A graphene loading heterogeneous hydrated forms iron based fluoride nanocomposite as novel and high-capacity cathode material for lithium/sodium ion batteries

A graphene loading heterogeneous hydrated forms iron based fluoride (abbreviated as FeF3 center dot xH(2)O/G) nanocomposite is successfully designed and synthesized for the first time by a sol-gel method. It found that the FeF3 center dot xH(2)O nanoparticles distribute randomly on the surface of the graphene, stacking together to form a nanocomposite with high specific surface and abundant mesporous structure. The FeF3 center dot xH(2)O was consisted of FeF3 center dot xH(2)O and FeF2.5 center dot 0.5H(2)O with pyrochlore phase structure and FeF3.0.33H(2)O with hexagonal-tungsten-bronze-type structure (HTB). The FeF3 center dot xH(2)O/G was used as cathode materials of rechargeable lithium/sodium batteries, respectively. It has been found that it can deliver a large reversible capacity exceeding 200 mAh g(-1) and excellent cyclic performance with a residual capacity of 183 mAh g(-1) after 100 cycles at 0.2C and 149 mAh g(-1) after 200 cycles at 1C, especially, an outstanding rate performance exceeding 130 mAh g(-1) at 5C in the voltage range of 1.5-4.5 V for Li-ion batteries. Moreover, when FeF3 center dot xH(2)O/G is used as cathode material of Na-ion batteries, it exhibits also a high reversible capacity of 101 mAh g(-1) after 30 cycles in the voltage range of 1.0-4.0 V at 0.1C. Therefore, FeF3 center dot xH(2)O/G will a promising cathode material for high-performance lithium/sodium ion batteries. (C) 2015 Elsevier B.V. All rights reserved.