JP3689948B2

JP3689948B2 - Electric double layer capacitor

Info

Publication number: JP3689948B2
Application number: JP32088495A
Authority: JP
Inventors: 学数原; 和也平塚; 剛森本; 克治池田
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 1994-12-27
Filing date: 1995-12-08
Publication date: 2005-08-31
Anticipated expiration: 2015-12-08
Also published as: JPH0955342A

Abstract

PROBLEM TO BE SOLVED: To provide a high energy density electric double layer capacitor which can be charged and discharged quickly, has a high withstand voltage, and is excellent in charging and discharge cycle durability. SOLUTION: An electric double layer capacitor is provided with a positive electrode 1 which is composed of a polarizable electrode and of a porous metal, with a negative electrode 5 which is composed of a carbon-based material formed in such a way that a carbon material which can occlude and desorb Li ions has occluded Li ions by a chemical method and/or an electrochemical method and of a collector by a porous metal and with a non-aqueous electrolytic solution 7 which contains a lithium salt.

Description

【０００１】
【発明の属する技術分野】
本発明はエネルギー密度が大きく、急速充放電ができ、充放電サイクル耐久性に優れた電気二重層キャパシタ（以下、ＥＤＬＣという）に関する。
【０００２】
【従来の技術】
従来のＥＤＬＣには、集電体に活性炭を主体とするシート状分極性電極を担持してなる対向する一対の電極の間にセパレータを挟んだ素子を、電解液とともに金属蓋と金属ケース及び両者間を絶縁する絶縁ガスケットによって金属ケース中に密封したコイン型のものと、対向する一対のシート状電極の間にセパレータを挟んだ状態で捲回してなる素子を、電解液とともに金属ケース中に収容し、ケースの開口部から電解液が蒸発しないように封口した捲回型のものがある。
【０００３】
また、特開平４−１５４１０６、特開平３−２０３３１１、特開平４−２８６１０８には、大電流大容量化を目的として電極とセパレータを多数積層してなる素子が組み込まれたＥＤＬＣが提案されている。すなわち、矩形の分極性電極の間にセパレータを配置して交互に多数積み重ねて素子とし、素子の各分極性電極の端部に正極リード部材と負極リード部材をかしめなどで接続した状態でケース中に収容し、素子に電解液を含浸して蓋で密封したものが開示されている。
【０００４】
これらのＥＤＬＣを構成する電極は、従来、正極と負極のいずれもが大きな比表面積を有する活性炭を主体する分極性電極である。また、大きな放電電流が得られるように、特開平６−２３６８２９には活性炭を主体とする両電極の集電体に多孔質ニッケルを用いたものが提案されている。
【０００５】
また、特開昭６４−１４８８２には、活性炭を主体とする電極を正極とし、Ｘ線回折による面間隔ｄ₀₀₂ （以下、面間隔ｄ₀₀₂ という）が０．３３８〜０．３５６ｎｍである炭素材料の成形体にあらかじめリチウムイオン（以下、Ｌｉ⁺ とする）を吸蔵させた複合体を負極とする２次電池が提案されている。
【０００６】
【発明が解決しようとする課題】
両電極に活性炭を主とする分極性電極を用いた従来のＥＤＬＣでは、組み合わせる溶媒と溶質の選択にもよるが、単位素子あたりの耐電圧は、水系電解液のＥＤＬＣで約１．０Ｖ、非水溶媒系電解液のＥＤＬＣで約２．５Ｖであり、より多くの電気エネルギを取り出せるように（エネルギ密度が大きくなるように）さらに高耐電圧のものが望まれている。
【０００７】
また、正極に活性炭を主とする分極性電極を用い、負極にリチウム又はＬｉ⁺ を吸蔵させた炭素質材料を用いるＥＤＬＣや電池は、その内部抵抗が大きいため急速充放電には向かず、充放電サイクル耐久性に欠ける難点がある。
【０００８】
ＥＤＬＣの容量を大きくするため、比表面積の大きな活性炭を用いて高容量化が図られているが、活性炭の比表面積は約３０００ｍ² ／ｇが限度であり、比表面積がさらに大きい活性炭を使用してもその気孔容積が大きいためエネルギ密度が向上しない。このため、大比表面積の活性炭を用いたＥＤＬＣの単位重量あたりの容量が制限されている。しかし、さらに長いバックアップ時間を確保するための高容量化が望まれている。
【０００９】
現在、小型のコイン型ＥＤＬＣはメモリバックアップ用に多く用いられている。ところで、ＩＣは従来５Ｖで駆動されていたため、二個以上のＥＤＬＣを直列に接続して５Ｖ超の耐電圧を得ていた。しかし、最近はＩＣが３Ｖで駆動されるようになり、メモリバックアップも３Ｖで済むようになった。このため、一個で３Ｖ超の耐電圧を有するＥＤＬＣの実現が望まれている。
【００１０】
また、１０Ａ以上の大電流で充放電できるＥＤＬＣは、電気自動車の電源用やその回生制動エネルギの一時的貯蔵等の用途に有望である。このため、エネルギ密度が充分に大きく、かつ急速充放電ができ、さらに充放電サイクル耐久性に優れたＥＤＬＣの実現が望まれている。
【００１１】
【課題を解決するための手段】
本発明は上記課題を達成すべくなされたものであり、本発明によるＥＤＬＣは、活性炭を主体とする分極性電極材料とアルミニウム又はステンレスからなる集電体とからなる正極と、リチウムイオンを吸蔵、脱離しうる炭素材料に化学的方法又は電気化学的方法でリチウムイオンを吸蔵させた炭素質材料と、リチウムと合金を形成しない気孔率８０％以上の多孔質ニッケルからなる集電体とからなり、厚さが０．１〜１ｍｍ、空隙率が５〜８０％である負極と、リチウム塩を含む非水系電解液とを有することを特徴とする。
【００１２】
本発明のＥＤＬＣには２種類の電極が使用されており、それぞれ吸着又は吸蔵されるイオンが異なる。すなわち、Ｌｉ⁺ を吸蔵、脱離しうる炭素材料にＬｉ⁺ を吸蔵させた炭素質材料を主体とする電極はＬｉ⁺ のみを吸蔵でき、この方が負極である。また、活性炭を主体とする分極性電極は、アニオンと、場合によってはカチオンにより、活性炭表面上に電気二重層を形成して電荷を蓄積でき、この方が正極である。
【００１３】
これら正極と負極の特性を能力一杯発揮させるため、本発明のＥＤＬＣに用いられる電解液には分解電圧の高い非水系溶媒が使用される。また、電解液中の電解質はカチオンがＬｉ⁺ であるリチウム塩に限られる。このリチウム塩には、ＬｉＣｌＯ₄ 、ＬｉＣＦ₃ ＳＯ₃ 、ＬｉＢＦ₄ 、ＬｉＰＦ₆ 、ＬｉＡｓＦ₆ 、ＬｉＳｂＦ₆ 、ＬｉＣＦ₃ ＣＯ₂ 及びＬｉＮ（ＣＦ₃ ＳＯ₂ ）₂ が使用できる。これらのうち、ＬｉＣｌＯ₄ 、ＬｉＢＦ₄ 、ＬｉＮ（ＣＦ₃ ＳＯ₂ ）₂ 及びＬｉＰＦ₆ が安定性が高く、電気伝導度が良好な点で特に好ましいリチウム塩である。
【００１４】
非水系電解液の溶媒には、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、γ−ブチロラクトン、ジメチルスルホキシド、スルホラン、ホルムアミド、ジメチルホルムアミド、ジオキソラン、リン酸トリエステル、無水マレイン酸、無水コハク酸、無水フタル酸、１，３−プロパンスルトン、プロピレンカーボネート誘導体、エチレンカーボネート誘導体、４，５−ジヒドロピラン誘導体、ニトロベンゼン、１，３−ジオキサン、１，４−ジオキサン、３−メチル−２−オキサゾリジノン、１，２−ジメトキシエタン、テトラヒドロフラン、テトラヒドロフラン誘導体、シドノン誘導体、２−メチルテトラヒドロフラン、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、アセトニトリル、ニトロメタン、アルコキシエタン、ジメチルアセトアミド及びトルエンから選ばれる１種以上からなる非水系溶媒が使用できる。
【００１５】
これらのうちで、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、スルホラン及びジメトキシエタンから選ばれる１種以上からなる非水系溶媒が、化学的及び電気化学的な安定性が高く、電気伝導度及び低温特性が良好な点で特に好ましい。
【００１６】
本発明のＥＤＬＣの活性炭を主体とする分極性電極の正極には、活性炭の他に電子伝導性を向上させる導電材が含まれる。この用途の分極性電極は種々の方法で形成できる。たとえば、活性炭とカーボンブラック（導電材）とフェノール系樹脂を混合し、プレス成形後不活性ガス雰囲気中及び水蒸気雰囲気中で焼成、賦活すると、活性炭とカーボンブラックのみからなる分極性電極が得られる。次にこの分極性電極をステンレス鋼板等の集電体に導電性接着等で接合する。コイン型ＥＤＬＣの場合は、ステンレス鋼板等からなるケース又は蓋を集電体又は端子として使用するのが好ましい。
【００１７】
他に、活性炭粉末、カーボンブラック（導電材）及び結合材にアルコールを加えて混練し、シート状に成形後乾燥して得られた分極性電極のシートを所要の寸法に切断し、次いでこれを導電性接着材等で集電体に接合して正極とする形成方法もある。この結合材には、好ましくはポリテトラフルオロエチレン（以下、ＰＴＦＥとする）が使用される。
【００１８】
また、活性炭粉末、カーボンブラック及び結合材に溶媒を混合してスラリとし、このスラリを集電体とする金属箔上に塗布し、塗布層を乾燥して集電体と一体の正極とする形成方法がある。集電体は電気化学的、化学的に耐食性のある導電体であればよい。正極の集電体には、ステンレス、アルミニウム、チタン、タンタル等の板や箔が使用できる。これらのうちステンレス又はアルミニウムの板や箔が性能と価格の両面で好ましい集電体である。ニッケルは酸化されやすく、正極の集電体に使用するとＥＤＬＣの耐電圧が低下する傾向がある。分極性電極と集電体は導電性接着材等で電気的に接合され、正極とされる。
【００１９】
正極に使用できる活性炭には、やしがら系活性炭、フェノール樹脂系活性炭、石油コークス系活性炭等がある。これらのうち、大容量のＥＤＬＣが得られるので、フェノール樹脂系活性炭又は石油コークス系活性炭を使用するのが好ましい。また、活性炭の賦活処理法には、水蒸気賦活処理法、溶融ＫＯＨ賦活処理等がある。これらの賦活処理法のうち、大容量のＥＤＬＣを得られるので、溶融ＫＯＨ賦活処理法による活性炭を使用するのが特に好ましい。
【００２０】
正極に混合する導電材には、カーボンブラック、天然黒鉛、人造黒鉛、金属ファイバ、酸化チタン、酸化ルテニウム等がある。少量でも混合効果の大きい、カーボンブラックの１種であるケッチェンブラック又はアセチレンブラックを使用するのが好ましい。導電材の配合量があまり多いと正極の容量が減少するので、良好な導電性と大きい容量を同時に確保できるように、正極中の導電材の配合量は活性炭との合量中３〜５０重量％、特に５〜３０重量％とするのが好ましい。また、活性炭には、好ましくは平均粒径が２０μｍ以下で比表面積が１０００〜３０００ｍ² ／ｇのものを使用する。これによってＥＤＬＣの容量を大きく、かつ内部抵抗を低くできる。
【００２１】
また、Ｌｉ^＋を吸蔵、脱離しうる炭素材料にＬｉ^＋を吸蔵させた炭素質材料を集電体と組み合わせた負極は、たとえばＬｉ^＋を吸蔵しうる炭素材料、結合材及び集電体から構成される。本発明のＥＤＬＣでは、この負極の炭素質材料の集電体に多孔質ニッケルを用いて一体化してあることによって内部抵抗を小さくし、大電流による急速充放電を可能としている。負極の多孔質金属の材料は、リチウムと合金を形成せず、負極側の使用条件で安定な材料であればよく、好ましくは気孔率が８０〜９９．５％のニッケル、銅又はこれらの合金が使用されるが、本発明では多孔質ニッケルを使用する。
【００２２】
本発明の好ましいＥＤＬＣでは、負極が、集電体とする気孔率８０％以上、特に気孔率９０％以上の多孔質金属に、Ｌｉ⁺ を吸蔵、脱離しうる炭素材料と結合材の混合物を担持させ、圧縮して厚さを０．１〜１ｍｍ、空隙率を５〜８０％とした後炭素材料にＬｉ⁺ を吸蔵させて炭素質材料としたものである。負極を圧縮してその空隙率を適度に小さな値に制御することがＥＤＬＣを高性能化するためにきわめて有効である。空隙率は好ましくは５〜８０％とする。空隙率が５％未満であると、電解液が電極内部に侵入し難くなって負極内の電極材料の一部が働かない。空隙率が８０％超であると、負極が容量の割りに嵩高くなって好ましくない。空隙率は特に好ましくは１０〜６０％とする。
【００２３】
また、負極の厚さは０．１〜１ｍｍ、特には０．２〜０．７ｍｍとするのが好ましい。結合材は、電極材料の粒子を互いに縛りつけて電極材料の粒子間の電気的接触が充放電サイクルによって緩まないように保持する働きをする。特に多孔質金属が集電体に使用された場合には、多孔質金属の集電体と結合材が協同して電極材料の粒子間及び電極材料の粒子と集電体の間の電気的接触が緩まないように保持する働きをする。
【００２４】
本発明の好ましいＥＤＬＣでは、負極に使用される多孔質金属が、気孔率８０〜９９％の多孔質ニッケルであり、その断面に引いた長さ１ｃｍの直線が横切る平均孔数（以下、単に平均孔数という）が５以上である。多孔質金属は適当な厚さと空隙率を有する負極を作りやすいように厚さが０．３〜３ｍｍのシート状のものを使用するのが好ましい。特には、気孔率が９０〜９９％で、平均孔数が５以上の多孔質ニッケルを使用するのが好ましい。
【００２５】
この平均孔数を測定するには、多孔質金属を樹脂中に埋めて樹脂を硬化させ、その切断面上に引いた直線が横切る平均孔数を数え、その数を直線の長さで割ればよい。多孔質ニッケルは負極の条件下で安定であり、炭素質材料をその気孔中に収容して良好な集電性を確保できる。さらに好ましくは、多孔質ニッケルと一体化した負極をプレスなどで圧縮して負極中の余分の空隙を減らし、必要にして十分の電解液が含浸させる。
【００２６】
負極を製造するには、好ましくは、海綿状のシート状多孔質金属に、炭素材料に溶媒を加えて混練したスラリを塗布等によって気孔中に注入し、負極材料と集電体とを一体化する。多孔質金属は、良好な集電性を確保できるように、平均孔数が５〜５０個のものを使用するのが好ましい。次にスラリを注入したシートを乾燥後に圧縮して負極の空隙率を調整するのが好ましい。スラリに加える結合材には、ポリフッ化ビニリデン、フルオロオレフィン／オレフィン共重合体架橋ポリマー、フルオロオレフィン／ビニルエーテル共重合体架橋ポリマー、カルボキシメチルセルロ−ス、ポリビニルピロリドン、ポリビニルアルコール及びポリアクリル酸のいずれかを用いるのが好ましい。
【００２７】
スラリの溶媒にはこれらの結合材を溶解する溶媒を使用するのが好ましく、Ｎ−メチルピロリドン、ジメチルホルムアミド、トルエン、キシレン、イソホロン、メチルエチルケトン、酢酸エチル、酢酸メチル、フタル酸ジメチル、エタノール、メタノール、ブタノール、水等が適宜選択される。また、上記架橋ポリマーの架橋には、アミン類、ポリアミン類、ポリイソシアネート類、ビスフェノール類、パーオキシド類が使用できる。これらの結合材と溶媒は、正極である分極性電極材料のスラリの製造にも好ましく使用できる。
【００２８】
負極の炭素質材料の主成分であるＬｉ⁺ を吸蔵、脱離しうる炭素材料には、天然黒鉛、人造黒鉛、黒鉛化メソカーボン小球体、黒鉛ウィスカ、黒鉛化炭素繊維、気相成長炭素繊維等の黒鉛系材料、石炭コークス、石油コークス、ピッチコークス等を熱処理した易黒鉛化性炭素材料、フルフリルアルコール樹脂の焼成品、ノボラック樹脂の焼成品、フェノール樹脂の焼成品等の高容量系炭素材料が好ましく使用できる。これらのうち、Ｌｉ⁺ の吸蔵、脱離容量が大きい天然黒鉛、人造黒鉛、黒鉛化メソカーボン小球体、フルフリルアルコール樹脂の焼成品、フェノール樹脂の焼成品、ノボラック樹脂の焼成品、石炭コークスの熱処理品又はピッチコークスの熱処理品を使用するのが特に好ましい。
【００２９】
天然黒鉛は、結晶構造が発達した、不純物の少ないものを使用するのが好ましい。ここで、結晶構造の発達した天然黒鉛とは、面間隔ｄ₀₀₂ が０．３３６ｎｍ未満であり、結晶子サイズＬ_C が１５０ｎｍ以上のものをいう。結晶構造が発達した天然黒鉛は、Ｌｉ⁺ を吸蔵、脱離する能力が大きい。また、不純物の少ない天然黒鉛を使用すれば、優れた充放電サイクル耐久性を確保できる。
【００３０】
天然黒鉛中の不純物を減らすには、硝酸、硫酸、フッ酸等による酸処理を行うが、灰分を効果的に除けることから、最終的にフッ酸処理を行った炭素の純度が９９重量％以上の天然黒鉛を使用するのが好ましい。
【００３１】
人造黒鉛は、結晶構造が発達した不純物の少ないものを使用するのが好ましい。ここで、結晶構造が発達した人造黒鉛とは、前記ｄ₀₀₂ が０．３３６５ｎｍ以下であり、前記Ｌ_C が５０ｎｍ以上のものをいう。人造黒鉛は出発物質を選択することで高純度のものが得られるので、炭素の純度が９９．５重量％以上のものを使用するのが好ましい。
【００３２】
黒鉛化メソカーボン小球体は、２５００℃以上の高温で熱処理された黒鉛の結晶構造が発達した、不純物の少ないものを使用するのが好ましい。ここで、結晶構造の発達したものとは、前記ｄ₀₀₂ が０．３３７ｎｍ以下であり、前記Ｌ_C が２０ｎｍ以上のものをいう。
【００３３】
黒鉛化ウィスカは、結晶構造が発達した不純物の少ないものを使用するのが好ましい。ここで、結晶構造が発達したものとは、前記ｄ₀₀₂ が０．３３６５ｎｍ以下であり、前記Ｌ_C が１０ｎｍ以上のものをいう。
【００３４】
黒鉛化炭素繊維は、アクリロニトリル樹脂等の繊維を２５００℃以上の温度で熱処理した黒鉛の結晶構造が発達した、不純物の少ないものを使用するのが好ましい。ここで、結晶構造の発達したものとは、前記ｄ₀₀₂ が０．３３６５ｎｍ以下であり、前記Ｌ_C が１０ｎｍ以上であるものをいう。
【００３５】
フルフリルアルコール樹脂焼成品は、フルフリルアルコール樹脂を１０００〜１５００℃で熱処理した不純物の少ないものを使用するのが好ましい。また、熱処理して前記ｄ₀₀₂ が０．３７５〜０．３９ｎｍであるものを使用するのが好ましい。
【００３６】
ノボラック樹脂焼成品は、ノボラック樹脂を７００℃以下の温度で熱処理したＨ／Ｃ原子比が０．２５〜０．２８で、前記ｄ₀₀₂ が０．３８ｎｍ以上のものを使用するのが好ましい。
【００３７】
フェノール樹脂焼成品は、フェノール樹脂を熱処理して得られる前記ｄ₀₀₂ が０．３６５〜０．３９０ｎｍのものを使用するのが好ましい。
【００３８】
易黒鉛化性炭素材料としては、コークス類、たとえば石炭コークス、石油コークス、ピッチコークス等を熱処理した炭素材料が挙げられる。これらのうち、炭素の純度の高いもの、又は不純物を除く処理をした炭素の純度の高いものを使用するのが好ましい。これらのコークスを８００〜１５００℃で熱処理すると、面間隔ｄ₀₀₂ が０．３４０〜０．３５５ｎｍのＬｉ⁺ を吸蔵できる炭素材料となる。
【００３９】
これらの炭素材料のうち、面間隔ｄ₀₀₂ が０．３６５〜０．３９０ｎｍの炭素材料を負極に使用すると、ＥＤＬＣの充放電サイクル耐久性が向上するので特に好ましい。また、負極に使用する炭素材料の粉末は、ＥＤＬＣの容量を大きくでき、かつその内部抵抗を小さくできるので、平均粒径が３０μｍ以下のものを使用するのが好ましい。しかし、あまり細かい粉は嵩高いので、平均粒径は２μｍ以上を使用するのが好ましい。
