JP3733403B2

JP3733403B2 - Electrode wound type battery

Info

Publication number: JP3733403B2
Application number: JP02794899A
Authority: JP
Inventors: 吾朗渡辺; 英之正木; 辰視日置; 勇一伊藤; 昭中野; 耕野崎; 明人秋本
Original assignee: Denso Corp; Toyota Motor Corp
Current assignee: Denso Corp; Toyota Motor Corp
Priority date: 1999-02-04
Filing date: 1999-02-04
Publication date: 2006-01-11
Anticipated expiration: 2019-02-04
Also published as: JP2000228182A

Description

【０００１】
【発明の属する技術分野】
本発明は、シート状の正極および負極を捲回させて構成する電極捲回型電池、さらに詳しくは、集電処理が簡便でかつ出力密度、エネルギ密度の高い電極捲回型電池に関する。
【０００２】
【従来の技術】
リチウムイオン二次電池等の円筒型電池は、帯状の金属箔集電体の表面に活物質を含む電極合材を塗工してシート状の電極を形成させ、この電極を薄膜のセパレータを介して渦巻状に捲回することにより、電極体を構成させ、この電極体を電解液とともに円筒型のケースに収納するという方式を採るのが一般的である。このような電極捲回型電池において、電極体から外部に通じる端子への集電方法は、通常、集電体に設けた複数の短冊状の集電用リードによって行われている。
【０００３】
環境問題、資源問題から電気自動車の開発が急がれ、リチウムイオン二次電池等を電気自動車に採用する動向にもある。これら電極捲回型電池の大型化は、電極全体からの均一な集電を要求されることから、集電処理の方法をより複雑化することにつながり、効率的な集電処理の方法が開発が望まれていた。
従来、大型の電極捲回型電池の集電方法として、特開平９−９２３３５号公報、特開平９−９２３３８号公報等に示すものがあった。これらに示す集電処理の方法は、以下のようなものである。まず、帯状の集電体の表面に幅方向の一端部に未塗工部を残すようにして電極合材を塗工し、この未塗工部を切り欠くことにより集電用リードを形成させたシート状の電極を作成する（図１４参照）。次に、これらの電極を、互いの集電用リードが背向するように位置させ、セパレータを挟装させて、これらを捲回し、電極体を形成させる（図１５、図１６参照）。そして、電極体の巻回端面に突出した集電用リードを、電極体の巻回端面に配置させた集電端子のフランジ部の外周に集め、これをリングを用いて押さえつけてレーザ溶接する（図１７参照）、あるいは、集めた集電用リードをフランジ外周に押さえつけるように数箇所の超音波接合を行う（図１８参照）という方法である。
【０００４】
なお、集電用リードの形成については、上記の切り欠きによるものの他、未塗工部に短冊状の金属箔を超音波接合、抵抗溶接等の手段を用いて接合することにより形成する方法でも行われていた（図１９参照）。
【０００５】
【発明が解決しようとする課題】
しかしながら、上記従来の方法は、以下の欠点があった。
（１）電極合材塗工後、未塗工部を短冊状にカットして、あるいは未塗工部に短冊状の金属箔を接合することにより、集電用リードを複数形成させなければならず、この工程に多くの工数を必要とし、電池の製造コストが上昇する。
【０００６】
（２）リングを用いてレーザ溶接する場合は、リングにより押さえつける工程を必要とし、またレーザ溶接を行うためにリングおよびフランジ部からはみ出た集電用リードを切りそろえる工程をも必要とし、やはり製造コストの増加につながる。さらにレーザ溶接はスパッタが発生し、このスパッタが電極体に入り込婿とによって電極間の短絡の原因となる可能性がある。
【０００７】
（３）超音波接合する場合は、リング等の押え金具を用いないため、複数のバラバラに集まってくる集電用リードがスプリングバックにより元に戻ろうとするため、これをうまく捌いて超音波接合を行うのは非常に作業性が悪く、やはり多くの工数を必要とし製造コストが増加してしまう。
（４）レーザ溶接、超音波接合のいずれの方法であっても、大きなフランジ部を有する円盤状の集電端子を必要とするため、集電端子の重量が大きく、電池自体の重量も増加し、電池の重要な特性である出力密度、エネルギ密度が減少してしまうことになる。
【０００８】
本発明は、電極捲回型電池の従来の集電処理方法が抱える上記実情に鑑みてなされたものであり、集電処理に多くの工数を必要とせず、また大きな重量の端子部品を必要としない集電処理方法を開発することを課題とし、集電処理のためのコストが安く、かつ出力密度、エネルギ密度の高い電極捲回型電池を提供することを目的としている。
【０００９】
【課題を解決するための手段】
上記課題を解決すべく、請求項１の電極捲回型電池は、それぞれの帯状金属箔集電体とその表面に塗工されたそれぞれの電極合材とをもつ正極シートおよび負極シートと、該正極シートと負極シートとの間に挟装されたセパレータとを、巻芯の周囲に渦巻状に捲回して形成された電極体を有する電極捲回型電池であって、前記正極シートと負極シートとの少なくとも一方は、幅方向において連続して一体に形成され、幅方向の一端部に所定幅をＨ（ｍｍ）とする全長にわたる電極合材未塗工部を有し、かつ該電極合材未塗工部をセパレータおよび前記正極シートと負極シートとの他方から突出させるように捲回されており、
該巻芯の端部が集電端子となり、かつ、該電極合材未塗工部は、該巻芯の端部に重ね合わさるように接合された接合部と該巻芯の端部に接合されていない非接合部とを形成するように接合されており、さらに、該電極体の正極シート、負極シートおよびセパレータとが捲回されて層状をなす部分の最内周と最外周とによって決定される半径方向の厚さをＴ（ｍｍ）とした場合に、ＨとＴが次式で表される関係を有することを特徴とする。
Ｔ≧５かつＨ≦４５
かつＴ＜Ｈ≦１．５Ｔ＋１５
また、請求項２の電極捲回型電池は、集電端子以外は請求項１の電極捲回型電池と同じ構成であるが、集電端子は、該巻芯の端部に結合した或いは該巻芯とは物理的に隔離した別体の部品であって、かつ、該電極合材未塗工部は、該集電端子に重ね合わさるように接合された接合部と該集電端子に接合されていない非接合部とを形成するように接合されていることを特徴とする。
【００１０】
つまり本発明の電極捲回型電池は、電極合材が塗工されていない未塗工部に切込みを設けるとか、また未塗工部を切り欠く若しくは未塗工部に短冊状のものを接合することによって集電用リードを形成させるといった特別な手段を施すことなく、この未塗工部を集電端子に重ね合わせるように接合することにより、集電処理に必要となる工数を大幅に削減することを可能にするものである。さらに本発明の電極捲回型電池では、従来のようなフランジ部を設けるなどした比較的重量のある集電端子部品を必要とせず、電池重量の軽減を図ることができ、さらに、電極合材未塗工部の幅Ｈ（ｍｍ）と電極の捲回厚さＴ（ｍｍ）の値について、実験結果から望ましい範囲を設けているので、その値にもとづいて電池の出力密度、エネルギ密度を確実に増大させることができる。
【００１１】
【発明の実施の形態】
以下に本発明の電極捲回型電池およびその製造方法の一実施形態であって、電極体の巻芯を集電端子とした実施形態について、リチウムイオン二次電池を例にとって、図面をも参照しつつ詳細に説明する。なお本発明の電極捲回型電池は、リチウムイオン二次電池に限定されるものではなく、電極合材を集電体表面に塗工して形成した電極を捲回して構成したすべての電池に適用できるものである。
【００１２】
〈正極シートおよび負極シートと電極合材未塗工部の形成〉
図１に、本発明の電極捲回型電池を構成する正極シートおよび負極シートの平面図を表す。正極シート１０は、帯状金属箔製の正極集電体１１とその表面に塗工された正極合材１２とからなり、負極シート２０は帯状金属箔製の負極集電体２１とその表面に塗工された負極合材２２とからなる。正極シート１０および負極シート２０の長さおよび幅については、作成しようとする電池の容量等に応じて任意のものとすることができる。
【００１３】
正極シート１０、負極シート２０とも、幅方向において連続して一体に形成されており、幅方向の一端部に所定幅で全長にわたって正極合材未塗工部１３および負極合材未塗工部２３がそれぞれ設けられている。この未塗工部１３、２３の幅は、後に詳しく説明するためここでの説明は省略する。なお電極合材１２、２２は、集電体１１、２１の片面に塗工するものでもよく、また集電体１１、２１の両面に塗工するものであってもよい。ただし、電池のエネルギ密度等を考慮すれば両面に塗工するのが望ましく、その場合は両面に未塗工部１３、２３を設け、両面の未塗工部１３、２３が幅方向の同じ一端部に位置するようにしなければならない。
【００１４】
