JP3185644B2 - Non-aqueous electrolyte secondary battery sealing plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved explosion-proof sealing plate used for sealing a battery having a high energy density, such as a sealed battery, particularly a lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, portable and cordless electronic devices have been rapidly advancing, and there is a high demand for a small and lightweight secondary battery having a high energy density as a drive power source for these devices. In this respect, non-aqueous secondary batteries, particularly lithium secondary batteries, are particularly expected as sealed batteries having high voltage and high energy density. However, sealed batteries may leak due to malfunctions, misuse, or long-term storage of equipment including the charger, causing damage to the equipment used. A petroleum pitch was applied to the inside of the gasket to prevent leakage of the electrolyte from the sealing portion.

[0003]

As described above, by applying a petroleum pitch to the inside of the inner gasket, it is possible to prevent leakage of the electrolyte from the sealing portion. However, when the petroleum pitch is dried, the liquid does not pass. Micropores are formed to allow gas to pass through. When the micropores are present, the electrolyte vapor permeates through the micropores to reach the PTC element, particularly during high-temperature storage, and attacks the resin (polyethylene) in the PTC element to increase the internal resistance of the battery. A decrease may be seen.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a sealing plate structure capable of preventing an increase in internal resistance of a battery due to electrolyte vapor reaching a PTC element.

[0005]

As described above, the leakage resistance is improved by applying a petroleum pitch to the inner side of the inner gasket, but the internal resistance of the battery increases due to the penetration of the electrolyte vapor into the PTC element. Since the battery characteristics such as load characteristics may be reduced, the resistance to liquid leakage is not impaired, and
Instead of oil pitch to prevent intrusion into TC element,
A sealant made of styrene butadiene rubber (hereinafter referred to as SBR), acrylonitrile rubber, or silicone rubber, which does not generate micropores after drying, alone or a mixture of two or more kinds is used.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS By using a sealing plate having such a structure, particularly during storage at a high temperature, electrolyte vapor permeates through micropores of a petroleum pitch inside an inner gasket and a PT
The polyethylene penetrates the polyethylene in the C element and increases its resistance. That is, the sealing material used in the present invention does not allow micropores to be formed even after drying, so that the sealing state of the sealing plate is improved and the PTC element is electrolyzed even during high-temperature storage. No liquid vapor reaches. As a result, it is possible to prevent the resistance of the PTC element from increasing and prevent the internal resistance of the battery from increasing.

[0007]

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

(Embodiment 1) FIG. 1 is a sectional view showing an essential part of an explosion-proof sealing plate for a sealed battery according to an embodiment of the present invention. The external terminal plate 7, the PTC element 6, and the explosion-proof valve body 5 are stacked and mounted in an insulating inner gasket 4 made of a resin such as polypropylene in a substantially L-shaped annular shape, and a bottom outer peripheral surface of the inner gasket. The inner terminal plate 3 is disposed near the center of the explosion-proof valve body 5 and is welded to the inner terminal plate 3 (in the figure, the upper surface of the protrusion) by ultrasonic welding or the like to electrically connect the two. After these are placed and accommodated in a metal dish-shaped lid plate 2 having a rising portion on the peripheral edge, the rising portion of the dish-shaped lid plate is bent inward, a caulked portion is formed, and integrally fastened, This is placed in the insulating gasket 1 to form an explosion-proof sealing plate.

Here, the battery used in the present embodiment is a positive electrode plate made of a lithium composite oxide powder (lithium cobaltate) conductive material and a binder, applied to a base material such as an aluminum foil, graphite powder, A negative electrode plate in which a paste such as a binder is applied to a base material such as copper foil is wound around a separator such as a microporous polyethylene film. The positive electrode lead plate (made of aluminum) is loaded into the battery case and fixed to the surface of the dish-shaped lid plate (made of aluminum) of the explosion-proof sealing plate by spot welding or laser welding through an upper insulating plate.

[0010] The sealing plate coated with petroleum pitch inside the inner gasket (comparative battery), the SBR coated (battery A of the present invention), and the acrylonitrile rubber shown in Table 1 (book) Battery B of the Invention) A battery coated with silicone rubber (Battery C of the present invention) was prepared, incorporated into a battery having the following structure, and stored at high temperature (85 ° C.
FIG. 2 shows a comparison of the behavior of the internal resistance at (day).

