JP4099852B2 - Porous sheet for forming gelled solid electrolyte and gelled solid electrolyte sheet using the same - Google Patents
Porous sheet for forming gelled solid electrolyte and gelled solid electrolyte sheet using the same Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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Description
【０００１】
【発明の属する技術分野】
本発明は、ゲル状固体電解質形成用多孔質シ−ト及びそれを用いたイオン導電性ゲル状固体電解質に関するものであり、更に詳しくは、サイクル特性に優れたゲル状オ−ル固体Ｌｉ二次電池を効率よく作るのに有効に用いるイオン導電性ゲル状固体電解質形成用多孔質シ−トに関するものである。
【０００２】
【従来の技術】
ＬｉＣｏＯ2、ＬｉＭｎＯ2、ＬｉＮｉＯ2の如きリチウムの複合酸化物を正極活物質とし、Ｌｉ合金や、Ｌｉを吸蔵、放出する能力を備えた炭素材を負極活物質とし、電解質を溶解した非水溶媒を電解質としたリチウム電池は、高性能であり、サイクル特性にも優れていることより、パソコン、携帯電話、ミニコンポ、ミニディスク等の電子機器用電源として大きな発展を遂げており、将来的には環境に易しいハイブリッド自動車や電気自動車用電源として活用することが検討されている。
【０００３】
従来開発されてきた非水電解質電池は、電解液としてエチレンカ−ボネ−トやプロピレンカ−ボネ−トなどの有機溶媒を用いているため、当該電池が高温雰囲気下に暴された場合や、当該電池を用いた電子機器において、当該電池に内部短絡や外部短絡などの不都合が生じ、電池温度が上昇した場合、電解液が揮散し、電池が爆発したり、火災発生を起こしたりするという難点があった。
【０００４】
このような難点のない固体電池として、ＬｉＣｌＯ4、ＬｉＢＦ4等の電解質塩、エチレンカ−ボネ−ト、プロピレンカ−ボネ−トの如き非水溶媒、及びポリアルキレンオキサイドとよりなるイオン導電性固体電解質を用いた固体電池が開発されているが、ポリアルキレンオキシドは吸水性が高く、Ｌｉとの反応性も高い事などが起因してサイクル特性に優れ爆発の危険のない固体電池としては未だ性能は十分な性能を有するものとは言えない。
【０００５】
特開平７−３２０７８１号公報には、非水溶媒により可塑化したアクリロニトリル系重合体、酢酸ビニル系重合体、塩化ビニル系重合体に電解質塩を溶解した固体電解質を用いた固体電池の発明が示されている。
【０００６】
【発明が解決しようとする課題】
上記特許に示された固体電解質の製法は、アクリロニトリル系重合体を溶解し、この溶液にＬｉＣｌＯ4を加えた溶液を流延し、溶媒を揮散せしめて固体電解質とする方法が示されているが、この固体電解質は非水溶媒が含まれていないため、電解質塩の重合体相への溶解性が悪く、固体電解質としてのイオン導電性は十分なものではない。また、この固体電解質のイオン導電性を高めるため、非水溶媒であるアセトニトリルを固体電解質内に残すと、アセトニトリルの沸点は８１℃であるため、該固体電解質を用いた固体電池は１００℃以上の高温に暴された場合、爆発や電池のフクレを生じるという難点がある。
【０００７】
また、同公報には上記と同様の方法により作成したビニル系重合体フィルムをプロピレンカ−ボネ−ト溶液に浸漬、膨潤する方法が示されているが、ビニル系重合体フィルムへの非水溶媒による、膨潤処理は極めて難しいという難点がある。
【０００８】
【課題を解決するための手段】
そこで、本発明者は均一な特性を備えたシ−ト状固体電解質を効率よく作るための工夫を重ねた結果、非水溶媒可溶性の重合体と非水溶媒に不溶の重合体の混合物よりなるシ−ト状物であって多孔質構造を有する重合体シ−トを用いることにより、その目的を達成しうることを見いだし本発明を完成したものであり、その要旨とするところは、正極、負極及び電解質塩を含む非水溶液を含浸したゲル状固体電解質シートを備える固体電解質電池に用いられ、非水溶媒可溶性重合体としてアクリロニトリル共重合量が５０モル％以上である共重合体と、非水溶媒に不溶なポリエチレン及び／又はポリプロピレンとの混合物よりなり、空孔率２０〜８０％の多孔質体よりなるゲル状固体電解質形成用多孔質シート及びそれを用いたゲル状固体電解質シ−トにある。
【０００９】
【発明の実施の形態】
本発明を実施するに際し用いる重合体は非水溶媒可溶性の重合体ならば、いかなるものをも用いえるが、当該重合体より形成したイオン導電性固体電解質のイオン導電性を高め、安全性確保の観点からすると、ビニル重合体であることが好ましい。ビニル重合体としては、アクリロニトリルとＣ１〜４のアルキル（メタ）アクリレ−トとの共重合体、アクリロニトリル−酢酸ビニル共重合体、アクリロニトリル−スチレン共重合体、アクリロニトリル−塩化ビニル又は塩化ビニリデン共重合体、スチレン−酢酸ビニル共重合体、ポリメチルメタクリレ−トなどをその具体例として挙げることができるが、これら重合体のうちでも比誘電率が５以上のアクリロニトリルの共重合体の共重合量が５０モル％以上、特に７０〜９８モル％が良好なイオン導電性を与えると共に、非水電解液の均一な分散を行い得た固体電解質とすることができる。
【００１０】
ここで言う固体電解質とは、電解液を構成する非水溶媒及び支持電解質塩と高分子重合体が実質的に均一に分散し流動状態を失っているものを指す。より詳しくは高分子鎖の三次元的ネットワークの中に溶剤及び解離したイオンが分布しうる状態であり、これはゲル状から硬膜状の外観を示し、このような状態は高分子を溶剤に加熱溶解しこれを冷却することにより実現できる。従ってここで言う溶媒が流動性を失った状態とは、従来のセパレーターなどの微細孔を有する材料中に液体が保持されているものとは明瞭に区別されるものである。
【００１１】
多孔質シ−トの製造方法としては湿式抄紙法、乾式抄紙法、不織布製造法の一種であるニ−ドルパンチ法、ウォ−タ−ジェット法、溶融押し出しシ−トの延伸多孔化や溶媒抽出による多孔化、流延シートの多孔化など公知の手法を用いることが出来る。
【００１２】
この多孔質シ−トを固体電解質として用いる場合、電池の内部抵抗を下げるために固体電解質層は薄い状態であることが必要であり、これら固体電解質シ−トの厚さは実質的に１００μｍ以下であることが望ましい。
【００１３】
ポリメチルメタクリレ−トやアクリロニトリル−スチレン共重合体、塩化ビニリデン共重合体などは溶融押し出しによるシ−ト成形が可能であるが、アクリロニトリルとＣ１〜４のアルキル（メタ）アクリレ−トとの共重合体、アクリロニトリル−酢酸ビニル共重合体、アクリロニトリル−塩化ビニル共重合体などは一般的に溶融成形は困難である。さらに本発明において良好なイオン導電性を与えるアクリロニトリルユニットが７０〜９８モル％のアクリロニトリル系重合体は明瞭な溶融現象を示さず、このため溶融成形を行うことは出来ない。
【００１４】
また高分子溶液を流延する事でシ−トを製造することもできる。この場合脱溶剤や多孔化工程が別途必要である。
