JP4288440B2 - Method for producing cross-linked polymer solid electrolyte - Google Patents

Description

（ここに、Ｒ¹は水素原子、メチル基又はエチル基、Ｒ²は水素原子又はメチル基、Ｒ³はアルキル基、アリール基、アシル基、シリル基又はシアノアルキル基、ｎは１〜１００の整数である。また、式中下記Ｉ−ａで表わされるグラフト鎖の数平均分子量は４５〜４，４００である。）
【００１７】
【化６】

（ここに、Ｒ⁴は水素原子、メチル基又はエチル基、ｙは２又は３である。）
【００１８】
【化７】

（ここに、Ｒ⁴及びＲ⁵は水素原子、メチル基又はエチル基、ｙは２又は３である。ｋとｍの総計は２００以上で、ｋとｍの構成比は９５：５〜５０：５０である。またその配列方式は、ランダムもしくは交互である。）
【００１９】
【化８】

（ここに、Ｒ⁶とＲ⁷は水素原子又はメチル基、Ｒ⁸はＨ₂Ｃ＝ＣＨＣＯ−、Ｈ₂Ｃ＝Ｃ（ＣＨ₃）ＣＯ−、ビニル基、アリル基、エポキシド、炭素数２５以下のアルキル基、フェニル基又は置換フェニル基、Ｒ⁹はエチレンオキサイド又はテトラメチレンオキサイドである。ｅとｆは共に０〜２５の整数であるが、同時に０になることはなく、一方が０の場合には必ず他方が１以上の整数になる。Ｘは−ＰｈＣ（ＣＨ₃）₂ＰｈＯ−又は単結合を示す。なお、Ｐｈはフェニレン基を示す。）
【００２０】
この方法は、自己架橋型ブロック−グラフト共重合体のグラフト成分に反応性ポリアルキレンオキサイドが相溶化し、ミクロ相分離構造が形成された状態で両者を同時に架橋できるため、共有結合で連結された幹分子がフィルムの機械的強度を高め、グラフト成分と架橋されたポリアルキレンオキサイドが連続相を形成して金属イオンの通路を確保し、しかもポリアルキレンオキサイドからは蒸気圧が全く発生しない、熱安定性の高いフィルムが形成できる。
【００２１】
そして、前記反応性ポリアルキレンオキサイドとしては、一般式ＩＶで表わされる１官能性或いは２官能性のアクリレート系、メタクリレート系、アリル系、エポキシド等を用い、例えば、電子線を照射すれば、反応性ポリアルキレンオキサイドの架橋反応を完結することができる。
【００２２】
この製造方法により、簡単かつ確実に高温時においても全く蒸気圧が発生せず、高イオン伝導性でフィルム強度の高い架橋型高分子固体電解質を製造することができるもので、本発明者らは、ブロック−グラフト共重合体の特性を生かして、高温時でも優れた機械的強度と高いイオン伝導性を維持し、しかも安全な高分子電解質を得るためには、自己架橋型ブロック−グラフト共重合体とこれに添加するポリアルキレンオキサイドの両方を同時に架橋し、三次元の網目状構造にすれば効果的であることを知見し、本発明を完成させたものである。
【００２３】
以下、本発明につき更に詳しく説明する。
本発明の架橋型高分子固体電解質の元になるブロック−グラフト共重合体は、上述したように、一般式Ｉで表わされる繰り返し単位からなるブロック鎖Ａと、一般式ＩＩで表わされる繰り返し単位からなるブロック鎖Ｂ及び／又は一般式ＩＩＩで表わされる繰り返し単位からなるブロック鎖Ｃから構成されるブロック−グラフト共重合体であり、特に好ましくは、前述の特許第１８４２０４７号と特開平１０−２３７１４３号公報に開示されているものと基本的には同一であるが、ここにあらためてその構造を示すと、一般式Ｉで表わされる繰り返し単位からなる少なくとも１種の重合度１０以上のブロック鎖Ａと、一般式ＩＩで表わされる繰返し単位からなる少なくとも１種の重合度３００以上のブロック鎖Ｂとから構成される、ブロック鎖Ａとブロック鎖Ｂの構成比（重合度比）が１：３０〜３０：１である重合度３１０以上のブロック−グラフト共重合体、或いは一般式Ｉで表わされる繰り返し単位からなる少なくとも１種の重合度１０以上のブロック鎖Ａと、一般式ＩＩＩで表わされる繰返し単位からなる少なくとも１種の重合度２００以上のブロック鎖Ｃとから構成される、ブロック鎖Ａとブロック鎖Ｃの構成比（重合度比）が１：２０〜２０：１である重合度２１０以上のブロック−グラフト共重合体である。
【００２４】
【化９】

（ここに、Ｒ¹は水素原子、メチル基又はエチル基、Ｒ²は水素原子又はメチル基、Ｒ³はアルキル基、アリール基、アシル基、シリル基又はシアノアルキル基、ｎは１〜１００の整数である。また、式中、下記Ｉ−ａで表わされるグラフト鎖の数平均分子量は４５〜４，４００である。）
【００２５】
【化１０】

【００２６】
ここで、Ｒ³のアルキル基としては、炭素数１〜１０、特に１〜２のものが好ましく、またアリール基としては、炭素数６〜１０、特に６〜８のものが挙げられ、特にフェニル基が好ましい。アシル基としては、炭素数１〜９、特に１〜２のものが挙げられ、具体的にはホルミル基、アセチル基等が例示される。シリル基としては、−ＳｉＲ₃（Ｒは互いに同一又は異種の炭素数３〜１５、特に３〜６の一価炭化水素基、好ましくはアルキル基である）で示されるものが挙げられる。シアノアルキル基としては、炭素数２〜１０、特に２〜４のアルキル基の水素原子の一部をシアノ基で置換した、例えばシアノエチル基、シアノプロピル基等が挙げられる。
【００２７】
【化１１】

（ここに、Ｒ⁴は水素原子、メチル基又はエチル基、ｙは２又は３である。）
【００２８】
【化１２】

（ここに、Ｒ⁴及びＲ⁵は水素原子、メチル基又はエチル基、ｙは２又は３である。ｋとｍの総計は２００以上で、ｋとｍの構成比は９５：５〜５０：５０である。またその配列方式は、ランダムもしくは交互である。）
【００２９】
このブロック−グラフト共重合体は、一般式Ｉで表わされる同種又は異種の繰り返し単位からなるブロック鎖Ａと、一般式ＩＩで表わされる同種又は異種の繰り返し単位からなるブロック鎖Ｂ及び／又は一般式ＩＩＩで表わされる同種又は異種の繰り返し単位からなるブロック鎖Ｃが、例えばＡＢ、ＡＣ、ＢＡＢ、ＢＡＢ’、ＣＡＣ、Ｃ’ＡＣ、ＢＡＣ、ＢＡＢ’ＡＢ、Ｃ’ＡＢＡＣというように任意に配列されてなるものであるが、好ましくはＢＡＢ、ＢＡＢ’、Ｂ’ＡＢＡＢ’、ＢＡＢ’ＡＢ、ＣＡＣ、ＣＡＣ’、Ｃ’ＡＣＡＣ’、ＣＡＣ’ＡＣ、更に好ましくはＢＡＢ、ＢＡＢ’、ＣＡＣ、ＣＡＣ’等の配列が挙げられる。なお、この配列例において、Ｂ，Ｂ’及びＣ，Ｃ’は、それぞれブロック鎖Ｂ、ブロック鎖Ｃに含まれるものであるが、Ｒ⁴やＲ⁵が相違したり、重合度が相違して互いに異なるブロック鎖であることを示す。
【００３０】
重合体のブロック鎖Ａの重合度は１０以上、同じくＢの重合度は３００以上、Ｃの重合度は２００以上であることが好ましく、この両ブロック鎖Ａ，Ｂの構成比は重合度比として１：３０〜３０：１、ブロック鎖ＡとＣでは１：２０〜２０：１であることが好ましい。また、共重合して得られるブロック−グラフト共重合体の重合度は、ブロック鎖ＡとＢの配列で３１０以上５００００以下、ブロック鎖ＡとＣの配列では２１０以上５００００以下であることが好ましい。
【００３１】
重合体のブロック鎖Ａは、高分子電解質としての機能を担う部分であり、重合度が１０未満では、このポリマーの特徴であるイオン伝導性ドメインが連続相となるミクロ相分離構造を示さない場合がある。また、ブロック鎖Ｂは、機械的強度を保持する部分のため、重合度が３００未満ではポリマー分子間の絡み合いが不十分でフィルムの機械的強度が低下してしまう。つまり、ブロック鎖ＡとＢの構成比が１：３０未満ではグラフト成分が少なすぎて、高分子電解質としての機能を保持するのが困難となり、また３０：１を超えるとブロック鎖としての幹成分が少なくなり、機械的強度が維持できなくなるおそれがある。但し、ブロック鎖Ｂに比べて重合体のＴｇが高いブロック鎖Ｃは、例外的に低い重合度でも機械的強度が維持できるため、ここでは重合度を２００以上、ブロック鎖Ａとの構成比（重合度比）を１：２０〜２０：１、共重合化して得られる共重合体の重合度を２１０以上とすることができる。
【００３２】
本発明の架橋型高分子固体電解質は、前記ブロック−グラフト共重合体に下記一般式ＩＶで表わされる反応性ポリアルキレンオキサイドとリチウム系無機塩を添加し、ブロック−グラフト共重合体及びこの反応性ポリアルキレンオキサイドを架橋反応させるものである。
【００３３】
【化１３】

