Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Reexamination Certificate
1999-10-21
2001-11-13
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,...
C429S184000, C429S231950
Reexamination Certificate
active
06316140
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10-303086 filed Oct. 23, 1998 which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nonaqueous-electrolyte secondary battery incorporating a battery device accommodated in a case constituted by a laminated film, and more particularly to an improvement in a portion for heat-welding leads of terminals of electrodes and the case of the battery to each other.
2. Description of the Related Art
In recent year, a variety of portable electronic apparatuses including a camcorder, a portable telephone and a portable computer have been marketed. Under the foregoing circumstances, reduction in the size and weight of the foregoing electronic apparatuses has been attempted. As a portable power source for the electronic apparatus, a battery, in particular, a secondary battery, and more particularly, nonaqueous-electrolyte secondary battery (a so-called lithium ion battery) have energetically been researched and developed to realize a battery which has a small thickness and which can be folded.
As an electrolyte of the shape variable battery, research and development of solidified electrolytic solution have energetically been performed. In particular, a solid polymer electrolyte having a structure that lithium salt is dissolved in a gel electrolyte which is a solid electrolyte containing a plasticizer has attracted attention.
On the other hand, research and development have been performed about a variety of batteries of a type which is encapsulated in laminated films obtained by bonding plastic films or a plastic film and a metal member to each other to use the advantages of the battery of the foregoing type that the thickness and weight can be reduced. It is an important fact for a battery of the foregoing type to realize reliable sealing characteristic as well as or better than that of a metal tube.
To meet the foregoing requirement, an attempt has been suggested in, for example, Japanese Patent Laid-Open No. 56-71278. According to the disclosure, leads coated with resin are used to draw out terminals of electrodes from a sheet member which encapsulates a battery so as to improve sealing characteristics.
In Japanese Patent Laid-Open No. 3-62447, an attempt has been suggested to improve the sealing characteristics by using polyethylene denatured with acrylic acid or polypropylene denatured with acrylic acid as the resin employed to form the seal portion of the encapsulating member.
Another attempt has been suggested in, for example, Japanese Patent Laid-Open No. 9-288998. According to the disclosure, leads coated with polyolefine resin denatured with maleic acid are used to draw out terminals of electrodes from a sheet shape member which encapsulates a battery. Also the sealing portion of the sheet shape member for encapsulating the battery is made of polyolefine resin denatured with maleic acid. Thus, the sealing characteristic can be improved.
The method disclosed in Japanese Patent Laid-Open No. 56-71278 having the structure that the member for encapsulating the battery is made of one type of the resin, however, encounters inward penetration of water through the resin. What is worse, penetration and volatilization of the electrolytic solution cannot be prevented. Therefore, the foregoing method cannot preferably be applied to a battery which uses a solid electrolyte composed of organic solvent.
The methods disclosed in Japanese Patent Laid-Open No. 3-62447 and Japanese Patent Laid-Open No. 9-288998 has a structure that the overall polarity of the resin is raised to improve the sealing characteristics with the terminals of the electrodes made of metal. Therefore, the affinity with water is undesirably enhanced in spite of improvement in the sealing characteristics. As a result, there arises a problem in that water is undesirably introduced in the long term.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to sufficiently maintain the sealing characteristics of leads of terminals of electrodes in the heat welding portion of the case without deterioration in the resistance against moisture penetration. Another object of the present invention to provide a nonaqueous-electrolyte secondary battery exhibiting excellent moisture resistance and long lifetime against charge-discharge cycles.
To achieve the foregoing objects according to one aspect of the present invention, there is provided a nonaqueous-electrolyte secondary battery comprising: a case constituted by laminated film: a battery element accommodated in the case and encapsulated in the case by heat welding,g and leads of terminals of electrodes electrically conducted with the electrodes which are exposed to the outside portion of the case such that the leads are surrounded by heat-welded portions, wherein a portion of at least either of the leads of the terminals of the electrodes corresponding to the heat-welded portion is coated with an olefine adhesive layer containing a titanate coupling material and a coating layer made of resin which is the same as resin which forms the inner most layer of each of the laminated films. The term “olefine” as used throughout the text of the specification means the same as and is interchangeable with the term “olefin”.
As described above, the portions of the leads of the terminals of the electrodes corresponding to the heat-welded portions are coated with the olefine adhesive layer containing the titanate coupling material. Thus, the adhesiveness of the metal leads of the terminals of the electrodes with respect to the resin can considerably be improved.
The refine adhesive layer is provided for only the portions corresponding to the leads of the terminals of the electrodes. Therefore, enhancement of the affinity with respect to water occurs in very small regions. Hence it follows that introduction of water can substantially be prevented.
As described above, the olefine adhesive layer is coated with the coating layer made of the resin which is the same as the resin which forms the innermost layer of each of the laminated films. The coating layer can be integrated with the case so that the adhesiveness is furthermore improved. Moreover, the olefine adhesive layer is coated with the foregoing coating layer so that introduction of water from the foregoing portion is satisfactorily prevented.
Other objects, features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.
REFERENCES:
patent: 0 852 404 A1 (1998-07-01), None
patent: 0 862 227 A1 (1998-09-01), None
patent: 0 938 145 A2 (1999-08-01), None
patent: 1-124953-A (1989-05-01), None
patent: WO97/24771 (1997-07-01), None
Hara Tomitara
Hatazawa Tsuyonobu
Hatsuta Kazuhito
Bell Boyd & Lloyd LLC
Chaney Carol
Sony Corporation
Tsang Susy
LandOfFree
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