JP4055307B2

JP4055307B2 - Cylindrical lithium-ion battery

Info

Publication number: JP4055307B2
Application number: JP32357799A
Authority: JP
Inventors: 賢治中井; 利明小貫; 健介弘中
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Shin Kobe Electric Machinery Co Ltd
Priority date: 1999-11-15
Filing date: 1999-11-15
Publication date: 2008-03-05
Anticipated expiration: 2019-11-15
Also published as: JP2001143759A

Description

【０００１】
【発明の属する技術分野】
本発明は円筒形リチウムイオン電池に係り、特に、正極集電体に充放電によりリチウムを放出・収容可能な正極活物質を塗着した帯状の正極と、負極集電体に充放電によりリチウムを収容・放出可能な負極活物質を塗着した帯状の負極とが、リチウムイオンが通過可能な帯状のセパレータを介して捲回された電極捲回群を有し、電極捲回群は円筒形電池容器に内蔵され、電池容器の両端面を封口する蓋板の少なくとも一方に該電池容器の内圧の上昇に応じてガスを放出する内圧低減機構を有する放電容量３０Ａｈ以上の円筒形リチウムイオン電池であって、電極捲回群の直径をＡ、電池容器内直径をＢとしたときに、Ａ／Ｂの値が０．９８以下である円筒形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、高出力、高エネルギー密度である点から、ＥＶ（電気自動車）用電源として注目されている。リチウムイオン二次電池はその形状で、円筒形と角形とに分類することができる。通常、円筒形電池の内部は、電極が正極、負極共に活物質が金属箔に塗着された帯状であり、正極、負極が直接接触しないようにセパレータを挟んで円筒状の軸芯の回りに断面が渦巻状に捲回され、電極捲回群が形成された捲回式構造が採られている。そして、電池容器となる円筒形の缶又は容器に電極捲回群が収納され、電解液注液後、封口し、初充電することで電池としての機能が付与される。
【０００３】
エネルギー密度の向上のためには、より多くの活物質を電池容器内に充填することが好ましく、電極捲回群は、比較的密に電池容器内に挿入されている。しかしながら、正極活物質にコバルト酸リチウムを、負極に黒鉛質の炭素材料を用いたリチウムイオン二次電池では、初充電時に正極、負極ともに活物質が体積膨張を起こし、これが原因で電極には種々の不都合な状況が発生し、容量低下や寿命低下を引き起こすことがあった。その対策として、現在ノートパソコンや携帯電話等に搭載される概ね容量２Ａｈ以下の民生用リチウムイオン二次電池では、著しい容量低下、エネルギー密度の低下を抑えられる範囲で、電極捲回群と電池容器間に若干の空間を設けた構造となっている。また、工業的に連続自動生産する場合においても、電極捲回群の電池容器への挿入性が向上するので、上記空間を設けることが望ましい。
【０００４】
一方、ＥＶ用電源用途に適した概ね容量３０Ａｈ以上のリチウムイオン二次電池においては、当然出力が高く、過充電状態に陥ったり、圧壊される等といった異常発生時の電池の破裂、発火を完全になくすことが必然となる。
【０００５】
また、高容量、高出力のリチウムイオン二次電池は、電池長さ、電池径ともに大きくなる。上述したように、活物質が金属箔に塗着された帯状の電極は、活物質の塗着量を増やして電極を厚くすると、活物質層が剥離、脱落して電極形状を維持できなくなる。このため、帯状の電極の捲回回数を多くすることで電極捲回群の径を大きくしている。
【０００６】
【発明が解決しようとする課題】
しかしながら、電極捲回群が長く、多数回捲回された電極捲回群を有する高放電容量電池においては、例えば、過充電やＥＶに搭載された場合の車両衝突等の異常時に電解液の分解等で発生したガスが電極捲回群内部に滞留しやすく、スムーズに安全弁等の内圧低減機構から排出できず、異常発熱と電池容器の著しい変形を伴う、という問題があった。本発明者らは懸命かつ精力的に調査改善活動に取り組んだ結果、高容量、高出力の円筒形リチウムイオン電池における安全性確保のためには、電極捲回群と電池容器との間には、空間が必要なことが分かった。すなわち、この空間は、比較的容量の小さい民生用リチウムイオン二次電池において設けられている空間とは異なった安全性確保の目的で設けられなければならない。
【０００７】
電池は、ＥＶに搭載し実走行すると振動を受ける。したがってＥＶ用電池は電気的特性だけでなく、耐振動性等の信頼性をも兼ね備えなければならない。前述のように、長く、大きな径の電極捲回群と電池容器との間に空間を設けると、振動が加わった場合に、大きな電極捲回群の自重による慣性モーメントのために、電極捲回群が電池容器内で移動し、電池内構成部品の損傷や電極捲回群自体の損傷が発生し、引き続いて内部短絡が起こって電池機能の喪失に至る、という問題を生ずる。
【０００８】
本発明は上記事案に鑑み、高容量、高出力でありながらも、安全性及び信頼性の高い円筒形リチウムイオン電池を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記目的を達成するために、本発明は、正極集電体に充放電によりリチウムを放出・収容可能な正極活物質を塗着した帯状の正極と、負極集電体に充放電によりリチウムを収容・放出可能な負極活物質を塗着した帯状の負極とが、リチウムイオンが通過可能な帯状のセパレータを介して捲回された電極捲回群を備え、前記電極捲回群は円筒形電池容器に内蔵され、前記電池容器の両端面を封口する蓋板の少なくとも一方に該電池容器の内圧の上昇に応じてガスを放出する内圧低減機構を有する放電容量３０Ａｈ以上の円筒形リチウムイオン電池であって、前記電極捲回群の直径をＡ、前記電池容器内直径をＢとしたときに、Ａ／Ｂの値が０．９８以下である円筒形リチウムイオン電池において、電気的絶縁性を有する樹脂製で、前記電池容器と前記電極捲回群との間かつ前記電極捲回群の両端部近傍に配置され、前記電極捲回群の外周を、該電極捲回群内部で発生するガス圧により該電極捲回群が電極捲回群直径方向に膨張することを許容する所定間隔の隙間を形成して、円弧状に取り巻くスペーサを備え、前記スペーサの電極捲回群円周方向長さは、前記電極捲回群の円周長さの７５％以上、９５％以下であることを特徴とする。
【００１０】
本発明では、スペーサを、電池容器と電極捲回群との間かつ電極捲回群の両端部近傍に配置したので、電池容器とスペーサが配置されていない電極捲回群中央部との間にはスペース（空間）が形成され、このスペースにより異常時に電極捲回群内部でガス圧が発生しても電極捲回群中央部は直径方向に膨張が可能となる。また、スペーサを、電極捲回群の外周を、該電極捲回群内部で発生するガス圧により該電極捲回群が電極捲回群直径方向に膨張することを許容する所定間隔の隙間を形成して、円弧状に取り巻くようにしたので、異常時に電極捲回群内部でガス圧が発生すると、発生したガスは電極捲回群両端部を電極捲回群直径方向に膨張させ電極捲回群両端部からスムーズに外部へ排出される。この電極捲回群両端部から排出されたガスは、電池容器の内圧が所定圧となると、内圧低減機構から放出される。従って、電極捲回群内部にガスが滞留せず、電池容器内での異常発熱や電池容器の著しい変形を引き起こさないので、電池の安全性を確保することができる。また、スペーサの電極捲回群円周方向長さを、電極捲回群の円周長さの７５％以上、９５％以下としたので、異常時に電極捲回群が電極捲回群直径方向にスムーズに膨張でき、電池の安全性を更に高めることができる。更に、スペーサを、電気的絶縁性を有する樹脂製で、電極捲回群の外周を円弧状に取り巻くようにしたので、電極捲回群とスペーサとは密着し電極捲回群はスペーサを介して電池容器に固定された状態となり、電極捲回群の長手方向への移動を抑制する。従って、耐振動性が向上し、振動による電極捲回群の損傷や内部短絡を引き起こさないので、電池の信頼性を高めることができる。
【００１１】
この場合において、電極捲回群内部からガスを穏やかに発生させ安全性を高めるために、正極活物質をリチウム・マンガン複酸化物とするのが好ましく、また、負極活物質を非晶質炭素とすることが好ましい。また、異常時の安全性を確保するために、スペーサをポリオレフィン系樹脂で形成することが望ましく、連続気泡型ポリオレフィン系樹脂発泡体で形成することが更に望ましい。更に、スペーサの電極捲回群長手方向幅を、電極捲回群の長手方向長さの５％以上、２５％以下とすれば、異常時に電極捲回群内部で発生するガスを電極捲回群外部へよりスムーズに案内することができるので、電池の安全性をより高めることができる。そして、スペーサを、少なくとも２片以上に分離し、互いに接触することなく間隙が形成され、スペーサの電極捲回群円周方向の長さの和を、間隙の長さの和よりも大きく、間隙の各長さを、電極捲回群の円周長さの２５％未満とすれば、スペーサ間の間隙を電極捲回群の周囲に分散させることが可能となるので、更に高い安全性及び信頼性を確保することができる。
【００１２】
【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ＥＶ搭載用円筒形リチウムイオン電池に適用した第１の実施の形態について説明する。
【００１３】
＜電池製造方法＞
[正極板の作製]
充放電によりリチウムを放出・収容可能な活物質であるコバルト酸リチウム（ＬｉＣｏＯ_２）粉末やマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）粉末と、導電剤として鱗片状黒鉛（平均粒径：２０μｍ）と、結着剤としてポリフッ化ビニリデン（ＰＶｄＦ）と、を後述する所定配合比で混合し、これに分散溶媒のＮ−メチル−２−ピロリドン（ＭＮＰ）を添加、混練したスラリを、厚さ２０μｍのアルミニウム箔（正極集電体）の両面に塗布した。このとき、正極板長寸方向の一方の側縁に幅５０ｍｍの未塗布部を残した。その後乾燥、プレス、裁断して幅３００ｍｍ、後述する所定長さ及び正極活物質合剤塗布部所定厚さの帯状の正極板を得た。正極活物質合剤層の空隙率はいずれも３５＋−１．５％とした。正極板のスラリ未塗布部に切り欠きを入れ、切り欠き残部をリード片とした。また、隣り合うリード片を２０ｍｍ間隔とし、リード片の幅は１０ｍｍとした。
【００１４】
[負極板の作製]
充放電によりリチウムを収容・放出可能な黒鉛質炭素である大阪ガスケミカル株式会社（以下、大阪ガスケミカルという。）製のＭＣＭＢ粉末や、非晶質炭素である呉羽化学工業株式会社（以下、呉羽化学という。）製カーボトロンＰ粉末９２重量部に結着剤として８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の圧延銅箔（負極集電体）の両面に塗布した。このとき、負極板長寸方向の一方の側縁に幅５０ｍｍの未塗布部を残した。その後乾燥、プレス、裁断して幅３０５ｍｍ、後述する所定長さ及び負極活物質塗布部所定厚さの帯状の負極板を得た。負極活物質層の空隙率はいずれも３５＋−１．５％とした。負極板のスラリ未塗布部に正極板と同様に切り欠きを入れ、切り欠き残部をリード片とした。また、隣り合うリード片を２０ｍｍ間隔とし、リード片の幅を１０ｍｍとした。
【００１５】
[電池の作製]
上記作製した帯状の正極板と負極板とを、これら両極板が直接接触しないように厚さ４０μｍ、幅３１０ｍｍのポリエチレン製セパレータと共に、直径１４ｍｍ、内径８ｍｍのポリプロピレン製中空管で捲回中心となる軸芯１１の回りに、４０回以上捲回した。このとき、正極板及び負極板のリード片（図１の符号９参照）が、それぞれ捲回群（電極捲回群）の互いに反対側の両端面に位置するようにした。捲回群径φは、正極板、負極板及びセパレータの長さを調整し、直径６３＋−０．１ｍｍとした。従って、捲回群周囲長さＰは、２π×（捲回群径φ）／２＝１９７．９２ｍｍとなる。
【００１６】
図１に示すように、正極板から導出されているリード片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９を鍔部７周面に接続し固定した。また、負極外部端子１’と負極板から導出されているリード片９との接続操作も、正極外部端子１と正極板から導出されているリード片９との接続操作と同様に行った。
【００１７】
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、捲回群６外周面全周にも及ぼした。絶縁被覆８には、基材がポリプロピレンで、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周面から捲回群６外周面に亘って少なくとも１周以上巻いて絶縁被覆８とした。
【００１８】
そして、図２及び図３に示すように、後述する所定幅Ａ（捲回群６長手方向の長さ、図２参照）、所定長さＢ（図３参照）、厚さ１．４ｍｍで電気的絶縁性をする所定材質のスペーサとしてのシート１２を１枚、絶縁被覆８が施された捲回群６の両端部に、一部隙間Ｋ（図３参照）設けて捲回群６を巻くように円弧状に絶縁被覆８に貼り付けた。なお、本実施形態では、積水化学工業株式会社製の両面テープ＃５７５を用いてシート１２を捲回群６円周方向にほぼ平行となるように貼り付けた。
【００１９】
次に、捲回群６を外径６７ｍｍ、内径６６ｍｍのステンレス製電池容器５内に挿入した後、アルミナ製で円盤状電池蓋４（蓋板）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、図１に示すように、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、図１に示すように、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開裂弁１０（内圧低減機構）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（１３０〜１８０Ｎ／ｃｍ^２）とした。
【００２０】
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内部の発電要素は外気から遮断される。
【００２１】
その後、電池蓋４に設けた注液口１５から電解液を所定量電池容器５内に注入し、その後注液口１５を封止することにより円筒形リチウムイオン電池２１を完成させた。
【００２２】
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の体積比１：１：１の混合溶液中へ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、円筒形リチウムイオン電池２１には、電池容器５の内圧の上昇に応じて電流を遮断する電流遮断機構は設けられていない。また、上述したように、捲回群６の直径は６３ｍｍであり、電池容器５の内（直）径は６６ｍｍであるので、（捲回群６の直径）／（電池容器５の内直径）の値は０．９５である。
【００２３】
（第２実施形態）
次に、本発明に係る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。本実施形態は、第１実施形態の一箇所の隙間Ｋに代えて隙間を２箇所とし、シート１２を２枚使用したものである。なお、本実施形態以下の実施形態において、第１実施形態と同一部材は同一の符号を付しその説明を省略し、異なる箇所のみ説明する。
【００２４】
図４に示すように、本実施形態では、後述するように電気的絶縁性をする所定材質で、後述する所定幅Ａ（図２参照）及びそれぞれ所定長さＢ１、Ｂ２、厚さ１．４ｍｍのシート１２を２枚、絶縁被覆８が施された捲回群６の両端部に、２箇所の隙間Ｋ１、Ｋ２を設けて捲回群６を巻くように円弧状に絶縁被覆８に貼り付けて、円筒形リチウムイオン電池２１を作製した。
【００２５】
（第３実施形態）
次に、本発明に係る円筒形リチウムイオン電池の第３の実施の形態について説明する。本実施形態は、第１実施形態の一箇所の隙間Ｋに代えて隙間を３箇所とし、シート１２を３枚使用したものである。
【００２６】
図５に示すように、本実施形態では、後述するように電気的絶縁性をする所定材質で、後述する所定幅Ａ（図２参照）及びそれぞれ所定長さＢ１、Ｂ２、Ｂ３、厚さ１．４ｍｍのシート１２を３枚、絶縁被覆８が施された捲回群６の両端部に、３箇所の隙間Ｋ１、Ｋ２、Ｋ３設けて捲回群６を巻くように円弧状に絶縁被覆８に貼り付けて、円筒形リチウムイオン電池２１を作製した。
【００２７】
（実施例）
次に、以上の実施形態に従って作製した円筒形リチウムイオン電池２１の実施例について説明する。まず、正極板及び負極板を次のように作製した。
【００２８】
＜正極板＞
[正極板Ｃ−１] 正極活物質に日本化学工業株式会社（以下、日本化学という。）製セルシードＣ−１０を用いたコバルト酸リチウムとし、コバルト酸リチウムと鱗片状黒鉛とＰＶｄＦとの配合比を重量％で６０：２９：１１とし、正極集電体を含んだ電極厚さ２４８μｍ、長さ６３６ｃｍの正極板を作製した（以下、この正極板を正極板Ｃ−１という。）。このときの正極活物質合剤層のかさ密度は２．１ｇ／ｃｍ^３とした。
[正極板Ｃ−２] 正極活物質に日本化学製セルシードＣ−１０を用いたコバルト酸リチウムとし、コバルト酸リチウムと鱗片状黒鉛とＰＶｄＦとの配合比を重量％で６５：２４：１１とし、正極集電体を含んだ電極厚さ２７６μｍ、長さ５６７ｃｍの正極板を作製した（以下、この正極板を正極板Ｃ−２という。）。このときの正極活物質合剤層のかさ密度は２．１５ｇ／ｃｍ^３とした。
[正極板Ｍ−１] 正極活物質に三井金属株式会社（以下、三井金属という。）製のマンガン酸リチウムを用い、マンガン酸リチウムと鱗片状黒鉛とＰＶｄＦとの配合比を重量％で７８：１２：１０とし、正極集電体を含んだ電極厚さ２５８μｍ、長さ６２０ｃｍの正極板を作製した（以下、この正極板を正極板Ｍ−１という。）。このときの正極活物質合剤層のかさ密度は２．３５ｇ／ｃｍ^３とした。[正極板Ｍ−２] 正極活物質に三井金属製のマンガン酸リチウムを用い、マンガン酸リチウムと鱗片状黒鉛とＰＶｄＦとの配合比を重量％で８５：１０：５とし、正極集電体を含んだ電極厚さ２４７μｍ、長さ６１８ｃｍの正極板を作製した（以下、この正極板を正極板Ｍ−２という。）。このときの正極活物質合剤層のかさ密度は２．５５ｇ／ｃｍ^３とした。
【００２９】
＜負極板＞
[負極板Ｂ−１] 黒鉛質炭素として、大阪ガスケミカル製のＭＣＭＢを用い、負極集電体を含んだ電極厚さ１２１μｍ、長さ６５４ｃｍの負極板を作製した（以下、この負極板を負極板Ｂ−１という。）。このときの負極活物質合剤層のかさ密度は１．３５ｇ／ｃｍ^３とした。
[負極板Ｂ−２] 黒鉛質炭素として、大阪ガスケミカル製のＭＣＭＢを用い、負極集電体を含んだ電極厚さ１２４μｍ、長さ６３８ｃｍの負極板を作製した（以下、この負極板を負極板Ｂ−２という。）。このときの負極活物質合剤層のかさ密度は１．３５ｇ／ｃｍ^３とした。
[負極板Ｐ−１] 非晶質炭素として、呉羽化学製カーボトロンＰを用い、負極集電体を含んだ電極厚さ１４７μｍ、長さ５８５ｃｍの負極板を作製した（以下、この負極板を負極板Ｐ−１という。）。このときの負極活物質合剤層のかさ密度は０．９８ｇ／ｃｍ^３とした。
[負極板Ｐ−２] 非晶質炭素として、呉羽化学製カーボトロンＰを用い、負極集電体を含んだ電極厚さ１３６μｍ、長さ６３６ｃｍの負極板を作製した（以下、この負極板を負極板Ｐ−２という。）。このときの負極活物質合剤層のかさ密度は０．９８ｇ／ｃｍ^３とした。
【００３０】
＜構成＞
（実施例１）下表１及び図２、３に示すように、正極板Ｃ−１と負極板Ｂ−１とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で幅Ａ４５ｍｍ、長さＢ１６５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。なお、表１において、「長さ割合」は捲回群６長手方向長さＬに対するシート１２の幅Ａの割合を示し（図２参照）、「Ｂ割合」は捲回群６周囲長さＰに対するシート１２の長さＢの割合を示している。
【００３１】
【表１】

