Chemistry: electrical current producing apparatus – product – and – Having specified venting – feeding or circulation structure – Venting structure
Reexamination Certificate
1999-11-09
2002-07-23
Brouillette, Gabrielle (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having specified venting, feeding or circulation structure
Venting structure
C429S056000
Reexamination Certificate
active
06423440
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to a closed battery capable of bursting at a prescribed pressure, especially at a low pressure, to rapidly release the internal pressure and at the same time to break the current, when the temperature or internal pressure of the battery is elevated, and to a closing member for use in the closed battery.
2. Prior Art
Recently, with increasing requirement of electronic devices that are made much smaller in size, light weight and have enhanced performance, the use of non-aqueous batteries with high energy density has become popular. Batteries which use an alkaline metal such as lithium, sodium, or potassium as an active material of negative electrode thereof employ battery containers of completely closed structure because the alkaline metal easily acts with water.
Such a complex closed battery has a merit of storability, but has the disadvantage in that its high sealability sometimes causes rupture of the battery itself due to the abnormally elevated internal pressure thereof in cases where the battery is exposed to high temperature, or a short circuit is formed inside or outside of the battery to cause a large flow of the current, or hydrogen gas is generated in the battery due to water contamination during in the manufacturing process thereof. In such a case, the device that has installed such a rupturing battery will be broken and moreover, there may be a danger of the broken device and battery harming the user. Accordingly, there should be a request for some pressure releasing mechanism before the internal pressure of the battery is increased to such a high extent as to cause rupture.
So far, several methods for releasing the internal pressure of a battery have been proposed and some of them have been used in practice. For instance, Japanese laid-open publication HEI 2-304861 discloses a safety valve for a battery, which comprises a valve chest provided at one part of the container of the battery and having a valve through hole to be communicated with the inside of the battery and an outlet to be communicated with the outside, the valve chest comprising a valve member at least whose surface opposed to the valve through hole is made of rubber, and an elastic member for pushing the above mentioned rubber surface of the valve member to the valve through hole. This safety valve holds the sealability of the battery by closing the valve through hole with the rubber-made valve member, and prevents the internal pressure of battery from rising in excess of a prescribed pressure by permitting the valve through hole to be opened when the internal pressure rises to the pressure prescribed for the elastic member.
Such a conventional safety valve has been widely used in Ni—Cd type batteries. However, it has not yet been used in the non-aqueous batteries which employ alkaline metals as the active material of the negative electrode, since, it is impossible to obtain such a high sealability as required for the non-aqueous batteries even if the elastic member presses the valve member to the valve through hole to thereby close the battery.
One of the methods for releasing the internal pressure of a battery which requires high sealability is disclosed in Japanese laid-open publication SHO 63-285859. In this method, the container of the battery is provided with a thinned portion at one part of its wall. This thinned portion is formed by cold rolling a sheet of the container using a press device until the thickness of the rolled portion of the sheet becomes half of the initial thickness thereof. Thus, the battery is provided with good sealability with regard to this thinned wall portion because it is only transformed from a part of the continuous wall of the container.
Another pressure releasing mechanism of this type is disclosed in Japanese laid-open publication HEI-6-215760. This releasing mechanism comprises a valve diaphragm fitted in an open end of the cylindrical container of a battery having a bottom and disposed above the electrode element of the battery, and a lead for breaking current disposed above the valve diaphragm. In this structure, when the internal pressure of the battery is elevated, the valve diaphragm is expanded to rupture the lead for breaking current to cut the current.
Problem to be Solved by the Invention
According to the method as disclosed in Japanese laid-open publication SHO-63-285859, it is necessary to obtain a thinned wall portion of the container so that the thinned portion can be ruptured at a relatively low pressure. However, when the wall portion is made too thinned, there may be formed fine or minute cracks during press-forming, thus impairing the sealability of the battery container.
Further, when metals are processed by cold working, they inevitably develop a work hardening problem. However, the hardening of the metals does not always take place uniformly, and therefore, there arises a problem that the operating pressure for such pressure releasing mechanism cannot regularly be controlled. There has been further proposed a half-etching method for making a thinner part of the wall of a battery container. It is extremely difficult to control the remaining thickness of the thinned portion after etching, and also difficult to obtain a good yield. Another problem is that the half-etched portion cannot be free from the formation of pinholes, and therefore, all the products need to be inspected.
On the other hand, according to the method as disclosed in Japanese laid-open publication HEI-6-215760, it is necessary to accurately control the depth of the cut portion formed in the lead. This is a severe problem in view of its working process. Another problem is that the current is not reliably broken at a prescribed pressure.
With the view to solving the conventional drawbacks as mentioned above, it is an object of the present invention to provide a closed battery incorporating a valve chip which can be stably and accurately burst at a prescribed pressure, especially at a low pressure, so as to release the internal pressure thereof and which can be manufactured easily, and also to provide a closing member for use in said closed battery.
Means for Solving the Problem
The present invention provides a closed battery which is comprised of an electrode element consisting of a positive electrode, a negative electrode, and a separator; an electrolyte; a battery vessel accommodating said electrode element together with said electrolyte; and a closing member fitted in the inner periphery of an open end portion of said battery container to close the open end portion of the battery container, wherein said closing member consists of a metal substrate, a valve element which is provided in said metal substrate so as to serve as a releasing chip such that when the internal pressure of the battery is elevated, the valve element is bent from a bending fulcrum so as to provide the metal substrate with an opening portion for releasing the internal pressure, and a metal foil which is adhered to the inner surface of the metal substrate, wherein said valve element is provided with a slit between the circumference thereof and the metal substrate, and provides a closing member for use in said closed battery.
According to the present invention, when the internal pressure of a battery is elevated due to short circuit, overcharge, reverse charge, or the like, a valve chip consisting of a metal substrate in which a valve element is provided for releasing the internal pressure of the battery, and a metal foil which has a uniform and accurate thickness and is laid over the metal substrate so as to close a through hole which is usually closed with the valve element, operates to transform itself and push and raise the valve element which is provided with a slit around the circumference thereof. When the valve chip is electrically disconnected and the internal pressure reaches to a prescribed pressure, the valve element is smoothly raised up owing to the formation of the slit and the metal foil bursts stabl
Isobe Yoshihiko
Saijo Kinji
Takada Akiyoshi
Yoshida Kazuo
Yoshimoto Nobuyuki
Brouillette Gabrielle
Browdy and Neimark
Ruthkosky Mark
Toyo Kohan Co. Ltd.
LandOfFree
Closed battery and closing member does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Closed battery and closing member, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Closed battery and closing member will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2897163