Supercritical carbon dioxide anchored Fe₃O₄ nanoparticles on graphene foam and lithium battery performance.

Magnetite (Fe3O4) is an attractive electrode material due to its high theoretical capacity, eco-friendliness, and natural abundance. However, its commercial application in lithium-ion batteries is still hindered by its poor cycling stability and low rate capacity resulting from large volume expansion and low conductivity. We present a new approach which makes use of supercritical carbon dioxide to efficiently anchor Fe3O4 nanoparticles (NPs) on graphene foam (GF), which was obtained by chemical vapor deposition in a single step. Without the use of any surfactants, we obtain moderately spaced Fe3O4 NPs arrays on the surface of GF. The particle size of the Fe3O4 NPs exhibits a narrow distribution (11 ± 4 nm in diameter). As a result, the composites deliver a high capacity of about 1200 mAh g(-1) up to 500 cycles at 1 C (924 mAh g(-1)) and about 300 mAh g(-1) at 20 C, which reaches a record high using Fe3O4 as anode material for lithium-ion batteries.