Preparation of a hollow cube NiCo2S4 and its application in supercapacitor

Here reports a hollow cube NiCo2S4 nanomaterial, which was prepared via facile hydroxylation and sulfuration steps using the self-prepared ZIF-67 as a precursor. This kind of NiCo2S4 as an electrode material for supercapacitor presents a specific capacitance high up to 1350 F g(-1) at 1 A g(-1) due to the contribution of pseudocapacitance. Particularly, the hybrid supercapacitor PC//NiCo2S4, assembled using the NiCo2S4 as the positive electrode material and the PC as the negative electrode material, delivers a high energy density of 33 Wh kg(-1) at the power density of 800 W kg(-1). Meanwhile, it presents a good cyclic stability with 67% capacitance retention after 10,000 cycles of charge-discharge at the current density of 5 A g(-1). However, the rate capability is not good enough because of the polarization effect of NiCo2S4 as a battery-type electrode material. Therefore, this research provides a reference for enhancing capacitance performance of an electrode material. For instance, reversibility in redox reaction and stability in structure are more important than the capacity in many cases.