JP4632005B2 - Lithium secondary battery - Google Patents

Description

【００３１】
また、グラファイトに、スズ酸化物，ケイ素酸化物等の金属酸化物、リン、ホウ素、アモルファスカーボン等を添加して改質を行うことも可能である。特に、グラファイトの表面を上記の方法によって改質することで、電解液の分解を抑制し電池特性を高めることが可能であり望ましい。さらに、グラファイトに対して、リチウム金属、リチウム−アルミニウム，リチウム−鉛，リチウム−スズ，リチウム−アルミニウム−スズ，リチウム−ガリウム，およびウッド合金等のリチウム金属含有合金等を併用することや、あらかじめ電気化学的に還元することによってリチウムが挿入されたグラファイト等も負極活物質として使用可能である。
【００３２】
また、正極活物質の粉体及び負極活物質の粉体の少なくとも表面層部分を電子伝導性やイオン伝導性の良いもの、あるいは疎水基を有する化合物で修飾することも可能である。例えば、金，銀，カーボン，ニッケル，銅等の電子伝導性のよい物質や、炭酸リチウム，ホウ素ガラス，固体電解質等のイオン伝導性のよい物質、あるいはシリコーンオイル等の疎水基を有する物質をメッキ，焼結，メカノフュージョン，蒸着，焼き付け等の技術を応用して被覆することが挙げられる。
【００３３】
正極活物質の粉体及び負極活物質の粉体は、平均粒子サイズ１００μｍ以下であることが望ましい。特に、正極活物質の粉体は、非水電解質電池の高出力特性を向上する目的で１０μｍ以下であることが望ましい。粉体を所定の形状で得るためには粉砕機や分級機が用いられる。例えば乳鉢、ボールミル、サンドミル、振動ボールミル、遊星ボールミル、ジェットミル、カウンタージェトミル、旋回気流型ジェットミルや篩等が用いられる。粉砕時には水、あるいはヘキサン等の有機溶剤を共存させた湿式粉砕を用いることもできる。分級方法としては、特に限定はなく、篩や風力分級機などが、乾式、湿式ともに必要に応じて用いられる。
【００３４】
以上、正極活物質および負極活物質について詳述したが、正極および負極には、主要構成成分である前記活物質の他に、導電剤、結着剤およびフィラーが、他の構成成分として含有されてもよい。
【００３５】
導電剤としては、電池性能に悪影響を及ぼさない電子伝導性材料であれば限定されないが、通常、天然黒鉛（鱗状黒鉛，鱗片状黒鉛，土状黒鉛等）、人造黒鉛、カーボンブラック、アセチレンブラック、ケッチェンブラック、カーボンウイスカー、炭素繊維、金属（銅，ニッケル，アルミニウム，銀，金等）粉、金属繊維、導電性セラミックス材料等の導電性材料を１種またはそれらの混合物として含ませることができる。
【００３６】
これらの中で、導電剤としては、導電性及び塗工性の観点よりアセチレンブラックとケッチャンブラックを併用することが望ましい。導電剤の添加量は、正極または負極の総質量に対して１質量％〜１０質量％が好ましく、特に３質量％〜６質量％にすると、電極密度の低下を最小限に抑えつつ、十分な伝導性が得られる点で好ましい。これらの混合方法は、物理的な混合であり、その理想とするところは均一混合である。そのため、Ｖ型混合機、Ｓ型混合機、擂かい機、ボールミル、遊星ボールミルといったような粉体混合機を乾式、あるいは湿式で混合することが可能である。
【００３７】
結着剤としては、通常、ポリテトラフルオロエチレン，ポリフッ化ビニリデン，ポリエチレン，ポリプロピレン等の熱可塑性樹脂、エチレン−プロピレンジエンターポリマー（ＥＰＤＭ），スルホン化ＥＰＤＭ，スチレンブタジエンゴム（ＳＢＲ）、フッ素ゴム等のゴム弾性を有するポリマー、カルボキシメチルセルロース等の多糖類等を１種または２種以上の混合物として用いることができる。また、多糖類の様にリチウムと反応する官能基を有する結着剤は、例えばメチル化するなどしてその官能基を失活させておくことが望ましい。結着剤の添加量は、正極または負極の総質量に対して１〜１０質量％が好ましく、特に３〜６質量％にすると、電極密度の低下を最小限に抑えつつ、十分な結着性が得られる点で好ましい。
【００３８】
フィラーとしては、電池性能に悪影響を及ぼさない材料であれば何でも良い。通常、ポリプロピレン，ポリエチレン等のオレフィン系ポリマー、アエロジル、ゼオライト、ガラス、炭素等が用いられる。フィラーの添加量は、正極または負極の総質量に対して添加量は３０質量％以下が好ましい。
【００３９】
正極および負極は、前記活物質、導電剤および結着剤をＮ−メチルピロリドン，トルエン等の有機溶媒に混合させた後、得られた混合液を下記に詳述する集電体の上に塗布し、乾燥することによって、好適に作製される。前記塗布方法については、例えば、アプリケーターロールなどのローラーコーティング、スクリーンコーティング、ドクターブレード方式、スピンコーティング、バーコーダー等の手段を用いて任意の厚さおよび任意の形状に塗布することが望ましいが、これらに限定されるものではない。
【００４０】
集電体としては、構成された電池において悪影響を及ぼさない電子伝導体であれば何でもよい。例えば、正極用集電体としては、アルミニウム、チタン、ステンレス鋼、ニッケル、焼成炭素、導電性高分子、導電性ガラス等の他に、接着性、導電性および耐酸化性向上の目的で、アルミニウムや銅等の表面をカーボン、ニッケル、チタンや銀等で処理した物を用いることができる。負極用集電体としては、銅、ニッケル、鉄、ステンレス鋼、チタン、アルミニウム、焼成炭素、導電性高分子、導電性ガラス、Ａｌ−Ｃｄ合金等の他に、接着性、導電性、耐酸化性向上の目的で、銅等の表面をカーボン、ニッケル、チタンや銀等で処理した物を用いることができる。これらの材料については表面を酸化処理することも可能である。
【００４１】
集電体の形状については、フォイル状の他、フィルム状、シート状、ネット状、パンチ又はエキスパンドされた物、ラス体、多孔質体、発砲体、繊維群の形成体等が用いられる。厚さの限定は特にないが、５〜３０μｍのものが用いられる。これらの集電体の中で、正極としては、耐酸化性に優れているアルミニウム箔が、負極としては、還元場において安定であり、且つ電導性に優れ、安価な銅箔、ニッケル箔、鉄箔、およびそれらの一部を含む合金箔を使用することが好ましい。さらに、粗面表面粗さが０．２μｍＲａ以上の箔であることが好ましく、これにより正極活物質または負極活物質と集電体との密着性は優れたものとなる。よって、このような粗面を有することから、電解箔を使用するのが好ましい。特に、ハナ付き処理を施した電解箔は最も好ましい。
【００４２】
非水電解質電池用セパレータとしては、優れた高率放電特性を示す多孔膜や不織布等を、単独あるいは併用することが好ましい。非水電解質電池用セパレータを構成する材料としては、例えばポリエチレン，ポリプロピレン等に代表されるポリオレフィン系樹脂、ポリエチレンテレフタレート，ポリブチレンテレフタレート等に代表されるポリエステル系樹脂、ポリフッ化ビニリデン、フッ化ビニリデン−ヘキサフルオロプロピレン共重合体、フッ化ビニリデン−パーフルオロビニルエーテル共重合体、フッ化ビニリデン−テトラフルオロエチレン共重合体、フッ化ビニリデン−トリフルオロエチレン共重合体、フッ化ビニリデン−フルオロエチレン共重合体、フッ化ビニリデン−ヘキサフルオロアセトン共重合体、フッ化ビニリデン−エチレン共重合体、フッ化ビニリデン−プロピレン共重合体、フッ化ビニリデン−トリフルオロプロピレン共重合体、フッ化ビニリデン−テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体、フッ化ビニリデン−エチレン−テトラフルオロエチレン共重合体等を挙げることができる。
【００４３】
非水電解質電池用セパレータの空孔率は強度の観点から９８体積％以下が好ましい。また、充放電特性の観点から空孔率は２０体積％以上が好ましい。 セパレータの孔径は、一般に電池に用いられる範囲のものであり、例えば０．０１〜１μｍである。また、その厚さについても同様で、一般に電池に用いられる範囲のものであり、例えば２０〜４０μｍである。
【００４４】
非水電解質電池用セパレータは、例えばアクリロニトリル、エチレンオキシド、プロピレンオキシド、メチルメタアクリレート、ビニルアセテート、ビニルピロリドン、ポリフッ化ビニリデン等のポリマーと電解液とで構成されるポリマーゲルを用いてもよい。
【００４５】
電解質の形態としては、例えば有機電解液、高分子固体電解質、無機固体電解質、溶融塩等を用いることができ、この中でも有機電解液を用いることが好ましい。
【００４６】
【実施例】
（実施例１）
正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと酸化ベリリウムと硼酸と硼酸をＬｉ：Ｍｎ：Ｂｅ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００４７】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｂｅ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ａとする。前記粉末Ａを正極活物質として用い、次のようにして図２に示す容量１６〜１７ｍＡｈのコイン型リチウム電池を試作した。
【００４８】
正極１は、粉末Ａ〜粉末Ｋとアセチレンブラック及びポリテトラフルオロエチレン粉末とを質量比８５：１０：５で混合し、トルエンを加えて十分混練した。これをローラープレスにより厚さ０．８ｍｍのシート状に成形した。次にこれを直径１６ｍｍの円形に打ち抜き、減圧下２００℃で１５時間乾燥し正極１を得た。正極１は正極集電体６の付いた正極缶４に圧着して用いた。負極活物質として、人造黒鉛（平均粒径；６μｍ、Ｘ線回折法による面間隔（ｄ₀₀₂）；０．３３７ｎｍで、ｃ軸方向の結晶の大きさ（Ｌｃ）；５５ｎｍ）とポリテトラフルオロエチレン粉末とを質量比９５：５で混合し、トルエンを加えて十分混練した。これをローラープレスにより厚さ０．１ｍｍのシート状に成形した。次にこれを直径１６ｍｍの円形に打ち抜き、減圧下２００℃で１５時間乾燥して負極２を得た。負極２は負極集電体７の付いた負極缶５に圧着して用いた。エチレンカーボネート、ジエチレンカーボネート及びジメチレンカーボネートの体積比１：１：１の混合溶剤にＬｉＰＦ₆を１ｍｏｌ／ｌの濃度で溶解した電解液を用い、セパレータ３にはポリプロピレン製微多孔膜を用いた。上記正極、負極、電解液及びセパレータを用いて直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を本発明電池Ａとする。
【００４９】
（参考例２）正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと水酸化アルミニウムと硼酸をＬｉ：Ｍｎ：Ａｌ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００５０】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ａｌ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｂとする。前記粉末Ｂを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を参考電池Ｂとする。
【００５１】
（実施例３）
正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと酸化珪素と硼酸をＬｉ：Ｍｎ：Ｓｉ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００５２】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｓｉ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｃとする。前記粉末Ｃを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を本発明電池Ｃとする。
