JP4380970B2

JP4380970B2 - Thin sealed battery and manufacturing method thereof

Info

Publication number: JP4380970B2
Application number: JP2002248391A
Authority: JP
Inventors: 康伸児玉; 和博奥田
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 2002-08-28
Filing date: 2002-08-28
Publication date: 2009-12-09
Anticipated expiration: 2022-08-28
Also published as: JP2004087364A

Description

【０００１】
【発明の属する技術分野】
本発明は、薄型密閉電池の改良に関し、より詳しくは、薄型密閉電池の体積エネルギー密度の向上と密閉性の向上に関する。
【０００２】
【従来の技術】
電池の外装体としては、従来、ステンレス等の硬い金属から成るものが用いられていた。しかし、このような外装体は強度に優れているものの、電池の薄型化を図りにくい。このため、薄く柔軟なラミネートフィルムで外装体を構成し、これを使用することにより、電池の薄型化を図る技術が開発されている。この技術を適用した薄型密閉電池は、図３に示すように、アルミニウムから成る金属層１１の両面に接着剤層１２を介してポリオレフィン製の樹脂層１３が形成してなるアルミラミネートフィルム同士を熱融着して袋状のアルミラミネートフィルム外装体となし、このアルミラミネートフィルム外装体の収納空間に、図４に示すような、正極と負極とセパレータ（図４においては図示せず）とを有する電極体を収納するとともに、封止部から正負両集電タブを取り出す構造である。このような構造の電池であれば、電池の一層の小型化を実現でき、しかも電池の体積エネルギー密度をも向上させることができる。
【０００３】
しかし、ラミネートフィルム外装体を用いた電池において、図４に示すような電極体を形成するためには、まず円形に巻回した電極体をプレスする必要がある。そして、正負両極に取り付けられた正負両集電タブには、角張った部分（バリ）が存在しており、電極体をプレスした際に、このバリによって、セパレータを突き破り他極と接触してショートが発生する。そこで、このようなショートを防止するため、上記バリ部分に保護テープ等の保護部材を配置することが行われている。
【０００４】
他方、ラミネートフィルム外装体は、ラミネートフィルムの内側の樹脂層同士を加圧溶着して封止されるが、ラミネートフィルム同士の接合の場合には、樹脂層と樹脂層とが向き合っており、それぞれの金属層同士は二枚分の樹脂層で十分に離間されている。しかし、集電タブが突出した封止部（タブ突出封止部）では、金属層が一枚分の樹脂層を介して集電タブと向き合っており、しかも加圧溶着によりこの樹脂層が薄くなっている。このため、ラミネートフィルムの金属層と集電タブとがショートし易い。
【０００５】
そこで、特開２０００−１７３５６２号公報では、図１１に示すように電極タブの形状に対応させた凹部を有する金型を用いることにより集電タブ部分に過度な圧力が加わって樹脂層が薄くなるのを防止しつつ、タブ突出封止部を封止する技術が提案されている。
【０００６】
しかし、最近では体積エネルギー密度を更に高めるために、電極体とタブ突出封止部との距離を短くすることが行われており、この場合には上記技術によっても十分にショートを防げない。この理由は、電極体とタブ突出封止部との距離を短くすると、タブ突出封止部に保護テープがかみ込まれて、当該部分の厚みが厚くなり、その結果、加圧溶着後の樹脂層（絶縁層）の厚みが薄くなるためである。他方、保護テープのかみ込みを避けるため、封止部の幅を狭くすると、封止部の幅が狭くなる分、密閉性が不十分になるという問題がある。
【０００７】
【発明が解決しようとする課題】
本発明は上記に鑑みなされたものであり、その目的は、体積エネルギー密度が高く、密閉性に優れ、且つ内部短絡の生じない安全な電池を提供することにある。
【０００８】
【課題を解決するための手段】
上記課題を解決するため、請求項１記載の発明は、次のように構成されている。集電タブを備えた正極と集電タブを備えた負極とを有する電極体が、金属と樹脂とが積層されたフィルムからなる外装体に収納された薄型密閉電池において、前記外装体は、正負集電タブの先端側が外装体外に突出したタブ突出封止部を有し、前記集電タブの前記正負極と重なる部分には保護部材が配置されており、前記タブ突出封止部は、集電タブの電極体近傍領域である第一領域（４１）と、前記第一領域以外で且つ保護部材が配置されていない集電タブ部分を含んだ状態で封止された第二領域（４２）と、他部材を含むことなく前記フィルム同士のみで封止された第三領域（４３）とを有し、前記第一領域（４１）における外装体全厚は、前記第二領域（４２）における外装体全厚、及び前記第三領域（４３）における外装体全厚のいずれよりも厚く、前記第一領域（４１）における前記フィルムの実厚は、前記第二領域（４２）におけるフィルムの実厚よりも厚いことを特徴とする。
【０００９】
ここで、上記構成における集電タブの電極体近傍領域とは、図４に示す電極体の図において、電極体から突出した集電タブと電極体との境界部近傍のことを指す。また、外装体全厚とは外装体、電極タブ、保護部材等全てを含んだ全体としての厚みであり、フィルムの実厚とはその場所におけるフィルム単体の厚みのことである。また、他部材とは、集電タブ、保護部材等のことを意味する。
【００１０】
この構成においては、タブ突出封止部の集電タブ部分の電極体近傍領域には第一領域（４１）が形成されており、第一領域（４１）における外装体全厚が、前記第二領域（４２）における外装体全厚、及び前記第三領域（４３）における外装体全厚のいずれよりも厚く、第一領域（４１）における前記フィルムの実厚が、前記第二領域（４２）におけるフィルムの実厚よりも厚く形成されている。したがって、この第一領域（４１）に保護部材が配置されている場合においても、内部圧力が過大にならないので、ラミネートフィルムの樹脂層が圧力で破損し金属層が露出するといったことがない。この結果、電極体近傍領域における内部短絡が防止できる。
また、上記構成においては、電極と重なる集電タブ部分に保護部材が配置されており、この保護部材が、集電タブのエッジによるセパレータの破損を防止するように作用する。よって、上記構成であると、安全性、信頼性に優れた薄型密閉型電池が提供できる。
【００１１】
請求項２記載の発明は、次のように構成されている。集電タブを備えた正極と集電タブを備えた負極とを有する電極体が、金属と樹脂とが積層されたフィルムからなる外装体に収納された薄型密閉電池の製造方法において、前記製造方法は、前記集電タブの正負極と重なる部分に保護部材を配置する保護部材配置工程と、前記保護部材配置工程の後、少なくとも正負極を有してなる電極体を作製する電極体作製工程と、前記電極体を、開口を有する外装体内に、正負集電タブの先端側を外装体外に突出した状態で収納する電極体収納工程と、前記電極体収納工程の後、前記開口を加圧して、タブ突出封止部を形成する加圧工程と、を有し、前記加圧工程が、集電タブの電極体近傍領域である第一領域（４１）と、前記第一領域以外で且つ保護部材が配置されていない集電タブ部分を含んだ状態で封止される第二領域（４２）と、他部材を含むことなく前記フィルム同士のみで封止される第三領域（４３）と、を下記数２の条件で同時または順次加圧することにより形成する工程である、ことを特徴とする。
【００１２】
【数２】

