JP4120353B2

JP4120353B2 - Secondary battery and manufacturing method thereof

Info

Publication number: JP4120353B2
Application number: JP2002319209A
Authority: JP
Inventors: 高久鳥塚; 幹男小熊
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Shin Kobe Electric Machinery Co Ltd
Priority date: 2002-11-01
Filing date: 2002-11-01
Publication date: 2008-07-16
Anticipated expiration: 2022-11-01
Also published as: JP2004152707A

Description

【０００１】
【発明の属する技術分野】
本発明は、二次電池及び二次電池の製造方法に係り、特に、金属製の有底電池容器内に、正、負極を有する電極群と電解液とが収容され、電極群の上部に配置された集電部材と金属製の蓋とがリード板により接続され、蓋により前記電池容器の開口が封口された二次電池及び二次電池の製造方法に関する。
【０００２】
【従来の技術】
従来、二次電池は、電池缶内に、集電用の集電部材が上部に配置された極板群が収容され、上蓋により電池缶の開口が封口されている。集電部材に集電した電気を電池の外部に導出するために、集電部材と上蓋とがリード板により接続されている。図４に示すように、極板群を構成する正極２２と上蓋を構成する蓋板２３とを接続するリード板２１が折り曲げられて構成された技術が開示されている（例えば、特許文献１参照）。
【０００３】
この二次電池を大電流用に適合させるためには、当然断面積の大きいリード板が要求され、リード板の厚さが大きくなる。リード板の厚さが大きくなると、折り曲げにくくなり、リード板を収容するための空間の高さが大きくなる。リード板が収容される空間は、発電には関与しない空間であり、電池にとっては、空間の高さは小さい方がよい。
【０００４】
また、特に、リチウムイオン二次電池の場合では、通常、リード板にアルミニウム材が用いられる。アルミニウム材を蓋板や集電部材に接続するときに、抵抗溶接やレーザ溶接が用いられる。
【０００５】
【特許文献１】
特開平第９−９２３２９号公報（図１、段落番号「００３１」「００３２」）
【０００６】
【発明が解決しようとする課題】
しかしながら、上記公報の技術では、リード板が収容される空間を小さくすることはできるが、リード板の断面積を確保できず大電流を得ることができない。また、リード板の厚さを大きくすると、リード板の断面積を確保することはできるが、リード板の折り曲げの曲率半径が大きくなり、リード板の収容される空間の高さを小さくすることは難しい。更に、リチウムイオン二次電池の場合では、リード板にアルミニウム材が用いられているため、無理してリード板を小さく折り曲げると亀裂を生じ破損する、という問題点がある。
【０００７】
また、アルミニウム材の接続に抵抗溶接を用いると、酸化膜やアルミニウム材の電極付着の問題で生産性が安定しない。一方、レーザ溶接を用いると、アルミニウム材のレーザ光の反射率が大きいため、高出力のレーザ溶接装置が必要となりコスト高になる。更に、アルミニウム材は融点が低いためレーザ光を吸収すると溶融が急激に進むため、溶融制御が難しい。そして、アルミニウム材は、凝固時の体積収縮率が大きく溶接箇所が割れやすいためレーザ溶接が難しい、という問題点がある。
【０００８】
本発明は上記事案に鑑み、リード板に破損がなく容積効率に優れた大電流用二次電池及び該製造方法を提供することを課題とする。
【０００９】
【課題を解決するための手段】
上記課題を解決するために、本発明の第１の態様は、金属製の有底電池容器内に、正、負極を有する電極群と電解液とが収容され、前記電極群の上部に配置された集電部材と金属製の蓋とがリード板により接続され、前記蓋により前記電池容器の開口が封口された二次電池において、前記リード板は、薄板を複数枚束ね積層して構成されている。第１の態様では、リード板が薄板を複数枚束ね積層して構成されたため、大電流を許容する断面積を確保することができると共に、薄板を破損することなく折り曲げることができる。
【００１０】
第１の態様において、リード板は２個のリード板で構成され、一方のリード板が一側端部で蓋に接続され他側で湾曲状に折り曲げられており、他方のリード板が一側端部で集電部材に接続され他側で湾曲状に折り曲げられており、２個のリード板の他側端部同士を重ね合わせて接続すれば、リード板が収容される空間が小さくなり体積効率を高めることができる。
【００１１】
上記課題を解決するために、本発明の第２の態様は、正、負極を有する電極群の上部に配置した集電部材と、金属製の蓋とを複数枚の薄板を積層した２個のリード板により接続する接続工程の後、前記蓋により前記電池容器の開口を封口する二次電池の製造方法であって、前記接続工程の前に、前記複数枚の薄板を予め束ねて仮止めする仮止め工程を含む。第２の態様では、集電部材と蓋とをリード板により接続する接続工程の前に、複数枚の薄板を予め束ねて仮止めするため、接続工程で複数枚の薄板がずれることを抑制することができる。
【００１２】
