JP3620512B2 - Non-aqueous electrolyte secondary battery - Google Patents

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【００２９】
（実施例２〜３）
表１に示すように、実施例２〜実施例３の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例１の電池と同様にした。実施例２の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例３の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００３０】
（実施例４）
表１に示すように、実施例４の電池では、正極活物質としてマンガン酸リチウム粉末を用いた以外は実施例１の電池と同様にした。
【００３１】
（実施例５〜６）
表１に示すように、実施例５〜実施例６の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例４の電池と同様にした。実施例５の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例６の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００３２】
（実施例７）
表１に示すように、実施例７の電池では、正極活物質としてコバルト置換マンガン酸リチウム（ＬｉＭｎ_１．８Ｃｏ_０．２Ｏ_４）粉末を用いた以外は実施例１の電池と同様にした。
【００３３】
（実施例８〜９）
表１に示すように、実施例８〜実施例９の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例７の電池と同様にした。実施例８の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例９の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００３４】
（実施例１０）
表１に示すように、実施例１０の電池では、正極活物質としてリチウム過剰のコバルト置換マンガン酸リチウム（Ｌｉ_１．０１Ｍｎ_１．９８Ｃｏ_０．０１Ｏ_４）粉末を用いた以外は実施例１の電池と同様にした。
【００３５】
（実施例１１〜１２）
表１に示すように、実施例１１〜実施例１２の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例１０の電池と同様にした。実施例１１の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例１２の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００３６】
（実施例１３）
表１に示すように、実施例１３の電池では、正極活物質としてリチウム過剰のコバルト置換マンガン酸リチウム（Ｌｉ_１．０５Ｍｎ_１．８５Ｃｏ_０．１Ｏ_４）粉末を用いた以外は実施例１の電池と同様にした。
【００３７】
（実施例１４〜１５）
表１に示すように、実施例１４〜実施例１５の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例１３の電池と同様にした。実施例１４の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例１５の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００３８】
（実施例１６）
表１に示すように、実施例１６の電池では、正極活物質としてリチウム過剰のコバルト置換マンガン酸リチウム（Ｌｉ_１．１Ｍｎ_１．６５Ｃｏ_０．２５Ｏ_４）粉末を用いた以外は実施例１の電池と同様にした。
【００３９】
（実施例１７〜１８）
表１に示すように、実施例１７〜実施例１８の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例１６の電池と同様にした。実施例１７の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例１８の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００４０】
（実施例１９）
表１に示すように、実施例１９の電池では、正極活物質としてリチウム過剰のコバルト置換マンガン酸リチウム（Ｌｉ_１．１２Ｍｎ_１．６１Ｃｏ_０．２７Ｏ_４）粉末を用いた以外は実施例１の電池と同様にした。
【００４１】
（実施例２０〜２１）
表１に示すように、実施例２０〜実施例２１の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例１９の電池と同様にした。実施例２０の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例２１の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００４２】
（実施例２２）
表１に示すように、実施例２２の電池では、正極活物質としてリチウム過剰のコバルト置換マンガン酸リチウム（Ｌｉ_１．０５Ｍｎ_１．８５Ｃｏ_０．１Ｏ_４）の結晶中にコバルト酸リチウムの結晶相が混在した結晶相混在マンガン酸リチウム粉末を用いた以外は実施例１の電池と同様にした。
【００４３】
（実施例２３〜２４）
表１に示すように、実施例２３〜実施例２４の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例２２の電池と同様にした。実施例２３の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例２４の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００４４】
（実施例２５）
表１に示すように、実施例２５の電池では、負極活物質として黒鉛を用いた以外は実施例１３の電池と同様にした。
【００４５】
（実施例２６〜２７）
表１に示すように、実施例２６〜実施例２７の電池では、合剤厚さＡ、粒子径Ｂ及び粒子径Ｃを変えた以外は実施例２５の電池と同様にした。実施例２６の電池では、粒子径Ｂを６μｍ、粒子径Ｃを２μｍ、合剤厚さＡを１００μｍとし、実施例２７の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを５μｍ、合剤厚さＡを２２０μｍとした。
【００４６】
（比較例１）
表１に示すように、比較例１の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを１０μｍとした以外は実施例１の電池と同様にした。
【００４７】
（比較例２）
表１に示すように、比較例２の電池では、粒子径Ｂを１４μｍ、粒子径Ｃを１０μｍとした以外は実施例１３の電池と同様にした。
【００４８】
（比較例３）
表１に示すように、比較例３の電池では、粒子径Ｂを１０μｍ、粒子径Ｃを５μｍ、合剤厚さＡを１００μｍとした以外は実施例１３の電池と同様にした。
【００４９】
＜試験・評価＞
次に、作製した実施例及び比較例の各電池について、以下の一連の試験を行った。
【００５０】
実施例及び比較例の各電池を充電した後放電し、放電容量を測定した。充電条件は、正極活物質１ｇあたり４０ｍＡとなる電流で、定電流連続充電し、電池電圧が４．２Ｖに到達するや否や４．２Ｖの定電圧充電とした。充電時間は５時間とした。放電条件は、正極活物質１ｇあたり４０ｍＡとなる電流で連続放電し、終止電圧２．８Ｖとした。
