JP4305035B2

JP4305035B2 - Winding cylindrical lithium-ion battery

Info

Publication number: JP4305035B2
Application number: JP2003112632A
Authority: JP
Inventors: 賢治中井
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Resonac Corp
Priority date: 2003-04-17
Filing date: 2003-04-17
Publication date: 2009-07-29
Anticipated expiration: 2023-04-17
Also published as: JP2004319311A

Description

【０００１】
【発明の属する技術分野】
本発明は捲回式円筒型リチウムイオン電池に係り、特に、正、負極集電体の長手方向一側に複数の短冊状正、負極リード片が形成され正、負極リード片に隣接して長手方向に未塗布部を残して活物質合剤が塗布された正、負極が、セパレータを介して正、負極リード片を互いに逆向きにして捲回された電極捲回群を具備する捲回式円筒型リチウムイオン電池を具備する捲回式円筒型リチウムイオン電池に関する。
【０００２】
【従来の技術】
捲回式円筒型リチウムイオン電池は、高エネルギ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。
【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にした電気自動車や、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、一部実用化の段階にきている。
【０００４】
電気自動車の電源となる電池には当然高出力、高エネルギが得られる特性が要求され、これらの要求にマッチした電池としてリチウムイオン電池が注目されている。これらの要求に応えるために、例えば、電極の集電体である金属箔の一部に活物質を塗布せずに残しておき、短冊状に加工し直接リード片を形成することで、電池の内部抵抗を小さくして高出力化を図る技術が知られている（例えば、特許文献１参照）。
【０００５】
一方、電極捲回群を有する円筒型電池においては、充放電効率の低下又は寿命特性、信頼性の観点から、図７に示すように、負極３１の周辺の一部、例えば、負極リード片側が正極２１の端部と対向しないように正、負極２１、３１が配設された技術が知られている（例えば、特許文献２、３参照）。
【０００６】
【特許文献１】
特開平９−９２３３５号公報（図１、図３、段落番号「００１６」、、「００２１」、「００２３」、）
【特許文献２】
特開平１−１２８３７０号公報（図２、図３）
【特許文献３】
実開平２−１５０７６０号公報（図１、図４）
【０００７】
【発明が解決しようとする課題】
しかしながら、上記特許文献の技術を再現したところ、電池を放置しておくと電池の異常な容量低下を引き起こす場合があった。本発明者が詳細に調査した結果、異常な容量低下を引き起こした電池は、電池の微小内部短絡による自己放電により電圧が異常に低下していることが判明した。この電池を解体すると、複数の短冊状リード片の一部の根元の加工端が、セパレータを貫通して微小に負極に到達している箇所が発見された。また、この加工端を詳しく調べると、リード加工時に形成されたバリがわずかながらに存在していた。リード片は、電極が捲回された後に集電部材に結束されているので、リード片の根元から結束方向に折り曲げられることになる。このとき、根元部分が対極の負極方向に押し付けられる力が働き、加工時のバリがあった場合等は特に振動等によってセパレータを貫通して負極に到達すると推察できる。
【０００８】
また、電圧が異常に低下していた別の電池では、正極の捲回始端又は捲回終端の活物質合剤未塗布部に形成されていた切断バリがセパレータを貫通して微小に負極に到達している箇所が発見された。
【０００９】
本発明は上記事案に鑑み、容量、出力を確保可能な捲回式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。
【００１０】
【課題を解決するための手段】
上記課題を解決するために、本発明は、正、負極集電体の長手方向一側に複数の短冊状正、負極リード片が形成され前記正、負極リード片に隣接して前記長手方向に未塗布部を残して活物質合剤が塗布された正、負極が、セパレータを介して前記正、負極リード片を互いに逆向きにして捲回された電極捲回群を具備する捲回式円筒型リチウムイオン電池において、前記負極集電体の前記負極リード片が形成されていない長手方向他側端が、前記長手方向と交差する幅方向で、前記正極集電体の前記未塗布部の部分に位置付けられるように配置されている。本発明では、負極集電体の負極リード片が形成されていない長手方向他側端が、長手方向と交差する幅方向で、正極集電体の未塗布部の部分に位置付けられるように配置されているため、正、負極リード片の形成箇所からバリが突出しセパレータを貫通しても正負極間で微小短絡が生じないので、電圧低下が抑制され容量、出力を確保することができる。
【００１１】
第１の態様において、正極集電体の未塗布部における正極集電体の幅方向両端が負極集電体の長手方向他側端部に交わるため、正極集電体の未塗布部における正極集電体の幅方向両端からバリが突出しセパレータを貫通して負極集電体の他側端部と短絡を生ずることがあるが、正極集電体の幅方向両端のうち少なくとも一端かつ正極集電体の未塗布部の部分と、負極集電体の長手方向他側端部との間に絶縁体を介在させれば、正極集電体の未塗布部における正極集電体の幅方向両端のうち少なくとも一端からバリが突出していても絶縁体でバリと負極との接触を防止することができるので、正負極間の微小短絡を防止することができる。
【００１３】
また、本発明において、絶縁体を正極集電体の幅方向両端のうち少なくとも一端かつ正極集電体の未塗布部の部分の表裏面に貼付された粘着テープとするようにしてもよい。
【００１４】
【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説明する。
【００１５】
（構成）
図１に示すように、本実施形態の円筒型リチウムイオン二次電池（以下、二次電池という。）４０は、帯状の正、負極板が厚さ４０μｍのポリエチレン製セパレータを介して捲回された電極捲回群６を備えている。
【００１６】
図２及び図３に示すように、正、負極板２０、３０は、基材となる正、負極集電体９、１９にアルミニウム箔、圧延銅箔がそれぞれ用いられている。正、負極集電体９、１９の長手方向一側には、短冊状の正、負極リード片９ａ、１９ａが所定間隔で形成されている。正、負極板２０、３０の両面には、正、負極リード片９ａ、１９ａに隣接して長手方向に未塗布部１３を残して正、負極活物質合剤がほぼ均等、均質に塗布され、正、負極活物質合剤層１７、１８が形成されている。正極活物質合剤には、正極活物質に充放電によりリチウムを放出、吸蔵可能なリチウム遷移金属複酸化物が用いられており、負極活物質合剤には、負極活物質に充放電によりリチウムを吸蔵、放出可能な非晶質炭素が用いられている。セパレータは、長手方向及び長手方向に交差する幅方向において正、負極集電体９、１９より大きな面積を有している。なお、図２では、正極リード片９ａの長さをＡ、未塗布部１３の幅をＢ、正極活物質合剤層１７の幅をＣで表している。
【００１７】
図３に示すように、正、負極板２０、３０は、捲回前に、正、負極リード片９ａ、１９ａを互いに逆向きにして配置される。このとき、正、負極リード片９ａ、１９ａが、幅方向で負、正極集電体１９、９の長手方向他側端部に対しそれぞれ上、下方にオフセット配置されている。すなわち、正、負極リード片９ａ、１９ａの形成端９ｂ、１９ｂは、幅方向で負、正極集電体１９、９の長手方向他側端部から上、下方にずらされている。上、下方のズレ幅は、未塗布部１３の幅Ｂのほぼ半分に設定されている。負極板３０の幅方向両端は、正極板２０の幅方向両端より左右にはみ出している。このため、負極活物質合剤層１８は正極活物質合剤層１７に対し長手方向及び幅方向にはみ出すように配置され、正極活物質合剤層１７は負極活物質合剤層１８に全面で対向する。なお、図３においてセパレータは捨象している。
