JPH10326610A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To short-circuit between the positive and negative pole terminals with a abnormally increased temperature so as to discharge stored energy to the outside of a battery and to increase the safety of the combined battery by providing a safety device in the opening part of a casing so as to be integral with a sealing member for turning ON/OFF between the pole terminals by a thermally-actuated bimetal switch and an explosioproof valve outside a hermetically sealed space having the bimetal. SOLUTION: A safety device 20 is incorporated with a bimetal switch 22. The bimetal switch 22 is bent up at a normal temperature to be moved away from the contact 6a of a positive pole terminal and the contact 7a of negative pole terminal to be turned OFF, and at a temperature higher than a specified level, it is suddenly inversely bent down, its contact 22a contacts with the contacts 6a and 7a to be turned ON, and short-circuiting occurs between the positive and negative pole terminals. An explosionproof valve is provided in a position for discharging gas jetted at abnormal time to the outside of a hermetically sealed space formed so as to envelope a switch casing 21 and the periphery of its flange part 21a with the peripheral part of a sealing member 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to non-aqueous water used as a power source for products such as mobile devices such as electric vehicles and electric carts, portable devices such as video cameras and personal computers, backup devices in the event of a power failure, and security devices. The present invention relates to the prevention of ignition or explosion due to abnormal heat generation of an electrolyte secondary battery, and to the safety of a battery used by separating and bypassing an abnormal battery.

[0002]

2. Description of the Related Art A conventional non-aqueous electrolyte secondary battery has a battery safety protection device which is used by separating and bypassing a power generating element having an abnormal temperature as disclosed in JP-A-6-290767. , A chemical battery having a battery reaction part, a battery container serving also as a positive or negative pole terminal and another pole terminal, connected to the electrode by a driving member driven by gas pressure or reaction heat generated during abnormal reaction of the battery. There is known a method of interrupting conduction between a partition plate sealing a battery container via an insulating material and a pole terminal, and short-circuiting the pole terminal and the battery container.

[0003]

However, the above-described conventional method of electrically disconnecting the electrode having an abnormal temperature from the external terminal and short-circuiting the positive and negative terminals to bypass the electrode has the following problems. . The method of simply shutting off the power generating element in the battery case at an abnormal temperature in an electric circuit is effective when an external cause such as an external short circuit or overcharging is present. In the case of a short circuit caused inside the power generating element itself due to precipitation or the like, shutting off the external electric circuit has no effect. In addition, there is a variety of protection measures for external factors because the battery and the external circuit need only be cut off.However, in the case of a short circuit in the battery, the energy stored between the positive electrode and the negative electrode in the power generation element itself is discharged. At present, there is no means to do so. Further, in the structure of the above-mentioned conventional example, a partition plate serving as an electric passage and serving as a sealing member seals the battery container with a caulking structure at an opening of the battery container via an insulating material. A pole terminal connected to the outside of the battery is installed movably by gas pressure between the inside of the opening end of the battery container bent inward and the partition plate.

Therefore, it is necessary to caulk the partition plate through a soft and thick insulating material such as polypropylene which acts as a packing for preventing leakage of the electrolyte, and the position of the partition plate is not stabilized in the vertical direction due to the caulking variation. Not only that, the sealing of the battery container is loosened due to a change in temperature of the soft thick resin with time, and liquid leakage is likely to occur. Further, since the distance and parallelism between the opening end of the battery container which is bent inward to become the electrical connection portion and the partition plate vary, there was a problem that contact and separation between the pole terminals were not reliably performed. . In addition, it is essential that the pole terminal is electrically connected to the outside and the pole terminal is movable, and the opening end of the battery container, which is one of the electrode connection portions, also forms a battery outer shell. However, the structure was not practically suitable for performing a switch function due to deformation or intrusion of dust or the like. Furthermore, since the electric contact portion is located in the battery or in the gas passage, the electric contact portion is corroded by the electrolytic solution or its high-temperature gas, so that not only poor contact and poor switching operation of the terminals are likely to occur, but also a flammable electrolytic solution. The high-temperature gas may be ignited by the contact arc.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide, among a plurality of non-aqueous electrolyte secondary batteries connected in series, a battery having an abnormally high temperature. Providing a non-aqueous electrolyte secondary battery that is easy to use while improving battery safety by short-circuiting the positive and negative terminals to release the stored energy out of the battery and bypassing and using only the abnormal battery. Is to do.

