JP4093699B2 - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery - Google Patents

Description

（式中、Ｒ ₁ 、Ｒ ₃ は炭素原子数１〜８のアルキル基、アルキニル基を、Ｒ ₂ は炭素原子数１〜４のアルキレン基、アルキニレン基を表し、但し、Ｒ ₁ 、Ｒ ₂ 、Ｒ ₃ のいずれか１つはアルキニル基又はアルキニレン基であり、Ｘ ₁ 及びＸ ₂ はエーテル結合、エステル結合、炭酸エステル結合を、ｎは０又は１の数を表す）
【０００９】
また、本発明は、非水電解液と正極と負極とを有する非水電解液二次電池において、活性水素を持たないアルキニル基及び／又はアルキニレン基を有する酸素含有脂肪族化合物を添加した上記非水電解液を用いたことを特徴とする非水電解液二次電池を提供するものである。
【００１０】
【発明の実施の形態】
以下に本発明を詳細に説明する。
【００１３】
上記一般式（Ｉ）において、Ｒ₁、Ｒ₃で表されるアルキル基としては、メチル、エチル、プロピル、ブチル、ペンチル、ヘキシル、ヘプチル、オクチル等が、アルキニル基としては、プロパルギル、１，１−ジメチル−２−プロピニル、１−メチル−２−エチル−２−プロピニル、１−メチル−１−イソブチル−２−プロピニル等が挙げられる。
【００１４】
Ｒ₂で表されるアルキレン基としては、エチレン、プロピレン等が、アルキニレン基としては、エチニレン、プロピニレン、２−ブチニレン、１，１，４，４−テトラメチル−２−ブチニレン、１，４−ジメチル−１，４−ジエチル−２−ブチニレン、１，４−ジメチル−１，４−ジイソブチル−２−ブチニレン等が挙げられる。
【００１５】
上記一般式（Ｉ）で表される化合物としては、より具体的には、以下の化合物No. １〜７が挙げられる。但し、本発明は、以下の化合物により何ら制限されるものではない。
【００１６】
【化６】

【００１７】
【化７】

【００１８】
【化８】

【００１９】
【化９】

【００２０】
【化１０】

【００２１】
【化１１】

【００２２】
【化１２】

【００２３】
上記一般式（Ｉ）で表される化合物は、プロパルギルアルコール等のアルキニル化合物を用いて通常のエステル化反応、エーテル化反応、炭酸エステル化反応を行うことで合成できる。
【００２４】
これらは、自己重合し易い化合物であり、サイクル初期に、電極界面において重合反応することにより、安定な被膜を形成し、サイクルに伴う界面抵抗の増加を抑制することができると考えられる。また、この効果を発現するためには、電解液中に、０．０１〜１０体積％の添加量で上記化合物を添加することが望ましく、０．１〜５体積％がより望ましい。
【００２５】
本発明において、活性酸素を持たないアルキニル基及び／又はアルキニレン基を有する酸素含有脂肪族化合物は、単独又は他の非水溶媒と組み合わされて電解液として用いられ、他の非水溶媒、特に、鎖状カーボネート及び環状カーボネートと組み合わせることが好ましい。このように組み合わせることでサイクル特性に優れるばかりでなく、電解液の粘度、得られる電池の電気容量、出力等のバランスのとれた電解液が提供できる。
【００２６】
本発明の非水電解液に用いられる他のの溶媒の例を以下に列挙する。しかしながら、特に限定されるものではなく、電解液全般に添加することにより、界面抵抗の増加を抑制することができる。
【００２７】
環状カーボネート化合物等は、比誘電率が高いため、電解液の誘電率を上げる役割を果たしており、具体的には、エチレンカーボネート、プロピレンカーボネート、ビニレンカーボネート、ブチレンカーボネート等の環状カーボネート、γ−ブチロラクトン、γ−バレロラクトン等の環状エステル、テトラメチルスルホラン、ジメチルスルフォキシド、Ｎ−メチルピロリドン、ジメチルフォルムアミドやこれらの誘導体等が挙げられる。
【００２８】
鎖状カーボネート等は、電解液の粘度を低くすることができる。そのため、電解質イオンの移動性を高くすることができる等、出力密度等の電池特性を優れたものにすることができる。また、低粘度であるため、低温での電解液の性能を高くすることができる。具体的には、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート、エチル−ｎ−ブチルカーボネート、メチル−ｔ−ブチルカーボネート、ジ−ｉ−プロピルカーボネート、ｔ−ブチル−ｉ−プロピルカーボネート等の鎖状カーボネート、ジメトキシエタン、エトキシメトキシエタン、ジエトキシエタン等の鎖状エーテル、テトラヒドロフラン、ジオキソラン、ジオキサン等の環状エーテル、蟻酸メチル、蟻酸エチル、酢酸メチル、酢酸エチル、プロピオン酸メチル、プロピオン酸エチル等の鎖状エステル、アセトニトリル、プロピオニトリル、ニトロメタンやこれらの誘導体等が挙げられる。
【００２９】
リン含有有機化合物は、電解液の難燃性を高いものにすることができる。そのために、非水電解液二次電池の安全性を高いものにすることができる。このリン含有有機化合物としては、リン酸エステル、ホスホン酸エステル又はホスフィン酸エステルからなる群から選ばれたリン含有化合物の少なくとも１種以上を用いることが望ましい。具体的には、トリメチルホスフェート、トリエチルホスフェート等のリン酸エステル類、ジエチルメタンホスホネート、ジ−（２，２，２−トリフルオロエチル）メタンホスホネート等のホスホン酸エステル類、ホスフィン酸エステル類等を用いることができる。また、これらの複数の混合物を使用してもよい。
【００３０】
下記一般式（II）で表されるアルキレンビスカーボネート化合物は、電解液の揮発性を低くすることができ、また、高温での保存特性に優れるため高温での電池特性を高いものにすることができる。この構造も、特に限定されるものではないが、１，２−ビス（メトキシカルボニルオキシ）エタンや、１，２−ビス（エトキシカルボニルオキシ）エタン、１，２−ビス（エトキシカルボニルオキシ）プロパン等を用いることができる。
【００３１】
【化１３】

