Role of precursor chemistry in the direct fluorination to form titanium based conversion anodes for lithium ion batteries

Abstract

A new synthetic route for the formation of titanium oxydifluoride (TiOF₂) through the process of direct fluorination via a fluidized bed reactor system and the associated electrochemical properties of the powders formed from this approach are reported. The flexibility of this synthetic route was demonstrated using precursor powders of titanium dioxide (TiO₂) nanoparticles, as well as a reduced TiO_xN_y. An advantage of this synthetic method is the ability to directly control the extent of fluorination as a function of reaction temperature and time. The TiOF₂ synthesized from TiO₂ and TiO_xN_y showed reversible capacities of 300 mA h g⁻¹ and 440 mA h g⁻¹, respectively, over 100 cycles. The higher reversible capacity of the TiOF₂ powders derived from TiO_xN_y likely relate to the partial reduction of the Ti in the fluorinated electrode material, highlighting a route to optimize the properties of conversion electrode materials.