JP2004055537A - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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Publication number
JP2004055537A
JP2004055537A JP2003149836A JP2003149836A JP2004055537A JP 2004055537 A JP2004055537 A JP 2004055537A JP 2003149836 A JP2003149836 A JP 2003149836A JP 2003149836 A JP2003149836 A JP 2003149836A JP 2004055537 A JP2004055537 A JP 2004055537A
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positive electrode
active material
negative electrode
electrode plate
electrode active
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JP4617065B2 (en
Inventor
Takeshi Minafuji
皆藤　豪
Futoshi Tanigawa
谷川　太志
Naoto Arai
荒井　直人
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

<P>PROBLEM TO BE SOLVED: To provide a wound-type lithium ion secondary battery capable of preventing short-circuiting between burr on a positive electrode collector and a negative electrode active material part to achieve high safety. <P>SOLUTION: This lithium ion secondary battery is provided with a positive electrode plate 110 comprising a positive electrode active material part 112 and a positive electrode collector 111 to carry that, a negative electrode plate 120 comprising a negative electrode active material part 122 and a negative electrode collector 121 to carry that, a separator 130 provided between the positive electrode plate 110 and the negative electrode plate 120, electrolyte, and a battery container to contain the positive electrode plate 110, the negative electrode plate 120, the separator 130, and the electrolyte. The positive electrode plate 110 and the negative electrode plate 120 are wound through the separator 130 between them to compose an electrode plate group. In the electrode plate group, both lengthwise end parts 111a and 111b of the positive electrode collector are positioned on the outer side of both lengthwise end parts 122a and 122b of the negative electrode active material part. <P>COPYRIGHT: (C)2004,JPO

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を設けることができる。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
１６０２　Ａｌ蒸着膜
１７０１　正極材料ペースト
１７０２　Ａｌ蒸着膜の露出部
１８１６　正極リード[0001]
TECHNICAL FIELD 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]
2. Description of the Related Art In recent years, portable and cordless electronic devices such as AV devices and personal computers have been rapidly developed, and demands for smaller and lighter secondary batteries as power sources for driving these devices and higher energy densities have been increasing. . 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 type battery is mainly used. A wound type battery is obtained by winding a positive electrode plate including a positive electrode active material portion and a positive electrode current collector supporting the same, and a negative electrode plate including a negative electrode active material portion and a negative electrode current collector supporting the same, with a separator interposed therebetween. It has a group of rotating electrode plates. The positive electrode active material portion contains a positive electrode active material that can occlude or release lithium ions by charging and discharging, and the negative electrode active material portion contains a negative electrode active material that can occlude or release lithium ions by charging and discharging. Have been. The electrode group is housed in the battery container together with the electrolytic solution.
[0004]
In the case of a wound type battery, the electrode plate and the separator are easily deformed at the bent portion and the curved portion when the electrode plate is wound. Such deformation can induce an internal short circuit. In addition, when the electrode plate is wound, the position of the separator is displaced, so that an internal short circuit may occur.
[0005]
In view of the above, the present inventors have focused on preventing a main cause of an internal short circuit in a wound type lithium ion secondary battery.
[0006]
The following four types can be considered as types of the internal short circuit.
(1) Short circuit between positive electrode active material part and negative electrode active material part
(2) Short circuit between positive electrode active material and negative electrode current collector
(3) Short circuit between positive electrode current collector and negative electrode active material
(4) Short circuit between positive and negative electrode current collectors
[0007]
The present inventors disassembled a battery in an overcharged state for each part, and observed the presence or absence of spark and ignition by directly contacting each part. 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), sparks occurred, but did not ignite.
[0008]
The following are considered from these results.
In the short-circuit modes (1) and (2), since the resistance of the positive electrode active material itself is large, a large current does not flow even when 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 thus does not ignite.
In the short-circuit mode (3), since both the positive electrode current collector and the negative electrode active material have conductivity, when they are short-circuited, a spark is generated and the flammable negative electrode active material is ignited.
[0010]
From the above considerations, the short circuit mode (3) is considered to be the main cause of the internal short circuit. The short-circuit mode (3) actually occurs when conductive burrs generated at the time of slitting the positive electrode current collector come into contact with 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 group formed by stacking a positive electrode plate and a negative electrode plate via an electrolyte layer has been proposed. In such a 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 short-circuit by controlling the dimensions of the electrode plate and the separator (see Patent Document 1). However, the manufacturing process of a laminated integrated electrode plate group is generally complicated, and it is difficult to increase the capacity. Further, in such an electrode plate group, from the viewpoint of reducing the weight of the battery, it has been proposed to use a current collector provided with a metal vapor-deposited film on the surface of a resin film such as a polyethylene terephthalate film (Patent Document 1). 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-described findings, and one of the objects of the present invention is to prevent short-circuit between a burr of a positive electrode current collector and a negative electrode active material portion, thereby providing a highly safe wound type. An object of the present invention 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 supporting 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 portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion can occlude or release lithium ions by charging and discharging. 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 electrolytic solution, and (e) a battery containing the positive electrode plate, the negative electrode plate, the separator and the electrolytic solution A container is provided.
[0015]
The positive electrode plate and the negative electrode plate constitute an electrode plate group by being wound via the separator. Here, the lithium ion secondary battery of the present invention has any of the following features [A] to [E] in the electrode group.
[0016]
[A] Both ends along the longitudinal direction of the positive electrode current collector are located outside the both ends along the longitudinal direction of the negative electrode active material portion.
