JPH05234614A - Cylindrical battery - Google Patents

Abstract

PURPOSE:To provide a cylindrical battery having an over-charge protective circuit or a device capable of avoiding over-charge with less space. CONSTITUTION:An automatic reset thermal switch A or a thermal fuse and a zener diode 5 are inserted, in series connection, into a secondary battery, at an air-gap part of a case C, which has the case C filled with a group of electrode P which comprises a negative electrode 3 and a positive electrode 1 winding spirally by intervening a separator 2, and electrolyte. And the automatic reset thermal switch 4 or the thermal fuse is electrically connected in parallel to the battery, and a Zener diode 5 is electrically connected in series to the battery. And then even in the case when the battery is over-charged, a cylindrical battery capable of avoiding over-charge for itself, avoiding deterioration of charge and discharge cycle life and having excellent overcharge proof is obtained owing to the Zener diode 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical battery, and more particularly to preventing a decrease in charge / discharge cycle life of a cylindrical secondary battery, particularly charge / discharge cycle life due to overcharge.

[0002]

2. Description of the Related Art In a cylindrical secondary battery in which a sheet-shaped positive electrode or negative electrode and a separator can be used,
In order to minimize the deterioration of battery characteristics due to discharge and charging with large current, the positive electrode and negative electrode are stacked with a separator in between and wound in a spiral to form a cylindrical electrode group, which is The battery is made by putting it in a container and enclosing the electrolytic solution. Further, in order to improve battery characteristics such as maximum charge / discharge current value and battery capacity, electrodes and separators may be thinned.

In a non-aqueous electrolyte secondary battery in which a non-aqueous solvent is used as the electrolyte, overcharging may reduce the charge / discharge cycle life. It is considered that the cause of this is that an electrochemical reaction which is not desirable as a battery reaction, such as decomposition of the electrolytic solution or dissolution of the positive electrode, progressed in the battery due to overcharge. Even in a secondary battery that uses an aqueous solution as the electrolyte, if a voltage higher than the decomposition voltage of water is applied during charging, electrolysis of water occurs, which is undesirable for a battery reaction. The battery characteristics were deteriorated in the same manner as in.

As a countermeasure against this, for example, during charging, the battery voltage is constantly monitored, and charging is stopped before the battery voltage reaches a specified value, or even if the battery voltage reaches a specified value, within a certain time. , The charging circuit may be used to charge the secondary battery. Further, when an irreversible battery reaction such as decomposition of the electrolytic solution is an exothermic reaction, a thermal fuse may be used which detects the heat generation by the outer wall of the battery container and stops the charging.

[0005]

By constantly monitoring the state of charge of the battery and using a thermal fuse, deterioration of battery characteristics such as a decrease in charge / discharge cycle life due to overcharge has been prevented. It was However, many problems still remain. One of them is that when a plurality of batteries are connected and charged, the voltage of each battery must be monitored separately during charging. This is because when the voltages of a plurality of batteries are collectively monitored, some batteries may be in an overcharged state due to variations in battery characteristics. 2. Description of the Related Art In recent years, with the multifunctionalization of portable electric devices, the power consumption of such devices has increased significantly. In order to deal with this, it has become common to use a plurality of batteries connected in series or in parallel as a battery pack and built in the device. In such cases, the situation is even more serious. Since it is a portable electric device, its size must be as small as possible and its handling should be simple, but the charging circuit becomes large and complicated, and the advantage of replacing batteries is that when batteries are packed. This is because ease of use is also lost.

Further, the following problems remain with respect to attaching the thermal fuse to the outer wall of the battery container. That is, even if the reaction such as the decomposition of the electrolytic solution caused by overcharging is an exothermic reaction and the charging can be expected to be stopped by the operation of the thermal fuse, the generated heat propagates through the electrode group and the battery container. Therefore, there is a time delay before reaching the thermal fuse on the outer wall of the container.

Therefore, there is a demand for an overcharge protection circuit or device that avoids overcharge and saves space.

