Comparison between electrochemical properties of aligned carbon nanotube array and entangled carbon nanotube electrodes

Carbon nanotubes (CNTs) are promising electrochemical double-layer capacitor electrode materials because they have excellent conductivity and mesopores (2-50 nm) dominated pore structures. Electrochemical properties of an ultralong (1.0 mm) aligned carbon nanotube array (ACNTA) electrode and an entangled CNT (ECNT) electrode in ionic liquid electrolyte were studied by cyclic voltammetry, galvanostatic charge/discharge, and ac impedance. The ACNTA electrode obtains higher specific capacitance, lower equivalent series resistance, and better rate capability than the ECNT electrode. The reason is that ACNTA electrode possesses larger pore size and more regular pore structure and conductive paths, which are revealed by N-2 adsorption and scanning electron microscopy results, than ECNT electrode. (C) 2007 The Electrochemical Society.