【００５１】
上述した充電条件で充電した後、充電状態の電池の放電出力を測定した。測定は、正極活物質１ｇあたり４０ｍＡ、８０ｍＡ、１６０ｍＡとなる電流で５秒目の電圧を読み取り、横軸電流値に対して縦軸に５秒目電圧をプロットし、３点を結ぶ近似直線が、２．８Ｖと交差するところの電流値と２．８Ｖとの積を出力とした。
【００５２】
寿命試験として、上述した条件で充放電サイクルを１００回繰り返した後充電した各電池について出力を測定し、さらに引き続き、４０°Ｃにて１ヶ月保存した後出力を測定し、充放電サイクル前の出力に対する充放電サイクル後の出力の百分率を出力維持率とした。当然のことながら、出力維持率が高いほど寿命特性がよいことになる。
【００５３】
充電、放電、出力の測定は、いずれも環境温度２５±１°Ｃの雰囲気で行った。出力維持率の測定結果を下表２に示す。
【００５４】
【表２】

【００５５】
表１及び表２に示すように、合剤厚さＡ、粒子径Ｂ及び粒子径ＣがＡ／１５＞Ｂ≧２Ｃを満足する実施例１〜２７の電池では、いずれも高い出力維持率が得られた。これに対して、Ａ／１５＞Ｂ≧２Ｃを満たしていない比較例１〜３の電池では、出力維持率が低下した。また、正極活物質にリチウムマンガン複酸化物のマンガン酸リチウムを用いた実施例４〜６の電池では、コバルト酸リチウムを用いた実施例１〜３の電池より高い出力維持率が得られた。
【００５６】
また、コバルト置換マンガン酸リチウムを用いた実施例７〜９の電池では、コバルト置換していないマンガン酸リチウムを用いた実施例４〜６の電池より高い出力維持率が得られた。これは、コバルト置換することで、マンガン酸リチウムの結晶構造が安定化したためと考えられる。更に、一般式がＬｉ_１＋ｘＭｎ_{２−ｘ−ｙ}Ｃｏ_ｙＯ_４（ｘは０＜ｘ≦０．１、ｙは０＜ｙ≦０．２５）で表されるリチウム過剰のコバルト置換マンガン酸リチウムを用いた実施例１０〜１８の電池では、コバルト置換マンガン酸リチウムを用いた実施例７〜９の電池と比べて更に高い出力維持率が得られた。ところが、一般式中のｘが０．１を超え、ｙが０．２５を超えた実施例１９〜２１の電池では、出力維持率が若干低下する傾向を示した。
【００５７】
更に、結晶相混在マンガン酸リチウムを用いた実施例２２〜２４の電池では、コバルト酸リチウムの結晶相が混在していないコバルト置換マンガン酸リチウムを用いた実施例１３〜１５の電池と比べて更に高い出力維持率が得られた。これは、結晶格子からリチウムイオンを放出すると結晶が収縮するリチウムマンガン複酸化物の結晶中に、層状構造の結晶からリチウムイオンを放出すると酸素原子の斥力により結晶が膨張するリチウムコバルト酸複酸化物の結晶相が混在しているので、リチウムマンガン複酸化物全体の結晶構造が安定化したためと考えられる。また、負極活物質として黒鉛を用いた実施例２５〜２７の電池では、非晶質炭素を用いた実施例１３〜１５の電池と比べて出力維持率が向上した。
【００５８】
以上のように、本実施形態のリチウムイオン電池では、正極活物質としてリチウム遷移金属複酸化物を用いた正極と、負極活物質として黒鉛を用いた負極と、を非水電解液に浸潤させたので、高容量、高出力を得ることができる。また、粒子径Ｂを、合剤厚さＡ及び粒子径Ｃに対してＡ／１５＞Ｂ≧２Ｃを満たす範囲としたので、長時間保存しても出力維持率に優れる。
【００５９】
すなわち、Ａ／１５＞Ｂは、合剤厚さＡが粒子径Ｂの１５倍を超える（Ａ＞１５Ｂ）とき、正極活物質粒子の結晶変化によるひずみが正極活物質合剤の厚さの中の正極活物質粒子間の隙間全体で吸収されることを意味する。一方、Ｂ≧２Ｃは、粒子径Ｃが粒子径Ｂの２分の１以下（Ｂ／２≧Ｃ）のとき、正極活物質粒子の結晶変化によるひずみが正極活物質粒子間に存在する導電材粒子に妨げられずに正極活物質粒子間の隙間で吸収されることを意味する。更に、Ｂ≧２Ｃについて詳述すれば、図２に示すように、正極活物質粒子Ｐの最密充填の場合でも粒子間に空間Ｓができるように、実際の正極活物質粒子間の空間に入る導電材粒子の大きさが考慮されている。
【００６０】
また、本実施形態のリチウムイオン電池では、正極活物質としてリチウムマンガン複酸化物を用いることで、リチウムコバルト複酸化物を用いた電池より出力維持率を向上させることができる。更に、結晶中のマンガンサイトをコバルトで置換したリチウムマンガン複酸化物を用いることで、出力維持率をより向上させることができる。このとき、一般式Ｌｉ_１＋ｘＭｎ_{２−ｘ−ｙ}Ｃｏ_ｙＯ_４（ｘは０＜ｘ≦０．１、ｙは０＜ｙ≦０．２５）で表されるリチウムマンガン複酸化物を用いることで、出力維持率を一層向上させることができる。また、負極活物質に黒鉛を用いることで、優れた出力維持率を得ることができる。
【００６１】
更に、リチウムマンガン複酸化物のマンガン酸リチウムの結晶とリチウムコバルト複酸化物のコバルト酸リチウムの結晶とは、充放電に伴う結晶変化が逆の挙動を示す。すなわち、下表３に示すように、マンガン酸リチウムの結晶は、充電時に収縮し放電時に膨張するのに対して、コバルト酸リチウムの結晶は、充電時に膨張し放電時に収縮する。このため、正極活物質全体の結晶構造が安定する。従って、リチウムマンガン複酸化物の結晶中にリチウムコバルト複酸化物の結晶相が混在したリチウムマンガン複酸化物を用いることで、出力維持率を更に向上させることができる。
【００６２】
【表３】

【００６３】
なお、本実施形態では、電気自動車用電源に用いられる大形の二次電池について例示したが、本発明は、電池の大きさ、電池容量には限定されず、電池容量としておおむね３Ａｈを超える電池に対して著しく効果を発揮することが確認されている。また、本実施形態では円筒型電池について例示したが、本発明は電池の形状についても限定されず、角形、その他の多角形の電池にも適用可能である。更に、本発明の適用可能な形状としては、上述した有底筒状容器（缶）に電池上蓋がカシメによって封口されている構造の電池以外であっても構わない。このような構造の一例として正負外部端子が電池蓋を貫通し電池容器内で軸芯を介して正負外部端子が押し合っている状態の電池を挙げることができる。
【００６４】
また、リチウムマンガン複合酸化物として、Ｌｉ／Ｍｎ比が０．５のマンガン酸リチウムを例示したが、本発明はこれに限定されるものではなく、リチウム塩と酸化マンガンの仕込み比を制御することによって所望のＬｉ／Ｍｎ比としたマンガン酸リチウムを用いることができる。更に、本実施形態では、リチウムマンガン複合酸化物以外のリチウム遷移金属複合酸化物として、コバルト酸リチウムを例示したが、本発明はこれに制限されることなく、ニッケル酸リチウムやニッケルの一部が他の元素で置換、ドープされたものを用いることもできる。また、リチウムマンガン複合酸化物の結晶中のマンガンサイトをコバルトで置換した例を示したが、コバルトを結晶中にドープするようにしてもよい。
【００６５】
更に、本実施形態以外で用いることのできるリチウムイオン電池用負極活物質としては、上記特許請求範囲に記載した事項以外に特に制限はない。例えば、天然黒鉛や、人造の各種黒鉛材、コークス、非晶質炭素などの炭素質材料等でよく、その粒子形状においても、鱗片状、球状、繊維状、塊状等、特に制限されるものではない。
【００６６】
また更に、本実施形態では、導電材として黒鉛粉末を例示したが、本発明はこれに限定されるものではなく、例えば、非晶質炭素などの一般に用いられる炭素材等を使用してもよい。
【００６７】
