Preparation and Properties of Fluoride-Graphite Intercalation Compounds with Different Oxidation Number of Intercalant

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Fluoride-graphite intercalation compounds(GICs) were prepared as follows, 1) <C_x(SbF_5)_n(SbF_6^-)_(1-n)> : reactions(0-200゜C) of graphite with <SbF_3> under one atmosphere fluorine pressure, 2) involatile fluoride based-GICs( <C_xSnF_y> , <C_xPbF_y> , <C_xBiF_y> ) : reactions(15゜C) of graphite with involatile fluorides dissolved in liquid HF under <F_2> bubbling, 3) fluorine-GICs( <C_xF> ) : reactions(20-200゜C) of graphite fibers and activated carbon fibers with one atmosphere <F_2> gas. The oxidation number of GICs <C_xMF_y> are + <III> , + <IV> and + <V> , which depends on preparative method and starting fluorides. The nature of C-F bond in <C_xF> varies from chemisorption to complete covalent bond depending on reaction temperature. <C_x(SbF_5)_n(SbF_6^-)_(1-n)> and <C_xSnF_y> show high in-plane electrical conductivity( <about> <10^5> S <cm^(-1)> and <C_xF> are semi-conductor or insulator.Electrochemical characteristics of GICs as a cathode material of lithium batteries were investigated by cells Li/1M <LiClO_4-PC/C_xMF_y> , <C_xF> . The <C_xSnF_y> cathode give very high open circuit voltage(OCV) ranging from 3.9 to 4.2 V, however overpotentials are considerably high and the discharge potentials at 0.1 mA/ <cm^2> are 1.2-2.5 V with cathode utility more than 80%. OCVs of <C_xF> cathodes are 3.6-3.7 V and discharge potentials at 0.5 mA/ <cm^2> are ca. 2.5 V with cathode utility ca. 80%. A certain extent of three dimensional structure of <C_xF> is required to be a cathode material with high performances.