[0006]

According to the present invention, in order to achieve the above object, a power generating element comprising a non-aqueous electrolyte and an electrode group in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween is provided in a battery case. Each electrode is connected to each pole terminal penetrated through the sealing member with a lead wire, and a safety device that is integrated with the sealing member and turns on and off between the pole terminals by a thermally responsive bimetal switch is provided at the opening of the battery case. The explosion-proof valve was installed outside the enclosed space with the bimetal switch. The safety device normally turns off between the positive and negative terminals,
When the temperature of the bimetal rises, the positive and negative terminals are turned on, so that the stored energy of the power generating element inside the battery case that has reached the abnormal temperature is consumed outside the battery, and only the abnormal battery is bypassed. What is used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a non-aqueous electrolyte secondary battery according to the present invention will be described below with reference to the drawings.
FIG. 1 is a structural vertical sectional view showing one embodiment of the nonaqueous electrolyte secondary battery of the present invention, FIG. 2 is a sectional view taken along line AA of FIG.
FIG. 3 is a sectional view taken along line BB of FIG. 2. In the figure, reference numeral 1 denotes a positive electrode, and a positive electrode mixture 1b (for example, LiMn ₂ O ₄ , Li as an active material) having an inorganic lithium intercalation material as a positive electrode active material is provided on both surfaces of a positive electrode current collector 1a made of aluminum foil.
(CoO ₂ , LiNiO _2, etc., prepared by mixing and adjusting carbon as a conductive agent and polyvinylidene fluoride as a binder). Reference numeral 2 denotes a negative electrode, and a negative electrode mixture 2b (for example, a mixture of graphite as an active material and polyvinylidene fluoride as a binder) on both surfaces of a negative electrode current collector 2a formed of a copper foil and having a lithium intercalation carbon material as a negative electrode active material. Adjusted). Reference numeral 3 denotes a separator made of a microporous polyethylene film or polypropylene film. When the temperature of the polyethylene film rises, the shutdown start temperature at which the micropores close due to melting of the film itself is about 130 ° C., and the shutdown start temperature of the polypropylene film is about 150 ° C.

The positive electrode 1 and the negative electrode 2 are spirally wound in a state where they face each other with the separator 3 interposed therebetween, thereby forming an electrode group 15. In this case, the separator 3 is wound slightly wider than the positive electrode 1 and the negative electrode 2, and is further wound several times alone at the core portion and the end portion of the winding, so that the separator 3 may be wound between the positive electrode and the negative electrode and around the electrode group. Has insulation properties. The electrode group 15 is immersed in a non-aqueous electrolyte (not shown) to become a power generating element. The non-aqueous electrolyte is LiPF
₆ , LiBF ₄ , LiClO ₄ , LiAsF _{6 and} other lithium salts as electrolytes and organic solvents (propylene carbonate,
Used alone or in a mixture of ethylene carbonate, diethyl carbonate, dimethyl carbonate and the like.

Reference numeral 10 denotes a battery case which is made of stainless steel, nickel-plated iron, nickel-plated copper or aluminum, houses the above-mentioned electrode group 15 and a power generating element made of a non-aqueous electrolyte in a bottomed cylindrical container, and has a sealing member. Battery device 10 via a gasket 19 over a safety device 20 having
Is sealed by caulking in the opening of the first embodiment. The sealing member 11 is made of a metal material having good heat conductivity such as stainless steel, nickel-plated iron, nickel-plated copper, and aluminum. Insulating plates 12a and 12b are provided on the side of the sealing member 11 in the battery case 10 and on the container bottom 10a in order to maintain electrical insulation between the battery charging section and the battery case 10. Reference numeral 4 denotes an aluminum material positive electrode lead, which is connected to the positive electrode current collector 1a of the positive electrode 1 and the aluminum material positive electrode terminal 6 by welding or the like. Reference numeral 5 denotes a nickel or copper negative electrode lead, which is connected to the negative electrode current collector 2a of the negative electrode 2 and a nickel or copper negative electrode terminal 7 by welding or the like. Numeral 13 denotes an insulation destant, which secures a space for collectively housing the positive electrode lead 4 and the negative electrode lead 5 between the electrode group 15 and the sealing member 11 and presses the electrode group 15 so as not to move in the battery case 10. I have.

The positive terminal 6 and the negative terminal 7 are connected to the sealing member 11.
A hermetic seal 8 which is electrically insulated with a glass or plastic layer interposed and has a sealing property.
Thus, the portion that penetrates through the switch case 21 and goes out of the terminal case serves as an electrical connection portion with the outside. The explosion-proof hole 11a provided in the sealing member 11 is sealed with an explosion-proof valve 9 (FIG. 3) made of a metal plate or a thin-film metal plate having a weak point such as a cut, so that the pressure inside the battery case 10 rises abnormally. Cleaves at high pressure
The explosion of the battery case 10 is prevented. A gas vent hole 21b is also formed in the flange portion 21a of the switch case 21 located at the explosion-proof valve 9 so that gas can be directly discharged to the outside atmosphere.

