Improved Electrochemical Performance of FeF 3 by Inlaying in a Nitrogen‐Doped Carbon Matrix

FeF 3 is favored by researchers because of its high theoretical specific capacity and high voltage. It is expected to be utilized as a cathode material for lithium‐ion batteries in the future. However, the poor electronic conductivity, inferior reaction kinetics, and severe volume expansion seriously prevents its practical application. Herein, a FeF 3 @N‐doped carbon nanocomposite was successfully produced by in situ fluorination and dehydration. In addition, the nanocomposite showed a reversible capacity of 84.9 mAh g −1 for 200th cycle after cycling at a high current of 2 C, which is approximately 300 times higher than that of bare FeF 3 . Benefitting from the N‐doped carbon matrix, the composite electrodes exhibited minor transfer resistance (117.4 Ω, only 44.0 % of that of bare FeF 3 ) and very low polarization voltage (ca. 0.19 V). Meanwhile, it provided a buffer for volume expansion during the insertion of Li + and maintained cycling stability. This work can supply a simple pathway for designing ultrahigh‐rate and long‐life FeF 3 cathode materials.