JP4617065B2

JP4617065B2 - Lithium ion secondary battery

Info

Publication number: JP4617065B2
Application number: JP2003149836A
Authority: JP
Inventors: 豪皆藤; 太志谷川; 直人荒井
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2002-05-30
Filing date: 2003-05-27
Publication date: 2011-01-19
Anticipated expiration: 2023-05-27
Also published as: JP2004055537A

Description

【０００１】
【発明の属する技術分野】
本発明は、正極集電体のバリと負極活物質部との短絡の可能性を低減した安全性の高い捲回型のリチウムイオン二次電池に関する。
【０００２】
【従来の技術】
近年、ＡＶ機器あるいはパソコン等の電子機器のポータブル化、コードレス化が急速に進んでおり、これらの駆動用電源となる二次電池の小型・軽量化および高エネルギー密度化への要求が高まっている。そのような二次電池のなかでも、リチウムを活物質とするリチウムイオン二次電池は、とりわけ高電圧・高エネルギー密度を有する。
【０００３】
従来のリチウムイオン二次電池としては、捲回型電池が主流である。捲回型電池は、正極活物質部およびこれを担持する正極集電体からなる正極板と、負極活物質部およびこれを担持する負極集電体からなる負極板とを、セパレータを介して捲回してなる極板群を有する。正極活物質部には、リチウムイオンを充放電により吸蔵または放出可能な正極活物質が含まれており、負極活物質部には、リチウムイオンを充放電により吸蔵または放出可能な負極活物質が含まれている。極板群は電解液とともに電池容器内に収容されている。
【０００４】
捲回型電池の場合、極板の捲回時に、折り曲げ部や湾曲部で極板やセパレータが変形を受けやすい。このような変形は、内部短絡を誘発する可能性がある。また、極板の捲回時に、セパレータの位置がずれることにより、内部短絡が発生する可能性もある。
【０００５】
本発明者らは、上記を鑑み、捲回型のリチウムイオン二次電池において、内部短絡の主要原因を防ぐことに着眼した。
【０００６】
内部短絡のタイプとしては、以下に述べる４つが考えられる。
（１）正極活物質部と負極活物質部との短絡
（２）正極活物質部と負極集電体との短絡
（３）正極集電体と負極活物質部との短絡
（４）正極集電体と負極集電体との短絡
【０００７】
本発明者らは、過充電状態の電池を各部品ごとに分解し、各部品同士を直接接触させることにより、スパークおよび着火の有無を観察した。その結果、短絡モード（１）および（２）では、スパークも着火も発生しなかったが、短絡モード（３）では、スパークと着火が発生した。短絡モード（４）では、スパークは発生するものの、着火はしなかった。
【０００８】
これらの結果から以下のことが考察される。
短絡モード（１）および（２）では、正極活物質自身の抵抗が大きいことから、正極活物質部と負極活物質部とを短絡させても大電流は流れない。
【０００９】
短絡モード（４）では、導電性を有する集電体同士の短絡により、スパークは発生するが、集電体自体は可燃性ではないことから、着火には至らない。
短絡モード（３）では、正極集電体と負極活物質とが共に導電性を有することから、これらが短絡するとスパークが発生するとともに、可燃性である負極活物質が着火に至る。
【００１０】
以上の考察から、短絡モード（３）が、内部短絡の主要原因であると考えられる。短絡モード（３）は、実際上は、正極集電体のスリット時に発生する導電性のバリが負極活物質部の表面と接触することにより発生する。
【００１１】
近年、従来のセパレータを用いる代わりに、電解質層を介して、正極板と負極板とを積層してなる極板群を有する積層型のリチウムイオン二次電池が提案されている。このように電解質層が正極板や負極板と一体化されている電池においては、極板やセパレータの寸法を制御することにより、短絡を防止する提案がなされている（特許文献１参照）。しかしながら、積層一体型の極板群は、一般的に製造工程が複雑であり、高容量化も困難である。また、このような極板群においては、電池を軽量化する観点から、ポリエチレンテレフタレートフィルムなどの樹脂フィルムの表面に、金属蒸着膜を設けた集電体を用いることも提案されている（特許文献２参照）。
【００１２】
【特許文献１】
特開２０００−３０７４２号公報
【特許文献２】
特開平９−２１３３３８号公報
【００１３】
【発明が解決しようとする課題】
本発明は、上記知見を鑑みてなされたものであり、本発明の目的の一つは、正極集電体のバリと負極活物質部との短絡を防止し、安全性の高い捲回型のリチウムイオン二次電池を提供することにある。
【００１４】
【課題を解決するための手段】
本発明のリチウムイオン二次電池は、（ａ）正極活物質部および前記正極活物質部を担持する正極集電体からなり、前記正極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な正極活物質を含む正極板、（ｂ）負極活物質部および前記負極活物質部を担持する負極集電体からなり、前記負極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な負極活物質を含む負極板、（ｃ）前記正極板と負極板との間に介在するセパレータ、（ｄ）電解液、ならびに（ｅ）前記正極板、負極板、セパレータおよび電解液を収容する電池容器を具備する。
【００１５】
前記正極板と負極板とは、前記セパレータを介して捲回されることにより、極板群を構成している。ここで、本発明のリチウムイオン二次電池は、前記極板群において以下の〔Ａ〕〜〔Ｅ〕のいずれかの特徴を有する。
【００１６】
〔Ａ〕前記正極集電体の長手方向に沿う両端部が、前記負極活物質部の長手方向に沿う両端部よりも外側に位置しており、前記正極活物質部の長手方向に沿う両端部に、それぞれリチウムイオンを充放電により吸蔵または放出しない非活物質部が設けられている。
〔Ｂ〕前記正極活物質部の長手方向に沿う両端部が、前記正極集電体の長手方向に沿う両端部よりも外側に位置している。
【００１７】
〔Ｃ〕前記負極活物質部の長手方向に沿う両端部が、前記正極集電体の長手方向に沿う両端部よりも外側に位置し、前記正極集電体の長手方向に沿う両端部が、前記正極活物質部の長手方向に沿う両端部よりも外側に位置し、さらに、前記正極集電体の前記正極活物質部で覆われていない露出部が、絶縁材料により被覆されている。
【００１８】
〔Ｄ〕前記正極集電体が、絶縁シートおよびその両面にそれぞれ形成された導電層からなり、前記絶縁シートの長手方向に沿う両端部には、前記絶縁シートの露出部が設けられている。
〔Ｅ〕前記正極板の長手方向に沿う両端部が、それぞれ絶縁材料により被覆されている。
なお、セパレータには、例えば、ポリオレフィンなどからなる織布、不織布、微多孔膜などが用いられる。
【００１９】
【発明の実施の形態】
実施形態１
本実施形態は、（ａ）正極活物質部および前記正極活物質部を担持する正極集電体からなり、前記正極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な正極活物質を含む正極板、（ｂ）負極活物質部および前記負極活物質部を担持する負極集電体からなり、前記負極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な負極活物質を含む負極板、（ｃ）前記正極板と負極板との間に介在するセパレータ、（ｄ）電解液、ならびに（ｅ）前記正極板、負極板、セパレータおよび電解液を収容する電池容器を具備するリチウムイオン二次電池であって、前記正極板と負極板とは、それらの間に前記セパレータを介して捲回されることにより、極板群を構成しており、前記極板群において、前記正極集電体の長手方向に沿う両端部が、前記負極活物質部の長手方向に沿う両端部よりも外側に位置しているリチウムイオン二次電池に関する。
【００２０】
正極集電体の長手方向に沿う両端部が、負極活物質部の長手方向に沿う両端部よりも外側に位置していることから、たとえスリット時に正極集電体の端部にバリが発生しても、そのバリと負極活物質部との短絡を防ぐことができる。
【００２１】
正極活物質部の長手方向に沿う両端部には、それぞれリチウムイオンを充放電により吸蔵または放出しない非活物質部が設けられている。非活物質部により、正極集電体の端部を安定化させることができる。さらに、正極集電体の長手方向に沿う両端部においては、非活物質部の厚さが正極活物質部の厚さと同一で、段差が無いことが、捲回時の巻ずれなどが起こりにくい点で好ましい。非活物質部として絶縁材料を用いる場合には、正極集電体のバリと負極活物質部との短絡以外の一般的な短絡までも抑制することができる。
【００２２】
極板群において、負極活物質部の長手方向に沿う両端部は、正極活物質部の長手方向に沿う両端部よりも外側に位置していることが好ましい。このような配置により、充電時に正極活物質より放出されるＬｉイオンを、対向する負極活物質によって確実に受けとめることができ、それによって、負極活物質の負荷の偏り、金属リチウムの析出などの不具合を防止することができる。
【００２３】
図１に、本実施形態の極板群における正極板１１０、負極板１２０およびセパレータ１３０の長手方向に対して垂直な断面の一例を概念的に示す。図１では、正極板１１０と負極板１２０とセパレータ１３０の配置関係を理解しやすいように、積層方向に間隔をあけて各要素を示す。
【００２４】
正極板１１０は、正極集電体１１１および正極活物質部１１２からなり、負極板１２０は、負極集電体１２１および負極活物質部１２２からなる。正極板１１０と負極板１２０とは、セパレータ１３０を介して対向している。正極集電体の端部１１１ａから正極活物質部の端部１１２ａまでの間、ならびに正極集電体の端部１１１ｂから正極活物質部の端部１１２ｂまでの間は、正極活物質の未塗工部でもよいが、非活物質部１１３を設ける方が好ましい。
【００２５】
正極集電体１１１の長手方向に沿う両端部１１１ａ、１１１ｂは、負極活物質部１２２の長手方向に沿う両端部１２２ａ、１２２ｂよりも外側に位置している。このような配置により、正極集電体の端部１１１ａもしくは１１１ｂにバリが発生し、そのバリがセパレータ１３０を突き破ったとしても、負極活物質部１２２と短絡することは無い。
【００２６】
図１のような構成を採用する場合、正極集電体の端部１１１ａから負極活物質部の端部１２２ａまでの間隔、ならびに正極集電体の端部１１１ｂから負極活物質部の端部１２２ｂまでの間隔は、それぞれ５０〜３００μｍであることが好ましい。これらの間隔は、正極集電体の断面において想定されるバリの長さから、正極活物質部の片面あたりの厚さとセパレータの厚さとの合計を差し引いた長さよりも大きいことが好ましい。なお、正極集電体の断面において想定されるバリの長さは、一般に５０〜１００μｍである。
【００２７】
図２には、従来の極板群における正極板２１０、負極板２２０およびセパレータ２３０の長手方向に対して垂直な断面を図１と同様に概念的に示す。
正極板２１０は、正極集電体２１１および正極活物質部２１２からなり、負極板２２０は、負極集電体２２１および負極活物質部２２２からなる。
【００２８】
正極集電体の長手方向に沿う両端部２１１ａ、２１１ｂは、負極活物質部２２２の長手方向に沿う両端部２２２ａ、２２２ｂよりも内側に位置している。こののような配置では、正極集電体の端部２１１ａもしくは２１１ｂにバリが発生し、そのバリがセパレータ２３０を突き破ると、負極活物質部２２２と短絡することになる。
【００２９】
実施形態２
本実施形態は、（ａ）正極活物質部および前記正極活物質部を担持する正極集電体からなり、前記正極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な正極活物質を含む正極板、（ｂ）負極活物質部および前記負極活物質部を担持する負極集電体からなり、前記負極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な負極活物質を含む負極板、（ｃ）前記正極板と負極板との間に介在するセパレータ、（ｄ）電解液、ならびに（ｅ）前記正極板、負極板、セパレータおよび電解液を収容する電池容器を具備するリチウムイオン二次電池であって、前記正極板と負極板とは、それらの間に前記セパレータを介して捲回されることにより、極板群を構成しており、前記極板群において、正極活物質部の長手方向に沿う両端部が、正極集電体の長手方向に沿う両端部よりも外側に位置しているリチウムイオン二次電池に関する。
【００３０】
正極活物質部の長手方向に沿う両端部が、正極集電体の長手方向に沿う両端部よりも外側に位置していることから、正極活物質部の端部付近をスリットする場合に、正極集電体と正極活物質部とが同時にスリットされることが無く、バリが発生しにくい。一方、図２のような従来の構成では、正極集電体２１１と正極活物質部２１２とが同時にスリットされるため、正極集電体の端部２１１ａもしくは２１１ｂにバリが発生し易い。
【００３１】
本実施形態においても、負極活物質部の長手方向に沿う両端部は、正極活物質部の長手方向に沿う両端部よりも外側に位置していることが好ましい。
正極集電体の長手方向に沿う両端部には、それぞれ正極集電体の面方向に延在する絶縁材料部が配置されていることが好ましい。このような絶縁材料部により、正極活物質部の端部を安定化させることができる。絶縁材料部は、正極集電体の長手方向に沿う端部の端面に接続されており、正極集電体と絶縁材料部とが一体化されていることが好ましい。正極集電体と絶縁材料部とが一体化されている場合には、これらを一つの芯材として取り扱うことができる。
【００３２】
正極集電体の面方向に延在する絶縁材料部は、加工性に優れ、絶縁性を有し、低コストであることが好ましい。このような絶縁材料部としては、ポリプロピレン、ポリエチレン、ポリフッ化ビニリデン、ポリエチレンテレフタレートなどを用いることができる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。
【００３３】
正極集電体は、正極活物質部により完全に覆われていることが好ましい。
正極集電体の面方向に延在する絶縁材料部は、必須の構成要素ではない。正極集電体の端部から正極活物質部の端部までの間には、正極活物質を充填することもできる。このような場合にも、正極集電体は、正極活物質部により完全に覆われる。
【００３４】
正極集電体の面方向に延在する絶縁材料部を設けない場合、正極集電体の長手方向に沿う両端部を、それぞれ絶縁材料で被覆することが好ましい。正極集電体の端部を被覆する絶縁材料としても、ポリプロピレン、ポリエチレン、ポリフッ化ビニリデン、ポリエチレンテレフタレートなどを用いることができる。また、アルミナなどのセラミックスを溶射することにより、正極集電体の端部をセラミックスで被覆することもできる。
【００３５】
図３に、本実施形態の極板群における正極板３１０、負極板３２０およびセパレータ３３０の長手方向に対して垂直な断面の一例を概念的に示す。図３では、正極板３１０と負極板３２０とセパレータ３３０の配置関係を理解しやすいように、積層方向に間隔をあけて各要素を示す。
【００３６】
正極板３１０は、正極集電体３１１および正極活物質部３１２からなり、負極板３２０は、負極集電体３２１および負極活物質部３２２からなる。正極板３１０と負極板３２０とは、セパレータ３３０を介して対向している。正極集電体の端部３１１ａから正極活物質部の端部３１２ａまでの間、ならびに正極集電体の端部３１１ｂから正極活物質部の端部３１２ｂまでの間には、絶縁材料部３１３が延在している。
【００３７】
正極活物質部の長手方向に沿う両端部３１２ａ、３１２ｂは、正極集電体の長手方向に沿う両端部３１１ａ、３１１ｂよりも外側に位置している。このような配置において、正極活物質部３１２と絶縁材料部３１３との積層部をスリットする場合には、正極集電体３１１はスリットされないことから、導電性のバリは発生しない。
【００３８】
図３のような構成を採用する場合、正極集電体の端部３１１ａから正極活物質部の端部３１２ａまでの間隔、ならびに正極集電体の端部３１１ｂから正極活物質部の端部３１２ｂまでの間隔は、特に限定されないが、それぞれ２ｍｍ以下であることが好ましい。
【００３９】
実施形態３
本実施形態は、（ａ）正極活物質部および前記正極活物質部を担持する正極集電体からなり、前記正極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な正極活物質を含む正極板、（ｂ）負極活物質部および前記負極活物質部を担持する負極集電体からなり、前記負極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な負極活物質を含む負極板、（ｃ）前記正極板と負極板との間に介在するセパレータ、（ｄ）電解液、ならびに（ｅ）前記正極板、負極板、セパレータおよび電解液を収容する電池容器を具備するリチウムイオン二次電池であって、前記正極板と負極板とは、それらの間に前記セパレータを介して捲回されることにより、極板群を構成しており、前記極板群において、前記負極活物質部の長手方向に沿う両端部が、前記正極集電体の長手方向に沿う両端部よりも外側に位置し、前記正極集電体の長手方向に沿う両端部が、前記正極活物質部の長手方向に沿う両端部よりも外側に位置し、さらに、前記正極集電体の前記正極活物質部で覆われていない露出部が、絶縁材料により被覆されているリチウムイオン二次電池に関する。
【００４０】
このような配置によれば、負極活物質部の長手方向に沿う両端部が、正極集電体の長手方向に沿う両端部よりも外側に位置し、正極集電体の長手方向に沿う両端部が、正極活物質部の長手方向に沿う両端部よりも外側に位置していることから、正極集電体の端部が負極活物質部の表面と対面することになる。しかしながら、正極集電体の正極活物質部で覆われていない露出部が、絶縁材料により被覆されていることから、正極集電体にバリが発生しても、バリが負極活物質部の表面と短絡することは無い。
【００４１】
正極集電体の露出部を覆う絶縁材料には、ポリプロピレン、ポリエチレン、ポリフッ化ビニリデン、ポリエチレンテレフタレートなどを用いることができる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。また、アルミナなどのセラミックスを溶射することにより、正極集電体の露出部をセラミックスで被覆することもできる。正極集電体の露出部に絶縁テープを貼りつけることもできる。絶縁テープには、ポリプロピレンなどからなる基材およびその片面に担持させたアクリル樹脂系の粘着材からなるテープを用いることが好ましい。
正極集電体の露出部を絶縁材料で覆う工程は、正極板のスリットの前後のどちらで行うこともできる。
【００４２】
図４に、本実施形態の極板群における正極板４１０、負極板４２０およびセパレータ４３０の長手方向に対して垂直な断面の一例を概念的に示す。図４では、正極板４１０と負極板４２０とセパレータ４３０の配置関係を理解しやすいように、積層方向に間隔をあけて各要素を示す。
【００４３】
正極板４１０は、正極集電体４１１および正極活物質部４１２からなり、負極板４２０は、負極集電体４２１および負極活物質部４２２からなる。正極板４１０と負極板４２０とは、セパレータ４３０を介して対向している。正極集電体の端部４１１ａから正極活物質部の端部４１２ａまでの間、ならびに正極集電体の端部４１１ｂから正極活物質部の端部４１２ｂまでの間は、絶縁材料４１３により被覆されている。
【００４４】
負極活物質部の長手方向に沿う両端部４２２ａ、４２２ｂは、正極集電体の長手方向に沿う両端部４１１ａ、４１１ｂよりも外側に位置している。また、正極集電体の長手方向に沿う両端部４１１ａ、４１１ｂは、正極活物質部の長手方向に沿う両端部４１２ａ、４１２ｂよりも外側に位置している。また、正極集電体の正極活物質部で覆われていない露出部は、絶縁材料４１３により被覆されている。このような正極板においては、正極集電体のバリが発生しても、そのバリが負極活物質部の表面と短絡することは無い。
【００４５】
図４のような構成を採用する場合、負極活物質部の端部４２２ａから正極集電体の端部４１１ａまでの間隔、ならびに負極活物質部の端部４２２ｂから正極集電体の端部４１１ｂまでの間隔は、特に限定されないが、それぞれ２ｍｍ以下であることが好ましい。また、正極集電体の端部４１１ａから正極活物質部の端部４１２ａまでの間隔、ならびに正極集電体の端部４１１ｂから正極活物質部の端部４１２ｂまでの間隔は、特に限定されないが、それぞれ２ｍｍ以下であることが好ましい。
【００４６】
実施形態４
本実施形態は、（ａ）正極活物質部および前記正極活物質部を担持する正極集電体からなり、前記正極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な正極活物質を含む正極板、（ｂ）負極活物質部および前記負極活物質部を担持する負極集電体からなり、前記負極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な負極活物質を含む負極板、（ｃ）前記正極板と負極板との間に介在するセパレータ、（ｄ）電解液、ならびに（ｅ）前記正極板、負極板、セパレータおよび電解液を収容する電池容器を具備するリチウムイオン二次電池であって、前記正極板と負極板とは、それらの間に前記セパレータを介して捲回されることにより、極板群を構成しており、前記正極集電体は、絶縁シートおよびその両面にそれぞれ形成された導電層からなり、前記絶縁シートの長手方向に沿う両端部には、前記絶縁シートの露出部が設けられているリチウムイオン二次電池に関する。
【００４７】
本実施形態に係る正極集電体は、大部分が絶縁シートからなることから、軽量である。また、このような集電体においては、スリットにより形成される断面が絶縁性を有することから、導電性のバリが発生することが無い。
【００４８】
絶縁シートの構成材料には、ポリプロピレン、ポリエチレン、ポリエチレンテレフタレートなどを用いることができる。これらの材料は、柔軟性を有する点でも都合がよい。導電層としては、アルミニウム、アルミニウム合金などの蒸着膜が好ましい。蒸着膜の形成工程には、電子線蒸着などの従来公知の蒸着法を適宜用いれば良い。
絶縁シートの厚さは１０〜３０μｍとすることが好ましく、導電層の厚さは１〜２０μｍとすることが好ましい。
【００４９】
本実施形態においても、負極活物質部の長手方向に沿う両端部は、正極活物質部の長手方向に沿う両端部よりも外側に位置していることが好ましい。
図５に、本実施形態の極板群における正極板５１０、負極板５２０およびセパレータ５３０の長手方向に対して垂直な断面の一例を概念的に示す。図５では、正極板５１０と負極板５２０とセパレータ５３０の配置関係を理解しやすいように、積層方向に間隔をあけて各要素を示す。
【００５０】
正極板５１０は、正極集電体５１１および正極活物質部５１２からなり、負極板５２０は、負極集電体５２１および負極活物質部５２２からなる。正極板５１０と負極板５２０とは、セパレータ５３０を介して対向している。正極集電体５１１は、絶縁シート５１１ｘおよびその両面にそれぞれ形成された導電層５１１ｙからなり、絶縁シート５１１ｘの長手方向に沿う両端部には、絶縁シートの露出部５１１ｘ’が設けられている。図５のような構成を採用する場合、絶縁シートの露出部５１１ｘ’の幅は、特に限定されないが、２ｍｍ以下であることが好ましい。
【００５１】
正極集電体５１１の長手方向に沿う両端部５１１ａ、５１１ｂは、絶縁シートの切断面を有することから、導電性を有するバリは発生し得ない。そのため、正極集電体５１１の長手方向に沿う両端部５１１ａ、５１１ｂが、負極活物質部５１２の表面と対向しているにもかかわらず、正極集電体と負極活物質部との短絡は防止される。
【００５２】
実施形態５
本実施形態は、（ａ）正極活物質部および前記正極活物質部を担持する正極集電体からなり、前記正極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な正極活物質を含む正極板、（ｂ）負極活物質部および前記負極活物質部を担持する負極集電体からなり、前記負極活物質部は、リチウムイオンを充放電により吸蔵または放出可能な負極活物質を含む負極板、（ｃ）前記正極板と負極板との間に介在するセパレータ、（ｄ）電解液、ならびに（ｅ）前記正極板、負極板、セパレータおよび電解液を収容する電池容器を具備するリチウムイオン二次電池であって、前記正極板と負極板とは、それらの間に前記セパレータを介して捲回されることにより、極板群を構成しており、前記正極板の長手方向に沿う両端部は、それぞれ絶縁材料により被覆されているリチウムイオン二次電池に関する。
【００５３】
正極板の長手方向に沿う両端部が、それぞれ絶縁材料により被覆されていることから、正極活物質部の端部付近をスリットする場合に、正極集電体にバリが発生したとしても、絶縁材料により、バリと負極活物質部との短絡は防止される。例えば、図２のような従来の構成の正極板の長手方向に沿う両端部を、それぞれ絶縁材料により被覆することにより、本実施形態を実現することができる。
【００５４】
正極板の長手方向に沿う両端部を被覆する絶縁材料には、ポリプロピレン、ポリエチレン、ポリフッ化ビニリデン、ポリエチレンテレフタレートなどを用いることができる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。
【００５５】
正極板の長手方向に沿う両端部を絶縁材料で被覆する工程は、正極板のスリットの前後のどちらで行うこともできるが、正極板をスリットした後では、スリットにより形成された断面全体を絶縁材料で被覆することができる。
本実施形態においても、負極活物質部の長手方向に沿う両端部は、正極活物質部の長手方向に沿う両端部よりも外側に位置していることが好ましい。
【００５６】
図６に、本実施形態の極板群における正極板６１０、負極板６２０およびセパレータ６３０の長手方向に対して垂直な断面の一例を概念的に示す。図６では、正極板６１０と負極板６２０とセパレータ６３０の配置関係を理解しやすいように、積層方向に間隔をあけて各要素を示す。
【００５７】
正極板６１０は、正極集電体６１１および正極活物質部６１２からなり、負極板６２０は、負極集電体６２１および負極活物質部６２２からなる。正極板６１０と負極板６２０とは、セパレータ６３０を介して対向している。正極板６１０の長手方向に沿う両端部は、絶縁材料６１３で被覆されていることから、正極集電体がバリを有する場合にも、バリと負極活物質部との短絡は防止される。
【００５８】
なお、実施形態１〜５においては、正極板の４辺のうち、長手方向に沿う両端部の配置や構成について説明したが、短手方向に沿う両端部の少なくとも一方においても、同様の配置や構成を採用することができる。その場合、短絡を防止する効果は、さらに大きくなる。また、実施形態１〜５において説明した正極板の配置や構成は、それぞれを単独で採用することも、複数を組み合わせて採用することもできる。
【００５９】
【実施例】
次に、実施例に基づいて、本発明をさらに具体例に説明する。ただし、以下の実施例は、本発明を限定するものではない。
【００６０】
《実施例１》
実施形態１の実施例の一つについて、図７〜１０を参照しながら説明する。
（ｉ）正極板の作製
正極板７０８は、正極集電体７０８ａの両面に、正極活物質部７０８ｂを担持させることで作製した。
正極活物質部７０８ｂは、正極材料ペーストを、正極集電体７０８ａの両面に塗工し、乾燥し、圧延することにより形成した。
【００６１】
正極材料ペーストは、正極活物質のＬｉＣｏＯ₂と、導電剤のアセチレンブラックと、結着剤のポリフッ化ビニリデンとを、それぞれ重量比９２：３：５の割合で混合することにより調製した。結着剤のポリフッ化ビニリデンは、Ｎ−メチル−２−ピロリドン（以下、ＮＭＰという）に溶解させて、ＮＭＰ溶液として用いた。なお、ポリフッ化ビニリデンのＮＭＰ溶液は、正極板作製時において、非活物質ペーストとしても用いた。
【００６２】
正極材料ペーストおよび非活物質ペーストは、厚さ２０μｍのアルミニウム箔からなる正極集電体７０８ａの両面に、ストライプ状に間欠塗工した。
図８に、正極材料ペースト８０１と非活物質ペースト８０２が塗工された正極集電体７０８ａの上面図を示す。正極材料ペーストおよび非活物質ペーストの未塗工部では、正極集電体７０８ａが露出しており、その露出部の間隔は４０ｍｍである。正極材料ペースト８０１および非活物質ペースト８０２の長さは、両方とも４１９ｍｍである。正極材料ペースト８０１の幅は５０ｍｍであり、非活物質ペースト８０２の幅は、中央が８ｍｍ、両端が６ｍｍである。正極集電体７０８ａの長手方向に沿う両端部における未塗工部の幅は１０ｍｍである。
