JP4470288B2 - Battery separator and lithium secondary battery using the same - Google Patents
Battery separator and lithium secondary battery using the same Download PDFInfo
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- JP4470288B2 JP4470288B2 JP2000206731A JP2000206731A JP4470288B2 JP 4470288 B2 JP4470288 B2 JP 4470288B2 JP 2000206731 A JP2000206731 A JP 2000206731A JP 2000206731 A JP2000206731 A JP 2000206731A JP 4470288 B2 JP4470288 B2 JP 4470288B2
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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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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Description
【０００１】
【発明の属する技術分野】
本発明は、サイクル特性や低温特性などの電池特性に優れるリチウム二次電池を提供することができる電池用セパレータ、及びそれを用いたリチウム二次電池に関する。
【０００２】
【従来の技術】
従来、電池用セパレータや電解コンデンサ用隔膜等としてポリオレフィン系多孔質フィルムが使用されている。特に、近年技術の高度化に伴い、リチウム電池等においては高精度、高機能のセパレータが要求されるようになってきた。
【０００３】
電池を例にとってみると、近年高エネルギー密度、高起電力、自己放電の少ないリチウム電池のような非水電解液電池、特にリチウム二次電池が開発、実用化されている。リチウム電池の負極としては例えば金属リチウム、リチウムと他の金属との合金、カーボンやグラファイト等のリチウムイオンを吸着する能力又はインターカレーションにより吸蔵する能力を有する炭素材料、リチウムイオンをドーピングした導電性高分子材料等が知られており、また正極としては例えば（ＣＦx）nで示されるフッ化黒鉛、ＭｎＯ2、Ｖ2Ｏ5、ＣｕＯ、Ａｇ2ＣｒＯ4、ＴｉＯ2、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4等の金属酸化物や硫化物、塩化物が知られている。
【０００４】
また、非水電解液として、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジメチルカーボネート、メチルエチルカーボネート、ジエチルカーボネート、γ−ブチロラクトン、アセトニトリル、１，２−ジメトキシエタン、テトラヒドロフラン等の有機溶媒にＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4、ＬｉＣＦ3ＳＯ3、ＬｉＮ（ＳＯ2ＣＦ3）2、ＬｉＮ（ＳＯ2Ｃ2Ｆ5）2等の電解質を溶解したものが使用されている。
【０００５】
このようなリチウム電池の構成材料であるセパレータの役割は、正負両極の短絡を防止するとともに電池反応を阻害しないことにあり、以下のような種々の多孔質フィルムが提案されている。
【０００６】
ポリエチレン、ポリプロピレン等の熱可塑性樹脂の単層の多孔質フィルム（特公昭４６−４０１１９号公報、特公昭５５−３２５３１号公報、特公昭５９−３７２９２号公報、特海昭６０−２３９５４号公報、特開平２−７５１５１号公報、米国特許第３６７９５３８号明細書等）。
ポリエチレン及びポリプロピレンからなる多孔質膜が複数枚積層された積層多孔質フィルム（特開昭６２−１０８５７号公報、特開平２−７７１０８号公報、特開平６−５５６２９号公報、特開平６−２０６７１号公報、特開平７−３０７１４６号公報）。
【０００７】
【発明が解決しようとする課題】
リチウム二次電池において、電気化学的な特性を損なう原因として、セパレータ、電解質及び非水電解液といった電池の構成部材に含まれる不純物の存在が挙げられる。セパレータに含まれる不純物としては、原料樹脂に添加される酸化防止剤由来の芳香族系アルコール類、安定化剤に由来する脂肪酸等がある。また、電解質及び非水電解液に含まれる不純物としては、アルコール類、水分或いはＨＦのような遊離酸等が知られている。
【０００８】
このような不純物は、電極−電解液界面の電気化学的な反応場において、電池の充放電反応に伴って副反応を引き起こす可能性がある。生成した副反応生成物は、リチウム二次電池のサイクル特性、電気容量、保存安定性などの電池性能を損なう原因となるため、前記不純物の除去又は低減が望まれている。
【０００９】
本発明の目的は、前記不純物を除去又は低減する能力を有する電池用セパレータを提供すること、並びに該電池用セパレータの不純物除去又は低減効果によって、特にサイクル特性に優れたリチウム二次電池を提供することにある。
【課題を解決するための手段】
【００１０】
本発明者らは、鋭意研究の結果、リチウム二次電池に含まれる前記不純物を吸着・固定することのできる特定の無機微粒子をポリオレフィン製の電池用セパレータに適切に配合することで、サイクル特性等の電池特性に優れたリチウム二次電池が得られることを見出した。不純物は、無機微粒子に吸着・固定されることで、電極−電解液界面の電気化学的な反応場では、見かけ上、除去又は低減され、電池の充放電に伴って引き起こされる副反応を抑制することができる。すなわち、本発明は、多数の貫通微細孔を有する多孔質ポリオレフィンフィルムからなる電池用セパレータであって、該多孔質ポリオレフィンフィルムが、酸化珪素、酸化アルミニウム、酸化マグネシウム、酸化亜鉛の群から選ばれる少なくとも１種の金属酸化物を主成分とする平均粒径０．１〜８μｍの塩基性の無機微粒子を１００〜４００００ｐｐｍ含有する電池用セパレータに関する。また、本発明は、リチウム含有金属化合物からなる正極、炭素材料からなる負極、非水電解液及び電池用セパレータを備えるリチウム二次電池であって、該電池用セパレータが前記記載の電池用セパレータであることを特徴とするリチウム二次電池に関する。
