JP3618219B2

JP3618219B2 - Non-aqueous battery and electrode terminal

Info

Publication number: JP3618219B2
Application number: JP06695798A
Authority: JP
Inventors: 尚南方; 昌聡笹山
Original assignee: Asahi Kasei EMD Corp
Current assignee: Asahi Kasei EMD Corp
Priority date: 1998-03-17
Filing date: 1998-03-17
Publication date: 2005-02-09
Anticipated expiration: 2018-03-17
Also published as: JPH11265704A

Description

【０００１】
【発明の属する技術分野】
本発明は、ポリマ−積層体からなる外装体でパッケージされた薄型非水系一次電池および二次電池並びに電池用電極端子に関するものである。
【０００２】
【従来の技術】
現在、パソコン、携帯電話、ビデオカメラなど種々の携帯機器に用いる電源として高エネルギー密度電池が開発されている。この電池として繰り返し充放電可能なリチウムイオン二次電池、ニッケル水素電池、ニッケルカドミウム電池などが利用されている。特にリチウムイオン二次電池はエネルギー密度が大きいことが特徴であり、電池の小型軽量化が可能となることから活発に開発が進められている。
【０００３】
従来、リチウムイオン二次電池は電極間のイオン移動媒体として電解液が用いられ、通常は電極と多孔質セパレータの積層体に電解液が含浸された構造を有する。しかしながら電極とセパレ−タは一体化しておらず、電極空孔部およびセパレ−タからの液漏れを防ぐため電池パッケージに重厚な金属材料が用いられている。
【０００４】
一方、固体電解質をイオン移動媒体とする電池は、従来の電解液をイオン移動媒体とする電池に比べ、電極とセパレ−タが一体化しているため実質的に液漏れがなく、電池の信頼性、安全性が高められる。また、積層体形成の容易さ、電池形態の自由度が高いことによる量産性、電池の薄型化、パッケージの簡略化、軽量化が期待されている。さらには、従来の電解液系電池で起こりうる液漏れが実質的に起こらないため製造工程管理が容易である、電極／固体電解質／電極積層体の直列接続積層による高電圧化も可能であるという利点も有している。
【０００５】
上記したように、この固体電解質をセパレ−タとする電池においては、ポリマ−積層体を該電池の外層体材料として用いることができ、この外装体は現在用いられている電池の金属容器に比較して薄膜で軽量であるため電池の軽量化、薄膜化が容易である。この電池を通常の動作で使用する場合、高い安全性と信頼性が確保できているが、さらに電極間短絡、過充電、高温環境保持などの異常状態や誤動作においても高い安全性と信頼性が確保されることが要求されている。
【０００６】
金属缶を外装体に用いた電池においては、電池内部の圧力増加によって電極端子の導通を遮断する安全機構が提案され、利用されている（特開平２−１１２１５１号公報）。該構造は防爆弁に端子リードが設置され、この防爆弁の内圧による変形を構造内部で吸収するように設計されており、このため該防爆弁は厚い構造となっている。また、該防爆弁は円筒型形状もしくは角型形状の金属缶に溶接またはかしめにより金属缶に接合されている。したがって、本発明のごとき薄型電池に利用することが出来ない。
【０００７】
また、ポリマー積層体を外装体に用いた薄型電池において、高温時で電流遮断を行なう素子（ＰｏｓｉｔｉｖｅＴｅｍｐｅｒａｔｕｒｅＣｏｅｆｆｉｃｉｅｎｔ素子またはＰＴＣ素子）を電極端子に接続した電池（米国特許第５４７８６６８号明細書、特願平８−２５２７１１号、特願平８−２６１６１８号）が提案されているが、この安全機構は、電池内部の圧力増加によって電極端子の導通を遮断する機構ではなく、ＰＣＴ素子が設置されている電極端子部の温度上昇を伴った場合のみ電流遮断を行なうものである。
【０００８】
【発明が解決しようとする課題】
本発明の課題は、異常動作や異常環境においても高い安全性と高信頼性を有する薄型、軽量の高容量非水系電池を提供することにある。特に、異常動作のうち過充電および充電状態の加熱、電極間短絡において高い安全性を有する薄型、軽量の非水系電池を提供することである。
【０００９】
【課題を解決するための手段】
本発明者らは、薄型軽量の非水系高エネルギ−密度電池を作製し、この異常作動時や異常環境における試験を行い、電池の外装体、電極端子など電池構造中に新たな安全機構を導入することによって高い安全性が確保できることを見出した。
【００１０】
即ち、本発明は、最内層に熱可塑性樹脂層を有するポリマー積層材料からなる袋状外装体内にイオン移動可能なセパレータを介して電極が接合された電極積層体が挿入され該電極積層体の正極および負極から該外装体の外側に延びる電極端子を封止した構造を有する非水系電池であって、
（１）電極端子の一部に断面積の小さい領域を設けこの断面積の小さい領域を挟んで少なくとも片側の電極端子が袋状外装体内面の熱可塑性樹脂層に密着固定された構造である非水系電池
（２）電極端子の一部が剥離可能な２層以上の金属平板積層体からなり該金属平板積層体の上下の最外層の少なくとも一方が袋状外装体内面の熱可塑性樹脂層に密着固定された構造である非水系電池
（３）金属平板積層体の金属層間を導電性フィラーと絶縁性樹脂からなるコンパウンドで接合した構造である（２）に記載の非水系電池
である。
【００１１】
以下、本発明を詳細に説明する。
本発明の電池は、ポリマー積層体材料からなる袋状外装体でパッケージされた非水系の薬１０ｍｍ〜役０．３ｍｍの厚みの薄型電池であり、該電池は、上記外装体、イオン移動可能なセパレータを介して電極が接合された電極積層体、該電極からの電流の注入取出のための電極端子から構成され、該袋状電池用外装体の膨張変形によって該電極端子の通電を遮断する機構を有する。
【００１２】
本発明の電池用外装体はポリマ−積層体材料からなる袋状構造であり、少なくとも最内層に熱可塑性樹脂層を有し、その外側に１層または２層以上の絶縁樹脂層を有し、さらに該熱可塑性樹脂層と最も外側の絶縁樹脂層との間に金属層を有する構造のポリマ−積層体シ−トを、最内層の熱可塑性樹脂層同士を熱融着などで袋状に加工したものである。
【００１３】
このポリマ−積層体材料の熱可塑性樹脂層として、ポリエチレン、ポリプロピレンなどのポリオレフィン、エチレン−ビニルアルコ−ル共重合体、エチレン−アクリル酸誘導体またはメタクリル酸誘導体共重合体、ポリフェニレンオキシドなどが用いられる。また、絶縁樹脂層として、ポリイミド、芳香族ポリアミド、脂肪族ポリアミド、ポリフェニレンオキシド、ポリフェニレンスルフィド、ポリエチレンナフタレ−ト、ポリエチレンフタレ−トなどが用いられる。金属層としてはアルミニウム、アルミニウム合金、銅、ニッケル、ステンレスなどが用いられる。
【００１４】
本発明の非水系電池は、この袋状外装体内にイオン移動可能なセパレ−タを介して電極が接合された電極積層体が挿入され、該電極積層体の正極および負極から該外装体の外側に延びる電極端子を封止した構造を有するものである。
この外装体の封止を例えば外装体最内層の熱可塑性樹脂層の熱融着で行なうに際しては、電極端子と外装体の積層構造中の金属層の短絡を防ぐ目的で、電極端子封止部分においてポリマ−積層体材料中の金属層が欠損した構造の外装体を用いることが好ましい。金属層の欠損部分は、電極端子封止部分において、外装体の先端から０．１ｍｍ以上存在することが好ましく、０．５ｍｍ以上存在することがより好ましい。この金属層の欠損部分が大きいことは、電極端子と外装体の短絡防止には好ましいが、金属層の無い領域では水蒸気バリア性が低下するため非水系電池として好ましくない。このことから、電池外装体表面中心から外装体の周辺に向かって、少なくとも金属層が熱可塑性樹脂層の厚みの１０倍以上の領域に亘って存在することが好ましく、より好ましくは２０倍以上、特に好ましくは３０倍以上存在することである。また、電極端子封止を熱融着で行う場合の熱融着幅は封止強度と電池形状によって決められ、好ましくは１ｍｍ以上、さらに好ましくは２ｍｍ以上であり、この熱融着幅によって電池が嵩張ることになるので、上限は５０ｍｍ、好ましくは３０ｍｍ以下である。また、外装体の電極端子封止部分の外装体の端面を絶縁処理することもできる。
