JP3749024B2

JP3749024B2 - battery

Info

Publication number: JP3749024B2
Application number: JP27383498A
Authority: JP
Inventors: 礼造前田; 義典松浦; 克彦新山; 育郎米津; 晃治西尾
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1998-09-28
Filing date: 1998-09-28
Publication date: 2006-02-22
Anticipated expiration: 2018-09-28
Also published as: JP2000106171A

Description

【０００１】
【発明の属する技術分野】
本発明は電池に関し、特にリチウムイオン電池等の非水電解液電池のうち外装缶が角型有底筒状を成す角型電池に関する。
【０００２】
【従来の技術】
近年、電池は各種電気機器に用いられる小型電池の他、電力貯蔵用或いは電気自動車用等の大型電池も盛んに開発されるようになってきており、このような用途の電池では複数の電池を電気的に接続して用いられることが多い。この場合、省スペース化ということを考慮するならば、複数の電池同士を密着することで、余分なスペースを少なくすることができる角型電池が望ましく、当該角型電池のうちでも高エネルギー密度で高出力密度のリチウムイオン電池が有望視されている。
【０００３】
ここで、上記角型リチウムイオン電池における電流取出構造としては、ＬｉＣｏＯ₂等から成る正極と炭素等から成る負極とに、それぞれ箔状等のリード線の一端を溶着し、当該リード線の他端を外部電極に溶着するような構造である。
【０００４】
【発明が解決しようとする課題】
しかしながら、上記従来の角型リチウムイオン電池では、リード線が箔状等であること、及びリード線の溶着箇所が２箇所ある等の理由により、電池内での抵抗が高くなるため、急激な出力変動を伴う電気自動車用電池等としては必ずしも十分な性能を有しているとはいえなかった。更に、リード線が正極及び負極の上部に溶着されている構成であるので、電流が電極体の上部に集中し、電池温度が高くなって、サイクル特性が低下する。加えて、リード線の溶着を高価なレーザー装置を用いて行わなければならず、製造コストが上昇するといった課題を有していた。
【０００５】
本発明は、上記従来の課題を考慮して成されたものであって、電池内での抵抗を低くすることにより、急激な出力変動を伴う電気自動車用電池等として最適であり、しかも電池温度の上昇を抑制してサイクル特性を向上させ、且つ製造コストの低減を図ることができる電池の提供を目的とする。
【０００６】
【課題を解決するための手段】
上記目的を達成する第 1 の発明は次のように構成されている。正極と負極とがセパレータを介して配置される電極体が外装缶内に配置され、且つ上記正極及び上記負極がそれぞれ正極用の外部端子及び負極用の外部端子と電気的に接続される構造の電池において、上記電極体は渦巻き型の電極体からなり、上記両外部端子のうち少なくとも一方の外部端子は、上記正極又は上記負極に直接接続される電流取出兼用端子からなり、当該電流取出兼用端子は、電池外に突出させる端子部と、この端子部と固着され且つ上記正極又は上記負極に接続される板状のリード体と、を有し、上記渦巻き型電極体の巻き芯方向と垂直する方向に配設されていることを特徴とする。
上記構成であれば、リード線を介することなく、外部端子と正極又は負極が直接接続されるので、電池内での抵抗が低くなり、急激な出力変動を伴う電気自動車用電池等として用いられた場合であっても、十分な性能を発揮することができる。
【０００７】
また、第２の発明は、上記第 1 の発明にかかる電池において、前記板状のリード体が、一方の面にリード体と一体的に突出形成された複数の突出部先端からなる電流取出部を有し、当該電流取出部が前記正極又は前記負極に溶着されることにより、前記リード体が前記正極又は前記負極と電気的に接続されていることを特徴とする。
このような構造の電流取出兼用端子を用いれば、電池外に突出される端子部の固着されたリード体と正極又は負極との溶着箇所は１箇所で済み、しかも、従来技術のリード線として作用するリード体が板状であるので、電池内での抵抗が格段に低くなる。更に、正極又は負極に溶着される電流取出部が複数突出形成されているので、電流が電極体の上部に集中するのを抑制でき、電池温度の上昇を抑えることができる。
【０００８】
また、第３の発明は、上記第２の発明にかかる電池において、前記電極体として、前記正極が前記セパレータの一方の端部よりはみ出し且つ前記負極が前記セパレータの他方の端部よりはみ出している電極体を用い、前記突出部先端が前記正極又は前記負極の端部に溶着されていることを特徴とする。
このように、正極が前記セパレータの一方の端部よりはみ出し、前記負極が前記セパレータの他方の端部よりはみ出していれば、電流取出部の突出部先端と正極又は負極の端部とを溶接する際に、短絡が発生するのを防止することができる。
【０００９】
なお、上記第２または 3 の発明にかかる電池において、前記電流取出部の断面形状が先細り状であるとすることができ、このようにすると、電流取出部の突出部先端と正極又は負極との接触面積が小さくなるので、突出部先端と正極又は負極との溶着を、簡易な抵抗溶接で行うことができる。したがって、電池の製造コストの低減を図ることができる。尚、断面形状が先細り状となっている例としては、断面形状が山型又は略半円型等となっている場合である。
また、第４の発明は、上記第２の発明にかかる電池において、前記リード体が、中央部に形成された溝により前記電池外に突出させる端子部との接続部分より先端側が 2 葉に分割された形状であることを特徴とする。
また、第５の発明は、正極と負極とがセパレータを介して配置される電極体が外装缶内に配置され、且つ上記正極及び上記負極がそれぞれ正極用の外部端子及び負極用の外部端子と電気的に接続される構造の電池において、上記両外部端子のうち少なくとも一方の外部端子は、上記正極又は上記負極に直接接続される電流取出兼用端子からなり、当該電流取出兼用端子は、電池外に突出させた端子部と、この端子部と固着され且つ上記正極又は上記負極に電気抵抗溶接された板状のリード体と、を有し、上記リード体は、中央部に形成された溝により上記電池外に突出させる端子部との接続部分より先端側が 2 葉に分割された形状であることを特徴とする。
