JP4389398B2

JP4389398B2 - Non-aqueous electrolyte secondary battery

Info

Publication number: JP4389398B2
Application number: JP2001070175A
Authority: JP
Inventors: 克典鈴木; 賢二原; 健介弘中
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Shin Kobe Electric Machinery Co Ltd
Priority date: 2001-03-13
Filing date: 2001-03-13
Publication date: 2009-12-24
Anticipated expiration: 2021-03-13
Also published as: JP2002270153A

Description

【０００１】
【発明の属する技術分野】
本発明は非水電解液二次電池に係り、特に、正極集電体に正極活物質合剤を塗工した正極と、負極集電体に負極活物質合剤を塗工した負極と、をセパレータを介して捲回した捲回群を備えた非水電解液二次電池に関する。
【０００２】
【従来の技術】
非水電解液二次電池を代表するリチウムイオン二次電池は、高エネルギー密度であるメリットを活かして、主にＶＴＲカメラやノートパソコン、携帯電話等のポータブル機器の電源に使用されている。この電池の内部構造は通常以下に示されるような捲回式にされる。電極は正極、負極共に活物質が金属箔に塗着された帯状であり、セパレータを挟んで正極、負極が直接接触しないように断面が渦巻状に捲回され、捲回群を形成している。そして電池容器となる円筒状の缶に捲回群が収納され、電解液注液後、封口されている。
【０００３】
一般的な円筒型リチウムイオン二次電池の寸法は、１８６５０型と呼ばれる、直径１８ｍｍ、高さ６５ｍｍであり、小形民生用リチウムイオン電池として広く普及している。１８６５０型リチウムイオン二次電池の正極活物質には、高容量、長寿命を特徴とするコバルト酸リチウムが主として用いられており、電池容量は、おおむね１．３Ａｈ〜１．７Ａｈ、出力はおよそ１０Ｗ程度である。
【０００４】
一方、自動車産業界においては環境問題に対応すべく、排出ガスのない、動力源を完全に電池のみにした電気自動車と、内燃機関エンジンと電池との両方を動力源とするハイブリッド（電気）自動車の開発が加速され、一部実用化の段階に到達している。
【０００５】
電気自動車の電源となる電池には当然高出力、高エネルギーが得られる特性が要求され、この要求にマッチする電池としてリチウムイオン二次電池が注目されている。電気自動車用リチウムイオン電池の場合、１００〜３５０Ｖ程度の高電圧を得るために約３０〜１００本の電池を直列接続し、大電流を流すため、電池の出力特性の良否が重要となる。このため、電気自動車用リチウムイオン電池では、電池の出力特性を上げるために、集電タブの数を増やして内部抵抗を低下させることや、活物質層を薄くして極板面積を広げること等で対処している。
【０００６】
【発明が解決しようとする課題】
しかしながら、内部抵抗を低下させるため集電タブの数を多くするほど、集電体を捲回して捲回群を作製するときや、集電タブを変形・接合するときの組立加工性が低下すると共にコスト高となる、という問題点がある。
【０００７】
本発明は上記事案に鑑み、組立加工性が良好で出力特性に優れた非水電解液二次電池を提供することを課題とする。
【０００８】
【課題を解決するための手段】
上記課題を解決するために、本発明は、正極集電体に正極活物質合剤を塗工した正極と、負極集電体に負極活物質合剤を塗工した負極と、をセパレータを介して捲回した捲回群を備えた非水電解液二次電池において、前記正極集電体がアルミニウム箔であり、該正極集電体から直接導出された複数のアルミニウム箔の集電用リード片の最細部断面積の総和が前記正極活物質合剤層の塗工面の面積に対して０．００６％〜０．０４８％であり、前記負極集電体が銅箔であり、該負極集電体から直接導出された複数の銅箔の集電用リード片の最細部断面積の総和が前記負極活物質合剤層の塗工面の面積に対して０．００４％〜０．０３％であることを特徴とする。このとき、捲回群が捲回中心となる軸芯を有しており、集電用リード片の幅が軸芯の外径の８０％以下であることが好ましい。
【０００９】
【発明の実施の形態】
以下、図面を参照して、本発明を電気自動車用の円筒型リチウムイオン二次電池に適用した実施の形態について説明する。
【００１０】
（正極板の作製）