第２の態様において、仮止め工程で、複数枚の薄板を予め束ねた一側端部を仮止めし、薄板の他側を湾曲状に折り曲げ、薄板の他側端部を仮止めすれば、薄板の他側端部を折り曲げるときに、各薄板の曲率の違いにより他端の長さが変わるので、薄板を破損することなく折り曲げることができると共に、リード板が収容される空間を小さくして体積効率を高めることができる。また、接続工程で、仮止め工程で仮止めした２個のリード板の一側端部をそれぞれ集電部材と蓋とに接続した後、２個のリード板の他側端部同士を接続すれば、湾曲状の２個のリード板の他側端部同士を重ね合わせて接続できるので、リード板が収容される空間を小さくして体積効率を更に高めることができる。このとき、仮止め及び接続に超音波溶接を用いることで、リード板の接続箇所の強度の大きくして接続の信頼性を向上させることができる。
【００１３】
【発明の実施の形態】
以下、図面を参照して本発明を円筒型リチウムイオン二次電池の作製方法について適用した実施の形態について説明する。
【００１４】
平均粒径１０μｍのマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）の粉末、平均粒径３μｍの炭素粉末及び結着剤のポリフッ化ビニリデン（ＰＶＤＦ）を溶媒のＮメチル２ピロリドンに分散させ混合してスラリを作製し、スラリを正極集電体となる厚さ２０μｍのアルミニウム箔の両表面に塗布、乾燥、プレスして一体化し、スラリの塗布部の幅が９４ｍｍとなるように一側を切断し、他側に集電するための一部を残して短冊状に裁断して作製した。
【００１５】
一方、平均粒径２０μｍの炭素粒子、結着剤のＰＶＤＦを溶媒のＮメチル２ピロリドンに分散させ混合してスラリを作製し、スラリを負極集電体となる厚さ１０μｍの銅箔の両表面に塗布、乾燥後、プレスして一体化し、スラリの塗布部の幅が９４．５ｍｍとなるように一側を切断し、他側に集電するための一部を残して短冊状に裁断して作製した。なお、正極集電体及び負極集電体の集電するために残した部分を、それぞれ正、負極タブとした。
【００１６】
図１に示すように、正極と負極とを厚さ２５μｍ、幅１００ｍｍのポリエチレン製微多孔薄膜のセパレータを介して外径９ｍｍ、内径７ｍｍ、高さ１００ｍｍのポリプロピレン製捲き芯３の周りに捲回し、極板群２を作製した。このとき、正極タブ及び負極タブを極板群２の互いに反対側の両端面に位置するように配置した。極板群２の外径を、３８ｍｍとした。
【００１７】
次に、複数枚のアルミニウム薄板を予め束ねて仮止めする仮止め工程について説明する。
【００１８】
図２（Ａ）に示すように、幅６ｍｍ、厚さ０．１０ｍｍのアルミニウムＡ３００３材を長さ５０ｍｍに切断してアルミニウム薄板１４とし、予め１０枚束ねて積層する。次に、図２（Ｂ）に示すように、束ねて積層したアルミニウム薄板１４の一側端部を超音波溶接で仮止めして仮止め部９とする。束ねて積層したアルミニウム薄板１４の一側端部を、ホーンと、固定されたアンビルとの間に挟み、ホーンに超音波振動を加え超音波溶接する。次いで、図２（Ｃ）に示すように、一側端部を仮止めしたアルミニウム薄板１４の他側を湾曲状に折り曲げた後、超音波溶接で他側端部を仮止めし仮止め部９とし、先端の不要部分を切除して集電リード板７を作製する。次に、図３（Ａ）に示すように、別のアルミニウム薄板１４を予め１０枚束ねて積層し、図３（Ｂ）に示すように、束ねて積層したアルミニウム薄板１４の一側端部を超音波溶接で仮止めして仮止め部８とする。そして、図３（Ｃ）に示すように、一側端部を仮止めしたアルミニウム薄板１４の他側を湾曲状に折り曲げた後、他側端部を仮止めし仮止め部８とし、先端の不要部分を切除して蓋板リード板５を作製する。
【００１９】
次に、仮止め工程で仮止めした集電リード板７及び蓋板リード板５を用いて、捲き芯３の上部に配置される環状の正極集電板６と、後述する上蓋を構成する金属製の蓋板ケース４とを接続する接続工程について説明する。
【００２０】
図２（Ｄ）に示すように、両端部に仮止め部９を有する集電リード板７の一側端部の仮止め部９を、正極集電板６の上面に超音波溶接する。一方、図３（Ｄ）に示すように、両端部に仮止め部８を有する蓋板リード板５の一側端部の仮止め部８を、周縁部が略垂直に折り曲げられた蓋板ケース４の底面に超音波溶接する。次に、図３（Ｅ）に示すように、蓋板ケース４に、電池内圧が所定圧に達すると開裂する開裂弁１１、開裂弁１１を支持する合成樹脂製で円環状のゴムシール１０を介して中央に凸部が形成された金属製のトップキャップ１２を載置する。次いで、トップキャップ１２の周縁部を蓋板ケース４の周縁部でカシメて、蓋板リード板５の仮止め部８が超音波溶接された上蓋１５を作製する。
【００２１】
捲き芯３の上下端に正、負極集電板を挿入して固定し、正、負極集電板の周縁に正、負極集電タブをそれぞれ超音波溶接し、負極集電板に断面逆ハット状の負極リード板を溶接する。深絞り成形しニッケルメッキを施した直径４０ｍｍ、厚さ０．５ｍｍの金属製の有底円筒状電池缶１内に極板群２を収容し、電池缶１と負極リード板とを抵抗溶接する。電池缶１の上端部近傍に溝を付け、カシメ用のパッキン１３を電池缶１内に挿入した状態で、集電リード板７の他側端部の仮止め部９を持ち上げ電池缶１の外に出す。蓋板リード板５の他側端部の仮止め部８と、持ち上げた仮止め部９とを超音波溶接する。
【００２２】
二次電池３０内に非水電解液を所定量注入した後、蓋板リード板５と集電リード板７とを曲げて、正極集電板６の上面と蓋板ケース４の底面とで画定される空間Ｓ内に収容し、上蓋１５の周縁部と電池缶１とをパッキン１３を介してカシメて電池缶１の開口を封口した。非水電解液には、例えば、６フッ化リン酸リチウムや４フッ化ホウ酸リチウムをエチレンカーボネート、ジメチルカーボネートなどの有機溶媒に１モル／リットル程度溶解した電解液を用いた。