[0008]

[Means for Solving the Problem] As a result of intensive studies by the present inventors in order to prevent overcharge of a secondary battery, as a result, a Zener diode used in an electric circuit for keeping a voltage constant has a The inventors have found that the present invention can be applied to the stabilization of, and have made the present invention based on this finding.

That is, the present invention relates to a secondary battery in which a negative electrode and a positive electrode are interposed between separators, and a spirally wound electrode plate group and an electrolytic solution are enclosed in a container. An automatic reset type temperature switch and Zener diode are inserted in the air gap, and a thermal fuse and Zener diode are inserted in series in the cylindrical void portion that exists in the center of the wound electrode plate group, and the automatic reset is performed. A cylindrical secondary battery is characterized in that the temperature switch is electrically connected in series to the battery, and the Zener diode is electrically connected in parallel to the battery.

Further, according to the present invention, in a secondary battery in which a negative electrode and a positive electrode have a separator interposed therebetween, a spirally wound electrode plate group and an electrolytic solution are enclosed in a container. The thermal fuse and the Zener diode are inserted in series in the cylindrical void existing in the center of the electrode plate group, and the thermal fuse is electrically connected in series to the battery, and the Zener diode is A cylindrical secondary battery, which is electrically connected in parallel to the battery.

The present invention will be described in more detail.

FIG. 1 and FIG. 2 are cross-sectional views of one constitutional example of the cylindrical secondary battery of the present invention. As is apparent from this figure, the positive electrode 1 is laminated with the negative electrode 3 via the separator 2. The electrode plate group P is created by winding this in a spiral shape. The electrode plate group P is housed in a cylindrical battery container C.

The automatic reset type temperature switch 4 and the Zener diode 5 shown in FIG. 1 are connected in series and inserted in a space in the container extending in the central axis direction of the spirally wound electrode plate group. One end of the automatic reset type temperature switch 4 is connected between the battery terminals 6, and one end of the Zener diode 5 is connected to the battery terminal 7. The lead wire from the positive electrode 1 in the electrode group P is connected to the automatic reset type temperature switch 4
And a Zener diode 5 are connected to each other so that the charging / discharging current to the battery always flows through the automatic reset type temperature switch 4. FIG. 2 shows an electric circuit in the above embodiment of the present invention shown in FIG.

FIG. 3 is a sectional view of the second cylindrical battery of the present invention, and FIG. 4 is its electric circuit. As is clear from these figures, the thermal fuse 8 and the Zener diode 5 are connected in series and inserted into the cylindrical void portion at the center of the spirally wound electrode plate group. One end of the zener diode 5 is connected between the battery terminals 6, and one end of the Zener diode 5 is connected to the battery terminal 7. The lead wire from the positive electrode 1 in the electrode group P is connected to the connection point between the thermal fuse 8 and the Zener diode 5, so that the charging / discharging current to the battery always flows through the thermal fuse 8.

It is the Zener diode that detects the overcharge condition and keeps the battery in good condition. When the battery is overcharged due to a failure of the charging device, the voltage of the battery exceeds the specified value and becomes high. If a zener diode is connected in parallel with the battery that causes zener breakdown when the battery voltage becomes higher than the specified value due to overcharge, current flows in the zener diode at the same time when the overcharge condition occurs. Initially, no voltage above the specified value is applied to the battery. Therefore, decomposition of the electrolytic solution due to overcharge can be avoided. That is, it is possible to avoid a decrease in the charge / discharge cycle life of the battery and the electrolysis of water.