【００１１】
【発明の実施の形態】
本発明の電池用セパレータに使用される材料としては、特に制限はなく、ポリプロピレン、ポリエチレン等のポリオレフィン樹脂が利用できる。また、本発明の多孔質フィルムは単層多孔質フィルム及び積層多孔質フィルムのいずれの構成であっても良く、積層多孔質フィルムである場合は、積層した多孔質フィルムの少なくとも１層に無機微粒子を含んでいれば良い。
【００１２】
多孔質フィルムの多孔化方法には、大別して延伸法（乾式法）と抽出法（湿式法）とがある。抽出法では、高密度ポリエチレンを主成分とした熱可塑性樹脂組成物に充填材や可塑剤を配合したものをフィルム状に押し出し成形し、その後フィルムから充填材や可塑剤を抽出することで多孔化を行う。一方、延伸法では、熱可塑性樹脂を溶融押し出しする過程で結晶構造を制御し、その後、延伸に伴うクレーズの発生及び成長によって多孔化を行う。
ここで、本発明の多孔質フィルムの製造工程における多孔化方法に関して特に制限はなく、いずれの方法によっても多孔質フィルムを製造することができる。
【００１３】
本発明に使用されるポリプロピレンは、数平均分子量が５万以上、より好ましくは７万以上、数平均分子量と重量平均分子量の比が８以下のものが機械的強度が高く好ましい。また、ポリプロピレンの結晶化温度は１１０℃以上、さらに好ましくは１１２℃以上が好適である。
【００１４】
本発明に使用されるポリエチレンとしては、高密度ポリエチレン、中密度ポリエチレン、直鎖低密度ポリエチレン等のいずれであっても良いが、好ましくは高密度ポリエチレンである。ポリエチレンの数平均分子量は１万以上、より好ましくは２万以上のものが機械的強度が高く好ましい。
【００１５】
本発明において、ポリプロピレン及びポリエチレンの数平均分子量は、WATERS社製１５０Ｃ型ゲル浸透クロマトグラフを用いて、標準ポリスチレン換算によって求めた。カラムにはShodex HT-806M２本を使用し、０．３wt／vol％に調製したオルトジクロロベンゼン中、１３５℃で測定を行った。
また、ポリプロピレンの融点は、パーキンエルマー社製ＤＳＣ−７を用いて測定した。試料は熱履歴を取除くために２３０℃で１０分間保持して完全融解した後、１０℃／ｍｉｎで室温まで冷却し、測定は昇温速度１０℃／ｍｉｎにて融解曲線の極大値を融点とした。
【００１６】
本発明の電池用セパレータに含まれる無機微粒子は、酸化珪素、酸化アルミニウム、酸化マグネシウム、酸化亜鉛の群から選ばれる少なくとも１種の金属酸化物を主成分とし、リチウム二次電池の構成材料である非水電解液に膨潤及び溶解しないことが望ましい。無機微粒子が非水電解液に溶解するような成分を含んでいると、電池内に存在する不純物を無機微粒子中又は無機微粒子表面に固定できなくなり、電池反応阻害因子の除去或いは低減効果が期待できなくなるので適当でない。また、無機微粒子の平均粒径は０．１〜８μｍ、さらに好ましくは０．５〜３μｍである。無機微粒子の平均粒径がこの範囲にないと、電池用セパレータに配合する際の分散不良によってセパレータの外観不良が生じるので適当でない。
【００１７】
本発明における無機微粒子は塩基性を有するものが使用され、特にＪＩＳ Ｋ・５１０１・２４に従って求められるｐＨが８〜１２である無機微粒子を使用することが好ましい。塩基性を有する無機微粒子は、セパレータに含まれている原料樹脂に添加される酸化防止剤に由来する芳香族系アルコール類、或いは安定化剤に由来する脂肪酸等の不純物を効率的に吸着・固定することができる。
ｐＨが８〜１２の無機微粒子としては、例えば酸化珪素、酸化アルミニウム、酸化マグネシウム、酸化亜鉛及びこれらの複合物を挙げることができ、より具体的には、アルミナシリケート、ハイドロタルサイト等を使用することができる。また、これらの金属酸化物及びその複合物が塩基性を示さない場合には、アミノシランカップリング剤等を使用して表面アルカリ処理を施して、塩基性を付与しても良い。
また、前記塩基性を有する無機微粒子は、電解質や電解液中に含まれるアルコール類、水分或いはＨＦのような遊離酸等の不純物を吸着除去することができる。電池用セパレータに対する無機微粒子の配合比率は、１００〜４００００ｐｐｍ、好ましくは３００〜１００００ｐｐｍ、さらに好ましくは５００〜３０００ｐｐｍとするのが良い。無機微粒子の配合量が前記範囲より過度に少ない場合、電池内不純物の低減効果が小さくなり、またこの範囲より過度に多い場合は、電池が異常時に陥った際の電池用セパレータのフィルム形状保持性が低下し電池の安全性が低下するので、電池用セパレータに対する無機微粒子の配合比率は前記範囲とするのが好ましい。
また、無機微粒子の酸化電位は、リチウムに対して＋４．５Ｖ以上、特に＋５Ｖ以上であることが電気化学的に安定で好ましい。
さらに、無機微粒子が電池に含まれる水分を吸着するためには、吸湿量が１〜５％の範囲にある無機微粒子を使用することが好ましい。吸湿量が過度に大きい無機微粒子を使用すると、逆に電池用セパレータをリチウム二次電池に組み込んだ際に水分を電池内部に持ち込む可能性があるので好ましくない。なお、この吸湿量は、湿度９０％の環境下、２４時間放置した際の重量増分として算定している。
【００１８】
本発明に示す酸化電位の測定は、ジメチルカーボネートにＬｉＰＦ6を溶解して１Ｍ／Ｌに調製した非水電解液を用いて行った。この非水電解液に該無機微粒子を０．０５Ｍ／Ｌになるように懸濁した後、室温（２０℃）下、参照電極及びカウンター電極には金属リチウム箔を、作用電極に白金電極を用いて、毎秒１０ｍＶの速度で±０Ｖ〜＋４．５Ｖまで電位を掃引し、０．１ｍＡの電流が検知された電圧を酸化電位とした。
【００１９】
本発明において、無機微粒子をポリプロピレン或いはポリエチレンに配合する方法については特に制限はないが、通常の混練機を用いた混練により配合することができる。例えば、一軸押出機、二軸押出機、ミキシングロール等を用いて溶融混練し、ペレットを得ることできる。また、ヘンシェルミキサー、タンブラー等を用いてドライブレンドによって配合しても良い。
