JP4486284B2

JP4486284B2 - Nonaqueous electrolyte secondary battery

Info

Publication number: JP4486284B2
Application number: JP2001247579A
Authority: JP
Inventors: 知雄秋山; 勉橋本; 英彦田島
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2001-08-17
Filing date: 2001-08-17
Publication date: 2010-06-23
Anticipated expiration: 2021-08-17
Also published as: JP2003059476A

Description

【０００１】
【発明の属する技術分野】
本発明は、例えばリチウム二次電池などの非水電解質二次電池の外装缶に備える安全弁に工夫をすることにより、短絡事故時などにおける熱暴走反応を抑制して安全性を高めたものである。
【０００２】
【従来の技術】
リチウム二次電池は、高電圧・高エネルギー密度を有し、且つ、貯蔵性能や低温動作性に優れるため、広く携帯用民生電気製品の電源として普及している。電子機器向けの小型で小容量のものにとどまらず、工場や病院などの非常電源設備や深夜電力貯蔵用電源、あるいは電気自動車の動力用電源としての可能性から、大型で大容量のリチウム２次電池の研究・開発が盛んに行われている。
【０００３】
図２は大型の箱型のリチウム二次電池１０を示すものである。図２において、１は電池の外装缶、２は正極、３は負極、４はセパレータ、５は正極端子、６は負極端子、７は破裂型の安全弁である。このリチウム二次電池１０では、外装缶１内に可燃性の有機材料でなる電解液（図示省略）が充填されている。
【０００４】
このようなリチウム二次電池１０を用いて蓄電システムを構成する場合、図３に示すように、複数（本例では４個）のリチウム二次電池１０をフレーム２０に収納し、複数のリチウム二次電池１０を直・並列接続してモジュール電池として使用されることが多い。
【０００５】
このようなリチウム二次電池１０では、内部短絡が発生すると短絡部分（正負極間）に大きな短絡電流が流れて発熱し、その熱による電池温度上昇により、正負極表面における電解液の分解発熱反応や電解液自体の発熱分解反応が加速され、電解液の気化や分解により、電池内部の圧力が急激に上昇するという、いわゆる熱暴走現象が発生する。このように内部圧力が急激に上昇すると外装缶１が破裂したり、外装缶１の破裂により電解液が周囲に飛散したり周辺機器を損傷させる恐れがある。
【０００６】
そこで、このような外装缶１の破裂・飛散という最悪の事態を回避するため、通常リチウム２次電池は安全弁７を備えている。即ち、外装缶１内の圧力が上昇し、この圧力が所定以上になると、破裂型の安全弁７が破裂・破断して開状態となり、ガスを外部に放出して圧力開放を行うようにしている。なお、電解液を加熱してガスを発生させ電池内部圧力を上昇させる原因となる電池異常としては、内部短絡，外部短絡，過大電流入力，過大電圧入力，過昇温等がある。
【０００７】
なお、図２の例では、４つの安全弁７が備えられており、この場合、４つの安全弁７は、内部圧力が所定圧力以上になったときに同時に破裂するような、同一の耐圧強度を持ったものとしている。
【０００８】
【発明が解決しようとする課題】
ところで、内部圧力が高くなり安全弁７が開放すると、高温のガスが短絡部分から安全弁７に向かって流れ、電池温度が急激に上昇し、この熱上昇が熱暴走を更に加速させる恐れがある。
【０００９】
即ち、耐圧強度が等しい４つの安全弁を備えたリチウム二次電池では、内部圧力が所定圧力を越えると、４つの安全弁が略同時に開放する。このため、短絡部分から第１の安全弁７に向かって高温のガスが流れ、同時に、短絡部分から第２〜第３の安全弁７に向かってそれぞれ高温のガスが流れる。このように、４つの経路に沿って、高温のガスが同時に流れ、高温ガスの流路周辺での熱暴走反応が誘起されるため、電池温度が急上昇する。
【００１０】
このように、従来技術では、安全弁の開放に伴い高温ガスが流れると、ガス流路周辺の電池温度が急上昇するため、熱暴走が加速するという不具合があった。
【００１１】
本発明は、上記従来技術に鑑み、安全弁を開放して高温ガスを外部に放出しても、電池温度の上昇を抑制して、熱暴走を阻止するようにした非水電解質二次電池を提供することを目的とする。
【００１２】
【課題を解決するための手段】
上記課題を解決する本発明の構成は、外装缶に耐圧強度の異なる複数の安全弁を備えた非水電解質二次電池であって、前記安全弁が破裂型であり、前記耐圧強度の異なる安全弁は前記外装缶の配置面において対角位置に配置されていることを特徴とする。
【００１３】
また本発明の構成は、外装缶に破裂型の安全弁を備えた非水電解質二次電池において、前記安全弁は４個備えられていると共に、前記４個の安全弁のうちの２個の安全弁で組となった第１の安全弁群と、前記４個の安全弁のうちの残りの２個の安全弁で組となった第２の安全弁群との耐圧強度が異なっており、しかも、第１の安全弁群を構成する２個の安全弁の耐圧強度は等しくこの２個の安全弁は、前記外装缶の配置面において第１の対角位置に配置されており、第２の安全弁群を構成する２個の安全弁の耐圧強度は等しくこの２個の安全弁は、前記外装缶の配置面において第２の対角位置に配置されていることを特徴とする。
【００１４】
【発明の実施の形態】
以下に本発明の実施の形態を図面に基づき詳細に説明する。
【００１５】
図１は本発明の実施の形態にかかる安全弁１０Ａを示す。図１において、１は電池の外装缶、２は正極、３は負極、４はセパレータ、５は正極端子、６は負極端子である。このリチウム二次電池１０Ａでは、外装缶１内に可燃性の有機材料でなる電解液（図示省略）が充填されている。
