One-Pot Synthesis of Iron Oxide Nanoblock Deposited on 3D Porous Graphene Architecture for Lithium Ion Storage

Abstract

The hierarchical architecturing and hybridization of iron oxide is very important for achieving multifunctional capability that makes it possible for practical applications. In particular, hierarchical architecturing of graphene/iron oxide hybrids in a three-dimensionally (3D) manner is expected to become an innovative chemical approach for full potential of respective functionality. In addition to intrinsic material properties, such a hierarchical structure constructed by graphene nanosheets and iron nanoparticles takes advantages of 3D interconnected macroscopic structure in terms of a large accessible area, fast mass and ion transport, percolated charge transfer, and structural integrity. In this study, hierarchically structured reduced graphene oxide (hrGO)/α-Fe2O3 nanoblock hybrids (hrGO/α-Fe) are synthesized via a one-pot, hydrothermal self-assembly process. All in one synthetic approach is very simple yet useful for simultaneously constructing 3D macroscopic rGO structures and growing α-Fe2O3 NBs. The 3D macroporous structure of hrGO/α-Fe NBhs is constructed, while α-Fe2O3 nanoblocks (NBs) in a proximate contact with the hrGO surface are simultaneously nucleated and grown during a hydrothermal treatment. The discrete α- Fe2O3 NBs are uniformly distributed on the surface of the hrGO/α-Fe and confined in the 3D architecture, thereby inhibiting the restacking of rGO layers and maximizing their functionalities. In order to demonstrate the superiority of the hrGO/α-Fe NBhs, we applied them into lithium ion battery anodes. The specific capacity of the commercial rGO/α-Fe dramatically decreased from 662.6 mAh/g at 50 mA/g to 83.6 mAh/g at 1000 mA/g with the capacity retention of 12.6%. In a sharp contrast to the commercial rGO/α-Fe, the hrGO/α-Fe NBhs exhibited better rate performance from 497.7 mAh/g to 210.3 mAh/g with the capacity retention of 42.3%. After 60 cycles at 100 mA/g, the commercial rGO/α-Fe showed highest initial discharge capacity of 566.5 mAh/g, but it was further decreased to 380.8 mAh/g (67.2%) of initial capacity. By contrast, the hrGO/α-Fe NBhs showed no capacity fading, maintaining initial capacity of 472.8 mAh/g. Despite lower coulombic efficienty and initial capacity, the hrGO/α-Fe NBhs show better rate and cyclic performances than those of commercial rGO/α-Fe due to the uniform distribution of discrete α-Fe2O3 NBs and electronic conductivity, macroporosity, and buffering effect of the hrGO for an application into lithium ion battery anode.