JP3742256B2 - Method for producing separator for alkaline battery and method for producing alkaline battery - Google Patents
Method for producing separator for alkaline battery and method for producing alkaline battery Download PDFInfo
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- JP3742256B2 JP3742256B2 JP25390999A JP25390999A JP3742256B2 JP 3742256 B2 JP3742256 B2 JP 3742256B2 JP 25390999 A JP25390999 A JP 25390999A JP 25390999 A JP25390999 A JP 25390999A JP 3742256 B2 JP3742256 B2 JP 3742256B2
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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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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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Description
【０００１】
【発明の属する技術分野】
本発明は、ニッケル・カドミウム電池やニッケル水素（金属水素化物）電池などのアルカリ電池およびそのセパレ−タの改良に関するものである。
【０００２】
【従来の技術】
近年、エレクトロニクスや通信の分野において、半導体の急速な進歩とともに電子機器の小型軽量化が図られてきたが、その進歩に伴って駆動源である電池の高性能化が求められている。これら用途で現在実用化されている電池として、ニッケル・カドミウム電池やニッケル水素電池などのアルカリ電池がある。アルカリ電池は負極と正極との間にセパレ−タを介在させ、電解液としてアルカリ水溶液を用いて構成されるが、電池のさらなる高性能化や低価格化を目指して、積極的にこれら構成材料の技術開発が展開されている。中でも、セパレ−タ技術の重要性が増してきている。
【０００３】
従来からアルカリ電池用セパレ−タとして、電解液への親水性や保液性に優れたポリアミド不織布であるナイロン・セパレ−タが主に用いられてきた。しかしながら、ポリアミド系セパレ−タは耐アルカリ性や耐酸化性に問題があり、高温下で電池が使用された場合、ナイロン繊維が容易に酸化分解されて劣化し、電池の短絡や内部抵抗の増大をきたしたり、分解生成物である窒素化合物が原因となり、電池の自己放電を加速するなどの欠点がある。
【０００４】
そこで、ポリアミド系不織布に代えて、耐アルカリ性や耐酸化性に優れたポリオレフィン系不織布がアルカリ電池、特にニッケル水素電池のセパレ−タとして適用されている。しかしながら、ポリプロピレンやポリエチレンに代表されるポリオレフィン繊維は本質的に疎水性であるために、電解液への親水性や保液性をいかに永続的に付与するかが大きな技術課題となっている。
【０００５】
現在主流の親水化方法の一つとして、ポリオレフィン繊維の表面に、アクリル酸などのビニルモノマ−をグラフ重合してカルボキシル基を導入するグラフト化処理がある。例えば、ビニルモノマ−と重合開始剤を含む溶液中に不織布を浸漬し加熱処理する方法や、不織布に電子線などを照射した後にビニルモノマ−溶液に接触させるか、光増感剤を含むビニルモノマ−溶液に不織布を含浸した後に紫外線照射する方法によってグラフト化されている。しかしながら、いずれも液相ラジカル反応系であるために、グラフト処理後に未反応モノマ−や溶媒の除去、副反応生成物であるホモポリマ−の除去などの工程が必要であり、製造法が煩雑であること、また、不織布の表層部での反応が起こり易く内部まで均一に極性基を導入できないこと、繊維表面にビニルモノマ−が枝状に重合付加されるために、不織布基布の目付量の増大や通気度の低下を伴い、品質制御や薄型化が困難であること等の問題があり、従来のグラフト重合法に替わる製造工程の簡素な品質制御が容易なカルボン酸基を不織布に導入する親水化技術が強く望まれている。
【０００６】
【発明が解決しようとする課題】
本発明は上記の技術課題や問題点に鑑みてなされたものであり、その目的とするところは、ポリオレフィン系不織布にカルボキシル基を導入し親水化する技術において、親水性および保液性に優れ、且つ品質制御が容易で簡素な工程で製造可能なアルカリ電池用セパレ−タを提供するものである。