【００１３】
上記の構成では、第一領域への加圧力を第二、第三の領域よりも小さくするので、内部短絡が生じやすい第一領域における樹脂層厚みが適正に保たれ、集電タブと、フィルム状外装体の金属層との短絡を防止することができる。また、電極体とタブ突出封止部の距離が短い場合においても封止性を損なうことなく、内部短絡を防止することができる。
【００１４】
また、前記加圧工程における加圧方法が、前記第三領域（４３）を加圧するための平坦部と、前記第一領域（４１）の形状に対応させた、第一領域（４１）を加圧するための第一凹部と、前記第二領域（４２）の形状に対応させた、第二領域（４２）を加圧するための第二凹部と、を有する加圧部材を用いて同時に加圧封止する方法である、とすることができる。
【００１５】
上記のような加圧部材を用いると、一度の加圧操作で上記数２を満たした条件でタブ突出封止部を封止することができるので、生産効率が高い。したがってこの構成によると、安全性、保存性に優れた薄型密閉電池を作製することができる。
【００１６】
【発明の実施の形態】
本発明の内容を説明すると共に、好ましい実施の形態を記述する。
【００１７】
図１はラミネートフィルム外装体を用いた本発明の実施の形態に係る薄型密閉電池の正面図、図２は図１のＡ−Ａ線矢視断面図、図３は薄型密閉電池に用いるラミネート外装体の断面図、図４は薄型密閉電池に用いる電極体の斜視図である。尚、同一の効果が得られる部材には、同一の符号を付している。
【００１８】
図２に示すように、本発明による薄型密閉電池は電極体１を有しており、この電極体１は収納空間２内に配置されている。この収納空間２は、図１に示すように、ラミネート外装体３の上下端と中央部とをそれぞれ封止部４ａ・４ｂ・４ｃで封口することにより形成される。また、収納空間２には、非水溶媒に、電解質塩としてＬｉＰＦ₆が１Ｍ（モル／リットル）の割合で溶解された電解液が注入されている。
【００１９】
上記薄型密閉電池は、前記封止部４ａにおいて、集電タブの電極体近傍領域である第一領域４１と、前記第一領域以外で且つ保護部材が配置されていない集電タブ部分を含んだ状態で封止された第二領域４２と、他部材を挟むことなくフィルム同士のみで封止された第三領域４３とを有し、前記第一領域４１における外装体全厚は、前記第二領域４２における外装体全厚、及び前記第三領域４３における外装体全厚のいずれよりも厚く、前記第一領域４１における前記フィルムの実厚は、前記第二領域４２における前記フィルムの実厚よりも厚く構成されている。
【００２０】
また、図１に示す前記第一領域の幅Ｌ１と、タブ突出封止部の幅Ｌとの比Ｌ１／Ｌは、０．０１以上０．７以下であることが好ましい。前記比Ｌ１／Ｌが０．７より大きいと、第一領域は他の領域と比べフィルムの樹脂層の実厚が厚いため十分に封止されておらず、電池の密閉性の低下を招く一方、０．０１より小さいと前記第二領域には保護部材が配置されてしまう可能性があり、内部短絡の危険性が生じる。また、前記比Ｌ１／Ｌが０．０５以上０．５以下であることがさらに好ましい。
【００２１】
また、図４に示すように、上記電極体１は、正極５と、負極６と、これら両電極を離間するセパレータ（図４においては図示せず）とを偏平渦巻状に巻回することにより作製される。前記セパレータは、有機溶媒との反応性が低く、安価なオレフィン系樹脂からなる微多孔膜（厚み：０．０２５ｍｍ）が用いられている。
【００２２】
更に、上記正極５はアルミニウムから成る正極タブ７に、また上記負極６はニッケルから成る負極タブ８にそれぞれ接続され、電池内部で生じた化学エネルギーを電気エネルギーとして外部へ取り出し得るようになっている。また、図４には示していないが、それぞれの集電タブと正負極と重なる部分には、ポリフェニレンサルファイド製の保護テープが貼り付けられている。
【００２３】
尚、図３に示すように、上記ラミネート外装体３の具体的な構造は、アルミニウム層１１（厚み：３０μｍ）の両面に、各々、変性ポリプロピレンから成る接着剤層１２・１２（厚み：５μｍ）を介してポリプロピレンから成る樹脂層１３・１３（厚み：３０μｍ）が接着される構造である。但し、接着剤層は図５、図９では図示していない。
【００２４】
正極材料としては、例えばリチウム含有遷移金属複合酸化物が単独で、あるいは二種以上混合して用いられる。具体例として、コバルト酸リチウム、ニッケル酸リチウム、マンガン酸リチウム、鉄酸リチウム、またはこれらの酸化物に含まれる遷移金属の一部を他の元素で置換した酸化物等が用いられる。
【００２５】
負極材料としては、例えば天然黒鉛、カーボンブラック、コークス、ガラス状炭素、炭素繊維、あるいはこれらの焼成体等の炭素質物、または該炭素質物と、リチウム、リチウム合金、およびリチウムを吸蔵・放出できる金属酸化物からなる群から選ばれる１種以上との混合物が用いられる。
【００２６】
また、電解液に用いる非水溶媒としては、例えばエチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、γ−ブチロラクトン等のリチウム塩の溶解度が高い高誘電率溶媒と、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネート、１，２−ジメトキシエタン、テトラヒドロフラン、アニソール、１，４−ジオキサン、４−メチル−２−ペンタノン、シクロヘキサノン、アセトニトリル、プロピオニトリル、ジメチルホルムアミド、スルホラン、蟻酸メチル、蟻酸エチル、酢酸メチル、酢酸エチル、酢酸プロピル、プロピオン酸エチル等の低粘性溶媒とを混合して用いられる。尚、高誘電率溶媒、低粘性溶媒が、それぞれ二種以上の混合溶媒であってもよい。
