Electrochemical behavior of graphite highly fluorinated by high oxidation state complex fluorides and elemental fluorine

Highly fluorinated graphites have been synthesized by using elemental fluorine under pressure and high oxidation state complex fluoride, K2NiF6 or KAgF4 in anhydrous hydrogen fluoride. Their electrochemical discharge as a cathode of primary lithium battery has been investigated in organic electrolyte solution. Main products were stage 1 compounds or the stage 1 involving stage 2 and 3 phases as minor components with approximate compositions of C1.6F. X-ray photoelectron spectra indicated the existence of nearly semi-ionic C–F bonds. Electrochemical studies demonstrated that the CxF samples prepared using KAgF4 and elemental fluorine exhibited high and flat discharge potentials of 3.2 V versus Li/Li+ and discharge capacities of ∼500 mA h g−1 at cut-off potential 1.5 V.