JP4023213B2 - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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JP4023213B2
JP4023213B2 JP2002144237A JP2002144237A JP4023213B2 JP 4023213 B2 JP4023213 B2 JP 4023213B2 JP 2002144237 A JP2002144237 A JP 2002144237A JP 2002144237 A JP2002144237 A JP 2002144237A JP 4023213 B2 JP4023213 B2 JP 4023213B2
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electrode plate
battery
negative electrode
positive electrode
lithium ion
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JP2003338276A (en
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一郎 松村
直人 荒井
太志 谷川
伸治 村重
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Panasonic Corp
Panasonic Holdings Corp
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Panasonic Corp
Matsushita Electric Industrial Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Connection Of Batteries Or Terminals (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明はリチウムイオン二次電池に関し、特に極板の集電構造に関するものである。
【０００２】
【従来の技術】
近年、ＡＶ機器あるいはパソコン等の電子機器のポータブル化、コードレス化が急速に進んでおり、これらの駆動用電源として小型、軽量で高エネルギー密度を有する二次電池への要求が高まっている。この中でリチウムを活物質とするリチウムイオン二次電池はとりわけ高電圧、高エネルギー密度を有する電池として主に使われている。
【０００３】
現在のリチウムイオン二次電池の集電構造は、主にリード方式がとられている。これは、図２に示すように正極集電体に正極材料を付着させて製造した正極板または負極集電体に負極材料を付着させて製造した負極板の長手方向の一方の端に未塗工部１ａを作り、そこに集電タブ２を溶接する。この集電タブ２を正極端子または負極端子に接続し、リードとするものである。この方法は、工法的にも簡単でコストも安く、極板と端子との接続が確実にできるという利点を有している。
【０００４】
また、ニッケル水素蓄電池、ニッケルカドミウム蓄電池、リチウムイオン二次電池などの二次電池の中で電動工具用などの高出力を必要とするものは、従来から集電構造が工夫されていた。その中でも、一般的なものは、タブレス構造と呼ばれるもので、図３に示すように正極集電体に正極材料を付着させて製造した正極板または負極集電体に負極材料を付着させて製造した負極板の幅方向の一方の端に未塗工部１ｂを作る。正極板と負極板を互いに上下方向にずらしてセパレータを介して渦巻き状に捲回して極板群とした後、この渦巻き状極板群の正極板端縁の未塗工部１ｂからなる集電体突出部に平板状正極集電板を溶接し、負極板端縁の未塗工部１ｂからなる集電体突出部に平板状負極集電板を溶接して電極体とする。この電極体を金属製外装缶に挿入し、負極集電板を外装缶の底部にスポット溶接し、正極集電板を、正極タブにより、正極端子を兼ねた封口板に溶接した構造である。この構造にすることにより、使用時の正極板における電流分布および負極における電流分布が均一になり、高率放電特性が向上する。
【０００５】
これらタブレス構造の中でも、特開２０００−３２３１１７号公報には、正極あるいは負極集電板を金属製外装缶と接触しない程度の大きさにしても、あるいは集電板を用いなくても極板群すべての部位の極板から集電できるようにするため、集電体突出部を内周部から外周部にむけて、順次、直角に折り曲げて平坦部を作ることが記載されている。さらに、前記平坦部に集電板を溶接する構造が提案されている。また、特開２０００−２９４２２２号公報に記載されているように、集電効率を高め、充放電時の温度上昇を小さくするために、集電体突出部を押圧して、突出部先端自身により平坦部を形成し、この平坦部に集電板を溶接する構造が提案されている。
