JP4968702B2 - Solid electrolyte and polymer solid electrolyte battery - Google Patents

Description

【００１２】
このユニット数３以下のエチレンオキサイド基を有する片末端アクリロイル基変性アルキレンオキシドモノマーとしては、例えば、トリエチレングリコールモノアクリレート、テトラエチレングリコールモノアクリレート、メトキシテトラエチレングリコールモノアクリレート、フェノキシテトラエチレングリコールモノアクリレート、トリエチレングリコールモノメタクリレート、２官能以上のポリエチレングリコールジアクリレート、ポリエチレングリコールジメタクレート、トリエチレングリコールトリメチロールプロパントリアクリレート、及び上記の化合物のエチレングリコール構造をプロピレングリコール構造に代えた化合物などが挙げられる。また、上記モノマーは、２種以上併用することができる。
【００１３】
本発明の固体電解質を構成する電解質塩としては、例えば、ＬｉＣｌＯ₄ 、ＬｉＰＦ₆ 、ＬｉＢＦ₄ 、ＬｉＡｓＦ₆ 、ＬｉＳｂＦ₆ 、ＬｉＣＦ₃ ＳＯ₃ 、ＬｉＣ₄ Ｆ₉ ＳＯ₃ 、ＬｉＣＦ₃ ＣＯ₂ 、Ｌｉ₂ Ｃ₂ Ｆ₄ （ＳＯ₃ ）₂ 、ＬｉＮ（ＣＦ₃ ＳＯ₂ ）₂ 、ＬｉＣ（ＣＦ₃ ＳＯ₂ ）₃ 、ＬｉＣn Ｆ_2n+1ＳＯ₃ （ｎ≧２）、ＬｉＮ（ＲｆＯＳＯ₂ ）₂ 〔ここでＲｆはフルオロアルキル基〕などの、少なくともＬｉ含む電解質塩が挙げられ、これらを単独もしくは複数で併用することができる。
【００１４】
上記電解質塩の含有量は、片末端アクリロイル基変性アルキレンオキシドモノマーのアルキレンオキシドユニットに対して、（電解質塩／ＥＯ）×１００（モル％）が好ましくは0.０５〜５０モル％、より好ましくは0.１〜３０モル％となる量である（上記式において、ＥＯはエチレンオキシドを示す）。上記電解質塩の含有量が多すぎると、過剰の電解質塩が解離せず、単に混在するのみになり、このためイオン伝導性が逆に低下する。また、含有量が少なすぎても、解離するイオンの数が小さくなり、イオン伝導性が低下する。
【００１５】
本発明では、ポリマーの運動性を向上させ、イオン伝導度を向上させる可塑剤として、先に述べた液状化合物を使用する。この液状化合物には、その誘電率が１０以下であることと、その沸点が１５０℃以上であることが求められる。誘電率が１０以下であると、エチレンオキサイド基を有するモノマーを重合して得られるポリマー中のエチレンオキサイド鎖によって解離したＬｉイオンとの相互作用が小さく、Ｌｉイオンの移動を妨げることがないため、固体電解質中のポリマーの濃度が増加してもイオン伝導性は良好に保持される。誘電率が１０より大きくなると、Ｌｉイオンとの相互作用が大きくなり、多くの化合物がＬｉイオンと錯体を形成することとなるため、イオン伝導性が低下する。特にこのときポリマーの濃度を高くすると、嵩高い錯体の運動性が大きく阻害され、かえってイオン伝導度が低下する。上述のごとく、液状化合物の誘電率は１０以下であれば低いほどよいが、実質的には、１〜８の範囲のものが使用される。
【００１６】
沸点が１５０℃未満であると、固体電解質から液状化合物が除々に気化して、イオン伝導性が低下するおそれがある。また、沸点が高いほど蒸気圧が減少して安全性が高まるため好ましく、沸点の上限については特に規定はされないが、沸点が高すぎるものは一般に分子量が大きく、系の粘度が増大することによりイオン伝導率の低下を招く傾向にあるため、およそ２００℃以下にあるものが好適に用いられる。
【００１７】
この液状化合物の含有量としては、全組成物（液状組成物）の重量に対して、１０ｗｔ％以上、８０ｗｔ％未満含ませることが好ましく、２０ｗｔ％以上、７０ｗｔ％以下の範囲がより好ましい。上記液状化合物の含有量が８０ｗｔ％以上となると、固体電解質の機械的性質が低下するとともに、蒸気圧が上昇し、好ましくない。また、１０ｗｔ％未満では、イオン伝導性が低下する。
【００１８】
本発明の液状組成物を硬化させる手段としては、紫外線、可視光線などの活性光線を照射する方法、もしくは加熱等の方法がとられる。
【００１９】
上記の活性光線を照射する方法による場合は、光重合開始剤としてベンゾイン、２−メチルベンゾイン、トリメチルシリルベンゾフェノン、４−メトキシベンゾフェノン、ベンゾインメチルエーテル、アセトフェノン、アントラキノン、２，２−ジメトキシ−２−フェニルアセトフェノンなどを添加しておくことが好ましい。
【００２０】
上記の加熱する方法による場合は、開始剤としてジアシルパーオキサイド、パーオキシジカーボネート、パーオキシエステルなどの過酸化物の添加が望ましい。具体的には、ベンソイルパーオキサイド、３，５，５−トリメチルヘキサノイルパーオキサイド、ラウロイルパーオキサイド、ステアロイルパーオキサイド、オクタノイルパーオキサイド、ジ−ｎ−プロピルパーオキシジカーボネート、ジイソプロピルパーオキシジカーボネート、ビス（４−ｔ−ブチルシクロヘキシル）パーオキシジカーボネート、ジ−２−エトキシエチルパーオキシジカーボネート、ジ−２−エチルヘキシルパーオキシジカーボネート、ジ−２−メトキシブチルパーオキシジカーボネート、ジ（３−メチル−３−メトキシブチル）パーオキシジカーボネート、１，１，３，３−テトラメチルブチルパーオキシネオデカネート、１−シクロヘキシル−１−メチルエチルパーオキシネオデカネート、ｔ−ヘキシルパーオキシネオデカネート、ｔ−ブチルパーオキシネオデカネート、ｔ−ヘキシルパーオキシピバレート、ｔ−ブチルパーオキシピバレート、１，１，３，３−テトラメチルブチルパーオキシ−２−エチルヘキサノエート、１−シクロヘキシル−１−メチルエチルパーオキシ−２−エチルヘキサノエート、ｔ−ヘキシルパーオキシ−２−エチルヘキサノエートを単独あるいは２種類以上併用することができる。
【００２１】
本発明において、多孔質シートを固体電解質の支持体として使用してもよい。例えば、不織布や微孔性フィルムなどが用いられる。上記不織布としては、例えば、ポリプロピレン、ポリエチレン、ポリエチレンテレフタレート、ポリブチレンテレフタレートなどの不織布などが挙げられる。また、微孔性フィルムとしては、例えば、ポリプロピレン、ポリエチレン、エチレン−プロピレン共重合体の微孔性フィルムなどが挙げられる。
