JP4218362B2

JP4218362B2 - Sealed battery

Info

Publication number: JP4218362B2
Application number: JP2003031224A
Authority: JP
Inventors: 哲橋本; 豪皆藤; 隆行白根; 太志谷川
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2003-02-07
Filing date: 2003-02-07
Publication date: 2009-02-04
Anticipated expiration: 2023-02-07
Also published as: JP2004241308A

Description

【０００１】
【発明の属する技術分野】
本発明は、密閉型電池における防爆機構に関するものである。
【０００２】
【従来の技術】
従来より密閉型電池で化学反応等にともなって発生するガスによる内部圧力上昇、過充電による発火、爆発に危険性に対する防爆機構として種々の機構が用いられてきている。
【０００３】
そのような中で、破断強度の異なる２枚の薄肉部を設けた金属箔を絶縁材料を介して２枚の金属箔の薄肉部を同軸上に設置し、軸上で電気的に接続した構造を有した防爆封口板が提案されている（例えば特許文献１参照）。
【０００４】
特許文献１に記載される電池の断面構造を図３に示している。
【０００５】
この電池の密閉構造は、下記の動作をして内圧の上昇を防止する。
【０００６】
▲１▼電池の内圧が設定圧よりも低い通常の状態
この状態においては、図３に示すように、上弁体１と下弁体２が電気的に接続されている。したがって、電池のキャップ６は、温度抵抗体５、上弁体１、下弁体２、下部フィルター４、リード線７とを介して発電素子８に接続できる状態となっている。
【０００７】
▲２▼電池の内圧が設定圧力よりも高く上昇した状態
電池の内圧が上昇すると、図４に示すように、矢印で示す発生したガスの流れ１１、１２、１３が起こり、下部弁体２が圧力で押し上げられる。このとき、下弁体薄肉部２ａが切断され、上弁体１と下弁体２が切り離される。したがって、電池は内部で電流を遮断する。この状態になると、電池に電流が流れなくなり、電池内部の化学反応は停止する。したがって、内圧の上昇は制限される。
【０００８】
▲３▼電流を遮断してもさらに内圧が上昇する場合
電流を遮断しても、電池の内圧はさらに高くなることがある。このとき、図５に示すように上弁体薄肉部１ａで破断される。破断した上弁体１は電池内のガスを矢印で示すガスの流れ１４のように排気する。上弁体１を通過したガスは、キャップ６のガス抜き孔９から電池の外部に排気される。
【０００９】
しかし、この防爆型密閉電池の構造では、使用設定外の大電流で過充電をしたとき、電池内残空間のバラツキの範囲で残空間の大きいものは、発火、爆発等の活物質の熱暴走に至るものがある。この原因は、電池内圧がそれほど上昇する前に活物質が熱暴走を起こしたためで、前記電流遮断手段が有効に機能しないという課題があった。
【００１０】
そのため、過充電時にガスを発生する添加剤と電流遮断手段を組み合わせた構成が提案されている（例えば特許文献２参照）。
【００１１】
【特許文献１】
特許第３１９６６０７号公報（請求項１、図２）
【特許文献２】
特許第３１１３６５２号公報（請求項１、図２）
【００１２】
【発明が解決しようとする課題】
しかしながら従来の電池では、電解液中にガス発生のための添加剤を添加しているため、高温保存中などに分解したり電解液と反応して電池の性能を劣化させるという課題があった。
【００１３】
そこで本発明は、かかる従来の実情に鑑みて提案されたもので、電流遮断手段を備えた非水電解質二次電池を大電流で過充電したときにおいても、上記電流遮断手段が確実に作動し、発火、爆発等の事故を防止することを可能にし、さらに高温保存時においても劣化しにくい非水電解質二次電池を提供することを目的とする。
【００１４】
【課題を解決するための手段】
上記の課題を解決するために本発明の密閉型電池は、発電要素を電解液と共に電池ケースに挿入し、封口板で密閉した密閉型電池において、前記封口板が、前記電池内部のガス圧により電流遮断を行なう防爆封口板であり、さらに封口板の内部であって前記電解液に触れない部分に、昇華性物質が配されていることを特徴としたものである。
【００１５】
通常の電池内圧上昇による防爆機構に加えて、電池の温度が上昇すると昇華性物質がガスを発生し、その圧力により確実に電流遮断を行なう。そして、電解液中に昇華性物質、熱分解性物質または蒸発性物質のいずれかを添加したわけではないので、高温保存時等でも電解液と反応して特性を落とすことはない。
【００１６】
