JP3759577B2

JP3759577B2 - Nonaqueous electrolyte secondary battery and manufacturing method thereof

Info

Publication number: JP3759577B2
Application number: JP2000241086A
Authority: JP
Inventors: 直哉中西; 広一佐藤; 俊之能間; 育郎米津
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1999-08-10
Filing date: 2000-08-09
Publication date: 2006-03-29
Anticipated expiration: 2020-08-09
Also published as: JP2001118563A

Description

【０００１】
【発明の属する技術分野】
本発明は、円筒型リチウムイオン二次電池の如く、密閉容器内に発電要素となる電極体が収容されて、該電極体が発生する電力を正極端子部及び負極端子部から外部へ取り出すことが可能な非水電解液二次電池、並びにその製造方法に関するものである。
【０００２】
【従来の技術】
この種の非水電解液二次電池においては、それぞれ帯状の正極と負極がセパレータを介して互いに重ねられ、これを渦巻き状に巻き取って巻き取り電極体が構成され、該巻き取り電極体は、密閉容器内に収容されている。
巻き取り電極体が発生する電力を外部へ取り出す方法としては、巻き取り電極体を構成する正極及び負極にそれぞれ、複数本の導電性タブの基端部を連結し、正極から引き出された複数本の正極集電タブの先端部は正極端子部に連結すると共に、負極から引き出された複数本の負極集電タブの先端部は負極端子部に連結する方法が、広く採用されている。
【０００３】
しかしながら、複数本の集電タブを用いた集電構造においては、比較的電流値の低い小型の非水電解液二次電池の場合は、十分な集電効果が得られるが、電流値の高い大型の非水電解液二次電池では、電極面積が大きくなることから、十分な集電効果を得ることが出来ない問題があった。
又、複数本の集電タブを電極端子部に連結する構造及び工程が複雑であり、作業性や生産性が悪い問題があった。
【０００４】
そこで、図７に示す如く、負極集電板(36)及び正極集電板(30)による集電構造を具えた円筒型非水電解液二次電池が提案されている。該非水電解液二次電池においては、筒体(15)の両端開口部に蓋体(16)(16)を固定して、電池缶(１)が構成され、該電池缶(１)の内部に巻き取り電極体(２)が収容されている。巻き取り電極体(２)の両端部には、負極集電板(36)及び正極集電板(30)が設置され、巻き取り電極体(２)にレーザ溶接されている。又、負極集電板(36)及び正極集電板(30)は、連結帯(37)(34)を介して、蓋体(16)(16)に取り付けられた負極端子機構(４)及び正極端子機構(40)に連結されている。
【０００５】
巻き取り電極体(２)は、それぞれ帯状の正極(23)、セパレータ(22)、及び負極(21)から構成される。正極(23)は、アルミニウム箔からなる芯体の表面に正極活物質を塗布して構成され、負極(21)は、銅箔からなる芯体の表面に負極活物質を塗布して構成されている。
正極(23)及び負極(21)はそれぞれセパレータ(22)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(２)の巻き軸方向の両端部の内、一方の端部では、セパレータ(22)の端縁よりも外方へ正極(23)の端縁が突出すると共に、他方の端部では、セパレータ(22)の端縁よりも外方へ負極(21)の端縁が突出している。尚、正極集電板(30)はアルミニウム製であり、負極集電板(36)は銅製である。
【０００６】
上述の如く、巻き取り電極体(２)の端部に集電板(36)(30)をレーザ溶接する集電構造によれば、溶接の際に集電板に圧力をかけることなく、非接触で溶接を行なうことが出来るので、作業性、生産性が向上する。
【０００７】
【発明が解決しようとする課題】
しかしながら、図７に示す非水電解液二次電池の製造工程において、巻き取り電極体(２)の負極(21)の端縁に負極集電板(36)を設置して、レーザ溶接を施す際、負極集電板(36)の材質である銅は、レーザビームに対する反射率が高いため、溶接部に十分なエネルギーを与えることが出来ず、溶接が不完全となって、巻き取り電極体(２)と負極集電板(36)の間の電気抵抗の増大により、集電効率が低下する問題があった。尚、負極集電板(36)をニッケル製とすれば、巻き取り電極体(２)に対する負極集電板(36)の溶接性は改善することが可能であるが、ニッケル製の負極集電板(36)は、銅製の負極集電板(36)に比べて電気抵抗が大きいため、集電効率が低下することになる。
【０００８】
そこで、本発明の目的は、電極体の端部に負極集電板を溶接固定する集電構造の非水電解液二次電池において、電極体に対する負極集電板の溶接性を改善して、高い集電効率を得ることが出来る非水電解液二次電池の構造と製造方法を提供することである。
【０００９】
【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は、巻き取り電極体(２)の巻き軸方向の両端部の内、一方の端部には負極(21)の端縁が突出して、該端縁に負極集電板(３)がレーザ接合され、該負極集電板(３)は負極端子部に電気接続されている。ここで、負極集電板(３)は、銅若しくは銅を主体とする合金からなる銅層部(31)と、リチウムと金属間化合物を形成しない金属であって且つ銅よりもレーザ光反射率が低い金属若しくは該金属を主体とする合金からなる金属層部とを有する複数層部からなり、銅層部(31)及び金属層部が両側の表面層を形成し、銅層部(31)を負極(21)の端縁に溶接されている。具体的には、負極集電板(３)の金属層部を形成する金属は、ニッケル、ステンレス鋼、チタン、クロム、モリブデンなどである。
【００１０】
上記本発明の非水電解液二次電池によれば、その製造工程において、負極集電板(３)を巻き取り電極体(２)の負極(21)の端縁にレーザ溶接する際、負極集電板(３)のレーザビーム受光側には、レーザ光反射率が低い金属層部が形成されているので、レーザビームのエネルギーが十分に吸収されて、完全な溶接が行なわれる。
【００１１】
又、負極集電板(３)の金属層部は、リチウムと金属間化合物を形成しない金属若しくは該金属を主体とする合金からなるので、非水電解液中のリチウムイオンを消費して合金を形成することがなく、これによって非水電解液中のリチウムイオン濃度の低下が防止される。
又、負極集電板(３)は、銅層部(31)と金属層部とを有する複数層構造を有しているので、銅層部の優れた導電性によって、金属層部のみからなるよりも電気抵抗が低くなり、高い電気導電性を発揮する。
更に、巻き取り電極体(２)の負極(21)の端縁は、全長に亘って負極集電板(３)の銅層部(31)と接合されているので、電池が大型化し、電極が長尺となった場合であっても、巻き取り電極体(２)の全体から均一に集電を行なうことが可能である。この結果、負極(21)の長手方向の電位勾配が小さくなり、電流分布は、偏りのない均一なものとなる。これによって、高い集電効率が達成される。
