JP3988384B2

JP3988384B2 - Non-aqueous electrolyte secondary battery

Info

Publication number: JP3988384B2
Application number: JP2000394023A
Authority: JP
Inventors: 賢治中井; 佳正小石川; 祐一高塚; 健介弘中
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Shin Kobe Electric Machinery Co Ltd
Priority date: 2000-12-26
Filing date: 2000-12-26
Publication date: 2007-10-10
Anticipated expiration: 2020-12-26
Also published as: JP2002198101A

Description

【０００１】
【発明の属する技術分野】
本発明は非水電解液二次電池に係り、特に、平均粒径０．１μｍ乃至２μｍの一次粒子の集合体で形成された二次粒子からなるリチウムマンガン複酸化物と導電材とを含む正極活物質合剤が帯状集電体の両面にほぼ均等量塗着された正極と、充放電によりリチウムイオンを吸蔵・放出可能な負極と、をセパレータを介して捲回した電極捲回群を、所定圧で内圧を開放する内圧開放機構を有する電池容器内に収容した非水電解液二次電池に関する。
【０００２】
【従来の技術】
非水電解液二次電池を代表するリチウムイオン二次電池は、高エネルギー密度であるメリットを活かして、主にＶＴＲカメラやノートパソコン、携帯電話等のポータブル機器の電源に使用されている。この電池の内部構造は、通常以下に示されるような捲回式とされている。電極は正極、負極共に活物質が金属箔に塗着された帯状であり、セパレ−タを挟んで正極、負極が直接接触しないように断面が渦巻状に捲回され、捲回群を形成している。この捲回群が電池容器となる円筒形の電池缶に収納され、電解液注液後、封口されている。
【０００３】
一般的な円筒形リチウムイオン二次電池の寸法は、１８６５０型と呼ばれる、直径が１８ｍｍ、高さ６５ｍｍであり、小形民生用リチウムイオン電池として広く普及している。１８６５０型リチウムイオン二次電池の正極活物質には、高容量、長寿命を特徴とするコバルト酸リチウムが主として用いられており、電池容量は、おおむね１．３Ａｈ〜１．７Ａｈ、出力はおよそ１０Ｗ程度である。
【０００４】
一方、自動車産業界においては環境問題に対応すべく、排出ガスのない、動力源を完全に電池のみにした電気自動車と、内燃機関エンジンと電池との両方を動力源とするハイブリッド（電気）自動車の開発が加速され、一部実用化の段階にきている。
【０００５】
電気自動車の電源となる電池には当然高出力、高エネルギーが得られる特性が要求され、この要求にマッチした電池としてリチウムイオン電池が注目されている。電気自動車の普及のためには、電池の低価格化が必須であり、そのためには、低コスト電池材料が求められ、例えば、正極活物質であれば、資源的に豊富なマンガンの酸化物が特に注目され、電池の高性能化を狙った改善がなされてきた。また、電気自動車用電池には、高容量だけではなく、加速性能などを左右する高出力化、つまり電池の内部抵抗の低減が求められる。電極反応面積の増大を狙って、正極活物質として比表面積の大きなマンガン酸リチウムとすることでこの要求に対応することができる。
【０００６】
具体的に比表面積を大くするには、マンガン酸リチウムの粒子径を小さくすることである。しかし、小さな粒子径では、電極製作時に粉体が飛散したり、集電体両面に塗布するのためのスラリ化がしにくいなどの弊害が生じる。これを改善するために、小さな粒子径である一次粒子を凝集させた二次粒子を形成したマンガン酸リチウムとすることで対処可能である。
【０００７】
【発明が解決しようとする課題】
しかしながら、リチウムイオン電池の場合、高容量、高出力になればなるほど安全性が低下する傾向にあり、特に上述したような、高出力化を狙ったマンガン酸リチウムを用いた場合には、電池が異常状態に陥ったときの現象がやや激しくなる傾向が見られる。電気自動車用電源に用いられるような高容量、高出力の電池ともなると、大電流充電、大電流放電がなされるために、１８６５０型リチウムイオン電池に一般に採用されているような、異常時の電池内圧上昇に応じて作動する電流遮断機構（一種の切断スイッチ）を電池構造内に設けることは実質的に不可能である。
【０００８】
人を乗せて走る電気自動車の場合、充電制御システムが故障してしまった場合の過充電時、不慮の衝突事故の場合に遭遇する可能性のある電池のクラッシュ時あるいは、異物突き刺し時、外部短絡時等の電池自体の安全性を確保することは、最低限必要な、非常に重要な電池特性である。なお、電池の安全性とは、電池が異常な状態にさらされた場合の電池の挙動が、人に身体的損害を与えないことは当然のことながら、車両への損傷を最小限の抑えることを意味する。
【０００９】
本発明は上記事案に鑑み、高容量、高出力でありながらも、極めて安全性の高い非水電解液二次電池を提供することを課題とする。
【００１０】
【課題を解決するための手段】
上記課題を解決するために、本発明は、平均粒径０．１μｍ乃至２μｍの一次粒子の集合体で形成された二次粒子からなるリチウムマンガン複酸化物と導電材とを含む正極活物質合剤が帯状集電体の両面にほぼ均等量塗着された正極と、充放電によりリチウムイオンを吸蔵・放出可能な負極と、をセパレータを介して捲回した電極捲回群を、所定圧で内圧を開放する内圧開放機構を有する電池容器内に収容した非水電解液二次電池において、前記導電材は黒鉛と無定型炭素との混合物であって、前記リチウムマンガン複酸化物の前記集電体片面あたりの塗着量が８０ｇ／ｍ^２乃至１６０ｇ／ｍ^２であり、かつ、前記正極活物質合剤に含有される導電材量が８重量％乃至１６重量％であることを特徴とする。
【００１１】
本発明では、高容量、高出力の非水電解液二次電池を確保するために、平均粒径０．１μｍ乃至２μｍの一次粒子の集合体で形成された二次粒子からなるリチウムマンガン複酸化物と導電材とを含む正極活物質合剤が帯状集電体の両面にほぼ均等量塗着された正極と、充放電によりリチウムイオンを吸蔵・放出可能な負極と、が用いられている。また、導電材に黒鉛と無定型炭素との混合物を用いることにより、より高出力の非水電解液二次電池とすることができる。高容量、高出力の非水電解液二次電池では、異常状態に陥ったときに、大電流充電又は大電流放電状態が維持され、非水電解液と活物質合剤との化学反応により電池容器内で急激かつ大量のガスが発生し、電池容器の内圧を上昇させる。一般に、非水電解液二次電池では、電池容器内の内圧上昇を防止するために、電池容器に所定圧で内圧を開放する内圧開放機構を有しているが、リチウムマンガン複酸化物の集電体片面あたりの塗着量が８０ｇ／ｍ^２乃至１６０ｇ／ｍ^２とし、かつ、正極活物質合剤に含有される導電材量を８重量％乃至１６重量％とすることにより、内圧開放機構からのガス放出が極めて穏やかに行われる。このため、本発明によれば、高容量、高出力でありながらも、極めて安全性の高い非水電解液二次電池を実現することができる。
【００１２】
この場合において、黒鉛の平均粒径を二次粒子の平均粒径の０．２倍乃至０．８倍及び／又は無定型炭素をアセチレンブラックとすれば、更に高出力の非水電解液二次電池を得ることができる。また、リチウムマンガン複酸化物のＬｉ／Ｍｎ比を０．５５乃至０．６０とすれば、容量の低下を伴うことなく出力維持率を向上させることができる。更に、負極の活物質に非晶質炭素を用いれば、高出力、高容量、かつ、安全性に一層優れた非水電解液二次電池とすることができる。
【００１３】
【発明の実施の形態】
以下、図面を参照して本発明に係る非水電解液二次電池を電気自動車用電源の円筒形リチウムイオン電池に適用した実施の形態について説明する。
【００１４】
（正極板の作製）
図１に示すように、正極活物質としてのマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）粉末と、導電材として後述する所定の炭素と、結着剤としてポリフッ化ビニリデン（ＰＶＤＦ）と、を所定混合比で混合し、これに分散溶媒のＮ−メチル−２−ピロリドン（ＮＭＰ）を添加、混練したスラリを、厚さ２０μｍのアルミニウム箔Ｗ１（正極集電体）の両面に塗布した。このとき、正極板長寸方向の一方の側縁に幅３０ｍｍの未塗布部を残した。その後乾燥、プレス、裁断して、幅８２ｍｍ、所定長さ、活物質合剤塗布部所定厚さの正極板を得た。正極活物質合剤層Ｗ２のかさ密度は２．６５ｇ／ｃｍ^３とした。上記未塗布部に切り欠きを入れ、切り欠き残部を正極リード片２とした。隣り合う正極リード片２を５０ｍｍ間隔とし、正極リード片２の幅を５ｍｍとした。
【００１５】
（負極板の作製）
所定の炭素粉末９２質量部に結着剤として８質量部のポリフッ化ビニリデンを添加し、これに分散溶媒のＮ−メチル−２−ピロリドンを添加、混練したスラリを厚さ１０μｍの圧延銅箔Ｗ３（負極集電体）の両面に塗布した。このとき、負極板長寸方向の一方の側縁に幅３０ｍｍの未塗布部を残した。その後乾燥、プレス、裁断して、幅８６ｍｍ、所定長さ、活物質塗布部所定厚さの負極板を得た。負極活物質合剤層Ｗ４の空隙率が約３５％となるように負極板を圧縮した。上記未塗布部に正極板と同様に切り欠きを入れ、切り欠き残部を負極リード片３とした。隣り合う負極リード片３を５０ｍｍ間隔とし、負極リード片３の幅を５ｍｍとした。
【００１６】
（電池の作製）
上記作製した正極板と負極板とを、これら両極板が直接接触しないように幅９０ｍｍ、厚さ４０μｍのポリエチレン製セパレータＷ５と共に捲回した。捲回の中心には、ポリプロピレン製の中空円筒状の軸芯１を用いた。このとき、正極リード片２と負極リード片３とが、それぞれ捲回群６の互いに反対側の両端面に位置するようにした。また、正極板、負極板、セパレータの長さを調整し、捲回群６の直径を３８±０．１ｍｍとした。
【００１７】
正極リード片２を変形させ、その全てを、捲回群６の軸芯１のほぼ延長線上にある正極集電リング４の周囲から一体に張り出している鍔部周面付近に集合、接触させた後、正極リード片２と鍔部周面とを超音波溶接して正極リード片２を鍔部周面に接続した。一方、負極集電リング５と負極リード片３との接続操作も、正極集電リング４と正極リード片２との接続操作と同様に実施した。
【００１８】
その後、正極集電リング４の鍔部周面全周に絶縁被覆を施した。この絶縁被覆には、基材がポリイミドで、その片面にヘキサメタアクリレートからなる粘着剤を塗布した粘着テープを用いた。この粘着テープを鍔部周面から捲回群６外周面に亘って一重以上巻いて絶縁被覆とし、捲回群６をニッケルメッキが施されたスチール製の電池容器７内に挿入した。電池容器７の外形は４０ｍｍ、内径は３９ｍｍである。
【００１９】
負極集電リング５には予め電気的導通のための負極リード板８が溶接されており、電池容器７に捲回群６を挿入後、電池容器７の底部と負極リード板８とを溶接した。
【００２０】
一方、正極集電リング４には、予め複数枚のアルミニウム製のリボンを重ね合わせて構成した正極リード９を溶接しておき、正極リード９の他端を、電池容器７を封口するための電池蓋の下面に溶接した。電池蓋には、円筒形リチウムイオン電池２０の内圧上昇に応じて開裂する内圧開放機構としての開裂弁１１が設けられている。開裂弁１１の開裂圧は、約９×１０^５Ｐａに設定した。電池蓋は、蓋ケース１２と、蓋キャップ１３と、気密を保つ弁押え１４と、開裂弁１１とで構成されており、これらが積層されて蓋ケース１２の周縁をカシメることによって組立てられている。
【００２１】
非水電解液を所定量電池容器７内に注入し、その後、正極リード９を折りたたむようにして電池蓋で電池容器７に蓋をし、ＥＰＤＭ樹脂製ガスケット１０を介してカシメて密封することにより円筒形リチウムイオン電池２０を完成させた。
【００２２】
非水電解液には、エチレンカーボネートとジメチルカーボネートとジエチルカーボネートの体積比１：１：１の混合溶液中へ６フッ化リン酸リチウム（ＬｉＰＦ_６）を１モル／リットル溶解したものを用いた。なお、円筒形リチウムイオン電池２０には、電池内圧の上昇に応じて電気的に作動する、例えば、ＰＴＣ(Positive Temperature Coefficient) 素子等の電流遮断機構は設けられていない。
【００２３】
【実施例】
次に、本実施形態に従って作製した円筒形リチウムイオン電池２０の実施例について説明する。なお、比較のために作製した比較例の電池についても併記する。
【００２４】
（実施例１）
下表１に示すように、実施例１では、正極活物質として一次粒子径約１〜２μｍ、二次粒子径約２０μｍ、ＬｉとＭｎの原子比（Ｌｉ／Ｍｎ比）０．５２のマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）粉末と、平均粒子径１８μｍの鱗片状黒鉛と、ポリフッ化ビニリデンと、の配合比を重量％で８３：１２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を８０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を７３μｍ、正極板の長さを４３４ｃｍとした。ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径は０．９倍である。一方、負極板には、負極活物質としてメソフェーズ系球状黒鉛であるＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を５３μｍ、長さを４４６ｃｍとした。なお、鱗片状黒鉛の平均粒子径は、篩分けによって調整することができる。
【００２５】
【表１】

