JP3738166B2

JP3738166B2 - Non-aqueous electrolyte secondary battery

Info

Publication number: JP3738166B2
Application number: JP2000070927A
Authority: JP
Inventors: 広一佐藤; 直哉中西; 俊之能間; 育郎米津
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 2000-03-14
Filing date: 2000-03-14
Publication date: 2006-01-25
Anticipated expiration: 2020-03-14
Also published as: JP2001256952A

Description

【０００１】
【発明の属する技術分野】
本発明は、電池缶の内部に二次電池要素となる巻き取り電極体が収容され、電池缶に設けた一対の電極端子部から巻き取り電極体の発生電力を取り出すことが出来る非水電解液二次電池に関するものである。
【０００２】
【従来の技術】
近年、携帯型電子機器、電気自動車等の電源として、エネルギー密度の高いリチウムイオン二次電池が注目されている。例えば電気自動車に用いられる比較的大きな容量の円筒型リチウムイオン二次電池は、図１１及び図１２に示す様に、筒体(11)の両端部に蓋体(12)(12)を溶接固定してなる円筒状の電池缶(１)の内部に、巻き取り電極体(４)を収容して構成されている。両蓋体(12)(12)には、正負一対の電極端子機構(９)(９)が取り付けられており、巻き取り電極体(４)の両極と両電極端子機構(９)(９)とが互いに接続されて、巻き取り電極体(４)が発生する電力を一対の電極端子機構(９)(９)から外部に取り出すことが可能となっている。又、各蓋体(12)には圧力開閉式のガス排出弁(13)が取り付けられている。
【０００３】
巻き取り電極体(４)は、図１３に示す様に、それぞれ帯状の正極(41)と負極(43)の間に帯状のセパレータ(42)を介在させて、これらを渦巻き状に巻回して構成されている。正極(41)は、アルミニウム箔からなる帯状芯体(45)の両面にリチウム複合酸化物からなる正極活物質(44)を塗布して構成され、負極(43)は、銅箔からなる帯状芯体(47)の両面に炭素材料を含む負極活物質(46)を塗布して構成されている。セパレータ(42)には、非水電解液が含浸されている。
【０００４】
ここで、正極(41)及び負極(43)はそれぞれセパレータ(42)上に幅方向へずらして重ね合わされ、渦巻き状に巻き取られている。これによって、巻き取り電極体(４)の巻き軸方向の両端部の内、一方の端部では、セパレータ(42)の端縁よりも外方へ正極(41)の芯体(45)の端縁(48)が突出すると共に、他方の端部では、セパレータ(42)の端縁よりも外方へ負極(43)の芯体(47)の端縁(48)が突出している。そして、巻き取り電極体(４)の両端部にはそれぞれ円板状の集電板(32)が抵抗溶接され、該集電板(32)がリード部材(33)を介して図１２に示す電極端子機構(９)の基端部に接続される。
【０００５】
電極端子機構(９)は、電池缶(１)の蓋体(12)を貫通して取り付けられた電極端子(91)を具え、該電極端子(91)の基端部には鍔部(92)が形成されている。蓋体(12)の貫通孔には絶縁パッキング(93)が装着され、蓋体(12)と電極端子(91)の間の電気的絶縁性とシール性が保たれている。電極端子(91)には、蓋体(12)の外側からワッシャ(94)が嵌められると共に、第１ナット(95)及び第２ナット(96)が螺合している。そして、第１ナット(95)を締め付けて、電極端子(91)の鍔部(92)とワッシャ(94)によって絶縁パッキング(93)を挟圧することにより、シール性を高めている。
尚、前記リード部材(33)の先端部は、電極端子(91)の鍔部(92)に、スポット溶接或いは超音波溶接によって固定されている。
【０００６】
しかしながら、図１２に示す集電構造を有する非水電解液二次電池においては、巻き取り電極体(４)の正極(41)及び負極(43)を構成する芯体(45)(47)の端縁(48)(48)の面積が小さいため、芯体端縁と集電板(32)の間の接触面積が小さく、これによって電池の内部抵抗が大きくなる問題があった。
特に電気自動車用の電源等として用いるリチウムイオン二次電池においては、高容量であると共に、高出力を得るために出来るだけ内部抵抗を低減させることが必要となる。更に、製造コスト削減のためには、生産性に優れた集電構造が必要となる。
【０００７】
そこで、生産性に優れた低抵抗な電池として、円板状の集電板に、先端角が９０°以下の断面Ｖ字状の複数の突起部を形成し、該集電板を芯体端縁に押さえ付けた状態で、前記突起部にレーザビームを照射することによって、集電板を極板群に溶接する構造が提案されている(特公平２−４１０２号)。
【０００８】
【発明が解決しようとする課題】
ところが、上記構造においては、集電板の突起部の断面形状が鋭角のＶ字状であるために、突起部と芯体端縁の間の接触面積が小さく、溶接部における接触抵抗が大きいばかりでなく、溶接部以外の領域では接触状態が悪いため、集電性能が低い問題点があった。然も、レーザビームを照射すべきＶ字状突起部と芯体端縁の間の接合面が、ビーム照射方向に対して鋭角を為すため、レーザビームが接合面の溶接に有効に作用せず、溶接不良が発生する虞れがあった。
【０００９】
そこで本発明の目的は、電極体を構成する芯体が極めて薄い場合にも芯体端縁と集電板の間に良好な接触状態が得られ、高い集電性能を発揮すると共に、生産性にも優れた集電構造を有する非水電解液二次電池を提供することである。
【００１０】
【課題を解決する為の手段】
本発明に係る非水電解液二次電池において、巻き取り電極体(４)の少なくとも何れか一方の端部には、正極(41)或いは負極(43)を構成する帯状芯体の端縁(48)が突出し、該端縁(48)を覆って集電板(５)が設置されている。
該集電板(５)には、芯体端縁(48)に向かって断面円弧状に突出する複数条の円弧状凸部(52)が形成されると共に、芯体端縁(48)に向かって切り起こした複数条の切り起し片(53)が形成され、これらの円弧状凸部(52)及び切起し片(53)が芯体端縁(48)に食い込んだ状態で、円弧状凸部(52)が芯体端縁(48)に溶接されている。
そして、集電板(５)が一方の電極端子部と連結されている。
【００１１】
上記本発明の非水電解液二次電池においては、巻き取り電極体(４)の芯体端縁(48)に集電板(５)を押し付けることによって、各円弧状凸部(52)が芯体端縁(48)に食い込んで、芯体端縁(48)には、凸部(52)の表面形状に応じた円筒面からなる接合面が形成される。該接合面は、凸部を断面Ｖ字状に形成した場合よりも大きな面積となる。又、各切り起し片(53)が芯体端縁(48)に深く食い込んで、溶接部以外の領域においても、集電板(５)と芯体端縁(48)の間に良好な接触状態が得られる。
従って、各円弧状凸部(52)と芯体端縁(48)の接合部にレーザビーム又は電子ビームを照射して、芯体端縁(48)に集電板(５)を溶接することによって、集電板(５)は大きな接触面積で芯体端縁(48)に接合されることとなり、この結果、接触抵抗が小さくなって、高い集電性能が得られる。
又、集電板(５)の凸部(52)と芯体端縁(48)の接合面は、その中央部にて、ビーム照射方向に対して９０°若しくはそれに近い角度を為すこととなるため、レーザビーム若しくは電子ビームが接合面の溶接に有効に作用し、この結果、大きな接合面積による高い溶接強度が得られることになる。
【００１２】
具体的構成において、集電板(５)は、円板状本体(51)の芯体端縁(48)との対向面に、前記複数条の円弧状凸部(52)及び切り起し片(53)を放射状に形成すると共に、円板状本体(51)の端部に短冊状のリード部(55)を突設して構成され、該リード部(55)の先端が電極端子部と連結されている。
該具体的構成によれば、巻き取り電極体(４)から発生する電流が集電板(５)によって集電され、リード部(55)を経て、電極端子部へ流れることになる。
【００１３】
更に具体的には、各切り起し片(53)は、芯体端縁(48)と接触する長さが集電板(５)の半径の０.５倍以上に形成されている。
これによって、集電板(５)と芯体端縁(48)の間に充分な広さの接触領域が確保されて、高い集電性能が得られる。
【００１４】
又、各切り起し片(53)は、芯体端縁(48)に向かって突出する長さが円弧状凸部(52)の突出長さの１.０倍以上、１ . ５倍以下に形成されている。
これによって、各円弧状凸部(52)が芯体端縁(48)と広い面積で接触すると共に、各切り起し片(53)が芯体端縁(48)に充分な深さで食い込むことになる。
【００１５】
尚、集電板(５)の材質としては、Ｃｕ、Ａｌ、Ｎｉ、ＳＵＳ、Ｔｉ、或いはこれらの金属の合金を採用することが出来る。これによって、非水電解液に対する耐腐食性や導電性に優れた電池を提供することが出来る。