従って本発明に好適な多孔質シ−トの製造方法としては、湿式及び乾式抄紙法が好ましく用いることが出来る。これら抄紙法においては、直径１０μｍ以下の繊維を用いる事により、厚さ１００μｍ以下の均一なシ−トを製造することが可能である。また製造されたシ−トには、繊維間に適度な空間を有しており、特別な多孔化処理を必要としない。またシ−トの空孔率は繊維直径や分岐度などの形状や、抄紙時のプレス圧などを変えることにより、制御することが可能である。
【００１５】
ゲル状固体電解質形成用多孔質シ−トに必要な要件としては、次に示す項目が挙げられる。一つはシ−トと電解液の濡れ性である。通常電池は正極と負極の間にセパレ−タ−を挟んだ積層構造を取る。正極や負極は予め金属箔の表面に活物質と呼ばれるリチウムイオンを吸放出する材料をバインダ−として用いることにより結着させてある連続したフィルム状物として調整される。セパレ−タ−は正極と負極が接触し短絡しないために用いられる物質で、保液性を有する多孔膜が通常用いられるが、電解液に対し溶解・膨潤などの効果を示さないポリオレフィン系の高分子が用いられている。正極、負極とセパレ−タ−は張力をかけた状態で積層して巻き取られ、電池の外殻を構成する金属製の缶に挿入される。このあと電解液を注入してセパレ−タ−部に含浸させる。
【００１６】
これと同様にゲル状固体電解質形成用多孔質シ−トも同様の工程を用いて巻き上げ電池容器中に挿入し、電解液を注入しシ−トに含浸させ熱処理等を行うことでゲル状固体電解質に転移させることが出来る。この場合溶剤の含浸時に気泡等が残らないために、シ−トの基材と溶剤との濡れ性が良好であることが求められる。
【００１７】
本請求項に記載されているアクリロニトリル系共重合体と非水溶媒の一例であるプロピレンカ−ボネ−トの接触角は５度以下であり、濡れ性は良好である。
二つ目はシートの強度である。前述の通り各部材は張力をかけてロ−ル状に巻き取る工程を通過する必要があるため、この巻き取り張力に対し破断しないだけの強度を有する必要がある。ここで必要とされる材料の破断強度は概ね１５ｋｇ／ｍｍ2程度である。
【００１８】
ここでこの様な強度を有するゲル状固体電解質形成用多孔質シ−トはアクリロニトリル系重合体からなる繊維状物のみで構成することが可能である。さらにシ−トの強度を向上させるために、シ−ト内部に非水溶媒に不溶な高分子重合体の連続層を形成することが有効である。例えばポリオレフィン系高分子のポリエチレンやポリプロピレンの繊維状あるいはパルプ状物をアクリロニトリル系共重合体と共にシ−トを形成することでこの目的が達成できる。さらにシ−トにした後、非水溶媒に不溶な高分子重合体の融点以上の温度で熱処理することにより、重合体同士が相互に接着しシ−トの強度は向上する。
【００１９】
三つ目はシ−トの空孔率である。シ−トの内部に形成された空間に電解液が侵入し、熱処理等によりゲル状固体電解質に転移させる場合、ゲル状固体電解質として適切なアクリロニトリル系重合体と電解液の組成領域が存在し、通常重合体は固体電解質において非水電解液量は５〜９５ｗｔ％の範囲にあることが望ましい。電解液によりシートを形成している重合体が膨潤するため、この体積増加分を吸収する空孔部分が必要となる。この空孔率の適切な範囲は概ね２０〜８０％の範囲にある。
【００２０】
空孔率が２０％より小さいとこの体積増加分を吸収することが困難でありまた、実質的にイオンが移動できる開口部分が少なくなり電池の内部抵抗が高くなるため好ましくない。また空孔率が８０％より大きいとシ−トの力学的な強度が低下するため好ましくない。
【００２１】
本発明を実施するに際して用いる電解質塩としてはＬｉＣｌＯ4，ＬｉＣＦ3ＳＯ4，ＬｉＰＦ6，ＬｉＢＦ4，ＬｉＰＦ4，ＬｉＮ（ＣＦ3ＳＯ4）2等を挙げることができる。
【００２２】
本発明を実施するに際して用いる非水溶媒としては例えばエチレンカ−ボネ−ト、プロピレンカ−ボネ−ト、ジメチルカ−ボネ−ト、γ−ブチロラクトン、ジエチルカ−ボネ−ト、ブチレンカ−ボネ−ト、スルホラン、ジメトキシエタン、テトラヒドロフラン、ジオキソラン等を挙げる事ができ、これら溶媒は単独で、或いは２種以上の混合物として用いる事ができるが、特に比誘電率が４０以上の溶媒を主たる成分とすることが好ましい。
【００２３】
本発明の空孔率２０〜８０％のシ−トは、その成形工程からして５０〜５００μｍと極めて薄膜の均質な膜で、非水電解液の均一含浸性に優れたものであり、良好な特性を備えた固体電解質を形成する事ができる。また、その膜厚も均一で機械的強度に富んだ取り扱い性の良好な多孔質シ−トであるため、固体電解質電池の作成工程をスム−スなものとすることができる。
【００２４】
【実施例】
以下、本発明を実施例により、更に具体的に説明する。
〔実施例１〕
ジャケット付きの２、０００ｍｌのガラス製反応容器に、水／モノマ−比が１４／１になるような条件でアクリロニトリルユニットを９３．６ｍｏｌ％、酢酸ビニルユニットを６．４ｍｏｌ％仕込み、重合触媒として反応液に対し１．０ｗｔ％のＮａ2ＳＯ3、１．５ｗｔ％のＮａＨＳＯ3、０．１２ｗｔ％のＨ2ＳＯ4を用いて水系懸濁重合を行った。反応温度は５５℃に保った。反応容器中に生成した重合物を回収し充分洗浄した後乾燥を行い、白色の粉末状物を得た。得られた粉体の重量から反応収率を計算したところ７３％であった。
得られた重合体の組成分析を元素分析により行ったところ、アクリロニトリルユニットが９６．０ｍｏｌ％、酢酸ビニルユニットが４．０ｍｏｌ％導入されていた。またこの重合体の分子量をＧＰＣにより測定したところ、ポリスチレン換算で５．１×１０5という値を示した。なおＧＰＣの測定は、溶媒として０．０１ＭＬｉＣｌ／ＤＭＦを用い、重合体濃度は０．１ｇ／ｄｌで行った。
【００２５】
プロピレンカ−ボネ−トに支持電解質としてＬｉＰＦ6を１．０ｍｏｌ／ｋｇになるように溶解した電解液を調製し、この電解液に上記アクリロニトリル系共重合体を室温で加え、スラリ−状にした。このスラリ−を１００℃で撹拌したところ、重合体は溶解し均一溶液を形成した。この溶液中での重合体濃度は１６ｗｔ％であった。この溶液を室温下で一昼夜放置すると溶液は流動性を無くし弾力のある白濁したゲル状を呈した。
このアクリロニトリル共重合体をジメチルアセトアミドに溶解し、１８ｗｔ％の濃度の重合体溶液を調製した。この重合体溶液をスライドグラス上に展開し、溶媒を自然乾燥することによりキャストフィルムを調整した。このキャストフィルムの平滑面に対するプロピレンカ−ボネ−ト及びジエチルカ−ボネ−トの接触角を接触角計により測定を試みたが、フィルムと液滴の馴染みが良く、フィルム上に液が広がり測定不能であった。
【００２６】
次にこの重合体溶液を、特開平９−２４１９１７号公報に開示されている手法に準じて、直径が０．２ｍｍφの溶液吐出口、直径が２ｍｍφ、長さが１．５ｍｍの円筒状の混合セル部、水蒸気流路がスリット状で開度を２５０μｍに調整し、溶液流路の中心線とスリット中心線のなす角度が６０度になるように作成したノズルを用いて、該高分子溶液の供給量を１８ｍｌ／ｍｉｎ、水蒸気の供給圧を１．５ｋｇ／ｃｍ2として、温度３０℃の水中へ噴出しパルプ状の高分子集合体を得た。
このパルプ状高分子集合体を、水に分散し家庭用ミキサ−で１０分間叩解処理を行った。この叩解処理後の水分散液を一部取り出し、乾燥して得たパルプ状繊維を走査型電子顕微鏡を用いて形態観察を行ったところ、直径５〜２０μｍの直径を有する繊維状の幹から、多数の直径０．２μｍ〜１μｍ程度のフィブリル状の繊維が分岐している構造が認められた。このパルプ状高分子の濾水度をカナディアンフリ−ネステスタ−を用いてＪＩＳ Ｐ−８２０７に準拠して行った。標準温度２０℃、標準濃度０．３％への補正を行った濾水度の値は３８７ｍｌであった。