【００４０】
電極に配合する結合材の量は、１重量％未満であると電極の強度が小さく、２０重量％超であるとＥＤＬＣの電気抵抗が増大して容量が減少するので、炭素材料との合量中１〜２０重量％とするのが好ましい。容量と強度のバランスを考慮すると、より好ましい結合材の配合量は３〜１２重量％である。
【００４１】
また、Ｌｉ⁺ を吸蔵、離脱しうる炭素材料にＬｉ⁺ を吸蔵させるには次の方法がある。まず、粉末状のリチウムをＬｉ⁺ を吸蔵、離脱しうる炭素材料の粉末に混ぜた成形体としておいて電解液を注入し、リチウムをイオン化させ、Ｌｉ⁺ を吸蔵、脱離しうる炭素材料中に取り込ませる化学的方法がある。次に、Ｌｉ⁺ を吸蔵、脱離しうる炭素材料と結合材からなる成形体に、箔状のリチウムを接触させた状態で電解液中に浸漬してリチウムをイオン化させ、Ｌｉ⁺ を吸蔵、脱離しうる炭素材料中に取り込ませる化学的方法がある。
【００４２】
他に、リチウム塩を電解質とする非水系溶媒の電解液中の、一方の側にＬｉ⁺ を吸蔵、離脱しうる炭素材料と結合材からなる形成体を置き、他方にリチウムの電極板を置いて電流を流し、炭素材料中にＬｉ⁺ を吸蔵させる電気化学的方法がある。これらの方法のうち、操作が簡単であるので、Ｌｉ⁺ を吸蔵、脱離しうる炭素材料と結合材からなる成形体に箔状のリチウムを接触させた状態で電解液中に浸漬してリチウムをイオン化させ、炭素材料中に取り込ませる化学的方法を採用するのが特に好ましい。
【００４３】
本発明の他の好ましいＥＤＬＣは、正極に使用される集電体が多孔質金属である。この構成にすると、ＥＤＬＣの正極の内部抵抗も負極の内部抵抗にバランスさせて小さくできる。よって、ＥＤＬＣ全体の内部抵抗をさらに小さくでき、急速充放電が可能になる。また、同時に充放電サイクル耐久性も向上する。正極の分極性電極は、好ましくは導電性を向上させるカーボンブラック等の導電材と結合材を含むものである。
【００４４】
正極は、好ましくは次のようにして作製する。すなわち、活性炭粉末、カーボンブラック及び結合材に溶媒を混合してスラリとする。次に、このスラリをシート状の多孔質金属に塗布又は含浸して乾燥し、集電体と一体のシート状電極とする。シート状電極を所要の寸法に切断後、好ましくは導電性接着剤によって接着、又は電気溶接等で溶接して端子又は金属容器の蓋又はケースに電気的に接続する。
【００４５】
正極の集電体に使用する多孔質金属の材料は、電気化学的及び化学的に耐食性のあるものであればよい。好ましい多孔質金属の材料には、ニッケル、アルミニウム、チタン、タンタル又はこれらの合金がある。多孔質ニッケルは、正極の集電体に使用すると耐電圧が少々低くなるが、微細な多孔構造を有するものを形成できるため良好な集電性が得られ、比較的安価に入手できる好ましい集電体である。アルミニウム、チタン又はタンタルの多孔質金属は、耐電圧が高い点で好ましい集電体である。特に、多孔質アルミニウムは安価に入手できるので好ましい集電体である。
【００４６】
多孔質アルミニウムは、活性炭、導電材及び結合材からなる分極性電極材料をその気孔中に収容して正極に良好な集電性を付与し、正極の内部抵抗を小さくする。たとえば、三次元構造を有する海綿状のシート状多孔質金属は、分極性電極材料のスラリをその気孔内に注入して乾燥すると、集電体と一体化した正極になる。塗工によって注入する場合は、所要量の分極性電極材料が担持できるまで、塗布と乾燥の操作を繰り返してもよい。
【００４７】
分極性電極材料をその気孔中に充填する他の好ましい方法に、１回の操作で工程が完了する圧入法がある。すなわち、活性炭粉末と導電材及びＰＴＦＥにエタノールを加えて混練し、シート状に成形する。このシートをシート状多孔質金属の上に載せ、又はこのシートの間にシート状多孔質金属を挟んでプレスすると、シート状多孔質金属と分極性電極材料が一体化した正極が得られる。この圧入するシートの厚さは、０．１〜１．５ｍｍ、特には０．１５〜１．０ｍｍとするのが好ましい。
【００４８】
本発明の他の好ましいＥＤＬＣは、気孔率８０％以上の多孔質金属に、比表面積１０００〜３０００ｍ² ／ｇの活性炭、導電性カーボンブラック及び結合材からなる分極性電極材料を担持させ、次いで圧縮して厚さを０．２〜２．０ｍｍ、空隙率を１０〜８０％とした正極を有する。
【００４９】
正極に使用される多孔質金属には、スラリが注入しやすく適当な厚さの正極が得やすいように、厚さ０．３〜５ｍｍのシート状多孔質金属を使用するのが好ましい。特に、気孔率が８５〜９９％で、平均孔数が５以上の多孔質金属を使用するのが好ましい。多孔質金属は、スラリの注入が容易であって、かつ良好な集電特性が得られるように、平均孔数が５〜５０のものを使用するのが好ましい。
【００５０】
本発明の他の好ましいＥＤＬＣは、正極に使用される多孔質金属が気孔率８０〜９９％の多孔質アルミニウムであり、平均孔数が５以上である。多孔質アルミニウムを組み合わせた電極では、電極に対向しない側の面にアルミニウムを溶射後、アルミニウムからなる蓋やケースに溶接して電気的に接合してもよい。溶接の方法としては、工程が簡単で電気的接続が確実であり、正極と負極のいずれにも適用できる電気溶接法によるのが特に好ましい。
【００５１】
多孔質金属の集電体と一体化した正極は、ロール等で圧縮して空隙率を小さくし、正極の空隙率を必要にして十分な小さい値に調整するのが好ましい。正極の空隙率を適度に小さな値に調整すれば、ＥＤＬＣの内部抵抗が低下し、エネルギ密度がさらに向上する。正極の空隙率は好ましくは１０〜８０％とする。空隙率が１０％未満であると、非水系電解液が正極の内部に侵入し難くなって内部の電極が十分に働かなくなる。また、正極の空隙率が８０％超であると、正極が嵩高くなって正極の体積あたりの容量が小さくなる。正極の空隙率は、より好ましくは１５〜６０％とする。同じ理由で、正極の厚さは０．１〜３ｍｍ、さらには０．２〜２ｍｍとするのが好ましい。
【００５２】
本発明の他の好ましいＥＤＬＣは、正極負極及び非水系電解液が、ケースと蓋からなる金属製のコイン型容器に収容されてなり、正極をステンレス鋼板又はアルミニウムとステンレス鋼の積層板からなるケース及び蓋のいずれか一方の側に配置し、負極をステンレス鋼板、ニッケル板、銅板又はステンレス鋼、ニッケル及び銅から選ばれる２種以上の積層板からなる蓋及びケースのいずれか他方の側に配置してなる。
【００５３】
コイン型ＥＤＬＣでは、炭素材料や分極性材料を多孔質金属に担持させた電極を、導電性接着材又は溶接でステンレス鋼板、ニッケル板又はアルミニウム板の蓋やケースに電気的に接続するのが好ましい。コイン型ＥＤＬＣの容器をこのような構成とすれば、コイン型容器の蓋とケースが長期間安定な端子として機能し、集電体との間の電気的な接続が確実であり、製品が安定した性能を発揮する。
【００５４】
本発明の他の好ましいＥＤＬＣは、正極である分極性電極の単極容量をｂ（単位：Ｆ）とし、負極のＬｉ⁺ 離脱容量をｄ（単位：ｍＡｈ）とし、電圧の作動範囲の電位差をｖ（単位：Ｖ）とするとき、比率ｂｖ／３．６ｄが０．０５〜０．９０の範囲にある。この比率ｂｖ／３．６ｄの値は、ＥＤＬＣの急速充放電特性と充放電サイクル耐久性に影響する。したがって、この比率の値を前記の範囲に設定するのが好ましい。ここで、正極の単極容量ｂは、一対の正極と同構成の電極をセパレータを挟んで対向させ、電解液中で直流電圧を印加後定電流で放電させたときの電圧の低下勾配から求める。
【００５５】
本発明によるＥＤＬＣの電圧の作動範囲は、たとえば２．０〜３．３Ｖ、２．０〜４．０Ｖ、３．３Ｖ〜４．５Ｖに設定できる。電圧の作動範囲は、好ましくはＥＤＬＣの耐久性を考慮してその劣化が少ない範囲を選ぶ。
【００５６】
電圧の作動範囲の上限をＶ₁ とし、下限をＶ₂ とし、この作動範囲で取り出せる電流量をＱ（単位：ｍＡｈ）とするとき、容量ＣはＣ＝３．６・Ｑ／（Ｖ₁ −Ｖ₂ ）によって計算できる。また、ＥＤＬＣの体積をＴ（Ｔは収納容器を含めた体積とする場合と、両電極にセパレータを組み合わせた素子のみの体積とする場合がある）とするとき、ＥＤＬＣのエネルギ密度Ｅ_D はＥ_D ＝Ｃ（Ｖ₁ ²−Ｖ₂ ²）／２Ｔによって計算できる。
【００５７】
負極から脱離しうるＬｉ⁺ 量ｄは、Ｌｉ⁺ を化学的方法又は電気化学的方法で炭素材料に吸蔵させた負極を、Ｌｉ⁺ ／Ｌｉ電極基準の電位で＋１．０Ｖまで１ｍＡ／ｃｍ² の電流密度で放電、すなわち離脱させたときの積算電気量（ｍＡｈ）に相当する。したがって、比率ｂｖ／３．６ｄはＥＤＬＣの構成が同一であっても、設定するキャパシタの電圧の作動範囲によって違うことになる。
【００５８】
比率ｂｖ／３．６ｄが０．０５未満であるとＥＤＬＣのエネルギ密度が小さくなる。一方、比率ｂｖ／３．６ｄが０．９０超であると初期のエネルギ密度は高くなるが急速充放電が困難となり、充放電サイクル耐久性が低下する。エネルギ密度及び急速充放電特性及び充放電サイクル耐久性を考慮し、比率ｂｖ／３．６ｄは０．１〜０．８とするのが特に好ましい。なお、本発明では、ＥＤＬＣの内部抵抗は、電流密度１０ｍＡ／ｃｍ² で定電流放電させたときの放電開始直後の電圧降下から求める。
【００５９】
【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、本発明はこれらによって限定されない。
【００６０】
［例１］
正極を次のように作製した。すなわち、石油コークス系の溶融ＫＯＨ賦活処理活性炭粉末（比表面積２０００ｍ² ／ｇ、平均粒径５μｍ、以下、活性炭Ａとする）８０重量％、ケッチェンブラック−ＥＣ（三菱化学社製の導電性カーボンブラック、以下、ＫＢとする）１０重量％、ＰＴＦＥ１０重量％からなる混合物にエタノール（以下、ＥＡとする）を添加して混練し、ロール圧延して幅１０ｃｍ長さ１０ｃｍ、厚さ０．５ｍｍのシートとし、２００℃で２時間乾燥した。
【００６１】
図１に示すコイン型ＥＤＬＣは、このシートを直径１２．５ｍｍの円板に打ち抜いた分極性電極１を、黒鉛系の導電性接着材（以下、導電性接着材という）２でステンレス３１６Ｌ製ケース３の内側に接着し正極としてある。この正極の単極容量ｂは３．６６Ｆ、すなわち２Ｖあたりの容量は２．０ｍＡｈであった。
【００６２】
次に負極を次のように作製した。すなわち、天然黒鉛粉末（純度９９．３％、前記ｄ₀₀₂ ＝０．３３５５ｎｍ、前記Ｌ_C ＝２００ｎｍ以上、平均粒径１０μｍ、以下、炭素材料Ａとする）９０重量％、ポリフッ化ビニリデン（以下、ＰＶＤＦとする）１０重量％からなる混合物にＮ−メチルピロリドン（以下、ＮＭＰとする）を重量比で３倍量加え、超音波を加えつつ撹拌混合し、炭素材料ＡがＰＶＤＦのＮＭＰ溶液に分散したスラリを得た。このスラリを厚さ２．０ｍｍ、気孔率９７％、目付け量５５０ｇ／ｍ² 、平均孔数が２５の多孔質ニッケルのシート（以下、多孔質Ｎｉ−Ａとする）に塗布し、２００℃で３０分間乾燥させた後、ロールで厚さ０．５ｍｍに圧縮して直径１２．５ｍｍの円板に打ち抜き、負極とした。
【００６３】
この圧縮された負極の空隙率は３５％であり、負極の炭素材料Ａの担持量は３６ｍｇ／ｃｍ² であった。この負極を図１のように、黒鉛系の導電性接着材（以下、導電性接着材という）２でＳＵＳ３０４製蓋４に接着し、１９０℃で１時間乾燥した。
【００６４】
この負極５側の蓋４とＳＵＳ３１６Ｌ製ケース３を集電体とする正極をさらに２００℃で４時間減圧下で乾燥した。これらをアルゴン雰囲気のグローブボックスに移し、負極５に直径１０ｍｍ、厚さ０．１ｍｍのリチウム金属箔６を圧着した。両電極の間にポリプロピレン（以下、ＰＰという）製セパレータ８を挟んで両電極を対向させて素子とし、１．２ｍｏｌ／ｌのＬｉＰＦ₆ を溶かしたエチレンカーボネート（以下、ＥＣという）とジエチルカーボネート（以下、ＤＥＣという）の容積比１：１の電解液７を容器中に注入して素子に含浸した。
【００６５】
次いで、ＰＰ製絶縁ガスケット９を用い、素子と電解液を容器中にかしめ封口した。得られたコイン型のＥＤＬＣの外寸は直径１８．３ｍｍ、厚さ２．０ｍｍである。このコイン型ＥＤＬＣを７０℃の恒温槽中に入れて１６時間放置した。この加温操作で電極５に圧着してあったリチウム箔がイオン化した状態で電極５に化学的に取り込まれる。この負極が脱離しうるＬｉ⁺ 量ｄは１２ｍＡｈであり、比率ｂｖ／３．６ｄは０．１７であった。
【００６６】
［例２］
例１において、炭素材料Ａに代えて人造黒鉛粉末（純度９９．９％、前記ｄ₀₀₂ ＝０．３３６５ｎｍ、前記Ｌ_C ＝５０ｎｍ以上、平均粒径７μｍ、以下炭素材料Ｂという）を負極に用い、正極側はＳＵＳ３０４板の内側にアルミニウムを積層したケースを用い、負極側の蓋にはその内側にニッケルをメッキしたＳＵＳ３０４を用いた他は例１と同様にしてコイン型のＥＤＬＣを組み立てた。このＥＤＬＣの負極が脱離しうるＬｉ⁺ 量は３．０ｍＡｈで、比率ｂｖ／３．６ｄは０．６７であった。
【００６７】
［例３］
例１において、天然黒鉛粉末に代えて黒鉛化メソカーボン小球体（純度９９．６％、前記ｄ₀₀₂ ＝０．３４８０ｎｍ、前記Ｌ_C ＝２ｎｍ以上、平均粒径１３μｍ、以下、炭素材料Ｃという）を負極に用い、他は例１と同様にしてコイン型ＥＤＬＣを組み立てた。負極の炭素材料Ｂの担持量は２９ｍｇ／ｃｍ² であり、この負極が脱離しうるＬｉ⁺ 量は８ｍＡｈであった。このＥＤＬＣの比率ｂｖ／３．６ｄは０．２５であった。
【００６８】
［例４］
例１において、炭素材料Ａの代わりに易黒鉛化性炭素材料である石油コークスの焼成品（焼成温度１４００℃、純度９９．９％、前記ｄ₀₀₂ ＝３．４５２、前記Ｌ_C ＝２ｎｍ以上、平均粒径５μｍ、以下、炭素材料Ｄという）を用い、電解液に１ｍｏｌ／ｌのＬｉＣｌＯ₄ をプロピレンカーボネート（以下、ＰＣという）に溶かしたものを用い、他は例１と同様にしてコイン型ＥＤＬＣを組み立てた。負極の炭素材料Ｄの担持量は２０ｍｇ／ｃｍ² であり、この負極が脱離しうるＬｉ⁺ 量は２．７ｍＡｈであった。このＥＤＬＣの比率ｂｖ／３．６ｄは０．７４であった。
【００６９】
［例５］
例１において、多孔質金属に厚さ２．０ｍｍ、気孔率９８％、目付け量３７０ｇ／ｍ² 、平均孔数が２０のシート状多孔質ニッケル（以下多孔質Ｎｉ−Ｂという）を用い、この多孔質Ｎｉ−Ｂにスラリを担持、乾燥後ロールプレスで厚さ０．３ｍｍに圧縮した。他は例１と同様にしてコイン型ＥＤＬＣを組み立てた。圧縮後の負極の空隙率は３９％、負極の炭素材料Ａの担持量は２５ｍｇ／ｃｍ² で、この負極が脱離しうるＬｉ⁺ 量は１０．６ｍＡｈであった。このＥＤＬＣの比率ｂｖ／３．６ｄは０．１９であった。
【００７０】
［例６］
例１で作製したのと同じ分極性電極のシートを１ｃｍ×１ｃｍに切り取り、幅１ｃｍ、長さ８ｃｍ、厚さ４５μｍのアルミニウム箔の先に導電性接着材で接着して正極とした。次に例１で作製した炭素材料Ａのスラリを、気孔率９７％、厚さ１．４ｍｍ、平均孔数２５、目付量３７０ｇ／ｍ² の多孔質ニッケル（以下多孔質Ｎｉ−Ｃという）のシートに塗布し、乾燥後厚さ０．３ｍｍに圧縮した。次に、１ｃｍ×１ｃｍに切り取った負極に、厚さ２０μｍ、幅１ｃｍ、長さ７ｃｍのニッケル箔の端部を電気溶接してリードとした。
【００７１】
この負極と１．３ｃｍ×１．３ｃｍで厚さ０．５ｍｍのリチウム板との間にＰＰ製セパレータを挟んで対向させ、１ｍｏｌ／ｌのＬｉＰＦ₆ を溶かしたＥＣとＤＥＣの容積比が１：１の電解液中に浸した。次いで、リチウム板の極に対し０（ゼロ）Ｖの電圧を１０時間印加して負極にＬｉ⁺ を電気化学的に吸蔵させた。この負極が脱離できるＬｉ⁺ 量は１０．３ｍＡｈであった。
【００７２】
次いで、正極とＬｉ⁺ を吸蔵させた負極の間に厚さ１８０μｍのＰＰ製セパレータを挟んで素子とした。この素子を電気化学的なＬｉ⁺ の吸蔵に用いたのと同組成の電解液に浸し、ガラス容器中にＥＤＬＣを組み立てた。この正極の単極容量ｂは３．２４Ｆ、すなわち２Ｖにつき１．８ｍＡｈであった。このＥＤＬＣの比率ｂｖ／３．６ｄは０．１７であり、素子の体積、すなわち正極、セパレータ及び負極の体積の合計は０．１０２５ｃｍ³ で、エネルギ密度は５０Ｗｈ／ｌであった。
【００７３】
［例７］
例６において、負極をロール圧延する圧力を高め、負極の厚さを０．１８ｍｍとし、負極の空隙率を３％とした。他は、例６と同様にして素子を作製し、ＥＤＬＣを組み立てた。この負極が脱離しうるＬｉ⁺ 量は６．５ｍＡｈであり、得られたＥＤＬＣの比率ｂｖ／３．６ｄは０．２８であった。また、素子の体積は０．０９０５ｃｃであり、エネルギ密度は５７Ｗｈ／ｌであった。
【００７４】
［例８］
負極をロール圧延する圧力を高め、負極の厚さを０．２０ｍｍとし、負極の空隙率を１０％とした。他は、例６と同様にして素子を作製し、ＥＤＬＣを組み立てた。この負極が脱離しうるＬｉ⁺ 量は８．５ｍＡｈであり、得られたＥＤＬＣの比率ｂｖ／３．６ｄは０．２８であった。また、素子の体積は０．０９２５ｃｃであり、そのエネルギ密度は５６Ｗｈ／ｌであった。
【００７５】
［例９］
正極と負極の両極に例１の正極と同じ分極性電極を使用し、導電性接着材でＳＵＳ３１６製ケース及びＳＵＳ３１６製蓋にそれぞれ接着して電極とした。両電極をＰＰ製セパレータを挟んで対向させた素子に、１ｍｏｌ／ｌのテトラエチルアンモニウムテトラフルオロボレート（以下、ＴＥＡＴＦＢという）を含むＰＣの電解液を含浸した。次いで、ＰＰ製絶縁ガスケットを用いてコイン型容器中にかしめ封口した。得られたコイン型ＥＤＬＣは直径１８．３ｍｍ、厚さ２．０ｍｍであった。
【００７６】
［例１０］
例１において、蓋に接着した負極に直径８ｍｍ、厚さ０．１ｍｍのリチウム箔を圧着せず、恒温槽による加温も行わず、他は例１と同様にしてコイン型ＥＤＬＣを組み立てた。
【００７７】
［例１１］
負極の集電体に多孔質Ｎｉ−Ａを用いず、炭素材料Ａ、ＰＶＤＦ及び溶媒のＮＭＰからなるスラリをＳＵＳ３１６Ｌ製蓋の内側に塗布し、２００℃で３０分乾燥して負極とした。他は例１と同様にしてコイン型ＥＤＬＣを組み立てた。この正極の単極容量は２．０ｍＡｈであった。この負極が脱離しうるＬｉ⁺ 量は１．８ｍＡｈであり、得られた比率ｂｖ／３．６ｄは１．１であった。
【００７８】
［例１２］
例１で作製した分極性電極のシートを１ｃｍ×１ｃｍに切り取り、幅１ｃｍ、長さ８ｃｍ、厚さ４５μｍのアルミニウム箔の先に導電性接着材で接合し、一対の分極性電極を得た。この一対の分極性電極の間にＰＰ製セパレータを挟んで素子とし、この素子に１ｍｏｌ／ｌのＴＥＡＴＦＢを含むＰＣの電解液を両電極に含浸し、ガラス容器中にＥＤＬＣを組み立てた。このＥＤＬＣ素子の体積は０．１２７ｃｃであり、そのエネルギ密度は１０Ｗｈ／ｌであった。
【００７９】
［例１３］
負極の集電体に多孔質Ｎｉ−Ｃを使用せず、厚さ２０μｍ、幅１ｃｍ、長さ１ｃｍのニッケル箔を使用し、他は例６と同様にしてＥＤＬＣ素子を組み立てた。この負極の炭素材料Ａの担持量は５．５ｍｇ／ｃｍ² であり、正極の単極容量は１．８ｍＡｈであった。この負極が脱離しうるＬｉ⁺ 量は１．８ｍＡｈであり、得られたＥＤＬＣの比率ｂｖ／３．６ｄは１．０であった。また、素子の体積は０．０７９５ｃｃであり、そのエネルギ密度は５９Ｗｈ／ｌと高かった。しかし、充放電サイクル耐久性と充電速度は不満足なものであった。
【００８０】
［例１４］
例１で用いた活性炭粉末と、導電材のＫＢと結合材のＰＶＤＦとを重量比で４５：４５：１０の割合で調合し、ＮＭＰを加えて粉砕、混合し、活性炭粉末のスラリとした。次に多孔質Ｎｉ−Ｃのシートにこのスラリを均等に塗工し、２００℃で１０時間乾燥した。このシートを圧延ローラで０．１７５ｍｍの厚さに圧縮した。圧縮したシートを１ｃｍ×１ｃｍに切り取った一対の分極性電極にリード端子を取り付け、両電極の間にＰＰのセパレータを挟んで素子とした。次に、１ｍｏｌ／ｌのＴＥＡＴＦＢを含むＰＣの電解液を入れたガラス容器中にこの素子を挿入し、ＥＤＬＣを組み立てた。この素子の体積は０．０５３ｃｃであり、エネルギ密度は６Ｗｈ／ｌであった。
【００８１】
上記の例１〜１４のＥＤＬＣの試作条件を表１〜６にまとめて示す。
【００８２】
【表１】