リチウムイオン二次電池の場合、正極集電体１１には、アルミニウム等の金属箔でその厚みは１０〜２０μｍ程度のものを使用するのが望ましい。この正極集電体１１に塗工される正極合材１２は、リチウム複合酸化物粉末等からなる活物質に黒鉛等の導電材、ポリフッ化ビニリデン等の結着剤を混合し、ｎ−メチルピロリドン等の溶剤を適量加えたもので、塗工前はペースト状となっているものを用いるのがよい。負極集電体２１には、銅等の金属箔でその厚みは５〜２０μｍ程度のものを使用するのが望ましい。この負極集電体２１に塗工される負極合材２２は、黒鉛等の炭素材料粉末からなる活物質に、ポリフッ化ビニリデン等の結着剤を混合し、ｎ−メチルピロリドン等の溶剤を適量加えたもので、正極合材１２同様、塗工前はペースト状となっているものを用いるのがよい。
【００１５】
正極シート１０、負極シート２０に電極合材未塗工部１３、２３を形成させる工程、つまり、電極合材未塗工部１３、２３を設けるように、集電体１１、２１の表面に電極合材１２、２２を塗工する工程は、種々の方法によって行うことができるが、連続的に塗布、乾燥が行えるコータと呼ばれる塗工機を用いて行うのが好ましい。図２に、コータの塗布装置の一例を概念的に表した図を掲げる。
【００１６】
この図が示す塗布装置７０は、リバースロール方式のもので、バックアップロール７１、塗布ロール７２、コンマロール７３の３本のロールにより構成されており、堰７４の中に貯えられた電極合材が、コンマロール７３により計量されて塗布ロール７２に供給され、塗布ロール７２上の電極合材１２、２２が、バックアップロール７１と塗布ロール７２の間を集電体１１、２１が通過する際に、この集電体１１、２１に転写されるという方式のものである。電極合材の粘度の影響が少なく、均一な塗布厚が得られるという利点がある。
【００１７】
堰７４の幅によって電極合材の塗布される幅が決定でき、集電体１１、２１の幅および集電体１１、１２を通過させる位置によって、電極合材未塗工部１３、２３の位置および幅を調整することができる。本実施形態の場合電極シート１０、２０の一端部のみに電極合材未塗工部１３、２３を設けているが、塗布時の電極合材のタレ等を考慮して、幅方向の他端部に若干の幅の未塗工部を設けるものであっても構わない。また電極合材１２、２２の塗布厚は、５０〜２５０μｍ程度とするのが好ましい。なおリチウムイオン二次電池の場合は、デンドライトの析出等を考慮して負極合材２２を正極合材１２よりも若干量幅広く塗工するのが望ましい。
【００１８】
このように電極合材１２、２２が塗布された集電体１１、２１は、塗布装置７０に連続している乾燥炉に移動させられ、乾燥によって電極合材１２，２２に含まれる溶剤分が蒸散させられる。乾燥炉には連続炉が用いられ、電極合材１２、２２が塗布された集電体が炉内を移動する間に乾燥が行われる。乾燥法式は熱風方式、赤外線方式等様々な方式を採用することができる。
【００１９】
この様な工程を経ることによって、正極シート１０および負極シート２０が形成される。なお乾燥完了後、必要に応じ、電極合材１２、２２の密度を高めるために、ロールプレス等を行ってもよい。また集電体１１、２１の両面に電極合材１２、２２を塗工する場合には上述した工程を２回繰り返せばよい。
〈電極体の形成〉
電極合材の塗工が完了して形成された正極シートおよび負極シートは、その間にセパレータを挟装されて、巻芯を中心にロール状に捲回され電極体が形成される。セパレータは、正極シートおよび負極シートを物理的に隔離し、電解液を保持する役割を果たすもので、厚さ２０〜４０μｍ程度のポリエチレン等の微多孔質膜を用いるのがよい。なお、セパレータの幅は、絶縁を担保するため、正極合材および負極合材の塗工幅より若干広くするのが望ましい。
【００２０】
巻芯は、樹脂、金属等の材質のものを用いることができるが、本実施形態の場合両端が集電端子を兼ねることから、巻芯の両端は正極集電体および負極集電体と同じ材質のものから形成されることが望ましい。本実施形態に使用する巻芯を図３に示す。図３に示すように正極側部材４１にはアルミニウム等の金属を、負極側部材４２には銅等の金属を用いており、正極側部材４１と負極側部材４２の間には、両者を絶縁するため、樹脂等でできた絶縁部材４３を介在させ、正極側部材４１、負極側部材４２、絶縁部材４３が結合されて一体として形成されている。
【００２１】
本実施形態の場合の巻芯４０は、正極側部材４１、負極側部材４２、絶縁部材４３とも中空に形成されている。これは、巻芯４０自体の重量を軽減させるためであり、また電池の充放電に伴って発生する電極体内部の熱を外部に放散させることを目的とするものである。従ってこの様な配慮を必要としない場合は、敢えて中空とする必要はなく、丸棒状のものであっても構わない。
【００２２】
巻芯４０の長さは、両端に正極シートおよび負極シートの電極合材未塗工部がそれぞれ接合されるため、少なくともセパレータの幅方向の端部よりも両端が突出するだけの長さが必要となる。なお本実施形態の巻芯４０の場合は、入出力端子の役割をも兼用させるため、正極側部材４１および負極側部材４２の両端に雄ネジ４４が形成されているが、入出力のための接続方式に応じ、正極側部材４１および負極側部材４２の端部は種々の形状に形成することができる。
【００２３】
次に巻芯を中心にして、正極シート、負極シート、セパレータを捲回する様子を図４に示す。また、正極シート、負極シート、セパレータを重ね合わせた様子を示す断面図を図５に示す。これらの図が示すように、セパレータ３０、負極シート２０、セパレータ３０、正極シート１０の４枚を層状に重ねて捲回する。この際、正極シート１０の正極合材未塗工部１３と負極シート２０の負極合材未塗工部２３が、幅方向で互いに背向し、正極合材未塗工部１３がセパレータ３０および負極シート２０より突出し、負極合材未塗工部２３がセパレータ３０および正極シート１０より突出するように重ね合わせる。
【００２４】
捲回は捲回機を用い、正極シート１０、負極シート２０、２枚のセパレータ３０のそれぞれに対して、長手方向にテンションをかけ、それぞれが弛まないように行う。捲き始めは、セパレータ３０、負極シート２０、セパレータ３０、正極シート１０、セパレータ３０・・・・の順となるようにし、捲き終わりは、・・・・セパレータ３０、正極シート１０、セパレータ３０、負極シート２０、セパレータ３０の順となるようにする。
【００２５】
このように捲回されたものは、ロール状（渦巻状）の電極体となる。形成された電極体を図６に示す。この図が示すように、電極体５０は、正極合材未塗工部１３および負極合材未塗工部２３が、正極合材および負極合材が重ね合わされて捲回されている部分より捲回軸方向の両側に突出した格好になっている。そして、正極合材未塗工部１３が巻芯４０の正極側部材４１の周囲に、負極合材未塗工部２３が巻芯４０の負極側部材４２の周囲にそれぞれ位置するものとなっている。
【００２６】
〈集電処理〉
電極シートから集電端子への集電処理は、正極シートおよび負極シートの電極合材未塗工部を集電端子へ重ね合わせるように接合することによって行う。本実施形態の場合は、巻芯の端部が集電端子を兼ねる構造となっていることから、正極シートの正極合材未塗工部を上述した巻芯の正極側部材に、負極シートの負極合材未塗工部を負極側部材にそれぞれ接合することによって行う。
【００２７】
接合の方法は、超音波接合、抵抗溶接、レーザ溶接、カシメ等様々な手段によって行うことができる。電極合材への熱影響、スパッタ、接合部における通電抵抗、作業性等を総合的に考慮すれば、超音波接合によって行うのが望ましい。接合方法の一例として、図７に、超音波接合によって電極合材未塗工部を巻芯に接合する様子を示す。
【００２８】
図７に示すように、超音波接合機６０は、受け台となるアンビル６２と、超音波振動を接合部に伝達させるホーン６１とからなる。本実施形態の場合、巻芯４０が中空に形成されているため、巻芯４０の中空部に挿入できるようなアンビル６２を用いている。そしてアンビル６２を巻芯４０の中空部に挿入して電極体５０をセットし、電極合材未塗工部１３、２３の最外周にホーン６１を当接させ、巻芯４０に向かって付勢して巻芯４０とホーン６１との間で電極合材未塗工部１３，２３を重ね合わせるように挟持し、ホーン６１から超音波振動を伝達させて接合を行う。
【００２９】
正極側、負極側それぞれ２箇所の接合を行った後の電極体を、図８に示す。接合は、巻芯４０のまわりにおいて、１箇所または複数箇所行うことができる。この際、巻芯４０の端部（正極側部材４１あるいは負極側部材４２）に接合された接合部６３と巻芯４０の端部に接合されていない非接合部６４とを形成するように接合するのが望ましい。巻芯４０の全周にわたって接合するのと異なり、非接合部６４を存在させることで、後に行う組付け時の電解液の含浸工程において、電解液を電極合材の隅々にまで注入できるという利点を有することとなる。また、電池に異常が生じて電解液がガス化したような場合においても、非接合部６４は電極体５０の内部のガスの通路となることから、非接合部６４を設けることは、安全上有利な構造の電池を構成することにもなる。
【００３０】
なお、多くの接合箇所を設けることにより電流経路が拡大し、電池の内部抵抗を低減でき、電池の出力密度の向上を図ることができる。これと反対に、接合箇所を少なくすることにより集電処理のための作業時間を削減することができる。したがって、接合箇所の数は、これらおよび上記非接合部の割合等を総合的に勘案して決定すればよい。
【００３１】
このように、電極体を構成する巻芯の端部に集電端子としての機能を兼ね備えさせ、この巻芯の端部に未塗工部を接合させて集電処理を行う場合には、別途集電処理のための部品を必要とすることなく、電池自体の重量の増加を抑制することを可能にしている。
