JP2003346766A - Lithium ion secondary battery - Google Patents
Lithium ion secondary batteryInfo
- Publication number
- JP2003346766A JP2003346766A JP2002148721A JP2002148721A JP2003346766A JP 2003346766 A JP2003346766 A JP 2003346766A JP 2002148721 A JP2002148721 A JP 2002148721A JP 2002148721 A JP2002148721 A JP 2002148721A JP 2003346766 A JP2003346766 A JP 2003346766A
- Authority
- JP
- Japan
- Prior art keywords
- separator
- battery
- secondary battery
- lithium ion
- ion secondary
- 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.)
- Granted
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
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、安全性の高い非水
電解質二次電池に関し、特に過充電時の高温環境下での
安全性の高い非水電解質二次電池のためのセパレータに
関する。The present invention relates to a highly safe non-aqueous electrolyte secondary battery, and more particularly to a separator for a highly safe non-aqueous electrolyte secondary battery in a high temperature environment during overcharge.
【０００２】[0002]
【従来の技術】非水電解質二次電池の正極と負極を電気
的に隔離する方法としては、大きく分けてセパレータを
用いる方法と固体電解質を用いる方法がある。2. Description of the Related Art Methods for electrically isolating a positive electrode and a negative electrode of a nonaqueous electrolyte secondary battery are roughly classified into a method using a separator and a method using a solid electrolyte.
【０００３】これらのうち、一般にセパレータが最も良
く使われ、その果す役割としては、通常時の正極、負極
間の短絡防止がある。さらに、正極、負極間に存在する
ため、電解液の保持や、リチウムイオンの透過などさま
ざまな性能が必要になる。そのため、セパレータの性能
を示す特性パラメータとしては、透気度、平均孔径、気
孔率、収縮率および突き刺し強度など様々なものがあ
る。これらはそれぞれ相関関係にあり、相反することが
多くて両立しにくい。これらの両立しがたいいくつかの
特性を向上させるために、材質は、同じポリオレフィン
を使用しているが、特性パラメータの違う２種の微多孔
膜を貼り合わせた積層構造をもつセパレータが提案され
ている（特開２０００−２１２３２２号公報、特開２０
００−２１２３２３号公報等）。[0003] Of these, the separator is generally most often used, and its role is to prevent short-circuiting between the positive electrode and the negative electrode during normal operation. Furthermore, since it exists between the positive electrode and the negative electrode, various performances such as retention of an electrolytic solution and permeation of lithium ions are required. For this reason, there are various characteristic parameters indicating the performance of the separator, such as air permeability, average pore diameter, porosity, shrinkage, and piercing strength. These are correlative with each other, and are often incompatible with each other and difficult to achieve. In order to improve some of these incompatible characteristics, a separator having a laminated structure in which two types of microporous films using the same polyolefin but different characteristic parameters are bonded together has been proposed. (JP-A-2000-212322, JP-A-20
No. 00-212323).
【０００４】ところで、非水電解質二次電池のセパレー
タに特有の機能として、多孔質ポリオレフィンセパレー
タなどでは、外部短絡による過剰電流等により電池温度
が著しく上昇した場合、多孔質セパレータが軟化するこ
とにより実質的に無孔質となり電流を流させなくする、
いわゆるシャットダウン機能がある。Incidentally, as a function unique to the separator of the nonaqueous electrolyte secondary battery, in the case of a porous polyolefin separator or the like, when the battery temperature rises significantly due to an excessive current or the like due to an external short circuit, the porous separator softens substantially. Become non-porous, preventing current from flowing,
There is a so-called shutdown function.
