JP4159383B2

JP4159383B2 - Cylindrical secondary battery

Info

Publication number: JP4159383B2
Application number: JP2003062855A
Authority: JP
Inventors: 秀雄萩野; 広一佐藤; 直哉中西; 淳浩船橋; 俊之能間
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 2003-03-10
Filing date: 2003-03-10
Publication date: 2008-10-01
Anticipated expiration: 2023-03-10
Also published as: JP2004273288A

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電極体の発生電力を取り出すことが出来る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。又、電気自動車の電源として、大容量の円筒型二次電池が注目されている。
【０００３】
例えば図８に示す円筒型二次電池は、封口板(９)と缶本体(11)からなる電池缶(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。封口板(９)には、電池缶(１)の内圧が所定値を越えたときに開放する弁膜(94)が形成されると共に、該弁膜(94)を覆って正極端子部(90)が取り付けられている。
【０００４】
巻き取り電極体(４)は、それぞれ帯状の正極(41)、セパレータ(42)及び負極(43)から構成されており、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て、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)の端縁が突出すると共に、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)の端縁が突出している。巻き取り電極体(４)の両端部には集電板(８)(80)が設置され、正極(41)或いは負極(43)の端縁と溶接接合されている。
【０００５】
正極側の集電板(８)は、図９に示す如く、円板状の本体(81)と、該本体(81)の円弧状外周縁に突設された帯状のリード板(85)とから構成され、前記本体(81)は巻き取り電極体(４)の外径と略同じ直径を有している。又、集電板(８)の本体(81)には、複数の貫通孔(83)が開設されると共に、中央部に中央孔(84)が開設されており、本体(81)とリード板(85)には、本体(81)の中央部からリード板(85)の先端に向かって伸びる１本のスリット(87)が形成されている。リード板(85)は、図８の如く集電板(８)の内側に向けて折り返され、先端部に設けられた溶接部(86)が封口板(９)にレーザ溶接により接合されている。
一方、負極(43)の端縁に接合されている集電板(80)は、缶本体(11)の底面に接合され、缶本体(11)の底部によって負極端子部(10)を構成している。
上記の構成によって、巻き取り電極体(４)が発生する電力を、正極端子部(90)と負極端子部(10)から外部へ取り出すことが出来る。
【０００６】
ところで、この種の円筒型二次電池の出力を増大させるには、内部抵抗を小さくすることが有効である。内部抵抗は、巻き取り電極体(４)が発生する電力が外部に取り出されるまでの電流経路における電気抵抗であり、図８に示す如く、正極側の経路には、集電板(８)の本体(81)、リード板(85)、封口板(９)及び正極端子部(90)が存在している。
【０００７】
上述の内部抵抗を小さくする方法として、図１０に示す如く、集電板(８)のリード板(85)を拡幅することが考えられる。図１０に示す集電板(８)によれば、電流経路となるリード板(85)の断面積が従来よりも大きくなるので、集電板(８)での電気抵抗を従来よりも小さくすることが出来、これによって、円筒型二次電池の内部抵抗が小さくなって、出力が増大する。
【０００８】
【特許文献１】
特開２００１−２４３９７２号公報(【０００１】〜【０００４】、【図６】)
【０００９】
【発明が解決しようとする課題】
しかしながら、図１０の如くリード板(85)の幅が大きな集電板(８)においては、図１１の如くリード板(85)を本体(81)の接線位置で折り曲げた場合、リード板(85)の図中Ｃで示す部分が本体(81)の外周縁から突出することとなり、この部分が電池缶(１)と干渉することになる。
【００１０】
そこで、従来は、図１２の如く集電板(８)のリード板(85)を本体(81)の接線位置よりも更に本体(81)の内側で折り曲げることが行なわれていた。しかしながら、これによって本体(81)の外周部がリード板(85)と共に折り曲げられることとなり、この結果、集電板(８)と巻き取り電極体(４)の接触面積が従来よりも小さくなり、集電板(８)の集電性能が低下する問題があった。更に、巻き取り電極体(４)の帯状芯体の端縁に対して集電板(８)の本体(81)が偏心して取り付けられることとなるので、外部からの衝撃力が帯状芯体の端縁に偏心して加わることとなり、これによって、集電板(８)の本体(81)と帯状芯体の端縁との溶接部分が剥離する虞があった。
【００１１】
そこで本発明の目的は、集電性能を低下させることなく、電池の内部抵抗を従来よりも低下させることが出来る筒型二次電池を提供することである。
【００１２】
【課題を解決する為の手段】
本発明に係る円筒型二次電池においては、筒状の電池缶(１)の内部に、それぞれ帯状の正極(41)と負極(43)の間にセパレータ(42)を介在させてこれらを渦巻状に巻き取った巻き取り電極体(４)が収容され、正極(41)及び負極(43)にはそれぞれ、帯状芯体の表面に活物質を塗布して構成され、巻き取り電極体(４)が発生する電力を一対の電極端子部から外部へ取り出すことが出来る。
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、該集電板(５)は、外周縁の少なくとも一部が円弧状を呈する平板状の本体(51)と、該本体(51)の前記円弧状外周縁に突設された帯状のリード板(55)とを具え、該リード板(55)には、前記本体(51)から離間する方向に伸びる複数本の切り込み(57)が施され、各切り込み(57)は、基端を前記本体(51)の円弧状外周縁又はその近傍に有し、該リード板(55)の先端部は、一方の電極端子部と連結されている。
【００１３】