正極活物質としてのマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）粉末と、導電剤として鱗片状黒鉛（平均粒径：２０μｍ）と、結着剤としてポリフッ化ビニリデン（ＰＶＤＦ）とを９０：５：５の質量比で混合し、これに分散溶媒のＮ−メチル−２−ピロリドンを添加、混練してスラリを作製した。作製したスラリを厚さ２０μｍの正極集電体としてのアルミニウム箔の両面に塗布、乾燥させ、アルミニウム箔上に片面あたり２００ｇ／ｍ^２の合剤層Ｌを形成した。このとき、アルミニウム箔の長寸方向の一側縁に幅５０ｍｍの未塗布部を残した。その後、プレス、裁断して幅５４ｍｍ、所定長さの帯状の正極板を得た。合剤層Ｌのかさ密度は２．７ｇ／ｃｍ^３とした。
【００１１】
図１に示すように、アルミニウム箔のスラリ未塗布部に切り欠き幅Ｗの切り欠きを入れ、切り欠き残部を集電用のリード片９とした。ここで、リード片９の最細部断面積ａの総和Ａｐ（アルミニウム箔にｎ個のリード片９を形成したとき、総和Ａｐ＝ｎ×最細部断面積ａ）を、合剤層Ｌのアルミニウム箔上の塗工面Ｂの面積（両面）に対して０．００６％〜０．０４８％とした。
【００１２】
（負極板の作製）
負極活物質としての非晶質炭素（呉羽化学工業株式会社製カーボトロンＰ）粉末９２重量部に結着剤として８重量部のポリフッ化ビニリデンを添加し、これに分散溶媒のＮ−メチル−２−ピロリドンを添加、混練してスラリを作製した。このスラリを厚さ１０μｍの負極集電体としての圧延銅箔の両面に塗布、乾燥させて、銅箔上に片面あたり５０ｇ／ｍ^２の合剤層Ｌを形成した。このとき、銅箔の一側縁に幅５０ｍｍの未塗布部を残した。その後、プレス、裁断して幅５６ｍｍ、所定長さの帯状の負極板を得た。合剤層Ｌのかさ密度は１．０ｇ／ｃｍ^３とした。
【００１３】
図１に示すように、銅箔のスラリ未塗布部に切り欠き幅Ｗの切り欠きを入れ、切り欠き残部を集電用のリード片９とした。リード片９の最細部断面積ａの総和Ａｎ（銅箔にｋ個のリード片９を形成したとき、総和Ａｎ＝ｋ×最細部断面積ａ）を、合剤層Ｌの銅箔上の塗工面Ｂの面積（両面）に対して０．００４％〜０．０３％とした。
【００１４】
なお、正極活物質と負極活物質の仕込み量は次のようにして決定した。セパレータを介して対向する単位面積あたりで、正極の充電終止電位４．５Ｖ（Ｌｉ／Ｌｉ^＋基準）までの充電可能容量と負極の終止電圧０Ｖ（Ｌｉ／Ｌｉ^＋基準）までの充電可能容量が同じになるようにした。ちなみに、マンガン酸リチウムの単位活物質重量あたりの充電可能容量は１０５ｍＡｈ／ｇであり、非晶質炭素の充電可能容量は４５０ｍＡｈ／ｇであった。
【００１５】
（電池の作製）
図２に示すように、作製した正極板及び負極板を、中空円筒状の軸芯１４の外径部に溶着した厚さ５０μｍのポリエチレン製セパレータとともに軸芯１４を中心として捲回して捲回群６を作製した。セパレータに微孔多孔性シートを用いた。このとき、正極板、負極板及びセパレータのそれぞれの長さは、正極板１０００ｍｍ、負極板１０５０ｍｍ、セパレータ長さ１２００ｍｍとし、正極のリード片９と負極のリード片９とが、捲回群６の互いに反対側の両端面に位置するように捲回した。
【００１６】
正極から導出されているリード片９を変形させ、その全てを、捲回群６軸心のほぼ延長線上にある極柱（正極外部端子１ａ）周囲から一体に張り出している鍔部７周面付近に集合、接触させ後、リード片９と鍔部７周面とを超音波溶接してリード片９を鍔部７周面に接続・固定した。負極外部端子１ｂと負極から導出されているリード片９との接続も、正極外部端子１ａと正極板から導出されているリード片９の接続と同様に実施した。
【００１７】
その後、正極外部端子１ａ及び負極外部端子１ｂの鍔部７周面全周に絶縁被覆８を施した。この絶縁被覆８は、捲回群６外周面全周にも及ぼした。絶縁被覆８には、基材がポリイミドで、その片面にヘキサメタアクリレートからなる粘着剤を塗布した粘着テープを用いた。この粘着テープを鍔部７周面から捲回群６外周面に亘って何重にも巻いて絶縁被覆８とした。捲回群６の最大径部が絶縁被覆８存在部となるように巻き数を調整し、該最大径をステンレス製の電池容器５内径よりも僅かに小さくして捲回群６を電池容器５内に挿入した。電池容器５の外形は６７ｍｍ、内径は６６ｍｍである。
【００１８】
円盤状電池蓋４の裏面と当接する部分の厚さが２ｍｍ、内径１６ｍｍ、外径２５ｍｍでアルミナ製の第２のセラミックワッシャ３ｂを、先端が正極外部端子１ａを構成する極柱、先端が負極外部端子１ｂを構成する極柱にそれぞれ嵌め込んだ。また、厚さが２ｍｍ、内径１６ｍｍ、外径２８ｍｍの平板状でアルミナ製の第１のセラミックワッシャ３ａを電池蓋４上に載置して、正極外部端子１ａ、負極外部端子１ｂをそれぞれ第１のセラミックワッシャ３ａに挿通した。その後、電池蓋４周端面を電池容器５の開口部に嵌合させ、双方の接触部全域をレーザ溶接した。このとき、正極外部端子１ａ、負極外部端子１ｂは、電池蓋４の中心に形成した穴を貫通して電池蓋４外部に突出している。第１のセラミックワッシャ３ａ、金属製ナット２の底面よりも平滑な金属ワッシャ１１を、この順に正極外部端子１ａ、負極外部端子１ｂにそれぞれ嵌め込んだ。
