Herein we report on the hydrothermal synthesis of niobium pentoxide on carbide-derived carbon (Nb2O5/CDC) with a layered structure. The presence of phenylphosphonic acid guides the deposition during preparation, leading to the formation of amorphous Nb2O5 particles which are 4-10 nm in diameter and homogeneously distributed on the CDC framework. Electrochemical testing of the Nb2O5/CDC electrode indicated that the highest capacitance and Coulombic efficiency occurred using an electrolyte comprised of 1 M lithium perchlorate in ethylene carbonateldimethyl carbonate. Subsequent heat treatment of Nb2O5/CDC in CO2 environment led to crystallization of the Nb2O5, allowing reversible Li+ intercalation/de-intercalation. For sweep rates corresponding to charging and discharging in under 3 min, a volumetric charge of 180 C cm(-3) and Coulombic efficiency of 99.2% were attained. (C) 2014 Elsevier B.V. All rights reserved.