JP4104291B2 - Electrolyte for electrochemical device, electrolyte or solid electrolyte thereof, and battery - Google Patents

Description

（１ａ）
の構造を有するアルミン酸リチウム誘導体と、ＬｉＮ（ＳＯ _２ Ｃ _２ Ｆ _５ ） _２ またはＬｉＮ（ＳＯ _２ ＣＦ _３ ）（ＳＯ _２ Ｃ _４ Ｆ _９ ）の構造を有するリチウム塩よりなる電気化学ディバイス用電解質であって、
上記アルミン酸リチウム誘導体と上記リチウム塩のモル比が、１：９９〜９９：１の範囲である、
上記電気化学ディバイス用電解質、
【０００７】
下記式（１ｂ）
【化５】

（１ｂ）
の構造を有するホウ酸リチウム誘導体と、ＬｉＮ（ＳＯ _２ ＣＦ _３ ） _２ の構造を有するリチウム塩よりなる電気化学ディバイス用電解質であって、
上記ホウ酸リチウム誘導体と上記リチウム塩のモル比が、１：９９〜９９：１の範囲である、
上記電気化学ディバイス用電解質
または下記式（１ｃ）
【化６】

（１ｃ）
の構造を有するアルミン酸リチウム誘導体と、ＬｉＮ（ＳＯ _２ ＣＦ _３ ）（ＳＯ _２ Ｃ _４ Ｆ _９ ）の構造を有するリチウム塩よりなる電気化学ディバイス用電解質であって、
上記アルミン酸リチウム誘導体と上記リチウム塩のモル比が、１：９９〜９９：１の範囲である、
上記電気化学ディバイス用電解質であり、
【０００８】
該電解質を非水溶媒に溶解したものよりなる電気化学ディバイス用電解液または該電解質をポリマーに溶解したものよりなる電気化学ディバイス用固体電解質、及び少なくとも正極、負極、電解液または固体電解質からなり、該電解液または固体電解質に該電解質を含む電池を提供するものである。
【００１０】
以下に、本発明をより詳細に説明する。
【００１１】
ここで、まず本発明で使用されるアルミン酸リチウム誘導体またはホウ酸リチウム誘導体を下記式（１ａ）、式（１ｂ）、および式（１ｃ）に示す。
【００１２】
【化７】

