Nickel\nCobalt Hydroxide @Reduced Graphene Oxide Hybrid Nanolayers for High\nPerformance Asymmetric Supercapacitors with Remarkable Cycling Stability

Abstract

Nanolayered structures present significantly\nenhanced electrochemical performance by facilitating the surface-dependent\nelectrochemical reaction processes for supercapacitors, which, however,\ncauses capacitance fade upon cycling due to their poor chemical stability.\nIn this work, we report a simple and effective approach to develop\na stable, high performance electrode material by integrating 2D transition\nmetal hydroxide and reduced graphene oxide sheets at nanometer scale.\nSpecifically, a hybrid nanolayer of Ni–Co hydroxide @reduced\ngraphene oxide (Ni,Co–OH/rGO) with an average thickness of\n1.37 nm is synthesized through an easy one-pot hydrothermal method.\nBenefiting from the face to face contact model between Ni–Co\nhydroxide and rGO sheets, such unique structure presents superior\nspecific capacitance and cycling performance as compared to the pure\nNi–Co hydroxide nanolayers. An asymmetric supercapacitor based\non Ni,Co–OH/rGO and three-dimensional (3D) hierarchical porous\ncarbon is developed, exhibiting a high energy density of 56.1 Wh kg^–1 along with remarkable cycling stability (80% retention\nafter 17 000 cycles), which holds great promise for practical\napplications in energy storage devices.