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An open-framework iron fluoride and reduced graphene oxide nanocomposite as a high-capacity cathode material for Na-ion batteries

Cathode materials with high capacity and good stability for rechargeable Na-ion batteries (NIBs) are few in number. Here, we report a composite of electrochemically active iron fluoride hydrate and reduced graphene oxide (rGO) as a promising cathode material for NIBs. Phase-pure FeF3·0.5H2O is synthesized by a non-aqueous precipitation method and a composite with rGO is prepared to enhance the electrical conductivity. The encapsulation of FeF3·0.5H2O nanoparticles between the rGO layers results in a lightweight and stable electrode with a three-dimensional network. The composite material delivers a substantially enhanced discharge capacity of 266 mA h g−1 compared to 158 mA h g−1 of the bare FeF3·0.5H2O at a current density of 0.05 C. This composite also shows a stable cycle performance with a high capacity retention of >86% after 100 cycles, demonstrating its potential as a cathode material for NIBs.