【００２０】
本発明の電池用セパレータの層構成としては、無機微粒子を含むポリエチレン或いはポリプロピレンの単層多孔質フィルム、無機微粒子を含むポリプロピレンで無機微粒子を含まないポリエチレンを挟み込んだ積層多孔質フィルム、無機微粒子を含まないポリプロピレンで無機微粒子を含むポリエチレンを挟み込んだ積層多孔質フィルム、無機微粒子を含むポリエチレンと無機微粒子を含まないポリエチレンからなる積層多孔質フィルム、無機微粒子を含むポリエチレンと無機微粒子を含むポリプロピレンからなる積層多孔質フィルム等が挙げられ、積層多孔質フィルムの場合、少なくとも１層に無機微粒子が含まれていれば良い。
【００２１】
本発明の電池用セパレータの具体的な製造方法としては、例えば、無機微粒子を含むポリプロピレンで無機微粒子を含まないポリエチレンを挟み込んだ積層多孔質フィルムを製造する場合は、無機微粒子を適宜配合したポリプロピレンとポリエチレンを溶融共押し出しした後延伸多孔化して積層多孔質フィルムを得る方法、無機微粒子を適宜配合したポリプロピレンとポリエチレンフィルムをそれぞれ別々に溶融押し出し積層した後延伸多孔化して積層多孔質フィルムを得る方法等がある。また、延伸多孔化工程において、フィルムの幅方向の長さが大きく減少して透気度、空孔率及び極大孔径等の多孔質フィルムの性能が損われる場合には、先に本発明者等が出願した特開平１１−２９７２９７号公報に記載の方法のように、フィルムの幅方向の両端をチャック、ピンチロール等で固定しつつ延伸する方法、フィルムを縦一軸に延伸した後に一軸延伸時に生じた幅方向のフィルム長さ減少を横延伸によって復元する方法等の手法によって改良することができる。いずれの方法でも本発明の電池用セパレータを製造することができる。
【００２２】
このようにして製造される電池用セパレータは、製造条件によっても異なるが、透気度が３０〜１０００秒／１００ｃｃ、特に１００〜８００秒／１００ｃｃのものが好ましい。また、極大孔径は０．０２〜３μｍのものが好ましく、さらに、空孔率は３０〜８５％のものが好ましい。透気度が高すぎるとリチウムイオン伝導性が低下するために電池用セパレータとしての機能が十分でなく、低すぎると機械的強度が低下するので上記範囲とするのが好ましい。また、極大孔径及び空孔率がこの範囲とすると、電池の容量特性が向上するので好ましい。
さらに、電池用セパレータの厚みは機械的強度、性能、小型化等の面から５〜１００μｍ、特に好ましくは１０〜４０μｍに調製される。
【００２３】
本発明では、電池用セパレータに特定の金属酸化物を主成分とする無機微粒子を適切に配合することで、電池部材に含まれる不純物を除去又は低減することが可能となった。この不純物の除去又は低減によって、サイクル特性等の電池性能に優れたリチウム二次電池を提供することができる。
本発明のリチウム電池は、前記セパレータを使用して通常の方法により、円筒型、角型、コイン型等の形状に作製される。
リチウム電池を構成するセパレータ以外の構成部材については特に限定されないが、以下のような構成部材が使用される。
【００２４】
例えば、正極材料（正極活物質）としては、リチウム含有金属酸化物、硫化物又は塩化物のようなリチウム含有金属化合物が使用される。リチウム含有金属酸化物としては、例えばコバルト、マンガン、ニッケル、クロム、鉄およびバナジウムからなる群より選ばれる少なくとも１種類以上の金属とリチウムとのリチウム複合酸化物が使用される。このようなリチウム複合酸化物としては、例えば、ＬｉＣｏＯ2、ＬｉＭｎ2Ｏ4、ＬｉＮｉＯ2などが挙げられる。
【００２５】
正極は、前記の正極材料をアセチレンブラック、カーボンブラックなどの導電剤およびポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）などの結着剤と混練して正極合剤とした後、この正極材料を集電体としてのアルミニウム箔やステンレス製のラス板に塗布して、乾燥、加圧成型後、５０℃〜２５０℃程度の温度で２時間程度真空下で加熱処理することにより作製される。
【００２６】
負極（負極活物質）としては、リチウムを吸蔵・放出可能なカーボン又はグラファイトを含む炭素材料、例えばコークス、天然黒鉛や人造黒鉛などの炭素材料、複合スズ酸化物が使用される。特に、格子面（００２）の面間隔（ｄ002）が０．３３５〜０．３４０ｎｍである黒鉛型結晶構造を有する炭素材料を使用することが好ましい。なお、粉末状の炭素材料はエチレンプロピレンジエンターポリマー（ＥＰＤＭ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）などの結着剤と混練して負極合剤として使用される。
【００２７】
非水電解液としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジメチルカーボネート、メチルエチルカーボネート、ジエチルカーボネート、γ−ブチロラクトン、アセトニトリル、１，２−ジメトキシエタン、テトラヒドロフラン等の有機溶媒に電解質を溶解したものが使用される。電解質としては、例えば、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4、ＣＦ3ＳＯ3Ｌｉ、（ＣＦ3ＳＯ2）2ＮＬｉ、（Ｃ2Ｆ5ＳＯ2）2ＮＬｉ、ＬｉＣ（ＳＯ2ＣＦ3）3などが挙げられる。これらの電解質は、１種類で使用してもよく、２種類以上組み合わせて使用してもよい。これら電解質は、前記の非水溶媒に通常０．１〜３Ｍ／Ｌ、好ましくは０．５〜１．５Ｍ／Ｌの濃度で溶解されて使用される。
【００２８】
上記構成部材を使用するリチウム電池の製造については特に限定されないが、例えば円筒型電池は以下のような方法により製造できる。
ＬｉＣｏＯ2（正極活物質）を８０重量％、アセチレンブラック（導電剤）を１０重量％、ポリフッ化ビニリデン（結着剤）を１０重量％の割合で混合し、これに１−メチル−２−ピロリドン溶剤を加えて混合したものをアルミニウム箔上に塗布し、乾燥、加圧成型、加熱処理して正極を調製する。グラファイト（負極活物質）を９０重量％、ポリフッ化ビニリデン（結着剤）を１０重量％の割合で混合し、これに１−メチル−２−ピロリドン溶剤を加え、混合したものを銅箔上に塗布し、乾燥、加圧成型、加熱処理して負極を調製する。そして、前記正極、負極及び本発明のセパレータを円筒状に捲回し、前記非水電解液を注入させて円筒型リチウム二次電池（直径１８ｍｍ、高さ６５ｍｍ）が作製できる。