このようにその中央部に溝が形成され、この溝により端子部との接続部分より先端側が 2 葉に分割された形状のリード体であると、抵抗溶接時の溶接が容易である。
【００１０】
また、第６の発明は、上記第５の発明にかかる電池において、前記電極体が正負両極とセパレータとを複数重ねた積層構造の電極体から成ることを特徴とする。
また、第７の発明は、上記第５の発明にかかる電池において、前記板状のリード体が、一方の面にリード体と一体的に突出形成された複数の突出部先端からなる電流取出部を有し、当該電流取出部が前記正極又は前記負極に溶着されることにより、前記リード体が前記正極又は前記負極と電気的に接続されていることを特徴とする。
また、第８の発明は、上記第１，２，３，４，５，６または７の発明にかかる電池において、前記外装缶が角型有底筒状を成す角型電池であることを特徴とする。
【００１１】
【発明の実施の形態】
〔第１の形態〕
本発明の第１の形態を、図１〜図８に基づいて、以下に説明する。図１は本発明の第１の形態に係るリチウムイオン電池の斜視図、図２は図１の電池の内部構造を示す分解斜視図、図３は図１の電池に用いる正極の正面図、図４は図１の電池に用いる電流取出兼用端子の斜視図、図５は図１の電池に用いる電流取出兼用端子の側面図、図６は図１の電池に用いる電流取出兼用端子の平面図、図７は図１の電池に用いる電流取出兼用端子の背面図、図８は図１の電池を作製時における抵抗溶接の際の通電箇所を示す説明図である。
図１に示すように、本発明の第１の形態に係るリチウムイオン電池はアルミニウムから成る角型電槽（角型外装缶）１（肉厚が２ｍｍで、内寸の高さが１００ｍｍ、長さが１００ｍｍ、幅が４０ｍｍ）を有しており、この角型電槽１の開口部には上蓋１５がレーザー溶接されている。この上蓋１５の上面からは、後述の正極側の電流取出兼用端子２の一部を構成する端子部２ａ（Ｍ８ボルトから成る）と、後述の負極側の電流取出兼用端子３の一部を構成する端子部３ａ（Ｍ８ボルトから成る）とが、絶縁体４・４を介して突出形成されており、且つ上蓋１５の上面には安全弁５が設けられている。
【００１２】
上記角型電槽１内には、図２に示すような電極体６が装填されており、この電極体６は、ＬｉＣｏＯ₂を主体とする正極７と、黒鉛粉末を主体とする負極９と、イオン透過性を有しポリプロピレン製の微多孔膜から成るセパレータ８とから構成される電極群１０と、を多数積層する構造である。上記正極７は、図３に示すように、活物質塗布部７ａ（幅Ｌ₁＝６０ｍｍ）と、後述の正極側の電流取出兼用端子２側に形成さた活物質未塗布部７ｂ（幅Ｌ₂ ＝２ｍｍ）とから構成されており、この活物質未塗布部７ｂが上記セパレータ８の一方の端部８ａよりはみ出すように配置される。一方、図示はしないが、上記負極９も、活物質塗布部と、後述の負極側の電流取出兼用端子３側に形成さた活物質未塗布部とから構成されており、この活物質未塗布部が上記セパレータ８の他方の端部８ｂよりはみ出すように配置されている。
【００１３】
上記正極７のはみ出し端部側（活物質未塗布部７ｂ側）には、ステンレスから成る正極側の電流取出兼用端子２が溶着されている（但し、図２では分解した状態で描いている）。この電流取出兼用端子２は、図４に示すように、中央部に溝２ｄが形成された板状のリード体２ｂと、このリード体２ｂの一方の面にリード体２ｂと一体的に複数突出形成される電流取出部２ｃ…と、上記リード体２ｂに螺着された端子部２ａとから成り、上記電流取出部２ｃ…の先端と前記正極７とが溶着されている。また、上記電流取出兼用端子２の具体的な寸法は、図５〜図７に示すように、電流取出兼用端子２の高さＬ₃ ＝１２０ｍｍ、電流取出部２ｃ…間のピッチＬ₄ ＝１０ｍｍ（共に、図５参照）、リード体２ｂの幅Ｌ₅ ＝３８ｍｍ、リード体２ｂの厚みＬ₆ ＝１０ｍｍ、電流取出部２ｃ…の高さＬ₇ ＝６ｍｍ（共に、図６参照）、リード体２ｂの高さＬ₈ ＝９０ｍｍ、溝２ｄの長さＬ₉ ＝８５ｍｍ、溝２ｄの幅Ｌ₁₀＝２ｍｍ（共に、図７参照）である。
【００１４】
一方、上記負極９のはみ出し端部側（活物質未塗布部９ｂ側）には、ニッケルから成る負極側の電流取出兼用端子３が溶着されている（但し、図２では分解した状態で描いている）。この負極側の電流取出兼用端子３は、上記正極側の電流取出兼用端子２と同様の構造であり、具体的には、中央部に溝３ｄが形成された板状のリード体３ｂと、このリード体３ｂの一方の面にリード体３ｂと一体的に複数突出形成される電流取出部３ｃ…と、上記リード体３ｂに螺着された端子部３ａとから成る。また、負極側の電流取出兼用端子３と正極側の電流取出兼用端子２とは対峙するように配置されている。
【００１５】
ここで、上記構造のリチウムイオン電池を、以下のようにして作製した。
（正極の作製）
先ず、平均粒径５μｍのＬｉＣｏＯ₂ から成る正極活物質と人造黒鉛とから成る導電剤とを重量比で９：１の割合で混合して正極合剤を作製した後、この正極合剤と、結着剤であるポリフッ化ビニリデン（ＰＶＤＦ）が５重量％の割合で溶解されたＮ−メチル−２−ピロリドン（ＮＭＰ）溶液とを、正極合剤とＰＶＤＦとの重量比が９５：５の割合となるように混練してスラリーを調整した。次に、このスラリーをアルミニウムから成る帯状の正極集電体（厚さ：２０μｍ）の両面にドクターブレード法により塗布した後、１５０℃で２時間真空乾燥して正極７を作製した。尚、上記スラリー塗布時において、正極側の電流取出兼用端子２と溶着される部位にはスラリーを塗布しなかった。これにより、活物質未塗布部７ｂが形成される。
【００１６】
（負極の作製）
先ず、炭素塊（ｄ₀₀₂ 値＝３．３５６Å、Ｌｃ値＞１０００Å）に空気流を噴射して、炭素塊を粉砕することにより黒鉛粉末を作製した。次に、この黒鉛粉末と、結着剤であるＰＶＤＦが５重量％の割合で溶解されたＮ−メチル−２−ピロリドン（ＮＭＰ）溶液とを、黒鉛粉末とＰＶＤＦとの重量比が８５：１５の割合となるように混練してスラリーを調整した。次に、このスラリーを銅から成る帯状の負極集電体（厚さ：２０μｍ）の両面にドクターブレード法により塗布した後、１５０℃で２時間真空乾燥して負極を作製した。尚、上記スラリー塗布時において、負極側の電流取出兼用端子３と溶着される部位にはスラリーを塗布しなかった。これにより、活物質未塗布部が形成される。