【００１９】
次いで、ナット２を正極外部端子１ａ、負極外部端子１ｂにそれぞれ螺着し、第２のセラミックワッシャ３ｂ、第１のセラミックワッシャ３ａ、金属ワッシャ１１を介して電池蓋４を鍔部７とナット２の間で締め付けにより固定した。締め付けトルク値は６．８６Ｎ・ｍとした。締め付け作業が終了するまで金属ワッシャ１１は回転しなかった。この状態で、電池蓋４裏面と鍔部７の間に介在させたゴム（ＥＰＤＭ）製Ｏリング１２の圧縮により、電池容器５内部の発電要素は外気から遮断される。
【００２０】
その後、電池蓋４に形成された注液口１３から非水電解液を所定量電池容器５内に注入し、その後注液口１３を封止することにより円筒型リチウムイオン電池２０を完成させた。非水電解液には、エチレンカーボネートとジメチルカーボネートとジエチルカーボネートとの体積比１：１：１の混合溶液中へ６フッ化リン酸リチウム（ＬｉＰＦ_６）を１モル／リットル溶解したものを用いた。
【００２１】
【実施例】
次に、本実施形態に従って切り欠き幅Ｗを変えることにより、正極及び負極合剤層の塗工面の面積Ｂに対してリード片９の最細部断面積の総和Ａを種々変更して作製した実施例の電池について説明する。なお、比較のために作製した比較例の電池についても併記する。
【００２２】
（実施例１〜４）
下表１に示すように、実施例１では、最細部断面積の総和Ａを、極板活物質塗工面の面積Ｂに対し正極リード片は０．０４８％、負極リード片は０．０３％とした。実施例２では、最細部断面積の総和Ａを、極板活物質塗工面の面積Ｂに対し正極リード片は０．０４８％、負極リード片は０．００４％とした。実施例３では、最細部断面積の総和Ａを、極板活物質塗工面の面積Ｂに対し正極リード片は０．００６％、負極リード片は０．０３％とした。実施例４では、最細部断面積の総和Ａを、極板活物質塗工面の面積Ｂに対し正極リード片は０．００６％、負極リード片は０．００４％とした。
【００２３】
【表１】

【００２４】
（比較例１、２）
表１に示すように、比較例１では、最細部断面積の総和Ａを、極板活物質塗工面の面積Ｂに対し正極リード片は０．００６％、負極リード片は０．００３％とした。また、比較例２では、最細部断面積の総和Ａを、極板活物質塗工面の面積Ｂに対し正極リード片は０．００５％、負極リード片は０．００４％とした。
【００２５】
（試験）
次に、作製した実施例及び比較例の各電池について、充電電圧４．２Ｖ、充電電流３Ａで４時間充電した後、日本蓄電池工業会規格ＳＢＡ８５０３の放電電流−電圧降下特性試験に準じ、５Ａ、１０Ａ、１５Ａで１０秒放電しその傾きから直流抵抗値を求めた。表１に放電電流−電圧降下特性試験により算出した各電池の直流抵抗値を示す。
【００２６】
表１に示すように、実施例１〜４の電池は、直流抵抗値が小さく、加工性も良かった。一方、比較例１、２の電池には直流抵抗の増加が見られた。また、アルミニウム箔、銅箔から導出されたリード片９の幅が、捲回時の軸心１４の外径の８０％を超えるものは捲回が困難であった。更に、極板活物質塗工面の面積Ｂに対する最細部断面積の総和Ａが、正極リード片で０．０５％、負極リード片０．０３％を超えるものは鍔部周面へ超音波溶接が困難であった。
【００２７】
なお、本実施形態では、アルミニウム箔及び銅箔から導出された複数のリード片の最細部断面積ａを一定とした例を示したが、最細部断面積ａに多少の差異があっても上述した実施例と同様の効果を得ることができる。中間部が細いリード片を用いた場合にはその最も細い断面の面積が最細部断面積ａとなる。
【００２８】
また、本実施形態では、電気自動車用電源等に用いられる大型の二次電池を例示したが、本発明は電池の大きさ、電池容量に限定されるものではなく、更に、有底筒状の電池容器（電池缶）に電池上蓋がかしめによって封口されている構造の円筒型電池にも適用可能である。電気自動車用電源には、特に高容量、高出力、高信頼性等の特性が要求されるので、本実施形態のように正負極外部端子が電池蓋から突出した構造の電池であることが好ましい。
【００２９】
更に、本実施形態では、絶縁被覆８に、基材がポリイミドで、その片面にヘキサメタアクリレートからなる粘着剤を塗布した粘着テープを例示したが、絶縁被膜に特に制限はない。例えば、基材がポリプロピレンやポリエチレン等のポリオレフィンで、その片面又は両面にヘキサメタアクリレートやブチルアクリレート等のアクリル系粘着剤を塗布した粘着テープや、粘着剤を塗布しないポリオレフィンやポリイミドからなるテープ等を好適に使用することができる。
