JP3663087B2

JP3663087B2 - Thin battery

Info

Publication number: JP3663087B2
Application number: JP23682199A
Authority: JP
Inventors: 竜司大下; 佳典喜田
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1999-08-24
Filing date: 1999-08-24
Publication date: 2005-06-22
Anticipated expiration: 2019-08-24
Also published as: JP2001068090A

Description

【０００１】
【発明の属する技術分野】
本発明は、電気・電子機器あるいは通信機器等の電源として使用される薄型電池に係り、特に、薄板状の発電要素を両側から挟み込んで被覆する外装体を備えた薄型電池の改良に関する。
【０００２】
【従来の技術】
小型軽量でかつ高容量で充放電可能な電池としてリチウム二次電池が実用化されるようになり、小型ビデオカメラ、携帯電話、ノートパソコン等の携帯用電子・通信機器等に用いられるようになった。この種のリチウム二次電池は、負極活物質としてリチウムイオンを吸蔵・脱離し得るカーボン系材料あるいはリチウム金属もしくはリチウム合金を用い、正極活物質として、ＬｉＣｏＯ₂，ＬｉＮｉＯ₂，ＬｉＭｎ₂Ｏ₄，ＬｉＦｅＯ₂等のリチウム含有金属酸化物を用い、有機溶媒に溶質としてリチウム塩を溶解した電解質を用いて構成される電池である。
【０００３】
通常、この種のリチウム二次電池は過充電によりガスが発生するため、安全のために過充電防止装置が設けられており、過充電状態となって電池内部で過剰なガスが発生した場合には、過充電防止装置が作動して充電電流を遮断するようになされている。また、電池内に安全弁を備えて、短絡等により電池内部で過剰なガスが発生した場合には、安全弁が作動して電池外部にガスを排出するようになされている。
【０００４】
ところで、近年、携帯用電子・通信機器の急速な普及に伴って、この種のリチウム二次電池の用途が拡大し、さらなる軽量化、小型化、薄型化が要求されるようになった。そこで、ヒートシール性を有する合成樹脂製の外装体を用い、この外装体の内部に、正極と負極と電解質からなる薄板状の発電要素を両側から挟み込んでその周縁部を密封するようにした薄型電池が提案されるようになった。
【０００５】
【発明が解決しようとする課題】
このような薄型電池にあっては、あらゆる応力に対する柔軟性に富む外装体を用いることが望ましく、外装体に金属箔に熱溶着性樹脂を積層したラミネートフィルムを用いるようになった。しかしながら、このようなラミネートフィルムを外装体に用いると、外装体の機械的強度が弱いため、過充電や外部短絡等の異常な状態になると、電池内で発生したガスの圧力が上昇し、やがては封止が破壊されて漏液が生じるという問題があった。また、上述したような過充電防止装置や安全弁を備える空間が充分に存在しないため、電池内に過充電防止装置や安全弁を備えるようにすることが困難であった。
【０００６】
そこで、電池の集電方法を改良して、過充電時や短絡時の電流遮断や、内圧上昇時の内圧緩和と液漏れ防止などの安全機構をできるだけ軽量で小型に、かつ簡単な方法で実現しようとした薄型電池が特開平１０−２９４０９７号公報において提案されるようになった。
しかしながら、特開平１０−２９４０９７号公報において提案された薄型電池にあっては、電流遮断するための構造が複雑であるとともに、過充電時や短絡時に確実に電流遮断が行えないという問題があり、未だ不十分で、さらなる改良が必要であった。
そこで、本発明は上記問題点を解消するためになされたものであって、簡単な構造で、過充電時や短絡時に確実に電流遮断が行え、かつ製造がしやすい薄型電池を提供することを目的とするものである。
【０００７】
【課題を解決するための手段およびその作用・効果】
このため、本発明の薄型電池においては、正極から延出する正極集電タブと、負極から延出する負極集電タブと、外装体の周縁部に挟み込まれるとともに同周縁部に固着されて同外装体より外部に延出する正極端子と、外装体の周縁部に挟み込まれるとともに同周縁部に固着されて同外装体より外部に延出する負極端子とを備え、正極端子と正極集電タブとの接続部あるいは負極端子と負極集電タブとの接続部の少なくとも一方の接続部が固着されることなく接触して接続されており、電池内圧の上昇時に接続部の接触が遮断されるようにしている。
【０００８】
このように、外装体の周縁部に固着されてこの外装体より外部に延出する正極端子と正極集電タブとの接続部あるいは負極端子と負極集電タブとの接続部の少なくとも一方の接続部が固着されることなく接触して接続されていると、通常の放電状態においては、これらの接続部を通して正・負極端子に放電電流が導出され、通常の充電状態においては、これらの正・負極端子からこれらの接続部を通して各集電タブに充電電流が導入されることとなる。
【０００９】
ここで、例えば、何らかの理由により過充電状態あるいは外部短絡状態が生じて、電池内にガスが発生するようになると、ガスの発生に伴って外装体は徐々に膨出するようになる。このような状態でさらにこれらの状態が継続すると、過剰なガスが電池内に充満するようなるが、正・負極端子と各集電タブとの少なくも一方の接続部は接触しているだけであるため、やがてはこの接続部の接触が遮断されて（接続部での端子と集電タブとの接続が離れて）、これ以上は充電電流あるいは短絡電流が流れなくなる。これにより、これ以上のガスの発生は起こらなくなり、漏液あるいは電池の破裂を防止できるようになる。したがって、正・負極端子と各集電タブとの少なくとも一方の接続部を接触させるだけの簡単な構造で、漏液あるいは電池の破裂を防止できるようになる。
【００１０】
そして、アルミニウム箔の両側にポリオレフィン系熱溶着フィルが積層されたラミネートフィルムで外装体を構成するようにすると、外装体の周縁部を熱圧着するだけで容易にヒートシールすることができるようになるため、この種の薄型電池の封着が容易になり、容易に製造できるようになる。
また、電解質としてゲル状のポリマー電解質を用いるようにすると、ヒートシールだけの簡単な封着であっても漏液を生じることを完全に防止できるようになる。
【００１１】
【発明の実施の形態】
以下に本発明の薄型電池の一実施形態を図に基づいて説明する。なお、図１は本発明の薄型電池を模式的に示す図であり、図１（ａ）はその断面を示す断面図であり、図１（ｂ）はその上面図である。図２は図１の要部を拡大して示す断面図であり、図２（ａ）は通常の状態を示す図であり、図２（ｂ）はガスが発生して電池が膨出した状態を示す図である。本発明は以下の実施の形態に何ら限定されるものではなく、その要旨を変更しない範囲において適宜変更して実施することが可能なものである。
【００１２】
１．正極の作製
８００℃の温度で熱処理したリチウム含有二酸化コバルト（ＬｉＣｏＯ₂）を正極活物質として用い、この正極活物質としてのリチウム含有二酸化コバルト（ＬｉＣｏＯ₂）８５重量％と、導電剤としてのカーボン粉末１０重量％と、結着剤としてのポリフッ化ビニリデン（ＰＶｄＦ）５重量％とを混合した。この後、この混合物にＮ−メチル−２−ピロリドン（ＮＭＰ）を加えて混合・混練して正極活物質スラリーを作製した。
【００１３】
ついで、この正極活物質スラリーをアルミニウム箔からなる正極集電体１２にドクターブレード法により塗着した後、圧延後の厚みが８０μｍとなるように圧延した。ついで、１３０℃の温度で真空乾燥した後、所定寸法に切断して、正極集電体１２の表面に正極合剤層１１を備えた正極を作製した。なお、切断時において、この正極の一部から正極集電タブ１２ａが突出（なお、この正極集電タブ１２ａの幅は約３ｍｍで、長さが５ｍｍになるように突出させている）し、残りが直径１０ｍｍの円板状になるように切断される。そして、正極集電タブ１２ａに塗着された正極活物質を除去して、集電のための導電性を確保するようにしている。