【００１２】
具体的には、負極集電板(３)の厚さは０.１０ｍｍ〜５.００ｍｍの範囲内である。負極集電板(３)の厚さが０.１０ｍｍよりも小さくなると、負極集電板(３)自体の電気抵抗が大きくなり、集電効率が低下するばかりでなく、レーザ溶接によって負極集電板(３)が過度に溶融し、溶接部に陥没が発生する。これに対し、負極集電板(３)の厚さが５.００ｍｍを超えると、負極集電板(３)の溶接に大きなパワーが必要となり、厚さ数十ミクロンの負極(21)の端縁に負極集電板(３)を溶接することが困難となる。
【００１３】
又、具体的には、負極集電板(３)の厚さに対する金属層部の厚さの比率は、５％以上、４５％以下の範囲である。これによって、金属層部がレーザ光反射率を低下させる機能を十分に発揮すると共に、銅層部(31)が電気抵抗を低下させる機能を十分に発揮する。即ち、金属層部の厚さの比率が５％よりも小さいときは、負極集電板(３)の溶接開始直後に金属層部が溶融して消失し、レーザ光反射率の高い表面が現われるため、溶接性が低下する。これに対し、金属層部の厚さの比率が４５％を超えると、負極集電板(３)の電気抵抗に関し金属層部が支配的となって、負極集電板(３)全体の電気抵抗が増大する。
【００１４】
又、本発明に係る非水電解液二次電池の製造方法は、
一方の端部に正極(23)の端縁が突出すると共に、他方の端部に負極(21)の端縁が突出する様に、セパレータ(22)を間に挟んで正極(23)と負極(21)とを重ね合わせ、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(２)を作製する工程と、
アルミニウム若しくはアルミニウムを主体とする合金からなる正極集電板(30)を作製する工程と、
銅若しくは銅を主体とする合金からなる銅層部(31)と、リチウムと金属間化合物を形成しない金属であって且つ銅よりもレーザ光反射率が低い金属若しくは該金属を主体とする合金からなる金属層部とを有する複数層部からなり、銅層部(31)及び金属層部が両側の表面層を形成する負極集電板(３)を作製する工程と、
正極(23)の端縁が突出した巻き取り電極体(２)の端部に、正極集電板(30)を設置し、該正極集電板(30)の表面へレーザビームを照射して、正極(23)の端縁に正極集電板(30)をレーザ溶接する工程と、
負極(21)の端縁が突出した巻き取り電極体(２)の端部に、銅層部(31)が負極(21)の端縁に接触する様に負極集電板(３)を設置し、該負極集電板(３)の金属層部の表面へレーザビームを照射して、負極(21)の端縁に負極集電板(３)をレーザ溶接する工程と、
巻き取り電極体(２)に溶接された正極集電板(30)及び負極集電板(３)をそれぞれ正極端子部及び負極端子部に電気接続して、二次電池を組み立てる工程
とを有している。
【００１５】
上記本発明の製造方法によれば、巻き取り電極体(２)の負極(21)の端縁に負極集電板(３)をレーザ溶接する工程において、レーザ光は、反射率の低い金属層部の表面に照射されるので、レーザビームのエネルギーが十分に、負極集電板(３)と負極(21)端縁の接合部に与えられ、この結果、負極集電板(３)と負極(21)端縁とは互いに完全に溶着する。
又、巻き取り電極体(２)の正極(23)の端縁に正極集電板(30)をレーザ溶接する工程では、正極集電板(30)の材質であるアルミニウムはレーザ光の反射率が低いため、レーザビームのエネルギーが十分に、正極集電板(30)と正極(23)端縁の接合部に与えられ、この結果、正極集電板(30)と正極(23)端縁とは互いに完全に溶着する。
その後、組立工程においては、正極集電板(30)及び負極集電板(３)をそれぞれ正極端子部及び負極端子部に電気接続する。
これによって、巻き取り電極体(２)から両端子部までの電気抵抗は十分に低くなって、高い集電効率が達成される。
【００１６】
【発明の効果】
本発明に係る非水電解液二次電池及びその製造方法によれば、巻き取り電極体に対する負極集電板の溶接性が向上して、高い集電効率を得ることが出来る。
【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。
本実施例の円筒型リチウムイオン二次電池は、図１に示す如く、筒体(15)の両端開口部に蓋体(16)(16)を固定して、電池缶(１)が構成され、該電池缶(１)の内部に巻き取り電極体(２)が収容されている。巻き取り電極体(２)の両端部には、銅層部(31)とリチウムと金属間化合物を形成しない金属であって且つ銅よりもレーザ光反射率が低い金属若しくは該金属を主体とする合金からなる金属層部( ニッケル層部 (32))の２層からなる負極集電板(３)及び正極集電板(30)が設置され、巻き取り電極体(２)の両端部にレーザ溶接されている。又、負極集電板(３)及び正極集電板(30)はそれぞれ、連結帯(33)(34)を介して、蓋体(16)(16)に取り付けられた負極端子機構(４)及び正極端子機構(40)に連結されている。
【００１８】
巻き取り電極体(２)は、図４に示す如く、それぞれ帯状の正極(23)、セパレータ(22)、及び負極(21)から構成される。正極(23)は、アルミニウム箔からなる芯体の表面にＬｉＣｏＯ_２からなる正極活物質(26)を塗布して構成され、負極(21)は、銅箔からなる芯体の表面に天然黒鉛からなる負極活物質(24)を塗布して構成されている。
正極(23)及び負極(21)はそれぞれセパレータ(22)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(２)の軸方向の両端部の内、一方の端部では、渦巻き状に巻き取られた負極(21)の端縁(非塗工部(25))が、セパレータ(22)の端縁よりも外方へ突出すると共に、他方の端部では、渦巻き状で巻き取られた正極(23)の端縁(非塗工部(27))が、セパレータ(22)の端縁よりも外方へ突出することになる。
例えば、各電極の活物質塗工部(24)(26)の幅Ａは数十ｍｍ、非塗工部(25)(27)の幅Ｂは１０ｍｍ程度、セパレータ(22)からの突出距離Ｓは１〜３ｍｍ程度に形成することが出来る。
【００１９】
負極集電板(３)は、図１及び図２に示す如く円盤状を呈して、厚さ２.４０ｍｍの銅層部(31)と、リチウムと金属間化合物を形成しない金属であって且つ銅よりもレーザ光反射率が低い金属であるニッケルからなる厚さ０.６０ｍｍのニッケル層部(32)とからなる２層構造を有している。該負極集電板(３)の端部には、銅製の連結帯(33)が突設されている。又、負極集電板(３)としては、図５に示す如く、ニッケル層部(32)にかえてステンレス鋼層部(35)を形成したものを採用することが可能である。更に、負極集電板(３)としては、図６に示す如く、銅層部(31)とニッケル層部(32)が両側の表面層を形成して、両表面層の間にステンレス鋼層部(35)が挟まれている３層構造に形成することも可能である。更に又、リチウムと金属間化合物を形成しない金属であって且つ銅よりもレーザ光反射率が低い金属を用いたものであれば、ニッケル層部(32)やステンレス鋼層部(35)にかえて、チタン層部、クロム層部、或いはモリブデン層部を採用することも可能である。一方、正極集電板(30)も同様に円盤状を呈して、厚さ１.００ｍｍのアルミニウム板から形成され、その端部には、図１の如く、アルミニウム製の連結帯(34)が突設されている。
