JP2004241170A

JP2004241170A - Non-aqueous electrolytic solution secondary battery

Info

Publication number: JP2004241170A
Application number: JP2003026746A
Authority: JP
Inventors: Takayuki Shirane; 隆行白根; Futoshi Tanigawa; 太志谷川; Satoru Hashimoto; 哲橋本; Takeshi Minafuji; 豪皆藤
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-02-04
Filing date: 2003-02-04
Publication date: 2004-08-26
Anticipated expiration: 2023-02-04
Also published as: JP4698929B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolytic solution secondary battery in which internal short circuit hardly occurs in the portion of separator only on the innermost circumferential part that is easily contracted, when the battery is exposed to very severe temperatures due to abnormal use or the like. <P>SOLUTION: This is a non-aqueous electrolytic solution secondary battery that comprises an electrode group in which a positive plate and a negative plate are wound through a separator. An uncoated part 2 is provided at the end part in the longitudinal direction on the innermost circumferential side of the positive plate, and an insulator 4 having heat resistance is pasted on a partial or the entire face including at least both end parts in short length direction of the uncoated part. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】本発明は非水電解液二次電池に関し、特に最内周部の構造に関するものである。
【０００２】
【従来の技術】
近年、ＡＶ機器あるいはパソコン等の電子機器のポータブル化、コードレス化が急速に進んでおり、これらの駆動用電源として小型、軽量で高エネルギー密度を有する二次電池への要求が高まっている。この中でリチウムを活物質とするリチウムイオン二次電池はとりわけ高電圧、高エネルギー密度を有する電池として期待が大きい。
また近年では各社で高容量化、高出力化、高信頼性の競合も激化している。そのような中、正極板や負極板の不必要な部分の合剤部を取り除き、つまりは正極板や負極板に未塗工部を設け、それに見合った分の極板長尺化などを行うことにより高容量化を図るなどの工夫がなされている。さらに、安全性、信頼性をより確実なものにするために、極板に未塗工部を設けた構成も提案されている。（例えば特許文献１参照）
通常、集電のためリードを極板内周側に溶接するため未塗工部が必要となる。また溶接したリードの補強、およびリード端部によるセパレータ破損を防止するためにリードに保護テープを施すのは一般的に行なわれている。（例えば特許文献２参照）
【０００３】
【特許文献１】
特開平９−３２０６４０号公報（請求項１、図４）
【特許文献２】
特開２０００−１００４６７号公報（第３頁、図２）
【０００４】
【発明が解決しようとする課題】
ところで、リチウムイオン二次電池では円筒型、角型に関わらず群構成機の構造上、最内周部にはセパレータのみが捲回されている部分が存在する。セパレータはポリエチレンやポリプロピレンを主成分としていることが多く、電池の異常使用などにより過酷な温度に曝された場合は収縮する。正極板、負極板に挟まれたセパレータは幾分収縮しにくいが、最内周部のセパレータのみの部分は特に収縮しやすい。この時、最内周部セパレータの収縮に伴って正極と負極が短絡するという課題があった。
【０００５】
しかしながら、前述の従来の技術では、未塗工部にはせいぜいリードのみに保護テープを施しているだけなので、上記課題を解決することは出来なかった。
【０００６】
【課題を解決するための手段】
上記課題を解決するために、本発明の非水電解液二次電池は、正極板の最内周側長手方向端部に未塗工部が設けてあり、前記未塗工部の少なくとも短手方向両端部を含む一部または全面に耐熱性をもつ絶縁物が貼付されているものである。これにより上記セパレータが収縮する問題が発生した場合においても、リードのみに保護テープを施している構成と違い正極板と負極板が短絡することを防止することができる。
【０００７】
【発明の実施の形態】
本発明の非水電解液二次電池は、正極板と負極板がセパレータを介して捲回された電極群を具備した非水電解液二次電池において、
正極板の最内周側長手方向端部に未塗工部が設けてあり、前記未塗工部の少なくとも短手方向両端部を含む一部または全面に耐熱性をもつ絶縁物が貼付されていることを特徴としたものであり、この電池用電極板では、異常加熱時のセパレータ収縮による内部短絡を防止することができる。
円筒型電池では巻芯径が３〜４ｍｍであるため、少なくとも最内周極板の一周分を保護するために、耐熱性をもつ絶縁物が貼付されている部分は長手方向に１５ｍｍ以上であることが望ましい。
絶縁物は耐熱性をもつ、ポリイミド樹脂テープ、ガラステープ、ＰＰＳテープのうち少なくとも一種類以上であることが望ましい。特にポリイミド樹脂テープは薄く電池内容積の占有率が小さくなるので好ましい。
負極板も同様に対応部分にテープ等を施すことで本発明の効果は得られるが、通常負極板は正極板よりも大きいため、テープ面積が正極板に行うよりも広くなり、電池内容積の減少につながり容量減少が懸念されるため、正極板に行なうのが好ましい。
【０００８】
【実施例】
以下、本発明の具体例について説明する。
【０００９】
コバルト酸リチウム（ＬｉＣｏＯ_２）からなる正極活物質、アセチレンブラック（ＡＢ）からなる導電材、ポリフッ化ビニリデン（ＰＶｄＦ）からなる結着剤、Ｎ−メチル−２−ピロリドン（ＮＭＰ）からなる溶剤を混練分散して作製した正極ペーストを、厚さ１５μｍのアルミニウム箔からなる集電体に塗着、乾燥した後、最内周部に相当する３０ｍｍ部分の表裏両面の正極合剤を剥離させ、活物質のみの密度が３．３ｇ／ｃｃになるよう圧延したのち、幅５４ｍｍ、未塗工部が１５ｍｍを含む全長が５５０ｍｍとなるように裁断した。
【００１０】
次に、図１から３により説明する以下の正極板１から４を作製した。
【００１１】
まず、図１に示すように、前述の塗工部１および未塗工部２からなる極板にリードを３溶接し、リード３の周辺部のみにポリイミド樹脂テープ４ａを施した正極板１を作製した。
【００１２】
また、図２に示すように未塗工部１全面にポリイミド樹脂テープ４ｂを施した以外は正極板１と同様の正極板２を作製した。
【００１３】
そして、図３に示すように短手方向両端部にポリイミド樹脂テープ４ｃを施した以外は正極板１と同様の正極板３を作成した。
【００１４】
最後にポリイミド樹脂テープを施した部分が１０ｍｍとなるようにした以外は正極板２と同様の正極板４を作成した。
【００１５】
次に、黒鉛型炭素材料からなる負極活物質、ＰＶｄＦからなる結着剤、ＮＭＰからなる混合溶剤を混練分散して作製した負極ペーストを厚さ１４μｍの銅箔からなる集電体に塗着、乾燥、活物質のみで１．４ｇ／ｃｃになるよう圧延し、幅５６ｍｍ、全長５８０ｍｍに裁断した後、最外周部にリードを溶接し、リードの周辺部のみにポリイミド樹脂テープを施した負極板を作製した。
【００１６】
このようにして得られた正極板と負極板とを厚さ２０μｍの微多孔性ポリエチレン樹脂からなるセパレータを介して、巻回した電極群を作製した。
【００１７】
上記の方法で作製した電極群に５Ｖの電圧を印加したまま、恒温槽にて室温から１５０℃まで昇温加熱を行い、電圧挙動を測定した。
【００１８】
（結果）正極板１から正極板４を用いた電極群における内部短絡の結果を（表１）に示す。
【００１９】
【表１】