【０００５】過充電状態においてリチウムのデンドライ
ト化などによってセパレータ内部では微小短絡が起こ
り、セパレータがシャットダウンする、つまり実質的に
無孔質になった場合でも、微小短絡部により電流が流れ
つづける場合がある。この場合、逆に微小短絡部に充電
電流が集中することになり、異常発熱を起こしてしまう
ことがある。逆に、過充電状態の初期においては、充電
電流が何らかの原因で切られた場合や、充電電流が小さ
い場合などは微小短絡により過充電状態が解消されるた
め、安全性が増す場合がある。したがって、過充電状態
の初期には微小短絡が発生していても、異常発熱に至る
高温状態の終期では、確実に微小短絡部の導通を切断す
る必要があった。[0005] In the overcharged state, a minute short circuit occurs inside the separator due to lithium dendrite or the like, and even when the separator shuts down, that is, when the separator becomes substantially nonporous, current may continue to flow due to the minute short circuit portion. . In this case, on the contrary, the charging current is concentrated on the minute short-circuited portion, which may cause abnormal heat generation. Conversely, in the early stage of the overcharge state, if the charging current is cut off for some reason or if the charging current is small, the overcharging state is resolved by a minute short circuit, which may increase safety. Therefore, even if a micro short circuit occurs at the beginning of the overcharge state, it is necessary to surely cut off the conduction of the micro short part at the end of the high temperature state that causes abnormal heat generation.
【０００６】[0006]
【発明が解決しようとする課題】しかし、従来の単層膜
のポリオレフィンセパレータや、前述の積層構造のセパ
レータでは、一度、微小短絡部が形成されると、セパレ
ータがシャットダウンした場合でも微小短絡部の導通が
切断されることはほとんど無い。However, in the conventional polyolefin separator having a single-layer film and the separator having the above-mentioned laminated structure, once a minute short-circuit portion is formed, even if the separator is shut down, the minute short-circuit portion is not removed. The continuity is rarely broken.
【０００７】本発明は、前述の課題を解決し、たとえ微
小短絡部が形成されても、異常発熱に至る高温状態の終
期では、確実に微小短絡部の導通を切断することによ
り、信頼性に優れたリチウムイオン二次電池を提供する
ことを目的とする。[0007] The present invention solves the above-mentioned problem, and even if a minute short-circuit portion is formed, at the end of a high-temperature state that causes abnormal heat generation, the conduction of the minute short-circuit portion is reliably cut off, thereby improving reliability. An object is to provide an excellent lithium ion secondary battery.
【０００８】[0008]
【課題を解決するための手段】上記課題を解決するため
に、本発明はセパレータとしての多孔性ポリエチレン膜
が一軸延伸された２枚のポリエチレン単位膜を少なくと
も含む積層構造を有し、前記単位膜のそれぞれの延伸方
向は互いに直交するように貼り合わされているものとし
た。In order to solve the above problems, the present invention has a laminated structure including at least two polyethylene unit films in which a porous polyethylene film as a separator is uniaxially stretched. Are bonded so that their respective stretching directions are orthogonal to each other.
【０００９】これにより、過充電状態の初期に発生した
微小短絡部を異常発熱に至る高温状態の終期では、確実
にその導通を切断することができ、結果として信頼性に
優れたリチウムイオン二次電池を提供することができ
る。As a result, conduction can be reliably cut off at the end of a high-temperature state that causes abnormal heating of the micro-short-circuit portion generated at the beginning of the overcharge state, and as a result, a lithium ion secondary battery having excellent reliability can be obtained. A battery can be provided.
【００１０】[0010]
【発明の実施の形態】本発明の請求項１に記載の発明
は、正極と負極とそれらの間にセパレータとして配置さ
れた多孔性高分子膜と、非水電解液を備えたリチウムイ
オン二次電池において、前記多孔性ポリエチレン膜が一
軸延伸された２枚のポリエチレン単位膜を少なくとも含
む積層構造を有し、前記単位膜のそれぞれの延伸方向は
互いに直交するように貼り合わされているとしたもので
あり、過充電状態の初期に発生した微小短絡部を異常発
熱に至る高温状態の終期では、確実にその導通を切断す
るという作用を有する。BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is directed to a lithium ion secondary battery provided with a non-aqueous electrolyte, a porous polymer membrane disposed as a separator between the positive electrode and the negative electrode, and a separator. In the battery, the porous polyethylene film has a laminated structure including at least two uniaxially stretched polyethylene unit films, and the stretching directions of the unit films are bonded so as to be orthogonal to each other. In addition, at the end of a high-temperature state that causes abnormal heat generation, the micro-short circuit portion generated at the beginning of the overcharge state has an effect of reliably cutting off conduction.
