JP4557329B2

JP4557329B2 - Battery terminal

Info

Publication number: JP4557329B2
Application number: JP06691599A
Authority: JP
Inventors: 正利真嶋; 諭氏家; えり子矢ヶ崎
Original assignee: Kansai Electric Power Co Inc; Sumitomo Electric Industries Ltd
Current assignee: Kansai Electric Power Co Inc; Sumitomo Electric Industries Ltd
Priority date: 1999-03-12
Filing date: 1999-03-12
Publication date: 2010-10-06
Anticipated expiration: 2019-03-12
Also published as: JP2000268806A

Description

【０００１】
【発明の属する技術分野】
本発明は、とくに大型のリチウム二次電池用として好適に使用される、電池用端子に関するものである。
【０００２】
【従来の技術】
リチウム二次電池は、エネルギー密度およびエネルギー効率が高く、単セルで、他の方式の電池に比べて高い電圧が得られることから、主として電子機器の小型化、コードレス化に対応した小型ないし超小型の電源として、たとえば携帯電話やノートパソコンなどに搭載すべく研究がなされてきたが近時、たとえば電気自動車、ハイブリッド自動車などの電源用として、あるいは一般家庭や商店、小工場などにおける小規模な電力貯蔵用としての、より大型の電池への利用が期待されている。
【０００３】
かかる大型電池用のリチウム二次電池としては、たとえば天然黒鉛などの、リチウムイオンをドープ、脱ドープしうる物質を負極活物質とする負極板と、たとえばリチウムを含む、または含まない遷移金属の酸化物などを正極活物質とする正極板と、そして非水性の有機溶媒に、電解質としてリチウム塩を溶解した非水性の有機電解液とを組み合わせたものが好適に使用される。
【０００４】
上記のリチウム二次電池は、通常のリチウム二次電池が持つ本来の特性である、前述した高いエネルギー密度、および高いエネルギー効率を有する上、負極活物質として金属リチウムを使用する場合に比べて、安全性が高く、かつ充放電を繰り返してもいわゆるデンドライトなどの析出物を生じないためにサイクル寿命が長いという特性を示す。
【０００５】
より具体的なリチウム二次電池の構成としては、たとえば上記正極板と負極板とを複数枚ずつ、それぞれ多孔質の板状のセパレータを挟むなどして交互に積層することで、電極積層体が形成され、この電極積層体に有機電解液を含浸させるとともに、上記電極積層体の、各正極板、および各負極板をそれぞれ、正負両極用の端子に電気的に接続した状態で、これらの各部を容器内に密封したものがあげられる。
【０００６】
端子９としては、たとえば図３(a)(b)にみるように、電極積層体ＥＬの、極板の積層方向に沿って配置される、正負両極用の一対の幹部材９１、９１と、各幹部材９１に一定間隔で配置され、各極板ＥＬ１を、当該各極板ＥＬ１から延設された薄い集電箔ＥＬ１ａを介して、それぞれその極性ごとに所定枚数ずつ（図の場合は３枚ずつ）まとめて接続するための複数本の枝部材９２…とを備えたものが一般的である。
【０００７】
なお図において符号９０は、容器外部に突出されて、回路などと接続される端子９の接続部である。
また図では、上記の構造を判りやすく説明するために、上記のように１つの枝部材９２に３枚ずつの極板ＥＬ１が接続されたように省略して記載しているが、実際にはもっと多数（具体的には３０〜４０枚程度）の極板ＥＬ１が、１つの枝部材９２に接続される。
【０００８】
【発明が解決しようとする課題】
前記正極活物質は、充放電の際に大きく膨張、収縮することが知られており、電極積層体ＥＬにおいてはこの膨張、収縮が、図(b)中に黒矢印で示すように、当該電極積層体ＥＬの、電極板の積層方向への伸縮として現れる。
たとえばその容量が５０Ａｈ未満であるような、中ないし小型のリチウム二次電池では、かかる伸縮は大した大きさではなく、したがって前記端子９は、幹部材９１と枝部材９２…とを剛結合して形成されていた。
【０００９】
ところが、たとえばその容量が５０〜１０００Ａｈ程度といった大型のリチウム二次電池においては、電極積層体ＥＬの、電極板の積層方向への伸縮量がこれまでよりも大きいために、上記のように幹部材９１と枝部材９２…とを剛結合した従来の端子構造をそのまま採用したのでは、充放電を繰り返すうちに、とくに極板ＥＬ１を枝部材９２に接続するために、当該極板ＥＬ１から延設された薄い集電箔ＥＬ１ａに、応力集中によって破断、破損を生じ、その結果、充放電のサイクル寿命が短くなるおそれがあった。
【００１０】
本発明の目的は、充放電を繰り返しても集電箔の破断、破損などを生じるおそれのない、とくに大型のリチウム二次電池用として適した、新規な電池用端子を提供することにある。
【００１１】
【課題を解決するための手段】
上記課題を解決するための、本発明の電池用端子は、正負両極板を多数、交互に積層した電極積層体の、極板の積層方向に沿って配置される幹部材と、当該幹部材に一定間隔で配置され、各正極板、または各負極板を、所定枚数ずつまとめて接続するための枝部材とを備えるとともに、上記各枝部材がそれぞれ、蝶番構造を介して、接続された極板の、電極積層体における極板の積層方向である幹部材の長手方向への移動を許容しつつ、当該幹部材に接続されていることを特徴とするものである。
また本発明の電池用端子は、正負両極板を多数、交互に積層した電極積層体の、極板の積層方向に沿って配置される幹部材と、当該幹部材に一定間隔で配置され、各正極板、または各負極板を、所定枚数ずつまとめて接続するための枝部材とを備えるとともに、上記各枝部材がそれぞれ、柔軟な接続体を介して、接続された極板の、電極積層体における極板の積層方向である幹部材の長手方向への移動を許容しつつ、当該幹部材に接続されていることを特徴とするものである。
【００１２】
