JP2004311146A

JP2004311146A - Method for manufacturing electrode plate of battery

Info

Publication number: JP2004311146A
Application number: JP2003101282A
Authority: JP
Inventors: Hideo Kaiya; 英男海谷; Fumio Oo; 文夫大尾; Masaru Nishimura; 賢西村; Munehisa Ikoma; 宗久生駒
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-04-04
Filing date: 2003-04-04
Publication date: 2004-11-04
Anticipated expiration: 2023-04-04
Also published as: JP4779287B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode plate for a battery enhancing the weight energy density of the battery and enhancing a battery protection function. <P>SOLUTION: A positive plate 1 and/or a negative plate are/is manufactured by joining a PTC element 4 to a positive current collector 10 or a negative current collector manufactured by forming a metallic film on a resin film, applying a positive active material layer 11 or a negative active material layer to the positive current collector 10 or the negative current collector, and forming an insulating cover 7 on the PTC element 4. The electrode plate manufactured like this is light and the battery with high weight energy density is constituted, and since the PTC element is fit to the electrode plate, the raised temperature of the electrode plate is rapidly transmitted to the PTC element 4, and the PTC element 4 can be operated without delaying. Double safety functions are constituted by current-shutting off by melting the resin film caused by an abnormal temperature rise together with the operation of the PTC element 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電池を過充電や短絡等から保護するＰＴＣ素子を備えた電池極板の製造方法に関するものである。
【０００２】
【従来の技術】
携帯電話機やＰＤＡなどの携帯電子機器の小型化あるいは薄型化、更には高機能化の進展は著しく、それに対応してその電源となる電池に小型、薄型で軽量化、高容量化が要求されている。小型で高容量化を可能にする電池としてリチウムイオン二次電池が有効であり、中でも扁平角形の電池は小型化、薄型化に好適であり、繰り返し使用ができる二次電池として携帯電子機器への適用が増加している。
【０００３】
前記リチウムイオン二次電池はエネルギー密度が高く、電解液として可燃性の有機溶媒を用いているため、安全性への配慮が重要となる。何らかの原因によって異常が生じたときにも人体や機器に損傷を与えないように安全性を確保する必要がある。例えば、電池の正極端子と負極端子との間が何らかの原因によって短絡した場合、エネルギー密度の高い電池では過大な短絡電流が流れ、内部抵抗によってジュール熱が発生して電池は温度上昇する。
【０００４】
電池が高温状態に陥る原因は上記外部短絡だけでなく、二次電池を過充電した場合や、電池を装填した携帯電子機器を暖房機の傍らに置いたり、炎天下に駐車した車内に放置した場合なども該当する。
【０００５】
電池が異常な状態に陥る原因は、電気的、機械的、熱的など種々の要因が考えられ、リチウムイオン二次電池をはじめとする非水電解質二次電池では、電池が異常状態に陥ることを防止すると共に、異常状態に陥った場合にも危険な状態にならないようにする機能が設けられる。電池自体の機能として、極板の活物質や電解液が過剰な反応を起こしにくいように工夫され、セパレータとして用いられるポリオレフィン系微多孔膜は異常な高温になると軟化して細孔が塞がれることによるシャットダウン機能が備わっている。また、リチウムイオン二次電池では、封口部に入出力回路と直列に接続したＰＴＣ（ＰｏｓｉｔｉｖｅＴｈｅｒｍａｌＣｏｅｆｆｃｉｅｎｔ）素子を配設して、外部短絡による過大電流を制限する保護機能が設けられている。電池内に前記ＰＴＣ素子が設けられていない電池では、外付けの回路部品としてＰＴＣ素子が配線接続され、二次電池と共にパックケース内に収容して電池パックの形態に構成されるのが一般的である。
【０００６】
ＰＴＣ素子を電池温度により速やかに作動させるためには、電池内部とＰＴＣ素子とが確実に熱結合されている必要があるが、ＰＴＣ素子を電池の外部に設けたり封口板に設けた場合には、電池内部の温度上昇がＰＴＣ素子に伝熱するまでに時間的な遅れが生じ、電池内部の異常温度上昇をＰＴＣ素子が確実に検出できない問題があった。この問題を解決すべく電池の外装体内に極板に接してＰＴＣ素子を配置する薄型電池が提案されている（特許文献１参照）。この薄型電池はＰＴＣ素子による温度感知を確実にすると共に、外装体をラミネートシートにより形成して薄型化した電池におけるＰＴＣ素子の配設位置を確保している。
【０００７】
また、リチウムイオン二次電池はニッケル−水素蓄電池やニッケル−カドミウム蓄電池などに比して軽量であり、重量エネルギー密度に優れた電池として携帯電子機器の電源として好適であるが、携帯電子機器の小型軽量化に伴って更なる軽量化が要求されている。この軽量化を実現すべく電池極板を構成する集電体を金属箔でなく樹脂フィルムの表面に金属薄膜を形成したものとし、この集電体を用いた極板とこの極板を用いた電池が提案されている（特許文献２参照）。
【０００８】
また、上記樹脂フィルムを基材とする集電体を用いた極板において、樹脂フィルムを電池が異常発熱したときに溶融する低融点樹脂で形成すると、電池が異常発熱したとき樹脂フィルムが溶融し、集電体としての機能が低下して、ほぼ絶縁体に近い状態となって異常発熱の原因となっている電流が遮断され、異常発熱に伴う不具合の発生を防止する機能を備えた二次電池が提案されている（特許文献３参照）。
【０００９】
【特許文献１】
特開２００２−３２４５４２号公報（第２〜３頁、図４）
【００１０】
【特許文献２】
特開２０００−３５７５１７号公報（第２〜３頁、図２）
【００１１】
【特許文献３】
特開平１１−１０２７１１号公報（第２〜３頁、図１）
【００１２】
【発明が解決しようとする課題】
しかしながら、上記特許文献１に示された構成のように極板にＰＴＣ素子を取付けると、ＰＴＣ素子は電解液中に浸されることになり、ＰＴＣ素子を構成する導電性ポリマに電解液が浸透して腐食劣化する問題点がある。
【００１３】
また、主として携帯電子機器の電源として用いられる電池は、小型薄型であることは勿論のこと軽量化が要求される。また、携帯電子機器は多様な環境下に曝されるため、高温や外部短絡等を受けやすい状態に陥る度合いも多くなる。従って、主たる使用目的が携帯電子機器の電源となる電池は、軽量化を図ると同時に、外部短絡や過充電などの電気的要因や、高温環境に曝されたときに不具合を生じさせない確実な電池保護機能を設けることが要求される。
