Engineering in situ: N-doped porous carbon-confined FeF3 for efficient lithium storage

Metal fluorides confined in heteroatom-doped carbon nanostructures are viewed as one of the most promising high capacity cathodes for high-performance lithium rechargeable batteries. Herein, we present a facile in situ reaction approach to synthesize nitrogen-doped porous carbon (NPC)-confined metal fluorides, which involves in situ etching toward a Schiff-base organic precursor and fluorination of metal oxides by polytetrafluoroethylene during a one-step heating process. The afforded NPC-confined FeF3 (FeF3@NPC) facilitates fast Li+/e− diffusion kinetics, accommodates severe volume fluctuation and reduces the FeF3 cathode dissolution, thus providing an outstanding high-rate capacity of 181 mA h g−1 at 5 C, accompanied by superior cycle life within 500 cycles at 2 C. This novel approach opens up new horizons to design high-performance nanoconfined metal fluoride-based materials for sustainable energy applications.