Electrophoretic deposition of nickel oxide electrode for high-rate electrochemical capacitors

Nanostructured nickel hydroxide electrode is fabricated directly by electrophoretic deposition (EPD) method. After annealing at 300 °C for 3 h, nickel hydroxide nanoplatelet converts into nickel oxide. EPD method is useful in depositing nickel hydroxide nanoplatelets from isopropyl alcohol suspension containing iodine and water additives. Hydrogen ions are generated by the reaction between iodine and water and then adsorbed on the nickel hydroxide, resulting in positively charged nickel hydroxide. Positively charged nanoplatelet of high zeta potential is beneficial to EPD and dispersion. An electrode deposited by EPD has better uniformity than one deposited by dip coating. Electrochemical performance of the electrodes is investigated by cyclic voltammetry in 0.5 M KOH. Specific capacitance of the nickel oxide electrode prepared by EPD is higher than that of prepared by dip coating even at a very high rate of 500 mV s−1. In addition, an electrode prepared by EPD also shows excellent cycle-life stability because its specific capacitance decreases only slightly after 5000 charging/discharging cycles.