かかる本発明の電池用端子においては、上記のように各正極板、または各負極板を、所定枚数ずつまとめて接続する枝部材が、蝶番構造または柔軟な接続体を介して、接続された極板の、電極積層体における極板の積層方向である、幹部材の長手方向への移動を許容した状態で、当該幹部材に接続されているため、たとえその容量が前記のように５０〜１０００Ａｈ程度といった大容量の、それゆえ充放電による電極積層体の、電極板の積層方向への伸縮量がこれまでよりも大きい電池であっても、極板を枝部材に接続するために、当該極板から突設された集電箔などに、応力集中と、それに伴なう破断、破損を生じるのが確実に防止される。したがって本発明の電池用端子によれば、とくに大型のリチウム二次電池のサイクル寿命を、これまでよりも大幅に引き伸ばすことが可能となる。
【００１３】
【発明の実施の形態】
以下に本発明を、その実施の形態の一例を示す図１(a)(b)を参照しつつ、説明する。
これらの図にみるようにこの例の電池用端子１は、電極積層体ＥＬの、極板の積層方向に沿って配置される、正負両極用の一対の幹部材１１、１１と、各幹部材１１に一定間隔で配置され、各極板ＥＬ１を、当該各極板ＥＬ１から延設された薄い集電箔ＥＬ１ａを介して、それぞれその極性ごとに所定枚数ずつ（図の場合は３枚ずつ）まとめて接続するための複数本（図の場合は１０本）の枝部材１２…とを備えている。
【００１４】
なお図において符号１０は、前記と同様に容器外部に突出されて、回路などと接続される端子１の接続部である。
また図では、上記の構造を判りやすく説明するために、上記のように１つの枝部材１２に３枚ずつの極板ＥＬ１が接続されたように省略して記載しているが、実際にはもっと多数（具体的には３０〜４０枚程度）の極板ＥＬ１が、１つの枝部材１２に接続される。
【００１５】
以上の構成は従来と同様である。
図の例の、従来との相違点は、上記各部のうち幹部材１１と、各枝部材１２…とを、それぞれ図(a)中に拡大して示したように、枝部材１２の基部に設けた丸孔１２ａに、幹部材１１側に設けた軸１１ａを挿通することで構成した蝶番構造１３を介して接続した点にある。
【００１６】
そしてこのことによって各枝部材１２は、上記蝶番構造１３の軸１１ａを中心として、図中実線の矢印で示すように、電極積層体ＥＬにおける極板ＥＬ１の積層方向である幹部材１１の長手方向へ個別に首振り自在とされて、前記集電箔ＥＬ１ａを介して接続された各極板ＥＬ１の、同方向への移動を許容している。
上記各部からなる図の例の電池用端子１おいては、充放電の際の陽極活物質の膨張、収縮に伴なって、電極積層体ＥＬが図(b)中に黒矢印で示す極板ＥＬ１の積層方向に伸縮すると、各枝部材１２が、上記の機構に基づいて、それぞれに接続された極板ＥＬ１の、同方向への移動を許容すべく、その移動量にあわせて首振りする。このため充放電を繰り返しても、各枝部材１２と各極板ＥＬ１とを繋ぐ薄い集電箔ＥＬ１ａは、応力集中による破断、破損などを生じにくいものとなり、電池の寿命が向上する。
【００１７】
電池用端子１を構成する上記の各部は、従来同様に、導電性を有し、しかも電解液に対する耐性を有する金属にて形成するのがよい。かかる金属としては、これに限定されないがたとえば銅やニッケルなどがあげられる。
幹部材１１と枝部材１２とを接続する構造は、上記の蝶番構造１３には限定されず、たとえば図２に示すようにもっと簡単に、上記の両者を、柔軟な接続体１４など直結するだけでもよい。柔軟な接続体１４としては、たとえば銅の細線を多数、撚り合わせた撚り線や、あるいは同じく銅の薄板などがあげられる。
【００１８】
以上で説明した各図の例の電池用端子１は、前記のようにとくに、充放電による正極活物質の膨張、収縮が著しく大きい、その容量がおよそ５０〜１０００Ａｈ程度といった大型のリチウム二次電池に好適に使用される。
かかる大型のリチウム二次電池において、正負両極用の電池用端子１と組み合わされる電極積層体ＥＬ、および非水性の有機電解液としては、従来のリチウム二次電池と同様のものが、いずれも使用可能である。
【００１９】
すなわち電極積層体ＥＬは、シート状の正極板と陰極板とを複数枚、多孔質のセパレータを介して交互に積層することで構成され、正極板および陰極板はそれぞれ、集電体としての金属箔の片面または両面に、正極活物質、または負極活物質の粉末と、樹脂バインダーとを含むペーストを塗布し、乾燥後にプレスするなどして形成される。
【００２０】
金属箔としては、導電性にすぐれ、かつ有機電解液に対する耐性にすぐれた種々の金属の箔が、いずれも使用可能である。かかる金属としては、たとえばアルミニウム、ニッケル、銅、ステンレス鋼、チタンなどがあげられ、とくにリチウム二次電池の性能などを考慮すると、正極にアルミニウム、負極に銅などの組み合わせが好適に使用される。金属箔の寸法、形状はリチウム二次電池の形状、構造および寸法にあわせて適宜、設定される。
【００２１】
正極活物質としては、たとえば一般式：
ＬｉＡｌ_xＣｏ_yＮｉ_1-x-yＯ₂
〔０≦ｘ≦０．３、０≦ｙ≦１、０≦ｘ＋ｙ≦１〕
や、あるいは一般式：
ＬｉＣｒ_nＭｎ_2-nＯ₄
〔０≦ｎ≦２〕
などの、リチウムを含む、または含まない遷移金属の酸化物や、あるいは硫化鉄などの硫化物、セレン化物などがあげられる。
一方、負極活物質としては、たとえばコークス、樹脂焼成体、炭素繊維、熱分解炭素、天然黒鉛、メソフェーズ小球体などの、リチウムイオンを可逆的にドープ、脱ドープしうる多孔質炭素が好適に使用される他、たとえばＬｉ_4/3Ｔｉ_5/3Ｏ₄などの、遷移金属の酸化物などを使用することもできる。
【００２２】
樹脂バインダーとしては、たとえばポリフッ化ビニリデン（ＰＶｄＦ）、ポリ４フッ化エチレン（ＰＴＦＥ）、フッ素ゴムなどのフッ素樹脂が、非水性の有機電解液に対する耐性にすぐれるため、好適に使用される。
有機電解液としては、たとえばプロピレンカーボネート、エチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、１，２−ジメトキシエタン、テトラヒドロフランなどの有機溶媒に、ＬｉＣｌＯ₄、ＬｉＢＦ₄、ＬｉＰＦ₆、ＬｉＡｓＦ₆などのリチウムイオンや、リチウムイオン伝導性の固体電解質などを溶解または分散した液が使用される。
【００２３】
