NOVELTY - An expanded graphite has bulk density of 1.3-1.8 kg/m3; and comprises ribbon-like particles having thickness of 2-3 nm and length of 13-100 nm, and comprising spaced apart graphene layers with spacing of 0.2-0.4 nm and specific surface of 150-500 (preferably 250-280) m2/g. The ribbon-like particles are randomly oriented relative to one another with pores.    USE - An expanded graphite used as electrode in electrochemical device, including negative electrode in rechargeable lithium battery, catalyst support in fuel cell, conductive catalyst support without additional conductivity promoting materials, or electrode material in supercapacitor. The expanded graphite is used for accommodating lithium ions as intercalating species between adjacent graphene layers (claimed). Can also be used in electrochromic device or in solar energy cell.    ADVANTAGE - The use of porous superfine expanded graphite as negative electrode in lithium-based electrochemical storage devices leads to high reversible capacities greater than 700 mAhour/g and sufficient cycling performance over wide voltage range (0-3 V). There is some fluorine present in carbon material, which increases capacity of structure which is beneficial for lithium intercalation, i.e. lithium storage properties, and provides excellent electronic conductivity and good lithium mobility. The carbon electrodes exhibit good reversibility and rate performance.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of expanded graphite material, comprising adding chlorine trifluoride (ClF3) in liquid form to solid carbon, heating mixture at 22-100 degrees C to form intercalated compounds of formula C2FxClF3 and chlorine monofluoride (ClF) gas with graphite fluoride (C2F) as solid material present in layers and ClF3 as gaseous material present between adjacent layers of C2F; and heating intercalated compound at 400-500 degrees C to expel ClF3 gas and to simultaneously form chlorine tetrafluoride gas, with gas formation and expulsion serving to expand structure formed by C2F layers, with the C2F layers changing composition to carbon layers with up to 5% fluorine. The solid carbon plus the sum of /2 and number of atoms of liquid chlorine trifluoride equals solid intercalated compound of formula C2FxClF3 plus /2 of chlorine monofluoride gas.    DESCRIPTION OF DRAWING(S) - The drawing shows a graph of a nitrogen adsorption/desorption isotherms of prepared expanded graphite sample.