【００３０】
また、本実施形態では、正極活物質にマンガン酸リチウム、負極活物質に非晶質炭素、非水電解液にエチレンカーボネートとジメチルカーボネートとジエチルカーボネートの混合溶液中へ６フッ化リン酸リチウムを溶解したものを例示したが、本発明はこれらに制限はなく、また結着剤、負極活物質、非水電解液も通常用いられているいずれのものも使用可能である。
【００３１】
更に、本実施形態に例示した以外で用いることのできる結着剤としては、テフロン、ポリエチレン、ポリスチレン、ポリブタジエン、ブチルゴム、ニトリルゴム、スチレン／ブタジエンゴム、多硫化ゴム、ニトロセルロース、シアノエチルセルロース、各種ラテックス、アクリロニトリル、フッ化ビニル、フッ化ビニリデン、フッ化プロピレン、フッ化クロロプレン等の重合体及びこれらの混合体などを挙げることができる。
【００３２】
また更に、本実施形態に例示した以外で用いることのできる正極活物質としては、リチウムを挿入・脱離可能な材料であり、予め十分な量のリチウムを挿入したリチウム・コバルト複合酸化物、リチウム・ニッケル複合酸化物、リチウム・マンガン複合酸化物を用いることができる。なお、高容量、高出力で、かつ安全性を確実に確保するためには、正極活物質として、リチウム・コバルト複合酸化物、リチウム・ニッケル複合酸化物ではなく、リチウムマンガン複合酸化物を用いることが好ましい。リチウム・マンガン複合酸化物を用いる場合には、スピネル構造を有したマンガン酸リチウムや、結晶中のマンガンやリチウムの一部をそれら以外の元素で置換あるいはドープしたものも好適に使用することができる。
【００３３】
更にまた、本実施形態に例示した以外で用いることのできる負極活物質にも特に制限はない。例えば、天然黒鉛や、人造の各種黒鉛材、コークスなどの炭素質材料等でよく、その粒子形状においても、鱗片状、球状、繊維状、塊状等、特に制限されるものではない。
【００３４】
そして、非水電解液としては、一般的なリチウム塩を電解質とし、これを有機溶媒に溶解した電解液を用いることができる。用いられるリチウム塩や有機溶煤にも特に制限されない。例えば、電解質としては、ＬｉＰＦ_６以外にＬｉＣｌＯ_４、ＬｉＡｓＦ_６、ＬｉＢＦ_４、ＬｉＢ（Ｃ_６Ｈ_５）_４、ＣＨ_３ＳＯ_３Ｌｉ、ＣＦ_３ＳＯ_３Ｌｉ等やこれらの混合物を用いることができる。非水電解液有機溶媒としては、プロピレンカーボネート、エチレンカーボネート、１，２−ジメトキシエタン、１，２−ジエトキシエタン、γ−ブチロラクトン、テトラヒドロフラン、１，３−ジオキソラン、４−メチル−１，３−ジオキソラン、ジエチルエーテル、スルホラン、メチルスルホラン、アセトニトリル、プロピオニトニル等またはこれら２種類以上の混合溶媒が用いられ、混合配合比についても限定されるものではない。
【００３５】
【発明の効果】
以上説明したように、本発明によれば、正極の集電体および集電用リード片をアルミニウム箔、負極の集電体および集電用リード片を銅箔とし、集電用リード片の最細部断面積の総和を活物質合剤層の塗工面の面積に対して正極０．００６％〜０．０４８％、負極０．００４％〜０．０３％に規定することで、組立加工性が良好で出力特性に優れた非水電解液二次電池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の形態の円筒型リチウムイオン電池の極板の部分斜視図である。
【図２】実施の形態の円筒型リチウムイオン電池の断面図である。
【符号の説明】
９リード片
２０円筒型リチウムイオン電池（非水電解液二次電池）
ａ最細部断面積
Ｂ塗工面
Ｌ合剤層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery, and in particular, a positive electrode obtained by applying a positive electrode active material mixture to a positive electrode current collector, and a negative electrode obtained by applying a negative electrode active material mixture to a negative electrode current collector. The present invention relates to a non-aqueous electrolyte secondary battery including a winding group wound through a separator.
