JP4007026B2

JP4007026B2 - Winding cylindrical battery

Info

Publication number: JP4007026B2
Application number: JP2002073634A
Authority: JP
Inventors: 亮小島; 竹規石津
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Resonac Corp
Priority date: 2002-03-18
Filing date: 2002-03-18
Publication date: 2007-11-14
Anticipated expiration: 2022-03-18
Also published as: JP2003272709A

Description

【０００１】
【発明の属する技術分野】
本発明は、捲回式円筒型電池に係り、特に正、負極をセパレータを介して捲回した捲回群を有する捲回式円筒型電池に関する。
【０００２】
【従来の技術】
従来、捲回式円筒型電池は、有底円筒状の電池容器内に、セパレータを介して集電のためのタブが導出された帯状の正負極を捲回した捲回群が、電解液に浸潤されて収容されている。このような捲回式円筒型電池において、電池外部からの応力などによる電池変形で生じる内圧上昇に対応するために、例えば、特開平第７−１９２７１２号公報には、電池内のガスを電池外に開放する安全弁や電池蓋と安全弁との間に網目状の開口を有する膜が設けた技術が開示されている。この技術によれば、電池内圧の上昇時に、安全弁を作動させガスを開放して電池内圧の上昇を抑制し、膜によりガス開放時の電池内の固形分の飛散を防止している。
【０００３】
【発明が解決しようとする課題】
しかしながら、近年のリチウムイオン二次電池に代表されるように、電池のエネルギー密度が高く、また電池系に用いられる活物質が熱暴走反応を起こし得、更に電解液にも可燃性の有機系電解液が用いられた電池の場合に、上記の如く電池が変形した際には、電解液の気化などに起因する急激なガス発生により、電池の内圧上昇速度が安全弁の作動による内圧開放速度を上回り、電池容器の内圧が極端に上昇するという現象がみられた。
【０００４】
本発明は上記事案に鑑み、安全性に優れた捲回式円筒型電池を提供することを課題とする。
【０００５】
【課題を解決するための手段】
上記課題を解決するために、本発明の第１の態様は、正、負極をセパレータを介して捲回した捲回群を有する捲回式円筒型電池において、前記捲回群は、該捲回群を隔絶する隔絶層によって同心円状かつ少なくとも２以上に隔絶されており、前記隔絶層は、該隔絶層に内接又は外接する捲回群から連続したセパレータであることを特徴とする。
【０００６】
第１の態様では、外からの応力付与などにより電池が変形して正極と負極とが押しつけられると、まず隔絶層に外接する捲回群で短絡が起こるが、捲回群が該捲回群を隔絶する隔絶層によって同心円状かつ少なくとも２以上に隔絶されているため、隔絶層に内接する捲回群での短絡を遅延することができるので、捲回群が即座に短絡するのを防止でき、隔絶層を有さない捲回群の場合に比べて、短絡に起因するガス発生が遅延され、電池全体として内圧上昇速度が低下させることができる。また、隔絶層を、隔絶層に内接又は外接する捲回群から連続するセパレータとしたので、電池部品数を削減することができると共に、捲回群の構造を簡単化することができる。本態様において、隔絶層に内接する捲回群の最外周の電極と、隔絶層に外接する捲回群の最内周の電極とを同極にすれば、隔絶層が破断しても短絡が生じないので、安全性を確保することができる。逆に、隔絶層に内接する捲回群の最外周の電極と、隔絶層に外接する捲回群の最内周の電極とを異極とすれば、隔絶層を介して電池反応が起こるので、隔絶層による電池のエネルギー密度の低下を補うことができる。
【０００７】
また、上記課題を解決するために、本発明の第２の態様は、正、負極をセパレータを介して捲回した捲回群を有する捲回式円筒型電池において、前記捲回群は、該捲回群を隔絶する隔絶層によって同心円状かつ少なくとも２以上に隔絶されており、前記隔絶層に内接する捲回群の最外周の電極と、前記隔絶層に外接する捲回群の最内周の電極とが同極であることを特徴とする。第２の態様では、第１の態様と同様に、外からの応力付与などにより電池が変形して正極と負極とが押しつけられると、まず隔絶層に外接する捲回群で短絡が起こるが、捲回群が該捲回群を隔絶する隔絶層によって同心円状かつ少なくとも２以上に隔絶されているため、隔絶層に内接する捲回群での短絡を遅延することができるので、捲回群が即座に短絡するのを防止でき、隔絶層を有さない捲回群の場合に比べて、短絡に起因するガス発生が遅延され、電池全体として内圧上昇速度が低下させることができると共に、隔絶層に内接する捲回群の最外周の電極と、隔絶層に外接する捲回群の最内周の電極とを同極としたので、隔絶層が破断しても短絡が生じないため、安全性を確保することができる。
【０００８】
【発明の実施の形態】
（第１実施形態）
以下、図面を参照して、本発明を円筒型リチウムイオン二次電池に適用した第１の実施の形態について、電池の作製手順に従って説明する。
【０００９】
（電極の作製）
リチウムマンガン複合酸化物の粉末と、導電材の炭素材料と、ポリフッ化ビニリデン（ＰＶＤＦ）とを固形分比（重量比）が９０：５：５となるように混合し、Ｎ−メチルピロリドン（ＮＭＰ）に溶解したバインダ溶液を撹拌して正極スラリを得た。この正極スラリを集電基体のアルミニウム箔に均一に塗布、乾燥し、櫛歯状に集電のためのタブを残してアルミニウム箔部分を切り取り、プレス加工して所定の厚さに成形した。これを有底円筒状の電池缶に合わせた寸法にスリット加工し、更に、捲回方向に２枚以上に分割して帯状の正極を２枚以上得た。
