは１５０μｍ以下とする。
【００１３】
本発明の電気二重層コンデンサの製造方法は、活性炭粉末、導電剤粉末及びＰＶＤＦを含む分極性電極材料にＮメチルピロリドンを混合、混練してペーストとし、エッチング処理されたアルミニウム箔の片面にのみ該ペーストを塗工、乾燥して乾燥状態の分極性電極層の担持量が１０〜５０ｇ／ｍ２の分極性電極シートとし、この分極性電極シートを切断してシート状分極性電極とし、一対のシート状分極性電極の間にセパレータを挟んで捲回して素子とし、該素子を非水系電解液とともに円筒状容器に封入することを特徴とする。
【００１４】
ＮメチルピロリドンはバインダーのＰＶＤＦを比較的よく溶かすので、分極性材料のペーストの溶媒として好ましく使用される。しかし、塗工されたペーストはその後に乾燥されるので、最終製品の電気二重層コンデンサにＮメチルピロリドンは残留しない。他方、バインダーのＰＶＤＦは、非水系電解液の溶媒であるプロピレンカーボネイトには溶けず、非水系電解液と共存しても変質しない。バインダーを溶かした溶媒を含むペーストを塗工することによって分極性電極層中のバインダーの分布が均一となり、バインダーをＰＶＤＦとすることによってバインダーの混合量が少量であっても良好な結合力を有する。
【００１５】
分極性電極層中に含まれるバインダーの量が多ければ分極性電極層の結合強度は大きくなるが分極性電極層の電気抵抗が大きくなり、バインダーの量が少ないと分極性電極層の結合強度が小さくなるので、分極性電極層の小さい内部抵抗と良好な結合強度を同時に確保できるように、分極性電極層中に含まれるバインダーの量は、好ましくは４〜２０重量％、さらに好ましくは６〜１５重量％とする。
【００１６】
導電剤粉末としては、細かいことによって狭い隙間に入り込みやすく、良好な導電性の付与効果が得られるので、カーボンブラックを使用するのが好ましい。非水系電解液を使用すると、非水系電解液の分解電圧が水系電解液の分解電圧より高いので電気二重層コンデンサの使用電圧を高くでき、結果としてエネルギー密度の大きい電気二重層コンデンサが得られるという利点がある。非水系電解液としては、安価であって比較的分解電圧が高く、電気抵抗が低いことから、プロピレンカーボネイトにテトラエチルアンモニウムテトラフルオロボレイトを溶解したものを使用するのが好ましい。電解液中のテトラエチルアンモニウムテトラフルオロボレイトの濃度は、薄いと電解液の電気抵抗が大きく、濃いと低温で電解液中に結晶が析出して安定した性能が得られないので、好ましくは０．６〜１．５モル／リットル、更に好ましくは０．８〜１．０モル／リットルとする。
【００１７】
【実施例】
以下、本発明を実施例によって具体的に説明するが、以下の実施例は本発明の一例であって本発明はこれらの実施例に限定されない。
【００１８】
溶融ＫＯＨ賦活された石油コークス系活性炭粉末（平均粒径１０μｍ、比表面積２０００ｍ２／ｇ）４０重量％、カーボンブラック１０重量％、ＰＶＤＦ１０重量％からなる混合物にＮメチルピロリドン４０重量％を加え、ボールミルで混合、混練してスラリーとした。このスラリーを厚さ１０μｍ、３０μｍ、５０μｍ、１００μｍおよび１５０μｍのエッチング処理されたアルミニウム箔の両面（＊印を付けた例）又は片面にそれぞれ塗工量を変えてコーターで塗工し、アルミニウム箔の表面に表１に示す量（乾燥後の量、両面塗工の場合は両面の塗工量を合わせた量）の分極性電極層を形成した。
【００１９】
得られた分極性電極シートを幅１３ｍｍのシート状に切断し、一対のシート状分極性電極の間に厚さ５０μｍのマニラ紙のセパレータを挟んで素子の外径が７ｍｍになるように捲回し、集電体であるアルミニウム箔に直接タブ付きリード線をかしめて接続した。他方、集電体の両面に分極性電極層を形成した比較例のシート状分極性電極については、いずれもその先端部の片面の分極性電極層を剥してから集電体にタブ付きリード線をかしめて接続した。
【００２０】
試作した各素子に取り付けたリード線を封口ゴムに通し、素子をアルミニウム容器に入れ、プロピレンカーボネイトに１モル／リットルのテトラエチルアンモニウムテトラフルオロボレイトを溶かした非水系電解液とともに素子を容器中に密封して外径８ｍｍ、高さ２１ｍｍの捲回型電気二重層コンデンサを得た。捲回型電気二重層コンデンサは各例につき各１０個を試作した。表１に示した例１〜１１の内、例１〜４は比較例であり、例１＊、例２＊では分極性電極層を集電体の両側に塗工した。例３〜１１は分極性電極層を集電体の片面のみに形成したものであり、例５〜１１は本発明の実施例である。
【００２１】
図１は試作した捲回型電気二重層コンデンサのうち、本発明に係る集電体の片面にのみ分極性電極層を形成した捲回型電気二重層コンデンサの概要を示す斜視図であり、図１の１は分極性電極層、２は集電体、３は素子、４はセパレータ、５はアルミニウム容器、６，７はタブ付きリード線、８は封口ゴムである。試作した各捲回型電気二重層コンデンサについて初期の静電容量と内部抵抗とを測定し、各例の捲回型電気二重層コンデンサの初期の静電容量の平均値と内部抵抗の平均値とを表１に併せて示した。次に、試作した各例の捲回型電気二重層コンデンサを７０℃に保持した恒温槽にいれ、２．５Ｖの電圧を印加して１０００時間保持する耐久性試験を行ない、その静電容量と内部抵抗の変化を調べた。耐久性試験後における静電容量の変化率と内部抵抗の平均値を表１に併せて示す。
【００２２】
【表１】
表１に得られた結果から、本発明による捲回型電気二重層コンデンサは内部抵抗が小さいことが分かる。さらに、加速耐久性試験後の静電容量の減少が少なく、試験後の内部抵抗も格段に小さいことから、耐久性に優れていることが分かる。
【００２４】
【発明の効果】
本発明によれば、内部抵抗が小さいので急速充放電ができ、耐久性にも優れ静電容量が劣化し難い捲回型電気二重層コンデンサが得られる。さらには集電体の片面のみに分極性電極層を形成したシート状分極性電極を用いることから、捲回型電気二重層コンデンサを生産性と歩留よく製造できる。
【図面の簡単な説明】
【図１】本発明による捲回型電気二重層コンデンサの概要を示す斜視図。
【符号の説明】
１ 分極性電極層
２ 集電体
３ 素子
４ セパレータ
５ アルミニウム容器
６，７ タブ付きリード線