[0002]
[Prior art]
Lithium ion secondary batteries, which are representative of non-aqueous electrolyte secondary batteries, are mainly used as power sources for portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of the high energy density. The internal structure of this battery is usually wound as shown below. The electrode is in the form of a band in which an active material is applied to a metal foil for both the positive electrode and the negative electrode, and the cross section is wound in a spiral shape so that the positive electrode and the negative electrode are not in direct contact across the separator to form a wound group. . And the winding group is accommodated in the cylindrical can used as a battery container, and it seals after electrolyte solution injection.
[0003]
A general cylindrical lithium ion secondary battery has a diameter of 18 mm and a height of 65 mm, which is called a 18650 type, and is widely used as a small consumer lithium ion battery. The positive electrode active material of the 18650 type lithium ion secondary battery mainly uses lithium cobaltate, which is characterized by high capacity and long life. The battery capacity is approximately 1.3 Ah to 1.7 Ah, and the output is approximately 10 W. Degree.
[0004]
On the other hand, in the automobile industry, in order to cope with environmental problems, there are no exhaust gas, an electric vehicle that uses only a power source as a power source, and a hybrid (electric) vehicle that uses both an internal combustion engine and a battery as power sources. Development has been accelerated, and some have reached the stage of practical application.
[0005]
Naturally, a battery serving as a power source for an electric vehicle is required to have characteristics of obtaining high output and high energy, and a lithium ion secondary battery is attracting attention as a battery that meets this requirement. In the case of a lithium ion battery for an electric vehicle, about 30 to 100 batteries are connected in series in order to obtain a high voltage of about 100 to 350 V, and a large current flows, so the quality of the output characteristics of the battery is important. For this reason, in the lithium ion battery for electric vehicles, in order to improve the output characteristics of the battery, the number of current collecting tabs is increased to reduce the internal resistance, the active material layer is thinned to increase the electrode plate area, etc. It is dealt with in.
[0006]
[Problems to be solved by the invention]
However, as the number of current collecting tabs is increased in order to reduce the internal resistance, the assembly processability when the current collector is wound to form a wound group or when the current collecting tab is deformed / joined decreases. At the same time, there is a problem of high costs.
[0007]
An object of the present invention is to provide a non-aqueous electrolyte secondary battery that has good assembly processability and excellent output characteristics.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a positive electrode obtained by applying a positive electrode active material mixture to a positive electrode current collector and a negative electrode obtained by applying a negative electrode active material mixture to a negative electrode current collector via a separator. In a non-aqueous electrolyte secondary battery having a wound group wound by winding, the positive electrode current collector is an aluminum foil, and a plurality of aluminum foil current collecting lead pieces directly derived from the positive electrode current collector The sum of the most detailed cross-sectional areas is 0.006% to 0.048% with respect to the area of the coated surface of the positive electrode active material mixture layer, the negative electrode current collector is a copper foil, and the negative electrode current collector The sum of the most detailed cross-sectional areas of the current collecting lead pieces of the plurality of copper foils directly derived from the body is 0.004% to 0.03% with respect to the area of the coated surface of the negative electrode active material mixture layer It is characterized by that. At this time, it is preferable that the winding group has an axis that is the winding center, and the width of the current collecting lead piece is 80% or less of the outer diameter of the axis.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments in which the present invention is applied to a cylindrical lithium ion secondary battery for an electric vehicle will be described below with reference to the drawings.
[0010]
(Preparation of positive electrode plate)
90: 5: 5 lithium manganate (LiMn ₂ O ₄ ) powder as a positive electrode active material, scaly graphite (average particle size: 20 μm) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder The mixture was mixed at a mass ratio, and N-methyl-2-pyrrolidone as a dispersion solvent was added thereto and kneaded to prepare a slurry. The prepared slurry was applied to both sides of an aluminum foil as a positive electrode current collector having a thickness of 20 μm and dried to form a mixture layer L of 200 g / m ² per side on the aluminum foil. At this time, an uncoated part having a width of 50 mm was left on one side edge of the aluminum foil in the longitudinal direction. Thereafter, pressing and cutting were performed to obtain a strip-like positive electrode plate having a width of 54 mm and a predetermined length. The bulk density of the mixture layer L was 2.7 g / cm ³ .
