JP2000067931A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electrolyte from leaking outside by providing an assembled sealing plate with a filter connected to one electrode through a lead plate, a sub-filter coming into surface contact with the filter, a valve body formed of a metal thin plate to be ruptured by a predetermined pressure, a valve body rupturing ring, and a flexible wiring board on which a safety circuit electrically connected to the filter is mounted. SOLUTION: A cylindrical lithium battery has a filter 48, a sub-filter 49, a valve body 47, and a valve body rupturing ring 46. Explosion-proofing slits G are formed in the valve body 47, which is welded to the filter 48. An electrolyte gasified by heat generation pushes up the valve body 47 toward a safety circuit side through holes H of the filter 48. At that time, the pressure of the gas ruptures the slits G formed in the valve body 47, and thereby, the gas is released outside through a hole E formed in the safety circuit, holes I formed in the controlled positive input and output, and holes J formed in a safety circuit-use negative electrode, so that an explosion-proof measure is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery in which a safety circuit composed of an electronic circuit including a current interrupting element made of a semiconductor is arranged at a sealing portion of a sealed battery such as a lithium ion secondary battery.

[0002]

2. Description of the Related Art Due to the high energy density of sealed secondary batteries, especially lithium ion secondary batteries, demand for power sources for driving small portable devices such as video cameras, mobile phones, and notebook computers has been increasing. I have. This lithium-ion secondary battery requires a safety device including a safety circuit to protect the battery from overcharge, overdischarge, and overcurrent, and usually incorporates the battery and an electric circuit as a safety circuit in a housing. Used as a battery pack. FIG. 4 is a schematic diagram of a pack-type battery using a lithium ion secondary battery. Reference numeral 1 denotes a case in which cylindrical lithium-ion secondary batteries 2 and 3 are shaped so that they can be attached to equipment using a pack-type battery; 4 denotes lithium-ion secondary batteries 2 and 3
And a safety circuit inserted between the terminals of the housing 1. The battery pack having such a configuration has problems as described below.

[0003] 1) Since the shape and design of the housing 1 are formed so that the battery pack can be easily mounted on the device to be supplied, the housing 1 may be dedicated to the device to be supplied. Many.

[0004] 2) Since the housing 1 has a shape and a design that can be easily mounted on the device to be supplied, the charger must also be adapted to the housing 1, and it is a dedicated charger corresponding to the device to be supplied. Often.

[0005] 3) The battery pack needs to have a shape and a terminal structure for mounting on a safety circuit or a supplied device, and the volume of these batteries is smaller than the volume of the lithium ion secondary batteries 2 and 3 to be stored. Extremely large.

[0006] 4) The general consumer has to purchase a battery pack and a charger adapted to each supplied device, which is uneconomical.

[0007] In order to solve such a problem, the present inventors have previously described a cap located at the top of the secondary battery, specifically, a cap located at the top of the sealing plate and a cap located below the cap. We proposed a structure in which a miniaturized safety circuit is placed between the current cutoff valve, that is, the part that does not directly touch the electrolyte in normal times. (Japanese Patent Application No. 08-178896) The above structure will be described below. FIG. 5 is a sectional view of the sealing portion, and FIG.
FIG. 6A is an exploded perspective view of the enclosed portion, and FIG. 6B is an exploded sectional view of the enclosed portion.

The sealing portion has a PTC element which is a current reducing function when the battery is heated, a current cutoff function when the internal pressure of the battery is increased, and an explosion-proof function when the internal pressure of the battery is increased. The sealing part is a filter 17, a sub-filter 18, an inner gasket 19, a valve body 20, a PTC
The flexible wiring board on which the safety circuit 27 is mounted is disposed on the PTC element 21 in the order of the elements 21. This safety circuit has a structure in which a waterproof or electrolytic solution is coated or sealed, and an opening or a part thereof is broken in the flexible plate.

The positive electrode side of the power generating element housed in the secondary battery is connected to a filter 17 having a hole C via a lead plate, and then comes into surface contact therewith so as to pass through a sub-filter 18 having a hole B. It has become. Furthermore, since the sub-filter 18 and the valve element 20 are welded at the central portion by welding, the current of the positive electrode passes through the valve element 20 and passes through the ring-shaped PTC element 21 which is in surface contact therewith, and the safety circuit 27 It is led to.

