【０００１】
【発明の属する技術分野】
本発明はラミネートフィルムからなる外装材で発電要素を封止した構造を有する薄型二次電池に係り、特に封止部からの水分侵入や内部短絡を防止し、電池の信頼性を確保した上で電池の体積エネルギー密度を高めることが可能な薄型二次電池に関する。
【０００２】
【従来の技術】
携帯電話やノートパソコンなど電子機器の急速な進歩に伴い、その駆動電源となる二次電池は、小型化，軽量化，大容量化，高性能化，コストダウンが絶えずに要請されてきた。これら携帯機器内に装着され駆動電源として使用される二次電池としては、従来からニッケルカドミウム電池やニッケル水素二次電池が使用されており、近年ではさらに高エネルギー密度化を実現できるリチウムイオン二次電池の需要が急速に拡大している。
【０００３】
また、二次電池の形状についても従来の円筒型，ボタン型の電池よりも収納時の体積効率が優れた角型電池，長円形電池の需要が高まると共に、高容量化，高エネルギー密度化に伴って、正極活物質や負極活物質など電極材料をよりエネルギー密度の高いものに変更したり、セパレータをより薄くしたり、電池の外装缶をステンレス鋼，鉄からアルミニウム合金に代替するなどの工夫改善が図られてきた。
【０００４】
しかし、これらの改善後でも技術的要求はさらに高度化し、未だ満足なレベルには到達しておらず、更なる小型化，軽量化，薄型化，大容量化，コストダウンが要請されている。最近では液状電解質，ゲル状電解質または固体高分子電解質等を発電要素中に含有させ、アルミニウム合金箔をバリア層として積層中間部に挟んだ高分子フィルムとのラミネートフィルムからなるラミネート外装材により発電要素を封止することにより、薄型化，小型化，軽量化を図った薄型二次電池が市販され普及しつつある。
【０００５】
このようなラミネートフィルム外装材により発電要素を封止した薄型二次電池としては、例えば図１１，図１２および図１３に示すラミネート外装構造を有する非水電解質薄型二次電池が公知である。
【０００６】
すなわち、ラミネート外装非水電解質薄型二次電池３０は、正極活物質１１ａを正極集電体１１ｂに塗工した正極１１、および負極活物質１２ａを負極集電体１２ｂに塗工した負極１２間にセパレータ１３を介在させて正負極集電体の未塗工部分１１ｃ，１２ｃに正極および負極外部リード端子１４，１５をそれぞれ接続させた発電要素１０を備える。
【０００７】
また、ラミネート外装材２０はラミネートフィルムから成り、このフィルム材の張り出し加工または深絞り加工によって前記発電要素１０を収納する凹部２１を形成し、この凹部の周囲近傍に熱融着にて封止するための開放した周縁部２２ａ，２２ｂ，２２ｃと、一辺の周縁部と対向し凹部近傍から折り返して凹部２１を覆う平面部２２ｄ（図１２）とが配置される。発電要素１０は、このラミネート外装材２０に収納されている。
【０００８】
上記ラミネート外装材２０は、一般に電解液やガスの透過を防止することが可能な薄く比重が小さいアルミニウムまたはアルミニウム合金箔をバリア材２０ｂとして用い、このアルミニウム合金箔の両面に薄い高分子フィルムを貼り合わせて構成される。すなわち、上記ラミネート外装材２０の外装側あるいは表面側には、機械的構造特性を発現する高分子フィルム２０ａが配置される。一方、上記ラミネート外装材の内装側または裏面側には、熱融着性を有するフィルム（シーラントフィルム）２０ｃが一体に貼り合わされている。
【０００９】
また、上記正極および負極の外部リード端子１４，１５を電池外部に延出し封止される周縁部分２２ａと、凹部近傍から折り返して凹部２１を覆う平面部２２ｄの端部は、熱融着時に正極および負極の外部リード端子１４，１５と接着して近傍の空隙を埋めるととともに、ラミネート外装材２０の端部と上記正極および負極の外部リード端子１４，１５の短絡を防止する絶縁フィルム１６が配置され、相互に気密絶縁封止されている。
【００１０】
前記ラミネート外装材の凹部２１には、非水電解液（図示せず）が注入され発電要素１０に含浸されるとともに、凹部周縁部２２ａ，２２ｂ，２２ｃが気密封止される。気密封止された前記凹部周縁部２２ａ，２２ｂ，２２ｃは、前記正極および負極の外部リード端子１４，１５を電池外部に延出して気密絶縁封止される周縁部分２２ａがテラス状トップシール部２４として形成され、それ以外の凹部周縁部２２ｂ，２２ｃは凹部に沿う様に折曲させたサイドシール部２５ａ，２５ｂとして形成された構造を有している。
【００１１】
上記構造を有するように構成されたラミネート外装薄型二次電池は、一般的に使用電子機器専用の電池パックとして機器パック内に実装して使用される。図１４，図１５，図１６および図１７に示すように、電池パック４０への加工手順は次のとおりである。すなわち、ラミネート外装薄型二次電池３０の外部に延出された正極及び負極の外部リード端子１４，１５には、二次電池の過充電，過放電等を保護する電子回路（モジュール）４２と、使用機器，充電機との電気的接続を可能にする端子台４３とが超音波溶接または抵抗溶接等により電気的に接続される。
【００１２】
図１７に示す電池パック４０の一対の外装ケース４１ａ，４１ｂは、一般的に樹脂等により形成された２分割の容器により構成され、二次電池，電子回路，端子台等が所定の位置に配置されるような凸形状のリブを配置している。前記電子回路４２と前記端子台４３が接続された上記ラミネート外装薄型二次電池３０は、前記テラス状トップシール部２４側に前記電子回路４２および前記端子台４３を配置し、電池パックの外装ケースに挿入可能な形状に正極及び負極の外部リード端子１４，１５に対して折り曲げ加工を実施した後に、図１６に示すように、一方の外装ケース４１ａに挿入して、両面テープや接着剤（図示せず）等で外装ケース内面に固定される。こうして、薄型二次電池，電子回路，端子台等が固定された一方の外装ケース４１ａに、他方の外装ケース４１ｂを接合，封止することにより、図１７に示すような電池パック４０が製造されていた。
【００１３】
しかしながら、薄型二次電池の高容量化がさらに進展するに伴って、二次電池の体積エネルギー密度の向上が求められている。前述した様な一般的な構造を有するラミネート外装薄型二次電池３０では、正極および負極の外部リード端子１４，１５を電池外部に延出して気密絶縁封止されるテラス状トップシール部２４の電池内での占有容積がデットスペースとなり易く、二次電池の体積効率を減少させる大きな要因になっていた。
【００１４】
また、薄型二次電池の高性能化が進捗するにつれて、二次電池を過充電や過放電等から保護する電子回路（モジュール）４２を必要としない安全性が高いラミネート外装薄型二次電池も製品化されている。この安全性が高いラミネート外装薄型二次電池を内蔵する電池パックには、ラミネート外装薄型二次電池３０と端子台４３のみが配置されることになり、従来の電子回路および端子台を共に配置する場合と比較して容積を減少させることが可能となった。
【００１５】
さらに薄型二次電池の体積効率を向上させる方法として、正極および負極の外部リード端子１４，１５を電池外部に延出して気密絶縁封止されるテラス状トップシール部２４をシール幅方向に減少させる方式がある。しかしながら、この方式では封止機能が不十分となり気密絶縁封止部からの水分の侵入を抑制することが困難であり、満足な電池信頼性を達成することが困難であった。
【００１６】
また、発電要素１０を収納するラミネート外装材２０の凹部（以下、「発電要素を収納した電池凸部」という。）２１の根元部において、電池凸部に沿うようにテラス状トップシール部２４を折曲することにより、テラス状トップシール部２４のデットスペースを抑制する構造が公知技術として存在する（例えば、特許文献１参照。）。
【００１７】
しかしながら、上記構造では、電池凸部２１の高さ以上の幅でテラス状トップシール部２４の気密絶縁封止幅を確保することが不可能であることから気密絶縁封止部からの水分の侵入を抑制することが困難であるとともに、折曲部が電池凸部２１の起立端部すなわち気密絶縁封止領域より電池凸部近傍の未封止領域に配置され、正極および負極の外部リード端子１４，１５の電池内部側に形成される折曲部がラミネート外装材２０のシーラントフィルム２０ｃに線状または点状に接触して突き抜け、さらに外力等によりラミネート外装材２０のバリア材２０ｂに到達して内部短絡を発生してしまう危険性があり、十分な動作信頼性を達成することが困難であった。
【００１８】
また、気密絶縁封止幅を十分に確保すること目的とした構造例として、発電要素１０を収納した電池凸部２１の根元から電池凸部と対向する平面側に沿うようにテラス状トップシール部２４を折曲することにより、テラス状トップシール部２４のデットスペースを抑制する構造も公知技術として存在する（例えば、特許文献２参照。）。
【００１９】
【特許文献１】
特開２００１−２５６９３３号公報
【００２０】
【特許文献２】
特開２００２−１４１０３０号公報
【００２１】
【発明が解決しようとする課題】
しかしながら、この構造においても、前記の公知技術と同様に折曲部が電池凸部（２１）の起立端部すなわち気密絶縁封止領域より電池凸部近傍の未封止領域に配置され、折曲角度も１８０度近い鋭角なものとなるため、正極および負極の外部リード端子１４，１５の電池内部側に形成される折曲部がラミネート外装材２０のシーラントフィルム２０ｃに線状または点状に接触し、ラミネート外装材２０のバリア材２０ｂまでに到達して内部短絡を発生してしまう危険性があった。
【００２２】