（ここに、Ｒ⁶とＲ⁷は水素原子又はメチル基、Ｒ⁸はＨ₂Ｃ＝ＣＨＣＯ−、Ｈ₂Ｃ＝Ｃ（ＣＨ₃）ＣＯ−、ビニル基、アリル基、エポキシド、炭素数２５以下のアルキル基、フェニル基又は置換フェニル基、Ｒ⁹はエチレンオキサイド又はテトラメチレンオキサイドである。ｅとｆは共に０〜２５の整数であるが、同時に０になることはなく、一方が０の場合には必ず他方が１以上の整数になる。Ｘは−ＰｈＣ（ＣＨ₃）₂ＰｈＯ−又は単結合を示す。なお、Ｐｈはフェニレン基を示す。）
【００３４】
上記Ｒ⁸のエポキシドとしては、下記式で示されるものが例示される。
【００３５】
【化１４】

（但し、ｐは１〜２５、ｑは１〜２５の整数である。）
また、Ｒ⁸の置換フェニル基としては、トリル基、キシリル基等が例示される。
【００３６】
ブロック−グラフト共重合体に添加する反応性ポリアルキレンオキサイドは、ポリアルキレングリコールのアクリレート誘導体、メタアクリレート誘導体、ビニル系誘導体などが適合し、その構造中に活性水素やハロゲン等を含まないものが好ましい。具体的には、メトキシエチレングリコールモノ（メタ）アクリレート、メトキシポリエチレングリコールモノ（メタ）アクリレート、オクトキシポリエチレングリコール−ｂｌｏｃｋ−ポリプロピレングリコールモノ（メタ）アクリレート、ラウロキシポリエチレングリコールモノ（メタ）アクリレート、ステアロキシポリエチレングリコールモノ（メタ）アクリレート、アリロキシポリエチレングリコールモノ（メタ）アクリレート、ノニルフェノキシポリエチレングリコールモノ（メタ）アクリレート、ノニルフェノキシポリプロピレングリコールモノ（メタ）アクリレート、ノニルフェノキシポリ（エチレングリコール−プロピレングリコール）モノ（メタ）アクリレート、エチレングリコールジ（メタ）アクリレート、ポリエチレングリコールジ（メタ）アクリレート、プロピレングリコールジ（メタ）アクリレート、ポリプロピレングリコールジ（メタ）アクリレート、ポリエチレングリコール−ｂｌｏｃｋ−ポリプロピレングリコール−ｂｌｏｃｋ−ポリエチレングリコールジ（メタ）アクリレート、ポリテトラメチレングリコールジ（メタ）アクリレート、ポリ（エチレングリコール−テトラメチレングリコール）ジ（メタ）アクリレート、ポリ（プロピレングリコール−テトラメチレングリコール）ジ（メタ）アクリレート等が挙げられる。またこの他に、ブロック鎖ｅとｆをビスフェノールＡで結合したエチレンオキサイド変性ビスフェノールＡジ（メタ）アクリレート、エチレンオキサイド−プロピレンオキサイド変性ビスフェノールＡジ（メタ）アクリレート、プロピレンオキサイド−テトラメチレンオキサイド変性ビスフェノールＡジ（メタ）アクリレート、エチレンオキサイド−ｂｌｏｃｋ−プロピレンオキサイド変性ビスフェノールＡジ（メタ）アクリレート等が挙げられる。
【００３７】
本発明においては、基本的には１官能性ポリアルキレンオキサイドと２官能性ポリアルキレンオキサイドを組み合わせて使用する。また、官能基数の同じポリアルキレンオキサイドを２種類以上混合して用いるのも効果的である。更に、ここには例示しなかったが、３官能以上のポリアルキレンオキサイドを使用するとより架橋密度が高くなるため、イオン伝導性を多少犠牲にしてもフィルム強度の向上を図りたい場合には有効な手段となる。
【００３８】
反応性ポリアルキレンオキサイドの添加量は、前記ブロック−グラフト共重合体に対して５重量％以上、好ましくは５０〜６００重量％で、１官能性ポリアルキレンオキサイドと２官能性ポリアルキレンオキサイドの混合比率は重量比として５：９５〜９５：５で、好ましくは１０：９０〜７０：３０である。また官能基数が等しく、種類の異なる反応性ポリアルキレンオキサイドの混合比率には、特に制限がない。
【００３９】
反応性ポリアルキレンオキサイドの添加方法は、例えばブロック−グラフト共重合体に添加して常温又は加熱下に機械的に混練する方法、ブロック−グラフト共重合体との共通溶媒に溶解したのちキャスト法で成膜する方法などいろいろあるが、本ブロック−グラフト共重合体は高分子相溶化剤としての高い機能も有しているため、種々の方法により添加されたアルキレンオキサイドは、自動的にグラフト相に集合しミクロ相分離構造を形成する。従って、添加方法は任意で特に制限はない。
【００４０】
前記ブロック−グラフト共重合体に添加するリチウム系無機塩類の種類は、ＬｉＣｌＯ₄，ＬｉＢＦ₄，ＬｉＰＦ₆，ＬｉＡｓＦ₆，ＬｉＣＦ₃ＳＯ₃及びＬｉＮ（ＣＦ₃ＳＯ₂）₂から選択される少なくとも１種の化合物がよい。また添加する割合は、ブロック−グラフト共重合体のグラフト鎖と添加した反応性ポリアルキレンオキサイドのアルキレンオキサイドユニットの総モル数に対して０．０１〜８０モル％、好ましくは０．０２〜１５モル％が適当であり、その添加方法もポリアルキレンオキサイドと同様に制限がない。
【００４１】
本発明では、ブロック−グラフト共重合体に添加した反応性ポリアルキレンオキサイドを架橋反応させる方法としては、熱によって架橋させる方法（熱架橋）、紫外線を照射して架橋させる方法（紫外線照射）、電子線を照射して架橋させる方法（電子線照射）が例示される。熱架橋は、予め２，２’−アゾビス（イソブチロニトリル）、過酸化ベンゾイル、過酸化メチルエチルケトン等の有機過酸化物を熱重合開始剤として添加しておき、成膜後に８５℃以上で所定時間の間加熱させる方法であり、紫外線照射は、予め２，２−ジメトキシ−２−フェニルアセトフェン、ベンジルメチルケタール、トリメチルシリルベンゾフェノン、２−メチルベンゾイン、４−メトキシベンゾフェノン、ベンゾインメチルエーテル、アントラキノン等の光重合開始剤を添加しておき、成膜後に例えば５００Ｗの高圧水銀ランプにて３分以上ＵＶ照射する方法である。また、電子線照射は、成膜後に電子線照射装置を用いて５〜１００Ｍｒａｄ．の照射線量の電子線を照射する方法である。熱架橋、紫外線照射では、上述したようにラジカル発生剤（重合開始剤）が必要であるが、これを使用することで反応系がより複雑になると同時に、場合によってはリチウムイオンの輸送に悪影響を及ぼすことも懸念される。そこで、本発明では、エネルギーレベルが高く、コントロールし易い上にラジカル発生剤を必要としない電子線（放射線）による架橋法が最適であり、例えば電子線照射装置として［岩崎電気製 ＣＢ２５０／３０／１８０Ｌ］を用い、加速電圧２００ｋＶ、５〜１００Ｍｒａｄ．で種々の試験を行ったところ、非常に優れた架橋方法であることが確認された。
【００４２】
本発明による高分子固体電解質は、その構成要素である自己架橋型ブロック−グラフト共重合体が、（１）明確なミクロ相分離構造を示す、（２）機械的強度の高い幹分子が疑似架橋構造を形成し、構造保持の役目を果たすと共に材料強度を高める、（３）グラフト成分が比較的低分子でも連続相を形成し、金属イオンの通路を確保する、（４）グラフト成分が相溶化剤としての機能を有するため、膜内に大量のポリアルキレンオキサイドを安定に保持できる、（５）系内に揮発成分が存在しないため、高温時の熱安定性に優れ、かつ安全性が高い、という諸特性を持っている。
【００４３】
従って、本発明の高分子固体電解質を例えば、今後実用化が期待されている電気自動車や夜間電力貯蔵用などの高温で作動するリチウムポリマー二次電池に応用すると、電池の軽量化、薄膜化に大変有効であると共に、極めて安全性の高い電池を作ることができる。
【００４４】
また、本発明の架橋型高分子電解質は、二次電池素子以外に、一次電池、コンデンサー、エレクトロクロミックディスプレイ又はセンサー等の各種固体電気化学素子に用いても有効である。
