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

Abstract

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)0.85Se, 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 supercapacitors. Characterization results indicate that the morphologies and chemical composition of (NixCo1-x)0.85Se can be regulated by altering the reaction time. Electrochemical tests suggest that (Ni0.5Co0.5)0.85Se nanosheet arrays possess the best electrochemical properties, i.e.: a maximum specific capacity of 430.87 mA h g−1 at 1 A g−1 and good cycling stability with 85.25% capacity retention after 3000 cycles. In addition, hybrid supercapacitors based on (Ni0.5Co0.5)0.85Se nanosheet arrays and nitrogen-doped porous carbon can deliver a high energy density of 70.58 Wh kg−1 at power density of 320.02 W kg−1, as well as 91.88% capacitance retention after 8000 cycles, indicating that (Ni0.5Co0.5)0.85Se nanosheet arrays has higher applicable value in energy-storage fields.