JPH1055794A - Porous film, battery separator, and battery - Google Patents
Porous film, battery separator, and batteryInfo
- Publication number
- JPH1055794A JPH1055794A JP8209455A JP20945596A JPH1055794A JP H1055794 A JPH1055794 A JP H1055794A JP 8209455 A JP8209455 A JP 8209455A JP 20945596 A JP20945596 A JP 20945596A JP H1055794 A JPH1055794 A JP H1055794A
- Authority
- JP
- Japan
- Prior art keywords
- battery
- porous film
- skin layer
- film
- separator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- 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
Landscapes
- Laminated Bodies (AREA)
- Cell Separators (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は電池セパレータ等に好適
に用いられる多孔質フイルム、該多孔質フイルムからな
る電池セパレータ及び該セパレータを組み込んでなる電
池に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous film suitably used as a battery separator and the like, a battery separator comprising the porous film, and a battery incorporating the separator.
【０００２】[0002]
【従来の技術】種々のタイプの電池が実用に供されてお
り、これらの電池には正・負極の短絡防止のために該両
極間にセパレータが介在させられる。最近、電子機器の
コードレス化等に対応する電池として、高エネルギー密
度、高起電力、自己放電の少なさから、リチウム電池が
注目を集めている。2. Description of the Related Art Various types of batteries have been put to practical use. In these batteries, a separator is interposed between the positive and negative electrodes to prevent a short circuit between the two electrodes. 2. Description of the Related Art Recently, lithium batteries have attracted attention as batteries corresponding to cordless electronic devices because of their high energy density, high electromotive force, and low self-discharge.
【０００３】このリチウム電池の正極構成材料として
は、（ＣＦ）n で示されるフッ化黒鉛、LiCoO2、LiNi
O2、LiM2O4、V2O5、CuO 、Ag2CrO4 等の金属酸化物、Ti
S2、CuS等の硫化物が知られている。一方、負極構成材
料としては、金属リチウム、リチウム合金、カーボンや
グラファイト等のリチウムイオンを吸蔵または吸着する
能力を有する材料、あるいはリチウムイオンをドーピン
グした導電性高分子等が知られている。また、電解液と
しては、エチレンカーボネート、プロピレンカーボネー
ト、アセトニトリル、γ−ブチロラクトン、１，２−ジ
メトキシエタン、テトラヒドロフラン等の有機溶媒にLi
ClO4、LiPF6 、LiAsF6等の電解質を溶解した有機溶媒系
電解液が知られている。[0003] Materials constituting the positive electrode of this lithium battery include fluorinated graphite represented by (CF) n , LiCoO 2 , and LiNi.
O 2, LiM 2 O 4, V 2 O 5, CuO, metal oxides such as Ag 2 CrO 4, Ti
Sulfides such as S 2 and CuS are known. On the other hand, as a negative electrode constituent material, a material having an ability to occlude or adsorb lithium ions, such as lithium metal, a lithium alloy, carbon or graphite, or a conductive polymer doped with lithium ions is known. As the electrolytic solution, an organic solvent such as ethylene carbonate, propylene carbonate, acetonitrile, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, or the like is used.
Organic solvent-based electrolytes in which electrolytes such as ClO 4 , LiPF 6 , and LiAsF 6 are dissolved are known.
【０００４】かような材料から構成されるリチウム電池
は、外部短絡や、正・負極の誤接続、充電機の故障、誤
作動等により異常電流が流れた場合、これによって電池
温度が著しく上昇し、この電池を組み込んだ装置に熱的
なダメージを与えるおそれがある。When an abnormal current flows due to an external short circuit, erroneous connection between the positive and negative electrodes, a failure of a charger, malfunction or the like, a lithium battery composed of such a material causes a remarkable increase in battery temperature. This may cause thermal damage to the device incorporating the battery.
