JP2004273306A

JP2004273306A - Manufacturing method of battery and separator used for the battery

Info

Publication number: JP2004273306A
Application number: JP2003063320A
Authority: JP
Inventors: Takuma Iida; 琢磨飯田; Naoyoshi Shibuya; 直慶渋谷; Hiroki Takeshima; 宏樹竹島
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-03-10
Filing date: 2003-03-10
Publication date: 2004-09-30
Anticipated expiration: 2023-03-10
Also published as: JP4443842B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery excellent in a self-discharging property, rich in hydrophilic property, and superior in discharging property. <P>SOLUTION: In the battery having an electrode group composed of a positive electrode plate, a negative electrode plate, and a separator sulfonated by hydrophilic treatment interposed between the electrodes, the ratio of SO<SB>4</SB>to SO<SB>3</SB>(SO<SB>4</SB>/SO<SB>3</SB>) of the sulfonic group in the sulfonated separator is made 0.4 to 2.5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電池の内部抵抗を低減し、特に電池の放電特性を向上させるものである。
【０００２】
【従来の技術】
近年、各種ポータブル型の電気機器の発達に伴い、その駆動電源となる電池が重要なキーデバイスの１つとして、その開発が重要視されている。その電池の中でも充電可能なニッケル−水素蓄電池やリチウムイオン電池といった二次電池は、携帯電話やノートパソコン等の駆動電源として高容量化が強く望まれている。
【０００３】
また、ニッケル−水素蓄電池をはじめとする水溶液系電池では、ハイレ−ト放電特性に優れている利点を生かして多セル直列使用によって高電圧化し、電動工具、電気自動車等の電源（パック）として用いられている。これらの直列使用による高電圧化電源（パック）では、パック内の電池容量バラツキが生じると電池が過充電しやすいため、寿命劣化しやすくなるという課題があった。
【０００４】
電池の容量バラツキには、初期電池の容量バラツキの他に、自己放電量のバラツキによる要因がある。このため自己放電によるバラツキを抑制するために自己放電特性に優れたセパレ−タを用いた電池が幅広く使用されている。これら自己放電に最も優れたセパレ−タとして、スルホン基をもつスルホン化セパレ−タが知られている（例えば、特許文献１参照）。
【０００５】
【特許文献１】
特開平０４−３６９５４号公報（第２頁）
【０００６】
【発明が解決しようとする課題】
しかしながら、スルホン基をもつスルホン化セパレ−タを電池に用いた場合、スルホン基の量を適性にしても、十分な親水性が得られず、電池の内部抵抗が高くなるという課題があった。
【０００７】
本発明は上記課題に鑑み、自己放電特性に優れ、かつ親水性に富み、内部抵抗が低く放電特性に優れた電池用セパレータを提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記目的を達成するために本発明は、正極板と、負極板と、その両者間に親水化処理としてスルホン化処理されたセパレータを配置した電極群を有する電池において、前記スルホン化処理されたセパレータ中のスルホン基のＳＯ_４とＳＯ_３の割合（ＳＯ_４／ＳＯ_３）が０．４〜２．５であるものとした。
【０００９】
これにより、自己放電特性に優れ、かつ親水性に優れ、内部抵抗も低いままで維持でき、なお且つ放電特性をも向上させることができる。
【００１０】
【発明の実施の形態】
本発明の請求項１記載の発明は、正極板と、負極板と、その両者間にスルホン化処理されたポリオレフィン系セパレータを配置した電極群を有する電池において、前記スルホン化処理されたセパレータ中のスルホン基のＳＯ_４とＳＯ_３の割合（ＳＯ_４／ＳＯ_３）が０．４〜２．５である電池とした。これは、セパレータ表面に存在するスルホン基のＳＯ_４／ＳＯ_３の割合が０．４〜２．５になることにより、セパレ−タの親水性が著しく向上することから内部抵抗が低減できるためである。
【００１１】
このセパレ−タに用いるポリオレフィン系繊維としては、ポリプロピレン、及びポリエチレンを主成分としており、さらにはこれらの混紡であってもかまわない。
【００１２】
また、前記セパレータの繊維径は３〜１５μｍであることが好ましい。これは、繊維径が３μｍより小さい場合、繊維強度が弱くなりすぎて不織布の強度が十分確保できなくなるためである。逆に繊維径が１５μｍより大きい場合は、細径分布が大きくなりすぎて、疎密が多くなり、電池の信頼性が低下するからである。
【００１３】
さらに、前記セパレータの平均細孔径は１０〜３０μｍであることが好ましい。前記セパレ−タの平均細孔径が１０μｍ未満の場合には、セパレ−タの通気性が低下し、電池内圧の上昇が大きかった。また平均細孔径が３０μｍを超えると、不織布の強度が低下し十分な信頼性を確保できなくなる。
【００１４】
【実施例】
次に、本発明の具体例について説明する。
【００１５】
（実施例１）
従来のセパレータとしては、ポリプロピレンの繊維表面をポリエチレンで混紡した１０μｍの繊維を水に分散してスラリーとし、このスラリーを湿式抄造法により抄紙してウェブを形成し、目付重量６４ｇ／ｍ^２の不織布を作製し、熱カレンダーロールによりセパレ−タの繊維がフィルム化しないようにセパレータの厚み調整を行った。これをスルホン化処理により、親水化処理を行った。スルホン化条件としては、ＳＯ_３ガスを１０％含む窒素ガスにより、室温で、３０秒処理を行った。これらをｐＨ１３のＮａＯＨ溶液のアルカリ槽で中和させ、その後、水洗・乾燥して、ＳＯ_４とＳＯ_３の割合（ＳＯ_４／ＳＯ_３）が１．０である本発明の実施例におけるセパレータ１を得た。スルホン化の時間を１５秒と６０秒に変更して、ＳＯ_４／ＳＯ_３が０．４のセパレータ２と、２．５のセパレ−タ３を得た。また比較のためにスルホン化の時間を４秒と１８０秒に変更してＳＯ_４／ＳＯ_３が０．１のセパレータ４と、３．０のセパレ−タ５を作製した。これらの物性を（表１）に示す。
【００１６】
【表１】

