Lithium secondary battery and method of manufacturing thereof

Details Lithium secondary battery and method of manufacturing thereof Lithium secondary battery and method of manufacturing thereof

2001-03-05

2003-09-30

Chaney, Carol (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Plural concentric or single coiled electrode

C429S300000, C429S303000

Reexamination Certificate

active

06627344

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 00-11040, filed Mar. 6, 2000, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lithium secondary battery and method of manufacturing thereof, and more particularly, to a lithium secondary battery having improved safety and reliability by preventing explosion of the battery due to thermal runaway.
2. Description of the Related Art
Accompanying the technological development of portable electronic devices which have become miniaturized and lightweight, there has become a high demand for high performance secondary batteries for supplying power to those portable electronic devices.
In accordance with such demand, as a higher energy density battery, lithium secondary batteries have been rapidly developed to substitute for lead batteries or nickel-cadmium batteries.
The lithium secondary batteries have higher energy density and processibility (easily made into a desired shape such as a cylindrical case or a battery pack) and can be easily manufactured, compared to other conventional batteries, thereby being easily adapted for electronic appliances. Therefore, much attention has been paid to the lithium secondary batteries as the most promising type of batteries. A lithium secondary battery generally utilizes lithium nickel oxide, lithium cobalt oxide or lithium manganese oxide as a cathode active material, and carbon, metallic lithium or an alloy thereof as an anode active material thereof. Also, usable electrolytes include a polymer solid electrolyte based on a polymer matrix, such as liquid a organic electrolyte, e.g., polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride.
Lithium secondary batteries are classified according to the kind of electrolyte used, into lithium ion batteries and lithium ion polymer batteries. The lithium ion batteries use a liquid electrolyte, whereas the lithium ion polymer batteries use a gel-type or solid electrolyte.
While the above-described lithium secondary batteries, compared to the other type batteries, have excellent lifetime and energy density characteristics, they may experience local internal shorting in the case where external shock, e.g., nail piercing, is applied thereto. Then, the temperature of the portion where the internal shorting has taken place increases intensively. In particular, if the internal shorting occurs at the active material layer formed on both surfaces of the electrode current collector, the internal temperature of the battery greatly rises. Also, when local shorting occurs, the separator cannot properly exert a shut-down function of suppressing current flow by suppressing migration of ions in the event of an increase in the internal temperature of the battery. Thus, the temperature rise due to local shorting causes thermal runaway, resulting in explosion of a battery.
FIG. 1
is a diagram showing a typical example of a cylindrical lithium ion battery.
Referring to
FIG. 1
, a cylindrical lithium secondary battery
10
includes a cylindrical case
15
and an electrode assembly
14
installed inside the case
15
. Here, the electrode assembly
14
is constructed such that a separator
13
is interposed between a cathode
11
and an anode
12
. A cap assembly
16
is connected to the upper portion of the electrode assembly
14
.
A process for preparing the aforementioned cylindrical lithium ion battery will now be described.
First, in a state in which the separator
13
is interposed between a cathode plate
11
and the anode plate
12
, the resultant is wound around a mandrel in a jelly-roll type configuration to fabricate the electrode assembly
14
. Then, the mandrel is removed, the electrode assembly
14
is put into a space of the case
15
and then an electrolytic solution is injected. When injection of the electrolytic solution is completed, the cap assembly
16
is connected to the upper portion of the case
15
, thereby completing the lithium ion battery shown in FIG.
1
.
As described above, if the mandrel is removed, an empty space is left inside the electrode assembly. Conventionally, a center pin has been inserted into the empty space to assist in maintaining the shape of the electrode assembly.
However, insertion of the center pin has only a trivial effect in maintaining the shape of the electrode assembly
14
or expansion of the electrode assembly
14
. Thus, currently, the empty space is allowed to exist at it is, to be used as an electrolytic solution inlet, a tip passage for welding an anode tap, or a gas existence area.
In order to increase the effective space of a battery, a method in which the empty space of a battery is reduced by reducing the diameter of the mandrel, has been proposed. However, according to this method, there is a risk of an electrode plate being cut during winding. Thus, since it is impossible to reduce the diameter of the mandrel to a predetermined level or below, the space remaining after removing the mandrel is necessarily left over.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a lithium secondary battery having improved reliability and safety by absorbing internal heat of the battery using an empty space of an electrode assembly to prevent explosion of the battery.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects, there is provided a lithium secondary battery having a winding-type electrode assembly and a case accommodating the electrode assembly, wherein ion-conductive polymer is contained in at least one of a hollow portion of the electrode assembly and an inner space of the case other than the hollow portion.
The ion-conductive polymer is preferably a material gelled by a non-aqueous electrolytic solution.


REFERENCES:
patent: 5681357 (1997-10-01), Eschbach et al.
patent: 6387561 (2002-05-01), Nemoto et al.
patent: 6387562 (2002-05-01), Akahira
patent: 6-96800 (1994-04-01), None
Dominey, in Lithium Batteries, New Materials . . . Industrial Chemistry Library, vol. 5, 1994, G. Pistoia, ed. p. 145.

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