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

Abstract A worm-like mesoporous structured iron-based fluoride (Fe 1.9 F 4.75 ·0.95H 2 O) is successfully synthesized for the first time by a rapid microwave irradiation heating route using ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF 4 ) as fluorine source and iron (III) nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O) as iron source. By controlling the amount of ionic liquid, a series of nanostructured iron-based 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.