【０００５】そこで、異常電流による電池温度の上昇に
際し、正・負極の短絡防止のために組み込んだセパレー
タの電気抵抗を増大させることにより電池反応を遮断
し、温度の過昇を防止して安全を確保することが提案さ
れている。このように電池の温度上昇に際し、電気抵抗
の増大により電池反応を遮断して温度の過昇を防止する
ことにより安全を確保する機能は一般にシャットダウン
特性（以下ＳＤ特性という）と呼ばれ、リチウム電池セ
パレータ等にとっては重要な特性である。Therefore, when the battery temperature rises due to an abnormal current, the battery reaction is interrupted by increasing the electric resistance of the separator incorporated to prevent a short circuit between the positive and negative electrodes, thereby preventing the temperature from rising excessively and ensuring safety. It is proposed to secure. In this way, when the battery temperature rises, the function of securing the safety by interrupting the battery reaction by increasing the electric resistance and preventing the temperature from rising excessively is generally called a shutdown characteristic (hereinafter referred to as SD characteristic), and is called a lithium battery. This is an important property for a separator or the like.
【０００６】このようなＳＤ特性を有するセパレータと
しては、例えば（ａ）多孔質フイルムの表面にヒューズ
材料（該多孔質フイルムよりも低融点の材料）を点在さ
せたもの（特開平１−１８６７５号公報、特開平３−６
２４４９号公報）、（ｂ）所定温度において実質的に無
孔構造に変化し得る多孔質層と該温度において多孔質構
造を維持し得る層からなる積層多孔質フイルム（特開昭
６２−１０８５７号公報、特開平４−１８１６５１号公
報）、あるいは（ｃ）ポリエチレン（以下「ＰＥ」とい
う）とポリプロピレン（以下「ＰＰ」という）の混合物
からなる多孔質フイルム（特開平４−２０６２５７号公
報）が知られている。As a separator having such SD characteristics, for example, (a) a porous film in which a fuse material (a material having a lower melting point than the porous film) is interspersed (Japanese Patent Laid-Open Publication No. Hei 18-18675). JP, JP-A-Heisei 3-6
2449), (b) a laminated porous film comprising a porous layer capable of changing to a substantially nonporous structure at a predetermined temperature and a layer capable of maintaining a porous structure at the temperature (Japanese Patent Application Laid-Open No. 62-10857). JP-A-4-181651) or (c) a porous film (JP-A-4-206257) composed of a mixture of polyethylene (hereinafter, referred to as "PE") and polypropylene (hereinafter, referred to as "PP"). Have been.
【０００７】これらのセパレータにおけるＳＤ特性の発
現機構は次の通りである。（ａ）のセパレータは電池の
温度が所定の温度を超えた場合、ヒューズ材料が融解
し、この融解成分により多孔質フイルムの微細孔が閉塞
され、その結果、電気抵抗が増大し、それ以上の温度上
昇が防止されるのであり、また、（ｂ）のセパレータは
電池の温度が所定の温度を超えた場合、一方の多孔質層
が無孔構造に変化することにより、電気抵抗が増大し、
それ以上の温度上昇が防止されるのであり、更に（ｃ）
のセパレータは電池の温度が所定の温度を超えた場合、
ＰＥが溶融し、このＰＥにより多孔質フイルムの微細孔
が閉塞され、その結果、電気抵抗が増大し、それ以上の
温度上昇が防止されるのである。The mechanism of developing SD characteristics in these separators is as follows. In the case of the separator (a), when the battery temperature exceeds a predetermined temperature, the fuse material is melted, and the melting component closes the micropores of the porous film. As a result, the electrical resistance increases, The temperature rise is prevented, and in the case of the separator (b), when the battery temperature exceeds a predetermined temperature, one of the porous layers changes to a non-porous structure, thereby increasing the electric resistance.
Further temperature rise is prevented, and (c)
When the battery temperature exceeds a predetermined temperature,
The PE melts and closes the micropores of the porous film, thereby increasing the electric resistance and preventing a further rise in temperature.