【００１４】
なお、正極活物質として、リチウム含有二酸化コバルト（ＬｉＣｏＯ₂）に代えて、改質二酸化マンガン（ＭｎＯ₂）、リチウム含有二酸化ニッケル（ＬｉＮｉＯ₂）、リチウム含有三酸化マンガン（ＬｉＭｎ₂Ｏ₄）などのリチウム含有酸化物、あるいはＬｉＭｎ_1.5Ｎｉ_0.5Ｏ₄、ＬｉＮｉ_0.6Ｃｏ_0.3Ｍｎ_0.1Ｏ₂などのリチウム含有複合酸化物、ポリアニリンなどの導電性ポリマー、ジスルフィドなどの硫黄化合物などを用いてもよい。
【００１５】
２．負極の作製
平均粒径１０μｍの天然黒鉛を負極活物質として用い、この負極活物質としの天然黒鉛９５重量％に、結着剤としてのポリフッ化ビニリデン（ＰＶｄＦ）５重量％とを混合した。この後、この混合物にＮ−メチル−２−ピロリドン（ＮＭＰ）を加えて混合・混練して負極活物質スラリーを作製した。ついで、この負極活物質スラリーを銅箔からなる負極集電体１４にドクターブレード法により塗着した後、圧延後の厚みが７０μｍとなるように圧延した。
【００１６】
ついで、１３０℃の温度で真空乾燥した後、所定寸法に切断して、負極集電体１４の表面に負極合剤層１３を備えた負極を作製した。なお、切断時において、この負極の一部から負極集電タブ１４ａが突出し、残りが直径１１ｍｍの円板状になるように切断される。そして、負極集電タブ１４ａに塗着された負極活物質を除去して、集電のための導電性を確保するようにしている。なお、負極活物質としては、天然黒鉛に代えて、人造黒鉛、コークス、有機物焼成体などを用いてもよいし、あるいはリチウム合金、リチウム金属、金属酸化物などを用いてもよい。
【００１７】
３．電解液の調製
エチレンカーボネート（ＥＣ：以下、単にＥＣという）とジエチルカーボネート（ＤＥＣ：以下、単にＤＥＣという）とを体積比で４０：６０となるように混合した混合溶媒に、ＬｉＰＦ₆を１．０モル／リットル溶解して電解液を調製した。
なお、電解液の溶媒としては、ＥＣおよびＤＥＣ以外にも、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、ジメチルカーボネート（ＤＭＣ）、スルホラン（ＳＬ）、ビニレンカーボネート（ＶＣ）、メチルエチルカーボネート（ＭＥＣ）、テトラヒドロフラン（ＴＨＦ）、１，２−ジエトキシエタン（ＤＥＥ）、１，２−ジメトキシエタン（ＤＭＥ）、エトキシメトキシエタン（ＥＭＥ）、γ−ブチロラクトン等の単体、あるいはこれらの二成分以上の混合溶媒を選択して用いても良い。また、この溶媒に溶解される溶質としては、ＬｉＰＦ₆以外にも、ＬｉＢＦ₄、ＬｉＣＦ₃ＳＯ₃、ＬｉＡｓＦ₆、ＬｉＮ（ＣＦ₃ＳＯ₂）₂、ＬｉＮ（Ｃ₂Ｆ₅ＳＯ₂）₂、ＬｉＣ（ＣＦ₃ＳＯ₂）₃、ＬｉＣＦ₃（ＣＦ₂）₃ＳＯ₃等を用いてもよい。
【００１８】
４．薄型電池の作製
（１）実施例１
まず、アルミニウム金属箔１６ａの両表面に変性ポリエチレンフィルム１６ｂ，１６ｂをラミネートした第１外装体１６と、同様にアルミニウム金属箔１７ａの両表面に変性ポリエチレンフィルム１７ｂ，１７ｂをラミネートした第２外装体１７とを用意する。なお、これらの各外装体１６，１７の大きさは上述した正極および負極よりも大きめに形成されている。
【００１９】
ついで、第１外装体１６上に、負極集電体１４が下方で負極合剤層１３が上方になるように上述のようにして作製した負極を配置し、この負極合剤層１３の上に、ポリエチレン製の微多孔膜からなるセパレータ１５を配置する。なお、このセパレータ１５は、厚みが３０μｍで、直径が１２ｍｍの円板状に形成されており、このセパレータ１５に上述のようにして調製された電解液が含浸されている。ついで、セパレータ１５上に、正極合剤層１１が下方で正極集電体１２が上方になるように上述のようにして作製した正極を配置し、この正極集電体１２の上に第２外装体１７を配置する。
【００２０】
ついで、負極集電体１４より延出する負極集電タブ１４ａの先端部と負極端子（なお、負極端子の幅は３ｍｍで、長さが１０ｍｍに形成されている）１８の先端部とが接触して重なるとともに、両外装体１６，１７より外部に突出するように、負極端子１８を両外装体１６，１７の周縁部の間に配置する。同様に、正極集電体１２より延出する正極集電タブ１２ａの先端部と正極端子（なお、正極端子の幅は３ｍｍで、長さが１０ｍｍに形成されている）１９の先端部とが接触して重なるとともに、両外装体１６，１７より突出するように、正極端子１９を両外装体１６，１７の周縁部の間に配置する。
【００２１】
なお、負極集電タブ１４ａの先端部と負極端子１８の先端部との重なり部（接続部）の長さ、および正極集電タブ１２ａの先端部と正極端子１９の先端部との重なり部（接続部）の長さは、約０．５ｍｍ〜１．５ｍｍになるようにするのが好ましいが、これらの長さに限定する必要はなく、要は、両部材が接触して接続部が形成されるようにすればよい。
この後、第１外装体１６と第２外装体１７との周縁部の上下面に、２００℃の温度に加熱された圧着板を押し当てて加圧した後、加圧状態で徐冷しながらしばらく放置し、これらの周縁部をヒートシールして実施例１の薄型電池を作製した。この薄型電池を電池Ａとした。
【００２２】
このヒートシールにより、ヒートシール性を有する変性ポリエチレンフィルム１６ｂと変性ポリエチレンフィルム１７ｂ同士が強固に結着されるとともに、各端子１８，１９も変性ポリエチレンフィルム１６ｂ，１７ｂにより強固に結着されるようになる。このとき、負極集電タブ１４ａの先端部と負極端子１８とが接触して接続部Ｘが形成されるとともに、正極集電タブ１２ａの先端部と正極端子１９とが接触して接続部Ｙが形成される。
【００２３】
（２）実施例２
アルミニウム金属箔１６ａの両表面に変性ポリプロピレンフィルム１６ｂ，１６ｂをラミネートした第１外装体１６と、同様にアルミニウム金属箔１７ａの両表面に変性ポリプロピレンフィルム１７ｂ，１７ｂをラミネートした第２外装体１７とを用いること以外は、上述した実施例１と同様にして実施例２の薄型電池を作製し、電池Ｂとした。
【００２４】
（３）実施例３
ステンレススチール（ＳＵＳ３０４）製金属箔１６ａの両表面に変性ポリエチレンフィルム１６ｂ，１６ｂをラミネートした第１外装体１６と、同様にステンレススチール（ＳＵＳ３０４）製金属箔１７ａの両表面に変性ポリエチレンフィルム１７ｂ，１７ｂをラミネートした第２外装体１７とを用いること以外は、上述した実施例１と同様にして実施例３の薄型電池を作製し、電池Ｃとした。
【００２５】
（４）実施例４
アルミニウム金属箔１６ａの両表面に変性ポリスチレンフィルム１６ｂ，１６ｂをラミネートした第１外装体１６と、同様にアルミニウム金属箔１７ａの両表面に変性ポリスチレンフィルム１７ｂ，１７ｂをラミネートした第２外装体１７とを用いること以外は、上述した実施例１と同様にして実施例４の薄型電池を作製し、電池Ｄとした。
【００２６】
（５）比較例１
正極集電体１２より延出する正極集電タブ１２ａの長さを長くして正極端子１９と一体とした正極集電体１２を用いるとともに、負極集電体１４より延出する負極集電タブ１４ａの長さを長くして負極端子１８と一体とした負極集電体１４を用いて、上述の実施例１と同様に正極および負極を作製した。これらの正極および負極を用いるとともに、実施例１と同様の外装体１６，１７を用いて、実施例１と同様にして比較例１の薄型電池を作製し、電池Ｘとした。
【００２７】
５．外部短絡試験
ついで、上述のようにして作製した各電池Ａ〜ＤおよびＸをそれぞれ１０個づつ用いて、これらの各１０個の電池Ａ〜ＤおよびＸを、室温（２５℃）で１ｍＡ／ｃｍ²の充電電流密度で電池電圧が４．２Ｖになるまで充電した。この後、これらの各電池Ａ〜ＤおよびＸに抵抗（抵抗値が約０．１Ωのもの）を接続して、両端子１８，１９間に短絡電流（この場合は約３５Ａの短絡電流である）を流す外部短絡試験を行った。この外部短絡試験により、電池の封口部（ヒートシールの箇所）が破壊されて漏液が生じたり、内部ガスが流出して漏液し、封口不良が発生した電池の個数を数えると、下記の表１に示すような結果となった。
【００２８】
【表１】

