Hybrids of iron oxide/ordered mesoporous carbon as anode materials for high-capacity and high-rate capability lithium-ion batteries

Abstract

A hybrid of iron oxide nanoparticle modified ordered mesoporous carbon (OMC) was successfully prepared via a controllable two-step route. Electrochemical lithium storage experimental results reveal that the FeO_x/OMC composites can effectively reduce the capacity decay caused by volume change, and decrease the irreversible capacity of ordered mesoporous carbon. The first discharge capacities of FeO_x/OMC and OMC are 1718 mA h g⁻¹ and 1685 mA h g⁻¹, respectively, while the first charge capacities of the FeO_x/OMC and OMC electrodes are 1004 mA h g⁻¹ and 528 mA h g⁻¹, respectively. Apparently, the FeO_x/OMC hybrids display a higher reversible capacity of more than 660 mA h g⁻¹ and higher initial coulombic efficiency (58.4%). More importantly, at high charge–discharge rates, even at a current density of 1600 mA g⁻¹, the capacity of the FeO_x/OMC electrode is still maintained at 320 mA h g⁻¹ even after 50 cycles, almost 5.4 times higher than the capacity of 50 mA h g⁻¹ for the pure OMC sample. The high rate of performance is important for applications where fast charge and discharge are needed. The prominent improvement of electrochemical performance can be attributed to the synergistic effects of the FeO_x/OMC composites. The FeO_x nanoparticles can reduce the large amounts of active sites due to the high specific surface of the OMC, which results in a high irreversible capacity. While the OMC in the composite not only provides an elastic buffer space to accommodate the volume expansion/contraction of FeO_x nanoparticles during the Li ions insertion/extraction process, but also efficiently prevents crumbling of electrode material upon continuous cycling, thus maintaining large capacity, good Coulombic efficiency, high rate capability and cycling stability. Furthermore, the OMC in the composite with good electrical conductivity can serve as the conductive channels between FeO_x nanoparticles. This excellent electrochemical performance of the FeO_x/OMC hybrid makes it a candidate anode material for commercial lithium-ion batteries.