【００１６】
【発明の効果】
本発明に係る非水電解液二次電池によれば、巻き取り電極体を構成する芯体が極めて薄い場合にも芯体端縁と集電板を大きな接触面積で接合せしめることが可能であって、生産性も良好となる。
【００１７】
【発明の実施の形態】
以下、本発明をリチウムイオン二次電池に実施した形態につき、図面に沿って具体的に説明する。
【００１８】
全体構成
本発明に係るリチウムイオン二次電池は、図１１及び図１に示す如く、筒体(11)の両端部に蓋体(12)(12)を溶接固定してなる円筒状の電池缶(１)の内部に、巻き取り電極体(４)を収容して構成されている。両蓋体(12)(12)には、正負一対の電極端子機構(９)(９)が取り付けられている。尚、電極端子機構(９)は、従来と同一の構成を具えている。又、各蓋体(12)には圧力開閉式のガス排出弁(13)が取り付けられている。
【００１９】
巻き取り電極体(４)の両端部にはそれぞれ集電板(５)が設置され、芯体端縁(48)にレーザ溶接されている。該集電板(５)の端部に突設されたリード部(55)の先端は、電極端子機構(９)を構成する電極端子(91)の鍔部(92)に、スポット溶接、超音波溶接或いはレーザ溶接によって接合されている。
【００２０】
巻き取り電極体 ( ４ )
巻き取り電極体(４)は、図２に示す様に、それぞれ帯状の正極(41)と負極(43)の間に帯状のセパレータ(42)を介在させて、これらを渦巻き状に巻回して構成されている。正極(41)は、アルミニウム箔からなる帯状芯体(45)の両面にリチウム複合酸化物からなる正極活物質(44)を塗布して構成され、負極(43)は、銅箔からなる帯状芯体(47)の両面に炭素材料を含む負極活物質(46)を塗布して構成されている。セパレータ(42)には、非水電解液が含浸されている。
【００２１】
正極(41)には、正極活物質(44)の塗布されている塗工部と、正極活物質の塗布されていない非塗工部とが形成されている。又、負極(43)にも、負極活物質(46)の塗布されている塗工部と、負極活物質の塗布されていない非塗工部とが形成されている。
正極(41)及び負極(43)は、それぞれセパレータ(42)上に幅方向へずらして重ね合わせ、正極(41)及び負極(43)の前記非塗工部をセパレータ(42)の両端縁からそれぞれ外側へ突出させる。そして、これらを渦巻き状に巻き取ることによって巻き取り電極体(４)が構成される。該巻き取り電極体(４)においては、巻き軸方向の両端部の内、一方の端部では、正極(41)の非塗工部の芯体端縁(48)が、セパレータ(42)の一方の端縁よりも外方へ突出し、他方の端部では、負極(43)の非塗工部の芯体端縁(48)が、セパレータ(42)の他方の端縁よりも外方へ突出している。
【００２２】
集電構造
集電板(５)は、図２〜図４に示す如く円板状本体(51)を具え、該円板状本体(51)には、中央孔(54)が開設されている。円板状本体(51)には、中央孔(54)を中心として放射状に伸びる複数条(実施例では４条)の円弧状凸部(52)が一体成型され、巻き取り電極体(４)側に突出している。又、円板状本体(51)には、隣接する円弧状凸部(52)(52)の間にそれぞれ、複数条(実施例では２条)の切り起し片(53)が形成され、巻き取り電極体(４)側に突出している。更に、円板状本体(51)の端部には、短冊状のリード部(55)が一体に形成されている。
尚、集電板(５)の円弧状凸部(52)は、図４に示す如く円板状本体(51)の半径線に直交する断面形状が半円の円弧を呈している。
【００２３】
製造方法
図１に示す電池缶(１)、電極端子機構(９)、図２に示す巻き取り電極体(４)、及び図３に示す集電板(５)をそれぞれ作製した後、図５及び図７に示す如く、巻き取り電極体(４)の各端部に形成されている芯体端縁(48)に集電板(５)を押し付ける。
これによって、集電板(５)の円弧状凸部(52)は、図６に示す如く巻き取り電極体(４)の芯体端縁(48)に食い込み、円弧状凸部(52)と芯体端縁(48)の間には、円筒面からなる接合面が形成される。
又、集電板(５)の切り起し片(53)は、図８に示す如く巻き取り電極体(４)の芯体端縁(48)に深く食い込み、芯体端縁(48)と圧着することになる。
【００２４】
この状態で、図６中に矢印で示す様に、集電板(５)の円弧状凸部(52)の内周面に向けてレーザビームを照射し、レーザ溶接を施す。
この結果、集電板(５)の円弧状凸部(52)と巻き取り電極体(４)の芯体端縁(48)とが、大きな接触面積で互いに接合されると共に、図８に示す切り起し片(53)と芯体端縁(48)の間の圧着状態が維持されることになる。
【００２５】
上記円筒型リチウムオン二次電池によれば、集電板(５)は、各円弧状凸部(52)と芯体端縁(48)の溶接部にて大きな接触面積で芯体端縁(48)に接合されると共に、該溶接部以外の領域では、各切り起し片(53)が芯体端縁(48)に食い込んで、良好な接触状態が得られるため、集電板(５)と巻き取り電極体(４)の間の接触抵抗が小さくなる。然も、集電板(５)に形成された複数条の切り起し片(53)によって、芯体端縁(48)の全域から集電が行なわれるので、高い集電性能が得られる。
又、集電板(５)の凸部(52)と芯体端縁(48)の接合面は、その中央部にて、ビーム照射方向に対して９０°若しくはそれに近い角度を為すこととなるため、レーザビームが接合面の溶接に有効に作用し、この結果、大きな接合面積による高い溶接強度が得られることになる。
【００２６】
【実施例】
次の様にして、本発明電池Ａ〜Ｐ及び比較電池Ｑを作製した。
本発明電池Ａ
本発明電池Ａについては、図２に示す如く、厚さ２０μｍのアルミニウム製の芯体(45)にコバルト酸リチウムからなる正極活物質(44)を塗布してなる正極(41)と、厚さ２０μｍの銅製の芯体(47)に黒鉛からなる負極活物質(46)を塗布してなる負極(43)と、イオン透過性のポリプロピレン製微多孔膜からなるセパレータ(42)とを重ね合わせ、これらを渦巻き状に巻き取って、巻き取り電極体(４)を作製した。尚、正極(41)及び負極(43)の幅方向の端部には、一定幅の非塗工部が設けられている。
【００２７】
又、半径２８ｍｍ、厚さ１ｍｍの円板状本体(51)に複数条の円弧状凸部(52)が放射状に形成されると共に、複数条の切り起し片(53)が放射状に形成されたアルミニウム製の集電板(５)を作製し、該集電板(５)を巻き取り電極体(４)の正極側の芯体端縁(48)に被せて、上部から治具により押さえ付けた。尚、図３及び図４に示す集電板(５)の円弧状凸部(52)の肉厚Ｔは１ｍｍ、内径Ｒ(＝円板状本体裏面からの突出長さＸ)は１.４ｍｍとした。又、切り起し片(53)の芯体端縁(48)との接触長さＬは１４ｍｍ、円板状本体裏面からの突出長さＹは２.１ｍｍとした。
【００２８】
この状態で集電板(５)の円弧状凸部(52)の内周面に向けて図６の如くレーザビームを照射し、集電板(５)の円弧状凸部(52)の外周面を芯体端縁(48)に溶接した。その後、厚さ１ｍｍのアルミニウム製リード片の基端部を集電板(５)の表面に、先端部をアルミニウム製電極端子の裏面にレーザ溶接し、正極側の集電構造を構成した。
又、電極端子、集電板、及びリード片がニッケル製であること以外は正極側の集電構造と同様に、負極側の集電構造を構成した。
【００２９】
その後、筒体(11)の内部に巻き取り電極体(４)を収容し、筒体(11)の両開口部にそれぞれ、電極端子機構(９)が組み付けられた蓋体(12)を溶接固定した後、電池缶(１)の内部にエステル系有機電解液を注入し、定格電力容量１８０Ｗｈの本発明電池Ａを組み立てた。
【００３０】
本発明電池Ｂ〜Ｊ
集電板(５)の切り起し片(53)の長さ(接触長さＬ)がそれぞれ、９ｍｍ、１１ｍｍ、１２ｍｍ、１４ｍｍ、１６ｍｍ、１８ｍｍ、１９ｍｍ、２２ｍｍ、２４ｍｍであること以外は本発明電池Ａと同様にして、本発明電池Ｂ〜Jを作製した。尚、本発明電池Ｅは本発明電池Ａと同一構成である。
【００３１】
本発明電池Ｋ〜Ｐ
集電板(５)の切り起し片(53)の突出長さＹがそれぞれ、１.２ｍｍ、１.４ｍｍ、１.８ｍｍ、２.１ｍｍ、２.２ｍｍ、２.４ｍｍであること以外は本発明電池Ａと同様にして、本発明電池Ｋ〜Ｐを作製した。尚、本発明電池Ｎは本発明電池Ａと同一構成である。
【００３２】
比較電池Ｑ
集電板(５)には円弧状凸部(52)のみが形成されて、切り起し片(53)が形成されていないこと以外は本発明電池Ａと同様にして、比較電池Ｑを作製した。
【００３３】
出力特性の比較
そして、本発明電池Ａ〜Ｐ及び比較電池Ｑについて後述の出力特性試験を行ない、出力特性の比較を行なった。
【００３４】
▲１▼ 本発明電池Ａと比較電池Ｑの比較
本発明電池Ａと比較電池Ｑについて、０.１２５Ｃで４.１Ｖまで充電を行なった後、０.５Ｃで４０％の放電深度まで電池を放電させ、その後、電流値：４Ｃ、放電時間：１０秒の条件で出力特性試験を行なった。その結果を表１に示す。尚、出力密度の算出に際しては、上記条件での電圧・電池特性をもとに出力値を算出し、その結果を電池の重量で除して出力密度とした。
【００３５】
【表１】

