Structure control at the nanoscale in fluorinated graphitized carbon blacks through the fluorination route

• Nano-sized graphitized carbon blacks were fluorinated using F2 and F.
• Their thermal, electrochemical and tribological properties were investigated.
• Those properties are correlated to their physical–chemical characteristic.

Two synthesis ways were applied to fluorination of a novel nano-sized graphitized carbon black: (i) direct fluorination (under a flux of pure molecular fluorine) and (ii) controlled fluorination by TbF4 thermal decomposition. The thermal, electrochemical and tribologic properties of the various fluorinated nanocarbons obtained have been investigated. Fluorinated compounds produced by means of controlled fluorination present higher thermal stability and better tribologic properties than those obtained using direct fluorination. On the other hand, the study of the electrochemical performances as electrode material in primary lithium battery underlines that the direct fluorination is more efficient than the controlled way taking into account the energy and power densities. Each fluorination way leads to specific mechanisms of covalent grafting of fluorine atoms onto nanocarbons. These mechanisms have been studied by deep physical–chemical characterizations by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and solid state nuclear magnetic resonance (NMR) with 13C and 19F nuclei in order to determine the CF bond nature, the structure and textural properties of the fluorocarbon compounds.

Graphitized carbon blacks appear an interesting for starting material of fluorination. According to the fluorination method: direct process under pure molecular fluorine flux, and controlled method using thermal decomposition of terbium fluoride solid fluorinating agent, different repartition of fluorinated and non-fluorinated regions (i.e. structure control at the nanoscale) can be obtained. Graphitized carbon blacks appear as intermediate between a closed structure (such as carbon nanofibers) and an opened one (such as carbon nanodiscs) and that change during fluorination. The electrochemical and tribologic properties of fluorinated graphitized carbon blacks seem to be directly related to the different repartition of fluorinated and unfluorinated regions in the carbonaceous lattice.Fluorination of GCB is intermediate and results in closed structure using TbF4 and opened one with F2. The damages in this latter case favor the diffusion of fluorine during electrochemical discharge.Figure optionsDownload as PowerPoint slide