【００２９】
上記表１より明らかなように、正極集電タブ１２ａと正極端子１９とを一体とした正極集電体１２および負極集電タブ１４ａと負極端子１８とを一体とした負極集電体１４を用いた比較例１の電池Ｘは、１０個の電池の全てに封口不良が発生したことが分かる。一方、負極集電タブ１４ａと負極端子１８とを接触させて接続部Ｘを形成するとともに、正極集電タブ１２ａと正極端子１９とを接触させて接続部Ｙを形成した実施例１〜４の電池Ａ〜Ｄは、封口不良の発生個数が減少していることが分かる。
【００３０】
これは、実施例１〜４の電池Ａ〜Ｄにおいては、電池が外部短絡状態となって電池内にガスが発生するようになると、ガスの発生に伴って外装体１６，１７は徐々に膨出するようになり、このような状態でさらに外部短絡が継続すると過剰なガスが電池内に充満するようなる。このとき、負極端子１８と負極集電タブ１４ａとは接続部Ｘで接触しているだけであり、正極端子１９と正極集電タブ１２ａとは接続部Ｙで接触しているだけであるため、図２（ｂ）に示すように、やがては負極端子１８と負極集電タブ１４との接触および正極端子１９と正極集電タブ１２ａとの接触が離れて（遮断されて）、これ以上は短絡電流が流れなくなる。これにより、これ以上のガスの発生は起こらなくなり、漏液あるいは電池の破裂を防止できるようになる。したがって、正・負極端子と各集電タブとを接触させるだけの簡単な構造で漏液あるいは電池の破裂を防止できるようになる。
【００３１】
また、外装体１６，１７を形成するラミネートフィルムの樹脂フィルム１６ｂ，１７ｂが共に変性ポリエチレンである実施例１の電池Ａと、実施例３の電池Ｃとを比較すると、電池Ａの封口不良個数が電池Ｃの封口不良個数より少ないことが分かる。これは、ラミネートフィルムの芯材として用いられる金属箔１６ａ，１７ａが、電池Ａのラミネートフィルムにあってはアルミニウム箔であり、電池ＣのラミネートフィルムにあってはＳＵＳ３０４のステンレススチール箔であることによるものと考えられる。このことは、アルミニウム箔をラミネートフィルムの芯材とすると、電池が膨出した際に接続部Ｘ，Ｙでの接触が外れやすいのに対して、ステンレススチール箔をラミネートフィルムの芯材とすると、電池が膨出した際に接続部Ｘ，Ｙでの接触が外れにくかったことを意味するものと推測できる。
【００３２】
さらに、外装体１６，１７を形成するラミネートフィルムの芯材となる金属箔１６ａ，１７ａが共にアルミニウムである実施例１の電池Ａと、実施例２の電池Ｂと、実施例４の電池Ｄとを比較すると、電池Ａ，Ｂの封口不良個数が電池Ｄの封口不良個数より少ないことが分かる。これは、ラミネートフィルムの樹脂フィルム１６ｂ，１７ｂが、電池Ａのラミネートフィルムにあっては変性ポリエチレンであり、電池Ｂのラミネートフィルムにあっては変性ポリプロピレンであり、電池Ｄのラミネートフィルムにあっては変性ポリスチレンであることによるものと考えられる。
【００３３】
このことは、変性ポリエチレンおよび変性ポリプロピレンをラミネートフィルムの樹脂フィルム１６ｂ，１７ｂとすると、ヒートシールの際の樹脂フィルム１６ｂ，１７ｂ同士の融着が強固で、封止部での剥がれが生じにくかったのに対して、変性ポリスチレンをラミネートフィルムの樹脂フィルム１６ｂ，１７ｂとすると、ヒートシールの際の樹脂フィルム１６ｂ，１７ｂ同士の融着が弱くて、封止部で剥がれが生じたことを意味するものと推測できる。
【００３４】
６．ポリマー電解質を用いた薄型電池
（１）実施例５
ポリエチレン製の微多孔膜からなるセパレータ１５に代えて、ポリフッ化ビニリデン（ＰＶｄＦ）膜１５を用い、このポリフッ化ビニリデン（ＰＶｄＦ）膜１５に、ＥＣとＤＥＣとを体積比で４０：６０となるように混合した混合溶媒にＬｉＰＦ₆を１．０モル／リットル溶解した電解液を含浸させてゲル状電解質（ポリマー電解質）を作製した。このポリマー電解質を用いること以外は上述した実質例１と同様にして、実施例５の薄型電池を作製し、電池Ｅとした。
【００３５】
（２）比較例２
上述の実施例５と同様にしてポリマー電解質を作製した後、このポリマー電解質を用いること以外は上述した比較例１と同様にして、比較例２の薄型電池を作製し、電池Ｙとした。
【００３６】
ついで、これらの各電池ＥおよびＹをそれぞれ１０個づつ用いて、これらの各１０個の電池ＥおよびＹを、室温（２５℃）で１ｍＡ／ｃｍ²の充電電流密度で電池電圧が４．２Ｖになるまで充電した後、これらの各電池ＥおよびＹに抵抗（抵抗値が約０．１Ωのもの）を接続して、外部短絡試験を行った。外部短絡試験により、電池の封口部（ヒートシールの箇所）が破壊されて漏液が生じたり、内部ガスが流出して封口不良が発生した電池の個数を数えると、下記の表２に示すような結果となった。なお、表２には実施例１の電池Ａの結果も併せて示している。
【００３７】
【表２】

