JP3920510B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

【０２３９】
【表２】

【０２４０】
表１、表２から明らかなように、厚さが０．３ｍｍ以下の外装材と、５０体積％より多く、９５体積％以下のＢＬを含む非水溶媒を含有する非水電解液を備えた実施例１〜１３の二次電池は、高温貯蔵時に外装材が膨れるのを抑制することができ、２Ｃでの放電容量及び３００サイクル後の容量維持率を向上できることがわかる。
【０２４１】
これに対し、比較例１、３、１１の二次電池は、高温貯蔵時の外装材の膨れを抑制できるものの、２Ｃでの放電容量及び３００サイクル後の容量維持率が実施例１〜１３に比べて劣ることがわかる。また、比較例５〜９の二次電池は、高温貯蔵時の外装材の膨れが実施例１〜１３に比べて大きいことがわかる。なお、比較例１の二次電池に含まれる非水電解液は、前述した特開平１１−９７０６２号公報に開示された非水電解液に相当するものである。また、比較例１１の二次電池に含まれる非水電解液は、前述した特開平４−１４７６９号公報に開示された非水電解液に相当するものである。
【０２４２】
（実施例１４）
外装材として厚さが０．３５ｍｍのアルミニウム缶を用い、電池寸法が実施例１と同様（厚さが３ｍｍ，幅が４０ｍｍ、高さが７０ｍｍ）になるように電極群の厚さを薄くすること以外は、前述した実施例１と同様にして薄型非水電解液二次電池を製造した。得られた二次電池は、容量が０．４Ａｈであった。
【０２４３】
（実施例１５）
非水電解液として、２４体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び１体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解したものを用いること以外は、前述した実施例１と同様にして薄型非水電解液二次電池を製造した。
【０２４４】
（実施例１６）
非水電解液として、２３体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び２体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解したものを用いること以外は、前述した実施例１と同様にして薄型非水電解液二次電池を製造した。
【０２４５】
（実施例１７）
非水電解液として、２４．５体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び０．５体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解したものを用いること以外は、前述した実施例１と同様にして薄型非水電解液二次電池を製造した。
【０２４６】
（実施例１８）
非水電解液として、２５体積％のエチレンカーボネート（ＥＣ）、７４体積％のγ―ブチロラクトン（ＢＬ）及び１体積％のトルエンからなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解したものを用いること以外は、前述した実施例１と同様にして薄型非水電解液二次電池を製造した。
【０２４７】
得られた実施例１５〜１８の二次電池について、前述した実施例１で説明したのと同様にして容量、内部インピーダンス、２Ｃ放電時の容量維持率、３００サイクル後の容量維持率及び８５℃で貯蔵後の膨れを測定し、その結果を下記表３に示す。
【０２４８】
【表３】

【０２４９】
表３から明らかなように、５０体積％より多く、９５体積％以下のＢＬ、ＥＣ及びＶＣを含む非水電解液を備えた実施例１５〜１７の二次電池は、実施例１の二次電池に比べて、３００サイクル後の容量維持率が高いことがわかる。
【０２５０】
（実施例１９）
セパレータとして、厚さが２５μｍで、１２０℃、１時間での熱収縮が２０％で、空気透過率が９０ｓｅｃ／１００ｃｍ³で、かつ多孔度が５０％のポリエチレン製多孔質フィルムを用いること以外は、前述した実施例１と同様にして薄型非水電解液二次電池を製造した。
【０２５１】
（実施例２０）
セパレータの多孔質フィルムの空気透過率を５８０ｓｅｃ／１００ｃｍ³にすること以外は、前述した実施例１９と同様にして薄型非水電解液二次電池を製造した。
【０２５２】
（実施例２１）
セパレータの多孔質シートの空気透過率を４００ｓｅｃ／１００ｃｍ³にすること以外は、前述した実施例１９と同様にして薄型非水電解液二次電池を製造した。
【０２５３】
（実施例２２）
セパレータの多孔質シートの空気透過率を１５０ｓｅｃ／１００ｃｍ³にすること以外は、前述した実施例１９と同様にして薄型非水電解液二次電池を製造した。
【０２５４】
得られた実施例１９〜２２の二次電池について、前述した実施例１で説明したのと同様にして容量、内部インピーダンス、２Ｃ放電時の容量維持率、３００サイクル後の容量維持率及び８５℃で貯蔵後の膨れを測定し、その結果を下記表４に示す。
【０２５５】
【表４】

【０２５６】
（実施例２３）
接着性を有する高分子を添加しないこと以外は、前述した実施例１で説明したのと同様にして電極群を作製した。得られた電極群を外装材である厚さが０．２０ｍｍのアルミニウム缶に収納した。次いで、８０℃の高温真空雰囲気において前記外装材に電極群の厚さ方向に沿って１０ｋｇ／ｃｍ²の圧力でプレスを施すことにより、正極、負極及びセパレータを前記正極及び負極に含まれる結着剤を熱硬化させて一体化した。
【０２５７】
２４．５体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び０．５体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解させ、非水電解液を調製した。前記アルミニウム缶内の電極群に前記非水電解液を電池容量１Ａｈ当たりの量が４．７ｇと同様となるように注入し、封口することにより厚さが３．２ｍｍ、幅が４０ｍｍ、高さが７０ｍｍの薄型非水電解液二次電池を組み立てた。
【０２５８】
（実施例２４）
接着性を有する高分子を添加しないこと以外は、前述した実施例１で説明したのと同様にして電極群を作製した。得られた電極群を外装材である厚さが０．２０ｍｍのアルミニウム缶に収納した。次いで、８０℃の高温真空雰囲気において前記外装材に電極群の厚さ方向に沿って１０ｋｇ／ｃｍ²の圧力でプレスを施すことにより、正極、負極及びセパレータを前記正極及び負極に含まれる結着剤を熱硬化させて一体化した。
【０２５９】
２３体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び２体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解させ、非水電解液を調製した。前記アルミニウム缶内の電極群に前記非水電解液を電池容量１Ａｈ当たりの量が４．７ｇと同様となるように注入し、厚さが３．２ｍｍ、幅が４０ｍｍ、高さが７０ｍｍの薄型非水電解液二次電池を組み立てた。
【０２６０】
得られた実施例２３〜２４の二次電池について、前述した実施例１で説明したのと同様にして容量、内部インピーダンス、２Ｃ放電時の容量維持率、３００サイクル後の容量維持率及び８５℃で貯蔵後の膨れを測定し、その結果を下記表５に示す。
【０２６１】
【表５】

【０２６２】
表５から明らかなように、実施例２３〜２４の二次電池は、高容量で、２Ｃ放電時及び３００サイクル後の容量維持率が高く、かつ８５℃で貯蔵した際の膨れを抑制できることがわかる。
【０２６３】
（実施例２５）
外装材として、アルミ箔の両面をポリプロピレンで覆った厚さ５００μｍのラミネートフィルムを用い、電池寸法を厚さが４ｍｍ、幅が１００ｍｍ、高さが２８０ｍｍにすること以外は、前述した実施例１と同様にして非水電解液二次電池を製造した。
【０２６４】
得られた実施例２５の二次電池について、前述した実施例１で説明したのと同様にして容量、２Ｃ放電時の容量維持率、３００サイクル後の容量維持率及び８５℃で貯蔵後の膨れを測定した。その結果、実施例２５の二次電池は、容量が６Ａｈで、２Ｃ放電時容量維持率が８５％で、３００サイクル後の容量維持率が９０％で、８５℃貯蔵後の膨れが３％であった。従って、５０体積％より多く、９５体積％以下のＢＬを含む非水溶媒を用いると、電気自動車のような大型の電池の外装材として厚さが０．５ｍｍのラミネートフィルムを使用できることを確認できた。
【０２６５】
（実施例２６）
＜正極の作製＞
まず、リチウムコバルト酸化物（Ｌｉ_x ＣｏＯ₂ ；但し、Ｘは０≦Ｘ≦１である）粉末９１重量％をアセチレンブラック２．５重量％、グラファイト３重量％及びポリフッ化ビニリデン（ＰＶｄＦ）４重量％とＮ―メチルピロリドン（ＮＭＰ）溶液を加えて共に混合し、厚さが１０μｍのアルミニウム箔からなる集電体の両面に塗布した後、乾燥し、プレスすることにより、集電体の各面に密度が３．３ｇ／ｃｍ³ で、空隙率が３４％で、厚さが４８μｍの正極活物質層が担持された構造の正極を作製した。
【０２６６】
＜負極の作製＞
炭素質材料として３０００℃で熱処理したメソフェーズピッチ系炭素繊維（繊維径が８μｍ、平均繊維長が２０μｍ、平均面間隔（ｄ₀₀₂ ）が０．３３６０ｎｍ）の粉末を９３重量％と、結着剤としてポリフッ化ビニリデン（ＰＶｄＦ）７重量％と、Ｎ―メチルピロリドン溶液を混合し、これを厚さが１０μｍの銅箔からなる集電体の両面に塗布し、乾燥し、プレスすることにより、集電体の各面に密度が１．３ｇ／ｃｍ³ で、空隙率が４１％で、厚さが４５μｍの負極活物質層が担持された構造の負極を作製した。
【０２６７】
＜セパレータ＞
厚さが２０μｍ、多孔度が５０％のポリエチレン製多孔質フィルムからなるセパレータを用意した。
【０２６８】
＜電極群の作製＞
前記正極及び前記負極をその間に前記セパレータを介して渦巻き状に捲回した後、偏平状に成形し、厚さが２．５ｍｍ、幅が３０ｍｍ、高さが５０ｍｍの偏平型電極群を作製した。
【０２６９】
＜非水電解液の調製＞
四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）をエチレンカーボネート（ＥＣ）とγ−ブチロラクトン（ＢＬ）の混合溶媒（混合体積比率２５：７５）に１．５モル／１溶解して非水電解液を調製した。
【０２７０】
次いで、アルミ箔の両面をポリプロピレンで覆った厚さ１００μｍのラミネートフィルムを袋状に成形し、これに前記電極群を収納し、厚さが２．７ｍｍになるように両面をホルダで挟んだ。接着性を有する高分子であるポリフッ化ビニリデン（ＰＶｄＦ）を有機溶媒であるジメチルフォルムアミド（沸点が１５３℃）に０．３重量％溶解させた。得られた溶液を前記ラミネートフィルム内の電極群に電池容量１００ｍＡｈ当たりの量が０．６ｍｌとなるように注入し、前記溶液を前記電極群の内部に浸透させると共に、前記電極群の表面全体に付着させた。
【０２７１】
次いで、前記ラミネートフィルム内の電極群に８０℃で真空乾燥を１２時間施すことにより前記有機溶媒を蒸発させ、正極、負極及びセパレータの空隙に接着性を有する高分子を保持させると共に、前記電極群の表面に多孔質な接着部を形成した。
【０２７２】
前記ラミネートフィルム内の電極群に前記非水電解液を電池容量１Ａｈ当たりの量が２ｇとなるように注入し、厚さが３ｍｍ、幅が３２ｍｍ、高さが５５ｍｍの薄型非水電解液二次電池を組み立てた。
【０２７３】
この非水電解液二次電池に対し、初充電工程として以下の処置を施した。まず、４０℃の高温環境下に５ｈ放置した後、その環境下で０．２Ｃ（１２０ｍＡ）で４．２Ｖまで定電流・定電圧充電を１０時間行った。その後０．２Ｃで２．７Ｖまで放電し、さらに２サイクル目も１サイクル目と同様な条件で充電を行い非水電解液二次電池を製造した。
【０２７４】
得られた非水溶媒二次電池の室温（２０℃）での大電流放電特性を調べるために３Ｃ放電時の容量維持率を測定した。この際、０．２Ｃでの放電容量を基準容量とした。また、充放電サイクル特性を調べるために０．７Ｃレートでの４．２Ｖ定電流・定電圧の３時間充電と１Ｃレートの２．７Ｖ放電のサイクルを繰り返し、３００サイクル後の容量維持率を測定した。また、４．２Ｖ充電後８５℃で１２０時間の高温度貯蔵後の膨れを測定した。以上の実施例２６の電池の初期容量、活物質層厚さ、電解液の溶媒のγ―ブチロラクトンの含有比率、及び電池特性を表６に示す。
【０２７５】
（実施例２７〜３７，Ａ，Ｂ及び比較例１２〜１３）
正極活物質層と負極活物質層の片面の厚さ、及び電解液の溶媒のγ―ブチロラクトンの含有比率を表６に示す如く変えた以外は実施例２６と同様にして薄型非水電解液二次電池を得て電池評価を行った。各電池の初期容量、活物質層厚さ、電解液の溶媒のγ―ブチロラクトンの含有比率、及び電池特性を表６に併記する。
【０２７６】
【表６】

【０２７７】
表６から明らかなように、正極活物質層の厚さが１０〜１００μｍである正極と、厚さが０．３ｍｍ以下の外装材と、４０〜９５体積％のＢＬを含む非水溶媒を含有する非水電解液を備えた実施例２６〜３７，Ａ，Ｂの二次電池は、高温貯蔵時に外装材が膨れるのを抑制することができ、初期容量、３Ｃでの放電容量及び３００サイクル後の容量維持率を向上できることがわかる。
【０２７８】
これに対し、比較例１２の二次電池は、３Ｃでの放電容量及び３００サイクル後の容量維持率が実施例２６〜３７，Ａ，Ｂに比べて劣ることがわかる。また、比較例１３の二次電池は、３Ｃでの放電容量が実施例２６〜３７，Ａ，Ｂに比べて劣ることがわかる。
【０２７９】
（実施例３８）
非水電解液として、２４．９体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び０．１体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解したものを用いること以外は、前述した実施例２６と同様にして薄型非水電解液二次電池を製造した。
【０２８０】
（実施例３９）
非水電解液として、２４体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び１体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解したものを用いること以外は、前述した実施例２６と同様にして薄型非水電解液二次電池を製造した。
【０２８１】
（実施例４０）
非水電解液として、２０体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び５体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解したものを用いること以外は、前述した実施例２６と同様にして薄型非水電解液二次電池を製造した。
【０２８２】
（実施例４１）
非水電解液として、２５体積％のエチレンカーボネート（ＥＣ）、７４体積％のγ―ブチロラクトン（ＢＬ）及び１体積％のトルエンからなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解したものを用いること以外は、前述した実施例２６と同様にして薄型非水電解液二次電池を製造した。
【０２８３】
得られた実施例３８〜４１の二次電池について、前述した実施例２６で説明したのと同様にして容量、３Ｃ放電時の容量維持率、３００サイクル後の容量維持率及び８５℃で貯蔵後の膨れを測定し、その結果を下記表７に示す。
【０２８４】
【表７】

【０２８５】
表７から明らかなように、４０〜９５体積％のＢＬ、ＥＣ及びＶＣを含む非水電解液を備えた実施例３８〜４０の二次電池と、４０〜９５体積％のＢＬ、ＥＣ及び芳香族化合物を含む非水電解液を備えた実施例４１の二次電池は、実施例２６の二次電池に比べて、３００サイクル後の容量維持率が高いことがわかる。
【０２８６】
（実施例４２）
セパレータとして、厚さが２５μｍで、１２０℃、１時間での熱収縮が２０％で、空気透過率が９０ｓｅｃ／１００ｃｍ³で、かつ多孔度が５０％のポリエチレン製多孔質フィルムを用いること以外は、前述した実施例２６と同様にして薄型非水電解液二次電池を製造した。
【０２８７】
（実施例４３）
セパレータの多孔質フィルムの空気透過率を５８０ｓｅｃ／１００ｃｍ³にすること以外は、前述した実施例４２と同様にして薄型非水電解液二次電池を製造した。
【０２８８】
（実施例４４）
セパレータの多孔質シートの空気透過率を４００ｓｅｃ／１００ｃｍ³にすること以外は、前述した実施例４２と同様にして薄型非水電解液二次電池を製造した。
【０２８９】
（実施例４５）
セパレータの多孔質シートの空気透過率を１５０ｓｅｃ／１００ｃｍ³にすること以外は、前述した実施例４２と同様にして薄型非水電解液二次電池を製造した。
【０２９０】
得られた実施例４２〜４５の二次電池について、前述した実施例２６で説明したのと同様にして容量、３Ｃ放電時の容量維持率、３００サイクル後の容量維持率及び８５℃で貯蔵後の膨れを測定し、その結果を下記表８に示す。
【０２９１】
【表８】

【０２９２】
（実施例４６）
接着性を有する高分子を添加しないこと以外は、前述した実施例２６で説明したのと同様にして電極群を作製した。得られた電極群を外装材である厚さが０．１８ｍｍのアルミニウム缶に収納した。次いで、８０℃の高温真空雰囲気において前記外装材に電極群の厚さ方向に沿って１０ｋｇ／ｃｍ²の圧力でプレスを施すことにより、正極、負極及びセパレータを前記正極及び負極に含まれる結着剤を熱硬化させて一体化した。
【０２９３】
２４．５体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び０．５体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解させ、非水電解液を調製した。前記アルミニウム缶内の電極群に前記非水電解液を電池容量１Ａｈ当たりの量が４．７ｇと同様となるように注入し、封口することにより厚さが３ｍｍ、幅が３２ｍｍ、高さが５５ｍｍの薄型非水電解液二次電池を組み立てた。
【０２９４】
（実施例４７）
接着性を有する高分子を添加しないこと以外は、前述した実施例２６で説明したのと同様にして電極群を作製した。得られた電極群を外装材である厚さが０．２５ｍｍのアルミニウム缶に収納した。次いで、８０℃の高温真空雰囲気において前記外装材に電極群の厚さ方向に沿って１０ｋｇ／ｃｍ²の圧力でプレスを施すことにより、正極、負極及びセパレータを前記正極及び負極に含まれる結着剤を熱硬化させて一体化した。
【０２９５】
２４体積％のエチレンカーボネート（ＥＣ）、７５体積％のγ―ブチロラクトン（ＢＬ）及び２体積％のビニレンカーボネート（ＶＣ）からなる非水溶媒に四フッ化ホウ酸リチウム（ＬｉＢＦ₄ ）を１．５モル／ｌ溶解させ、非水電解液を調製した。前記アルミニウム缶内の電極群に前記非水電解液を電池容量１Ａｈ当たりの量が４．７ｇと同様となるように注入し、厚さが３ｍｍ、幅が３２ｍｍ、高さが５５ｍｍの薄型非水電解液二次電池を組み立てた。
【０２９６】
得られた実施例４６〜４７の二次電池について、前述した実施例２６で説明したのと同様にして容量、３Ｃ放電時の容量維持率、３００サイクル後の容量維持率及び８５℃で貯蔵後の膨れを測定し、その結果を下記表９に示す。
【０２９７】
【表９】

