JP2007157609A - Sealing plate for sealed battery, and sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing plate for a nonaqueous electrolyte secondary battery capable of enhancing sealing performance and suppressing drop in electric characteristics caused by increase in internal resistance to the minimum. <P>SOLUTION: A metal cap also functioning as an outside terminal, a metallic explosion-proof valve body capable of deforming according to increase in internal pressure of a sealed battery, a PTC element, and an insulating inner gasket comprising a ring-shaped base part and a cylindrical part extending upward from the peripheral part of the base part are housed in a dish-shaped metal case with bottom having a gas vent, a projection is installed on the top surface of the ring-shaped base part of the inner gasket of the sealing plate for the sealed battery sealed by crimping inward the opening end part of the metal case, and a sealant is placed in the inner peripheral surface of the projection to prevent contact of the sealant to the PTC element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in a sealing plate of a sealed battery.

  A water-based electrolyte secondary battery typified by a high-capacity alkaline storage battery or a non-aqueous electrolyte secondary battery typified by a lithium secondary battery is used as a driving power source for a small portable device or the like. Among them, the non-aqueous electrolyte secondary battery is a sealed battery having high energy density and excellent electrical characteristics such as cycle characteristics. Sealed batteries are widely used in portable electronic devices and the like.

A conventional sealed battery has a structure in which an electrode plate group serving as a power generation element is housed in a bottomed cylindrical battery case together with an electrolyte, and an opening of the battery case is sealed with a sealing plate via a gasket. . The electrode plate group is composed of a separator film interposed between the positive electrode and the negative electrode. The sealing plate includes a metal cap that also serves as an external terminal, an explosion-proof valve body made of metal foil that can be deformed as the internal pressure of the battery increases, and a PTC (Positive Temperature) whose resistance value increases as the temperature increases.
An insulative inner gasket comprising an element, a ring-shaped base portion, and a cylindrical portion extending upward from the peripheral portion thereof is housed inside a bottomed dish-shaped metal case having a gas vent. Has a structure. The metal case is sealed by caulking the open end of the metal case. Here, the PTC element has a structure in which a thin metal plate is sandwiched between a resin such as polyethylene and a conductive material such as carbon black.

  In such a sealed battery, when tested in an abnormal environment such as high temperature and high humidity, there is a possibility of leakage from the sealing portion. The following four routes can be considered as locations where leakage occurs. The first route is between the battery case and the gasket, the second route is between the gasket and the sealing plate, the third route is between the sealing plate and the inner gasket, and the last route is the inner gasket. Inside. In particular, leakage from the inside of the inner gasket is likely to occur.

Therefore, as a measure to prevent leakage from the inside of the inner gasket, it is proposed to prevent leakage by applying a sealant such as styrene butadiene rubber, acrylonitrile rubber, or silicone rubber to the inside of the inner gasket. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 9-167603

  However, such a conventional sealed battery sealing plate can prevent liquid leakage by applying a sealant inside the inner gasket. However, the sealant is generally diluted with an organic solvent in order to dilute an elastic material such as styrene butadiene rubber so that it can be easily applied to the inner gasket. When the organic solvent comes into contact with the PTC element placed inside the inner gasket, the resistance of the PTC element increases by swelling the resin such as polyethylene in the PTC element. Along with this, the internal resistance of the sealing plate for the sealed battery also increases, and as a result, the electrical characteristics of the sealed battery may be deteriorated.

  Therefore, the present invention solves such a conventional problem, and by defining the application position of the sealant so that the organic solvent in the sealant does not touch the PTC element, the inside of the sealed battery is An object of the present invention is to provide a sealing type battery sealing plate excellent in hermeticity without increasing resistance.

