JP2004281199A

JP2004281199A - Film exterior battery

Info

Publication number: JP2004281199A
Application number: JP2003070025A
Authority: JP
Inventors: Makihiro Otohata; 牧宏乙幡; Hiroshi Yagata; 弘志屋ヶ田
Original assignee: NEC Lamilion Energy Ltd
Current assignee: NEC Lamilion Energy Ltd
Priority date: 2003-03-14
Filing date: 2003-03-14
Publication date: 2004-10-07
Anticipated expiration: 2023-03-14
Also published as: JP3751947B2

Abstract

<P>PROBLEM TO BE SOLVED: To prevent damage to a sheath material which occurs at sealing a battery element in a film-sheathed battery using the sheath material on which a recess to house the battery element is formed. <P>SOLUTION: Current collecting parts 7a, 7b of a positive electrode and a negative electrode are installed on the battery element 6, and lead terminals 5a, 5b are connected thereto. The battery element 6 is pinched from above and below by two sheath films 3, 4, and air-tightly sealed by joining peripheral parts of the sheath films 3, 4. In the one sheath film 3, the recess 3a which has nearly the same plane shape as that of the battery element 6, and of which the depth is nearly the same as a value subtracting thicknesses of the current collecting parts 7a, 7b from that of the battery element 6 is formed. In the other film 4, the recess 4a which has nearly the same plane shape as the sum of thicknesses of battery element 6 and the current collecting parts 7a, 7b, and of which the depth is nearly the same as the thicknesses of the current collecting parts 7a, 7b is formed. These recesses 3a, 4a are opposed to each other, and the housing part of the battery element 6 is formed. <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１５および図１６を参照して説明する。なお、図１５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１５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集電部１０７は、基部では電池要素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、外装材１０２に形成する凹部１０２ａの形状は、外装材１０２の深絞り成形の容易性の観点から、集電部１０７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１５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、集電部１０７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１６に示すように、大気圧によって余剰空間の部分で外装材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材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。外装材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、外装材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、この電池要素の正極および負極にそれぞれ、電池要素の厚み方向での一方の表面に沿って電池要素から突出して設けられた、電池要素よりも厚みの薄い中継部と、中継部を介して正極および負極とそれぞれ接続されたリード端子と、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リード端子を突出させて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ではさらに、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、電池要素の平面形状と略等しい平面形状を持ち、かつ、電池要素の厚さから中継部の厚さ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、中継部の厚さと略等しい深さの第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、電池要素および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】
本発明のフィルム外装電池において、リード端子は、中継部の、外装材の一方の側と対向する面に接続されていることが好ましい。第２の凹部は、中継部の深さと略等しい深さであるので、中継部のリード端子が接続された面は外装材同士が互いに接合される面とほぼ同一平面上にある。したがって、中継部の上記の面にリード端子を接続することで、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の凹部の、電池要素の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】
【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。
【００２１】
［第１の実施形態］
図１および図２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３および図４は、図１および図２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。なお、図１と図２、および図３と図４は表裏の関係にあり、以下の説明では、便宜上、図１および図３に示される側を表面側、図２および図４に示される側を裏面側とする。