【００２７】
また、電解質塩としては、例えばＬｉＮ（Ｃ₂Ｆ₅ＳＯ₂）₂、ＬｉＮ（ＣＦ₃ＳＯ₂）₂、ＬｉＣｌＯ₄、ＬｉＰＦ₆、ＬｉＢＦ₄等が単独で、あるいは２種以上混合して用いられる。また、前記非水溶媒に対する溶解量としては、例えば０．５〜２．０モル／リットルとする。
【００２８】
（実施例１）
本発明に係る薄型密閉電池を以下のようにして作製した。
コバルト酸リチウム（ＬｉＣｏＯ₂）からなる正極活物質と、アセチレンブラックからなる炭素系導電剤と、ポリビニリデンフルオライド（ＰＶｄＦ）からなる結着剤と、Ｎ−メチル−２−ピロリドン（ＮＭＰ）とを混合して活物質スラリーとした。
【００２９】
この活物質スラリーを、ドクターブレードにより厚み２０μｍのアルミニウム箔からなる正極芯体の両面に均一に塗布した後、乾燥機中を通過させて乾燥することにより、スラリー作製時に必要であった有機溶媒を除去した。次いで、この極板を厚みが０．１７ｍｍになるようにロールプレス機により圧延して正極５を作製した。
【００３０】
黒鉛からなる負極活物質９５質量部と、ポリビニリデンフルオライド（ＰＶｄＦ）からなる結着剤５質量部と、Ｎ−メチル−２−ピロリドン（ＮＭＰ）とを混合して活物質スラリーとした。この活物質スラリーを、ドクターブレードにより厚み２０μｍの銅箔からなる負極芯体の両面に均一に塗布した後、乾燥機中を通過させて乾燥することにより、スラリー作製時に必要であった有機溶媒を除去した。次いで、この極板を厚みが０．１４ｍｍになるようにロールプレス機により圧延して負極６を作製した。
【００３１】
上記のように作成した正極５と負極６に、それぞれ正極タブ７あるいは負極タブ８を取り付け、ポリフェニルサルファイド製の保護テープ９（図４では図示せず）を貼り付けた後、両極をオレフィン系樹脂からなる微多孔膜（厚み：０．０２５ｍｍ）からなるセパレータを間にし、かつ各極板の幅方向の中心線を一致させて重ね合わせた。この後、巻き取り機により巻回し、最外周をテープ止めすることにより偏平渦巻状電極体１を作製した。
【００３２】
樹脂層（ポリプロピレン）／接着剤層／アルミニウム合金層／接着剤層／樹脂層（ポリプロピレン）の５層構造から成るシート状のラミネート材を用意した後、アルミラミネート材における端部近傍同士の樹脂層を重ね合わせ、重ね合わせ部を溶着して封止部４ｃを形成した。次に、この筒状アルミラミネート材の収納空間２内に電極体１を挿入した。この際、筒状アルミラミネート材の一方の開口部から両集電タブ７，８が突出するように電極体１を配置した。
【００３３】
この後、両集電タブを変性ポリオレフィン製の樹脂からなるフィルム（図示せず）を介して外装体で狭持し、図７に示すように、ラミネートフィルム同士のみで封止される第三領域を加圧するための平坦部１４３と、集電タブの電極体近傍領域である第一領域の形状に対応させた第一凹部１４１と、前記第一領域以外且つ保護部材が配置されていない集電タブ部分を含んだ状態で封止された第二領域の形状に対応させた第二凹部１４２とを有する加圧部材を用いて上記開口部を加圧溶着して封止して、封止部４ａを形成した。
【００３４】
次に、エチレンカーボネートとジエチルカーボネートからなる混合溶媒に電解質塩としてＬｉＰＦ₆を１Ｍ（モル／リットル）となるように混合した電解液と、ポリエチレングリコールジアクリレートと、重合開始剤と、からなるプレゲルを、上記封止部とは反対側のアルミラミネート材の開口部から注入した後、前記開口部を機密に封口し、封止部４ｂを形成した。最後に、アルミラミネート外装体３を６０℃で３時間加熱して、アルミラミネート外装体内部のプレゲルをゲル化させ、実施例１に係る本発明電池Ａを作製した。尚、この電池のサイズは６０×６０×厚み３．８(ｍｍ)であった。
【００３５】
このようにして製造された電池は、集電タブの電極体近傍領域である第一領域に加えられる圧力は、前記第一領域以外で且つ保護部材が配置されていない集電タブ部分を含んだ状態で封止された第二領域に加えられる圧力よりも小さくなっており、図６に示すように、第一領域４１における外装体全厚は、第二領域４２における外装体全厚、及び第三領域４３における外装体全厚のいずれよりも厚くなっている。さらに、第一領域４１におけるラミネートフィルムの実厚は、前記第二領域４２におけるラミネートフィルムの実厚よりも厚くなっている。
【００３６】
（比較例１）
図１１に示すように、第三領域を加圧するための平坦部１４３と、集電タブの形状に対応させた凹部１４２のみを有する加圧部材を用いたこと以外は、上記実施例と同様にして、比較例１にかかる電池Ｘを作製した。このようにして製造された電池は、第一領域及び第二領域に加えられる圧力が等しいため、図８及び図１０に示すように外観からは第一領域の突出が見られない。
【００３７】
（比較例２）
比較例１の加圧部材よりも加圧面の幅が狭いこと以外は、上記比較例１と同様にして、比較例２にかかる電池Ｙを作製した。このようにして製造された電池は、第一領域には全く圧力が加えられないため、図１２、図１３に示すように比較電池Ｘよりも幅の狭い封止部となる。
【００３８】
尚、電池はそれぞれ５０個作製した。
【００３９】
〈ショートの検出〉
製造工程において、集電タブと外装体の金属層との導通を、テスターによって検出し、導通が確認されたものをショート発生としてカウントした。導通が確認された電池は、以下の試験には用いなかった。
【００４０】
〈封止性能試験〉
４０％充電された電池を、８０℃、湿度９０％の条件で３０日保存し、その電池厚みを計測した。ショートの発生と、封止性能試験結果を下記表１に示す。
【００４１】
【表１】