【００２０】
負極集電板(３)は、図３に示す如く、銅層部(31)が巻き取り電極体(２)の負極(21)の端縁(非塗工部(25))に接触する様に、巻き取り電極体(２)の端部に設置され、ニッケル層部(32)の表面へレーザビームを照射することによって、負極(21)の端縁に溶接されている。
又、正極集電板(30)も同様に、巻き取り電極体(２)の端部に設置され、その表面へレーザ光を照射することによって、正極(23)の端縁に溶接されている。
【００２１】
図１に示す如く、負極端子機構(４)は、ねじ軸部(42)の下端部に鍔部(43)を突設してなる端子部材(41)を具えている。端子部材(41)のねじ軸部(42)は、蓋体(16)を貫通し、端子部材(41)の周囲には、第１絶縁部材(45)及び第２絶縁部材(46)が装着されて、蓋体(16)と端子部材(41)の間の電気的絶縁と気密性が保たれている。又、端子部材(41)の先端部には、ワッシャ(47)が嵌まると共に、ナット(48)が螺合している。正極端子機構(40)も同じ構造を有している。
【００２２】
負極集電板(３)から伸びる連結帯(33)の先端部は、負極端子機構(４)の端子部材(41)の鍔部(43)に溶接されると共に、正極集電板(30)から伸びる連結帯(34)の先端部は、正極端子機構(40)の端子部材(41)の鍔部(43)に溶接されている。これによって、負極端子機構(４)と正極端子機構(40)から、巻き取り電極体(２)の発生電力を取り出すことが出来る。
【００２３】
次に、上記本発明のリチウムイオン二次電池の製造工程について説明する。
巻き取り電極体 ( ２ ) の作製
ＬｉＣｏＯ_２からなる正極活物質と、炭素から成る導電助剤と、ポリフッ化ビニリデン(ＰＶｄＦ)からなるバインダーとを混合して、正極合剤を調製し、該正極合剤を、図４に示すようにアルミニウム箔からなる帯状の正極芯体の両面に塗布して、正極(23)を作製する。尚、正極芯体の一方の端部には、正極活物質層の塗布されていない幅１０ｍｍの非塗工部(27)を形成する。
【００２４】
天然黒鉛からなる負極活物質と、ポリフッ化ビニリデン(ＰＶｄＦ)からなるバインダーとを混合して、負極合剤を調製し、該負極合剤を、銅箔からなる帯状の負極芯体の両面に塗布して、負極(21)を作製する。尚、負極芯体の一方の端部には、負極活物質の塗布されていない幅１０ｍｍの非塗工部(25)を形成する。
又、正極活物質塗工部及び負極活物質塗工部の幅Ａより若干大きな幅を有するセパレータ(22)を用意する。尚、セパレータ(22)は多孔性のポリエチレン及びポリプロピレンから形成される。
【００２５】
その後、図４の如く、正極(23)、セパレータ(22)及び負極(21)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(２)を作製する。この際、正極(23)の活物質非塗工部(27)と負極(21)の活物質非塗工部(25)の端縁が、セパレータ(22)の端縁から外側へ突出する様に重ね合わせる。
【００２６】
正極集電板 (30) 及び負極集電板 ( ３ ) の作製図２の如く、厚さ２.４０ｍｍの銅層部(31)と厚さ０.６０ｍｍのニッケル層部(32)からなる２層構造の負極集電板(３)、図５の如く銅層部 (31) とステンレス鋼層部(35)からなる２層構造の負極集電板(３)、或いは図６の如く厚さ２.４０ｍｍの銅層部(31)と厚さ０.３０ｍｍのニッケル層部(32)の間に厚さ０.３０ｍｍのステンレス鋼層部(35)が形成された３層構造の負極集電板(３)を作製し、負極集電板(３)の端部に、銅製の連結帯(33)の基端部を連結する。又、厚さ１.００ｍｍのアルミニウム板からなる正極集電板(30)を作製し、該正極集電板(30)の端部に、アルミニウム製の連結帯(34)の基端部を連結する。
【００２７】
電池の組立
巻き取り電極体(２)の負極(21)の端縁に銅層部(31)が接触する様に負極集電板(３)を設置し、該負極集電板(３)のニッケル層部(32)の表面へレーザビームを照射して、負極(21)の端縁に負極集電板(３)を溶接する。又、巻き取り電極体(２)の正極(23)の端縁に正極集電板(30)を設置し、該正極集電板(30)の表面へレーザビームを照射して、正極(23)の端縁に正極集電板(30)を溶接する。
【００２８】
その後、負極集電板(３)から伸びる連結帯(33)の先端部を負極端子機構(４)の端子部材(41)の鍔部(43)に超音波溶接すると共に、正極集電板(30)から伸びる連結帯(34)の先端部を正極端子機構(40)の端子部材(41)の鍔部(43)に超音波溶接する。又、両蓋体(16)(16)には負極端子機構(４)及び正極端子機構(40)を組み付ける。
そして、筒体(15)の内部に巻き取り電極体(２)を挿入し、筒体(15)の両開口部に蓋体(16)(16)を溶接固定した後、図示省略する電解液注入口から電解液を注入する。尚、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を体積比１：１で混合し、この混合溶媒にＬｉＰＦ_６を１モル／リットルの割合で溶解させたものである。最後に、電解液注入口を封止する。これによって、図１に示す円筒型リチウムイオン二次電池が完成する。
【００２９】
尚、正極活物質としては、上述のＬｉＣｏＯ_２に限定するものではなく、ＬｉＮｉＯ_２、ＬｉＭｎ_２Ｏ_４等を採用することが出来、更に負極活物質としては、上述の天然黒鉛に限定するものではなく、人造黒鉛、コークス等の他の炭素材料や、リチウムを吸蔵放出可能な材料を採用することが出来る。又、電解液としては、上述のものに限定するものではなく、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、ジエチルカーボネート、１，２−ジメトキシエタン、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ＬｉＣｌＯ_４、ＬｉＣＦ_３ＳＯ_４などの溶質を０.７〜１.５モル／リットルの割合で溶解させた溶液等を採用することが出来る。
【００３０】
実験
上記本発明の円筒型リチウムイオン二次電池において、図２に示す如く負極集電板(３)が２層からなり、ニッケル層部(32)の厚さと銅層部(31)の厚さを種々に変えた発明電池１〜１１を作製した。又、図５に示す如く負極集電板(３)が２層からなり、ステンレス鋼層部(35)の厚さと銅層部(31)の厚さを種々に変えた発明電池１２〜２２を作製した。更に、図６に示す如く負極集電板(３)が、ニッケル層部(32)、ステンレス鋼層部(35)及び銅層部(31)の３層構造からなる発明電池２３を作製した。一方、図７に示す如くニッケル板又は銅板からなる１層構造の負極集電板を具えていること以外は本発明電池と同様に、比較電池１及び２を作製した。そして、各電池の出力密度を求めた。尚、前記ステンレス鋼としては、オーステナイト系ステンレス鋼を用いた。
各電池の構成を表１〜表６に示す。
【００３１】
【表１】