【０２９８】
表９から明らかなように、実施例４６〜４７の二次電池は、高容量で、３Ｃ放電時及び３００サイクル後の容量維持率が高く、かつ８５℃で貯蔵した際の膨れを抑制できることがわかる。
【０２９９】
（実施例４８）
外装材として、アルミ箔の両面をポリプロピレンで覆った厚さ５００μｍのラミネートフィルムを用い、電池寸法を厚さが４ｍｍ、幅が８０ｍｍ、高さが２２０ｍｍにすること以外は、前述した実施例２６と同様にして非水電解液二次電池を製造した。
【０３００】
得られた実施例４８の二次電池について、前述した実施例２６で説明したのと同様にして容量、３Ｃ放電時の容量維持率、３００サイクル後の容量維持率及び８５℃で貯蔵後の膨れを測定した。その結果、実施例４８の二次電池は、容量が３．２Ａｈで、３Ｃ放電時容量維持率が９６％で、３００サイクル後の容量維持率が９０％で、８５℃貯蔵後の膨れが３％であった。従って、正極活物質層の厚さを１０〜１００μｍにし、かつ４０〜９５体積％のＢＬを含む非水溶媒を用いると、電気自動車のような大型の電池の外装材として厚さが０．５ｍｍのラミネートフィルムを使用できることを確認できた。
【０３０１】
【発明の効果】
以上詳述したように、本発明によれば、高温で貯蔵した際の外装材の変形が抑制され、重量エネルギー密度、体積エネルギー密度、大電流放電特性及び充放電サイクル特性が向上された非水電解液二次電池を提供することができる。
【図面の簡単な説明】
【図１】発明に係わる第１の非水電解液二次電池の一例を示す断面図。
【図２】図１のＡ部を示す拡大断面図。
【図３】図１の二次電池における正極、セパレータ及び負極の境界付近を示す模式図。
【図４】本発明に係わる第２の非水電解液二次電池における正極活物質層の厚さを説明するための断面図。
【図５】本発明に係わる第２の非水電解液二次電池の一例を示す断面図。
【図６】図５のＢ部を示す拡大断面図。
【図７】図５の二次電池における正極、セパレータ及び負極の境界付近を示す模式図。
【符号の説明】
１…外装材、
２…電極群、
３…セパレータ、
４…正極層、
５…正極集電体、
６…負極層、
７…負極集電体、
８…接着層、
９…接着性を有する高分子、
１２…正極、
１３…負極、
２１…外装材、
２２…電極群、
２３…セパレータ、
２４…正極層、
２５…正極集電体、
２６…負極層、
２７…負極集電体、
２８…接着層、
２９…接着性を有する高分子、
３２…正極、
３３…負極。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery.
[0002]
[Prior art]
Currently, lithium ion secondary batteries are commercialized as non-aqueous electrolyte secondary batteries for portable devices such as mobile phones. This battery has a lithium cobalt oxide (LiCoO) on the positive electrode. ₂ ), A graphite material or a carbonaceous material for the negative electrode, an organic solvent in which a lithium salt is dissolved in a non-aqueous electrolyte, and a porous film for the separator. A non-aqueous solvent having a low viscosity and a low boiling point is used as the solvent for the electrolytic solution.
[0003]
For example, Japanese Patent Application Laid-Open No. Hei 4-14769 discloses a non-electrolytic solution comprising an electrolytic solution mainly composed of a mixed solvent composed of propylene carbonate, ethylene carbonate and γ-butyrolactone, and the ratio of γ-butyrolactone is 10 to 50% by volume of the whole solvent. A water electrolyte secondary battery is described. This publication aims to improve the low-temperature discharge characteristics of a cylindrical non-aqueous electrolyte secondary battery.
[0004]
By the way, it is desired to reduce the thickness of the battery as the portable device becomes thinner. For this purpose, it is necessary to reduce the thickness of the exterior material that houses the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte. However, a lithium ion secondary battery provided with a non-aqueous electrolyte containing a solvent having a γ-butyrolactone content of 10 to 50% by volume described in JP-A-4-14769 described above is a negative electrode during initial charging. Therefore, when the gas is increased or stored at a high temperature of 60 ° C. or higher, the positive electrode and the non-aqueous electrolyte react to cause oxidative decomposition of the non-aqueous electrolyte, resulting in gas generation. For this reason, when the thickness of the exterior material is reduced, there arises a problem that the exterior material is expanded and deformed by the generation of gas. If the exterior material is deformed, the battery may not fit in the electronic device, or the electronic device may malfunction.
[0005]
On the other hand, JP-A-11-97062 discloses lithium borofluoride (LiBF) as a solvent in which the ratio of γ-butyrolactone is 100% by volume. _Four ) Is dissolved as a non-aqueous electrolyte solution, and a non-aqueous electrolyte secondary battery is disclosed. This publication aims to suppress the oxidative decomposition of a positive electrode containing a lithium cobalt composite oxide as an active material by a non-aqueous electrolyte.
[0006]
However, lithium borofluoride (LiBF) is used as a solvent disclosed in JP-A-11-97062 in which the ratio of γ-butyrolactone is 100% by volume. _Four ) Is easily reacted with the negative electrode to cause reductive decomposition. As a result, current concentration is likely to occur in the negative electrode, so that lithium metal is deposited on the negative electrode surface, or the impedance at the negative electrode interface is increased, the charge / discharge efficiency of the negative electrode is lowered, and charge / discharge cycle characteristics are degraded.
[0007]
Further, in non-aqueous electrolyte secondary batteries, further improvements in large current discharge characteristics and charge / discharge cycle characteristics are desired.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to suppress the generation of gas when stored at a high temperature, thereby suppressing the swelling of the exterior material and improving the large current discharge characteristics and charge / discharge cycle characteristics. The next battery is to be provided.
[0009]
[Means for Solving the Problems]
According to the present invention, a positive electrode, a negative electrode including a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode are provided. The positive electrode, the negative electrode and the separator are integrated. A non-aqueous electrolyte solution containing a non-aqueous solvent impregnated in the electrode group and a lithium salt dissolved in the non-aqueous solvent; An exterior material made of a laminate film of 5 mm or less;
The non-aqueous solvent contains more than 50% by volume of the whole non-aqueous solvent and 95% by volume or less of γ-butyrolactone and ethylene carbonate,
The lithium salt is LiPF ₆ Or LiBF _Four A non-aqueous electrolyte secondary battery containing is provided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The first non-aqueous electrolyte secondary battery according to the present invention includes an electrode group including a positive electrode, a negative electrode including a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode; A non-aqueous electrolyte containing a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent; and an exterior material in which the electrode group is housed. The non-aqueous solvent contains γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume of the whole non-aqueous solvent.
[0014]
In this secondary battery, the positive electrode, the negative electrode, and the separator do not have to be integrated, but it is preferable that they are integrated under the conditions described in (a) or (b) below. .
[0015]
(A) Adhesion in which the positive electrode and the separator are integrated by an adhesive polymer present at at least a part of these boundaries, and the negative electrode and the separator are present at at least a part of these boundaries It is integrated with a polymer having properties. In particular, the positive electrode and the separator are integrated with an adhesive polymer scattered in the interior and boundary thereof, and the negative electrode and the separator have adhesiveness scattered in the interior and boundary thereof. It is desirable that they are integrated by a polymer.
[0016]
(B) The positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode.
[0017]
By adopting the configuration of (a) or (b), the swelling of the exterior material can be further reduced.
[0018]
The secondary battery preferably has a product of battery capacity (Ah) and 1 kHz battery internal impedance (mΩ) of 10 mΩ · Ah or more and 110 mΩ · Ah or less. By setting the product of the capacity and the impedance within the above range, the large current discharge characteristics and the charge / discharge cycle characteristics can be further improved. Here, the battery capacity is a nominal capacity or a discharge capacity when discharged at 0.2C. A more preferable range is 20 mΩ · Ah or more and 60 mΩ · Ah or less.
[0019]
The product of the battery capacity and the impedance can be 10 mΩ · Ah or more and 110 mΩ · Ah or less, for example, by the manufacturing method (I) described later or the manufacturing method (II) described later. However, in (I), the addition amount of the adhesive polymer, the distribution of the adhesive polymer, and the initial charging conditions are set so that the product of the battery capacity and the impedance is 10 mΩ · Ah or more and 110 mΩ · Ah or less. In (II), the temperature, press pressure, and initial charge condition when forming the electrode group are set so that the product of the battery capacity and impedance is 10 mΩ · Ah or more and 110 mΩ · Ah or less.
[0020]
Hereinafter, a non-aqueous electrolyte secondary battery including an electrode group that satisfies the above-described (a) will be described.
[0021]
1) Positive electrode
This positive electrode has a structure in which a positive electrode layer containing an active material is supported on one side or both sides of a current collector.
[0022]
The positive electrode layer includes a positive electrode active material and a conductive agent. In addition, the positive electrode layer includes a binder that binds the positive electrode active materials to each other, apart from the adhesive polymer.
[0023]
Examples of the positive electrode active material include various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt oxide, lithium-containing nickel cobalt oxide, lithium-containing iron oxide, and lithium. Examples thereof include vanadium oxide and chalcogen compounds such as titanium disulfide and molybdenum disulfide. Among them, lithium-containing cobalt oxide (for example, LiCoO ₂ ), Lithium-containing nickel cobalt oxide (eg, LiNi _0.8 Co _0.2 O ₂ ), Lithium manganese composite oxide (for example, LiMn ₂ O _Four LiMnO ₂ ) Is preferable because a high voltage can be obtained.
[0024]
Examples of the conductive agent include acetylene black, carbon black, and graphite.
[0025]
The binder has a function of holding the active material on the current collector and connecting the active materials to each other. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR).
[0026]
The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.
[0027]
As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, aluminum, stainless steel, or nickel.
[0028]
Above all, a hole with a diameter of 3 mm or less is 10 cm. ² It is preferable to use a conductive substrate having a two-dimensional porous structure present at a rate of one or more per unit. That is, when the diameter of the hole opened in the conductive substrate is larger than 3 mm, there is a possibility that sufficient positive electrode strength cannot be obtained. On the other hand, if the proportion of holes having a diameter of 3 mm or less is smaller than the above range, it is difficult to uniformly infiltrate the non-aqueous electrolyte into the electrode group, so that sufficient charge / discharge cycle characteristics may not be obtained. . The diameter of the hole is more preferably in the range of 0.1 to 1 mm. Moreover, the presence ratio of the hole is 10 cm. ² More preferably, the range is 10 to 20 per unit.
[0029]
The aforementioned hole with a diameter of 3 mm or less is 10 cm. ² It is preferable that the thickness of the conductive substrate having a two-dimensional porous structure present at a ratio of one or more per unit be in the range of 15 to 100 μm. If the thickness is less than 15 μm, sufficient positive electrode strength may not be obtained. On the other hand, if the thickness exceeds 100 μm, the battery weight and the thickness of the electrode group increase, which may make it difficult to sufficiently increase the weight energy density and volume energy density of the thin secondary battery. A more preferable range of the thickness is 30 to 80 μm.
[0030]
2) Negative electrode
The negative electrode has a structure in which a negative electrode layer is supported on one side or both sides of a current collector.
[0031]
The negative electrode layer includes a carbonaceous material that occludes / releases lithium ions. The negative electrode layer contains a binder for binding the negative electrode material, in addition to the adhesive polymer.
[0032]
Examples of the carbonaceous material include graphite materials such as graphite, coke, carbon fiber, and spherical carbon or carbonaceous materials, thermosetting resins, isotropic pitches, mesophase pitches, mesophase pitch-based carbon fibers, mesophase microspheres, etc. And a mesophase pitch-based carbon fiber is preferable because the capacity and charge / discharge cycle characteristics are increased), and a graphite material or a carbonaceous material obtained by heat treatment at 500 to 3000 ° C. can be used. In particular, the heat treatment temperature is 2000 ° C. or higher, and the (002) plane spacing d is obtained. ₀₀₂ It is preferable to use a graphite material having a graphite crystal having a thickness of 0.340 nm or less. A nonaqueous electrolyte secondary battery including a negative electrode containing such a graphite material as a carbonaceous material can greatly improve battery capacity and large current discharge characteristics. The surface spacing d ₀₀₂ Is more preferably 0.336 nm or less.
[0033]
Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like. be able to.
[0034]
The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder.
[0035]
As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel.
[0036]
Above all, a hole with a diameter of 3 mm or less is 10 cm. ² It is preferable to use a conductive substrate having a two-dimensional porous structure present at a rate of one or more per unit. That is, when the diameter of the hole of the conductive substrate is larger than 3 mm, there is a possibility that sufficient negative electrode strength cannot be obtained. On the other hand, if the proportion of holes having a diameter of 3 mm or less is smaller than the above range, it is difficult to uniformly infiltrate the non-aqueous electrolyte into the electrode group, so that sufficient charge / discharge cycle characteristics may not be obtained. . The diameter of the hole is more preferably in the range of 0.1 to 1 mm. Moreover, the presence ratio of the hole is 10 cm. ² More preferably, the range is 10 to 20 per unit.
[0037]
The aforementioned hole with a diameter of 3 mm or less is 10 cm. ² It is preferable that the thickness of the conductive substrate having a two-dimensional porous structure present at a ratio of one or more per unit be in the range of 10 to 50 μm. If the thickness is less than 10 μm, sufficient negative electrode strength may not be obtained. On the other hand, if the thickness exceeds 50 μm, the weight of the battery and the thickness of the electrode group increase, and it may be difficult to sufficiently increase the weight energy density and volume energy density of the thin secondary battery.
[0038]
The negative electrode layer is made of a metal such as aluminum, magnesium, tin, or silicon, a metal oxide, a metal sulfide, or a metal nitride, in addition to the carbon material that occludes / releases lithium ions. It may contain a selected metal compound or lithium alloy.
[0039]
Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide.
[0040]
Examples of the metal sulfide include tin sulfide and titanium sulfide.
[0041]
Examples of the metal nitride include lithium cobalt nitride, lithium iron nitride, and lithium manganese nitride.
[0042]
Examples of the lithium alloy include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy.
[0043]
3) Separator
This separator is formed from a porous sheet.
[0044]
For example, a porous film or a non-woven fabric can be used as the porous sheet. The porous sheet is preferably made of at least one material selected from, for example, polyolefin and cellulose. Examples of the polyolefin include polyethylene and polypropylene. Among these, a porous film made of polyethylene, polypropylene, or both is preferable because it can improve the safety of the secondary battery.
[0045]
The thickness of the porous sheet is preferably 30 μm or less. If the thickness exceeds 30 μm, the distance between the positive and negative electrodes may be increased and the internal resistance may be increased. Further, the lower limit value of the thickness is preferably 5 μm. If the thickness is less than 5 μm, the strength of the separator is remarkably lowered and an internal short circuit is likely to occur. The upper limit value of the thickness is more preferably 25 μm, and the lower limit value is more preferably 10 μm.
[0046]
The porous sheet preferably has a heat shrinkage rate of 20% or less at 120 ° C. for 1 hour. If the heat shrinkage rate exceeds 20%, it may be difficult to make the adhesive strength between the positive and negative electrodes and the separator sufficient. The heat shrinkage rate is more preferably 15% or less.
[0047]
The porous sheet preferably has a porosity in the range of 30 to 60%. This is due to the following reason. If the porosity is less than 30%, it may be difficult to obtain high electrolyte retention in the separator. On the other hand, if the porosity exceeds 60%, sufficient separator strength may not be obtained. A more preferable range of the porosity is 35 to 50%.
[0048]
The porous sheet has an air permeability of 600 seconds / 100 cm. ^Three The following is preferable. Air permeability is 100cm ^Three Means the time (seconds) required for the air to pass through the porous sheet. Air permeability is 600 seconds / 100cm ^Three If it exceeds 1, it may be difficult to obtain high lithium ion mobility in the separator. The lower limit of the air permeability is 100 seconds / 100 cm. ^Three It is preferable to make it. Air permeability is 100 seconds / 100cm ^Three If it is less than this, there is a possibility that sufficient separator strength cannot be obtained. The upper limit of air permeability is 500 seconds / 100cm ^Three The upper limit is more preferably 400 seconds / 100 cm. ^Three It is. The lower limit is 150 seconds / 100 cm. ^Three More preferably.
[0049]
4) Non-aqueous electrolyte
The non-aqueous electrolyte is a mixture of a non-aqueous solvent mainly composed of γ-butyrolactone (BL) and a lithium salt dissolved therein. The composition ratio of BL is more than 50% by volume of the total mixed non-aqueous solvent, and 95% by volume. It is as follows. When the ratio is 50% by volume or less, gas is likely to be generated at a high temperature. Further, when the mixed non-aqueous solvent contains BL and cyclic carbonate, the ratio of the cyclic carbonate becomes relatively high, so that the solvent viscosity increases and the conductivity of the non-aqueous electrolyte decreases. As a result, the charge / discharge cycle characteristics, the large current discharge characteristics, and the discharge characteristics under a low temperature environment around −20 ° C. are deteriorated. On the other hand, if the ratio exceeds 95% by volume, the reaction between the negative electrode and BL occurs, and the charge / discharge cycle characteristics deteriorate. That is, when the negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions) reacts with BL to cause reductive decomposition of the non-aqueous electrolyte, a coating that inhibits the charge / discharge reaction is formed on the surface of the negative electrode. The As a result, current concentration is likely to occur in the negative electrode, so that lithium metal is deposited on the negative electrode surface, or the impedance at the negative electrode interface is increased, the charge / discharge efficiency of the negative electrode is lowered, and charge / discharge cycle characteristics are degraded. A more preferable range is 60% by volume or more and 95% by volume or less. By setting it within this range, it is possible to further increase the effect of suppressing gas generation during high-temperature storage, and to further improve the discharge capacity in a low temperature environment around −20 ° C. A more preferable range is 65 volume% or more and 90 volume% or less.
[0050]
As a solvent mixed with BL, a cyclic carbonate is desirable in terms of increasing the charge / discharge efficiency of the negative electrode.
[0051]
As the cyclic carbonate, propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC), trifluoropropylene carbonate (TFPC) and the like are desirable. In particular, when EC is used as a solvent mixed with BL, charge / discharge cycle characteristics and large current discharge characteristics can be significantly improved. Moreover, as another solvent mixed with BL, a third solvent consisting of at least one selected from the group consisting of PC, VC, TFPC, diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and an aromatic compound, and EC The mixed solvent is desirable in terms of enhancing the charge / discharge cycle characteristics.
[0052]
Further, from the viewpoint of lowering the solvent viscosity, a low-viscosity solvent may be contained in an amount of 20% by volume or less. Examples of the low viscosity solvent include chain carbonates, chain ethers, cyclic ethers and the like.
[0053]
More preferred compositions of the non-aqueous solvent according to the present invention include BL and EC, BL and PC, BL and EC and DEC, BL and EC and MEC, BL and EC and MEC and VC, BL and EC and VC, and BL and PC. And VC, or BL, EC, PC, and VC. At this time, the volume ratio of EC is preferably 5 to 40% by volume. This is due to the following reason. If the EC ratio is less than 5% by volume, it may be difficult to cover the negative electrode surface densely with a protective film, so that the reaction between the negative electrode and BL occurs, and the charge / discharge cycle characteristics can be sufficiently improved. It can be difficult. On the other hand, if the EC ratio exceeds 40% by volume, the viscosity of the non-aqueous electrolyte solution is increased and the ionic conductivity may be lowered. Therefore, sufficient charge / discharge cycle characteristics, large current discharge characteristics, and low temperature discharge characteristics are sufficiently obtained. It can be difficult to improve. A more preferable range of the EC ratio is 10 to 35% by volume. Moreover, the solvent which consists of at least 1 sort (s) chosen from DEC, MEC, PC, and VC forms the dense protective film on the surface of a negative electrode, and makes the effect | action which reduces the interface impedance of a negative electrode. The amount of the solvent added is not particularly limited, and is set to such an amount that this action occurs. However, when the ratio of at least one solvent selected from DEC, MEC, PC and VC in the non-aqueous solvent exceeds 10% by volume, the non-aqueous electrolyte is sufficiently suppressed from being oxidatively decomposed in a high temperature environment. May be difficult, or the viscosity of the non-aqueous electrolyte solution may increase and the ionic conductivity may decrease. For this reason, it is desirable that the volume ratio of at least one solvent selected from DEC, MEC, PC and VC in the non-aqueous solvent is 10% by volume or less. A more preferable volume ratio is 2% by volume or less. The lower limit of the volume ratio is preferably 0.001% by volume, and a more preferable lower limit is 0.05% by volume.
[0054]
In particular, a non-aqueous solvent containing BL, EC and VC of more than 50% by volume and not more than 95% by volume is preferable. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte containing a non-aqueous solvent and a negative electrode containing a carbonaceous material that occludes and releases lithium ions can greatly reduce the impedance at the interface of the negative electrode. Since it is possible to suppress the deposition of metallic lithium on the negative electrode, the charge / discharge efficiency of the negative electrode can be improved. As a result, it is possible to suppress deformation of the exterior material by suppressing gas generation during high-temperature storage while realizing excellent large current discharge characteristics and a long life. It is estimated that the negative electrode characteristics are improved in this way due to the action described below. In the secondary battery, in addition to forming a protective film by EC on the surface of the negative electrode, a thin and dense film by VC is formed. As a result, since the reaction between BL and the negative electrode is further suppressed, it is considered that the reduction in impedance and the prevention of precipitation of metallic lithium are achieved.
[0055]
Moreover, as a non-aqueous solvent, you may use what contains BL, EC, and an aromatic compound of more than 50 volume% and 95 volume% or less instead of what has the composition mentioned above. Examples of the aromatic compound include at least one selected from benzene, toluene, xylene, biphenyl, and terphenyl. EC adheres to the surface of a negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions) to form a protective film, and can suppress the reaction between the negative electrode and BL. At this time, the volume ratio of EC is preferably 5 to 40% by volume for the same reason as described above. Further, a more preferable range of the EC ratio is 10 to 35% by volume. On the other hand, since the benzene ring of the aromatic compound is easily adsorbed on the surface of the negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions), the reaction between the negative electrode and BL can be suppressed. Therefore, a non-aqueous electrolyte solution containing a non-aqueous solvent containing BL, EC and aromatic compound in an amount of more than 50% by volume and not more than 95% by volume can sufficiently suppress the reaction between the negative electrode and BL. The charge / discharge cycle characteristics of the secondary battery can be improved. Such a non-aqueous solvent preferably further contains at least one solvent selected from DEC, MEC, PC, TFPC and VC. By adding at least one solvent selected from DEC, MEC, PC, TFPC and VC, the reaction between the negative electrode and BL can be further suppressed, so that the charge / discharge cycle characteristics can be further improved. . Of these, VC is preferable. The addition amount of the third solvent consisting of at least one selected from the aromatic compound, DEC, MEC, PC, TFPC and VC is not particularly limited, and is set to such an amount that this action occurs. However, if the ratio of the third solvent in the non-aqueous solvent exceeds 10% by volume, it may be difficult to sufficiently prevent the non-aqueous electrolyte from undergoing oxidative decomposition in a high temperature environment, or the non-aqueous electrolyte. There is a possibility that the ionic conductivity may be lowered due to an increase in the viscosity of. For this reason, the volume ratio of the third solvent in the non-aqueous solvent is desirably 10% by volume or less. A more preferable volume ratio is 2% by volume or less. The lower limit of the volume ratio is preferably 0.001% by volume, and a more preferable lower limit is 0.05% by volume.
[0056]
Examples of the electrolyte contained in the non-aqueous electrolyte include lithium perchlorate (LiClO). _Four ), Lithium hexafluorophosphate (LiPF) ₆ ), Lithium borofluoride (LiBF) _Four ), Lithium hexafluoroarsenide (LiAsF) ₆ ), Lithium trifluorometasulfonate (LiCF) _Three SO _Three ), Bistrifluoromethylsulfonylimide lithium [(LiN (CF _Three SO ₂ ) ₂ ] Lithium salt (electrolyte). Among them, LiPF ₆ Or LiBF _Four Is preferably used.
[0057]
The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / l.
[0058]
The amount of the non-aqueous electrolyte is preferably 0.2 to 0.6 g per 100 mAh of battery unit capacity. This is due to the following reason. If the amount of nonaqueous electrolysis is less than 0.2 g / 100 mAh, the ionic conductivity of the positive electrode and the negative electrode may not be sufficiently maintained. On the other hand, if the amount of the non-aqueous electrolyte exceeds 0.6 g / 100 mAh, the amount of the electrolyte may become so large that sealing with a film exterior material may be difficult. A more preferable range of the amount of the non-aqueous electrolyte is 0.4 to 0.55 g / 100 mAh.
[0059]
5) Adhesive polymer
It is desirable that the polymer having adhesiveness is one that can maintain high adhesiveness while holding a nonaqueous electrolytic solution. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Specific examples include polyacrylonitrile (PAN), polyacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC), and polyethylene oxide (PEO). In particular, polyvinylidene fluoride is preferable. Polyvinylidene fluoride can hold a non-aqueous electrolyte, and if it contains a non-aqueous electrolyte, it partially gels, so that the ionic conductivity can be further improved.
[0060]
The polymer having adhesiveness preferably has a porous structure having fine pores in the gaps of the positive electrode, the negative electrode, and the separator. The adhesive polymer having a porous structure can hold a non-aqueous electrolyte.
[0061]
The total amount of adhesive polymer contained in the battery is preferably 0.1 to 6 mg per 100 mAh of battery capacity. This is due to the following reason. If the total amount of the polymer having adhesiveness is less than 0.1 mg per 100 mAh of battery capacity, it may be difficult to sufficiently improve the adhesion between the positive electrode, the separator and the negative electrode. On the other hand, if the total amount exceeds 6 mg per 100 mAh of battery capacity, the lithium ion conductivity of the secondary battery may decrease and the internal resistance may increase, improving the discharge capacity, large current discharge characteristics, and charge / discharge cycle characteristics. It can be difficult to do. A more preferable range of the total amount of the polymer having adhesiveness is 0.2 to 1 mg per 100 mAh of battery capacity.
[0062]
6) Exterior material
As the exterior material, a first exterior material made of a sheet having a thickness of 0.5 mm or less including the resin layer or a second exterior material having a thickness of 0.3 mm or less is used. Although the first and second exterior materials are lightweight and can increase the energy density per weight of the battery, they are generated from the electrode group or the non-aqueous electrolyte in order to have flexibility. Easily deformed by gas.
[0063]
The resin layer included in the first exterior material can be formed from, for example, polyethylene, polypropylene, or the like. Specifically, the first exterior material is a sheet in which a metal layer and protective layers disposed on both surfaces of the metal layer are integrated. The metal layer serves to block moisture. Examples of the metal layer include aluminum, stainless steel, iron, copper, and nickel. Among these, aluminum that is lightweight and has a high function of blocking moisture is preferable. The metal layer may be formed from one type of metal, but may be formed from a combination of two or more types of metal layers. Of the two protective layers, the protective layer in contact with the outside serves to prevent damage to the metal layer. This external protective layer is formed of one type of resin layer or two or more types of resin layers. On the other hand, the internal protective layer plays a role of preventing the metal layer from being corroded by the non-aqueous electrolyte. This internal protective layer is formed of one type of resin layer or two or more types of resin layers. Further, a heat-fusible resin can be disposed on the surface of the internal protective layer.
[0064]
When the thickness of the first exterior material exceeds 0.5 mm, the capacity per weight of the battery decreases. The thickness of the first exterior material is preferably 0.3 mm or less, more preferably 0.25 mm or less, and most preferably 0.15 mm or less. On the other hand, if the thickness is less than 0.05 mm, deformation or breakage tends to occur. For this reason, the lower limit value of the thickness is preferably 0.05 mm. A more preferred lower limit is 0.08 mm, and a most preferred range is 0.1 mm.
[0065]
As the second exterior material, for example, a metal can or a film having a function of blocking moisture can be used. The metal can can be formed from, for example, iron, stainless steel, or aluminum. On the other hand, examples of the film include a laminate film including a metal layer and a flexible synthetic resin layer formed on at least a part of the metal layer. Examples of the metal layer include aluminum, stainless steel, iron, copper, and nickel. Among these, aluminum that is lightweight and has a high function of blocking moisture is preferable. Examples of the synthetic resin include polyethylene and polypropylene.
[0066]
If the thickness of the second exterior material is greater than 0.3 mm, the effect of thinning is small, that is, it is difficult to sufficiently increase the weight energy density. The thickness of the second exterior material is preferably 0.25 mm or less, and more preferably 0.15 mm or less. On the other hand, if the thickness is less than 0.05 mm, deformation or breakage tends to occur. For this reason, the lower limit value of the thickness is preferably 0.05 mm. A more preferred lower limit is 0.08 mm, and a most preferred range is 0.1 mm. In particular, the thickness of the second exterior material is preferably in the range of 0.05 to 0.3 mm. A more preferable range is 0.08 to 0.15 mm.
[0067]
The thickness of the exterior material is measured by the method described below. That is, in the region excluding the sealing portion of the exterior material, three points that are separated from each other by 1 cm or more are arbitrarily selected, the thickness of each point is measured, an average value is calculated, and this value is calculated as the thickness of the exterior material. Say it. In addition, when the foreign material (for example, resin) has adhered to the surface of the said exterior material, thickness is measured after removing this foreign material. For example, when PVdF adheres to the surface of the exterior material, the PVdF is removed by wiping the surface of the exterior material with a dimethylformamide solution, and then the thickness is measured.
[0068]
When the film exterior material is used, it is desirable that the electrode group is adhered to the inner surface of the exterior material by an adhesive layer formed on at least a part of the surface thereof. With such a configuration, since the exterior material can be fixed to the surface of the electrode group, it is possible to prevent the electrolyte from penetrating between the electrode group and the exterior material.
[0069]
A thin lithium ion secondary battery which is an example of this non-aqueous electrolyte secondary battery will be described in detail with reference to FIGS.
[0070]
FIG. 1 is a cross-sectional view showing a thin lithium ion secondary battery as an example of a first non-aqueous electrolyte secondary battery according to the present invention, FIG. 2 is an enlarged cross-sectional view showing part A of FIG. 1, and FIG. FIG. 2 is a schematic diagram showing the vicinity of a boundary between a positive electrode layer, a separator, and a negative electrode layer in the secondary battery of FIG. 1.
[0071]
As shown in FIG. 1, an exterior material 1 made of, for example, a film surrounds an electrode group 2. The electrode group 2 has a structure in which a laminate composed of a positive electrode, a separator, and a negative electrode is wound into a flat shape. As shown in FIG. 2, the laminate includes a separator 3, a positive electrode layer 4, a positive electrode current collector 5, a positive electrode 12 including a positive electrode layer 4, a separator 3, a negative electrode layer 6, and a negative electrode collector. A negative electrode 13 including a current collector 7 and a negative electrode layer 6, a separator 3, a positive electrode layer 4, a positive electrode current collector 5, a positive electrode 12 including a positive electrode layer 4, a separator 3, a negative electrode layer 6, and a negative electrode current collector 7 are provided. The negative electrode 13 is formed by laminating in this order. In the electrode group 2, the negative electrode current collector 7 is located in the outermost layer. An adhesive portion 8 is present on the surface of the electrode group 2. The inner surface of the exterior material 1 is bonded to the bonding portion 8. As shown in FIG. 3, adhesive polymers 9 are held in the gaps of the positive electrode layer 4, the separator 3, and the negative electrode layer 6. The positive electrode 12 and the separator 3 are bonded to each other by a polymer 9 having adhesive properties scattered in the positive electrode layer 4 and the separator 3 and at the boundary between them. On the other hand, the negative electrode 13 and the separator 3 are bonded to each other by the polymer 9 having adhesive properties scattered in the negative electrode layer 6 and the separator 3 and at the boundary between them. The non-aqueous electrolyte is impregnated in the electrode group 2 in the exterior material 1. One end of the strip-like positive electrode lead 10 is connected to the positive electrode current collector 5 of the electrode group 2, and the other end is extended from the exterior material 1. On the other hand, one end of the strip-like negative electrode lead 11 is connected to the negative electrode current collector 7 of the electrode group 2 and the other end is extended from the exterior material 1.
[0072]
In FIG. 1 described above, the bonding portion 8 is formed on the entire surface of the electrode group 2, but the bonding portion 8 may be formed on a part of the electrode group 2. When forming the adhesion part 8 in a part of electrode group 2, it is preferable to form in the surface equivalent to the outermost periphery of an electrode group at least. Further, the bonding portion 8 may not be provided.
[0073]
The non-aqueous electrolyte secondary battery including the electrode group that satisfies the above-described condition (a) is manufactured by, for example, the method (I) described below. However, the manufacturing method of the non-aqueous electrolyte secondary battery according to the present invention is not limited to the following embodiment as long as it is within the scope of the present invention.
[0074]
<Manufacturing method (I)>
(First step)
An electrode group is prepared by interposing a porous sheet as a separator between the positive electrode and the negative electrode.
[0075]
The electrode group is formed by winding the positive electrode and the negative electrode in a spiral shape through a separator having no polymer between them, or compressing in a radial direction after winding in a spiral shape, or positive electrode It is desirable that the negative electrode is fabricated by bending a plurality of times through a separator having no polymer between them and having an adhesive property therebetween. When produced by such a method, in the second step described later, while the polymer solution having adhesiveness is infiltrated into the positive electrode, the negative electrode, and the separator, the solution is applied to the entire boundary between the positive electrode and the separator and the entire boundary between the negative electrode and the separator. Infiltration can be prevented. As a result, it is possible to intersperse the polymer having adhesiveness to the positive electrode, the negative electrode and the separator, and to interpose the polymer having adhesiveness to the boundary between the positive electrode and the separator and the boundary between the negative electrode and the separator. it can.
[0076]
The positive electrode is produced, for example, by suspending a conductive agent and a binder in an appropriate solvent in a positive electrode active material, applying the suspension to a current collector, and drying to form a thin plate. Examples of the positive electrode active material, the conductive agent, the binder, and the current collector include the same materials as those described in the section of (1) Positive electrode described above.
