ABSTRACT
Conversion-type cathodes such as metal fluorides, especially FeF2 and FeF3 , are potential candidates to replace intercalation cathodes for the next generation of lithium ion batteries. However, the application of iron fluorides is impeded by their poor electronic conductivity, iron/fluorine dissolution, and unstable cathode electrolyte interfaces (CEIs). A facile route to fabricate a mechanical strong electrode with hierarchical electron pathways for FeF2 nanoparticles is reported here. The FeF2 /Li cell demonstrates remarkable cycle performances with a capacity of 300 mAh g-1 after a record long 4500 cycles at 1C. Meanwhile, a record stable high area capacity of over 6 mAh cm-2 is achieved. Furthermore, ultra-high rate capabilities at 20C and 6C for electrodes with low and high mass loading, respectively, are attained. Advanced electron microscopy reveals the formation of stable CEIs. The results demonstrate that the construction of viable electronic connections and favorable CEIs are the key to boost the electrochemical performances of FeF2 cathode.