A free-standing NiMoO4@Mg-Co(OH)F core-shell nanocomposites supported on Ni foam for asymmetric supercapacitor applications

In this paper, a facile hydrothermal treatment method was employed to successfully synthesize the NiMoO4@Mg-Co(OH)F/NF (NM-MCF) nanocomposites by taking NiMoO4 nanorods as cores, and assembling them with the shell of Mg-Co(OH)F nanosheets. The high conductivity of Mg-Co-F was combined with the nanosheet-assembled core-shell structure, and the multivalent states of Ni, Mg, and Co increased the number of active sites and improved the synergy, contributing greatly to excellent performance of NM-MCF. As expected, the optimized NM-MCF nanocomposite electrode exhibits superb capacitive performance, including excellent specific capacitance of 1630 F g −1 at 1 A g −1 and remarkable cycle stability with 86 % after 6000 cycles. Notably, the NM-MCF exhibits a regular rate capability of 56.5 % from 1 to 15 A g−1, superior to that of NiMoO4 (56.4 %) and Mg-Co(OH)F (28.8 %). Employing the as-prepared NM-MCF composites as positive electrode and activated carbon as negative electrode, the hybrid supercapacitor device with spectacular capacity of maximum energy density and power density up to 28.2 Wh kg−1 and 0.7 kW kg−1 and impressive long-term stability of 73.3 % retention after 6000 cycles is assembled.