【００３６】
表１から明らかな様に、本発明電池Ａは比較電池Ｑよりも出力特性が高くなっている。これは、本発明電池Ａにおいては集電板(５)に切り起し片(53)が設けられているために、集電板(５)と巻き取り電極体(４)の芯体端縁(48)との間の接触状態が改善されて、接触抵抗が低減したことよるものと考えられる。
【００３７】
▲２▼ 本発明電池Ｂ〜Ｊの比較
次に、本発明電池Ｂ〜Ｊについて出力特性の比較を行なった。その結果を表２に示す。又、表２をグラフ化したものを図９に示す。
【００３８】
【表２】

【００３９】
表２及び図９から明らかな様に、集電板(５)の切り起し片(53)の芯体端縁(48)との接触長さＬが、円板状本体(51)の半径(２８ｍｍ)の０.５倍(１４ｍｍ)より小さくなると、出力密度が急激に小さくなっている。これは、切り起し片(53)と芯体端縁(48)の間の接触面積が小さくなって、集電抵抗の低下に寄与する度合いが急激に小さくなるためであると考えられる。
従って、集電板(５)の切り起し片(53)は、接触長さＬを円板状本体(51)の半径の０.５倍以上に形成することが望ましい。
【００４０】
▲３▼ 本発明電池Ｋ〜Ｐの比較
更に、本発明電池Ｋ〜Ｐについて出力特性の比較を行なった。その結果を表３に示す。又、表３をグラフ化したものを図１０に示す。
【００４１】
【表３】