【００３２】
（実施例２）表１及び図２、３に示すように、正極板Ｃ−２と負極板Ｐ−１とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１６５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例３）表１及び図２、３に示すように、正極板Ｍ−１と負極板Ｂ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１６５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例４））表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１６５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例５）表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ１３ｍｍ、長さＢ１６５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
【００３３】
（実施例６）表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ１６ｍｍ、長さＢ１６５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例７）表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ７５ｍｍ、長さＢ１６５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例８）表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ８０ｍｍ、長さＢ１６５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例９）表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１４０ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例１０）表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１５０ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例１１）表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１８５ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
（実施例１２）表１及び図２、３に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１９０ｍｍのシート１２を１枚貼り付けて電池２１を作製した。
【００３４】
（実施例１３）下表２及び図２、４に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１、Ｂ２とも８０ｍｍのシート１２を２枚、各々１９ｍｍの間隙Ｋ１、Ｋ２を設けて貼り付けて電池２１を作製した。なお、表２において、「長さ割合」は表１に示した場合と同じく捲回群６長手方向長さＬに対するシート１２の幅Ａの割合を示し（図２参照）、「Ｋ１割合」、「Ｋ２割合」及び「Ｋ３割合」はそれぞれ捲回群６周囲長さＰに対する間隙Ｋ１、Ｋ２、Ｋ３の割合を示し、「ΣＢ割合」は捲回群６周囲長さＰに対する（長さＢ１＋長さＢ２＋長さＢ３）の割合を示している。
【００３５】
【表２】

【００３６】
（実施例１４）表２及び図２、４に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１が５０ｍｍ、長さＢ２が１００ｍｍのシート１２を２枚、間隙Ｋ１が２０ｍｍ、間隙Ｋ２が２８ｍｍの間隙を設けて貼り付けて電池２１を作製した。
（実施例１５）表２及び図２、４に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１、Ｂ２とも７０ｍｍのシート１２を２枚、間隙Ｋ１が５ｍｍ、間隙Ｋ２が５３ｍｍの間隙を設けて貼り付けて電池２１を作製した。
【００３７】
（実施例１６）表２及び図２、５に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ＥＰＤＭゴム製で、幅Ａ４５ｍｍ、長さＢ１、Ｂ２及びＢ３とも５０ｍｍのシート１２を３枚、各々１６ｍｍの間隙Ｋ１、Ｋ２、Ｋ３を設けて貼り付けて電池２１を作製した。
（実施例１７）表２及び図２、５に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ポリエチレン（ＰＥ）製で、幅Ａ４５ｍｍ、長さＢ１、Ｂ２及びＢ３とも５０ｍｍのシート１２を３枚、各々１６ｍｍの間隙Ｋ１、Ｋ２、Ｋ３を設けて貼り付けて電池２１を作製した。なお、本実施例のシート１２の厚さも以上の実施例と同様に１．４ｍｍとした。
（実施例１８）表２及び図２、４に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ポリエチレン（ＰＥ）製連続気泡発泡体で、幅Ａ４５ｍｍ、長さＢ１、Ｂ２、Ｂ３とも５０ｍｍのシート１２を３枚、各々１６ｍｍの間隙Ｋ１、Ｋ２、Ｋ３を設けて貼り付けて電池２１を作製した。なお、本実施例のシート１２の厚さも以上の実施例と同様に１．４ｍｍとした。
【００３８】
＜比較例の構成＞
また、以上の実施例と比較するために、同時に比較例１及び比較例２の円筒形リチウムイオン電池を作製した。
（比較例１）表２及び図２、４に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部に、ポリエチレン製で、幅Ａ１５５ｍｍ、長さＢ１、Ｂ２とも９５ｍｍのシート１２を２枚、各々５ｍｍ、８ｍｍの間隙Ｋ１、Ｋ２を設けて貼り付けて電池を作製した。
（比較例２）表２に示すように、正極板Ｍ−２と負極板Ｐ−２とを組み合わせた捲回群６を作製し、捲回群６の両端部には、シート１２を貼り付けないで電池を作製した。
【００３９】
＜試験・評価＞
[試験]
次に、以上のように作製した実施例及び比較例の各電池について、２５＋−３°Ｃにて、４．２Ｖ定電圧、電流制限（上限）３０Ａ、４時間の充電の後、３０Ａ定電流、終止電圧２．５Ｖの条件で放電し、放電容量を計測した。
【００４０】
その後、２５＋−３°Ｃにて、電池の直径方向（長さ方向とは垂直な方向）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。この振動試験の後、実施例及び比較例の各電池の電圧を測り、加振前後の電圧変化を調べ、更に電池を解体し、軸芯１１の損傷の程度を目視にて観察した。
【００４１】
また、電池が異常事態に陥った場合を想定し、３０Ａ定電流で、外観から何がしかの現象が確認されるまで連続充電をする、いわゆる過充電試験を行った。過充電時の電池は、電圧の異常上昇による電解液の分解、ガス化で電池内部圧力が上昇し、開裂弁１０が開裂、ガス噴出する現象がみられる。ガスの噴出の仕方がスムーズでない場合には、電池の内容物を伴って噴出するので、現象後の電池重量は軽くなる。従って、現象前後の電池重量の変化（現象前に対する現象後の電池重量の割合）から、電池の挙動の優劣を判断することができる。
【００４２】
[試験結果]
放電容量測定結果、振動試験結果及び過充電試験結果を下表３に示す。
【００４３】
【表３】