【００４２】
上記表１から、本発明電池Ａ１は、ショートが発生せず、保存後の電池膨れも比較電池Ｘとほぼ同じ程度と良好な封止性能が確認されたのに対し、比較電池Ｘではその２８％がショートし、また、比較電池Ｙでは保存後の電池厚みの増加量が、保存後の本発明電池Ａの電池厚みの増加量に比べ０．３８ｍｍ大きくなっていることがわかる。
【００４３】
ここで、比較電池Ｘでは、図１１に示すように、集電タブの形状に対応させた凹部１４２のみを有し、第一領域の形状に対応させた第一凹部を有さない加圧部材を用いているので、第一領域に加えられる圧力は第二領域と等しくなる。このため、図９に示すように封止部に保護テープがかみ込まれて、当該部分の樹脂層の厚みが薄くなり、集電タブとラミネート材の金属層とがショートし易くなる。
【００４４】
また、比較電池Ｙでは比較例１の加圧部材よりも幅が狭く、第一領域には全く圧力がかからない加圧部材を用いているので、封止部の幅が狭くなる。この結果、密閉性が低下して、この封止部から水分等が浸入しやすくなり、混入した水分により、保存後の電池厚みが大きくなる。
【００４５】
他方、本発明電池Ａでは、図７に示すように第一領域の形状に対応させた第一凹部１４１と、第二領域の形状に対応させた第２凹部１４２と、第三領域を加圧する平坦部１４３が形成された加圧部材を用いて加圧溶着しているので、第一領域に加えられる圧力が、第二領域に加えられる圧力よりも小さくなり、当該部分の樹脂層が非封止部分の厚みと同じ程度に保たれるため、ショートを防止することができ、しかも密閉性を低下させない。それゆえ、上記表１に示す結果になったものと考えられる。
【００４６】
尚、上記実施の形態では第一凹部、第二凹部の形状が、図７に示すようにそれぞれ直方体状に切り抜かれている金型からなる加圧部材を用いたが、本発明はこの形状に限定されるものではなく、本発明の要旨をそこなわない範囲において自由に変形が可能である。例えば、第一凹部、第二凹部の形状が円柱状、台形柱状、楕円体状等に切り抜かれた金型を用いても同様の効果が得られる。また、第一領域、第二領域の形状も、円柱状、台形柱状、楕円体状等であってもよい。
【００４７】
また、ラミネート外装体の樹脂層としては上記ポリプロピレンに限定されるものではなく、例えば、ポリエチレン等のポリオレフィン系高分子、ポリエチレンテレフタレート等のポリエステル系高分子、ポリフッ化ビニリデン、ポリ塩化ビニリデン等のポリビニリデン系高分子、ナイロン６、ナイロン６６、ナイロン７等のポリアミド系高分子等を使用できる。更に、ラミネート外装体の構造は、上記の５層構造に限定されるものではない。
【００４８】
また、上記実施の形態では、集電タブと外装体との接着性を高めるために、別部材としてのフィルムを用いたが、このようなフィルム等を用いなくてもよい。
【００４９】
また、上記実施例ではポリフェニルサルファイド製の保護テープを用いたが、これに限定されるものではなく、例えばポリオレフィン、ポリイミド等からなる保護部材であってもよい。
【００５０】
【発明の効果】
以上で説明したように、本発明では、集電タブの電極体近傍領域のフィルム状外装体の実厚を非封止部分の実厚とをほぼ等しくすることにより、タブ突出封止部と電極体との距離を小さくした電池においても、密閉性を損なうことなく集電タブとフィルムの金属層とのショートを防止し得た、安全性と保存性に優れた薄型密閉電池を安価に提供することができる。この電池はタブ突出封止部と電極体との幅を狭くできる点において、体積エネルギー密度にも優れる。
【図面の簡単な説明】
【図１】本発明に係る薄型密閉電池の正面図。
【図２】図１のＡ−Ａ線矢視断面図。
【図３】本発明に係る薄型密閉電池に用いるラミネート外装体の断面図。
【図４】本発明に係る薄型密閉電池に用いる集電タブが突出した電極体の斜視図。
【図５】図１のＢ−Ｂ線矢視断面概略図。
【図６】本発明に係る薄型密閉電池のタブ突出封止部の斜視図。
【図７】本発明に係る薄型密閉電池に用いられる金型の斜視図。
【図８】従来の技術による薄型密閉電池の正面図。
【図９】図８のＣ−Ｃ矢視断面概略図。
【図１０】従来の技術による薄型密閉電池のタブ突出封止部の斜視図。
【図１１】従来の技術による薄型密閉電池に用いられる金型の斜視図。
【図１２】従来の技術による他の形状の薄型密閉電池の正面図。
【図１３】従来の技術による他の形状の薄型密閉電池のタブ突出封止部の斜視図。
【符号の説明】
１電極体
２収納空間
３アルミラミネート外装体
４ａ、４ｂ、４ｃ封止部
４１第一領域
４２第二領域
４３第三領域
５正極
６負極
７正極タブ
８負極タブ
９保護部材
１４１第１凹部
１４２第２凹部
１４３平坦部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a thin sealed battery, and more particularly, to an improvement in volume energy density and an improvement in sealing performance of a thin sealed battery.
[0002]
[Prior art]
Conventionally, a battery made of a hard metal such as stainless steel has been used as a battery casing. However, although such an exterior body is excellent in strength, it is difficult to reduce the thickness of the battery. For this reason, a technique for reducing the thickness of a battery has been developed by forming an exterior body with a thin and flexible laminate film and using it. As shown in FIG. 3, a thin sealed battery to which this technology is applied heats aluminum laminate films in which a polyolefin resin layer 13 is formed on both surfaces of a metal layer 11 made of aluminum via an adhesive layer 12. A bag-shaped aluminum laminate film outer package is formed by fusing, and a storage space for the aluminum laminate film outer package includes a positive electrode, a negative electrode, and a separator (not shown in FIG. 4) as shown in FIG. The electrode body is housed and the positive and negative current collecting tabs are taken out from the sealing portion. If the battery has such a structure, the battery can be further miniaturized and the volume energy density of the battery can be improved.
[0003]
However, in order to form an electrode body as shown in FIG. 4 in a battery using a laminate film exterior body, it is necessary to first press the electrode body wound in a circle. The positive and negative current collecting tabs attached to both the positive and negative electrodes have square portions (burrs), and when the electrode body is pressed, the burrs break through the separator and contact with the other electrodes. Occurs. Therefore, in order to prevent such a short circuit, a protective member such as a protective tape is disposed on the burr portion.
[0004]
On the other hand, the laminate film exterior body is sealed by pressure welding the resin layers inside the laminate film, but in the case of bonding between the laminate films, the resin layer and the resin layer face each other. These metal layers are sufficiently separated by two resin layers. However, in the sealing portion where the current collecting tab protrudes (tab protruding sealing portion), the metal layer faces the current collecting tab through one resin layer, and this resin layer is thinned by pressure welding. It has become. For this reason, the metal layer of the laminate film and the current collecting tab are easily short-circuited.
[0005]
Therefore, in Japanese Patent Application Laid-Open No. 2000-173562, by using a mold having a recess corresponding to the shape of the electrode tab as shown in FIG. 11, an excessive pressure is applied to the current collecting tab portion and the resin layer becomes thin. There has been proposed a technique for sealing the tab protruding sealing portion while preventing this.
[0006]
However, recently, in order to further increase the volume energy density, the distance between the electrode body and the tab protrusion sealing portion has been shortened. In this case, the above technique cannot sufficiently prevent a short circuit. The reason for this is that when the distance between the electrode body and the tab protruding sealing part is shortened, the protective tape is bitten into the tab protruding sealing part, and the thickness of the part increases, resulting in the resin after pressure welding. This is because the thickness of the layer (insulating layer) is reduced. On the other hand, if the width of the sealing portion is reduced in order to avoid biting of the protective tape, there is a problem that the sealing performance becomes insufficient as the width of the sealing portion is reduced.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above, and an object of the present invention is to provide a safe battery having a high volumetric energy density, excellent sealing properties, and no internal short circuit.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the invention described in claim 1 is configured as follows. In a thin sealed battery in which an electrode body having a positive electrode with a current collecting tab and a negative electrode with a current collecting tab is housed in an outer body made of a film in which a metal and a resin are laminated, the outer body has positive and negative The current collector tab has a tab protrusion sealing portion that protrudes out of the exterior body, and a protective member is disposed on a portion of the current collection tab that overlaps with the positive and negative electrodes. The second region (42) sealed in a state including the first region (41), which is a region near the electrode body of the electric tab, and the current collecting tab portion other than the first region and where no protective member is disposed. And the third region (43) sealed only with the films without including other members, and the total thickness of the exterior body in the first region (41) is in the second region (42). The total thickness of the outer package and the total thickness of the outer package in the third region (43) Thicker than Re, Jitsuatsu of said film in said first region (41) is characterized by thicker than the actual thickness of the film in the second region (42).
[0009]
Here, the region near the electrode body of the current collector tab in the above configuration refers to the vicinity of the boundary between the current collector tab protruding from the electrode body and the electrode body in the diagram of the electrode body shown in FIG. The total thickness of the outer package is the total thickness including all of the outer package, electrode tabs, protective members, etc. The actual thickness of the film is the thickness of the film alone at that location. The other member means a current collecting tab, a protective member, or the like.
[0010]
In this configuration, the first region (41) is formed in the electrode body vicinity region of the current collecting tab portion of the tab protruding sealing portion, and the total thickness of the exterior body in the first region (41) is the second region. The actual thickness of the film in the first region (41) is greater than both the total thickness of the outer package in the region (42) and the total thickness of the outer package in the third region (43), and the second region (42). It is formed thicker than the actual thickness of the film. Therefore, even when the protective member is arranged in the first region (41), the internal pressure does not become excessive, so that the resin layer of the laminate film is not damaged by the pressure and the metal layer is not exposed. As a result, an internal short circuit in the electrode body vicinity region can be prevented.
Moreover, in the said structure, the protection member is arrange | positioned at the current collection tab part which overlaps with an electrode, and this protection member acts so that the damage of the separator by the edge of a current collection tab may be prevented. Therefore, with the above configuration, a thin sealed battery excellent in safety and reliability can be provided.
[0011]
The invention described in claim 2 is configured as follows. In the manufacturing method of a thin sealed battery in which an electrode body having a positive electrode with a current collecting tab and a negative electrode with a current collecting tab is housed in an exterior body made of a film in which a metal and a resin are laminated, A protective member arranging step of arranging a protective member in a portion overlapping the positive and negative electrodes of the current collecting tab, and an electrode body producing step of producing an electrode body having at least a positive and negative electrode after the protective member arranging step; The electrode body is housed in an exterior body having an opening in a state where the leading end side of the positive and negative current collecting tabs protrudes outside the exterior body, and after the electrode body housing process, the opening is pressurized. And a pressurizing step for forming a tab projecting sealing portion, and the pressurizing step is a first region (41) that is a region near the electrode body of the current collecting tab, and is protected except for the first region In the state including the current collection tab part where the member is not arranged The second region (42) to be stopped and the third region (43) sealed only by the films without including other members are formed by simultaneously or sequentially pressing under the condition of the following formula 2. It is a process.
[0012]
[Expression 2]

