Nanocrystalline nickel cobalt hydroxides/ultrastable Y zeolite composite for electrochemical capacitors

A novel nanocomposite of Co(OH)(2)-Ni(OH)(2) and ultrastable Y molecular sieves was synthesized by an improved chemical precipitation method for electrochemical capacitors. The Co(OH)(2)-Ni(OH)(2)/ultrastable Y zeolite (USY) composite and its microstructure were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Electrochemical characterization was performed by cyclic voltammetry and galvanostatic charge-discharge measurements. The results show that Co(OH)(2)-Ni(OH)(2)/USY microstructure applied for the electrochemical energy storage has displayed superior capacitive performance. The effect of heat treatment conditions on specific capacitance properties was also systemically explored. Upon annealing at 250 degrees C, the maximum specific capacitance was up to 479 F/g (or 1,710 F/g after correcting for the weight percent of Co(OH)(2)-Ni(OH)(2) phase). Annealing temperatures higher than 250 degrees C may cause the hydroxide to form oxide phase and decrease the surface activity of the oxide, thereby leading to a decline of the specific capacitance.