Safety device for preventing overcharge and secondary battery therewith

摘要

Disclosed are a safety device and a secondary battery using the same. The safety device includes a voltage sensitive heating device generating heat when a voltage difference between both ends thereof exceeds a predetermined voltage level and a temperature sensitive device having a reversible current ON/OFF function according to a temperature. The temperature sensitive device is coupled with the voltage sensitive heating device such that the temperature sensitive device detects the heat generated from the voltage sensitive heating device.

主权项

1. A safety device consisting of:
a voltage sensitive heating device including a zener diode or a varistor, configured to generate heat when a voltage difference between both ends thereof exceeds a predetermined voltage level; and a temperature sensitive device including a positive temperature coefficient (PTC) device or a bimetal, having a reversible current ON/OFF function according to a temperature, wherein a lateral surface of the voltage sensitive heating device is coupled with a lateral surface of the temperature sensitive device such that the temperature sensitive device detects the heat generated from the voltage sensitive heating device and the temperature sensitive device is operated by the heat generated from the voltage sensitive heating device upon reaching an operating temperature; wherein the voltage sensitive heating device is connected to a cathode and an anode of a secondary battery in parallel; wherein the temperature sensitive device is connected to the cathode or the anode of the secondary battery in series; wherein a breakdown voltage of the voltage sensitive heating device is at least 15% higher than the predetermined voltage, the predetermined voltage being approximately equal to a full charge voltage of the battery, such that the voltage sensitive heating device has a leakage current value wherein the leakage current value obtained for one hour is less than 0.05% of battery capacity under the full charge voltage; and wherein the operating temperature to trigger the operation of the temperature sensitive device is in a range of 50 to 150° C.