【００１８】
＜正極板の作製＞
正極活物質にリチウム遷移金属複酸化物としてマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）を選定し、マンガン酸リチウム粉末と、導電剤として平均粒径５μｍの鱗片状黒鉛と、結着剤としてポリフッ化ビニリデンとを質量比８５：１０：５で混合し、これに分散溶媒のＮ−メチル−２−ピロリドンを添加、混練したスラリを厚さ２０μｍの正極集電体９の両面に塗布し正極活物質合剤層１７とした。このとき、正極集電体９の長手方向一側に幅Ａ＋Ｂの未塗布部を残した。その後、乾燥、プレス、裁断して正極活物質合剤層１７の幅Ｃが３００ｍｍ、長さが６０００ｍｍ、厚さ（アルミニウム箔含む）が２３０μｍの正極板２０を得た。乾燥後の正極活物質合剤の塗布量は、２８０ｇ／ｍ^２とした。
【００１９】
上記幅Ａ＋Ｂの未塗布部を切り欠き、切り欠き残部を長さＡの正極リード片９ａとした。隣り合う正極リード片９ａを、２０ｍｍ間隔で設けた。また、正極リード片９ａの幅を１０ｍｍとし、未塗布部１３の幅Ｂを６ｍｍとした。
【００２０】
＜負極板の作製＞
非晶質炭素として呉羽化学工業株式会社製カーボトロンＰ粉末９０重量部に、結着剤として１０重量部のポリフッ化ビニリデンを添加し、これに分散溶媒のＮ−メチル−２−ピロリドンを添加、混練したスラリを厚さ１０μｍの負極集電体１９の両面に塗布し負極活物質合剤層１８とした。このとき、負極集電体１９の長手方向の一側に幅Ａ＋Ｂの未塗布部を残した。その後、乾燥、プレス、裁断して負極活物質合剤層１８の幅が３０６ｍｍ、長さが６２００ｍｍ、厚さ（圧延銅箔含む）が１４０μｍの負極板３０を得た。乾燥後の負極活物質合剤の塗布量は、６６ｇ／ｍ^２とした。
【００２１】
正極板２０と同様に幅Ａ＋Ｂの未塗布部を切り欠き、切り欠き残部を負極リード片１９ａとした。隣り合う負極リード片１９ａを、２０ｍｍ間隔で設けた。また、負極リード片１９ａの幅を１０ｍｍとし、負極リード片１９ａに隣接する未塗布部２３の幅を２ｍｍとした。
【００２２】
＜電池の作製＞
図１及び図３に示すように、作製した正極板２０と負極板３０とを、これら両極板が直接接触しないようにセパレータを介して正、負極リード片９ａ、１９ａを互いに逆向きに配置し捲回して電極捲回群６を作製した。このとき、正、負極リード片９ａ、１９ａの形成端９ｂ、１９ｂが、幅方向で負、正極集電体１９、９の長手方向の他側端部から上、下方にズレるようにした。電極捲回群６の径を６１±０．５ｍｍに調整した。
【００２３】
正極板２０に形成された正極リード片９を変形させ、その全てを、軸芯１１のほぼ延長線上にある極柱（正極外部端子１）周囲から一体に張り出している鍔部７周面付近に集合、接触させた後、リード片９と鍔部７周面とを超音波溶接してリード片９ａを鍔部７周面に接続し固定した。また、負極外部端子１’と負極板３０に形成された負極リード片１９ａとの接続操作も、正極外部端子１と正極リード片９ａとの接続操作と同様に行った。
【００２４】
その後、正極外部端子１及び負極外部端子１’の鍔部７周面全周に絶縁被覆８を施した。この絶縁被覆８は、電極捲回群６外周面全周にも及ぼした。絶縁被覆８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７周面から電極捲回群６外周面に亘って何重にも巻いて絶縁被覆８とした。電極捲回群６の最大径部が絶縁被覆８存在部となるように巻き数を調整し、該最大径を電池容器５の内径より僅かに小さくして電極捲回群６を電池容器５内に挿入した。電池容器５には、外径６７ｍｍ、内径６６ｍｍのステンレス製円筒を用いた。
【００２５】
そして、アルミナ製で円盤状電池蓋４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３’を、先端が正極外部端子１を構成する極柱、先端が負極外部端子１’を構成する極柱にそれぞれ嵌め込んだ。また、アルミナ製で厚さ２ｍｍ、内径１６ｍｍ、外径２８ｍｍの平板状の第１のセラミックワッシャ３を電池蓋４に載置し、正極外部端子１、負極外部端子１’をそれぞれ第１のセラミックワッシャ３に通した。その後、電池蓋４周端面を電池容器５開口部に嵌合し、双方の接触部全域をレーザ溶接した。このとき、正極外部端子１、負極外部端子１’は、電池蓋４の中心に形成された穴を貫通して電池蓋４外部に突出している。そして、第１のセラミックワッシャ３、金属製ナット２底面よりも平滑な金属ワッシャ１４を、この順に正極外部端子１、負極外部端子１’にそれぞれ嵌め込んだ。なお、電池蓋４には電池の内圧上昇に応じて開裂する内圧低減機構としての開裂弁１０が設けられている。開裂弁１０の開裂圧は、１．３×１０^６〜１．８×１０^６Ｐａとした。
【００２６】
次いで、ナット２を正極外部端子１、負極外部端子１’にそれぞれ螺着し、第２のセラミックワッシャ３’、第１のセラミックワッシャ３、金属ワッシャ１４を介して電池蓋４を鍔部７とナット２の間で締め付けにより固定した。このときの締め付けトルク値は約７Ｎ・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１４は回転しなかった。この状態で、電池蓋４裏面と鍔部７の間に介在させたゴム（ＥＰＤＭ）製Ｏリング１６の圧縮により電池容器５内部の主として電極捲回群６の発電要素は外気から遮断される。
【００２７】
その後、電池蓋４に設けた注液口１５から４８０ｇの非水電解液を電池容器５内に注液し、その後注液口１５を封止することにより二次電池４０を完成させた。
【００２８】
非水電解液には、エチレンカーボネートとジメチルカーボネートとジエチルカーボネートとの体積比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。なお、二次電池４０には、電池容器５の温度の上昇に応じて電流を遮断する、例えば、ＰＴＣ（Positive Temperature Coefficient）素子や、内圧の上昇に応じて電気的接続が切断されるような電流遮断機構は設けられていない。
【００２９】
（作用等）
本実施形態の二次電池４０では、正、負極リード片９ａ、１９ａが、正極集電体９の幅方向で負、正極集電体１９、９の長手方向他側端部からそれぞれ上、下方にオフセット配置されている。このため、正、負極リード片９ａ、１９ａの形成端９ｂ、１９ｂからバリが突出しセパレータを貫通しても正、負極板２０、３０間で微小短絡が生じない。従って、二次電池４０は電圧低下が抑制され容量、出力を確保することができる。
【００３０】
また、本実施形態の二次電池４０では、正、負極板２０、３０は、負極活物質合剤層１８が正極活物質合剤層１７に対し長手方向及び幅方向にずらされて配設されており、正極活物質合剤層１７は、負極活物質合剤層１８に全面で対向されている。このため、正極活物質合剤層１７及び負極活物質合剤層１８の対向面積が大きくなる。従って、高容量、高出力の二次電池４０を得ることができる。
【００３１】
更に、本実施形態の二次電池４０では、正、負極板２０、３０の幅Ａ＋Ｂの未塗布部を切り欠くことで複数の正、負極リード片９ａ、１９ａが形成されている。このため、正、負極リード片９ａ、１９ａでの抵抗を抑制することができるので、高出力の二次電池４０とすることができる。
【００３２】
（第２実施形態）
次に、本発明を円筒型リチウムイオン二次電池に適用した第２の実施の形態について説明する。なお、上述した第１実施形態と同一の部材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。
【００３３】
