Fluorine doping induced accelerated Li+ kinetics in conversion-type Fe3O4 anode

Magnetite (Fe 3 O 4 ) is a potential anode for high-energy-density lithium-ion batteries thanks to its high theoretical capacity and cost-effectiveness. Yet, the capacity decay and limited kinetics induced by the structure damage along the conversion process need to be emphasized before its practical application. In this study, we propose an intrinsic modulation of Fe 3 O 4 using fluorine doping to considerably boost the cycle stability and rate capability. Benefiting from the enlarged metal-anion distance and improved electronic conductivity induced by the fluorine dopants, the as-prepared Fe 3 O 3.94 F 0.06 anode provides a low-energy-barrier path for the Li + intercalation, which is responsible for the enhanced kinetics. The present study emphasizes the essential role of anion modification on conversion-type transition metal oxides that enable boosting the electrochemical performance towards high-energy-density battery applications.