JP3959774B2 - Non-aqueous electrolyte and secondary battery using the same - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は過充電や短絡等の異常時に起きる熱暴走をくい止めることができる新規な非水電解液およびそれを用いた非水電解液二次電池に関するものである。このものは特に電気自動車用大型電池およびそれに用いる電解液に有用である。
【０００２】
【従来の技術】
近年非水電解液を用いた二次電池は、高電圧・高エネルギー密度を有し、かつ貯蔵性に優れていることから、ハンディビデオカメラや携帯用パソコン等の民生用電子機器の電源として広く用いられている。さらには環境問題等から電気自動車が注目を集めており、エネルギー密度が高く、かつ密閉型でメンテナンスフリーの非水電解液二次電池を電気自動車用に用いることが提案されている。
【０００３】
かかる非水電解液二次電池の電解液の溶媒には誘電率が高く電解質を溶媒和しやすい高誘電率溶媒（例えばエチレンカーボネートやプロピレンカーボネート）に、電解液の粘度を下げてイオンの伝導度を上げるための低粘度溶媒（例えば、1,2-ジメトキシエタン、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネート等）を混合したものが一般に用いられており、できる限り電解液の導電率を高めるべく溶媒の種類や配合比、電解質の種類や濃度が選択されている。また、自己放電特性等、電池の保存特性を改善する目的で各種の添加剤を添加することが行われている（特開平８ー３２１３１１号、同８ー３２１３１２号及び同８ー３２１３１３号）。
【０００４】
しかしながら電池の安全性を考えた場合、電解液は導電率だけでなく耐電圧性が重要になってくる。すなわち電池に電池電圧を上回る高電圧や通常値を上回る高電流が負荷された場合でも、十分耐えうるものであることが必要である。例えば電源回路や充電器の故障、あるいはユーザーの誤使用によって所定以上の電気量が負荷されて過充電状態になったり、外部あるいは内部短絡などにより通常値を上回る大電流が流れたりすると電極表面で電解液が分解されガス発生や分解時の熱発生が起き、さらにこの状態が継続されると電池の破裂・発火につながる。特に正極に通常用いられているＬｉＣｏＯ2 、ＬｉＮｉＯ2 あるいはＬｉＭｎ2 Ｏ4 等のリチウムと遷移金属の複合酸化物は過充電時に不安定な酸化物となり酸素を放出する事が知られている。（例えばＪ．Ｒ．Ｄａｈｎ ｅｔ ａｌ．， Ｓｏｌｉｄ Ｓｔａｔｅ Ｉｏｎｉｃｓ ６９（１９９４）２６５）従って過充電時には電解液が正極上で酸化分解されて大きな発熱が起こり熱暴走反応につながっていくと考えられる。しかし前述の従来用いられている電解液は、耐酸化性に劣り、電池の安全性、信頼性の観点からは十分満足のいくものとは言えない。
【０００５】
【発明が解決しようとする課題】
本発明は電池の過充電や短絡等の異常時に起きる熱暴走をくい止めることのできる電解液および、その電解液を用いることによって安全性に優れた非水電解液二次電池を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明は、負極と、正極活物質としてリチウムと遷移金属の複合酸化物を含む正極と、電解液を有する非水系電解液二次電池に用いられる非水電解液であって、比誘電率が５０以上の高誘電率溶媒か、あるいは比誘電率５０以上の高誘電率溶媒と２５℃における粘度が１センチポイズ以下の低粘度溶媒とを混合した電解質溶媒に電解質を溶かした電解液に、一般式Ｉ
【０００７】
【化４】
（式中、Ｒ1は、炭素数４以上の炭化水素基を表し、Ｒ2及びＲ3は、水素原子又は電子供与性基を表し、互いに異なっていてもよい）
で示されるフェノール系酸化防止剤、
一般式II
【０００９】
【化５】
（式中、Ｒ4は、炭素数３以上の炭化水素基を表し、Ｒ5及びＲ6は、互いに異なっていてもよい炭化水素基を表わす）
で示されるホスファイト系酸化防止剤、並びに、
一般式III
【００１１】
【化６】
（式中、Ｒ７は、炭素数３以上の炭化水素基を表し、Ｒ８は、炭化水素基を表し、ｎは、１又は２を表す。ただし、１，８−ジスルフィドナフタレンを除く。）
で示されるスルフィド系酸化防止剤からなる群から選ばれた１種の化合物または２種以上の化合物を電解液中の濃度として、０．０１から１０重量％含有することを特徴とする非水電解液、を提供するものである。
また、本発明は、負極と、正極と、電解液を有し、１ｍＡ／ｃｍ ２ の定電流密度で電池電圧が５Ｖに到達するまで充電したときの、電池内部温度が最高７０℃以下の非水系電解液二次電池に用いられる非水電解液であって、比誘電率が５０以上の高誘電率溶媒か、あるいは比誘電率５０以上の高誘電率溶媒と２５℃における粘度が１センチポイズ以下の低粘度溶媒とを混合した電解質溶媒に電解質を溶かした電解液に、一般式Ｉ
【化１０】
【化１１】
【化１２】
さらに、本発明は、比誘電率が５０以上の高誘電率溶媒か、あるいは比誘電率５０以上の高誘電率溶媒と２５℃における粘度が１センチポイズ以下の低粘度溶媒とを混合した電解質溶媒に電解質を溶かした電解液に、一般式 III
【化１３】
【００１３】
【作用】
上記構成の非水電解液とすることにより、二次電池の異常時即ち過充電時や電池の短絡時に発生する発熱が抑えられ、安全性に優れた非水電解液二次電池が提供できる。
【００１４】
【発明の実施の形態】
以下、本発明を詳細に説明する。
比誘電率が５０以上、好ましくは５０〜１００の高誘電率溶媒としては例えば、プロピレンカーボネートあるいはエチレンカーボネートがあげられ、これらのどちらかの溶媒または両者のいずれでも使用可能である。
【００１５】