（式中、Ｒ₄ 、Ｒ₆ は各々独立に炭素原子数１〜４のアルキル基を、Ｒ₅ は炭素原子数１〜３の直鎖又は分岐のアルキレン基を表す）
【００３２】
ここで、Ｒ₄ 、Ｒ₆ で表されるアルキル基としては、メチル、エチル、プロピル、ブチル等が、Ｒ₅ で表されるアルキレン基としては、エチレン等が挙げられる。
【００３３】
上記鎖状カーボネートとしては、下記一般式（III ）で表される化合物が特に電気的特性が優れるので好ましい。
【００３４】
【化１４】

（式中、Ｒ₇ 、Ｒ₈ は各々独立に炭素原子数１〜４のアルキル基を表し、少なくとも一方は炭素原子数３以上のアルキル基を表す）
【００３５】
ここで、Ｒ₇ 、Ｒ₈ で表されるアルキル基としては、メチル、エチル、プロピル、ブチル等が挙げられる。
【００３６】
下記一般式（IV）で表されるグリコールジエーテル化合物は、末端基がフッ素原子で置換されているために、電極界面において、界面活性剤のような作用を発揮して、非水電解液の電極への親和性を高めることができ、初期の電池内部抵抗の低減やリチウムイオンの移動性を高めることができる。この構造も、特に限定されるものではないが、エチレングリコールビス（トリフルオロエチル）エーテル、ｉ−プロピレングリコール（トリフルオロエチル）エーテル、エチレングリコールビス（トリフルオロメチル）エーテル、ジエチレングリコールビス（トリフルオロエチル）エーテル等を用いることができる。
【００３７】
【化１５】

