JP4698929B2

JP4698929B2 - Non-aqueous electrolyte secondary battery

Info

Publication number: JP4698929B2
Application number: JP2003026746A
Authority: JP
Inventors: 隆行白根; 太志谷川; 哲橋本; 豪皆藤
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2003-02-04
Filing date: 2003-02-04
Publication date: 2011-06-08
Anticipated expiration: 2023-02-04
Also published as: JP2004241170A

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、前記未塗工部の全面または、前記未塗工部の短手方向両端部の全部を少なくとも含む前記未塗工部の一部に耐熱性をもつ絶縁物が貼付されており、前記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（ＬｉＣｏＯ₂）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
The present invention relates to a nonaqueous electrolyte secondary battery, and more particularly to the structure of the innermost periphery.
[0002]
[Prior art]
In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless, and there is an increasing demand for secondary batteries having a small size, light weight, and high energy density as power sources for driving these devices. Among them, a lithium ion secondary battery using lithium as an active material is particularly expected as a battery having a high voltage and a high energy density.
In recent years, competition for high capacity, high output, and high reliability has intensified in each company. In such a situation, the unnecessary portion of the positive electrode plate or negative electrode plate is removed, that is, an uncoated portion is provided on the positive electrode plate or negative electrode plate, and the length of the electrode plate is increased accordingly. In order to increase the capacity, various measures have been taken. Furthermore, in order to ensure safety and reliability, a configuration in which an uncoated portion is provided on the electrode plate has been proposed. (For example, see Patent Document 1)
Usually, an uncoated part is required to weld the lead to the inner peripheral side of the electrode plate for current collection. In addition, in order to reinforce the welded lead and prevent breakage of the separator due to the end portion of the lead, a protective tape is generally applied to the lead. (For example, see Patent Document 2)
[0003]
[Patent Document 1]
JP-A-9-320640 (Claim 1, FIG. 4)
[Patent Document 2]
Japanese Patent Laid-Open No. 2000-1000046 (page 3, FIG. 2)
[0004]
[Problems to be solved by the invention]
By the way, in the lithium ion secondary battery, there is a portion where only the separator is wound in the innermost peripheral part regardless of the cylindrical type or the rectangular type because of the structure of the group constituting machine. The separator is mainly composed of polyethylene or polypropylene, and shrinks when exposed to severe temperatures due to abnormal use of the battery. Although the separator sandwiched between the positive electrode plate and the negative electrode plate is somewhat difficult to contract, the innermost peripheral part of the separator alone is particularly easily contracted. At this time, there was a problem that the positive electrode and the negative electrode were short-circuited as the innermost peripheral separator contracted.
[0005]
However, the above-described conventional technique cannot solve the above problem because the uncoated portion is only provided with a protective tape only on the leads.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, the non-aqueous electrolyte secondary battery of the present invention is provided with an uncoated portion at the innermost circumferential longitudinal end of the positive electrode plate, or the entire surface of the uncoated portion, A portion where an insulating material having heat resistance is affixed to a part of the uncoated portion including at least all of both ends in the short direction of the uncoated portion, and the insulating material having the heat resistance is affixed Is 15 mm or more in the longitudinal direction . Thus, even when the problem of contraction of the separator occurs, it is possible to prevent the positive electrode plate and the negative electrode plate from being short-circuited unlike the configuration in which the protective tape is applied only to the leads.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery comprising an electrode group in which a positive electrode plate and a negative electrode plate are wound through a separator.
An uncoated portion is provided at the innermost circumferential longitudinal end of the positive electrode plate, and an insulating material having heat resistance is affixed to a part or the entire surface including at least both lateral ends of the uncoated portion. This battery electrode plate can prevent internal short circuit due to separator contraction during abnormal heating.
In the cylindrical battery, the core diameter is 3 to 4 mm. Therefore, in order to protect at least one turn of the innermost peripheral electrode plate, the portion to which the heat-resistant insulating material is attached is 15 mm or more in the longitudinal direction. It is desirable.
It is desirable that the insulator is at least one of polyimide resin tape, glass tape, and PPS tape having heat resistance. In particular, a polyimide resin tape is preferable because it is thin and occupies a small volume in the battery.
In the same way, the effect of the present invention can be obtained by applying a tape or the like to the corresponding part of the negative electrode plate. Since it leads to reduction and there is a concern about capacity reduction, it is preferable to carry out the positive electrode plate.
[0008]
【Example】
Hereinafter, specific examples of the present invention will be described.
[0009]
A positive electrode active material composed of lithium cobaltate (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) The positive electrode paste prepared by dispersion was applied to a current collector made of aluminum foil having a thickness of 15 μm and dried, and then the positive electrode mixture on both the front and back surfaces of the 30 mm portion corresponding to the innermost peripheral portion was peeled off to obtain an active material After rolling to a density of only 3.3 g / cc, the entire length including a width of 54 mm and an uncoated part of 15 mm was cut to 550 mm.
[0010]
Next, the following positive electrode plates 1 to 4 described with reference to FIGS. 1 to 3 were produced.
[0011]
First, as shown in FIG. 1, a positive electrode plate 1 in which three leads are welded to the electrode plate composed of the above-described coated portion 1 and uncoated portion 2 and a polyimide resin tape 4 a is applied only to the peripheral portion of the lead 3. Produced.
[0012]
Moreover, as shown in FIG. 2, the positive electrode plate 2 similar to the positive electrode plate 1 was produced except having applied the polyimide resin tape 4b to the whole uncoated part 1 surface.
[0013]
And as shown in FIG. 3, the positive electrode plate 3 similar to the positive electrode plate 1 was produced except having applied the polyimide resin tape 4c to the both ends of the transversal 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 paste made by kneading and dispersing a negative electrode active material made of graphite-type carbon material, a binder made of PVdF, and a mixed solvent made of NMP was applied to a current collector made of copper foil having a thickness of 14 μm, After drying and rolling to 1.4 g / cc with only the active material, after cutting to a width of 56 mm and a total length of 580 mm, a lead is welded to the outermost periphery, and a polyimide resin tape is applied only to the periphery of the lead Was made.
[0016]
An electrode group in which the positive electrode plate and the negative electrode plate thus obtained were wound through a separator made of a microporous polyethylene resin having a thickness of 20 μm was produced.
[0017]
While the voltage of 5 V was applied to the electrode group produced by the above method, heating was performed from room temperature to 150 ° C. in a thermostatic chamber, and the voltage behavior was measured.
[0018]
(Results) The results of the internal short circuit in the electrode group using the positive electrode plate 1 to the positive electrode plate 4 are shown in (Table 1).
[0019]
[Table 1]

