JP4911813B2 - Crosslinkable composition for solid electrolyte, polymer solid electrolyte lithium ion secondary battery, and method for producing polymer solid electrolyte lithium ion secondary battery - Google Patents

Description

の脂環式エポキシ化合物や、ビスフェノール系エポキシ化合物の２種のみが例示されているにすぎず、本発明のオキセタン環含有ラジカル共重合ポリマーとは明らかに相違する。
また、該先行特許の高分子固体電解質中のポリマー含有量は、たとえばその実施例２の配合組成から算出すると、約４７％にも及び、イオン伝導度も５×１０^-4Ｓ／cm（２５℃）とあり、実用的レベルとは云えない。これに対して、本発明ではポリマー含有量５％以下が特徴で、イオン伝導度（イオン導電性）も後記実施例に示される通り、前者の１０倍乃至２０倍もの値を示すことが認められる。
【００１０】
すなわち、本発明は、（１）オキセタン環含有ポリマー、
（２）カチオン重合開始剤、
（３）電解液溶媒、および
（４）リチウム電解質塩
から成り、上記オキセタン環含有ポリマー（１）が総量中５％以下である液状の固体電解質用架橋性組成物（以下、液状組成物と称す）を、リチウムイオン２次電池用に架橋によってゲル化せしめポリマー固体電解質化したことを特徴とするポリマー固体電解質リチウムイオン２次電池を提供するものである。
【００１１】
本発明におけるオキセタン環含有ポリマー（１）は、ポリマー構造内にオキセタン環を複数個有するポリマーであって、ポリマーの骨格構造を問うものではないが、簡便なラジカル重合でも容易に得ることができる。すなわち、オキセタン環を有するラジカル重合性モノマー（以下、オキセタン重合モノマーと称す）および必要に応じてエポキシ基を有するラジカル重合性モノマー（以下、エポキシ重合モノマーと称す）と、他のラジカル重合性モノマーとをラジカル重合させることによって製造され、通常分子量が１００００以上に設定されている。分子量が１００００未満であると、ゲルを形成するのに必要なポリマー量が多く必要になる傾向にある。なお、分子量の上限には特に制限はないが、後記液状組成物の液状（溶液状態）を維持する上で、上限を１００万程度、好ましくは５０万程度に抑えることが適当である。
【００１２】
上記ラジカル重合は通常、ラジカル重合開始剤［たとえばＮ,Ｎ'−アゾビスイソブチロニトリル、ジメチルＮ,Ｎ'−アゾビス（２−メチルプロピオネート）、ベンゾイルパーオキシド、ラウロイルパーオキシド等］および必要に応じてメルカプタン類などの分子量調整剤を用いて行なうことができ、その際、得られるポリマーの分子量が比較的大きいため、溶媒中６０〜８０℃程度の温度で行なう溶液重合が好適である。溶媒としては、後記電解液溶媒（３）に例示される環状炭酸エステル類、鎖状炭酸エステル類、低分子カルボン酸エステル類の使用が好ましい。
【００１３】
上記オキセタン重合モノマーとしては、たとえば式：
【化６】

（式中、Ｒ₁はＨまたはＣＨ₃；およびＲ₂はＨまたは炭素数１〜６のアルキルである）
の（メタ）アクリルモノマー、具体的には、（３−オキセタニル）メチル（メタ）アクリレート、（３−メチル−３−オキセタニル）メチル（メタ）アクリレート、（３−エチル−３−オキセタニル）メチル（メタ）アクリレート、（３−ブチル−３−オキセタニル）メチル（メタ）アクリレート、（３−ヘキシル−３−オキセタニル）メチル（メタ）アクリレート等が挙げられ、これらの少なくとも１種を使用する。使用量は通常、上記エポキシ重合モノマーを用いない場合、モノマー全量中５〜５０％、好ましくは１０〜３０％の範囲で選定する。５％未満では、ゲル化に要するポリマー量の増大を招き、また５０％を越えると、ゲルから電解液が分離（ブリード）する傾向にある。
なお、本明細書において、「（メタ）アクリル」とは、アクリルとメタクリルを意味し、「（メタ）アクリレート」とは、アクリレートとメタクリレートを意味する。
【００１４】
上記必要に応じて用いられるエポキシ重合モノマーとしては、たとえば
【化７】

（式中、Ｒ₅はＨまたはＣＨ₃；およびＲ₆は
【化８】

である）
の（メタ）アクリレート、具体的には、３,４−エポキシシクロヘキシルメチル（メタ）アクリレート、グリシジル（メタ）アクリレートが挙げられ、これらの少なくとも１種を使用する。使用量は通常、オキセタン重合モノマーとの合計量中エポキシ重合モノマーの割合が９０％以下となるように、および該両モノマーの合計量がモノマー全量中５〜５０％、好ましくは１０〜３０％となるように選定すればよい。
【００１５】
上記他のラジカル重合性モノマーとしては、式：
【化９】

