Manufacturing method of batteries

Details Manufacturing method of batteries Manufacturing method of batteries

2000-04-25

2002-04-16

Maples, John S. (Department: 1745)

Metal working

Method of mechanical manufacture

Electrical device making

C429S127000, C429S162000

Reexamination Certificate

active

06371996

ABSTRACT:

FIELD OF THE INVENTION
The present inventions relates to a manufacturing method of batteries.
DESCRIPTION OF THE RELATED ART
So far, secondary batteries for instance such as non-aqueous solvent type batteries are in broad use as a power source for portable telephones, video cameras or the like. In batteries for power source, as the aforementioned instruments become smaller in size and higher in performance, demands on smaller size, lighter weight, higher voltage, larger capacity and so on are increasingly stronger. Corresponding to these demands, in for instance Japanese Patent Laid-open Application Nos. HEI 3-230474, HEI 3-225765 and so on, polymer batteries of approximately 1 mm thickness are disclosed.
That is, in these batteries, a battery element, after aligning to accommodate in an envelope film body (exterior envelope body/bag body) having one open-end, is wrapped therewith. Then, from the opening thereof a prescribed electrolytic solution is injected. Thereafter, the opening is hot-melted to constitute a hermetic-sealed battery. In manufacturing the above battery, there is another method where after sandwiching the battery element by the envelope film and folding together the film with the battery element inside thereof, opposite peripheries of both sides of the film are mutually hot-melted to seal, resulting in formation of an enveloped body. Further, the battery element can be formed planar by pressing a cylindrically wound body.
FIG. 3
is a cross section showing a substantial constitution of a battery. Here, the battery element
1
comprises a positive sheet electrode
1
a
and a negative sheet electrode
1
b
, a sheet electrolyte
1
c
, a current collector sheet not shown in the figure, and a positive electrode terminal
1
a
′ and a negative electrode terminal
1
b
′. The positive and negative sheet electrodes
1
a
and
1
b
are facing to each other. The sheet electrolyte
1
c
is hermetically interposed between the both electrodes
1
a
and
1
b
. The current collector sheets connect electrically to the electrodes
1
a
and
1
b
respectively. The positive electrode terminal
1
a
′ and the negative electrode terminal
1
b
′ are separated from the current collectors of the positive and negative electrodes
1
a
and
1
b
. Here, the positive and negative electrode terminals
1
a
′ and
1
b
′ are extended outside of an envelope film body
2
.
The positive sheet electrode
1
a
is composed with lithium ion storing and ejecting lithium containing metal oxides (for instance, lithium manganese compound oxide, lithium containing cobalt oxide) or manganese dioxide as main constituents. The negative sheet electrode
1
b
is composed of lithium metal or lithium storing and ejecting carbonaceous material, and lithium alloy. The polymer electrolyte
1
c
is constituted by impregnating or charging ethylene carbonate solution of lithium salt that is non-aqueous electrolytic solution, in separator base material consisting of nonwoven fabric of polypropylene or the like.
SUMMARY OF THE INVENTION
These kinds of planar secondary batteries, compared with lead storage batteries and nickel-cadmium secondary batteries, can be made larger in capacity and lighter in weight. By contrast, there are the following inconveniences. That is, in the steps of manufacturing the batteries, after aligning and accommodating the battery element
1
in the envelope film body
2
, a prescribed electrolytic solution is injected.
The reason for the inconveniences is as follows. As a battery is made larger in capacity, the battery element
1
is made finer to result in a decrease of a space for impregnating the electrolytic solution. That is, in order to improve a volume efficiency of a battery, a gap space inside of the envelope film body
2
is made as small as possible. However, reducing the gap space in the envelope film body
2
as small as possible invites a difficulty when the prescribed electrolytic solution is injected. As a result, there is a possibility that the prescribed amount of the electrolytic solution is not injected and is not held inside thereof, resulting in liability to invite fluctuation of battery performance and quality.
To avoid occurrence of such problems, a method has been adopted in which injection and impregnation of the electrolytic solution into the envelope film body
2
therein the battery element
1
is accommodated are repeated a plurality of times. However, a plurality of times of repetition of injection of the electrolytic solution results in an increase of the time needed to inject the electrolytic solution. As a result, due to evaporation of the component of the injected electrolytic solution or to accumulated error of the amount of injection caused by separated injection of the electrolytic solution, accuracy of, the amount of injection of the electrolytic solution is lowered.
The present invention is performed taking into account the above circumstances. The object of the present invention is to provide a manufacturing method of batteries that can not only make the batteries smaller and lighter but also can mass-produce the batteries of high reliability.
A present manufacturing method of batteries comprises the steps of:
accommodating a battery element in an envelope film body of which one end side is opened to form an opening for injecting electrolytic solution; and
sealing the opening after the electrolytic solution is injected through the opening of the envelope film body;
wherein the opening side of the envelope film body is made larger in shape and dimension than prescribed ones to form a temporary reservoir of an injected electrolytic solution and after a prescribed amount of the electrolytic solution is injected, a region of the prescribed shape and dimension is sealed and cut to form a battery.
In the above manufacturing method of batteries, in accommodating the battery element, a laminate film formed by disposing resin layers on both surfaces of a metallic layer can be used as an envelope film body.
In the above manufacturing method of batteries, the envelope film body can be sealed by hot-melting the hot-melt film disposed on a sealing region outside of at least the region of prescribed shape and dimension.
In the present invention, relative to the battery element, the opening side of the envelope film body of which one end is opened is made longer. The longer opening side, after utilizing as a temporary reservoir of the electrolytic solution during injection of the solution, is sealed and cut at a region of the prescribed shape and dimension. That is, in the manufacturing steps of the batteries, the opening side that is an opening through which the electrolytic solution is injected in the envelope film body is extended longer than a region to seal and cut at the final stage of production. The extended region of the envelope film body is utilized as an electrolytic solution reservoir (funnel). Thereby, without invoking to inconvenient operations and equipment, with high precision, a definite amount of electrolytic solution can be injected.
In the present invention, for the battery element, a laminate or a planar body can be cited. The laminate is formed by interposing an electrolyte sheet, which concurrently works as a separator of a battery, between the positive and negative sheet electrodes. The planar body is obtained by rolling a winding body in which the electrolyte sheet that concurrently works as a separator of a battery is interposed between the positive and negative sheet electrodes. That is, the battery element comprises a positive sheet electrode, a negative sheet electrode and a polymer-electrolyte system. The positive sheet electrode is formed by laminating a positive electrode containing an active material such as metal oxide, non-aqueous electrolyte and electrolyte holding polymer onto a current collector. The negative sheet electrode is formed by laminating a negative electrode containing an active material storing and ejecting lithium ions, non-aqueous electrolyte and electrolyte holding polymer onto

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