【０００６】
【発明が解決しようとする課題】
前述のリード方式を、高出力を必要とする用途に使うと集電効率が悪くて、放電特性が劣るという課題があった。また、前述のタブレス構造では、端子との接続のためには、未塗工部に集電板またはリードを溶接しなければならないが、この工程は、溶接強度を強くすると、セパレータに穴があくなどの極板群を損傷することになり、弱すぎると外れ易くなるなど、調整が難しく、コストが高くなるという課題があった。さらに、電池に落下等により衝撃が加わり、極板群と電池ケースにねじれる力が加わると、溶接はずれが起こりやすいという課題があった。
【０００７】
本発明の目的は、上記の課題を解決し、安定した導電接続を簡便かつ安価に行なったリチウムイオン二次電池を提供することにある。
【０００８】
【課題を解決するための手段】
上記の課題を解決するために、本発明のリチウムイオン二次電池は、電池缶と同じ極性を持つ極板は、長手方向の一方の端と幅手方向の一方の端に未塗工部があり、長手方向の未塗工部と前記電池缶の底部とはリードにより接続されており、かつ、前記極板群の前記底部側端部において幅手方向の未塗工部が突出して渦巻状の突出部を形成しており、捲回により対向している突出部内の未塗工部同士の一部または全部は電気的に接続されていることを特徴とするものである。
【０００９】
この構成により、大電流放電に適し、かつ低コストであり、落下等の衝撃による溶接はずれの不良の少ないリチウムイオン二次電池が提供できる。
【００１０】
【発明の実施の形態】
本発明のリチウムイオン二次電池は、正極集電体に正極材料を付着させて製造した正極板と負極集電体に負極材料を付着させて製造した負極板とをセパレータを介して捲回して作成した極板群を電解液とともに、電池缶および封口板よりなる電池容器内に収容したリチウムイオン二次電池において、電池缶と同じ極性を持つ極板は、長手方向の一方の端と幅手方向の一方の端に未塗工部があり、長手方向の未塗工部と前記電池缶の底部とはリードにより接続されており、かつ、前記極板群の前記底部側端部において幅手方向の未塗工部が突出して渦巻状の突出部を形成しており、捲回により対向している突出部内の未塗工部同士の一部または全部は電気的に接続されていることを特徴としたものである。
【００１１】
本実施例において、極板はリードにより電池缶の底部と強固に電気的かつ機械的に接続されている。また、幅手方向の幅手方向の未塗工部が突出して渦巻状の突出部を形成しており、捲回により対向している突出部内の未塗工部同士の一部または全部は電気的に接続されているため、極板の集電が効率的に行なえる。この際、突出部の電気的な接続は、少なくとも極板群の端面において巻芯に垂直な方向、つまり巻芯から放射状に伸びる方向に行なわれていると、総集電経路が統計的に短くなるため好ましい。
【００１２】
また、本実施例において前記電池缶と同じ極性を持つ極板は、負極であると、電池缶として強度のあるスチール缶などが使えるため好ましい。
【００１３】
さらに、電気的に接続する方法には、突出部にバーリングを溶接する方法や、集電板を使う方法、導電ペーストを未塗工部間に充填する方法、金属を端面に溶射する方法などが使用できるが、前記捲回により対向している突出部内の未塗工部同士の一部または全部を折り曲げて圧接することにより電気的に接続されていると、集電板や導電ペーストなどの部品とその取り付け工程が不要になり、低コストになるため好ましい。
【００１４】
図１に本実施の形態における電池缶と同じ極性を持つ極板の構造図を示す。図１において、長手方向の一方の端にある未塗工部１ａに予め取りつけられた集電タブ２があり、幅手方向の一方の端にも未塗工部１ｂがある。
【００１５】
さらに、図４に本実施の形態におけるリチウムイオン二次電池の縦断面図を示す。図４において ３は正極板、４は負極板で、微多孔ポリエチレンフィルムから成るセパレータ５を介して互いに対向された状態で渦巻き状に巻回されて極板群６が構成され、この極板群６が電解液とともに電池容器７内に収納配置されている。電池容器７は負極端子となる円筒容器状の電池缶８と正極端子となる電池蓋９にて構成され、電池缶８の上端開口部内周と電池蓋９の外周との間に介装された絶縁パッキン１０にて相互に絶縁されるとともに電池容器７が密閉されている。なお、極板群６と電池缶８の内周との間にもセパレータ５は介装されている。
【００１６】
正極板３は、正極集電体の両面に正極材料を塗工して構成され、図２に示した構成のとおり極板の長手方向の端部の未塗工部１ａに予め取りつけられた集電タブ２が、図４における正極リード２ａとなって正極板３と電池蓋９を接続している。正極板３においては、正極リード２ａは、巻初めの巻芯部１３にあり上部絶縁板１１ａの中央の穴から引き出されている。
【００１７】