【００２２】
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。
【００２３】
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。
【００２４】
ここで、電池要素６について、図５を参照して説明する。
【００２５】
図５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。
【００２６】
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３および図４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、超音波溶接は、電池要素６を平らな台上に置いて行うので、正極集電部７ａおよび負極集電部７ｂは、電池要素６裏面に沿って電池要素６から突出している。つまり、電池要素６の裏面と正極集電部７ａおよび負極集電部７ｂの裏面とは、ほぼ同一平面上にある。
【００２７】
正極リード端子５ａおよび負極リード端子５ｂは、それぞれ正極集電部７ａおよび負極集電部７ｂの、表面側の外装フィルム３と対向する面の、ほぼ一定の厚みとなった平らな箇所で接続される。
【００２８】
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。
【００２９】
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。
【００３０】
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の平面形状と略等しく、かつ、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、正極集電部７ａ、および負極集電部７ｂを合わせた平面形状と略等しくなるように設定される。
【００３１】
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。
【００３２】
また、各凹部３ａ，４ａの深さは、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、電池要素６の厚みから集電部７（図６では、正極と負極とを区別せず、両者を総称して単に集電部７として示している。また、以下の説明においても、正極と負極を区別せず単に集電部と称することがある。リード端子についても同様である。）の先端部での厚みを減じた値と略等しく、かつ、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、集電部７の先端部での厚みと略等しくなるように設定される。
【００３３】
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，４ａを対向させて形成される空間は、電池要素６および集電部７を合わせた形状に合致しており、電池要素６および集電部７と外装フィルム３，４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。
【００３４】
また、各外装フィルム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、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の外装フィルム３，４への加圧面は平面でよく、ポンチ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。
【００３５】
さらに、図６にも示したように、本実施形態では、リード端子５は集電部７のフィルム３と対向する面のほぼ一定の厚みとなった平らな箇所で集電部７と接続されているが、裏側のフィルム４に形成された凹部４ａの深さは集電部７のリード端子５が接続された箇所での厚みと略等しいので、集電部７のリード端子５が接続された面は、フィルム３，４同士の接合面とほぼ同一平面上にある。そのため、このようにリード端子５を接続することで、リード端子５を曲げ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。
【００３６】
ところで、前述したように、集電部７は、その基部においては電池要素６の厚みとほぼ等しく、そこから先端に向かって厚みが薄くなる形状であるので、表面側の外装フィルム３の凹部３ａをその平面形状が電池要素６の平面形状と等しくなるように形成した場合、集電部７の根元部分が凹部３ａに収まりきれなくなることが懸念される。しかし、外装フィルム３，４は可撓性を有しており凹部３ａは集電部７の根元部分の形状に合わせて広がることもできるので、集電部７の根元部分の影響はそれほど大きくない。
【００３７】
しかも、凹部３ａを深絞り成形によって加工する場合、実際には、深絞り成形に使用するポンチとダイスとの間にクリアランスが必要であり、このクリアランスによって凹部３ａの側壁はテーパ状となる。このテーパを利用すれば、集電部７の根元部分の影響をより少なくすることができる。
【００３８】
最も好ましいのは、外装フィルム３に凹部３ａを深絞り成形で加工する際、ポンチとダイスとのクリアランスを、所望のテーパ形状が得られるように適宜設定することである。すなわち、図７に示すように、外装フィルム３に形成しようとする凹部３ａの集電部７（図６参照）が突出する辺に対応する部位での、ポンチ１２とダイス１１とのクリアランスＣ１を、残りの３辺に対応する部位でのポンチ１２とダイス１１とのクリアランスＣ２よりも大きくする。
【００３９】
これにより、電池要素６の集電部７が突出した辺に対応する凹部３ａの側壁の、凹部３ａの底面に対する傾斜角度が、残りの３辺に対応する側壁と比べて小さくなる。そして、クリアランスＣ１の大きさを、形成される凹部３ａのこの部分での傾斜が集電部７の根元部分での傾斜と略等しくなるように設定すれば、集電部７の根元部分も含めて、電池要素６を凹部３ａ内に良好に収めることができる。
【００４０】
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。
【００４１】
［第２の実施形態］
図８および図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および図１１は、図８および図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。本実施形態においても、第１の実施形態と同様に、図８および図１０はフィルム外装電池を表面側から見た図を示し、図９および図１１はフィルム外装電池を裏面側から見た図を示している。
【００４２】
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の反対側の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。また、外装体２２を構成する２枚の外装フィルム２３，２４にそれぞれ形成する凹部２３ａ，２４ａについても、表側の外装フィルム２３に形成する凹部２３ａは第１の実施形態と同様であるが、裏側の外装フィルム２４に形成する凹部２４ａは、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、平面形状が第１の実施形態に対して変更されている。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。
【００４３】
