Structure and electrochemistry of carbon-metal fluoride nanocomposites fabricated by solid-state redox conversion reaction

Utilizing a solid-state redox-driven conversion reaction enabled by mechanochemistry, conductive C:FeF3 nanocomposites were fabricated from insulative CF1 :FeF2 precursors. All reactions were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The latter provided insights to the progression of the CF and C phases and the metal fluoride during the course of the reaction. Such nanocomposites resulted in a four order of magnitude increase in electrical conductivity and enabled excellent specific capacity approaching 500 mAh/g vs. Li with good reversibility, although at slow rates. Utilizing the theoretical basis of the technique, other couples were examined to experimentally isolate the oxidative power of CF,. In the process, we have also shown that a composite of CF1 :CrF2 can be easily converted to C:CrF3. The resulting nanocomposite exhibited a specific capacity of 682 mAh/g at-an average voltage of approximately 1.9 V. The technique is also a powerful method for the fabrication of single phase metal fluoride solid solutions, as demonstrated with the fabrication of Cr0.5Fe0.5F3. (C) 2004 The Electrochemical Society. All rights reserved.