【００１１】セパレータには、大きく分けて一軸延伸さ
れたものと二軸延伸されたものの２種類がある。このう
ち一軸延伸されたセパレータが高温状態にさらされる
と、その延伸方向（以下、ＭＤという）が、特異的に収
縮する。本発明のセパレータは、そのＭＤが直交して貼
り合わされているため、セパレータが収縮するほどの高
温状態になると、その収縮方向の違いにより微小短絡部
が引き千切られて導通が切断される。The separator is roughly classified into two types, one uniaxially stretched and one biaxially stretched. When the uniaxially stretched separator is exposed to a high temperature, the stretching direction (hereinafter, referred to as MD) contracts specifically. Since the MD of the separator of the present invention is adhered perpendicularly to the MD, when the separator is in a high temperature state in which the separator shrinks, the minute short-circuit portion is cut off due to the difference in the shrinking direction and the conduction is cut off.
【００１２】本発明の請求項２に記載の発明は、請求項
１記載のリチウムイオン二次電池において、前記単位膜
の一方の延伸方向は、前記セパレータの長手方向と一致
し、他方の延伸方向はセパレータの短手方向と一致させ
たものであり、製造したセパレータのフープから電池組
み立て用に切り出す時に、無駄が少なく切り出すことが
できるという効果を有する。According to a second aspect of the present invention, in the lithium ion secondary battery according to the first aspect, one extending direction of the unit film coincides with a longitudinal direction of the separator, and the other extending direction. Are aligned with the lateral direction of the separator, and have an effect that the waste can be cut out with little waste when cut out from the manufactured separator hoop for battery assembly.
【００１３】[0013]
【実施例】次に、実施例を用いて、本発明の具体例につ
いて説明する。Next, specific examples of the present invention will be described with reference to examples.
【００１４】まず、セパレータに関して、条件を変えて
以下に述べる各種の特性を持つセパレータを製造した。First, separators having the following various characteristics were manufactured under different conditions.
【００１５】＜セパレータの製造＞本実施例では、セパ
レータの単位膜としてポリエチレン（ＰＥ）膜を作製し
た。<Production of Separator> In this example, a polyethylene (PE) film was produced as a unit film of the separator.
【００１６】まず、以下に述べる方法で、ＰＥ膜を製造
した。First, a PE film was manufactured by the method described below.
【００１７】高密度ポリエチレン（平均分子量２０万）
１７重量部と高密度ポリエチレン（平均分子量３０万）
２３重量部と流動パラフィン６０重部とを二軸押出機内
で溶融混練した。コートハンガーダイから冷却ロール上
に押出キャストすることにより高分子ゲルシートを作製
した。厚みはこの時点で２ｍｍであった。この高分子ゲ
ルシートをロール延伸機を用いて延伸温度１１０℃で７
倍に抽出前延伸をし、さらに、延伸温度１２２度の多段
ロール延伸機でＭＤに順次延伸して７倍まで熱延伸し
た。その後、塩化メチレン中に浸漬して流動パラフィン
を抽出除去した。さらに、テンターを用いて、１２５℃
でＭＤと直角の幅手方向（ＴＤ）に２倍に延伸した後、
ＴＤの延伸を１７％緩和させつつ熱処理した。以上述べ
た工程で、厚さ１４μｍのＰＥ膜を作製し、セパレータ
の単位膜Ａとした。High density polyethylene (average molecular weight 200,000)
17 parts by weight and high density polyethylene (average molecular weight 300,000)
23 parts by weight and 60 parts by weight of liquid paraffin were melt-kneaded in a twin-screw extruder. A polymer gel sheet was prepared by extrusion casting from a coat hanger die onto a cooling roll. The thickness was 2 mm at this point. The polymer gel sheet was rolled at 110 ° C. for 7
The film was stretched before extraction by a factor of 2 and further stretched in the MD sequentially by a multi-stage roll stretching machine at a stretching temperature of 122 ° C. and hot stretched to 7 times. Then, it was immersed in methylene chloride to extract and remove liquid paraffin. Further, using a tenter, 125 ° C.