[0077]
The negative electrode is, for example, kneaded with a carbonaceous material that occludes / releases lithium ions and a binder in the presence of a solvent, and the resulting suspension is applied to a current collector and dried, followed by a desired pressure. It is produced by pressing once or multistage pressing 2-5 times.
[0078]
Examples of the carbonaceous material, the binder, and the current collector include the same materials as those described in the section of (2) Negative electrode.
[0079]
As the porous sheet of the separator, the same sheet as described in the section of (3) Separator described above can be used.
[0080]
(Second step)
The electrode group is accommodated in a bag-shaped exterior material so that the laminated surface can be seen from the opening. A solution obtained by dissolving a polymer having adhesiveness in a solvent is injected into the electrode group in the exterior material from the opening, and the electrode group is impregnated with the solution.
[0081]
Examples of the exterior material include the same materials as those described in the section of (6) Exterior material described above.
[0082]
Examples of the adhesive polymer include the same polymers as described in the column of the adhesive polymer (5) described above. In particular, PVdF is preferable.
[0083]
As the solvent, it is desirable to use an organic solvent having a boiling point of 200 ° C. or lower. An example of such an organic solvent is dimethylformamide (boiling point 153 ° C.). If the boiling point of the organic solvent exceeds 200 ° C., the drying time may take a long time when the vacuum drying temperature described below is set to 100 ° C. or lower. The lower limit of the boiling point of the organic solvent is preferably 50 ° C. If the boiling point of the organic solvent is less than 50 ° C., the organic solvent may evaporate while the solution is injected into the electrode group. The upper limit of the boiling point is more preferably 180 ° C., and the lower limit of the boiling point is further preferably 100 ° C.
[0084]
The concentration of the polymer having adhesiveness in the solution is preferably in the range of 0.05 to 2.5% by weight. This is due to the following reason. If the concentration is less than 0.05% by weight, it may be difficult to bond the positive and negative electrodes and the separator with sufficient strength. On the other hand, if the concentration exceeds 2.5% by weight, it may be difficult to obtain a sufficient porosity to hold the non-aqueous electrolyte, and the interface impedance of the electrode may be significantly increased. As the interfacial impedance increases, the capacity and large current discharge characteristics are significantly reduced. A more preferable range of the concentration is 0.1 to 1.5% by weight.
[0085]
The amount of the solution injected is preferably in the range of 0.1 to 2 ml per 100 mAh of battery capacity when the concentration of the polymer having adhesiveness in the solution is 0.05 to 2.5% by weight. This is due to the following reason. If the injection amount is less than 0.1 ml, it may be difficult to sufficiently improve the adhesion between the positive electrode, the negative electrode, and the separator. On the other hand, if the injection amount exceeds 2 ml, the lithium ion conductivity of the secondary battery may be decreased and the internal resistance may be increased, which may improve the discharge capacity, large current discharge characteristics, and charge / discharge cycle characteristics. It can be difficult. A more preferable range of the injection amount is 0.15 to 1 ml per 100 mAh of battery capacity.
[0086]
(Third step)
By subjecting the electrode group to vacuum drying, the solvent in the solution is evaporated, and an adhesive polymer is present in the gaps of the positive electrode, the negative electrode, and the separator. By this step, the positive electrode and the separator are adhered by a polymer having adhesiveness scattered in the inside and the boundary thereof, and the negative electrode and the separator have adhesiveness scattered in the interior and the boundary thereof. Bonded by polymer. Moreover, the moisture contained in the electrode group can be removed simultaneously by this vacuum drying.
[0087]
In addition, the said electrode group accept | permits containing a trace amount solvent.
[0088]
The vacuum drying is preferably performed at 100 ° C. or lower. This is due to the following reason. When the temperature of vacuum drying exceeds 100 ° C., the separator may be significantly heat-shrinked. When the thermal shrinkage increases, the separator warps, and it becomes difficult to firmly bond the positive electrode, the negative electrode, and the separator. In addition, the above-described heat shrinkage tends to occur remarkably when a porous film containing polyethylene or polypropylene is used as a separator. Although the thermal shrinkage of the separator can be suppressed as the vacuum drying temperature becomes lower, if the temperature of the vacuum drying is lower than 40 ° C., it may be difficult to sufficiently evaporate the solvent. For this reason, it is more preferable that the vacuum drying temperature is 40 to 100 ° C.
[0089]
(4th process)
After injecting a non-aqueous electrolyte into the electrode group in the exterior material, a thin non-aqueous electrolyte secondary battery is assembled by sealing the opening of the exterior material.
[0090]
As said non-aqueous electrolyte, the thing similar to what was demonstrated in the column of (4) non-aqueous electrolyte mentioned above can be used.
[0091]
In the manufacturing method described above, the solution in which the adhesive polymer is dissolved is injected after the electrode group is stored in the exterior material. However, the injection may be performed without being stored in the exterior material. In this case, first, an electrode group is produced by interposing a separator between the positive electrode and the negative electrode. After the electrode group is impregnated with the solution, the electrode group is vacuum-dried to evaporate the solvent of the solution, and the adhesive polymer is present in the gaps of the positive electrode, the negative electrode, and the separator. A thin non-aqueous electrolyte secondary battery can be manufactured by injecting such a group of electrodes into an exterior material, then injecting a non-aqueous electrolyte and performing sealing or the like. You may apply | coat an adhesive agent to the electrode group outer periphery before the accommodation to an exterior material. Thereby, an electrode group can be adhere | attached on an exterior material. In this case, a metal can can be used as an exterior material instead of a film.
[0092]
(5th process)
The secondary battery assembled as described above is initially charged at a charge rate of 0.05 C or more and 0.5 C or less under a temperature condition of 30 ° C. to 80 ° C. Charging under this condition may be performed only for one cycle or may be performed for two or more cycles. Moreover, you may store for about 1 hour-20 hours on 30 degreeC-80 degreeC temperature conditions before the first charge.
[0093]
Here, the 1C charging rate is a current value necessary for charging the nominal capacity (Ah) in one hour.
[0094]
The reason for defining the initial charging temperature within the above range is as follows. If the initial charging temperature is less than 30 ° C., the viscosity of the nonaqueous electrolyte solution remains high, so that it is difficult to uniformly impregnate the nonaqueous electrolyte solution in the positive electrode, negative electrode, and separator, and the internal impedance increases. Moreover, the utilization factor of an active material falls. On the other hand, when the initial charging temperature exceeds 80 ° C., the binder contained in the positive electrode and the negative electrode is deteriorated.
[0095]
By making the charge rate of the initial charge in the range of 0.05 to 0.5 C, the expansion of the positive electrode and the negative electrode due to the charge can be moderately slowed, so that the nonaqueous electrolyte uniformly penetrates the positive electrode and the negative electrode be able to.
[0096]
By providing such a process, the non-aqueous electrolyte can be uniformly impregnated in the gaps of the electrodes and the separator, so that the internal impedance of 1 kHz of the non-aqueous electrolyte secondary battery can be reduced. The product of the capacity and the internal impedance of 1 kHz can be in the range of 10 mΩ · Ah to 110 mΩ · Ah. As a result, since the utilization factor of the active material can be increased, the substantial capacity of the battery can be increased. Moreover, the charge / discharge cycle characteristics and the large current discharge characteristics of the battery can be improved.
[0097]
Next, a non-aqueous electrolyte secondary comprising an electrode group satisfying the above-mentioned (b) and a non-aqueous electrolyte containing a non-aqueous solvent containing γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume. The battery will be described.
[0098]
In this secondary battery, the positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode.
[0099]
As the separator, the same separator as described in the section of (3) Separator described above is used. Moreover, as an exterior material which accommodates the said electrode group, the thing similar to what was demonstrated in the column of (6) exterior material mentioned above is used.
[0100]
The positive electrode has a structure in which a positive electrode layer containing an active material, a binder, and a conductive agent is supported on one side or both sides of a current collector. As the active material, the binder, the conductive agent, and the current collector, the same materials as those described in the section of (1) Positive electrode described above are used.
[0101]
The negative electrode has a structure in which a negative electrode layer containing a carbonaceous material that occludes / releases lithium ions and a binder is supported on one side or both sides of a current collector. As the carbonaceous material, the binder, and the current collector, the same materials as those described in the section of (2) Negative electrode are used.
[0102]
The negative electrode layer is made of a metal such as aluminum, magnesium, tin, or silicon, a metal oxide, a metal sulfide, or a metal nitride, in addition to the carbon material that occludes / releases lithium ions. It may contain a selected metal compound or lithium alloy. As the metal oxide, the metal sulfide, the metal nitride, and the lithium alloy, the same materials as those described in the section of (2) Negative electrode are used.
[0103]
This secondary battery is manufactured by, for example, the method (II) described below.
[0104]
<Production method (II)>
(First step)
An electrode group is produced by the method described in the following (a) to (c).
[0105]
(A) The positive electrode and the negative electrode are wound spirally with a separator interposed therebetween.
[0106]
(B) The positive electrode and the negative electrode are wound spirally with a separator interposed therebetween, and then compressed in the radial direction.
[0107]
(C) The positive electrode and the negative electrode are bent twice or more with a separator interposed therebetween.
[0108]
(Second step)
The electrode group is housed in a bag-shaped film exterior material.
[0109]
(Third step)
The electrode group is molded while being heated to 40 to 120 ° C.
[0110]
The molding is compressed in the radial direction when the electrode group is produced by the method (a), and compressed in the laminating direction when the electrode group is produced by the method (b) or (c). To be done.
[0111]
The molding can be performed, for example, by press molding or insertion into a mold.
[0112]
The reason why the electrode group is heated when forming the electrode group will be described. The electrode group does not contain an adhesive polymer. For this reason, when this electrode group is molded at room temperature, springback occurs after molding, that is, gaps are formed between the positive electrode and the separator and between the negative electrode and the separator. As a result, the contact area between the positive electrode and the separator and the contact area between the negative electrode and the separator are reduced, so that the internal impedance is increased. By forming the electrode group at 40 ° C. or higher, the binder contained in the positive electrode and the negative electrode can be thermally cured, so that the hardness of the electrode group can be increased. As a result, since the spring back after molding can be suppressed, the contact area between the positive electrode and the separator and the contact area between the negative electrode and the separator can be improved, and the contact area can be maintained even after repeated charge / discharge cycles. Can do. On the other hand, when the temperature of the electrode group exceeds 120 ° C., the separator may be significantly heat-shrinked. A more preferable temperature is 60 to 100 ° C.
[0113]
The molding while heating to the specific temperature described above can be performed, for example, under normal pressure, under reduced pressure, or under vacuum. It is desirable to perform under reduced pressure or under vacuum because the water removal efficiency from the electrode group is improved.
[0114]
When the molding is performed by press molding, the press pressure is 0.01 to 20 kg / cm. ² It is preferable to be in the range. This is due to the following reason. Press pressure 0.01kg / cm ² If it is lower, it may be difficult to suppress the spring back after molding. On the other hand, the press pressure is 20 kg / cm. ² If it is higher, the porosity in the electrode group may be reduced, and therefore the amount of nonaqueous electrolyte retained in the electrode group may be insufficient.
[0115]
(4th process)
After injecting a nonaqueous electrolyte into the electrode group in the exterior material, the nonaqueous electrolyte secondary battery described above is assembled by sealing the opening of the exterior material.
[0116]
In the manufacturing method described above, the electrode group is housed in the exterior material and then molded while heating the electrode group to a specific temperature. However, the heat molding described above may be performed before housing in the exterior material. In this case, first, an electrode group is fabricated by the first process described above. The electrode group is molded while being heated to 40 to 120 ° C. Next, after the electrode group is housed in an exterior material, the nonaqueous electrolyte secondary battery described above can be assembled by injecting a nonaqueous electrolyte and performing sealing or the like. At this time, a metal can can be used as an exterior material instead of a film.
[0117]
(5th process)
The secondary battery assembled as described above is initially charged at a charge rate of 0.05 C or more and 0.5 C or less under a temperature condition of 30 ° C. to 80 ° C. Charging under this condition may be performed only for one cycle or may be performed for two or more cycles. Moreover, you may store for about 1 hour-20 hours on 30 degreeC-80 degreeC temperature conditions before the first charge.
[0118]
The reason why the temperature of the initial charge and the charge rate of the initial charge are defined in the range is for the same reason as described above.
[0119]
By providing such a process, the non-aqueous electrolyte can be uniformly impregnated in the gaps of the electrodes and the separator, so that the internal impedance of 1 kHz of the non-aqueous electrolyte secondary battery can be reduced. The product of the capacity and the internal impedance of 1 kHz can be in the range of 10 mΩ · Ah to 110 mΩ · Ah. As a result, since the utilization factor of the active material can be increased, the substantial capacity of the battery can be increased. Moreover, the charge / discharge cycle characteristics and the large current discharge characteristics of the battery can be improved.
[0120]
The first nonaqueous electrolyte secondary battery according to the present invention has a structure in which a can made of aluminum or the like is used as an exterior material, and an electrode group consisting of a positive electrode, a negative electrode, and a separator is wound and inserted into the can. Also good. In that case, there is no need for an adhesive part or a polymer having adhesiveness.
[0121]
Next, the second nonaqueous electrolyte secondary battery according to the present invention will be described.
[0122]
The secondary battery includes a positive electrode current collector and a positive electrode including a positive electrode active material layer carried on one or both surfaces of the positive electrode current collector, a negative electrode current collector, and one or both surfaces of the negative electrode current collector. An electrode group including a negative electrode including a negative electrode active material layer that is supported and includes a material that absorbs and releases lithium ions; and a separator disposed between the positive electrode and the negative electrode;
A non-aqueous electrolyte solution impregnated in the electrode group and comprising a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent;
An exterior material in which the electrode group is housed.
[0123]
The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The positive electrode active material layer has a thickness of 10 to 100 μm. Further, the non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume based on the total amount of the non-aqueous solvent.
[0124]
In this secondary battery, the positive electrode, the negative electrode, and the separator do not have to be integrated, but it is preferable that they are integrated under the conditions described in (a) or (b) below. .
[0125]
(A) Adhesion in which the positive electrode and the separator are integrated by an adhesive polymer present at at least a part of these boundaries, and the negative electrode and the separator are present at at least a part of these boundaries It is integrated with a polymer having properties. In particular, the positive electrode and the separator are integrated with an adhesive polymer scattered in the interior and boundary thereof, and the negative electrode and the separator have adhesiveness scattered in the interior and boundary thereof. It is desirable that they are integrated by a polymer.
[0126]
(B) The positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode.
[0127]
By adopting the configuration of (a) or (b), the swelling of the exterior material can be further reduced.
[0128]
The secondary battery preferably has a product of battery capacity (Ah) and 1 kHz battery internal impedance (mΩ) of 10 mΩ · Ah or more and 110 mΩ · Ah or less. By setting the product of the capacity and the impedance within the above range, the large current discharge characteristics and the charge / discharge cycle characteristics can be further improved. Here, the battery capacity is a nominal capacity or a discharge capacity when discharged at 0.2C. A more preferable range is 20 mΩ · Ah or more and 60 mΩ · Ah or less.
[0129]
The product of the battery capacity and the impedance can be 10 mΩ · Ah or more and 110 mΩ · Ah or less, for example, by the manufacturing method (I) described above or the manufacturing method (II) described above. However, in (I), the addition amount of the adhesive polymer, the distribution of the adhesive polymer, and the initial charging conditions are set so that the product of the battery capacity and the impedance is 10 mΩ · Ah or more and 110 mΩ · Ah or less. In (II), the temperature, press pressure, and initial charge condition when forming the electrode group are set so that the product of the battery capacity and impedance is 10 mΩ · Ah or more and 110 mΩ · Ah or less.
[0130]
Hereinafter, a non-aqueous electrolyte secondary battery including an electrode group that satisfies the above-described (a) will be described.
[0131]
1) Positive electrode
This positive electrode has a structure in which a positive electrode active material layer containing an active material, a conductive agent, an adhesive polymer, and a binder is supported on one side or both sides of a current collector.
[0132]
Examples of the active material, the conductive agent, the adhesive polymer, and the binder include the same materials as those described in the first non-aqueous electrolyte secondary battery.
[0133]
The positive electrode active material layer has a thickness in the range of 10 to 100 μm. Here, the thickness of the positive electrode active material layer means the distance between the surface of the positive electrode active material facing the separator and the surface of the positive electrode active material in contact with the current collector. For example, as shown in FIG. 4, when the positive electrode active material layer P is supported on both surfaces of the current collector S, the positive electrode active material surface P facing the separator is used. ₁ And positive electrode active material surface P in contact with current collector ₂ Is the thickness T of the positive electrode active material layer. Therefore, when the positive electrode active material layer is supported on both surfaces of the positive electrode current collector, the thickness of one surface of the positive electrode active material layer is 10 to 100 μm, and the total thickness of the positive electrode active material layer is 20 to 200 μm. Become. When the thickness of the positive electrode active material layer is less than 10 μm, the weight ratio of the current collector and the volume ratio increase, so that the energy density decreases. A preferable lower limit value of the thickness is 30 μm, and a more preferable lower limit value is 50 μm. On the other hand, when the thickness of the positive electrode active material layer exceeds 100 μm, the non-aqueous electrolyte concentrates on the surface of the positive electrode during the rapid charge / discharge cycle, and the electrode reaction inside the positive electrode hardly proceeds, so that the cycle life is reduced. A preferable upper limit value of the thickness is 85 μm, and a more preferable upper limit value is 60 μm. In particular, the thickness of the positive electrode active material layer is preferably in the range of 10 to 60 μm. Within this range, the large current discharge characteristics and cycle life are greatly improved. A more preferable range is 30 to 50 μm.
[0134]
The thickness of the positive electrode active material layer is measured by the method described below. First, 10 points that are separated from each other by 1 cm or more are arbitrarily selected, the thickness of each point is measured, and the average value is calculated to measure the thickness of the positive electrode. However, when the positive electrode to be measured has a structure in which the positive electrode active material layer is supported on both sides of the current collector, the thickness of the positive electrode is measured after removing one of the positive electrode active material layers. Next, the positive electrode active material layer is removed from the current collector, and the thickness of the current collector is measured. The thickness of the current collector can be obtained by arbitrarily selecting 10 points that are separated from each other by 1 cm or more, measuring the thickness of each point, and calculating the average value. The difference between the thickness of the positive electrode and the thickness of the current collector is taken as the thickness of the positive electrode active material layer to be obtained.
[0135]
The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The porosity of the positive electrode active material layer is preferably in the range of 25 to 40%. This is due to the following reason. If the porosity is less than 25%, it may be difficult to uniformly infiltrate the non-aqueous electrolyte even if the thickness of the positive electrode active material layer is regulated. On the other hand, if the porosity exceeds 40%, a high capacity, that is, a high energy density may not be obtained. A more preferable range of the porosity is 30 to 35%.
[0136]
As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, aluminum, stainless steel, or nickel. The thickness of the current collector is preferably in the range of 5 to 20 μm. This is because within this range, the balance between the positive electrode strength and the weight reduction can be achieved.
[0137]
2) Negative electrode
This negative electrode has a structure in which a negative electrode active material layer containing a carbonaceous material that occludes / releases lithium ions, an adhesive polymer, and a binder is supported on one side or both sides of a current collector.
[0138]
The carbonaceous material that absorbs and releases lithium ions, the conductive agent, the adhesive polymer, the binder, and the current collector are the same as those described in the first nonaqueous electrolyte secondary battery. Things can be mentioned.
[0139]
The thickness of the negative electrode active material layer is preferably in the range of 10 to 100 μm. Here, the thickness of the negative electrode active material layer means the distance between the surface of the negative electrode active material facing the separator and the surface of the negative electrode active material in contact with the current collector. When the negative electrode active material layer is supported on both surfaces of the negative electrode current collector, the thickness of one side of the negative electrode active material layer is set to 10 to 100 μm, and the total thickness of the negative electrode active material layer is in the range of 20 to 200 μm. It is desirable to make it. If the thickness of the negative electrode active material layer is less than 10 μm, the weight ratio of the current collector and the volume ratio are increased, which may make it difficult to sufficiently improve the energy density. A preferable lower limit value of the thickness is 30 μm, and a more preferable lower limit value is 50 μm. On the other hand, when the thickness of the negative electrode active material layer exceeds 100 μm, the non-aqueous electrolyte tends to concentrate on the surface of the negative electrode, which may make it difficult to sufficiently improve the cycle life. A preferable upper limit value of the thickness is 85 μm, and a more preferable upper limit value is 60 μm. In particular, the thickness of the negative electrode active material layer is preferably in the range of 10 to 60 μm. Within this range, the large current discharge characteristics and cycle life are greatly improved. A more preferable range is 30 to 50 μm.
[0140]
The thickness of the negative electrode active material layer is measured by the method described below. First, 10 points that are separated from each other by 1 cm or more are arbitrarily selected, the thickness of each point is measured, and the average value is calculated to measure the thickness of the negative electrode. However, when the negative electrode to be measured has a structure in which the negative electrode active material layer is supported on both sides of the current collector, the thickness of the negative electrode is measured after removing one of the negative electrode active material layers. Next, the negative electrode active material layer is removed from the current collector, and the thickness of the current collector is measured. The thickness of the current collector can be obtained by arbitrarily selecting 10 points that are separated from each other by 1 cm or more, measuring the thickness of each point, and calculating the average value. The difference between the thickness of the negative electrode and the thickness of the current collector is taken as the thickness of the desired negative electrode active material layer.
[0141]
The porosity of the negative electrode active material layer is preferably in the range of 35 to 50%. This is due to the following reason. If the porosity is less than 35%, the distribution of the non-aqueous electrolyte may become non-uniform, so that lithium dendride may be deposited. On the other hand, if the porosity exceeds 50%, a high capacity, that is, a high energy density may not be obtained. A more preferable range of the porosity is 35 to 45%.
[0142]
The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder. In particular, the carbonaceous material is 10 to 70 g / cm on one side in a state where a negative electrode is produced. ² It is preferable to be in the range.
[0143]
The negative electrode active material layer has a density of 1.20 to 1.50 g / cm. ^Three It is preferable to be in the range.
[0144]
As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel. The thickness of the current collector is preferably in the range of 5 to 20 μm. This is because the negative electrode strength and weight reduction can be balanced within this range.
[0145]
The negative electrode active material layer is made of a metal such as aluminum, magnesium, tin, or silicon, a metal oxide, a metal sulfide, or a metal nitridation instead of the carbon material that absorbs and releases lithium ions. It may contain a metal compound selected from those or a lithium alloy.
[0146]
Examples of the metal oxide, the metal sulfide, the metal nitride, and the lithium alloy include the same as those described in the first nonaqueous electrolyte secondary battery.
[0147]
3) Separator
This separator is formed from a porous sheet.
[0148]
Examples of the porous sheet include the same ones as described in the first non-aqueous electrolyte secondary battery.
[0149]
4) Non-aqueous electrolyte
The non-aqueous electrolytic solution is obtained by dissolving a lithium salt in a mixed non-aqueous solvent containing γ-butyrolactone (BL), and the BL composition ratio is 40% by volume or more and 95% by volume or less of the entire mixed non-aqueous solvent. . In the mixed non-aqueous solvent, it is preferable that the BL composition ratio is maximized. When the ratio is less than 40% by volume, gas is likely to be generated at a high temperature even if the thickness of the positive electrode active material layer is regulated. In addition, when the mixed non-aqueous solvent contains BL and cyclic carbonate, the ratio of cyclic carbonate becomes relatively high, so that the solvent viscosity is remarkably increased. As a result, the conductivity and permeability of the non-aqueous electrolyte solution are greatly reduced. Therefore, even if the thickness of the positive electrode active material layer is regulated, the charge / discharge cycle characteristics, the large current discharge characteristics, and the low temperature environment around −20 ° C. The discharge characteristics at are deteriorated. On the other hand, if the ratio exceeds 95% by volume, the reaction between the negative electrode and BL occurs, and the charge / discharge cycle characteristics deteriorate. That is, when the negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions) reacts with BL to cause reductive decomposition of the non-aqueous electrolyte, a coating that inhibits the charge / discharge reaction is formed on the surface of the negative electrode. The As a result, current concentration is likely to occur in the negative electrode, so that lithium metal is deposited on the negative electrode surface, or the impedance at the negative electrode interface is increased, the charge / discharge efficiency of the negative electrode is lowered, and charge / discharge cycle characteristics are degraded. A more preferable range is 60% by volume or more and 90% by volume or less. By setting it within this range, it is possible to further increase the effect of suppressing gas generation during high-temperature storage, and to further improve the discharge capacity in a low temperature environment around −20 ° C. A more preferable range is 75% by volume or more and 90% by volume or less.
[0150]
As a solvent mixed with BL, a cyclic carbonate is desirable in terms of increasing the charge / discharge efficiency of the negative electrode.
[0151]
As the cyclic carbonate, propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC), trifluoropropylene carbonate (TFPC) and the like are desirable. In particular, when EC is used as a solvent mixed with BL, charge / discharge cycle characteristics and large current discharge characteristics can be significantly improved. Moreover, as another solvent mixed with BL, a third solvent consisting of at least one selected from the group consisting of PC, VC, TFPC, diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and an aromatic compound, and EC The mixed solvent is desirable in terms of enhancing the charge / discharge cycle characteristics.
[0152]
Further, from the viewpoint of lowering the solvent viscosity, a low-viscosity solvent may be contained in an amount of 20% by volume or less. Examples of the low viscosity solvent include chain carbonates, chain ethers, cyclic ethers and the like.
[0153]
More preferred compositions of the non-aqueous solvent according to the present invention include BL and EC, BL and PC, BL and EC and DEC, BL and EC and MEC, BL and EC and MEC and VC, BL and EC and VC, and BL and PC. And VC, or BL, EC, PC, and VC. At this time, the volume ratio of EC is preferably 5 to 40% by volume. This is due to the following reason. If the EC ratio is less than 5% by volume, it may be difficult to cover the negative electrode surface densely with a protective film, so that the reaction between the negative electrode and BL occurs, and the charge / discharge cycle characteristics can be sufficiently improved. It can be difficult. On the other hand, if the EC ratio exceeds 40% by volume, the viscosity of the non-aqueous electrolyte solution is increased and the ionic conductivity may be lowered. Therefore, sufficient charge / discharge cycle characteristics, large current discharge characteristics, and low temperature discharge characteristics are sufficiently obtained. It can be difficult to improve. A more preferable range of the EC ratio is 10 to 35% by volume. Moreover, the solvent which consists of at least 1 sort (s) chosen from DEC, MEC, PC, and VC forms the dense protective film on the surface of a negative electrode, and makes the effect | action which reduces the interface impedance of a negative electrode. The amount of the solvent added is not particularly limited, and is set to such an amount that this action occurs. However, when the ratio of at least one solvent selected from DEC, MEC, PC and VC in the non-aqueous solvent exceeds 10% by volume, the non-aqueous electrolyte is sufficiently suppressed from being oxidatively decomposed in a high temperature environment. May be difficult, or the viscosity of the non-aqueous electrolyte solution may increase and the ionic conductivity may decrease. For this reason, it is desirable that the volume ratio of at least one solvent selected from DEC, MEC, PC and VC in the non-aqueous solvent is 10% by volume or less. A more preferable volume ratio is 2% by volume or less. The lower limit of the volume ratio is preferably 0.001% by volume, and a more preferable lower limit is 0.05% by volume.
[0154]
In particular, a non-aqueous solvent containing 40 to 95% by volume of BL, EC and VC is preferable. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte containing a non-aqueous solvent and a negative electrode containing a carbonaceous material that occludes and releases lithium ions can greatly reduce the impedance at the interface of the negative electrode. Since it is possible to suppress the deposition of metallic lithium on the negative electrode, the charge / discharge efficiency of the negative electrode can be improved. As a result, it is possible to suppress deformation of the exterior material by suppressing gas generation during high-temperature storage while realizing excellent large current discharge characteristics and a long life. It is estimated that the negative electrode characteristics are improved in this way due to the action described below. In the secondary battery, in addition to forming a protective film by EC on the surface of the negative electrode, a thin and dense film by VC is formed. As a result, since the reaction between BL and the negative electrode is further suppressed, it is considered that the reduction in impedance and the prevention of precipitation of metallic lithium are achieved.
[0155]
Moreover, as a nonaqueous solvent, you may use what contains 40-95 volume% BL, EC, and an aromatic compound instead of what has the composition mentioned above. Examples of the aromatic compound include at least one selected from benzene, toluene, xylene, biphenyl, and terphenyl. EC adheres to the surface of a negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions) to form a protective film, and can suppress the reaction between the negative electrode and BL. At this time, the volume ratio of EC is preferably 5 to 40% by volume for the same reason as described above. Further, a more preferable range of the EC ratio is 10 to 35% by volume. On the other hand, since the benzene ring of the aromatic compound is easily adsorbed on the surface of the negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions), the reaction between the negative electrode and BL can be suppressed. Therefore, since the non-aqueous electrolyte containing a non-aqueous solvent containing 40 to 95% by volume of BL, EC, and an aromatic compound can sufficiently suppress the reaction between the negative electrode and BL, charging and discharging of the secondary battery Cycle characteristics can be improved. Such a non-aqueous solvent preferably further contains at least one solvent selected from DEC, MEC, PC, TFPC and VC. By adding at least one solvent selected from DEC, MEC, PC, TFPC and VC, the reaction between the negative electrode and BL can be further suppressed, so that the charge / discharge cycle characteristics can be further improved. . Of these, VC is preferable. The addition amount of the third solvent consisting of at least one selected from the aromatic compound, DEC, MEC, PC, TFPC and VC is not particularly limited, and is set to such an amount that this action occurs. However, if the ratio of the third solvent in the non-aqueous solvent exceeds 10% by volume, it may be difficult to sufficiently prevent the non-aqueous electrolyte from undergoing oxidative decomposition in a high temperature environment, or the non-aqueous electrolyte. There is a possibility that the ionic conductivity may be lowered due to an increase in the viscosity of. For this reason, the volume ratio of the third solvent in the non-aqueous solvent is desirably 10% by volume or less. A more preferable volume ratio is 2% by volume or less. The lower limit of the volume ratio is preferably 0.001% by volume, and a more preferable lower limit is 0.05% by volume.
[0156]
Examples of the electrolyte contained in the non-aqueous electrolyte include the same ones as described in the first non-aqueous electrolyte secondary battery. Among them, LiPF ₆ Or LiBF _Four Is preferably used.
[0157]
The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / l.
[0158]
In order to improve the paintability with the separator, a surfactant such as trioctyl phosphate may be added to the non-aqueous electrolyte in the range of 0.1 to 1%.
[0159]
The amount of the non-aqueous electrolyte is preferably 0.2 to 0.6 g per 100 mAh battery unit capacity for the same reason as described in the first non-aqueous electrolyte secondary battery. A more preferable range of the amount of the non-aqueous electrolyte is 0.4 to 0.55 g / 100 mAh.