[B] Both ends along the longitudinal direction of the positive electrode active material part are located outside the both ends 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, An exposed portion, which is located outside both ends 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 formed on both surfaces of the insulating sheet, and exposed portions of the insulating sheet are provided at both ends along the longitudinal direction of the insulating sheet.
[E] Both ends along the longitudinal direction of the positive electrode plate are coated with an insulating material.
For the separator, for example, a woven fabric, a nonwoven fabric, a microporous film, or the like made of polyolefin or the like is used.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1
The present embodiment includes (a) a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion contains a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging. A positive electrode plate comprising: (b) a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging. A negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) an electrolyte, and (e) a lithium including a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte. In the ion secondary battery, the positive electrode plate and the negative electrode plate are wound with the separator interposed therebetween to form an electrode group, and in the electrode group, the positive electrode 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 the both ends along the longitudinal direction of the positive electrode current collector are located outside the both ends along the longitudinal direction of the negative electrode active material part, burrs are generated at the end of the positive electrode current collector at the time of slitting. However, a short circuit between the burr and the negative electrode active material portion can be prevented.
[0021]
At both ends 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 can be provided. The end portion of the positive electrode current collector can be stabilized by the inactive material portion. Furthermore, at both end portions 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 it is unlikely that a winding shift or the like during winding will occur. It is preferred in that respect. When an insulating material is used as the non-active material portion, 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 portion 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 located outside the both end portions along the longitudinal direction of the positive electrode active material portion. With such an arrangement, Li ions released from the positive electrode active material at the time of charging can be reliably received by the opposite negative electrode active material, thereby causing uneven load of the negative electrode active material, deposition of metallic lithium, and the like. Can be prevented.
[0023]
FIG. 1 conceptually shows an example of a cross section perpendicular to the longitudinal direction of the positive electrode plate 110, the negative electrode plate 120, and the separator 130 in the electrode plate group of the present embodiment. In FIG. 1, each element is shown at intervals in the stacking direction so that the arrangement relationship between 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 part 112, and the negative electrode plate 120 includes a negative electrode current collector 121 and a negative electrode active material part 122. The positive electrode plate 110 and the negative electrode plate 120 face each other with a 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, the positive electrode active material is not coated. Although a work portion may be used, it is preferable to provide the inactive material portion 113.
[0025]
Both ends 111a and 111b along the longitudinal direction of the positive electrode current collector 111 are located outside of both ends 122a and 122b along the longitudinal direction of the negative electrode active material portion 122. With such an arrangement, even if burrs are generated at the end 111a or 111b of the positive electrode current collector and the burrs break through the separator 130, there is no short circuit with the negative electrode active material portion 122.
[0026]
When the configuration as shown in FIG. 1 is employed, 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 distance from the end 111b of the positive electrode current collector to the end 122b of the negative electrode active material part Is preferably 50 to 300 μm. These intervals are preferably larger than the length obtained by subtracting the sum of the thickness per one side of the positive electrode active material portion and the thickness of the separator from the length of the burr assumed in the cross section of the positive electrode current collector. In addition, the length of the burr assumed in the cross section of the positive electrode current collector is generally 50 to 100 μm.
[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, similarly to FIG.
The positive electrode plate 210 includes a positive electrode current collector 211 and a positive electrode active material part 212, and the negative electrode plate 220 includes a negative electrode current collector 221 and a negative electrode active material part 222.
[0028]
Both ends 211a and 211b along the longitudinal direction of the positive electrode current collector are located inside the both ends 222a and 222b along the longitudinal direction of the negative electrode active material portion 222. In such an arrangement, a burr is generated at the end 211 a or 211 b of the positive electrode current collector, and if the burr breaks through the separator 230, a short circuit occurs with the negative electrode active material part 222.
[0029]
Embodiment 2
The present embodiment includes (a) a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion contains a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging. A positive electrode plate comprising: (b) a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging. A negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) an electrolyte, and (e) a lithium including a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte. In the ion secondary battery, the positive electrode plate and the negative electrode plate constitute a group of electrodes by being wound therebetween with the separator interposed therebetween. 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 ends along the longitudinal direction of the positive electrode active material part are located outside the both ends along the longitudinal direction of the positive electrode current collector, when slitting near the end of the positive electrode active material part, the positive electrode Since the current collector and the positive electrode active material part are not slit at the same time, burrs do not easily 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 simultaneously slit, burrs are likely to be generated at the end 211a or 211b of the positive electrode current collector.
[0031]
Also in the present embodiment, it is preferable that both end portions along the longitudinal direction of the negative electrode active material portion are located outside the both end portions along the longitudinal direction of the positive electrode active material portion.
It is preferable that insulating material portions extending in the plane direction of the positive electrode current collector are respectively disposed at both ends along the longitudinal direction of the positive electrode current collector. With such an insulating material portion, the end portion of the positive electrode active material portion can be stabilized. The insulating material portion is connected to the end face of the end portion along the longitudinal direction of the positive electrode current collector, and it is preferable that the positive electrode current collector and the insulating material portion are integrated. When the positive electrode current collector and the insulating material portion are integrated, they can be handled as one core material.
[0032]
The insulating material portion extending in the surface direction of the positive electrode current collector preferably has excellent workability, has insulating properties, 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]
It is preferable that the positive electrode current collector is 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. The space between the end of the positive electrode current collector and the end of the positive electrode active material portion may be filled with the positive electrode active material. Also in such a case, the positive electrode current collector is completely covered by the positive electrode active material portion.