このように、正極リード端子２５ａと負極リード端子２５ｂとを互いに異な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。
【００４４】
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の互いに反対側の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。
【００４５】
［第３の実施形態］
図１２は、本発明の第２の実施形態によるフィルム外装電池の構成を示す分解斜視図であり、図１３は、図１２に示す表側の外装フィルムを裏側から見た平面図である。
【００４６】
本実施形態のフィルム外装電池３１では、表側の外装フィルム３３に形成する凹部３３ａの形状が、第１の実施形態と異なっている。より詳しくは、凹部３３ａの、電池要素３６の正極集電部３７ａおよび負極集電部３７ｂが設けられた辺に対応する側壁が、正極集電部３７ａおよび負極集電部３７ｂと対向する部位で、凹部３３ａの底面に対する傾斜角度が他の部位と比べて小さくなるように形成されている。その他、裏面側の外装フィルム３４の凹部３４ａの形状、凹部３３ａ，３４ａのそれぞれの深さ、正極リード端子３５ａが接続される正極集電部３７ａおよび負極リード端子３５ｂが接続される負極集電部３７ｂが電池要素３６の同じ辺に位置することは、第１の実施形態と同様である。
【００４７】
このような凹部３３ａは、深絞り成形で加工する場合には、図１４に示すように、ダイス４１の穴４３の形状を、各集電部に対応する位置にそれぞれ切り込み部４３ａを有する形状とするだけで、ポンチ４２については第１の実施形態と同様の、凹部３３ａ（図１３参照）の底面形状に等しい加圧面を有するものを用いて容易に形成することができる。
【００４８】
上述した形状に凹部３３ａを形成することで、各凹部３３ａ，３４ａを向き合わせて構成される電池要素収納部の形状を、正極集電部３７ａおよび負極集電部３７ｂを合わせた電池要素３６の外形状に、より適合させることができる。その結果、電池要素３６の封止時の、外装フィルム３３，３４の変形をより抑えることができ、外装フィルム３３，３４にクラックが発生するのをより効果的に防止することができる。
【００４９】
本実施形態では、外装体を２枚の外装フィルム３３，３４で構成した例を示したが、１枚の外装フィルムで構成することもできる。また、正極リード電極３５ａおよび負極リード端子３５ｂを外装体の同じ辺から突出させた例を示したが、互いに異なる辺から突出させてもよい。
【００５０】
【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。
【００５１】
〈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。
【００５２】
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。
【００５３】
〈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。
【００５４】
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。
【００５５】
〈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５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）。
【００５６】
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。
【００５７】
〈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。
【００５８】
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。
【００５９】
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。
【００６０】
電解液は、１ｍｏｌ／リットルのＬｉＰＦ_６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。
【００６１】
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。
【００６２】
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。
【００６３】
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。
【００６４】
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。
【００６５】
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。
【００６６】
【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。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。
【００６７】
また、リード端子を、中継部の、外装材の一方の側と対向する面に接続した構成とすれば、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裏面側から見た斜視図である。
【図３】図１に示したフィルム外装電池の分解斜視図である。
【図４】図１に示したフィルム外装電池の裏面側から見た分解斜視図である。
【図５】図２および図４に示した電池要素の構成を示す分解斜視図である。
【図６】図１に示したフィルム外装電池の、集電部近傍でのリード端子の突出方向に沿った断面図である。
【図７】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８】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９】図８に示したフィルム外装電池の裏面側から見た斜視図である。
【図１０】図８に示したフィルム外装電池の分解斜視図である。
【図１１】図８に示したフィルム外装電池の裏面側から見た分解斜視図である。
【図１２】本発明の第３の実施形態によるフィルム外装電池を表面側から見た状態で示す分解斜視図である。
【図１３】図１２に示した表面側の外装フィルムを裏面側から見た平面図である。
【図１４】図１２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１５】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１６】図１５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】
１，２１，３１フィルム外装電池
２，２２外装体
３，４，２３，２４，３３，３４外装フィルム
３ａ，４ａ，２３ａ，２４ａ，３３ａ，３４ａ凹部
５リード端子
５ａ，２５ａ，３５ａ正極リード端子
５ｂ，５ｂ，３５ｂ負極リード端子
６，２６，３６電池要素
７集電部
７ａ，２７ａ，３７ａ正極集電部
７ｂ，２７ｂ，３７ｂ負極集電部
８正極電極板
９負極電極板
１０セパレータ
１１，４１ダイス
１２，４２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. 15 and 16. In FIG. 15, the exterior material is seen through so that the internal structure can be seen.
