JP4304304B2

JP4304304B2 - Film outer battery

Info

Publication number: JP4304304B2
Application number: JP2003137321A
Authority: JP
Inventors: 牧宏乙幡; 弘志屋ケ田
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2003-05-15
Filing date: 2003-05-15
Publication date: 2009-07-29
Anticipated expiration: 2023-05-15
Also published as: JP2004342449A

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filmed battery using an envelope having a recess for housing a battery element prevented from the damage of the envelope when sealing the battery element. <P>SOLUTION: A positive electrode current collector part 7a arranged so as to protrude toward a part leaned to one surface side in a direction of thickness, and a negative electrode current collector part 7b arranged so as to protrude toward a part leaned to the other surface side in the direction of thickness are arranged at the battery element 6, and lead terminals 5a, 5b are connected to the electrode current collector parts, respectively. The lead terminals 5a, 5b are arranged at almost the same level of height in the direction of thickness. The battery element is interposed between an upper and a lower enveloping films 3, 4, and peripheral edge parts of the enveloping films 3, 4 are joined and airtightly sealed. Recesses 3a, 4a having a prescribed shape and depth corresponding to respective battery elements 6 and current collector parts 7a, 7b are formed on respective enveloping films 3, 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電池要素を可撓性を有する外装材に収納したフィルム外装電池に関する。
【０００２】
【従来の技術】
近年、携帯機器等の電源としての電池は、軽量化、薄型化が強く要求されている。そこで、電池の外装材に関しても、軽量化、薄型化に限界のある従来の金属缶に代わり、さらなる軽量化、薄型化が可能であり、金属缶に比べて自由な形状を採ることが可能な外装材として、金属薄膜フィルム、または金属薄膜と熱融着性樹脂フィルムとを積層したラミネートフィルムを用いたものが使用されるようになった。
【０００３】
電池の外装材に用いられるラミネートフィルムの代表的な例としては、金属薄膜であるアルミニウム薄膜の片面にヒートシール層である熱融着性樹脂フィルムを積層するとともに、他方の面に保護フィルムを積層した３層ラミネートフィルムが挙げられる。
【０００４】
外装材にラミネートフィルムを用いたフィルム外装電池においては、一般に、正極、負極、および電解質等で構成される電池要素を、熱融着性樹脂フィルムが内側になるようにして外装材で包囲し、電池要素の周囲で外装材を熱融着することによって電池要素を気密封止（以下、単に封止という）している。熱融着性樹脂フィルムには、例えばポリエチレンフィルムやポリプロピレンフィルムが用いられ、保護フィルムには、例えばナイロンフィルムやポリエチレンテレフタレートフィルムが用いられる。
【０００５】
ここで、電池要素の正極および負極を外装材の外部へ引き出すために、正極および負極にはそれぞれリード端子が接続され、これらリード端子を外装材から突出させている。電池要素へのリード端子の接続は、電池要素の封止に先立って、超音波溶接などによって行われる。また、電池要素の封止にあたっては、２枚の外装材を用い、これら２枚の外装材で電池要素を挟み、外装材の周縁部を熱融着する。外装材の熱融着は、外装材の３辺を先に熱融着して袋状とした後、外装材の内部から空気を排気して外装材の内部を真空として大気圧によって外装材を電池要素に密着させ、この状態で残りの１辺を熱融着する。
【０００６】
この際、電池要素がある程度の厚みを持っている場合には、一方の外装材を、電池要素を収納し易いように、深絞り成形によって鍔付きの容器状に形成しておき、この容器状に形成した外装材を、電池要素の上から被せることが一般に行われている。
【０００７】
例えば、特許文献１には、それぞれタブが突出した複数の正極板および負極板を、電解質を介在させて多層に積層することによって電池要素を構成し、正極板のタブおよび負極板のタブをそれぞれ一括して超音波溶接することによって正極および負極の集電部とし、これら集電部をそれぞれ正極および負極のリード端子と接続した後、電池要素を、平らな外装材の上に載置し、さらにその上に、容器状に形成した外装材を被せ、２枚の外装材の周縁部を熱融着したフィルム外装電池が開示されている。この種のフィルム外装電池では、集電部は正極板および負極板のタブを超音波溶接用のヘッドで上方から加圧することによって形成し、上記のような外装材を用いて電池要素を封止しているため、リード端子は電池要素の下面近傍から引き出されている。
【０００８】
なお、上記のように正極板と負極板を交互に積層して電池要素を構成した電池は積層型電池と呼ばれる。また、帯状の正極と負極をセパレートシートを介在させて重ね、これを捲回した後、扁平状に圧縮することによって、正極と負極が交互に積層された構造の電池要素を用いた電池は、捲回型電池と呼ばれる。
【０００９】
また電池要素としては、リチウム電池やニッケル水素電池などの化学電池のほかに、キャパシタのような蓄電機能を持ったものも、ラミネートフィルムを外装材として用いられるようになった。
【００１０】
さらに、ハイブリッド自動車などの大型機器向けの電池においても、外装材にフィルムを用いることで、金属缶を用いた電池に比べて薄型・軽量ながら電極面積を大きくすることができるため、電池要素収納部の凹部をより広くて深い形状としたラミネートフィルムが、高出力・大容量の電池用の外装材として使われ始めている。
【００１１】
【特許文献１】
特開２００１−１２６６７８号公報
【００１２】
【発明が解決しようとする課題】
しかしながら、上述した従来のフィルム外装電池では、電池要素の封止時にフィルムが過剰に変形し易く、フィルムにクラックが入ってしまうことがあるという問題点があった。以下に、この現象について図１３から図１５を参照して説明する。なお、図１３では、内部構造が見えるように外装材を透視した状態で示している。
【００１３】
図１３に示すように、電池要素１０６の正極用および負極用のタブをそれぞれ一括して接続することによって形成された正極集電部１０７ａおよび負極集電部１０７ｂは、基部では電池要素１０６の厚みとほぼ等しい厚みであるが先端に向かって厚みが徐々に薄くなる形状を有している。そのため、外装体１０２に形成する凹部１０２ａの形状は、外装体１０２の深絞り成形の容易性の観点から、正極集電部１０７ａおよび負極集電部１０７ｂが収納される部分も含めて全体として略矩形状に形成される。また、図１３では積層型の電池要素１０６を示しているが、捲回型であっても、高出力化・低抵抗化のために正極および負極からそれぞれ複数のタブを導出して集電部を形成することがあり、そのような場合にも、外装材の凹部は同様に形成される。
【００１４】
したがって、電池要素１０６の封止前の状態では、図１４に示すように、正極集電部１０７ａおよび負極集電部１０７ｂ（図示せず）の近傍に大きな余剰空間が形成される。この余剰空間が存在することによって、電池要素１０６の封止時には、図１５に示すように、大気圧によって余剰空間の部分で外装体１０２が大きくへこんでしまう。大きな余剰空間を有する外装体１０２がへこむと、鋭角に折れ曲がった角部が形成され、その部分にクラックが発生するおそれがある。外装体１０２は、内部の電解液などのバリア層としての機能を持つので、外装体１０２にクラックが入ると、そこからの電解液漏れなどが生じ、フィルム外装電池としての性能や信頼性が大きく損なわれるおそれがある。
【００１５】
本発明の目的は、電池要素を収納するための凹部が設けられた外装材を用いたフィルム外装電池において、電池要素の封止時に生じる外装材のへこみを最小限に抑えることによって外装材の損傷を防止することである。
【００１６】
【課題を解決するための手段】
上記目的を達成するために本発明のフィルム外装電池は、正極と負極とが対向した構造を有する電池要素と、電池要素の正極に、電池要素の厚み方向での一方の表面側に偏って電池要素から突出して設けられ、先端部において電池要素よりも厚みの薄い正極中継部と、電池要素の負極に、電池要素の厚み方向での他方の表面側に偏って電池要素から突出して設けられ、先端部において電池要素よりも厚みの薄い負極中継部と、正極中継部を介して正極と接続された正極リード端子と、負極中継部を介して負極と接続された負極リード端子と電池要素をその厚み方向両側から挟んで配され、電池要素を収納する収納部が形成されるとともに、周縁部が互いに接合されることで前記正極リード端子および負極リード端子を突出させて前記電池要素を気密封止した外装材とを有する。そして、本発明のフィルム外装電池は、正極リード端子と、負極リード端子は、電池要素の厚み方向に対し略同じ高さに設けられ、収納部は、電池要素を挟む外装材の一方の側に設けられた、電池要素と正極中継部とを合わせた平面形状と略等しい平面形状を持ち、かつ、電池要素の厚みから、正極中継部または負極中継部のいずれかの、先端部における厚みを減じた値に略等しい深さの第１の凹部と、電池要素を挟む外装材の他方の側に設けられた、電池要素と負極中継部とを合わせた平面形状と略等しい平面形状を持ち、かつ、電池要素の厚みから、前記の値を減じた値に略等しい深さの第２の凹部と、を対向させて形成されている。
【００１７】
本発明のフィルム外装電池は、電池要素を収納する収納部が、それぞれ上記の平面形状および深さを有する２つの凹部を対向させて形成されるので、収納部を構成する空間は、電池要素、正極中継部および負極中継部を合わせた形状にほぼ合致する。このことにより、電池要素を外装材で封止した際に、大気圧による外装材のへこみは殆ど発生せず、その結果、外装材の折れ曲がりによる損傷が防止される。しかも、第１の凹部および第２の凹部は、それぞれ深さが一定であるので、外装材への凹部の加工も容易である。
【００１８】
また、正極リード端子と負極リード端子とは電池要素の厚み方向に対してほぼ同じ高さにあるため、外装材を熱融着する際にも各リード端子を曲げることなく外装材から突出させることができる。
【００１９】
収納部を構成する空間を、電池要素と正極、負極のいずれかの中継部とを合わせた形状により適合させるためには、第１の凹部（または第２の凹部）を、電池要素の中継部が突出した辺に対応する側壁の、第１の凹部（または第２の凹部）の底面に対する傾斜角度が、電池要素の他の辺に対応する側壁と比べて小さく形成することである。また、最も好ましくは、第１の凹部（または第２の凹部）の、電池要素の正極中継部（または負極中継部）が突出した辺に対応する側壁を、中継部と対向する部位での第１の凹部（または第２の凹部）の底面に対する傾斜角度を他の部位と比べて小さく形成する。第１の凹部および第２の凹部は、深絞り成形によって、容易に成形することが可能である。
【００２０】
さらに、正極中継部と負極中継部とがともに、電池要素の同一の辺に設けられる場合においては、正極中継部と負極中継部を、その形状および寸法を略同一とし、かつその辺の中点に関して略対称の位置に設定することにより、第１の凹部と第２の凹部の形状を一致させることができる。この結果、電池要素を挟む２つの外装材は同じものを使用することが可能となる。
【００２１】
【発明の実施の形態】
次に、本発明の実施の形態について、図を参照して説明する。
【００２２】
［第1の実施形態］
図１は、本発明の第１の実施形態によるフィルム外装電池の外観を示す斜視図、図２は、図１に示すフィルム外装電池の構成を示す分解斜視図、図３は図１に示すフィルム外装電池の電池要素を示す斜視図である。また、以下の説明上、電池要素６の厚み方向の面のうち、図２に現れている面を電池要素６の表面とする。
【００２３】
本実施形態のフィルム外装電池１は、電池要素６と、電池要素６に設けられた正極集電部７ａおよび負極集電部７ｂと、電池要素６を電解液とともに収納する外装体２と、正極集電部７ａに接続された正極リード端子５ａと、負極集電部７ｂに接続された負極リード端子５ｂとを有する。
【００２４】
外装体２は、電池要素６を上下から挟んで包囲する２枚の外装フィルム３，４からなり、これら外装フィルム３，４の周縁部を熱融着することで、電池要素６が封止される。この際、外装フィルム３，４の３辺を先に熱融着して外装体２を袋状としておき、その袋状となった外装体２の、開放している残りの１辺から内部の空気を排気し、その後、残りの１辺を熱融着することで、電池要素６は、大気圧によって外装体２が密着した状態で封止される。
【００２５】
ここで、電池要素６について、図４を参照して説明する。
【００２６】
図４に示すように、電池要素６は、複数の正極電極板８と複数の負極電極板９とを有し、最も外側が負極電極板９となるように、これらが交互に積層されている。正極電極板８と負極電極板９との間、および最も外側の負極電極板９のさらに外側には、それぞれセパレータ１０が配置されている。正極電極板８および負極電極板９の１辺からは、それぞれタブ８ａ，９ａが突出して設けられている。正極電極板８のタブ８ａと負極電極板９のタブ９ａは、正極電極板８のタブ８ａ同士、および負極電極板９のタブ９ａ同士が重なるように、互いに異なる位置に設けられている。
【００２７】
これら正極電極板８のタブ８ａ同士、および負極電極板９のタブ９ａ同士は一括して超音波溶接され、図２および図３に示すように、それぞれ正極集電部７ａおよび負極集電部７ｂを形成する。超音波溶接は、各正極電極板８および各負極電極板９からそれぞれ延びたタブ８ａ，９ａの先端部分を溶接ヘッドで加圧して行うので、正極集電部７ａおよび負極集電部７ｂは、基部では電池要素６の厚みとほぼ等しい厚みを有し、そこから先端に向かって厚みが薄くなり、超音波ヘッドが加圧された箇所ではほぼ一定の厚みとなっている。また、正極集電部７ａおよび負極集電部７ｂを形成する際は、電池要素６を台上に置き、負極集電部７ｂの形状に合わせて溶接ヘッドで加圧して形成する。その後、電池要素６を天地逆転させ、同様に正極集電部７ａを溶接ヘッドで加圧して形成する。この結果、正極集電部７ａは、電池要素６の表面側に偏って電池要素６から突出し、負極集電部７ｂは、電池要素６の裏面側に偏って電池要素６から突出する。
【００２８】
正極リード端子５ａは電池要素６の表面側から見て正極集電部７ａの裏側の、負極リード端子５ｂは電池要素６の表面側から見て負極集電部７ｂの表側の、ほぼ一定の厚みとなった平らな箇所でそれぞれ接続される。
【００２９】
外装フィルム３，４としては、金属薄膜と熱融着性樹脂とを積層したラミネートフィルムなど、フィルム外装電池に一般に用いられる周知の外装材を用いることができる。
【００３０】
外装フィルム３，４にはそれぞれ凹部３ａ，４ａが互いに対向する位置に形成されており、これら凹部３ａ，４ａが向き合わせられることによって、電池要素６を収納するための電池要素収納部が形成される。凹部３ａ，４ａは、例えば深絞り成形によって形成することができる。電池要素６の封止に際しては、外装フィルム３，４の凹部３ａ，４ａの周囲の、外装フィルム３，４同士が対面している部分が熱融着される。
【００３１】
表面側の外装フィルム３に形成される凹部３ａの平面形状は、電池要素６の平面形状と正極集電部７ａとを合わせた形状に略等しく、裏面側の外装フィルム４に形成される凹部４ａの平面形状は、電池要素６と負極集電部７ｂとを合わせた平面形状と略等しくなるように設定される。
【００３２】
ここで、本発明において平面形状とは、対象となる要素を電池要素６の厚み方向（別の言い方をすれば凹部３ａ，４ａの深さ方向）と垂直な平面に投影したときに得られる形状をいい、特に、凹部３ａ，４ａの平面形状と言った場合には、凹部３ａ，４ａの底面形状そのものをいう。
【００３３】
また、各凹部３ａ，４ａの深さは、図５および図６に示すように設定される。すなわち、表面側の外装フィルム３に形成される凹部３ａの深さｈ１は、図５に示すように、電池要素６の厚みから負極集電部７ｂの先端部での厚みを減じた値と略等しくなるように設定される。また、裏面側の外装フィルム４に形成される凹部４ａの深さｈ２は、図６に示すように、電池要素６の厚みからｈ１を減じた値に略等しくなるように設定される。実際には、正極集電部７ａの先端部の厚みと負極集電部７ｂの先端部の厚みはほぼ同一であるため、ｈ１とｈ２は電池要素６の厚みの略半分に等しい。また、この結果、正極リード端子５ａと負極リード端子５ｂとは、ともに電池要素６の厚み方向のほぼ中央位置に設置される。
【００３４】
さらに、正極集電部７ａと負極集電部７ｂの形状および寸法は略同一に設定され、かつ、正極集電部７ａと負極集電部７ｂとが電池要素６に取り付く平面位置は、取り付く辺の中心に関してほぼ対称となるよう選定される。
【００３５】
以上のように構成された本実施形態においては、以下に述べるような効果を生ずる。
まず、第１に、以上のように凹部３ａ，４ａを形成することで、外装フィルム３，４で電池要素６を挟んだ状態では、凹部３ａにより形成される空間は、電池要素６および正極集電部７ａを合わせた形状に合致しており、また、凹部３ｂにより形成される空間は、電池要素６および負極集電部７ｂを合わせた形状に合致する。この結果、電池要素６と正極集電部７ａと負極集電部７ｂとを包絡した外表面と、外装フィルム３，４で形成される内部空間との間には、隙間は殆ど形成されない。そのため、電池要素６の封止の際に外装フィルム３，４内の空気を排気しても、大気圧による外装フィルム３，４のへこみは殆ど発生しない。したがって、外装フィルム３，４に、鋭角に折れ曲がる角部が発生することはなくなるので、外装フィルム３，４の折れ曲がりによるクラックなどの損傷を防止し、結果的に、内部に収納されている電解液の漏れなどによる、フィルム外装電池１の性能や信頼性の低下を防止することができる。
