JP2011016973A - Heat-resistant complex polyolefin microporous film and method for producing the same - Google Patents
Heat-resistant complex polyolefin microporous film and method for producing the same Download PDFInfo
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- LXEJRKJRKIFVNY-UHFFFAOYSA-N terephthaloyl chloride Chemical compound ClC(=O)C1=CC=C(C(Cl)=O)C=C1 LXEJRKJRKIFVNY-UHFFFAOYSA-N 0.000 description 2
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- IQNTUYCIRRCRDY-UHFFFAOYSA-N 2,5-dichlorobenzene-1,4-dicarbonyl chloride Chemical compound ClC(=O)C1=CC(Cl)=C(C(Cl)=O)C=C1Cl IQNTUYCIRRCRDY-UHFFFAOYSA-N 0.000 description 1
- HQCHAOKWWKLXQH-UHFFFAOYSA-N 2,6-Dichloro-para-phenylenediamine Chemical compound NC1=CC(Cl)=C(N)C(Cl)=C1 HQCHAOKWWKLXQH-UHFFFAOYSA-N 0.000 description 1
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- QDBOAKPEXMMQFO-UHFFFAOYSA-N 4-(4-carbonochloridoylphenyl)benzoyl chloride Chemical compound C1=CC(C(=O)Cl)=CC=C1C1=CC=C(C(Cl)=O)C=C1 QDBOAKPEXMMQFO-UHFFFAOYSA-N 0.000 description 1
- XPAQFJJCWGSXGJ-UHFFFAOYSA-N 4-amino-n-(4-aminophenyl)benzamide Chemical compound C1=CC(N)=CC=C1NC(=O)C1=CC=C(N)C=C1 XPAQFJJCWGSXGJ-UHFFFAOYSA-N 0.000 description 1
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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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- Application Of Or Painting With Fluid Materials (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Cell Separators (AREA)
Abstract
Description
リチウムイオン二次電池用セパレータとその製造方法に関する。具体的には、ポリオレフィン微多孔膜の表裏両面に耐熱性ポリマーの塗工液を塗布し均一な厚みの塗膜を形成する塗工方法を利用して得られる耐熱性複合ポリオレフィン微多孔膜とその製造方法に関する。
またリチウムイオン二次電池の安全性を高めるセパレータに関するものである。The present invention relates to a separator for a lithium ion secondary battery and a manufacturing method thereof. Specifically, a heat-resistant composite polyolefin microporous membrane obtained by using a coating method in which a coating solution of a heat-resistant polymer is applied to both surfaces of the polyolefin microporous membrane to form a uniform thickness coating film and its It relates to a manufacturing method.
The present invention also relates to a separator that enhances the safety of the lithium ion secondary battery.
リチウムイオン二次電池は近年、例えばノートブックパソコン、携帯電話、１体型カムコーダー等の携帯用電子機器の主電源として広範に普及している。これらの携帯用電子機器の更なる高性能化と長時間駆動の要求からそれらの電源としてのリチウムイオン二次電池において、さらなる高エネルギー密度化・高容量化・高出力化のための技術開発が進められている。一方、ハイブリッド車さらには電気自動車用電源としても高エネルギー密度化・高容量化・高出力化の要求に応えていくため、大型電源用リチウムイオン二次電池の高度な安全性を確保する技術がより一層重要となってきている。
現状のリチウムイオン二次電池のセパレータにはポリエチレンを主体としたポリオレフィン微多孔膜が用いられており、電池の安全性を確保するための機能としてシャットダウン特性が備わっている。この特性は、日本国特許第２６４２２０６号公報に記載されている。
このシャットダウン特性はセパレータ構成材料のポリオレフィンが溶融し気孔を閉塞することでセパレータの抵抗が格段に上昇することにより発現する。ポリエチレンからなるセパレータの場合は各種ポリエチレン材質の融点近傍の１３０℃から１４０℃付近程度で電流を遮断することができ、電池のさらなる発熱を防止し、発煙・発火・爆発を防ぐことができる。
ポリプロピレンの場合は１６５℃程度でこの機能が作動する。このシャットダウン特性は、確実に電池の安全性を確保するという観点からも、比較的に低温で作動することが好ましく、このためポリエチレンの方が一般的に用いられている。
電池に異常が生じ温度上昇が起こっても、この特性により電池の内部抵抗が高くなるため、実質的に電流が流れなくなり急激な発熱が抑制されて電池缶外部からの冷却が十分である場合は、安全性が確保されるとされている。In recent years, lithium ion secondary batteries have become widespread as main power sources for portable electronic devices such as notebook personal computers, mobile phones, and single-camcorders. Due to the demand for higher performance and longer driving time of these portable electronic devices, technology development for higher energy density, higher capacity, and higher output has been made in lithium ion secondary batteries as their power source. It is being advanced. On the other hand, in order to meet the demands for higher energy density, higher capacity, and higher output as power sources for hybrid vehicles and even for electric vehicles, there are technologies that ensure the high level of safety of lithium-ion secondary batteries for large power sources. It has become even more important.
The separator of the current lithium ion secondary battery uses a polyolefin microporous membrane mainly composed of polyethylene, and has a shutdown characteristic as a function for ensuring the safety of the battery. This characteristic is described in Japanese Patent No. 2642206.
This shutdown characteristic is manifested when the separator component material melts and closes the pores, thereby significantly increasing the resistance of the separator. In the case of a separator made of polyethylene, the current can be cut off at about 130 ° C. to 140 ° C. near the melting point of various polyethylene materials, further heat generation of the battery can be prevented, and smoke, ignition, and explosion can be prevented.
In the case of polypropylene, this function operates at about 165 ° C. This shutdown characteristic preferably operates at a relatively low temperature from the viewpoint of ensuring the safety of the battery, and therefore polyethylene is generally used.
Even if an abnormality occurs in the battery and the temperature rises, the internal resistance of the battery increases due to this characteristic, so if current does not flow substantially and sudden heat generation is suppressed and cooling from the outside of the battery can is sufficient It is said that safety is ensured.
一方で、リチウムイオン二次電池のセパレータには、高容量、高出力の電池になると一旦電池温度が上昇すると気孔は、閉鎖されても急に温度上昇が止まらない場合、セパレータとしてはさらに高温に曝されることになる。シャットダウン特性は構成材料の溶融による気孔の閉塞を作動原理としているから電池がより高温に晒された事態になると熱によりセパレータが溶融し、フィルム状となり、最終的には破膜してしまう。また対峙する正極と負極の端部がセパレータの膜収縮により短絡し、再度電流が流れて発煙・発火にいたることも起きうる。シャットダウン特性に加え、十分な耐熱性を有することも要求されている。
そのため高エネルギー密度化・高出力化・大型化した場合、リチウムイオン二次電池のセパレータには、ポリプロピレンとポリエチレンからなる複層微多孔膜が用いられているが、電池の安全性を確保する上で、従来のシャットダウン特性を保持したまま更に耐熱性が高いものが必要となってきている。On the other hand, when a battery with a high capacity and high output is used for a separator of a lithium ion secondary battery, once the battery temperature rises, if the pores do not stop rising suddenly even if they are closed, the separator has a higher temperature. Will be exposed. Since the shutdown characteristic is based on the principle of clogging of pores due to melting of the constituent materials, when the battery is exposed to a higher temperature, the separator is melted by heat to form a film, and finally the film is broken. In addition, the opposite ends of the positive electrode and the negative electrode may be short-circuited due to contraction of the separator film, and current may flow again, resulting in smoke and fire. In addition to the shutdown characteristics, it is also required to have sufficient heat resistance.
Therefore, when the energy density, output, and size are increased, a multilayer microporous membrane made of polypropylene and polyethylene is used as the separator for lithium ion secondary batteries. Therefore, a material having higher heat resistance while maintaining the conventional shutdown characteristic is required.
シャットダウン特性と破膜、過度の膜収縮を抑制する耐熱性を両立させるため、ポリオレフィン微多孔膜と耐熱性樹脂からなる多孔膜を積層する例は特開平１０−３８９８号公報、特開２００２−２５５２６号公報、特開２００３−１２３７２４号公報、特開２００５−２８５３８５号公報等で提案されている。
しかしながら、シャットダウン特性を有するポリオレフィン微多孔膜と耐熱性多孔膜のように性質の異なる２枚の膜の積層は膜間の寸法ズレ、ソリ等を生じやすく技術的に難しい。
生産性の観点からも実用性があるとは言い難たかった。また、電池の高エネルギー密度化という観点からセパレータには薄膜化が要求されている。２枚の膜を積層させて現状のセパレータ厚みと同等レベルにするためには、それぞれの膜１枚の厚みは十分に薄くする必要があるが、そのためにより薄い膜を生産することはより技術的により一層困難であり取り扱いも難しい。Examples of laminating a polyolefin microporous film and a porous film made of a heat resistant resin in order to achieve both shutdown characteristics and heat resistance that suppresses excessive film shrinkage are disclosed in JP-A-10-3898 and JP-A-2002-25526. No. 3, JP-A 2003-123724, JP-A 2005-285385, and the like.
However, lamination of two films having different properties such as a polyolefin microporous film having a shutdown characteristic and a heat-resistant porous film tends to cause dimensional deviation and warpage between the films, and is technically difficult.
It was hard to say that it was practical from the viewpoint of productivity. Further, the separator is required to be thin from the viewpoint of increasing the energy density of the battery. In order to stack two films to the same level as the current separator thickness, the thickness of each film needs to be sufficiently thin, but it is more technical to produce a thinner film for that purpose. It is even more difficult and difficult to handle.