【００１０】
非晶質炭素粉末と、ポリフッ化ビニリデン（ＰＶＤＦ）とを固形分比（重量比）が９０：１０となるように混合し、Ｎ−メチルピロリドン（ＮＭＰ）に溶解したバインダ溶液を撹拌して負極スラリを得た。この負極スラリを集電基体の銅箔に均一に塗布、乾燥し、正極と同様に櫛歯状に集電のためのタブを残して銅箔部分を切り取り、プレス加工して所定の厚さに成形した。これを電池缶に合わせた寸法にスリット加工し、更に、捲回方向に２枚以上に分割して帯状の負極を２枚以上得た。
【００１１】
（電極群の作製）
図１（Ａ）に示すように、作製した正極及び負極を微孔を有する厚さ４０μmのポリエチレン製薄膜セパレータを介して、ポリプロピレン製の軸芯４の周りに最外周が負極となるように捲回し内側捲回群２を作製した。なお、図示しない正極のタブと負極のタブとを互いに上下反対側に位置させた。その後、内側捲回群２の幅よりも約１％幅が大きく、厚さ約０．１ｍｍのＰＴＦＥ（ポリテトラフルオロエチレン）シートを、内側捲回群２の外側に少なくとも１周捲回し隔絶層１を形成した。更に、その後、内側捲回群２の作製と同様に、正極及び負極をセパレータを介して隔絶層１の外側に最内周が負極となるように捲回して外側捲回群３を作製し、内側捲回群２と外側捲回群３とが隔絶層１により同心円状となるように隔絶された電極群１０を作製した。なお、外側捲回群３の最外周には１周分以上セパレータを捲回した。
【００１２】
従って、電極群１０は、軸芯４を中心として、正極及び負極がセパレータを介して最外周が負極となるように捲回された内側捲回群２を有している。内側捲回群２の外側には、内側捲回群２の幅よりも幅が大きいＰＴＦＥシートが捲回され、隔絶層１が形成されている。隔絶層１の外側には、正極及び負極がセパレータを介して最内周が負極となるように捲回された外側捲回群３が同心円状に配置されている。このため、電極群１０は、隔絶層１に内接する内側捲回群２及び外接する外側捲回群３が隔絶層１により隔絶されている。
【００１３】
図１（Ｂ）に示すように、隔絶層１に内接する内側捲回群２の最外周の電極は、負極２Ｂとされている。負極２Ｂの内側には、負極２Ｂより捲回方向に長いセパレータ２Ｃを介して正極２Ａが配置され、更に正極２Ａの内側にはもう一枚のセパレータ２Ｃが配設されている。また、隔絶層１に外接する外側捲回群３の最内周の電極は、負極３Ｂとされている。負極３Ｂの外側には、負極３Ｂより捲回方向に長いセパレータ３Ｃを介して正極３Ａが配置され、更に正極３Ａの外側にはもう一枚のセパレータ３Ｃが配設されている。従って、内側捲回群２の最外周の電極と、外側捲回群３の最内周の電極とは同極（負極）となる。
【００１４】
（電池の組立）
図３（Ａ）に示すように、アルミニウム製で円盤状の正極集電極柱６の底面に正極２Ａ、３Ａのタブを、銅製で円盤状の負極集電極柱７の底面に負極２Ｂ、３Ｂのタブを、それぞれ超音波溶接した。負極集電極柱７の底面とは反対側の面に図示しない負極リード板を溶接した。図３（Ｂ）に示すように、この電極群１０を鉄にニッケルメッキを施した有底円筒状の電池缶９（寸法φ４０ｍｍ×１４５ｍｍ）内に挿入し、電池缶９の底に負極リード板を介して負極集電極柱７を抵抗溶接し、正極集電極柱６をリード板を介して、金属薄膜に馬蹄形の薄肉部が形成された安全弁（破裂弁）を有するアルミニウム製の電池蓋８に超音波溶接した。
【００１５】
この電池内に露点−４０゜Ｃ以下の乾燥空気雰囲気でエチルカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）の混合溶媒に六フッ化リン酸リチウム（ＬｉＰＦ_６）を溶解した電解質溶液を注入し、更に電池蓋８と電池缶９をとＰＦＡ樹脂製のガスケットを介してカシメて封口して円筒型リチウムイオン二次電池を得た。この電池を公称容量の２時間率をもって数サイクルの充放電を繰り返し、炭素材料の不可逆容量を飽和させ、電池機能を付与した。このとき、充電の終止電圧を４．２Ｖ、放電の終止電圧を２．７Ｖとした。
【００１６】
（作用）
次に、本実施形態の円筒型リチウムイオン二次電池の作用等について説明する。
【００１７】
本実施形態の円筒型リチウムイオン二次電池では、電池外部から応力が加わると、電池が変形して正極２Ａ、３Ａと負極２Ｂ、３Ｂとが押しつけられ、外側捲回群３で短絡が起こる。このとき、電極群１０が隔絶層１によって同心円状に隔絶されているので、同時には内側捲回群２側では短絡が生じない（その後、応力の程度により内側捲回群２側で短絡が生じることもある）。このため、電極群１０全体が即座に短絡するのを防止でき（短絡が段階的に生じ）、隔絶層１を有しない電極群の場合に比べて、短絡に起因するガス発生現象が遅延され、電池全体として電池内で発生するガスの発生速度が低下し、安全弁から穏やかにガスを放出することが可能となる。換言すれば、ガス発生速度が安全弁の内圧開放速度（開裂速度）を上回る場合が少なくなるので、電池缶９内の極端な内圧上昇などの電池挙動の発生確率を低減することができ、電池の安全性を確保することができる。
【００１８】
また、本実施形態では、万一隔絶層１が破断しても、負極２Ｂと、負極３Ｂとが同極（負極）なので、隔絶層１を介しての短絡を防止することができると共に、電池反応に関与しない負極２Ｂと負極３Ｂとが対向する部分を、リチウムイオン二次電池においてはより軽い（薄い）負極を選択し、隔絶層１の箇所数も１箇所に留めたので、エネルギー密度の低下を最小限に抑えることができる。
【００１９】