８ 封口ゴム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric double layer capacitor that is excellent in productivity, has low internal resistance, and can be rapidly charged and discharged, and a method for manufacturing the same.
[0002]
[Prior art]
The electric double layer capacitor has a polarizable electrode layer mainly composed of activated carbon powder having a large specific surface area on a current collector, and a pair of sheet-shaped polarizable electrodes each having a lead wire fixed to the current collector. Capacitor that accumulates electric charges by using an electric double layer formed in an electrolyte solution in contact with the large surface of activated carbon powder by immersing the element with a separator placed between them in the electrolyte solution It is characterized by an extremely large capacitance compared to the type of capacitor. In addition, in comparison with a secondary battery that involves a chemical reaction when charging and discharging, in principle, an electric double layer capacitor that does not involve a chemical reaction is characterized by very little deterioration in capacitance even after repeated charging and discharging. .
[0003]
However, since the electric resistance in the polarizable electrode layer mainly composed of activated carbon powder is considerably large, carbon black finer than the activated carbon powder is mixed as a conductive agent to lower the electrical resistance. There is a problem that the resistance cannot be sufficiently reduced, and there is an electrical resistance between the current collector and the polarizable electrode layer, and charge / discharge with a large current as required cannot be performed. In order to clear this problem, the aluminum foil of the current collector is etched to form an aluminum foil with irregularities on the surface, the polarizable electrode sheet is rolled, the gap between the current collector and the polarizable electrode sheet Methods such as bonding with a conductive adhesive mainly composed of graphite or combining an electrolytic solution having a low electric resistance have been studied.
[0004]
Furthermore, in JP-A-8-55761, a fluorine-containing polymer such as polyvinylidene fluoride soluble in an organic solvent such as N-methylpyrrolidone is used as a binder for a polarizable electrode, and N-methylpyrrolidone is added and mixed. A paste of kneaded polarizable electrode material is applied on both sides of the aluminum etching foil of the current collector, dried and then rolled and rolled to form a device with a separator sandwiched between a pair of polarizable electrodes. The element is enclosed in a container together with a non-aqueous electrolyte solution in which tetraethylphosphonium tetrafluoroborate is dissolved in propylene carbonate to obtain an electric double layer capacitor having a low internal resistance.