【００４４】
比較例１の電池では、捲回群６の周囲の殆どにシート１２を貼り付けているので、捲回群６が広がるための余地空間が殆ど設けられていないために、過充電時のガス噴出が激しくなり、電池容器５は膨らみ、その一部は開口していた。また、比較例２の電池では、振動試験によって、軸芯１１が捲回群６を支持固定することが不可能となる軸芯１１の破損が見られ、これが加振後の電池電圧の低下につながったと思われる。
【００４５】
一方、各実施例の電池においては、電圧低下につながるような規模の軸芯１１の破損は認められていない。また、実施例１〜実施例４の電池の過充電試験後の電池重量残存割合を比較すると、正極活物質にリチウム・マンガン酸複酸化物のマンガン酸リチウムを、負極活物質に非晶質炭素を、用いた電池がよりスムーズなガス噴出となっていた。
【００４６】
実施例４、６、７の電池では、シート１２の幅Ａの長さ割合（捲回群６長手方向長さＬに対するシート１２の幅Ａの割合）を２５％以下としたので、長さ割合が２５％を超える実施例８の電池に比べて過充電試験後の電池重量残存割合が大きく、よりスムーズ（穏やか）なガス噴出となっていた。逆に、長さ割合が５％未満である実施例５の電池では、振動試験後の軸芯１１がやや変形していたことから、捲回群６の支持固定能力がやや劣ることとなることが分かる。
【００４７】
実施例４、１０、１１の電池では、シート１２のＢ割合（捲回群６周囲長さＰに対するシート１２の長さＢの割合）を９５％以下とすることで、Ｂ割合が９５％を超える実施例１２の電池に比べて過充電試験後の電池重量残存割合が大きく、よりスムーズなガス噴出となっていた。逆に、Ｂ割合が７５％未満である実施例９の電池では、振動試験後の軸芯１１がやや変形していたことから、捲回群６の支持固定能力がやや劣ることとなることが分かる。
【００４８】
実施例１３、１４の電池では、シート１２を２枚とし、互いに接触することなく間隙Ｋ１、Ｋ２を設けて配置され、両シート１２の捲回群６円周方向の長さの和（長さＢ１＋長さＢ２）は、間隙Ｋ１、Ｋ２の長さの和（間隙Ｋ１＋間隙Ｋ２）よりも大きく、間隙Ｋ１、Ｋ２の長さを捲回群周囲長さＰの２５％未満としたことで、２５％以上である実施例１５の電池に対して振動試験後の軸芯１１の変形を完全に回避することができた。シート１２を２枚以上とすることでシート１２間の間隙を捲回群６の周囲に分散させることが可能となるので、よりガス噴出がスムーズとなる。この効果は、シート１２の枚数を３とした実施例１６の電池においても示されている。
【００４９】
実施例１７の電池では、シート１２の材質をポリオレフィン系樹脂であるポリエチレンとしたことで、過充電試験後の電池重量残存割合が大きく、よりスムーズなガス噴出となった。実施例１８の電池では、シート１２の材質をポリオレフィン系樹脂であるポリエチレンの連続気泡発泡体としたことで、過充電試験後の電池重量残存割合が更に大きく、更にスムーズなガス噴出となっていた。
【００５０】
以上の実施形態の円筒形リチウムイオン電池は、電池が異常な状態にさらされた場合の挙動が極めて穏やかで、安全性に優れ、加振状態においても電池性能を十分維持できる、信頼性に優れた電池であるといえる。このように、高容量、高出力で、極めて安全性、信頼性の高い電池は、特に電気自動車の電源に適している。
【００５１】
なお、以上の実施形態では、図１にも示したように、シート１２を捲回群６端に揃えるように配置したが、電池内構造を損ねない範囲で、多少はみだしても、逆に、引っ込んでいてもよく、概ね捲回群６端に配置されていればよい。
【００５２】
また、以上の実施形態では、捲回群６と電池容器５との間に発生した隙間を埋めるために１重のシート１２を用いた例を示したが、より薄いシートを複数重ねて用いても良く、更に、シート１２を配置していても、捲回群６と電池容器５との間に若干発生した隙間は、絶縁テープ等を用いて埋めるようにしても良い。
【００５３】
また、以上の実施形態では、電気自動車用電源等に用いられる大形の二次電池について例示したが、実質容量３０Ａｈ以上の電池であれば、電池の用途や大きさには限定されないことはいうまでもない。また、有底筒状容器（缶）に電池上蓋がカシメによって封口されている構造の円筒形リチウムイオン電池にも本発明の適用が可能である。
【００５４】
更に、以上の実施形態では、電流遮断機構を備えない円筒形リチウムイオン電池について例示したが、本発明は電流遮断機構を備えた電池に適用するようにしてもよい。このようにすれば、車両衝突事故等の異常時に電気系の電流遮断機構が作動しなくても機械系の開裂弁１０等の内圧低減機構が作動するので、車載電池のより高い安全性が確保される。
【００５５】
また、以上の実施形態では、絶縁被覆８に、基材がポリプロピレンで、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、これに限定されるものではなく、例えば、基材がポリイミド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することができる。
【００５６】
更に、以上の実施形態では、リチウムイオン電池用の正極にコバルト酸リチウムやマンガン酸リチウム、負極に黒鉛質炭素や非晶質炭素、電解液に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の体積比１：１：１の混合液中へ６フッ化リン酸リチウムを１モル／リットル溶解したものを用いたが、本発明の電池の製造方法には特に制限はなく、また結着剤、負極活物質、非水電解液も通常用いられているいずれのものも使用可能である。ＥＶ用途向け高容量、高出力の電池で、かつ安全性を確実に確保するためには、正極活物質としてリチウム・コバルト複合酸化物やリチウム・ニッケル複合酸化物を用いるよりも、リチウムマンガン複酸化物であるマンガン酸リチウムを用いることがより望ましい。
【００５７】
また、以上の実施形態ではポリフッ化ビニリデンを結着剤として使用したが、リチウムイオン電池用極板活物質結着剤としては、テフロン、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等の重合体及びこれらの混合体等を用いてもよい。
【００５８】
更に、以上の実施形態に示した以外のリチウム二次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又はドープした材料を使用してもよい。また、リチウムとマンガンとの原子比が化学量論比からずれた活物質を使用しても以上の実施形態と同様の効果を得ることができる。
【００５９】
また更に、以上の実施形態に示した以外のリチウムイオン電池用負極活物質を使用しても本発明の適用は制限されない。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を使用してもよく、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。
【００６０】
また、電解液としては、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を使用してもく、リチウム塩や有機溶媒にも特に制限されるものではない。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。
【００６１】
そして、本実施形態以外の非水電解液有機溶媒としては、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、ビニレンカーボネート、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、プロピオニトリル等又はこれら２種類以上の混合溶媒を用いることができ、更に、混合配合比についても限定されるものではない。
【００６２】
【発明の効果】
以上説明したように、本発明によれば、異常時に電極捲回群内部でガス圧が発生しても電極捲回群中央部が直径方向へ膨張可能とし、ガスが電極捲回群両端部を電極捲回群直径方向に膨張させ電極捲回群両端部からスムーズに外部へ排出できるようにしたので、電極捲回群内部にはガスが滞留せず、電池容器内での異常発熱や電池容器の著しい変形を引き起こさないことから、電池の安全性を確保することができ、また、スペーサの電極捲回群円周方向長さを、電極捲回群の円周長さの７５％以上、９５％以下としたので、異常時に電極捲回群が電極捲回群直径方向にスムーズに膨張することができ、電池の更に安全性を高めることができると共に、電極捲回群とスペーサとは密着し電極捲回群はスペーサを介して電池容器に固定された状態となるようにしたので、電極捲回群の長手方向への移動を抑制し振動による電極捲回群の損傷や内部短絡を引き起こさないことから、電池の信頼性を高めることができる、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ＥＶ搭載用円筒形リチウムイオン電池の断面図である。
【図２】第１実施形態の円筒形リチウムイオン電池の捲回群の概略側面図である。
【図３】第１実施形態の円筒形リチウムイオン電池の円周方向断面を示す概略図である。
【図４】本発明の適用が可能な第２実施形態の円筒形リチウムイオン電池の円周方向断面を示す概略図である。
【図５】本発明の適用が可能な第３実施形態の円筒形リチウムイオン電池の円周方向断面を示す概略図である。
【符号の説明】
４電池蓋（蓋板）
５電池容器
６捲回群（電極捲回群）
１０開裂弁（内圧低減機構）
１２シート（スペーサ）
２１円筒形リチウムイオン電池[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical lithium ion battery, and in particular, a positive electrode current collector coated with a positive electrode active material capable of releasing and accommodating lithium by charging and discharging, and a negative electrode current collector by charging and discharging. A strip-shaped negative electrode coated with a negative electrode active material that can be accommodated / released has an electrode winding group wound through a strip-shaped separator through which lithium ions can pass, and the electrode winding group is a cylindrical battery A cylindrical lithium ion battery having a discharge capacity of 30 Ah or more having an internal pressure reduction mechanism that discharges gas in response to an increase in internal pressure of the battery container on at least one of cover plates that are built in the container and seals both end faces of the battery container. The present invention relates to a cylindrical lithium ion battery having an A / B value of 0.98 or less, where A is the diameter of the electrode winding group and B is the inner diameter of the battery container.
[0002]
[Prior art]
Lithium ion secondary batteries are attracting attention as power sources for EVs (electric vehicles) because of their high output and high energy density. Lithium ion secondary batteries can be classified into cylindrical shapes and rectangular shapes according to their shapes. Normally, the inside of a cylindrical battery is in the form of a strip with the active material applied to the metal foil for both the positive and negative electrodes, and around the cylindrical axis with a separator so that the positive and negative electrodes are not in direct contact. A winding structure in which the cross section is wound in a spiral shape and an electrode winding group is formed is adopted. And the electrode winding group is accommodated in the cylindrical can or container used as the battery container, and after the electrolyte solution injection, it is sealed, and the function as the battery is imparted by first charging.
[0003]
In order to improve the energy density, it is preferable to fill the battery container with more active material, and the electrode winding group is inserted into the battery container relatively densely. However, in a lithium ion secondary battery using lithium cobaltate as the positive electrode active material and a graphite carbon material as the negative electrode, the active material causes volume expansion of both the positive electrode and the negative electrode during the initial charge. Inconvenient situations may occur, causing a decrease in capacity and life. As countermeasures, in the lithium ion secondary battery for consumer use with a capacity of approximately 2 Ah or less that is currently installed in notebook computers and mobile phones, the electrode winding group and the battery container are within a range that can suppress a significant decrease in capacity and energy density. It has a structure with some space in between. Also, in the case of industrial continuous automatic production, it is desirable to provide the above-mentioned space because the insertion property of the electrode winding group into the battery container is improved.
[0004]
On the other hand, lithium-ion secondary batteries with a capacity of approximately 30 Ah or more suitable for EV power supply applications are naturally high in output and completely rupture and ignite when an abnormality occurs, such as falling into an overcharged state or being crushed. It is inevitable that they will be lost.
[0005]
In addition, a high-capacity, high-power lithium ion secondary battery has a large battery length and battery diameter. As described above, in the band-shaped electrode in which the active material is applied to the metal foil, when the amount of the active material applied is increased and the electrode is thickened, the active material layer is peeled off and cannot be maintained. For this reason, the diameter of the electrode winding group is increased by increasing the number of times of winding the band-shaped electrode.
[0006]
[Problems to be solved by the invention]
However, in the case of a high discharge capacity battery having a long electrode winding group and an electrode winding group that has been wound many times, for example, when the electrolyte is decomposed in the event of an abnormality such as overcharge or vehicle collision when mounted on an EV As a result, there is a problem in that the gas generated by the gas etc. tends to stay inside the electrode winding group and cannot be smoothly discharged from the internal pressure reduction mechanism such as a safety valve, resulting in abnormal heat generation and significant deformation of the battery container. As a result of hard and vigorous investigation and improvement activities, the present inventors have found that, in order to ensure safety in a high-capacity, high-power cylindrical lithium ion battery, there is a gap between the electrode winding group and the battery container. I found that I needed space. In other words, this space must be provided for the purpose of ensuring safety different from the space provided in a consumer-use lithium ion secondary battery having a relatively small capacity.
[0007]
The battery is subjected to vibration when mounted on an EV and actually travels. Therefore, an EV battery must have not only electrical characteristics but also reliability such as vibration resistance. As described above, when a space is provided between the long and large-diameter electrode winding group and the battery case, the electrode winding is caused by the inertial moment due to the weight of the large electrode winding group when vibration is applied. The group moves within the battery container, causing damage to the internal components of the battery and damage to the electrode winding group itself, and subsequently causes an internal short circuit, resulting in a loss of battery function.
[0008]
An object of the present invention is to provide a cylindrical lithium ion battery that has high capacity and high output, yet has high safety and reliability.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a positive electrode current collector coated with a positive electrode active material capable of releasing and accommodating lithium by charging and discharging, and a negative electrode current collector containing lithium by charging and discharging. A strip-shaped negative electrode coated with a releasable negative electrode active material and an electrode winding group wound through a strip-shaped separator through which lithium ions can pass, the electrode winding group being a cylindrical battery container A cylindrical lithium ion battery having a discharge capacity of 30 Ah or more having an internal pressure reducing mechanism for releasing gas in response to an increase in the internal pressure of the battery container in at least one of the lid plates sealing both end faces of the battery container. In a cylindrical lithium ion battery having an A / B value of 0.98 or less, where A is the diameter of the electrode winding group and B is the inner diameter of the battery container, a resin having electrical insulation. Made of the battery container The electrode winding group is arranged between the electrode winding group and in the vicinity of both ends of the electrode winding group, and the electrode winding group has an electrode around the outer periphery of the electrode winding group by gas pressure generated inside the electrode winding group. Provided with a spacer surrounding the circular arc, forming a gap at a predetermined interval allowing expansion in the winding group diameter direction The electrode winding group circumferential length of the spacer is 75% or more and 95% or less of the circumferential length of the electrode winding group. .
[0010]
In the present invention, since the spacer is disposed between the battery container and the electrode winding group and in the vicinity of both ends of the electrode winding group, the spacer is provided between the battery container and the center part of the electrode winding group where the spacer is not disposed. A space (space) is formed, and even if a gas pressure is generated inside the electrode winding group at the time of abnormality, the central portion of the electrode winding group can expand in the diameter direction. In addition, the spacer forms a gap at a predetermined interval that allows the electrode winding group to expand in the diameter direction of the electrode winding group due to gas pressure generated inside the electrode winding group on the outer periphery of the electrode winding group. Then, when the gas pressure is generated inside the electrode winding group at the time of abnormality, the generated gas expands both ends of the electrode winding group in the electrode winding group diameter direction, and the electrode winding group Ejected smoothly from both ends. The gas discharged from both ends of the electrode winding group is released from the internal pressure reduction mechanism when the internal pressure of the battery container reaches a predetermined pressure. Therefore, gas does not stay inside the electrode winding group, and abnormal heat generation in the battery container and significant deformation of the battery container are not caused, so that the safety of the battery can be ensured. Further, since the circumferential direction length of the electrode winding group of the spacer is set to 75% or more and 95% or less of the circumferential length of the electrode winding group, the electrode winding group moves in the electrode winding group diameter direction at the time of abnormality. It can be expanded smoothly, and the safety of the battery can be further enhanced. Furthermore, since the spacer is made of an electrically insulating resin and the outer periphery of the electrode winding group is surrounded by an arc, the electrode winding group and the spacer are in close contact with each other, and the electrode winding group is interposed via the spacer. It will be in the state fixed to the battery container, and the movement to the longitudinal direction of an electrode winding group will be suppressed. Therefore, the vibration resistance is improved, and the electrode winding group is not damaged or caused by internal short circuit due to vibration, so that the reliability of the battery can be improved.
[0011]