電解質溶媒としてはこの高誘電率溶媒のみでもいいが、さらに、２５℃における粘度が１センチポイズ以下の低粘度溶媒を上記高誘電率溶媒に対して９０％以下、好ましくは９０〜１０％の比率で、併用すると導電率が向上しより好ましい。低粘度溶媒の比率が大きくなると、今度は電解質の解離度が下がり電導度が低下することから、通常上記の範囲でで用いられる。２５℃における粘度が１センチポイズ以下の低粘度溶媒としては1,2-ジメトキシエタン、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネート等が用いられ、これらの１種または２種以上の混合溶媒が使用可能である。
【００１６】
また電解質としては例えば、ＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＢＦ4、ＬｉＢ（Ｃ6Ｈ5）4、ＬｉＣｌ、ＬｉＢｒ、ＣＨ3ＳＯ3ＬｉおよびＣＦ3ＳＯ3Ｌｉ等のリチウム塩が単独もしくは２種以上を混合して用いられる。
電解液中の電解質の濃度は、通常、０．１〜３モル／ｌ、好ましくは０．５〜１．５モル／ｌである。
本発明において電解液に存在させるフェノール系酸化防止剤は下記式Ｉに示される水酸基の２つのオルト位の少なくとも片方にかさ高い炭素数４以上の炭化水素基を有する特徴がある。
【００１７】
【化７】
Ｒ1は、炭素数４以上の炭化水素基であり、好ましくは、炭素数４〜１５、特に好ましくは炭素数４〜１０の脂肪族炭化水素基が挙げられる。具体的には、ｔ−ブチル基、フェニル基、ｔ−ブチルフェニル基等が挙げられる。Ｒ2及びＲ3は、水素原子又は電子供与性基であり、互いに異なっていても良く、電子供与性基としては、具体的には、メチル基、エチル基等の炭素数１〜１５の、好ましくは炭素数１〜１０のアルキル基、メトキシ基、エトキシ基等の炭素数１〜５のアルコキシ基等が挙げられる。具体的には、例えば、２，６−ジ−ｔ−ブチルフェノール、２−ｔ−ブチル−４−メトキシフェノール、２，４−ジメチル−６−ｔ−ブチルフェノール、２，６−ジ−ｔ−ブチル−ｐ−クレゾール、２，６−ジ−ｔーブチル−４−エチルフェノール等が挙げられる。
【００１９】
またホスファイト系酸化防止剤は、下記式IIに示されるリンに３つのアルコキシ基がついた亜リン酸エステルの基本骨格を持ち、少なくとも一つのアルコキシ基の炭素数が３以上のかさ高い炭化水素基であることを特徴とする。
【００２０】
【化８】
Ｒ4は、炭素数３以上の炭化水素基であり、好ましくは、プロピル基、ｔ−ブチル基等の炭素数３〜１５の、好ましくは炭素数３〜１０のアルキル基、フェニル基、ｔ−ブチルフェニル基、トリメチルフェニル基、ジメチルフェニル基等の炭素数６〜１５の置換基を有していてもよいアリール基等が挙げられる。Ｒ5及びＲ6は、炭化水素基であり、互いに異なっていても良く、好ましくは、メチル基、エチル基、プロピル基、ｔ−ブチル基等の炭素数１〜１５の、好ましくは炭素数１〜１０のアルキル基、フェニル基、ｔ−ブチルフェニル基、トリメチルフェニル基、ジメチルフェニル基等の炭素数６〜１５の置換基を有していてもよいアリール基等が挙げられる。
【００２２】
具体的には、例えば、フェニルジイソアルキル（Ｃ１〜Ｃ１０）ホスファイト、ジフェニルイソアルキル（Ｃ１〜Ｃ１０）ホスファイト、トリフェニルホスファイト、トリス−（２，４−ジ−ｔ−ブチルフェニル）ホスファイト等が挙げられる。またスルフィド系酸化防止剤は下記式IIIで示される少なくとも一つの炭素数３以上の大きな脂肪族炭化水素基を有することを特徴とするジスルフィドである。
【００２３】
【化９】
Ｒ7は、炭素数３以上の炭化水素基であり、好ましくは、プロピル基、ｔ−ブチル基等の炭素数３〜１５の、好ましくは炭素数３〜１０のアルキル基、フェニル基、ｔ−ブチルフェニル基、トリメチルフェニル基等の炭素数６〜１５の置換基を有していてもよいアリール基が挙げられる。Ｒ8は、炭化水素基であり、好ましくは、メチル基、エチル基、プロピル基、ｔ−ブチル基等の炭素数１〜１５の、好ましくは炭素数１〜１０のアルキル基、フェニル基、ｔ−ブチルフェニル基、トリメチルフェニル基等の炭素数６〜１５の置換基を有していてもよいアリール基等が挙げられる。
【００２５】
具体的には、例えば、ジフェニルジスルフィド等が挙げられる。なお、上記した各一般式（Ｉ）、（II）及び（III）で示される酸化防止剤は、その酸化防止機能を発現する限りにおいて、任意の置換基を有していてもよい。電池の異常時、すなわち例えば電源回路や充電器の故障、あるいはユーザーの誤使用によって所定以上の電気量が負荷されて過充電状態になったり、外部あるいは内部短絡などにより通常値を上回る大電流が流れた際には、電極表面で電解液が分解されガス発生や分解時の熱発生が起る。特に正極に通常用いられているＬｉＣｏＯ2、ＬｉＮｉＯ2あるいはＬｉＭｎ2Ｏ4等のリチウムと遷移金属の複合酸化物は過充電時に不安定な酸化物となり活性な酸素を放出し、電解液を酸化分解するため大きな発熱が生じる。これらの電解液の分解反応はラジカル連鎖反応と考えられ、一旦反応が始まると電池が熱暴走する可能性が高い。
【００２６】
本発明に用いられる酸化防止剤は電解液が分解して生じるペルオキシラジカルあるいはヒドロペルオキシド等の活性な有機ラジカルと反応し、熱暴走に至る連鎖反応をくい止めることができる。
すなわち、電解液に添加するフェノール系酸化防止剤は構造式Ｉのように水酸基の２つのオルト位のすくなくとも片方にかさ高いｔ−炭化水素基を有するため、電池の異常時に電解液の分解によって生じるペルオキシラジカルと反応し、水酸基の水素原子がとれて自身が比較的安定なラジカルになる。つまり活性なラジカルを捕捉するラジカル安定化剤として働くため電解液の分解によって起きる連鎖反応、すなわち暴走反応をくい止めることができる。もし２つのオルト位のどちらにもこのようなかさ高い基を有しないフェノール系化合物を用いてもペルオキシラジカルを有効に捕捉できない。
【００２７】