【００２３】
従って、電池缶１内に極板群２と非水電解液とが収容されており、電池缶１の開口が上蓋１５により封口されている。電極群２の上部に固定された正極集電板６の上面には、集電リード板７の一側端部の仮止め部９が超音波溶接されている。集電リード板７の他側は湾曲状に折り曲げられており、蓋板リード板５の他側は湾曲状に折り曲げられている。また、蓋板ケース４の底面には蓋板リード板５の一側端部の仮止め部８が超音波溶接されており、集電リード板７の他側端部の仮止め部９と蓋板リード板５の他側端部の仮止め部８とが、正極集電板６に略平行に重ね合わされて超音波溶接されている。
【００２４】
次に、本実施形態の二次電池２０の作用等について説明する。
【００２５】
本実施形態の二次電池２０は、アルミニウム薄板１４を１０枚積層して蓋板リード板５及び集電リード板７とするため、大電流を許容する断面積を確保できる。このため、大電流用の二次電池２０とすることができる。また、集電リード板７及び蓋板リード板５の他側端部の仮止め部９、８同士が正極集電板６に略平行に重ね合わされて超音波溶接されている。このため、蓋板リード板５及び集電リード板７が収容される空間Ｓの縦方向のサイズを小さくすることができる。従って、大電流用二次電池２０の体積効率を向上させることができる。
【００２６】
また、本実施形態の二次電池２０では、正極集電板６、蓋板ケース４に、集電リード板７、蓋板リード板５をそれぞれ超音波溶接する前に、仮止め工程で１０枚のアルミニウム薄板１４の一側端部を仮止めしたので、正極集電板６、蓋板ケース４に集電リード板７、蓋板リード板５をそれぞれ超音波溶接するときにアルミニウム薄板１４がずれるのを抑制することができる。
【００２７】
更に、本実施形態の二次電池２０では、仮止め工程で、１０枚のアルミニウム薄板１４の一側端部を仮止めした後、他側を湾曲状に折り曲げて、他側端部を仮止めして集電リード板７及び蓋板リード板５を作製する。このため、アルミニウム薄板１４を折り曲げるときに、各薄板の曲率の違いにより他端の長さが変わる。従って、アルミニウム薄板１４を破損することなく折り曲げることができるので、空間Ｓの縦方向のサイズを小さくして電池の体積効率を高めることができる。
【００２８】
また、本実施形態の二次電池２０では、トップキャップ１２の中央に凸部が形成されているため、上蓋１５には構造上空間が形成されている。上蓋１５を作製した後、蓋板リード板５の仮止め部８を、直接、蓋板ケース４に超音波溶接することはできない。このため、本実施形態では、上蓋１５を組み立てる前の部品の段階（図３（Ｄ）参照）で、集電リード板７の仮止め部９を正極集電板６に超音波溶接し、蓋板リード板５の仮止め部８を蓋板ケース４に超音波溶接する。超音波溶接後、集電リード板７と蓋板リード板５との他側端部の仮止め部９、８同士を超音波溶接する。これにより、正極集電板６に略平行に集電リード板７及び蓋板リード板５の他側端部の仮止め部９、８同士を重ね合わせて超音波溶接することができる。
【００２９】
更に、本実施形態の二次電池２０では、蓋板リード板５及び集電リード板７のの仮止め部８、９の接続に超音波溶接を用いる。このため、抵抗溶接を用いる場合の酸化膜やアルミニウム材の電極付着の問題を回避できるので、生産性を安定させることができる。また、レーザ溶接を用いる場合に溶接箇所が割れるのを回避することができるので、溶接箇所の強度を確保して仮止め部８、９の接続の信頼性を向上させることができる。
【００３０】
なお、本実施形態では、接続工程で、集電リード板７の仮止め部９を正極集電板６に超音波溶接した後に、蓋板リード板５の仮止め部８を蓋板ケース４に超音波溶接する例を示したが、順番はこれに限定されず逆にしてもよい。
【００３１】
また、本実施形態では、集電リード板７及び蓋板リード板５に幅６ｍｍ、厚さ０．１０ｍｍのアルミニウム薄板１４をそれぞれ１０枚用いる例を示したが、これらの数値は限定されるものではなく、例えば、より薄いアルミニウム薄板をより多く積層するようにしてもよい。このようにすれば、よりアルミニウム薄板を湾曲状により小さく折り曲げて、電池の体積効率を向上させることができる。
【００３２】
【発明の効果】
以上説明したように、本発明の第１の態様によれば、リード板が薄板を複数枚束ね積層して構成されたため、大電流を許容する断面積を確保することができと共に、薄板を破損することなく折り曲げることができ、リード板が２個のリード板で構成され、一方のリード板が一側端部で蓋に接続され他側で湾曲状に折り曲げられており、他方のリード板が一側端部で集電部材に接続され他側で湾曲状に折り曲げられており、２個のリード板の他側端部同士を重ね合わせて接続すれば、リード板が収容される空間が小さくなり体積効率を高めることができるでき、第２の態様によれば、集電部材と蓋とをリード板により接続する接続工程の前に、複数枚の薄板を予め束ねて仮止めするため、接続工程で複数枚の薄板がずれることを抑制することができ、仮止め工程で、複数枚の薄板を予め束ねた一側端部を仮止めし、薄板の他側を湾曲状に折り曲げ、薄板の他側端部を仮止めすれば、薄板の他側端部を折り曲げるときに、各薄板の曲率の違いにより他端の長さが変わるので、薄板を破損することなく折り曲げることができ、リード板が収容される空間を小さくして体積効率を高めることができる、という効果を得ることができる。
