Nickel-shell assisted growth of nickel-cobalt hydroxide nanofibres and their symmetric/asymmetric supercapacitive characteristics

Using polyurethane foam as template, we introduce a facile method to synthesize cost-effective macroporous nickel-shell (NS) which plays vital role in the synthesis of alpha-Ni-Co(OH)(2). Nanofibrous morphology of alpha-Ni-Co(OH)(2) is obtained by the aid of polyethylene glycol (structure directing reagent) and no precipitating agent is used. Our results indicate that no metal (Ni/Co) hydroxides can be synthesized if NS is isolated from the reaction vessel which ensures the role of NS in formation of alpha-Ni-Co(OH)(2) nanofibres. Prepared alpha-Ni-Co(OH)(2)@NS electrode shows a typical enhanced interlayer spacing (similar to 8.0 angstrom) which results in significantly high specific capacitance (2962 F g(-1) at 5 mV s(-1)). Furthermore, the symmetric supercapacitor cell (alpha-Ni-Co(OH)(2)@NS parallel to alpha-Ni-Co(OH)(2)@NS) exhibits a maximum specific capacitance of 668 F g(-1) with coulombic efficiency similar to 98% over 3000 charge/discharge cycles at high current density (4 A g(-1)). The energy and power density obtained for alpha-Ni-Co(OH)(2)@NS parallel to alpha-NiCo(OH)(2)@NS cell are 18.2 Wh kg(-1) at 242 W kg(-1) and 1980 W kg(-1) at 5.5 Wh kg(-1) respectively. Moreover, in asymmetric supercapacitor using lacey reduced graphene oxide nanoribbon (LRGONR) as a negative electrode, a remarkable increase in energy (107 Wh kg(-1) at 1610 W kg(-1)) and power density (7 kW kg(-1) at 42 Wh kg(-1)) is observed. (C) 2016 Elsevier B.V. All rights reserved.