また、ホスファイト系酸化防止剤およびスルフィド系酸化防止剤はリンあるいはイオウの非共有電子対が、電解液が分解して生じるペルオキシラジカルあるいはヒドロペルオキシド等の活性な有機ラジカルと反応するため不活性な生成物を作ることができる。また構造式IIや構造式III で表されるように酸化防止剤が大きな置換基を有する必要があるのは、これらの化合物の反応性を下げ、効果の持続性を高めると共に、本来の電池反応に悪影響を与えないためである。
【００２８】
なお電解液中に加える酸化防止剤の添加量は少なすぎると効果がなく、下限を０．０１重量％、より好ましくは、０．０５重量％にする必要がある。逆に多すぎると電解液の導電率を下げるため電池の性能劣化につながるので、上限は１０重量％、より好ましくは５重量％とする必要がある。
図１に、二次電池の一例を示す。図中、１は、負極集電体、２は負極、３はセパレータ、４は正極集電体、５は正極、６は電解液、７はポリプロピレン容器、８は正電極、９は負電極である。
【００２９】
非水電解液二次電池を構成する負極としては、通常、負極活物質と結着剤（バインダー）とを溶媒でスラリー化したものを集電体に塗布し、乾燥してシート状にしたものが使用される。負極活物質としては、リチウムおよびリチウム合金であっても良いが、より安全性の高いリチウムイオンを吸蔵、放出できる炭素材料が好ましい。この炭素材料は特に限定されないが、黒鉛及び、石油系コークス、石炭系コークス、石油系ピッチの炭化物、石炭系ピッチの炭化物、フェノール樹脂・結晶セルロース等樹脂の炭化物等およびこれらを一部炭化した炭素材、ファーネスブラック、アセチレンブラック、ピッチ系炭素繊維、ＰＡＮ系炭素繊維等が挙げられる。
【００３０】
正極としては、通常、正極活物質と結着剤（バインダー）と導電材とをスラリー化したものを集電体に塗布し、乾燥してシート状にしたものが使用される。正極活物質としては、リチウムと遷移金属の複合酸化物が好ましく、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4、ＬｉＭｎＯ2、ＬｉＶ2Ｏ3等が使用可能である。
負極および正極活物質の結着剤（バインダー）としては、例えば、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、ＥＰＤＭ（エチレン−プロピレン−ジエン三元共重合体）、ＳＢＲ（スチレン−ブタジエンゴム）、ＮＢＲ（アクリロニトリル−ブタジエンゴム）、フッ素ゴム等が掲げられるが、これらに限定されない。
【００３１】
正極の導電剤としては、黒鉛の微粒子、アセチレンブラック等のカーボンブラック、ニードルコークス等の無定形炭素の微粒子等が使用されるが、これらに限定されない。
スラリー化する溶媒としては、通常は結着剤を溶解する有機溶剤が使用される。例えば、Ｎ−メチルピロリドン、ジメチルホルムアミド、ジメチルアセトアミド、メチルエチルケトン、シクロヘキサノン、酢酸メチル、アクリル酸メチル、ジエチルトリアミン，Ｎ−Ｎ−ジメチルアミノプロピルアミン、エチレンオキシド、テトラヒドロフラン等を掲げる事ができるがこれらに限定されない。また、水に分散剤、増粘剤等を加えてＳＢＲ等のラテックスで活物質をスラリー化する場合もある。
【００３２】
負極の集電体には、通常、銅、ニッケル、ステンレス鋼、ニッケルメッキ鋼等が使用され、正極集電体には、通常、アルミニウム、ステンレス鋼、ニッケルメッキ鋼等が使用される。
【００３３】
【実施例】
以下、本発明を実施例を挙げてさらに詳細に説明するが、本発明は、その要旨を越えない限り以下の実施例によって限定されるものではない。尚、実施例中の評価方法は下記のとおりである。実施例および比較例中、「部」とあるのは「重量部」を示す。
【００３４】
（負極の製造）
平均粒径１０μｍの石炭系ニードルコークス９０部を、ポリフッ化ビニリデン１０部のＮ−メチルピロリドン溶液（２重量％）と混合し、負極合剤スラリーとした。２０μｍ厚さの銅箔の両面に塗布し、乾燥して溶媒を蒸発させ、ロール処理をして負極を作る。負極合剤の塗布部の大きさは縦１２ｃｍ、横１５ｃｍ、厚さは片面１２０μｍとした。また銅箔の左肩には、電極端子との接続用に縦２５ｍ、横１５ｍｍの耳を設けておいた。
【００３５】
（正極の製造）
まず炭酸リチウム１モルと炭酸コバルト２モルとをボールミルで混合粉砕し、８５０℃で５時間空気中で加熱処理後、再度ボールミルで混合粉砕し、更に８５０℃で５時間空気中で加熱処理してＬｉＣｏＯ2を得た。次にこのＬｉＣｏＯ2 ９０部に、導電剤としてアセチレンブラックを５部加えて混合したものをポリフッ化ビニリデン５部のＮ−メチルピロリドン溶液（２重量％）と混合し、正極合剤スラリーとした。２５μｍ厚さのアルミニウム箔の両面に塗布し、乾燥して溶媒を蒸発させ、ロール処理をして正極を作成した。正極合剤の塗布部の大きさは縦１２ｃｍ、横１５ｃｍ、厚さは片面１２０μｍとした。またアルミニウム箔の右肩には、電極端子との接続用に縦２５ｍ、横１５ｍｍの耳を設けておいた。
【００３６】
（電池の組立）
まず上記、負極と正極とを交互にセパレータを介して電気的に絶縁されるように積層した。積層は負極と正極を一組にした場合２５組とし、両端の電極は電極合剤を片面のみ塗布したものを使用した。次に負極及び正極の耳の部分をそれぞれ別々に束ね金属製電極端子に溶接した。
次にこの積層型電池をポリプロピレン製の容器に収納し、１×１０-2Ｔｏｒｒ以下で真空脱気した後、Ａｒガスで置換しておいたドライボックス中に投入した。さらに電解液を注入して、上蓋を閉めた。この時、上蓋を貫通して、各単電池の負極端子、正極の端子が容器の上部に突きだした形となる。最後にこの端子を上蓋の貫通部分で、適当な封止剤で封止し、積層型電池を作成した。
図１はこの積層型電池の断面の概念図である。なお電池の中央部には内部温度測定用の熱伝対を電極間に挿入しておいた。
【００３７】
【実施例１】