【００８３】
【表２】

【００８４】
【表３】

【００８５】
【表４】

【００８６】
【表５】

【００８７】
【表６】

【００８８】
次に、実施例である例１〜８及び比較例である例９〜１４のＥＤＬＣについて充電電流密度を最大２ｍＡ／ｃｍ² として２時間充電し、定電流放電を１ｍＡ／ｃｍ² で行った。各ＥＤＬＣの初期容量と選定した充電電圧と電圧の作動範囲を求めた結果を表７にまとめて示す。表７の例１〜５を例９〜１１と比べ、例６〜８を例１２、１４と較べると、初期容量及び作動電圧範囲において本発明のＥＤＬＣが顕著に優れることが分かる。
【００８９】
次に、例６〜８及び例１３のＥＤＬＣについて、２．０〜３．３Ｖの作動範囲で１０ｍＡ／ｃｍ² を最大電流として３０分間充電し、３０分間の充電量を１００とした場合の充電達成率（％）を測定し、表８に示した。表８の結果から、充電速度において本発明のＥＤＬＣが優れることが分かる。また、例６〜８及び例１３のＥＤＬＣについて、２．０〜３．３Ｖの作動範囲で、１０ｍＡ／ｃｍ² を最大充電電流とし、定電流放電電流を１ｍＡ／ｃｍ² として充放電サイクルテストを行い、容量変化の測定結果を表９に示した。表９から、充放電サイクル耐久性において本発明のＥＤＬＣが優れることが分かる。
【００９０】
【表７】

