Disclosed are an electrolyte for a secondary battery, and a secondary battery including the same, the electrolyte including an electrolyte salt; an electrolyte solvent; and a compound generating heat through oxidation at voltages higher than drive voltage of a cathode, wherein the compound can decompose or evaporate electrolyte components by oxidation heat, thereby causing gas generation. Also, the compound is included in an internal pressure increase accelerant for a battery. Upon overcharge, since a compound 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. Accordingly, it is possible to operate a safety means 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.