【００３８】
上記表２より明らかなように、正極集電タブ１２ａと正極端子１９とを一体とした正極集電体１２および負極集電タブ１４ａと負極端子１８とを一体とした負極集電体１４を用いた比較例２の電池Ｙは、１０個の電池の全てに封口不良が発生したことが分かる。一方、負極集電タブ１４ａと負極端子１８とを接触させて接続部Ｘを形成するとともに、正極集電タブ１２ａと正極端子１９とを接触させて接続部Ｙを形成した実施例５の電池Ｅは、封口不良の発生個数が０に激減していることが分かる。また、電解液を用いた電池Ａと、ポリマー電解質を用いた電池Ｅとを比較すると、電池Ｅの方が封口不良の個数が少ないことが分かる。このことから、本発明はポリマー電解質を用いた方がより効果的であるということができる。
【００３９】
なお、上述した実施形態においては、負極集電タブ１４ａと負極端子１８とを接触させて接続部Ｘを形成するとともに、正極集電タブ１２ａと正極端子１９とを接触させて接続部Ｙを形成した例について説明したが、これらの接続部はＸあるいはＹのどちらか一方のみを形成するようにすれば、上述とほぼ同様な結果が期待できる。この場合、正極集電体と負極集電体のどちらか一方は、集電タブと端子を一体的に形成した集電体を用いるようにすればよい。
【００４０】
また、上述した実施形態においては、ラミネートフィルムよりなる外装体として、第１外装体１６と第２外装体１７とを用いる例について説明したが、これらの外装体は一体的に形成されたラミネートフィルムを用いるようにしてもよい。この場合、一体的に形成されたラミネートフィルムを中心部で折り曲げて使用するようにすればよい。
【００４１】
また、上述した実施形態においては、ラミネートフィルム同士を押圧してヒートシールする温度を２００℃とした例について説明したが、ヒートシールの温度は２００℃に限らず、ラミネートフィルム同士が強固に結着すれば何度でもよいが、１５０℃〜２００℃の温度とするのが好ましい。この場合、ラミネートフィルムに用いられる樹脂フィルムの材質により押圧時間を調製するようにすればよい。
さらに、上述した実施形態においては、本発明を円形状の薄型電池に適用する例について説明したが、電池形状は円形状に限らず、方形、楕円形等の様々の形状の薄型電池に本発明は適用可能である。
【図面の簡単な説明】
【図１】本発明の薄型電池を模式的に示す図であり、図１（ａ）はその断面を示す断面図であり、図１（ｂ）はその上面図である。
【図２】図１の要部を拡大して示す断面図であり、図２（ａ）は通常の状態を示す図であり、図２（ｂ）ガスが発生して電池が膨出した状態を示す図である。
【符号の説明】
１０…薄型電池、１１…正極合剤層、１２…正極集電体、１２ａ…正極集電タブ、１３…負極合剤層、１４…負極集電体、１４ａ…負極集電タブ、１５…セパレータ、１６，１７…外装体（ラミネートフィルム）、１６ａ，１７ａ…ラミネートフィルム金属箔、１６ｂ，１７ｂ…ラミネートフィルムの樹脂フィルム、１８…正極端子、１９…負極端子、Ｘ，Ｙ…接続部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin battery used as a power source for an electric / electronic device or a communication device, and more particularly to an improvement of a thin battery including an exterior body that covers a thin plate-shaped power generation element sandwiched from both sides.
[0002]
[Prior art]
Lithium secondary batteries have come into practical use as compact, lightweight, high-capacity chargeable / dischargeable batteries, and are used in portable electronic and communication devices such as small video cameras, mobile phones, and notebook computers. It was. This type of lithium secondary battery uses a carbon-based material or lithium metal or lithium alloy capable of inserting and extracting lithium ions as the negative electrode active material, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFeO as the positive electrode active material. A battery comprising a lithium-containing metal oxide such as ₂ and an electrolyte in which a lithium salt is dissolved as a solute in an organic solvent.
[0003]
Normally, this type of lithium secondary battery generates gas due to overcharge, so an overcharge prevention device is provided for safety, and when excessive gas is generated inside the battery due to overcharge. The overcharge prevention device is activated to cut off the charging current. Also, a safety valve is provided in the battery, and when excessive gas is generated inside the battery due to a short circuit or the like, the safety valve is activated to discharge the gas to the outside of the battery.
[0004]
By the way, with the rapid spread of portable electronic / communication devices in recent years, applications of this type of lithium secondary battery have been expanded, and further weight reduction, size reduction, and thickness reduction have been required. Therefore, a thin resin-made exterior body made of a synthetic resin having heat sealability is used, and a thin plate-like power generation element composed of a positive electrode, a negative electrode, and an electrolyte is sandwiched from both sides to seal the peripheral portion of the exterior body. Batteries have been proposed.
[0005]
[Problems to be solved by the invention]
In such a thin battery, it is desirable to use an exterior body that is highly flexible against various stresses, and a laminate film in which a metal foil and a heat-weldable resin are laminated on the exterior body has been used. However, when such a laminate film is used for an exterior body, since the mechanical strength of the exterior body is weak, when an abnormal state such as overcharge or external short circuit occurs, the pressure of the gas generated in the battery increases, and eventually Has a problem that the sealing is broken and leakage occurs. Moreover, since there is not enough space for the overcharge prevention device and the safety valve as described above, it is difficult to provide the overcharge prevention device and the safety valve in the battery.
[0006]
Therefore, the battery current collection method has been improved to realize safety mechanisms such as current interruption during overcharge and short circuit, internal pressure relaxation and prevention of liquid leakage when internal pressure rises, in a light, compact and easy way. A thin battery intended to be used has been proposed in Japanese Patent Laid-Open No. 10-294097.
However, in the thin battery proposed in Japanese Patent Laid-Open No. 10-294097, there is a problem that the structure for interrupting the current is complicated and the current cannot be reliably interrupted at the time of overcharge or short circuit, It was still insufficient and further improvements were needed.
Accordingly, the present invention has been made to solve the above-described problems, and provides a thin battery that has a simple structure, can reliably cut off a current when overcharged or short-circuited, and is easy to manufacture. It is the purpose.
[0007]
[Means for solving the problems and their functions and effects]
For this reason, in the thin battery of the present invention, the positive electrode current collector tab extending from the positive electrode, the negative electrode current collector tab extending from the negative electrode, and the outer peripheral body are sandwiched and fixed to the peripheral edge portion. A positive electrode terminal and a positive electrode current collecting tab, comprising: a positive electrode terminal extending outside from the outer package; and a negative electrode terminal sandwiched between the outer periphery and fixed to the outer periphery and extending outward from the outer package. Or at least one of the connecting portions of the negative electrode terminal and the negative electrode current collecting tab is in contact without being fixed, so that the contact of the connecting portion is cut off when the battery internal pressure increases. I have to.
[0008]
As described above, at least one connection of the connecting portion between the positive electrode terminal and the positive electrode current collecting tab or the connecting portion between the negative electrode terminal and the negative electrode current collecting tab which is fixed to the peripheral edge portion of the outer case body and extends to the outside from the outer case body. If the parts are connected in contact without being fixed, in a normal discharge state, a discharge current is derived to the positive and negative terminals through these connection parts. In a normal charge state, these positive and negative terminals are connected. A charging current is introduced from the negative electrode terminal to each current collecting tab through these connections.