【００１５】
本発明の非水系電池は、袋状外装体内でガス発生が起こって外装体が膨れ、変形した際に電極端子の通電を遮断する機構を有する。袋状外装体内部に装填された電極積層体が、外部端子を通じて過充電、大電流放電された場合や、短絡により異常反応を起こした場合には、外装体内部の電極積層体中の化学反応および／または異常な温度上昇によってガス発生が起こり、外装体が膨れて変形することが有る。本発明の非水系電池は、このような場合に電極端子の通電を遮断する機能を有する。この機能によって、電池異常作動における発火、爆発、熱暴走が阻止でき、電池の安全性が高めることができる。
【００１６】
外装体の膨張変形によって電極と電極端子の溶接部分または電極端子の一部が切断されて電流遮断する構造としては、例えば、１）電極端子の一部が剥離可能な２層以上の金属平板積層体からなり、該金属平板積層体の上下の最外層の少なくとも一方が袋状外装体内面の熱可塑性樹脂層に密着固定された構造、より好ましくは上下の最外層がそれぞれ袋状外装体内面の上部および下部の熱可塑性樹脂層に密着固定された構造であることである。上下の最外層がともに外装体内面に密着固定されていると、より小さな膨張変形によっても電流遮断機構が作動することから好ましい。２）電極端子の一部に断面積の小さい領域を設け、この断面積の小さい領域を挟んで少なくとも片側の電極端子が袋状外装体内面の熱可塑性樹脂層に密着固定された構造。３）電極端子の一部に切れ込みを設け、この切れ込み部を挟んで少なくとも片側の電極端子が袋状外装体内面の熱可塑性樹脂層に密着固定された構造。４）電極積層体の電極に溶接接合された正極および負極電極端子の少なくとも一方が、袋状外装体内面の熱可塑性樹脂層に密着固定された構造、より好ましくは正極および負極電極端子がそれぞれ袋状外装体内面の熱可塑性樹脂層の上部および下部に密着固定された構造であることである。正極および負極電極端子がともに外装体内面に密着固定されていると、より小さな膨張変形によっても電流遮断機構が作動することから好ましい。
【００１７】
また、これらの外装体の膨張変形によって電極と電極端子の溶接部分または電極端子の一部が切断されて電流遮断する機構で用いられる電極端子は、大電流通電時に発熱溶融して電流遮断するような機構を兼ね備えることも可能である。例えば、上記１）の場合には金属平板積層体を低融点金属を積層した構造にすることで大電流通電時に電流遮断することができる。上記２）、３）においては、断面積の小さい領域や切れ込み部が発熱溶融することで大電流通電時に電流遮断する機構も有している。
【００１８】
電極端子材料として、銅、アルミニウム、ステンレス、ニッケル、鉄、カ−ボンなど金属材料が用いられる。電極端子は電極集電体と接合されるため、この接合加工性や電気化学安定性を考慮して、電極集電体と同種の電極端子材料を用いることが好ましく、リチウムイオン二次電池の場合、正極端子にアルミニウム、負極端子に金属銅が利用される。しかしながら、電極端子がイオン移動媒体と接触しない場合には電極端子材料として各種金属を採用することができ、上記に限定されない。
【００１９】
本発明において、電極端子を外装体内面の熱可塑性樹脂層に密着固定する方法としては、電極端子を熱可塑性樹脂層に圧着加熱して熱融着させる方法、熱可塑性樹脂層と電極端子の間に接着剤や粘着シートを介在させ固定する方法が挙げられる。また、電極集電体と電極端子との接合は、超音波溶接、スポット溶接、アーク溶接、レーザー溶接などの溶接法、導電性ペースト、導電粘着テープなどにより接合する方法が挙げられる。
【００２０】
上記電流遮断する構造１）の構造において、電極端子の剥離可能な２層以上の金属平板積層体領域の金属層間の接合は、超音波溶接、レ−ザ−溶接、スポットベルダ−などの金属溶接や導電性塗料塗布接着で行い、接合材料や接合方法、接合面積により金属層間の強度を調整することが可能である。また２）の構造において、断面積の小さい領域の断面積と、電極端子として用いる金属材料の破断強度によって電流遮断条件が調節できる。３）の構造において、電極端子に形成する切れ込みの形状により破断強度が調整可能である。４）の構造において、電極積層体の集電体または活物質層と電極端子との接合強度を調節して電流遮断条件が調節できる。この例として超音波溶接により接合する場合には、溶接する部位の形状（例えば、超音波溶接機のアンビルとホーンの形状）、超音波周波数やパワー、接合面積、接合数によって調整できる。
【００２１】
また、電極端子遮断部分の電極端子を外装体内面の熱可塑性樹脂層に密着固定する際の密着固定する面積及び形状によっても電流遮断条件を調整することができる。このことから、電極端子に未密着部分を設ける必要がある。この未密着部分は、たとえば、未密着部分として残す電極端子表面に熱可塑性樹脂と密着しにくい材料、たとえばテフロンなどのフッ素樹脂をシ−ト形状または粉末状態で付着させ、電極端子部分と熱可塑性樹脂層との密着工程を施すことにより密着固定部分と未密着固定部分を形成することができる。用いる電極端子の破断強度は、電池容量や電池構造によるので一概に限定することができないが、通常、１０ｇから５０ｋｇの範囲である。
【００２２】
さらに電極端子の一部に温度上昇により通電が遮断される素子（ＰＴＣ素子）を接続することができる。この素子は導電性フイラ−と絶縁性樹脂からなるコンパウンドからなり、導電性フィラ−と樹脂の熱膨張係数の差を利用して高温時の抵抗を高め電流遮断する機能を有する。この素子は、通常平板状金属／導電性フイラ−・樹脂コンパウンド／平板状金属からなるため、上記の電極端子に直列に電池外装体内部または外部に接続できる。また前記の電流遮断部分の構造１）の導電性接着剤による金属層間の接合構造に代替して用いることもできる。この際、ＰＴＣ素子の導電性フイラ−・絶縁性樹脂コンパウンドの面積、強度を調整して破断強度を設計する。
【００２３】
上記のようにして構成した電池は、電極端子に外部から異常電流を通電した場合、安全に電流遮断を行い危険な状況を回避できる。また、ＰＴＣ素子を併設することにより、温度上昇時の通電遮断でき、さらに安全性が高められる。
本発明は、リチウム電池、リチウムイオン電池などの非水系電池に関し、用いられる電極積層体は、正極／セパレ−タ／負極をユニットとしてこの単位を少なくとも１つ含むものである。この製造法として例えば電極とセパレ−タ−を正極／セパレ−タ／負極の構成で積層し、一体化する方法が利用できる。この積層し、一体化する方法として、平板プレス、ロ−ルまたはベルトによるラミネ−ションプレスなどが挙げられ、積層時に加熱して電極とセパレータ間を融着させることが好ましい。また電極表面に粘着物を塗布することなどを併用してもよい。
【００２４】
電極は、粒子状の電極活物質がバインダ−とともに塗布形成された活物質層と、電極への電流の注入および流出を助ける、金属からなる集電体とから構成される。加工する電極の形状として、短冊状、長尺状いずれも利用可能である。
例えば本発明の非水系電池がリチウムイオン電池の場合、正極の活物質としては、リチウムイオンの電気化学的なド−ピング、脱ド−ピングが可能な電気化学的な電位の高い物質であり、例えば、コバルト酸リチウム、マンガン酸リチウム、ニッケル酸リチウム、コバルト・ニッケル酸リチウム、リチウムバナジウム複合酸化物、ニオブ酸リチウムなどの遷移金属リチウム複合酸化物、リチウムチタン硫化物、リチウムモリブデン硫化物、リチウムセレン化ニオブなどの金属カルコゲナイド、ポリピロ−ル、ポリチオフェン、ポリアニリン、ポリアセン化合物、ポリアセチレン、ポリアリレンビニレン、ジチオ−ル誘導体、ジスルフィド誘導体などの有機化合物、およびこれらの混合体を挙げることができる。正極の集電体として、金属アルミニウム、金属アルミニウム／ポリマ−積層体、ステンレス、カ−ボン、チタンなどを用いることができるが、金属アルミニウムが加工性および量産性の点から好ましい。