【０００７】
特に、電池の高エネルギ−密度化に対しては、電池容量とは無関係なセパレ−タの占有体積を極限まで削減しなければならず、セパレ−タの薄型化が不可欠となってきている。しかしながら、従来のグラフト重合法では、適正な親水性・保液性を得るにはグラフト率５〜１５重量％を要し、しかも繊維表面に枝状ポリマ−として付加するので、基布自体の目付量の増大に加えて厚み増加を伴う。そのため、所要のセパレ−タ（目付、厚さ）を得るには、より低目付のより薄い不織布を基布として用いる必要があり、セパレ−タ厚さとして０．１２ｍｍが限界となっている。
【０００８】
本発明は、図１に示すように、アクリル酸のグラフト重合法とは異なり、カルボキシル基のみを高分子の主鎖に付加するものであり、基布の特性を損なうことなく親水化可能なために、セパレータの薄型化が容易であり、電池の高エネルギー密度化対応の親水性に優れたポリオレフィン系の薄型セパレータを提供できるものである。
【０００９】
【課題を解決するための手段】
本発明は、上記目的を達成するために、分子構造中に炭素・水素（ＣＨ）結合を持つ高分子材料から構成され、該高分子材料を構成する高分子の主鎖にカルボキシル基のみを付加したアルカリ電池用セパレータの製造方法に係り、前記高分子材料を、塩化オキサリル〔（ＣＯＣｌ）2〕を含む反応ガス中にて、あるいは塩化オキサリルを含有させた状態にて、活性エネルギー線の照射下で処理してクロロカルボニル化した後、水により加水分解することでクロロカルボニル基をカルボキシル基に変換することを特徴とするアルカリ電池用セパレータの製造方法である。
【００１０】
前記反応ガスは主成分である塩化オキサリルと不活性ガスとの混合ガスであり、活性エネルギ−線が紫外線からなる紫外光である。
【００１１】
前記高分子材料は、ポリオレフィン系繊維の不織布、織布あるいは多孔性のポリオレフィン・フィルムである。
【００１２】
また、本発明は、正極と負極がセパレータを介して構成されるアルカリ電池の製造方法において、該セパレータが分子構造中に炭素・水素（ＣＨ）結合を持つ高分子材料から構成され、該高分子材料を構成する高分子の主鎖にカルボキシル基のみを付加したアルカリ電池用セパレータであって、前記高分子材料を、塩化オキサリル〔（ＣＯＣｌ）2〕を含む反応ガス中にて、あるいは塩化オキサリルを含有した状態にて、活性エネルギー線の照射下で処理してクロロカルボニル化した後、水により加水分解することでクロロカルボニル基をカルボキシル基に変換したセパレータを適用することを特徴とするアルカリ電池の製造方法である。
【００１３】
前記セパレ−タの基布はポリオレフィン系不織布であり、そのイオン交換能はカリウムのイオン交換量にして０．０２〜０．２ミリ当量／ｇ、通気度（透気度）が６〜３０ｃｃ／ｃｍ2 ／秒である。
【００１４】
【発明の実施の形態】
本発明は、炭化水素構造を持つ高分子材料から構成されるセパレ−タ基布を、▲１▼塩化オキサリルを含む反応ガス中にて、あるいは塩化オキサリルを含有させた状態にて、活性エネルギ−線の照射下で処理して、クロロカルボニル化した後に、▲２▼水で加水分解してカルボキシル基に変換し、親水化するものである。▲１▼の反応は、次式に示すように、気相での光化学反応であるので、セパレ−タ基布の形状を維持した状態で処理することが可能であり、基布の表面のみならず内部にまで均一に極性基を導入することができる。
【００１５】
Ｒ−Ｈ＋ (ＣＯＣｌ)2 → Ｒ−ＣＯＣｌ＋ＣＯ＋ＨＣｌ
ｈν
塩化オキサリル〔（ＣＯＣｌ）2 〕は、沸点６３℃の常温で液体の化合物であり、高い蒸気圧を持つため気相での常圧処理が容易であり、また、高分子材料を浸漬することで容易に塩化オキサリルを含有させることができる。反応ガスとしては、塩化オキサリルと窒素、アルゴン、ヘリウムなどの不活性ガスとの混合気体が望ましい。また、活性エネルギ−線としては、Ｘ線や電子線などが使用できるが、紫外線からなる紫外光が最も好ましい。
【００１６】
クロロカルボニル化の導入量は、即ち最終的にはカルボン酸基の導入量は、反応ガス中の塩化オキサリルの濃度や基布との接触時間を調整することで容易に制御できる。
【００１７】
高分子材料としては、ポリアミド、ポリビニルアルコ−ル、ポリエステル、ポリプロピレン、ポリエチレンなどや、これらの共重合体などから構成される不織布、織布、多孔性フィルムが適用される。特に、ニッケル水素電池用セパレ−タの基布としては、ポリオレフィン系繊維の不織布が適しており、目付量：３０〜１００ｇ／ｍ2 、厚さ：０．１〜０．３ｍｍ、通気度：６〜３０ｃｃ／ｃｍ2 ／秒の範囲のものが用いられる。
【００１８】
▲２▼の反応は、次式に示すような加水分解反応であり、前記のクロロカルボニル化したセパレ−タを水中に浸漬し、カルボン酸基とするものである。また、アルカリ水溶液中で処理してもよく、その場合には、アルカリ塩となる。