【００１７】
（電解液の調製）
体積混合比率が１：１のエチレンカーボネートとジエチルカーボネートとの混合溶媒に、ＬｉＰＦ₆ を１Ｍ（モル／リットル）の割合で溶かして非水電解液を調製した。
【００１８】
（電池の組立）
先ず、上記正極７と上記負極９とを、イオン透過性を有しポリプロピレン製の微多孔膜から成るセパレータ８を介して配置する構造の電極群１０を、多数積層して電極体６を作製した。尚、この電極体６の作製時には、正極７の活物質未塗布部７ｂがセパレータ８の一方の端部８ａよりはみ出すように配置し、負極９の活物質未塗布部がセパレータ８の他方の端部８ｂよりはみ出すように配置した。次に、上記正極７のはみ出し端部と正極側の電流取出兼用端子２の電流取出部２ｃ…の突出部先端及び上記負極９のはみ出し端部と負極側の電流取出兼用端子３の電流取出部３ｃ…の突出部先端とを、下記の条件で抵抗溶接した。尚、この際、図８に示すように、電流取出兼用端子の背面側の通電箇所１１ａ…・１１ｂ…に、それぞれ溶接機（図示せず）のプラス側の通電端子とマイナス側の通電端子とを電気的に接続することにより行った。
【００１９】
・溶接条件
出力：６００Ｗ
溶接端子の材質：タングステン
溶接部分の面積：電流取出部と電極との接触部分１箇所当たり２ｍｍ² 以下
この後、電流取出兼用端子２・３が溶着された電極体６を角型電槽１内に挿入し、上蓋１５を角型電槽１の開口部にレーザー溶接した。最後に、非水電解液を安全弁取付用の穴から注液した後、安全弁取付用の穴に安全弁５を取り付けて、理論容量５０Ａｈのリチウムイオン電池を作製した。
【００２０】
〔第２の形態〕
本発明の第２の形態を、図９に示すリチウムイオン電池の斜視図に基づいて、以下に説明する。
図９に示すように、電極体として、帯状の正極１３と帯状の負極１４とを帯状のセパレータ（図９においては図示せず）を介して、楕円形渦巻き状に巻回した渦巻き電極体１２を用いる他は、上記第１の形態と同様の構造である。
【００２１】
〔第３の形態〕
本発明の第３の形態を、図１０に示す電流取出兼用端子の側面図に基づいて、以下に説明する。
図１０に示すように、電流取出兼用端子２として、電流取出部２ｃ…の数が少なく、しかも電流取出部２ｃ…の高さＬ₁₁が２ｍｍのものを用いる他は、上記第１の形態と同様の構造である。
【００２２】
尚、本発明の電池は、上記リチウムイオン電池に限定されるものではなく、ニッケル−水素蓄電池、ニッケル−カドミウム蓄電池等のアルカリ蓄電池等にも用いることができることは勿論である。但し、本構造の電池は電極の厚みが小さく、したがって大型の電池を構成した際に多数の電極を積層する電極体（第１の形態に示すような電極体）、多数回巻いて作製する渦巻き電極体（第２の形態に示すような電極体）を有するリチウムイオン電池に最適である。
【００２３】
また、電流取出兼用端子２・３としては、前記のものに限定するものではなく、例えば、図１１に示すように、電流取出部２ｃ…（高さＬ₁₂＝２ｍｍ）の断面形状が方形状のもの、図１２に示すように、電流取出部２ｃ…（高さＬ₁₃＝６ｍｍ）の断面形状が半円形状のもの、図１３に示すように、電流取出部２ｃ…（高さＬ₁₄＝２ｍｍ）の断面形状が台形状のものを用いることも可能である。
更に、電流取出兼用端子２・３に形成されている溝２ｄ・３ｄは必ずしも必要ではないが、溝２ｄ・３ｄが形成されていない場合には電流取出兼用端子２・３の抵抗が低くなるので、抵抗溶接時に大電流が必要となる。したがって、抵抗溶接時の溶接容易性を考慮すれば、電流取出兼用端子２・３に溝２ｄ・３ｄを形成するのが望ましい。
【００２４】
加えて、電流取出兼用端子２・３の材質としては、前記のものに限定するものではなく、正極側の電流取出兼用端子２としてはアルミニウム、チタン等が例示され、また負極側の電流取出兼用端子３としてはステンレス、銅等が例示される。
また、前記実施の形態ではリード体２ｂと端子部２ａとは螺着されているが、このような構造に限定するものではなく、リード体２ｂに形成された穴に端子部２ａを嵌合するよな構造であっても良く、更にリード体２ｂと端子部２ａとを一体成形するような構造であっても良い。
【００２５】
更に、上述したように、本発明の電池はリチウムイオン電池に最適であるが、このような電池における正極活物質としては上記ＬｉＣｏＯ₂ に限定されるものではなく、例えばＬｉＮｉＯ₂ 、ＬｉＭｎＯ₂ 、ＬｉＦｅＯ₂ であっても良い。負極活物質としては上記黒鉛に限定されるものではなく、例えばリチウムイオンを吸蔵、放出し得る合金及び金属リチウムが例示される。非水系電解液としては、上記発明の実施の形態に示すものの他、ビニレンカーボネート、プロピレンカーボネートなどの有機溶媒や、これらとジメチルカーボネート、１，２−ジメトキシエタン、１，２−ジエトキシエタン、エトキシメトキシエタンなどの低沸点溶媒との混合溶媒に、ＬｉＣｌＯ₄ 、ＬｉＣＦ₃ ＳＯ₃ などの溶質を０．７〜１．５Ｍ（モル／リットル）の割合で溶かした溶液が例示される。
【００２６】
【実施例】
（実施例１）
実施例１としては、上記発明の実施の形態における第１の形態に示したリチウムイオン電池を用いた。
このような構造の電池を、以下本発明電池Ａ１と称する。
【００２７】
（実施例２）
実施例２としては、上記発明の実施の形態における第２の形態に示したリチウムイオン電池を用いた。
このような構造の電池を、以下本発明電池Ａ２と称する。
（実施例３）
実施例３としては、上記発明の実施の形態における第３の形態に示したリチウムイオン電池を用いた。
このような構造の電池を、以下本発明電池Ａ３と称する。
【００２８】
（比較例）
正極及び負極に箔状のリード線を溶着し、このリード線の他端を端子と溶接した他は、上記実施例１と同様の構造の電池である。尚、本比較例は、特開平７−１１１１６１号公報に記載の電池と略同様の電池である。
このような構造の電池を、以下比較電池Ｘと称する。
【００２９】
〔実験１〕
上記本発明電池Ａ１、Ａ２と比較電池Ｘとにおける、放電特性を調べたので、その結果を表１に示す。尚、本実験における実験条件は、１０Ａの電流で電池電圧が４．１Ｖとなるまで充電した後、４．１Ｖの定電圧充電で電流値が１Ａ以下となるまで充電し、１時間の休止の後、１０Ａの電流で１０秒間放電し、１０秒経過時の電圧を計測した。
【００３０】
【表１】