【００１４】
本発明が目的とするところは、電池の軽量化及び確実な電池保護機能を実現するＰＴＣ素子を備えた電池極板の製造方法を提供することにある。
【００１５】
【課題を解決するための手段】
上記目的を達成するための本願第１発明に係る電池極板の製造方法は、正極板又は負極板を形成するいずれか一方の集電体上の所要部位に一方電極を接合してＰＴＣ素子を取り付け、集電体の前記ＰＴＣ素子の取り付け部位を除く部位に活物質層を塗着し、他方の集電体上に活物質層を塗着して正極板及び負極板を形成し、前記ＰＴＣ素子を被覆して耐電解液性の絶縁材料を塗布し、正極リード、負極のリードの一端を前記ＰＴＣ素子の他方電極とＰＴＣ素子が接合されていない極板の集電体にそれぞれ接合することを特徴とする。
【００１６】
上記電池極板の製造方法によれば、正極板又は負極板にＰＴＣ素子を配設して電池極板を製造することができるので、この電池極板を用いて電池を構成すると、電池極板の温度上昇は速やかにＰＴＣ素子に伝熱し、極板の温度が熱暴走に至る以前に電流回路を遮断して電池が高温状態になることを防止することができる。また、ＰＴＣ素子は耐電解液性の絶縁材料によって被覆されるので、電解液によってＰＴＣ素子が劣化することを防止することができる。
【００１７】
また、本願第２発明に係る電池極板の製造方法は、正極板及び負極板を形成する少なくとも一方の集電体を樹脂フィルムの表面に導電性膜を形成して構成し、正極板又は負極板を形成するいずれか一方の集電体上の所要部位に一方電極を接合してＰＴＣ素子を取り付け、集電体の前記ＰＴＣ素子の取り付け部位を除く部位に活物質層を塗着し、他方の集電体上に活物質層を塗着して正極板及び負極板を形成し、前記ＰＴＣ素子を被覆して耐電解液性の絶縁材料を塗布し、正極リード、負極リードの一端を前記ＰＴＣ素子の他方の電極とＰＴＣ素子が接合されていない極板の集電体にそれぞれ接合することを特徴とする。
【００１８】
上記電池極板の製造方法によれば、正極板または負極板にＰＴＣ素子を配設して電池極板を製造することができるので、この電池極板を用いて電池を構成すると、電池極板の温度上昇は速やかにＰＴＣ素子に伝熱し、極板の温度が熱暴走に至る以前に電流回路を遮断して電池が熱暴走に至ることを防止することができる。また、ＰＴＣ素子は絶縁材料によって被覆されているので、電解液によってＰＴＣ素子が劣化することを防止することができる。このＰＴＣ素子が万が一正常に作動しなかったとき、温度上昇が進行するが、集電体を構成する樹脂フィルムが溶融するので、電流回路が遮断される。即ち、二重の電池保護機能を備えた電池極板を構成することができる。また、集電体を樹脂フィルムを基材として構成することができるので、電池極板としての軽量化を図ることができ、携帯電子機器等の電源として好適な重量エネルギー密度の高い電池を得ることができる。
【００１９】
上記製造方法において、絶縁材料をＰＴＣ素子の他方電極上を除く部位に塗布した後、他方電極上にそれを被覆する正極リード又は負極リードの一端を接合することにより、ＰＴＣ素子は絶縁材料と正極リード又は負極リードの一端とによって被覆されるので、ＰＴＣ素子は電解液に曝されることがなく、電解液によるＰＴＣ素子の腐食劣化を防ぐことができる。
【００２０】
また、ＰＴＣ素子の他方電極上に正極リード又は負極リードの一端を接合した後、ＰＴＣ素子及び正極リード又は負極リードの一端を被覆して絶縁材料を塗布することにより、ＰＴＣ素子はリードの一端を含めて絶縁材料によって被覆されるので、ＰＴＣ素子は電解液に曝されることがなく、電解液によるＰＴＣ素子の腐食劣化を防ぐことができる。
【００２１】
また、正極板及び負極板を両極板の間にセパレータを配して巻回することにより、対極面積の大きい電池極板を容易に形成することができ、円筒形あるいは扁平角形の電池に適用するのに好適な電池極板が得られる。
【００２２】
また、ＰＴＣ素子を巻回される正極板または負極板の巻き始め側となる端部に取り付けることにより、ＰＴＣ素子は巻回された電池極板の中心部に配設された状態となり、電池極板の温度上昇が速やかにＰＴＣ素子に伝熱して、遅延なく保護動作を作動させることができる。
【００２３】
また、ＰＴＣ素子を巻回される正極板又は負極板の内面側となる部位に取り付けることにより、極板の温度が外部放散される以前にＰＴＣ素子に伝熱するので、温度上昇に伴うＰＴＣ素子の作動が確実になされる。
【００２４】
【発明の実施の形態】
以下、添付図面を参照して本発明の実施の形態について説明し、本発明の理解に供する。尚、以下に示す実施の形態は本発明を具体化した一例であって、本発明の技術的範囲を限定するものではない。
【００２５】
本実施の形態は、主として携帯電子機器の電池電源に適用すべく軽量化を図ると共に、外部短絡や過充電あるいは高温状態などから電池を保護する機能を備えたリチウムイオン二次電池を実現するための電池極板の製造方法について示すものである。
【００２６】
図１は、実施形態に係る電池極板の製造方法によって製造された電池極板Ａを構成する正極板１を展開状態で示すものである。正極板１は、図１（ｃ）にＢ−Ｂ線矢視断面として示すように、正極集電体１０の両面に正極活物質層１１を所定厚さに塗着して形成されている。前記正極集電体１０は、図１（ｄ）に拡大図示するように、ポリオレフィン樹脂を用いた樹脂フィルム３０の両面に金属薄膜（ここではアルミニウム）３１をスパッタリング法、蒸着法等の手段により成膜したものである。尚、樹脂フィルム３０の両面に形成される金属薄膜３１は、樹脂フィルム３０に形成されたスルーホールあるいは樹脂フィルム３０に含ませた金属粉等の導電材料により電気的に導通した状態に形成される。また、正極板１の一端側にはＰＴＣ素子４が接合されている。
【００２７】
図２は、実施形態に係る電池極板の製造方法によって製造された電池極板Ａを構成する負極板２を展開状態で示すものである。負極板２は、図２（ｂ）にＣ−Ｃ線矢視断面として示すように、負極集電体２０の両面に負極活物質層２１を所定厚さに塗着して形成されている。前記負極集電体２０は、ポリオレフィン樹脂を用いた樹脂フィルム４０の両面に金属薄膜（ここでは銅）４１をスパッタリング法、蒸着法等の手段により成膜したものである。負極板２の他端側には、負極集電体２０に一端を接合して負極リード６が取り付けられている。
【００２８】
尚、電池の軽量化を図るためには、正極板１及び負極板２は上記構成が好ましいが、正極板１又は負極板２のいずれか一方の集電体は、アルミニウム箔又は銅箔によって形成することもできる。
【００２９】
上記電池極板Ａは、図３に示す製造手順により製造される。まず、図３（ａ）に示すように、樹脂フィルム３０の両面に金属薄膜３１を成膜して正極集電体１０を形成する。このとき、一方面の金属薄膜３１は樹脂フィルム３０の一端側に、ＰＴＣ接合部３１ａを突出形成することにより、一端側に逆コの字状に金属薄膜３１のない部位が形成される。ここでは、樹脂フィルム３０として厚さ１０μｍのポリエチレンテレフタレートフィルム上に、金属薄膜３１として０．５μｍ厚さのアルミニウム層を真空蒸着により形成した。
【００３０】
前記ＰＴＣ接合部３１ａには、図３（ｂ）に示すように、厚さ３０μｍのシート状に形成されたＰＴＣ素子４をその一方電極で接合する。次に、接合されたＰＴＣ素子４の周囲に、図３（ｃ）に示すように、耐電解液性の絶縁材料を塗布して絶縁被覆７を形成する。次いで、図３（ｄ）に示すように、ＰＴＣ接合部３１ａを除く金属薄膜３１上に正極活物質層１１を所定厚さに塗着する。更に、ＰＴＣ素子４の他方電極に、図３（ｅ）に示すように、ＰＴＣ素子４の他方電極を覆って正極リード５の一端を接合する。ここでは、前記正極活物質層１１として、正極活物質とするＬｉＣｏＯ、導電材とするアセチレンブラック、結着剤とするフッ化ビニリデンを重量比で９４：４：２の割合で混合してペースト化したものを前記正極集電体１０の両面にそれぞれ７０μｍの厚さに塗工した。また、絶縁被覆７としてポリエチレン、正極リード５としてアルミニウム箔を用いた。
【００３１】
前記絶縁被覆７の形成は、図４（ａ）に示すように、ＰＴＣ素子４の他方電極に正極リード５を接合した後、図４（ｂ）に示すように、ＰＴＣ素子４の全体及び正極リード５の接合端側を包み込んで耐電解液性の絶縁材料を塗布するようにすると、ＰＴＣ素子４をより確実に電解液から隔離することができる。但し、図４（ｃ）に示すように、絶縁被覆７を正極活物質層１１の厚さを越えないように形成することが好ましく、電池極板Ａとして巻回したときに隙間を発生させることなく、密に巻回することができる。