上記積層型電池を組み立てる際に用いる電解液にエチレンカーボネート（比誘電率９０）と１，２−ジメトキシエタン（比誘電率７．２、粘度（２５℃）０．４６ｃｐ）との体積割合１：１の混合溶媒に電解質としてヘキサフルオロリン酸リチウム塩（ＬｉＰＦ6）を１モル／ｌ溶解したものに、フェノール系酸化防止剤の２，６−ジ−ｔ−ブチル−ｐ−クレゾールを電解液中の濃度として、３重量％添加し溶解させたものを用いた。
この電池を２５℃の恒温槽において上限電池電圧５Ｖの過充電試験に供した。即ち、１ｍＡ／ｃｍ2の定電流密度で電池電圧が５Ｖに到達するまで充電し、電池内部温度と電池の様子を観察した。その結果内部温度は最高５０℃まで上昇したが、電流停止後温度が下がり電池に外観上の異常は見られなかった。
【００３８】
【実施例２】
電解液として、エチレンカーボネートと１，２−ジメトキシエタンとの体積割合１：１の混合溶媒に電解質としてヘキサフルオロリン酸リチウム塩（ＬｉＰＦ6）を１モル／ｌ溶解したものに、ホスファイト系酸化防止剤のトリフェニルホスファイトを電解液中の濃度として３重量％添加し溶解させたものを用いた他は実施例１と同様にして評価した。 その結果電池内部温度は最高７０℃まで上昇したが、電流停止後温度が下がり電池に外観上の異常は見られなかった。
【００３９】
【実施例３】
電解液として、エチレンカーボネートと１，２−ジメトキシエタンとの体積割合１：１の混合溶媒に電解質としてヘキサフルオロリン酸リチウム塩（ＬｉＰＦ6）を１モル／ｌ溶解したものに、スルフィド系酸化防止剤のジフェニルジスルフィドを電解液中の濃度として３重量％添加し溶解させたものを用いた他は実施例１と同様にして評価した。
その結果電池内部温度は最高７０℃まで上昇したが、電流停止後温度が下がり電池に外観上の異常は見られなかった。
【００４０】
【実施例４】
電解液として、エチレンカーボネートと１，２−ジメトキシエタンとの体積割合１：１の混合溶媒に電解質としてヘキサフルオロリン酸リチウム塩（ＬｉＰＦ6）を１モル／ｌ溶解したものに、フェノール系酸化防止剤の２，６−ジ−ｔ−ブチル−ｐ−クレゾールを２重量％、イオウ系酸化防止剤のジフェニルジスルフィドを電解液中の濃度として、１重量％添加し、溶解させたものを用いた他は実施例１と同様にして評価した。
その結果電池内部温度は最高４０℃まで上昇したが、電流停止後温度が下がり電池に外観上の異常は見られなかった。
【００４１】
【比較例１】
電解液として、エチレンカーボネートと１，２−ジメトキシエタンとの体積割合１：１の混合溶媒に電解質としてヘキサフルオロリン酸リチウム塩（ＬｉＰＦ6）を１モル／ｌ溶解したものを用いた他は実施例１と同様にして評価した。
その結果電池電圧が４．６Ｖに到達した時点で急激に電池内部温度が上昇しはじめ１８０℃に到達したときにセパレーターの溶融とみられる内部短絡により電圧が一気に０Ｖになるとともに、電池容器が破裂し、さらに発火が起きた。
【００４２】
【比較例２】
電解液として、エチレンカーボネートと１，２−ジメトキシエタンとの体積割合１：１の混合溶媒に電解質としてヘキサフルオロリン酸リチウム塩（ＬｉＰＦ6）を１モル／ｌ溶解したものに、クレゾールを３重量％添加し溶解させたものを用いた他は実施例１と同様にして評価した。
その結果電池電圧が４．７Ｖに到達した時点で急激に電池内部温度が上昇しはじめ１８０℃に到達したときにセパレーターの溶融とみられる内部短絡により電圧が一気に０Ｖになるとともに、電池容器が破裂しさらに発火が起きた。
【００４３】
【比較例３】
電解液にエチレンカーボネートと１，２−ジメトキシエタンとの体積割合１：１の混合溶媒に電解質としてヘキサフルオロリン酸リチウム塩（ＬｉＰＦ6）を１モル／ｌ溶解したものに、トリメチルホスファイトを３重量％添加し溶解させたものを用いた他は実施例１と同様にして評価した。
その結果電池電圧が４．８Ｖに到達した時点で急激に電池内部温度が上昇しはじめ１８０℃に到達したときにセパレーターの溶融とみられる内部短絡により電圧が一気に０Ｖになるとともに、電池容器が破裂しさらに発火が起きた。
【００４４】
【比較例４】
電解液として、エチレンカーボネートと１，２−ジメトキシエタンとの体積割合１：１の混合溶媒に電解質としてヘキサフルオロリン酸リチウム塩（ＬｉＰＦ6）を１モル／ｌ溶解したものに、ジメチルスルフィドを３重量％添加し溶解させたものを用いた他は実施例１と同様にして評価した。
その結果電池電圧が４．８Ｖに到達した時点で急激に電池内部温度が上昇しはじめ１８０℃に到達したときにセパレーターの溶融とみられる内部短絡により電圧が一気に０Ｖになるとともに、電池容器が破裂しさらに発火が起きた。
以上の結果をまとめて第１表に示す。
【００４５】
【表１】
【発明の効果】
電池の過充電や短絡等の異常時に起きる熱暴走をくい止めることができる電解液を用いているため、安全性に優れた非水電解液二次電池を得られる。
【図面の簡単な説明】
【図１】本発明の一実施例を示す積層型二次電池の断面図である。
【符号の説明】
１：負極集電体
２：負極
３：セパレータ
４：正極集電体
５：正極
６：電解液
７：ポリプロピレン容器
８：正電極
９：負電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel non-aqueous electrolyte solution capable of preventing thermal runaway that occurs when an abnormality such as overcharge or short-circuit occurs, and a non-aqueous electrolyte secondary battery using the same. This is particularly useful for large batteries for electric vehicles and electrolytes used therefor.
