Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Flat-type unit cell and specific unit cell components
Reexamination Certificate
1999-02-19
2001-08-21
Brouillette, Gabrielle (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Flat-type unit cell and specific unit cell components
C429S185000, C429S179000, C429S181000, C029S623200, C029S623500, C428S035700
Reexamination Certificate
active
06277516
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lead for use with a lithium-ion secondary cell, a lead ribbon, a lithium-ion secondary cell and a method of sealing a container of the lithium-ion secondary cell.
2. Description of the Related Art
Recently, as a demand of cordless and portable electronic devices increases, there have been developed a variety of portable electronic devices which are miniaturized, made light in weight and thin in thickness one after another. Concurrently therewith, a battery serving as an energy source of such an electronic device shares a large ration of the whole of the electronic device. Further, as an electronic device becomes a multifunction electronic device, a power consumption thereof increases so that a capacity of a cell unavoidably increases considerably, thereby resulting in a volume of a secondary cell being increased. Thus, there is an increasing demand of a miniaturized secondary cell having a high energy density.
As secondary cells that have been used heretofore, there are known a lead storage battery and a nickel-cadmium battery. Also, as a new secondary cell, a nickel-hydrogen cell and a lithium-ion cell are now commercially-available on the market. Since these secondary cells use liquid as an electrolyte, they cannot avoid a problem of a leakage thereof. A solidification of electrolyte, i.e. solid electrolyte battery is a powerful means for solving the problem. As typical powerful means, there is a polymer lithium-ion secondary cell using a polymer electrolyte in which a plasticizer is mixed into a polymer. Thus, it becomes possible to manufacture a secondary cell having no risk of leakage and which may be miniaturized, made light in weight and reduced in thickness, thereby resulting in a secondary cell with a high energy density.
As a fundamental arrangement of a polymer lithium-ion secondary cell, a polymer lithium-ion secondary cell is generally comprised of a positive electrode, a negative electrode and a polymer electrolyte. While a variety of polymer electrolytes are developed, electrolytes such as polyacrylonitrile (PAN), polyethylene oxide (PEO), polyvinylidene fluoride (PVdF) and so on are typically known as major electrolytes.
An arrangement of a polymer lithium-ion secondary cell will be described next.
FIGS. 1A and 1B
are respectively diagrams showing a structure of a polymer lithium-ion cell obtained when a polyacrylonitrile (PAN) system gel electrolyte is used. As shown in
FIGS. 1A and 1B
, an activator made of LiCoO
2
and graphite is laminated on a positive electrode current collector
9
made of an aluminum thin plate and an activator made of MCMB, carbon and natural graphite is laminated on a negative electrode current collector
14
, which form electrodes. An isolating material (polypropylene, etc.) called a separator is disposed between the positive electrode current collector
9
and the negative electrode current collector
14
, and a polyacrylonitrile (PAN) system gel electrolyte is filled into clearances thereof, thereby resulting in a sandwich structure being obtained.
As a container for the sandwich structure, the product is packed/packaged by a laminate material made of an aluminum film and a plastic film. In that case, a cell may be reduced in thickness and increased in capacity by selectively laminating one elemental cell (unit cell) having the sandwich structure as shown in
FIG. 2A
, rewinding one unit cell as shown in
FIG. 2B
or folding one unit cell as shown in
FIG. 2C
or combining the above-mentioned laminated structure, the rewound structure or the folded structure.
Then, the assembly process of the polymer lithium-ion secondary cell will be described with reference to
FIGS. 3A
to
3
D to
FIGS. 5A
to
5
E.
Initially, in the mixing process shown in
FIG. 3A
, a positive electrode material or a negative electrode material is manufactured by preparing/mixing materials made of an activator, a conductive material, a binder, a volatile solvent or the like. In the next coating process, as shown in
FIG. 3B
, this positive electrode material or negative electrode material is coated on the positive electrode
egative electrode current collector by a roll coater, baked and then dried. While the roll coater has been described as an example of a coating method, the coating method is not limited thereto, and any method may be used so long as the positive electrode material or the negative electrode material may be coated uniformly. In the next press process as shown in
FIG. 3C
, the resultant electrode material in which this positive electrode material or the negative electrode material is baked and dried on the positive electrode
egative electrode current collector is pressed in the equal direction by an interlaminar press treatment, thereby resulting in an electrode density being increased. In the next slitter process, as shown in
FIG. 3D
, the resultant product in which the electrode material is pressed in the equal direction by this interlaminar press treatment is cut as a ribbon-shaped having a constant width.
In the next vacuum dry process shown in
FIG. 4A
, the resultant product of ribbon-shape having the constant width is dried in the vacuum as shown in FIG.
4
A. According to the next lead welding process, in the resultant process which was dried in the vacuum as shown in
FIG. 4B
, a lead
3
is welded to the surface of a metal on which the positive electrode material or the negative electrode material is not coated. In the next electrolysis solution vacuum impregnation process as shown in
FIG. 4C
, the electrolysis solution is impregnated into the positive electrode material or the negative electrode material by using vacuum suction. In the next electrolyte gel coating and rewinding process as shown in
FIG. 4D
, a gel electrolyte is uniformly coated on both surfaces of the separator, and the separator, the positive electrode current collector in which the positive electrode is formed and the negative electrode current collector in which the negative electrode is formed are rewound in the order of the positive electrode current collector, the separator and the negative electrode current collector, thereby resulting in a unit cell being formed. At that time, a unit cell having a width and a laminated thickness matched with a required arbitrary size and a cell capacity may be completed by selecting a unit cell rewinding method, a unit cell laminating method, a unit cell folding method or the like.
In the packing process shown in
FIG. 5A
, the product in which the separator, the positive electrode current collector and the negative electrode current collector are rewound in the order of the positive electrode current collector, the separator and the negative electrode current collector is packed into a laminate film (e.g. three-layer structure of polyethylene terephthalate/aluminum film
on-elongated polypropyrene) which serves as a thin container
5
for a polymer lithium-ion secondary cell. In the next press process as shown in
FIG. 5B
, a resultant product in which the unit cell is packed into the container is pressed. In the next vacuum sealing process as shown in
FIG. 5C
, only the lead is exposed from the container thus pressed with the unit cell under reduced pressure atmosphere, and one side of the container is sealed. Although a heat fusion-bonding method (hot plate adhesion method, impulse adhesion method, ultrasonic adhesion method, high-frequency adhesion method and hot-air adhesion method) is convenient as a method of sealing a laminate film, so long as a sealing performance and a moisture permeability resistance are excellent, an adhesive system and an adhesive coating method (hot-melt method and cold-glue method) are also possible. In the next charging and discharging method as shown in
FIG. 5D
, it is inspected by repeatedly charging and discharging a resultant product in which the container with the unit cell therein is sealed whether or not a predetermined battery characteristic is obtained. After the above-mentioned proce
Muto Koichi
Ohba Hisashi
Sasaki Yoshinari
Alejandro Raymond
Brouillette Gabrielle
Sonnenschein Nath & Rosenthal
Sony Corporation
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