【００２２】
本発明の重合性組成物により製造される固体電解質の構成成分を列挙したが、本発明の目的を損なわない限り、他成分を添加することも可能である。例えば、各種無機微粒子を添加した複合電解質としても使用でき、そうすることにより強度、膜厚均一性が改善するばかりでなく、無機微粒子と高分子間に微細な空孔が生じることになり、強度改善効果を損ねることなく、逆にイオン伝導度、移動度を増加させることもできる。また、無機微粒子を添加することにより、重合性組成物の粘度が上昇し、高分子と溶媒の相溶性が不十分な場合にもその分離を抑える効果が現われる。
【００２３】
使用する無機微粒子としては非電子伝導性のもの、電気化学的に安定なものが選ばれる。またイオン伝導性を有するものであればさらに好ましい。具体的にはα、β、γ−アルミナ、シリカ等のイオン伝導性または非電導性セラミックス製微粒子が挙げられる。無機微粒子の具体例としてはアエロジル（日本アエロジル（株）製）のようなシリカ超微粒子、アルミナ超微粒子が挙げられ、安定性、複合効率からアルミナ超微粒子が特に好ましい。
【００２４】
本発明に係る固体電解質は、図１に示すようなポリマー電解質電池に適用される。そこでは、活物質とバインダーポリマーとを含む正極合剤層を集電体上に積層してなる正極１と、活物質とバインダーポリマーとを含む負極合剤層を集電体上に積層してなる負極２とを、電解質セパレータ３を介して対向させてなる。これらはラミネートフィルムからなる外装体４で外装されている。正極１および負極２からそれぞれリード部５・６が外装体４の外部に引き出されている。本発明においては、これら正・負極１・２および電解質セパレータ３として、上記の固体電解質を用いる。
【００２５】
正負極１・２のバインダーポリマーとしては、高度な結晶性を有すると共に、電池作動温度上限（８０℃）においてもその結晶性を良好に維持し、活物質どうしを強固に結び付けておけるポリマーが望ましい。また、これらのポリマーには、電池組み立て後の加熱処理においても、その電解質中での結晶構造を保つことが必要である。このようなポリマーに求められる性質は、その溶融温度が１５０℃以上であることが要求され、その電解液への溶解温度が少なくとも１００℃以上、望ましくは１２０℃以上であることが要求される。このようなポリマー成分としては、例えばポリフッ化ビニリデンのような結晶性のポリマーなどが挙げられる。
【００２６】
本発明において、正極１の集電体としてはアルミニウム製の箔、パンチングメタル、網、エキスパンドメタルなどを用い得るが、通常、アルミニウム箔が用いられる。この正極１の集電体は、正極全体の厚みを薄くする関係上、厚みが３０μｍ以下のものが好ましく、本発明では、そのように薄いものであっても、その露出部が外装体４のシール部分より外部に出ないので、破損する恐れが少ない。
【００２７】
ただし、あまりにも薄すぎると、正極の作製にあたって、正極合剤含有ペーストを塗布した際に皺が発生したり、引っ張りにより破れが生じたりする恐れがあるので、その厚みが上記のように３０μｍ以下で１０μｍ以上が好ましい。
【００２８】
正極１側のリード部５は、通常、正極作製時にアルミニウム製の集電体の一部に正極合剤層を形成せずに集電体の露出部を残し、そこをリード部とすることによって設けられる。ただし、リード部５は必ずしも当初から集電体と一体化されたものであることは要求されず、集電体にアルミニウム製の箔などを後から接続することによって設けても良い。
【００２９】
負極２の集電体としては銅製の箔、パンチングメタル、網、エキスパンドメタルなどを用い得るが、通常、銅箔が用いられる、この負極２の集電体は、負極全体の厚みを薄くする関係上、厚みが３０μｍ以下のものが好ましく、本発明では、そのように薄いものであっても、その露出部が外装体４のシール部分より外部に出ないので、破損するおそれが少ない。
【００３０】
ただし、あまりにも薄すぎると、負極の作製にあたって、負極合剤含有ペーストを塗布した際に皺が発生したり、引っ張りにより破れが生じたりする恐れがあるので、その厚みは上記のように３０μｍ以下で５μｍ以上が好ましい。
【００３１】
また、負極２側のリード部６も、通常、負極作製時に銅製の集電体の一部に負極合剤層を形成せずに集電体の露出部を残し、そこをリード部６とすることによって設けられる。ただし、この負極側のリード部６は必ずしも当初から集電体と一体化されたものであることは要求されず、集電体に銅製の箔などを後から接続することによって設けても良い。
【００３２】
〔実施例〕
以下に本発明の実施例を比較例と共に挙げ、本発明を更に詳細に説明する。
【００３３】
（実施例１）
固体電解質フィルム（固体電解質）の作製
片末端アクリロイル基変性アルキレンオキシドモノマーとしてジエチレングリコールモノアクリレート（新中村化学社製、ＡＭ−９０Ｇ）を、電解質塩として過塩素酸リチウム（ＬｉＣｌＯ₄ ）を、液状化合物としてエトキシジエチレンオキサイド（ナカライテスク社製）を、重合開始剤としてLucirinTPO（２，４，６−トリメチルベンゾイルジフェニルホスフィンオキサイド）（BASF社製）を、橋かけ剤としてトリエチレングリコールジメタクリレート（新中村化学社製、９Ｇ）を用い、これらを以下の割合で混合し、均一溶液とした。この均一溶液とした液状組成物を、６０℃で４時間重合し、固体電解質フィルムを得た。
ジエチレングリコールモノアクリレート １０ｇ
トリエチレングリコールジメタクリレート 0.５ｇ
過塩素酸リチウム（ＬｉＣｌＯ₄ ） ３ｇ
エトキシジエチレンオキサイド １3.５ｇ
LucirinTPO 0.０１ｇ
【００３４】
正極の作製：