【００２９】
【実施例】
次に実施例及び比較例を示し、本発明について更に詳細に説明するが、本発明はこれらに限定されるものではない。
【００３０】
実施例１
ポリプロピレン及びポリエチレンに一般的に使用される安定化剤（ステアリン酸カルシウム）に含まれる脂肪酸であるステアリン酸を、ＣＨＣｌ3に対して６００ｐｐｍになるように溶解した。この疑似不純物含有溶液に、酸化珪素を主成分とする平均粒径２．１μｍ、ｐＨ１０．７、吸湿量３％の無機微粒子を、５０００ｐｐｍ加えて、室温にて１時間攪拌した。攪拌後に、ろ過によって無機微粒子を取り除き、溶液内に残存するステアリン酸量をガスクロマトグラフィー法により測定した。また、前記無機微粒子による脂肪酸吸着処理を施していない疑似不純物含有溶液についても、同様のステアリン酸量の測定を行なった。結果を表１に示す。無機微粒子による脂肪酸吸着効果によって、約半量のステアリン酸を除去することができた。
【００３１】
数平均分子量７００００、結晶化温度１１２℃のポリプロピレンに、前記無機微粒子を、ポリプロピレン樹脂に対して２０００ｐｐｍになるように配合した。無機微粒子の酸化電位はリチウムに対して＋４．５Ｖ以上であった。この無機微粒子配合ポリプロピレンは、Ｔダイ成形装置を使用して膜厚１１．４μｍのフィルム状に溶融押出しした後、引取り方向を固定された状態で、１３５℃に６０秒間熱処理された。
【００３２】
ポリエチレンとして、数平均分子量２００００、密度０．９６４、融点１３４℃の高密度ポリエチレンを、Ｔダイ成型機を使用して膜厚８μｍのフィルム状に溶融押出しした。ポリエチレンフィルムは、引取り方向を固定された状態で、１２０℃に６０秒間熱処理した後、室温まで冷却された。
【００３３】
熱処理した無機微粒子配合ポリプロピレンフィルム及びポリエチレンフィルムは、無機微粒子配合ポリプロピレンを表面層に、ポリエチレンを内層（中間層）に配した三層構成に積層された。積層は、三組のロールスタンドから該ポリプロピレンフィルム及びポリエチレンフィルムをそれぞれ巻出し速度６．５ｍ／ｍｉｎで巻出し、加熱ロールに導き、温度１２０℃、線圧１．８ｋｇ／ｃｍで熱圧着し、その後同速度で５０℃の冷却ロールに導いて巻き取った。巻取り速度は６．５ｍ／ｍｉｎ、巻出し張力は０．９ｋｇであった。
得られた未延伸積層フィルムの膜厚は３１．６μｍであった。
【００３４】
未延伸積層フィルムは、３０℃に保持されたニップロール間で２５％低温延伸された。この時のロール間は３５０ｍｍ、供給側のロール速度は２ｍ／ｍｉｎであった。
低温延伸した積層フィルムは、引続き１２３℃に加熱された熱風循環オーブン中に導かれ、ロール周速差を利用してロール間で総延伸量１８０％になるまで高温延伸された後、１２３℃に加熱されたロールで３０％緩和させて７２秒間熱固定され、連続的に積層多孔質フィルム、すなわち電池用セパレータを得た。
【００３５】
得られた電池用セパレータの膜厚、透気度、極大孔径、空孔率を表２に示す。また、上記評価の方法は以下に従って行った。
１）透気度
ＪＩＳ Ｐ８１１７に準じて測定した。
測定装置としてＢ型ガーレーデンソメーター（東洋精機社製）を使用した。
試料片を直径２８．６ｍｍ、面積６４５ｍｍ2の円孔に締付ける。内筒重量５６７ｇにより、筒内の空気を試験円孔部から筒外へ通過させる。空気１００ｃｃが通過する時間を測定し、透気度（ガーレー値）とした。
２）空孔率、極大孔径
ユアサアイオニクス社製の水銀ポロシメータを用いて測定した。試料を０．０３〜０．０７ｇ秤量してガラス製のセル中で真空とした後、水銀を圧入、充填する。充填の際の水銀圧及び圧入水銀量から極大孔径及び空孔率を求めた。
【００３６】
正極活物質としてＬｉＣＯ2を用いた正極、負極活物質としてグラファイト（ペトカ社製ＭＣＦ）を用いた負極、及び前記実施例に示した電池用セパレータを捲回して、捲回型電池素子を作成した。非水電解液としては、エチレンカーボネート：メチルエチルカーボネート（容量比）＝３／７の非水溶媒を調整し、これにＬｉＰＦ6を１Ｍ／Ｌの濃度になるように溶解した。前記電池素子にこの非水電解液を注入して、円筒型リチウム二次電池を作成した。
【００３７】
このリチウム二次電池を用いて、室温（２０℃）下、１４００ｍＡ（１Ｃ）の定電流及び定電圧で、終止電圧４．２Ｖまで充電し、次に１４００ｍＡの定電流下、終止電圧２．７Ｖまで放電し、この充放電を繰り返した。初期放電容量を１００％とした場合の、２００及び３００サイクル後の放電容量維持率を表３に示す。
【００３８】
前記リチウム二次電池を用いて、室温（２０℃）下、１４００ｍＡ（１Ｃ）の定電流及び定電圧で、終止電圧４．２Ｖまで充電し、次に−２０℃の温度下、５６０ｍＡ（０．４Ｃ）及び１４００ｍＡ（１Ｃ）の定電流下、終止電圧２．７Ｖまで放電した。この放電容量を、前記室温（２０℃）下、１４００ｍＡの定電流下での初期放電容量を１００％とした場合の放電容量比として表３に示す。
【００３９】
比較例１
ポリプロピレンに無機微粒子を配合しない以外は、実施例１と同様に積層多孔質フィルム、すなわち電池用セパレータを得た。
得られた電池用セパレータの膜厚、透気度、極大孔径、空孔率を表２に、この電池用セパレータを用いたリチウム二次電池の放電容量維持率及び放電容量比を表３に示す。
【００４０】
【表１】
【表２】
【表３】
【発明の効果】
本発明によれば、サイクル特性や低温特性などの電池特性に優れるリチウム二次電池を提供することができる電池用セパレータ、及びそれを用いたリチウム二次電池を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery separator capable of providing a lithium secondary battery excellent in battery characteristics such as cycle characteristics and low-temperature characteristics, and a lithium secondary battery using the same.