上記本発明の円筒型二次電池において、集電板(５)のリード板(55)は、前記複数本の切り込み(57)によって複数のリード部(58)に分割されているので、該リード部(58)を、個々に切り込み(57)の基端位置から折り曲げることが可能となる。これによって、リード板(55)は、リード部(58)毎に前記本体(51)の円弧状外周縁に沿って折り曲げられることとなり、この結果、前記本体(51)の円弧状外周縁から突出するリード板(55)の突出部分を従来よりも小さくすることが出来る。
従って、集電板(５)は、本体(51)の全表面にて巻き取り電極体(４)の帯状芯体の端縁(48)と接触すると共に、リード板(55)にて電池缶(１)と干渉することはない。又、上述の如くリード部(58)毎に折り曲げることが出来るので、集電板(５)のリード板(55)を折り曲げる作業は従来よりも容易となる。
【００１４】
又、具体的構成において、リード板(55)の先端部には、リード板(55)を一方の電極端子部に溶接するための溶接部(56)が設けられており、前記切り込み(57)は、先端を溶接部(56)の近傍に有している。
該具体的構成においては、リード板(55)のリード部(58)は、溶接部(56)にて一体となっているので、リード板(55)を電極端子部に溶接する作業が一度で済む。従って、組立工程の工数が増えることはない。
【００１５】
更に具体的な構成において、前記複数本の切り込み(57)は、互いに平行に伸びている。
該具体的構成においては、リード板(55)のリード部(58)の幅は一定であり、これによってリード部(58)の断面積は一定となる。従って、リード部(58)にて局所的に電気抵抗が大きくなることはなく、リード板(55)全体としての電気抵抗が従来よりも増大することはない。
【００１６】
【発明の効果】
上記本発明に係る円筒型電池によれば、集電性能を低下させることなく、電池の内部抵抗を従来よりも低下させることが出来る。
【００１７】
【発明の実施の形態】
以下、本発明を円筒型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
本発明に係る円筒型リチウムイオン二次電池において、電池缶(１)は、図１に示す如く、一方の端部に開口部を有する円筒状の缶本体(11)と、該開口部に固定されて開口部を塞ぐ封口板(２)と、缶本体(11)と封口板(２)の間に介在する電気絶縁性部材(12)とから構成されており、電池缶(１)の内部には巻き取り電極体(４)が収容されている。封口板(２)には、電池缶(１)の内圧が所定値を越えたときに開放する弁膜(24)が形成されると共に、該弁膜(24)を覆って正極端子部(20)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)(６)が設置され、両集電板(５)(６)が巻き取り電極体(４)にレーザ溶接により接合されている。正極側の集電板(５)の端部に突設されたリード板(55)の先端は、封口板(２)にレーザ溶接して接続される。負極側の集電板(６)は、缶本体(11)の底部にスポット溶接、超音波溶接或いはレーザ溶接によって接合されており、缶本体(11)の底部によって負極端子部(10)を構成している。
これによって、巻き取り電極体(４)が発生する電力を、正極端子部(20)と負極端子部(10)とから、外部に取り出すことが出来る。
【００２０】
巻き取り電極体 ( ４ )
巻き取り電極体(４)は、図３に示す如く、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
正極側の集電板(５)は、図３〜図５に示す如く円板状の本体(51)と該本体(51)の外周縁に突設された帯状のリード板(55)とから構成されており、前記本体(51)には、中央孔(54)が開設されている。又、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。該円弧状凸部(52)は、前記本体(51)の半径線に直交する断面形状が半円の円弧状を呈している。
又、集電板(５)の本体(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。該切り起し片(53)の切り起こしに伴って形成された貫通孔は、後述の組立工程にて巻き取り電極体(４)に電解液を含浸させる際の電解液の通路となる。
【００２３】
又、図３及び図４に示す如く、集電板(５)のリード板(55)の先端部には、リード板(55)と封口板(２)とを溶接接合するための溶接部(56)が設けられている。又、リード板(55)には、前記本体(51)から溶接部(56)に向かって伸びる複数本(実施例では５本)の切り込み(57)が互いに平行であると共に等間隔となるように施されており、該切り込み(57)は、基端を前記本体(51)の外周縁に有すると共に先端を溶接部(56)の近傍に有している。これによって、リード板(55)は、前記本体(51)の外周縁から溶接部(56)までを複数(実施例では６つ)のリード部(58)に分割されている。
【００２４】
図３に示す如く、負極側の集電板(６)は、円板状の本体(61)を具え、該本体(61)の中央部(64)が、缶本体(11)の底部にスポット溶接されることとなる。又、本体(61)には、中央部(64)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(62)が一体成型され、巻き取り電極体(４)側に突出している。該円弧状凸部(62)は、前記本体(61)の半径線に直交する断面形状が半円の円弧状を呈している。
又、集電板(６)の本体(61)には、隣接する円弧状凸部(62)(62)の間にそれぞれ、複数条(実施例では２条)の切り起し片(63)が形成され、巻き取り電極体(４)側に突出している。
【００２５】
封口板 ( ２ )
封口板(２)は、図２に示す如く、円板状の第１金属板(21)と、該第１金属板(21)よりも厚さが大きい第２金属板(22)とから構成されており、両金属板(21)(22)は、前記第１金属板(21)の上面に第２金属板(22)を重ね合わせ、第１金属板(21)の下面から数箇所をスポット溶接して接合されている。
【００２６】
第１金属板(21)の中央部には、該第１金属板(21)の製造工程にて一体成型された薄膜状の弁膜(24)が形成され、第２金属板(22)の中央部には、前記弁膜(24)と対向する位置に、ガス排出孔(26)が開設されている。又、第２金属板(22)の上面には、ガス排出孔(26)を覆って正極端子部(20)が取り付けられている。又、正極端子部(20)の外周面には、複数の通気孔(27)が開設されており、これによって、弁膜(24)の表面が外気に接することとなる。
