Multiwalled carbon nanotubes (MWCNTs) were longitudinally split to be unzipped by a facile chemical oxidative etching. Transmission electron microscope images and Raman spectra confirmed that most of MWCNTs were opened and some were transformed to multi-layered graphene nanoribbons. Scanning electron microscope images showed that unzipped carbon nanotubes (UCNTs) were interwined each other to form a tridimensional porous film. The N-2 adsorption/desorption analysis showed that the UCNTs had larger specific surface area and more mesopores compared to MWCNTs. The galvanostatic chargedischarge experiments showed that the reversible capacity of UCNTs were up to 765 mAh g(-1) at 0.1 A g-1 and kept 635 mAh g(-1) at various current densities. The reversible capacity remained stable around 420 and 330 mAh g(-1) at current rates of 0.6 and 1 A g(-1) with coulombic efficiency above 99% over 300 cycles. (C) 2014 Elsevier Ltd. All rights reserved.