Worm-like mesoporous structured iron-based fluoride: Facile preparation and application as cathodes for rechargeable lithium ion batteries

A worm-like mesoporous structured iron-based fluoride (Fe _1.9F_4.75.0.95H₂O) is successfully synthesized for the first time by a rapid microwave irradiation heating route using ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) as fluorine source and iron (III) nitrate nonahydrate (Fe(NO₃)₃. 9H₂O) as iron source. By controlling the amount of ionic liquid, a series of nanostructured ironbased fluoride materials with different morphologies are obtained. A possible formation mechanism related to the role of the ionic liquid is proposed. The electrochemical performances of the worm-like mesoporous structured iron-based fluoride as cathodes for rechargeable lithium batteries are investigated. A high discharge plateau around 2.7 V at the first cycle, a reversible discharge capacity as high as 145 mAh g^-1 at a current density of 14 mA g^-1 and a good rate performance with a high rate capacity of 125 mAh g^-1 even at 71 mA g^-1 are obtained.