（１ａ）
【化８】

（１ｂ）
【化９】

（１ｃ）
【００２４】
本発明の構成の一部である上記式（１ａ）、式（１ｃ）で示されるアルミン酸リチウム誘導体または式（１ｂ）で示されるホウ酸リチウム誘導体は、イオン性金属錯体構造を採っており、その中心となる金属はＡｌまたはＢである。ＡｌまたはＢの場合、比較的合成も容易であり、さらにＡｌまたはＢの場合、合成の容易性のほか、低毒性、安定性、コストとあらゆる面で優れた特性を有する。
【００２７】
次に、式（１ａ）の構造を有するアルミン酸リチウム誘導体と混合して使用される電解質は、ＬｉＮ（ＳＯ _２ Ｃ _２ Ｆ _５ ） _２ またはＬｉＮ（ＳＯ _２ ＣＦ _３ ）（ＳＯ _２ Ｃ _４ Ｆ _９ ）の構造を有するリチウム塩である。
また、式（１ｂ）の構造を有するホウ酸リチウム誘導体と混合して使用される電解質は、ＬｉＮ（ＳＯ _２ ＣＦ _３ ） _２ の構造を有するリチウム塩である。さらには、式（１ｃ）の構造を有するアルミン酸リチウム誘導体と混合して使用される電解質は、ＬｉＮ（ＳＯ _２ ＣＦ _３ ）（ＳＯ _２ Ｃ _４ Ｆ _９ ）の構造を有するリチウム塩である。これらの電解質は単独で使用すると、電池内のアルミニウムの集電体を電位がかかった状態で腐食するため、充放電サイクルを繰り返すと容量が低下するという問題点を有する。本発明においては、これらのスルホニル基を有する電解質と、式（１ａ）、式（１ｃ）の構造を有するアルミン酸リチウム誘導体または式（１ｂ）の構造を有するホウ酸リチウム誘導体の電解質を混合して使用することで、このアルミニウムの集電体の腐食を防止することが可能となった。その原理の詳細は明らかではないが、式（１ａ）、式（１ｃ）の構造を有するアルミン酸リチウム誘導体または式（１ｂ）の構造を有するホウ酸リチウム誘導体の電解質が電極表面でわずかに分解してアルミニウム表面にその配位子からなる皮膜が形成され、その腐食を防止するものと推測される。
【００２８】
これらの電解質の使用割合は電気化学ディバイスのサイクル特性や保存安定性の向上効果を考慮すると、以下に示す範囲が好ましい。式（１ａ）、式（１ｃ）の構造を有するアルミン酸リチウム誘導体または式（１ｂ）の構造を有するホウ酸リチウム誘導体の電解質と、ＬｉＮ（ＳＯ _２ ＣＦ _３ ） _２ 、ＬｉＮ（ＳＯ _２ Ｃ _２ Ｆ _５ ） _２ 、またはＬｉＮ（ＳＯ _２ ＣＦ _３ ）（ＳＯ _２ Ｃ _４ Ｆ _９ ）の構造を有するリチウム塩の電解質のモル比は、１：９９〜９９：１であり、好ましくは２０：８０〜８０：２０である。式（１ａ）、式（１ｃ）の構造を有するアルミン酸リチウム誘導体または式（１ｂ）の構造を有するホウ酸リチウム誘導体の電解質が１より少ない場合は、アルミニウムの腐食防止の効果が小さいため、サイクル特性、保存安定性が悪くなるし、また、９９より大きい場合は、ＬｉＮ（ＳＯ _２ ＣＦ _３ ） _２ 、ＬｉＮ（ＳＯ _２ Ｃ _２ Ｆ _５ ） _２ 、またはＬｉＮ（ＳＯ _２ ＣＦ _３ ）（ＳＯ _２ Ｃ _４ Ｆ _９ ）の構造を有するリチウム塩のイオン伝導性の高さ、電気化学的安定性が充分に発揮できない。
【００２９】
本発明の電解質を用いて電気化学ディバイスを構成する場合、その基本構成要素としては、イオン伝導体、負極、正極、集電体、セパレーターおよび容器等から成る。
【００３０】
イオン伝導体としては、電解質と非水系溶媒又はポリマーの混合物が用いられる。非水系溶媒を用いれば、一般にこのイオン伝導体は電解液と呼ばれ、ポリマーを用いれば、ポリマー固体電解質と呼ばれるものになる。ポリマー固体電解質には可塑剤として非水系溶媒を含有するものも含まれる。
【００３１】
非水溶媒としては、本発明の電解質を溶解できる非プロトン性の溶媒であれば特に限定されるものではなく、例えば、カーボネート類、エステル類、エーテル類、ラクトン類、ニトリル類、アミド類、スルホン類等が使用できる。また、単一の溶媒だけでなく、二種類以上の混合溶媒でもよい。具体例としては、プロピレンカーボネート、エチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、ジメトキシエタン、アセトニトリル、プロピオニトリル、テトラヒドロフラン、２−メチルテトラヒドロフラン、ジオキサン、ニトロメタン、Ｎ，Ｎ−ジメチルホルムアミド、ジメチルスルホキシド、スルホラン、およびγ−ブチロラクトン等を挙げることができる。
【００３２】
ただし、二種類以上の混合溶媒にする場合、これらの非水溶媒のうち誘電率が２０以上の非プロトン性溶媒と誘電率が１０以下の非プロトン性溶媒からなる混合溶媒に溶解することにより電解液を調製することが好ましい。特にリチウム塩ではジエチルエーテル、ジメチルカーボネート等の誘電率が１０以下の非プロトン性溶媒に対する溶解度が低く単独では十分なイオン伝導度が得られず、また、逆に誘電率２０以上の非プロトン性溶媒単独では溶解度は高いもののその粘度も高いため、イオンが移動しにくくなりやはり十分なイオン伝導度が得られない。これらを混合すれば、適当な溶解度と移動度を確保することができ十分なイオン伝導度を得ることができる。
【００３３】
また、電解質を溶解するポリマーとしては、非プロトン性のポリマーであれば特に限定されるものではない。例えば、ポリエチレンオキシドを主鎖または側鎖に持つポリマー、ポリビニリデンフロライドのホモポリマーまたはコポリマー、メタクリル酸エステルポリマー、ポリアクリロニトリルなどが挙げられる。これらのポリマーに可塑剤を加える場合は、上記の非プロトン性非水溶媒が使用可能である。これらのイオン伝導体中における本発明の混合電解質濃度は、０．１ｍｏｌ／ｄｍ³以上、飽和濃度以下、好ましくは、０．５ｍｏｌ／ｄｍ³以上、１．５ｍｏｌ／ｄｍ³以下である。０．１ｍｏｌ／ｄｍ³より濃度が低いとイオン伝導度が低いため好ましくない。
【００３４】
負極材料としては、特に限定されないが、リチウム電池の場合、リチウム金属やリチウムと他の金属との合金が使用される。また、リチウムイオン電池の場合、ポリマー、有機物、ピッチ等を焼成して得られたカーボンや天然黒鉛、金属酸化物等のインターカレーションと呼ばれる現象を利用した材料が使用される。電気二重層キャパシタの場合、活性炭、多孔質金属酸化物、多孔質金属、導電性ポリマー等が用いられる。
【００３５】
正極材料としては、特に限定されないが、リチウム電池及びリチウムイオン電池の場合、例えば、ＬｉＣｏＯ₂ 、ＬｉＮｉＯ₂ 、ＬｉＭｎＯ₂ 、ＬｉＭｎ₂ Ｏ₄ 等のリチウム含有酸化物、ＴｉＯ₂ 、Ｖ₂ Ｏ₅ 、ＭｏＯ₃ 等の酸化物、ＴｉＳ₂ 、ＦｅＳ等の硫化物、あるいはポリアセチレン、ポリパラフェニレン、ポリアニリン、およびポリピロール等の導電性高分子が使用される。電気二重層キャパシタの場合、活性炭、多孔質金属酸化物、多孔質金属、導電性ポリマー等が用いられる。
【００３６】
【実施例】
以下、実施例により本発明を具体的に説明するが、本発明はかかる実施例により限定されるものではない。
【００３７】
実施例１
プロピレンカーボネート５０ｖｏｌ％とジメチルカーボネート５０ｖｏｌ％の混合溶媒中に、
【００３８】
【化１３】