また、気密絶縁封止領域における折曲方向が平面側であるため、折り曲げた封止領域の一部が電池の厚さ方向に突出し、電池厚さ方向のロスが新たに発生し、電池としての体積効率を必ずしも向上できる構造ではなかった。
【００２３】
本発明は上記課題を解決するためになされたものであり、気密絶縁封止された外部リード端子の延出部を、ラミネート外装材の気密絶縁封止領域において、気密絶縁封止部の長手方向と平行に折曲させることによって封止部からの水分侵入を抑制し、かつ封止部の占める体積を可及的に低減して電池の体積エネルギー密度を増加させた高信頼性薄型二次電池を提供することを目的とする。
【００２４】
【課題を解決するための手段】
上記目的を達成するため、本発明に係る薄型二次電池は、アルミニウム合金箔と高分子フィルムとのラミネートフィルムからなるラミネート外装材と、このラミネート外装材に挿入される正極および負極とこれら正負極間に介在されたセパレータ或いは固体電解質層とからなる発電要素と、上記正極および負極それぞれに電気的に接続され、上記ラミネート外装材の周辺部を通して外部に延出された正極および負極外部リード端子とを具備し、前記発電要素を挿入したラミネート外装材の周辺部を気密封止し、上記外部リード端子の延出部が気密絶縁封止された薄型二次電池において、上記外部リード端子延出部を前記気密絶縁封止領域内で気密絶縁封止部の長手方向と平行に折曲させたことを特徴とする。
【００２５】
また上記薄型二次電池において、前記気密絶縁封止部とそれ以外の気密封止部とが交差する前記ラミネート外装材の角部を切り欠くと共に、この切欠部と発電要素の角部との間に、気密絶縁封止部の幅および気密封止部の幅のいずれか小さい幅以上の幅で封止部を残すように上記切欠部を形成することが好ましい。
【００２６】
上記構成に係る薄型二次電池によれば、外部リード端子延出部を前記気密絶縁封止領域内で気密絶縁封止部の長手方向と平行に折曲させているため、気密絶縁封止部の電池内での占有容積が大幅に低減され、二次電池の体積効率を大幅に向上させることができる。一方、電池内部側に形成される外部リード端子の折曲部がラミネート外装材のシーラントフィルムに接触する恐れは無く、またラミネート外装材のバリア材までに到達して内部短絡を発生させる危険性も少ないため、信頼性が高い二次電池が得られる。
【００２７】
また曲折部を含めて広い幅で封止部を形成することができるため、封止機能が十分に確保され、気密絶縁封止部からの水分の侵入を効果的に抑制することが可能になり、電池特性の劣化が少なく、高い信頼性を有する二次電池が得られる。
【００２８】
さらに、前記気密絶縁封止部とそれ以外の気密封止部とが交差する前記ラミネート外装材の角部を切り欠くことにより、このラミネート外装材の周縁部を電池の厚さ方向に折り曲げた場合においても、電池の高さ方向に折り曲げ片が突出することが無く、厚さ方向へ電池部品容積が増大する悪影響を回避することができる。
【００２９】
また、上記切欠部を形成するに際して、切欠部と発電要素の角部との間に、気密絶縁封止部の幅および気密封止部の幅のいずれか小さい幅以上の幅で封止部を残すように上記切欠部を形成することにより、封止幅を十分に確保でき、切欠部からの水分の侵入を効果的に抑制することが可能になり、電池特性の劣化が少なく、高い信頼性を有する二次電池が得られる。
【００３０】
【発明の実施の形態】
以下、本発明に係る薄型二次電池の実施形態として、ラミネート外装材を使用した薄型リチウムイオン二次電池を例にとり、添付図面を参照して詳細に説明する。図１は本発明に係る薄型二次電池の一実施例の斜視図であり、図２はその展開斜視図であり，図３は外部リード端子を挿通した絶縁気密封止領域およびその他の気密封止領域を表す平面図であり，図４は気密絶縁封止部の折曲部の断面模式図であり，図５（ａ），図５（ｂ），図５（ｃ），図５（ｄ）は、絶縁気密封止部と気密封止部との交差部における角部の切欠き加工の形状例をそれぞれ表す平面図であり，図６は比較例１に係る二次電池の気密絶縁封止部の断面模式図であり，図７は比較例２に係る二次電池の気密絶縁封止部の断面模式図であり，図８は比較例３に係る二次電池における気密絶縁封止部の折曲部の断面模式図であり，図９は比較例４に係る二次電池における気密絶縁封止部の折曲部の断面模式図であり，図１０は比較例５に係る二次電池における気密絶縁封止部の折曲部の断面模式図である。
【００３１】
【実施例１】
＜正極の作製＞
正極活物質として組成式がＬｉＣｏＯ３で表されるリチウムコバルト複合酸化物と、導電材と、結着材とを混合しペースト化した後、外形寸法５０ｍｍ×３９０ｍｍ，厚さ３０μｍのアルミニウム箔からなる正極集電体１１ｂ上に、片側のエッジ部分が２３ｍｍの未塗工部分１１ｃと、他方の未塗工部（図示せず）を残して両面に上記ペーストを塗布し、乾燥，加圧プレスした後、前記未塗工部分１１ｃに厚さ０．１ｍｍ，幅４ｍｍ，長さ５０ｍｍのアルミニウム製の正極外部リード端子１４を溶接により取り付けた。この正極外部リード端子１４は、厚さ０．１ｍｍ，幅４ｍｍ，長さ６０ｍｍの純アルミニウム系合金条（日本工業規格：ＪＩＳ Ｈ ４１６０ Ａ１Ｎ３０）の完全焼鈍材（調質：Ｏ）を使用した。
【００３２】
＜負極の作製＞
負極活物質としてメソフェーズピッチ系炭素繊維を粉砕後に熱処理した粉末と、結着材とを混合しペースト化した後、外形寸法５１．５ｍｍ×４００ｍｍ，厚さ１５μｍの銅箔からなる負極集電体１２ｂ上に、片側のエッジ部分が４６ｍｍの未塗工部分１２ｃと、他方の未塗工部（図示せず）を残して両面に上記ペーストを塗布し、乾燥，加圧プレスした後、前記未塗工部分１２ｃに厚さ０．１ｍｍ，幅４ｍｍ，長さ５３ｍｍのニッケル層（図示せず）の間に純銅層（図示せず）を配置した負極外部リード端子１５を溶接により取り付けた。この負極外部リード端子１５の外形は、厚さ０．１ｍｍ，幅４ｍｍ，長さ６０ｍｍであり、厚さ比率で純ニッケル２５：純銅５０：純ニッケル２５の層構成比率でクラッド法により積層形成された完全焼鈍材（調質：Ｏ）を使用した。
【００３３】
＜発電要素の形成＞
正極外部リード端子（１４）が溶接された前記帯状正極（１１）と、負極外部リード端子（１５）が溶接された前記帯状負極（１２）とを、厚さ２５μｍ×幅５４ｍｍ×長さ４４５ｍｍのポリエチレン製微多孔膜からなるセパレータ（１３）を介して、正極／セパレータ／負極／セパレータの順に積層し、扁平状の巻芯で渦巻き状に捲回し、更に油圧式プレスで圧縮し、外部リード端子を除く外形寸法が高さ５４ｍｍ，幅３３ｍｍ，厚さ３．４ｍｍの扁平状の発電要素１０を作製した。
【００３４】
＜外装材の作製＞
厚さ２５μｍの延伸ナイロンフィルムと、厚さ４０μｍのアルミニウム合金箔（ＪＩＳ Ｈ ４１６０ Ａ８０７９材）と、厚さ３０μｍの直鎖状低密度ポリエチレン（シーラントフィルム）とをこの順序でウレタン系接着材を介して積層接着したラミネート外装フィルムを作製した。このラミネート外装フィルムを外形寸法１７０ｍｍ×１３０ｍｍに切り出し、シーラントフィルム側から張り出し加工または深絞り加工を実施することにより、長さ５５ｍｍ，幅３４ｍｍ，深さ３．４ｍｍであり、前記発電要素１０を収容するための凹部（電池凸部）２１を形成した。凹部２１の周縁には、陵部から水平方向に延出された幅５ｍｍの３箇所の周縁部（２２ａ），（２２ｂ），（２２ｃ）と、幅６０ｍｍの１箇所の平面部（２２ｄ）とを裁断形成したラミネート外装材２０を作製した。
【００３５】
＜非水電解液の調製＞
エチレンカーボネート（ＥＣ）とγ−ブチロラクトン（ＧＢＬ）とを体積比が１：２となる割合で混合して、非水溶媒に電解質としての四フッ化硼酸リチウム（ＬｉＢＦ４）をその濃度が１．５モル／Ｌになるように溶解させて、液状非水電解質を調製した。
【００３６】
＜薄型電池の作製＞
図１〜図４に示すように、前記発電要素１０を前記ラミネート外装材２０の凹部２１に収納すると共に、前記外部リード端子１４，１５をラミネート外装材２０の幅５ｍｍの周縁部２２ａを通して外部に延出した。前記正極および負極の外部リード端子１４，１５を延出した周縁部２２ａと反対側の幅６０ｍｍの平面部２２ｄを折返し部２３から１８０°折り返し、前記正極および負極の外部リード端子１４，１５を延出した側の周縁部２２ａに重ね合わせた。前記正極および負極の外部リード端子１４，１５を電池外部に延出し、封止される周縁部分２２ａには、ヒートシール時に前記正極および負極の外部リード端子１４，１５と接着して近傍の空隙を埋めるととともに、前記ラミネート外装材２０の端部に露出するアルミニウム合金箔のバリア材２０ｂと前記正極および負極の外部リード端子１４，１５の短絡を防止する絶縁フィルム１６が配置されている。
【００３７】
この絶縁フィルム１６は上記正極および負極の外部リード端子１４，１５の幅よりも大きく、かつ気密絶縁封止幅よりも広い大きさに形成され、前記ラミネート外装材２０の端部から１ｍｍ延出し、封止される周縁部分２２ａと折返し部２３から１８０°だけ折り返した平面部２２ｄ側の両面に配置した。このような構成とした外部リード端子の延出部２２ａについて、前記正極および負極の外部リード端子１４，１５を挟みながら、１８０°折り返した幅６０ｍｍの平面部２２ｄとの重なり部分（以下、「テラス状トップシール部２４」という。）を４ｍｍ幅で熱融着により気密絶縁封止した。
【００３８】
上記正極および負極の外部リード端子１４，１５の延出量は、テラス状トップシール端部から８ｍｍとしている。次に上記テラス状トップシール部２４と垂直方向に配置される一方の幅５ｍｍの周縁部２２ｂまたは２２Ｃを熱融着により気密封止し、サイドシール部２５ａを形成し１箇所の気密絶縁封止部と、１箇所の気密封止部と、１箇所の折り返し部２３と、１箇所の開口した周縁部を形成した。