（式中、Ｒ₉、Ｒ₁₁は炭素原子数１〜８のアルキル基又は末端がハロゲン原子で置換されたアルキル基を、Ｒ₁₀は炭素原子数１〜４の分岐又は直鎖のアルキレン基を、ｎ２は１≦ｎ２≦４の数を表し、Ｒ₉ 、Ｒ₁₁のいずれか１つは末端がハロゲン原子で置換されたアルキル基を表す）
【００３８】
ここで、Ｒ₉ 、Ｒ₁₁で示されるアルキル基としては、メチル、エチル、プロピル、ブチル、ペンチル、ヘキシル、ヘプチル、オクチル等が、Ｒ₁₀で示されるアルキレン基としては、エチレン、プロピレン等が挙げられる。
【００３９】
電解質としては、従来公知の電解質が用いられ、例えば、ＬｉＰＦ₆ 、ＬｉＢＦ₄ 、ＬｉＡｓＦ₆ 、ＬｉＣＦ₃ ＳＯ₃ 、ＬｉＮ（ＣＦ₃ ＳＯ₂ ）₂ 、ＬｉＣ（ＣＦ₃ ＳＯ₂ ）₃ 、ＬｉＳｂＦ₆ 、ＬｉＳｉＦ₅ 、ＬｉＡｌＦ₄ 、ＬｉＳＣＮ、ＬｉＣｌＯ₄ 、ＬｉＣｌ、ＬｉＦ、ＬｉＢｒ、ＬｉＩ、ＬｉＡｌＣｌ₄ 、ＮａＣｌＯ₄ 、ＮａＢＦ₄ 、ＮａＩ等が挙げられ、中でも、ＬｉＰＦ₆ 、ＬｉＢＦ₄ 、ＬｉＣｌＯ₄ 、ＬｉＡｓＦ₆ 等の無機塩、並びに、ＣＦ₃ ＳＯ₃ Ｌｉ、Ｎ（ＣＦ₃ ＳＯ₂ ）₂ Ｌｉ、Ｃ（ＣＦ₃ ＳＯ₂ ）₃ Ｌｉ等の有機塩からなる群より選ばれる一種又は二種以上の塩の組合せが電気特性に優れるので好ましい。
【００４０】
上記電解質は、電解液中の濃度が、０．１〜３．０モル／リットル、特に０．５〜２．０モル／リットルとなるように、上記有機溶媒に溶解することが好ましい。該電解液の濃度が０．１モル／リットルより小さいと充分な電流密度を得られないことがあり、３．０モル／リットルより大きいと電解液の安定性を損なう恐れがある。
【００４１】
本発明の電解液は、一次又は二次電池、特に後述する非水電解液二次電池を構成する非水電解液として好適に使用できる。
【００４２】
電極材料としては、正極及び負極があり、正極としては、正極活物質と結着剤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、ＴｉＳ₂ 、ＴｉＳ₃ 、ＭｏＳ₃ 、ＦｅＳ₂ 、Ｌｉ_(1-x) ＭｎＯ₂ 、Ｌｉ_(1-x) Ｍｎ₂ Ｏ₄ 、Ｌｉ_(1-x) ＣｏＯ₂ 、Ｌｉ_(1-x) ＮｉＯ₂ 、ＬｉＶ₂ Ｏ₃ 、Ｖ₂ Ｏ₅ 等が挙げられる。なお、該正極活物質の例示におけるＸは０〜１の数を示す。これら正極活物質のうち、リチウムと遷移金属の複合酸化物が好ましく、ＬｉＣｏＯ₂ 、ＬｉＮｉＯ₂ 、ＬｉＭｎ₂ Ｏ₄ 、ＬｉＭｎＯ₂ 、ＬｉＶ₂ Ｏ₃ 等が好ましい。負極及び正極活物質の結着剤としては、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、ＳＢＲ、ＮＢＲ、フッ素ゴム等が挙げられるが、これらに限定されない。
【００４３】
負極としては、通常、負極活物質と結着剤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、リチウム合金、スズ化合物等の無機化合物、炭素質材料、導電性ポリマー等が挙げられる。特に、安全性の高いリチウムイオンを吸蔵、放出できる炭素質材料が好ましい。この炭素質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、結晶セルロース等の樹脂の炭化物等及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。
【００４４】
正極の導電材としては、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挙げることができるがこれに限定されない。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。
【００４５】
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。
【００４６】
本発明の非水電解液二次電池では正極と負極の間にセパレータを用いるが、通常用いられる高分子の微多孔フィルムを特に限定なく使用できる。例えば、ポリエチレン、ポリプロピレン、ポリフッ化ビニリデン、ポリ塩化ビニリデン、ポリアクリロニトリル、ポリアクリルアミド、ポリテトラフルオロエチレン、ポリスルホン、ポリエーテルスルホン、ポリカーボネート、ポリアミド、ポリイミド、ポリエチレンオキシドやポリプロピレンオキシド等のポリエーテル類、カルボキシメチルセルロースやヒドロキシプロピルセルロース等の種々のセルロース類、ポリ（メタ）アクリル酸及びその種々のエステル類等を主体とする高分子化合物やその誘導体、これらの共重合体や混合物からなるフィルム等が挙げられる。また、このようなフィルムを単独で用いてもよいし、これらのフィルムを重ね合わせた複層フィルムでもよい。さらにこれらのフィルムには種々の添加剤を用いてもよく、その種類や含有量は特に制限されない。これらの微多孔フィルムの中で、本発明の非水電解液二次電池にはポリエチレンやポリプロピレン、ポリフッ化ビニリデン、ポリスルホンが好ましく用いられる。
【００４７】
これらのセパレータフィルムは、電解液がしみ込んでイオンが透過し易いように、微多孔化がなされている。この微多孔化の方法としては、高分子化合物と溶剤の溶液をミクロ相分離させながら製膜し、溶剤を抽出除去して多孔化する「相分離法」と、溶融した高分子化合物を高ドラフトで押し出し製膜した後に熱処理し、結晶を一方向に配列させさらに延伸によって結晶間に間隙を形成して多孔化をはかる「延伸法」等が挙げられ、用いられる高分子フィルムによって適宜選択される。特に、本発明に好ましく用いられるポリエチレンやポリフッ化ビニリデンに対しては、相分離法が好ましく用いられる。
【００４８】
上記構成からなる本発明の非水電解液二次電池は、その形状には特に制限を受けず、コイン型、円筒型、角型等、種々の形状の電池として使用できる。図１は、本発明の非水電解液二次電池のコイン型電池の例を、図２及び図３は円筒型電池の例を示したものである。
【００４９】
図１〜３においては、１は負極、１' は負極板、１" は負極リード、２ は負極集電体、３は正極も３' は正極板、３" は正極リード、４は正極集電体、５は電解液、６はセパレーター、７は正極端子、８は負極端子、１０は非水電解液二次電池、１１はケース、１２は絶縁板、１３はガスケット、１４は安全弁、１５ＰＴＣ素子をそれぞれ示す。
【００５０】
本発明の作用については明確ではないが、初期サイクルにおいて、本発明で用いられる活性水素を持たないアルキニル基及び／又はアルキニレン基を有する酸素含有脂肪族化合物が電極界面において重合反応することにより、被膜を形成するためであると考えられる。このために、初期の内部抵抗は、無添加に比べて増加するが、被膜が安定なために、サイクルに伴う電極と電解液の副反応が抑制でき、サイクルによる内部抵抗の増加を抑制することができると考えられる。
【００５１】
【実施例】
以下に、実施例により本発明を詳細に説明する。但し、以下の実施例により本発明はなんら制限されるものではない。
【００５２】
（正極の作成）
ＬｉＭｎ₂ Ｏ₄ ９０重量部、グラファイト６重量部及びポリフッ化ビニリデン４重量部を混合して、正極材料とした。この正極材料をＮ−メチル−２−ピロリドンに分散させ、スラリー状とした。このスラリーをアルミニウム製の正極集電体に塗布し、乾燥後、プレス成型して、正極電極とした。
【００５３】
（負極の作成）
炭素材料粉末を９０重量部にポリフッ化ビニリデン１０重量部を混合して、負極材料とした。この負極材料をＮ−メチル−２−ピロリドンに分散させてスラリー状とした。このスラリーを銅製の負極集電体に塗布し、乾燥後、プレス成型して、負極電極とした。
【００５４】
（電解液の作成）
有機溶媒を実施例１−１〜１−８及び比較例１−１〜１−５に記載の各体積％で混合し、さらに、ＬｉＰＦ₆ を１モル／リットルの濃度で溶解し、試験化合物（表１及び表２記載）を表１及び表２記載の配合量（体積％）で添加して非水電解液とした。
【００５５】
（電池の作成）
上述の電極をケースに溶接し、厚さ２５μｍの微孔ポリプロピレン製のフィルムを介し、電解液を含有する上記した図１で示すコイン型非水電解液二次電池を作成した。
【００５６】
（評価方法）
上記非水電解液二次電池を用いて、２０℃及び６０℃で、４．２Ｖ、１ｍＡ／ｃｍ² 、４時間の定電流定電圧による充電、及び０．５ｍＡ／ｃｍ² の定電流で終止電圧を３．０Ｖとする放電の充放電を行い、放電容量（ｍＡｈ）、内部抵抗（Ω）の初期値及び充放電５０サイクル後の放電容量維持率（％）と内部抵抗、すなわち抵抗維持（Ω）からサイクル特性（安定性）を評価した。２０℃の結果を表１に、６０℃の結果を表２にそれぞれ示す。
【００５７】
〔実施例１−１〜１−９及び比較例１−１〜１−３〕
エチレンカーボネートとジメチルカーボネートの体積比１：１の混合溶媒に、ＬｉＰＦ６を１モル／リットルの濃度で溶解した電解液に、試験化合物（表１参照）を加えて電解液とした。
【００５８】
〔実施例１−１０及び比較例１−４〕
エチレンカーボネートを３０体積％、ジエチルカーボネートを６０体積％、トリエチルホスフェートを１０体積％の混合溶媒に、ＬｉＰＦ₆ を１モル／リットルの濃度で溶解した電解液に、試験化合物（表１及び表２参照）を加えて電解液とした。
【００５９】
〔実施例１−１１及び比較例１−５〕
エチレンカーボネートを３０体積％、１，２−ビス（エトキシカルボニルオキシ）エタンを１０体積％、エチル−ｎ−ブチルカーボネートを４０体積％、エチレングリコールビス（トリフルオロエチル）エーテルを１０体積％、トリエチルホスフェートを１０体積％の混合溶媒に、ＬｉＰＦ₆ を１モル／リットルの濃度で溶解した電解液に、試験化合物（表１及び表２参照）を加えて電解液とした。
【００６０】
【表１】