[0013]
In the above configuration, the pressure applied to the first region is smaller than that of the second and third regions, so that the resin layer thickness in the first region where internal short circuit is likely to occur is properly maintained, and the current collecting tab and film A short circuit with the metal layer of the outer casing can be prevented. Moreover, even when the distance between the electrode body and the tab protruding sealing portion is short, an internal short circuit can be prevented without impairing the sealing performance.
[0014]
Also, pressurizing method in the pressurizing step, before Symbol a flat portion for pressurizing the third region (43), said to correspond to the shape of the first region (41), a first region (41) Simultaneous pressurization using a pressurizing member having a first recess for pressurization and a second recess for pressurizing the second region (42) corresponding to the shape of the second region (42) It can be said that it is the method of sealing.
[0015]
When the pressurizing member as described above is used, the tab projecting sealing portion can be sealed under the condition that satisfies the above-described Expression 2 by a single pressurizing operation, and thus the production efficiency is high. Therefore, according to this configuration, a thin sealed battery excellent in safety and storage can be produced.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
While describing the contents of the present invention, a preferred embodiment is described.
[0017]
1 is a front view of a thin sealed battery according to an embodiment of the present invention using a laminate film outer package, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a laminate package used for the thin sealed battery. FIG. 4 is a perspective view of an electrode body used for a thin sealed battery. In addition, the same code | symbol is attached | subjected to the member from which the same effect is acquired.
[0018]
As shown in FIG. 2, the thin sealed battery according to the present invention has an electrode body 1, and the electrode body 1 is disposed in a storage space 2. As shown in FIG. 1, the storage space 2 is formed by sealing the upper and lower ends and the center portion of the laminate outer package 3 with sealing

