Electrochemical characteristics of lithiated graphite (LiC6) in PC based electrolytes

The influence of the surface film formed on the graphite surface in ethylene carbonate (EC) on the lithium intercalation reaction into graphite in other electrolyte solutions including propylene carbonate (PC) was investigated. A graphite sample could be charged and discharged in PC+DME, while no lithium intercalation occurred in either PC+DMC or in PC+DEC. However, the lithiated graphite (LiC6) obtained from a charge in EC with 1 mol dm3 LiPF6 exhibited a reversible intercalation reaction with a large discharge capacity (370 mAh g−1) and a good cycle performance even in PC+DMC. This result suggests that nature of the surface film formed in EC is a dominant factor in the reactivity of graphite with lithium ions in PC+DM, In PC+DME, the reversible capacity was smaller in both cases of the as-manufactured graphite and the LiC6 obtained in EC. An XRD analysis indicated that the reduction in the crystalline size along the c-axis during the initial lithium intercalation is responsible for the smaller capacity.