Metal–organic framework-templated synthesis of sulfur-doped core–sheath nanoarrays and nanoporous carbon for flexible all-solid-state asymmetric supercapacitors

Metal-organic frameworks (MOFs) provide great opportunities for synthesizing advanced electrode materials with hierarchical hollow architectures for energy storage. Herein, we report the facile fabrication of core-sheath nanoarrays (NAs) on carbon cloth (CC@CoO@S-Co3O4) for binder-free electrode materials with MOFs as versatile scaffolds. The hollow S-doped Co3O4 sheath has been facilely prepared using a two-step synthetic protocol, which includes the surface etching of CoO nanowires for synchronous in situ growth of well-aligned ZIF-67 and its following hydrothermal process. The synergistic effect between CC nanofibers and hollow ordered NAs ensures efficient mass and electron transport. The pseudocapacitive NAs present a highest areal specific capacitance of 1013 mF cm-2 at 1 mA cm-2. By assembling the same MOF-derived nanoporous carbons and NAs as the corresponding binder-free anode and cathode, the flexible all-solid-state asymmetric supercapacitors deliver a highest energy density of 0.71 mW h cm-3 at 21.3 mW cm-3 power density, together with 87.9% capacitance retention over 5000 continuous cycles.