【００１９】
Ｒ−ＣＯＣｌ＋Ｈ2 Ｏ → Ｒ−ＣＯＯＨ＋ＨＣｌ
Ｒ−ＣＯＣｌ＋２ＫＯＨ → Ｒ−ＣＯＯＫ＋ＫＣｌ＋Ｈ2 Ｏ
アルカリ電池用セパレ−タとして充分な親水性を保持するには、イオン交換能が、カリウムのイオン交換量にして０．０２〜０．２ミリ当量／ｇの範囲であればよい。０．０２ミリ当量／ｇ未満では親水性・保液性が乏しく、０．２ミリ当量／ｇでほぼ反応が飽和し、それ以上の付加は基布の目付量の増大や通気度の低下を生じる。
【００２０】
このような本発明のセパレ−タは、親水性および保液性に優れるために、アルカリ電池、例えば、ニッケル・カドミウム電池、ニッケル水素電池、ニッケル亜鉛電池、空気亜鉛電池、アルカリマンガン電池などの１次電池および２次電池に適用した場合、長期にわたって安定した性能を持続することができるものである。
【００２１】
以下に、本発明のセパレ−タの実施例を記載するが、本発明はこれら実施例に限定されるものではない。
【００２２】
【実施例】
ポリオレフィン系繊維の不織布（厚さ０．１０ｍｍ，目付量４０ｇ／ｍ2 ）を基布として、図２に示すような装置を用いて、ガラス製の反応容器内に収容した後に、塩化オキサリルと乾燥窒素ガスの混合気体を常圧下で反応容器内に導入し、高圧水銀灯（３００Ｗ）の硫酸銅水溶液透過光（３６６ｎｍ）を照射して、クロロカルボニル化を行った。同処理は、浸漬によって塩化オキサリル液を含有させた基布を用いても同様であった。クロロカルボニル化率は反応時間（光量子数）を変えることで調整した。一例を図３に示す。その後、クロロカルボニル化した基布を、水に浸漬し加水分解し、カルボキシル基に変換し、アルカリ電池用セパレ−タを作製した。ここでは、ポリオレフィン系繊維の不織布として、ポリプロピレンとポリエチレンからなる複合分割型繊維を湿式抄造し水流絡合して作製したものを用いた。
【００２３】
こうして得られたセパレ−タは、そのイオン交換能が０．０２〜０．２ミリ当量／ｇの範囲において、親水性および保液性に優れるが、０．０２ミリ当量／ｇ未満ではアルカリ電解液の吸液速度が遅く、且つ保液率が低下した。本発明のセパレ−タの代表的特性値を表１に示す。
【００２４】
【表１】
本発明セパレ−タの親水持続性を見るために、７モル／ｌのＫＯＨ水溶液中で８０℃にて３ケ月間浸漬した後のイオン交換量を調べた。イオン交換量の低下はほとんど認められず、親水性は持続されることがわかった。
【００２６】
次に、このセパレ−タを用いて円筒型密閉式ニッケル水素電池を作製して性能評価した。正極には、９５％多孔度のニッケル繊維あるいは発泡状基板に水酸化ニッケルを主成分とした活物質を充填し、所定の寸法・厚みとしたニッケル電極を用いた。また、負極には、ＭｍＮｉＣｏＡｌＭｎの５元系の希土類系水素吸蔵合金粉末に導電剤とバインダ−を混合してペ−スト状とし、穿孔鋼板に塗布した後に、所定の寸法・厚みとした水素吸蔵合金電極を用いた。これら正極と負極を前記セパレ−タを介して渦巻状に巻いて、電槽に挿入し、７モル／ｌのＫＯＨ水溶液を電解液として注液した後に、封口・密閉してＡＡサイズ電池を作製した。比較例として、従来のナイロンセパレ−タおよびアニオン系界面活性剤にて処理したポリオレフィン系不織布をそれぞれ用いて前記と同様の電池を作製した。本発明電池と比較電池の温度４５℃での寿命特性を図４に示す。ナイロンセパレ−タおよび界面活性剤処理セパレ−タを使用した電池は早期に容量低下を来したのに対して、本発明セパレ−タ使用電池は良好な特性を示した。電池を解体してセパレ−タを調べたところ、ナイロンセパレ−タは酸化分解し短繊維化しており、界面活性剤処理セパレ−タは親水性および保液性の低下が見られ電気抵抗が著しく増大していた。本発明セパレ−タは初期と同様の親水性、保液性、イオン交換量を保持しており、劣化はほとんど認められなかった。
【００２７】
また、電池の容量保持特性においても、本発明セパレ−タの優位性が認められた。４５℃にて１４日間放置後の容量保持率は、ナイロンセパレ−タ使用電池では３３％、本発明セパレ−タ使用電池では７２％であり、本発明セパレ−タはニッケル水素電池の自己放電を抑制する効果を合わせ持つことがわかった。
【００２８】
【発明の効果】
以上のように、本発明によれば、ポリオレフィン系不織布あるいは多孔性のポリオレフィンフィルムを塩化オキサリルの光化学反応にてクロロカルボニル化してカルボキシル基を導入するという簡素な製造工程にて、親水性に優れた高エネルギ−密度対応の薄型セパレ−タが作製可能となり、寿命や容量保持性に優れたアルカリ電池を提供できるものである。
【図面の簡単な説明】
【図１】本発明とグラフト重合法の分子構造の模式図である。
【図２】本発明によるクロロカルボニル化反応装置の概略図である。
【図３】本発明におけるセパレータのイオン交換量と反応時間との関係図である。