従来、シャットダウン特性と耐熱性の両方をセパレータに付与するために、ポリオレフィン微多孔膜にポリイミドや芳香族ポリアミドなどの耐熱性樹脂からなる多孔質層をコーティングして一体化させた複合多孔膜が提案されている。（例えば、特許３１７５７３０号公報、特開２００１−２３６００号公報、特開２００２−３５５９３８号公報等）。
ポリオレフィン微多孔膜に耐熱性多孔質層をコーティングして一体化したものは上記の積層したもののような課題はない。然しながら、特許３１７５７３０号に開示された構成は、耐熱性含窒素芳香族重合体及びセラミック粉末を含む多孔質層をポリエチレン微多孔膜上に形成したものであり、耐熱性多孔質層による耐熱性の向上が図られているが、ポリエチレン微多孔膜の気孔への塗布時の溶液の浸入するために目詰りを起さない範囲での複合膜の設計にとどまる。両面にコーティングする工業的な手法は特開２００１−２０６９７３号公報、特開２００２−１６６２１８号公報、特開２００５−２０９５７０号公報、特開２００８−３００３６２号公報、特開２００９−２１２６５号公報、再公表特許ＷＯ２００６／１２３８１１、再公表特許ＷＯ２００７／０１３１７９に開示されているが、いずれもすでに気孔が形成されたポリエチレン系微多孔膜を使用する結果、気孔内へ耐熱性樹脂が入り込むのを抑制できる透気度の範囲にとどまり、良好な急速充放電性を得るには難があった。
基材のポリオレフィン微多孔膜の気孔内の耐熱性樹脂被覆が顕著になると、いわゆる気孔の目詰まりを起こしてしまい、耐熱性を重視しすぎるとポリオレフィン微多孔膜の気孔閉鎖が困難となり、シャットダウン特性が発現出来なくなる結果を招くことになる。Conventionally, in order to impart both shutdown characteristics and heat resistance to the separator, a composite porous membrane in which a polyolefin microporous membrane is coated and integrated with a porous layer made of a heat-resistant resin such as polyimide or aromatic polyamide has been proposed. Has been. (For example, Japanese Patent No. 3175730, Japanese Patent Laid-Open No. 2001-23600, Japanese Patent Laid-Open No. 2002-355938, etc.).
A polyolefin microporous membrane coated with a heat-resistant porous layer and integrated does not have the same problems as those obtained by laminating. However, the configuration disclosed in Japanese Patent No. 3175730 is obtained by forming a porous layer containing a heat-resistant nitrogen-containing aromatic polymer and ceramic powder on a polyethylene microporous film. Although improvement has been achieved, the design of the composite membrane is limited to a range in which clogging does not occur because the solution penetrates into the pores of the polyethylene microporous membrane. Industrial methods for coating on both sides are disclosed in Japanese Patent Application Laid-Open Nos. 2001-209773, 2002-166218, 2005-209570, 2008-300362, and 2009-21265. As disclosed in the published patent WO2006 / 123811 and the republished patent WO2007 / 013179, both use a polyethylene microporous membrane in which pores have already been formed. As a result, it is possible to suppress penetration of heat-resistant resin into the pores. There was a difficulty in obtaining good rapid charge / discharge characteristics within the range of temperament.
When the heat-resistant resin coating in the pores of the polyolefin microporous membrane of the base material becomes prominent, so-called pore clogging occurs. Will result in the inability to express.
基材のポリエチレン微多孔膜を薄くして他のより耐熱性の高いセパレータを同時に巻回する先行技術例（特開２００５−２８５３８５号公報）が示されているが、通常はこのような４μｍの厚さのポリエチレン微多孔膜単独では、熱による膜の溶融破断、対峙する正極と負極の端部が膜収縮で短絡に対して耐えることができない。
一方、薄膜化という観点では、耐熱性多孔質層を薄く形成することも考えられる。しかし、耐熱性多孔質層の膜厚を薄くしようとすると、所望の高い耐熱性を得ることが出来ず、また基材のポリエチレン微多孔膜の気孔内への耐熱性樹脂の入り込みが不可避であり気孔径の制約、すなわち良好な急速放電特性を得るうえで重要な透気度の良好なポリエチレン微多孔膜を使用できない欠点もあり薄膜化に制約があった。
セパレータに要求される膜厚みは、内容積が一定の電池容器（レトルトパック型も含む）ではセパレータ膜厚を減じて正極と負極の対峙する面積を増加させて電池容量増加を図ろうとする近年の技術動向の中で膜厚２０μｍ以下になる傾向であることを考慮すれば、総厚み２０μｍ以下で良好な急速放電特性を得るうえで重要な透気度の良好な耐熱性複合ポリオレフィン微多孔膜を得ることは従来の方法での実用化は、難しい。
すなわち、従来の耐熱性複合ポリオレフィン微多孔膜では、ポリオレフィン微多孔膜の気孔内まで耐熱性樹脂が入り込む結果、気孔内への耐熱性樹脂被覆は避けられず、コーティングした耐熱性樹脂からなる複合多孔質層セパレータのシャットダウン特性は、透気度の良好な気孔径の大きな基材のオレフィン微多孔膜を使用とするとその気孔の耐熱性樹脂被覆に伴い、いわゆる気孔の目詰まりを起こしてしまうので透気度に制約を生じる。また耐熱性を重視しすぎるとポリオレフィン微多孔膜気孔の溶融閉鎖が困難となり、シャットダウン特性が発現出来なくなる結果を招くことになる。Although a prior art example (Japanese Patent Laid-Open No. 2005-285385) in which a polyethylene microporous film as a base material is thinned and another higher heat-resistant separator is simultaneously wound is shown, A polyethylene microporous film having a thickness alone cannot withstand short-circuiting due to melt-fracturing of the film due to heat and contraction of the opposite ends of the positive and negative electrodes.
On the other hand, from the viewpoint of thinning, it is conceivable to form a heat-resistant porous layer thinly. However, if the thickness of the heat-resistant porous layer is made thin, the desired high heat resistance cannot be obtained, and it is inevitable that the heat-resistant resin enters the pores of the polyethylene microporous film of the base material. There was a limitation on pore size, that is, there was a defect that a polyethylene microporous film with good air permeability, which is important for obtaining good rapid discharge characteristics, could not be used, and there was a limitation on thinning.
The membrane thickness required for the separator is a battery container (including retort pack type) with a constant internal volume. In recent years, the separator thickness has been reduced to increase the area where the positive and negative electrodes face each other, thereby increasing the battery capacity. Considering the tendency of the film thickness to be 20 μm or less in the technical trend, a heat-resistant composite polyolefin microporous film having good air permeability, which is important for obtaining good rapid discharge characteristics with a total thickness of 20 μm or less It is difficult to obtain the practical application by the conventional method.
That is, in the conventional heat-resistant composite polyolefin microporous membrane, as a result of the heat-resistant resin entering the pores of the polyolefin microporous membrane, the heat-resistant resin coating into the pores is inevitable, and the composite porous composed of the coated heat-resistant resin is inevitable The shutdown characteristic of the porous separator is that if a microporous membrane having a large pore diameter and a good pore size is used, the pores are clogged with the heat-resistant resin coating of the pores. This creates a constraint on the temperament. On the other hand, if the heat resistance is too important, it becomes difficult to melt and close the pores of the polyolefin microporous membrane, resulting in the failure to exhibit the shutdown characteristics.
このように、現状では、ポリエチレン微多孔膜および耐熱性多孔質層を一体化したセパレータにおいて、十分な急速充放電特性、シャットダウン特性および耐熱性を総合的に満足し、さらに薄膜化可能な技術は未だ開示されていないと言える。Thus, at present, the separator that integrates a polyethylene microporous membrane and a heat-resistant porous layer has comprehensively satisfied sufficient rapid charge / discharge characteristics, shutdown characteristics, and heat resistance, and the technology that can further reduce the film thickness is It can be said that it has not been disclosed yet.
取り扱いが良好で、シャットダウン特性と耐熱性を兼ね備え、急速充放電に有利な透気性の良好な比較的大口径のポリオレフィン微多孔膜を用いて目詰まりの問題を解決する適切な界面設計を施すことで電池性能の低下もないセパレータとなる耐熱性複合ポリオレフィン微多孔膜及びその製造方法を提供することにある。Appropriate interface design that solves clogging problem using a relatively large-diameter polyolefin microporous membrane that is easy to handle, has both shutdown characteristics and heat resistance, and has good air permeability that is advantageous for rapid charge and discharge. It is another object of the present invention to provide a heat-resistant composite polyolefin microporous membrane that can be a separator that does not deteriorate battery performance and a method for producing the same.
リチウムイオン二次電池用セパレータとして急速充放電性と良好な容量保持に貢献する透気性の良好なポリオレフィン微多孔膜の特長を生かし、且つ耐熱性を付与する目的で、透気性の良好な比較的大口径のポリオレフィン微多孔膜の表裏に連通した孔をあらかじめ溶剤抽出可能な物質で抱埋しておいた後に両面同時塗工方法により当該膜の表裏に均一な厚みの耐熱性ポリマー塗膜を形成させた後、表裏に連通した孔を抱埋していた樹脂を溶剤で抽出することを特徴とする耐熱性複合ポリオレフィン微多孔膜およびその製造方法とする。
また、リチウムイオン二次電池用セパレータとして提供する。As a separator for lithium ion secondary batteries, taking advantage of the polyolefin microporous membrane with good air permeability that contributes to rapid charge / discharge characteristics and good capacity retention, and for the purpose of imparting heat resistance, it has relatively good air permeability. Pre-embed the pores communicating with the front and back of a large-diameter polyolefin microporous membrane with a solvent extractable material, and then form a heat-resistant polymer coating with a uniform thickness on the front and back of the membrane using a double-sided simultaneous coating method Then, a resin having embedded the holes communicating with the front and back is extracted with a solvent, and a heat-resistant composite polyolefin microporous membrane and a method for producing the same are obtained.
Moreover, it provides as a separator for lithium ion secondary batteries.
