JP2005285624A - Secondary battery with self-restoration type safety mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To consume energy inside a secondary battery quickly and safely when internal temperature of the battery rises. <P>SOLUTION: This secondary battery with the self-restoration type safety mechanism is provided with the secondary battery, a movable arm having an electrical connection contact for connecting electrically with the outside in an end part and deforming by corresponding to temperature change, and a fixed connection terminal in contact with the electrical connection contact of the movable arm. The movable arm and the fixed connection terminal are stored in a case body. When temperature of the case body exceeds predetermined temperature, the electrical connection contact of the movable arm and the fixed connection terminal come into contact mutually to short circuit the secondary battery with the outside. When temperature of the case body is less than the predetermined temperature, contact of the electrical connection contact and the fixed connection terminal is released to shut off short circuit with the outside. This secondary battery with the self-restoration type safety mechanism has resistance for reducing a current value when short circuiting with the outside, and the resistance is arranged at a position where generated Joule heat does not affect operation of the movable arm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a secondary battery with a self-returning safety mechanism that quickly and safely consumes energy inside the battery when the internal temperature of the battery rises.

  In recent years, mobile information terminals such as mobile phones, notebook computers, and PDAs have been rapidly reduced in size and weight, and batteries as drive power sources are required to have higher capacity and higher energy density. A non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery has a high energy density and a high capacity, and is therefore widely used as a driving power source for the mobile information terminal as described above.

  Active materials used in such non-aqueous electrolyte secondary batteries have low thermal stability in the charged state, and when exposed to high temperature conditions in the charged state, the crystal structure of the active material collapses, leading to thermal runaway. Or the battery performance deteriorates.

  By the way, the following patent documents 1-3 are mentioned as a technique which improves the safety | security of the battery at the time of a temperature rise.

Japanese Patent Laid-Open No. 10-326610 (second page, FIG. 1) JP 2002-298807 A (page 2-3) JP-A-11-162449 (paragraphs 0005-0018)

In the above-mentioned Patent Document 1, a safety device that turns on and off between terminals by a thermally responsive bimetal switch is installed in the sealing part of the battery case, and the positive and negative electrodes are short-circuited when the battery temperature rises abnormally, thereby short-circuiting the bimetal switch A battery is described in which a current can be passed to suppress a temperature rise in the battery.
However, in this technique, since the bimetal switch and the battery are connected in parallel, even if the bimetal switch is operated, a current flows through the battery. This current degrades an active material, an electrolyte solution, and the like inside the battery, so that the battery cannot be used again.

Patent Document 2 includes a plurality of solders provided with a breaker that is switched off to protect the battery when an overcurrent flows through the battery or the battery temperature becomes higher than a set temperature, and the breaker is fixed to a casing. It has terminals, and one or more solder terminals are fixed to the printed circuit board by reflow soldering, and the printed circuit board is connected to the battery via the leads and disposed at a fixed position in the case. A battery pack in which a breaker is fixed at a fixed position in a case through a substrate is described.
According to this technology, it is easy to assemble, the breaker can be placed in an accurate position, and the breaker can be accurately operated to effectively protect the battery and be used safely. However, if the breaker operates in a state where the energy inside the battery is high, the above-described problems of battery performance degradation and thermal runaway occur.

In Patent Document 3, temperature detection means for detecting the temperature inside the secondary battery, discharge means including a resistor sufficiently lower than the internal resistance of the secondary battery, and the temperature detection means outputs a normal temperature signal. The element member includes an operation switching means that is electrically connected in response to the operation and forms a closed loop circuit between the positive and negative power sources of the secondary battery and an external circuit, and is housed in the case of the secondary battery. A secondary battery is described.
According to this technology, it is said that the chemical reaction that is the cause can be stopped quickly and surely until the temperature rise phenomenon in the secondary battery reaches the temperature point causing the explosion.

  However, when an abnormal temperature signal is output due to reaching the dangerous temperature, the operation switching means is activated to form a closed loop circuit between the discharging means and the secondary battery, and the battery is reduced to 0 V by this closed loop circuit. It is discharged (paragraph 0015). When the charged secondary battery is discharged to 0 V, the active material inside the battery deteriorates, so that the battery cannot be used again.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a secondary battery with a safety mechanism that has high safety when exposed to high temperature conditions and does not deteriorate the secondary battery. .