なお、本実施形態では、隔絶層１にＰＴＦＥシートを例示したが、これに限定されるのもではなく、例えば、ポリエチレンシートとするようにしてもよい。また、本発明は隔絶層１の厚さや幅についても限定されるものではなく、例えば、厚さを約０．０５ｍｍにしてもよいし、幅も電極群１０の幅より約２％程度長くしてもよい。更に、隔絶層１を１箇所有する電池を例示したが、隔絶層１は、任意箇所設けることができる。しかし、エネルギー密度の点から隔絶層１の箇所数は１又は２箇所とするのが望ましい。
【００２０】
また、本実施形態では、内側捲回群２の最外周の電極（負極２Ｂ）と、外側捲回群３の最内周の電極（負極３Ｂ）とが同極（負極）の電池を例示したが、同極に限定されるものではなく、異極となるようにしてもよい。また、電池系が異なるときには、隔絶層１を介して正極同士が対向するように捲回してもよい。
【００２１】
（第２実施形態）
次に、本発明を捲回式円筒型電池に適用した第２の実施の形態について説明する。本実施形態は、隔絶層に内側捲回群のセパレータから連続したセパレータを用いたものである。なお、本実施形態において、上述した第１実施形態と同一の構成要素には同一の符号を付してその説明を省略し、異なる箇所のみ説明する。
【００２２】
図２に示すように、正極２Ａ及び負極２Ｂをセパレータ２Ｃより長いセパレータ２Ｄを介して、軸芯の周りに最外周が負極２Ｂとなるように捲回し内側捲回群を作製した。内側捲回群から連続するセパレータ２Ｄを内側捲回群の外側に同心円状に少なくとも１周捲回して隔絶層とした。その後、セパレータ２Ｄ（隔絶層）の外側に、正極３Ａ及び負極３Ｂを、セパレータ３Ｃを介して最内周が負極３Ｂとなるように捲回して外側捲回群を作製し、内側捲回群と外側捲回群とが隔絶層により同心円状に隔絶された電極群を作製した。
【００２３】
従って、電極群は、軸芯を中心として、正極２Ａ及び負極２Ｂをセパレータ２Ｃより捲回方向に長いセパレータ２Ｄを介して最外周が負極２Ｂとなるように捲回された内側捲回群を有している。内側捲回群の外側には、内側捲回群から連続するセパレータ２Ｄが少なくとも１周捲回されて隔絶層が形成されている。隔絶層の外側には、外側捲回群の最内周の電極が負極３Ｂとなるように正極３Ａ及び負極３Ｂがセパレータ３Ｃを介して捲回された外側捲回群が同心円状に配置されている。このため、電極群は、隔絶層に内接する内側捲回群及び外接する外側捲回群が隔絶層により隔絶されている。隔絶層に内接する内側捲回群の最外周の電極は、負極２Ｂ、隔絶層に外接する外側捲回群の最内周の電極は、負極３Ｂとされている。従って、内側捲回群の最外周の電極と、外側捲回群の最内周の電極とは同極（負極）とされている。
【００２４】
本実施形態の円筒型リチウムイオン二次電池では、電池外部からの応力が掛かり電池が変形して正極２Ａ、３Ａと負極２Ｂ、３Ｂとが押しつけられても、電極群が隔絶層によって同心円状かつ２つに隔絶されているため、電極群全体が即座に短絡するのを防止でき（短絡が段階的に生じ）、短絡に起因するガス発生現象が遅延され、電池全体として電池内で発生するガスの発生速度を低下させることができる。従って、第１実施形態と同様に、安全弁による内圧開放速度をガス発生速度が上回る場合が少なくなり、電池缶９の極端な内圧上昇などの電池挙動の発生確率を低減することができる。
【００２５】
また、本実施形態では、内側捲回群から連続するセパレータ２Ｄを内側捲回群の外周に少なくとも１周捲回して隔絶層を形成したために、隔絶層のための別の部材が不要となると共に、電極群の構造を簡単化して電極群の作製を簡単化することができる。
【００２６】
更に、本実施形態では、万一隔絶層（セパレータ２Ｄ）が破断しても、負極２Ｂと、負極３Ｂとが同極（負極）なので、短絡を防止することができると共に、電池反応に関与しない負極２Ｂと負極３Ｂとが対向する部分を、リチウムイオン二次電池においてはより軽い（薄い）負極を選択し、隔絶層の箇所数も１箇所に留めたので、エネルギー密度の低下を最小限に抑えることができる。
【００２７】
なお、本実施形態では、内側捲回群から連続するセパレータ２Ｄを内側捲回群の外周に少なくとも１周捲回して隔絶層を形成した例を示したが、外側捲回群から連続するセパレータを内側捲回群の外周に１周以上捲回して隔絶層を形成するようにしても類似の効果を期待することができる。また、セパレータ２Ｄの材質についても、ポリエチレンに限定されるものではなく、ポリプロピレンやこれらを層状に重ねたセパレータを用いるようにしてもよい。
【００２８】
また、本実施形態では、内側捲回群の最外周の電極（負極２Ｂ）と、外側捲回群の最内周の電極（負極３Ｂ）とが同極（負極）の電池を例示したが、同極（負極）に限定されるものではなく、異極となるようにすることで、隔絶層を介して電池反応が起きるので、電池のエネルギー密度の低下を抑制できる。また、隔絶層を介して正極同士が対向するように捲回してもよい。
【００２９】
更に、上記実施形態の電池では、正、負極の短絡によるガス発生現象が遅延されるだけでなく、例えば、過充電時の温度上昇などの現象も隔絶層により電池全体として遅延させることができる。また、外側捲回群で先に短絡が生じるときだけでなく、内側捲回群で先に短絡などが生じたときにも効果がある。
【００３０】
また、上記実施形態では、円筒型リチウムイオン二次電池を例示したが、これに限定されるものではなく、電池内でガス発生が起こり得る電池系、例えば、鉛蓄電池などにも適用可能である。
【００３１】
【実施例】
次に、上記実施形態に従って作製した実施例の円筒型リチウムイオン二次電池について説明する。なお、比較のために作製した比較例の電池についても併記する。
【００３２】
（実施例１）
下表１に示すように、実施例１では、隔絶層１が厚さ０．１ｍｍのＰＴＦＥシートで、内側捲回群２の最外周の電極及び外側捲回群３の最内周の電極が共に負極２Ｂ、３Ｂの電池を作製した。
【００３３】
【表１】

