For applications that require power densities greater than 500 W/kg, electrochemical capacitors are better suited than batteries because of their high power and long cycle life, but improvement in their energy density is still desired. Creating sophisticated surface morphologies and utilizing faradaic materials have been successful in improving the energy density of electrochemical capacitors. However, to our knowledge, there have been no studies exploring coating carbon material with non-transition metal oxides as a means to improve energy storage of electrochemical capacitors. By utilizing SiO2 nanoparticles coated on a variety of carbon substrates, we can increase the energy density of electrochemical capacitors between 10% and 29% at 500 W/kg and between 30% and 85% at 1000 W/kg in organic electrolytes. We have also shown that these coatings can increase the capacitance normalized to specific surface area between 39% and 47%. (C) 2011 Elsevier Ltd. All rights reserved.