【００３９】
の構造を有するアルミン酸リチウム誘導体０．０５ｍｏｌ／ｌとＬｉＮ（ＳＯ₂Ｃ₂Ｆ₅）₂０．９５ｍｏｌ／ｌとを溶解した電解液を調製し、この電解液を用いてアルミニウム集電体の腐食試験を実施した。試験用セルは作用極としてアルミニウム、対極及び参照極としてリチウム金属を有するビーカー型のものを用いた。作用極を５Ｖ（Ｌｉ／Ｌｉ⁺）に保持したところ、全く電流は流れなかった。試験後に作用極表面をＳＥＭで観察したが試験前と比べて変化は認められなかった。
【００４０】
さらに、この電解液を用いてＬｉＣｏＯ₂を正極材料としてハーフセルを作製し、実際に電池の充放電試験を実施した。試験用セルは以下のように作製した。ＬｉＣｏＯ₂粉末９０重量部に、バインダーとして５重量部のポリフッ化ビニリデン（ＰＶＤＦ）、導電材としてアセチレンブラックを５重量部混合し、さらにＮ，Ｎ−ジメチルホルムアミドを添加し、ペースト状にした。このペーストをアルミニウム箔上に塗布して、乾燥させることにより、試験用正極体とした。負極にはリチウム金属を使用した。そして、グラスファイバーフィルターをセパレーターとしてこのセパレータに電解液を浸み込ませてセルを組み立てた。
【００４１】
次に、以下のような条件で定電流充放電試験を実施した。充電、放電ともに電流密度０．３５ｍＡ／ｃｍ² で行い、充電は、４．２Ｖ、放電は、３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ⁺ ）まで行った。その結果、初回の放電容量は、１１８ｍＡｈ／ｇ（正極の容量）であった。また、１００回充放電を繰り返したが１００回目の容量は初回の９１％という結果が得られた。
【００４２】
実施例２
エチレンカーボネート５０ｖｏｌ％とジエチルカーボネート５０ｖｏｌ％の混合溶媒中に、
【００４３】
【化１４】

【００４４】
の構造を有するホウ酸リチウム誘導体０．１０ｍｏｌ／ｌとＬｉＮ（ＳＯ₂ＣＦ₃）₂０．９０ｍｏｌ／ｌとを溶解した電解液を調製し、実施例１と同様に、この電解液を用いてアルミニウム集電体の腐食試験を実施した。作用極を５Ｖ（Ｌｉ／Ｌｉ⁺）に保持したところ、全く電流は流れなかった。試験後に作用極表面をＳＥＭで観察したが試験前と比べて変化は認められなかった。
【００４５】
さらに、この電解液を用いてＬｉＣｏＯ₂を正極材料、天然黒鉛を負極材料としてセルを作製し、実際に電池の充放電試験を実施した。試験用セルは以下のように作製した。
【００４６】
ＬｉＣｏＯ₂粉末９０重量部に、バインダーとして５重量部のポリフッ化ビニリデン（ＰＶＤＦ）、導電材としてアセチレンブラックを５重量部混合し、さらにＮ，Ｎ−ジメチルホルムアミドを添加し、ペースト状にした。このペーストをアルミニウム箔上に塗布して、乾燥させることにより、試験用正極体とした。また、天然黒鉛粉末９０重量部に、バインダーとして１０重量部のポリフッ化ビニリデン（ＰＶＤＦ）を混合し、さらにＮ，Ｎ−ジメチルホルムアミドを添加し、スラリー状にした。このスラリーを銅箔上に塗布して、１５０℃で１２時間乾燥させることにより、試験用負極体とした。そして、ポリエチレン製セパレータに電解液を浸み込ませてセルを組み立てた。
【００４７】
次に、以下のような条件で定電流充放電試験を実施した。充電、放電ともに電流密度０．３５ｍＡ／ｃｍ² で行い、充電は、４．２Ｖ、放電は、３．０Ｖまで、行った。その結果、５００回充放電を繰り返したが５００回目の容量は初回の９４％という結果が得られた。
【００４８】
実施例３
エチレンカーボネート５０ｖｏｌ％とジメチルカーボネート５０ｖｏｌ％の混合溶媒中に、
【００４９】
【化１５】

