The electrolytic conductivities of lithium trifluoromethanesulfate (LiCF3SO3) and lithium hexafluorophosphate (LiPF6) have been investigated as a function of the solvent composition. The organic solvent tested was ethylene carbonate (EC) or propylene carbonate mixed with 1,2-dimethoxyethane, diethyl carbonate, or dimethyl carbonate (DMC). For each solvent system, the electrolytes containing LiCF3SO3 showed nearly half the values of the conductivity of the corresponding systems with LiPF6. High discharge capacities (ca. 200 mAh g-1) for charge-discharge cycling of the carbon fiber electrode with a graphite structure were obtained in LiCF3SO3/EC-based electrolytes. Especially, the highest coulombic efficiency (98%) was obtained in the LiCF3SO3/EC-DMC system. The EC-based electrolyte systems containing LiCF3SO3 were found to be more compatible with the carbon fiber electrode than the systems containing LiPF6.