Encapsulation of a Core-Shell Porous Fe3O4@Carbon Material with Reduced Graphene Oxide for Li+ Battery Anodes with Long Cyclability.

Anode materials are critical for energy devices based on Li-ion batteries (LIBs). This work reports on a facile method to produce anodes based on carbon-coated Fe3O4 (CP-Fe3O4) that is encapsulated in reduced graphene oxide (rGO) layers forming a porous core-shell structure Fe3O4@carbon (rGO-CP-Fe3O4). First, Fe3O4 particles were coated with carbon by hydrothermal and carbothermal reduction methods leading to an intermediate product termed CP-Fe3O4. Next, CP-Fe3O4 was encapsulated by two-dimensional layered rGO to obtain CP-Fe3O4 composites with a three-dimensional structure. The Fe3O4 volume expansion during LIB cycling was inhibited by carbon and rGO and a three-dimensional electron transport network was generated by the introduction of rGO. The rGO-CP-Fe3O4 composite showed excellent electrochemical properties (839 mA h g-1 at 0.3 A g-1 after 200 cycles) and rate capacities (165 mA h g-1 at 6.0 A g-1). In addition, the rGO-CP-Fe3O4 pseudocapacitance was equal to 65% of the overall capacity at 5 mV s-1.