【００５０】
の構造を有するアルミン酸リチウム誘導体０．７０ｍｏｌ／ｌとＬｉＮ（ＳＯ₂ＣＦ₃）（ＳＯ₂Ｃ₄Ｆ₉）０．３０ｍｏｌ／ｌとを溶解した電解液を調製し、実施例１と同様に、この電解液を用いてアルミニウム集電体の腐食試験を実施した。作用極を５Ｖ（Ｌｉ／Ｌｉ⁺）に保持したところ、全く電流は流れなかった。試験後に作用極表面をＳＥＭで観察したが試験前と比べて変化は認められなかった。
【００５１】
さらに、この電解液を用いて実施例１と同様にＬｉＣｏＯ₂を正極材料としたハーフセルを作製し、以下のような条件で定電流充放電試験を実施した。充電、放電ともに電流密度０．３５ｍＡ／ｃｍ² で行い、充電は、４．２Ｖ、放電は、３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ⁺ ）まで行った。その結果、初回の放電容量は、１２０ｍＡｈ／ｇ（正極の容量）であった。また、１００回充放電を繰り返したが１００回目の容量は初回の９０％という結果が得られた。
【００５２】
実施例４
平均分子量１００００のポリエチレンオキシド７０重量部にアセトニトリルを添加して溶液を調整し、この溶液に実施例１と同様の構造を有するアルミン酸リチウム誘導体を５重量部、ＬｉＮ（ＳＯ₂ＣＦ₃）（ＳＯ₂Ｃ₄Ｆ₉）を２５重量部加え、これをガラス上にキャストし、乾燥して溶媒のアセトニトリルを除去することにより高分子固体電解質膜を作製した。
【００５３】
次に、この高分子固体電解質膜を用いてアルミニウム集電体の腐食試験を実施した。この膜を作用極のアルミニウム電極とリチウム電極で挟み、圧着し測定を行った。作用極を５Ｖ（Ｌｉ／Ｌｉ⁺）に保持したところ、全く電流は流れなかった。試験後に作用極表面をＳＥＭで観察したが試験前と比べて変化は認められなかった。
【００５４】
次に、この高分子固体電解質膜を電解液とセパレータの代わりとして用いて実施例１と同様にＬｉＣｏＯ₂を正極材料としたハーフセルを作製し、７０℃で以下のような条件で定電流充放電試験を実施した。充電、放電ともに電流密度０．１ｍＡ／ｃｍ² で行い、充電は、４．２Ｖ、放電は、３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ⁺ ）まで行った。その結果、初回の放電容量は、１２０ｍＡｈ／ｇ（正極の容量）であった。また、１００回充放電を繰り返したが１００回目の容量は初回の８５％という結果が得られた。
【００５５】
比較例１
エチレンカーボネート５０ｖｏｌ％とジメチルカーボネート５０ｖｏｌ％の混合溶媒中に、ＬｉＮ（ＳＯ₂Ｃ₂Ｆ₅）₂を１．０ｍｏｌ／ｌ溶解した電解液を調製し、実施例１と同様に、この電解液を用いてアルミニウム集電体の腐食試験を実施した。作用極を５Ｖ（Ｌｉ／Ｌｉ⁺）に保持したところ、腐食電流が観察された。また、試験後に作用極表面をＳＥＭで観察したところ、その表面に腐食によるものと思われるピットが多数観察された。
【００５６】
次に、この電解液を用いて実施例１と同様にＬｉＣｏＯ₂を正極材料としたハーフセルを作製し、以下のような条件で定電流充放電試験を実施した。充電、放電ともに電流密度０．３５ｍＡ／ｃｍ² で行い、充電は、４．２Ｖ、放電は、３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ⁺ ）まで行った。その結果、初回の放電容量は、１１７ｍＡｈ／ｇ（正極の容量）であった。また、１００回充放電を繰り返したが１００回目の容量は初回の６９％という結果が得られた。
【００５７】
比較例２
プロピレンカーボネート５０ｖｏｌ％とジエチルカーボネート５０ｖｏｌ％の混合溶媒中に、ＬｉＮ（ＳＯ₂ＣＦ₃）₂を１．０ｍｏｌ／ｌ溶解した電解液を調製し、実施例１と同様に、この電解液を用いてアルミニウム集電体の腐食試験を実施した。作用極を５Ｖ（Ｌｉ／Ｌｉ⁺）に保持したところ、腐食電流が観察された。また、試験後に作用極表面をＳＥＭで観察したところ、その表面に腐食によるものと思われるピットが多数観察された。
【００５８】
次に、この電解液を用いて実施例１と同様にＬｉＣｏＯ₂を正極材料としたハーフセルを作製し、以下のような条件で定電流充放電試験を実施した。充電、放電ともに電流密度０．３５ｍＡ／ｃｍ² で行い、充電は、４．２Ｖ、放電は、３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ⁺ ）まで行った。その結果、初回の放電容量は、１１２ｍＡｈ／ｇ（正極の容量）であった。また、１００回充放電を繰り返したが１００回目の容量は初回の６１％という結果が得られた。
【００５９】
比較例３
エチレンカーボネート５０ｖｏｌ％とジメチルカーボネート５０ｖｏｌ％の混合溶媒中に、ＬｉＮ（ＳＯ₂ＣＦ₃）（ＳＯ₂Ｃ₄Ｆ₉）を１．０ｍｏｌ／ｌ溶解した電解液を調製し、実施例１と同様に、この電解液を用いてアルミニウム集電体の腐食試験を実施した。作用極を５Ｖ（Ｌｉ／Ｌｉ⁺）に保持したところ、腐食電流が観察された。また、試験後に作用極表面をＳＥＭで観察したところ、その表面に腐食によるものと思われるピットが多数観察された。
【００６０】
次に、この電解液を用いて実施例１と同様にＬｉＣｏＯ₂を正極材料としたハーフセルを作製し、以下のような条件で定電流充放電試験を実施した。充電、放電ともに電流密度０．３５ｍＡ／ｃｍ² で行い、充電は、４．２Ｖ、放電は、３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ⁺ ）まで行った。その結果、初回の放電容量は、１１８ｍＡｈ／ｇ（正極の容量）であった。また、１００回充放電を繰り返したが１００回目の容量は初回の７２％という結果が得られた。
【００６１】
【発明の効果】
本発明は、リチウム電池、リチウムイオン電池、電気二重層キャパシタ等の電気化学ディバイス用として利用される従来の電解質に比べ、優れたサイクル特性、保存特性を有する電解質であり、その電解液または固体電解質並びにこれらを用いた電池を可能としたものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrolyte, an electrolytic solution, or a solid electrolyte that exhibits excellent cycle characteristics used for electrochemical devices such as lithium batteries, lithium ion batteries, and electric double layer capacitors, and a battery using the same.
[0002]
[Prior art]
With the development of portable devices in recent years, the development of electrochemical devices using electrochemical phenomena such as batteries and capacitors as a power source has become active. Further, as an electrochemical device other than the power source, an electrochromic display (ECD) in which a color change is caused by an electrochemical reaction can be given.
[0003]
These electrochemical devices are generally composed of a pair of electrodes and an ionic conductor filling them. As the ionic conductor, a solution in which a salt (AB) composed of a cation (A ⁺ ) and an anion (B ⁻ ) called an electrolyte is dissolved in a solvent, a polymer, or a mixture thereof is used. When this electrolyte is dissolved, it dissociates into a cation and an anion, and conducts ions. In order to obtain the ionic conductivity necessary for the device, it is necessary that this electrolyte is dissolved in a sufficient amount in a solvent or a polymer. Actually, a solvent other than water is often used as a solvent, and there are currently only a few types of electrolytes having sufficient solubility in such organic solvents and polymers. For example, as an electrolyte for a lithium battery, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) and LiCF ₃ SO ₃ only. The cation portion is often determined by the device, such as the lithium ion of a lithium battery, but the anion portion can be used if the condition that the solubility is high is satisfied.
[0004]
While the application range of devices is diversifying, the optimum electrolyte for each application is being searched for, but at present, optimization is reaching its limit because there are few types of anions. Moreover, the existing electrolyte has various problems, and an electrolyte having a novel anion portion is desired. Specifically, ClO ₄ ions are explosive and AsF ₆ ions are toxic and cannot be used for safety reasons. The only practically used LiPF ₆ also has problems such as heat resistance and hydrolysis resistance. Also, LiN (CF ₃ SO ₂ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) and LiCF ₃ SO ₃ are highly stable and have ionic conductivity. It is a very good electrolyte because it is high in degree, but it is difficult to use because the aluminum current collector in the battery is corroded in a state where a potential is applied.
[0005]
[Concrete means for solving the problem]
As a result of intensive studies in view of the problems of the prior art, the present inventors have found that an excellent characteristic can be obtained by a system in which an electrolyte having a novel chemical structural feature and a conventional electrolyte are combined. It has been reached.
[0006]
That is, the present invention provides the following formula (1a)
[Formula 4]

