Conductivity variation of the liquid electrolyte, EC : PC : LiCF3SO3 with salt concentration

It is a well known fact that liquid electrolytes inherit better conductivity values than other electrolytes such as solid electrolytes and polymer electrolytes. Basically, a liquid electrolyte consists of a salt dissolved in a solvent or a mixture of solvents. Their conductivity values therefore depend on the salt concentration as well as solvent concentration. Present study is based on the liquid electrolyte, ethylene carbonate (EC), propylene carbonate (PC) and lithium trifluoromethane sulfonate (LiCF 3 SO 3 – LiTF). Its conductivity variation with the salt concentration was investigated using AC impedance spectroscopy. The maximum conductivity observed at room temperature (RT) was 2.80 x 10 -3 S cm -1 at the salt concentration of 0.85 mol kg -1 . To explore the reasons governing the conductivity below and above that salt concentration, viscosity measurements were done using a Ostwalds viscometer. Upto the salt concentration of 0.85 mol kg -1 , conductivity increases. Hence, it can be assumed that due to the increment of charge carrier concentration with salt concentration, conductivity increases upto 0.85 mol kg -1 . After that, the effect of viscosity may dominate resulting in conductivity reduction. According to the observations, with the salt concentration, viscosity increased. The carrier mobility and hence, the conductivity decrease with viscosity. Conductivity variation with temperature of all samples followed the Vogel Tamman Fulcher (VTF) behaviour.