【０００８】[0008]
【発明が解決しようとする課題】上記のような従来のセ
パレータはいずれも正・負極間の電気伝導性を確保する
ために、多孔構造となっている。金属リチウムを負極と
して用いるリチウム２次電池では、充電の際に負極上に
リチウムを析出させる。また、負極にリチウムイオンを
吸蔵することのできるカーボンや黒鉛を用いる、いわゆ
るリチウムイオン（２次）電池では急速充電や過充電時
に、本来は析出しない金属リチウムが負極上に析出す
る。これらの負極上に析出した金属リチウムは析出量が
増えると、セパレータの孔内に侵入し、充電が進むにつ
れて成長し、遂には正極表面に到達し、いわゆるデンド
ライトショートに至る。このようなデンドライトショー
トが発生した部分は、他の部分よりも電気抵抗が極めて
小さいため、この部分に電流が集中し、ジュール熱によ
る発熱が極めて大きくなる。このため、電池温度が上昇
し、上記のＳＤ特性によりセパレータの電気抵抗が増大
するが、デンドライトショートした部分は析出リチウム
により導通したままなので、電流が流れ続け、さらに発
熱し電池温度が上昇する。また、デンドライトショート
が発生すると、充電時にデンドライトショートした部分
に流れた電流は電池の充電反応に使われないので、放電
容量が低下し、充放電効率が低下してしまう。All of the above-mentioned conventional separators have a porous structure in order to ensure electrical conductivity between the positive and negative electrodes. In a lithium secondary battery using metallic lithium as a negative electrode, lithium is deposited on the negative electrode during charging. Further, in a so-called lithium ion (secondary) battery using carbon or graphite capable of occluding lithium ions in the negative electrode, metallic lithium which is not originally deposited is deposited on the negative electrode during rapid charging or overcharging. When the amount of deposited metal lithium on the negative electrode increases, it penetrates into the pores of the separator, grows as charging progresses, and finally reaches the positive electrode surface, leading to so-called dendrite short-circuit. Since the electrical resistance of the portion where such a dendrite short-circuit has occurred is much lower than that of the other portions, the current is concentrated in this portion, and the heat generated by Joule heat becomes extremely large. For this reason, the battery temperature rises and the electrical resistance of the separator increases due to the above-mentioned SD characteristics. However, since the portion where the dendrite is short-circuited remains conductive due to the deposited lithium, current continues to flow, further generating heat and increasing the battery temperature. In addition, when a dendrite short occurs, the current flowing to the portion where the dendrite short has occurred during charging is not used for the charging reaction of the battery, so that the discharge capacity is reduced and the charge / discharge efficiency is reduced.
【０００９】[0009]
【課題を解決するための手段】本発明者らは、鋭意研究
した結果、多孔質フイルムの少なくとも一方の表面に特
定の開孔状態としたスキン層を形成することにより、上
記の問題点が解決できることを見い出し、本発明を完成
するに至ったものである。すなわち、本発明の多孔質フ
イルムは、多孔質フイルムの少なくとも一方の表面に、
フイルムの厚み方向中央部よりも低い開孔率で且つ０．
１％以上１０％未満の開孔率であるスキン層を形成した
ことを主たる特徴とし、また本発明の電池セパレータは
かような構成の多孔質フイルムからなるものである。Means for Solving the Problems As a result of intensive studies, the present inventors have solved the above-mentioned problems by forming a skin layer having a specific aperture on at least one surface of a porous film. They have found what can be done and have completed the present invention. That is, the porous film of the present invention, on at least one surface of the porous film,
The opening ratio is lower than that of the center of the film in the thickness direction and the opening ratio is lower than the center.
The main feature is that a skin layer having a porosity of 1% or more and less than 10% is formed, and the battery separator of the present invention comprises a porous film having such a configuration.
【００１０】本発明を構成する多孔質フイルムとして
は、ＰＥまたはＰＰを成分とする多孔質フイルム、また
は、ＰＥとＰＰの両方を成分として有する多孔質フイル
ムが好適に使用される。ＰＥとＰＰの両方を成分とする
多孔質フイルムの場合には、その組成比は任意であり、
また、特開平７−２１６１１８号公報に示されるような
フイルムの厚さ方向においてその組成比が変化している
ものでもよく、使用する電池系に応じて適宜選択して使
用することができる。多孔質フイルムの作製は、上記公
報に記載されているようにフイルムの熱処理によりポリ
マーの結晶度を増大させ、次いでロール等で延伸するこ
とにより結晶部のラメラ間を破壊して微細孔を形成する
ことによって行なうことができる。As the porous film constituting the present invention, a porous film containing PE or PP as a component, or a porous film containing both PE and PP as a component is preferably used. In the case of a porous film containing both PE and PP, the composition ratio is arbitrary,
Further, a film whose composition ratio changes in the thickness direction of the film as disclosed in Japanese Patent Application Laid-Open No. 7-216118 may be appropriately selected and used according to the battery system to be used. As described in the above publication, the production of a porous film increases the crystallinity of the polymer by heat treatment of the film, and then breaks the lamella of the crystal part by stretching with a roll or the like to form micropores. It can be done by doing.