【００３９】
続いて開口している１箇所の周縁部を通して、前記非水電解液（図示せず）を上記ラミネート外装材２０の凹部２１に注入し、内部に収納されている発電要素１０に前記非水電解液（図示せず）を含浸させた。続いて上記ラミネート外装材２０の開口周縁部を熱融着により気密封止して、もう一方のサイドシール部２５ｂを形成した。続いて２つのサイドシール部２５ａ，２５ｂを、幅３ｍｍを残して切断し、テラス状トップシール部幅（Ｗ２４）が５ｍｍでサイドシール部幅（Ｗ２５）が３ｍｍであるラミネート外装薄型リチウムイオン二次電池を得た。
【００４０】
＜気密絶縁封止部および気密封止部の加工＞
このようにして作成された薄型二次電池は、この形態のままでは電池外方に延びた３箇所の封止部が電池としての体積効率を低下させることになる。そこで図４に示すように、この薄型二次電池について、上記テラス状トップシール部２４から延出した前記正極および負極の外部リード端子１４，１５を上記ラミネート外装材２０の端部から延出した絶縁フィルム１６と共に、上記テラス状トップシール部２４の前記平面部２２ｄ側に折り返した。次に気密絶縁封止した前記テラス状トップシール部２４の上端部から３ｍｍ内側を絶縁気密封止部の長手方向と平行にラミネート外装材２０の発電要素１０を収納する凹部（発電要素を収納した電池凸部）２１側に折曲させ、気密絶縁封止折曲部２６を形成した。
【００４１】
なお、上記凹部２１の端部から上記気密絶縁封止折曲部２６までの平坦部の幅は、封止機能および折り曲げ加工性を良好にする観点から１．５ｍｍ以上、好ましくは２ｍｍ以上に設定することが好ましい。
【００４２】
前記テラス状トップシール部２４両端とサイドシール部２５ａ，２５ｂとを電池凸部側に折り曲げることにより、外形寸法３５．０ｍｍ×５８．０ｍｍ×３．８ｍｍで、放電容量７７０ｍＡｈのラミネート外装薄型リチウムイオン二次電池を作製した。
【００４３】
【実施例２】
前記実施例１において説明した薄形二次電池の構成の内、下記の構成を変えて実施例２に係る薄形二次電池を調製した。すなわち、図５ａに示すようにテラス状トップシール部２４とサイドシール部２５ａ，２５ｂが交差する封止領域の角部に切り欠き部２７を設けた。切り欠き部２７は、この切り欠き部と発電要素１０の角部との間に、気密絶縁封止部（テラス状トップシール部）２４の幅（Ｗ２４）および気密封止部（サイドシール部）の幅（Ｗ２５）のいずれか小さい幅以上の幅（Ｗ２７）で封止部を残すように形成した。具体的には残す封止部の幅（Ｗ２７）を３ｍｍとし、トップシール部２４の端部から７０度の傾斜角度で切り欠いて上記切り欠き部２７を形成した。
【００４４】
なお、上記実施例２では角部の切り欠き形状は、図５ａに示すように直線状に切り欠いているが、切り欠き部と発電要素１０の角部との間に、テラス状トップシール部幅（Ｗ２４）とサイドシール幅（Ｗ２５）との何れか少ない方と同じかそれ以上の封止幅（Ｗ２７）が確保できる限りは、切り欠き角度や形状は実施例２と異なっても構わず、特に限定されない。具体的には、図５ｂに示すように，切欠角度を４５度にした直線状の切り欠き部２７でも良い。また、図５ｃに示すように、曲線状に切断して形成した切り欠き部２７でも良い。さらに、図５ｄに示すように矩形状に切断して形成した切り欠き部２７でも良い。
【００４５】
上記切り欠き部２７を形成した以降の処理および加工は、実施例１に記述した気密絶縁封止部および気密封止部の加工内容と同様とすることにより、外形寸法が３５．０ｍｍ×５８．０ｍｍ×３．８ｍｍであり、放電容量が７７０ｍＡｈである実施例２に係るラミネート外装薄型リチウムイオン二次電池を作製した。
【００４６】
上記実施例２に係るラミネート外装薄型リチウムイオン二次電池によれば、テラス状トップシール部２４とサイドシール部２５ａ，２５ｂとが交差する封止部領域の角部に切り欠き部２７を設けているため、テラス状トップシール部２４の両端とサイドシール部２５ａ，２５ｂの交差部分が電池の厚さ方向に突出することがなく、折り曲げ加工を容易に実施することが可能である。
【００４７】
【比較例１】
前記実施例１において説明した薄形二次電池の構成の内、下記の構成を変えて比較例１に係る薄形二次電池を調製した。すなわち、図１に示すように、気密絶縁封止部および気密封止部の加工をサイドシール部２５ａ，２５ｂを電池凸部側に折り曲げるのみとする一方、テラス状トップシール部（２４）についての折り曲げ加工は実施しないことにより、外形寸法が３５ｍｍ×６０．５ｍｍ×３．８ｍｍであり、放電容量が７７０ｍＡｈである比較例１に係るラミネート外装薄型リチウムイオン二次電池を作製した。
【００４８】
【比較例２】
前記比較例１において説明した薄形二次電池の構成の内、下記の構成を変えて比較例２に係る薄形二次電池を調製した。すなわち、ラミネート外装材の凹部２１の周縁に延出する周辺部を、幅３ｍｍである１箇所の周縁部２２ａと、幅５ｍｍである２箇所の周縁部２２ｂ，２２ｃと、幅５８ｍｍである１箇所の周縁部２２ｄとして裁断形成した。このラミネート外装材のトップシール部２４を２ｍｍ幅で熱融着した。図７に示すように、テラス状トップシール部２４と直角方向に配置した２つのサイドシール部２５ａ，２５ｂを幅３ｍｍだけ残して切断し、テラス状トップシール部の幅（Ｗ２４）を３ｍｍとし、サイドシール部の幅（Ｗ２５）を３ｍｍとした。続いて図１に示すようにサイドシール部２５ａ，２５ｂを電池凸部側に折り曲げることにより、外形寸法が３５．０ｍｍ×５８．０ｍｍ×３．８ｍｍであり、放電容量が７７０ｍＡｈである比較例２に係るラミネート外装薄型リチウムイオン二次電池を作製した。
【００４９】
【比較例３】
前記実施例１において説明した薄形二次電池の構成の内、下記の構成を変えて比較例３に係る薄形二次電池を調製した。すなわち、図８に示すように、気密絶縁封止したテラス状トップシール部を電池凸部２１の根元から絶縁気密封止部の長手方向と平行にラミネート外装材２０の電池凸部２１側に折曲させ、封止根元折曲部２８を形成した。続いてテラス状トップシール部２４両端とサイドシール部２５ａ，２５ｂを電池凸部側に折り曲げ加工した。この時、テラス状トップシール部２４両端とサイドシール部２５ａ，２５ｂの交差部は、双方向からの曲げ加工で角状に突出するので、突出部を再度トップシール部側に折り畳む加工を実施することにより、外形寸法が３５．０ｍｍ×５６．５ｍｍ×４．５ｍｍであり、放電容量が７７０ｍＡｈである比較例３に係るラミネート外装薄型リチウムイオン二次電池を作製した。
【００５０】
上記比較例３に係る薄形二次電池において、電池厚さが実施例より大きくなった理由は下記の通りである。すなわち、テラス状トップシール部の幅（Ｗ２４）が５ｍｍであるため、根元から折り曲げたテラス状トップシール部は電池凸部より電池厚さ方向に突出してしまったためである。
【００５１】
【比較例４】
前記比較例３において説明した薄形二次電池の構成の内、下記の構成を変えて比較例４に係る薄形二次電池を調製した。すなわち、図９に示すように、ラミネート外装材の凹部２１の周縁に延出する周辺部を、比較例２と同様に幅が３ｍｍである１箇所の周縁部（２２ａ）と、幅が５ｍｍである２箇所の周縁部２２ｂ，２２ｃと、幅が５８ｍｍである１箇所の周縁部２２ｄとして裁断形成した。それ以降の処理および加工は比較例３にて実施した気密絶縁封止部および気密封止部の加工内容と同様とすることにより、外形寸法が３５．０ｍｍ×５６．５ｍｍ×３．８ｍｍであり、放電容量が７７０ｍＡｈである比較例４に係るラミネート外装薄型リチウムイオン二次電池を作製した。
【００５２】
【比較例５】
前記比較例３において説明した薄形二次電池の構成の内、下記の構成を変えて比較例５に係る薄形二次電池を調製した。すなわち、図１０に示すように、気密絶縁封止したテラス状トップシール部を根元から絶縁気密封止部の長手方向と平行に電池凸部２１の根元から絶縁気密封止部の長手方向と平行にラミネート外装材２０の電池凸部２１と対向する平面側に沿うように１８０度の折り曲げ角度で折曲させ、封止根元折曲部２８を形成した。正極および負極の外部リード端子１４，１５をラミネート外装材２０の端部から延出した絶縁フィルム１６と共に封止根元折曲部側に折り返した。続いてテラス状トップシール部２４両端とサイドシール部２５ａ，２５ｂとを電池凸部側に折り曲げ加工を施すことにより、外形寸法が３６．０ｍｍ×５５．５ｍｍ×４．５ｍｍであり、放電容量が７７０ｍＡｈである比較例５に係るラミネート外装薄型リチウムイオン二次電池を作製した。
【００５３】
上記比較例５に係る薄形二次電池において、電池厚さおよび電池幅が実施例より大きくなった理由は下記の通りである。すなわち、テラス状トップシール部を電池凸部と対向する平面側に沿うように折曲させたことにより、電池凸部の厚さにテラス状トップシール部の厚さが加算されてしまう結果、厚さ方向の容積損失が大きくなること、およびサイドシール部の折り曲げがテラス状トップシール部と二重に重なる部位（両シール部の交差領域）が存在することで幅方向の損失も大きくなってしまうためである。
【００５４】
上記のように調製した実施例１〜２および比較例１〜５に係る各ラミネート外装薄型リチウムイオン二次電池の比較パラメーター（気密絶縁封止幅，折曲位置，折曲方向，角部の切欠の有無）について下記表１にまとめて示す。
【００５５】
