The effect of ethylene carbonate and salt concentration on the conductivity of propylene carbonate vertical bar lithium perchlorate electrolytes

Propylene carbonate (PC) is a common organic solvent used in lithium batter ies due to its high dielectric constant and high chemical stability with li thium. However, the conductivity of PC-based electrolytes is about two orde rs of magnitude lower than those of aqueous electrolytes. To increase the c onductivity of PC-based electrolytes, a co-solvent, ethylene carbonate (EC) , is added to the electrolyte to form a mixed solvent. In this research, th e conductivity of electrolytes as a function of lithium perchlorate (LiClO4 ) salt concentration and EC/PC molar ratio have been studied. The highest c onductivity, 1.4 x 10(-2) S cm(-1), occurs when the salt concentration is a bout 1 mol L-1 and the EC/PC molar ratio is about one. To understand the co mposition dependence of the conductivity, the interaction between Li+ and E C molecule has been studied using Raman spectroscopy. These results showed that the solvation number of Li+ increases with increasing the EC/PC molar ratio at constant LiClO4 concentration and the solvation number of Li+ decr eases with increasing the LiClO4 concentration at constant EC/PC molar rati o. (C) 2000 The Electrochemical Society. S0013-4651(99)06-046-2. All rights reserved.