第２に、正極集電部７ａと負極集電部７ｂの形状および寸法は略同一であり、かつ電池要素６の辺上で正極集電部７ａと負極集電部７ｂとが取り付く位置は、これらの集電部の取り付く辺の中心に関してほぼ対称となるよう選定されているため、外装フィルム３，４は全く同一のものとすることができ、部品点数の削減によるコスト低減が実現され、部品管理も容易となる。
【００３６】
第３に、外装フィルム３，４に形成される凹部３ａ，４ａの深さはそれぞれ一定であるので、後述するように凹部３ａ，４ａを深絞り成形で加工する場合、深絞り成形で使用するポンチ１２の外装フィルム３，４への加圧面は平面でよく、ポンチ１２全体の形状も単純な形状とすることができる。そのため、外装フィルム３，４への凹部３ａ，４ａの加工を極めて容易に行うことができる。
【００３７】
第４に、上述したように、本実施形態では、正極リード端子５ａと負極リード端子５ｂとは電池要素６の厚み方向に対してほぼ同じ高さに設定される。そのため、外装フィルム３，４を融着させる際に、正極リード端子５ａと負極リード端子５ｂとを、過大な曲げを生じさせることなく、外装フィルム３，４の接合面から突出させることができる。
次に、凹部３ａ、４ａの形成方法について説明する。以下では凹部３ａを対象に説明するが、凹部４ａについてもまったく同様である。
凹部３ａを形成するには、図７に示すように、ポンチ１２の平面形状を、正極集電部７ａに対応する部位に突起部１２ａを有する形状のものとして、深絞り成形すればよい。これにより正極集電部７ａの部分は突起部１２ａの形状に合わせて形成され、正極集電部７ａが良好に収められる空間が確保されることになる。
一方、正極集電部７ａと同一辺上に隣接して設けられる負極集電部７ｂには、図５に示すように、その基部から外側に向けて徐々に薄くなるテーパ部７ｃが設けられている。外装フィルム３は可撓性を有しており、凹部３ａはテーパ部７ｃの形状に合わせて広がることもできるので、テーパ部７ｃの影響はそれほど大きくない。しかし、凹部３ａをテーパ部７ｃに適合した形状に可能な限り成形することが望ましいことはいうまでもない。
ここで、一般に深絞り成形によって加工する場合、深絞り成形に使用するポンチとダイスとの間にはクリアランスが必要であり、また、このクリアランスにより絞り部の側壁はテーパ状となるのであるが、クリアランスを調整することでテーパの傾斜を任意に調整できることが知られている。すなわち、図８に示すように、ポンチ１２とダイス１１とのクリアランスＣ１を、他の辺のおけるクリアランスＣ２よりも大きくすることで、クリアランスＣ１に対応する部位のテーパの傾斜を緩くすることができる。
これを本実施形態について見ると、図７に示すように、負極集電部７ｂに対応するポンチ１２の部位には突起部１２ａがないため、ダイス１１とポンチ１２との間に大きなクリアランスが形成され、負極集電部７ｂのテーパ部７ｃにより適合した形状に形成できることになる。
この結果、正極集電部７ａおよび負極集電部７ｂを、全体として凹部３ａ内に良好に収めることが可能となる。
【００３８】
本実施形態では、外装体２を２枚の外装フィルム３，４で構成しているが、１枚の外装材を２つ折りにして電池要素６を挟み、開放している３辺を熱融着することによって電池要素６を封止する構造としてもよい。この場合は、外装材の、２つ折りにしたときに電池要素６を間においた両側の部分に、電池要素収納部を構成する凹部を形成する。この場合でも、各凹部の平面形状および深さは前述したのと同様に形成すればよい。
【００３９】
［第２の実施形態］
図９は、本発明の第２の実施形態によるフィルム外装電池の外観を示す斜視図であり、図１０は、図９に示すフィルム外装電池の構成を示す分解斜視図である。
図１１は、図９に示すフィルム外装電池の、正極リード端子および負極リード端子の突出方向に沿った断面図である。
【００４０】
第１の実施形態では、正極リード端子および負極リード端子がともに外装体の同じ辺から突出したものとして説明したが、本実施形態のフィルム外装電池２１では、正極リード端子２５ａと負極リード端子２５ｂとが、フィルム外装電池２１の互いに相対する辺から突出している。それに伴って、外装体２２の内部に収納されている電池要素２６に設けられる正極集電部２７ａおよび負極集電部２７ｂの位置も、正極リード端子２５ａあるいは負極リード端子２５ｂに対応した位置とされる。ここで、正極リード端子２５ａと負極リード端子２５ｂは、図１１に示すように、電池要素２６の厚み方向に対して同じ高さに設けられている。
また、外装体２２を構成する２枚の外装フィルム２３，２４にそれぞれ形成される凹部２３ａ，２４ａについても、正極集電部２７ａおよび負極集電部２７ｂの位置および形状に合わせて、第１の実施形態に対して変更されている。凹部２３ａは電池要素２６と負極集電部２７ｂとを合わせた平面形状にほぼ近く、凹部２４ａは電池要素２６と正極集電部２７ａとを合わせた平面形状にほぼ近い。ただし、本実施形態では、正極集電部２７ａおよび負極集電部２７ｂの幅はそれらが設けられる電池要素６の辺の長さと同程度のため、凹部２３ａ、２４ａの対応する辺の形状は、一律これらの集電部の形状に合わせたものとしている。
その他の構成は、第１の実施形態と同様であるので、その説明は省略する。
【００４１】
このように、正極リード端子２５ａと負極リード端子２５ｂを互いに相対する辺から突出させることで、同じ辺から突出させたときと比べて、正極リード端子２５ａおよび負極リード端子２５ｂの幅を大きくすることができる。これにより、正極リード端子２５ａおよび負極リード端子２５ｂの電気抵抗を小さくすることができるので、正極リード端子２５ａおよび負極リード端子２５ｂによる損失を抑え、結果的に、高出力のフィルム外装電池２１とすることができる。
なお、本実施形態では、正極リード端子２５ａと負極リード端子２５ｂとを外装体２２の互いに相対する辺から突出させた場合を示したが、互いに隣り合う辺から突出させてもよい。また、本実施形態においても、外装体２２を２枚の外装フィルム２３，２４ではなく１枚の外装フィルムで構成することができる。
【００４２】
［第３の実施形態］
図１２は、本発明の第３の実施形態によるフィルム外装電池の外観を示す斜視図である。正極リード端子４５ａおよび負極リード端子４５ｂの幅をそれほど大きく取る必要がない場合は、これらを、より小さい幅で設置することも可能である。本実施形態では、正極リード端子４５ａおよび負極リード端子４５ｂを、それらが設けられる辺の中心付近に設置し、外装フィルム４３，４４の変形を抑止するため、凹部４３ａの平面形状は電池要素４６と負極集電部４７ｂとを合わせた形状に、凹部４４ａの平面形状は電池要素４６と正極集電部４７ａとを合わせた形状に設定している。
【００４３】
また、本実施形態においては、正極リード端子４５ａおよび負極リード端子４５ｂを、上記のように各辺の中心付近に設ける代わりに、電池要素４６の表面の中心点に関し点対称の位置に設けることも可能である。いずれの形態によっても、外装フィルム４３，４４は同一のもので構成することが可能であり、実施形態１、２と同様、部品点数の削減によるコスト低減が実現され、部品管理も容易となる。
【００４４】
【実施例】
次に、本発明の具体的な実施例について、上述した第１の実施形態のフィルム外装電池１を例に挙げて、第１の実施形態の説明に用いた図を参照しつつ説明する。
【００４５】
〈正極の製作〉
スピネル構造を持つマンガン酸リチウム粉末、炭素質導電性付与材、およびポリフッ化ビニリデンを９０：５：５の質量比でＮ−メチルピロリドン（ＮＭＰと表すことがある）に混合分散、攪拌してスラリーとした。ＮＭＰの量はスラリーが適当な粘度になるように調整した。このスラリーを、ドクターブレードを用いて、正極電極板８となる厚さ２０μｍのアルミニウム箔の片面に均一に塗布した。塗布時には、わずかに未塗布部（アルミニウム箔が露出している部分）が筋状にできるようにした。次に、これを１００℃で２時間真空乾燥させた。その後、アルミニウム箔のもう一方の面にも同様に、スラリーを塗布し、真空乾燥させた。この際、表裏の未塗布部が一致するようにスラリーの塗布を行った。
【００４６】
このようにして両面に活物質を塗布したアルミニウム箔をロールプレスした。これを、活物質の未塗布部を含めて矩形に切り出し、正極電極板８とした。活物質の未塗布部は片側の一部を矩形に残した他は切り取り、残った部分をタブ８ａとした。
【００４７】
〈負極の製作〉
アモルファスカーボン粉末、ポリフッ化ビニリデンを９１：９の質量比でＮＭＰに混合、分散、攪拌してスラリーとした。ＮＭＰの量はスラリーが適当な粘度になるように調整した。このスラリーを、ドクターブレードを用いて、負極電極板９となる厚さ１０μｍの銅箔の片面に均一に塗布した。塗布時には、わずかに未塗布部（銅箔が露出している部分）が筋状にできるようにした。次に、これを１００℃で２時間真空乾燥した。なお、このとき負極電極板９の単位面積あたりの理論容量と正極電極板８の単位面積あたりの理論容量が１：１となるように、活物質の塗布厚を調整した。その後、銅箔のもう一方の面にも同様に、スラリーを塗布し、真空乾燥した。
【００４８】
このようにして両面に活物質を塗布した銅箔をロールプレスした。これを正極電極板８のサイズよりも縦横２ｍｍずつ大きいサイズに、未塗布部を含めて矩形に切り出し、負極電極板９とした。活物質の未塗布部は片側の一部を矩形に残した他は切り取り、残った部分をタブ９ａとした。
【００４９】
〈電池要素の製作〉
上記のようにして作製した正極電極板８と負極電極板９、およびポリプロピレン層／ポリエチレン層／ポリプロピレン層の三層構造を持つマイクロポーラスシートからなるセパレータ１０を図４に示すように交互に積層し、厚さ３ｍｍの積層体とした。この際、最も外側の電極板は負極電極板９となるようにし、その負極電極板９のさらに外側にセパレータ１０を設置した（つまり、セパレータ／負極電極板／セパレータ／正極電極板／セパレータ／・・・・・・／負極電極板／セパレータ、という順番）。
【００５０】
次いで、正極電極板８、セパレータ１０、および負極電極板９の積層体である電池要素６を平らな台の上に載置し、正極電極板８のタブ８ａと、厚さ０．１ｍｍのアルミニウム板からなる正極リード端子５ａとを一括して超音波溶接し、正極集電部７ａとした。同様に、負極電極板９のタブ９ａと、厚さ０．１ｍｍのニッケル板からなる負極リード端子５ｂとを一括して超音波溶接し、負極集電部７ｂとした。このとき、正極リード端子５ａと負極リード端子５ｂは、図３に示すように、電池要素６の厚み方向に対してほぼ中心の高さとし、集電部７ａ、７ｂは電池要素６の厚み方向に対してそれぞれ逆位置となるようにした。
【００５１】
〈電池要素の封止〉
外装材として、ナイロン層／アルミニウム層／酸変性ポリプロピレン層／ポリプロピレン層の四層構造を持つアルミラミネートフィルムである２枚の外装フィルム３，４を用いた。一方の外装フィルム３に、電池要素６の平面形状と略等しい平面形状を有する凹部３ａを、深絞り成形によって、電池要素６の厚みから集電部７の先端部での厚みを減じた値と略等しい深さで、ポリプロピレン層側が凹状となるように設けた。もう一方の外装フィルム４には、電池要素６と正極および負極の集電部７とを合わせた平面形状と略等しい平面形状を有する凹部４ａを、集電部７の先端部での厚みと略等しい深さで、ポリプロピレン層側が凹状となるように設けた。
【００５２】
上記の電池要素６を、正極リード端子５ａおよび負極リード端子５ｂのみが外装フィルム３，４から突出するように、２枚の外装フィルム３，４を重ね合わせて各凹部３ａ，４ａで構成される電池要素収納部に電池要素６を収納させて、外装フィルム３，４の周囲３辺を熱融着によって接合した。
【００５３】
次に、接合してない残りの1辺から、電池要素６を収納した外装フィルム３，４の内部に電解液を注入した。
【００５４】
電解液は、１ｍｏｌ／リットルのＬｉＰＦ₆を支持塩とし、プロピレンカーボネートとエチレンカーボネートの混合溶媒（質量比５０：５０）を溶媒とするものを用いた。電解液の注入後、外装フィルム３，４の開放した残りの１辺から内部の空気を排気し、残りの１辺を熱融着することによって電池要素６を封止し、ラミネートフィルムからなる外装体２を有するリチウム二次電池であるフィルム外装電池１を得た。
【００５５】
得られたフィルム外装電池１は、電池要素６を封止したときの、大気圧による外装フィルム３，４の変形が若干見られたものの、外装フィルム３，４にクラックを生じさせるような鋭角の角部は見られなかった。
【００５６】
以上、代表的な幾つかの実施形態、および具体的な実施例を挙げて本発明を説明したが、本発明はこれらに限定されるものではなく、本発明の技術的思想の範囲内において適宜変更され得ることは明らかである。
【００５７】
例えば、可撓性を有する外装材として、金属薄膜と熱融着性樹脂とのラミネートフィルムを用いたが、電池要素を封止するのに十分なバリア性を有するものであれば他の材料を用いることもできる。
【００５８】
また、電池要素としては、正極板と負極板とを交互に積層した積層型のものを例に挙げたが、本発明は捲回型にも適用することができる。この場合、リード端子との接続のために正極板および負極板にはそれぞれ複数のタブが設けられ、正極板のタブ同士、および負極板のタブ同士をそれぞれ一括して接合して集電部が形成される。また、捲回型の場合、正極板および負極板にそれぞれ設けられるタブの位置は、捲回された正極板および負極板を扁平状に圧縮したときに、正極板に設けられたタブ同士、および負極板に設けられたタブ同士がそれぞれ重なり合うような位置とされる。
【００５９】
また、電池要素としてチウム二次電池の電池要素を例にして説明したが、ニッケル水素電池、ニッケルカドミウム電池、リチウムメタル一次電池あるいは二次電池、リチウムポリマー電池等、他の種類の化学電池の電池要素、さらにはキャパシタ要素などにも適用することができる。
【００６０】
【発明の効果】
以上説明したように本発明によれば、電池要素を収納する収納部を形成する２つの凹部が電池要素および中継部の平面形状および厚さに基づいて最適かつ単純な形状で形成されるので、電池要素の封止時に生じる外装材の変形による外装材の損傷を防止することができる。その結果、外装材からの電解液の漏れなどによるフィルム外装電池の性能や信頼性の低下を防止することができる。
また、正極ならびに負極は、その中継部の形状、寸法を略同一とし、かつこれらが設けられる電池要素の辺の中心点に関し対称となる平面位置に設定されるので、表面側と裏側の外装フィルムは全く同一のものを使用可能であり、部品点数の削減によるコスト低減が実現され、部品管理も容易となる。
しかも、各凹部はそれぞれ深さが一定であるので、各凹部の形成も容易に行うことができる。
【００６１】
また、正極リード端子と負極リード端子を電池要素の厚み方向に対してほぼ同じ高さに設けているので、外装フィルムの融着の際、各リード端子を曲げることなく外装材から突出させることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態によるフィルム外装電池の表面側から見た斜視図である。
【図２】図１に示したフィルム外装電池の分解斜視図である。
【図３】図１に示したフィルム外装電池の電池要素の斜視図である。
【図４】図２および図３に示した電池要素の構成を示す分解斜視図である。
【図５】図１に示したフィルム外装電池の、負極集電部近傍での負極リード端子の突出方向に沿った断面図である。
【図６】図１に示したフィルム外装電池の、正極集電部近傍での正極リード端子の突出方向に沿った断面図である。
【図７】図１に示した表面側の外装フィルムを形成するのに用いられる深絞り成形用のダイスおよびポンチの一例の平面図である。
【図８】外装フィルムに深絞り成形によって凹部を形成する場合に、意図的にテーパをつけて形成するときの、ダイスとポンチとの関係を示す断面図である。
【図９】本発明の第２の実施形態によるフィルム外装電池の表面側から見た斜視図である。
【図１０】図９に示したフィルム外装電池の分解斜視図である。
【図１１】図９に示したフィルム外装電池の、正極リード端子および負極リード端子の突出方向に沿った断面図である。
【図１２】本発明の第３の実施形態によるフィルム外装電池の表面側から見た斜視図である。
【図１３】従来のフィルム外装電池の、電池要素の封止前の、外装材を透視して示す斜視図である。
【図１４】図１３に示す外装電池の、リード端子の突出方向に沿った断面図である。
【図１５】図１３に示す外装電池の、電池要素の封止後の斜視図である。
【符号の説明】
１，２１フィルム外装電池
２，２２外装体
３，４，２３，２４，４３，４４外装フィルム
３ａ，４ａ，２３ａ，２４ａ，４３ａ，４４ａ凹部
５ａ，２５ａ，４５ａ正極リード端子
５ｂ，２５ｂ，４５ｂ負極リード端子
６，２６，４６電池要素
７ａ，２７ａ，４７ａ正極集電部
７ｂ，２７ｂ，４７ｂ負極集電部
７ｃテーパ部
８正極電極板
９負極電極板
１０セパレータ
１１ダイス
１２ポンチ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film-clad battery in which a battery element is housed in a flexible packaging material.
[0002]
[Prior art]
In recent years, batteries as power sources for portable devices and the like are strongly required to be light and thin. Therefore, the battery exterior material can be further reduced in weight and thickness in place of conventional metal cans that are limited in weight and thickness, and can have a free shape compared to metal cans. As the exterior material, a metal thin film or a laminate film obtained by laminating a metal thin film and a heat-fusible resin film has been used.
[0003]
A typical example of a laminate film used as a battery exterior material is to laminate a heat-sealable resin film as a heat seal layer on one side of an aluminum thin film as a metal thin film and a protective film on the other side. Three-layer laminated film.
[0004]
In a film-clad battery using a laminate film as a packaging material, generally, a battery element composed of a positive electrode, a negative electrode, an electrolyte, and the like is surrounded by a packaging material so that the heat-fusible resin film is inside, The battery element is hermetically sealed (hereinafter simply referred to as sealing) by heat-sealing the exterior material around the battery element. For example, a polyethylene film or a polypropylene film is used as the heat-fusible resin film, and a nylon film or a polyethylene terephthalate film is used as the protective film, for example.
