We use a Flory-Huggins type approach and the random phase approximation (RPA) to describe a microphase separation in the mixture of ionic and nonionic liquids. The mixture is modeled as a "three-component" system including anions, cations, and neutral molecules. Each ion is considered to consist of a charged group surrounded by a neutral "bulky" shell. The shells of the anion and cation are assumed to have different affinities to the neutral molecules. We show that, if the difference of the Flory-Huggins parameters describing affinities of the anions and cations to the neutral molecules is higher than a certain value, the microphase separation can occur. The physical reason for the separation is a delicate balance between the short-range segregating interactions and the long-range Coulomb interactions.