JP4631234B2

JP4631234B2 - Cylindrical lithium-ion battery

Info

Publication number: JP4631234B2
Application number: JP2001251171A
Authority: JP
Inventors: 賢治中井; 健介弘中
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Shin Kobe Electric Machinery Co Ltd
Priority date: 2001-08-22
Filing date: 2001-08-22
Publication date: 2011-02-16
Anticipated expiration: 2021-08-22
Also published as: JP2003059539A

Description

【０００１】
【発明の属する技術分野】
本発明は、円筒型リチウムイオン電池に関し、特に、所定圧で内圧を開放する内圧開放機構を有する電池容器内に、正極活物質を含む正極活物質層と正極集電体を有する帯状の正極と、負極活物質に炭素材を用いた負極活物質層と負極集電体を有する帯状の負極とをセパレータを介して軸芯を中心に３０回以上捲回した電極捲回群を備え、前記軸芯の両端が正極集電部材及び負極集電部材に支持又は固定され電解液に浸潤された円筒型リチウムイオン電池であって、実質放電容量が７Ａｈ以上の円筒型リチウムイオン電池に関する。
【０００２】
【従来の技術】
リチウムイオン二次電池は、高エネルギー密度であるメリットを活かして、主にＶＴＲカメラやノートパソコン、携帯電話等のポータブル機器の電源に使用されている。この電池の内部構造は、通常以下に示されるような捲回式とされている。電極は、正極及び負極共に活物質が金属箔に塗着された帯状であり、セパレータを挟んでこれら両電極が直接接触しないように軸芯を中心にして断面が渦巻状に捲回され、捲回群を形成している。この捲回群が円筒状の電池缶に収納され、電解液注液後、封口されている。電池缶内では、捲回群は軸芯に支持又は固定されている。一般的な円筒型リチウムイオン二次電池の外形寸法は直径１８ｍｍ、高さ６５ｍｍであり、１８６５０型と呼ばれ、小型民生用リチウムイオン電池として広く普及している。
【０００３】
一方、自動車産業界においては環境問題に対応すべく、排出ガスのない、動力源を完全に電池のみとした電気自動車の開発や内燃機関エンジンと電池との両方を動力源とするハイブリッド（電気）自動車の開発が加速され、一部実用段階に到達している。電気自動車の電源となる二次電池には当然高出力、高エネルギーが得られる特性が要求され、この要求を満足する二次電池としてリチウムイオン電池が注目されている。
【０００４】
しかしながら、高エネルギー密度のリチウムイオン二次電池とはいえ、電気自動車に使用する場合の大電流放電、大電流充電に耐え得るためには、電極構造のみならず、電極から電池端子への集電構造にも工夫が必要となる。例えば、特開平第８−１１５７４４号公報、特開平第９−５５２１３号公報、特開平第９−９２２３８号公報、特開平第９−９２２４１号公報、特開平第９−９２３３５号公報には、電極の集電体である金属箔を活物質層から延出させ、そのまま、又は短冊状に加工して集電リング等の接続部に溶接等により接続して、一旦接続部を介して電池端子へと導くリード接続方式を採用し、大電流放電、大電流充電時の電圧降下（ｉＲドロップ）を低減させる技術が提案されている。これらの公報にも開示されているように、大電流放電、大電流充電時の電圧降下を低減させるためには、円筒型リチウムイオン電池内にリード接続部を収納するためのスペースが必要となる。
【０００５】
ところで、電池を電気自動車に搭載するにあたっては、電気自動車ユーザーの多様な要望に応えるために、車体設計、特に電池のパッケージングに自由度を持たせることが好ましい。そのためには、搭載電池の占める空間体積を最小にする必要があり、その最も有効な手段は電池の体積あたりのエネルギー密度（Ｗｈ／ｄｍ^３）を最大にすることである、といわれている。すなわち、電気自動車に搭載される電池は、通常複数の単電池が並列、直列に接続されてモジュールを形成しているが、単電池の体積あたりのエネルギー密度を大きくすることが、モジュールサイズの低減には効果的である。
【０００６】
【発明が解決しようとする課題】
しかしながら、体積エネルギー密度を大きくしても、電池の長さに対する直径の比（直径／長さ）によっては、電極捲回群の軸芯への保持力が低下するので、電気自動車に搭載した場合に加わる振動により電池内部の捲回群の移動が起こり、電極と接続部材とを電気的につなげるリードが切断する。また、概ね７Ａｈ以上の容量を有する電池においては、過充電状態等の電池異常時に、大電流充電又は大電流放電状態が維持され、非水電解液と活物質との化学反応により電池容器内で急激かつ大量のガスが発生し、電池容器の内圧を上昇させる。一般に、リチウム二次電池では、この内圧上昇を防止するために、電池容器に所定圧で内圧を開放する内圧開放機構を有しているが、電池の直径／長さの比によって過充電時の電池挙動が異なり、内圧が上昇するので、安全性が低下する。
【０００７】
本発明は上記事案に鑑み、耐振性が高く、かつ安全性が高い円筒型リチウムイオン電池を提供することを課題とする。
【０００８】
【課題を解決するための手段】
本発明は、上記課題を解決するために、所定圧で内圧を開放する内圧開放機構を有する電池容器内に、正極活物質を含む正極活物質層と正極集電体を有する帯状の正極と、負極活物質に炭素材を用いた負極活物質層と負極集電体を有する帯状の負極とをセパレータを介して軸芯を中心に３０回以上捲回した電極捲回群を備え、前記軸芯の両端が正極集電部材及び負極集電部材に支持又は固定され電解液に浸潤された円筒型リチウムイオン電池であって、実質放電容量が７Ａｈ以上の円筒型リチウムイオン電池において、前記電池容器の直径をＤ（ｍｍ）とし、長さをＬ（ｍｍ）としたとき、前記長さＬに対する直径Ｄの比Ｄ／Ｌを０．４乃至０．６としたものである。
【０００９】
本発明では、大きな体積エネルギー密度を確保するために正負両極がセパレータを介して軸芯を中心に３０回以上捲回された電極捲回群を有している。電池缶内では、電極捲回群は軸芯に支持された状態となる。電極捲回群の長さに対して電極捲回群の直径が大きいと、電池に振動が加わったときに軸芯が電極捲回群を支持しきれなくなり電極捲回群が捲回位置から移動するので、電極と接続部材との電気的接続部が切断され電池の機能を損なう。また、逆に電極捲回群の直径に対して長さが大きいと、電池異常時に電池容器内で発生する急激かつ大量のガスが電池内を移動し、内圧開放機構を通じて電池外に開放されるまでに長時間を要するので、電池の内圧が上昇して安全性が低下する。本発明によれば、電池容器の直径をＤ（ｍｍ）とし、長さをＬ（ｍｍ）としたとき、長さＬに対する直径Ｄの比Ｄ／Ｌを０．４乃至０．６とすることで、電極捲回群を確実に支持して電極捲回群の移動を防止することができると共に、過充電時に発生したガスを速やかに電池外に開放することができるので、耐振性が高く、かつ安全性が高い円筒型リチウムイオン電池を実現することができる。
【００１０】
この場合において、正極活物質をリチウムマンガン複酸化物とすれば、電池異常時の電解液との反応が穏やかなためガスの発生を低減することができるので、安全性を高めることができる。また、電池の長手方向両端部に内圧開放機構を配設すれば、電池異常時に電池内で発生したガスを電池の両端部から電池外に開放することができるので、安全性を高めることができる。
【００１１】
【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適用した円筒型リチウムイオン電池の第１の実施の形態について説明する。
【００１２】
＜正極及び負極の作製＞
図１に示すように、本実施形態に係る円筒型リチウムイオン電池２０は、正極集電体Ｗ１の両面に正極活物質層Ｗ２が形成された帯状の正極と、負極集電体Ｗ３の両面に負極活物質層Ｗ４が形成された帯状の負極とが帯状のセパレータＷ５を介して巻き芯（軸芯）１７を中心に断面渦巻状に捲回された捲回群（電極捲回群）Ｗを備えている。
【００１３】
正極集電体Ｗ１は厚さ２０μｍのアルミニウム箔である。正極活物質層Ｗ２は、正極活物質としてのリチウムコバルト複酸化物であるコバルト酸リチウム又はリチウムマンガン複酸化物であるマンガン酸リチウムと、導電助剤のグラファイト及びアセチレンブラック（電気化学工業（株）製、商品名デンカブラック）と、バインダー（結着剤）のポリフッ化ビニリデン（ＰＶＤＦ）と、電解液と、を構成物質としている。負極集電体Ｗ３は厚さ１０μｍの銅箔である。負極活物質層Ｗ４は、リチウムイオンを電極反応種とし充電、放電に伴いリチウムイオンを吸蔵、放出する負極活物質の非晶質炭素又は黒鉛炭素と、導電材の気相成長炭素繊維（昭和電工（株）製、商品名ＶＧＣＦ）（以下、ＣＦと略記する。）と、バインダーのＰＶＤＦと、電解液と、を構成物質としている。
【００１４】
正極活物質層Ｗ２を作製するには、マンガン酸リチウム（平均粒径約１０〜２０μｍ）又はコバルト酸リチウム（平均粒径約１０〜２０μｍ）と、グラファイト（平均粒径約５μｍ）及びアセチレンブラックと、ＰＶＤＦとを８５：８：２：５の質量比で混合し、そこへ分散溶媒となるＮ−メチル−２−ピロリドン（ＮＭＰ）を適量加え、十分に混練、分散させ、スラリー状にする。この混練物をロールからロールへの転写（ロール・ツー・ロール転写）で正極集電体Ｗ１の両面が実質上均等かつ同じ厚さに塗着し、乾燥させた後、プレスにより正極厚さＴ_Ｐが正極集電体を含めて２３１±２μｍ又は１０３±２μｍとなるまで圧縮し、正極活物質層Ｗ２を得る。正極活物質層Ｗ２の密度は２．６５ｇ／ｃｍ^３である。ただし、この段階では電解液を含んではいない。正極活物質層Ｗ２を作製した後、後述する所定の幅Ｗ_Ｐ、所定の長さＬ_Ｐに裁断して帯状の正極を得た。
【００１５】
一方、負極活物質層Ｗ４を作製するには、平均粒径５〜２０μｍの非晶質炭素（呉羽化学工業（株）製、商品名カーボトロン）又はメソフェーズ系球状黒鉛（川崎製鉄（株）製、商品名ＫＭＦＣ）と、ＣＦと、ＰＶＤＦとを８７．６：４．８：７．６の質量比で混合し、そこへ分散溶媒となるＮＭＰを適量加え、十分に混練、分散させ、スラリー状にする。この混練物をロール・ツー・ロール転写で負極集電体Ｗ３の両面が実質上均等かつ同じ厚さに塗着し、乾燥させた後、プレスにより負極厚さＴ_Ｎが負極集電体を含めて７３〜２０１±２μｍとなるまで圧縮し、負極活物質層Ｗ４を得る。負極活物質層Ｗ４の密度は０．９８ｇ／ｃｍ^３又は１．４ｇ／ｃｍ^３である。この密度は、負極活物質層Ｗ４中の空隙率（負極活物質層Ｗ４全体に対する電解液が充填される空孔の割合）が約３５％となるように決定した。ただし、この段階では電解液を含んではいない。負極活物質層Ｗ４を作製した後、後述する所定の幅Ｗ_Ｎ、所定の長さＬ_Ｎに裁断して帯状の負極を得た。なお、幅Ｗ_Ｎは、正負極を捲回したときに正極活物質層Ｗ２が負極活物質層Ｗ４からはみ出さないように、幅Ｗ_Ｐに対して６ｍｍ大きくし、かつ、長さＬ_Ｎは長さＬ_Ｐに対して１８ｃｍ大きくした。また、負極がセパレータからはみ出すことがないように、セパレータの幅は幅Ｗ_Ｎに対して６ｍｍ大きくした。
【００１６】
＜電池の作製＞
直径Ｄ_Ｓの巻き芯１７の周囲に、正極、負極の間に厚さＴ_Ｓが４０μｍの微多孔性のポリエチレン製セパレータＷ５を介して捲回数Ｎ_Ｗで捲回して直径Ｄ_Ｗの捲回群Ｗを得た。捲回群Ｗの両端に正極集電リング１０、負極集電リング１１を配置し、各集電リング周縁にはそれぞれ正極集電体Ｗ１、負極集電体Ｗ３を溶接した。正極集電リング１０、負極集電リング１１はそれぞれ正極集電リング支え８、負極集電リング支え９を介して巻き芯１７の端部に固定してある。この集電リング付き捲回群Ｗを、負極集電リング１１側が缶底側になるように電池缶（電池容器）１６に挿入し、そして負極集電リング１１に予め溶接させておいた負極リード板１４を電池缶１６に溶接する。その際、負極集電リング１１と電池缶１６との間に、捲回群Ｗを固定するために負極集電リングスペーサ７を配置する。また、正極集電リング１０上面には、正極リード板Ｂ１３の一端を予め溶接し他端を自由端としておく。
【００１７】
一方、上蓋キャップ１、上蓋ケース２、安全弁３、弁押さえ４、で構成された上蓋を別途作製し、上蓋ケース２には、正極リード板Ａ１２の一端を溶接によって取り付け他端を自由端としておく。
【００１８】
正極集電リング１０の周縁上部に捲回群Ｗを固定するための正極集電リングスペーサ６を配置する。正極リード板Ａ１２及び正極リード板Ｂ１３の自由端同士を溶接し、上蓋と集電リング付き捲回群Ｗとを接続する。この状態で電解液０．１８０ｄｍ^３を電池缶１６内に注入する。その後、絶縁性のガスケット５を介して上蓋を電池缶１６上部に配置し、かしめることによって、定格容量２７Ａｈ又は７Ａｈの円筒型リチウムイオン電池２０を組み立てた。なお、電解液は、エチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）とジエチルカーボネート（ＤＥＣ）とを体積比３０：５０：２０で混合した混合溶媒に、６フッ化リン酸リチウム（ＬｉＰＦ_６）を１モル濃度で溶解したものを用いた。また、図１中参照番号１５は正極側と負極側とを絶縁する絶縁フィルムである。
【００１９】
円筒型リチウムイオン電池２０の上蓋には、電池の内圧上昇に応じて開裂する内圧開放機構としての安全弁３が配設されており、安全弁３の開裂圧は約９×１０^５Ｐａに設定されている。また、電池缶１６の底部にも開放弁が配設されている。図２に示すように、開放弁２５は、電池缶１６の底部に形成された２個の円弧状溝２５ａと、円弧状溝２５ａの両端部及び略中央部に底部の中心から外周に向かって放射状に形成された放射状溝２５ｂとで構成されている。
【００２０】
図１に示すように、本実施形態の円筒型リチウムイオン電池２０は、電池缶１６の平均外径をＤ（以下、直径Ｄという。）（単位；ｍｍ）、長さをＬ（以下、長さＬという。）（単位；ｍｍ）としたとき、長さＬに対する直径Ｄの比Ｄ／Ｌを後述する所定の範囲とした。また、正極側、負極側共に捲回群Ｗと各極端子とを接続する接続部材が設けられている。この接続のために必要なスペースの大きさは、捲回群Ｗの上端から正極端子上面までの長さをＡ（ｍｍ）とし、捲回群Ｗの下端から電池底面までの長さをＢ（ｍｍ）としたとき、Ａ、Ｂあわせて３５ｍｍに設定されている（図１のＡ＋Ｂ＝３５ｍｍ）。電池の長さＬから３５ｍｍを減じた長さが捲回群Ｗの長さ、すなわちセパレータＷ５の幅に相当する。なお、電池缶１６の厚さは０．５ｍｍであり、また、捲回群Ｗを電池缶１６内に収容しやすくするため、電解液注入前の捲回群Ｗの直径は電池缶１６の内径より小さく設定し、捲回群Ｗと電池缶１６との間に両側あわせて捲回群Ｗの直径の３％に相当する隙間を形成した。
【００２１】
（第２実施形態）
次に、本発明を適用した円筒形リチウムイオン電池の第２の実施の形態について説明する。
【００２２】
＜正極及び負極の作製＞
本実施形態では、正極集電体Ｗ１の材質及び厚さ、正極活物質層Ｗ２の構成物質及び作製方法、負極集電体Ｗ３の材質及び厚さ、負極活物質層Ｗ４の構成物質及び作製方法、並びにセパレータＷ５の材質及び厚さは第１実施形態と同様にした。但し、正負両極共に活物質を集電体に塗布するときに集電体長寸方向の一方の側縁に幅５０ｍｍの未塗布部を残して正負両極を作製し、この未塗布部に切り欠きを入れ、切り欠き残部をリード片１０９とした。隣り合うリード片１０９は５０ｍｍ間隔とし、リード片１０９の幅は１０ｍｍとした。
【００２３】
＜電池の作製＞
図３に示すように、本実施形態に係る円筒形リチウムイオン電池１２０は、第１実施形態と同様、正極集電体Ｗ１の両面に正極活物質層Ｗ２が形成された帯状の正極と、負極集電体Ｗ３の両面に負極活物質層Ｗ４が形成された帯状の負極とを、これらが直接接触しないように帯状のセパレータＷ５を挟んで断面渦巻状に捲回された捲回群Ｗ’を備えている。捲回群Ｗ’は、正極のリード片１０９と負極のリード片１０９とが、それぞれ捲回群Ｗ’の互いに反対側の両端面に位置するように捲回されている。
【００２４】
正極から導出されているリード片１０９を変形させ、その全てを、捲回群Ｗ’の軸芯１１７のほぼ延長線上にある極柱（正極外部端子１０１）周囲から一体に張り出している鍔部１０７周面付近に集合、接触させる。リード片１０９と鍔部１０７周面とを超音波溶接してリード片１０９を鍔部１０７周面に接続し固定する。
【００２５】
負極外部端子１０１’と負極から導出されているリード片１０９との接続操作も、上述した正極外部端子１０１と正極から導出されているリード片１０９との接続操作と同様に行う。
【００２６】
その後、正極外部端子１０１及び負極外部端子１０１’の鍔部１０７周面全周に絶縁被覆１０８を施す。この絶縁被覆１０８は、捲回群Ｗ’外周面全周にも及ぼす。絶縁被覆１０８には、基材がポリイミドで、その片面にヘキサメタアクリレートからなる粘着剤を塗布した粘着テープを用いた。この粘着テープを鍔部１０７周面から捲回群Ｗ’外周面に亘って何重にも巻いて絶縁被覆１０８とする。捲回群Ｗ’の最大径部が絶縁被覆１０８存在部となるように巻き数を調整し、該最大径をステンレス製の電池容器１１６内径よりも僅かに小さくして捲回群Ｗ’を電池容器１１６内に挿入する。電池容器１１６の厚さは０．５ｍｍであり、捲回群Ｗ’と電池容器１１６との間の隙間は両側あわせて捲回群Ｗ’の直径の３％に相当する。
【００２７】
次に、アルミナ製で電池蓋１０４裏面と当接する部分の厚さ２ｍｍ、内径１６ｍｍ、外径２５ｍｍの第２のセラミックワッシャ１０３’を、図３に示すように先端が正極外部端子１０１を構成する極柱、先端が負極外部端子１０１’を構成する極柱にそれぞれ嵌め込む。また、第１のセラミックワッシャ１０３を電池蓋１０４に載置し、正極外部端子１０１、負極外部端子１０１’をそれぞれ第１のセラミックワッシャ１０３に通す。その後円盤状電池蓋１０４周端面を電池容器１１６の開口部に嵌合し、双方の接触部全域をレーザ溶接する。このとき正極外部端子１０１、負極外部端子１０１’は、電池蓋１０４の中心にある穴を貫通して電池蓋１０４外部に突出している。そして図３に示すように、アルミナ製で厚さ２ｍｍ、内径１６ｍｍ、外径２８ｍｍの平状の第１のセラミックワッシャ１０３、ナット１０２底面よりも平滑な金属ワッシャ１１１を、この順に正極外部端子１０１、負極外部端子１０１’にそれぞれ嵌め込む。電池蓋１０４には、正極側、負極側共に、電池の内圧上昇に応じて開裂する開裂弁１１０が配設されている。なお、開裂弁１１０の開裂圧は１．３〜１．８ＭＰａに設定した。
【００２８】
次に、金属製のナット１０２を正極外部端子１０１、負極外部端子１０１’にそれぞれ螺着し、第２のセラミックワッシャ１０３’、第１のセラミックワッシャ１０３、金属ワッシャ１１１を介して電池蓋１０４を鍔部１０７とナット１０２間で締め付けて固定する。このときの締め付けトルク値は７０ｋｇｆ・ｃｍ（６．８６Ｎ・ｍ）とした。なお、締め付け作業が終了するまで金属ワッシャ１１１は回転しなかった。この状態では、電池蓋１０４裏面と鍔部１０７の間に介在させたゴム（ＥＰＤＭ）製Ｏリング１１２の圧縮により電池容器１１６内部の発電要素は外気から遮断されている。
【００２９】
その後、電池蓋１０４に配設された注液口１１３から電解液を所定量電池容器１１６内に注入し、その後注液口１１３を封止することにより円筒形リチウムイオン電池１２０を完成させた。なお、円筒形リチウムイオン電池１２０は、電池容器１１６の内圧の上昇に応じて電流を遮断する電流遮断機構は有していない。また、電解液には、ＥＣとＤＭＣとＤＥＣの体積比１：１：１の混合溶媒中へ６フッ化リン酸リチウム（ＬｉＰＦ_６）を１モル／リットル溶解したものを用いた。
【００３０】
図３に示すように、本実施形態の円筒型リチウムイオン電池１２０は、電池容器１１６の平均外径をＤ（以下、直径Ｄという。）（単位；ｍｍ）、正極側電池蓋の外表面から負極側電池蓋の外表面までの長さをＬ（以下、長さＬという。）（単位；ｍｍ）としたとき、長さＬに対する直径Ｄの比Ｄ／Ｌを後述する所定の範囲とした。また、正極側、負極側共に捲回群Ｗ‘と各極端子とを接続する接続部材が設けられている。この接続のために必要なスペースの大きさは、捲回群Ｗ’の正極側端部から正極側電池蓋１０４の表面までの長さをＡ（ｍｍ）とし、捲回群Ｗ’の負極側端部から負極側電池蓋１０４の表面までの長さをＢ（ｍｍ）としたとき、Ａ、Ｂあわせて３５ｍｍに設定されている（図３のＡ＋Ｂ＝３５ｍｍ）。電池の長さＬから３５ｍｍを減じた長さが捲回群Ｗ’の長さ、すなわちセパレータの幅に相当する。
【００３１】
【実施例】
次に、上記実施形態に従って作製した円筒形リチウムイオン電池２０、１２０の実施例の詳細について説明する。また、本実施例の効果が明確となるように同時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、第１実施形態に従い、次の正極、負極を組み合わせた円筒型リチウム二次電池２０を作製した。正極は、正極活物質に平均粒径約１０μｍのコバルト酸リチウム（日本化学工業（株）製、商品名セルシード）を用い、幅Ｗ_Ｐを１０６ｍｍ、長さＬ_Ｐを４５０ｃｍ、集電体を含めた厚さＴ_Ｐを２３１μｍとした。負極は、負極活物質に平均粒径約２０μｍの非晶質炭素（呉羽化学工業（株）製、商品名カーボトロン）を用い、幅Ｗ_Ｎを１１２ｍｍ、長さＬ_Ｎを４６８ｃｍ、集電体を含めた厚さＴ_Ｎを２０１μｍとした。巻き芯はポリプロピレン製で直径Ｄ_Ｓが１３ｍｍのものを用いた。捲回数Ｎ_Ｗは約４２回とし、捲回群の直径Ｄ_Ｗは５６．８ｍｍであった。電池缶は、直径Ｄが６１．２ｍｍ、長さＬが１５３ｍｍであり、比Ｄ／Ｌは０．４であった。電池缶の厚さは０．５ｍｍのため、電池缶の内径Ｄ_Ｉは６０．２ｍｍであった。従って、捲回群と電池缶との隙間は１．７ｍｍであり、この隙間は捲回群の直径Ｄ_Ｗの約３％に相当する。また、実施例１で用いた電池は底部に開放弁を有していない。なお、表１において、正極の活物質については、Ｃｏはコバルト酸リチウムを、Ｍｎはマンガン酸リチウムを、それぞれ示し、負極の活物質については、ＡＣは非晶質炭素を、Ｇは黒鉛を、それぞれ示す。
【００３３】
（実施例１−２）
下表１に示すように、実施例１−２では、第１実施形態に従い、電池缶の底部に開放弁を配設する以外は実施例１と同様にした。
【００３４】
（実施例２）
下表１に示すように、実施例２では、第１実施形態に従い、幅Ｗ_Ｐを８７ｍｍ、長さＬ_Ｐを５５０ｃｍ、幅Ｗ_Ｎを９３ｍｍ、長さＬ_Ｎを５６８ｃｍ、捲回数Ｎ_Ｗを約４７回、捲回群直径Ｄ_Ｗを６２．３ｍｍ、電池缶の直径Ｄを６７．０ｍｍ、電池缶の長さＬを１３４ｍｍとする以外は実施例１と同様にした。比Ｄ／Ｌは０．５であった。電池缶の内径Ｄ_Ｉは６６．０ｍｍで、捲回群と電池缶との隙間は１．８５ｍｍであった。
【００３５】
（実施例３）
下表１に示すように、実施例３では、第１実施形態に従い、幅Ｗ_Ｐを７４ｍｍ、長さＬ_Ｐを６５４ｃｍ、幅Ｗ_Ｎを８０ｍｍ、長さＬ_Ｎを６７２ｃｍ、捲回数Ｎ_Ｗを約５２回、捲回群直径Ｄ_Ｗを６７．５ｍｍ、電池缶の直径Ｄを７２．６ｍｍ、電池缶の長さＬを１２１ｍｍとする以外は実施例１と同様にした。比Ｄ／Ｌは０．６であった。電池缶の内径Ｄ_Ｉは７１．６ｍｍで、捲回群と電池缶との隙間は２．０５ｍｍであった。
【００３６】
【表１】

