Hierarchical core-shell structure of NiCo2O4 nanosheets@HfC nanowires networks for high performance flexible solid-state hybrid supercapacitor

Abstract

• The hierarchical free-standing core-shell NiCo 2 O 4NSs @HfC NWs /CC was obtained. • HfC NWs network was used as the superhighway for electron transport. • NiCo 2 O 4NSs @HfC NWs /CC exhibits excellent electrochemical properties. • The hybrid supercapacitor shows good performance stability and flexibility. Rationally constructing the electrode with the hierarchical structure, different components, and the flexibility is a promising approach to further improve the electrochemical properties and meet the demand for flexible electronic devices. In this paper, for the first time, hafnium carbide nanowires (HfC NWs ) networks, with the metrics of large specific surface area, excellent conductivity, and chemical/physical stability, are served as nanoscale conductive skeletons on carbon cloth (CC) for supporting the porous NiCo 2 O 4 nanosheets (NSs). Benefiting from the structural advantages, the as-formed free-standing core-shell NiCo 2 O 4NSs @HfC NWs /CC exhibits a high specific capacitance of 2102 F g −1 at a current density of 1 A g −1 , good rate capability (85% capacitance retention at 20 A g −1 ) and outstanding cycling stability (98% capacitance retention after 5000 cycles at 10 A g −1 ). Additionally, assembled with the NiCo 2 O 4NSs @HfC NWs /CC and activated carbon (AC)/CC, the flexible solid-state hybrid supercapacitor displays a high energy density of 53 Wh kg −1 at a power density of 800 W kg −1 and excellent performance stability with good flexibility. More impressively, our work could not only further widen the application of HfC NWs , but also put forward the new thinking of rational construction of high-performance flexible supercapacitors.