【００２７】
上記の如くして得たパルプ状繊維の水分散液を用いて、標準角形シートマシンを用いてＪＩＳ Ｐ−８２０９法に準じて湿式抄紙を行った。得られたポリアクリロニトリル系共重合体よりなる繊維質シ−ト状物の坪量は２５ｇ／ｍ2、シ−ト平均厚みをＪＩＳ Ｐ−８１１８に準じて測定したところ１５５μｍであった。このシ−トを裁断し短冊状の試験片を調整し、ＪＩＳ Ｐ−８１１３に準じて試験片の引っ張り強さ試験を行った。１５ｍｍ幅の試験片は１８Ｎ／１５ｍｍの破断強度を有していた。このシートの空孔率を水銀圧入式ポロシメ−タ−（ＣＡＲＬＯ ＥＲＢＡ ＩＮＳＴＲＵＭＥＮＴ社製 ＰＯＲＯＳＩＭＥＴＥＲ ４０００）を用いて測定したところ、空孔率は６８％であった。
このアクリロニトリル系共重合体のパルプ状よりなるシ−トは、非水電解液可溶であり、かつ空孔率６８％を有するゲル状固体電解質形成用の多孔質シ−トであった。
【００２８】
〔実施例２〕
実施例１と同様にレドックス系触媒を用いて水系懸濁重合法により、組成がアクリロニトリル１００モル％の重合体を調製し、特開平９−２４１９１７号公報に開示されている手法に準じてパルプ状の高分子集合体を得た。このパルプ状のアクリロニトリル重合体を用いて、湿式抄紙法によりゲル状固体電解質形成用多孔質シ−トの調製を行った。
【００２９】
〔実施例３〕
実施例１と同様にレドックス系触媒を用いて水系懸濁重合法により、組成がアクリロニトリル９９．０モル％、酢酸ビニル１．０モル％の重合体を調製し、特開平９−２４１９１７号公報に開示されている手法に準じてパルプ状の高分子集合体を得た。このパルプ状のアクリロニトリル系共重合体を用いて、湿式抄紙法によりゲル状固体電解質形成用多孔質シ−トの調製を行った。
【００３０】
〔実施例４〕
実施例１と同様にレドックス系触媒を用いて水系懸濁重合法により、組成がアクリロニトリル９３．０モル％、アクリル酸エチル７．０モル％の重合体を調製し、特開平９−２４１９１７号公報に開示されている手法に準じてパルプ状の高分子集合体を得た。このパルプ状のアクリロニトリル系共重合体を用いて、湿式抄紙法によりゲル状固体電解質形成用多孔質シ−トの調製を行った。
【００３１】
〔実施例５〕
実施例１と同様にレドックス系触媒を用いて水系懸濁重合法により、組成がアクリロニトリル９３．８モル％、アクリル酸ブチル６．２モル％の重合体を調製し、特開平９−２４１９１７号公報に開示されている手法に準じてパルプ状の高分子集合体を得た。このパルプ状のアクリロニトリル系共重合体を用いて、湿式抄紙法によりゲル状固体電解質形成用多孔質シ−トの調製を行った。
【００３２】
〔実施例６〕
実施例１と同様にレドックス系触媒を用いて水系懸濁重合法により、組成がアクリロニトリル７５．２モル％、メタクリル酸ブチル２４．８モル％の重合体を調製し、特開平９−２４１９１７号公報に開示されている手法に準じてパルプ状の高分子集合体を得た。このパルプ状のアクリロニトリル系共重合体を用いて、湿式抄紙法によりゲル状固体電解質形成用多孔質シ−トの調製を行った。
【００３３】
〔実施例７〕
実施例１と同様にレドックス系触媒を用いて水系懸濁重合法により、組成がアクリロニトリル８５．０モル％、酢酸ビニル１５．０モル％の重合体を調製し、特開平９−２４１９１７号公報に開示されている手法に準じてパルプ状の高分子集合体を得た。このパルプ状のアクリロニトリル系共重合体を用いて、湿式抄紙法によりゲル状固体電解質形成用多孔質シ−トの調製を行った。
【００３４】
下記の表１に各実施例１〜７において作成した多孔質シ−トの坪量、シ−ト厚、引っ張り強度、空孔率を示した。
【００３５】
【表１】
表１に示すようにアクリロニトリル共重合体のパルプ状物から湿式抄紙法により調製したシ−トは適度な強度と空孔率を有するイオン導電性ゲル状固体電解質形成用の多孔体シ−ト状物であった。
【００３７】
〔実施例８〕
実施例１で調製したゲル状固体電解質形成用の多孔質シ−トを打ち抜き器を用いて直径４２ｍｍの丸形に打ち抜いた。支持電解質として１モル／ｋｇのＬｉＰＦ6を含むプロピレンカ−ボネ−ト溶液を、本打ち抜きシ−トに含浸させたものは該繊維質シ−トの２．８倍の非水電解質溶液を担持した。
非水電解液含浸操作後のシ−トを密閉容器中に移し８０℃で１２時間保持し熱処理したものを偏光顕微鏡を用いてクロスニコル下で観察したところ、熱処理前のものはパルプ状重合体に基づく異方性構造が観察されたが、熱処理後のものにはこの異方性構造は観察されなかった。熱処理を施したシ−トの引っ張り強度は含浸処理前の繊維質シ−トの引っ張り強度の９０％程度であった。このシ−トは半透明状態であり、厚み方向に圧縮性を有しかつ圧縮による溶剤の浸みだしなどは観察されなかった。
【００３８】
このシ−トの電気的特性の評価を、ヒュ−レットパッカ−ド製プレシジョンＬＣＲメーター４２８４Ａを用い、交流インピ−ダンス法により測定した。
測定に用いた電気伝導度測定用のアタッチメントは、対向する直径１４．８ｍｍの円盤状ステンレス製電極よりなり、この電極間に高分子固体電解質を挟んだ。測定時は、バネを利用して両極間に１１．８kPaの荷重を与え、試料とステンレス製電極との密着性を一定に保った。なおこれらの操作はアルゴン置換したグロ−ブボックス中で行った。
【００３９】
周波数１００Ｈｚ〜１ＭＨｚの範囲でピーク電圧２０ｍＶの交流を印加し、試料の複素インピ−ダンスを測定した。測定で得られた複素インピ−ダンスの軌跡をコールコールプロット法により解析し、高周波側で実軸上と交わる点を試料の抵抗値として、電極面積と電極間距離より電気伝導度を導出した。２５℃での試料の電気伝導度は５．４×１０-3Ｓ／ｃｍであった。
このアクリロニトリル系共重合体のパルプ状物よりなる固体電解質形成用の多孔質シ−トに電解液を含浸させ熱処理を行った材料は、電解液を含んだゲル状の電解質であり室温で高い伝導度を示すゲル状固体電解質シ−トであった。
【００４０】
〔実施例９〜１４〕
実施例２〜７で調製したゲル状固体電解質形成用多孔質シ−トを、実施例８と同様に支持電解質塩を含む電解液に含浸し、熱処理を施した。なお熱処理はイオン伝導度測定用のアタッチメント中に封入し荷重をかけた状態で行った。この処理後のシ−トの強度保持率と電気伝導度を測定した。測定結果を表２に示した。
【００４１】
【表２】
表２に示すようにアクリロニトリル共重合体から調製した多孔質シ−トは電解液の含浸操作により、良好な保液性と電気伝導度をもつ固体電解質シ−トとしての特徴を示した。
【００４３】
〔実施例１５〕
実施例１で調製したアクリロニトリル系共重合体をジメチルアセトアミドに溶解し、１５ｗｔ％の濃度の重合体溶液を調製した。この高分子溶液を３０μｍφの直径を有する紡糸口金よりジメチルアセトアミド３０ｗｔ％の水溶液中に紡出した。紡出糸を沸水で洗浄後、熱水中で３倍に延伸した後、さらに表面温度１５０℃〜２００℃の加熱ロ−ラ−上で１．５倍〜２倍の延伸を行い、単繊維繊度０．２〜０．５デニールの繊維を得た。この繊維を５ｍｍ程度に裁断しチョップドファイバ−を調製した。このチョップドファイバ−５重量部と実施例１で調製した濾水度３８７ｍｌのパルプ状アクリロニトリル共重合体１０重量部を混合し、この混合物の水分散液から湿式抄紙法によりシ−トを調製した。
【００４４】
シ−トの坪量は２５ｇ／ｍ2、シ−ト厚１８０μｍ、引っ張り強度１１Ｎ／１５ｍｍ、空孔率８０％のゲル状固体電解質形成用多孔質シ−トであった。