【００４５】
【実施例】
以下に、本発明の実施形態を実施例を挙げて具体的に説明するが、本発明はこれらに限定されるものではない。なお、実施例中のブロック共重合体は各成分を−ｂ−で繋いで、例えばポリブテニルスチレン、ポリ−ｐ−ヒドロキシスチレン、ポリブテニルスチレンの３成分ブロック共重合体をポリ（ブテニルスチレン−ｂ−ｐ−ヒドロキシスチレン−ｂ−ブテニルスチレン）と表記し、ポリブテニルスチレンとポリスチレンの［ランダム／交互］共重合体からなるブロック鎖を−ＣＯ−、グラフト鎖は−ｇ−で繋いで表わす。
【００４６】
［実施例１］反応性ポリアルキレンオキサイドとリチウム系無機塩を添加した自己架橋型ブロック−グラフト共重合体フィルムの電子線架橋Ｉ
実施例１で使用したブロック−グラフト共重合体の分子構造と各ブロック鎖の構成比、並びにグラフト鎖の組成等を以下に示した。
【００４７】
ブロック−グラフト共重合体のサンプルＮｏ．Ｂ−１
（１）分子構造：
ポリ［ブテニルスチレン−ｂ−（ｐ−ヒドロキシスチレン−ｇ−エチレンオキサイド）−ｂ−ブテニルスチレン］
（２）ブロック鎖Ａ（一般式Ｉ）：
Ｒ¹＝水素原子、Ｒ²＝水素原子、Ｒ³＝メチル基、重合度＝２５０
（３）ブロック鎖Ｂ（一般式ＩＩ）：
Ｒ⁴＝水素原子、ｙ＝２、重合度＝５００
（４）ブロック鎖の配列方式：
ＢＡＢ（トリブロック共重合体）
（５）ブロック鎖の構成比（重合度比）：
Ｂ：Ａ：Ｂ＝５００：２５０：５００＝２：１：２（２Ｂ：Ａ＝４：１）
（６）グラフト鎖（一般式Ｉ−ａ）：
Ｒ²＝水素原子、Ｒ³＝メチル基、ｎ（重合度）＝１５、数平均分子量（Ｍｎ）＝６６０
上記自己架橋型ブロック−グラフト共重合体（サンプルＮｏ．Ｂ−１）５．０ｇと、メトキシポリエチレングリコールモノメタクリレート（Ｍｎ＝２７６）２．０ｇとポリエチレングリコールジアクリレート（Ｍｎ＝２１４）１．０ｇ及びＬｉＣｌＯ₄０．５ｇをジメチルカーボネート６０ｍｌに溶解した後、テフロンシャーレ内に流延した。この試料をアルゴン気流下、室温で約２０時間静置して過剰な溶媒を除去した後、更に８０℃で２時間加熱乾燥することにより膜厚２０μｍのフィルムを得た。このフィルムに加速電圧２００ｋＶ、線量１０Ｍｒａｄ．の電子線を照射したのち、得られた試料を示差熱天秤ＤＳＣ−２０（セイコー電子工業社製商品名）で熱分析した。その結果、９０℃付近にジメチルカーボネートに起因すると思われる１％以下の重量減量がみられたものの、その後は２５０℃に至るまで重量変化が観測されなかったことから、ブロック−グラフト共重合体に添加した反応性ポリアルキレンオキサイドは完全に架橋され、１００〜２５０℃の高温においても揮発せず、従って蒸気圧を発生することもなく、グラフト相中に安定に保持されていることがわかった。
【００４８】
［実施例２］反応性ポリアルキレンオキサイドとリチウム系無機塩を添加した自己架橋型ブロック−グラフト共重合体フィルムの電子線架橋ＩＩ
実施例１と同じ処方で作製した電子線照射前のフィルムに、加速電圧２００ｋＶ、線量１〜３Ｍｒａｄ．の電子線を照射して得た試料を熱分析したところ、１５０℃付近から急激な重量減量が観測された。一方、５〜１００Ｍｒａｄ．の線量を照射した試料はいずれも２５０℃まで安定で、溶媒以外の重量減量が全く観測されなかった。そこで、これ以降の実施例では、添加した反応性ポリアルキレンオキサイドを完全に架橋することが可能で、１００〜２５０℃の高温においても蒸気圧を発生することのない照射線量１０Ｍｒａｄ．を基準照射量とした。
【００４９】
［実施例３］
実施例１と同じ処方で作製したフィルムに加速電圧２００ｋＶ、線量１０Ｍｒａｄ．の電子線を照射し、得られた試料を１００℃で２０時間真空乾燥することにより、膜厚２０μｍの架橋型高分子固体電解質フィルムを得た。得られたフィルムは多量のポリアルキレンオキサイドを含有しているにもかかわらず強靱で、動的粘弾性試験機ＲＳＡ−ＩＩ（Ｒｅｏｍｅｔｒｉｃ Ｉｎｃ．製商品名）から求められた貯蔵弾性率は３０℃で９．５×１０⁶Ｐａ、８０℃でも８．４×１０⁶Ｐａ以上を示した。また、本電解質フィルムを２０℃で１００ｋｇ／ｃｍ²の荷重で圧縮しても、内部に含有されたポリアルキレンオキサイドは全く滲出しなかった。
【００５０】
このフィルムを直径１０ｍｍの円板状に切り出し、その両面をリチウム金属極板で挟んで電極を形成し、周波数５Ｈｚ〜５ＭＨｚの交流インピダンス測定装置（マルチフリクェンシーＬＣＲＸメーター４１９２Ａ、横河ヒューレットパッカード社製商品名）を用い、複素インピーダンス法によりイオン伝導度を算出した。その結果、８０℃で０．７×１０^-3Ｓ／ｃｍの値を得た。
【００５１】
［実施例４〜９］
実施例４〜９に使用した自己架橋型ブロック−グラフト共重合体（サンプルＮｏ．Ｂ−２〜ＢＴ−２）の分子構造、各ブロック鎖の構成比並びにグラフト鎖の組成等を以下に示した。また、下記自己架橋型ブロック−グラフト共重合体に種類の異なる反応性ポリアルキレンオキサイドとリチウム系無機塩類を添加した後、電子線の照射により架橋した架橋型高分子固体電解質フィルムを用いて、実施例３と同様な評価を行ったところ、表１に示したような結果を得た。
【００５２】
サンプルＮｏ．Ｂ−２
（１）分子構造：
ポリ［ブテニルスチレン−ｂ−（ｐ−ヒドロキシスチレン−ｇ−エチレンオキサイド）−ｂ−ブテニルスチレン］
（２）ブロック鎖Ａ（一般式Ｉ）：
Ｒ¹＝水素原子、Ｒ²＝水素原子、Ｒ³＝メチル基、重合度＝２５０
（３）ブロック鎖Ｂ（一般式ＩＩ）：
Ｒ⁴＝水素原子、ｙ＝２、重合度＝５００
（４）ブロック鎖の配列方式：
ＢＡＢ（トリブロック共重合体）
（５）ブロック鎖の構成比（重合度比）：
Ｂ：Ａ：Ｂ＝５００：２５０：５００＝２：１：２（２Ｂ：Ａ＝４：１）
（６）グラフト鎖（一般式Ｉ−ａ）：
Ｒ²＝水素原子、Ｒ³＝メチル基、ｎ＝２３、数平均分子量（Ｍｎ）＝１０１０
【００５３】
サンプルＮｏ．ＢＴ−１
（１）分子構造：
ポリ［（スチレン−ｃｏ−ブテニルスチレン）−ｂ−（ｐ−ヒドロキシスチレン−ｇ−エチレンオキサイド）−ｂ−（スチレン−ｃｏ−ブテニルスチレン）］
（２）ブロック鎖Ａ（一般式Ｉ）：
Ｒ¹＝水素原子、Ｒ²＝水素原子、Ｒ³＝メチル基、重合度＝２５０
（３）ブロック鎖Ｃ（一般式ＩＩＩ）：
Ｒ⁴＝水素原子、Ｒ⁵＝水素原子、ｙ＝２、ｍ（重合度）＝１００、ｋ（重合度）＝４００
（４）ブロック鎖の配列方式：
ＣＡＣ（トリブロック共重合体）
（５）ブロック鎖の構成比（重合度比）：
Ｃ：Ａ：Ｃ＝（１００＋４００）：２５０：（１００＋４００）＝２：１：２（２Ｃ：Ａ＝４：１）
（６）グラフト鎖（一般式Ｉ−ａ）：
Ｒ²＝水素原子、Ｒ³＝メチル基、ｎ＝９、数平均分子量（Ｍｎ）＝４００
【００５４】
サンプルＮｏ．ＢＴ−２
（１）分子構造：
ポリ［（スチレン−ｃｏ−ブテニルスチレン）−ｂ−（ｐ−ヒドロキシスチレン−ｇ−エチレンオキサイド）−ｂ−（スチレン−ｃｏ−ブテニルスチレン）］
（２）ブロック鎖Ａ（一般式Ｉ）：
Ｒ¹＝水素原子、Ｒ²＝水素原子、Ｒ³＝メチル基、重合度＝２５０
（３）ブロック鎖Ｃ（一般式ＩＩＩ）：
Ｒ⁴＝水素原子、Ｒ⁵＝水素原子、ｙ＝２、ｍ（重合度）＝５０、ｋ（重合度）＝４５０
（４）ブロック鎖の配列方式：
ＣＡＣ（トリブロック共重合体）
（５）ブロック鎖の構成比（重合度比）：
Ｃ：Ａ：Ｃ＝（５０＋４５０）：２５０：（５０＋４５０）＝２：１：２（２Ｃ：Ａ＝４：１）
（６）グラフト鎖（一般式Ｉ−ａ）：
Ｒ²＝水素原子、Ｒ³＝メチル基、ｎ＝１４、数平均分子量（Ｍｎ）＝６２０
【００５５】
【表１】