又、第１金属板(21)及び第２金属板(22)には、前記絶縁性部材(12)と接触する位置に、両金属板(21)(22)の外周部の全周に沿って溝部(28)が形成されている。
【００２７】
組立工程
先ず、図１に示す缶本体(11)、図２に示す封口板(２)、図３に示す巻き取り電極体(４)、及び図４に示す集電板(５)をそれぞれ作製する。
次に、巻き取り電極体(４)の両端部に形成されている芯体端縁(48)(48)に集電板(５)(６)を押し付ける。これによって、集電板(５)(６)の円弧状凸部(52)(62)は、巻き取り電極体(４)の芯体端縁(48)(48)に食い込み、円弧状凸部(52)(62)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)(６)の切り起し片(53)(63)は、巻き取り電極体(４)の芯体端縁(48)(48)に深く食い込み、芯体端縁(48)(48)と圧着することになる。
この状態で、集電板(５)(６)の円弧状凸部(52)(62)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)(６)の円弧状凸部(52)(62)と巻き取り電極体(４)の芯体端縁(48)(48)とが、大きな接触面積で互いに接合されると共に、切り起し片(53)(63)と芯体端縁(48)(48)の間の圧着状態が維持されることになる。
【００２８】
次に、正極側の集電板(５)のリード板(55)を、図６及び図７の如く本体(51)の内側に向けて折り返す。このとき、リード板(55)の複数本(実施例では５本)の切り込み(57)によって分割された複数(実施例では６つ)のリード部(58)を個々に切り込み(57)の基端位置から折り曲げる。これによって、リード板(55)は、リード部(58)毎に本体(51)の外周縁に沿って折り曲げられることとなる。
【００２９】
上述の如く巻き取り電極体(４)の帯状芯体の両端縁(48)(48)に集電板(５)(６)を設置した後、これを缶本体(11)内に収容し、負極側の集電板(６)を缶本体(11)の底部に抵抗溶接する。そして、正極側の集電板(５)のリード板(55)の溶接部(56)を封口板(２)の第１金属板(21)の裏面に溶接する。このとき、正極側の集電板(５)のリード板(55)のリード部(58)は、溶接部(56)にて一体となっているので、リード板(55)を正極端子部となる封口板(２)に溶接する作業は一度で済む。
その後、缶本体(11)内に電解液を注入し、該缶本体(11)の開口部に絶縁性部材(12)を介して封口板(２)をかしめ固定し、本実施例の円筒型リチウムイオン二次電池を完成する。
尚、封口板(２)の両金属板(21)(22)の溝部(28)に絶縁性部材(12)が局所的に食い込むことにより、両金属板(21)(22)の外周部の全周に沿って高い接触圧の線状接触部が形成されることにより、電池缶(１)内は高気密に保たれる。
【００３０】
【実施例】
図３に示す如く、厚さ１５μｍのアルミニウム製の芯体(45)に、ＬｉＣｏＯ_２からなる正極活物質(44)を塗布してなる正極(41)と、厚さ１０μｍ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。
【００３１】
又、直径３４ｍｍ、厚さ０.５ｍｍの円板状の本体(51)に４条の円弧状凸部(52)が放射状に形成されると共に、８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、円弧状凸部(52)の内周面に向けてレーザ溶接を施し、集電板(５)を芯体端縁(48)に接続した。集電板(５)には、本体(51)の外周縁に幅２１ｍｍのリード板(55)が突設されており、該リード板(55)には前記本体(51)の外周縁から溶接部(56)に向けて５本の切り込み(57)が３.５ｍｍ間隔で施されている。この状態で、リード板(55)を、図６及び図７の如く本体(51)の内側に向けて折り返す。このとき、リード板(55)は、複数本(実施例では５本)の切り込み(57)によって複数(実施例では６つ)のリード部(58)に分割されており、各リード部(58)を切り込み(57)の基端位置から折り曲げる。これによって、リード板(55)は、本体(51)の外周縁に沿って折り曲げられることとなる。
又、集電板(６)の材質がニッケルであり、リード板が突設されておらず、中央孔が開設されていないこと以外は正極側の集電構造と同様にして、負極側の集電構造を構成した。
【００３２】
次に、中央部に弁膜(24)が形成されたアルミニウム製の円板状の第１金属板(21)の上面に、中央部にガス排出孔(26)が開設されたニッケル製の第２金属板(22)を重ねあわせ、第１金属板(21)の下面から数箇所をスポット溶接することにより両金属板(21)(22)を接合して、封口板(２)を作製した。該封口板(２)の上部には、複数の通気孔(27)が開設されたニッケル製の正極端子部(20)が取り付けられることにより、弁膜(24)は、正極端子部(20)によって覆われる。
【００３３】
その後、巻き取り電極体(４)を缶本体(11)内に収容し、負極側の集電板(５)を缶本体(11)の底部に抵抗溶接する。そして、正極側の集電板(５)のリード板(55)の溶接部(56)を封口板(２)を構成するアルミニウム製の第１金属板(21)の裏面に溶接する。
そして、缶本体(11)内にドライボックス中で電解液を注入する。電解液は、エチレンカーボネートとジエチルカーボネートとの体積比を１：１とした混合液にＬｉＰＦ_６を１ｍｏｌ／ｌ溶解したものである。
最後に、該缶本体(11)の開口部に絶縁性部材(12)を介して封口板(２)をかしめ固定し、本実施例のリチウムイオン二次電池を完成する。
【００３４】
上記本発明のリチウムイオン二次電池においては、集電板(５)の本体(51)の円弧状外周縁から突出するリード板(55)の突出部分を従来よりも小さくすることが出来る。従って、集電板(５)は、本体(51)の全表面にて巻き取り電極体(４)の帯状芯体の端縁(48)と接触し、リード板(55)にて電池缶(１)と干渉することはない。又、集電板(５)のリード板(55)を折り曲げる作業は従来よりも容易となる。
又、リード板(55)のリード部(58)の幅は一定であり、これによってリード部(58)の断面積は一定となるので、リード部(58)にて局所的に電気抵抗が大きくなることはなく、リード板(55)全体としての電気抵抗が従来よりも増大することはない。
【００３５】
上記本発明に係る円筒型リチウムイオン二次電池によれば、集電性能を低下させることなく、電池の内部抵抗を従来よりも低下させることが出来る。
【００３６】
図４に示す実施例の正極側の集電板と従来の正極側の集電板の許容電流を比較し、本発明の効果を確認した。