8 and 9, the electrodes of the PTC element 21 are in surface contact with a flexible wiring board 38 made of a polyimide material and are connected to the safety circuit 27 through through holes and wires. E denotes a hole provided in the flexible wiring board 38 for an explosion-proof structure. On the other hand, the safety circuit negative electrode 37 is in surface contact with the flexible wiring board 38 and is connected to the safety circuit 27 through wiring. The input / output terminal of the secondary battery 28 controlled by the safety circuit 27 becomes a controlled plus input / output 39 of the secondary battery through surface contact through the flexible wiring board 38. F is a waterproof and electrolyte-resistant coating of the safety circuit 27, 41 and 42 are thermosetting adhesives such as epoxy, and 40 and 45 are a safety circuit negative electrode 37 and a controlled plus of the secondary battery. ABS fixed between input and output 39
An insulating material such as a resin, and 44 is a sealing plate ring.

The current reduction function uses the characteristics of a PTC element whose resistance value rises rapidly when the temperature reaches a specified temperature.
Alternatively, the battery temperature rises due to a large discharge current, for example, a current equal to or greater than the current value corresponding to a one-hour discharge, and when the battery temperature reaches a specified temperature, the resistance value rises to reduce the current. It is intended to prevent the situation from becoming unsafe.

On the other hand, in the current interruption function, the electrolyte gasified by heat generation pushes up the valve body 20 to the outside of the battery through the hole C of the filter 17 and the hole B provided in the sub-filter 18. At this time, when the pressure of the gas exceeds the welding force between the sub-filter 18 and the valve body 20, the welding is disconnected, so that the electrical connection is cut off and the current is cut off.

The explosion-proof function functions as follows.
That is, after the current cutoff by the sub-filter 18 and the valve element 20 is activated, the electrolytic solution gasified by heat generation is:
The valve body 20 is further pushed up. On the other hand, since the periphery of the valve body 20 is fixed, the slit A provided in the valve body 20 is broken by the pressure of the gas, and at that time, the gasified electrolyte is discharged to the outside.

Next, the configuration of the safety circuit 27 will be described with reference to FIG. In FIG. 7, the + terminal is a safety circuit 27.
The input / output terminal and the S terminal to the outside of the secondary battery 28 controlled by the negative electrode of the safety circuit 27 are formed on the outer peripheral surface or the bottom surface of the secondary battery 28 on the side of the supplied device or the charger. Connect with -Terminal is a secondary battery 28
Is a minus pole formed on the outer peripheral surface or the bottom surface of.

When the S terminal is connected to the negative electrode of the secondary battery 28 on the side of the device to be supplied or the charger,
When the voltage between the output side of the PTC element 21 and the S terminal is within a specified value, the voltage detector 31 built in the sealing portion
The current interrupting element 32 such as ET is turned on to enable charging from the charger. On the other hand, when the voltage between the output side of the PTC element 21 and the S terminal becomes higher than a specified value, the voltage detector 3
1 turns off the current interrupting element 32 such as an FET and protects the secondary battery 28 from overcharging.

Although the safety circuit 27 exhibits the above function, when the FET is used as the current interrupting element 32,
Is turned off, the secondary battery 28 can be discharged through the + terminal by the body diode effect.

[0017]

In the sealing portion having the above structure, the PTC element 21 is an element whose resistance value rises sharply at a specified temperature, and is made of a conductive polymer material. When an overcharge or a large discharge current is applied to a battery having a PTC element, for example, a current greater than a current value corresponding to one hour of discharge is applied, the battery temperature rises. The value is increased (hereinafter, referred to as a trip state). As a result, the current applied to the battery is reduced, thereby preventing the battery from being in an unsafe state. The PTC element expands in a temperature range where the resistance value rises, and contracts when returning to a normal temperature range. Therefore, the PCT element is accompanied by a volume change with its operation.

