Ni(OH)2 nanoflakes electrodeposited on Ni foam-supported vertically oriented graphene nanosheets for application in asymmetric supercapacitors

Binderless Ni(OH)(2) nanoflakes grown on Ni foam (NF)-supported vertically oriented graphene nanosheets (V-GNs) has been fabricated as a positive electrode material for asymmetric supercapacitor (ASC), coupled with activated carbon (AC) as a counter electrode material. The introduction of V-GNs leads to dense growth of nanocrystalline beta-Ni(OH)(2) that is confirmed by X-ray diffraction, transmission electron microscopic and scanning electron microscopic analyses. The electrochemical performances of the Ni(OH)(2)/GNs/NF electrode are characterized by cyclic voltammetry and charge-discharge tests, which exhibit high specific capacitance of 2215 F g(-1) at a scan current density of 2.3 A g(-1), enhanced cycling stability and high rate capability. The Ni(OH)(2)/GNs/NF-AC-based ASC can achieve a cell voltage of 1.4 V and a specific energy density of 11.11 Wh kg(-1) at 0.5 mA cm(-2) with a nearly 100% coulombic efficiency at room temperature. (C) 2013 Elsevier Ltd. All rights reserved.