Half-cell electrochemical characterizations were conducted on carbon nanotube-vanadium oxide (CNT-VO x ) yarn electrodes in an 8 M LiCl aqueous electrolyte. A supercritical fluid deposition and in-situ oxidation process was utilized to deposit nanoscale coatings of vanadium oxide on carbon nanotube (CNT) surfaces throughout the porous structure of CNT yarns. The high surface area, interconnected pore structure and high electrical conductivity of the CNT yarn enabled extraordinary rate capabilities from the high capacity Li/VO x system. High-rate cyclic voltammetry scans, requiring current densities of hundreds of amperes per gram of electrode mass, produced rectangular voltammograms with distinguishable redox peaks from Li-ion intercalation/deintercalation. Capacitances of over 150 F g−1 were achieved at a scan rate of 5 V s−1 over a 1.2 V potential window resulting in an energy density of >32 Wh kg−1 (>30 Wh L−1) for the yarn electrode. The charge storage also showed good reversibility when cycled over this large potential window, maintaining 90% of the capacitance after 100 cycles at a scan rate of 2 V s−1. Electrochemical impedance spectroscopy shows the frequency dependent behavior is distinctly lacking of the characteristic responses from the rate-limiting processes associated with faradaic charge storage in VO x .