【００５３】
（実施例４）
正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと酸化スカンジウムと硼酸をＬｉ:Ｍｎ:Ｓｃ:Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００５４】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｓｃ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｄとする。前記粉末Ｄを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を本発明電池Ｄとする。
【００５５】
（実施例５）
正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと酸化チタンと硼酸をＬｉ:Ｍｎ:Ｔｉ:Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００５６】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｔｉ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｅとする。前記粉末Ｅを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を本発明電池Ｅとする。
【００５７】
（参考例６）正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと水酸化コバルトと硼酸をＬｉ：Ｍｎ：Ｃｏ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００５８】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｃｏ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｆとする。前記粉末Ｆを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を参考電池Ｆとする。
【００５９】
（参考例７）正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと水酸化ニッケルと硼酸をＬｉ：Ｍｎ：Ｎｉ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００６０】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｎｉ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｇとする。前記粉末Ｇを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を参考電池Ｇとする。
【００６１】
（参考例８）正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと酸化銅と硼酸をＬｉ：Ｍｎ：Ｃｕ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００６２】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｃｕ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｈとする。前記粉末Ｈを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を参考電池Ｈとする。
【００６３】
（参考例９）正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと酸化亜鉛と硼酸をＬｉ：Ｍｎ：Ｚｎ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００６４】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｚｎ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｉとする。前記粉末Ｉを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を参考電池Ｉとする。
【００６５】
（参考例１０）正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと酸化ガリウムと硼酸をＬｉ：Ｍｎ：Ｇａ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００６６】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849 Ｇａ _0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｊとする。前記粉末Ｊを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を参考電池Ｊとする。
【００６７】
（参考例１１）正極活物質の調整にあたっては、市販試薬特級の水酸化リチウムと二酸化マンガンと水酸化アルミニウムと硼酸をＬｉ：Ｍｎ：Ａｌ：Ｂの原子比が１．１０：１．８０９：０．０９：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００６８】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.809Ａｌ_0.09Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｋとする。前記粉末Ｋを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を参考電池Ｋとする。
【００６９】
（比較例１）
市販試薬特級の水酸化リチウムと二酸化マンガンと水酸化マグネシウムと硼酸をＬｉ：Ｍｎ：Ｍｇ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００７０】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｍｇ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｌとする。前記粉末Ｌを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を比較電池Ｌとする。
【００７１】
（比較例２）
市販試薬特級の水酸化リチウムと二酸化マンガンと水酸化カルシウムと硼酸をＬｉ：Ｍｎ：Ｃａ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００７２】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｃａ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｍとする。前記粉末Ｍを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を比較電池Ｍとする。
【００７３】
（比較例３）
市販試薬特級の水酸化リチウムと二酸化マンガンと酸化クロムと硼酸をＬｉ：Ｍｎ：Ｃｒ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００７４】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｃｒ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｎとする。前記粉末Ｎを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を比較電池Ｎとする。
【００７５】
（比較例４）
市販試薬特級の水酸化リチウムと二酸化マンガンと酸化鉄と硼酸をＬｉ：Ｍｎ：Ｆｅ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００７６】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.849Ｆｅ_0.05Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｏとする。前記粉末Ｏを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を比較電池Ｏとする。
【００７７】
（比較例５）
市販試薬特級の水酸化リチウムと二酸化マンガンと酸化ゲルマニウムと硼酸をＬｉ：Ｍｎ：Ｇｅ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００７８】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物の一部のマンガンとゲルマニウムが置換するものの、多くの酸化イットリウムが分離して得られていることが分かった。この粉末を粉末Ｐとする。前記粉末Ｐを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を比較電池Ｐとする。
【００７９】
（比較例６）
市販試薬特級の水酸化リチウムと二酸化マンガンと酸化イットリウムと硼酸をＬｉ：Ｍｎ：Ｙ：Ｂの原子比が１．１０：１．８４９：０．０５：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００８０】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物の一部のマンガンとイットリウムが置換するものの、多くの酸化イットリウムが分離して得られていることが分かった。この粉末を粉末Ｑとする。前記粉末Ｑを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を比較電池Ｑとする。
【００８１】
（比較例７）
市販試薬特級の水酸化リチウムと二酸化マンガンと硼酸をＬｉ：Ｍｎ：Ｂの原子比が１．１０：１．８９９：０．００１になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００８２】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.899Ｂ_0.001Ｏであることが判った。この粉末を粉末Ｒとする。前記粉末Ｒを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を比較電池Ｒとする。
【００８３】
（比較例８）
市販試薬特級の水酸化リチウムと二酸化マンガンをＬｉ：Ｍｎの原子比が１．１０：１．９０になるようにボールミルで粉砕しながら十分混合し、混合物をアルミナ坩堝に入れて空気中６５０℃で５時間仮焼成した後、８５０℃で２０時間焼成した。
【００８４】
得られた焼成物を粉砕し、エックス線回折法による解析を行った結果、スピネル構造を有するリチウムマンガン複合酸化物が得られていることが分かった。更にこの生成物について化学定量分析を行ったところ、その組成はＬｉ_1.10Ｍｎ_1.90Ｏであることが判った。この粉末を粉末Ｓとする。前記粉末Ｓを正極活物質として用い、実施例１と同様の方法で直径２０ｍｍ、厚さ１．６ｍｍのコイン型リチウム電池を作製した。この電池を比較電池Ｓとする。