[0005]
Here, in order to draw out the positive electrode and the negative electrode of the battery element to the outside of the exterior material, lead terminals are connected to the positive electrode and the negative electrode, respectively, and these lead terminals protrude from the exterior material. Connection of the lead terminal to the battery element is performed by ultrasonic welding or the like prior to sealing of the battery element. In sealing the battery element, two exterior members are used, the battery element is sandwiched between the two exterior members, and the peripheral portion of the exterior member is heat-sealed. Heat sealing of the exterior material is performed by first heat-sealing the three sides of the exterior material into a bag shape, and then exhausting the air from the interior of the exterior material to evacuate the interior of the exterior material by atmospheric pressure. In close contact with the battery element, the remaining one side is heat-sealed.
[0006]
At this time, if the battery element has a certain thickness, one of the outer packaging materials is formed into a hooked container shape by deep drawing so that the battery element can be easily stored. In general, the exterior material formed on the battery element is covered from above the battery element.
[0007]
For example, in Patent Document 1, a plurality of positive electrode plates and negative electrode plates each having a protruding tab are stacked in multiple layers with an electrolyte interposed therebetween, and a positive electrode tab and a negative electrode plate tab are respectively formed. The current collector is connected to the positive electrode and negative electrode lead terminals by ultrasonic welding in a batch, and then the battery element is placed on a flat exterior material. Furthermore, a film-clad battery is disclosed in which an outer packaging material formed in a container shape is covered thereon and the peripheral portions of the two outer packaging materials are heat-sealed. In this type of film-clad battery, the current collector is formed by pressing the tabs of the positive electrode plate and the negative electrode plate from above with an ultrasonic welding head, and the battery element is sealed using the above-described exterior material. Therefore, the lead terminal is pulled out from the vicinity of the lower surface of the battery element.
[0008]
A battery in which a positive electrode plate and a negative electrode plate are alternately stacked to constitute a battery element as described above is called a stacked battery. In addition, a battery using a battery element having a structure in which a positive electrode and a negative electrode are alternately laminated by stacking a belt-like positive electrode and a negative electrode with a separate sheet interposed therebetween, winding this, and then compressing it into a flat shape, It is called a wound battery.
[0009]
As battery elements, in addition to chemical batteries such as lithium batteries and nickel metal hydride batteries, those having a storage function such as capacitors can be used with laminate films as exterior materials.
[0010]
Furthermore, even in batteries for large equipment such as hybrid vehicles, the use of a film as the exterior material allows the electrode area to be increased while being thinner and lighter than batteries using metal cans. Laminate films with wider and deeper recesses are starting to be used as exterior materials for high-power, large-capacity batteries.
[0011]
[Patent Document 1]
JP 2001-126678 A
[0012]
[Problems to be solved by the invention]
However, the above-described conventional film-clad battery has a problem that the film is easily deformed excessively when the battery element is sealed, and the film may crack. Hereinafter, this phenomenon will be described with reference to FIGS. In FIG. 13, the exterior material is seen through so that the internal structure can be seen.
[0013]
As shown in FIG. 13, the positive electrode current collector 107a and the negative electrode current collector 107b formed by collectively connecting the positive electrode and negative electrode tabs of the battery element 106 together have the thickness of the battery element 106 at the base. However, the thickness gradually decreases toward the tip. Therefore, the shape of the concave portion 102a formed in the outer package 102 is substantially the whole including the portion in which the positive electrode current collector 107a and the negative electrode current collector 107b are accommodated from the viewpoint of ease of deep drawing of the outer package 102. It is formed in a rectangular shape. 13 shows the laminated battery element 106, but even in the wound type, a plurality of tabs are led out from the positive electrode and the negative electrode for high output and low resistance, respectively. In such a case, the recess of the exterior material is formed in the same manner.
[0014]
Therefore, in a state before the battery element 106 is sealed, as shown in FIG. 14, a large surplus space is formed in the vicinity of the positive electrode current collector 107a and the negative electrode current collector 107b (not shown). Due to the existence of this excess space, when the battery element 106 is sealed, as shown in FIG. 15, the exterior body 102 is greatly dented in the portion of the excess space due to atmospheric pressure. When the exterior body 102 having a large surplus space is dented, a corner portion that is bent at an acute angle is formed, and cracks may occur in the portion. Since the exterior body 102 has a function as a barrier layer for the electrolyte solution inside, if a crack occurs in the exterior body 102, leakage of the electrolyte solution occurs from the crack, and the performance and reliability as a film exterior battery are large. There is a risk of damage.
[0015]
An object of the present invention is to damage a packaging material by minimizing the dent of the packaging material that occurs when sealing the battery element in a film packaging battery using a packaging material provided with a recess for accommodating the battery element. Is to prevent.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, a film-clad battery of the present invention is a battery element having a structure in which a positive electrode and a negative electrode face each other, a positive electrode of the battery element, and a battery biased toward one surface side in the thickness direction of the battery element. Protruding from the element, provided at the leading end of the positive electrode relay portion having a thickness smaller than that of the battery element, and the negative electrode of the battery element, being provided to protrude from the battery element while being biased toward the other surface side in the thickness direction of the battery element, A negative electrode relay portion having a thickness smaller than that of the battery element at the tip, a positive electrode lead terminal connected to the positive electrode via the positive electrode relay portion, a negative electrode lead terminal connected to the negative electrode via the negative electrode relay portion, and the battery element The battery element is disposed between both sides of the thickness direction, and a storage part for storing the battery element is formed, and the positive electrode lead terminal and the negative electrode lead terminal are protruded by joining the peripheral parts to each other, so that the battery element And a hermetically-sealed exterior material. In the film-clad battery of the present invention, the positive electrode lead terminal and the negative electrode lead terminal are provided at substantially the same height with respect to the thickness direction of the battery element, and the storage portion is on one side of the outer packaging material sandwiching the battery element. It has a planar shape that is substantially equal to the planar shape of the battery element and the positive electrode relay portion provided, and the thickness at the tip of either the positive electrode relay portion or the negative electrode relay portion is reduced from the thickness of the battery element. A first concave portion having a depth substantially equal to the measured value and a planar shape substantially equal to the planar shape of the battery element and the negative electrode relay portion provided on the other side of the exterior member sandwiching the battery element, and The second concave portion having a depth substantially equal to a value obtained by subtracting the above value from the thickness of the battery element is formed so as to face each other.