正極活物質であるＬｉＣｏＯ₂ ８５重量部、導電助剤であるアセチレンブラック１０重量部、ポリフッ化ビニリデン５重量部とをＮ−メチルピロリドンを溶剤として均一になるように混合し、正極合剤含有ペーストを調製した。そのペーストを集電体となる厚さ２０μｍのアルミニウム箔の両面に塗布し、乾燥した後、カレンダー処理を行って、全厚が１３０μｍになるように正極合剤層の厚みを調整し、活物質塗布面積部分が７０mm×４０mmになるように切断して正極を作製した。ただし、上記正極の作製にあたっては、アルミニウム箔の一部に正極合剤含有ペーストを塗布せず、アルミニウム箔の露出部をリード部として残し、そのリード部を正極端子との接続部分とした。作製した正極をポリエチレン製の袋に入れ、固体電解質を作製したものと同組成の液状化合物を注入し、ポリエチレン製袋を真空封止した。３時間放置後、６０℃で４時間加熱し、電極内部の液状化合物を硬化させた。袋を切断し正極を取り出した。
【００３５】
負極の作製：
負極活物質である黒鉛９０重量部とポリフッ化ビニリデン１０重量部とをＮ−メチルピロリドンを溶剤として均一になるように混合して負極合剤含有ペーストを調製し、銅箔からなる厚さ１０μｍの集電体の両面に塗布し、乾燥した後、カレンダー処理を行って全厚が１３０μｍになるように負極合剤層の厚みを調整し、活物質塗布面積部分が７２mm×４２mmになるように切断して負極Ａを作製した。切断は、負極端子との接続部分となるリード部を、電極の幅方向に対して中央位置になるようにした。また、上記正極同様、負極Ａの作製にあたっても、リード部分には負極合剤含有ペーストを塗布せず、銅箔の露出部をリード部として残した。作製した負極をポリエチレン製の袋に入れ、固体電解質を作製したものと同組成の液状化合物を注入し、ポリエチレン製袋を真空封止した。３時間放置後、６０℃で４時間加熱し、電極内部の液状化合物を硬化させた。袋を切断し負極を取り出した。
【００３６】
上記のようにして得た、正極と固体電解質フィルムおよび負極を貼り合わせ単層セルとした。このセルをポリエステルフィルム−アルミニウムフィルム−変性ポリオレフィンフィルムの三層構造のラミネートフィルムからなる外装体に挿入し封止して、図１に示すようなポリマー固体電解質電池を作製した。
【００３７】
（実施例２）
エトキシジエチレンオキサイド１3.５ｇに代えて、エチルブチルカーボネート１3.５ｇを使用した以外は、実施例１と同様にして固体電解質フィルムとポリマー固体電解質電池を得た。
【００３８】
（実施例３）
ジエチレングリコールモノアクリレート１０ｇに代えて、トリエチレングリコールモノアクリレート１０ｇを使用した以外は、実施例１と同様にして固体電解質フィルムとポリマー固体電解質電池を得た。
【００３９】
（実施例４）
エトキシジエチレンオキサイド１3.５ｇに代えてエチルブチルカーボネート１3.５ｇとし、ジエチレングリコールモノアクリレート１０ｇに代えてトリエチレングリコールモノアクリレート１０ｇとした以外は、実施例１と同様にして固体電化質フィルムとポリマー固体電解質電池を得た。
【００４０】
（実施例５）
エトキシジエチレンオキサイド１3.５ｇに代えて、エトキシジエチレンオキサイド1.５ｇを使用し、ＬｉＣｌＯ₄ を1.５ｇとした以外は、実施例１と同様にして固体電解質フィルムと電池を得た。
【００４１】
（比較例１）
ジエチレングリコールモノアクリレート１０ｇ、エトキシジエチレンオキサイド１3.５ｇをそれぞれ4.４ｇ、３２ｇに変化させた以外は実施例１と同様にして固体電解質フィルムおよび電池を得た。
【００４２】
（比較例２）
エトキシジエチレンオキサイドに代えて、プロピレンカーボネート（誘電率≒７０）を使用した以外は実施例１と同様にして固体電解質フィルムおよび電池を得た。
【００４３】
（比較例３）
ジエチレングリコールモノアクリレート１０ｇ、エトキシジエチレンオキサイド１3.５ｇをそれぞれ、ジエチレングリコールモノアクリレート4.４ｇ、プロピレングリコール３２ｇに変更した以外は実施例１と同様にして固体電解質フィルムおよび電池を得た。
【００４４】
（比較例４）
エトキシジエチレンオキサイド１3.５ｇに代えて、ジエチルカーボネート１3.５ｇを使用した以外は実施例１と同様にして固体電解質フィルムおよび電池を得た。
【００４５】
（比較例５）
ジエチレングリコールモノアクリレート１０ｇに代えて、ポリエチレングリコールモノアクリレート１０ｇを使用した以外は実施例１と同様にして固体電解質フィルムおよび電池を得た。
【００４６】
（比較例６）
エトキシジエチレンオキサイド１3.５ｇを1.０ｇに、ＬｉＣｌＯ₄ ３ｇを1.５ｇとした以外は実施例１と同様にして固体電解質フィルムおよび電池を得た。
【００４７】
〔評価〕
これら作製した固体電解質フィルムのイオン伝導度（σ）を複素インピーダンス法（室温）で測定した。
【００４８】
また、作製した電池について以下の式にて放電容量割合を計算した。
・放電容量割合＝１Ｃの放電容量／0.２Ｃの放電容量×１００
【００４９】
さらに、電解質フィルムをアルミラミネートフィルムに入れ、真空封止した後、１２０℃／２４時間放置後、袋の膨れを観察した。評価は以下の基準で行った。
○：膨れなし。
△：袋がたるむ程度若干膨れがみられる。
×：袋が変形する程の膨れがみられる。
これらの結果を表１に示す。
【００５０】
【表１】

【００５１】
表１より、実施例１〜５は、イオン伝導度が１０‐⁴ 以上であり、しかもガス発生による袋の膨れも観察されなかったことから、イオン伝導性と安全性を併せ持つ電解質材料であることがわかる。比較例１、３より、液状化合物の割合が８０％以上となると、イオン伝導性は良好となるが、若干のガス発生が観察され、安全性に不具合が生じることが確認された。比較例２より、液状化合物の誘電率が高いと、電解質のイオン伝導性が低下することがわかった。比較例４より、液状化合物の沸点が１５０℃未満であると、ガスが多量に発生し、安全性に不具合が生じることが確認された。比較例５より、ＰＥＯユニット数が長いとイオン伝導性の低下がみられた。比較例６より、液状化合物の割合が１０％未満では、イオン伝導率が低下し、電池とした場合、容量が取り出せないことがわかる。
【００５２】
【発明の効果】
以上説明したように、本発明では、ユニット数３以下のエチレンオキサイド基を有する片末端アクリロイル基変性アルキレンオキシドモノマーと、電解質塩と、誘電率が2.５〜１０であり、かつ沸点が１５０℃以上である液状化合物とを含む液状組成物を硬化させることにより、優れたイオン伝導性を有するとともに、安全性に優れた固体電解質を得ることができた。
【図面の簡単な説明】