【００１１】上記の多孔質フイルムの微細孔の寸法はそ
の長径が０．０１〜３μｍ、短径が０．００５〜１μｍ
の範囲のものが好適に用いられ、長径が０．０１〜０．
５μｍ、短径が０．０１〜０．３μｍの範囲のものがさ
らに好適に用いられる。多孔質フイルム全体の開孔率
は、通常、２０〜８０％、好ましくは３０〜６０％の範
囲であるものが好適に使用される。ここで開孔率とは、
多孔質フイルムの厚み方向と垂直な平面でのフイルム面
積中に占める微細孔の面積（率）のことをいう。The pores of the porous film have a major axis of 0.01 to 3 μm and a minor axis of 0.005 to 1 μm.
Are preferably used, and the major axis is 0.01 to 0.1.
Those having a diameter of 5 μm and a minor axis in the range of 0.01 to 0.3 μm are more preferably used. The pore ratio of the entire porous film is usually 20 to 80%, preferably 30 to 60%. Here, the porosity is
The area (ratio) of micropores in the film area on a plane perpendicular to the thickness direction of the porous film.
【００１２】本発明における多孔質フイルムは、通常２
０〜１００μｍの厚さのものが好適に用いられる。これ
は、フイルムが厚すぎるとセパレータ部分の電気抵抗が
大きくなり、また、電池体積中のセパレータの占める体
積が大きくなるため、電池の容量が小さくなってしまう
からである。また、フイルムが薄すぎると、フイルムの
強度が小さくなり、電池作製時にフイルムが破断して作
製できなかったり、電池作製後に電極のバリや微小異物
等でフイルムが破断して内部短絡を引き起こすおそれが
あるためである。[0012] The porous film in the present invention is usually 2
Those having a thickness of 0 to 100 μm are preferably used. This is because if the film is too thick, the electrical resistance of the separator part increases, and the volume occupied by the separator in the battery volume increases, so that the battery capacity decreases. Also, if the film is too thin, the strength of the film will be reduced, and the film may be broken at the time of manufacturing the battery, making it impossible to manufacture the film, or after the battery is manufactured, the film may be broken by electrode burrs or minute foreign matter, causing an internal short circuit. Because there is.
【００１３】本発明では、該多孔質フイルムの少なくと
も一方の表面に、フイルムの厚み方向中央部よりも開孔
率の低いスキン層を有するものである。かかるスキン層
を形成するには、例えば、加熱ロールによるフイルムの
延伸による多孔質化に際して、フイルムの進行方向に配
置された３本の加熱ロールのうち中間の加熱ロールの回
転速度を低減させてその接触面を若干溶融することによ
って行なうことができる。In the present invention, at least one surface of the porous film has a skin layer having a lower porosity than the center in the thickness direction of the film. In order to form such a skin layer, for example, when the film is made porous by stretching the film with a heating roll, the rotation speed of the middle heating roll among the three heating rolls arranged in the film traveling direction is reduced to reduce the rotation speed. This can be done by slightly melting the contact surface.
【００１４】また、すでに作製された多孔質フイルムに
対してスキン層を形成するには、該フイルムの融点より
も５〜２０℃程度低い温度に設定した加熱ロールを用
い、加熱ロールの回転速度をフイルムの走行速度よりも
低減させることによって同様に加熱ロールの接触面側に
スキン層を形成することができる。Further, in order to form a skin layer on a porous film that has already been produced, a heating roll set at a temperature lower by about 5 to 20 ° C. than the melting point of the film is used, and the rotation speed of the heating roll is reduced. A skin layer can be similarly formed on the contact surface side of the heating roll by lowering the running speed of the film.
【００１５】上記いずれの場合でも、回転速度を低減さ
せる加熱ロールは回転させなくてもスキン層を形成する
ことができる。In any of the above cases, the skin layer can be formed without rotating the heating roll for reducing the rotation speed.
【００１６】しかして、上記のスキン層の開孔率は、
０．１％以上１０％未満となるように調整されるのがよ
い。スキン層の開孔率が０．１％未満であると、多孔質
フイルムとしての機能が十分に発揮できず、１０％を超
えると後述するスキン層による析出リチウムの正極への
到達を阻止できなくなるおそれがあるので、好ましくな
いものである。Thus, the above-mentioned skin layer has a porosity of
It is preferable to adjust the amount to be 0.1% or more and less than 10%. If the porosity of the skin layer is less than 0.1%, the function as a porous film cannot be sufficiently exhibited, and if it exceeds 10%, it becomes impossible to prevent the lithium deposited by the skin layer described below from reaching the positive electrode. This is not preferable because there is a possibility of it.