【００２６】
なお、作製した電極板は、捲回したときに、捲回最内周では捲回方向に正極板が負極板からはみ出すことがなく、また最外周でも捲回方向に正極板が負極板からはみ出すことがないように負極板の長さは正極板の長さよりも１２ｃｍ長くなるようにした。また、捲回方向と垂直方向においても正極活物質塗布部Ｗ２が負極活物質塗布部Ｗ４からはみ出すことがないように、負極活物質塗布部Ｗ４の幅は、正極活物質塗布部Ｗ２の幅よりも４ｍｍ長くした（以下の実施例及び比較例においても同じ。）。
【００２７】
（実施例２）
表１に示すように、実施例２では、マンガン酸リチウムの塗着量を１２０ｇ／ｍ^２とし、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、正極板の長さを３４２ｃｍ、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、負極板の長さを３５４ｃｍとした以外は実施例１と同様に電池を作製した。
【００２８】
（実施例２−２〜２−５）
表１に示すように、実施例２−２〜実施例２−５では、マンガン酸リチウムのＬｉ／Ｍｎ比をそれぞれ、０．５５、０．５８、０．６０、０．６１とした以外は実施例２と同様に電池を作製した。
【００２９】
（実施例３）
表１に示すように、実施例３では、マンガン酸リチウムの塗着量を１６０ｇ／ｍ^２とし、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１４６μｍ、正極板の長さを２８２ｃｍ、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を１０６μｍ、負極板の長さを２９４ｃｍとした以外は実施例１と同様に電池を作製した。
【００３０】
（実施例４）
表１に示すように、実施例４では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１８μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．９倍）と、ポリフッ化ビニリデンとの配合比を、重量％で８７：８：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０４μｍ、正極板の長さを３４８ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３６０ｃｍとして、電池を作製した。
【００３１】
（実施例５）
表１に示すように、実施例５では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１８μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．９倍）と、ポリフッ化ビニリデンとの配合比を、重量％で７９：１６：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１１５μｍ、正極板の長さを３３６ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３４８ｃｍとして、電池を作製した。
【００３２】
（実施例６）
表１に示すように、実施例６では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１８μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．９倍）と、ケッチェンブラック（ＫＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、正極板の長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００３３】
（実施例７）
表１に示すように、実施例７では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径２μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．１倍）と、ケッチェンブラック（ＫＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、正極板の長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００３４】
（実施例８）
表１に示すように、実施例８では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径４μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．２倍）と、ケッチェンブラック（ＫＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、正極板の長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００３５】
（実施例９）
表１に示すように、実施例９では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１０μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．５倍）と、ケッチェンブラック（ＫＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００３６】
（実施例１０）
表１に示すように、実施例１０では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１６μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．８倍）と、ケッチェンブラック（ＫＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００３７】
（実施例１１）
表１に示すように、実施例１１では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１０μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．５倍）と、アセチレンブラック（ＡＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００３８】
（実施例１２）
表１に示すように、実施例１２では、正極活物質として一次粒子径約１〜２μｍ、二次粒子径約２０μｍ、ＬｉとＭｎの原子比（Ｌｉ／Ｍｎ比）０．５５のマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）粉末と、平均粒子径１０μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．５倍）と、アセチレンブラック（ＡＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００３９】
（実施例１３）
表１に示すように、実施例１３では、正極活物質として一次粒子径約１〜２μｍ、二次粒子径約２０μｍ、ＬｉとＭｎの原子比（Ｌｉ／Ｍｎ比）０．５８のマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）粉末と、平均粒子径１０μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．５倍）と、アセチレンブラック（ＡＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００４０】
（実施例１４）
表１に示すように、実施例１４では、正極活物質として一次粒子径約１〜２μｍ、二次粒子径約２０μｍ、ＬｉとＭｎの原子比（Ｌｉ／Ｍｎ比）０．６０のマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）粉末と、平均粒子径１０μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．５倍）と、アセチレンブラック（ＡＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００４１】
（実施例１５）
表１に示すように、実施例１５では、正極活物質として一次粒子径約１〜２μｍ、二次粒子径約２０μｍ、ＬｉとＭｎの原子比（Ｌｉ／Ｍｎ比）０．６１のマンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）粉末と、平均粒子径１０μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．５倍）と、アセチレンブラック（ＡＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００４２】
（実施例１６）
表１に示すように、実施例１６では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１０μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．５倍）と、アセチレンブラック（ＡＢ）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１０：２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質として非晶質炭素を用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００４３】
（実施例１６−２〜１６−５）
表１に示すように、実施例１６−２〜実施例１６−５では、マンガン酸リチウムのＬｉ／Ｍｎ比をそれぞれ、０．５５、０．５８、０．６０、０．６１とした以外は実施例１６と同様に電池を作製した。
【００４４】
（実施例１７）
表１に示すように、実施例１７では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１０μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．５倍）と、ポリフッ化ビニリデンとの配合比を、重量％で８３：１２：５とし、正極活物質合剤層（活物質塗布部）Ｗ２の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）Ｗ２の厚さ（集電体厚さは含まない。）を１０９μｍ、長さを３４２ｃｍとした。一方、負極板には、負極活物質として非晶質炭素を用い、負極活物質合剤層（活物質塗布部）Ｗ４の厚さ（集電体厚さは含まない。）を７９μｍ、長さを３５４ｃｍとして、電池を作製した。
【００４５】
（実施例１７−２〜１７−５）
表１に示すように、実施例１７−２〜実施例１７−５では、マンガン酸リチウムのＬｉ／Ｍｎ比をそれぞれ、０．５５、０．５８、０．６０、０．６１とした以外は実施例１７と同様に電池を作製した。
【００４６】
（比較例１）
表１に示すように、比較例１では、マンガン酸リチウムの塗着量を７５ｇ／ｍ^２とし、正極活物質合剤層（活物質塗布部）の厚さ（集電体厚さは含まない。）を６８μｍ、長さを４５０ｃｍとし、負極活物質合剤層（活物質塗布部）の厚さ（集電体厚さは含まない。）を５０μｍ、負極板の長さを４６２ｃｍとした以外は実施例１と同様の電池を作製した。
【００４７】
（比較例２）
表１に示すように、比較例２では、マンガン酸リチウムの塗着量を１６５ｇ／ｍ^２とし、正極活物質合剤層（活物質塗布部）の厚さ（集電体厚さは含まない。）を１５０μｍ、長さを２７６ｃｍとし、負極活物質合剤層（活物質塗布部）の厚さ（集電体厚さは含まない。）を１０９μｍ、負極板の長さを２８８ｃｍとした以外は実施例１と同様の電池を作製した。
【００４８】
（比較例３）
表１に示すように、比較例３では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１８μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．９倍）と、ポリフッ化ビニリデンとの配合比を、重量％で８８：７：５とし、正極活物質合剤層（活物質塗布部）の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）の厚さ（集電体厚さは含まない。）を１０３μｍ、正極板の長さを３４９ｃｍとし、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）の厚さ（集電体厚さは含まない。）を８０μｍ、負極板の長さを３６１ｃｍとして、電池を作製した。
【００４９】
（比較例４）
表１に示すように、比較例４では、実施例１と同様のマンガン酸リチウム粉末と、平均粒子径１８μｍの鱗片状黒鉛（ＬｉＭｎ_２Ｏ_４の二次粒径に対する鱗片状黒鉛の平均粒径：０．９倍）と、ポリフッ化ビニリデンとの配合比を、重量％で７８：１７：５とし、正極活物質合剤層（活物質塗布部）の集電体片面あたりのマンガン酸リチウムの塗着量を１２０ｇ／ｍ^２、正極活物質合剤層（活物質塗布部）の厚さ（集電体厚さは含まない。）を１１６μｍ、正極板の長さを３３４ｃｍとした。一方、負極板には、負極活物質としてＭＣＭＢを用い、負極活物質合剤層（活物質塗布部）の厚さ（集電体厚さは含まない。）を８０μｍ、負極板の長さを３４６ｃｍとして、電池を作製した。
【００５０】
＜試験・評価＞
次に、以上のようにして作製した実施例及び比較例の各電池について、以下の一連の試験を行った。
【００５１】
実施例及び比較例の各電池を、充電した後放電し、放電容量を測定した。充電条件は、４．２Ｖ定電圧、制限電流５Ａ、３．５時間とした。放電条件は、５Ａ定電流、終止電圧２．７Ｖとした。
【００５２】
また、上記条件で充電状態の電池の放電出力を測定した。測定条件は、１Ａ、３Ａ、６Ａ、各放電電流で５秒目の電圧を読み取り、横軸電流値に対して縦軸にプロットし、３点を結ぶ近似直線が、２．７Ｖと交差するところの電流値と、２．７Ｖとの積を出力とした。
【００５３】
更に、実施例、比較例の各電池を、上記条件で充放電を１００回繰り返した後、出力（容量）を測定し、初期の出力に対する維持率を百分率で示した。当然のことながら、この維持率が高いほうが寿命特性がよいことになる。
【００５４】
これら充電、放電、出力の測定は、いずれも環境温度２５±1°Ｃの雰囲気で行った。
【００５５】
その後、作製した電池を、常温で、２０Ａ定電流で連続充電し、電池挙動を観察した。その結果を下表２に示す。現象は、開裂弁開裂の後、電解液の揮発物からなるガス放出が起こる。このガス放出の程度を比較するために、現象発生直後の電池表面温度を測定した。また、ガス放出後、電池容器の変形の有無を確認した。なお、表２において、「○」は電池容器の変形が全く認められなかったもの、「△」は電池容器の若干の変形が認められたもの、「×」は電池容器が大きく変形したものを示している。
【００５６】
【表２】