As shown in FIG. 5, the outer periphery of the PCT element in the sealing portion is fixed by caulking with an inner gasket 19 and a filter 17. PCT
Repeatedly returns to the trip state and the normal state.
Due to the volume change of the T element, stress is applied to the swaged portion. The swaged part becomes loose. A minute gap is generated in this portion. Further, there is a problem that the electrolyte leaks out through the gap to generate an electrolyte.

[0019]

SUMMARY OF THE INVENTION In order to solve the above problems, a secondary battery according to the present invention relates to an assembled sealing plate for closing an opening of a battery case accommodating a battery element. A board has a filter, a valve body, and a flexible wiring board having a safety circuit mounted thereon in that order, and the electronic circuit having a current interrupting element and a temperature detecting means is used for the safety circuit, so that the positive temperature sensitivity of the PTC element is obtained. In place of the resistance function, a current interruption by abnormal temperature detection is performed.

For this reason, in the conventional assembled sealing plate, by eliminating the PTC element inserted between the safety circuit and the valve body, it is possible to prevent the loosening of the swaged sealing due to the volume change of the PTC element. In addition, generation of liquid leakage can be suppressed.

[0021]

Embodiments of the present invention will be described below.

According to the first aspect of the present invention, there is provided a secondary battery including a battery case accommodating a power generating element, and an assembled sealing plate attached to an opening of the battery case via a gasket. A filter connected to one electrode of the power generating element via a lead plate, a sub-filter having a through hole in the center in surface contact with the filter, a valve body made of a thin metal plate which breaks at a predetermined pressure, A valve body breaking ring having a hole, a flexible wiring board on which a safety circuit electrically connected to a filter is mounted, and a cap electrically connected to the safety circuit and having a through hole are mounted. And the safety circuit has a temperature detecting means and a current cutoff element.

According to this configuration, it is possible to avoid the loosening of the swaged portion after the trip, which is likely to occur in the assembled sealing plate in which the PTC is built in and the swaged sealing is performed, and the occurrence of liquid leakage due to this.

Also, by eliminating the PTC element, the PTC
The internal resistance due to the resistance of the element can be reduced. Specifically, when the configuration of the present invention is applied to a battery size of 18650 (manufactured by Matsushita Battery Industry Co., Ltd.), PT
The removal of about 50 mΩ corresponding to the resistance value of the C element has a specific effect of reducing the internal resistance value of the battery unit by about 40%.

Further, since the secondary battery of the present battery uses a safety circuit using an electronic circuit including a temperature detecting means and a current interrupting element, the current interrupting function in the valve body is also achieved by utilizing the current interrupting element. It is also possible to provide them together.

According to a third aspect of the present invention, there is provided a secondary battery including a battery case accommodating a power generation element, and an assembled sealing plate attached to an opening of the battery case via a gasket, A filter whose assembled sealing plate is connected to one electrode of a power generating element via a lead plate, a sub-filter having a through hole in the center in surface contact with the filter, and a valve made of a thin metal plate that breaks at a predetermined pressure. A body, a valve body breaking ring having a through hole, a flexible wiring board on which a safety circuit electrically connected to the filter is mounted, and a cap electrically connected to the safety circuit and having a through hole are mounted. And a safety circuit having a current interrupting element and a battery internal pressure detecting means.

According to this configuration, the safety circuit detects the rise in the internal pressure by welding the filter and the valve element in the conventional assembly sealing plate in order to detect the rise in the internal pressure of the battery. And a function of interrupting the electrical connection between the filter and the valve element. The abolition of this current cutoff valve function makes it possible to eliminate the need to control the welding strength between the sub-filter and the valve body to allow the current cutoff mechanism to operate at the specified pressure, greatly improving the efficiency of the assembly sealing plate manufacturing process. Can be measured. The valve element only performs an explosion-proof function when the battery internal pressure rises abnormally.

Further, by welding the central portion of the valve body to the filter to reduce the displacement of the valve body when the internal pressure of the battery rises, the assembly sealing plate can be made thinner and simpler.

Hereinafter, the structure of the secondary battery according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a block diagram of a safety circuit according to an embodiment of the present invention. According to this circuit configuration, PTC
The element and the current cutoff valve have been eliminated. Except that the function of the PTC element and the function of the current cutoff valve are eliminated, the circuit configuration is the same as that of the conventional example, and the description of the operation is omitted.