(1a)
And an electrolyte for an electrochemical device comprising a lithium aluminate derivative having the structure: and a lithium salt having a structure of LiN (SO ₂ C ₂ F ₅ ) ₂ or LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ). There,
The molar ratio of the lithium aluminate derivative to the lithium salt is in the range of 1:99 to 99: 1.
Electrolyte for the above electrochemical device ,
[0007]
The following formula (1b)
[Chemical formula 5]

(1b)
An electrolyte for an electrochemical device comprising a lithium borate derivative having the structure of: and a lithium salt having the structure of LiN (SO ₂ CF ₃ ) ₂ ,
The molar ratio of the lithium borate derivative to the lithium salt is in the range of 1:99 to 99: 1.
Electrolyte for the above electrochemical device
Or the following formula (1c)
[Chemical 6]

(1c)
An electrolyte for an electrochemical device comprising a lithium aluminate derivative having the structure: and a lithium salt having a structure of LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ),
The molar ratio of the lithium aluminate derivative to the lithium salt is in the range of 1:99 to 99: 1.
An electrolyte for an electrochemical device,
[0008]
An electrolyte for an electrochemical device comprising a solution of the electrolyte in a nonaqueous solvent or a solid electrolyte for an electrochemical device comprising a solution of the electrolyte in a polymer, and at least a positive electrode, a negative electrode, an electrolytic solution or a solid electrolyte, A battery including the electrolyte in the electrolyte solution or the solid electrolyte is provided.
[0010]
Hereinafter, the present invention will be described in more detail.
[0011]
Here, first, the lithium aluminate derivative or lithium borate derivative used in the present invention is represented by the following formulas (1a), (1b), and (1c) .
[0012]
[Chemical 7]

(1a)
[Chemical 8]

(1b)
[Chemical 9]