[0013]
As shown in FIG. 15, the current collector 107 formed by collectively connecting the positive electrode and negative electrode tabs of the battery element 106 has a thickness substantially equal to the thickness of the battery element at the base, but the tip It has a shape in which the thickness is gradually reduced toward. Therefore, the shape of the recess 102a formed in the exterior material 102 is formed in a substantially rectangular shape as a whole including the portion in which the current collector 107 is accommodated from the viewpoint of easy deep drawing of the exterior material 102. FIG. 15 shows the stacked 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, a large surplus space is formed in the vicinity of the current collector 107 before the battery element 106 is sealed. Due to the presence of this surplus space, when the battery element 106 is sealed, as shown in FIG. 16, the exterior material 102 is greatly dented in the surplus space due to atmospheric pressure. When the exterior material 102 having a large surplus space is recessed, a corner portion that is bent at an acute angle is formed, and there is a possibility that a crack may occur in the portion. Since the exterior material 102 has a function as a barrier layer such as an internal electrolyte, if the exterior material 102 is cracked, an electrolyte leaks 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, the film-clad battery of the present invention has a battery element having a structure in which a positive electrode and a negative electrode face each other, and a positive electrode and a negative electrode of the battery element, respectively, on one surface in the thickness direction of the battery element. A relay portion that is provided so as to protrude from the battery element along the line, is thinner than the battery element, is connected to the positive electrode and the negative electrode via the relay portion, and the battery element is sandwiched from both sides in the thickness direction. In addition, a housing portion for housing the battery element is formed, and a peripheral portion is joined to each other so that the lead terminal protrudes to have an exterior material that hermetically seals the battery element. Further, in the film-clad battery of the present invention, the storage portion has a planar shape that is provided on one side of the packaging material that sandwiches the battery element and that is substantially equal to the planar shape of the battery element, and the thickness of the battery element. The first concave portion having a depth substantially equal to the value obtained by subtracting the thickness of the relay portion from the above and the planar shape of the battery element and the relay portion, which are provided on the other side of the exterior material sandwiching the battery element, are substantially the same. A second concave portion having the same planar shape and having a depth substantially equal to the thickness of the relay portion is formed to face each other.
[0017]
In the film-clad battery according to 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, respectively. It almost matches the combined shape of the relay parts. 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]
In the film-clad battery of the present invention, it is preferable that the lead terminal is connected to a surface of the relay portion facing one side of the packaging material. Since the second recess has a depth substantially equal to the depth of the relay portion, the surface of the relay portion to which the lead terminals are connected is substantially flush with the surface where the exterior materials are joined to each other. Therefore, by connecting the lead terminal to the above-mentioned surface of the relay portion, the lead terminal can be projected from the exterior material without being bent.
[0019]
In order to adapt the space constituting the storage portion by the shape of the battery element and the relay portion combined, the first recess is formed on the side wall corresponding to the side from which the relay portion of the battery element protrudes. The inclination angle with respect to the bottom surface of the battery element 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 recess corresponding to the side from which the relay part of the battery element protrudes is compared with the other part in the inclination angle with respect to the bottom surface of the first recess at the part facing the relay part. To make small. The first recess and the second recess can be easily formed by deep drawing.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0021]
[First Embodiment]
1 and 2 are perspective views showing the appearance of the film-clad battery according to the first embodiment of the present invention, and FIGS. 3 and 4 are exploded perspective views showing the configuration of the film-clad battery shown in FIG. 1 and FIG. It is. 1 and FIG. 2 and FIG. 3 and FIG. 4 are in a front-back relationship. In the following description, for convenience, the side shown in FIG. 1 and FIG. 3 is the front side, and the side shown in FIG. 2 and FIG. Is the back side.
[0022]
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.
[0023]
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.
[0024]
Here, the battery element 6 will be described with reference to FIG.
[0025]
As shown in FIG. 5, the battery element 6 includes 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.
[0026]
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. 3 and 4, 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. In addition, since ultrasonic welding is performed with the battery element 6 placed on a flat table, the positive electrode current collector 7 a and the negative electrode current collector 7 b protrude from the battery element 6 along the back surface of the battery element 6. That is, the back surface of the battery element 6 and the back surfaces of the positive electrode current collector 7a and the negative electrode current collector 7b are substantially on the same plane.