【００３２】
負極板２は、樹脂フィルム４０の両面に金属薄膜４１を形成して負極集電体２０を形成し、負極リード６を接合する部位を除く金属薄膜４１上に負極活物質層２１を塗着形成し、負極活物質層２１が形成されずに負極集電体２０が露出した部位に負極リード６の一端を接合して形成する。ここでは、樹脂フィルム４０として厚さ１０μｍのポリエチレンテレフタレートフィルムを用いて、その上に金属薄膜４１として０．５μｍ厚さの銅層を真空蒸着により形成して負極集電体２０を形成した。この負極集電体２０の両面には、グラファイトに結着剤としてフッ化ビニリデンを重量比で９５：５の割合で混合してペースト化したものを負極活物質層２１として７０μｍの厚さに塗工した。また、負極リード６として、銅箔を用いた。
【００３３】
上記構成になる正極板１と負極板２とは、それらの間にポリエチレン微多孔性膜（ここでは、厚さ２０μｍ）により形成されたセパレータ３を介在させ、正極板１はＰＴＣ接合部３１ａが形成された一端側を巻き始め側とし、負極板２は負極リード６が接合されていない一端側を巻き始め側として巻回し、図５に示すように、扁平な有底角筒に形成された電池缶１２に収容することができる扁平な電池極板Ａに形成する。
【００３４】
このようにＰＴＣ素子４を接合した側を巻き始め側として巻回することにより、ＰＴＣ素子４は電池極板Ａの略中心部分に配設されるので、電池極板Ａの温度が伝熱されやすくなり、電池極板Ａの温度上昇を速やかに検出することができる。ＰＴＣ素子４の配設位置は、正極板１または負極板２の端部とするのが極板の反応面積を減少させることがないので、上記構成のように正極板１の端部に配設し、ＰＴＣ素子４の配設端側を巻き始めとして巻回すると、極板の温度上昇を速やかに検出することができる。逆にＰＴＣ素子４の配設端側を巻き終わり側として巻回すると、ＰＴＣ素子４を外側に配した電池極板Ａに構成され、電池が高温環境に曝された状態を検知するのに好適なものとなるが、極板が温度上昇した状態を検知するのに遅れが生じる恐れがあるので、巻回される内面側に配設するのが好ましい。
【００３５】
上記電池極板Ａは、図６に示すように、扁平な有底角筒に形成された電池缶１２内に挿入され、電池極板Ａから引き出されている正極リード５は封口板１３にそれと絶縁して取り付けられた正極端子１４に接合され、負極リード６は封口板１３に接合される。リード接合がなされた封口板１３は電池缶１２の開口端に溶接され、電池缶１２内が封口される。この後、封口板１３に形成された注液口１５から電池缶１２内に所定量の電解液が注入され、注液口１５は封栓１６により閉じられ、扁平角形の二次電池Ｂに形成される。前記電解液として、ここでは、溶媒としてエチレンカーボネートとジエチレンカーボネートとを等量混合したものに、溶質として６フッ化リン酸ナトリウムを１モル／ｌの濃度で溶解したものを用いた。
【００３６】
上記構成に用いられるＰＴＣ素子４は、炭素粒子等の導電性材料と高分子材料とを混合した導電性ポリマをシート状に形成し、その両面に金属箔からなる電極板を接合して所定形状サイズに切り出されたものである。温度が低い状態では導電性材料による導電パスにより両電極間の抵抗値はｍΩ台の低い状態にあるので、電池としての内部抵抗を増加させることは僅少である。短絡電流等の過大電流がＰＴＣ素子４に流れると、過大電流に伴う自己発熱により温度上昇し、ポリマの熱膨張により導電性材料による導電パスが切断されていき、緩やかな抵抗値の上昇を示し、所定温度に達したとき一気に抵抗値が増加するので、過大電流は制限されて短絡等による温度上昇は抑止される。この温度上昇に伴う抵抗値の増加は、過充電による温度上昇や周囲温度の温度上昇によっても生じるので、過充電状態の継続を阻止し、高温状態での電池使用を停止させることができる。
【００３７】
上記構成において、電池極板Ａ内に配設されたＰＴＣ素子４は電池極板Ａに充填される電解液中に浸された状態になるが、絶縁被覆７によってＰＴＣ素子４の導電性ポリマの部分は電解液と隔離されるので、電解液によって導電性ポリマが劣化してＰＴＣ素子４としての機能が低下することはない。
【００３８】
また、上記構成になる二次電池Ｂは、図７に回路図として示すように、正極回路と直列にＰＴＣ素子４が接続され、ＰＴＣ素子４は電池極板Ａ内に配設されているので、正極端子１４と負極端子（封口板１３及び電池缶１２）との間が何らかの原因によって短絡された外部短絡が生じた場合に、短絡による過大電流によりＰＴＣ素子４は温度上昇し、所定のトリップ温度を越えたとき抵抗値を急増させるので、短絡電流は制限されて電池が高温化することを防止する。また、充電回路等の故障によって過充電状態に陥ったとき、電池極板Ａの温度上昇は速やかにＰＴＣ素子４に伝熱するので、その温度が所定のトリップ温度を越えたとき、ＰＴＣ素子４は抵抗値を急増させるので、充電電流は制限されて過充電状態の継続による電池の破損が防止される。
【００３９】
ＰＴＣ素子４が抵抗値を急増させるトリップ温度は、高分子材料及び添加物の種類や量によって決定され、８０〜１２０℃に設定すると、二次電池Ｂの活物質が熱暴走を起こす１５０〜１８０℃に至る以前に電池回路を停止状態にすることができる。このＰＴＣ素子４による電池回路を停止させる動作が正常になされなかった場合、二次電池Ｂは熱暴走に至る恐れがあるが、本実施形態に係る電池極板Ａは正極及び／又は負極の集電体が樹脂フィルム３０，４０を基材として構成されているので、二重の電池保護機能が構成される。即ち、樹脂フィルム３０，４０として適用したポリオレフィン樹脂の融点が１３０〜１７０℃であるため、万が一ＰＴＣ素子４が正常に動作しなかった場合に、温度上昇が進行して電池極板Ａの温度が樹脂フィルム３０，４０の溶融温度にまで上昇すると、樹脂フィルム３０，４０の溶融により電池極板Ａの電流回路が遮断され、溶融熱により異常発熱が沈静化されるので、二次電池Ｂが破裂や発火に至ることが防止される。
【００４０】
次に、上記のように電池極板にＰＴＣ素子４を取り付けた構成の有効性について、実施例構成の二次電池と比較対象とする比較例構成の二次電池について短絡テストを実施した結果を以下に示す。
【００４１】
実施例とする電池極板Ａの正極板１及び負極板２は、上記実施形態に具体例として示した材料構成のものを幅５０ｍｍ、長さ２００ｍｍに形成し、正極板１に厚さ３０μｍで２０×２０ｍｍ角のＰＴＣ素子４をその一方電極で正極集電体１０に接合した。
【００４２】
この正極板１と負極板２とを厚さ２０μｍのポリエチレン製微多孔膜に形成したセパレータ３を介して重ね合わせ、実施例とする電池極板Ａは、ＰＴＣ素子４を接合した側を巻き始めとして巻回して電池極板Ａを形成した。
【００４３】
この電池極板Ａを電池缶１２に挿入し、リード接続を行った後、電池缶１２の開口端に封口板１３を溶接して封口し、注液口１５から電解液を注入して封栓１６で注液口１５を封じ、二次電池Ｂに構成した。電解液は上記実施形態に具体例として示した組成のものを使用した。
【００４４】
実施例▲１▼の二次電池Ｂは、ＰＴＣ素子４を被覆する絶縁被覆７として、フッ化ピッチを用いた。
【００４５】
実施例▲２▼の二次電池Ｂは、ＰＴＣ素子４を被覆する絶縁被覆７として、上記実施形態において具体例と示したポリエチレンを用いた。
【００４６】
実施例▲３▼の二次電池Ｂは、ＰＴＣ素子４を被覆する絶縁被覆７として、ポリエチレンテレフタレートを用いた。
【００４７】
比較例▲１▼として、ＰＴＣ素子４に絶縁被覆７を設けないで製作した電池極板を用いて二次電池を製作した。
【００４８】
比較例▲２▼として、ＰＴＣ素子４を設けないで製作した電池極板を用いて二次電池を製作した。
【００４９】
比較例▲３▼として、実施例▲１▼と同一の構成であるが、ＰＴＣ素子４を接合した側を巻き終わり側として巻回した電池極板を用いて二次電池を製作した。
【００５０】
上記実施例▲１▼▲２▼▲３▼及び比較例▲１▼▲２▼▲３▼に示した構成の二次電池をそれぞれ１００個製作し、短絡テストを実施して、３分後、１０分後に二次電池の表面温度が１００℃を越えた割合について検証した。この結果を、表１及び表２に示す。尚、表１は製作した二次電池を常温で３ヶ月保存した後、表２は雰囲気温度が８５℃の環境下で１週間保存した後に、それぞれ短絡テストを実施した場合である。
【００５１】
【表１】