portions

4a, 4b, and 4c, respectively. In addition, an electrolytic solution in which LiPF ₆ as an electrolyte salt is dissolved at a rate of 1 M (mol / liter) is injected into the storage space 2 in a non-aqueous solvent.
[0019]
The thin sealed battery includes, in the sealing portion 4a, a first region 41 that is a region near the electrode body of the current collecting tab, and a current collecting tab portion that is not disposed on the first region and in which a protective member is not disposed. A second region 42 sealed in a state, and a third region 43 sealed only by films without sandwiching other members, and the total thickness of the exterior body in the first region 41 is the second region It is thicker than any of the total thickness of the outer package in the region 42 and the total thickness of the outer package in the third region 43, and the actual thickness of the film in the first region 41 is greater than the actual thickness of the film in the second region 42. It is also made thick.
[0020]
Moreover, it is preferable that ratio L1 / L of the width | variety L1 of said 1st area | region shown in FIG. 1 and the width | variety L of a tab protrusion sealing part is 0.01 or more and 0.7 or less. If the ratio L1 / L is greater than 0.7, the first region is not sufficiently sealed because the actual thickness of the resin layer of the film is thicker than the other regions, leading to a decrease in battery sealing performance. If it is smaller than 0.01, a protective member may be disposed in the second region, resulting in a risk of an internal short circuit. The ratio L1 / L is more preferably 0.05 or more and 0.5 or less.
[0021]
As shown in FIG. 4, the electrode body 1 is formed by winding a positive electrode 5, a negative electrode 6, and a separator (not shown in FIG. 4) separating these two electrodes into a flat spiral shape. Produced. As the separator, a microporous film (thickness: 0.025 mm) made of an inexpensive olefin resin is used which has low reactivity with an organic solvent.
[0022]
Further, the positive electrode 5 is connected to a positive electrode tab 7 made of aluminum, and the negative electrode 6 is connected to a negative electrode tab 8 made of nickel, so that chemical energy generated inside the battery can be taken out as electric energy to the outside. . Moreover, although not shown in FIG. 4, the protective tape made from polyphenylene sulfide is affixed on the part which overlaps each current collection tab and positive and negative electrodes.
[0023]
In addition, as shown in FIG. 3, the specific structure of the laminate outer package 3 is such that adhesive layers 12 and 12 (thickness: 5 μm) made of modified polypropylene are formed on both sides of the aluminum layer 11 (thickness: 30 μm), respectively. In this structure, resin layers 13 and 13 (thickness: 30 μm) made of polypropylene are bonded to each other. However, the adhesive layer is not shown in FIGS.
[0024]
As the positive electrode material, for example, a lithium-containing transition metal composite oxide is used alone or in combination of two or more. As specific examples, lithium cobaltate, lithium nickelate, lithium manganate, lithium ferrate, or an oxide obtained by substituting a part of the transition metal contained in these oxides with another element, or the like is used.
[0025]
As the negative electrode material, for example, natural graphite, carbon black, coke, glassy carbon, carbon fiber, or a carbonaceous material such as a fired body thereof, or the carbonaceous material, lithium, a lithium alloy, and a metal capable of inserting and extracting lithium A mixture with one or more selected from the group consisting of oxides is used.
[0026]
Examples of the non-aqueous solvent used in the electrolytic solution include a high dielectric constant solvent having high lithium salt solubility such as ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1 , 2-dimethoxyethane, tetrahydrofuran, anisole, 1,4-dioxane, 4-methyl-2-pentanone, cyclohexanone, acetonitrile, propionitrile, dimethylformamide, sulfolane, methyl formate, ethyl formate, methyl acetate, ethyl acetate, acetic acid It is used by mixing with a low viscosity solvent such as propyl and ethyl propionate. The high dielectric constant solvent and the low viscosity solvent may be two or more mixed solvents.
[0027]
As the electrolyte salt, for example, LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiClO ₄ , LiPF ₆ , LiBF _4, etc. are used alone or in combination of two or more. . Further, the amount dissolved in the non-aqueous solvent is, for example, 0.5 to 2.0 mol / liter.
[0028]
Example 1
A thin sealed battery according to the present invention was produced as follows.
A positive electrode active material made of lithium cobaltate (LiCoO ₂ ), a carbon-based conductive agent made of acetylene black, a binder made of polyvinylidene fluoride (PVdF), and N-methyl-2-pyrrolidone (NMP) The mixture was mixed to obtain an active material slurry.
[0029]
The active material slurry is uniformly applied to both surfaces of a positive electrode core body made of an aluminum foil having a thickness of 20 μm by a doctor blade, and then passed through a dryer to be dried, thereby removing the organic solvent necessary for slurry preparation. Removed. Subsequently, this electrode plate was rolled by a roll press so that the thickness was 0.17 mm, and the positive electrode 5 was produced.
[0030]
An active material slurry was prepared by mixing 95 parts by mass of a negative electrode active material made of graphite, 5 parts by mass of a binder made of polyvinylidene fluoride (PVdF), and N-methyl-2-pyrrolidone (NMP). This active material slurry is uniformly applied to both surfaces of a negative electrode core made of a copper foil having a thickness of 20 μm by a doctor blade, and then passed through a drier to dry the organic solvent necessary for slurry preparation. Removed. Next, this electrode plate was rolled by a roll press so that the thickness was 0.14 mm, and a negative electrode 6 was produced.
[0031]
A positive electrode tab 7 or a negative electrode tab 8 is attached to the positive electrode 5 and the negative electrode 6 prepared as described above, respectively, and a protective tape 9 (not shown in FIG. 4) made of polyphenyl sulfide is attached. A separator made of a microporous film made of resin (thickness: 0.025 mm) was placed between them, and the center lines in the width direction of the electrode plates were made to coincide with each other. Thereafter, the flat wound electrode body 1 was produced by winding with a winder and tapering the outermost periphery.
[0032]
After preparing a sheet-like laminate material consisting of a five-layer structure of resin layer (polypropylene) / adhesive layer / aluminum alloy layer / adhesive layer / resin layer (polypropylene), resin layers near the edges of the aluminum laminate material The sealing portion 4c was formed by welding the overlapping portions. Next, the electrode body 1 was inserted into the storage space 2 of the cylindrical aluminum laminate material. At this time, the electrode body 1 was disposed so that the