[0005]
However, since the polarizable electrode of this electric double layer capacitor is rolled after forming the polarizable electrode layer on the surface of the aluminum etching foil, shear stress is generated at the boundary between the polarizable electrode layer and the current collector. To do. For this reason, this electric double layer capacitor has a problem that the polarizable electrode layer easily peels off from the current collector when the process setting conditions are changed. In addition, since a polarizable electrode layer is formed by sandwiching a separator between a pair of sheet-shaped polarizable electrodes formed on both sides of an aluminum etching foil, the sheet-shaped polarizable electrode is a little thicker and thicker. There is a problem that a large compressive or tensile strain is applied to the polar electrode layer to increase the internal resistance of the polarizable electrode, or the polarizable electrode layer is peeled off from the current collector to reduce the yield. Furthermore, in order to connect the polarizable electrode to the lead wire, a part of the polarizable electrode layer is peeled off, or a masking tape is applied to the current collector before forming the polarizable electrode layer by coating, and the lead is attached to this part. There is a problem that a laborious process such as attaching a wire is necessary.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide an electric double layer capacitor that eliminates the above-described problems, is excellent in productivity and yield, has a low internal resistance, and can be rapidly charged and discharged, and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
The electric double layer capacitor of the present invention is a sheet-like polarizable electrode in which a polarizable electrode layer containing a binder of activated carbon powder, conductive agent powder and polyvinylidene fluoride is supported on the current collector, and the current collector is etched. The polarizable electrode layer is formed by applying a polarizable electrode material paste only on one side of the current collector, and the dry amount of the polarizable electrode layer on the current collector is 10 to 10%. 50 g / m 2 and is formed such that, elements made by winding in a state of sandwiching the separator between the pair of sheet-like polarizable electrode, enclosed together with the non-aqueous electrolyte into the cylindrical container It is characterized by being made.
[0008]
In the electric double layer capacitor of the present invention, a polyvinylidene fluoride (hereinafter abbreviated as PVDF) that can be dissolved in a solvent as a binder, has high bonding strength even when used in a small amount, and has elasticity. Therefore, the increase in the internal resistance of the polarizable electrode layer due to the use of the binder can be reduced. In addition, a polarizable electrode layer is formed by applying a paste of a polarizable electrode material only on one surface of an aluminum foil having irregularities on the etched surface, so that a gap between the current collector and the polarizable electrode layer is formed. The adhesion strength is high, and even when the sheet-like polarizable electrode is wound with a separator interposed therebetween, the strain applied to the polarizable electrode layer is small, and the polarizable electrode layer is hardly peeled off or damaged. In addition, since an aluminum foil that is stable under the conditions of use as a current collector and has excellent electrical conductivity and is easily bent is used, it exhibits stable performance even when used for a long period of time. By applying a polarizable electrode material paste to form a polarizable electrode layer, it is easy to form a thin polarizable electrode layer, and the electrical resistance at the junction between the polarizable electrode layer and the current collector is stable. And small.
[0009]
The reason why the polarizable electrode layer is formed only on one side of the current collector is to avoid introducing a large strain into the polarizable electrode layer when winding the polarizable electrode, This is effective in avoiding an increase in internal resistance or partial non-uniformity in internal resistance. In this case, since the current collector of aluminum foil is exposed on one side of the polarizable electrode, when attaching a lead wire to the polarizable electrode, the lead wire is attached to that portion after peeling off a part of the polarizable electrode layer. There is an advantage that a lead wire with a tab is not required to be carried out, but can be directly attached by ultrasonic welding or cold welding.
[0010]
Furthermore, the amount of supported onto an aluminum foil of the polarizable electrode layer was 10 to 50 g / m 2, the amount of carrier is small capacitance per electric double-layer capacitor unit volume is less than 10 g / m 2 This is because if it exceeds 50 g / m 2, the average distance between the aluminum foil of the current collector and the polarizable electrode increases, and as a result, the internal resistance of the electric double layer capacitor increases. Since the capacitance decreases when the polarizable electrode layer is thin, the preferred loading amount of the polarizable electrode layer on the aluminum foil is 10 to 50 g / m 2 .
[0011]
Although the thickness of the polarizable electrode layer supported on the aluminum foil varies slightly depending on the configuration of the polarizable electrode material, the supported amount of 10 to 50 g / m 2 is 20 to 100 μm in terms of the thickness of the polarizable electrode layer. It corresponds to. According to the method of forming the polarizable electrode layer by coating, it is easy to form a relatively thin polarizable electrode layer of 10 to 50 g / m 2 on the current collector with good adhesion. A polarizable electrode layer having a low electric resistance between the surface and the polarizable electrode layer can be formed, and as a result, an electric double layer capacitor having a low internal resistance can be obtained. The particle size of the activated carbon powder used is preferably 10 μm or less so that the coated surface is not uneven.