【００５２】
【表２】

上記検証結果からわかるように、ＰＴＣ素子４を設けない場合では、短絡により二次電池は高温状態に陥ることになる。また、ＰＴＣ素子４に絶縁被覆７を設けない場合には、ＰＴＣ素子４が劣化して正常に機能しないと考えられる状態が高い確率で発生している。また、ＰＴＣ素子４を電池極板の外周部位に配設した場合には、短絡による温度上昇を検知するまでに時間を要するものと考えられる状態が見受けられる。これに比して実施例構成では、絶縁被覆７が効果的に作用しており、電解液の影響によってＰＴＣ素子４が劣化することがなく、短絡による温度上昇が確実に抑えられていることがわかる。
【００５３】
上記のような効果が得られる耐電解液性の絶縁被覆７として適用できる材料は、上記実施例に適用した材料の他、下記の材料を用いることができる。
【００５４】
ポリプロピレン、ポリメチルペンテンなどのオレフィン系ポリマー、ポリブチレンテレフタレート、ポリシクロヘキシレンジメチレンテレフタレート、ポリアレレート、ポリカーボネートなどのエステル系ポリマー、ポリエチレンオキシド、ポリプロピレンオキシド、ポリアセタール、ポリフェニレンエーテル、ポリエーテルエーテルケトン、ポリエーテルイミドなどのエーテル系ポリマー、ポリスルホン、ポリエーテルスルホンなどのスルホン系ポリマー、ポリアクリロニトリル、ＡＳ樹脂、ＡＢＳ樹脂などのアクリロニトリル系ポリマー、ポリフェニレンサルファイドなどのチオエーテル系ポリマー、ポリスチレンなどの芳香族ビニル系ポリマー、ポリイミド、アラミド誦しなどの窒素含有ポリマー、ポリ４フッ化エチレン、ポリフッ化ビニリデンなどのフッ化ポリマー、ポリフッ化ビニリデンなどのフッ素ポリマー、ポリメタクリル酸メチルなどのアクリル系ポリマーなどの有機化合物を用いることができる。これらは単独でも２種類以上を組み合わせたコポリマー、ポリマーアロイ、ポリマーブレンドなどとして用いることができる。また、加熱やＵＶ照射により重合固化して得られるポリマーを用いることもできる。また、真空脱気を行って材料中の空気を排除したピッチ、アスファルト等の瀝青剤を用いることもできる。
【００５５】
以上説明した実施形態の構成においては、ＰＴＣ素子４を正極板１に取り付け、正極回路と直列にＰＴＣ素子４が接続されるようにしているが、負極板２にＰＴＣ素子４を取り付け、負極回路と直列にＰＴＣ素子４が接続されるように構成しても、同様の作用効果が得られる。
【００５６】
また、電池極板Ａを適用する二次電池Ｂは、リチウムイオン二次電池に限定されるものではなく、他の種類の電池に同様の構成を適用することもできる。また、二次電池Ｂの外装体は実施形態の構成に示した金属製の電池缶１２に限定されるものではなく、例えば、金属箔を含むラミネートシートを用いて外装体を形成し、電解液としてゲル状のものを用いたリチウムポリマー電池に適用することもできる。リチウムポリマー電池は外装体が樹脂フィルムであるため、ＰＴＣ素子４の取り付け部位がなく、熱伝導性も悪いので、ＰＴＣ素子４は電池パックとして設けることになるが、短絡等の過電流には対応できても過充電や過熱には正常に作動させることが困難であったが、本実施形態に係る電池極板の適用により、過充電や過熱等の温度上昇に正確に対応させることが可能となる。
【００５７】
【発明の効果】
以上説明した通り、本発明に係る製造方法によって製造された電池極板は、極板にＰＴＣ素子が配設されているので、極板の発熱や外部加熱に伴う極板の温度上昇が速やかにＰＴＣ素子に伝熱し、電池が熱暴走に至る以前の温度でＰＴＣ素子が作動し、短絡等の電気的原因による過大電流を制限し、高温状態における電池動作を停止させることができる。このように極板にＰＴＣ素子を配設した場合にＰＴＣ素子は電解液に浸された状態になるが、絶縁材料により被覆されているので、ＰＴＣ素子の劣化を防止して経年変化を生じさせることなくＰＴＣ素子の機能を保つことができる。また、樹脂フィルムを基材として集電体を形成しているので電池極板として軽量化を図ることができ、これを用いた電池は携帯電子機器等の電池電源として軽量化されたものを提供することができる。また、ＰＴＣ素子の作動が正常になされなかった場合においては、温度上昇の進行により樹脂フィルムを基材として形成された集電体が溶融し、電池動作は停止して熱暴走に至る状態は沈静化される。従って、本発明に係る製造方法によって製造された電池極板を用いた電池は、電池自体が二重に安全機能を備えたものに構成することができ、軽量化もあいまって携帯電子機器のように様々な環境下に曝される機器の電池電源として好適なものが得られる。
【図面の簡単な説明】
【図１】実施形態に係る電池極板を構成する正極板を展開状態で示す（ａ）は平面図、（ｂ）（ｃ）は所要部位の断面図、（ｄ）は集電体の構成を示す断面図。
【図２】実施形態に係る電池極板を構成する負極板を展開状態で示す（ａ）は平面図、（ｂ）は断面図。
【図３】正極板を製造する手順を示す平面図。
【図４】絶縁被覆の形成方法の別態様を示す平面図。
【図５】実施形態に係る電池極板の構成を示す斜視図。
【図６】同上電池極板を用いた二次電池の組み立てを説明する斜視図。
【図７】実施形態に係る二次電池の構成を示す回路図。
【符号の説明】
Ａ電池極板
Ｂ二次電池（電池）
１正極板
２負極板
４ＰＴＣ素子
５正極リード
６負極リード
７絶縁被覆
１０正極集電体
１１正極活物質層
１２電池缶
１３封口板
１４正極端子
２０負極集電体
２１負極活物質層
３０、４０樹脂フィルム
３１、４１金属薄膜[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a battery electrode plate provided with a PTC element that protects a battery from overcharge, short circuit, and the like.
[0002]
[Prior art]
Mobile electronic devices such as mobile phones and PDAs have been significantly reduced in size and thickness, and further advanced in functions. In response to this, there has been a demand for smaller, thinner, lighter and higher-capacity batteries as power sources. I have. Lithium-ion secondary batteries are effective as small and high-capacity batteries. Among them, flat-shaped batteries are suitable for miniaturization and thinning. Applications are increasing.
[0003]
Since the lithium ion secondary battery has a high energy density and uses a flammable organic solvent as an electrolyte, it is important to consider safety. It is necessary to ensure safety so as not to damage the human body or equipment even when an abnormality occurs for some reason. For example, if a short circuit occurs between the positive electrode terminal and the negative electrode terminal of a battery for some reason, an excessive short-circuit current flows in a battery having a high energy density, and Joule heat is generated by internal resistance, and the temperature of the battery rises.
[0004]
The cause of the battery falling into a high temperature condition is not only the above-mentioned external short circuit, but also when the secondary battery is overcharged, when the portable electronic device with the battery is placed beside the heater, or left in the car parked under the scorching sun And so on.
[0005]
Various causes such as electrical, mechanical, and thermal can be considered as the cause of the battery being in an abnormal state. For non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, the battery may be in an abnormal state. And a function for preventing a dangerous state from occurring when an abnormal state occurs. As a function of the battery itself, the active material and the electrolyte of the electrode plate are devised so as not to cause an excessive reaction, and the microporous polyolefin-based membrane used as a separator is softened at abnormally high temperatures and the pores are closed. Shutdown function. Further, in the lithium ion secondary battery, a PTC (Positive Thermal Coeffcient) element connected in series to the input / output circuit is provided in the sealing portion to provide a protection function for limiting an excessive current due to an external short circuit. In a battery in which the PTC element is not provided in the battery, a PTC element is generally wired and connected as an external circuit component, and is housed in a pack case together with a secondary battery to be configured in a battery pack form. It is.
[0006]
In order for the PTC element to operate quickly according to the battery temperature, it is necessary that the inside of the battery and the PTC element are thermally coupled reliably. However, when the PTC element is provided outside the battery or provided on the sealing plate, However, there is a time delay until the temperature rise inside the battery is transferred to the PTC element, and there is a problem that the PTC element cannot reliably detect the abnormal temperature rise inside the battery. In order to solve this problem, there has been proposed a thin battery in which a PTC element is disposed in contact with an electrode plate inside a battery exterior (see Patent Document 1). This thin battery ensures temperature sensing by the PTC element, and secures an arrangement position of the PTC element in the thin battery by forming the exterior body with a laminate sheet.
[0007]
Lithium ion secondary batteries are lighter in weight than nickel-hydrogen storage batteries and nickel-cadmium storage batteries, and are suitable as a power source for portable electronic devices as batteries having excellent weight energy density. Along with the weight reduction, further weight reduction is required. In order to realize this weight reduction, the current collector constituting the battery electrode plate is not a metal foil but a metal thin film formed on the surface of a resin film, and the electrode plate using this current collector and this electrode plate are used. A battery has been proposed (see Patent Document 2).
[0008]
Further, in the electrode plate using the current collector having the resin film as a base, if the resin film is formed of a low melting point resin that melts when the battery abnormally generates heat, the resin film melts when the battery abnormally generates heat. The secondary function is equipped with a function to prevent the occurrence of malfunctions caused by abnormal heat generation by interrupting the current that causes abnormal heat generation by reducing the function as a current collector and becoming almost like an insulator. A battery has been proposed (see Patent Document 3).
[0009]
[Patent Document 1]
JP-A-2002-324542 (pages 2-3, FIG. 4)
[0010]
[Patent Document 2]
JP-A-2000-357517 (pages 2-3, FIG. 2)
[0011]
[Patent Document 3]
JP-A-11-102711 (pages 2-3, FIG. 1)
[0012]
[Problems to be solved by the invention]
However, when the PTC element is attached to the electrode plate as in the configuration disclosed in Patent Document 1, the PTC element is immersed in the electrolyte, and the electrolyte penetrates the conductive polymer constituting the PTC element. Corrosion and deterioration.
[0013]
