Self-supported Co-Ni-S@CoNi-LDH electrode with a nanosheet-assembled core-shell structure for a high-performance supercapacitor

In this work, a nanosheet-assembled core-shell structure composite of Co-Ni-S@CoNi-LDH was prepared on Ni foam via hydrothermal synthesis , in which Co-Ni-S nanowires as cores were assembled with the shell of CoNi-LDH nanosheets. The combination of the high conductivity of Co-Ni-S, the high specific surface area of CoNi-LDH and the multivalent state of Ni and Co provided more active sites, short and effective ion transport paths, and great synergy, which played significant roles in the excellent performance of Co-Ni-S@CoNi-LDH. Meanwhile, the nanosheet-assembled core-shell structure improved the overall stability. Based on the characterisation and the performance measurements, the Co-Ni-S@CoNi-LDH electrode showed an excellent electrochemical performance. The Co-Ni-S@CoNi-LDH electrode acquired a specific capacitance of 2414 F/g at a 1 A/g current density and a high cycle stability with an 89.7% retention after 3000 cycles. The assembled hybrid supercapacitor Co-Ni-S@CoNi-LDH//AC delivered a high energy density of 59.11 Wh kg −1 at an 855.43 W kg −1 power density, as well as an excellent rate performance of 81% after 5000 cycles at a 5 A/g current density, showing good potential for practical applications.