Characterization of oxidized boron-doped carbon fiber anodes for Li-ion batteries by analysis of heat of immersion

Surface oxidation treatment in the temperature range of 500-1400degreesC was applied to a graphitized boron-doped mesophase-pitch-based carbon fiber (B-MCF), anode material for Li-ion battery. The correlation between physical properties and lithium intercalation of B-MCF was investigated from measurement of heat of immersion. The surface analysis of heat of immersion and X-ray photoelectron spectroscopy (XPS) indicated that the strength of surface electrostatic field of B-MCF increased with the composition of oxygen on the surface as a result of treatment of the oxidation. Analysis of electrochemical impedance spectroscopy (EIS) indicated that the charge transfer resistance of lithium intercalated B-MCF anode decreased with increase of surface electrostatic field strength. Oxygen atoms on surface as a result of treatment of oxidation caused high surface electrostatic field strength that enhanced an affinity of B-MCF for electrolytes. It was supposed that the low impedance of oxidized B-MCF anode was due to the enhancement of surface polarity and the affinity. (C) 2004 Elsevier Ltd. All rights reserved.