The location of the explosion-proof valve is not limited to the sealing member but may be any location as long as the blast gas is discharged to the outside of the enclosed switch housing of the switch case 21. The operating pressure of the explosion-proof valve 9 is determined from the temperature rise limit in the battery case and the strength at which the battery case itself and the crimped portion do not break first, and is 10 kg / cm ^{2 to} 20 kg / cm ^2.
Is desirable. The safety device 20 includes a flanged cap-shaped terminal case 21 made of an insulating material such as plastic and its flange 21a.
The periphery is swaged so as to be wrapped by the periphery of the sealing member 11 to form an integrated closed space, and a thermally responsive bimetal switch 22 is built therein.

The positive terminal 6 and the negative terminal 7 are bent in a crank shape on the surface of the sealing member 11 in the switch case 21, and have a positive terminal contact 6a and a negative terminal contact 7a in a horizontal portion thereof. Between the positive terminal contact 6a and the negative terminal contact 7a, a bimetal switch 22 is screwed into the bottom of the terminal case 21 by a support rod 23 via a spring 24, and then fixed by a nut 25. By adjusting the screwing amount of the support rod 23, the position of the bimetal switch 22 can be adjusted, and the contact pressure of the bimetal contact can be made appropriate.

The bimetal switch 22 is a double-contact bimetal having contacts 22a at both ends of the bimetal. At normal temperature, the bimetal switch 22 is bent upward and separated from the positive terminal contact 6a and the negative terminal contact 7a to be in an off state.
When the temperature rises above the set temperature, the contact 22a of the bimetal switch comes into contact with the positive terminal contact 6a and the negative terminal contact 7a, and turns on. That is, when the temperature of the power generating element becomes abnormal due to a rise in temperature, the positive electrode terminal and the negative electrode terminal are short-circuited by the bimetal switch. The spring 24 presses the bimetal switch 22 against the end of the support bar 23 and absorbs vibration when the bimetal switch 22 performs an inversion operation to prevent chattering of the contact.

FIG. 4 is a sectional view showing another embodiment of the safety device 20. As shown in FIG. In this figure, only the structure of the bimetal switch 22 is different from that of the embodiment shown in FIGS.
That is, the bimetal switch 22 is a single-contact bimetal having only one end and a contact 22 a on one surface, and the other end of the bimetal switch 22 is connected to the terminal case 21.
Rivet 28 on the horizontal part bent in a crank shape inside
Are connected by crimping. The contact 22a of the bimetal switch 22 is disposed above the contact 7a of the negative electrode terminal 7 and is normally bent upward to be in an off state. Short-circuit with 7a. That is, as in the case of the first embodiment, when the temperature rises to an abnormal temperature, the positive terminal and the negative terminal are short-circuited.

FIG. 5 is an electric circuit block diagram when a plurality of nonaqueous electrolyte secondary batteries of the present invention are connected in series and used. The figure shows a battery pack 31 in which n unit cells (30a to 30n) are connected in series. The output terminal XY of the battery pack 31 is connected to a control circuit 3 via a fuse 32 and a main switch 33.
4, connected to the load 35. Reference numeral 36 denotes a current sensor for detecting a current flowing through the battery pack 31, and reference numeral 37 denotes a temperature sensor for detecting the temperature of the battery pack, which is input to the control circuit 34, respectively. An output signal 38 is output from the control circuit 34 when the current sensor 36 or the temperature sensor 37 detects an abnormal current or an abnormal temperature.
Works to cut three.

In this circuit, assuming that the voltage of the unit cell is E (V), the voltage between the output terminals XY of the assembled battery is n × E (V). a is a positive electrode terminal 6 connected to the positive electrode of the power generating element, b
Denotes a negative electrode terminal 7 connected to the negative electrode of the power generating element. Normally, the terminals a and b are in the off state, and are switched to the on state when the temperature rises to an abnormal temperature.

Next, a method for assembling the non-aqueous electrolyte secondary battery according to the present invention will be described. First, the positive electrode lead 4 and the negative electrode lead 5 are attached to the positive electrode 1 and the negative electrode 2, respectively, by spot welding or ultrasonic welding. At this time, the number of leads to be attached is increased or decreased depending on the size of the battery capacity.