【図面の簡単な説明】
【図１】本発明が適用可能な実施形態の円筒型リチウムイオン二次電池の断面図である。
【図２】実施形態の円筒型リチウムイオン二次電池の集電リード板の仮止め工程及び接続工程を示す断面図であり、（Ａ）はアルミニウム薄板を予め束ねて積層した状態、（Ｂ）はアルミニウム薄板の一側端部を仮止めした状態、（Ｃ）はアルミニウム薄板の他側を湾曲状に折り曲げて他側端部を仮止めした状態、（Ｄ）は集電リード板の一側端部を正極集電板に超音波溶接した状態を示す。
【図３】実施形態の円筒型リチウムイオン二次電池の蓋板リード板の仮止め工程及び接続工程を示す断面図であり、（Ａ）はアルミニウム薄板を予め束ねて積層した状態、（Ｂ）はアルミニウム薄板の一側端部を仮止めした状態、（Ｃ）はアルミニウム薄板の他側を湾曲状に折り曲げて他側端部を仮止めした状態、（Ｄ）は蓋板リード板の一側端部を蓋板ケースに超音波溶接した状態、（Ｅ）は蓋板ケースの周縁をカシメて上蓋を作製した状態を示す。
【図４】従来の二次電池の断面図である。
【符号の説明】
１電池缶（電池容器）
２極板群（電極群）
４蓋板ケース
５蓋板リード板（リード板）
６正極集電板（集電部材）
７集電リード板（リード板）
８、９仮止め部
１２トップキャップ
１４アルミニウ薄板（薄板）
１５上蓋（蓋）
２０円筒型リチウムイオン二次電池（二次電池）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary battery and a method for manufacturing the secondary battery, and in particular, an electrode group having positive and negative electrodes and an electrolytic solution are accommodated in a metal bottomed battery container, and disposed on the upper part of the electrode group. The present invention relates to a secondary battery in which a current collecting member and a metal lid are connected by a lead plate, and an opening of the battery container is sealed by the lid, and a method for manufacturing the secondary battery.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a secondary battery, an electrode plate group in which a current collecting member for current collection is disposed in an upper part is accommodated in a battery can, and an opening of the battery can is sealed by an upper lid. In order to lead the electricity collected by the current collecting member to the outside of the battery, the current collecting member and the upper lid are connected by a lead plate. As shown in FIG. 4, a technique is disclosed in which a lead plate 21 that connects a positive electrode 22 constituting an electrode plate group and a lid plate 23 constituting an upper lid is bent (see, for example, Patent Document 1). ).
[0003]
In order to adapt the secondary battery to a large current, a lead plate having a large cross-sectional area is naturally required, and the thickness of the lead plate is increased. When the thickness of the lead plate increases, it becomes difficult to bend, and the height of the space for accommodating the lead plate increases. The space in which the lead plate is accommodated is a space that does not participate in power generation, and for the battery, the height of the space should be small.
