Ternary nickel-cobalt selenide nanosheet arrays with enhanced electrochemical performance for hybrid supercapacitors

Ternary nickel-cobalt compounds with nano-arrayed structures can be used as promising electrodes to obtain high-performance electrochemical energy storage devices. Thus, ternary nickel-cobalt selenide, (NixCo1-x)(0.85)Se, nanosheet arrays are successfully synthesized via a two-step method consisting of hydrothermal and cation-exchange process, then directly used as binder-free electrodes for super-capacitors. Characterization results indicate that the morphologies and chemical composition of (NixCo1-x)(0.85)Se can be regulated by altering the reaction time. Electrochemical tests suggest that (Ni0.5Co0.5)(0.85)Se nanosheet arrays possess the best electrochemical properties, i.e.: a maximum specific capacity of 430.87 mA h g(-1) at 1 Ag-1 and good cycling stability with 85.25% capacity retention after 3000 cycles. In addition, hybrid supercapacitors based on (Ni0.5Co0.5)(0.85)Se nanosheet arrays and nitrogen-doped porous carbon can deliver a high energy density of 70.58 Wh kg(-1) at power density of 320.02W kg(-1), as well as 91.88% capacitance retention after 8000 cycles, indicating that (Ni0.5Co0.5)(0.85)Se nanosheet arrays has higher applicable value in energy-storage fields. (C) 2018 Elsevier B.V. All rights reserved.