〈電池の完成〉
集電処理が完了した電極体は、電池ケースに挿設されて組付けに供される。組付け時には、電極合材およびセパレータに非水電解液を含浸させる。リチウムイオン二次電池の場合、非水電解液は、エチレンカーボネート、ジエチルカーボネート等の有機溶媒にＬｉＢＦ₄、ＬｉＰＦ₆等の電解質を溶解させたものを使用する。含浸終了後、電池ケースに蓋を被せ、この蓋にカシメ等を施して電池ケースを密封し、電池を完成させる。なお本実施形態の電極捲回型電池の場合は、巻芯の端部が入出力端子をも兼ねているため、巻芯の端部を電池ケースより突出させるようにする。
【００３２】
〈電極合材未塗工部の幅について〉
集電処理の作業性、集電処理のためのスペース等を考慮すれば、電極合材未塗工部の幅には望ましい範囲が存在する。本発明の電極捲回型電池がその効果を充分に発揮するのは、放電容量が１Ａｈを超える大型電池である。したがって大型電池における電極合材未塗工部の望ましい幅について以下に説明する。
【００３３】
上記電極体の説明で示した図６を参照すれば、電極体の外径をＤとし、巻芯の外径をｄとした場合に、電極体５０の正極シート１０、負極シート２０およびセパレータ３０とが捲回されて層状をなす部分の最内周と最外周とによって決定される半径方向の厚さ（以下「捲回厚さ」という）Ｔは、一般に、Ｔ＝（Ｄ−ｄ）／２で表される。大型電池の場合は、捲回厚さＴが、５≦Ｔ≦２０の範囲にあるのが通常である。
【００３４】
電極合材未塗工部１３、２３の幅、つまり集電処理のため集電端子との接合により押し潰される部分の幅を、Ｈとすれば、様々な実験を重ねた結果、本発明の電極捲回型電池の集電処理では、Ｈ＞Ｔの範囲で接合可能であることが判った。一方、Ｈ＞４５ｍｍの範囲では電池性能に寄与しない部分が正極側と負極側とを合わせて９０ｍｍを超え、体積実装効率（電池全長に対する電極合材塗工部幅の比）が極めて小さくなる。また、Ｔ≦２０ｍｍ程度の比較的小さい電池では、Ｈ＞１．５Ｔ＋１５ｍｍの領域では体積実装効率がやはり小さくなる。
【００３５】
上記のことを総合して判断すれば、捲回厚さＴ（ｍｍ）、未塗工部幅Ｈ（ｍｍ）とすれば、未塗工部幅Ｈは、Ｔ≧５かつＨ≦４５かつＴ＜Ｈ≦１．５Ｔ＋１５の範囲にあるのが望ましいといえる。巻芯を集電端子とした場合の、この望ましい未塗工部幅の範囲については、図９に示す。
なお、上述した実施形態は、正極側および負極側の両方とも巻芯を集電端子として集電処理を行っているが、これに代え、正極側または負極側のいずれか一方を板端子を用いる方法で集電処理を行うものであってもよい。また、正極側または負極側のいずれか一方について上記のいずれかの集電処理を行い、他方については、従来から実施されている公知の方法によって集電処理を行うものであってもよい。
【００３６】
〈本発明の電極捲回型電池の他の実施形態〉
上記の実施形態は、巻芯の端部を集電端子とした実施形態である。これと異なり、板状の集電端子を巻芯とは別に設け、この板状の端子に集電処理を行う実施形態を採用することもできる。板状端子への集電処理を行った実施形態を図１０に示す。集電端子を別部品とすることによって、軸芯を軽量な樹脂によって形成することができ、電池の軽量化が図れ、電池のエネルギ密度、出力密度を高めることができる。
【００３７】
また、図１０に示すように、板状集電端子９０を電極体５０の正極シート１０、負極シート２０およびセパレータ３０とが捲回されて層状をなす部分の最内周と最外周とのちょうど中間(Ｔ／２の位置）に位置させて、端子９０の両側から電極合材未塗工部１３、２３を接合させれば、未塗工部幅ＨがＨ＞Ｔ／２の範囲で接合させることが可能となる。このことは、未塗工部幅の減少がはかれることとなり、体積実装率の向上につながる。
【００３８】
ちなみに拡大した未塗工幅の望ましい範囲は、Ｔ≧５かつＨ≦４５かつＴ／２＜Ｈ≦１．５Ｔ＋１５となる。板状集電端子を捲回厚さの中心に位置させた場合の、この望ましい未塗工幅の範囲については、図１１に示す。
集電端子を巻芯とは別体の部品とした他の実施形態を、図１２に示す。この場合、集電端子部品４６は中実丸棒状のものであってもよいが、この図に示す様な有底のカップ状のもの、あるいはパイプ状のもの等を採用すれば、図７を用いて説明した方法と同様の方法で超音波接合ができ、また、軽量化を達成することができる。さらに、巻芯は捲回工程で必要となるが、さらなる軽量化を目的とし、捲回後に巻芯を抜き取って無くすという実施形態を採用することもできる。巻芯が無い状態であっても、集電端子と電極合材未塗工部とを接合する際に問題となることはない。
【００３９】
【実施例】
上記実施形態に基づいて、電極捲回型リチウムイオン二次電池を実施例として作製し、また、従来技術に基づく電池を比較例として作製した。そしてこの実施例、比較例の電極捲回型電池に対して、それぞれの構成および集電処理のための工数、エネルギ密度等について比較評価を行った。以下にこの結果を示す。
【００４０】
〈実施例〉
上記実施形態に基づく電極捲回型電池であって、巻芯の端部を集電端子とする集電処理を行った電池を作製した。正極シートは、厚さ１５μｍ、幅１８０ｍｍのアルミニウム箔集電体の両面に、片面あたり１２０μｍの厚さで正極合材を塗工した。正極合材の塗工幅は１６０ｍｍで、正極シートの幅方向の一端部に幅２０ｍｍの正極合材未塗工部を設けた。同様に、負極シートは、厚さ１０μｍ、幅１８４ｍｍの銅箔集電体の両面に、片面あたり６０μｍの厚さで負極合材を塗工した。負極合材の塗工幅は、１６４ｍｍで、負極シートの幅方向の一端部に幅２０ｍｍの負極合材未塗工部を設けた（図１参照）。正極シート、負極シートは、その長さをそれぞれ２１５０ｍｍ、２２５０ｍｍに裁断して使用した。これらの正極シート、負極シートを、捲回して電極体を作製した。巻芯は、正極側部材にアルミニウムを、負極側部材に銅を使用し、ポリフェニレンサルファイドの絶縁部材を挟んで、外径１０ｍｍφの中空のパイプ状に一体として形成されたものを使用した（図３参照）。巻芯全長は約２２４ｍｍで、電極体形成後、電極合材の幅方向の端部より、正極側および負極側にそれぞれ３０ｍｍずつ突出するような長さとなっている。また両端の先端部には約１０ｍｍの長さで雄ネジか形成され、この部分を除く２０ｍｍの部分が集電端子としての機能を果たす部分となっている。
【００４１】
正極シートおよび負極シートに挟装させるセパレータは、厚さ２５μｍのポリエチレンシートで、幅１６６ｍｍのものを使用した。正極シートおよび負極シートを、それぞれの電極合材未塗工部が幅方向で背向しかつ他極シートの電極合材部およびセパレータより突出するように位置させ（図５参照）、捲回機を用いて捲回させた（図４参照）。捲回して形成された電極体（図６参照）の外径は３０ｍｍφとなった。
【００４２】
電極合材未塗工部の接合は、超音波接合によって行った（図７参照）。接合箇所が、それぞれの極で２箇所となるように接合された電極体（図８参照）と、１箇所となるように接合された電極体との、２種類の電極体を作製した。それぞれの電極体を電解液とともに電池ケースに密封し電池を完成させた。接合箇所が各極あたり２箇所のものを実施例１の電極捲回型電池と、１箇所のものを実施例２の電極捲回型電池とした。
【００４３】
〈比較例〉
従来技術の集電処理方法を採用した電極捲回型電池である。正極シートおよび負極シートは、実施例のものと同様の集電体、電極合材を使用している。ただし、正極シートおよび負極シートの幅をそれぞれ１７０ｍｍ、１７４ｍｍとし、電極合材の塗工幅は実施例のものと同じであるが、電極合材未塗工部の幅をそれぞれ１０ｍｍにしているところが実施例のものと異なるところである。そしてこの未塗工部に、厚さ４０μｍ、幅１０ｍｍの短冊状（タブ状）の集電用リードを超音波接合し、この集電用リードを利用して集電処理を行うようにした。集電用リードは、正極シート、負極シートとも、５０ｍｍピッチで約４５本接合した（図１９参照）。なおこの集電用リードの接合は、下記で説明する捲回工程の最中に、正極シートおよび負極シートの捲回の進行に合わせて１本ずつ順次行った。
【００４４】
それぞれの集電用リードが反対側の巻回端面にくるように、正極シート、負極シートをセパレータを挟装させて捲回し、電極体を形成した（図１５参照）。使用したセパレータは、実施例のものと同様のものであり、形成した電極体の外径も実施例のものと同様である。ただし巻芯は、ポリフェニレンサルファイド製の中空状のもので、電極体から突出しない長さのものを使用した。
【００４５】
集電端子には、正極側にはアルミニウム製の、負極側には銅製の、円盤状のフランジ部を有する部品を使用し、この集電端子のフランジ部の外周に、集電用リードを１本ずつ折り曲げることによって集め、その後に１つの端子あたり８箇所の超音波接合を行った（図１８参照）。なお集電処理に要するスペースは実施例の場合と同様２０ｍｍとした。この電極体を電解液とともに電池ケースに密封して、比較例の電極捲回型電池を完成させた。
【００４６】
〈電池の構成、集電処理工数、エネルギ密度等の比較評価〉
実施例１、実施例２、比較例の電極捲回型電池の集電処理の状態を比較して模式的に表した図を、図１３に掲載する。また、正極シートおよび負極シートを中心とした電池の構成を比較した表を下記表１に、電池の集電処理に要する時間、電池のエネルギ密度等を比較した表を下記表２にそれぞれ掲載する。
【００４７】
【表１】