上記の各部を密封する容器としては、従来同様に金属板などの剛直な材料で形成された箱体が使用される他、たとえば水の浸入による電池の劣化と、有機電解液中の有機溶媒の逃げ出しによる組成変化とを防止すべく、この両者の透過をともに良好に阻止しうるように各層を考慮した積層フィルムなどで形成した袋型容器を採用することもできる。かかる袋型容器を用いたリチウム二次電池は、これまでよりもその重量を軽量化できるという利点がある。
【００２４】
なお袋型容器を用いる場合は、とくに前記のように正極活物質の粉末を、樹脂バインダーを用いて、集電体としての金属箔の表面に結合した構造の正極において、その結合構造が、充放電時の正極活物質の膨張、収縮によって緩んで抵抗値が増加し、それによって充放電のサイクル寿命が短くなるおそれがある。
そこでかかる問題の発生を防止するために、袋型容器を使用する場合は、当該袋型容器を、前述した電極積層体の、極板の積層方向への伸縮を押さえる手段（押圧手段）としての、たとえば薄板ばねや、あるいは袋型容器よりわずかに大きい金属製の枠体（箱体）などと組み合わせて使用するのが好ましい。
【００２５】
なお本発明の電池用端子の構成は、以上で説明した大型のリチウム二次電池用には限定されず、小型のリチウム電池や、その他の大型の電池など、種々の電池用の端子に適用することができる。
その他、本発明の要旨を変更しない範囲で種々の設計変更を施すことができる。
【００２６】
【実施例】
以下に本発明を、実施例、比較例に基づいて説明する。
実施例１
〈正極板の作製〉
正極活物質としてのＬｉＣｏＯ₂粉末１００重量部に、グラファイト１０重量部、ＰＶｄＦ１０重量部を混合し、Ｎ−メチル−２−ピロリドンを加えてペースト状としたのち、このペーストを、厚み０．０２ｍｍのアルミニウム箔の両面に塗布して乾燥させた。そしてロールプレスしたのちカットして、厚み０．１８ｍｍ、縦２００ｍｍ、横２００ｍｍの正極板を作製した。
【００２７】
〈負極板の作製〉
負極活物質としての鱗片状天然黒鉛粉末１００重量部にＰＶｄＦ２０重量部を混合し、Ｎ−メチル−２−ピロリドンを加えてペースト状としたのち、このペーストを、厚み０．０２ｍｍの銅箔の両面に塗布して乾燥させた。そしてロールプレスしたのちカットして、厚み０．２８ｍｍ、縦２００ｍｍ、横２００ｍｍの負極板を作製した。
【００２８】
〈リチウム二次電池の製造〉
上記で作製した正極板および負極板を、厚み０．０２５ｍｍ、縦２００ｍｍ、横２００ｍｍのポリプロピレン製微多孔膜をセパレータとして、正極−セパレータ−負極−セパレータ−…の順に、合計３６０枚積層して電極積層体ＥＬを得た。
【００２９】
また、ポリプロピレン層、ＰＥＴ層、アルミニウム層、およびＰＥＴ層の４層構造を有する積層体を所定の形状に切り出し、ポリプロピレン層が内側になるように組み立てて、略箱型で、かつ縦２５ｃｍ、横２２ｃｍ、高さ２５ｃｍの柔軟な袋型容器を作製した。
さらに、図１(a)(b)に示すように１本の幹部材１１と１０本の枝部材１２とが、それぞれ蝶番構造１３にて接続された構造を有する、その全体が銅製の電池用端子１を、正負両極用に１本ずつ計２本、用意した。
【００３０】
つぎに、上記の電極積層体ＥＬを袋型容器内へ収容したところへ、エチレンカーボネートとジエチルカーボネートの体積比１：１の混合物に、電解質としてＬｉＰＦ₄を溶解した非水性の有機電解液（電解質濃度１Ｍ）を注入して、４００ｍｍＨｇの減圧下で９６時間、含浸させた。
つぎに、上記の電極積層体ＥＬを構成する各正極板ＥＬ１から延設された薄い集電箔ＥＬ１ａを約３５枚分ずつまとめて、正極用の電池用端子１の、１本の枝部材１２の先端部に接続する操作を端から順に繰り返し行って、全ての正極板ＥＬ１を正極用の電池用端子１に接続した。また同様に、電極積層体ＥＬを構成する各負極板ＥＬ１から延設された薄い集電箔ＥＬ１ａを約３５枚分ずつまとめて、負極用の電池用端子１の、１本の枝部材１２の先端部に接続する操作を端から順に繰り返し行って、全ての負極板ＥＬ１を負極用の電池用端子１に接続した。
【００３１】
そして最後に袋型容器の口を、両接続端子１の一対の接続部１０のみ容器外部へ突出させた状態で、ヒートシールにより封止して、容量４００Ａｈのリチウム二次電池を製造した。
〈電池特性試験〉
上記で製造したリチウム二次電池を、それ自体が押圧手段を兼ねる、厚み４ｍｍのアルミニウム板で形成した、内法寸法が縦２６ｃｍ、横２３ｃｍ、深さ２６ｃｍの箱体内に収容した。
【００３２】
そしてこの収容状態において、上記のリチウム二次電池を、初期電流密度０．１５ｍＡ／ｃｍ²、上限電圧４．１Ｖの充電条件で８〜１０時間、定電流、定電圧充電したのち、電流密度０．１５ｍＡ／ｃｍ²の放電条件で３．０Ｖまで定電流放電させるサイクルを繰り返し行い、容量が初期容量の７０％となったサイクル数を、電池の寿命として求めたところ、５３０サイクルであった。
【００３３】
また、上記の状態のリチウム二次電池を解体して内部を観察したところ、電池用電極１、集電箔ＥＬ１ａ、および電極積層体ＥＬなどには外観上、異常は見られなかった。
実施例２
正負両極用の電池用端子１として、図２に示すように幹部材１１と枝部材１２とが、柔軟な接続体１４としての銅細線の撚り線にて接続されたものを用いたこと以外は実施例１と同様にして、容量４００Ａｈのリチウム二次電池を製造した。
【００３４】
上記リチウム二次電池を前記と同寸法の箱体内に収容した状態で、リチウム二次電池を前記と同条件で充放電させて寿命を求めたところ、５５０サイクルであった。
また、上記の状態のリチウム二次電池を解体して内部を観察したところ、この場合もやはり電池用電極１、集電箔ＥＬ１ａ、および電極積層体ＥＬなどには外観上、異常は見られなかった。
【００３５】
比較例１
正負両極用の電池用端子として、幹部材と枝部材とが溶接により強固に剛結合されたものを用いたこと以外は実施例１と同様にして、容量４００Ａｈのリチウム二次電池を製造した。
上記リチウム二次電池を前記と同寸法の箱体内に収容した状態で、リチウム二次電池を前記と同条件で充放電させて寿命を求めたところ、２７０サイクルであった。
【００３６】
また、上記の状態のリチウム二次電池を解体して内部を観察したところ、電池用電極１、および電極積層体ＥＬには外観上、異常は見られなかったが、集電箔ＥＬ１ａが多数、破断しているのが確認された。
以上の結果を表１に示す。
【００３７】
【表１】