Ａ：メトキシポリエチレングリコールモノメタクリレート（Ｍｎ＝２７６）
Ｂ：ポリエチレングリコールジアクリレート（Ｍｎ＝３０２）
Ｃ：メトキシポリエチレングリコールモノアクリレート（Ｍｎ＝４６６）
Ｄ：ポリプロピレングリコールジメタクリレート（Ｍｎ＝３８６）
Ｅ：メトキシポリエチレングリコールモノメタクリレート（Ｍｎ＝４９６）
Ｆ：アリロキシポリエチレングリコールモノメタクリレート（Ｍｎ＝２１４）
Ｇ：オクトキシポリエチレングリコール−ポリプロピレングリコールモノメタクリレート（Ｍｎ＝８９８）
Ｈ：ポリプロピレングリコールジアクリレート（Ｍｎ＝３０２）
Ｉ：ポリ（エチレングリコール−テトラメチレングリコール）ジメタアクリレート（Ｍｎ＝６００）
Ｊ：ラウロキシポリエチレングリコールモノアクリレート（Ｍｎ＝４００）
Ｋ：ポリプロピレングリコールジアクリレート（Ｍｎ＝５１８）
Ｌ：メトキシポリエチレングリコールモノアクリレート（Ｍｎ＝４８２）
Ｍ：アリロキシポリエチレングリコールモノアクリレート（Ｍｎ＝３８０）
【００５６】
これらの結果から、本発明によって製造される架橋型高分子固体電解質は、多量のポリアルキレンオキサイドとリチウム系無機塩類をフィルム中に含有しているにもかかわらず、１００℃以上の高温時でも蒸気圧が発生することなく、高イオン伝導性で高いフィルム強度を有していることがわかった。
【００５７】
［比較例１］
米国特許第５２９６３１８号に記載されている高分子固体電解質の形成方法に従い、膜厚１００μｍのフィルム状固体電解質を作製した。方法は、ＶｄＦ／ＨＦＰコポリマー[Ａｔｏｃｈｅｍ Ｋｙｎｅｒ ＦＬＥＸ ２８０１（商品名）］５．０ｇとメトキシポリエチレングリコールモノメタクリレート（Ｍｎ＝２７３）２．０ｇ、ポリエチレングリコールジアクリレート（Ｍｎ＝２１４）１．０ｇ及びＬｉＣｌＯ₄０．５ｇを５０ｍｌのテトラヒドロフランに溶解混合した後、テフロンシャーレ内に流延した。この試料をアルゴン気流下、室温で約２０時間静置して過剰な溶媒を除去した後、更に８０℃で２時間加熱乾燥した。しかしながら、Ａｔｏｃｈｅｍ Ｋｙｎｅｒ ＦＬＥＸ ２８０１とポリアルキレンオキサイドが全く相溶化しなかったため、マクロな相分離が発生し、完全に固化しない半固形状フィルムしか得ることができなかった。
【００５８】
［比較例２］
比較例１で作製した半固形状フィルムを加速電圧２００ｋＶ、線量１０Ｍｒａｄ．の電子線を照射したところ、マクロな相分離が生じたままの不均質なフィルムが得られた。また５０Ｍｒａｄ．以上の電子線線量では、Ａｔｏｃｈｅｍ Ｋｙｎｅｒ ＦＬＥＸ ２８０１の分解反応が進行し、フッ素ガスが発生した。
【００５９】
【発明の効果】
本発明によれば、優れたフィルム強度と高イオン伝導性及びフィルムへの成形、加工性の良好な、大型二次電池等として好適に用いられる架橋型高分子固体電解質が得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polymer solid electrolyte suitable for use in the production of primary batteries, secondary batteries, and the like, particularly high temperature operation type secondary batteries for electric vehicles and nighttime power storage.
[0002]
[Prior art]
Solid electrolytes that have been researched and developed in the past include β-alumina, Li₂TiO_Three, RbAg_Fourl_FiveSo-called inorganic materials such as silver iodide and phosphotungstic acid are widely known. However, the disadvantages of inorganic materials are (1) heavy specific gravity, (2) cannot be molded into any shape, (3) flexible and thin film cannot be obtained, and (4) ion conductivity at room temperature is low. Has become a practical problem.
[0003]
In recent years, organic materials have attracted attention as materials for improving the above-mentioned drawbacks. The general composition of organic materials is that LiClO is used as a polymer such as polyalkylene oxide, silicone rubber, fluororesin or polyphosphazene._Four, LiBF_FourIt is composed of a solid polymer electrolyte (SPE) in which an electrolyte serving as a carrier is mixed and dissolved. Such SPE has the characteristics that it is lighter and more flexible than inorganic materials, and that it can be easily formed and processed into a film. Research and development for constructing a realistic SPE is being actively conducted.
[0004]
The application fields of SPE are broadly classified into (1) a small-sized consumer secondary battery that operates at room temperature, and (2) a high-temperature large-sized secondary battery that operates at high temperature. Here, (1) is a secondary battery using a so-called gel-like SPE as a diaphragm whose ion conductivity is improved by absorbing and holding a low-boiling point aprotic organic electrolyte in a polymer material. However, since the configuration of the battery is almost the same as that of the lithium ion battery, it has already been put to practical use as a small and ultra-thin battery with a low output.
[0005]
On the other hand, (2) is a lithium polymer battery that assumes the use of lithium metal for the negative electrode, and is expected to be applied to electric vehicles and large-sized secondary batteries for nighttime power storage in the near future. However, in these large batteries, the amount of heat generated during charging and discharging becomes enormous, and the temperature of the battery itself rises considerably. Therefore, when the gel-based SPE as in (1) is used, the outer can of the battery is caused by the vapor pressure of the electrolyte. It has been pointed out the danger of swelling or exploding in the worst case. Therefore, in order to solve these problems, a so-called high temperature operation type large secondary battery in which ion conductivity is increased by raising the temperature of a single SPE (dry type) to 60 to 80 ° C. has been proposed, mainly in Europe and the United States. Long-term research and development has been conducted. However, SPE which has high safety even in such a high temperature region, has excellent film strength, and does not generate any vapor pressure in the battery system is not yet obtained.
[0006]
[Problems to be solved by the invention]
As a research example of the above (2), for example, Watanabe et al, So1id State Ionics 79, (1995) 306-312. And S. Kohjiya et al., Second International Symposium on Polymer Electronics, ed. by B. Scrosati, Elsevier, Appl. Sci. , London (1990), pp. 187-196. However, any SPE has an ionic conductivity of about 10 at room temperature.^-FourAlthough it reaches the S / cm range, it cannot be said that the film strength is sufficient and has not yet been put to practical use.
[0007]
On the other hand, the present applicants have previously described Japanese Patent No. 1842047 (Japanese Patent Publication No. 5-51612) and Makromol. Chem. Macromol. Symp. 25 (1989) 249, Reactive and Functional Polymers, 37 (1998) 169-182. And J.A. Polym. Sci. Part A: Polym. Chem. , 36, (1998) 3021-3034, etc., proposed a method for synthesizing a block-graft copolymer as a model of the present invention.
[0008]
In addition, in Patent No. 1842048 (Japanese Patent Publication No. 5-51632), in order to use this block-graft copolymer as an ion conductive solid, 0.05 to 80 mol% of the alkylene oxide unit is used. A block-graft copolymer composition in which an inorganic salt containing at least one element selected from Li, Na, K, Cs, Ag, Cu and Mg is mixed is proposed as SPE. The present inventors have proposed a Li battery in which a composite of a similar block-graft copolymer with a Li ion salt is incorporated as an electrolyte. However, none of the above proposals have been put into practical use because of their low ionic conductivity at room temperature.
[0009]
In view of this, the present applicant, for the purpose of improving the ionic conductivity at room temperature, disclosed in JP-A-3-188151 is a block obtained by adding a polyalkylene oxide to an inorganic ion salt composite of a block-graft copolymer. Although a graft copolymer composition was proposed, if too much polyalkylene oxide is added to the block-graft copolymer, some polystyrene domains that maintain the mechanical strength will dissolve, resulting in weak film strength. It turned out that.
[0010]
In order to solve this newly derived problem, the present applicant has disclosed in Japanese Patent Laid-Open No. 10-237143, a block having polystyrene as a block chain, which is not soluble in various polyalkylene oxides and substituted with a silyl group. -A graft copolymer was developed, and a block-graft copolymer composition in which a polyalkylene oxide was added was proposed. In JP-A-10-208545, in order to protect the polystyrene domain from the solubility of polyalkylene oxide added in a large amount to the block-graft copolymer, the polystyrene domain is chemically crosslinked using a crosslinking agent. A cross-linked SPE with a mesh structure was proposed. Furthermore, in Japanese Patent Application Laid-Open Nos. 10-222302 and 10-245427, self-crosslinking can easily crosslink polystyrene domains only by irradiation with high energy rays without adding a crosslinking agent. A type block-graft copolymer was proposed.
[0011]
As a result, an SPE with greatly improved ion conductivity and film strength is completed not only near room temperature but also at high temperatures (60 to 80 ° C.), and a practical high-temperature battery can be easily produced in large quantities. It became so.
[0012]
However, some polyalkylene oxides added to the block-graft copolymer exhibit some vapor pressure in the temperature range of 60 to 80 ° C. In addition, when this SPE is applied to a large battery operating at a high temperature, the temperature may increase by several tens of degrees from the assumed temperature range depending on the operating conditions of the battery. A wider and safer battery has come to be demanded.
[0013]
Therefore, the object of the present invention is to provide a three-dimensional network structure by simultaneously crosslinking a self-crosslinking block-graft copolymer and an added reactive polyalkylene oxide with respect to a polymer solid electrolyte. An attempt is made to provide a method for producing a crosslinked polymer solid electrolyte that does not generate vapor pressure even at a high temperature of 100 ° C. or higher, has high ion conductivity and high film strength, and is excellent in moldability and processability. Is.
[0014]
Means for Solving the Problem and Embodiment of the Invention
In order to solve such problems, the present invention provides a block chain A composed of repeating units represented by the following general formula I, a block chain B composed of repeating units represented by the following general formula II, and / or the following general formula: A reactive polyalkylene oxide represented by the following general formula IV and a lithium-based inorganic salt are added to a self-crosslinking block-graft copolymer composed of a block chain C composed of repeating units represented by III, and the self-crosslinking Provided is a method for producing a cross-linked solid polymer electrolyte, characterized in that a cross-linking reaction of a type block-graft copolymer and the reactive polyalkylene oxide is carried out.
[0015]
In this case, in particular, at least one block chain A having a degree of polymerization of 10 or more consisting of repeating units represented by the general formula I and at least one block having a degree of polymerization of 300 or more consisting of repeating units represented by the general formula II. A self-crosslinking block-graft copolymer having a degree of polymerization of 310 or more, wherein the constituent ratio (polymerization degree ratio) of the block chain A and the block chain B is 1:30 to 30: 1. It is composed of at least one block chain A composed of repeating units represented by the formula I having a degree of polymerization of 10 or more and at least one block chain C composed of repeating units represented by the general formula III having a degree of polymerization of 200 or more. A self-crosslinking block-graft copolymer having a degree of polymerization of 210 or more, wherein the composition ratio (polymerization degree ratio) of block chain A and block chain C is 1:20 to 20: 1. By adding a reactive polyalkylene oxide represented by the general formula IV, preferably a monofunctional and bifunctional polyalkylene oxide in combination, and adding a lithium-based inorganic salt, preferably by irradiating an electron beam The self-crosslinking block-graft copolymer and the reactive polyalkylene oxide are preferably subjected to a crosslinking reaction.
[0016]
[Chemical formula 5]