【表１】
【００５６】
上記の実施例１〜２および比較例１〜５に係る各ラミネート外装薄型リチウムイオン二次電池を評価するために、以下の特性項目について比較調査を実施した。
【００５７】
＜封止部からの水分透過量の比較＞
実施例１〜２および比較例１〜５に係るラミネート外装薄形リチウムイオン二次電池を各３個ずつサンプリングし、未充電状態の状態で温度が６５℃であり、相対湿度ＲＨが９０％に調整した環境に３０日間放置した。その後、電池内から非水電解液をマイクロシリンジで０．５ｃｃ抽出し、非水電解液中の水分量をカールフィッシャー水分量測定装置で測定した。なお各電池の水分透過量は比較例１に係る二次電池の水分透過量を基準値（１００％）として、相対値として算出した。測定算出結果を表２に示す。
【００５８】
＜外力による内部短絡発生比較＞
実施例１〜２および比較例１〜５に係るラミネート外装薄形リチウムイオン二次電池の各１０個について、室温において１Ｃで４．２Ｖまで定電流・定電圧充電を実施した。その後、室温において１Ｃで３．０Ｖまで放電し、基準放電容量を測定し、さらに室温において１Ｃで３．８５Ｖまで定電流・定電圧充電を実施した。この状態の各ラミネート外装薄形リチウムイオン二次電池をダミーパックのケースに実装し、高さ１．５ｍから樫の木材表面に自然落下させるという過酷な条件設定のもとに実施した。
【００５９】
各二次電池を落下させる方向は、外部リード端子，テラス状トップシール部および気密絶縁封止折曲部に引張り・圧縮方向の落下衝撃が加わるように電池の縦方向の姿勢をとった落下とし、上下方向を逆にした落下の繰り返しを１サイクルとして１００サイクルまで実施した。１０サイクル毎に内部短絡が発生しているか否かについてダミーパックに設けた端子穴から外部リード端子の電圧を測定することにより確認した。落下試験後の内部短絡発生回数と発生個数について測定し、比較例１の二次電池の内部短絡発生回数と発生個数を基準値（１００％）として、相対値として算出した。測定算出結果を表２に示す。
【００６０】
＜電池寸法（体積効率）比較＞
実施例１〜２および比較例１〜５に係る各ラミネート外装薄形リチウムイオン二次電池について、電池高さ，電池幅，電池厚さの各寸法から電池体積を算出し、それぞれの電池の放電容量から体積容量密度を算出し比較した。なお各二次電池の体積容量密度は比較例１に係る二次電池の体積容量密度を基準値（１００％）として、相対値として算出した。測定算出結果を下記表２にまとめて示す。
【００６１】
【表２】
【００６２】
上記表１および表２に示す結果から明らかなように、外部リード端子延出部を気密絶縁封止領域内で気密絶縁封止部の長手方向と平行に折曲させた各実施例１〜２に係る二次電池においては、気密絶縁封止部の電池内での占有容積が低減されるため、体積容量密度が増加し、二次電池の体積効率を向上させることができた。
【００６３】
また、外部リード端子延出部を気密絶縁封止領域内で折曲させているため、電池内部側に位置する外部リード端子がラミネート外装材に接触する恐れは無く、またラミネート外装材のバリア材までに到達して内部短絡を発生させる危険性も少ないため、信頼性が高い二次電池が得られた。
【００６４】
また曲折部を含めて広い幅で封止部を形成することができるため、封止機能が十分に確保され、水分透過量は増加せず、気密絶縁封止部からの水分の侵入を効果的に抑制することが可能になり、電池特性の劣化が少なく、高い信頼性を有する二次電池が得られた。
【００６５】
さらに、前記気密絶縁封止部とそれ以外の気密封止部とが交差する前記ラミネート外装材の角部を切り欠いて切り欠き部２７を形成した実施例２に係る電池においては、このラミネート外装材の周縁部を電池の厚さ方向に折り曲げた場合においても、電池の高さ方向に折り曲げ片が突出することが無く、厚さ方向へ電池部品容積が増大する悪影響を回避することができた。
【００６６】
また、上記切り欠き部２７を形成するに際して、この切り欠き部２７と発電要素１０の角部との間に、気密絶縁封止部の幅（Ｗ−２４）および気密封止部の幅（Ｗ−２５）のいずれか小さい幅以上の幅で封止部を残すように上記切欠部を形成することにより、封止幅を十分に確保でき、切り欠き部２７からの水分の侵入を効果的に抑制することが可能になり、電池特性の劣化が少なく、高い信頼性を有する二次電池が得られた。
【００６７】
一方、外部リード端子延出部を折曲していない比較例１に係る二次電池においては、端子端部の体積ロスが大きくなった。また、気密絶縁封止部の幅を小さくした比較例２に係る二次電池においては、体積容量密度は増加するが、水分侵入の抑止効果が不十分であった。さらに、比較例３のように、外部リード端子延出部を、気密絶縁封止領域外である封止根元で折曲した二次電池においては、端子材が曲折部方向に引っ張られて内部短絡の発生率が上昇すると共に、折曲部が電池の厚さ方向に突出するため、体積容量密度が低下した。
【００６８】
また、比較例４のように、気密絶縁封止部の幅を小さくする一方、外部リード端子延出部を封止部の根元で折曲した二次電池においては、体積容量密度は増加するが、封止機能が不十分であり、水分侵入の抑止効果が不十分であった。また、外部リード端子延出部を、気密絶縁封止領域外である封止根元で折曲しているため、端子材が曲折部方向に引っ張られて内部短絡の発生率が上昇した。さらに、比較例５のように、外部リード端子延出部を、気密絶縁封止領域外である封止根元で裏側に折曲しているため、端子材が曲折部方向に引っ張られて内部短絡の発生率が上昇した。さらに、裏側に折曲した曲折部の厚さが電池厚さに加算されて電池全体に厚さとなるため、体積効率は大幅に悪化した。
【００６９】
【発明の効果】
以上詳述したように、本発明に係る薄型二次電池によれば、発電要素を収納するラミネート外装材と気密絶縁封止された正極および負極の外部リード端子延出部を、ラミネート外装材の気密絶縁封止領域内で気密絶縁封止部の長手方向と平行に折曲させた構造とすることによって気密絶縁封止幅を十分に確保することができ、封止部からの水分侵入を抑え、折曲部が気密絶縁封止領域内であることにより折曲部の正極および負極外部リード端子とラミネート外装材間の内部短絡を防止し、かつ封止部の占める体積を出来るだけ小さくして電池の体積エネルギー密度を増加させた薄型二次電池を提供することができる。
【図面の簡単な説明】
【図１】本発明に係る薄型二次電池の斜視図。
【図２】本発明に係る薄型二次電池の展開斜視図。
【図３】本発明に係る薄型二次電池の絶縁気密封止領域および気密封止領域を表す平面図。
【図４】本発明に係る薄型二次電池の気密絶縁封止部の折曲部を模式的に示す部分断面図。
【図５】本発明に係る薄型二次電池の絶縁気密封止部と気密封止部との交差部である角部に形成する切り欠き部の形状を示す平面図であり、（ａ）は実施例２に係る二次電池に形成した切欠部（切断角度：７０度）を示す平面図、（ｂ）は４５度の切断角度で切り欠いて形成した切り欠き部の形状を示す平面図、（ｃ）は封止部を曲線状に切断して形成した切り欠き部の形状を示す平面図、（ｄ）は封止部を矩形状に切断して形成した切り欠き部の形状を示す平面図。
【図６】比較例１に係る薄型二次電池の気密絶縁封止部を模式的に示す部分断面図。
【図７】比較例２に係る薄型二次電池の気密絶縁封止部を模式的に示す部分断面図。
【図８】比較例３に係る薄型二次電池の気密絶縁封止部を模式的に示す部分断面図。
【図９】比較例４に係る薄型二次電池の気密絶縁封止部を模式的に示す部分断面図。
【図１０】比較例５に係る薄型二次電池の気密絶縁封止部を模式的に示す部分断面図。
【図１１】従来の薄型二次電池の構成を示す斜視図。
【図１２】従来の薄型二次電池の構造を示す展開斜視図。
【図１３】従来の薄型二次電池の気密絶縁封止部を模式的に示す部分断面図。
【図１４】外部リード端子、電子回路および端子台の接合状態を示す斜視図。
【図１５】外部リード端子の折り曲げ加工状態を示す斜視図。
【図１６】電池パックの構成を示す展開斜視図。
【図１７】電池パックの組立て状態を示す斜視図。
【符号の説明】
１０ 発電要素
１１ 正極
１１ａ 正極活物質
１１ｂ 正極集電体
１１ｃ 正極未塗工部分
１２ 負極
１２ａ 負極活物質
１２ｂ 負極集電体
１２ｃ 負極未塗工部分
１３ セパレータ
１４ 正極外部リード端子
１５ 負極外部リード端子
１６ 絶縁フィルム
２０ ラミネート外装材
２０ａ 表面側樹脂フィルム
２０ｂ バリア材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin secondary battery having a structure in which a power generation element is sealed with an exterior material made of a laminate film, and in particular, after preventing moisture intrusion and internal short circuit from the sealing portion and ensuring the reliability of the battery. The present invention relates to a thin secondary battery capable of increasing the volumetric energy density of the battery.