【００２０】
いずれの電極群においても試験後の分解観察を行うと同時に、短絡した電極群に関しては短絡個所の特定を行った。
【００２１】
正極板１を用いた電極群のうち短絡が発生したものは約１３０℃であった。分解観察では最内周部セパレータは収縮が見られ、正極板の端部が露呈しており、この部分で短絡していることが確認された。
【００２２】
正極板２および正極板３を用いた電極群に短絡が発生したものは無かった。これらの電極群を分解すると、正極板１の電極群と同様にセパレータが収縮し正極板のポリイミド樹脂テープが露呈していた。このため短絡には至っていない。
【００２３】
正極板４を用いた電極群にも短絡発生はあったが、正極板１の電極群に比べると、発生率は低かった。１０ｍｍの被覆でも効果は得られるが、１５ｍｍ以上であるほうが望ましい。
【００２４】
以上述べたように正極板２から４を使用した本発明の電極群は、内部短絡の発生率が低いため、電解液と共に金属ケースに密閉して非水電解液二次電池を作成すれば、異常使用などで過酷な温度に電池が曝された場合にも、セパレータの収縮による内部短絡を防止することが可能な電池が提供できる。
【００２５】
【発明の効果】
以上のように、本発明の非水電解液二次電池に関し、特に最内周部の構造に関するものによれば、異常使用などで過酷な温度に電池が曝された場合にも、セパレータの収縮による内部短絡を防止することが可能となる。
【図面の簡単な説明】
【図１】本発明の実施例で使用した正極板１の概念構造図
【図２】本発明の実施例で使用した正極板２の概念構造図
【図３】本発明の実施例で使用した正極板３の概念構造図
【符号の説明】
１塗工部
２未塗工部
３リード
４ａ，４ｂ，４ｃテープ[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonaqueous electrolyte secondary battery, and more particularly to a structure of an innermost peripheral portion.
[0002]
[Prior art]
2. Description of the Related Art In recent years, portable and cordless electronic devices such as AV devices and personal computers have been rapidly advanced, and there has been an increasing demand for small, lightweight, high-energy-density secondary batteries as power sources for these devices. Among them, a lithium ion secondary battery using lithium as an active material is particularly expected to be a battery having a high voltage and a high energy density.
Further, in recent years, competition for higher capacity, higher output, and higher reliability has been intensifying among companies. Under such circumstances, remove the mixture portion of unnecessary portions of the positive electrode plate and the negative electrode plate, that is, provide an uncoated portion on the positive electrode plate and the negative electrode plate, and make the electrode plate length corresponding to it. In this way, various measures have been taken to increase the capacity. Furthermore, in order to further ensure safety and reliability, a configuration in which an uncoated portion is provided on an electrode plate has been proposed. (For example, see Patent Document 1)
Usually, an uncoated portion is required to weld the lead to the inner peripheral side of the electrode plate for current collection. It is common practice to apply a protective tape to the leads in order to reinforce the welded leads and prevent separator breakage due to the ends of the leads. (For example, see Patent Document 2)
[0003]
[Patent Document 1]
JP-A-9-320640 (Claim 1, FIG. 4)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-10047 (page 3, FIG. 2)
[0004]
[Problems to be solved by the invention]
By the way, in the lithium ion secondary battery, regardless of the cylindrical type or the square type, due to the structure of the group component machine, there is a portion where only the separator is wound at the innermost peripheral portion. The separator often contains polyethylene or polypropylene as a main component, and contracts when exposed to severe temperature due to abnormal use of the battery. The separator sandwiched between the positive electrode plate and the negative electrode plate does not easily shrink somewhat, but the innermost portion of the separator alone is particularly likely to shrink. At this time, there was a problem that the positive electrode and the negative electrode were short-circuited with the contraction of the innermost peripheral separator.
[0005]
However, in the above-mentioned conventional technology, the above-described problem cannot be solved because the protection tape is applied only to the lead at the most in the uncoated portion.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the non-aqueous electrolyte secondary battery of the present invention is provided with an uncoated portion at an innermost circumferential end of the positive electrode plate, and at least a short side of the uncoated portion is provided. An insulating material having heat resistance is attached to a part or the whole surface including both ends in the direction. Thereby, even when the separator shrinks, a short circuit between the positive electrode plate and the negative electrode plate can be prevented unlike the configuration in which the protective tape is applied only to the leads.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery including an electrode group in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween.