[0034]
When the 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 coated with the insulating material. Polypropylene, polyethylene, polyvinylidene fluoride, polyethylene terephthalate, or the like can also be used as an insulating material covering the end of the positive electrode current collector. Further, by spraying a ceramic such as alumina, the end of the positive electrode current collector can be coated with the ceramic.
[0035]
FIG. 3 conceptually shows an example of a cross section perpendicular to the longitudinal direction of the positive electrode plate 310, the negative electrode plate 320, and the separator 330 in the electrode plate group of the present embodiment. In FIG. 3, each element is shown at intervals in the stacking direction so that the arrangement relationship between 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 part 312, and the negative electrode plate 320 includes a negative electrode current collector 321 and a negative electrode active material part 322. The positive electrode plate 310 and the negative electrode plate 320 face each other with a 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 provided. Extending.
[0037]
Both ends 312a and 312b along the longitudinal direction of the positive electrode active material portion are located outside of both ends 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 as 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 portion, and the distance from the end 311b of the positive electrode current collector to the end 312b of the positive electrode active material portion The distance between them is not particularly limited, but each is preferably 2 mm or less.
[0039]
Embodiment 3
The present embodiment includes (a) a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion contains a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging. A positive electrode plate comprising: (b) a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging. A negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) an electrolyte, and (e) a lithium including a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte. In an ion secondary battery, the positive electrode plate and the negative electrode plate are wound with the separator interposed therebetween to form an electrode group, and in the electrode group, the negative electrode Active material section longitudinal direction Both ends along the longitudinal direction of the positive electrode current collector are located outside the both ends along the longitudinal direction of the positive electrode current collector, and both ends along the longitudinal direction of the positive electrode current collector are both ends along the longitudinal direction of the positive electrode active material part. The present invention relates to a lithium ion secondary battery in which an exposed portion which is located outside of a portion and which is not covered with the cathode active material portion of the cathode 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. Are located outside both ends along the longitudinal direction of the positive electrode active material portion, so that the end portion of the positive electrode current collector faces the surface of the negative electrode active material portion. 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 the insulating material, even if burrs are generated on the positive electrode current collector, the burrs are formed on the surface of the negative electrode active material portion. There is no short circuit.
[0041]
As an insulating material covering the exposed portion of the positive electrode current collector, polypropylene, polyethylene, polyvinylidene fluoride, polyethylene terephthalate, or the like can be used. These may be used alone or in combination of two or more. Further, the exposed portion of the positive electrode current collector can be coated with ceramics by spraying ceramics such as 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 tape made of a base material made of polypropylene or the like and an acrylic resin-based adhesive material carried on one surface thereof.
The step of covering the exposed portion of the positive electrode current collector with the 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 arrangement relationship between 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 part 412, and the negative electrode plate 420 includes a negative electrode current collector 421 and a negative electrode active material part 422. The positive electrode plate 410 and the negative electrode plate 420 face each other with a separator 430 interposed therebetween. An insulating material 413 covers the portion from the end portion 411a of the positive electrode current collector to the end portion 412a of the positive electrode active material portion and the portion from the end portion 411b of the positive electrode current collector to the end portion 412b of the positive electrode active material portion. ing.
[0044]
Both ends 422a and 422b along the longitudinal direction of the negative electrode active material portion are located outside of both ends 411a and 411b along the longitudinal direction of the positive electrode current collector. Further, both end portions 411a and 411b along the longitudinal direction of the positive electrode current collector are located outside of both end portions 412a and 412b along the longitudinal direction of the positive electrode active material portion. Further, an exposed portion of the positive electrode current collector which is not covered with the positive electrode active material portion is covered with the insulating material 413. In such a positive electrode plate, even when 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 employed, 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 distance from the end 422b of the negative electrode active material portion to the end 411b of the positive electrode current collector The distance between them is not particularly limited, but each is preferably 2 mm or less. 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 411b of the positive electrode current collector to the end 412b of the positive electrode active material part are not particularly limited. Is preferably 2 mm or less.
[0046]
Embodiment 4
The present embodiment includes (a) a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion contains a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging. A positive electrode plate comprising: (b) a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging. A negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) an electrolyte, and (e) a lithium including a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte. An ion secondary battery, wherein the positive electrode plate and the negative electrode plate are wound with the separator interposed therebetween to form an electrode plate group, and the positive electrode current collector is insulated. On the sheet and on 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 the present embodiment is lightweight because most of the current collector is made of an insulating sheet. Further, in such a current collector, since the cross section formed by the slit has an insulating property, conductive burrs do not occur.
[0048]
As a constituent material of the insulating sheet, polypropylene, polyethylene, polyethylene terephthalate, or the like can be used. These materials are also advantageous in that they have flexibility. As the conductive layer, a deposited film of aluminum, an aluminum alloy, or the like is preferable. In the step of forming the deposition film, a conventionally known deposition method such as electron beam deposition may be used as appropriate.
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 the present embodiment, it is preferable that both end portions along the longitudinal direction of the negative electrode active material portion are located outside the both end portions along the longitudinal direction of the positive electrode active material portion.