本発明者は上記の課題に対し鋭意検討した結果、（ｉ）複合多孔膜の基材として透気性の良好な比較的大口径のポリオレフィン微多孔膜を選定して（ｉｉ）あらかじめその気孔を溶剤抽出可能な物質で閉鎖しておき、（ｉｉｉ）耐熱性多孔質層を構成する耐熱性ポリマーを選定し、（ｉｖ）その溶液をポリオレフィン微多孔膜の両面に塗工し、適切に耐熱性多孔質層を形成した後に（ｖ）耐熱性多孔質層を介して気孔を閉鎖していた物質を抽出・除去することを特徴とする耐熱性複合ポリオレフィン微多孔膜及びその製造方法を見出した。
耐熱性複合ポリオレフィン微多孔膜としての取り扱いに優れており、シャットダウン特性、耐熱性を有し、かつポリオレフィン微多孔膜の気孔の目詰まりの問題も生じないリチウムイオン透過性の阻害も起きない急速充放電特性に優れたリチウムイオン二次電池用セパレータの提供を可能とする。As a result of intensive studies on the above problems, the present inventor has selected (i) a relatively large-diameter polyolefin microporous membrane having good air permeability as a base material for the composite porous membrane, and (ii) preliminarily removing the pores as a solvent. Close with extractable material, (iii) select heat-resistant polymer that constitutes heat-resistant porous layer, and (iv) apply the solution to both sides of polyolefin microporous membrane, and properly heat-resistant porous After the formation of the porous layer, (v) a heat-resistant composite polyolefin microporous membrane characterized by extracting and removing the substance whose pores were closed through the heat-resistant porous layer, and a method for producing the same were found.
Excellent handling as a heat-resistant composite polyolefin microporous membrane, has a shutdown characteristic, heat resistance, and does not cause problems of pore clogging of the polyolefin microporous membrane. It is possible to provide a separator for a lithium ion secondary battery having excellent discharge characteristics.
すなわち本発明は、ポリオレフィン微多孔膜の両面が耐熱性ポリマーの多孔質層で被覆されている複合ポリオレフィン微多孔膜であり、（１）総厚みが７μｍ以上２０μｍ以下であり、透気度（ガーレー値；ＪＩＳＰ８１１７）が１３秒／１００ｍｌ・μｍ以下４秒／１００ｍｌ・μｍ以上、好ましくは１２秒／１００ｍｌ・μｍ以下６秒／１００ｍｌ・μｍ以上であることを特徴とする耐熱性複合ポリオレフィン微多孔膜。（２）耐熱ポリマーがポリメタフェニレンイソフタルアミド、ポリパラフェニレンテレフタルアミド、ポリパラフェニレンテレフタルアミドと３，４−オキシジフェニレンテレフタルアミドとその共重合体あるいはそれらの混合物であり、少なくともその１種からなることを特徴とする複合ポリオレフィン微多孔膜。（３）ポリオレフィン微多孔膜を、あらかじめ溶剤抽出可能な物質で表裏に連通した孔を抱埋しておき、当該耐熱性ポリマー溶液を両面に同時に塗布をできる塗工装置内を通過させて均一な厚みの塗工膜を形成した後、（４）表裏に連通したポリオレフィン微多孔膜の孔を抱埋している樹脂を溶剤で抽出することを特徴とする耐熱性複合ポリオレフィン微多孔膜の製造方法。（５）抱埋しておく物質が、ポリ（２，６‐ジメチルー１，４−フェニレンエーテル）、パラフィンワックス、マイクロクリスタリンワックス、流動パラフィン、フタル酸エステル、セバシン酸エステル、トリメリット酸エステル等の中から選ばれた少なくとも１種であることを特徴とする耐熱性複合ポリオレフィン微多孔膜の製造方法。
特に好ましいのは、超高分子量ポリエチレンに可塑剤としてのパラフィンワックス、マイクロクリスタリンワックス、流動パラフィン、フタル酸エステル、セバシン酸エステル、トリメリット酸エステル等の中から選ばれた少なくとも１種を使用して２軸押出機等で溶融混合してから冷却ロールを経て機械方向（ＭＤ方向）と横方向（ＴＤ方向）に２軸延伸をかけて厚みも所望の範囲に薄くする常法で得られるセパレータの先駆体フィルムを本来付すべき可塑剤抽出工程の前で塗工装置内へ移し、前記の当該耐熱性ポリマー溶液を両面に同時に塗布をできる装置内を通過させて均一な厚みの塗工膜を形成した後、可塑剤の抽出工程にかけることにより製造工程を簡便に連続的操作を可能にした製造方法である。
（６）上記耐熱性複合ポリオレフィン微多孔膜からなることを特徴とするリチウムイオン二次電池用セパレータである。That is, the present invention is a composite polyolefin microporous membrane in which both surfaces of a polyolefin microporous membrane are coated with a porous layer of a heat-resistant polymer. (1) The total thickness is 7 μm or more and 20 μm or less, and the air permeability (Gurley) Value: JISP 8117) is 13 seconds / 100 ml · μm or less 4 seconds / 100 ml · μm or more, preferably 12 seconds / 100 ml · μm or less 6 seconds / 100 ml · μm or more . (2) The heat-resistant polymer is polymetaphenylene isophthalamide, polyparaphenylene terephthalamide, polyparaphenylene terephthalamide, 3,4-oxydiphenylene terephthalamide and a copolymer thereof, or a mixture thereof, and at least one of them A composite polyolefin microporous membrane characterized by: (3) The polyolefin microporous membrane is previously embedded with holes communicating with the front and back with a solvent-extractable substance, and passed through a coating apparatus capable of simultaneously applying the heat-resistant polymer solution on both sides. (4) A method for producing a heat-resistant composite polyolefin microporous membrane comprising: (4) extracting a resin embedding pores of a polyolefin microporous membrane communicating with the front and back with a solvent after forming a coating film having a thickness . (5) The substance to be embedded is poly (2,6-dimethyl-1,4-phenylene ether), paraffin wax, microcrystalline wax, liquid paraffin, phthalate ester, sebacic acid ester, trimellitic acid ester, etc. A method for producing a heat-resistant composite polyolefin microporous membrane, characterized in that it is at least one selected from among them.
Particularly preferably, at least one selected from paraffin wax, microcrystalline wax, liquid paraffin, phthalic acid ester, sebacic acid ester, trimellitic acid ester and the like as a plasticizer is used for ultra high molecular weight polyethylene. A separator obtained by a conventional method in which the thickness is reduced to a desired range by biaxial stretching in the machine direction (MD direction) and transverse direction (TD direction) through a cooling roll after being melt-mixed by a biaxial extruder or the like. The precursor film is transferred into the coating device before the plasticizer extraction process to be originally applied, and the coating film having a uniform thickness is formed by passing the above heat-resistant polymer solution through the device capable of simultaneously coating both sides. Then, it is a production method that enables continuous operation of the production process simply by subjecting it to a plasticizer extraction process.
(6) A separator for a lithium ion secondary battery comprising the heat resistant composite polyolefin microporous membrane.
本発明の耐熱性微多孔膜の製造方法についてより具体的に説明する。すなわち、本発明に使用するポリオレフィン微多孔膜は厚さ４μｍ以上１８μｍ以下であり、５μｍ以上１８μｍ以下が好適である。
透気度（ガーレー値；ＪＩＳＰ８１１７）が１３秒／１００ｍｌ・μｍ以下４秒／１００ｍｌ・μｍ以上、更には１２秒／１００ｍｌ・μｍ以下６秒／１００ｍｌ・μｍ以上であることが好ましい。当該透気度はポリオレフィン微多孔膜の形態を反映したものであり、この数値が小さいほどポリオレフィン微多孔膜は大きい孔径の孔からなり曲路率は小さいものとなり、良好な透気度を示す。また、大きいとその逆で、小さい孔径の孔からなり曲路率は大きくなっている。上記透気度が１３秒／１００ｍｌ・μｍより小さくても、当該耐熱性ポリマーがポリオレフィン微多孔膜の孔へ入り込み目詰まりを起こさせる先行技術で見られる現象に対して、本発明のセパレータでは、あらかじめ孔に耐熱性ポリマーが入り込まないように気孔を特定の物質で抱埋しておく結果、目詰まりを起こすことは全くないために充放電特性の低下もなく、良好な急速充放電特性を保持できる。また、基材のポリオレフィン微多孔膜の気孔を保持しているのでシャットダウン性も、十分に発現できる。The method for producing the heat-resistant microporous membrane of the present invention will be described more specifically. That is, the polyolefin microporous membrane used in the present invention has a thickness of 4 μm to 18 μm, and preferably 5 μm to 18 μm.
The air permeability (Gurley value; JISP8117) is preferably 13 seconds / 100 ml · μm or less, 4 seconds / 100 ml · μm or more, and more preferably 12 seconds / 100 ml · μm or less, 6 seconds / 100 ml · μm or more. The air permeability reflects the form of the polyolefin microporous membrane. The smaller this value, the larger the polyolefin microporous membrane is, and the smaller the curvature is, and the better the air permeability is. On the other hand, if it is large, the opposite is true, and the curvature is large due to the small hole diameter. In the separator of the present invention, in contrast to the phenomenon seen in the prior art in which the heat resistant polymer enters the pores of the polyolefin microporous membrane even if the air permeability is smaller than 13 seconds / 100 ml · μm, As a result of embedding pores with a specific substance so that heat-resistant polymer does not enter the pores in advance, clogging will not occur at all, so there is no deterioration in charge / discharge characteristics and good rapid charge / discharge characteristics are maintained. it can. Further, since the pores of the polyolefin microporous film as the base material are retained, the shutdown property can be sufficiently exhibited.