【００２５】
また、負極の活物質として、上記正極に対して電気化学的に低い電位を有するリチウムイオンの電気化学的なド−ピング、脱ド−ピング可能な材料を用いる。この例として、グラファイト、コ−クス、不定形炭素などの炭素系材料、すず系複合酸化物、シリカ系複合酸化物などの複合酸化物、酸化チタン、酸化鉄などの金属酸化物のリチウム固溶体、リチウム窒化マンガン、リチウム窒化鉄、リチウム窒化ニッケル、リチウム窒化銅、リチウム窒化アルミニウムなどの窒化物などのセラミックスが用いられる。負極集電体としては、金属銅、ニッケル、銅やニッケルメッキしたポリマ−材料、ステンレス、炭素などを用いることができる。中でも、金属銅は電気抵抗が低く、リチウムド−ピングを受けにくく、耐久性に優れることから好ましい。
【００２６】
上記の活物質を所定の形状に加工して電極を構成する。この形態として集電体表面に活物質粉末をバインダ−で分散結合させた形態、活物質をたとえば薄膜とした連続体の形態が挙げられる。粉末状の活物質をバインダ−で分散した形態では、集電体と電極活物質層との電気抵抗を低減するため、カ−ボン、金属などの導電助剤を添加して活物質層の抵抗を低減することが好ましい。
【００２７】
セパレ−タ材料としては、イオン伝導度として１０^−６Ｓ／ｃｍ以上であることが好ましく、さらに好ましくは１０^−４Ｓ／ｃｍ以上である。この材料として、多孔質膜材料にイオン導電性の液状媒体を含浸した材料、イオン伝導性ゲル材料、イオン伝導性固体電解質材料を用いることができる。このうち、イオン伝導性ゲル材料は電極との密着性に優れ、電極積層体として一体化の加工を経ても高いイオン伝導度を持つ。固体電解質材料や多孔質材料の表面にイオン伝導性ゲル材料を積層、含浸させた材料も利用できる。このイオン伝導性ゲル材料として、例えばポリマ−マトリックスに電解液を保持させたポリマ−ゲル、イオン透過性セラミックス材料のゲル材料が挙げられる。このうち前者はフレキシブルであり、電極との密着化ができるため好ましい。
【００２８】
このポリマ−マトリックス材料として、例えば、架橋されたポリ弗化ビニリデンや弗化ビニリデン共重合体およびこれらの混合体、さらに他のポリマ−との混合物としても利用できる。この弗化ビニリデン共重合体の例として、弗化ビニリデン−ヘキサフルオロプロピレン共重合体、弗化ビニリデン−トリフルオロエチレン共重合体を挙げることができる。ポリ弗化ビニリデン、弗化ビニリデン共重合体は電気化学的に安定な領域が広く、高強度であるため、電池に利用する場合、加工性、電池性能に優れることから好ましい。このポリマ−の構造として、バルク、多孔質構造、発泡体構造、粉末焼結体、粉末圧縮体などの成形体に電解液を含浸した形態、ポリマ−と電解液を溶媒や加熱溶融によって均一化した後、所定の形状に成形した形態が用いられる。多孔質構造を用い、電極との積層一体化工程において微多孔構造が閉塞されてしまった場合においても、該ポリマ−が電解液に含浸されてイオン伝導性を発現することから、ポリオレフィンセパレ−タでみられるようなイオン輸送阻害は起こらない。
【００２９】
電解液としては、本発明の非水系電池がリチウムイオン電池の場合、リチウム塩を有機溶媒に溶解した溶液が用いられる。このリチウム塩としては、弗化ホウ酸リチウム、弗化燐酸リチウム、過塩素酸リチウム、弗化ヒ素酸リチウム、トリフルオロメタンスルホン酸リチウム、トリフルオロメタンスルホニルイミドリチウム、パ−フルオロブタンスルホン酸リチウムなどのリチウム塩、これらの混合物、複数の塩を混合した溶融塩が用いられる。この溶融塩の場合、室温で液状のものもあり、必ずしも電解液溶媒が含まれなくても利用可能である。また電解液溶媒として、エチレンカ−ボネ−ト、プロピレンカ−ボネ−ト、ブチレンカ−ボネ−トなどの環状カ−ボネ−ト化合物、ジメチルカ−ボネ−ト、ジエチルカ−ボネ−ト、メチルエチルカ−ボネ−トなどの鎖状カ−ボネ−ト、テトラヒドロフラン、ジオキサンなどのエ−テル化合物、γ−ブチルラクトン、プロピオラクトン、酢酸メチルなどのエステル化合物、アセトニトリル、プロピオ二トリルなどの二トリル化合物、スルホラン、ホスファゼンなどの化合物などの単体、混合物、前記のポリマ−マトリックスの液状オリゴマ−やオリゴマ−と溶媒の混合物などが用いられる。
【００３０】
セパレ−タと電極の積層前に、上記の電解液や電解液にポリマ−マトリックス材料を溶解、分散した溶液やスラリ−、電解液溶媒を前記の電極活物質表面に塗布、含浸させて電極とセパレ−タの密着性や電極活物質層のイオン移動を向上させることができる。また、電極／セパレ−タ積層後、電解液、電解液にポリマ−マトリックス材料を溶解、分散した溶液、スラリ−、電解液溶媒を含浸させることもできる。
【００３１】
【発明の実施の形態】
以下実施例で本発明を詳細に説明する。
【００３２】
【実施例１】
ＬｉＣｏＯ_２電極（平均粒径５μｍのＬｉＣｏＯ_２を１００重量部、バインダーにポリフッ化ビニリデン３重量部およびアセチレンブラック３重量部をＮ−メチルピロリドンに分散、１５μｍアルミ集電体上に塗工、加熱プレスした膜厚１１０μｍ片面塗工シ−ト）を正極として幅２９ｍｍ、長さ１１０ｍｍに切断後、長さ方向に幅１０ｍｍで電極活物質層を剥離してアルミ集電体を露出させた。負極としてグラファイト長尺シート（平均粒径１０μｍのグラファイトＭＣＭＢ（大阪ガス（株）製）１００重量部、スチレン−ブタジエンラテックスの水分散スラリ−を固形分換算で２重量部、およびカルボキシメチルセルロ−ス０．８重量部を溶かした水溶液を混ぜ合わせて得られた、水に均一分散したスラリ−を１２μｍの銅集電体上に塗布、加熱プレスした膜厚８５μｍ片面塗工シ−ト）を幅３０ｍｍ、長さ１１０ｍｍで切断し、長さ方向に幅９ｍｍで活物質層を剥離して銅集電体を露出させた。
【００３３】
ポリフッ化ビニリデン−ヘキサフルオロプロピレン共重合体（ヘキサフルオロプロピレン含量３重量％、エルフアトケム社製カイナ−ル２８５０）のバルクシ−ト（膜厚５０μｍ）に電子線照射（照射量１０Ｍｒａｄ）を行い架橋処理した後、フロン（ＨＦＣ−１３４ａ）を７重量部含浸、加熱延伸処理して得られた発泡体シート（発泡倍率４倍、膜厚６０μｍ）に、電解液としてエチレンカ−ボネ−ト、γ−ブチルラクトンを体積比１：１で混合した液にＬｉＢＦ_４を溶解して得られた１．５モル／リットル溶液を含浸させて固体電解質（電解液含量７５重量％、平均膜厚幅６５μｍ、幅１０２ｍｍの長尺シ−ト）を得、セパレ−タとした。このセパレ−タを幅３２ｍｍで切断して短冊状とした後、電極の表面に上記の電解液をロ−ルコ−タ−で塗布した。塗布量は正極３０ｇ／ｍ^２、負極４０ｇ／ｍ^２とした。上記の正極、セパレータ、負極をこの順に、負極活物質層から正極活物質層がはみださないようにセパレータを介して活物質層を対向させ、さらにアルミ集電体がはみ出した側と反対側に銅集電体をはみ出させる構成で積層し、加熱ロ−ルのラミネ−タ（ロ−ル温度１３０℃、ロ−ル速度６００ｍｍ／ｍｉｎ）で積層一体化させた。このようにして、８枚の積層体を作製した。この８枚の積層体を正極／負極／負極／正極／正極／負極・・・・の順に、アルミ集電体のみがはみ出た側と銅集電体のみがはみ出た側が形成されるように重ね合わせ、それぞれの集電体の重ね合わせた部分の中央部を３ｍｍ角で超音波溶接して接合し電極積層体を束ねた。次いで、幅１０ｍｍ、長さ３０ｍｍの銅およびアルミシ−ト（厚さ３０μｍ）を電極端子として用い、上記超音波溶接部分に超音波溶接固定（溶接部は３ｍｍ角）した。
【００３４】
ポリマ−シ−ト（ポリエチレンテレフタレ−ト２５μｍ、金属アルミニウムシ−ト１２μｍ、ポリプロピレン５０μｍを順次積層したシ−ト）を袋状に加工した外装体（幅４０ｍｍの筒状、長さ１１０ｍｍの側面を幅３ｍｍで融着）に、得られた電極積層体を挿入してアルミおよび銅の電極端子を外部にはみ出させてから、該アルミおよび銅の電極端子面を、それぞれ袋状外装体内面の上面および下面のポリプロピレン樹脂層に熱融着固定した後、真空引きを行いながら開口部分を熱融着して封止し、電池を作製した。
【００３５】