FIG. 5 conceptually shows an example of a cross section perpendicular to the longitudinal direction of the positive electrode plate 510, the negative electrode plate 520, and the separator 530 in the electrode plate group of the present embodiment. In FIG. 5, each element is shown at intervals in the stacking direction so that the arrangement relationship between 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 part 512, and the negative electrode plate 520 includes a negative electrode current collector 521 and a negative electrode active material part 522. The positive electrode plate 510 and the negative electrode plate 520 face each other with a separator 530 interposed therebetween. The positive electrode current collector 511 includes an insulating sheet 511x and conductive layers 511y formed on both surfaces thereof. Exposed portions 511x ′ of the insulating sheet are provided at both ends of the insulating sheet 511x along the longitudinal direction. 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 cut surfaces of the insulating sheet, conductive burrs cannot be generated. Therefore, the short-circuit between the positive electrode current collector and the negative electrode active material part is prevented even though both ends 511a and 511b along the longitudinal direction of the positive electrode current collector 511 face the surface of the negative electrode active material part 512. Is done.
[0052]
Embodiment 5
The present embodiment includes (a) a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion contains a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging. A positive electrode plate comprising: (b) a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging. A negative electrode plate, (c) a separator interposed between the positive electrode plate and the negative electrode plate, (d) an electrolyte, and (e) a lithium including a battery container containing the positive electrode plate, the negative electrode plate, the separator and the electrolyte. In the ion secondary battery, the positive electrode plate and the negative electrode plate constitute an electrode group by being wound therebetween with the separator interposed therebetween, and extend along the longitudinal direction of the positive electrode plate. Both ends are respectively A lithium ion secondary battery is covered by the edge material.
[0053]
Since both ends along the longitudinal direction of the positive electrode plate are coated with an insulating material, even when burrs are generated on the positive electrode current collector when slitting the vicinity of the end of the positive electrode active material portion, the insulating material is used. Thereby, a short circuit between the burr and the negative electrode active material portion is prevented. For example, the present embodiment can be realized by coating both ends 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 step of coating 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. It can be coated with a material.
Also in the present embodiment, it is preferable that both end portions along the longitudinal direction of the negative electrode active material portion are located outside the both end portions along the longitudinal direction of the positive electrode active material portion.
[0056]
FIG. 6 conceptually shows an example of a cross section perpendicular to the longitudinal direction of the positive electrode plate 610, the negative electrode plate 620, and the separator 630 in the electrode plate group of the present embodiment. In FIG. 6, each element is shown at intervals in the stacking direction so that the arrangement relationship between 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 part 612, and the negative electrode plate 620 includes a negative electrode current collector 621 and a negative electrode active material part 622. The positive electrode plate 610 and the negative electrode plate 620 face each other with the separator 630 interposed therebetween. Since both ends 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 Embodiments 1 to 5, of the four sides of the positive electrode plate, the arrangement and configuration of both ends along the longitudinal direction have been described. However, the same arrangement and configuration can be applied to at least one of both ends along the lateral direction. A configuration can be employed. In that case, the effect of preventing a short circuit is further increased. In addition, the arrangement and configuration of the positive electrode plates described in Embodiments 1 to 5 can be employed alone or in combination.
[0059]
【Example】
Next, the present invention will be described in further detail with reference to examples. 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) Production of positive electrode plate
The positive electrode plate 708 was manufactured by supporting a positive electrode active material portion 708b on both surfaces of a 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 And acetylene black as a conductive agent and polyvinylidene fluoride as a binder in a weight ratio of 92: 3: 5, respectively. Polyvinylidene fluoride as a binder was dissolved in N-methyl-2-pyrrolidone (hereinafter referred to as NMP) and used as an NMP solution. Note that the NMP solution of polyvinylidene fluoride was also used as a non-active material paste at the time of manufacturing 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 to which a positive electrode material paste 801 and a non-active material paste 802 are applied. In the uncoated portion of the positive electrode material paste and the non-active 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 ends along the longitudinal direction of the positive electrode current collector 708a is 10 mm.
[0063]
Next, as shown in FIG. 9, a non-active material paste 802 ′ was also applied to the intermittent portions of the paste. The thicknesses of the coating films 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 surfaces after drying was 280 μm. The total thickness including the thickness of the positive electrode current collector 708a was 300 μm.
[0064]
Thereafter, the resultant was rolled with a roller having a diameter of 300 mm until the entire thickness became 180 μm to obtain a positive electrode plate hoop having a stripe-shaped positive electrode active material portion and a non-active material portion. The positive electrode plate hoop was slit at the non-active 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]
FIG. 10 shows a top view of the positive electrode plate. 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, similarly to the coating film of the positive electrode material paste. A non-active material portion 1003 having a width of 2 mm is arranged 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 a part of the inactive material portion 1003 with a width of 5 mm. The welded part of the positive electrode lead 716 was covered with an insulating tape.
[0067]
(Ii) Preparation of negative electrode plate
The negative electrode plate 709 was produced by carrying a negative electrode active material portion 709b on both surfaces of a 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 on 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 styrene butadiene rubber (SBR) as a binder at a weight ratio of 97: 3. 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. Then, rolling was performed with a roller having a diameter of 300 mm until the entire thickness including the coating film of the negative electrode material paste and the negative electrode current collector was 196 μm, to obtain a negative electrode plate hoop having a negative electrode active material portion.
[0070]
The obtained negative electrode plate hoop was slit into a size larger than the positive electrode active material portion and smaller than the entire positive electrode plate including the non-active material portion, to obtain a negative electrode plate. The negative electrode material density of the obtained negative electrode plate was 1.4 g / cc. The length in the longitudinal direction of the negative electrode plate 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 an 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 part of the negative electrode lead 717 was covered with an insulating tape.