Next, the electrical rating of the Zener diode used in the present invention will be described. First, the Zener voltage is ideally slightly higher than the specified maximum charging voltage. Since the E-24 series is often adopted as the nominal value of the Zener voltage, in reality, a Zener diode having a Zener voltage higher than the specified maximum voltage value of the charging voltage and closest to that voltage value is used. Good to use. Regarding the allowable loss, in the case of a battery with a large charging current, it is necessary to use a Zener diode with a large allowable loss. However, the Zener diode having a large allowable loss has a large shape, and there is a possibility that the Zener diode cannot be housed in the void existing in the center of the wound electrode group. If the charging current in an AA battery whose maximum charging voltage is 3 to 4 V is about 50 to 200 mA, it is realistic to use a planar zener diode having a permissible loss of about 100 to 1000 mW. Ah

Next, the automatic reset type temperature switch will be described. When the overcharged state continues and current continues to flow through the Zener diode, the Zener diode itself generates heat due to the flowing current.However, it is the adjacent to the Zener diode that keeps the battery in a good condition even under these circumstances. It is an automatic reset type temperature switch. Due to the heat generated by the Zener diode, the adjacent automatic reset type temperature switch operates and the charging circuit is cut off in the battery. That is, the electrical connection between the electrode plate group P and the battery terminal 6 is cut off. This series of mechanisms stops the charging of the battery and prevents the generation of organic gas in the battery. In this state, the electrode group is electrically disconnected from the battery terminal, so that the electrode group can no longer be discharged.

When charging is stopped and the temperature of the Zener diode drops, the conduction state of the automatic reset type temperature switch is restored, and the battery can be discharged or charged.

The operating temperature of the automatic reset type temperature switch must be determined by examining the heat generation amount of the Zener diode. However, when the battery itself is heated, the charge / discharge cycle life becomes extremely short. Considering the above, it is realistic that the operating temperature of the automatic reset type temperature switch is 150 ° C. or less, ideally about 100 to 150 ° C. Alternatively, as disclosed by the inventors of the present invention in Japanese Patent Application No. 3-216167, an automatic reset type temperature switch that operates below the softening point temperature of the separator or a boiling point below the softening point temperature of the separator. If an electrolyte solvent such as is used is used, an automatic reset type temperature switch that operates below this boiling point may be used.

The connection interval and method of the automatic reset type temperature switch and the Zener diode can be determined as follows. Since the heat recovery type Zener diode detects heat generation due to overcharging, it is desirable that the distance between the auto recovery type temperature switch and the Zener diode be as small as possible. The automatic reset type temperature switch and the Zener diode may be molded in one container, but considering cost and the like, it is realistic to connect these two elements by soldering or crimping.

The shape of the automatic reset type temperature switch is not particularly limited, but it is preferable that it is disk-shaped or cylindrical so as to fit in the void of the battery container.

Even if the Zener diode is internally short-circuited for some reason, the heat generation of the Zener diode due to the short-circuit current causes the automatic reset type temperature switch to operate, so that the battery can be maintained in a safe state.

Next, the thermal fuse will be described. When the overcharged state continues and current continues to flow through the Zener diode, the Zener diode itself generates heat due to the flowing current.However, it is the adjacent to the Zener diode that keeps the battery in a good condition even under these circumstances. It is a thermal fuse. The adjacent thermal fuse operates due to the heat generated by the Zener diode, and the charging circuit is cut off in the battery. That is, the electrical connection between the electrode plate group P and the battery terminal 6 is cut off. This series of mechanisms stops the charging of the battery and prevents the generation of organic gas in the battery. Therefore, the operating temperature of the thermal fuse must be determined by examining the amount of heat generated by the Zener diode, but considering that the charging / discharging cycle life becomes extremely short when the battery itself is heated, The operating temperature of the thermal fuse is 100 ℃ or less, ideally 70-80
It would be realistic to set the temperature to about ℃. Alternatively, as disclosed by the inventors of the present invention in Japanese Patent Application No. 3-216167, a thermal fuse that operates below the softening point temperature of the separator or a boiling point below the softening point temperature of the separator. If an electrolyte solvent is used, a thermal fuse that operates below this boiling point may be used.

The connection interval and method of the thermal fuse and the Zener diode can be determined as follows. Since the thermal fuse detects heat generation of the Zener diode due to overcharge, it is desirable that the distance between the thermal fuse and the Zener diode be as small as possible. The thermal fuse and the Zener diode may be molded into one container, but considering cost and the like, it may be realistic to connect these two elements by soldering or crimping.