【図１】本発明に係るポリマー電解質電池の内部構成図である。
【符号の説明】
１ 正極
２ 負極
３ セパレータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid electrolyte and a polymer solid electrolyte battery using the same.
[0002]
[Prior art]
With polymer electrolyte batteries, it has become possible to produce thin batteries with a large area such as A4 and B5 plates, so that they can be applied to various thin products such as portable electronic devices. Is spreading greatly. In addition, this polymer electrolyte battery has unprecedented characteristics that it has excellent safety and storage characteristics including leakage resistance, is thin and flexible, and can be designed to match the shape of the equipment. ing.
[0003]
In particular, a solid electrolyte using a polymer substance (polymer) has an advantage that a uniform thin film can be easily processed into an arbitrary shape. Therefore, solid electrolytes using various polymers have been proposed. For example, JP-A-55-98480, 58-108667, 58-188062, 58-188063, 59-71263, and the like include polymers such as polyethylene oxide and polypropylene oxide. , Li, Na, and other solid electrolyte compositions composed of combinations with inorganic ion salts, and batteries using these compositions have been proposed. However, these compositions do not have sufficient ionic conductivity at room temperature, and therefore there are many restrictions such as the operating temperature of the battery being limited to 60 ° C. or higher, which is higher than the softening point of the polymer. It has not yet been put into practical use except for the above applications.
[0004]
[Problems to be solved by the invention]
In order to solve this problem, an organic electrolyte used in an organic lithium ion battery or the like is added to a polymer solid electrolyte composition such as vinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, or acrylate. There has been proposed a method of producing an added gel polymer solid electrolyte and improving the ionic conductivity while remaining in a solid state (for example, JP-A Nos. 59-149601 and 58-75799). However, the gel polymer solid electrolyte to which the organic electrolyte is added in this way has the same lithium ion conduction mechanism as that of the organic electrolyte, so in order to improve the ionic conductivity, the addition of the organic electrolyte It is necessary to increase the concentration as close to 100% as possible, and since such an electrolyte has a low boiling point, the vapor pressure of the electrolyte also increases in a solid electrolyte. For this reason, the characteristics of the solid electrolyte, which are superior in safety compared to the liquid system, are lost.