【図４】本発明電池と比較電池の温度４５℃での寿命特性図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an alkaline battery such as a nickel-cadmium battery or a nickel hydride (metal hydride) battery and an improvement of the separator.
[0002]
[Prior art]
In recent years, in the fields of electronics and communication, electronic devices have been reduced in size and weight with the rapid progress of semiconductors. With the progress, higher performance of a battery as a driving source is required. Batteries currently in practical use for these applications include alkaline batteries such as nickel / cadmium batteries and nickel metal hydride batteries. Alkaline batteries are composed of a separator between the negative electrode and the positive electrode, and an alkaline aqueous solution is used as the electrolytic solution. However, these components are actively used in order to achieve higher performance and lower price of the battery. Technology development is being developed. Above all, the importance of the separator technology is increasing.
[0003]
Conventionally, as a separator for an alkaline battery, a nylon separator, which is a polyamide nonwoven fabric excellent in hydrophilicity and liquid retention to an electrolytic solution, has been mainly used. However, polyamide separators have problems with alkali resistance and oxidation resistance. When batteries are used at high temperatures, nylon fibers are easily oxidized and degraded, resulting in short circuits and increased internal resistance. There are drawbacks such as accelerating the self-discharge of the battery due to the nitrogen compounds as decomposition products and the nitrogen compounds.
[0004]
Therefore, in place of the polyamide-based nonwoven fabric, a polyolefin-based nonwoven fabric excellent in alkali resistance and oxidation resistance is applied as a separator for alkaline batteries, particularly nickel-metal hydride batteries. However, since polyolefin fibers typified by polypropylene and polyethylene are essentially hydrophobic, how to permanently impart hydrophilicity and liquid retention to an electrolytic solution is a major technical issue.