【００３８】
【発明の効果】
以上、詳述したように本発明によれば、充放電を繰り返しても集電箔の破断、破損などを生じるおそれのない、とくに大型のリチウム二次電池用として適した、新規な電池用端子を提供できるという特有の作用効果を奏する。
【図面の簡単な説明】
【図１】本発明の電池用端子の、実施の形態の一例を示す図であって、同図(a)は平面図、同図(b)は正面図である。
【図２】本発明の電池用端子の、実施の形態の他の例の要部を示す部分拡大平面図である。
【図３】従来の電池用端子の一例を示す図であって、同図(a)は平面図、同図(b)は正面図である。
【符号の説明】
１電池用端子
１１幹部材
１２枝部材
１３蝶番構造
ＥＬ電極積層体
ＥＬ１極板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery terminal that is suitably used particularly for a large lithium secondary battery.
[0002]
[Prior art]
Lithium secondary batteries are high in energy density and energy efficiency, and can be obtained in a single cell with a higher voltage than other types of batteries. Therefore, they are mainly small and ultra-compact in response to downsizing and cordless electronic devices. Recently, research has been conducted to install them in mobile phones, notebook computers, etc., but for the power supply of electric cars, hybrid cars, etc., or in small households, shops, small factories, etc. It is expected to be used for larger batteries for storage.
[0003]
Such a lithium secondary battery for a large battery includes, for example, a negative electrode plate made of a material capable of doping and undoping lithium ions, such as natural graphite, and an oxidation of a transition metal containing or not containing lithium, for example. A combination of a positive electrode plate using a material as a positive electrode active material and a non-aqueous organic solvent in which a lithium salt is dissolved as an electrolyte in a non-aqueous organic solvent is preferably used.
[0004]
The above lithium secondary battery has the above-mentioned high energy density and high energy efficiency, which are the original characteristics of a normal lithium secondary battery, as compared with the case where metallic lithium is used as the negative electrode active material, It exhibits high safety and long cycle life because it does not produce deposits such as so-called dendrites even after repeated charge and discharge.
[0005]
As a more specific configuration of the lithium secondary battery, for example, a plurality of the positive electrode plates and the negative electrode plates are alternately laminated by sandwiching a porous plate-like separator, respectively, so that the electrode laminate is The electrode laminate is impregnated with an organic electrolyte, and each positive electrode plate and each negative electrode plate of the electrode laminate are electrically connected to positive and negative terminals, respectively. Is sealed in a container.
[0006]
As the terminal 9, for example, as shown in FIGS. 3 (a) and 3 (b), a pair of