[0011]
As shown in FIG. 1, a notch having a notch width W was put in an uncoated portion of the aluminum foil, and the remaining notch was used as a lead piece 9 for current collection. Here, the sum Ap of the most detailed cross-sectional area a of the lead piece 9 (the total Ap = n × the most detailed cross-sectional area a when n lead pieces 9 are formed on the aluminum foil) is the aluminum foil of the mixture layer L It was made into 0.006%-0.048% with respect to the area (both surfaces) of the upper coated surface B.
[0012]
(Preparation of negative electrode plate)
8 parts by weight of polyvinylidene fluoride as a binder is added to 92 parts by weight of amorphous carbon (Carbotron P manufactured by Kureha Chemical Co., Ltd.) as a negative electrode active material, and N-methyl-2- Pyrrolidone was added and kneaded to prepare a slurry. This slurry was applied to both sides of a rolled copper foil as a negative electrode current collector having a thickness of 10 μm and dried to form a mixture layer L of 50 g / m ² per side on the copper foil. At this time, an uncoated portion having a width of 50 mm was left on one side edge of the copper foil. Thereafter, pressing and cutting were performed to obtain a strip-shaped negative electrode plate having a width of 56 mm and a predetermined length. The bulk density of the mixture layer L was 1.0 g / cm ³ .
[0013]
As shown in FIG. 1, a notch having a notch width W was put in an uncoated portion of the copper foil, and the remaining notch was used as a lead piece 9 for current collection. Apply the sum An of the most detailed cross-sectional area a of the lead piece 9 (the total An = k × the most detailed cross-sectional area a when k lead pieces 9 are formed on the copper foil) on the copper foil of the mixture layer L It was made into 0.004%-0.03% with respect to the area (both surfaces) of the construction surface B.
[0014]
In addition, the preparation amount of the positive electrode active material and the negative electrode active material was determined as follows. The chargeable capacity up to 4.5V (Li / Li ⁺ reference) of the positive charge and the chargeable capacity up to 0V (Li / Li ⁺ reference) of the negative charge per unit area facing each other through the separator I tried to be the same. Incidentally, the chargeable capacity per unit active material weight of lithium manganate was 105 mAh / g, and the chargeable capacity of amorphous carbon was 450 mAh / g.
[0015]
(Production of battery)
As shown in FIG. 2, the produced positive and negative plates are wound around a shaft core 14 together with a 50 μm thick polyethylene separator welded to the outer diameter portion of a hollow cylindrical shaft core 14. 6 was produced. A microporous sheet was used for the separator. At this time, the length of each of the positive electrode plate, the negative electrode plate, and the separator is 1000 mm for the positive electrode plate, 1050 mm for the negative electrode plate, and 1200 mm for the separator, and the lead piece 9 for the positive electrode and the lead piece 9 for the negative electrode are It wound so that it might be located in the both end surfaces on the opposite side.
[0016]
The lead piece 9 led out from the positive electrode is deformed, and all of the lead piece 9 is in the vicinity of the peripheral surface of the collar portion 7 integrally projecting from the periphery of the pole column (positive electrode external terminal 1a) substantially on the extension line of the winding group 6 axis. After the assembly and contact, the lead piece 9 and the circumferential surface of the collar portion 7 were ultrasonically welded to connect and fix the lead piece 9 to the circumferential surface of the collar portion 7. The connection between the negative electrode external terminal 1b and the lead piece 9 led out from the negative electrode was performed in the same manner as the connection between the positive electrode external terminal 1a and the lead piece 9 led out from the positive electrode plate.
[0017]
Thereafter, an insulating coating 8 was applied to the entire periphery of the collar 7 peripheral surface of the positive electrode external terminal 1a and the negative electrode external terminal 1b. This insulating coating 8 also exerted on the entire outer periphery of the wound group 6. For the insulating coating 8, an adhesive tape in which the base material was polyimide and an adhesive made of hexamethacrylate was applied on one side thereof was used. This adhesive tape was wound several times from the peripheral surface of the collar portion 7 to the outer peripheral surface of the wound group 6 to form an insulating coating 8. The number of windings is adjusted so that the maximum diameter portion of the wound group 6 becomes the insulating coating 8 existing portion, and the maximum diameter is slightly smaller than the inner diameter of the battery container 5 made of stainless steel so that the wound group 6 is battery container 5. Inserted inside. The battery container 5 has an outer diameter of 67 mm and an inner diameter of 66 mm.
[0018]
A second ceramic washer 3b made of alumina having a thickness of 2 mm, an inner diameter of 16 mm, an outer diameter of 25 mm, and a tip that constitutes the positive electrode external terminal 1a, and a tip that is a negative electrode. Each was fitted into a pole column constituting the external terminal 1b. Further, a first ceramic washer 3a made of alumina having a thickness of 2 mm, an inner diameter of 16 mm, and an outer diameter of 28 mm is placed on the battery lid 4, and the positive external terminal 1 a and the negative external terminal 1 b are respectively connected to the first. The ceramic washer 3a was inserted. Thereafter, the peripheral end surface of the battery lid 4 was fitted into the opening of the battery container 5, and the entire contact portion was laser welded. At this time, the positive electrode external terminal 1 a and the negative electrode external terminal 1 b pass through a hole formed in the center of the battery cover 4 and protrude outside the battery cover 4. The first ceramic washer 3a and the metal washer 11 smoother than the bottom surface of the metal nut 2 were fitted into the positive external terminal 1a and the negative external terminal 1b in this order.