The positive electrode 1 and the negative electrode 2 are wound with a separator 3 interposed therebetween.
make. Insulating plate from the bottom 10a side of the bottomed double cylindrical container
12b, the electrode group 15, and the insulating distant 13 are placed in this order, and the positive electrode lead 4 and the negative electrode lead 5 are bundled and put together. Next, the insulating plate 12a is connected to the sealing member 11 of the safety device 20.
The positive electrode lead 4 and the negative electrode lead 5 are welded to the positive electrode terminal 6 and the negative electrode terminal 7 of the sealing member 11. Next, necking is formed near the opening of the battery case 10, and then an electrolytic solution is injected, and the safety device 20 is sealed by caulking via a gasket 19 to complete the safety device 20. Thus, the safety device 2
Since the non-aqueous electrolyte secondary battery provided with 0 can be assembled without changing from the conventional assembly process, workability is good.

Next, the operation of the nonaqueous electrolyte secondary battery according to the present invention will be described. When the battery is overcharged to a voltage equal to or higher than the set voltage due to a failure in the charging circuit, a chemical reaction other than the battery reaction as lithium intercalation is performed to decompose the electrolytic solution, thereby deteriorating the battery and increasing the temperature of the battery. If the discharge circuit is overdischarged below the set voltage due to a failure of the discharge circuit, lithium metal precipitates on the negative electrode due to the dentite reaction, breaks through the separator 3 and causes a short circuit between the positive electrode and the negative electrode. Become. Furthermore, the battery also generates heat and becomes abnormal temperature due to use at a high temperature exceeding the normal use temperature range of the battery, external short-circuit due to misuse, and internal short-circuit in the battery for some reason.
When the temperature of the non-aqueous electrolyte secondary battery rises, the film of the separator 3 between the positive electrode 1 and the negative electrode 2 becomes 130 ° C. to 150 ° C.
It melts at a temperature of ° C. and acts to shut off the current by a shutdown effect that stops the movement of lithium ions between the positive and negative electrodes by closing the microporous film.

However, a polyethylene film or a polypropylene film, which is a material of the separator, may melt and shrink due to a further rise in temperature, and may fail to secure insulation between the positive and negative electrodes, resulting in a short circuit between the electrodes. When the temperature inside the battery exceeds 150 ° C., the positive electrode active material used for the electrode causes a thermal runaway, which is a dangerous temperature range where smoke, ignition, and explosion occur. In other words, LiM which is a positive electrode active material
Due to an oxygen desorption reaction from a crystal lattice of n ₂ O ₄ , LiCoO ₂ , LiNiO _2, etc., rapid heat generation occurs and a thermal runaway state occurs. The oxygen desorption start temperature varies depending on the type of the active material and the composition ratio of each element, but is in the range of 150 ° C to 400 ° C.

When the battery abnormally rises in temperature for some reason, the electrolyte in the battery decomposes, and the electrolyte and the positive electrode,
The active material of the negative electrode causes a chemical reaction to generate gas, and the pressure in the battery case rapidly rises. When pressure within the cell becomes 10Kg / cm ² ~20Kg / cm ² rises, explosion-proof valve 9 by releasing cleaved gas outside the battery case, to reduce the explosive power of the battery. At this time, the high-temperature gas is released from the gas vent hole 21b outside the sealed space where the bimetal switch is located, so that the switch is not corroded and the high-temperature gas of the electrolyte is not ignited.

On the other hand, the abnormal temperature rise of the battery raises the temperature of the bimetal switch 22 of the safety device 20 through the sealing member 11 having good heat conduction, and the bimetal is inverted, and the positive terminal 6 and the negative terminal 7 connect the power generating element. Short-circuited. That is, a short circuit occurs between a and b of the abnormal unit cell in FIG. Therefore, the electrodes of the abnormal unit cell are short-circuited,
The abnormal unit cell is cut off to form a bypass-connected series circuit, and the output voltage continues to operate at (n-1) × E (V). At this time, when the temperature of the battery rises due to an internal short circuit, the stored energy of the sealed power generating element is discharged between the positive electrode and the negative electrode inside the battery and the bimetal switch 2
2 also discharges to the outside of the battery case 10, which has the effect of suppressing the rise in temperature inside the battery.

That is, in the case of an internal short circuit, the stored energy completes the supply and consumption in the battery. However, according to the present invention, a part of the stored energy is consumed outside the battery. The temperature rise is reduced, and the possibility of a dangerous temperature condition that leads to the worst explosion can be reduced. When the temperature of the battery rises due to an external short circuit, the current sensor 36 and the temperature sensor 37 of the control circuit detect the temperature.
The output signal 38 is issued, the main switch 33 is turned off, and the battery pack 31 and the load 35 are protected.