[0002]
[Prior art]
In recent years, secondary batteries using non-aqueous electrolytes have a high voltage, high energy density, and are excellent in storage, so they are widely used as power sources for consumer electronic devices such as handy video cameras and portable PCs. It is used. Furthermore, electric vehicles are attracting attention due to environmental problems and the like, and it has been proposed to use a non-aqueous electrolyte secondary battery having a high energy density and a maintenance type that is free of maintenance for electric vehicles.
[0003]
The electrolyte solvent of such a non-aqueous electrolyte secondary battery has a high dielectric constant and a high dielectric constant solvent (e.g., ethylene carbonate or propylene carbonate) that easily solvates the electrolyte. A mixture of low-viscosity solvents (for example, 1,2-dimethoxyethane, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, etc.) is generally used, and the solvent should be used to increase the conductivity of the electrolyte as much as possible. Type, compounding ratio, electrolyte type and concentration are selected. Various additives have been added for the purpose of improving the storage characteristics of the battery, such as self-discharge characteristics (Japanese Patent Application Laid-Open Nos. 8-321313, 8-321313, and 8-321313).
[0004]
However, considering the safety of the battery, not only the conductivity but also the withstand voltage becomes important for the electrolyte. That is, even when a high voltage exceeding the battery voltage or a high current exceeding the normal value is loaded on the battery, the battery needs to be able to withstand sufficiently. For example, if the power supply circuit or charger fails or the user misuses it and the battery is overcharged due to overload, or if a large current exceeding the normal value flows due to an external or internal short circuit, the electrode surface The electrolyte is decomposed to generate gas and heat at the time of decomposition, and if this state continues, it will lead to battery explosion and ignition. In particular, it is known that a composite oxide of lithium and a transition metal such as LiCoO 2 , LiNiO 2 or LiMn 2 O 4 usually used for a positive electrode becomes an unstable oxide during overcharge and releases oxygen. (For example, JR Dahn et al., Solid State Ionics 69 (1994) 265) Therefore, it is considered that during overcharging, the electrolyte is oxidized and decomposed on the positive electrode to generate a large amount of heat and lead to a thermal runaway reaction. However, the above-described electrolytic solution used in the past is inferior in oxidation resistance, and cannot be said to be sufficiently satisfactory from the viewpoint of battery safety and reliability.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide an electrolytic solution capable of preventing thermal runaway that occurs in the event of an abnormality such as overcharge or short circuit of a battery, and a non-aqueous electrolyte secondary battery excellent in safety by using the electrolytic solution. And
[0006]
[Means for Solving the Problems]
The present invention relates to a non-aqueous electrolyte used for a non-aqueous electrolyte secondary battery having a negative electrode, a positive electrode containing a composite oxide of lithium and a transition metal as a positive electrode active material, and an electrolytic solution, and having a relative dielectric constant. An electrolytic solution in which an electrolyte is dissolved in an electrolyte solvent in which a high dielectric constant solvent of 50 or more or a high dielectric constant solvent of 50 or more in relative dielectric constant and a low viscosity solvent having a viscosity of 1 centipoise or less at 25 ° C. is mixed. I
[0007]
[Formula 4]
(Wherein R 1 represents a hydrocarbon group having 4 or more carbon atoms, and R 2 and R 3 represent a hydrogen atom or an electron donating group, and may be different from each other).
A phenolic antioxidant represented by
Formula II
[0009]
[Chemical formula 5]
(In the formula, R 4 represents a hydrocarbon group having 3 or more carbon atoms, and R 5 and R 6 represent a hydrocarbon group which may be different from each other.)
A phosphite-based antioxidant represented by:
Formula III
[0011]
[Chemical 6]
(In the formula, R 7 represents a hydrocarbon group having 3 or more carbon atoms, R 8 represents a hydrocarbon group, and n represents 1 or 2. However, 1,8-disulfide naphthalene is excluded. )
Non-aqueous electrolysis comprising 0.01 to 10% by weight of one or more compounds selected from the group consisting of sulfide antioxidants represented by the formula Liquid.
The present invention also includes a negative electrode, a positive electrode, and an electrolyte solution . When the battery is charged at a constant current density of 1 mA / cm 2 until the battery voltage reaches 5 V, the battery internal temperature is a maximum of 70 ° C. or less. A non-aqueous electrolyte used for an aqueous electrolyte secondary battery, which is a high dielectric constant solvent having a relative dielectric constant of 50 or more, or a high dielectric constant solvent having a relative dielectric constant of 50 or more and a viscosity at 25 ° C. of 1 centipoise or less In an electrolytic solution obtained by dissolving an electrolyte in an electrolyte solvent mixed with a low-viscosity solvent of the formula I
[Chemical Formula 10]
Embedded image
Embedded image
Furthermore, the present invention relates to an electrolyte solvent obtained by mixing a high dielectric constant solvent having a relative dielectric constant of 50 or higher, or a high dielectric constant solvent having a relative dielectric constant of 50 or higher and a low viscosity solvent having a viscosity at 25 ° C. of 1 centipoise or lower. In the electrolyte containing the electrolyte, the general formula III
Embedded image
[0013]
[Action]
By using the non-aqueous electrolyte having the above-described configuration, heat generation that occurs when the secondary battery is abnormal, that is, when overcharged or when the battery is short-circuited can be suppressed, and a non-aqueous electrolyte secondary battery that is excellent in safety can be provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
Examples of the high dielectric constant solvent having a relative dielectric constant of 50 or more, preferably 50 to 100 include propylene carbonate and ethylene carbonate, and any one of these solvents or both can be used.