【００８５】
（常温充放電サイクル性能試験）本発明電池（又は参考電池）Ａ〜Ｋ及び比較電池Ｌ〜Ｓをそれぞれ複数個用いて充放電試験を行なった。まず、試験温度２５℃で定電流充放電を５サイクル行った。充電終止電圧４．２Ｖ、放電終止電圧３．０Ｖ、充放電電流０．０５ｍＡとした。得られた５サイクル目の放電容量を「２５℃５サイクル目放電容量」として表１に示した。続いて、充放電電流を１ｍＡに変え、定電流充放電を続けた。得られた１００サイクル目の放電容量の結果を、「２５℃５サイクル目放電容量」と比較し、「２５℃１００サイクル目放電容量率」として表１に併せて示した。
【００８６】
（高温充放電サイクル性能試験）本発明電池（又は参考電池）Ａ〜Ｋ及び比較電池Ｌ〜Ｓをそれぞれ複数個用いて充放電試験を行なった。まず、試験温度２５℃で定電流充放電を５サイクル行った。充電終止電圧４．２Ｖ、放電終止電圧３．０Ｖ、充放電電流０．０５ｍＡとした。続いて、充放電電流を１ｍＡに変え、温度を５０℃とし、定電流充放電を続けた。得られた１００サイクル目の放電容量の結果を、「２５℃５サイクル目放電容量」と比較し、「５０℃１００サイクル目放電容量率」として表１に併せて示した。
【００８７】
（高温保存試験）本発明電池（又は参考電池）Ａ〜Ｋ及び比較電池Ｌ〜Ｓをそれぞれ複数個用いて充放電試験を行なった。まず、試験温度２５℃で定電流充放電を５サイクル行った。充電終止電圧４．２Ｖ、放電終止電圧３．０Ｖ、充放電電流１ｍＡとした。６サイクル目の充電後、回路を開放し、８０℃の高温槽中で２週間保存した。保存後、温度を２５℃に戻し、再び同じ条件で定電流充放電を３サイクル行った。最終サイクルの放電容量を、８０℃放置前の５サイクル目容量と比較し、「高温保存後回復容量維持率」として表１に併せて示した。
【００８８】
【表１】
【００８９】
また、表１に示された結果のうち、「５０℃１００サイクル目放電容量」と「高温保存後回復容量維持率」について、置換元素Ｍの原子番号の順に整理した結果を図１に示した。
【００９０】
（結果の考察）置換元素にＢのみを用いた比較電池Ｒや、置換元素を用いない比較電池Ｓに比べ、本発明電池（又は参考電池）Ａ〜Ｋでは、初期の放電容量は低下するものの、充放電サイクル性能、高温保存性能の何れも大きく向上している。
【００９１】
参考電池Ｂ、Ｋは、いずれも置換元素にＡｌを用いているが、置換元素の量は後者の方が多い。両者の結果から、置換量が多い方が初期の放電容量は低下するものの、充放電サイクル性能、高温保存性能の何れも向上している。
【００９２】
置換元素にＣａを用いた比較電池Ｍや、置換元素にＦｅを用いた比較電池Ｏでは、これらの置換元素を用いない比較電離Ｒに比べ、充放電サイクル性能は向上しているものの、高温保存性能は悪くなっている。この原因は必ずしも明らかではないが、標準水素電極より１．２Ｖ以上貴な電位において形成されるこれらの元素の酸化物または水酸化物が有機電解液中で不動態化せず、可溶であるため、これらの元素が溶出した後、該置換元素が一部抜け落ちた状態であるリチウムマンガン複合酸化物のマンガンが溶解し易くなっている為と考えられる。また、前記溶出は高温下において発生しやすいものと考えられる。
【００９３】
置換元素にＧｅを用いた比較電池Ｐや、置換元素にＹを用いた比較電池Ｑでは、本発明電池（又は参考電池）Ａ〜Ｋや比較電池Ｌ〜Ｏと比べると、充放電サイクル性能、高温保存性能のいずれも非常に悪い結果となった。これら劣化後の比較電池Ｐ、Ｑを解体し、電解液および負極中の元素を分析した結果、Ｇｅ、Ｙ共に僅かながら検出されたものの、Ｍｎの検出量は他の全ての電池に比較して非常に大きいことが判った。この原因は必ずしも明らかでないが、原子半径がＧｅ以上に大きい元素は一部のＭｎとしか置換せず、置換に供さなかった元素が溶解して炭素質電極上に不良な被膜が生成して容量が低下するだけでなく、これらの元素が溶出した後、該置換元素が一部抜け落ちた状態であるリチウムマンガン複合酸化物のマンガンが溶解し易くなっている為と考えられる。しかしながら、これらの元素は一部ではあるがＭｎと置換される性質を持っているので、焼成条件等を最適化することによって、完全な置換が可能となり、置換元素として有効に用いられる可能性がある。
【００９４】
置換元素にＭｇを用いた比較電池Ｌや、置換元素にＣｒを用いた比較電池Ｎでは、ＬｉとＢを除くＭｎ以外の元素を置換していない比較電池Ｒと比較し、これらの置換元素を用いない比較電離Ｒに比べ、充放電サイクル性能は向上しているものの、高温保存性能は比較電池Ｒと同等以上には向上していない。しかしながら、これら２つの元素については、電解液の成分、支持塩の選択、電解液の水分管理等を検討することで、標準水素電極より１．２Ｖ以上貴な電位において形成される酸化物または水酸化物が有機電解液中で不動態化し、溶解が抑制できる場合がある。このため、これらの元素については今後、電解液の開発の進展等によって、置換元素として有効に用い用いられる可能性がある。
【００９５】
以上のように、本発明によれば、電解質塩の分解を抑え、これによってフッ酸の生成が抑制されるため、Ｍｎ等の正極構成元素の溶出が抑制されるので、負極の炭素質材料表面に生成する表面被膜が、抵抗の高いフッ化リチウムやマンガンを含む被膜等ではなく、フッ素の含有が少なく、比較的抵抗の低い炭酸リチウムや酸化リチウム等の被膜が形成され、界面抵抗増大が抑制され、良好な充放電サイクル性能を有したリチウム電池を提供することができる。
【００９６】
また、標準水素電極より１．２Ｖ以上貴な電位において形成される酸化物または水酸化物が有機電解液中で不動態化する性質を有する元素を用いたため、８０℃での高温保存においても置換元素が溶解せず、リチウムマンガン複合酸化物正極の安定性を向上でき、高温保存特性に優れたリチウム電池を提供することができる。
【００９７】
ホウ素については、上述したように初期の充放電試験において、正極から溶出し電解液、負極から検出される。従って、Ｂ量は置換元素としては最小限で良く、０．０００５〜０．０１であれば十分である。
【００９８】
又、負極材料として人造黒鉛を用いたリチウム二次電池について実施例を挙げたが、同様の効果がその他の負極材料についても確認された。
【００９９】
なお、本発明は上記実施例に記載された活物質の出発原料、製造方法、正極、負極、電解質、セパレータ及び電池形状などに限定されるものではない。
【０１００】
【発明の効果】
本発明は上述の如く構成されているので、高温保存後容量回復維持率の優れたリチウム二次電池を提供できる。
【図面の簡単な説明】
【図１】 高温サイクル性能及び高温保存性能を置換元素Ｍとの関係で示したグラフである[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte battery, and more particularly to a positive electrode active material for a non-aqueous electrolyte battery.
[0002]
[Prior art]
Currently, as a positive electrode active material for 4V lithium secondary batteries, LiCoO₂, LiNiO₂Α-NaFeO₂A lithium-containing oxide having a structure, a lithium-containing oxide having a spinel structure such as a lithium manganese composite oxide, and the like are used. Among them, LiMn having a spinel structure₂O_FourIs a positive electrode active material with low material cost and high safety.
[0003]
On the other hand, when a carbonaceous material is used for the negative electrode, the state of the film formed between the electrolyte and the surface of the carbonaceous material is the reaction of occlusion and release (intercalation, deintercalation) of lithium into the carbonaceous material. It has a big impact. For example, as represented by the case where lithium metal is used for the negative electrode active material, when it has a dense and highly ion conductive film, its battery characteristics are also excellent, and conversely, a thick and low ion conductive film. When it has, it is known that a high rate discharge characteristic and charge / discharge cycle performance are bad. Here, it is reported that the former is a film mainly composed of lithium carbonate, lithium oxide or the like, and the latter is a film mainly composed of lithium fluoride or the like. The same can be said for the film formed on the surface of the carbonaceous material. That is, one of the factors that increase the interfacial resistance of an electrode using a carbonaceous material is the formation of a film having low ionic conductivity on the surface of the carbonaceous material. As a film having low ionic conductivity, in addition to the film such as lithium fluoride, for example, MnF₂And a film made of a compound of fluorine and an element dissolved from the positive electrode. That is, elution of elements such as manganese from the manganese compound used for the positive electrode was one of the causes of the performance deterioration.
