Synthesis and electrochemical performance of vertical carbon nanotubes on few-layer graphene as an anode material for Li-ion batteries

Abstract

Bulk graphite is widely used in today's Li-ion batteries as an anode material due to its high cycling stability. However, graphite's low capacity and rate capability prevent its application in high power density batteries. Here, a nanostructured carbon, consisting of vertical carbon nanotubes on few-layer graphene, has been synthesized and tested as an anode material for high capacity Li-ion batteries. In this synthesis, a simple hydrothermal method was used to assemble homogeneous distributed Fe2O3 nanoparticles on few-layer graphene based on van der Waals interaction, and these were then used as a catalyst to grow carbon nanotubes further by means of a chemical vapor deposition method. The electrochemical properties of the nanocomposites were measured. A reversible capacity of 525 mAh g−1 after 1000 cycles at 500 mA g−1 with Coulombic efficiency in excess of 98% was accomplished. Voids between vertical carbon nanotubes provide a short diffusion path for both electron and Li-ion, and the defects in carbon nanotubes provide more storage sites for lithium. Three kinds of nanocomposites with different carbon nanotube diameters were synthesized and characterized. The influence of the carbon nanotube diameter and morphology on the lithium storage properties of these nanocomposites was also studied.