【００５７】
表２に示すように、実施例１〜実施例５の電池では、高容量、高出力な電池が得られ、かつ、連続充電時の電池挙動も穏やかなものであった。このときの電池の表面温度は、最高で１５０°Ｃ〜２２０°Ｃであった。マンガン酸リチウムの塗着量が８０ｇ／ｍ^２を下回った比較例1の電池では、高容量、高出力な電池が得られるものの、連続充電時の電池挙動は、電池の変形を伴った激しいものとなり、電池表面温度は、３００°Ｃを超える結果となった。逆に、１６０ｇ／ｍ^２を上回った比較例２の電池では、連続充電時の電池挙動は穏やかであったが、出力の低下を伴い、電気自動車用電池としてはふさわしくない結果となった。同様に、比較例３の電池は、正極導電材の黒鉛の量が８重量％を下回っており、出力の低下を招く結果となった。一方、正極導電材の黒鉛の量が１６重量％を上回っている比較例４の電池では、高容量、高出力な電池が得られるものの、連続充電時の電池挙動は、電池の変形を伴った激しいものとなり、電池表面温度は、３１０°Ｃとなる結果となった。
【００５８】
正極導電材に黒鉛と無定型炭素を混合して用いた実施例６〜実施例１６−５の電池では、出力の高い電池を得ることができた。無定型炭素にケッチェンブラックを用いた実施例６〜１０の電池では、正極活物質のマンガン酸リチウムの二次粒子径に対する導電材黒鉛の粒子径の比が、０．２〜０．８である実施例８〜実施例１０の電池が、中でもより高出力が得られている。マンガン酸リチウムの二次粒子径に対する導電材黒鉛の粒子径の比が、０．２を下回っている実施例７の電池では、連続充電時の電池表面温度が２１０°Ｃと、実施例８〜１０の電池と比べて若干高い。
【００５９】
無定型炭素にアセチレンブラックを用いた実施例１１〜実施例１６−５の電池では、より高出力が得られており、かつ、１００回充放電後における出力維持率も高い。
【００６０】
マンガン酸リチウムのＬｉ／Ｍｎ比が、０．５５以上である実施例１２〜実施例１４、実施例２−２〜実施例２−４、実施例１６−２〜実施例１６−４、実施例１７−２〜実施例１７−４の電池は、出力維持率が極めて高い。ところが、マンガン酸リチウムのＬｉ／Ｍｎ比が０．６０を上回る実施例１５、実施例２−５、実施例１６−５、実施例１７−５の電池では、容量の低下を伴う結果となり、Ｌｉ／Ｍｎ比は、０．５５〜０．６０の範囲が好ましいことがわかる。
【００６１】
負極板に非晶質炭素を用いた実施例１６、実施例１６−２〜実施例１６−５、実施例１７、実施例１７−２〜実施例１７−５の電池は、極めて高い出力、かつ、極めて高い出力維持率、最も低い連続充電時の電池表面温度が得られた。従って、これら実施例１６、１６−２〜１６−５、１７、１７−２〜１７−５の電池は、高容量、高出力で、かつ、安全性に優れる、全体バランスのとれた電池であるということができる。
【００６２】
以上のように、本実施形態の円筒形リチウムイオン電池２０は、電池が異常な状態にさらされた場合の挙動が極めて穏やかで、安全性に優れた電池である。このように、高容量、高出力で、極めて安全性の高い電池は、特に電気自動車の電源に適している。
【００６３】
なお、本実施形態では、電気自動車用電源に用いられる大形の二次電池について例示したが、電池の大きさ、電池容量には限定されず、電池容量としておおむね３〜１０Ａｈ程度の電池に対して本発明は効果を著しく発揮することが確認されている。また、本実施形態では円筒形電池について例示したが、本発明は電池の形状についても限定されず、角形、その他の多角形の電池にも適用可能である。更に、本発明の適用可能な形状としては、上述した有底筒状容器（缶）に電池上蓋がカシメによって封口されている構造の電池以外であっても構わない。このような構造の一例として正負外部端子が電池蓋を貫通し電池容器内で軸芯を介して正負外部端子が押し合っている状態の電池を挙げることができる。
【００６４】
また、本実施形態では、絶縁被覆に、基材がポリイミドで、その片面にヘキサメタアクリレートからなる粘着剤を塗布した粘着テープを用いた例を示したが、例えば、基材がポリプロピレンやポリエチレン等のポリオレフィンで、その片面又は両面にヘキサメタアクリレートやブチルアクリレート等のアクリル系粘着剤を塗布した粘着テープや、粘着剤を塗布しないポリオレフィンやポリイミドからなるテープ等も好適に使用することができる。
【００６５】
更に、本実施形態では、リチウムイオン電池用の正極にマンガン酸リチウム、負極に非晶質炭素、電解液にエチレンカーボネートとジメチルカーボネートとジエチルカーボネートの体積比１：１：１の混合溶液中へ６フッ化リン酸リチウムを１モル／リットル溶解したものを用いたが、本発明の電池には特に制限はなく、また、導電材、結着剤も通常用いられているいずれのものも使用可能である。なお、一般に、マンガン酸リチウムは、適当なリチウム塩と酸化マンガンとを混合、焼成して合成することができるが、リチウム塩と酸化マンガンの仕込み比を制御することによって所望のＬｉ／Ｍｎ比とすることができる。
【００６６】
また、本実施形態以外で用いることのできるリチウムイオン電池用極板活物質結着剤としては、テフロン、ポリエチレン、ポリスチレン、ポリブタジエン、ブチルゴム、ニトリルゴム、スチレン／ブタジエンゴム、多硫化ゴム、ニトロセルロース、シアノエチルセルロース、各種ラテックス、アクリロニトリル、フッ化ビニル、フッ化ビニリデン、フッ化プロピレン、フッ化クロロプレン等の重合体及びこれらの混合体などがある。
【００６７】
また更に、本実施形態以外で用いることのできるリチウムイオン電池用正極活物質としては、リチウムを挿入・脱離可能な材料であり、予め十分な量のリチウムを挿入したリチウムマンガン複酸化物が好ましく、スピネル構造を有したマンガン酸リチウムや、結晶中のマンガンやリチウムの一部をそれら以外の元素で置換あるいはドープした材料を使用するようにしてもよい。
【００６８】
更にまた、本実施形態以外で用いることのできるリチウムイオン電池用負極活物質も上記特許請求範囲に記載した事項以外に特に制限はない。例えば、天然黒鉛や、人造の各種黒鉛材、コークス、非晶質炭素などの炭素質材料等でよく、その粒子形状においても、鱗片状、球状、繊維状、塊状等、特に制限されるものではない。
【００６９】
また、非水電解液としては、一般的なリチウム塩を電解質とし、これを有機溶媒に溶解した電解液が用いられる。しかし、用いられるリチウム塩や有機溶媒は特に制限されない。例えば、電解質としては、ＬｉＣｌＯ₄、ＬｉＡｓＦ₆、ＬｉＰＦ₆、ＬｉＢＦ₄、ＬｉＢ（Ｃ₆Ｈ₅）₄、ＣＨ₃ＳＯ₃Ｌｉ、ＣＦ₃ＳＯ₃Ｌｉ等やこれらの混合物を用いることができる。非水電解液有機溶媒としては、プロピレンカーボネート、エチレンカーボネート、１，２−ジメトキシエタン、１，２−ジエトキシエタン、γ−ブチロラクトン、テトラヒドロフラン、１，３−ジオキソラン、４−メチル−１，３−ジオキソラン、ジエチルエーテル、スルホラン、メチルスルホラン、アセトニトリル、プロピオニトニル等またはこれら２種類以上の混合溶媒を用いるようにしてもよく、混合配合比についても限定されるものではない。
【００７０】
【発明の効果】
以上説明したように、本発明によれば、平均粒径０．１μｍ乃至２μｍの一次粒子の集合体で形成された二次粒子からなるリチウムマンガン複酸化物と、黒鉛と無定型炭素との混合物の導電材とを含む活物質合剤が帯状集電体の両面にほぼ均等量塗着された正極と充放電によりリチウムイオンを吸蔵・放出可能な負極とを用いたので、高容量、高出力とすることができると共に、活物質合剤を、集電体片面あたりの塗着量が８０ｇ／ｍ^２乃至１６０ｇ／ｍ^２とし、かつ、導電材量を８重量％乃至１６重量％としたので、内圧開放機構からのガス放出が極めて穏やかに行われるため、高容量、高出力でありながらも、極めて安全性の高い非水電解液二次電池を実現することができる、という効果を得ることができる。
【図面の簡単な説明】
【図１】本発明が適用可能な実施形態の円筒形リチウムイオン電池の断面図である。
【符号の説明】
１軸芯
２正極リード片
３負極リード片
４正極集電リング
５負極集電リング
６捲回群（電極捲回群）
７電池容器
８負極リード板
９正極リード
１０ガスケット
１１開裂弁（内圧開放機構）
１２蓋ケース
１３蓋キャップ
１４弁押え
２０円筒形リチウムイオン電池（非水電解液二次電池）
Ｗ１正極集電体（集電体）
Ｗ２正極活物質合剤層
Ｗ３負極集電体
Ｗ４負極活物質合剤層
Ｗ５セパレータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery, and in particular, a positive electrode including a lithium manganese complex oxide composed of secondary particles formed of an aggregate of primary particles having an average particle diameter of 0.1 μm to 2 μm and a conductive material. An electrode winding group in which a positive electrode in which an active material mixture is applied to both sides of a belt-like current collector in an approximately equal amount and a negative electrode capable of inserting and extracting lithium ions by charging and discharging are wound through a separator, The present invention relates to a non-aqueous electrolyte secondary battery housed in a battery container having an internal pressure release mechanism that releases an internal pressure at a predetermined pressure.
[0002]
[Prior art]
Lithium ion secondary batteries, which are representative of non-aqueous electrolyte secondary batteries, are mainly used as power sources for portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of the high energy density. The internal structure of this battery is usually a winding type as shown below. The electrode is in the form of a strip in which an active material is applied to a metal foil for both the positive electrode and the negative electrode. ing. The wound group is housed in a cylindrical battery can serving as a battery container, and sealed after injecting the electrolyte.
[0003]
A typical cylindrical lithium ion secondary battery has a diameter of 18 mm and a height of 65 mm, which is called 18650 type, and is widely used as a small consumer lithium ion battery. The positive electrode active material of the 18650 type lithium ion secondary battery mainly uses lithium cobaltate, which is characterized by high capacity and long life. The battery capacity is approximately 1.3 Ah to 1.7 Ah, and the output is approximately 10 W. Degree.
[0004]
On the other hand, in the automobile industry, in order to cope with environmental problems, there are no exhaust gas, an electric vehicle that uses only a power source as a power source, and a hybrid (electric) vehicle that uses both an internal combustion engine and a battery as power sources. Development has been accelerated, and part of it has been put to practical use.
[0005]
Naturally, a battery serving as a power source for an electric vehicle is required to have high output and high energy characteristics. Lithium ion batteries are attracting attention as batteries that meet this requirement. For the popularization of electric vehicles, it is essential to reduce the price of the battery. For this purpose, a low-cost battery material is required. For example, in the case of a positive electrode active material, a resource-rich manganese oxide is used. Particular attention has been paid to improvements aimed at improving battery performance. In addition, batteries for electric vehicles are required to have not only high capacity but also high output that affects acceleration performance and the like, that is, reduction of internal resistance of the battery. With the aim of increasing the electrode reaction area, this requirement can be met by using lithium manganate having a large specific surface area as the positive electrode active material.
[0006]