The shape of the thermal fuse is not particularly limited, but it is preferable that it is smaller than the cylindrical void existing at the center of the wound electrode plate group, and is cylindrical so as to fit in the void without any gap.

Even if the Zener diode is internally short-circuited for some reason, the thermal fuse operates due to the heat generation of the Zener diode due to the short-circuit current, and the battery can be maintained in a safe state.

In the present invention, since the Zener diode is always connected to both ends of the battery in the battery, the Zener diode is a defective product in case of emergency, and when the internal short circuit occurs, An internal short circuit is formed inside and an unexpectedly large current flows, and heat generation of the battery is expected. However, in such a case, a normal current operation type fuse may be inserted between the Zener diode and the negative electrode terminal of the battery container. The operating current value needs to be set at least larger than the charging current value. However, if it is unnecessarily increased, the current cutoff at the time of a Zener diode internal short circuit cannot be expected, so it is necessary to make it smaller than the maximum discharge current value of the battery no matter how large.

[0028]

In a secondary battery in which a negative electrode and a positive electrode have a separator interposed between them, a spirally wound electrode plate group and an electrolytic solution are enclosed in a container, a gap is automatically formed in a void portion in the container. A reset type temperature switch and a Zener diode are inserted, or a temperature fuse and a Zener diode are inserted in series in a cylindrical void portion existing in the center of the wound electrode plate group, and an automatic reset type temperature switch or The thermal fuse is electrically connected in series to the battery, and the Zener diode is electrically connected in parallel to the battery so that the discharge cycle life does not decrease even under the condition where it can be overcharged, or It is possible to obtain an excellent cylindrical secondary battery in which electrolysis of water does not occur.

Further, a plurality of cylindrical secondary batteries of the present invention,
When connected in series or in parallel and used as a battery pack, the load or charge is not biased to only one of the batteries. This is because the Zener diode electrically connected in parallel to each battery acts so as not to apply a voltage higher than the Zener voltage to the battery.

[0030]

The present invention will be described in detail below with reference to preferred embodiments.

In the following test, a cylindrical lithium secondary battery using a non-aqueous solvent having the constitution shown in FIGS. 1 to 4 as shown below was prepared and used for the test. However, as described above, it is clear that the present invention can exert its effect regardless of whether it is an aqueous solution or a non-aqueous solution of an electrolytic solution used for a cylindrical secondary battery, and the present invention is The effect is not limited to the cylindrical non-aqueous electrolyte secondary battery as in this embodiment.

Positive electrode: Amorphized vanadium pentoxide powder and ethylene propylene terpolymer (EPDM)
A mixture of a 2.5 wt% cyclohexane solution and acetylene black (weight ratio 90: 3: 7) applied on a metal current collector and dried.

Negative electrode: metallic lithium

Electrolyte solution: 1.5M concentration of lithium hexafluoroarsenate (LiAsF ₆ ) ethylene carbonate (EC)
/ 2 methyltetrahydrofuran (2MeTHF) (volume ratio 1/1) solution

Separator: 25 μm-thick polypropylene porous film (softening point 141 ° C.)

Battery charge / discharge test: Charge current 0.5 mA /
cm ² and discharge current 3.0 mA / cm ² constant current, 1.
Charge and discharge are repeated 5 times in the voltage range of 8 to 3.3 V, and after the fifth discharge, the charge and discharge voltage range of the battery is 1.8 to 4.1 V.
The setting was changed to and the charge / discharge cycle was continued. When the battery voltage did not increase even after continuing the charging, the charging was stopped at the time when the voltage did not increase, and the discharging in the next cycle was started.

[0037]

Example 1 A positive electrode and a negative electrode were superposed with a polypropylene porous film interposed therebetween, sandwiched in a groove of a winding rod having a diameter of 3.5 mm, and the electrode was wound. When the winding rod was pulled out after the winding was completed, a cylindrical void having a diameter of about 3 mm was formed at the center of the wound electrode group. It was also confirmed that when this electrode group was housed in a cylindrical battery container, a disk-shaped void having a thickness of about 4 mm was formed near the positive electrode terminal inside the battery container.