図４及び図５に示すように、本実施形態では、正極集電体９の幅方向両端（捲回始端、捲回終端）のうち少なくとも一端かつ正極集電体９の未塗布部１３の部分１３ａ（及び／又は、１３ｂ）と、負極集電体１９の長手方向他側端部との間に、ポリプロピレン製で片面に接着剤が塗着された略矩形状の粘着テープ２５が介在している。すなわち、粘着テープ２５は、部分１３ａ（１３ｂ）の表面に貼付されており、長手方向及び幅方向において未塗布部１３から僅かにずれて（はみ出して）いる。部分１３ａ（１３ｂ）の裏面には、粘着テープ２５と同形状、同材質で不図示の粘着テープが粘着テープ２５と対向して貼付されている。
【００３４】
本実施形態の二次電池では、正極集電体９の幅方向両端のうち少なくとも一端かつ正極集電体９の未塗布部１３の部分１３ａ（１３ｂ）と、負極集電体１９の長手方向他側端部との間に、粘着テープ２５が介在されている。このため、正極集電体９の未塗布部１３における正極集電体９の幅方向両端のうち少なくとも一端から切断バリが突出していても粘着テープ２５で切断バリと負極板３０との接触を防止することができる。従って、正、負極板２０、３０間の微小短絡を抑制して電池の容量、出力を確保することができる。
【００３５】
また、本実施形態の二次電池では、２枚の粘着テープは、未塗布部１３の部分１３ａ（１３ｂ）の表裏面に貼付されている。このため、正、負極板２０、３０が捲回されたときに、部分１３ｂの表裏面側にそれぞれ位置する負極板３０に切断バリが接触することを抑制することができる。従って、より微小短絡を防止することができる。更に、粘着テープ２５を部分１３ａ（１３ｂ）に貼付することで容易に固定することができるので、作業性を向上させることができる。
【００３６】
なお、本実施形態では、正、負極リード片９ａ、１９ａの形成端９ｂ、１９ｂが、幅方向で負、正極板３０、２０の長手方向他側端部から上、下方にずらされている例を示したが、正、負極リード片９ａ、１９ａの形成端９ｂ、１９ｂと負、正極板３０、２０の長手方向他側端部とが対向するようにしてもよい。このようにしても、正極集電体９の未塗布部１３における正極集電体９の幅方向両端のうち少なくとも一端から切断バリが突出するときにバリが負極板３０に接触することを防止することができる。
【００３７】
また、本実施形態では、２枚の粘着テープが部分１３ａ（１３ｂ）の表裏面に貼付されている例を示したが、１枚の粘着テープを折り曲げて部分１３ａ（１３ｂ）の表裏面に貼付するようにしてもよいし、複数枚の粘着テープ２５を貼付するようにしてもよいし、粘着テープ２５の形状も限定されるものではない。
【００３８】
更に、上記実施形態では、正極板２０において正極リード片９ａの長さＡ、未塗布部１３の幅Ｂ、正極活物質合剤層の幅Ｃがそれぞれ４４、６、３００ｍｍに設定されている例を示したが、これらの値は限定されるものではなく、例えは、正極活物質合剤層１７の幅Ｃをより大きくすることで、より高容量、高出力の電池とすることができる。
【００３９】
また、上記実施形態では、正、負極リード片９ａ、１９ａの負、正極集電体１９、９の長手方向他側端部に対する上、下方のズレ幅が未塗布部１３の幅Ｂのほぼ半分に設定されている例を示したが、ズレ幅はこれに限定されず、例えば、ズレ幅をより大きくすることで、微小短絡の発生を更に抑制することができる。
【００４０】
更に、上記実施形態では、電気自動車用電源等に用いられる大形の二次電池４０を例示したが、電池の大きさ、電池容量には限定されず、有底筒状容器（缶）に電池上蓋がカシメ封口されている構造の円筒型電池に適用してもよい。特に電気自動車用電源に用いられる電池は、高容量、高出力な特性が要求されるため、本発明の適用は好ましい。
【００４１】
更にまた、上記実施形態では、絶縁被覆８に、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が、特にこれに限定されるものではない。例えば、基材がポリプロピレンやポリエチレン等のポリオレフィンで、その片面又は両面にヘキサメタアクリレートやブチルアクリレート等のアクリル系粘着剤を塗布した粘着テープや、粘着剤を塗布しないポリオレフィンやポリイミドからなるテープ等を好適に使用してもよい。
【００４２】
また更に、上記実施形態では、正極活物質に、マンガン酸リチウムを用いる例を示したが、リチウムコバルト複合酸化物であるコバルト酸リチウム、リチウムニッケル複合酸化物であるニッケル酸リチウム、リチウムマンガン複酸化物であるマンガン酸リチウムはもちろんのこと、リチウムとコバルト、ニッケル、マンガンの任意の組合せの複酸化物を用いてもよいし、これらの複酸化物に更に異種金属のドープがなされたものを用いてもよい。また、層状岩塩構造を有するマンガン酸リチウム（ＬｉＭｎＯ_２）、結晶中のリチウムやマンガンの一部を異種金属で置換又はドープした材料や結晶中の酸素の一部をＳ、Ｐ等で置換又はドープした材料を使用するようにしてもよい。
【００４３】
また、上記実施形態では、リチウムイオン電池用極板活物質の結着剤としてポリフッ化ビニリデンを用いる例を示したが、ポリテトラフルオロエチレン、ポリエチレン、ポリスチレン、ポリブタジエン、ブチルゴム、ニトリルゴム、スチレン／ブタジエンゴム、多硫化ゴム、ニトロセルロース、シアノエチルセルロース、各種ラテックス、アクリロニトリル、フッ化ビニル、フッ化ビニリデン、フッ化プロピレン、フッ化クロロプレン、ビニルアルコール等の重合体及びこれらの混合体などを用いてもよい。
【００４４】
更にまた、上記実施形態では、リチウムイオン電池用負極活物質に非晶質炭素をと用いる例を示したが、例えば、天然黒鉛や、人造の各種黒鉛材、コークスなどの炭素質材料等でよく、その粒子形状においても、鱗片状、球状、繊維状、塊状等、特に制限されるものではない。
【００４５】
更に、上記実施形態では、非水電解液として、一般的なリチウム塩を電解質とし、これを有機溶媒に溶解した電解液が用いられる例を示したが、リチウム塩や有機溶媒は特に制限されない。例えば、電解質としては、ＬｉＣｌＯ_４、ＬｉＡｓＦ_６、ＬｉＰＦ_６、ＬｉＢＦ_４、ＬｉＢ（Ｃ_６Ｈ_５）_４、ＣＨ_３ＳＯ_３Ｌｉ、ＣＦ_３ＳＯ_３Ｌｉ等やこれらの混合物を用いることができる。
【００４６】
そして、上記実施形態では、非水電解液の有機溶媒としてエチレンカーボネートとジメチルカーボネートとジエチルカ−ボネ−トの体積比１：１：１の混合溶液を用いる例を示したが、プロピレンカーボネート、エチレンカーボネート、エチルメチルカーボネート、１，２−ジメトキシエタン、１，２−ジエトキシエタン、γ−ブチロラクトン、テトラヒドロフラン、１，３−ジオキソラン、４−メチル−１，３−ジオキソラン、ジエチルエーテル、スルホラン、メチルスルホラン、アセトニトリル、プロピオニトニル等またはこれら２種類以上の混合溶媒を用いるようにしてもよいし、混合配合比についても限定されるものではない。
【００４７】
【実施例】
以下、上記実施形態に従って作製した実施例の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。
【００４８】
（実施例１）
実施例１では、第１実施形態に従って、正、負極リード片９ａ、１９ａが、幅方向で負、正極集電体１９、９の長手方向他側端部からそれぞれ上、下方にオフセット配置され正、負極板２０、３０が捲回された捲回群を用いて二次電池４０を作製した。
【００４９】
（実施例２）
実施例２では、第２実施形態に従って、正極板２０の部分１３ａに更に２枚の粘着テープ２５を貼付した以外は実施例１と同様に二次電池を作製した。
【００５０】
（比較例１）
図６及び図７に示すように、比較例１では、正極リード片の長さＤを４８ｍｍ、正極活物質合剤塗布部の幅Ｆを３００ｍｍ、未塗布部の幅Ｅを２ｍｍとし、正極リード片の形成端と負極板３１の他側とを対向させて捲回した捲回群を用いて二次電池を作製した。すなわち、比較例１では、正、負極リード片が、実施例１のように幅方向で負、正極集電体の長手方向他側端部からそれぞれ上、下方にオフセット配置されていない。
【００５１】
＜試験・評価＞
次に、上述した実施例及び比較例の各電池をそれぞれ５０個作製し、室温で充電した後放置し、放置期間中の電圧を追跡し、電圧が低下した電池の個数（電圧低下電池数）を調べた。充電条件は、４．２Ｖ定電圧、制限電流８０Ａ、３．５時間とした。放置温度条件は、２５±２゜Ｃとした。下表１に、試験結果を示す。
【００５２】
【表１】

