JPH1027596A - Explosion-proof sealing plate for sealed batteries - Google Patents

Abstract

(57) [Problem] To provide an explosion-proof sealing plate for a sealed battery excellent in battery characteristics in which an electrolyte does not invade a PTC element even during high-temperature storage and the internal resistance does not increase. SOLUTION: A water-repellent porous film 9 is provided between a cover plate 5 having a gas discharge hole 5a and an explosion-proof valve body 6, and does not affect the operation characteristics of the safety valve and has excellent battery storage characteristics. An explosion-proof sealing plate for a sealed battery can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an explosion-proof sealing plate for a sealed battery.

[0002]

2. Description of the Related Art In recent years, the current consumption of equipment used has tended to be small, and accordingly, the service life of batteries has tended to be prolonged. Therefore, in terms of battery design, stable hermeticity and airtightness are required over a long period of time, and an extremely airtight sealing is performed.

FIG. 4 shows a cylindrical lithium ion secondary battery using a conventional explosion-proof sealing plate. In the drawing, A is an explosion-proof sealing plate, B is a power generation element group, and the positive electrode 10 is a lithium-containing composite oxide of a transition metal as a main material, to which a conductive material and a binder are added. The negative electrode 11 uses a carbon material. The positive electrode 10 and the negative electrode 11 are formed in a spiral shape through a separator 12 made of a polyethylene or polypropylene film. A mixture of a solvent such as ethyl carbonate and ethyl methyl carbonate is used as an electrolytic solution for this electrode group, and LiPF ₆ is used as a solute as a solute.
A power generating element is formed by impregnating a solution obtained by dissolving the above components as an electrolytic solution. Reference numeral 13 denotes a battery container which also serves as a negative electrode terminal. As the material thereof, iron having a thickness of about 0.2 mm and subjected to contact-resistant plating is used. 14 is a positive electrode lead plate connected to the positive electrode 10 and the explosion-proof sealing plate A, and 15 is a negative electrode 11
And a negative electrode lead plate for connecting the battery case 13 to the battery case 13, 16 a lower insulating ring, and 17 an upper insulating ring. The explosion-proof sealing plate A has the configuration shown in FIG.

That is, in FIG. 5, 1 is an inner gasket, 2 is a sealing plate ring, 3 is an external terminal, 4 is a safety element (hereinafter referred to as a safety element) having a characteristic of having a small resistance value at normal temperature and increasing as the temperature rises. , PTC element), 5
Is a cover plate for attaching a lead, 6 is an explosion-proof valve body, 7 is an inner terminal plate, and 8 is an outer gasket for separating the battery container 13 and the explosion-proof sealing plate A.

The external terminal 3, cover plate 5 and inner terminal plate 7 are provided with gas discharge holes 3a, 5a and 7a, respectively.
If the battery is externally short-circuited, internally short-circuited or overcharged, gas is generated inside the battery, and if the battery internal pressure rises abnormally, the battery may be ruptured.

Therefore, a thin plate in which a metal foil is bonded to a synthetic resin film is inserted into an explosion-proof sealing plate A of the battery.
The explosion-proof valve body 6 is torn when the internal pressure of the battery rises, so that gas in the battery is released. further,
The PTC element 4 is formed between the explosion-proof valve 6 and the periphery of the external terminal 3.

In such a conventional configuration, since the electrolyte enters the explosion-proof valve 6 through the gas discharge hole 5a of the cover plate 5 and the gas discharge hole 7a of the inner terminal plate 7, the PTC element is increased when the internal pressure in the battery rises. The possibility that the electrolyte solution reached 4 was very high.

[0008]

In the actual use of a battery, the battery may be left and stored at a high temperature. Therefore, in the conventional configuration, the gas discharge hole 5a of the cover plate 5 and the gas of the inner terminal plate 7 are not used. The electrolyte that has entered through the discharge hole 7a enters the PTC element 4 due to an increase in battery internal pressure during high-temperature storage, and
There is a problem that the resistance of the PTC element 4 increases due to the reaction between the C element 4 and the electrolytic solution, and the internal resistance of the battery increases.

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a battery in which an electrolyte does not penetrate into a PTC element even during high-temperature storage and the internal resistance does not increase.

[0010]

In order to achieve the above-mentioned object, an explosion-proof sealing plate for a sealed battery according to the present invention is formed by deforming a metal external terminal, a PTC element, and an outward with an increase in battery internal pressure. A metal explosion-proof valve body, an inner terminal plate made of metal and having gas exhaust holes, and a lid plate attached with a lead made of metal and having gas exhaust holes and stacked in an insulating gasket. A water-repellent porous film is provided between the inner terminal plate and the cover plate.

