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AssigneeLG Chem, Ltd.
InventorsSung Kyun Chang, Jae Hyun Lee, Joon Hwan Lee, Soo Hyun Ha, Jeong Ju Cho
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An object of the present invention is to provide the device for protecting a secondary battery safely from overvoltage and overheating caused by the overcharge by using simple safety device, which provides a contacted safety device which connects between a constant voltage element showing a discharge characteristic in the state of overvoltage and a MIT (metal insulator transition) element showing a discharge characteristic in the state of overheating. Each of the constant voltage element and the MIT element are connected in parallel between a cathode lead and an anode lead of the secondary battery. The contacted safety device has a characteristic combining a discharge/heat dissipation characteristic of the constant voltage element and a discharge characteristic of the MIT element which immediately responds to the heat dissipation of the constant voltage element, resulting in effect of preventing overcharge advantageously since the contacted safety device makes discharge in terms of 2 factors of voltage and temperature in case of overcharge.
A contacted safety device having a constant voltage element and a metal insulator transition (MIT) element combined, said constant voltage element having discharge/heat dissipation characteristic at more than a predetermined voltage, said MIT element having charge emitting characteristic at more than a predetermined temperature, said MIT element having an insulator-to-metal transition characteristic so that resistance of said MIT element decreases by a factor of about 1000 over a 20° C. change in temperature staffing at the predetermined temperature, wherein a critical temperature of said MIT element is equal to and above 50° C. and below 80° C.
Dependencies are inferred from the claim text.