【００６１】
【表２】

【００６２】
上記の表１及び表２の評価結果から明らかなように、実施例１−１〜１−１１に示した、本発明に係る活性水素を持たないアルキニル基及び／又はアルキニレン基を有する酸素含有脂肪族化合物を添加した電解液を用いた非水電解液二次電池は、６０℃でも充放電による放電容量の低下や内部抵抗の上昇が小さい。しかし、未添加の比較例１−１と１−４及び１−５では充放電後の放電容量が大きく低下し、内部抵抗の増加も大きい。また、活性水素を有するアルキニル基を有する化合物を添加した比較例１−２や活性水素を持たないアルキニル基を有する酸素含有芳香族化合物を添加した比較例１−３では初期の放電容量が小さく、内部抵抗は大きい。また、５０サイクル後の容量維持率が小さく、内部抵抗の上昇が大きい。
【００６３】
【発明の効果】
以上説明したように、活性水素を持たないアルキニル基及び／又はアルキニレン基を有する酸素含有脂肪族化合物を添加した本発明の非水電解液を用いることで、充放電の繰り返し時に電気容量や内部抵抗の変化率が小さく、サイクル特性に優れた非水電解液二次電池を提供できる。
【図面の簡単な説明】
【図１】図１は、本発明のコイン型非水電解液二次電池の構造の一例を概略的に示す縦断面図である。
【図２】図２は、本発明の非水電解液二次電池としてのリチウム二次電池（円筒型）の基本構成を示す概略図である。
【図３】図３は、本発明の非水電解液二次電池としてのリチウム二次電池（円筒型）の内部構造を断面として示す斜視図である。
【符号の説明】
１ ：負極
１' ：負極板
１" ：負極リード
２ ：負極集電体
３ ：正極
３' ：正極板
３" ：正極リード
４ ：正極集電体
５ ：電解液
６ ：セパレーター
７ ：正極端子
８ ：負極端子
１０：非水電解液二次電池
１１：ケース
１２：絶縁板
１３：ガスケット
１４：安全弁
１５：ＰＴＣ素子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte solution to which a compound having a specific carbon-carbon triple bond is added, and a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte solution, and specifically, has no active hydrogen. A non-aqueous electrolyte and a non-aqueous electrolyte secondary battery having a small rate of change in electric capacity and internal resistance when charging and discharging are repeated by adding an oxygen-containing aliphatic compound having a carbon-carbon triple bond to the electrolyte It is.
[0002]
[Prior art and problems to be solved by the invention]
With the spread of portable electronic devices such as portable personal computers and handy video cameras in recent years, non-aqueous electrolyte secondary batteries having high voltage and high energy density have been widely used as power sources. In addition, due to environmental problems, battery cars and hybrid cars using batteries as a part of power have been put into practical use.
[0003]
However, the non-aqueous electrolyte secondary battery shows a decrease in electric capacity and an increase in internal resistance due to repeated charge and discharge, and lacks reliability as a stable power supply source.
[0004]
In order to improve the stability of the nonaqueous electrolyte secondary battery, various additives have been proposed for the electrolyte. For example, JP-A-6-84523 proposes to add an amine compound, and although the cycle characteristics are improved, there is a disadvantage that the capacity is lowered. JP-A-10-64591 discloses an arylalkyl ether. Compounds and arylaryl ether compounds have been proposed, but these were not satisfactory. Japanese Patent Application Laid-Open No. 5-159787 proposes to suppress a decrease in circuit voltage during storage by adding an alcohol such as propargyl alcohol having a carbon-carbon triple bond. However, the addition of alcohols having active hydrogen is impractical because it impairs the safety of the electrolyte.
[0005]
Thus, additives selected from known compounds as various organic stabilizers are not satisfactory, although they show a stabilizing effect, and there is a significant difference in cycle characteristics due to alkyl groups and alkynyl groups. Has not been suggested to occur.
[0006]
Accordingly, an object of the present invention is to provide a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery in which the rate of change in electric capacity and internal resistance is small when charging and discharging are repeated and the cycle characteristics of the battery are improved. .
[0007]
[Means for Solving the Problems]
As a result of the study, the present inventors have achieved the above object by adding an oxygen-containing aliphatic compound having a carbon-carbon triple bond having no active hydrogen to the electrolyte when producing a non-aqueous electrolyte. I found out that
[0008]
The present invention has been made on the basis of the above knowledge, and in a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in an organic solvent, an alkynyl group and / or an alkynylene group having no active hydrogen represented by the following general formula (I): The present invention provides a non-aqueous electrolyte for a secondary battery , characterized by adding an oxygen-containing aliphatic compound having
[Chemical formula 5]