また、前記封口板は、絶縁ガスケットを介して上下に２枚の金属箔を配していて、各金属箔にはＯ型形状もしくはＣ型形状の箔肉部を中心部が同軸上となるように設け、前記同軸上で上下の金属箔を電気的に接続しており、下方の金属箔の箔肉部の破断強度は上方の金属箔の箔肉部の破断強度より小さく、かつ上方の金属箔の箔肉部内に下方の金属箔の箔肉部が位置した防爆封口板であると、昇華性物質が発生したガスによる電流遮断が行なわれ易くなるため好ましい。
【００１７】
上記の封口板において、前記上下の金属箔の間に昇華性物質を配すると、電池が振動した時など、どのような場合においても電解液と接することがないので特に好適である。
【００１８】
なお、昇華性物質、熱分解性物質または蒸発性物質としては、ジクロルナフタリン、シュウ酸、パラフィン、樟脳、テトラクロルベンゼン、ヘキサクロロエタン、ヨウ素化合物、塩化セレン、ポリビニルピロリドン、ポロビニルブチノールなどがある。その中でも８０〜１３０℃の範囲で昇華、蒸発し、取り扱いの易しいナフタリン化合物が特に望ましく、このような化合物としては、ジクロルナフタリンがある。
【００１９】
【発明の実施の形態】
本発明の実施の形態の一例の電池の断面構造を図１に示す。図１において図３に示す従来の電池の封口板のように、上弁体１と下弁体２が電気的に接続されている。したがって、電池のキャップ６は、温度抵抗体５、上弁体１、下弁体２、下部フィルター４、リード線７とを介して発電素子８に接続できる状態となっている。さらに、上弁体１および下弁体２の間に、昇華性物質からなるガス発生剤１０を配置する。
【００２０】
この配置する方法としては、ガス発生剤を塗工したり、粉体を充填するなどのいろいろ方法があり、リング状に成形して嵌合するようにするのが、組み立てが簡単になるので好ましい。
【００２１】
二次電池は過充電すると電池温度が上昇する性質がある。それは、過充電状態になると、電池への入力電力を充電に使用する割合が少なくなって、熱エネルギーとなって消費されるからである。本発明の防爆型封口板は、この性質を利用することで非水電解質二次電池を過充電したときに、通常の電池内圧上昇による防爆機構に加えて、昇華性物質の性質を利用した上記の電流遮断機構を作動させることで確実に発火、爆発等の事故を防止することができる。
【００２２】
具体的には、本発明の防爆型の封口板は、通常の電池内圧上昇による防爆機構に加えて、電池の温度がガス発生剤１０のガス発生温度以上になると、ガス発生、例えば昇華性物質なら昇華性物質の固体から気体への変化による体積膨張によって、図２に示すように上弁体１が圧力で押し上げられる。このとき、下弁体薄肉部２ａが切断され、上弁体１と下弁体２が切り離される。このように電池は内部で電流を遮断する。この状態になると、電池に電流が流れなくなり、電池内部の化学反応は停止し、温度の上昇もなくなるため、内圧の上昇は制限される。つまり、電流遮断により発火、爆発等の事故を防止できることになる。
【００２３】
【実施例】
次に、本発明の具体例について実施例をもちいて詳細に説明する。
【００２４】
（比較例１）
まず、図３に示す構造をもつ従来の電池の封口板を作成した。
【００２５】
厚さ０．１０ｍｍ、外径φ１２．７ｍｍのアルミニウム製金属箔７の中央部に外径φ４．０ｍｍのＣ型形状の刻印を用いて薄肉部７ａを設け、厚さ０．１０ｍｍ、外径φ１３．５ｍｍでφ１．５ｍｍの通気孔を４つ持つアルミニウム製金属箔８に外径２．５ｍｍのＯ型形状の刻印を用いて薄肉部８ａを設けこの二枚の金属箔を絶縁ガスケット３を介してそれぞれの箔の中央部を溶接した。ここで、下方の金属箔の薄肉部の破断強度は１０〜１３ｋｇ／ｃｍ²であり、上方の金属箔の薄肉部の破断強度は１８〜２４ｋｇ／ｃｍ²である。これをφ１．５ｍｍの通気孔を４つ持つアルミ製金属ケースの中に挿入し、その上部に温度抵抗体５および、φ１．５ｍｍの通気孔を４つ持つ金属性キャップ６をのせて、かしめて比較例１の封口板を得た。
【００２６】
（実施例１）
次に、図１に示す構造を持つ実施例の電池の封口板を作成した。図３と同じ構造の封口板において、絶縁ガスケットを介してある上下に２枚の金属箔の間に昇華性物質として固形のジクロルナフタレンを配した以外は比較例１とまったく同じ実施例１の封口板を得た。配置の方法は、２ｍｇのジクロルナフタレンをリング状に成形してはめ込んだ。
【００２７】
実施例１および比較例１で得た封口板を用いて、直径１８ｍｍ、高さ６５ｍｍ、容量１２００ｍＡｈの円筒型非水系電解液を用いるリチウム二次電池にした。なお、電池内残空間は製造上のバラツキで最大となる２．０ｃｃにした。その電池を各々２０個づつ電流５Ａで過充電状態にすることによって電池の発火、爆発等の不安全現象が生じる発生率を調査した。その結果を（表１）に示す。
【００２８】
【表１】

