A general strategy toward graphene@metal oxide core-shell nanostructures for high-performance lithium storage

We demonstrate a simple, efficient, yet versatile method for the realization of core-shell assembly of graphene around various metal oxide (MO) nanostructures, including nanowires (NWs) and nanoparticles (NPs). The process is driven by (i) the ring-opening reaction between the epoxy groups and amine groups in graphene oxide (GO) platelets and amine-modified MO nanostructures, respectively, and (ii) electrostatic interaction between these two components. Nearly every single NW or NP is observed to be wrapped by graphene. To the best of our knowledge, this is the first report that substrate-supported MO NWs are fully coated with a graphene shell. As an example of the functional properties of these compound materials, the graphene at α-Fe₂O₃ core-shell NPs are investigated as the lithium-ion battery (LIB) electrode, which show a high reversible capacity, improved cycling stability, and excellent rate capability with respect to the pristine α-Fe₂O ₃. The superior performance of the composite electrode is presumably attributed to the effectiveness of the graphene shell in preventing the aggregation, buffering the volume change, maintaining the integrity of NPs, as well as improving the conductivity of the electrode.