【００３２】
【表２】

【００３３】
【表３】

【００３４】
【表４】

【００３５】
【表５】

【００３６】
【表６】

【００３７】
各電池について、放電深度５０％にて異なる電流値で１０秒間の放電を行ない、その１０秒後の電池電圧とそのときの電流値との関係から、各電池の出力密度を求めた。その結果を表７〜表９に示す。
【００３８】
【表７】

【００３９】
【表８】

【００４０】
【表９】

【００４１】
表７及び表８から明らかな様に、発明電池１〜１１及び１２〜２２においては、比較電池１及び２よりも高い出力密度が得られている。これは、発明電池では、銅層部(31)とニッケル層部(32)またはステンレス鋼層部(35)とからなる二層構造の負極集電板(３)を装備したことにより、負極集電板(３)を巻き取り電極体(２)にレーザ溶接する際のレーザ光の反射が抑制されて、負極集電板(３)が負極(21)の端縁に確実に溶接されたため、集電効率が向上したものである。
【００４２】
これに対し、比較電池１においては、銅製の負極集電板の表面でレーザ光が反射して、溶接が不十分となり、集電効率が低下したものであり、比較電池２においては、ニッケル製の負極集電板の電気抵抗が大きいために、集電効率が低下したものである。
【００４３】
又、負極集電板(３)の全体の厚さが０.１０ｍｍ〜５.００ｍｍの範囲である発明電池２〜５及び１３〜１６において、この範囲外の発明電池１及び６、１２及び１７よりも出力密度が増大している。これは、負極集電板(３)の厚さが０.１０ｍｍよりも小さくなると、負極集電板(３)自体の電気抵抗が大きくなって、集電効率が低下するからであり、又、負極集電板(３)の厚さが５.００ｍｍを超えると、溶接が不十分となって、集電効率が低下するからである。
【００４４】
更に又、負極集電板(３)の厚さに対するニッケル層部(32)の厚さの比率が５％〜４５％の範囲である発明電池４及び８〜１０において、この範囲外の発明電池７及び１１よりも出力密度が増大している。同様に、負極集電板(３)の厚さに対するステンレス鋼層部(35)の厚さの比率が５％〜４５％の範囲である発明電池１５及び１９〜２１において、この範囲外の発明電池１８及び２２よりも出力密度が増大している。これは、ニッケル層部(32)またはステンレス鋼層部(35)の厚さの比率が５％よりも小さいときは、負極集電板(３)の溶接開始直後に銅層部(31)の表面が現われて、レーザ光反射率が増大し、溶接が不十分となって、集電効率が低下するからであり、又、ニッケル層部(32)またはステンレス鋼層部(35)の厚さの比率が４５％を超えると、負極集電板(３)の電気抵抗が増大して、集電効率が低下するからである。
【００４５】
更に、表９から明らかな様に、発明電池２３においては、比較電池１及び２よりも高い出力密度が得られている。これは、ニッケル層部(32)と銅層部(31)の間にステンレス鋼層部(35)が形成された３層構造の負極集電板(３)を用いた場合も、同様の効果が得られることを示している。
【００４６】
以上の結果から、銅層部(31)とニッケル層部(32)またはステンレス鋼層部(35)とを具えた負極集電板(３)を装備することによって、集電効率の向上ひいては出力密度の増大が可能であることがわかる。又、負極集電板(３)の厚さは０.１０ｍｍ〜５.００ｍｍの範囲が好ましく、負極集電板(３)全体の厚さに対するニッケル層部(32)またはステンレス鋼層部(35)の厚さの比率は５％〜４５％が好ましいと言える。又、前記範囲内であれば、負極集電板(３)は２層以上の構成が可能であることがわかる。
【００４７】
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、負極集電板(３)の金属層部の材質としては、フェライト系ステンレス鋼、或いはマルテンサイト系ステンレス鋼を用いることも出来る。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。又、本発明は、リチウムイオン二次電池に限らず、広く非水電解液二次電池に実施が可能である。
【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断面図である。
【図２】負極集電板の斜視図である。
【図３】巻き取り電極体に負極集電板をレーザ溶接する工程を表わす断面図である。
【図４】巻き取り電極体の一部展開斜視図である。
【図５】他の構造を有する負極集電板の斜視図である。
【図６】更に他の構造を有する負極集電板の斜視図である。
【図７】従来の円筒型リチウムイオン二次電池の断面図である。
【符号の説明】
（１）電池缶
（15）筒体
（16）蓋体
（２）巻き取り電極体
（21）負極
（22）セパレータ
（23）正極
（３）負極集電板
（31）銅層部
（32）ニッケル層部
（33）連結帯
（30）正極集電板
（34）連結帯
（４）負極端子機構
（40）正極端子機構[0001]
BACKGROUND OF THE INVENTION
In the present invention, like a cylindrical lithium ion secondary battery, an electrode body serving as a power generation element is accommodated in a sealed container, and the electric power generated by the electrode body can be taken out from the positive terminal portion and the negative terminal portion. The present invention relates to a possible nonaqueous electrolyte secondary battery and a method for manufacturing the same.
[0002]
[Prior art]
In this type of non-aqueous electrolyte secondary battery, a belt-like positive electrode and a negative electrode are overlapped with each other via a separator, and a wound electrode body is formed by winding this in a spiral shape. In a sealed container.
As a method of extracting the electric power generated by the winding electrode body to the outside, the base end portions of a plurality of conductive tabs are connected to the positive electrode and the negative electrode constituting the winding electrode body, respectively, and a plurality of wires are drawn from the positive electrode. A method of widely connecting a front end portion of the positive current collector tab to the positive terminal portion and a front end portion of a plurality of negative current collector tabs drawn from the negative electrode to the negative terminal portion is widely used.
[0003]
However, in a current collecting structure using a plurality of current collecting tabs, a small non-aqueous electrolyte secondary battery having a relatively low current value can provide a sufficient current collecting effect, but has a high current value. A large non-aqueous electrolyte secondary battery has a problem that a sufficient current collecting effect cannot be obtained due to an increase in electrode area.
Further, the structure and process for connecting a plurality of current collecting tabs to the electrode terminal portion are complicated, and there is a problem that workability and productivity are poor.
[0004]
Therefore, as shown in FIG. 7, a cylindrical nonaqueous electrolyte secondary battery having a current collecting structure including a negative electrode current collecting plate (36) and a positive electrode current collecting plate (30) has been proposed. In the non-aqueous electrolyte secondary battery, lids (16), (16) are fixed to both ends of the cylindrical body (15) to form a battery can (1), and the inside of the battery can (1) The take-up electrode body (2) is accommodated. A negative electrode current collector plate (36) and a positive electrode current collector plate (30) are installed at both ends of the winding electrode body (2), and are laser-welded to the winding electrode body (2). The negative electrode current collector plate (36) and the positive electrode current collector plate (30) include a negative electrode terminal mechanism (4) and a negative electrode terminal mechanism (4) attached to the lids (16) and (16) via connecting bands (37) and (34). The positive electrode terminal mechanism (40) is connected.
[0005]
The winding electrode body (2) is composed of a strip-like positive electrode (23), a separator (22), and a negative electrode (21). The positive electrode (23) is configured by applying a positive electrode active material to the surface of the core made of aluminum foil, and the negative electrode (21) is configured by applying a negative electrode active material to the surface of the core made of copper foil. Yes.
The positive electrode (23) and the negative electrode (21) are respectively superimposed on the separator (22) while being shifted in the width direction and wound in a spiral shape. As a result, the edge of the positive electrode (23) protrudes outward from the edge of the separator (22) at one end of both ends in the winding axis direction of the winding electrode body (2). At the other end, the edge of the negative electrode (21) protrudes outward from the edge of the separator (22). The positive current collector (30) is made of aluminum, and the negative current collector (36) is made of copper.
[0006]
As described above, according to the current collecting structure in which the current collecting plates (36) and (30) are laser-welded to the end of the winding electrode body (2), pressure is not applied to the current collecting plate during welding. Since welding can be performed by contact, workability and productivity are improved.
[0007]
[Problems to be solved by the invention]
However, in the manufacturing process of the non-aqueous electrolyte secondary battery shown in FIG. 7, the negative electrode current collector plate (36) is installed at the edge of the negative electrode (21) of the winding electrode body (2), and laser welding is performed. At this time, copper, which is the material of the negative electrode current collector plate (36), has a high reflectivity with respect to the laser beam, so that sufficient energy cannot be given to the welded portion, welding becomes incomplete, and the winding electrode body There was a problem that the current collection efficiency was lowered due to an increase in electrical resistance between (2) and the negative electrode current collector plate (36). If the negative electrode current collector plate (36) is made of nickel, the weldability of the negative electrode current collector plate (36) to the winding electrode body (2) can be improved, but the negative electrode current collector made of nickel can be improved. Since the plate (36) has a larger electric resistance than the copper negative electrode current collector plate (36), the current collection efficiency is lowered.
[0008]
Therefore, the object of the present invention is to improve the weldability of the negative electrode current collector plate to the electrode body in a non-aqueous electrolyte secondary battery having a current collector structure in which the negative electrode current collector plate is welded and fixed to the end of the electrode body. The object is to provide a structure and a manufacturing method of a non-aqueous electrolyte secondary battery capable of obtaining high current collection efficiency.
[0009]
[Means for solving the problems]
In the non-aqueous electrolyte secondary battery according to the present invention, among the end portions of the winding axis direction of the wound electrode body (2), the one end portion and projecting edge of the negative electrode (21), said end The negative electrode current collector plate (3) is laser-bonded to the edge, and the negative electrode current collector plate (3) is electrically connected to the negative electrode terminal portion. Here, the negative electrode current collector plate (3) includes a copper layer portion (31) made of copper or an alloy mainly composed of copper, a metal that does not form an intermetallic compound with lithium, and has a laser beam reflectance higher than that of copper. A plurality of layer portions having a low-layer metal or a metal layer portion made of an alloy mainly composed of the metal, the copper layer portion (31) and the metal layer portion form both surface layers, and the copper layer portion (31) Is welded to the edge of the negative electrode (21). Specifically, the metal forming the metal layer portion of the negative electrode current collector plate (3) is nickel, stainless steel, titanium, chromium, molybdenum or the like.
[0010]
According to the non-aqueous electrolyte secondary battery of the present invention, when the negative electrode current collector plate (3) is laser welded to the edge of the negative electrode (21) of the winding electrode body (2) in the manufacturing process, the negative electrode Since a metal layer portion having a low laser beam reflectivity is formed on the laser beam receiving side of the current collector plate (3), the energy of the laser beam is sufficiently absorbed and complete welding is performed.
[0011]