[0072]
(Iii) Preparation of electrolyte solution
As the electrolyte, a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) mixed at a volume ratio of 1: 1 was mixed with lithium hexafluorophosphate (LiPF) as a solute. 6 ) Is 1 mol / dm 3 Used at a concentration of 1.
(Iv) Assembly process of cylindrical battery
[0073]
As shown in FIG. 7, a cylindrical lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm was assembled. The design capacity of the battery was 1400 mAh.
The positive electrode plate 708 and the negative electrode plate 709 were opposed to each other via a separator 710 made of a microporous polyethylene film in the arrangement shown in FIG. 1 and spirally wound to form an electrode plate group 711. In the electrode group 711, an upper insulating plate 718 and a lower insulating plate 719 are arranged above and below the electrode group 711, and are housed in a battery container 712 together with an electrolyte (not shown). For the battery container 712, a cylindrical battery can 713 also serving as a negative electrode terminal and a sealing plate 714 also serving as a positive electrode terminal were used in combination. 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 center hole of the upper insulating plate 718. The negative electrode lead 717 of the negative electrode plate 709 bypassed the outer periphery of the lower insulating plate 719 and was interposed between the lower insulating plate 719 and the bottom of the battery can 713. The negative electrode lead 717 and the bottom of the battery can 713 were welded inside the center 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, and the opening of the battery can 713 was sealed with the sealing plate 714 to seal the battery container 712.
[0075]
In the electrode plate group of the battery of Example 1, since both ends along the longitudinal direction of the positive electrode current collector are located outside the both ends along the longitudinal direction of the negative electrode active material portion, the positive electrode current collector It is considered that even if the burr generated at the end of the electrode breaks through the separator, the burr does not short-circuit with the negative electrode active material portion. Further, since an inactive material portion made of an insulating material is provided near the end of the positive electrode plate, the positive electrode current collector is stabilized, and a general short circuit is unlikely to occur. Further, since the thickness of the non-active material portion and the thickness of the positive electrode active material portion were the same and there was no step, it was difficult to cause winding deviation during winding.
[0076]
<< Example 2 >>
One example of the second embodiment will be described with reference to FIGS.
(I) Production 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 provided. Configured. The width of the aluminum foil 1101 was 48 mm, and the width of both polypropylene films 1102 disposed at both ends along the longitudinal direction was 5 mm. The positive electrode core material composed of the three constituent members was installed 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 to both surfaces of the positive electrode core material with a width of 52 mm so as to cover the insulating material portion made of the polypropylene film 1102. In FIG. 12, a broken line indicates a boundary between the aluminum foil and the polypropylene film.
Incidentally, it is also possible to arrange the aluminum foil and the polypropylene film in five rows, seven rows,... To efficiently produce more positive electrode plates.
[0078]
As in Example 1, the overall thickness including the dried coating film and the positive electrode current collector was 300 μm, and the entire thickness was rolled to 180 μm to obtain a positive electrode having a positive electrode active material portion. I got a board hoop. The positive electrode plate hoop was slit at the laminated portion of the polypropylene film 1102 serving as an insulating material portion and the positive electrode active material portion to obtain a positive electrode plate.
FIG. 13 shows a top view of the positive electrode plate. In FIG. 13, the length in the longitudinal direction of the positive electrode plate is 428 mm, and the width is 50 mm.
[0079]
A positive electrode lead 1316 similar to that of Example 1 was provided on an 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. At both ends along the longitudinal direction of the positive electrode plate, a laminated portion of a polypropylene film having a width of 1 mm and a positive electrode active material portion was left.
[0080]
(Ii) Preparation of negative electrode plate
The negative electrode plate was manufactured by slitting a negative electrode plate hoop manufactured in the same manner as in Example 1 to a size larger than the positive electrode plate. The structure and dimensions of the negative electrode plate are the same as in Example 1.
[0081]
(Iii) Assembly process of cylindrical battery
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 above are opposed to each other in the arrangement shown in FIG. 3 via a separator made of a microporous polyethylene membrane, and are spirally wound to form an electrode plate group. did. Then, a battery of Example 2 similar to that of Example 1 was assembled except that this electrode group was used.
[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 and the positive electrode active material portion serving as the insulating material portion, the conductive portion was formed at the end along the longitudinal direction of the positive electrode plate. It is considered that no burrs occurred.
[0083]
<< Example 3 >>
One example of the third embodiment will be described with reference to FIGS. (I) Production of positive electrode plate
As shown in FIG. 14, the same positive electrode material paste 1402 as prepared in Example 1 was applied on both surfaces of the same positive electrode current collector 1401 as used in Example 1 in a stripe shape. In FIG. 14, the width of the positive electrode material paste is 50 mm in both rows, and the width of the exposed portion of the current collector is 8 mm at the center and 4 mm at both ends.
[0084]
As in Example 1, the entire thickness including the coating film on both sides after drying and the positive electrode current collector was set to 300 μm, and was rolled until the entire thickness became 180 μm to have the 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 a 1 mm-wide insulating tape 1509 to obtain a positive electrode plate.
[0085]
In FIG. 15, the length of the positive electrode plate in the longitudinal direction is 428 mm and the width is 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) Preparation of negative electrode plate
The negative electrode plate was manufactured by slitting a negative electrode plate hoop manufactured in the same manner as in Example 1 to a size larger than the positive electrode plate. The structure and dimensions of the negative electrode plate are the same as in Example 1.