【００５３】
表１に示すように、実施例１の電池では、正、負極リード片９ａ、１９ａの形成端９ｂ、１９ｂが、幅方向で負、正極板３０、２０の長手方向の他側から上、下方にオフセット配置されているため、正極リード片の形成端が負極板３１と対向してる比較例１の電池に比べて異常な電圧低下を起こす率（電圧低下電池数／製作数×１００）が低いことが判明した。また、実施例２の電池では、部分１３ａ及び１３ｂの少なくとも一方に、粘着テープ２５が貼付されているので、異常な電圧低下を起こす率が更に低いことが判明した。
【００５４】
【発明の効果】
以上説明したように、本発明によれば、負極集電体の負極リード片が形成されていない長手方向他側端が、長手方向と交差する幅方向で、正極集電体の未塗布部の部分に位置付けられるように配置されているため、正、負極リード片の形成箇所からバリが突出しセパレータを貫通しても正負極間で微小短絡が生じないので、電圧低下が抑制され容量、出力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実施形態の円筒型リチウムイオン二次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二次電池の正極板の正面図である。
【図３】第１実施形態の円筒型リチウムイオン二次電池の正、負極板の正面図である。
【図４】第２実施形態の円筒型リチウムイオン二次電池の粘着テープが貼付された正極板の正面図である。
【図５】第２実施形態の円筒型リチウムイオン二次電池の正、負極板の正面図である。
【図６】従来の円筒型リチウムイオン二次電池の正極板の正面図である。
【図７】従来の円筒型リチウムイオン二次電池の正、負極板の正面図である。
【符号の説明】
６電極捲回群
９正極集電体
９ａ、１９ａ正極リード片、負極リード片
９ｂ、１９ｂ形成箇所
１３、２３未塗布部
１３ａ、１３ｂ部分
１９負極集電体
２５粘着テープ（絶縁体）
２０正極板（正極）
３０負極板（負極）
４０円筒型リチウムイオン二次電池（円筒型リチウムイオン電池）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wound cylindrical lithium ion battery, and in particular, a plurality of strip-like positive and negative electrode lead pieces are formed on one side of the positive and negative electrode current collectors in the longitudinal direction, and are adjacent to the positive and negative electrode lead pieces. Winding type comprising an electrode winding group in which a positive electrode and a negative electrode coated with an active material mixture leaving an uncoated portion in the direction are wound with a positive electrode and a negative electrode lead piece in opposite directions through a separator The present invention relates to a wound cylindrical lithium ion battery including a cylindrical lithium ion battery.
[0002]
[Prior art]
Winding cylindrical lithium ion 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.
[0003]
On the other hand, in the automobile industry, in order to deal with environmental problems, there are no exhaust gas, electric vehicles that use only batteries as power sources, and hybrid (electric) vehicles that use both internal combustion engine and batteries as power sources. Development has been accelerated, and part of it has been put to practical use.
[0004]
Naturally, a battery serving as a power source for an electric vehicle is required to have characteristics of obtaining high output and high energy, and a lithium ion battery is attracting attention as a battery that meets these requirements. In order to meet these demands, for example, by leaving the active material on a part of the metal foil that is the current collector of the electrode without applying the active material, processing into a strip shape and directly forming the lead piece, A technique for increasing the output by reducing the internal resistance is known (for example, see Patent Document 1).
[0005]
On the other hand, in a cylindrical battery having an electrode winding group, from the viewpoint of reduction in charge / discharge efficiency or life characteristics and reliability, as shown in FIG. A technique is known in which positive and