After stretching twice in the transverse direction (TD) perpendicular to MD with
Heat treatment was performed while relaxing the stretching of the TD by 17%. Through the steps described above, a PE film having a thickness of 14 μm was produced and used as a unit film A of the separator.
【００１８】単位膜ＡをＭＤに１４９６ｍｍ、ＴＤに５
９ｍｍ切り取ったものと、逆にＭＤに５９ｍｍ、ＴＤに
１４９６ｍｍ切り取ったものを形をそろえて貼り合わせ
て２層構造のセパレータＢを作成した。The unit film A is 1496 mm in MD and 5 in TD.
A separator B having a two-layer structure was formed by attaching a cutout of 9 mm and a cutout of 59 mm in MD and 1496 mm in TD in the same shape and bonding them together.
【００１９】単位膜ＡをＭＤに１４９６ｍｍ、ＴＤに５
９ｍｍ切り取ったものを形をそろえて２枚貼り合わせて
２層構造のセパレータＣを作成した。The unit film A is 1496 mm in MD and 5 in TD.
9 mm cut-out pieces were aligned and two sheets were stuck together to form a separator C having a two-layer structure.
【００２０】単位膜ＡをＭＤに５９ｍｍ、ＴＤに１４９
６ｍｍ切り取ったものを形をそろえて２枚貼り合わせて
２層構造のセパレータＤを作成した。The unit film A is 59 mm in MD and 149 in TD.
6 mm cut pieces were aligned and two sheets were stuck together to form a separator D having a two-layer structure.
【００２１】＜電池の作製＞本発明の電池の過充電時の
温度変化を評価するため、以下に説明する円筒形電池を
作製した。<Production of Battery> To evaluate the temperature change during overcharging of the battery of the present invention, a cylindrical battery described below was produced.
【００２２】本発明の円筒形電池の構造は、正極と負極
とセパレータを捲回して、電池ケース内に非水溶媒に電
解質塩を溶解した非水電解質とともに内蔵し、封口板で
密閉したものである。The structure of the cylindrical battery according to the present invention is such that a positive electrode, a negative electrode, and a separator are wound, built in a battery case together with a non-aqueous electrolyte obtained by dissolving an electrolyte salt in a non-aqueous solvent, and sealed with a sealing plate. is there.
【００２３】封口板には、一般の市販電池においては、
安全弁やＰＴＣ素子などの安全素子が組み込まれている
が、実施例の電池においては安全性試験のために、封口
板には一切の安全機構は組み込まなかった。[0023] In a sealing plate, in a general commercial battery,
Although safety elements such as a safety valve and a PTC element were incorporated, in the batteries of Examples, no safety mechanism was incorporated in the sealing plate for a safety test.
【００２４】正極は、コバルト酸リチウム粉末８５重量
％に対し、導電剤の炭素粉末１０重量％と結着剤のポリ
弗化ビニリデン樹脂（ＰＶｄＦ樹脂）５重量％を混合
し、これらを脱水ＮＭＰに分散させてスラリーを作製
し、アルミ箔からなる正極集電体上に塗布し、乾燥後、
圧延した。その後、長さ５９３ｍｍ、幅５４ｍｍに成形
した。For the positive electrode, 10% by weight of carbon powder as a conductive agent and 5% by weight of polyvinylidene fluoride resin (PVdF resin) as a binder are mixed with 85% by weight of lithium cobalt oxide powder, and these are mixed with dehydrated NMP. Disperse to make a slurry, apply it on a positive electrode current collector made of aluminum foil, and after drying,
Rolled. Thereafter, it was formed to have a length of 593 mm and a width of 54 mm.
