Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer or spacer insulating structure
Reexamination Certificate
1999-11-29
2002-05-14
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer or spacer insulating structure
C429S162000, C029S623300
Reexamination Certificate
active
06387564
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/JP98/00839 which has an International filing date of Feb. 27, 1998, which designated the United States of America.
TECHNICAL FIELD
The present invention relates to a novel non-aqueous secondary battery and a method of manufacturing the same
BACKGROUND ART
In recent years, development for high performance batteries have been proceeded positively along with demands for making electronic equipments to be reduced in the size and the weight and have multiple functions, and adaptable to a cordless system. Recently, lithium ion secondary batteries have, particularly, acquired wide markets more and more because of the light weight is reduced in spite of high voltage, high capacity and high power, compared with secondary batteries used generally so far such as lead storage batteries and nickel-cadmium batteries.
An electrode plate laminate of such a lithium ion secondary battery is usually manufactured by winding or laminating a sheet-like electrode of a predetermined shape cut out of a large sheet-like electrode together with a separator. The sheet-like electrode before cutting is generally manufactured by kneading active material particles together with a binder and a solvent into a slurry, coating he same on a metal foil (current collector sheet), then evaporating the solvent and fixing the active material particles on the metal foil.
Therefore, it may be a worry that active material particles near the end face (cut face) of the sheet-like electrode chip down during manufacture of the electrode plate laminate or upon containment of the laminate into a battery can, to cause internal short circuit with the fallen active material particles. As a result, this lowers the yield of the battery and increases the manufacturing cost.
An object of the present invention is to prevent the falling of the active material particles from the end face of the sheet-like electrode thereby preventing occurrence of internal short circuit caused by manufacturing steps.
Further, an electrode plate laminate of a conventional wound-type battery has been manufactured by spirally winding up strip-like positive electrode, negative electrode and separator. A polyethylene microporous film has been usually used for the separator and it is manufactured, for example, by forming fine pores in a film and then applying stretching.
In such a wound type battery, the width (size in the direction of a winding axis) and a length (winding length) of a separator are designed larger than those of the positive electrode and the negative electrode in view of deviation or the like during winding. Particularly, in the lithium ion secondary battery, the width and the length of the negative electrode are designed to be larger than those of the positive electrode with an aim of preventing short circuit at the ends of electrodes during charge/discharge (refer to Japanese Utility Model Registration No. 2506572).
Accordingly, in a lithium ion secondary battery in particular, since the substantial electrode area of the electrode plate laminate is equal to the entire area of the positive electrode active material layer, the size of the electrode plate laminate (size in the direction of the winding axis) is determined by the width of the separator and the width of the positive electrode is smaller than the width of the negative electrode which is further smaller than that of the separator, then, there is a limit for increasing the area of the positive electrode active material layer for an electrode plate laminate of an identical size. The battery capacity for the battery can of a same size may be increased by increasing the thickness of the active material layer for the positive and negative electrodes, but the film resistance increases as the thickness of the active material layer is increased to lower the output characteristics.
An object of the present invention is to increase the battery capacity of the electrode plate laminate contained in a battery can of a same size without increasing the thickness of the active material layer.
On the other hand, development has been proceeded recently for a sheet-type cell referred to as “polymer battery” that basically utilizes the principle of the lithium ion secondary battery. The positive electrode and the negative electrode of the polymer battery are constituted with the same material as that for the conventional lithium ion secondary battery, but a polymeric solid electrolyte serving both as a separator and an electrolyte, instead of a separator having an electrolyte solution permeability, is interposed between the active materials of both of the electrodes. Then, the polymer battery is manufactured by preparing a flat electrode plate laminate by integrating both of the electrodes and the polymeric solid electrolyte, putting the electrode plate laminate into a flexible casing and sealing the same without pouring the electrolyte solution.
In view of the material and the manufacturing method described above, it has been said that the polymer battery has advantages that the degree of freedom for the battery shape is relatively high, the thickness and the weight can be reduced and the safety is improved. However, since the ionic conductivity of the solid electrolyte is lower compared with the liquid electrolyte used in the lithium ion secondary battery, the polymer battery involves a problem in view of the discharging characteristics at a high current density compared with the lithium ion secondary battery.
Further, when a flat electrode plate laminate is prepared by integrating a conventional separator made of microporous film of polyolefin, instead of the solid electrolyte, between both of electrodes, putting the electrode plate laminate into a flexible casing, pouring electrolyte solution into the casing and sealing that thereby, manufacturing a lithium ion secondary battery, the battery is inferior to the conventional battery of using a metal battery can as a vessel in view of discharging characteristics at a high current density and cycle characteristics. This is attributable to that gaps are liable to be formed between the separator and the electrode since the urging pressure between the electrode and the separator is lower in the flexible casing compared with the metal battery can. Further, it is difficult to integrate the separator comprising the microporous polyolefin film with the electrode in order to prevent the formation of gaps.
As described above, a non-aqueous secondary battery equipped with a flat electrode plate laminate in a flexible casing having a relatively high degree of freedom for battery shape and thin thickness (sheet-type battery), and having characteristics equal to those of conventional lithium ion secondary batteries using the metal battery can as a casing has not yet been obtained.
An object of the present invention is to provide a non-aqueous secondary battery equipped with a flat electrode plate laminate in a flexible container having a relatively high degree of freedom for the battery shape and thin thickness, which is excellent in discharging characteristics at a high current density and cycle characteristics.
DISCLOSURE OF THE INVENTION
The present invention provides a non-aqueous secondary battery having, in a casing, an electrode plate laminate having at least a positive electrode and a negative electrode in which an active material layer is fixed to at least one surface of a current collector and a separator having an electrolyte solution permeability interposed between the active material layers of both of the electrodes, with a non-aqueous electrolyte solution being poured and sealed in the casing, wherein the separator is an aggregation layer of insulating material particles formed by bonding insulating material particles to each other by a binder and fixed to at least one of the positive electrode and the negative electrode, and an end face of at least one of the positive electrode active material layer and the negative electrode active material layer
Ogawa Yuko
Oki Shunsuke
Yamashita Masaya
Asahi Kasei Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Chaney Carol
Tsang Susy
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