従来の正極側の集電板として、直径３４ｍｍ、厚さ０.５ｍｍの円板状本体に４条の円弧状凸部が放射状に形成されると共に、８条の切り起し片が放射状に形成されたアルミニウム製の本体に、幅１０ｍｍのリード板(55)が突設されているものを採用した。
【００３７】
図４に示す実施例の集電板(５)のリード板(55)の許容電流と、比較例の集電板のリード板の許容電流を計測した。その結果、実施例の集電板(５)のリード板(55)の許容電流は約５５Ａであるのに対し、比較例の集電板のリード板の許容電流は約４４Ａであった。
従って、本実施例の集電構造を具えた円筒型リチウムイオン二次電池によれば、従来の集電構造よりも許容電流を約２５％向上させることが出来る。
【００３８】
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、リード板(55)の切り込み(57)の先端をリード板(55)の端部に設け、リード板(55)が完全に複数のリード部(58)に分割されている集電板(５)を具えた円筒型二次電池の構造を採用しても、上記実施例と同様の効果が得られる。
【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断面図である。
【図２】該円筒型リチウムイオン二次電池の要部を示す断面図である。
【図３】一部を展開した巻き取り電極体と集電板を示す斜視図である。
【図４】集電板の平面図である。
【図５】図４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６】集電板のリード板を折り曲げた状態を示す平面図である。
【図７】集電板のリード板を折り曲げた状態を示す正面図である。
【図８】従来の円筒型二次電池の断面図である。
【図９】従来の集電板の平面図である。
【図１０】他の従来の集電板の平面図である。
【図１１】該集電板を折り曲げた状態を示す平面図である。
【図１２】該集電板を本体寄りの折り曲げ位置で折り曲げた状態を示す平面図である。
【符号の説明】
(１) 電池缶
(10) 負極端子部
(11) 缶本体
(12) 絶縁性部材
(２) 封口板
(20) 正極端子部
(４) 巻き取り電極体
(41) 正極
(42) セパレータ
(43) 負極
(５) 集電板
(51) 本体
(55) リード板
(56) 溶接部
(57) 切り込み
(58) リード部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary battery in which an electrode body serving as a secondary battery element is accommodated in a battery can and power generated by the electrode body can be taken out from a pair of electrode terminal portions provided in the battery can.
[0002]
[Prior art]
In recent years, lithium ion secondary batteries with high energy density have attracted attention as power sources for portable electronic devices. Further, a large capacity cylindrical secondary battery has attracted attention as a power source for electric vehicles.
[0003]
For example, the cylindrical secondary battery shown in FIG. 8 is configured by accommodating a winding electrode body (4) inside a battery can (1) comprising a sealing plate (9) and a can body (11). The sealing plate (9) is formed with a valve membrane (94) that opens when the internal pressure of the battery can (1) exceeds a predetermined value, and the positive electrode terminal portion (90) covers the valve membrane (94). It is attached.
[0004]
The take-up electrode body (4) is composed of a strip-like positive electrode (41), a separator (42) and a negative electrode (43), respectively, and the positive electrode (41) and the negative electrode (43) have a width on the separator (42). They are stacked in a staggered direction and wound up in a spiral. As a result, the edge of the positive electrode (41) protrudes outward from the edge of the separator (42) at one end of both ends in the winding axis direction of the winding electrode body (4). At the other end, the edge of the negative electrode (43) protrudes outward from the edge of the separator (42). Current collector plates (8) and (80) are installed at both ends of the take-up electrode body (4), and are welded to the edge of the positive electrode (41) or the negative electrode (43).