(Wherein R ₁ and R ₃ represent an alkyl group having 1 to 8 carbon atoms and an alkynyl group, and R ₂ represents an alkylene group having 1 to 4 carbon atoms and an alkynylene group, provided that R ₁ , R ₂ , Any one of R ₃ is an alkynyl group or an alkynylene group, X ₁ and X ₂ are an ether bond, an ester bond, and a carbonate ester bond, and n is a number of 0 or 1.
[0009]
Further, the present invention provides a nonaqueous electrolyte secondary battery having a nonaqueous electrolyte, a positive electrode, and a negative electrode, wherein the oxygen-containing aliphatic compound having an alkynyl group and / or an alkynylene group having no active hydrogen is added. The present invention provides a non-aqueous electrolyte secondary battery using an aqueous electrolyte.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[0013]
In the general formula (I), the alkyl group represented by R _1, R _3, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl and the like, as A Rukiniru group, propargyl, 1, Examples thereof include 1-dimethyl-2-propynyl, 1-methyl-2-ethyl-2-propynyl, 1-methyl-1-isobutyl-2-propynyl and the like.
[0014]
The alkylene group represented by R _2, ethylene and propylene, as the A Rukiniren group, ethynylene, propynylene, 2-butynylene, 1,1,4,4-tetramethyl-2-butynylene, 1,4 Examples thereof include dimethyl-1,4-diethyl-2-butynylene, 1,4-dimethyl-1,4-diisobutyl-2-butynylene and the like.
[0015]
More specific examples of the compound represented by the general formula (I) include the following compound Nos. 1 to 7. However, this invention is not restrict | limited at all by the following compounds.
[0016]
[Chemical 6]

[0017]
[Chemical 7]

[0018]
[Chemical 8]

[0019]
[Chemical 9]

[0020]
[Chemical Formula 10]

[0021]
Embedded image

[0022]
Embedded image

[0023]
The compound represented by the general formula (I) can be synthesized by performing a normal esterification reaction, etherification reaction, or carbonic acid esterification reaction using an alkynyl compound such as propargyl alcohol.
[0024]
These are compounds that are easily self-polymerized, and it is considered that a stable coating can be formed by performing a polymerization reaction at the electrode interface at the beginning of the cycle, and an increase in interfacial resistance associated with the cycle can be suppressed. Moreover, in order to express this effect, it is desirable to add the said compound with the addition amount of 0.01-10 volume% in electrolyte solution, and 0.1-5 volume% is more desirable.
[0025]
In the present invention, an oxygen-containing aliphatic compound having an alkynyl group and / or an alkynylene group having no active oxygen is used as an electrolyte solution alone or in combination with another non-aqueous solvent, and other non-aqueous solvents, in particular, It is preferable to combine with a chain carbonate and a cyclic carbonate. By combining in this way, not only the cycle characteristics are excellent, but also an electrolytic solution in which the viscosity of the electrolytic solution, the electric capacity of the obtained battery, the output and the like are balanced can be provided.
[0026]
Examples of other solvents used in the non-aqueous electrolyte of the present invention are listed below. However, it is not particularly limited, and an increase in interfacial resistance can be suppressed by adding to the entire electrolyte.
[0027]
Cyclic carbonate compounds and the like play a role of increasing the dielectric constant of the electrolyte solution because of their high relative dielectric constants. Specifically, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, γ-butyrolactone, Examples thereof include cyclic esters such as γ-valerolactone, tetramethylsulfolane, dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide, and derivatives thereof.
[0028]
A chain carbonate or the like can lower the viscosity of the electrolytic solution. Therefore, battery characteristics such as power density can be improved, such as the mobility of electrolyte ions can be increased. Moreover, since it is low-viscosity, the performance of the electrolyte solution at low temperatures can be enhanced. Specifically, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, Chain ethers such as dimethoxyethane, ethoxymethoxyethane and diethoxyethane, cyclic ethers such as tetrahydrofuran, dioxolane and dioxane, chain esters such as methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate and ethyl propionate , Acetonitrile, propionitrile, nitromethane, and derivatives thereof.
[0029]
The phosphorus-containing organic compound can increase the flame retardancy of the electrolytic solution. Therefore, the safety of the nonaqueous electrolyte secondary battery can be increased. As the phosphorus-containing organic compound, it is desirable to use at least one or more phosphorus-containing compounds selected from the group consisting of phosphate esters, phosphonate esters or phosphinate esters. Specifically, phosphoric acid esters such as trimethyl phosphate and triethyl phosphate, phosphonic acid esters such as diethyl methanephosphonate and di- (2,2,2-trifluoroethyl) methanephosphonate, and phosphinic acid esters are used. be able to. A mixture of these may also be used.
[0030]
The alkylene biscarbonate compound represented by the following general formula (II) can reduce the volatility of the electrolytic solution, and also has high battery characteristics at high temperatures because of excellent storage characteristics at high temperatures. it can. Although this structure is not particularly limited, 1,2-bis (methoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) propane, etc. Can be used.
[0031]
Embedded image