Further, batteries used mainly as power sources for portable electronic devices are required to be small and thin, as well as light in weight. In addition, since the portable electronic device is exposed to various environments, the degree to which the portable electronic device is easily subjected to a high temperature, an external short circuit, and the like increases. Therefore, batteries whose main purpose of use is to supply power to portable electronic devices are not only lightweight, but also reliable batteries that do not cause electrical factors such as external short-circuiting or overcharging, and do not cause problems when exposed to high-temperature environments. It is required to provide a protection function.
[0014]
It is an object of the present invention to provide a method for manufacturing a battery electrode plate provided with a PTC element that realizes a lightweight battery and a reliable battery protection function.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a method for manufacturing a battery electrode plate according to the first invention of the present application is a method of manufacturing a PTC element by joining one electrode to a required portion on one of current collectors forming a positive electrode plate or a negative electrode plate. An active material layer is applied to a portion of the current collector other than the mounting portion of the PTC element, and an active material layer is applied on the other current collector to form a positive electrode plate and a negative electrode plate. The element is coated and an electrolyte-resistant insulating material is applied, and one end of a positive electrode lead and one end of a negative electrode lead are respectively joined to the other electrode of the PTC element and a current collector of an electrode plate to which the PTC element is not joined. It is characterized by.
[0016]
According to the method for manufacturing a battery electrode plate, a PTC element can be provided on a positive electrode plate or a negative electrode plate to manufacture a battery electrode plate. The temperature rise quickly transfers heat to the PTC element, so that the current circuit can be cut off before the temperature of the electrode plate reaches thermal runaway, thereby preventing the battery from becoming high temperature. Further, since the PTC element is covered with an insulating material having resistance to an electrolytic solution, it is possible to prevent the PTC element from being deteriorated by the electrolytic solution.
[0017]
Further, the method for manufacturing a battery electrode plate according to the second invention of the present application is configured such that at least one of the current collectors forming the positive electrode plate and the negative electrode plate is formed by forming a conductive film on the surface of a resin film; A PTC element is attached by joining one electrode to a required portion on one of the current collectors forming the plate, and an active material layer is applied to a portion of the current collector other than a portion where the PTC element is attached, and An active material layer is applied on the current collector to form a positive electrode plate and a negative electrode plate, and the PTC element is coated and an electrolyte-resistant insulating material is applied. It is characterized in that the other electrode of the PTC element and the PTC element are respectively joined to a current collector of an electrode plate that is not joined.
[0018]
According to the method for manufacturing a battery electrode plate, a PTC element can be provided on a positive electrode plate or a negative electrode plate to manufacture a battery electrode plate. The temperature rise quickly transfers heat to the PTC element, and the current circuit can be shut off before the temperature of the electrode plate reaches thermal runaway, thereby preventing the battery from going into thermal runaway. Further, since the PTC element is covered with the insulating material, it is possible to prevent the PTC element from being deteriorated by the electrolytic solution. If the PTC element does not operate normally, the temperature rises, but the current circuit is interrupted because the resin film constituting the current collector melts. That is, a battery electrode plate having a dual battery protection function can be configured. In addition, since the current collector can be configured using a resin film as a base material, the weight can be reduced as a battery electrode plate, and a battery having a high weight energy density suitable as a power source for a portable electronic device or the like can be obtained. Can be.
[0019]
In the above-mentioned manufacturing method, after applying an insulating material to a portion of the PTC element other than on the other electrode, one end of a positive electrode lead or a negative electrode lead covering the other electrode is joined to the other electrode, so that the PTC element is connected to the insulating material and the positive electrode. Since the PTC element is covered with one end of the lead or the negative electrode lead, the PTC element is not exposed to the electrolytic solution, thereby preventing the PTC element from being corroded and deteriorated by the electrolytic solution.
[0020]
Also, after joining one end of the positive electrode lead or the negative electrode lead on the other electrode of the PTC element, the PTC element covers one end of the PTC element and the positive electrode lead or the negative electrode lead, and applies an insulating material. Since the PTC element is covered with the insulating material, the PTC element is not exposed to the electrolytic solution, thereby preventing the PTC element from being corroded and deteriorated by the electrolytic solution.
[0021]
Also, by arranging and winding the positive electrode plate and the negative electrode plate between the two electrode plates and winding them, a battery electrode plate having a large counter electrode area can be easily formed, which is applicable to a cylindrical or flat rectangular battery. A suitable battery plate is obtained.
[0022]
Also, by attaching the PTC element to the end of the wound positive electrode plate or the negative electrode plate on the winding start side, the PTC element is disposed at the center of the wound battery electrode plate, and The rise in the temperature of the plate quickly transfers heat to the PTC element, and the protection operation can be activated without delay.
[0023]
In addition, by mounting the PTC element on the inner side of the wound positive electrode plate or negative electrode plate, heat is transferred to the PTC element before the temperature of the electrode plate is radiated to the outside. Is reliably performed.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings to facilitate understanding of the present invention. The embodiment described below is an example embodying the present invention, and does not limit the technical scope of the present invention.
[0025]
The present embodiment is intended to realize a lithium ion secondary battery having a function of protecting a battery from external short-circuiting, overcharging, high temperature, and the like, while reducing the weight so as to be mainly applied to a battery power supply of a portable electronic device. 1 is a method for manufacturing a battery electrode plate of the present invention.
[0026]