【００４２】
表３及び図１０から明らかな様に、集電板(５)の切り起し片(53)の突出長さＹが円弧状凸部(52)の突出長さＸ(１.４ｍｍ)の１.５倍(２.１ｍｍ)よりも大きくなると、出力密度が急激に小さくなっている。これは、切り起し片(53)の突出長さが過大となるために、円弧状凸部(52)が芯体端縁(48)と十分に接触することが出来なくなり、レーザ溶接による接合が不十分となって、接触抵抗が増大するからである。
又、集電板(５)の切り起し片(53)の突出長さＹが円弧状凸部(52)の突出長さＸ(１.４ｍｍ)の１.０倍(１.４ｍｍ)よりも小さくなると、出力密度が急激に小さくなっている。これは、切り起し片(53)の突出長さが過小となって、切り起し片(53)が芯体端縁(48)に深く食い込むことが出来なくなるために、集電板(５)と芯体端縁(48)の間の接触状態が充分に改善されなくなるからである。
従って、集電板(５)の切り起し片(53)の突出長さＹは、円弧状凸部(52)の突出長さＸの１.０倍以上、１.５倍以下に形成することが望ましい。
【００４３】
尚、本発明の各部構成は上記実施の形態に限らず、特許請求の範囲に記載の技術的範囲内で種々の変形が可能である。例えば、集電板(５)と電極端子機構(９)の間の接続には、図１に示すリード部(55)による接続構造に限らず、周知の種々の接続構造を採用することが出来る。又、上記の実施例では、集電板の溶接にレーザビームを用いたが、これに限らず、電子ビームによる溶接を採用することも可能である。
【図面の簡単な説明】
【図１】本発明に係る円筒型リチウムイオン二次電池の要部を示す一部破断正面図である。
【図２】巻き取り電極体及び集電板の分解斜視図である。
【図３】集電板の平面図である。
【図４】図３のＡ−Ａ線に沿う拡大断面とＢ−Ｂ線に沿う拡大断面を示す図である。
【図５】巻き取り電極体に集電板の円弧状凸部を押し付ける工程を示す斜視図である。
【図６】芯体端縁に集電板の円弧状凸部が食い込んだ状態を示す断面図である。
【図７】巻き取り電極体に集電板の切り起し片を押し付ける工程を示す斜視図である。
【図８】芯体端縁に集電板の切り起し片が食い込んだ状態を示す断面図である。
【図９】集電板の切り起し片の接触長さと出力密度の関係を示すグラフである。
【図１０】集電板の切り起し片の突出長さと出力密度の関係を示すグラフである。
【図１１】円筒型リチウムイオン二次電池の外観を示す斜視図である。
【図１２】従来のリチウムイオン二次電池の要部を示す一部破断正面図である。
【図１３】該リチウムイオン二次電池に用いられている巻き取り電極体の一部展開斜視図である。
【符号の説明】
(１) 電池缶
(11) 筒体
(12) 蓋体
(４) 巻き取り電極体
(41) 正極
(43) 負極
(45) 芯体
(47) 芯体
(48) 芯体端縁
(５) 集電板
(51) 円板状本体
(52) 円弧状凸部
(53) 切り起し片[0001]
BACKGROUND OF THE INVENTION
The present invention provides a non-aqueous electrolyte in which a wound electrode body serving as a secondary battery element is accommodated inside a battery can, and power generated by the wound electrode body can be taken out from a pair of electrode terminal portions provided in the battery can. The present invention relates to a secondary battery.
[0002]
[Prior art]
In recent years, lithium ion secondary batteries with high energy density have attracted attention as power sources for portable electronic devices and electric vehicles. For example, in a relatively large capacity cylindrical lithium ion secondary battery used in an electric vehicle, as shown in FIGS. 11 and 12, lids (12) and (12) are fixed to both ends of a cylindrical body (11) by welding. A winding electrode body (4) is housed in a cylindrical battery can (1). A pair of positive and negative electrode terminal mechanisms (9), (9) is attached to both the lids (12), (12), and both poles of the winding electrode body (4) and both electrode terminal mechanisms (9), (9) Are connected to each other, and the electric power generated by the winding electrode body (4) can be taken out from the pair of electrode terminal mechanisms (9) and (9). Each lid (12) is provided with a pressure open / close gas discharge valve (13).
[0003]
As shown in FIG. 13, the take-up electrode body (4) is formed by interposing a strip-shaped separator (42) between a strip-shaped positive electrode (41) and a negative electrode (43), and winding them in a spiral shape. It is configured. The positive electrode (41) is configured by applying a positive electrode active material (44) made of a lithium composite oxide on both surfaces of a belt-like core (45) made of an aluminum foil, and the negative electrode (43) is made of a belt-like core made of a copper foil. The negative electrode active material (46) containing a carbon material is applied to both surfaces of the body (47). The separator (42) is impregnated with a non-aqueous electrolyte.
[0004]
Here, the positive electrode (41) and the negative electrode (43) are superimposed on the separator (42) while being shifted in the width direction, and wound in a spiral shape. As a result, the end of the core body (45) of the positive electrode (41) is more outward than the edge of the separator (42) at one end of both ends in the winding axis direction of the winding electrode body (4). The edge (48) protrudes, and at the other end, the end edge (48) of the core (47) of the negative electrode (43) protrudes outward from the end edge of the separator (42). Then, a disk-shaped current collector plate (32) is resistance-welded to both ends of the winding electrode body (4), and the current collector plate (32) is shown in FIG. 12 via a lead member (33). Connected to the base end of the electrode terminal mechanism (9).
[0005]
The electrode terminal mechanism (9) includes an electrode terminal (91) attached through the lid (12) of the battery can (1), and the base end of the electrode terminal (91) has a flange (92). ) Is formed. An insulating packing (93) is attached to the through hole of the lid (12), and electrical insulation and sealing between the lid (12) and the electrode terminal (91) are maintained. A washer (94) is fitted to the electrode terminal (91) from the outside of the lid (12), and a first nut (95) and a second nut (96) are screwed together. The first nut (95) is tightened, and the insulating packing (93) is clamped by the flange (92) and the washer (94) of the electrode terminal (91), thereby improving the sealing performance.
The tip of the lead member (33) is fixed to the flange (92) of the electrode terminal (91) by spot welding or ultrasonic welding.
[0006]
However, in the non-aqueous electrolyte secondary battery having the current collecting structure shown in FIG. 12, the cores (45) and (47) constituting the positive electrode (41) and the negative electrode (43) of the winding electrode body (4). Since the areas of the edges (48) and (48) are small, there is a problem that the contact area between the edge of the core body and the current collector plate (32) is small, thereby increasing the internal resistance of the battery.
In particular, in a lithium ion secondary battery used as a power source for an electric vehicle, etc., it is necessary to reduce the internal resistance as much as possible in order to obtain a high output as well as a high capacity. Furthermore, in order to reduce manufacturing costs, a current collecting structure with excellent productivity is required.
[0007]
Therefore, as a low-resistance battery excellent in productivity, a plurality of protrusions having a V-shaped cross section with a tip angle of 90 ° or less are formed on a disk-shaped current collector plate, and the current collector plate is connected to the end of the core body. There has been proposed a structure in which a current collector plate is welded to an electrode plate group by irradiating the projection with a laser beam while being pressed against an edge (Japanese Patent Publication No. 2-4102).
[0008]
[Problems to be solved by the invention]
However, in the above structure, since the cross-sectional shape of the protruding portion of the current collector plate is an acute V shape, the contact area between the protruding portion and the core edge is small, and the contact resistance at the welded portion is high. In addition, there is a problem that the current collecting performance is low because the contact state is poor in the region other than the welded portion. However, since the joint surface between the V-shaped protrusion to be irradiated with the laser beam and the edge of the core body makes an acute angle with respect to the beam irradiation direction, the laser beam does not effectively act on the welding of the joint surface. There was a risk of poor welding.
[0009]
Therefore, an object of the present invention is to obtain a good contact state between the edge of the core body and the current collector plate even when the core body constituting the electrode body is extremely thin, exhibiting high current collection performance, and also to productivity. To provide a non-aqueous electrolyte secondary battery having an excellent current collecting structure.
[0010]
[Means for solving the problems]
In the non-aqueous electrolyte secondary battery according to the present invention, at least one end of the winding electrode body (4) has an edge of a strip-shaped core body constituting the positive electrode (41) or the negative electrode (43) ( 48) protrudes, and a current collecting plate (5) is installed to cover the edge (48).
