Graphene-nanosheet wrapped cobalt sulphide as a binder free hybrid electrode for asymmetric solid-state supercapacitor

A binder-free graphene-nanosheets wrapped Co3S4 hybrid electrode is prepared on conductive Ni-foam via a simple two-step hydrothermal process. The physicochemical characterization such as X-ray diffraction, Raman spectroscopy, and electron microscopy revealed the formation of a Co3S4-rGO hybrid electrode with a large specific surface area (30 m(2) g(-1)). The integrated structure of the Co3S4-rGO hybrid electrode exhibits an areal and specific capacitance of 8.33 F cm(-2) and 2314 F g(-1), respectively. The Co3S4-rGO hybrid electrode charges within 30 s, while the energy density remains high as 54.32 Wh kg(-1) at an outstanding power density of 6.25 kW kg(-1) with 92.6% excellent electrochemical cyclic stability over 1000 cycles. The asymmetric supercapacitor device is fabricated using Co3S4 and Co3S4-rGO as positive and negative electrodes, respectively, which exhibit an areal capacitance of -164 mF cm(-2) with reasonable cyclic stability (89.56% over 5000 cycles). The Co3S4/Co3S4-rGO supercapacitor reveals a high energy density of 1.09 Wh kg(-1) at a power density of 398 W kg(-1), and 0.31 Wh kg(-1) energy density can be retained even at a power density of 750 W kg(-1). The superior electrochemical activities of the Co3S4 based electrode suggest considerable promise for high-performance energy storage applications. (C) 2016 Elsevier B.V. All rights reserved.