【００３１】
表１から明らかなように、比較電池Ｘでは１０秒経過時の電圧が３．７Ｖであるのに対して、本発明電池Ａ１及びＡ２ではそれぞれ１０秒経過時の電圧が３．９２Ｖ、３．９４Ｖであって、比較電池Ｘに比べて格段に電圧が高くなっていることが認められる。これは、本発明電池Ａ１及びＡ２では、電流取出兼用端子と正極及び負極とが直接溶着されているため、電池の内部抵抗が低減するのに対して、比較電池Ｘではリード線により正極及び負極と端子とが接続されているため、電池の内部抵抗が高くなるという理由によるものと考えられる。
【００３２】
〔実験２〕
上記本発明電池Ａ１、Ａ２と比較電池Ｘとにおける、サイクル特性を調べたので、その結果を表２に示す。尚、本実験における充放電条件は、１０Ａの電流で電池電圧が４．１Ｖとなるまで充電した後、１０Ａの電流で電池電圧が２．７Ｖとなるまで放電するという条件であり、サイクル経過後の電池容量が初期容量の８０％となった時点で電池寿命とした。
【００３３】
【表２】

【００３４】
表２から明らかなように、比較電池Ｘでは４２０サイクルで電池寿命となっているのに対して、本発明電池Ａ１及びＡ２ではそれぞれ５３０サイクル、５４０サイクルで電池寿命となっていることが認められる。これは、本発明電池Ａ１及びＡ２では、電流取出兼用端子の電流取出部が多数形成され、正極及び負極の上端から下端に至るまで均一な電流分布となるので、充放電時に電池温度が高くなるのが抑制されるのに対して、比較電池Ｘではリード線が正極及び負極の上部でのみ接続されているため、電流が正極及び負極の上部に集中し、充放電時に電池温度が高くなるという理由によるものと考えられる。
【００３５】
〔実験３〕
上記本発明電池Ａ１、Ａ２と比較電池Ｘとにおいて、電解液注液前の内部短絡による不良品の発生率を調べたので、その結果を表３に示す。
【００３６】
【表３】