FIG. 2 is a sectional view of an assembled sealing plate in a cylindrical lithium ion secondary battery for explaining the present invention. In this figure, an assembling sealing plate, a filter 48 connected to one electrode of a power generating element via a lead plate, a surface contact with the filter, a sub-filter 49 having a through hole in the center, and breaking at a predetermined pressure. A valve element 47 made of a thin metal plate, a valve element breaking ring 46 having a through hole, a flexible wiring board 27 on which a safety circuit electrically connected to a filter is mounted, and a through hole that is electrically connected to the safety circuit. Having a cap mounted thereon. Valve element 47
Is provided with a slit G for explosion protection, and is further welded to the filter 48. The electrolyte gasified by heat generation pushes up the valve body 47 through the hole H of the filter 48 to the safety circuit 27 side. At this time, the gas pressure breaks the slit G provided in the valve body 47,
It is discharged to the outside through a hole E provided in the safety circuit 27, a hole I provided in the controlled plus input / output, and a hole J provided in the minus pole for the safety circuit, and subjected to explosion-proof treatment.

FIG. 3 is a view showing a state immediately before the operation of the explosion-proof valve 47 shown in FIG. 2. By displacing the valve body in an oblique direction, the thickness of the sealing plate can be reduced.

[0033]

The rechargeable battery of the present invention as described above has an advantageous effect that it can solve the problem of loosening of the swaged portion due to the trip of the PTC element and the accompanying problem of liquid leakage.

[Brief description of the drawings]

FIG. 1 is a block diagram of a safety circuit according to an embodiment.

FIG. 2 is a sectional view of an assembled sealing plate according to the embodiment.

FIG. 3 is a diagram showing an operation state of a valve body according to the embodiment.

FIG. 4 is a schematic view of a battery pack.

FIG. 5 is a sectional view of an assembled sealing plate in Japanese Patent Application No. 08-178896.

FIG. 6 is an exploded perspective view of the same.

FIG. 7 is a view showing the configuration of the same part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 2, 3 Cylindrical lithium ion secondary battery 4 Safety circuit 5 Positive terminal 6 PTC element 7, 8 FET 9 Thermal fuse 44 Sealing plate ring 46 Valve body breaking ring 47 Valve body

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02J 7/10 H02J 7/10 LF term (Reference) 5G003 BA01 CB01 CB04 CC02 FA03 FA04 5H012 AA01 BB04 CC01 DD02 DD05 EE04 FF01 GG01 5H022 AA09 CC02 CC06 KK01 5H029 AJ12 AK00 AL00 AM01 BJ02 5H030 AA03 AA07 AA10 AS05 AS11 BB01 FF43

Claims (4)

[Claims] 1. A secondary battery comprising: a battery case accommodating a power generating element; and an assembled sealing plate attached to an opening of the battery case via a gasket, wherein the assembled sealing plate is one of the power generating elements. Filter connected through a lead plate to the electrode, a sub-filter in surface contact with this filter and having a through hole in the center, a valve body made of a thin metal plate that breaks at a predetermined pressure, and a valve body with a through hole A ring, a flexible wiring board on which a safety circuit electrically connected to the filter is mounted, and a structure electrically connected to the safety circuit and having a cap having a through hole mounted thereon; Has a temperature detecting means and a circuit. 2. The secondary battery according to claim 1, wherein said cap comprises an inner cap and an outer cap which are electrically insulated from each other. 3. A secondary battery comprising: a battery case accommodating a power generating element; and an assembled sealing plate mounted on an opening of the battery case via a gasket, wherein the assembled sealing plate is one of the power generating elements. Filter connected through a lead plate to the electrode, a sub-filter in surface contact with this filter and having a through hole in the center, a valve body made of a thin metal plate that breaks at a predetermined pressure, and a valve body with a through hole A ring, a flexible wiring board on which a safety circuit electrically connected to the filter is mounted, and a structure electrically connected to the safety circuit and having a cap having a through hole mounted thereon; A secondary battery according to claim 1, wherein the safety circuit has a current interrupting element and a battery internal pressure detecting means. 4. The secondary battery according to claim 3, wherein a central portion of the valve body and the filter are connected.