[0017]
In the film-clad battery of the present invention, the storage portion for storing the battery element is formed by opposing the two concave portions having the above-described planar shape and depth, so that the space constituting the storage portion is the battery element, It almost matches the combined shape of the positive electrode relay portion and the negative electrode relay portion. As a result, when the battery element is sealed with the exterior material, the exterior material is hardly dented due to atmospheric pressure, and as a result, damage due to bending of the exterior material is prevented. In addition, since the first recess and the second recess each have a constant depth, it is easy to process the recess into the exterior material.
[0018]
Moreover, since the positive electrode lead terminal and the negative electrode lead terminal are substantially at the same height with respect to the thickness direction of the battery element, each lead terminal can be protruded from the outer packaging material without being bent when the outer packaging material is heat-sealed. Can do.
[0019]
In order to adapt the space that constitutes the storage portion by the shape of the battery element and the relay portion of either the positive electrode or the negative electrode, the first recess (or the second recess) is replaced with the relay portion of the battery element. The inclination angle of the side wall corresponding to the side from which the protrusion protrudes from the bottom surface of the first recess (or second recess) is smaller than that of the side wall corresponding to the other side of the battery element. Most preferably, the side wall of the first concave portion (or the second concave portion) corresponding to the side from which the positive electrode relay portion (or negative electrode relay portion) of the battery element protrudes is formed at the portion facing the relay portion. An inclination angle with respect to the bottom surface of one concave portion (or the second concave portion) is formed smaller than that of other portions. The first recess and the second recess can be easily formed by deep drawing.
[0020]
Further, in the case where both the positive electrode relay portion and the negative electrode relay portion are provided on the same side of the battery element, the positive electrode relay portion and the negative electrode relay portion have substantially the same shape and dimensions, and the midpoint of the side. By setting the position substantially symmetrical with respect to, the shapes of the first recess and the second recess can be matched. As a result, it is possible to use the same two exterior materials sandwiching the battery element.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0022]
[First embodiment]
1 is a perspective view showing an appearance of a film-clad battery according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view showing a configuration of the film-clad battery shown in FIG. 1, and FIG. 3 is a film shown in FIG. It is a perspective view which shows the battery element of an exterior battery. Moreover, the surface which appears in FIG. 2 among the surfaces of the thickness direction of the battery element 6 is made into the surface of the battery element 6 on the following description.
[0023]
The film-clad battery 1 of the present embodiment includes a battery element 6, a positive electrode current collector 7a and a negative electrode current collector 7b provided in the battery element 6, an outer package 2 that houses the battery element 6 together with an electrolyte, and a positive electrode It has a positive electrode lead terminal 5a connected to the current collector 7a and a negative electrode lead terminal 5b connected to the negative electrode current collector 7b.
[0024]
The exterior body 2 is composed of two exterior films 3 and 4 that sandwich and surround the battery element 6 from above and below, and the battery element 6 is sealed by heat-sealing the peripheral portions of the exterior films 3 and 4. The At this time, three sides of the exterior films 3 and 4 are first heat-sealed to leave the exterior body 2 in a bag shape, and from the remaining open side of the exterior body 2 in the bag shape to the inside The battery element 6 is sealed in a state in which the exterior body 2 is in close contact with the atmospheric pressure by exhausting air and then heat-sealing the remaining one side.
[0025]
Here, the battery element 6 will be described with reference to FIG.
[0026]
As shown in FIG. 4, the battery element 6 has a plurality of positive electrode plates 8 and a plurality of negative electrode plates 9, which are alternately stacked so that the outermost side is the negative electrode plate 9. . Separators 10 are respectively disposed between the positive electrode plate 8 and the negative electrode plate 9 and further outside the outermost negative electrode plate 9. From one side of the positive electrode plate 8 and the negative electrode plate 9, tabs 8a and 9a are respectively provided so as to protrude. The tab 8a of the positive electrode plate 8 and the tab 9a of the negative electrode plate 9 are provided at different positions so that the tabs 8a of the positive electrode plate 8 and the tabs 9a of the negative electrode plate 9 overlap each other.
[0027]
The tabs 8a of the positive electrode plate 8 and the tabs 9a of the negative electrode plate 9 are ultrasonically welded together, and as shown in FIGS. 2 and 3, the positive current collector 7a and the negative current collector 7b, respectively. Form. Since ultrasonic welding is performed by pressing the tip portions of the tabs 8a and 9a extending from the respective positive electrode plates 8 and the respective negative electrode plates 9 with a welding head, the positive electrode current collector 7a and the negative electrode current collector 7b are The base portion has a thickness substantially equal to the thickness of the battery element 6, and the thickness decreases from the thickness toward the tip thereof. The portion where the ultrasonic head is pressurized has a substantially constant thickness. Further, when forming the positive electrode current collector 7a and the negative electrode current collector 7b, the battery element 6 is placed on a table and formed by pressing with a welding head in accordance with the shape of the negative electrode current collector 7b. Thereafter, the battery element 6 is turned upside down, and similarly, the positive electrode current collector 7a is pressed by the welding head and formed. As a result, the positive electrode current collector 7 a is biased toward the surface of the battery element 6 and protrudes from the battery element 6, and the negative electrode current collector 7 b is biased toward the back surface of the battery element 6 and protrudes from the battery element 6.
[0028]
The positive electrode lead terminal 5a is on the back side of the positive electrode current collector 7a when viewed from the front surface side of the battery element 6, and the negative electrode lead terminal 5b is on the front side of the negative electrode current collector portion 7b when viewed from the front surface side of the battery element 6. They are connected at the flat points.
[0029]
As the exterior films 3 and 4, well-known exterior materials generally used for film exterior batteries, such as a laminate film obtained by laminating a metal thin film and a heat-fusible resin, can be used.
[0030]
Recesses 3a and 4a are formed in the exterior films 3 and 4 at positions facing each other, and the recesses 3a and 4a face each other to form a battery element storage portion for storing the battery element 6. The The recesses 3a and 4a can be formed by, for example, deep drawing. When the battery element 6 is sealed, the portions around the recesses 3a and 4a of the exterior films 3 and 4 where the exterior films 3 and 4 face each other are heat-sealed.
[0031]