当該ポリオレフィン微多孔膜の孔径は０．００５μｍ以上０．４０μｍ以下であればよく、０．０２μｍ以上０．４μｍ以下の範囲が好適である。ここで、孔径は走査型電子顕微鏡（ＳＥＭ）による観察で求めることが可能である。本発明においては、ＳＥＭで該ポリオレフィン微多孔膜の表面を観察し、任意に２０点の孔を選定しそれぞれ孔径を求めこれらを平均することで算出された数値を孔径とする。本発明の耐熱性複合ポリオレフィン微多孔膜の場合、ポリオレフィン微多孔膜の両面を耐熱性ポリマーで被覆するが、ポリオレフィン微多孔膜の孔径が十分に大きくとも本発明により気孔径が保持されるのでリチウムイオンの透過も容易であり、急速充放電特性を損ねずに好ましい設計が可能となる。The pore diameter of the polyolefin microporous membrane may be 0.005 μm or more and 0.40 μm or less, and a range of 0.02 μm or more and 0.4 μm or less is suitable. Here, the hole diameter can be obtained by observation with a scanning electron microscope (SEM). In the present invention, the surface of the polyolefin microporous membrane is observed with an SEM, 20 pores are arbitrarily selected, the respective pore sizes are obtained and averaged, and the numerical value calculated is taken as the pore size. In the case of the heat-resistant composite polyolefin microporous membrane of the present invention, both surfaces of the polyolefin microporous membrane are coated with a heat-resistant polymer, but the pore size is maintained by the present invention even if the pore size of the polyolefin microporous membrane is sufficiently large. Ion permeation is easy, and a favorable design can be achieved without impairing rapid charge / discharge characteristics.
当該ポリオレフィン微多孔膜を構成する材料はポリエチレンが好ましい。ポリエチレンが最も良好なシャットダウン特性を発現させることができる。本発明のポリエチレンは分子量が粘度平均分子量として４０万から４００万、好ましくは５０万以上３００万の範囲の超高分子量ポリエチレンを、少なくとも７０％以上含まれることが好ましい。
また形成される微多孔膜は、超高分子量ポリエチレンのミクロフィブリルから構成されておりフィブリル間の空隙がセパレータとしての気孔となっているものである。The material constituting the polyolefin microporous membrane is preferably polyethylene. Polyethylene can exhibit the best shutdown characteristics. The polyethylene of the present invention preferably contains at least 70% or more of ultrahigh molecular weight polyethylene having a molecular weight of 400,000 to 4 million, preferably 500,000 to 3,000,000 as a viscosity average molecular weight.
Further, the formed microporous film is composed of ultra high molecular weight polyethylene microfibrils, and voids between the fibrils are pores as separators.
耐熱ポリマーとしてはポリメタフェニレンイソフタルアミド、ポリパラフェニレンテレフタルアミド、ポリパラフェニレンテレフタルアミドと３，４’−オキシジフェニレンテレフタルアミドとその共重合体あるいはその混合物である。例えばメタフェニレンジアミン、パラフェニレンジアミン、３，４’−オキシジフェニレンジアミン、４，４’−ジアミノビフェニル、２−メチルーパラフェニレンジアミン、２−クロローパラフェニレンジアミン、２，６−ジクロローパラフェニレンジアミン、２，６−ナフタレンジアミン、１，５−ナフタレンジアミン、４，４’−ジアミノベンズアニリド、３、４’−ジアミノジフェニルエーテル等の少なくとも１種のジアミンを１．００モルとイソフタル酸ジクロライド、テレフタル酸ジクロライド、ビフェニルー４，４’−ジカルボン酸ジクロライド、２−クロロテレフタル酸ジクロライド、２，５−ジクロロテレフタル酸ジクロライド、２−メチルテレフタル酸ジクロライド、１，５−ナフタレンジカルボン酸ジクロライド、２、６−ナフタレンジカルボン酸ジクロライド等の少なくとも１種のジクロライドを０．９５モルから０．９９モルをＮ−メチル−２−ピロリドン、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド等を主体とする溶剤中に添加して−２０℃から５０℃の温度で縮合重合して、水洗、乾燥して得られる。耐熱性ポリマーの極限粘度は、０．５〜３．０ｄｌ／ｇの範囲にあり、塗工液としての粘性と塗膜形成が出来るものであれば良い。好ましくは０．８〜２．０ｄｌ／ｇの極限粘度範囲である。Examples of the heat-resistant polymer include polymetaphenylene isophthalamide, polyparaphenylene terephthalamide, polyparaphenylene terephthalamide, 3,4'-oxydiphenylene terephthalamide and a copolymer thereof, or a mixture thereof. For example, metaphenylenediamine, paraphenylenediamine, 3,4'-oxydiphenylenediamine, 4,4'-diaminobiphenyl, 2-methyl-paraphenylenediamine, 2-chloro-paraphenylenediamine, 2,6-dichloro-paraphenylenediamine , 1.00 mol of at least one diamine such as 2,6-naphthalenediamine, 1,5-naphthalenediamine, 4,4′-diaminobenzanilide, 3,4′-diaminodiphenyl ether, isophthalic acid dichloride, terephthalic acid Dichloride, biphenyl-4,4'-dicarboxylic acid dichloride, 2-chloroterephthalic acid dichloride, 2,5-dichloroterephthalic acid dichloride, 2-methylterephthalic acid dichloride, 1,5-naphthalenedicarboxylic acid dichloride, 2 0.95 mol to 0.99 mol of at least one dichloride such as 6-naphthalenedicarboxylic acid dichloride is mainly composed of N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and the like. It is added to a solvent, subjected to condensation polymerization at a temperature of -20 ° C to 50 ° C, washed with water and dried. The intrinsic viscosity of the heat-resistant polymer is in the range of 0.5 to 3.0 dl / g, as long as the viscosity as the coating liquid and the coating film can be formed. Preferably, it is an intrinsic viscosity range of 0.8 to 2.0 dl / g.
耐熱ポリマーの溶剤としてＮ，Ｎ−ジメチルアセトアミド、Ｎ−メチル−２−ピロリドン、Ｎ，Ｎ−ジメチルホルムアミド等を主体とする溶剤が使用される。少なくともその１種からなる多孔質層を形成するに適度な塗工粘度を有する耐熱性ポリマー溶液を作製する。As a solvent for the heat-resistant polymer, a solvent mainly composed of N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N, N-dimethylformamide or the like is used. A heat-resistant polymer solution having an appropriate coating viscosity for forming a porous layer composed of at least one of them is prepared.
ポリオレフィン微多孔膜と耐熱性ポリマーの良好な界面形成に適する溶液中の当該耐熱性ポリマー濃度は、１〜１５重量％の範囲で使用する。好ましくは１〜１０重量％の範囲である。
ポリメタフェニレンイソフタルアミドおよびその誘導体がポリマーとして比較的に吸湿性が低く、しかも溶剤に対する溶解性が高く塗布液の作製が容易であるという点で生産性の観点からも好ましい。ポリメタフェニレンイソフタルアミドおよびその誘導体を主成分として使用することが好ましい。The concentration of the heat resistant polymer in a solution suitable for forming a good interface between the polyolefin microporous membrane and the heat resistant polymer is in the range of 1 to 15% by weight. Preferably it is the range of 1-10 weight%.
Polymetaphenylene isophthalamide and its derivatives are preferable from the viewpoint of productivity in that they are relatively low in hygroscopicity as a polymer, are highly soluble in solvents, and are easy to prepare coating solutions. It is preferable to use polymetaphenylene isophthalamide and its derivatives as main components.
当該耐熱ポリマー溶液をポリオレフィン微多孔膜の両面に塗布する工程として特に限定されるものではないが、例えば、二つのロールのクリアランスおよびロールの回転方向、回転周速や回転周速比を制御することにより、気孔があらかじめ溶剤抽出可能な物質で抱埋されたポリオレフィン微多孔膜両面に付着する塗工液量を制御し、所望の表裏の塗工膜の厚みを得る。
ロールとして巻き線式のワイヤーバーまたは溝切りロールを使用することも可能である。
巻き線式ワイヤーバーを使用する場合にはワイヤーバーの巻き線の径を変えることで塗膜の厚みの制御が容易となるので好ましい。溝切りロールを使用する場合には溝切りロールの溝の深さおよび／または溝の幅および／または溝のピッチを変えることでも塗膜の厚みの制御が可能である。塗工膜等の目付けは、１０ｃｍ角の正方形に切り出して、その重量（ｇ）を測定して、重量を面積で割ることで目付を求め、ｇ／ｍ２の単位で算出する。
また、耐熱性ポリマーの両面への塗工量合計は、複合ポリオレフィン微多孔膜の目付からポリオレフィン微多孔膜の目付を引くことで算出する。
塗工量合計は０．５ｇ／ｍ２以上５．０ｇ／ｍ２以下、好ましくは１．５ｇ／ｍ２以上３．０ｇ／ｍ２以下の範囲である。塗布量が０．５ｇ／ｍ２より少ないと耐熱性ポリマー被覆の効果が十分に得られない。また、５．０ｇ／ｍ２より多いと安価ではない耐熱性ポリマーのコストが高まり、好ましくない。Although it is not particularly limited as a step of applying the heat-resistant polymer solution to both surfaces of the polyolefin microporous membrane, for example, to control the clearance between the two rolls, the rotation direction of the rolls, the rotational peripheral speed and the rotational peripheral speed ratio. By controlling the amount of the coating solution adhering to both surfaces of the polyolefin microporous membrane embedded with a solvent-extractable substance in advance, the desired thickness of the coating film on the front and back sides is obtained.
It is also possible to use a wound wire bar or a grooving roll as the roll.
When using a wound wire bar, the thickness of the coating film can be easily controlled by changing the diameter of the wire bar. When a grooving roll is used, the thickness of the coating film can also be controlled by changing the groove depth and / or groove width and / or groove pitch of the grooving roll. The basis weight of the coating film or the like is cut out into a 10 cm square, the weight (g) is measured, the basis weight is obtained by dividing the weight by the area, and is calculated in units of g / m2.
Further, the total coating amount of the heat-resistant polymer on both sides is calculated by subtracting the basis weight of the polyolefin microporous membrane from the basis weight of the composite polyolefin microporous membrane.
The total coating amount is 0.5 g / m 2 or more and 5.0 g / m 2 or less, preferably 1.5 g / m 2 or more and 3.0 g / m 2 or less. When the coating amount is less than 0.5 g / m 2 , the effect of the heat resistant polymer coating cannot be sufficiently obtained. On the other hand, if it is more than 5.0 g / m 2 , the cost of a heat-resistant polymer that is not inexpensive increases, which is not preferable.