Specifically, to increase the specific surface area, it is necessary to reduce the particle size of lithium manganate. However, when the particle size is small, there are problems such as powder scattering during the manufacture of the electrode and difficulty in forming a slurry for application to both sides of the current collector. In order to improve this, it can be coped with by using lithium manganate in which secondary particles are formed by agglomerating primary particles having a small particle diameter.
[0007]
[Problems to be solved by the invention]
However, in the case of a lithium ion battery, the higher the capacity and the higher the output, the lower the safety, and in particular, when using lithium manganate aimed at higher output as described above, the battery There is a tendency that the phenomenon when it falls into an abnormal state becomes somewhat intense. High capacity and high output batteries used for power sources for electric vehicles are charged with large currents and discharged with large currents. Therefore, such batteries are used in 18650 type lithium ion batteries in an abnormal state. It is virtually impossible to provide a current interruption mechanism (a kind of disconnection switch) that operates in response to an increase in internal pressure in the battery structure.
[0008]
In the case of an electric vehicle that carries people, overcharging when the charging control system breaks down, battery crash that may occur in case of accidental collision, foreign object piercing, external short circuit Ensuring the safety of the battery itself, such as time, is a very important battery characteristic that is necessary at a minimum. Battery safety means that the behavior of the battery when exposed to abnormal conditions does not cause any physical damage to the person, but minimizes damage to the vehicle. Means.
[0009]
An object of the present invention is to provide a non-aqueous electrolyte secondary battery that has a high capacity and a high output, yet has a very high safety.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a positive electrode active material compound comprising a lithium manganese complex oxide composed of secondary particles formed of an aggregate of primary particles having an average particle diameter of 0.1 μm to 2 μm and a conductive material. An electrode winding group in which a positive electrode in which an agent is applied on both surfaces of a strip-shaped current collector and a negative electrode capable of occluding and releasing lithium ions by charging and discharging is wound through a separator at a predetermined pressure. In a non-aqueous electrolyte secondary battery housed in a battery container having an internal pressure release mechanism for releasing internal pressure, The conductive material is a mixture of graphite and amorphous carbon, The coating amount of the lithium manganese complex oxide per side of the current collector is 80 g / m ² ~ 160g / m ² And the amount of the conductive material contained in the positive electrode active material mixture is 8 wt% to 16 wt%.
[0011]
In the present invention, in order to secure a high-capacity, high-power non-aqueous electrolyte secondary battery, lithium manganese double oxidation composed of secondary particles formed of an aggregate of primary particles having an average particle size of 0.1 μm to 2 μm. There are used a positive electrode in which a positive electrode active material mixture including a conductive material and a conductive material is applied on both sides of a strip-shaped current collector in an approximately equal amount, and a negative electrode capable of inserting and extracting lithium ions by charging and discharging. Further, by using a mixture of graphite and amorphous carbon as the conductive material, a higher output non-aqueous electrolyte secondary battery can be obtained. In non-aqueous electrolyte secondary batteries with high capacity and high output, when an abnormal state occurs, a large current charge or discharge state is maintained, and the battery is caused by a chemical reaction between the non-aqueous electrolyte and the active material mixture. A sudden and large amount of gas is generated in the container, increasing the internal pressure of the battery container. In general, a non-aqueous electrolyte secondary battery has an internal pressure release mechanism that releases an internal pressure at a predetermined pressure in the battery container in order to prevent an increase in internal pressure in the battery container. The coating amount per side of the electric body is 80g / m ² ~ 160g / m ² In addition, by setting the amount of the conductive material contained in the positive electrode active material mixture to 8% by weight to 16% by weight, the gas release from the internal pressure release mechanism is performed extremely gently. Therefore, according to the present invention, it is possible to realize a non-aqueous electrolyte secondary battery with extremely high safety while having high capacity and high output.
[0012]
In this case ,black If the average particle size of lead is 0.2 to 0.8 times the average particle size of secondary particles and / or amorphous carbon is acetylene black, a higher output non-aqueous electrolyte secondary battery can be obtained. Can do. Further, when the Li / Mn ratio of the lithium manganese complex oxide is set to 0.55 to 0.60, the output maintenance ratio can be improved without accompanying a decrease in capacity. Furthermore, if amorphous carbon is used as the negative electrode active material, a non-aqueous electrolyte secondary battery with higher output, higher capacity, and higher safety can be obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which a nonaqueous electrolyte secondary battery according to the present invention is applied to a cylindrical lithium ion battery of an electric vehicle power source will be described with reference to the drawings.
[0014]
(Preparation of positive electrode plate)
As shown in FIG. 1, lithium manganate (LiMn) as a positive electrode active material ₂ O ₄ ) Powder, predetermined carbon described later as a conductive material, and polyvinylidene fluoride (PVDF) as a binder are mixed at a predetermined mixing ratio, and N-methyl-2-pyrrolidone (NMP) as a dispersion solvent is mixed therewith. The added and kneaded slurry was applied to both surfaces of a 20 μm thick aluminum foil W1 (positive electrode current collector). At this time, an uncoated portion having a width of 30 mm was left on one side edge in the longitudinal direction of the positive electrode plate. Thereafter, drying, pressing, and cutting were performed to obtain a positive electrode plate having a width of 82 mm, a predetermined length, and a predetermined thickness of the active material mixture application portion. The bulk density of the positive electrode active material mixture layer W2 is 2.65 g / cm. ³ It was. A notch was formed in the uncoated part, and the remaining part of the notch was used as the positive electrode lead piece 2. Adjacent positive electrode lead pieces 2 were spaced 50 mm apart, and the width of the positive electrode lead pieces 2 was 5 mm.
