Disclosed is an electrolyte comprising: (a) an electrolyte salt; (b) a non-aqueous electrolyte solvent; and (c) a binary or multinary metal oxide salt. An electrochemical device comprising the same electrolyte is also disclosed. The metal oxide salt used in the electrolyte is dissolved in a non-aqueous solvent and generates oxyanions capable of improving corrosion resistance of metals. Therefore, the electrolyte prevents corrosion of metallic materials present in an electrochemical device, caused by extreme conditions, such as overcharge, overdischarge and high-temperature storage conditions, to which the device is exposed. Further, the electrolyte prevents degradation in the quality of an electrochemical device, caused by corrosion of metallic materials.