[0004]
In particular, in the case of a lithium ion secondary battery, an aluminum material is usually used for the lead plate. Resistance welding or laser welding is used when connecting an aluminum material to a lid plate or a current collecting member.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-92329 (FIG. 1, paragraph numbers “0031” and “0032”)
[0006]
[Problems to be solved by the invention]
However, with the technique of the above publication, the space in which the lead plate is accommodated can be reduced, but the cross-sectional area of the lead plate cannot be secured and a large current cannot be obtained. In addition, if the thickness of the lead plate is increased, the cross-sectional area of the lead plate can be secured, but the radius of curvature of bending of the lead plate is increased, and the height of the space in which the lead plate is accommodated is reduced. difficult. Further, in the case of a lithium ion secondary battery, since an aluminum material is used for the lead plate, there is a problem in that if the lead plate is forcibly bent to a small size, it will crack and break.
[0007]
Moreover, when resistance welding is used for the connection of aluminum materials, productivity is not stable due to the problem of electrode adhesion of oxide films and aluminum materials. On the other hand, when laser welding is used, the reflectance of the laser beam of the aluminum material is large, so that a high-power laser welding apparatus is required and the cost is increased. Furthermore, since aluminum material has a low melting point, melting rapidly proceeds when laser light is absorbed, so that melting control is difficult. The aluminum material has a problem that laser welding is difficult because the volume shrinkage rate during solidification is large and the welded portion is easily cracked.
[0008]
An object of the present invention is to provide a secondary battery for large current that has no damage to a lead plate and is excellent in volume efficiency, and a method for manufacturing the same.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a first aspect of the present invention is a metal bottomed battery container in which an electrode group having a positive electrode and a negative electrode and an electrolytic solution are accommodated and disposed above the electrode group. and other current collecting member and the metal lid are connected by lead plates, wherein the secondary battery opening of the battery case is sealed by a lid, wherein the lead plate is formed by stacking bundling a plurality of thin plates Yes . In the first aspect, since the lead plate is formed by bundling and laminating a plurality of thin plates, a cross-sectional area allowing a large current can be secured and the thin plate can be bent without being damaged .
[0010]
In the first aspect, the lead plate is composed of two lead plates, one lead plate is connected to the lid at one end and bent to the other side, and the other lead plate is on one side. Connected to the current collecting member at the end and bent in a curved shape on the other side. If the other end portions of the two lead plates are overlapped and connected, the space in which the lead plate is accommodated is reduced and the volume is reduced. Efficiency can be increased.
[0011]
In order to solve the above-described problem, the second aspect of the present invention includes two current-collecting members arranged on the upper part of an electrode group having positive and negative electrodes and a metal lid laminated with a plurality of thin plates. A method of manufacturing a secondary battery in which an opening of the battery container is sealed with the lid after a connecting step of connecting with a lead plate, wherein the plurality of thin plates are bundled in advance and temporarily fixed before the connecting step. Includes a temporary fixing step. In the second aspect, before the connecting step of connecting the current collecting member and the lid with the lead plate, the plurality of thin plates are bundled and temporarily fixed, so that the plurality of thin plates are prevented from shifting in the connecting step. be able to.
[0012]
In the second aspect, in the temporary fixing step, temporarily fixing one side end portion of a plurality of thin plates bundled in advance, bending the other side of the thin plate in a curved shape, and temporarily fixing the other side end portion of the thin plate, When bending the other side end of the thin plate, the length of the other end changes due to the difference in curvature of each thin plate, so that the thin plate can be bent without damaging it, and the space in which the lead plate is accommodated is reduced. Volumetric efficiency can be increased. In the connection process, after connecting one end of the two lead plates temporarily fixed in the temporary fixing process to the current collecting member and the lid, respectively, connect the other end of the two lead plates to each other. In this case, since the other end portions of the two curved lead plates can be overlapped and connected, the space in which the lead plates are accommodated can be reduced to further increase the volume efficiency. At this time, by using ultrasonic welding for temporary fixing and connection, the strength of the connection location of the lead plate can be increased and the connection reliability can be improved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments in which the present invention is applied to a method for manufacturing a cylindrical lithium ion secondary battery will be described below with reference to the drawings.
[0014]
A slurry of lithium manganate (LiMn ₂ O ₄ ) having an average particle diameter of 10 μm, carbon powder having an average particle diameter of 3 μm, and polyvinylidene fluoride (PVDF) as a binder are dispersed in N-methyl-2-pyrrolidone as a solvent and mixed. The slurry is applied to both surfaces of a 20 μm-thick aluminum foil serving as a positive electrode current collector, dried and pressed to be integrated, and one side is cut so that the width of the slurry application portion is 94 mm. It was cut into a strip shape, leaving a part for collecting current on the side.