[0002]
[Prior art]
With the rapid advancement of electronic devices such as mobile phones and notebook computers, secondary batteries that serve as the driving power source have been constantly required to be smaller, lighter, larger in capacity, higher in performance, and lower in cost. Conventionally, nickel cadmium batteries and nickel metal hydride secondary batteries have been used as secondary batteries that are mounted in these portable devices and used as drive power sources. In recent years, lithium ion secondary batteries that can achieve higher energy density have been used. Battery demand is expanding rapidly.
[0003]
As for the shape of secondary batteries, the demand for prismatic batteries and oval batteries with higher volumetric efficiency during storage than conventional cylindrical and button batteries will increase, and the capacity and energy density will increase. At the same time, the electrode materials such as the positive electrode active material and the negative electrode active material are changed to those with higher energy density, the separator is made thinner, and the battery cans are replaced with stainless steel or iron instead of aluminum alloy. Improvements have been made.
[0004]
However, even after these improvements, technical requirements have become more advanced and have not yet reached a satisfactory level, and further miniaturization, weight reduction, thinning, large capacity, and cost reduction are required. Recently, a power generation element is made of a laminate outer material made of a polymer film containing a liquid electrolyte, gel electrolyte, solid polymer electrolyte, etc. in a power generation element, and a polymer film sandwiched between aluminum laminate foils as a barrier layer and laminated in the middle. By sealing the battery, thin secondary batteries that are thin, small, and light are being marketed and spreading.
[0005]
As a thin secondary battery in which a power generation element is sealed with such a laminate film exterior material, for example, a nonaqueous electrolyte thin secondary battery having a laminate exterior structure shown in FIGS. 11, 12 and 13 is known.
[0006]
That is, the laminated outer non-aqueous electrolyte thin secondary battery 30 includes a positive electrode 11 in which the positive electrode active material 11a is applied to the positive electrode current collector 11b, and a negative electrode 12 in which the negative electrode active material 12a is applied to the negative electrode current collector 12b. A power generating element 10 is provided in which positive and negative electrode external lead terminals 14 and 15 are connected to uncoated portions 11c and 12c of a positive and negative electrode current collector through a separator 13, respectively.
[0007]
The laminate exterior material 20 is made of a laminate film, and a recess 21 for housing the power generation element 10 is formed by overhanging or deep drawing of the film material, and sealing is performed in the vicinity of the periphery of the recess by heat sealing. An open peripheral portion 22a, 22b, and 22c for opening, and a flat portion 22d (FIG. 12) that faces the peripheral portion of one side and is folded back from the vicinity of the concave portion to cover the concave portion 21 are arranged. The power generation element 10 is accommodated in the laminate exterior material 20.
[0008]
The laminate outer material 20 is generally made of aluminum or aluminum alloy foil having a small specific gravity capable of preventing permeation of electrolyte and gas as the barrier material 20b, and thin polymer films are pasted on both surfaces of the aluminum alloy foil. It is configured together. That is, on the exterior side or the surface side of the laminate exterior material 20, a polymer film 20a that exhibits mechanical structural characteristics is disposed. On the other hand, a film (sealant film) 20c having heat-fusibility is integrally bonded to the interior side or the back side of the laminate exterior material.
[0009]
The positive and negative external lead terminals 14 and 15 are extended to the outside of the battery and sealed, and the end portion of the flat portion 22d that is folded back from the vicinity of the concave portion and covers the concave portion 21 is positive during thermal fusion. The insulating film 16 is disposed so as to adhere to the external lead terminals 14 and 15 of the negative electrode and fill the gap in the vicinity, and to prevent a short circuit between the end portion of the laminate exterior material 20 and the external lead terminals 14 and 15 of the positive and negative electrodes. And hermetically sealed with each other.
[0010]
A nonaqueous electrolyte (not shown) is injected into the concave portion 21 of the laminate outer packaging material and impregnated in the power generation element 10, and the peripheral portions 22 a, 22 b, and 22 c of the concave portion are hermetically sealed. The recessed peripheral portions 22a, 22b, and 22c that are hermetically sealed are extended from the positive and negative external lead terminals 14 and 15 to the outside of the battery, and the peripheral portion 22a that is hermetically insulated and sealed is a terrace-shaped top seal portion 24. The other recess peripheral portions 22b and 22c are formed as side seal portions 25a and 25b bent along the recess.
[0011]
The laminated exterior thin secondary battery configured to have the above structure is generally used by being mounted in a device pack as a battery pack dedicated to the electronic device used. As shown in FIGS. 14, 15, 16 and 17, the processing procedure for the battery pack 40 is as follows. In other words, the external lead terminals 14 and 15 of the positive electrode and the negative electrode extended to the outside of the laminated exterior thin secondary battery 30 have an electronic circuit (module) 42 for protecting the secondary battery from overcharge, overdischarge, etc. The terminal block 43 that enables electrical connection with the equipment used and the charger is electrically connected by ultrasonic welding or resistance welding.
[0012]
A pair of outer cases 41a and 41b of the battery pack 40 shown in FIG. 17 is generally composed of a two-divided container formed of resin or the like, and a secondary battery, an electronic circuit, a terminal block, etc. are arranged at predetermined positions. Convex-shaped ribs are arranged. In the laminated exterior thin secondary battery 30 to which the electronic circuit 42 and the terminal block 43 are connected, the electronic circuit 42 and the terminal block 43 are arranged on the terrace-shaped top seal portion 24 side, and an exterior case of a battery pack is provided. After the positive and negative external lead terminals 14 and 15 are bent into a shape that can be inserted into the external case, as shown in FIG. 16, it is inserted into one outer case 41a and double-sided tape or adhesive (see FIG. (Not shown) or the like. Thus, the battery pack 40 as shown in FIG. 17 is manufactured by joining and sealing the other outer case 41b to the one outer case 41a to which the thin secondary battery, the electronic circuit, the terminal block, etc. are fixed. It was.
[0013]
However, as the capacity of thin secondary batteries further increases, improvement in the volume energy density of secondary batteries is required. In the laminated exterior thin secondary battery 30 having the general structure as described above, the battery of the terrace-like top seal portion 24 in which the positive and negative external lead terminals 14 and 15 are extended to the outside of the battery and hermetically insulated and sealed. The occupied volume tends to be a dead space, which is a major factor for reducing the volume efficiency of the secondary battery.
[0014]
In addition, as the performance of thin secondary batteries progresses, a highly safe laminated exterior thin secondary battery that does not require an electronic circuit (module) 42 that protects the secondary battery from overcharge and overdischarge is also a product. It has become. In the battery pack containing the laminated outer thin type secondary battery with high safety, only the laminated outer thin type secondary battery 30 and the terminal block 43 are arranged, and the conventional electronic circuit and the terminal block are arranged together. The volume can be reduced compared to the case.
[0015]
Further, as a method for improving the volumetric efficiency of the thin secondary battery, the terrace-shaped top seal portion 24 which extends the positive and negative external lead terminals 14 and 15 to the outside of the battery and is hermetically insulated and sealed is reduced in the seal width direction. There is a method. However, in this method, the sealing function is insufficient, and it is difficult to suppress the intrusion of moisture from the hermetic insulating sealing portion, and it is difficult to achieve satisfactory battery reliability.
[0016]
In addition, a terrace-shaped top seal portion 24 is formed along the battery convex portion at the base portion of the concave portion (hereinafter referred to as “battery convex portion accommodating the power generating element”) 21 of the laminate exterior member 20 that houses the power generating element 10. A structure that suppresses the dead space of the terrace-like top seal portion 24 by bending exists as a known technique (for example, see Patent Document 1).
[0017]
However, in the above structure, since it is impossible to ensure the hermetic insulating sealing width of the terrace-shaped top seal portion 24 with a width equal to or higher than the height of the battery convex portion 21, moisture enters from the hermetic insulating sealing portion. The bent portion is disposed in the standing end portion of the battery convex portion 21, that is, in the unsealed region near the battery convex portion from the airtight insulating sealing region, and the external lead terminal 14 of the positive electrode and the negative electrode 15, the bent portion formed on the inner side of the battery contacts the sealant film 20 c of the laminate exterior material 20 in a linear or dotted manner, and further reaches the barrier material 20 b of the laminate exterior material 20 by an external force or the like. There is a risk of causing an internal short circuit, and it has been difficult to achieve sufficient operation reliability.
[0018]
In addition, as an example of a structure intended to ensure a sufficient hermetic insulation sealing width, a terrace-shaped top seal portion extends from the base of the battery convex portion 21 housing the power generation element 10 to the plane side facing the battery convex portion. A structure that suppresses the dead space of the terrace-shaped top seal portion 24 by bending 24 is also known in the art (see, for example, Patent Document 2).
[0019]
[Patent Document 1]
JP 2001-256933 A
[0020]
[Patent Document 2]
JP 2002-141030 A
[0021]
[Problems to be solved by the invention]
However, also in this structure, the bent portion is arranged in the unsealed region near the battery convex portion from the standing end portion of the battery convex portion (21), that is, the airtight insulating sealed region, as in the above-described known technique. Since the angle is also an acute angle close to 180 degrees, the bent portions formed on the battery inner side of the positive and negative external lead terminals 14 and 15 contact the sealant film 20c of the laminate exterior material 20 in a linear or dotted manner. However, there was a risk of reaching the barrier material 20b of the laminate exterior material 20 and causing an internal short circuit.
[0022]
In addition, since the folding direction in the hermetic insulating sealing region is the plane side, a part of the bent sealing region protrudes in the thickness direction of the battery, and a loss in the battery thickness direction is newly generated. The volume efficiency was not necessarily improved.
[0023]
The present invention has been made in order to solve the above-described problem, and the extended portion of the external lead terminal that is hermetically insulated and sealed is arranged in the longitudinal direction of the hermetic insulating and sealed portion in the hermetic insulating and sealed region of the laminate exterior material Highly reliable thin secondary battery that suppresses moisture intrusion from the sealing part by bending in parallel with the battery and reduces the volume occupied by the sealing part as much as possible to increase the volume energy density of the battery The purpose is to provide.
