Sandwich-structured nanocomposites of N-doped graphene and nearly monodisperse Fe₃O₄ nanoparticles as high-performance Li-ion battery anodes

Iron oxides have attracted considerable interest as abundant materials for high-capacity Li-ion battery anodes. However, their fast capacity fading owing to poorly controlled reversibility of the conversion reactions greatly hinders their application. Here, a sandwich-structured nanocomposite of N-doped graphene and nearly monodisperse Fe₃O₄ nanoparticles were developed as high-performance Li-ion battery anode. N-doped graphene serves as a conducting framework for the self-assembled structure and controls Fe₃O₄ nucleation through the interaction of N dopants, surfactant molecules, and iron precursors. Fe₃O₄ nanoparticles were well dispersed with a uniform diameter of ~15 nm. The unique sandwich structure enables good electron conductivity and Li-ion accessibility and accommodates a large volume change. Hence, it delivers good cycling reversibility and rate performance with a capacity of ~1, 227 mA·h·g^–1 and 96.8% capacity retention over 1, 000 cycles at a current density of 3 A·g^–1. Our work provides an ideal structure design for conversion anodes or other electrode materials requiring a large volume change.