【００１６】
外装缶１の上面には破裂型の２組の安全弁群７ａ，７ｂを備えている。安全弁群７ａ，７ｂは、外装缶１の上面においてそれぞれ対角位置に配置されており、両安全弁群７ａ，７ｂの耐圧強度は異なっている。例えば、安全弁群７ａの耐圧強度は３Kgf/cm²であり、安全弁群７ｂの耐圧強度は５Kgf/cm²である。
【００１７】
このリチウム二次電池１０Ａにおいて内部短絡が発生し、内部圧力が上昇すると、まず先に第１の対角位置にある安全弁群７ａが破裂開放し、その後、時間的に遅れて第２の対角位置にある安全弁群７ｂが破裂開放する。このため、高温のガスは、短絡部分から安全弁群７ａに向かう第１の経路に沿って流れ、時間的に遅れて、短絡部分から安全弁群７ｂに向かう第２の経路に沿っても流れだす。
【００１８】
このため、高温のガスは、最初は第１の経路に沿って流れ、その後、時間的に遅れて、第１の経路と第２の経路に別れて流れ第１の経路に沿うガス流れが減少する。このように、ガスの流れる経路が、時間的に移動していくため、高温ガスの移動による熱暴走反応の加速が抑制され、電池温度が急上昇することなく安全性を確保することができる。
【００１９】
実験では、リチウム二次電池１０，１０Ａを横置きして、それぞれの中央部に、直径が８ｍｍの鉄製釘を貫通させて内部短絡を起こして、温度上昇の変化を観察した。この実験においては、図１のように耐圧強度の異なる２組の安全弁群７ａ，７ｂを設けたリチウム二次電池１０Ａは、図２のように耐圧強度の等しい４つの安全弁７を設けたリチウム二次電池１０に比べて、温度上昇が低いことが確認できた。
【００２０】
また、安全弁群７ａ，７ｂが外装缶１の上面において対角位置に配置されているため、リチウム二次電池１０Ａが横に置かれた場合（即ち外装缶１の上面が垂直面になるように置かれた場合）であっても、短絡事故が発生すると、安全弁群７ａ，７ｂのうち少なくとも一方（上側に位置する安全弁）からガスの放出ができるため、安全である。
【００２１】
なお図１の例では、耐圧強度の異なる２組の安全弁群７ａ，７ｂを備えているが、耐圧強度の異なる３組以上の安全弁群を備えるようにしてもよい。
【００２２】
【発明の効果】
以上、実施の形態と共に具体的に説明したように、本発明では、外装缶に耐圧強度の異なる複数の安全弁を備えた非水電解質二次電池であって、前記安全弁が破裂型であり、前記耐圧強度の異なる安全弁は前記外装缶の配置面において対角位置に配置されている構成とした。
このため、内部短絡が発生しても、高温のガスの流れ経路が変化していき、電池温度が急上昇することなく安全性が高まる。
【００２３】
また本発明では、外装缶に破裂型の安全弁を備えた非水電解質二次電池において、前記安全弁は４個備えられていると共に、前記４個の安全弁のうちの２個の安全弁で組となった第１の安全弁群と、前記４個の安全弁のうちの残りの２個の安全弁で組となった第２の安全弁群との耐圧強度が異なっており、しかも、第１の安全弁群を構成する２個の安全弁の耐圧強度は等しくこの２個の安全弁は、前記外装缶の配置面において第１の対角位置に配置されており、第２の安全弁群を構成する２個の安全弁の耐圧強度は等しくこの２個の安全弁は、前記外装缶の配置面において第２の対角位置に配置されている構成とした。
このため、内部短絡が発生しても、高温のガスの流れ経路が変化していき、電池温度が急上昇することなく安全性が高まる。更に、電池を横置きしても、安全弁としての機能を確保することができる。
【００２４】
また本発明をリチウム二次電池に適用することにより、リチウム二次電池の安全性を高めることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態にかかるリチウム二次電池を破断して示す構成図。
【図２】従来のリチウム二次電池を破断して示す構成図。
【図３】リチウム二次電池によるモジュール電池を示す斜視図。
【符号の説明】
１外装缶
２正極
３負極
４セパレータ
５正極端子
６負極端子
７破裂型の安全弁
７ａ，７ｂ破裂型の安全弁群
１０，１０Ａリチウム二次電池
２０フレーム[0001]
BACKGROUND OF THE INVENTION
In the present invention, for example, a safety valve provided in an outer can of a non-aqueous electrolyte secondary battery such as a lithium secondary battery is devised, thereby suppressing a thermal runaway reaction at the time of a short circuit accident or the like and improving safety. .
[0002]
[Prior art]
Lithium secondary batteries have high voltage and high energy density, and are excellent in storage performance and low-temperature operability, so that they are widely used as power sources for portable consumer electronic products. Not only small and small capacity for electronic devices, but also large power and large capacity lithium secondary due to the possibility of emergency power supply facilities such as factories and hospitals, power sources for late-night power storage, or power sources for electric vehicles. Batteries are actively researched and developed.