[0009]
Here, for example, when an overcharged state or an external short-circuit state occurs for some reason and gas is generated in the battery, the exterior body gradually swells as the gas is generated. If these conditions continue in such a state, the battery will be filled with excess gas, but at least one connection between the positive and negative terminals and each current collecting tab is in contact. For this reason, the contact of the connection portion is eventually cut off (the connection between the terminal and the current collecting tab at the connection portion is released), and the charging current or the short-circuit current no longer flows. As a result, no more gas is generated, and leakage or battery rupture can be prevented. Accordingly, it is possible to prevent liquid leakage or battery rupture with a simple structure in which at least one connecting portion between the positive / negative terminal and each current collecting tab is brought into contact.
[0010]
When the exterior body is made of a laminate film in which a polyolefin-based heat-welded film is laminated on both sides of the aluminum foil, it can be easily heat-sealed only by thermocompression bonding of the peripheral portion of the exterior body. Therefore, this type of thin battery can be easily sealed and manufactured easily.
Further, when a gel polymer electrolyte is used as the electrolyte, it is possible to completely prevent leakage even with simple sealing only by heat sealing.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a thin battery of the present invention will be described with reference to the drawings. 1 is a diagram schematically showing a thin battery of the present invention, FIG. 1 (a) is a sectional view showing a section thereof, and FIG. 1 (b) is a top view thereof. 2 is an enlarged cross-sectional view showing the main part of FIG. 1, FIG. 2 (a) is a diagram showing a normal state, and FIG. 2 (b) is a state where gas is generated and the battery is expanded. FIG. The present invention is not limited to the following embodiments, and can be appropriately modified and implemented without departing from the scope of the present invention.
[0012]
1. Preparation of positive electrode Lithium-containing cobalt dioxide (LiCoO ₂ ) heat-treated at a temperature of 800 ° C. is used as a positive electrode active material, and 85 wt% of lithium-containing cobalt dioxide (LiCoO ₂ ) as a positive electrode active material and carbon powder as a conductive agent 10% by weight and 5% by weight of polyvinylidene fluoride (PVdF) as a binder were mixed. Thereafter, N-methyl-2-pyrrolidone (NMP) was added to the mixture and mixed and kneaded to prepare a positive electrode active material slurry.
[0013]
Next, this positive electrode active material slurry was applied to the positive electrode current collector 12 made of aluminum foil by a doctor blade method, and then rolled so that the thickness after rolling was 80 μm. Subsequently, after vacuum-drying at a temperature of 130 ° C., it was cut into a predetermined size, and a positive electrode provided with the positive electrode mixture layer 11 on the surface of the positive electrode current collector 12 was produced. At the time of cutting, the positive electrode current collecting tab 12a protrudes from a part of the positive electrode (note that the positive electrode current collecting tab 12a has a width of about 3 mm and a length of 5 mm), The remainder is cut into a disk shape having a diameter of 10 mm. And the positive electrode active material applied to the positive electrode current collection tab 12a is removed, and the electroconductivity for current collection is ensured.
[0014]
As the positive electrode active material, instead of lithium-containing cobalt dioxide (LiCoO ₂ ), modified manganese dioxide (MnO ₂ ), lithium-containing nickel dioxide (LiNiO ₂ ), lithium-containing manganese trioxide (LiMn ₂ O ₄ ), etc. Lithium-containing oxides, lithium-containing composite oxides such as LiMn _1.5 Ni _0.5 O ₄ and LiNi _0.6 Co _0.3 Mn _0.1 O ₂ , conductive polymers such as polyaniline, and sulfur compounds such as disulfide may also be used.
[0015]
2. Production of Negative Electrode Natural graphite having an average particle diameter of 10 μm was used as a negative electrode active material, and 95% by weight of natural graphite as a negative electrode active material was mixed with 5% by weight of polyvinylidene fluoride (PVdF) as a binder. Thereafter, N-methyl-2-pyrrolidone (NMP) was added to this mixture and mixed and kneaded to prepare a negative electrode active material slurry. Next, this negative electrode active material slurry was applied to the negative electrode current collector 14 made of copper foil by the doctor blade method, and then rolled so that the thickness after rolling was 70 μm.
[0016]
Subsequently, after vacuum-drying at a temperature of 130 ° C., it was cut into a predetermined size, and a negative electrode provided with the negative electrode mixture layer 13 on the surface of the negative electrode current collector 14 was produced. At the time of cutting, the negative electrode current collecting tab 14a protrudes from a part of the negative electrode, and the rest is cut into a disk shape having a diameter of 11 mm. And the negative electrode active material applied to the negative electrode current collection tab 14a is removed, and the electroconductivity for current collection is ensured. As the negative electrode active material, artificial graphite, coke, an organic fired body, or the like may be used instead of natural graphite, or a lithium alloy, lithium metal, metal oxide, or the like may be used.
[0017]
3. 1. Preparation of Electrolyte Solution LiPF ₆ was added to a mixed solvent in which ethylene carbonate (EC: hereinafter simply referred to as EC) and diethyl carbonate (DEC: hereinafter simply referred to as DEC) were mixed at a volume ratio of 40:60. An electrolyte was prepared by dissolving 0 mol / liter.
In addition to EC and DEC, electrolyte solvents include propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), sulfolane (SL), vinylene carbonate (VC), methyl ethyl carbonate (MEC). ), Tetrahydrofuran (THF), 1,2-diethoxyethane (DEE), 1,2-dimethoxyethane (DME), ethoxymethoxyethane (EME), γ-butyrolactone, or a mixture of two or more of these components A solvent may be selected and used. In addition to LiPF ₆ , solutes dissolved in this solvent include LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC. (CF ₃ SO ₂ ) ₃ , LiCF ₃ (CF ₂ ) ₃ SO ₃ or the like may be used.
[0018]
4). Production of thin battery (1) Example 1
First, the first exterior body 16 in which the modified polyethylene films 16b and 16b are laminated on both surfaces of the aluminum metal foil 16a, and the second exterior body 17 in which the modified polyethylene films 17b and 17b are similarly laminated on both surfaces of the aluminum metal foil 17a. And prepare. In addition, the size of each of the