[0015]
On the other hand, carbon particles having an average particle diameter of 20 μm and PVDF as a binder are dispersed in N-methyl-2-pyrrolidone as a solvent and mixed to prepare a slurry, and both surfaces of a 10 μm thick copper foil serving as a negative electrode current collector After coating, drying, pressing and integrating, cut one side so that the width of the slurry application part is 94.5 mm, and cut into a strip shape, leaving a part for current collection on the other side Made. The portions left for collecting the positive electrode current collector and the negative electrode current collector were defined as positive and negative electrode tabs, respectively.
[0016]
As shown in FIG. 1, a positive electrode and a negative electrode are wound around a polypropylene core 3 having an outer diameter of 9 mm, an inner diameter of 7 mm, and a height of 100 mm through a separator made of polyethylene microporous thin film having a thickness of 25 μm and a width of 100 mm. Electrode plate group 2 was produced. At this time, the positive electrode tab and the negative electrode tab were arranged so as to be positioned on both end surfaces on the opposite sides of the electrode plate group 2. The outer diameter of the electrode plate group 2 was 38 mm.
[0017]
Next, a temporary fixing process for preliminarily bundling a plurality of aluminum thin plates in advance will be described.
[0018]
As shown in FIG. 2A, an aluminum A3003 material having a width of 6 mm and a thickness of 0.10 mm is cut into a length of 50 mm to form an aluminum thin plate 14, which is previously bundled and laminated. Next, as shown in FIG. 2 (B), one end of the aluminum thin plate 14 bundled and laminated is temporarily fixed by ultrasonic welding to form a temporary fixing portion 9. One end of the bundled aluminum thin plates 14 is sandwiched between a horn and a fixed anvil, and ultrasonic vibration is applied to the horn for ultrasonic welding. Next, as shown in FIG. 2 (C), after bending the other side of the thin aluminum plate 14 temporarily fixed at one end, the other end is temporarily fixed by ultrasonic welding to temporarily fix the portion 9. Then, the current collecting lead plate 7 is manufactured by cutting off an unnecessary portion at the tip. Next, as shown in FIG. 3 (A), another aluminum thin plate 14 is bundled and laminated in advance, and as shown in FIG. 3 (B), one side end portion of the bundled and laminated aluminum thin plates 14 is formed. Temporary fastening is performed by ultrasonic welding to form a temporary fastening portion 8. Then, as shown in FIG. 3 (C), after bending the other side of the thin aluminum plate 14 with the one side end part temporarily fixed in a curved shape, the other side end part is temporarily fixed to form a temporary fixing part 8. The lid plate lead plate 5 is produced by cutting away unnecessary portions.
[0019]
Next, using the current collector lead plate 7 and the lid plate lead plate 5 temporarily fixed in the temporary fixing step, the annular positive electrode current collector plate 6 disposed on the upper part of the core 3 and the metal constituting the upper lid described later A connection process for connecting the lid case 4 made of metal will be described.
[0020]
As shown in FIG. 2D, the temporary fixing portion 9 at one end of the current collecting lead plate 7 having the temporary fixing portions 9 at both ends is ultrasonically welded to the upper surface of the positive electrode current collecting plate 6. On the other hand, as shown in FIG. 3D, a lid plate case in which the peripheral portion of the temporary fastening portion 8 at one end of the lid plate lead plate 5 having the temporary fastening portions 8 at both ends is bent substantially vertically. 4 is ultrasonically welded to the bottom surface. Next, as shown in FIG. 3E, the lid plate case 4 is provided with a cleavage valve 11 that is cleaved when the battery internal pressure reaches a predetermined pressure, and a synthetic resin-made annular rubber seal 10 that supports the cleavage valve 11. A metal top cap 12 having a convex portion at the center is placed. Next, the upper cap 15 is produced by crimping the peripheral portion of the top cap 12 with the peripheral portion of the cover plate case 4 to which the temporary fixing portion 8 of the cover plate lead plate 5 is ultrasonically welded.
[0021]
The positive and negative current collector plates are inserted and fixed to the upper and lower ends of the winding core 3, and the positive and negative current collector tabs are ultrasonically welded to the periphery of the positive and negative electrode current collector plates, respectively, and the cross-section reverse hat is attached to the negative electrode current collector plate. A negative electrode lead plate is welded. The electrode plate group 2 is housed in a metal bottomed cylindrical battery can 1 having a diameter of 40 mm and a thickness of 0.5 mm that has been deep-drawn and nickel-plated, and the battery can 1 and the negative electrode lead plate are resistance-welded. . A groove is formed in the vicinity of the upper end portion of the battery can 1, and the temporary fastening portion 9 at the other end of the current collecting lead plate 7 is lifted up with the caulking packing 13 inserted into the battery can 1. Put out. The temporary fixing part 8 at the other end of the lid plate lead plate 5 and the raised temporary fixing part 9 are ultrasonically welded.
[0022]
After injecting a predetermined amount of non-aqueous electrolyte into the secondary battery 30, the lid plate lead plate 5 and the current collector lead plate 7 are bent to define the upper surface of the positive electrode current collector plate 6 and the bottom surface of the lid plate case 4. The opening of the battery can 1 was sealed by crimping the peripheral edge of the upper lid 15 and the battery can 1 via the packing 13. As the nonaqueous electrolytic solution, for example, an electrolytic solution in which about 6 mol / liter of lithium hexafluorophosphate or lithium tetrafluoroborate was dissolved in an organic solvent such as ethylene carbonate or dimethyl carbonate was used.