更にまた、本実施形態以外で用いることのできるリチウムイオン電池用極板活物質結着剤としては、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリエチレン、ポリスチレン、ポリブタジエン、ブチルゴム、ニトリルゴム、スチレン／ブタジエンゴム、多硫化ゴム、ニトロセルロース、シアノエチルセルロース、各種ラテックス、アクリロニトリル、フッ化ビニル、フッ化ビニリデン、フッ化プロピレン、フッ化クロロプレン、ポリビニルアルコール等の重合体及びこれらの変性体や混合体などがある。
【００６８】
また、本実施形態では、絶縁被覆に、基材がポリイミドで、その片面にヘキサメタアクリレートからなる粘着剤を塗布した粘着テープを用いた例を示したが、例えば、基材がポリプロピレンやポリエチレン等のポリオレフィンで、その片面又は両面にヘキサメタアクリレートやブチルアクリレート等のアクリル系粘着剤を塗布した粘着テープや、粘着剤を塗布しないポリオレフィンやポリイミドからなるテープ等も好適に使用することができる。
【００６９】
更に、非水電解液としては、エチレンカーボネートとジメチルカーボネートとジエチルカーボネートの体積比１：１：１の混合溶媒中へ６フッ化リン酸リチウムを１モル／リットル溶解したものを例示したが、本発明の電池には特に制限はなく、一般的なリチウム塩を電解質とし、これを有機溶媒に溶解した電解液が用いられる。しかし、用いられるリチウム塩や有機溶媒は特に制限されない。例えば、電解質としては、ＬｉＣｌＯ_４、ＬｉＡｓＦ_６、ＬｉＢＦ_４、ＬｉＢ（Ｃ_６Ｈ_５）_４、ＣＨ_３ＳＯ_３Ｌｉ、ＣＦ_３ＳＯ_３Ｌｉ等やこれらの混合物を用いることができる。非水電解液有機溶媒としては、プロピレンカーボネート、エチレンカーボネート、１，２−ジメトキシエタン、１，２−ジエトキシエタン、γ−ブチロラクトン、テトラヒドロフラン、１，３−ジオキソラン、４−メチル−１，３−ジオキソラン、ジエチルエーテル、スルホラン、メチルスルホラン、アセトニトリル、プロピオニトリル等又はこれら２種類以上の混合溶媒を用いるようにしてもよく、混合配合比についても限定されるものではない。
【００７０】
【発明の効果】
以上説明したように、本発明によれば、マンガンは資源が豊富に存在するので、正極活物質をリチウムマンガン複酸化物とすることで、電池のコストが低減でき、結晶中のマンガンサイトをＣｏで置換したリチウムマンガン複酸化物とすることで、正極活物質が安定な結晶構造となるので、電池保存時の出力維持特性を向上させることができると共に、平均粒子径Ｂを、Ａ／１５＞Ｂ≧２Ｃ、かつ、Ｂ≦３Ｃを満たす範囲とすることで、正極活物質の結晶変化によるひずみは、平均粒子径Ｂの１５倍を超える正極活物質合剤の厚さＡ（Ａ＞１５Ｂ）の中の正極活物質粒子間の隙間全体で吸収され、正極活物質粒子間に存在する平均粒子径Ｂの２分の１以下（Ｂ／２≧Ｃ）となる平均粒子径Ｃの導電材に妨げられずに正極活物質粒子間の隙間で吸収されるので、電池保存時の出力維持特性に優れた非水電解液二次電池を実現することができる、という効果を得ることができる。
【図面の簡単な説明】
【図１】本発明が適用可能な実施形態の円筒型リチウムイオン電池の断面図である。
【図２】正極活物質粒子の最密充填の状態を模式的に示す説明図である。
【符号の説明】
６ 捲回群
２０ 円筒形リチウムイオン電池（非水電解液二次電池）
Ｗ１ 正極集電体（集電体）
Ｗ２ 正極活物質合剤層
Ｐ 正極活物質粒子
Ｓ 空間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery, and in particular, a cathode active material mixture including a cathode active material and a conductive material using a lithium transition metal double oxide is applied to both sides of a current collector in an approximately equal amount. The present invention relates to a non-aqueous electrolyte secondary battery in which a non-aqueous electrolyte is infiltrated with a negative electrode coated with a negative electrode active material mixture containing a negative electrode active material capable of occluding and releasing lithium ions by charge and discharge.
[0002]
[Prior art]
Lithium ion secondary batteries, which are representative of non-aqueous electrolyte secondary batteries, are mainly used as power sources for portable devices such as VTR cameras, notebook computers, and mobile phones, taking advantage of the high energy density. The internal structure of the lithium ion secondary battery is usually a winding type as shown below. The electrode has a strip shape in which the active material is applied to a metal foil (current collector) for both the positive electrode and the negative electrode, and the cross section is wound in a spiral shape so that the positive electrode and the negative electrode are not in direct contact via the separator. A group is formed. This wound group is accommodated in a cylindrical battery can serving as a battery container, and sealed after injecting the electrolyte.
[0003]
A general cylindrical lithium ion secondary battery has a diameter of 18 mm and a height of 65 mm, which is called 18650 type, and is widely used as a small consumer lithium ion battery. The positive electrode active material of the 18650 type lithium ion secondary battery mainly uses lithium cobalt oxide, which is characterized by high capacity and long life. The battery capacity is approximately 1.3 Ah to 1.8 Ah, and the output is approximately 10 W. Degree.