The planar shape of the recess 3a formed on the front surface side exterior film 3 is substantially equal to the combined shape of the planar shape of the battery element 6 and the positive electrode current collector 7a, and the recess 4a formed on the back surface side exterior film 4 is formed. The planar shape is set to be substantially equal to the planar shape of the battery element 6 and the negative electrode current collector 7b.
[0032]
Here, in the present invention, the planar shape is a shape obtained when a target element is projected onto a plane perpendicular to the thickness direction of the battery element 6 (in other words, the depth direction of the recesses 3a and 4a). In particular, when the planar shape of the recesses 3a and 4a is referred to, it means the bottom shape itself of the recesses 3a and 4a.
[0033]
Moreover, the depth of each recessed part 3a, 4a is set as shown in FIG. 5 and FIG. That is, as shown in FIG. 5, the depth h1 of the recess 3a formed in the exterior film 3 on the front side is substantially equal to the value obtained by subtracting the thickness at the tip of the negative electrode current collector 7b from the thickness of the battery element 6. Set to be equal. Further, as shown in FIG. 6, the depth h2 of the recess 4a formed in the backside exterior film 4 is set to be approximately equal to the value obtained by subtracting h1 from the thickness of the battery element 6. Actually, the thickness of the front end portion of the positive electrode current collector 7a and the thickness of the front end portion of the negative electrode current collector 7b are substantially the same, so h1 and h2 are equal to approximately half the thickness of the battery element 6. As a result, both the positive electrode lead terminal 5 a and the negative electrode lead terminal 5 b are installed at substantially the center position in the thickness direction of the battery element 6.
[0034]
Furthermore, the shape and size of the positive electrode current collector 7a and the negative electrode current collector 7b are set to be substantially the same, and the planar position where the positive electrode current collector 7a and the negative electrode current collector 7b are attached to the battery element 6 is Is selected so as to be substantially symmetric with respect to the center.
[0035]
In the present embodiment configured as described above, the following effects are produced.
First, by forming the recesses 3a and 4a as described above, in the state where the battery element 6 is sandwiched between the exterior films 3 and 4, the space formed by the recess 3a is the battery element 6 and the positive electrode assembly. The space formed by the recesses 3b matches the shape of the combined electric parts 7a, and matches the shape of the combined battery element 6 and the negative electrode current collector 7b. As a result, almost no gap is formed between the outer surface enveloping the battery element 6, the positive electrode current collector 7 a, and the negative electrode current collector 7 b and the internal space formed by the exterior films 3 and 4. Therefore, even if the air in the exterior films 3 and 4 is exhausted when the battery element 6 is sealed, the exterior films 3 and 4 are hardly dented due to atmospheric pressure. Therefore, since the corner portions that are bent at an acute angle are not generated in the exterior films 3 and 4, damage such as cracks due to the bending of the exterior films 3 and 4 can be prevented, and as a result, the electrolyte contained in the interior It is possible to prevent the performance and reliability of the film-clad battery 1 from being lowered due to leakage of the film.
Secondly, the shape and dimensions of the positive electrode current collector 7a and the negative electrode current collector 7b are substantially the same, and the positions where the positive electrode current collector 7a and the negative electrode current collector 7b attach on the sides of the battery element 6 are as follows: Since these current collectors are selected so as to be substantially symmetric with respect to the center of the side to which they are attached, the exterior films 3 and 4 can be exactly the same, and the cost can be reduced by reducing the number of parts. Management is also easy.
[0036]
Third, since the depths of the recesses 3a and 4a formed in the exterior films 3 and 4 are constant, when the recesses 3a and 4a are processed by deep drawing as described later, they are used by deep drawing. The pressing surface of the punch 12 on the exterior films 3 and 4 may be flat, and the entire shape of the punch 12 may be a simple shape. Therefore, it is possible to process the recesses 3a and 4a on the exterior films 3 and 4 very easily.
[0037]
Fourthly, as described above, in the present embodiment, the positive electrode lead terminal 5 a and the negative electrode lead terminal 5 b are set at substantially the same height with respect to the thickness direction of the battery element 6. Therefore, when the exterior films 3 and 4 are fused, the positive electrode lead terminal 5a and the negative electrode lead terminal 5b can be protruded from the joint surface of the exterior films 3 and 4 without causing excessive bending.
Next, a method for forming the recesses 3a and 4a will be described. In the following description, the recess 3a will be described, but the same applies to the recess 4a.
In order to form the recess 3a, as shown in FIG. 7, the punch 12 may be deep-drawn so that the planar shape of the punch 12 has a protrusion 12a at a portion corresponding to the positive electrode current collector 7a. As a result, the positive electrode current collector portion 7a is formed in accordance with the shape of the protrusion 12a, and a space in which the positive electrode current collector portion 7a can be satisfactorily secured is secured.
On the other hand, as shown in FIG. 5, the negative electrode current collector 7b provided adjacent to the positive electrode current collector 7a on the same side is provided with a tapered portion 7c that gradually becomes thinner from the base to the outside. Yes. Since the exterior film 3 has flexibility, and the recessed part 3a can also expand according to the shape of the taper part 7c, the influence of the taper part 7c is not so large. However, it goes without saying that it is desirable to form the concave portion 3a as much as possible in a shape suitable for the tapered portion 7c.
Here, in general, when processing by deep drawing, a clearance is required between the punch and the die used for deep drawing, and the side wall of the drawn portion is tapered due to this clearance. It is known that the inclination of the taper can be arbitrarily adjusted by adjusting the clearance. That is, as shown in FIG. 8, by making the clearance C1 between the punch 12 and the die 11 larger than the clearance C2 on the other side, the taper slope of the portion corresponding to the clearance C1 can be relaxed. .
Looking at this embodiment, as shown in FIG. 7, since there is no projection 12a in the portion of the punch 12 corresponding to the negative electrode current collector 7b, a large clearance is formed between the die 11 and the punch 12. Thus, it can be formed in a more suitable shape by the tapered portion 7c of the negative electrode current collecting portion 7b.
As a result, the positive electrode current collector 7a and the negative electrode current collector 7b can be satisfactorily accommodated in the recess 3a as a whole.
[0038]
In this embodiment, the exterior body 2 is composed of two exterior films 3 and 4, but the exterior element 2 is folded in half to sandwich the battery element 6, and the three open sides are heat-sealed. It is good also as a structure which seals the battery element 6 by doing. In this case, recesses constituting the battery element storage portion are formed on both sides of the exterior material with the battery element 6 interposed therebetween when folded in half. Even in this case, the planar shape and depth of each recess may be formed in the same manner as described above.
[0039]
[Second Embodiment]
FIG. 9 is a perspective view showing the appearance of the film-clad battery according to the second embodiment of the present invention, and FIG. 10 is an exploded perspective view showing the configuration of the film-clad battery shown in FIG.
FIG. 11 is a cross-sectional view of the film-clad battery shown in FIG. 9 along the protruding direction of the positive electrode lead terminal and the negative electrode lead terminal.
[0040]