【００３７】
（実施例４）
表１に示すように、実施例４では、第１実施形態に従い、正極活物質に平均粒径約１５μｍのマンガン酸リチウムを用い、幅Ｗ_Ｐを１１２ｍｍ、長さＬ_Ｐを５４１ｃｍとし、負極活物質に平均粒径約１５μｍのメソフェーズ系球状黒鉛（川崎製鉄（株）製、商品名ＫＭＦＣ）を用い、幅Ｗ_Ｎを１１８ｍｍ、長さＬ_Ｎを５５９ｃｍ、集電体を含めた厚さＴ_Ｎを１５４μｍとし、捲回数Ｎ_Ｗを約４８回、捲回群直径Ｄ_Ｗを５９．０ｍｍ、電池缶の直径Ｄを６３．６ｍｍ、長さＬを１５９ｍｍとする以外は実施例１と同様にした。比Ｄ／Ｌは０．４であった。電池缶の内径Ｄ_Ｉは６２．６ｍｍで、捲回群と電池缶との隙間は１．８ｍｍであった。
【００３８】
（実施例４−２）
表１に示すように、実施例４−２では、第１実施形態に従い、電池缶の底部に開放弁を配設する以外は実施例４と同様にした。
【００３９】
（実施例５）
表１に示すように、実施例５では、第１実施形態に従い、幅Ｗ_Ｐを９２ｍｍ、長さＬ_Ｐを６５８ｃｍ、幅Ｗ_Ｎを９８ｍｍ、長さＬ_Ｎを６７６ｃｍ、捲回数Ｎ_Ｗを約５４回、捲回群直径Ｄ_Ｗを６４．７ｍｍ、電池缶の直径Ｄを６９．５ｍｍ、電池缶の長さＬを１３９ｍｍとする以外は実施例４と同様にした。比Ｄ／Ｌは０．５であった。電池缶の内径Ｄ_Ｉは６８．５ｍｍで、捲回群と電池缶との隙間は１．９ｍｍであった。
【００４０】
（実施例６）
表１に示すように、実施例６では、第１実施形態に従い、幅Ｗ_Ｐを７８ｍｍ、長さＬ_Ｐを７７５ｃｍ、幅Ｗ_Ｎを８４ｍｍ、長さＬ_Ｎを７９３ｃｍ、捲回数Ｎ_Ｗを約６０回、捲回群直径Ｄ_Ｗを６９．８ｍｍ、電池缶の直径Ｄを７５．０ｍｍ、電池缶の長さＬを１２５ｍｍとする以外は実施例４と同様にした。比Ｄ／Ｌは０．６であった。電池缶の内径Ｄ_Ｉは７４．０ｍｍで、捲回群と電池缶との隙間は２．１ｍｍであった。
【００４１】
（実施例７）
表１に示すように、実施例７では、第１実施形態に従い、幅Ｗ_Ｐを１１５．５ｍｍ、長さＬ_Ｐを５８３ｃｍとし、負極活物質に平均粒径約２０μｍの非晶質炭素を用い、幅Ｗ_Ｎを１２１．５ｍｍ、長さＬ_Ｎを６０１ｃｍ、集電体を含めた厚さＴ_Ｎを１４２μｍとし、捲回数Ｎ_Ｗを約５１回、捲回群直径Ｄ_Ｗを６０．４ｍｍ、電池缶の直径Ｄを６５．０ｍｍ、長さＬを１６２．５ｍｍとする以外は実施例４と同様にした。比Ｄ／Ｌは０．４であった。電池缶の内径Ｄ_Ｉは６４．０ｍｍで、捲回群と電池缶との隙間は１．８ｍｍであった。
【００４２】
（実施例７−２）
表１に示すように、実施例７−２では、第１実施形態に従い、電池缶の底部に開放弁を配設する以外は実施例７と同様にした。
【００４３】
（実施例８）
表１に示すように、実施例８では、第１実施形態に従い、幅Ｗ_Ｐを９５ｍｍ、長さＬ_Ｐを７０８ｃｍ、幅Ｗ_Ｎを１０１ｍｍ、長さＬ_Ｎを７２６ｃｍ、捲回数Ｎ_Ｗを約５７回、捲回群直径Ｄ_Ｗを６６．１ｍｍ、電池缶の直径Ｄを７１．０ｍｍ、電池缶の長さＬを１４２ｍｍとする以外は実施例７と同様にした。比Ｄ／Ｌは０．５であった。電池缶の内径Ｄ_Ｉは７０．０ｍｍで、捲回群と電池缶との隙間は１．９５ｍｍであった。
【００４４】
（実施例９）
表１に示すように、実施例９では、第１実施形態に従い、幅Ｗ_Ｐを８１ｍｍ、長さＬ_Ｐを８３７ｃｍ、幅Ｗ_Ｎを８７ｍｍ、長さＬ_Ｎを８５５ｃｍ、捲回数Ｎ_Ｗを約６３回、捲回群直径Ｄ_Ｗを７１．５ｍｍ、電池缶直の径Ｄを７６．８ｍｍ、電池缶の長さＬを１２８ｍｍとする以外は実施例７と同様にした。比Ｄ／Ｌは０．６であった。電池缶の内径Ｄ_Ｉは７５．８ｍｍで、捲回群と電池缶との隙間は２．１５ｍｍであった。
【００４５】
（実施例１０）
表１に示すように、実施例１０では、第１実施形態に従い、幅Ｗ_Ｐを７７．５ｍｍ、長さＬ_Ｐを５９８ｃｍ、集電体を含めた厚さＴ_Ｐを１０３μｍとし、負極活物質に平均粒径約５μｍの非晶質炭素を用い、幅Ｗ_Ｎを８３．５ｍｍ、長さＬ_Ｎを６１６ｃｍ、集電体を含めた厚さＴ_Ｎを７３μｍとし、軸芯の直径Ｄ_Ｓは１０ｍｍのものを用い、捲回数Ｎ_Ｗを約７０回、捲回群直径Ｄ_Ｗを４６．０ｍｍ、電池缶の直径Ｄを４９．８ｍｍ、長さＬを１２４．５ｍｍとする以外は実施例４と同様にした。比Ｄ／Ｌは０．４であった。電池缶の内径Ｄ_Ｉは４８．８ｍｍで、捲回群と電池缶との隙間は１．４ｍｍであった。
【００４６】
（実施例１０−２）
表１に示すように、実施例１０−２では、第１実施形態に従い、電池缶の底部に開放弁を配設する以外は実施例１０と同様にした。
【００４７】
（実施例１１）
表１に示すように、実施例１１では、第１実施形態に従い、幅Ｗ_Ｐを６２．５ｍｍ、長さＬ_Ｐを７３６ｃｍ、幅Ｗ_Ｎを６８．５ｍｍ、長さＬ_Ｎを７５４ｃｍ、捲回数Ｎ_Ｗを約７９回、捲回群直径Ｄ_Ｗを５０．７ｍｍ、電池缶の直径Ｄを５４．７ｍｍ、電池缶の長さＬを１０９．５ｍｍとする以外は実施例１０と同様にした。比Ｄ／Ｌは０．５であった。電池缶の内径Ｄ_Ｉは５３．７ｍｍで、捲回群と電池缶との隙間は１．５ｍｍであった。
【００４８】
（実施例１２）
表１に示すように、実施例１２では、第１実施形態に従い、幅Ｗ_Ｐを５２ｍｍ、長さＬ_Ｐを８８０ｃｍ、幅Ｗ_Ｎを５８ｍｍ、長さＬ_Ｎを８９８ｃｍ、捲回数Ｎ_Ｗを約８８回、捲回群直径Ｄ_Ｗを５５．１ｍｍ、電池缶の直径Ｄを５９．４ｍｍ、電池缶の長さＬを９９ｍｍとする以外は実施例１０と同様にした。比Ｄ／Ｌは０．６であった。電池缶の内径Ｄ_Ｉは５８．４ｍｍで、捲回群と電池缶との隙間は１．６５ｍｍであった。
【００４９】
（実施例１３）
表１に示すように、実施例１３では、第２実施形態に従い、次の正極、負極を組み合わせた円筒型リチウム二次電池１２０を作製した。正極は、正極活物質に平均粒径約１５μｍのマンガン酸リチウムを用い、幅Ｗ_Ｐを１１２ｍｍ、長さＬ_Ｐを５４１ｃｍとし、集電体を含めた厚さＴ_Ｐを２３１μｍとした。負極は、負極活物質に平均粒径約１５μｍのメソフェーズ系球状黒鉛を用い、幅Ｗ_Ｎを１１８ｍｍ、長さＬ_Ｎを５５９ｃｍ、集電体を含めた厚さＴ_Ｎを１５４μｍとした。軸芯はポリプロピレン製で直径Ｄ_Ｓが１３ｍｍのものを用いた。捲回数Ｎ_Ｗを約４８回、捲回群直径Ｄ_Ｗを５９．０ｍｍ、電池缶の直径Ｄを６３．６ｍｍ、長さＬを１５９ｍｍとした。比Ｄ／Ｌは０．４であった。電池缶の厚さは０．５ｍｍのため、電池缶の内径Ｄ_Ｉは６２．６ｍｍであった。従って、捲回群と電池缶との隙間は１．８ｍｍであり、この隙間は捲回群の直径Ｄ_Ｗの約３％に相当する。
また、実施例１３の電池では電池容器の両端に開放弁を有している。
【００５０】
（実施例１４）
表１に示すように、実施例１４では、第２実施形態に従い、幅Ｗ_Ｐを９２ｍｍ、長さＬ_Ｐを６５８ｃｍ、幅Ｗ_Ｎを９８ｍｍ、長さＬ_Ｎを６７６ｃｍ、捲回数Ｎ_Ｗを約５４回、捲回群直径Ｄ_Ｗを６４．７ｍｍ、電池缶の直径Ｄを６９．５ｍｍ、長さＬを１３９ｍｍとする以外は実施例１３と同様にした。比Ｄ／Ｌは０．５であった。電池缶の内径Ｄ_Ｉは６８．５ｍｍで、捲回群と電池缶との隙間は１．９ｍｍであった。
【００５１】
（実施例１５）
表１に示すように、実施例１５では、第２実施形態に従い、幅Ｗ_Ｐを７８ｍｍ、長さＬ_Ｐを７７５ｃｍ、幅Ｗ_Ｎを８４ｍｍ、長さＬ_Ｎを７９３ｃｍ、捲回数Ｎ_Ｗを約６０回、捲回群直径Ｄ_Ｗを６９．８ｍｍ、電池缶の直径Ｄを７５．０ｍｍ、長さＬを１２５ｍｍとする以外は実施例１３と同様にした。比Ｄ／Ｌは０．６であった。電池缶の内径Ｄ_Ｉは７４．０ｍｍで、捲回群と電池缶との隙間は２．１ｍｍであった。
【００５２】
（比較例１）
下表２に示すように、比較例１では、第１実施形態に従い、幅Ｗ_Ｐを１１９ｍｍ、長さＬ_Ｐを４００ｃｍ、幅Ｗ_Ｎを１２５ｍｍ、長さＬ_Ｎを４１８ｃｍ、捲回数Ｎ_Ｗを約３９回、捲回群直径Ｄ_Ｗを５３．９ｍｍ、電池缶の直径Ｄを５８．１ｍｍ、電池缶の長さＬを１６６ｍｍとする以外は実施例１と同様にした。比Ｄ／Ｌは０．３５であった。電池缶の内径Ｄ_Ｉは５７．１ｍｍで、捲回群と電池缶との隙間は１．６ｍｍであった。
【００５３】
（比較例２）
下表２に示すように、比較例２では、第１実施形態に従い、電池缶の底部に開放弁を配設する以外は比較例１と同様にした。
【００５４】
（比較例３）
下表２に示すように、比較例３では、第１実施形態に従い、幅Ｗ_Ｐを６８ｍｍ、長さＬ_Ｐを６９６ｃｍ、幅Ｗ_Ｎを７４ｍｍ、長さＬ_Ｎを７１４ｃｍ、捲回数Ｎ_Ｗを約５４回、捲回群直径Ｄ_Ｗを６９．５ｍｍ、電池缶の直径Ｄを７４．７ｍｍ、電池缶の長さＬを１１５ｍｍとする以外は比較例１と同様にした。比Ｄ／Ｌは０．６５であった。電池缶の内径Ｄ_Ｉは７３．７ｍｍで、捲回群と電池缶との隙間は２．１ｍｍであった。
【００５５】
【表２】