[0015]
As the electrolyte solvent, only this high dielectric constant solvent may be used. Further, a low viscosity solvent having a viscosity of 1 centipoise or less at 25 ° C. is 90% or less, preferably 90 to 10% with respect to the high dielectric constant solvent. When used in combination, the electrical conductivity is improved, which is more preferable. When the ratio of the low-viscosity solvent increases, the degree of dissociation of the electrolyte decreases and the electrical conductivity decreases, so that the solvent is usually used in the above range. 1,2-dimethoxyethane, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, etc. are used as low viscosity solvents having a viscosity of 1 centipoise or less at 25 ° C., and one or more of these mixed solvents can be used. is there.
[0016]
Examples of the electrolyte include lithium salts such as LiClO 4 , LiPF 6 , LiAsF 6 , LiBF 4 , LiB (C 6 H 5 ) 4 , LiCl, LiBr, CH 3 SO 3 Li and CF 3 SO 3 Li alone or 2. A mixture of seeds or more is used.
The concentration of the electrolyte in the electrolytic solution is usually 0.1 to 3 mol / l, preferably 0.5 to 1.5 mol / l.
In the present invention, the phenolic antioxidant present in the electrolytic solution is characterized by having a bulky hydrocarbon group having 4 or more carbon atoms in at least one of two ortho positions of the hydroxyl group represented by the following formula I.
[0017]
[Chemical 7]
R 1 is a hydrocarbon group having 4 or more carbon atoms, preferably an aliphatic hydrocarbon group having 4 to 15 carbon atoms, particularly preferably 4 to 10 carbon atoms. Specifically, t-butyl group, phenyl group, t-butylphenyl group and the like can be mentioned. R 2 and R 3 are a hydrogen atom or an electron-donating group, and may be different from each other. Specific examples of the electron-donating group include those having 1 to 15 carbon atoms such as a methyl group and an ethyl group. Preferably, a C1-C10 alkoxy group, such as a C1-C10 alkyl group, a methoxy group, an ethoxy group, etc. are mentioned. Specifically, for example, 2,6-di-t-butylphenol, 2-t-butyl-4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl- p-cresol, 2,6-di-tert-butyl-4-ethylphenol and the like can be mentioned.
[0019]
The phosphite antioxidant has a phosphorous ester basic skeleton in which three alkoxy groups are attached to phosphorus represented by the following formula II, and at least one alkoxy group is a bulky hydrocarbon having 3 or more carbon atoms. It is a group.
[0020]
[Chemical 8]
R 4 is a hydrocarbon group having 3 or more carbon atoms, preferably an alkyl group having 3 to 15 carbon atoms such as propyl group or t-butyl group, preferably 3 to 10 carbon atoms, phenyl group, t- Examples thereof include an aryl group which may have a substituent having 6 to 15 carbon atoms such as a butylphenyl group, a trimethylphenyl group, and a dimethylphenyl group. R 5 and R 6 are hydrocarbon groups, which may be different from each other, preferably having 1 to 15 carbon atoms, such as a methyl group, an ethyl group, a propyl group, or a t-butyl group, preferably 1 carbon atom. And an aryl group which may have a substituent having 6 to 15 carbon atoms, such as an alkyl group of 1 to 10, an phenyl group, a t-butylphenyl group, a trimethylphenyl group, and a dimethylphenyl group.
[0022]
Specifically, for example, phenyl diisoalkyl (C1-C10) phosphite, diphenyl isoalkyl (C1-C10) phosphite, triphenyl phosphite, tris- (2,4-di-t-butylphenyl) phos Fight etc. are mentioned. The sulfide-based antioxidant is a disulfide having at least one large aliphatic hydrocarbon group having 3 or more carbon atoms represented by the following formula III .
[0023]
[Chemical 9]
R 7 is a hydrocarbon group having 3 or more carbon atoms, preferably an alkyl group having 3 to 15 carbon atoms such as propyl group or t-butyl group, preferably 3 to 10 carbon atoms, phenyl group, t- Examples include an aryl group which may have a substituent having 6 to 15 carbon atoms such as a butylphenyl group and a trimethylphenyl group. R 8 is a hydrocarbon group, preferably an alkyl group having 1 to 15 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a t-butyl group, preferably a phenyl group, t -An aryl group which may have a substituent having 6 to 15 carbon atoms such as a butylphenyl group and a trimethylphenyl group.
[0025]
Specifically, diphenyl disulfide etc. are mentioned, for example. The antioxidants represented by the general formulas (I), (II), and (III) may have any substituent as long as the antioxidant functions are exhibited. When the battery is abnormal, i.e., the power supply circuit or charger is faulty, or the user is overloaded with a certain amount of electricity due to overuse, or a large current exceeding the normal value due to an external or internal short circuit, etc. When flowing, the electrolyte solution is decomposed on the electrode surface, generating gas and generating heat during decomposition. In particular, lithium and transition metal complex oxides such as LiCoO 2 , LiNiO 2, and LiMn 2 O 4 that are usually used for positive electrodes become unstable oxides during overcharge, releasing active oxygen, and oxidative decomposition of the electrolyte Large heat is generated. The decomposition reaction of these electrolytes is considered a radical chain reaction, and once the reaction starts, there is a high possibility that the battery will run out of heat.
[0026]
The antioxidant used in the present invention reacts with active organic radicals such as peroxy radicals or hydroperoxides generated by the decomposition of the electrolyte, and can prevent the chain reaction leading to thermal runaway.
That is, the phenolic antioxidant added to the electrolytic solution has a bulky t-hydrocarbon group on at least one of the two ortho positions of the hydroxyl group as in the structural formula I, and is caused by decomposition of the electrolytic solution when the battery is abnormal. It reacts with peroxy radicals and removes the hydrogen atom of the hydroxyl group, making itself a relatively stable radical. In other words, since it acts as a radical stabilizer that traps active radicals, chain reactions, that is, runaway reactions caused by the decomposition of the electrolyte can be prevented. If a phenolic compound that does not have such a bulky group at either of the two ortho positions is used, a peroxy radical cannot be effectively captured.