[0002]
[Prior art]
Conventionally, polyolefin-based porous films have been used as separators for batteries, diaphragms for electrolytic capacitors, and the like. In particular, with the advancement of technology in recent years, high-precision and high-performance separators have been required for lithium batteries and the like.
[0003]
Taking a battery as an example, in recent years, a non-aqueous electrolyte battery such as a lithium battery having a high energy density, a high electromotive force, and a low self-discharge, in particular, a lithium secondary battery has been developed and put into practical use. Examples of negative electrodes of lithium batteries include metallic lithium, alloys of lithium and other metals, carbon materials having the ability to adsorb lithium ions such as carbon and graphite, or the ability to occlude by intercalation, and conductivity doped with lithium ions. Polymer materials and the like are known, and as the positive electrode, for example, fluorinated graphite represented by (CF x ) n , MnO 2 , V 2 O 5 , CuO, Ag 2 CrO 4 , TiO 2 , LiCoO 2 , LiNiO 2 Metal oxides such as LiMn 2 O 4 , sulfides, and chlorides are known.
[0004]
In addition, as a non-aqueous electrolyte, LiPF 6 , LiBF in an organic solvent such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, 1,2-dimethoxyethane, tetrahydrofuran, etc. 4 , LiClO 4 , LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2, etc. are used.
[0005]
The role of the separator, which is a constituent material of such a lithium battery, is to prevent the positive and negative electrodes from being short-circuited and not to inhibit the battery reaction, and various porous films as described below have been proposed.
[0006]
Single layer porous film of thermoplastic resin such as polyethylene and polypropylene (Japanese Patent Publication No. 46-40119, Japanese Patent Publication No. 55-32531, Japanese Patent Publication No. 59-37292, Japanese Patent Publication No. 60-23594, (Kaihei 2-75151, US Pat. No. 3,679,538, etc.).
A laminated porous film in which a plurality of porous films made of polyethylene and polypropylene are laminated (Japanese Patent Laid-Open Nos. 62-10857, 2-77108, 6-55629, and 6-20671. Gazette, JP-A-7-307146).
[0007]
[Problems to be solved by the invention]
In a lithium secondary battery, the presence of impurities contained in battery components such as a separator, an electrolyte, and a non-aqueous electrolyte can be cited as a cause of impairing electrochemical characteristics. Examples of the impurities contained in the separator include aromatic alcohols derived from antioxidants added to the raw material resin, fatty acids derived from stabilizers, and the like. Further, as impurities contained in the electrolyte and the non-aqueous electrolyte, alcohols, moisture, free acids such as HF, and the like are known.
[0008]
Such an impurity may cause a side reaction in the electrochemical reaction field at the electrode-electrolyte interface with the charge / discharge reaction of the battery. The produced side reaction product causes deterioration of battery performance such as cycle characteristics, electric capacity, storage stability and the like of the lithium secondary battery. Therefore, removal or reduction of the impurities is desired.
[0009]
An object of the present invention is to provide a battery separator having the ability to remove or reduce the impurities, and to provide a lithium secondary battery particularly excellent in cycle characteristics due to the effect of removing or reducing the impurities of the battery separator. There is.
[Means for Solving the Problems]
[0010]
As a result of diligent research, the present inventors have appropriately blended specific inorganic fine particles capable of adsorbing and fixing the impurities contained in the lithium secondary battery into a polyolefin battery separator, thereby providing cycle characteristics and the like. It was found that a lithium secondary battery having excellent battery characteristics can be obtained. Impurities are adsorbed and fixed on the inorganic fine particles, so that they are apparently removed or reduced in the electrochemical reaction field at the electrode-electrolyte interface and suppress side reactions caused by charging / discharging of the battery. be able to. That is, at least the present invention is a battery separator composed of a porous polyolefin film having a large number of through micropores, porous polyolefin film, silicon oxide, aluminum oxide, magnesium oxide, selected from the group consisting of zinc oxide the average particle size 0.1~8μm basic inorganic fine particles of one metal oxide as a main component a battery separator containing 100～40000Ppm. The present invention also provides a lithium secondary battery comprising a positive electrode made of a lithium-containing metal compound, a negative electrode made of a carbon material, a non-aqueous electrolyte, and a battery separator, wherein the battery separator is the battery separator described above. The present invention relates to a lithium secondary battery.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
There is no restriction | limiting in particular as a material used for the battery separator of this invention, Polyolefin resin, such as a polypropylene and polyethylene, can be utilized. In addition, the porous film of the present invention may have any structure of a single layer porous film and a laminated porous film, and when it is a laminated porous film, inorganic fine particles are formed in at least one layer of the laminated porous film. Should be included.
[0012]
Porous methods of porous films are roughly classified into a stretching method (dry method) and an extraction method (wet method). In the extraction method, a thermoplastic resin composition containing high-density polyethylene as a main component and a filler or plasticizer blended is extruded into a film, and then the filler and plasticizer are extracted from the film to make it porous. I do. On the other hand, in the stretching method, the crystal structure is controlled in the process of melting and extruding the thermoplastic resin, and thereafter, porosity is generated by generation and growth of crazes accompanying stretching.
Here, there is no restriction | limiting in particular regarding the porosity forming method in the manufacturing process of the porous film of this invention, A porous film can be manufactured by any method.
[0013]
The polypropylene used in the present invention preferably has a number average molecular weight of 50,000 or more, more preferably 70,000 or more and a ratio of the number average molecular weight to the weight average molecular weight of 8 or less because of high mechanical strength. The crystallization temperature of polypropylene is preferably 110 ° C. or higher, more preferably 112 ° C. or higher.
[0014]
The polyethylene used in the present invention may be any of high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, and the like, but is preferably high-density polyethylene. Polyethylene having a number average molecular weight of 10,000 or more, more preferably 20,000 or more is preferred because of its high mechanical strength.
[0015]
In the present invention, the number average molecular weights of polypropylene and polyethylene were determined by standard polystyrene conversion using a 150C gel permeation chromatograph manufactured by WATERS. Two Shodex HT-806M columns were used for the column, and measurement was performed at 135 ° C. in orthodichlorobenzene prepared to 0.3 wt / vol%.