【００３４】
（実施例２）
表１に示すように、実施例２では、隔絶層が内側捲回群から連続するセパレータ（ＰＥ）２Ｄである以外は、実施例１と同様に電池を作製した。
【００３５】
（実施例３）
表１に示すように、実施例３では、外側捲回群３の最内周の電極が正極３Ａである以外は実施例１と同様に電池を作製した。
【００３６】
（実施例４）
表１に示すように、実施例４では、隔絶層が内側捲回群から連続するセパレータ（ＰＥ）２Ｄで、外側捲回群の最内周の電極が正極３Ａである以外は、実施例１と同様に電池を作製した。
【００３７】
（比較例１）
表１に示すように、比較例１では、隔絶層１を有さない電池を作製した。
【００３８】
（試験・評価）
次に、上述した実施例及び比較例のリチウムイオン二次電池に公称容量の２時間率を以て４．２Ｖ定電圧−定電流充電を４ｈ施し、満充電状態とした。これらを水平に寝かせて、電池缶９の直径と等しい直径のステンレス製半円筒状圧壊治具を油圧プレス機にて押し当てて、電池缶９の直径の１／２まで潰す圧壊による圧壊試験を実施した。この圧壊試験をそれぞれ５個の電池（ｎ＝５）で実施した。圧壊試験の試験結果を下表２に示す。なお、安全弁のみが作動した場合を「破裂なし」とし、それ以外の部分（電池蓋８のカシメ部や電池缶９底）がはずれたり裂けたりした場合を「破裂あり」として計数した。
【００３９】
【表２】