[0004]
In order to improve the charge / discharge cycle performance of the lithium manganese composite oxide, JP-A-4-233161, JP-A-5-21067, and JP-A-6-187993 disclose a lithium manganese composite oxide having a spinel structure. A technique for substituting a part of manganese with an element other than manganese is shown. By performing such substitution, the formation of a film such as lithium fluoride and the dissolution of the lithium manganese composite oxide are suppressed to some extent.
[0005]
However, depending on the type of the substitution element, particularly when left at a high temperature in the end-of-charge state, the substitution element dissolves in the electrolytic solution, and accordingly, the crystal structure of the lithium manganese composite oxide having a spinel structure is distorted, There has been a problem that the lithium manganese composite oxide itself is dissolved and the charge / discharge capacity of the battery is lowered.
[0006]
As described above, even when these conventional techniques are used, elution of the manganese element and elution of the substitution element cannot be sufficiently suppressed particularly when the battery is left at a high temperature. In particular, when a carbonaceous material is used for the negative electrode, the eluted elements such as manganese form a defective film on the surface of the negative carbonaceous material, thereby reducing the charge / discharge capacity of the negative electrode, There was a problem that battery performance deteriorated due to storage.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and in a battery using a lithium manganese composite oxide for the positive electrode, the elution of the positive electrode constituent elements into the electrolytic solution is suppressed even when left at high temperature, and the performance of the carbonaceous negative electrode An object of the present invention is to provide a lithium secondary battery that prevents deterioration, has a high capacity, a high energy density, and is excellent in charge / discharge cycle performance.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the lithium secondary battery of the present invention is,In a lithium secondary battery using, as a positive electrode, a lithium-manganese composite oxide in which a part of Mn is substituted with at least the element M and Li, the element M is contained in the organic electrolyte used in the lithium secondary battery. The oxide or hydroxide of the element M is selected from elements having a passivating property.
[0009]
That is, as a result of intensive studies to solve the above problems, the present inventors surprisingly use a specific law in selecting an element that replaces a part of the manganese element of the lithium manganese composite oxide, It was found that even when the battery was stored at a high temperature, elution of manganese elements and substitutional elements could be suppressed to a high degree. That is, the substitution element M is at least LiPF.₆The element M is selected from elements having a property that the oxide or hydroxide of the element M is passivated and becomes insoluble or hardly soluble in the electrolyte. Therefore, a lithium secondary battery excellent in charge / discharge cycle performance and high-temperature storage performance can be provided by using a lithium manganese composite oxide substituted with such an element for the positive electrode.
[0010]
Here, the reason why the lithium battery of the present invention is excellent in charge / discharge characteristics, particularly high-temperature storage characteristics, is not necessarily clear, but is considered as follows. Generally, the battery contains various impurities that are not involved in charging / discharging of the battery. For example, LiPF₆Is used as the electrolyte salt, the moisture contained in the electrolyte salt and the trace amount of water contained in the battery or in the solvent react with the electrolyte salt to produce hydrofluoric acid (HF) or the like. When lithium ions are occluded in the negative electrode carbonaceous material, a film with high ion conductivity such as lithium carbonate is formed between the electrolyte and the carbonaceous material on the surface of the carbonaceous material. Later, in the presence of an acid such as hydrofluoric acid, a film made of lithium halide having low ion conductivity is formed. Such a film made of lithium halide increases the interfacial resistance of the negative electrode and prevents the occlusion / release of lithium ions into the carbonaceous material, resulting in a reduction in discharge capacity. In the process of generating hydrofluoric acid by the reaction between the electrolyte salt and water, it is considered that the lithium manganese composite oxide, which is the positive electrode active material, catalytically promotes decomposition of the electrolyte salt. Therefore, by using a lithium manganese composite oxide having a spinel structure in which a part of manganese is substituted with a specific element, the catalytic activity is reduced and the generation of hydrofluoric acid is suppressed.
[0011]
The lithium secondary battery of the present invention is,In a lithium secondary battery using, as a positive electrode, a lithium-manganese composite oxide in which a part of Mn is substituted with at least the element M and Li, the element M is contained in the organic electrolyte used in the lithium secondary battery. The oxide or hydroxide of the element M is selected from elements having a property of being passivated and formed at a potential 1.2 V or more higher than the standard hydrogen electrode potential.
[0012]
The oxide or hydroxide of the substitution element M is preferably insoluble and infusible over the entire operating voltage range of the battery. For example, when Ca or Fe is used as a substitution element, these oxides or hydroxides can be used in an organic solvent at the end-of-charge potential of a lithium battery of 4.2 V, that is, 1.2 V with respect to a standard hydrogen electrode potential. Since it is dissolved, there is a possibility that elution into the electrolytic solution may occur. Therefore, a lithium secondary battery excellent in charge / discharge cycle performance and high-temperature storage performance can be provided by using a lithium manganese composite oxide substituted with such an element for the positive electrode.
[0013]
On the other hand, LiMn having a spinel structure₂O_FourIs partially γ-MnO in the end-of-charge state₂May be generated. The γ-MnO₂Is a substance with extremely high catalytic activity. However, when the substitutional element does not elute even at the charging potential and is retained in the crystal structure of the lithium manganese composite oxide, the γ-MnO₂The effect of suppressing the generation of can be expected.
[0014]
The lithium secondary battery of the present invention is,The element M is selected from elements whose atomic radius of the element M is equal to or less than that of manganese.
[0015]
According to such a configuration, since the substitution element is selected from elements having an atomic radius equal to or less than the atomic radius of manganese, the substitution element can exist stably in the crystal structure of the lithium manganese composite oxide. Therefore, elution into the electrolytic solution is unlikely to occur. Therefore, a lithium secondary battery excellent in charge / discharge cycle performance and high-temperature storage performance can be provided by using a lithium manganese composite oxide substituted with such an element for the positive electrode.
[0016]
The lithium secondary battery of the present invention is,The element M is selected from the group consisting of Be, Al, Si, Sc, Ti, Co, Ni, Cu, Zn, and Ga. According to such a configuration, since the substitution element is selected from elements that can stably exist in the crystal structure of the lithium manganese composite oxide, elution into the electrolytic solution hardly occurs. Therefore, a lithium secondary battery excellent in charge / discharge cycle performance and high-temperature storage performance can be provided by using a lithium manganese composite oxide substituted with such an element for the positive electrode.
[0017]
The lithium secondary battery of the present invention is,The lithium manganese composite oxide contains boron.
[0018]
That is, when boron is used as a substitution element, the effect of the present invention can be further increased. Although boron used as a substitution element is dissolved by high-temperature storage of the battery and detected from the electrolyte and the negative electrode, the dissolved boron element has little adverse effect on the charge / discharge cycle performance of the battery. Although the reason for this is not necessarily clear, boron element has the effect of assisting crystal growth and good particle growth when synthesizing lithium-manganese composite oxide, thereby improving the charge / discharge cycle performance of the battery. It is considered that there is an action to improve and suppress a decrease in capacity when left at high temperature. In addition, when lithium manganese composite oxide combined with boron element as a substitute element is stored in the air, boric acid is liberated, but even if lithium manganese composite oxide from which boric acid is liberated is used for the electrode, There is no change in the effect of suppressing the capacity drop. Furthermore, the boron element elutes from the lithium manganese composite oxide in the electrolytic solution along with charge and discharge, migrates to the negative electrode surface, and the boron concentration in the surface part of the lithium manganese composite oxide is greatly reduced. There is no change in the effect of suppressing the capacity drop during storage. Therefore, it is considered that the boron element is not necessarily present in the lithium manganese composite oxide as a substitution element.
[0019]
Here, the lithium secondary battery of the present invention is a lithium secondary battery using a lithium manganese composite oxide having a composition represented by the following general formula as a positive electrode, as described in claim 1.