FIG. 1 shows an expanded state of a positive electrode plate 1 constituting a battery electrode plate A manufactured by the method for manufacturing a battery electrode plate according to the embodiment. The positive electrode plate 1 is formed by applying a positive electrode active material layer 11 to both surfaces of a positive electrode current collector 10 to a predetermined thickness as shown in a cross section taken along line BB in FIG. As shown in FIG. 1 (d), the positive electrode current collector 10 is formed by forming a metal thin film (here, aluminum) 31 on both surfaces of a resin film 30 using a polyolefin resin by a sputtering method, a vapor deposition method, or the like. It is a film. Note that the metal thin films 31 formed on both surfaces of the resin film 30 are formed in a state of being electrically conducted by a conductive material such as a through hole formed in the resin film 30 or a metal powder contained in the resin film 30. . A PTC element 4 is joined to one end of the positive electrode plate 1.
[0027]
FIG. 2 shows a developed state of the negative electrode plate 2 constituting the battery electrode plate A manufactured by the method for manufacturing a battery electrode plate according to the embodiment. The negative electrode plate 2 is formed by applying a negative electrode active material layer 21 to both surfaces of a negative electrode current collector 20 to a predetermined thickness, as shown in a cross section taken along line CC in FIG. The negative electrode current collector 20 is formed by forming a metal thin film (here, copper) 41 on both surfaces of a resin film 40 using a polyolefin resin by means of a sputtering method, an evaporation method, or the like. A negative electrode lead 6 is attached to the other end of the negative electrode plate 2 with one end joined to a negative electrode current collector 20.
[0028]
In order to reduce the weight of the battery, the positive electrode plate 1 and the negative electrode plate 2 preferably have the above-described configuration. However, the current collector of one of the positive electrode plate 1 and the negative electrode plate 2 is formed of aluminum foil or copper foil. You can also.
[0029]
The battery plate A is manufactured by the manufacturing procedure shown in FIG. First, as shown in FIG. 3A, a metal thin film 31 is formed on both surfaces of a resin film 30 to form a positive electrode current collector 10. At this time, the metal thin film 31 on one side is formed by projecting the PTC bonding portion 31a on one end side of the resin film 30 so that a portion without the metal thin film 31 is formed on one end side in an inverted U-shape. Here, an aluminum layer having a thickness of 0.5 μm was formed as a metal thin film 31 by vacuum evaporation on a polyethylene terephthalate film having a thickness of 10 μm as the resin film 30.
[0030]
As shown in FIG. 3B, a PTC element 4 formed in a sheet having a thickness of 30 μm is joined to the PTC joint 31a with one electrode. Next, as shown in FIG. 3C, an insulating material having an electrolytic solution is applied around the joined PTC element 4 to form an insulating coating 7. Next, as shown in FIG. 3D, the positive electrode active material layer 11 is applied to a predetermined thickness on the metal thin film 31 excluding the PTC bonding portion 31a. Further, one end of the positive electrode lead 5 is joined to the other electrode of the PTC element 4 so as to cover the other electrode of the PTC element 4 as shown in FIG. Here, as the positive electrode active material layer 11, LiCoO as a positive electrode active material, acetylene black as a conductive material, and vinylidene fluoride as a binder were mixed at a weight ratio of 94: 4: 2 to form a paste. This was coated on both surfaces of the positive electrode current collector 10 to a thickness of 70 μm. Further, polyethylene was used as the insulating coating 7 and aluminum foil was used as the positive electrode lead 5.
[0031]
The insulating coating 7 is formed by bonding a positive electrode lead 5 to the other electrode of the PTC element 4 as shown in FIG. 4A, and then, as shown in FIG. If an insulating material resistant to an electrolytic solution is applied so as to wrap the joining end side of the lead 5, the PTC element 4 can be more reliably isolated from the electrolytic solution. However, as shown in FIG. 4C, it is preferable that the insulating coating 7 is formed so as not to exceed the thickness of the positive electrode active material layer 11, and a gap is generated when the battery electrode plate A is wound. And can be wound tightly.
[0032]
The negative electrode plate 2 forms the negative electrode current collector 20 by forming the metal thin film 41 on both surfaces of the resin film 40, and forms the negative electrode active material layer 21 on the metal thin film 41 except for the portion where the negative electrode lead 6 is joined. Then, one end of the negative electrode lead 6 is joined to a portion where the negative electrode current collector 20 is exposed without forming the negative electrode active material layer 21. Here, a 10 μm-thick polyethylene terephthalate film was used as the resin film 40, and a 0.5 μm-thick copper layer was formed as a metal thin film 41 thereon by vacuum evaporation to form the negative electrode current collector 20. On both surfaces of the negative electrode current collector 20, a paste obtained by mixing graphite with vinylidene fluoride at a weight ratio of 95: 5 as a binder was applied as a negative electrode active material layer 21 to a thickness of 70 μm. Worked. Further, a copper foil was used as the negative electrode lead 6.
[0033]
The positive electrode plate 1 and the negative electrode plate 2 having the above-described configuration have a separator 3 formed of a microporous polyethylene film (here, 20 μm in thickness) interposed therebetween, and the positive electrode plate 1 has a PTC bonding portion 31a. The formed one end side was set as the winding start side, and the negative electrode plate 2 was wound with the one end side to which the negative electrode lead 6 was not joined as the winding start side, and was formed into a flat bottomed square tube as shown in FIG. It is formed into a flat battery electrode plate A that can be accommodated in the battery can 12.
[0034]
By winding the PTC element 4 in such a manner that the side where the PTC element 4 is joined is the winding start side, the PTC element 4 is disposed substantially at the center of the battery electrode plate A, so that the temperature of the battery electrode plate A is transferred. The temperature rise of the battery plate A can be quickly detected. The position of the PTC element 4 is set at the end of the positive electrode plate 1 or the end of the negative electrode plate 2 so that the reaction area of the electrode plate is not reduced. However, when the winding is performed starting from the end of the PTC element 4 where the PTC element 4 is provided, the temperature rise of the electrode plate can be quickly detected. Conversely, when the winding is performed with the end side of the PTC element 4 disposed at the winding end side, the PTC element 4 is formed on the battery electrode plate A disposed outside, and is suitable for detecting a state in which the battery is exposed to a high temperature environment. However, there is a possibility that a delay may occur in detecting a state in which the temperature of the electrode plate has risen.
[0035]
As shown in FIG. 6, the battery electrode plate A is inserted into a battery can 12 formed in a flat bottomed square tube, and the positive electrode lead 5 pulled out from the battery electrode plate A is attached to the sealing plate 13. The positive electrode terminal 14 is insulated and joined to the positive electrode terminal 14, and the negative electrode lead 6 is joined to the sealing plate 13. The sealing plate 13 to which the lead has been joined is welded to the open end of the battery can 12 to seal the inside of the battery can 12. Thereafter, a predetermined amount of electrolyte is injected into the battery can 12 from a liquid inlet 15 formed in the sealing plate 13, and the liquid inlet 15 is closed by a plug 16 to form a flat rectangular secondary battery B. Is done. Here, as the electrolytic solution, a solution obtained by dissolving sodium hexafluorophosphate at a concentration of 1 mol / l as a solute in a mixture obtained by mixing equal amounts of ethylene carbonate and diethylene carbonate as a solvent was used.
