Different graphite oxyfluorides were synthesized via Hummer's oxidation of sub-fluorinated graphites in order to maintain sp2 carbon atoms available for the oxidation, C–F bonds being non-reactive. In comparison with the graphite fluoride precursors, significant improvement of the energy density in primary lithium battery is achieved when the graphite oxyfluorides are used as cathode. When the Hummer's oxidation was carried out on graphite fluoride with both CF0.60 composition and a homogenous dispersion of non-fluorinated regions into fluorinated lattice, oxidation focused on the remaining sp2 carbon atoms and decomposed them. Defected graphite fluorides were then synthesized. The highest ever measured energy density in primary lithium battery with fluorinated carbons as cathode, i.e. 2825 Wh.Kg−1, was reached with this particular sample. Solid state NMR allowed the functional groups C–F, COC, COH, COOH and sp2 C to be quantified in graphite oxyfluorides and fluorides and their role in electrochemical processes to be highlighted.