(Here, R¹Is a hydrogen atom, a methyl group or an ethyl group, R²Is a hydrogen atom or a methyl group, R^ThreeIs an alkyl group, aryl group, acyl group, silyl group or cyanoalkyl group, and n is an integer of 1 to 100. In addition, the number average molecular weight of the graft chain represented by the following Ia in the formula is 45 to 4,400. )
[0017]
[Chemical 6]

(Here, R^FourIs a hydrogen atom, a methyl group or an ethyl group, and y is 2 or 3. )
[0018]
[Chemical 7]

(Here, R^FourAnd R^FiveIs a hydrogen atom, a methyl group or an ethyl group, and y is 2 or 3. The total of k and m is 200 or more, and the composition ratio of k and m is 95: 5 to 50:50. The arrangement method is random or alternating. )
[0019]
[Chemical 8]

(Here, R⁶And R⁷Is a hydrogen atom or a methyl group, R⁸Is H₂C = CHCO-, H₂C = C (CH_Three) CO-, vinyl group, allyl group, epoxide, alkyl group having 25 or less carbon atoms, phenyl group or substituted phenyl group, R⁹Is ethylene oxide or tetramethylene oxide. e and f are both integers of 0 to 25, but are not 0 at the same time. When one is 0, the other is always an integer of 1 or more. X is -PhC (CH_Three)₂PhO- or a single bond is shown. Ph represents a phenylene group. )
[0020]
In this method, reactive polyalkylene oxide is compatible with the graft component of the self-crosslinking type block-graft copolymer, and both can be cross-linked at the same time in a state in which a microphase separation structure is formed. The trunk molecule increases the mechanical strength of the film, the polyalkylene oxide cross-linked with the graft component forms a continuous phase to secure the passage of metal ions, and no vapor pressure is generated from the polyalkylene oxide. A highly reliable film can be formed.
[0021]
As the reactive polyalkylene oxide, a monofunctional or bifunctional acrylate-based, methacrylate-based, allyl-based, epoxide or the like represented by the general formula IV is used. The crosslinking reaction of polyalkylene oxide can be completed.
[0022]
By this production method, it is possible to produce a crosslinked polymer solid electrolyte having a high ion conductivity and a high film strength without generating any vapor pressure even at a high temperature easily and reliably. In order to make use of the properties of block-graft copolymers to maintain excellent mechanical strength and high ionic conductivity even at high temperatures and to obtain a safe polymer electrolyte, self-crosslinking block-graft copolymer The present invention has been completed by discovering that it is effective if both the coalescence and the polyalkylene oxide added thereto are simultaneously crosslinked to form a three-dimensional network structure.
[0023]
Hereinafter, the present invention will be described in more detail.
As described above, the block-graft copolymer that is the basis of the crosslinked polymer solid electrolyte of the present invention comprises a block chain A composed of a repeating unit represented by the general formula I and a repeating unit represented by the general formula II. A block-graft copolymer composed of a block chain B and / or a block chain C composed of repeating units represented by the general formula III, particularly preferably the above-mentioned Japanese Patent No. 1842047 and JP-A-10-237143. The structure is basically the same as that disclosed in the publication, but here again the structure thereof, at least one block chain A having a degree of polymerization of 10 or more consisting of repeating units represented by the general formula I, A block composed of at least one block chain B having a degree of polymerization of 300 or more and comprising a repeating unit represented by the general formula II A block-graft copolymer having a degree of polymerization of 310 or more having a composition ratio (polymerization degree ratio) of A and block chain B of 1:30 to 30: 1, or at least one kind of repeating unit represented by the general formula I Composition ratio of block chain A and block chain C (polymerization) composed of block chain A having a polymerization degree of 10 or more and at least one block chain C having a polymerization degree of 200 or more composed of repeating units represented by general formula III Degree ratio) is a block-graft copolymer having a degree of polymerization of 210 or more and a ratio of 1:20 to 20: 1.
[0024]
[Chemical 9]