（式中、Ｒ₃はＨまたはＣＨ₃；およびＲ₄は−ＣＯＯＣＨ₃、−ＣＯＯＣ₂Ｈ₅、−ＣＯＯＣ₃Ｈ₇、−ＣＯＯＣ₄Ｈ₉、−ＣＯＯ(ＣＨ₂ＣＨ₂Ｏ)_{1 〜 3}ＣＨ₃、−ＣＯＯ(ＣＨ₂ＣＨ₂Ｏ)_{1 〜 3}Ｃ₂Ｈ₅、−ＣＯＯ(ＣＨ₂ＣＨ(ＣＨ₃)Ｏ)_{1 〜 3}ＣＨ₃、−ＣＯＯ(ＣＨ₂ＣＨ(ＣＨ₃)Ｏ)_{1 〜 3}Ｃ₂Ｈ₅、−ＯＣＯＣＨ₃、または−ＯＣＯＣ₂Ｈ₅である）
のビニル系もしくは（メタ）アクリル系モノマーが好適である。なお、これら以外のものも使用可能であるが、使用する電解液溶媒（３）との親和性が低いと、ゲルから電解液が分離（ブリード）する場合がある。
このようにして製造されるオキセタン環含有ポリマー（１）を単独で使用、あるいは該オキセタン環含有ポリマー（１）の一部に、上記エポキシ基を有するラジカル重合性モノマーと他のラジカル重合性モノマーとを上記と同様な条件下でラジカル共重合させることにより得られる分子量１００００以上のエポキシ基含有ポリマーを併用してもよい。
【００１６】
本発明におけるカチオン重合開始剤（２）としては、各種のオニウム塩（たとえばアンモニウム、ホスホニウム、アルソニウム、スチボニウム、スルホニウム、ヨードニウムなどのカチオンの、−ＢＦ₄、−ＰＦ₆、−ＳｂＦ₆、−ＣＦ₃ＳＯ₃、−ＣｌＯ₄などのアニオン塩等）が使用できるが、本発明でこれらオニウム塩を使用せずとも、リチウム電解質塩（４）であるヘキサフルオロリン酸リチウムおよび／またはテトラフルオロホウ酸リチウムを利用すれば、本来のリチウム電解質塩の作用に加え、当該カチオン重合開始剤としても作用することができ、好都合である。カチオン重合開始剤の使用は、電解質にとって余分な成分であり、その分イオン導電性の低下につながり、その他製造工程の煩雑化、コストの上昇等を伴なう。
当然、カチオン重合開始剤の一部として、オニウム塩にヘキサフルオロリン酸リチウムやテトラフルオロホウ酸リチウムを併用することも可能である。
【００１７】
本発明における電解液溶媒（３）としては、たとえば環状炭酸エステル類（炭酸エチレン、炭酸プロピレン、炭酸ブチレンなど）；鎖状炭酸エステル類（炭酸ジメチル、炭酸ジエチル、炭酸メチル・エチル、炭酸メチル・ｎ−プロピルなどの対称および非対称型を包含）；環状エステル類（ラクトン類）（γ−ブチロラクトン、γ−バレロラクトンなど）；環状エーテル類（テトラヒドロフラン、メチルテトラヒドロフランなど）；低分子カルボン酸エステル類（酢酸エチル、酢酸プロピル、酢酸ブチル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸プロピル、酪酸メチル、酪酸ブチルなど）；鎖状エーテル類（ジメトキシエタン、メトキシエトキシエタンなど）；シアノエチル基含有化合物（メチル・２−シアノエチルエーテル、エチル・２−シアノエチルエーテル、ビス２−シアノエチルエーテル、炭酸メチル・２−シアノエチル、プロピオン酸２−シアノエチルなど）が挙げられ、これらの群から選ばれる少なくとも１種を用いる。特に、環状炭酸エステル類、環状エステル類の高誘電率溶媒に鎖状炭酸エステル類、低分子カルボン酸エステル類を混合して用いることが好ましく、更には、環状炭酸エステル類である炭酸エチレン、炭酸プロピレンと、鎖状炭酸エステル類である炭酸ジメチル、炭酸ジエチル、炭酸メチル・エチルと低分子カルボン酸エステル類の内、分子を構成する炭素の総数が４〜６の鎖状エステルである酢酸エチル、酢酸プロピル、酢酸ブチル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸プロピル、酪酸メチルとの混合物を用いることが好ましく、更に、これらの内、炭素総数５の鎖状エステルである酢酸プロピル、プロピオン酸エチル、酪酸メチルの使用が好ましい。また、その混合比率を、環状炭酸エステル類／鎖状炭酸エステル類／低分子カルボン酸エステル類＝１０〜５０：０〜５０：５０〜９０（重量比）に設定し、かつ低分子カルボン酸エステル類を溶媒全体の５０％以上に設定することが好ましい。
なお、上記低分子カルボン酸エステル類にあって、分子を構成する炭素の総数が４未満では、溶媒の沸点が低すぎ、電池にした場合、高温時に電池内圧がアップするという問題が生じ易く、また炭素総数７以上では、イオン導電性が低下して電池の特性が低下する傾向にある。
これら電解液溶媒（３）にあって、その種類および配合割合はイオン導電性への影響度が大きく、その結果、電池の内部抵抗、電流負荷特性、低温時の電流負荷特性等の電池の充放電特性、および溶媒の化学構造による電気化学的な安定性等の影響による電池の寿命に対して、大きな影響を与えるため、慎重に決定される。
【００１８】
本発明におけるリチウム電解質塩（４）は、電解液溶媒（３）への溶解性に優れ、高イオン導電性と酸化〜還元電位に高耐性の陰イオン（酸基）で構成されるものが好ましく、特に限定されるものではないが、たとえば過塩素酸リチウム、テトラフルオロホウ酸リチウム、ヘキサフルオロリン酸リチウム、トリフルオロメタンスルホン酸リチウム等が挙げられ、これらの少なくとも１種を用いる。特に、テトラフルオロホウ酸リチウムとヘキサフルオロリン酸リチウムは、良好なイオン導電性が得られる上、オキセタン環含有ポリマー（１）を架橋する作用を併せ持つため好ましい存在である。これらリチウム電解質塩（４）の濃度は通常、１モル／ｄｍ³前後が適用されるが、特に限定するものではない。
【００１９】
【発明の実施の形態】
本発明に係るポリマー固体電解質リチウムイオン２次電池は、上述のオキセタン環含有ポリマー（１）またはこれにエポキシ基含有ポリマーを併用したもの、カチオン重合開始剤（２）、電解液溶媒（３）およびリチウム電解質塩（４）を成分とし、これらを混合溶解して得られる低粘度の液状組成物を、固体電解質用架橋性組成物として使用することを特徴とし、以下の手順に従って製造することができる。
【００２０】
先ず、上記液状組成物総量中におけるオキセタン環含有ポリマー（１）および必要に応じてエポキシ基含有ポリマー（これらを合せて架橋性ポリマーと称す）の占める割合を５％以下にする。すなわち、形成される固体電解質中のポリマー含有量をできるだけ低い値に設定して、イオン導電性の安定維持を行なう。
次に、液状組成物をそのポットライフ（液状状態の保持によって注入等の取扱いが可能である時間）の制限時間内に、リチウムイオン２次電池用の、電極やセパレータ等のユニットを組み込んだ密閉容器に注入し、電極とセパレータ等のギャップに浸入させた後、常温乃至１００℃程度の温度にて、架橋性ポリマーを常温または加熱架橋させることによって容易にゲル化せしめ、ポリマー固体電解質の形成により、目的のポリマー固体電解質リチウムイオン２次電池を得る。
【００２１】
このようにして、従来の電池生産と同様の工程で新設備も必要とせず、特性と安定性に優れたポリマー固体電解質リチウムイオン２次電池を得ることができる。
従来のポリマーゲル型高分子固体電解質は、イオン導電性にとって有害無益な高分子成分をいかに低減させるかが重要なポイントであるが、むやみに架橋密度を上げても、電解液のゲル保持性の低下によって電解液が分離し易く、またゲルを構成するポリマーの構造自体も大変重要となるが、本発明は、架橋性ポリマーの使用によって、これらの諸問題を解決したものと云える。
なお、本発明で用いる液状組成物は、電解液溶媒およびリチウム電解質塩を変更することにより、リチウムイオン２次電池以外にも、リチウム電池、リチウム２次電池、電気２重層キャパシター、ケミカルコンデンサー、エレクトロクロミックデバイス等のポリマーゲル型高分子固体電解質として使用することもできる。
【００２２】
【実施例】
次に製造例、実施例および比較例を挙げて、本発明をより具体的に説明する。
製造例１（オキセタン環含有ポリマーの製造）
予め乾燥窒素ガスで十分に乾燥した１０００ｍｌの三口コルベンにて、予めモレキュラーシーブで脱水したメチルメタクリレート１０８ｇ、予めモレキュラーシーブで脱水した（３−エチル−３−オキセタニル）メチルアクリレート３６ｇ、予めモレキュラーシーブで脱水し、減圧蒸留した加温常態の炭酸エチレン４３２ｇの混合液に、ジメチルＮ，Ｎ’−アゾビス（２−メチルプロピオネート）０．２２５ｇを加え、乾燥窒素ガスを導入しながら７０℃で攪拌し、そのまま１２時間加熱攪拌を続けラジカル重合を行なう。次に温度を４０〜５０℃に下げ、予めモレキュラーシーブで乾燥し、減圧蒸留したプロピオン酸エチル３７８ｇを加え、全体が均一になるまで攪拌溶解して、オキセタン環含有ポリマーの１５％溶液を得る。
このポリマー溶液は、無色透明な粘稠液体で、赤外線吸収スペクトル測定の結果、波数９８０／ｃｍに明確なオキセタン環の特性吸収を有することを確認した。
【００２３】
実施例１（液状組成物Ａの調製）
乾燥窒素ガスを充満したグローブボックス内で、製造例１で得たオキセタン環含有ポリマーの溶液１０ｇと、ヘキサフルオロリン酸リチウムを１モル濃度に溶解した炭酸エチレン／炭酸ジエチル／炭酸ジメチル（１０／１０／４０、重量比）の混合溶媒溶液４０ｇを混合溶解して、液状組成物Ａを調製する。液状組成物Ａ中のポリマー濃度は、３．０％である。
この液状組成物Ａを７０℃で加熱架橋せしめ、ゲル化性、ゲルの状態およびイオン伝導度（１０^-3Ｓ／ｃｍ）を評価した。ゲル化性とゲル状態は目視にて；イオン伝導度は、金メッキ電極を組み込んだ密閉セル中に該液状組成物を注入し、密閉状態で７０℃×５時間加熱した後冷却して測定用試験体とし、測定はＬＣＺメーターを用い、周波数１ＫＨｚ、測定温度２０℃または−２０℃で行なった。結果を下記表１に示す。
【００２４】
実施例２（液状組成物Ｂの調製）
実施例１と同様にして、製造例１で得たオキセタン環含有ポリマーの溶液１０ｇと、ヘキサフルオロリン酸リチウムを１．３モル濃度に溶解した炭酸エチレン／炭酸ジメチル／プロピオン酸エチル（１５／１５／７０、重量比）の混合溶媒溶液４０ｇを混合溶解して、液状組成物Ｂ（ポリマー濃度３．０％）を調製する。
実施例１と同様に、この液状組成物Ｂについてゲル化性、ゲル状態およびイオン伝導度を評価し、結果を下記表１に示す。
【表１】

