Synthesis of hierarchical NiS microflowers for high performance asymmetric supercapacitor

In this work, the hierarchical NiS microflowers were synthesized using Ni(OH)2 as precursors through sulfuration process. The microstructure and chemical composition of as-prepared NiS was confirmed by means of SEM, TEM, XRD, BET and XPS. The SEM analysis results demonstrated that the NiS microflowers were composed of hierarchical nanoplates, and its surface was much rougher compared to that of Ni(OH)2 templates after sulfidation. Electrochemical characterization revealed that NiS presented high specific capacitance in 3 M KOH electrolyte (1122.7 F·g−1 at current density of 1 A·g−1) and good electrochemical cycling stability (97.8% of the specific capacitance is retained after 1000 charge-discharge cycles at current density of 10 A·g−1). Furthermore, an asymmetric supercapacitor, NiS as the positive electrode and activated carbon as the negative electrode, delivered high energy density of 31 Wh·kg−1 at power density of 0.9 kW·kg−1 under operating voltage window of 1.8 V.