正極板は、発泡メタル基板に、水酸化ニッケルを主成分としてなる正極活物質ペーストを、後に集電体を溶接するための芯材露出部を設けて塗布させ、乾燥させた後、厚み０．５ｍｍになるまで圧延し、高さ４５ｍｍ、芯材露出幅１ｍｍ、長さ２００ｍｍになるように切断して作製した。
【００１７】
また、負極板は６０μｍのパンチングメタル芯材に水素吸蔵合金を主成分とする負極活物質ペーストを、後に集電体を溶接するための芯材露出部を設けて塗布・乾燥させた後、厚み０．３ｍｍになるまで圧延し、高さ４５ｍｍ、芯材露出幅１ｍｍ、長さ２４０ｍｍになるように切断して作製した。
【００１８】
上記のように作製した正極板と負極板との間に、（表１）に示したセパレータを介在させ、正極板の芯材が露出した部分を上方に、負極板の芯材の露出した部分を下方突出させながら巻回させて、高さ４７．２ｍｍの電極群Ｎｏ．１〜５を作製した。
【００１９】
ついで、上方の正極板の芯材露出部に正極集電体を溶接し、下方の負極板の芯材露出部に負極集電体を溶接する。集電体が溶接された電極群を上部が開口した電池ケースに収納し、注液前の電池Ｎｏ．１〜５を作製した。電池への注液は、比重１．３ｇ／ｃｃのＫＯＨを主成分とする電解液を遠心注液法を用いて、４ｃｃ注液した。
【００２０】
電池ケースの上部開口部を封口板で密閉してＡサイズ（標準容量２５００ｍＡｈ）の電池Ｎｏ．１〜５を組み立てた。これを周囲温度２５℃で１２時間放置後、初充放電（充電は０．１Ｉｔ（２５０ｍＡ）の電流値で１５時間、放電は０．２Ｉｔ（５００ｍＡ）の電流値で４時間）を行い、本発明のニッケル−水素蓄電池Ｎｏ．１〜３と比較の電池Ｎｏ．４〜５を得た。これらの電池を初充放電後に内部抵抗を測定した結果を（表２）に示す。
【００２１】
次に大電流放電特性の評価を行った。大電流放電特性の評価方法としては、１Ｉｔ（充電は２．６Ａ）の充電電流で１．２時間充電をした後、１０Ａの放電電流で放電終止電圧が０．８Ｖになるまで放電させて、放電時間から放電容量を算出して大電流放電容量とした。
【００２２】
次に自己放電特性の評価を行った。自己放電特性の評価方法としては、１Ｉｔ（充電は２．６Ａ）の充電電流で１．２時間充電をした後、１．０Ｉｔ（２．６Ａ）の放電電流で放電終止電圧が１．０Ｖになるまで放電させて、放電時間から放電容量を算出して初期容量とした。
【００２３】
この電池を１Ｉｔで１．２時間充電をして満充電した後に、４５℃の環境下で２週間放置した後、１．０Ｉｔ（２．６Ａ）の放電電流で放電終止電圧が１．０Ｖになるまで放電させて、放電時間から放電容量を算出して保存後の容量とした。
【００２４】
これらから容量維持率を算出し、自己放電特性の評価を行った。
【００２５】
容量維持率（％）＝保存後の容量／初期容量
上記の電池特性を（表２）に示す
【００２６】
【表２】

