A lithium secondary battery including an electrode assembly composed of positive and negative electrode plates wound up spirally with a separator and disposed in a cell casing filled with electrolyte containing lithium salt dissolved in organic solvent wherein the cell casing is provided with a current interrupt device for cutting off a charge current of the battery when an internal gas pressure of the battery exceeds a predetermined value, and wherein the organic solvent contains aklylbenzene derivative or cycloalkylbenzene derivative having tertiary carbon adjacent a phenyl group.