exterior bodies

16 and 17 is formed larger than the positive electrode and the negative electrode described above.
[0019]
Next, the negative electrode produced as described above is disposed on the first exterior body 16 so that the negative electrode current collector 14 is downward and the negative electrode mixture layer 13 is upward. A separator 15 made of a polyethylene microporous film is disposed. The separator 15 is formed in a disc shape having a thickness of 30 μm and a diameter of 12 mm. The separator 15 is impregnated with the electrolytic solution prepared as described above. Next, the positive electrode produced as described above is disposed on the separator 15 so that the positive electrode mixture layer 11 is downward and the positive electrode current collector 12 is upward, and the second exterior is disposed on the positive electrode current collector 12. The body 17 is arranged.
[0020]
Next, the tip of the negative electrode current collector tab 14 a extending from the negative electrode current collector 14 contacts the tip of the negative electrode terminal 18 (the width of the negative electrode terminal is 3 mm and the length is 10 mm). Thus, the negative electrode terminal 18 is disposed between the peripheral portions of the

outer casings

16 and 17 so as to overlap and protrude outward from the

outer casings

16 and 17. Similarly, the tip of the positive electrode current collector tab 12a extending from the positive electrode current collector 12 and the tip of the positive electrode terminal 19 (the width of the positive electrode terminal is 3 mm and the length is 10 mm) 19 are formed. The positive terminal 19 is disposed between the peripheral portions of the