trunk members

91, 91 for positive and negative electrodes, which are arranged in the electrode stacking direction of the electrode laminate EL, Each electrode plate EL1 is arranged on each trunk member 91 at a constant interval, and a predetermined number of each electrode plate EL1 for each polarity (three in the case of the figure) via a thin current collecting foil EL1a extending from each electrode plate EL1. It is common to have a plurality of branch members 92 for connecting together.
[0007]
In the figure, reference numeral 90 denotes a connection portion of the terminal 9 that protrudes outside the container and is connected to a circuit or the like.
In addition, in the figure, in order to explain the above structure in an easy-to-understand manner, three electrode plates EL1 are omitted so as to be connected to one branch member 92 as described above. A larger number (specifically, about 30 to 40) of electrode plates EL1 are connected to one branch member 92.
[0008]
[Problems to be solved by the invention]
The positive electrode active material is known to greatly expand and contract during charge and discharge, and in the electrode laminate EL, this expansion and contraction is indicated by the black arrow in FIG. Appears as expansion / contraction of the laminate EL in the stacking direction of the electrode plates.
For example, in a medium to small-sized lithium secondary battery having a capacity of less than 50 Ah, such expansion and contraction is not large. Therefore, the terminal 9 rigidly couples the trunk member 91 and the branch member 92. Was formed.
[0009]
However, in a large-sized lithium secondary battery having a capacity of, for example, about 50 to 1000 Ah, the amount of expansion and contraction of the electrode stack EL in the electrode plate stacking direction is larger than before, so that the trunk member as described above. If the conventional terminal structure in which 91 and the branch member 92 are rigidly coupled is employed as it is, the electrode plate EL1 is extended from the electrode plate EL1 in order to connect the electrode plate EL1 to the branch member 92 as charging and discharging are repeated. The thin current collector foil EL1a was broken or damaged by stress concentration, and as a result, the cycle life of charge / discharge could be shortened.
[0010]
An object of the present invention is to provide a novel battery terminal suitable for a large-sized lithium secondary battery that does not cause breakage or breakage of the current collector foil even when charging and discharging are repeated.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, a battery terminal of the present invention comprises a trunk member arranged along the laminating direction of the electrode plate, in which a large number of positive and negative electrode plates are alternately laminated, and the stem member. The electrode plates are arranged at regular intervals, and each of the positive plates or the negative plates is connected to each other by a predetermined number, and each of the branch members is connected via a hinge structure. This is characterized in that it is connected to the trunk member while allowing movement in the longitudinal direction of the trunk member, which is the lamination direction of the electrode plates in the electrode laminate.
In addition, the battery terminal of the present invention is an electrode laminate in which a large number of positive and negative bipolar plates are alternately laminated, a trunk member arranged along the lamination direction of the electrode plates, and arranged on the trunk member at regular intervals. A positive electrode plate or a branch member for connecting a predetermined number of each negative electrode plate together, and each of the branch members is connected to each other via a flexible connector. It is characterized in that it is connected to the trunk member while allowing movement in the longitudinal direction of the trunk member, which is the laminating direction of the electrode plates.
[0012]
In such a battery terminal of the present invention, as described above, each of the positive plates or the negative members connected together by a predetermined number of pieces is connected via a hinge structure or a flexible connector. Since the plate is connected to the trunk member in a state in which movement of the plate in the longitudinal direction of the electrode member in the electrode laminate is allowed in the longitudinal direction, the capacity is 50 to 1000 Ah as described above. In order to connect the electrode plate to the branch member, even if the battery has a large capacity, and therefore the amount of expansion / contraction of the electrode laminate by charge / discharge in the electrode stacking direction is larger than before, It is possible to reliably prevent stress concentration and the accompanying breakage and breakage from occurring in the current collecting foil or the like protruding from the plate. Therefore, according to the battery terminal of the present invention, the cycle life of a particularly large-sized lithium secondary battery can be greatly extended compared to the past.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to FIGS. 1 (a) and 1 (b) showing an example of the embodiment.
As shown in these drawings, the battery terminal 1 of this example includes a pair of positive and

