Chemistry: electrical current producing apparatus – product – and – With control means responsive to battery condition sensing...
Utility Patent
1998-12-18
2001-01-02
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With control means responsive to battery condition sensing...
C429S057000, C429S094000, C429S175000
Utility Patent
active
06168879
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a secondary battery and, more particularly, to a cap assembly of a prism-type secondary battery which can enhance safety of the battery.
2. Description of the Prior Art
A secondary battery is rechargeable and is designed to a small size but having a large capacity. Nickel metal hydride, Lithium, and Lithium-ion batteries are now widely used as secondary batteries.
In the Lithium-ion battery, a Li-transition metal oxide material is used as a positive active material, and as a negative active material, a carbon, or a carbon compound is used. Charging and discharging of the Lithium-ion battery is realized by moving the lithium ions between positive and negative electrodes on which positive and negative active materials are deposited, respectively.
FIG. 3
shows a conventional Lithium-ion battery.
As shown in the drawing, the conventional Lithium-ion battery comprises a roll electrode assembly
2
consisting of a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes; a can
4
into which the roll electrode assembly
2
is received, the can
4
contacting the negative electrode of the roll electrode assembly
2
; and a cap assembly
6
close-tightly mounted on an upper end of the can
4
. Internal insulating plates
8
are provided at upper and lower ends of the roll electrode assembly
2
to prevent the electrode assembly from contacting the cap assembly
6
and the can
4
.
The cap assembly
6
comprises a negative plate
10
welded on the upper end of the can
4
and a positive plate
12
disposed on a center portion of the cap assembly
6
, and an insulating plate
14
disposed between the negative and positive plates
10
and
12
. A rivet
16
penetrates through a center of the negative and positive plates
10
and
12
and is connected to the positive electrode of the roll electrode assembly
2
through a tab
18
. The rivet
16
is insulated from the negative plate
10
by a gasket
20
disposed there between.
Electrolyte is injected into the battery through an injection hole
22
formed in the negative plate
10
, after which a plug is inserted into the hole
22
and welded therein to seal the hole
22
.
In addition, to prevent the battery from exploding by an excessive increase in internal pressure, a safety groove
24
is formed, through an etching process or an electro-foaming process, on the negative plate
10
of the cap assembly
6
.
In the above described Lithium-ion battery, when a short occurs in the battery by an outer conductive material, an overcurrent flows. The overcurrent may cause the battery to explode by a thermal runway phenomenon.
To solve the above problem, as shown in
FIG. 4
, a current control member
28
is disposed on a bottom of a can
26
to prevent the battery from exploding. The current control member
28
quickly reduces a conductivity when the battery is heated, thereby preventing the explosion of the battery.
The current control member
28
can be easily mounted inside the battery when the battery is cylindrical-shaped, which can be manufactured by clamping the cap assembly on the upper end of the can. However, when the battery is a prism-type battery the cap assembly is mounted on the upper end of the can by only laser welding. Accordingly, the current control member
28
cannot be mounted inside the battery but must be outside as shown in FIG.
4
.
Therefore, to mount the current control member
28
, the effective length of the prism-type battery has to be reduced by a thickness of the current control member
28
. Therefore, the capacity of the conventional prism-type battery is reduced. In addition, since the current control member
28
is exposed outside, the structure of the battery becomes unstable.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above described problems of the prior prism-type battery.
It is an object of the present invention to provide a battery where a current control member is mounted in an inner space which is not used in the battery, thereby increasing an effective volume of the battery to increase a capacity thereof.
To achieve the above objective, the present invention provides a cap assembly for a secondary battery having a can and a roll electrode assembly received in the can. The cap assembly comprises a negative plate for mounting on an upper end of the can, a positive plate disposed on the negative plate, an insulating member disposed between the negative and positive plates, a current control member disposed on the positive plate, and a rivet penetrating central portions of the negative and positive plates, the rivet being insulated from the negative plate by a gasket and connected to the roll electrode assembly through a tab.
Preferably, the negative plate is indented toward an inside the can. The indented depth of the negative plate is the same as a thickness of the current control member. The thickness of the current control member is about 0.8~1.0 mm.
The cap assembly further comprises a positive terminal disposed on the positive plate. The positive terminal is spaced away and insulated from the current control member but encapsulates the current control member to isolate the same from the outside.
According to another aspect, the present invention provides a secondary battery comprising a can, a roll electrode assembly received in the can, the roll electrode assembly comprising negative and positive electrodes and a separator disposed between the negative and positive electrodes, and a cap assembly. The cap assembly comprises a negative plate welded on an upper end of the can, the negative plate being electrically coupled to the negative electrode contacting the can, a positive plate insulated from the negative plate. a current control member disposed on the positive plate, and a rivet penetrating central portions of the negative and positive plates, the rivet being insulated from the negative plate by a gasket and connected to the roll electrode assembly through a tab.
REFERENCES:
patent: 4897323 (1990-01-01), Hennrich et al.
Baker & McKenzie
Maples John S.
Samsung Display Devices Co. Ltd.
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