Facile fabrication of Ni0.85Se nanowires by the composite alkali salt method as a novel cathode material for asymmetric supercapacitors

The search for Earth-abundant and efficient electrode materials is significant for advanced supercapacitors. Here we introduce a facile strategy for one-step synthesis of Ni0.85Se nanowires via a composite alkali salt method. When used as an electrode material in supercapacitors, the as-prepared Ni0.85Se nanowires exhibit a high specific capacitance of 1354 F g(-1) at a current density of 1 A g(-1), and still retain 671 F g(-1) at 30 A g(-1). The superior electrochemical performance of the Ni0.85Se electrode can be attributed to the metallic conductivity of nickel selenides and fast electrical transport along the axial direction due to the nanowire morphology. For practical applications, an asymmetric supercapacitor was assembled by using Ni0.85Se and activated carbon, which delivered a high energy density of 40.7 W h kg(-1) at a power density of 800 W kg(-1) and 12.1 W h kg(-1) at 16 kW kg(-1). Moreover, the device retained 92.4% specific capacitance after 20000 cycles at a high current density of 5 A g(-1), showing its promising application prospects.