耐熱ポリマー溶液が塗布されている当該ポリオレフィン微多孔膜は、表裏両面が凝固液と同時に接するように凝固液に進入させる。これにより両面同時に凝固させることができ、表裏同時に一体化することが可能となる。またこの手法を採用することで表裏同等の形態を有する耐熱性ポリマーからなる多孔質層が形成させるので、本発明の複合膜セパレータには表裏異方性がない。このためカールといった不具合は発生し難く、電池製造工程での取り扱いが良好なものとなる。さらに製品の管理も容易となり、使用する際にも表裏を考慮に入れる必要がなくなる。
凝固液は耐熱性ポリマー溶液に使用した溶剤と水との混合液が使用されることが好ましい。
凝固液中の水の割合が２０〜９０重量％であり、３０〜８０重量％の範囲が特に好ましい。
耐熱ポリマー多孔質を形成する製造方法を提供できる。多孔質層の気孔率は４０％以上６０％の範囲とするのが好ましい。The polyolefin microporous film coated with the heat-resistant polymer solution is allowed to enter the coagulation liquid so that both the front and back surfaces are in contact with the coagulation liquid simultaneously. As a result, both sides can be coagulated at the same time, and the front and back can be integrated simultaneously. Moreover, since the porous layer which consists of a heat resistant polymer which has a form equivalent to front and back is formed by employ | adopting this method, the composite membrane separator of this invention does not have front and back anisotropy. For this reason, problems such as curling are unlikely to occur, and handling in the battery manufacturing process is good. In addition, the product can be easily managed, and it is not necessary to take the front and back into consideration when using it.
The coagulation liquid is preferably a mixed liquid of a solvent and water used for the heat resistant polymer solution.
The ratio of water in the coagulation liquid is 20 to 90% by weight, and a range of 30 to 80% by weight is particularly preferable.
A production method for forming a heat-resistant polymer porous material can be provided. The porosity of the porous layer is preferably in the range of 40% to 60%.
さらに、当該耐熱ポリマー溶液が相分離剤を含有し、その相分離剤の濃度は全溶剤量を１００としたとき、５〜５０重量％の範囲が好ましい。相分離剤としては、ポリプロピレングリコール、トリプロピレングリコール、エチレンカーボネート、プロピレンカーボネート、ポリオキシエチレンオレイルエーテル、ポリオキシエチレンステアリルエーテル、エチレングリコール、メタノール、エタノール、ブタンジオール、ポリビニルピロリドン等が挙げられる。Further, the heat-resistant polymer solution contains a phase separation agent, and the concentration of the phase separation agent is preferably in the range of 5 to 50% by weight when the total solvent amount is 100. Examples of the phase separation agent include polypropylene glycol, tripropylene glycol, ethylene carbonate, propylene carbonate, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, ethylene glycol, methanol, ethanol, butanediol, and polyvinylpyrrolidone.
またこの塗工液にはポリオレフィン微多孔膜の基材とのぬれ性改善の目的から界面活性剤等の第３成分を添加および／またはこの基材表面の洗浄とか親水化処理をほどこしても構わない。また塗工液には複合膜の強度を向上する等の目的から無機粒子等の第３成分を添加しても構わない。当該耐熱性ポリマー溶液を塗工してから凝固させるまでに当該耐熱性ポリマー溶液がポリオレフィン微多孔膜中へしみ込まないようにすることが肝要である。
これは当該耐熱ポリマー溶液の粘度と塗布から凝固へ至る時間の兼ね合いで決まり、本発明の製造方法においては搬送速度と塗布装置凝固浴間の距離の適正な設定により容易に調整可能である。Further, for the purpose of improving the wettability of the polyolefin microporous membrane with the base material, a third component such as a surfactant may be added to the coating liquid and / or the surface of the base material may be washed or hydrophilized. Absent. Further, a third component such as inorganic particles may be added to the coating solution for the purpose of improving the strength of the composite film. It is important to prevent the heat-resistant polymer solution from penetrating into the polyolefin microporous film after the heat-resistant polymer solution is applied and solidified.
This is determined by the balance between the viscosity of the heat-resistant polymer solution and the time from application to coagulation, and in the production method of the present invention, it can be easily adjusted by appropriately setting the conveyance speed and the distance between the application device coagulation baths.
さらに、凝固された複合ポリオレフィン微多孔膜を水洗する。水洗の方法は特に限定されない。
十分に溶剤が洗浄できる条件を採用すればよい。Further, the solidified composite polyolefin microporous membrane is washed with water. The method of washing with water is not particularly limited.
Conditions that can sufficiently wash the solvent may be adopted.
乾燥工程も特に限定されず、従来の方法を適切に用いればよい。
水分除去には、例えば、ポリオレフィン微多孔膜中に抱埋されている物質が溶融流失しない温度範囲の熱風で常圧乾燥させる方法、熱ローラに接触させて乾燥する方法、減圧下に加熱乾燥する方法等が挙げられる。The drying process is not particularly limited, and a conventional method may be appropriately used.
For removing moisture, for example, a method of drying at normal pressure with hot air in a temperature range in which the substance embedded in the polyolefin microporous film does not melt and flow away, a method of drying by contacting with a heat roller, and heat drying under reduced pressure Methods and the like.
複合膜のポリオレフィン微多孔膜部分の孔を抱埋している物質を抽出・除去する工程には、抱埋している物質の溶剤が使用されるが、塩化メチレンあるいはフロン系、臭素系の湿式２軸延伸後のポリオレフィン可塑剤の抽出に使用されるのと同じ溶剤が好ましい。In the process of extracting and removing the material embedding pores in the polyolefin microporous membrane part of the composite membrane, a solvent of the embedding material is used, but methylene chloride or CFC-based, bromine-based wet The same solvent used for extraction of the polyolefin plasticizer after biaxial stretching is preferred.
被覆する多孔質層はポリオレフィン微多孔膜に比べ十分に孔径が大きい方がポリオレフィン微多孔膜中に抱埋していた物質の抽出・除去操作を容易にする上でも好ましい。It is preferable that the porous layer to be coated has a sufficiently large pore diameter compared to the polyolefin microporous membrane in order to facilitate the extraction / removal operation of the substance embedded in the polyolefin microporous membrane.
以上の工程を順番に経て耐熱性複合ポリオレフィン微多孔膜は製造される。The heat-resistant composite polyolefin microporous membrane is manufactured through the above steps in order.
当該耐熱性微多孔膜では表裏に連通した孔をあらかじめ溶剤抽出可能な物質で抱埋しておいた後に、当該膜の表裏に均一な厚みの塗膜を形成する。その後に、表裏に連通した孔を抱埋している樹脂を溶剤で抽出することに起因してポリオレフィン微多孔膜の表裏の適度なミクロの凹凸形状が残り、セパレータとしての巻回終了時の巻き芯からの脱離も容易にできる。滑り性の問題は、特に発生しない。In the heat-resistant microporous film, pores communicating with the front and back surfaces are pre-embedded with a substance capable of solvent extraction, and then a coating film having a uniform thickness is formed on the front and back surfaces of the film. After that, due to the extraction of the resin embedding the holes communicating with the front and back with a solvent, moderate micro uneven shapes on the front and back of the polyolefin microporous membrane remain, and the winding at the end of winding as a separator Detachment from the core can be easily performed. There is no particular problem with slipperiness.
本発明の塗工方法によれば、塗工筋や塗工斑がなく、長時間の連続運転が可能であり、取り扱いが良好で、シャットダウン特性と耐熱性を兼ね備え、さらにポリオレフィン微多孔膜の気孔目詰まりを起こさない適切な界面設計を施すことで電池性能の低下もなく、急速放電特性にも優れたリチウムイオン二次電池用セパレータとなる耐熱性複合ポリオレフィン微多孔膜及びその製造方法を提供出来る。According to the coating method of the present invention, there are no coating streaks or coating spots, long-term continuous operation is possible, handling is good, both shutdown characteristics and heat resistance are provided, and the pores of the polyolefin microporous membrane By providing an appropriate interface design that does not cause clogging, it is possible to provide a heat-resistant composite polyolefin microporous membrane that can be used as a separator for a lithium ion secondary battery that is excellent in rapid discharge characteristics without deterioration in battery performance and a method for producing the same. .