  In order to solve the above problems, the present invention provides a secondary battery, a movable arm having an electrical connection contact for electrical connection to the outside, and deformed in response to a temperature change, and the electrical power of the movable arm. A fixed connection terminal in contact with a connection contact, wherein the movable arm and the fixed connection terminal are accommodated in a casing, the casing is disposed in the vicinity of the secondary battery, and one electrode of the secondary battery And the movable arm are electrically connected, the other electrode of the secondary battery and the fixed connection terminal are electrically connected, and when the casing is at a predetermined temperature or higher, the electrical connection contact of the movable arm When the fixed connection terminal comes into contact and externally shorts the secondary battery, and the casing is below a predetermined temperature, the contact between the electrical connection contact and the fixed connection terminal is released and the external short circuit is cut off. Self-return type of structure A secondary battery with a mechanism, wherein the secondary battery with a self-recovering safety mechanism further has a resistor that lowers a current value at the time of an external short circuit, and the resistor has a movable Joule heat generated from the resistor. It is characterized by being arranged at a position that does not affect the operation of the arm.

  Here, the vicinity of the secondary battery means a position where the temperature of the secondary battery and the temperature of the casing are substantially equal, and specifically, directly or thermally conductively on the exterior body of the secondary battery. It means a position that contacts through a member having a high height.

  The resistor may be arranged between the fixed connection terminal and an electrode to which the fixed connection terminal is connected.

  Further, the resistor can be arranged outside the casing.

  Further, the movable arm can be made of bimetal.

  The movable arm may be composed of a movable arm body and a bimetal switch, and the movable arm body may be moved by the bimetal switch.

  Moreover, it can be set as the structure whose said predetermined temperature is 60-100 degreeC.

  The secondary battery may be a nonaqueous electrolyte secondary battery.

  According to the present invention, as shown in FIG. 1A, the electrical connection contact 2a of the movable arm 2 and the fixed connection terminal 3 are not connected under normal temperature conditions, but the casing reaches a predetermined temperature. Then, as shown in FIG.1 (b), the electrical connection contact 2a of the movable arm 2 and the fixed connection terminal 3 are electrically connected, and the secondary battery 1 is externally short-circuited.

  This external short-circuit current is reduced to such an extent that the active material and the electrolytic solution are not deteriorated by passing through the resistor 4.

  Further, since the resistor 4 is arranged at a position where Joule heat generated from the resistor 4 does not affect the operation of the movable arm 2, when the secondary battery 1 again becomes a predetermined temperature or less, the movable arm is quickly The contact between the second electrical connection contact 2a and the fixed connection terminal 3 is released, and the external short circuit is interrupted. In the secondary battery 1, the charge level is reduced to a safe level due to the external short circuit, but the external short circuit is completed before the secondary battery 1 is overdischarged. Therefore, the secondary battery 1 can be used again.

  Further, examples of the position where the Joule heat due to the resistance does not affect the operation of the movable arm are between the fixed connection terminal and the electrode to which the fixed connection terminal is connected, or outside the casing. it can.

  In addition, when the energization method in which the movable arm is made of bimetal or the non-energization method in which the movable arm is made of the movable arm body and the bimetal switch, the electric connection contact and the fixed connection terminal of the movable arm can be easily contacted at low cost.・ Can be released.

  Moreover, the separator used for the secondary battery is improved in safety by melting (shutdown) and shutting off the current between the positive and negative electrodes when the battery temperature reaches about 130 to 150 ° C. The later secondary battery cannot be used again. However, if the predetermined temperature is 60 to 100 ° C., the battery can be externally short-circuited before the secondary battery shuts down to improve safety, so the secondary battery does not shut down and can be re-used as a battery. Can be used.

  Moreover, since the nonaqueous electrolyte secondary battery uses a flammable organic solvent for the electrolyte, there is a high risk when the battery is exposed to high temperature conditions. When the self-returning safety mechanism according to the present invention is attached to this non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery with a self-returning safety mechanism that is safe even under high temperature conditions can be obtained.

  The best mode for carrying out the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following form, In the range which does not change the summary, it can change suitably and can implement.

(Embodiment 1)
As shown in FIG. 1 (a), the secondary battery with a safety mechanism according to the first embodiment has the secondary battery 1 and an electrical connection contact 2a for electrical connection to the outside, and changes in temperature. The movable arm 2 is deformed corresponding to the above, and the fixed connection terminal 3 is in contact with the electrical connection contact 2a of the movable arm. The negative electrode 1a of the secondary battery and the movable arm 2 are electrically connected, and the positive electrode 1b of the secondary battery and the fixed connection terminal 3 are electrically connected.

Further, the movable arm 2 and the fixed connection terminal 3 are accommodated in a casing 5, and the casing 5 is disposed at a position in contact with the secondary battery.
Furthermore, the resistor 4 is provided, and the resistor 4 is disposed outside the housing 5 so that Joule heat generated from the resistor 4 does not affect the operation of the movable arm 2.