  In order to solve the above-mentioned conventional problems, the sealing plate for a sealed battery according to the present invention is a battery case in which an electrode plate group composed of an isolation film interposed between a positive electrode and a negative electrode is housed in a bottomed cylindrical battery case. The opening of the case is sealed with a sealing plate for a sealed battery through a gasket. The sealing plate for the sealed battery includes a metal cap that also serves as an external terminal, a metal explosion-proof valve body that can be deformed as the internal pressure of the sealed battery increases, a PTC element, and a ring-shaped base portion and its peripheral portion An insulative inner gasket composed of a cylindrical portion extending to the inside is housed in a bottomed dish-shaped metal case having a gas vent. The metal case is sealed by caulking the open end of the metal case. A protrusion is provided on the upper surface of the upper base of the ring of the inner gasket. A sealant is applied to the inner peripheral surface of the protrusion.

  By doing so, the organic solvent contained in the sealant applied to the inner gasket can be prevented from coming into contact with the PTC element by the protrusion on the upper surface of the ring upper base of the inner gasket. An increase in internal resistance of the battery sealing plate can be prevented. As a result, a sealed battery having good electrical characteristics can be obtained.

  According to the present invention, the sealant to be applied to the inner gasket is applied only to the inner peripheral side of the protrusion provided on the upper surface of the upper ring base portion of the inner gasket. By doing so, the sealing agent does not flow out to the outer peripheral side of the protrusion, and the organic solvent in the sealing agent does not come into contact with the PTC element, thereby preventing an increase in the resistance of the PTC element. As a result, an increase in internal resistance of the sealing plate for the sealed battery can be prevented, and a sealed battery having good electrical characteristics can be provided.

The sealed battery sealing plate in the embodiment of the present invention,
A sealing plate for a sealed battery in which an electrode plate group consisting of an isolation film interposed between a positive electrode and a negative electrode is housed in a bottomed cylindrical battery case, and an opening of the battery case is sealed with a sealing plate via a gasket It is. The sealing battery sealing plate is configured as follows. A metal cap that also serves as an external terminal, a metal explosion-proof valve body, a PTC element, and an insulating inner gasket are housed inside a bottomed dish-shaped metal case. It is a sealing type battery sealing plate in which the opening end of the metal case is crimped inward and sealed. The inner gasket is a sealing plate for a sealed battery, in which a protrusion is provided on the upper surface of the upper base of the ring, and a sealing agent is interposed on the inner peripheral surface of the protrusion.

  Here, the metal explosion-proof valve body is a valve body that can be deformed as the internal pressure of the sealed battery increases. An insulating inner gasket is a gasket composed of a ring-shaped base portion and a cylindrical portion extending upward from its peripheral edge portion. The bottomed dish-shaped metal case has a gas vent.

  By doing so, the organic solvent contained in the sealant applied to the inner gasket can be prevented from coming into contact with the PTC element by the protrusion on the upper surface of the ring-shaped base of the inner gasket. An increase in the internal resistance of the battery sealing plate can be prevented.

  Here, the PTC element is an element whose resistance value increases as the temperature rises, and PTC stands for Positive Temperature Coefficientette. The function of the PTC element functions as a safety mechanism when the temperature of the sealed battery suddenly rises during an abnormality.

  This is a sealed battery using the sealing plate for a sealed battery described above.

  By doing so, an increase in internal resistance of the sealed battery can be prevented, and a sealed battery with good electrical characteristics can be obtained.

  Next, the present invention will be specifically described based on examples, but the following examples are not limited to the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example 1
FIG. 1 is a schematic longitudinal sectional view of a sealing battery sealing plate according to an embodiment of the present invention, and FIG. 2 is a schematic longitudinal sectional view of a caulking portion of the cylindrical battery sealing plate according to an embodiment of the present invention. Insulating properties in which a metal cap 6 that also serves as an external terminal, a PTC element 5 and a metal upper explosion-proof valve body 4 are molded into a cylindrical portion that extends upward from a ring-shaped base portion and its peripheral portion with a resin such as polypropylene. The lower explosion-proof valve body 2 made of metal is disposed on the outer peripheral surface of the bottom portion of the inner gasket 3, and the lower explosion-proof valve body (in the figure, near the center of the upper explosion-proof valve body 4). The upper surface of the protrusion a) was welded by laser welding to electrically connect them. After these are placed and housed in a bottomed dish-shaped metal case 1, the rising portion of the case 1 is bent inward to form a caulking portion and fastened together. The sealed battery sealing plate was configured by placing.