The current collector plate (5) is formed with a plurality of arc-shaped convex portions (52) protruding in an arc shape in cross section toward the core body edge (48), and at the core body edge (48). A plurality of cut-and-raised pieces (53) cut and raised toward the core are formed, and these arcuate convex portions (52) and cut-and-raised pieces (53) bite into the core body edge (48), The arcuate convex portion (52) is welded to the core body edge (48).
The current collector plate (5) is connected to one of the electrode terminal portions.
[0011]
In the non-aqueous electrolyte secondary battery of the present invention, each arcuate protrusion (52) is formed by pressing the current collector plate (5) against the core body edge (48) of the winding electrode body (4). The core body edge (48) bites into the core body edge (48), and a joining surface comprising a cylindrical surface corresponding to the surface shape of the convex portion (52) is formed. The joint surface has a larger area than when the convex portion is formed in a V-shaped cross section. In addition, each cut and raised piece (53) bites deeply into the core body edge (48), and even in a region other than the welded portion, a good gap between the current collector plate (5) and the core body edge (48) is obtained. A contact state is obtained.
Therefore, the current collector plate (5) is welded to the core body edge (48) by irradiating a laser beam or an electron beam to the joint between each arc-shaped convex part (52) and the core body edge (48). Thus, the current collector plate (5) is joined to the core body edge (48) with a large contact area. As a result, the contact resistance is reduced and high current collecting performance is obtained.
In addition, the joint surface between the convex portion (52) of the current collector plate (5) and the core end edge (48) forms an angle of 90 ° or close to the beam irradiation direction at the central portion. Therefore, the laser beam or the electron beam effectively acts on the welding of the joining surface, and as a result, a high welding strength with a large joining area can be obtained.
[0012]
In a specific configuration, the current collector plate (5) has a plurality of arc-shaped convex portions (52) and cut and raised pieces on a surface facing the core body edge (48) of the disc-shaped main body (51). (53) is formed in a radial shape, and a strip-shaped lead portion (55) protrudes from the end of the disc-shaped main body (51), and the tip of the lead portion (55) is connected to the electrode terminal portion. It is connected.
According to this specific configuration, the current generated from the winding electrode body (4) is collected by the current collector plate (5), and flows to the electrode terminal portion via the lead portion (55).
[0013]
More specifically, each cut-and-raised piece (53) is formed such that the length of contact with the core body edge (48) is 0.5 times or more the radius of the current collector plate (5).
As a result, a sufficiently wide contact area is secured between the current collecting plate (5) and the core end edge (48), and high current collecting performance is obtained.
[0014]
Further, the cut-and-raised pieces (53), core edge (48) in towards the length protruding arcuate protrusion (52) projecting length of 1.0 times or more of 1.5 times or less Is formed.
As a result, each arcuate protrusion (52) contacts the core body edge (48) over a wide area, and each cut-and-raised piece (53) bites into the core body edge (48) with a sufficient depth. It will be.
[0015]
In addition, as a material of a current collecting plate (5), Cu, Al, Ni, SUS, Ti, or an alloy of these metals can be adopted. As a result, it is possible to provide a battery excellent in corrosion resistance and conductivity with respect to the non-aqueous electrolyte.
[0016]
【The invention's effect】
According to the nonaqueous electrolyte secondary battery of the present invention, it is possible to join the edge of the core body and the current collector plate with a large contact area even when the core body constituting the winding electrode body is extremely thin. Productivity is also improved.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the embodiment in which the present invention is applied to a lithium ion secondary battery will be specifically described with reference to the drawings.
[0018]
Overall configuration As shown in Figs. 11 and 1, a lithium ion secondary battery according to the present invention is a cylinder formed by welding and fixing lids (12) and (12) to both ends of a cylinder (11). The cylindrical battery can (1) is configured to accommodate the winding electrode body (4). A pair of positive and negative electrode terminal mechanisms (9) and (9) are attached to the lids (12) and (12). The electrode terminal mechanism (9) has the same configuration as the conventional one. Each lid (12) is provided with a pressure open / close gas discharge valve (13).
[0019]
Current collector plates (5) are installed at both ends of the winding electrode body (4), and are laser-welded to the core body edge (48). The tip of the lead portion (55) protruding from the end portion of the current collector plate (5) is spot welded or super welded to the flange portion (92) of the electrode terminal (91) constituting the electrode terminal mechanism (9). They are joined by sonic welding or laser welding.
[0020]
Winding electrode body ( 4 )
As shown in FIG. 2, the take-up electrode body (4) is formed by interposing a strip-shaped separator (42) between the strip-shaped positive electrode (41) and the negative electrode (43), and winding them in a spiral shape. It is configured. The positive electrode (41) is configured by applying a positive electrode active material (44) made of a lithium composite oxide on both surfaces of a band-shaped core (45) made of an aluminum foil, and the negative electrode (43) is made of a band-shaped core made of a copper foil. The negative electrode active material (46) containing a carbon material is applied to both surfaces of the body (47). The separator (42) is impregnated with a non-aqueous electrolyte.
[0021]
The positive electrode (41) is formed with a coated portion where the positive electrode active material (44) is applied and a non-coated portion where the positive electrode active material is not applied. The negative electrode (43) is also formed with a coated portion where the negative electrode active material (46) is applied and a non-coated portion where the negative electrode active material is not applied.
The positive electrode (41) and the negative electrode (43) are respectively superimposed on the separator (42) while being shifted in the width direction, and the uncoated portions of the positive electrode (41) and the negative electrode (43) are separated from both end edges of the separator (42). Each protrudes outward. And a winding electrode body (4) is comprised by winding up these in the shape of a spiral. In the wound electrode body (4), the core body edge (48) of the non-coated portion of the positive electrode (41) is at one end of the both ends in the winding axis direction of the separator (42). Projects outward from one edge, and at the other end, the core body edge (48) of the non-coated part of the negative electrode (43) is outward from the other edge of the separator (42). It protrudes.
[0022]
Current collecting structure The current collecting plate (5) includes a disc-shaped main body (51) as shown in FIGS. 2 to 4, and the disc-shaped main body (51) has a central hole (54). It has been established. The disc-shaped main body (51) is integrally formed with a plurality of (four in the embodiment) arc-shaped convex portions (52) extending radially around the central hole (54), and the winding electrode body (4) Protrudes to the side. Further, the disc-shaped main body (51) is formed with a plurality of (two in the embodiment) cut and raised pieces (53) between the adjacent arc-shaped convex portions (52) and (52), It protrudes to the winding electrode body (4) side. Further, a strip-shaped lead portion (55) is integrally formed at the end of the disc-shaped main body (51).