【００９１】
【表８】

【００９２】
【表９】

【００９３】
上記表７〜９に示された結果から、本発明によるＥＤＣＬは、耐電圧が高く、容量が大きく、急速充放電ができ、充放電サイクル耐久性が顕著に優れることが分かる。
【００９４】
［例２１］
フェノール樹脂系の溶融ＫＯＨ賦活処理活性炭粉末（比表面積２１００ｍ² ／ｇ、平均粒径約５μｍ、以下、活性炭Ｂという）７３重量％、ＫＢ１７重量％、ＰＶＤＦ１０重量％からなる混合物にＮＭＰを添加して混合したスラリを、多孔質Ｎｉ−Ａのシートに塗布し、２００℃で３０分乾燥した。次いでこのシートをロールで厚さ１．０ｍｍに圧縮した。圧縮したシートの空隙率は３５％であった。このシートを直径１２．５ｍｍの円板に打ち抜いて分極性電極を得た。
【００９５】
この分極性電極を、コイン型ＥＤＬＣのステンレス３１６Ｌ製ケースの内側に導電性接着材で接着し正極とした。この正極の単極容量ｂは６．２Ｆ、すなわち電圧の作動範囲２．０〜３．３Ｖにおける容量は２．２ｍＡｈであった。
【００９６】
次いで、負極を作製した。すなわち、炭素材料Ａ９０重量％、ＰＶＤＦ１０重量％からなる混合物にＮＭＰを加え、超音波を与えつつ撹拌混合し、ＰＶＤＦのＮＭＰ溶液に炭素材料Ａが分散したスラリを得た。このスラリを厚さ１．７ｍｍ、気孔率９８％、目付け量３７０ｇ／ｍ² 、平均孔数が２５の多孔質ニッケルのシート（以下、多孔質Ｎｉ−Ｄという）に塗布し、２００℃で３０分間乾燥した。次いで、このシートをロールで厚さ０．３ｍｍに圧縮して空隙率を３５％とした。
【００９７】
圧縮したシートを直径１２．５ｍｍの円板に打ち抜いた負極の炭素材料Ａの担持量は３０ｍｇ／ｃｍ² であった。この負極をＳＵＳ３０４製蓋に電気溶接し、２００℃で１時間乾燥した。
【００９８】
この負極を溶接した蓋と、正極を導電性接着材で接着したＳＵＳ３１６Ｌ製ケースをさらに２００℃の減圧下で４時間乾燥した。これらをアルゴン雰囲気のグローブボックスに移し、負極に直径１０ｍｍ、厚さ０．７ｍｍのリチウム箔を圧着した。次に、ＰＰ製セパレータを両電極の間に挟んで対向させ、１．０ｍｏｌ／ｌのＬｉＰＦ₆ を溶かしたＥＣとＤＥＣ（容積比１：１）の非水系電解液をケースに注入して両電極に非水系電解液を含浸した。次いで、ＰＰ製絶縁ガスケットを用い、素子と電解液を容器中にかしめ封口した。
【００９９】
得られたコイン型のＥＤＬＣは直径１８．３ｍｍ、厚さ２．０ｍｍである。このコイン型のＥＤＬＣを７０℃の恒温槽に入れて２日間保持した。この加温操作によって負極５に圧着してあったリチウム箔がイオン化した状態で負極の炭素材料に取り込まれた（化学的方法）。この負極が脱離しうるＬｉ⁺ 量ｄは１０ｍＡｈであり、比率ｂｖ／３．６ｄは０．２２であった。また、このＥＤＬＣの電圧の作動範囲は２．０〜３．３Ｖ、初期の静電容量は５．８Ｆ、内部抵抗は２０Ωであった。
【０１００】
このコイン型のＥＤＬＣを最大充電電流１０ｍＡ／ｃｍ² として３０分間充電し、次いで１ｍＡ／ｃｍ² で定電流放電させる充放電サイクル試験を行った。２．０〜３．３Ｖ間の充放電を５０サイクル行ったところ、容量の低下は認められなかった。次いで行った２．０〜４．０Ｖの充放電サイクル試験を行った結果、５０サイクル後に容量が初期容量の３０％に低下した。
【０１０１】
［例２２］
負極の炭素材料にフェノール樹脂の焼成品（純度９９．９％、面間隔ｄ₀₀₂ ＝０．３８ｎｍ、以下、炭素材料Ｅという）を用い、その結合材にポリイミド（以下、ＰＩという）を用い、負極側のケースに内側にニッケルメッキしたＳＵＳ３０４の板を用いた。また、正極の蓋にＳＵＳ３０４の内側にアルミニウムを積層した積層板を用い、正極の集電体に厚さ２ｍｍ、気孔率９２％、平均孔数が１７の多孔質アルミニウムのシート（以下、多孔質Ａｌ−Ａという）を用いた。
【０１０２】
正極は、多孔質Ａｌ−Ａのシートに例２１で調製した分極性材料のスラリを塗布し、乾燥後プレスして厚さ１．０ｍｍに圧縮した。この圧縮したシートの空隙率は３０％であった。このシートを円板に打ち抜いた正極を導電性接着材で蓋に接着した。この正極の単極容量は５．５Ｆであった。また、負極の炭素材料Ａの担持量は２３ｍｇ／ｃｍ² 、厚さは０．２ｍｍ、空隙率は２７％で、負極が脱離しうるＬｉ⁺ 量は６．８ｍＡｈであった。
【０１０３】
次に、非水系電解液としてＬｉＣｌＯ₄ をＰＣに１ｍｏｌ／ｌ溶かしたものを用い、他は例２１と同様にしてコイン型ＥＤＬＣを組み立てた。このＥＤＬＣの電圧の作動範囲は２．０〜４．０Ｖで、この作動範囲における容量は３．１ｍＡｈであり、比率ｂｖ／３．６ｄは０．４６となった。また、このＥＤＬＣの初期の静電容量は５．０Ｆ、内部抵抗は１８Ωであった。
【０１０４】
［例２３］
負極に炭素材料Ｃを用い、ＬｉＮ（ＣＦ₃ ＳＯ₂ ）₂ をＥＣとエチルメチルカーボネート（以下、ＥＭＣという）の容積比が１対１の混合溶媒に１ｍｏｌ／ｌ溶かした非水系電解液を用い、他は例２１と同様にしてコイン型ＥＤＬＣを組み立てた。負極の炭素材料Ｃの担持量は３５ｍｇ／ｃｍ² であり、負極が脱離しうるＬｉ⁺ 量は５．０ｍＡｈであり、得られたＥＤＬＣの比率ｂｖ／３．６ｄは０．４５であった。また、このＥＤＬＣの電圧の作動範囲は２．０〜３．３Ｖ、初期の静電容量は５．０Ｆ、内部抵抗は２４Ωであった。
【０１０５】
［例２４］
負極に炭素材料Ｄを用い、１ｍｏｌ／ｌのＬｉＢＦ₄ をＥＣとＤＥＣの容積比が１対１の混合溶媒に１ｍｏｌ／ｌ溶かした非水系電解液を用い、他は例２１と同様にしてコイン型ＥＤＬＣを組み立てた。負極の炭素材料Ｄの担持量は３０ｍｇ／ｃｍ² 、厚さは０．３ｍｍ、空隙率は４７％であり、負極が脱離しうるＬｉ⁺ 量は３．８ｍＡｈであった。得られたＥＤＬＣの比率ｂｖ／３．６ｄは０．５９であり、電圧の作動範囲は２．０〜３．３Ｖ、初期の静電容量は４．５Ｆ、内部抵抗は２５Ωであった。
【０１０６】
［例２５］
負極の集電体に厚さ１．４ｍｍ、気孔率９７％、平均孔数２０、目付量３７０ｇ／ｍ² の多孔質ニッケルのシート（以下、多孔質Ｎｉ−Ｅという）を用い、このシートに例２２で作製した炭素材料Ｅのスラリを塗布、乾燥後ロールで厚さを０．３ｍｍに圧縮して負極とした。圧縮した負極の空隙率は４６％、炭素材料Ｅの担持量は２５ｍｇ／ｃｍ² であり、負極が脱離しうるＬｉ⁺ 量は７．３ｍＡｈであった。これにスルホラン（以下、ＳＦという）とＤＥＣの容積比が４：１の混合溶媒にＬｉＢＦ₄ を１ｍｏｌ／ｌ溶かした非水系電解液を使用し、他は実施例２２と同様にしてコイン型ＥＤＬＣを組み立てた。正極の単極容量ｂは５．５Ｆ、得られたＥＤＬＣの電圧の作動範囲は２．０〜３．７Ｖ、初期の静電容量は５．２Ｆ、比率ｂｖ／３．６ｄは０．４２、内部抵抗は１９Ωであった。
【０１０７】
［例２６］
多孔質Ａｌ−Ａを幅１ｃｍ、長さ７ｃｍに切り取り、片端の１ｃｍを除く６ｃｍをプレスにより厚さ０．２ｍｍに圧縮して正極のリードとし、圧縮されていない１ｃｍ×１ｃｍの部分に例２２で調製した分極性電極材料のスラリを塗布し、これを２００℃で３０分乾燥した。分極性電極材料を担持した部分をプレスで厚さ１．０ｍｍに圧縮して正極とした。この正極の空隙率は２８％、単極容量ｂは５．４Ｆであった。
【０１０８】
次に例２２で用いた多孔質Ｎｉ−Ｄのシートを幅１ｃｍ、長さ７ｃｍに切り取り、片端の１ｃｍを除く６ｃｍをプレスで厚さ０．２ｍｍに圧縮して負極のリードとし、圧縮されていない１ｃｍ角の部分に例２２で調製した炭素材料Ｅのスラリを塗布し２００℃で３０分乾燥した。この炭素材料の担持部をプレスで厚さ０．３ｍｍに圧縮し、空隙率が３５％の負極とした。
【０１０９】
この負極と１．３ｃｍ×１．３ｃｍで厚さ０．５ｍｍのリチウム板との間にＰＰ製のセパレータを挟んで対向させ、１ｍｏｌ／ｌのＬｉＣＬＯ₄ を溶かしたＰＣの非水系電解液中に浸した。次いで、リチウム板の極に対し０．０１Ｖの電圧を１０時間印加して負極の炭素材料にＬｉ⁺ を電気化学的に吸蔵させた。この負極の脱離できるＬｉ⁺ 量は５．６ｍＡｈであった。
【０１１０】
次いで、分極性電極材料を担持した正極とＬｉ⁺ を吸蔵させた負極の間に厚さ１８０μｍのＰＰ製セパレータを挟んで素子とし、この素子にＬｉ⁺ の吸蔵に用いた非水系電解液を含浸し、ＰＰ容器中にＥＤＬＣを組み立てた。
【０１１１】
このＥＤＬＣの電圧の作動範囲は２．０〜４．０Ｖであり、初期の静電容量は３．０ｍＡｈ、比率ｂｖ／３．６ｄは０．５４、内部抵抗は２７Ωであった。また、この素子の正極、セパレータ及び負極を合わせた体積は０．１４８ｃｃであり、エネルギ密度は４０Ｗｈ／リットルであった。このＥＤＬＣに最大充電電流１０ｍＡ／ｃｍ² で３０分間充電し、１ｍＡ／ｃｍ² で定電流放電させる２．０〜４．０Ｖ間における充放電サイクルテストを行った。その結果、５００サイクル後の容量は初期容量の９０％であった。
【０１１２】
［例２７］
例２６において、正極と負極を圧縮するプレス圧を高め、圧縮後の正極及び負極の空隙率をいずれも８％とした。他は例２６と同様にしてＥＤＬＣを組み立てた。正極の単極容量は５．１Ｆであり、このキャパシタの初期の静電容量は４．０Ｆ、電圧の作動範囲２．０〜４．０Ｖにおける容量は２．８ｍＡｈ、比率ｂｖ／３．６ｄは０．６７、内部抵抗は３８Ωであった。例２６と同様に２．０〜４．０Ｖの範囲で充放電サイクル試験を行った結果、５０サイクル後の容量が初期容量の７０％となった。
【０１１３】
［例２８］
活性炭Ｂ６０重量％、ＫＢ３０重量％及びＰＴＦＥ１０重量％の混合物にＥＡを加えて混練し、厚さ０．５ｍｍのシートに成形した。このシートから１ｃｍ×１ｃｍの小シートを２枚切り取った。次に、厚さ２．７ｍｍ、気孔率９０％、平均孔数２０の多孔質アルミニウムのシート（以下、多孔質Ａｌ−Ｂとする）を幅１ｃｍ、長さ７ｃｍに切り取り、片側１ｃｍを除く６ｃｍをプレスで圧縮して厚さが０．４ｍｍのリードとした。多孔質Ａｌ−Ｂのシートの圧縮されていない１ｃｍ×１ｃｍの部分の両側に上記２枚の小シートを置き、プレスで圧縮して多孔質Ａｌ−Ｂのシート中に分極性電極材料を圧入し、１７０℃で乾燥して厚さ０．８ｍｍの正極を得た。
【０１１４】
炭素材料に平均粒径１０μｍ、純度９９．５重量％、面間隔ｄ₀₀₂ が０．３４５ｎｍのノボラック樹脂の焼成品（以下、炭素材料Ｆとする）を使用し、炭素材料Ｆ９０重量％に対してＰＩ１０重量％を含むＮＭＰを媒体とするスラリを作製した。また、多孔質Ｎｉ−Ｄから幅１ｃｍ、長さ７ｃｍのシートを切り取り、片側１ｃｍを除く６ｃｍをプレスで圧縮して厚さが０．２ｍｍのリードとした。多孔質Ｎｉ−Ｄの圧縮されていない１ｃｍ×１ｃｍの部分に上記のスラリを塗布し、２００℃で３０分乾燥後、プレスで厚さ０．３ｍｍの圧縮して空隙率が３５％の負極を得た。
【０１１５】
この負極と１．３ｃｍ×１．３ｃｍで厚さ０．５ｍｍのリチウム板の間にＰＰのセパレータを挟み、これらを１ｍｏｌ／ｌのＬｉＣｌＯ₄ を溶かしたＰＣの非水系電解液に浸した。この状態でリチウム板の極に０．０１Ｖの電圧を１０時間印加し、負極の炭素材料にＬｉ⁺ を吸蔵させた。この負極が離脱しうるＬｉ⁺ 量は８．７ｍＡｈであった。次いで例２６と同様にしてＥＤＬＣを組み立てた。このＥＤＬＣの初期の静電容量は２．７Ｆ、電圧の作動範囲２．０〜４．０Ｖにおける容量は１．６ｍＡｈ、比率ｂｖ／３．６ｄは０．１７、内部抵抗は２２Ωであった。また、素子の体積は０．１２６ｃｍ³ で、エネルギ密度は３６Ｗｈ／リットルであった。
【０１１６】
［例２９］
例２６において正極の作製に使用したスラリを、例２１で用いた多孔質Ｎｉ−Ａのシートに塗布して２００℃で３０分乾燥後、プレスで厚さ０．６ｍｍに圧縮し、２００℃で２時間乾燥したものを直径１２．５ｍｍの円板に打ち抜いた。得られた２枚の分極性電極を、ＳＵＳ３１６Ｌ製ケース及びＳＵＳ３１６Ｌ製蓋にそれぞれ電気溶接した。この両電極の空隙率は３５％、正極の単極容量は３．８Ｆであった。
【０１１７】
両電極の間にＰＰ製セパレータを挟んで素子とし、この素子をＳＵＳ３１６Ｌ製のコイン型ケースに収容し、ケース中に１ｍｏｌ／ｌのＬｉＣｌＯ₄ を溶かしたＰＣの非水系電解液を注入した。次いで、ＰＰ製絶縁ガスケットを用い、ＳＵＳ３１６Ｌ製の蓋で素子と非水系電解液をケース中にかしめ封口した。このコイン型ＥＤＬＣの電圧の作動範囲は０〜２．０Ｖ、初期の静電容量は１．９Ｆ、容量は１．１ｍＡｈ、内部抵抗は１５Ωであった。
【０１１８】
［例３０］
厚さ０．１ｍｍの平滑なニッケル箔を負極の集電体とし、これに例２１で調製した炭素材料Ｂのスラリを塗布して負極とし、他は例２１と同様にしてコイン型ＥＤＬＣを組み立てた。このとき、電極層をニッケル箔の集電体に厚く塗布すると、電極層が集電体から剥離しやすく、集電特性が不安定になるため、電極層の厚さを０．０８ｍｍとした。この負極から離脱しうるＬｉ⁺ 量は３．５ｍＡｈであった。正極の単極容量ｂは６．２Ｆであり、得られたＥＤＬＣの電圧の作動範囲２．０〜３．３Ｖにおける容量は２．２ｍＡｈ、初期の静電容量は４．５Ｆ、ｂｖ／３．６ｄは０．６４、内部抵抗は３３Ωであった。
【０１１９】
［例３１］
例１のＰＶＤＦに代えて正極の結合材にＰＴＦＥ１０重量％を使用し、ＥＡを媒体として混練し、混練物を厚さ１．０ｍｍのシートに成形し、２００℃で３時間乾燥した。このシートを直径１２．５ｍｍの円板に打ち抜いた分極性電極を、導電性接着剤でＳＵＳ３１６Ｌのケースに接着し正極とした。その他は例２１と同様にしてコイン型ＥＤＬＣを組み立てた。この正極の単極容量ｂは６．４Ｆであり、得られたＥＤＬＣの初期容量は４．９Ｆ、電圧の作動範囲２．２〜３．５Ｖにおける容量は２．３ｍＡｈであった。また、負極が脱離しうるＬｉ⁺ 量は１０．３ｍＡｈであり、得られたＥＤＬＣの比率ｂｖ／３．６ｄは０．２２、内部抵抗は４０Ωであった。
【０１２０】
なお、上記各例で使用した多孔質ニッケルは住友電気化学工業社製のもの（商品名セルメット）であり、多孔質アルミニウムは米国エナジーリサーチジェネレーション社製のもの（商品名ＤＵＯＣＥＬ）である。
【０１２１】
上述の例２０〜例３１のＥＤＬＣの試作条件と試験結果を表１０〜１３にまとめて示す。
【０１２２】
【表１０】