【００５６】
（比較例４）
表２に示すように、比較例４では、第１実施形態に従い、正極活物質に平均粒径約１５μｍのマンガン酸リチウムを用い、幅Ｗ_Ｐを１２５．５ｍｍ、長さＬ_Ｐを４８２ｃｍとし、負極活物質に平均粒径約１５μｍのメソフェーズ系球状黒鉛を用い、幅Ｗ_Ｎを１３１．５ｍｍ、長さＬ_Ｎを５００ｃｍ、集電体を含めた厚さＴ_Ｎを１５４μｍとし、捲回数Ｎ_Ｗを約４５回、捲回群直径Ｄ_Ｗを５６．０ｍｍ、電池缶の直径Ｄを６０．４ｍｍ、長さＬを１７２．５ｍｍとする以外は比較例１と同様にした。比Ｄ／Ｌは０．３５であった。電池缶の内径Ｄ_Ｉは５９．４ｍｍで、捲回群と電池缶との隙間は１．７ｍｍであった。
【００５７】
（比較例５）
表２に示すように、比較例５では、第１実施形態に従い、電池缶の底部に開放弁を配設する以外は比較例４と同様にした。
【００５８】
（比較例６）
表２に示すように、比較例６では、第１実施形態に従い、幅Ｗ_Ｐを７２．５ｍｍ、長さＬ_Ｐを８３６ｃｍ、幅Ｗ_Ｎを７８．５ｍｍ、長さＬ_Ｎを８５４ｃｍ、捲回数Ｎ_Ｗを約６３回、捲回群直径Ｄ_Ｗを７２．３ｍｍ、電池缶の直径Ｄを７７．７ｍｍ、長さＬを１１９．５ｍｍとする以外は比較例４と同様にした。比Ｄ／Ｌは０．６５であった。電池缶の内径Ｄ_Ｉは７６．７ｍｍで、捲回群と電池缶との隙間は２．２ｍｍであった。
【００５９】
（比較例７）
表２に示すように、比較例７では、第１実施形態に従い、幅Ｗ_Ｐを１２９ｍｍ、長さＬ_Ｐを５１８ｃｍとし、負極活物質に平均粒径約２０μｍの非晶質炭素を用い、幅Ｗ_Ｎを１３５ｍｍ、長さＬ_Ｎを５３６ｃｍ、集電体を含めた厚さＴ_Ｎを１４２μｍとし、捲回数Ｎ_Ｗを約４８回、捲回群直径Ｄ_Ｗを５７．２ｍｍ、電池缶の直径Ｄを６１．６ｍｍ、長さＬを１７６ｍｍとする以外は比較例４と同様にした。比Ｄ／Ｌは０．３５であった。電池缶の内径Ｄ_Ｉは６０．６ｍｍで、捲回群と電池缶との隙間は１．７ｍｍであった。
【００６０】
（比較例８）
表２に示すように、比較例８では、第１実施形態に従い、電池缶の底部に開放弁を配設する以外は比較例７と同様にした。
【００６１】
（比較例９）
表２に示すように、比較例９では、第１実施形態に従い、幅Ｗ_Ｐを７５ｍｍ、長さＬ_Ｐを８９７ｃｍ、幅Ｗ_Ｎを８１ｍｍ、長さＬ_Ｎを９１５ｃｍ、捲回数Ｎ_Ｗを約６６回、捲回群直径Ｄ_Ｗを７３．９ｍｍ、電池缶の直径Ｄを７９．３ｍｍ、長さＬを１２２ｍｍとする以外は比較例７と同様にした。比Ｄ／Ｌは０．６５であった。電池缶の内径Ｄ_Ｉは７８．３ｍｍで、捲回群と電池缶との隙間は２．２ｍｍであった。
【００６２】
（比較例１０）
表２に示すように、比較例１０では、第１実施形態に従い、幅Ｗ_Ｐを８７ｍｍ、長さＬ_Ｐを５２３ｃｍ、集電体を含めた厚さＴ_Ｐを１０３μｍとし、負極活物質に平均粒径約５μｍの非晶質炭素を用い、幅Ｗ_Ｎを９３ｍｍ、長さＬ_Ｎを５４１ｃｍ、集電体を含めた厚さＴ_Ｎを７３μｍとし、捲回数Ｎ_Ｗを約６５回、捲回群直径Ｄ_Ｗを４３．３ｍｍ、電池缶の直径Ｄを４６．９ｍｍ、長さＬを１３４ｍｍとする以外は比較例４と同様にした。比Ｄ／Ｌは０．３５であった。電池缶の内径Ｄ_Ｉは４５．９ｍｍで、捲回群と電池缶との隙間は１．３ｍｍであった。
【００６３】
（比較例１１）
表２に示すように、比較例１１では、第１実施形態に従い、電池缶の底部に開放弁を配設する以外は比較例１０と同様にした。
【００６４】
（比較例１２）
表２に示すように、比較例１２では、第１実施形態に従い、幅Ｗ_Ｐを４８ｍｍ、長さＬ_Ｐを９５５ｃｍ、幅Ｗ_Ｎを５４ｍｍ、長さＬ_Ｎを９７３ｃｍ、捲回数Ｎ_Ｗを約９２回、捲回群直径Ｄ_Ｗを５７．３ｍｍ、電池缶の直径Ｄを６１．８ｍｍ、長さＬを９５ｍｍとする以外は比較例１０と同様にした。比Ｄ／Ｌは０．６５であった。電池缶の内径Ｄ_Ｉは６０．８ｍｍで、捲回群と電池缶との隙間は１．７５ｍｍであった。
【００６５】
（比較例１３）
表２に示すように、比較例１３では、第２実施形態に従い、幅Ｗ_Ｐを１２５．５ｍｍ、長さＬ_Ｐを４８２ｃｍ、幅Ｗ_Ｎを１３１．５ｍｍ、長さＬ_Ｎを５００ｃｍ、捲回数Ｎ_Ｗを約４５回、捲回群直径Ｄ_Ｗを５６．０ｍｍ、電池缶の直径Ｄを６０．４ｍｍ、長さＬを１７２．５ｍｍとする以外は実施例１３と同様にした。比Ｄ／Ｌは０．３５であった。電池缶の内径Ｄ_Ｉは５９．４ｍｍで、捲回群と電池缶との隙間は１．７ｍｍであった。
【００６６】
（比較例１４）
表２に示すように、比較例１４では、第２実施形態に従い、幅Ｗ_Ｐを７２．５ｍｍ、長さＬ_Ｐを８３６ｃｍ、幅Ｗ_Ｎを７８．５ｍｍ、長さＬ_Ｎを８５４ｃｍ、捲回数Ｎ_Ｗを約６３回、捲回群直径Ｄ_Ｗを７２．３ｍｍ、電池缶の直径Ｄを７７．７ｍｍ、長さＬを１１９．５ｍｍとする以外は比較例１３と同様にした。比Ｄ／Ｌは０．６５であった。電池缶の内径Ｄ_Ｉは７６．７ｍｍで、捲回群と電池缶との隙間は２．２ｍｍであった。
【００６７】
（測定／評価）
次に、このようにして完成した実施例及び比較例の電池を２５±２°Ｃの雰囲気温度にて、次の条件で充電し、満充電状態にして以下の測定１〜３の測定を行った。
（充電条件）
実施例１〜９；４．２Ｖ定電圧、制限電流２７Ａ、３．５時間
実施例１０〜１２；４．２Ｖ定電圧、制限電流７Ａ、３．５時間
実施例１３〜１５；４．２Ｖ定電圧、制限電流２７Ａ、３．５時間
比較例１〜９；４．２Ｖ定電圧、制限電流２７Ａ、３．５時間
比較例１０〜１２；４．２Ｖ定電圧、制限電流７Ａ、３．５時間
比較例１３〜１４；４．２Ｖ定電圧、制限電流２７Ａ、３．５時間
【００６８】
［測定１］
満充電状態の電池を、実施例１〜９、実施例１３〜１５、比較例１〜９及び比較例１３〜１４の電池は９Ａ定電流、放電終止電圧２．７Ｖ、２５±２°Ｃで放電し、実施例１０〜１２及び比較例１０〜１２の電池は３Ａ定電流、放電終止電圧２．７Ｖ、２５±２°Ｃで放電し、放電容量を確認した。また、各電池の大きさから電池の容積を求め、エネルギー密度を算出した。
【００６９】
［測定２］
満充電状態の電池を、実施例１〜９、実施例１３〜１５、比較例１〜９及び比較例１３〜１４の電池は２７Ａ定電流、２５±２°Ｃで、実施例１０〜１２及び比較例１０〜１２は７Ａ定電流、２５±２°Ｃでそれぞれ連続充電し、最終的な電池の状況を観察し、過充電後外観とした。
【００７０】
［測定３］
満充電状態の電池を、環境温度３０±３°Ｃにて、電池の長さ方向（軸芯の長さ方向）に、振幅１ｍｍ、振動数１０Ｈｚで６時間、５０Ｈｚで６時間、１００Ｈｚで６時間、振動を加える振動試験を行った。各振動数で振動を加えた後、電池を解体し、電極捲回群の移動とリードの切断の有無を目視にて観察した。
【００７１】
測定１〜３の測定結果を下表３及び下表４に示す。
【００７２】
【表３】