The arcuate convex portion (52) of the current collector plate (5) has a semicircular arc whose cross-sectional shape is perpendicular to the radial line of the disc-like body (51) as shown in FIG.
[0023]
Manufacturing method The battery can (1), electrode terminal mechanism (9) shown in FIG. 1, the wound electrode body (4) shown in FIG. 2, and the current collector plate (5) shown in FIG. 3 were produced. Thereafter, as shown in FIGS. 5 and 7, the current collector plate (5) is pressed against the core body edge (48) formed at each end of the winding electrode body (4).
As a result, the arc-shaped convex part (52) of the current collector plate (5) bites into the core body edge (48) of the winding electrode body (4) as shown in FIG. Between the core body edges (48), a joining surface comprising a cylindrical surface is formed.
Further, as shown in FIG. 8, the cut and raised piece (53) of the current collector plate (5) bites deeply into the core body edge (48) of the winding electrode body (4), and the core body edge (48) and It will be crimped.
[0024]
In this state, as indicated by an arrow in FIG. 6, a laser beam is irradiated toward the inner peripheral surface of the arc-shaped convex portion (52) of the current collector plate (5) to perform laser welding.
As a result, the arc-shaped convex part (52) of the current collector plate (5) and the core body edge (48) of the winding electrode body (4) are joined to each other with a large contact area, as shown in FIG. The pressure-bonded state between the cut and raised piece (53) and the core body edge (48) is maintained.
[0025]
According to the above-described cylindrical lithium-on secondary battery, the current collector plate (5) has a large contact area at the welded portion between each arc-shaped convex portion (52) and the core end edge (48) ( 48), and in the region other than the welded portion, each cut-and-raised piece (53) bites into the core body edge (48) and a good contact state is obtained. ) And the take-up electrode body (4). However, since current is collected from the entire area of the core end edge (48) by the plurality of cut and raised pieces (53) formed on the current collecting plate (5), high current collecting performance is obtained.
In addition, the joint surface between the convex portion (52) of the current collector plate (5) and the core end edge (48) forms an angle of 90 ° or close to the beam irradiation direction at the central portion. Therefore, the laser beam effectively acts on the welding of the joint surface, and as a result, a high welding strength with a large joint area can be obtained.
[0026]
【Example】
Inventive batteries A to P and comparative battery Q were produced as follows.
Invention battery A
As shown in FIG. 2, the battery A of the present invention has a positive electrode (41) obtained by applying a positive electrode active material (44) made of lithium cobaltate to an aluminum core (45) having a thickness of 20 μm, and a thickness thereof. A negative electrode (43) formed by applying a negative electrode active material (46) made of graphite to a 20 μm copper core (47) and a separator (42) made of an ion-permeable polypropylene microporous membrane were superimposed, These were wound up in a spiral shape to produce a wound electrode body (4). A non-coating portion having a constant width is provided at the end in the width direction of the positive electrode (41) and the negative electrode (43).
[0027]
In addition, a plurality of arc-shaped convex portions (52) are formed radially on a disk-shaped main body (51) having a radius of 28 mm and a thickness of 1 mm, and a plurality of cut and raised pieces (53) are formed radially. An aluminum current collector plate (5) is prepared, and the current collector plate (5) is put on the core end edge (48) on the positive electrode side of the take-up electrode body (4) and pressed from above by a jig. I attached. 3 and 4 has a thickness T of 1 mm and an inner diameter R (= projection length X from the back of the disk-shaped body) of 1.4 mm. It was. Further, the contact length L of the cut and raised piece (53) with the core edge (48) was 14 mm, and the protruding length Y from the back surface of the disc-shaped body was 2.1 mm.
[0028]
In this state, a laser beam is irradiated as shown in FIG. 6 toward the inner peripheral surface of the arc-shaped convex portion (52) of the current collector plate (5), and the outer periphery of the arc-shaped convex portion (52) of the current collector plate (5). The face was welded to the core edge (48). Thereafter, the base end portion of the aluminum lead piece having a thickness of 1 mm was laser-welded to the surface of the current collector plate (5), and the tip end portion was laser-welded to the back surface of the aluminum electrode terminal to constitute a current collecting structure on the positive electrode side.
Further, the current collector structure on the negative electrode side was configured in the same manner as the current collector structure on the positive electrode side, except that the electrode terminal, the current collector plate, and the lead piece were made of nickel.
[0029]
Thereafter, the wound electrode body (4) is accommodated inside the cylinder body (11), and the lid body (12) with the electrode terminal mechanism (9) assembled to both openings of the cylinder body (11) is welded. After fixing, an ester-based organic electrolyte was injected into the battery can (1) to assemble the battery A of the present invention having a rated power capacity of 180 Wh.
[0030]
Invention batteries B to J
Except that the length (contact length L) of the cut and raised piece (53) of the current collector plate (5) is 9 mm, 11 mm, 12 mm, 14 mm, 16 mm, 18 mm, 19 mm, 22 mm, and 24 mm, respectively. In the same manner as the battery A, the batteries B to J of the present invention were produced. The present invention battery E has the same configuration as the present invention battery A.
[0031]
Invention batteries K to P
The protruding length Y of the cut and raised piece (53) of the current collector plate (5) is 1.2 mm, 1.4 mm, 1.8 mm, 2.1 mm, 2.2 mm, 2.4 mm, respectively. Inventive batteries K to P were produced in the same manner as Inventive battery A. The present invention battery N has the same configuration as the present invention battery A.
[0032]
Comparative battery Q
A comparative battery Q is produced in the same manner as the battery A of the present invention except that only the arc-shaped convex part (52) is formed on the current collector plate (5) and the cut and raised piece (53) is not formed. did.
[0033]
Comparison of output characteristics Then, the output characteristics test described below was performed on the batteries A to P of the present invention and the comparative battery Q, and the output characteristics were compared.
[0034]
(1) Comparison between the present invention battery A and the comparison battery Q About the present invention battery A and the comparison battery Q, after charging to 4.1V at 0.125C, the battery is discharged to a discharge depth of 40% at 0.5C. Thereafter, an output characteristic test was conducted under the conditions of current value: 4 C and discharge time: 10 seconds. The results are shown in Table 1. In calculating the output density, the output value was calculated based on the voltage and battery characteristics under the above conditions, and the result was divided by the weight of the battery to obtain the output density.
[0035]
[Table 1]