【００３７】
表３から明らかなように、比較電池Ｘでは不良品の発生率が３％であるのに対して、本発明電池Ａ１〜Ａ３では不良品の発生率が２％以下であることが認められる。特に、本発明電池Ａ３では不良品の発生率が１％と極めて低くなっていることが認められる。これは、本発明電池Ａ１及びＡ２では、電流取出兼用端子の電流取出部の高さが大きいので、電流取出部が正極又は負極を押圧する力が大きくなって、電池内部での短絡が生じるのに対して、電流取出兼用端子の電流取出部の高さが小さいので、電流取出部が正極又は負極を押圧する力が小さくなって、電池内部での短絡が生じ難くなるという理由によるものと考えられる。
【００３８】
【発明の効果】
以上で説明したように本発明によれば、電池内での抵抗を低くすることができるので、急激な出力変動を伴う電気自動車用電池等として対応可能であり、しかも電池温度の上昇を抑制してサイクル特性を向上させ、且つ製造コストの低減と内部短絡による不良率の低減とを達成することができるといった優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明の第１の形態に係るリチウムイオン電池の斜視図である。
【図２】図１の電池の内部構造を示す分解斜視図である。
【図３】図１の電池に用いる正極の正面図である。
【図４】図１の電池に用いる電流取出兼用端子の斜視図である。
【図５】図１の電池に用いる電流取出兼用端子の側面図である。
【図６】図１の電池に用いる電流取出兼用端子の平面図である。
【図７】図１の電池に用いる電流取出兼用端子の背面図である。
【図８】図１の電池を作製時における抵抗溶接の際の通電箇所を示す説明図である。
【図９】本発明の第２の形態に係るリチウムイオン電池の斜視図である。
【図１０】本発明の第３の形態に係るリチウムイオン電池に用いる電流取出兼用端子の側面図である。
【図１１】電流取出兼用端子の変形例を示す側面図である。
【図１２】電流取出兼用端子の他の変形例を示す側面図である。
【図１３】電流取出兼用端子の更に他の変形例を示す側面図である。
【符号の説明】
１：角型電槽
２：電流取出兼用端子
２ａ：端子部
２ｂ：リード体
２ｃ：電流取出部
３：電流取出兼用端子
３ａ：端子部
３ｂ：リード体
３ｃ：電流取出部
６：電極体
７：正極
７ｂ：活物質未塗布部
８：セパレータ
９：負極
１２：渦巻き電極体
１３：正極
１４：負極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery, and more particularly to a prismatic battery in which an outer can has a prismatic bottomed cylindrical shape among nonaqueous electrolyte batteries such as lithium ion batteries.
[0002]
[Prior art]
In recent years, in addition to small batteries used for various electric devices, large batteries for power storage or electric vehicles have been actively developed. In such batteries, a plurality of batteries are used. Often used in electrical connection. In this case, if space saving is taken into consideration, a prismatic battery that can reduce an extra space by adhering a plurality of batteries to each other is desirable. Among the prismatic batteries, a high energy density is desirable. High power density lithium-ion batteries are promising.
[0003]
Here, as a current extraction structure in the prismatic lithium ion battery, one end of a lead wire such as a foil is welded to a positive electrode made of LiCoO ₂ or the like and a negative electrode made of carbon or the like, and the other end of the lead wire is made. Is welded to the external electrode.
[0004]
[Problems to be solved by the invention]
However, in the conventional prismatic lithium ion battery, since the resistance in the battery is increased due to the fact that the lead wire is foil-like and there are two locations where the lead wire is welded, a rapid output is required. It could not be said that it has sufficient performance as a battery for electric vehicles with fluctuations. Further, since the lead wire is welded to the upper part of the positive electrode and the negative electrode, the current is concentrated on the upper part of the electrode body, the battery temperature is increased, and the cycle characteristics are deteriorated. In addition, the welding of the lead wire has to be performed using an expensive laser device, which has a problem that the manufacturing cost increases.
[0005]
The present invention has been made in consideration of the above-described conventional problems, and is optimal as a battery for an electric vehicle or the like with sudden output fluctuations by reducing the resistance in the battery, and the battery temperature. It is an object of the present invention to provide a battery capable of improving the cycle characteristics by suppressing the rise of the battery and reducing the manufacturing cost.
[0006]
[Means for Solving the Problems]
The first invention that achieves the above object is configured as follows. An electrode body in which a positive electrode and a negative electrode are arranged via a separator is arranged in an outer can, and the positive electrode and the negative electrode are electrically connected to an external terminal for positive electrode and an external terminal for negative electrode, respectively. In the battery, the electrode body is a spiral electrode body, and at least one of the external terminals is a current extraction / use terminal directly connected to the positive electrode or the negative electrode, the current extraction / use terminal. Has a terminal part projecting out of the battery, and a plate-like lead body fixed to the terminal part and connected to the positive electrode or the negative electrode, and perpendicular to the core direction of the spiral electrode body It is characterized by being arranged in a direction .
If it is the said structure, since the external terminal and the positive electrode or the negative electrode are directly connected without going through a lead wire, the resistance in the battery is lowered, and it was used as a battery for an electric vehicle or the like with sudden output fluctuations. Even if it is a case, sufficient performance can be exhibited.
[0007]
According to a second aspect of the present invention, in the battery according to the first aspect of the present invention, the plate-like lead body includes a plurality of projecting portion tips formed integrally with the lead body on one surface. The lead body is electrically connected to the positive electrode or the negative electrode by welding the current extraction part to the positive electrode or the negative electrode.
With the current extraction multipurpose terminal having such a structure, welding points between the anchored lead body and the positive electrode or the negative electrode terminal part protrudes outside the battery requires only one place, moreover, acts as a prior art lead wire Since the lead body to be performed is plate-shaped, the resistance in the battery is remarkably reduced. Furthermore, since a plurality of current extraction portions that are welded to the positive electrode or the negative electrode are formed so as to protrude, it is possible to suppress the current from being concentrated on the upper portion of the electrode body, and to suppress an increase in battery temperature.
[0008]
According to a third invention, in the battery according to the second invention, as the electrode body, the positive electrode protrudes from one end portion of the separator and the negative electrode protrudes from the other end portion of the separator. using the electrode body, the protrusion tip, characterized in that it is welded to an end portion of the positive electrode or the negative electrode.
Thus, if the positive electrode protrudes from one end of the separator and the negative electrode protrudes from the other end of the separator, the tip of the protruding portion of the current extraction portion and the end of the positive or negative electrode are welded. In this case, it is possible to prevent a short circuit from occurring.
[0009]
In the battery according to the second or third invention, the current extraction portion may have a tapered cross-sectional shape , and in this way, the protrusion of the current extraction portion and the positive electrode or the negative electrode Since the contact area is reduced, the tip of the protruding portion and the positive electrode or the negative electrode can be welded by simple resistance welding. Therefore, the manufacturing cost of the battery can be reduced. An example in which the cross-sectional shape is tapered is a case where the cross-sectional shape is a mountain shape or a substantially semicircular shape.
According to a fourth aspect of the present invention, in the battery according to the second aspect of the invention, the lead body is divided into two leaves on the tip side from the connection portion with the terminal portion that protrudes out of the battery by a groove formed in the center portion. It is the shape made .
According to a fifth aspect of the present invention, an electrode body in which a positive electrode and a negative electrode are disposed via a separator is disposed in an outer can, and the positive electrode and the negative electrode are a positive external terminal and a negative external terminal, respectively. In the battery having a structure to be electrically connected, at least one of the external terminals is a current extraction / combination terminal directly connected to the positive electrode or the negative electrode, and the current extraction / exclusion terminal is outside the battery. And a plate-like lead body fixed to the terminal part and electrically resistance-welded to the positive electrode or the negative electrode, and the lead body is formed by a groove formed in the central part. It is characterized in that the tip side is divided into two leaves from the connection part with the terminal part protruding outside the battery .
Thus, when the lead body has a shape in which a groove is formed in the central portion and the tip side is divided into two leaves from the connection portion with the terminal portion by the groove , welding at the time of resistance welding is easy.
[0010]
According to a sixth aspect of the present invention, in the battery according to the fifth aspect of the present invention, the electrode body comprises an electrode body having a laminated structure in which a plurality of positive and negative electrodes and separators are stacked.
According to a seventh aspect of the present invention, in the battery according to the fifth aspect of the invention, the plate-like lead body includes a plurality of projecting portion tips formed integrally with the lead body on one surface. The lead body is electrically connected to the positive electrode or the negative electrode by welding the current extraction part to the positive electrode or the negative electrode.
According to an eighth aspect of the present invention, in the battery according to the first , second , third , fourth , fifth , sixth or seventh aspect , the outer can is a rectangular battery having a rectangular bottomed cylindrical shape. And
[0011]
DETAILED DESCRIPTION OF THE INVENTION
[First embodiment]
A first embodiment of the present invention will be described below based on FIGS. 1 is a perspective view of a lithium ion battery according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view showing the internal structure of the battery of FIG. 1, and FIG. 3 is a front view of a positive electrode used in the battery of FIG. 4 is a perspective view of a current extraction / use terminal used in the battery of FIG. 1, FIG. 5 is a side view of the current extraction / use terminal used in the battery of FIG. 1, and FIG. 6 is a plan view of the current extraction / use terminal used in the battery of FIG. FIG. 7 is a rear view of the current extraction / use terminal used in the battery of FIG. 1, and FIG. 8 is an explanatory diagram showing energized locations during resistance welding in producing the battery of FIG.
As shown in FIG. 1, a lithium ion battery according to a first embodiment of the present invention is a rectangular battery case (square outer can) 1 made of aluminum (thickness is 2 mm, inner dimension is 100 mm, long The upper lid 15 is laser welded to the opening of the square battery case 1. From the upper surface of the upper lid 15, a terminal portion 2 a (consisting of M8 volts) that constitutes a part of a positive-current-carrying terminal 2 described later and a part of a negative-current-carrying terminal 3 that will be described later are constructed. A terminal portion 3a (consisting of M8 bolts) is formed so as to protrude through