【００６３】
次いで、図９に示すように、ペーストの間欠部分にも、非活物質ペースト８０２’を塗工した。非活物質ペースト８０２、８０２’の塗膜の厚さと、正極材料ペースト８０１の塗膜の厚さは同じとし、乾燥後の両面の塗膜の厚さの合計は２８０μｍとした。正極集電体７０８ａの厚さを含めた全体の厚さは３００μｍとした。
【００６４】
その後、全体の厚さが１８０μｍになるまで、直径３００ｍｍのローラで圧延し、ストライプ状の正極活物質部と非活物質部とを有する正極板フープを得た。正極板フープを非活物質部でスリットし、正極板とした。得られた正極板の正極材料密度は３．１ｇ／ｃｃであった。
【００６５】
正極板の上面図を図１０に示す。図１０において、正極板の長手方向の長さは４２８ｍｍ、幅は５４ｍｍである。正極活物質部１００２は、正極材料ペーストの塗膜と同じく、長さ４１９ｍｍ、幅５０ｍｍである。正極活物質部１００２の周囲には、幅２ｍｍの非活物質部１００３が配置されている。
【００６６】
非活物質部１００３の一部を５ｍｍ幅で剥離して形成した正極集電体７０８ａの露出部には、長さ７５ｍｍ、幅３ｍｍの正極リード７１６を溶接した。正極リード７１６の溶接部は絶縁テープで被覆した。
【００６７】
（ii）負極板の作製
負極板７０９は、従来公知の方法で、負極集電体７０９ａの両面に、負極活物質部７０９ｂを担持させることで作製した。
負極活物質部７０９ｂは、負極材料ペーストを、負極集電体７０９ａの両面に塗工し、乾燥し、圧延することにより形成した。
【００６８】
負極材料ペーストは、人造黒鉛と、結着剤のスチレンブタジエンゴム（ＳＢＲ）とを、重量比９７：３の割合で混合して調製した。結着剤のスチレンブタジエンゴムは、水に分散させて、水性分散液として用いた。
【００６９】
負極材料ペーストは、厚さ１４μｍの銅箔からなる負極集電体７０９ａの両面に塗工した。次いで、負極材料ペーストの塗膜と負極集電体とを含めた全体の厚さが１９６μｍになるまで、直径３００ｍｍのローラで圧延し、負極活物質部を有する負極板フープを得た。
【００７０】
得られた負極板フープを、正極活物質部より大きく、かつ、非活物質部を含む正極板全体より小さい寸法にスリットし、負極板とした。得られた負極板の負極材料密度は１．４ｇ／ｃｃであった。負極板の長手方向の長さは５１３ｍｍ、幅は５２ｍｍであった。
【００７１】
負極活物質部の一部を５ｍｍ幅で剥離して形成した負極集電体７０９ａの露出部には、長さ７５ｍｍ、幅３ｍｍの負極リード７１７を溶接した。負極リード７１７の溶接部は絶縁テープで被覆した。
【００７２】
（iii）電解液の調製
電解液には、エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）とを体積比１：１で混合した混合溶媒に、溶質として６フッ化リン酸リチウム（ＬｉＰＦ₆）を１ｍｏｌ／ｄｍ³の濃度に溶解したものを用いた。
（iv）円筒形電池の組み立て工程
【００７３】
図７に示すような、直径１８ｍｍ、高さ６５ｍｍの円筒形のリチウムイオン二次電池を組み立てた。電池の設計容量は１４００ｍＡｈとした。
正極板７０８と負極板７０９とを、ポリエチレン製微多孔膜からなるセパレータ７１０を介して、図１に示した配置で対向させ、渦巻き状に捲回することにより、極板群７１１を構成した。極板群７１１は、その上下に上部絶縁板７１８および下部絶縁板７１９を配置して、電解液（図示せず）とともに電池容器７１２内に収容した。電池容器７１２には、負極端子を兼ねる円筒状の電池缶７１３と正極端子を兼ねる封口板７１４とを組み合わせて用いた。極板群７１１と電池缶７１３の内周との間にもセパレータ７１０を介装した。
【００７４】
正極板７０８の正極リード７１６は、上部絶縁板７１８の中央の穴を通して、封口板７１４の裏面に接続した。負極板７０９の負極リード７１７は、下部絶縁板７１９の外周を迂回させて、下部絶縁板７１９と電池缶７１３の底部との間に介在させた。負極リード７１７と電池缶７１３の底部は、下部絶縁板７１９の中央の穴の内側で溶接した。電池缶７１３の開口端部と封口板７１４の周縁部との間に絶縁パッキン７１５を介装して、封口板７１４で電池缶７１３の開口を封口し、電池容器７１２を密閉した。
【００７５】
実施例１の電池の極板群においては、正極集電体の長手方向に沿う両端部が、負極活物質部の長手方向に沿う両端部よりも外側に位置しているため、正極集電体の端部に発生したバリがセパレータを突き破る事態になっても、そのバリが負極活物質部と短絡することは無いと考えられる。また、正極板の端部付近には、絶縁材料からなる非活物質部が設けられていることから、正極集電体が安定化するとともに、一般的な短絡も起こりにくくなっている。さらに、非活物質部の厚さと正極活物質部の厚さとが同一で段差が無いことから、捲回時の巻ずれなどは起こりにくかった。
【００７６】
《実施例２》
実施形態２の実施例の一つについて、図１１〜１３を参照しながら説明する。
（ｉ）正極板の作製
図１１に示すように、正極集電体となる厚さ２０μｍのアルミニウム箔１１０１と、絶縁材料部となる２本の厚さ２０μｍのポリプロピレンフィルム１１０２とを、３列に配置し、正極芯材を構成した。アルミニウム箔１１０１の幅は４８ｍｍ、その長手方向に沿う両端部に配置したポリプロピレンフィルム１１０２の幅は両方とも５ｍｍとした。３つの構成部材からなる正極芯材は、正極材料ペーストの塗工機に設置した。
【００７７】
図１２に示すように、ポリプロピレンフィルム１１０２からなる絶縁材料部上にかかるように、正極芯材の両面に、実施例１で調製したのと同じ正極材料ペースト１２０１を幅５２ｍｍで塗工した。図１２中、破線はアルミニウム箔とポリプロピレンフィルムとの境界を示す。
なお、アルミニウム箔とポリプロピレンフィルムとを、５列、７列、・・・に配置して、より多くの正極板を効率的に作製することも可能である。
【００７８】
実施例１と同様に、乾燥後の両面の塗膜と正極集電体を含めた全体の厚さは３００μｍとし、全体の厚さが１８０μｍになるまで圧延して、正極活物質部を有する正極板フープを得た。正極板フープを絶縁材料部となるポリプロピレンフィルム１１０２と正極活物質部との積層部でスリットし、正極板とした。
正極板の上面図を図１３に示す。図１３において、正極板の長手方向の長さは４２８ｍｍ、幅は５０ｍｍである。
【００７９】
正極活物質部１３０２の一部を５ｍｍ幅で剥離して形成したアルミニウム箔１１０１の露出部には、実施例１と同様の正極リード１３１６を設けた。正極板の長手方向に沿う両端部には、それぞれ幅１ｍｍのポリプロピレンフィルムと正極活物質部との積層部を残した。
【００８０】
（ii）負極板の作製
負極板は、実施例１と同様に作製した負極板フープを、正極板より大きい寸法にスリットして作製した。負極板の構造および寸法は、実施例１と同様である。
【００８１】
（iii）円筒形電池の組み立て工程
実施例１と同様に、直径１８ｍｍ、高さ６５ｍｍ、設計容量１４００ｍＡｈの円筒形のリチウムイオン二次電池を組み立てた。
すなわち、上記で作製した正極板と負極板とを、ポリエチレン製微多孔膜からなるセパレータを介して、図３に示した配置で対向させ、渦巻き状に捲回することにより、極板群を構成した。そして、この極板群を用いたこと以外、実施例１と同様の実施例２の電池を組み立てた。
【００８２】
実施例２の電池の極板群においては、正極板フープを絶縁材料部となるポリプロピレンフィルムと正極活物質部との積層部でスリットしたことから、正極板の長手方向に沿う端部には導電性のバリが発生していないと考えられる。
【００８３】
《実施例３》
実施形態３の実施例の一つについて、図１４〜１５を参照しながら説明する。
（ｉ）正極板の作製
実施例１で用いたのと同じ正極集電体１４０１の両面に、図１４に示すように、実施例１で調製したのと同じ正極材料ペースト１４０２をストライプ状に塗工した。図１４において、正極材料ペーストの幅は２列とも５０ｍｍであり、集電体露出部の幅は中央が８ｍｍ、両端が４ｍｍである。
【００８４】
実施例１と同様に、乾燥後の両面の塗膜と正極集電体を含めた全体の厚さは３００μｍとし、全体の厚さが１８０μｍになるまで圧延して、正極活物質部１５０１を有する正極板フープを得た。正極板フープを、集電体露出部でスリットし、図１５に示すように、残された集電体露出部を幅１ｍｍの絶縁テープ１５０９で被覆して正極板とした。
【００８５】
図１５において、正極板の長手方向の長さは４２８ｍｍ、幅は５２ｍｍである。正極活物質部１５０１の一部を５ｍｍ幅で剥離して形成した正極集電体１４０１の露出部には、実施例１と同様の正極リード１５１６を設けた。
【００８６】
（ii）負極板の作製
負極板は、実施例１と同様に作製した負極板フープを、正極板より大きい寸法にスリットして作製した。負極板の構造および寸法は、実施例１と同様である。
【００８７】
（iii）円筒形電池の組み立て工程
実施例１と同様に、直径１８ｍｍ、高さ６５ｍｍ、設計容量は１４００ｍＡｈの円筒形のリチウムイオン二次電池を組み立てた。
すなわち、上記で作製した正極板と負極板とを、ポリエチレン製微多孔膜からなるセパレータを介して、図４に示したような配置で対向させ、渦巻き状に捲回することにより、極板群を構成した。そして、この極板群を用いたこと以外、実施例１と同様の実施例３の電池を組み立てた。
【００８８】
実施例３の電池の極板群においては、正極集電体の端部が絶縁テープにより被覆されていることから、正極集電体の端部にバリが発生しても、そのバリと負極活物質部とが短絡することは無いと考えられる。
【００８９】
《実施例４》
実施形態４の実施例の一つについて、図１６〜１８を参照しながら説明する。
（ｉ）正極板の作製
厚さ２０μｍのフープ状のポリプロピレンシート１６０１の両面の同じ位置に、図１６に示すように、前後左右に１０ｍｍ以上のポリプロピレンシートの露出部を残して、厚さ５μｍのＡｌ蒸着膜１６０２を形成した。Ａｌ蒸着膜１６０２は、長さ４２６ｍｍ、幅４８ｍｍとした。
【００９０】
次に、図１７に示すように、実施例１と同様に調製した正極材料ペースト１７０１を、ポリプロピレンシート１６０１の両面の同じ位置に、片面ずつ塗工した。この時、Ａｌ蒸着膜１６０２の一方の幅５ｍｍの端部には、正極材料ペーストが塗工されないＡｌ蒸着膜の露出部１７０２を残した。Ａｌ蒸着膜の露出部１７０２は、ポリプロピレンシートの両面の同じ位置に設けた。
【００９１】
実施例１と同様に、乾燥後の両面の塗膜と正極集電体を含めた全体の厚さは３００μｍとし、全体の厚さが１８０μｍになるまで圧延して、正極活物質部を有する正極板フープを得た。正極板フープを、Ａｌ蒸着膜の無い箇所でスリットし、図１８に示すような正極板とした。正極板の長さは４２８ｍｍ、幅は５０ｍｍである。正極集電体の両面に設けた幅５ｍｍのＡｌ蒸着膜の露出部１７０２には、それぞれ長さ７５ｍｍ、幅３ｍｍの正極リード１８１６を導電性接着剤で固定し、それらの自由端は互いに溶接した。正極リード１８１６の接着固定部は絶縁テープで被覆した。正極板の長手方向に沿う幅１ｍｍの端部には、Ａｌ蒸着膜が無く、ポリプロピレンシート上に直接正極活物質部が担持されている。
【００９２】
（ii）負極板の作製
負極板は、実施例１と同様に作製した負極板フープを、正極板より大きい寸法にスリットして作製した。負極板の構造および寸法は、実施例１と同様である。
【００９３】
（iii）円筒形電池の組み立て工程
実施例１と同様に、直径１８ｍｍ、高さ６５ｍｍ、設計容量１４００ｍＡｈの円筒形のリチウムイオン二次電池を組み立てた。
すなわち、上記で作製した正極板と負極板とを、ポリエチレン製微多孔膜からなるセパレータを介して、図５に示したような配置で対向させ、渦巻き状に捲回することにより、極板群を構成した。そして、この極板群を用いたこと以外、実施例１と同様の実施例４の電池を組み立てた。
【００９４】
実施例４の電池においては、正極集電体のスリット部分が絶縁材料であることから、導電性のバリが発生することがなく、バリによる短絡は起こらないと考えられる。
【００９５】
《実施例５》
実施形態５の実施例の一つについて説明する。
（ｉ）正極板の作製
実施例１で用いたのと同じ正極集電体の両面の全面に、実施例１で調製したのと同じ正極材料ペーストを塗工した。
【００９６】
実施例１と同様に、乾燥後の両面の塗膜と正極集電体を含めた全体の厚さは３００μｍとし、全体の厚さが１８０μｍになるまで圧延して、正極活物質部を有する正極板フープを得た。正極板フープを、幅５０ｍｍ、長さ４２８ｍｍにスリットし、その長手方向に沿う幅２ｍｍの両端部を、ポリエチレン粉末（融点約１００℃）の分散液中に浸漬し、乾燥後、両端部に付着したポリエチレン粉末を溶融させてポリエチレンの被膜を形成した。
正極活物質部の一部を５ｍｍ幅で剥離して形成した正極集電体の露出部には、実施例１と同様の正極リードを設けた。
【００９７】
（ii）負極板の作製
負極板は、実施例１と同様に作製した負極板フープを、正極板より大きい寸法にスリットして作製した。負極板の構造および寸法は、実施例１と同様である。
【００９８】
（iii）円筒形電池の組み立て工程
実施例１と同様に、直径１８ｍｍ、高さ６５ｍｍ、設計容量１４００ｍＡｈの円筒形のリチウムイオン二次電池を組み立てた。
すなわち、上記で作製した正極板と負極板とを、ポリエチレン製微多孔膜からなるセパレータを介して、図６に示したような配置で対向させ、渦巻き状に捲回することにより、極板群を構成した。そして、この極板群を用いたこと以外、実施例１と同様の実施例５の電池を組み立てた。
【００９９】
実施例５の電池においては、正極板のスリット時にバリが発生しても、正極板の端部に設けられたポリエチレンの被膜により、バリと負極活物質部との短絡は防止される。
【０１００】
《比較例１》
実施例５と同様の正極板フープを作製し、これを幅５０ｍｍ、長さ４２８ｍｍにスリットした。こうして得られた正極板を、その長手方向に沿う両端部にポリエチレンの被膜を形成することなく、そのまま用いて、実施例５と同様の直径１８ｍｍ、高さ６５ｍｍ、設計容量１４００ｍＡｈの円筒形のリチウムイオン二次電池を組み立てた。
【０１０１】
［評価］
実施例１〜５および比較例１の電池を以下の手順で評価した。
（ｉ）各電池を、それぞれ１００個用意し、これらを５００ｍＡで、電池電圧が４．４Ｖの過充電状態になるまで充電した。
（ii）過充電状態の電池を、その電圧が低下し始めるまで、平板で抑えて圧壊させた。
（iii）圧壊後に温度が上昇し、ガス発生により安全弁が作動した電池の個数を調べた。
【０１０２】
結果を以下に示す。
実施例１：安全弁が作動した電池の個数は、１００個中０個であった。
実施例２：安全弁が作動した電池の個数は、１００個中０個であった。
実施例３：安全弁が作動した電池の個数は、１００個中０個であった。
実施例４：安全弁が作動した電池の個数は、１００個中０個であった。
実施例５：安全弁が作動した電池の個数は、１００個中０個であった。
比較例１：安全弁が作動した電池の個数は、１００個中２６個であった。
【０１０３】
【発明の効果】
以上のように、本発明のリチウムイオン二次電池によれば、正極集電体のスリット時にバリが発生するのを防止したり、バリが発生しても、バリと負極活物質部との短絡は防止される。
【図面の簡単な説明】
【図１】本発明の実施形態１の極板群における正極板、負極板およびセパレータの長手方向に対して垂直な断面の一例を概念的に示す図である。
【図２】従来の極板群における正極板、負極板およびセパレータの長手方向に対して垂直な断面の一例を概念的に示す図である。
【図３】本発明の実施形態２の極板群における正極板、負極板およびセパレータの長手方向に対して垂直な断面の一例を概念的に示す図である。
【図４】本発明の実施形態３の極板群における正極板、負極板およびセパレータの長手方向に対して垂直な断面の一例を概念的に示す図である。
【図５】本発明の実施形態４の極板群における正極板、負極板およびセパレータの長手方向に対して垂直な断面の一例を概念的に示す図である。
【図６】本発明の実施形態５の極板群における正極板、負極板およびセパレータの長手方向に対して垂直な断面の一例を概念的に示す図である。
【図７】本発明の実施例１のリチウムイオン二次電池の縦断面図である。
【図８】本発明の実施例１に係る正極板の製造工程を説明するための正極集電体の上面図である。
【図９】本発明の実施例１に係る正極板の製造工程を説明するための正極集電体の別の上面図である。
【図１０】本発明の実施例１に係る正極板の正面図である。
【図１１】本発明の実施例２に係る正極板の製造工程を説明するための正極集電体の上面図である。
【図１２】本発明の実施例２に係る正極板の製造工程を説明するための正極集電体の別の上面図である。
【図１３】本発明の実施例２に係る正極板の正面図である。
【図１４】本発明の実施例３に係る正極板の製造工程を説明するための正極集電体の上面図である。
【図１５】本発明の実施例３に係る正極板の正面図である。
【図１６】本発明の実施例４に係る正極板の製造工程を説明するための正極集電体の上面図である。
【図１７】本発明の実施例４に係る正極板の製造工程を説明するための正極集電体の別の上面図である。
【図１８】本発明の実施例４に係る正極板の正面図である。
【符号の説明】
１１０正極板
１１１正極集電体
１１１ａ、ｂ正極集電体の端部
１１２正極活物質部
１１２ａ、ｂ正極活物質部の端部
１１３非活物質部
１２０負極板
１２１負極集電体
１２２負極活物質部
１２２ａ、ｂ負極活物質部の端部
１３０セパレータ
２１０正極板
２１１正極集電体
２１２正極活物質部
２２０負極板
２２１負極集電体
２２２負極活物質部
２３０セパレータ
２１１ａ、ｂ正極集電体の端部
２２２ａ、ｂ負極活物質部の端部
３１０正極板
３１１正極集電体
３１１ａ、ｂ正極集電体の端部
３１２正極活物質部
３１２ａ、ｂ正極活物質部の端部
３１３絶縁材料部
３２０負極板
３２１負極集電体
３２２負極活物質部
３３０セパレータ
４１０正極板
４１１正極集電体
４１１ａ、ｂ正極集電体の端部
４１２正極活物質部
４１２ａ、ｂ正極活物質部の端部
４１３絶縁材料
４２０負極板
４２１負極集電体
４２２負極活物質部
４２２ａ、ｂ負極活物質部の端部
４３０セパレータ
５１０正極板
５１１正極集電体
５１１ａ、ｂ正極集電体の端部
５１１ｘ絶縁シート
５１１ｘ’ 絶縁シートの露出部
５１１ｙ導電層
５１２正極活物質部
５２０負極板
５２１負極集電体
５２２負極活物質部
５３０セパレータ
６１０正極板
６１１正極集電体
６１２正極活物質部
６１３絶縁材料
６２０負極板
６２１負極集電体
６２２負極活物質部
６３０セパレータ
７０８正極板
７０８ａ正極集電体
７０８ｂ正極活物質部
７０９負極板
７０９ａ負極集電体
７０９ｂ負極活物質部
７１０セパレータ
７１１極板群
７１２電池容器
７１３電池缶
７１４封口板
７１５絶縁パッキン
７１６正極リード
７１７負極リード
７１８上部絶縁板
７１９下部絶縁板
８０１正極材料ペースト
８０２、８０２’ 非活物質ペースト
１００２正極活物質部
１００３非活物質部
１１０１アルミニウム箔
１１０２ポリプロピレンフィルム
１２０１正極材料ペースト
１３０２正極活物質部
１３１６正極リード
１４０１正極集電体
１４０２正極材料ペースト
１５０１正極活物質部
１５０９絶縁テープ
１５１６正極リード
１６０１ポリプロピレンシート
１６０２Ａｌ蒸着膜
１７０１正極材料ペースト
１７０２Ａｌ蒸着膜の露出部
１８１６正極リード[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a highly safe wound lithium ion secondary battery in which the possibility of a short circuit between a burr of a positive electrode current collector and a negative electrode active material portion is reduced.
[0002]
[Prior art]
In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless, and there is an increasing demand for smaller, lighter and higher energy density secondary batteries serving as driving power sources. . Among such secondary batteries, a lithium ion secondary battery using lithium as an active material has particularly high voltage and high energy density.
[0003]
As a conventional lithium ion secondary battery, a wound battery is the mainstream. A wound battery includes a positive electrode plate made of a positive electrode active material portion and a positive electrode current collector carrying the positive electrode active material portion, and a negative electrode plate made of a negative electrode active material portion and a negative electrode current collector carrying the positive electrode active material portion. It has a rotating electrode plate group. The positive electrode active material part includes a positive electrode active material capable of inserting or extracting lithium ions by charging and discharging, and the negative electrode active material part includes a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging. It is. The electrode plate group is accommodated in the battery container together with the electrolytic solution.
[0004]
In the case of a wound battery, the electrode plate and the separator are easily deformed at the bent portion or the curved portion when the electrode plate is wound. Such deformation can induce an internal short circuit. Further, when the electrode plate is wound, an internal short circuit may occur due to the shift of the separator position.
[0005]
In view of the above, the present inventors have focused on preventing the main cause of internal short-circuiting in a wound lithium ion secondary battery.
[0006]
The following four types of internal short circuits are conceivable.
(1) Short circuit between the positive electrode active material part and the negative electrode active material part
(2) Short circuit between the positive electrode active material portion and the negative electrode current collector
(3) Short circuit between the positive electrode current collector and the negative electrode active material part
(4) Short circuit between the positive electrode current collector and the negative electrode current collector
[0007]
The present inventors have observed the presence or absence of sparks and ignition by disassembling the overcharged battery for each part and bringing the parts into direct contact with each other. As a result, in the short circuit modes (1) and (2), neither spark nor ignition occurred, but in the short circuit mode (3), spark and ignition occurred. In the short-circuit mode (4), sparking occurred, but no ignition occurred.
[0008]
The following is considered from these results.
In the short-circuit modes (1) and (2), since the resistance of the positive electrode active material itself is large, no large current flows even if the positive electrode active material portion and the negative electrode active material portion are short-circuited.
[0009]
In the short-circuit mode (4), a spark is generated due to a short circuit between the current collectors having conductivity, but the current collector itself is not flammable and therefore does not ignite.
In the short circuit mode (3), since the positive electrode current collector and the negative electrode active material are both conductive, when they are short-circuited, sparks are generated and the flammable negative electrode active material is ignited.
[0010]
From the above consideration, it is considered that the short circuit mode (3) is the main cause of the internal short circuit. The short-circuit mode (3) is actually generated when a conductive burr generated when the positive electrode current collector is slit contacts the surface of the negative electrode active material portion.