[0087]
(Iii) Assembly process of cylindrical battery
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 prepared above are opposed to each other in the arrangement shown in FIG. 4 via a separator made of a microporous polyethylene film, and are spirally wound to form an electrode plate group. Was configured. Then, a battery of Example 3 similar to that of Example 1 was assembled except that this electrode group was used.
[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 burrs 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) Production of positive electrode plate
As shown in FIG. 16, a 5 μm-thick Al vapor-deposited film 1602 was formed at the same position on both sides of a 20 μm-thick hoop-shaped polypropylene sheet 1601, leaving the exposed portions of the polypropylene sheet 10 mm or more in front, rear, left and right. . The Al deposited film 1602 was 426 mm long and 48 mm wide.
[0090]
Next, as shown in FIG. 17, a cathode material paste 1701 prepared in the same manner as in Example 1 was applied to the same position on both surfaces of the polypropylene sheet 1601 one by one. At this time, an exposed portion 1702 of the Al-deposited film to which the positive electrode material paste was not applied was left at one end of the Al-deposited film 1602 having a width of 5 mm. The exposed portion 1702 of the Al vapor-deposited film was provided at the same position on both surfaces of the polypropylene sheet.
[0091]
As in Example 1, the entire thickness including the dried coating film and the positive electrode current collector was 300 μm, and the entire thickness was rolled to 180 μm to obtain a positive electrode having a positive electrode active material portion. I got a board hoop. The positive electrode plate hoop was slit at a portion where no Al vapor-deposited film was formed to obtain a positive electrode plate as shown in FIG. The length of the positive electrode plate is 428 mm and the width is 50 mm. A 75 mm long, 3 mm wide positive electrode lead 1816 was fixed to the exposed portion 1702 of the 5 mm wide Al vapor-deposited film provided on both surfaces of the positive electrode current collector with a conductive adhesive, and their free ends were welded to each other. . The adhesive fixing portion of the positive electrode lead 1816 was covered with an insulating tape. At the end of the positive electrode plate having a width of 1 mm along the longitudinal direction, there is no Al vapor-deposited film, and the positive electrode active material portion is directly carried on the polypropylene sheet.
[0092]
(Ii) Preparation of negative electrode plate
The negative electrode plate was manufactured by slitting a negative electrode plate hoop manufactured in the same manner as in Example 1 to a size larger than the positive electrode plate. The structure and dimensions of the negative electrode plate are the same as in Example 1.
[0093]
(Iii) Assembly process of cylindrical battery
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 prepared above are opposed to each other in a layout as shown in FIG. 5 via a separator made of a microporous polyethylene film, and are spirally wound to form an electrode plate group. Was configured. Then, a battery of Example 4 similar to that of Example 1 was assembled except that this electrode group was used.
[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 no conductive burrs are generated and no short circuit is caused by the burrs.
[0095]
<< Example 5 >>
One example of the fifth embodiment will be described.
(I) Production of positive electrode plate
The same positive electrode material paste as prepared in Example 1 was applied to the entire surface on both sides of the same positive electrode current collector used in Example 1.
[0096]
As in Example 1, the entire thickness including the dried coating film and the positive electrode current collector was 300 μm, and the entire thickness was rolled to 180 μm to obtain a positive electrode having a positive electrode active material portion. I got a board hoop. The positive electrode plate hoop is slit into a width of 50 mm and a length of 428 mm, and both ends having a width of 2 mm along the longitudinal direction are immersed in a dispersion of polyethylene powder (melting point: about 100 ° C.), dried, and adhered to both ends. The polyethylene powder thus obtained was melted to form a polyethylene coating.
The same positive electrode lead as in Example 1 was provided on the exposed portion of the positive electrode current collector formed by peeling off a part of the positive electrode active material portion with a width of 5 mm.
[0097]
(Ii) Preparation of negative electrode plate
The negative electrode plate was manufactured by slitting a negative electrode plate hoop manufactured in the same manner as in Example 1 to a size larger than the positive electrode plate. The structure and dimensions of the negative electrode plate are the same as in Example 1.
[0098]
(Iii) Assembly process of cylindrical battery
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 above are opposed to each other in the arrangement shown in FIG. 6 via a separator made of a microporous polyethylene film, and are spirally wound to form an electrode plate group. Was configured. Then, a battery of Example 5 similar to that of Example 1 was assembled except that this electrode plate group was used.
[0099]
In the battery of Example 5, even if burrs are generated at the time of slitting the positive electrode plate, a short circuit between the burrs and the negative electrode active material portion is prevented by the polyethylene coating provided on the end of the positive electrode plate.
[0100]
<< Comparative Example 1 >>
A positive electrode plate hoop similar to that in Example 5 was produced, and this was slit into 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 coating on both ends along the longitudinal direction, and was the same as that of Example 5 in a cylindrical lithium having a diameter of 18 mm, a height of 65 mm, and a design capacity of 1400 mAh. An ion secondary battery was assembled.
[0101]
[Evaluation]
The batteries of Examples 1 to 5 and Comparative Example 1 were evaluated according to the following procedure.
(I) 100 batteries were prepared and charged at 500 mA until the battery voltage reached an overcharged state of 4.4 V.
(Ii) The overcharged battery was crushed down with a flat plate until its voltage began to drop.
(Iii) The number of batteries in which the temperature increased after the crush and the safety valve was activated by gas generation was examined.
[0102]
The results are shown below.
Example 1: The number of batteries for which the safety valve was activated was 0 out of 100 batteries.
Example 2: The number of batteries for which the safety valve was activated was 0 out of 100 batteries.