insulators

4 and 4, and a safety valve 5 is provided on the upper surface of the upper lid 15.
[0012]
The square battery case 1 is loaded with an electrode body 6 as shown in FIG. 2, which comprises a positive electrode 7 mainly composed of LiCoO ₂ and a negative electrode 9 mainly composed of graphite powder. In this structure, a large number of electrode groups 10 each made up of a separator 8 made of a polypropylene microporous film having ion permeability are stacked. As shown in FIG. 3, the positive electrode 7 includes an active material application portion 7 a (width L ₁ = 60 mm) and an active material non-application portion 7 b (width L) formed on the current extraction / use terminal 2 side described later. ₂ = 2 mm), and this active material uncoated portion 7 b is arranged so as to protrude from one end portion 8 a of the separator 8. On the other hand, although not shown, the negative electrode 9 is also composed of an active material application part and an active material non-application part formed on the side of the current extraction / use terminal 3 on the negative electrode side described later. The part is arranged so as to protrude from the other end 8 b of the separator 8.
[0013]
On the protruding end side (active material uncoated portion 7b side) of the positive electrode 7, the positive electrode side current extraction and use terminal 2 made of stainless steel is welded (however, it is shown in an exploded state in FIG. 2). . As shown in FIG. 4, the current extraction / use terminal 2 includes a plate-like lead body 2b having a groove 2d formed in the center portion, and a plurality of integrally projecting lead bodies 2b on one surface of the lead body 2b. The current extraction portions 2c ... formed and the terminal portions 2a screwed to the lead body 2b, and the tip of the current extraction portions 2c ... and the positive electrode 7 are welded. Further, as shown in FIGS. 5 to 7, the specific dimensions of the current extraction / use terminal 2 are as follows: the height L ₃ of the current extraction / use terminal 2 is 120 mm, and the pitch L ₄ between the current extraction portions 2c is 10 mm. (Both refer to FIG. 5), the width L ₅ = 38 mm of the lead body 2b, the thickness L ₆ = 10 mm of the lead body 2b, the height L ₇ = 6 mm of the current extraction portion 2c (both refer to FIG. 6), the lead body The height L _{8 of} 2b is 90 mm, the length L _{9 of} the groove 2d is 85 mm, and the width L _{10 of the} groove 2d is 2 mm (both see FIG. 7).
[0014]
On the other hand, the negative electrode side current extraction / use terminal 3 made of nickel is welded to the protruding end portion side (active material uncoated portion 9b side) of the negative electrode 9 (however, in FIG. 2, it is drawn in an exploded state). ) The negative electrode side current extraction / use terminal 3 has the same structure as the positive electrode side current extraction / use terminal 2, and more specifically, a plate-like lead body 3b having a groove 3d formed at the center thereof, The lead body 3b includes a current extraction portion 3c formed so as to project integrally with the lead body 3b on one surface, and a terminal portion 3a screwed to the lead body 3b. Further, the current extraction / use terminal 3 on the negative electrode side and the current extraction / use terminal 2 on the positive electrode side are arranged to face each other.
[0015]
Here, the lithium ion battery having the above-described structure was produced as follows.
(Preparation of positive electrode)
First, after preparing a positive electrode mixture by mixing a positive electrode active material composed of LiCoO _{2 having} an average particle size of 5 μm and a conductive agent composed of artificial graphite at a weight ratio of 9: 1, this positive electrode mixture, An N-methyl-2-pyrrolidone (NMP) solution in which polyvinylidene fluoride (PVDF), which is a binder, is dissolved at a ratio of 5% by weight, is a ratio of the weight ratio of the positive electrode mixture and PVDF of 95: 5. The slurry was adjusted by kneading so that Next, this slurry was applied to both surfaces of a strip-shaped positive electrode current collector (thickness: 20 μm) made of aluminum by a doctor blade method, and then vacuum-dried at 150 ° C. for 2 hours to produce a positive electrode 7. In addition, at the time of the slurry application, the slurry was not applied to the portion to be welded to the positive electrode side current extraction / use terminal 2. Thereby, the active material non-application part 7b is formed.
[0016]
(Preparation of negative electrode)
First, a graphite powder was produced by injecting an air stream onto a carbon lump (d ₀₀₂ value = 3.356 Å, Lc value> 1000 Å) to pulverize the carbon lump. Next, this graphite powder and an N-methyl-2-pyrrolidone (NMP) solution in which PVDF as a binder is dissolved at a ratio of 5% by weight, the weight ratio of the graphite powder to PVDF is 85:15. The slurry was adjusted by kneading so that the ratio of Next, this slurry was applied to both surfaces of a strip-shaped negative electrode current collector (thickness: 20 μm) made of copper by a doctor blade method, and then vacuum dried at 150 ° C. for 2 hours to produce a negative electrode. At the time of applying the slurry, no slurry was applied to the portion to be welded with the current extraction / use terminal 3 on the negative electrode side. Thereby, an active material non-application part is formed.
[0017]
(Preparation of electrolyte)
A non-aqueous electrolyte was prepared by dissolving LiPF ₆ in a mixed solvent of ethylene carbonate and diethyl carbonate having a volume mixing ratio of 1: 1 at a ratio of 1 M (mol / liter).
[0018]
(Battery assembly)
First, a large number of electrode groups 10 having a structure in which the positive electrode 7 and the negative electrode 9 are arranged via a separator 8 made of polypropylene and having a microporous membrane made of an ion are laminated to produce an electrode body 6. . When the electrode body 6 is manufactured, the active material uncoated portion 7b of the positive electrode 7 is disposed so as to protrude from one end portion 8a of the separator 8, and the active material uncoated portion of the negative electrode 9 is disposed at the other end of the separator 8. It arrange | positions so that it may protrude from the part 8b. Next, the protruding end of the positive electrode 7 and the tip of the protruding portion of the current extracting portion 2c of the current extraction / use terminal 2 on the positive electrode side, and the protruding end portion of the negative electrode 9 and the current extraction portion of the current extraction / use terminal 3 on the negative electrode side The tip of the protruding portion 3c was resistance welded under the following conditions. At this time, as shown in FIG. 8, the energization locations 11a... 11b on the back side of the current extraction / use terminal are respectively connected to the plus energization terminal and the minus energization terminal of the welding machine (not shown). Was performed by electrically connecting the two.
[0019]
・ Welding condition output: 600W
Material of welding terminal: Tungsten weld area: 2mm ² or less per contact portion between the current extraction part and the electrode After this, the electrode body 6 on which the current extraction and use terminals 2 and 3 are welded is placed in the rectangular battery case 1. The upper lid 15 was laser welded to the opening of the square battery case 1. Finally, after injecting nonaqueous electrolyte from the hole for attaching the safety valve, the safety valve 5 was attached to the hole for attaching the safety valve to produce a lithium ion battery having a theoretical capacity of 50 Ah.
[0020]
[Second form]
A second embodiment of the present invention will be described below based on the perspective view of the lithium ion battery shown in FIG.
As shown in FIG. 9, a spiral electrode body 12 in which a strip-like positive electrode 13 and a strip-like negative electrode 14 are wound in an elliptical spiral shape through a strip-like separator (not shown in FIG. 9) as an electrode body. The structure is the same as that of the first embodiment except that is used.
[0021]
[Third embodiment]
A third embodiment of the present invention will be described below based on the side view of the current extraction / use terminal shown in FIG.
As shown in FIG. 10, as the current extraction / use terminal 2, the number of the current extraction portions 2c... Is small and the height L ₁₁ of the current extraction portions 2c. Similar structure.
[0022]
The battery of the present invention is not limited to the above lithium ion battery, but can of course be used for alkaline storage batteries such as nickel-hydrogen storage batteries and nickel-cadmium storage batteries. However, the battery of this structure has a small electrode thickness. Therefore, when a large battery is formed, an electrode body (electrode body as shown in the first embodiment) in which a large number of electrodes are stacked, and a spiral wound by making many turns It is most suitable for a lithium ion battery having an electrode body (electrode body as shown in the second embodiment).
[0023]
Further, the current extraction shared terminals 2 and 3 are not limited to those described above. For example, as shown in FIG. 11, the current extraction portion 2 c (height L ₁₂ = 2 mm) has a square cross-sectional shape. As shown in FIG. 12, the current extraction portion 2c (height L ₁₃ = 6 mm) has a semicircular cross section, and as shown in FIG. 13, the current extraction portion 2c (height L _14). = 2 mm), the cross-sectional shape may be trapezoidal.
Further, the