The presence of the water-repellent porous membrane prevents the electrolyte in the battery container from rising, and prevents the electrolyte from coming into contact with the PTC element. Therefore, the electrolyte and the PTC element do not react to increase the resistance of the PTC element, and the internal resistance of the battery does not increase.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As set forth in claim 1, an electrode group consisting of a positive electrode, a negative electrode and a separator, and an explosion-proof sealing plate for sealing a battery container containing an electrolytic solution are provided with metal external terminals. A PTC element, a metal explosion-proof valve body that deforms outward with an increase in battery internal pressure, an inner terminal plate made of metal having gas exhaust holes, and a cover plate to which a metal lead having gas exhaust holes is attached. The present invention can be implemented by disposing a water-repellent porous membrane between the inner terminal plate and the cover plate in a configuration in which the insulating gasket is stacked in the insulating gasket.

According to the above-described embodiment, the water-repellent porous membrane prevents the electrolyte from rising, so that the electrolyte does not come into contact with the PTC element. And the internal resistance of the battery is not increased.

In addition, the water-repellent porous membrane can be pressed between the cover plate and the inner terminal plate as described in claim 2, and has water-repellency as described in claim 3. It can be carried out by attaching a porous membrane to a lid plate or an inner terminal plate.

Further, the water-repellent porous film may be a porous polytetrafluoroethylene film or a polyolefin resin porous film, or the Gurley number may be 10 to 300. By using a porous polytetrafluoroethylene membrane or a polyolefin resin porous membrane having an air permeability of seconds, the effects of the present invention can be effectively exhibited.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 shows an explosion-proof sealing plate provided with a water-repellent porous membrane according to the present invention.
The same parts as those of the conventional example shown in FIG.

As shown in FIG. 1, a water-repellent porous film 9 is placed on the cover plate 5 on a horizontal portion 5b at the bottom of the cover plate 5,
An inner terminal plate 7 having a gas discharge hole 7a and a flat peripheral edge 7b; an inner gasket 1, an explosion-proof valve body 6, and a PTC;
The element 4 and the external terminal 3 are fitted, and the opening
c is crimped inward with a mold, and a horizontal portion 5b at the bottom of the lid plate 5 is formed.
And the external terminal is pressed and fixed by the peripheral flat portion 3b. At this time, the water-repellent porous film 9 is pressed and fixed by the horizontal portion 5b at the bottom of the cover plate 5 and the peripheral portion 7b of the inner terminal plate 7.

In this embodiment, a porous polytetrafluoroethylene film is used as the porous film 9 having water repellency.

(Embodiment 2) FIG. 2 shows an explosion-proof sealing plate according to Embodiment 2 of the present invention. In FIG. 2, the porous polytetrafluoroethylene film 9 has one surface subjected to a surface bonding treatment. It is bonded so as to close the gas discharge hole 7a of the terminal plate 7.

(Embodiment 3) FIG. 3 shows an embodiment 3 of the explosion-proof sealing plate of the present invention. In FIG. 3, the porous polytetrafluoroethylene film 9 is subjected to a surface bonding treatment in the same manner as in the embodiment 2. It is bonded so as to close the gas discharge hole 5a of the cover plate 5.

Comparative Example As a comparative example, FIG. 5 shows a configuration of a conventional explosion-proof sealing plate.

The electrolyte enters the explosion-proof valve 6 through the gas discharge hole 5a of the case and the gas discharge hole 7a of the filter.

Next, the Gurley number 10, 100, 300,
Using a porous polytetrafluoroethylene membrane of 500 or 1000 seconds, 10 explosion-proof sealing plates each having a configuration according to Examples 1 to 3 were produced, each 30 in total, and 30 comparative examples were prepared.
The operation characteristics of the safety mechanism were compared and confirmed.

The Gurley number is 10 at a constant pressure.
The air permeability is expressed by the time (seconds) required for permeation of 0 cc gas. The test method was a method in which a specified pressure was applied and the current interruption pressure and the vent pressure of the explosion-proof valve 6 were measured.

The results are shown in Table 1.

[0027]

[Table 1]

As is clear from Table 1, a battery safety valve using a membrane having a Gurley number of 10 to 300 seconds has a current interruption pressure and a vent pressure equivalent to those of a conventional one, and a porous polytetrafluoroethylene membrane. It can be seen that the operation characteristics are not affected by the presence of.