[0011]
In recent years, instead of using a conventional separator, a stacked lithium ion secondary battery having an electrode plate group in which a positive electrode plate and a negative electrode plate are stacked via an electrolyte layer has been proposed. Thus, in the battery in which the electrolyte layer is integrated with the positive electrode plate and the negative electrode plate, a proposal has been made to prevent a short circuit by controlling the dimensions of the electrode plate and the separator (see Patent Document 1). However, the laminated integrated electrode plate group generally has a complicated manufacturing process, and it is difficult to increase the capacity. Further, in such an electrode plate group, it has been proposed to use a current collector provided with a metal vapor deposition film on the surface of a resin film such as a polyethylene terephthalate film from the viewpoint of reducing the weight of the battery (Patent Literature). 2).
[0012]
[Patent Document 1]
JP 2000-30742 A
[Patent Document 2]
JP-A-9-213338
[0013]
[Problems to be solved by the invention]
The present invention has been made in view of the above knowledge, and one of the objects of the present invention is to prevent a short circuit between the burr of the positive electrode current collector and the negative electrode active material part, and to achieve a highly safe wound type. The object is to provide a lithium ion secondary battery.
[0014]
[Means for Solving the Problems]
The lithium ion secondary battery of the present invention comprises (a) a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, and the positive electrode active material part can occlude or release lithium ions by charging and discharging. A positive electrode plate containing a positive electrode active material, (b) a negative electrode active material part, and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part can occlude or release lithium ions by charge and discharge A negative electrode plate containing a negative electrode active material, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) an electrolyte solution, and (e) a battery containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte solution A container is provided.
[0015]
The positive electrode plate and the negative electrode plate constitute an electrode plate group by being wound through the separator. Here, the lithium ion secondary battery of the present invention has any one of the following features [A] to [E] in the electrode plate group.
[0016]
[A] Both end portions along the longitudinal direction of the positive electrode current collector are located outside both end portions along the longitudinal direction of the negative electrode active material portion. In addition, at both end portions along the longitudinal direction of the positive electrode active material portion, inactive material portions that do not occlude or release lithium ions by charging and discharging are provided, respectively. Yes.
[B] Both end portions along the longitudinal direction of the positive electrode active material portion are positioned outside both end portions along the longitudinal direction of the positive electrode current collector.
[0017]
[C] Both end portions along the longitudinal direction of the negative electrode active material portion are located outside both end portions along the longitudinal direction of the positive electrode current collector, and both end portions along the longitudinal direction of the positive electrode current collector are An exposed portion which is located outside both end portions along the longitudinal direction of the positive electrode active material portion and is not covered with the positive electrode active material portion of the positive electrode current collector is covered with an insulating material.
[0018]
[D] The positive electrode current collector includes an insulating sheet and conductive layers respectively formed on both surfaces thereof, and exposed portions of the insulating sheet are provided at both ends along the longitudinal direction of the insulating sheet.
[E] Both end portions along the longitudinal direction of the positive electrode plate are respectively covered with an insulating material.
For the separator, for example, a woven fabric, a nonwoven fabric, a microporous film, or the like made of polyolefin is used.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
This embodiment includes (a) a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, and the positive electrode active material part contains a positive electrode active material that can occlude or release lithium ions by charging and discharging. And (b) a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part contains a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging. Lithium comprising a negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) electrolyte, and (e) a battery container containing the positive electrode plate, negative electrode plate, separator and electrolyte In the ion secondary battery, the positive electrode plate and the negative electrode plate are wound through the separator between them to constitute an electrode plate group. In the electrode plate group, the positive electrode plate Longitudinal direction of current collector Both end portions along is a lithium ion secondary battery than both end portions along the longitudinal direction is located outside of the negative electrode active material portion.
[0020]
Since both end portions along the longitudinal direction of the positive electrode current collector are positioned outside both end portions along the longitudinal direction of the negative electrode active material portion, burrs are generated at the end portions of the positive electrode current collector even when slitting. However, the short circuit between the burr and the negative electrode active material portion can be prevented.
[0021]
Inactive material portions that do not occlude or release lithium ions by charging and discharging at both ends along the longitudinal direction of the positive electrode active material portion But Establishment Being The The end portion of the positive electrode current collector can be stabilized by the inactive material portion. Furthermore, at both ends along the longitudinal direction of the positive electrode current collector, the thickness of the non-active material portion is the same as the thickness of the positive electrode active material portion, and there is no step, so that winding misalignment or the like during winding is unlikely to occur. This is preferable. In the case where an insulating material is used as the non-active material part, even a general short circuit other than a short circuit between the burr of the positive electrode current collector and the negative electrode active material part can be suppressed.
[0022]
In the electrode plate group, it is preferable that both end portions along the longitudinal direction of the negative electrode active material portion are positioned outside both end portions along the longitudinal direction of the positive electrode active material portion. With this arrangement, Li ions released from the positive electrode active material during charging can be reliably received by the opposing negative electrode active material, thereby causing problems such as uneven load on the negative electrode active material and precipitation of metallic lithium. Can be prevented.
[0023]
In FIG. 1, an example of a cross section perpendicular | vertical with respect to the longitudinal direction of the positive electrode plate 110 in the electrode group of this embodiment, the negative electrode plate 120, and the separator 130 is shown notionally. In FIG. 1, each element is shown at intervals in the stacking direction so that the positional relationship among the positive electrode plate 110, the negative electrode plate 120, and the separator 130 can be easily understood.
[0024]
The positive electrode plate 110 includes a positive electrode current collector 111 and a positive electrode active material portion 112, and the negative electrode plate 120 includes a negative electrode current collector 121 and a negative electrode active material portion 122. The positive electrode plate 110 and the negative electrode plate 120 face each other with the separator 130 interposed therebetween. Between the end portion 111a of the positive electrode current collector and the end portion 112a of the positive electrode active material portion, and between the end portion 111b of the positive electrode current collector and the end portion 112b of the positive electrode active material portion, uncoated positive electrode active material. Although an engineering part may be used, it is preferable to provide the inactive material part 113.
[0025]
Both end portions 111 a and 111 b along the longitudinal direction of the positive electrode current collector 111 are positioned outside both end portions 122 a and 122 b along the longitudinal direction of the negative electrode active material portion 122. With such an arrangement, burrs are generated at the end 111a or 111b of the positive electrode current collector, and even if the burrs break through the separator 130, there is no short circuit with the negative electrode active material portion 122.
[0026]
When the configuration shown in FIG. 1 is adopted, the distance from the end 111a of the positive electrode current collector to the end 122a of the negative electrode active material part, and the end 122b of the negative electrode active material part from the end 111b of the positive electrode current collector. It is preferable that the space | interval is 50-300 micrometers respectively. These intervals are preferably larger than the length of burrs assumed in the cross section of the positive electrode current collector, minus the sum of the thickness per one side of the positive electrode active material portion and the thickness of the separator. In addition, generally the length of the burr | flash assumed in the cross section of a positive electrode electrical power collector is 50-100 micrometers.
[0027]
FIG. 2 conceptually shows a cross section perpendicular to the longitudinal direction of the positive electrode plate 210, the negative electrode plate 220, and the separator 230 in the conventional electrode plate group, as in FIG.
The positive electrode plate 210 includes a positive electrode current collector 211 and a positive electrode active material portion 212, and the negative electrode plate 220 includes a negative electrode current collector 221 and a negative electrode active material portion 222.
[0028]
Both end portions 211 a and 211 b along the longitudinal direction of the positive electrode current collector are located inside the both end portions 222 a and 222 b along the longitudinal direction of the negative electrode active material portion 222. In such an arrangement, a burr is generated at the end 211a or 211b of the positive electrode current collector, and when the burr penetrates the separator 230, a short circuit with the negative electrode active material unit 222 occurs.
[0029]
Embodiment 2
This embodiment includes (a) a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, and the positive electrode active material part contains a positive electrode active material that can occlude or release lithium ions by charging and discharging. And (b) a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part contains a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging. Lithium comprising a negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) electrolyte, and (e) a battery container containing the positive electrode plate, negative electrode plate, separator and electrolyte In the ion secondary battery, the positive electrode plate and the negative electrode plate are wound through the separator between them to constitute an electrode plate group. In the longitudinal direction of the material part Cormorants both ends, a lithium ion secondary battery is positioned outward from both ends in the longitudinal direction of the positive electrode current collector.
[0030]