An uncoated portion is provided at the innermost peripheral longitudinal end of the positive electrode plate, and a heat-resistant insulator is attached to at least a part or entire surface of the uncoated portion including at least the short-direction ends. In this battery electrode plate, an internal short circuit due to separator shrinkage during abnormal heating can be prevented.
Since the core diameter of the cylindrical battery is 3 to 4 mm, the portion where the heat-resistant insulator is attached is at least 15 mm in the longitudinal direction to protect at least one round of the innermost peripheral plate. It is desirable.
The insulator is desirably at least one of a polyimide resin tape, a glass tape, and a PPS tape having heat resistance. In particular, a polyimide resin tape is preferable because it is thin and the occupancy of the internal volume of the battery is small.
Similarly, the effect of the present invention can be obtained by applying a tape or the like to the corresponding portion of the negative electrode plate.However, since the negative electrode plate is usually larger than the positive electrode plate, the tape area becomes wider than that of the positive electrode plate, and the internal volume of the battery is reduced. It is preferable to perform the process on the positive electrode plate because it leads to a decrease in the capacity and a fear of a decrease in the capacity.
[0008]
【Example】
Hereinafter, specific examples of the present invention will be described.
[0009]
A positive electrode active material composed of lithium cobalt oxide (LiCoO ₂ ), a conductive material composed of acetylene black (AB), a binder composed of polyvinylidene fluoride (PVdF), and a solvent composed of N-methyl-2-pyrrolidone (NMP) are kneaded. The positive electrode paste prepared by dispersion is applied to a current collector made of aluminum foil having a thickness of 15 μm, dried, and then, the positive electrode mixture on both the front and back surfaces of a 30 mm portion corresponding to the innermost peripheral portion is peeled off. After rolling to a density of 3.3 g / cc alone, the sheet was cut so as to have a width of 54 mm and a total length of 15 mm including an uncoated portion of 550 mm.
[0010]
Next, the following positive plates 1 to 4 described with reference to FIGS.
[0011]
First, as shown in FIG. 1, a lead 3 was welded to an electrode plate consisting of the above-mentioned coated portion 1 and uncoated portion 2 and a polyimide resin tape 4a was applied only to the peripheral portion of the lead 3. Produced.
[0012]
Also, as shown in FIG. 2, a positive electrode plate 2 similar to the positive electrode plate 1 was prepared except that a polyimide resin tape 4b was applied to the entire uncoated portion 1.
[0013]
Then, as shown in FIG. 3, a positive electrode plate 3 similar to the positive electrode plate 1 was prepared except that polyimide resin tapes 4c were applied to both ends in the short direction.
[0014]
Finally, a positive electrode plate 4 similar to the positive electrode plate 2 was prepared except that the portion to which the polyimide resin tape was applied was 10 mm.
[0015]
Next, a negative electrode active material made of a graphite-type carbon material, a binder made of PVdF, and a negative electrode paste produced by kneading and dispersing a mixed solvent made of NMP were applied to a current collector made of a copper foil having a thickness of 14 μm, A negative electrode plate which is dried and rolled to 1.4 g / cc using only the active material, cut into a width of 56 mm and a total length of 580 mm, then welded to the outermost peripheral portion, and applied a polyimide resin tape only to the peripheral portion of the lead. Was prepared.
[0016]
An electrode group was prepared by winding the positive electrode plate and the negative electrode plate thus obtained through a separator made of a microporous polyethylene resin having a thickness of 20 μm.
[0017]
With the voltage of 5 V applied to the electrode group produced by the above method, heating was performed from room temperature to 150 ° C. in a constant temperature bath, and the voltage behavior was measured.
[0018]
(Results) The results of internal short circuits in the electrode groups using the positive electrode plates 1 to 4 are shown in (Table 1).
[0019]
[Table 1]

