Fabrication of hierarchical NiCo2S4 nanotubes@NiMn-LDH nanosheets core-shell hybrid arrays on Ni foam for high-performance asymmetric supercapacitors

Abstract

The present study successfully synthesized NiCo2S4 nanotubes@NiMn-LDH nanosheets core-shell hybrid structure on Ni foam through a controllable three-step facile hydrothermal method, the NiMn-layered double hydroxides (LDHs) nanosheets with unlike thicknesses adhere to the outer layer of NiCo2S4 nanotubes by adjusting the heating time of hydrothermal reaction. The optimized NiCo2S4@NiMn-LDH electrode was able to transmit a high specific capacity of 822.64 C g−1 (4.36 C cm−2) at a high current density of 50 mA cm−2, and maintained 92.7% of its initial specific capacity after 5000 cycles at a current density of 50 mA cm−2 when 2 M KOH was used as the electrolyte. Furthermore, an asymmetric supercapacitor (ASC) device fabricated with NiCo2S4@NiMn-LDH as the positive electrode and activated carbon (AC) as the negative electrode, and it achieved a maximal energy density of 53.10 W h kg−1 at a power density of 370.82 W kg−1 also maintained 94.3% retention of the initial specific capacitance after 10,000 cycles at a high current density of 20 mA cm−2. With the excellent electrochemical properties, the as-prepared core-shell structured NiCo2S4@NiMn-LDH hybrid arrays have extraordinary application potential in the energy storage field.