In this case, in order to gently generate gas from the inside of the electrode winding group and enhance safety, it is preferable that the positive electrode active material is lithium-manganese double oxide, and the negative electrode active material is amorphous carbon. It is preferable to do. In order to ensure safety in the event of an abnormality, the spacer is preferably formed of a polyolefin resin, and more preferably formed of an open cell polyolefin resin foam. Further, if the longitudinal direction width of the spacer in the electrode winding group is set to 5% or more and 25% or less of the length in the longitudinal direction of the electrode winding group, the gas generated inside the electrode winding group at the time of abnormality is discharged into the electrode winding group. The battery can be guided more smoothly to the outside, so the safety of the battery can be further increased. . So Then, the spacer is separated into at least two pieces, a gap is formed without contacting each other, and the sum of the lengths of the spacers in the electrode winding group circumferential direction is larger than the sum of the lengths of the gaps, If each length of the gap is less than 25% of the circumferential length of the electrode winding group, it becomes possible to disperse the gap between the spacers around the electrode winding group. Reliability can be ensured.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment in which the present invention is applied to an EV-mounted cylindrical lithium ion battery will be described with reference to the drawings.
[0013]
<Battery manufacturing method>
[Preparation of positive electrode plate]
Lithium cobaltate (LiCoO), an active material that can release and contain lithium by charging and discharging ₂ ) Powder or lithium manganate (LiMn) ₂ O ₄ ) Powder, scaly graphite (average particle size: 20 μm) as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder at a predetermined blending ratio described later, and a dispersion solvent N-methyl- A slurry in which 2-pyrrolidone (MNP) was added and kneaded was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 20 μm. At this time, an uncoated part with a width of 50 mm was left on one side edge in the longitudinal direction of the positive electrode plate. Thereafter, drying, pressing, and cutting were performed to obtain a belt-like positive electrode plate having a width of 300 mm, a predetermined length described later, and a predetermined thickness of the positive electrode active material mixture application portion. The porosity of the positive electrode active material mixture layer was 35 + -1.5%. A notch was cut in the slurry uncoated portion of the positive electrode plate, and the remaining notch was used as a lead piece. Adjacent lead pieces were spaced 20 mm apart, and the width of the lead pieces was 10 mm.
[0014]
[Preparation of negative electrode plate]
MCMB powder manufactured by Osaka Gas Chemical Co., Ltd. (hereinafter referred to as Osaka Gas Chemical), which is a graphitic carbon that can store and release lithium by charging and discharging, and Kureha Chemical Industry Co., Ltd. (hereinafter referred to as Kureha), which is amorphous carbon. This is called chemical.) To 92 parts by weight of Carbotron P powder, 8 parts by weight of polyvinylidene fluoride as a binder was added, and N-methyl-2-pyrrolidone as a dispersion solvent was added thereto, and the kneaded slurry was 10 μm thick. The rolled copper foil (negative electrode current collector) was coated on both sides. At this time, an uncoated part having a width of 50 mm was left on one side edge in the longitudinal direction of the negative electrode plate. Thereafter, drying, pressing, and cutting were performed to obtain a strip-shaped negative electrode plate having a width of 305 mm, a predetermined length described later, and a predetermined thickness of the negative electrode active material application portion. The porosity of the negative electrode active material layer was 35 + -1.5%. A notch was cut into the slurry-uncoated portion of the negative electrode plate in the same manner as the positive electrode plate, and the remainder of the notch was used as a lead piece. Adjacent lead pieces were spaced 20 mm apart, and the width of the lead pieces was 10 mm.
[0015]
[Battery fabrication]
The produced strip-shaped positive electrode plate and negative electrode plate are wound together with a polypropylene separator having a thickness of 14 mm and an inner diameter of 8 mm together with a polyethylene separator having a thickness of 40 μm and a width of 310 mm so that these two plates do not directly contact each other. Wound about 40 times or more around the shaft core 11. At this time, the lead pieces (see reference numeral 9 in FIG. 1) of the positive electrode plate and the negative electrode plate were respectively positioned on opposite end surfaces of the wound group (electrode wound group). The wound group diameter φ was adjusted to the length of the positive electrode plate, the negative electrode plate, and the separator to be 63 + −0.1 mm in diameter. Therefore, the wound group circumference length P is 2π × (winding group diameter φ) /2=197.92 mm.
[0016]
As shown in FIG. 1, the lead piece 9 led out from the positive electrode plate is deformed, and all of the lead pieces 9 are integrally projected 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 in the vicinity of the peripheral surface of the portion 7, the lead piece 9 and the peripheral surface of the flange portion 7 were ultrasonically welded to connect and fix the lead piece 9 to the peripheral surface of the flange portion 7. The connection operation between the negative electrode external terminal 1 ′ and the lead piece 9 led out from the negative electrode plate was performed in the same manner as the connection operation between the positive electrode external terminal 1 and the lead piece 9 led out from the positive electrode plate.
[0017]
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 periphery of the wound group 6. For the insulating coating 8, an adhesive tape in which the base material was polypropylene and a pressure sensitive adhesive made of hexamethacrylate was applied on one side thereof was used. This adhesive tape was wound around at least one round from the circumferential surface of the collar portion 7 to the outer circumferential surface of the wound group 6 to obtain an insulating coating 8.
[0018]
2 and 3, a predetermined width A (length in the longitudinal direction of the wound group 6; see FIG. 2), a predetermined length B (see FIG. 3), and a thickness of 1.4 mm, which will be described later. Winding group 6 is wound with a gap K (see FIG. 3) provided at both ends of winding group 6 on which insulating coating 8 is applied and one sheet 12 as a spacer made of a predetermined material having a specific insulating property. In this way, the insulating coating 8 was attached in an arc shape. In addition, in this embodiment, the sheet | seat 12 was affixed so that it might become substantially parallel to the winding group 6 circumferential direction using Sekisui Chemical Co., Ltd. double-sided tape # 575.
[0019]
Next, the wound group 6 is inserted into a stainless steel battery container 5 having an outer diameter of 67 mm and an inner diameter of 66 mm, and then a portion made of alumina in contact with the back surface of the disk-shaped battery lid 4 (cover plate) has a thickness of 2 mm and an inner diameter of 16 mm. As shown in FIG. 1, a second ceramic washer 3 ′ having an outer diameter of 25 mm was fitted into a pole column having a tip constituting the positive electrode external terminal 1 and a tip having a tip 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. As shown in FIG. 1, 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 (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 is 1.3 × 10 ⁶ ~ 1.8 × 10 ⁶ Pa (130 to 180 N / cm ² ).
[0020]
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 7 N · m. Note that the metal washer 14 did not rotate until the tightening operation was completed. In this state, the power generation element inside the battery container 5 is blocked 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.
[0021]
Thereafter, a predetermined amount of electrolytic solution was injected into the battery container 5 from the injection port 15 provided in the battery lid 4, and then the injection port 15 was sealed to complete the cylindrical lithium ion battery 21.
[0022]
The electrolyte used was lithium hexafluorophosphate (LiPF) in a mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1: 1: 1. ₆ ) Was dissolved at 1 mol / liter. The cylindrical lithium ion battery 21 is not provided with a current interrupting mechanism that interrupts current in response to an increase in the internal pressure of the battery container 5. Further, as described above, the diameter of the wound group 6 is 63 mm, and the inner (straight) diameter of the battery container 5 is 66 mm, so (diameter of the wound group 6) / (inner diameter of the battery container 5). The value of is 0.95.
[0023]
(Second Embodiment)
Next, a second embodiment of the cylindrical lithium ion battery according to the present invention will be described. In this embodiment, two gaps are used instead of the gap K at one place in the first embodiment, and two sheets 12 are used. In addition, in embodiment below this embodiment, the same member as 1st Embodiment attaches | subjects the same code | symbol, the description is abbreviate | omitted, and only a different location is demonstrated.
[0024]
As shown in FIG. 4, in this embodiment, as will be described later, a predetermined material having electrical insulation, a predetermined width A (see FIG. 2) described later, a predetermined length B1, B2, and a thickness of 1.4 mm, respectively. Two sheets 12 of the above are attached to the insulating coating 8 in an arc shape so as to wind the winding group 6 by providing two gaps K1 and K2 at both ends of the wound group 6 to which the insulating coating 8 is applied. Thus, a cylindrical lithium ion battery 21 was produced.
[0025]
(Third embodiment)
Next, a third embodiment of the cylindrical lithium ion battery according to the present invention will be described. In the present embodiment, three gaps are used instead of the one gap K in the first embodiment, and three sheets 12 are used.
[0026]
As shown in FIG. 5, in the present embodiment, as will be described later, a predetermined material having electrical insulation, a predetermined width A (see FIG. 2) described later, and predetermined lengths B1, B2, B3, thickness 1 respectively. Insulating coating 8 in a circular arc shape so as to wind three windings 6 by providing three gaps K1, K2, K3 at both ends of winding group 6 to which three sheets of 4 mm 12 and insulating coating 8 are applied. A cylindrical lithium ion battery 21 was produced.
[0027]
(Example)
Next, examples of the cylindrical lithium ion battery 21 manufactured according to the above embodiment will be described. First, a positive electrode plate and a negative electrode plate were produced as follows.
[0028]
<Positive electrode plate>
[Positive Electrode Plate C-1] Lithium cobaltate using cell seed C-10 manufactured by Nippon Chemical Industry Co., Ltd. (hereinafter referred to as “Nippon Chemical”) as the positive electrode active material, and the blending ratio of lithium cobaltate, flake graphite, and PVdF Was 60:29:11 by weight%, and a positive electrode plate having a thickness of 248 μm and a length of 636 cm including a positive electrode current collector was produced (hereinafter, this positive electrode plate is referred to as a positive electrode plate C-1). The bulk density of the positive electrode active material mixture layer at this time is 2.1 g / cm ³ It was.
[Positive electrode plate C-2] Lithium cobaltate using Nippon Chemical Co., Ltd. cell seed C-10 as the positive electrode active material, and the blending ratio of lithium cobaltate, flake graphite and PVdF was 65:24:11 by weight%, A positive electrode plate including a positive electrode current collector and having an electrode thickness of 276 μm and a length of 567 cm was produced (hereinafter, this positive electrode plate is referred to as a positive electrode plate C-2). The bulk density of the positive electrode active material mixture layer at this time is 2.15 g / cm ³ It was.
[Positive electrode plate M-1] Lithium manganate manufactured by Mitsui Kinzoku Co., Ltd. (hereinafter referred to as Mitsui Metals) was used as the positive electrode active material, and the mixing ratio of lithium manganate, flake graphite, and PVdF was 78% by weight. A positive electrode plate having an electrode thickness of 258 μm and a length of 620 cm including a positive electrode current collector was prepared at 12:10 (hereinafter, this positive electrode plate is referred to as a positive electrode plate M-1). The bulk density of the positive electrode active material mixture layer at this time was 2.35 g / cm. ³ It was. [Positive electrode plate M-2] Using lithium manganate made by Mitsui Metals as a positive electrode active material, the blending ratio of lithium manganate, flake graphite and PVdF was 85: 10: 5 by weight%, and the positive electrode current collector was A positive electrode plate having an electrode thickness of 247 μm and a length of 618 cm was prepared (hereinafter, this positive electrode plate is referred to as a positive electrode plate M-2). The bulk density of the positive electrode active material mixture layer at this time is 2.55 g / cm ³ It was.
[0029]
<Negative electrode plate>
[Negative Electrode B-1] As graphitic carbon, MCMB manufactured by Osaka Gas Chemical was used to produce a negative electrode plate having a negative electrode current collector of 121 μm and a length of 654 cm (hereinafter, this negative electrode plate was referred to as a negative electrode). It is called plate B-1.) At this time, the bulk density of the negative electrode active material mixture layer was 1.35 g / cm. ³ It was.
[Negative Electrode B-2] As graphitic carbon, MCMB manufactured by Osaka Gas Chemical was used to produce a negative electrode plate having a negative electrode current collector of 124 μm and a length of 638 cm (hereinafter, this negative electrode plate was referred to as a negative electrode). Referred to as plate B-2). At this time, the bulk density of the negative electrode active material mixture layer was 1.35 g / cm. ³ It was.
[Negative Electrode Plate P-1] As amorphous carbon, Kaboha Chemical's Carbotron P was used to prepare a negative electrode plate having a negative electrode current collector thickness of 147 μm and a length of 585 cm (hereinafter, this negative electrode plate was referred to as a negative electrode). Referred to as plate P-1.). The bulk density of the negative electrode active material mixture layer at this time is 0.98 g / cm ³ It was.
[Negative Electrode P-2] As amorphous carbon, Kaboha Chemical's Carbotron P was used to produce a negative electrode plate having a negative electrode current collector of 136 μm and a length of 636 cm (hereinafter, this negative electrode plate was referred to as a negative electrode). Referred to as plate P-2). The bulk density of the negative electrode active material mixture layer at this time is 0.98 g / cm ³ It was.
[0030]
<Configuration>
(Example 1) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which the positive electrode plate C-1 and the negative electrode plate B-1 are combined is prepared. One sheet 12 made of EPDM rubber and having a width A of 45 mm and a length of B 165 mm was attached to prepare a battery 21. In Table 1, “length ratio” indicates the ratio of the width A of the sheet 12 to the longitudinal length L of the wound group 6 (see FIG. 2), and “B ratio” indicates the wound group 6 circumferential length P. The ratio of the length B of the sheet 12 to the above is shown.
[0031]
[Table 1]