As shown in FIGS. 1 and 2, an automatic reset type temperature switch 4 having a diameter of about 10 mm and a thickness of about 3.0 mm (trade name: poly switch, product number RXEO90, manufactured by Raychem Co., Ltd., temperature fuse operating temperature: 125 ° C.) ) Is a planer type glass-sealed Zener diode 5 (RD
3.9E, power dissipation 500mW) are connected in series, the lead wire is pulled out from the connection portion, the automatic reset type temperature switch 4 is placed in the disk-shaped space near the positive terminal, and the Zener diode 5 is placed at the center of the electrode group P. Was inserted into the cylindrical void.

The polarity of the Zener diode is set so that no current will flow through the diode even if the Zener diode is connected across the battery due to the Zener voltage.

Connect the lead wire from the connecting portion to the positive electrode 1,
The lead wire of the automatic reset type temperature switch 4 was covered with an insulating tube and then connected to the positive electrode terminal 6 of the battery container. The lead wire from the Zener diode 5 was connected to the bottom portion 7 of the battery container which also serves as the negative electrode terminal. In this way, the automatic reset type temperature switch 4 and the Zener diode 5 were inserted into the container C. The negative electrode final body positioned on the outermost periphery of the negative electrode was connected to a battery container which also serves as a negative electrode terminal. Then, the non-aqueous electrolyte solution was sealed in the battery container C to prepare a cylindrical non-aqueous electrolyte secondary battery A.

A charging / discharging test was conducted on the completed battery A.

FIG. 5A shows the relationship between the number of charge / discharge cycles and the utilization rate of the positive electrode when the initial capacity is 100%.
It can be seen that the decrease in discharge capacity due to charge / discharge is small and that the charge / discharge cycle continues smoothly. This is the device side
Even though the battery was set to charge up to 4.1V, the voltage of the battery was actually 3.9V at maximum according to the present invention, and deterioration of the battery characteristics such as decomposition of the electrolytic solution occurred. It was thought that it was because there was not.

[0043]

[Example 2] A positive electrode and a negative electrode were superposed with a polypropylene porous film interposed therebetween, sandwiched in a groove of a winding rod having a diameter of 3.5 mm, and the electrode was wound. When the winding rod was pulled out after the winding was completed, a cylindrical void having a diameter of about 3 mm was formed at the center of the wound electrode group.

As shown in FIGS. 3 and 4, the diameter is about 2.3 mm.
Thermal fuse 8 (trade name ELCUT. No. 320,
Uchihashi STEC Co., Ltd., thermal fuse operating temperature 76
C) and a planar glass-sealed Zener diode 5 (RD3.9E, power dissipation 500 mW) with a diameter of about 2 mm is connected in series, a lead wire is drawn out from the connection portion, and is placed in the cylindrical void at the center of the electrode group P. Inserted.

The polarity of the Zener diode is set so that no current flows through the diode even if the Zener diode is connected across the battery due to the Zener voltage.

The lead wire from the connecting portion is connected to the positive electrode 1,
The lead wire of the thermal fuse 8 was connected to the positive electrode terminal 6 of the battery container after covering the insulating tube. The lead wire from the Zener diode 5 is a battery container that also serves as a negative terminal.
It was connected to the bottom 7. In this way, the electrode group P in which the Zener diode 5 and the thermal fuse 8 were inserted was housed in the battery container C. The negative electrode final body positioned on the outermost periphery of the negative electrode was connected to a battery container which also serves as a negative electrode terminal. Then, the non-aqueous electrolyte solution was sealed in the battery container C to prepare a cylindrical non-aqueous electrolyte secondary battery A.

A charging / discharging test was conducted on the completed battery A.

FIG. 6A shows the relationship between the number of charge / discharge cycles and the utilization rate of the positive electrode when the initial capacity is 100%.
It can be seen that the decrease in discharge capacity due to charge / discharge is small and that the charge / discharge cycle continues smoothly. This is the device side
Even though the battery was set to charge up to 4.1V, the voltage of the battery was actually 3.9V at maximum according to the present invention, and deterioration of the battery characteristics such as decomposition of the electrolytic solution occurred. It was thought that it was because there was not.