（表１）から明らかなようにＳＯ_４／ＳＯ_３の割合が０．４未満、又は２．５以上になると急減に内部抵抗が上昇しているのがわかる。このことから本発明の範囲内のセパレータを用いた電池であれば、内部抵抗は抑制できることが分かる。さらに内部抵抗が抑制できるため、１０Ａの放電容量も著しく向上している。
【００２７】
また、スルホン化したセパレ−タを用いることにより自己放電特性も容量維持率が高くなっている。
【００２８】
本発明のセパレ−タを用いた電池は、自己放電特性を確保しつつ、内部抵抗が抑制できるため大電流放電特性が著しく向上している。
【００２９】
これは、この２つの親水基構造が、両方とも４面体構造を有しているが、ＳＯ_３では、硫黄原子の電子構造が、３個の酸素原子と結合し、ｓｐ^３混成軌道のうち１隅を非共有電子対が占めるのに対し、ＳＯ_４は４個の酸素原子と結合して、ｓｐ^３混成軌道をとるため、イオンとしては安定な状態にある。ＳＯ_４基の方が安定なため、親水性に優れ、内部抵抗が低減したと推定している。
【００３０】
以上のことから、セパレータ表面に存在するスルホン基のＳＯ_４／ＳＯ_３の割合は０．４〜２．５であることが好ましい。
【００３１】
（実施例２）
同様な方法で、セパレ−タの繊維径を３〜１５μｍの範囲のものを用いてセパレ−タＮｏ．６〜９を作製した。これをスルホン化処理により、親水化処理を行い、スルホン化度（セパレ−タ中の硫黄とカ−ボンの割合（Ｓ／Ｃ）が０．００３で、ＳＯ_４とＳＯ_３の割合（ＳＯ_４／ＳＯ_３）が１．０になるように親水化処理を行った。これらの物性値を（表３）に示す。
【００３２】
【表３】

これらのセパレ−タを実施例１と同様な方法で電池Ｎｏ．６〜９を作製した。これらの電池の１Ｉｔ（２５００ｍＡ）で１２０％充電したときの電池内圧を測定した結果を（表４）に示す。
【００３３】
【表４】