negative stem members

11, 11 arranged along the electrode stacking direction of the electrode laminate EL, and each stem member. 11 are arranged at regular intervals, and each electrode plate EL1 is passed through a thin current collector foil EL1a extending from each electrode plate EL1, and a predetermined number (three in the case of the figure) for each polarity. A plurality of (ten in the case of the figure) branch members 12 for connecting together are provided.
[0014]
In addition, the code | symbol 10 is a connection part of the terminal 1 which protrudes outside a container similarly to the above, and is connected with a circuit etc. similarly to the above.
In addition, in the figure, in order to explain the above-described structure in an easy-to-understand manner, three electrode plates EL1 are omitted so as to be connected to one branch member 12 as described above. A larger number (specifically, about 30 to 40) of electrode plates EL1 are connected to one branch member 12.
[0015]
The above configuration is the same as the conventional one.
In the example of the figure, the difference from the prior art is that the trunk member 11 and the branch members 12 of the above-mentioned parts are respectively enlarged at the base of the branch member 12 as shown in FIG. It exists in the point connected via the hinge structure 13 comprised by inserting the axis | shaft 11a provided in the trunk member 11 side to the provided round hole 12a.
[0016]
As a result, each branch member 12 is centered on the axis 11a of the hinge structure 13 and the longitudinal direction of the trunk member 11 which is the stacking direction of the electrode plates EL1 in the electrode stack EL as shown by the solid arrows in the figure. Each electrode plate EL1 connected through the current collector foil EL1a is allowed to move in the same direction.
In the battery terminal 1 of the example of the figure consisting of the above parts, the electrode laminate EL is indicated by a black arrow in the figure (b) as the anode active material expands and contracts during charging and discharging. When expanding and contracting in the stacking direction of EL1, each branch member 12 swings according to the amount of movement to allow the electrode plate EL1 connected thereto to move in the same direction based on the above mechanism. . For this reason, even if charging / discharging is repeated, the thin current collector foil EL1a that connects each branch member 12 and each electrode plate EL1 is less prone to breakage and breakage due to stress concentration, thereby improving the battery life.
[0017]
Each of the above-mentioned parts constituting the battery terminal 1 is preferably made of a metal having conductivity and resistance to the electrolyte as in the prior art. Examples of such metal include, but are not limited to, copper and nickel.
The structure for connecting the trunk member 11 and the branch member 12 is not limited to the hinge structure 13 described above. For example, as shown in FIG. But you can. Examples of the flexible connector 14 include a stranded wire obtained by twisting a large number of copper thin wires, or a copper thin plate.
[0018]
As described above, the battery terminal 1 in the example of each figure explained above is particularly large-sized lithium secondary battery in which the positive electrode active material is significantly expanded and contracted by charging and discharging, and its capacity is about 50 to 1000 Ah. Is preferably used.
In such a large lithium secondary battery, the electrode laminate EL combined with the positive and negative battery terminals 1 and the non-aqueous organic electrolyte are the same as those of the conventional lithium secondary battery. Is possible.
[0019]
That is, the electrode laminate EL is configured by alternately laminating a plurality of sheet-like positive and negative plates through a porous separator, and each of the positive and negative plates is a metal as a current collector. It is formed by applying a paste containing a positive electrode active material or a powder of a negative electrode active material and a resin binder on one side or both sides of the foil, pressing after drying, and the like.
[0020]
As the metal foil, any of various metal foils having excellent conductivity and resistance to organic electrolytes can be used. Examples of such metals include aluminum, nickel, copper, stainless steel, titanium, and the like. Particularly, considering the performance of the lithium secondary battery, a combination of aluminum for the positive electrode and copper for the negative electrode is preferably used. The dimensions and shape of the metal foil are appropriately set according to the shape, structure and dimensions of the lithium secondary battery.
[0021]
Examples of the positive electrode active material include a general formula:
LiAl _x Co _y Ni _1-xy O ₂
[0 ≦ x ≦ 0.3, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1]
Or the general formula:
LiCr _n Mn _2-n O ₄
[0 ≦ n ≦ 2]
Examples thereof include transition metal oxides containing or not containing lithium, sulfides such as iron sulfide, and selenides.
On the other hand, as the negative electrode active material, for example, porous carbon that can be reversibly doped and dedoped with lithium ions, such as coke, resin fired body, carbon fiber, pyrolytic carbon, natural graphite, and mesophase microspheres is preferably used. In addition, oxides of transition metals such as Li _4/3 Ti _5/3 O ₄ can also be used.
[0022]
As the resin binder, for example, a fluororesin such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), and fluororubber is excellent in resistance to a non-aqueous organic electrolytic solution, and thus is preferably used.
As the organic electrolyte, for example, an organic solvent such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, lithium ions such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , A liquid in which a lithium ion conductive solid electrolyte or the like is dissolved or dispersed is used.
[0023]
As a container for sealing each of the above parts, a box made of a rigid material such as a metal plate is used as in the prior art. For example, deterioration of the battery due to ingress of water and the organic solvent in the organic electrolyte solution are used. In order to prevent compositional change due to escape, a bag-type container formed of a laminated film or the like that considers each layer so as to satisfactorily block both permeation can be employed. The lithium secondary battery using such a bag-type container has an advantage that its weight can be reduced more than before.
[0024]
In the case of using a bag-type container, in particular, in the positive electrode having a structure in which the positive electrode active material powder is bonded to the surface of the metal foil as a current collector using a resin binder as described above, the bonding structure is There is a possibility that the resistance value increases due to expansion and contraction of the positive electrode active material during discharge, thereby shortening the cycle life of charge and discharge.