[0003]
FIG. 2 shows a large box-type lithium secondary battery 10. In FIG. 2, 1 is a battery outer can, 2 is a positive electrode, 3 is a negative electrode, 4 is a separator, 5 is a positive electrode terminal, 6 is a negative electrode terminal, and 7 is a rupture-type safety valve. In the lithium secondary battery 10, the outer can 1 is filled with an electrolyte solution (not shown) made of a combustible organic material.
[0004]
When a power storage system is configured using such lithium secondary batteries 10, as shown in FIG. 3, a plurality (four in this example) of lithium secondary batteries 10 are housed in a frame 20, and a plurality of lithium secondary batteries 10 are stored. The secondary battery 10 is often used as a module battery by connecting it in series or in parallel.
[0005]
In such a lithium secondary battery 10, when an internal short circuit occurs, a large short circuit current (between the positive and negative electrodes) flows and generates heat, and due to the rise in battery temperature due to the heat, decomposition heat generation reaction of the electrolyte solution on the positive and negative electrode surfaces In addition, an exothermic decomposition reaction of the electrolyte solution itself is accelerated, and a so-called thermal runaway phenomenon occurs in which the pressure inside the battery rapidly increases due to the evaporation or decomposition of the electrolyte solution. If the internal pressure rises rapidly in this way, the outer can 1 may rupture, the outer can 1 may rupture, and the electrolyte may scatter around and damage peripheral devices.
[0006]
Therefore, in order to avoid such a worst situation that the outer can 1 is ruptured and scattered, the lithium secondary battery is usually provided with a safety valve 7. That is, when the pressure in the outer can 1 rises and this pressure exceeds a predetermined value, the burstable safety valve 7 is ruptured and broken to open, and the gas is released to release the pressure. . Note that battery abnormalities that cause the electrolyte to heat and generate gas to increase the internal pressure of the battery include internal short circuits, external short circuits, excessive current input, excessive voltage input, excessive temperature rise, and the like.