[0032]
(Example 2) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which a positive electrode plate C-2 and a negative electrode plate P-1 were combined was prepared, and EPDM was formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 45 mm and a length of B 165 mm was attached to prepare a battery 21.
(Example 3) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which a positive electrode plate M-1 and a negative electrode plate B-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 45 mm and a length of B 165 mm was attached to prepare a battery 21.
(Example 4) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which the positive electrode plate M-2 and the negative electrode plate P-2 are combined is prepared. One sheet 12 made of EPDM rubber and having a width A of 45 mm and a length of B 165 mm was attached to prepare a battery 21.
(Example 5) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 were combined was prepared, and EPDM was formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 13 mm and a length of B 165 mm was attached to produce a battery 21.
[0033]
(Example 6) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which the positive electrode plate M-2 and the negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 16 mm and a length of B 165 mm was attached to prepare a battery 21.
(Example 7) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 75 mm and a length of B 165 mm was attached to prepare a battery 21.
(Example 8) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which the positive electrode plate M-2 and the negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 80 mm and a length of B 165 mm was attached to produce a battery 21.
(Example 9) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 45 mm and a length of B 140 mm was pasted to produce a battery 21.
(Example 10) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 45 mm and a length of B 150 mm was attached to prepare a battery 21.
(Example 11) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 45 mm and a length of B 185 mm was attached to produce a battery 21.
(Example 12) As shown in Table 1 and FIGS. 2 and 3, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. One sheet 12 made of rubber and having a width A of 45 mm and a length of B 190 mm was attached to prepare a battery 21.
[0034]
(Example 13) As shown in Table 2 and FIGS. 2 and 4 below, a wound group 6 in which the positive electrode plate M-2 and the negative electrode plate P-2 are combined is prepared. Two sheets 12 made of EPDM rubber and having a width A of 45 mm and a length of B1 and B2 of 80 mm were attached to each other with 19 mm gaps K1 and K2, respectively. In Table 2, the “length ratio” indicates the ratio of the width A of the sheet 12 to the longitudinal length L of the wound group 6 as in Table 1 (see FIG. 2), “K1 ratio”, “K2 ratio” and “K3 ratio” indicate the ratios of the gaps K1, K2, and K3 with respect to the wound group 6 circumference length P, respectively, and “ΣB ratio” represents (length B1 + length with respect to the wound group 6 circumference length P). The ratio of (B2 + length B3) is shown.
[0035]
[Table 2]