【００４８】
【表２】

図１３および表１、表２から判るように、集電処理方法が異なっても、集電処理に要するスペースは同じであり、電池自体の体積は同じになっている。しかし電池の重量は、比較例の電池が、別部品の集電端子を採用していることから、実施例の電池より３０ｇも重いものとなっている。なお、表２から判るように放電容量および体積実装効率についてはどの電池も同じ値を示している。
【００４９】
集電処理に要する時間は、集電用リードを接合する時間つまり正極シートおよび負極シートを捲回して電極体を形成するのに要する時間と、集電用リードを折り曲げて集電端子に集める作業に要する時間と、超音波接合に要する時間とを合計した時間を合計して比較することによって評価することができる。比較例の電池の場合は、正極側および負極側を合わせて、集電処理に要する時間は電池１個あたり、１２分＋７分×２＋３分×２＝３２分を要した。これに対して実施例１の電池の場合は、２０秒＋３０秒×２＝１分２０秒を要し、実施例２の電池の場合は、２０秒＋１５秒×２＝５０秒を要した。このことから、本発明の電極捲回型電池は、集電処理のために必要な作業工数を著しく少なくできることが確認できた。
【００５０】
接合面積と電流経路の違いから、実施例１、実施例２および比較例の電池は内部抵抗の異なるものとなることが予想された。実際に接合面積の最も大きい比較例の電池が、内部抵抗が小さく、出力特性に優れることが確認されたが、上述したように集電端子をフランジ部を設けた別部品としたことから電池重量が増加し、出力密度では劣ることが確認できた。また同様に、エネルギ密度においても実施例の電池が優るものとなっていることが確認できた。
【００５１】
【発明の効果】
本発明の電極捲回型電池は、正極シート、負極シートに電極合材未塗工部を設け、この未塗工部に集電用リードを設けることなく、直接この未塗工部を集電端子に接合させるという構成を採っている。この様な構成にしたことにより、本発明の電極捲回型電池を製造する場合は、集電用リードを設ける工程および集電用リードを折り曲げて集める工程を必要とせず、電極捲回型電池の生産性の向上および製造コストの低減を図ることが可能となる。
【００５２】
また本発明の電極捲回型電池では、集電端子として重量の大きな部品を必要とすることがなく、電池自体の重量の軽減を図ることが可能となる。この結果、本発明の電極捲回型電池は、出力密度およびエネルギ密度の高い優秀な電池となる。
【図面の簡単な説明】
【図１】本発明の実施形態の電極捲回型電池を構成する正極シートおよび負極シートを示す平面図
【図２】本発明の実施形態の電極捲回型電池において、集電体表面に電極合材を塗布する塗布装置を示す斜視図
【図３】本発明の実施形態の電極捲回型電池を構成する巻芯を示す斜視図
【図４】本発明の実施形態の電極捲回型電池において、正極シート、負極シートおよびセパレータを捲回する様子を示す斜視図
【図５】本発明の実施形態の電極捲回型電池において、正極シート、負極シートおよびセパレータを重ね合わせた様子を示す断面図
【図６】本発明の実施形態の電極捲回型電池において、正極シート、負極シートおよびセパレータを捲回して形成された電極体を示す斜視図
【図７】本発明の実施形態の電極捲回型電池において、超音波接合によって電極合材未塗工部を巻芯に接合する様子を示す図
【図８】本発明の実施形態の電極捲回型電池において、正極側、負極側それぞれ２箇所の超音波接合を行った後の電極体を示す斜視図
【図９】本発明の実施形態の電極捲回型電池において、望ましい電極合材未塗工部幅の範囲を示す図
【図１０】本発明のもう一つの実施形態の電極捲回型電池であって、板状の集電端子に接合して集電処理を行った電極捲回型電池の電極体を示す斜視図
【図１１】板状端子に集電処理を行った本発明のもう一つの実施形態において、望ましい電極合材未塗工部幅の範囲を示す図
【図１２】本発明の実施形態の電極捲回型電池において、巻芯および巻芯とは別体の集電端子を示す斜視図
【図１３】実施例１、実施例２、比較例のそれぞれの電極捲回型電池の集電処理の状態を模式的に表した図
【図１４】従来の電極捲回型電池において、集電用リードが切り欠きによって形成された正極シートおよび負極シートを示す平面図
【図１５】従来の電極捲回型電池において、正極シート、負極シートおよびセパレータを捲回する様子を示す斜視図
【図１６】従来の電極捲回型電池において、正極シート、負極シートおよびセパレータを捲回して形成された電極体を示す斜視図
【図１７】従来の電極捲回型電池において、レーザー溶接によって集電処理された電極体を示す斜視図
【図１８】従来の電極捲回型電池において、超音波接合によって集電処理された電極体を示す斜視図
【図１９】従来の電極捲回型電池において、集電用リードが超音波接合によって形成された正極シートおよび負極シートを示す平面図
【符号の説明】
１０：正極シート
１１：正極集電体１２：正極合材
１３：正極合材未塗工部
１４：正極集電用リード１５：リード接合部
２０：負極シート
２１：負極集電体２２：負極合材
２３：負極合材未塗工部
２４：負極集電用リード２５：リード接合部
３０：セパレータ
４０：巻芯
４１：正極側部材４２：負極側部材
４３：絶縁部材４４：雄ネジ部
４６：集電端子部品
５０：電極体
６０：超音波接合機
６１：ホーン６２：アンビル６３：接合部
６４：非接合部
７０：塗布装置
７１：バックアップロール７２：塗布ロール
７３：コンマロール７４：堰
８０
８１：集電端子部品８２：リング
８３：レーザ光線８４：溶接ビード
８５：超音波接合部
９０：板状集電端子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode winding type battery formed by winding a sheet-like positive electrode and a negative electrode, and more particularly to an electrode winding type battery that is easy to collect current and has high output density and energy density.
[0002]
[Prior art]
Cylindrical batteries such as lithium ion secondary batteries form a sheet-like electrode by applying an electrode mixture containing an active material on the surface of a strip-shaped metal foil current collector, and this electrode is inserted through a thin film separator. In general, an electrode body is formed by winding in a spiral shape, and this electrode body is housed in a cylindrical case together with an electrolytic solution. In such an electrode winding type battery, the current collecting method from the electrode body to the terminal leading to the outside is usually performed by a plurality of strip-shaped current collecting leads provided on the current collector.
[0003]
The development of electric vehicles is urgently caused by environmental problems and resource issues, and there is a trend to adopt lithium ion secondary batteries and the like for electric vehicles. The increase in the size of these electrode winding type batteries requires uniform current collection from the entire electrode, leading to a more complicated current collection method, and the development of an efficient current collection method. Was desired.
Conventionally, as a method of collecting current of a large electrode winding type battery, there are those shown in JP-A-9-92335, JP-A-9-92338 and the like. The method of current collection processing shown in these is as follows. First, an electrode mixture is applied on the surface of the strip-shaped current collector so that an uncoated part is left at one end in the width direction, and a current collecting lead is formed by cutting out the uncoated part. A sheet-like electrode is prepared (see FIG. 14). Next, these electrodes are positioned so that the current collecting leads face each other, a separator is sandwiched between them, and these are wound to form an electrode body (see FIGS. 15 and 16). Then, the current collecting leads protruding from the winding end face of the electrode body are collected on the outer periphery of the flange portion of the current collecting terminal disposed on the winding end face of the electrode body, and this is pressed using a ring and laser welded ( 17), or a method of performing ultrasonic bonding at several points so as to press the collected current collecting leads against the outer periphery of the flange (see FIG. 18).
[0004]
As for the formation of the current collecting lead, in addition to the above-described notch, a method of forming a strip-shaped metal foil on an uncoated part by means of ultrasonic joining, resistance welding or the like is also used. (See FIG. 19).
[0005]
[Problems to be solved by the invention]
However, the conventional method has the following drawbacks.
(1) After coating the electrode mixture, a plurality of current collecting leads must be formed by cutting the uncoated part into a strip or joining a strip of metal foil to the uncoated part. However, this process requires a lot of man-hours and increases the manufacturing cost of the battery.
[0006]
(2) When laser welding is performed using a ring, a process of pressing with the ring is required, and a process of trimming the current collecting leads protruding from the ring and the flange part is necessary for laser welding, which is also a manufacturing cost. Leads to an increase in Further, spatter is generated in laser welding, and this spatter may enter the electrode body and cause a short circuit between the electrodes.
[0007]
(3) In the case of ultrasonic bonding, since a holding metal fitting such as a ring is not used, the current collecting leads gathered in pieces tend to return to the original state by springback. However, the workability is very poor, and it still requires a lot of man-hours and increases the manufacturing cost.
(4) In either method of laser welding or ultrasonic bonding, since a disk-shaped current collecting terminal having a large flange portion is required, the weight of the current collecting terminal is large and the weight of the battery itself is also increased. Therefore, the output density and energy density, which are important characteristics of the battery, are reduced.
[0008]
The present invention has been made in view of the above-described actual situation of a conventional current collecting treatment method for an electrode wound battery, and does not require a large number of man-hours for the current collecting treatment, and requires a heavy weight terminal component. An object of the present invention is to provide an electrode-wound battery that is low in cost and high in output density and energy density.
[0009]
[Means for Solving the Problems]
  To solve the above problems,Claim 1The electrode-wound battery of this type is sandwiched between a positive electrode sheet and a negative electrode sheet each having a strip-shaped metal foil current collector and a respective electrode mixture coated on the surface thereof, and the positive electrode sheet and the negative electrode sheet. An electrode winding type battery having an electrode body formed by winding a mounted separator in a spiral around the core, wherein at least one of the positive electrode sheet and the negative electrode sheet is continuous in the width direction. And is formed integrally with one end in the width direction.Is H (mm)The electrode mixture uncoated portion over the entire length, and the electrode mixture uncoated portion is wound so as to protrude from the other of the separator and the positive electrode sheet and the negative electrode sheet,
  The end of the core serves as a current collecting terminal, and the uncoated portion of the electrode mixture is joined to a joint joined so as to overlap the end of the core and the end of the core. Are joined to form a non-joined part, and further, the positive electrode sheet, the negative electrode sheet, and the separator of the electrode body are determined by the innermost circumference and the outermost circumference of the layered portion. When the thickness in the radial direction is T (mm), H and T have a relationship represented by the following formula.
        T ≧ 5 and H ≦ 45
  And T <H ≦ 1.5T + 15
  Further, the electrode wound type battery of claim 2 has the same configuration as the electrode wound type battery of claim 1 except for the current collecting terminal, but the current collecting terminal is coupled to the end of the core or the The core is a separate part physically separated, and the uncoated part of the electrode mixture is joined to the current collector terminal and the current collector terminal. It is characterized by being joined so as to form a non-joined part.
[0010]
  In other words, the electrode wound battery of the present invention is provided with a cut in an uncoated part where the electrode mixture is not coated, or a notch is formed on the uncoated part or a strip-shaped part is joined to the uncoated part. In this way, the number of man-hours required for the current collection process can be greatly reduced by joining the uncoated parts so as to overlap the current collection terminals without applying any special means such as forming a current collection lead. It is possible to do. Furthermore, the electrode winding of the present inventionType electricThe pond does not require a relatively heavy current collecting terminal part such as a conventional flange, and can reduce the battery weight.Furthermore, since a desirable range is provided from the experimental results for the values of the width H (mm) of the electrode mixture uncoated portion and the wound thickness T (mm) of the electrode, based on the values.The output density and energy density of the batterycertainlyCan be increased.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an electrode winding type battery and a method for manufacturing the same according to the present invention, in which the core of the electrode body is a current collecting terminal, a lithium ion secondary battery is taken as an example, and the drawings are also referred to However, this will be described in detail. The electrode wound battery of the present invention is not limited to a lithium ion secondary battery, but can be applied to all batteries configured by winding an electrode formed by coating an electrode mixture on the surface of a current collector. Applicable.
[0012]
<Formation of positive electrode sheet and negative electrode sheet and electrode mixture uncoated portion>
In FIG. 1, the top view of the positive electrode sheet and negative electrode sheet which comprise the electrode winding type battery of this invention is represented. The positive electrode sheet 10 is composed of a positive electrode current collector 11 made of a strip-shaped metal foil and a positive electrode mixture 12 coated on the surface thereof, and the negative electrode sheet 20 is coated on the negative electrode current collector 21 made of a strip-shaped metal foil and the surface thereof. It consists of the processed negative electrode composite material 22. About the length and the width | variety of the positive electrode sheet 10 and the negative electrode sheet 20, it can be made into arbitrary things according to the capacity | capacitance etc. of the battery to produce.
[0013]
Both the positive electrode sheet 10 and the negative electrode sheet 20 are integrally formed continuously in the width direction, and the positive electrode mixture uncoated portion 13 and the negative electrode mixture uncoated portion 23 are formed at one end in the width direction over the entire length with a predetermined width. Are provided. The widths of the