電極端子を充放電機に接続して充放電試験（２３０ｍＡ定電流、４．２Ｖ定電位充電、２３０ｍＡ定電流放電をおこなった結果、初回放電量７３０ｍＡｈ、平均電圧３．７Ｖ（２．７Ｗｈ）であり繰り返し充放電が可能であった。充電状態の該電池の外装体表面中心部および電極端子が熱融着された外装体封止部表面に熱電対を貼付け、該電池の電極端子を充放電機に接続、２８８０ｍＡの電流で定電流定電圧充電（電圧１５Ｖ）で過充電を行なった結果、約１９分で外装体が膨れだし、さらに１５秒後電極端子が切断され通電できなくなり電池の温度が低下した。この際の電池の電極端子付近の最大温度は３８℃、電池外装体中心部の最大温度は４２℃であった。
【００３６】
【実施例２】
実施例１で作製したＬｉＣｏＯ_２電極、グラファイト負極、ポリフッ化ビニリデン−ヘキサフルオロプロピレン共重合体発泡体シートに電解液を含浸させた固体電解質をセパレ−タに用い、実施例１と同様の方法で積層し、加熱ロ−ルのラミネ−タで積層一体化させた８枚の積層体を作製し、超音波溶接して電極積層体を束ねた。
【００３７】
次いで、幅１０ｍｍ、長さ２０ｍｍのアルミシ−ト（厚さ３０μｍ）２枚を幅を揃えて長さ方向に重ね、重なり合う長さが１０ｍｍとなるようにした。この重なり合い部分の中心を超音波溶接して３ｍｍ角の溶接部分で２枚のアルミシ−トを接合した電極端子を作製した（接合後、幅１０ｍｍ、長さ３０ｍｍ）。一方、幅１０ｍｍ、長さ２０ｍｍの金属銅シ−トを同様にして重ね合わせ、溶接して電極端子を作製した（接合後、幅１０ｍｍ、長さ３０ｍｍ）。これらアルミおよび金属銅の電極端子をそれぞれ正極および負極集電体の超音波溶接部分に溶接して、電極集電体端から電極端子が２５ｍｍはみ出した構造とした。該正極および負極の電極端子のそれぞれ２枚の金属シ−トにおいて、融着固定する部位以外の外装体内面に接触する恐れのある部分をテフロンシ−トで被覆した後、それぞれの電極端子の金属シ−トの一方が外装体（外装体は実施例１と同様の袋を用いた）の上面の熱可塑性樹脂層に、もう一つの金属シ−トを外装体下面の熱可塑性樹脂層に熱融着固定した。その後、電極端子を外装体から引出して開口部を幅２０ｍｍで熱融着して封止した。
【００３８】
電極端子を充放電機に接続して充放電試験（２３０ｍＡ定電流、４．２Ｖ定電位充電、２３０ｍＡ定電流放電をおこなった結果、初回放電量７３２ｍＡｈ、平均電圧３．７Ｖ（２．７Ｗｈ）であり繰り返し充放電が可能であった。充電状態の該電池の外装体に実施例１と同様に熱電対を貼付け、該電池の電極端子を充放電機に接続、２８８０ｍＡの電流で定電流定電圧充電（電圧１５Ｖ）で過充電を行なった結果、約１９分で外装体が膨れだし、さらに２０秒後電極端子が切断され通電できなくなりセルの温度が低下した。この際のセルの電極端子付近の最大温度は４０℃、セルの表面中心部分の温度は４２℃であった。
【００３９】
【実施例３】
実施例１で作製したＬｉＣｏＯ_２電極、グラファイト負極、ポリフッ化ビニリデン−ヘキサフルオロプロピレン共重合体発泡体シートに電解液を含浸させた固体電解質をセパレ−タに用い、実施例１と同様の方法で８枚の積層体を作製し、超音波溶接して電極積層体を束ねた。
【００４０】
次いで、この超音波溶接部分に幅１０ｍｍ、長さ３０ｍｍのアルミおよび金属銅シ−ト（厚さ３０μｍ）の長さ方向の中央部分を幅が３ｍｍ、長さが１０ｍｍの矩形形状を真ん中に残すように、はさみでカットして電極端子とした。これらアルミおよび金属銅の電極端子の片端をそれぞれ正極集電体および負極集電体の超音波溶接部分に溶接して、電極集電体端から電極端子が２５ｍｍはみ出した構造とした。該アルミ電極端子の、幅が３ｍｍの矩形形状の部分を挟んで集電体に溶接した側をテフロンシ−トで被覆し、反対側の電極端子封止部分側の電極端子を外装体（外装体は実施例１と同様の袋を用いた）内面の熱可塑性樹脂層に融着固定させた後、電極端子を外装体から引出し開口部を熱融着して封止した。
【００４１】
電極端子を充放電機に接続して充放電試験（２３０ｍＡ定電流、４．２Ｖ定電位充電、２３０ｍＡ定電流放電をおこなった結果、初回放電量７２９ｍＡｈ、平均電圧３．７Ｖ（２．７Ｗｈ）であり繰り返し充放電が可能であった。充電状態の該電池の外装体に実施例１と同様に熱電対を貼付け、該電池の電極端子を充放電機に接続、２８８０ｍＡの電流で定電流定電圧充電（電圧１５Ｖ）で過充電を行なった結果、約１９分で外装体が膨れだし、さらに１分後電極端子が切断され通電できなくなり電池の温度が低下した。この際の電池の電極端子封止部分付近の最大温度は５６℃、電池の外装体中心部分の最大温度は５３℃であった。
【００４２】
【実施例４】
実施例１で作製したＬｉＣｏＯ_２正極、グラファイト負極、ポリフッ化ビニリデン−ヘキサフルオロプロピレン共重合体発泡体シートに電解液を含浸させた固体電解質をセパレ−タに用い、実施例１と同様の方法で積層し、加熱ロ−ルのラミネ−タで積層一体化させた８枚の積層体を作製し、超音波溶接して電極積層体を束ねた。
【００４３】
次いで、幅１０ｍｍ、長さ３０ｍｍのアルミおよび金属銅シ−ト（厚さ３０μｍ）の長さ方向の中央部分をはさみで約６０度の角度で斜めに切り込みを入れ、電極端子の接続幅が３ｍｍとなる短冊を電極端子として作製した。これらアルミおよび金属銅の電極端子の片端をそれぞれ正極および負極集電体側の超音波溶接部分に溶接して、電極集電体端から電極端子が２５ｍｍはみ出した構造とした。該アルミの電極端子の、切り込み部分を挟んで集電体に溶接した側の電極端子をテフロンシ−トで被覆し、反対側の電極端子封止部分側の電極端子を外装体（外装体は実施例１と同様の袋を用いた）内面の熱可塑性樹脂層に融着固定させた後、電極端子を外装体から引出して開口部を熱融着して封止した。
【００４４】
電極端子を充放電機に接続して充放電試験（２３０ｍＡ定電流、４．２Ｖ定電位充電、２３０ｍＡ定電流放電をおこなった結果、初回放電量７３５ｍＡｈ、平均電圧３．７Ｖであり繰り返し充放電が可能であった。充電状態の該電池の外装体に実施例１と同様に熱電対を貼付け、該電池の電極端子を充放電機に接続、２８８０ｍＡの電流で定電流定電圧充電（電圧１５Ｖ）で過充電を行なった結果、約２０分で外装体が膨れだし、さらに４０秒後電極端子が切断され通電できなくなり電池の温度が低下した。この際の電池の電極端子付近の最大温度は６５℃、電池の中心部分の最大温度は５０℃であった。
【００４５】
【比較例１】
実施例１で作製したＬｉＣｏＯ_２電極、グラファイト負極、ポリフッ化ビニリデン−ヘキサフルオロプロピレン共重合体発泡体シートに電解液を含浸させた固体電解質をセパレ−タに用い、実施例１と同様の方法で積層し、加熱ロ−ルのラミネ−タで積層一体化させた８枚の積層体を作製し、超音波溶接して電極積層体を束ねた。
【００４６】
次いで、幅１０ｍｍ、長さ３０ｍｍのアルミおよび金属銅シ−ト（厚さ３０μｍ）を電極端子として、これらアルミおよび金属銅の電極端子の片端をそれぞれ正極および負極集電体の超音波溶接部分に溶接して、電極集電体端から電極端子が２５ｍｍはみ出した構造とした。外装体は実施例１と同様の袋を用い、電極端子を外装体から引出して開口部を熱融着して封止した。
【００４７】
電極端子を充放電機に接続して充放電試験（２３０ｍＡ定電流、４．２Ｖ定電位充電、２３０ｍＡ定電流放電をおこなった結果、初回放電量７３１ｍＡｈ、平均電圧３．７Ｖであり繰り返し充放電が可能であった。充電状態の該電池の外装体に実施例１と同様に熱電対を貼付け、該電池の電極端子を充放電機に接続、２８８０ｍＡの電流で定電流定電圧充電（電圧１５Ｖ）で過充電を行なった結果、約２０分で外装体が膨れだし、さらに２分後電圧が１５Ｖに到達して電流が収束した。この際のセルの電極端子付近の最大温度は９５℃、セルの中心部分の最大温度は９１℃であった。
【００４８】
【発明の効果】
本発明は、高い安全性を供え、高エネルギ−密度で、高信頼性の軽量、薄型のリチウムイオン二次電池の提供を可能にするものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin non-aqueous primary battery and secondary battery packaged with an outer package made of a polymer laminate, and an electrode terminal for a battery.
