NOVELTY - An electrolyte for a secondary battery, comprises an electrolyte salt; an electrolyte solvent; and a compound generating heat through oxidation at voltages higher than drive voltage of a cathode. The compound can decompose or evaporate electrolyte components by oxidation heat, thereby causing generation of gas.    USE - In a secondary battery (claimed) useful as energy source in portable phones, camcorders, notebook computers, personal computers and electric cars.    ADVANTAGE - In the battery, the compound is capable of improving overcharge safety of the battery without degrading performance of the battery. Upon overcharge, since a compound is subjected to oxidation at voltages higher than normal drive voltage of a cathode generates heat, electrolyte components can be decomposed or evaporated, thereby generating gas by the oxidation heat. Thus, it is possible to operate a safety element of a battery, without using an internal pressure increasing material directly generating gas through oxidation at overcharge voltage as the electrolyte additive, and thus to improve the overcharge safety of a secondary battery. The electrolyte additive has an oxidation potential higher than the drive voltage of a cathode, and thus can be oxidized at overcharge voltage of a secondary battery. The heat generated by the oxidation increases the internal temperature of the battery, and causes gas generation through decomposition or evaporation of the above mentioned electrolyte components, especially an electrolyte solvent, thereby increasing the internal pressure of the battery. As a result, the temperature and/or internal pressure of the battery can be increased at required overcharge timing, thereby allowing a safety unit of the battery to operate. Therefore, it is possible to prevent fire and rupture of the battery. Upon overcharge, the pressure within the battery is increased, and thus a safety unit such as vent operates, thereby securing the safety of the battery.    DETAILED DESCRIPTION - An electrolyte for a secondary battery, comprises an electrolyte salt; an electrolyte solvent; and a compound generating heat through oxidation at voltages higher than drive voltage of a cathode. The compound can decompose or evaporate electrolyte components by oxidation heat, thereby causing generation of gas. The amount of the heat generated by oxidation of the compound is equal to or more than a range, where the electrolyte components are decomposed or evaporated; and is less than a range, where structural breakdown of a cathode active material is caused. The compound is subjected to the reversible redox shuttle reaction to generate heat at both oxidation and reduction. The amount of the gas generated by the compound is within a range, where a safety elements sensing pressure change within the battery can operate. The compound is present in an amount of 0.05-5 parts by weight, based on 100 parts by weight of the electrolyte. INDEPENDENT CLAIMS are included for the following:    (1) a secondary battery comprising a cathode; an anode; and the electrolyte; and    (2) an internal pressure increase accelerant for a battery, comprising a compound subjected to oxidation at voltages higher than drive voltage of a cathode, where an amount of heat generated by the oxidation is within a range, and electrolyte components can be decomposed or evaporated, thereby generating gas.