[0024]
[Means for Solving the Problems]
In order to achieve the above object, a thin secondary battery according to the present invention includes a laminate outer package made of a laminate film of an aluminum alloy foil and a polymer film, a positive electrode and a negative electrode inserted into the laminate outer package, and these positive and negative electrodes A power generation element composed of a separator or a solid electrolyte layer interposed between the positive electrode and the negative electrode, and a positive electrode and a negative electrode external lead terminal that are electrically connected to the positive electrode and the negative electrode, respectively, and extend to the outside through the peripheral portion of the laminate exterior material; A thin secondary battery in which the peripheral portion of the laminate exterior material into which the power generating element is inserted is hermetically sealed, and the extended portion of the external lead terminal is hermetically insulated and sealed, the external lead terminal extending portion Is bent in parallel with the longitudinal direction of the hermetic insulating sealing portion in the hermetic insulating sealing region.
[0025]
Further, in the thin secondary battery, a corner portion of the laminate exterior material where the hermetic insulating sealing portion and the other hermetic sealing portion intersect is cut out, and between the cutout portion and the corner of the power generation element. In addition, it is preferable to form the notch so as to leave the sealing part with a width equal to or larger than one of the width of the hermetic insulating sealing part and the width of the hermetic sealing part.
[0026]
According to the thin secondary battery having the above-described configuration, the external lead terminal extension is bent in the airtight insulating sealing region in parallel with the longitudinal direction of the hermetic insulating sealing portion. The volume occupied in the battery is greatly reduced, and the volume efficiency of the secondary battery can be greatly improved. On the other hand, there is no risk that the bent part of the external lead terminal formed on the battery inner side will come into contact with the sealant film of the laminate exterior material, and it may reach the barrier material of the laminate exterior material to cause an internal short circuit. Therefore, a highly reliable secondary battery can be obtained.
[0027]
In addition, since the sealing portion can be formed with a wide width including the bent portion, the sealing function is sufficiently secured, and it is possible to effectively suppress the intrusion of moisture from the hermetic insulating sealing portion. Thus, a secondary battery with little deterioration in battery characteristics and high reliability can be obtained.
[0028]
Further, when the peripheral portion of the laminate exterior material is folded in the thickness direction of the battery by cutting out the corner of the laminate exterior material where the hermetic insulation seal portion and the other airtight seal portion intersect. However, the bent piece does not protrude in the height direction of the battery, and the adverse effect of increasing the battery component volume in the thickness direction can be avoided.
[0029]
Further, when forming the cutout portion, the sealing portion is formed between the cutout portion and the corner portion of the power generation element with a width equal to or larger than one of the width of the hermetic insulating sealing portion and the width of the hermetic sealing portion. By forming the cutout part so that it remains, it is possible to ensure a sufficient sealing width, effectively suppress the intrusion of moisture from the cutout part, reduce battery characteristics, and have high reliability. A secondary battery having
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, as an embodiment of a thin secondary battery according to the present invention, a thin lithium ion secondary battery using a laminate exterior material will be described as an example and described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view of an embodiment of a thin secondary battery according to the present invention, FIG. 2 is a developed perspective view thereof, and FIG. 3 is an insulating hermetic seal region through which external lead terminals are inserted and other hermetic seals. FIG. 4 is a schematic cross-sectional view of the bent portion of the hermetic insulating sealing portion, and FIG. 5 (a), FIG. 5 (b), FIG. 5 (c), FIG. FIG. 6 is a plan view showing an example of the shape of notch processing at the corners at the intersection between the insulating hermetic sealing portion and the hermetic sealing portion, and FIG. 6 shows the hermetic sealing of the secondary battery according to Comparative Example 1. FIG. 7 is a schematic cross-sectional view of a stopper, FIG. 7 is a schematic cross-sectional view of a hermetic insulating sealing part of a secondary battery according to Comparative Example 2, and FIG. 8 is an hermetic insulating sealing part of a secondary battery according to Comparative Example 3. 9 is a schematic cross-sectional view of the bent portion of FIG. 9, FIG. 9 is a schematic cross-sectional view of the bent portion of the hermetic insulating sealing portion in the secondary battery according to Comparative Example 4, and FIG. Of a rechargeable battery according to 5 are cross-sectional schematic view of a bent portion of the hermetic insulating sealing portion.
[0031]
[Example 1]
<Preparation of positive electrode>
The composition formula is LiCoO as the positive electrode active material. 3 After mixing the lithium cobalt composite oxide represented by the above, a conductive material, and a binder into a paste, one side is placed on the positive electrode current collector 11b made of an aluminum foil having an outer dimension of 50 mm × 390 mm and a thickness of 30 μm. The above-mentioned paste is applied to both sides, leaving an uncoated portion 11c having an edge portion of 23 mm and the other uncoated portion (not shown), dried and pressed, and then applied to the uncoated portion 11c. A positive electrode external lead terminal 14 made of aluminum having a thickness of 0.1 mm, a width of 4 mm, and a length of 50 mm was attached by welding. This positive external lead terminal 14 was made of a pure annealing material (tempered: O) of a pure aluminum alloy strip (Japanese Industrial Standard: JIS H 4160 A1N30) having a thickness of 0.1 mm, a width of 4 mm, and a length of 60 mm.
[0032]
<Production of negative electrode>
A powder obtained by pulverizing mesophase pitch-based carbon fibers as a negative electrode active material and a binder are mixed to form a paste, and then a negative electrode current collector 12b made of copper foil having an outer dimension of 51.5 mm × 400 mm and a thickness of 15 μm. On top, the above-mentioned paste is applied on both sides, leaving an uncoated portion 12c with an edge portion of 46 mm on one side and the other uncoated portion (not shown), dried and pressed, and then the uncoated portion A negative electrode external lead terminal 15 in which a pure copper layer (not shown) is disposed between nickel layers (not shown) having a thickness of 0.1 mm, a width of 4 mm, and a length of 53 mm was attached to the processed portion 12c by welding. The negative electrode external lead terminal 15 has an outer shape of a thickness of 0.1 mm, a width of 4 mm, and a length of 60 mm. The negative electrode external lead terminal 15 is laminated by a clad method at a thickness ratio of pure nickel 25: pure copper 50: pure nickel 25. A completely annealed material (tempering: O) was used.
[0033]
<Formation of power generation elements>
The belt-like positive electrode (11) to which the positive external lead terminal (14) is welded and the belt-like negative electrode (12) to which the negative external lead terminal (15) is welded are 25 μm thick × 54 mm wide × 445 mm long. Laminated in the order of positive electrode / separator / negative electrode / separator through a separator (13) made of polyethylene microporous membrane, wound in a spiral shape with a flat core, and further compressed with a hydraulic press, external lead terminal A flat power generating element 10 having outer dimensions of 54 mm in height, 33 mm in width, and 3.4 mm in thickness was prepared.
[0034]
<Production of exterior material>
A stretched nylon film having a thickness of 25 μm, an aluminum alloy foil having a thickness of 40 μm (JIS H 4160 A8079 material), and a linear low-density polyethylene (sealant film) having a thickness of 30 μm in this order via a urethane-based adhesive. A laminated exterior film was laminated and adhered. The laminate outer film is cut out to an outer dimension of 170 mm × 130 mm and subjected to overhanging processing or deep drawing processing from the sealant film side, so that the length is 55 mm, the width is 34 mm, and the depth is 3.4 mm. A concave portion (battery convex portion) 21 was formed. On the periphery of the recess 21 are three peripheral portions (22a), (22b), (22c) having a width of 5 mm extending in a horizontal direction from the ridge portion, and one flat portion (22d) having a width of 60 mm. A laminate exterior material 20 was cut and formed.
[0035]
<Preparation of non-aqueous electrolyte>
Ethylene carbonate (EC) and γ-butyrolactone (GBL) are mixed at a volume ratio of 1: 2, and lithium tetrafluoroborate (LiBF) as an electrolyte in a non-aqueous solvent. 4 ) Was dissolved to a concentration of 1.5 mol / L to prepare a liquid non-aqueous electrolyte.
[0036]
<Production of thin battery>
As shown in FIGS. 1 to 4, the power generation element 10 is housed in the concave portion 21 of the laminate exterior member 20, and the external lead terminals 14 and 15 are exposed to the outside through a peripheral portion 22 a having a width of 5 mm of the laminate exterior member 20. Extended. A flat surface portion 22d having a width of 60 mm opposite to the peripheral edge portion 22a from which the positive and negative external lead terminals 14 and 15 are extended is folded back 180 ° from the folded portion 23, and the positive and negative external lead terminals 14 and 15 are extended. It overlapped with the peripheral portion 22a on the protruding side. The positive and negative external lead terminals 14 and 15 are extended to the outside of the battery, and the peripheral portion 22a to be sealed is bonded to the positive and negative external lead terminals 14 and 15 at the time of heat sealing to form a gap in the vicinity. In addition, an insulating film 16 for preventing a short circuit between the barrier member 20b made of an aluminum alloy foil and the external lead terminals 14 and 15 of the positive electrode and the negative electrode, which are exposed at the end of the laminate outer material 20, is disposed.
[0037]
The insulating film 16 is formed to have a size larger than the width of the external lead terminals 14 and 15 of the positive electrode and the negative electrode and wider than the hermetic insulating sealing width, and extends 1 mm from the end of the laminate outer packaging material 20. It arrange | positioned on both surfaces by the side of the plane part 22d turned back 180 degrees from the peripheral part 22a and the turned-up part 23 to be sealed. The extended portion 22a of the external lead terminal having such a configuration overlaps with the flat portion 22d (hereinafter referred to as “terrace”) that is folded back by 180 ° while sandwiching the positive and negative external lead terminals 14 and 15 therebetween. The shape-like top seal portion 24 ") was hermetically insulated and sealed by heat sealing with a width of 4 mm.
[0038]
The extension amount of the external lead terminals 14 and 15 of the positive electrode and the negative electrode is 8 mm from the end of the terrace top seal. Next, the peripheral portion 22b or 22C having a width of 5 mm, which is arranged in a direction perpendicular to the terrace-shaped top seal portion 24, is hermetically sealed by thermal fusion, and a side seal portion 25a is formed to form a single hermetic insulating seal. Part, one hermetic sealing part, one folding part 23, and one opened peripheral part.
