where σ is conductivity (s/m), F is Faraday's constant (96,485 C/mol), ui is the mobility of species (m 2 .mol/J.s), ci is the concentration of species (mol/m 3 ), zi is charge of species. The neat RTIL and RTIL/solvent systems have two species, i.e., cation and anion; therefore, the conductivity of the RTILs system could be expressed as follows from eq. (1):