outer casings

16 and 17 so as to be in contact with each other and to protrude from the

outer casings

16 and 17.
[0021]
Note that the length of the overlapping portion (connecting portion) between the tip portion of the negative electrode current collecting tab 14 a and the tip portion of the negative electrode terminal 18, and the overlapping portion between the tip portion of the positive electrode current collecting tab 12 a and the tip portion of the positive electrode terminal 19 ( The length of the connection portion) is preferably about 0.5 mm to 1.5 mm, but it is not necessary to limit to these lengths. In short, both members are in contact with each other to form the connection portion. What should I do?
Then, after pressing and pressing the pressure-bonding plate heated to a temperature of 200 ° C. on the upper and lower surfaces of the peripheral portions of the first exterior body 16 and the second exterior body 17, while gradually cooling in the pressurized state The thin battery of Example 1 was produced by leaving for a while and heat-sealing these peripheral portions. This thin battery was designated as Battery A.
[0022]
By this heat sealing, the modified polyethylene film 16b having heat sealing properties and the modified polyethylene film 17b are firmly bound together, and the terminals 18 and 19 are also firmly bound by the modified polyethylene films 16b and 17b. Become. At this time, the tip end portion of the negative electrode current collecting tab 14a and the negative electrode terminal 18 come into contact with each other to form the connection portion X, and the tip portion of the positive electrode current collecting tab 12a and the positive electrode terminal 19 come into contact with each other to form the connection portion Y. It is formed.
[0023]
(2) Example 2
First exterior body 16 in which modified polypropylene films 16b and 16b are laminated on both surfaces of aluminum metal foil 16a, and second exterior body 17 in which modified polypropylene films 17b and 17b are similarly laminated on both surfaces of aluminum metal foil 17a. A thin battery of Example 2 was produced in the same manner as Example 1 described above except that it was used, and battery B was obtained.
[0024]
(3) Example 3
First exterior body 16 in which modified polyethylene films 16b and 16b are laminated on both surfaces of stainless steel (SUS304) metal foil 16a, and modified polyethylene films 17b and 17b on both surfaces of stainless steel (SUS304) metal foil 17a. A thin battery of Example 3 was produced in the same manner as in Example 1 described above except that the second exterior body 17 laminated with was used as Battery C.
[0025]
(4) Example 4
First exterior body 16 in which modified polystyrene films 16b and 16b are laminated on both surfaces of aluminum metal foil 16a, and second exterior body 17 in which modified polystyrene films 17b and 17b are similarly laminated on both surfaces of aluminum metal foil 17a. A thin battery of Example 4 was produced in the same manner as Example 1 described above except that it was used, and battery D was obtained.
[0026]
(5) Comparative Example 1
The positive electrode current collector tab 12 a extending from the positive electrode current collector 12 is made longer and the positive electrode current collector 12 integrated with the positive electrode terminal 19 is used, and the negative electrode current collector tab extended from the negative electrode current collector 14 A positive electrode and a negative electrode were produced in the same manner as in Example 1 described above, using the negative electrode current collector 14 that was integrated with the negative electrode terminal 18 by increasing the length of 14a. A thin battery of Comparative Example 1 was produced in the same manner as in Example 1 using these positive electrode and negative electrode, and the same

outer packagings

16 and 17 as in Example 1, and designated as Battery X.
[0027]
5. Next, 10 each of the batteries A to D and X produced as described above were used, and each of these 10 batteries A to D and X was 1 mA / cm at room temperature (25 ° C.). ^The battery was charged at a charging current density of ² until the battery voltage was 4.2V. Thereafter, a resistance (with a resistance value of about 0.1Ω) is connected to each of these batteries A to D and X, and a short-circuit current (in this case, a short-circuit current of about 35 A) between both terminals 18 and 19. ) Was conducted. In this external short circuit test, the sealing part (heat seal part) of the battery is broken and leakage occurs, or the internal gas flows out and leaks. The results shown in Table 1 were obtained.
[0028]
[Table 1]

[0029]
As apparent from Table 1 above, the positive electrode current collector 12 in which the positive electrode current collector tab 12a and the positive electrode terminal 19 are integrated, and the negative electrode current collector 14 in which the negative electrode current collector tab 14a and the negative electrode terminal 18 are integrated are used. It can be seen that the battery X of Comparative Example 1 had a sealing failure in all 10 batteries. On the other hand, while the negative electrode current collection tab 14a and the negative electrode terminal 18 were made to contact, the connection part X was formed, and the positive electrode current collection tab 12a and the positive electrode terminal 19 were made to contact, and the connection part Y was formed. It can be seen that the batteries A to D have a reduced number of occurrences of poor sealing.
[0030]
In the batteries A to D of Examples 1 to 4, when the battery is in an external short circuit state and gas is generated in the battery, the

exterior bodies

16 and 17 are gradually expanded as the gas is generated. When the external short-circuit continues further in such a state, an excessive gas is filled in the battery. At this time, the negative electrode terminal 18 and the negative electrode current collecting tab 14a are only in contact at the connection portion X, and the positive electrode terminal 19 and the positive electrode current collector tab 12a are only in contact at the connection portion Y. As shown in FIG. 2 (b), the contact between the negative electrode terminal 18 and the negative electrode current collecting tab 14 and the contact between the positive electrode terminal 19 and the positive electrode current collecting tab 12a are eventually separated (blocked), and no more is short-circuited. Current stops flowing. As a result, no more gas is generated, and leakage or battery rupture can be prevented. Therefore, leakage or battery rupture can be prevented with a simple structure in which the positive / negative terminal and each current collecting tab are brought into contact with each other.
[0031]
Further, when the battery A of Example 1 and the battery C of Example 3 in which both the resin films 16b and 17b of the laminate film forming the

exterior bodies

16 and 17 are modified polyethylene are compared, the number of defective sealing of the battery A is It can be seen that the number is less than the number of defective sealing of battery C. This is because the metal foils 16a and 17a used as the core material of the laminate film are aluminum foils in the laminate film of the battery A and SUS304 stainless steel foils in the laminate film of the battery C. It is considered a thing. This means that when the aluminum foil is used as the core material of the laminate film, when the battery swells, the contact at the connecting portions X and Y tends to come off, whereas when the stainless steel foil is used as the core material of the laminate film, It can be inferred that the contact at the connecting portions X and Y was difficult to come off when the battery expanded.
[0032]
Furthermore, the battery A of Example 1, the battery B of Example 2, and the battery D of Example 4 in which the metal foils 16a and 17a, which are the cores of the laminate film forming the