[0005]
As shown in FIG. 9, the current collector plate (8) on the positive electrode side includes a disc-shaped main body (81), and a strip-shaped lead plate (85) protruding from the arc-shaped outer periphery of the main body (81). The main body (81) has a diameter substantially the same as the outer diameter of the winding electrode body (4). In addition, the main body (81) of the current collector plate (8) has a plurality of through holes (83) and a central hole (84) in the center, and the main body (81) and the lead plate (85) is formed with one slit (87) extending from the center of the main body (81) toward the tip of the lead plate (85). The lead plate (85) is folded back toward the inside of the current collector plate (8) as shown in FIG. 8, and the welded portion (86) provided at the tip is joined to the sealing plate (9) by laser welding. .
On the other hand, the current collector plate (80) joined to the edge of the negative electrode (43) is joined to the bottom surface of the can body (11), and the bottom portion of the can body (11) forms the negative electrode terminal portion (10). ing.
With the configuration described above, the electric power generated by the winding electrode body (4) can be taken out from the positive terminal portion (90) and the negative terminal portion (10).
[0006]
By the way, to increase the output of this type of cylindrical secondary battery, it is effective to reduce the internal resistance. The internal resistance is an electric resistance in a current path until the electric power generated by the winding electrode body (4) is taken out to the outside. As shown in FIG. A main body (81), a lead plate (85), a sealing plate (9), and a positive electrode terminal portion (90) are present.
[0007]
As a method for reducing the above-described internal resistance, it is conceivable to widen the lead plate (85) of the current collector plate (8) as shown in FIG. According to the current collector plate (8) shown in FIG. 10, since the cross-sectional area of the lead plate (85) serving as a current path is larger than that of the conventional one, the electric resistance at the current collector plate (8) is made smaller than that of the conventional one. This can reduce the internal resistance of the cylindrical secondary battery and increase the output.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-243972 ([0001] to [0004], [FIG. 6])
[0009]
[Problems to be solved by the invention]
However, in the current collector plate (8) having a large lead plate (85) as shown in FIG. 10, when the lead plate (85) is bent at the tangential position of the main body (81) as shown in FIG. ) In FIG. 4A protrudes from the outer peripheral edge of the main body (81), and this part interferes with the battery can (1).
[0010]
Therefore, conventionally, as shown in FIG. 12, the lead plate (85) of the current collector plate (8) has been bent further inside the main body (81) than the tangential position of the main body (81). However, this causes the outer peripheral portion of the main body (81) to be bent together with the lead plate (85). As a result, the contact area between the current collector plate (8) and the winding electrode body (4) becomes smaller than before, There was a problem that the current collecting performance of the current collecting plate (8) was lowered. Further, since the body of the wound electrode body current collector plate against the edge of the strip core (4) (8) (81) so that the eccentrically mounted, impact force from the outside of the belt-shaped core will be joining eccentrically to the edge, thereby, there is a risk that welded portion between the main body (81) and the edge of the strip core of the current collector plate (8) is peeled off.
[0011]
Accordingly, an object of the present invention is to provide a cylindrical secondary battery capable of reducing the internal resistance of the battery as compared with the conventional one without reducing the current collecting performance.
[0012]
[Means for solving the problems]
In the cylindrical secondary battery according to the present invention, a separator (42) is interposed between a strip-shaped positive electrode (41) and a negative electrode (43) in a cylindrical battery can (1), respectively, and these are spirally wound. A take-up electrode body (4) wound in a shape is accommodated, and each of the positive electrode (41) and the negative electrode (43) is configured by applying an active material to the surface of a strip-shaped core body. ) Can be taken out from the pair of electrode terminal portions.
The edge (48) of the strip-shaped core constituting the positive electrode (41) or the negative electrode (43) protrudes at the end of at least one of the winding electrode body (4) and covers the edge (48). A current collector plate (5), the current collector plate (5) comprising: a flat plate-like main body (51) in which at least a part of the outer peripheral edge has an arc shape; and the arc-shaped outer portion of the main body (51). A strip-shaped lead plate (55) protruding from the periphery, the lead plate (55) is provided with a plurality of cuts (57) extending in a direction away from the main body (51), each cut (57) has a proximal end at or near the arcuate outer periphery of the main body (51), and the leading end of the lead plate (55) is connected to one of the electrode terminal portions.
[0013]
In the cylindrical secondary battery of the present invention, the lead plate (55) of the current collector plate (5) is divided into a plurality of lead portions (58) by the plurality of cuts (57). The portions (58) can be individually bent from the base end position of the cut (57). Accordingly, the lead plate (55) is bent along the arc-shaped outer peripheral edge of the main body (51) for each lead portion (58), and as a result, protrudes from the arc-shaped outer peripheral edge of the main body (51). The projecting portion of the lead plate (55) can be made smaller than before.
Therefore, the current collector plate (5) contacts the edge (48) of the strip-shaped core of the winding electrode body (4) on the entire surface of the main body (51), and the battery can on the lead plate (55). There is no interference with (1). Moreover, since it can be bent for each lead portion (58) as described above, the work of bending the lead plate (55) of the current collector plate (5) is easier than before.
[0014]
Further, in a specific configuration, a welding portion (56) for welding the lead plate (55) to one electrode terminal portion is provided at the tip of the lead plate (55), and the notch (57) Has a tip in the vicinity of the weld (56).
In the specific configuration, since the lead portion (58) of the lead plate (55) is integrated with the weld portion (56), the work of welding the lead plate (55) to the electrode terminal portion is performed once. That's it. Therefore, the number of steps in the assembly process does not increase.
