β-NiS 3D micro-flower-based electrode for aqueous asymmetric supercapacitors†
Designing transition metal sulfide-based hierarchical microarchitectures has great importance in electrochemical supercapacitors due to their distinct morphological properties. Herein, we prepared hierarchical β-nickel sulfide (β-NiS) three-dimensional (3D) micro-flowers via a hydrothermal method. The structural and morphological properties of the prepared β-NiS materials were analyzed using various characterization techniques. A three-electrode electrochemical investigation was performed on the hierarchical β-NiS 3D micro-flower-based electrode in an aqueous alkali to demonstrate the potentiality of the material for high-performance supercapacitors. Remarkably, the fabricated β-NiS 3D micro-flower-based electrode (coated on Ni foam) exhibited a maximum specific capacitance of 1529 F g−1 at 2 A g−1 owing to the hierarchical synergetic features. At high current density (10 A g−1), the β-NiS@Ni electrode retained an 888 F g−1 capacitance value, further suggesting a good rate capability behavior of the corresponding electrode. Besides, the high-performance β-NiS@Ni was utilized as a cathode (positive) electrode to construct an aqueous asymmetric supercapacitor (ASC) device using activated carbon (AC) as an anode (negative) electrode. The designed β-NiS@Ni//AC@Ni-based ASC device showed good capacitance (136 F g−1 at 1 A g−1) and high energy density (40 W h kg−1). Finally, eleven green colored light-emitting diodes and a toy motor fan were successfully tested to explore the potential applicability of the devices in the energy storage field.