Raman spectra and transport properties of lithium perchlorate in ethylene carbonate based binary solvent systems for lithium batteries

Electrolyte solutions formed by the addition of lithium perchlorate to a binary solvent mixture obtained by mixing ethylene carbonate (EC) with propylene carbonate (PC), diethyl carbonate (DEC), or dimethyl carbonate (DMC) were studied. The Raman spectra, conductivity, and viscosity of the EC based binary solvent electrolytes were measured. The salt concentration was optimized for maximum conductivity. Conductivity increases with increasing lithium perchlorate concentration in the EC/PC/LiClO4 electrolyte until a maximum of 6.1 k Omega(-1) cm(-1) is reached at 0.82 M LiClO4 (EC/PC/LiClO4 = 8/8/1). For the optimized salt concentration, the conductivity and viscosity dependence on the percent EC content of each electrolyte was measured at 25 degrees C. The maximum conductivity is observed for the EC/DMC/LiClO4 electrolyte at about 60% EC. The temperature dependence of conductivity and viscosity in the -30 degrees to 60 degrees C range was also examined. The spectroscopic evidence for specific Li+ coordination is supported by quantum chemical calculations.