[0012]
The thickness of the aluminum foil is such that there is almost no influence of the resistance to the current flowing through the current collector, and the aluminum foil is easily etched, so that the aluminum foil can be damaged when winding the polarizable electrode. In order to prevent this, the thickness is preferably 5 μm or more. On the other hand, even if the thickness of the aluminum foil exceeds 150 μm, there is no effect of reducing the internal resistance, the volume of the aluminum foil occupying the unit volume of the device increases, and as a result, per unit volume of the electric double layer capacitor. Since the electrostatic capacity is small, it is preferably 150 μm or less.
[0013]
The manufacturing method of the electric double layer capacitor of the present invention is such that N methylpyrrolidone is mixed and kneaded into a polarizable electrode material containing activated carbon powder, conductive agent powder and PVDF to form a paste, and is applied only to one side of an etched aluminum foil. A paste is applied and dried to form a polarizable electrode sheet having a dry polarizable electrode layer carrying amount of 10 to 50 g / m 2 , and the polarizable electrode sheet is cut into a sheet-like polarizable electrode. A separator is sandwiched between sheet-like polarizable electrodes to form an element, and the element is enclosed in a cylindrical container together with a non-aqueous electrolyte.
[0014]
N-methylpyrrolidone dissolves the binder PVDF relatively well and is therefore preferably used as a solvent for the polarizable material paste. However, since the applied paste is then dried, no N-methylpyrrolidone remains in the final electric double layer capacitor. On the other hand, the PVDF binder does not dissolve in propylene carbonate, which is a solvent for the non-aqueous electrolyte, and does not change even when coexisting with the non-aqueous electrolyte. By applying a paste containing a solvent in which the binder is dissolved, the distribution of the binder in the polarizable electrode layer becomes uniform. By using PVDF as the binder, the binder has a good bonding strength even if the amount of the binder mixed is small. .
[0015]
If the amount of binder contained in the polarizable electrode layer is large, the bond strength of the polarizable electrode layer increases, but the electric resistance of the polarizable electrode layer increases, and if the amount of binder is small, the bond strength of the polarizable electrode layer increases. Therefore, the amount of the binder contained in the polarizable electrode layer is preferably 4 to 20% by weight, and more preferably 6 to 6% so that a small internal resistance and good bonding strength of the polarizable electrode layer can be secured at the same time. 15% by weight.
[0016]
As the conductive agent powder, it is preferable to use carbon black because it is fine and easily enters a narrow gap and provides a good conductivity imparting effect. When a non-aqueous electrolyte is used, the decomposition voltage of the non-aqueous electrolyte is higher than the decomposition voltage of the aqueous electrolyte, so that the operating voltage of the electric double layer capacitor can be increased, resulting in an electric double layer capacitor having a large energy density. There are advantages. As the non-aqueous electrolyte solution, it is preferable to use a solution obtained by dissolving tetraethylammonium tetrafluoroborate in propylene carbonate because it is inexpensive, has a relatively high decomposition voltage, and has a low electric resistance. If the concentration of tetraethylammonium tetrafluoroborate in the electrolytic solution is thin, the electrical resistance of the electrolytic solution is large. If the concentration is high, crystals precipitate in the electrolytic solution at low temperatures, and stable performance cannot be obtained. It is 6 to 1.5 mol / liter, more preferably 0.8 to 1.0 mol / liter.
[0017]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the following examples are examples of the present invention, and the present invention is not limited to these examples.
[0018]
A ball mill is prepared by adding 40% by weight of N-methylpyrrolidone to a mixture of 40% by weight of petroleum coke activated carbon powder (average particle size 10 μm, specific surface area 2000 m 2 / g) activated by molten KOH, 10% by weight of carbon black and 10% by weight of PVDF. And kneaded to make a slurry. This slurry was coated on the both sides (example marked with *) of the etched aluminum foil having a thickness of 10 μm, 30 μm, 50 μm, 100 μm and 150 μm, or on one side with a coater while changing the coating amount. A polarizable electrode layer was formed on the surface in the amount shown in Table 1 (the amount after drying, or in the case of double-sided coating, the combined amount of both sides).
