Wide potential window and high specific capacitance triggered via rough NiCo2S4 nanorod arrays with open top for symmetric supercapacitors

NiCo2S4 is generally studied as cathode material for supercapacitors owing to its electrochemical activity in positive voltage region (i.e., 0-0.6 V). Here, we demonstrate it can be used as supercapacitor anodes in potential window of −1∼0 V in 1 M KOH. NiCo2S4 nanorod arrays (NiCoS NRAs) with open top are synthesized through a facile two-step method, delivering high capacitive property of 494 F g-1 at 5 mA cm−2 as anode for supercapacitors. By contrary, when tested in positive potential window (0-0.6 V), the NiCoS NRAs show a maximum specific capacitance of ∼800 F g-1 at 12 mA cm−2. Symmetric supercapacitors (SSCs) which are configurated by both NiCoS NRAs cathode and anode distinctly extend the working potential window (1.6 V) and deliver high energy density of 55.1 Wh kg−1 and power density of 3200 W kg−1, respectively.