[0011]

[Table 1]

From the results, it can be seen that the comparative battery has a greater increase in internal resistance than the batteries A, B, and C of the present invention. To investigate the cause, disassemble each battery,
As a result of the investigation, it was found that the resistance of the PTC element of the sealing plate of the comparative battery significantly increased (shown in FIG. 3).
As a cause of this, when the petroleum pitch is dried, liquid does not permeate when dried, but micropores are formed that allow gas to permeate.Especially at the time of high-temperature storage, the vapor of the electrolytic solution reaches the PTC element through these micropores and removes the resin in the PTC element. It has been found that they invade and increase resistance. On the other hand, those coated with SBR, acrylonitrile rubber, and silicone rubber do not generate micropores even when dried, and prevent electrolyte vapor from entering the PTC element, thereby preventing an increase in resistance. . A similar experiment was conducted with a mixture of two or more of these sealing materials, and the same effect was obtained as when the sealing material was used alone. However, as shown in (Table 2), the application amount of the sealing material was 0.006 mg to 0.039 per 1 mm ² of the application surface.
It is necessary to apply in the range of mg.

[0013]

[Table 2]

If the coating amount is less than this range, the sealing material cannot be applied uniformly, and a gap is formed, whereby the sealing property of the sealing plate is deteriorated and the electrolyte leaks. In addition, when the amount is large, the sealing material protrudes from the inner gasket, enters the inside of the battery, and the workability is extremely deteriorated.

[0015]

As described above, the present invention reduces the internal resistance of the battery during high-temperature storage by making the sealing material of the inner gasket of the sealing plate such as SBR, acrylonitrile rubber, or silicone rubber that does not generate micropores during drying. It is possible to realize a non-aqueous electrolyte secondary battery with small rise and stable characteristics after storage.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a sealing plate for a cylindrical battery used in an example of the present invention.

FIG. 2 is a diagram showing an increase in internal resistance of a battery during high-temperature storage in Example 1.

FIG. 3 is a diagram showing a resistance increase behavior of a PTC element during high-temperature storage in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulation gasket 2 Dish-shaped lid plate 3 Inner terminal plate 4 Inner gasket 5 Explosion-proof valve body 6 PTC element 7 Outer terminal plate

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kunio Tsuruta 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Fumio Oo 1006 Odaka Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-6-215747 (JP, A) JP-A-57-87063 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 2/02- 2/08

Claims (4)

(57) [Claims] 1. An electrode plate group comprising a positive electrode plate, a negative electrode plate and a separator, and a sealing plate for sealing a battery case containing an electrolytic solution. The sealing plate is made of a terminal member such as a metal external terminal plate and a battery. A metal explosion-proof valve body and a PTC element that deform outwardly with an increase in internal pressure are stacked in an insulating inner gasket having a substantially L-shaped cross section, and the metal gasket passes through the outer peripheral surface side of the inner gasket. The one provided with the inner terminal plate having pores is accommodated in a metal dish-shaped lid plate having a ventilation hole and a rising portion on the periphery, and the rising portion of the dish-shaped lid plate is bent inward. And a sealing plate for a battery that is integrally fastened and configured to prevent a non-aqueous electrolyte vapor from entering the PTC element by applying a sealing material made of styrene-butadiene rubber to the inside of the inner gasket. Non-aqueous electrolysis characterized by Sealing plate for a secondary battery. Wherein the inside inner gasket, said styrene
2. The non-aqueous electrolyte according to claim 1, wherein a seal material made of acrylonitrile rubber is applied in place of the seal material made of nbutadiene rubber to prevent the non-aqueous electrolyte vapor from entering the PTC element. Sealing plate for water electrolyte secondary battery. Wherein the inside inner gasket, said styrene
2. The non-aqueous electrolyte according to claim 1, wherein a sealing material made of silicone rubber is applied instead of the sealing material made of n-butadiene rubber to prevent the non-aqueous electrolyte vapor from entering the PTC element. Sealing plate for water electrolyte secondary battery. 4. The styling is provided inside the inner gasket.
Instead of a seal material made of butadiene rubber, a seal material made of a mixture of two or more of styrene butadiene rubber, acrylonitrile rubber, and silicone rubber is applied so as to prevent the non-aqueous electrolyte vapor from entering the PTC element. The sealing plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the sealing plate is configured.