grooves

2d and 3d formed in the current extraction / use terminals 2 and 3 are not necessarily required, but if the

grooves

2d and 3d are not formed, the resistance of the current extraction / use terminals 2 and 3 is lowered. A large current is required during resistance welding. Therefore, considering the ease of welding at the time of resistance welding, it is desirable to form the

grooves

2d and 3d in the current extraction / use terminals 2 and 3.
[0024]
In addition, the material for the current extraction and use terminals 2 and 3 is not limited to the above-described materials. Examples of the current extraction and use terminal 2 on the positive electrode side include aluminum and titanium. Examples of the terminal 3 include stainless steel and copper.
In the above embodiment, the lead body 2b and the terminal portion 2a are screwed. However, the present invention is not limited to such a structure, and the terminal portion 2a is fitted into a hole formed in the lead body 2b. Alternatively, the lead body 2b and the terminal portion 2a may be integrally formed.
[0025]
Furthermore, as described above, the battery of the present invention is optimal for a lithium ion battery, but the positive electrode active material in such a battery is not limited to the above LiCoO ₂ , for example, LiNiO ₂ , LiMnO ₂ , LiFeO ₂ may be sufficient. The negative electrode active material is not limited to the above graphite, and examples thereof include alloys and metal lithium that can occlude and release lithium ions. Examples of the non-aqueous electrolyte include organic solvents such as vinylene carbonate and propylene carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, and ethoxy in addition to those shown in the embodiment of the present invention. Examples thereof include a solution in which a solute such as LiClO ₄ and LiCF ₃ SO ₃ is dissolved in a mixed solvent with a low boiling point solvent such as methoxyethane at a ratio of 0.7 to 1.5 M (mol / liter).
[0026]
【Example】
Example 1
As Example 1, the lithium ion battery shown in the first embodiment in the embodiment of the present invention was used.
The battery having such a structure is hereinafter referred to as the present invention battery A1.
[0027]
(Example 2)
As Example 2, the lithium ion battery shown in the second embodiment in the embodiment of the present invention was used.
The battery having such a structure is hereinafter referred to as the present invention battery A2.
Example 3
As Example 3, the lithium ion battery shown in the third embodiment in the embodiment of the present invention was used.
The battery having such a structure is hereinafter referred to as a present invention battery A3.
[0028]
(Comparative example)
The battery has the same structure as in Example 1 except that a foil-like lead wire is welded to the positive electrode and the negative electrode, and the other end of the lead wire is welded to the terminal. In addition, this comparative example is a battery substantially the same as the battery described in JP-A-7-111161.
The battery having such a structure is hereinafter referred to as a comparative battery X.
[0029]
[Experiment 1]
Since the discharge characteristics of the present invention batteries A1 and A2 and the comparative battery X were examined, the results are shown in Table 1. The experimental conditions in this experiment are that the battery voltage is charged to 4.1 V with a current of 10 A, then the battery is charged with a constant voltage of 4.1 V until the current value becomes 1 A or less, and the rest of 1 hour is stopped. Thereafter, the battery was discharged at a current of 10 A for 10 seconds, and the voltage when 10 seconds passed was measured.
[0030]
[Table 1]

[0031]
As is clear from Table 1, the voltage at the time when 10 seconds elapses in the comparative battery X is 3.7 V, while the voltages at the time when 10 seconds elapse are 3.92 V and 3.2 V according to the present invention batteries A1 and A2. It is 94V, and it is recognized that the voltage is significantly higher than that of the comparative battery X. This is because, in the batteries A1 and A2 of the present invention, since the current extraction terminal and the positive electrode and the negative electrode are directly welded, the internal resistance of the battery is reduced, whereas in the comparative battery X, the positive and negative electrodes are connected by the lead wires. This is presumably because the internal resistance of the battery is increased.
[0032]
[Experiment 2]
Since the cycle characteristics of the present invention batteries A1 and A2 and the comparative battery X were examined, the results are shown in Table 2. In this experiment, the charge / discharge conditions are such that the battery voltage is charged to 10V with a current of 10A and then discharged until the battery voltage reaches 2.7V with a current of 10A. The battery life was determined when the battery capacity reached 80% of the initial capacity.
[0033]
[Table 2]