  Li_(1-z)[Mn_(2-xyw)M_xB_wLi_yO_Four]
  However,
  x = 0.01-0.1
  y = 0-0.2
  x + y + w ≦ 0.2
  w = 0.005-0.01
  0 ≦ z ≦ 1
  M; Be,Si, Sc, TiofAt least one element selected from the inside.
[0020]
The greater the amount of the substitution element of the present invention, the greater the effect of the present invention, while the smaller the amount of Li that can be used reversibly, the lower the battery capacity. For this reason, when the general formula of the lithium manganese composite oxide is expressed by the above formula, it is preferable that x + y + w ≦ 0.2.
[0021]
Further, since boron has an effect of improving crystallinity, it is preferable to add it at the time of synthesis. However, boron does not remain in the synthesized lithium manganese composite oxide or a slight amount remains, which is mostly Dissolves in the electrolyte. Therefore, the smaller the amount of boron added, the better the crystallinity. When w = 0.005 to 0.01, it is preferable in that sufficient crystallinity can be improved and the influence of lithium manganate due to dissolution is small.
[0022]
Further, Li as a substitution element exhibits an effect of improving the charge / discharge cycle performance in proportion to the substitution amount, but even if the value of y is larger than 0.2, the effect on the addition amount is not proportional, Since it is not possible to expect a great improvement in the effect, y = 0 to 0.2 is preferable.
[0023]
In addition, the amount of the substitution element M is effective when the substitution element amount is x = 0.01 or more. However, even if the value of x is greater than 0.1, the effect does not change, so x = 0.01. ~ 0.1 is preferred.
[0024]
Here, the above numerical range shows the uniform composition portion inside the lithium manganese composite oxide particles of the present invention, and these values are greatly different in the surface layer portion. Specifically, the numerical value range is as follows.
Li_(1-z)[Mn_(2-xyw)M_xB_wLi_yO_Four]
However, x = 0.05 or more
y = 0-0.2
x + y + w ≦ 0.2
w = 0.05 or more
0 ≦ z ≦ 1
[0025]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited by these description. As a method for adding a substitution element, at the time of synthesis of a lithium manganese composite oxide, a method of previously adding a substance containing the substitution element to the firing raw material, an ion exchange method for a lithium manganese composite oxide not containing a substitution element, etc. However, the method is not limited to these.
[0026]
Examples of the organic solvent of the organic electrolyte include esters such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, and γ-butyrolactone, and these can be used alone or as a mixed solvent.
[0027]
Examples of the electrolyte salt include LiClO._Four, LiBF_Four, LiAsF₆, LiPF₆, LiCF_ThreeSO_Three, LiN (CF_ThreeSO₂)₂, LiN (C₂F_FiveSO₂)₂, LiN (CF_ThreeSO₂) (C_FourF₉SO₂)₂, LiSCN, LiBr, LiI, Li₂SO_Four, Li₂B_TenCl_Ten, NaClO_Four, NaI, NaSCN, NaBr, KClO_Four, KSCN, and other inorganic ion salts containing one of lithium (Li), sodium (Na) or potassium (K), LiN (CF_ThreeSO₂)₂, LiN (C₂F_FiveSO₂)₂, (CH_Three)_FourNBF_Four, (CH_Three)_FourNBr, (C₂H_Five)_FourNClO_Four, (C₂H_Five)_FourNI, (C_ThreeH₇)_FourNBr, (n-C_FourH₉)_FourNClO_Four, (N-C_FourH₉)_FourNI, (C₂H_Five)_FourN-maleate, (C₂H_Five)_FourN-benzoate, (C₂H_Five)_FourExamples include organic ionic salts such as quaternary ammonium salts such as N-phtalate, lithium stearyl sulfonate, lithium octyl sulfonate, lithium dodecylbenzene sulfonate, etc., and these ionic compounds are used alone or in admixture of two or more. It is possible.
[0028]
In addition, other positive electrode active materials may be mixed with the lithium-containing compound, and examples of other positive electrode active materials include CuO and Cu.₂O, Ag₂O, CuS, CuSO_FourGroup I metal compounds such as TiS₂, SiO₂Group IV metal compounds such as SnO, V₂O_Five, V₆O₁₂, VO_x, Nb₂O_Five, Bi₂O_Three, Sb₂O_ThreeGroup V metal compounds such as CrO_Three, Cr₂O_Three, MoO_Three, MoS₂, WO_Three, SeO₂Group VI metal compounds such as MnO₂, Mn₂O_ThreeGroup VII metal compounds such as Fe₂O_Three, FeO, Fe_ThreeO_Four, Ni₂O_Three, NiO, CoO_ThreeGroup VIII metal compounds such as CoO, or the general formula Li_xMX₂, Li_xMN_yX₂(M and N represent metals of groups I to VIII, X represents a chalcogen compound such as oxygen and sulfur), and the like, for example, a metal such as a lithium-cobalt composite oxide or a lithium-manganese composite oxide Examples of such compounds include, but are not limited to, conductive polymer compounds such as disulfide, polypyrrole, polyaniline, polyparaphenylene, polyacetylene, and polyacene materials, pseudographite-structured carbonaceous materials, and the like.
[0029]
The negative electrode active material, which is the main component of the negative electrode, is modified by adding carbonaceous materials, metal oxides such as tin oxide and silicon oxide, and adding phosphorus and boron to these materials for the purpose of improving negative electrode characteristics. The material etc. which performed were mentioned. Among carbonaceous materials, graphite has a working potential very close to that of metallic lithium, so that when lithium salt is used as an electrolyte salt, self-discharge can be reduced, and irreversible capacity in charge / discharge can be reduced, which is preferable as a negative electrode active material. .
[0030]
Below, the analysis result by X-ray diffraction etc. of the graphite which can be used suitably is shown;

[0031]
It is also possible to modify graphite by adding a metal oxide such as tin oxide or silicon oxide, phosphorus, boron, amorphous carbon or the like. In particular, by modifying the surface of graphite by the above method, it is possible to suppress the decomposition of the electrolytic solution and improve the battery characteristics, which is desirable. In addition to graphite, lithium metal-containing alloys such as lithium metal, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloys can be used in combination. Graphite in which lithium is inserted by chemical reduction can also be used as the negative electrode active material.
[0032]
It is also possible to modify at least the surface layer portion of the positive electrode active material powder and the negative electrode active material powder with a material having good electron conductivity or ion conductivity, or a compound having a hydrophobic group. For example, plating materials with good electron conductivity such as gold, silver, carbon, nickel, copper, materials with good ion conductivity such as lithium carbonate, boron glass, solid electrolyte, or materials having hydrophobic groups such as silicone oil Coating by applying techniques such as sintering, mechanofusion, vapor deposition, and baking.
[0033]
The positive electrode active material powder and the negative electrode active material powder preferably have an average particle size of 100 μm or less. In particular, the positive electrode active material powder is desirably 10 μm or less for the purpose of improving the high output characteristics of the non-aqueous electrolyte battery. In order to obtain the powder in a predetermined shape, a pulverizer or a classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air flow type jet mill or a sieve is used. At the time of pulverization, wet pulverization in the presence of water or an organic solvent such as hexane may be used. There is no particular limitation on the classification method, and a sieve, an air classifier, or the like is used as needed for both dry and wet methods.
[0034]
As described above, the positive electrode active material and the negative electrode active material have been described in detail. The positive electrode and the negative electrode contain, in addition to the active material as the main component, a conductive agent, a binder, and a filler as other components. May be.
[0035]
The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance. Usually, natural graphite (such as scaly graphite, scaly graphite, earthy graphite), artificial graphite, carbon black, acetylene black, Conductive materials such as ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, and conductive ceramic material can be included as one kind or a mixture thereof. .
[0036]
Among these, as the conductive agent, it is desirable to use acetylene black and Ketchan black in combination from the viewpoints of conductivity and coatability. The amount of conductive agent added is the total amount of positive electrode or negative electrode.mass1 againstmass% -10mass% Is preferred, especially 3mass% ~ 6mass% Is preferable in that sufficient conductivity can be obtained while minimizing the decrease in electrode density. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, powder mixers such as V-type mixers, S-type mixers, crackers, ball mills, and planetary ball mills can be mixed dry or wet.
