A. Funabiki et al., Influence of defects on the phase-boundary movement in a stage transformation of lithium-graphite intercalation compounds, CARBON, 37(10), 1999, pp. 1591-1598
The influence of defects on the phase-boundary movement in the stage transf
ormation from random stage (dilute stage 1) to stage 4 of lithium-graphite
intercalation compounds was investigated using highly oriented pyrolytic gr
aphite (HOPG). Potential-step chronoamperometry and in situ optical microsc
opy coupled with micro Raman spectroscopy were used to clarify macroscopic
and microscopic influence of defects. Potential-step chronoamperometry conf
irmed that the diffusion limited rate of the phase-boundary movement in the
bulk of HOPG was independent of the crystallinity of the samples. This res
ult indicates that defects have macroscopically no appreciable influence on
the phase-boundary movement. In situ optical microscopy on the basal plane
of HOPG revealed that the nucleation and growth of the stage-4 phase took
place quite inhomogeneously in the initial stage. The rate of the phase-bou
ndary movement in the surface region of HOPG was roughly evaluated to be in
the range of 5 to 10 mu m min(-1). The phase-boundary movement was serious
ly retarded by cracks formed on the basal plane during the stage transforma
tion. (C) 1999 Elsevier Science Ltd. All rights reserved.