[0036]
(Embodiment 14) As shown in Table 2 and FIGS. 2 and 4, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. A battery 21 was fabricated by attaching two sheets 12 made of rubber, each having a width A of 45 mm, a length B1 of 50 mm, and a length B2 of 100 mm, a gap K1 of 20 mm, and a gap K2 of 28 mm.
Example 15 As shown in Table 2 and FIGS. 2 and 4, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 are combined is prepared, and EPDM is formed at both ends of the wound group 6. A battery 21 was fabricated by attaching two sheets 12 made of rubber and having a width A of 45 mm and a length of B1 and B2 of 70 mm, a gap K1 of 5 mm, and a gap K2 of 53 mm.
[0037]
(Example 16) As shown in Table 2 and FIGS. 2 and 5, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 were combined was prepared, and EPDM was formed at both ends of the wound group 6. Three sheets 12 made of rubber and having a width A of 45 mm and lengths B1, B2, and B3 of 50 mm were attached to each other with gaps K1, K2, and K3 of 16 mm, respectively.
(Example 17) As shown in Table 2 and FIGS. 2 and 5, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 were combined was prepared, and polyethylene was formed at both ends of the wound group 6. A battery 21 was fabricated by attaching three sheets 12 made of (PE) and having a width A of 45 mm and lengths B1, B2, and B3 of 50 mm, each having 16 mm gaps K1, K2, and K3. In addition, the thickness of the sheet | seat 12 of a present Example was also 1.4 mm similarly to the above Example.
Example 18 As shown in Table 2 and FIGS. 2 and 4, a wound group 6 in which a positive electrode plate M-2 and a negative electrode plate P-2 were combined was prepared, and polyethylene was formed at both ends of the wound group 6. A battery 21 was prepared by attaching three sheets 12 of (PE) open-cell foams each having a width A of 45 mm and lengths B1, B2, and B3 of 50 mm, each having 16 mm gaps K1, K2, and K3. In addition, the thickness of the sheet | seat 12 of a present Example was also 1.4 mm similarly to the above Example.
[0038]
<Configuration of Comparative Example>
Moreover, in order to compare with the above Example, the cylindrical lithium ion battery of the comparative example 1 and the comparative example 2 was produced simultaneously.
Comparative Example 1 As shown in Table 2 and FIGS. 2 and 4, a wound group 6 in which the positive electrode plate M-2 and the negative electrode plate P-2 are combined is prepared, and polyethylene is formed at both ends of the wound group 6. Two batteries 12 having a width A of 155 mm and a length of B1 and B2 of 95 mm were both attached and provided with gaps K1 and K2 of 5 mm and 8 mm, respectively, to produce a battery.
(Comparative Example 2) As shown in Table 2, a wound group 6 is produced by combining the positive electrode plate M-2 and the negative electrode plate P-2, and sheets 12 are attached to both ends of the wound group 6. The battery was made without.
[0039]
<Test and evaluation>
[test]
Next, for each of the batteries of Examples and Comparative Examples prepared as described above, at 25 + -3 ° C., 4.2 V constant voltage, current limit (upper limit) 30 A, after charging for 4 hours, 30 A constant current The battery was discharged under the condition of a final voltage of 2.5 V, and the discharge capacity was measured.
[0040]
Thereafter, at 25 + -3 ° C., vibration is applied in the battery diameter direction (direction perpendicular to the length direction) 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 was performed. After this vibration test, the voltage of each battery of the example and the comparative example was measured, the voltage change before and after the vibration was examined, the battery was further disassembled, and the degree of damage to the shaft core 11 was visually observed.
[0041]
Further, assuming a case where the battery is in an abnormal state, a so-called overcharge test was performed in which the battery was continuously charged at a constant current of 30 A until some phenomenon was confirmed from the appearance. In the battery at the time of overcharge, there is a phenomenon that the internal pressure of the battery rises due to decomposition and gasification of the electrolyte due to an abnormal increase in voltage, the cleavage valve 10 is cleaved, and gas is ejected. When the gas is not smoothly ejected, the gas is ejected with the contents of the battery, so that the battery weight after the phenomenon is reduced. Therefore, the superiority or inferiority of the behavior of the battery can be determined from the change in the battery weight before and after the phenomenon (ratio of the weight of the battery after the phenomenon before the phenomenon).
[0042]
[Test results]
The discharge capacity measurement results, vibration test results, and overcharge test results are shown in Table 3 below.
[0043]
[Table 3]