【００７３】
【表４】

【００７４】
表３及び表４に示すように、放電容量の測定結果では、第１実施形態の実施例１〜９及び比較例１〜９の電池、並びに第２実施形態の実施例１３〜１５及び比較例１３〜１４の電池は約２７Ａｈ、第１実施形態の実施例１０〜１２及び比較例１０〜１２の電池は約７Ａｈであり、ほぼ定格容量どおりの放電容量が得られ、高いエネルギー密度が得られた。
【００７５】
測定２の結果では、比Ｄ／Ｌを０．４〜０．６の範囲とした実施例１〜１５の電池は、一部で電池缶の膨れが見られたものの、ほぼ外観を維持していた。これに対して、比Ｄ／Ｌが０．４を下回る比較例１、２、４、５、７、８、１０、１１の第１実施形態の電池は、電池缶底部の開放弁の有無にかかわらず、かしめ部から上蓋が外れた。また、比較例１３の第２実施形態の電池は、電池容器の膨れが見られた。特に、正極活物質にコバルト酸リチウムを用いた比較例１、２の電池では、電池缶開口部から側面部にかけての破開も見られた。なお、全ての電池において、上蓋部の安全弁、底部の開放弁は全て開裂していた。
【００７６】
測定２においては、連続過充電により電池電圧が上昇して電解液の分解、ガス化が起こり、更に分解が進むと発熱を伴い、セパレータが収縮して正極、負極が接触する、いわゆる内部短絡が起こる。そうなると、短絡電流によってさらに温度が上昇し、電解液のガス化が急激になり、電池の内圧が急上昇する。即座に上蓋の安全弁及び底部の開放弁が開裂し、内圧を電池外へ開放することとなる。捲回群内部で発生したガスは、捲回群の両端方向、すなわち上蓋部の安全弁、底部の開放弁の方向へ移動する。しかし、比Ｄ／Ｌが０．４を下回る電池においては、捲回群両端までの長さが大きく、特にガスが急発生した場合には電池缶を膨らませたり、またそのガス塊が、一気に開放弁を通過しようとしたときには、上蓋をかしめ部から外してしまうほどの勢いを持つものと思われる。従って、不慮の事態として、電池が過充電などの異常状態に陥った場合の安全性を確保するには比Ｄ／Ｌを０．４以上とすることが好ましいことが判明した。
【００７７】
正極活物質にコバルト酸リチウム、負極に非晶質炭素を用い、底部に開放弁を有する実施例１−２の電池では電池缶の膨れが観察されているのに対して、正極にマンガン酸リチウムを用いた同様な実施例７−２の電池では、底部の開放弁が開裂している以外の外観の異常は認められなかった。従って正極活物質には、マンガン酸リチウムに代表されるリチウムマンガン複酸化物を用いることが好ましいことがわかった。また、底部に開放弁を有していない実施例４、７、１０の電池では、電池缶の膨れが見られたのに対して、同じ仕様で底部に開放弁を有している実施例４−２、７−２、１０−２の電池では、底部の開放弁が開裂している以外の外観の異常は認められなかった。従って、底部に開放弁を配設する、すなわち、電池の長手方向両端部に内圧開放弁を有する電池は安全性に優れることが明らかとなった。
【００７８】
測定３の結果では、全ての実施例の電池は、振動試験後の異常は認められなかった。これに対して、比Ｄ／Ｌが０．６を超える比較例３、６、９、１２の第１実施形態の電池及び比較例１４の第２実施形態の電池は、捲回群が軸芯の長さ方向の一方へ移動しており、それによって、電極から導出されているリードが切断されていた。比Ｄ／Ｌが大きい、つまり、長さＬに対して直径Ｄが大きいと、軸芯と近接接触する電極の面積が小さくなり、捲回群を保持しきれなくなったものと思われる。従って、比Ｄ／Ｌは０．６以下とすることが好ましいことが判明した。
【００７９】
上述したように、上記実施形態の円筒形リチウムイオン電池２０、１２０では、電池構造にかかわらず、電池容器の長さＬに対する直径Ｄの比Ｄ／Ｌを０．４〜０．６としたことにより、電極捲回群Ｗ、Ｗ’を確実に支持して移動を防止することができ、過充電時に発生したガスを速やかに電池外に開放することができた。従って、耐振性が高く、かつ安全性が高い円筒型リチウムイオン電池を実現することができた。また、正極活物質をリチウムマンガン複酸化物としたことで、過充電時のガスの発生を低減することができ、安全性を高めることができた。更に、電池の長手方向両端部に開放弁を配設したことで、過充電時に電池内で発生したガスを電池の両端部から電池外に開放することができ、安全性を高めることができた。
【００８０】
なお、本発明は上記実施形態で説明した直径Ｄ及び高さＬに限定されるものではなく、正極活物質の種類、正極合剤中の導電剤、負極活物質中の炭素材の種類や製造方法に特に限定されるものでもない。また、実施例、比較例の状況から明らかなように、本発明は特に電池容量７Ａｈ以上、捲回数３０回以上の電池において顕著に作用し、軸芯の直径、電極の厚さに限定されるものではない。更に、上記実施形態では、軸芯の周囲に電極を捲回して捲回群を作製したが、電極を捲回した後に捲回した電極の中心部に軸芯を挿入して捲回群としてもよい。
【００８１】
また、本実施形態以外で用いることのできるリチウムイオン電池用正極活物質としては、リチウムを挿入・脱離可能な材料であり、予め十分な量のリチウムを挿入したリチウムマンガン複酸化物が好ましく、スピネル構造を有したマンガン酸リチウムや、結晶中のマンガンやリチウムの一部をそれら以外の元素で置換あるいはドープした材料を使用するようにしてもよい。例えばリチウムマンガン複酸化物のＬｉ／Ｍｎ比が０．５を超えるものとしたり、リチウムマンガン複酸化物を、Ｌｉ_１＋ｘＭｎ_{２−ｘ−ｙ}Ｍ_ｙＯ_４（ここで、０＜ｘ＜０．１、０＜ｙ＜０．３、Ｍは、Ａｌ、Ｃｒ、Ｎｉ、Ｃｏ、Ｍｇ、の群より選ばれる少なくとも１種以上の元素である。）であらわされるものとしてもよい。一般に、マンガン酸リチウムは、適当なリチウム塩と酸化マンガンとを混合、焼成して合成することができるが、リチウム塩と酸化マンガンの仕込み比を制御することによって所望のＬｉ／Ｍｎ比とすることができる。
【００８２】
【発明の効果】
以上説明したように、本発明によれば、電極捲回群を確実に支持して電極捲回群の移動を防止することができると共に、過充電時に発生したガスを速やかに電池外に開放することができるので、耐振性が高く、かつ安全性が高い円筒型リチウムイオン電池を実現することができる、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実施形態の円筒型リチウムイオン電池の断面図である。
【図２】第１実施形態の円筒型リチウムイオン電池の電池缶の底面図である。
【図３】本発明が適用可能な第２実施形態の円筒型リチウムイオン電池の断面図である。
【符号の説明】
３安全弁（内圧開放機構）
１６電池缶（電池容器）
１７巻き芯（軸芯）
２０、１２０円筒型リチウムイオン電池
２５、１１０開放弁（内圧開放機構）
１１６電池容器
１１７軸芯
Ｗ、Ｗ’ 捲回群（電極捲回群）
Ｗ１アルミニウム箔（正極集電体）
Ｗ２正極活物質層
Ｗ３銅箔（負極集電体）
Ｗ４負極活物質層
Ｗ５セパレータ
Ｄ電池直径
Ｌ電池長さ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical lithium ion battery, and in particular, in a battery container having an internal pressure release mechanism that releases an internal pressure at a predetermined pressure, a positive electrode active material layer containing a positive electrode active material and a belt-like positive electrode having a positive electrode current collector An electrode winding group in which a negative electrode active material layer using a carbon material as a negative electrode active material and a strip-shaped negative electrode having a negative electrode current collector are wound around a shaft core at least 30 times through a separator, A cylindrical lithium ion battery in which both ends of a core are supported or fixed on a positive electrode current collector and a negative electrode current collector and infiltrated with an electrolyte solution, and a substantial discharge capacity 7 The present invention relates to a cylindrical lithium ion battery of Ah or higher.
[0002]
[Prior art]
Lithium ion secondary batteries are mainly used as power sources for portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of the high energy density. The internal structure of this battery is usually a winding type as shown below. The electrodes are in the form of a band in which an active material is applied to a metal foil for both the positive electrode and the negative electrode, and the cross section is wound in a spiral shape around the axis so that these electrodes are not in direct contact across the separator. It forms a group of times. The wound group is housed in a cylindrical battery can and sealed after the electrolyte solution is injected. Within the battery can, the wound group is supported or fixed to the shaft core. A general cylindrical lithium ion secondary battery has an outer diameter of 18 mm and a height of 65 mm, which is called 18650 type, and is widely used as a small consumer lithium ion battery.
[0003]
On the other hand, in the automobile industry, in order to respond to environmental problems, the development of an electric vehicle with no exhaust gas and a power source completely made of only a battery, or a hybrid (electric) that uses both an internal combustion engine and a battery as a power source. The development of automobiles has been accelerated, and some have reached the practical stage. Naturally, a secondary battery serving as a power source for an electric vehicle is required to have characteristics capable of obtaining high output and high energy, and a lithium ion battery is attracting attention as a secondary battery that satisfies this requirement.
[0004]
However, even though it is a high-energy density lithium ion secondary battery, in order to withstand large current discharge and large current charge when used in an electric vehicle, not only the electrode structure but also the current collection from the electrode to the battery terminal The structure also needs to be devised. For example, JP-A-8-115744, JP-A-9-55213, JP-A-9-92238, JP-A-9-92241, JP-A-9-92335 include electrodes. The metal foil, which is a current collector, is extended from the active material layer, processed as it is or into a strip shape, and connected to a connection part such as a current collection ring by welding or the like, and once to the battery terminal via the connection part A technique for reducing the voltage drop (iR drop) during large current discharge and large current charge has been proposed. As disclosed in these publications, in order to reduce the voltage drop during large current discharge and large current charge, a space for accommodating the lead connection portion in the cylindrical lithium ion battery is required. .
[0005]
By the way, when mounting a battery on an electric vehicle, it is preferable to provide flexibility in vehicle body design, in particular, battery packaging, in order to meet various needs of electric vehicle users. For this purpose, it is necessary to minimize the space volume occupied by the on-board battery, and the most effective means is the energy density (Wh / dm) per volume of the battery. ³ ) Is maximized. In other words, a battery mounted on an electric vehicle usually has a plurality of single cells connected in parallel and in series to form a module. However, increasing the energy density per unit cell volume reduces the module size. It is effective.
[0006]
[Problems to be solved by the invention]
However, even if the volume energy density is increased, depending on the ratio of the diameter to the length of the battery (diameter / length), the holding force on the axis of the electrode winding group is reduced. Due to the vibration applied to the battery, movement of the winding group inside the battery occurs, and the lead that electrically connects the electrode and the connecting member is cut. In addition, in a battery having a capacity of approximately 7 Ah or more, a large current charge or large current discharge state is maintained when a battery abnormality such as an overcharge state occurs, and the chemical reaction between the nonaqueous electrolyte and the active material causes A sudden and large amount of gas is generated, increasing the internal pressure of the battery container. In general, a lithium secondary battery has an internal pressure release mechanism that releases the internal pressure at a predetermined pressure in the battery container in order to prevent this increase in internal pressure. However, depending on the ratio of the diameter / length of the battery, The battery behavior is different and the internal pressure increases, so the safety decreases.
[0007]
An object of the present invention is to provide a cylindrical lithium ion battery having high vibration resistance and high safety in view of the above-mentioned cases.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a battery container having an internal pressure release mechanism that releases an internal pressure at a predetermined pressure, a positive electrode active material layer containing a positive electrode active material, and a strip-like positive electrode having a positive electrode current collector, An electrode winding group in which a negative electrode active material layer using a carbon material as a negative electrode active material and a strip-shaped negative electrode having a negative electrode current collector are wound around a shaft core at least 30 times through a separator; Is a cylindrical lithium ion battery supported or fixed on a positive electrode current collector member and a negative electrode current collector member and infiltrated with an electrolyte solution, and has a substantial discharge capacity 7 In a cylindrical lithium ion battery of Ah or more, when the diameter of the battery container is D (mm) and the length is L (mm), the ratio D / L of the diameter D to the length L is 0.4 to 0.4. 0.6.
[0009]
In the present invention, in order to ensure a large volumetric energy density, the positive and negative electrodes have an electrode winding group in which the positive and negative electrodes are wound about 30 times or more around the axis through a separator. In the battery can, the electrode winding group is supported by the shaft core. If the diameter of the electrode winding group is larger than the length of the electrode winding group, the shaft core cannot support the electrode winding group when vibration is applied to the battery, and the electrode winding group moves from the winding position. Therefore, the electrical connection portion between the electrode and the connection member is cut, and the function of the battery is impaired. On the other hand, if the length is large relative to the diameter of the electrode winding group, a sudden and large amount of gas generated in the battery container at the time of battery abnormality moves inside the battery and is released outside the battery through the internal pressure release mechanism. Since it takes a long time to complete, the internal pressure of the battery increases and the safety decreases. According to the present invention, when the diameter of the battery case is D (mm) and the length is L (mm), the ratio D / L of the diameter D to the length L is 0.4 to 0.6. Thus, the electrode winding group can be reliably supported to prevent movement of the electrode winding group, and the gas generated during overcharge can be quickly released out of the battery, so the vibration resistance is high, In addition, a highly safe cylindrical lithium ion battery can be realized.
[0010]
In this case, if the positive electrode active material is a lithium manganese complex oxide, the reaction with the electrolytic solution at the time of battery abnormality is gentle, so that the generation of gas can be reduced, so that safety can be improved. In addition, if an internal pressure release mechanism is provided at both ends of the battery in the longitudinal direction, the gas generated in the battery when the battery is abnormal can be released from the both ends of the battery to the outside of the battery, thus improving safety. .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of a cylindrical lithium ion battery to which the present invention is applied will be described with reference to the drawings.
[0012]
<Preparation of positive electrode and negative electrode>
As shown in FIG. 1, a cylindrical lithium ion battery 20 according to this embodiment includes a strip-shaped positive electrode in which a positive electrode active material layer W2 is formed on both surfaces of a positive electrode current collector W1, and both surfaces of a negative electrode current collector W3. A wound group (electrode wound group) W in which a strip-shaped negative electrode on which the negative electrode active material layer W4 is formed is wound in a spiral shape with a winding core (axial core) 17 around a strip-shaped separator W5. I have.
[0013]
The positive electrode current collector W1 is an aluminum foil having a thickness of 20 μm. The positive electrode active material layer W2 is composed of lithium cobalt oxide, which is a lithium cobalt complex oxide or lithium manganate, which is a lithium manganese complex oxide, and graphite and acetylene black as conductive assistants (Electrochemical Industry Co., Ltd.). Manufactured by trade name Denka Black), polyvinylidene fluoride (PVDF) as a binder (binder), and an electrolytic solution. The negative electrode current collector W3 is a copper foil having a thickness of 10 μm. The negative electrode active material layer W4 comprises lithium ion as an electrode reactive species, negative electrode active material amorphous carbon or graphite carbon that absorbs and discharges lithium ions upon charge and discharge, and conductive material vapor grown carbon fiber (Showa Denko) (Product name: VGCF) (hereinafter abbreviated as CF), binder PVDF, and electrolytic solution are used as constituents.
[0014]
In order to produce the positive electrode active material layer W2, lithium manganate (average particle size of about 10 to 20 μm) or lithium cobaltate (average particle size of about 10 to 20 μm), graphite (average particle size of about 5 μm), and acetylene black , PVDF are mixed at a mass ratio of 85: 8: 2: 5, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) serving as a dispersion solvent is added thereto, sufficiently kneaded and dispersed to form a slurry. After this kneaded material is transferred from roll to roll (roll-to-roll transfer), both surfaces of the positive electrode current collector W1 are applied to substantially the same thickness and dried, and then the positive electrode thickness T is measured by pressing. _P Is compressed to 231 ± 2 μm or 103 ± 2 μm including the positive electrode current collector to obtain the positive electrode active material layer W2. The density of the positive electrode active material layer W2 is 2.65 g / cm. ³ It is. However, the electrolyte solution is not included at this stage. After producing the positive electrode active material layer W2, a predetermined width W described later _P , Predetermined length L _P To obtain a belt-like positive electrode.