[0049]

Comparative Example A battery B shown in FIG. 7 was produced in the same manner as in the example except that the Zener diode, the automatic reset type temperature switch and the temperature fuse were not used. That is, the positive electrode 1
Is laminated with the negative electrode 3 via the separator 2, and this is wound in a spiral shape to produce the electrode plate group P. The electrode plate group P is housed in a cylindrical battery container C. In this case, a lead wire was directly connected to the positive electrode terminal 6 from the positive electrode 1.

This battery B was also subjected to the charge / discharge test as in the example.

FIG. 5 and FIG. 6B show the relationship between the number of charge / discharge cycles and the utilization factor of the positive electrode when the initial capacity is 100%. The discharge capacity significantly decreases with the charge / discharge cycle. It was considered that this was because the electrolyte was decomposed because the battery was charged up to 4.1V.

[0052]

As is apparent from the above results, the secondary battery in which the negative electrode and the positive electrode are interposed between the separators, and the electrode plate group spirally wound and the electrolytic solution are enclosed in a container. The automatic reset type temperature switch or temperature fuse and the Zener diode are inserted in the void in the container in series connection with the void in the container, and the automatic reset type temperature switch or temperature fuse is connected to the battery. Even if the battery is overcharged because it is electrically connected in series and the zener diode is electrically connected in parallel to the battery, the zener diode works and the battery itself It is possible to obtain a cylindrical secondary battery that is excellent in overcharge resistance and that is not overcharged and does not deteriorate in charge / discharge cycle life.

Further, even if the overcharged state is continued, it is expected that the charging is stopped by the functions of the automatic reset type temperature switch and the temperature fuse to improve the safety of the battery.

When the overcharge is stopped and the heat generation of the Zener diode is stopped, the temperature switch is restored and the battery can be charged and discharged again.

Therefore, the industrial value of the present invention is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of an example of a non-aqueous electrolyte secondary battery according to the present invention.

FIG. 2 is a schematic vertical cross-sectional view of an example of a non-aqueous electrolyte secondary battery according to the present invention.

FIG. 3 is a diagram showing an electric circuit of one configuration example of the present invention shown in FIG.

FIG. 4 is a diagram showing an electric circuit of one configuration example of the present invention shown in FIG.

FIG. 5 is a diagram showing the relationship between the number of charge / discharge cycles and the positive electrode utilization rate when the initial capacity is 100% in the non-aqueous electrolyte secondary batteries according to Example 1 and Comparative Example of the present invention.

FIG. 6 is a graph showing the relationship between the number of charge / discharge cycles and the positive electrode utilization rate when the initial capacity is 100% in the non-aqueous electrolyte secondary batteries according to Example 2 and Comparative Example of the present invention.

FIG. 7 is a schematic vertical sectional view of an example of a battery according to a comparative example of the present invention.

[Explanation of symbols]

 1 Positive electrode 2 Separator 3 Negative electrode 4 Automatic reset type temperature switch 5 Zener diode 6 Positive electrode terminal 7 Negative electrode terminal 8 Thermal fuse C Battery container P Electrode group

Claims (2)

[Claims] 1. A secondary battery in which a negative electrode and a positive electrode have a separator interposed therebetween, and a spirally wound electrode plate group and an electrolytic solution are enclosed in a container. , The automatic reset type temperature switch and the Zener diode are connected in series, the automatic reset type temperature switch is electrically connected in series to the battery, and the Zener diode is electrically connected in parallel to the battery Cylindrical battery characterized by being made. 2. A secondary battery in which a negative electrode and a positive electrode have a separator interposed therebetween, and a spirally wound electrode plate group and an electrolytic solution are enclosed in a container. A thermal fuse and a Zener diode are inserted in series in the cylindrical void existing in the center of the group, and the thermal fuse is electrically connected in series to the battery, and the Zener diode is connected to the battery. Cylindrical battery characterized by being electrically connected in parallel.