SECONDARY BATTERY

The present invention relates to a secondary battery which is capable of improving safety. As an example, a secondary battery which comprises an electrode assembly; a case which accommodates the electrode assembly; a cap assembly which is coupled to an upper portion of the case, and a gasket which is interposed between the cap assembly and the case, wherein the cap assembly comprises a cap-up, a safety vent which is installed at a lower portion of the cap-up, a cap-down which is installed at a lower portion of the safety vent, an insulator which is interposed between the safety vent and the cap-down, and a sub-plate which is located on a lower surface of the cap-down, and an insulation layer is formed on one surface of the safety vent, is disclosed.