以下、本発明を実施例により詳細に説明する。本発明に用いる測定方法について具体的に説明する。
［孔径］
ポリオレフィン微多孔膜、塗工膜の表面を走査型電子顕微鏡（ＳＥＭ）で観察する。任意に孔を２０点選び、これら孔の孔径を求め平均することで孔径を算出する。
［膜厚］
ポリオレフィン微多孔膜厚、被覆された多孔質層膜厚は、断面を走査型電子顕微鏡（ＳＥＭ）で観察し、任意に１０ヶ所を選び、これら断面の厚みを求め平均することで膜厚を算出する。
［透気度］
透気度はＪＩＳ Ｐ８１１７に準拠のガーレー式透気度計を使用して測定する。
［単位厚み当たりの透気度］
透気度を膜厚で割ることで単位厚み当たりの透気度として算出する。
［突刺強度］
針先端の曲率半径０．５ｍｍ、突き刺し速度２ｍｍ／ｓｅｃで突刺試験を行い、最大突刺荷重ｇを突刺強度とする。
［シャットダウン特性］
シャットダウン特性の評価は、セパレータに電解液（１Ｍ ＬｉＰＦ６／ＥＣ：ＥＭＣ（１／２容積比））を含浸させ、直径１０ｍｍの銅板に挟み、これを電池評価用スクリュー容器に封入する。このスクリュー容器を１９０度に保温している熱風乾燥機に入れ、スクリュー容器の温度とインピーダンス値を測定する。インピーダンス値は交流法にて振幅１０ｍＶ、周波数１ｋＨｚの交流を１０ｍＡの範囲内で印加し、温度に対しインピーダンス値をプロットし、シャットダウン温度を測定する。シャットダウン温度はインピーダンス値が上昇していく過程で１０００ｏｈｍ以上になる温度とする。
［メルトダウン特性］
上記シャットダウン温度測定の後、継続して上昇するスクリュー容器温度を計測し、１９０℃到達後１０分間を経ても短絡が発生しない場合を合格とする。
［電池性能の測定方法］
正極活物質としてコバルト酸リチウム（ＬｉＣｏＯ２；１０ミクロン）粉末９２重量部とアセチレンブラック（電気化学工業社製）粉末２重量部、微粉黒鉛（日本黒鉛社製）２重量部、ポリフッ化ビニリデン（クレハ化学工業株式会社製）の乾燥重量が４重量部となるようにポリフッ化ビニリデンのＮ−メチルピロリドン溶液を用い、正極剤ペーストを作製する。
得られたペーストを厚さ１５μｍのアルミ箔上へ塗工し、乾燥後プレスして正極を作製する。
負極活物質の黒鉛化カーボン（日立化成社製）粉末９８重量部とＣＭＣ（カルボキシメチルセルロース）（ダイキン社製）１重量部とカルボキシ変性ブタジエン系ラテックス（日本ゼオン社製）の固形分１重量部とからなる水溶液を用い、負極剤ペーストを作製する。得られたペーストを厚さ１０μｍの銅箔上へ塗工し、乾燥後プレスして負極を作製する。
上記正極を２０ｍｍ×５０ｍｍのサイズに切り出しタブを付けた。また上記負極は２２ｍｍ×５２ｍｍのサイズに切り出しタブを付けた。セパレータは２６ｍｍ×５６ｍｍのサイズに切り出した。これら正極／セパレータ／負極と接合し、電解液を注入してアルミラミネートフィルム内に封入することでアルミラミネート外装セルを作製した。ここで電解液には１ＭでＬｉＰＦ６をエチレンカーボネート／エチルメチルカーボネート（３／７容積比）に溶解したものを用いる。
該セルにおいて０．２Ｃと２Ｃにおける放電電気量を測定し、（２Ｃにおける放電電気量）／（０．２Ｃにおける放電電気量）×１００を電池性能とした。ここで、充電条件は０．２Ｃ ４．２Ｖ ＣＣ／ＣＶ８時間とし、放電条件は２．７５ＶカットオフのＣＣ放電とする。Hereinafter, the present invention will be described in detail with reference to examples. The measurement method used in the present invention will be specifically described.
[Pore diameter]
The surfaces of the polyolefin microporous film and the coating film are observed with a scanning electron microscope (SEM). Arbitrarily 20 holes are selected, and the diameters of these holes are calculated and averaged.
[Film thickness]
Polyolefin microporous film thickness and coated porous layer film thickness are calculated by observing the cross section with a scanning electron microscope (SEM), arbitrarily selecting 10 locations, and calculating and averaging the thickness of these cross sections. To do.
[Air permeability]
The air permeability is measured using a Gurley type air permeability meter according to JIS P8117.
[Air permeability per unit thickness]
The air permeability per unit thickness is calculated by dividing the air permeability by the film thickness.
[Puncture strength]
A piercing test is performed at a radius of curvature of the needle tip of 0.5 mm and a piercing speed of 2 mm / sec, and the maximum piercing load g is defined as the piercing strength.
[Shutdown characteristics]
For the evaluation of the shutdown characteristics, the separator is impregnated with an electrolytic solution (1M LiPF6 / EC: EMC (1/2 volume ratio)), sandwiched between copper plates having a diameter of 10 mm, and enclosed in a screw container for battery evaluation. This screw container is put into a hot air drier maintained at 190 ° C., and the temperature and impedance value of the screw container are measured. The impedance value is an alternating current method in which an alternating current with an amplitude of 10 mV and a frequency of 1 kHz is applied within a range of 10 mA, the impedance value is plotted against the temperature, and the shutdown temperature is measured. The shutdown temperature is a temperature that becomes 1000 ohms or higher in the process of increasing the impedance value.
[Meltdown characteristics]
After the shutdown temperature measurement, the screw container temperature continuously rising is measured, and a case where no short circuit occurs even after 10 minutes after reaching 190 ° C. is regarded as acceptable.
[Battery performance measurement method]
As the positive electrode active material, 92 parts by weight of lithium cobaltate (LiCoO 2 ; 10 micron) powder, 2 parts by weight of acetylene black (manufactured by Denki Kagaku Kogyo), 2 parts by weight of fine graphite (manufactured by Nippon Graphite), polyvinylidene fluoride (Kureha) A positive electrode agent paste is prepared using an N-methylpyrrolidone solution of polyvinylidene fluoride so that the dry weight of Chemical Industries, Ltd.) is 4 parts by weight.
The obtained paste is applied onto an aluminum foil having a thickness of 15 μm, dried and pressed to produce a positive electrode.
98 parts by weight of graphitized carbon (manufactured by Hitachi Chemical Co., Ltd.) powder of negative electrode active material, 1 part by weight of CMC (carboxymethylcellulose) (manufactured by Daikin), and 1 part by weight of solid content of carboxy-modified butadiene latex (manufactured by Nippon Zeon) A negative electrode paste is prepared using an aqueous solution of The obtained paste is applied onto a copper foil having a thickness of 10 μm, dried and pressed to produce a negative electrode.
The positive electrode was cut into a size of 20 mm × 50 mm and attached with a tab. The negative electrode was cut into a size of 22 mm × 52 mm and attached with a tab. The separator was cut into a size of 26 mm × 56 mm. These positive electrode / separator / negative electrode were joined, an electrolytic solution was injected, and sealed in an aluminum laminate film to produce an aluminum laminate exterior cell. Here, a 1M solution of LiPF 6 dissolved in ethylene carbonate / ethyl methyl carbonate (3/7 volume ratio) is used as the electrolyte.
The amount of electricity discharged at 0.2C and 2C in the cell was measured, and the amount of electricity discharged at 2C / (amount of electricity discharged at 0.2C) × 100 was defined as the battery performance. Here, the charging condition is 0.2 C 4.2 V CC / CV 8 hours, and the discharging condition is CC discharge with a 2.75 V cutoff.
［実施例１］
２軸押出機で溶融したポリエチレンに融点５８℃を有するパラフィンワックスと流動パラフィンの加熱混合物を注入し、２軸方向に延伸して冷却して得られたポリオレフィン微多孔膜の先駆体Ａを得る。ポリメタフェニレンイソフタルアミド（極限粘度１．６）７重量％、Ｎ−メチル−２−ピロリドン６６重量％、エチレンプロピオネート４重量％、トリプロピレングリコール２３重量％の耐熱性ポリマー溶液を作製し、このポリオレフィン微多孔膜の先駆体の両面に引き続き供給して塗工する。
ついで、かかる塗工された膜をＮ−メチル−２−ピロリドン４０重量％、トリプロピレングリコール１０重量％、水５０重量％の凝固液に両面が接するように浸漬する。更に水洗・脱水を行う。
ついで、塩化メチレンによる当該膜中からのパラフィンワックスと流動パラフィン混合物の抽出を行う。塩化メチレンによる洗浄を経て乾燥する。ポリオレフィン微多孔膜の両面が耐熱性ポリマーのポリメタフェニレンイソフタルアミド多孔質層で被覆されている耐熱性複合ポリオレフィン微多孔膜を得る。
得られた耐熱性複合オレフィン微多孔膜の特性を表１に示す。[Example 1]
A precursor A of a microporous polyolefin membrane obtained by injecting a heated mixture of paraffin wax having a melting point of 58 ° C. and liquid paraffin into polyethylene melted by a biaxial extruder, stretching in biaxial directions and cooling is obtained. Preparing a heat-resistant polymer solution of 7% by weight of polymetaphenylene isophthalamide (intrinsic viscosity 1.6), 66% by weight of N-methyl-2-pyrrolidone, 4% by weight of ethylene propionate, and 23% by weight of tripropylene glycol; The polyolefin microporous membrane is subsequently supplied and coated on both sides of the precursor of the polyolefin microporous membrane.
Then, the coated film is immersed in a coagulating liquid of 40% by weight of N-methyl-2-pyrrolidone, 10% by weight of tripropylene glycol, and 50% by weight of water so that both surfaces are in contact with each other. Further washing and dehydration are performed.
Next, the mixture of paraffin wax and liquid paraffin is extracted from the membrane with methylene chloride. Dry after washing with methylene chloride. A heat resistant composite polyolefin microporous membrane is obtained in which both surfaces of the polyolefin microporous membrane are coated with a polymetaphenylene isophthalamide porous layer of a heat resistant polymer.
Table 1 shows the characteristics of the obtained heat-resistant composite olefin microporous membrane.
［実施例２］
２軸押出機で溶融したポリエチレンに融点５８℃を有するパラフィンワックスと流動パラフィンの加熱混合物を注入し、２軸方向に延伸して冷却して得られた実施例１と同じポリオレフィン微多孔膜の先駆体Ａを得る。パラフェニレンジアミン０．８モル、メタフェニレンジアミン０．２モルとテレフタル酸ジクロライド０．７９モル、イソフタル酸ジクロライド０．２０モルから得られた共重合体の耐熱性ポリマー（極限粘度１．４）１．３重量％、Ｎ−メチル−２−ピロリドン７４．７重量％、エチレンプロピオネート２重量％、トリプロピレングリコール２２重量％の耐熱性ポリマー溶液を作製し、このポリオレフィン微多孔膜の先駆体Ａの両面に供給して塗工する。
ついで、かかる塗工された膜をＮ−メチル−２−ピロリドン４０重量％、トリプロピレングリコール１０重量％、水５０重量％の凝固液に両面が接するように浸漬する。更に水洗・脱水を行う。
ついで、塩化メチレンによる当該膜中からのパラフィンワックスと流動パラフィン混合物の抽出を行う。塩化メチレンによる洗浄を経て乾燥する。ポリオレフィン微多孔膜の両面が当該共重合体の耐熱性ポリマー多孔質層で被覆されている耐熱性複合ポリオレフィン微多孔膜を得る。
得られた耐熱性複合ポリオレフィン微多孔膜の特性を表１に示す。
なお、実施例１、実施例２に使用したポリオレフィン微多孔膜の先駆体Ａを別途、塩化メチレンによりパラフィンワックスと流動パラフィン混合物の抽出を行い、塩化メチレンによる洗浄を経て乾燥して得たポリオレフィン微多孔膜の特性を参考例１として表１に示す。[Example 2]
A precursor of the same polyolefin microporous membrane as in Example 1 obtained by injecting a heated mixture of paraffin wax having a melting point of 58 ° C. and liquid paraffin into polyethylene melted by a biaxial extruder, stretching in biaxial directions and cooling. Obtain body A. Heat-resistant polymer of copolymer obtained from 0.8 mol of paraphenylenediamine, 0.2 mol of metaphenylenediamine, 0.79 mol of terephthalic acid dichloride, and 0.20 mol of isophthalic acid dichloride (intrinsic viscosity 1.4) 1 A precursor A of this polyolefin microporous membrane was prepared by preparing a heat-resistant polymer solution of 3 wt%, N-methyl-2-pyrrolidone 74.7 wt%,
Then, the coated film is immersed in a coagulating liquid of 40% by weight of N-methyl-2-pyrrolidone, 10% by weight of tripropylene glycol, and 50% by weight of water so that both surfaces are in contact with each other. Further washing and dehydration are performed.