[0002]
[Prior art]
Currently, high energy density batteries have been developed as power sources for various portable devices such as personal computers, mobile phones, and video cameras. As this battery, a lithium ion secondary battery, a nickel metal hydride battery, a nickel cadmium battery, and the like that can be repeatedly charged and discharged are used. In particular, lithium ion secondary batteries are characterized by a high energy density, and are being actively developed because they can be reduced in size and weight.
[0003]
Conventionally, a lithium ion secondary battery uses an electrolyte as an ion transfer medium between electrodes, and usually has a structure in which a laminate of electrodes and a porous separator is impregnated with an electrolyte. However, the electrode and the separator are not integrated, and a heavy metal material is used for the battery package in order to prevent liquid leakage from the electrode hole and the separator.
[0004]
On the other hand, a battery using a solid electrolyte as an ion transfer medium has substantially no leakage due to the integration of the electrode and the separator, compared with a battery using a conventional electrolyte as an ion transfer medium. , Safety is enhanced. In addition, it is expected to be easy to form a laminated body, mass productivity due to a high degree of freedom of battery form, thin battery, simplified package, and light weight. Furthermore, the liquid leakage that can occur in the conventional electrolyte solution battery does not substantially occur, so that the manufacturing process management is easy, and it is possible to increase the voltage by the serial connection lamination of the electrode / solid electrolyte / electrode laminate. It also has advantages.
[0005]
As described above, in a battery using this solid electrolyte as a separator, a polymer laminate can be used as an outer layer material of the battery, and this outer package is compared with a metal container of a currently used battery. Since the thin film is lightweight, the battery can be easily reduced in weight and thickness. When this battery is used in normal operation, high safety and reliability are ensured, but it is also highly safe and reliable in abnormal states and malfunctions such as short-circuiting between electrodes, overcharging, and maintaining a high temperature environment. It is required to be secured.
[0006]
In a battery using a metal can as an exterior body, a safety mechanism that interrupts conduction of electrode terminals due to an increase in pressure inside the battery has been proposed and used (Japanese Patent Laid-Open No. 2-112151). The structure is designed such that a terminal lead is installed on the explosion-proof valve and the deformation due to the internal pressure of the explosion-proof valve is absorbed inside the structure, and thus the explosion-proof valve has a thick structure. The explosion-proof valve is joined to the metal can by welding or caulking to a cylindrical or square metal can. Therefore, it cannot be used for a thin battery as in the present invention.
[0007]
In addition, in a thin battery using a polymer laminate as an exterior body, a battery in which an element (Positive Temperature Coefficient element or PTC element) that cuts off current at high temperature is connected to an electrode terminal (US Pat. No. 5,478,668, Japanese Patent Application No. Japanese Patent Application No. 8-252711 and Japanese Patent Application No. 8-261618 have been proposed. However, this safety mechanism is not a mechanism that cuts off the electrical connection of the electrode terminal due to an increase in pressure inside the battery, but a PCT element is installed. Current interruption is performed only when the temperature of the electrode terminal portion is increased.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a thin, lightweight, high-capacity non-aqueous battery having high safety and high reliability even in abnormal operation or abnormal environment. In particular, it is to provide a thin and lightweight non-aqueous battery having high safety in overheating, heating in a charged state, and short circuit between electrodes during abnormal operation.
[0009]
[Means for Solving the Problems]
The present inventors manufactured a thin and light non-aqueous high energy density battery, and conducted a test in the abnormal operation or in an abnormal environment, and introduced a new safety mechanism in the battery structure such as a battery outer casing and an electrode terminal. By doing so, it was found that high safety can be secured.
[0010]
That is, the present inventionAn electrode laminate in which electrodes are joined via a separator capable of ion migration is inserted into a bag-like outer package made of a polymer laminate material having a thermoplastic resin layer as the innermost layer, and the outer package from the positive electrode and the negative electrode of the electrode laminate A non-aqueous battery having a structure in which an electrode terminal extending outward is sealed,
(1) A structure in which a region having a small cross-sectional area is provided in a part of the electrode terminal and at least one electrode terminal is tightly fixed to the thermoplastic resin layer on the inner surface of the bag-like exterior body with the region having a small cross-sectional area sandwiched therebetween Water battery
(2) A part of the electrode terminal is composed of two or more layers of metal plate laminates that can be peeled, and at least one of the upper and lower outermost layers of the metal plate laminate is adhered and fixed to the thermoplastic resin layer on the inner surface of the bag-like exterior body. Non-aqueous battery
(3) The nonaqueous battery according to (2), which has a structure in which the metal layers of the flat metal plate laminate are joined with a compound made of a conductive filler and an insulating resin.
It is.
[0011]
Hereinafter, the present invention will be described in detail.
The battery of the present invention is a thin battery having a thickness of 10 mm to 0.3 mm, which is a non-aqueous medicine packaged with a bag-shaped outer package made of a polymer laminate material, and the battery is capable of ion migration. An electrode laminate in which electrodes are joined via a separator, and electrode terminals for injecting and extracting current from the electrodes,It has a mechanism for cutting off the energization of the electrode terminal by the expansion deformation of the bag-shaped battery case.
[0012]
The battery outer body of the present invention has a bag-like structure made of a polymer laminate material, has at least an innermost layer of a thermoplastic resin layer, and has one or more insulating resin layers on the outside thereof. Furthermore, a polymer laminate sheet having a structure having a metal layer between the thermoplastic resin layer and the outermost insulating resin layer is processed into a bag shape by bonding the innermost thermoplastic resin layers to each other. It is a thing.
[0013]
As the thermoplastic resin layer of the polymer laminate material, polyolefin such as polyethylene and polypropylene, ethylene-vinyl alcohol copolymer, ethylene-acrylic acid derivative or methacrylic acid derivative copolymer, polyphenylene oxide and the like are used. As the insulating resin layer, polyimide, aromatic polyamide, aliphatic polyamide, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, polyethylene phthalate, or the like is used. As the metal layer, aluminum, an aluminum alloy, copper, nickel, stainless steel, or the like is used.
[0014]
In the non-aqueous battery of the present invention, an electrode laminate in which an electrode is joined via a separator capable of ion migration is inserted into the bag-like outer package, and the outer side of the outer package is formed from the positive electrode and the negative electrode of the electrode laminate. It has the structure which sealed the electrode terminal extended to.
When sealing the exterior body by, for example, heat-sealing the thermoplastic resin layer as the innermost layer of the exterior body, the electrode terminal sealing portion is used for the purpose of preventing a short circuit of the metal layer in the laminated structure of the electrode terminal and the exterior body. It is preferable to use an outer package having a structure in which the metal layer in the polymer laminate material is missing. The defect portion of the metal layer is preferably present at 0.1 mm or more, more preferably 0.5 mm or more from the tip of the outer package at the electrode terminal sealing portion. A large defect portion of the metal layer is preferable for preventing a short circuit between the electrode terminal and the outer package, but in a region without the metal layer, the water vapor barrier property is lowered, which is not preferable as a non-aqueous battery. From this, it is preferable that at least the metal layer exists over a region of 10 times or more the thickness of the thermoplastic resin layer, more preferably 20 times or more, from the center of the surface of the battery outer case toward the periphery of the outer case. It is particularly preferably 30 times or more. In addition, when the electrode terminal is sealed by thermal fusion, the thermal fusion width is determined by the sealing strength and the battery shape, and is preferably 1 mm or more, more preferably 2 mm or more. Since it will be bulky, the upper limit is 50 mm, preferably 30 mm or less. Moreover, the end surface of the exterior body of the electrode terminal sealing part of an exterior body can also be insulated.
[0015]
The non-aqueous battery of the present invention has a mechanism for interrupting energization of the electrode terminal when gas generation occurs in the bag-shaped outer package and the outer package expands and deforms. When the electrode stack loaded inside the bag-shaped outer package is overcharged or discharged with a large current through an external terminal, or when an abnormal reaction occurs due to a short circuit, the chemical reaction in the electrode stack inside the outer package Gas generation may occur due to an abnormal temperature rise, and the exterior body may swell and deform. The non-aqueous battery of the present invention has a function of interrupting energization of the electrode terminal in such a case. With this function, it is possible to prevent ignition, explosion, and thermal runaway in abnormal battery operation, and the safety of the battery can be improved.