[0044]
In the battery of Comparative Example 1, since the sheet 12 is affixed almost to the periphery of the wound group 6, there is almost no room for the wound group 6 to expand. The battery container 5 swelled and part of it opened. Further, in the battery of Comparative Example 2, the shaft core 11 is broken by the vibration test, which makes it impossible for the shaft core 11 to support and fix the wound group 6, and this reduces the battery voltage after vibration. It seems to have connected.
[0045]
On the other hand, in the battery of each Example, the damage of the shaft core 11 of the scale which leads to a voltage drop is not recognized. Further, comparing the battery weight remaining ratio after the overcharge test of the batteries of Examples 1 to 4, lithium manganate of lithium / manganate double oxide as the positive electrode active material and amorphous carbon as the negative electrode active material The battery used had a smoother gas ejection.
[0046]
In the batteries of Examples 4, 6, and 7, the length ratio of the width A of the sheet 12 (the ratio of the width A of the sheet 12 to the longitudinal length L of the wound group 6) was set to 25% or less. Compared with the battery of Example 8 in which over 25%, the battery weight remaining ratio after the overcharge test was large, and the gas was jetted more smoothly (gentle). On the other hand, in the battery of Example 5 having a length ratio of less than 5%, the shaft core 11 after the vibration test was slightly deformed, so that the supporting and fixing ability of the wound group 6 is slightly inferior. I understand.
[0047]
In the batteries of Examples 4, 10, and 11, the B ratio of the sheet 12 (the ratio of the length B of the sheet 12 to the peripheral length P of the wound group 6) is 95% or less, so that the B ratio is 95%. Compared with the battery of Example 12 that exceeds this, the remaining weight ratio of the battery after the overcharge test was large, resulting in smoother gas ejection. On the other hand, in the battery of Example 9 in which the B ratio is less than 75%, the support core fixing ability of the wound group 6 may be slightly inferior because the shaft core 11 after the vibration test was slightly deformed. I understand.
[0048]
In the batteries of Examples 13 and 14, two sheets 12 are provided and are provided with gaps K1 and K2 without contacting each other, and the sum of the lengths of the winding groups 6 in the circumferential direction of both sheets 12 (length) B1 + length B2) is larger than the sum of the lengths of the gaps K1, K2 (gap K1 + gap K2), and the length of the gaps K1, K2 is less than 25% of the winding group peripheral length P. It was possible to completely avoid the deformation of the shaft core 11 after the vibration test for the battery of Example 15 which was 25% or more. By using two or more sheets 12, it is possible to disperse the gaps between the sheets 12 around the wound group 6, so that gas ejection is smoother. This effect is also shown in the battery of Example 16 in which the number of sheets 12 is three.
[0049]
In the battery of Example 17, since the material of the sheet 12 was made of polyethylene, which is a polyolefin resin, the ratio of remaining battery weight after the overcharge test was large, resulting in smoother gas ejection. In the battery of Example 18, since the material of the sheet 12 was an open-cell foam of polyethylene, which is a polyolefin resin, the battery weight remaining ratio after the overcharge test was further increased, and gas was smoothly ejected. .
[0050]
The cylindrical lithium ion battery of the above embodiment has extremely gentle behavior when the battery is exposed to an abnormal state, excellent safety, can maintain battery performance sufficiently even under vibration, and has excellent reliability. Battery. Thus, a battery with high capacity, high output, and extremely high safety and reliability is particularly suitable for a power source of an electric vehicle.
[0051]
In the above embodiment, as shown in FIG. 1, the sheet 12 is arranged so as to be aligned with the end of the wound group 6. However, in the range that does not impair the internal structure of the battery, It may be withdrawn and it should just be arrange | positioned at the winding group 6 end in general.
[0052]
Moreover, in the above embodiment, although the example which used the single sheet | seat 12 in order to fill the gap | interval which generate | occur | produced between the winding group 6 and the battery container 5 was shown, using a several thin sheet | seat in piles In addition, even if the sheet 12 is disposed, a slight gap generated between the wound group 6 and the battery container 5 may be filled with an insulating tape or the like.
[0053]
Moreover, in the above embodiment, although illustrated about the large-sized secondary battery used for the electric vehicle power supply etc., if it is a battery of substantial capacity 30Ah or more, it is said that it is not limited to the use and magnitude | size of a battery. Not too long. The present invention can also be applied to a cylindrical lithium ion battery having a structure in which a battery upper lid is sealed by caulking on a bottomed cylindrical container (can).
[0054]
Further, in the above embodiment, the cylindrical lithium ion battery not provided with the current interruption mechanism is illustrated, but the present invention may be applied to a battery provided with the current interruption mechanism. In this way, since the internal pressure reduction mechanism such as the mechanical cleavage valve 10 operates even if the electric current interruption mechanism does not operate in the event of an abnormality such as a vehicle collision accident, higher safety of the in-vehicle battery is ensured. Is done.
[0055]
Moreover, in the above embodiment, although the base material was polypropylene and the adhesive tape which apply | coated the adhesive which consists of hexamethacrylate on the one side was used for the insulation coating 8, it is not limited to this, For example, The base material is polyolefin such as polyimide or polyethylene, and adhesive tape with acrylic adhesive such as hexamethacrylate or butyl acrylate applied on one or both sides, or tape made of polyolefin or polyimide that does not apply adhesive is suitable. Can be used.
[0056]
Furthermore, in the above embodiment, lithium cobalt oxide or lithium manganate is used as the positive electrode for lithium ion batteries, graphitic carbon or amorphous carbon is used as the negative electrode, and the volume ratio of ethylene carbonate, dimethyl carbonate and diethyl carbonate is used as the electrolyte solution is 1: A solution obtained by dissolving 1 mol / liter of lithium hexafluorophosphate in a 1: 1 mixed solution was used, but the method for producing the battery of the present invention is not particularly limited, and a binder, a negative electrode active material, Any commonly used non-aqueous electrolyte can be used. In order to ensure high-capacity, high-power batteries for EV applications and to ensure safety, lithium-manganese composite oxidation rather than using lithium-cobalt composite oxide or lithium-nickel composite oxide as the positive electrode active material It is more desirable to use lithium manganate which is a product.
[0057]
In the above embodiment, polyvinylidene fluoride is used as a binder, but as an electrode plate active material binder for lithium ion batteries, Teflon, polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber Polymers such as polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and mixtures thereof may be used.
[0058]
Further, as the positive electrode active material for lithium secondary batteries other than those shown in the above embodiment, lithium can be inserted / desorbed material, and lithium manganese complex oxide in which a sufficient amount of lithium is inserted in advance is preferable. Alternatively, 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. Further, even when an active material in which the atomic ratio of lithium and manganese deviates from the stoichiometric ratio is used, the same effect as in the above embodiment can be obtained.
[0059]
Furthermore, the use of the negative electrode active material for lithium ion batteries other than those shown in the above embodiments is not limited. For example, natural graphite, various artificial graphite materials, carbonaceous materials such as coke, etc. may be used, and the particle shape is not particularly limited, such as scaly, spherical, fibrous, massive, etc. .
[0060]
Further, as the electrolytic solution, an electrolytic solution in which a general lithium salt is used as an electrolyte and dissolved in an organic solvent may be used, and the electrolytic solution is not particularly limited to a lithium salt or an organic solvent. For example, as an 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 the like or a mixture thereof can be used.
[0061]
And as non-aqueous electrolyte organic solvents other than this embodiment, propylene carbonate, ethylene carbonate, ethyl methyl carbonate, vinylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, etc. or a mixed solvent of two or more of these can be used. Is not limited.
[0062]
【The invention's effect】
As described above, according to the present invention, even if a gas pressure is generated inside the electrode winding group at the time of abnormality, the center portion of the electrode winding group can be expanded in the diametrical direction, and the gas can flow at both ends of the electrode winding group. The electrode winding group is expanded in the diameter direction so that it can be smoothly discharged from both ends of the electrode winding group. Therefore, no gas stays inside the electrode winding group, and abnormal heat generation in the battery container or battery container occurs. Does not cause significant deformation of the battery, ensuring the safety of the battery. In addition, since the electrode winding group circumferential length of the spacer is set to 75% or more and 95% or less of the circumferential length of the electrode winding group, the electrode winding group in the electrode winding group diameter direction at the time of abnormality Can expand smoothly and can further enhance the safety of the battery In addition, since the electrode winding group and the spacer are in close contact with each other and the electrode winding group is fixed to the battery container via the spacer, the movement of the electrode winding group in the longitudinal direction is suppressed and vibration is caused. Since damage to the electrode winding group and internal short circuit are not caused, an effect that the reliability of the battery can be improved can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion battery for EV mounting according to a first embodiment to which the present invention is applicable.
FIG. 2 is a schematic side view of a wound group of the cylindrical lithium ion battery according to the first embodiment.
FIG. 3 is a schematic view showing a circumferential cross section of the cylindrical lithium ion battery according to the first embodiment;
FIG. 4 is a schematic diagram showing a circumferential cross section of a cylindrical lithium ion battery of a second embodiment to which the present invention can be applied.
FIG. 5 is a schematic view showing a circumferential cross section of a cylindrical lithium ion battery of a third embodiment to which the present invention can be applied.
[Explanation of symbols]
4 Battery cover (cover plate)
5 Battery container
6 Winding group (electrode winding group)
10 Cleavage valve (Internal pressure reduction mechanism)
12 Sheet (spacer)
21 Cylindrical lithium-ion battery

