Electrochemical properties of graphite electrode are studied in propylene carbonate (PC) electrolytes containing both LiN(SO2CF3)2 and Ca(N(SO2CF3)2)2 salts, and the influence of the salt concentrations on the intercalation/de-intercalation properties of graphite electrode is clarified. In the higher concentration electrolytes, reversible lithium-ion intercalation/de-intercalation at graphite electrode takes place. In contrast, only the exfoliation of graphite occurs in the lower concentration electrolytes. The effect of the salt concentrations on the electrochemical properties of graphite is discussed.