(Here, R¹Is a hydrogen atom, a methyl group or an ethyl group, R²Is a hydrogen atom or a methyl group, R^ThreeIs an alkyl group, aryl group, acyl group, silyl group or cyanoalkyl group, and n is an integer of 1 to 100. In the formula, the number average molecular weight of the graft chain represented by the following Ia is 45 to 4,400. )
[0025]
[Chemical Formula 10]

[0026]
Where R^ThreeAs the alkyl group, those having 1 to 10 carbon atoms, particularly 1 to 2 carbon atoms are preferable, and examples of the aryl group include those having 6 to 10 carbon atoms, particularly 6 to 8 carbon atoms, and phenyl group is particularly preferable. Examples of the acyl group include those having 1 to 9 carbon atoms, particularly 1 to 2 carbon atoms, and specific examples include formyl group and acetyl group. As the silyl group, —SiR_Three(R is the same or different carbon number 3-15, especially 3-6 monovalent hydrocarbon group, preferably an alkyl group). The cyanoalkyl group includes, for example, a cyanoethyl group, a cyanopropyl group, etc. in which a part of hydrogen atoms of an alkyl group having 2 to 10 carbon atoms, particularly 2 to 4 carbon atoms, is substituted with a cyano group.
[0027]
Embedded image

(Here, R^FourIs a hydrogen atom, a methyl group or an ethyl group, and y is 2 or 3. )
[0028]
Embedded image

(Here, R^FourAnd R^FiveIs a hydrogen atom, a methyl group or an ethyl group, and y is 2 or 3. The total of k and m is 200 or more, and the composition ratio of k and m is 95: 5 to 50:50. The arrangement method is random or alternating. )
[0029]
This block-graft copolymer comprises a block chain A composed of the same or different repeating units represented by the general formula I, a block chain B composed of the same or different repeating units represented by the general formula II and / or the general formula A block chain C composed of the same or different repeating units represented by III is arbitrarily arranged, for example, AB, AC, BAB, BAB ′, CAC, C′AC, BAC, BAB′AB, C′ABAC. Preferably, BAB, BAB ', B'ABAB', BAB'AB, CAC, CAC ', C'ACAC', CAC'AC, more preferably BAB, BAB ', CAC, CAC', etc. Examples include sequences. In this arrangement example, B, B ′ and C, C ′ are included in the block chain B and the block chain C, respectively.^FourOr R^FiveAre different, or have different degrees of polymerization, indicating different block chains.
[0030]
The degree of polymerization of the block chain A of the polymer is preferably 10 or more, the degree of polymerization of B is preferably 300 or more, and the degree of polymerization of C is preferably 200 or more. It is preferable that the ratio is 1:30 to 30: 1, and the block chains A and C are 1:20 to 20: 1. The degree of polymerization of the block-graft copolymer obtained by copolymerization is preferably 310 to 50000 in the arrangement of block chains A and B, and 210 to 50000 in the arrangement of block chains A and C.
[0031]
The block chain A of the polymer is a part responsible for the function as a polymer electrolyte. When the degree of polymerization is less than 10, the ion-conductive domain that is characteristic of this polymer does not show a microphase separation structure that becomes a continuous phase. There is. In addition, since the block chain B is a portion that retains mechanical strength, if the degree of polymerization is less than 300, the entanglement between the polymer molecules is insufficient and the mechanical strength of the film is lowered. That is, when the composition ratio of the block chains A and B is less than 1:30, there are too few graft components and it is difficult to maintain the function as a polymer electrolyte, and when it exceeds 30: 1, the trunk component as a block chain There is a risk that the mechanical strength cannot be maintained. However, the block chain C having a polymer Tg higher than that of the block chain B can maintain the mechanical strength even at an exceptionally low degree of polymerization. The polymerization degree ratio) is 1:20 to 20: 1, and the degree of polymerization of the copolymer obtained by copolymerization can be 210 or more.
[0032]
The cross-linked solid polymer electrolyte of the present invention is obtained by adding a reactive polyalkylene oxide represented by the following general formula IV and a lithium-based inorganic salt to the block-graft copolymer, and the block-graft copolymer and its reactivity. A polyalkylene oxide is subjected to a crosslinking reaction.
[0033]
Embedded image

(Here, R⁶And R⁷Is a hydrogen atom or a methyl group, R⁸Is H₂C = CHCO-, H₂C = C (CH_Three) CO-, vinyl group, allyl group, epoxide, alkyl group having 25 or less carbon atoms, phenyl group or substituted phenyl group, R⁹Is ethylene oxide or tetramethylene oxide. e and f are both integers of 0 to 25, but are not 0 at the same time. When one is 0, the other is always an integer of 1 or more. X is -PhC (CH_Three)₂PhO- or a single bond is shown. Ph represents a phenylene group. )
[0034]
R above⁸Examples of the epoxide include those represented by the following formula.
[0035]
Embedded image