[0037]
As the binder, usually, thermoplastic resins such as polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and polypropylene, ethylene-propylene diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, and the like These polymers having rubber elasticity, polysaccharides such as carboxymethylcellulose, and the like can be used as one or a mixture of two or more. In addition, it is desirable that a binder having a functional group that reacts with lithium, such as a polysaccharide, be deactivated by, for example, methylation. The amount of binder added is the total amount of positive electrode or negative electrode.mass1 to 10mass% Is preferred, especially 3-6mass%,It is preferable in that sufficient binding properties can be obtained while minimizing the decrease in electrode density.
[0038]
As the filler, any material that does not adversely affect the battery performance may be used. Usually, olefin polymers such as polypropylene and polyethylene, aerosil, zeolite, glass, carbon and the like are used. The amount of filler added is the total amount of positive electrode or negative electrode.massThe amount added is 30mass% Or less is preferable.
[0039]
The positive electrode and the negative electrode are prepared by mixing the active material, the conductive agent and the binder in an organic solvent such as N-methylpyrrolidone and toluene, and then applying the obtained mixture onto the current collector described in detail below. Then, it is preferably produced by drying. About the application method, for example, it is desirable to apply to any thickness and any shape using means such as roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coder, etc. It is not limited to.
[0040]
The current collector may be anything as long as it is an electronic conductor that does not adversely affect the constructed battery. For example, as a current collector for positive electrode, aluminum, titanium, stainless steel, nickel, calcined carbon, conductive polymer, conductive glass, etc. are used for the purpose of improving adhesion, conductivity and oxidation resistance. A material obtained by treating the surface of copper or copper with carbon, nickel, titanium, silver or the like can be used. In addition to copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., the negative electrode current collector is adhesive, conductive, and oxidation resistant. For the purpose of improving the property, a material obtained by treating the surface of copper or the like with carbon, nickel, titanium, silver or the like can be used. The surface of these materials can be oxidized.
[0041]
Regarding the shape of the current collector, a film shape, a sheet shape, a net shape, a punched or expanded object, a lath body, a porous body, a foamed body, a formed body of a fiber group, and the like are used in addition to a foil shape. The thickness is not particularly limited, but a thickness of 5 to 30 μm is used. Among these current collectors, an aluminum foil excellent in oxidation resistance is used as a positive electrode, and as a negative electrode, copper foil, nickel foil, iron, which is stable in a reduction field, has excellent conductivity, and is inexpensive. It is preferred to use foils and alloy foils containing parts thereof. Furthermore, a foil having a rough surface surface roughness of 0.2 μmRa or more is preferable, whereby the adhesion between the positive electrode active material or the negative electrode active material and the current collector is excellent. Therefore, it is preferable to use an electrolytic foil because it has such a rough surface. In particular, an electrolytic foil that has been subjected to a cracking treatment is most preferable.
[0042]
As a separator for a nonaqueous electrolyte battery, it is preferable to use a porous film or a nonwoven fabric exhibiting excellent high rate discharge characteristics alone or in combination. Examples of the material constituting the separator for nonaqueous electrolyte batteries include polyolefin resins typified by polyethylene, polypropylene, etc., polyester resins typified by polyethylene terephthalate, polybutylene terephthalate, etc., polyvinylidene fluoride, vinylidene fluoride-hexa. Fluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, fluorine Vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride - tetrafluoroethylene - hexafluoropropylene copolymer, vinylidene fluoride - ethylene - can be mentioned tetrafluoroethylene copolymer.
[0043]
The porosity of the non-aqueous electrolyte battery separator is preferably 98% by volume or less from the viewpoint of strength. Further, the porosity is preferably 20% by volume or more from the viewpoint of charge / discharge characteristics. The pore diameter of the separator is in a range generally used for batteries, and is, for example, 0.01 to 1 μm. Moreover, it is the same also about the thickness, and is a thing of the range generally used for a battery, for example, 20-40 micrometers.
[0044]
As the separator for a nonaqueous electrolyte battery, for example, a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinyl pyrrolidone, polyvinylidene fluoride, and an electrolytic solution may be used.
[0045]
As the form of the electrolyte, for example, an organic electrolyte, a polymer solid electrolyte, an inorganic solid electrolyte, a molten salt, or the like can be used, and among these, the organic electrolyte is preferably used.
[0046]
【Example】
Example 1
In preparing the positive electrode active material, lithium reagent, manganese dioxide, beryllium oxide, boric acid, and boric acid, which are special grades of commercially available reagents, have an atomic ratio of Li: Mn: Be: B of 1.10: 1.849: 0.05: 0. The mixture was sufficiently mixed while being pulverized with a ball mill so as to be 0.001, and the mixture was placed in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours, and then baked at 850 ° C. for 20 hours.
[0047]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Be_0.05B_0.001It turned out to be O. This powder is referred to as powder A. Using the powder A as a positive electrode active material, a coin-type lithium battery having a capacity of 16 to 17 mAh shown in FIG.
[0048]
The positive electrode 1 includes powders A to K, acetylene black, and polytetrafluoroethylene powder.massThe mixture was mixed at a ratio of 85: 10: 5, and toluene was added and kneaded sufficiently. This was formed into a sheet having a thickness of 0.8 mm by a roller press. Next, this was punched out into a circle having a diameter of 16 mm and dried at 200 ° C. under reduced pressure for 15 hours to obtain a positive electrode 1. The positive electrode 1 was used by being crimped to a positive electrode can 4 with a positive electrode current collector 6 attached thereto. Artificial graphite (average particle size: 6 μm, surface spacing by X-ray diffraction method (d₀₀₂); 0.337 nm, c-axis direction crystal size (Lc); 55 nm) and polytetrafluoroethylene powdermassThe mixture was mixed at a ratio of 95: 5, and toluene was added and kneaded sufficiently. This was formed into a sheet having a thickness of 0.1 mm by a roller press. Next, this was punched out into a circle having a diameter of 16 mm and dried at 200 ° C. under reduced pressure for 15 hours to obtain a negative electrode 2. The negative electrode 2 was used by being pressure-bonded to the negative electrode can 5 with the negative electrode current collector 7 attached thereto. LiPF in a mixed solvent of ethylene carbonate, diethylene carbonate and dimethylene carbonate with a volume ratio of 1: 1: 1₆Was used at a concentration of 1 mol / l, and a polypropylene microporous membrane was used for the separator 3. A coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was manufactured using the positive electrode, the negative electrode, the electrolytic solution, and the separator. This battery is referred to as a battery A of the present invention.
[0049]
(referenceExample 2) In preparing the positive electrode active material, a commercially available reagent-grade lithium hydroxide, manganese dioxide, aluminum hydroxide, and boric acid were mixed in an atomic ratio of Li: Mn: Al: B of 1.10: 1.849: 0.05. : Sufficiently mixed while being pulverized by a ball mill so as to be 0.001, and the mixture was put in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours, and then baked at 850 ° C. for 20 hours.
[0050]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Al_0.05B_0.001It turned out to be O. This powder is referred to as powder B. Using the powder B as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This batteryreferenceBattery B is assumed.
[0051]
(Example 3)
In preparing the positive electrode active material, a commercially available reagent-grade lithium hydroxide, manganese dioxide, silicon oxide, and boric acid are mixed with an atomic ratio of Li: Mn: Si: B of 1.10: 1.849: 0.05: 0.001. The mixture was sufficiently mixed while being pulverized with a ball mill, and the mixture was placed in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours, and then baked at 850 ° C. for 20 hours.
[0052]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Si_0.05B_0.001It turned out to be O. This powder is referred to as powder C. Using the powder C as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a battery C of the present invention.
[0053]
Example 4
In preparing the positive electrode active material, lithium reagent, manganese dioxide, scandium oxide, and boric acid, which are special grades of commercially available reagents, have an atomic ratio of Li: Mn: Sc: B of 1.10: 1.849: 0.05: 0.001. The mixture was sufficiently mixed while being pulverized with a ball mill, and the mixture was placed in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours, and then baked at 850 ° C. for 20 hours.
[0054]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Sc_0.05B_0.001It turned out to be O. This powder is referred to as powder D. Using the powder D as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a battery D of the present invention.
[0055]
(Example 5)
In preparing the positive electrode active material, a commercially available reagent-grade lithium hydroxide, manganese dioxide, titanium oxide, and boric acid have an atomic ratio of Li: Mn: Ti: B of 1.10: 1.849: 0.05: 0.001. The mixture was sufficiently mixed while being pulverized with a ball mill, and the mixture was placed in an alumina crucible and pre-baked in air at 650 ° C for 5 hours, and then baked at 850 ° C for 20 hours.