上記の結果より、細孔径を小さくした電池の電池内圧は、高いことが分かる。
【００３４】
これらアルカリ蓄電池では、充電末期になると、正極で酸素発生反応が水酸化ニッケルの充電反応と競合して起こる。その際、発生したガスを負極での還元反応により消費させるために負極容量を正極容量に対して大きくして電池内の圧力を一定範囲内に保持する構成がとられている。この時、セパレ−タの通気性が低下すると正極で発生したガスを効率よく負極で消費することができなくなるため電池内圧が上昇する。通常細孔径が小さい場合、通気性が低下するため電池内圧は上昇する。
【００３５】
種々検討の結果、セパレータの繊維径としては３〜１５μｍ、細孔径としては、１０〜３０μｍであることが好ましいことがわかった。
【００３６】
【発明の効果】
正極板と、負極板と、その両者間に親水化処理としてスルホン化されたセパレータを配置した電極群を有する電池において、前記スルホン化されたセパレータ中のスルホン基のＳＯ_４とＳＯ_３の割合（ＳＯ_４／ＳＯ_３）を０．４〜２．５とすることにより、自己放電特性に優れ、放電特性に優れた電池が得られる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention reduces the internal resistance of a battery, and particularly improves the discharge characteristics of the battery.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the development of various types of portable electric devices, development of batteries as driving power sources has been regarded as important as one of the important key devices. Among these batteries, secondary batteries such as rechargeable nickel-hydrogen storage batteries and lithium-ion batteries are strongly desired to have high capacity as driving power sources for mobile phones, notebook computers and the like.
[0003]
In addition, in an aqueous battery such as a nickel-hydrogen storage battery, taking advantage of its excellent high-rate discharge characteristics, the voltage is increased by using multiple cells in series and used as a power source (pack) for electric tools, electric vehicles, and the like. Have been. In these high-voltage power supplies (packs) that are used in series, if the battery capacity in the pack varies, the battery is likely to be overcharged, and the life is likely to deteriorate.
[0004]
Battery capacity variations include factors due to variations in the amount of self-discharge in addition to variations in the initial battery capacity. For this reason, in order to suppress variations due to self-discharge, batteries using a separator having excellent self-discharge characteristics are widely used. As a separator excellent in such self-discharge, a sulfonated separator having a sulfone group is known (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-04-36954 (page 2)
[0006]
[Problems to be solved by the invention]
However, when a sulfonated separator having a sulfone group is used in a battery, there is a problem that even if the amount of the sulfone group is appropriate, sufficient hydrophilicity cannot be obtained and the internal resistance of the battery increases.
[0007]
In view of the above problems, an object of the present invention is to provide a battery separator having excellent self-discharge characteristics, high hydrophilicity, low internal resistance, and excellent discharge characteristics.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention relates to a battery having an electrode group in which a positive electrode plate, a negative electrode plate, and a separator that has been subjected to a sulfonation treatment as a hydrophilization treatment are disposed between both, wherein the sulfonated separator is provided. The ratio of SO ₄ and SO ₃ (SO ₄ / SO ₃ ) in the sulfone group in the sample was 0.4 to 2.5.
[0009]
Thereby, the self-discharge characteristics are excellent, the hydrophilicity is excellent, the internal resistance can be maintained at a low level, and the discharge characteristics can be improved.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The invention according to claim 1 of the present invention is directed to a battery having an electrode group in which a positive electrode plate, a negative electrode plate, and a sulfonated polyolefin-based separator are arranged between both, wherein the sulfonated separator contains A battery having a sulfone group ratio of SO ₄ to SO ₃ (SO ₄ / SO ₃ ) of 0.4 to 2.5 was obtained. This is because when the ratio of SO ₄ / SO ₃ of the sulfone group present on the separator surface becomes 0.4 to 2.5, the hydrophilicity of the separator is remarkably improved, and the internal resistance can be reduced. is there.
[0011]
The polyolefin-based fibers used in the separator are mainly composed of polypropylene and polyethylene, and may be a blend of these.
[0012]
Preferably, the fiber diameter of the separator is 3 to 15 μm. This is because, if the fiber diameter is smaller than 3 μm, the fiber strength becomes too weak and the strength of the nonwoven fabric cannot be sufficiently secured. Conversely, if the fiber diameter is larger than 15 μm, the fine diameter distribution becomes too large, the density increases, and the reliability of the battery decreases.
[0013]
Further, the separator preferably has an average pore diameter of 10 to 30 μm. When the average pore diameter of the separator was less than 10 μm, the gas permeability of the separator decreased, and the internal pressure of the battery increased significantly. On the other hand, if the average pore diameter exceeds 30 μm, the strength of the nonwoven fabric decreases, and sufficient reliability cannot be secured.
[0014]
【Example】
Next, a specific example of the present invention will be described.
[0015]
(Example 1)
As a conventional separator, a 10 μm fiber obtained by blending a polypropylene fiber surface with polyethylene is dispersed in water to form a slurry, and the slurry is made into a paper by a wet papermaking method to form a web, and a nonwoven fabric having a basis weight of 64 g / m ² is formed. Was prepared, and the thickness of the separator was adjusted by a hot calender roll so that the fiber of the separator did not turn into a film. This was subjected to a hydrophilization treatment by a sulfonation treatment. As a sulfonation condition, a treatment was performed for 30 seconds at room temperature with a nitrogen gas containing 10% of SO ₃ gas. These are neutralized in an alkaline bath of a NaOH solution having a pH of 13, and then washed with water and dried to obtain a separator 1 according to an embodiment of the present invention in which the ratio of SO ₄ to SO ₃ (SO ₄ / SO ₃ ) is 1.0. Got. By changing the sulfonation time to 15 seconds and 60 seconds, a separator 2 having an SO ₄ / SO ₃ of 0.4 and a separator ₃ of 2.5 were obtained. For comparison, the sulfonation time was changed to 4 seconds and 180 seconds to produce a separator 4 with SO ₄ / SO ₃ of 0.1 and a separator 5 with 3.0. These physical properties are shown in (Table 1).
[0016]
[Table 1]