[0019]
Next, the nut 2 is screwed to the positive electrode external terminal 1a and the negative electrode external terminal 1b, and the battery lid 4 is connected to the flange portion 7 and the nut 2 via the second ceramic washer 3b, the first ceramic washer 3a, and the metal washer 11. And fixed by tightening. The tightening torque value was 6.86 N · m. The metal washer 11 did not rotate until the tightening operation was completed. In this state, the power generation element inside the battery container 5 is blocked from the outside air by the compression of the rubber (EPDM) O-ring 12 interposed between the back surface of the battery lid 4 and the flange portion 7.
[0020]
Thereafter, a predetermined amount of non-aqueous electrolyte was injected into the battery container 5 from the injection port 13 formed in the battery lid 4, and then the injection port 13 was sealed to complete the cylindrical lithium ion battery 20. . As the non-aqueous electrolyte, a solution obtained by dissolving 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) in a mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1: 1: 1 was used. .
[0021]
【Example】
Next, by changing the notch width W according to this embodiment, the total A of the finest cross-sectional areas of the lead pieces 9 was variously changed with respect to the area B of the coating surface of the positive electrode and negative electrode mixture layers. An example battery will be described. In addition, it describes together about the battery of the comparative example produced for the comparison.
[0022]
(Examples 1-4)
As shown in Table 1 below, in Example 1, the sum A of the most detailed cross-sectional areas is 0.048% for the positive electrode lead piece and 0.03% for the negative electrode lead piece with respect to the area B of the electrode plate active material coated surface. It was. In Example 2, the sum A of the most detailed cross-sectional areas was 0.048% for the positive electrode lead piece and 0.004% for the negative electrode lead piece with respect to the area B of the electrode plate active material coated surface. In Example 3, the sum A of the most detailed cross-sectional areas was 0.006% for the positive electrode lead piece and 0.03% for the negative electrode lead piece with respect to the area B of the electrode plate active material coated surface. In Example 4, the sum A of the most detailed cross-sectional areas was 0.006% for the positive electrode lead piece and 0.004% for the negative electrode lead piece with respect to the area B of the electrode plate active material coated surface.
[0023]
[Table 1]

[0024]
(Comparative Examples 1 and 2)
As shown in Table 1, in Comparative Example 1, the total cross-sectional area A is 0.006% for the positive electrode lead piece and 0.003% for the negative electrode lead piece with respect to the area B of the electrode plate active material coating surface. did. In Comparative Example 2, the sum A of the most detailed cross-sectional areas was 0.005% for the positive electrode lead piece and 0.004% for the negative electrode lead piece with respect to the area B of the electrode plate active material coated surface.
[0025]
(test)
Next, about each battery of the produced Example and Comparative Example, after charging for 4 hours at a charging voltage of 4.2 V and a charging current of 3 A, 5 A according to the discharge current-voltage drop characteristic test of Japan Storage Battery Industry Association Standard SBA8503 The discharge was performed at 10A and 15A for 10 seconds, and the DC resistance value was obtained from the slope. Table 1 shows the DC resistance value of each battery calculated by the discharge current-voltage drop characteristic test.
[0026]
As shown in Table 1, the batteries of Examples 1 to 4 had small DC resistance values and good workability. On the other hand, the batteries of Comparative Examples 1 and 2 showed an increase in DC resistance. In addition, when the width of the lead piece 9 derived from the aluminum foil and the copper foil exceeds 80% of the outer diameter of the axis 14 at the time of winding, it is difficult to wind. Furthermore, when the sum A of the finest cross-sectional area with respect to the area B of the electrode plate active material coated surface exceeds 0.05% for the positive electrode lead piece and 0.03% for the negative electrode lead piece, ultrasonic welding is performed on the peripheral surface of the buttock. It was difficult.
[0027]
In the present embodiment, the example in which the most detailed cross-sectional area a of the plurality of lead pieces derived from the aluminum foil and the copper foil is constant has been described. The same effects as those of the embodiment described above can be obtained. When a lead piece with a thin intermediate part is used, the area of the narrowest cross section is the finest cross sectional area a.