[0020]
In any of the electrode groups, the disassembly observation after the test was performed, and at the same time, the short-circuited portion was identified for the short-circuited electrode group.
[0021]
Of the electrode group using the positive electrode plate 1, the one where a short circuit occurred was about 130 ° C. In the decomposition observation, it was confirmed that the innermost peripheral separator contracted, the end of the positive electrode plate was exposed, and this part was short-circuited.
[0022]
None of the electrode groups using the positive electrode plate 2 and the positive electrode plate 3 were short-circuited. When these electrode groups were disassembled, the separator contracted in the same way as the electrode group of the positive electrode plate 1, and the polyimide resin tape of the positive electrode plate was exposed. For this reason, it has not led to a short circuit.
[0023]
Although the electrode group using the positive electrode plate 4 was also short-circuited, the generation rate was lower than that of the electrode group of the positive electrode plate 1. The effect can be obtained even with a coating of 10 mm, but it is desirable that the coating is 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 incidence of internal short circuit, so if a non-aqueous electrolyte secondary battery is made by sealing it 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, a battery capable of preventing an internal short circuit due to contraction of the separator can be provided.
[0025]
【The invention's effect】
As described above, according to the non-aqueous electrolyte secondary battery of the present invention, in particular, according to the structure of the innermost peripheral portion, even when the battery is exposed to severe temperatures due to abnormal use, the separator shrinks. 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. Conceptual structure diagram of positive electrode plate 3 [Explanation of symbols]
1 Coated part 2 Uncoated part 3

Lead

4a, 4b, 4c Tape

Claims

In a non-aqueous electrolyte secondary battery comprising an electrode group in which a positive electrode plate and a negative electrode plate are wound through a separator,
The uncoated portion is provided with an uncoated portion at an innermost circumferential longitudinal end of the positive electrode plate, and includes at least the entire surface of the uncoated portion or all of both ends in the short direction of the uncoated portion. some parts have insulator having heat resistance is affixed to the portion insulator having the heat resistance is attached, the non-aqueous electrolyte secondary, characterized in that it is longitudinally 15mm or more battery.

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