[0056]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Ti_0.05B_0.001It turned out to be O. This powder is designated as powder E. Using the powder E as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a battery E of the present invention.
[0057]
(referenceExample 6) In preparing the positive electrode active material, a commercially available reagent-grade lithium hydroxide, manganese dioxide, cobalt hydroxide, and boric acid were mixed in an atomic ratio of Li: Mn: Co: B of 1.10: 1.849: 0.05. : Sufficiently mixed while being pulverized by a ball mill so as to be 0.001, and the mixture was put in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours, and then baked at 850 ° C. for 20 hours.
[0058]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Co_0.05B_0.001It turned out to be O. This powder is designated as powder F. Using the powder F as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This batteryreferenceThe battery F is assumed.
[0059]
(referenceExample 7) In preparing the positive electrode active material, a commercially available reagent-grade lithium hydroxide, manganese dioxide, nickel hydroxide, and boric acid were mixed in an atomic ratio of Li: Mn: Ni: B of 1.10: 1.849: 0.05. : Sufficiently mixed while being pulverized by a ball mill so as to be 0.001, and the mixture was put in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours, and then baked at 850 ° C. for 20 hours.
[0060]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Ni_0.05B_0.001It turned out to be O. This powder is referred to as powder G. Using the powder G as the positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This batteryreferenceBattery G is assumed.
[0061]
(referenceExample 8) In preparing the positive electrode active material, lithium reagent, manganese dioxide, copper oxide, and boric acid, which are special grades of commercially available reagents, have an atomic ratio of Li: Mn: Cu: B of 1.10: 1.849: 0.05: The mixture was sufficiently mixed while being pulverized with a ball mill to 0.001 and the mixture was placed in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours and then baked at 850 ° C. for 20 hours.
[0062]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Cu_0.05B_0.001It turned out to be O. This powder is referred to as powder H. Using the powder H as the positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This batteryreferenceBattery H is assumed.
[0063]
(referenceExample 9) In preparing the positive electrode active material, a commercially available reagent-grade lithium hydroxide, manganese dioxide, zinc oxide, and boric acid were mixed in an atomic ratio of Li: Mn: Zn: B of 1.10: 1.849: 0.05: The mixture was sufficiently mixed while being pulverized with a ball mill to 0.001 and the mixture was placed in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours and then baked at 850 ° C. for 20 hours.
[0064]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Zn_0.05B_0.001It turned out to be O. This powder is referred to as Powder I. Using the powder I as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This batteryreferenceBattery I.
[0065]
(referenceExample 10) In preparing the positive electrode active material, commercially available reagent-grade lithium hydroxide, manganese dioxide, gallium oxide and boric acid were mixed with Li: Mn:Ga: B is sufficiently mixed while being pulverized with a ball mill so that the atomic ratio is 1.10: 1.849: 0.05: 0.001, and the mixture is placed in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours. And then baked at 850 ° C. for 20 hours.
[0066]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849 Ga _0.05B_0.001It turned out to be O. This powder is designated as powder J. Using the powder J as the positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This batteryreferenceAssume battery J.
[0067]
(referenceExample 11) In preparing the positive electrode active material, a commercially available reagent-grade lithium hydroxide, manganese dioxide, aluminum hydroxide, and boric acid were mixed with an atomic ratio of Li: Mn: Al: B of 1.10: 1.809: 0.09. : Sufficiently mixed while being pulverized by a ball mill so as to be 0.001, and the mixture was put in an alumina crucible and pre-baked in air at 650 ° C. for 5 hours, and then baked at 850 ° C. for 20 hours.
[0068]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.809Al_0.09B_0.001It turned out to be O. This powder is designated as powder K. Using the powder K as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This batteryreferenceBattery K is assumed.
[0069]
(Comparative Example 1)
Commercially available reagent-grade lithium hydroxide, manganese dioxide, magnesium hydroxide and boric acid were pulverized with a ball mill so that the atomic ratio of Li: Mn: Mg: B was 1.10: 1.849: 0.05: 0.001. The mixture was placed in an alumina crucible and calcined at 650 ° C. for 5 hours in air, and then calcined at 850 ° C. for 20 hours.
[0070]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Mg_0.05B_0.001It turned out to be O. This powder is designated as powder L. Using the powder L as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a comparative battery L.
[0071]
(Comparative Example 2)
Commercially available reagent-grade lithium hydroxide, manganese dioxide, calcium hydroxide, and boric acid are pulverized with a ball mill so that the atomic ratio of Li: Mn: Ca: B is 1.10: 1.849: 0.05: 0.001. The mixture was placed in an alumina crucible and calcined at 650 ° C. for 5 hours in air, and then calcined at 850 ° C. for 20 hours.
[0072]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Ca_0.05B_0.001It turned out to be O. This powder is referred to as powder M. Using the powder M as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a comparative battery M.
[0073]
(Comparative Example 3)
Commercially available reagent-grade lithium hydroxide, manganese dioxide, chromium oxide and boric acid were pulverized with a ball mill so that the atomic ratio of Li: Mn: Cr: B was 1.10: 1.849: 0.05: 0.001. The mixture was placed in an alumina crucible and calcined in air at 650 ° C. for 5 hours and then calcined at 850 ° C. for 20 hours.
[0074]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Cr_0.05B_0.001It turned out to be O. This powder is referred to as powder N. Using the powder N as the positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a comparative battery N.
[0075]
(Comparative Example 4)
Commercially available reagent-grade lithium hydroxide, manganese dioxide, iron oxide, and boric acid were pulverized with a ball mill so that the atomic ratio of Li: Mn: Fe: B was 1.10: 1.849: 0.05: 0.001. The mixture was placed in an alumina crucible and calcined in air at 650 ° C. for 5 hours and then calcined at 850 ° C. for 20 hours.
[0076]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.849Fe_0.05B_0.001It turned out to be O. This powder is referred to as powder O. Using the powder O as the positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a comparative battery O.
[0077]
(Comparative Example 5)
Commercially available reagent-grade lithium hydroxide, manganese dioxide, germanium oxide, and boric acid were pulverized with a ball mill so that the atomic ratio of Li: Mn: Ge: B was 1.10: 1.849: 0.05: 0.001. The mixture was placed in an alumina crucible and calcined in air at 650 ° C. for 5 hours and then calcined at 850 ° C. for 20 hours.
[0078]
The obtained fired product was pulverized and analyzed by the X-ray diffraction method. As a result, although some manganese and germanium in the lithium manganese composite oxide having a spinel structure were replaced, many yttrium oxides were obtained. I found out. This powder is designated as powder P. Using the powder P as the positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a comparative battery P.
[0079]
(Comparative Example 6)
Commercially available reagent-grade lithium hydroxide, manganese dioxide, yttrium oxide, and boric acid were pulverized with a ball mill so that the atomic ratio of Li: Mn: Y: B was 1.10: 1.849: 0.05: 0.001. The mixture was placed in an alumina crucible and calcined in air at 650 ° C. for 5 hours and then calcined at 850 ° C. for 20 hours.
[0080]
The obtained fired product was pulverized and analyzed by the X-ray diffraction method. As a result, although some manganese and yttrium in the lithium manganese composite oxide having a spinel structure were substituted, many yttrium oxides were obtained. I found out. This powder is designated as powder Q. Using the powder Q as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a comparative battery Q.
[0081]
(Comparative Example 7)
Commercially available reagent-grade lithium hydroxide, manganese dioxide, and boric acid were sufficiently mixed while being pulverized with a ball mill so that the Li: Mn: B atomic ratio was 1.10: 1.899: 0.001, and the mixture was mixed with an alumina crucible. And calcined in air at 650 ° C. for 5 hours and then calcined at 850 ° C. for 20 hours.
[0082]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.899B_0.001It turned out to be O. This powder is designated as powder R. Using the powder R as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a comparative battery R.
[0083]
(Comparative Example 8)
Commercially available reagent-grade lithium hydroxide and manganese dioxide were sufficiently mixed while being pulverized with a ball mill so that the atomic ratio of Li: Mn was 1.10: 1.90, and the mixture was placed in an alumina crucible at 650 ° C. in air. After calcination for 5 hours, calcination was performed at 850 ° C. for 20 hours.