また、負極板４は、負極集電体の両面に負極材料を塗工して構成され、図１に示した構成のとおり極板の長手方向の端部の未塗工部１ａに予め取りつけられた集電タブ２と幅手方向の未塗工部１ｂがあり、集電タブ２は、図４における負極リード２ｂとなって負極板４と電池蓋９を接続している。負極板４においては、負極リード２ｂは、巻終わりの最外周部にあり、下部絶縁板１１ｂの周辺から巻芯部１３に向かって伸ばされ、巻芯部１３で溶接棒により電池缶８に底部溶接されている。さらに、未塗工部１ｂは、極板群６より突出して突出部１２を形成し、突出部１２は、折り曲げられて圧接することにより突出部１２内のそれぞれの未塗工部同士の全部が電気的に接続している。セパレータ５は正極板３及び負極板４の塗工部の両側縁よりも外側に突出されている。
【００１８】
以上のような電池においては、リード方式の極板より放電特性が良くなる。この理由を、以下に模式的に説明する。
【００１９】
例えば、図１の導電タブ２より最も遠い地点であるＡ点における活物質がリチウムの吸蔵放出にともない、放出した電子は、最短の伝導経路により外部端子へ流れる時は、集電体より未塗工部１ｂに最短経路を伝わって流れ、その後は、未塗工部間の電気的接続が、ショートパスとなり、導電タブ２から外部端子に流れる。これに対し、図２のようなリード方式では、導電タブ２より最も遠い地点であるＡ点における活物質がリチウムの吸蔵放出にともない、放出した電子は、集電体内を捲回された極板の長手方向にそって導電タブ２まで流れるため、伝導経路が長くなり、その電気抵抗も大きいものとなる。したがって、突出部１２は、集電的にはすべての部位で、最短経路が取れるよう未塗工部同士の全部が電気的に接続しているのが好ましいが、折り曲げられて圧接する場合などは、加工に手間がかかるため、一部でも構わない。この時、図５のように折り曲げ部１４が、巻芯部１３から放射状に伸びる方向に行なわれていると（図５では、対称的に４方向）、総集電経路が統計的に短くなるため好ましい。
【００２０】
本実施例とタブレス方式では、集電に関してはタブレス方式のほうが優れているが、導電タブ２により極板が電池缶の底部と強固に電気的かつ機械的に接続され、かつ、その加工も捲回前の極板への導電タブ２の溶接と捲回後の溶接棒による底部溶接で行なえるので、簡便かつ低コストである。
【００２１】
【実施例】
以下、本発明の二次電池の一実施例のリチウムイオン二次電池について添付図面を参照して具体的に説明する。
【００２２】
図１において、本電池のサイズは、直径１８ｍｍ、電池高６５ｍｍであり、電池容量は容量１２００ｍＡｈである。電池缶２は、内側がニッケルメッキされたスチール缶で厚みは側面が０．２ｍｍ、底面が０．５ｍｍである。
【００２３】
正極板３は、電解二酸化マンガン（ＥＭＤ：ＭｎＯ2）と炭酸リチウム（Ｌｉ2ＣＯ3）とをＬｉ／Ｍｎ＝１／２となるように混合し、８００℃で２０時間大気中で焼成して製造した正極活物質のＬｉＭｎ2Ｏ4と、導電剤のアセチレンブラックと、結着剤のポリフッ化ビニリデンとを、それぞれ重量比で９２：３：５の割合で混合したものを正極材料とした。
【００２４】
なお、正極材料をペースト状に混練するために結着剤としてのポリフッ化ビニリデンはＮメチルピロリドンディスパージョン液を用いた。上記混合比率は固形分としての割合である。この正極材料ペーストを、厚み１５μｍのアルミ箔から成る正極集電体の両面に塗工し、正極材料層を形成した。正極材料層の両膜厚は同じで、塗工、乾燥後の両膜厚の和は１５０μｍで、正極板の厚さを１６５μｍとした。その後、正極板の厚みが１００μｍになるように直径３００ｍｍのプレスロールにより圧縮成形した。このとき、正極材料密度は２．８ｇ／ｃｍ3であった。正極板の一方の端を掻きとって未塗工部１ａを作り、正極リード２ａを超音波溶接で取りつけた。
【００２５】
負極板４は、人造黒鉛と結着剤のスチレンブタジエンゴム（ＳＢＲ）とを重量比９７：３の割合で混合したものを負極材料とした。なお、負極材料をペースト状に混練するために結着剤としてのスチレンブタジエンゴムは水溶性のディスパージョン液を用いた。上記混合比率は固形分としての割合である。この負極合剤ペーストを厚み１４μｍの銅箔から成る負極集電体の両面に一側縁部に幅４ｍｍの未塗工部１ｂを残した状態で塗工し、負極材料層を形成した。その後、負極板の厚みが１１０μｍになるように直径３００ｍｍのプレスロールにより圧縮成形した。このとき、負極材料密度は１．３ｇ／ｃｍ3であった。さらに、負極板の一方の端を掻きとって未塗工部１ａを作り、負極リード２ｂを超音波溶接で取りつけた。
【００２６】
電解液は、エチレンカーボネイト（ＥＣ）とジエチレンカーボネイト（ＤＥＣ）を体積比１：１の配合比で混合した混合溶媒に、溶質として６フッ化リン酸リチウム（ＬｉＰＦ6）を１ｍｏｌ／ｄｍ3の濃度に溶解したものを用いた。
【００２７】
上記のようにして作製した正極板と負極板をセパレータを介して対向させた状態で負極の集電体の未塗工部１ｂを突出させた状態で渦巻き状に捲回して極板群６を形成した。突出部１２の長さは２ｍｍとした。
【００２８】