Example 3: The number of batteries for which the safety valve was activated was 0 out of 100 batteries.
Example 4: The number of batteries for which the safety valve was activated was 0 out of 100 batteries.
Example 5: The number of batteries for which the safety valve was activated was 0 out of 100 batteries.
Comparative Example 1: The number of batteries for which the safety valve was activated was 26 out of 100 batteries.
[0103]
【The invention's effect】
As described above, according to the lithium ion secondary battery of the present invention, it is possible to prevent burrs from being generated at the time of slitting the positive electrode current collector, and even if burrs occur, short-circuit between the burrs and the negative electrode active material portion. Is prevented.
[Brief description of the drawings]
FIG. 1 is a view conceptually showing 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 Embodiment 1 of the present invention.
FIG. 2 is a view conceptually showing an example of a cross section perpendicular to the longitudinal direction of a positive electrode plate, a negative electrode plate, and a separator in a conventional electrode plate group.
FIG. 3 is a view 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 Embodiment 2 of the present invention.
FIG. 4 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 Embodiment 3 of the present invention.
FIG. 5 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 Embodiment 4 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 Embodiment 5 of the present invention.
FIG. 7 is a longitudinal sectional view of the lithium ion secondary battery of Example 1 of the present invention.
FIG. 8 is a top view of the positive electrode current collector for describing a manufacturing process of the positive electrode plate according to the first embodiment of the present invention.
FIG. 9 is another top view of the positive electrode current collector for describing the manufacturing process of the positive electrode plate according to Example 1 of the present 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 explaining a manufacturing process of a positive electrode plate according to Example 2 of the present invention.
FIG. 12 is another top view of the positive electrode current collector for describing the manufacturing process of the positive electrode plate according to the second embodiment of the present 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 describing a manufacturing process of a positive electrode plate according to Example 3 of the present invention.
FIG. 15 is a front view of a positive electrode plate according to Example 3 of the present invention.
FIG. 16 is a top view of a positive electrode current collector for describing a manufacturing process of a positive electrode plate according to Example 4 of the present invention.
FIG. 17 is another top view of the positive electrode current collector for describing the manufacturing process of the positive electrode plate according to Example 4 of the present 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 electrode current collector
111a, b End of positive electrode current collector
112 Positive electrode active material
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 section
122a, b End of negative electrode active material part
130 separator
210 Positive electrode plate
211 Positive electrode current collector
212 Positive electrode active material section
220 negative electrode plate
221 Negative electrode current collector
222 negative electrode active material section
230 separator
211a, b End of positive electrode current collector
222a, b End of negative electrode active material part
310 Positive electrode plate
311 Positive electrode current collector
311a, b End of positive electrode current collector
312 Positive electrode active material section
312a, b End of positive electrode active material part
313 Insulation material section
320 negative electrode plate
321 Negative electrode current collector
322 Negative electrode active material section
330 separator
410 Positive electrode plate
411 Positive electrode current collector
411a, b End of positive electrode current collector
412 Positive electrode active material section
412a, b End of positive electrode active material part
413 Insulating material
420 negative electrode plate
421 Negative electrode current collector
422 negative electrode active material section
422a, b Ends of negative electrode active material part
430 separator
510 positive plate
511 Positive electrode current collector
511a, b Ends of positive electrode current collector
511x insulation sheet
511x 'Exposed part of insulating sheet
511y conductive layer
512 Positive electrode active material section
520 negative electrode plate
521 Negative electrode current collector
522 Negative electrode active material section
530 separator
610 Positive electrode plate
611 positive electrode current collector
612 Positive electrode active material section
613 Insulation material
620 negative electrode plate
621 Negative electrode current collector
622 Negative electrode active material section
630 separator
708 Positive electrode plate
708a positive electrode current collector
708b Positive electrode active material section
709 negative electrode plate
709a Negative electrode current collector
709b Negative electrode active material part
710 separator
711 Electrode group
712 Battery container
713 Battery Can
714 sealing plate
715 Insulation packing
716 Positive electrode lead
717 Negative electrode lead
718 Upper insulating plate
719 Lower insulating plate
801 cathode material paste
802, 802 'Inactive material paste
1002 Positive electrode active material section
1003 Inactive material section
1101 Aluminum foil
1102 Polypropylene film
1201 cathode material paste
1302 Positive electrode active material section
1316 Positive electrode lead
1401 positive electrode current collector
1402 Positive electrode material paste
1501 Positive electrode active material section
1509 Insulation tape
1516 Positive electrode lead
1601 Polypropylene sheet
1602 Al deposited film
1701 Positive electrode material paste
1702 Exposed part of Al deposited film
1816 positive electrode lead

Claims (15)

（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。(A) a positive electrode plate including a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion includes a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(B) a negative electrode plate including a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate,
(D) an electrolytic solution, and (e) a lithium ion secondary battery including a battery container containing the positive electrode plate, the negative electrode plate, the separator, and the electrolytic solution,