Claims

A positive electrode current collector coated with a positive electrode active material capable of releasing and accommodating lithium by charge and discharge, and a negative electrode current collector coated with a negative electrode active material capable of accommodating and releasing lithium by charge and discharge And an electrode winding group wound through a strip-shaped separator through which lithium ions can pass, the electrode winding group being built in a cylindrical battery container, and sealing both end faces of the battery container A cylindrical lithium ion battery having a discharge capacity of 30 Ah or more having an internal pressure reducing mechanism for releasing gas in response to an increase in the internal pressure of the battery container on at least one of the lid plates, wherein the diameter of the electrode winding group is A, In the cylindrical lithium ion battery having an A / B value of 0.98 or less, where B is the inner diameter of the battery container, the battery container and the electrode winding group are made of resin having electrical insulation. And between the electrodes A predetermined group which is disposed near both ends of the group and allows the outer periphery of the electrode winding group to expand in the electrode winding group diameter direction by the gas pressure generated inside the electrode winding group. Spacers are provided that form a gap and are surrounded by a circular arc, and the electrode winding group circumferential length of the spacer is 75% or more and 95% or less of the circumferential length of the electrode winding group. A cylindrical lithium ion battery characterized by the above.

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

The cylindrical lithium ion battery according to claim 1, wherein the negative electrode active material is amorphous carbon.

The cylindrical lithium ion battery according to any one of claims 1 to 3, wherein the spacer is made of a polyolefin-based resin.

The cylindrical lithium ion battery according to claim 4, wherein the spacer is formed of an open cell polyolefin resin foam.

6. The electrode winding group longitudinal width of the spacer is 5% or more and 25% or less of the length of the electrode winding group in the longitudinal direction. 6. The cylindrical lithium ion battery described.

The spacer is separated into at least two pieces, and the gap is formed without contacting each other. The sum of the lengths of the spacers in the circumferential direction of the electrode winding group is greater than the sum of the lengths of the gaps. The cylindrical lithium according to any one of claims 1 to 6 , wherein each length of the gap is less than 25% of a circumferential length of the electrode winding group. Ion battery.