さらに、突出部１２の集電体の一部を折り曲げて圧接し、折り曲げ部１４を作成した。
【００２９】
そして、この極板群６を下部絶縁板１１ｂとともに電池缶８内に収容し、直径約３．５ｍｍの巻芯部に溶接棒を差し込み、負極リード２ｂを電池缶８に底部溶接した。
【００３０】
そして、ＰＰ製で厚さ０．５ｍｍの上部絶縁板１１ａに正極リード２ａを通し、極板群６の上に配置した。
【００３１】
その後、かしめ封口のための溝いれ加工を電池缶８に行ない、正極リード２ａを電池蓋９に溶接し、前述の電解液を注液した。最後に、電池蓋９を絶縁パッキン１０とともにかしめ封口を行い電池を密閉した。
【００３２】
以上述べたとおり、本実施例において集電構造の加工は、簡便にかつ低コストにできた。
【００３３】
数回の充放電で電池を活性化した後、内部抵抗を測定してみると、１５ｍΩであり、タブレス方式と同等のもので、リード方式の約半分の値であった。また、耐久試験として試験用ドラム内で２時間回転（６０ｒｐｍ）させても、リードはずれは無かった。
【００３４】
【発明の効果】
以上説明した通り、本発明のリチウムイオン二次電池によれば、極板の集電構造が優れているため、高出力を必要とする電池において安定した導電接続を簡便かつ安価に行うリチウムイオン二次電池を提供することが提供できる。
【図面の簡単な説明】
【図１】本発明の一実施形態における極板の構造図
【図２】従来のリード方式の極板の構造図
【図３】従来のタブレス方式の極板の構造図
【図４】本発明の一実施形態におけるリチウムイオン二次電池の縦断面図
【図５】本発明の一実施形態における突出部の正面図
【符号の説明】
１ａ，１ｂ 未塗工部
２ 集電タブ
２ａ 正極リード
２ｂ 負極リード
３ 正極板
４ 負極板
５ セパレータ
６ 極板群
７ 電池容器
８ 電池缶
９ 電池蓋
１０ 絶縁パッキン
１１ａ 上部絶縁板
１１ｂ 下部絶縁板
１２ 突出部
１３ 巻芯部
１４ 折り曲げ部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lithium ion secondary battery, and more particularly to a current collecting structure of an electrode plate.
[0002]
[Prior art]
In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless, and there is an increasing demand for secondary batteries having a small size, light weight, and high energy density as power sources for driving these devices. Among these, lithium ion secondary batteries using lithium as an active material are mainly used as batteries having high voltage and high energy density.
[0003]
The current collecting structure of the lithium ion secondary battery is mainly a lead method. As shown in FIG. 2, this is not applied to one end in the longitudinal direction of a positive electrode plate manufactured by attaching a positive electrode material to a positive electrode current collector or a negative electrode plate manufactured by attaching a negative electrode material to a negative electrode current collector. The construction part 1a is made, and the current collecting tab 2 is welded thereto. The current collecting tab 2 is connected to a positive terminal or a negative terminal to form a lead. This method has an advantage that it is simple in construction and low in cost, and can reliably connect the electrode plate and the terminal.