Since both end portions along the longitudinal direction of the positive electrode active material portion are positioned outside both end portions along the longitudinal direction of the positive electrode current collector, when the vicinity of the end portion of the positive electrode active material portion is slit, The current collector and the positive electrode active material portion are not slit at the same time, and burrs are less likely to occur. On the other hand, in the conventional configuration as shown in FIG. 2, since the positive electrode current collector 211 and the positive electrode active material part 212 are slit simultaneously, burrs are likely to occur at the end part 211a or 211b of the positive electrode current collector.
[0031]
Also in this embodiment, it is preferable that the both ends along the longitudinal direction of the negative electrode active material portion are located outside the both ends along the longitudinal direction of the positive electrode active material portion.
It is preferable that an insulating material portion extending in the surface direction of the positive electrode current collector is disposed at both ends along the longitudinal direction of the positive electrode current collector. Such an insulating material portion can stabilize the end portion of the positive electrode active material portion. The insulating material part is connected to the end face of the end part along the longitudinal direction of the positive electrode current collector, and the positive electrode current collector and the insulating material part are preferably integrated. When the positive electrode current collector and the insulating material portion are integrated, they can be handled as one core material.
[0032]
It is preferable that the insulating material portion extending in the surface direction of the positive electrode current collector is excellent in workability, has an insulating property, and is low in cost. As such an insulating material portion, polypropylene, polyethylene, polyvinylidene fluoride, polyethylene terephthalate, or the like can be used. These may be used alone or in combination of two or more.
[0033]
The positive electrode current collector is preferably completely covered with the positive electrode active material portion.
The insulating material portion extending in the surface direction of the positive electrode current collector is not an essential component. A space between the end portion of the positive electrode current collector and the end portion of the positive electrode active material portion can be filled with the positive electrode active material. Even in such a case, the positive electrode current collector is completely covered with the positive electrode active material portion.
[0034]
In the case where an insulating material portion extending in the surface direction of the positive electrode current collector is not provided, it is preferable that both end portions along the longitudinal direction of the positive electrode current collector are respectively covered with an insulating material. Polypropylene, polyethylene, polyvinylidene fluoride, polyethylene terephthalate, or the like can also be used as an insulating material that covers the end of the positive electrode current collector. Moreover, the edge part of a positive electrode electrical power collector can also be coat | covered with ceramics by spraying ceramics, such as an alumina.
[0035]
In FIG. 3, an example of a cross section perpendicular | vertical with respect to the longitudinal direction of the positive electrode plate 310 in the electrode group of this embodiment, the negative electrode plate 320, and the separator 330 is shown notionally. In FIG. 3, each element is shown at intervals in the stacking direction so that the positional relationship among the positive electrode plate 310, the negative electrode plate 320, and the separator 330 can be easily understood.
[0036]
The positive electrode plate 310 includes a positive electrode current collector 311 and a positive electrode active material portion 312, and the negative electrode plate 320 includes a negative electrode current collector 321 and a negative electrode active material portion 322. The positive electrode plate 310 and the negative electrode plate 320 face each other with the separator 330 interposed therebetween. Between the end 311a of the positive electrode current collector and the end 312a of the positive electrode active material part, and between the end 311b of the positive electrode current collector and the end 312b of the positive electrode active material part, an insulating material part 313 is formed. It is extended.
[0037]
Both end portions 312a and 312b along the longitudinal direction of the positive electrode active material portion are positioned outside both end portions 311a and 311b along the longitudinal direction of the positive electrode current collector. In such an arrangement, when the stacked portion of the positive electrode active material portion 312 and the insulating material portion 313 is slit, the positive electrode current collector 311 is not slit, so that no conductive burrs are generated.
[0038]
When the configuration shown in FIG. 3 is adopted, the distance from the end 311a of the positive electrode current collector to the end 312a of the positive electrode active material part, and the end 312b of the positive electrode current collector to the end 312b of the positive electrode active material part. Although the space | interval to is not specifically limited, It is preferable that it is each 2 mm or less.
[0039]
Embodiment 3
This embodiment includes (a) a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, and the positive electrode active material part contains a positive electrode active material that can occlude or release lithium ions by charging and discharging. And (b) a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part contains a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging. Lithium comprising a negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) electrolyte, and (e) a battery container containing the positive electrode plate, negative electrode plate, separator and electrolyte In the ion secondary battery, the positive electrode plate and the negative electrode plate are wound through the separator between them to constitute an electrode plate group, and the negative electrode plate includes the negative electrode Longitudinal direction of the active material part Both end portions along the longitudinal direction of the positive electrode current collector are positioned outside the both end portions along the longitudinal direction of the positive electrode current collector, and both end portions along the longitudinal direction of the positive electrode current collector are both ends along the longitudinal direction of the positive electrode active material portion The present invention also relates to a lithium ion secondary battery in which an exposed portion that is located outside the portion and is not covered with the positive electrode active material portion of the positive electrode current collector is covered with an insulating material.
[0040]
According to such an arrangement, both end portions along the longitudinal direction of the negative electrode active material portion are located outside both end portions along the longitudinal direction of the positive electrode current collector, and both end portions along the longitudinal direction of the positive electrode current collector However, since it is located outside the both ends along the longitudinal direction of the positive electrode active material part, the end part of the positive electrode current collector faces the surface of the negative electrode active material part. However, since the exposed portion of the positive electrode current collector that is not covered with the positive electrode active material portion is covered with an insulating material, even if burrs are generated on the positive electrode current collector, the burrs are on the surface of the negative electrode active material portion. There is no short circuit.
[0041]
Polypropylene, polyethylene, polyvinylidene fluoride, polyethylene terephthalate, or the like can be used for the insulating material that covers the exposed portion of the positive electrode current collector. These may be used alone or in combination of two or more. Moreover, the exposed part of a positive electrode electrical power collector can also be coat | covered with ceramics by spraying ceramics, such as an alumina. An insulating tape can be attached to the exposed portion of the positive electrode current collector. As the insulating tape, it is preferable to use a base material made of polypropylene or the like and a tape made of an acrylic resin-based adhesive material carried on one side thereof.
The step of covering the exposed portion of the positive electrode current collector with an insulating material can be performed either before or after the slit of the positive electrode plate.
[0042]
FIG. 4 conceptually shows an example of a cross section perpendicular to the longitudinal direction of the positive electrode plate 410, the negative electrode plate 420, and the separator 430 in the electrode plate group of the present embodiment. In FIG. 4, each element is shown at intervals in the stacking direction so that the positional relationship among the positive electrode plate 410, the negative electrode plate 420, and the separator 430 can be easily understood.
[0043]
The positive electrode plate 410 includes a positive electrode current collector 411 and a positive electrode active material portion 412, and the negative electrode plate 420 includes a negative electrode current collector 421 and a negative electrode active material portion 422. The positive electrode plate 410 and the negative electrode plate 420 are opposed to each other with the separator 430 interposed therebetween. Between the end 411a of the positive electrode current collector and the end 412a of the positive electrode active material part and between the end 411b of the positive electrode current collector and the end part 412b of the positive electrode active material part are covered with an insulating material 413. ing.
[0044]
Both end portions 422a and 422b along the longitudinal direction of the negative electrode active material portion are positioned outside both end portions 411a and 411b along the longitudinal direction of the positive electrode current collector. Moreover, the both ends 411a and 411b along the longitudinal direction of the positive electrode current collector are located outside the both ends 412a and 412b along the longitudinal direction of the positive electrode active material portion. The exposed portion of the positive electrode current collector that is not covered with the positive electrode active material portion is covered with an insulating material 413. In such a positive electrode plate, even if burrs of the positive electrode current collector occur, the burrs do not short-circuit with the surface of the negative electrode active material portion.
[0045]
When the configuration as shown in FIG. 4 is adopted, the distance from the end 422a of the negative electrode active material portion to the end 411a of the positive electrode current collector, and the end portion 422b of the negative electrode active material portion to the end 411b of the positive electrode current collector. Although the space | interval to is not specifically limited, It is preferable that it is each 2 mm or less. Further, the distance from the end 411a of the positive electrode current collector to the end 412a of the positive electrode active material part and the distance from the end part 411b of the positive electrode current collector to the end part 412b of the positive electrode active material part are not particularly limited. , Each is preferably 2 mm or less.
[0046]
Embodiment 4
This embodiment includes (a) a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, and the positive electrode active material part contains a positive electrode active material that can occlude or release lithium ions by charging and discharging. And (b) a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part contains a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging. Lithium comprising a negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) electrolyte, and (e) a battery container containing the positive electrode plate, negative electrode plate, separator and electrolyte In the ion secondary battery, the positive electrode plate and the negative electrode plate are wound through the separator between them to constitute an electrode plate group, and the positive electrode current collector is insulated On the sheet and both sides Consist respectively formed conductive layer, wherein the both end portions along the longitudinal direction of the insulating sheet, a lithium ion secondary battery exposed portion is provided in the insulating sheet.
