Three-Dimensional Nanocomposite of Iron-Based Fluoride Loaded in N-Doped Porous Carbon as a High-Performance Cathode for Rechargeable Li-Ion Batteries

摘要

Iron-based fluorides are considered to be some of the most promising candidate cathode materials for high-performance Li-ion batteries, owing to their large capacities and high working potential. In this work, a three-dimensional (3D) hybrid nano-composite of Fe2F5.H2O (FF) loaded in N-doped porous carbon (NPC) is successfully synthesized through a facile and scalable ionic-liquid-based precipitation followed by a mild heat treatment strategy. The 3D Fe2F5.H2O@NPC (FFNPC) nanocomposite with a hierarchical framework utilized as a cathode delivers a high reversible capacity of 185 mAhg(-1) at 0.25 C (1 C= 200 mAg(-1)) and 163 mAhg(-1) at 0.5 C in the voltage range of 1.7-4.5 V (vs. Li/Li+) at room temperature. Moreover, the 3D FFNPC cathode shows robust long-term cycling stability, maintaining 118 mAhg(-1) after 200 cycles even at 2 C. The rate performance shows a specific capacity of 115 mAhg(-1) at the high current rate of 5 C. The improved electrochemical properties of the 3D FFNPC cathode can be attributed to the combination of the small-sized iron fluoride nanoparticles and the NPC matrix, which not only provides a large surface area for the reaction, but also shortens the diffusion length for Li+ and increases the electrical conductivity.