(1c)
[0024]
The lithium aluminate derivative represented by the above formula (1a), the formula (1c) or the lithium borate derivative represented by the formula (1b) , which is a part of the configuration of the present invention, has an ionic metal complex structure, The central metal is Al or B. In the case of Al or B , the synthesis is relatively easy, and in the case of Al or B , in addition to the ease of synthesis, it has excellent properties in all aspects such as low toxicity, stability and cost.
[0027]
Next, the electrolyte used by mixing with the lithium aluminate derivative having the structure of the formula (1a) is LiN (SO ₂ C ₂ F ₅ ) ₂ or LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) .
The electrolyte used by mixing with the lithium borate derivative having the structure of the formula (1b) is a lithium salt having the structure of LiN (SO ₂ CF ₃ ) ₂ . Furthermore, the electrolyte used by mixing with the lithium aluminate derivative having the structure of the formula (1c) is a lithium salt having a structure of LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ). When these electrolytes are used alone, the aluminum current collector in the battery is corroded in a state where an electric potential is applied, so that there is a problem that the capacity decreases when the charge / discharge cycle is repeated. In the present invention, the electrolyte having these sulfonyl groups is mixed with an electrolyte of a lithium aluminate derivative having a structure of formula (1a) or (1c) or a lithium borate derivative having a structure of formula (1b). By using it, it was possible to prevent corrosion of the aluminum current collector. Although the details of the principle are not clear, the electrolyte of the lithium aluminate derivative having the structure of the formula (1a) or the formula (1c) or the lithium borate derivative having the structure of the formula (1b) is slightly decomposed on the electrode surface. Thus, it is presumed that a film composed of the ligand is formed on the aluminum surface and prevents the corrosion.
[0028]
The usage ratio of these electrolytes is preferably in the following range in consideration of the cycle characteristics of the electrochemical device and the effect of improving the storage stability. An electrolyte of a lithium aluminate derivative having the structure of formula (1a) or formula (1c) or a lithium borate derivative having the structure of formula (1b) , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F _{5) 2} or _{LiN (SO} 2 CF ₃₎ (molar ratio of the electrolyte of the lithium salt having the structure of SO ₂ C 4 _{F 9),} is 1: 99 to 99: 1, preferably 20: 80 to 80 : 20. When the electrolyte of the lithium aluminate derivative having the structure of the formula (1a) or the formula (1c) or the lithium borate derivative having the structure of the formula (1b) is less than 1, the effect of preventing the corrosion of aluminum is small. The characteristics and storage stability deteriorate, and when it is greater than 99, LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or LiN (SO ₂ CF ₃ ) (SO ₂ C _The lithium salt having the structure of ₄ F ₉ ) cannot sufficiently exhibit high ion conductivity and electrochemical stability.
[0029]
When an electrochemical device is constituted using the electrolyte of the present invention, its basic components are composed of an ion conductor, a negative electrode, a positive electrode, a current collector, a separator, a container, and the like.
[0030]
As the ionic conductor, a mixture of an electrolyte and a non-aqueous solvent or polymer is used. If a non-aqueous solvent is used, this ionic conductor is generally called an electrolytic solution, and if a polymer is used, it becomes a polymer solid electrolyte. The polymer solid electrolyte includes those containing a non-aqueous solvent as a plasticizer.
[0031]
The non-aqueous solvent is not particularly limited as long as it is an aprotic solvent capable of dissolving the electrolyte of the present invention, and examples thereof include carbonates, esters, ethers, lactones, nitriles, amides, sulfones. Can be used. Moreover, not only a single solvent but 2 or more types of mixed solvents may be sufficient. Specific examples include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide. , Sulfolane, and γ-butyrolactone.
[0032]
However, when two or more kinds of mixed solvents are used , electrolysis is achieved by dissolving them in a mixed solvent composed of an aprotic solvent having a dielectric constant of 20 or more and an aprotic solvent having a dielectric constant of 10 or less. It is preferable to prepare a liquid. In particular, lithium salts have low solubility in an aprotic solvent having a dielectric constant of 10 or less, such as diethyl ether and dimethyl carbonate, so that sufficient ionic conductivity cannot be obtained by themselves, and conversely, an aprotic solvent having a dielectric constant of 20 or more. Independently, the solubility is high, but the viscosity is also high, so that ions are difficult to move and sufficient ionic conductivity cannot be obtained. If these are mixed, appropriate solubility and mobility can be ensured, and sufficient ionic conductivity can be obtained.
[0033]
The polymer that dissolves the electrolyte is not particularly limited as long as it is an aprotic polymer. Examples thereof include polymers having polyethylene oxide in the main chain or side chain, homopolymers or copolymers of polyvinylidene fluoride, methacrylic acid ester polymers, polyacrylonitrile and the like. When a plasticizer is added to these polymers, the above-mentioned aprotic non-aqueous solvent can be used. Mixing the electrolyte concentration of the present invention in these ion conductors in the, 0.1 mol / dm ³ or more, the saturation concentration or less, preferably, 0.5 mol / dm ³ or more and 1.5 mol / dm ³ or less. When the concentration is lower than 0.1 mol / dm ³ , the ionic conductivity is low, which is not preferable.
[0034]
Although it does not specifically limit as a negative electrode material, In the case of a lithium battery, the alloy of lithium metal and lithium and another metal is used. In the case of a lithium ion battery, a material that uses a phenomenon called intercalation such as carbon, natural graphite, or metal oxide obtained by firing a polymer, an organic material, pitch, or the like is used. In the case of an electric double layer capacitor, activated carbon, porous metal oxide, porous metal, conductive polymer, or the like is used.
[0035]
As the cathode material is not particularly limited, a lithium battery and a lithium ion battery, for _{example, LiCoO 2, LiNiO 2, LiMnO} 2, lithium-containing oxides such as _{LiMn 2 O 4, TiO 2,} V 2 O 5, MoO Oxides such as ₃ , sulfides such as TiS ₂ and FeS, or conductive polymers such as polyacetylene, polyparaphenylene, polyaniline, and polypyrrole are used. In the case of an electric double layer capacitor, activated carbon, porous metal oxide, porous metal, conductive polymer, or the like is used.
[0036]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by this Example.
[0037]
Example 1
In a mixed solvent of 50 vol% propylene carbonate and 50 vol% dimethyl carbonate,
[0038]
Embedded image