表１中、○はゲル化していることを示す。
【００２５】
比較例１
式：
【化１０】

の低分子脂環式エポキシ化合物（ダイセル工業（株）製、「セロキサイド２０２１Ｐ」）２．５ｇを、ヘキサフルオロリン酸リチウムを１．０モル濃度に溶解した炭酸エチレン／炭酸ジメチル／プロピオン酸エチル（１５／１５／７０、重量比）の混合溶媒溶液４７．５ｇに溶解して、液状組成物Ｃ（低分子脂環式エポキシ化合物濃度５％）を調製する。
実施例１と同様に、この液状組成物Ｃを７０℃で加熱重合せしめ、ゲル化性、ゲル状態およびイオン伝導度を評価し、結果を下記表２に示す。
【００２６】
比較例２，３
比較例１において、低分子脂環式エポキシ化合物の濃度をそれぞれ、６％（比較例２）または８％（比較例３）とする以外は、同様にして液状組成物Ｄ，Ｅを調製し、ゲル化性、ゲル状態およびイオン伝導度の評価結果を下記表２に示す。
【００２７】
比較例４
式：
【化１１】

の低分子オキセタン環含有化合物（宇部興産（株）製、「ＸＤＯ」）３ｇを、ヘキサフルオロリン酸リチウムを１．０モル濃度に溶解した炭酸エチレン／炭酸ジメチル／プロピオン酸エチル（１５／１５／７０、重量比）の混合溶媒溶液４７ｇに溶解して、液状組成物Ｆ（低分子オキセタン環含有化合物濃度６％）を調製する。
実施例１と同様に、この液状組成物Ｆを７０℃で加熱重合せしめ、ゲル化性、ゲル状態およびイオン伝導度を評価し、結果を下記表２に示す。
【００２８】
比較例５，６
比較例４において、低分子オキセタン環含有化合物の濃度をそれぞれ、８％（比較例５）または１０％（比較例６）とする以外は、同様にして液状組成物Ｇ，Ｈを調製し、ゲル化性、ゲル状態およびイオン伝導度の評価結果を下記表２に示す。
【００２９】
【表２】

表２中、
×は液状のままでゲル化していない状態
○はゲル化している
表２の結果から、低分子脂環式エポキシ化合物あるいは低分子オキセタン環含有化合物［モノマー］を単に重合せしめゲル化させた場合、ポリマー含有量５％程度（該モノマーが１００％ポリマーに転化したと仮定し、モノマー含有量をポリマー含有量とする）では、ゲル化せず（比較例１，４）、６％程度以上ではゲル化するものの、液体成分がブリードし、良好なゲル形成ができず、イオン伝導度も良い結果が得られないことが認められる。
【００３０】
実施例３（リチウムイオン２次電池Ａの作成）
予め用意しておいたリチウムイオン電池用の電極、不織布からなるユニットを組み込んだアルミニウムラミネートフイルム製の袋状容器に、実施例１の液状組成物Ａ１．８５ｇを注入し、真空含浸を行った後密封し、７０℃で１９時間加熱して架橋によるゲル化を行い、薄型のポリマー固体電解質リチウムイオン２次電池Ａを作成する。
なお、上記で用いた薄型リチウムイオン２次電池のユニットは、正極と負極を不織布を介して捲回した構造を有し、正極はアルミニウム箔の両面にコバルト酸リチウム主体からなる活物質を塗布したもので、そのサイズは５０×８０ｍｍで、負極は銅箔に炭素系材料を塗布したもので、そのサイズは５２×１１０ｍｍであり、不織布はポリエステル細繊維製の２０μｍ厚品で、このユニットを、周囲を熱溶着した袋状のアルミニウムラミネートフイルム（内面：ポリエチレン、外面：ポリプロピレン）中に組み込んだものである。電池の容量は、１８０ｍＡＨのもので、同じ電池を６個（Ｎｏ．１〜６）作成した。
【００３１】
実施例４（リチウムイオン２次電池Ｂの作成）
実施例３と同様に、実施例２の液状組成物Ｂを用いて、薄型のポリマー固体電解質リチウムイオン２次電池Ｂ（６個）を作成する。
実施例３および４で作成した薄型ポリマー固体電解質リチウムイオン２次電池ＡおよびＢを用いた、充放電繰り返し試験と常温時の負荷特性、低温時の負荷特性の結果をそれぞれ、下記表３および４に示す。
なお、充放電繰り返し試験の条件は、充放電共１Ｃ（１８０ｍＡ）で充放電サイクルを繰返し、初期１サイクル時の容量、１０サイクル後の容量と保持率を示す。常温時の負荷特性は、充電はすべて０．２Ｃ（３６ｍＡ）、放電は０．２Ｃ、１Ｃ、２Ｃ（３６０ｍＡ）、それぞれの放電容量および０．２Ｃ放電容量に対する保持率を示す。低温時の負荷特性は、−２０℃における充放電共０．５Ｃ（９０ｍＡ）放電容量、および常温における充放電共０．５Ｃ（９０ｍＡ）放電容量に対する容量保持率を測定したものである。
すべて充電は定電流で４．２Ｖに達するまでとし、放電はすべて定電流で２．７５Ｖに達するまでとしている。
【００３２】
【表３】

