Superior high-rate capability of hierarchically structured flower-like magnetite-carbon-graphene composite for Li-ion anode

A nano/micro hierarchical composite structure is prepared by solvothermal synthesis from iron alkoxide in an inert atmosphere. It consists of graphene sheet and flower-like Fe3O4 particle covered by carbon coating (designated as Fe3O4@C). The synthesized composite is an excellent anode for Li-ion batteries. This is attributed to its double structure of current collector. High reversible lithium storage capacity (1439 mA h/g at 0.2 C after 47 cycles) and superior high-rate capability (619 mA h/g at 5 C) are examples of this property. The carbon coating of the Fe3O4@C is in direct contact with the Fe3O4 particles to form local conductive connections, Fe3O4@C tightly covering graphene sheets can be employed as the current collector as well as bridge connection of the Fe3O4@C particles. Therefore, the double structure of current collector can form superior-conductivity networks, providing an efficient electron transport between active materials and Cu current collectors. This double structure prevents the break down of electric connection between the active material and the current collector during protracted cycles of charge and discharge.