Next, the mixture of paraffin wax and liquid paraffin is extracted from the membrane with methylene chloride. Dry after washing with methylene chloride. A heat-resistant composite polyolefin microporous membrane in which both surfaces of the polyolefin microporous membrane are coated with the heat-resistant polymer porous layer of the copolymer is obtained.
Table 1 shows the characteristics of the obtained heat-resistant composite polyolefin microporous membrane.
The polyolefin microporous membrane precursor A used in Example 1 and Example 2 was separately extracted by extracting a mixture of paraffin wax and liquid paraffin with methylene chloride, drying with methylene chloride, and drying. The characteristics of the porous membrane are shown in Table 1 as Reference Example 1.
［実施例３］
表１の参考例２に示すポリオレフィン微多孔膜に６０℃で溶融してある融点４７℃のパラフィンワックスを含浸し、乾燥する。塩化メチレンで塗工膜表面を洗浄して乾燥する。かかる塗膜をポリメタフェニレンイソフタルアミド８重量％、Ｎ−メチル−２−ピロリドン６６重量％、エチレンカーボネート５重量％、トリプロピレングリコール２１重量％の耐熱性ポリマー溶液を作製し、このあらかじめパラフィンワックスにより気孔が抱埋されているポリオレフィン微多孔膜の両面に供給して塗工する。
ついで、かかる塗工された膜をＮ−メチル−２−ピロリドン４０重量％、トリプロピレングリコール１０重量％、水５０重量％の凝固液に両面が接するように浸漬する。更に水洗・脱水を行う。
ついで、塩化メチレンによる当該膜中からのパラフィンワックスの抽出を行い、さらに塩化メチレンによる仕上げ洗浄を経て乾燥する。ポリオレフィン微多孔膜の両面が耐熱性ポリマーのポリメタフェニレンイソフタルアミド多孔質層で被覆されている耐熱性複合ポリオレフィン微多孔膜を得る。
得られた耐熱性複合ポリオレフィン微多孔膜の特性を表１に示す。[Example 3]
A polyolefin microporous membrane shown in Reference Example 2 in Table 1 is impregnated with paraffin wax having a melting point of 47 ° C. melted at 60 ° C. and dried. The coated film surface is washed with methylene chloride and dried. A heat-resistant polymer solution of 8% by weight of polymetaphenylene isophthalamide, 66% by weight of N-methyl-2-pyrrolidone, 5% by weight of ethylene carbonate, and 21% by weight of tripropylene glycol was prepared from this coating film. Supply is applied to both sides of the polyolefin microporous membrane in which the pores are embedded.
Then, the coated film is immersed in a coagulating liquid of 40% by weight of N-methyl-2-pyrrolidone, 10% by weight of tripropylene glycol, and 50% by weight of water so that both surfaces are in contact with each other. Further washing and dehydration are performed.
Subsequently, the paraffin wax is extracted from the film with methylene chloride, and is further dried after finishing washing with methylene chloride. A heat resistant composite polyolefin microporous membrane is obtained in which both surfaces of the polyolefin microporous membrane are coated with a polymetaphenylene isophthalamide porous layer of a heat resistant polymer.
Table 1 shows the characteristics of the obtained heat-resistant composite polyolefin microporous membrane.
［実施例４］
表１の参考例２に示すポリオレフィン微多孔膜にポリ（２，６‐ジメチルー１，４−フェニレンエーテル）粉末をトルエンに溶解した溶液を含浸し、乾燥する。塩化メチレンで塗工膜表面を洗浄して乾燥する。かかる塗膜をポリメタフェニレンイソフタルアミド（極限粘度１．１）８重量％、Ｎ−メチル−２−ピロリドン６６重量％、エチレンカーボネート５重量％、トリプロピレングリコール２１重量％の耐熱性ポリマー溶液を作製し、このあらかじめポリ（２，６‐ジメチルー１，４−フェニレンエーテル）により気孔が抱埋されているポリオレフィン微多孔膜の両面に供給して塗工する。
ついで、かかる塗工された膜をＮ−メチル−２−ピロリドン４０重量％、トリプロピレングリコール１０重量％、水５０重量％の凝固液に両面が接するように浸漬する。更に水洗・脱水を行う。
ついで、トルエンによる当該膜中からのポリ（２，６‐ジメチルー１，４−フェニレンエーテル）の抽出を行い、さらに塩化メチレンに仕上げ抽出を行い、塩化メチレンによる洗浄を経て乾燥する。ポリオレフィン微多孔膜の両面が耐熱性ポリマーのポリメタフェニレンイソフタルアミド多孔質層で被覆されている耐熱性複合オレフィン微多孔膜を得る。
得られた耐熱性複合ポリオレフィン微多孔膜の特性を表１に示す。[Example 4]
A polyolefin microporous membrane shown in Reference Example 2 in Table 1 is impregnated with a solution of poly (2,6-dimethyl-1,4-phenylene ether) powder in toluene and dried. The coated film surface is washed with methylene chloride and dried. A heat resistant polymer solution of 8% by weight of polymetaphenylene isophthalamide (ultimate viscosity 1.1), 66% by weight of N-methyl-2-pyrrolidone, 5% by weight of ethylene carbonate, and 21% by weight of tripropylene glycol was prepared from this coating film. Then, it is supplied and coated on both surfaces of the polyolefin microporous film in which pores are embedded in advance with poly (2,6-dimethyl-1,4-phenylene ether).
Then, the coated film is immersed in a coagulating liquid of 40% by weight of N-methyl-2-pyrrolidone, 10% by weight of tripropylene glycol, and 50% by weight of water so that both surfaces are in contact with each other. Further washing and dehydration are performed.
Next, poly (2,6-dimethyl-1,4-phenylene ether) is extracted from the film with toluene, and further extracted into methylene chloride, washed with methylene chloride, and dried. A heat-resistant composite olefin microporous film in which both surfaces of the polyolefin microporous film are coated with a polymetaphenylene isophthalamide porous layer of a heat-resistant polymer is obtained.
Table 1 shows the characteristics of the obtained heat-resistant composite polyolefin microporous membrane.
［実施例５］
２軸押出機で溶融したポリエチレンにフタル酸ジオクチルを注入し、２軸方向に延伸して冷却して得られたポリオレフィン微多孔膜の先駆体Ｂを得る。ポリメタフェニレンイソフタルアミド（極限粘度１．４）７重量％、Ｎ−メチル−２−ピロリドン６６重量％、エチレンカーボネート６重量％、トリプロピレングリコール２１重量％の耐熱性ポリマー溶液を作製し、このポリオレフィン微多孔膜の先駆体Ｂの両面に供給して塗工する。
ついで、かかる塗工された膜をＮ−メチル−２−ピロリドン４０重量％、トリプロピレングリコール１０重量％、水５０重量％の凝固液に両面が接するように浸漬する。更に水洗・脱水を行う。
ついで、塩化メチレンによる当該膜中からのフタル酸ジオクチルの抽出を行う。塩化メチレンによる洗浄を経て乾燥する。ポリオレフィン微多孔膜の両面が耐熱性ポリマーのポリメタフェニレンイソフタルアミド多孔質層で被覆されている耐熱性複合ポリオレフィン微多孔膜を得る。
得られた耐熱性複合ポリオレフィン微多孔膜の特性を表１に示す。なお実施例５に使用したポリオレフィン微多孔膜の先駆体Ｂを別途、塩化メチレンによりフタル酸ジオクチルの抽出を行い、塩化メチレンによる洗浄を経て乾燥して得たポリオレフィン微多孔膜の特性を参考例３として表１に示す。[Example 5]
A precursor B of a polyolefin microporous membrane obtained by injecting dioctyl phthalate into polyethylene melted by a biaxial extruder, stretching in biaxial directions and cooling is obtained. A heat-resistant polymer solution of 7% by weight of polymetaphenylene isophthalamide (intrinsic viscosity 1.4), 66% by weight of N-methyl-2-pyrrolidone, 6% by weight of ethylene carbonate and 21% by weight of tripropylene glycol was prepared. Supply to both sides of precursor B of the microporous membrane and apply.
Then, the coated film is immersed in a coagulating liquid of 40% by weight of N-methyl-2-pyrrolidone, 10% by weight of tripropylene glycol, and 50% by weight of water so that both surfaces are in contact with each other. Further washing and dehydration are performed.
Next, dioctyl phthalate is extracted from the membrane with methylene chloride. Dry after washing with methylene chloride. A heat resistant composite polyolefin microporous membrane is obtained in which both surfaces of the polyolefin microporous membrane are coated with a polymetaphenylene isophthalamide porous layer of a heat resistant polymer.
