Highly Stable Fluorine-Intercalated Graphite Fibers Coated with Graphite Fluoride Film

Abstract

The stability of fluorine-intercalated graphite fibers were improved by the surface coating of the fibers with graphite fluoride film. The preparation process of the GIC was composed of two steps. In the first step, the pitch-based graphite fibers were pre-treated with elemental fluorine at the temperature range of 300-410°C, so that the surface of the fibers were coated with graphite fluoride which has an excellent water-repellency. Then, in the second step, thus surface-coated fibers were intercalated by F2 below 100°C.The graphite fluoride-coated GICs showed higher stability than the non-coated one from the viewpoints of the change in weight decrease and electrical conductivity as a function of exposure time to air. Furthermore, X-ray diffractions showed no decomposition of the former GICs in air. Where as, the latter decomposed within a few days.