[0015]
(Preparation of negative electrode plate)
8 parts by mass of polyvinylidene fluoride as a binder is added to 92 parts by mass of a predetermined carbon powder, N-methyl-2-pyrrolidone as a dispersion solvent is added to this, and the kneaded slurry is rolled copper foil W3 having a thickness of 10 μm. It apply | coated to both surfaces of (negative electrode electrical power collector). At this time, an uncoated portion having a width of 30 mm was left on one side edge in the longitudinal direction of the negative electrode plate. Thereafter, drying, pressing, and cutting were performed to obtain a negative electrode plate having a width of 86 mm, a predetermined length, and a predetermined thickness of the active material application portion. The negative electrode plate was compressed so that the porosity of the negative electrode active material mixture layer W4 was about 35%. A cutout was made in the uncoated portion in the same manner as the positive electrode plate, and the remaining cutout was used as the negative electrode lead piece 3. Adjacent negative electrode lead pieces 3 were spaced 50 mm apart, and the width of the negative electrode lead pieces 3 was 5 mm.
[0016]
(Production of battery)
The positive electrode plate and the negative electrode plate produced above were wound together with a polyethylene separator W5 having a width of 90 mm and a thickness of 40 μm so that the two electrode plates do not directly contact each other. A hollow cylindrical shaft core 1 made of polypropylene was used at the center of winding. At this time, the positive electrode lead piece 2 and the negative electrode lead piece 3 were respectively positioned on opposite end surfaces of the wound group 6. Further, the lengths of the positive electrode plate, the negative electrode plate, and the separator were adjusted so that the diameter of the wound group 6 was 38 ± 0.1 mm.
[0017]
The positive electrode lead piece 2 was deformed, and all of the positive electrode lead pieces 2 were gathered and brought into contact with the vicinity of the flange peripheral surface integrally projecting from the periphery of the positive electrode current collecting ring 4 substantially on the extension line of the shaft core 1 of the winding group 6. Thereafter, the positive electrode lead piece 2 and the collar surface were ultrasonically welded to connect the positive electrode lead piece 2 to the collar surface. On the other hand, the connection operation between the negative electrode current collection ring 5 and the negative electrode lead piece 3 was performed in the same manner as the connection operation between the positive electrode current collection ring 4 and the positive electrode lead piece 2.
[0018]
Thereafter, an insulation coating was applied to the entire circumference of the collar peripheral surface of the positive electrode current collecting ring 4. For this insulation coating, an adhesive tape in which the base material was polyimide and an adhesive made of hexamethacrylate was applied on one side thereof was used. The adhesive tape was wound one or more times from the peripheral surface of the collar part to the outer peripheral surface of the wound group 6 to form an insulation coating, and the wound group 6 was inserted into a nickel-plated steel battery container 7. The battery container 7 has an outer shape of 40 mm and an inner diameter of 39 mm.
[0019]
A negative electrode lead plate 8 for electrical continuity is welded to the negative electrode current collecting ring 5 in advance, and after inserting the wound group 6 into the battery container 7, the bottom of the battery container 7 and the negative electrode lead plate 8 are welded. .
[0020]
On the other hand, the positive electrode current collecting ring 4 is welded with a positive electrode lead 9 formed by previously superposing a plurality of aluminum ribbons, and a battery for sealing the battery container 7 at the other end of the positive electrode lead 9. Welded to the bottom of the lid. The battery lid is provided with a cleavage valve 11 as an internal pressure release mechanism that cleaves in response to an increase in internal pressure of the cylindrical lithium ion battery 20. The cleavage pressure of the cleavage valve 11 is about 9 × 10 ⁵ Pa was set. The battery lid is composed of a lid case 12, a lid cap 13, an airtight valve presser 14, and a cleavage valve 11, and these are stacked and assembled by crimping the periphery of the lid case 12. Yes.
[0021]
A predetermined amount of non-aqueous electrolyte is injected into the battery container 7, and then the battery container 7 is covered with a battery cover so that the positive electrode lead 9 is folded, and then crimped and sealed with an EPDM resin gasket 10. A cylindrical lithium ion battery 20 was completed.
[0022]
Non-aqueous electrolyte includes lithium hexafluorophosphate (LiPF) into a mixed solution of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1. ₆ ) Was dissolved at 1 mol / liter. The cylindrical lithium ion battery 20 is not provided with a current interruption mechanism such as a PTC (Positive Temperature Coefficient) element that is electrically operated in response to an increase in the internal pressure of the battery.
[0023]
【Example】
Next, examples of the cylindrical lithium ion battery 20 manufactured according to the present embodiment will be described. In addition, it describes together about the battery of the comparative example produced for the comparison.
[0024]
Example 1
As shown in Table 1 below, in Example 1, manganic acid having a primary particle diameter of about 1 to 2 μm, a secondary particle diameter of about 20 μm, and an atomic ratio of Li to Mn (Li / Mn ratio) of 0.52 as the positive electrode active material. Lithium (LiMn ₂ O ₄ ) The current collector of the positive electrode active material mixture layer (active material application part) W2 in which the blending ratio of the powder, the scaly graphite having an average particle diameter of 18 μm, and polyvinylidene fluoride was 83: 12: 5 by weight%. The coating amount of lithium manganate per side is 80g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 73 μm, and the length of the positive electrode plate was 434 cm. LiMn ₂ O ₄ The average particle size of the flake graphite with respect to the secondary particle size is 0.9 times. On the other hand, for the negative electrode plate, MCMB, which is mesophase-based spherical graphite, is used as the negative electrode active material, and the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 53 μm. The length was 446 cm. In addition, the average particle diameter of scaly graphite can be adjusted by sieving.
[0025]
[Table 1]