[0160]
5) Adhesive polymer
It is desirable that the polymer having adhesiveness is one that can maintain high adhesiveness while holding a nonaqueous electrolytic solution. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Specifically, the same thing as having demonstrated with the 1st non-aqueous-electrolyte secondary battery mentioned above can be mentioned. In particular, polyvinylidene fluoride is preferable.
[0161]
The polymer having adhesiveness preferably has a porous structure having fine pores in the gaps of the positive electrode, the negative electrode, and the separator. The adhesive polymer having a porous structure can hold a non-aqueous electrolyte.
[0162]
The total amount of the polymer having adhesiveness contained in the battery is 0.1 to 6 mg per 100 mAh of battery capacity for the same reason as described in the first non-aqueous electrolyte secondary battery. preferable. A more preferable range of the total amount of the polymer having adhesiveness is 0.2 to 1 mg per 100 mAh of battery capacity.
[0163]
6) Exterior material
As the exterior material, a first exterior material including a resin layer and a thickness of 0.5 mm or less or a second exterior material having a thickness of 0.3 mm or less is used. The first exterior material and the second exterior material are as described in the first non-aqueous electrolyte secondary battery.
[0164]
When the film exterior material is used, it is desirable that the electrode group is adhered to the inner surface of the exterior material by an adhesive layer formed on at least a part of the surface thereof. With such a configuration, since the exterior material can be fixed to the surface of the electrode group, it is possible to prevent the electrolyte from penetrating between the electrode group and the exterior material.
[0165]
A thin lithium ion secondary battery which is an example of this non-aqueous electrolyte secondary battery will be described in detail with reference to FIGS.
[0166]
FIG. 5 is a cross-sectional view showing a thin lithium ion secondary battery which is an example of a second non-aqueous electrolyte secondary battery according to the present invention, FIG. 6 is an enlarged cross-sectional view showing part B of FIG. 5, and FIG. FIG. 6 is a schematic diagram showing the vicinity of a boundary between a positive electrode layer, a separator, and a negative electrode layer in the secondary battery of FIG. 5.
[0167]
As shown in FIG. 5, an exterior material 21 made of, for example, a film surrounds the electrode group 22. The electrode group 22 has a structure in which a laminate composed of a positive electrode, a separator, and a negative electrode is wound into a flat shape. As shown in FIG. 6, the laminate includes a separator 23, a positive electrode layer 24, a positive electrode current collector 25, and a positive electrode 32 including a positive electrode layer 24, a separator 23, a negative electrode layer 26, and a negative electrode collector. A negative electrode 33 including a current collector 27 and a negative electrode layer 26, a separator 23, a positive electrode layer 24, a positive electrode current collector 25, a positive electrode 32 including a positive electrode layer 24, a separator 23, a negative electrode layer 26, and a negative electrode current collector 27 are provided. The negative electrode 33 is formed by laminating in this order. In the electrode group 22, the negative electrode current collector 27 is located in the outermost layer. An adhesive portion 28 exists on the surface of the electrode group 22. The inner surface of the exterior material 21 is bonded to the bonding portion 28. As shown in FIG. 7, a polymer 29 having adhesiveness is held in the gaps of the positive electrode layer 24, the separator 23, and the negative electrode layer 26. The positive electrode 32 and the separator 23 are bonded to each other by a polymer 29 having adhesiveness scattered in the positive electrode layer 24 and the separator 23 and at the boundary between them. On the other hand, the negative electrode 33 and the separator 23 are bonded to each other by a polymer 29 having adhesive properties scattered in the negative electrode layer 26 and the separator 23 and at the boundary between them. The non-aqueous electrolyte is impregnated in the electrode group 22 in the exterior material 21. One end of the strip-like positive electrode lead 30 is connected to the positive electrode current collector 25 of the electrode group 22, and the other end is extended from the exterior member 21. On the other hand, one end of the strip-shaped negative electrode lead 31 is connected to the negative electrode current collector 27 of the electrode group 22, and the other end is extended from the exterior material 21.
[0168]
In FIG. 5 described above, the bonding portion 28 is formed on the entire surface of the electrode group 22, but the bonding portion 28 may be formed on a part of the electrode group 2. When forming the adhesion part 28 in a part of electrode group 22, it is preferable to form in the surface equivalent to the outermost periphery of an electrode group at least. Further, the adhesive portion 28 may not be provided.
[0169]
The non-aqueous electrolyte secondary battery including the electrode group that satisfies the above-described condition (a) is, for example, the manufacturing method (I) described in the first non-aqueous electrolyte secondary battery, that is, the positive electrode. And a step of producing an electrode group by interposing a porous sheet as a separator between the negative electrode, a step of impregnating the electrode group with a solution obtained by dissolving an adhesive polymer in a solvent, A step of vacuum drying the electrode group, a step of assembling a thin non-aqueous electrolyte secondary battery by impregnating the electrode group with a non-aqueous electrolyte and then sealing the electrode group in the exterior material; The secondary battery is manufactured at a temperature of 30 ° C. to 80 ° C. at a charge rate of 0.05 C or more and 0.5 C or less. However, the manufacturing method of the non-aqueous electrolyte secondary battery according to the present invention is not limited to the above embodiment as long as it is within the scope of the present invention.
[0170]
Next, a non-aqueous electrolyte secondary battery including an electrode group satisfying the above-described (b) and a non-aqueous electrolyte containing a non-aqueous solvent containing 40 to 95% by volume of γ-butyrolactone will be described.
[0171]
In this secondary battery, the positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode.
[0172]
As the separator, the same separator as described in the section of (3) Separator in the above-described second nonaqueous electrolyte secondary battery is used. Moreover, as the exterior material for housing the electrode group, the same material as that described in the section of (6) exterior material in the above-described second nonaqueous electrolyte secondary battery is used.
[0173]
The positive electrode has a structure in which a positive electrode active material layer containing an active material, a binder, and a conductive agent is supported on one side or both sides of a current collector. As the active material, the binder, the conductive agent, and the current collector, the same materials as those described in the column of (1) positive electrode in the above-described second nonaqueous electrolyte secondary battery are used.
[0174]
The thickness of the positive electrode active material layer is set in the range of 10 to 100 μm for the same reason as described above. In addition, when the positive electrode active material layer is carry | supported on both surfaces of a positive electrode electrical power collector, the total thickness of a positive electrode active material layer becomes the range of 20-200 micrometers. The lower limit value of the positive electrode active material layer is preferably 30 μm, and more preferably 50 μm. On the other hand, the upper limit of the positive electrode active material layer is preferably 85 μm, and more preferably 60 μm. The thickness of the positive electrode active material layer is preferably in the range of 10 to 60 μm for the same reason as described in the second non-aqueous electrolyte secondary battery described above. A more preferable range is 30 to 50 μm.
[0175]
The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The porosity of the positive electrode active material layer is preferably in the range of 25 to 40% for the same reason as described above. A more preferable range of the porosity is 30 to 35%.
[0176]
The negative electrode has a structure in which a negative electrode active material layer containing a carbonaceous material that occludes / releases lithium ions and a binder is supported on one side or both sides of a current collector. As the carbonaceous material, the binder, and the current collector, the same materials as those described in the column of (2) negative electrode in the above-described second nonaqueous electrolyte secondary battery are used.
[0177]
The thickness of the negative electrode active material layer is preferably in the range of 10 to 100 μm for the same reason as described above. In addition, when the negative electrode active material layer is carry | supported on both surfaces of a negative electrode collector, it is desirable to make the total thickness of a negative electrode active material layer into the range of 20-200 micrometers. The lower limit value of the negative electrode active material layer is preferably 30 μm, and more preferably 50 μm. On the other hand, the upper limit value of the negative electrode active material layer is preferably 85 μm, and more preferably 60 μm. The thickness of the negative electrode active material layer is preferably in the range of 10 to 60 μm for the same reason as described in the second non-aqueous electrolyte secondary battery described above. A more preferable range is 30 to 50 μm.
[0178]
The porosity of the negative electrode active material layer is preferably in the range of 35 to 50% for the same reason as described above. A more preferable range of the porosity is 35 to 45%.
[0179]
The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder. In particular, the carbonaceous material is 10 to 70 g / cm on one side in a state where a negative electrode is produced. ² It is preferable to be in the range.
[0180]
The negative electrode active material layer has a density of 1.20 to 1.50 g / cm. ^Three It is preferable to be in the range.
[0181]
This secondary battery is, for example, the manufacturing method (II) described in the first nonaqueous electrolyte secondary battery described above, that is, a step of creating an electrode group with a separator interposed between the positive electrode and the negative electrode, A step of forming the electrode group while heating to 40 to 120 ° C., and impregnating the electrode group with a nonaqueous electrolyte solution, and then sealing the electrode group with an exterior material, thereby forming a nonaqueous electrolyte secondary battery It is manufactured by a method comprising an assembling step and a step of subjecting the secondary battery to initial charging at a charging rate of 0.05 C or more and 0.5 C or less under a temperature condition of 30 ° C. to 80 ° C.
[0182]
The second nonaqueous electrolyte secondary battery according to the present invention has a structure in which a can made of aluminum or the like is used as an exterior material, and an electrode group consisting of a positive electrode, a negative electrode, and a separator is wound and inserted into the can. Also good. In that case, there is no need for an adhesive part or a polymer having adhesiveness.
[0183]
As described above in detail, the nonaqueous electrolyte secondary battery according to the present invention includes a positive electrode, a negative electrode containing a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode. An electrode group; a nonaqueous electrolyte solution containing a nonaqueous solvent impregnated in the electrode group and a lithium salt dissolved in the nonaqueous solvent; a packaging material having a thickness of 0.3 mm or less in which the electrode group is accommodated Comprising. The non-aqueous solvent contains γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume of the whole non-aqueous solvent.
[0184]
In the nonaqueous electrolyte secondary battery, it is desired to reduce the thickness to about 3 to 4 mm. It is not preferable to reduce the thickness of the electrode group in order to reduce the thickness because the battery capacity decreases. In order to reduce the thickness without sacrificing the battery capacity, it is necessary to reduce the thickness of the exterior material. However, when the thickness of the exterior material is 0.3 mm or less, the exterior material is deformed by the gas generated during high-temperature storage. For this reason, it is difficult to use an exterior material having a thickness of 0.3 mm or less, and the battery capacity is sacrificed to make the battery thinner.
[0185]
Since γ-butyrolactone is excellent in chemical stability, the positive electrode active material and non-aqueous electrolyte react when stored under high temperature conditions by containing a specific amount of γ-butyrolactone in a non-aqueous solvent. Thus, the oxidative decomposition of the nonaqueous electrolytic solution can be suppressed. As a result, since the amount of gas generated can be reduced, it is possible to suppress the expansion of a thin exterior material having a thickness of 0.3 mm or less. Accordingly, it is possible to reduce the thickness while maintaining practical large current discharge characteristics and charge / discharge cycle characteristics and almost without sacrificing battery capacity. A thin non-aqueous electrolyte secondary battery having high weight energy density and high volume energy density can be realized.
[0186]
When the secondary battery is initially charged, the non-aqueous electrolyte is prepared by reacting the negative electrode with γ-butyrolactone by setting the charging temperature to 30 to 80 ° C. and the charging rate to 0.05 to 0.5 C. Can be suppressed from reductive decomposition, so that the interfacial impedance of the negative electrode can be lowered and precipitation of metallic lithium can be suppressed. Therefore, the large current discharge characteristics and charge / discharge cycle characteristics of the secondary battery can be improved.
[0187]
In the secondary battery according to the present invention, the ionic conductivity of the non-aqueous electrolyte can be improved by setting the concentration of the lithium salt in the non-aqueous electrolyte to 0.5 mol / l or more. In addition, the cycle life can be further improved.
[0188]
In the secondary battery according to the present invention, when a negative electrode containing a carbonaceous material that occludes and releases lithium ions is used, the nonaqueous solvent further contains ethylene carbonate, thereby forming a protective film on the surface of the negative electrode. Therefore, the reaction between the negative electrode and γ-butyrolactone can be further suppressed, and the large current discharge characteristics and cycle life can be further improved. The non-aqueous solvent further contains a third solvent made of at least one selected from vinylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, trifluoropropylene, and an aromatic compound, whereby the surface of the negative electrode is covered with a protective film. Since it can cover densely, reaction of a negative electrode and (gamma) -butyrolactone can be reduced significantly, and a large current discharge characteristic and cycle life can be improved further.
[0189]
In the secondary battery according to the present invention, the product of the battery capacity (Ah) and the battery internal impedance (mΩ) of 1 kHz is made 10 mΩ · Ah or more and 110 mΩ · Ah or less to further improve the large current discharge characteristics and cycle life. Can be made.
[0190]
In the secondary battery according to the present invention, the separator has an air permeability of 600 seconds / 100 cm. ^Three By including the following porous sheet, the separator can be uniformly impregnated with the nonaqueous electrolytic solution containing a specific amount of the aforementioned γ-butyrolactone. As a result, since the ion conductivity of the separator can be improved, the large current discharge characteristics and the cycle life can be further improved.
[0191]
By the way, the outer packaging material having a thickness of 0.3 mm or less included in the secondary battery according to the present invention easily deforms following the expansion / contraction of the electrode group accompanying the charge / discharge reaction, and has a force to sandwich the electrode group. weak. For this reason, when a charging / discharging cycle progresses, there exists a possibility that the contact area of a positive electrode and a separator and the contact area of a negative electrode and a separator may reduce. The positive electrode and the separator are integrated with an adhesive polymer present at at least a part of these boundaries, and the negative electrode and the separator are integrated at least a part of these boundaries with an adhesive polymer. By integrating, the positive electrode and the separator and the negative electrode and the separator can be adhered even if the charge / discharge cycle proceeds. As a result, an increase in internal impedance can be suppressed, so that the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.
[0192]
In the secondary battery according to the present invention, the positive electrode and the separator are integrated with an adhesive polymer scattered in the inside and the boundary, and the negative electrode and the separator are scattered in the inside and the boundary. By integrating with a polymer having adhesive properties, the adhesive strength between the positive electrode and the separator and the adhesive strength between the negative electrode and the separator can be improved while keeping the internal resistance low. As a result, an increase in internal impedance can be suppressed, so that the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.
[0193]
In the secondary battery according to the present invention, the positive electrode, the negative electrode, and the separator are integrated by thermally curing the binder contained in the positive electrode and the negative electrode, thereby keeping the internal resistance low. The contact area between the separator and the contact area between the negative electrode and the separator can be improved, and the contact area can be maintained even after repeated charge / discharge cycles. As a result, an increase in internal impedance can be suppressed, so that the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.
[0194]
Moreover, the manufacturing method of the non-aqueous-electrolyte secondary battery concerning this invention is an electrode group provided with a positive electrode, the negative electrode containing the material which occludes / releases lithium ion, and the separator arrange | positioned between a positive electrode and a negative electrode; A non-aqueous electrolyte secondary battery manufacturing method comprising: a non-aqueous electrolyte solution impregnated in the electrode group and including a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. The solvent contains γ-butyrolactone in an amount of 55% to 95% by volume of the entire non-aqueous solvent, and the initial charge is performed at a temperature of 30 ° C. to 80 ° C. at a charge rate of 0.05C to 0.5C. The process to perform is comprised.
[0195]
According to the method for producing a non-aqueous electrolyte secondary battery of the present invention, since the non-aqueous electrolyte can be well permeated into the electrode or the separator, the impedance of the secondary battery can be reduced, and the active material Utilization rate can be increased, and substantial battery capacity can be improved.
[0196]
The non-aqueous electrolyte secondary battery according to the present invention includes an electrode group including a positive electrode, a negative electrode including a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode; A non-aqueous electrolyte comprising a non-aqueous solvent impregnated in an electrode group and a lithium salt dissolved in the non-aqueous solvent; from a sheet having a thickness of 0.5 mm or less containing the electrode group and including a resin layer The exterior material which comprises. The non-aqueous solvent contains γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume of the whole non-aqueous solvent.
[0197]
According to such a secondary battery, since the amount of gas generation can be reduced, it is possible to prevent the exterior material made of a sheet having a thickness of 0.5 mm or less including the resin layer from expanding. As a result, it is possible to use a lightweight exterior material, and furthermore, it is possible to maintain practical large current discharge characteristics and charge / discharge cycle characteristics, so that it has excellent large current discharge characteristics, long life, and weight energy density. A non-aqueous electrolyte secondary battery having a high value can be realized.
[0198]
The non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode current collector, a positive electrode including a positive electrode active material layer supported on one or both surfaces of the positive electrode current collector, a negative electrode current collector, and the negative electrode current collector. An electrode group comprising a negative electrode including a negative electrode active material layer that is supported on one or both surfaces of an electric body and includes a material that absorbs and releases lithium ions; and a separator disposed between the positive electrode and the negative electrode; And a non-aqueous electrolyte solution containing a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent; and a packaging material having a thickness of 0.3 mm or less in which the electrode group is accommodated. The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The positive electrode active material layer has a thickness of 10 to 100 μm. Further, the non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume based on the total amount of the non-aqueous solvent.
[0199]
In a non-aqueous electrolyte secondary battery, if the distribution of the non-aqueous electrolyte in the negative electrode is uneven, current concentration occurs in the negative electrode, and lithium dendride tends to precipitate. In order to avoid this, the porosity of the negative electrode is increased and the permeability of the non-aqueous electrolyte is improved. On the other hand, not only such a problem does not occur in the positive electrode, but if the porosity is the same as that of the negative electrode, the positive electrode active material layer density decreases and a high capacity cannot be obtained. For this reason, the porosity of the positive electrode active material is made lower than that of the negative electrode active material layer.
[0200]
By the way, the non-aqueous electrolyte containing γ-butyrolactone tends to hardly penetrate into electrodes such as a positive electrode and a negative electrode. If the above-mentioned positive electrode having a low porosity is impregnated with this non-aqueous electrolyte, only the surface can be impregnated, and the cycle life is significantly reduced.
[0201]
As in the present invention, by setting the thickness of the positive electrode active material layer having a low porosity to 10 to 100 μm, the electrolyte permeability of the positive electrode active material layer can be improved. As a result, the non-aqueous electrolyte containing γ-butyrolactone can be uniformly permeated into both the positive electrode active material layer and the negative electrode active material layer, so that the excellent oxidation resistance characteristic of γ-butyrolactone is fully utilized. The non-aqueous electrolyte containing a non-aqueous solvent containing 40% by volume or more and 95% by volume or less of γ-butyrolactone can suppress the generation of gas when stored under high temperature conditions, and has a thickness. Can be prevented from swelling as thin as 0.3 mm or less. Therefore, it is possible to reduce the thickness without sacrificing the battery capacity while maintaining practical large current discharge characteristics and charge / discharge cycle characteristics. Therefore, it has excellent high current discharge characteristics, long life, and weight. A thin non-aqueous electrolyte secondary battery with high energy density and volume energy density can be realized.
[0202]
When the secondary battery is initially charged, the non-aqueous electrolyte is prepared by reacting the negative electrode with γ-butyrolactone by setting the charging temperature to 30 to 80 ° C. and the charging rate to 0.05 to 0.5 C. Can be suppressed from reductive decomposition, so that the interfacial impedance of the negative electrode can be lowered and precipitation of metallic lithium can be suppressed. Therefore, the large current discharge characteristics and charge / discharge cycle characteristics of the secondary battery can be improved.
[0203]
In the secondary battery according to the present invention, the electrolyte solution permeability of the negative electrode active material layer can be improved by setting the thickness of the negative electrode active material layer to 10 to 100 μm. Furthermore, it can reduce, and can improve a large current discharge characteristic and charging / discharging cycling characteristics more.
[0204]
In the secondary battery according to the present invention, the ionic conductivity of the non-aqueous electrolyte can be improved by setting the concentration of the lithium salt in the non-aqueous electrolyte to 0.5 mol / l or more. In addition, the cycle life can be further improved.
[0205]
In the secondary battery according to the present invention, when a negative electrode containing a carbonaceous material that occludes and releases lithium ions is used, the nonaqueous solvent further contains ethylene carbonate, thereby forming a protective film on the surface of the negative electrode. Therefore, the reaction between the negative electrode and γ-butyrolactone can be further suppressed, and the large current discharge characteristics and cycle life can be further improved. The non-aqueous solvent further contains a third solvent made of at least one selected from vinylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, trifluoropropylene, and an aromatic compound, whereby the surface of the negative electrode is covered with a protective film. Since it can cover densely, reaction of a negative electrode and (gamma) -butyrolactone can be reduced significantly, and a large current discharge characteristic and cycle life can be improved further.
[0206]
In the secondary battery according to the present invention, the separator has an air permeability of 600 seconds / 100 cm. ^Three By including the following porous sheet, the separator can be uniformly impregnated with the nonaqueous electrolytic solution containing a specific amount of the aforementioned γ-butyrolactone. As a result, since the ion conductivity of the separator can be improved, the large current discharge characteristics and the cycle life can be further improved.
[0207]
In the secondary battery according to the present invention, the positive electrode and the separator are integrated with an adhesive polymer present at at least part of these boundaries, and the negative electrode and the separator are integrated at least part of these boundaries. By integrating with a polymer having adhesiveness existing in, an increase in internal impedance accompanying the progress of the charge / discharge cycle can be suppressed, so that the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.
[0208]
In the secondary battery according to the present invention, the positive electrode and the separator are integrated with an adhesive polymer scattered in the inside and the boundary, and the negative electrode and the separator are scattered in the inside and the boundary. By integrating with a polymer having adhesive properties, the internal impedance at the beginning of the charge / discharge cycle can be lowered, and the value can be maintained even if the charge / discharge cycle progresses. Can be improved. At the same time, gas generation at high temperatures can be further reduced.
[0209]
In the secondary battery according to the present invention, by integrating the positive electrode, the negative electrode, and the separator by thermosetting the binder contained in the positive electrode and the negative electrode, the internal impedance at the initial stage of the charge / discharge cycle is lowered. Since the value can be maintained even when the charge / discharge cycle proceeds, the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.
[0210]
The non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode current collector, a positive electrode including a positive electrode active material layer carried on one or both surfaces of the positive electrode current collector, a negative electrode current collector, An electrode group comprising a negative electrode including a negative electrode active material layer supported on one or both surfaces of a negative electrode current collector and containing a material that absorbs and releases lithium ions; and a separator disposed between the positive electrode and the negative electrode; A non-aqueous electrolyte containing a non-aqueous solvent impregnated in the electrode group and a lithium salt dissolved in the non-aqueous solvent; a sheet containing the electrode group and including a resin layer and having a thickness of 0.5 mm or less The exterior material which consists of; The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The positive electrode active material layer has a thickness of 10 to 100 μm. Further, the non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume based on the total amount of the non-aqueous solvent.
[0211]
According to such a secondary battery, since the amount of gas generation can be reduced, it is possible to prevent the exterior material made of a sheet having a thickness of 0.5 mm or less including the resin layer from expanding. As a result, it is possible to use a lightweight exterior material, and furthermore, it is possible to maintain practical large current discharge characteristics and charge / discharge cycle characteristics, so that it has excellent large current discharge characteristics, long life, and weight energy density. A non-aqueous electrolyte secondary battery having a high value can be realized.
[0212]
【Example】
Hereinafter, preferred embodiments of the present invention will be described in detail.
[0213]
Example 1
<Preparation of positive electrode>
First, lithium cobalt oxide (Li _x CoO ₂ Wherein X is 0 ≦ X ≦ 1) 91% by weight of powder is mixed with 3.5% by weight of acetylene black, 3.5% by weight of graphite and 2% by weight of ethylene propylene diene monomer powder and toluene. 10cm ² After coating on both sides of a current collector made of a porous aluminum foil (thickness: 15 μm) having pores of 0.5 mm in diameter at a ratio of 10 per electrode, the electrode density is 3 g / cm by pressing. ^Three Thus, a positive electrode having a structure in which the positive electrode layer was supported on both surfaces of the current collector was produced.
[0214]
<Production of negative electrode>
Mesophase pitch carbon fiber heat treated at 3000 ° C. as a carbonaceous material (fiber diameter is 8 μm, average fiber length is 20 μm, average spacing (d ₀₀₂ ) Is 0.3360 nm) and 93% by weight of a powder and 7% by weight of polyvinylidene fluoride (PVdF) as a binder, ² The electrode density is 1.3 g / cm by applying to a current collector made of a porous copper foil (thickness: 15 μm) having pores with a diameter of 0.5 mm at a ratio of 10 per hole, drying and pressing. ^Three Thus, a negative electrode having a structure in which the negative electrode layer was supported on the current collector was produced.
[0215]
<Separator>
A separator made of a polyethylene porous film having a thickness of 25 μm, a heat shrinkage of 20% at 120 ° C. for 1 hour, and a porosity of 50% was prepared.
[0216]
<Preparation of non-aqueous electrolyte>
Lithium tetrafluoroborate (LiBF _Four ) Was dissolved in a mixed solvent of ethylene carbonate (EC) and γ-butyrolactone (BL) (mixed volume ratio 25:75) at 1.5 mol / l to prepare a non-aqueous electrolyte.
[0217]
<Production of electrode group>
A belt-like positive electrode lead was welded to the positive electrode current collector, and a belt-like negative electrode lead was welded to the negative electrode current collector, and then the positive electrode and the negative electrode were spirally wound through the separator therebetween. Then, it shape | molded in flat shape and produced the electrode group.
[0218]
A laminate film having a thickness of 100 μm in which both surfaces of an aluminum foil were covered with polypropylene was formed into a bag shape, and the electrode group was accommodated in the bag so that the laminated surface shown in FIG. 3 described above could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF) which is an adhesive polymer was dissolved in 0.3% by weight in dimethylformamide (boiling point: 153 ° C.) which is an organic solvent. The obtained solution was injected into the electrode group in the laminate film so that the amount per battery capacity of 100 mAh was 0.2 ml, and the solution was infiltrated into the electrode group, and was applied to the entire surface of the electrode group. Attached.
[0219]
Next, the electrode group in the laminate film is vacuum-dried at 80 ° C. for 12 hours to evaporate the organic solvent, and hold the polymer having adhesiveness in the gaps between the positive electrode, the negative electrode, and the separator, and the electrode group A porous adhesive part was formed on the surface of the film. The total amount of PVdF was 0.6 mg per 100 mAh battery capacity.
[0220]
The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per battery capacity of 1 Ah is 4.7 g, and has the structure shown in FIGS. A thin nonaqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.
[0221]
The following treatment was applied to the non-aqueous electrolyte secondary battery as an initial charging step. First, after being left in a high temperature environment of 40 ° C. for 5 hours, constant current / constant voltage charging was performed for 10 hours to 4.2 V at 0.2 C (120 mA) in that environment. Thereafter, the battery was discharged at 2.7 C to 2.7 V, and the second cycle was charged under the same conditions as in the first cycle to produce a nonaqueous electrolyte secondary battery.
[0222]
The capacity of the obtained nonaqueous solvent secondary battery and the internal impedance of 1 kHz were measured. Moreover, in order to investigate a large current discharge characteristic, the capacity maintenance rate at the time of 2C discharge at room temperature (20 degreeC) was measured. In order to investigate the charge / discharge cycle characteristics, the capacity retention rate after 300 cycles was measured by repeating a cycle of 4.2 V constant current / constant voltage at 0.5 C rate for 3 hours and 1 C rate 2.7 V discharge. . Moreover, the swelling after high-temperature storage for 120 hours at 85 degreeC after 4.2V charge was measured. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Example 1 described above.
[0223]
(Example 2 to Example 7)
A thin non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that the composition of the solvent of the electrolyte solution was changed as shown in Table 1. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of each example.
[0224]
(Example 8)
Example 8 uses an aluminum can having a thickness of 0.2 mm as an exterior material, does not add an adhesive polymer, and the outer dimensions are 3.2 mm in thickness, 40 mm in width, and 70 mm in height. A thin nonaqueous electrolyte secondary battery was obtained in the same manner as the thin nonaqueous electrolyte secondary battery of Example 1, and the battery was evaluated. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Example 8.
[0225]
(Example 9 to Example 11)
A thin nonaqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that Example 1 and the initial charging temperature were changed as shown in Table 1. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the batteries of each example.
[0226]
(Examples 12 and 13)
A thin non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that the composition of the solvent of the electrolyte was changed as shown in Table 1. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of each example.
[0227]
(Comparative Example 1)
As nonaqueous electrolyte solution, 1.5 mol / l LiBF in 100% BL _Four A thin non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that a solution obtained by dissolving was used. Table 2 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 1.
[0229]
(Comparative Example 3)
Non-aqueous electrolyte with BL and EC (volume ratio 50:50) 1.5 mol / l LiBF _Four A thin non-aqueous electrolyte secondary battery similar to that of Example 1 was obtained, and the battery was evaluated except that the temperature and charge rate at the time of initial charge were changed. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 3.
[0231]
(Comparative Example 5)
In nonaqueous electrolyte, 1.5 mol / l LiBF in BL and EC (volume ratio 25:75) _Four A thin non-aqueous electrolyte secondary battery similar to that of Example 1 was obtained except that a solution obtained by dissolving was used, and the battery was evaluated. Table 2 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 5.
[0232]
(Comparative Example 6)
In non-aqueous electrolyte BL and EC (volume ratio 50:50) 0.8 mol / l LiPF ₆ A thin non-aqueous electrolyte secondary battery similar to that of Example 1 was obtained except that the temperature at the initial charge was 25 ° C., and the battery was evaluated. Table 2 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 6.
[0233]
(Comparative Example 7)
Non-aqueous electrolyte with BL and EC (volume ratio 50:50) 1.5 mol / l LiBF _Four A thin non-aqueous electrolyte secondary battery similar to that in Example 8 was obtained except that the temperature at the initial charge was 25 ° C., and the battery was evaluated. Table 2 shows the electrolytic solution composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 7.
[0234]
(Comparative Example 8)
1.5 mol / l LiBF in BL and EC (volume ratio 99: 1) in non-aqueous electrolyte _Four A thin non-aqueous electrolyte secondary battery similar to that of Example 1 was obtained except that the temperature at the initial charge was 25 ° C., and the battery was evaluated. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 8.
[0235]
(Comparative Example 9)
Non-aqueous electrolyte with BL, EC and DEC (volume ratio 50:25:25) 1.5 mol / l LiBF _Four A thin non-aqueous electrolyte secondary battery similar to that of Example 1 was obtained except that a solution obtained by dissolving was used, and the battery was evaluated. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 9.
[0237]
(Comparative Example 11)
As non-aqueous electrolyte, 1.5 mol / l LiBF in BL, PC and EC (volume ratio 50:25:25) _Four A thin non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that a solution obtained by dissolving was used. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 11.
[0238]
[Table 1]

