Disclosed is a nonaqueous electrolyte for a lithium-ion secondary battery that contains an addictive for preventing destruction of a solid electrolyte interface (SEI) layer and hence decomposition of the electrolyte that may cause generation of a gas, thereby preventing swelling of the battery caused by the gas generated from the inside of the battery at a high temperature. More specifically, the present invention provides an electrolyte that includes, as an additive, 2-sulfobenzoic acid cyclic anhydride represented by the formula 1: The electrolyte contains the additive in an amount of 0.1 to 10.0 wt. %. ##STR00001##