【００４０】
表２に示すように、実施例の電池では、いずれも比較例の電池に対し破裂数が少なくなり、電池缶８の変形に対する安全性が向上することが示された。これは、実施例の電池において、電池内の電極群の短絡が内部の隔絶層により段階的に起こるようになり、単位時間当たりの電池缶８内でのガス発生量を低減できることによるものである。ここでは実施例の電池の効果を確認する試験として、条件として十分に過酷であると想定される短時間に大きな面積で短絡が起きる電池の大きさに対し比較的大きな圧壊治具で圧壊試験を行ったが、実施例の電池の安全性向上の対象事象を限定するものではない。
【００４１】
【発明の効果】
以上説明したように、本発明の第１の態様によれば、外からの応力付与などにより電池が変形して正極と負極とが押しつけられると、まず隔絶層に外接する捲回群で短絡が起こるが、同心円状に配置された捲回群同士が隔絶層により隔絶されて隔絶されているため、隔絶層に内接する捲回群での短絡を遅延することができるので、捲回群同士が即座に短絡するのを防止でき、隔絶層を有さない電極群の場合に比べて、短絡に起因するガス発生現象が遅延され、電池全体として電池内で発生するガスの発生速度を低下させることができ、また、隔絶層を、隔絶層に内接又は外接する捲回群から連続するセパレータとしたので、電池部品数を削減することができると共に、捲回群の構造を簡単化することができる、という効果を得ることができる。また、本発明の第２の態様によれば、外からの応力付与などにより電池が変形して正極と負極とが押しつけられると、まず隔絶層に外接する捲回群で短絡が起こるが、捲回群が該捲回群を隔絶する隔絶層によって同心円状かつ少なくとも２以上に隔絶されているため、隔絶層に内接する捲回群での短絡を遅延することができるので、捲回群が即座に短絡するのを防止でき、隔絶層を有さない捲回群の場合に比べて、短絡に起因するガス発生が遅延され、電池全体として内圧上昇速度が低下させることができると共に、隔絶層に内接する捲回群の最外周の電極と、隔絶層に外接する捲回群の最内周の電極とを同極としたので、隔絶層が破断しても短絡が生じないため、安全性を確保することができる、という効果を得ることができる。
【図面の簡単な説明】
【図１】本発明が適用可能な第１の実施の形態の電極群を模式的に示し、（Ａ）は外観斜視図、（Ｂ）は断面図である。
【図２】本発明が適用可能な第２の実施の形態の電極群を模式的に示す断面図である。
【図３】第１の実施の形態の電池作製過程を模式的に示す外観斜視図であり、（Ａ）は電池缶へ挿入前の電極群、（Ｂ）は電池缶へ挿入後の電極群を示す。
【符号の説明】
１隔絶層
２内側捲回群（捲回群の一部）
２Ａ、３Ａ正極
２Ｂ、３Ｂ負極
２Ｃ、２Ｄ、３Ｃセパレータ
３外側捲回群（捲回群の一部）
１０電極群（捲回群）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wound cylindrical battery, and more particularly to a wound cylindrical battery having a wound group in which positive and negative electrodes are wound through a separator.
[0002]
[Prior art]
Conventionally, a wound-type cylindrical battery has a wound group in which a strip-shaped positive and negative electrode, in which a tab for current collection is led out via a separator, is wound in a bottomed cylindrical battery container as an electrolyte. Infiltrated and contained. In such a wound cylindrical battery, in order to cope with an increase in internal pressure caused by battery deformation due to stress from the outside of the battery, for example, Japanese Patent Laid-Open No. 7-192712 discloses gas in the battery outside the battery. In other words, a technology is disclosed in which a safety valve that is opened to the outside or a membrane having a mesh-like opening is provided between the battery lid and the safety valve. According to this technique, when the battery internal pressure rises, the safety valve is operated to release the gas to suppress the battery internal pressure rise, and the membrane prevents the solid content in the battery from scattering when the gas is released.
[0003]
[Problems to be solved by the invention]
However, as typified by recent lithium-ion secondary batteries, the energy density of the battery is high, the active material used in the battery system can cause a thermal runaway reaction, and the electrolyte also contains flammable organic electrolysis. In the case of a battery that uses a liquid, when the battery is deformed as described above, the internal pressure increase rate of the battery exceeds the internal pressure release speed due to the operation of the safety valve due to rapid gas generation due to evaporation of the electrolyte, etc. There was a phenomenon that the internal pressure of the battery container increased extremely.
[0004]
An object of the present invention is to provide a wound cylindrical battery excellent in safety in view of the above-mentioned case.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problem, a first aspect of the present invention is a wound cylindrical battery having a wound group in which a positive electrode and a negative electrode are wound through a separator. It is characterized in that it is concentrically separated by at least two or more isolating layers that isolate the group, and the isolating layer is a separator continuous from a wound group that is inscribed or circumscribed to the isolating layer .
[0006]
In the first aspect , when the battery is deformed by applying stress from the outside and the positive electrode and the negative electrode are pressed, a short circuit first occurs in the wound group that circumscribes the isolation layer. As the concentric layers are isolated by at least two or more confined layers, the short circuit in the wound group inscribed in the isolated layer can be delayed, so that the wound group can be prevented from being short-circuited immediately. Compared to the wound group having no isolation layer, the gas generation due to the short circuit is delayed, and the internal pressure increase rate of the battery as a whole can be reduced. Moreover, since the isolation layer is a separator that is continuous from the wound group inscribed or circumscribed to the isolated layer, the number of battery parts can be reduced and the structure of the wound group can be simplified. In this aspect, if the outermost electrode of the wound group inscribed in the isolated layer and the innermost electrode of the wound group inscribed in the isolated layer have the same polarity, even if the isolated layer breaks, a short circuit occurs. Since it does not occur, safety can be ensured. Conversely, if the outermost electrode of the wound group inscribed in the isolated layer is different from the innermost electrode of the wound group inscribed in the isolated layer, a cell reaction occurs through the isolated layer. The decrease in the energy density of the battery due to the isolation layer can be compensated.
[0007]
In order to solve the above-mentioned problem, a second aspect of the present invention is a wound cylindrical battery having a wound group in which a positive electrode and a negative electrode are wound through a separator. An outermost electrode of the wound group that is concentrically separated by an isolated layer that isolates the wound group and is at least two or more inscribed, and an innermost circumference of the wound group that circumscribes the isolated layer The electrode is the same polarity. In the second aspect, as in the first aspect, when the battery is deformed by applying stress from the outside and the positive electrode and the negative electrode are pressed, a short circuit first occurs in the wound group circumscribing the isolation layer. Since the wound group is concentrically separated by at least two or more isolated layers that isolate the wound group, the short circuit in the wound group inscribed in the isolated layer can be delayed. Compared to the wound group that does not have an isolation layer, it is possible to prevent a short circuit from occurring immediately, the gas generation due to the short circuit is delayed, the internal pressure increase rate can be reduced as a whole battery, and the isolation layer Since the outermost electrode of the wound group inscribed in the electrode and the innermost electrode of the wound group inscribed in the isolated layer have the same polarity, no short circuit will occur even if the isolated layer breaks. Can be secured.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, with reference to the drawings, a first embodiment in which the present invention is applied to a cylindrical lithium ion secondary battery will be described in accordance with a battery manufacturing procedure.
[0009]
(Production of electrodes)
A powder of lithium manganese composite oxide, a carbon material for a conductive material, and polyvinylidene fluoride (PVDF) are mixed so that a solid content ratio (weight ratio) is 90: 5: 5, and N-methylpyrrolidone (NMP) is mixed. ) Was stirred to obtain a positive electrode slurry. This positive electrode slurry was uniformly applied to the aluminum foil of the current collecting base and dried, and the aluminum foil portion was cut out in a comb-like shape leaving a tab for collecting current, and pressed to form a predetermined thickness. This was slit to a size matched to the bottomed cylindrical battery can, and further divided into two or more in the winding direction to obtain two or more strip-shaped positive electrodes.
[0010]
Amorphous carbon powder and polyvinylidene fluoride (PVDF) were mixed so that the solid content ratio (weight ratio) was 90:10, and the binder solution dissolved in N-methylpyrrolidone (NMP) was stirred to prepare a negative electrode I got a slurry. This negative electrode slurry is uniformly applied to the copper foil of the current collecting substrate, dried, and the copper foil portion is cut out in a comb-like shape, leaving the tabs for collecting current in the same manner as the positive electrode, and pressed to a predetermined thickness. Molded. This was slit to a size matched to the battery can, and further divided into two or more in the winding direction to obtain two or more strip-shaped negative electrodes.
[0011]
(Production of electrode group)
As shown in FIG. 1 (A), the produced positive and negative electrodes were placed through a polyethylene thin film separator having a thickness of 40 μm so that the outermost periphery becomes a negative electrode around a polypropylene core 4. The inner winding group 2 was produced. Note that a positive electrode tab and a negative electrode tab (not shown) were positioned on opposite sides. Thereafter, a PTFE (polytetrafluoroethylene) sheet having a width of about 1% larger than the width of the inner winding group 2 and a thickness of about 0.1 mm is wound around the outer side of the inner winding group 2 for at least one turn. 1 was formed. Further, similarly to the production of the inner winding group 2, the outer winding group 3 is produced by winding the positive electrode and the negative electrode to the outside of the isolation layer 1 through the separator so that the innermost circumference is a negative electrode, An electrode group 10 was produced in which the inner wound group 2 and the outer wound group 3 were isolated by the isolation layer 1 so as to be concentric. In addition, the separator was wound on the outermost circumference of the outer winding group 3 for one or more rounds.
[0012]
Therefore, the electrode group 10 has the inner winding group 2 in which the positive electrode and the negative electrode are wound around the shaft core 4 through the separator so that the outermost periphery becomes the negative electrode. A PTFE sheet having a width larger than the width of the inner winding group 2 is wound outside the inner winding group 2 to form the isolation layer 1. Outside the isolation layer 1, an outer winding group 3 in which a positive electrode and a negative electrode are wound through a separator so that the innermost periphery is a negative electrode is disposed concentrically. For this reason, in the electrode group 10, the inner winding group 2 that is inscribed in the isolation layer 1 and the outer winding group 3 that is in contact with the isolation layer 1 are isolated by the isolation layer 1.
[0013]
As shown in FIG. 1B, the outermost electrode of the inner winding group 2 inscribed in the isolation layer 1 is a negative electrode 2B. A positive electrode 2A is disposed inside the negative electrode 2B via a separator 2C that is longer in the winding direction than the negative electrode 2B, and another separator 2C is disposed inside the positive electrode 2A. The innermost electrode of the outer winding group 3 that circumscribes the isolation layer 1 is a negative electrode 3B. A positive electrode 3A is disposed outside the negative electrode 3B via a separator 3C that is longer in the winding direction than the negative electrode 3B, and another separator 3C is disposed outside the positive electrode 3A. Therefore, the outermost electrode of the inner winding group 2 and the innermost electrode of the outer winding group 3 have the same polarity (negative electrode).
[0014]
(Battery assembly)
As shown in FIG. 3A, the tabs of the