【００１７】本発明におけるスキン層は余り厚すぎると
フイルム全体の通気性が低くなり、電池の容量特性が維
持しにくくなる。また、スキン層が余り薄すぎると、使
用時にスキン層が他物体との摩擦等により剥離・破損し
てしまう可能性がある。例えば電池作製時に正負極との
摩擦によってスキン層が剥離・破損するおそれがある。
このため、本発明におけるスキン層の厚さは好ましくは
０．００１〜０．１μｍ、さらに好ましくは０．０１〜
０．０５μｍに設定される。If the skin layer in the present invention is too thick, the air permeability of the entire film becomes low, and it becomes difficult to maintain the capacity characteristics of the battery. Further, if the skin layer is too thin, the skin layer may peel or break due to friction with other objects during use. For example, the skin layer may peel or break due to friction with the positive and negative electrodes during battery fabrication.
Therefore, the thickness of the skin layer in the present invention is preferably 0.001 to 0.1 μm, more preferably 0.01 to 0.1 μm.
It is set to 0.05 μm.
【００１８】上述した本発明のスキン層付多孔質フイル
ムをリチウム２次電池用セパレータとして使用するに
は、リチウム２次電池を構成する正極、負極構成材料の
間に介在せしめて電池に組み込まれる。In order to use the above-described porous film with a skin layer of the present invention as a separator for a lithium secondary battery, it is incorporated into a battery by interposing it between a positive electrode and a negative electrode constituting materials of a lithium secondary battery.
【００１９】電池に組み込んだときに、スキン層が正極
側に配置されるように多孔質フイルムを正極負極間に介
在させることが好ましい。すなわち、開孔率の小さなス
キン層の側を正極側に向けて介在させることにより、充
電時に負極上に析出した金属リチウムが多孔質フイルム
の孔内へ侵入してもスキン層の開孔率が小さいため、成
長した析出リチウムの正極表面側への到達を有効に阻止
することができる。It is preferable that a porous film is interposed between the positive electrode and the negative electrode so that the skin layer is disposed on the positive electrode side when assembled in the battery. That is, by interposing the side of the skin layer having a small porosity toward the positive electrode side, the porosity of the skin layer is reduced even if metallic lithium deposited on the negative electrode during charging enters the pores of the porous film. Since it is small, it is possible to effectively prevent the grown deposited lithium from reaching the positive electrode surface side.
【００２０】この場合には、スキン層はフイルムの一方
の表面だけに設けられていてもよいため、フイルムの通
気性を必要以上に低下させることもない。勿論、多孔質
フイルムの両面に上述のスキン層を形成しても本発明の
主旨を損なうものでないことはいうまでもない。In this case, since the skin layer may be provided only on one surface of the film, the air permeability of the film is not reduced more than necessary. Of course, it goes without saying that forming the above-mentioned skin layers on both surfaces of the porous film does not impair the gist of the present invention.
【００２１】[0021]
【実施例】正極活物質としてコバルト酸リチウム、導電
材として炭素粉末および結着材としてフッ素樹脂粉末を
Ｎ−メチル−２−ピロリドン（ＮＭＰ）に加えてスラリ
ーを調製し、このスラリーを厚さ２５μｍのアルミ箔上
に塗布した後、１００℃で乾燥しＮＭＰを除去し、ロー
ルプレスにて圧着し正極を作製した。負極活物質として
黒鉛、結着材としてフッ素樹脂粉末をＮＭＰに加えてス
ラリーを調製し、このスラリーを厚さ２５μｍの銅箔上
に塗布した後、１００℃で乾燥しＮＭＰを除去し、ロー
ルプレスにて圧着し負極を作製した。EXAMPLE A slurry was prepared by adding lithium cobalt oxide as a positive electrode active material, carbon powder as a conductive material, and fluororesin powder as a binder to N-methyl-2-pyrrolidone (NMP), and the slurry was formed to a thickness of 25 μm. , And dried at 100 ° C. to remove NMP, and pressed by a roll press to produce a positive electrode. A slurry was prepared by adding graphite as a negative electrode active material and a fluororesin powder as a binder to NMP, and the slurry was applied on a copper foil having a thickness of 25 μm, and then dried at 100 ° C. to remove NMP. To produce a negative electrode.