【００３３】
【表４】

【００３４】
【発明の効果】
表３および４の結果から、本発明に係るポリマー固体電解質リチウムイオン２次電池は、負荷特性、特に大電流（２Ｃ特性で表される）負荷特性および低温時負荷特性において優れた特性を示しており、ポリマー固体電解質を使用したリチウムイオン２次電池の実用上の意義は非常に大きいことが認められる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polymer solid electrolyte lithium ion secondary battery, and more particularly, a rechargeable secondary battery having a cylindrical shape, a square shape, a sheet shape, or the like, in which the electrolytic solution is changed from a conventional liquid to a polymer. Lithium ion secondary battery using a polymer solid electrolyte that eliminates leakage of the electrolyte and improves current load characteristics, particularly current load characteristics at low temperatures, a method for producing the same, and the above solid The present invention relates to a liquid crosslinkable composition for an electrolyte.
[0002]
[Prior art and problems to be solved by the invention]
Lithium-ion rechargeable batteries are small, lightweight, rechargeable batteries with a large storage capacity per unit volume or unit weight, and portable electronic devices: mobile phones, notebook computers, portable personal computers, personal digital assistants (PDAs), MD decks It is actively used in video cameras, digital cameras, and the like, and is indispensable for various portable devices that are small, light and relatively large in power consumption.
By the way, most of the current lithium ion secondary batteries use a liquid electrolyte in which a lithium electrolyte salt is dissolved in an electrolyte solvent mainly composed of propylene carbonate, ethylene carbonate or the like, that is, an electrolyte. It is.
However, batteries using such electrolytes may leak or increase in temperature (due to heat generation during use or charging / discharging; misuse: short-circuited, using multiple batteries, some of which are reversed) When inserted and used; when exposed to high temperatures in the environment of use; or when the internal pressure rises due to soldering during device integration (due to the vapor pressure of the solvent in the electrolyte, resulting in a low boiling point As the internal pressure increases so much, there are safety problems such as leakage, rupture and risk of ignition, and solidification of the electrolyte, that is, development of a solid electrolyte is being actively carried out.
[0003]
For this solid electrolyte, a polymer material is generally used, and various materials such as a material having a polyoxyethylene chain have been studied, and the ionic conductivity that is the most basic characteristic of these materials has been studied. The properties are far inferior to liquid electrolytes and have not yet reached a practical level.
Therefore, recently, development of a polymer gel type solid electrolyte in which a liquid electrolyte is made into a gel state with a polymer material has been activated, and at present, ionic conductivity close to that of a liquid electrolyte is being obtained. It is being put to practical use in applications.
[0004]
In sheet-shaped thin batteries, (1) after forming positive and negative electrodes, a separator or non-woven fabric inserted between this electrode surface or between positive and negative electrodes is coated with polyvinylidene fluoride or polyacrylonitrile. The polymer is made into a solution, emulsion, dispersion, etc. using a solvent or dispersion medium, or is heated and melted to liquefy and applied, and dried (in the case of emulsion, dispersion, polymer particles are integrated rather than simply dried) : Film formation is also necessary) and then swelled in an electrolyte solution consisting of an electrolyte salt and an electrolyte solvent to form a gel;
(2) Applying an electrolyte containing a crosslinkable monomer or oligomer to the electrode surface or a separator or non-woven fabric inserted between the positive and negative electrodes, crosslinking the polymer with heat or radiation such as ultraviolet rays, A method in which both the positive and negative electrodes are bonded together with a separator or a nonwoven fabric sandwiched between them, or a method in which a polymer is crosslinked and heated to form a gel after bonding.
Various methods are employed, but any method requires dedicated equipment for each process such as coating, drying (including film formation), bonding, and swelling.
[0005]
In addition, the polymer used in the method (1) must not be dissolved in the electrolytic solution (it is necessary to swell), but on the other hand, in order to apply, some method (solution or emulsion using a solvent or dispersion medium) It is necessary to be a non-crosslinked polymer because it is required to be liquid (for example, a dispersion) (a crosslinked polymer cannot be used as a solution, and cannot be formed into an emulsion or dispersion). Usable polymers are limited to polyvinylidene fluoride, polyacrylonitrile, and the like, and form gels by spontaneous swelling. Therefore, swelling is likely to be uneven and insufficient, and the amount of polymer forming the gel increases. Furthermore, it is convenient to swell after winding, laminating or laminating electrodes, separators or nonwoven fabrics, but in that case, the electrolyte is difficult to spread sufficiently, and the swelling tends to be incomplete, and the swelling takes a long time. There is a problem that it takes.
[0006]
In addition, in the method (2), at the time of coating, a gel is formed in a lump by crosslinking using an electrolytic solution containing a low molecular weight monomer, oligomer, etc., and it is not necessary to take a means such as natural swelling. Although it seems to be ideal, since it is applied in a state containing an electrolyte solvent, it has a problem that the electrolyte solvent easily evaporates at the time of coating and crosslinking, and an electrolyte solvent having a low boiling point cannot be used. Low boiling point electrolyte solution is an important solvent for obtaining good ionic conductivity (especially ionic conductivity at low temperatures) (good characteristics for conventional batteries such as cylindrical and square types using liquid electrolyte) (2) In order to obtain good properties particularly at low temperatures, low-boiling electrolyte solvents such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dimethoxyethane, methyl propionate, ethyl propionate, etc. are suitably used) In the sheet mold produced by this method, these low-boiling-point electrolyte solutions cannot be used, and there is a big problem that it is difficult to obtain good characteristics.
Therefore, high-boiling ethylene carbonate and propylene carbonate that can be used must be the center, but ethylene carbonate has a high boiling point (36 ° C.) and cannot be used alone, and propylene carbonate (melting point: − 49 ° C) alone or mixed with ethylene carbonate. Propylene carbonate cannot use a graphite-based carbon material for the negative electrode (propylene carbonate decomposes), and the usable carbon material has a limitation of an amorphous material such as hard carbon.
This graphite-based carbon material has an excellent characteristic that it is easy to maintain a voltage during discharge at a constant value, but it also has a disadvantage that it cannot be used unfortunately in a battery by the method (2). .
[0007]
In addition, these polymer gel type solid electrolytes described above are still inferior to liquid electrolytes and require a relatively large discharge current, although ionic conductivity close to that of liquid electrolytes is being obtained. It can only be used to replace batteries that use conventional liquid electrolytes. (It is being put to practical use for small discharge current applications that can be used even if the internal resistance is a little high. A conventional sheet type battery is a typical example).
The biggest factor is that a gel cannot be formed unless it contains a relatively large amount of components that are completely harmful and detrimental to the ionic conductivity of a polymer in order to obtain a solid state of gel. In order to improve the ionic conductivity of this polymer gel type solid electrolyte, studies have been made on both the polymer content and the polymer structure, such as reduction of the amount of polymer components in the gel and the use of a high dielectric constant polymer.
[0008]
[Means for Solving the Problems]
As a result of diligent research to solve these problems, the present inventors crosslink an oxetane ring-containing polymer in an electrolyte solvent and a lithium electrolyte salt solution (electrolytic solution) in the presence of a cationic polymerization initiator. As a result, it was found that even in an extremely small amount of polymer content of 5% (% by weight or less), the electrolyte solution does not separate (bleed) from the gel, so that a good gel can be formed. In addition, if a specific lithium electrolyte salt is used, the cation polymerization initiator can be omitted, and the ionic conductivity can be dramatically improved by using a specific combination as an electrolyte solvent, in particular, low molecular carboxylic acid esters. I also found.
Based on these findings, the present inventors can use a liquid cross-linkable composition for a solid electrolyte containing the above components, and cross-link it for an existing lithium ion secondary battery similar to a conventional liquid electrolyte. For example, the gelation of the system occurs due to the formation of a polymer solid, and the above-mentioned problems are solved at once, and the polymer gel type has excellent characteristics that are not inferior to those of a lithium ion secondary battery using a liquid electrolyte. The present inventors have found that a solid electrolyte lithium ion secondary battery can be obtained and have completed the present invention.
[0009]
In addition, regarding a polymer electrolyte using cationic polymerization, in Japanese Patent No. 2925231 (issued on July 28, 1999), “a polymer compound formed by cationic ring-opening polymerization of epoxies of a compound having an epoxy group” Has been proposed that contains an ionic salt (including a lithium electrolyte salt) and a compound (including an electrolyte solution solvent) that is compatible with the ionic salt. Thus, the compound having the epoxy group herein is defined as “a polymer compound having a network structure by polymerization”. Specifically, the compound represented by the formula:
[Chemical formula 5]