(However, p is an integer of 1-25 and q is an integer of 1-25.)
R⁸Examples of the substituted phenyl group include a tolyl group and a xylyl group.
[0036]
As the reactive polyalkylene oxide added to the block-graft copolymer, acrylate derivatives, methacrylate derivatives, vinyl derivatives, etc. of polyalkylene glycol are suitable, and those containing no active hydrogen or halogen in the structure are preferable. . Specifically, methoxyethylene glycol mono (meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate, octoxypolyethylene glycol-block-polypropylene glycol mono (meth) acrylate, lauroxypolyethylene glycol mono (meth) acrylate, stearoxy Polyethylene glycol mono (meth) acrylate, allyloxy polyethylene glycol mono (meth) acrylate, nonylphenoxy polyethylene glycol mono (meth) acrylate, nonylphenoxypolypropylene glycol mono (meth) acrylate, nonylphenoxypoly (ethylene glycol-propylene glycol) mono ( (Meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene Recall di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, Examples include poly (ethylene glycol-tetramethylene glycol) di (meth) acrylate and poly (propylene glycol-tetramethylene glycol) di (meth) acrylate. In addition, ethylene oxide-modified bisphenol A di (meth) acrylate, ethylene oxide-propylene oxide-modified bisphenol A di (meth) acrylate, and propylene oxide-tetramethylene oxide-modified bisphenol A in which block chains e and f are bonded with bisphenol A. Examples include di (meth) acrylate, ethylene oxide-block-propylene oxide-modified bisphenol A di (meth) acrylate, and the like.
[0037]
In the present invention, basically, a monofunctional polyalkylene oxide and a bifunctional polyalkylene oxide are used in combination. It is also effective to use a mixture of two or more polyalkylene oxides having the same number of functional groups. Further, although not exemplified here, the use of a tri- or higher functional polyalkylene oxide increases the cross-linking density, so it is effective when it is desired to improve the film strength even if the ion conductivity is somewhat sacrificed. It becomes a means.
[0038]
The addition amount of the reactive polyalkylene oxide is 5% by weight or more, preferably 50 to 600% by weight, based on the block-graft copolymer, and the mixing ratio of monofunctional polyalkylene oxide and bifunctional polyalkylene oxide. Is a weight ratio of 5:95 to 95: 5, preferably 10:90 to 70:30. Moreover, there is no restriction | limiting in particular in the mixing ratio of the reactive polyalkylene oxide from which a functional group number is equal and from which a kind differs.
[0039]
The addition method of the reactive polyalkylene oxide is, for example, a method in which it is added to the block-graft copolymer and mechanically kneaded at room temperature or under heating, and is dissolved in a common solvent with the block-graft copolymer, followed by a casting method. There are various methods such as film formation, but since this block-graft copolymer also has a high function as a polymer compatibilizing agent, alkylene oxide added by various methods is automatically converted into the graft phase. Aggregates to form a microphase separation structure. Therefore, the addition method is arbitrary and is not particularly limited.
[0040]
The type of lithium-based inorganic salt added to the block-graft copolymer is LiClO._Four, LiBF_Four, LiPF₆, LiAsF₆, LiCF_ThreeSO_ThreeAnd LiN (CF_ThreeSO₂)₂At least one compound selected from is preferred. The ratio of addition is 0.01 to 80 mol%, preferably 0.02 to 15 mol based on the total number of moles of alkylene oxide units of the reactive polyalkylene oxide added to the graft chain of the block-graft copolymer. % Is appropriate, and the addition method is not limited as in the case of polyalkylene oxide.
[0041]
In the present invention, the reactive polyalkylene oxide added to the block-graft copolymer is subjected to a crosslinking reaction by a method of crosslinking by heat (thermal crosslinking), a method of crosslinking by irradiation with ultraviolet rays (ultraviolet irradiation), an electron An example is a method of irradiating a beam to crosslink (electron beam irradiation). In the thermal crosslinking, an organic peroxide such as 2,2′-azobis (isobutyronitrile), benzoyl peroxide, methyl ethyl ketone or the like is added in advance as a thermal polymerization initiator, and is predetermined at 85 ° C. or higher after film formation. It is a method of heating for a period of time, and ultraviolet irradiation is performed in advance by using 2,2-dimethoxy-2-phenylacetophene, benzylmethyl ketal, trimethylsilylbenzophenone, 2-methylbenzoin, 4-methoxybenzophenone, benzoin methyl ether, anthraquinone, etc. In this method, a photopolymerization initiator is added, and UV irradiation is performed for 3 minutes or more with a 500 W high-pressure mercury lamp after film formation. Moreover, electron beam irradiation is 5-100 Mrad. Using an electron beam irradiation apparatus after film-forming. This is a method of irradiating an electron beam with an irradiation dose of. As described above, a radical generator (polymerization initiator) is necessary for thermal crosslinking and ultraviolet irradiation, but the use of this makes the reaction system more complicated and may adversely affect the transport of lithium ions. There is also concern about the effect. Therefore, in the present invention, the crosslinking method using an electron beam (radiation) which has a high energy level and is easy to control and does not require a radical generator is optimal. For example, as an electron beam irradiation device [CB250 / 30 / manufactured by Iwasaki Electric Co., Ltd. 180L], acceleration voltage 200 kV, 5-100 Mrad. When various tests were conducted, it was confirmed that this was a very excellent crosslinking method.
[0042]
In the solid polymer electrolyte according to the present invention, a self-crosslinking block-graft copolymer as a constituent element thereof has (1) a clear microphase separation structure, and (2) a trunk molecule having high mechanical strength is pseudo-crosslinked. Forms the structure, plays a role in maintaining the structure and enhances the material strength. (3) Forms a continuous phase even when the graft component is relatively low in molecular weight and secures a passage for metal ions. (4) Graft component is compatibilized. Since it has a function as an agent, a large amount of polyalkylene oxide can be stably held in the film. (5) Since there is no volatile component in the system, it has excellent thermal stability at high temperatures and high safety. It has various characteristics.
[0043]
Therefore, when the polymer solid electrolyte of the present invention is applied to, for example, a lithium polymer secondary battery that operates at a high temperature such as an electric vehicle or a nighttime power storage that is expected to be put to practical use in the future, the battery can be reduced in weight and thinned. A battery that is very effective and extremely safe can be produced.
[0044]
In addition to the secondary battery element, the crosslinked polymer electrolyte of the present invention is also effective when used in various solid electrochemical elements such as a primary battery, a capacitor, an electrochromic display, or a sensor.
[0045]
【Example】
Embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In addition, the block copolymer in an Example connects each component by -b-, for example, the poly-butenyl styrene, poly-p-hydroxy styrene, polybutenyl styrene three-component block copolymer is poly (butenyl). Styrene-b-p-hydroxystyrene-b-butenylstyrene), a block chain made of a [random / alternate] copolymer of polybutenylstyrene and polystyrene is -CO-, and a graft chain is -g-. Connect and express.
[0046]
[Example 1] Electron beam crosslinking I of a self-crosslinking block-graft copolymer film to which a reactive polyalkylene oxide and a lithium-based inorganic salt were added I
The molecular structure of the block-graft copolymer used in Example 1, the composition ratio of each block chain, the composition of the graft chain, and the like are shown below.
[0047]
Sample No. of block-graft copolymer B-1
(1) Molecular structure:
Poly [butenylstyrene-b- (p-hydroxystyrene-g-ethylene oxide) -b-butenylstyrene]
(2) Block chain A (general formula I):
R¹= Hydrogen atom, R²= Hydrogen atom, R^Three= Methyl group, degree of polymerization = 250
(3) Block chain B (general formula II):
R^Four= Hydrogen atom, y = 2, polymerization degree = 500
(4) Block chain arrangement method:
BAB (triblock copolymer)
(5) Block chain composition ratio (polymerization degree ratio):
B: A: B = 500: 250: 500 = 2: 1: 2 (2B: A = 4: 1)
(6) Graft chain (general formula Ia):
R²= Hydrogen atom, R^Three= Methyl group, n (degree of polymerization) = 15, number average molecular weight (Mn) = 660
5.0 g of the above self-crosslinking block-graft copolymer (Sample No. B-1), 2.0 g of methoxypolyethylene glycol monomethacrylate (Mn = 276), 1.0 g of polyethylene glycol diacrylate (Mn = 214) and LiClO_FourAfter 0.5 g was dissolved in 60 ml of dimethyl carbonate, it was cast into a Teflon petri dish. This sample was allowed to stand at room temperature for about 20 hours under an argon stream to remove excess solvent, and further heated and dried at 80 ° C. for 2 hours to obtain a film having a thickness of 20 μm. An acceleration voltage of 200 kV and a dose of 10 Mrad. After the electron beam was irradiated, the obtained sample was subjected to thermal analysis with a differential thermal balance DSC-20 (trade name, manufactured by Seiko Electronics Industry Co., Ltd.). As a result, although a weight loss of 1% or less, which seems to be caused by dimethyl carbonate, was observed around 90 ° C., no change in weight was observed until 250 ° C. Thereafter, the block-graft copolymer was It has been found that the added reactive polyalkylene oxide is completely crosslinked and does not volatilize even at high temperatures of 100 to 250 ° C., and therefore does not generate vapor pressure and is stably held in the graft phase.
[0048]
[Example 2] Electron beam crosslinking of a self-crosslinking block-graft copolymer film to which a reactive polyalkylene oxide and a lithium-based inorganic salt are added II
The film before electron beam irradiation produced by the same formulation as Example 1 was applied with an acceleration voltage of 200 kV and a dose of 1 to 3 Mrad. As a result of thermal analysis of the sample obtained by irradiating the electron beam, rapid weight loss was observed from around 150 ° C. On the other hand, 5-100 Mrad. All of the samples irradiated with the above dose were stable up to 250 ° C., and no weight loss other than the solvent was observed. Therefore, in the following examples, it is possible to completely crosslink the added reactive polyalkylene oxide, and an irradiation dose of 10 Mrad. At which no vapor pressure is generated even at a high temperature of 100 to 250 ° C. Was used as a reference dose.
[0049]
[Example 3]
An acceleration voltage of 200 kV, a dose of 10 Mrad. The resulting sample was vacuum dried at 100 ° C. for 20 hours to obtain a crosslinked polymer solid electrolyte film having a thickness of 20 μm. The obtained film was tough despite containing a large amount of polyalkylene oxide, and the storage elastic modulus obtained from a dynamic viscoelasticity tester RSA-II (trade name, manufactured by Reometric Inc.) was 30 ° C. 9.5 × 10⁶Pa, 8.4 × 10 even at 80 ° C.⁶Pa or higher was shown. Further, the electrolyte film was 100 kg / cm at 20 ° C.²The polyalkylene oxide contained therein did not exude at all even when compressed with a load of.
[0050]
This film is cut into a disk shape having a diameter of 10 mm, and electrodes are formed by sandwiching both sides of the electrode with a lithium metal electrode plate, and an AC impedance measuring apparatus (multi-frequency LCRX meter 4192A, manufactured by Yokogawa Hewlett-Packard Co., Ltd.) The ion conductivity was calculated by the complex impedance method. As a result, 0.7 × 10 at 80 ° C.^-3A value of S / cm was obtained.
[0051]
[Examples 4 to 9]
The molecular structure of the self-crosslinking block-graft copolymer (Sample Nos. B-2 to BT-2) used in Examples 4 to 9, the composition ratio of each block chain, the composition of the graft chain, etc. are shown below. . In addition, after adding different types of reactive polyalkylene oxide and lithium-based inorganic salts to the following self-crosslinking block-graft copolymer, a cross-linked polymer solid electrolyte film crosslinked by electron beam irradiation was used. When the same evaluation as in Example 3 was performed, the results shown in Table 1 were obtained.
[0052]
Sample No. B-2
(1) Molecular structure:
Poly [butenylstyrene-b- (p-hydroxystyrene-g-ethylene oxide) -b-butenylstyrene]
(2) Block chain A (general formula I):
R¹= Hydrogen atom, R²= Hydrogen atom, R^Three= Methyl group, degree of polymerization = 250
(3) Block chain B (general formula II):
R^Four= Hydrogen atom, y = 2, polymerization degree = 500
(4) Block chain arrangement method:
BAB (triblock copolymer)
(5) Block chain composition ratio (polymerization degree ratio):
B: A: B = 500: 250: 500 = 2: 1: 2 (2B: A = 4: 1)
(6) Graft chain (general formula Ia):
R²= Hydrogen atom, R^Three= Methyl group, n = 23, number average molecular weight (Mn) = 1010
[0053]
Sample No. BT-1
(1) Molecular structure:
Poly [(styrene-co-butenylstyrene) -b- (p-hydroxystyrene-g-ethylene oxide) -b- (styrene-co-butenylstyrene)]
(2) Block chain A (general formula I):
R¹= Hydrogen atom, R²= Hydrogen atom, R^Three= Methyl group, degree of polymerization = 250
(3) Block chain C (general formula III):
R^Four= Hydrogen atom, R^Five= Hydrogen atom, y = 2, m (degree of polymerization) = 100, k (degree of polymerization) = 400
(4) Block chain arrangement method:
CAC (triblock copolymer)
(5) Block chain composition ratio (polymerization degree ratio):
C: A: C = (100 + 400): 250: (100 + 400) = 2: 1: 2 (2C: A = 4: 1)
(6) Graft chain (general formula Ia):
R²= Hydrogen atom, R^Three= Methyl group, n = 9, number average molecular weight (Mn) = 400
[0054]
Sample No. BT-2
(1) Molecular structure:
Poly [(styrene-co-butenylstyrene) -b- (p-hydroxystyrene-g-ethylene oxide) -b- (styrene-co-butenylstyrene)]
(2) Block chain A (general formula I):
R¹= Hydrogen atom, R²= Hydrogen atom, R^Three= Methyl group, degree of polymerization = 250
(3) Block chain C (general formula III):
R^Four= Hydrogen atom, R^Five= Hydrogen atom, y = 2, m (degree of polymerization) = 50, k (degree of polymerization) = 450
(4) Block chain arrangement method:
CAC (triblock copolymer)
(5) Block chain composition ratio (polymerization degree ratio):
C: A: C = (50 + 450): 250: (50 + 450) = 2: 1: 2 (2C: A = 4: 1)
(6) Graft chain (general formula Ia):
R²= Hydrogen atom, R^Three= Methyl group, n = 14, number average molecular weight (Mn) = 620
[0055]
[Table 1]