[0015]
On the other hand, to produce the negative electrode active material layer W4, amorphous carbon having an average particle size of 5 to 20 μm (manufactured by Kureha Chemical Industry Co., Ltd., trade name Carbotron) or mesophase-based spherical graphite (manufactured by Kawasaki Steel Corporation), (Trade name KMFC), CF, and PVDF are mixed at a mass ratio of 87.6: 4.8: 7.6, and an appropriate amount of NMP as a dispersion solvent is added thereto, and kneaded and dispersed sufficiently. To. The kneaded material is roll-to-roll transferred so that both surfaces of the negative electrode current collector W3 are coated on the substantially uniform and the same thickness, dried, and then pressed to form a negative electrode thickness T _N Is compressed to 73 to 201 ± 2 μm including the negative electrode current collector to obtain the negative electrode active material layer W4. The density of the negative electrode active material layer W4 is 0.98 g / cm. ³ Or 1.4 g / cm ³ It is. This density was determined so that the porosity in the negative electrode active material layer W4 (ratio of the pores filled with the electrolyte with respect to the entire negative electrode active material layer W4) was about 35%. However, the electrolyte solution is not included at this stage. After preparing the negative electrode active material layer W4, a predetermined width W described later _N , Predetermined length L _N To obtain a strip-shaped negative electrode. Width W _N Is a width W so that the positive electrode active material layer W2 does not protrude from the negative electrode active material layer W4 when the positive and negative electrodes are wound. _P 6mm larger than the length L _N Is the length L _P 18 cm larger. In addition, the width of the separator is the width W so that the negative electrode does not protrude from the separator. _N 6 mm larger.
[0016]
<Production of battery>
Diameter D _S A thickness T between the positive electrode and the negative electrode around the winding core 17 _S Is N through the microporous polyethylene separator W5 of 40 μm _W Turn to diameter D _W The wound group W was obtained. The positive electrode current collector ring 10 and the negative electrode current collector ring 11 were disposed at both ends of the wound group W, and the positive electrode current collector W1 and the negative electrode current collector W3 were welded to the periphery of each current collector ring. The positive electrode current collecting ring 10 and the negative electrode current collecting ring 11 are fixed to the end of the winding core 17 via the positive electrode current collecting ring support 8 and the negative electrode current collecting ring support 9, respectively. The negative electrode lead previously inserted into the battery can (battery container) 16 so that the negative electrode current collector ring 11 side becomes the bottom side of the negative electrode current collector ring 11 and the negative electrode lead previously welded to the negative electrode current collector ring 11 The plate 14 is welded to the battery can 16. At that time, the negative electrode current collector ring spacer 7 is disposed between the negative electrode current collector ring 11 and the battery can 16 in order to fix the wound group W. Further, one end of the positive electrode lead plate B13 is previously welded to the upper surface of the positive electrode current collecting ring 10, and the other end is set as a free end.
[0017]
On the other hand, an upper lid composed of the upper lid cap 1, the upper lid case 2, the safety valve 3, and the valve retainer 4 is separately manufactured. One end of the positive electrode lead plate A12 is attached to the upper lid case 2 by welding, and the other end is set as a free end. .
[0018]
A positive current collector ring spacer 6 for fixing the winding group W is disposed on the periphery of the positive current collector ring 10. The free ends of the positive electrode lead plate A12 and the positive electrode lead plate B13 are welded to connect the upper lid and the wound group W with the current collecting ring. In this state, the electrolyte is 0.180 dm ³ Is injected into the battery can 16. Thereafter, the upper lid was placed on the upper part of the battery can 16 via the insulating gasket 5 and caulked to assemble the cylindrical lithium ion battery 20 having a rated capacity of 27 Ah or 7 Ah. The electrolytic solution was lithium hexafluorophosphate (LiPF) in a mixed solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 30:50:20. ₆ ) Was dissolved at 1 molar concentration. Further, reference numeral 15 in FIG. 1 is an insulating film for insulating the positive electrode side and the negative electrode side.
[0019]
On the upper lid of the cylindrical lithium ion battery 20, a safety valve 3 is disposed as an internal pressure release mechanism that cleaves in response to an increase in the internal pressure of the battery. The cleavage pressure of the safety valve 3 is about 9 × 10. ⁵ Pa is set. An open valve is also provided at the bottom of the battery can 16. As shown in FIG. 2, the open valve 25 includes two arc-shaped grooves 25 a formed at the bottom of the battery can 16, and both ends and substantially the center of the arc-shaped groove 25 a from the center of the bottom toward the outer periphery. It is comprised by the radial groove | channel 25b formed radially.
[0020]
As shown in FIG. 1, in the cylindrical lithium ion battery 20 of the present embodiment, the average outer diameter of the battery can 16 is D (hereinafter, referred to as diameter D) (unit: mm), and the length is L (hereinafter, long). The ratio D / L of the diameter D to the length L is set to a predetermined range described later. Moreover, the connection member which connects the winding group W and each pole terminal is provided in the positive electrode side and the negative electrode side. The size of the space necessary for this connection is defined as A (mm) from the upper end of the winding group W to the upper surface of the positive electrode terminal, and B ( mm), A and B are set to 35 mm (A + B = 35 mm in FIG. 1). The length obtained by subtracting 35 mm from the length L of the battery corresponds to the length of the wound group W, that is, the width of the separator W5. In addition, the thickness of the battery can 16 is 0.5 mm, and the diameter of the wound group W before electrolyte injection is set to the inner diameter of the battery can 16 so that the wound group W can be easily accommodated in the battery can 16. The gap was set to be smaller and a gap corresponding to 3% of the diameter of the wound group W was formed between the wound group W and the battery can 16 on both sides.
[0021]
(Second Embodiment)
Next, a second embodiment of a cylindrical lithium ion battery to which the present invention is applied will be described.
[0022]
<Preparation of positive electrode and negative electrode>
In this embodiment, the material and thickness of the positive electrode current collector W1, the constituent material and manufacturing method of the positive electrode active material layer W2, the material and thickness of the negative electrode current collector W3, and the constituent material and manufacturing method of the negative electrode active material layer W4 The material and thickness of the separator W5 are the same as those in the first embodiment. However, when applying the active material to the current collector for both the positive and negative electrodes, a positive and negative electrode is prepared by leaving an uncoated part with a width of 50 mm on one side edge in the longitudinal direction of the current collector, and a notch is formed in the uncoated part. The remaining notch was used as the lead piece 109. Adjacent lead pieces 109 were spaced 50 mm apart, and the width of the lead pieces 109 was 10 mm.
[0023]
<Production of battery>
As shown in FIG. 3, the cylindrical lithium ion battery 120 according to this embodiment includes a strip-like positive electrode in which a positive electrode active material layer W2 is formed on both surfaces of a positive electrode current collector W1, and a negative electrode, as in the first embodiment. A winding group W ′ wound in a spiral shape with a strip-shaped separator W5 sandwiched between a strip-shaped negative electrode having a negative electrode active material layer W4 formed on both surfaces of the current collector W3 so that they do not directly contact each other. I have. The wound group W ′ is wound so that the positive electrode lead piece 109 and the negative electrode lead piece 109 are respectively positioned on opposite end surfaces of the wound group W ′.
[0024]
The lead piece 109 led out from the positive electrode is deformed, and all of the lead piece 109 projects integrally from the periphery of the pole column (positive electrode external terminal 101) substantially on the extension line of the axis 117 of the winding group W ′. Gather and contact near the circumference. The lead piece 109 and the circumferential surface of the flange portion 107 are ultrasonically welded to connect and fix the lead piece 109 to the circumferential surface of the flange portion 107.
[0025]
The connection operation between the negative electrode external terminal 101 ′ and the lead piece 109 led out from the negative electrode is performed in the same manner as the connection operation between the positive electrode external terminal 101 and the lead piece 109 led out from the positive electrode.
[0026]
Thereafter, an insulating coating 108 is applied to the entire periphery of the flange 107 of the positive electrode external terminal 101 and the negative electrode external terminal 101 ′. This insulating coating 108 also affects the entire circumference of the wound group W ′. For the insulating coating 108, an adhesive tape in which the base material was polyimide and an adhesive made of hexamethacrylate was applied on one side thereof was used. This adhesive tape is wound several times from the circumferential surface of the collar portion 107 to the outer circumferential surface of the wound group W ′ to form the insulating coating 108. The number of turns is adjusted so that the maximum diameter portion of the wound group W ′ becomes the insulating coating 108 existing portion, and the maximum diameter is slightly smaller than the inner diameter of the battery container 116 made of stainless steel so that the wound group W ′ is a battery. Insert into container 116. The thickness of the battery container 116 is 0.5 mm, and the gap between the wound group W ′ and the battery container 116 corresponds to 3% of the diameter of the wound group W ′ on both sides.
[0027]
Next, a second ceramic washer 103 ′ made of alumina and having a thickness of 2 mm, an inner diameter of 16 mm, and an outer diameter of 25 mm at the portion in contact with the back surface of the battery lid 104, the tip constitutes the positive electrode external terminal 101 as shown in FIG. The pole column and the tip are respectively fitted into the pole columns constituting the negative electrode external terminal 101 ′. Further, the first ceramic washer 103 is placed on the battery lid 104, and the positive external terminal 101 and the negative external terminal 101 ′ are passed through the first ceramic washer 103. Thereafter, the peripheral end surface of the disk-shaped battery lid 104 is fitted into the opening of the battery container 116, and the entire contact portions of both are laser-welded. At this time, the positive electrode external terminal 101 and the negative electrode external terminal 101 ′ pass through a hole in the center of the battery cover 104 and project outside the battery cover 104. As shown in FIG. 3, a flat first ceramic washer 103 made of alumina and having a thickness of 2 mm, an inner diameter of 16 mm, and an outer diameter of 28 mm, and a metal washer 111 smoother than the bottom of the nut 102 are arranged in this order. And fitted into the negative electrode external terminal 101 ′. The battery lid 104 is provided with a cleavage valve 110 that cleaves as the internal pressure of the battery increases on both the positive electrode side and the negative electrode side. The cleavage pressure of the cleavage valve 110 was set to 1.3 to 1.8 MPa.
[0028]
Next, a metal nut 102 is screwed to the positive electrode external terminal 101 and the negative electrode external terminal 101 ′, and the battery cover 104 is attached via the second ceramic washer 103 ′, the first ceramic washer 103, and the metal washer 111. Tighten and fix between the flange 107 and the nut 102. The tightening torque value at this time was 70 kgf · cm (6.86 N · m). The metal washer 111 did not rotate until the tightening operation was completed. In this state, the power generation element inside the battery container 116 is blocked from the outside air by the compression of the rubber (EPDM) O-ring 112 interposed between the back surface of the battery lid 104 and the flange 107.
[0029]
Thereafter, a predetermined amount of electrolyte was injected into the battery container 116 from the injection port 113 provided in the battery lid 104, and then the injection port 113 was sealed to complete the cylindrical lithium ion battery 120. The cylindrical lithium ion battery 120 does not have a current interrupting mechanism that interrupts current in response to an increase in the internal pressure of the battery container 116. In addition, the electrolyte includes lithium hexafluorophosphate (LiPF) in a mixed solvent with a volume ratio of 1: 1: 1 of EC, DMC, and DEC. ₆ ) Was dissolved at 1 mol / liter.
[0030]
As shown in FIG. 3, in the cylindrical lithium ion battery 120 of this embodiment, the average outer diameter of the battery container 116 is D (hereinafter referred to as a diameter D) (unit: mm), and from the outer surface of the positive battery lid. When the length to the outer surface of the negative electrode side battery lid is L (hereinafter referred to as length L) (unit: mm), the ratio D / L of the diameter D to the length L is within a predetermined range described later. . Further, a connecting member for connecting the wound group W ′ and each electrode terminal is provided on both the positive electrode side and the negative electrode side. The size of the space necessary for this connection is defined as A (mm) from the positive electrode side end of the wound group W ′ to the surface of the positive electrode side battery cover 104, and the negative electrode side of the wound group W ′. When the length from the end to the surface of the negative electrode side battery cover 104 is B (mm), A and B are set to 35 mm (A + B = 35 mm in FIG. 3). The length obtained by subtracting 35 mm from the length L of the battery corresponds to the length of the wound group W ′, that is, the width of the separator.
[0031]
【Example】
Next, the detail of the Example of the cylindrical