positive electrodes

2A and 3A are formed on the bottom surface of the aluminum-made disc-shaped positive electrode collector column 6, and the

negative electrodes

2B and 3B are formed on the bottom surface of the disc-shaped negative electrode collector column 7 made of copper. Each tab was ultrasonically welded. A negative electrode lead plate (not shown) was welded to the surface opposite to the bottom surface of the negative electrode collector column 7. As shown in FIG. 3 (B), this electrode group 10 is inserted into a bottomed cylindrical battery can 9 (size φ40 mm × 145 mm) in which nickel is plated on iron, and a negative electrode lead plate is placed on the bottom of the battery can 9. The negative electrode collector column 7 is resistance-welded through the lead plate, and the positive electrode collector column 6 is connected to the battery cover 8 made of aluminum having a safety valve (rupture valve) in which a horseshoe-shaped thin portion is formed on the metal thin film through the lead plate. Ultrasonic welding.
[0015]
An electrolyte in which lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a mixed solvent of ethyl carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a dry air atmosphere having a dew point of −40 ° C. or less in the battery. The solution was poured, and the battery lid 8 and the battery can 9 were caulked and sealed through a gasket made of PFA resin to obtain a cylindrical lithium ion secondary battery. This battery was repeatedly charged and discharged several times at a 2-hour rate of the nominal capacity to saturate the irreversible capacity of the carbon material and to give a battery function. At this time, the final voltage for charging was 4.2V, and the final voltage for discharging was 2.7V.
[0016]
(Function)
Next, the operation and the like of the cylindrical lithium ion secondary battery of this embodiment will be described.
[0017]
In the cylindrical lithium ion secondary battery of this embodiment, when stress is applied from the outside of the battery, the battery is deformed and the