[0007]
In the example of FIG. 2, four safety valves 7 are provided. In this case, the four safety valves 7 have the same pressure resistance strength so that they burst simultaneously when the internal pressure exceeds a predetermined pressure. It is assumed.
[0008]
[Problems to be solved by the invention]
By the way, when the internal pressure becomes high and the safety valve 7 is opened, high-temperature gas flows from the short-circuited portion toward the safety valve 7, the battery temperature rapidly increases, and this heat increase may further accelerate the thermal runaway.
[0009]
That is, in a lithium secondary battery provided with four safety valves having the same pressure resistance, when the internal pressure exceeds a predetermined pressure, the four safety valves are opened almost simultaneously. For this reason, high-temperature gas flows from the short-circuit portion toward the first safety valve 7, and at the same time, high-temperature gas flows from the short-circuit portion toward the second to third safety valves 7. In this way, high-temperature gas flows simultaneously along the four paths, and a thermal runaway reaction is induced around the flow path of the high-temperature gas, so that the battery temperature rapidly rises.
[0010]
As described above, in the conventional technology, when a high-temperature gas flows as the safety valve is opened, the battery temperature in the vicinity of the gas flow path rapidly increases, so that the thermal runaway is accelerated.
[0011]
In view of the above prior art, the present invention provides a non-aqueous electrolyte secondary battery that prevents a thermal runaway by suppressing a rise in battery temperature even when a safety valve is opened and high temperature gas is released to the outside. The purpose is to do.
[0012]
[Means for Solving the Problems]
Configuration of the present invention for solving the aforementioned problems is a non-aqueous electrolyte secondary battery provided with a plurality of safety valves having different compression strength in the outer can, the safety valve is a burst type, different safety valve of the pressure resistance is the It arrange | positions in the diagonal position in the arrangement | positioning surface of an exterior can .
[0013]
Further, according to the configuration of the present invention, in the non-aqueous electrolyte secondary battery provided with a rupture-type safety valve in an outer can, four safety valves are provided, and two of the four safety valves are assembled. The first safety valve group is different from the first safety valve group and the second safety valve group formed by the remaining two safety valves of the four safety valves, and the first safety valve group These two safety valves are arranged at the first diagonal position on the arrangement surface of the outer can, and the two safety valves constituting the second safety valve group are equal in pressure resistance strength. These two safety valves have the same pressure-resistant strength, and are arranged at a second diagonal position on the arrangement surface of the outer can.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0015]
FIG. 1 shows a safety valve 10A according to an embodiment of the present invention. In FIG. 1, 1 is a battery outer can, 2 is a positive electrode, 3 is a negative electrode, 4 is a separator, 5 is a positive electrode terminal, and 6 is a negative electrode terminal. In this lithium secondary battery 10A, the outer can 1 is filled with an electrolyte solution (not shown) made of a combustible organic material.
[0016]
On the upper surface of the outer can 1, two burst type safety valve groups 7 a and 7 b are provided. The safety valve groups 7a and 7b are arranged at diagonal positions on the upper surface of the outer can 1, and the pressure resistance strengths of the safety valve groups 7a and 7b are different. For example, the pressure resistance of the safety valve group 7a is 3 kgf / cm ² , and the pressure strength of the safety valve group 7b is 5 kgf / cm ² .
[0017]
When an internal short circuit occurs in the lithium secondary battery 10A and the internal pressure rises, the safety valve group 7a at the first diagonal position first bursts and opens, and then the second diagonal is delayed with time. The safety valve group 7b in the position is burst open. Therefore, the high-temperature gas flows along the first path from the short-circuited part toward the safety valve group 7a, and also flows along the second path from the short-circuited part toward the safety valve group 7b with a time delay.
[0018]
For this reason, the hot gas first flows along the first path, and then flows in a time-delayed manner and flows separately into the first path and the second path, and the gas flow along the first path decreases. To do. Thus, since the gas flow path moves with time, the acceleration of the thermal runaway reaction due to the movement of the high-temperature gas is suppressed, and safety can be ensured without the battery temperature rapidly rising.