[0039]
Subsequently, the non-aqueous electrolyte (not shown) is injected into the concave portion 21 of the laminate exterior material 20 through one peripheral edge portion that is open, and the non-aqueous electrolysis is applied to the power generation element 10 housed inside. A liquid (not shown) was impregnated. Subsequently, the peripheral edge of the opening of the laminate exterior material 20 was hermetically sealed by heat sealing to form another side seal portion 25b. Subsequently, the two side seal portions 25a and 25b are cut leaving a width of 3 mm, and a laminated exterior thin lithium ion secondary having a terrace-like top seal portion width (W24) of 5 mm and a side seal portion width (W25) of 3 mm. A battery was obtained.
[0040]
<Processing of hermetic insulating sealing part and hermetic sealing part>
If the thin secondary battery produced in this way remains in this form, the three sealing portions extending outward from the battery will reduce the volume efficiency of the battery. Therefore, as shown in FIG. 4, in the thin secondary battery, the positive and negative external lead terminals 14 and 15 extending from the terrace-shaped top seal portion 24 are extended from the end portion of the laminate exterior material 20. Together with the insulating film 16, the terrace-shaped top seal portion 24 was folded back toward the flat surface portion 22 d. Next, a recess (containing the power generation element) is stored 3 mm from the upper end of the terrace-shaped top seal portion 24 hermetically insulated and sealed in parallel with the longitudinal direction of the insulating hermetic seal portion. (Battery convex part) 21 was bent to the airtight insulating sealing bent part 26.
[0041]
Note that the width of the flat portion from the end of the recess 21 to the hermetic insulating sealed bent portion 26 is set to 1.5 mm or more, preferably 2 mm or more from the viewpoint of improving the sealing function and bending workability. It is preferable to do.
[0042]
By folding the both ends of the terrace-shaped top seal portion 24 and the side seal portions 25a and 25b toward the battery convex portion side, a laminated exterior thin lithium ion having an outer dimension of 35.0 mm × 58.0 mm × 3.8 mm and a discharge capacity of 770 mAh. A secondary battery was produced.
[0043]
[Example 2]
A thin secondary battery according to Example 2 was prepared by changing the following configuration among the configurations of the thin secondary battery described in Example 1. That is, as shown in FIG. 5a, a notch 27 is provided at the corner of the sealing region where the terrace-shaped top seal portion 24 and the side seal portions 25a and 25b intersect. The notch 27 has a width (W24) of the hermetic insulating sealing part (terrace top seal part) 24 and an hermetic sealing part (side seal part) between the notch and the corner of the power generation element 10. It was formed so that the sealing portion was left with a width (W27) equal to or larger than any one of the widths (W25). Specifically, the width (W27) of the remaining sealing portion was 3 mm, and the cutout portion 27 was formed by cutting out from the end portion of the top seal portion 24 at an inclination angle of 70 degrees.
[0044]
In Example 2 described above, the cutout shape of the corner is notched linearly as shown in FIG. 5 a, but the terrace-shaped top seal portion is provided between the cutout and the corner of the power generation element 10. As long as a sealing width (W27) equal to or greater than the smaller one of the width (W24) and the side seal width (W25) can be secured, the notch angle and shape may be different from those of the second embodiment. There is no particular limitation. Specifically, as shown in FIG. 5b, a linear notch 27 having a notch angle of 45 degrees may be used. Further, as shown in FIG. 5c, a cutout portion 27 formed by cutting in a curved shape may be used. Further, as shown in FIG. 5d, a cutout portion 27 formed by cutting into a rectangular shape may be used.
[0045]
The processing and processing after forming the cutout portion 27 are the same as the processing contents of the hermetic insulating sealing portion and the hermetic sealing portion described in the first embodiment, so that the outer dimensions are 35.0 mm × 58. A laminate-packaged thin lithium ion secondary battery according to Example 2 having a size of 0 mm × 3.8 mm and a discharge capacity of 770 mAh was produced.
[0046]
According to the laminated exterior thin lithium ion secondary battery according to Example 2, the notch 27 is provided at the corner of the sealing portion region where the terrace-like top seal portion 24 and the side seal portions 25a and 25b intersect. Therefore, the intersection of the both ends of the terrace-like top seal portion 24 and the side seal portions 25a and 25b does not protrude in the thickness direction of the battery, and the bending process can be easily performed.
[0047]
[Comparative Example 1]
A thin secondary battery according to Comparative Example 1 was prepared by changing the following configuration among the configurations of the thin secondary battery described in Example 1. That is, as shown in FIG. 1, the processing of the hermetic insulating sealing portion and the hermetic sealing portion is only to bend the side seal portions 25a and 25b to the battery convex portion side, while the terrace-shaped top seal portion (24) is By not performing the bending process, a laminated exterior thin lithium ion secondary battery according to Comparative Example 1 having an outer dimension of 35 mm × 60.5 mm × 3.8 mm and a discharge capacity of 770 mAh was produced.
[0048]
[Comparative Example 2]
A thin secondary battery according to Comparative Example 2 was prepared by changing the following configuration among the configurations of the thin secondary battery described in Comparative Example 1. That is, the peripheral part extending to the peripheral edge of the concave portion 21 of the laminate exterior material is composed of one peripheral part 22a having a width of 3 mm, two peripheral parts 22b and 22c having a width of 5 mm, and one part having a width of 58 mm. It was cut and formed as the peripheral portion 22d. The top seal portion 24 of this laminate exterior material was heat-sealed with a width of 2 mm. As shown in FIG. 7, two side seal portions 25a and 25b arranged in a direction perpendicular to the terrace-shaped top seal portion 24 are cut leaving a width of 3 mm, and the width (W24) of the terrace-shaped top seal portion is set to 3 mm. The width (W25) of the side seal part was 3 mm. Subsequently, as shown in FIG. 1, the side seal portions 25a and 25b are bent toward the battery convex portion, so that the outer dimensions are 35.0 mm × 58.0 mm × 3.8 mm, and the discharge capacity is 770 mAh. A laminated exterior thin lithium ion secondary battery according to the present invention was produced.
[0049]
[Comparative Example 3]
A thin secondary battery according to Comparative Example 3 was prepared by changing the following configuration among the configurations of the thin secondary battery described in Example 1. That is, as shown in FIG. 8, the terrace-shaped top seal portion that is hermetically insulated and sealed is folded from the root of the battery convex portion 21 toward the battery convex portion 21 side of the laminate exterior member 20 in parallel with the longitudinal direction of the insulating hermetic sealed portion. It was made to bend and the sealing root bending part 28 was formed. Subsequently, both ends of the terrace-like top seal portion 24 and the side seal portions 25a and 25b were bent to the battery convex portion side. At this time, the intersections between the both ends of the terrace-like top seal portion 24 and the side seal portions 25a and 25b project in a square shape by bi-directional bending, so that the projecting portion is again folded to the top seal portion side. Thus, a laminate-coated thin lithium ion secondary battery according to Comparative Example 3 having an outer dimension of 35.0 mm × 56.5 mm × 4.5 mm and a discharge capacity of 770 mAh was produced.
[0050]
In the thin secondary battery according to the comparative example 3, the reason why the battery thickness is larger than that of the example is as follows. That is, since the width (W24) of the terrace-shaped top seal portion is 5 mm, the terrace-shaped top seal portion bent from the base protrudes in the battery thickness direction from the battery convex portion.
[0051]
[Comparative Example 4]
A thin secondary battery according to Comparative Example 4 was prepared by changing the following configuration among the configurations of the thin secondary battery described in Comparative Example 3. That is, as shown in FIG. 9, the peripheral portion extending to the peripheral edge of the concave portion 21 of the laminate exterior material is the same peripheral portion (22a) having a width of 3 mm as in Comparative Example 2, and the width is 5 mm. Two peripheral edges 22b and 22c and one peripheral edge 22d having a width of 58 mm were cut and formed. Subsequent processing and processing are the same as the processing contents of the hermetic insulating sealing portion and the hermetic sealing portion performed in Comparative Example 3, so that the outer dimensions are 35.0 mm × 56.5 mm × 3.8 mm. A laminate-packaged thin lithium ion secondary battery according to Comparative Example 4 having a discharge capacity of 770 mAh was produced.
[0052]
[Comparative Example 5]
A thin secondary battery according to Comparative Example 5 was prepared by changing the following configuration among the configurations of the thin secondary battery described in Comparative Example 3. That is, as shown in FIG. 10, the terrace-shaped top seal portion hermetically insulated and sealed is parallel to the longitudinal direction of the insulating hermetic sealing portion from the root and parallel to the longitudinal direction of the insulating hermetic sealing portion from the root of the battery protrusion 21. Were folded at a folding angle of 180 degrees along the plane side facing the battery convex portion 21 of the laminate outer packaging material 20 to form a sealing root bent portion 28. The external lead terminals 14 and 15 of the positive electrode and the negative electrode were folded back together with the insulating film 16 extending from the end portion of the laminate outer packaging material 20 toward the sealing root bent portion. Subsequently, by bending the both ends of the terrace-shaped top seal portion 24 and the side seal portions 25a and 25b to the battery convex portion side, the outer dimensions are 36.0 mm × 55.5 mm × 4.5 mm, and the discharge capacity is A laminate-packaged thin lithium ion secondary battery according to Comparative Example 5 having 770 mAh was produced.
[0053]
In the thin secondary battery according to the comparative example 5, the reason why the battery thickness and the battery width are larger than those of the example is as follows. That is, as a result of the terrace-shaped top seal portion being bent along the flat surface facing the battery convex portion, the thickness of the terrace-shaped top seal portion is added to the thickness of the battery convex portion. The volume loss in the vertical direction increases, and the loss in the width direction also increases due to the presence of a portion where the side seal portion is bent and overlapped with the terrace-shaped top seal portion (intersection region of both seal portions). Because.