[0027]
Phosphite antioxidants and sulfide antioxidants are inactive because phosphorus or sulfur unshared electron pairs react with active organic radicals such as peroxy radicals or hydroperoxides generated by the decomposition of the electrolyte. A product can be made. In addition, as represented by Structural Formula II and Structural Formula III, it is necessary that the antioxidant has a large substituent. This is because the reactivity of these compounds is lowered, the durability of the effect is increased, and the original battery reaction. This is because it does not adversely affect
[0028]
In addition, if there is too little addition amount of antioxidant added in electrolyte solution, it will not be effective, and it is necessary to make a minimum into 0.01 weight%, More preferably, it is 0.05 weight%. On the other hand, if the amount is too large, the conductivity of the electrolytic solution is lowered, leading to battery performance deterioration. Therefore, the upper limit needs to be 10% by weight, more preferably 5% by weight.
FIG. 1 shows an example of a secondary battery. In the figure, 1 is a negative electrode current collector, 2 is a negative electrode, 3 is a separator, 4 is a positive electrode current collector, 5 is a positive electrode, 6 is an electrolyte, 7 is a polypropylene container, 8 is a positive electrode, and 9 is a negative electrode. is there.
[0029]
As a negative electrode constituting a nonaqueous electrolyte secondary battery, a slurry obtained by slurrying a negative electrode active material and a binder (binder) is usually applied to a current collector and dried to form a sheet. Is used. The negative electrode active material may be lithium or a lithium alloy, but is preferably a carbon material that can occlude and release safer lithium ions. The carbon material is not particularly limited, but graphite, petroleum-based coke, coal-based coke, petroleum-based pitch carbide, coal-based pitch carbide, phenolic resin / crystalline cellulose resin carbide, etc., and partially carbonized carbon. Examples thereof include materials, furnace black, acetylene black, pitch-based carbon fibers, and PAN-based carbon fibers.
[0030]
As the positive electrode, a material obtained by applying a slurry of a positive electrode active material, a binder (binder) and a conductive material to a current collector and drying it to form a sheet is usually used. As the positive electrode active material, a composite oxide of lithium and a transition metal is preferable, and LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiMnO 2 , LiV 2 O 3 and the like can be used.
Examples of the binder (binder) for the negative electrode and the positive electrode active material include polyvinylidene fluoride, polytetrafluoroethylene, EPDM (ethylene-propylene-diene terpolymer), SBR (styrene-butadiene rubber), NBR ( (Acrylonitrile-butadiene rubber), fluororubber and the like, but are not limited thereto.
[0031]
As the conductive agent for the positive electrode, fine particles of graphite, carbon black such as acetylene black, and amorphous carbon fine particles such as needle coke are used, but are not limited thereto.
As the solvent for forming a slurry, an organic solvent that dissolves the binder is usually used. For example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like can be mentioned, but not limited thereto. . Moreover, a dispersing agent, a thickener, etc. are added to water, and an active material may be slurried with latex, such as SBR.
[0032]
Copper, nickel, stainless steel, nickel-plated steel or the like is usually used for the negative electrode current collector, and aluminum, stainless steel, nickel-plated steel or the like is usually used for the positive electrode current collector.
[0033]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited by a following example, unless the summary is exceeded. In addition, the evaluation method in an Example is as follows. In the examples and comparative examples, “parts” means “parts by weight”.
[0034]
(Manufacture of negative electrode)
90 parts of coal-based needle coke having an average particle size of 10 μm was mixed with an N-methylpyrrolidone solution (2 wt%) of 10 parts of polyvinylidene fluoride to obtain a negative electrode mixture slurry. It is applied to both sides of a 20 μm-thick copper foil, dried to evaporate the solvent, and roll-processed to make a negative electrode. The size of the application part of the negative electrode mixture was 12 cm long, 15 cm wide, and the thickness was 120 μm on one side. Further, an ear having a length of 25 m and a width of 15 mm was provided on the left shoulder of the copper foil for connection to the electrode terminal.
[0035]
(Manufacture of positive electrode)
First, 1 mol of lithium carbonate and 2 mol of cobalt carbonate are mixed and pulverized with a ball mill, heated in air at 850 ° C. for 5 hours, mixed and pulverized again with a ball mill, and further heated in air at 850 ° C. for 5 hours. LiCoO 2 was obtained. Next, 90 parts of LiCoO 2 and 5 parts of acetylene black added as a conductive agent and mixed were mixed with an N-methylpyrrolidone solution (2 wt%) of 5 parts of polyvinylidene fluoride to obtain a positive electrode mixture slurry. It apply | coated on both surfaces of the 25-micrometer-thick aluminum foil, it dried, the solvent was evaporated, the roll process was carried out, and the positive electrode was created. The size of the application part of the positive electrode mixture was 12 cm long, 15 cm wide, and the thickness was 120 μm on one side. Further, an ear having a length of 25 m and a width of 15 mm was provided on the right shoulder of the aluminum foil for connection to the electrode terminal.
[0036]
(Battery assembly)
First, the negative electrode and the positive electrode were alternately laminated so as to be electrically insulated through separators. When the negative electrode and the positive electrode were combined as one set, 25 sets were used, and the electrodes at both ends were coated with an electrode mixture on one side only. Next, the ears of the negative electrode and the positive electrode were separately bundled and welded to metal electrode terminals.
Next, this laminated battery was stored in a polypropylene container, vacuum deaerated at 1 × 10 −2 Torr or less, and then put into a dry box that had been replaced with Ar gas. Further, an electrolyte solution was injected and the upper lid was closed. At this time, the negative electrode terminal and the positive electrode terminal of each unit cell protrude through the upper part of the container through the upper lid. Finally, this terminal was sealed with a suitable sealant at the penetrating portion of the upper lid, to produce a laminated battery.
FIG. 1 is a conceptual view of a cross section of this stacked battery. A thermocouple for measuring the internal temperature was inserted between the electrodes at the center of the battery.
[0037]
[Example 1]
The volume ratio of ethylene carbonate (relative dielectric constant 90) and 1,2-dimethoxyethane (relative dielectric constant 7.2, viscosity (25 ° C.) 0.46 cp) to the electrolyte used when assembling the above laminated battery 1: In the electrolyte solution, 2,6-di-t-butyl-p-cresol, a phenolic antioxidant, was dissolved in 1 mol / l of hexafluorophosphate lithium salt (LiPF 6 ) as an electrolyte in the mixed solvent 1 The concentration of 3 wt% was added and dissolved.