【００２５】負極は、負極活物質として人造黒鉛粉末を
用い、これの９５重量％に対して、結着剤のＰＶｄＦ樹
脂を５重量％を混合し、これらを脱水ＮＭＰに分散させ
てスラリーを作製し、銅箔からなる負極集電体上に塗布
し、乾燥後、圧延した。その後、長さ６７５ｍｍ、幅５
６ｍｍに成形した。For the negative electrode, artificial graphite powder was used as a negative electrode active material, 95% by weight of the powder was mixed with 5% by weight of PVdF resin as a binder, and these were dispersed in dehydrated NMP to prepare a slurry. Then, it was applied on a negative electrode current collector made of copper foil, dried, and then rolled. After that, 675mm in length and 5 in width
It was molded to 6 mm.
【００２６】また、非水電解質には、エチレンカーボネ
ート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）の
体積比１：１の混合溶媒にＬｉＰＦ6を１モル／リット
ル溶解したものを使用した。As the non-aqueous electrolyte, one obtained by dissolving 1 mol / l of LiPF 6 in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 1: 1 was used.
【００２７】なお、この作製した円筒形電池は直径１８
ｍｍ、高さ６５ｍｍである。本サイズの設計容量は１８
００ｍＡｈとした。電解液量は、約３．８ｍｌである。The manufactured cylindrical battery had a diameter of 18 mm.
mm and a height of 65 mm. The design capacity of this size is 18
00 mAh. The amount of the electrolyte is about 3.8 ml.
【００２８】＜実施例１＞セパレータＢを、前述の電池
に組み立てた。この電池を実施例１の電池とする。<Example 1> A separator B was assembled in the battery described above. This battery is referred to as the battery of Example 1.
【００２９】＜比較例１＞実施例１と同様の方法でセパ
レータＣを用い、電池に組み立てた。この電池を比較例
１の電池とする。Comparative Example 1 A battery was assembled using the separator C in the same manner as in Example 1. This battery is referred to as a battery of Comparative Example 1.
【００３０】＜比較例２＞実施例１と同様の方法でセパ
レーＤを用い、電池に組み立てた。この電池を比較例２
の電池とする。Comparative Example 2 A battery was assembled using Separation D in the same manner as in Example 1. Comparative Example 2
Battery.
【００３１】＜電池の評価＞これら作製した電池、計３
個を以下に述べる方法で評価した。<Evaluation of batteries>
Each was evaluated by the method described below.
【００３２】電池の設計容量は、１８００ｍＡｈであ
る。まず、９００ｍＡの定電流で、４．２Ｖになるまで
充電した後、９００ｍＡの定電流で３．０Ｖになるまで
放電する充放電サイクルを１０サイクル繰り返した。こ
の１０サイクル目の放電容量を各電池の初期容量とし
た。３個の全ての電池で、初期容量が設計容量を満足し
ていた。また、充放電は２０℃の恒温槽の中で行った。
その後、各電池を完全放電状態から１８００ｍＡの定電
流で２時間の過充電試験を行った。この過程での電池の
表面温度の測定を行い、電池の熱安定性を評価した。こ
れらの結果と電池電圧の変化を、図１から図３に示す。The design capacity of the battery is 1800 mAh. First, 10 charge / discharge cycles were repeated at a constant current of 900 mA until the voltage reached 4.2 V and then discharged at a constant current of 900 mA until the voltage reached 3.0 V. The discharge capacity at the 10th cycle was defined as the initial capacity of each battery. The initial capacity of all three batteries satisfied the design capacity. The charge and discharge were performed in a thermostat at 20 ° C.
