Packaging material for hermetically sealed batteries

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Reexamination Certificate

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C428S335000, C428S354000

Reexamination Certificate

active

06207271

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to packaging material, and more particularly, to a flexible laminate for packaging and hermetically sealing an electrochemical device. The invention is particularly applicable for packaging electrolytic cells and batteries, and will be described with particular reference thereto. Although, it will be appreciated that the present invention may find advantageous application in packaging electrochemical devices that utilize polymer electrolytes or that require hermetic packaging to isolate the device from the environment.
BACKGROUND OF THE INVENTION
Improvements in microelectronics have increased the demand for electrolytic cells that can be directly incorporated into electronic devices so as to produce a portable, finished package. As the improvements in microelectronics reduce the size of the electronic device, the space and weight allotted to a power supply within such device have likewise decreased. It is therefore important to maximize the power-per-unit space that a battery can provide, but at the same time, minimize weight and fully utilize the space allotted to a power supply within an electronic device. The use of flexible packaging to enclose an electrolytic battery or cell is one way to reduce the weight of a battery or cell, and such packaging lends itself to unusual shapes. Flexible packaging can still provide hermetic containment of a battery, and in addition, is lighter than traditional packaging, i.e., metal cans or molded plastic cases. Flexible packaging also conforms more easily to the shape of the battery structure.
The flexible packaging may be formed of a single layer of a polymer film or single layer of a metal foil, but is typically comprised of a multi-layer material having a polymer layer for toughness, a metal foil layer to form a hermetic barrier and a third layer of an adhesive or sealant material. This multi-layer material is dimensioned to be tightly wrapped, e.g., to be folded, around a battery or cell. Heat and pressure are typically applied to overlapping edges of the material to form a seal enclosing the cell or battery. Operations such as folding of the material and the tight wrapping necessary for efficient packaging of the battery or cell place considerable stress on the various layers forming the material. Such stresses may lead to cracks forming in the metal foil layer. Such cracks, in addition to “pinhole imperfections” that may exist in the foil, can destroy the hermeticity of the packaging and allow solvents to escape from the battery or water vapor and oxygen to penetrate into the battery. Increasing the thickness of the foil layer sufficiently to avoid hermeticity issues can require undesirable increases in weight, thickness, stiffness and cost.
The present invention overcomes these and other problems and provides a multi-layer, flexible material for forming a package for an electrochemical device such as an electrolytic battery or cell.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a flexible, multi-layer material for packaging a polymer electrolytic cell or battery, comprising:
a first metallic foil layer;
a second metallic foil layer;
an intermediate separation layer disposed between said first and second metallic foil layer, said intermediate separation layer establishing a predetermined spacing between said first metallic foil layer and said second metallic foil layer;
a first self-sealing layer on said first metallic foil layer, the first self-sealing layer formed of a material having adhesive-like properties and having a thickness of less than about 76 &mgr;m; and
a second self-sealing layer on the second metallic foil layer, the second self-sealing layer formed of a material having adhesive-like properties and having a thickness of less than about 76 &mgr;m.
In accordance with another aspect of the present invention, there is provided a flexible, multi-layer material for packaging a polymer electrolytic cell, comprising:
a first layer and a second layer of an aluminum foil, the aluminum foil layers having a thickness of about 2 &mgr;m to about 100 &mgr;m; and
a layer of a thermoplastic material having a thickness of about 2 &mgr;m to about 100 &mgr;m disposed between the aluminum foil layers;
layers of a sealant-adhesive material applied to each of the aluminum foil layers, the adhesive layers formed of a thermoplastic polymer.
It is an object of the present invention to provide a laminate material for packaging an electrochemical device.
Another object of the present invention is to provide a laminate as described above for packaging an electrolytic cell or battery.
Another object of the present invention is to provide a laminate material as described above that is self-sealing upon the application of heat and pressure.
A still further object of the present invention is to provide a laminate material as described above having multiple layers of metal foil to insure hermetic packaging.
These and other objects will become apparent from the following description of a preferred embodiment taken together with the accompanying drawings.


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Surlyn 1652—For Blown/Cast Film and Extrusion Coating.
Surlyn—Premium Performance for Superior Packaging Value.
Surlyn/Nucrel—Safety in Handling and Use.

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