  A protrusion a is provided on the upper surface of the ring-shaped base of the inner gasket 3 of the sealing plate, and a sealing agent b containing an organic solvent as a diluent is applied to the inner peripheral surface of the protrusion a.

(Comparative Example 1)
The sealing agent b was applied in a state where there was no protrusion a on the upper surface of the ring-shaped base of the inner gasket 3 of Example 1. The inner gasket 3 was applied to the entire upper surface of the ring-shaped base.

  In Example 1, when the caulking process was performed, the caulking process was completed without the sealant leaking outside the protruding portion of the inner gasket. Therefore, the sealant did not contact the PTC element. As a result, it was possible to construct a sealed battery sealing plate with excellent sealing performance without increasing the resistance of the sealing plate.

  In Comparative Example 1, when the caulking process was performed, the sealant scooped up along the inner surface of the cylindrical peripheral edge portion of the inner gasket. As a result, the sealant reached the outer periphery of the PTC element, the organic solvent of the sealant contacted the resin part in the PTC element, and the resistance of the sealing plate was increased.

  Using the above-mentioned results as a supporting experiment, the behavior of the resistance values of the PTC elements when the PTC elements used in the sealing plates of Examples and Comparative Examples were immersed in a sealant was measured. The experimental method is as follows.

  The resistance value of n = 10 PTCs before immersion was measured with a milliohm meter, and placed in a metallic pan-type container containing a sealant containing an organic solvent component. Then, it was left to stand for 1 hour in the immersed state. After leaving, all the PTC simple substance n = 10 was taken out, and the resistance value immediately after taking out and the resistance value after leaving as shown in FIG. 3 were measured. The results are shown in FIG.

  From this result, it was found that the resistance value increases when the PTC element comes into contact with the sealant. Moreover, after immersion, the PTC element was taken out from the sealant and allowed to stand, and regular measurement was performed. As a result, the resistance value of the PTC element did not return to the initial value even when the organic solvent in the sealant adhered to the sealing plate was volatilized.

  Since the sealing plate for a sealed battery of the present invention has excellent sealing performance and stable internal resistance, it is possible to provide a sealed battery with good electrical characteristics, and the demand for higher energy density is increased. It is useful as a portable power source.

1 is a schematic longitudinal sectional view of a cylindrical battery sealing plate in one embodiment of the present invention. 1 is a schematic longitudinal sectional view of a caulking portion of a cylindrical battery sealing plate according to an embodiment of the present invention. The figure which showed the behavior of the PTC element resistance value when a PTC element was immersed in sealing agent

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Lower explosion-proof valve body 3 Inner gasket 4 Upper explosion-proof valve body 5 PTC element 6 Cap 7 Insulation gasket a Inner gasket protrusion part b Sealant

Claims (2)

An electrode plate group consisting of a separator film interposed between the positive electrode and the negative electrode is housed in a bottomed cylindrical battery case, and the opening of the battery case is sealed with a sealing battery sealing plate via a gasket. And
The sealed battery sealing plate includes a metal cap that also serves as an external terminal, a metal explosion-proof valve body that can be deformed as the internal pressure of the sealed battery increases, a PTC element, a ring-shaped base portion, and a peripheral portion thereof. An insulative inner gasket consisting of a cylindrical part extending upward is housed inside a bottomed dish-shaped metal case having a gas vent, and the opening end of the metal case is crimped inward and sealed. Type battery sealing plate,
The inner gasket has a protrusion on the upper surface of the base on the ring,
A sealing battery sealing plate in which a sealing agent is interposed on the inner peripheral surface of the protrusion. A sealed battery using the sealed battery sealing plate according to claim 1.