Thereafter, each battery was subjected to an overcharge test for 2 hours at a constant current of 1800 mA from a completely discharged state. During this process, the surface temperature of the battery was measured to evaluate the thermal stability of the battery. These results and changes in battery voltage are shown in FIGS.
【００３３】図１は、実施例１の電池の電池電圧および
電池温度と充電時間との関係を示す図である。図１にお
いて点線は電池の表面温度を示し、実線は電池電圧を示
す。FIG. 1 is a diagram showing the relationship between the battery voltage and battery temperature of the battery of Example 1 and the charging time. In FIG. 1, a dotted line indicates the surface temperature of the battery, and a solid line indicates the battery voltage.
【００３４】充電時間が１時間（１ｈ）を超えると過充
電領域に入る。充電時間が１．６ｈをこえると電池温度
が上昇し始め、１．８ｈあたりで急上昇する。この時、
１．８ｈでは、電池電圧も下がり始め、過充電により何
らかの導電物質が、セパレータ内に析出し、これが極板
間を導通することによる微小短絡が起こっていると考え
られる。この微小短絡部は、過充電が進むにつれ、温度
の上昇に伴い多くなる。ポリエチレンセパレータでは、
温度が高くなるとセパレータが収縮し、シャットダウン
と呼ばれる実質的に無孔化することにより充電電流を遮
断する機能があるが、この微小短絡部のためこの機能が
働かない。When the charging time exceeds one hour (1 h), the operation enters the overcharge area. When the charging time exceeds 1.6 h, the battery temperature starts to rise, and rises rapidly at around 1.8 h. At this time,
At 1.8 h, it is considered that the battery voltage also started to drop, and some conductive substance was deposited in the separator due to overcharging, and this caused a short circuit due to conduction between the electrode plates. The number of the micro short-circuit portions increases as the temperature rises as the overcharge progresses. For polyethylene separators,
When the temperature rises, the separator shrinks and has a function of shutting off the charging current by making it substantially non-porous, which is called a shutdown. However, this function does not work due to the minute short-circuit portion.
【００３５】しかし、充電時間が１．８５ｈを超えると
セパレータがさらに収縮し、多層セパレータの単位膜の
収縮方向が直交していることにより、微小短絡部の導電
物質の析出による極板間の導通が切断され、シャットダ
ウン機能が働き、電池電圧が充電電圧（約１２Ｖ）まで
上昇するし、実質的に充電が止まる。それに伴い電池温
度も緩やかに下降し、安全に過充電が終了した。However, when the charging time exceeds 1.85 hours, the separator shrinks further, and the contraction directions of the unit films of the multi-layer separator are orthogonal to each other. Is cut off, the shutdown function is activated, the battery voltage rises to the charging voltage (about 12 V), and charging stops substantially. As a result, the battery temperature gradually decreased, and overcharging was completed safely.
【００３６】これに対し、図２および図３に示す比較例
の電池では、電池の異常発熱が発生した。On the other hand, in the batteries of the comparative examples shown in FIGS. 2 and 3, abnormal heat generation of the batteries occurred.
【００３７】図２は、比較例１の電池の電池電圧および
電池温度と充電時間との関係を示す図である。図１と同
様に、点線は電池の表面温度を示し、実線は電池電圧を
示す。セパレータＣ自体は、実施例１の電池と同じ材質
および厚さなので、充電時間が１．６ｈをこえると電池
温度が上昇し始め、１．８ｈあたりで急上昇する。さら
に、１．８ｈでは、微小短絡部により電池電圧も下がり
始める。この内部短絡は、過充電が進むにつれ、温度の
上昇に伴い多くなる。そして、この微小短絡部の発生
が、１．９ｈ近くになっても切断されることはなく、微
小短絡部による発熱が大きくなりすぎ異常発熱を起こし
た。FIG. 2 is a diagram showing the relationship between the battery voltage and the battery temperature of the battery of Comparative Example 1 and the charging time. As in FIG. 1, the dotted line indicates the surface temperature of the battery, and the solid line indicates the battery voltage. Since the separator C itself has the same material and thickness as the battery of Example 1, when the charging time exceeds 1.6 h, the battery temperature starts to rise and rises rapidly at around 1.8 h. Further, at 1.8 h, the battery voltage starts to drop due to the minute short-circuit portion. This internal short-circuit increases as the temperature rises as overcharging proceeds. Then, even when the generation of the minute short-circuit portion was nearly 1.9 h, the short-circuit portion was not cut off, and the heat generation by the minute short-circuit portion became excessively large, causing abnormal heat generation.