Therefore, in order to prevent the occurrence of such a problem, when using a bag-type container, the bag-type container is used as a means (pressing means) for suppressing expansion and contraction of the electrode laminate in the stacking direction of the electrode plates. For example, it is preferable to use in combination with a thin plate spring or a metal frame (box) slightly larger than a bag-type container.
[0025]
The configuration of the battery terminal of the present invention is not limited to the large lithium secondary battery described above, and is applied to various battery terminals such as a small lithium battery and other large batteries. be able to.
In addition, various design changes can be made without departing from the scope of the present invention.
[0026]
【Example】
Hereinafter, the present invention will be described based on examples and comparative examples.
Example 1
<Preparation of positive electrode plate>
After mixing 10 parts by weight of graphite and 10 parts by weight of PVdF with 100 parts by weight of LiCoO ₂ powder as a positive electrode active material and adding N-methyl-2-pyrrolidone to make a paste, this paste was made into a 0.02 mm thick It applied to both surfaces of the aluminum foil and dried. Then, it was cut after roll pressing to produce a positive electrode plate having a thickness of 0.18 mm, a length of 200 mm, and a width of 200 mm.
[0027]
<Preparation of negative electrode plate>
After mixing 100 parts by weight of scaly natural graphite powder as a negative electrode active material with 20 parts by weight of PVdF and adding N-methyl-2-pyrrolidone to make a paste, this paste is formed on both sides of a copper foil having a thickness of 0.02 mm. And dried. Then, it was cut after roll pressing to produce a negative electrode plate having a thickness of 0.28 mm, a length of 200 mm, and a width of 200 mm.
[0028]
<Manufacture of lithium secondary batteries>
A total of 360 layers of the positive electrode plate and the negative electrode plate produced above were laminated in the order of positive electrode-separator-negative electrode-separator -... using a polypropylene microporous film having a thickness of 0.025 mm, a length of 200 mm, and a width of 200 mm as an electrode. A laminate EL was obtained.
[0029]
Also, a laminate having a four-layer structure of a polypropylene layer, a PET layer, an aluminum layer, and a PET layer is cut into a predetermined shape and assembled so that the polypropylene layer is on the inside. A flexible bag-shaped container having a height of 22 cm and a height of 25 cm was produced.
Further, as shown in FIGS. 1 (a) and 1 (b), one trunk member 11 and ten branch members 12 are connected by a hinge structure 13, respectively, and the whole is for a battery made of copper. Two terminals 1 were prepared, one for each of the positive and negative electrodes.
[0030]
Next, a non-aqueous organic electrolytic solution (electrolyte) obtained by dissolving LiPF ₄ as an electrolyte in a mixture of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1 to a place where the electrode laminate EL is accommodated in a bag-type container. 1M) was injected and impregnated for 96 hours under a reduced pressure of 400 mmHg.
Next, about 35 thin current-collecting foils EL1a extended from each positive electrode plate EL1 constituting the electrode laminate EL described above are collected together, and one branch member 12 of the battery terminal 1 for positive electrode is collected. The operation of connecting to the tip of each was repeated in order from the end to connect all the positive electrode plates EL1 to the battery terminal 1 for the positive electrode. Similarly, about 35 thin current-collecting foils EL1a extending from each negative electrode plate EL1 constituting the electrode laminate EL are gathered together to form one branch member 12 of the battery terminal 1 for the negative electrode. The operation of connecting to the tip portion was repeated in order from the end to connect all the negative electrode plates EL1 to the battery terminal 1 for negative electrode.
[0031]
Finally, the mouth of the bag-type container was sealed by heat sealing with only the pair of connection portions 10 of both connection terminals 1 protruding to the outside of the container, and a lithium secondary battery having a capacity of 400 Ah was manufactured.
<Battery characteristics test>
The lithium secondary battery manufactured as described above was housed in a box having an internal dimension of 26 cm in length, 23 cm in width, and 26 cm in depth formed of an aluminum plate having a thickness of 4 mm, which itself also serves as a pressing means.
[0032]
In this accommodated state, the lithium secondary battery was charged at a constant current and a constant voltage for 8 to 10 hours under a charging condition of an initial current density of 0.15 mA / cm ² and an upper limit voltage of 4.1 V, and then the current density was 0. A cycle in which a constant current was discharged to 3.0 V under a discharge condition of .15 mA / cm ² was repeated, and the number of cycles at which the capacity became 70% of the initial capacity was determined as the battery life, and was 530 cycles.
[0033]
Further, when the lithium secondary battery in the above state was disassembled and the inside was observed, no abnormality was found in appearance in the battery electrode 1, the current collector foil EL1a, the electrode laminate EL, and the like.
Example 2
As the battery terminal 1 for both positive and negative electrodes, except that a trunk member 11 and a branch member 12 are connected by a copper fine wire stranded wire as a flexible connector 14 as shown in FIG. In the same manner as in Example 1, a lithium secondary battery having a capacity of 400 Ah was manufactured.
[0034]
When the lithium secondary battery was charged and discharged under the same conditions as described above in a state where the lithium secondary battery was housed in a box having the same dimensions as above, it was 550 cycles.
In addition, when the lithium secondary battery in the above state was disassembled and the inside was observed, in this case as well, no abnormality was seen in appearance in the battery electrode 1, the current collector foil EL1a, the electrode laminate EL, and the like. It was.
[0035]
Comparative Example 1
A lithium secondary battery having a capacity of 400 Ah was manufactured in the same manner as in Example 1 except that a battery terminal for positive and negative electrodes was used in which a trunk member and a branch member were firmly and rigidly joined by welding.
When the lithium secondary battery was charged and discharged under the same conditions as described above in a state where the lithium secondary battery was housed in a box having the same dimensions as described above, it was 270 cycles.
[0036]
In addition, when the lithium secondary battery in the above state was disassembled and the inside was observed, no abnormality was found in appearance in the battery electrode 1 and the electrode laminate EL, but there were many current collector foils EL1a, It was confirmed that it was broken.
The results are shown in Table 1.
[0037]
[Table 1]