[0016]
Examples of the structure in which the welded portion of the electrode and the electrode terminal or a part of the electrode terminal is cut off due to the expansion deformation of the exterior body to cut off the current include, for example, 1) Two or more metal flat plate layers that can be partially peeled off from the electrode terminal A structure in which at least one of the upper and lower outermost layers of the flat metal plate laminate is intimately fixed to the thermoplastic resin layer on the inner surface of the bag-shaped outer package, more preferably, the upper and lower outermost layers are each formed on the inner surface of the bag-shaped outer package. This is a structure in which the upper and lower thermoplastic resin layers are tightly fixed. It is preferable that the upper and lower outermost layers are both tightly fixed to the inner surface of the exterior body because the current interrupting mechanism operates even with a smaller expansion deformation. 2) A structure in which a region having a small cross-sectional area is provided in a part of the electrode terminal, and at least one of the electrode terminals is tightly fixed to the thermoplastic resin layer on the inner surface of the bag-shaped exterior body across the region having the small cross-sectional area. 3) A structure in which a cut is provided in a part of the electrode terminal, and at least one electrode terminal is tightly fixed to the thermoplastic resin layer on the inner surface of the bag-like exterior body with the cut portion interposed therebetween. 4) A structure in which at least one of the positive electrode and the negative electrode terminal welded to the electrode of the electrode laminate is closely fixed to the thermoplastic resin layer on the inner surface of the bag-shaped outer package, more preferably the positive electrode and the negative electrode terminal are each a bag. This is a structure in which the thermoplastic resin layer on the inner surface of the outer casing is closely fixed to the upper and lower portions. It is preferable that both the positive electrode and the negative electrode terminal are firmly fixed to the inner surface of the exterior body because the current interrupting mechanism operates even with a smaller expansion deformation.
[0017]
In addition, the electrode terminal used in the mechanism that cuts off the current by cutting the welded part of the electrode and the electrode terminal or a part of the electrode terminal due to the expansion and deformation of the outer package so that the heat is melted and interrupts the current when a large current is applied. It is also possible to have a simple mechanism. For example, in the case of the above 1), the current can be interrupted when a large current is applied by forming a structure in which the flat metal laminate is laminated with a low melting point metal. In the above 2) and 3), there is also a mechanism that cuts off the current when a large current is applied by heat-melting a region having a small cross-sectional area or a cut portion.
[0018]
As the electrode terminal material, a metal material such as copper, aluminum, stainless steel, nickel, iron or carbon is used. Since the electrode terminal is bonded to the electrode current collector, it is preferable to use the same type of electrode terminal material as the electrode current collector in consideration of the bonding processability and electrochemical stability. In the case of a lithium ion secondary battery Aluminum is used for the positive terminal and metallic copper is used for the negative terminal. However, when the electrode terminal is not in contact with the ion transfer medium, various metals can be adopted as the electrode terminal material, and the present invention is not limited to the above.
[0019]
In the present invention, as a method for tightly fixing the electrode terminal to the thermoplastic resin layer on the inner surface of the exterior body, a method in which the electrode terminal is heat-bonded to the thermoplastic resin layer by heat-bonding, a space between the thermoplastic resin layer and the electrode terminal. And fixing with an adhesive or a pressure sensitive adhesive sheet interposed therebetween. Examples of the joining between the electrode current collector and the electrode terminal include joining methods such as ultrasonic welding, spot welding, arc welding, laser welding, and the like, conductive paste, and conductive adhesive tape.
[0020]
In the structure of the above-described structure 1) for cutting off the current, the joining between the metal layers in the two or more layers of the metal flat plate laminate where the electrode terminals can be peeled is performed by metal welding such as ultrasonic welding, laser welding, spot belldering, etc. It is possible to adjust the strength between the metal layers according to the bonding material, bonding method, and bonding area. In the structure 2), the current interruption condition can be adjusted by the cross-sectional area of the region having a small cross-sectional area and the breaking strength of the metal material used as the electrode terminal. In the structure 3), the breaking strength can be adjusted by the shape of the cut formed in the electrode terminal. In the structure 4), the current interruption condition can be adjusted by adjusting the bonding strength between the current collector or active material layer of the electrode laminate and the electrode terminal. When joining by ultrasonic welding as this example, it can adjust by the shape (for example, the shape of the anvil and horn of an ultrasonic welding machine), ultrasonic frequency and power, a joining area, and the number of joining.
[0021]
In addition, the current interruption condition can be adjusted by the area and shape of the electrode terminal of the electrode terminal interruption portion that are closely fixed when closely fixing the electrode terminal to the thermoplastic resin layer on the inner surface of the exterior body. For this reason, it is necessary to provide a non-contact portion on the electrode terminal. This non-adhered part is made of, for example, a material that hardly adheres to the thermoplastic resin, for example, a fluororesin such as Teflon, in the form of a sheet or powder on the electrode terminal surface that remains as the non-adhered part. By performing an adhesion process with the resin layer, an adhesion-fixed part and an unadhered-fixed part can be formed. The breaking strength of the electrode terminal used depends on the battery capacity and the battery structure and cannot be generally limited, but is usually in the range of 10 g to 50 kg.
[0022]
Furthermore, an element (PTC element) that is interrupted by energization due to temperature rise can be connected to a part of the electrode terminal. This element is made of a compound made of a conductive filler and an insulating resin, and has a function of increasing the resistance at high temperature and blocking the current by utilizing the difference in thermal expansion coefficient between the conductive filler and the resin. Since this element is usually composed of a flat metal / conductive filler / resin compound / flat metal, it can be connected in series or externally to the above-mentioned electrode terminal. Moreover, it can replace with the junction structure between the metal layers by the conductive adhesive of the structure 1) of the said electric current interruption part. At this time, the breaking strength is designed by adjusting the area and strength of the conductive filler / insulating resin compound of the PTC element.
[0023]
The battery configured as described above can safely cut off the current and avoid a dangerous situation when an abnormal current is applied to the electrode terminal from the outside. Further, by providing a PTC element, it is possible to cut off the energization when the temperature rises, and the safety is further improved.
The present invention relates to a non-aqueous battery such as a lithium battery or a lithium ion battery, and the electrode laminate used includes at least one unit of a positive electrode / separator / negative electrode as a unit. As this manufacturing method, for example, a method in which an electrode and a separator are laminated in a positive electrode / separator / negative electrode configuration and integrated can be used. As a method of laminating and integrating, there is a flat plate press, a lamination press using a roll or a belt, and the like, and it is preferable to heat the electrodes during lamination to fuse the electrode and the separator. Moreover, you may use together applying an adhesive to the electrode surface.
[0024]
The electrode is composed of an active material layer in which a particulate electrode active material is applied and formed together with a binder, and a current collector made of metal that assists injecting and discharging current to and from the electrode. As the shape of the electrode to be processed, either a strip shape or a long shape can be used.
For example, when the non-aqueous battery of the present invention is a lithium ion battery, the positive electrode active material is a substance having a high electrochemical potential capable of electrochemical doping and de-doping of lithium ions, For example, lithium cobalt oxide, lithium manganate, lithium nickelate, cobalt lithium nickelate, lithium vanadium composite oxide, transition metal lithium composite oxide such as lithium niobate, lithium titanium sulfide, lithium molybdenum sulfide, lithium selenium And metal chalcogenides such as niobium chloride, polypyrrole, polythiophene, polyaniline, polyacene compounds, polyacetylene, polyarylene vinylene, dithiol derivatives, disulfide derivatives and other organic compounds, and mixtures thereof. As the positive electrode current collector, metal aluminum, metal aluminum / polymer laminate, stainless steel, carbon, titanium, or the like can be used, but metal aluminum is preferred from the viewpoint of workability and mass productivity.
[0025]
Further, as the negative electrode active material, a material capable of electrochemical doping and de-doping of lithium ions having an electrochemically low potential with respect to the positive electrode is used. Examples of this include carbon-based materials such as graphite, coke, and amorphous carbon, tin-based composite oxides, composite oxides such as silica-based composite oxides, lithium solid solutions of metal oxides such as titanium oxide and iron oxide, Ceramics such as nitrides such as lithium manganese nitride, lithium iron nitride, lithium nickel nitride, lithium copper nitride, and lithium aluminum nitride are used. As the negative electrode current collector, metallic copper, nickel, copper, nickel-plated polymer material, stainless steel, carbon, or the like can be used. Among these, metallic copper is preferable because of its low electrical resistance, resistance to lithium doping, and excellent durability.
[0026]
The above active material is processed into a predetermined shape to form an electrode. Examples of this form include a form in which the active material powder is dispersed and bonded to the surface of the current collector with a binder, and a form in which the active material is a thin film, for example. In the form in which the powdered active material is dispersed with a binder, in order to reduce the electrical resistance between the current collector and the electrode active material layer, a conductive assistant such as carbon or metal is added to increase the resistance of the active material layer. Is preferably reduced.