[0015]
In a more specific configuration, the plurality of cuts (57) extend parallel to each other.
In the specific configuration, the width of the lead portion (58) of the lead plate (55) is constant, and thereby the cross-sectional area of the lead portion (58) is constant. Therefore, the electrical resistance does not increase locally at the lead portion (58), and the electrical resistance of the entire lead plate (55) does not increase as compared with the conventional case.
[0016]
【The invention's effect】
According to the cylindrical battery according to the present invention, the internal resistance of the battery can be reduced as compared with the conventional one without reducing the current collecting performance.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention applied to a cylindrical lithium ion secondary battery will be described in detail with reference to the drawings.
[0018]
Overall configuration In the cylindrical lithium ion secondary battery according to the present invention, the battery can (1) includes a cylindrical can body (11) having an opening at one end, as shown in FIG. A sealing plate (2) fixed to the opening and closing the opening, and an electrically insulating member (12) interposed between the can body (11) and the sealing plate (2). A winding electrode body (4) is accommodated in the can (1). The sealing plate (2) is formed with a valve membrane (24) that opens when the internal pressure of the battery can (1) exceeds a predetermined value, and the positive terminal portion (20) covers the valve membrane (24). It is attached.
[0019]
Current collecting plates (5) and (6) are installed at both ends of the winding electrode body (4), and both current collecting plates (5) and (6) are joined to the winding electrode body (4) by laser welding. ing. The tip of the lead plate (55) protruding from the end of the positive current collector plate (5) is connected to the sealing plate (2) by laser welding. The current collector plate (6) on the negative electrode side is joined to the bottom of the can body (11) by spot welding, ultrasonic welding or laser welding, and the bottom of the can body (11) constitutes the negative electrode terminal (10). is doing.
Thereby, the electric power generated by the winding electrode body (4) can be taken out from the positive terminal portion (20) and the negative terminal portion (10).
[0020]
Winding electrode body ( 4 )
As shown in FIG. 3, the wound 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. Has been. 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.
[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 As shown in Figs. 3 to 5, the current collector plate (5) on the positive electrode side has a disk-shaped main body (51) and a belt-like shape protruding from the outer peripheral edge of the main body (51). The main body (51) is provided with a central hole (54). Further, the 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) side is formed. Protruding. The arcuate protrusion (52) has an arcuate shape with a semicircular cross-section perpendicular to the radial line of the main body (51).
Further, the main body (51) of the current collector plate (5) has a plurality of strips (53 in the embodiment) cut and raised pieces (53) between the adjacent arc-shaped convex portions (52) and (52). Is formed and protrudes toward the winding electrode body (4). The through-hole formed as the cut-and-raised piece (53) is cut and raised serves as a passage for the electrolytic solution when the winding electrode body (4) is impregnated with the electrolytic solution in the assembly process described later.
[0023]
Further, as shown in FIGS. 3 and 4, a welded portion for welding and joining the lead plate (55) and the sealing plate (2) to the tip of the lead plate (55) of the current collector plate (5). 56). Also, the lead plate (55) has a plurality of (five in the embodiment) cuts (57) extending from the main body (51) toward the welded portion (56) so that they are parallel to each other and at equal intervals. The notch (57) has a proximal end on the outer peripheral edge of the main body (51) and a distal end in the vicinity of the welded portion (56). Thus, the lead plate (55) is divided into a plurality of (six in the embodiment) lead portions (58) from the outer peripheral edge of the main body (51) to the welded portion (56).
[0024]
As shown in FIG. 3, the current collector plate (6) on the negative electrode side has a disc-shaped main body (61), and the central portion (64) of the main body (61) is spotted on the bottom of the can main body (11). It will be welded. Further, the main body (61) is integrally formed with a plurality of (four in the embodiment) arc-shaped convex portions (62) extending radially around the central portion (64), and the winding electrode body (4) side. Protruding. The arcuate convex part (62) has an arcuate shape with a semicircular cross section perpendicular to the radial line of the main body (61).
Further, the main body (61) of the current collector plate (6) has a plurality of (two in the embodiment) cut and raised pieces (63) between the adjacent arc-shaped convex portions (62) and (62). Is formed and protrudes toward the winding electrode body (4).
[0025]
Sealing plate ( 2 )
As shown in FIG. 2, the sealing plate (2) is composed of a disc-shaped first metal plate (21) and a second metal plate (22) having a thickness larger than that of the first metal plate (21). The two metal plates (21) and (22) are overlapped with the second metal plate (22) on the upper surface of the first metal plate (21), and several points are formed from the lower surface of the first metal plate (21). Joined by spot welding.
[0026]
At the center of the first metal plate (21) is formed a thin film-like valve membrane (24) integrally formed in the manufacturing process of the first metal plate (21), and the center of the second metal plate (22). The part is provided with a gas discharge hole (26) at a position facing the valve membrane (24). A positive electrode terminal portion (20) is attached to the upper surface of the second metal plate (22) so as to cover the gas discharge hole (26). In addition, a plurality of vent holes (27) are formed in the outer peripheral surface of the positive electrode terminal portion (20), whereby the surface of the valve membrane (24) comes into contact with the outside air.
In addition, the first metal plate (21) and the second metal plate (22) are in contact with the insulating member (12) along the entire circumference of the outer peripheries of the metal plates (21) and (22). Thus, a groove (28) is formed.