【００２９】
以上の結果から本発明の構造を有する封口板は過充電時に電流遮断し、発火、爆発等の事故を防止できることがわかった。
【００３０】
以上、本発明を適用した実施例について説明したが、本発明がこれら実施例に限定されるものではなく、電池の構造や形状、寸法、材質等は本発明の要旨を逸脱しない範囲で任意である。
【００３１】
【発明の効果】
以上のように本発明は発火、爆発等の事故をより精度よく防止するために、通常の使用範囲では電池特性に影響することなく、過充電等の異常な電池温度上昇に対して確実に遮断できる封口板を実現することができる。
【図面の簡単な説明】
【図１】本発明の密閉二次電池の一例を示す上部断面図
【図２】図１において内圧が上昇して電流を遮断した状態を示す上部断面図
【図３】従来の防爆型の密閉二次電池の一例を示す上部断面図
【図４】図３において内圧が上昇して電流を遮断した状態を示す上部断面図
【図５】図４よりさらに上昇して安全弁を開弁した状態を示す上部断面図
【符号の説明】
１上弁体
１ａ上弁体薄肉部
２下弁体
２ａ下弁体薄肉部
３絶縁ガスケット
４下部フィルター
５温度抵抗体
６キャップ
７リード線
８発電素子
９ガス抜き孔
１０ガス発生剤[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an explosion-proof mechanism in a sealed battery.
[0002]
[Prior art]
Conventionally, various mechanisms have been used as an explosion-proof mechanism against danger of internal pressure rise due to gas generated by a chemical reaction or the like in a sealed battery, ignition by overcharge, and explosion.
[0003]
Under such circumstances, a structure in which a metal foil provided with two thin portions having different breaking strengths is installed coaxially through an insulating material and electrically connected on an axis. An explosion-proof sealing plate having the above has been proposed (see, for example, Patent Document 1).
[0004]
The cross-sectional structure of the battery described in Patent Document 1 is shown in FIG.
[0005]
This battery sealing structure prevents the internal pressure from increasing by the following operation.
[0006]
(1) Normal state where the internal pressure of the battery is lower than the set pressure In this state, the upper valve body 1 and the lower valve body 2 are electrically connected as shown in FIG. Therefore, the battery cap 6 can be connected to the power generation element 8 via the temperature resistor 5, the upper valve body 1, the lower valve body 2, the lower filter 4, and the lead wire 7.
[0007]
(2) When the internal pressure of the battery rises higher than the set pressure When the internal pressure of the battery rises, as shown in FIG. 4, the generated gas flows 11, 12, and 13 shown by arrows occur, and the lower valve body 2 Pushed up by pressure. At this time, the lower valve body thin portion 2a is cut, and the upper valve body 1 and the lower valve body 2 are separated. Therefore, the battery cuts off the current internally. In this state, no current flows through the battery, and the chemical reaction inside the battery stops. Therefore, the increase in internal pressure is limited.
[0008]
(3) When the internal pressure further increases even if the current is cut off Even if the current is cut off, the internal pressure of the battery may be further increased. At this time, the upper valve body thin portion 1a is broken as shown in FIG. The broken upper valve body 1 exhausts the gas in the battery as a gas flow 14 indicated by an arrow. The gas that has passed through the upper valve body 1 is exhausted from the gas vent hole 9 of the cap 6 to the outside of the battery.
[0009]
However, with this explosion-proof sealed battery structure, when overcharging is performed with a large current that is not set for use, the battery with large remaining space within the range of the remaining space in the battery is subject to thermal runaway of active materials such as ignition and explosion. There are things that lead to. This is because the active material caused thermal runaway before the internal pressure of the battery increased so much, and there was a problem that the current interrupting means did not function effectively.
[0010]
For this reason, a configuration has been proposed in which an additive that generates gas during overcharge and a current interrupting means are combined (see, for example, Patent Document 2).
[0011]
[Patent Document 1]
Japanese Patent No. 3196607 (Claim 1, FIG. 2)
[Patent Document 2]
Japanese Patent No. 3113652 (Claim 1, FIG. 2)
[0012]
[Problems to be solved by the invention]
However, in the conventional battery, since an additive for generating gas is added to the electrolytic solution, there is a problem that the battery performance is deteriorated by being decomposed or reacted with the electrolytic solution during high temperature storage.
[0013]
Therefore, the present invention has been proposed in view of such conventional circumstances, and even when a non-aqueous electrolyte secondary battery equipped with a current interrupting means is overcharged with a large current, the current interrupting means operates reliably. An object of the present invention is to provide a non-aqueous electrolyte secondary battery that can prevent accidents such as ignition and explosion, and that is not easily deteriorated even during high-temperature storage.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, a sealed battery according to the present invention is a sealed battery in which a power generation element is inserted into a battery case together with an electrolytic solution and sealed with a sealing plate. An explosion-proof sealing plate that cuts off current, and further, a sublimation substance is disposed in a portion of the sealing plate that is not in contact with the electrolytic solution.
[0015]
In addition to the normal explosion-proof mechanism by increasing the internal pressure of the battery, when the temperature of the battery increases, the sublimable substance generates gas, and the current is reliably interrupted by the pressure. In addition, since any sublimable substance, thermally decomposable substance, or evaporable substance is not added to the electrolytic solution, it does not deteriorate characteristics by reacting with the electrolytic solution even when stored at a high temperature.
[0016]