【０１２３】
【表１１】

【０１２４】
【表１２】

【０１２５】
【表１３】

【０１２６】
請求項６の実施例である例２１〜２８をその比較例である例２９〜３１（ここで例３１は本発明のＥＤＬＣの実施例であるが、請求項６のＥＤＬＣの比較例である）と比べると、容量、電圧の作動範囲、内部抵抗、充放電サイクル耐久性及びエネルギ密度において、実施例６の構成のＥＤＬＣが顕著に優れることが分かる。
【０１２７】
【発明の効果】
本発明によるＥＤＬＣは、集電体に多孔質金属を使用し、負極にＬｉ⁺ を吸蔵、脱離しうる炭素材料に化学的方法及び／又は電気化学的方法でＬｉ⁺ を吸蔵させた炭素質材料を使用する等の構成を有することによって耐電圧が高く、容量が大きく、内部抵抗が小さい。その結果急速充放電ができ、充放電サイクル耐久性に優れ、従来のＥＤＬＣの２倍以上のエネルギ密度を有するＥＤＬＣとなる。
【０１２８】
また、本発明のＥＤＬＣは、コイン型のような比較的小サイズのものにも有用であるが、静電容量が１００〜１００００Ｆ、又は充放電電流が５〜１０００Ａの超大容量、大電流用途向けのＥＤＬＣに特に好適である。本発明のＥＤＬＣは高い耐電圧を有するので、３Ｖのメモリバックアップの用途には単位素子で対応でき、今後実用化されるはずの電気自動車の動力性能を顕著に向上させるとともに電気自動車等の回生制動エネルギを有効活用できるので、その産業上の利用価値は多大である。
【図面の簡単な説明】
【図１】本発明によるコイン型ＥＤＬＣの一例を示す断面図
【符号の説明】
１：正極
２：導電性接着材（黒鉛系）
３：ＳＵＳ３１６製ケース
４：ＳＵＳ３１６製蓋
５：負極
６：リチウム箔
７：電解液
８：セパレータ
９：絶縁ガスケット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric double layer capacitor (hereinafter referred to as EDLC) having a large energy density, capable of rapid charge / discharge, and excellent charge / discharge cycle durability.
[0002]
[Prior art]
In a conventional EDLC, an element having a separator sandwiched between a pair of opposing electrodes each having a current collector and a sheet-shaped polarizable electrode mainly composed of activated carbon, a metal lid, a metal case, and both together with an electrolyte A coin type sealed in a metal case with an insulating gasket that insulates it, and an element that is wound with a separator between a pair of opposed sheet-like electrodes, together with an electrolyte, is contained in the metal case However, there is a wound type that is sealed so that the electrolyte does not evaporate from the opening of the case.
[0003]
Japanese Patent Laid-Open No. 4-154106, Japanese Patent Laid-Open No. 3-203111, and Japanese Patent Laid-Open No. 4-286108 propose an EDLC in which an element in which a large number of electrodes and separators are stacked is incorporated for the purpose of increasing current and capacity. . That is, separators are arranged between rectangular polarizable electrodes, and a plurality of elements are alternately stacked to form an element, and a positive electrode lead member and a negative electrode lead member are connected to the end of each polarizable electrode of the element by caulking or the like. In which the element is impregnated with an electrolytic solution and sealed with a lid.
[0004]
Conventionally, the electrodes constituting these EDLCs are polarizable electrodes mainly composed of activated carbon in which both the positive electrode and the negative electrode have a large specific surface area. In order to obtain a large discharge current, Japanese Patent Laid-Open No. 6-236829 proposes a method using porous nickel as a current collector for both electrodes mainly composed of activated carbon.
[0005]
Japanese Patent Application Laid-Open No. 64-14882 discloses an electrode mainly composed of activated carbon as a positive electrode and a surface interval d by X-ray diffraction.₀₀₂ (Hereinafter, surface spacing d₀₀₂ Lithium ion (hereinafter referred to as Li) (hereinafter referred to as Li ion).⁺ A secondary battery having a negative electrode made of a composite in which is stored is proposed.
[0006]
[Problems to be solved by the invention]
In the conventional EDLC using polarizable electrodes mainly composed of activated carbon for both electrodes, the withstand voltage per unit element is about 1.0 V in the EDLC of the aqueous electrolyte, although it depends on the choice of the solvent and solute to be combined. An EDLC of an aqueous solvent electrolyte is about 2.5 V, and a higher withstand voltage is desired so that more electric energy can be taken out (so that the energy density is increased).
[0007]
In addition, a polarizable electrode mainly composed of activated carbon is used for the positive electrode, and lithium or Li is used for the negative electrode.⁺ EDLCs and batteries using carbonaceous materials with occluded are not suitable for rapid charge / discharge because of their large internal resistance, and have a drawback of lacking charge / discharge cycle durability.
[0008]
In order to increase the capacity of EDLC, active carbon with a large specific surface area is used to increase the capacity, but the specific surface area of activated carbon is about 3000 m.² Even if activated carbon having a larger specific surface area is used, the energy density is not improved because the pore volume is large. For this reason, the capacity per unit weight of EDLC using activated carbon with a large specific surface area is limited. However, it is desired to increase the capacity to secure a longer backup time.
[0009]
Currently, a small coin-type EDLC is often used for memory backup. By the way, since the IC was conventionally driven at 5V, two or more EDLCs were connected in series to obtain a withstand voltage exceeding 5V. However, recently, ICs have been driven with 3V, and memory backup has been completed with 3V. For this reason, realization of EDLC which has a withstand voltage exceeding 3V by one piece is desired.
[0010]
Further, EDLC that can be charged and discharged with a large current of 10 A or more is promising for applications such as electric vehicle power supply and temporary storage of regenerative braking energy. Therefore, it is desired to realize an EDLC having a sufficiently large energy density, rapid charge / discharge, and excellent charge / discharge cycle durability.
[0011]
[Means for Solving the Problems]
  The present invention has been made to achieve the above-mentioned problems, and an EDLC according to the present invention comprises a polarizable electrode material mainly composed of activated carbon.Made of aluminum or stainless steelA positive electrode comprising a current collector, and a carbonaceous material in which lithium ions are occluded by a chemical method or an electrochemical method in a carbon material that can occlude and desorb lithium ions.,Porous with a porosity of 80% or more that does not form an alloy with lithiumnickelCurrent collector andThe thickness is 0.1 to 1 mm and the porosity is 5 to 80%.And a non-aqueous electrolyte containing a lithium salt.
[0012]
Two types of electrodes are used in the EDLC of the present invention, and ions to be adsorbed or occluded are different. That is, Li⁺ Li is a carbon material that can absorb and desorb Li⁺ An electrode mainly composed of a carbonaceous material occluded is Li⁺ This is the negative electrode. In addition, a polarizable electrode mainly composed of activated carbon can accumulate an electric charge by forming an electric double layer on the activated carbon surface by an anion and optionally a cation, and this is the positive electrode.
[0013]
In order to make full use of the characteristics of the positive electrode and the negative electrode, a non-aqueous solvent having a high decomposition voltage is used for the electrolytic solution used in the EDLC of the present invention. The electrolyte in the electrolyte solution has a cation of Li⁺ Is limited to lithium salt. This lithium salt includes LiClO._Four , LiCF_Three SO_Three , LiBF_Four , LiPF₆ , LiAsF₆ , LiSbF₆ , LiCF_Three CO₂ And LiN (CF_Three SO₂ )₂ Can be used. Of these, LiClO_Four , LiBF_Four , LiN (CF_Three SO₂ )₂ And LiPF₆ Is a particularly preferred lithium salt in terms of high stability and good electrical conductivity.
[0014]
Nonaqueous electrolyte solvents include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, dimethyl sulfoxide, sulfolane, formamide, dimethylformamide, dioxolane, phosphate triester, maleic anhydride, succinic anhydride, phthalic anhydride 1,3-propane sultone, propylene carbonate derivative, ethylene carbonate derivative, 4,5-dihydropyran derivative, nitrobenzene, 1,3-dioxane, 1,4-dioxane, 3-methyl-2-oxazolidinone, 1,2- Dimethoxyethane, tetrahydrofuran, tetrahydrofuran derivative, sydnone derivative, 2-methyltetrahydrofuran, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile Nitromethane, alkoxy ethane, nonaqueous solvent consisting of one or more selected from dimethylacetamide and toluene can be used.
[0015]
Among these, a non-aqueous solvent composed of one or more selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, sulfolane, and dimethoxyethane is chemically and electrochemically stable. Is particularly preferable from the viewpoint of high electrical conductivity and low temperature characteristics.
[0016]
The positive electrode of the polarizable electrode mainly composed of activated carbon of EDLC of the present invention contains a conductive material for improving electron conductivity in addition to activated carbon. Polarizable electrodes for this application can be formed by various methods. For example, when activated carbon, carbon black (conductive material), and a phenolic resin are mixed and fired and activated in an inert gas atmosphere and a water vapor atmosphere after press molding, a polarizable electrode composed only of activated carbon and carbon black is obtained. Next, this polarizable electrode is joined to a current collector such as a stainless steel plate by conductive adhesion or the like. In the case of a coin-type EDLC, it is preferable to use a case or lid made of a stainless steel plate or the like as a current collector or terminal.
[0017]
In addition, the polarizable electrode sheet obtained by adding alcohol to the activated carbon powder, carbon black (conductive material) and binder, kneading, forming into a sheet and drying, is then cut into the required dimensions, There is also a method of forming a positive electrode by bonding to a current collector with a conductive adhesive or the like. For this binder, polytetrafluoroethylene (hereinafter referred to as PTFE) is preferably used.
[0018]
Also, the activated carbon powder, carbon black and binder are mixed with a solvent to form a slurry, and this slurry is applied onto a metal foil as a current collector, and the coating layer is dried to form a positive electrode integrated with the current collector. There is a way. The current collector may be a conductor that is electrochemically and chemically corrosion resistant. A plate or foil of stainless steel, aluminum, titanium, tantalum or the like can be used for the positive electrode current collector. Of these, stainless steel or aluminum plates and foils are preferred current collectors in terms of both performance and cost. Nickel is easily oxidized, and when used as a positive electrode current collector, the withstand voltage of EDLC tends to decrease. The polarizable electrode and the current collector are electrically joined with a conductive adhesive or the like to form a positive electrode.
[0019]
Examples of the activated carbon that can be used for the positive electrode include ashigara activated carbon, phenol resin activated carbon, and petroleum coke activated carbon. Among these, since large-capacity EDLC is obtained, it is preferable to use phenol resin activated carbon or petroleum coke activated carbon. In addition, activated carbon activation treatment methods include a steam activation treatment method and a molten KOH activation treatment. Among these activation treatment methods, it is particularly preferable to use activated carbon obtained by a molten KOH activation treatment method because a large-capacity EDLC can be obtained.
[0020]
Examples of the conductive material mixed with the positive electrode include carbon black, natural graphite, artificial graphite, metal fiber, titanium oxide, and ruthenium oxide. It is preferable to use ketjen black or acetylene black, which is a kind of carbon black, which has a large mixing effect even in a small amount. If the amount of the conductive material is too large, the capacity of the positive electrode decreases. Therefore, the amount of the conductive material in the positive electrode is 3 to 50% of the total amount with the activated carbon so that good conductivity and large capacity can be secured at the same time. %, Particularly 5 to 30% by weight. The activated carbon preferably has an average particle size of 20 μm or less and a specific surface area of 1000 to 3000 m.² / G is used. As a result, the capacity of the EDLC can be increased and the internal resistance can be reduced.
[0021]
  Li⁺Li is a carbon material that can absorb and desorb Li⁺A negative electrode that combines a carbonaceous material occluded with a current collector is, for example, Li⁺It is comprised from the carbon material which can occlude, a binder, and a collector. In the EDLC of the present invention, the current collector of the carbonaceous material of the negative electrode is integrated using porous nickel, thereby reducing the internal resistance and enabling rapid charge / discharge with a large current. The material for the porous metal of the negative electrode may be any material that does not form an alloy with lithium and is stable under the use conditions on the negative electrode side, and preferably has a porosity of 80 to 99.5% nickel, copper, or an alloy thereof. Is usedHowever, in the present invention, porous nickel is used..
[0022]
In the preferred EDLC of the present invention, the negative electrode is made of a porous metal having a porosity of 80% or more, particularly a porosity of 90% or more as a current collector.⁺ Is supported by a mixture of a carbon material and a binder that can be occluded and desorbed, and compressed to a thickness of 0.1 to 1 mm and a porosity of 5 to 80%.⁺ Is made into a carbonaceous material. It is extremely effective to improve the performance of EDLC by compressing the negative electrode and controlling its porosity to a moderately small value. The porosity is preferably 5 to 80%. When the porosity is less than 5%, the electrolyte does not easily enter the electrode, and part of the electrode material in the negative electrode does not work. When the porosity is more than 80%, the negative electrode becomes bulky with respect to the capacity, which is not preferable. The porosity is particularly preferably 10 to 60%.
[0023]
The thickness of the negative electrode is preferably 0.1 to 1 mm, particularly preferably 0.2 to 0.7 mm. The binder serves to bind the particles of the electrode material to each other and keep the electrical contact between the particles of the electrode material from being loosened by the charge / discharge cycle. In particular, when a porous metal is used for the current collector, the porous metal current collector and the binder cooperate to make electrical contact between the electrode material particles and between the electrode material particles and the current collector. It works to keep it from loosening.
[0024]
In a preferred EDLC of the present invention, the porous metal used for the negative electrode is porous nickel having a porosity of 80 to 99%, and the average number of pores crossed by a 1 cm long straight line drawn in the cross section (hereinafter simply referred to as average) The number of holes) is 5 or more. The porous metal is preferably used in the form of a sheet having a thickness of 0.3 to 3 mm so that a negative electrode having an appropriate thickness and porosity can be easily formed. In particular, it is preferable to use porous nickel having a porosity of 90 to 99% and an average number of pores of 5 or more.
[0025]
To measure this average number of holes, bury the porous metal in the resin, cure the resin, count the average number of holes crossed by the straight line drawn on the cut surface, and divide that number by the length of the line. Good. Porous nickel is stable under the conditions of the negative electrode, and a good current collecting property can be ensured by containing a carbonaceous material in the pores. More preferably, the negative electrode integrated with the porous nickel is compressed by a press or the like to reduce excess voids in the negative electrode, and impregnated with a sufficient amount of electrolyte as necessary.
[0026]
In order to manufacture the negative electrode, preferably, a slurry obtained by adding a solvent to a carbon material and kneading into a sponge-like porous metal is injected into the pores by coating or the like, and the negative electrode material and the current collector are integrated. To do. It is preferable to use a porous metal having an average number of pores of 5 to 50 so as to ensure good current collection. Next, it is preferable to adjust the porosity of the negative electrode by compressing the sheet injected with the slurry after drying. The binder added to the slurry is any one of polyvinylidene fluoride, fluoroolefin / olefin copolymer crosslinked polymer, fluoroolefin / vinyl ether copolymer crosslinked polymer, carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohol, and polyacrylic acid. Is preferably used.
[0027]
It is preferable to use a solvent that dissolves these binders as the slurry solvent. N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, dimethyl phthalate, ethanol, methanol, Butanol, water and the like are appropriately selected. In addition, amines, polyamines, polyisocyanates, bisphenols, and peroxides can be used for crosslinking of the crosslinked polymer. These binders and solvents can be preferably used in the production of a slurry of a polarizable electrode material that is a positive electrode.
[0028]
Li, the main component of the carbonaceous material of the negative electrode⁺ Carbon materials that can occlude and desorb carbon include graphite-based materials such as natural graphite, artificial graphite, graphitized mesocarbon spherules, graphite whiskers, graphitized carbon fiber, vapor-grown carbon fiber, coal coke, petroleum coke, pitch High-capacity carbon materials such as graphitizable carbon materials obtained by heat-treating coke, etc., calcined products of furfuryl alcohol resin, calcined products of novolac resin, and calcined products of phenol resin can be preferably used. Of these, Li⁺ Of natural graphite, artificial graphite, graphitized mesocarbon spherules, fired furfuryl alcohol resin, fired phenol resin, fired novolak resin, heat treated coal coke or pitch coke It is particularly preferable to use a heat-treated product.
[0029]
It is preferable to use natural graphite having a developed crystal structure and few impurities. Here, the natural graphite having a developed crystal structure is the surface spacing d.₀₀₂ Is less than 0.336 nm and the crystallite size L_C Means 150 nm or more. Natural graphite with a developed crystal structure is Li⁺ The ability to occlude and desorb is great. In addition, if natural graphite with few impurities is used, excellent charge / discharge cycle durability can be secured.
[0030]
In order to reduce impurities in natural graphite, acid treatment with nitric acid, sulfuric acid, hydrofluoric acid, etc. is performed, but since the ash is effectively removed, the purity of the carbon finally subjected to hydrofluoric acid treatment is 99% by weight or more. It is preferable to use natural graphite.
[0031]
It is preferable to use artificial graphite having a developed crystal structure and a small amount of impurities. Here, the artificial graphite having a developed crystal structure is the d₀₀₂ Is 0.3365 nm or less, and the L_C Means 50 nm or more. Since artificial graphite can be obtained in high purity by selecting a starting material, it is preferable to use carbon having a purity of 99.5% by weight or more.
[0032]
As the graphitized mesocarbon microspheres, it is preferable to use a graphitized mesocarbon spherule with a low impurity content in which the crystal structure of graphite heat-treated at a high temperature of 2500 ° C. or higher is developed. Here, the developed crystal structure means the above d.₀₀₂ Is 0.337 nm or less, and the L_C Means 20 nm or more.
[0033]
As the graphitized whisker, it is preferable to use a graphitized whisker having a less developed impurity. Here, the crystal structure developed means that the above d.₀₀₂ Is 0.3365 nm or less, and the L_C Means 10 nm or more.
[0034]
As the graphitized carbon fiber, it is preferable to use a graphitized carbon fiber that has developed a crystal structure of graphite obtained by heat-treating a fiber such as acrylonitrile resin at a temperature of 2500 ° C. or higher. Here, the developed crystal structure means the above d.₀₀₂ Is 0.3365 nm or less, and the L_C Means 10 nm or more.
[0035]
As the furfuryl alcohol resin fired product, it is preferable to use a furfuryl alcohol resin that is a heat-treated furfuryl alcohol resin at 1000 to 1500 ° C. and has few impurities. Also, after heat treatment, d₀₀₂ It is preferable to use one having a thickness of 0.375 to 0.39 nm.
[0036]
The novolak resin fired product has an H / C atomic ratio of 0.25 to 0.28 obtained by heat-treating the novolak resin at a temperature of 700 ° C. or less, and the d₀₀₂ Is preferably 0.38 nm or more.
[0037]
The phenol resin fired product is obtained by heat-treating a phenol resin.₀₀₂ Is preferably 0.365 to 0.390 nm.
[0038]
Examples of the graphitizable carbon material include carbon materials obtained by heat treating cokes such as coal coke, petroleum coke, and pitch coke. Among these, it is preferable to use one having a high carbon purity or one having a high carbon purity after treatment for removing impurities. When these cokes are heat-treated at 800-1500 ° C., the surface separation d₀₀₂ Li of 0.340 to 0.355 nm⁺ It becomes a carbon material that can occlude.
[0039]
Among these carbon materials, the surface spacing d₀₀₂ It is particularly preferable to use a carbon material having a thickness of 0.365 to 0.390 nm for the negative electrode because the charge / discharge cycle durability of EDLC is improved. The carbon material powder used for the negative electrode is preferably one having an average particle size of 30 μm or less because the EDLC capacity can be increased and the internal resistance can be reduced. However, since too fine powder is bulky, it is preferable to use an average particle size of 2 μm or more.
[0040]
If the amount of the binder compounded in the electrode is less than 1% by weight, the strength of the electrode is small, and if it exceeds 20% by weight, the electric resistance of the EDLC increases and the capacity decreases. The content is preferably 1 to 20% by weight. Considering the balance between capacity and strength, a more preferable binder content is 3 to 12% by weight.
[0041]
Li⁺ Li in carbon materials that can occlude and release⁺ There are the following methods for storing occlusion. First, powdered lithium is Li⁺ In a molded body mixed with carbon material powder that can occlude and desorb, electrolyte is injected, lithium is ionized, and Li⁺ There is a chemical method in which carbon is incorporated into a carbon material that can occlude and desorb. Next, Li⁺ Lithium is ionized by immersing it in an electrolyte solution in a state where foil-like lithium is in contact with a molded body composed of a carbon material and a binder that can occlude and desorb lithium.⁺ There is a chemical method in which carbon is incorporated into a carbon material that can occlude and desorb.
[0042]