[0239]
[Table 2]

[0240]
As is apparent from Tables 1 and 2, a non-aqueous electrolyte solution containing a non-aqueous solvent containing a packaging material having a thickness of 0.3 mm or less and a BL containing more than 50% by volume and 95% by volume or less of BL was provided. It turns out that the secondary battery of Examples 1-13 can suppress that an exterior material swells at the time of high temperature storage, and can improve the discharge capacity in 2C, and the capacity maintenance rate after 300 cycles.
[0241]
In contrast, Comparative Example 1 , Although the secondary batteries of Nos. 3 and 11 can suppress swelling of the exterior material during high-temperature storage, it can be seen that the discharge capacity at 2C and the capacity retention rate after 300 cycles are inferior to those of Examples 1-13. Comparative example 5-9 It can be seen that in the secondary battery, the swelling of the exterior material during high-temperature storage is larger than in Examples 1-13. Note that the non-aqueous electrolyte contained in the secondary battery of Comparative Example 1 corresponds to the non-aqueous electrolyte disclosed in Japanese Patent Laid-Open No. 11-97062 described above. Further, the non-aqueous electrolyte contained in the secondary battery of Comparative Example 11 corresponds to the non-aqueous electrolyte disclosed in the above-mentioned JP-A-4-14769.
[0242]
(Example 14)
An aluminum can with a thickness of 0.35 mm is used as the exterior material, and the thickness of the electrode group is reduced so that the battery dimensions are the same as in Example 1 (thickness is 3 mm, width is 40 mm, and height is 70 mm). Except for this, a thin nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 described above. The obtained secondary battery had a capacity of 0.4 Ah.
[0243]
(Example 15)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent composed of 24% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 1% by volume of vinylene carbonate (VC). _Four ) Was dissolved in the same manner as in Example 1 except that 1.5 mol / l dissolved was used to produce a thin non-aqueous electrolyte secondary battery.
[0244]
(Example 16)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent consisting of 23% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 2% by volume of vinylene carbonate (VC). _Four ) Was dissolved in the same manner as in Example 1 except that 1.5 mol / l dissolved was used to produce a thin non-aqueous electrolyte secondary battery.
[0245]
(Example 17)
As a non-aqueous electrolyte, boron tetrafluoride was added to a non-aqueous solvent comprising 24.5% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 0.5% by volume of vinylene carbonate (VC). Lithium acid (LiBF _Four ) Was dissolved in the same manner as in Example 1 except that 1.5 mol / l dissolved was used to produce a thin non-aqueous electrolyte secondary battery.
[0246]
(Example 18)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent composed of 25% by volume of ethylene carbonate (EC), 74% by volume of γ-butyrolactone (BL) and 1% by volume of toluene. _Four ) Was dissolved in the same manner as in Example 1 except that 1.5 mol / l dissolved was used to produce a thin non-aqueous electrolyte secondary battery.
[0247]
Regarding the obtained secondary batteries of Examples 15 to 18, the capacity, the internal impedance, the capacity retention rate at the time of 2C discharge, the capacity maintenance rate after 300 cycles, and 85 ° C. were the same as described in Example 1 above. The swelling after storage was measured and the results are shown in Table 3 below.
[0248]
[Table 3]