【００２２】実施例１〜６は、セパレータとして材質が
表１に示されるようにＰＥ又はＰＰ単独もしくはその混
合物（ＰＰ／ＰＥ＝６／４とあるのは重量比が６対４で
あることを示す）であって表１に示されるように概ね厚
さ２５μｍとされた多孔質フイルムを使用した。この多
孔質フイルムの孔径をＳＥＭ（走査型電子顕微鏡）写真
により観察したところ、長径が０．０４μｍ、短径が
０．０１μｍであり、開孔率は表１に示される通りであ
った。そして各々の多孔質フイルムに１１５℃に設定し
た加熱ロールをロールを回転させずにその表面を接触さ
せると共に、多孔質フイルムを０．５ｍ／分の移動速度
で引き取ることにより一方の表面にのみ開孔率が低下し
たスキン層を形成した。実施例１〜６のスキン層の開孔
率は、加熱温度及びフイルムの移動速度を調整すること
によって変化させたものである。In Examples 1 to 6, PE or PP alone or a mixture thereof (PP / PE = 6/4) has a weight ratio of 6: 4 as shown in Table 1 for the material of the separator. As shown in Table 1, a porous film having a thickness of about 25 μm was used. Observation of the pore diameter of this porous film by a SEM (scanning electron microscope) photograph revealed that the major axis was 0.04 μm and the minor axis was 0.01 μm, and the porosity was as shown in Table 1. A heating roll set at 115 ° C. is brought into contact with each surface of the porous film without rotating the roll, and the porous film is taken out at a moving speed of 0.5 m / min to open only one surface. A skin layer with reduced porosity was formed. The porosity of the skin layers of Examples 1 to 6 was changed by adjusting the heating temperature and the moving speed of the film.
【００２３】なお、実施例３についてはＰＥを含まない
ので、加熱ロールの設定温度を１５５℃とした。各々の
フイルムを厚さ方向に切断し、スキン層の厚さを測定し
たところ、表１に示す通りであった。Since Example 3 does not contain PE, the set temperature of the heating roll was set to 155 ° C. Each film was cut in the thickness direction, and the thickness of the skin layer was measured.
【００２４】次いで、正負極を１cm×１cm角の正方形と
なるように切断し、リード線を付け、アルゴン雰囲気の
グローブボックス内で、セパレータのスキン層を有する
側を正極側に向けて正負極間に配置されるようにして積
層し、次いで六フッ化リン酸リチウムをエチレンカーボ
ネートとジエチルカーボネートとの混合溶媒（体積比１
／１）に濃度が１mol/l となるように溶解した電解液に
浸漬して簡易電池Ａを作製した。Next, the positive and negative electrodes were cut into a square of 1 cm × 1 cm square, and a lead wire was attached. In a glove box in an argon atmosphere, the side having the skin layer of the separator was turned to the positive electrode side. And then lithium hexafluorophosphate is mixed with a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio: 1).
The battery was immersed in an electrolytic solution dissolved so as to have a concentration of 1 mol / l in (/ 1) to prepare a simple battery A.
【００２５】実施例１の場合には、この簡易電池を上記
ブローブボックス内で、０．２ｍＡで５回充放電を繰り
返した後、３ｍＡで充電したところ電池電圧は徐々に増
加し、３０分後には４．３Ｖとなり、デンドライトショ
ートによる電圧の低下は見られなかった。この電池をさ
らに３ｍＡで充電したところ、２．７Ｖの電圧に下がる
までに２９分かかり、９７％の良好な充放電効率が得ら
れた。ここで充放電効率とは、ある充放電サイクルにお
いて、下記数１で求めた値をいう。In the case of Example 1, the simple battery was repeatedly charged and discharged at 0.2 mA in the probe box five times, and then charged at 3 mA. When the battery was charged at 3 mA, the battery voltage gradually increased. Was 4.3 V, and no decrease in voltage due to dendrite short was observed. When the battery was further charged at 3 mA, it took 29 minutes to decrease to a voltage of 2.7 V, and a good charge / discharge efficiency of 97% was obtained. Here, the charging / discharging efficiency refers to a value obtained by the following equation 1 in a certain charging / discharging cycle.
