LiF/Fe nanocomposite as a lithium-rich and high capacity conversion cathode material for Li-ion batteries

Lithium-rich LiF/Fe nanocomposite is prepared by a simple route of mechanical ball-milling of lithium fluoride and iron using rigid TiN nanoparticles as the grinding powders, and studied as a lithium-rich cathode material for satisfying the present Li-ion battery technology. The structural characterizations reveal that the nanocomposite is composed of well-dispersed and intimately contacted LiF and Fe particles created by high-energy ball-milling, forming appropriate electrode-active nanodomains for the reversible conversion reaction of LiF and Fe. Electrochemical measurements demonstrate that the LiF/Fe nanocomposite containing 50 wt% active materials of LiF and Fe can deliver a high reversible capacity of 568 mAh g−1 at 20 mA g−1 (calculated using the weight of LiF and Fe only), approaching the theoretical capacity of the composite (600 mAh g−1), and also show a strong power capability with a reversible capacity of ∼300 mAh g−1 even at a very high rate of 500 mA g−1 at room temperature. CV and XRD analyses confirm that the LiF/Fe nanocomposite can nearly realize a three-electron transfer through electrochemical conversion of LiF/Fe to FeF3 and vice versa. These results suggest the possibility to utilize the inexpensive lithium-rich composites of lithium fluoride and metals as high-capacity cathode materials for future-generation Li-ion batteries through the electrochemical conversion.

► The composite was prepared by a simple ball-milling of LiF and Fe powders. ► The composite delivers 568 mAh g−1 at 20 mA g−1 and exhibits a high rate capability. ► The composite can realize the conversion reaction of LiF/Fe to FeF3 and vice versa.