【００３８】図３は、比較例２の電池の電池電圧および
電池温度と充電時間との関係を示す図である。図１と同
様に、点線は電池の表面温度を示し、実線は電池電圧を
示す。セパレータＤ自体は、実施例１の電池と同じ材質
および厚さなので、充電時間が１．６ｈをこえると電池
温度が上昇し始め、１．８ｈあたりで急上昇する。この
あたりで、セパレータＤが収縮し始めるが、収縮方向の
ＭＤが、極板の幅方向であるため、少しの収縮で正負極
の極板が接触することになり、過大な電流がその時流れ
るため、異常発熱を起こした。FIG. 3 is a diagram showing the relationship between the battery voltage and battery temperature of the battery of Comparative Example 2 and the charging time. As in FIG. 1, the dotted line indicates the surface temperature of the battery, and the solid line indicates the battery voltage. Since the separator D itself has the same material and thickness as the battery of Example 1, when the charging time exceeds 1.6 h, the battery temperature starts to rise and rapidly rises at around 1.8 h. In this area, the separator D starts to contract, but since the MD in the contraction direction is the width direction of the electrode plate, the positive and negative electrode plates come into contact with a slight contraction, and an excessive current flows at that time. , Causing abnormal fever.
【００３９】これらの比較例のとおり、セパレータが収
縮しても、同じ方向にのみ収縮する場合、微小短絡部の
極板間の導通が、平行移動するだけで切られることが無
く、また収縮方向によっては、比較例２のようにさらに
危険な状態になる。したがって、本発明の実施例１の電
池のようにセパレータが、多層セパレータの単位膜の収
縮方向が直交しているのが好ましい。As in these comparative examples, when the separator shrinks only in the same direction even if the separator shrinks, the continuity between the electrode plates of the minute short-circuit portion is not cut off only by the parallel movement, and the contraction direction In some cases, the state becomes more dangerous as in Comparative Example 2. Therefore, as in the battery of Example 1 of the present invention, it is preferable that the direction of shrinkage of the unit films of the multilayer separator be perpendicular to each other.
【００４０】[0040]
【発明の効果】以上述べた通り、本発明によれば、過充
電状態の初期に発生した微小短絡を、確実に切断できる
ので、非水電解質二次電池の高温状況下での安全性を高
めることができる。As described above, according to the present invention, it is possible to surely break a micro short circuit generated in the early stage of an overcharged state, thereby improving the safety of the nonaqueous electrolyte secondary battery under high temperature conditions. be able to.
【図１】実施例１の電池の電池電圧および電池温度と充
電時間との関係を示す図FIG. 1 is a diagram showing a relationship between a battery voltage and a battery temperature of a battery of Example 1 and a charging time.
【図２】比較例１の電池の電池電圧および電池温度と充
電時間との関係を示す図FIG. 2 is a diagram showing a relationship between a battery voltage and a battery temperature of a battery of Comparative Example 1 and a charging time.
【図３】比較例２の電池の電池電圧および電池温度と充
電時間との関係を示す図FIG. 3 is a diagram showing a relationship between a battery voltage and a battery temperature of a battery of Comparative Example 2 and a charging time.