[0039]
An electrolytic solution in which 0.05 mol / l of a lithium aluminate derivative having the following structure and LiN (SO ₂ C ₂ F ₅ ) ₂ 0.95 mol / l was prepared was prepared, and an aluminum current collector was prepared using this electrolytic solution. A corrosion test was performed. The test cell was a beaker type having aluminum as a working electrode, a counter electrode and lithium metal as a reference electrode. When the working electrode was held at 5 V (Li / Li ⁺ ), no current flowed. After the test, the surface of the working electrode was observed with SEM, but no change was observed compared to before the test.
[0040]
Furthermore, using this electrolytic solution, a half cell was produced using LiCoO ₂ as a positive electrode material, and a battery charge / discharge test was actually performed. The test cell was produced as follows. To 90 parts by weight of LiCoO ₂ powder, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder and 5 parts by weight of acetylene black as a conductive material were mixed, and N, N-dimethylformamide was further added to form a paste. The paste was applied on an aluminum foil and dried to obtain a test positive electrode body. Lithium metal was used for the negative electrode. Then, using the glass fiber filter as a separator, an electrolyte was immersed in the separator to assemble a cell.
[0041]
Next, a constant current charge / discharge test was performed under the following conditions. Both charging and discharging were performed at a current density of 0.35 mA / cm ² , charging was performed at 4.2 V, and discharging was performed up to 3.0 V (vs. Li / Li ⁺ ). As a result, the initial discharge capacity was 118 mAh / g (capacity of the positive electrode). Moreover, although charging / discharging was repeated 100 times, the capacity | capacitance of the 100th time obtained the result of 91% of the first time.
[0042]
Example 2
In a mixed solvent of 50 vol% ethylene carbonate and 50 vol% diethyl carbonate,
[0043]
Embedded image

[0044]
An electrolytic solution in which 0.10 mol / l of a lithium borate derivative having the structure of ## STR1 ## and 0.90 mol / l of LiN (SO ₂ CF ₃ ) ₂ were dissolved was prepared, and this electrolytic solution was used in the same manner as in Example 1. A corrosion test was conducted on the aluminum current collector. When the working electrode was held at 5 V (Li / Li ⁺ ), no current flowed. After the test, the surface of the working electrode was observed with SEM, but no change was observed compared to before the test.
[0045]
Furthermore, using this electrolytic solution, a cell was fabricated using LiCoO ₂ as a positive electrode material and natural graphite as a negative electrode material, and a battery charge / discharge test was actually performed. The test cell was produced as follows.
[0046]
To 90 parts by weight of LiCoO ₂ powder, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder and 5 parts by weight of acetylene black as a conductive material were mixed, and N, N-dimethylformamide was further added to form a paste. The paste was applied on an aluminum foil and dried to obtain a test positive electrode body. Further, 90 parts by weight of natural graphite powder was mixed with 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and N, N-dimethylformamide was further added to form a slurry. This slurry was applied on a copper foil and dried at 150 ° C. for 12 hours to obtain a test negative electrode body. Then, the electrolyte was immersed in a polyethylene separator to assemble the cell.
[0047]
Next, a constant current charge / discharge test was performed under the following conditions. Both charging and discharging were performed at a current density of 0.35 mA / cm ² , charging was performed at 4.2 V, and discharging was performed up to 3.0 V. As a result, charging / discharging was repeated 500 times, but the capacity at the 500th time was 94% of the first time.
[0048]
Example 3
In a mixed solvent of 50% by volume of ethylene carbonate and 50% by volume of dimethyl carbonate,
[0049]
Embedded image