  The movable arm 2 includes a movable arm main body 21 and a bimetal switch 22.

  When the temperature of the secondary battery 1 reaches a predetermined temperature, the housing 5 also reaches the predetermined temperature at the same time. As shown in FIG. 1B, the bimetal switch 22 is reversed by heat and the electric connection contact 2a of the movable arm. And the fixed connection terminal 3 come into contact with each other, and the secondary battery 1 is externally short-circuited. The current value at the time of this external short circuit is lowered to a level that does not adversely affect the battery by the resistor 4.

  In addition, since the resistor 4 is disposed outside the housing 5, the Joule heat has little influence on the bimetal switch 22. Therefore, when the temperature of the secondary battery 1 becomes equal to or lower than the predetermined temperature, the bimetal switch 22 immediately cuts off the contact between the electric connection contact 2a of the movable arm and the fixed connection terminal 3, and as shown in FIG. Return to the state.

  As described above, since the secondary battery 1 quickly self-resets to the normal state before overdischarge occurs, the active material of the secondary battery 1 is not deteriorated and can be used again as a battery.

(Embodiment 2)
In the second embodiment, an example in which the movable arm is a bimetal will be described.

  The second embodiment is different from the second embodiment except that the movable arm 2 is a bimetal as shown in FIG. 2A and the resistor 4 is disposed between the fixed connection terminal 3 and the positive electrode 1b. 1 is the same configuration.

  When the temperature of the secondary battery 1 reaches a predetermined temperature, the electric connection contact 2a of the movable arm made of bimetal and the fixed connection terminal 3 come into contact with each other as shown in FIG. External short circuit. This external short-circuit current is lowered to a level that does not adversely affect the battery by the resistor 4.

  Further, since the resistor 4 is disposed outside the housing 5 and between the positive electrode 1b and the fixed connection terminal 3, the Joule heat has little influence on the movable arm 2 made of bimetal. Therefore, when the temperature of the secondary battery 1 becomes equal to or lower than the predetermined temperature, the secondary battery 1 operates to quickly cut off the connection between the electric connection contact 2a of the movable arm made of bimetal and the fixed connection terminal 3, as shown in FIG. 2 (a). To return to the normal state.

  As described above, since the secondary battery 1 quickly self-resets to the normal state before overdischarge occurs, the active material of the secondary battery 1 is not deteriorated and can be used again as a battery.

(Example)
Hereinafter, the present invention will be described in more detail with reference to examples using a nonaqueous electrolyte secondary battery as a secondary battery.

(Example 1)
A positive electrode having lithium cobaltate, a negative electrode having graphite, and a polyethylene microporous film (melting point: 130 ° C.) were wound to form an electrode body.

  The electrode assembly was inserted into a separately prepared rectangular outer can, and an electrolytic solution in which LiPF6 was dissolved at a ratio of 1 mol / liter was mixed in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1. Liquid. Then, the opening part of the armored can was sealed by laser welding, and the nonaqueous electrolyte secondary battery was produced. The theoretical capacity of this nonaqueous electrolyte secondary battery is 1000 mAh.

  The safety mechanism according to the first embodiment was attached to the non-aqueous electrolyte secondary battery as shown in FIG. 3, and a secondary battery with a self-returning safety mechanism according to Example 1 was produced. The bimetal operating temperature is 70 ° C., and the resistance is 2Ω.

(Example 2)
A secondary battery with a self-returning safety mechanism according to Example 2 was produced in the same manner as in Example 1 except that the safety mechanism according to Embodiment 2 was attached as shown in FIG. The bimetal operating temperature is 80 ° C. and the resistance is 3Ω.

(Comparative Example 1)
A secondary battery according to Comparative Example 1 was fabricated in the same manner as in Example 1 except that the self-returning safety mechanism was not attached.

(Comparative Example 2)
As shown in FIG. 5, Comparative Example 2 was used in the same manner as in Example 1 except that a safety mechanism was used in which the resistor 104 was arranged inside the housing 105 and between the movable arm main body 121 and the negative electrode 101 a. A secondary battery with such a self-returning safety mechanism was produced.

[Safety test]
The secondary battery with a safety mechanism produced above was charged at 1000 mA to 4.2 V, and then charged at 4.2 V until 100 mA. This battery was put into an oven at 100 ° C., and after 30 minutes, the battery was taken out and cooled to room temperature (25 ° C.).