[0004]
Further, among secondary batteries such as nickel metal hydride storage batteries, nickel cadmium storage batteries, and lithium ion secondary batteries that require high output for power tools, etc., a current collecting structure has been conventionally devised. Among them, a general one is called a tabless structure, and is manufactured by attaching a negative electrode material to a positive electrode plate or a negative electrode current collector manufactured by attaching a positive electrode material to a positive electrode current collector as shown in FIG. An uncoated portion 1b is formed at one end in the width direction of the negative electrode plate. The positive electrode plate and the negative electrode plate are shifted from each other in the vertical direction and wound in a spiral shape through a separator to form an electrode plate group, and then a current collector composed of an uncoated portion 1b at the edge of the positive electrode plate of the spiral electrode plate group A plate-like positive current collector plate is welded to the body protruding portion, and a plate-like negative electrode current collector plate is welded to the current collector protruding portion consisting of the uncoated portion 1b at the negative electrode plate edge to form an electrode body. This electrode body is inserted into a metal outer can, the negative electrode current collector plate is spot welded to the bottom of the outer can, and the positive electrode current collector plate is welded to the sealing plate that also serves as the positive electrode terminal by the positive electrode tab. By adopting this structure, the current distribution in the positive electrode plate and the current distribution in the negative electrode during use become uniform, and the high rate discharge characteristics are improved.
[0005]
Among these tabless structures, Japanese Patent Application Laid-Open No. 2000-323117 discloses an electrode plate group in which a positive electrode or a negative electrode current collector plate is sized so as not to contact a metal outer can, or a current collector plate is not used. In order to be able to collect current from the electrode plates of all parts, it is described that the current collector protruding portion is bent from the inner peripheral portion to the outer peripheral portion and then bent at right angles to form a flat portion. Furthermore, a structure in which a current collector plate is welded to the flat portion has been proposed. Further, as described in Japanese Patent Application Laid-Open No. 2000-294222, in order to increase the current collection efficiency and reduce the temperature rise during charging / discharging, the current collector protrusion is pressed and A structure has been proposed in which a flat portion is formed and a current collector plate is welded to the flat portion.
[0006]
[Problems to be solved by the invention]
When the above-described lead method is used for an application requiring high output, there is a problem that current collection efficiency is poor and discharge characteristics are inferior. In the above-mentioned tabless structure, the current collector plate or lead must be welded to the uncoated part for connection to the terminal. In this process, when the welding strength is increased, the separator is perforated. There is a problem that the adjustment is difficult and the cost is high, for example, the electrode plate group is damaged, and if it is too weak, the electrode plate group is easily detached. Furthermore, when an impact is applied to the battery by dropping or the like, and a twisting force is applied to the electrode plate group and the battery case, there is a problem that welding is likely to be dislodged.
[0007]
An object of the present invention is to solve the above-described problems and provide a lithium ion secondary battery in which stable conductive connection is easily and inexpensively performed.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the lithium ion secondary battery of the present invention has an electrode plate having the same polarity as the battery can, and has an uncoated portion at one end in the longitudinal direction and one end in the width direction. Yes, the uncoated part in the longitudinal direction and the bottom part of the battery can are connected by a lead, and the uncoated part in the width direction protrudes from the bottom side end of the electrode plate group to form a spiral shape. The protruding portions are formed, and part or all of the uncoated portions in the protruding portions facing each other by winding are electrically connected.
[0009]
With this configuration, it is possible to provide a lithium ion secondary battery that is suitable for large-current discharge and is low in cost, and that is less susceptible to welding slippage due to impact such as dropping.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The lithium ion secondary battery of the present invention is formed by winding a positive electrode plate manufactured by attaching a positive electrode material to a positive electrode current collector and a negative electrode plate manufactured by attaching a negative electrode material to a negative electrode current collector through a separator. In a lithium ion secondary battery in which the prepared electrode plate group is housed in a battery container composed of a battery can and a sealing plate together with an electrolyte, the electrode plate having the same polarity as the battery can has one end in the longitudinal direction and a width There is an uncoated portion at one end in the direction, the uncoated portion in the longitudinal direction and the bottom portion of the battery can are connected by a lead, and the width of the electrode plate group is wide at the bottom side end portion. The uncoated part in the direction protrudes to form a spiral protruding part, and part or all of the uncoated parts in the protruding part facing each other by winding are electrically connected. It is a feature.