exterior bodies

16 and 17, are both aluminum. , It can be seen that the number of defective sealing of the batteries A and B is smaller than the number of defective sealing of the battery D. This is because the laminated film resin films 16b and 17b are modified polyethylene in the laminated film of the battery A, modified polypropylene in the laminated film of the battery B, and in the laminated film of the battery D. This is considered to be due to the modified polystyrene.
[0033]
This is because when the modified polyethylene and the modified polypropylene are used as the resin films 16b and 17b of the laminate film, the fusion of the resin films 16b and 17b at the time of heat sealing is strong, and peeling at the sealing portion is difficult to occur. On the other hand, when modified polystyrene is used as the resin films 16b and 17b of the laminate film, it means that the fusion between the resin films 16b and 17b at the time of heat sealing is weak and peeling occurs at the sealing portion. I can guess.
[0034]
6). Thin battery using polymer electrolyte (1) Example 5
Instead of the separator 15 made of a polyethylene microporous membrane, a polyvinylidene fluoride (PVdF) film 15 is used, and the volume ratio of EC and DEC is 40:60 in the polyvinylidene fluoride (PVdF) film 15. A gel electrolyte (polymer electrolyte) was prepared by impregnating a mixed solvent mixed with the above with an electrolytic solution in which LiPF ₆ was dissolved at 1.0 mol / liter. Except for using this polymer electrolyte, a thin battery of Example 5 was produced in the same manner as in Example 1 described above, and battery E was obtained.
[0035]
(2) Comparative Example 2
After producing a polymer electrolyte in the same manner as in Example 5 described above, a thin battery of Comparative Example 2 was produced in the same manner as in Comparative Example 1 described above except that this polymer electrolyte was used.
[0036]
Then, using 10 of each of these batteries E and Y, each of these 10 batteries E and Y has a battery voltage of 4.2 V at a charging current density of 1 mA / cm ² at room temperature (25 ° C.). Then, a resistance (having a resistance value of about 0.1Ω) was connected to each of these batteries E and Y, and an external short circuit test was performed. Table 2 below shows the number of batteries in which the sealing part (heat sealing part) of the battery is broken by the external short-circuit test and liquid leakage occurs or the internal gas flows out to cause sealing failure. It became a result. Table 2 also shows the results of the battery A of Example 1.
[0037]
[Table 2]

[0038]
As is clear from Table 2 above, the positive electrode current collector 12 in which the positive electrode current collector tab 12a and the positive electrode terminal 19 are integrated, and the negative electrode current collector 14 in which the negative electrode current collector tab 14a and the negative electrode terminal 18 are integrated are used. It can be seen that the battery Y of Comparative Example 2 had a sealing failure in all 10 batteries. On the other hand, the negative electrode current collecting tab 14a and the negative electrode terminal 18 are brought into contact with each other to form the connection portion X, and the positive electrode current collecting tab 12a and the positive electrode terminal 19 are brought into contact with each other to form the connection portion Y. It can be seen that the number of occurrences of poor sealing is drastically reduced to zero. Further, when comparing the battery A using the electrolytic solution and the battery E using the polymer electrolyte, it can be seen that the battery E has a smaller number of sealing defects. From this, it can be said that the present invention is more effective when a polymer electrolyte is used.
[0039]
In the above-described embodiment, the negative electrode current collecting tab 14a and the negative electrode terminal 18 are brought into contact with each other to form the connection portion X, and the positive electrode current collecting tab 12a and the positive electrode terminal 19 are brought into contact with each other to form the connection portion Y. However, if only one of X and Y is formed in these connecting portions, the same result as described above can be expected. In this case, either the positive electrode current collector or the negative electrode current collector may be a current collector in which a current collecting tab and a terminal are integrally formed.
[0040]
In the embodiment described above, the example in which the first exterior body 16 and the second exterior body 17 are used as the exterior body made of the laminate film has been described. However, these exterior bodies are integrally formed laminate films. May be used. In this case, an integrally formed laminate film may be bent at the center for use.
[0041]
In the above-described embodiment, the example in which the temperature for pressing and heat-sealing the laminate films is 200 ° C. has been described. However, the heat-sealing temperature is not limited to 200 ° C., and the laminate films are firmly bound to each other. However, it is preferable to set the temperature to 150 ° C. to 200 ° C. In this case, the pressing time may be adjusted according to the material of the resin film used for the laminate film.
Furthermore, in the above-described embodiment, the example in which the present invention is applied to a circular thin battery has been described. However, the battery shape is not limited to a circular shape, and the present invention is applied to thin batteries having various shapes such as a rectangular shape and an elliptical shape. Is applicable.
[Brief description of the drawings]
FIG. 1 is a view schematically showing a thin battery of the present invention, FIG. 1 (a) is a sectional view showing the section thereof, and FIG. 1 (b) is a top view thereof.
2 is an enlarged cross-sectional view showing the main part of FIG. 1, FIG. 2 (a) is a diagram showing a normal state, and FIG. 2 (b) is a state where gas is generated and the battery is expanded. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Thin battery, 11 ... Positive electrode mixture layer, 12 ... Positive electrode collector, 12a ... Positive electrode current collection tab, 13 ... Negative electrode mixture layer, 14 ... Negative electrode current collector, 14a ... Negative electrode current collection tab, 15 ...

Separator

16, 17 ... exterior body (laminate film), 16a, 17a ... laminate film metal foil, 16b, 17b ... resin film of laminate film, 18 ... positive electrode terminal, 19 ... negative electrode terminal, X, Y ... connection part

Claims

A thin battery comprising a thin plate-shaped power generation element composed of a positive electrode, a negative electrode, and an electrolyte, and an outer package in which the power generation element is sandwiched from both sides and the periphery thereof is sealed,
A positive electrode current collecting tab extending from the positive electrode;
A negative electrode current collecting tab extending from the negative electrode;
A positive electrode terminal which is sandwiched between the outer peripheral parts of the outer package and is fixed to the outer peripheral parts and extends to the outside from the outer package;
A negative electrode terminal sandwiched between the outer peripheral portion and fixed to the outer peripheral portion and extending to the outside from the outer peripheral body,
Contact between the positive electrode terminal and the positive electrode current collecting tab at the peripheral edge portion or at least one of the negative electrode terminal and the negative electrode current collector tab at the peripheral edge connection portion is not fixed. Connected,
And the thin battery characterized by the contact of the said connection part being interrupted | blocked when the battery internal pressure rises.

2. The thin battery according to claim 1, wherein the positive current collector tab extends from a positive current collector disposed on the positive electrode and is integrally formed with the positive current collector.

The thin battery according to claim 1, wherein the negative electrode current collecting tab extends from a negative electrode current collector disposed on the negative electrode and is integrally formed with the negative electrode current collector.

The thin battery according to any one of claims 1 to 3, wherein the outer package is a laminate film in which a polyolefin-based heat welding film is laminated on both sides of an aluminum foil.

The thin battery according to any one of claims 1 to 4, wherein the electrolyte is a gel polymer electrolyte.