[0050]
An electrolyte solution in which 0.70 mol / l of a lithium aluminate derivative having the following structure and LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) 0.30 mol / l were dissolved was prepared. The corrosion test of the aluminum current collector was carried out using this electrolytic solution. When the working electrode was held at 5 V (Li / Li ⁺ ), no current flowed. After the test, the surface of the working electrode was observed with SEM, but no change was observed compared to before the test.
[0051]
Furthermore, a half cell using LiCoO ₂ as a positive electrode material was produced in the same manner as in Example 1 using this electrolytic solution, and a constant current charge / discharge test was performed under the following conditions. Both charging and discharging were performed at a current density of 0.35 mA / cm ² , charging was performed at 4.2 V, and discharging was performed up to 3.0 V (vs. Li / Li ⁺ ). As a result, the initial discharge capacity was 120 mAh / g (capacity of the positive electrode). Moreover, although charging / discharging was repeated 100 times, the capacity of the 100th time was 90% of the first time.
[0052]
Example 4
Acetonitrile was added to 70 parts by weight of polyethylene oxide having an average molecular weight of 10000 to prepare a solution. To this solution, 5 parts by weight of a lithium aluminate derivative having the same structure as in Example 1, LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) was added in an amount of 25 parts by weight, which was cast on glass and dried to remove the solvent acetonitrile, thereby preparing a polymer solid electrolyte membrane.
[0053]
Next, a corrosion test of the aluminum current collector was performed using this polymer solid electrolyte membrane. This film was sandwiched between an aluminum electrode and a lithium electrode as working electrodes, and measured by pressure bonding. When the working electrode was held at 5 V (Li / Li ⁺ ), no current flowed. After the test, the surface of the working electrode was observed with SEM, but no change was observed compared to before the test.
[0054]
Next, using this polymer solid electrolyte membrane as an electrolyte and a separator, a half cell using LiCoO ₂ as a positive electrode material was prepared in the same manner as in Example 1, and constant current charge / discharge was performed at 70 ° C. under the following conditions. The test was conducted. Both charging and discharging were performed at a current density of 0.1 mA / cm ² , charging was performed at 4.2 V, and discharging was performed up to 3.0 V (vs. Li ^/ Li ⁺ ). As a result, the initial discharge capacity was 120 mAh / g (capacity of the positive electrode). Moreover, although charging / discharging was repeated 100 times, the capacity | capacitance of the 100th time obtained the result of 85% of the first time.
[0055]
Comparative Example 1
An electrolyte solution prepared by dissolving 1.0 mol / l of LiN (SO ₂ C ₂ F ₅ ) ₂ in a mixed solvent of 50% by volume of ethylene carbonate and 50% by volume of dimethyl carbonate was prepared. The corrosion test of the aluminum current collector was performed. When the working electrode was held at 5 V (Li / Li ⁺ ), a corrosion current was observed. Further, when the surface of the working electrode was observed with an SEM after the test, many pits that were thought to be due to corrosion were observed on the surface.
[0056]
Next, a half cell using LiCoO ₂ as a positive electrode material was prepared in the same manner as in Example 1 using this electrolytic solution, and a constant current charge / discharge test was performed under the following conditions. Both charging and discharging were performed at a current density of 0.35 mA / cm ² , charging was performed at 4.2 V, and discharging was performed up to 3.0 V (vs. Li / Li ⁺ ). As a result, the initial discharge capacity was 117 mAh / g (capacity of the positive electrode). Moreover, although charging / discharging was repeated 100 times, the capacity | capacitance of the 100th time obtained the result of 69% of the first time.
[0057]
Comparative Example 2
An electrolytic solution in which 1.0 mol / l of LiN (SO ₂ CF ₃ ) ₂ was dissolved in a mixed solvent of 50 vol% propylene carbonate and 50 vol% diethyl carbonate was prepared, and this electrolytic solution was used in the same manner as in Example 1. A corrosion test was conducted on the aluminum current collector. When the working electrode was held at 5 V (Li / Li ⁺ ), a corrosion current was observed. Further, when the surface of the working electrode was observed with an SEM after the test, many pits that were thought to be due to corrosion were observed on the surface.
[0058]
Next, a half cell using LiCoO ₂ as a positive electrode material was prepared in the same manner as in Example 1 using this electrolytic solution, and a constant current charge / discharge test was performed under the following conditions. Both charging and discharging were performed at a current density of 0.35 mA / cm ² , charging was performed at 4.2 V, and discharging was performed up to 3.0 V (vs. Li / Li ⁺ ). As a result, the initial discharge capacity was 112 mAh / g (positive electrode capacity). Moreover, although charging / discharging was repeated 100 times, the capacity | capacitance of the 100th time obtained the result of 61% of the first time.
[0059]
Comparative Example 3
An electrolytic solution in which 1.0 mol / l of LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ) was dissolved in a mixed solvent of 50% by volume of ethylene carbonate and 50% by volume of dimethyl carbonate was prepared. The corrosion test of the aluminum current collector was carried out using this electrolytic solution. When the working electrode was held at 5 V (Li / Li ⁺ ), a corrosion current was observed. Further, when the surface of the working electrode was observed with an SEM after the test, many pits that were thought to be due to corrosion were observed on the surface.
[0060]
Next, a half cell using LiCoO ₂ as a positive electrode material was prepared in the same manner as in Example 1 using this electrolytic solution, and a constant current charge / discharge test was performed under the following conditions. Both charging and discharging were performed at a current density of 0.35 mA / cm ² , charging was performed at 4.2 V, and discharging was performed up to 3.0 V (vs. Li / Li ⁺ ). As a result, the initial discharge capacity was 118 mAh / g (capacity of the positive electrode). Moreover, although charging / discharging was repeated 100 times, the capacity | capacitance of the 100th time obtained the result of 72% of the first time.
[0061]
【The invention's effect】
The present invention is an electrolyte having excellent cycle characteristics and storage characteristics as compared with conventional electrolytes used for electrochemical devices such as lithium batteries, lithium ion batteries, and electric double layer capacitors. In addition, a battery using these is made possible.

Claims (7)

The following formula (1a)

In a lithium aluminate derivative having the _{structure, LiN (SO 2 C 2 F} 5) 2 or _{LiN (SO} 2 CF ₃₎ Electrochemical devices for electrolyte consisting of a lithium salt having a structure of _{(SO 2} C 4 _{F 9)} There,
The molar ratio of the lithium aluminate derivative to the lithium salt is in the range of 1:99 to 99: 1.
Electrolyte for the above electrochemical device . The following formula (1b)

An electrolyte for an electrochemical device comprising a lithium borate derivative having the structure of: and a lithium salt having the structure of LiN (SO ₂ CF ₃ ) ₂ ,
The molar ratio of the lithium borate derivative to the lithium salt is in the range of 1:99 to 99: 1.
Electrolyte for the above electrochemical device. The following formula (1c)

An electrolyte for an electrochemical device comprising a lithium aluminate derivative having the structure: and a lithium salt having a structure of LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ),
The molar ratio of the lithium aluminate derivative to the lithium salt is in the range of 1:99 to 99: 1.
Electrolyte for the above electrochemical device. An electrolytic solution for an electrochemical device, comprising the electrolyte according to claim 1 , claim 2 or claim 3 dissolved in a non-aqueous solvent.   5. The electrolytic solution for an electrochemical device according to claim 4, wherein the non-aqueous solvent is a mixed solvent comprising an aprotic solvent having a dielectric constant of 20 or more and an aprotic solvent having a dielectric constant of 10 or less. A solid electrolyte for an electrochemical device comprising the electrolyte according to claim 1, 2 or 3 dissolved in a polymer. A battery comprising at least a positive electrode, a negative electrode, an electrolytic solution, or a solid electrolyte, wherein the electrolytic solution or the solid electrolyte includes the electrolyte according to claim 1 , claim 2, or claim 3 .