Facile synthesis of Ni0.85Se on Ni foam for high-performance asymmetric capacitors

Ni0.85Se was in situ grown on Ni foam via a facile hydrothermal process as a high-performance electrode for supercapacitors. The as-obtained Ni0.85Se electrode exhibited excellent electrochemical properties with a higher specific capacitance of 1115 F g(-1) (1.34 F cm(-2)) and remarkable cycling stability (91.7% of the initial capacitance value remained after 1000 cycles). An asymmetric supercapacitor was fabricated successfully based on Ni0.85Se (positive electrode) and activated carbon (negative electrode). The Ni0.85Se//AC ASC can expand the operating voltage as high as 1.6 V, which led to an ultrahigh energy density of 32.2 Wh kg(-1) at a power density of 789.6 W kg(-1). Further, the ASC had a highlight cycle performance (only 1.7% of CT loss after 2000 cycles), so it holds promise as a potential candidate for energy storage devices.