[0011]
In this embodiment, the electrode plate is firmly and electrically and mechanically connected to the bottom of the battery can by a lead. In addition, the uncoated portion in the width direction in the width direction protrudes to form a spiral-shaped protruding portion, and part or all of the uncoated portions in the protruding portions facing each other by winding are electrically Therefore, the current collecting of the electrode plates can be performed efficiently. At this time, if the electrical connection of the protrusions is made in a direction perpendicular to the core at least on the end face of the electrode plate group, that is, a direction extending radially from the core, the total current collecting path is statistically short. Therefore, it is preferable.
[0012]
In the present embodiment, the electrode plate having the same polarity as the battery can is preferably a negative electrode because a strong steel can can be used as the battery can.
[0013]
Furthermore, methods for electrical connection include a method of welding a burring to a protruding portion, a method of using a current collector plate, a method of filling a conductive paste between uncoated portions, a method of spraying metal onto an end face, and the like. Parts that can be used but are electrically connected by bending and pressing some or all of the uncoated parts in the projecting parts facing each other by winding, such as current collectors and conductive paste This is preferable because the attachment process is unnecessary and the cost is reduced.
[0014]
FIG. 1 shows a structural diagram of an electrode plate having the same polarity as the battery can in the present embodiment. In FIG. 1, there is a current collecting tab 2 attached in advance to an uncoated portion 1a at one end in the longitudinal direction, and an uncoated portion 1b is also present at one end in the width direction.
[0015]
FIG. 4 is a longitudinal sectional view of the lithium ion secondary battery in this embodiment. In FIG. 4, 3 is a positive electrode plate, 4 is a negative electrode plate, wound in a spiral shape in a state of being opposed to each other via a separator 5 made of a microporous polyethylene film, and an electrode plate group 6 is formed. 6 is accommodated in the battery container 7 together with the electrolytic solution. The battery container 7 includes a cylindrical container-shaped battery can 8 serving as a negative electrode terminal and a battery lid 9 serving as a positive electrode terminal. The battery container 7 is interposed between the inner periphery of the upper end opening of the battery can 8 and the outer periphery of the battery cover 9. The battery case 7 is sealed while being insulated from each other by the insulating packing 10. The separator 5 is also interposed between the electrode plate group 6 and the inner periphery of the battery can 8.
[0016]
The positive electrode plate 3 is configured by applying a positive electrode material to both surfaces of the positive electrode current collector, and is a pre-attached to the uncoated portion 1a at the end in the longitudinal direction of the electrode plate as shown in FIG. The electric tab 2 serves as the positive electrode lead 2 a in FIG. 4 and connects the positive electrode plate 3 and the battery lid 9. In the positive electrode plate 3, the positive electrode lead 2 a is in the core portion 13 at the beginning of winding and is drawn out from the central hole of the upper insulating plate 11 a.
[0017]
Further, the negative electrode plate 4 is configured by applying a negative electrode material on both surfaces of the negative electrode current collector, and is attached in advance to the uncoated portion 1a at the end in the longitudinal direction of the electrode plate as shown in FIG. The current collecting tab 2 and the uncoated portion 1b in the width direction are provided, and the current collecting tab 2 serves as the negative electrode lead 2b in FIG. 4 and connects the negative electrode plate 4 and the battery lid 9. In the negative electrode plate 4, the negative electrode lead 2 b is at the outermost peripheral part at the end of winding, and extends from the periphery of the lower insulating plate 11 b toward the core part 13, and the bottom part is attached to the battery can 8 by a welding rod at the core part 13. Welded. Furthermore, the uncoated part 1b protrudes from the electrode plate group 6 to form a protruding part 12, and the protruding part 12 is bent and pressed so that all of the uncoated parts in the protruding part 12 are brought together. Electrically connected. The separator 5 protrudes outward from both side edges of the coating portions of the positive electrode plate 3 and the negative electrode plate 4.
[0018]
The battery as described above has better discharge characteristics than the lead type electrode plate. The reason for this will be schematically described below.