[0026]
In addition, when the produced electrode plate is wound, the positive electrode plate does not protrude from the negative electrode plate in the winding direction at the innermost periphery of the winding, and the positive electrode plate protrudes from the negative electrode plate in the winding direction at the outermost periphery. To prevent this, the length of the negative electrode plate was set to be 12 cm longer than the length of the positive electrode plate. Further, the negative electrode active material application part W4 is wider than the positive electrode active material application part W2 so that the positive electrode active material application part W2 does not protrude from the negative electrode active material application part W4 in the winding direction and the vertical direction. Was also 4 mm longer (the same applies to the following examples and comparative examples).
[0027]
(Example 2)
As shown in Table 1, in Example 2, the coating amount of lithium manganate was 120 g / m. ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) is 109 μm, the length of the positive electrode plate is 342 cm, and the negative electrode active material mixture layer (active material application) Part) A battery was fabricated in the same manner as in Example 1 except that the thickness of W4 (not including the current collector thickness) was 79 μm and the length of the negative electrode plate was 354 cm.
[0028]
(Examples 2-2 to 2-5)
As shown in Table 1, in Examples 2-2 to 2-5, the Li / Mn ratio of lithium manganate was set to 0.55, 0.58, 0.60, and 0.61, respectively. A battery was produced in the same manner as in Example 2.
[0029]
(Example 3)
As shown in Table 1, in Example 3, the coating amount of lithium manganate was 160 g / m. ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) is 146 μm, the length of the positive electrode plate is 282 cm, and the negative electrode active material mixture layer (active material application) Part) A battery was fabricated in the same manner as in Example 1 except that the thickness of W4 (not including the current collector thickness) was 106 μm and the length of the negative electrode plate was 294 cm.
[0030]
(Example 4)
As shown in Table 1, in Example 4, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 18 μm ₂ O ₄ The ratio of the average particle size of the flake graphite to the secondary particle size of: 0.9 times the polyvinylidene fluoride was 87: 8: 5 by weight%, and the positive electrode active material mixture layer (active material coating) Part) The coating amount of lithium manganate per one side of the current collector of W2 is 120 g / m. ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 104 μm, and the length of the positive electrode plate was 348 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, and the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm and the length is 360 cm. A battery was produced.
[0031]
(Example 5)
As shown in Table 1, in Example 5, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 18 μm ₂ O ₄ The ratio of the average particle size of the flake graphite with respect to the secondary particle size is 0.9: 16 and the blend ratio of polyvinylidene fluoride is 79: 16: 5 by weight%, and the positive electrode active material mixture layer (active material coating) Part) The coating amount of lithium manganate per one side of the current collector of W2 is 120 g / m. ² The thickness of the positive electrode active material mixture layer (active material application part) W2 (not including the current collector thickness) was 115 μm, and the length of the positive electrode plate was 336 cm. On the other hand, for the negative electrode plate, MCMB was used as the negative electrode active material, and the thickness of the negative electrode active material mixture layer (active material application part) W4 (not including the current collector thickness) was 79 μm and the length was 348 cm. A battery was produced.
[0032]
(Example 6)
As shown in Table 1, in Example 6, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 18 μm ₂ O ₄ The average particle size of the flake graphite with respect to the secondary particle size of: 0.9 times), the ratio of ketjen black (KB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, The coating amount of lithium manganate per one side of the current collector of the positive electrode active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm, and the length of the positive electrode plate was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0033]
(Example 7)
As shown in Table 1, in Example 7, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 2 μm ₂ O ₄ The average particle size of the flake graphite with respect to the secondary particle size: 0.1 times), ketjen black (KB), and polyvinylidene fluoride in a mixing ratio of 83: 10: 2: 5 by weight%, The coating amount of lithium manganate per one side of the current collector of the positive electrode active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm, and the length of the positive electrode plate was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0034]
(Example 8)
As shown in Table 1, in Example 8, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 4 μm ₂ O ₄ The average particle size of the flake graphite with respect to the secondary particle size: 0.2 times), the blend ratio of ketjen black (KB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, The coating amount of lithium manganate per one side of the current collector of the positive electrode active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm, and the length of the positive electrode plate was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0035]
Example 9
As shown in Table 1, in Example 9, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 10 μm ₂ O ₄ The average particle size of the flake graphite with respect to the secondary particle size: 0.5 times), the ratio of ketjen black (KB), and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, The coating amount of lithium manganate per one side of the current collector of the positive electrode active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0036]
(Example 10)
As shown in Table 1, in Example 10, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 16 μm ₂ O ₄ The average particle size of the flake graphite with respect to the secondary particle size of: 0.8 times), the blending ratio of ketjen black (KB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, The coating amount of lithium manganate per one side of the current collector of the positive electrode active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0037]
(Example 11)
As shown in Table 1, in Example 11, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 10 μm ₂ O ₄ The average particle size of the flaky graphite with respect to the secondary particle size of: 0.5 times), the blending ratio of acetylene black (AB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, and the positive electrode The coating amount of lithium manganate per one side of the current collector of the active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0038]
(Example 12)
As shown in Table 1, in Example 12, as the positive electrode active material, lithium manganate having a primary particle size of about 1 to 2 μm, a secondary particle size of about 20 μm, and an atomic ratio of Li to Mn (Li / Mn ratio) of 0.55. (LiMn ₂ O ₄ ) Powder and flake graphite (LiMn) with an average particle size of 10 μm ₂ O ₄ The average particle size of the flaky graphite with respect to the secondary particle size of: 0.5 times), the blending ratio of acetylene black (AB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, and the positive electrode The coating amount of lithium manganate per one side of the current collector of the active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0039]
(Example 13)
As shown in Table 1, in Example 13, as the positive electrode active material, lithium manganate having a primary particle diameter of about 1 to 2 μm, a secondary particle diameter of about 20 μm, and an atomic ratio of Li to Mn (Li / Mn ratio) of 0.58. (LiMn ₂ O ₄ ) Powder and flake graphite (LiMn) with an average particle size of 10 μm ₂ O ₄ The average particle size of the flaky graphite with respect to the secondary particle size of: 0.5 times), the blending ratio of acetylene black (AB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, and the positive electrode The coating amount of lithium manganate per one side of the current collector of the active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0040]
(Example 14)
As shown in Table 1, in Example 14, lithium manganate having a primary particle size of about 1 to 2 μm, a secondary particle size of about 20 μm, and an atomic ratio of Li to Mn (Li / Mn ratio) of 0.60 as the positive electrode active material. (LiMn ₂ O ₄ ) Powder and flake graphite (LiMn) with an average particle size of 10 μm ₂ O ₄ The average particle size of the flaky graphite with respect to the secondary particle size of: 0.5 times), the blending ratio of acetylene black (AB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, and the positive electrode The coating amount of lithium manganate per one side of the current collector of the active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0041]
(Example 15)
As shown in Table 1, in Example 15, lithium manganate having a primary particle size of about 1 to 2 μm, a secondary particle size of about 20 μm, and an atomic ratio of Li to Mn (Li / Mn ratio) of 0.61 as the positive electrode active material. (LiMn ₂ O ₄ ) Powder and flake graphite (LiMn) with an average particle size of 10 μm ₂ O ₄ The average particle size of the flaky graphite with respect to the secondary particle size of: 0.5 times), the blending ratio of acetylene black (AB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, and the positive electrode The coating amount of lithium manganate per one side of the current collector of the active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, MCMB is used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application portion) W4 (not including the current collector thickness) is 79 μm, and the length is 354 cm. A battery was produced.
[0042]
(Example 16)
As shown in Table 1, in Example 16, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 10 μm ₂ O ₄ The average particle size of the flaky graphite with respect to the secondary particle size of: 0.5 times), the blending ratio of acetylene black (AB) and polyvinylidene fluoride was 83: 10: 2: 5 by weight%, and the positive electrode The coating amount of lithium manganate per one side of the current collector of the active material mixture layer (active material application part) W2 is 120 g / m ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, amorphous carbon is used as the negative electrode active material, and the thickness of the negative electrode active material mixture layer (active material application part) W4 (not including the current collector thickness) is 79 μm and length. Was set to 354 cm to prepare a battery.
[0043]
(Examples 16-2 to 16-5)
As shown in Table 1, in Examples 16-2 to 16-5, the Li / Mn ratio of lithium manganate was changed to 0.55, 0.58, 0.60, and 0.61, respectively. A battery was produced in the same manner as in Example 16.
[0044]
(Example 17)
As shown in Table 1, in Example 17, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 10 μm ₂ O ₄ The ratio of the average particle size of the flake graphite to the secondary particle size of: 0.5 times the polyvinylidene fluoride was 83: 12: 5 by weight%, and the positive electrode active material mixture layer (active material coating) Part) The coating amount of lithium manganate per one side of the current collector of W2 is 120 g / m. ² The thickness of the positive electrode active material mixture layer (active material application portion) W2 (not including the current collector thickness) was 109 μm and the length was 342 cm. On the other hand, for the negative electrode plate, amorphous carbon is used as the negative electrode active material, and the thickness of the negative electrode active material mixture layer (active material application part) W4 (not including the current collector thickness) is 79 μm and length. Was set to 354 cm to prepare a battery.
[0045]
(Examples 17-2 to 17-5)
As shown in Table 1, in Examples 17-2 to 17-5, the Li / Mn ratio of lithium manganate was changed to 0.55, 0.58, 0.60, and 0.61, respectively. A battery was produced in the same manner as in Example 17.
[0046]
(Comparative Example 1)
As shown in Table 1, in Comparative Example 1, the coating amount of lithium manganate was 75 g / m. ² The thickness of the positive electrode active material mixture layer (active material application portion) (current collector thickness is not included) is 68 μm, the length is 450 cm, and the negative electrode active material mixture layer (active material application portion) A battery was prepared in the same manner as in Example 1 except that the thickness (not including the current collector thickness) was 50 μm and the length of the negative electrode plate was 462 cm.
[0047]
(Comparative Example 2)
As shown in Table 1, in Comparative Example 2, the coating amount of lithium manganate was 165 g / m. ² The thickness of the positive electrode active material mixture layer (active material application part) (not including the current collector thickness) is 150 μm, the length is 276 cm, and the negative electrode active material mixture layer (active material application part) A battery was prepared in the same manner as in Example 1 except that the thickness (not including the current collector thickness) was 109 μm and the length of the negative electrode plate was 288 cm.
[0048]
(Comparative Example 3)
As shown in Table 1, in Comparative Example 3, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 18 μm ₂ O ₄ The ratio of the average particle size of the flake graphite to the secondary particle size of: 0.9 times) and polyvinylidene fluoride was 88: 7: 5 by weight%, and the positive electrode active material mixture layer (active material coating) Part) of the current collector is 120 g / m. ² The positive electrode active material mixture layer (active material application portion) has a thickness (not including the current collector thickness) of 103 μm, the positive electrode plate has a length of 349 cm, MCMB is used as the negative electrode active material, and the negative electrode active material A battery was fabricated with the thickness of the mixture layer (active material application portion) (not including the current collector thickness) being 80 μm and the length of the negative electrode plate being 361 cm.
[0049]
(Comparative Example 4)
As shown in Table 1, in Comparative Example 4, the same lithium manganate powder as in Example 1 and flaky graphite (LiMn) having an average particle diameter of 18 μm ₂ O ₄ The ratio of the average particle size of the scaly graphite to the secondary particle size of: 0.9 times the polyvinylidene fluoride was 78: 17: 5 by weight%, and the positive electrode active material mixture layer (active material coating) Part) of the current collector is 120 g / m. ² The thickness of the positive electrode active material mixture layer (active material application portion) (not including the current collector thickness) was 116 μm, and the length of the positive electrode plate was 334 cm. On the other hand, for the negative electrode plate, MCMB was used as the negative electrode active material, the thickness of the negative electrode active material mixture layer (active material application part) (not including the current collector thickness) was 80 μm, and the length of the negative electrode plate was A battery was manufactured at 346 cm.
[0050]
<Test and evaluation>
Next, the following series of tests were performed on the batteries of Examples and Comparative Examples manufactured as described above.
[0051]
Each battery of the examples and comparative examples was charged and then discharged, and the discharge capacity was measured. The charging conditions were a 4.2 V constant voltage, a limiting current of 5 A, and 3.5 hours. The discharge conditions were a 5 A constant current and a final voltage of 2.7 V.
[0052]
Further, the discharge output of the charged battery was measured under the above conditions. The measurement conditions are 1A, 3A, 6A, the voltage at 5 seconds is read for each discharge current, plotted on the vertical axis against the horizontal axis current value, and the approximate straight line connecting the three points crosses 2.7V The product of the current value of 2.7 and 2.7 V was used as the output.
[0053]
Furthermore, after charging and discharging each battery of the example and comparative example 100 times under the above conditions, the output (capacity) was measured, and the maintenance ratio relative to the initial output was shown as a percentage. Naturally, the higher the maintenance ratio, the better the life characteristics.
[0054]
These measurements of charge, discharge, and output were all performed in an atmosphere having an environmental temperature of 25 ± 1 ° C.
[0055]
Thereafter, the produced battery was continuously charged at a constant current of 20 A at room temperature, and the behavior of the battery was observed. The results are shown in Table 2 below. The phenomenon is that gas release consisting of volatiles of electrolyte occurs after cleavage valve cleavage. In order to compare the degree of gas release, the battery surface temperature immediately after the occurrence of the phenomenon was measured. Further, after the gas was released, the battery container was checked for deformation. In Table 2, “◯” indicates that no deformation of the battery container was observed, “Δ” indicates that the battery container was slightly deformed, and “×” indicates that the battery container was greatly deformed. Show.
[0056]
[Table 2]