このゲル状固体電解質形成用多孔質シ−トに実施例８と同様に電解液を含浸させ熱処理し、強度保持率と電気伝導度を測定した。強度保持率は７９％、電気伝導度は５．８×１０-3Ｓ／ｃｍの固体電解質シートであった。
【００４５】
〔実施例１６〕
実施例１で調製した濾水度３８７ｍｌのパルプ状アクリロニトリル共重合体１０重量部とパルプ状ポリプロピレン（三井化学製 ＳＷＰ Ｙ６００）１０重量部を混合し、この混合物の水分散液から湿式抄紙法によりシートを調製した。
シートの坪量は２５ｇ／ｍ2、シート厚１４０μｍ、引っ張り強度２１Ｎ／１５ｍｍ、空孔率７２％のゲル状固体電解質形成用多孔質シ−トであった。
このゲル状固体電解質形成用多孔質シ−トに実施例８と同様に電解液を含浸させ熱処理し、強度保持率と電気伝導度を測定した。強度保持率は９８％、電気伝導度は８．６×１０-3Ｓ／ｃｍの固体電解質シ−トであった。
【００４６】
〔実施例１７〕
実施例１６で調製したゲル状固体電解質形成用多孔質シ−トを表面温度１７５℃に設定したプレスロ−ルを用いてプレス熱処理を行った。プレス熱処理後のシ−トは、坪量２５ｇ／ｍ2、シート厚８５μｍ、引っ張り強度３３Ｎ／１５ｍｍ、空孔率５２％のゲル状固体電解質形成用多孔質シ−トであった。
このゲル状固体電解質形成用多孔質シ−トに実施例８と同様に電解液を含浸させ熱処理し、強度保持率と電気伝導度を測定した。強度保持率は９８％、電気伝導度は１．１×１０-4Ｓ／ｃｍの固体電解質シ−トであった。
【００４７】
〔実施例１８〕
実施例１５で調製した単繊維繊度０．２から０．５デニ−ルのチョップドファイバ−５重量部と実施例１で調整した濾水度３８７ｍｌのパルプ状アクリロニトリル共重合体１０重量部及びパルプ状ポリプロピレン（三井化学製 ＳＷＰ Ｙ６００）１０重量部を混合し、この混合物の水分散液から湿式抄紙法によりシ−トを調製した。
シートの坪量は２５ｇ／ｍ2、シ−ト厚１７０μｍ、引っ張り強度１８Ｎ／１５ｍｍ、空孔率６８％の多孔質シ−トであった。
この多孔質シ−トを表面温度１７５℃に設定したプレスロ−ルを用いてプレス熱処理を行った。プレス熱処理後のシ−トは、坪量２５ｇ／ｍ２、シ−ト厚１１０μｍ、引っ張り強度２７Ｎ／１５ｍｍ、空孔率４９％のゲル状固体電解質形成用多孔質シ−トであった。
このゲル状固体電解質形成用多孔質シ−トに実施例８と同様に電解液を含浸させ熱処理し、強度保持率と電気伝導度を測定した。強度保持率は９９％、電気伝導度は８．７×１０-3Ｓ／ｃｍの固体電解質シートであった。
【００４８】
〔実施例１９〕
実施例１で調製した濾水度３８７ｍｌのパルプ状アクリロニトリル共重合体１０重量部及びパルプ状ポリプロピレン（三井化学製 ＳＷＰ Ｙ６００）１０重量部を混合し、この混合物を乾燥状態のまま、電圧変換器を用いて回転数を落とした家庭用ミキサ−にて分散処理を行ったところ両者は均一に混合され、空気にて搬送可能な状態まで開繊された。
この開繊された混合物をエア−レイ法により乾式不織布に加工した。この不織布を表面温度１７５℃に設定したプレスロ−ルを用いてプレス熱処理を行った。プレス熱処理後の不織布シ−トは、坪量３２ｇ／ｍ2、シ−ト厚９５μｍ、引っ張り強度２４Ｎ／１５ｍｍ、空孔率４２％のゲル状固体電解質形成用多孔質シ−トであった。
このゲル状固体電解質形成用多孔質シ−トに実施例８と同様に電解液を含浸させ熱処理し、強度保持率と電気伝導度を測定した。強度保持率は９９％、電気伝導度は７．５×１０-3Ｓ／ｃｍの固体電解質シ−トであった。
【００４９】
【発明の効果】
本発明の多孔質シ−トは高分子ゲル電解質形成用シ−トとして用いた場合、非水電解液との濡れ性及び含浸性、均一ゲル化を容易に行わしめることが出来、また良好な力学的特性も有している。
また本発明の固体電解質シ−トは、その取り扱い性も良好であり、かつ高いイオン伝導性を有するにもかかわらず、電解液の漏れがないという大きな特徴を有するものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a porous sheet for forming a gel-like solid electrolyte and an ion conductive gel-like solid electrolyte using the same, and more particularly, a gel-like solid-solid Li secondary having excellent cycle characteristics. The present invention relates to a porous sheet for forming an ion conductive gel-like solid electrolyte that is effectively used to efficiently produce a battery.
[0002]
[Prior art]
LiCoO 2 LiMnO 2 , LiNiO 2 A lithium battery using a composite oxide of lithium as a positive electrode active material, a Li alloy, a carbon material having the ability to occlude and release Li as a negative electrode active material, and a nonaqueous solvent in which an electrolyte is dissolved as an electrolyte, Due to its high performance and excellent cycle characteristics, it has been greatly developed as a power source for electronic devices such as personal computers, mobile phones, minicomponents, and minidiscs. Utilization as a power source is being studied.
[0003]
Conventionally developed non-aqueous electrolyte batteries use an organic solvent such as ethylene carbonate or propylene carbonate as the electrolyte, so if the battery is exposed to a high temperature atmosphere, In an electronic device using a battery, inconvenience such as an internal short circuit or an external short circuit occurs in the battery, and when the battery temperature rises, there is a difficulty that the electrolytic solution is volatilized and the battery explodes or causes a fire. there were.