[0019]
For example, when the active material at point A, which is the farthest point from the conductive tab 2 in FIG. 1, occludes and releases lithium, the emitted electrons flow to the external terminal through the shortest conduction path. After flowing along the shortest path to the work part 1b, the electrical connection between the uncoated parts becomes a short path and flows from the conductive tab 2 to the external terminal. On the other hand, in the lead method as shown in FIG. 2, the active material at point A which is the farthest point from the conductive tab 2 is absorbed and released by lithium, and the released electrons are wound around the current collector. Therefore, the conductive path becomes long and the electric resistance is large. Therefore, it is preferable that all of the uncoated parts are electrically connected so that the shortest path can be taken at all parts in terms of current collection, but in the case where the protruding part 12 is bent and pressed. Since it takes time for processing, a part of it may be used. At this time, as shown in FIG. 5, when the bent portion 14 is radially extended from the core portion 13 (symmetrically in four directions in FIG. 5), the total current collecting path is statistically shortened. Therefore, it is preferable.
[0020]
In this embodiment and the tabless system, the tabless system is superior in terms of current collection, but the electrode plate is firmly and electrically and mechanically connected to the bottom of the battery can by the conductive tab 2, and the processing is also difficult. Since it can be performed by welding the conductive tab 2 to the electrode plate before turning and bottom welding with the welding rod after winding, it is simple and inexpensive.
[0021]
【Example】
Hereinafter, a lithium ion secondary battery according to an embodiment of the secondary battery of the present invention will be specifically described with reference to the accompanying drawings.
[0022]
In FIG. 1, the size of the battery is 18 mm in diameter, the battery height is 65 mm, and the battery capacity is 1200 mAh. The battery can 2 is a steel can plated with nickel on the inside, and has a thickness of 0.2 mm on the side surface and 0.5 mm on the bottom surface.
[0023]
The positive electrode plate 3 is obtained by mixing electrolytic manganese dioxide (EMD: MnO 2 ) and lithium carbonate (Li 2 CO 3 ) so that Li / Mn = 1/2, and firing in the atmosphere at 800 ° C. for 20 hours. A positive electrode material was prepared by mixing the produced positive electrode active material LiMn 2 O 4 , the conductive agent acetylene black, and the binder polyvinylidene fluoride in a weight ratio of 92: 3: 5, respectively.
[0024]
In order to knead the positive electrode material into a paste, N-methylpyrrolidone dispersion liquid was used as polyvinylidene fluoride as a binder. The mixing ratio is a ratio as a solid content. This positive electrode material paste was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm to form a positive electrode material layer. Both film thicknesses of the positive electrode material layer were the same, the sum of both film thicknesses after coating and drying was 150 μm, and the thickness of the positive electrode plate was 165 μm. Thereafter, the positive electrode plate was compression-molded by a press roll having a diameter of 300 mm so that the thickness of the positive electrode plate was 100 μm. At this time, the positive electrode material density was 2.8 g / cm 3 . One end of the positive electrode plate was scraped to create an uncoated portion 1a, and the positive electrode lead 2a was attached by ultrasonic welding.
[0025]
The negative electrode plate 4 was prepared by mixing artificial graphite and a binder styrene butadiene rubber (SBR) at a weight ratio of 97: 3. In order to knead the negative electrode material into a paste, a water-soluble dispersion liquid was used as the styrene butadiene rubber as a binder. The mixing ratio is a ratio as a solid content. This negative electrode mixture paste was applied on both sides of a negative electrode current collector made of a copper foil having a thickness of 14 μm with an uncoated portion 1b having a width of 4 mm left on one side edge portion to form a negative electrode material layer. Thereafter, the negative electrode plate was compression-molded by a press roll having a diameter of 300 mm so that the thickness of the negative electrode plate was 110 μm. At this time, the negative electrode material density was 1.3 g / cm 3 . Further, one end of the negative electrode plate was scraped to form an uncoated portion 1a, and the negative electrode lead 2b was attached by ultrasonic welding.
[0026]
The electrolyte was a mixed solvent in which ethylene carbonate (EC) and diethylene carbonate (DEC) were mixed at a mixing ratio of 1: 1 by volume, and lithium hexafluorophosphate (LiPF 6 ) was used as a solute at a concentration of 1 mol / dm 3 . What was melt | dissolved in was used.
[0027]
With the positive electrode plate and negative electrode plate produced as described above facing each other with a separator interposed therebetween, the uncoated portion 1b of the negative electrode current collector is protruded and spirally wound to form the electrode plate group 6 Formed. The length of the protruding portion 12 was 2 mm.
