The electrochemical performance of carbon nanotube array (CNTA) and entangled carbon nanotube (ECNT) electrodes are studied as anodes for Li-ion batteries. CNTA anodes display higher capacity (373 mAh g(-1)) and much better rate and cycle performances than ECNT anodes. The performance of CNTA electrode shows length dependencies, i.e., shorter CNTA electrodes present higher specific capacity and better rate performance. The energy storage characteristics of CNTA electrodes are discussed on the basis of experimental results of SEM, TEM, and Raman spectra. The inner graphene layers of CNTs in CNTA electrode, which can form electron conductive paths and ensure a high conductivity, are retained during Li-ion insertion/extraction. These mechanically robust inner graphene layers can avoid the loss of outer active materials during Li-ion insertion/extraction, which, in turn, results in a good cycle performance. (C) 2010 Elsevier Ltd. All rights reserved.