Ionic conductivity is one of the most important properties that characterize the electrochemical performance of electrolytes. Ionic conductivity quantifies how mobile the ions are for the electrochemical reactions . It is determined by the number of ions, the magnitude of the ionic charge and the mobility of ions . For any given ions, therefore, the value the ionic conductivity essentially depends on both diffusivity and the number of ions participating in carrying charges . The larger the diffusivity of ions, the higher will be the value of ionic conductivity. However, formation of ion pairs of cations and anions decrease ionic conductivity because the formation of pairs of cations and anions is closely related with a decrease in diffusivity due to an increasing size of ionic clusters in addition to a decrease in the number of ions contributing the ionic conductivity. Solvents may solvate the ions preventing the cations and anions from forming pairs and even clusters. Solvents can enhance the mobility of ions by forming a proper solvation shell of cations. Generally speaking, solvents of larger dielectric constant enhance the ion pairing process, but this comes at the cost of decreasing the mobility of ions due to its large viscosity. In sharp contrast, solvents of lower dielectric constant can enhance the mobility of ions due to their lower viscosity, but such solvents with lower dielectric constant do not enhance the solvation process of the ions. Thus, no single-solvent strategy satisfies all the requirements of LIB electrolytes. For this reason, therefore, state-of-the-art LIB electrolytes adopt multiple-solvent strategy to compromise both properties: the mobility and the ion-pairing . For example, EC has a large dielectric constant (ε~9 at 4 °C) owever, its high viscosity (η~1 9 c at 4 °C) dis ualifies it from being chosen as a sole solvent On the other hand, DMC has low viscosity (η~ 59 c at 2 °C) but smaller dielectric constant (ε~3 1 at 25 °C). Therefore, a mixture of both EC and DMC has been suggested as a candidate of efficient electrolytes to be satisfied with two important properties . In this work, we explore the effects adding a mixture ratio of EC: DMC=50%:50% co-solvents on the achieviable ionic conductivity of [EMI][TFSI] consisting of 1M LiFSI salt at 298K. We consider the ionic conductivities of these mixtures and investigate how they are affected by solvent properties. In accordance with prior reported studies, we comput the ionic conductivity by using the ideal ionic conductivity as a proxy. The limiting value of the selfdiffusion coefficient of an ion (D Si ) at infinite dilution (denoted by ∞) is given by ernst's relation :