[0249]
As is clear from Table 3, the secondary batteries of Examples 15 to 17 each including a non-aqueous electrolyte containing BL, EC, and VC of more than 50% by volume and not more than 95% by volume. Is It can be seen that the capacity retention rate after 300 cycles is higher than that of the secondary battery of Example 1.
[0250]
Example 19
As a separator, the thickness is 25 μm, the heat shrinkage at 120 ° C. for 1 hour is 20%, and the air permeability is 90 sec / 100 cm. ^Three A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that a polyethylene porous film having a porosity of 50% was used.
[0251]
(Example 20)
Air permeability of porous film of separator is 580sec / 100cm ^Three A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 19 described above except that.
[0252]
(Example 21)
Air permeability of porous sheet of separator is 400sec / 100cm ^Three A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 19 described above except that.
[0253]
(Example 22)
The air permeability of the separator porous sheet is 150 sec / 100 cm. ^Three A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 19 described above except that.
[0254]
For the obtained secondary batteries of Examples 19 to 22, the capacity, the internal impedance, the capacity retention rate at the time of 2C discharge, the capacity retention rate after 300 cycles, and 85 ° C. were the same as described in Example 1 above. The swelling after storage was measured and the results are shown in Table 4 below.
[0255]
[Table 4]

[0256]
(Example 23)
An electrode group was prepared in the same manner as described in Example 1 except that no polymer having adhesiveness was added. The obtained electrode group was accommodated in an aluminum can having a thickness of 0.20 mm as an exterior material. Next, 10 kg / cm along the thickness direction of the electrode group on the exterior material in a high-temperature vacuum atmosphere at 80 ° C. ² The positive electrode, the negative electrode, and the separator were integrated by thermosetting the binder contained in the positive electrode and the negative electrode.
[0257]
Lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent consisting of 24.5% by volume ethylene carbonate (EC), 75% by volume γ-butyrolactone (BL) and 0.5% by volume vinylene carbonate (VC). _Four ) Was dissolved at 1.5 mol / l to prepare a non-aqueous electrolyte. The non-aqueous electrolyte is injected into the electrode group in the aluminum can so that the amount per battery capacity of 1 Ah is the same as 4.7 g, and sealed to provide a thickness of 3.2 mm, a width of 40 mm, and a height. A thin non-aqueous electrolyte secondary battery having a thickness of 70 mm was assembled.
[0258]
(Example 24)
An electrode group was prepared in the same manner as described in Example 1 except that no polymer having adhesiveness was added. The obtained electrode group was accommodated in an aluminum can having a thickness of 0.20 mm as an exterior material. Next, 10 kg / cm along the thickness direction of the electrode group on the exterior material in a high-temperature vacuum atmosphere at 80 ° C. ² The positive electrode, the negative electrode, and the separator were integrated by thermosetting the binder contained in the positive electrode and the negative electrode.
[0259]
Lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent consisting of 23% by volume ethylene carbonate (EC), 75% by volume γ-butyrolactone (BL) and 2% by volume vinylene carbonate (VC). _Four ) Was dissolved at 1.5 mol / l to prepare a non-aqueous electrolyte. The non-aqueous electrolyte solution is injected into the electrode group in the aluminum can so that the amount per battery capacity of 1Ah is the same as 4.7 g, and the thickness is 3.2 mm, the width is 40 mm, and the height is 70 mm. A non-aqueous electrolyte secondary battery was assembled.
[0260]
For the obtained secondary batteries of Examples 23 to 24, the capacity, the internal impedance, the capacity maintenance rate at 2C discharge, the capacity maintenance rate after 300 cycles, and 85 ° C. were the same as described in Example 1 above. The swelling after storage was measured and the results are shown in Table 5 below.
[0261]
[Table 5]