[0004]
On the other hand, in the automobile industry, in order to cope with environmental problems, there are no exhaust gas, an electric vehicle that uses only a power source as a power source, and a hybrid (electric) vehicle that uses both an internal combustion engine and a battery as power sources. Development has been accelerated, and part of it has been put to practical use. A battery that serves as a power source for an electric vehicle is naturally required to have characteristics of obtaining high output and high energy that influence acceleration performance and the like, and a lithium ion battery is attracting attention as a battery that meets this requirement. For the spread of electric vehicles, it is indispensable to reduce the price of the battery. For example, in the case of a positive electrode active material, a resource-rich manganese oxide is particularly noticed, aiming to improve the performance of the battery. Improvements have been made. In addition, it is required to extend the life of the battery in order to cope with a long use period of the electric vehicle. The extension of the life here means satisfying not only the battery capacity but also the electric energy supply capability necessary for running the electric vehicle by reducing the deterioration rate of the output over a long period of time.
[0005]
[Problems to be solved by the invention]
However, in non-aqueous electrolyte secondary batteries with high capacity and high output, not only does the capacity and output decrease due to repeated charging and discharging, but also the crystalline structure of the active material during storage of the battery, particularly in high temperature environments. Since the reversibility of the active material that causes change and occludes and releases lithium ions decreases, the capacity and output decrease. In general, not only an electric vehicle but also an automobile has an overwhelmingly longer parking time in which a battery is not used than a boarding time in which the battery is used (vehicle driving time). For this reason, in order to extend the life of the battery, it is important to suppress a decrease in capacity and output during battery storage.
[0006]
An object of the present invention is to provide a non-aqueous electrolyte secondary battery that is excellent in output maintaining characteristics during storage of a battery while having high capacity and high output.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides: Lithium manganese complex oxide in which some of the manganese atoms in the crystal are replaced by cobalt atoms (Co) Positive electrode active material using Particle shape with an average particle diameter of 2 μm or more Apply almost equal amount of positive electrode active material mixture containing conductive material on both sides of current collector Then dry and press A negative electrode active material mixture containing a negative electrode active material that can absorb and release lithium ions by charging and discharging Then dry and press Non-aqueous electrolyte secondary battery infiltrated with negative electrode and non-aqueous electrolyte Because The above After press When the thickness of the positive electrode active material mixture is A (μm), the average particle diameter of the positive electrode active material is B (μm), and the average particle diameter of the conductive material is C (μm), the average particle diameter B Is A / 15> B ≧ 2C And B ≦ 3C It is in the range which satisfy | fills.
[0008]
In the present invention, in order to ensure high capacity and high output, Lithium manganese complex oxide in which some of the manganese atoms in the crystal are replaced by cobalt atoms (Co) Positive electrode active material using Particle shape with an average particle diameter of 2 μm or more Apply almost equal amount of positive electrode active material mixture containing conductive material on both sides of current collector Then dry and press A negative electrode active material mixture containing a negative electrode active material that can absorb and release lithium ions by charging and discharging Then dry and press The negative electrode is infiltrated with the non-aqueous electrolyte. According to the present invention, Since manganese is abundant in resources, the cost of the battery can be reduced by using a lithium manganese double oxide as the positive electrode active material, and a lithium manganese double oxide in which manganese sites in the crystal are replaced with Co. In addition, since the positive electrode active material has a stable crystal structure, it can improve output maintaining characteristics during battery storage, Average particle diameter B is A / 15> B ≧ 2C And B ≦ 3C By satisfying the range, the strain due to the crystal change of the positive electrode active material is between positive electrode active material particles in the thickness A (A> 15B) of the positive electrode active material mixture exceeding 15 times the average particle diameter B. Between the positive electrode active material particles without being obstructed by the conductive material having an average particle diameter C that is absorbed by the entire gap and is less than or equal to half the average particle diameter B existing between the positive electrode active material particles (B / 2 ≧ C) Therefore, it is possible to realize a non-aqueous electrolyte secondary battery having excellent output maintaining characteristics during battery storage.
[0009]
In this case , Lithium manganese oxide is represented by the general formula Li _{1 + x} Mn _2-xy Co _y O ₄ It is preferable to use a lithium manganese complex oxide where x is 0 <x ≦ 0.1 and y is 0 <y ≦ 0.25. Further, if the lithium manganese double oxide in which the crystal phase of lithium cobalt double oxide is mixed in the crystal, when the crystal shrinks due to the release of lithium ions, the crystal is in the lithium manganese double oxide crystal. Since the crystal phase of the expanding lithium cobalt acid complex oxide is mixed, the crystal structure of the entire lithium manganese complex oxide can be stabilized. The negative electrode active material is preferably graphite.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments in which the present invention is applied to a cylindrical lithium ion battery of an electric vehicle power source will be described below with reference to the drawings.
[0011]
(Preparation of positive electrode active material)
As lithium transition metal double oxide (positive electrode active material), lithium cobaltate (LiCoO) ₂ ), Lithium manganate (LiMn) ₂ O ₄ ), Lithium manganate in which the manganese site in the crystal is substituted with cobalt (hereinafter referred to as cobalt-substituted lithium manganate), and lithium manganate in which the crystal phase of lithium cobaltate is mixed in the crystal (hereinafter referred to as crystal phase) Mixed lithium manganate) was prepared as follows.
[0012]
Lithium cobaltate is cobalt oxide (Co ₃ O ₄ ) And lithium carbonate were sufficiently mixed so that the atomic ratio (Li / Co) of lithium and cobalt was 1, and the mixture was heated to 800 to 1000 ° C. in air.
[0013]
Lithium manganate is manganese oxide (MnO ₂ ) And lithium carbonate were sufficiently mixed so that the atomic ratio of lithium to manganese (Li / Mn) was 0.5, and heated to 800 to 1000 ° C. in air.
[0014]
The cobalt-substituted lithium manganate is obtained by filtering and drying a precipitate obtained by dissolving cobalt oxide and manganese oxide in an acid and coprecipitating as a carbonate, and then converting the obtained carbonate and lithium carbonate into lithium, It was prepared by sufficiently mixing so that the atomic ratio (Li / (Mn + Co)) with respect to the total amount of manganese and cobalt was 0.5 or more, and heating to 800 to 1000 ° C. in air. At this time, by changing the mixing ratio of cobalt oxide, manganese oxide and lithium carbonate, the cobalt-substituted lithium manganate having the elemental composition described later and the general formula are Li _{1 + x} Mn _2-xy Co _y O ₄ A lithium-excess cobalt-substituted lithium manganate represented by (x is 0 <x ≦ 0.1, y is 0 <y ≦ 0.25) was prepared.