[0027]
As a separator material, the ionic conductivity is 10^-6S / cm or more is preferable, more preferably 10^-4S / cm or more. As this material, a material obtained by impregnating a porous membrane material with an ion conductive liquid medium, an ion conductive gel material, or an ion conductive solid electrolyte material can be used. Among these, the ion conductive gel material is excellent in adhesiveness with the electrode, and has high ionic conductivity even after being integrated as an electrode laminate. A material obtained by laminating and impregnating an ion conductive gel material on the surface of a solid electrolyte material or a porous material can also be used. Examples of the ion conductive gel material include a polymer gel in which an electrolytic solution is held in a polymer matrix and a gel material of an ion permeable ceramic material. Among these, the former is preferable because it is flexible and can be in close contact with the electrode.
[0028]
The polymer matrix material can be used, for example, as a crosslinked polyvinylidene fluoride, a vinylidene fluoride copolymer, a mixture thereof, or a mixture with another polymer. Examples of the vinylidene fluoride copolymer include a vinylidene fluoride-hexafluoropropylene copolymer and a vinylidene fluoride-trifluoroethylene copolymer. Polyvinylidene fluoride and polyvinylidene fluoride copolymers are preferable because they have a wide electrochemically stable region and high strength, and therefore are excellent in processability and battery performance when used in batteries. The polymer structure is a bulk, porous structure, foam structure, powder-sintered body, compacted body such as a powder compact, and the polymer and electrolyte are homogenized by solvent and heat melting After that, a form molded into a predetermined shape is used. Even when the porous structure is used and the microporous structure is clogged in the step of stacking and integrating with the electrode, the polymer is impregnated in the electrolyte solution and exhibits ionic conductivity. Inhibition of ion transport as seen in
[0029]
As the electrolytic solution, when the non-aqueous battery of the present invention is a lithium ion battery, a solution in which a lithium salt is dissolved in an organic solvent is used. Examples of the lithium salt include lithium such as lithium fluoroborate, lithium fluorophosphate, lithium perchlorate, lithium arsenate fluoride, lithium trifluoromethanesulfonate, lithium trifluoromethanesulfonylimide, and lithium perfluorobutanesulfonate. A salt, a mixture thereof, or a molten salt obtained by mixing a plurality of salts is used. Some of these molten salts are liquid at room temperature and can be used without necessarily containing an electrolyte solvent. Further, as electrolyte solvents, cyclic carbonate compounds such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, etc. Chain carbonates such as toluene, ether compounds such as tetrahydrofuran and dioxane, γ-butyllactone, propiolactone, ester compounds such as methyl acetate, nitrile compounds such as acetonitrile and propionitrile, sulfolane, A simple substance such as a compound such as phosphazene, a mixture, a liquid oligomer of the polymer matrix, a mixture of an oligomer and a solvent, or the like is used.
[0030]
Before laminating the separator and the electrode, the surface of the electrode active material is coated and impregnated with a solution or slurry obtained by dissolving and dispersing the polymer matrix material in the above-mentioned electrolyte solution or electrolyte solution, and the electrode solution. Separator adhesion and ion migration of the electrode active material layer can be improved. Further, after electrode / separator lamination, the electrolytic solution, a solution obtained by dissolving and dispersing the polymer matrix material in the electrolytic solution, a slurry, and an electrolytic solution solvent may be impregnated.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to examples.
[0032]
[Example 1]
LiCoO₂Electrode (LiCoO with an average particle size of 5 μm₂100 parts by weight, 3 parts by weight of polyvinylidene fluoride and 3 parts by weight of acetylene black in a binder are dispersed in N-methylpyrrolidone, coated on a 15 μm aluminum current collector, and heated and pressed. Was cut into a width of 29 mm and a length of 110 mm, and the electrode active material layer was peeled off in the length direction with a width of 10 mm to expose the aluminum current collector. As a negative electrode, a graphite long sheet (graphite MCMB (Osaka Gas Co., Ltd.) having an average particle size of 10 μm) 100 parts by weight, an aqueous dispersion slurry of styrene-butadiene latex in 2 parts by weight in terms of solid content, and carboxymethyl cellulose A slurry obtained by mixing 0.8 parts by weight of an aqueous solution, uniformly dispersed in water, coated on a 12 μm copper current collector, and heated and pressed to a thickness of 85 μm on one side coating sheet) It cut | disconnected by 30 mm and length 110mm, the active material layer was peeled by width 9mm in the length direction, and the copper collector was exposed.
[0033]
A bulk sheet (film thickness 50 μm) of polyvinylidene fluoride-hexafluoropropylene copolymer (hexafluoropropylene content 3% by weight, Elf Atchem Kynar 2850) was subjected to electron beam irradiation (irradiation amount 10 Mrad) for crosslinking treatment. Thereafter, 7 parts by weight of chlorofluorocarbon (HFC-134a) was impregnated and heated and stretched, and a foam sheet (foaming ratio 4 times, film thickness 60 μm) was used as an electrolyte with ethylene carbonate and γ-butyllactone. To the liquid mixed at a volume ratio of 1: 1 to LiBF₄A solid electrolyte (electrolytic solution content 75% by weight, average film thickness width 65 μm, width 102 mm long sheet) was obtained by impregnating a 1.5 mol / liter solution obtained by dissolving did. After this separator was cut into a strip shape with a width of 32 mm, the above electrolytic solution was applied to the surface of the electrode with a roll coater. The coating amount is 30 g / m for the positive electrode.², Negative electrode 40 g / m²It was. The above positive electrode, separator, and negative electrode are arranged in this order so that the positive electrode active material layer faces the active material layer through the separator so that the positive electrode active material layer does not protrude from the negative electrode active material layer. The copper current collectors were laminated so as to protrude from the side, and were laminated and integrated with a heating roll laminator (roll temperature: 130 ° C., roll speed: 600 mm / min). In this manner, eight laminates were produced. These 8 laminates are stacked in the order of positive electrode / negative electrode / negative electrode / positive electrode / positive electrode / negative electrode,..., So that the side where only the aluminum current collector protrudes and the side where only the copper current collector protrudes are formed. In addition, the central part of the overlapped portions of the current collectors was joined by ultrasonic welding with a 3 mm square to bundle the electrode laminate. Subsequently, copper and aluminum sheet (thickness 30 μm) having a width of 10 mm and a length of 30 mm were used as electrode terminals, and ultrasonic welding was fixed to the ultrasonic welding portion (the welding portion was 3 mm square).
[0034]
An exterior body (cylindrical shape with a width of 40 mm, a side with a length of 110 mm) obtained by processing a polymer sheet (sheet of polyethylene terephthalate 25 μm, metal aluminum sheet 12 μm, and polypropylene 50 μm in order) into a bag shape After the electrode laminate of aluminum and copper is protruded to the outside by inserting the obtained electrode laminate, the aluminum and copper electrode terminal surfaces are respectively connected to the inner surface of the bag-like outer package. After heat-sealing and fixing to the upper and lower polypropylene resin layers, the opening was heat-sealed and sealed while vacuuming to produce a battery.
[0035]
Charge / discharge test (230 mA constant current, 4.2 V constant potential charge, 230 mA constant current discharge as a result of connecting the electrode terminal to the charger / discharger, resulting in an initial discharge amount of 730 mAh and an average voltage of 3.7 V (2.7 Wh) Charge and discharge were possible repeatedly.A thermocouple was attached to the center of the outer surface of the outer case of the battery in the charged state and the outer surface of the outer case sealing part where the electrode terminals were heat-sealed, and the electrode terminals of the battery were charged and discharged. As a result of overcharging with constant current and constant voltage charging (voltage 15 V) at a current of 2880 mA as a result of connecting to an electric machine, the outer body swells after about 19 minutes, and after 15 seconds, the electrode terminal is cut off and the current cannot be supplied. At this time, the maximum temperature in the vicinity of the electrode terminal of the battery was 38 ° C., and the maximum temperature in the center of the battery outer package was 42 ° C.
[0036]
[Example 2]
LiCoO produced in Example 1₂The electrode, graphite negative electrode, polyvinylidene fluoride-hexafluoropropylene copolymer foam sheet and a solid electrolyte impregnated with an electrolyte solution were used as a separator, laminated in the same manner as in Example 1, and the heating roll Eight laminates laminated and integrated with a laminator were produced and ultrasonically welded to bundle the electrode laminate.