lithium ion batteries

20 and 120 produced according to the said embodiment is demonstrated. In addition, the battery of the comparative example manufactured at the same time so that the effect of the present example becomes clear will also be described.
[0032]
Example 1
As shown in Table 1 below, in Example 1, according to the first embodiment, a cylindrical lithium secondary battery 20 in which the following positive electrode and negative electrode were combined was produced. The positive electrode uses lithium cobaltate having an average particle size of about 10 μm as the positive electrode active material (trade name Cell Seed, manufactured by Nippon Chemical Industry Co., Ltd.). _P 106mm, length L _P 450cm, thickness T including current collector _P Was 231 μm. For the negative electrode, amorphous carbon (made by Kureha Chemical Industry Co., Ltd., trade name Carbotron) having an average particle diameter of about 20 μm is used as the negative electrode active material, and the width W _N 112mm, length L _N 468cm, thickness T including current collector _N Was 201 μm. The winding core is made of polypropylene and has a diameter D _S Used was 13 mm. Number of dredging N _W Is about 42 times, and the diameter D of the wound group _W Was 56.8 mm. The battery can had a diameter D of 61.2 mm, a length L of 153 mm, and a ratio D / L of 0.4. Since the thickness of the battery can is 0.5 mm, the inner diameter D of the battery can _I Was 60.2 mm. Therefore, the gap between the wound group and the battery can is 1.7 mm, and this gap is the diameter D of the wound group. _W Equivalent to about 3%. Further, the battery used in Example 1 does not have an open valve at the bottom. In Table 1, for the positive electrode active material, Co represents lithium cobaltate, Mn represents lithium manganate, and for the negative electrode active material, AC represents amorphous carbon, G represents graphite, Each is shown.
[0033]
(Example 1-2)
As shown in Table 1 below, Example 1-2 was the same as Example 1 except that an open valve was provided at the bottom of the battery can according to the first embodiment.
[0034]
(Example 2)
As shown in Table 1 below, in Example 2, according to the first embodiment, the width W _P 87mm, length L _P 550cm, width W _N 93mm, length L _N 568cm, number of wrinkles N _W About 47 times, wound group diameter D _W Was 62.3 mm, the battery can diameter D was 67.0 mm, and the battery can length L was 134 mm. The ratio D / L was 0.5. Inner diameter D of battery can _I Was 66.0 mm, and the gap between the wound group and the battery can was 1.85 mm.
[0035]
(Example 3)
As shown in Table 1 below, in Example 3, according to the first embodiment, the width W _P 74mm, length L _P 654cm, width W _N 80mm, length L _N 672cm, number of wrinkles N _W About 52 times, wound group diameter D _W Was 67.5 mm, the battery can diameter D was 72.6 mm, and the battery can length L was 121 mm. The ratio D / L was 0.6. Inner diameter D of battery can _I Was 71.6 mm, and the gap between the wound group and the battery can was 2.05 mm.
[0036]
[Table 1]