[0027]
Assembly process First, the can body (11) shown in FIG. 1, the sealing plate (2) shown in FIG. 2, the winding electrode body (4) shown in FIG. 3, and the current collector plate (5 shown in FIG. 4). ) Respectively.
Next, the current collector plates (5) and (6) are pressed against the core body edges (48) and (48) formed at both ends of the winding electrode body (4). As a result, the arc-shaped protrusions (52) and (62) of the current collector plates (5) and (6) bite into the core body edges (48) and (48) of the winding electrode body (4), and the arc-shaped protrusions. (52) Between the core end edge (48) and the core body edge (48), a joining surface comprising a cylindrical surface is formed. Further, the cut and raised pieces (53) and (63) of the current collector plates (5) and (6) deeply bite into the core body edges (48) and (48) of the winding electrode body (4), and the core body edges. (48) It will be crimped to (48).
In this state, laser welding is performed by irradiating laser beams toward the inner peripheral surfaces of the arc-shaped convex portions (52) and (62) of the current collector plates (5) and (6). As a result, the arc-shaped convex portions (52) and (62) of the current collector plates (5) and (6) and the core end edges (48) and (48) of the take-up electrode body (4) are mutually connected with a large contact area. At the same time, the crimped state between the cut and raised pieces (53) and (63) and the core body edges (48) and (48) is maintained.
[0028]
Next, the lead plate (55) of the current collector plate (5) on the positive electrode side is folded back toward the inside of the main body (51) as shown in FIGS. At this time, a plurality of (six in the embodiment) lead portions (58) divided by a plurality of (seven in the embodiment) notches (57) of the lead plate (55) are individually formed on the basis of the notches (57). Bend from the end position. As a result, the lead plate (55) is bent along the outer peripheral edge of the main body (51) for each lead portion (58).
[0029]
After the current collector plates (5) and (6) are installed at both end edges (48) and (48) of the belt-like core of the winding electrode body (4) as described above, this is accommodated in the can body (11), The current collector plate (6) on the negative electrode side is resistance-welded to the bottom of the can body (11). And the welding part (56) of the lead plate (55) of the current collector plate (5) on the positive electrode side is welded to the back surface of the first metal plate (21) of the sealing plate (2). At this time, since the lead portion (58) of the lead plate (55) of the current collector plate (5) on the positive electrode side is integrated with the weld portion (56), the lead plate (55) is connected to the positive electrode terminal portion. The work of welding to the sealing plate (2) is completed only once.
Thereafter, an electrolytic solution is injected into the can body (11), and the sealing plate (2) is caulked and fixed to the opening of the can body (11) via the insulating member (12). Complete the lithium ion secondary battery.
The insulating member (12) locally bites into the grooves (28) of the metal plates (21) and (22) of the sealing plate (2), so that the outer peripheral portions of the metal plates (21) and (22) By forming a linear contact portion having a high contact pressure along the entire circumference, the inside of the battery can (1) is kept highly airtight.
[0030]
【Example】
As shown in FIG. 3, an aluminum core having a thickness of 15 [mu] m (45), consisting of LiCoO ₂ positive electrode active with a substance (44) positive electrode (41) formed by coating a thickness 10μm copper core of ( 47) and a negative electrode (43) formed by applying a negative electrode active material (46) made of graphite and a separator (42) made of an ion-permeable polypropylene microporous film, and these are wound up in a spiral shape. Thus, a wound electrode body (4) was produced. 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).
[0031]
In addition, four arc-shaped convex portions (52) are formed radially on a disc-shaped main body (51) having a diameter of 34 mm and a thickness of 0.5 mm, and eight cut and raised pieces (53) are radially formed. A current collector plate (5) made of aluminum is formed, and the current collector plate (5) is placed on the core edge (48) on the positive electrode side of the winding electrode body (4) to form an arc-shaped convex Laser welding was performed toward the inner peripheral surface of the part (52), and the current collector plate (5) was connected to the core body edge (48). On the current collecting plate (5), a lead plate (55) having a width of 21 mm is projected from the outer peripheral edge of the main body (51), and the lead plate (55) is welded from the outer peripheral edge of the main body (51). Five cuts (57) are made at intervals of 3.5 mm toward the part (56). In this state, the lead plate (55) is folded back toward the inside of the main body (51) as shown in FIGS. At this time, the lead plate (55) is divided into a plurality of (six in the embodiment) lead portions (58) by a plurality of (seven in the embodiment) cuts (57), and each lead portion (58 ) Is bent from the base end position of the notch (57). As a result, the lead plate (55) is bent along the outer peripheral edge of the main body (51).
Further, the current collector plate (6) is made of nickel, the lead plate is not protruded, and the central hole is not opened. An electric structure was constructed.
[0032]
Next, on the upper surface of the aluminum disk-shaped first metal plate (21) having the valve membrane (24) formed in the central portion, a second nickel-made metal having a gas discharge hole (26) opened in the central portion. The metal plates (22) were overlapped, and several metal plates (21) and (22) were joined by spot welding from the lower surface of the first metal plate (21) to produce a sealing plate (2). A nickel positive electrode terminal portion (20) having a plurality of vent holes (27) is attached to the upper portion of the sealing plate (2), so that the valve membrane (24) is formed by the positive electrode terminal portion (20). Covered.
[0033]
Thereafter, the take-up electrode body (4) is accommodated in the can body (11), and the current collector plate (5) on the negative electrode side is resistance-welded to the bottom of the can body (11). And the welding part (56) of the lead plate (55) of the current collector plate (5) on the positive electrode side is welded to the back surface of the first metal plate (21) made of aluminum constituting the sealing plate (2).
