Liquid Processing of Interfacially Grown Iron-Oxide Flowers into 2D-Platelets yields Lithium-ion Battery Anodes with Capacities of Twice the Theoretical Value

Iron oxide is an abundant and potentially low-cost material for fabricating lithium-ion battery anodes. Here we demonstrate the growth of a-Fe₂O₃ nano-flowers at an electrified liquid-liquid interface. Sonication can be used to convert these flowers into quasi-2D platelets with lateral sizes in the range of hundreds of nanometers and thicknesses in the range of tens of nanometers. These nanoplatelets can be combined with carbon nanotubes to form porous, conductive composites which can be used as electrodes in lithium-ion batteries. Using a standard activation process, these anodes displayed good cycling stability, reasonable rate performance and low-rate capacities approaching 1500 mAh g^-1, consistent with the current state-of-the-art for Fe₂O₃. However, we found that, by using an extended activation process, we could significantly change the morphology of these composites, rendering the iron oxide amorphous and significantly increasing the porosity and internal surface area. These morphological changes yielded anodes with very good cycling stability and low-rate capacity exceeding 2000 mAh g^-1, which is competitive with the best anode materials in the literature. However, our data implies that, after activation, the iron oxide displays a reduced solid-state lithium-ion diffusion coefficient resulting in somewhat degraded rate performance.