[0036]
As is apparent from Table 1, the battery A of the present invention has higher output characteristics than the comparative battery Q. This is because, in the battery A of the present invention, the current collector plate (5) is provided with the cut and raised pieces (53), so the edge of the core body of the current collector plate (5) and the winding electrode body (4) It is considered that the contact state with (48) was improved and the contact resistance was reduced.
[0037]
(2) Comparison of Invention Batteries B to J Next, the output characteristics of the invention batteries B to J were compared. The results are shown in Table 2. A graph of Table 2 is shown in FIG.
[0038]
[Table 2]

[0039]
As is apparent from Table 2 and FIG. 9, the contact length L of the cut and raised piece (53) of the current collector plate (5) with the core body edge (48) is the radius of the disc-shaped body (51). When it is smaller than 0.5 times (14 mm) of (28 mm), the output density is rapidly reduced. This is presumably because the contact area between the cut-and-raised piece (53) and the core edge (48) is reduced, and the degree of contribution to the reduction of the current collecting resistance is rapidly reduced.
Therefore, it is desirable that the cut-and-raised piece (53) of the current collector plate (5) is formed so that the contact length L is 0.5 times or more the radius of the disc-shaped body (51).
[0040]
{Circle around (3)} Comparison of Invention Batteries K to P Furthermore, output characteristics of the invention batteries K to P were compared. The results are shown in Table 3. A graph of Table 3 is shown in FIG.
[0041]
[Table 3]