uncoated portions

13 and 23 will be described in detail later, and will not be described here. The

electrode composites

12 and 22 may be applied to one side of the

current collectors

11 and 21, or may be applied to both sides of the

current collectors

11 and 21. However, in consideration of the energy density of the battery, it is desirable to apply on both surfaces. In that case, the

uncoated portions

13 and 23 are provided on both surfaces, and the

uncoated portions

13 and 23 on both surfaces are the same end in the width direction. Must be located in the section.
[0014]
In the case of a lithium ion secondary battery, it is desirable to use a metal foil such as aluminum having a thickness of about 10 to 20 μm as the positive electrode current collector 11. The positive electrode mixture 12 applied to the positive electrode current collector 11 is obtained by mixing a conductive material such as graphite and a binder such as polyvinylidene fluoride into an active material made of lithium composite oxide powder or the like, and adding n-methylpyrrolidone. It is preferable to use a paste in which a suitable amount of a solvent is added and is in the form of a paste before coating. As the negative electrode current collector 21, it is desirable to use a metal foil such as copper having a thickness of about 5 to 20 μm. The negative electrode mixture 22 applied to the negative electrode current collector 21 is a mixture of an active material made of carbon material powder such as graphite and a binder such as polyvinylidene fluoride, and an appropriate amount of a solvent such as n-methylpyrrolidone. In addition, like the positive electrode mixture 12, it is preferable to use a paste-like material before coating.
[0015]
The step of forming the electrode mixture

uncoated portions

13 and 23 on the positive electrode sheet 10 and the negative electrode sheet 20, that is, the electrodes on the surfaces of the

current collectors

11 and 21 so as to provide the electrode mixture

uncoated portions

13 and 23. The process of applying the

composite materials

12 and 22 can be performed by various methods, but it is preferable to perform using a coating machine called a coater capable of continuous application and drying. FIG. 2 is a diagram conceptually showing an example of a coater coating apparatus.
[0016]
The coating device 70 shown in this figure is of a reverse roll type, and is constituted by three rolls of a backup roll 71, a coating roll 72, and a comma roll 73, and an electrode mixture stored in the weir 74 is When the

current collectors

11 and 21 pass between the backup roll 71 and the coating roll 72 when the

electrode composites

12 and 22 on the coating roll 72 are measured by the comma roll 73 and supplied to the coating roll 72. This is a method of transferring to the

current collectors

11 and 21. There is an advantage that a uniform coating thickness can be obtained with little influence of the viscosity of the electrode mixture.
[0017]
The width to which the electrode mixture is applied can be determined by the width of the weir 74, and the positions of the electrode mixture

uncoated portions

13, 23 depending on the width of the

current collectors

11, 21 and the position through which the

current collectors

11, 12 pass. And width can be adjusted. In the case of this embodiment, the electrode mixture