The melting point of polypropylene was measured using DSC-7 manufactured by PerkinElmer. In order to remove the thermal history, the sample was kept at 230 ° C. for 10 minutes and completely melted, then cooled to room temperature at 10 ° C./min. It was.
[0016]
The inorganic fine particles contained in the battery separator of the present invention are composed of at least one metal oxide selected from the group consisting of silicon oxide, aluminum oxide, magnesium oxide, and zinc oxide, and are constituent materials for lithium secondary batteries. It is desirable not to swell or dissolve in the non-aqueous electrolyte. If the inorganic fine particle contains a component that dissolves in the non-aqueous electrolyte, impurities existing in the battery cannot be fixed in the inorganic fine particle or on the surface of the inorganic fine particle, and an effect of removing or reducing the battery reaction inhibiting factor can be expected. It is not appropriate because it disappears. Moreover, the average particle diameter of inorganic fine particles is 0.1-8 micrometers, More preferably, it is 0.5-3 micrometers. If the average particle size of the inorganic fine particles is not within this range, the appearance of the separator is poor due to poor dispersion when blended with the battery separator, which is not appropriate.
[0017]
The inorganic fine particles used in the present invention have basicity, and it is particularly preferable to use inorganic fine particles having a pH of 8 to 12 determined according to JIS K · 5101 · 24. Basic inorganic fine particles efficiently adsorb and fix impurities such as aromatic alcohols derived from antioxidants added to the raw material resin contained in the separator or fatty acids derived from stabilizers. can do.
Examples of the inorganic fine particles having a pH of 8 to 12 include silicon oxide, aluminum oxide, magnesium oxide, zinc oxide, and a composite thereof. More specifically, alumina silicate, hydrotalcite, or the like is used. be able to. Moreover, when these metal oxides and their composites do not show basicity, surface alkali treatment may be performed using an aminosilane coupling agent or the like to impart basicity.
In addition, the basic inorganic fine particles can adsorb and remove impurities such as alcohols, moisture, or free acids such as HF contained in the electrolyte or the electrolytic solution. The blending ratio of the inorganic fine particles to the battery separator is 100 to 40000 ppm, preferably 300 to 10000 ppm, more preferably 500 to 3000 ppm. If the amount of inorganic fine particles is excessively less than the above range, the effect of reducing impurities in the battery will be small, and if excessively greater than this range, the film shape retention of the battery separator when the battery falls into an abnormal state Therefore, the blending ratio of the inorganic fine particles to the battery separator is preferably within the above range.
Further, the oxidation potential of the inorganic fine particles is preferably +4.5 V or more, particularly +5 V or more with respect to lithium, since it is electrochemically stable.
Furthermore, in order for the inorganic fine particles to adsorb moisture contained in the battery, it is preferable to use inorganic fine particles having a moisture absorption in the range of 1 to 5%. If inorganic fine particles having an excessively high moisture absorption amount are used, water may be brought into the battery when the battery separator is incorporated into the lithium secondary battery. This moisture absorption is calculated as a weight increment when left for 24 hours in an environment of 90% humidity.
[0018]
The measurement of the oxidation potential shown in the present invention was performed using a nonaqueous electrolytic solution prepared by dissolving LiPF 6 in dimethyl carbonate to 1 M / L. After suspending the inorganic fine particles in this non-aqueous electrolyte solution at 0.05 M / L, a metal lithium foil is used for the reference electrode and the counter electrode, and a platinum electrode is used for the working electrode at room temperature (20 ° C.). The potential was swept from ± 0 V to +4.5 V at a rate of 10 mV per second, and the voltage at which a current of 0.1 mA was detected was defined as the oxidation potential.
[0019]
In the present invention, the method of blending the inorganic fine particles with polypropylene or polyethylene is not particularly limited, but can be blended by kneading using an ordinary kneader. For example, a pellet can be obtained by melt-kneading using a single screw extruder, a twin screw extruder, a mixing roll, or the like. Moreover, you may mix | blend by dry blend using a Henschel mixer, a tumbler, etc.
[0020]
The layer structure of the battery separator of the present invention includes a polyethylene or polypropylene single-layer porous film containing inorganic fine particles, a laminated porous film in which polyethylene containing inorganic fine particles and polyethylene not containing inorganic fine particles are sandwiched, and inorganic fine particles included Laminated porous film with polyethylene containing inorganic fine particles sandwiched between polypropylene, laminated porous film made of polyethylene containing inorganic fine particles and polyethylene containing no inorganic fine particles, laminated porous film made of polyethylene containing inorganic fine particles and polypropylene containing inorganic fine particles In the case of a laminated porous film, at least one layer may contain inorganic fine particles.
[0021]
As a specific method for producing the battery separator of the present invention, for example, when producing a laminated porous film in which polyethylene containing inorganic fine particles is sandwiched with polyethylene containing inorganic fine particles, A method for obtaining a laminated porous film by melting and coextrusion of polyethylene to obtain a laminated porous film, a method for obtaining a laminated porous film by subjecting polypropylene and polyethylene film, which are appropriately blended with inorganic fine particles, to melt and extrusion separately, respectively, and then drawing to obtain a laminated porous film, etc. There is. Further, in the stretch porosification step, when the length of the film in the width direction is greatly reduced and the performance of the porous film such as air permeability, porosity, and maximum pore diameter is impaired, the present inventors As in the method described in Japanese Patent Application Laid-Open No. 11-297297 filed by, and a method of stretching while fixing both ends in the width direction of the film with a chuck, a pinch roll, etc. The reduction in the film length in the width direction can be improved by a technique such as a method of restoring by transverse stretching. Either method can produce the battery separator of the present invention.
[0022]
The battery separator manufactured in this manner varies depending on the manufacturing conditions, but preferably has an air permeability of 30 to 1000 seconds / 100 cc, particularly 100 to 800 seconds / 100 cc. The maximum pore diameter is preferably 0.02 to 3 μm, and the porosity is preferably 30 to 85%. If the air permeability is too high, the lithium ion conductivity is lowered, so that the function as a battery separator is not sufficient, and if it is too low, the mechanical strength is lowered. In addition, it is preferable that the maximum pore diameter and the porosity are within this range because the capacity characteristics of the battery are improved.
