In situ processing of fluorinated carbon-Lithium fluoride nanocomposites

Lithiumfluoride (LiF) and fluoride additives in carbon-based materials are currently under research as electrode materials for energy storage applications. Herein we demonstrate a simple and novel method for the in situ fabrication of fluorinated carbon-LiF nanocomposites both as powder and as supported thin films. The starting solution of polyvinylidene fluoride (PVDF) and lithiumnitrate (LiNO3) in N,N Dimethylformamide is poured into a mould or applied to a thermally resistant substrate as a thin film. Pre-tempering and further pyrolysis at 550 degrees C yield LiF doped amorphous and fluorinated carbon (AC) powder or film. The precursor solution can be additionally modified with multi-walled carbon nanotubes (MWCNT) to yield porous AC-MWCNT-LiF-nanocomposites. Structural and morphological characterization (scanning electron and energy dispersive X-ray spectroscopy, X-ray diffraction as well as solid-state Li-7 magic angle spinning nuclearmagnetic resonance spectroscopy) show a fine dispersion of faceted LiF-nanoparticles in the carbon matrix or decorating the MWCNTs. The formation mechanism involves the thermally activated reaction of Li-ions with the fluorine of the polymer during pyrolysis thus allowing an in situ nanocomposite to be obtained. Finally the electrochemical capacitance properties in a two-electrode set-up using LiNO3 in ethylene glycol as electrolyte are reported and discussed in comparison to LiF-free electrodes. (C) 2018 Elsevier Ltd. All rights reserved.