Superior electrochemical performance of N-doped nanocrystalline FeF3/C with single-step solid-state process

Abstract

FeF3 is a promising cathodematerial for lithium ion batteries but its poor electronic conductivity makes it non-practical. Here, we significantly improve the electrochemical activity of FeF3 by reducing the strong ionic character of Fe-F with the replacement of some F with N atoms. N-doped nanocrystalline FeF3/C achieves the best electrochemical performance among FeF3 compounds reported to date: similar to 95 mA h g(-1) at 21.1C discharge rate for 250 cycles. The results illustrate that the poor electronic conductivity of metal fluorides can be controlled by doping and this enables FeF3 or metal fluorides to be practically utilized in possible applications including energy conversion and storage.