uncoated portions

13 and 23 are provided only on one end of the

electrode sheets

10 and 20, but the other end in the width direction is taken into consideration when sagging of the electrode mixture at the time of application. An uncoated part having a slight width may be provided in the part. The coating thickness of the

electrode composites

12 and 22 is preferably about 50 to 250 μm. In the case of a lithium ion secondary battery, it is desirable that the negative electrode mixture 22 be applied in a slightly larger amount than the positive electrode mixture 12 in consideration of precipitation of dendrites and the like.
[0018]
Thus, the

current collectors

11 and 21 coated with the

electrode mixture

12 and 22 are moved to a drying furnace continuous with the coating apparatus 70, and the solvent contained in the

electrode mixture

12 and 22 is dried. Transpiration. A continuous furnace is used as the drying furnace, and drying is performed while the current collector coated with the

electrode composites

12 and 22 moves in the furnace. As the drying method, various methods such as a hot air method and an infrared method can be adopted.
[0019]
Through such a process, the positive electrode sheet 10 and the negative electrode sheet 20 are formed. In addition, you may perform a roll press etc. in order to raise the density of the

electrode compound materials

12 and 22 as needed after completion of drying. Moreover, what is necessary is just to repeat the process mentioned above twice, when applying the

electrode compound materials

12 and 22 on both surfaces of the

electrical power collectors

11 and 21. FIG.
<Formation of electrode body>
The positive electrode sheet and the negative electrode sheet that are formed after the application of the electrode mixture is sandwiched between the separators, and wound in a roll shape around the core to form an electrode body. The separator physically separates the positive electrode sheet and the negative electrode sheet and holds the electrolytic solution, and it is preferable to use a microporous film such as polyethylene having a thickness of about 20 to 40 μm. Note that the width of the separator is preferably slightly wider than the coating width of the positive electrode mixture and the negative electrode mixture in order to ensure insulation.
[0020]
The core can be made of a material such as resin or metal. However, in the case of this embodiment, since both ends serve as current collecting terminals, both ends of the core are the same as the positive electrode current collector and the negative electrode current collector. It is desirable to be formed from a material. A winding core used in this embodiment is shown in FIG. As shown in FIG. 3, a metal such as aluminum is used for the positive electrode side member 41 and a metal such as copper is used for the negative electrode side member 42, and the positive electrode side member 41 and the negative electrode side member 42 are insulated from each other. For this purpose, an insulating member 43 made of resin or the like is interposed, and the positive electrode side member 41, the negative electrode side member 42, and the insulating member 43 are combined and formed integrally.
[0021]
In the case of this embodiment, the core 40 has a positive electrode side member 41, a negative electrode side member 42, and an insulating member 43 that are formed hollow. The purpose of this is to reduce the weight of the core 40 itself and to dissipate the heat inside the electrode body generated by charging and discharging of the battery to the outside. Therefore, when such consideration is not required, it is not necessary to make it hollow, and it may be a round bar.
[0022]
Since the length of the core 40 is bonded to the both ends of the electrode sheet uncoated portions of the positive electrode sheet and the negative electrode sheet, at least the length of the both ends is required to protrude from the end in the width direction of the separator. It becomes. In the case of the core 40 of the present embodiment, male screws 44 are formed at both ends of the positive electrode side member 41 and the negative electrode side member 42 in order to also serve as an input / output terminal. Depending on the connection method, the end portions of the positive electrode side member 41 and the negative electrode side member 42 can be formed in various shapes.
[0023]
Next, FIG. 4 shows a state in which the positive electrode sheet, the negative electrode sheet, and the separator are wound around the core. FIG. 5 is a cross-sectional view showing a state in which the positive electrode sheet, the negative electrode sheet, and the separator are overlapped. As shown in these figures, four sheets of the separator 30, the negative electrode sheet 20, the separator 30, and the positive electrode sheet 10 are wound in layers. At this time, the positive electrode mixture uncoated portion 13 of the positive electrode sheet 10 and the negative electrode mixture uncoated portion 23 of the negative electrode sheet 20 face each other in the width direction, and the positive electrode mixture uncoated portion 13 is the separator 30 and The negative electrode sheet 20 is overlaid so that the negative electrode mixture uncoated portion 23 protrudes from the separator 30 and the positive electrode sheet 10.
[0024]
The winding is performed using a winding machine so that tension is applied in the longitudinal direction to each of the positive electrode sheet 10, the negative electrode sheet 20, and the two separators 30 so as not to loosen. At the beginning, the separator 30, the negative electrode sheet 20, the separator 30, the positive electrode sheet 10, the separator 30... Are arranged in this order, and at the end, the separator 30, the positive electrode sheet 10, the separator 30, the negative electrode The sheet 20 and the separator 30 are arranged in this order.
[0025]
What is wound in this way becomes a roll-shaped (spiral) electrode body. The formed electrode body is shown in FIG. As shown in this figure, the electrode body 50 has a positive electrode mixture uncoated portion 13 and a negative electrode mixture uncoated portion 23 that are wound from a portion where the positive electrode mixture and the negative electrode mixture are overlapped and wound. It looks like it protrudes on both sides in the rotation axis direction. The positive electrode mixture uncoated portion 13 is positioned around the positive electrode side member 41 of the core 40, and the negative electrode mixture uncoated portion 23 is positioned around the negative electrode side member 42 of the core 40. Yes.
[0026]
<Current collection processing>
The current collecting process from the electrode sheet to the current collecting terminal is performed by joining the uncoated portions of the positive electrode sheet and the negative electrode sheet so as to overlap the current collecting terminal. In the case of this embodiment, since the end portion of the core also serves as a current collecting terminal, the positive electrode mixture uncoated portion of the positive electrode sheet is connected to the positive electrode side member of the core described above, and the negative electrode sheet This is performed by joining the negative electrode mixture uncoated portion to the negative electrode side member.
[0027]
The joining method can be performed by various means such as ultrasonic joining, resistance welding, laser welding, and caulking. In consideration of the thermal effect on the electrode mixture, sputtering, current-carrying resistance at the joint, workability, etc., it is desirable to perform ultrasonic bonding. As an example of the joining method, FIG. 7 shows a state where the electrode mixture uncoated portion is joined to the core by ultrasonic joining.
[0028]
As shown in FIG. 7, the ultrasonic bonding machine 60 includes an anvil 62 serving as a cradle and a horn 61 that transmits ultrasonic vibrations to the bonding portion. In the case of this embodiment, since the core 40 is formed in the hollow, the anvil 62 which can be inserted in the hollow part of the core 40 is used. Then, the anvil 62 is inserted into the hollow portion of the core 40 to set the electrode body 50, the horn 61 is brought into contact with the outermost periphery of the electrode mixture

uncoated portions

13 and 23, and urged toward the core 40. Then, the electrode mixture

uncoated portions

13 and 23 are sandwiched between the core 40 and the horn 61 so as to overlap each other, and ultrasonic vibration is transmitted from the horn 61 to perform bonding.
[0029]
FIG. 8 shows the electrode body after bonding at two locations on the positive electrode side and the negative electrode side. The joining can be performed at one place or a plurality of places around the core 40. At this time, the joining part 63 joined to the end part (positive electrode side member 41 or negative electrode side member 42) of the winding core 40 and the non-joining part 64 not joined to the end part of the winding core 40 are formed. It is desirable to do. Unlike joining over the entire circumference of the core 40, the presence of the non-joined portion 64 allows the electrolyte to be injected into every corner of the electrode mixture in the subsequent step of impregnating the electrolyte during assembly. Will have advantages. In addition, even when an abnormality occurs in the battery and the electrolytic solution is gasified, the non-joining portion 64 becomes a gas passage inside the electrode body 50. This also constitutes a battery having an advantageous structure.
[0030]
In addition, by providing many joint locations, the current path can be expanded, the internal resistance of the battery can be reduced, and the output density of the battery can be improved. On the other hand, the work time for the current collection process can be reduced by reducing the number of joints. Accordingly, the number of joints may be determined by comprehensively considering these and the ratio of the non-joint part.
[0031]
In this way, if the end of the core constituting the electrode body also has a function as a current collector terminal, and the uncoated portion is joined to the end of this core to perform current collection processing, This makes it possible to suppress an increase in the weight of the battery itself without requiring parts for current collection processing.
<Completion of battery>
The electrode body that has completed the current collection process is inserted into the battery case and used for assembly. At the time of assembly, the electrode mixture and the separator are impregnated with a non-aqueous electrolyte. In the case of a lithium ion secondary battery, the non-aqueous electrolyte is LiBF in an organic solvent such as ethylene carbonate or diethyl carbonate._Four, LiPF₆A solution in which an electrolyte such as the above is dissolved is used. After the impregnation, the battery case is covered with a lid, and the lid is caulked to seal the battery case to complete the battery. In the case of the electrode wound battery of the present embodiment, since the end of the core also serves as an input / output terminal, the end of the core is projected from the battery case.
[0032]
<About the width of the uncoated electrode mixture>
Considering the workability of the current collection process, the space for the current collection process, and the like, there is a desirable range for the width of the electrode mixture uncoated portion. The electrode winding type battery of the present invention sufficiently exhibits its effect in a large battery having a discharge capacity exceeding 1 Ah. Therefore, the desirable width of the electrode mixture uncoated portion in the large battery will be described below.
[0033]
Referring to FIG. 6 shown in the description of the electrode body, when the outer diameter of the electrode body is D and the outer diameter of the core is d, the positive electrode sheet 10, the negative electrode sheet 20, and the separator 30 of the electrode body 50. In general, the radial thickness T (hereinafter referred to as “winding thickness”) T determined by the innermost circumference and the outermost circumference of the portion that is wound and forms a layer is generally T = (D−d) / It is represented by 2. In the case of a large battery, the wound thickness T is usually in the range of 5 ≦ T ≦ 20.
[0034]
Assuming that the width of the electrode mixture