Only two types of alicyclic epoxy compounds and bisphenol-based epoxy compounds are exemplified, which is clearly different from the oxetane ring-containing radical copolymer of the present invention.
The polymer content in the polymer solid electrolyte of the prior patent is, for example, about 47% when calculated from the composition of Example 2, and the ionic conductivity is 5 × 10.^-FourS / cm (25 ° C.), which is not a practical level. On the other hand, the present invention is characterized by a polymer content of 5% or less, and the ionic conductivity (ionic conductivity) is recognized to be 10 to 20 times the value of the former as shown in Examples below. .
[0010]
That is, the present invention provides (1) an oxetane ring-containing polymer,
(2) a cationic polymerization initiator,
(3) electrolyte solution solvent, and
(4) Lithium electrolyte salt
A liquid crosslinkable composition for a solid electrolyte (hereinafter referred to as a liquid composition) in which the oxetane ring-containing polymer (1) is 5% or less in the total amount is gelled by crosslinking for a lithium ion secondary battery The present invention provides a polymer solid electrolyte lithium ion secondary battery characterized in that it is made into a caulking polymer solid electrolyte.
[0011]
The oxetane ring-containing polymer (1) in the present invention is a polymer having a plurality of oxetane rings in the polymer structure, and does not ask for the skeleton structure of the polymer, but can be easily obtained by simple radical polymerization. That is, a radical polymerizable monomer having an oxetane ring (hereinafter referred to as an oxetane polymerization monomer), and a radical polymerizable monomer having an epoxy group (hereinafter referred to as an epoxy polymerization monomer) if necessary, and other radical polymerizable monomers Is usually produced by radical polymerization, and the molecular weight is usually set to 10,000 or more. When the molecular weight is less than 10,000, a large amount of polymer is required to form a gel. The upper limit of the molecular weight is not particularly limited, but it is appropriate to keep the upper limit to about 1 million, preferably about 500,000 in order to maintain the liquid state (solution state) of the liquid composition described later.
[0012]
The radical polymerization is usually performed by radical polymerization initiators [for example, N, N′-azobisisobutyronitrile, dimethyl N, N′-azobis (2-methylpropionate), benzoyl peroxide, lauroyl peroxide, etc.] and If necessary, it can be carried out using a molecular weight regulator such as mercaptans. At that time, since the molecular weight of the obtained polymer is relatively large, solution polymerization carried out in a solvent at a temperature of about 60 to 80 ° C. is suitable. . As the solvent, it is preferable to use cyclic carbonates, chain carbonates, and low-molecular carboxylic acid esters exemplified in the electrolyte solution solvent (3) described later.
[0013]
Examples of the oxetane polymerization monomer include the formula:
[Chemical 6]

(Wherein R₁Is H or CH_ThreeAnd R₂Is H or alkyl having 1 to 6 carbon atoms)
(Meth) acrylic monomers, specifically, (3-oxetanyl) methyl (meth) acrylate, (3-methyl-3-oxetanyl) methyl (meth) acrylate, (3-ethyl-3-oxetanyl) methyl (meth) ) Acrylate, (3-butyl-3-oxetanyl) methyl (meth) acrylate, (3-hexyl-3-oxetanyl) methyl (meth) acrylate, and the like, and at least one of these is used. The amount used is usually selected in the range of 5 to 50%, preferably 10 to 30%, based on the total amount of the monomer when the above epoxy polymerization monomer is not used. If it is less than 5%, the amount of polymer required for gelation increases, and if it exceeds 50%, the electrolyte tends to separate (bleed) from the gel.
In this specification, “(meth) acryl” means acryl and methacryl, and “(meth) acrylate” means acrylate and methacrylate.
[0014]
As an epoxy polymerization monomer used as necessary, for example,
[Chemical 7]

(Wherein R_FiveIs H or CH_ThreeAnd R₆Is
[Chemical 8]

Is)
(Meth) acrylates, specifically 3,4-epoxycyclohexylmethyl (meth) acrylate and glycidyl (meth) acrylate, and at least one of them is used. The amount used is usually such that the proportion of the epoxy polymerization monomer in the total amount with the oxetane polymerization monomer is 90% or less, and the total amount of both monomers is 5 to 50%, preferably 10 to 30% in the total amount of monomers. The selection should be such that
[0015]
Examples of the other radical polymerizable monomers include the formula:
[Chemical 9]