[0004]
As a solid battery without such difficulties, LiClO Four , LiBF Four A solid battery using an ionic conductive solid electrolyte composed of an electrolyte salt such as ethylene carbonate, non-aqueous solvent such as propylene carbonate, and polyalkylene oxide has been developed. Has a high water-absorbing property and high reactivity with Li, so that it cannot be said that the battery has sufficient performance as a solid battery having excellent cycle characteristics and no danger of explosion.
[0005]
Japanese Patent Application Laid-Open No. 7-320781 discloses an invention of a solid battery using a solid electrolyte in which an electrolyte salt is dissolved in an acrylonitrile polymer, a vinyl acetate polymer, or a vinyl chloride polymer plasticized with a nonaqueous solvent. Has been.
[0006]
[Problems to be solved by the invention]
In the method for producing a solid electrolyte shown in the above patent, an acrylonitrile-based polymer is dissolved, and LiClO is added to this solution. Four Although a method of casting a solution with a solvent and volatilizing the solvent to form a solid electrolyte is shown, this solid electrolyte does not contain a non-aqueous solvent, so the solubility of the electrolyte salt in the polymer phase However, the ionic conductivity as a solid electrolyte is not sufficient. Moreover, in order to increase the ionic conductivity of this solid electrolyte, if acetonitrile which is a non-aqueous solvent is left in the solid electrolyte, the boiling point of acetonitrile is 81 ° C., so a solid battery using the solid electrolyte has a temperature of 100 ° C. or higher. When exposed to high temperatures, there is a drawback of causing explosions and battery blistering.
[0007]
In addition, the publication discloses a method of immersing and swelling a vinyl polymer film prepared by the same method as described above in a propylene carbonate solution. The swelling process is extremely difficult.
[0008]
[Means for Solving the Problems]
Therefore, as a result of repeated efforts to efficiently produce a sheet-like solid electrolyte having uniform characteristics, the present inventor has obtained a non-aqueous solvent-soluble polymer. Of polymers insoluble in water and non-aqueous solvents The present invention has been completed by finding out that the object can be achieved by using a polymer sheet having a porous structure and a sheet having a porous structure. Used for a solid electrolyte battery comprising a gelled solid electrolyte sheet impregnated with a non-aqueous solution containing a positive electrode, a negative electrode and an electrolyte salt, Non-aqueous solvent soluble polymer As a mixture of a copolymer having an acrylonitrile copolymerization amount of 50 mol% or more and polyethylene and / or polypropylene insoluble in a non-aqueous solvent A porous sheet for forming a gel solid electrolyte comprising a porous body having a porosity of 20 to 80% and a gel solid electrolyte sheet using the same.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The polymer used in carrying out the present invention can be any polymer that is soluble in a non-aqueous solvent. However, the ionic conductivity of an ionic conductive solid electrolyte formed from the polymer is increased, and safety is ensured. From the viewpoint, a vinyl polymer is preferable. Examples of vinyl polymers include copolymers of acrylonitrile and C1-4 alkyl (meth) acrylates, acrylonitrile-vinyl acetate copolymers, acrylonitrile-styrene copolymers, acrylonitrile-vinyl chloride or vinylidene chloride copolymers. Specific examples thereof include styrene-vinyl acetate copolymer and polymethyl methacrylate. Among these polymers, the copolymerization amount of an acrylonitrile copolymer having a relative dielectric constant of 5 or more is included. 50 mol% or more, particularly 70 to 98 mol%, can give a good ionic conductivity, and a solid electrolyte obtained by uniformly dispersing the nonaqueous electrolytic solution can be obtained.
[0010]
The solid electrolyte as used herein refers to a solid solution in which the nonaqueous solvent and supporting electrolyte salt constituting the electrolytic solution and the polymer are substantially uniformly dispersed and have lost their fluid state. More specifically, a state in which a solvent and dissociated ions can be distributed in a three-dimensional network of polymer chains, which shows a gel-like to dura-like appearance, and this state uses a polymer as a solvent. This can be realized by heating and melting and cooling. Therefore, the state where the solvent loses its fluidity is clearly distinguished from the case where the liquid is held in a material having fine pores such as a conventional separator.
[0011]
Porous sheet production methods include wet papermaking, dry papermaking, needle punching, which is a kind of nonwoven fabric manufacturing method, water jet method, stretching and pore formation of melt-extruded sheets, and solvent extraction. Known methods such as porosity and casting sheet can be used.
[0012]
When this porous sheet is used as a solid electrolyte, the solid electrolyte layer needs to be thin in order to reduce the internal resistance of the battery, and the thickness of these solid electrolyte sheets is substantially 100 μm or less. It is desirable that
[0013]
Polymethylmethacrylate, acrylonitrile-styrene copolymer, vinylidene chloride copolymer, etc. can be formed by melt extrusion, but the copolymer of acrylonitrile and C1-4 alkyl (meth) acrylate can be used. Polymers, acrylonitrile-vinyl acetate copolymers, acrylonitrile-vinyl chloride copolymers and the like are generally difficult to melt mold. Furthermore, in the present invention, an acrylonitrile-based polymer having 70 to 98 mol% of acrylonitrile units giving good ionic conductivity does not show a clear melting phenomenon, and therefore cannot be melt-molded.
[0014]
A sheet can also be produced by casting a polymer solution. In this case, a solvent removal and a porosification process are separately required.
Therefore, as a method for producing a porous sheet suitable for the present invention, wet and dry papermaking methods can be preferably used. In these papermaking methods, a uniform sheet having a thickness of 100 μm or less can be produced by using fibers having a diameter of 10 μm or less. Further, the manufactured sheet has an appropriate space between the fibers, and does not require a special porous treatment. Further, the porosity of the sheet can be controlled by changing the shape such as the fiber diameter and the degree of branching, the press pressure during papermaking, and the like.
[0015]
The following items are listed as requirements for the porous sheet for forming a gel solid electrolyte. One is the wettability between the sheet and the electrolyte. Usually, a battery has a laminated structure in which a separator is sandwiched between a positive electrode and a negative electrode. The positive electrode and the negative electrode are prepared as a continuous film-like material that is previously bound on the surface of the metal foil by using a material that absorbs and releases lithium ions called an active material as a binder. Separator is a substance used to prevent the short circuit between the positive electrode and the negative electrode, and a porous film having liquid retention properties is usually used. However, it is a polyolefin-based polymer that does not exhibit effects such as dissolution and swelling in the electrolyte. A molecule is used. The positive electrode, the negative electrode, and the separator are stacked and wound in a tensioned state, and inserted into a metal can that forms the outer shell of the battery. Thereafter, an electrolytic solution is injected to impregnate the separator portion.
[0016]
In the same way, the gel-like solid electrolyte forming porous sheet is also wound up by using the same process and inserted into the battery container, the electrolyte is injected, the sheet is impregnated, heat-treated, etc. It can be transferred to the electrolyte. In this case, since no bubbles or the like remain when the solvent is impregnated, it is required that the wettability between the base material of the sheet and the solvent is good.
[0017]
The contact angle between the acrylonitrile copolymer described in this claim and propylene carbonate which is an example of a non-aqueous solvent is 5 degrees or less, and the wettability is good.
The second is the strength of the sheet. As described above, each member needs to pass through a step of winding in a roll shape under tension, and therefore it is necessary to have a strength that does not break against the winding tension. The breaking strength of the material required here is approximately 15 kg / mm. 2 Degree.
[0018]
Here, the porous sheet for forming a gel-like solid electrolyte having such strength can be constituted only by a fibrous material made of an acrylonitrile-based polymer. In order to further improve the strength of the sheet, it is effective to form a continuous layer of a high molecular polymer insoluble in a non-aqueous solvent inside the sheet. For example, this object can be achieved by forming a sheet of a polyolefin polymer or polyethylene fiber or pulp together with an acrylonitrile copolymer. Further, the sheet is heat treated at a temperature equal to or higher than the melting point of the polymer insoluble in the non-aqueous solvent, whereby the polymers are bonded to each other and the sheet strength is improved.