[0037]
Example 4
As shown in Table 1, in Example 4, according to the first embodiment, lithium manganate having an average particle size of about 15 μm was used as the positive electrode active material, and the width W _P 112mm, length L _P 541 cm, mesophase-based spherical graphite (trade name: KMFC, manufactured by Kawasaki Steel Corporation) having an average particle size of about 15 μm is used as the negative electrode active material, and the width W _N 118mm, length L _N 559cm, thickness T including current collector _N Is set to 154 μm, and the number of sputum N _W About 48 times, wound group diameter D _W Was 59.0 mm, the diameter D of the battery can was 63.6 mm, and the length L was 159 mm. The ratio D / L was 0.4. Inner diameter D of battery can _I Was 62.6 mm, and the gap between the wound group and the battery can was 1.8 mm.
[0038]
(Example 4-2)
As shown in Table 1, Example 4-2 was the same as Example 4 except that an open valve was provided at the bottom of the battery can according to the first embodiment.
[0039]
(Example 5)
As shown in Table 1, in Example 5, the width W according to the first embodiment. _P 92mm, length L _P 658cm, width W _N 98mm, length L _N 676cm, number of wrinkles N _W About 54 times, wound group diameter D _W Was 64.7 mm, the battery can diameter D was 69.5 mm, and the length L of the battery can was 139 mm. The ratio D / L was 0.5. Inner diameter D of battery can _I Was 68.5 mm, and the gap between the wound group and the battery can was 1.9 mm.
[0040]
(Example 6)
As shown in Table 1, in Example 6, according to the first embodiment, the width W _P 78mm, length L _P 775cm, width W _N 84mm, length L _N 793cm, number of wrinkles N _W About 60 times, wound group diameter D _W Was 69.8 mm, the battery can diameter D was 75.0 mm, and the battery can length L was 125 mm. The ratio D / L was 0.6. Inner diameter D of battery can _I Was 74.0 mm, and the gap between the wound group and the battery can was 2.1 mm.
[0041]
(Example 7)
As shown in Table 1, in Example 7, according to the first embodiment, the width W _P 115.5mm, length L _P 583 cm, amorphous carbon having an average particle diameter of about 20 μm is used as the negative electrode active material, and the width W _N 121.5mm, length L _N 601cm, thickness T including current collector _N Is 142μm, and the number of wrinkles N _W About 51 times, wound group diameter D _W Was 60.4 mm, the battery can diameter D was 65.0 mm, and the length L was 162.5 mm. The ratio D / L was 0.4. Inner diameter D of battery can _I Was 64.0 mm, and the gap between the wound group and the battery can was 1.8 mm.
[0042]
(Example 7-2)
As shown in Table 1, Example 7-2 was the same as Example 7 except that an open valve was provided at the bottom of the battery can according to the first embodiment.
[0043]
(Example 8)
As shown in Table 1, in Example 8, according to the first embodiment, the width W _P 95mm, length L _P 708cm, width W _N 101mm, length L _N 726cm, number of wrinkles N _W About 57 times, wound group diameter D _W Was 66.1 mm, the battery can diameter D was 71.0 mm, and the battery can length L was 142 mm. The ratio D / L was 0.5. Inner diameter D of battery can _I Was 70.0 mm, and the gap between the wound group and the battery can was 1.95 mm.
[0044]
Example 9
As shown in Table 1, in Example 9, the width W according to the first embodiment. _P 81mm, length L _P 837cm, width W _N 87mm, length L _N 855cm, number of wrinkles N _W About 63 times, wound group diameter D _W Is 71.5 mm, the diameter D of the battery can is 76.8 mm, and the length L of the battery can is 128 mm. The ratio D / L was 0.6. Inner diameter D of battery can _I Was 75.8 mm, and the gap between the wound group and the battery can was 2.15 mm.
[0045]
(Example 10)
As shown in Table 1, in Example 10, the width W according to the first embodiment. _P 77.5mm, length L _P 598cm, thickness T including current collector _P Is 103 μm, amorphous carbon having an average particle diameter of about 5 μm is used for the negative electrode active material, and the width W _N 83.5mm, length L _N 616cm, thickness T including current collector _N Is 73 μm and the diameter D of the shaft core _S Use a 10 mm one and use N _W About 70 times, wound group diameter D _W Was 46.0 mm, the battery can diameter D was 49.8 mm, and the length L was 124.5 mm. The ratio D / L was 0.4. Inner diameter D of battery can _I Was 48.8 mm, and the gap between the wound group and the battery can was 1.4 mm.
[0046]
(Example 10-2)
As shown in Table 1, Example 10-2 was the same as Example 10 except that an open valve was provided at the bottom of the battery can according to the first embodiment.
[0047]
(Example 11)
As shown in Table 1, in Example 11, the width W according to the first embodiment. _P 62.5mm, length L _P 736cm, width W _N 68.5mm, length L _N 754cm, number of wrinkles N _W About 79 times, wound group diameter D _W Was 50.7 mm, the battery can diameter D was 54.7 mm, and the battery can length L was 109.5 mm. The ratio D / L was 0.5. Inner diameter D of battery can _I Was 53.7 mm, and the gap between the wound group and the battery can was 1.5 mm.
[0048]
(Example 12)
As shown in Table 1, in Example 12, according to the first embodiment, the width W _P 52mm, length L _P 880cm, width W _N 58mm, length L _N 898cm, number of wrinkles N _W About 88 times, wound group diameter D _W Was 55.1 mm, the battery can diameter D was 59.4 mm, and the battery can length L was 99 mm. The ratio D / L was 0.6. Inner diameter D of battery can _I Was 58.4 mm, and the gap between the wound group and the battery can was 1.65 mm.
[0049]
(Example 13)
As shown in Table 1, in Example 13, a cylindrical lithium secondary battery 120 in which the following positive electrode and negative electrode were combined according to the second embodiment was produced. The positive electrode uses lithium manganate having an average particle size of about 15 μm as the positive electrode active material, and has a width W _P 112mm, length L _P 541cm, thickness T including current collector _P Was 231 μm. The negative electrode uses mesophase-based spherical graphite having an average particle diameter of about 15 μm as the negative electrode active material, and has a width W _N 118mm, length L _N 559cm, thickness T including current collector _N Was 154 μm. The shaft core is made of polypropylene and has a diameter D _S Used was 13 mm. Number of dredging N _W About 48 times, wound group diameter D _W Was 59.0 mm, the diameter D of the battery can was 63.6 mm, and the length L was 159 mm. The ratio D / L was 0.4. Since the thickness of the battery can is 0.5 mm, the inner diameter D of the battery can _I Was 62.6 mm. Therefore, the gap between the wound group and the battery can is 1.8 mm, and this gap is the diameter D of the wound group. _W Equivalent to about 3%.
The battery of Example 13 has open valves at both ends of the battery container.
[0050]
(Example 14)
As shown in Table 1, in Example 14, the width W according to the second embodiment. _P 92mm, length L _P 658cm, width W _N 98mm, length L _N 676cm, number of wrinkles N _W About 54 times, wound group diameter D _W Was 64.7 mm, the battery can diameter D was 69.5 mm, and the length L was 139 mm. The ratio D / L was 0.5. Inner diameter D of battery can _I Was 68.5 mm, and the gap between the wound group and the battery can was 1.9 mm.
[0051]
(Example 15)
As shown in Table 1, in Example 15, according to the second embodiment, the width W _P 78mm, length L _P 775cm, width W _N 84mm, length L _N 793cm, number of wrinkles N _W About 60 times, wound group diameter D _W Was 69.8 mm, the battery can diameter D was 75.0 mm, and the length L was 125 mm. The ratio D / L was 0.6. Inner diameter D of battery can _I Was 74.0 mm, and the gap between the wound group and the battery can was 2.1 mm.
[0052]
(Comparative Example 1)
As shown in Table 2 below, in Comparative Example 1, according to the first embodiment, the width W _P 119mm, length L _P 400cm, width W _N 125mm, length L _N 418cm, number of wrinkles N _W About 39 times, wound group diameter D _W Was 33.9 mm, the battery can diameter D was 58.1 mm, and the battery can length L was 166 mm. The ratio D / L was 0.35. Inner diameter D of battery can _I Was 57.1 mm, and the gap between the wound group and the battery can was 1.6 mm.
[0053]
(Comparative Example 2)
As shown in Table 2 below, Comparative Example 2 was the same as Comparative Example 1 except that an open valve was provided at the bottom of the battery can according to the first embodiment.
[0054]
(Comparative Example 3)
As shown in Table 2 below, in Comparative Example 3, the width W according to the first embodiment. _P 68mm, length L _P 696cm, width W _N 74mm, length L _N 714cm, number of wrinkles N _W About 54 times, wound group diameter D _W Was 69.5 mm, the battery can diameter D was 74.7 mm, and the battery can length L was 115 mm. The ratio D / L was 0.65. Inner diameter D of battery can _I Was 73.7 mm, and the gap between the wound group and the battery can was 2.1 mm.
[0055]
[Table 2]