[0028]
Furthermore, a part of the current collector of the protruding portion 12 was bent and pressed to create a bent portion 14.
[0029]
Then, this electrode plate group 6 was accommodated in the battery can 8 together with the lower insulating plate 11b, a welding rod was inserted into the core portion having a diameter of about 3.5 mm, and the negative electrode lead 2b was welded to the battery can 8 at the bottom.
[0030]
Then, the positive electrode lead 2 a was passed through the upper insulating plate 11 a made of PP and having a thickness of 0.5 mm, and arranged on the electrode plate group 6.
[0031]
Thereafter, grooving for caulking and sealing was performed on the battery can 8, the positive electrode lead 2 a was welded to the battery lid 9, and the above-described electrolyte was injected. Finally, the battery lid 9 was caulked with the insulating packing 10 to seal the battery.
[0032]
As described above, in the present example, the processing of the current collecting structure can be performed easily and at low cost.
[0033]
When the internal resistance was measured after the battery was activated by charging and discharging several times, it was 15 mΩ, which was the same as that of the tabless method and about half the value of the lead method. Further, as a durability test, there was no deviation of the lead even if the test drum was rotated for 2 hours (60 rpm).
[0034]
【The invention's effect】
As described above, according to the lithium ion secondary battery of the present invention, since the current collecting structure of the electrode plate is excellent, the lithium ion secondary battery that performs stable conductive connection easily and inexpensively in a battery that requires high output. Providing a secondary battery can be provided.
[Brief description of the drawings]
FIG. 1 is a structural diagram of an electrode plate according to an embodiment of the present invention. FIG. 2 is a structural diagram of a conventional lead type electrode plate. FIG. 3 is a structural diagram of a conventional tabless type electrode plate. FIG. 5 is a longitudinal sectional view of a lithium ion secondary battery according to an embodiment of the present invention. FIG. 5 is a front view of a protruding portion according to an embodiment of the present invention.
1a, 1b Uncoated part 2 Current collecting tab 2a Positive electrode lead 2b Negative electrode lead 3 Positive electrode plate 4 Negative electrode plate 5 Separator 6 Electrode plate group 7 Battery container 8 Battery can 9 Battery lid 10 Insulating packing 11a Upper insulating plate 11b Lower insulating plate 12 Protrusion part 13 Core part 14 Bending part

Claims (2)

正極集電体に正極材料を付着させて製造した正極板と負極集電体に負極材料を付着させて製造した負極板とをセパレータを介して渦巻き状に捲回して作成した極板群を電解液とともに、電池缶および封口板よりなる電池容器内に収容した円筒型リチウムイオン二次電池において、
電池缶と同じ極性を持つ極板は、長手方向の一方の端と幅手方向の一方の端に未塗工部があり、長手方向の未塗工部と前記電池缶の底部とは集電タブにより前記極板群の巻芯部の直下で接続されており、かつ、前記極板群の前記底部側端部において幅手方向の未塗工部が突出して渦巻状の突出部を形成しており、捲回により対向している突出部内の未塗工部同士の一部または全部を折り曲げて圧接することにより電気的に接続されているリチウムイオン二次電池。Electrolyze an electrode plate group produced by winding a positive electrode plate produced by attaching a positive electrode material to a positive electrode current collector and a negative electrode plate produced by attaching a negative electrode material to a negative electrode current collector in a spiral shape through a separator. In a cylindrical lithium ion secondary battery housed in a battery container consisting of a battery can and a sealing plate together with a liquid,
Plates having the same polarity as the battery can has one end in the uncoated portion of the one end and the width direction of the longitudinal current collecting the bottom of the battery can to the longitudinal direction of the uncoated portion The tabs are connected directly below the core portion of the electrode plate group, and the uncoated portion in the width direction protrudes from the bottom side end portion of the electrode plate group to form a spiral protrusion. A lithium ion secondary battery that is electrically connected by bending and pressing a part or all of uncoated parts in the projecting parts facing each other by winding. 前記電池缶と同じ極性を持つ極板は、負極である請求項１記載のリチウムイオン二次電池。  The lithium ion secondary battery according to claim 1, wherein the electrode plate having the same polarity as the battery can is a negative electrode.
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