In addition, in one side of an electrolyte solution of a non-aqueous solvent using a lithium salt as an electrolyte, Li⁺ Place a formed body composed of a carbon material and a binder that can occlude and desorb, and place a lithium electrode plate on the other side to pass an electric current.⁺ There is an electrochemical method for storing occlusion. Of these methods, the operation is simple, so Li⁺ A chemical method is adopted in which lithium is ionized by immersion in an electrolytic solution in a state where foil-like lithium is in contact with a molded body composed of a carbon material and a binder that can occlude and desorb lithium, and is incorporated into the carbon material. Is particularly preferred.
[0043]
In another preferred EDLC of the present invention, the current collector used for the positive electrode is a porous metal. With this configuration, the internal resistance of the positive electrode of the EDLC can be reduced by balancing with the internal resistance of the negative electrode. Therefore, the internal resistance of the entire EDLC can be further reduced, and rapid charging / discharging becomes possible. At the same time, the charge / discharge cycle durability is also improved. The polarizable electrode of the positive electrode preferably contains a conductive material such as carbon black and a binder that improve the conductivity.
[0044]
The positive electrode is preferably produced as follows. That is, a solvent is mixed with activated carbon powder, carbon black, and a binder to form a slurry. Next, this slurry is applied or impregnated into a sheet-like porous metal and dried to obtain a sheet-like electrode integrated with the current collector. After cutting the sheet-like electrode to a required size, it is preferably bonded by a conductive adhesive or welded by electric welding or the like and electrically connected to the terminal or the lid or case of the metal container.
[0045]
The porous metal material used for the current collector of the positive electrode may be any material that is electrochemically and chemically corrosion resistant. Preferred porous metal materials include nickel, aluminum, titanium, tantalum or alloys thereof. Porous nickel has a slightly lower withstand voltage when used as a current collector for a positive electrode, but it can form a fine porous structure, so that a good current collecting property can be obtained and a preferred current collector that can be obtained relatively inexpensively. Is the body. A porous metal such as aluminum, titanium, or tantalum is a preferred current collector in terms of high withstand voltage. In particular, porous aluminum is a preferred current collector because it is available at low cost.
[0046]
  ManyPorous aluminum contains a polarizable electrode material made of activated carbon, a conductive material, and a binder in its pores, imparts good current collection to the positive electrode, and reduces the internal resistance of the positive electrode. For example, a sponge-like sheet-like porous metal having a three-dimensional structure becomes a positive electrode integrated with a current collector when a slurry of polarizable electrode material is injected into the pores and dried. When injecting by coating, the application and drying operations may be repeated until a required amount of polarizable electrode material can be supported.
[0047]
Another preferred method of filling the polar electrode material into the pores is a press-fitting method in which the process is completed in one operation. That is, activated carbon powder, a conductive material, and PTFE are added with ethanol and kneaded to form a sheet. When this sheet is placed on a sheet-like porous metal or pressed with the sheet-like porous metal sandwiched between the sheets, a positive electrode in which the sheet-like porous metal and the polarizable electrode material are integrated is obtained. The thickness of the press-fitted sheet is preferably 0.1 to 1.5 mm, particularly 0.15 to 1.0 mm.
[0048]
Another preferred EDLC of the present invention is a porous metal having a porosity of 80% or more and a specific surface area of 1000 to 3000 m.² / G of activated carbon, conductive carbon black, and a polarizable electrode material composed of a binder, and then compressed to have a positive electrode having a thickness of 0.2 to 2.0 mm and a porosity of 10 to 80%.
[0049]
The porous metal used for the positive electrode is preferably a sheet-like porous metal having a thickness of 0.3 to 5 mm so that slurry can be easily injected and a positive electrode having an appropriate thickness can be easily obtained. In particular, it is preferable to use a porous metal having a porosity of 85 to 99% and an average number of pores of 5 or more. It is preferable to use a porous metal having an average number of pores of 5 to 50 so that slurry can be easily injected and good current collecting characteristics can be obtained.
[0050]
  In another preferred EDLC of the present invention, porous aluminum used in the positive electrode has a porosity of 80 to 99%.InYes, the average number of holes is 5 or more. In an electrode combined with porous aluminum, aluminum may be sprayed on the surface not facing the electrode, and then welded to a lid or case made of aluminum to be electrically joined. As a welding method, it is particularly preferable to use an electric welding method that can be applied to both the positive electrode and the negative electrode because the process is simple and the electrical connection is reliable.
[0051]
The positive electrode integrated with the porous metal current collector is preferably compressed with a roll or the like to reduce the porosity, and the positive electrode porosity is preferably adjusted to a sufficiently small value. If the porosity of the positive electrode is adjusted to a moderately small value, the internal resistance of the EDLC is lowered and the energy density is further improved. The porosity of the positive electrode is preferably 10 to 80%. When the porosity is less than 10%, the non-aqueous electrolyte does not easily enter the positive electrode, and the internal electrode does not work sufficiently. Further, when the porosity of the positive electrode is more than 80%, the positive electrode is bulky and the capacity per volume of the positive electrode is reduced. The porosity of the positive electrode is more preferably 15 to 60%. For the same reason, the thickness of the positive electrode is preferably 0.1 to 3 mm, more preferably 0.2 to 2 mm.
[0052]
Another preferred EDLC of the present invention is a case in which a positive electrode negative electrode and a non-aqueous electrolyte are accommodated in a metal coin-shaped container made of a case and a lid, and the positive electrode is made of a stainless steel plate or a laminate of aluminum and stainless steel. And the negative electrode on the other side of the lid and case made of two or more laminated plates selected from stainless steel plate, nickel plate, copper plate or stainless steel, nickel and copper Do it.
[0053]
In the coin-type EDLC, it is preferable to electrically connect an electrode in which a carbon material or a polarizable material is supported on a porous metal to a lid or case of a stainless steel plate, a nickel plate, or an aluminum plate by a conductive adhesive or welding. . If the coin-type EDLC container has such a configuration, the lid and case of the coin-type container function as a stable terminal for a long period of time, and the electrical connection between the current collector and the product is stable, and the product is stable. Performance.
[0054]
In another preferred EDLC of the present invention, a single electrode capacity of a polarizable electrode that is a positive electrode is b (unit: F), and Li⁺ When the separation capacity is d (unit: mAh) and the potential difference in the voltage operating range is v (unit: V), the ratio bv / 3.6d is in the range of 0.05 to 0.90. The value of this ratio bv / 3.6d affects the rapid charge / discharge characteristics and charge / discharge cycle durability of EDLC. Therefore, it is preferable to set the value of this ratio within the above range. Here, the single electrode capacity b of the positive electrode is obtained from a voltage decrease gradient when a pair of positive electrodes having the same configuration is opposed to each other with a separator interposed therebetween and a DC voltage is applied and then discharged at a constant current in the electrolyte. .
[0055]
The operating range of the voltage of the EDLC according to the present invention can be set, for example, to 2.0-3.3V, 2.0-4.0V, 3.3V-4.5V. The voltage operating range is preferably selected in consideration of the durability of the EDLC with less deterioration.
[0056]
The upper limit of the voltage operating range is V₁ And the lower limit is V₂ When the amount of current that can be taken out in this operating range is Q (unit: mAh), the capacity C is C = 3.6 · Q / (V₁ -V₂ ). In addition, when the volume of the EDLC is T (T may be a volume including the storage container or a volume of only an element in which a separator is combined with both electrodes), the energy density E of the EDLC._D Is E_D = C (V₁ ²-V₂ ²) / 2T.
[0057]
Li desorbable from the negative electrode⁺ The quantity d is Li⁺ A negative electrode in which a carbon material is occluded by a chemical method or an electrochemical method,⁺ 1mA / cm up to + 1.0V at / Li electrode reference potential² This corresponds to an integrated electric quantity (mAh) when the battery is discharged at a current density of, that is, separated. Accordingly, the ratio bv / 3.6d varies depending on the operating range of the capacitor voltage to be set even if the EDLC configuration is the same.
[0058]
When the ratio bv / 3.6d is less than 0.05, the energy density of the EDLC becomes small. On the other hand, if the ratio bv / 3.6d is more than 0.90, the initial energy density increases, but rapid charge / discharge becomes difficult, and the charge / discharge cycle durability decreases. In consideration of energy density, rapid charge / discharge characteristics, and charge / discharge cycle durability, the ratio bv / 3.6d is particularly preferably 0.1 to 0.8. In the present invention, the internal resistance of the EDLC is 10 mA / cm current density.² It is obtained from the voltage drop immediately after the start of discharge when constant current discharge is performed.
[0059]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these.
[0060]
[Example 1]
The positive electrode was produced as follows. That is, petroleum coke-based molten KOH activated activated carbon powder (specific surface area 2000 m² / G, average particle size 5 μm, hereinafter referred to as activated carbon A) 80% by weight, ketjen black-EC (conductive carbon black manufactured by Mitsubishi Chemical, hereinafter referred to as KB) 10% by weight, PTFE 10% by weight Ethanol (hereinafter referred to as EA) was added to the mixture, kneaded, and roll-rolled to obtain a sheet having a width of 10 cm, a length of 10 cm, and a thickness of 0.5 mm, and dried at 200 ° C. for 2 hours.
[0061]
In the coin-type EDLC shown in FIG. 1, a polarizable electrode 1 obtained by punching this sheet into a disk having a diameter of 12.5 mm is made of a stainless steel 316L case with a graphite-based conductive adhesive (hereinafter referred to as a conductive adhesive) 2. 3 is adhered to the inside of the electrode 3 as a positive electrode. The single electrode capacity b of this positive electrode was 3.66 F, that is, the capacity per 2 V was 2.0 mAh.
[0062]
Next, the negative electrode was produced as follows. That is, natural graphite powder (purity 99.3%, the d₀₀₂ = 0.3355 nm, L_C = 200 nm or more, average particle size 10 μm, hereinafter referred to as carbon material A) 90% by weight, polyvinylidene fluoride (hereinafter referred to as PVDF) 10% by weight, N-methylpyrrolidone (hereinafter referred to as NMP) Three times the weight ratio was added and stirred and mixed while applying ultrasonic waves to obtain a slurry in which the carbon material A was dispersed in the PVDF NMP solution. This slurry is 2.0 mm thick, has a porosity of 97%, and has a basis weight of 550 g / m.² The film was applied to a porous nickel sheet having an average number of pores of 25 (hereinafter referred to as porous Ni-A), dried at 200 ° C. for 30 minutes, and then compressed to a thickness of 0.5 mm with a roll to obtain a diameter of 12 A negative electrode was punched into a 5 mm disc.
[0063]
The porosity of the compressed negative electrode is 35%, and the amount of the carbon material A supported on the negative electrode is 36 mg / cm.² Met. As shown in FIG. 1, this negative electrode was adhered to the SUS304 lid 4 with a graphite-based conductive adhesive (hereinafter referred to as conductive adhesive) 2 and dried at 190 ° C. for 1 hour.
[0064]
The positive electrode using the lid 4 on the negative electrode 5 side and the case 3 made of SUS316L as a current collector was further dried at 200 ° C. under reduced pressure for 4 hours. These were transferred to a glove box in an argon atmosphere, and a lithium metal foil 6 having a diameter of 10 mm and a thickness of 0.1 mm was pressure bonded to the negative electrode 5. An element is formed by sandwiching a polypropylene (hereinafter referred to as PP) separator 8 between the two electrodes to face each other, and a 1.2 mol / l LiPF.₆ An electrolysis solution 7 having a volume ratio of 1: 1 of ethylene carbonate (hereinafter referred to as EC) and diethyl carbonate (hereinafter referred to as DEC) in which was dissolved was injected into the container and impregnated into the device.
[0065]
Subsequently, the PP insulating gasket 9 was used, and the element and the electrolyte were caulked and sealed in a container. The outer dimensions of the obtained coin-type EDLC are 18.3 mm in diameter and 2.0 mm in thickness. The coin-type EDLC was placed in a constant temperature bath at 70 ° C. and left for 16 hours. The lithium foil that has been pressure-bonded to the electrode 5 by this heating operation is chemically taken into the electrode 5 in an ionized state. Li can be removed from this negative electrode⁺ The quantity d was 12 mAh and the ratio bv / 3.6d was 0.17.
[0066]
[Example 2]
In Example 1, instead of the carbon material A, artificial graphite powder (purity 99.9%, the d₀₀₂ = 0.3365 nm, L_C = 50 nm or more, average particle size 7 μm, hereinafter referred to as carbon material B) is used for the negative electrode, and the positive electrode side is a case in which aluminum is laminated on the inner side of the SUS304 plate, and the negative electrode side lid is nickel plated on the inner side. A coin-type EDLC was assembled in the same manner as in Example 1 except that was used. Li which can be detached from the negative electrode of this EDLC⁺ The amount was 3.0 mAh and the ratio bv / 3.6d was 0.67.
[0067]
[Example 3]
In Example 1, instead of natural graphite powder, graphitized mesocarbon microspheres (purity 99.6%, d₀₀₂ = 0.3480 nm, L_C = 2 nm or more, average particle diameter of 13 μm, hereinafter referred to as carbon material C) was used for the negative electrode, and the others were assembled in the same manner as in Example 1 to assemble a coin type EDLC. The amount of carbon material B supported on the negative electrode is 29 mg / cm² Li, from which this negative electrode can be detached⁺ The amount was 8 mAh. The ratio bv / 3.6d of this EDLC was 0.25.
[0068]
[Example 4]
In Example 1, instead of carbon material A, a calcined product of petroleum coke which is a graphitizable carbon material (calcination temperature 1400 ° C., purity 99.9%, d₀₀₂ = 3.452, L_C = 2 nm or more, average particle diameter 5 μm, hereinafter referred to as carbon material D), and 1 mol / l LiClO in the electrolyte_Four A coin-type EDLC was assembled in the same manner as in Example 1 except that was used in which propylene carbonate was dissolved in propylene carbonate (hereinafter referred to as PC). The amount of carbon material D supported on the negative electrode is 20 mg / cm² Li, from which this negative electrode can be detached⁺ The amount was 2.7 mAh. The EDLC ratio bv / 3.6d was 0.74.
[0069]
[Example 5]
In Example 1, the thickness of the porous metal is 2.0 mm, the porosity is 98%, and the basis weight is 370 g / m.² Then, a sheet-like porous nickel having an average number of pores of 20 (hereinafter referred to as porous Ni-B) was used. A slurry was supported on the porous Ni-B, dried, and then compressed to a thickness of 0.3 mm by a roll press. Other than that, a coin-type EDLC was assembled in the same manner as in Example 1. The porosity of the negative electrode after compression is 39%, and the amount of carbon material A supported on the negative electrode is 25 mg / cm² Thus, this negative electrode can be detached from Li⁺ The amount was 10.6 mAh. The EDLC ratio bv / 3.6d was 0.19.
[0070]
[Example 6]
A sheet of the same polarizable electrode as prepared in Example 1 was cut into 1 cm × 1 cm, and bonded to the tip of an aluminum foil having a width of 1 cm, a length of 8 cm, and a thickness of 45 μm with a conductive adhesive to obtain a positive electrode. Next, the slurry of the carbon material A produced in Example 1 was prepared with a porosity of 97%, a thickness of 1.4 mm, an average number of holes of 25, and a basis weight of 370 g / m.² Was applied to a sheet of porous nickel (hereinafter referred to as porous Ni-C), dried and then compressed to a thickness of 0.3 mm. Next, the end of a nickel foil having a thickness of 20 μm, a width of 1 cm, and a length of 7 cm was electrically welded to the negative electrode cut to 1 cm × 1 cm to obtain a lead.
[0071]
A PP separator is sandwiched between the negative electrode and a lithium plate of 1.3 cm × 1.3 cm and a thickness of 0.5 mm, and 1 mol / l LiPF₆ The sample was immersed in an electrolyte having a volume ratio of EC and DEC of 1: 1. Next, a voltage of 0 (zero) V was applied to the electrode of the lithium plate for 10 hours to apply Li to the negative electrode.⁺ Was occluded electrochemically. Li from which this negative electrode can be desorbed⁺ The amount was 10.3 mAh.
[0072]
Next, the positive electrode and Li⁺ A PP separator having a thickness of 180 μm was sandwiched between the negative electrodes that occluded the element to obtain an element. This element is electrochemical Li⁺ The EDLC was assembled in a glass container by immersing it in an electrolytic solution having the same composition as that used for occlusion of the ash. The single electrode capacity b of this positive electrode was 3.24F, that is, 1.8 mAh per 2V. The EDLC ratio bv / 3.6d is 0.17, and the volume of the element, that is, the total volume of the positive electrode, the separator, and the negative electrode is 0.1025 cm.^Three The energy density was 50 Wh / l.
[0073]
[Example 7]
In Example 6, the pressure for roll-rolling the negative electrode was increased, the thickness of the negative electrode was 0.18 mm, and the porosity of the negative electrode was 3%. Otherwise, an element was fabricated in the same manner as in Example 6, and an EDLC was assembled. Li can be removed from this negative electrode⁺ The amount was 6.5 mAh and the EDLC ratio bv / 3.6d obtained was 0.28. Further, the volume of the element was 0.0905 cc, and the energy density was 57 Wh / l.
[0074]
[Example 8]
The pressure for roll rolling the negative electrode was increased, the thickness of the negative electrode was 0.20 mm, and the porosity of the negative electrode was 10%. Otherwise, an element was fabricated in the same manner as in Example 6, and an EDLC was assembled. Li can be removed from this negative electrode⁺ The amount was 8.5 mAh, and the EDLC ratio bv / 3.6d obtained was 0.28. The volume of the element was 0.0925 cc, and the energy density was 56 Wh / l.
[0075]
[Example 9]
The same polarizable electrode as the positive electrode of Example 1 was used for both the positive electrode and the negative electrode, and each electrode was adhered to a SUS316 case and a SUS316 lid with a conductive adhesive. A device in which both electrodes are opposed to each other with a PP separator interposed therebetween was impregnated with an electrolytic solution of PC containing 1 mol / l tetraethylammonium tetrafluoroborate (hereinafter referred to as TEATFB). Next, it was caulked and sealed in a coin-type container using a PP insulating gasket. The obtained coin-type EDLC had a diameter of 18.3 mm and a thickness of 2.0 mm.
[0076]
[Example 10]
In Example 1, a coin-type EDLC was assembled in the same manner as in Example 1 except that a lithium foil having a diameter of 8 mm and a thickness of 0.1 mm was not pressure-bonded to the negative electrode adhered to the lid, and heating was not performed in a thermostatic bath.
[0077]
[Example 11]
Instead of using porous Ni-A as the current collector of the negative electrode, a slurry made of carbon material A, PVDF and NMP as a solvent was applied to the inside of a SUS316L lid, and dried at 200 ° C. for 30 minutes to obtain a negative electrode. Other than that, a coin-type EDLC was assembled in the same manner as in Example 1. The single electrode capacity of this positive electrode was 2.0 mAh. Li can be removed from this negative electrode⁺ The amount was 1.8 mAh and the ratio bv / 3.6d obtained was 1.1.
[0078]
[Example 12]
The sheet of polarizable electrode produced in Example 1 was cut into 1 cm × 1 cm, and joined to the tip of an aluminum foil having a width of 1 cm, a length of 8 cm, and a thickness of 45 μm with a conductive adhesive to obtain a pair of polarizable electrodes. A PP separator was sandwiched between the pair of polarizable electrodes to form an element, and both electrodes were impregnated with an electrolytic solution of PC containing 1 mol / l TEATFB, and an EDLC was assembled in a glass container. The volume of this EDLC element was 0.127 cc, and its energy density was 10 Wh / l.
[0079]
[Example 13]
An EDLC element was assembled in the same manner as in Example 6 except that porous Ni—C was not used for the current collector of the negative electrode, a nickel foil having a thickness of 20 μm, a width of 1 cm, and a length of 1 cm was used. The amount of carbon material A supported on this negative electrode is 5.5 mg / cm.² The single electrode capacity of the positive electrode was 1.8 mAh. Li can be removed from this negative electrode⁺ The amount was 1.8 mAh, and the EDLC ratio bv / 3.6d obtained was 1.0. The volume of the element was 0.0795 cc, and the energy density was as high as 59 Wh / l. However, the charge / discharge cycle durability and the charge rate were unsatisfactory.
[0080]
[Example 14]
The activated carbon powder used in Example 1, KB of the conductive material, and PVDF of the binder were mixed at a weight ratio of 45:45:10, pulverized and mixed with NMP to obtain a slurry of the activated carbon powder. Next, this slurry was applied evenly to a porous Ni—C sheet, and dried at 200 ° C. for 10 hours. This sheet was compressed to a thickness of 0.175 mm with a rolling roller. A lead terminal was attached to a pair of polarizable electrodes obtained by cutting the compressed sheet into 1 cm × 1 cm, and a PP separator was sandwiched between the two electrodes to form an element. Next, this element was inserted into a glass container containing a PC electrolyte solution containing 1 mol / l TEATFB to assemble an EDLC. The volume of this element was 0.053 cc, and the energy density was 6 Wh / l.
[0081]
The trial production conditions of the EDLC of Examples 1 to 14 are summarized in Tables 1 to 6.
[0082]
[Table 1]