A: Methoxypolyethylene glycol monomethacrylate (Mn = 276)
B: Polyethylene glycol diacrylate (Mn = 302)
C: Methoxypolyethylene glycol monoacrylate (Mn = 466)
D: Polypropylene glycol dimethacrylate (Mn = 386)
E: Methoxypolyethylene glycol monomethacrylate (Mn = 496)
F: Allyloxy polyethylene glycol monomethacrylate (Mn = 214)
G: Octoxy polyethylene glycol-polypropylene glycol monomethacrylate (Mn = 898)
H: Polypropylene glycol diacrylate (Mn = 302)
I: Poly (ethylene glycol-tetramethylene glycol) dimethacrylate (Mn = 600)
J: Lauroxy polyethylene glycol monoacrylate (Mn = 400)
K: Polypropylene glycol diacrylate (Mn = 518)
L: Methoxypolyethylene glycol monoacrylate (Mn = 482)
M: Allyloxy polyethylene glycol monoacrylate (Mn = 380)
[0056]
From these results, the cross-linked solid polymer electrolyte produced according to the present invention contains a large amount of polyalkylene oxide and lithium-based inorganic salt in the film, but it is vaporized even at a high temperature of 100 ° C. or higher. It was found that the film has high ion conductivity and high film strength without generating pressure.
[0057]
[Comparative Example 1]
According to the method for forming a solid polymer electrolyte described in US Pat. No. 5,296,318, a film-shaped solid electrolyte having a thickness of 100 μm was prepared. The method consists of 5.0 g of VdF / HFP copolymer [Atochem Kyner FLEX 2801 (trade name)], 2.0 g of methoxypolyethylene glycol monomethacrylate (Mn = 273), 1.0 g of polyethylene glycol diacrylate (Mn = 214) and LiClO._Four0.5 g was dissolved and mixed in 50 ml of tetrahydrofuran, and then cast into a Teflon petri dish. The sample was allowed to stand at room temperature for about 20 hours under an argon stream to remove excess solvent, and further heated and dried at 80 ° C. for 2 hours. However, since Atochem Kyner FLEX 2801 and polyalkylene oxide were not compatibilized at all, macro phase separation occurred and only a semi-solid film that was not completely solidified could be obtained.
[0058]
[Comparative Example 2]
The semi-solid film produced in Comparative Example 1 was subjected to an acceleration voltage of 200 kV and a dose of 10 Mrad. When the electron beam was irradiated, a heterogeneous film with macro phase separation still occurred was obtained. Also 50 Mrad. With the above electron beam dose, the decomposition reaction of Atochem Kyner FLEX 2801 proceeded and fluorine gas was generated.
[0059]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the bridge | crosslinking type polymer solid electrolyte used suitably as a large sized secondary battery etc. with the outstanding film intensity | strength, high ion conductivity, and the shaping | molding to a film and favorable workability is obtained.

Claims (5)

Self-crosslinking composed of a block chain A composed of repeating units represented by the general formula I, a block chain B composed of repeating units represented by the general formula II and / or a block chain C composed of repeating units represented by the general formula III A reactive polyalkylene oxide represented by general formula IV and a lithium-based inorganic salt are added to the block-graft copolymer, and the self-crosslinking block-graft copolymer and the reactive polyalkylene oxide are crosslinked. A method for producing a cross-linked polymer solid electrolyte.

(Where R ¹ is a hydrogen atom, methyl group or ethyl group, R ² is a hydrogen atom or methyl group, R ³ is an alkyl group, aryl group, acyl group, silyl group or cyanoalkyl group, and n is 1-100. The number average molecular weight of the graft chain represented by the following Ia in the formula is 45 to 4,400.)

(Here, R ⁴ is a hydrogen atom, a methyl group or an ethyl group, and y is 2 or 3.)

(Here, R ⁴ and R ⁵ are a hydrogen atom, a methyl group or an ethyl group, and y is 2 or 3. The total of k and m is 200 or more, and the composition ratio of k and m is 95: 5 to 50: 50. The arrangement method is random or alternating.)

(Where R ⁶ and R ⁷ are hydrogen atoms or methyl groups, R ⁸ is H ₂ C═CHCO—, H ₂ C═C (CH ₃ ) CO—, vinyl group, allyl group, epoxide, carbon number 25 or less. An alkyl group, a phenyl group or a substituted phenyl group, R ⁹ is ethylene oxide or tetramethylene oxide, e and f are both integers of 0 to 25, but are not 0 at the same time, and one is 0 The other is an integer greater than or equal to 1. X represents —PhC (CH ₃ ) ₂ PhO— or a single bond, where Ph represents a phenylene group. The block chain A having at least one polymerization degree 10 or more composed of repeating units represented by the general formula I and at least one block chain having at least one polymerization degree 300 or more consisting of repeating units represented by the general formula II. A self-crosslinking block-graft copolymer having a degree of polymerization of 310 or more and having a composition ratio (polymerization degree ratio) of block chain A and block chain B of 1:30 to 30: 1, A cross-linked solid polymer electrolyte, characterized by adding a reactive polyalkylene oxide represented by IV and a lithium-based inorganic salt to cause the self-cross-linking block-graft copolymer and the reactive polyalkylene oxide to undergo a cross-linking reaction Manufacturing method. The block chain A having at least one polymerization degree of 10 or more consisting of repeating units represented by the general formula I and at least one block chain having a degree of polymerization of 200 or more consisting of repeating units represented by the general formula III. A self-crosslinking block-graft copolymer having a polymerization degree of 210 or more and a composition ratio (polymerization degree ratio) of block chain A to block chain C of 1:20 to 20: 1, A cross-linked solid polymer electrolyte, characterized by adding a reactive polyalkylene oxide represented by IV and a lithium-based inorganic salt to cause the self-cross-linking block-graft copolymer and the reactive polyalkylene oxide to undergo a cross-linking reaction Manufacturing method. The method for producing a crosslinked polymer solid electrolyte according to any one of claims 1 to 3, wherein a crosslinking reaction is performed by irradiation with an electron beam. The production of a crosslinked polymer solid electrolyte according to any one of claims 1 to 4, wherein a monofunctional polyalkylene oxide and a bifunctional polyalkylene oxide are used in combination as the reactive polyalkylene oxide represented by the general formula IV. Method.