[0027]
The positive electrode lead terminal 5a and the negative electrode lead terminal 5b are connected at a flat portion having a substantially constant thickness on the surface of the positive electrode current collector portion 7a and the negative electrode current collector portion 7b facing the exterior film 3 on the surface side. The
[0028]
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.
[0029]
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.
[0030]
The planar shape of the concave portion 3a formed on the front surface side exterior film 3 is substantially the same as the planar shape of the battery element 6, and the planar shape of the concave portion 4a formed on the rear surface side exterior film 4 is the battery element 6, It is set to be substantially equal to the planar shape of the positive electrode current collector 7a and the negative electrode current collector 7b.
[0031]
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.
[0032]
Moreover, the depth of each recessed part 3a, 4a is set as shown in FIG. That is, the depth h1 of the recess 3a formed in the exterior film 3 on the surface side is determined by the current collector 7 (the positive electrode and the negative electrode are not distinguished from each other in FIG. In the following description, the positive electrode and the negative electrode may be referred to simply as a current collector, and the same applies to the lead terminal. The depth h2 of the recess 4a formed on the back surface side exterior film 4 is set so as to be substantially equal to the thickness at the front end of the current collector 7.
[0033]
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 facing the recesses 3a and 4a is the battery element 6 and the current collector. 7, the gap between the battery element 6 and the current collector 7 and the exterior films 3 and 4 is hardly formed. 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 deteriorated due to leakage or the like.
[0034]
Further, since the depths of the recesses 3a and 4a formed in the respective exterior films 3 and 4 are constant, when the recesses 3a and 4a are processed by deep drawing, the outer packaging film 3 of the punch used for deep drawing is used. , 4 may be a flat pressing surface, and the shape of the entire punch can be a simple shape. Therefore, it is possible to process the recesses 3a and 4a on the exterior films 3 and 4 very easily.
[0035]
Further, as shown in FIG. 6, in this embodiment, the lead terminal 5 is connected to the current collector 7 at a flat portion having a substantially constant thickness on the surface facing the film 3 of the current collector 7. However, since the depth of the recess 4a formed in the film 4 on the back side is substantially equal to the thickness at the location where the lead terminal 5 of the current collector 7 is connected, the lead terminal 5 of the current collector 7 is connected. The surface is substantially flush with the bonding surface between the films 3 and 4. Therefore, by connecting the lead terminal 5 in this way, the lead terminal 5 can be projected from the joint surface of the exterior films 3 and 4 without bending.
[0036]
By the way, as described above, the current collector 7 has a shape that is substantially equal to the thickness of the battery element 6 at the base and decreases in thickness toward the tip thereof. Is formed so that the planar shape thereof is equal to the planar shape of the battery element 6, there is a concern that the root portion of the current collector 7 cannot be accommodated in the recess 3 a. However, since the exterior films 3 and 4 have flexibility and the recessed part 3a can also expand according to the shape of the base part of the current collection part 7, the influence of the base part of the current collection part 7 is not so large. .
[0037]
Moreover, when the recess 3a is processed by deep drawing, a clearance is actually required between the punch used for deep drawing and the die, and the side wall of the recess 3a becomes tapered due to this clearance. If this taper is used, the influence of the base portion of the current collector 7 can be reduced.
[0038]
Most preferably, when the recess 3a is processed in the exterior film 3 by deep drawing, the clearance between the punch and the die is appropriately set so as to obtain a desired tapered shape. That is, as shown in FIG. 7, the clearance C <b> 1 between the punch 12 and the die 11 at the portion corresponding to the side from which the current collector 7 (see FIG. 6) of the recess 3 a to be formed in the exterior film 3 protrudes. The clearance C2 between the punch 12 and the die 11 at the portion corresponding to the remaining three sides is made larger.
[0039]
Thereby, the inclination angle of the side wall of the recess 3a corresponding to the side from which the current collecting part 7 of the battery element 6 protrudes is smaller than the side wall corresponding to the remaining three sides. And if the magnitude | size of clearance C1 is set so that the inclination in this part of the recessed part 3a formed may become substantially equal to the inclination in the root part of the current collection part 7, the root part of the current collection part 7 is also included. Thus, the battery element 6 can be satisfactorily accommodated in the recess 3a.
[0040]
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.
