Pushing the theoretical limit of Li-CF_x batteries using fluorinated nanostructured carbon nanodiscs

Li-CF_x battery using a specific fluorinated nanocarbon as cathode material exhibits a capacity exceeding the expected theoretical value when used as an electrode material in primary lithium battery. Carbon nanodiscs were partially fluorinated by atomic fluorine released by thermal decomposition of TbF₄, and the capacity of this material was up to 1180 mAh g^-1, whereas a theoretical value of 847 mAh g^-1 for the CF_0.95 sample was calculated. The obtained value is also higher than the maximum one of 865 mAh g^-1 expected for CF₁ carbon fluorides. The discharge mechanism was investigated using mainly SEM and solid state NMR in order to understand this "extra-capacity". Both the un-fluorinated carbon and the LiF covering, which is formed outside the carbon lattice during the discharge mechanism, play a key role for the achievement of the extra-capacity by the consumption of Li⁺ to form Li₂F⁺ species stabilized by the carbon host structure formed after the electrochemical de-fluorination.