[0042]
As apparent from Table 3 and FIG. 10, the protruding length Y of the cut and raised piece (53) of the current collector plate (5) is 1 of the protruding length X (1.4 mm) of the arcuate convex portion (52). When it becomes larger than 0.5 times (2.1 mm), the output density decreases rapidly. This is because the protruding length of the cut-and-raised piece (53) becomes excessive, so that the arc-shaped convex portion (52) cannot sufficiently contact the edge of the core body (48), and joining by laser welding. This is because the contact resistance increases.
Further, the protruding length Y of the cut and raised piece (53) of the current collector plate (5) is 1.0 times (1.4 mm) of the protruding length X (1.4 mm) of the arcuate convex portion (52). As the value decreases, the power density decreases rapidly. This is because the protruding length of the cut-and-raised piece (53) becomes too small and the cut-and-raised piece (53) cannot deeply bite into the edge (48) of the core body. ) And the edge of the core body (48) is not sufficiently improved.
Therefore, the protruding length Y of the cut-and-raised piece (53) of the current collector plate (5) is formed to be not less than 1.0 times and not more than 1.5 times the protruding length X of the arc-shaped convex portion (52). It is desirable.
[0043]
In addition, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim. For example, the connection between the current collector plate (5) and the electrode terminal mechanism (9) is not limited to the connection structure using the lead portion (55) shown in FIG. 1, and various known connection structures can be employed. . In the above embodiment, the laser beam is used for welding the current collector plate. However, the present invention is not limited to this, and welding using an electron beam can also be employed.
[Brief description of the drawings]
FIG. 1 is a partially broken front view showing a main part of a cylindrical lithium ion secondary battery according to the present invention.
FIG. 2 is an exploded perspective view of a winding electrode body and a current collector plate.
FIG. 3 is a plan view of a current collector plate.
4 is a diagram showing an enlarged cross section along line AA in FIG. 3 and an enlarged cross section along line BB. FIG.
FIG. 5 is a perspective view showing a step of pressing an arc-shaped convex portion of a current collector plate on a winding electrode body.
FIG. 6 is a cross-sectional view showing a state where an arc-shaped convex portion of a current collector plate bites into an edge of a core body.
FIG. 7 is a perspective view showing a step of pressing a cut and raised piece of a current collector plate onto a winding electrode body.
FIG. 8 is a cross-sectional view showing a state where a cut-and-raised piece of a current collector plate bites into an edge of a core body.
FIG. 9 is a graph showing the relationship between the contact length of the cut and raised pieces of the current collector plate and the output density.
FIG. 10 is a graph showing the relationship between the protruding length of the cut and raised pieces of the current collector plate and the output density.
FIG. 11 is a perspective view showing an appearance of a cylindrical lithium ion secondary battery.
FIG. 12 is a partially broken front view showing a main part of a conventional lithium ion secondary battery.
FIG. 13 is a partially developed perspective view of a winding electrode body used in the lithium ion secondary battery.
[Explanation of symbols]
(1) Battery can
(11) Tube
(12) Lid
(4) Winding electrode body
(41) Positive electrode
(43) Negative electrode
(45) Core
(47) Core
(48) Core edge
(5) Current collector
(51) Disc-shaped body
(52) Arc-shaped convex part
(53) Cut and raised pieces

Claims

Inside the battery can (1), a winding electrode body (4) wound in a spiral shape with a separator (42) interposed between a strip-shaped positive electrode (41) and a negative electrode (43) is accommodated. Each of (41) and the negative electrode (43) is configured by applying an active material to the surface of the belt-like core body, and the electric power generated by the winding electrode body (4) can be taken out from the pair of electrode terminal portions to the outside. In the nonaqueous electrolyte secondary battery, the edge (48) of the belt-shaped core constituting the positive electrode (41) or the negative electrode (43) protrudes from at least one end of the wound electrode body (4). A current collecting plate (5) is installed so as to cover the end edge (48), and the current collecting plate (5) has a plurality of circles protruding in a circular arc shape toward the core end edge (48). An arc-shaped convex part (52) is formed, and a plurality of cut and raised pieces (53) cut and raised toward the core edge (48) are formed. Raising piece (53) on core edge (48) Non-aqueous electrolysis characterized by arcuate convex part (52) being welded to core body edge (48) in a state of being bitten, and current collector plate (5) being connected to one electrode terminal part. Liquid secondary battery.

The current collector plate (5) has a plurality of arc-shaped convex portions (52) and cut and raised pieces (53) radially formed on a surface of the disc-shaped main body (51) facing the core edge (48). And a strip-shaped lead portion (55) protruding from the end of the disc-shaped main body (51), and the tip of the lead portion (55) is connected to the electrode terminal portion. Item 4. The nonaqueous electrolyte secondary battery according to Item 1.

2. The non-aqueous solution according to claim 1 , wherein each of the cut-and-raised pieces (53) is formed to have a length that is in contact with the core edge (48) at least 0.5 times the radius of the current collector (5). Electrolyte secondary battery.

Each cut-and-raised pieces (53) are arc-shaped convex portion length for protruding toward the core edge (48) (52) projecting length of 1.0 times or more, formation to 1. 5 times less The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3.