[0262]
As is clear from Table 5, the secondary batteries of Examples 23 to 24 have a high capacity, a high capacity retention rate during 2C discharge and after 300 cycles, and can suppress swelling when stored at 85 ° C. Recognize.
[0263]
(Example 25)
As the exterior material, a laminated film having a thickness of 500 μm in which both surfaces of an aluminum foil are covered with polypropylene is used, and the battery dimensions are 4 mm, width is 100 mm, and height is 280 mm. Similarly, a nonaqueous electrolyte secondary battery was produced.
[0264]
About the obtained secondary battery of Example 25, in the same manner as described in Example 1 above, the capacity, the capacity maintenance rate at the time of 2C discharge, the capacity maintenance rate after 300 cycles, and the swelling after storage at 85 ° C. Was measured. As a result, the secondary battery of Example 25 had a capacity of 6 Ah, a capacity maintenance ratio during 2C discharge of 85%, a capacity maintenance ratio after 300 cycles of 90%, and a swelling after storage at 85 ° C. of 3%. there were. Therefore, when a non-aqueous solvent containing BL of more than 50% by volume and 95% by volume or less is used, it can be confirmed that a laminate film having a thickness of 0.5 mm can be used as an exterior material of a large battery such as an electric vehicle. It was.
[0265]
(Example 26)
<Preparation of positive electrode>
First, lithium cobalt oxide (Li _x CoO ₂ Wherein X is 0 ≦ X ≦ 1) 91% by weight of powder, 2.5% by weight of acetylene black, 3% by weight of graphite, 4% by weight of polyvinylidene fluoride (PVdF) and N-methylpyrrolidone (NMP) solution In addition, they were mixed together and applied to both sides of a current collector made of an aluminum foil having a thickness of 10 μm, then dried and pressed, so that the density on each side of the current collector was 3.3 g / cm 3. ^Three Thus, a positive electrode having a structure in which a positive electrode active material layer having a porosity of 34% and a thickness of 48 μm was supported was produced.
[0266]
<Production of negative electrode>
Mesophase pitch carbon fiber heat treated at 3000 ° C. as a carbonaceous material (fiber diameter is 8 μm, average fiber length is 20 μm, average spacing (d ₀₀₂ ) Is 0.3360 nm), 93% by weight of a powder, 7% by weight of polyvinylidene fluoride (PVdF) as a binder, and an N-methylpyrrolidone solution are mixed, and this is made of a copper foil having a thickness of 10 μm. The density is 1.3 g / cm on each side of the current collector by applying to both sides of the current, drying and pressing. ^Three Thus, a negative electrode having a structure in which a negative electrode active material layer having a porosity of 41% and a thickness of 45 μm was supported was produced.
[0267]
<Separator>
A separator made of a polyethylene porous film having a thickness of 20 μm and a porosity of 50% was prepared.
[0268]
<Production of electrode group>
The positive electrode and the negative electrode were spirally wound through the separator therebetween, and then formed into a flat shape to produce a flat electrode group having a thickness of 2.5 mm, a width of 30 mm, and a height of 50 mm. .
[0269]
<Preparation of non-aqueous electrolyte>
Lithium tetrafluoroborate (LiBF _Four ) Was dissolved in a mixed solvent of ethylene carbonate (EC) and γ-butyrolactone (BL) (mixed volume ratio 25:75) at 1.5 mol / l to prepare a non-aqueous electrolyte.
[0270]
Next, a laminate film having a thickness of 100 μm in which both surfaces of the aluminum foil were covered with polypropylene was formed into a bag shape, and the electrode group was accommodated in this, and both surfaces were sandwiched by holders so that the thickness was 2.7 mm. Polyvinylidene fluoride (PVdF) which is an adhesive polymer was dissolved in 0.3% by weight in dimethylformamide (boiling point: 153 ° C.) which is an organic solvent. The obtained solution was injected into the electrode group in the laminate film so that the amount per battery capacity of 100 mAh was 0.6 ml, and the solution was infiltrated into the electrode group, and over the entire surface of the electrode group. Attached.
[0271]
Next, the electrode group in the laminate film is vacuum-dried at 80 ° C. for 12 hours to evaporate the organic solvent, and hold the polymer having adhesiveness in the gaps between the positive electrode, the negative electrode, and the separator, and the electrode group A porous adhesive part was formed on the surface of the film.
[0272]
The non-aqueous electrolyte solution is injected into the electrode group in the laminate film so that the amount per battery capacity 1Ah is 2 g, and the thin non-aqueous electrolyte secondary solution has a thickness of 3 mm, a width of 32 mm, and a height of 55 mm. I assembled the battery.
[0273]
The following treatment was applied to the non-aqueous electrolyte secondary battery as an initial charging step. First, after being left in a high temperature environment of 40 ° C. for 5 hours, constant current / constant voltage charging was performed for 10 hours to 4.2 V at 0.2 C (120 mA) in that environment. Thereafter, the battery was discharged at 2.7 C to 2.7 V, and the second cycle was charged under the same conditions as in the first cycle to produce a nonaqueous electrolyte secondary battery.
[0274]
In order to examine the large current discharge characteristics at room temperature (20 ° C.) of the obtained nonaqueous solvent secondary battery, the capacity retention rate during 3C discharge was measured. At this time, the discharge capacity at 0.2 C was set as the reference capacity. Also, in order to investigate the charge / discharge cycle characteristics, a cycle of 4.2V constant current / constant voltage for 3 hours at 0.7C rate and 2.7V discharge at 1C rate was repeated, and the capacity retention rate after 300 cycles was measured. did. Moreover, the swelling after high-temperature storage for 120 hours at 85 degreeC after 4.2V charge was measured. Table 6 shows the initial capacity, the active material layer thickness, the content ratio of γ-butyrolactone as the solvent of the electrolytic solution, and the battery characteristics of the battery of Example 26 described above.
[0275]
(Examples 27-37, A, B and Comparative Examples 12-13)
A thin non-aqueous electrolyte solution 2 was prepared in the same manner as in Example 26 except that the thicknesses of one surface of the positive electrode active material layer and the negative electrode active material layer and the content ratio of γ-butyrolactone as the solvent of the electrolyte solution were changed as shown in Table 6. A secondary battery was obtained and evaluated. Table 6 shows the initial capacity of each battery, the thickness of the active material layer, the content ratio of γ-butyrolactone as a solvent of the electrolytic solution, and battery characteristics.
[0276]
[Table 6]