[0005]
Further, a composite solid electrolyte in which polyethylene glycol having a molecular weight of 400 is further added to a system of polymethacrylic acid and lithium perchlorate has been reported (see Solid State Ionics Vol. 11, pp. 127, 1983). Japanese Laid-Open Patent Publication No. 59-71263 proposes a composite solid electrolyte comprising polymethacrylate, a lithium salt and polyethylene glycol (or polypropylene oxide). However, these solid electrolytes are insufficient in ionic conductivity, although problems of vaporization and oozing in the composition to which the organic solvent is added are small.
[0006]
Furthermore, Japanese Patent Application Laid-Open No. 58-82477 proposes a solid electrolyte having a network structure of a composition comprising polyethylene oxide, an alkali salt and a polymer capable of forming a network structure. However, this solid electrolyte has a high molecular weight (5,000 to 7,000,000) of polyethylene oxide that is preferably used, and easily forms a crystalline complex with an alkali salt. It is necessary to maintain an amorphous state, and ion conductivity is insufficient.
[0007]
Further, Japanese Patent Publication No. 6-96699 proposes a solid electrolyte of a composite composed of an alkylene oxide having an acryloyl group at one end, a lithium salt, and polyethylene glycol (or polypropylene oxide). However, polyethylene glycol has a large molecular weight, and these solid electrolytes have insufficient ion conductivity.
[0008]
An object of the present invention is to improve a defect of a conventional solid electrolyte, and to obtain a solid electrolyte having excellent ion conductivity and excellent safety, and a polymer solid electrolyte battery using the same.
[0009]
[Means for Solving the Problems]
The present invention is constituted by the one terminal acryloyl-modified alkylene oxide monomer having a unit having 3 or less of ethylene oxide groups, and an electrolyte salt, and a dielectric constant of 10 or less and a boiling point of liquid compound is 0.99 ° C. or higher A solid electrolyte comprising a polymer obtained by curing a liquid composition containing the liquid compound in a proportion of 10 wt% or more and less than 80 wt% and polymerizing the monomer.
[0010]
The one-terminal acryloyl group-modified alkylene oxide monomer having an ethylene oxide group having 3 or less units constituting the solid electrolyte of the present invention means a monomer represented by Chemical Formula ¹ (wherein R ¹ and R ² are hydrogen atoms) Or an alkali group, R ³ represents an alkyl group having 3 or less carbon atoms, and n is 3 or 2 or 1. A polymer obtained by polymerizing such a monomer has a short ethylene oxide group having 3 or less units as a side chain. However, a monomer having such a short side chain has many highly mobile terminals. The molecular mobility is high. As a result, the diffusion coefficient of lithium ions is increased, and high lithium ion conductivity is exhibited. When the number of units is 4 or more, side chain entanglement and crystallization become remarkable, so that the diffusion coefficient of lithium ions becomes small and the lithium ion conductivity becomes low.
[0011]
[Chemical 1]

[0012]
Examples of the one-terminal acryloyl group-modified alkylene oxide monomer having an ethylene oxide group having 3 or less units include triethylene glycol monoacrylate, tetraethylene glycol monoacrylate, methoxytetraethylene glycol monoacrylate, phenoxytetraethylene glycol monoacrylate, Examples include triethylene glycol monomethacrylate, bifunctional or higher functional polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, triethylene glycol trimethylolpropane triacrylate, and compounds obtained by replacing the ethylene glycol structure of the above compound with a propylene glycol structure. . Moreover, the said monomer can be used together 2 or more types.
[0013]
As the electrolyte salt constitutes a solid electrolyte of the present invention, for _{example, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiCF 3 CO 2, Li 2 C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiCn F _{2n + 1} SO ₃ (n ≧ 2), LiN (RfOSO ₂ ) ₂ [where Rf And an electrolyte salt containing at least Li, such as a fluoroalkyl group], and these can be used alone or in combination.
[0014]
The content of the electrolyte salt is preferably (electrolyte salt / EO) × 100 (mol%), preferably 0.05 to 50 mol%, more preferably, based on the alkylene oxide unit of the one-end acryloyl group-modified alkylene oxide monomer. The amount is from 0.1 to 30 mol% (in the above formula, EO represents ethylene oxide). When there is too much content of the said electrolyte salt, excess electrolyte salt will not dissociate and it will only be mixed, and, for this reason, ionic conductivity will fall conversely. Moreover, even if there is too little content, the number of the ion to dissociate will become small and ion conductivity will fall.
[0015]
In the present invention, the liquid compound described above is used as a plasticizer for improving the mobility of the polymer and the ionic conductivity. This liquid compound is required to have a dielectric constant of 10 or less and a boiling point of 150 ° C. or more. When the dielectric constant is 10 or less, the interaction with the Li ion dissociated by the ethylene oxide chain in the polymer obtained by polymerizing the monomer having an ethylene oxide group is small, and movement of the Li ion is not hindered. Even if the concentration of the polymer in the solid electrolyte increases, the ionic conductivity is maintained well. When the dielectric constant is larger than 10, the interaction with Li ions increases, and many compounds form complexes with Li ions, so that the ion conductivity is lowered. In particular, if the concentration of the polymer is increased at this time, the mobility of the bulky complex is greatly inhibited, and the ionic conductivity is lowered. As described above, the dielectric constant of the liquid compound is preferably as low as 10 or less, but substantially the range of 1 to 8 is used.