In addition, the sealing plate has two metal foils arranged on the upper and lower sides through an insulating gasket, and each metal foil has an O-shaped or C-shaped foil flesh portion coaxially at the center. The upper and lower metal foils are electrically connected on the same axis, and the breaking strength of the foil portion of the lower metal foil is smaller than the breaking strength of the foil portion of the upper metal foil, and the upper metal It is preferable that the explosion-proof sealing plate has the metal foil portion of the lower metal foil located in the foil portion of the foil because current interruption due to the gas generated by the sublimable substance is easily performed.
[0017]
In the above-described sealing plate, it is particularly preferable to dispose a sublimable substance between the upper and lower metal foils, since it does not come into contact with the electrolytic solution in any case such as when the battery vibrates.
[0018]
Examples of sublimable, thermally decomposable or evaporable substances include dichloronaphthalene, oxalic acid, paraffin, camphor, tetrachlorobenzene, hexachloroethane, iodine compound, selenium chloride, polyvinylpyrrolidone, and polyvinylbutynol. is there. Among them, a naphthalene compound that sublimates and evaporates in the range of 80 to 130 ° C. and is easy to handle is particularly desirable, and such a compound is dichloronaphthalene.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a cross-sectional structure of an example battery according to an embodiment of the present invention. In FIG. 1, the upper valve body 1 and the lower valve body 2 are electrically connected like the sealing plate of the conventional battery shown in FIG. Therefore, the battery cap 6 can be connected to the power generation element 8 via the temperature resistor 5, the upper valve body 1, the lower valve body 2, the lower filter 4, and the lead wire 7. Further, a gas generating agent 10 made of a sublimable substance is disposed between the upper valve body 1 and the lower valve body 2.
[0020]
As this arrangement method, there are various methods such as coating with a gas generating agent and filling with powder, and it is preferable to form and fit in a ring shape because it is easy to assemble. .
[0021]
Secondary batteries have the property of increasing battery temperature when overcharged. This is because when the battery is overcharged, the proportion of the input power to the battery used for charging is reduced and consumed as thermal energy. The explosion-proof sealing plate of the present invention utilizes the above-mentioned properties utilizing the properties of the sublimable substance in addition to the normal explosion-proof mechanism due to the increase in the internal pressure of the battery when the non-aqueous electrolyte secondary battery is overcharged by utilizing this property. By operating the current interrupting mechanism, accidents such as ignition and explosion can be surely prevented.
[0022]
Specifically, the explosion-proof sealing plate of the present invention is capable of generating gas when the battery temperature is equal to or higher than the gas generation temperature of the gas generating agent 10 in addition to the normal explosion-proof mechanism by increasing the internal pressure of the battery. Then, the upper valve body 1 is pushed up by pressure as shown in FIG. 2 due to volume expansion due to the change of the sublimable substance from solid to gas. At this time, the lower valve body thin portion 2a is cut, and the upper valve body 1 and the lower valve body 2 are separated. In this way, the battery cuts off the current internally. In this state, no current flows through the battery, the chemical reaction inside the battery stops, and the temperature does not increase, so the increase in internal pressure is limited. That is, accidents such as ignition and explosion can be prevented by interrupting the current.
[0023]
【Example】
Next, specific examples of the present invention will be described in detail using examples.
[0024]
(Comparative Example 1)
First, a conventional battery sealing plate having the structure shown in FIG. 3 was prepared.
[0025]
A thin-walled portion 7a is provided at the center of an aluminum metal foil 7 having a thickness of 0.10 mm and an outer diameter of φ12.7 mm using a C-shaped stamp having an outer diameter of φ4.0 mm, and has a thickness of 0.10 mm and an outer diameter of φ13. A thin metal part 8a is formed on an aluminum metal foil 8 having four vent holes of .5 mm and φ1.5 mm using an O-shaped stamp with an outer diameter of 2.5 mm. The center of each foil was welded. Here, the breaking strength of the thin portion of the lower metal foil is 10 to 13 kg / cm ² , and the breaking strength of the thin portion of the upper metal foil is 18 to 24 kg / cm ² . This is inserted into an aluminum metal case having four φ1.5 mm vents, and a temperature resistor 5 and a metal cap 6 having four φ1.5 mm vents are placed on the top. The sealing plate of Comparative Example 1 was obtained.
[0026]
Example 1
Next, a battery sealing plate of the example having the structure shown in FIG. 1 was prepared. In the sealing plate having the same structure as in FIG. 3, Example 1 is exactly the same as Comparative Example 1 except that solid dichloronaphthalene is disposed as a sublimation substance between two upper and lower metal foils via an insulating gasket. A sealing plate was obtained. As a method of arrangement, 2 mg of dichloronaphthalene was molded into a ring shape and fitted.
[0027]
Using the sealing plates obtained in Example 1 and Comparative Example 1, a lithium secondary battery using a cylindrical non-aqueous electrolyte solution having a diameter of 18 mm, a height of 65 mm, and a capacity of 1200 mAh was obtained. The remaining space in the battery was 2.0 cc, which is the largest due to manufacturing variations. The rate of occurrence of unsafe phenomena such as ignition and explosion of the battery was investigated by putting each of the batteries into an overcharged state with a current of 5A. The results are shown in (Table 1).
[0028]
[Table 1]