[0057]
As shown in Table 2, in the batteries of Examples 1 to 5, high-capacity and high-power batteries were obtained, and the battery behavior during continuous charging was gentle. At this time, the surface temperature of the battery was 150 ° C. to 220 ° C. at the maximum. The amount of lithium manganate applied is 80 g / m ² In the battery of Comparative Example 1 that is less than 1, a high-capacity and high-power battery can be obtained, but the battery behavior during continuous charging becomes intense with deformation of the battery, and the battery surface temperature exceeds 300 ° C. As a result. Conversely, 160 g / m ² In the battery of Comparative Example 2 that exceeded the above, the battery behavior during continuous charging was moderate, but with a decrease in output, the result was not suitable as a battery for electric vehicles. Similarly, in the battery of Comparative Example 3, the amount of graphite of the positive electrode conductive material was less than 8% by weight, resulting in a decrease in output. On the other hand, in the battery of Comparative Example 4 in which the amount of the graphite of the positive electrode conductive material exceeds 16% by weight, a battery with high capacity and high output can be obtained, but the battery behavior during continuous charging was accompanied by deformation of the battery. As a result, the battery surface temperature was 310 ° C.
[0058]
In the batteries of Examples 6 to 16-5 in which graphite and amorphous carbon were mixed in the positive electrode conductive material, a battery with high output could be obtained. In the batteries of Examples 6 to 10 using ketjen black for amorphous carbon, the ratio of the particle diameter of the conductive graphite to the secondary particle diameter of lithium manganate as the positive electrode active material was 0.2 to 0.8. Among the batteries of Examples 8 to 10, a higher output is obtained. In the battery of Example 7 in which the ratio of the particle diameter of the conductive material graphite to the secondary particle diameter of lithium manganate is less than 0.2, the battery surface temperature during continuous charging was 210 ° C., and Examples 8 to It is slightly higher than 10 batteries.
[0059]
In the batteries of Examples 11 to 16-5 using acetylene black for amorphous carbon, a higher output was obtained and the output retention rate after 100 times of charge / discharge was also high.
[0060]
Example 12 to Example 14, Example 2-2 to Example 2-4, Example 16-2 to Example 16-4, Example in which Li / Mn ratio of lithium manganate is 0.55 or more The batteries of 17-2 to Example 17-4 have an extremely high output retention rate. However, in the batteries of Example 15, Example 2-5, Example 16-5, and Example 17-5 in which the Li / Mn ratio of lithium manganate exceeds 0.60, the result is accompanied by a decrease in capacity. It can be seen that the / Mn ratio is preferably in the range of 0.55 to 0.60.
[0061]
The batteries of Example 16, Example 16-2 to Example 16-5, Example 17, and Example 17-2 to Example 17-5 using amorphous carbon for the negative electrode plate had extremely high output power and An extremely high output retention rate and the lowest battery surface temperature during continuous charging were obtained. Therefore, the batteries of Examples 16, 16-2 to 16-5, 17, 17-2 to 17-5 are high-capacity, high-output, and excellent in safety, and are well-balanced. It can be said.
[0062]
As described above, the cylindrical lithium ion battery 20 of the present embodiment is a battery that exhibits extremely gentle behavior when the battery is exposed to an abnormal state and is excellent in safety. Thus, a battery with high capacity, high output, and extremely high safety is particularly suitable for a power source of an electric vehicle.
[0063]
In the present embodiment, a large secondary battery used for a power source for an electric vehicle has been illustrated. However, the size and battery capacity of the battery are not limited, and the battery capacity is approximately 3 to 10 Ah. Thus, it has been confirmed that the present invention exerts remarkable effects. In the present embodiment, the cylindrical battery is exemplified, but the present invention is not limited to the shape of the battery, and can be applied to a rectangular battery or other polygonal batteries. Furthermore, the shape to which the present invention can be applied may be other than a battery having a structure in which the upper lid of the battery is sealed by caulking in the above-described bottomed cylindrical container (can). An example of such a structure is a battery in which positive and negative external terminals pass through the battery lid and the positive and negative external terminals are pressed against each other through an axis in the battery container.
[0064]
Moreover, in this embodiment, although the base material is a polyimide and the example which used the adhesive tape which apply | coated the adhesive which consists of hexamethacrylate to the one side was shown for insulation coating, for example, a base material is polypropylene, polyethylene, etc. In particular, an adhesive tape in which an acrylic adhesive such as hexamethacrylate or butyl acrylate is applied to one or both surfaces thereof, a tape made of polyolefin or polyimide to which no adhesive is applied, and the like can be suitably used.
[0065]
Furthermore, in this embodiment, lithium manganate is used as the positive electrode for the lithium ion battery, amorphous carbon is used as the negative electrode, and a mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1: 1: 1 is used as the electrolytic solution. A solution obtained by dissolving 1 mol / liter of lithium fluorophosphate was used, but the battery of the present invention is not particularly limited, and any of the conductive materials and binders that are usually used can be used. is there. In general, lithium manganate can be synthesized by mixing and baking an appropriate lithium salt and manganese oxide. By controlling the charging ratio of the lithium salt and manganese oxide, the desired Li / Mn ratio can be obtained. can do.
[0066]
In addition, as an electrode plate active material binder for lithium ion batteries that can be used in other embodiments, Teflon, polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, Examples thereof include polymers such as cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, and chloroprene fluoride, and mixtures thereof.
[0067]
Further, as the positive electrode active material for lithium ion batteries that can be used in other embodiments, lithium is a material capable of inserting / extracting lithium, and lithium manganese complex oxide in which a sufficient amount of lithium is inserted in advance is preferable. Alternatively, lithium manganate having a spinel structure, or a material obtained by substituting or doping a part of manganese or lithium in a crystal with an element other than those may be used.
[0068]
Furthermore, the negative electrode active material for lithium ion batteries that can be used other than in the present embodiment is not particularly limited other than the matters described in the claims. For example, natural graphite, various artificial graphite materials, carbonaceous materials such as coke, amorphous carbon, etc. may be used, and the particle shape is not particularly limited, such as scaly, spherical, fibrous, massive, etc. Absent.
[0069]
As the nonaqueous electrolytic solution, an electrolytic solution in which a general lithium salt is used as an electrolyte and this is dissolved in an organic solvent is used. However, the lithium salt and organic solvent used are not particularly limited. For example, as an electrolyte, LiClO _Four , LiAsF ₆ , LiPF ₆ , LiBF _Four , LiB (C ₆ H _Five ) _Four , CH _Three SO _Three Li, CF _Three SO _Three Li or the like or a mixture thereof can be used. Nonaqueous electrolyte organic solvents include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3- Dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propiontonyl, or a mixed solvent of two or more of these may be used, and the mixing ratio is not limited.
[0070]
【The invention's effect】
As described above, according to the present invention, lithium manganese complex oxide composed of secondary particles formed of an aggregate of primary particles having an average particle size of 0.1 μm to 2 μm and Of a mixture of graphite and amorphous carbon Since the active material mixture containing the conductive material was applied to the both sides of the strip current collector in a substantially equal amount and the negative electrode capable of inserting and extracting lithium ions by charging and discharging, high capacity and high output The active material mixture has a coating amount of 80 g / m on one side of the current collector. ² ~ 160g / m ² In addition, since the amount of the conductive material is set to 8 to 16% by weight, the gas release from the internal pressure release mechanism is performed very gently, so that the high capacity and high output are achieved, but the safety is extremely high. The effect that a water electrolyte secondary battery is realizable can be acquired.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion battery according to an embodiment to which the present invention is applicable.
[Explanation of symbols]
1 shaft core
2 Positive lead piece
3 Negative lead piece
4 Positive current collector ring
5 Negative current collector ring
6 Winding group (electrode winding group)
7 Battery container
8 Negative lead plate
9 Positive lead
10 Gasket
11 Cleavage valve (Internal pressure release mechanism)
12 Lid case
13 Lid cap
14 Valve presser foot
20 Cylindrical lithium ion battery (non-aqueous electrolyte secondary battery)
W1 Cathode current collector (current collector)
W2 cathode active material mixture layer
W3 Negative electrode current collector
W4 Negative electrode active material mixture layer
W5 separator