In the first embodiment, it has been described that both the positive electrode lead terminal and the negative electrode lead terminal protrude from the same side of the outer package. However, in the film-clad battery 21 of the present embodiment, the positive electrode lead terminal 25a, the negative electrode lead terminal 25b, However, it protrudes from the mutually opposing sides of the film-clad battery 21. Along with this, the positions of the positive electrode current collector 27a and the negative electrode current collector 27b provided in the battery element 26 housed in the exterior body 22 are also positions corresponding to the positive electrode lead terminal 25a or the negative electrode lead terminal 25b. The Here, as shown in FIG. 11, the positive electrode lead terminal 25 a and the negative electrode lead terminal 25 b are provided at the same height with respect to the thickness direction of the battery element 26.
In addition, the recesses 23a and 24a formed in the two exterior films 23 and 24 constituting the exterior body 22 are also in accordance with the positions and shapes of the positive electrode current collector 27a and the negative electrode current collector 27b. There are changes to the embodiment. The concave portion 23a is substantially close to a planar shape combining the battery element 26 and the negative electrode current collecting portion 27b, and the concave portion 24a is substantially close to a planar shape combining the battery element 26 and the positive electrode current collecting portion 27a. However, in the present embodiment, the widths of the positive electrode current collector portion 27a and the negative electrode current collector portion 27b are approximately the same as the length of the side of the battery element 6 on which the positive electrode current collector portion 27a and the negative electrode current collector portion 27b are provided. It is assumed that it is consistent with the shape of these current collectors.
Since other configurations are the same as those of the first embodiment, the description thereof is omitted.
[0041]
In this way, by projecting the positive electrode lead terminal 25a and the negative electrode lead terminal 25b from the sides facing each other, the widths of the positive electrode lead terminal 25a and the negative electrode lead terminal 25b are made larger than when projecting from the same side. Can do. Thereby, since the electrical resistance of the positive electrode lead terminal 25a and the negative electrode lead terminal 25b can be reduced, the loss by the positive electrode lead terminal 25a and the negative electrode lead terminal 25b is suppressed, and as a result, the high-power film-covered battery 21 is obtained. be able to.
In the present embodiment, the case where the positive electrode lead terminal 25a and the negative electrode lead terminal 25b are protruded from opposite sides of the exterior body 22 is shown, but may be protruded from adjacent sides. Also in the present embodiment, the exterior body 22 can be constituted by a single exterior film instead of the two exterior films 23 and 24.
[0042]
[Third Embodiment]
FIG. 12 is a perspective view showing an appearance of a film-clad battery according to the third embodiment of the present invention. When it is not necessary to make the widths of the positive electrode lead terminal 45a and the negative electrode lead terminal 45b so large, it is possible to install them with a smaller width. In the present embodiment, the positive electrode lead terminal 45a and the negative electrode lead terminal 45b are installed in the vicinity of the center of the side where the positive electrode lead terminal 45a and the negative electrode lead terminal 45b are provided, and the deformation of the exterior films 43 and 44 is prevented. The planar shape of the recess 44a is set to the shape of the negative electrode current collector 47b and the shape of the battery element 46 and the positive electrode current collector 47a.
[0043]
In the present embodiment, the positive electrode lead terminal 45a and the negative electrode lead terminal 45b may be provided in a point-symmetrical position with respect to the center point of the surface of the battery element 46, instead of being provided near the center of each side as described above. Is possible. In any form, the exterior films 43 and 44 can be made of the same material. As in the first and second embodiments, the cost can be reduced by reducing the number of parts and the parts can be easily managed.
[0044]
【Example】
Next, specific examples of the present invention will be described with reference to the drawings used for the description of the first embodiment, taking the film-clad battery 1 of the first embodiment as an example.
[0045]
<Production of positive electrode>
A lithium manganate powder having a spinel structure, a carbonaceous conductivity imparting material, and polyvinylidene fluoride in a mass ratio of 90: 5: 5 are mixed and dispersed in N-methylpyrrolidone (sometimes referred to as NMP), and stirred to form a slurry. It was. The amount of NMP was adjusted so that the slurry had an appropriate viscosity. This slurry was uniformly applied to one side of an aluminum foil having a thickness of 20 μm to be the positive electrode plate 8 using a doctor blade. At the time of application, the unapplied part (part where the aluminum foil was exposed) was made to be slightly streaked. Next, this was vacuum-dried at 100 ° C. for 2 hours. Thereafter, the slurry was similarly applied to the other surface of the aluminum foil and vacuum-dried. At this time, the slurry was applied so that the uncoated portions on the front and back sides coincided.
[0046]
Thus, the aluminum foil which apply | coated the active material on both surfaces was roll-pressed. This was cut into a rectangle including an uncoated portion of the active material, and a positive electrode plate 8 was obtained. The non-coated part of the active material was cut out except that a part of one side was left in a rectangle, and the remaining part was used as a tab 8a.
[0047]
<Production of negative electrode>
Amorphous carbon powder and polyvinylidene fluoride were mixed in NMP at a mass ratio of 91: 9, dispersed and stirred to form a slurry. The amount of NMP was adjusted so that the slurry had an appropriate viscosity. This slurry was uniformly applied to one side of a 10 μm thick copper foil to be the negative electrode plate 9 using a doctor blade. At the time of application, the unapplied part (part where the copper foil was exposed) was made to be a streak. Next, this was vacuum-dried at 100 ° C. for 2 hours. At this time, the coating thickness of the active material was adjusted so that the theoretical capacity per unit area of the negative electrode plate 9 and the theoretical capacity per unit area of the positive electrode plate 8 were 1: 1. Thereafter, the slurry was similarly applied to the other surface of the copper foil and vacuum-dried.
[0048]
Thus, the copper foil which apply | coated the active material on both surfaces was roll-pressed. This was cut into a rectangle including an uncoated portion into a size 2 mm longer and wider than the size of the positive electrode plate 8 to obtain a negative electrode plate 9. The non-coated part of the active material was cut out except that a part of one side was left in a rectangle, and the remaining part was used as a tab 9a.
[0049]
<Manufacture of battery elements>
As shown in FIG. 4, the positive electrode plate 8 and the negative electrode plate 9 produced as described above and the separator 10 made of a microporous sheet having a three-layer structure of polypropylene layer / polyethylene layer / polypropylene layer are alternately laminated. The laminate was 3 mm thick. At this time, the outermost electrode plate is the negative electrode plate 9, and the separator 10 is disposed on the outer side of the negative electrode plate 9 (that is, separator / negative electrode plate / separator / positive electrode plate / separator /. ... / negative electrode plate / separator).
[0050]
Next, the battery element 6, which is a laminate of the positive electrode plate 8, the separator 10, and the negative electrode plate 9, is placed on a flat base, and the tab 8 a of the positive electrode plate 8 and aluminum having a thickness of 0.1 mm are placed. The positive electrode lead terminal 5a made of a plate was collectively ultrasonically welded to obtain a positive electrode current collector 7a. Similarly, the tab 9a of the negative electrode plate 9 and the negative electrode lead terminal 5b made of a nickel plate having a thickness of 0.1 mm were collectively ultrasonically welded to form a negative electrode current collector 7b. At this time, as shown in FIG. 3, the positive electrode lead terminal 5 a and the negative electrode lead terminal 5 b have a substantially central height with respect to the thickness direction of the battery element 6, and the current collectors 7 a and 7 b are in the thickness direction of the battery element 6. On the other hand, the positions were reversed.
