One-step sulfuration synthesis of hierarchical NiCo2S4@NiCo2S4 nanotube/nanosheet arrays on carbon cloth as advanced electrodes for high-performance flexible solid-state hybrid supercapacitors

To obtain high-performance hybrid supercapacitors (HSCs), a new class of battery-type electrode materials with hierarchical core/shell structure, high conductivity and rich porosity are needed. Herein, we propose a facile one-step sulfuration approach to achieve the fabrication of hierarchical NiCo2S4@NiCo2S4 hybrid nanotube/nanosheet arrays (NTSAs) on carbon cloth, by taking hydrothermally grown Ni–Co precursor@Ni–Co precursor nanowire/nanosheet arrays (NWSAs) as the starting templates. The optimized electrode of NiCo2S4@NiCo2S4 hybrid NTSAs demonstrates an enhanced areal capacity of 245 μA h cm−2 at 2 mA cm−2 with outstanding rate capability (73% from 2 to 20 mA cm−2) and cycling stability (86% at 10 mA cm−2 over 3000 cycles). In addition, flexible solid-state HSC devices are assembled by using NiCo2S4@NiCo2S4 hybrid NTSAs and activated carbon as the positive and negative electrodes, respectively, which manifest a maximum volumetric energy density of 1.03 mW h cm−3 at a power density of 11.4 mW cm−3, with excellent cycling stability. Our work indicates the feasibility of designing and fabricating core/shell structured metal sulfides through such a facile one-step sulfuration process and the great potential of these materials as advanced electrodes for high-performance HSC devices.