Asymmetric supercapacitors based on stabilized α-Ni(OH)2 and activated carbon

In this work, stabilized Al-substituted alpha-Ni(OH)(2) materials were successfully synthesized by a chemical coprecipitation method. The experimental results showed that the 7.5% Al-substituted alpha-Ni(OH)(2) materials exhibited high specific capacitance (2.08 x 10(3) F/g) and excellent rate capability due to the high stability of Al-substituted alpha-Ni(OH)(2) structures in alkaline media, suggesting its potential application in electrode material for supercapacitors. To enhance energy density, an asymmetric type pseudo/electric double-layer capacitor was considered where alpha-Ni(OH)(2) materials and activated carbon act as the positive and negative electrodes, respectively. Values for the maximum specific capacitance of 127 F/g and specific energy of 42 W center dot h/kg were demonstrated for a cell voltage between 0.4 and 1.6 V. By using the alpha-Ni(OH)(2) electrode, the asymmetric supercapacitor exhibited high energy density and stable power characteristics. The hybrid supercapacitor also exhibited a good electrochemical stability with 82% of the initial capacitance over consecutive 1,000 cycle numbers.