Improvement of electrochemical capacitor electrodes using SiO2 nanoparticles

► SiO2 nanoparticles were coated on three carbon electrodes having different surface areas. ► Gravimetric capacitance of the coated electrodes increased with increased discharge rate. ► The SiO2 coating increased the energy density at power densities exceeding 500 W/kg. ► Capacitance normalized to specific surface area was higher for the SiO2 coated electrodes.