[0019]
The third is the sheet porosity. When the electrolyte enters the space formed inside the sheet and is transferred to the gel solid electrolyte by heat treatment or the like, there is a composition region of an acrylonitrile-based polymer and electrolyte suitable for the gel solid electrolyte, Usually, it is desirable for the polymer to have a non-aqueous electrolyte amount in the range of 5 to 95 wt% in the solid electrolyte. Since the polymer forming the sheet is swelled by the electrolytic solution, a hole portion for absorbing this volume increase is required. A suitable range for this porosity is generally in the range of 20-80%.
[0020]
If the porosity is less than 20%, it is difficult to absorb this volume increase, and the number of openings through which ions can substantially move is reduced, which increases the internal resistance of the battery, which is not preferable. On the other hand, if the porosity is higher than 80%, the mechanical strength of the sheet decreases, which is not preferable.
[0021]
The electrolyte salt used in practicing the present invention is LiClO. Four , LiCF Three SO Four , LiPF 6 , LiBF Four , LiPF Four , LiN (CF Three SO Four ) 2 Etc.
[0022]
Non-aqueous solvents used in the practice of the present invention include, for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, γ-butyrolactone, diethyl carbonate, butylene carbonate, sulfolane, Dimethoxyethane, tetrahydrofuran, dioxolane and the like can be mentioned, and these solvents can be used alone or as a mixture of two or more, but it is particularly preferable to use a solvent having a relative dielectric constant of 40 or more as a main component.
[0023]
The sheet having a porosity of 20 to 80% according to the present invention is a very thin homogeneous film of 50 to 500 μm from the molding step, and is excellent in the uniform impregnation property of the nonaqueous electrolyte. A solid electrolyte having various characteristics can be formed. Further, since the film thickness is uniform and the mechanical strength is excellent and the porous sheet is easy to handle, the production process of the solid electrolyte battery can be made smooth.
[0024]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[Example 1]
A 2,000 ml glass reaction vessel with a jacket is charged with 93.6 mol% of acrylonitrile unit and 6.4 mol% of vinyl acetate unit under the condition that the water / monomer ratio is 14/1, and reacted as a polymerization catalyst. 1.0 wt% Na with respect to the liquid 2 SO Three 1.5 wt% NaHSO Three 0.12 wt% H 2 SO Four Aqueous suspension polymerization was performed using The reaction temperature was kept at 55 ° C. The polymer produced in the reaction vessel was collected, washed thoroughly and then dried to obtain a white powder. The reaction yield calculated from the weight of the obtained powder was 73%.
When the composition analysis of the obtained polymer was performed by elemental analysis, 96.0 mol% of acrylonitrile units and 4.0 mol% of vinyl acetate units were introduced. Moreover, when the molecular weight of this polymer was measured by GPC, it was found to be 5.1 × 10 5 in terms of polystyrene. Five The value was shown. GPC was measured by using 0.01 M LiCl / DMF as a solvent and a polymer concentration of 0.1 g / dl.
[0025]
LiPF as a supporting electrolyte in propylene carbonate 6 Was dissolved at 1.0 mol / kg, and the acrylonitrile copolymer was added to the electrolyte at room temperature to form a slurry. When this slurry was stirred at 100 ° C., the polymer was dissolved to form a uniform solution. The polymer concentration in this solution was 16 wt%. When this solution was allowed to stand at room temperature for a whole day and night, the solution lost fluidity and exhibited an elastic, cloudy gel.
This acrylonitrile copolymer was dissolved in dimethylacetamide to prepare a polymer solution having a concentration of 18 wt%. This polymer solution was spread on a slide glass and the cast film was prepared by naturally drying the solvent. Attempts were made to measure the contact angle of propylene carbonate and diethyl carbonate on the smooth surface of this cast film with a contact angle meter, but the familiarity between the film and the droplets was good and the liquid spread on the film, making it impossible to measure. Met.
[0026]
Next, this polymer solution was mixed in a cylindrical shape with a diameter of 0.2 mmφ, a diameter of 2 mmφ, and a length of 1.5 mm in accordance with the method disclosed in Japanese Patent Application Laid-Open No. 9-241917. The cell portion and the water vapor flow path are slit-shaped, the opening degree is adjusted to 250 μm, and the nozzle formed so that the angle formed by the center line of the solution flow path and the slit center line is 60 degrees, Supply amount is 18ml / min, water vapor supply pressure is 1.5kg / cm 2 As a result, it was ejected into water at a temperature of 30 ° C. to obtain a pulp-like polymer aggregate.
This pulp polymer aggregate was dispersed in water and beaten with a household mixer for 10 minutes. A part of the aqueous dispersion after the beating treatment was taken out, and the morphology of the pulp-like fiber obtained by drying was measured using a scanning electron microscope. From the fibrous trunk having a diameter of 5 to 20 μm, A structure in which a large number of fibrillar fibers having a diameter of about 0.2 μm to 1 μm were branched was observed. The freeness of the pulp polymer was measured in accordance with JIS P-8207 using a Canadian freeness tester. The freeness value corrected to a standard temperature of 20 ° C. and a standard concentration of 0.3% was 387 ml.
[0027]
Using the aqueous dispersion of pulp-like fibers obtained as described above, wet papermaking was performed according to JIS P-8209 method using a standard square sheet machine. The basis weight of the fibrous sheet-like material comprising the obtained polyacrylonitrile-based copolymer is 25 g / m. 2 The sheet average thickness was measured according to JIS P-8118 to be 155 μm. The sheet was cut to prepare a strip-shaped test piece, and the tensile strength test of the test piece was performed according to JIS P-8113. The 15 mm wide test piece had a breaking strength of 18 N / 15 mm. When the porosity of this sheet was measured using a mercury intrusion porosimeter (POROSIMETER 4000 manufactured by CARLO ERBA INSTRUMENT), the porosity was 68%.
The sheet made of pulp of this acrylonitrile copolymer was a porous sheet for forming a gel-like solid electrolyte that is soluble in nonaqueous electrolyte and has a porosity of 68%.
[0028]
[Example 2]
In the same manner as in Example 1, a polymer having an acrylonitrile composition of 100 mol% was prepared by an aqueous suspension polymerization method using a redox catalyst, and a pulp-like material was prepared according to the method disclosed in JP-A-9-241919. A polymer assembly was obtained. Using this pulp-like acrylonitrile polymer, a porous sheet for forming a gel-like solid electrolyte was prepared by a wet papermaking method.
[0029]
Example 3
In the same manner as in Example 1, a polymer having a composition of 99.0 mol% acrylonitrile and 1.0 mol% vinyl acetate was prepared by an aqueous suspension polymerization method using a redox catalyst, and disclosed in JP-A-9-241917. A pulp-like polymer aggregate was obtained according to the disclosed technique. Using this pulp-like acrylonitrile copolymer, a porous sheet for forming a gel-like solid electrolyte was prepared by a wet papermaking method.
[0030]
Example 4
In the same manner as in Example 1, a polymer having a composition of 93.0 mol% acrylonitrile and 7.0 mol% ethyl acrylate was prepared by an aqueous suspension polymerization method using a redox catalyst, and JP-A-9-241717. A pulp-like polymer aggregate was obtained according to the method disclosed in 1). Using this pulp-like acrylonitrile copolymer, a porous sheet for forming a gel-like solid electrolyte was prepared by a wet papermaking method.
