▎ 摘　　要

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 similar to 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 similar to 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.