negative electrodes

21 and 31 are arranged so as not to face the end of the positive electrode 21 (see, for example, Patent Documents 2 and 3).
[0006]
[Patent Document 1]
JP-A-9-92335 (FIGS. 1 and 3, paragraph numbers “0016”, “0021”, “0023”)
[Patent Document 2]
JP-A-1-128370 (FIGS. 2 and 3)
[Patent Document 3]
Japanese Utility Model Publication No. 2-150760 (FIGS. 1 and 4)
[0007]
[Problems to be solved by the invention]
However, when the technology of the above-mentioned patent document is reproduced, if the battery is left unattended, an abnormal capacity reduction of the battery may occur. As a result of detailed investigations by the inventor, it has been found that a battery that has caused an abnormal capacity reduction has an abnormally low voltage due to self-discharge due to a minute internal short circuit of the battery. When this battery was disassembled, it was found that a part of the base processed ends of a plurality of strip-shaped lead pieces penetrated the separator and reached the negative electrode minutely. Further, when this processed end was examined in detail, there were a few burrs formed during the lead processing. Since the lead piece is bound to the current collecting member after the electrode is wound, the lead piece is bent in the binding direction from the root of the lead piece. At this time, it can be inferred that a force pressing the root portion in the direction of the negative electrode of the counter electrode acts and penetrates the separator to reach the negative electrode by vibration or the like particularly when there is a burr during processing.
[0008]
In another battery in which the voltage has been abnormally reduced, the cutting burr formed on the active material mixture uncoated part at the winding start end or winding end of the positive electrode penetrates the separator and reaches the negative electrode minutely. A spot was found.
[0009]
An object of the present invention is to provide a wound cylindrical lithium ion battery capable of securing capacity and output in view of the above-mentioned cases.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present onset Ming, positive, the longitudinally adjacent one longitudinal more in side strip JoTadashi, negative electrode lead pieces are formed the positive, the negative electrode lead piece of the negative electrode current collector A wound type comprising an electrode winding group in which an active material mixture is applied with an uncoated portion left and is wound with a positive electrode and a negative electrode lead piece wound in opposite directions through a separator. In the cylindrical lithium ion battery, the other end in the longitudinal direction where the negative electrode lead piece of the negative electrode current collector is not formed is a width direction intersecting the longitudinal direction, and the uncoated portion of the positive electrode current collector is It is arranged to be positioned on the part . In the present invention , the other end in the longitudinal direction where the negative electrode lead piece of the negative electrode current collector is not formed is disposed so as to be positioned in the uncoated portion of the positive electrode current collector in the width direction intersecting the longitudinal direction. Therefore, even if a burr protrudes from the location where the positive and negative electrode lead pieces are formed and penetrates the separator, a minute short circuit does not occur between the positive and negative electrodes, so that a voltage drop is suppressed and a capacity and output can be secured.
[0011]
In the first aspect, since both ends in the width direction of the positive electrode current collector in the uncoated part of the positive electrode current collector intersect with the other end in the longitudinal direction of the negative electrode current collector, the positive electrode current collection in the uncoated part of the positive electrode current collector A burr protrudes from both ends of the current collector in the width direction and penetrates through the separator to cause a short circuit with the other end of the negative electrode current collector. At least one end of the positive current collector in the width direction and the positive current collector If an insulator is interposed between the uncoated portion and the other end in the longitudinal direction of the negative electrode current collector, the width of the positive electrode current collector in the uncoated portion of the positive electrode current collector Even if the burrs protrude from at least one end, the insulator can prevent the burrs and the negative electrode from coming into contact with each other, so that a minute short circuit between the positive and negative electrodes can be prevented.
[0013]
Further, in the present invention , the insulator may be an adhesive tape attached to at least one end of the positive electrode current collector in the width direction and the front and back surfaces of the uncoated portion of the positive electrode current collector.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment in which the present invention is applied to a cylindrical lithium ion secondary battery will be described with reference to the drawings.
[0015]
(Constitution)
As shown in FIG. 1, a cylindrical lithium ion secondary battery (hereinafter referred to as a secondary battery) 40 according to the present embodiment has a belt-like positive and negative electrode plate wound through a polyethylene separator having a thickness of 40 μm. The electrode winding group 6 is provided.
[0016]
As shown in FIGS. 2 and 3, the positive and

negative electrode plates

20 and 30 are made of aluminum foil and rolled copper foil for the positive and negative electrode

current collectors

9 and 19 serving as base materials, respectively. On one side in the longitudinal direction of the positive and negative

current collectors

9 and 19, strip-shaped positive and negative

electrode lead pieces

9a and 19a are formed at predetermined intervals. On both sides of the positive and

negative electrode plates

20 and 30, the positive and negative electrode active material mixture is applied almost uniformly and homogeneously, leaving the uncoated portion 13 in the longitudinal direction adjacent to the positive and negative

electrode lead pieces

9a and 19a. Positive and negative electrode active

material mixture layers

17 and 18 are formed. The positive electrode active material mixture uses a lithium transition metal double oxide capable of releasing and occluding lithium by charging and discharging the positive electrode active material, and the negative electrode active material mixture is lithium by charging and discharging the negative electrode active material. Amorphous carbon capable of occluding and releasing is used. The separator has a larger area than the positive and negative electrode

current collectors

9 and 19 in the longitudinal direction and the width direction intersecting the longitudinal direction. In FIG. 2, the length of the positive electrode lead piece 9 a is represented by A, the width of the uncoated portion 13 is represented by B, and the width of the positive electrode active material mixture layer 17 is represented by C.
[0017]
As shown in FIG. 3, the positive and

negative electrode plates

20 and 30 are arranged with the positive and negative

electrode lead pieces

9a and 19a in opposite directions before winding. At this time, the positive and negative

electrode lead pieces

9a and 19a are offset in the width direction and offset upward and downward with respect to the other ends in the longitudinal direction of the positive electrode

current collectors

19 and 9, respectively. That is, the formation ends 9b and 19b of the positive and negative

electrode lead pieces

9a and 19a are negative in the width direction and are shifted upward and downward from the other end portions in the longitudinal direction of the positive electrode

