Charge/discharge behavior of plasma-fluorinated natural graphites in propylene carbonate-containing solvent

Plasma-fluorination of natural graphite samples with average particle sizes of 5 mu m, 10 mu m and 15 mu m (NG5 mu m, NG10 mu m and NG15 mu m) was performed using CF4 and charge/discharge characteristics of surface-fluorinated samples were investigated in 1 mol dm(-3) LiClO4-ethylene carbonate (EC)/diethyl carbonate (DEC)/propylene carbonate (PC) (1: 1: 1, v/v/v). Fluorine contents obtained by elemental analysis were in the range of 0.3-0.6 at.% and surface fluorine concentrations determined by X-ray photoelectron microscopy (XPS) were 14.8-17.3 at.%. Plasma-fluorination increased surface disorder of natural graphite samples though reduced surface areas due to its surface etching effect. Electrochemical decomposition of PC was highly reduced on surface-fluorinated NG10 mu m and NG15 mu m with high disorder. First coulombic efficiencies of plasma-fluorinated NG10 mu m and NG15 mu m increased by 9.7 and 19.3% at 150 mA g(-1), respectively. (C) 2007 Elsevier B.V. All rights reserved.