[0051]
<Battery element sealing>
As the exterior material, two exterior films 3 and 4 that are aluminum laminate films having a four-layer structure of nylon layer / aluminum layer / acid-modified polypropylene layer / polypropylene layer were used. A value obtained by subtracting the thickness of the battery element 6 from the thickness of the battery element 6 from the thickness of the battery element 6 by deep drawing a recess 3a having a planar shape substantially equal to the planar shape of the battery element 6 on one exterior film 3. It was provided so that the polypropylene layer side was concave at substantially the same depth. The other exterior film 4 has a recess 4 a having a planar shape substantially equal to the planar shape of the battery element 6 and the positive and negative current collectors 7 combined with the thickness at the tip of the current collector 7. It was provided with an equal depth so that the polypropylene layer side was concave.
[0052]
The battery element 6 is composed of the recesses 3a and 4a by overlapping the two exterior films 3 and 4 so that only the positive electrode lead terminal 5a and the negative electrode lead terminal 5b protrude from the exterior films 3 and 4. The battery element 6 was housed in the battery element housing portion, and the three sides around the exterior films 3 and 4 were joined by thermal fusion.
[0053]
Next, an electrolytic solution was injected into the exterior films 3 and 4 housing the battery element 6 from the remaining one side that was not joined.
[0054]
The electrolyte is 1 mol / liter LiPF ₆ Was used as a supporting salt, and a mixed solvent of propylene carbonate and ethylene carbonate (mass ratio 50:50) was used as a solvent. After injecting the electrolyte, the internal air is exhausted from the remaining one side of the exterior films 3 and 4 and the battery element 6 is sealed by heat-sealing the remaining one side to form an exterior made of a laminate film. A film-clad battery 1 which is a lithium secondary battery having the body 2 was obtained.
[0055]
The obtained film-clad battery 1 has an acute angle that causes cracks in the exterior films 3 and 4 although the exterior films 3 and 4 are slightly deformed by atmospheric pressure when the battery element 6 is sealed. The corner was not seen.
[0056]
As described above, the present invention has been described with some typical embodiments and specific examples. However, the present invention is not limited to these, and may be appropriately selected within the scope of the technical idea of the present invention. Obviously, it can be changed.
[0057]
For example, a laminate film of a metal thin film and a heat-fusible resin was used as a flexible exterior material, but other materials can be used as long as they have sufficient barrier properties to seal battery elements. It can also be used.
[0058]
Moreover, as a battery element, the laminated type thing which laminated | stacked the positive electrode plate and the negative electrode plate alternately was mentioned as an example, However, This invention is applicable also to a wound type. In this case, a plurality of tabs are provided on each of the positive electrode plate and the negative electrode plate for connection with the lead terminals, and the current collector portion is formed by joining the tabs of the positive electrode plate and the tabs of the negative electrode plate together. It is formed. In the case of the wound type, the positions of the tabs provided respectively on the positive electrode plate and the negative electrode plate are the tabs provided on the positive electrode plate when the wound positive electrode plate and negative electrode plate are compressed into a flat shape, and The tabs provided on the negative electrode plate are positioned so as to overlap each other.
[0059]
Moreover, although the battery element of the lithium secondary battery has been described as an example of the battery element, the battery of other types of chemical batteries such as a nickel hydrogen battery, a nickel cadmium battery, a lithium metal primary battery or a secondary battery, a lithium polymer battery, etc. The present invention can also be applied to elements, capacitor elements, and the like.
[0060]
【The invention's effect】
As described above, according to the present invention, the two concave portions forming the storage portion for storing the battery element are formed in an optimal and simple shape based on the planar shape and thickness of the battery element and the relay portion. It is possible to prevent damage to the exterior material due to deformation of the exterior material that occurs when the battery element is sealed. As a result, it is possible to prevent a decrease in performance and reliability of the film-clad battery due to leakage of the electrolyte from the packaging material.
Further, since the positive electrode and the negative electrode have substantially the same shape and size of the relay portion and are set to plane positions that are symmetric with respect to the center point of the side of the battery element on which they are provided, the front and back exterior films The same can be used, the cost can be reduced by reducing the number of parts, and parts management becomes easy.
Moreover, since each recess has a constant depth, each recess can be easily formed.
[0061]
In addition, since the positive electrode lead terminal and the negative electrode lead terminal are provided at substantially the same height with respect to the thickness direction of the battery element, each lead terminal can be protruded from the exterior material without being bent when the exterior film is fused. it can.
[Brief description of the drawings]
FIG. 1 is a perspective view seen from the surface side of a film-clad battery according to a first embodiment of the present invention.
2 is an exploded perspective view of the film-clad battery shown in FIG. 1. FIG.
3 is a perspective view of a battery element of the film-clad battery shown in FIG. 1. FIG.
4 is an exploded perspective view showing the configuration of the battery element shown in FIGS. 2 and 3. FIG.
5 is a cross-sectional view of the film-clad battery shown in FIG. 1 along the protruding direction of the negative electrode lead terminal in the vicinity of the negative electrode current collector.
6 is a cross-sectional view of the film-clad battery shown in FIG. 1 along the protruding direction of the positive electrode lead terminal in the vicinity of the positive electrode current collector.
7 is a plan view of an example of a deep drawing die and punch used for forming the outer surface side exterior film shown in FIG. 1; FIG.
FIG. 8 is a cross-sectional view showing a relationship between a die and a punch when a recess is formed in the exterior film by deep drawing and is intentionally tapered.
FIG. 9 is a perspective view seen from the front side of a film-clad battery according to a second embodiment of the present invention.
10 is an exploded perspective view of the film-clad battery shown in FIG. 9. FIG.
11 is a cross-sectional view of the film-clad battery shown in FIG. 9 along the protruding direction of the positive electrode lead terminal and the negative electrode lead terminal.
FIG. 12 is a perspective view seen from the surface side of a film-clad battery according to a third embodiment of the present invention.
FIG. 13 is a perspective view of a conventional film-clad battery seen through the exterior material before sealing the battery element.
14 is a cross-sectional view of the external battery shown in FIG. 13 along the protruding direction of the lead terminal.
FIG. 15 is a perspective view of the exterior battery shown in FIG. 13 after sealing the battery element.
[Explanation of symbols]
1,21 Film exterior battery
2,22 Exterior body
3,4,23,24,43,44 Exterior film
3a, 4a, 23a, 24a, 43a, 44a Recess
5a, 25a, 45a Positive lead terminal
5b, 25b, 45b Negative lead terminal
6, 26, 46 Battery element
7a, 27a, 47a Cathode current collector
7b, 27b, 47b Negative electrode current collector
7c Taper part
8 Positive electrode plate
9 Negative electrode plate
10 Separator
11 Dice
12 punches