[0036]
The PTC element 4 used in the above configuration is formed by forming a conductive polymer in which a conductive material such as carbon particles is mixed with a polymer material into a sheet shape, and bonding an electrode plate made of a metal foil to both surfaces thereof to a predetermined shape. It is cut out to size. When the temperature is low, the resistance value between the two electrodes is low, on the order of mΩ, due to the conductive path of the conductive material, so that the internal resistance of the battery is hardly increased. When an excessive current such as a short-circuit current flows through the PTC element 4, the temperature rises due to self-heating caused by the excessive current, and the conductive path of the conductive material is cut off due to the thermal expansion of the polymer, indicating a gradual increase in the resistance value. When the temperature reaches a predetermined temperature, the resistance value increases at a stretch, so that an excessive current is limited and a rise in temperature due to a short circuit or the like is suppressed. Since the increase in the resistance value due to the temperature rise is also caused by a rise in temperature due to overcharge and a rise in ambient temperature, the continuation of the overcharge state can be prevented, and the use of the battery in a high temperature state can be stopped.
[0037]
In the above configuration, the PTC element 4 disposed in the battery electrode plate A is immersed in the electrolytic solution filled in the battery electrode plate A. Since the portion is isolated from the electrolytic solution, the function as the PTC element 4 does not deteriorate due to the deterioration of the conductive polymer due to the electrolytic solution.
[0038]
In the secondary battery B having the above configuration, as shown in the circuit diagram of FIG. 7, the PTC element 4 is connected in series with the positive electrode circuit, and the PTC element 4 is disposed in the battery electrode plate A. When an external short-circuit occurs between the positive terminal 14 and the negative terminal (the sealing plate 13 and the battery can 12) for some reason, an excessive current caused by the short-circuit causes the temperature of the PTC element 4 to rise and a predetermined trip. When the temperature is exceeded, the resistance value is sharply increased, so that the short-circuit current is limited to prevent the battery from becoming hot. In addition, when the charging circuit or the like falls into an overcharged state, the temperature rise of the battery electrode plate A is quickly transferred to the PTC element 4, so that when the temperature exceeds a predetermined trip temperature, the PTC element 4 Rapidly increases the resistance value, the charging current is limited, and the battery is prevented from being damaged due to the continuation of the overcharged state.
[0039]
The trip temperature at which the PTC element 4 rapidly increases the resistance value is determined by the type and amount of the polymer material and the additive. When the trip temperature is set at 80 to 120 ° C., the active material of the secondary battery B causes thermal runaway 150 to 180. The battery circuit can be stopped before the temperature reaches ° C. If the operation of stopping the battery circuit by the PTC element 4 is not performed normally, the secondary battery B may cause thermal runaway, but the battery electrode plate A according to the present embodiment has a positive electrode and / or a negative electrode collection. Since the electric body is formed using the resin films 30 and 40 as a base material, a double battery protection function is formed. That is, since the melting point of the polyolefin resin used as the resin films 30 and 40 is 130 to 170 ° C., if the PTC element 4 does not operate normally, the temperature rises and the temperature of the battery plate A decreases. When the temperature rises to the melting temperature of the resin films 30 and 40, the current circuit of the battery electrode plate A is interrupted by the melting of the resin films 30 and 40, and the abnormal heat is calmed by the heat of melting. And ignition is prevented.
[0040]
Next, regarding the effectiveness of the configuration in which the PTC element 4 is attached to the battery electrode plate as described above, the results of performing a short-circuit test on the secondary battery of the example configuration and the secondary battery of the comparative example configuration to be compared are shown. It is shown below.
[0041]
The positive electrode plate 1 and the negative electrode plate 2 of the battery electrode plate A as examples are formed of the material configuration shown as a specific example in the above embodiment in a width of 50 mm and a length of 200 mm, and the positive electrode plate 1 has a thickness of 30 μm. A 20 × 20 mm square PTC element 4 was joined to the positive electrode current collector 10 at one electrode.
[0042]
The positive electrode plate 1 and the negative electrode plate 2 are overlapped with each other via a separator 3 formed of a 20 μm-thick polyethylene microporous film, and the battery electrode plate A according to the embodiment starts winding around the side where the PTC element 4 is joined. To form a battery electrode plate A.
[0043]
After inserting the battery electrode plate A into the battery can 12 and performing lead connection, a sealing plate 13 is welded to the open end of the battery can 12 to seal the battery can 12, and an electrolyte is injected from the liquid inlet 15 to seal the battery. The injection port 15 was closed at 16 to form a secondary battery B. The electrolyte used had the composition shown as a specific example in the above embodiment.
[0044]
In the secondary battery B of Example (1), a pitch fluoride was used as the insulating coating 7 covering the PTC element 4.
[0045]
In the secondary battery B of Example (2), the polyethylene shown as a specific example in the above embodiment was used as the insulating coating 7 for covering the PTC element 4.
[0046]
In the secondary battery B of Example (3), polyethylene terephthalate was used as the insulating coating 7 for covering the PTC element 4.
[0047]
As Comparative Example (1), a secondary battery was manufactured using a battery electrode plate manufactured without providing the insulating coating 7 on the PTC element 4.
[0048]
As Comparative Example (2), a secondary battery was manufactured using a battery electrode plate manufactured without the PTC element 4.
[0049]
As Comparative Example (3), a secondary battery was manufactured using the battery electrode plate having the same configuration as that of Example (1), but wound with the side where the PTC element 4 was joined was used as the winding end side.
[0050]
100 secondary batteries having the configurations shown in the above Examples (1), (2) and (3) and Comparative Examples (1), (2) and (3) were manufactured and subjected to a short-circuit test. After 10 minutes, the ratio at which the surface temperature of the secondary battery exceeded 100 ° C. was verified. The results are shown in Tables 1 and 2. Table 1 shows the case where the manufactured secondary batteries were stored at room temperature for 3 months, and Table 2 was the case where the storage batteries were stored for 1 week in an environment at an ambient temperature of 85 ° C. and then subjected to a short-circuit test.
[0051]
[Table 1]