(Wherein R ₄ and R ₆ each independently represents an alkyl group having 1 to 4 carbon atoms, and R ₅ represents a linear or branched alkylene group having 1 to 3 carbon atoms)
[0032]
Here, examples of the alkyl group represented by R ₄ and R ₆ include methyl, ethyl, propyl, and butyl, and examples of the alkylene group represented by R ₅ include ethylene and the like.
[0033]
As the chain carbonate, a compound represented by the following general formula (III) is particularly preferable because of its excellent electrical characteristics.
[0034]
Embedded image

(Wherein R ₇ and R ₈ each independently represents an alkyl group having 1 to 4 carbon atoms, and at least one represents an alkyl group having 3 or more carbon atoms)
[0035]
Here, examples of the alkyl group represented by R ₇ and R ₈ include methyl, ethyl, propyl, and butyl.
[0036]
Since the glycol diether compound represented by the following general formula (IV) has a terminal group substituted with a fluorine atom, it exhibits an action like a surfactant at the electrode interface, The affinity for the electrode can be increased, the initial battery internal resistance can be reduced, and the mobility of lithium ions can be increased. This structure is not particularly limited, but ethylene glycol bis (trifluoroethyl) ether, i-propylene glycol (trifluoroethyl) ether, ethylene glycol bis (trifluoromethyl) ether, diethylene glycol bis (trifluoroethyl) ) Ether or the like can be used.
[0037]
Embedded image