Further, the metal layer portion of the negative electrode current collector plate (3) is made of a metal that does not form an intermetallic compound with lithium or an alloy mainly composed of the metal. Therefore, the lithium ion in the non-aqueous electrolyte is consumed to form the alloy. It does not form, thereby preventing a decrease in the lithium ion concentration in the non-aqueous electrolyte.
Moreover, since the negative electrode current collector plate (3) has a multi-layer structure having a copper layer portion (31) and a metal layer portion, the negative electrode current collector plate (3) is composed only of the metal layer portion due to the excellent conductivity of the copper layer portion. The electric resistance is lower than that, and high electrical conductivity is exhibited.
Furthermore, since the edge of the negative electrode (21) of the winding electrode body (2) is joined to the copper layer part (31) of the negative electrode current collector plate (3) over the entire length, the battery becomes larger and the electrode Even when the length is long, it is possible to uniformly collect current from the entire winding electrode body (2). As a result, the potential gradient in the longitudinal direction of the negative electrode (21) is reduced, and the current distribution is uniform with no bias. Thereby, high current collection efficiency is achieved.
[0012]
Specifically, the thickness of the negative electrode current collector plate (3) is in the range of 0.10 mm to 5.00 mm. When the thickness of the negative electrode current collector plate (3) is smaller than 0.10 mm, the electrical resistance of the negative electrode current collector plate (3) itself increases, and the current collection efficiency is lowered. The plate (3) is melted excessively, and the weld is depressed. On the other hand, if the thickness of the negative electrode current collector plate (3) exceeds 5.00 mm, a large power is required for welding the negative electrode current collector plate (3), and the end of the negative electrode (21) having a thickness of several tens of microns is required. It becomes difficult to weld the negative electrode current collector plate (3) to the edge.
[0013]
Specifically, the ratio of the thickness of the metal layer portion to the thickness of the negative electrode current collector plate (3) is in the range of 5% to 45%. As a result, the metal layer part sufficiently exhibits the function of reducing the laser beam reflectance, and the copper layer part (31) sufficiently exhibits the function of reducing the electrical resistance. That is, when the ratio of the thickness of the metal layer portion is smaller than 5%, the metal layer portion melts and disappears immediately after the start of welding of the negative electrode current collector plate (3), and a surface having a high laser beam reflectance appears. Therefore, weldability is reduced. On the other hand, when the ratio of the thickness of the metal layer portion exceeds 45%, the metal layer portion becomes dominant with respect to the electric resistance of the negative electrode current collector plate (3), and the electric current of the entire negative electrode current collector plate (3) is increased. Resistance increases.
[0014]
In addition, the method for producing a non-aqueous electrolyte secondary battery according to the present invention is as follows.
Positive electrode (23) and negative electrode with separator (22) in between, so that the edge of positive electrode (23) protrudes at one end and the edge of negative electrode (21) protrudes at the other end (21) are superposed and wound into a spiral shape to produce a wound electrode body (2);
Producing a positive electrode current collector plate (30) made of aluminum or an aluminum-based alloy; and
From a copper layer (31) made of copper or an alloy mainly composed of copper, and a metal that does not form an intermetallic compound with lithium and has a lower laser beam reflectivity than copper or an alloy mainly composed of the metal A step of producing a negative electrode current collector plate (3) comprising a plurality of layer portions having a metal layer portion, wherein the copper layer portion (31) and the metal layer portion form surface layers on both sides;
A positive current collector (30) is installed at the end of the winding electrode body (2) from which the edge of the positive electrode (23) protrudes, and the surface of the positive current collector (30) is irradiated with a laser beam. A step of laser welding the positive electrode current collector plate (30) to the edge of the positive electrode (23);
The negative electrode current collector plate (3) is installed at the end of the take-up electrode body (2) from which the edge of the negative electrode (21) protrudes so that the copper layer part (31) contacts the edge of the negative electrode (21). Irradiating the surface of the metal layer portion of the negative electrode current collector plate (3) with a laser beam to laser weld the negative electrode current collector plate (3) to the edge of the negative electrode (21);
A step of assembling a secondary battery by electrically connecting the positive electrode current collector plate (30) and the negative electrode current collector plate (3) welded to the winding electrode body (2) to the positive electrode terminal portion and the negative electrode terminal portion, respectively. is doing.
[0015]
According to the manufacturing method of the present invention, in the step of laser welding the negative electrode current collector plate (3) to the edge of the negative electrode (21) of the winding electrode body (2), the laser beam is a metal layer having a low reflectance. Since the laser beam is irradiated on the surface of the portion, the energy of the laser beam is sufficiently applied to the joint between the negative electrode current collector plate (3) and the negative electrode (21) edge. As a result, the negative electrode current collector plate (3) and the negative electrode (21) The edges are completely welded together.
Further, in the step of laser welding the positive electrode current collector plate (30) to the edge of the positive electrode (23) of the winding electrode body (2), aluminum which is the material of the positive electrode current collector plate (30) is the reflectance of the laser beam. Therefore, the energy of the laser beam is sufficiently applied to the junction between the positive current collector plate (30) and the positive electrode (23) edge, and as a result, the positive current collector plate (30) and the positive electrode (23) edge And completely weld to each other.
Thereafter, in the assembly process, the positive electrode current collector plate (30) and the negative electrode current collector plate (3) are electrically connected to the positive electrode terminal portion and the negative electrode terminal portion, respectively.
As a result, the electrical resistance from the winding electrode body (2) to both terminal portions is sufficiently low, and high current collection efficiency is achieved.
[0016]
【The invention's effect】
According to the nonaqueous electrolyte secondary battery and the manufacturing method thereof according to the present invention, the weldability of the negative electrode current collector plate to the winding electrode body is improved, and high current collection efficiency can be obtained.
[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.
As shown in FIG. 1, the cylindrical lithium ion secondary battery of the present embodiment has a battery can (1) configured by fixing lids (16) and (16) to both ends of the cylindrical body (15). The winding electrode body (2) is accommodated in the battery can (1). At both ends of the take-up electrode body (2), a metal which does not form an intermetallic compound with lithium and the copper layer part (31), or has a lower laser beam reflectivity than copper or mainly contains the metal A negative electrode current collector plate (3) and a positive electrode current collector plate (30) composed of two layers of a metal layer portion ( nickel layer portion (32)) made of an alloy are installed, and laser is applied to both ends of the winding electrode body (2). Welded. Moreover, the negative electrode current collector plate (3) and the positive electrode current collector plate (30) are respectively connected to the lid bodies (16) and (16) through the connecting bands (33) and (34), and the negative electrode terminal mechanism (4). And a positive electrode terminal mechanism (40).
[0018]
As shown in FIG. 4, the winding electrode body (2) is composed of a strip-like positive electrode (23), a separator (22), and a negative electrode (21). The positive electrode (23) is formed by applying a positive electrode active material (26) made of LiCoO ₂ to the surface of a core made of aluminum foil, and the negative electrode (21) is made of natural graphite on the surface of the core made of copper foil. The negative electrode active material (24) is applied.
The positive electrode (23) and the negative electrode (21) are respectively superimposed on the separator (22) while being shifted in the width direction and wound in a spiral shape. As a result, the end edge (non-coated portion (25)) of the negative electrode (21) wound in a spiral shape is formed at one end portion of both end portions in the axial direction of the wound electrode body (2). Projecting outward from the edge of the separator (22), and at the other end, the edge (non-coated part (27)) of the positive electrode (23) wound in a spiral shape is separated from the separator (22 ) Will protrude outward from the edge of.
For example, the width A of the active material coated portions (24) and (26) of each electrode is several tens of mm, the width B of the non-coated portions (25) and (27) is about 10 mm, and the protruding distance S from the separator (22). Can be formed to about 1 to 3 mm.
[0019]