[0034]
As is clear from Table 2, the battery life of the comparative battery X is 420 cycles, whereas the batteries A1 and A2 of the present invention have a battery life of 530 cycles and 540 cycles, respectively. . In the batteries A1 and A2 of the present invention, a large number of current extraction portions of the current extraction / use terminal are formed, and a uniform current distribution is obtained from the upper end to the lower end of the positive electrode and the negative electrode. In contrast, in Comparative Battery X, the lead wire is connected only at the top of the positive and negative electrodes, so that current concentrates on the top of the positive and negative electrodes, and the battery temperature increases during charge and discharge. This is probably due to the reason.
[0035]
[Experiment 3]
Table 3 shows the results of the occurrence of defective products due to internal short circuits before electrolyte injection in the above-described inventive batteries A1 and A2 and comparative battery X.
[0036]
[Table 3]

[0037]
As is clear from Table 3, it is recognized that the rate of occurrence of defective products in the comparative battery X is 3%, whereas the rate of occurrence of defective products is 2% or less in the batteries A1 to A3 of the present invention. In particular, it can be seen that the incidence of defective products is extremely low at 1% in the battery A3 of the present invention. In the present invention batteries A1 and A2, the height of the current extraction portion of the current extraction / use terminal is large, so that the force with which the current extraction portion presses the positive electrode or the negative electrode is increased, causing a short circuit inside the battery. On the other hand, since the height of the current extraction part of the current extraction / use terminal is small, the force with which the current extraction part presses the positive electrode or the negative electrode is reduced, and it is considered that the short circuit inside the battery is less likely to occur. It is done.
[0038]
【The invention's effect】
As described above, according to the present invention, the resistance in the battery can be lowered, so that it can be used as a battery for an electric vehicle with a sudden output fluctuation, and the rise in battery temperature is suppressed. As a result, the cycle characteristics can be improved, and the manufacturing cost can be reduced and the defective rate due to the internal short circuit can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view of a lithium ion battery according to a first embodiment of the present invention.
2 is an exploded perspective view showing an internal structure of the battery shown in FIG. 1. FIG.
3 is a front view of a positive electrode used in the battery of FIG. 1. FIG.
4 is a perspective view of a current extraction / use terminal used in the battery of FIG. 1. FIG.
FIG. 5 is a side view of a current extraction / use terminal used in the battery of FIG. 1;
6 is a plan view of a current extraction / use terminal used in the battery shown in FIG. 1. FIG.
7 is a rear view of a current extraction / use terminal used in the battery of FIG. 1. FIG.
8 is an explanatory diagram showing energized locations during resistance welding when the battery of FIG. 1 is manufactured.
FIG. 9 is a perspective view of a lithium ion battery according to a second embodiment of the present invention.
FIG. 10 is a side view of a current extraction / use terminal used in a lithium ion battery according to a third embodiment of the present invention.
FIG. 11 is a side view showing a modification of the current extraction / use terminal.
FIG. 12 is a side view showing another modified example of the current extraction / use terminal.
FIG. 13 is a side view showing still another modified example of the current extraction / use terminal.
[Explanation of symbols]
1: Square battery case 2: Current extraction combined terminal 2a: Terminal portion 2b: Lead body 2c: Current extraction section 3: Current extraction combined terminal 3a: Terminal section 3b: Lead body 3c: Current extraction section 6: Electrode body 7: Positive electrode 7b: active material uncoated portion 8: separator 9: negative electrode 12: spiral electrode body 13: positive electrode 14: negative electrode

Claims

An electrode body in which a positive electrode and a negative electrode are arranged via a separator is arranged in an outer can, and the positive electrode and the negative electrode are electrically connected to an external terminal for positive electrode and an external terminal for negative electrode, respectively. In batteries,
The electrode body comprises a spiral electrode body,
At least one of the external terminals is a current extraction / use terminal directly connected to the positive electrode or the negative electrode ,
The current extraction / use terminal includes a terminal portion that protrudes outside the battery, and a plate-like lead body that is fixed to the terminal portion and connected to the positive electrode or the negative electrode, and the winding of the spiral electrode body. Arranged in a direction perpendicular to the core direction,
A battery characterized by that.

The plate-like lead body has a current extraction part composed of a plurality of projecting part tips formed integrally with the lead body on one surface,
The lead body is electrically connected to the positive electrode or the negative electrode by welding the current extraction part to the positive electrode or the negative electrode.
The battery according to claim 1.

As the electrode body, an electrode body in which the positive electrode protrudes from one end portion of the separator and the negative electrode protrudes from the other end portion of the separator, and the tip of the protruding portion is an end portion of the positive electrode or the negative electrode. Has been welded to the
The battery according to claim 2.

The lead body has a shape in which the tip side is divided into two leaves from the vicinity of the connection portion with the terminal portion that protrudes out of the battery by a groove formed in the center portion .
The battery according to claim 2 .

An electrode body in which a positive electrode and a negative electrode are disposed via a separator is disposed in an outer can, and the positive electrode and the negative electrode are electrically connected to an external terminal for positive electrode and an external terminal for negative electrode, respectively. In batteries,
At least one of the external terminals is a current extraction / use terminal directly connected to the positive electrode or the negative electrode,
The current extraction combined terminal has a terminal portion protruding outside the battery, and a plate-like lead body fixed to the terminal portion and welded to the positive electrode or the negative electrode,
The lead body has a distal end side that is connected to a terminal portion that protrudes out of the battery by a groove formed in a central portion. 2 The shape is divided into leaves,
A battery characterized by that.

The electrode body comprises an electrode body having a laminated structure in which a plurality of electrode groups each composed of positive and negative electrodes and a separator are stacked.
The battery according to claim 5.

The plate-like lead body has a current extraction part composed of a plurality of projecting part tips formed integrally with the lead body on one surface,
The lead body is electrically connected to the positive electrode or the negative electrode by welding the current extraction part to the positive electrode or the negative electrode.
The battery according to claim 5.

The outer can is a square battery having a square bottomed cylindrical shape,
The battery according to claim 1, 2 , 3 , 4 , 5 , 6, or 7 .