[0029]
From the above results, it was found that the sealing plate having the structure of the present invention cuts off the current when overcharged and can prevent accidents such as ignition and explosion.
[0030]
Although the embodiments to which the present invention is applied have been described above, the present invention is not limited to these embodiments, and the structure, shape, dimensions, material, and the like of the battery are arbitrarily set within the scope of the present invention. is there.
[0031]
【The invention's effect】
As described above, in order to prevent accidents such as ignition and explosion more accurately, the present invention reliably shuts off abnormal battery temperature rises such as overcharge without affecting battery characteristics in the normal use range. A sealing plate that can be realized can be realized.
[Brief description of the drawings]
FIG. 1 is an upper cross-sectional view showing an example of a sealed secondary battery of the present invention. FIG. 2 is an upper cross-sectional view showing a state where an internal pressure is increased and an electric current is interrupted in FIG. FIG. 4 is a top cross-sectional view showing an example of a secondary battery. FIG. 4 is a top cross-sectional view showing a state where the internal pressure is increased and the current is cut off in FIG. 3. FIG. Upper cross section shown [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Upper valve body 1a Upper valve body thin part 2 Lower valve body 2a Lower valve body thin part 3 Insulation gasket 4 Lower filter 5 Temperature resistor 6 Cap 7 Lead wire 8 Power generation element 9 Gas vent hole 10 Gas generating agent

Claims

In a sealed battery in which a power generation element is inserted into a battery case together with an electrolytic solution and sealed with a sealing plate, the sealing plate is an explosion-proof sealing plate that cuts off current by gas pressure inside the battery, and further inside the sealing plate A sealed battery characterized in that a sublimation substance is disposed on a portion that does not touch the electrolyte solution ,
A sealed battery, wherein the sublimable substance is a naphthalene compound that sublimes in the range of 80 to 130 ° C.

The sealing plate has two metal foils arranged on the upper and lower sides through insulating gaskets, and each metal foil is provided with an O-shaped or C-shaped foil wall portion so that the central portion is coaxial. The upper and lower metal foils are electrically connected on the same axis, and the breaking strength of the foil portion of the lower metal foil is smaller than the breaking strength of the foil portion of the upper metal foil, and the upper metal foil 2. The sealed battery according to claim 1, which is an explosion-proof sealing plate in which a metal foil portion of the lower metal foil is located in the metal foil portion.

The sealed battery according to claim 2, wherein the sublimable substance is disposed between the upper and lower metal foils.