The negative electrode current collector plate (3) has a disk shape as shown in FIGS. 1 and 2, and is a metal that does not form an intermetallic compound with lithium and a copper layer portion (31) having a thickness of 2.40 mm. It has a two-layer structure composed of a nickel layer portion (32) having a thickness of 0.60 mm made of nickel, which is a metal having a lower laser beam reflectance than copper. At the end of the negative electrode current collector plate (3), a copper connecting band (33) is projected. Further, as the negative electrode current collector plate (3), as shown in FIG. 5, it is possible to adopt a plate in which a stainless steel layer portion (35) is formed instead of the nickel layer portion (32). Further, as shown in FIG. 6, the negative electrode current collector plate (3) has a copper layer portion (31) and a nickel layer portion (32) forming surface layers on both sides, and a stainless steel layer between the two surface layers. It is also possible to form a three-layer structure in which the part (35) is sandwiched. Furthermore, if a metal that does not form an intermetallic compound with lithium and has a lower laser beam reflectance than copper, the nickel layer (32) or the stainless steel layer (35) is used instead. It is also possible to employ a titanium layer portion, a chromium layer portion, or a molybdenum layer portion. On the other hand, the positive electrode current collector plate (30) has a disk shape and is formed of an aluminum plate having a thickness of 1.00 mm, and an end of the positive electrode current collector plate (30) has an aluminum connecting band (34) as shown in FIG. Projected.
[0020]
As shown in FIG. 3, the negative electrode current collector plate (3) has a copper layer part (31) in contact with the edge (non-coated part (25)) of the negative electrode (21) of the wound electrode body (2). Further, it is installed at the end of the winding electrode body (2), and is welded to the end edge of the negative electrode (21) by irradiating the surface of the nickel layer portion (32) with a laser beam.
Similarly, the positive electrode current collector plate (30) is installed at the end of the take-up electrode body (2) and is welded to the edge of the positive electrode (23) by irradiating the surface with laser light. .
[0021]
As shown in FIG. 1, the negative electrode terminal mechanism (4) includes a terminal member (41) formed by projecting a flange portion (43) at the lower end portion of the screw shaft portion (42). The screw shaft portion (42) of the terminal member (41) penetrates the lid (16), and the first insulating member (45) and the second insulating member (46) are mounted around the terminal member (41). Thus, electrical insulation and airtightness between the lid (16) and the terminal member (41) are maintained. Further, a washer (47) is fitted to the tip of the terminal member (41), and a nut (48) is screwed. The positive electrode terminal mechanism (40) also has the same structure.
[0022]
The tip of the connecting band (33) extending from the negative current collector (3) is welded to the flange (43) of the terminal member (41) of the negative terminal mechanism (4) and the positive current collector (30). The tip of the connecting band (34) extending from the terminal is welded to the flange (43) of the terminal member (41) of the positive electrode terminal mechanism (40). Thereby, the electric power generated by the winding electrode body (2) can be taken out from the negative electrode terminal mechanism (4) and the positive electrode terminal mechanism (40).
[0023]
Next, the manufacturing process of the lithium ion secondary battery of the present invention will be described.
Preparation of Winding Electrode Body ( 2 ) A positive electrode active material made of LiCoO ₂ , a conductive auxiliary agent made of carbon, and a binder made of polyvinylidene fluoride (PVdF) were mixed to prepare a positive electrode mixture, and the positive electrode As shown in FIG. 4, the mixture is applied to both surfaces of a strip-like positive electrode core made of an aluminum foil to produce a positive electrode (23). Note that a non-coated portion (27) having a width of 10 mm and not coated with a positive electrode active material layer is formed at one end of the positive electrode core.
[0024]
A negative electrode active material made of natural graphite and a binder made of polyvinylidene fluoride (PVdF) are mixed to prepare a negative electrode mixture, and the negative electrode mixture is applied to both surfaces of a strip-like negative electrode core made of copper foil. Thus, the negative electrode (21) is produced. Note that a non-coated portion (25) having a width of 10 mm and not coated with a negative electrode active material is formed at one end of the negative electrode core.
In addition, a separator (22) having a width slightly larger than the width A of the positive electrode active material coating portion and the negative electrode active material coating portion is prepared. The separator (22) is made of porous polyethylene and polypropylene.
[0025]
Thereafter, as shown in FIG. 4, the positive electrode (23), the separator (22), and the negative electrode (21) are superposed and wound into a spiral shape to produce a wound electrode body (2). At this time, the edges of the active material non-coated part (27) of the positive electrode (23) and the active material non-coated part (25) of the negative electrode (21) are projected outward from the edge of the separator (22). To overlay.
[0026]
Production of Positive Current Collector Plate (30) and Negative Current Collector Plate ( 3 ) As shown in FIG. 2, a copper layer portion (31) having a thickness of 2.40 mm and a nickel layer portion (32) having a thickness of 0.60 mm were used. A negative electrode current collector plate (3) having a layer structure, a negative electrode current collector plate (3) having a two-layer structure comprising a copper layer portion (31) and a stainless steel layer portion (35) as shown in FIG. 5, or a thickness as shown in FIG. Negative electrode current collector having a three-layer structure in which a stainless steel layer portion (35) having a thickness of 0.30 mm is formed between a copper layer portion (31) having a thickness of 2.40 mm and a nickel layer portion (32) having a thickness of 0.30 mm. A plate (3) is prepared, and the base end portion of the copper connecting strip (33) is connected to the end portion of the negative electrode current collector plate (3). In addition, a positive electrode current collector plate (30) made of an aluminum plate having a thickness of 1.00 mm was produced, and a base end portion of an aluminum connecting band (34) was connected to an end portion of the positive electrode current collector plate (30). To do.
[0027]
Assembling the battery A negative electrode current collector plate (3) is installed so that the copper layer part (31) contacts the edge of the negative electrode (21) of the winding electrode body (2), and the negative electrode current collector plate The surface of the nickel layer part (32) of (3) is irradiated with a laser beam, and the negative electrode current collector plate (3) is welded to the edge of the negative electrode (21). Further, a positive electrode current collector plate (30) is installed at the edge of the positive electrode (23) of the winding electrode body (2), and the surface of the positive electrode current collector plate (30) is irradiated with a laser beam to obtain the positive electrode (23 The positive electrode current collector plate (30) is welded to the edge of).
[0028]
Thereafter, the tip of the connecting band (33) extending from the negative electrode current collector (3) is ultrasonically welded to the flange (43) of the terminal member (41) of the negative electrode terminal mechanism (4), and the positive current collector ( The tip of the connecting band (34) extending from 30) is ultrasonically welded to the flange (43) of the terminal member (41) of the positive electrode terminal mechanism (40). Further, the negative terminal mechanism (4) and the positive terminal mechanism (40) are assembled to the lids (16) and (16).
Then, the wound electrode body (2) is inserted into the cylindrical body (15), the lid bodies (16) and (16) are welded and fixed to both openings of the cylindrical body (15), and then the electrolyte solution (not shown) is shown. Inject electrolyte from the inlet. The electrolytic solution is prepared by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 and dissolving LiPF _{6 in} this mixed solvent at a ratio of 1 mol / liter. Finally, the electrolyte injection port is sealed. Thereby, the cylindrical lithium ion secondary battery shown in FIG. 1 is completed.
[0029]
The positive electrode active material is not limited to the above-described LiCoO ₂ , and LiNiO ₂ , LiMn ₂ O _{4 and the} like can be adopted, and the negative electrode active material is not limited to the above-mentioned natural graphite. In addition, other carbon materials such as artificial graphite and coke, and materials capable of occluding and releasing lithium can be employed. In addition, the electrolytic solution is not limited to the above-described ones, and organic solvents such as vinylene carbonate and propylene carbonate, and low boiling points such as dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, ethoxymethoxyethane and the like. A solution or the like in which a solute such as LiClO ₄ or LiCF ₃ SO ₄ is dissolved at a rate of 0.7 to 1.5 mol / liter in a mixed solvent with the solvent can be employed.
[0030]
Experiment In the cylindrical lithium ion secondary battery of the present invention, as shown in FIG. 2, the negative electrode current collector plate (3) is composed of two layers, the thickness of the nickel layer portion (32) and the copper layer portion (31). Inventive batteries 1 to 11 having different thicknesses were prepared. In addition, as shown in FIG. 5, the inventive current collectors 12 to 22 are composed of two negative electrode current collector plates (3) with various thicknesses of the stainless steel layer portion (35) and the copper layer portion (31). Produced. Further, as shown in FIG. 6, an inventive battery 23 in which the negative electrode current collector plate (3) has a three-layer structure of a nickel layer portion (32), a stainless steel layer portion (35), and a copper layer portion (31) was produced. On the other hand,

