Reversible Three-Electron Redox Behaviors of FeF3 Nanocrystals as High-Capacity Cathode-Active Materials for Li-Ion Batteries

Three types of FeF3 nanocrystals were synthesized by different chemical routes and investigated as a cathode-active material for rechargeable lithium batteries. XRD and TEM analyses revealed that the as-synthesized FeF3 samples have a pure ReO3-type structure with a uniformly distributed crystallite size of similar to 10 to 20 run. Charge-discharge experiments in combination with cyclic voltammetric and XRD evidence demonstrated that the FeF3 in the nanocomposite electrode can realize a reversible electrochemical conversion reaction from Fe3+ to Fe-0 and vice versa, enabling a complete utilization of its three-electron redox capacity (similar to 712 mAh . g(-1)). Particularly, the FeF3/C nanocomposites can be well cycled at very high rates of 1000-2000 mA . g(-1), giving I considerably high capacity of similar to 500 mAh . g(-1). These results seem to indicate that the electrochemical conversion reaction can not only give a high capacity but also proceed reversibly and rapidly at room temperature as long Lis the electroactive FeF3 particles are sufficiently downsized, electrically wired, and well-protected from aggregation. The high-rate capability of the FeF3/C nanocomposite also Suggests its potential applications for high-capacity rechargeable lithium batteries.