A novel asymmetric supercapacitor with buds-like Co(OH)2 used as cathode materials and activated carbon as anode materials

In this work, Co(OH)(2) buds direct growth on Ni foam (Co(OH)(2) buds/Ni foam) is prepared via a hydrothermal method. Their structure and morphologies are characterized by using X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. Result shows that the Co(OH)(2) buds are assembled by several nanorods and uniformly covered on the surface of Ni foam. Due to its unique structure, the Co(OH)(2) buds/Ni foam electrode shows high capacitive performance and long cycle life. The specific capacitance of Co(OH)(2) buds/Ni foam is as high as 2041 F g(-1) at a current density of 3 mA cm(-2) in 6 M KOH electrolyte, and 811 F g(-1) even at a high current density of 60 mA cm(-2). The capacitance of the Co(OH)(2) buds/Ni foam electrode remained 72.4% after 1000 cycles at 18 mA cm(-2). An asymmetric supercapacitor was successfully assembled, in which Co(OH)(2) buds/Ni foam and AC used as positive and negative electrode, respectively. The energy density of the AC//Co(OH)(2) buds/Ni foam supercapacitor reaches to 20.3 W h kg(-1) at a power density of 90.6 W kg(-1). Our result shows that the Co(OH)(2) materials are promising candidate for electrochemical energy applications. (C) 2015 Elsevier B.V. All rights reserved.