[0056]
(Comparative Example 4)
As shown in Table 2, in Comparative Example 4, according to the first embodiment, lithium manganate having an average particle size of about 15 μm was used as the positive electrode active material, and the width W _P 125.5mm, length L _P 482 cm, mesophase spherical graphite having an average particle size of about 15 μm is used as the negative electrode active material, _N 131.5mm, length L _N 500cm, thickness T including current collector _N Is set to 154 μm, and the number N _W About 45 times, wound group diameter D _W Was 56.0 mm, the battery can diameter D was 60.4 mm, and the length L was 172.5 mm. The ratio D / L was 0.35. Inner diameter D of battery can _I Was 59.4 mm, and the gap between the wound group and the battery can was 1.7 mm.
[0057]
(Comparative Example 5)
As shown in Table 2, Comparative Example 5 was the same as Comparative Example 4 except that an open valve was provided at the bottom of the battery can according to the first embodiment.
[0058]
(Comparative Example 6)
As shown in Table 2, in Comparative Example 6, according to the first embodiment, the width W _P 72.5mm, length L _P 836cm, width W _N 78.5mm, length L _N 854cm, number of wrinkles N _W About 63 times, wound group diameter D _W Was 72.3 mm, the battery can diameter D was 77.7 mm, and the length L was 119.5 mm. The ratio D / L was 0.65. Inner diameter D of battery can _I Was 76.7 mm, and the gap between the wound group and the battery can was 2.2 mm.
[0059]
(Comparative Example 7)
As shown in Table 2, in Comparative Example 7, according to the first embodiment, the width W _P 129mm, length L _P Is 518 cm, amorphous carbon having an average particle diameter of about 20 μm is used as the negative electrode active material, _N 135mm, length L _N 536cm, thickness T including current collector _N Is 142μm, and the number of wrinkles N _W About 48 times, wound group diameter D _W Was 57.2 mm, the battery can diameter D was 61.6 mm, and the length L was 176 mm. The ratio D / L was 0.35. Inner diameter D of battery can _I Was 60.6 mm, and the gap between the wound group and the battery can was 1.7 mm.
[0060]
(Comparative Example 8)
As shown in Table 2, Comparative Example 8 was the same as Comparative Example 7 except that an open valve was provided at the bottom of the battery can according to the first embodiment.
[0061]
(Comparative Example 9)
As shown in Table 2, in the comparative example 9, the width W according to the first embodiment. _P 75mm, length L _P 897cm, width W _N 81mm, length L _N 915cm, number of wrinkles N _W About 66 times, wound group diameter D _W Is 73.9 mm, the battery can diameter D is 79.3 mm, and the length L is 122 mm. The ratio D / L was 0.65. Inner diameter D of battery can _I Was 78.3 mm, and the gap between the wound group and the battery can was 2.2 mm.
[0062]
(Comparative Example 10)
As shown in Table 2, in Comparative Example 10, according to the first embodiment, the width W _P 87mm, length L _P 523cm, thickness T including current collector _P Is 103 μm, amorphous carbon having an average particle diameter of about 5 μm is used for the negative electrode active material, and the width W _N 93mm, length L _N 541cm, thickness T including current collector _N Is 73 μm, and the number of wrinkles N _W About 65 times, wound group diameter D _W Was 43.3 mm, the battery can diameter D was 46.9 mm, and the length L was 134 mm. The ratio D / L was 0.35. Inner diameter D of battery can _I Was 45.9 mm, and the gap between the wound group and the battery can was 1.3 mm.
[0063]
(Comparative Example 11)
As shown in Table 2, Comparative Example 11 was the same as Comparative Example 10 except that an open valve was provided at the bottom of the battery can according to the first embodiment.
[0064]
(Comparative Example 12)
As shown in Table 2, in Comparative Example 12, the width W is according to the first embodiment. _P 48mm, length L _P 955cm, width W _N 54mm, length L _N 973 cm, number of wrinkles N _W About 92 times, wound group diameter D _W Was set to 57.3 mm, the battery can diameter D was 61.8 mm, and the length L was 95 mm. The ratio D / L was 0.65. Inner diameter D of battery can _I Was 60.8 mm, and the gap between the wound group and the battery can was 1.75 mm.
[0065]
(Comparative Example 13)
As shown in Table 2, in Comparative Example 13, according to the second embodiment, the width W _P 125.5mm, length L _P 482cm, width W _N 131.5mm, length L _N 500cm, number of wrinkles N _W About 45 times, wound group diameter D _W Was 66.0 mm, the battery can diameter D was 60.4 mm, and the length L was 172.5 mm. The ratio D / L was 0.35. Inner diameter D of battery can _I Was 59.4 mm, and the gap between the wound group and the battery can was 1.7 mm.
[0066]
(Comparative Example 14)
As shown in Table 2, in Comparative Example 14, the width W according to the second embodiment. _P 72.5mm, length L _P 836cm, width W _N 78.5mm, length L _N 854cm, number of wrinkles N _W About 63 times, wound group diameter D _W Was 72.3 mm, the battery can diameter D was 77.7 mm, and the length L was 119.5 mm. The ratio D / L was 0.65. Inner diameter D of battery can _I Was 76.7 mm, and the gap between the wound group and the battery can was 2.2 mm.
[0067]
(Measurement / Evaluation)
Next, the batteries of Examples and Comparative Examples completed in this way were charged at the ambient temperature of 25 ± 2 ° C. under the following conditions to obtain a fully charged state, and the following measurements 1 to 3 were performed. It was.
(Charging conditions)
Examples 1 to 9; 4.2 V constant voltage, limiting current 27 A, 3.5 hours
Examples 10-12; 4.2V constant voltage, limiting current 7A, 3.5 hours
Examples 13 to 15; 4.2 V constant voltage, limiting current 27 A, 3.5 hours
Comparative Examples 1-9; 4.2V constant voltage, limiting current 27A, 3.5 hours
Comparative Examples 10-12; 4.2 V constant voltage, limiting current 7 A, 3.5 hours
Comparative Examples 13 to 14; 4.2V constant voltage, limiting current 27A, 3.5 hours
[0068]
[Measurement 1]
The fully charged batteries of Examples 1-9, Examples 13-15, Comparative Examples 1-9, and Comparative Examples 13-14 are 9 A constant current, final discharge voltage 2.7 V, 25 ± 2 ° C. The batteries of Examples 10 to 12 and Comparative Examples 10 to 12 were discharged at a constant current of 3 A, a final discharge voltage of 2.7 V, and 25 ± 2 ° C., and the discharge capacity was confirmed. Moreover, the volume of the battery was calculated from the size of each battery, and the energy density was calculated.
[0069]
[Measurement 2]
The fully charged batteries of Examples 1-9, Examples 13-15, Comparative Examples 1-9 and Comparative Examples 13-14 are 27 A constant current, 25 ± 2 ° C., and Examples 10-12 and Comparative Examples 10 to 12 were each continuously charged at a constant current of 7 A and 25 ± 2 ° C., and the final battery condition was observed to give an appearance after overcharging.
[0070]
[Measurement 3]
A fully charged battery at an environmental temperature of 30 ± 3 ° C., in the length direction of the battery (axial direction of the axis), with an amplitude of 1 mm, a frequency of 10 Hz for 6 hours, 50 Hz for 6 hours, and 100 Hz for 6 hours A vibration test for applying vibration for a time was conducted. After applying vibration at each frequency, the battery was disassembled and the presence or absence of movement of the electrode winding group and cutting of the lead was visually observed.
[0071]
The measurement results of Measurements 1 to 3 are shown in Table 3 and Table 4 below.
[0072]
[Table 3]

[0073]
[Table 4]

[0074]
As shown in Tables 3 and 4, in the measurement results of the discharge capacity, the batteries of Examples 1-9 and Comparative Examples 1-9 of the first embodiment, and Examples 13-15 of the second embodiment and Comparative Examples The batteries of 13 to 14 are about 27 Ah, the batteries of Examples 10 to 12 of the first embodiment and the batteries of Comparative Examples 10 to 12 are about 7 Ah. A discharge capacity almost equal to the rated capacity is obtained, and a high energy density is obtained. It was.
[0075]
As a result of measurement 2, the batteries of Examples 1 to 15 in which the ratio D / L was in the range of 0.4 to 0.6 maintained almost the appearance, although some of the battery cans were swollen. It was. On the other hand, the batteries according to the first embodiment of Comparative Examples 1, 2, 4, 5, 7, 8, 10, and 11 in which the ratio D / L is less than 0.4 indicate whether or not there is an open valve at the bottom of the battery can. Regardless, the upper lid was removed from the caulking portion. Moreover, the battery of 2nd Embodiment of the comparative example 13 showed the swelling of a battery container. In particular, in the batteries of Comparative Examples 1 and 2 using lithium cobalt oxide as the positive electrode active material, breakage from the battery can opening to the side surface was also observed. In all the batteries, the safety valve on the upper lid part and the release valve on the bottom part were all cleaved.
[0076]
In measurement 2, the battery voltage rises due to continuous overcharge, decomposition and gasification of the electrolyte occurs, and further decomposition causes heat generation, so that the separator contracts and the so-called internal short circuit is brought into contact with the positive and negative electrodes. Occur. When this happens, the temperature further rises due to the short-circuit current, the gasification of the electrolytic solution becomes abrupt, and the internal pressure of the battery rises rapidly. Immediately, the safety valve on the upper lid and the opening valve on the bottom are opened, and the internal pressure is released to the outside of the battery. The gas generated inside the winding group moves in the direction of both ends of the winding group, that is, in the direction of the safety valve on the upper lid and the opening valve on the bottom. However, in a battery having a ratio D / L of less than 0.4, the length to both ends of the wound group is large. Especially when gas is suddenly generated, the battery can is inflated or the gas lump is released at once. When trying to pass through the valve, it seems to have a momentum to remove the upper lid from the caulking portion. Therefore, as an unexpected situation, it has been found that the ratio D / L is preferably set to 0.4 or more in order to ensure safety when the battery falls into an abnormal state such as overcharge.
[0077]
In the battery of Example 1-2, in which lithium cobaltate was used for the positive electrode active material, amorphous carbon was used for the negative electrode, and an open valve was provided at the bottom, swelling of the battery can was observed, whereas lithium manganate was used for the positive electrode. In the battery of Example 7-2 using the same, no abnormality in the appearance was observed except that the open valve at the bottom was cleaved. Therefore, it was found that it is preferable to use a lithium manganese complex oxide typified by lithium manganate as the positive electrode active material. In addition, in the batteries of Examples 4, 7, and 10 that did not have an open valve at the bottom, the battery can swelled, whereas the batteries with the same specifications had an open valve at Example 4 In the batteries of -2, 7-2, and 10-2, no abnormality in appearance was observed except that the open valve at the bottom was cleaved. Therefore, it has been clarified that a battery having an open valve at the bottom, that is, a battery having internal pressure release valves at both ends in the longitudinal direction of the battery is excellent in safety.
[0078]
As a result of measurement 3, no abnormality after the vibration test was observed in the batteries of all the examples. On the other hand, in the batteries of the first embodiment of Comparative Examples 3, 6, 9, and 12 where the ratio D / L exceeds 0.6, and the battery of the second embodiment of Comparative Example 14, the wound group has an axial core. The lead led out from the electrode was cut off. When the ratio D / L is large, that is, when the diameter D is large with respect to the length L, the area of the electrode that is in close contact with the shaft core is small, and it seems that the wound group cannot be held. Therefore, it was found that the ratio D / L is preferably 0.6 or less.
[0079]
As described above, in the cylindrical

lithium ion batteries

20 and 120 of the above embodiment, the ratio D / L of the diameter D to the length L of the battery container is set to 0.4 to 0.6 regardless of the battery structure. Thus, the electrode winding groups W and W ′ can be reliably supported and prevented from moving, and the gas generated during overcharge can be quickly released out of the battery. Therefore, a cylindrical lithium ion battery having high vibration resistance and high safety could be realized. Moreover, by using lithium manganese double oxide as the positive electrode active material, it was possible to reduce the generation of gas during overcharge and to improve safety. Furthermore, by providing release valves at both ends in the longitudinal direction of the battery, the gas generated in the battery during overcharging can be released from the both ends of the battery to the outside of the battery, improving safety. .
[0080]
In addition, this invention is not limited to the diameter D and height L which were demonstrated in the said embodiment, The kind of positive electrode active material, the electrically conductive agent in positive mix, the kind and manufacture of the carbon material in a negative electrode active material The method is not particularly limited. Further, as is clear from the situation of the examples and comparative examples, the present invention works particularly remarkably in batteries having a battery capacity of 7 Ah or more and a battery count of 30 times or more, and is limited to the diameter of the shaft core and the thickness of the electrodes. It is not a thing. Furthermore, in the above-described embodiment, the wound group is produced by winding the electrode around the shaft core, but the wound group may be formed by inserting the shaft core into the center of the wound electrode after winding the electrode. Good.
[0081]
Further, as the positive electrode active material for lithium ion batteries that can be used other than the present embodiment, lithium is a material that can be inserted and desorbed, and a lithium manganese complex oxide in which a sufficient amount of lithium is inserted in advance is preferable, A lithium manganate having a spinel structure or a material obtained by substituting or doping a part of manganese or lithium in a crystal with an element other than those may be used. For example, the Li / Mn ratio of the lithium manganese complex oxide exceeds 0.5, or the lithium manganese complex oxide is changed to Li _{1 + x} Mn _2-xy M _y O ₄ (Where 0 <x <0.1, 0 <y <0.3, and M is at least one element selected from the group consisting of Al, Cr, Ni, Co, and Mg). It is good also as a thing. In general, lithium manganate can be synthesized by mixing and baking an appropriate lithium salt and manganese oxide, but the desired Li / Mn ratio should be achieved by controlling the charging ratio of the lithium salt and manganese oxide. Can do.
[0082]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably support the electrode winding group and prevent the electrode winding group from moving, and to quickly release the gas generated during overcharge to the outside of the battery. Therefore, an effect that a cylindrical lithium ion battery having high vibration resistance and high safety can be realized can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion battery according to a first embodiment to which the present invention is applicable.
FIG. 2 is a bottom view of the battery can of the cylindrical lithium ion battery according to the first embodiment.
FIG. 3 is a cross-sectional view of a cylindrical lithium ion battery according to a second embodiment to which the present invention is applicable.
[Explanation of symbols]
3 Safety valve (Internal pressure release mechanism)
16 Battery can (battery container)
17 Winding core (shaft core)
20, 120 Cylindrical lithium ion battery
25, 110 Release valve (Internal pressure release mechanism)
116 Battery container
117 shaft core
W, W 'wound group (electrode wound group)
W1 aluminum foil (positive electrode current collector)
W2 cathode active material layer
W3 Copper foil (Negative electrode current collector)
W4 Negative electrode active material layer
W5 separator
D Battery diameter
L Battery length

Claims

In a battery container having an internal pressure release mechanism that releases an internal pressure at a predetermined pressure, a positive electrode active material layer containing a positive electrode active material, a strip-like positive electrode having a positive electrode current collector, and a negative electrode active material using a carbon material for the negative electrode active material An electrode winding group in which a layer and a strip-shaped negative electrode having a negative electrode current collector are wound around a shaft core at least 30 times through a separator, and both ends of the shaft core are a positive current collector and a negative current collector A cylindrical lithium ion battery supported or fixed on and infiltrated with an electrolyte solution, wherein the battery container has a diameter D (mm) and a length of the cylindrical lithium ion battery having a substantial discharge capacity of 7 Ah or more. A cylindrical lithium ion battery characterized in that a ratio D / L of the diameter D to the length L is 0.4 to 0.6 when L (mm).

The cylindrical lithium ion battery according to claim 1, wherein the positive electrode active material is a lithium manganese complex oxide.

The cylindrical lithium ion battery according to claim 1 or 2, wherein the cylindrical lithium ion battery has the internal pressure release mechanism at both ends in the longitudinal direction of the battery.