[0047]
The positive electrode current collector according to this embodiment is light because most of the positive electrode current collector is made of an insulating sheet. Further, in such a current collector, since the cross section formed by the slits is insulative, no conductive burrs are generated.
[0048]
Polypropylene, polyethylene, polyethylene terephthalate, or the like can be used as the constituent material of the insulating sheet. These materials are also advantageous in that they have flexibility. As the conductive layer, a deposited film such as aluminum or aluminum alloy is preferable. A conventionally known vapor deposition method such as electron beam vapor deposition may be appropriately used for the process of forming the vapor deposition film.
The thickness of the insulating sheet is preferably 10 to 30 μm, and the thickness of the conductive layer is preferably 1 to 20 μm.
[0049]
Also in this embodiment, it is preferable that the both ends along the longitudinal direction of the negative electrode active material portion are located outside the both ends along the longitudinal direction of the positive electrode active material portion.
In FIG. 5, an example of a cross section perpendicular | vertical with respect to the longitudinal direction of the positive electrode plate 510 in the electrode group of this embodiment, the negative electrode plate 520, and the separator 530 is shown notionally. In FIG. 5, each element is shown at intervals in the stacking direction so that the positional relationship among the positive electrode plate 510, the negative electrode plate 520, and the separator 530 can be easily understood.
[0050]
The positive electrode plate 510 includes a positive electrode current collector 511 and a positive electrode active material portion 512, and the negative electrode plate 520 includes a negative electrode current collector 521 and a negative electrode active material portion 522. The positive electrode plate 510 and the negative electrode plate 520 are opposed to each other with the separator 530 interposed therebetween. The positive electrode current collector 511 includes an insulating sheet 511x and conductive layers 511y respectively formed on both surfaces thereof, and exposed portions 511x ′ of the insulating sheet are provided at both ends along the longitudinal direction of the insulating sheet 511x. When the configuration as shown in FIG. 5 is adopted, the width of the exposed portion 511x ′ of the insulating sheet is not particularly limited, but is preferably 2 mm or less.
[0051]
Since both end portions 511a and 511b along the longitudinal direction of the positive electrode current collector 511 have a cut surface of the insulating sheet, a conductive burr cannot be generated. Therefore, although both ends 511a and 511b along the longitudinal direction of the positive electrode current collector 511 are opposed to the surface of the negative electrode active material part 512, a short circuit between the positive electrode current collector and the negative electrode active material part is prevented. Is done.
[0052]
Embodiment 5
This embodiment includes (a) a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, and the positive electrode active material part contains a positive electrode active material that can occlude or release lithium ions by charging and discharging. And (b) a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part contains a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging. Lithium comprising a negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) electrolyte, and (e) a battery container containing the positive electrode plate, negative electrode plate, separator and electrolyte In the ion secondary battery, the positive electrode plate and the negative electrode plate are wound through the separator between them to form an electrode plate group, and are along the longitudinal direction of the positive electrode plate Both ends are A lithium ion secondary battery is covered by the edge material.
[0053]
Since both end portions along the longitudinal direction of the positive electrode plate are respectively coated with an insulating material, even if burrs occur in the positive electrode current collector when slitting the vicinity of the end portion of the positive electrode active material portion, the insulating material This prevents a short circuit between the burr and the negative electrode active material portion. For example, this embodiment can be realized by covering both end portions along the longitudinal direction of a positive electrode plate having a conventional configuration as shown in FIG. 2 with an insulating material.
[0054]
Polypropylene, polyethylene, polyvinylidene fluoride, polyethylene terephthalate, or the like can be used as an insulating material that covers both ends along the longitudinal direction of the positive electrode plate. These may be used alone or in combination of two or more.
[0055]
The process of covering both ends along the longitudinal direction of the positive electrode plate with an insulating material can be performed either before or after the slit of the positive electrode plate, but after slitting the positive electrode plate, the entire cross section formed by the slit is insulated. Can be coated with material.
Also in this embodiment, it is preferable that the both ends along the longitudinal direction of the negative electrode active material portion are located outside the both ends along the longitudinal direction of the positive electrode active material portion.
[0056]
In FIG. 6, an example of a cross section perpendicular | vertical with respect to the longitudinal direction of the positive electrode plate 610, the negative electrode plate 620, and the separator 630 in the electrode group of this embodiment is shown notionally. In FIG. 6, each element is shown at intervals in the stacking direction so that the arrangement relationship among the positive electrode plate 610, the negative electrode plate 620, and the separator 630 can be easily understood.
[0057]
The positive electrode plate 610 includes a positive electrode current collector 611 and a positive electrode active material portion 612, and the negative electrode plate 620 includes a negative electrode current collector 621 and a negative electrode active material portion 622. The positive electrode plate 610 and the negative electrode plate 620 are opposed to each other with the separator 630 interposed therebetween. Since both end portions along the longitudinal direction of the positive electrode plate 610 are covered with the insulating material 613, even when the positive electrode current collector has burrs, a short circuit between the burrs and the negative electrode active material portion is prevented.
[0058]
In the first to fifth embodiments, among the four sides of the positive electrode plate, the arrangement and configuration of both end portions along the longitudinal direction have been described. A configuration can be employed. In that case, the effect of preventing a short circuit is further increased. Moreover, the arrangement | positioning and structure of the positive electrode plate which were demonstrated in Embodiment 1-5 can also employ | adopt each independently, and can also employ | adopt combining several.
[0059]
【Example】
Next, based on an Example, this invention is further demonstrated to a specific example. However, the following examples do not limit the present invention.
[0060]
Example 1
One example of the first embodiment will be described with reference to FIGS.
(I) Preparation of positive electrode plate
The positive electrode plate 708 was produced by supporting the positive electrode active material portion 708b on both surfaces of the positive electrode current collector 708a.
The positive electrode active material portion 708b was formed by applying a positive electrode material paste to both surfaces of the positive electrode current collector 708a, drying, and rolling.
[0061]
The positive electrode material paste is LiCoO as a positive electrode active material. ₂ The conductive agent acetylene black and the binder polyvinylidene fluoride were mixed at a weight ratio of 92: 3: 5, respectively. The binder, polyvinylidene fluoride, was dissolved in N-methyl-2-pyrrolidone (hereinafter referred to as NMP) and used as an NMP solution. The NMP solution of polyvinylidene fluoride was also used as an inactive material paste during the production of the positive electrode plate.
[0062]
The positive electrode material paste and the inactive material paste were intermittently applied in stripes on both surfaces of a positive electrode current collector 708a made of an aluminum foil having a thickness of 20 μm.
FIG. 8 shows a top view of a positive electrode current collector 708a on which a positive electrode material paste 801 and an inactive material paste 802 are applied. In the uncoated portion of the positive electrode material paste and the inactive material paste, the positive electrode current collector 708a is exposed, and the interval between the exposed portions is 40 mm. The lengths of the positive electrode material paste 801 and the inactive material paste 802 are both 419 mm. The width of the positive electrode material paste 801 is 50 mm, and the width of the inactive material paste 802 is 8 mm at the center and 6 mm at both ends. The width of the uncoated portion at both end portions along the longitudinal direction of the positive electrode current collector 708a is 10 mm.
[0063]
Next, as shown in FIG. 9, the inactive material paste 802 ′ was also applied to the intermittent portion of the paste. The coating thicknesses of the non-active material pastes 802 and 802 ′ and the coating thickness of the positive electrode material paste 801 were the same, and the total thickness of the coating films on both sides after drying was 280 μm. The total thickness including the thickness of the positive electrode current collector 708a was 300 μm.
[0064]
Then, it rolled with the roller of diameter 300mm until the whole thickness became 180 micrometers, and obtained the positive electrode plate hoop which has a striped positive electrode active material part and a non-active material part. A positive electrode plate hoop was slit at the inactive material portion to obtain a positive electrode plate. The positive electrode material density of the obtained positive electrode plate was 3.1 g / cc.
[0065]
A top view of the positive electrode plate is shown in FIG. In FIG. 10, the length of the positive electrode plate in the longitudinal direction is 428 mm, and the width is 54 mm. The positive electrode active material portion 1002 has a length of 419 mm and a width of 50 mm, similar to the coating film of the positive electrode material paste. A non-active material portion 1003 having a width of 2 mm is disposed around the positive electrode active material portion 1002.
[0066]
A positive electrode lead 716 having a length of 75 mm and a width of 3 mm was welded to an exposed portion of the positive electrode current collector 708a formed by peeling off a part of the inactive material portion 1003 with a width of 5 mm. The welded portion of the positive electrode lead 716 was covered with an insulating tape.
[0067]
(Ii) Production of negative electrode plate
The negative electrode plate 709 was produced by supporting the negative electrode active material portion 709b on both surfaces of the negative electrode current collector 709a by a conventionally known method.
The negative electrode active material portion 709b was formed by applying a negative electrode material paste to both surfaces of the negative electrode current collector 709a, drying, and rolling.
[0068]
The negative electrode material paste was prepared by mixing artificial graphite and binder styrene butadiene rubber (SBR) in a weight ratio of 97: 3. The styrene butadiene rubber as a binder was dispersed in water and used as an aqueous dispersion.
[0069]