current collectors

19 and 9, respectively. The upper and lower deviation widths are set to almost half of the width B of the unapplied portion 13. Both ends in the width direction of the negative electrode plate 30 protrude to the left and right from both ends in the width direction of the positive electrode plate 20. Therefore, the negative electrode active material mixture layer 18 is disposed so as to protrude in the longitudinal direction and the width direction with respect to the positive electrode active material mixture layer 17, and the positive electrode active material mixture layer 17 is disposed on the negative electrode active material mixture layer 18 over the entire surface. opposite. In FIG. 3, the separator is omitted.
[0018]
<Preparation of positive electrode plate>
As the positive electrode active material, lithium manganate (LiMn ₂ O ₄ ) is selected as a lithium transition metal complex oxide, lithium manganate powder, scaly graphite having an average particle size of 5 μm as a conductive agent, and polyvinylidene fluoride as a binder. Are mixed at a mass ratio of 85: 10: 5, N-methyl-2-pyrrolidone as a dispersion solvent is added thereto, and a kneaded slurry is applied to both surfaces of a positive electrode current collector 9 having a thickness of 20 μm. The agent layer 17 was obtained. At this time, an uncoated portion having a width A + B was left on one side in the longitudinal direction of the positive electrode current collector 9. Thereafter, drying, pressing, and cutting were performed to obtain a positive electrode plate 20 having a positive electrode active material mixture layer 17 having a width C of 300 mm, a length of 6000 mm, and a thickness (including aluminum foil) of 230 μm. The coating amount of the positive electrode active material mixture after drying was 280 g / m ² .
[0019]
The uncoated portion with the width A + B was cut out, and the remaining portion of the cutout was used as a positive electrode lead piece 9a with a length A. Adjacent positive electrode lead pieces 9a were provided at intervals of 20 mm. Moreover, the width of the positive electrode lead piece 9a was 10 mm, and the width B of the uncoated portion 13 was 6 mm.
[0020]
<Preparation of negative electrode plate>
10 parts by weight of polyvinylidene fluoride as a binder is added to 90 parts by weight of Kaboha Chemical Industry Co., Ltd., Carbotron P powder as amorphous carbon, and N-methyl-2-pyrrolidone as a dispersion solvent is added to this and kneaded The slurry was applied to both surfaces of a negative electrode current collector 19 having a thickness of 10 μm to form a negative electrode active material mixture layer 18. At this time, an uncoated portion having a width A + B was left on one side in the longitudinal direction of the negative electrode current collector 19. Thereafter, drying, pressing and cutting were performed to obtain a negative electrode plate 30 having a negative electrode active material mixture layer 18 with a width of 306 mm, a length of 6200 mm, and a thickness (including a rolled copper foil) of 140 μm. The coating amount of the negative electrode active material mixture after drying was 66 g / m ² .
[0021]
Similarly to the positive electrode plate 20, the uncoated part with the width A + B was cut out, and the remaining part of the cutout was used as the negative electrode lead piece 19a. Adjacent negative electrode lead pieces 19a were provided at intervals of 20 mm. Further, the width of the negative electrode lead piece 19a was 10 mm, and the width of the uncoated portion 23 adjacent to the negative electrode lead piece 19a was 2 mm.
[0022]
<Production of battery>
As shown in FIG. 1 and FIG. 3, the positive electrode plate 20 and the negative electrode plate 30 are arranged so that the positive and negative

electrode lead pieces

9a and 19a are arranged in opposite directions through a separator so that the two electrode plates do not directly contact each other. The electrode winding group 6 was produced by winding. At this time, the formation ends 9b and 19b of the positive and negative

electrode lead pieces

9a and 19a were negative in the width direction and shifted upward and downward from the other side end portions of the positive electrode

current collectors

19 and 9 in the longitudinal direction. The diameter of the electrode winding group 6 was adjusted to 61 ± 0.5 mm.
[0023]
The positive electrode lead piece 9 formed on the positive electrode plate 20 is deformed, and all of the positive electrode lead pieces 9 are formed in the vicinity of the peripheral surface of the collar portion 7 that integrally projects from the periphery of the pole column (positive electrode external terminal 1) substantially on the extension line of the shaft core 11. After gathering and contacting, the lead piece 9 and the flange 7 peripheral surface were ultrasonically welded to connect and fix the lead piece 9a to the flange 7 peripheral surface. The connection operation between the negative electrode external terminal 1 ′ and the negative electrode lead piece 19a formed on the negative electrode plate 30 was performed in the same manner as the connection operation between the positive electrode external terminal 1 and the positive electrode lead piece 9a.
[0024]
Thereafter, an insulating coating 8 was applied to the entire periphery of the collar 7 peripheral surface of the positive electrode external terminal 1 and the negative electrode external terminal 1 ′. This insulating coating 8 also exerted on the entire outer circumferential surface of the electrode winding group 6. For the insulating coating 8, 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 was wound several times from the peripheral surface of the collar portion 7 to the outer peripheral surface of the electrode winding group 6 to form an insulating coating 8. The number of turns is adjusted so that the maximum diameter portion of the electrode winding group 6 becomes the insulating coating 8 existing portion, and the maximum diameter is slightly smaller than the inner diameter of the battery container 5 so that the electrode winding group 6 is within the battery container 5. Inserted into. As the battery container 5, a stainless steel cylinder having an outer diameter of 67 mm and an inner diameter of 66 mm was used.
[0025]
Then, the second ceramic washer 3 ′ 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 disc-shaped battery lid 4, the pole column constituting the positive electrode external terminal 1 at the tip, Each was fitted into a pole column constituting the negative electrode external terminal 1 ′. Further, a flat plate-like first ceramic washer 3 made of alumina and having a thickness of 2 mm, an inner diameter of 16 mm, and an outer diameter of 28 mm is placed on the battery lid 4, and the positive electrode external terminal 1 and the negative electrode external terminal 1 ′ are respectively connected to the first ceramic. Passed through washer 3. Thereafter, the peripheral end surface of the battery lid 4 was fitted into the opening of the battery container 5, and the entire contact portions were laser welded. At this time, the positive electrode external terminal 1 and the negative electrode external terminal 1 ′ protrude through the hole formed in the center of the battery lid 4 and project outside the battery lid 4. Then, the first ceramic washer 3 and the metal washer 14 smoother than the bottom surface of the metal nut 2 were fitted into the positive external terminal 1 and the negative external terminal 1 ′ in this order. The battery lid 4 is provided with a cleavage valve 10 as an internal pressure reduction mechanism that cleaves in response to an increase in the internal pressure of the battery. The cleavage pressure of the cleavage valve 10 was set to 1.3 × 10 ^{6 to} 1.8 × 10 ⁶ Pa.
[0026]
Next, the nut 2 is screwed to the positive electrode external terminal 1 and the negative electrode external terminal 1 ′, and the battery lid 4 is connected to the flange portion 7 via the second ceramic washer 3 ′, the first ceramic washer 3, and the metal washer 14. The nut 2 was fixed by tightening. The tightening torque value at this time was about 7 N · m. Note that the metal washer 14 did not rotate until the tightening operation was completed. In this state, the power generation elements mainly in the electrode winding group 6 inside the battery container 5 are shielded from the outside air by the compression of the rubber (EPDM) O-ring 16 interposed between the back surface of the battery lid 4 and the flange portion 7.
[0027]
Thereafter, 480 g of non-aqueous electrolyte was injected into the battery container 5 from the injection port 15 provided on the battery lid 4, and then the injection port 15 was sealed to complete the secondary battery 40.
[0028]
As the non-aqueous electrolyte, a solution obtained by dissolving 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1: 1: 1 was used. . It should be noted that the secondary battery 40 cuts off current in response to an increase in the temperature of the battery container 5, for example, a PTC (Positive Temperature Coefficient) element, or an electrical connection that is disconnected in response to an increase in internal pressure. There is no current interrupt mechanism.
[0029]
(Action etc.)
In the secondary battery 40 of the present embodiment, the positive and negative

