LITHIUM ION RECHARGEABLE BATTERY HAVING WINDOW FOR LEAKAGE ACKNOWLEDGEMENT

摘要

A lithium ion secondary battery is provided to allow the leakage of an electrolyte solution to be sensed more easily by a window, thereby preventing the damage of an equipment. A lithium ion secondary battery comprises a bare cell which comprises an electrode assembly, a case(100), and an electrolyte solution; a mark(180') which is installed in at least some part of the outer surface of the bare cell to react with the certain component of the electrolyte solution, thereby changing the appearance; an external material which wraps at least some part of the outer surface of the bare cell and is provided with a window(60) capable of ascertaining the mark formed at the mark-installed part.