Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Flat-type unit cell and specific unit cell components
Reexamination Certificate
2000-05-22
2002-09-17
Ryan, Patrick (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Flat-type unit cell and specific unit cell components
C429S172000
Reexamination Certificate
active
06451478
ABSTRACT:
BACKGROUND
The present invention relates to a coin-shaped battery suitable for power sources and the like in thin electronic devices, and to a method for producing such a coin-shaped battery.
Coin-shaped organic electrolyte batteries comprise elements for electromotive force comprising a positive electrode featuring the use of manganese dioxide or the like, a negative electrode featuring the use of lithium or an alloy thereof, and an electrolyte featuring the use of an organic electrolyte, which are housed in a flat battery case also serving as the positive electrode terminal. A characteristic feature of such coin-shaped batteries is the high energy density resulting from the use of lithium in the negative electrode active material. Such batteries not only allow devices to be made smaller and more light-weight, but are also highly reliable, and are thus used as the main source of power in various types of electronic devices and as memory back up power sources. Particularly in recent years, the ability to make thinner electronic device casings has been accompanied by increasing demand to make thinner coin-shaped batteries, which are housed in such devices. The structure of a conventional coin-shaped battery is described below.
FIG. 12
depicts the cross sectional structure of a coin-shaped organic electrolyte battery in which manganese dioxide is used for the positive electrode and metallic lithium is used for the negative electrode. In the figure, reference numeral
21
is a metal case serving also as the positive electrode terminal;
24
is the positive electrode mix comprising a compression molded mixture of manganese dioxide, graphite, and a binder;
26
is a separator comprising a polypropylene nonwoven fabric;
25
is the negative electrode metallic lithium;
22
is a metal sealing plate generally in the shape of a dish, which also serves as the negative electrode terminal; and
23
is an insulating gasket. There have been studies on making such coin-shaped batteries thinner by changing the shape of the various aforementioned structural components, that is, by making the various structural components thinner.
The aforementioned insulating gasket is generally produced by injection molding, primarily using resins such as polypropylene. To make thinner gaskets by injection molding, it is necessary to reduce the gap through which the resin flows in the mold. However, due to the low fluidity of such resins in molten states, the resin is not sufficiently packed into the more detailed sections of the mold, which can result in resin deficiencies, leading to so-called short shot. In gaskets affected by such short shot, the parts with insufficiently packed resin are thinner than the other parts. As a consequence, coin-shaped batteries using such gaskets are not sealed as well in parts where the case is crimped, resulting in drawbacks such as leakage. The ability to produce thinner gaskets featuring the use of a resin such as polypropylene is thus limited, making it extremely difficult to achieve a thinness of about 0.2 mm or less.
Other problems with thin gaskets formed by injection molding are that the resin shrinks after molding, and that thinner gaskets suffer from inadequate strength, resulting in deformation during transport and battery assembly. Still other problems that occur when gaskets are placed on top of each other are that the gaskets are difficult to pick up during the manufacturing process, resulting in lower productivity.
Thin gaskets thus produced by injection molding suffer from the aforementioned drawbacks. It is thus difficult to make thinner coin-shaped batteries using thinner gaskets, and only coin-shaped batteries that are about 1.2 mm thick can be mass produced.
Furthermore, since the various components forming such thinner coin-shaped batteries are all smaller and thinner, they are more susceptible to breakage and deformation while handled, and must therefore be manually assembled with great care. The gasket
23
which is used to seal the portions where the battery case is sealed by crimping the sealing plate
22
and the battery case
21
or the separator
26
is a thin resin component which tends to deform and is troublesome to handle, thus complicating assembly and acting as a major impediment in the productivity and cost reduction of thin coin-shaped batteries.
In the process disclosed in U.S. Pat. No. 5,603,157 as a means for resolving such drawbacks, a UV curable resin is applied in the form of a thin ring using a screen printing technique to the surface of a thin metal sheet forming the case of the coin-shaped battery, the resin is then irradiated with UV rays and cured, and a disk that has a diameter which is concentric with the aforementioned UV curable resin applied in the form of a ring but which is somewhat larger than the ring-shaped resin is then punched from the electrode case metal sheet coated with the aforementioned UV curable resin and is drawn to produce a coin-shaped battery case with the gasket attached. In this case, extremely high productivity may be anticipated, yet it may also be assumed that it would be difficult to produce a uniform UV curable resin ring of the prescribed thickness consistently in the radial direction, and it may furthermore be assumed that UV curable resins capable of withstanding lithium battery non-aqueous electrolytes are neither currently unavailable for commercial purposes nor likely to be developed in the future.
SUMMARY OF THE INVENTION
An object of the present invention is to improve the structure of a gasket suitable for use in coin-shaped batteries so as to provide a coin-shaped battery with better battery properties and productivity, particularly a coin-shaped battery with a thickness of no more than 1.0 mm, as well as a method for producing such a coin-shaped battery.
In the coin-shaped battery manufacturing process of the present invention, the gasket is supplied to the battery assembly step in the form of an integrated component with the gasket assembled on the battery case, thereby eliminating smaller and thinner parts that are susceptible to deformation from the assembly step, while simultaneously reducing the number of parts that are supplied to the assembly step, reducing the number of assembly steps and the number of steps for controlling parts, as well as using parts with stable shapes that are easy to handle, in an effort to promote the total automation of the assembly step.
To achieve the aforementioned object, the present invention provides a coin-shaped battery comprising elements for electromotive force sealed therein by crimping the periphery of a sealing plate and the internal periphery of a metal case, with a gasket comprising an insulated resin being interposed therebetween, wherein the gasket comprises a resin film formed into a bottomed cylindrical shape with a round hole in the bottom, the aforementioned gasket being crimped while integrated by adhesion to the inside surface of the case. The gasket preferably comprises a resin selected from any of polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and polypropylene (PP).
In the present invention, the resin film preferably ranges in thickness from 20 &mgr;m to 150 &mgr;m, the adhesive used to integrate the gasket to the inside surface of the case is preferably any of styrene butadiene rubber, butyl rubber, polyolefin, styrene propylene, fluorine, or epoxy adhesives, and the battery preferably ranges in thickness from 0.2 mm to 1.0 mm.
The present invention has greater effect when used as an organic electrolyte battery in which metallic lithium is used as the negative electrode.
Because the gasket is formed by reshaping the resin film into the bottomed cylindrical shape in the present invention described above, it can be made thinner more easily than gaskets obtained by conventional injection molding. In addition, a film having a uniform thickness is used to avoid resin deficiencies that cause short shot during injection molding. Batteries can thus be made thinner to more easily obtain co
Ikehata Toshihiko
Kaneda Masaaki
Murakami Kaoru
Okahisa Mitsugu
Takeuchi Tetsuya
Jordan and Hamburg LLP
Ryan Patrick
Wills Monique
LandOfFree
Coin-shaped battery and method for producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coin-shaped battery and method for producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coin-shaped battery and method for producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2858973