electrode lead pieces

9 a and 19 a are negative in the width direction of the positive electrode current collector 9, and the upper and lower sides from the other end in the longitudinal direction of the positive electrode

current collectors

19 and 9, respectively. Is offset. For this reason, even if a burr protrudes from the formation ends 9b and 19b of the positive and negative

electrode lead pieces

9a and 19a and penetrates the separator, a minute short circuit does not occur between the positive and

negative electrode plates

20 and 30. Therefore, the secondary battery 40 can suppress the voltage drop and ensure the capacity and output.
[0030]
In the secondary battery 40 of the present embodiment, the positive and

negative electrode plates

20 and 30 are arranged such that the negative electrode active material mixture layer 18 is shifted in the longitudinal direction and the width direction with respect to the positive electrode active material mixture layer 17. The positive electrode active material mixture layer 17 is opposed to the negative electrode active material mixture layer 18 on the entire surface. For this reason, the opposing area of the positive electrode active material mixture layer 17 and the negative electrode active material mixture layer 18 is increased. Therefore, the secondary battery 40 with high capacity and high output can be obtained.
[0031]
Furthermore, in the secondary battery 40 of the present embodiment, a plurality of positive and negative

electrode lead pieces

9a and 19a are formed by cutting out the uncoated portions of the positive and

negative electrode plates

20 and 30 with the width A + B. For this reason, since resistance in the positive and negative

electrode lead pieces

9a and 19a can be suppressed, a high output secondary battery 40 can be obtained.
[0032]
(Second Embodiment)
Next, a second embodiment in which the present invention is applied to a cylindrical lithium ion secondary battery will be described. In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment mentioned above, the description is abbreviate | omitted, and only a different location is demonstrated.
[0033]
As shown in FIGS. 4 and 5, in the present embodiment, at least one end of the positive electrode current collector 9 in the width direction (winding start end, winding end) and a portion of the uncoated portion 13 of the positive electrode current collector 9. 13a (and / or 13b) and a substantially rectangular adhesive tape 25 made of polypropylene and coated with an adhesive on one side is interposed between the negative electrode current collector 19 and the other end in the longitudinal direction. Yes. That is, the adhesive tape 25 is affixed to the surface of the portion 13a (13b), and is slightly shifted (extruded) from the uncoated portion 13 in the longitudinal direction and the width direction. An adhesive tape (not shown) having the same shape and the same material as the adhesive tape 25 is attached to the back surface of the portion 13a (13b) so as to face the adhesive tape 25.
[0034]
In the secondary battery according to the present embodiment, at least one end of the positive electrode current collector 9 in the width direction, the portion 13a (13b) of the uncoated portion 13 of the positive electrode current collector 9, the longitudinal direction of the negative electrode current collector 19, and the like. An adhesive tape 25 is interposed between the side ends. For this reason, even if a cutting burr protrudes from at least one of the widthwise ends of the positive electrode current collector 9 in the uncoated portion 13 of the positive electrode current collector 9, the adhesive tape 25 prevents the cutting burr and the negative electrode plate 30 from contacting each other. can do. Therefore, the short circuit between the positive and

negative electrode plates

20 and 30 can be suppressed, and the capacity and output of the battery can be secured.
[0035]
Moreover, in the secondary battery of this embodiment, the two adhesive tapes are affixed on the front and back surfaces of the portion 13a (13b) of the uncoated portion 13. For this reason, when the positive and

negative electrode plates

20 and 30 are wound, it is possible to prevent the cutting burrs from coming into contact with the negative electrode plates 30 respectively located on the front and back surfaces of the portion 13b. Therefore, it is possible to prevent a minute short circuit. Furthermore, since it can fix easily by sticking the adhesive tape 25 to the part 13a (13b), workability | operativity can be improved.
[0036]
In the present embodiment, the formation ends 9b and 19b of the positive and negative

electrode lead pieces

9a and 19a are negative in the width direction, and are shifted upward and downward from the other longitudinal ends of the positive and

negative plates

30 and 20. However, the forming ends 9b and 19b of the positive and negative

electrode lead pieces

9a and 19a may be opposed to the negative side and the other end of the positive and

negative electrodes

30 and 20 in the longitudinal direction. This also prevents the burr from coming into contact with the negative electrode plate 30 when the cutting burr protrudes from at least one of the widthwise ends of the positive electrode current collector 9 in the uncoated portion 13 of the positive electrode current collector 9. be able to.
[0037]
Moreover, in this embodiment, although the example in which two adhesive tapes were affixed on the front and back of the part 13a (13b) was shown, one adhesive tape is bent and affixed on the front and back of the part 13a (13b) Alternatively, a plurality of adhesive tapes 25 may be attached, and the shape of the adhesive tape 25 is not limited.
[0038]
Furthermore, in the above embodiment, in the positive electrode plate 20, the length A of the positive electrode lead piece 9a, the width B of the uncoated portion 13 and the width C of the positive electrode active material mixture layer are set to 44, 6, and 300 mm, respectively. However, these values are not limited. For example, by increasing the width C of the positive electrode active material mixture layer 17, a battery with higher capacity and higher output can be obtained.
[0039]
Further, in the above embodiment, the positive and

negative lead pieces

9a and 19a are negative, the upper and lower deviation widths of the positive electrode

