Unusual formation of α-Fe2O3 hexagonal nanoplatelets in N-doped sandwiched graphene chamber for high-performance lithium-ions batteries

Abstract

Nowadays, 2D nanosheets or nanoplatelets have attracted great attention due to their wide applications. However, the synthesis of 2D α-Fe<inf>2</inf>O<inf>3</inf> nanosheets with well-defined hexagonal shape is extremely challenging, because the selective growth along one specific facet is very hard to be realized. In our work, we studied the non-capping ligand mediated reaction within graphene layer chamber, and successfully synthesized α-Fe<inf>2</inf>O<inf>3</inf> hexagonal nanoplatelets sandwiched between graphene layers (HP-Fe-G). These materials exhibit an improved electrochemical performance compared with the pre-existing α-Fe<inf>2</inf>O<inf>3</inf> nanoparticles loaded graphene (G-Fe<inf>2</inf>O<inf>3</inf>) composites because of the uniqueness of such architectures: thin nanoplatelets, large enough sandwiched spaces to buffer the volume expansion and N-doped graphene. HP-Fe-G delivered an ultrahigh reversible capacity of 1100mAh/g after 50 cycles, thus higher than their theoretical value (926mAh/g); while G-Fe<inf>2</inf>O<inf>3</inf> composites showed relatively low capacity retention even after only 20 cycles (582mAh/g). In addition, HP-Fe-G also reveal superior rate capability, 887mAh/g at 1C; in comparison, this value was only 135mAh/g at 1C for G-Fe<inf>2</inf>O<inf>3</inf>. © 2012 Elsevier Ltd.