[0031]
Example 5
A polymer having a composition of 93.8 mol% acrylonitrile and 6.2 mol% butyl acrylate was prepared by an aqueous suspension polymerization method using a redox catalyst in the same manner as in Example 1, and Japanese Patent Application Laid-Open No. 9-241917. A pulp-like polymer aggregate was obtained according to the method disclosed in 1). Using this pulp-like acrylonitrile copolymer, a porous sheet for forming a gel-like solid electrolyte was prepared by a wet papermaking method.
[0032]
Example 6
A polymer having a composition of 75.2 mol% acrylonitrile and 24.8 mol% butyl methacrylate was prepared by an aqueous suspension polymerization method using a redox catalyst in the same manner as in Example 1, and JP-A-9-241919. A pulp-like polymer aggregate was obtained according to the method disclosed in 1). Using this pulp-like acrylonitrile copolymer, a porous sheet for forming a gel-like solid electrolyte was prepared by a wet papermaking method.
[0033]
Example 7
In the same manner as in Example 1, a polymer having an acrylonitrile composition of 85.0 mol% and vinyl acetate 15.0 mol% was prepared by an aqueous suspension polymerization method using a redox catalyst, and disclosed in JP-A-9-241717. A pulp-like polymer aggregate was obtained according to the disclosed technique. Using this pulp-like acrylonitrile copolymer, a porous sheet for forming a gel-like solid electrolyte was prepared by a wet papermaking method.
[0034]
Table 1 below shows the basis weight, sheet thickness, tensile strength, and porosity of the porous sheets prepared in Examples 1 to 7.
[0035]
[Table 1]
As shown in Table 1, a sheet prepared from the acrylonitrile copolymer pulp-like material by a wet papermaking method has an appropriate strength and porosity, and is a porous sheet for forming an ion conductive gel solid electrolyte. It was a thing.
[0037]
Example 8
The porous sheet for forming the gel solid electrolyte prepared in Example 1 was punched into a round shape having a diameter of 42 mm using a punching device. 1 mol / kg LiPF as supporting electrolyte 6 The one obtained by impregnating the punched sheet with a propylene carbonate solution containing 2.8 supported a non-aqueous electrolyte solution 2.8 times that of the fibrous sheet.
The sheet after the impregnation operation with the non-aqueous electrolyte was transferred into a closed container and kept at 80 ° C. for 12 hours and heat-treated, and observed under a crossed Nicol using a polarizing microscope. An anisotropic structure was observed, but this anisotropic structure was not observed in the heat-treated one. The tensile strength of the heat-treated sheet was about 90% of the tensile strength of the fibrous sheet before the impregnation treatment. This sheet was in a translucent state and had compressibility in the thickness direction, and no soaking of the solvent due to compression was observed.
[0038]
The evaluation of the electrical characteristics of the sheet was measured by an alternating impedance method using a Precision LCR meter 4284A manufactured by Hewlett-Packard.
The attachment for electrical conductivity measurement used for the measurement was composed of opposing disc-shaped stainless steel electrodes having a diameter of 14.8 mm, and a polymer solid electrolyte was sandwiched between the electrodes. During the measurement, a load of 11.8 kPa was applied between both electrodes using a spring, and the adhesion between the sample and the stainless steel electrode was kept constant. These operations were performed in a glove box substituted with argon.
[0039]
An alternating current having a peak voltage of 20 mV was applied in the frequency range of 100 Hz to 1 MHz, and the complex impedance of the sample was measured. The locus of the complex impedance obtained by the measurement was analyzed by the Cole-Cole plot method, and the electrical conductivity was derived from the electrode area and the distance between the electrodes, with the point of intersection with the real axis on the high frequency side as the resistance value of the sample. The electrical conductivity of the sample at 25 ° C. is 5.4 × 10 -3 S / cm.
A material obtained by impregnating an electrolyte solution in a porous sheet for forming a solid electrolyte made of a pulp-like material of this acrylonitrile copolymer and performing a heat treatment is a gel electrolyte containing the electrolyte solution and has high conductivity at room temperature. It was a gel-like solid electrolyte sheet showing a degree.
[0040]
[Examples 9 to 14]
The porous sheet for forming a gel-like solid electrolyte prepared in Examples 2 to 7 was impregnated with an electrolytic solution containing a supporting electrolyte salt in the same manner as in Example 8 and subjected to heat treatment. The heat treatment was performed in a state of being enclosed in an attachment for measuring ionic conductivity and loaded. The strength retention and electrical conductivity of the sheet after this treatment were measured. The measurement results are shown in Table 2.
[0041]
[Table 2]
As shown in Table 2, the porous sheet prepared from the acrylonitrile copolymer exhibited characteristics as a solid electrolyte sheet having good liquid retention and electrical conductivity by the impregnation operation of the electrolytic solution.
[0043]
Example 15
The acrylonitrile copolymer prepared in Example 1 was dissolved in dimethylacetamide to prepare a polymer solution having a concentration of 15 wt%. This polymer solution was spun into a 30 wt% aqueous solution of dimethylacetamide from a spinneret having a diameter of 30 μmφ. The spun yarn is washed with boiling water, then stretched 3 times in hot water, and then further stretched 1.5 times to 2 times on a heated roller having a surface temperature of 150 ° C to 200 ° C to obtain a single fiber Fibers having a fineness of 0.2 to 0.5 denier were obtained. This fiber was cut to about 5 mm to prepare a chopped fiber. 5 parts by weight of this chopped fiber and 10 parts by weight of a acrylonitrile copolymer having a freeness of 387 ml prepared in Example 1 were mixed, and a sheet was prepared from an aqueous dispersion of this mixture by a wet papermaking method.
[0044]
Sheet basis weight is 25 g / m 2 The gel sheet was a porous sheet for forming a solid electrolyte having a thickness of 180 μm, a tensile strength of 11 N / 15 mm, and a porosity of 80%.
The gel-like solid electrolyte-forming porous sheet was impregnated with an electrolyte solution and heat treated in the same manner as in Example 8, and the strength retention and electrical conductivity were measured. Strength retention is 79%, electrical conductivity is 5.8 × 10 -3 The solid electrolyte sheet was S / cm.
[0045]
Example 16
10 parts by weight of a pulp-like acrylonitrile copolymer having a freeness of 387 ml prepared in Example 1 and 10 parts by weight of a pulp-like polypropylene (SWP Y600 manufactured by Mitsui Chemicals) are mixed, and a sheet is obtained from the aqueous dispersion of this mixture by a wet papermaking method. Was prepared.
The basis weight of the sheet is 25 g / m 2 The gel sheet was a porous sheet for forming a gel solid electrolyte having a sheet thickness of 140 μm, a tensile strength of 21 N / 15 mm, and a porosity of 72%.
The gel-like solid electrolyte-forming porous sheet was impregnated with an electrolyte solution and heat treated in the same manner as in Example 8, and the strength retention and electrical conductivity were measured. Strength retention is 98%, electrical conductivity is 8.6 × 10 -3 The solid electrolyte sheet was S / cm.
[0046]
Example 17
Press heat treatment was performed using a press roll in which the surface temperature of the porous sheet for forming a gel-like solid electrolyte prepared in Example 16 was set to 175 ° C. The sheet after the press heat treatment has a basis weight of 25 g / m. 2 The gel sheet was a porous sheet for forming a solid electrolyte having a thickness of 85 μm, a tensile strength of 33 N / 15 mm, and a porosity of 52%.
The gel-like solid electrolyte-forming porous sheet was impregnated with an electrolyte solution and heat treated in the same manner as in Example 8, and the strength retention and electrical conductivity were measured. Strength retention is 98%, electrical conductivity is 1.1 × 10 -Four The solid electrolyte sheet was S / cm.
