Nonaqueous secondary battery

Details Nonaqueous secondary battery Nonaqueous secondary battery

1997-07-11

2001-02-20

Chaney, Carol (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S233000, C429S231100, C429S231950

Reexamination Certificate

active

06190803

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a nonaqueous secondary battery having improved storage properties in which the current collector of the positive electrode has improved strength and improved anticorrosion so that the electrode sheet may be prevented from being cut on rolling in assembly of batteries and during a charge of the batteries.
BACKGROUND OF THE INVENTION
With the recent spread of portable electronic equipment, such as mobile phones, video cameras and notebook computers, the demand for high-capacity secondary batteries as a current source, especially nonaqueous secondary batteries utilizing the intercalation-deintercalation reaction of lithium ions, has been increasing. As the functions of the electronic equipment are improved, the demand for higher capacity of secondary batteries has also been desired. Packing an active material into a battery container as much as possible is one approach to achievement of high capacity. Along this line, it has been attempted to reduce elements other than an active material, for example, to make a reduction in thickness of a current collector and to displace the decrease with an active material. However, a current collector having a reduced thickness has reduced strength and tends to be cut on receipt of stress on rolling of an electrode sheet or during a charge. In particular, a positive electrode current collector of a nonaqueous secondary battery is generally made of aluminum foil having relatively low strength among metals and is liable to be cut when its thickness is reduced.
The inventors of the present invention have previously achieved an increase in capacity by using a specific metal oxide having high ability of lithium ion intercalation as a negative electrode active material. However, lithium ion intercalation is accompanied by expansion of the negative electrode active material, which imposes pressure on the positive electrode sheet, causing the sheet to be cut.
Various aluminum alloys (JP-A-2-204976, the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and high purity aluminum (JP-A-6-267542) have been proposed for use as a positive electrode current collector of a nonaqueous secondary battery, but these materials are insufficient in mechanical strength under the above situation.
SUMMARY OF THE INVENTION
An object of the present invention is to improve strength and anticorrosion of a positive electrode current collector to prevent it from being cut during rolling or charging thereby to provide a nonaqueous secondary battery having improved storage properties.
The above object is accomplished by a nonaqueous secondary battery comprising a positive electrode sheet containing a lithium-containing transition metal oxide as a positive electrode active material, a negative electrode sheet containing a negative electrode material capable of intercalating and deintercalating lithium, and a nonaqueous electrolyte containing a lithium salt, wherein a current collector of the positive electrode sheet is made of an aluminum foil containing 0.6 to 2% by weight of manganese and not more than 1.5% by weight of magnesium and has a thickness of 5 to 200 &mgr;m.


REFERENCES:
patent: 5683834 (1997-11-01), Fujimoto et al.
patent: 311569 (1989-12-01), None
patent: 2-204976 (1990-08-01), None
patent: 6-267542 (1994-09-01), None
ASM Handbook, vol. 2, Library of Congress, ASM International, pp. 15-18, 33, 36-37, 82-87, 1990 No Month.
ASM Handbook, vol. 4, Library of Congress, ASM International, pp. 869-872, 878, 1991 No Month.

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