Further, the thickness of the battery separator is adjusted to 5 to 100 μm, particularly preferably 10 to 40 μm from the viewpoint of mechanical strength, performance, miniaturization, and the like.
[0023]
In the present invention, it is possible to remove or reduce impurities contained in the battery member by appropriately blending inorganic fine particles mainly containing a specific metal oxide into the battery separator. By removing or reducing the impurities, a lithium secondary battery excellent in battery performance such as cycle characteristics can be provided.
The lithium battery of the present invention is produced into a cylindrical shape, a rectangular shape, a coin shape, or the like by the usual method using the separator.
Although it does not specifically limit about structural members other than the separator which comprises a lithium battery, The following structural members are used.
[0024]
For example, as the positive electrode material (positive electrode active material), a lithium-containing metal compound such as a lithium-containing metal oxide, sulfide, or chloride is used. As the lithium-containing metal oxide, for example, a lithium composite oxide of at least one metal selected from the group consisting of cobalt, manganese, nickel, chromium, iron, and vanadium and lithium is used. Examples of such a lithium composite oxide include LiCoO 2 , LiMn 2 O 4 , and LiNiO 2 .
[0025]
The positive electrode is prepared by kneading the positive electrode material with a conductive agent such as acetylene black or carbon black and a binder such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) to form a positive electrode mixture. It is produced by applying the material to an aluminum foil or stainless steel lath plate as a current collector, drying and press molding, and then heat-treating it under vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. .
[0026]
As the negative electrode (negative electrode active material), carbon capable of occluding and releasing lithium or a carbon material containing graphite, for example, carbon materials such as coke, natural graphite and artificial graphite, and composite tin oxide are used. In particular, it is preferable to use a carbon material having a graphite-type crystal structure in which a lattice spacing ( 002 ) (d 002 ) is 0.335 to 0.340 nm. The powdery carbon material is kneaded with a binder such as ethylene propylene diene terpolymer (EPDM), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF) and used as a negative electrode mixture.
[0027]
As non-aqueous electrolyte, an electrolyte is dissolved in an organic solvent such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, 1,2-dimethoxyethane, tetrahydrofuran, etc. Is used. Examples of the electrolyte include LiPF 6 , LiBF 4 , LiClO 4 , CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) 2 NLi, and LiC (SO 2 CF 3 ) 3. Is mentioned. These electrolytes may be used alone or in combination of two or more. These electrolytes are used by being dissolved in the non-aqueous solvent usually at a concentration of 0.1 to 3 M / L, preferably 0.5 to 1.5 M / L.
[0028]
Although it does not specifically limit about manufacture of the lithium battery which uses the said structural member, For example, a cylindrical battery can be manufactured with the following methods.
80% by weight of LiCoO 2 (positive electrode active material), 10% by weight of acetylene black (conductive agent), and 10% by weight of polyvinylidene fluoride (binder) are mixed, and this is mixed with 1-methyl-2-pyrrolidone. A mixture obtained by adding a solvent is applied onto an aluminum foil, dried, pressure-molded, and heat-treated to prepare a positive electrode. 90% by weight of graphite (negative electrode active material) and 10% by weight of polyvinylidene fluoride (binder) are mixed, and a 1-methyl-2-pyrrolidone solvent is added thereto, and the resulting mixture is placed on a copper foil. The negative electrode is prepared by coating, drying, pressure molding, and heat treatment. And the said positive electrode, a negative electrode, and the separator of this invention are wound cylindrically, The said nonaqueous electrolyte solution is inject | poured, and a cylindrical lithium secondary battery (diameter 18mm, height 65mm) can be produced.
[0029]
【Example】
EXAMPLES Next, although an Example and a comparative example are shown and this invention is demonstrated further in detail, this invention is not limited to these.
[0030]
Example 1
Stearic acid, which is a fatty acid contained in a stabilizer (calcium stearate) generally used for polypropylene and polyethylene, was dissolved to 600 ppm with respect to CHCl 3 . To this pseudo-impurity-containing solution, 5000 ppm of inorganic fine particles having an average particle size of 2.1 μm, a pH of 10.7, and a moisture absorption of 3% mainly composed of silicon oxide was added and stirred at room temperature for 1 hour. After stirring, inorganic fine particles were removed by filtration, and the amount of stearic acid remaining in the solution was measured by gas chromatography. The same amount of stearic acid was also measured for the pseudo-impurity-containing solution that was not subjected to the fatty acid adsorption treatment with the inorganic fine particles. The results are shown in Table 1. About half of the stearic acid could be removed by the fatty acid adsorption effect by the inorganic fine particles.
[0031]
The inorganic fine particles were blended in polypropylene having a number average molecular weight of 70,000 and a crystallization temperature of 112 ° C. so as to be 2000 ppm with respect to the polypropylene resin. The oxidation potential of the inorganic fine particles was +4.5 V or more with respect to lithium. This polypropylene blended with inorganic fine particles was melt-extruded into a film having a film thickness of 11.4 μm using a T-die molding apparatus, and then heat-treated at 135 ° C. for 60 seconds with the take-up direction fixed.
[0032]
As polyethylene, high-density polyethylene having a number average molecular weight of 20,000, a density of 0.964, and a melting point of 134 ° C. was melt-extruded into a film having a thickness of 8 μm using a T-die molding machine. The polyethylene film was heat-treated at 120 ° C. for 60 seconds with the take-up direction fixed, and then cooled to room temperature.
[0033]
The heat-treated inorganic fine particle-containing polypropylene film and the polyethylene film were laminated in a three-layer structure in which the inorganic fine particle-containing polypropylene was disposed on the surface layer and polyethylene was disposed on the inner layer (intermediate layer). Lamination is performed by unwinding the polypropylene film and the polyethylene film from three sets of roll stands respectively at an unwinding speed of 6.5 m / min, leading to a heating roll, and thermocompression bonding at a temperature of 120 ° C. and a linear pressure of 1.8 kg / cm. Then, it was guided to a 50 ° C. cooling roll at the same speed and wound up. The winding speed was 6.5 m / min, and the unwinding tension was 0.9 kg.
The film thickness of the obtained unstretched laminated film was 31.6 μm.