The negative electrode material paste was applied to both surfaces of a negative electrode current collector 709a made of a copper foil having a thickness of 14 μm. Subsequently, it rolled with the roller of diameter 300mm until the whole thickness including the coating film of a negative electrode material paste and a negative electrode collector became 196 micrometers, and the negative electrode plate hoop which has a negative electrode active material part was obtained.
[0070]
The obtained negative electrode plate hoop was slit to a size larger than the positive electrode active material part and smaller than the whole positive electrode plate including the non-active material part to obtain a negative electrode plate. The negative electrode material density of the obtained negative electrode plate was 1.4 g / cc. The length of the negative electrode plate in the longitudinal direction was 513 mm, and the width was 52 mm.
[0071]
A negative electrode lead 717 having a length of 75 mm and a width of 3 mm was welded to the exposed portion of the negative electrode current collector 709a formed by peeling a part of the negative electrode active material portion with a width of 5 mm. The welded portion of the negative electrode lead 717 was covered with an insulating tape.
[0072]
(Iii) Preparation of electrolyte
As the electrolyte, lithium hexafluorophosphate (LiPF) was used as a solute in a mixed solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1. ₆ ) 1 mol / dm ^Three What was dissolved in the concentration of was used.
(Iv) Cylindrical battery assembly process
[0073]
A cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm as shown in FIG. 7 was assembled. The design capacity of the battery was 1400 mAh.
The positive electrode plate 708 and the negative electrode plate 709 are opposed to each other in the arrangement shown in FIG. 1 through a separator 710 made of a polyethylene microporous film, and are wound in a spiral shape to constitute an electrode plate group 711. In the electrode plate group 711, an upper insulating plate 718 and a lower insulating plate 719 are disposed above and below the electrode plate group 711 and are housed in a battery container 712 together with an electrolytic solution (not shown). A cylindrical battery can 713 that also serves as a negative electrode terminal and a sealing plate 714 that also serves as a positive electrode terminal were used in combination for the battery container 712. A separator 710 was also interposed between the electrode plate group 711 and the inner periphery of the battery can 713.
[0074]
The positive electrode lead 716 of the positive electrode plate 708 was connected to the back surface of the sealing plate 714 through the central hole of the upper insulating plate 718. The negative electrode lead 717 of the negative electrode plate 709 bypasses the outer periphery of the lower insulating plate 719 and is interposed between the lower insulating plate 719 and the bottom of the battery can 713. The bottoms of the negative electrode lead 717 and the battery can 713 were welded inside the central hole of the lower insulating plate 719. An insulating packing 715 was interposed between the opening end of the battery can 713 and the peripheral edge of the sealing plate 714, the opening of the battery can 713 was sealed with the sealing plate 714, and the battery container 712 was sealed.
[0075]
In the electrode plate group of the battery of Example 1, both end portions along the longitudinal direction of the positive electrode current collector are positioned outside the both end portions along the longitudinal direction of the negative electrode active material portion. Even if the burr generated at the end of the metal breaks through the separator, it is considered that the burr does not short-circuit with the negative electrode active material part. In addition, since an inactive material portion made of an insulating material is provided in the vicinity of the end portion of the positive electrode plate, the positive electrode current collector is stabilized and a general short circuit is less likely to occur. Further, since the thickness of the non-active material portion and the thickness of the positive electrode active material portion are the same and there are no steps, winding deviation during winding is unlikely to occur.
[0076]
Example 2
One example of the second embodiment will be described with reference to FIGS.
(I) Preparation of positive electrode plate
As shown in FIG. 11, an aluminum foil 1101 having a thickness of 20 μm serving as a positive electrode current collector and two polypropylene films 1102 having a thickness of 20 μm serving as an insulating material portion are arranged in three rows, and a positive electrode core material is formed. Configured. The width of the aluminum foil 1101 was 48 mm, and the widths of the polypropylene films 1102 disposed at both ends along the longitudinal direction were 5 mm. A positive electrode core material composed of three components was placed in a positive electrode material paste coating machine.
[0077]
As shown in FIG. 12, the same positive electrode material paste 1201 as prepared in Example 1 was applied on both surfaces of the positive electrode core material with a width of 52 mm so as to be on the insulating material portion made of the polypropylene film 1102. In FIG. 12, the broken line indicates the boundary between the aluminum foil and the polypropylene film.
In addition, it is also possible to arrange more aluminum foils and polypropylene films in 5 rows, 7 rows,.
[0078]
Similarly to Example 1, the total thickness including the coating film on both sides after drying and the positive electrode current collector was 300 μm, and rolled until the total thickness became 180 μm, and the positive electrode having the positive electrode active material part A board hoop was obtained. The positive electrode plate hoop was slit at the laminated portion of the polypropylene film 1102 serving as the insulating material portion and the positive electrode active material portion to obtain a positive electrode plate.
A top view of the positive electrode plate is shown in FIG. In FIG. 13, the length of the positive electrode plate in the longitudinal direction is 428 mm, and the width is 50 mm.
[0079]
A positive electrode lead 1316 similar to that in Example 1 was provided on the exposed portion of the aluminum foil 1101 formed by peeling a part of the positive electrode active material portion 1302 with a width of 5 mm. A laminated portion of a polypropylene film having a width of 1 mm and a positive electrode active material portion was left at both end portions along the longitudinal direction of the positive electrode plate.
[0080]
(Ii) Production of negative electrode plate
The negative electrode plate was produced by slitting a negative electrode plate hoop produced in the same manner as in Example 1 to a size larger than that of the positive electrode plate. The structure and dimensions of the negative electrode plate are the same as in Example 1.
[0081]
(Iii) Cylindrical battery assembly process
As in Example 1, a cylindrical lithium ion secondary battery having a diameter of 18 mm, a height of 65 mm, and a design capacity of 1400 mAh was assembled.
That is, the positive electrode plate and the negative electrode plate produced as described above are opposed to each other in the arrangement shown in FIG. 3 through a separator made of a polyethylene microporous film, and the electrode plate group is formed by winding in a spiral shape. did. And the battery of Example 2 similar to Example 1 was assembled except having used this electrode group.
[0082]
In the electrode plate group of the battery of Example 2, since the positive electrode plate hoop was slit at the laminated portion of the polypropylene film serving as the insulating material portion and the positive electrode active material portion, the end portion along the longitudinal direction of the positive electrode plate was electrically conductive. It is considered that no sex burr has occurred.
[0083]
Example 3
One example of the third embodiment will be described with reference to FIGS.
(I) Preparation of positive electrode plate
As shown in FIG. 14, the same positive electrode material paste 1402 prepared in Example 1 was applied in a stripe pattern on both surfaces of the same positive electrode current collector 1401 used in Example 1. In FIG. 14, the width of the positive electrode material paste is 50 mm in both rows, and the width of the current collector exposed portion is 8 mm at the center and 4 mm at both ends.
[0084]
As in Example 1, the entire thickness including the coating films on both sides after drying and the positive electrode current collector is 300 μm, and rolled to a total thickness of 180 μm to have a positive electrode active material portion 1501. A positive electrode plate hoop was obtained. The positive electrode plate hoop was slit at the current collector exposed portion, and as shown in FIG. 15, the remaining current collector exposed portion was covered with an insulating tape 1509 having a width of 1 mm to obtain a positive electrode plate.
[0085]
In FIG. 15, the positive electrode plate has a length in the longitudinal direction of 428 mm and a width of 52 mm. A positive electrode lead 1516 similar to that of Example 1 was provided on an exposed portion of the positive electrode current collector 1401 formed by peeling a part of the positive electrode active material portion 1501 with a width of 5 mm.
[0086]
(Ii) Production of negative electrode plate
The negative electrode plate was produced by slitting a negative electrode plate hoop produced in the same manner as in Example 1 to a size larger than that of the positive electrode plate. The structure and dimensions of the negative electrode plate are the same as in Example 1.
[0087]
(Iii) Cylindrical battery assembly process
As in Example 1, a cylindrical lithium ion secondary battery having a diameter of 18 mm, a height of 65 mm, and a design capacity of 1400 mAh was assembled.
That is, the positive electrode plate and the negative electrode plate produced as described above are opposed to each other in the arrangement as shown in FIG. 4 through a separator made of a polyethylene microporous film, and are wound in a spiral shape, whereby the electrode plate group Configured. And the battery of Example 3 similar to Example 1 was assembled except having used this electrode group.
[0088]
In the electrode plate group of the battery of Example 3, since the end of the positive electrode current collector was covered with the insulating tape, even if burrs occurred at the end of the positive electrode current collector, the burr and the negative electrode active It is considered that there is no short circuit with the material part.
[0089]
Example 4
One example of the fourth embodiment will be described with reference to FIGS.
(I) Preparation of positive electrode plate
As shown in FIG. 16, an Al deposited film 1602 having a thickness of 5 μm was formed at the same position on both sides of a 20 μm-thick hoop-shaped polypropylene sheet 1601, leaving exposed portions of the polypropylene sheet of 10 mm or more on the front, rear, left and right. . The Al vapor deposition film 1602 had a length of 426 mm and a width of 48 mm.
[0090]
Next, as shown in FIG. 17, the positive electrode material paste 1701 prepared in the same manner as in Example 1 was applied to the same position on both sides of the polypropylene sheet 1601 one by one. At this time, an exposed portion 1702 of the Al vapor deposition film on which the positive electrode material paste was not applied was left at one end of the Al vapor deposition film 1602 having a width of 5 mm. The exposed portion 1702 of the Al vapor deposition film was provided at the same position on both sides of the polypropylene sheet.
[0091]
Similarly to Example 1, the total thickness including the coating film on both sides after drying and the positive electrode current collector was 300 μm, and rolled until the total thickness became 180 μm, and the positive electrode having the positive electrode active material part A board hoop was obtained. The positive electrode plate hoop was slit at a place where there was no Al vapor deposition film to obtain a positive electrode plate as shown in FIG. The positive electrode plate has a length of 428 mm and a width of 50 mm. A positive electrode lead 1816 having a length of 75 mm and a width of 3 mm is fixed to each exposed portion 1702 of the Al deposited film having a width of 5 mm provided on both surfaces of the positive electrode current collector with a conductive adhesive, and their free ends are welded to each other. . The adhesive fixing portion of the positive electrode lead 1816 was covered with an insulating tape. There is no Al vapor deposition film at the end of 1 mm width along the longitudinal direction of the positive electrode plate, and the positive electrode active material part is supported directly on the polypropylene sheet.