(Wherein R_ThreeIs H or CH_ThreeAnd R_FourIs -COOCH_Three, -COOC₂H_Five, -COOC_ThreeH₇, -COOC_FourH₉, -COO (CH₂CH₂O)_{1 ~ Three}CH_Three, -COO (CH₂CH₂O)_{1 ~ Three}C₂H_Five, -COO (CH₂CH (CH_Three) O)_{1 ~ Three}CH_Three, -COO (CH₂CH (CH_Three) O)_{1 ~ Three}C₂H_Five, -OCOCH_ThreeOr -OCOC₂H_FiveIs)
Of these, vinyl or (meth) acrylic monomers are preferred. In addition, although things other than these can also be used, when affinity with the electrolyte solution solvent (3) to be used is low, electrolyte solution may isolate | separate from a gel (bleed).
The oxetane ring-containing polymer (1) produced as described above is used alone, or a part of the oxetane ring-containing polymer (1) is combined with a radical polymerizable monomer having the epoxy group and another radical polymerizable monomer. An epoxy group-containing polymer having a molecular weight of 10,000 or more obtained by radical copolymerization under the same conditions as described above may be used in combination.
[0016]
As the cationic polymerization initiator (2) in the present invention, various onium salts (for example, -BF of cations such as ammonium, phosphonium, arsonium, stibonium, sulfonium, iodonium, etc.)_Four, -PF₆, -SbF₆, -CF_ThreeSO_Three, -ClO_FourAnion salts such as the above can be used, but even if these onium salts are not used in the present invention, if lithium hexafluorophosphate and / or lithium tetrafluoroborate, which is the lithium electrolyte salt (4), is utilized, In addition to the action of the lithium electrolyte salt, it can also act as the cationic polymerization initiator, which is advantageous. The use of a cationic polymerization initiator is an extra component for the electrolyte, which leads to a decrease in ionic conductivity, and complicates the manufacturing process and increases costs.
Naturally, as part of the cationic polymerization initiator, lithium hexafluorophosphate or lithium tetrafluoroborate can be used in combination with the onium salt.
[0017]
Examples of the electrolyte solution solvent (3) in the present invention include cyclic carbonates (ethylene carbonate, propylene carbonate, butylene carbonate, etc.); chain carbonate esters (dimethyl carbonate, diethyl carbonate, methyl carbonate / ethyl carbonate, methyl carbonate / n). Including symmetric and asymmetric types such as propyl); cyclic esters (lactones) (γ-butyrolactone, γ-valerolactone, etc.); cyclic ethers (tetrahydrofuran, methyltetrahydrofuran, etc.); low molecular carboxylates (acetic acid) Ethyl, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, butyl butyrate, etc.); chain ethers (dimethoxyethane, methoxyethoxyethane, etc.); cyanoethyl group-containing compounds (methyl-2 -Cyanoethyl ether Ethyl 2-cyanoethyl ether, bis 2-cyanoethyl ether, methyl 2-cyanoethyl carbonate, 2-cyanoethyl propionate, etc.), and at least one selected from these groups is used. In particular, it is preferable to use a mixture of a chain carbonate ester and a low-molecular carboxylic acid ester in a cyclic carbonate, a high dielectric constant solvent of the cyclic ester, and further, ethylene carbonate, Propylene and chain carbonates such as dimethyl carbonate, diethyl carbonate, methyl carbonate and ethyl carbonate and low molecular weight carboxylic acid esters, ethyl acetate which is a chain ester having 4 to 6 carbon atoms constituting the molecule, It is preferable to use a mixture of propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and among these, propyl acetate, ethyl propionate, which is a chain ester having 5 carbon atoms. The use of methyl butyrate is preferred. The mixing ratio is set to cyclic carbonates / chain carbonates / low molecular carboxylic acid esters = 10 to 50: 0 to 50:50 to 90 (weight ratio), and low molecular carboxylic acid esters. Is preferably set to 50% or more of the total solvent.
In the low molecular weight carboxylic acid esters, if the total number of carbon atoms constituting the molecule is less than 4, the boiling point of the solvent is too low, and when the battery is used, there is a problem that the internal pressure of the battery is increased at high temperatures. On the other hand, when the total number of carbons is 7 or more, the ionic conductivity tends to decrease and the battery characteristics tend to deteriorate.
In these electrolyte solvents (3), the type and blending ratio have a large influence on the ionic conductivity, and as a result, the battery charge such as the internal resistance, current load characteristics, and current load characteristics at low temperature of the battery can be improved. It is determined carefully because it has a great influence on the battery life due to the influence of the discharge characteristics and the electrochemical stability due to the chemical structure of the solvent.
[0018]
The lithium electrolyte salt (4) in the present invention is preferably composed of an anion (acid group) which is excellent in solubility in the electrolyte solvent (3) and has high ionic conductivity and high resistance to oxidation to reduction potential. Although not particularly limited, for example, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, and the like are used, and at least one of these is used. In particular, lithium tetrafluoroborate and lithium hexafluorophosphate are preferable because they have good ionic conductivity and also have an action of crosslinking the oxetane ring-containing polymer (1). The concentration of these lithium electrolyte salts (4) is usually 1 mol / dm.^ThreeBefore and after are applied, but not particularly limited.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The polymer solid electrolyte lithium ion secondary battery according to the present invention includes the above-mentioned oxetane ring-containing polymer (1) or a combination thereof with an epoxy group-containing polymer, a cationic polymerization initiator (2), an electrolyte solution solvent (3), and A low-viscosity liquid composition obtained by mixing and dissolving the lithium electrolyte salt (4) as a component is used as a crosslinkable composition for a solid electrolyte, and can be produced according to the following procedure. .
[0020]
First, the proportion of the oxetane ring-containing polymer (1) and, if necessary, the epoxy group-containing polymer (collectively referred to as a crosslinkable polymer) in the total amount of the liquid composition is adjusted to 5% or less. That is, the ionic conductivity is stably maintained by setting the polymer content in the formed solid electrolyte as low as possible.
Next, the liquid composition is hermetically sealed by incorporating a unit such as an electrode or a separator for a lithium ion secondary battery within the time limit of the pot life (a time during which the injection and the like can be handled by maintaining the liquid state). After injecting into the container and entering the gap between the electrode and the separator, the crosslinkable polymer is easily gelled by room temperature or heat crosslinking at a temperature of about room temperature to 100 ° C. By forming a polymer solid electrolyte The target polymer solid electrolyte lithium ion secondary battery is obtained.
[0021]
In this manner, a polymer solid electrolyte lithium ion secondary battery excellent in characteristics and stability can be obtained without the need for new equipment in the same process as the conventional battery production.
In conventional polymer gel type polymer solid electrolytes, the important point is how to reduce polymer components that are detrimental to ionic conductivity. However, even if the crosslink density is increased, the gel retention property of the electrolyte is not enough. The electrolyte is easily separated by the decrease, and the structure of the polymer constituting the gel is very important. However, the present invention can be said to have solved these problems by using a crosslinkable polymer.
In addition to the lithium ion secondary battery, the liquid composition used in the present invention can be replaced with a lithium battery, a lithium secondary battery, an electric double layer capacitor, a chemical capacitor, an electro It can also be used as a polymer gel type polymer solid electrolyte such as a chromic device.
[0022]
【Example】
Next, the present invention will be described more specifically with reference to production examples, examples and comparative examples.
Production Example 1 (Production of Oxetane Ring-Containing Polymer)
108 g of methyl methacrylate previously dehydrated with molecular sieves, 36 g of (3-ethyl-3-oxetanyl) methyl acrylate previously dehydrated with molecular sieves in a 1000 ml three-necked Kolben sufficiently dried with dry nitrogen gas beforehand, dehydrated with molecular sieves in advance Then, 0.225 g of dimethyl N, N′-azobis (2-methylpropionate) is added to a mixed solution of 432 g of heated normal ethylene carbonate distilled under reduced pressure and stirred at 70 ° C. while introducing dry nitrogen gas. Then, heating and stirring are continued for 12 hours, and radical polymerization is performed. Next, the temperature is lowered to 40 to 50 ° C., 378 g of ethyl propionate previously dried with molecular sieves and distilled under reduced pressure is added, and the mixture is stirred and dissolved until the whole becomes uniform to obtain a 15% solution of the oxetane ring-containing polymer.
This polymer solution was a colorless and transparent viscous liquid. As a result of infrared absorption spectrum measurement, it was confirmed that the polymer solution had a clear characteristic absorption of an oxetane ring at a wave number of 980 / cm.
[0023]
Example 1 (Preparation of liquid composition A)
In a glove box filled with dry nitrogen gas, 10 g of the oxetane ring-containing polymer solution obtained in Production Example 1 and ethylene carbonate / diethyl carbonate / dimethyl carbonate (10/10) in which lithium hexafluorophosphate was dissolved at a molar concentration. A liquid composition A is prepared by mixing and dissolving 40 g of a mixed solvent solution (40 / weight ratio). The polymer concentration in the liquid composition A is 3.0%.
This liquid composition A was heated and cross-linked at 70 ° C. to obtain gelation property, gel state and ionic conductivity (10^-3S / cm) was evaluated. Gelability and gel state are visually observed; ionic conductivity is measured by injecting the liquid composition into a closed cell incorporating a gold-plated electrode, heating in a sealed state at 70 ° C. for 5 hours, and then cooling. The measurement was performed using an LCZ meter at a frequency of 1 KHz and a measurement temperature of 20 ° C or -20 ° C. The results are shown in Table 1 below.
[0024]
Example 2 (Preparation of liquid composition B)
In the same manner as in Example 1, 10 g of the oxetane ring-containing polymer solution obtained in Production Example 1 and ethylene carbonate / dimethyl carbonate / ethyl propionate (15/15) in which lithium hexafluorophosphate was dissolved at 1.3 molar concentration. / 70, weight ratio) is mixed and dissolved to prepare a liquid composition B (polymer concentration: 3.0%).
In the same manner as in Example 1, the liquid composition B was evaluated for gelation property, gel state, and ionic conductivity, and the results are shown in Table 1 below.
[Table 1]