Claims

A battery element having a structure in which a positive electrode and a negative electrode face each other;
A positive electrode relay portion that is provided on the positive electrode of the battery element so as to protrude from the battery element so as to be biased toward one surface side in the thickness direction of the battery element, and is thinner at the tip than the battery element;
A negative electrode relay portion that is provided on the negative electrode of the battery element so as to protrude from the battery element while being biased toward the other surface side in the thickness direction of the battery element, and having a thickness smaller than that of the battery element at the tip portion;
A positive electrode lead terminal connected to the positive electrode via the positive electrode relay portion;
A negative electrode lead terminal connected to the negative electrode via the negative electrode relay portion and the battery element are arranged to sandwich the battery element from both sides in the thickness direction, and a storage portion for storing the battery element is formed, and peripheral portions are joined to each other And having an exterior material that hermetically seals the battery element by projecting the positive electrode lead terminal and the negative electrode lead terminal,
The positive electrode lead terminal and the negative electrode lead terminal are provided at substantially the same height with respect to the thickness direction of the battery element,
The storage section is
The positive electrode relay is provided on one side of the exterior material sandwiching the battery element, has a planar shape substantially equal to the planar shape of the battery element and the positive electrode relay portion combined, and the thickness of the battery element A first recess having a depth substantially equal to a value obtained by reducing the thickness at the tip of either the negative electrode portion or the negative electrode relay portion;
Provided on the other side of the packaging material sandwiching the battery element, has a planar shape that is substantially equal to the planar shape of the battery element and the negative electrode relay portion combined, and from the thickness of the battery element, the value is A second recess having a depth substantially equal to the reduced value;
A film-clad battery formed by facing each other.

The film-clad battery according to claim 1, wherein the positive electrode lead terminal and the negative electrode lead terminal are provided at a substantially central height in the thickness direction of the battery element.

The positive electrode relay part and the negative electrode relay part are current collectors formed by collectively joining a plurality of tabs protruding from the positive electrode and a plurality of tabs protruding from the negative electrode, respectively. 2. The film-clad battery according to 2.

The first recess has an inclination angle of a side wall corresponding to the side from which the positive electrode relay portion of the battery element protrudes with respect to a side wall corresponding to the other side of the battery element. And the second recess has an inclination angle of the side wall corresponding to the side from which the negative electrode relay portion of the battery element protrudes with respect to the bottom surface of the second recess. The film-clad battery according to claim 3, which is smaller than a corresponding side wall.

The side wall of the first recess corresponding to the side from which the positive electrode relay portion of the battery element protrudes has an inclination angle with respect to the bottom surface of the first recess at a portion facing the positive electrode relay portion. The side wall of the second recess corresponding to the side from which the negative electrode relay portion of the battery element protrudes has an inclination angle with respect to the bottom surface of the second recess at a portion facing the negative electrode relay portion. The film-clad battery according to claim 4, which is smaller than other parts.

The positive electrode relay part and the negative electrode relay part have substantially the same shape and the same dimensions, and both are provided on the same side of the battery element so as to protrude from the battery element at a substantially symmetrical position with respect to the midpoint of the side. Item 6. The film-clad battery according to any one of Items 1 to 5.

The film-clad battery according to claim 1, wherein the positive electrode lead terminal and the negative electrode lead terminal are connected to the battery element at different sides of the battery element.

The film-clad battery according to claim 7, wherein the positive electrode lead terminal and the negative electrode lead terminal are connected to the battery element at opposite sides of the battery element.

The positive electrode relay portion and the negative electrode relay portion have substantially the same shape and the same dimensions, and are provided so as to protrude from the battery element at positions substantially symmetrical with respect to the center point of one surface in the thickness direction of the battery element. The film-clad battery according to claim 8.

The film-clad battery according to any one of claims 1 to 9, wherein the first recess and the second recess are formed by deep drawing.

The film-clad battery according to any one of claims 1 to 10, wherein the battery element is a chemical battery element or a capacitor element.