positive electrodes

2A, 3A and the

negative electrodes

2B, 3B are pressed, and a short circuit occurs in the outer winding group 3. At this time, since the electrode group 10 is concentrically isolated by the isolation layer 1, no short circuit occurs at the same time on the inner winding group 2 side (then, a short circuit occurs on the inner winding group 2 side depending on the degree of stress). Sometimes). For this reason, it is possible to prevent the entire electrode group 10 from being short-circuited immediately (short circuit occurs in a stepwise manner), and the gas generation phenomenon due to the short-circuit is delayed compared to the case of the electrode group not having the isolation layer 1, As a whole battery, the generation rate of gas generated in the battery is reduced, and it becomes possible to gently release the gas from the safety valve. In other words, since the gas generation rate is less likely to exceed the internal pressure release rate (cleavage rate) of the safety valve, the probability of occurrence of battery behavior such as an extreme increase in internal pressure in the battery can 9 can be reduced. Safety can be ensured.
[0018]
In the present embodiment, even if the isolation layer 1 is broken, since the negative electrode 2B and the negative electrode 3B are the same polarity (negative electrode), a short circuit through the isolation layer 1 can be prevented, and the battery In the lithium ion secondary battery, the lighter (thin) negative electrode is selected as the portion where the negative electrode 2B and the negative electrode 3B that do not participate in the reaction are opposed, and the number of the isolation layers 1 is also kept at one location. Degradation can be minimized.
[0019]
In the present embodiment, the PTFE sheet is exemplified for the isolation layer 1, but the present invention is not limited to this. For example, a polyethylene sheet may be used. Further, the present invention is not limited to the thickness and width of the isolation layer 1. For example, the thickness may be about 0.05 mm, and the width is about 2% longer than the width of the electrode group 10. May be. Furthermore, although the battery which has one isolation layer 1 was illustrated, the isolation layer 1 can be provided in arbitrary places. However, from the point of energy density, the number of the isolated layers 1 is preferably 1 or 2.
[0020]
In the present embodiment, the outermost electrode (negative electrode 2B) of the inner winding group 2 and the innermost electrode (negative electrode 3B) of the outer winding group 3 are illustrated as batteries having the same polarity (negative electrode). However, it is not limited to the same polarity, and may be different. Further, when the battery system is different, the battery systems may be wound so that the positive electrodes face each other through the isolation layer 1.
[0021]
(Second Embodiment)
Next, a second embodiment in which the present invention is applied to a wound cylindrical battery will be described. In this embodiment, a separator that is continuous from the separators of the inner winding group is used for the isolation layer. In the present embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, description thereof is omitted, and only different portions will be described.
[0022]
As shown in FIG. 2, the positive electrode 2A and the negative electrode 2B were wound around a shaft core so as to have the outermost periphery of the negative electrode 2B through a separator 2D longer than the separator 2C, thereby producing an inner winding group. The separator 2D continuous from the inner winding group was wound at least once around the outer side of the inner winding group in a concentric manner to form an isolated layer. Thereafter, outside the separator 2D (isolation layer), the positive electrode 3A and the negative electrode 3B are wound through the separator 3C so that the innermost circumference becomes the negative electrode 3B, thereby producing an outer winding group. An electrode group was produced in which the outer wound group was isolated concentrically by the isolation layer.
[0023]
Accordingly, the electrode group has an inner winding group in which the positive electrode 2A and the negative electrode 2B are wound around the shaft core so that the outermost periphery becomes the negative electrode 2B through the separator 2D longer in the winding direction than the separator 2C. is doing. On the outside of the inner winding group, a separator 2D continuous from the inner winding group is wound at least once to form an isolation layer. Outside the isolation layer, an outer winding group in which the positive electrode 3A and the negative electrode 3B are wound through the separator 3C is arranged concentrically so that the innermost electrode of the outer winding group becomes the negative electrode 3B. Yes. For this reason, in the electrode group, the inner winding group inscribed in the isolation layer and the outer winding group in contact with the isolation layer are isolated by the isolation layer. The outermost electrode of the inner winding group inscribed in the isolation layer is the negative electrode 2B, and the innermost electrode of the outer winding group in contact with the isolation layer is the negative electrode 3B. Therefore, the outermost electrode of the inner winding group and the innermost electrode of the outer winding group have the same polarity (negative electrode).
[0024]
In the cylindrical lithium ion secondary battery of the present embodiment, even when stress is applied from the outside of the battery and the battery is deformed and the

positive electrodes

2A, 3A and the

negative electrodes

2B, 3B are pressed, the electrode group is concentrically formed by the isolation layer and Since the two electrodes are isolated from each other, it is possible to prevent the entire electrode group from being short-circuited immediately (short-circuiting occurs in stages), and the gas generation phenomenon due to the short-circuit is delayed, and the gas generated in the battery as a whole battery The generation rate of can be reduced. Therefore, as in the first embodiment, the gas generation rate is less likely to exceed the internal pressure release rate by the safety valve, and the probability of occurrence of battery behavior such as an extreme increase in internal pressure of the battery can 9 can be reduced.
[0025]
In this embodiment, since the separator 2D continuous from the inner winding group is wound around the outer periphery of the inner winding group at least once to form the isolation layer, another member for the isolation layer becomes unnecessary. The structure of the electrode group can be simplified and the production of the electrode group can be simplified.
[0026]
Furthermore, in this embodiment, even if the isolation layer (separator 2D) breaks, the negative electrode 2B and the negative electrode 3B are the same polarity (negative electrode), so that a short circuit can be prevented and the battery reaction is not involved. In the lithium ion secondary battery, the lighter (thin) negative electrode is selected as the portion where the negative electrode 2B and the negative electrode 3B face each other, and the number of isolated layers is also kept at one, so that the decrease in energy density is minimized. Can be suppressed.
[0027]
In the present embodiment, the separator 2D continuous from the inner winding group is wound around the outer periphery of the inner winding group to form an isolation layer. However, the separator continuous from the outer winding group is formed. A similar effect can be expected even if the isolated layer is formed by winding one or more rounds on the outer periphery of the inner winding group. Further, the material of the separator 2D is not limited to polyethylene, and polypropylene or a separator in which these layers are stacked may be used.
[0028]
In the present embodiment, the outermost electrode (negative electrode 2B) of the inner winding group and the innermost electrode (negative electrode 3B) of the outer winding group are illustrated as batteries having the same polarity (negative electrode). It is not limited to the same polarity (negative electrode), but by making the electrodes different from each other, a battery reaction occurs through the isolation layer, so that a decrease in the energy density of the battery can be suppressed. Moreover, you may wind so that positive electrodes may oppose through an isolation layer.
[0029]
Further, in the battery of the above embodiment, not only the gas generation phenomenon due to the short circuit of the positive and negative electrodes is delayed, but also the phenomenon such as the temperature rise at the time of overcharging can be delayed as a whole battery by the isolation layer. Moreover, it is effective not only when a short-circuit occurs first in the outer winding group but also when a short-circuit occurs first in the inner winding group.
[0030]
Moreover, in the said embodiment, although the cylindrical lithium ion secondary battery was illustrated, it is not limited to this, It is applicable also to battery systems which can generate gas within a battery, for example, a lead storage battery etc. .
[0031]
【Example】
Next, the cylindrical lithium ion secondary battery of the example produced according to the said embodiment is demonstrated. In addition, it describes together about the battery of the comparative example produced for the comparison.
[0032]
(Example 1)
As shown in Table 1 below, in Example 1, the isolation layer 1 is a PTFE sheet having a thickness of 0.1 mm, and the outermost electrode of the inner winding group 2 and the innermost electrode of the outer winding group 3 are Both batteries of

negative electrodes

2B and 3B were produced.
[0033]
[Table 1]