In Table 1, ○ indicates gelation.
[0025]
Comparative Example 1
formula:
[Chemical Formula 10]

Of low molecular weight alicyclic epoxy compound ("Celoxide 2021P" manufactured by Daicel Industries, Ltd.), ethylene carbonate / dimethyl carbonate / ethyl propionate (lithium hexafluorophosphate dissolved in 1.0 molar concentration) 15/15/70, weight ratio) is dissolved in 47.5 g of a mixed solvent solution to prepare a liquid composition C (low molecular weight alicyclic epoxy compound concentration 5%).
In the same manner as in Example 1, this liquid composition C was polymerized by heating at 70 ° C., and the gelation property, gel state and ionic conductivity were evaluated. The results are shown in Table 2 below.
[0026]
Comparative Examples 2 and 3
In Comparative Example 1, liquid compositions D and E were prepared in the same manner except that the concentration of the low molecular weight alicyclic epoxy compound was 6% (Comparative Example 2) or 8% (Comparative Example 3), respectively. The evaluation results of gelling property, gel state and ionic conductivity are shown in Table 2 below.
[0027]
Comparative Example 4
formula:
Embedded image

3 g of a low molecular oxetane ring-containing compound (“XDO” manufactured by Ube Industries, Ltd.), ethylene carbonate / dimethyl carbonate / ethyl propionate (15/15 / 70, weight ratio) is dissolved in 47 g of a mixed solvent solution to prepare a liquid composition F (low molecular oxetane ring-containing compound concentration 6%).
Similarly to Example 1, this liquid composition F was heated and polymerized at 70 ° C. to evaluate gelation properties, gel state and ionic conductivity, and the results are shown in Table 2 below.
[0028]
Comparative Examples 5 and 6
In Comparative Example 4, liquid compositions G and H were prepared in the same manner except that the concentration of the low molecular oxetane ring-containing compound was 8% (Comparative Example 5) or 10% (Comparative Example 6), respectively. Table 2 shows the evaluation results of the chemical properties, gel state, and ionic conductivity.
[0029]
[Table 2]

In Table 2,
X is in a liquid state and not gelled
○ is gelled
From the results shown in Table 2, when the low molecular weight alicyclic epoxy compound or the low molecular weight oxetane ring-containing compound [monomer] is simply polymerized and gelled, the polymer content is about 5% (the monomer is converted to 100% polymer) Assuming that the monomer content is the polymer content), the gel does not gel (Comparative Examples 1 and 4) and gels at about 6% or more, but the liquid component bleeds and a good gel cannot be formed. It can be seen that the ion conductivity is not good.
[0030]
Example 3 (Preparation of lithium ion secondary battery A)
After injecting 1.85 g of the liquid composition A of Example 1 into a bag-like container made of an aluminum laminate film incorporating a unit made of a lithium ion battery electrode and a nonwoven fabric prepared in advance and vacuum impregnating Sealed and heated at 70 ° C. for 19 hours for gelation by crosslinking to produce a thin polymer solid electrolyte lithium ion secondary battery A.
In addition, the unit of the thin lithium ion secondary battery used above has a structure in which the positive electrode and the negative electrode are wound through a nonwoven fabric, and the positive electrode is coated with an active material mainly composed of lithium cobalt oxide on both surfaces of the aluminum foil. The size is 50 × 80 mm, the negative electrode is a copper foil coated with a carbon-based material, the size is 52 × 110 mm, the nonwoven fabric is a 20 μm thick product made of polyester fine fiber, and this unit is It is incorporated in a bag-like aluminum laminate film (inner surface: polyethylene, outer surface: polypropylene) with heat-welded surroundings. The capacity of the battery was 180 mAH, and six identical batteries (No. 1 to 6) were prepared.
[0031]
Example 4 (Preparation of lithium ion secondary battery B)
Similarly to Example 3, thin polymer solid electrolyte lithium ion secondary batteries B (six) are prepared using the liquid composition B of Example 2.
Tables 3 and 4 below show the results of charge / discharge repetition tests, load characteristics at normal temperature, and load characteristics at low temperature, respectively, using the thin polymer solid electrolyte lithium ion secondary batteries A and B prepared in Examples 3 and 4. Shown in
In addition, the conditions of a charging / discharging repetition test show the capacity | capacitance at the time of an initial 1 cycle, the capacity | capacitance after 10 cycles, and a retention rate, repeating a charging / discharging cycle by 1C (180mA) charge / discharge. The load characteristics at normal temperature are 0.2 C (36 mA) for all charging, 0.2 C, 1 C, 2 C (360 mA) for discharging, and the respective discharge capacities and retention rates for 0.2 C discharging capacities. The load characteristics at low temperature are obtained by measuring capacity retention ratios for both charge and discharge at −20 ° C. for 0.5 C (90 mA) discharge capacity and charge and discharge at room temperature for 0.5 C (90 mA) discharge capacity.
All charging is performed until reaching 4.2V at a constant current, and discharging is performed until reaching 2.75V at a constant current.
[0032]
[Table 3]

[0033]
[Table 4]

[0034]
【The invention's effect】
From the results shown in Tables 3 and 4, the polymer solid electrolyte lithium ion secondary battery according to the present invention exhibits excellent characteristics in load characteristics, particularly large current (expressed by 2C characteristics) and low temperature load characteristics. It is recognized that the practical significance of the lithium ion secondary battery using the polymer solid electrolyte is very large.