[0054]
Comparative parameters of each laminated exterior thin lithium ion secondary battery according to Examples 1 and 2 and Comparative Examples 1 to 5 prepared as described above (airtight insulating sealing width, bending position, bending direction, corner notch) The presence or absence) is summarized in Table 1 below.
[0055]
[Table 1]
[0056]
In order to evaluate each laminate-sheathed thin lithium ion secondary battery according to Examples 1-2 and Comparative Examples 1-5, a comparative survey was performed on the following characteristic items.
[0057]
<Comparison of moisture permeation from the sealing part>
Sampling each of three laminated exterior thin lithium ion secondary batteries according to Examples 1 and 2 and Comparative Examples 1 to 5, the temperature is 65 ° C. in an uncharged state, and the relative humidity RH is 90%. It was left in the adjusted environment for 30 days. Thereafter, 0.5 cc of the non-aqueous electrolyte was extracted from the battery with a microsyringe, and the water content in the non-aqueous electrolyte was measured with a Karl Fischer water content measuring device. The water permeation amount of each battery was calculated as a relative value with the water permeation amount of the secondary battery according to Comparative Example 1 as a reference value (100%). Table 2 shows the measurement calculation results.
[0058]
<Comparison of internal short circuit occurrence due to external force>
For each of the 10 laminated outer thin lithium ion secondary batteries according to Examples 1-2 and Comparative Examples 1-5, constant current / constant voltage charging was performed at room temperature up to 4.2 V at 1C. Then, it discharged to 3.0V at 1C at room temperature, measured the reference discharge capacity, and further carried out constant current / constant voltage charging to 1.85V at 1C at room temperature. Each laminated outer thin lithium-ion secondary battery in this state was mounted on a dummy pack case, and it was carried out under severe conditions such as allowing it to fall naturally from a height of 1.5 m onto a wood surface of a firewood.
[0059]
The direction in which each secondary battery is dropped is a drop that takes the vertical orientation of the battery so that a drop impact in the tension / compression direction is applied to the external lead terminal, terrace-shaped top seal part, and hermetic insulation sealing bent part. The repetition of dropping with the up and down direction reversed was carried out up to 100 cycles. Whether or not an internal short circuit occurred every 10 cycles was confirmed by measuring the voltage of the external lead terminal from the terminal hole provided in the dummy pack. The number of occurrences of internal short circuit and the number of occurrences after the drop test were measured, and the number of occurrences of internal short circuit and the number of occurrences of the secondary battery of Comparative Example 1 were calculated as relative values using the reference value (100%). Table 2 shows the measurement calculation results.
[0060]
<Comparison of battery dimensions (volumetric efficiency)>
For each laminated exterior thin lithium ion secondary battery according to Examples 1-2 and Comparative Examples 1-5, the battery volume is calculated from the dimensions of battery height, battery width, and battery thickness, and the discharge of each battery is calculated. The volume capacity density was calculated from the capacity and compared. The volume capacity density of each secondary battery was calculated as a relative value using the volume capacity density of the secondary battery according to Comparative Example 1 as a reference value (100%). The measurement calculation results are summarized in Table 2 below.
[0061]
[Table 2]
[0062]
As is clear from the results shown in Tables 1 and 2 above, Examples 1 to 2 in which the external lead terminal extension portion was bent in the airtight insulating sealing region in parallel with the longitudinal direction of the airtight insulating sealing portion. In the secondary battery according to the invention, since the occupied volume of the hermetic insulating sealing portion in the battery is reduced, the volume capacity density is increased, and the volume efficiency of the secondary battery can be improved.
[0063]
In addition, since the external lead terminal extension is bent in the hermetic insulation sealing region, there is no possibility that the external lead terminal located inside the battery contacts the laminate exterior material, and the barrier material for the laminate exterior material A secondary battery with high reliability was obtained because there was little risk of reaching an internal short circuit and causing an internal short circuit.
[0064]
In addition, since the sealing part can be formed with a wide width including the bent part, the sealing function is sufficiently ensured, the moisture permeation amount does not increase, and the intrusion of moisture from the hermetic insulating sealing part is effective. Thus, a secondary battery having high reliability and little deterioration in battery characteristics was obtained.
[0065]
Furthermore, in the battery according to Example 2 in which the cutout portion 27 is formed by cutting out the corner portion of the laminate outer covering material where the hermetic insulating sealing portion and the other hermetic sealing portion intersect, this laminate outer covering is formed. Even when the peripheral part of the material was folded in the thickness direction of the battery, the bent piece did not protrude in the height direction of the battery, and the adverse effect of increasing the battery component volume in the thickness direction could be avoided. .
[0066]
Moreover, when forming the said notch part 27, between this notch part 27 and the corner | angular part of the electric power generation element 10, the width | variety (W-24) of an airtight insulation sealing part and the width | variety (W of an airtight sealing part) −25) By forming the cutout portion so as to leave the sealing portion with a width equal to or smaller than any one of the smaller widths, it is possible to secure a sufficient sealing width and effectively prevent moisture from entering through the cutout portion 27. Thus, a secondary battery having high reliability and little deterioration in battery characteristics can be obtained.
[0067]
On the other hand, in the secondary battery according to Comparative Example 1 in which the external lead terminal extension portion was not bent, the volume loss at the terminal end portion was large. Further, in the secondary battery according to Comparative Example 2 in which the width of the hermetic insulating sealing portion was reduced, the volume capacity density was increased, but the effect of suppressing moisture penetration was insufficient. Further, in the secondary battery in which the external lead terminal extension portion is bent at the sealing root outside the hermetic insulating sealing region as in Comparative Example 3, the terminal material is pulled in the direction of the bending portion, and the internal short circuit is caused. The volume capacity density decreased because the bent portion protruded in the thickness direction of the battery.
[0068]
Further, as in Comparative Example 4, in the secondary battery in which the width of the hermetic insulating sealing portion is reduced while the external lead terminal extension portion is bent at the root of the sealing portion, the volume capacity density increases. In addition, the sealing function is insufficient, and the effect of preventing moisture penetration is insufficient. In addition, since the external lead terminal extension portion is bent at the sealing root that is outside the hermetic insulating sealing region, the terminal material is pulled in the direction of the bent portion, thereby increasing the incidence of internal short circuit. Further, as in Comparative Example 5, the external lead terminal extension is bent to the back side at the sealing base outside the hermetic insulating sealing region, so that the terminal material is pulled in the direction of the bent portion, causing an internal short circuit. The incidence of has increased. Furthermore, since the thickness of the bent portion bent to the back side is added to the battery thickness and becomes the thickness of the entire battery, the volume efficiency is greatly deteriorated.
[0069]
【The invention's effect】
As described above in detail, according to the thin secondary battery according to the present invention, the laminate outer packaging material for housing the power generation element and the external lead terminal extending portions of the positive and negative electrodes sealed in an airtight insulating manner are connected to the laminated outer packaging material. By making the structure bent in parallel with the longitudinal direction of the hermetic insulating sealing part in the hermetic insulating sealing region, a sufficient width of the hermetic insulating sealing can be secured, and moisture intrusion from the sealing part is suppressed. In addition, since the bent portion is in the hermetic insulating sealing region, internal short circuit between the positive and negative electrode external lead terminals of the bent portion and the laminate exterior material is prevented, and the volume occupied by the sealing portion is made as small as possible. A thin secondary battery in which the volumetric energy density of the battery is increased can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view of a thin secondary battery according to the present invention.
FIG. 2 is an exploded perspective view of a thin secondary battery according to the present invention.
FIG. 3 is a plan view showing an insulating hermetic sealing region and a hermetic sealing region of a thin secondary battery according to the present invention.
FIG. 4 is a partial cross-sectional view schematically showing a bent portion of an airtight insulating sealing portion of a thin secondary battery according to the present invention.
FIG. 5 is a plan view showing a shape of a notch formed at a corner portion that is an intersection of an insulating hermetic sealing portion and an hermetic sealing portion of a thin secondary battery according to the present invention, FIG. The top view which shows the notch part (cutting angle: 70 degree | times) formed in the secondary battery which concerns on Example 2, (b) is a top view which shows the shape of the notch part formed by notching with the cutting angle of 45 degree | times, (C) is a plan view showing the shape of a cutout portion formed by cutting the sealing portion into a curved shape, and (d) is a plane showing the shape of the cutout portion formed by cutting the sealing portion into a rectangular shape. Figure.
6 is a partial cross-sectional view schematically showing an airtight insulating sealing portion of a thin secondary battery according to Comparative Example 1. FIG.
7 is a partial cross-sectional view schematically showing an airtight insulating sealing portion of a thin secondary battery according to Comparative Example 2. FIG.
8 is a partial cross-sectional view schematically showing an airtight insulating sealing portion of a thin secondary battery according to Comparative Example 3. FIG.
9 is a partial cross-sectional view schematically showing an airtight insulating sealing portion of a thin secondary battery according to Comparative Example 4. FIG.
10 is a partial cross-sectional view schematically showing an airtight insulating sealing portion of a thin secondary battery according to Comparative Example 5. FIG.
FIG. 11 is a perspective view showing a configuration of a conventional thin secondary battery.
FIG. 12 is an exploded perspective view showing a structure of a conventional thin secondary battery.
FIG. 13 is a partial cross-sectional view schematically showing a hermetic insulating sealing part of a conventional thin secondary battery.
FIG. 14 is a perspective view showing a joined state of an external lead terminal, an electronic circuit, and a terminal block.
FIG. 15 is a perspective view showing a bent state of an external lead terminal.
FIG. 16 is an exploded perspective view showing the configuration of the battery pack.
FIG. 17 is a perspective view showing an assembled state of the battery pack.
[Explanation of symbols]
10 Power generation elements
11 Positive electrode
11a Cathode active material
11b Positive electrode current collector
11c Positive electrode uncoated part
12 Negative electrode
12a Negative electrode active material
12b Negative electrode current collector
12c Negative electrode uncoated part
13 Separator
14 Positive external lead terminal
15 Negative external lead terminal
16 Insulating film
20 Laminate exterior material
20a Surface side resin film
20b Barrier material