[0016]
If the boiling point is less than 150 ° C., the liquid compound gradually evaporates from the solid electrolyte, and the ionic conductivity may decrease. In addition, the higher the boiling point, the lower the vapor pressure and the higher the safety, which is preferable. The upper limit of the boiling point is not particularly specified, but those having a boiling point that is too high are generally high in molecular weight and increase in viscosity of the system. Since there exists a tendency for the fall of conductivity to occur, what is about 200 degrees C or less is used suitably.
[0017]
The content of the liquid compound is preferably 10 wt% or more and less than 80 wt%, more preferably 20 wt% or more and 70 wt% or less, based on the weight of the entire composition (liquid composition). When the content of the liquid compound is 80 wt% or more, the mechanical properties of the solid electrolyte are lowered and the vapor pressure is increased, which is not preferable. Moreover, if it is less than 10 wt%, ion conductivity will fall.
[0018]
As a means for curing the liquid composition of the present invention, a method of irradiating actinic rays such as ultraviolet rays and visible rays, or a method such as heating is employed.
[0019]
In the case of the above-mentioned method of irradiating with actinic rays, benzoin, 2-methylbenzoin, trimethylsilylbenzophenone, 4-methoxybenzophenone, benzoin methyl ether, acetophenone, anthraquinone, 2,2-dimethoxy-2-phenylacetophenone as a photopolymerization initiator Etc. are preferably added in advance.
[0020]
In the case of the above heating method, it is desirable to add a peroxide such as diacyl peroxide, peroxydicarbonate, peroxyester as an initiator. Specifically, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, stearoyl peroxide, octanoyl peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate Bis (4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-2-methoxybutyl peroxydicarbonate, di (3 -Methyl-3-methoxybutyl) peroxydicarbonate, 1,1,3,3-tetramethylbutylperoxyneodecanate, 1-cyclohexyl-1-methylethylperoxyneodecane, t-hexylperoxyne Decanate, t-butylperoxyneodecanate, t-hexylperoxypivalate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 1- Cyclohexyl-1-methylethylperoxy-2-ethylhexanoate and t-hexylperoxy-2-ethylhexanoate can be used alone or in combination of two or more.
[0021]
In the present invention, a porous sheet may be used as a solid electrolyte support. For example, a nonwoven fabric or a microporous film is used. Examples of the nonwoven fabric include nonwoven fabrics such as polypropylene, polyethylene, polyethylene terephthalate, and polybutylene terephthalate. Examples of the microporous film include polypropylene, polyethylene, and a microporous film of an ethylene-propylene copolymer.
[0022]
Although the constituent components of the solid electrolyte produced by the polymerizable composition of the present invention are listed, other components can be added as long as the object of the present invention is not impaired. For example, it can be used as a composite electrolyte with various inorganic fine particles added, which not only improves the strength and film thickness uniformity, but also creates fine pores between the inorganic fine particles and the polymer. Conversely, ion conductivity and mobility can be increased without impairing the improvement effect. Further, by adding inorganic fine particles, the viscosity of the polymerizable composition is increased, and an effect of suppressing the separation appears even when the compatibility between the polymer and the solvent is insufficient.
[0023]
As the inorganic fine particles to be used, non-electron conductive ones and electrochemically stable ones are selected. Moreover, it is more preferable if it has ion conductivity. Specific examples include fine particles made of ionic conductive or nonconductive ceramics such as α, β, γ-alumina, and silica. Specific examples of the inorganic fine particles include silica ultrafine particles such as Aerosil (manufactured by Nippon Aerosil Co., Ltd.) and alumina ultrafine particles, and alumina ultrafine particles are particularly preferred from the viewpoint of stability and composite efficiency.
[0024]
The solid electrolyte according to the present invention is applied to a polymer electrolyte battery as shown in FIG. There, a positive electrode 1 formed by laminating a positive electrode mixture layer containing an active material and a binder polymer on a current collector, and a negative electrode mixture layer containing an active material and a binder polymer are laminated on the current collector. The negative electrode 2 is made to face the electrolyte separator 3. These are packaged with a package 4 made of a laminate film. Lead portions 5 and 6 are drawn out of the exterior body 4 from the positive electrode 1 and the negative electrode 2, respectively. In the present invention, the solid electrolyte is used as the positive / negative electrodes 1 and 2 and the electrolyte separator 3.
[0025]
The binder polymer for the positive and negative electrodes 1 and 2 is preferably a polymer that has high crystallinity, maintains good crystallinity even at the battery operating temperature upper limit (80 ° C.), and can firmly connect the active materials. . In addition, these polymers are required to maintain a crystal structure in the electrolyte even in heat treatment after battery assembly. The properties required for such a polymer are required to have a melting temperature of 150 ° C. or higher, and a melting temperature in the electrolyte of at least 100 ° C., preferably 120 ° C. or higher. Examples of such a polymer component include a crystalline polymer such as polyvinylidene fluoride.
[0026]
In the present invention, an aluminum foil, a punching metal, a net, an expanded metal, or the like can be used as the current collector of the positive electrode 1, but an aluminum foil is usually used. The current collector of the positive electrode 1 preferably has a thickness of 30 μm or less in view of reducing the thickness of the entire positive electrode. In the present invention, even if the current collector is thin, the exposed portion of the current collector 4 Since it does not come out from the seal part, there is little risk of breakage.