[0023]
Therefore, the electrode plate group 2 and the nonaqueous electrolyte are accommodated in the battery can 1, and the opening of the battery can 1 is sealed by the upper lid 15. A temporary fixing portion 9 at one end of the current collecting lead plate 7 is ultrasonically welded to the upper surface of the positive electrode current collecting plate 6 fixed to the upper portion of the electrode group 2. The other side of the current collecting lead plate 7 is bent in a curved shape, and the other side of the lid plate lead plate 5 is bent in a curved shape. Further, a temporary fixing portion 8 at one end portion of the cover plate lead plate 5 is ultrasonically welded to the bottom surface of the cover plate case 4, and the temporary fixing portion 9 at the other end portion of the current collecting lead plate 7 and the lid. The temporary fixing portion 8 at the other end of the plate lead plate 5 is superposed on the positive current collector plate 6 in a substantially parallel manner and is ultrasonically welded.
[0024]
Next, the operation and the like of the secondary battery 20 of the present embodiment will be described.
[0025]
In the secondary battery 20 of the present embodiment, ten aluminum thin plates 14 are stacked to form the cover plate lead plate 5 and the current collecting lead plate 7, so that a cross-sectional area allowing a large current can be secured. For this reason, it can be set as the secondary battery 20 for large currents. Further, the temporary fixing portions 9 and 8 at the other end portions of the current collecting lead plate 7 and the cover plate lead plate 5 are superposed on the positive current collecting plate 6 in parallel and ultrasonically welded. For this reason, the vertical size of the space S in which the cover plate lead plate 5 and the current collecting lead plate 7 are accommodated can be reduced. Therefore, the volumetric efficiency of the secondary battery 20 for large current can be improved.
[0026]
Further, in the secondary battery 20 of the present embodiment, 10 sheets of the current collector lead plate 7 and the lid plate lead plate 5 are ultrasonically welded to the positive electrode current collector plate 6 and the lid plate case 4 respectively in the temporary fixing step. Since one end of the aluminum thin plate 14 is temporarily fixed, the aluminum thin plate 14 is displaced when the current collecting lead plate 7 and the cover plate lead plate 5 are ultrasonically welded to the positive electrode current collecting plate 6 and the cover plate case 4, respectively. Can be suppressed.
[0027]
Furthermore, in the secondary battery 20 of the present embodiment, after temporarily fixing one end of the ten aluminum thin plates 14 in the temporary fixing step, the other side is bent into a curved shape, and the other end is temporarily fixed. Thus, the current collecting lead plate 7 and the cover plate lead plate 5 are produced. For this reason, when the aluminum thin plate 14 is bent, the length of the other end changes due to the difference in curvature of each thin plate. Therefore, since the aluminum thin plate 14 can be bent without being damaged, the size of the space S in the vertical direction can be reduced to increase the volumetric efficiency of the battery.
[0028]
Further, in the secondary battery 20 of the present embodiment, since a convex portion is formed at the center of the top cap 12, a structural space is formed in the upper lid 15. After the upper lid 15 is manufactured, the temporary fixing portion 8 of the lid plate lead plate 5 cannot be ultrasonically welded directly to the lid plate case 4. For this reason, in the present embodiment, at the stage of the parts before assembling the upper lid 15 (see FIG. 3D), the temporary fixing portion 9 of the current collecting lead plate 7 is ultrasonically welded to the positive current collecting plate 6, and the lid The temporary fixing portion 8 of the plate lead plate 5 is ultrasonically welded to the lid plate case 4. After the ultrasonic welding, the temporary fixing portions 9 and 8 at the other end portions of the current collecting lead plate 7 and the cover plate lead plate 5 are ultrasonically welded. As a result, the current collector lead plate 7 and the temporary fixing portions 9 and 8 at the other end of the lid plate lead plate 5 can be superposed and ultrasonically welded substantially parallel to the positive electrode current collector plate 6.
[0029]
Furthermore, in the secondary battery 20 of the present embodiment, ultrasonic welding is used to connect the temporary fixing portions 8 and 9 of the lid plate lead plate 5 and the current collecting lead plate 7. For this reason, since the problem of the electrode adhesion of the oxide film and aluminum material in the case of using resistance welding can be avoided, productivity can be stabilized. Further, since cracking of the welded portion can be avoided when using laser welding, the strength of the welded portion can be ensured and the reliability of the connection between the temporary fixing portions 8 and 9 can be improved.
[0030]
In the present embodiment, the temporary fixing portion 9 of the current collecting lead plate 7 is ultrasonically welded to the positive current collecting plate 6 in the connecting step, and then the temporary fixing portion 8 of the lid plate lead plate 5 is attached to the lid plate case 4. Although an example of ultrasonic welding has been shown, the order is not limited to this and may be reversed.