[0015]
The crystal phase mixed lithium manganate is a mixture of manganese oxide, cobalt oxide and lithium carbonate, sufficiently mixed so that the atomic ratio of lithium and the total amount of manganese and cobalt exceeds 0.5, and 800-1000 ° in the air. Prepared by heating to C.
[0016]
Each of the prepared positive electrode active materials was confirmed in elemental composition by chemical analysis such as X-ray diffraction and ICP (Inductively Coupled Plasma) analysis. In addition to confirming the elemental composition of the crystalline phase-mixed lithium manganate, the lithium cobalt oxide particles and manganese were confirmed by EDX (Energy Dispersive X-ray Spectrometer), EPMA (Electron Probe Micro Analyzer), etc. It was confirmed that the crystal phase of lithium cobaltate was mixed in the crystal of lithium manganate, not the mixture with lithium acid particles. By pulverizing and classifying the prepared positive electrode active material, the average particle diameter of the positive electrode active material (hereinafter referred to as particle diameter B, unit μm) is set to the thickness of the positive electrode active material mixture described later (positive electrode current collector). In the following, A / 15 with respect to the average particle diameter (hereinafter referred to as particle diameter C, unit μm) of the graphite powder of the conductive material. Adjustment was made to satisfy> B ≧ 2C.
[0017]
(Preparation of positive electrode)
As shown in FIG. 1, a predetermined lithium transition metal double oxide powder, a graphite powder having a predetermined particle diameter C as a main conductive material and a secondary conductive material acetylene black, and polyvinylidene fluoride (a binder) as a binder (binder) Hereinafter, it is referred to as PVDF.) And a mass ratio of 85: 8: 2: 5 was mixed to obtain a positive electrode active material mixture. A slurry obtained by adding and kneading N-methyl-2-pyrrolidone (hereinafter referred to as NMP) as a dispersion solvent was applied to both sides of an aluminum foil W1 (positive electrode current collector) having a thickness of 20 μm in an approximately equal amount. At this time, an uncoated portion with a width of 30 mm was left on one side edge in the positive electrode longitudinal direction. Thereafter, drying, pressing, and cutting were performed to obtain a positive electrode having a width of 82 mm, a predetermined length, and a predetermined mixture thickness A. The porosity of the positive electrode active material mixture layer W2 after pressing was 30%. A notch was formed in the uncoated part, and the remaining part of the notch was used as the positive electrode lead piece 2. Adjacent positive electrode lead pieces 2 were spaced 50 mm apart, and the width of the positive electrode lead pieces 2 was 5 mm.
[0018]
(Preparation of negative electrode)
8 parts by mass of PVDF as a binder is added to 92 parts by mass of amorphous carbon or graphite as a negative electrode active material, NMP as a dispersion solvent is added thereto, and the kneaded slurry is rolled copper foil W3 (negative electrode) It was applied to both sides of the current collector. At this time, an uncoated part with a width of 30 mm was left on one side edge in the negative electrode longitudinal direction. Thereafter, drying, pressing and cutting were performed to obtain a negative electrode. The width of the negative electrode is larger than the width of the positive electrode so that the positive electrode active material mixture layer W2 does not protrude from the negative electrode active material mixture layer W4 in the direction perpendicular to the winding direction when wound as described later. The length was 86 mm, which was 4 mm longer. The amount of the negative electrode active material applied to the copper foil W3 was determined such that the amount of lithium ions released from the positive electrode during the initial charge of the battery and the amount of lithium ions stored in the negative electrode during the initial charge were 1: 1. . The porosity of the negative electrode active material mixture layer W4 after pressing was set to about 35%. A cutout was made in the uncoated portion in the same manner as the positive electrode, and the remaining cutout was used as the negative electrode lead piece 3. Adjacent negative electrode lead pieces 3 were spaced 50 mm apart, and the width of the negative electrode lead pieces 3 was 5 mm.
[0019]
(Production of battery)
The produced positive electrode and negative electrode were wound together with a polyethylene separator W5 having a width of 90 mm and a thickness of 40 μm so that the two electrodes do not directly contact each other. A hollow cylindrical shaft core 1 made of polypropylene was used at the center of winding. At this time, the positive electrode lead piece 2 and the negative electrode lead piece 3 were respectively positioned on opposite end surfaces of the wound group 6. Moreover, the length of the positive electrode, the negative electrode, and the separator was adjusted so that the diameter of the wound group 6 was 38 ± 0.1 mm. When winding, the length of the negative electrode is the same as that of the positive electrode so that the positive electrode does not protrude from the negative electrode in the winding direction at the innermost periphery of the winding and the positive electrode does not protrude from the negative electrode in the winding direction even at the outermost periphery. The length was 12 cm longer than the length.
[0020]
The positive electrode lead piece 2 was deformed, and all of the positive electrode lead pieces 2 were gathered and brought into contact with the vicinity of the collar surface projecting integrally from the periphery of the positive electrode current collecting ring 4 substantially on the extension line of the axis 1 of the winding group 6. Then, the positive electrode lead piece 2 and the buttocks circumferential surface were ultrasonically welded to connect the positive electrode lead piece 2 to the buttocks circumferential surface. On the other hand, the connection operation between the negative electrode current collection ring 5 and the negative electrode lead piece 3 was performed in the same manner as the connection operation between the positive electrode current collection ring 4 and the positive electrode lead piece 2.
[0021]
Thereafter, an insulation coating was applied to the entire circumference of the collar peripheral surface of the positive electrode current collecting ring 4. For this insulation coating, an adhesive tape in which the base material was polyimide and an adhesive made of hexamethacrylate was applied on one side thereof was used. One or more layers of this adhesive tape were wound from the circumferential surface of the collar portion to the outer circumferential surface of the wound group 6 to form an insulating coating, and the wound group 6 was inserted into the battery container 7. The battery container 7 was a steel bottomed can having an outer diameter of 40 mm, an inner diameter of 39 mm, and plated with nickel.