[0027]
However, if it is too thin, when producing the positive electrode, there is a possibility that wrinkles may occur when the positive electrode mixture-containing paste is applied, or tearing may occur due to pulling, so the thickness is 30 μm or less as described above. Is preferably 10 μm or more.
[0028]
The lead portion 5 on the positive electrode 1 side is usually formed by leaving an exposed portion of the current collector without forming a positive electrode mixture layer on a part of the aluminum current collector during the production of the positive electrode, and using that as the lead portion. Provided. However, the lead part 5 is not necessarily required to be integrated with the current collector from the beginning, and may be provided by connecting an aluminum foil or the like to the current collector later.
[0029]
As the current collector of the negative electrode 2, copper foil, punching metal, net, expanded metal, and the like can be used. However, the current collector of the negative electrode 2, in which copper foil is usually used, reduces the thickness of the entire negative electrode. In addition, those having a thickness of 30 μm or less are preferable. In the present invention, even if it is so thin, the exposed portion does not come out from the seal portion of the exterior body 4, so there is little risk of breakage.
[0030]
However, if it is too thin, there is a risk that wrinkles may occur when the negative electrode mixture-containing paste is applied in the production of the negative electrode, and tearing may occur due to pulling. Therefore, the thickness is 30 μm or less as described above. Is preferably 5 μm or more.
[0031]
Further, the lead portion 6 on the negative electrode 2 side also usually leaves an exposed portion of the current collector without forming a negative electrode mixture layer on a part of the copper current collector at the time of producing the negative electrode, which is used as the lead portion 6. Is provided. However, the negative electrode side lead portion 6 is not necessarily integrated with the current collector from the beginning, and may be provided by later connecting a copper foil or the like to the current collector.
[0032]
〔Example〕
Examples of the present invention will be given below together with comparative examples to explain the present invention in more detail.
[0033]
Example 1
Production of Solid Electrolyte Film (Solid Electrolyte) Diethylene glycol monoacrylate (manufactured by Shin-Nakamura Chemical Co., AM-90G) as a single terminal acryloyl group-modified alkylene oxide monomer, lithium perchlorate (LiClO ₄ ) as an electrolyte salt, and liquid compound Ethoxydiethylene oxide (manufactured by Nacalai Tesque), LucirinTPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) (BASF) as a polymerization initiator, and triethylene glycol dimethacrylate (Shin Nakamura Chemical Co., Ltd.) as a crosslinking agent 9G), and these were mixed in the following proportions to obtain a uniform solution. The liquid composition made into this homogeneous solution was polymerized at 60 ° C. for 4 hours to obtain a solid electrolyte film.
Diethylene glycol monoacrylate 10g
Triethylene glycol dimethacrylate 0.5g
Lithium perchlorate (LiClO ₄ ) 3g
Ethoxydiethylene oxide 13.5g
LucirinTPO 0.01g
[0034]
Production of positive electrode:
85 parts by weight of LiCoO _{2 as a} positive electrode active material, 10 parts by weight of acetylene black as a conductive auxiliary agent, and 5 parts by weight of polyvinylidene fluoride are mixed uniformly using N-methylpyrrolidone as a solvent, and a positive electrode mixture-containing paste Was prepared. The paste was applied to both sides of a 20 μm thick aluminum foil serving as a current collector, dried, and then subjected to calendering to adjust the thickness of the positive electrode mixture layer so that the total thickness became 130 μm. The positive electrode was produced by cutting so that the coated area was 70 mm × 40 mm. However, in producing the positive electrode, the positive electrode mixture-containing paste was not applied to a part of the aluminum foil, the exposed portion of the aluminum foil was left as a lead portion, and the lead portion was used as a connection portion with the positive electrode terminal. The produced positive electrode was put into a polyethylene bag, a liquid compound having the same composition as that of the solid electrolyte was injected, and the polyethylene bag was vacuum-sealed. After standing for 3 hours, the mixture was heated at 60 ° C. for 4 hours to cure the liquid compound inside the electrode. The bag was cut and the positive electrode was taken out.
[0035]
Production of negative electrode:
A negative electrode active material-containing paste was prepared by mixing 90 parts by weight of graphite as a negative electrode active material and 10 parts by weight of polyvinylidene fluoride so as to be uniform using N-methylpyrrolidone as a solvent, and having a thickness of 10 μm made of copper foil. After coating on both sides of the current collector and drying, calendering is performed to adjust the thickness of the negative electrode mixture layer so that the total thickness is 130 μm, and the active material coating area is cut to 72 mm × 42 mm. Thus, a negative electrode A was produced. The cutting was performed such that the lead portion serving as a connection portion with the negative electrode terminal was at the center position with respect to the width direction of the electrode. Similarly to the above positive electrode, in preparing the negative electrode A, the negative electrode mixture-containing paste was not applied to the lead portion, and the exposed portion of the copper foil was left as the lead portion. The prepared negative electrode was put into a polyethylene bag, a liquid compound having the same composition as that of the solid electrolyte was injected, and the polyethylene bag was vacuum-sealed. After standing for 3 hours, the mixture was heated at 60 ° C. for 4 hours to cure the liquid compound inside the electrode. The bag was cut and the negative electrode was taken out.
[0036]
The positive electrode, the solid electrolyte film, and the negative electrode obtained as described above were bonded to obtain a single layer cell. This cell was inserted into an outer package made of a laminate film having a three-layer structure of polyester film-aluminum film-modified polyolefin film and sealed to prepare a polymer solid electrolyte battery as shown in FIG.