The positive electrode plate is formed by applying a positive electrode active material paste containing nickel hydroxide as a main component to a foamed metal substrate, providing an exposed portion of a core material for welding a current collector later, and then drying the paste. It was rolled to 5 mm and cut to a height of 45 mm, a core exposed width of 1 mm, and a length of 200 mm.
[0017]
The negative electrode plate is coated with a negative electrode active material paste containing a hydrogen storage alloy as a main component on a 60 μm punched metal core material, provided with a core material exposed portion for welding a current collector later, and dried and then coated. It was rolled to 0.3 mm and cut to a height of 45 mm, a core exposed width of 1 mm, and a length of 240 mm.
[0018]
The separator shown in (Table 1) is interposed between the positive electrode plate and the negative electrode plate manufactured as described above, and the portion where the core material of the positive electrode plate is exposed is upward, and the portion where the core material of the negative electrode plate is exposed. Is wound while protruding downward, and the electrode group No. having a height of 47.2 mm is wound. 1 to 5 were produced.
[0019]
Next, the positive electrode current collector is welded to the exposed core material of the upper positive electrode plate, and the negative electrode current collector is welded to the exposed core material of the lower negative electrode plate. The electrode group to which the current collector was welded was housed in a battery case having an open top, and the battery No. before the injection was charged. 1 to 5 were produced. For injection into the battery, 4 cc of an electrolyte mainly containing KOH having a specific gravity of 1.3 g / cc was injected by a centrifugal injection method.
[0020]
The upper opening of the battery case was sealed with a sealing plate, and the A-size (standard capacity 2500 mAh) battery No. 1 to 5 were assembled. After leaving this at an ambient temperature of 25 ° C. for 12 hours, the first charge / discharge (charging for 15 hours at a current value of 0.1 It (250 mA) and discharging for 4 hours at a current value of 0.2 It (500 mA)) is performed. The nickel-hydrogen storage battery No. of the invention. Battery Nos. 4-5 were obtained. The results of measuring the internal resistance after initial charging and discharging of these batteries are shown in (Table 2).
[0021]
Next, large current discharge characteristics were evaluated. As a method for evaluating the large current discharge characteristics, the battery was charged at a charge current of 1 It (charging was 2.6 A) for 1.2 hours, and then discharged at a discharge current of 10 A until the discharge termination voltage reached 0.8 V. The discharge capacity was calculated from the discharge time to obtain a large current discharge capacity.
[0022]
Next, the self-discharge characteristics were evaluated. As a method for evaluating the self-discharge characteristics, after charging for 1.2 hours with a charging current of 1 It (charging is 2.6 A), the discharge end voltage is reduced to 1.0 V with a discharging current of 1.0 It (2.6 A). The discharge was performed until the discharge capacity was reached, and the discharge capacity was calculated from the discharge time to obtain the initial capacity.
[0023]
This battery was charged at 1 It for 1.2 hours, fully charged, and then allowed to stand at 45 ° C. for 2 weeks. After that, the discharge end voltage reached 1.0 V with a discharge current of 1.0 It (2.6 A). The discharge capacity was calculated until the discharge capacity was reached, and the discharge capacity was calculated from the discharge time to obtain the capacity after storage.
[0024]
From these, the capacity retention rate was calculated, and the self-discharge characteristics were evaluated.
[0025]
Capacity maintenance rate (%) = capacity after storage / initial capacity The above battery characteristics are shown in (Table 2).
[Table 2]