uncoated portions

13 and 23, that is, the width of the portion to be crushed by the junction with the current collector terminal for current collection processing, is H, the results of various experiments were repeated. It was found that the current collecting treatment of the electrode wound battery can be joined in the range of H> T. On the other hand, in the range of H> 45 mm, the portion not contributing to the battery performance exceeds 90 mm in total on the positive electrode side and the negative electrode side, and the volume mounting efficiency (ratio of the electrode mixture coating portion width to the total battery length) becomes extremely small. In addition, in a relatively small battery of T ≦ 20 mm, the volume mounting efficiency is still small in the region of H> 1.5T + 15 mm.
[0035]
Judging from the above overall, if the winding thickness is T (mm) and the uncoated part width H (mm), the uncoated part width H is T ≧ 5 and H ≦ 45 and T It can be said that it is desirable to be in the range of <H ≦ 1.5T + 15. FIG. 9 shows a preferable range of the uncoated portion width when the winding core is a current collecting terminal.
In the above-described embodiment, both the positive electrode side and the negative electrode side perform the current collecting process using the winding core as a current collecting terminal, but instead of this, a plate terminal is used for either the positive electrode side or the negative electrode side. The current collecting process may be performed by a method. Further, any one of the above-described current collecting processes may be performed on either the positive electrode side or the negative electrode side, and the other current collecting process may be performed by a known method that has been conventionally performed.
[0036]
<Another embodiment of the electrode wound battery of the present invention>
The above-described embodiment is an embodiment in which the end portion of the core is a current collecting terminal. Unlike this, it is also possible to employ an embodiment in which a plate-like current collecting terminal is provided separately from the core and current collecting processing is performed on this plate-like terminal. FIG. 10 shows an embodiment in which current collection processing is performed on a plate-like terminal. By using the current collecting terminal as a separate part, the shaft core can be formed of a light resin, the battery can be reduced in weight, and the energy density and output density of the battery can be increased.
[0037]
Further, as shown in FIG. 10, the plate-like current collecting terminal 90 is just the innermost circumference and the outermost circumference of the portion where the positive electrode sheet 10, the negative electrode sheet 20 and the separator 30 of the electrode body 50 are wound to form a layer. If the electrode mixture

uncoated parts

13 and 23 are joined from both sides of the terminal 90 in the middle (position T / 2), the uncoated part width H is joined in the range of H> T / 2. It becomes possible to make it. This reduces the uncoated portion width and leads to an improvement in volume mounting rate.
[0038]
By the way, the desired range of the uncoated width is as follows: T ≧ 5 and H ≦ 45 and T / 2 <H ≦ 1.5T + 15. FIG. 11 shows this desirable uncoated width range when the plate-like current collecting terminal is positioned at the center of the wound thickness.
FIG. 12 shows another embodiment in which the current collecting terminal is a separate part from the winding core. In this case, the current collecting terminal component 46 may be in the shape of a solid round bar, but if a bottomed cup shape or a pipe shape as shown in FIG. Ultrasonic bonding can be performed by the same method as described above, and weight reduction can be achieved. Furthermore, although the winding core is required in the winding process, an embodiment in which the winding core is removed after winding for the purpose of further weight reduction can be adopted. Even when there is no core, there is no problem when the current collector terminal and the electrode mixture uncoated portion are joined.
[0039]
【Example】
Based on the above embodiment, an electrode wound lithium ion secondary battery was produced as an example, and a battery based on the prior art was produced as a comparative example. And comparative evaluation was performed about each structure, the man-hour for an electrical power collection process, energy density, etc. with respect to the electrode winding type battery of this Example and the comparative example. The results are shown below.
[0040]
<Example>
A battery that is an electrode winding type battery based on the above-described embodiment and that has been subjected to current collection processing using the end of the core as a current collecting terminal was produced. In the positive electrode sheet, a positive electrode mixture was applied to both surfaces of an aluminum foil current collector having a thickness of 15 μm and a width of 180 mm with a thickness of 120 μm per side. The coating width of the positive electrode mixture was 160 mm, and a positive electrode mixture uncoated portion having a width of 20 mm was provided at one end in the width direction of the positive electrode sheet. Similarly, the negative electrode sheet was coated with a negative electrode mixture with a thickness of 60 μm per side on both sides of a copper foil current collector having a thickness of 10 μm and a width of 184 mm. The coating width of the negative electrode mixture was 164 mm, and a negative electrode mixture uncoated portion having a width of 20 mm was provided at one end in the width direction of the negative electrode sheet (see FIG. 1). The positive electrode sheet and the negative electrode sheet were cut into lengths of 2150 mm and 2250 mm, respectively. These positive electrode sheet and negative electrode sheet were wound to produce an electrode body. The core used was a single-piece hollow pipe with an outer diameter of 10 mmφ, using aluminum for the positive electrode side member, copper for the negative electrode side member, and sandwiching a polyphenylene sulfide insulating member (FIG. 3). reference). The total length of the core is about 224 mm, and the length is such that, after the electrode body is formed, 30 mm each protrudes from the end in the width direction of the electrode mixture to the positive electrode side and the negative electrode side. Further, a male screw is formed with a length of about 10 mm at the tip of both ends, and a portion of 20 mm excluding this portion serves as a current collecting terminal.
[0041]
The separator sandwiched between the positive electrode sheet and the negative electrode sheet was a polyethylene sheet having a thickness of 25 μm and a width of 166 mm. The positive electrode sheet and the negative electrode sheet are positioned so that the respective electrode mixture uncoated portions face back in the width direction and protrude from the electrode mixture portion and the separator of the other electrode sheet (see FIG. 5). (See FIG. 4). The outer diameter of the electrode body (see FIG. 6) formed by winding was 30 mmφ.
[0042]
Bonding of the electrode mixture uncoated portion was performed by ultrasonic bonding (see FIG. 7). Two types of electrode bodies were produced: an electrode body (see FIG. 8) that was joined so that there were two places at each pole, and an electrode body that was joined so as to be one place. Each electrode body was sealed together with the electrolyte in a battery case to complete the battery. The electrode winding type battery of Example 1 was used as the electrode winding type battery of Example 1, and the electrode winding type battery of Example 2 was used as the one having two bonding points for each electrode.
[0043]
<Comparative example>
It is an electrode winding type battery that employs a conventional current collecting method. The positive electrode sheet and the negative electrode sheet use the same current collector and electrode mixture as in the examples. However, the widths of the positive electrode sheet and the negative electrode sheet are 170 mm and 174 mm, respectively, and the coating width of the electrode mixture is the same as that of the example, but the width of the uncoated portion of the electrode mixture is 10 mm. This is different from the embodiment. Then, a strip-shaped (tab-shaped) current collecting lead having a thickness of 40 μm and a width of 10 mm was ultrasonically bonded to the uncoated portion, and current collecting processing was performed using the current collecting lead. About 45 current collecting leads were bonded to each of the positive electrode sheet and the negative electrode sheet at a pitch of 50 mm (see FIG. 19). The current collecting leads were sequentially joined one by one in accordance with the progress of winding of the positive electrode sheet and the negative electrode sheet during the winding process described below.
[0044]
A positive electrode sheet and a negative electrode sheet were wound with a separator interposed therebetween so that each current collecting lead came to the opposite winding end face, thereby forming an electrode body (see FIG. 15). The separator used was the same as in the example, and the outer diameter of the formed electrode body was the same as in the example. However, the winding core was a hollow body made of polyphenylene sulfide and had a length that did not protrude from the electrode body.
[0045]
The current collecting terminal is made of aluminum on the positive electrode side and made of copper on the negative electrode side, and has a disk-shaped flange portion. A current collecting lead is attached to the outer periphery of the flange portion of the current collecting terminal. They were collected by bending them one by one, and thereafter, ultrasonic bonding was performed at 8 locations per terminal (see FIG. 18). The space required for the current collection process was set to 20 mm as in the example. This electrode body was sealed in a battery case together with an electrolytic solution to complete a comparative electrode wound battery.
[0046]
<Comparison evaluation of battery configuration, current collection man-hours, energy density, etc.>
FIG. 13 shows a diagram schematically showing a comparison of the state of current collection processing of the electrode winding type batteries of Example 1, Example 2, and Comparative Example. In addition, a table comparing the configurations of the batteries centering on the positive electrode sheet and the negative electrode sheet is shown in Table 1 below, and a table comparing the time required for the current collecting process of the battery, the energy density of the battery, etc. is shown in Table 2 below. .
[0047]
[Table 1]