[0005]
As one of the mainstream hydrophilization methods, there is a grafting treatment in which a vinyl monomer such as acrylic acid is graph-polymerized to introduce a carboxyl group on the surface of a polyolefin fiber. For example, a method of immersing a non-woven fabric in a solution containing a vinyl monomer and a polymerization initiator and heat-treating, or irradiating the non-woven fabric with an electron beam or the like, or bringing it into contact with the vinyl monomer solution, It is grafted by a method in which a nonwoven fabric is impregnated and then irradiated with ultraviolet rays. However, since both are liquid phase radical reaction systems, steps such as removal of unreacted monomer and solvent and removal of homopolymer as a side reaction product after grafting are necessary, and the production method is complicated. In addition, the reaction at the surface layer portion of the nonwoven fabric is likely to occur, and the polar group cannot be uniformly introduced to the inside, and the vinyl monomer is polymerized and added to the fiber surface in a branch shape. Hydrophilization that introduces carboxylic acid groups into the nonwoven fabric, which has problems such as difficulty in quality control and thinning, accompanied by a decrease in air permeability, and easy quality control in the manufacturing process replacing the conventional graft polymerization method Technology is highly desired.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above technical problems and problems, and the object thereof is excellent in hydrophilicity and liquid retention in a technology for introducing a carboxyl group into a polyolefin-based nonwoven fabric to make it hydrophilic. The present invention also provides a separator for an alkaline battery that can be manufactured in a simple process with easy quality control.
[0007]
In particular, to increase the energy density of a battery, the occupied volume of the separator, which is irrelevant to the battery capacity, must be reduced to the utmost limit, and it is indispensable to reduce the thickness of the separator. However, the conventional graft polymerization method requires a graft ratio of 5 to 15% by weight to obtain appropriate hydrophilicity and liquid retention, and is added as a branched polymer to the fiber surface. In addition to the increase in quantity, there is an increase in thickness. Therefore, in order to obtain a required separator (weight per unit area, thickness), it is necessary to use a thinner non-woven fabric as a base fabric, and the separator thickness is limited to 0.12 mm.
[0008]
The present invention, as shown in FIG. 1, different from the graft polymerization of acrylic acid, which adds only carboxyl group in the main chain of high-molecular, capable hydrophilic without compromising the properties of the base fabric Therefore, it is easy to make the separator thin, and it is possible to provide a polyolefin-based thin separator excellent in hydrophilicity for high energy density of the battery.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a polymer material having a carbon / hydrogen (CH) bond in the molecular structure, and only a carboxyl group is present in the main chain of the polymer constituting the polymer material. Irradiation of active energy rays in a method for producing an added alkaline battery separator , wherein the polymer material is irradiated in a reaction gas containing oxalyl chloride [(COCl) 2 ] or containing oxalyl chloride. A method for producing a separator for an alkaline battery, characterized in that a chlorocarbonyl group is converted to a carboxyl group by hydrolyzing with water after being treated with chlorocarbonyl under treatment.
[0010]
The reaction gas is a mixed gas of oxalyl chloride as a main component and an inert gas, and the active energy ray is ultraviolet light composed of ultraviolet light.
[0011]
The polymer material is a polyolefin-based non-woven fabric, woven fabric, or porous polyolefin film.
[0012]
Further, the present invention provides a method for producing an alkaline battery in which a positive electrode and a negative electrode are interposed via a separator, wherein the separator is composed of a polymer material having a carbon / hydrogen (CH) bond in the molecular structure , A separator for an alkaline battery in which only a carboxyl group is added to a main chain of a polymer constituting a molecular material, wherein the polymer material is used in a reaction gas containing oxalyl chloride [(COCl) 2 ] or oxalyl chloride. An alkaline battery characterized by applying a separator in which a chlorocarbonyl group is converted to a carboxyl group by hydrolyzing with water after treatment with irradiation of active energy rays in a state of containing chlorocarbonyl. It is a manufacturing method .