[0020]
In each of the electrode groups, decomposition observation after the test was performed, and at the same time, the short-circuited portion was specified for the short-circuited electrode group.
[0021]
The temperature of the electrode group using the positive electrode plate 1 where a short circuit occurred was about 130 ° C. In the disassembly observation, shrinkage was observed in the innermost peripheral part, and the end of the positive electrode plate was exposed, and it was confirmed that a short circuit occurred in this part.
[0022]
No short circuit occurred in the electrode group using the positive electrode plate 2 and the positive electrode plate 3. When these electrode groups were disassembled, the separator shrunk similarly to the electrode group of the positive electrode plate 1, exposing the polyimide resin tape of the positive electrode plate. Therefore, no short circuit has occurred.
[0023]
Although a short circuit occurred in the electrode group using the positive electrode plate 4, the occurrence rate was lower than that in the electrode group of the positive electrode plate 1. Although an effect can be obtained with a coating of 10 mm, it is preferable that the thickness be 15 mm or more.
[0024]
As described above, the electrode group of the present invention using the positive electrode plates 2 to 4 has a low occurrence rate of internal short-circuit, so if the non-aqueous electrolyte secondary battery is sealed in a metal case together with the electrolyte, Even when the battery is exposed to a severe temperature due to abnormal use or the like, it is possible to provide a battery capable of preventing an internal short circuit due to contraction of the separator.
[0025]
【The invention's effect】
As described above, the non-aqueous electrolyte secondary battery of the present invention, and particularly according to the structure of the innermost peripheral portion, the separator shrinks even when the battery is exposed to severe temperatures due to abnormal use or the like. It is possible to prevent an internal short circuit due to.
[Brief description of the drawings]
FIG. 1 is a conceptual structural diagram of a positive electrode plate 1 used in an embodiment of the present invention. FIG. 2 is a conceptual structural diagram of a positive electrode plate 2 used in an embodiment of the present invention. FIG. Conceptual structure diagram of positive electrode plate 3
1 Coated part 2 Uncoated part 3

Leads

4a, 4b, 4c Tape

Claims

In a nonaqueous electrolyte secondary battery including an electrode group in which a positive electrode plate and a negative electrode plate are wound via a separator,
An uncoated portion is provided at the innermost peripheral longitudinal end of the positive electrode plate, and a heat-resistant insulator is attached to at least a part or entire surface of the uncoated portion including at least the short-direction ends. Non-aqueous electrolyte secondary battery.

The non-aqueous electrolyte secondary battery according to claim 1, wherein the portion to which the heat-resistant insulator is attached is 15 mm or more in a longitudinal direction.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the insulator is at least one of a polyimide resin tape, a glass tape, and a PPS tape.