  The battery after cooling had a battery voltage of 3.2 V in Example 1 and 3.35 V in Example 2, and the charge level had dropped to a safe level. Further, both batteries could be charged and discharged thereafter.

On the other hand, in Comparative Example 1 in which the safety mechanism was not attached, the battery voltage was maintained, but the active material was deteriorated by heat, the thickness of the battery was increased, and the battery characteristics were greatly deteriorated to 70% or less. It was.
Further, in Comparative Example 2, since the state in which the bimetal was operated was maintained even after the battery was taken out of the oven, the battery voltage was overdischarged to 1.0 V, and the subsequent charge / discharge was possible. The capacity was greatly deteriorated to 50% or less of Example 1.

(Other matters)
In the above-described embodiment, the secondary battery including the square outer can is described as an example, but a cylindrical battery, a laminate outer body, or the like may be used. Moreover, as a secondary battery which can be used for this invention, a nonaqueous electrolyte secondary battery, a nickel-cadmium secondary battery (storage battery), a nickel-hydrogen secondary battery (storage battery), etc. can be illustrated.

  The present invention can also be applied to an assembled battery in which a plurality of secondary batteries with a self-recovering safety mechanism are connected in series and / or in parallel. In this case, it is preferable that each secondary battery is provided with a self-returning safety mechanism.

  As described above, according to the present invention, by attaching a simple self-recovering safety mechanism to the secondary battery, the safety when the battery temperature rises abnormally is high, and after the battery temperature falls Can use the battery again. Therefore, industrial applicability is great.

FIG. 1 is an enlarged view of a main part of the self-returning safety mechanism according to the first embodiment. FIG. 1 (a) shows a normal state, and FIG. 1 (b) shows when the battery temperature rises. FIG. 2 is an enlarged view of a main part of the self-returning safety mechanism according to the second embodiment. FIG. 2 (a) shows a normal state, and FIG. 2 (b) shows when the battery temperature rises. FIG. 3 is an enlarged view of a main part of the secondary battery with a self-returning safety mechanism according to the first embodiment. FIG. 4 is an enlarged view of a main part of the secondary battery with a self-returning safety mechanism according to the second embodiment. FIG. 5 is an enlarged view of a main part of the self-returning safety mechanism according to the second comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Movable arm 3 Fixed connection terminal 4 Resistance 5 Case

Claims (7)

A secondary battery,
A movable arm having an electrical connection contact for electrical connection to the outside at the end and deforming in response to a temperature change;
A fixed connection terminal in contact with an electrical connection contact of the movable arm;
With
The movable arm and the fixed connection terminal are accommodated in a casing, and the casing is disposed in the vicinity of the secondary battery,
And when one electrode of the secondary battery and the movable arm are electrically connected, the other electrode of the secondary battery and the fixed connection terminal are electrically connected, and the casing is at a predetermined temperature or higher. When the electrical connection contact of the movable arm and the fixed connection terminal come into contact with each other, the secondary battery is externally short-circuited, and the contact between the electrical connection contact and the fixed connection terminal is released when the casing is below a predetermined temperature. A secondary battery with a self-recovering safety mechanism having a structure in which the external short circuit is cut off,
The secondary battery with a self-recovering safety mechanism further has a resistor that lowers the current value at the time of external short circuit, and the resistor is a position where Joule heat generated from the resistor does not affect the operation of the movable arm. Located in the
A secondary battery with a self-returning safety mechanism. The secondary battery with a self-returning safety mechanism according to claim 1,
The resistor is disposed between the fixed connection terminal and an electrode to which the fixed connection terminal is connected;
A secondary battery with a self-returning safety mechanism. The secondary battery with a self-returning safety mechanism according to claim 1 or 2,
The resistor is disposed outside the housing;
A secondary battery with a self-returning safety mechanism. The secondary battery with a self-returning safety mechanism according to claim 1, 2, or 3,
The movable arm is made of bimetal;
A secondary battery with a self-returning safety mechanism. The secondary battery with a self-returning safety mechanism according to claim 1, 2, or 3,
The movable arm is composed of a movable arm body and a bimetal switch, and the movable arm body is movable by the bimetal switch.
A secondary battery with a self-returning safety mechanism. The secondary battery with a self-returning safety mechanism according to claim 1, 2, 3, 4 or 5,
The predetermined temperature is 60 to 100 ° C.
A secondary battery with a self-returning safety mechanism. The secondary battery with a self-returning safety mechanism according to claim 1, 2, 3, 4, 5 or 6,
The secondary battery is a non-aqueous electrolyte secondary battery.
A secondary battery with a self-returning safety mechanism.
A secondary battery with a safety mechanism.

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