Doping is an effective way to improve the conductivity and capacitance of materials. Its effect depends on two factors: electronegativity and ionic radius. When the radius and valence state of the doped ions are similar, no obvious lattice distortion will result and the original crystal structure will remain unchanged as a result of doping. With proper doped ions, high electric negative ions tend to improve the conductivity of the material as against low electronegative ions. This study takes Co ion doped alpha-Ni(OH)(2) as the research direction. The test results exhibit a high specific capacitance of 2879.76 F g(-1) (1295.89 C g(-1)) at a current density of 1 A g(-1). Furthermore, Co doped alpha-Ni(OH)(2)//AC asymmetric supercapacitor is assembled, and an excellent energy density of 111.87Wh kg(-1) can be achieved under the power density of 225 W kg(-1). (C) 2018 Published by Elsevier Ltd.