【００２６】[0026]
【数１】 (Equation 1)
【００２７】実施例２以下も同様に簡易電池を作製し同
様に充放電を繰り返してデンドライトショートの発生の
有無を確かめ、充放電効率を算出した。In the same manner as in Example 2 and thereafter, a simple battery was prepared, and charging and discharging were repeated in the same manner to check whether or not a dendrite short circuit occurred, and the charging and discharging efficiency was calculated.
【００２８】[0028]
【比較例】比較例１〜６は、厚さが２５μｍ程度で開孔
率が厚さ方向に略変化のない（本発明におけるスキン層
を持たない）多孔質フイルムまたはスキン層の開孔率を
高くした以外は実施例と同様に簡易電極を作製した。な
お、この多孔質フイルムの孔径をＳＥＭ写真により観察
したところ、長径が０．３μｍ、短径が０．０５μｍで
あった。[Comparative Examples] Comparative Examples 1 to 6 show that the porous film or skin layer having a thickness of about 25 µm and having substantially no change in the opening ratio in the thickness direction (having no skin layer in the present invention) is used. A simple electrode was prepared in the same manner as in the example except that the height was increased. When the pore size of this porous film was observed with a SEM photograph, the major axis was 0.3 μm and the minor axis was 0.05 μm.
【００２９】比較例１の場合には、この簡易電池を上記
ブローブボックス内で、０．２ｍＡで５回充放電を繰り
返した後、３ｍＡで充電したところ電池電圧は最初は徐
々に増加したが１０分後に４．０Ｖとなった後急激に低
下し１１分後には３．３Ｖとなりデンドライトショート
による電圧の降下が観察された。その後、電圧は徐々に
低下し、３０分後には３．１０Ｖとなった。この電池を
さらに３ｍＡで放電したところ、２．７Ｖの電圧に下が
るまでの時間は１６．５分であり、充放電効率は６８％
と低い値となった。In the case of Comparative Example 1, this simple battery was repeatedly charged and discharged at 0.2 mA in the above-described probe box five times, and then charged at 3 mA. After 4.0 minutes, the voltage rapidly dropped after reaching 4.0 V, and after 11 minutes, dropped to 3.3 V, and a voltage drop due to dendrite short-circuit was observed. Thereafter, the voltage gradually decreased to reach 3.10 V after 30 minutes. When the battery was further discharged at 3 mA, the time until the voltage dropped to 2.7 V was 16.5 minutes, and the charge / discharge efficiency was 68%.
It was a low value.
【００３０】比較例２以下も同様に簡易電池を作製し同
様に充放電を繰り返してデンドライトショートの発生の
有無を確かめ、充放電効率を算出した。以上の結果を表
１に示す。In Comparative Example 2 and subsequent figures, a simple battery was prepared in the same manner, and charging and discharging were repeated in the same manner to check for the occurrence of dendrite short circuit, and the charging and discharging efficiency was calculated. Table 1 shows the above results.
【００３１】[0031]
【表１】 [Table 1]
【発明の効果】以上のように、本発明のスキン層付多孔
質フイルムをリチウム２次電池用セパレータとして用い
ることにより、充電時に負極上に析出した金属リチウム
が正極側へ到達するのを、開孔率の低いスキン層で有効
に阻止することができる。従って、本発明の多孔質フイ
ルムをセパレータとして組み込んだ電池においては、析
出金属リチウムの成長による正負極間のデンドライトシ
ョートの発生頻度を少なくすることができ、電池の充
電、急速充電、および過充電時のデンドライトショート
による異常発熱や充放電効率の低下を防止することがで
きるという効果がある。As described above, by using the porous film with a skin layer of the present invention as a separator for a lithium secondary battery, it is possible to prevent the metal lithium deposited on the negative electrode from reaching the positive electrode during charging. It can be effectively prevented by a skin layer having a low porosity. Therefore, in a battery incorporating the porous film of the present invention as a separator, the frequency of dendrite short-circuiting between the positive and negative electrodes due to the growth of deposited metal lithium can be reduced, and the battery can be charged, rapidly charged, and overcharged. This has the effect of preventing abnormal heat generation and reduction in charge / discharge efficiency due to dendrite short-circuit.