[0041]
[Second Embodiment]
8 and 9 are perspective views showing the appearance of the film-clad battery according to the second embodiment of the present invention, and FIGS. 10 and 11 are exploded views showing the configuration of the film-clad battery shown in FIGS. 8 and 9. It is a perspective view. Also in the present embodiment, as in the first embodiment, FIGS. 8 and 10 show the film-covered battery as viewed from the front side, and FIGS. 9 and 11 are views of the film-covered battery as viewed from the back side. Is shown.
[0042]
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 opposite side 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 Further, as for the recesses 23a and 24a formed in the two exterior films 23 and 24 constituting the exterior body 22, respectively, the recesses 23a formed in the front exterior film 23 are the same as those in the first embodiment, but the back side The recess 24a formed in the exterior film 24 has a planar shape changed from that of the first embodiment in accordance with the position and shape of the positive electrode current collector 27a and the negative electrode current collector 27b. Since other configurations are the same as those of the first embodiment, the description thereof is omitted.
[0043]
In this manner, by projecting the positive electrode lead terminal 25a and the negative electrode lead terminal 25b from different sides, the widths of the positive electrode lead terminal 25a and the negative electrode lead terminal 25b can be 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.
[0044]
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.
[0045]
[Third Embodiment]
FIG. 12 is an exploded perspective view showing the configuration of the film-clad battery according to the second embodiment of the present invention, and FIG. 13 is a plan view of the front-side exterior film shown in FIG. 12 viewed from the back side.
[0046]
In the film-clad battery 31 of this embodiment, the shape of the recessed part 33a formed in the exterior film 33 on the front side is different from that of the first embodiment. More specifically, the side wall of the recess 33a corresponding to the side where the positive electrode current collector 37a and the negative electrode current collector 37b of the battery element 36 are provided is opposed to the positive electrode current collector 37a and the negative electrode current collector 37b. The inclination angle with respect to the bottom surface of the recess 33a is smaller than those of other portions. In addition, the shape of the recess 34a of the exterior film 34 on the back side, the depth of each of the recesses 33a and 34a, the positive current collector 37a to which the positive lead terminal 35a is connected, and the negative current collector to which the negative lead terminal 35b is connected. 37b is located on the same side of the battery element 36 as in the first embodiment.
[0047]
When such a concave portion 33a is processed by deep drawing, as shown in FIG. 14, the shape of the hole 43 of the die 41 has a shape having a cut portion 43a at a position corresponding to each current collecting portion. As a result, the punch 42 can be easily formed using a punch having the same pressing surface as the bottom surface of the recess 33a (see FIG. 13), as in the first embodiment.
[0048]
By forming the concave portion 33a in the shape described above, the shape of the battery element housing portion configured by facing the concave portions 33a and 34a is changed to the shape of the battery element 36 including the positive electrode current collector portion 37a and the negative electrode current collector portion 37b. It can be more adapted to the outer shape. As a result, the deformation of the exterior films 33 and 34 when the battery element 36 is sealed can be further suppressed, and the occurrence of cracks in the exterior films 33 and 34 can be more effectively prevented.
[0049]
In this embodiment, the example which comprised the exterior body by the two exterior films 33 and 34 was shown, However, It can also comprise by one exterior film. Further, although the example in which the positive electrode lead electrode 35a and the negative electrode lead terminal 35b are protruded from the same side of the exterior body has been shown, they may be protruded from different sides.
[0050]
【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.
[0051]
<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.
[0052]
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.
[0053]
<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.
[0054]
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.
[0055]
<Manufacture of battery elements>
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 as shown in FIG. 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).
[0056]
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 which consists of a board was ultrasonically welded collectively, and it was set as the positive electrode current collection part 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.
[0057]
<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.
[0058]
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.
[0059]
Next, an electrolytic solution was injected into the exterior films 3 and 4 containing the battery element 6 from the remaining one side that was not joined.
[0060]
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.
[0061]
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.
[0062]
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.
[0063]
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.
[0064]
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.
[0065]
In addition, the battery element of the lithium secondary battery has been described as an example of the battery element. The present invention can also be applied to elements, capacitor elements, and the like.
