Lithium intercalation and deintercalation processes occur through solid ele
ctrolyte interfaces (SEIs) on the zigzag and armchair faces of graphite. Su
ch SEIs are formed by reaction of surface groups on the graphite with lithi
um upon charging. The nature of this interface to a large extent determines
the reversible and irreversible capacities of the graphite. We have invest
igated the influence of mild oxidation of samples of natural graphite and c
arbon nanotubes on the surface characteristics of the films formed on these
materials upon lithium intercalation. The surface groups formed upon oxida
tion have been characterized using Fourier transform infrared (FT-IR) spect
roscopy. The reversible and irreversible capacities of the thermally oxidiz
ed samples are discussed in terms of the surface film composition as well a
s enhanced surface area that contributes to increased number of sites for l
ithium intercalation. (C) 2001 Published by Elsevier Science B.V.