current collecting tabs

7 and 8 protruded from one opening of the cylindrical aluminum laminate material.
[0033]
Thereafter, both current collecting tabs are sandwiched by an exterior body through a film (not shown) made of a modified polyolefin resin, and as shown in FIG. 7, the third region is sealed only with laminate films. A flat portion 143 for pressurizing the electrode, a first concave portion 141 corresponding to the shape of the first region which is a region near the electrode body of the current collector tab, and a current collector other than the first region and where no protective member is arranged The opening is pressure-welded and sealed using a pressure member having a second recess 142 corresponding to the shape of the second region sealed in a state including the tab portion, and the sealing portion 4a was formed.
[0034]
Next, a pregel composed of an electrolytic solution obtained by mixing LiPF ₆ as an electrolyte salt in a mixed solvent composed of ethylene carbonate and diethyl carbonate so as to be 1 M (mol / liter), polyethylene glycol diacrylate, and a polymerization initiator is prepared. After injecting from the opening of the aluminum laminate material opposite to the sealing portion, the opening was sealed secretly to form the sealing portion 4b. Finally, the aluminum laminate outer package 3 was heated at 60 ° C. for 3 hours to gel the pregel inside the aluminum laminate outer package, thereby producing the battery A of the present invention according to Example 1. The size of the battery was 60 × 60 × thickness 3.8 (mm).
[0035]
In the battery manufactured in this way, the pressure applied to the first region, which is the region near the electrode body of the current collecting tab, includes the current collecting tab portion other than the first region and where the protective member is not disposed. The pressure applied to the second region sealed in the state is smaller, and as shown in FIG. 6, the total thickness of the exterior body in the first region 41 is the total thickness of the exterior body in the second region 42, and It is thicker than any of the total thickness of the exterior body in the three regions 43. Furthermore, the actual thickness of the laminate film in the first region 41 is larger than the actual thickness of the laminate film in the second region 42.
[0036]
(Comparative Example 1)
As shown in FIG. 11, the same as in the above embodiment, except that a pressing member having only a flat portion 143 for pressing the third region and a concave portion 142 corresponding to the shape of the current collecting tab was used. Thus, a battery X according to Comparative Example 1 was produced. In the battery manufactured in this way, since the pressure applied to the first region and the second region is equal, the protrusion of the first region is not seen from the appearance as shown in FIGS.
[0037]
(Comparative Example 2)
A battery Y according to Comparative Example 2 was produced in the same manner as Comparative Example 1 except that the width of the pressure surface was narrower than that of the pressure member of Comparative Example 1. Since the battery manufactured in this way does not have any pressure applied to the first region, it becomes a sealed portion narrower than the comparative battery X as shown in FIGS.
[0038]
In addition, 50 batteries were produced for each.
[0039]
<Short detection>
In the manufacturing process, continuity between the current collecting tab and the metal layer of the exterior body was detected by a tester, and those for which continuity was confirmed were counted as occurrence of a short circuit. The battery confirmed to be conductive was not used in the following tests.
[0040]
<Sealing performance test>
The 40% charged battery was stored for 30 days under conditions of 80 ° C. and 90% humidity, and the thickness of the battery was measured. The occurrence of short circuit and the sealing performance test results are shown in Table 1 below.
[0041]
[Table 1]

