Fe3O4 nanocrystals confined in mesocellular carbon foam (MSU-F-C) are synthesized by a "host-guest" approach and tested as an anode material for lithium-ion batteries (LIBs). Briefly, an iron oxide precursor, Fe(NO3)3·9H2O, is impregnated in MSU-F-C having uniform cellular pores ∼30 nm in diameter, followed by heat-treatment at 400 °C for 4 h under Ar. Magnetite Fe3O 4 nanocrystals with sizes between 13-27 nm are then successfully fabricated inside the pores of the MSU-F-C, as confirmed by transmission electron microscopy (TEM), dark-field scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and nitrogen sorption isotherms. The presence of the carbon most likely allows for reduction of some of the Fe3+ ions to Fe2+ ions via a carbothermoreduction process. A Fe3O4/MSU-F-C nanocomposite with 45 wt% Fe3O4 exhibited a first charge capacity of 1007 mA h g-1 (Li+ extraction) at 0.1 A g -1 (∼0.1 C rate) with 111% capacity retention at the 150 th cycle, and retained 37% capacity at 7 A g-1 (∼7 C rate). Because the three dimensionally interconnected open pores are larger than the average nanosized Fe3O4 particles, the large volume expansion of Fe3O4 upon Li-insertion is easily accommodated inside the pores, resulting in excellent electrochemical performance as a LIB anode. Furthermore, when an ultrathin Al2O 3 layer (<4 Å) was deposited on the composite anode using atomic layer deposition (ALD), the durability, rate capability and undesirable side reactions are significantly improved. Fe3O4 nanocrystals confined in mesocellular carbon foam (MSU-F-C) exhibit capacities larger than 1000 mA h g-1 at 0.1 A g-1 with excellent cycling performance and rate capability as an anode material for lithium-ion batteries. The combined effect of nanosized Fe3O4, extra pore volume to accommodate volume expansion of Fe3O4, and large three dimensional interconnected mesoporous carbon pores with excellent electronic connectivity accounts for the excellent performance.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics