Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Reexamination Certificate
2000-04-28
2002-09-17
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Cell enclosure structure, e.g., housing, casing, container,...
C429S167000, C429S177000
Reexamination Certificate
active
06451479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a secondary battery and, more particularly, to a case of a secondary battery having an improved structure at a portion for sealing a battery unit.
2. Description of the Related Art
Lithium secondary batteries are classified into liquid electrolyte batteries and polymer electrolyte batteries according to the type of electrolyte used. Generally, batteries using liquid electrolyte are called lithium ion batteries and batteries using polymer electrolyte are called lithium polymer batteries.
Among these batteries, lithium polymer batteries use a polymer electrolyte so that they are free of danger of explosion. Also, the lithium polymer batteries have solved the shortcoming of lowering of the battery performance due to byproducts produced during charging or discharging. Further, the lithium polymer batteries are relatively flexible in design shape.
FIGS. 1A and 1B
illustrate an example of a conventional lithium polymer battery
10
.
As shown in
FIG. 1A
, the conventional lithium polymer battery
10
includes a battery unit
14
having a plurality of assembled batteries, each battery having a positive electrode
11
, a negative electrode
12
, and a separator
13
interposed therebetween and laminated. A positive electrode tab
15
is drawn out from one side periphery of the positive electrode
11
and a negative electrode tab
16
is drawn out from one side periphery of the negative electrode
12
. The positive and negative electrode tabs
15
and
16
are welded to positive and negative electrode terminals
17
and
18
, respectively.
The aforementioned battery unit
14
is mounted in a case
19
having a space in which the battery unit
14
is accommodated. The case
19
includes upper and lower case bodies
19
a
and
19
b
which are capable of being separated.
Here, the case
19
has a multi-layered structure.
As shown in
FIG. 1B
, the case
19
has a structure in which a first poly(ethylene-co-acrylic acid) (EAA) layer
110
, a polyethylene (PE) layer
120
, a first nylon layer
130
, a second EAA layer
140
, an aluminum film
150
, and a second nylon layer
160
are sequentially laminated.
Here, the above-stated multiple layers function differently. In other words, the first EAA layer
110
and the second EAA layer
140
prevents a swelling effect of an electrolytic solution so that the electrolytic solution does not stick to the aluminum film
150
during the operation of the battery
10
. The PE layer
120
enhances the formability of the case
19
. The aluminum foil layer
150
prevents moisture from infiltrating into the battery
19
and suppresses the loss of the electrolytic solution. Also, the first and second nylon layers
130
and
160
prevent cracks from being generated in the case
19
and enhance formability.
However, in the case
19
having the aforementioned configuration, since the first and second EAA layers
110
and
140
or the PE layer
120
are not completely insoluble in a small amount of the electrolytic solution injected into the case
19
, they may react with the battery
10
during the operation or storage thereof, causing contamination. Also, since the case
19
is weakened by heat, deformation of the battery
10
may be caused due to a raised internal temperature during the operation of the battery
10
, deteriorating the battery performance.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a case of a secondary battery having an improved structure for improving the battery performance.
Accordingly, to achieve the above object, there is provided a case of a secondary battery, in which a battery unit having a positive electrode, a separator, and a negative electrode laminated in sequence, is accommodated to then be sealed, the case including a fluorocarbon resin based polymer layer as the innermost layer of the case, a nylon layer as the outermost layer of the case, and an aluminum foil layer between the fluorocarbon resin based polymer layer and the nylon layer.
Preferably, the fluorocarbon resin based polymer layer is a polytetrafluoroethylene (PTFE) layer. Here, the PTFE layer is a single layer of an aqueous emulsion type.
Further, the PTFE layer is preferably a double layer consisting of a first PTFE layer of an aqueous emulsion type, formed as the innermost layer of the case, and a second PTFE layer formed between the first PTFE layer and the aluminum foil layer, for improving adhesion by adding acid and a plasticizer.
A polyethylene terephthalate (PET) layer may be further formed on the nylon layer.
REFERENCES:
patent: 6042704 (2000-03-01), Joshi et al.
patent: 6245456 (2001-06-01), Fukuda et al.
Chaney Carol
Leydig , Voit & Mayer, Ltd.
Samsung SDI & Co., Ltd.
Yuan Dah-Wei D.
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