[0037]
Next, two aluminum sheets (thickness: 30 μm) having a width of 10 mm and a length of 20 mm were aligned in the length direction so that the overlapping length was 10 mm. The center of the overlapping portion was ultrasonically welded to produce an electrode terminal in which two aluminum sheets were joined by a 3 mm square welded portion (after joining, width 10 mm, length 30 mm). On the other hand, a metal copper sheet having a width of 10 mm and a length of 20 mm was overlapped and welded in the same manner to produce an electrode terminal (after joining, a width of 10 mm and a length of 30 mm). These aluminum and metal copper electrode terminals were welded to the ultrasonic welding portions of the positive electrode and negative electrode current collectors, respectively, so that the electrode terminals protruded 25 mm from the ends of the electrode current collectors. In each of the two metal sheets of the positive electrode and the negative electrode terminal, a portion that may come into contact with the inner surface of the exterior body other than the portion to be fused and fixed is covered with a Teflon sheet, and then the metal of each electrode terminal One of the sheets is heated on the thermoplastic resin layer on the upper surface of the outer package (the outer package uses the same bag as in Example 1), and the other metal sheet is heated on the thermoplastic resin layer on the lower surface of the outer package. Fused and fixed. Thereafter, the electrode terminal was pulled out from the outer package, and the opening was thermally fused with a width of 20 mm and sealed.
[0038]
Charge / discharge test (230 mA constant current, 4.2 V constant potential charge, 230 mA constant current discharge as a result of connecting electrode terminals to a charger / discharger, resulting in an initial discharge amount of 732 mAh and an average voltage of 3.7 V (2.7 Wh) Charge and discharge were possible repeatedly.A thermocouple was attached to the outer package of the battery in the same manner as in Example 1, the electrode terminal of the battery was connected to a charger / discharger, and a constant current and constant voltage at a current of 2880 mA. As a result of overcharging with charging (voltage of 15 V), the outer body started to swell in about 19 minutes, and after 20 seconds, the electrode terminal was cut off and the current could not be supplied, resulting in a decrease in the cell temperature. The maximum temperature was 40 ° C., and the temperature at the center of the cell surface was 42 ° C.
[0039]
[Example 3]
LiCoO produced in Example 1₂An electrode, a graphite negative electrode, a polyvinylidene fluoride-hexafluoropropylene copolymer foam sheet and a solid electrolyte impregnated with an electrolyte solution were used as a separator, and eight laminates were produced in the same manner as in Example 1. The electrode laminate was bundled by ultrasonic welding.
[0040]
Subsequently, a rectangular shape having a width of 3 mm and a length of 10 mm is left in the center of the ultrasonic welded portion at the center in the length direction of aluminum and metal copper sheet (thickness 30 μm) having a width of 10 mm and a length of 30 mm. Thus, it cut with scissors and set it as the electrode terminal. One end of these aluminum and metal copper electrode terminals was welded to the ultrasonic welding portions of the positive electrode current collector and the negative electrode current collector, respectively, so that the electrode terminal protruded 25 mm from the electrode current collector end. The side of the aluminum electrode terminal that is welded to the current collector across a rectangular portion with a width of 3 mm is covered with a Teflon sheet, and the electrode terminal on the opposite side of the electrode terminal sealing portion side is covered with an exterior body (exterior body). (The same bag as in Example 1 was used) After being fused and fixed to the thermoplastic resin layer on the inner surface, the electrode terminal was pulled out from the exterior body and the opening was thermally fused and sealed.
[0041]
Charge / discharge test (230 mA constant current, 4.2 V constant potential charge, 230 mA constant current discharge as a result of connecting the electrode terminal to the charger / discharger, resulting in an initial discharge amount of 729 mAh and an average voltage of 3.7 V (2.7 Wh) Charge and discharge were possible repeatedly.A thermocouple was attached to the outer package of the battery in the same manner as in Example 1, the electrode terminal of the battery was connected to a charger / discharger, and a constant current and constant voltage at a current of 2880 mA. As a result of overcharging by charging (voltage of 15 V), the exterior body started to swell after about 19 minutes, and after another minute, the electrode terminal was cut and no current could be supplied, and the temperature of the battery decreased. The maximum temperature in the vicinity of the stop portion was 56 ° C., and the maximum temperature in the central portion of the battery exterior body was 53 ° C.
[0042]
[Example 4]
LiCoO produced in Example 1₂A solid electrolyte obtained by impregnating a positive electrode, a graphite negative electrode, a polyvinylidene fluoride-hexafluoropropylene copolymer foam sheet with an electrolyte solution was used as a separator, and was laminated in the same manner as in Example 1. Eight laminates laminated and integrated with a laminator were produced and ultrasonically welded to bundle the electrode laminate.
[0043]
Next, a central portion in the length direction of aluminum and metal copper sheet (thickness 30 μm) having a width of 10 mm and a length of 30 mm is cut obliquely at an angle of about 60 degrees with scissors, and the connection width of the electrode terminals is 3 mm. The strip which becomes was made as an electrode terminal. One end of these aluminum and metal copper electrode terminals was welded to the ultrasonic welding portions on the positive electrode and negative electrode current collector sides, respectively, so that the electrode terminal protruded 25 mm from the electrode current collector end. The electrode terminal on the side of the aluminum electrode terminal that is welded to the current collector across the notch portion is covered with a Teflon sheet, and the electrode terminal on the opposite electrode terminal sealing portion side is covered with an exterior body (the exterior body is implemented). After using the same bag as in Example 1 to be fused and fixed to the thermoplastic resin layer on the inner surface, the electrode terminal was pulled out from the exterior body, and the opening was heat sealed and sealed.
[0044]
Charge / discharge test (230mA constant current, 4.2V constant potential charge, 230mA constant current discharge as a result of connecting the electrode terminal to the charger / discharger. As a result, the initial discharge amount was 735mAh and the average voltage was 3.7V. A thermocouple was attached to the outer package of the battery in a charged state in the same manner as in Example 1, the electrode terminal of the battery was connected to a charger / discharger, and constant current / constant voltage charging with a current of 2880 mA (voltage 15V). As a result of overcharging the battery, the outer body started to swell in about 20 minutes, and after 40 seconds, the electrode terminal was cut off and the battery could not be energized, resulting in a decrease in the battery temperature. The maximum temperature in the center part of the battery was 50 ° C.
[0045]
[Comparative Example 1]
LiCoO produced in Example 1₂The electrode, graphite negative electrode, polyvinylidene fluoride-hexafluoropropylene copolymer foam sheet and a solid electrolyte impregnated with an electrolyte solution were used as a separator, laminated in the same manner as in Example 1, and the heating roll Eight laminates laminated and integrated with a laminator were produced and ultrasonically welded to bundle the electrode laminate.
[0046]
Next, aluminum and metal copper sheets (thickness: 30 μm) having a width of 10 mm and a length of 30 mm are used as electrode terminals, and one end of each of the aluminum and metal copper electrode terminals is used as an ultrasonic welding portion of the positive electrode and the negative electrode current collector, respectively. It was welded to have a structure in which the electrode terminal protruded 25 mm from the end of the electrode current collector. The exterior body used the same bag as in Example 1, the electrode terminal was pulled out from the exterior body, and the opening was thermally fused to be sealed.
[0047]
Charge / discharge test (230mA constant current, 4.2V constant potential charge, 230mA constant current discharge as a result of connecting the electrode terminal to the charger / discharger. As a result, the initial discharge amount was 731 mAh and the average voltage was 3.7V. A thermocouple was attached to the outer package of the battery in a charged state in the same manner as in Example 1, the electrode terminal of the battery was connected to a charger / discharger, and constant current / constant voltage charging with a current of 2880 mA (voltage 15V). As a result of overcharging at about 20 minutes, the exterior body started to swell, and after 2 minutes, the voltage reached 15 V and the current converged, at which the maximum temperature near the electrode terminal of the cell was 95 ° C. The maximum temperature of the central part of this was 91 ° C.
[0048]
【The invention's effect】
The present invention makes it possible to provide a lithium ion secondary battery with high safety, high energy density, high reliability, light weight, and thinness.

Claims

An electrode laminate in which an electrode is joined via a separator capable of ion migration is inserted into a bag-like outer package made of a polymer laminate material having a thermoplastic resin layer as the innermost layer, and the outer package from the positive electrode and the negative electrode of the electrode laminate Non-aqueous battery having a structure in which an electrode terminal extending outside is sealed, and a region having a small cross-sectional area is provided in a part of the electrode terminal, and at least one electrode terminal is in a bag shape across the region having a small cross-sectional area A non-aqueous battery having a structure in which the outer surface of the exterior body is closely fixed to the thermoplastic resin layer.

An electrode laminate in which an electrode is joined via a separator capable of ion migration is inserted into a bag-like outer package made of a polymer laminate material having a thermoplastic resin layer as the innermost layer, and the outer package from the positive electrode and the negative electrode of the electrode laminate A non-aqueous battery having a structure in which electrode terminals extending outside are sealed, and a part of the electrode terminals is composed of two or more layers of metal plate laminates that can be peeled off. A non-aqueous battery having a structure in which at least one is closely fixed to a thermoplastic resin layer on the inner surface of a bag-like outer package.

The non-aqueous battery according to claim 2, which has a structure in which metal layers of a metal flat plate laminate are joined with a compound made of a conductive filler and an insulating resin.