[0034]
(Example 2)
As shown in Table 1, in Example 2, a battery was produced in the same manner as in Example 1 except that the isolation layer was a separator (PE) 2D continuous from the inner winding group.
[0035]
Example 3
As shown in Table 1, in Example 3, a battery was fabricated in the same manner as in Example 1 except that the innermost electrode of the outer winding group 3 was the positive electrode 3A.
[0036]
Example 4
As shown in Table 1, in Example 4, Example 1 except that the isolation layer is a separator (PE) 2D continuous from the inner winding group, and the innermost electrode of the outer winding group is the positive electrode 3A. A battery was prepared in the same manner as described above.
[0037]
(Comparative Example 1)
As shown in Table 1, in Comparative Example 1, a battery without the isolation layer 1 was produced.
[0038]
(Test / Evaluation)
Next, 4.2 V constant voltage-constant current charging was applied to the lithium ion secondary batteries of the above-described Examples and Comparative Examples for 2 hours at a 2-hour rate of the nominal capacity to obtain a fully charged state. Laying them horizontally, pressing a stainless steel semi-cylindrical crushing jig with a diameter equal to the diameter of the battery can 9 with a hydraulic press machine, and performing a crushing test by crushing to crush to half the diameter of the battery can 9 Carried out. This crush test was carried out with 5 batteries (n = 5) each. The test results of the crush test are shown in Table 2 below. The case where only the safety valve was operated was regarded as “no rupture”, and the case where the other parts (the crimped portion of the battery lid 8 or the bottom of the battery can 9) were detached or torn was counted as “with rupture”.
[0039]
[Table 2]

[0040]
As shown in Table 2, it was shown that in the batteries of the examples, the number of ruptures decreased compared to the battery of the comparative example, and the safety against deformation of the battery can 8 was improved. This is because, in the battery of the example, the short circuit of the electrode group in the battery occurs stepwise by the internal isolation layer, and the amount of gas generated in the battery can 8 per unit time can be reduced. . Here, as a test for confirming the effect of the battery of the example, a crush test is performed with a relatively large crushing jig for the size of the battery in which a short circuit occurs in a large area in a short time that is assumed to be sufficiently severe as a condition. Although it went, it does not limit the target event of the safety | security improvement of the battery of an Example.
[0041]
【The invention's effect】
As described above, according to the first aspect of the present invention , when the battery is deformed by applying stress from the outside and the positive electrode and the negative electrode are pressed, a short circuit is first generated in the wound group circumscribing the isolation layer. However, since the wound groups arranged concentrically are separated from each other by the isolation layer, the short circuit in the wound group inscribed in the isolation layer can be delayed. Compared to an electrode group that does not have an isolation layer, it can prevent a short circuit from occurring immediately, delaying the gas generation phenomenon caused by the short circuit, and reducing the rate of gas generation in the battery as a whole. In addition, since the isolation layer is a separator continuous from the wound group inscribed or circumscribed to the isolated layer, the number of battery parts can be reduced and the structure of the wound group can be simplified. possible, the effect can be obtained that Further, according to the second aspect of the present invention, when the battery is deformed due to external stress application and the positive electrode and the negative electrode are pressed, a short circuit occurs first in the wound group circumscribing the isolation layer. Since the time group is concentric and separated by at least two or more by the isolation layer that isolates the wound group, a short circuit in the wound group inscribed in the isolated layer can be delayed, so that the wound group is immediately Compared to the case of a wound group that does not have an isolation layer, the gas generation due to the short circuit is delayed, and the internal pressure rise rate can be reduced as a whole battery, and the isolation layer Since the innermost electrode of the wound group that is inscribed and the innermost electrode of the wound group that is circumscribed to the isolation layer have the same polarity, even if the isolation layer breaks, a short circuit does not occur. The effect that it can ensure can be acquired.
[Brief description of the drawings]
FIG. 1 schematically shows an electrode group according to a first embodiment to which the present invention can be applied, in which (A) is an external perspective view and (B) is a cross-sectional view.
FIG. 2 is a cross-sectional view schematically showing an electrode group according to a second embodiment to which the present invention is applicable.
FIGS. 3A and 3B are external perspective views schematically showing a battery manufacturing process according to the first embodiment, in which FIG. 3A is an electrode group before being inserted into a battery can, and FIG. 3B is an electrode group after being inserted into the battery can; Indicates.
[Explanation of symbols]
1 isolated layer 2 inner wound group (part of wound group)
2A,

3A Positive electrode

2B, 3B

Negative electrode

2C, 2D, 3C Separator 3 Outer winding group (part of winding group)
10 Electrode group (winding group)

Claims

In a wound cylindrical battery having a wound group in which a positive electrode and a negative electrode are wound through a separator, the wound group is concentrically separated by at least two or more by a separating layer that separates the wound group. The wound cylindrical battery is characterized in that the isolated layer is a separator continuous from a wound group inscribed or circumscribed on the isolated layer .

In a wound cylindrical battery having a wound group in which a positive electrode and a negative electrode are wound through a separator, the wound group is concentrically separated by at least two or more by a separating layer that separates the wound group. A wound cylindrical battery characterized in that the outermost electrode of the wound group inscribed in the isolated layer and the innermost electrode of the wound group inscribed in the isolated layer have the same polarity .

Winding according to claim 1, characterized in that the electrodes of the outermost periphery of the winding group to be inscribed in the separator layer, and the innermost electrode winding group circumscribing the separator layer is a same polarity Type cylindrical battery.

Winding according to claim 1 in which the electrodes of the outermost periphery of the winding group to be inscribed in the separator layer, and the innermost electrode winding group circumscribing said shielding layer is characterized in that it is a heteropolar Type cylindrical battery.