[0052]
[Table 2]

As can be seen from the above verification results, when the PTC element 4 is not provided, the secondary battery falls into a high temperature state due to a short circuit. Further, when the PTC element 4 is not provided with the insulating coating 7, a state in which the PTC element 4 is considered to be deteriorated and not functioning normally occurs with a high probability. Further, when the PTC element 4 is disposed on the outer peripheral portion of the battery electrode plate, a state is considered in which it takes time to detect a temperature rise due to a short circuit. In contrast, in the configuration of the embodiment, the insulating coating 7 is effectively acting, the PTC element 4 is not deteriorated by the influence of the electrolytic solution, and the temperature rise due to the short circuit is reliably suppressed. Understand.
[0053]
The following materials can be used as the material that can be used as the electrolyte-resistant insulating coating 7 that achieves the above-described effects, in addition to the materials used in the above-described embodiment.
[0054]
Olefin polymers such as polypropylene and polymethylpentene, ester polymers such as polybutylene terephthalate, polycyclohexylene dimethylene terephthalate, polyarylate, and polycarbonate, polyethylene oxide, polypropylene oxide, polyacetal, polyphenylene ether, polyether ether ketone, and poly Ether polymers such as ether imide, polysulfone, sulfone polymers such as polyether sulfone, polyacrylonitrile, AS resin, acrylonitrile polymers such as ABS resin, thioether polymers such as polyphenylene sulfide, aromatic vinyl polymers such as polystyrene, Nitrogen-containing polymers such as polyimide, aramid, polytetrafluoroethylene, polyfluoride Fluorinated polymers such as vinylidene, fluoropolymers such as polyvinylidene fluoride, can be used organic compounds such as an acrylic polymer such as polymethyl methacrylate. These can be used alone or as a copolymer, polymer alloy, polymer blend or the like in which two or more kinds are combined. Further, a polymer obtained by polymerization and solidification by heating or UV irradiation can also be used. Further, a bitumin such as pitch or asphalt, which has been subjected to vacuum degassing to eliminate air in the material, can also be used.
[0055]
In the configuration of the embodiment described above, the PTC element 4 is attached to the positive electrode plate 1 so that the PTC element 4 is connected in series with the positive electrode circuit. The same operation and effect can be obtained even if the PTC element 4 is configured to be connected in series.
[0056]
In addition, the secondary battery B to which the battery electrode plate A is applied is not limited to a lithium ion secondary battery, and the same configuration can be applied to other types of batteries. Further, the outer package of the secondary battery B is not limited to the metal battery can 12 shown in the configuration of the embodiment. For example, the outer package is formed using a laminate sheet including a metal foil, and the electrolytic solution is formed. The present invention can also be applied to a lithium polymer battery using a gelled material. Since the exterior body of the lithium polymer battery is a resin film, there is no mounting portion for the PTC element 4 and the thermal conductivity is poor. Therefore, the PTC element 4 is provided as a battery pack. Although it was difficult to operate normally for overcharging and overheating even if possible, the application of the battery electrode plate according to the present embodiment makes it possible to accurately respond to temperature rise such as overcharging and overheating. Become.
[0057]
【The invention's effect】
As described above, in the battery electrode plate manufactured by the manufacturing method according to the present invention, since the PTC element is disposed on the electrode plate, heat generation of the electrode plate and temperature rise of the electrode plate due to external heating are promptly increased. Heat is transferred to the PTC element, and the PTC element operates at a temperature before the battery reaches thermal runaway, whereby excessive current due to an electrical cause such as a short circuit can be limited, and battery operation in a high temperature state can be stopped. When the PTC element is disposed on the electrode plate as described above, the PTC element is immersed in the electrolytic solution. However, since the PTC element is covered with the insulating material, deterioration of the PTC element is prevented and aging occurs. The function of the PTC element can be maintained without any problem. In addition, since the current collector is formed using a resin film as a base material, the weight can be reduced as a battery electrode plate, and a battery using the same is provided as a battery power source for a portable electronic device or the like. can do. In addition, when the operation of the PTC element is not performed normally, the current collector formed using the resin film as a base material melts due to the progress of the temperature rise, and the battery operation stops and the state of the thermal runaway is calmed. Be transformed into Therefore, the battery using the battery electrode plate manufactured by the manufacturing method according to the present invention can be configured so that the battery itself is provided with a double safety function, and is lightweight and can be used as a portable electronic device. Suitable as a battery power source for devices exposed to various environments.
[Brief description of the drawings]
FIG. 1A is a plan view, FIG. 1B is a plan view, FIG. 1C is a cross-sectional view of a required portion, and FIG. 1D is a configuration of a current collector. FIG.
FIGS. 2A and 2B are a plan view and a cross-sectional view, respectively, showing a negative electrode plate constituting the battery electrode plate according to the embodiment in an unfolded state.
FIG. 3 is a plan view showing a procedure for manufacturing a positive electrode plate.
FIG. 4 is a plan view showing another embodiment of the method for forming an insulating coating.
FIG. 5 is a perspective view showing a configuration of a battery electrode plate according to the embodiment.
FIG. 6 is a perspective view illustrating the assembly of a secondary battery using the battery electrode plate.
FIG. 7 is a circuit diagram showing a configuration of a secondary battery according to the embodiment.
[Explanation of symbols]
A Battery plate B Secondary battery (battery)
REFERENCE SIGNS LIST 1 positive electrode plate 2 negative electrode plate 4 PTC element 5 positive electrode lead 6 negative electrode lead 7 insulating coating 10 positive electrode current collector 11 positive electrode active material layer 12 battery can 13 sealing plate 14 positive electrode terminal 20 negative electrode current collector 21 negative electrode active material layer 30, 40 Resin film 31, 41 Metal thin film

Claims

A PTC element is attached by joining one electrode to a required portion on one of the current collectors forming the positive electrode plate or the negative electrode plate, and an active material layer is applied to a portion of the current collector except for the portion where the PTC element is attached. Then, an active material layer is applied on the other current collector to form a positive electrode plate and a negative electrode plate, and the PTC element is covered, and an insulating material having resistance to an electrolytic solution is applied. Characterized in that the other end of the PTC element is joined to the current collector of the electrode plate to which the PTC element is not joined.

At least one of the current collectors forming the positive electrode plate and the negative electrode plate is formed by forming a conductive film on the surface of the resin film, and a predetermined portion on one of the current collectors forming the positive electrode plate or the negative electrode plate is formed. One electrode is joined to attach a PTC element, an active material layer is applied to a portion of the current collector other than the portion where the PTC element is attached, and an active material layer is applied to the other current collector to form a positive electrode plate. And forming a negative electrode plate, coating the PTC element with an electrolyte-resistant insulating material, and connecting one end of a positive electrode lead and a negative electrode lead to the other electrode of the PTC element and an electrode plate not joined to the PTC element. A method for producing a battery electrode plate, wherein the battery electrode plate is bonded to a current collector.

The method according to claim 1, wherein the insulating material is applied to a portion of the PTC element other than on the other electrode, and then one end of a positive electrode lead or a negative electrode lead covering the other electrode is joined to the other electrode.

The battery electrode plate according to claim 1 or 2, wherein after joining one end of the positive electrode lead or the negative electrode lead on the other electrode of the PTC element, the PTC element and one end of the positive electrode lead or the negative electrode lead are coated and an insulating material is applied. Production method.

The method for manufacturing a battery electrode plate according to any one of claims 1 to 4, wherein the positive electrode plate and the negative electrode plate are wound with a separator disposed between the two electrode plates.

The method for manufacturing a battery electrode plate according to claim 5, wherein the PTC element is attached to an end of the wound positive electrode plate or the negative electrode plate on the winding start side.

The method for manufacturing a battery electrode plate according to claim 5, wherein the PTC element is attached to a portion on the inner surface side of the wound positive electrode plate or negative electrode plate.