[0037]
(Example 2)
A solid electrolyte film and a polymer solid electrolyte battery were obtained in the same manner as in Example 1 except that 13.5 g of ethyl butyl carbonate was used instead of 13.5 g of ethoxydiethylene oxide.
[0038]
(Example 3)
A solid electrolyte film and a polymer solid electrolyte battery were obtained in the same manner as in Example 1 except that 10 g of triethylene glycol monoacrylate was used instead of 10 g of diethylene glycol monoacrylate.
[0039]
Example 4
The solid electrolyte film and the polymer solid electrolyte were the same as in Example 1 except that 13.5 g of ethyl butyl carbonate was used instead of 13.5 g of ethoxydiethylene oxide and 10 g of triethylene glycol monoacrylate was substituted for 10 g of diethylene glycol monoacrylate. A battery was obtained.
[0040]
(Example 5)
A solid electrolyte film and a battery were obtained in the same manner as in Example 1 except that 1.5 g of ethoxydiethylene oxide was used instead of 13.5 g of ethoxydiethylene oxide and 1.5 g of LiClO ₄ was used.
[0041]
(Comparative Example 1)
A solid electrolyte film and a battery were obtained in the same manner as in Example 1 except that 10 g of diethylene glycol monoacrylate and 13.5 g of ethoxydiethylene oxide were changed to 4.4 g and 32 g, respectively.
[0042]
(Comparative Example 2)
A solid electrolyte film and a battery were obtained in the same manner as in Example 1 except that propylene carbonate (dielectric constant≈70) was used instead of ethoxydiethylene oxide.
[0043]
(Comparative Example 3)
A solid electrolyte film and a battery were obtained in the same manner as in Example 1 except that 10 g of diethylene glycol monoacrylate and 13.5 g of ethoxydiethylene oxide were changed to 4.4 g of diethylene glycol monoacrylate and 32 g of propylene glycol, respectively.
[0044]
(Comparative Example 4)
A solid electrolyte film and a battery were obtained in the same manner as in Example 1 except that 13.5 g of diethyl carbonate was used instead of 13.5 g of ethoxydiethylene oxide.
[0045]
(Comparative Example 5)
A solid electrolyte film and a battery were obtained in the same manner as in Example 1 except that 10 g of polyethylene glycol monoacrylate was used instead of 10 g of diethylene glycol monoacrylate.
[0046]
(Comparative Example 6)
A solid electrolyte film and a battery were obtained in the same manner as in Example 1 except that 13.5 g of ethoxydiethylene oxide was changed to 1.0 g and 3 g of LiClO ₄ was changed to 1.5 g.
[0047]
[Evaluation]
The ionic conductivity (σ) of these produced solid electrolyte films was measured by the complex impedance method (room temperature).
[0048]
Moreover, the discharge capacity ratio was calculated by the following formula for the produced battery.
・ Discharge capacity ratio = 1C discharge capacity / 0.2C discharge capacity × 100
[0049]
Further, the electrolyte film was put in an aluminum laminate film, vacuum sealed, and allowed to stand at 120 ° C. for 24 hours, and then the swelling of the bag was observed. Evaluation was performed according to the following criteria.
○: No swelling.
Δ: Slightly swollen to the extent that the bag sags.
X: Swelling to the extent that the bag is deformed is observed.
These results are shown in Table 1.
[0050]
[Table 1]

[0051]
From Table 1, Examples 1-5 are in ionic conductivity 10 ⁴ or more, yet since it was not observed swelling of the bag by the gas generator, it is an electrolyte material having both ionic conductivity and safety I understand. From Comparative Examples 1 and 3, it was confirmed that when the ratio of the liquid compound was 80% or more, the ionic conductivity was good, but a slight gas generation was observed, causing a problem in safety. From Comparative Example 2, it was found that when the dielectric constant of the liquid compound was high, the ionic conductivity of the electrolyte was lowered. From Comparative Example 4, it was confirmed that when the boiling point of the liquid compound was less than 150 ° C., a large amount of gas was generated, causing a problem in safety. From the comparative example 5, when the number of PEO units was long, the fall of ion conductivity was seen. From Comparative Example 6, it can be seen that when the proportion of the liquid compound is less than 10%, the ionic conductivity is lowered, and when the battery is used, the capacity cannot be taken out.
[0052]
【Effect of the invention】
As described above, in the present invention, one-end acryloyl group-modified alkylene oxide monomer having an ethylene oxide group having 3 or less units, an electrolyte salt, a dielectric constant of 2.5 to 10, and a boiling point of 150 ° C. By curing the liquid composition containing the liquid compound as described above, it was possible to obtain a solid electrolyte having excellent ion conductivity and excellent safety.
[Brief description of the drawings]
FIG. 1 is an internal configuration diagram of a polymer electrolyte battery according to the present invention.
[Explanation of symbols]
1 Positive electrode 2 Negative electrode 3 Separator

Claims (2)

A liquid compound comprising a one-terminal acryloyl group-modified alkylene oxide monomer having an ethylene oxide group of 3 or less units, an electrolyte salt, and a liquid compound having a dielectric constant of 10 or less and a boiling point of 150 ° C. or more, A solid electrolyte comprising a polymer obtained by curing a liquid composition containing 10 wt% or more and less than 80 wt% and polymerizing the monomer. A polymer solid electrolyte battery comprising a positive electrode, a negative electrode and a solid electrolyte,
The polymer solid electrolyte battery according to claim 1 , wherein the solid electrolyte is the solid electrolyte according to claim 1 .

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