As is clear from (Table 1), when the ratio of SO ₄ / SO ₃ is less than 0.4 or 2.5 or more, the internal resistance increases rapidly. This indicates that the battery using the separator within the scope of the present invention can suppress the internal resistance. Further, since the internal resistance can be suppressed, the discharge capacity of 10 A is significantly improved.
[0027]
In addition, the use of a sulfonated separator has a high self-discharge characteristic and a high capacity retention rate.
[0028]
In the battery using the separator of the present invention, the internal resistance can be suppressed while the self-discharge characteristic is secured, so that the large-current discharge characteristic is remarkably improved.
[0029]
This is because the two hydrophilic group structures both have a tetrahedral structure, but in SO ₃ , the electronic structure of the sulfur atom is bonded to ^three oxygen atoms and one of the sp ³ hybrid orbitals. While the corner is occupied by a lone electron pair, SO ₄ is bonded to four oxygen atoms to form a sp ³ hybrid orbital, so that it is in a stable state as an ion. It is presumed that since the SO ₄ group is more stable, it has excellent hydrophilicity and the internal resistance is reduced.
[0030]
From the above, the ratio of SO ₄ / SO ₃ of the sulfone group present on the separator surface is preferably 0.4 to 2.5.
[0031]
(Example 2)
In the same manner, a separator having a fiber diameter of 3 to 15 .mu.m is used. Nos. 6 to 9 were produced. This is subjected to a hydrophilization treatment by a sulfonation treatment, and the degree of sulfonation (the ratio of sulfur to carbon in the separator (S / C) is 0.003, and the ratio of SO ₄ and SO ₃ (SO ₄ / SO ₃ ) was subjected to a hydrophilization treatment so as to be 1.0, and their physical property values are shown in (Table 3).
[0032]
[Table 3]

Using these separators in the same manner as in Example 1, the battery Nos. Nos. 6 to 9 were produced. The results of measuring the internal pressure of these batteries when they were charged at 120% at 1 It (2500 mA) are shown in Table 4 below.
[0033]
[Table 4]

From the above results, it can be seen that the battery internal pressure of the battery having a reduced pore diameter is high.
[0034]
In these alkaline storage batteries, at the end of charging, an oxygen generation reaction occurs at the positive electrode in competition with a charging reaction of nickel hydroxide. At that time, in order to consume the generated gas by the reduction reaction at the negative electrode, the capacity of the negative electrode is made larger than that of the positive electrode to maintain the pressure in the battery within a certain range. At this time, if the gas permeability of the separator decreases, the gas generated at the positive electrode cannot be efficiently consumed at the negative electrode, so that the internal pressure of the battery increases. Usually, when the pore diameter is small, the gas permeability decreases, and the internal pressure of the battery increases.
[0035]
As a result of various studies, it was found that the fiber diameter of the separator is preferably 3 to 15 μm, and the pore diameter is preferably 10 to 30 μm.
[0036]
【The invention's effect】
In a battery having an electrode group in which a positive electrode plate, a negative electrode plate, and a sulfonated separator are disposed between both of them as a hydrophilic treatment, the ratio of SO ₄ and SO ₃ of sulfone groups in the sulfonated separator ( By setting (SO ₄ / SO ₃ ) to 0.4 to 2.5, a battery having excellent self-discharge characteristics and excellent discharge characteristics can be obtained.

Claims

In a battery having an electrode group in which a positive electrode plate, a negative electrode plate, and a separator containing a sulfonated polyolefin-based fiber as a main component are disposed between both, the ratio of SO ₄ and SO ₃ of sulfone groups in the separator is A battery characterized in that (SO ₄ / SO ₃ ) is 0.4 to 2.5.

The battery according to claim 1, wherein the separator has an average fiber diameter of 3 to 15 m.

The battery according to claim 1, wherein the separator has an average pore diameter of 10 to 30 m.