Further, when the control circuit 34 fails and an overcurrent flows, the fuse 32 is blown and double protected.
The operating temperature of the bimetal switch 22 is desirably 80 ° C. to 130 ° C. from the relationship between a range that does not impair the actual operating temperature of the battery and a temperature at which battery deterioration is accelerated. Further, the operation temperature of the bimetal switch 22 at the time of external short circuit needs to be set higher than the operation by the control circuit 34. That is,
If the bimetal switch 22 is actuated earlier than the control circuit 34 due to abnormal temperature rise due to an external short circuit, the load is protected because power is not supplied to the load because the positive and negative terminals are short-circuited. This is because the external short-circuit state is continued by the bimetal switch until the battery is completely discharged, and the temperature rise due to the internal resistance Joule heat of the battery cannot be protected.

[0025]

As described above, according to the present invention, a power generation element composed of a non-aqueous electrolyte and an electrode group in which a positive electrode and a negative electrode are opposed via a separator are housed in a battery case, and each electrode is thermally responsive. The opening of the battery case is sealed by a safety device that can turn on the positive and negative terminals by a bimetal switch.The safety device usually has an open state between the positive and negative terminals, and when the temperature of the bimetal rises, the positive and negative terminals are closed. The gap was made conductive through the bimetal. Therefore, in the case of an assembled battery in which a plurality of cells are used in series, when a certain cell rises in abnormal temperature, the positive and negative terminals of the abnormal battery are short-circuited and bypassed, and the remaining normal cells can be continuously used. So easy to use.

In addition, even when an abnormal temperature rise occurs due to an internal short circuit, the stored energy of the power generating element is short-circuited through the bimetal switch, and energy is released outside the battery case. Therefore, the abnormal temperature rise in the battery is suppressed, and safety is improved. .
In addition, since the sealing member serving as the heat receiving plate of the safety device is a single metal plate having good heat conductivity, it has good thermal response to a change in heat inside the battery, and the sealing reliability of the battery case sealing portion is high.
Furthermore, since the contact switching circuit by the bimetal switch is closed by the switch case 21 and the sealing member 11 and the explosion-proof valve is outside the enclosed space where the bimetal switch is located, there is no possibility of dust or gas entering the contact switch. It is possible to provide a safety device with less contact failure and no risk of ignition of the high-temperature gas of the flammable electrolyte ejected by the arc of the contact.

[Brief description of the drawings]

FIG. 1 is a structural sectional view showing one embodiment of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 2;

FIG. 4 is a structural sectional view showing another embodiment of the safety device for a non-aqueous electrolyte secondary battery of the present invention.

FIG. 5 is an electric circuit block diagram using the non-aqueous electrolyte secondary batteries of the present invention connected in series.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 1a ... Positive electrode collector, 1b ... Positive electrode mixture, 2 ... Negative electrode, 2a ... Negative electrode collector, 2b ... Negative electrode mixture, 3 ... Separator, 4 ... Positive electrode lead, 5 ... Negative electrode lead, 6 ... Positive terminal,
6a: contact of positive terminal, 7: negative terminal, 7a: contact of negative terminal, 8: hermetic seal, 9: explosion-proof valve, 10 ...
Battery case, 10a: bottom of container, 11: sealing member, 11
a: Explosion-proof hole, 12a, 12b: Insulating plate, 13: Insulating distant, 15: Electrode group, 19: Gasket, 20: Safety device, 21: Switch case, 21a: Flange, 21b ...
Gas vent hole, 22: bimetal switch, 22a: bimetal switch contact, 23: support rod, 24: spring, 25: nut, 26: lid, 28: rivet, 30
a, 30b, 30n: single cell, 31: assembled battery, 32: fuse, 33: main switch, 34: control circuit, 35
... load, 36 ... current sensor, 37 ... temperature sensor, 38 ...
Output signal.

Claims (1)

[Claims] An electrode group having a positive electrode and a negative electrode opposed to each other with a separator interposed therebetween and a power generating element made of a non-aqueous electrolyte are housed in a battery case, and the positive electrode and the negative electrode of the electrode group penetrate through a sealing member with a lead wire. Opening of the battery case is performed by a safety device which is connected to a positive electrode terminal and a negative electrode terminal and has a built-in bimetal switch for turning on and off a positive electrode terminal and a negative electrode terminal in a sealed space integrally formed by the sealing member and the switch case. A non-aqueous electrolyte secondary battery, wherein a discharge part of an explosion-proof valve is provided outside the sealed space of the switch case and opened when a gas pressure in the battery case exceeds a set value.