Patent ID: 8455123

Claim:
A secondary battery comprising a safety switch wherein: (A) the safety switch comprises a heat shrinkage tube that shrinks when exposed to temperatures in excess of a predetermined temperature level as a member for securing the safety of the battery when the battery is overheated (“safety member”) and which is mounted at the outside of a battery cell, (B) in response to temperature the length of the heat shrinkage tube is changeable to control current conduction, (C) the cross-section of the heat shrinkage tube is constructed in the form of a geometrical hollow structure, (D) a support member, as a fixing shaft, is located toward one end of the geometrical hollow structure, in the geometrical hollow structure, and (1) one end of the heat shrinkage tube is fixed, and a variable member, connected to an electric wire connection part, is located toward the other end of the geometrical hollow structure, in the geometrical hollow structure, (2) the other end of the heat shrinkage tube is connected to an electric wire connection part, such that current conduction or current interruption is accomplished by the change in length of the heat shrinkage tube when the heat shrinkage tube length is varied due to heat, and wherein, (i) when the secondary battery is overheated, the heat shrinkage tube shrinks to convert the electric wire connection part into a current interruption state; and (ii) when the temperature of the secondary battery is lowered to a level not in excess of the predetermined level in (A), the heat shrinkage tube expands to its original state, thereby restoring the electrical wire connection, and, (E) the heat shrinkage tube is made of one or more materials selected from a group consisting of polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, ethylene propylene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, nitrile butadiene rubber, and polytetrafluoroethylene.