[0092]
(Ii) Production of negative electrode plate
The negative electrode plate was produced by slitting a negative electrode plate hoop produced in the same manner as in Example 1 to a size larger than that of the positive electrode plate. The structure and dimensions of the negative electrode plate are the same as in Example 1.
[0093]
(Iii) Cylindrical battery assembly process
As in Example 1, a cylindrical lithium ion secondary battery having a diameter of 18 mm, a height of 65 mm, and a design capacity of 1400 mAh was assembled.
That is, the positive electrode plate and the negative electrode plate produced as described above are opposed to each other in the arrangement as shown in FIG. 5 through a separator made of a polyethylene microporous film, and are wound in a spiral shape, whereby the electrode plate group Configured. And the battery of Example 4 similar to Example 1 was assembled except having used this electrode group.
[0094]
In the battery of Example 4, since the slit portion of the positive electrode current collector is made of an insulating material, it is considered that conductive burrs do not occur and no short circuit due to burrs occurs.
[0095]
Example 5
One example of the fifth embodiment will be described.
(I) Preparation of positive electrode plate
The same positive electrode material paste as that prepared in Example 1 was applied to the entire surface of both surfaces of the same positive electrode current collector used in Example 1.
[0096]
Similarly to Example 1, the total thickness including the coating film on both sides after drying and the positive electrode current collector was 300 μm, and rolled until the total thickness became 180 μm, and the positive electrode having the positive electrode active material part A board hoop was obtained. The positive electrode plate hoop is slit to a width of 50 mm and a length of 428 mm, and both end portions with a width of 2 mm along the longitudinal direction are immersed in a dispersion of polyethylene powder (melting point: about 100 ° C.), dried, and then attached to both end portions. The polyethylene powder was melted to form a polyethylene film.
A positive electrode lead similar to that of Example 1 was provided on the exposed portion of the positive electrode current collector formed by peeling a part of the positive electrode active material portion with a width of 5 mm.
[0097]
(Ii) Production of negative electrode plate
The negative electrode plate was produced by slitting a negative electrode plate hoop produced in the same manner as in Example 1 to a size larger than that of the positive electrode plate. The structure and dimensions of the negative electrode plate are the same as in Example 1.
[0098]
(Iii) Cylindrical battery assembly process
As in Example 1, a cylindrical lithium ion secondary battery having a diameter of 18 mm, a height of 65 mm, and a design capacity of 1400 mAh was assembled.
That is, the positive electrode plate and the negative electrode plate produced as described above are opposed to each other in the arrangement as shown in FIG. 6 through a separator made of a polyethylene microporous film, and are wound in a spiral shape, whereby the electrode plate group Configured. And the battery of Example 5 similar to Example 1 was assembled except having used this electrode group.
[0099]
In the battery of Example 5, even if burrs are generated when the positive electrode plate is slit, a short circuit between the burrs and the negative electrode active material portion is prevented by the polyethylene coating provided at the end of the positive electrode plate.
[0100]
<< Comparative Example 1 >>
A positive electrode plate hoop similar to that of Example 5 was prepared, and slit to a width of 50 mm and a length of 428 mm. The positive electrode plate thus obtained was used as it was without forming a polyethylene film on both end portions along the longitudinal direction, and the cylindrical lithium having a diameter of 18 mm, a height of 65 mm, and a design capacity of 1400 mAh as in Example 5 was used. An ion secondary battery was assembled.
[0101]
[Evaluation]
The batteries of Examples 1 to 5 and Comparative Example 1 were evaluated by the following procedure.
(I) 100 batteries were prepared and charged at 500 mA until the battery voltage reached an overcharged state of 4.4V.
(Ii) The overcharged battery was crushed by being restrained by a flat plate until the voltage began to drop.
(Iii) The number of batteries whose temperature rose after crushing and whose safety valve was activated by gas generation was examined.
[0102]
The results are shown below.
Example 1: The number of batteries in which the safety valve was activated was 0 out of 100.
Example 2: The number of batteries in which the safety valve was activated was 0 out of 100.
Example 3: The number of batteries in which the safety valve was activated was 0 out of 100.
Example 4: The number of batteries in which the safety valve was activated was 0 out of 100.
Example 5: The number of batteries in which the safety valve was activated was 0 out of 100.
Comparative Example 1: The number of batteries in which the safety valve was operated was 26 out of 100.
[0103]
【The invention's effect】
As described above, according to the lithium ion secondary battery of the present invention, burrs are prevented from being generated when the positive electrode current collector is slit, or even if burrs are generated, a short circuit between the burrs and the negative electrode active material portion. Is prevented.
[Brief description of the drawings]
FIG. 1 is a diagram conceptually illustrating an example of a cross section perpendicular to a longitudinal direction of a positive electrode plate, a negative electrode plate, and a separator in an electrode plate group according to Embodiment 1 of the present invention.
FIG. 2 is a diagram conceptually illustrating an example of a cross section perpendicular to a longitudinal direction of a positive electrode plate, a negative electrode plate, and a separator in a conventional electrode plate group.
FIG. 3 is a diagram conceptually illustrating an example of a cross section perpendicular to a longitudinal direction of a positive electrode plate, a negative electrode plate, and a separator in an electrode plate group according to a second embodiment of the present invention.
FIG. 4 is a diagram conceptually illustrating an example of a cross section perpendicular to a longitudinal direction of a positive electrode plate, a negative electrode plate, and a separator in an electrode plate group according to a third embodiment of the present invention.
FIG. 5 is a diagram conceptually illustrating an example of a cross section perpendicular to a longitudinal direction of a positive electrode plate, a negative electrode plate, and a separator in an electrode plate group according to a fourth embodiment of the present invention.
FIG. 6 is a diagram conceptually illustrating an example of a cross section perpendicular to the longitudinal direction of a positive electrode plate, a negative electrode plate, and a separator in an electrode plate group according to a fifth embodiment of the present invention.
7 is a longitudinal sectional view of a lithium ion secondary battery according to Example 1 of the present invention. FIG.
FIG. 8 is a top view of a positive electrode current collector for illustrating a manufacturing process of a positive electrode plate according to Example 1 of the invention.
FIG. 9 is another top view of the positive electrode current collector for explaining the manufacturing process of the positive electrode plate according to the first embodiment of the invention.
FIG. 10 is a front view of a positive electrode plate according to Example 1 of the present invention.
FIG. 11 is a top view of a positive electrode current collector for illustrating a manufacturing process of a positive electrode plate according to Example 2 of the invention.
FIG. 12 is another top view of the positive electrode current collector for explaining the production process of the positive electrode plate according to Example 2 of the invention.
FIG. 13 is a front view of a positive electrode plate according to Example 2 of the present invention.
FIG. 14 is a top view of a positive electrode current collector for illustrating a manufacturing process of a positive electrode plate according to Example 3 of the invention.
FIG. 15 is a front view of a positive electrode plate according to Example 3 of the invention.
FIG. 16 is a top view of a positive electrode current collector for illustrating a manufacturing process of a positive electrode plate according to Example 4 of the invention.
FIG. 17 is another top view of the positive electrode current collector for illustrating a manufacturing process of the positive electrode plate according to Example 4 of the invention.
FIG. 18 is a front view of a positive electrode plate according to Example 4 of the present invention.
[Explanation of symbols]
110 Positive electrode plate
111 Positive Current Collector
111a, b End of positive electrode current collector
112 Positive electrode active material part
112a, b End of positive electrode active material part
113 Inactive material part
120 Negative electrode plate
121 Negative electrode current collector
122 Negative electrode active material part
122a, b End of negative electrode active material portion
130 Separator
210 Positive electrode plate
211 Positive Current Collector
212 Cathode active material part
220 Negative electrode plate
221 Negative electrode current collector
222 Negative electrode active material part
230 Separator
211a, b End of positive electrode current collector
222a, b End of negative electrode active material portion
310 Positive electrode plate
311 Positive Current Collector
311a, b End of positive electrode current collector
312 Positive electrode active material part
312a, b End of positive electrode active material
313 Insulation material part
320 Negative electrode plate
321 Negative electrode current collector
322 Negative electrode active material part
330 Separator
410 Positive electrode plate
411 positive electrode current collector
411a, b End of positive electrode current collector
412 Positive electrode active material part
412a, b End of positive electrode active material portion
413 Insulation material
420 Negative electrode plate
421 Negative electrode current collector
422 Negative electrode active material part
422a, b End of negative electrode active material portion
430 Separator
510 positive electrode plate
511 positive electrode current collector
511a, b End of positive electrode current collector
511x insulation sheet
511x 'exposed part of insulating sheet
511y conductive layer
512 Positive electrode active material part
520 negative electrode plate
521 Negative electrode current collector
522 Negative electrode active material part
530 separator
610 positive electrode plate
611 positive electrode current collector
612 Cathode active material part
613 Insulation material
620 Negative electrode plate
621 Negative electrode current collector
622 Negative electrode active material part
630 separator
708 positive electrode plate
708a Positive electrode current collector
708b Cathode active material part
709 Negative electrode plate
709a Negative electrode current collector
709b Negative electrode active material part
710 Separator
711 plate group
712 Battery container
713 Battery can
714 Sealing plate
715 Insulation packing
716 Positive lead
717 Negative electrode lead
718 Upper insulation plate
719 Lower insulation plate
801 Positive electrode material paste
802, 802 'Inactive material paste
1002 Cathode active material part
1003 Inactive material part
1101 Aluminum foil
1102 Polypropylene film
1201 Positive electrode material paste
1302 Cathode active material part
1316 Positive electrode lead
1401 Positive electrode current collector
1402 Positive electrode material paste
1501 Cathode active material part
1509 Insulation tape
1516 positive lead
1601 Polypropylene sheet
1602 Al deposition film
1701 Positive electrode material paste
1702 Exposed portion of Al deposited film
1816 positive lead

