Fabrication of free-standing aligned multiwalled carbon nanotube array for Li-ion batteries

• Detachment of vertically aligned MWCNT array from Si substrate by a CCl4 treatment.
• Assembling of free-standing MWCNT array with Ni foam for Li-ion battery electrode.
• Ni foam support decreases resistance of the array in electrochemical cell.
• Higher capacity of the array in comparison with that of the disordered MWCNTs.

We show that a high-temperature CCl4 vapor treatment of vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) grown on silicon substrate allows carefully detach the array from the substrate. Moreover, this procedure partially purifies the VA-MWCNTs from the residual iron catalyst. To improve electrical connectivity of free-standing VA-MWCNTs in an electrochemical cell, the array was placed between the layers of Ni foam. Such assembly demonstrated the better performance in Li-battery as compared to the disordered MWCNTs. After 50 cycles, the specific capacity of VA-MWCNT array synthesized from 0.5 wt% ferrocene solution in toluene was 350 mAh g−1 at a current density of 0.1 A g−1, while the battery with the disordered MWCNTs achieved 197 mAh g−1 only. By the results of electrochemical impedance spectroscopy, the higher capacity of VA-MWCNTs was attributed to larger surface area available for electrolyte and Li ions due to the absence of binder coating.