This battery was subjected to an overcharge test with an upper limit battery voltage of 5 V in a constant temperature bath at 25 ° C. That is, the battery was charged at a constant current density of 1 mA / cm 2 until the battery voltage reached 5 V, and the battery internal temperature and the state of the battery were observed. As a result, the internal temperature rose to a maximum of 50 ° C., but the temperature dropped after the current stopped and no abnormality in the appearance of the battery was observed.
[0038]
[Example 2]
Phosphite-based oxidation was performed by dissolving 1 mol / l of hexafluorophosphate lithium salt (LiPF 6 ) as an electrolyte in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1 as an electrolytic solution. Evaluation was made in the same manner as in Example 1 except that 3% by weight of the inhibitor triphenyl phosphite as a concentration in the electrolytic solution was added and dissolved. As a result, the internal temperature of the battery rose to a maximum of 70 ° C., but the temperature dropped after the current stopped and no abnormal appearance was seen in the battery.
[0039]
[Example 3]
As an electrolytic solution, a sulfide-based antioxidant was used in which 1 mol / l of hexafluorophosphoric acid lithium salt (LiPF 6 ) was dissolved as an electrolyte in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1. Evaluation was conducted in the same manner as in Example 1 except that 3% by weight of diphenyl disulfide as an agent was added and dissolved.
As a result, the internal temperature of the battery rose to a maximum of 70 ° C., but the temperature dropped after the current stopped and no abnormal appearance was seen in the battery.
[0040]
[Example 4]
As an electrolytic solution, a phenol-based antioxidant is used in which 1 mol / l of hexafluorophosphoric acid lithium salt (LiPF 6 ) is dissolved as an electrolyte in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1. 2% by weight of 2,6-di-t-butyl-p-cresol, and 1% by weight of sulfur-based antioxidant diphenyl disulfide as the concentration in the electrolytic solution was used. Was evaluated in the same manner as in Example 1.
As a result, the internal temperature of the battery rose to a maximum of 40 ° C., but the temperature dropped after the current stopped and no abnormal appearance was observed in the battery.
[0041]
[Comparative Example 1]
Implementation was performed except that the electrolyte used was a solution of 1 mol / l of hexafluorophosphate lithium salt (LiPF 6 ) as an electrolyte in a 1: 1 mixed solvent of ethylene carbonate and 1,2-dimethoxyethane. Evaluation was performed in the same manner as in Example 1.
As a result, when the battery voltage reaches 4.6V, the internal temperature of the battery starts to rise suddenly, and when it reaches 180 ° C, the voltage suddenly becomes 0V due to an internal short circuit that is considered to be the melting of the separator, and the battery container bursts. And there was another fire.
[0042]
[Comparative Example 2]
As an electrolytic solution, 3 wt. Of cresol was dissolved in 1 mol / l of hexafluorophosphate lithium salt (LiPF 6 ) as an electrolyte in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1. Evaluation was carried out in the same manner as in Example 1 except that the product dissolved and added in% was used.
As a result, when the battery voltage reaches 4.7V, the internal temperature of the battery starts to rise suddenly, and when it reaches 180 ° C, the voltage suddenly becomes 0V due to an internal short circuit that seems to melt the separator, and the battery container bursts. A further fire broke out.
[0043]
[Comparative Example 3]
3 ml of trimethyl phosphite was dissolved in 1 mol / l of hexafluorophosphate lithium salt (LiPF 6 ) as an electrolyte in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1 in the electrolytic solution. The evaluation was performed in the same manner as in Example 1 except that a solution dissolved by addition of wt% was used.
As a result, when the battery voltage reaches 4.8V, the internal temperature of the battery suddenly starts to rise, and when it reaches 180 ° C, the voltage suddenly becomes 0V due to an internal short circuit that seems to melt the separator, and the battery container bursts. A further fire broke out.
[0044]
[Comparative Example 4]
As an electrolytic solution, 3 mol of dimethyl sulfide was dissolved in 1 mol / l of hexafluorophosphoric acid lithium salt (LiPF 6 ) as an electrolyte in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1. The evaluation was performed in the same manner as in Example 1 except that a solution dissolved by addition of wt% was used.
As a result, when the battery voltage reaches 4.8V, the internal temperature of the battery suddenly starts to rise, and when it reaches 180 ° C, the voltage suddenly becomes 0V due to an internal short circuit that seems to melt the separator, and the battery container bursts. A further fire broke out.
The above results are summarized in Table 1.
[0045]
[Table 1]
【The invention's effect】
Since an electrolytic solution capable of preventing thermal runaway that occurs in the event of an abnormality such as overcharge or short circuit of the battery is used, a non-aqueous electrolyte secondary battery excellent in safety can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a stacked secondary battery showing an embodiment of the present invention.
[Explanation of symbols]
1: Negative electrode current collector 2: Negative electrode 3: Separator 4: Positive electrode current collector 5: Positive electrode 6: Electrolytic solution 7: Polypropylene container 8: Positive electrode 9: Negative electrode
Claims (8)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP04888897A JP3959774B2 (en) | 1997-03-04 | 1997-03-04 | Non-aqueous electrolyte and secondary battery using the same |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP04888897A JP3959774B2 (en) | 1997-03-04 | 1997-03-04 | Non-aqueous electrolyte and secondary battery using the same |
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| Publication Number | Publication Date |
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| JPH10247517A JPH10247517A (en) | 1998-09-14 |
| JP3959774B2 true JP3959774B2 (en) | 2007-08-15 |
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| JP04888897A Expired - Fee Related JP3959774B2 (en) | 1997-03-04 | 1997-03-04 | Non-aqueous electrolyte and secondary battery using the same |
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- 1997-03-04 JP JP04888897A patent/JP3959774B2/en not_active Expired - Fee Related
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| US8741479B2 (en) | 2011-03-30 | 2014-06-03 | Samsung Electronics Co., Ltd. | Electrolyte for lithium secondary battery and lithium secondary battery including the same |
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