[0022]
A negative electrode lead plate 8 for electrical continuity is welded to the negative electrode current collecting ring 5 in advance, and after inserting the wound group 6 into the battery container 7, the bottom of the battery container 7 and the negative electrode lead plate 8 are welded. .
[0023]
On the other hand, one end of a positive electrode lead 9 formed by previously superposing a plurality of aluminum ribbons is welded to the positive electrode current collecting ring 4, and the other end of the positive electrode lead 9 is sealed with a battery container 7. Welded to the bottom of the lid. The battery lid is provided with a cleavage valve 11 as an internal pressure release mechanism that cleaves in response to an increase in the internal pressure of the battery. The battery lid is composed of a lid case 12, a lid cap 13, an airtight valve presser 14, and a cleavage valve 11. The battery lid is laminated and assembled by crimping the periphery of the lid case 12. Yes. In this embodiment, the cleavage pressure of the cleavage valve 11 is about 9 × 10. ⁵ Pa was set.
[0024]
A predetermined amount of non-aqueous electrolyte is injected into the battery container 7, and then the battery container 7 is covered with a battery cover so that the positive electrode lead 9 is folded, and then crimped and sealed with an EPDM resin gasket 10. A cylindrical lithium ion battery 20 was completed.
[0025]
The non-aqueous electrolyte includes lithium hexafluorophosphate (LiPF) in a mixed solvent of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1. ₆ ) Was dissolved at 1 mol / liter. The lithium ion battery 20 is electrically operated in response to an increase in battery temperature, for example, a PTC (Positive Temperature Coefficient) element, or a positive or negative electrical lead is disconnected in response to an increase in battery internal pressure. There is no current interruption mechanism.
[0026]
【Example】
Next, examples of the cylindrical lithium ion battery 20 produced by changing the mixture thickness A, the particle diameter B, and the particle diameter C according to the present embodiment will be described. In addition, it describes together about the battery of the comparative example produced for the comparison.
[0027]
(Example 1)
As shown in Table 1 below, in the battery of Example 1, lithium cobaltate powder was used as the positive electrode active material, the particle diameter B was 8 μm, the particle diameter C was 4 μm, and the mixture thickness A was 150 μm. Amorphous carbon was used as the negative electrode active material. The particle diameter B satisfies A / 15> B ≧ 2C.
[0028]
[Table 1]

[0029]
(Examples 2-3)
As shown in Table 1, the batteries of Examples 2 to 3 were the same as the battery of Example 1 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 2, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 3, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0030]
(Example 4)
As shown in Table 1, the battery of Example 4 was the same as the battery of Example 1 except that lithium manganate powder was used as the positive electrode active material.
[0031]
(Examples 5-6)
As shown in Table 1, the batteries of Examples 5 to 6 were the same as the battery of Example 4 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 5, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 6, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0032]
(Example 7)
As shown in Table 1, in the battery of Example 7, cobalt-substituted lithium manganate (LiMn) was used as the positive electrode active material. _1.8 Co _0.2 O ₄ ) The battery was the same as in Example 1 except that powder was used.
[0033]
(Examples 8 to 9)
As shown in Table 1, the batteries of Examples 8 to 9 were the same as the battery of Example 7 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 8, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 9, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0034]
(Example 10)
As shown in Table 1, in the battery of Example 10, lithium-excess cobalt-substituted lithium manganate (Li _1.01 Mn _1.98 Co _0.01 O ₄ ) The battery was the same as in Example 1 except that powder was used.
[0035]
(Examples 11 to 12)
As shown in Table 1, the batteries of Examples 11 to 12 were the same as the battery of Example 10 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 11, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 12, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0036]
(Example 13)
As shown in Table 1, in the battery of Example 13, lithium-excess cobalt-substituted lithium manganate (Li _1.05 Mn _1.85 Co _0.1 O ₄ ) The battery was the same as in Example 1 except that powder was used.
[0037]
(Examples 14 to 15)
As shown in Table 1, the batteries of Example 14 to Example 15 were the same as those of Example 13 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 14, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 15, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0038]
(Example 16)
As shown in Table 1, in the battery of Example 16, lithium-excess cobalt-substituted lithium manganate (Li _1.1 Mn _1.65 Co _0.25 O ₄ ) The battery was the same as in Example 1 except that powder was used.
[0039]
(Examples 17 to 18)
As shown in Table 1, the batteries of Examples 17 to 18 were the same as the battery of Example 16 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 17, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 18, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0040]
(Example 19)
As shown in Table 1, in the battery of Example 19, lithium-excess cobalt-substituted lithium manganate (Li _1.12 Mn _1.61 Co _0.27 O ₄ ) The battery was the same as in Example 1 except that powder was used.
[0041]
(Examples 20 to 21)
As shown in Table 1, the batteries of Example 20 to Example 21 were the same as those of Example 19 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 20, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 21, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0042]
(Example 22)
As shown in Table 1, in the battery of Example 22, lithium-excess cobalt-substituted lithium manganate (Li _1.05 Mn _1.85 Co _0.1 O ₄ The battery of Example 1 was used except that the crystal phase mixed lithium manganate powder in which the crystal phase of lithium cobaltate was mixed in the crystal of).
[0043]
(Examples 23 to 24)
As shown in Table 1, the batteries of Example 23 to Example 24 were the same as those of Example 22 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 23, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 24, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0044]
(Example 25)
As shown in Table 1, the battery of Example 25 was the same as the battery of Example 13 except that graphite was used as the negative electrode active material.
[0045]
(Examples 26 to 27)
As shown in Table 1, the batteries of Examples 26 to 27 were the same as the battery of Example 25 except that the mixture thickness A, particle diameter B, and particle diameter C were changed. In the battery of Example 26, the particle diameter B is 6 μm, the particle diameter C is 2 μm, and the mixture thickness A is 100 μm. In the battery of Example 27, the particle diameter B is 14 μm, the particle diameter C is 5 μm, and the mixture thickness. The thickness A was 220 μm.
[0046]
(Comparative Example 1)
As shown in Table 1, the battery of Comparative Example 1 was the same as the battery of Example 1 except that the particle diameter B was 14 μm and the particle diameter C was 10 μm.
[0047]
(Comparative Example 2)
As shown in Table 1, the battery of Comparative Example 2 was the same as the battery of Example 13 except that the particle diameter B was 14 μm and the particle diameter C was 10 μm.