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 5H021 BB05 CC04 EE04 5H029 AJ01 AK03 AL07 AM03 AM05 DJ04 ────────────────────────────────────────────────── ─── Continuation of front page F term (reference) 5H021 BB05 CC04 EE04 5H029 AJ01 AK03 AL07 AM03 AM05 DJ04
Claims (2)
して配置された多孔性高分子膜と、非水電解液を備えた
リチウムイオン二次電池において、前記多孔性ポリエチ
レン膜が一軸延伸された２枚のポリエチレン単位膜を少
なくとも含む積層構造を有し、前記単位膜のそれぞれの
延伸方向は互いに直交するように貼り合わされているこ
とを特徴とするリチウムイオン二次電池。1. A lithium ion secondary battery comprising a positive electrode, a negative electrode, a porous polymer film disposed as a separator between them, and a non-aqueous electrolyte, wherein the porous polyethylene film is uniaxially stretched. A lithium ion secondary battery having a laminated structure including at least one polyethylene unit film, wherein the unit films are bonded so that their extending directions are orthogonal to each other.
パレータの長手方向と一致し、他方の延伸方向はセパレ
ータの短手方向と一致することを特徴とする請求項１記
載のリチウムイオン二次電池。2. The lithium ion secondary battery according to claim 1, wherein one extending direction of the unit film coincides with a longitudinal direction of the separator, and the other extending direction coincides with a lateral direction of the separator. Next battery.
Priority Applications (1)
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|---|---|---|---|
| JP2002148721A JP4744773B2 (en) | 2002-05-23 | 2002-05-23 | Lithium ion secondary battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002148721A JP4744773B2 (en) | 2002-05-23 | 2002-05-23 | Lithium ion secondary battery |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2009229454A Division JP2010027617A (en) | 2009-10-01 | 2009-10-01 | Lithium-ion secondary battery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2003346766A true JP2003346766A (en) | 2003-12-05 |
| JP4744773B2 JP4744773B2 (en) | 2011-08-10 |
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ID=29767155
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2002148721A Expired - Fee Related JP4744773B2 (en) | 2002-05-23 | 2002-05-23 | Lithium ion secondary battery |
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|---|---|---|---|---|
| EP2122740A1 (en) * | 2006-12-19 | 2009-11-25 | Byd Company Limited | Stacked-type lithium ion battery |
| US20100297502A1 (en) * | 2009-05-19 | 2010-11-25 | Nanosys, Inc. | Nanostructured Materials for Battery Applications |
| WO2011077989A1 (en) * | 2009-12-24 | 2011-06-30 | Ｎｅｃエナジーデバイス株式会社 | Laminate-type secondary battery |
| KR101386824B1 (en) | 2011-10-04 | 2014-04-17 | 닛산 지도우샤 가부시키가이샤 | Electrical device |
| KR101532380B1 (en) * | 2012-08-03 | 2015-06-29 | 주식회사 엘지화학 | Separator for electrochemical device and electrochemical device including the same |
| CN113078415A (en) * | 2020-01-06 | 2021-07-06 | 天能帅福得能源股份有限公司 | Soft package lithium ion battery capable of improving impact property of heavy object and preparation method thereof |
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|---|---|---|---|---|
| EP2122740A1 (en) * | 2006-12-19 | 2009-11-25 | Byd Company Limited | Stacked-type lithium ion battery |
| EP2122740A4 (en) * | 2006-12-19 | 2011-11-16 | Byd Co Ltd | Stacked-type lithium ion battery |
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| KR101386824B1 (en) | 2011-10-04 | 2014-04-17 | 닛산 지도우샤 가부시키가이샤 | Electrical device |
| KR101532380B1 (en) * | 2012-08-03 | 2015-06-29 | 주식회사 엘지화학 | Separator for electrochemical device and electrochemical device including the same |
| CN113078415A (en) * | 2020-01-06 | 2021-07-06 | 天能帅福得能源股份有限公司 | Soft package lithium ion battery capable of improving impact property of heavy object and preparation method thereof |
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|---|---|
| JP4744773B2 (en) | 2011-08-10 |
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