The positive electrode plate and the negative electrode plate are wound therebetween with the separator interposed therebetween to form an electrode plate group, and in the electrode plate group, along the longitudinal direction of the positive electrode current collector. A lithium ion secondary battery in which both ends are located outside both ends along the longitudinal direction of the negative electrode active material part. 前記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請求項１記載のリチウムイオン二次電池。2. The lithium ion secondary battery according to claim 1, wherein non-active material portions that do not occlude or release lithium ions by charging and discharging are provided at both ends of the positive electrode active material portion along the longitudinal direction. 前記非活物質部は、絶縁材料からなる請求項２記載のリチウムイオン二次電池。3. The lithium ion secondary battery according to claim 2, wherein the non-active material portion is made of an insulating material. 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、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請求項１記載のリチウムイオン二次電池。2. The lithium ion secondary battery according to claim 1, wherein, in the electrode plate group, both ends along the longitudinal direction of the negative electrode active material portion are located outside both ends along the longitudinal direction of the positive electrode active material portion. 3. （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。(A) a positive electrode plate including a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion includes a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(B) a negative electrode plate including a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate,
(D) an electrolytic solution, and (e) a lithium ion secondary battery including a battery container containing the positive electrode plate, the negative electrode plate, the separator, and the electrolytic solution,
The positive electrode plate and the negative electrode plate constitute an electrode group by being wound therebetween with the separator interposed therebetween, and in the electrode group, both ends along the longitudinal direction of the positive electrode active material portion. The lithium ion secondary battery in which the portion is located outside both ends along the longitudinal direction of the positive electrode current collector. 前記正極集電体の長手方向に沿う両端部には、それぞれ前記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請求項５記載のリチウムイオン二次電池。The lithium ion secondary battery according to claim 5, wherein insulating material portions extending in a surface direction of the positive electrode current collector are disposed at both ends of the positive electrode current collector along the longitudinal direction. 前記絶縁材料部は、前記正極集電体の長手方向に沿う端部の端面に接続されている請求項６記載のリチウムイオン二次電池。7. The lithium ion secondary battery according to claim 6, wherein the insulating material portion is connected to an end face of an end portion of the positive electrode current collector along a longitudinal direction. 前記絶縁材料部は、ポリプロピレン、ポリエチレン、ポリフッ化ビニリデンおよびポリエチレンテレフタレートよりなる群から選ばれる少なくとも１種からなる請求項６記載のリチウムイオン二次電池。7. The lithium ion secondary battery according to claim 6, wherein the insulating material portion is made of at least one selected from the group consisting of polypropylene, polyethylene, polyvinylidene fluoride, and polyethylene terephthalate. 前記正極集電体は、前記正極活物質部により完全に覆われている請求項５記載のリチウムイオン二次電池。The lithium ion secondary battery according to claim 5, wherein the positive electrode current collector is completely covered by the positive electrode active material part. 前記正極集電体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請求項５記載のリチウムイオン二次電池。The lithium ion secondary battery according to claim 5, wherein both end portions along the longitudinal direction of the positive electrode current collector are respectively coated with an insulating material. 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、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請求項５記載のリチウムイオン二次電池。6. The lithium ion secondary battery according to claim 5, wherein, in the electrode plate group, both ends along the longitudinal direction of the negative electrode active material portion are located outside both ends along the longitudinal direction of the positive electrode active material portion. 7. （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。(A) a positive electrode plate including a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion includes a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(B) a negative electrode plate including a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate,
(D) an electrolytic solution, and (e) a lithium ion secondary battery including a battery container containing the positive electrode plate, the negative electrode plate, the separator, and the electrolytic solution,
The positive electrode plate and the negative electrode plate are wound therebetween with the separator interposed therebetween to form an electrode plate group, and in the electrode plate group, along the longitudinal direction of the negative electrode active material portion. Both ends are located outside both ends along the longitudinal direction of the positive electrode current collector, and both ends along the longitudinal direction of the positive electrode current collector are both ends along the longitudinal direction of the positive electrode active material part. A lithium ion secondary battery in which an 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. （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。(A) a positive electrode plate including a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion includes a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(B) a negative electrode plate including a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate,
(D) an electrolytic solution, and (e) a lithium ion secondary battery including a battery container containing the positive electrode plate, the negative electrode plate, the separator, and the electrolytic solution,
The positive electrode plate and the negative electrode plate constitute an electrode plate group by being wound therebetween with the separator therebetween, and the positive electrode current collector is formed on an insulating sheet and both surfaces thereof, respectively. A lithium ion secondary battery comprising a conductive layer, and exposed portions of the insulating sheet are provided at both ends along the longitudinal direction of the insulating sheet. （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。(A) a positive electrode plate including a positive electrode active material portion and a positive electrode current collector supporting the positive electrode active material portion, wherein the positive electrode active material portion includes a positive electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(B) a negative electrode plate including a negative electrode active material portion and a negative electrode current collector supporting the negative electrode active material portion, wherein the negative electrode active material portion includes a negative electrode active material capable of occluding or releasing lithium ions by charging and discharging;
(C) a separator interposed between the positive electrode plate and the negative electrode plate,
(D) an electrolytic solution, and (e) a lithium ion secondary battery including a battery container containing the positive electrode plate, the negative electrode plate, the separator, and the electrolytic solution,
The positive electrode plate and the negative electrode plate are wound therebetween with the separator interposed therebetween to form an electrode plate group, and both ends along the longitudinal direction of the positive electrode plate are each formed of an insulating material. Lithium-ion secondary battery covered. 前記絶縁材料は、ポリプロピレン、ポリエチレン、ポリフッ化ビニリデンおよびポリエチレンテレフタレートよりなる群から選ばれる少なくとも１種からなる請求項１４記載のリチウムイオン二次電池。The lithium-ion secondary battery according to claim 14, wherein the insulating material is at least one selected from the group consisting of polypropylene, polyethylene, polyvinylidene fluoride, and polyethylene terephthalate.
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