Table 1 shows the characteristics of the obtained heat-resistant composite polyolefin microporous membrane. In addition, the characteristic of the polyolefin microporous membrane obtained by extracting the precursor B of the polyolefin microporous membrane used in Example 5 separately from dioctyl phthalate with methylene chloride, washing with methylene chloride and drying is shown in Reference Example 3. As shown in Table 1.
［実施例６］
２軸押出機で溶融したポリエチレンに融点５８℃を有するパラフィンワックスと流動パラフィンの加熱混合物を注入し、２軸方向に延伸して冷却して得られたポリオレフィン微多孔膜の先駆体Ｃを得る。ポリメタフェニレンイソフタルアミド（極限粘度１．６）７重量％、Ｎ−メチル−２−ピロリドン６６重量％、エチレンプロピオネート４重量％、トリプロピレングリコール２３重量％の耐熱性ポリマー溶液を作製し、このポリオレフィン微多孔膜の先駆体の両面に引き続き供給して塗工する。
ついで、かかる塗工された膜をＮ−メチル−２−ピロリドン４０重量％、トリプロピレングリコール１０重量％、水５０重量％の凝固液に両面が接するように浸漬する。更に水洗・脱水を行う。
ついで、塩化メチレンによる当該膜中からのパラフィンワックスと流動パラフィン混合物の抽出を行う。塩化メチレンによる洗浄を経て乾燥する。ポリオレフィン微多孔膜の両面が耐熱性ポリマーのポリメタフェニレンイソフタルアミド多孔質層で被覆されている耐熱性複合ポリオレフィン微多孔膜を得る。
得られた耐熱性複合オレフィン微多孔膜の特性を表１に示す。なお実施例６に使用したポリオレフィン微多孔膜の先駆体Ｃを別途、塩化メチレンによりパラフィンワックスと流動パラフィン混合物の抽出を行い、塩化メチレンによる洗浄を経て乾燥して得たポリオレフィン微多孔膜の特性を参考例４として表１に示す。[Example 6]
A precursor C of a microporous polyolefin membrane obtained by injecting a heated mixture of paraffin wax having a melting point of 58 ° C. and liquid paraffin into polyethylene melted by a biaxial extruder, stretching in biaxial directions and cooling is obtained. Preparing a heat-resistant polymer solution of 7% by weight of polymetaphenylene isophthalamide (intrinsic viscosity 1.6), 66% by weight of N-methyl-2-pyrrolidone, 4% by weight of ethylene propionate, and 23% by weight of tripropylene glycol; The polyolefin microporous membrane is subsequently supplied and coated on both sides of the precursor of the polyolefin microporous membrane.
Then, the coated film is immersed in a coagulating liquid of 40% by weight of N-methyl-2-pyrrolidone, 10% by weight of tripropylene glycol, and 50% by weight of water so that both surfaces are in contact with each other. Further washing and dehydration are performed.
Next, the mixture of paraffin wax and liquid paraffin is extracted from the membrane with methylene chloride. Dry after washing with methylene chloride. A heat resistant composite polyolefin microporous membrane is obtained in which both surfaces of the polyolefin microporous membrane are coated with a polymetaphenylene isophthalamide porous layer of a heat resistant polymer.
Table 1 shows the characteristics of the obtained heat-resistant composite olefin microporous membrane. The characteristics of the polyolefin microporous membrane obtained by extracting the precursor C of the microporous polyolefin membrane used in Example 6 separately from the mixture of paraffin wax and liquid paraffin with methylene chloride, washing with methylene chloride, and drying. It is shown in Table 1 as Reference Example 4.
［比較例１］
実施例１に使用したポリオレフィン微多孔膜の先駆体Ａを別途、塩化メチレンによりパラフィンワックスと流動パラフィン混合物の抽出を行い、塩化メチレンによる洗浄を経て乾燥して得たポリオレフィン微多孔膜の参考例１と同じポリオレフィン微多孔膜にポリメタフェニレンイソフタルアミド（極限粘度１．１）７重量％、Ｎ−メチル−２−ピロリドン６６重量％、エチレンカーボネート６重量％、トリプロピレングリコール２１重量％の耐熱性ポリマー溶液を作製し、このポリオレフィン微多孔膜の両面に供給して塗工する。
ついで、かかる塗工された膜をＮ−メチル−２−ピロリドン４０重量％、トリプロピレングリコール１０重量％、水５０重量％の凝固液に両面が接するように浸漬する。更に水洗・脱水・乾燥を行う。
得られた耐熱性複合ポリオレフィン微多孔膜の特性を表１に示す。[Comparative Example 1]
Reference Example 1 of a polyolefin microporous membrane obtained by separately extracting the precursor A of the microporous polyolefin membrane used in Example 1 from a mixture of paraffin wax and liquid paraffin with methylene chloride, washing with methylene chloride, and drying. Heat resistant polymer of 7% by weight of polymetaphenylene isophthalamide (ultimate viscosity 1.1), 66% by weight of N-methyl-2-pyrrolidone, 6% by weight of ethylene carbonate, 21% by weight of tripropylene glycol A solution is prepared and applied to both sides of the polyolefin microporous membrane.
Then, the coated film is immersed in a coagulating liquid of 40% by weight of N-methyl-2-pyrrolidone, 10% by weight of tripropylene glycol, and 50% by weight of water so that both surfaces are in contact with each other. Furthermore, it is washed with water, dehydrated and dried.
Table 1 shows the characteristics of the obtained heat-resistant composite polyolefin microporous membrane.
［比較例２］
参考例４に示すポリオレフィン微多孔膜にポリメタフェニレンイソフタルアミド（極限粘度１．６）６重量％、Ｎ−メチル−２−ピロリドン６７重量％、プロピレンカーボネート５重量％、トリプロピレングリコール２２重量％の耐熱性ポリマー溶液を作製し、このポリオレフィン微多孔膜の両面に供給して塗工する。
ついで、かかる塗工された膜をＮ−メチル−２−ピロリドン４０重量％、トリプロピレングリコール１０重量％、水５０重量％の凝固液に両面が接するように浸漬する。更に水洗・脱水・乾燥を行う。
得られた耐熱性複合ポリオレフィン微多孔膜の特性を表１に示す。[Comparative Example 2]
Polyolefin microporous membrane shown in Reference Example 4 having 6% by weight of polymetaphenylene isophthalamide (extreme viscosity 1.6), 67% by weight of N-methyl-2-pyrrolidone, 5% by weight of propylene carbonate, and 22% by weight of tripropylene glycol A heat-resistant polymer solution is prepared and supplied to both sides of the polyolefin microporous membrane for coating.
Then, the coated film is immersed in a coagulating liquid of 40% by weight of N-methyl-2-pyrrolidone, 10% by weight of tripropylene glycol, and 50% by weight of water so that both surfaces are in contact with each other. Furthermore, it is washed with water, dehydrated and dried.
Table 1 shows the characteristics of the obtained heat-resistant composite polyolefin microporous membrane.
本発明によれば高エネルギー密度化・高出力化・大型化した高性能なリチウムイオン二次電池に望まれるシャットダウン特性と耐熱性を兼ね備え、セパレータとして取り扱いやすい、リチウムイオン透過性に優れ、急速充放電特性の良好なリチウムイオン二次電池用セパレータとその製造方法の提供が可能となる。
１、２、ロール
３、溶剤抽出可能な物質で表裏に連通した孔を抱埋されているポリオレフィン微多孔膜
４、浸漬槽
５、耐熱性ポリマー溶液
５’、余剰耐熱性ポリマー溶液
６、接触式ブレード掻き落とし装置
７、８、ダイ
Ｌ、ロール間クリアランス1, 2,
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2012137847A1 (en) * | 2011-04-05 | 2012-10-11 | ダブル・スコープ株式会社 | Porous membrane and method for producing same |
| CN103531736A (en) * | 2013-10-27 | 2014-01-22 | 中国乐凯集团有限公司 | High-heat-resistance lithium-ion battery diaphragm and preparation method thereof |
| JPWO2016068286A1 (en) * | 2014-10-31 | 2017-04-27 | 株式会社東芝 | Nonaqueous electrolyte battery and battery pack |
| CN112538162A (en) * | 2019-09-20 | 2021-03-23 | 青岛蓝科途膜材料有限公司 | Modified aramid polymer, aramid film casting liquid, lithium battery diaphragm, preparation method and lithium battery |
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2009
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2012137847A1 (en) * | 2011-04-05 | 2012-10-11 | ダブル・スコープ株式会社 | Porous membrane and method for producing same |
| JP5062794B1 (en) * | 2011-04-05 | 2012-10-31 | ダブル・スコープ 株式会社 | Porous membrane and method for producing the same |
| CN103531736A (en) * | 2013-10-27 | 2014-01-22 | 中国乐凯集团有限公司 | High-heat-resistance lithium-ion battery diaphragm and preparation method thereof |
| JPWO2016068286A1 (en) * | 2014-10-31 | 2017-04-27 | 株式会社東芝 | Nonaqueous electrolyte battery and battery pack |
| EP3214689A4 (en) * | 2014-10-31 | 2018-05-02 | Kabushiki Kaisha Toshiba | Nonaqueous electrolyte battery and battery pack |
| EP3474365A1 (en) * | 2014-10-31 | 2019-04-24 | Kabushiki Kaisha Toshiba | Positive electrode and electrode group comprising the positive electrode |
| US10541398B2 (en) | 2014-10-31 | 2020-01-21 | Kabushiki Kaisha Toshiba | Nonaqueous electrolyte battery, battery pack and positive electrode |
| US11362398B2 (en) | 2014-10-31 | 2022-06-14 | Kabushiki Kaisha Toshiba | Nonaqueous electrolyte battery, battery pack and positive electrode |
| CN112538162A (en) * | 2019-09-20 | 2021-03-23 | 青岛蓝科途膜材料有限公司 | Modified aramid polymer, aramid film casting liquid, lithium battery diaphragm, preparation method and lithium battery |
| CN112538162B (en) * | 2019-09-20 | 2023-10-31 | 青岛蓝科途膜材料有限公司 | Modified aramid polymer, aramid film casting solution, lithium battery diaphragm, preparation method and lithium battery |
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