[0066]
【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. Damage to the exterior material due to deformation of the exterior material that occurs when the battery element is sealed can be prevented. As a result, it is possible to prevent a decrease in performance and reliability of the film-clad battery due to leakage of the electrolytic solution from the packaging material. In addition, since the depth of each recess is constant, each recess can be easily formed.
[0067]
Further, if the lead terminal is connected to the surface of the relay portion facing one side of the exterior material, the lead terminal can be projected from the exterior material without bending.
[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 a perspective view of the film-clad battery shown in FIG. 1 as viewed from the back side.
FIG. 3 is an exploded perspective view of the film-clad battery shown in FIG.
4 is an exploded perspective view of the film-clad battery shown in FIG. 1 viewed from the back side.
5 is an exploded perspective view showing the configuration of the battery element shown in FIGS. 2 and 4. FIG.
6 is a cross-sectional view of the film-clad battery shown in FIG. 1 along the protruding direction of the lead terminal in the vicinity of the current collector.
FIG. 7 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. 8 is a perspective view seen from the front side of a film-clad battery according to a second embodiment of the present invention.
9 is a perspective view of the film-clad battery shown in FIG. 8 as seen from the back side.
10 is an exploded perspective view of the film-clad battery shown in FIG.
11 is an exploded perspective view seen from the back side of the film-clad battery shown in FIG.
FIG. 12 is an exploded perspective view showing a film-clad battery according to a third embodiment of the present invention as seen from the front side.
13 is a plan view of the front surface side exterior film shown in FIG. 12 as viewed from the back surface side.
14 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. 12. FIG.
FIG. 15 is a perspective view of a conventional film-clad battery seen through the exterior material before sealing of the battery element.
16 is a perspective view of the exterior battery shown in FIG. 15 after the battery element is sealed. FIG.
[Explanation of symbols]
1,21,31 Film exterior battery
2,22 Exterior body
3, 4, 23, 24, 33, 34 Exterior film
3a, 4a, 23a, 24a, 33a, 34a Recess
5 Lead terminal
5a, 25a, 35a Positive lead terminal
5b, 5b, 35b Negative lead terminal
6, 26, 36 Battery element
7 Current collector
7a, 27a, 37a Positive current collector
7b, 27b, 37b Negative electrode current collector
8 Positive electrode plate
9 Negative electrode plate
10 Separator
11,41 dice
12,42 punch

Claims

A battery element having a structure in which a positive electrode and a negative electrode face each other;
A relay portion having a thickness smaller than that of the battery element, which is provided on each of the positive electrode and the negative electrode of the battery element so as to protrude from the battery element along one surface in the thickness direction of the battery element,
Lead terminals respectively connected to the positive electrode and the negative electrode through the relay portion;
The battery element is arranged to sandwich the battery element from both sides in the thickness direction, and a storage part for storing the battery element is formed, and peripheral parts are joined to each other so that the lead terminal protrudes to hermetically seal the battery element. With the outer packaging material stopped,
The storage section is
Provided on one side of the packaging material sandwiching the battery element, has a planar shape substantially equal to the planar shape of the battery element, and a value obtained by subtracting the thickness of the relay portion from the thickness of the battery element A first recess of substantially equal depth;
Provided on the other side of the packaging material sandwiching the battery element, has a planar shape substantially equal to the planar shape of the battery element and the relay portion combined, and has a depth substantially equal to the thickness of the relay portion. A second recess,
A film-clad battery formed by facing each other.

2. The film-clad battery according to claim 1, wherein the relay portion is a current collecting portion formed by collectively joining a plurality of tabs protruding from the positive electrode and a plurality of tabs protruding from the negative electrode.

3. The film-clad battery according to claim 1, wherein the lead terminal is connected to a surface of the relay unit that faces one side of the exterior material.

The first recess has an inclination angle of the side wall corresponding to the side from which the relay portion of the battery element protrudes with respect to the bottom surface of the first recess compared to the side wall corresponding to the other side of the battery element. The film-clad battery according to any one of claims 1 to 3, which is small.

The side wall of the first recess corresponding to the side from which the 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 relay portion as compared with other portions. The film-clad battery according to any one of claims 1 to 3, which is small.

The film-clad battery according to any one of claims 1 to 5, 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 6, 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 any one of claims 1 to 7, wherein the battery element is a chemical battery element or a capacitor element.