Claims (5)
に、フイルムの厚み方向中央部よりも低い開孔率で且つ
０．１％以上１０％未満の開孔率であるスキン層を形成
したことを特徴とする多孔質フイルム。1. A skin layer having an opening ratio lower than that of a central portion in the thickness direction of the film and having an opening ratio of 0.1% or more and less than 10% on at least one surface of the porous film. Characterized porous film.
である請求項１記載の多孔質フイルム。2. The thickness of the skin layer is 0.001 to 0.1 μm.
The porous film according to claim 1, wherein
なる電池セパレータ。3. A battery separator comprising the porous film according to claim 1.
極間に介在せしめられてなる電池。4. A battery comprising the battery separator according to claim 3 interposed between a positive electrode and a negative electrode.
厚み方向中央部よりも低い開孔率であるスキン層を形成
してなるセパレータが正極、負極間に介在せしめられる
と共に前記スキン層側が正極側に配置されていることを
特徴とする電池。5. A separator in which a skin layer having a lower porosity than the center in the thickness direction of the film is formed on one surface of the porous film, and a separator is interposed between the positive electrode and the negative electrode. A battery characterized by being disposed on the side.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8209455A JPH1055794A (en) | 1996-08-08 | 1996-08-08 | Porous film, battery separator, and battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8209455A JPH1055794A (en) | 1996-08-08 | 1996-08-08 | Porous film, battery separator, and battery |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH1055794A true JPH1055794A (en) | 1998-02-24 |
Family
ID=16573165
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8209455A Pending JPH1055794A (en) | 1996-08-08 | 1996-08-08 | Porous film, battery separator, and battery |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH1055794A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6335114B1 (en) | 1998-11-16 | 2002-01-01 | Denso Corporation | Laminate-type battery and process for its manufacture |
| JP2010067376A (en) * | 2008-09-09 | 2010-03-25 | Nitto Denko Corp | Separator for battery and manufacturing method thereof, and lithium-ion secondary battery and manufacturing method thereof |
| WO2011108235A1 (en) * | 2010-03-04 | 2011-09-09 | パナソニック株式会社 | Separator for battery, battery using same and method for producing battery |
| DE102022000955A1 (en) | 2021-03-19 | 2022-09-22 | Sumitomo Chemical Company, Limited | Separator, member for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery |
| KR20220131190A (en) | 2021-03-19 | 2022-09-27 | 스미또모 가가꾸 가부시키가이샤 | Separator and nonaqueous electrolyte secondary battery |
| KR20220131495A (en) | 2021-03-19 | 2022-09-28 | 스미또모 가가꾸 가부시키가이샤 | Nonaqueous electrolyte secondary battery laminate, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery |
-
1996
- 1996-08-08 JP JP8209455A patent/JPH1055794A/en active Pending
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6335114B1 (en) | 1998-11-16 | 2002-01-01 | Denso Corporation | Laminate-type battery and process for its manufacture |
| JP2010067376A (en) * | 2008-09-09 | 2010-03-25 | Nitto Denko Corp | Separator for battery and manufacturing method thereof, and lithium-ion secondary battery and manufacturing method thereof |
| WO2011108235A1 (en) * | 2010-03-04 | 2011-09-09 | パナソニック株式会社 | Separator for battery, battery using same and method for producing battery |
| JP5340408B2 (en) * | 2010-03-04 | 2013-11-13 | パナソニック株式会社 | Battery separator, battery using the same, and battery manufacturing method |
| US8652671B2 (en) | 2010-03-04 | 2014-02-18 | Panasonic Corporation | Separator for battery, and battery and method for producing battery including the same |
| DE102022000955A1 (en) | 2021-03-19 | 2022-09-22 | Sumitomo Chemical Company, Limited | Separator, member for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery |
| KR20220131191A (en) | 2021-03-19 | 2022-09-27 | 스미또모 가가꾸 가부시키가이샤 | Separator, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery |
| KR20220131190A (en) | 2021-03-19 | 2022-09-27 | 스미또모 가가꾸 가부시키가이샤 | Separator and nonaqueous electrolyte secondary battery |
| KR20220131495A (en) | 2021-03-19 | 2022-09-28 | 스미또모 가가꾸 가부시키가이샤 | Nonaqueous electrolyte secondary battery laminate, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery |
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