[0083]
[Table 2]

[0084]
[Table 3]

[0085]
[Table 4]

[0086]
[Table 5]

[0087]
[Table 6]

[0088]
Next, the charging current density is maximum 2 mA / cm for the EDLCs of Examples 1 to 8 which are Examples and Examples 9 to 14 which are Comparative Examples.² As for 2 hours charging, constant current discharge 1mA / cm² I went there. Table 7 summarizes the results obtained for the initial capacity of each EDLC, the selected charging voltage, and the operating range of the voltage. Comparing Examples 1 to 5 in Table 7 with Examples 9 to 11 and Examples 6 to 8 with Examples 12 and 14, it can be seen that the EDLC of the present invention is remarkably superior in the initial capacity and operating voltage range.
[0089]
Next, for the EDLCs of Examples 6-8 and Example 13, 10 mA / cm at an operating range of 2.0-3.3V.² The charging achievement rate (%) was measured when charging was performed for 30 minutes with the maximum current as 30 and the charging amount for 30 minutes was defined as 100. From the results in Table 8, it can be seen that the EDLC of the present invention is excellent in the charge rate. Also, for the EDLCs of Examples 6-8 and Example 13, at an operating range of 2.0-3.3 V, 10 mA / cm² Is the maximum charging current and the constant current discharging current is 1 mA / cm.² As shown in Table 9, the charge / discharge cycle test was performed, and the measurement results of the capacity change are shown in Table 9. From Table 9, it can be seen that the EDLC of the present invention is excellent in charge / discharge cycle durability.
[0090]
[Table 7]

[0091]
[Table 8]

[0092]
[Table 9]