[0034]
The unstretched laminated film was 25% cold-stretched between nip rolls maintained at 30 ° C. The distance between the rolls at this time was 350 mm, and the roll speed on the supply side was 2 m / min.
The laminated film that has been stretched at a low temperature is continuously introduced into a hot-air circulating oven heated to 123 ° C., and is stretched at a high temperature until the total stretching amount becomes 180% between rolls using a difference in roll peripheral speed. The film was relaxed by 30% with a heated roll and heat-fixed for 72 seconds to continuously obtain a laminated porous film, that is, a battery separator.
[0035]
Table 2 shows the film thickness, air permeability, maximum pore diameter, and porosity of the obtained battery separator. The evaluation method was performed as follows.
1) Air permeability Measured according to JIS P8117.
A B-type Gurley Densometer (manufactured by Toyo Seiki Co., Ltd.) was used as a measuring device.
The sample piece is clamped in a circular hole having a diameter of 28.6 mm and an area of 645 mm 2 . With the inner cylinder weight of 567 g, the air in the cylinder is allowed to pass out of the cylinder from the test circular hole. The time required for 100 cc of air to pass through was measured and used as the air permeability (Gurley value).
2) Porosity and maximum pore diameter Measured using a mercury porosimeter manufactured by Yuasa Ionics. 0.03 to 0.07 g of a sample is weighed and evacuated in a glass cell, and then mercury is injected and filled. The maximum pore diameter and porosity were determined from the mercury pressure and the amount of mercury injected during filling.
[0036]
A positive electrode using LiCO 2 as the positive electrode active material, a negative electrode using graphite (MCF manufactured by Petka Co., Ltd.) as the negative electrode active material, and the battery separator shown in the above example were wound to create a wound battery element. . As the non-aqueous electrolyte, a non-aqueous solvent of ethylene carbonate: methyl ethyl carbonate (volume ratio) = 3/7 was prepared, and LiPF 6 was dissolved in this to a concentration of 1 M / L. This non-aqueous electrolyte was injected into the battery element to produce a cylindrical lithium secondary battery.
[0037]
Using this lithium secondary battery, it was charged at a constant current and a constant voltage of 1400 mA (1C) at room temperature (20 ° C.) to a final voltage of 4.2 V, and then at a constant current of 1400 mA and a final voltage of 2.7 V. This charge and discharge was repeated. Table 3 shows discharge capacity retention rates after 200 and 300 cycles when the initial discharge capacity is 100%.
[0038]
Using the lithium secondary battery, the battery was charged at a constant current and a constant voltage of 1400 mA (1 C) at room temperature (20 ° C.) to a final voltage of 4.2 V, and then at a temperature of −20 ° C., 560 mA (0. Under a constant current of 4C) and 1400 mA (1C), the battery was discharged to a final voltage of 2.7V. This discharge capacity is shown in Table 3 as a discharge capacity ratio when the initial discharge capacity under the constant temperature of 1400 mA at room temperature (20 ° C.) is 100%.
[0039]
Comparative Example 1
A laminated porous film, that is, a battery separator was obtained in the same manner as in Example 1 except that the inorganic fine particles were not blended with polypropylene.
Table 2 shows the film thickness, air permeability, maximum pore diameter, and porosity of the obtained battery separator, and Table 3 shows the discharge capacity retention ratio and discharge capacity ratio of the lithium secondary battery using this battery separator. .
[0040]
[Table 1]
[Table 2]
[Table 3]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the separator for batteries which can provide the lithium secondary battery which is excellent in battery characteristics, such as cycling characteristics and low-temperature characteristics, and a lithium secondary battery using the same can be provided.
Claims (6)
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000206731A JP4470288B2 (en) | 2000-07-07 | 2000-07-07 | Battery separator and lithium secondary battery using the same |
| CNB001374796A CN1236508C (en) | 1999-11-10 | 2000-11-10 | Battery spacing membranes and lithium secondary battery |
| US09/709,623 US6627346B1 (en) | 1999-11-10 | 2000-11-10 | Battery separator and lithium secondary battery |
| HK01107893A HK1038100A1 (en) | 1999-11-10 | 2001-11-09 | Battery separator and lithium secondary battery |
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| JP2000206731A JP4470288B2 (en) | 2000-07-07 | 2000-07-07 | Battery separator and lithium secondary battery using the same |
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| JP2002025531A JP2002025531A (en) | 2002-01-25 |
| JP4470288B2 true JP4470288B2 (en) | 2010-06-02 |
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Families Citing this family (28)
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| JP4635432B2 (en) * | 2003-12-15 | 2011-02-23 | 三菱化学株式会社 | Non-aqueous electrolyte secondary battery |
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| JP4929593B2 (en) * | 2004-02-10 | 2012-05-09 | 三菱化学株式会社 | Non-aqueous electrolyte secondary battery |
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| US8999585B2 (en) | 2007-07-18 | 2015-04-07 | Panasonic Intellectual Property Management Co., Ltd. | Nonaqueous electrolyte secondary battery |
| US7662510B2 (en) * | 2007-09-20 | 2010-02-16 | Celgard Llc | X-ray sensitive battery separator and a method for detecting the position of a separator in a battery |
| CN102942706A (en) | 2008-12-19 | 2013-02-27 | 旭化成电子材料株式会社 | Polyolefin microporous membrane and separator for lithium ion secondary battery |
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| JP5381636B2 (en) * | 2009-11-18 | 2014-01-08 | コニカミノルタ株式会社 | Solid electrolyte for battery and lithium ion secondary battery |
| US9453805B2 (en) * | 2010-01-19 | 2016-09-27 | Celgard, Llc | X-ray sensitive battery separators and related methods |
| JP5039817B2 (en) * | 2010-08-16 | 2012-10-03 | 三菱樹脂株式会社 | Porous laminate |
| KR101173867B1 (en) | 2010-10-28 | 2012-08-14 | 삼성에스디아이 주식회사 | Rechargeable lithium battery |
| JP2015133333A (en) * | 2015-04-20 | 2015-07-23 | ソニー株式会社 | secondary battery |
| JP2017098201A (en) * | 2015-11-27 | 2017-06-01 | 住友化学株式会社 | Insulating porous layer for non-aqueous electrolyte secondary battery and laminated separator for non-aqueous electrolyte secondary battery |
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