Abstract: The composite electrodes consisting of carbon nanotubes and spherical Ni(OH)₂ are developed by mixing nickel hydroxide, carbon nanotubes and carbonyl nickel powder together in 8׃1׃1 ratio. A maximum capacitance of 311 F/g is obtained for an electrode prepared with the precipitation process. In order to enhance energy density, an asymmetric type pseudo-capacitor/electric double layer capacitor is considered and its electrochemical properties are investigated. Values for the specific energy and maximum specific power of 25.8 W∙h/kg and 2.8 kW/kg, respectively, are demonstrated for a cell voltage between 0 and 1.6 V. By using the modified cathode of a Ni(OH)₂/carbon nanotube composite electrode, the asymmetric supercapacitor exhibits high energy density and stable power characteristics.

Key words: nickel hydroxide; carbon nanotubes; activated carbon; asymmetric supercapacitor