Claims (17)

(1) Oxetane ring-containing polymer,
(2) a cationic polymerization initiator,
(3) electrolyte solution solvent, and (4) a radically polymerizable monomer comprising a lithium electrolyte salt, wherein the oxetane ring-containing polymer (1) has an oxetane ring:

(Wherein R ₁ is H or CH ₃ ; and R ₂ is H or alkyl having 1 to 6 carbon atoms)
(Meth) acrylic monomer,
Other radical polymerizable monomers:

Wherein R ₃ is H or CH ₃ ; and R ₄ is —COOCH ₃ , —COOC ₂ H ₅ , —COOC ₃ H ₇ , —COOC ₄ H ₉ , —COO (CH ₂ CH ₂ O) _{1 to 3 CH 3, -COO (CH 2 CH} 2 O) 1 ~ 3 C 2 H 5, -COO (CH 2 CH (CH 3) O) 1 ~ 3 CH 3, -COO (CH 2 CH (CH 3) O) _{1 to 3} C ₂ H ₅ , —OCOCH ₃ , or —OCOC ₂ H ₅ )
Vinyl or (meth) acrylic monomers
A liquid crosslinkable composition for a solid electrolyte , wherein the polymer has a molecular weight of 10,000 or more obtained by radical copolymerization with the oxetane ring-containing polymer (1) in a total amount of 5% by weight or less. The crosslinkable composition for a solid electrolyte according to claim 1 , wherein the amount of the radically polymerizable monomer having an oxetane ring is 5 to 50% by weight based on the total amount of the monomers. The crosslinkable composition for a solid electrolyte according to claim 1 or 2, wherein the cationic polymerization initiator (2) is an onium salt. The electrolyte solvent (3) is a cyclic carbonate, chain carbonate, cyclic carboxylic acid ester, cyclic ether, low molecular chain carboxylic acid ester, low molecular chain ether, or cyanoethyl group-containing compound. The crosslinkable composition for a solid electrolyte according to any one of claims 1 to 3 , which is at least one selected from the group. The crosslinkable composition for a solid electrolyte according to any one of claims 1 to 3, wherein the electrolyte solvent (3) is at least one selected from the group of cyclic carbonates and chain carbonates. The electrolyte solution solvent (3) is obtained by adding low molecular chain carboxylic acid esters to at least one selected from the group consisting of cyclic carbonates, chain carbonates and cyclic carboxylic acid esters. The crosslinkable composition for a solid electrolyte according to any one of 1 to 3 . Lithium electrolyte salt (4) is lithium perchlorate, any one of claims 1 to 6 is at least one selected lithium tetrafluoroborate, from the group of lithium hexafluorophosphate and lithium trifluoromethane sulfonate A crosslinkable composition for a solid electrolyte as described in 1. 8. The lithium hexafluorophosphate and / or lithium tetrafluoroborate used as the lithium electrolyte salt (4) is used as part or all of the cationic polymerization initiator (2) according to claim 1. Crosslinkable composition for solid electrolyte . 9. A polymer solid electrolyte lithium, wherein the crosslinkable composition composition for a solid electrolyte according to claim 1 is gelled by crosslinking for a lithium ion secondary battery to form a polymer solid electrolyte. Ion secondary battery. The crosslinkable composition for a solid electrolyte according to any one of claims 1 to 8 is injected into a sealable container or case incorporating a unit such as an electrode or a separator for a lithium ion secondary battery, A method for producing a polymer solid electrolyte lithium ion secondary battery, wherein the polymer solid electrolyte is formed by gelation by crosslinking. Oxetane ring-containing polymer (1)
Radical polymerizable monomer comprising the electrolyte solution solvent (3) and lithium hexafluorophosphate and / or lithium tetrafluoroborate as the lithium electrolyte salt (4) , wherein the oxetane ring-containing polymer (1) has an oxetane ring:

(Wherein R ₁ is H or CH ₃ ; and R ₂ is H or alkyl having 1 to 6 carbon atoms)
(Meth) acrylic monomer,
Other radical polymerizable monomers:

Wherein R ₃ is H or CH ₃ ; and R ₄ is —COOCH ₃ , —COOC ₂ H ₅ , —COOC ₃ H ₇ , —COOC ₄ H ₉ , —COO (CH ₂ CH ₂ O) _{1 to 3 CH 3, -COO (CH 2 CH} 2 O) 1 ~ 3 C 2 H 5, -COO (CH 2 CH (CH 3) O) 1 ~ 3 CH 3, -COO (CH 2 CH (CH 3) O) _{1 to 3} C ₂ H ₅ , —OCOCH ₃ , or —OCOC ₂ H ₅ )
Vinyl or (meth) acrylic monomers
A liquid crosslinkable composition for a solid electrolyte , wherein the polymer has a molecular weight of 10,000 or more obtained by radical copolymerization with the oxetane ring-containing polymer (1) in a total amount of 5% by weight or less. The crosslinkable composition for a solid electrolyte according to claim 11, wherein the amount of the radical polymerizable monomer having an oxetane ring is 5 to 50% by weight based on the total amount of the monomers. The electrolyte solvent (3) is a cyclic carbonate, chain carbonate, cyclic carboxylic acid ester, cyclic ether, low molecular chain carboxylic acid ester, low molecular chain ether, or cyanoethyl group-containing compound. The crosslinkable composition for a solid electrolyte according to claim 11 or 12, which is at least one selected from the group. The crosslinkable composition for a solid electrolyte according to claim 11 or 12, wherein the electrolyte solvent (3) is at least one selected from the group of cyclic carbonates and chain carbonates. The electrolyte solution solvent (3) is obtained by adding low molecular chain carboxylic acid esters to at least one selected from the group consisting of cyclic carbonates, chain carbonates and cyclic carboxylic acid esters. 13. The crosslinkable composition for a solid electrolyte according to 11 or 12. A solid polymer electrolyte lithium, wherein the crosslinkable composition composition for a solid electrolyte according to any one of claims 11 to 15 is gelled by crosslinking for a lithium ion secondary battery to form a polymer solid electrolyte. Ion secondary battery. Injecting the crosslinkable composition for a solid electrolyte according to any one of claims 11 to 15 into a sealable container or case incorporating a unit such as an electrode or a separator for a lithium ion secondary battery, A method for producing a polymer solid electrolyte lithium ion secondary battery, wherein the polymer solid electrolyte is formed by gelation by crosslinking.