[0084]
The obtained fired product was pulverized and analyzed by X-ray diffraction. As a result, it was found that a lithium manganese composite oxide having a spinel structure was obtained. Furthermore, when this product was subjected to chemical quantitative analysis, its composition was Li._1.10Mn_1.90It turned out to be O. This powder is designated as powder S. Using the powder S as a positive electrode active material, a coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced in the same manner as in Example 1. This battery is referred to as a comparative battery S.
[0085]
(Normal temperature charge / discharge cycle performance test) Battery of the present invention(Or reference battery)A charge / discharge test was performed using a plurality of A to K and a plurality of comparative batteries L to S. First, 5 cycles of constant current charge / discharge were performed at a test temperature of 25 ° C. The final charge voltage was 4.2V, the final discharge voltage was 3.0V, and the charge / discharge current was 0.05 mA. The obtained discharge capacity at the fifth cycle is shown in Table 1 as “25 ° C. fifth cycle discharge capacity”. Subsequently, the charge / discharge current was changed to 1 mA, and constant current charge / discharge was continued. The obtained discharge capacity results at the 100th cycle were compared with “25 ° C. 5th cycle discharge capacity” and are shown in Table 1 as “25 ° C. 100th cycle discharge capacity rate”.
[0086]
(High temperature charge / discharge cycle performance test) Battery of the present invention(Or reference battery)A charge / discharge test was performed using a plurality of A to K and a plurality of comparative batteries L to S. First, 5 cycles of constant current charge / discharge were performed at a test temperature of 25 ° C. The final charge voltage was 4.2V, the final discharge voltage was 3.0V, and the charge / discharge current was 0.05 mA. Subsequently, the charge / discharge current was changed to 1 mA, the temperature was set to 50 ° C., and constant current charge / discharge was continued. The obtained discharge capacity results at the 100th cycle were compared with “25 ° C. 5th cycle discharge capacity” and are shown in Table 1 as “50 ° C. 100th cycle discharge capacity rate”.
[0087]
(High temperature storage test) Battery of the present invention(Or reference battery)A charge / discharge test was performed using a plurality of A to K and a plurality of comparative batteries L to S. First, 5 cycles of constant current charge / discharge were performed at a test temperature of 25 ° C. The charge end voltage was 4.2 V, the discharge end voltage was 3.0 V, and the charge / discharge current was 1 mA. After charging at the sixth cycle, the circuit was opened and stored in a high-temperature bath at 80 ° C. for 2 weeks. After the storage, the temperature was returned to 25 ° C., and constant current charge / discharge was repeated 3 cycles under the same conditions. The discharge capacity of the final cycle was compared with the capacity of the fifth cycle before being left at 80 ° C., and is also shown in Table 1 as “recovery capacity retention rate after high-temperature storage”.
[0088]
[Table 1]
[0089]
In addition, among the results shown in Table 1, FIG. 1 shows the results of arranging the “discharging capacity at the 50th cycle at 100 ° C.” and the “recovery capacity retention rate after high-temperature storage” in order of the atomic number of the substitution element M. .
[0090]
(Consideration of results) Compared to the comparative battery R using only B as the substitution element and the comparison battery S not using the substitution element, the battery of the present invention.(Or reference battery)In AK, although the initial discharge capacity is reduced, both the charge / discharge cycle performance and the high-temperature storage performance are greatly improved.
[0091]
referenceThe batteries B and K both use Al as a substitution element, but the latter has a larger amount of substitution element. From both results, although the initial discharge capacity decreases as the amount of substitution increases, both the charge / discharge cycle performance and the high-temperature storage performance are improved.
[0092]
In the comparative battery M using Ca as the substitution element and the comparison battery O using Fe as the substitution element, the charge / discharge cycle performance is improved as compared with the comparison ionization R not using these substitution elements, but it is stored at high temperature. Performance is getting worse. The cause of this is not necessarily clear, but the oxides or hydroxides of these elements formed at a potential no less than 1.2 V above the standard hydrogen electrode are not passivated in the organic electrolyte and are soluble. Therefore, it is considered that after these elements are eluted, manganese of the lithium manganese composite oxide, in which the substitution element is partially removed, is easily dissolved. The elution is likely to occur at high temperatures.
[0093]
In the comparative battery P using Ge as the substitution element and the comparison battery Q using Y as the substitution element, the charge / discharge cycle performance, compared to the present invention batteries (or reference batteries) A to K and the comparison batteries L to O, Both high-temperature storage performances were very bad. As a result of disassembling these deteriorated comparative batteries P and Q and analyzing elements in the electrolytic solution and the negative electrode, both Ge and Y were detected, but the detected amount of Mn was higher than that of all other batteries. It turned out to be very big. The reason for this is not necessarily clear, but elements with an atomic radius larger than Ge can only be replaced by a portion of Mn, and the elements that have not been used for replacement dissolve and a defective film is formed on the carbonaceous electrode. This is presumably because not only the capacity is reduced, but also the manganese of the lithium manganese composite oxide, in which some of the substituted elements are missing after the elution of these elements, is easily dissolved. However, since these elements are partially substituted with Mn, they can be completely replaced by optimizing the firing conditions and the like, and may be used effectively as replacement elements. is there.
[0094]
The comparative battery L using Mg as a substitution element and the comparison battery N using Cr as a substitution element are compared with the comparison battery R in which elements other than Mn except Li and B are not substituted. Although the charge / discharge cycle performance is improved as compared with the comparative ionization R that is not used, the high-temperature storage performance is not improved to be equal to or higher than that of the comparative battery R. However, for these two elements, the oxide or water formed at a noble potential of 1.2 V or more from the standard hydrogen electrode by examining the components of the electrolyte, the selection of the supporting salt, the moisture management of the electrolyte, etc. In some cases, the oxide is passivated in the organic electrolyte, and dissolution can be suppressed. For this reason, these elements may be used effectively as replacement elements in the future due to the progress of the development of electrolytes.
[0095]
As described above, according to the present invention, since the decomposition of the electrolyte salt is suppressed, and thus the generation of hydrofluoric acid is suppressed, the elution of the positive electrode constituent elements such as Mn is suppressed. The surface film produced on the surface is not a film containing high resistance lithium fluoride or manganese, but a film containing less fluorine and relatively low resistance such as lithium carbonate or lithium oxide is formed, suppressing an increase in interface resistance. Thus, a lithium battery having good charge / discharge cycle performance can be provided.
[0096]
In addition, since the oxide or hydroxide formed at a noble potential of 1.2 V or more from the standard hydrogen electrode is used in an organic electrolyte solution, it is replaced even when stored at a high temperature of 80 ° C. It is possible to provide a lithium battery that does not dissolve the element, can improve the stability of the lithium manganese composite oxide positive electrode, and has excellent high-temperature storage characteristics.
[0097]
As described above, boron is eluted from the positive electrode and detected from the electrolytic solution and the negative electrode in the initial charge / discharge test. Therefore, the amount of B may be a minimum as a substitution element, and 0.0005 to 0.01 is sufficient.
[0098]
Moreover, although the Example was given about the lithium secondary battery using artificial graphite as negative electrode material, the same effect was confirmed also about the other negative electrode material.
[0099]
In addition, this invention is not limited to the starting material of the active material described in the said Example, the manufacturing method, a positive electrode, a negative electrode, an electrolyte, a separator, a battery shape, etc.
[0100]
【The invention's effect】
Since the present invention is configured as described above,A lithium secondary battery having an excellent capacity recovery maintenance rate after high-temperature storage can be provided.
[Brief description of the drawings]
FIG. 1 is a graph showing high-temperature cycle performance and high-temperature storage performance in relation to a substitution element M.

Claims (3)

A lithium secondary battery comprising a positive electrode, a negative electrode, and an organic electrolyte , wherein a lithium manganese composite oxide having a composition represented by the following general formula is used for the positive electrode.
Li _(1-z) [Mn _(2-xyw) M _x B _w Li _y O ₄ ]
However,
x = 0.01-0.1
y = 0-0.2
x + y + w ≦ 0.2
w = 0.005-0.01
0 ≦ z ≦ 1
M; Be, Si, Sc, at least one element selected from among Ti. The lithium secondary battery according to claim 1, wherein a carbonaceous material is used for the negative electrode. The organic electrolyte is LiPF ₆ The lithium secondary battery according to claim 1 or 2, wherein

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