[0047]
Example 18
5 parts by weight of chopped fiber having a single fiber fineness of 0.2 to 0.5 denier prepared in Example 15 and 10 parts by weight of a pulp acrylonitrile copolymer having a freeness of 387 ml prepared in Example 1 and pulp 10 parts by weight of polypropylene (Mitsui Chemicals SWP Y600) was mixed, and a sheet was prepared from an aqueous dispersion of this mixture by a wet papermaking method.
The basis weight of the sheet is 25 g / m 2 The sheet was 170 μm thick, the tensile strength was 18 N / 15 mm, and the porosity was 68%.
This porous sheet was subjected to press heat treatment using a press roll whose surface temperature was set to 175 ° C. The sheet after the press heat treatment was a gel-like solid electrolyte forming porous sheet having a basis weight of 25 g / m 2, a sheet thickness of 110 μm, a tensile strength of 27 N / 15 mm, and a porosity of 49%.
The gel-like solid electrolyte-forming porous sheet was impregnated with an electrolyte solution and heat treated in the same manner as in Example 8, and the strength retention and electrical conductivity were measured. Strength retention is 99%, electrical conductivity is 8.7 × 10 -3 The solid electrolyte sheet was S / cm.
[0048]
Example 19
10 parts by weight of a pulp-like acrylonitrile copolymer having a freeness of 387 ml prepared in Example 1 and 10 parts by weight of a pulp-like polypropylene (Mitsui Chemicals SWP Y600) were mixed. When the dispersion process was performed using a home mixer with a reduced number of rotations, both were uniformly mixed and opened to a state where they could be conveyed by air.
The opened mixture was processed into a dry nonwoven fabric by an air-lay method. The nonwoven fabric was subjected to press heat treatment using a press roll whose surface temperature was set to 175 ° C. The nonwoven fabric sheet after the press heat treatment has a basis weight of 32 g / m 2 The gel sheet was a porous sheet for forming a solid electrolyte having a thickness of 95 μm, a tensile strength of 24 N / 15 mm, and a porosity of 42%.
The gel-like solid electrolyte-forming porous sheet was impregnated with an electrolyte solution and heat treated in the same manner as in Example 8, and the strength retention and electrical conductivity were measured. Strength retention is 99%, electrical conductivity is 7.5 × 10 -3 The solid electrolyte sheet was S / cm.
[0049]
【The invention's effect】
When the porous sheet of the present invention is used as a sheet for forming a polymer gel electrolyte, it can be easily wetted and impregnated with a non-aqueous electrolyte, and can be uniformly gelled. It also has mechanical properties.
Further, the solid electrolyte sheet of the present invention has a great feature that it is easy to handle and has high ionic conductivity, but does not leak electrolyte.
Claims (6)
非水溶媒可溶性重合体としてアクリロニトリル共重合量が５０モル％以上である共重合体と、非水溶媒に不溶なポリエチレン及び／又はポリプロピレンとの混合物より形成された空孔率が２０〜８０％であるイオン導電性ゲル状固体電解質形成用多孔質シ−ト。 In the porous sheet for forming a gel solid electrolyte used for the gel solid electrolyte sheet of the solid electrolyte battery comprising a gel solid electrolyte sheet impregnated with a non-aqueous solution containing a positive electrode, a negative electrode and an electrolyte salt,
The porosity formed from a mixture of a copolymer having an acrylonitrile copolymerization amount of 50 mol% or more as a nonaqueous solvent-soluble polymer and polyethylene and / or polypropylene insoluble in the nonaqueous solvent is 20 to 80%. A porous sheet for forming an ion conductive gel-like solid electrolyte.
非水溶媒可溶性重合体としてアクリロニトリル共重合量が５０モル％以上である共重合体と、非水溶媒に不溶なポリエチレン及び／又はポリプロピレンとの混合物より形成された空孔率２０〜８０％の多孔質シ−トに、上記電解質塩を含む非水溶液を含浸させゲル化させたことを特徴とするゲル状固体電解質シ−ト。 In the gelled solid electrolyte sheet of the solid electrolyte battery comprising a gelled solid electrolyte sheet impregnated with a non-aqueous solution containing a positive electrode, a negative electrode and an electrolyte salt,
Non-aqueous solvent-soluble and the copolymer of acrylonitrile copolymer amount is 50 mol% or more as a polymer, porosity 20-80% of porosity of the mixture formed from the insoluble polyethylene and / or polypropylene in a non-aqueous solvent A gel-like solid electrolyte sheet obtained by impregnating a non-aqueous solution containing the above electrolyte salt into a porous sheet to cause gelation.
非水溶媒可溶性重合体としてアクリロニトリル共重合量が５０モル％以上である共重合体と、非水溶媒に不溶なポリエチレン及び／又はポリプロピレンとの混合物をその成分として含む請求項１〜４のいずれかに記載のゲル状固体電解質形成用多孔質シ−トを用いることを特徴とするゲル状固体電解質シ−ト。 In the gelled solid electrolyte sheet of the solid electrolyte battery comprising a gelled solid electrolyte sheet impregnated with a non-aqueous solution containing a positive electrode, a negative electrode and an electrolyte salt,
A nonaqueous copolymer acrylonitrile copolymer amount is 50 mol% or more as a solvent-soluble polymer, any one of claims 1-4 comprising a mixture thereof component of the non-aqueous solvent-insoluble polyethylene and / or polypropylene A gel-like solid electrolyte sheet, characterized by using the porous sheet for forming a gel-like solid electrolyte described in 1.
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| JP07784298A JP4099852B2 (en) | 1998-03-25 | 1998-03-25 | Porous sheet for forming gelled solid electrolyte and gelled solid electrolyte sheet using the same |
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| JP07784298A JP4099852B2 (en) | 1998-03-25 | 1998-03-25 | Porous sheet for forming gelled solid electrolyte and gelled solid electrolyte sheet using the same |
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| JP2002151149A (en) * | 2000-11-13 | 2002-05-24 | Japan Vilene Co Ltd | Support for solid electrolyte |
| WO2003037425A1 (en) | 2001-10-31 | 2003-05-08 | R & R Ventures Incorporation | Iontophoresis device |
| AU2006211357A1 (en) | 2005-02-03 | 2006-08-10 | Tti Ellebeau, Inc. | Iontophoresis apparatus |
| US20090299265A1 (en) | 2005-09-30 | 2009-12-03 | Tti Ellebeau, Inc. | Electrode Assembly for Iontophoresis Having Shape-Memory Separator and Iontophoresis Device Using the Same |
| WO2007037474A1 (en) | 2005-09-30 | 2007-04-05 | Tti Ellebeau, Inc. | Electrode structure for iontophoresis used to administer drug enclosed in nanoparticle and iontophoresis device making use of the same |
| WO2007037476A1 (en) | 2005-09-30 | 2007-04-05 | Tti Ellebeau, Inc. | Iontophoresis apparatus capable of controlling dose and timing of administration of sleep inducer and analeptic agent |
| WO2007043605A1 (en) | 2005-10-12 | 2007-04-19 | Tti Ellebeau, Inc. | Iontophoresis apparatus sticking to mucosa |
| EP2072079A1 (en) | 2006-10-10 | 2009-06-24 | TTI ellebeau, Inc. | Artificial tooth-type iontophoresis device |
| US20080193514A1 (en) | 2006-11-02 | 2008-08-14 | Transcu Ltd. | Compostions and methods for iontophoresis delivery of active ingredients through hair follicles |
| WO2008087803A1 (en) | 2007-01-16 | 2008-07-24 | Hokkaido University | Liposome preparation for iontophoresis having antioxidant component encapsulated therein |
| WO2013069681A1 (en) | 2011-11-08 | 2013-05-16 | 株式会社カネカ | Vinyl chloride-based copolymer porous body and method for producing same |
| JP6007211B2 (en) * | 2014-07-04 | 2016-10-12 | 本田技研工業株式会社 | Lithium ion secondary battery |
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