Hierarchical Co₃O₄@Co₉S₈ nanowall structures assembled by many nanosheets for high performance asymmetric...

Herein, we report hierarchical Co₃O₄@Co₉S₈ nanowalls assembled by many nanosheets. The as-synthesized products are characterized in detail using various characterization methods. They can be directly used as supercapacitor electrodes with excellent electrochemical performance due to the synergy effect between Co₃O₄ and Co₉S₈. Furthermore, a flexible asymmetric supercapacitor is fabricated by using the as-synthesized Co₃O₄@Co₉S₈ structures as the cathode and the active carbon as the anode, which reveals a specific capacitance of 266.6 mF cm^-2 at a current density of 4 mA cm^-2. In addition, the supercapacitor shows an excellent capacity retention rate of 86.5% after 10 000 cycles at a current density of 10 mA cm^-2. Finally, three supercapacitor devices connected in series can light a blue LED lamp for 5 min.