Nonaqueous electrolyte secondary battery

Abstract

The invention provides a nonaqueous electrolyte secondary battery excellent in output characteristic such as large current discharge or pulse discharge in ordinary use, high in safety by preventing destruction due to suppression of current in an abnormality such as external short-circuiting, and further large in capacity. The nonaqueous electrolyte secondary battery comprises an external can opened at one end thereof, an electrode assembly contained in the external can, and comprising a negative electrode, a separator and a positive electrode, a nonaqueous electrolyte contained in the external can, and a sealing lid group tightly sealed at the opening of the external can by way of an insulating member, wherein the sealing lid group includes an intact plate-like PTC element having a fragile portion to be easily broken due to elevation of internal pressure by gas generation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This is a Continuation Application of PCT Application No. PCT / JP2004 / 004846, filed Apr. 2, 2004, which was published under PCT Article 21(2) in Japanese. [0002] This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-102021, filed Apr. 4, 2003, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention relates to a nonaqueous electrolyte secondary battery. [0005] 2. Description of the Related Art [0006] Recently, along with a downsizing trend of electronic appliances such as cellular phones and portable personal computers and an increase in demand for them, there is a mounting demand for higher performance in secondary batteries used as a power source of these electronic appliances. To meet such a demand, nonaqueous electrolyte batteries using a material, such as a carbon material, c...

AI Technical Summary

Benefits of technology

[0015] It is hence an object of the invention to provide a nonaqueous electrolyte secondary battery excellent in output characteristic such as large current discharge or pulse discharge in ordinary use, and effective in current suppression at an abnormal time such as external short-circuiting.

Problems solved by technology

However, when plural current collecting leads are connected to the electrodes as disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 11-317218 and 11-339758, the assembly procedure is complicated, and consequently, productivity of batteries is lowered.

In addition, when the battery is designed by reducing the thickness of the electrodes as in Jpn. Pat. Appln. KOKAI Publication No. 2002-110254, the occupying rate of current collectors in electrodes is larger, and the quantity of reaction substances such as active materials of electrodes is inevitably decreased.

This is significantly disadvantageous in terms of advance of larger capacity of the secondary battery.

On the other hand, the lithium ion secondary battery has other problems, that is, overcurrent flows in the battery in the event of an abnormality such as overcharge or short-circuiting, a nonaqueous electrolysis solution is decomposed, and a decomposition reaction of the electrolysis solution causes heat generation to raise the battery temperature, or liquid leaks or causes a rupture.

In the PTC element, however, since its material configuration and shape, especially shape aspects, function as relatively large resistance components, elevation of output of the secondary battery may be hindered.

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