comparative batteries

1 and 2 were prepared in the same manner as the battery of the present invention except that a negative electrode current collector plate having a single layer structure made of a nickel plate or a copper plate was provided as shown in FIG. And the output density of each battery was calculated | required. As the stainless steel, austenitic stainless steel was used.
Tables 1 to 6 show the configuration of each battery.
[0031]
[Table 1]

[0032]
[Table 2]

[0033]
[Table 3]

[0034]
[Table 4]

[0035]
[Table 5]

[0036]
[Table 6]

[0037]
Each battery was discharged for 10 seconds at a different current value at a discharge depth of 50%, and the output density of each battery was determined from the relationship between the battery voltage 10 seconds later and the current value at that time. The results are shown in Tables 7-9.
[0038]
[Table 7]

[0039]
[Table 8]

[0040]
[Table 9]

[0041]
As is clear from Tables 7 and 8, the inventive batteries 1 to 11 and 12 to 22 have higher output densities than the

comparative batteries

1 and 2. This is because the inventive battery is equipped with a negative electrode current collector plate (3) having a two-layer structure comprising a copper layer part (31) and a nickel layer part (32) or a stainless steel layer part (35). Since the reflection of the laser beam when the electrode plate (3) is laser welded to the winding electrode body (2) is suppressed, the negative electrode current collector plate (3) is securely welded to the edge of the negative electrode (21). The current collection efficiency is improved.
[0042]
On the other hand, in the comparative battery 1, the laser beam is reflected on the surface of the copper negative electrode current collector plate, welding is insufficient, and the current collection efficiency is lowered. Since the negative electrode current collector plate has a large electric resistance, the current collection efficiency is lowered.
[0043]
Further, in the inventive batteries 2 to 5 and 13 to 16 in which the total thickness of the negative electrode current collector plate (3) is in the range of 0.10 mm to 5.00 mm, the inventive batteries 1 and 6, 12 and 17 outside this range are used. The power density has increased. This is because when the thickness of the negative electrode current collector plate (3) is smaller than 0.10 mm, the electrical resistance of the negative electrode current collector plate (3) itself increases, and the current collection efficiency decreases. It is because welding will become inadequate and current collection efficiency will fall when the thickness of a negative electrode current collecting plate (3) exceeds 5.00 mm.
[0044]
Furthermore, in the invention batteries 4 and 8 to 10 in which the ratio of the thickness of the nickel layer portion (32) to the thickness of the negative electrode current collector plate (3) is in the range of 5% to 45%, the invention batteries outside this range. The power density is higher than 7 and 11. Similarly, in invention batteries 15 and 19 to 21 in which the ratio of the thickness of the stainless steel layer portion (35) to the thickness of the negative electrode current collector plate (3) is in the range of 5% to 45%, the invention outside this range The power density is higher than that of the batteries 18 and 22. This is because when the ratio of the thickness of the nickel layer portion (32) or the stainless steel layer portion (35) is less than 5%, the copper layer portion (31) immediately after the start of welding of the negative electrode current collector plate (3). This is because the surface appears, the laser light reflectance increases, the welding becomes insufficient, and the current collection efficiency decreases, and the thickness of the nickel layer part (32) or the stainless steel layer part (35) If the ratio exceeds 45%, the electrical resistance of the negative electrode current collector plate (3) increases and the current collection efficiency decreases.
[0045]
Further, as apparent from Table 9, the inventive battery 23 has a higher output density than the