[0277]
As is apparent from Table 6, the positive electrode active material layer has a positive electrode having a thickness of 10 to 100 μm, an exterior material having a thickness of 0.3 mm or less, and a nonaqueous solvent containing 40 to 95% by volume of BL. The secondary batteries of Examples 26 to 37, A, and B including the non-aqueous electrolyte that can suppress the expansion of the exterior material during high temperature storage, the initial capacity, the discharge capacity at 3C, and after 300 cycles It can be seen that the capacity retention rate of the can be improved.
[0278]
On the other hand, it can be seen that the secondary battery of Comparative Example 12 is inferior to Examples 26 to 37, A, and B in the discharge capacity at 3C and the capacity retention rate after 300 cycles. Moreover, it turns out that the secondary battery of the comparative example 13 is inferior to Examples 26-37, A, and B in the discharge capacity in 3C.
[0279]
(Example 38)
As a non-aqueous electrolyte, boron tetrafluoride was added to a non-aqueous solvent comprising 24.9% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 0.1% by volume of vinylene carbonate (VC). Lithium acid (LiBF _Four ) Was dissolved in the same manner as in Example 26 except that 1.5 mol / l dissolved was used to produce a thin nonaqueous electrolyte secondary battery.
[0280]
(Example 39)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent composed of 24% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 1% by volume of vinylene carbonate (VC). _Four ) Was dissolved in the same manner as in Example 26 except that 1.5 mol / l dissolved was used to produce a thin nonaqueous electrolyte secondary battery.
[0281]
(Example 40)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent composed of 20% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 5% by volume of vinylene carbonate (VC). _Four ) Was dissolved in the same manner as in Example 26 except that 1.5 mol / l dissolved was used to produce a thin nonaqueous electrolyte secondary battery.
[0282]
(Example 41)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent composed of 25% by volume of ethylene carbonate (EC), 74% by volume of γ-butyrolactone (BL) and 1% by volume of toluene. _Four ) Was dissolved in the same manner as in Example 26 except that 1.5 mol / l dissolved was used to produce a thin nonaqueous electrolyte secondary battery.
[0283]
For the obtained secondary batteries of Examples 38 to 41, the capacity, the capacity maintenance rate at the time of 3C discharge, the capacity maintenance rate after 300 cycles, and the storage at 85 ° C. were the same as described in Example 26 above. The results are shown in Table 7 below.
[0284]
[Table 7]

[0285]
As is apparent from Table 7, the secondary battery of Examples 38 to 40 with a non-aqueous electrolyte containing 40 to 95% by volume of BL, EC and VC, and 40 to 95% by volume of BL, EC and fragrance It can be seen that the secondary battery of Example 41 provided with the non-aqueous electrolyte containing a group compound has a higher capacity retention rate after 300 cycles than the secondary battery of Example 26.
[0286]
(Example 42)
As a separator, the thickness is 25 μm, the heat shrinkage at 120 ° C. for 1 hour is 20%, and the air permeability is 90 sec / 100 cm. ^Three A thin nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 26 described above except that a polyethylene porous film having a porosity of 50% was used.
[0287]
(Example 43)
Air permeability of porous film of separator is 580sec / 100cm ^Three A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 42 described above except that.
[0288]
(Example 44)
Air permeability of porous sheet of separator is 400sec / 100cm ^Three A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 42 described above except that.
[0289]
(Example 45)
The air permeability of the separator porous sheet is 150 sec / 100 cm. ^Three A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 42 described above except that.
[0290]
For the obtained secondary batteries of Examples 42 to 45, the capacity, the capacity maintenance rate at the time of 3C discharge, the capacity maintenance rate after 300 cycles, and the storage at 85 ° C. were the same as described in Example 26 above. The results are shown in Table 8 below.
[0291]
[Table 8]

[0292]
(Example 46)
An electrode group was produced in the same manner as described in Example 26 except that no polymer having adhesiveness was added. The obtained electrode group was accommodated in an aluminum can having a thickness of 0.18 mm as an exterior material. Next, 10 kg / cm along the thickness direction of the electrode group on the exterior material in a high-temperature vacuum atmosphere at 80 ° C. ² The positive electrode, the negative electrode, and the separator were integrated by thermosetting the binder contained in the positive electrode and the negative electrode.
[0293]
Lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent consisting of 24.5% by volume ethylene carbonate (EC), 75% by volume γ-butyrolactone (BL) and 0.5% by volume vinylene carbonate (VC). _Four ) Was dissolved at 1.5 mol / l to prepare a non-aqueous electrolyte. The non-aqueous electrolyte is injected into the electrode group in the aluminum can so that the amount per battery capacity of 1 Ah is the same as 4.7 g, and sealed to provide a thickness of 3 mm, a width of 32 mm, and a height of 55 mm. A thin non-aqueous electrolyte secondary battery was assembled.
[0294]
(Example 47)
An electrode group was produced in the same manner as described in Example 26 except that no polymer having adhesiveness was added. The obtained electrode group was accommodated in an aluminum can having a thickness of 0.25 mm as an exterior material. Next, 10 kg / cm along the thickness direction of the electrode group on the exterior material in a high-temperature vacuum atmosphere at 80 ° C. ² The positive electrode, the negative electrode, and the separator were integrated by thermosetting the binder contained in the positive electrode and the negative electrode.
[0295]
Lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent consisting of 24% by volume ethylene carbonate (EC), 75% by volume γ-butyrolactone (BL) and 2% by volume vinylene carbonate (VC). _Four ) Was dissolved at 1.5 mol / l to prepare a non-aqueous electrolyte. The non-aqueous electrolyte is injected into the electrode group in the aluminum can so that the amount per battery capacity of 1 Ah is the same as 4.7 g, and is a thin non-aqueous water having a thickness of 3 mm, a width of 32 mm, and a height of 55 mm. An electrolyte secondary battery was assembled.
[0296]
For the obtained secondary batteries of Examples 46 to 47, the capacity, the capacity maintenance rate at the time of 3C discharge, the capacity maintenance rate after 300 cycles, and the storage at 85 ° C. were the same as described in Example 26 above. The results are shown in Table 9 below.
[0297]
[Table 9]

[0298]
As is clear from Table 9, the secondary batteries of Examples 46 to 47 have a high capacity, a high capacity retention rate at the time of 3C discharge and after 300 cycles, and can suppress swelling when stored at 85 ° C. Recognize.
[0299]
(Example 48)
As the exterior material, a laminated film having a thickness of 500 μm in which both surfaces of an aluminum foil are covered with polypropylene is used, and the battery dimensions are 4 mm in thickness, 80 mm in width, and 220 mm in height. Similarly, a nonaqueous electrolyte secondary battery was produced.
[0300]
For the obtained secondary battery of Example 48, the capacity, the capacity maintenance rate at the time of 3C discharge, the capacity maintenance rate after 300 cycles, and the swelling after storage at 85 ° C. were the same as described in Example 26 above. Was measured. As a result, the secondary battery of Example 48 had a capacity of 3.2 Ah, a capacity retention rate at 3C discharge of 96%, a capacity retention rate of 300% after 300 cycles, and a swelling after storage at 85 ° C. of 3%. %Met. Therefore, when the thickness of the positive electrode active material layer is 10 to 100 μm and a nonaqueous solvent containing 40 to 95% by volume of BL is used, the thickness is 0.5 mm as an exterior material of a large battery such as an electric vehicle. It was confirmed that the laminate film can be used.
[0301]
【The invention's effect】
As described above in detail, according to the present invention, deformation of the exterior material when stored at a high temperature is suppressed, and non-water with improved weight energy density, volume energy density, large current discharge characteristics, and charge / discharge cycle characteristics is achieved. An electrolyte secondary battery can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a first nonaqueous electrolyte secondary battery according to the invention.
2 is an enlarged cross-sectional view showing a portion A of FIG.
3 is a schematic diagram showing the vicinity of a boundary between a positive electrode, a separator, and a negative electrode in the secondary battery of FIG. 1. FIG.
FIG. 4 is a cross-sectional view for explaining the thickness of a positive electrode active material layer in a second nonaqueous electrolyte secondary battery according to the present invention.
FIG. 5 is a cross-sectional view showing an example of a second non-aqueous electrolyte secondary battery according to the present invention.
6 is an enlarged cross-sectional view showing a portion B of FIG.
7 is a schematic diagram showing the vicinity of a boundary between a positive electrode, a separator, and a negative electrode in the secondary battery of FIG.
[Explanation of symbols]
1 ... exterior material,
2 ... Electrode group,
3 ... Separator,
4 ... positive electrode layer,
5 ... positive electrode current collector,
6 ... negative electrode layer,
7 ... negative electrode current collector,
8 ... adhesive layer,
9: polymer having adhesiveness,
12 ... positive electrode,
13 ... negative electrode,
21 ... exterior material,
22 ... Electrode group,
23 ... separator,
24 ... positive electrode layer,
25 ... positive electrode current collector,
26 ... negative electrode layer,
27 ... negative electrode current collector,
28 ... adhesive layer,
29 ... polymer having adhesiveness,
32 ... positive electrode,
33 ... negative electrode.

Claims (22)

Positive and a negative electrode containing a material capable of absorbing and releasing lithium ions, the positive electrode and the negative electrode and a separator disposed between the positive electrode and the negative electrode and the separator electrodes that are integrated;
A non-aqueous electrolyte solution impregnated in the electrode group and comprising a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent;
An exterior material made of a laminate film having a thickness of 0.5 mm or less including the resin group and containing the resin layer;
The non-aqueous solvent contains more than 50% by volume of the whole non-aqueous solvent and 95% by volume or less of γ-butyrolactone and ethylene carbonate,
The non-aqueous electrolyte secondary battery, wherein the lithium salt contains LiPF ₆ or LiBF ₄ . The lithium salt, a non-aqueous electrolyte secondary battery according to claim 1, wherein it is LiBF _4.   3. The non-aqueous electrolyte secondary battery according to claim 1, wherein a ratio of γ-butyrolactone as the non-aqueous solvent is 60% by volume or more and 95% by volume or less.   4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the ratio of ethylene carbonate as the non-aqueous solvent is in the range of 5 to 40% by volume.   The non-aqueous solvent further includes a third solvent consisting of at least one selected from propylene carbonate, vinylene carbonate, trifluoropropylene, diethyl carbonate, methyl ethyl carbonate, and an aromatic compound. The non-aqueous electrolyte secondary battery according to any one of claims.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous solvent further contains 10% by volume or less of vinylene carbonate.   The non-aqueous electrolyte secondary battery according to claim 6, wherein a ratio of vinylene carbonate in the non-aqueous solvent is in a range of 0.001 to 10% by volume. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 4 , wherein the nonaqueous solvent further contains propylene carbonate . The non-aqueous electrolyte secondary battery according to claim 1 , wherein the non-aqueous electrolyte contains 0.1 to 1% of a surfactant . The non-aqueous electrolyte secondary battery according to claim 9 , wherein the surfactant includes trioctyl phosphate . The non-aqueous electrolyte secondary battery according to claim 1 , wherein the separator includes a porous sheet having an air permeability of 600 seconds / 100 cm ³ or less . Material, graphite, coke, claims 1-11 any one which comprises at least one of graphite material or carbonaceous material selected from carbon fibers and spherical carbon absorbing and releasing lithium ions The nonaqueous electrolyte secondary battery as described. The non-aqueous electrolyte secondary battery according to claim 12 , wherein the carbon fiber is a mesophase pitch-based carbon fiber . The non-aqueous electrolyte secondary battery according to claim 1, wherein the material that absorbs and releases lithium ions includes lithium titanium oxide . The non-aqueous electrolyte secondary battery according to claim 1 , wherein the laminate film further includes a metal layer . The non-aqueous electrolyte secondary battery according to claim 1 , wherein the resin layer contains at least one of polyethylene and polypropylene . The positive electrode, the lithium manganese composite oxide, claims 1 to 16, characterized in that it comprises at least one lithium-containing nickel oxide is selected from the group consisting of lithium-containing cobalt oxide and lithium-containing nickel cobalt oxide The non-aqueous electrolyte secondary battery according to any one of claims. The positive electrode and the separator are integrated with an adhesive polymer that exists in at least a part of these boundaries, and the negative electrode and the separator have an adhesive property that exists in at least a part of these boundaries. The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous electrolyte secondary battery is integrated with a polymer . The non-aqueous solution according to any one of claims 1 to 17, wherein the positive electrode, the negative electrode, and the separator are integrated by thermosetting a binder contained in the positive electrode and the negative electrode. Electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode group is subjected to a heat press at 40 to 120 ° C. 18. 21. The nonaqueous electrolyte solution according to claim 1 , wherein the product of the battery capacity (Ah) and the battery internal impedance (mΩ) at 1 kHz is 10 mΩ · Ah or more and 110 mΩ · Ah or less. Next battery. The product of the battery capacity (Ah) and the battery internal impedance (mΩ) at 1 kHz is 20 mΩ · Ah or more and 60 mΩ · Ah or less. Next battery.

Images