[0031]
Further, in the present embodiment, an example is shown in which ten aluminum thin plates 14 each having a width of 6 mm and a thickness of 0.10 mm are used for the current collecting lead plate 7 and the cover plate lead plate 5, but these numerical values are limited. Instead, for example, more thin aluminum plates may be stacked. In this way, the volume efficiency of the battery can be improved by bending the aluminum thin plate smaller in a curved shape.
[0032]
【The invention's effect】
As described above, according to the first aspect of the present invention, since the lead plate is configured by bundling and laminating a plurality of thin plates, a cross-sectional area allowing a large current can be secured and the thin plate is damaged. The lead plate is composed of two lead plates, one lead plate is connected to the lid at one end and bent to the other side, and the other lead plate is Connected to the current collecting member at one side end and bent in a curved shape on the other side. If the other side ends of the two lead plates are overlapped and connected, the space for accommodating the lead plate is small. According to the second aspect, before the connecting step of connecting the current collecting member and the lid with the lead plate, a plurality of thin plates are bundled in advance and temporarily fixed. Suppressing displacement of multiple thin plates in the process In the temporary fixing step, if one end of a plurality of thin plates previously bundled is temporarily fixed, the other side of the thin plate is bent into a curved shape, and the other end of the thin plate is temporarily fixed, the other side of the thin plate When bending the end, the length of the other end changes due to the difference in curvature of each thin plate, so that the thin plate can be bent without damaging it, and the volume in which the lead plate is accommodated is reduced to increase volume efficiency The effect of being able to be obtained can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion secondary battery according to an embodiment to which the present invention is applicable.
FIG. 2 is a cross-sectional view showing a temporary fixing step and a connecting step of a current collecting lead plate of a cylindrical lithium ion secondary battery of an embodiment, (A) is a state in which aluminum thin plates are bundled and laminated in advance, (B) Is a state where one end of the aluminum thin plate is temporarily fixed, (C) is a state where the other side of the aluminum thin plate is bent in a curved shape, and the other end is temporarily fixed, and (D) is one side of the current collecting lead plate The state where the end was ultrasonically welded to the positive electrode current collector plate is shown.
FIG. 3 is a cross-sectional view showing a temporary fixing process and a connecting process of the lid plate lead plate of the cylindrical lithium ion secondary battery of the embodiment, in which (A) is a state in which aluminum thin plates are previously bundled and stacked; Is a state where one end of the aluminum thin plate is temporarily fixed, (C) is a state where the other side of the aluminum thin plate is bent in a curved shape, and the other end is temporarily fixed, and (D) is one side of the lid plate lead plate The state where the end is ultrasonically welded to the lid plate case, (E) shows the state where the upper lid is produced by crimping the periphery of the lid plate case.
FIG. 4 is a cross-sectional view of a conventional secondary battery.
[Explanation of symbols]
1 Battery can (battery container)
2 Electrode plate group (electrode group)
4 Cover plate case 5 Cover plate lead plate (lead plate)
6 Positive current collector (current collector)
7 Current collecting lead plate (Lead plate)
8, 9 Temporary fixing part 12 Top cap 14 Arminium thin plate (thin plate)
15 Top lid (lid)
20 Cylindrical lithium ion secondary battery (secondary battery)

Claims

In a metal bottomed battery container, an electrode group having positive and negative electrodes and an electrolytic solution are accommodated, and a current collector and a metal lid arranged on the upper part of the electrode group are connected by a lead plate, in the secondary battery in which an opening of the battery case is sealed by the lid, the lead plate, a secondary battery characterized by being constituted by stacking bundling a plurality of thin plates.

The lead plate is composed of two lead plates, and one lead plate is connected to the lid at one side end and is bent in a curved shape on the other side, and the other lead plate is at the one side end. 2. The secondary battery according to claim 1, wherein the secondary battery is connected to a current collecting member and bent in a curved shape on the other side, and the other end portions of the two lead plates are overlapped and connected. .

After the connecting step of connecting the current collecting member arranged on the upper part of the electrode group having the positive and negative electrodes and the metal lid with two lead plates in which a plurality of thin plates are laminated, the lid of the battery container A method for manufacturing a secondary battery for sealing an opening, comprising: a temporary fixing step in which the plurality of thin plates are bundled in advance and temporarily fixed before the connecting step.

The temporary fixing step includes temporarily fixing one side end portion of the plurality of thin plates previously bundled, bending the other side of the thin plate into a curved shape, and temporarily fixing the other side end portion of the thin plate. A method for manufacturing a secondary battery according to claim 3.

In the connecting step, after connecting one end portions of the two lead plates temporarily fixed in the temporary fixing step to the current collecting member and the lid, the other end portions of the two lead plates are connected to each other. The method of manufacturing a secondary battery according to claim 4, wherein:

The method for manufacturing a secondary battery according to any one of claims 3 to 5, wherein ultrasonic welding is used for the temporary fixing and connection.