Self-assembling NiCo2S4 nanorods arrays and T-Nb2O5 nanosheets/three-dimensional nitrogen-doped garphene hybrid nanoarchitectures for advanced asymmetric supercapacitor

In this study, NiCo2S4 nanorods arrays on nickel foam (NiCo2S4/NF) have been developed using a simple solvothermal method and T-Nb2O5 nanosheets/three-dimensional nitrogen-doped graphene hybrid (T-Nb2O5/3DNG) have been synthesized by hydrothermal accompanying an annealing calcination treatment. In a three-electrode system, NiCo2S4/NF nanorod and T-Nb2O5/3DNG electrodes display excellent specific capacitances of 1709.2 F g(-1) and 952.7 F g(-1) at the current density of 1 A g(-1), respectively, with the capacitance retention of 93.1% and 90.8% after 5000 cycles. Furthermore, a hybrid asymmetric supercapacitor device consisting of a binder-free NiCo2S4/NF nanorods arrays as a positive electrode and T-Nb2O5/3DNG as a negative electrode in 6 M KOH electrolyte is designed, which exhibits an expanded potential voltage window up to 1.8 V, presents extremely high capacitance of 203.4 F g(-1) at 0.5A g(-1) and a remarkable energy density of 45.4 Wh kg(-1) while delivering a power density of 9568.3 Wkg(-1). Encouragingly, the device also delivers outstanding cycling stability of 93.6% and a coulombic efficiency close to 100% after 10,000 charge-discharge cycles. This strategy for the reasonable design of the efficient positive and negative electrode materials provides a promising route for asymmetric supercapacitor and opens new avenues with production of high energy and long life capacitor equipment in modern electronic industries.