[0013]
The separator base fabric is a polyolefin nonwoven fabric, and its ion exchange capacity is 0.02 to 0.2 meq / g in terms of potassium ion exchange, and the air permeability (air permeability) is 6 to 30 cc / cm 2 / sec.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a separator base fabric composed of a polymer material having a hydrocarbon structure is used in (1) a reaction gas containing oxalyl chloride or in a state containing oxalyl chloride. It is treated under irradiation of rays and chlorocarbonylated, and then hydrolyzed with water (2) to be converted into a carboxyl group to be hydrophilized. Since the reaction (1) is a photochemical reaction in the gas phase as shown in the following formula, it can be treated while maintaining the shape of the separator base fabric. The polar group can be uniformly introduced into the interior.
[0015]
R-H + (COCl) 2 → R-COCl + CO + HCl
hν
Oxalyl chloride [(COCl) 2 ] is a liquid compound at room temperature with a boiling point of 63 ° C., and since it has a high vapor pressure, it can be easily treated at atmospheric pressure in the gas phase. Oxalyl chloride can be easily contained. The reaction gas is preferably a mixed gas of oxalyl chloride and an inert gas such as nitrogen, argon, or helium. In addition, as the active energy ray, X-rays, electron beams and the like can be used, but ultraviolet light composed of ultraviolet rays is most preferable.
[0016]
The introduction amount of chlorocarbonylation, that is, the introduction amount of carboxylic acid groups can be easily controlled by adjusting the concentration of oxalyl chloride in the reaction gas and the contact time with the base fabric.
[0017]
As the polymer material, polyamide, polyvinyl alcohol, polyester, polypropylene, polyethylene and the like, and nonwoven fabrics, woven fabrics, and porous films composed of copolymers thereof are applied. In particular, as a base fabric of a separator for a nickel metal hydride battery, a polyolefin fiber non-woven fabric is suitable. The basis weight is 30 to 100 g / m 2 , the thickness is 0.1 to 0.3 mm, and the air permeability is 6 Those in the range of ˜30 cc / cm 2 / second are used.
[0018]
The reaction (2) is a hydrolysis reaction as shown in the following formula, wherein the chlorocarbonylated separator is immersed in water to form a carboxylic acid group. Moreover, you may process in alkaline aqueous solution, and become an alkali salt in that case.
[0019]
R-COCl + H 2 O → R-COOH + HCl
R-COCl + 2KOH → R-COOK + KCl + H 2 O
In order to maintain sufficient hydrophilicity as a separator for an alkaline battery, the ion exchange capacity may be in the range of 0.02 to 0.2 meq / g in terms of potassium ion exchange. If it is less than 0.02 meq / g, the hydrophilicity and liquid retention are poor, and if 0.2 meq / g, the reaction is almost saturated, and addition beyond this will increase the basis weight of the fabric and decrease the air permeability. Arise.
[0020]
Such a separator of the present invention is excellent in hydrophilicity and liquid retention, so that it can be used for alkaline batteries such as nickel cadmium batteries, nickel metal hydride batteries, nickel zinc batteries, air zinc batteries, alkaline manganese batteries and the like. When applied to a secondary battery and a secondary battery, stable performance can be maintained over a long period of time.
[0021]
Examples of the separator of the present invention will be described below, but the present invention is not limited to these examples.
[0022]
【Example】
A polyolefin-based nonwoven fabric (thickness: 0.10 mm, basis weight: 40 g / m 2 ) as a base fabric and housed in a glass reaction vessel using an apparatus as shown in FIG. 2, and then dried with oxalyl chloride. A mixed gas of nitrogen gas was introduced into the reaction vessel under normal pressure, and chlorocarbonylation was performed by irradiation with a copper sulfate aqueous solution transmitted light (366 nm) of a high-pressure mercury lamp (300 W). This treatment was the same even when a base fabric containing an oxalyl chloride solution by dipping was used. The chlorocarbonylation rate was adjusted by changing the reaction time (photon number). An example is shown in FIG. Thereafter, the chlorocarbonylated base fabric was immersed in water for hydrolysis and converted to a carboxyl group to produce a separator for an alkaline battery. Here, as the nonwoven fabric of polyolefin-based fibers, those prepared by wet papermaking and hydroentangling composite split fibers made of polypropylene and polyethylene were used.