[0048]
(Comparative Example 3)
As shown in Table 1, the battery of Comparative Example 3 was the same as the battery of Example 13 except that the particle diameter B was 10 μm, the particle diameter C was 5 μm, and the mixture thickness A was 100 μm.
[0049]
<Test and evaluation>
Next, the following series of tests were performed for each of the batteries of Examples and Comparative Examples.
[0050]
The batteries of Examples and Comparative Examples were charged and then discharged, and the discharge capacity was measured. The charging conditions were a constant current continuous charge at a current of 40 mA per 1 g of the positive electrode active material and a constant voltage charge of 4.2 V as soon as the battery voltage reached 4.2 V. The charging time was 5 hours. The discharge conditions were a continuous discharge at a current of 40 mA per 1 g of the positive electrode active material, and a final voltage of 2.8V.
[0051]
After charging under the above-described charging conditions, the discharge output of the charged battery was measured. In the measurement, the voltage at the 5th second is read at currents of 40 mA, 80 mA, and 160 mA per 1 g of the positive electrode active material, the voltage at the 5th second is plotted on the vertical axis against the current value on the horizontal axis, and an approximate straight line connecting the three points is obtained. The product of the current value at the intersection of 2.8V and 2.8V was used as the output.
[0052]
As a life test, the output was measured for each battery charged after repeating the charge / discharge cycle 100 times under the above-mentioned conditions, and the output was further measured after being stored for one month at 40 ° C, before the charge / discharge cycle. The output percentage after the charge / discharge cycle with respect to the output was defined as the output maintenance ratio. Of course, the higher the output maintenance ratio, the better the life characteristics.
[0053]
Charging, discharging, and output were all measured in an atmosphere having an environmental temperature of 25 ± 1 ° C. The measurement results of the output retention rate are shown in Table 2 below.
[0054]
[Table 2]

[0055]
As shown in Tables 1 and 2, in the batteries of Examples 1 to 27 in which the mixture thickness A, the particle diameter B, and the particle diameter C satisfy A / 15> B ≧ 2C, all have high output maintenance ratios. Obtained. On the other hand, in the batteries of Comparative Examples 1 to 3 that did not satisfy A / 15> B ≧ 2C, the output maintenance ratio decreased. Moreover, in the batteries of Examples 4 to 6 using lithium manganese oxide, which is a lithium manganese complex oxide, as the positive electrode active material, a higher output retention rate was obtained than the batteries of Examples 1 to 3 using lithium cobaltate.
[0056]
Moreover, in the batteries of Examples 7 to 9 using cobalt-substituted lithium manganate, a higher output retention rate was obtained than the batteries of Examples 4 to 6 using lithium manganate not substituted with cobalt. This is considered to be because the crystal structure of lithium manganate was stabilized by cobalt substitution. Furthermore, the general formula is Li _{1 + x} Mn _2-xy Co _y O ₄ In the batteries of Examples 10 to 18 using lithium-excess cobalt-substituted lithium manganate represented by (x is 0 <x ≦ 0.1, y is 0 <y ≦ 0.25), the cobalt-substituted lithium manganate As compared with the batteries of Examples 7 to 9 using the above, a higher output retention rate was obtained. However, in the batteries of Examples 19 to 21 in which x in the general formula exceeded 0.1 and y exceeded 0.25, the output retention ratio tended to decrease slightly.
[0057]
Furthermore, in the batteries of Examples 22 to 24 using the lithium manganate with mixed crystal phases, the batteries of Examples 13 to 15 using cobalt-substituted lithium manganate with no mixed crystal phases of lithium cobaltate were further used. A high output retention rate was obtained. This is because lithium cobalt oxide double oxide, in which the crystal shrinks when lithium ions are released from the crystal lattice, and the crystal expands due to repulsion of oxygen atoms when lithium ions are released from the crystal with a layered structure. This is considered to be because the crystal structure of the entire lithium manganese complex oxide was stabilized. Moreover, in the batteries of Examples 25 to 27 using graphite as the negative electrode active material, the output retention ratio was improved as compared with the batteries of Examples 13 to 15 using amorphous carbon.
[0058]
As described above, in the lithium ion battery of the present embodiment, the positive electrode using the lithium transition metal double oxide as the positive electrode active material and the negative electrode using graphite as the negative electrode active material were infiltrated into the non-aqueous electrolyte. Therefore, high capacity and high output can be obtained. Further, since the particle diameter B is in a range satisfying A / 15> B ≧ 2C with respect to the mixture thickness A and particle diameter C, the output retention rate is excellent even when stored for a long time.
[0059]
That is, A / 15> B indicates that when the mixture thickness A exceeds 15 times the particle diameter B (A> 15B), the strain due to crystal change of the positive electrode active material particles is within the thickness of the positive electrode active material mixture. It is absorbed in the entire gap between the positive electrode active material particles. On the other hand, B ≧ 2C is a conductive material in which strain due to crystal change of the positive electrode active material particles exists between the positive electrode active material particles when the particle size C is equal to or less than half of the particle size B (B / 2 ≧ C). It means that it is absorbed in the gaps between the positive electrode active material particles without being obstructed by the particles. Further, B ≧ 2C will be described in detail. As shown in FIG. 2, the space between the actual positive electrode active material particles is formed so that a space S is formed between the particles even when the positive electrode active material particles P are closely packed. The size of the conductive material particles entering is taken into account.
[0060]
Moreover, in the lithium ion battery of this embodiment, an output maintenance factor can be improved from the battery using lithium cobalt double oxide by using lithium manganese double oxide as a positive electrode active material. Furthermore, the output maintenance factor can be further improved by using a lithium manganese complex oxide in which manganese sites in the crystal are substituted with cobalt. At this time, the general formula Li _{1 + x} Mn _2-xy Co _y O ₄ By using a lithium manganese complex oxide represented by (x is 0 <x ≦ 0.1, y is 0 <y ≦ 0.25), the output maintenance ratio can be further improved. Moreover, the outstanding output maintenance factor can be obtained by using graphite for a negative electrode active material.
[0061]
Furthermore, the lithium manganese oxide crystal of the lithium manganese complex oxide and the lithium cobalt oxide crystal of the lithium cobalt complex oxide exhibit opposite behavior in terms of crystal change accompanying charge / discharge. That is, as shown in Table 3 below, lithium manganate crystals contract during charging and expand during discharge, while lithium cobaltate crystals expand during charging and contract during discharge. For this reason, the crystal structure of the whole positive electrode active material is stabilized. Therefore, the output maintenance factor can be further improved by using the lithium manganese double oxide in which the crystal phase of the lithium cobalt double oxide is mixed in the crystal of the lithium manganese double oxide.
