Secondary battery

Abstract

The invention discloses a secondary battery, which comprises: a casing with positive and negative electrodes; a safety device attached to the surface of the casing, whose resistance value changes with the expansion of the casing; and a protective device installed on one side of the casing. The circuit module is electrically connected to the safety device. The resistance of the safety device changes as the housing expands, and the protection circuit module can reduce or interrupt the charging / discharging current in response thereto. The safety device can be used on all secondary batteries irrespective of the capacity, can react quickly to a sudden rise in internal temperature and rapid expansion, and can reliably prevent expansion that occurs above the allowable temperature.

Description

[0001] priority claim [0002] This application claims priority under 35 U.S.C. §119 to an application entitled Secondary Batteries filed with the Korean Intellectual Property Office earlier than October 28, 2004 and subsequently granted serial number 2004-0086897, which is hereby incorporated Reference. technical field [0003] The present invention relates to a secondary battery, and more particularly, to a secondary battery capable of automatically stopping charging or discharging when swelling occurs to improve safety. Background technique [0004] It is well known in the art that when a secondary battery such as a lithium ion secondary battery is overcharged to about 4.5V or higher, the internal temperature of the battery tends to rise. Taking advantage of this trend, safety devices have been developed to interrupt overcharging of secondary batteries, a typical example being a positive temperature coefficient (PTC) thermistor connected in series to a large current path...

AI Technical Summary

Problems solved by technology

On the other hand, when a conventional PTC thermistor is used in a battery with a large capacity, it must be cut off at high current and have a small resistance value

Since the produced batteries have different capacities, it is difficult to set the resistance value of the PTC thermistor according to the capacity of each battery

[0010] Second, the conventional PTC thermistor is difficult to quickly suppress the expansion phenomenon caused by the sudden rise in the internal temperature of the battery due to structural reasons

In such a case, although the conventional PTC thermistor is activated, the safety vent of the battery case is opened and the internal electrolyte leaks, or the case may even explode or burn

[0011] Third, all batteries generally have a predetermined allowable expansion thickness, and when it expands beyond the predetermined thickness, the safety vent usually opens, or the case explodes and burns

So the conventional PTC thermistor itself will consume e.g. discharge current, and it will reduce the overall battery capacity and shorten the service life

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