Next, a cylindrical lithium ion secondary battery was manufactured using the explosion-proof sealing plate having the configuration according to the embodiment of the present invention and that of the comparative example, and the characteristics during high-temperature storage were compared.

The air permeability of the porous polytetrafluoroethylene membrane used in the examples was one having a Gurley number of 10 to 300 seconds.

The size of the manufactured cylindrical battery is 18 mm in diameter and 65 mm in total height. The test method was such that each battery was left in an atmosphere of 60 ° C. for 60 days, and the internal resistance was measured.

The results are shown in Table 2.

[0033]

[Table 2]

As is clear from Table 2, the internal resistance of the battery according to the comparative example gradually increases with the lapse of storage, but the internal resistance of the batteries according to Examples 1, 2, and 3 of the present invention does not change. You can see that. The reason why the internal resistance of the battery according to the comparative example increases is that the resistance of the PTC element increases due to the reaction between the electrolyte and the PTC element due to the electrolyte penetrating into the PTC element as the internal pressure of the battery increases due to gas generation during high temperature storage. .

In the battery using the explosion-proof sealing plate according to Examples 1, 2 and 3 of the present invention, the internal resistance does not increase because the electrolyte does not reach the PTC element even when the internal pressure of the battery increases during high-temperature storage. .

In Examples 2 and 3, the porous polytetrafluoroethylene film was bonded and integrated using a surface-bonded film, but the film was electrostatically pressed and ultrasonically welded. The same effect was obtained by laminating with a hot roller.

In this example, a porous polytetrafluoroethylene film was used as the water-repellent porous film. However, similar results were obtained by using a polyolefin resin porous film such as polypropylene or polyethylene.

[0038]

As is apparent from the above description, according to the present invention, an explosion-proof sealing plate in which a water-repellent porous film is disposed between a cover plate having a gas discharge hole and an explosion-proof valve body. Therefore, even during high-temperature storage, it is possible to obtain a sealed battery having excellent storage characteristics in which the electrolyte does not penetrate into the PTC element and the internal resistance does not increase.

[Brief description of the drawings]

FIG. 1 is a sectional view of an explosion-proof sealing plate according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an explosion-proof sealing plate according to a second embodiment of the present invention.

FIG. 3 is a sectional view of an explosion-proof sealing plate according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a configuration of a cylindrical lithium ion secondary battery.

FIG. 5 is a sectional view of a conventional explosion-proof sealing plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner gasket 2 Sealing plate ring 3 External terminal 3a, 5a, 7a Gas exhaust hole 3b Peripheral flat part 4 PTC element 5 Cover plate 5b Horizontal part 5c Opening bent edge 6 Explosion-proof valve body 7 Inner terminal plate 7b Peripheral part 8 Outer gasket 9 Water-repellent porous membrane

Claims (5)

[Claims] An explosion-proof sealing plate for sealing a battery container containing an electrolytic solution and an electrode plate group comprising a positive electrode, a negative electrode, and a separator has a metal external terminal and a small resistance value at normal temperature to increase the temperature. Then, a safety element with the characteristic of increasing the resistance value, a metal explosion-proof valve body that deforms outward as the battery internal pressure increases, an inner terminal plate made of metal and having a gas exhaust hole, and a metal gas In a configuration in which a lid plate for attaching a lead having a discharge hole is stacked and accommodated in an insulating gasket, a water-repellent porous film is disposed between the inner terminal plate and the lid plate. Explosion-proof sealing plate for rechargeable batteries. 2. The sealed battery according to claim 1, wherein a water-repellent porous membrane is pressed between the lid plate and the inner terminal plate to electrically connect the lid plate and the inner terminal plate. Explosion-proof sealing plate. 3. A water-repellent porous membrane is attached to the cover plate or the inner terminal plate so as to close the gas discharge hole of the cover plate or the gas discharge hole of the inner terminal plate. An explosion-proof sealing plate for a sealed battery according to claim 1 or 2. 4. The explosion proof for a sealed battery according to claim 1, wherein a porous polytetrafluoroethylene film or a polyolefin resin porous film is used as the water-repellent porous film. Sealing plate. 5. The sealing according to claim 1, wherein a porous polytetrafluoroethylene membrane having a Gurley number of 10 to 300 seconds or a polyolefin resin porous membrane is used. Explosion-proof sealing plate for rechargeable batteries.