[0048]
[Table 2]

As can be seen from FIG. 13 and Tables 1 and 2, even if the current collection processing method is different, the space required for the current collection processing is the same, and the volume of the battery itself is the same. However, the weight of the battery is 30 g heavier than the battery of the example because the battery of the comparative example employs a separate current collecting terminal. As can be seen from Table 2, all batteries have the same values for discharge capacity and volume mounting efficiency.
[0049]
The time required for the current collecting process is the time for joining the current collecting leads, that is, the time required for winding the positive electrode sheet and the negative electrode sheet to form the electrode body, and the work for folding the current collecting leads and collecting them on the current collecting terminals. It is possible to evaluate by totaling and comparing the time required for the ultrasonic bonding and the time required for ultrasonic bonding. In the case of the battery of the comparative example, the time required for the current collection process for the positive electrode side and the negative electrode side was 12 minutes + 7 minutes × 2 + 3 minutes × 2 = 32 minutes per battery. On the other hand, in the case of the battery of Example 1, 20 seconds + 30 seconds × 2 = 1 minute 20 seconds were required, and in the case of the battery of Example 2, 20 seconds + 15 seconds × 2 = 50 seconds were required. From this, it has been confirmed that the electrode wound battery of the present invention can significantly reduce the number of work steps required for the current collecting treatment.
[0050]
From the difference in junction area and current path, the batteries of Example 1, Example 2 and Comparative Example were expected to have different internal resistances. It was confirmed that the battery of the comparative example having the largest bonding area actually has low internal resistance and excellent output characteristics. However, as described above, the current collecting terminal is a separate part provided with a flange portion, so the battery weight It was confirmed that the output density was inferior. Similarly, it was confirmed that the battery of the example was superior in energy density.
[0051]
【The invention's effect】
In the electrode wound battery of the present invention, an electrode mixture uncoated portion is provided on the positive electrode sheet and the negative electrode sheet, and the uncoated portion is directly collected without providing a current collecting lead on the uncoated portion. It is configured to be joined to the terminal. With this configuration, when the electrode wound battery of the present invention is manufactured, there is no need for a process of providing a current collecting lead and a process of folding and collecting the current collecting lead. It is possible to improve productivity and reduce manufacturing costs.
[0052]
In the electrode wound battery of the present invention, a heavy component is not required as a current collecting terminal, and the weight of the battery itself can be reduced. As a result, the electrode wound battery of the present invention is an excellent battery having high output density and energy density.
[Brief description of the drawings]
FIG. 1 is a plan view showing a positive electrode sheet and a negative electrode sheet constituting an electrode wound battery according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a coating apparatus for coating an electrode mixture on the surface of a current collector in an electrode wound battery according to an embodiment of the present invention.
FIG. 3 is a perspective view showing a winding core constituting the electrode wound battery according to the embodiment of the invention.
FIG. 4 is a perspective view showing a state in which a positive electrode sheet, a negative electrode sheet, and a separator are wound in an electrode wound battery according to an embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a state in which a positive electrode sheet, a negative electrode sheet, and a separator are overlaid in an electrode wound battery according to an embodiment of the present invention.
FIG. 6 is a perspective view showing an electrode body formed by winding a positive electrode sheet, a negative electrode sheet, and a separator in an electrode wound battery according to an embodiment of the present invention.
FIG. 7 is a view showing a state in which an electrode mixture uncoated portion is bonded to a core by ultrasonic bonding in the electrode wound battery according to the embodiment of the present invention.
FIG. 8 is a perspective view showing the electrode body after performing ultrasonic bonding at two locations on the positive electrode side and the negative electrode side in the electrode wound battery according to the embodiment of the present invention.
FIG. 9 is a view showing a preferable range of the uncoated portion width of the electrode mixture in the electrode wound battery according to the embodiment of the present invention.
FIG. 10 is a perspective view showing an electrode body of an electrode wound battery according to another embodiment of the present invention, the electrode wound battery being joined to a plate-like current collecting terminal and subjected to a current collecting process.
FIG. 11 is a diagram showing a preferable range of the uncoated portion width of the electrode mixture in another embodiment of the present invention in which a current collecting process is performed on a plate-shaped terminal;
FIG. 12 is a perspective view showing a winding core and a current collecting terminal separate from the winding core in the electrode wound battery according to the embodiment of the present invention.
FIG. 13 is a diagram schematically illustrating a state of current collection processing of each of the electrode winding type batteries of Example 1, Example 2, and Comparative Example.
FIG. 14 is a plan view showing a positive electrode sheet and a negative electrode sheet in which current collecting leads are formed by notches in a conventional electrode wound battery;
FIG. 15 is a perspective view showing a state in which a positive electrode sheet, a negative electrode sheet, and a separator are wound in a conventional electrode wound battery.
FIG. 16 is a perspective view showing an electrode body formed by winding a positive electrode sheet, a negative electrode sheet, and a separator in a conventional electrode winding type battery.
FIG. 17 is a perspective view showing an electrode body collected by laser welding in a conventional electrode winding type battery.
FIG. 18 is a perspective view showing an electrode body that is collected by ultrasonic bonding in a conventional electrode winding type battery.
FIG. 19 is a plan view showing a positive electrode sheet and a negative electrode sheet in which current collecting leads are formed by ultrasonic bonding in a conventional electrode wound type battery.
[Explanation of symbols]
10: Positive electrode sheet
11: Positive electrode current collector 12: Positive electrode mixture
13: Positive electrode mixture uncoated part
14: Lead for collecting positive electrode 15: Lead joint
20: Negative electrode sheet
21: Negative electrode current collector 22: Negative electrode mixture
23: Negative electrode composite uncoated part
24: Negative electrode current collecting lead 25: Lead joint
30: Separator
40: winding core
41: Positive electrode side member 42: Negative electrode side member
43: Insulating member 44: Male thread
46: Current collecting terminal parts
50: Electrode body
60: Ultrasonic bonding machine
61: Horn 62: Anvil 63: Joint
64: Non-joined part
70: Coating device
71: Backup roll 72: Application roll
73: Commaroll 74: Weir
80
81: Current collecting terminal parts 82: Ring
83: Laser beam 84: Weld bead
85: Ultrasonic junction
90: Plate current collector terminal

Claims

A positive electrode sheet and a negative electrode sheet each having a respective strip-shaped metal foil current collector and each electrode composite coated on the surface thereof, and a separator sandwiched between the positive electrode sheet and the negative electrode sheet, An electrode winding type battery having an electrode body formed by spirally winding around a core,
At least one of the positive electrode sheet and the negative electrode sheet is continuously and integrally formed in the width direction, and has an electrode mixture uncoated portion covering the entire length with a predetermined width of H (mm) at one end portion in the width direction. And the electrode mixture uncoated portion is wound so as to protrude from the other of the separator and the positive electrode sheet and the negative electrode sheet,
The end of the core serves as a current collecting terminal, and the uncoated portion of the electrode mixture is joined to a joint joined so as to overlap the end of the core and the end of the core. Are joined to form a non-joined part,
Furthermore, when the thickness in the radial direction determined by the innermost circumference and the outermost circumference of the portion where the positive electrode sheet, the negative electrode sheet, and the separator of the electrode body are wound to form a layer is defined as T (mm), An electrode wound battery, wherein H and T have a relationship represented by the following formula:
T ≧ 5 and H ≦ 45
And T <H ≦ 1.5T + 15

A positive electrode sheet and a negative electrode sheet each having a respective strip-shaped metal foil current collector and each electrode composite coated on the surface thereof, and a separator sandwiched between the positive electrode sheet and the negative electrode sheet, An electrode winding type battery having an electrode body formed by spirally winding around a core,
At least one of the positive electrode sheet and the negative electrode sheet is continuously and integrally formed in the width direction, and has an electrode mixture uncoated portion covering the entire length with a predetermined width of H (mm) at one end portion in the width direction. And the electrode mixture uncoated portion is wound so as to protrude from the other of the separator and the positive electrode sheet and the negative electrode sheet,
Collector terminal, the bound or the winding core at an end portion of the winding core a separate component which is physically isolated, and the electrode mixture material uncoated portion is in the current collector terminal It is joined to form a joined part that is joined so as to overlap and a non-joined part that is not joined to the current collecting terminal ,
Furthermore, when the thickness in the radial direction determined by the innermost circumference and the outermost circumference of the portion where the positive electrode sheet, the negative electrode sheet, and the separator of the electrode body are wound to form a layer is defined as T (mm), An electrode wound battery, wherein H and T have a relationship represented by the following formula:
T ≧ 5 and H ≦ 45
And T <H ≦ 1.5T + 15