[0023]
The separator thus obtained is excellent in hydrophilicity and liquid retention when the ion exchange capacity is in the range of 0.02 to 0.2 meq / g. The liquid absorption speed was slow, and the liquid retention rate decreased. Table 1 shows typical characteristic values of the separator of the present invention.
[0024]
[Table 1]
In order to observe the hydrophilic durability of the separator of the present invention, the amount of ion exchange after immersion in a 7 mol / l aqueous KOH solution at 80 ° C. for 3 months was examined. It was found that there was almost no decrease in the amount of ion exchange, and hydrophilicity was maintained.
[0026]
Next, using this separator, a cylindrical sealed nickel-metal hydride battery was produced and performance was evaluated. As the positive electrode, a nickel electrode having a predetermined size and thickness obtained by filling a 95% -porosity nickel fiber or a foamed substrate with an active material mainly composed of nickel hydroxide was used. The negative electrode is made of MmNiCoAlMn ternary rare earth hydrogen storage alloy powder mixed with a conductive agent and a binder to form a paste, which is applied to a perforated steel sheet, and then has a predetermined size and thickness. An alloy electrode was used. These positive electrode and negative electrode are spirally wound through the separator, inserted into the battery case, injected with 7 mol / l KOH aqueous solution as an electrolyte, and sealed and sealed to produce an AA size battery. did. As a comparative example, a battery similar to the above was produced using a polyolefin nonwoven fabric treated with a conventional nylon separator and an anionic surfactant, respectively. FIG. 4 shows the life characteristics of the battery of the present invention and the comparative battery at a temperature of 45 ° C. The battery using the nylon separator and the surfactant-treated separator had a capacity drop early, whereas the battery using the separator of the present invention showed good characteristics. When the battery was disassembled and the separator was examined, the nylon separator was oxidized and decomposed into short fibers, and the surfactant-treated separator showed a decrease in hydrophilicity and liquid retention, and the electrical resistance was remarkable. It was increasing. The separator of the present invention maintained the same hydrophilicity, liquid retention and ion exchange amount as in the initial stage, and almost no deterioration was observed.
[0027]
The superiority of the separator of the present invention was also recognized in the capacity retention characteristics of the battery. The capacity retention after standing for 14 days at 45 ° C. is 33% for the battery using the nylon separator and 72% for the battery using the separator of the present invention, and the separator of the present invention performs self-discharge of the nickel metal hydride battery. It turns out that it also has the inhibitory effect.
[0028]
【The invention's effect】
As described above, according to the present invention, a hydrophilic non-woven fabric or a porous polyolefin film is excellent in hydrophilicity by a simple production process in which a carboxyl group is introduced by chlorocarbonylation by photochemical reaction of oxalyl chloride. A thin separator compatible with high energy density can be produced, and an alkaline battery excellent in life and capacity retention can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of the molecular structure of the present invention and a graft polymerization method.
FIG. 2 is a schematic view of a chlorocarbonylation reaction apparatus according to the present invention.
FIG. 3 is a graph showing the relationship between the ion exchange amount of the separator and the reaction time in the present invention.
FIG. 4 is a life characteristic diagram of the battery of the present invention and a comparative battery at a temperature of 45 ° C.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25390999A JP3742256B2 (en) | 1999-09-08 | 1999-09-08 | Method for producing separator for alkaline battery and method for producing alkaline battery |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25390999A JP3742256B2 (en) | 1999-09-08 | 1999-09-08 | Method for producing separator for alkaline battery and method for producing alkaline battery |
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| Publication Number | Publication Date |
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| JP2001076705A JP2001076705A (en) | 2001-03-23 |
| JP3742256B2 true JP3742256B2 (en) | 2006-02-01 |
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| JP2006265452A (en) * | 2005-03-25 | 2006-10-05 | Kyoto Institute Of Technology | Method for modifying spherical polymer material by liquid-phase chemical reaction and modified spherical polymer material |
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