[0019]
The obtained polarizable electrode sheet was cut into a sheet having a width of 13 mm, and a 50 μm-thick manila paper separator was sandwiched between a pair of sheet-like polarizable electrodes and wound so that the outer diameter of the element became 7 mm. The lead wire with the tab was directly caulked and connected to the aluminum foil as the current collector. On the other hand, for the sheet-like polarizable electrode of the comparative example in which the polarizable electrode layers are formed on both surfaces of the current collector, the lead wire with tabs is attached to the current collector after peeling off the polarizable electrode layer on one side at the tip. And connected.
[0020]
Lead wires attached to each prototype device are passed through a sealing rubber, the device is placed in an aluminum container, and the device is sealed in a container together with a non-aqueous electrolyte in which 1 mol / liter of tetraethylammonium tetrafluoroborate is dissolved in propylene carbonate. Thus, a wound electric double layer capacitor having an outer diameter of 8 mm and a height of 21 mm was obtained. Ten wound electric double layer capacitors were manufactured for each example. Of Examples 1 to 11 shown in Table 1, Examples 1 to 4 are comparative examples. In Examples 1 * and 2 *, polarizable electrode layers were applied to both sides of the current collector. In Examples 3 to 11, polarizable electrode layers are formed only on one side of the current collector, and Examples 5 to 11 are examples of the present invention.
[0021]
FIG. 1 is a perspective view showing an outline of a wound type electric double layer capacitor in which a polarizable electrode layer is formed only on one side of a current collector according to the present invention, among the prototyped wound type electric double layer capacitors. 1 of 1 is a polarizable electrode layer, 2 is a current collector, 3 is an element, 4 is a separator, 5 is an aluminum container, 6 and 7 are lead wires with tabs, and 8 is a sealing rubber. The initial capacitance and internal resistance of each wound type electric double layer capacitor that was prototyped were measured, and the average value of the initial capacitance and the average value of the internal resistance of each example of the wound type electric double layer capacitor were Is also shown in Table 1. Next, the prototype electric wound type electric double layer capacitor was put in a thermostatic chamber maintained at 70 ° C., and a durability test was performed by applying a voltage of 2.5 V and maintaining it for 1000 hours. Changes in internal resistance were examined. Table 1 also shows the rate of change in capacitance and the average value of internal resistance after the durability test.
[0022]
[Table 1]
From the results obtained in Table 1, it can be seen that the wound electric double layer capacitor according to the present invention has a small internal resistance. Furthermore, since the decrease in the electrostatic capacity after the accelerated durability test is small and the internal resistance after the test is remarkably small, it can be seen that the durability is excellent.
[0024]
【The invention's effect】
According to the present invention, it is possible to obtain a wound type electric double layer capacitor that can be rapidly charged / discharged because of its low internal resistance, has excellent durability, and does not easily deteriorate its capacitance. Furthermore, since a sheet-like polarizable electrode in which a polarizable electrode layer is formed only on one side of the current collector is used, a wound electric double layer capacitor can be manufactured with high productivity and yield.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an outline of a wound electric double layer capacitor according to the present invention.
[Explanation of symbols]
1
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35398996A JP3680883B2 (en) | 1996-12-18 | 1996-12-18 | Electric double layer capacitor and manufacturing method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35398996A JP3680883B2 (en) | 1996-12-18 | 1996-12-18 | Electric double layer capacitor and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10177935A JPH10177935A (en) | 1998-06-30 |
| JP3680883B2 true JP3680883B2 (en) | 2005-08-10 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35398996A Expired - Lifetime JP3680883B2 (en) | 1996-12-18 | 1996-12-18 | Electric double layer capacitor and manufacturing method thereof |
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| JP (1) | JP3680883B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004221531A (en) * | 2002-12-26 | 2004-08-05 | Toin Gakuen | Light chargeable laminated electric double-layered capacitor |
| TW200631046A (en) * | 2004-12-21 | 2006-09-01 | Teijin Ltd | Electric double-layer capacitor |
| JP4971729B2 (en) * | 2006-09-04 | 2012-07-11 | 富士重工業株式会社 | Lithium ion capacitor |
| CN117153567A (en) * | 2017-06-30 | 2023-12-01 | 京瓷Avx元器件公司 | Heat dissipation in balancing circuits for supercapacitor modules |
| JP7389739B2 (en) | 2017-06-30 | 2023-11-30 | キョーセラ・エイブイエックス・コンポーネンツ・コーポレーション | Electrode assembly for ultracapacitors |
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1996
- 1996-12-18 JP JP35398996A patent/JP3680883B2/en not_active Expired - Lifetime
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| Publication number | Publication date |
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| JPH10177935A (en) | 1998-06-30 |
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