Claims

(A) a positive electrode plate comprising a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, wherein the positive electrode active material part comprises a positive electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(B) a negative electrode plate comprising a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part comprises a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate;
(D) an electrolyte solution, and (e) a lithium ion secondary battery comprising a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte solution,
The positive electrode plate and the negative electrode plate constitute an electrode plate group by being wound through the separator between them, and the electrode plate group extends along the longitudinal direction of the positive electrode current collector. Both end portions are located outside both end portions along the longitudinal direction of the negative electrode active material portion, and lithium ions are not occluded or released by charging / discharging at both end portions along the longitudinal direction of the positive electrode active material portion. A lithium ion secondary battery provided with an inactive material part .

The inactive material unit, the lithium ion secondary battery according to claim 1, wherein an insulating material.

2. The lithium ion secondary battery according to claim 1, wherein in the electrode plate group, both end portions along the longitudinal direction of the negative electrode active material portion are positioned outside both end portions along the longitudinal direction of the positive electrode active material portion.

(A) a positive electrode plate comprising a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, wherein the positive electrode active material part comprises a positive electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(B) a negative electrode plate comprising a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part comprises a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate;
(D) an electrolyte solution, and (e) a lithium ion secondary battery comprising a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte solution,
The positive electrode plate and the negative electrode plate constitute an electrode plate group by being wound through the separator between them, and both ends along the longitudinal direction of the positive electrode active material portion in the electrode plate group The lithium ion secondary battery in which the part is located outside both ends along the longitudinal direction of the positive electrode current collector.

5. The lithium ion secondary battery according to claim 4, wherein insulating material portions extending in a surface direction of the positive electrode current collector are disposed at both ends along the longitudinal direction of the positive electrode current collector.

The lithium ion secondary battery according to claim 5 , wherein the insulating material portion is connected to an end face of an end portion along a longitudinal direction of the positive electrode current collector.

The lithium ion secondary battery according to claim 5 , wherein the insulating material portion is made of at least one selected from the group consisting of polypropylene, polyethylene, polyvinylidene fluoride, and polyethylene terephthalate.

The lithium ion secondary battery according to claim 4 , wherein the positive electrode current collector is completely covered with the positive electrode active material part.

The lithium ion secondary battery according to claim 4 , wherein both end portions along the longitudinal direction of the positive electrode current collector are covered with an insulating material.

5. The lithium ion secondary battery according to claim 4 , wherein in the electrode plate group, both end portions along the longitudinal direction of the negative electrode active material portion are positioned outside both end portions along the longitudinal direction of the positive electrode active material portion.

(A) a positive electrode plate comprising a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, wherein the positive electrode active material part comprises a positive electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(B) a negative electrode plate comprising a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part comprises a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate;
(D) an electrolyte solution, and (e) a lithium ion secondary battery comprising a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte solution,
The positive electrode plate and the negative electrode plate constitute an electrode plate group by being wound through the separator between them, and in the electrode plate group, along the longitudinal direction of the negative electrode active material portion Both end portions are located outside both end portions along the longitudinal direction of the positive electrode current collector, and both end portions along the longitudinal direction of the positive electrode current collector are from both end portions along the longitudinal direction of the positive electrode active material portion. Is a lithium ion secondary battery in which an exposed portion that is not covered with the positive electrode active material portion of the positive electrode current collector is covered with an insulating material.

(A) a positive electrode plate comprising a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, wherein the positive electrode active material part comprises a positive electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(B) a negative electrode plate comprising a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part comprises a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate;
(D) an electrolyte solution, and (e) a lithium ion secondary battery comprising a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte solution,
The positive electrode plate and the negative electrode plate are wound through the separator between them to constitute an electrode plate group, and the positive electrode current collector is formed on each of the insulating sheet and both surfaces thereof. The lithium ion secondary battery which consists of the electrically conductive layer, and the exposed part of the said insulating sheet is provided in the both ends along the longitudinal direction of the said insulating sheet.

(A) a positive electrode plate comprising a positive electrode active material part and a positive electrode current collector carrying the positive electrode active material part, wherein the positive electrode active material part comprises a positive electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(B) a negative electrode plate comprising a negative electrode active material part and a negative electrode current collector carrying the negative electrode active material part, wherein the negative electrode active material part comprises a negative electrode active material capable of inserting or extracting lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate;
(D) an electrolyte solution, and (e) a lithium ion secondary battery comprising a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte solution,
The positive electrode plate and the negative electrode plate are wound through the separator between them to constitute an electrode plate group, and both end portions along the longitudinal direction of the positive electrode plate are made of an insulating material, respectively. Covered lithium ion secondary battery.

The lithium ion secondary battery according to claim 13 , wherein the insulating material is at least one selected from the group consisting of polypropylene, polyethylene, polyvinylidene fluoride, and polyethylene terephthalate.