comparative batteries

1 and 2. The same effect is obtained when a negative electrode current collector plate (3) having a three-layer structure in which a stainless steel layer portion (35) is formed between a nickel layer portion (32) and a copper layer portion (31) is used. Is obtained.
[0046]
From the above results, it is possible to improve the current collection efficiency and output by equipping the negative electrode current collector plate (3) with the copper layer part (31) and the nickel layer part (32) or the stainless steel layer part (35). It can be seen that the density can be increased. The thickness of the negative electrode current collector plate (3) is preferably in the range of 0.10 mm to 5.00 mm. The nickel layer portion (32) or the stainless steel layer portion (35) with respect to the total thickness of the negative electrode current collector plate (3). ) Thickness ratio is preferably 5% to 45%. Moreover, if it is in the said range, it turns out that the negative electrode current collecting plate (3) can comprise two or more layers.
[0047]
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, ferritic stainless steel or martensitic stainless steel can be used as the material of the metal layer portion of the negative electrode current collector plate (3). 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. The present invention is not limited to lithium ion secondary batteries and can be widely applied to non-aqueous electrolyte secondary batteries.
[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 perspective view of a negative electrode current collector plate.
FIG. 3 is a cross-sectional view showing a step of laser welding a negative electrode current collector plate to a wound electrode body.
FIG. 4 is a partially developed perspective view of a wound electrode body.
FIG. 5 is a perspective view of a negative electrode current collector having another structure.
FIG. 6 is a perspective view of a negative electrode current collector having still another structure.
FIG. 7 is a cross-sectional view of a conventional cylindrical lithium ion secondary battery.
[Explanation of symbols]
(1) Battery can (15) Cylindrical body (16) Cover body (2) Winding electrode body (21) Negative electrode (22) Separator (23) Positive electrode (3) Negative electrode current collector plate (31) Copper layer part (32) Nickel layer part (33) connection band (30) positive electrode current collector plate (34) connection band (4) negative electrode terminal mechanism (40) positive electrode terminal mechanism

Claims

A wound electrode body (2), in which a separator (22) is interposed between a belt-like positive electrode (23) and a negative electrode (21), is accommodated in the sealed container, and the positive electrode (23) and the negative electrode (21) are Each is configured by applying an active material to the surface of a core body made of foil, and the electric power generated by the winding electrode body (2) is taken out from the positive terminal portion and the negative terminal portion provided in the sealed container. a non-aqueous electrolyte secondary battery capable of, among both end portions of the winding axis direction of the wound electrode body (2), the one end portion and projecting edge of the negative electrode (21), said In the non-aqueous electrolyte secondary battery in which the negative electrode current collector plate (3) is joined to the edge and the negative electrode current collector plate (3) is electrically connected to the negative electrode terminal portion, the negative electrode current collector plate (3) A copper layer (31) made of copper or a copper-based alloy and a metal that does not form an intermetallic compound with lithium and has a lower laser beam reflectance than copper. Or a multi-layer part having a metal layer part composed of an alloy mainly composed of the metal, the copper layer part (31) and the metal layer part form both surface layers, and a laser is applied to the surface of the metal layer part. A non-aqueous electrolyte secondary battery , wherein the copper layer portion (31) is laser welded to the edge of the negative electrode (21) by irradiating a beam .

The non-aqueous electrolyte secondary battery according to claim 1, wherein the metal forming the metal layer portion of the negative electrode current collector plate (3) is nickel.

The non-aqueous electrolyte secondary battery according to claim 1, wherein the metal forming the metal layer portion of the negative electrode current collector plate (3) is stainless steel.

The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the thickness of the negative electrode current collector plate (3) is in the range of 0.10 mm to 5.00 mm.

The nonaqueous electrolyte secondary battery according to claim 2, wherein the ratio of the thickness of the nickel layer portion (32) to the thickness of the negative electrode current collector plate (3) is in the range of 5% to 45%.

The nonaqueous electrolyte secondary battery according to claim 3, wherein the ratio of the thickness of the stainless steel layer portion (35) to the thickness of the negative electrode current collector plate (3) ranges from 5% to 45%.

A wound electrode body (2), in which a separator (22) is interposed between a belt-like positive electrode (23) and a negative electrode (21), is accommodated in the sealed container, and the positive electrode (23) and the negative electrode (21) are Each is configured by applying an active material to the surface of a core body made of foil, and the electric power generated by the winding electrode body (2) is taken out from the positive terminal portion and the negative terminal portion provided in the sealed container. In a method for producing a non-aqueous electrolyte secondary battery capable of
Positive electrode (23) and negative electrode with separator (22) in between, so that the edge of positive electrode (23) protrudes at one end and the edge of negative electrode (21) protrudes at the other end (21) are superposed and wound into a spiral shape to produce a wound electrode body (2);
Producing a positive electrode current collector plate (30) made of aluminum or an aluminum-based alloy; and
From a copper layer (31) made of copper or an alloy mainly composed of copper, and a metal that does not form an intermetallic compound with lithium and has a lower laser beam reflectivity than copper or an alloy mainly composed of the metal A step of producing a negative electrode current collector plate (3) comprising a plurality of layer parts having a metal layer part comprising:
A positive current collector (30) is installed at the end of the winding electrode body (2) from which the edge of the positive electrode (23) protrudes, and the surface of the positive current collector (30) is irradiated with a laser beam. A step of laser welding the positive electrode current collector plate (30) to the edge of the positive electrode (23);
The negative electrode current collector plate (3) is installed at the end of the take-up electrode body (2) from which the edge of the negative electrode (21) protrudes so that the copper layer part (31) contacts the edge of the negative electrode (21). Irradiating the surface of the metal layer portion of the negative electrode current collector plate (3) with a laser beam to laser weld the negative electrode current collector plate (3) to the edge of the negative electrode (21);
A step of assembling a secondary battery by electrically connecting the positive electrode current collector plate (30) and the negative electrode current collector plate (3) welded to the winding electrode body (2) to the positive electrode terminal portion and the negative electrode terminal portion, respectively. A method for producing a non-aqueous electrolyte secondary battery.