Then, an electrolytic solution is injected into the can body (11) in a dry box. The electrolytic solution is obtained by dissolving 1 mol / l of LiPF ₆ in a mixed solution in which the volume ratio of ethylene carbonate and diethyl carbonate is 1: 1.
Finally, the sealing plate (2) is caulked and fixed to the opening of the can body (11) via the insulating member (12), thereby completing the lithium ion secondary battery of this example.
[0034]
In the lithium ion secondary battery of the present invention, the protruding portion of the lead plate (55) protruding from the arcuate outer peripheral edge of the main body (51) of the current collector plate (5) can be made smaller than before. Therefore, the current collector plate (5) contacts the edge (48) of the belt-like core of the winding electrode body (4) on the entire surface of the main body (51), and the battery can ( There is no interference with 1). Also, the work of bending the lead plate (55) of the current collector plate (5) is easier than before.
Further, the width of the lead portion (58) of the lead plate (55) is constant, and thereby the cross-sectional area of the lead portion (58) is constant, so that the electrical resistance is locally increased at the lead portion (58). The electrical resistance of the lead plate (55) as a whole does not increase as compared with the conventional case.
[0035]
According to the cylindrical lithium ion secondary battery according to the present invention, the internal resistance of the battery can be reduced as compared with the conventional one without reducing the current collecting performance.
[0036]
The effect of the present invention was confirmed by comparing the allowable currents of the positive current collector plate of the example shown in FIG. 4 and the conventional positive current collector plate.
As a current collector plate on the positive electrode side, four arc-shaped convex portions are radially formed on a disc-shaped body having a diameter of 34 mm and a thickness of 0.5 mm, and eight cut and raised pieces are radially formed. The aluminum body was used, and a lead plate (55) having a width of 10 mm was projected.
[0037]
The allowable current of the lead plate (55) of the current collector plate (5) of the example shown in FIG. 4 and the allowable current of the lead plate of the current collector plate of the comparative example were measured. As a result, the allowable current of the lead plate (55) of the current collector plate (5) of the example was about 55A, while the allowable current of the lead plate of the current collector plate of the comparative example was about 44A.
Therefore, according to the cylindrical lithium ion secondary battery having the current collecting structure of this embodiment, the allowable current can be improved by about 25% compared to the conventional current collecting structure.
[0038]
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, a current collector plate (55) in which the tip of the notch (57) of the lead plate (55) is provided at the end of the lead plate (55), and the lead plate (55) is completely divided into a plurality of lead portions (58) ( Even if the structure of the cylindrical secondary battery having 5) is adopted, the same effect as in the above embodiment can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion secondary battery according to the present invention.
FIG. 2 is a cross-sectional view showing a main part of the cylindrical lithium ion secondary battery.
FIG. 3 is a perspective view showing a winding electrode body and a current collector plate partially expanded.
FIG. 4 is a plan view of a current collector plate.
5 is a diagram showing an enlarged cross section along the line AA in FIG. 4 and an enlarged cross section along the line BB. FIG.
FIG. 6 is a plan view showing a state where a lead plate of a current collector plate is bent.
FIG. 7 is a front view showing a state where a lead plate of a current collector plate is bent.
FIG. 8 is a cross-sectional view of a conventional cylindrical secondary battery.
FIG. 9 is a plan view of a conventional current collector plate.
FIG. 10 is a plan view of another conventional current collector plate.
FIG. 11 is a plan view showing a state in which the current collector plate is bent.
FIG. 12 is a plan view showing a state in which the current collector plate is bent at a bending position close to the main body.
[Explanation of symbols]
(1) Battery can
(10) Negative terminal
(11) Can body
(12) Insulating material
(2) Sealing plate
(20) Positive terminal
(4) Winding electrode body
(41) Positive electrode
(42) Separator
(43) Negative electrode
(5) Current collector
(51) Body
(55) Lead plate
(56) Welded part
(57) Notch
(58) Lead part

Claims

A take-up electrode body (4) in which a separator (42) is interposed between a strip-like positive electrode (41) and a negative electrode (43) in a cylindrical battery can (1) and wound in a spiral shape. Each of the positive electrode (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) is supplied from the pair of electrode terminal portions. In the cylindrical secondary battery that can be taken out,
The edge (48) of the strip-shaped core constituting the positive electrode (41) or the negative electrode (43) protrudes at the end of at least one of the winding electrode body (4) and covers the edge (48). A current collector plate (5), the current collector plate (5) comprising: a flat plate-like main body (51) in which at least a part of the outer peripheral edge has an arc shape; and the arc-shaped outer portion of the main body (51). A strip-shaped lead plate (55) protruding from the periphery, the lead plate (55) is provided with a plurality of cuts (57) extending in a direction away from the main body (51), each cut (57) has a base end at or near the arcuate outer peripheral edge of the main body (51), and the leading end of the lead plate (55) is connected to one of the electrode terminal portions. A cylindrical secondary battery.

The leading end of the lead plate (55) is provided with a welded portion (56) for welding the lead plate (55) to one of the electrode terminal portions, and the notch (57) 56) The cylindrical secondary battery according to claim 1, which is provided in the vicinity of 56).

The cylindrical secondary battery according to claim 1 or 2, wherein the plurality of cuts (57) extend parallel to each other.