Wherein R ₉ and R ₁₁ are alkyl groups having 1 to 8 carbon atoms or alkyl groups substituted at the ends with halogen atoms, and R ₁₀ is a branched or straight chain alkylene group having 1 to 4 carbon atoms. N2 represents a number of 1 ≦ n2 ≦ 4, and any one of R ₉ and R ₁₁ represents an alkyl group whose terminal is substituted with a halogen atom)
[0038]
Here, examples of the alkyl group represented by R ₉ and R ₁₁ include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl and the like, and examples of the alkylene group represented by R ₁₀ include ethylene and propylene. It is done.
[0039]
As the electrolyte, a conventionally known electrolyte is used. For example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSiF ₅ , LiAlF ₄ , LiSCN, LiClO ₄ , LiCl, LiF, LiBr, LiI, LiAlCl ₄ , NaClO ₄ , NaBF ₄ , NaI, etc., among them, inorganic salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ And a combination of one or two or more salts selected from the group consisting of organic salts such as CF ₃ SO ₃ Li, N (CF ₃ SO ₂ ) ₂ Li, and C (CF ₃ SO ₂ ) ₃ Li It is preferable because it is excellent.
[0040]
The electrolyte is preferably dissolved in the organic solvent so that the concentration in the electrolytic solution is 0.1 to 3.0 mol / liter, particularly 0.5 to 2.0 mol / liter. If the concentration of the electrolytic solution is less than 0.1 mol / liter, a sufficient current density may not be obtained, and if it is more than 3.0 mol / liter, the stability of the electrolytic solution may be impaired.
[0041]
The electrolyte solution of the present invention can be suitably used as a non-aqueous electrolyte solution constituting a primary or secondary battery, particularly a non-aqueous electrolyte secondary battery described later.
[0042]
As the electrode material, there are a positive electrode and a negative electrode. As the positive electrode, a material obtained by applying a slurry of a positive electrode active material, a binder and a conductive material to a current collector and drying it into a sheet is used. The Examples of the positive electrode active material include TiS ₂ , TiS ₃ , MoS ₃ , FeS ₂ , Li _(1-x) MnO ₂ , Li _(1-x) Mn ₂ O ₄ , Li _(1-x) CoO ₂ , Li _{(1 -x) NiO 2, LiV 2 O} 3, V 2 O 5 and the like. In addition, X in the illustration of this positive electrode active material shows the number of 0-1. Of these positive electrode active materials, composite oxides of lithium and transition metals are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO ₂ , LiV ₂ O _{3 and the} like are preferable. Examples of the binder for the negative electrode and the positive electrode active material include, but are not limited to, polyvinylidene fluoride, polytetrafluoroethylene, EPDM, SBR, NBR, and fluororubber.
[0043]
As the negative electrode, a negative electrode active material and a binder that are slurried with a solvent are applied to a current collector and dried to form a sheet. Examples of the negative electrode active material include inorganic compounds such as lithium, lithium alloys, and tin compounds, carbonaceous materials, and conductive polymers. In particular, a carbonaceous material that can occlude and release highly safe lithium ions is preferable. Although this carbonaceous material is not particularly limited, graphite, petroleum-based coke, coal-based coke, petroleum-based pitch carbide, coal-based pitch carbide, phenolic resin, carbonized resin resin such as crystalline cellulose, and the like are partially carbonized. Examples thereof include carbon materials, furnace black, acetylene black, pitch-based carbon fibers, and PAN-based carbon fibers.
[0044]
As the conductive material 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. Examples thereof include, but are not limited to, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. . Moreover, a dispersing agent, a thickener, etc. are added to water, and an active material may be slurried with latex, such as SBR.
[0045]
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.
[0046]
In the non-aqueous electrolyte secondary battery of the present invention, a separator is used between the positive electrode and the negative electrode, and a commonly used polymer microporous film can be used without any particular limitation. For example, polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyethers such as polyethylene oxide and polypropylene oxide, carboxymethylcellulose And various celluloses such as hydroxypropyl cellulose, polymer compounds mainly composed of poly (meth) acrylic acid and various esters thereof, derivatives thereof, and films made of copolymers or mixtures thereof. Moreover, such a film may be used independently and the multilayer film which overlap | superposed these films may be sufficient. Furthermore, various additives may be used for these films, and the kind and content thereof are not particularly limited. Among these microporous films, polyethylene, polypropylene, polyvinylidene fluoride, and polysulfone are preferably used for the nonaqueous electrolyte secondary battery of the present invention.
[0047]
These separator films are microporous so that the electrolyte can penetrate and ions can easily pass therethrough. The microporosity method includes a phase separation method in which a polymer compound and a solvent solution are formed into a film while microphase separation is performed, and the solvent is extracted and removed to make it porous. The film is extruded and then heat treated, the crystals are aligned in one direction, and a gap is formed between the crystals by stretching to create a porosity, which is appropriately selected depending on the polymer film used. . In particular, the phase separation method is preferably used for polyethylene and polyvinylidene fluoride preferably used in the present invention.
[0048]
The non-aqueous electrolyte secondary battery of the present invention having the above configuration is not particularly limited in shape, and can be used as batteries of various shapes such as a coin shape, a cylindrical shape, and a square shape. FIG. 1 shows an example of a coin-type battery of the nonaqueous electrolyte secondary battery of the present invention, and FIGS. 2 and 3 show examples of a cylindrical battery.
[0049]
1-3, 1 is a negative electrode, 1 'is a negative electrode plate, 1 "is a negative electrode lead, 2 is a negative electrode current collector, 3 is a positive electrode and 3' is a positive electrode plate, 3" is a positive electrode lead, and 4 is a positive electrode collector. Electrical body, 5 is electrolyte, 6 is separator, 7 is positive terminal, 8 is negative terminal, 10 is non-aqueous electrolyte secondary battery, 11 is case, 12 is insulating plate, 13 is gasket, 14 is safety valve, 15PTC Each element is shown.
[0050]
Although the action of the present invention is not clear, in the initial cycle, the oxygen-containing aliphatic compound having no alkynyl group and / or alkynylene group used in the present invention undergoes a polymerization reaction at the electrode interface, thereby forming a film. This is thought to be because of For this reason, the initial internal resistance increases compared to the case of no addition, but because the coating is stable, the side reaction between the electrode and the electrolyte accompanying the cycle can be suppressed, and the increase in internal resistance due to the cycle can be suppressed. It is thought that you can.
[0051]
【Example】
Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples.
[0052]
(Creation of positive electrode)
90 parts by weight of LiMn ₂ O ₄ , 6 parts by weight of graphite and 4 parts by weight of polyvinylidene fluoride were mixed to obtain a positive electrode material. This positive electrode material was dispersed in N-methyl-2-pyrrolidone to form a slurry. This slurry was applied to a positive electrode current collector made of aluminum, dried, and press-molded to obtain a positive electrode.
[0053]
(Creation of negative electrode)
90 parts by weight of the carbon material powder was mixed with 10 parts by weight of polyvinylidene fluoride to obtain a negative electrode material. This negative electrode material was dispersed in N-methyl-2-pyrrolidone to form a slurry. This slurry was applied to a copper negative electrode current collector, dried, and press-molded to obtain a negative electrode.
[0054]
(Creation of electrolyte)
An organic solvent was mixed in each volume% described in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-5, and LiPF ₆ was dissolved at a concentration of 1 mol / liter to obtain a test compound ( Table 1 and Table 2) were added at the blending amounts (% by volume) shown in Table 1 and Table 2 to obtain a non-aqueous electrolyte.
[0055]
(Battery creation)
The above-mentioned electrode was welded to the case, and a coin-type non-aqueous electrolyte secondary battery shown in FIG. 1 containing the electrolytic solution was produced via a 25 μm-thick microporous polypropylene film.
[0056]
(Evaluation methods)
Using the non-aqueous electrolyte secondary battery, charging at 20 ° C. and 60 ° C. with 4.2 V, 1 mA / cm ² , constant current and constant voltage for 4 hours, and termination at a constant current of 0.5 mA / cm ² Charge / discharge is performed with a voltage of 3.0V, and the discharge capacity (mAh), the initial value of internal resistance (Ω), the discharge capacity maintenance rate (%) after 50 cycles of charge and discharge, and the internal resistance, that is, resistance maintenance ( The cycle characteristics (stability) were evaluated from Ω). The results at 20 ° C. are shown in Table 1, and the results at 60 ° C. are shown in Table 2, respectively.
[0057]
[Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-3]
A test compound (see Table 1) was added to an electrolytic solution in which LiPF6 was dissolved at a concentration of 1 mol / liter in a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 1 to obtain an electrolytic solution.
[0058]
[Example 1-10 and Comparative Example 1-4]
A test compound (see Tables 1 and 2) was prepared in an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1 mol / liter in a mixed solvent of 30% by volume of ethylene carbonate, 60% by volume of diethyl carbonate, 10% by volume of triethyl phosphate. ) Was added to obtain an electrolyte solution.
[0059]
[Example 1-11 and Comparative Example 1-5]
30% by volume of ethylene carbonate, 10% by volume of 1,2-bis (ethoxycarbonyloxy) ethane, 40% by volume of ethyl-n-butyl carbonate, 10% by volume of ethylene glycol bis (trifluoroethyl) ether, triethyl phosphate Was added to a 10 volume% mixed solvent and LiPF ₆ was dissolved at a concentration of 1 mol / liter to add a test compound (see Tables 1 and 2) to obtain an electrolytic solution.
[0060]
[Table 1]