[0062]
[Table 3]

[0063]
In the present embodiment, a large secondary battery used for a power source for an electric vehicle is illustrated, but the present invention is not limited to the size and battery capacity of the battery, and the battery capacity generally exceeds 3 Ah. It has been confirmed that the effect is remarkably exhibited. Further, in the present embodiment, the cylindrical battery is illustrated, but the present invention is not limited to the shape of the battery, and can be applied to a rectangular battery or other polygonal batteries. Furthermore, the shape to which the present invention can be applied may be other than a battery having a structure in which the upper lid of the battery is sealed by caulking in the above-described bottomed cylindrical container (can). An example of such a structure is a battery in which positive and negative external terminals pass through the battery lid and the positive and negative external terminals are pressed against each other through an axis in the battery container.
[0064]
Moreover, although lithium manganate having a Li / Mn ratio of 0.5 was exemplified as the lithium manganese composite oxide, the present invention is not limited to this, and the charging ratio of lithium salt and manganese oxide is controlled. Thus, lithium manganate having a desired Li / Mn ratio can be used. Furthermore, in this embodiment, lithium cobaltate was exemplified as the lithium transition metal composite oxide other than the lithium manganese composite oxide, but the present invention is not limited to this, and lithium nickelate or a part of nickel is used. Those substituted or doped with other elements can also be used. Moreover, although the example which substituted the manganese site in the crystal | crystallization of lithium manganese complex oxide with cobalt was shown, you may make it dope cobalt in a crystal | crystallization.
[0065]
Furthermore, there is no restriction | limiting in particular as the negative electrode active material for lithium ion batteries which can be used except this embodiment other than the matter described in the said claim. For example, natural graphite, various artificial graphite materials, carbonaceous materials such as coke, amorphous carbon, etc. may be used, and the particle shape is not particularly limited, such as scaly, spherical, fibrous, massive, etc. Absent.
[0066]
Furthermore, in this embodiment, graphite powder is exemplified as the conductive material, but the present invention is not limited to this, and for example, a commonly used carbon material such as amorphous carbon may be used. .
[0067]
Furthermore, as an electrode plate active material binder for lithium ion batteries that can be used in other embodiments, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, There are polymers such as polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, polyvinyl alcohol, and modified or mixed products thereof.
[0068]
Moreover, in this embodiment, although the base material is a polyimide and the example which used the adhesive tape which apply | coated the adhesive which consists of hexamethacrylate to the one side was shown for insulation coating, for example, a base material is polypropylene, polyethylene, etc. In particular, an adhesive tape in which an acrylic adhesive such as hexamethacrylate or butyl acrylate is applied to one or both surfaces thereof, a tape made of polyolefin or polyimide to which no adhesive is applied, and the like can be suitably used.
[0069]
Furthermore, as the non-aqueous electrolyte, a solution in which 1 mol / liter of lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1: 1: 1 is exemplified. The battery of the invention is not particularly limited, and an electrolytic solution in which a general lithium salt is used as an electrolyte and this is dissolved in an organic solvent is used. However, the lithium salt and organic solvent used are not particularly limited. For example, as an electrolyte, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li or the like or a mixture thereof can be used. Nonaqueous electrolyte organic solvents include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3- Dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile and the like or a mixed solvent of two or more of these may be used, and the mixing ratio is not limited.
[0070]
【The invention's effect】
As explained above, according to the present invention, Since manganese is abundant in resources, the cost of the battery can be reduced by using a lithium manganese double oxide as the positive electrode active material, and a lithium manganese double oxide in which manganese sites in the crystal are replaced with Co. In addition, since the positive electrode active material has a stable crystal structure, it can improve output maintaining characteristics during battery storage, Average particle diameter B is A / 15> B ≧ 2C And B ≦ 3C By satisfying the range, the strain due to the crystal change of the positive electrode active material is between positive electrode active material particles in the thickness A (A> 15B) of the positive electrode active material mixture exceeding 15 times the average particle diameter B. Between the positive electrode active material particles without being obstructed by the conductive material having an average particle diameter C that is absorbed by the entire gap and is less than or equal to half the average particle diameter B existing between the positive electrode active material particles (B / 2 ≧ C) Because it is absorbed in the gap , Electric The effect that the nonaqueous electrolyte secondary battery excellent in the output maintenance characteristic at the time of pond preservation | save is realizable can be acquired.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion battery according to an embodiment to which the present invention is applicable.
FIG. 2 is an explanatory view schematically showing a state of closest packing of positive electrode active material particles.
[Explanation of symbols]
6 Twist group
20 Cylindrical lithium ion battery (non-aqueous electrolyte secondary battery)
W1 Cathode current collector (current collector)
W2 cathode active material mixture layer
P positive electrode active material particles
S space

Claims (4)

A positive electrode active material using a lithium manganese complex oxide in which a part of manganese atoms in a crystal is substituted with a cobalt atom (Co) and a positive electrode active material mixture including a particulate conductive material having an average particle diameter of 2 μm or more are collected. A negative electrode that has been applied to both sides of an electrical conductor by applying an almost equal amount , dried and pressed, and a negative electrode active material mixture containing a negative electrode active material capable of occluding and releasing lithium ions by charge and discharge , and then dried and pressed . If, a non-aqueous electrolyte secondary battery that has infiltrated into non-aqueous electrolyte solution, the thickness of the positive electrode active material mixture after the press a ([mu] m), an average particle diameter of the positive electrode active material B (Μm), when the average particle diameter of the conductive material is C (μm), the average particle diameter B is in a range satisfying A / 15> B ≧ 2C and B ≦ 3C. Non-aqueous electrolyte secondary battery. The lithium manganese complex oxide is represented by the general formula Li _{1 + x} Mn _2−xy Co _y O ₄ (x is 0 <x ≦ 0.1, y is 0 <y ≦ 0.25). The non-aqueous electrolyte secondary battery according to claim 1 . 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode active material contains a crystal phase of a lithium cobalt complex oxide in a crystal of a lithium manganese complex oxide. . The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3 , wherein the negative electrode active material is graphite.

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