[0038]
【The invention's effect】
As described above in detail, according to the present invention, a novel battery terminal suitable for a large-sized lithium secondary battery that does not cause breakage, breakage, etc. of the current collector foil even when charging and discharging are repeated. There is a specific effect that can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an embodiment of a battery terminal of the present invention, where FIG. 1 (a) is a plan view and FIG. 1 (b) is a front view.
FIG. 2 is a partially enlarged plan view showing a main part of another example of the embodiment of the battery terminal of the present invention.
3A and 3B are diagrams showing an example of a conventional battery terminal, where FIG. 3A is a plan view and FIG. 3B is a front view.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Battery terminal 11 Trunk member 12 Branch member 13 Hinge structure EL Electrode laminated body EL1 Electrode plate

Claims

A large number of positive and negative electrode plates, alternately stacked electrode members, a trunk member arranged along the lamination direction of the electrode plates, and arranged at regular intervals on the stem member, each positive electrode plate, or each negative electrode plate, A battery terminal comprising a branch member for connecting a predetermined number of sheets together, wherein each of the branch members is connected to each other via a hinge structure, and the electrode plates in the electrode stack are stacked. A battery terminal characterized by being connected to the trunk member while allowing movement of the trunk member, which is a direction, in the longitudinal direction.

A large number of positive and negative electrode plates, alternately stacked electrode members, a trunk member arranged along the lamination direction of the electrode plates, and arranged at regular intervals on the stem member, each positive electrode plate, or each negative electrode plate, A battery terminal comprising branch members for connecting a predetermined number of pieces together, wherein each of the branch members is connected to each other via a flexible connector , in the electrode laminate. A battery terminal characterized in that it is connected to the trunk member while allowing movement of the trunk member in the longitudinal direction, which is the stacking direction.

Capacity of 50～1000Ah, according to claim 1 or 2 battery terminal, wherein the lithium secondary battery of large.