[0019]
In the experiment, the lithium secondary batteries 10 and 10A were placed horizontally, an iron nail having a diameter of 8 mm was penetrated through each central portion, an internal short circuit was caused, and changes in temperature were observed. In this experiment, the lithium secondary battery 10A provided with two sets of safety valve groups 7a and 7b having different pressure resistances as shown in FIG. 1 is a lithium secondary battery 10A provided with four safety valves 7 having the same pressure resistance strength as shown in FIG. It was confirmed that the temperature rise was lower than that of the secondary battery 10.
[0020]
Further, since the safety valve groups 7a and 7b are arranged diagonally on the upper surface of the outer can 1, the lithium secondary battery 10A is placed sideways (that is, the upper surface of the outer can 1 is a vertical surface). Even when a short circuit accident occurs, it is safe because gas can be released from at least one of the safety valve groups 7a and 7b (the safety valve located on the upper side).
[0021]
In the example of FIG. 1, two sets of safety valve groups 7a and 7b having different pressure strengths are provided, but three or more sets of safety valve groups having different pressure strengths may be provided.
[0022]
【The invention's effect】
As has been specifically described in conjunction with the embodiments, the present invention provides a nonaqueous electrolyte secondary battery provided with a plurality of safety valves having different compression strength in the outer can, the safety valve is a burst type, wherein The safety valves having different pressure strengths were arranged at diagonal positions on the arrangement surface of the outer can .
For this reason, even if an internal short circuit occurs, the flow path of the high-temperature gas changes, and the safety is improved without the battery temperature rapidly increasing.
[0023]
According to the present invention, in the non-aqueous electrolyte secondary battery provided with a rupture-type safety valve in an outer can, four safety valves are provided, and two safety valves of the four safety valves are combined. The first safety valve group and the second safety valve group formed by the remaining two safety valves of the four safety valves are different in pressure resistance strength, and constitute the first safety valve group The two safety valves have the same pressure resistance strength, and these two safety valves are arranged at the first diagonal position on the arrangement surface of the outer can, and the pressure resistance of the two safety valves constituting the second safety valve group The two safety valves having the same strength are arranged at the second diagonal position on the arrangement surface of the outer can.
For this reason, even if an internal short circuit occurs, the flow path of the high-temperature gas changes, and the safety is improved without the battery temperature rapidly increasing. Furthermore, the function as a safety valve can be secured even when the battery is placed horizontally.
[0024]
Moreover, the safety | security of a lithium secondary battery can be improved by applying this invention to a lithium secondary battery.
[Brief description of the drawings]
FIG. 1 is a structural view showing a lithium secondary battery according to an embodiment of the present invention in a cutaway manner.
FIG. 2 is a configuration diagram showing a conventional lithium secondary battery in a broken view.
FIG. 3 is a perspective view showing a module battery using a lithium secondary battery.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exterior can 2 Positive electrode 3 Negative electrode 4 Separator 5 Positive electrode terminal 6 Negative electrode terminal 7 Burst type safety valve 7a, 7b Burst type safety valve group 10, 10A Lithium secondary battery 20 Frame

Claims

A non-aqueous electrolyte secondary battery provided with a plurality of safety valves having different compression strength in the outer can,
The non-aqueous electrolyte secondary battery according to claim 1, wherein the safety valve is a bursting type, and the safety valves having different pressure strengths are arranged at diagonal positions on the arrangement surface of the outer can .

In a non-aqueous electrolyte secondary battery with a bursting safety valve on the outer can,
Four safety valves are provided, and a first safety valve group formed by two safety valves of the four safety valves and a remaining two safety valves of the four safety valves. The pressure resistance strength of the second safety valve group is different,
Moreover, the two safety valves constituting the first safety valve group have the same pressure resistance strength, and these two safety valves are arranged at the first diagonal position on the arrangement surface of the outer can,
The non-aqueous electrolyte is characterized in that the two safety valves constituting the second safety valve group have the same pressure resistance strength, and the two safety valves are arranged at the second diagonal position on the arrangement surface of the outer can. Secondary battery.