current collectors

19 and 9 with respect to the other end in the longitudinal direction are approximately half of the width B of the uncoated part 13. However, the deviation width is not limited to this. For example, the occurrence of a minute short circuit can be further suppressed by increasing the deviation width.
[0040]
Furthermore, in the said embodiment, although the large-sized secondary battery 40 used for the electric vehicle power supply etc. was illustrated, it is not limited to the magnitude | size of a battery and a battery capacity, A battery is used for a bottomed cylindrical container (can). You may apply to the cylindrical battery of the structure where the upper cover is crimped-sealed. In particular, a battery used for a power source for an electric vehicle is required to have high capacity and high output characteristics, and therefore, the application of the present invention is preferable.
[0041]
Furthermore, in the said embodiment, although the base material was a polyimide and the adhesive tape which apply | coated the adhesive which consists of hexamethacrylate on the single side | surface was used for the insulating coating 8, it does not specifically limit to this. For example, the base material is a polyolefin such as polypropylene or polyethylene, and an adhesive tape with an acrylic adhesive such as hexamethacrylate or butyl acrylate applied on one or both sides, or a tape made of polyolefin or polyimide that does not apply an adhesive. You may use suitably.
[0042]
Furthermore, in the above embodiment, an example in which lithium manganate is used as the positive electrode active material has been described. However, lithium cobaltate, which is a lithium cobalt composite oxide, lithium nickelate, which is a lithium nickel composite oxide, and lithium manganese double oxide. In addition to lithium manganate, it is possible to use a double oxide of any combination of lithium and cobalt, nickel and manganese, or a double oxide doped with a different metal. May be. Further, lithium manganate (LiMnO ₂ ) having a layered rock salt structure, a material in which a part of lithium or manganese in the crystal is substituted or doped with a different metal, or a part of oxygen in the crystal is substituted or doped with S, P, or the like The material may be used.
[0043]
Moreover, in the said embodiment, although the example which uses a polyvinylidene fluoride as a binder of the electrode plate active material for lithium ion batteries was shown, polytetrafluoroethylene, polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene Polymers such as rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, vinyl alcohol, and mixtures thereof may be used. .
[0044]
Furthermore, in the above embodiment, an example in which amorphous carbon is used as the negative electrode active material for a lithium ion battery has been shown. However, for example, natural graphite, various artificial graphite materials, carbonaceous materials such as coke, etc. may be used. Also, the particle shape is not particularly limited, such as a scale shape, a spherical shape, a fiber shape, or a lump shape.
[0045]
Furthermore, in the above-described embodiment, an example in which a general lithium salt is used as an electrolyte and an electrolyte obtained by dissolving this in an organic solvent is used as the nonaqueous electrolytic solution. However, the lithium salt and the organic solvent are not particularly limited. For example, as the electrolyte, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, or a mixture thereof can be used.
[0046]
And in the said embodiment, although the example using the mixed solution of the volume ratio 1: 1: 1 of ethylene carbonate, a dimethyl carbonate, and diethyl carbonate was shown as an organic solvent of a non-aqueous electrolyte, propylene carbonate, ethylene carbonate Ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, Acetonitrile, propiontonyl or the like or a mixed solvent of two or more of these may be used, and the mixing ratio is not limited.
[0047]
【Example】
Hereinafter, the 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.
[0048]
Example 1
In Example 1, according to the first embodiment, the positive and negative

electrode lead pieces

9a and 19a are arranged negatively in the width direction and offset upward and downward from the other end in the longitudinal direction of the positive electrode

current collectors

19 and 9, respectively. A secondary battery 40 was fabricated using a wound group in which the

negative electrode plates

20 and 30 were wound.
[0049]
(Example 2)
In Example 2, a secondary battery was produced in the same manner as in Example 1 except that two more adhesive tapes 25 were attached to the portion 13a of the positive electrode plate 20 according to the second embodiment.
[0050]
(Comparative Example 1)
As shown in FIGS. 6 and 7, in Comparative Example 1, the length D of the positive electrode lead piece is 48 mm, the width F of the positive electrode active material mixture coating portion is 300 mm, and the width E of the uncoated portion is 2 mm. A secondary battery was manufactured by using a wound group wound with the formation end of the piece and the other side of the negative electrode plate 31 facing each other. That is, in Comparative Example 1, the positive and negative electrode lead pieces are not offset in the width direction as in Example 1, and are offset from the other end in the longitudinal direction of the positive electrode current collector.
[0051]
<Test and evaluation>
Next, 50 batteries of each of the above-described Examples and Comparative Examples were prepared, charged at room temperature and left standing, followed by tracking the voltage during the standing period, and the number of batteries whose voltage dropped (the number of voltage-reducing batteries). I investigated. The charging conditions were a 4.2 V constant voltage, a limiting current of 80 A, and 3.5 hours. The standing temperature condition was 25 ± 2 ° C. Table 1 below shows the test results.
[0052]
[Table 1]

[0053]
As shown in Table 1, in the battery of Example 1, the forming ends 9b and 19b of the positive and negative

electrode lead pieces

9a and 19a are negative in the width direction, and the upper side and the lower side from the other side in the longitudinal direction of the

positive plates

30 and 20 Because of the offset arrangement, the rate of occurrence of abnormal voltage drop (voltage drop battery number / manufacturing number × 100) is low as compared with the battery of Comparative Example 1 in which the positive electrode lead piece forming end faces the negative electrode plate 31. It has been found. Moreover, in the battery of Example 2, since the adhesive tape 25 was stuck to at least one of the

parts

13a and 13b, it turned out that the rate which causes an abnormal voltage drop is still lower.
[0054]
【The invention's effect】
As described above, according to this onset bright, other longitudinal end of the negative electrode lead piece of the negative electrode current collector is not formed, in the width direction intersecting the longitudinal direction, uncoated portions of the positive electrode current collector Since the burr protrudes from the location where the positive and negative electrode lead pieces are formed and penetrates the separator, a minute short circuit does not occur between the positive and negative electrodes. it is possible to obtain an effect that it is as possible out to secure.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion secondary battery according to a first embodiment to which the present invention is applicable.
FIG. 2 is a front view of a positive electrode plate of the cylindrical lithium ion secondary battery according to the first embodiment.
FIG. 3 is a front view of positive and negative electrode plates of the cylindrical lithium ion secondary battery of the first embodiment.
FIG. 4 is a front view of a positive electrode plate to which an adhesive tape of a cylindrical lithium ion secondary battery according to a second embodiment is attached.
FIG. 5 is a front view of positive and negative electrode plates of a cylindrical lithium ion secondary battery according to a second embodiment.
FIG. 6 is a front view of a positive electrode plate of a conventional cylindrical lithium ion secondary battery.
FIG. 7 is a front view of positive and negative electrode plates of a conventional cylindrical lithium ion secondary battery.
[Explanation of symbols]
6 Electrode winding group 9 Positive electrode

current collector

9a, 19a Positive electrode lead piece, negative

electrode lead piece

9b,

19b Formation place

13, 23

Uncoated part

13a, 13b Part 19 Negative electrode current collector 25 Adhesive tape (insulator)
20 Positive electrode plate (positive electrode)
30 Negative electrode plate (negative electrode)
40 Cylindrical lithium ion secondary battery (cylindrical lithium ion battery)

Claims

A plurality of strip-shaped positive and negative electrode lead pieces are formed on one side in the longitudinal direction of the positive and negative electrode current collectors, and an active material mixture is applied adjacent to the positive and negative electrode lead pieces, leaving an uncoated portion in the longitudinal direction. In a wound cylindrical lithium ion battery comprising an electrode winding group in which the positive and negative electrodes are wound with a positive electrode and a negative electrode lead piece in opposite directions with a separator interposed therebetween , and wherein the other longitudinal end of the negative electrode lead piece is not formed, the in the longitudinal direction and the width direction intersecting, it arranged to be positioned on a portion of the uncoated portion of the positive electrode current collector A wound cylindrical lithium-ion battery.

An insulator is interposed between at least one end of the positive electrode current collector in the width direction and the uncoated portion of the positive electrode current collector and the other end portion in the longitudinal direction of the negative electrode current collector. The wound cylindrical lithium ion battery according to claim 1.

The said insulator is an adhesive tape affixed to the front and back of at least one end of the widthwise ends of the positive electrode current collector and the uncoated portion of the positive electrode current collector. 2. A wound cylindrical lithium ion battery according to 2.