Claims

A positive electrode active material mixture containing a lithium manganese complex oxide composed of secondary particles formed of an aggregate of primary particles having an average particle size of 0.1 μm to 2 μm and a conductive material is substantially equal in amount on both sides of the belt-shaped current collector In a battery container having an internal pressure release mechanism that releases an internal pressure at a predetermined pressure by an electrode winding group in which a coated positive electrode and a negative electrode capable of inserting and extracting lithium ions by charging and discharging are wound through a separator. In the non-aqueous electrolyte secondary battery housed in the battery, the conductive material is a mixture of graphite and amorphous carbon, and the coating amount of the lithium manganese complex oxide per one side of the current collector is 80 g / m ^2. to a 160 g / m ^2, and the positive electrode active material non-aqueous electrolyte secondary batteries, characterized by conductive material amount contained in the mixture is 8% to 16% by weight.

Nonaqueous electrolyte secondary battery according to claim 1, wherein the average particle diameter of the graphite, wherein said is 0.2 times to 0.8 times the average particle size of the secondary particles.

The amorphous carbon nonaqueous electrolyte secondary battery according to claim 1 or claim 2, wherein the acetylene black.

The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3 , wherein a Li / Mn ratio of the lithium manganese complex oxide is 0.55 to 0.60.

The non-aqueous electrolyte secondary cell of any one of claims 1 to 4 active material of the negative electrode is characterized by an amorphous carbon.