[0093]
From the results shown in Tables 7 to 9, it can be seen that EDCL according to the present invention has a high withstand voltage, a large capacity, rapid charge / discharge, and remarkably excellent charge / discharge cycle durability.
[0094]
[Example 21]
Phenol resin-based molten KOH activated activated carbon powder (specific surface area 2100 m² / G, average particle size of about 5 μm, hereinafter referred to as activated carbon B) A slurry of 73 wt%, KB 17 wt%, and PVDF 10 wt% added with NMP and mixed is applied to a porous Ni-A sheet. And dried at 200 ° C. for 30 minutes. Next, this sheet was compressed to a thickness of 1.0 mm with a roll. The porosity of the compressed sheet was 35%. This sheet was punched into a disc having a diameter of 12.5 mm to obtain a polarizable electrode.
[0095]
This polarizable electrode was adhered to the inside of a coin-type EDLC stainless steel 316L case with a conductive adhesive to form a positive electrode. The single electrode capacity b of this positive electrode was 6.2 F, that is, the capacity in the voltage operating range of 2.0 to 3.3 V was 2.2 mAh.
[0096]
Next, a negative electrode was produced. That is, NMP was added to a mixture composed of 90% by weight of carbon material A and 10% by weight of PVDF, and stirred and mixed while applying ultrasonic waves to obtain a slurry in which carbon material A was dispersed in an NMP solution of PVDF. This slurry has a thickness of 1.7 mm, a porosity of 98%, and a basis weight of 370 g / m.² Then, it was applied to a porous nickel sheet having an average number of pores of 25 (hereinafter referred to as porous Ni-D) and dried at 200 ° C. for 30 minutes. Subsequently, this sheet was compressed with a roll to a thickness of 0.3 mm to obtain a porosity of 35%.
[0097]
The amount of the carbon material A supported on the negative electrode obtained by punching the compressed sheet into a disk having a diameter of 12.5 mm is 30 mg / cm.² Met. This negative electrode was electrically welded to a SUS304 lid and dried at 200 ° C. for 1 hour.
[0098]
The lid made by welding the negative electrode and the case made of SUS316L in which the positive electrode was bonded with a conductive adhesive were further dried under reduced pressure at 200 ° C. for 4 hours. These were transferred to a glove box in an argon atmosphere, and a lithium foil having a diameter of 10 mm and a thickness of 0.7 mm was pressure bonded to the negative electrode. Next, a PP separator is sandwiched between the two electrodes so as to face each other, and 1.0 mol / l LiPF₆ A non-aqueous electrolyte solution of EC and DEC (volume ratio of 1: 1) dissolved in was poured into the case, and both electrodes were impregnated with the non-aqueous electrolyte solution. Next, using a PP insulating gasket, the element and the electrolyte were caulked and sealed in a container.
[0099]
The obtained coin-shaped EDLC has a diameter of 18.3 mm and a thickness of 2.0 mm. This coin-shaped EDLC was placed in a constant temperature bath at 70 ° C. and held for 2 days. The lithium foil that had been pressure-bonded to the negative electrode 5 by this heating operation was taken into the carbon material of the negative electrode in an ionized state (chemical method). Li can be removed from this negative electrode⁺ The quantity d was 10 mAh and the ratio bv / 3.6d was 0.22. Further, the operating range of the voltage of this EDLC was 2.0 to 3.3 V, the initial capacitance was 5.8 F, and the internal resistance was 20Ω.
[0100]
This coin-type EDLC has a maximum charging current of 10 mA / cm.² Charge for 30 minutes, then 1 mA / cm² A charge / discharge cycle test for discharging at constant current was conducted. When 50 cycles of charging and discharging between 2.0 and 3.3 V were performed, no decrease in capacity was observed. Next, as a result of conducting a 2.0 to 4.0 V charge / discharge cycle test, the capacity decreased to 30% of the initial capacity after 50 cycles.
[0101]
[Example 22]
Firing product of phenolic resin on the carbon material of the negative electrode (purity 99.9%, surface spacing d₀₀₂ = 0.38 nm, hereinafter referred to as carbon material E), polyimide (hereinafter referred to as PI) was used as the binding material, and a nickel-plated SUS304 plate was used in the negative electrode side case. Further, a laminated plate in which aluminum is laminated on the inside of SUS304 is used for the positive electrode lid, and the positive electrode current collector is a porous aluminum sheet having a thickness of 2 mm, a porosity of 92%, and an average pore number of 17 (hereinafter referred to as porous). Al-A) was used.
[0102]
For the positive electrode, a slurry of the polarizable material prepared in Example 21 was applied to a porous Al-A sheet, dried, pressed, and compressed to a thickness of 1.0 mm. The porosity of the compressed sheet was 30%. The positive electrode obtained by punching this sheet into a disc was bonded to the lid with a conductive adhesive. The single electrode capacity of this positive electrode was 5.5F. The amount of the carbon material A supported on the negative electrode is 23 mg / cm.² The thickness is 0.2 mm, the porosity is 27%, and the Li can be removed from the negative electrode.⁺ The amount was 6.8 mAh.
[0103]
Next, LiClO is used as a non-aqueous electrolyte._Four A coin-type EDLC was assembled in the same manner as in Example 21 except that 1 mol / l was dissolved in PC. The operating range of the voltage of this EDLC was 2.0 to 4.0 V, the capacity in this operating range was 3.1 mAh, and the ratio bv / 3.6d was 0.46. The initial capacitance of the EDLC was 5.0 F, and the internal resistance was 18Ω.
[0104]
[Example 23]
Carbon material C is used for the negative electrode, and LiN (CF_Three SO₂ )₂ A coin-type EDLC was assembled in the same manner as in Example 21 except that a non-aqueous electrolyte solution in which 1 mol / l of EC and ethyl methyl carbonate (hereinafter referred to as EMC) was dissolved in a mixed solvent having a volume ratio of 1: 1 was used. The amount of carbon material C supported on the negative electrode is 35 mg / cm² Li, from which the negative electrode can be detached⁺ The amount was 5.0 mAh, and the resulting EDLC ratio bv / 3.6d was 0.45. The EDLC voltage operating range was 2.0-3.3 V, the initial capacitance was 5.0 F, and the internal resistance was 24Ω.
[0105]
[Example 24]
Using carbon material D for the negative electrode, 1 mol / l LiBF_Four A coin-type EDLC was assembled in the same manner as in Example 21 except that a non-aqueous electrolyte solution in which 1 mol / l was dissolved in a mixed solvent having a volume ratio of EC to DEC of 1: 1 was used. The amount of carbon material D supported on the negative electrode is 30 mg / cm² The thickness is 0.3 mm, the porosity is 47%, and Li can be detached from the negative electrode.⁺ The amount was 3.8 mAh. The EDLC ratio bv / 3.6d obtained was 0.59, the voltage operating range was 2.0 to 3.3 V, the initial capacitance was 4.5 F, and the internal resistance was 25Ω.
[0106]
[Example 25]
The negative electrode current collector has a thickness of 1.4 mm, a porosity of 97%, an average number of holes of 20, and a basis weight of 370 g / m.² A porous nickel sheet (hereinafter referred to as porous Ni-E) was applied to this sheet, and the slurry of the carbon material E produced in Example 22 was applied to the sheet. After drying, the thickness was reduced to 0.3 mm with a roll and the negative electrode It was. The porosity of the compressed negative electrode is 46%, and the loading amount of the carbon material E is 25 mg / cm.² Li, from which the negative electrode can be detached⁺ The amount was 7.3 mAh. In addition, LiBF was added to a mixed solvent having a volume ratio of sulfolane (hereinafter referred to as SF) and DEC of 4: 1._Four A coin-type EDLC was assembled in the same manner as in Example 22 except that a non-aqueous electrolyte in which 1 mol / l was dissolved was used. The single electrode capacity b of the positive electrode is 5.5F, the operating range of the voltage of the obtained EDLC is 2.0 to 3.7V, the initial capacitance is 5.2F, the ratio bv / 3.6d is 0.42, The internal resistance was 19Ω.
[0107]
[Example 26]
Porous Al-A was cut to a width of 1 cm and a length of 7 cm, and 6 cm excluding 1 cm at one end was compressed to a thickness of 0.2 mm by pressing to form a positive electrode lead. The slurry of polarizable electrode material prepared in (1) was applied and dried at 200 ° C. for 30 minutes. The portion carrying the polarizable electrode material was compressed to a thickness of 1.0 mm with a press to obtain a positive electrode. The porosity of this positive electrode was 28%, and the single electrode capacity b was 5.4F.
[0108]
Next, the porous Ni-D sheet used in Example 22 was cut into a width of 1 cm and a length of 7 cm, and 6 cm excluding 1 cm at one end was compressed to a thickness of 0.2 mm with a press to form a negative electrode lead. The slurry of the carbon material E prepared in Example 22 was applied to a 1 cm square portion that was not present, and dried at 200 ° C. for 30 minutes. The carbon material carrying part was compressed to a thickness of 0.3 mm with a press to obtain a negative electrode having a porosity of 35%.
[0109]
A PP separator is sandwiched between the negative electrode and a lithium plate having a thickness of 0.5 mm and a thickness of 1.3 cm × 1.3 cm._Four It was immersed in a non-aqueous electrolyte solution of PC in which was dissolved. Next, a voltage of 0.01 V was applied to the electrode of the lithium plate for 10 hours, and the carbon material of the negative electrode was Li⁺ Was occluded electrochemically. Li can be removed from this negative electrode⁺ The amount was 5.6 mAh.
[0110]
Next, a positive electrode carrying a polarizable electrode material and Li⁺ A PP separator with a thickness of 180 μm is sandwiched between the negative electrodes that occlude the material, and this element is formed into Li.⁺ The EDLC was assembled in a PP container by impregnating with the non-aqueous electrolyte solution used for occlusion.
[0111]
The operating range of the voltage of this EDLC was 2.0 to 4.0 V, the initial capacitance was 3.0 mAh, the ratio bv / 3.6d was 0.54, and the internal resistance was 27Ω. The combined volume of the positive electrode, separator and negative electrode of this device was 0.148 cc, and the energy density was 40 Wh / liter. This EDLC has a maximum charging current of 10 mA / cm.² Charge for 30 minutes at 1 mA / cm² A charge / discharge cycle test was performed between 2.0 and 4.0 V at a constant current discharge. As a result, the capacity after 500 cycles was 90% of the initial capacity.
[0112]
[Example 27]
In Example 26, the press pressure for compressing the positive electrode and the negative electrode was increased, and the porosity of the positive electrode and the negative electrode after compression was both 8%. An EDLC was assembled in the same manner as in Example 26. The single electrode capacity of the positive electrode is 5.1 F, the initial capacitance of this capacitor is 4.0 F, the capacity in the voltage operating range of 2.0 to 4.0 V is 2.8 mAh, and the ratio bv / 3.6d is The internal resistance was 0.67. As a result of conducting a charge / discharge cycle test in the range of 2.0 to 4.0 V in the same manner as in Example 26, the capacity after 50 cycles became 70% of the initial capacity.
[0113]
[Example 28]
EA was added to a mixture of 60% by weight of activated carbon B, 30% by weight of KB and 10% by weight of PTFE and kneaded to form a sheet having a thickness of 0.5 mm. Two small sheets of 1 cm × 1 cm were cut from this sheet. Next, a porous aluminum sheet (hereinafter referred to as porous Al-B) having a thickness of 2.7 mm, a porosity of 90%, and an average number of pores of 20 is cut into a width of 1 cm and a length of 7 cm, and 6 cm excluding 1 cm on one side. Was compressed with a press to obtain a lead having a thickness of 0.4 mm. Place the above two small sheets on both sides of the uncompressed 1 cm × 1 cm portion of the porous Al-B sheet, and compress it with a press to press the polarizable electrode material into the porous Al-B sheet. And dried at 170 ° C. to obtain a positive electrode having a thickness of 0.8 mm.
[0114]
Carbon material has an average particle diameter of 10 μm, a purity of 99.5% by weight, and a surface spacing d.₀₀₂ Using a fired product of novolak resin having a thickness of 0.345 nm (hereinafter referred to as carbon material F), a slurry using NMP containing 10% by weight of PI with respect to 90% by weight of the carbon material F as a medium was prepared. Further, a sheet having a width of 1 cm and a length of 7 cm was cut from the porous Ni-D, and 6 cm excluding 1 cm on one side was compressed with a press to obtain a lead having a thickness of 0.2 mm. Apply the above slurry to an uncompressed 1 cm x 1 cm portion of porous Ni-D, dry it at 200 ° C for 30 minutes, and then compress it to 0.3 mm thick with a press to form a negative electrode with a porosity of 35%. Obtained.
[0115]
A PP separator is sandwiched between the negative electrode and a lithium plate having a thickness of 1.3 cm × 1.3 cm and a thickness of 0.5 mm, and these are bonded to 1 mol / l LiClO._Four It was immersed in a non-aqueous electrolyte solution of PC in which was dissolved. In this state, a voltage of 0.01 V is applied to the electrode of the lithium plate for 10 hours, and the carbon material of the negative electrode is Li⁺ Occluded. Li can be removed from this negative electrode⁺ The amount was 8.7 mAh. An EDLC was then assembled as in Example 26. The initial capacitance of the EDLC was 2.7 F, the capacitance in the voltage operating range of 2.0 to 4.0 V was 1.6 mAh, the ratio bv / 3.6d was 0.17, and the internal resistance was 22Ω. The element volume is 0.126 cm.^Three The energy density was 36 Wh / liter.
[0116]
[Example 29]
The slurry used for producing the positive electrode in Example 26 was applied to the porous Ni-A sheet used in Example 21, dried at 200 ° C. for 30 minutes, and then compressed to a thickness of 0.6 mm with a press at 200 ° C. What was dried for 2 hours was punched into a disc having a diameter of 12.5 mm. The two polarizable electrodes obtained were electrically welded to a SUS316L case and a SUS316L lid, respectively. The porosity of both electrodes was 35%, and the single electrode capacity of the positive electrode was 3.8F.
[0117]
A PP separator is sandwiched between both electrodes to form an element, which is housed in a coin-type case made of SUS316L, and 1 mol / l LiClO in the case._Four A non-aqueous electrolyte solution of PC in which was dissolved was injected. Next, using an insulating gasket made of PP, the element and the non-aqueous electrolyte solution were caulked and sealed in a case with a lid made of SUS316L. This coin type EDLC had a voltage operating range of 0 to 2.0 V, an initial capacitance of 1.9 F, a capacitance of 1.1 mAh, and an internal resistance of 15Ω.
[0118]
[Example 30]
A smooth nickel foil with a thickness of 0.1 mm is used as a negative electrode current collector, and a slurry of the carbon material B prepared in Example 21 is applied thereto to form a negative electrode. Otherwise, a coin type EDLC is assembled in the same manner as in Example 21. It was. At this time, if the electrode layer was applied thickly to a nickel foil current collector, the electrode layer was easily peeled off from the current collector and the current collection characteristics became unstable, so the thickness of the electrode layer was set to 0.08 mm. Li which can be detached from this negative electrode⁺ The amount was 3.5 mAh. The single electrode capacity b of the positive electrode is 6.2 F, the capacity of the obtained EDLC voltage in the operating range of 2.0 to 3.3 V is 2.2 mAh, the initial capacitance is 4.5 F, and bv / 3. 6d was 0.64, and the internal resistance was 33Ω.
[0119]
[Example 31]
Instead of PVDF in Example 1, 10% by weight of PTFE was used as a positive electrode binder, EA was used as a medium, and the mixture was formed into a sheet having a thickness of 1.0 mm and dried at 200 ° C. for 3 hours. A polarizable electrode obtained by punching this sheet into a disk having a diameter of 12.5 mm was bonded to a SUS316L case with a conductive adhesive to form a positive electrode. Otherwise, a coin-type EDLC was assembled in the same manner as in Example 21. The single electrode capacity b of this positive electrode was 6.4 F, the initial capacity of the obtained EDLC was 4.9 F, and the capacity in the voltage operating range of 2.2 to 3.5 V was 2.3 mAh. In addition, Li can be removed from the negative electrode⁺ The amount was 10.3 mAh, the ratio bv / 3.6d of the obtained EDLC was 0.22, and the internal resistance was 40Ω.
[0120]
The porous nickel used in each of the above examples is manufactured by Sumitomo Electric Chemical Co., Ltd. (trade name Celmet), and the porous aluminum is manufactured by US Energy Research Generation Co., Ltd. (trade name DUOCEL).
[0121]
The trial production conditions and test results of EDLC of Examples 20 to 31 are summarized in Tables 10 to 13.
[0122]
[Table 10]

[0123]
[Table 11]

[0124]
[Table 12]

[0125]
[Table 13]

[0126]
Examples 21 to 28 which are examples of claim 6 are examples 29 to 31 which are comparative examples (where example 31 is an example of EDLC of the present invention, but is an example of EDLC of claim 6) It can be seen that the EDLC of the configuration of Example 6 is remarkably superior in terms of capacity, voltage operating range, internal resistance, charge / discharge cycle durability, and energy density.
[0127]
【The invention's effect】
The EDLC according to the present invention uses a porous metal for the current collector and Li for the negative electrode.⁺ Lithium can be absorbed and desorbed by a chemical method and / or an electrochemical method.⁺ By having a configuration such as using a carbonaceous material that occludes, the withstand voltage is high, the capacity is large, and the internal resistance is small. As a result, rapid charge / discharge can be achieved, charge / discharge cycle durability is excellent, and an EDLC having an energy density more than twice that of a conventional EDLC is obtained.
[0128]
The EDLC of the present invention is also useful for a coin-type relatively small size, but for ultra-high capacity, high current applications with a capacitance of 100 to 10000 F or a charge / discharge current of 5 to 1000 A. It is particularly suitable for EDLC. Since the EDLC of the present invention has a high withstand voltage, it can be used as a unit element for 3V memory backup applications, significantly improving the power performance of an electric vehicle that should be put to practical use in the future, and regenerative braking of an electric vehicle or the like. Since energy can be used effectively, its industrial utility value is great.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a coin-type EDLC according to the present invention.
[Explanation of symbols]
1: Positive electrode
2: Conductive adhesive (graphite type)
3: Case made of SUS316
4: SUS316 lid
5: Negative electrode
6: Lithium foil
7: Electrolyte
8: Separator
9: Insulating gasket

Claims

Lithium ions were occluded by a chemical method or an electrochemical method into a positive electrode composed of a polarizable electrode material mainly composed of activated carbon and a current collector made of aluminum or stainless steel, and a carbon material capable of occluding and desorbing lithium ions. a carbonaceous material, Ri do and a current collector made of an alloy with lithium without the formation porosity from 80 to 99% of the porous nickel, Ru is 0.1 to 1 mm, a porosity of 5% to 80% der thickness An electric double layer capacitor comprising a negative electrode and a non-aqueous electrolyte containing a lithium salt.

The porous nickel is porosity from 90 to 99% of the porous nickel, if a straight line is drawn in its cross-section, according to claim 1, wherein the average pore number of straight lines crossing per length 1cm is 5 or more Electric double layer capacitor.

The electric double layer capacitor according to claim 1 or 2 , wherein the carbon material capable of inserting and extracting lithium ions is a graphite material, a high-capacity carbon material, or a graphitizable carbon material.

The electric distance according to any one of claims 1 to 3 , wherein a [002] plane interval d ₀₀₂ measured by X-ray diffraction of a carbon material capable of inserting and extracting lithium ions is 0.365 to 0.390 nm. Multilayer capacitor.

The electric double layer capacitor according to any one of claims 1 to 4 , wherein the current collector used for the positive electrode is porous aluminum .

The positive electrode carries a polar electrode material composed of activated carbon, a conductive carbon black and a binder having a specific surface area of 1000 to 3000 m ² / g on porous aluminum having a porosity of 80% or more, and is compressed to have a thickness of 0. The electric double layer capacitor according to claim 5 , wherein the electric double layer capacitor has a porosity of 2 to 2.0 mm and a porosity of 10 to 80%.

The porous aluminum used for the positive electrode, a porous aluminum having a porosity of 80 to 99%, or claim 5 average pore number of straight lines crossing 1cm long drawn in its cross-section is 5 or more 6 The electric double layer capacitor described in 1.

The lithium salt is at least one selected from LiClO ₄ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ and LiPF ₆ , and the solvent of the non-aqueous electrolyte is ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl The electric double layer capacitor according to any one of claims 1 to 7 , comprising at least one selected from carbonate, diethyl carbonate, ethyl methyl carbonate, sulfolane, and dimethoxyethane.

The positive electrode, the negative electrode, and the non-aqueous electrolyte are accommodated in a metal coin-shaped container made of a case and a lid, and the positive electrode is made of either a stainless steel plate or a laminated plate of aluminum and stainless steel. placed in a stainless steel negative electrode, a nickel plate, according to claim 1-8 in which the copper plate or stainless steel, is disposed in the other side of the lid and the case of two or more laminate selected from nickel and copper comprising The electric double layer capacitor according to any one of the above.

When the unipolar capacity of the polarizable electrode as the positive electrode is b (unit: F), the lithium ion detachment capacity of the negative electrode is d (unit: mAh), and the potential difference in the voltage operating range is v (unit: V). The electric double layer capacitor according to any one of claims 1 to 9 , wherein the ratio bv / 3.6d is in the range of 0.05 to 0.90.

Lithium ions were occluded by a chemical method or an electrochemical method into a positive electrode composed of a polarizable electrode material mainly composed of activated carbon and a current collector made of aluminum or stainless steel, and a carbon material capable of occluding and desorbing lithium ions. A method for producing an electric double layer capacitor comprising a carbonaceous material, a negative electrode comprising a porous nickel current collector that does not form an alloy with lithium, and a non-aqueous electrolyte containing a lithium salt, the porosity being 80% The porous nickel is loaded with a mixture of a carbon material and a binder that can occlude and desorb lithium ions, and compressed to a thickness of 0.1 to 1 mm and a porosity of 5 to 80%. A method for producing an electric double layer capacitor, comprising obtaining a negative electrode by occluding lithium ions in a carbon material.