[0061]
[Table 2]

[0062]
As is clear from the evaluation results of Table 1 and Table 2 above, the oxygen-containing fat having an alkynyl group and / or alkynylene group having no active hydrogen according to the present invention shown in Examples 1-1 to 1-11 A non-aqueous electrolyte secondary battery using an electrolytic solution to which a group compound is added has little reduction in discharge capacity and increase in internal resistance due to charge / discharge even at 60 ° C. However, in Comparative Examples 1-1, 1-4 and 1-5 without addition, the discharge capacity after charging / discharging is greatly reduced, and the increase in internal resistance is also large. In Comparative Example 1-2 in which a compound having an alkynyl group having active hydrogen was added and in Comparative Example 1-3 in which an oxygen-containing aromatic compound having an alkynyl group having no active hydrogen was added, the initial discharge capacity was small. Internal resistance is large. In addition, the capacity retention rate after 50 cycles is small, and the increase in internal resistance is large.
[0063]
【The invention's effect】
As described above, by using the non-aqueous electrolyte of the present invention to which an oxygen-containing aliphatic compound having an alkynyl group and / or an alkynylene group having no active hydrogen is added, the electric capacity and internal resistance during repeated charging and discharging are used. A non-aqueous electrolyte secondary battery having a small change rate and excellent cycle characteristics can be provided.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing an example of the structure of a coin-type non-aqueous electrolyte secondary battery of the present invention.
FIG. 2 is a schematic diagram showing a basic configuration of a lithium secondary battery (cylindrical type) as a non-aqueous electrolyte secondary battery of the present invention.
FIG. 3 is a perspective view showing a cross section of the internal structure of a lithium secondary battery (cylindrical type) as a nonaqueous electrolyte secondary battery of the present invention.
[Explanation of symbols]
1: Negative electrode 1 ': Negative electrode plate 1 ": Negative electrode lead 2: Negative electrode current collector 3: Positive electrode 3': Positive electrode plate 3": Positive electrode lead 4: Positive electrode current collector 5: Electrolytic solution 6: Separator 7: Positive electrode terminal 8 : Negative electrode terminal 10: Nonaqueous electrolyte secondary battery 11: Case 12: Insulating plate 13: Gasket 14: Safety valve 15: PTC element

Claims (7)

In a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in an organic solvent, an oxygen-containing aliphatic compound having an alkynyl group and / or an alkynylene group having no active hydrogen represented by the following general formula (I) is added: A non-aqueous electrolyte for a secondary battery .

(Wherein R ₁ and R ₃ represent an alkyl group having 1 to 8 carbon atoms and an alkynyl group, and R ₂ represents an alkylene group having 1 to 4 carbon atoms and an alkynylene group, provided that R ₁ , R ₂ , Any one of R ₃ is an alkynyl group or an alkynylene group, X ₁ and X ₂ are an ether bond, an ester bond, and a carbonate ester bond, and n is a number of 0 or 1. The compound represented by formula (I) is present in the electrolyte solution, nonaqueous electrolyte solution for a secondary battery according to claim 1, wherein the is present from 0.01 to 10% by volume. The nonaqueous electrolytic solution for a secondary battery according to claim 1 or 2, wherein the electrolytic solution contains at least one cyclic carbonate compound and at least one chain carbonate compound. Phosphoric acid esters, non-aqueous electrolyte solution for a secondary battery according to claim 1, further comprising a phosphorus-containing compound selected from the group consisting of phosphonic acid esters or phosphinic acid ester 1 or more. The nonaqueous electrolytic solution for a secondary battery according to claim 1, comprising at least one compound represented by any one of the following general formulas (II), (III) and (IV).

(In the formula ( II ) , R ₄ and R ₆ each independently represents an alkyl group having 1 to 4 carbon atoms, and R ₅ represents a linear or branched alkylene group having 1 to 3 carbon atoms)

(In the formula ( III ) , R ₇ and R ₈ each independently represents an alkyl group having 1 to 4 carbon atoms, and at least one represents an alkyl group having 3 or more carbon atoms)

(In the formula ( IV ) , R ₉ and R ₁₁ are alkyl groups having 1 to 8 carbon atoms or alkyl groups substituted at the ends with halogen atoms, and R ₁₀ is a branched or straight chain having 1 to 4 carbon atoms. An alkylene group , n2 represents a number of 1 ≦ n2 ≦ 4, and any one of R ₉ and R ₁₁ represents an alkyl group whose terminal is substituted with a halogen atom) The electrolyte salt is an inorganic salt composed of lithium ion and an anion selected from PF ₆ , BF ₄ , ClO ₄ and AsF ₆ , and lithium ion and SO ₃ CF ₃ , N (CF ₃ SO ₂ ) _{2. , C (CF 3 SO 2)} 3 and according to any one of claims 1 to 5 consisting of a combination of one or more salts selected from the group consisting of organic salts made from these derivatives Nonaqueous electrolyte for secondary batteries . In the nonaqueous electrolyte secondary battery having a non-aqueous electrolyte and the positive electrode and the negative electrode, a nonaqueous electrolyte secondary battery, characterized by using a non-aqueous electrolyte according to claim 1-6.

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