Ultra-dispersed island-like Co9S8 nanoparticles composed of nanosheets in-situ grown on nitrogen-doped graphene for asymmetric supercapacitor

Island-like Co9S8 nanoparticles composed of two-dimensional (2D) Co9S8 nanosheets in-situ grew and were dispersed evenly on the surface of 2D N-doping graphene (NGR), which produced the Co9S8@NGR nanocomposites using a simple solvothermal method. In this solvothermal process, graphene oxides were reduced and doped with nitrogen (N) simultaneously. The Co9S8@NGR nanocomposites delivered an ultra-high specific capacitance of 2992 Fg(-1) in a potential window of 0.5 Vat 1 A g(-1). Moreover, an asymmetric supercapacitor (ASC) constructed by Co9S8@NGR as the positive electrode and by activated carbon (AC) as the negative electrode showed the density of 88.81 W h kg(-1) at a power density of 0.63 kW kg(-1), the power density of 21.80 kW kg(-1) at the energy density of 30.30 W h kg(-1), and the favorable cycle stability with 80.61% specific capacity retention at a current density of 10 A g(-1) after 10000 cycles. (C) 2018 Elsevier Ltd. All rights reserved.