Three-dimensional Co3O4@C@Ni3S2 sandwich-tructured nanoneedle arrays: towards high-performance flexible all-solid-state asymmetric supercapacitors

In this paper, we report the design and fabrication of a novel hierarchical Co3O4@C@Ni3S2 sandwich-structured nanoneedle array (NNA) electrode for supercapacitor application. The supercapacitor performance based on Co3O4@C@Ni3S2 NNA electrodes is investigated in detail. A lightweight and flexible asymmetric supercapacitor (ASC) is successfully fabricated using Co3O4@C@Ni3S2 NNAs as the positive electrode and activated carbon (AC) as the negative electrode, which delivers an output voltage of 1.8 V and high energy/power density (1.52 mW h cm(-3) at 6 W cm(-3) and 0.920 mW h cm(-3) at 60 W cm(-3)), as well as remarkable cycling stability (similar to 91.43% capacitance retention after 10 000 cycles), owing to the unique 3D porous sandwich-structured nanoneedle array architecture and a rational combination of the three electrochemically active materials. As a result, the ternary hybrid architectural design demonstrated in this study provides a new approach to fabricate high-performance metal oxide/sulfide composite nanostructure arrays for next-generation energy storage devices.