[0028]
Further, in the present embodiment, a large secondary battery used for an electric vehicle power source or the like has been exemplified, but the present invention is not limited to the size of the battery and the battery capacity, and further has a bottomed cylindrical shape. The present invention can also be applied to a cylindrical battery having a structure in which a battery upper lid is sealed with a battery container (battery can) by caulking. Since the power source for electric vehicles is required to have characteristics such as high capacity, high output, and high reliability, it is preferable that the battery has a structure in which positive and negative external terminals protrude from the battery lid as in this embodiment. .
[0029]
Furthermore, in this embodiment, although the base material is a polyimide and the adhesive tape which apply | coated the adhesive which consists of hexamethacrylates to the single side | surface was illustrated to the insulating coating 8, there is no restriction | limiting in particular in an insulating film. For example, the base material is a polyolefin such as polypropylene or polyethylene, and an adhesive tape with an acrylic adhesive such as hexamethacrylate or butyl acrylate applied on one or both sides, or a tape made of polyolefin or polyimide that does not apply an adhesive. It can be preferably used.
[0030]
In this embodiment, lithium manganate is dissolved in the positive electrode active material, lithium carbon is used as the negative electrode active material, amorphous carbon is used as the negative electrode active material, and lithium hexafluorophosphate is dissolved in a mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in the non-aqueous electrolyte. However, the present invention is not limited to these, and any of the commonly used binders, negative electrode active materials, and non-aqueous electrolytes can be used.
[0031]
Furthermore, binders that can be used other than those exemplified in the present embodiment include Teflon, polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, and various latexes. And polymers such as acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and mixtures thereof.
[0032]
Furthermore, as a positive electrode active material that can be used other than those exemplified in the present embodiment, lithium is a material capable of inserting / extracting lithium, and a lithium / cobalt composite oxide in which a sufficient amount of lithium is inserted in advance, lithium -Nickel composite oxide and lithium-manganese composite oxide can be used. To ensure high capacity, high output, and safety, use lithium manganese composite oxide as the positive electrode active material instead of lithium / cobalt composite oxide or lithium / nickel composite oxide. Is preferred. In the case of using a lithium-manganese composite oxide, lithium manganate having a spinel structure, or manganese or a part of lithium in the crystal substituted or doped with other elements can be suitably used. .
[0033]
Furthermore, there are no particular limitations on the negative electrode active material that can be used other than those exemplified in this embodiment. For example, natural graphite, various types of artificial graphite materials, carbonaceous materials such as coke, and the like may be used, and the particle shape is not particularly limited, such as scaly, spherical, fibrous, or massive.
[0034]
As the non-aqueous electrolyte, an electrolyte obtained by using a general lithium salt as an electrolyte and dissolving it in an organic solvent can be used. There are no particular restrictions on the lithium salt or organic hot metal used. For example, as the electrolyte, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, and the like can be used in addition to LiPF ₆ . Nonaqueous electrolyte organic solvents include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3- Dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propiontonyl and the like, or a mixed solvent of two or more of these are used, and the mixing ratio is not limited.
[0035]
【The invention's effect】
As described above, according to the present invention, the positive electrode current collector and the current collecting lead piece are made of aluminum foil, the negative electrode current collector and the current collecting lead piece are made of copper foil, and By defining the sum of the detailed cross sectional areas to be 0.006% to 0.048% of the positive electrode and 0.004% to 0.03% of the negative electrode with respect to the area of the coated surface of the active material mixture layer, assembly workability is improved. A non-aqueous electrolyte secondary battery having good output characteristics can be obtained.
[Brief description of the drawings]
FIG. 1 is a partial perspective view of an electrode plate of a cylindrical lithium ion battery according to an embodiment to which the present invention is applicable.
FIG. 2 is a cross-sectional view of a cylindrical lithium ion battery according to an embodiment.
[Explanation of symbols]
9 Lead piece 20 Cylindrical lithium ion battery (non-aqueous electrolyte secondary battery)
a Maximum cross-sectional area B Coating surface L Mixture layer

Claims

A non-aqueous device comprising a winding group in which a positive electrode obtained by applying a positive electrode active material mixture to a positive electrode current collector and a negative electrode obtained by applying a negative electrode active material mixture to a negative electrode current collector through a separator. In the electrolyte secondary battery, the positive electrode current collector is an aluminum foil, and the sum of the most detailed cross-sectional areas of current collecting lead pieces of a plurality of aluminum foils directly derived from the positive electrode current collector is the positive electrode active material 0.006% to 0.048% with respect to the area of the coating surface of the mixture layer, the negative electrode current collector is a copper foil, and a collection of a plurality of copper foils directly derived from the negative electrode current collector The non-aqueous electrolyte secondary battery characterized in that the sum of the most detailed cross-sectional areas of the electric lead pieces is 0.004% to 0.03% with respect to the area of the coated surface of the negative electrode active material mixture layer .

The winding group has an axis serving as a winding center, and the width of the current collecting lead piece is 80% or less of the outer diameter of the axis. Non-aqueous electrolyte secondary battery.