[0042]
From Table 1 above, it was confirmed that the battery A1 of the present invention did not cause a short circuit and the battery swell after storage was almost the same as that of the comparative battery X, and the good sealing performance was 28 for the comparative battery X. % Is short-circuited, and in the comparative battery Y, the increase in battery thickness after storage is 0.38 mm larger than the increase in battery thickness of the present invention battery A after storage.
[0043]
Here, in the comparative battery X, as shown in FIG. 11, the pressure member has only the concave portion 142 corresponding to the shape of the current collecting tab and does not have the first concave portion corresponding to the shape of the first region. Is used, the pressure applied to the first region is equal to that of the second region. For this reason, as shown in FIG. 9, the protective tape is inserted into the sealing portion, the thickness of the resin layer in the portion is reduced, and the current collecting tab and the metal layer of the laminate material are easily short-circuited.
[0044]
Moreover, since the comparison battery Y uses a pressure member that is narrower than the pressure member of Comparative Example 1 and does not apply any pressure to the first region, the width of the sealing portion is reduced. As a result, the airtightness is lowered, and moisture and the like easily enter from the sealing portion, and the battery thickness after storage increases due to the mixed water.
[0045]
On the other hand, in the present invention battery A, as shown in FIG. 7, the first recess 141 corresponding to the shape of the first region, the second recess 142 corresponding to the shape of the second region, and the third region are pressurized. Since pressure welding is performed using the pressure member in which the flat portion 143 is formed, the pressure applied to the first region is smaller than the pressure applied to the second region, and the resin layer of the portion is not sealed. Since it is maintained at the same level as the thickness of the stop portion, a short circuit can be prevented and the sealing performance is not deteriorated. Therefore, it is considered that the results shown in Table 1 were obtained.
[0046]
In the above embodiment, the first concave portion and the second concave portion are each formed of a pressure member made of a die cut out in a rectangular parallelepiped shape as shown in FIG. 7, but the present invention has this shape. The present invention is not limited, and can be freely modified without departing from the scope of the present invention. For example, the same effect can be obtained by using a mold in which the first concave portion and the second concave portion are cut into a columnar shape, a trapezoidal columnar shape, an ellipsoidal shape, or the like. Further, the shapes of the first region and the second region may be a columnar shape, a trapezoidal columnar shape, an ellipsoidal shape, or the like.
[0047]
In addition, the resin layer of the laminate outer package is not limited to the above-mentioned polypropylene. For example, a polyolefin polymer such as polyethylene, a polyester polymer such as polyethylene terephthalate, a polyvinylidene such as polyvinylidene fluoride and polyvinylidene chloride. Polyamide polymers such as nylon polymers, nylon 6, nylon 66, nylon 7, etc. can be used. Furthermore, the structure of the laminate outer package is not limited to the above five-layer structure.
[0048]
Moreover, in the said embodiment, in order to improve the adhesiveness of a current collection tab and an exterior body, although the film as another member was used, such a film etc. do not need to be used.
[0049]
Moreover, in the said Example, although the protective tape made from polyphenyl sulfide was used, it is not limited to this, For example, the protective member which consists of polyolefin, a polyimide, etc. may be sufficient.
[0050]
【The invention's effect】
As described above, in the present invention, the actual thickness of the film-shaped outer package in the vicinity of the electrode body of the current collecting tab is made substantially equal to the actual thickness of the non-sealed portion, so that the tab protruding sealing portion and the electrode Even in a battery with a reduced distance from the body, a low-profile sealed battery excellent in safety and storability that can prevent a short circuit between the current collecting tab and the metal layer of the film without impairing the sealing performance is provided at a low cost. be able to. This battery is excellent in volume energy density in that the width between the tab protruding sealing portion and the electrode body can be narrowed.
[Brief description of the drawings]
FIG. 1 is a front view of a thin sealed battery according to the present invention.
2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a cross-sectional view of a laminate outer package used for a thin sealed battery according to the present invention.
FIG. 4 is a perspective view of an electrode body from which a current collecting tab protrudes for use in a thin sealed battery according to the present invention.
FIG. 5 is a schematic cross-sectional view taken along line BB in FIG. 1;
FIG. 6 is a perspective view of a tab protruding sealing portion of a thin sealed battery according to the present invention.
FIG. 7 is a perspective view of a mold used for a thin sealed battery according to the present invention.
FIG. 8 is a front view of a conventional thin sealed battery.
9 is a schematic cross-sectional view taken along the line CC in FIG.
FIG. 10 is a perspective view of a tab protruding sealing portion of a thin sealed battery according to a conventional technique.
FIG. 11 is a perspective view of a mold used in a conventional thin sealed battery.
FIG. 12 is a front view of another shape thin sealed battery according to the prior art.
FIG. 13 is a perspective view of a tab protruding sealing portion of another shape thin sealed battery according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electrode body 2 Storage space 3 Aluminum laminate

exterior body

4a, 4b, 4c Sealing part 41 1st area | region 42 2nd area | region 43 3rd area | region 5 Positive electrode 6 Negative electrode 7 Positive electrode tab 8 Negative electrode tab 9 Protection member 141 1st recessed part 142 1st 2 concave part 143 flat part

Claims

In a thin sealed battery in which an electrode body having a positive electrode with a current collecting tab and a negative electrode with a current collecting tab is housed in an exterior body made of a film in which a metal and a resin are laminated,
The exterior body has a tab protruding sealing portion in which the front end side of the positive and negative current collecting tabs protrudes outside the exterior body, and a protective member is disposed on a portion overlapping the positive and negative electrodes of the current collection tab,
The tab protruding sealing portion is sealed in a state including a first region (41) that is a region in the vicinity of the electrode body of the current collecting tab and a current collecting tab portion other than the first region where no protective member is disposed. The second region (42) stopped and the third region (43) sealed only with the films without including other members,
The exterior body total thickness in the first region (41) is thicker than any of the exterior body total thickness in the second region (42) and the exterior body total thickness in the third region (43).
The thin sealed battery according to claim 1, wherein an actual thickness of the film in the first region (41) is larger than an actual thickness of the film in the second region (42).

In the manufacturing method of a thin sealed battery in which an electrode body having a positive electrode with a current collecting tab and a negative electrode with a current collecting tab is housed in an exterior body made of a film in which a metal and a resin are laminated,
The manufacturing method includes:
A protective member arranging step of arranging a protective member on a portion overlapping the positive and negative electrodes of the current collecting tab;
After the protective member arranging step, an electrode body preparation step for producing an electrode body having at least positive and negative electrodes,
An electrode body housing step of housing the electrode body in an exterior body having an opening in a state in which a tip end side of a positive and negative current collecting tab protrudes outside the exterior body;
After the electrode body storing step, pressurizing the opening to form a tab protruding sealing portion, and
The pressurizing step is sealed in a state including a first region (41) that is a region near the electrode body of the current collecting tab and a current collecting tab portion other than the first region where no protective member is disposed. Forming the second region (42) and the third region (43) sealed only by the films without including other members by simultaneously or sequentially pressing under the condition of the following formula 1. is there,
A method for producing a thin sealed battery, wherein

In the manufacturing method of the thin sealed battery of Claim 2,
The pressurizing method in the pressurizing step pressurizes the first region (41) corresponding to the flat portion for pressurizing the third region (43) and the shape of the first region (41). And pressurizing and sealing simultaneously using a pressure member having a first recess and a second recess for pressurizing the second region (42) corresponding to the shape of the second region (42). A method for producing a thin sealed battery, wherein the method is a method.